source: vbox/trunk/src/VBox/ExtPacks/VBoxDTrace/onnv/uts/common/dtrace/dtrace.c@ 53647

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * DTrace - Dynamic Tracing for Solaris
 *
 * This is the implementation of the Solaris Dynamic Tracing framework
 * (DTrace).  The user-visible interface to DTrace is described at length in
 * the "Solaris Dynamic Tracing Guide".  The interfaces between the libdtrace
 * library, the in-kernel DTrace framework, and the DTrace providers are
 * described in the block comments in the <sys/dtrace.h> header file.  The
 * internal architecture of DTrace is described in the block comments in the
 * <sys/dtrace_impl.h> header file.  The comments contained within the DTrace
 * implementation very much assume mastery of all of these sources; if one has
 * an unanswered question about the implementation, one should consult them
 * first.
 *
 * The functions here are ordered roughly as follows:
 *
 *   - Probe context functions
 *   - Probe hashing functions
 *   - Non-probe context utility functions
 *   - Matching functions
 *   - Provider-to-Framework API functions
 *   - Probe management functions
 *   - DIF object functions
 *   - Format functions
 *   - Predicate functions
 *   - ECB functions
 *   - Buffer functions
 *   - Enabling functions
 *   - DOF functions
 *   - Anonymous enabling functions
 *   - Consumer state functions
 *   - Helper functions
 *   - Hook functions
 *   - Driver cookbook functions
 *
 * Each group of functions begins with a block comment labelled the "DTrace
 * [Group] Functions", allowing one to find each block by searching forward
 * on capital-f functions.
 */
#ifndef VBOX
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/modctl.h>
#include <sys/conf.h>
#include <sys/systm.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/cpuvar.h>
#include <sys/kmem.h>
#include <sys/strsubr.h>
#include <sys/sysmacros.h>
#include <sys/dtrace_impl.h>
#include <sys/atomic.h>
#include <sys/cmn_err.h>
#include <sys/mutex_impl.h>
#include <sys/rwlock_impl.h>
#include <sys/ctf_api.h>
#include <sys/panic.h>
#include <sys/priv_impl.h>
#include <sys/policy.h>
#include <sys/cred_impl.h>
#include <sys/procfs_isa.h>
#include <sys/taskq.h>
#include <sys/mkdev.h>
#include <sys/kdi.h>
#include <sys/zone.h>
#include <sys/socket.h>
#include <netinet/in.h>

#else  /* VBOX */
# include <sys/dtrace_impl.h>
# include <iprt/assert.h>
# include <iprt/cpuset.h>
# include <iprt/mp.h>
# include <iprt/string.h>
# include <iprt/process.h>
# include <iprt/thread.h>
# include <iprt/timer.h>
# include <limits.h>

/*
 * Use asm.h to implemente some of the simple stuff in dtrace_asm.s.
 */
# include <iprt/asm.h>
# include <iprt/asm-amd64-x86.h>
# define dtrace_casptr(a_ppvDst, a_pvOld, a_pvNew) \
        VBoxDtCompareAndSwapPtr((void * volatile *)a_ppvDst, a_pvOld, a_pvNew)
DECLINLINE(void *) VBoxDtCompareAndSwapPtr(void * volatile *ppvDst, void *pvOld, void *pvNew)
{
        void *pvRet;
        ASMAtomicCmpXchgExPtrVoid(ppvDst, pvNew, pvOld, &pvRet);
        return pvRet;
}

# define dtrace_cas32(a_pu32Dst, a_pu32Old, a_pu32New) \
        VBoxDtCompareAndSwapU32(a_pu32Dst, a_pu32Old, a_pu32New)
DECLINLINE(uint32_t) VBoxDtCompareAndSwapU32(uint32_t volatile *pu32Dst, uint32_t u32Old, uint32_t u32New)
{
        uint32_t u32Ret;
        ASMAtomicCmpXchgExU32(pu32Dst, u32New, u32Old, &u32Ret);
        return u32Ret;
}

#define dtrace_membar_consumer()                ASMReadFence()
#define dtrace_membar_producer()                ASMWriteFence()
#define dtrace_interrupt_disable()              ASMIntDisableFlags()
#define dtrace_interrupt_enable(a_EFL)  ASMSetFlags(a_EFL)

/*
 * NULL must be set to 0 or we'll end up with a billion warnings(=errors).
 */
# undef NULL
# define NULL (0)
#endif /* VBOX */

/*
 * DTrace Tunable Variables
 *
 * The following variables may be tuned by adding a line to /etc/system that
 * includes both the name of the DTrace module ("dtrace") and the name of the
 * variable.  For example:
 *
 *   set dtrace:dtrace_destructive_disallow = 1
 *
 * In general, the only variables that one should be tuning this way are those
 * that affect system-wide DTrace behavior, and for which the default behavior
 * is undesirable.  Most of these variables are tunable on a per-consumer
 * basis using DTrace options, and need not be tuned on a system-wide basis.
 * When tuning these variables, avoid pathological values; while some attempt
 * is made to verify the integrity of these variables, they are not considered
 * part of the supported interface to DTrace, and they are therefore not
 * checked comprehensively.  Further, these variables should not be tuned
 * dynamically via "mdb -kw" or other means; they should only be tuned via
 * /etc/system.
 */
int             dtrace_destructive_disallow = 0;
dtrace_optval_t dtrace_nonroot_maxsize = (16 * 1024 * 1024);
size_t          dtrace_difo_maxsize = (256 * 1024);
dtrace_optval_t dtrace_dof_maxsize = (256 * 1024);
size_t          dtrace_global_maxsize = (16 * 1024);
size_t          dtrace_actions_max = (16 * 1024);
size_t          dtrace_retain_max = 1024;
dtrace_optval_t dtrace_helper_actions_max = 32;
dtrace_optval_t dtrace_helper_providers_max = 32;
dtrace_optval_t dtrace_dstate_defsize = (1 * 1024 * 1024);
size_t          dtrace_strsize_default = 256;
dtrace_optval_t dtrace_cleanrate_default = 9900990;             /* 101 hz */
dtrace_optval_t dtrace_cleanrate_min = 200000;                  /* 5000 hz */
dtrace_optval_t dtrace_cleanrate_max = (uint64_t)60 * NANOSEC;  /* 1/minute */
dtrace_optval_t dtrace_aggrate_default = NANOSEC;               /* 1 hz */
dtrace_optval_t dtrace_statusrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t dtrace_statusrate_max = (hrtime_t)10 * NANOSEC;  /* 6/minute */
dtrace_optval_t dtrace_switchrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t dtrace_nspec_default = 1;
dtrace_optval_t dtrace_specsize_default = 32 * 1024;
dtrace_optval_t dtrace_stackframes_default = 20;
dtrace_optval_t dtrace_ustackframes_default = 20;
dtrace_optval_t dtrace_jstackframes_default = 50;
dtrace_optval_t dtrace_jstackstrsize_default = 512;
int             dtrace_msgdsize_max = 128;
hrtime_t        dtrace_chill_max = 500 * (NANOSEC / MILLISEC);  /* 500 ms */
hrtime_t        dtrace_chill_interval = NANOSEC;                /* 1000 ms */
int             dtrace_devdepth_max = 32;
int             dtrace_err_verbose;
hrtime_t        dtrace_deadman_interval = NANOSEC;
hrtime_t        dtrace_deadman_timeout = (hrtime_t)10 * NANOSEC;
hrtime_t        dtrace_deadman_user = (hrtime_t)30 * NANOSEC;

/*
 * DTrace External Variables
 *
 * As dtrace(7D) is a kernel module, any DTrace variables are obviously
 * available to DTrace consumers via the backtick (`) syntax.  One of these,
 * dtrace_zero, is made deliberately so:  it is provided as a source of
 * well-known, zero-filled memory.  While this variable is not documented,
 * it is used by some translators as an implementation detail.
 */
const char      dtrace_zero[256] = { 0 };       /* zero-filled memory */

/*
 * DTrace Internal Variables
 */
static dev_info_t       *dtrace_devi;           /* device info */
static vmem_t           *dtrace_arena;          /* probe ID arena */
static vmem_t           *dtrace_minor;          /* minor number arena */
#ifndef VBOX
static taskq_t          *dtrace_taskq;          /* task queue */
#endif
static dtrace_probe_t   **dtrace_probes;        /* array of all probes */
static VBDTTYPE(uint32_t,int) dtrace_nprobes;           /* number of probes */
static dtrace_provider_t *dtrace_provider;      /* provider list */
static dtrace_meta_t    *dtrace_meta_pid;       /* user-land meta provider */
static int              dtrace_opens;           /* number of opens */
static int              dtrace_helpers;         /* number of helpers */
static void             *dtrace_softstate;      /* softstate pointer */
static dtrace_hash_t    *dtrace_bymod;          /* probes hashed by module */
static dtrace_hash_t    *dtrace_byfunc;         /* probes hashed by function */
static dtrace_hash_t    *dtrace_byname;         /* probes hashed by name */
static dtrace_toxrange_t *dtrace_toxrange;      /* toxic range array */
static int              dtrace_toxranges;       /* number of toxic ranges */
static int              dtrace_toxranges_max;   /* size of toxic range array */
static dtrace_anon_t    dtrace_anon;            /* anonymous enabling */
static kmem_cache_t     *dtrace_state_cache;    /* cache for dynamic state */
static uint64_t         dtrace_vtime_references; /* number of vtimestamp refs */
static kthread_t        *dtrace_panicked;       /* panicking thread */
static dtrace_ecb_t     *dtrace_ecb_create_cache; /* cached created ECB */
static dtrace_genid_t   dtrace_probegen;        /* current probe generation */
static dtrace_helpers_t *dtrace_deferred_pid;   /* deferred helper list */
static dtrace_enabling_t *dtrace_retained;      /* list of retained enablings */
static dtrace_genid_t   dtrace_retained_gen;    /* current retained enab gen */
static dtrace_dynvar_t  dtrace_dynhash_sink;    /* end of dynamic hash chains */
static int              dtrace_dynvar_failclean; /* dynvars failed to clean */

/*
 * DTrace Locking
 * DTrace is protected by three (relatively coarse-grained) locks:
 *
 * (1) dtrace_lock is required to manipulate essentially any DTrace state,
 *     including enabling state, probes, ECBs, consumer state, helper state,
 *     etc.  Importantly, dtrace_lock is _not_ required when in probe context;
 *     probe context is lock-free -- synchronization is handled via the
 *     dtrace_sync() cross call mechanism.
 *
 * (2) dtrace_provider_lock is required when manipulating provider state, or
 *     when provider state must be held constant.
 *
 * (3) dtrace_meta_lock is required when manipulating meta provider state, or
 *     when meta provider state must be held constant.
 *
 * The lock ordering between these three locks is dtrace_meta_lock before
 * dtrace_provider_lock before dtrace_lock.  (In particular, there are
 * several places where dtrace_provider_lock is held by the framework as it
 * calls into the providers -- which then call back into the framework,
 * grabbing dtrace_lock.)
 *
 * There are two other locks in the mix:  mod_lock and cpu_lock.  With respect
 * to dtrace_provider_lock and dtrace_lock, cpu_lock continues its historical
 * role as a coarse-grained lock; it is acquired before both of these locks.
 * With respect to dtrace_meta_lock, its behavior is stranger:  cpu_lock must
 * be acquired _between_ dtrace_meta_lock and any other DTrace locks.
 * mod_lock is similar with respect to dtrace_provider_lock in that it must be
 * acquired _between_ dtrace_provider_lock and dtrace_lock.
 */
static kmutex_t         dtrace_lock;            /* probe state lock */
static kmutex_t         dtrace_provider_lock;   /* provider state lock */
static kmutex_t         dtrace_meta_lock;       /* meta-provider state lock */

/*
 * DTrace Provider Variables
 *
 * These are the variables relating to DTrace as a provider (that is, the
 * provider of the BEGIN, END, and ERROR probes).
 */
static dtrace_pattr_t   dtrace_provider_attr = {
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
};

static void
dtrace_nullop(void)
{}

static int
dtrace_enable_nullop(void)
{
        return (0);
}

static dtrace_pops_t    dtrace_provider_ops = {
        (void (*)(void *, const dtrace_probedesc_t *))dtrace_nullop,
        (void (*)(void *, struct modctl *))dtrace_nullop,
        (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop,
        (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
        (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
        (void (*)(void *, dtrace_id_t, void *))dtrace_nullop,
        NULL,
        NULL,
        NULL,
        (void (*)(void *, dtrace_id_t, void *))dtrace_nullop
};

static dtrace_id_t      dtrace_probeid_begin;   /* special BEGIN probe */
static dtrace_id_t      dtrace_probeid_end;     /* special END probe */
dtrace_id_t             dtrace_probeid_error;   /* special ERROR probe */

/*
 * DTrace Helper Tracing Variables
 */
uint32_t dtrace_helptrace_next = 0;
uint32_t dtrace_helptrace_nlocals;
char    *dtrace_helptrace_buffer;
int     dtrace_helptrace_bufsize = 512 * 1024;

#ifdef DEBUG
int     dtrace_helptrace_enabled = 1;
#else
int     dtrace_helptrace_enabled = 0;
#endif

/*
 * DTrace Error Hashing
 *
 * On DEBUG kernels, DTrace will track the errors that has seen in a hash
 * table.  This is very useful for checking coverage of tests that are
 * expected to induce DIF or DOF processing errors, and may be useful for
 * debugging problems in the DIF code generator or in DOF generation .  The
 * error hash may be examined with the ::dtrace_errhash MDB dcmd.
 */
#ifdef DEBUG
static dtrace_errhash_t dtrace_errhash[DTRACE_ERRHASHSZ];
static const char *dtrace_errlast;
static kthread_t *dtrace_errthread;
static kmutex_t dtrace_errlock;
#endif

/*
 * DTrace Macros and Constants
 *
 * These are various macros that are useful in various spots in the
 * implementation, along with a few random constants that have no meaning
 * outside of the implementation.  There is no real structure to this cpp
 * mishmash -- but is there ever?
 */
#define DTRACE_HASHSTR(hash, probe)     \
        dtrace_hash_str(*((char **)((uintptr_t)(probe) + (hash)->dth_stroffs)))

#define DTRACE_HASHNEXT(hash, probe)    \
        (dtrace_probe_t **)((uintptr_t)(probe) + (hash)->dth_nextoffs)

#define DTRACE_HASHPREV(hash, probe)    \
        (dtrace_probe_t **)((uintptr_t)(probe) + (hash)->dth_prevoffs)

#define DTRACE_HASHEQ(hash, lhs, rhs)   \
        (strcmp(*((char **)((uintptr_t)(lhs) + (hash)->dth_stroffs)), \
            *((char **)((uintptr_t)(rhs) + (hash)->dth_stroffs))) == 0)

#define DTRACE_AGGHASHSIZE_SLEW         17

#define DTRACE_V4MAPPED_OFFSET          (sizeof (uint32_t) * 3)

/*
 * The key for a thread-local variable consists of the lower 61 bits of the
 * t_did, plus the 3 bits of the highest active interrupt above LOCK_LEVEL.
 * We add DIF_VARIABLE_MAX to t_did to assure that the thread key is never
 * equal to a variable identifier.  This is necessary (but not sufficient) to
 * assure that global associative arrays never collide with thread-local
 * variables.  To guarantee that they cannot collide, we must also define the
 * order for keying dynamic variables.  That order is:
 *
 *   [ key0 ] ... [ keyn ] [ variable-key ] [ tls-key ]
 *
 * Because the variable-key and the tls-key are in orthogonal spaces, there is
 * no way for a global variable key signature to match a thread-local key
 * signature.
 */
#ifndef VBOX
#define DTRACE_TLS_THRKEY(where) { \
        uint_t intr = 0; \
        uint_t actv = CPU->cpu_intr_actv >> (LOCK_LEVEL + 1); \
        for (; actv; actv >>= 1) \
                intr++; \
        ASSERT(intr < (1 << 3)); \
        (where) = ((curthread->t_did + DIF_VARIABLE_MAX) & \
            (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#else
#define DTRACE_TLS_THRKEY(where) do { \
        (where) = (((uintptr_t)RTThreadNativeSelf() + DIF_VARIABLE_MAX) & (RT_BIT_64(61) - 1)) \
                        | (RTThreadIsInInterrupt(NIL_RTTHREAD) ? RT_BIT_64(61) : 0); \
} while (0)
#endif

#define DT_BSWAP_8(x)   ((x) & 0xff)
#define DT_BSWAP_16(x)  ((DT_BSWAP_8(x) << 8) | DT_BSWAP_8((x) >> 8))
#define DT_BSWAP_32(x)  ((DT_BSWAP_16(x) << 16) | DT_BSWAP_16((x) >> 16))
#define DT_BSWAP_64(x)  ((DT_BSWAP_32(x) << 32) | DT_BSWAP_32((x) >> 32))

#define DT_MASK_LO 0x00000000FFFFFFFFULL

#define DTRACE_STORE(type, tomax, offset, what) \
        *((type *)((uintptr_t)(tomax) + (uintptr_t)offset)) = (type)(what);

#ifndef __i386
#define DTRACE_ALIGNCHECK(addr, size, flags)                            \
        if (addr & (size - 1)) {                                        \
                *flags |= CPU_DTRACE_BADALIGN;                          \
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval = addr;   \
                return (0);                                             \
        }
#else
#define DTRACE_ALIGNCHECK(addr, size, flags)
#endif

/*
 * Test whether a range of memory starting at testaddr of size testsz falls
 * within the range of memory described by addr, sz.  We take care to avoid
 * problems with overflow and underflow of the unsigned quantities, and
 * disallow all negative sizes.  Ranges of size 0 are allowed.
 */
#define DTRACE_INRANGE(testaddr, testsz, baseaddr, basesz) \
        ((testaddr) - (baseaddr) < (basesz) && \
        (testaddr) + (testsz) - (baseaddr) <= (basesz) && \
        (testaddr) + (testsz) >= (testaddr))

/*
 * Test whether alloc_sz bytes will fit in the scratch region.  We isolate
 * alloc_sz on the righthand side of the comparison in order to avoid overflow
 * or underflow in the comparison with it.  This is simpler than the INRANGE
 * check above, because we know that the dtms_scratch_ptr is valid in the
 * range.  Allocations of size zero are allowed.
 */
#define DTRACE_INSCRATCH(mstate, alloc_sz) \
        ((mstate)->dtms_scratch_base + (mstate)->dtms_scratch_size - \
        (mstate)->dtms_scratch_ptr >= (alloc_sz))

#define DTRACE_LOADFUNC(bits)                                           \
/*CSTYLED*/                                                             \
VBDTSTATIC uint##bits##_t                                               \
dtrace_load##bits(uintptr_t addr)                                       \
{                                                                       \
        size_t size = bits / NBBY;                                      \
        /*CSTYLED*/                                                     \
        uint##bits##_t rval;                                            \
        int i;                                                          \
        processorid_t me = VBDT_GET_CPUID();                            \
        volatile uint16_t *flags = (volatile uint16_t *)                \
            &cpu_core[me].cpuc_dtrace_flags;                            \
                                                                        \
        DTRACE_ALIGNCHECK(addr, size, flags);                           \
                                                                        \
        for (i = 0; i < dtrace_toxranges; i++) {                        \
                if (addr >= dtrace_toxrange[i].dtt_limit)               \
                        continue;                                       \
                                                                        \
                if (addr + size <= dtrace_toxrange[i].dtt_base)         \
                        continue;                                       \
                                                                        \
                /*                                                      \
                 * This address falls within a toxic region; return 0.  \
                 */                                                     \
                *flags |= CPU_DTRACE_BADADDR;                           \
                cpu_core[me].cpuc_dtrace_illval = addr;                 \
                return (0);                                             \
        }                                                               \
                                                                        \
        *flags |= CPU_DTRACE_NOFAULT;                                   \
        /*CSTYLED*/                                                     \
        rval = *((volatile uint##bits##_t *)addr);                      \
        *flags &= ~CPU_DTRACE_NOFAULT;                                  \
                                                                        \
        return (!(*flags & CPU_DTRACE_FAULT) ? rval : 0);               \
}

#ifdef _LP64
#define dtrace_loadptr  dtrace_load64
#else
#define dtrace_loadptr  dtrace_load32
#endif

#define DTRACE_DYNHASH_FREE     0
#define DTRACE_DYNHASH_SINK     1
#define DTRACE_DYNHASH_VALID    2

#define DTRACE_MATCH_FAIL       -1
#define DTRACE_MATCH_NEXT       0
#define DTRACE_MATCH_DONE       1
#define DTRACE_ANCHORED(probe)  ((probe)->dtpr_func[0] != '\0')
#define DTRACE_STATE_ALIGN      64

#define DTRACE_FLAGS2FLT(flags)                                         \
        (((flags) & CPU_DTRACE_BADADDR) ? DTRACEFLT_BADADDR :           \
        ((flags) & CPU_DTRACE_ILLOP) ? DTRACEFLT_ILLOP :                \
        ((flags) & CPU_DTRACE_DIVZERO) ? DTRACEFLT_DIVZERO :            \
        ((flags) & CPU_DTRACE_KPRIV) ? DTRACEFLT_KPRIV :                \
        ((flags) & CPU_DTRACE_UPRIV) ? DTRACEFLT_UPRIV :                \
        ((flags) & CPU_DTRACE_TUPOFLOW) ?  DTRACEFLT_TUPOFLOW :         \
        ((flags) & CPU_DTRACE_BADALIGN) ?  DTRACEFLT_BADALIGN :         \
        ((flags) & CPU_DTRACE_NOSCRATCH) ?  DTRACEFLT_NOSCRATCH :       \
        ((flags) & CPU_DTRACE_BADSTACK) ?  DTRACEFLT_BADSTACK :         \
        DTRACEFLT_UNKNOWN)

#define DTRACEACT_ISSTRING(act)                                         \
        ((act)->dta_kind == DTRACEACT_DIFEXPR &&                        \
        (act)->dta_difo->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING)

static size_t dtrace_strlen(const char *, size_t);
static dtrace_probe_t *dtrace_probe_lookup_id(dtrace_id_t id);
static void dtrace_enabling_provide(dtrace_provider_t *);
static int dtrace_enabling_match(dtrace_enabling_t *, int *);
static void dtrace_enabling_matchall(void);
static dtrace_state_t *dtrace_anon_grab(void);
static uint64_t dtrace_helper(int, dtrace_mstate_t *,
    dtrace_state_t *, uint64_t, uint64_t);
static dtrace_helpers_t *dtrace_helpers_create(proc_t *);
static void dtrace_buffer_drop(dtrace_buffer_t *);
static intptr_t dtrace_buffer_reserve(dtrace_buffer_t *, size_t, size_t,
    dtrace_state_t *, dtrace_mstate_t *);
static int dtrace_state_option(dtrace_state_t *, dtrace_optid_t,
    dtrace_optval_t);
static int dtrace_ecb_create_enable(dtrace_probe_t *, void *);
static void dtrace_helper_provider_destroy(dtrace_helper_provider_t *);

/*
 * DTrace Probe Context Functions
 *
 * These functions are called from probe context.  Because probe context is
 * any context in which C may be called, arbitrarily locks may be held,
 * interrupts may be disabled, we may be in arbitrary dispatched state, etc.
 * As a result, functions called from probe context may only call other DTrace
 * support functions -- they may not interact at all with the system at large.
 * (Note that the ASSERT macro is made probe-context safe by redefining it in
 * terms of dtrace_assfail(), a probe-context safe function.) If arbitrary
 * loads are to be performed from probe context, they _must_ be in terms of
 * the safe dtrace_load*() variants.
 *
 * Some functions in this block are not actually called from probe context;
 * for these functions, there will be a comment above the function reading
 * "Note:  not called from probe context."
 */
void
dtrace_panic(const char *format, ...)
{
        va_list alist;

        va_start(alist, format);
        dtrace_vpanic(format, alist);
        va_end(alist);
}

int
dtrace_assfail(const char *a, const char *f, int l)
{
        dtrace_panic("assertion failed: %s, file: %s, line: %d", a, f, l);

        /*
         * We just need something here that even the most clever compiler
         * cannot optimize away.
         */
        return (a[(uintptr_t)f]);
}

/*
 * Atomically increment a specified error counter from probe context.
 */
static void
dtrace_error(uint32_t *counter)
{
        /*
         * Most counters stored to in probe context are per-CPU counters.
         * However, there are some error conditions that are sufficiently
         * arcane that they don't merit per-CPU storage.  If these counters
         * are incremented concurrently on different CPUs, scalability will be
         * adversely affected -- but we don't expect them to be white-hot in a
         * correctly constructed enabling...
         */
        uint32_t oval, nval;

        do {
                oval = *counter;

                if ((nval = oval + 1) == 0) {
                        /*
                         * If the counter would wrap, set it to 1 -- assuring
                         * that the counter is never zero when we have seen
                         * errors.  (The counter must be 32-bits because we
                         * aren't guaranteed a 64-bit compare&swap operation.)
                         * To save this code both the infamy of being fingered
                         * by a priggish news story and the indignity of being
                         * the target of a neo-puritan witch trial, we're
                         * carefully avoiding any colorful description of the
                         * likelihood of this condition -- but suffice it to
                         * say that it is only slightly more likely than the
                         * overflow of predicate cache IDs, as discussed in
                         * dtrace_predicate_create().
                         */
                        nval = 1;
                }
        } while (dtrace_cas32(counter, oval, nval) != oval);
}

/*
 * Use the DTRACE_LOADFUNC macro to define functions for each of loading a
 * uint8_t, a uint16_t, a uint32_t and a uint64_t.
 */
DTRACE_LOADFUNC(8)
DTRACE_LOADFUNC(16)
DTRACE_LOADFUNC(32)
DTRACE_LOADFUNC(64)

static int
dtrace_inscratch(uintptr_t dest, size_t size, dtrace_mstate_t *mstate)
{
        if (dest < mstate->dtms_scratch_base)
                return (0);

        if (dest + size < dest)
                return (0);

        if (dest + size > mstate->dtms_scratch_ptr)
                return (0);

        return (1);
}

static int
dtrace_canstore_statvar(uint64_t addr, size_t sz,
    dtrace_statvar_t **svars, int nsvars)
{
        int i;

        for (i = 0; i < nsvars; i++) {
                dtrace_statvar_t *svar = svars[i];

                if (svar == NULL || svar->dtsv_size == 0)
                        continue;

                if (DTRACE_INRANGE(addr, sz, svar->dtsv_data, svar->dtsv_size))
                        return (1);
        }

        return (0);
}

/*
 * Check to see if the address is within a memory region to which a store may
 * be issued.  This includes the DTrace scratch areas, and any DTrace variable
 * region.  The caller of dtrace_canstore() is responsible for performing any
 * alignment checks that are needed before stores are actually executed.
 */
static int
dtrace_canstore(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        /*
         * First, check to see if the address is in scratch space...
         */
        if (DTRACE_INRANGE(addr, sz, mstate->dtms_scratch_base,
            mstate->dtms_scratch_size))
                return (1);

        /*
         * Now check to see if it's a dynamic variable.  This check will pick
         * up both thread-local variables and any global dynamically-allocated
         * variables.
         */
        if (DTRACE_INRANGE(addr, sz, (uintptr_t)vstate->dtvs_dynvars.dtds_base,
            vstate->dtvs_dynvars.dtds_size)) {
                dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
                uintptr_t base = (uintptr_t)dstate->dtds_base +
                    (dstate->dtds_hashsize * sizeof (dtrace_dynhash_t));
                uintptr_t chunkoffs;

                /*
                 * Before we assume that we can store here, we need to make
                 * sure that it isn't in our metadata -- storing to our
                 * dynamic variable metadata would corrupt our state.  For
                 * the range to not include any dynamic variable metadata,
                 * it must:
                 *
                 *      (1) Start above the hash table that is at the base of
                 *      the dynamic variable space
                 *
                 *      (2) Have a starting chunk offset that is beyond the
                 *      dtrace_dynvar_t that is at the base of every chunk
                 *
                 *      (3) Not span a chunk boundary
                 *
                 */
                if (addr < base)
                        return (0);

                chunkoffs = (addr - base) % dstate->dtds_chunksize;

                if (chunkoffs < sizeof (dtrace_dynvar_t))
                        return (0);

                if (chunkoffs + sz > dstate->dtds_chunksize)
                        return (0);

                return (1);
        }

        /*
         * Finally, check the static local and global variables.  These checks
         * take the longest, so we perform them last.
         */
        if (dtrace_canstore_statvar(addr, sz,
            vstate->dtvs_locals, vstate->dtvs_nlocals))
                return (1);

        if (dtrace_canstore_statvar(addr, sz,
            vstate->dtvs_globals, vstate->dtvs_nglobals))
                return (1);

        return (0);
}


/*
 * Convenience routine to check to see if the address is within a memory
 * region in which a load may be issued given the user's privilege level;
 * if not, it sets the appropriate error flags and loads 'addr' into the
 * illegal value slot.
 *
 * DTrace subroutines (DIF_SUBR_*) should use this helper to implement
 * appropriate memory access protection.
 */
static int
dtrace_canload(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        volatile uintptr_t *illval = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval;

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
                return (1);

        /*
         * You can obviously read that which you can store.
         */
        if (dtrace_canstore(addr, sz, mstate, vstate))
                return (1);

        /*
         * We're allowed to read from our own string table.
         */
        if (DTRACE_INRANGE(addr, sz, (uintptr_t)mstate->dtms_difo->dtdo_strtab,
            mstate->dtms_difo->dtdo_strlen))
                return (1);

        DTRACE_CPUFLAG_SET(CPU_DTRACE_KPRIV);
        *illval = addr;
        return (0);
}

/*
 * Convenience routine to check to see if a given string is within a memory
 * region in which a load may be issued given the user's privilege level;
 * this exists so that we don't need to issue unnecessary dtrace_strlen()
 * calls in the event that the user has all privileges.
 */
static int
dtrace_strcanload(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        size_t strsz;

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
                return (1);

        strsz = 1 + dtrace_strlen((char *)(uintptr_t)addr, sz);
        if (dtrace_canload(addr, strsz, mstate, vstate))
                return (1);

        return (0);
}

/*
 * Convenience routine to check to see if a given variable is within a memory
 * region in which a load may be issued given the user's privilege level.
 */
static int
dtrace_vcanload(void *src, dtrace_diftype_t *type, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        size_t sz;
        ASSERT(type->dtdt_flags & DIF_TF_BYREF);

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
                return (1);

        if (type->dtdt_kind == DIF_TYPE_STRING)
                sz = dtrace_strlen(src,
                    vstate->dtvs_state->dts_options[DTRACEOPT_STRSIZE]) + 1;
        else
                sz = type->dtdt_size;

        return (dtrace_canload((uintptr_t)src, sz, mstate, vstate));
}

/*
 * Compare two strings using safe loads.
 */
static int
dtrace_strncmp(char *s1, char *s2, size_t limit)
{
        uint8_t c1, c2;
        volatile uint16_t *flags;

        if (s1 == s2 || limit == 0)
                return (0);

        flags = (volatile uint16_t *)&cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;

        do {
                if (s1 == NULL) {
                        c1 = '\0';
                } else {
                        c1 = dtrace_load8((uintptr_t)s1++);
                }

                if (s2 == NULL) {
                        c2 = '\0';
                } else {
                        c2 = dtrace_load8((uintptr_t)s2++);
                }

                if (c1 != c2)
                        return (c1 - c2);
        } while (--limit && c1 != '\0' && !(*flags & CPU_DTRACE_FAULT));

        return (0);
}

/*
 * Compute strlen(s) for a string using safe memory accesses.  The additional
 * len parameter is used to specify a maximum length to ensure completion.
 */
static size_t
dtrace_strlen(const char *s, size_t lim)
{
        uint_t len;

        for (len = 0; len != lim; len++) {
                if (dtrace_load8((uintptr_t)s++) == '\0')
                        break;
        }

        return (len);
}

/*
 * Check if an address falls within a toxic region.
 */
static int
dtrace_istoxic(uintptr_t kaddr, size_t size)
{
        uintptr_t taddr, tsize;
        int i;

        for (i = 0; i < dtrace_toxranges; i++) {
                taddr = dtrace_toxrange[i].dtt_base;
                tsize = dtrace_toxrange[i].dtt_limit - taddr;

                if (kaddr - taddr < tsize) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval = kaddr;
                        return (1);
                }

                if (taddr - kaddr < size) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval = taddr;
                        return (1);
                }
        }

        return (0);
}

/*
 * Copy src to dst using safe memory accesses.  The src is assumed to be unsafe
 * memory specified by the DIF program.  The dst is assumed to be safe memory
 * that we can store to directly because it is managed by DTrace.  As with
 * standard bcopy, overlapping copies are handled properly.
 */
static void
dtrace_bcopy(const void *src, void *dst, size_t len)
{
        if (len != 0) {
                uint8_t *s1 = dst;
                const uint8_t *s2 = src;

                if (s1 <= s2) {
                        do {
                                *s1++ = dtrace_load8((uintptr_t)s2++);
                        } while (--len != 0);
                } else {
                        s2 += len;
                        s1 += len;

                        do {
                                *--s1 = dtrace_load8((uintptr_t)--s2);
                        } while (--len != 0);
                }
        }
}

/*
 * Copy src to dst using safe memory accesses, up to either the specified
 * length, or the point that a nul byte is encountered.  The src is assumed to
 * be unsafe memory specified by the DIF program.  The dst is assumed to be
 * safe memory that we can store to directly because it is managed by DTrace.
 * Unlike dtrace_bcopy(), overlapping regions are not handled.
 */
static void
dtrace_strcpy(const void *src, void *dst, size_t len)
{
        if (len != 0) {
                uint8_t *s1 = dst, c;
                const uint8_t *s2 = src;

                do {
                        *s1++ = c = dtrace_load8((uintptr_t)s2++);
                } while (--len != 0 && c != '\0');
        }
}

/*
 * Copy src to dst, deriving the size and type from the specified (BYREF)
 * variable type.  The src is assumed to be unsafe memory specified by the DIF
 * program.  The dst is assumed to be DTrace variable memory that is of the
 * specified type; we assume that we can store to directly.
 */
static void
dtrace_vcopy(void *src, void *dst, dtrace_diftype_t *type)
{
        ASSERT(type->dtdt_flags & DIF_TF_BYREF);

        if (type->dtdt_kind == DIF_TYPE_STRING) {
                dtrace_strcpy(src, dst, type->dtdt_size);
        } else {
                dtrace_bcopy(src, dst, type->dtdt_size);
        }
}

/*
 * Compare s1 to s2 using safe memory accesses.  The s1 data is assumed to be
 * unsafe memory specified by the DIF program.  The s2 data is assumed to be
 * safe memory that we can access directly because it is managed by DTrace.
 */
static int
dtrace_bcmp(const void *s1, const void *s2, size_t len)
{
        volatile uint16_t *flags;

        flags = (volatile uint16_t *)&cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;

        if (s1 == s2)
                return (0);

        if (s1 == NULL || s2 == NULL)
                return (1);

        if (s1 != s2 && len != 0) {
                const uint8_t *ps1 = s1;
                const uint8_t *ps2 = s2;

                do {
                        if (dtrace_load8((uintptr_t)ps1++) != *ps2++)
                                return (1);
                } while (--len != 0 && !(*flags & CPU_DTRACE_FAULT));
        }
        return (0);
}

/*
 * Zero the specified region using a simple byte-by-byte loop.  Note that this
 * is for safe DTrace-managed memory only.
 */
static void
dtrace_bzero(void *dst, size_t len)
{
        uchar_t *cp;

        for (cp = dst; len != 0; len--)
                *cp++ = 0;
}

static void
dtrace_add_128(uint64_t *addend1, uint64_t *addend2, uint64_t *sum)
{
        uint64_t result[2];

        result[0] = addend1[0] + addend2[0];
        result[1] = addend1[1] + addend2[1] +
            (result[0] < addend1[0] || result[0] < addend2[0] ? 1 : 0);

        sum[0] = result[0];
        sum[1] = result[1];
}

/*
 * Shift the 128-bit value in a by b. If b is positive, shift left.
 * If b is negative, shift right.
 */
static void
dtrace_shift_128(uint64_t *a, int b)
{
        uint64_t mask;

        if (b == 0)
                return;

        if (b < 0) {
                b = -b;
                if (b >= 64) {
                        a[0] = a[1] >> (b - 64);
                        a[1] = 0;
                } else {
                        a[0] >>= b;
                        mask = 1LL << (64 - b);
                        mask -= 1;
                        a[0] |= ((a[1] & mask) << (64 - b));
                        a[1] >>= b;
                }
        } else {
                if (b >= 64) {
                        a[1] = a[0] << (b - 64);
                        a[0] = 0;
                } else {
                        a[1] <<= b;
                        mask = a[0] >> (64 - b);
                        a[1] |= mask;
                        a[0] <<= b;
                }
        }
}

/*
 * The basic idea is to break the 2 64-bit values into 4 32-bit values,
 * use native multiplication on those, and then re-combine into the
 * resulting 128-bit value.
 *
 * (hi1 << 32 + lo1) * (hi2 << 32 + lo2) =
 *     hi1 * hi2 << 64 +
 *     hi1 * lo2 << 32 +
 *     hi2 * lo1 << 32 +
 *     lo1 * lo2
 */
static void
dtrace_multiply_128(uint64_t factor1, uint64_t factor2, uint64_t *product)
{
        uint64_t hi1, hi2, lo1, lo2;
        uint64_t tmp[2];

        hi1 = factor1 >> 32;
        hi2 = factor2 >> 32;

        lo1 = factor1 & DT_MASK_LO;
        lo2 = factor2 & DT_MASK_LO;

        product[0] = lo1 * lo2;
        product[1] = hi1 * hi2;

        tmp[0] = hi1 * lo2;
        tmp[1] = 0;
        dtrace_shift_128(tmp, 32);
        dtrace_add_128(product, tmp, product);

        tmp[0] = hi2 * lo1;
        tmp[1] = 0;
        dtrace_shift_128(tmp, 32);
        dtrace_add_128(product, tmp, product);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the user credentials of the process that enabled the
 * invoking ECB match the target credentials
 */
static int
dtrace_priv_proc_common_user(dtrace_state_t *state)
{
        cred_t *cr, *s_cr = state->dts_cred.dcr_cred;

        /*
         * We should always have a non-NULL state cred here, since if cred
         * is null (anonymous tracing), we fast-path bypass this routine.
         */
        ASSERT(s_cr != NULL);

        if ((cr = CRED()) != NULL &&
            s_cr->cr_uid == cr->cr_uid &&
            s_cr->cr_uid == cr->cr_ruid &&
            s_cr->cr_uid == cr->cr_suid &&
            s_cr->cr_gid == cr->cr_gid &&
            s_cr->cr_gid == cr->cr_rgid &&
            s_cr->cr_gid == cr->cr_sgid)
                return (1);

        return (0);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the zone of the process that enabled the invoking ECB
 * matches the target credentials
 */
static int
dtrace_priv_proc_common_zone(dtrace_state_t *state)
{
        cred_t *cr, *s_cr = state->dts_cred.dcr_cred;

        /*
         * We should always have a non-NULL state cred here, since if cred
         * is null (anonymous tracing), we fast-path bypass this routine.
         */
        ASSERT(s_cr != NULL);

        if ((cr = CRED()) != NULL &&
            s_cr->cr_zone == cr->cr_zone)
                return (1);

        return (0);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the process has not setuid or changed credentials.
 */
static int
dtrace_priv_proc_common_nocd(VBDTVOID)
{
        proc_t *proc;

        if ((proc = VBDT_GET_PROC()) != NULL &&
            !(proc->p_flag & SNOCD))
                return (1);

        return (0);
}

static int
dtrace_priv_proc_destructive(dtrace_state_t *state)
{
        int action = state->dts_cred.dcr_action;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE) == 0) &&
            dtrace_priv_proc_common_zone(state) == 0)
                goto bad;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER) == 0) &&
            dtrace_priv_proc_common_user(state) == 0)
                goto bad;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG) == 0) &&
            dtrace_priv_proc_common_nocd() == 0)
                goto bad;

        return (1);

bad:
        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_proc_control(dtrace_state_t *state)
{
        if (state->dts_cred.dcr_action & DTRACE_CRA_PROC_CONTROL)
                return (1);

        if (dtrace_priv_proc_common_zone(state) &&
            dtrace_priv_proc_common_user(state) &&
            dtrace_priv_proc_common_nocd())
                return (1);

        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_proc(dtrace_state_t *state)
{
        if (state->dts_cred.dcr_action & DTRACE_CRA_PROC)
                return (1);

        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_kernel(dtrace_state_t *state)
{
        if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL)
                return (1);

        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

        return (0);
}

static int
dtrace_priv_kernel_destructive(dtrace_state_t *state)
{
        if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL_DESTRUCTIVE)
                return (1);

        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

        return (0);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) from outside of probe context to
 * clean the dirty dynamic variable lists on all CPUs.  Dynamic variable
 * cleaning is explained in detail in <sys/dtrace_impl.h>.
 */
VBDTSTATIC void
dtrace_dynvar_clean(dtrace_dstate_t *dstate)
{
        dtrace_dynvar_t *dirty;
        dtrace_dstate_percpu_t *dcpu;
        dtrace_dynvar_t **rinsep;
        int i, j, work = 0;

        for (i = 0; i < NCPU; i++) {
                dcpu = &dstate->dtds_percpu[i];
                rinsep = &dcpu->dtdsc_rinsing;

                /*
                 * If the dirty list is NULL, there is no dirty work to do.
                 */
                if (dcpu->dtdsc_dirty == NULL)
                        continue;

                if (dcpu->dtdsc_rinsing != NULL) {
                        /*
                         * If the rinsing list is non-NULL, then it is because
                         * this CPU was selected to accept another CPU's
                         * dirty list -- and since that time, dirty buffers
                         * have accumulated.  This is a highly unlikely
                         * condition, but we choose to ignore the dirty
                         * buffers -- they'll be picked up a future cleanse.
                         */
                        continue;
                }

                if (dcpu->dtdsc_clean != NULL) {
                        /*
                         * If the clean list is non-NULL, then we're in a
                         * situation where a CPU has done deallocations (we
                         * have a non-NULL dirty list) but no allocations (we
                         * also have a non-NULL clean list).  We can't simply
                         * move the dirty list into the clean list on this
                         * CPU, yet we also don't want to allow this condition
                         * to persist, lest a short clean list prevent a
                         * massive dirty list from being cleaned (which in
                         * turn could lead to otherwise avoidable dynamic
                         * drops).  To deal with this, we look for some CPU
                         * with a NULL clean list, NULL dirty list, and NULL
                         * rinsing list -- and then we borrow this CPU to
                         * rinse our dirty list.
                         */
                        for (j = 0; j < NCPU; j++) {
                                dtrace_dstate_percpu_t *rinser;

                                rinser = &dstate->dtds_percpu[j];

                                if (rinser->dtdsc_rinsing != NULL)
                                        continue;

                                if (rinser->dtdsc_dirty != NULL)
                                        continue;

                                if (rinser->dtdsc_clean != NULL)
                                        continue;

                                rinsep = &rinser->dtdsc_rinsing;
                                break;
                        }

                        if (j == NCPU) {
                                /*
                                 * We were unable to find another CPU that
                                 * could accept this dirty list -- we are
                                 * therefore unable to clean it now.
                                 */
                                dtrace_dynvar_failclean++;
                                continue;
                        }
                }

                work = 1;

                /*
                 * Atomically move the dirty list aside.
                 */
                do {
                        dirty = dcpu->dtdsc_dirty;

                        /*
                         * Before we zap the dirty list, set the rinsing list.
                         * (This allows for a potential assertion in
                         * dtrace_dynvar():  if a free dynamic variable appears
                         * on a hash chain, either the dirty list or the
                         * rinsing list for some CPU must be non-NULL.)
                         */
                        *rinsep = dirty;
                        dtrace_membar_producer();
                } while (dtrace_casptr(&dcpu->dtdsc_dirty,
                    dirty, NULL) != dirty);
        }

        if (!work) {
                /*
                 * We have no work to do; we can simply return.
                 */
                return;
        }

        dtrace_sync();

        for (i = 0; i < NCPU; i++) {
                dcpu = &dstate->dtds_percpu[i];

                if (dcpu->dtdsc_rinsing == NULL)
                        continue;

                /*
                 * We are now guaranteed that no hash chain contains a pointer
                 * into this dirty list; we can make it clean.
                 */
                ASSERT(dcpu->dtdsc_clean == NULL);
                dcpu->dtdsc_clean = dcpu->dtdsc_rinsing;
                dcpu->dtdsc_rinsing = NULL;
        }

        /*
         * Before we actually set the state to be DTRACE_DSTATE_CLEAN, make
         * sure that all CPUs have seen all of the dtdsc_clean pointers.
         * This prevents a race whereby a CPU incorrectly decides that
         * the state should be something other than DTRACE_DSTATE_CLEAN
         * after dtrace_dynvar_clean() has completed.
         */
        dtrace_sync();

        dstate->dtds_state = DTRACE_DSTATE_CLEAN;
}

/*
 * Depending on the value of the op parameter, this function looks-up,
 * allocates or deallocates an arbitrarily-keyed dynamic variable.  If an
 * allocation is requested, this function will return a pointer to a
 * dtrace_dynvar_t corresponding to the allocated variable -- or NULL if no
 * variable can be allocated.  If NULL is returned, the appropriate counter
 * will be incremented.
 */
VBDTSTATIC dtrace_dynvar_t *
dtrace_dynvar(dtrace_dstate_t *dstate, uint_t nkeys,
    dtrace_key_t *key, size_t dsize, dtrace_dynvar_op_t op,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        uint64_t hashval = DTRACE_DYNHASH_VALID;
        dtrace_dynhash_t *hash = dstate->dtds_hash;
        dtrace_dynvar_t *free, *new_free, *next, *dvar, *start, *prev = NULL;
        processorid_t me = VBDT_GET_CPUID(), cpu = me;
        dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[me];
        size_t bucket, ksize;
        size_t chunksize = dstate->dtds_chunksize;
        uintptr_t kdata, lock, nstate;
        uint_t i;

        ASSERT(nkeys != 0);

        /*
         * Hash the key.  As with aggregations, we use Jenkins' "One-at-a-time"
         * algorithm.  For the by-value portions, we perform the algorithm in
         * 16-bit chunks (as opposed to 8-bit chunks).  This speeds things up a
         * bit, and seems to have only a minute effect on distribution.  For
         * the by-reference data, we perform "One-at-a-time" iterating (safely)
         * over each referenced byte.  It's painful to do this, but it's much
         * better than pathological hash distribution.  The efficacy of the
         * hashing algorithm (and a comparison with other algorithms) may be
         * found by running the ::dtrace_dynstat MDB dcmd.
         */
        for (i = 0; i < nkeys; i++) {
                if (key[i].dttk_size == 0) {
                        uint64_t val = key[i].dttk_value;

                        hashval += (val >> 48) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += (val >> 32) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += (val >> 16) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += val & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);
                } else {
                        /*
                         * This is incredibly painful, but it beats the hell
                         * out of the alternative.
                         */
                        uint64_t j, size = key[i].dttk_size;
                        uintptr_t base = (uintptr_t)key[i].dttk_value;

                        if (!dtrace_canload(base, size, mstate, vstate))
                                break;

                        for (j = 0; j < size; j++) {
                                hashval += dtrace_load8(base + j);
                                hashval += (hashval << 10);
                                hashval ^= (hashval >> 6);
                        }
                }
        }

        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_FAULT))
                return (NULL);

        hashval += (hashval << 3);
        hashval ^= (hashval >> 11);
        hashval += (hashval << 15);

        /*
         * There is a remote chance (ideally, 1 in 2^31) that our hashval
         * comes out to be one of our two sentinel hash values.  If this
         * actually happens, we set the hashval to be a value known to be a
         * non-sentinel value.
         */
        if (hashval == DTRACE_DYNHASH_FREE || hashval == DTRACE_DYNHASH_SINK)
                hashval = DTRACE_DYNHASH_VALID;

        /*
         * Yes, it's painful to do a divide here.  If the cycle count becomes
         * important here, tricks can be pulled to reduce it.  (However, it's
         * critical that hash collisions be kept to an absolute minimum;
         * they're much more painful than a divide.)  It's better to have a
         * solution that generates few collisions and still keeps things
         * relatively simple.
         */
        bucket = hashval % dstate->dtds_hashsize;

        if (op == DTRACE_DYNVAR_DEALLOC) {
                volatile uintptr_t *lockp = &hash[bucket].dtdh_lock;

                for (;;) {
                        while ((lock = *lockp) & 1)
                                continue;

                        if (dtrace_casptr((void *)lockp,
                            (void *)lock, (void *)(lock + 1)) == (void *)lock)
                                break;
                }

                dtrace_membar_producer();
        }

top:
        prev = NULL;
        lock = hash[bucket].dtdh_lock;

        dtrace_membar_consumer();

        start = hash[bucket].dtdh_chain;
        ASSERT(start != NULL && (start->dtdv_hashval == DTRACE_DYNHASH_SINK ||
            start->dtdv_hashval != DTRACE_DYNHASH_FREE ||
            op != DTRACE_DYNVAR_DEALLOC));

        for (dvar = start; dvar != NULL; dvar = dvar->dtdv_next) {
                dtrace_tuple_t *dtuple = &dvar->dtdv_tuple;
                dtrace_key_t *dkey = &dtuple->dtt_key[0];

                if (dvar->dtdv_hashval != hashval) {
                        if (dvar->dtdv_hashval == DTRACE_DYNHASH_SINK) {
                                /*
                                 * We've reached the sink, and therefore the
                                 * end of the hash chain; we can kick out of
                                 * the loop knowing that we have seen a valid
                                 * snapshot of state.
                                 */
                                ASSERT(dvar->dtdv_next == NULL);
                                ASSERT(dvar == &dtrace_dynhash_sink);
                                break;
                        }

                        if (dvar->dtdv_hashval == DTRACE_DYNHASH_FREE) {
                                /*
                                 * We've gone off the rails:  somewhere along
                                 * the line, one of the members of this hash
                                 * chain was deleted.  Note that we could also
                                 * detect this by simply letting this loop run
                                 * to completion, as we would eventually hit
                                 * the end of the dirty list.  However, we
                                 * want to avoid running the length of the
                                 * dirty list unnecessarily (it might be quite
                                 * long), so we catch this as early as
                                 * possible by detecting the hash marker.  In
                                 * this case, we simply set dvar to NULL and
                                 * break; the conditional after the loop will
                                 * send us back to top.
                                 */
                                dvar = NULL;
                                break;
                        }

                        goto next;
                }

                if (dtuple->dtt_nkeys != nkeys)
                        goto next;

                for (i = 0; i < nkeys; i++, dkey++) {
                        if (dkey->dttk_size != key[i].dttk_size)
                                goto next; /* size or type mismatch */

                        if (dkey->dttk_size != 0) {
                                if (dtrace_bcmp(
                                    (void *)(uintptr_t)key[i].dttk_value,
                                    (void *)(uintptr_t)dkey->dttk_value,
                                    dkey->dttk_size))
                                        goto next;
                        } else {
                                if (dkey->dttk_value != key[i].dttk_value)
                                        goto next;
                        }
                }

                if (op != DTRACE_DYNVAR_DEALLOC)
                        return (dvar);

                ASSERT(dvar->dtdv_next == NULL ||
                    dvar->dtdv_next->dtdv_hashval != DTRACE_DYNHASH_FREE);

                if (prev != NULL) {
                        ASSERT(hash[bucket].dtdh_chain != dvar);
                        ASSERT(start != dvar);
                        ASSERT(prev->dtdv_next == dvar);
                        prev->dtdv_next = dvar->dtdv_next;
                } else {
                        if (dtrace_casptr(&hash[bucket].dtdh_chain,
                            start, dvar->dtdv_next) != start) {
                                /*
                                 * We have failed to atomically swing the
                                 * hash table head pointer, presumably because
                                 * of a conflicting allocation on another CPU.
                                 * We need to reread the hash chain and try
                                 * again.
                                 */
                                goto top;
                        }
                }

                dtrace_membar_producer();

                /*
                 * Now set the hash value to indicate that it's free.
                 */
                ASSERT(hash[bucket].dtdh_chain != dvar);
                dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

                dtrace_membar_producer();

                /*
                 * Set the next pointer to point at the dirty list, and
                 * atomically swing the dirty pointer to the newly freed dvar.
                 */
                do {
                        next = dcpu->dtdsc_dirty;
                        dvar->dtdv_next = next;
                } while (dtrace_casptr(&dcpu->dtdsc_dirty, next, dvar) != next);

                /*
                 * Finally, unlock this hash bucket.
                 */
                ASSERT(hash[bucket].dtdh_lock == lock);
                ASSERT(lock & 1);
                hash[bucket].dtdh_lock++;

                return (NULL);
next:
                prev = dvar;
                continue;
        }

        if (dvar == NULL) {
                /*
                 * If dvar is NULL, it is because we went off the rails:
                 * one of the elements that we traversed in the hash chain
                 * was deleted while we were traversing it.  In this case,
                 * we assert that we aren't doing a dealloc (deallocs lock
                 * the hash bucket to prevent themselves from racing with
                 * one another), and retry the hash chain traversal.
                 */
                ASSERT(op != DTRACE_DYNVAR_DEALLOC);
                goto top;
        }

        if (op != DTRACE_DYNVAR_ALLOC) {
                /*
                 * If we are not to allocate a new variable, we want to
                 * return NULL now.  Before we return, check that the value
                 * of the lock word hasn't changed.  If it has, we may have
                 * seen an inconsistent snapshot.
                 */
                if (op == DTRACE_DYNVAR_NOALLOC) {
                        if (hash[bucket].dtdh_lock != lock)
                                goto top;
                } else {
                        ASSERT(op == DTRACE_DYNVAR_DEALLOC);
                        ASSERT(hash[bucket].dtdh_lock == lock);
                        ASSERT(lock & 1);
                        hash[bucket].dtdh_lock++;
                }

                return (NULL);
        }

        /*
         * We need to allocate a new dynamic variable.  The size we need is the
         * size of dtrace_dynvar plus the size of nkeys dtrace_key_t's plus the
         * size of any auxiliary key data (rounded up to 8-byte alignment) plus
         * the size of any referred-to data (dsize).  We then round the final
         * size up to the chunksize for allocation.
         */
        for (ksize = 0, i = 0; i < nkeys; i++)
                ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

        /*
         * This should be pretty much impossible, but could happen if, say,
         * strange DIF specified the tuple.  Ideally, this should be an
         * assertion and not an error condition -- but that requires that the
         * chunksize calculation in dtrace_difo_chunksize() be absolutely
         * bullet-proof.  (That is, it must not be able to be fooled by
         * malicious DIF.)  Given the lack of backwards branches in DIF,
         * solving this would presumably not amount to solving the Halting
         * Problem -- but it still seems awfully hard.
         */
        if (sizeof (dtrace_dynvar_t) + sizeof (dtrace_key_t) * (nkeys - 1) +
            ksize + dsize > chunksize) {
                dcpu->dtdsc_drops++;
                return (NULL);
        }

        nstate = DTRACE_DSTATE_EMPTY;

        do {
retry:
                free = dcpu->dtdsc_free;

                if (free == NULL) {
                        dtrace_dynvar_t *clean = dcpu->dtdsc_clean;
                        void *rval;

                        if (clean == NULL) {
                                /*
                                 * We're out of dynamic variable space on
                                 * this CPU.  Unless we have tried all CPUs,
                                 * we'll try to allocate from a different
                                 * CPU.
                                 */
                                switch (dstate->dtds_state) {
                                case DTRACE_DSTATE_CLEAN: {
                                        void *sp = &dstate->dtds_state;

                                        if (++cpu >= NCPU)
                                                cpu = 0;

                                        if (dcpu->dtdsc_dirty != NULL &&
                                            nstate == DTRACE_DSTATE_EMPTY)
                                                nstate = DTRACE_DSTATE_DIRTY;

                                        if (dcpu->dtdsc_rinsing != NULL)
                                                nstate = DTRACE_DSTATE_RINSING;

                                        dcpu = &dstate->dtds_percpu[cpu];

                                        if (cpu != me)
                                                goto retry;

                                        (void) dtrace_cas32(sp,
                                            DTRACE_DSTATE_CLEAN, nstate);

                                        /*
                                         * To increment the correct bean
                                         * counter, take another lap.
                                         */
                                        goto retry;
                                }

                                case DTRACE_DSTATE_DIRTY:
                                        dcpu->dtdsc_dirty_drops++;
                                        break;

                                case DTRACE_DSTATE_RINSING:
                                        dcpu->dtdsc_rinsing_drops++;
                                        break;

                                case DTRACE_DSTATE_EMPTY:
                                        dcpu->dtdsc_drops++;
                                        break;
                                }

                                DTRACE_CPUFLAG_SET(CPU_DTRACE_DROP);
                                return (NULL);
                        }

                        /*
                         * The clean list appears to be non-empty.  We want to
                         * move the clean list to the free list; we start by
                         * moving the clean pointer aside.
                         */
                        if (dtrace_casptr(&dcpu->dtdsc_clean,
                            clean, NULL) != clean) {
                                /*
                                 * We are in one of two situations:
                                 *
                                 *  (a) The clean list was switched to the
                                 *      free list by another CPU.
                                 *
                                 *  (b) The clean list was added to by the
                                 *      cleansing cyclic.
                                 *
                                 * In either of these situations, we can
                                 * just reattempt the free list allocation.
                                 */
                                goto retry;
                        }

                        ASSERT(clean->dtdv_hashval == DTRACE_DYNHASH_FREE);

                        /*
                         * Now we'll move the clean list to our free list.
                         * It's impossible for this to fail:  the only way
                         * the free list can be updated is through this
                         * code path, and only one CPU can own the clean list.
                         * Thus, it would only be possible for this to fail if
                         * this code were racing with dtrace_dynvar_clean().
                         * (That is, if dtrace_dynvar_clean() updated the clean
                         * list, and we ended up racing to update the free
                         * list.)  This race is prevented by the dtrace_sync()
                         * in dtrace_dynvar_clean() -- which flushes the
                         * owners of the clean lists out before resetting
                         * the clean lists.
                         */
                        dcpu = &dstate->dtds_percpu[me];
                        rval = dtrace_casptr(&dcpu->dtdsc_free, NULL, clean);
                        ASSERT(rval == NULL);
                        goto retry;
                }

                dvar = free;
                new_free = dvar->dtdv_next;
        } while (dtrace_casptr(&dcpu->dtdsc_free, free, new_free) != free);

        /*
         * We have now allocated a new chunk.  We copy the tuple keys into the
         * tuple array and copy any referenced key data into the data space
         * following the tuple array.  As we do this, we relocate dttk_value
         * in the final tuple to point to the key data address in the chunk.
         */
        kdata = (uintptr_t)&dvar->dtdv_tuple.dtt_key[nkeys];
        dvar->dtdv_data = (void *)(kdata + ksize);
        dvar->dtdv_tuple.dtt_nkeys = nkeys;

        for (i = 0; i < nkeys; i++) {
                dtrace_key_t *dkey = &dvar->dtdv_tuple.dtt_key[i];
                size_t kesize = key[i].dttk_size;

                if (kesize != 0) {
                        dtrace_bcopy(
                            (const void *)(uintptr_t)key[i].dttk_value,
                            (void *)kdata, kesize);
                        dkey->dttk_value = kdata;
                        kdata += P2ROUNDUP(kesize, sizeof (uint64_t));
                } else {
                        dkey->dttk_value = key[i].dttk_value;
                }

                dkey->dttk_size = kesize;
        }

        ASSERT(dvar->dtdv_hashval == DTRACE_DYNHASH_FREE);
        dvar->dtdv_hashval = hashval;
        dvar->dtdv_next = start;

        if (dtrace_casptr(&hash[bucket].dtdh_chain, start, dvar) == start)
                return (dvar);

        /*
         * The cas has failed.  Either another CPU is adding an element to
         * this hash chain, or another CPU is deleting an element from this
         * hash chain.  The simplest way to deal with both of these cases
         * (though not necessarily the most efficient) is to free our
         * allocated block and tail-call ourselves.  Note that the free is
         * to the dirty list and _not_ to the free list.  This is to prevent
         * races with allocators, above.
         */
        dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

        dtrace_membar_producer();

        do {
                free = dcpu->dtdsc_dirty;
                dvar->dtdv_next = free;
        } while (dtrace_casptr(&dcpu->dtdsc_dirty, free, dvar) != free);

        return (dtrace_dynvar(dstate, nkeys, key, dsize, op, mstate, vstate));
}

/*ARGSUSED*/
static void
dtrace_aggregate_min(uint64_t *oval, uint64_t nval, uint64_t arg)
{
        if ((int64_t)nval < (int64_t)*oval)
                *oval = nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_max(uint64_t *oval, uint64_t nval, uint64_t arg)
{
        if ((int64_t)nval > (int64_t)*oval)
                *oval = nval;
}

static void
dtrace_aggregate_quantize(uint64_t *quanta, uint64_t nval, uint64_t incr)
{
        int i, zero = DTRACE_QUANTIZE_ZEROBUCKET;
        int64_t val = (int64_t)nval;

        if (val < 0) {
                for (i = 0; i < zero; i++) {
                        if (val <= DTRACE_QUANTIZE_BUCKETVAL(i)) {
                                quanta[i] += incr;
                                return;
                        }
                }
        } else {
                for (i = zero + 1; i < VBDTCAST(int)DTRACE_QUANTIZE_NBUCKETS; i++) {
                        if (val < DTRACE_QUANTIZE_BUCKETVAL(i)) {
                                quanta[i - 1] += incr;
                                return;
                        }
                }

                quanta[DTRACE_QUANTIZE_NBUCKETS - 1] += incr;
                return;
        }

#ifndef VBOX
        ASSERT(0);
#else
        AssertFatalFailed();
#endif
}

static void
dtrace_aggregate_lquantize(uint64_t *lquanta, uint64_t nval, uint64_t incr)
{
        uint64_t arg = *lquanta++;
        int32_t base = DTRACE_LQUANTIZE_BASE(arg);
        uint16_t step = DTRACE_LQUANTIZE_STEP(arg);
        uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg);
        int32_t val = (int32_t)nval, level;

        ASSERT(step != 0);
        ASSERT(levels != 0);

        if (val < base) {
                /*
                 * This is an underflow.
                 */
                lquanta[0] += incr;
                return;
        }

        level = (val - base) / step;

        if (level < levels) {
                lquanta[level + 1] += incr;
                return;
        }

        /*
         * This is an overflow.
         */
        lquanta[levels + 1] += incr;
}

/*ARGSUSED*/
static void
dtrace_aggregate_avg(uint64_t *data, uint64_t nval, uint64_t arg)
{
        data[0]++;
        data[1] += nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_stddev(uint64_t *data, uint64_t nval, uint64_t arg)
{
        int64_t snval = (int64_t)nval;
        uint64_t tmp[2];

        data[0]++;
        data[1] += nval;

        /*
         * What we want to say here is:
         *
         * data[2] += nval * nval;
         *
         * But given that nval is 64-bit, we could easily overflow, so
         * we do this as 128-bit arithmetic.
         */
        if (snval < 0)
                snval = -snval;

        dtrace_multiply_128((uint64_t)snval, (uint64_t)snval, tmp);
        dtrace_add_128(data + 2, tmp, data + 2);
}

/*ARGSUSED*/
static void
dtrace_aggregate_count(uint64_t *oval, uint64_t nval, uint64_t arg)
{
        *oval = *oval + 1;
}

/*ARGSUSED*/
static void
dtrace_aggregate_sum(uint64_t *oval, uint64_t nval, uint64_t arg)
{
        *oval += nval;
}

/*
 * Aggregate given the tuple in the principal data buffer, and the aggregating
 * action denoted by the specified dtrace_aggregation_t.  The aggregation
 * buffer is specified as the buf parameter.  This routine does not return
 * failure; if there is no space in the aggregation buffer, the data will be
 * dropped, and a corresponding counter incremented.
 */
static void
dtrace_aggregate(dtrace_aggregation_t *agg, dtrace_buffer_t *dbuf,
    intptr_t offset, dtrace_buffer_t *buf, uint64_t expr, uint64_t arg)
{
        dtrace_recdesc_t *rec = &agg->dtag_action.dta_rec;
        uint32_t i, ndx, size, fsize;
        uint32_t align = sizeof (uint64_t) - 1;
        dtrace_aggbuffer_t *agb;
        dtrace_aggkey_t *key;
        uint32_t hashval = 0, limit, isstr;
        caddr_t tomax, data, kdata;
        dtrace_actkind_t action;
        dtrace_action_t *act;
        uintptr_t offs;

        if (buf == NULL)
                return;

        if (!agg->dtag_hasarg) {
                /*
                 * Currently, only quantize() and lquantize() take additional
                 * arguments, and they have the same semantics:  an increment
                 * value that defaults to 1 when not present.  If additional
                 * aggregating actions take arguments, the setting of the
                 * default argument value will presumably have to become more
                 * sophisticated...
                 */
                arg = 1;
        }

        action = agg->dtag_action.dta_kind - DTRACEACT_AGGREGATION;
        size = rec->dtrd_offset - agg->dtag_base;
        fsize = size + rec->dtrd_size;

        ASSERT(dbuf->dtb_tomax != NULL);
        data = dbuf->dtb_tomax + offset + agg->dtag_base;

        if ((tomax = buf->dtb_tomax) == NULL) {
                dtrace_buffer_drop(buf);
                return;
        }

        /*
         * The metastructure is always at the bottom of the buffer.
         */
        agb = (dtrace_aggbuffer_t *)(tomax + buf->dtb_size -
            sizeof (dtrace_aggbuffer_t));

        if (buf->dtb_offset == 0) {
                /*
                 * We just kludge up approximately 1/8th of the size to be
                 * buckets.  If this guess ends up being routinely
                 * off-the-mark, we may need to dynamically readjust this
                 * based on past performance.
                 */
                uintptr_t hashsize = (buf->dtb_size >> 3) / sizeof (uintptr_t);

                if ((uintptr_t)agb - hashsize * sizeof (dtrace_aggkey_t *) <
                    (uintptr_t)tomax || hashsize == 0) {
                        /*
                         * We've been given a ludicrously small buffer;
                         * increment our drop count and leave.
                         */
                        dtrace_buffer_drop(buf);
                        return;
                }

                /*
                 * And now, a pathetic attempt to try to get a an odd (or
                 * perchance, a prime) hash size for better hash distribution.
                 */
                if (hashsize > (DTRACE_AGGHASHSIZE_SLEW << 3))
                        hashsize -= DTRACE_AGGHASHSIZE_SLEW;

                agb->dtagb_hashsize = hashsize;
                agb->dtagb_hash = (dtrace_aggkey_t **)((uintptr_t)agb -
                    agb->dtagb_hashsize * sizeof (dtrace_aggkey_t *));
                agb->dtagb_free = (uintptr_t)agb->dtagb_hash;

                for (i = 0; i < agb->dtagb_hashsize; i++)
                        agb->dtagb_hash[i] = NULL;
        }

        ASSERT(agg->dtag_first != NULL);
        ASSERT(agg->dtag_first->dta_intuple);

        /*
         * Calculate the hash value based on the key.  Note that we _don't_
         * include the aggid in the hashing (but we will store it as part of
         * the key).  The hashing algorithm is Bob Jenkins' "One-at-a-time"
         * algorithm: a simple, quick algorithm that has no known funnels, and
         * gets good distribution in practice.  The efficacy of the hashing
         * algorithm (and a comparison with other algorithms) may be found by
         * running the ::dtrace_aggstat MDB dcmd.
         */
        for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
                i = act->dta_rec.dtrd_offset - agg->dtag_base;
                limit = i + act->dta_rec.dtrd_size;
                ASSERT(limit <= size);
                isstr = DTRACEACT_ISSTRING(act);

                for (; i < limit; i++) {
                        hashval += data[i];
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        if (isstr && data[i] == '\0')
                                break;
                }
        }

        hashval += (hashval << 3);
        hashval ^= (hashval >> 11);
        hashval += (hashval << 15);

        /*
         * Yes, the divide here is expensive -- but it's generally the least
         * of the performance issues given the amount of data that we iterate
         * over to compute hash values, compare data, etc.
         */
        ndx = hashval % agb->dtagb_hashsize;

        for (key = agb->dtagb_hash[ndx]; key != NULL; key = key->dtak_next) {
                ASSERT((caddr_t)key >= tomax);
                ASSERT((caddr_t)key < tomax + buf->dtb_size);

                if (hashval != key->dtak_hashval || key->dtak_size != size)
                        continue;

                kdata = key->dtak_data;
                ASSERT(kdata >= tomax && kdata < tomax + buf->dtb_size);

                for (act = agg->dtag_first; act->dta_intuple;
                    act = act->dta_next) {
                        i = act->dta_rec.dtrd_offset - agg->dtag_base;
                        limit = i + act->dta_rec.dtrd_size;
                        ASSERT(limit <= size);
                        isstr = DTRACEACT_ISSTRING(act);

                        for (; i < limit; i++) {
                                if (kdata[i] != data[i])
                                        goto next;

                                if (isstr && data[i] == '\0')
                                        break;
                        }
                }

                if (action != key->dtak_action) {
                        /*
                         * We are aggregating on the same value in the same
                         * aggregation with two different aggregating actions.
                         * (This should have been picked up in the compiler,
                         * so we may be dealing with errant or devious DIF.)
                         * This is an error condition; we indicate as much,
                         * and return.
                         */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        return;
                }

                /*
                 * This is a hit:  we need to apply the aggregator to
                 * the value at this key.
                 */
                agg->dtag_aggregate((uint64_t *)(kdata + size), expr, arg);
                return;
next:
                continue;
        }

        /*
         * We didn't find it.  We need to allocate some zero-filled space,
         * link it into the hash table appropriately, and apply the aggregator
         * to the (zero-filled) value.
         */
        offs = buf->dtb_offset;
        while (offs & (align - 1))
                offs += sizeof (uint32_t);

        /*
         * If we don't have enough room to both allocate a new key _and_
         * its associated data, increment the drop count and return.
         */
        if ((uintptr_t)tomax + offs + fsize >
            agb->dtagb_free - sizeof (dtrace_aggkey_t)) {
                dtrace_buffer_drop(buf);
                return;
        }

        /*CONSTCOND*/
        ASSERT(!(sizeof (dtrace_aggkey_t) & (sizeof (uintptr_t) - 1)));
        key = (dtrace_aggkey_t *)(agb->dtagb_free - sizeof (dtrace_aggkey_t));
        agb->dtagb_free -= sizeof (dtrace_aggkey_t);

        key->dtak_data = kdata = tomax + offs;
        buf->dtb_offset = offs + fsize;

        /*
         * Now copy the data across.
         */
        *((dtrace_aggid_t *)kdata) = agg->dtag_id;

        for (i = sizeof (dtrace_aggid_t); i < size; i++)
                kdata[i] = data[i];

        /*
         * Because strings are not zeroed out by default, we need to iterate
         * looking for actions that store strings, and we need to explicitly
         * pad these strings out with zeroes.
         */
        for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
                int nul;

                if (!DTRACEACT_ISSTRING(act))
                        continue;

                i = act->dta_rec.dtrd_offset - agg->dtag_base;
                limit = i + act->dta_rec.dtrd_size;
                ASSERT(limit <= size);

                for (nul = 0; i < limit; i++) {
                        if (nul) {
                                kdata[i] = '\0';
                                continue;
                        }

                        if (data[i] != '\0')
                                continue;

                        nul = 1;
                }
        }

        for (i = size; i < fsize; i++)
                kdata[i] = 0;

        key->dtak_hashval = hashval;
        key->dtak_size = size;
        key->dtak_action = action;
        key->dtak_next = agb->dtagb_hash[ndx];
        agb->dtagb_hash[ndx] = key;

        /*
         * Finally, apply the aggregator.
         */
        *((uint64_t *)(key->dtak_data + size)) = agg->dtag_initial;
        agg->dtag_aggregate((uint64_t *)(key->dtak_data + size), expr, arg);
}

/*
 * Given consumer state, this routine finds a speculation in the INACTIVE
 * state and transitions it into the ACTIVE state.  If there is no speculation
 * in the INACTIVE state, 0 is returned.  In this case, no error counter is
 * incremented -- it is up to the caller to take appropriate action.
 */
static int
dtrace_speculation(dtrace_state_t *state)
{
        int i = 0;
        dtrace_speculation_state_t current;
        uint32_t *stat = &state->dts_speculations_unavail, count;

        while (i < state->dts_nspeculations) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];

                current = spec->dtsp_state;

                if (current != DTRACESPEC_INACTIVE) {
                        if (current == DTRACESPEC_COMMITTINGMANY ||
                            current == DTRACESPEC_COMMITTING ||
                            current == DTRACESPEC_DISCARDING)
                                stat = &state->dts_speculations_busy;
                        i++;
                        continue;
                }

                if (dtrace_cas32((uint32_t *)&spec->dtsp_state,
                    current, DTRACESPEC_ACTIVE) == current)
                        return (i + 1);
        }

        /*
         * We couldn't find a speculation.  If we found as much as a single
         * busy speculation buffer, we'll attribute this failure as "busy"
         * instead of "unavail".
         */
        do {
                count = *stat;
        } while (dtrace_cas32(stat, count, count + 1) != count);

        return (0);
}

/*
 * This routine commits an active speculation.  If the specified speculation
 * is not in a valid state to perform a commit(), this routine will silently do
 * nothing.  The state of the specified speculation is transitioned according
 * to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_commit(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_buffer_t *src, *dest;
        uintptr_t daddr, saddr, dlimit;
        dtrace_speculation_state_t current, new VBDTUNASS(-1);
        intptr_t offs;

        if (which == 0)
                return;

        if (which > VBDTCAST(unsigned)state->dts_nspeculations) {
                cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return;
        }

        spec = &state->dts_speculations[which - 1];
        src = &spec->dtsp_buffer[cpu];
        dest = &state->dts_buffer[cpu];

        do {
                current = spec->dtsp_state;

                if (current == DTRACESPEC_COMMITTINGMANY)
                        break;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_DISCARDING:
                        return;

                case DTRACESPEC_COMMITTING:
                        /*
                         * This is only possible if we are (a) commit()'ing
                         * without having done a prior speculate() on this CPU
                         * and (b) racing with another commit() on a different
                         * CPU.  There's nothing to do -- we just assert that
                         * our offset is 0.
                         */
                        ASSERT(src->dtb_offset == 0);
                        return;

                case DTRACESPEC_ACTIVE:
                        new = DTRACESPEC_COMMITTING;
                        break;

                case DTRACESPEC_ACTIVEONE:
                        /*
                         * This speculation is active on one CPU.  If our
                         * buffer offset is non-zero, we know that the one CPU
                         * must be us.  Otherwise, we are committing on a
                         * different CPU from the speculate(), and we must
                         * rely on being asynchronously cleaned.
                         */
                        if (src->dtb_offset != 0) {
                                new = DTRACESPEC_COMMITTING;
                                break;
                        }
                        /*FALLTHROUGH*/

                case DTRACESPEC_ACTIVEMANY:
                        new = DTRACESPEC_COMMITTINGMANY;
                        break;

                default:
#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalMsgFailed(("%d\n",  current));
#endif
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        /*
         * We have set the state to indicate that we are committing this
         * speculation.  Now reserve the necessary space in the destination
         * buffer.
         */
        if ((offs = dtrace_buffer_reserve(dest, src->dtb_offset,
            sizeof (uint64_t), state, NULL)) < 0) {
                dtrace_buffer_drop(dest);
                goto out;
        }

        /*
         * We have the space; copy the buffer across.  (Note that this is a
         * highly subobtimal bcopy(); in the unlikely event that this becomes
         * a serious performance issue, a high-performance DTrace-specific
         * bcopy() should obviously be invented.)
         */
        daddr = (uintptr_t)dest->dtb_tomax + offs;
        dlimit = daddr + src->dtb_offset;
        saddr = (uintptr_t)src->dtb_tomax;

        /*
         * First, the aligned portion.
         */
        while (dlimit - daddr >= sizeof (uint64_t)) {
                *((uint64_t *)daddr) = *((uint64_t *)saddr);

                daddr += sizeof (uint64_t);
                saddr += sizeof (uint64_t);
        }

        /*
         * Now any left-over bit...
         */
        while (dlimit - daddr)
                *((uint8_t *)daddr++) = *((uint8_t *)saddr++);

        /*
         * Finally, commit the reserved space in the destination buffer.
         */
        dest->dtb_offset = offs + src->dtb_offset;

out:
        /*
         * If we're lucky enough to be the only active CPU on this speculation
         * buffer, we can just set the state back to DTRACESPEC_INACTIVE.
         */
        if (current == DTRACESPEC_ACTIVE ||
            (current == DTRACESPEC_ACTIVEONE && new == DTRACESPEC_COMMITTING)) {
                uint32_t rval = dtrace_cas32((uint32_t *)&spec->dtsp_state,
                    DTRACESPEC_COMMITTING, DTRACESPEC_INACTIVE);

                ASSERT(rval == DTRACESPEC_COMMITTING);
        }

        src->dtb_offset = 0;
        src->dtb_xamot_drops += src->dtb_drops;
        src->dtb_drops = 0;
}

/*
 * This routine discards an active speculation.  If the specified speculation
 * is not in a valid state to perform a discard(), this routine will silently
 * do nothing.  The state of the specified speculation is transitioned
 * according to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_discard(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_speculation_state_t current, new;
        dtrace_buffer_t *buf;

        if (which == 0)
                return;

        if (which > VBDTCAST(unsigned)state->dts_nspeculations) {
                cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return;
        }

        spec = &state->dts_speculations[which - 1];
        buf = &spec->dtsp_buffer[cpu];

        do {
                current = spec->dtsp_state;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_COMMITTINGMANY:
                case DTRACESPEC_COMMITTING:
                case DTRACESPEC_DISCARDING:
                        return;

                case DTRACESPEC_ACTIVE:
                case DTRACESPEC_ACTIVEMANY:
                        new = DTRACESPEC_DISCARDING;
                        break;

                case DTRACESPEC_ACTIVEONE:
                        if (buf->dtb_offset != 0) {
                                new = DTRACESPEC_INACTIVE;
                        } else {
                                new = DTRACESPEC_DISCARDING;
                        }
                        break;

                default:
#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalMsgFailed(("%d\n", current));
#endif
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        buf->dtb_offset = 0;
        buf->dtb_drops = 0;
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously from cross call context to clean any speculations that are
 * in the COMMITTINGMANY or DISCARDING states.  These speculations may not be
 * transitioned back to the INACTIVE state until all CPUs have cleaned the
 * speculation.
 */
static void
dtrace_speculation_clean_here(dtrace_state_t *state)
{
        dtrace_icookie_t cookie;
        processorid_t cpu = VBDT_GET_CPUID();
        dtrace_buffer_t *dest = &state->dts_buffer[cpu];
        dtrace_specid_t i;

        cookie = dtrace_interrupt_disable();

        if (dest->dtb_tomax == NULL) {
                dtrace_interrupt_enable(cookie);
                return;
        }

        for (i = 0; i < VBDTCAST(unsigned)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];
                dtrace_buffer_t *src = &spec->dtsp_buffer[cpu];

                if (src->dtb_tomax == NULL)
                        continue;

                if (spec->dtsp_state == DTRACESPEC_DISCARDING) {
                        src->dtb_offset = 0;
                        continue;
                }

                if (spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                        continue;

                if (src->dtb_offset == 0)
                        continue;

                dtrace_speculation_commit(state, cpu, i + 1);
        }

        dtrace_interrupt_enable(cookie);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) to clean any speculations that
 * are in the COMMITTINGMANY or DISCARDING states.  If it discovers that there
 * is work to be done, it cross calls all CPUs to perform that work;
 * COMMITMANY and DISCARDING speculations may not be transitioned back to the
 * INACTIVE state until they have been cleaned by all CPUs.
 */
static void
dtrace_speculation_clean(dtrace_state_t *state)
{
        int work = 0, rv;
        dtrace_specid_t i;

        for (i = 0; i < VBDTCAST(unsigned)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];

                ASSERT(!spec->dtsp_cleaning);

                if (spec->dtsp_state != DTRACESPEC_DISCARDING &&
                    spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                        continue;

                work++;
                spec->dtsp_cleaning = 1;
        }

        if (!work)
                return;

        dtrace_xcall(DTRACE_CPUALL,
            (dtrace_xcall_t)dtrace_speculation_clean_here, state);

        /*
         * We now know that all CPUs have committed or discarded their
         * speculation buffers, as appropriate.  We can now set the state
         * to inactive.
         */
        for (i = 0; i < VBDTCAST(unsigned)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];
                dtrace_speculation_state_t current, new;

                if (!spec->dtsp_cleaning)
                        continue;

                current = spec->dtsp_state;
                ASSERT(current == DTRACESPEC_DISCARDING ||
                    current == DTRACESPEC_COMMITTINGMANY);

                new = DTRACESPEC_INACTIVE;

                rv = dtrace_cas32((uint32_t *)&spec->dtsp_state, current, new);
                ASSERT(VBDTCAST(dtrace_speculation_state_t)rv == current);
                spec->dtsp_cleaning = 0;
        }
}

/*
 * Called as part of a speculate() to get the speculative buffer associated
 * with a given speculation.  Returns NULL if the specified speculation is not
 * in an ACTIVE state.  If the speculation is in the ACTIVEONE state -- and
 * the active CPU is not the specified CPU -- the speculation will be
 * atomically transitioned into the ACTIVEMANY state.
 */
static dtrace_buffer_t *
dtrace_speculation_buffer(dtrace_state_t *state, processorid_t cpuid,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_speculation_state_t current, new VBDTUNASS(-1);
        dtrace_buffer_t *buf;

        if (which == 0)
                return (NULL);

        if (which > VBDTCAST(unsigned)state->dts_nspeculations) {
                cpu_core[cpuid].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (NULL);
        }

        spec = &state->dts_speculations[which - 1];
        buf = &spec->dtsp_buffer[cpuid];

        do {
                current = spec->dtsp_state;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_COMMITTINGMANY:
                case DTRACESPEC_DISCARDING:
                        return (NULL);

                case DTRACESPEC_COMMITTING:
                        ASSERT(buf->dtb_offset == 0);
                        return (NULL);

                case DTRACESPEC_ACTIVEONE:
                        /*
                         * This speculation is currently active on one CPU.
                         * Check the offset in the buffer; if it's non-zero,
                         * that CPU must be us (and we leave the state alone).
                         * If it's zero, assume that we're starting on a new
                         * CPU -- and change the state to indicate that the
                         * speculation is active on more than one CPU.
                         */
                        if (buf->dtb_offset != 0)
                                return (buf);

                        new = DTRACESPEC_ACTIVEMANY;
                        break;

                case DTRACESPEC_ACTIVEMANY:
                        return (buf);

                case DTRACESPEC_ACTIVE:
                        new = DTRACESPEC_ACTIVEONE;
                        break;

                default:
#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalMsgFailed(("%d\n", current));
#endif
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        ASSERT(new == DTRACESPEC_ACTIVEONE || new == DTRACESPEC_ACTIVEMANY);
        return (buf);
}

/*
 * Return a string.  In the event that the user lacks the privilege to access
 * arbitrary kernel memory, we copy the string out to scratch memory so that we
 * don't fail access checking.
 *
 * dtrace_dif_variable() uses this routine as a helper for various
 * builtin values such as 'execname' and 'probefunc.'
 */
VBDTSTATIC uintptr_t
dtrace_dif_varstr(uintptr_t addr, dtrace_state_t *state,
    dtrace_mstate_t *mstate)
{
        uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
        uintptr_t ret;
        size_t strsz;

        /*
         * The easy case: this probe is allowed to read all of memory, so
         * we can just return this as a vanilla pointer.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
                return (addr);

        /*
         * This is the tougher case: we copy the string in question from
         * kernel memory into scratch memory and return it that way: this
         * ensures that we won't trip up when access checking tests the
         * BYREF return value.
         */
        strsz = dtrace_strlen((char *)addr, size) + 1;

        if (mstate->dtms_scratch_ptr + strsz >
            mstate->dtms_scratch_base + mstate->dtms_scratch_size) {
                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                return (NULL);
        }

        dtrace_strcpy((const void *)addr, (void *)mstate->dtms_scratch_ptr,
            strsz);
        ret = mstate->dtms_scratch_ptr;
        mstate->dtms_scratch_ptr += strsz;
        return (ret);
}

/*
 * This function implements the DIF emulator's variable lookups.  The emulator
 * passes a reserved variable identifier and optional built-in array index.
 */
static uint64_t
dtrace_dif_variable(dtrace_mstate_t *mstate, dtrace_state_t *state, uint64_t v,
    uint64_t ndx)
{
        /*
         * If we're accessing one of the uncached arguments, we'll turn this
         * into a reference in the args array.
         */
        if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9) {
                ndx = v - DIF_VAR_ARG0;
                v = DIF_VAR_ARGS;
        }

        switch (v) {
        case DIF_VAR_ARGS:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_ARGS);
                if (ndx >= sizeof (mstate->dtms_arg) /
                    sizeof (mstate->dtms_arg[0])) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;
                        dtrace_provider_t *pv;
                        uint64_t val;

                        pv = mstate->dtms_probe->dtpr_provider;
                        if (pv->dtpv_pops.dtps_getargval != NULL)
                                val = pv->dtpv_pops.dtps_getargval(pv->dtpv_arg,
                                    mstate->dtms_probe->dtpr_id,
                                    mstate->dtms_probe->dtpr_arg, ndx, aframes);
                        else
                                val = dtrace_getarg(ndx, aframes);

                        /*
                         * This is regrettably required to keep the compiler
                         * from tail-optimizing the call to dtrace_getarg().
                         * The condition always evaluates to true, but the
                         * compiler has no way of figuring that out a priori.
                         * (None of this would be necessary if the compiler
                         * could be relied upon to _always_ tail-optimize
                         * the call to dtrace_getarg() -- but it can't.)
                         */
                        if (mstate->dtms_probe != NULL)
                                return (val);

#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalFailed();
#endif
                }

                return (mstate->dtms_arg[ndx]);

        case DIF_VAR_UREGS: {
#ifndef VBOX
                klwp_t *lwp;

                if (!dtrace_priv_proc(state))
                        return (0);

                if ((lwp = curthread->t_lwp) == NULL) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval = NULL;
                        return (0);
                }

                return (dtrace_getreg(lwp->lwp_regs, ndx));
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif
        }

        case DIF_VAR_CURTHREAD:
                if (!dtrace_priv_kernel(state))
                        return (0);
#ifndef VBOX
                return ((uint64_t)(uintptr_t)curthread);
#else
                return ((uintptr_t)RTThreadNativeSelf());
#endif

        case DIF_VAR_TIMESTAMP:
                if (!(mstate->dtms_present & DTRACE_MSTATE_TIMESTAMP)) {
                        mstate->dtms_timestamp = dtrace_gethrtime();
                        mstate->dtms_present |= DTRACE_MSTATE_TIMESTAMP;
                }
                return (mstate->dtms_timestamp);

        case DIF_VAR_VTIMESTAMP:
#ifndef VBOX
                ASSERT(dtrace_vtime_references != 0);
                return (curthread->t_dtrace_vtime);
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif

        case DIF_VAR_WALLTIMESTAMP:
                if (!(mstate->dtms_present & DTRACE_MSTATE_WALLTIMESTAMP)) {
                        mstate->dtms_walltimestamp = dtrace_gethrestime();
                        mstate->dtms_present |= DTRACE_MSTATE_WALLTIMESTAMP;
                }
                return (mstate->dtms_walltimestamp);

        case DIF_VAR_IPL:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_IPL)) {
                        mstate->dtms_ipl = dtrace_getipl();
                        mstate->dtms_present |= DTRACE_MSTATE_IPL;
                }
                return (mstate->dtms_ipl);

        case DIF_VAR_EPID:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_EPID);
                return (mstate->dtms_epid);

        case DIF_VAR_ID:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (mstate->dtms_probe->dtpr_id);

        case DIF_VAR_STACKDEPTH:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_STACKDEPTH)) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                        mstate->dtms_stackdepth = dtrace_getstackdepth(aframes);
                        mstate->dtms_present |= DTRACE_MSTATE_STACKDEPTH;
                }
                return (mstate->dtms_stackdepth);

        case DIF_VAR_USTACKDEPTH:
                if (!dtrace_priv_proc(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_USTACKDEPTH)) {
                        /*
                         * See comment in DIF_VAR_PID.
                         */
                        if (DTRACE_ANCHORED(mstate->dtms_probe) &&
                            CPU_ON_INTR(CPU)) {
                                mstate->dtms_ustackdepth = 0;
                        } else {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                mstate->dtms_ustackdepth =
                                    dtrace_getustackdepth();
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                        }
                        mstate->dtms_present |= DTRACE_MSTATE_USTACKDEPTH;
                }
                return (mstate->dtms_ustackdepth);

        case DIF_VAR_CALLER:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_CALLER)) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                        if (!DTRACE_ANCHORED(mstate->dtms_probe)) {
                                /*
                                 * If this is an unanchored probe, we are
                                 * required to go through the slow path:
                                 * dtrace_caller() only guarantees correct
                                 * results for anchored probes.
                                 */
                                pc_t caller[2];

                                dtrace_getpcstack(caller, 2, aframes,
                                    (uint32_t *)(uintptr_t)mstate->dtms_arg[0]);
                                mstate->dtms_caller = caller[1];
                        } else if ((mstate->dtms_caller =
                            dtrace_caller(aframes)) == VBDTCAST(uintptr_t)-1) {
                                /*
                                 * We have failed to do this the quick way;
                                 * we must resort to the slower approach of
                                 * calling dtrace_getpcstack().
                                 */
                                pc_t caller;

                                dtrace_getpcstack(&caller, 1, aframes, NULL);
                                mstate->dtms_caller = caller;
                        }

                        mstate->dtms_present |= DTRACE_MSTATE_CALLER;
                }
                return (mstate->dtms_caller);

        case DIF_VAR_UCALLER:
                if (!dtrace_priv_proc(state))
                        return (0);

                if (!(mstate->dtms_present & DTRACE_MSTATE_UCALLER)) {
                        uint64_t ustack[3];

                        /*
                         * dtrace_getupcstack() fills in the first uint64_t
                         * with the current PID.  The second uint64_t will
                         * be the program counter at user-level.  The third
                         * uint64_t will contain the caller, which is what
                         * we're after.
                         */
                        ustack[2] = NULL;
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_getupcstack(ustack, 3);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                        mstate->dtms_ucaller = ustack[2];
                        mstate->dtms_present |= DTRACE_MSTATE_UCALLER;
                }

                return (mstate->dtms_ucaller);

        case DIF_VAR_PROBEPROV:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_provider->dtpv_name,
                    state, mstate));

        case DIF_VAR_PROBEMOD:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_mod,
                    state, mstate));

        case DIF_VAR_PROBEFUNC:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_func,
                    state, mstate));

        case DIF_VAR_PROBENAME:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_name,
                    state, mstate));

        case DIF_VAR_PID:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * Note that we are assuming that an unanchored probe is
                 * always due to a high-level interrupt.  (And we're assuming
                 * that there is only a single high level interrupt.)
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (pid0.pid_id);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * Further, it is always safe to dereference the p_pidp member
                 * of one's own proc structure.  (These are truisms becuase
                 * threads and processes don't clean up their own state --
                 * they leave that task to whomever reaps them.)
                 */
                return ((uint64_t)curthread->t_procp->p_pidp->pid_id);
#else
                return (RTProcSelf());
#endif

        case DIF_VAR_PPID:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (pid0.pid_id);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * (This is true because threads don't clean up their own
                 * state -- they leave that task to whomever reaps them.)
                 */
                return ((uint64_t)curthread->t_procp->p_ppid);
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0); /** @todo parent pid? */
#endif

        case DIF_VAR_TID:
#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                return ((uint64_t)curthread->t_tid);
#else
                return (RTThreadNativeSelf()); /** @todo proper tid? */
#endif

        case DIF_VAR_EXECNAME:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return ((uint64_t)(uintptr_t)p0.p_user.u_comm);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * (This is true because threads don't clean up their own
                 * state -- they leave that task to whomever reaps them.)
                 */
                return (dtrace_dif_varstr(
                    (uintptr_t)curthread->t_procp->p_user.u_comm,
                    state, mstate));
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0); /** @todo execname */
#endif

        case DIF_VAR_ZONENAME:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return ((uint64_t)(uintptr_t)p0.p_zone->zone_name);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * (This is true because threads don't clean up their own
                 * state -- they leave that task to whomever reaps them.)
                 */
                return (dtrace_dif_varstr(
                    (uintptr_t)curthread->t_procp->p_zone->zone_name,
                    state, mstate));
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif

        case DIF_VAR_UID:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return ((uint64_t)p0.p_cred->cr_uid);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * (This is true because threads don't clean up their own
                 * state -- they leave that task to whomever reaps them.)
                 *
                 * Additionally, it is safe to dereference one's own process
                 * credential, since this is never NULL after process birth.
                 */
                return ((uint64_t)curthread->t_procp->p_cred->cr_uid);
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif

        case DIF_VAR_GID:
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return ((uint64_t)p0.p_cred->cr_gid);

                /*
                 * It is always safe to dereference one's own t_procp pointer:
                 * it always points to a valid, allocated proc structure.
                 * (This is true because threads don't clean up their own
                 * state -- they leave that task to whomever reaps them.)
                 *
                 * Additionally, it is safe to dereference one's own process
                 * credential, since this is never NULL after process birth.
                 */
                return ((uint64_t)curthread->t_procp->p_cred->cr_gid);
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif

        case DIF_VAR_ERRNO: {
#ifndef VBOX
                klwp_t *lwp;
#endif
                if (!dtrace_priv_proc(state))
                        return (0);

#ifndef VBOX
                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                /*
                 * It is always safe to dereference one's own t_lwp pointer in
                 * the event that this pointer is non-NULL.  (This is true
                 * because threads and lwps don't clean up their own state --
                 * they leave that task to whomever reaps them.)
                 */
                if ((lwp = curthread->t_lwp) == NULL)
                        return (0);

                return ((uint64_t)lwp->lwp_errno);
#else
                cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (0);
#endif
        }
        default:
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                return (0);
        }
}

/*
 * Emulate the execution of DTrace ID subroutines invoked by the call opcode.
 * Notice that we don't bother validating the proper number of arguments or
 * their types in the tuple stack.  This isn't needed because all argument
 * interpretation is safe because of our load safety -- the worst that can
 * happen is that a bogus program can obtain bogus results.
 */
static void
dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
    dtrace_key_t *tupregs, int nargs,
    dtrace_mstate_t *mstate, dtrace_state_t *state)
{
        volatile uint16_t *flags = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;
        volatile uintptr_t *illval = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval;
        dtrace_vstate_t *vstate = &state->dts_vstate;

#ifndef VBOX
        union {
                mutex_impl_t mi;
                uint64_t mx;
        } m;

        union {
                krwlock_t ri;
                uintptr_t rw;
        } r;
#endif

        switch (subr) {
        case DIF_SUBR_RAND:
                regs[rd] = (dtrace_gethrtime() * 2416 + 374441) % 1771875;
                break;

        case DIF_SUBR_MUTEX_OWNED:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                if (MUTEX_TYPE_ADAPTIVE(&m.mi))
                        regs[rd] = MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER;
                else
                        regs[rd] = LOCK_HELD(&m.mi.m_spin.m_spinlock);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_MUTEX_OWNER:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                if (MUTEX_TYPE_ADAPTIVE(&m.mi) &&
                    MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER)
                        regs[rd] = (uintptr_t)MUTEX_OWNER(&m.mi);
                else
                        regs[rd] = 0;
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_MUTEX_TYPE_ADAPTIVE:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                regs[rd] = MUTEX_TYPE_ADAPTIVE(&m.mi);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_MUTEX_TYPE_SPIN:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                regs[rd] = MUTEX_TYPE_SPIN(&m.mi);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_RW_READ_HELD: {
#ifndef VBOX
                uintptr_t tmp;

                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_READ_HELD(&r.ri, tmp);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;
        }

        case DIF_SUBR_RW_WRITE_HELD:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_WRITE_HELD(&r.ri);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_RW_ISWRITER:
#ifndef VBOX
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                    mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_ISWRITER(&r.ri);
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_BCOPY: {
                /*
                 * We need to be sure that the destination is in the scratch
                 * region -- no other region is allowed.
                 */
                uintptr_t src = tupregs[0].dttk_value;
                uintptr_t dest = tupregs[1].dttk_value;
                size_t size = tupregs[2].dttk_value;

                if (!dtrace_inscratch(dest, size, mstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                }

                if (!dtrace_canload(src, size, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                dtrace_bcopy((void *)src, (void *)dest, size);
                break;
        }

        case DIF_SUBR_ALLOCA:
        case DIF_SUBR_COPYIN: {
                uintptr_t dest = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
                uint64_t size =
                    tupregs[subr == DIF_SUBR_ALLOCA ? 0 : 1].dttk_value;
                size_t scratch_size = (dest - mstate->dtms_scratch_ptr) + size;

                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */

                /*
                 * Rounding up the user allocation size could have overflowed
                 * a large, bogus allocation (like -1ULL) to 0.
                 */
                if (scratch_size < size ||
                    !DTRACE_INSCRATCH(mstate, scratch_size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                if (subr == DIF_SUBR_COPYIN) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }

                mstate->dtms_scratch_ptr += scratch_size;
                regs[rd] = dest;
                break;
        }

        case DIF_SUBR_COPYINTO: {
                uint64_t size = tupregs[1].dttk_value;
                uintptr_t dest = tupregs[2].dttk_value;

                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */
                if (!dtrace_inscratch(dest, size, mstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                break;
        }

        case DIF_SUBR_COPYINSTR: {
                uintptr_t dest = mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];

                if (nargs > 1 && tupregs[1].dttk_value < size)
                        size = tupregs[1].dttk_value + 1;

                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */
                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                dtrace_copyinstr(tupregs[0].dttk_value, dest, size, flags);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                ((char *)dest)[size - 1] = '\0';
                mstate->dtms_scratch_ptr += size;
                regs[rd] = dest;
                break;
        }

        case DIF_SUBR_MSGSIZE:
        case DIF_SUBR_MSGDSIZE: {
#ifndef VBOX
                uintptr_t baddr = tupregs[0].dttk_value, daddr;
                uintptr_t wptr, rptr;
                size_t count = 0;
                int cont = 0;

                while (baddr != NULL && !(*flags & CPU_DTRACE_FAULT)) {

                        if (!dtrace_canload(baddr, sizeof (mblk_t), mstate,
                            vstate)) {
                                regs[rd] = NULL;
                                break;
                        }

                        wptr = dtrace_loadptr(baddr +
                            offsetof(mblk_t, b_wptr));

                        rptr = dtrace_loadptr(baddr +
                            offsetof(mblk_t, b_rptr));

                        if (wptr < rptr) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = tupregs[0].dttk_value;
                                break;
                        }

                        daddr = dtrace_loadptr(baddr +
                            offsetof(mblk_t, b_datap));

                        baddr = dtrace_loadptr(baddr +
                            offsetof(mblk_t, b_cont));

                        /*
                         * We want to prevent against denial-of-service here,
                         * so we're only going to search the list for
                         * dtrace_msgdsize_max mblks.
                         */
                        if (cont++ > dtrace_msgdsize_max) {
                                *flags |= CPU_DTRACE_ILLOP;
                                break;
                        }

                        if (subr == DIF_SUBR_MSGDSIZE) {
                                if (dtrace_load8(daddr +
                                    offsetof(dblk_t, db_type)) != M_DATA)
                                        continue;
                        }

                        count += wptr - rptr;
                }

                if (!(*flags & CPU_DTRACE_FAULT))
                        regs[rd] = count;

#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;
        }

        case DIF_SUBR_PROGENYOF: {
#ifndef VBOX
                pid_t pid = tupregs[0].dttk_value;
                proc_t *p;
                int rval = 0;

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

                for (p = curthread->t_procp; p != NULL; p = p->p_parent) {
                        if (p->p_pidp->pid_id == pid) {
                                rval = 1;
                                break;
                        }
                }

                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                regs[rd] = rval;
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;
        }

        case DIF_SUBR_SPECULATION:
                regs[rd] = dtrace_speculation(state);
                break;

        case DIF_SUBR_COPYOUT: {
                uintptr_t kaddr = tupregs[0].dttk_value;
                uintptr_t uaddr = tupregs[1].dttk_value;
                uint64_t size = tupregs[2].dttk_value;

                if (!dtrace_destructive_disallow &&
                    dtrace_priv_proc_control(state) &&
                    !dtrace_istoxic(kaddr, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_copyout(kaddr, uaddr, size, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }
                break;
        }

        case DIF_SUBR_COPYOUTSTR: {
                uintptr_t kaddr = tupregs[0].dttk_value;
                uintptr_t uaddr = tupregs[1].dttk_value;
                uint64_t size = tupregs[2].dttk_value;

                if (!dtrace_destructive_disallow &&
                    dtrace_priv_proc_control(state) &&
                    !dtrace_istoxic(kaddr, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_copyoutstr(kaddr, uaddr, size, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }
                break;
        }

        case DIF_SUBR_STRLEN: {
                size_t sz;
                uintptr_t addr = (uintptr_t)tupregs[0].dttk_value;
                sz = dtrace_strlen((char *)addr,
                    state->dts_options[DTRACEOPT_STRSIZE]);

                if (!dtrace_canload(addr, sz + 1, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                regs[rd] = sz;

                break;
        }

        case DIF_SUBR_STRCHR:
        case DIF_SUBR_STRRCHR: {
                /*
                 * We're going to iterate over the string looking for the
                 * specified character.  We will iterate until we have reached
                 * the string length or we have found the character.  If this
                 * is DIF_SUBR_STRRCHR, we will look for the last occurrence
                 * of the specified character instead of the first.
                 */
                uintptr_t saddr = tupregs[0].dttk_value;
                uintptr_t addr = tupregs[0].dttk_value;
                uintptr_t limit = addr + state->dts_options[DTRACEOPT_STRSIZE];
                char c, target = (char)tupregs[1].dttk_value;

                for (regs[rd] = NULL; addr < limit; addr++) {
                        if ((c = dtrace_load8(addr)) == target) {
                                regs[rd] = addr;

                                if (subr == DIF_SUBR_STRCHR)
                                        break;
                        }

                        if (c == '\0')
                                break;
                }

                if (!dtrace_canload(saddr, addr - saddr, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                break;
        }

        case DIF_SUBR_STRSTR:
        case DIF_SUBR_INDEX:
        case DIF_SUBR_RINDEX: {
                /*
                 * We're going to iterate over the string looking for the
                 * specified string.  We will iterate until we have reached
                 * the string length or we have found the string.  (Yes, this
                 * is done in the most naive way possible -- but considering
                 * that the string we're searching for is likely to be
                 * relatively short, the complexity of Rabin-Karp or similar
                 * hardly seems merited.)
                 */
                char *addr = (char *)(uintptr_t)tupregs[0].dttk_value;
                char *substr = (char *)(uintptr_t)tupregs[1].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                size_t len = dtrace_strlen(addr, size);
                size_t sublen = dtrace_strlen(substr, size);
                char *limit = addr + len, *orig = addr;
                int notfound = subr == DIF_SUBR_STRSTR ? 0 : -1;
                int inc = 1;

                regs[rd] = notfound;

                if (!dtrace_canload((uintptr_t)addr, len + 1, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!dtrace_canload((uintptr_t)substr, sublen + 1, mstate,
                    vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                /*
                 * strstr() and index()/rindex() have similar semantics if
                 * both strings are the empty string: strstr() returns a
                 * pointer to the (empty) string, and index() and rindex()
                 * both return index 0 (regardless of any position argument).
                 */
                if (sublen == 0 && len == 0) {
                        if (subr == DIF_SUBR_STRSTR)
                                regs[rd] = (uintptr_t)addr;
                        else
                                regs[rd] = 0;
                        break;
                }

                if (subr != DIF_SUBR_STRSTR) {
                        if (subr == DIF_SUBR_RINDEX) {
                                limit = orig - 1;
                                addr += len;
                                inc = -1;
                        }

                        /*
                         * Both index() and rindex() take an optional position
                         * argument that denotes the starting position.
                         */
                        if (nargs == 3) {
                                int64_t pos = (int64_t)tupregs[2].dttk_value;

                                /*
                                 * If the position argument to index() is
                                 * negative, Perl implicitly clamps it at
                                 * zero.  This semantic is a little surprising
                                 * given the special meaning of negative
                                 * positions to similar Perl functions like
                                 * substr(), but it appears to reflect a
                                 * notion that index() can start from a
                                 * negative index and increment its way up to
                                 * the string.  Given this notion, Perl's
                                 * rindex() is at least self-consistent in
                                 * that it implicitly clamps positions greater
                                 * than the string length to be the string
                                 * length.  Where Perl completely loses
                                 * coherence, however, is when the specified
                                 * substring is the empty string ("").  In
                                 * this case, even if the position is
                                 * negative, rindex() returns 0 -- and even if
                                 * the position is greater than the length,
                                 * index() returns the string length.  These
                                 * semantics violate the notion that index()
                                 * should never return a value less than the
                                 * specified position and that rindex() should
                                 * never return a value greater than the
                                 * specified position.  (One assumes that
                                 * these semantics are artifacts of Perl's
                                 * implementation and not the results of
                                 * deliberate design -- it beggars belief that
                                 * even Larry Wall could desire such oddness.)
                                 * While in the abstract one would wish for
                                 * consistent position semantics across
                                 * substr(), index() and rindex() -- or at the
                                 * very least self-consistent position
                                 * semantics for index() and rindex() -- we
                                 * instead opt to keep with the extant Perl
                                 * semantics, in all their broken glory.  (Do
                                 * we have more desire to maintain Perl's
                                 * semantics than Perl does?  Probably.)
                                 */
                                if (subr == DIF_SUBR_RINDEX) {
                                        if (pos < 0) {
                                                if (sublen == 0)
                                                        regs[rd] = 0;
                                                break;
                                        }

                                        if (VBDTCAST(uint64_t)pos > len)
                                                pos = len;
                                } else {
                                        if (pos < 0)
                                                pos = 0;

                                        if (VBDTCAST(uint64_t)pos >= len) {
                                                if (sublen == 0)
                                                        regs[rd] = len;
                                                break;
                                        }
                                }

                                addr = orig + pos;
                        }
                }

                for (regs[rd] = notfound; addr != limit; addr += inc) {
                        if (dtrace_strncmp(addr, substr, sublen) == 0) {
                                if (subr != DIF_SUBR_STRSTR) {
                                        /*
                                         * As D index() and rindex() are
                                         * modeled on Perl (and not on awk),
                                         * we return a zero-based (and not a
                                         * one-based) index.  (For you Perl
                                         * weenies: no, we're not going to add
                                         * $[ -- and shouldn't you be at a con
                                         * or something?)
                                         */
                                        regs[rd] = (uintptr_t)(addr - orig);
                                        break;
                                }

                                ASSERT(subr == DIF_SUBR_STRSTR);
                                regs[rd] = (uintptr_t)addr;
                                break;
                        }
                }

                break;
        }

        case DIF_SUBR_STRTOK: {
                uintptr_t addr = tupregs[0].dttk_value;
                uintptr_t tokaddr = tupregs[1].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t limit, toklimit = tokaddr + size;
                uint8_t c VBDTUNASS(0), tokmap[32];      /* 256 / 8 */
                char *dest = (char *)mstate->dtms_scratch_ptr;
                VBDTTYPE(unsigned,int) i;

                /*
                 * Check both the token buffer and (later) the input buffer,
                 * since both could be non-scratch addresses.
                 */
                if (!dtrace_strcanload(tokaddr, size, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                if (addr == NULL) {
                        /*
                         * If the address specified is NULL, we use our saved
                         * strtok pointer from the mstate.  Note that this
                         * means that the saved strtok pointer is _only_
                         * valid within multiple enablings of the same probe --
                         * it behaves like an implicit clause-local variable.
                         */
                        addr = mstate->dtms_strtok;
                } else {
                        /*
                         * If the user-specified address is non-NULL we must
                         * access check it.  This is the only time we have
                         * a chance to do so, since this address may reside
                         * in the string table of this clause-- future calls
                         * (when we fetch addr from mstate->dtms_strtok)
                         * would fail this access check.
                         */
                        if (!dtrace_strcanload(addr, size, mstate, vstate)) {
                                regs[rd] = NULL;
                                break;
                        }
                }

                /*
                 * First, zero the token map, and then process the token
                 * string -- setting a bit in the map for every character
                 * found in the token string.
                 */
                for (i = 0; i < sizeof (tokmap); i++)
                        tokmap[i] = 0;

                for (; tokaddr < toklimit; tokaddr++) {
                        if ((c = dtrace_load8(tokaddr)) == '\0')
                                break;

                        ASSERT((c >> 3) < sizeof (tokmap));
                        tokmap[c >> 3] |= (1 << (c & 0x7));
                }

                for (limit = addr + size; addr < limit; addr++) {
                        /*
                         * We're looking for a character that is _not_ contained
                         * in the token string.
                         */
                        if ((c = dtrace_load8(addr)) == '\0')
                                break;

                        if (!(tokmap[c >> 3] & (1 << (c & 0x7))))
                                break;
                }

                if (c == '\0') {
                        /*
                         * We reached the end of the string without finding
                         * any character that was not in the token string.
                         * We return NULL in this case, and we set the saved
                         * address to NULL as well.
                         */
                        regs[rd] = NULL;
                        mstate->dtms_strtok = NULL;
                        break;
                }

                /*
                 * From here on, we're copying into the destination string.
                 */
                for (i = 0; addr < limit && i < size - 1; addr++) {
                        if ((c = dtrace_load8(addr)) == '\0')
                                break;

                        if (tokmap[c >> 3] & (1 << (c & 0x7)))
                                break;

                        ASSERT(i < size);
                        dest[i++] = c;
                }

                ASSERT(i < size);
                dest[i] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                mstate->dtms_strtok = addr;
                break;
        }

        case DIF_SUBR_SUBSTR: {
                uintptr_t s = tupregs[0].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                char *d = (char *)mstate->dtms_scratch_ptr;
                int64_t index = (int64_t)tupregs[1].dttk_value;
                int64_t remaining = (int64_t)tupregs[2].dttk_value;
                size_t len = dtrace_strlen((char *)s, size);
                int64_t i;

                if (!dtrace_canload(s, len + 1, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                if (nargs <= 2)
                        remaining = (int64_t)size;

                if (index < 0) {
                        index += len;

                        if (index < 0 && index + remaining > 0) {
                                remaining += index;
                                index = 0;
                        }
                }

                if (VBDTCAST(uint64_t)index >= len || index < 0) {
                        remaining = 0;
                } else if (remaining < 0) {
                        remaining += len - index;
                } else if (VBDTCAST(uint64_t)index + remaining > size) {
                        remaining = size - index;
                }

                for (i = 0; i < remaining; i++) {
                        if ((d[i] = dtrace_load8(s + index + i)) == '\0')
                                break;
                }

                d[i] = '\0';

                mstate->dtms_scratch_ptr += size;
                regs[rd] = (uintptr_t)d;
                break;
        }

        case DIF_SUBR_GETMAJOR:
#ifndef VBOX
#ifdef _LP64
                regs[rd] = (tupregs[0].dttk_value >> NBITSMINOR64) & MAXMAJ64;
#else
                regs[rd] = (tupregs[0].dttk_value >> NBITSMINOR) & MAXMAJ;
#endif
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_GETMINOR:
#ifndef VBOX
#ifdef _LP64
                regs[rd] = tupregs[0].dttk_value & MAXMIN64;
#else
                regs[rd] = tupregs[0].dttk_value & MAXMIN;
#endif
#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;

        case DIF_SUBR_DDI_PATHNAME: {
#ifndef VBOX
                /*
                 * This one is a galactic mess.  We are going to roughly
                 * emulate ddi_pathname(), but it's made more complicated
                 * by the fact that we (a) want to include the minor name and
                 * (b) must proceed iteratively instead of recursively.
                 */
                uintptr_t dest = mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                char *start = (char *)dest, *end = start + size - 1;
                uintptr_t daddr = tupregs[0].dttk_value;
                int64_t minor = (int64_t)tupregs[1].dttk_value;
                char *s;
                int i, len, depth = 0;

                /*
                 * Due to all the pointer jumping we do and context we must
                 * rely upon, we just mandate that the user must have kernel
                 * read privileges to use this routine.
                 */
                if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) == 0) {
                        *flags |= CPU_DTRACE_KPRIV;
                        *illval = daddr;
                        regs[rd] = NULL;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                *end = '\0';

                /*
                 * We want to have a name for the minor.  In order to do this,
                 * we need to walk the minor list from the devinfo.  We want
                 * to be sure that we don't infinitely walk a circular list,
                 * so we check for circularity by sending a scout pointer
                 * ahead two elements for every element that we iterate over;
                 * if the list is circular, these will ultimately point to the
                 * same element.  You may recognize this little trick as the
                 * answer to a stupid interview question -- one that always
                 * seems to be asked by those who had to have it laboriously
                 * explained to them, and who can't even concisely describe
                 * the conditions under which one would be forced to resort to
                 * this technique.  Needless to say, those conditions are
                 * found here -- and probably only here.  Is this the only use
                 * of this infamous trick in shipping, production code?  If it
                 * isn't, it probably should be...
                 */
                if (minor != -1) {
                        uintptr_t maddr = dtrace_loadptr(daddr +
                            offsetof(struct dev_info, devi_minor));

                        uintptr_t next = offsetof(struct ddi_minor_data, next);
                        uintptr_t name = offsetof(struct ddi_minor_data,
                            d_minor) + offsetof(struct ddi_minor, name);
                        uintptr_t dev = offsetof(struct ddi_minor_data,
                            d_minor) + offsetof(struct ddi_minor, dev);
                        uintptr_t scout;

                        if (maddr != NULL)
                                scout = dtrace_loadptr(maddr + next);

                        while (maddr != NULL && !(*flags & CPU_DTRACE_FAULT)) {
                                uint64_t m;
#ifdef _LP64
                                m = dtrace_load64(maddr + dev) & MAXMIN64;
#else
                                m = dtrace_load32(maddr + dev) & MAXMIN;
#endif
                                if (m != minor) {
                                        maddr = dtrace_loadptr(maddr + next);

                                        if (scout == NULL)
                                                continue;

                                        scout = dtrace_loadptr(scout + next);

                                        if (scout == NULL)
                                                continue;

                                        scout = dtrace_loadptr(scout + next);

                                        if (scout == NULL)
                                                continue;

                                        if (scout == maddr) {
                                                *flags |= CPU_DTRACE_ILLOP;
                                                break;
                                        }

                                        continue;
                                }

                                /*
                                 * We have the minor data.  Now we need to
                                 * copy the minor's name into the end of the
                                 * pathname.
                                 */
                                s = (char *)dtrace_loadptr(maddr + name);
                                len = dtrace_strlen(s, size);

                                if (*flags & CPU_DTRACE_FAULT)
                                        break;

                                if (len != 0) {
                                        if ((end -= (len + 1)) < start)
                                                break;

                                        *end = ':';
                                }

                                for (i = 1; i <= len; i++)
                                        end[i] = dtrace_load8((uintptr_t)s++);
                                break;
                        }
                }

                while (daddr != NULL && !(*flags & CPU_DTRACE_FAULT)) {
                        ddi_node_state_t devi_state;

                        devi_state = dtrace_load32(daddr +
                            offsetof(struct dev_info, devi_node_state));

                        if (*flags & CPU_DTRACE_FAULT)
                                break;

                        if (devi_state >= DS_INITIALIZED) {
                                s = (char *)dtrace_loadptr(daddr +
                                    offsetof(struct dev_info, devi_addr));
                                len = dtrace_strlen(s, size);

                                if (*flags & CPU_DTRACE_FAULT)
                                        break;

                                if (len != 0) {
                                        if ((end -= (len + 1)) < start)
                                                break;

                                        *end = '@';
                                }

                                for (i = 1; i <= len; i++)
                                        end[i] = dtrace_load8((uintptr_t)s++);
                        }

                        /*
                         * Now for the node name...
                         */
                        s = (char *)dtrace_loadptr(daddr +
                            offsetof(struct dev_info, devi_node_name));

                        daddr = dtrace_loadptr(daddr +
                            offsetof(struct dev_info, devi_parent));

                        /*
                         * If our parent is NULL (that is, if we're the root
                         * node), we're going to use the special path
                         * "devices".
                         */
                        if (daddr == NULL)
                                s = "devices";

                        len = dtrace_strlen(s, size);
                        if (*flags & CPU_DTRACE_FAULT)
                                break;

                        if ((end -= (len + 1)) < start)
                                break;

                        for (i = 1; i <= len; i++)
                                end[i] = dtrace_load8((uintptr_t)s++);
                        *end = '/';

                        if (depth++ > dtrace_devdepth_max) {
                                *flags |= CPU_DTRACE_ILLOP;
                                break;
                        }
                }

                if (end < start)
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);

                if (daddr == NULL) {
                        regs[rd] = (uintptr_t)end;
                        mstate->dtms_scratch_ptr += size;
                }

#else
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                break;
        }

        case DIF_SUBR_STRJOIN: {
                char *d = (char *)mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t s1 = tupregs[0].dttk_value;
                uintptr_t s2 = tupregs[1].dttk_value;
                VBDTTYPE(unsigned,int) i = 0;

                if (!dtrace_strcanload(s1, size, mstate, vstate) ||
                    !dtrace_strcanload(s2, size, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                for (;;) {
                        if (i >= size) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = NULL;
                                break;
                        }

                        if ((d[i++] = dtrace_load8(s1++)) == '\0') {
                                i--;
                                break;
                        }
                }

                for (;;) {
                        if (i >= size) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = NULL;
                                break;
                        }

                        if ((d[i++] = dtrace_load8(s2++)) == '\0')
                                break;
                }

                if (i < size) {
                        mstate->dtms_scratch_ptr += i;
                        regs[rd] = (uintptr_t)d;
                }

                break;
        }

        case DIF_SUBR_LLTOSTR: {
                int64_t i = (int64_t)tupregs[0].dttk_value;
                int64_t val = i < 0 ? i * -1 : i;
                uint64_t size = 22;     /* enough room for 2^64 in decimal */
                char *end = (char *)mstate->dtms_scratch_ptr + size - 1;

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                for (*end-- = '\0'; val; val /= 10)
                        *end-- = '0' + (val % 10);

                if (i == 0)
                        *end-- = '0';

                if (i < 0)
                        *end-- = '-';

                regs[rd] = (uintptr_t)end + 1;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_HTONS:
        case DIF_SUBR_NTOHS:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint16_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_16((uint16_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_HTONL:
        case DIF_SUBR_NTOHL:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint32_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_32((uint32_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_HTONLL:
        case DIF_SUBR_NTOHLL:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint64_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_64((uint64_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_DIRNAME:
        case DIF_SUBR_BASENAME: {
                char *dest = (char *)mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t src = tupregs[0].dttk_value;
                int i, j, len = VBDTCAST(int)dtrace_strlen((char *)src, size);
                int lastbase = -1, firstbase = -1, lastdir = -1;
                int start, end;

                if (!dtrace_canload(src, len + 1, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                /*
                 * The basename and dirname for a zero-length string is
                 * defined to be "."
                 */
                if (len == 0) {
                        len = 1;
                        src = (uintptr_t)".";
                }

                /*
                 * Start from the back of the string, moving back toward the
                 * front until we see a character that isn't a slash.  That
                 * character is the last character in the basename.
                 */
                for (i = len - 1; i >= 0; i--) {
                        if (dtrace_load8(src + i) != '/')
                                break;
                }

                if (i >= 0)
                        lastbase = i;

                /*
                 * Starting from the last character in the basename, move
                 * towards the front until we find a slash.  The character
                 * that we processed immediately before that is the first
                 * character in the basename.
                 */
                for (; i >= 0; i--) {
                        if (dtrace_load8(src + i) == '/')
                                break;
                }

                if (i >= 0)
                        firstbase = i + 1;

                /*
                 * Now keep going until we find a non-slash character.  That
                 * character is the last character in the dirname.
                 */
                for (; i >= 0; i--) {
                        if (dtrace_load8(src + i) != '/')
                                break;
                }

                if (i >= 0)
                        lastdir = i;

                ASSERT(!(lastbase == -1 && firstbase != -1));
                ASSERT(!(firstbase == -1 && lastdir != -1));

                if (lastbase == -1) {
                        /*
                         * We didn't find a non-slash character.  We know that
                         * the length is non-zero, so the whole string must be
                         * slashes.  In either the dirname or the basename
                         * case, we return '/'.
                         */
                        ASSERT(firstbase == -1);
                        firstbase = lastbase = lastdir = 0;
                }

                if (firstbase == -1) {
                        /*
                         * The entire string consists only of a basename
                         * component.  If we're looking for dirname, we need
                         * to change our string to be just "."; if we're
                         * looking for a basename, we'll just set the first
                         * character of the basename to be 0.
                         */
                        if (subr == DIF_SUBR_DIRNAME) {
                                ASSERT(lastdir == -1);
                                src = (uintptr_t)".";
                                lastdir = 0;
                        } else {
                                firstbase = 0;
                        }
                }

                if (subr == DIF_SUBR_DIRNAME) {
                        if (lastdir == -1) {
                                /*
                                 * We know that we have a slash in the name --
                                 * or lastdir would be set to 0, above.  And
                                 * because lastdir is -1, we know that this
                                 * slash must be the first character.  (That
                                 * is, the full string must be of the form
                                 * "/basename".)  In this case, the last
                                 * character of the directory name is 0.
                                 */
                                lastdir = 0;
                        }

                        start = 0;
                        end = lastdir;
                } else {
                        ASSERT(subr == DIF_SUBR_BASENAME);
                        ASSERT(firstbase != -1 && lastbase != -1);
                        start = firstbase;
                        end = lastbase;
                }

                for (i = start, j = 0; i <= end && VBDTCAST(unsigned)j < size - 1; i++, j++)
                        dest[j] = dtrace_load8(src + i);

                dest[j] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_CLEANPATH: {
                char *dest = (char *)mstate->dtms_scratch_ptr, c;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t src = tupregs[0].dttk_value;
                int i = 0, j = 0;

                if (!dtrace_strcanload(src, size, mstate, vstate)) {
                        regs[rd] = NULL;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = NULL;
                        break;
                }

                /*
                 * Move forward, loading each character.
                 */
                do {
                        c = dtrace_load8(src + i++);
next:
                        if (j + 5 >= VBDTCAST(int64_t)size)     /* 5 = strlen("/..c\0") */
                                break;

                        if (c != '/') {
                                dest[j++] = c;
                                continue;
                        }

                        c = dtrace_load8(src + i++);

                        if (c == '/') {
                                /*
                                 * We have two slashes -- we can just advance
                                 * to the next character.
                                 */
                                goto next;
                        }

                        if (c != '.') {
                                /*
                                 * This is not "." and it's not ".." -- we can
                                 * just store the "/" and this character and
                                 * drive on.
                                 */
                                dest[j++] = '/';
                                dest[j++] = c;
                                continue;
                        }

                        c = dtrace_load8(src + i++);

                        if (c == '/') {
                                /*
                                 * This is a "/./" component.  We're not going
                                 * to store anything in the destination buffer;
                                 * we're just going to go to the next component.
                                 */
                                goto next;
                        }

                        if (c != '.') {
                                /*
                                 * This is not ".." -- we can just store the
                                 * "/." and this character and continue
                                 * processing.
                                 */
                                dest[j++] = '/';
                                dest[j++] = '.';
                                dest[j++] = c;
                                continue;
                        }

                        c = dtrace_load8(src + i++);

                        if (c != '/' && c != '\0') {
                                /*
                                 * This is not ".." -- it's "..[mumble]".
                                 * We'll store the "/.." and this character
                                 * and continue processing.
                                 */
                                dest[j++] = '/';
                                dest[j++] = '.';
                                dest[j++] = '.';
                                dest[j++] = c;
                                continue;
                        }

                        /*
                         * This is "/../" or "/..\0".  We need to back up
                         * our destination pointer until we find a "/".
                         */
                        i--;
                        while (j != 0 && dest[--j] != '/')
                                continue;

                        if (c == '\0')
                                dest[++j] = '/';
                } while (c != '\0');

                dest[j] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_INET_NTOA:
        case DIF_SUBR_INET_NTOA6:
        case DIF_SUBR_INET_NTOP: {
#ifndef VBOX
                size_t size;
                int af, argi, i;
                char *base, *end;

                if (subr == DIF_SUBR_INET_NTOP) {
                        af = (int)tupregs[0].dttk_value;
                        argi = 1;
                } else {
                        af = subr == DIF_SUBR_INET_NTOA ? AF_INET: AF_INET6;
                        argi = 0;
                }

                if (af == AF_INET) {
                        ipaddr_t ip4;
                        uint8_t *ptr8, val;

                        /*
                         * Safely load the IPv4 address.
                         */
                        ip4 = dtrace_load32(tupregs[argi].dttk_value);

                        /*
                         * Check an IPv4 string will fit in scratch.
                         */
                        size = INET_ADDRSTRLEN;
                        if (!DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = NULL;
                                break;
                        }
                        base = (char *)mstate->dtms_scratch_ptr;
                        end = (char *)mstate->dtms_scratch_ptr + size - 1;

                        /*
                         * Stringify as a dotted decimal quad.
                         */
                        *end-- = '\0';
                        ptr8 = (uint8_t *)&ip4;
                        for (i = 3; i >= 0; i--) {
                                val = ptr8[i];

                                if (val == 0) {
                                        *end-- = '0';
                                } else {
                                        for (; val; val /= 10) {
                                                *end-- = '0' + (val % 10);
                                        }
                                }

                                if (i > 0)
                                        *end-- = '.';
                        }
                        ASSERT(end + 1 >= base);

                } else if (af == AF_INET6) {
                        struct in6_addr ip6;
                        int firstzero, tryzero, numzero, v6end;
                        uint16_t val;
                        const char digits[] = "0123456789abcdef";

                        /*
                         * Stringify using RFC 1884 convention 2 - 16 bit
                         * hexadecimal values with a zero-run compression.
                         * Lower case hexadecimal digits are used.
                         *      eg, fe80::214:4fff:fe0b:76c8.
                         * The IPv4 embedded form is returned for inet_ntop,
                         * just the IPv4 string is returned for inet_ntoa6.
                         */

                        /*
                         * Safely load the IPv6 address.
                         */
                        dtrace_bcopy(
                            (void *)(uintptr_t)tupregs[argi].dttk_value,
                            (void *)(uintptr_t)&ip6, sizeof (struct in6_addr));

                        /*
                         * Check an IPv6 string will fit in scratch.
                         */
                        size = INET6_ADDRSTRLEN;
                        if (!DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = NULL;
                                break;
                        }
                        base = (char *)mstate->dtms_scratch_ptr;
                        end = (char *)mstate->dtms_scratch_ptr + size - 1;
                        *end-- = '\0';

                        /*
                         * Find the longest run of 16 bit zero values
                         * for the single allowed zero compression - "::".
                         */
                        firstzero = -1;
                        tryzero = -1;
                        numzero = 1;
                        for (i = 0; i < sizeof (struct in6_addr); i++) {
                                if (ip6._S6_un._S6_u8[i] == 0 &&
                                    tryzero == -1 && i % 2 == 0) {
                                        tryzero = i;
                                        continue;
                                }

                                if (tryzero != -1 &&
                                    (ip6._S6_un._S6_u8[i] != 0 ||
                                    i == sizeof (struct in6_addr) - 1)) {

                                        if (i - tryzero <= numzero) {
                                                tryzero = -1;
                                                continue;
                                        }

                                        firstzero = tryzero;
                                        numzero = i - i % 2 - tryzero;
                                        tryzero = -1;

                                        if (ip6._S6_un._S6_u8[i] == 0 &&
                                            i == sizeof (struct in6_addr) - 1)
                                                numzero += 2;
                                }
                        }
                        ASSERT(firstzero + numzero <= sizeof (struct in6_addr));

                        /*
                         * Check for an IPv4 embedded address.
                         */
                        v6end = sizeof (struct in6_addr) - 2;
                        if (IN6_IS_ADDR_V4MAPPED(&ip6) ||
                            IN6_IS_ADDR_V4COMPAT(&ip6)) {
                                for (i = sizeof (struct in6_addr) - 1;
                                    i >= DTRACE_V4MAPPED_OFFSET; i--) {
                                        ASSERT(end >= base);

                                        val = ip6._S6_un._S6_u8[i];

                                        if (val == 0) {
                                                *end-- = '0';
                                        } else {
                                                for (; val; val /= 10) {
                                                        *end-- = '0' + val % 10;
                                                }
                                        }

                                        if (i > DTRACE_V4MAPPED_OFFSET)
                                                *end-- = '.';
                                }

                                if (subr == DIF_SUBR_INET_NTOA6)
                                        goto inetout;

                                /*
                                 * Set v6end to skip the IPv4 address that
                                 * we have already stringified.
                                 */
                                v6end = 10;
                        }

                        /*
                         * Build the IPv6 string by working through the
                         * address in reverse.
                         */
                        for (i = v6end; i >= 0; i -= 2) {
                                ASSERT(end >= base);

                                if (i == firstzero + numzero - 2) {
                                        *end-- = ':';
                                        *end-- = ':';
                                        i -= numzero - 2;
                                        continue;
                                }

                                if (i < 14 && i != firstzero - 2)
                                        *end-- = ':';

                                val = (ip6._S6_un._S6_u8[i] << 8) +
                                    ip6._S6_un._S6_u8[i + 1];

                                if (val == 0) {
                                        *end-- = '0';
                                } else {
                                        for (; val; val /= 16) {
                                                *end-- = digits[val % 16];
                                        }
                                }
                        }
                        ASSERT(end + 1 >= base);

                } else {
                        /*
                         * The user didn't use AH_INET or AH_INET6.
                         */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        regs[rd] = NULL;
                        break;
                }

inetout:        regs[rd] = (uintptr_t)end + 1;
                mstate->dtms_scratch_ptr += size;
#else  /* VBOX */
                regs[rd] = 0;
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif /* VBOX */
                break;
        }

        }
}

/*
 * Emulate the execution of DTrace IR instructions specified by the given
 * DIF object.  This function is deliberately void of assertions as all of
 * the necessary checks are handled by a call to dtrace_difo_validate().
 */
static uint64_t
dtrace_dif_emulate(dtrace_difo_t *difo, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate, dtrace_state_t *state)
{
        const dif_instr_t *text = difo->dtdo_buf;
        const uint_t textlen = difo->dtdo_len;
        const char *strtab = difo->dtdo_strtab;
        const uint64_t *inttab = difo->dtdo_inttab;

        uint64_t rval = 0;
        dtrace_statvar_t *svar;
        dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
        dtrace_difv_t *v;
        volatile uint16_t *flags = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;
        volatile uintptr_t *illval = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval;

        dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
        uint64_t regs[DIF_DIR_NREGS];
        uint64_t *tmp;

        uint8_t cc_n = 0, cc_z = 0, cc_v = 0, cc_c = 0;
        int64_t cc_r;
        uint_t pc = 0, id, opc VBDTUNASS(0);
        uint8_t ttop = 0;
        dif_instr_t instr;
        uint_t r1, r2, rd;

        /*
         * We stash the current DIF object into the machine state: we need it
         * for subsequent access checking.
         */
        mstate->dtms_difo = difo;

        regs[DIF_REG_R0] = 0;           /* %r0 is fixed at zero */

        while (pc < textlen && !(*flags & CPU_DTRACE_FAULT)) {
                opc = pc;

                instr = text[pc++];
                r1 = DIF_INSTR_R1(instr);
                r2 = DIF_INSTR_R2(instr);
                rd = DIF_INSTR_RD(instr);

                switch (DIF_INSTR_OP(instr)) {
                case DIF_OP_OR:
                        regs[rd] = regs[r1] | regs[r2];
                        break;
                case DIF_OP_XOR:
                        regs[rd] = regs[r1] ^ regs[r2];
                        break;
                case DIF_OP_AND:
                        regs[rd] = regs[r1] & regs[r2];
                        break;
                case DIF_OP_SLL:
                        regs[rd] = regs[r1] << regs[r2];
                        break;
                case DIF_OP_SRL:
                        regs[rd] = regs[r1] >> regs[r2];
                        break;
                case DIF_OP_SUB:
                        regs[rd] = regs[r1] - regs[r2];
                        break;
                case DIF_OP_ADD:
                        regs[rd] = regs[r1] + regs[r2];
                        break;
                case DIF_OP_MUL:
                        regs[rd] = regs[r1] * regs[r2];
                        break;
                case DIF_OP_SDIV:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = (int64_t)regs[r1] /
                                    (int64_t)regs[r2];
                        }
                        break;

                case DIF_OP_UDIV:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = regs[r1] / regs[r2];
                        }
                        break;

                case DIF_OP_SREM:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = (int64_t)regs[r1] %
                                    (int64_t)regs[r2];
                        }
                        break;

                case DIF_OP_UREM:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = regs[r1] % regs[r2];
                        }
                        break;

                case DIF_OP_NOT:
                        regs[rd] = ~regs[r1];
                        break;
                case DIF_OP_MOV:
                        regs[rd] = regs[r1];
                        break;
                case DIF_OP_CMP:
                        cc_r = regs[r1] - regs[r2];
                        cc_n = cc_r < 0;
                        cc_z = cc_r == 0;
                        cc_v = 0;
                        cc_c = regs[r1] < regs[r2];
                        break;
                case DIF_OP_TST:
                        cc_n = cc_v = cc_c = 0;
                        cc_z = regs[r1] == 0;
                        break;
                case DIF_OP_BA:
                        pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BE:
                        if (cc_z)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BNE:
                        if (cc_z == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BG:
                        if ((cc_z | (cc_n ^ cc_v)) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGU:
                        if ((cc_c | cc_z) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGE:
                        if ((cc_n ^ cc_v) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGEU:
                        if (cc_c == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BL:
                        if (cc_n ^ cc_v)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLU:
                        if (cc_c)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLE:
                        if (cc_z | (cc_n ^ cc_v))
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLEU:
                        if (cc_c | cc_z)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_RLDSB:
                        if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSB:
                        regs[rd] = (int8_t)dtrace_load8(regs[r1]);
                        break;
                case DIF_OP_RLDSH:
                        if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSH:
                        regs[rd] = (int16_t)dtrace_load16(regs[r1]);
                        break;
                case DIF_OP_RLDSW:
                        if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSW:
                        regs[rd] = (int32_t)dtrace_load32(regs[r1]);
                        break;
                case DIF_OP_RLDUB:
                        if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUB:
                        regs[rd] = dtrace_load8(regs[r1]);
                        break;
                case DIF_OP_RLDUH:
                        if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUH:
                        regs[rd] = dtrace_load16(regs[r1]);
                        break;
                case DIF_OP_RLDUW:
                        if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUW:
                        regs[rd] = dtrace_load32(regs[r1]);
                        break;
                case DIF_OP_RLDX:
                        if (!dtrace_canstore(regs[r1], 8, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDX:
                        regs[rd] = dtrace_load64(regs[r1]);
                        break;
                case DIF_OP_ULDSB:
                        regs[rd] = (int8_t)
                            dtrace_fuword8((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDSH:
                        regs[rd] = (int16_t)
                            dtrace_fuword16((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDSW:
                        regs[rd] = (int32_t)
                            dtrace_fuword32((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDUB:
                        regs[rd] =
                            dtrace_fuword8((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDUH:
                        regs[rd] =
                            dtrace_fuword16((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDUW:
                        regs[rd] =
                            dtrace_fuword32((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_ULDX:
                        regs[rd] =
                            dtrace_fuword64((void *)(uintptr_t)regs[r1]);
                        break;
                case DIF_OP_RET:
                        rval = regs[rd];
                        pc = textlen;
                        break;
                case DIF_OP_NOP:
                        break;
                case DIF_OP_SETX:
                        regs[rd] = inttab[DIF_INSTR_INTEGER(instr)];
                        break;
                case DIF_OP_SETS:
                        regs[rd] = (uint64_t)(uintptr_t)
                            (strtab + DIF_INSTR_STRING(instr));
                        break;
                case DIF_OP_SCMP: {
                        size_t sz = state->dts_options[DTRACEOPT_STRSIZE];
                        uintptr_t s1 = regs[r1];
                        uintptr_t s2 = regs[r2];

                        if (s1 != NULL &&
                            !dtrace_strcanload(s1, sz, mstate, vstate))
                                break;
                        if (s2 != NULL &&
                            !dtrace_strcanload(s2, sz, mstate, vstate))
                                break;

                        cc_r = dtrace_strncmp((char *)s1, (char *)s2, sz);

                        cc_n = cc_r < 0;
                        cc_z = cc_r == 0;
                        cc_v = cc_c = 0;
                        break;
                }
                case DIF_OP_LDGA:
                        regs[rd] = dtrace_dif_variable(mstate, state,
                            r1, regs[r2]);
                        break;
                case DIF_OP_LDGS:
                        id = DIF_INSTR_VAR(instr);

                        if (id >= DIF_VAR_OTHER_UBASE) {
                                uintptr_t a;

                                id -= DIF_VAR_OTHER_UBASE;
                                svar = vstate->dtvs_globals[id];
                                ASSERT(svar != NULL);
                                v = &svar->dtsv_var;

                                if (!(v->dtdv_type.dtdt_flags & DIF_TF_BYREF)) {
                                        regs[rd] = svar->dtsv_data;
                                        break;
                                }

                                a = (uintptr_t)svar->dtsv_data;

                                if (*(uint8_t *)a == UINT8_MAX) {
                                        /*
                                         * If the 0th byte is set to UINT8_MAX
                                         * then this is to be treated as a
                                         * reference to a NULL variable.
                                         */
                                        regs[rd] = NULL;
                                } else {
                                        regs[rd] = a + sizeof (uint64_t);
                                }

                                break;
                        }

                        regs[rd] = dtrace_dif_variable(mstate, state, id, 0);
                        break;

                case DIF_OP_STGS:
                        id = DIF_INSTR_VAR(instr);

                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        svar = vstate->dtvs_globals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;

                                ASSERT(a != NULL);
                                ASSERT(svar->dtsv_size != 0);

                                if (regs[rd] == NULL) {
                                        *(uint8_t *)a = UINT8_MAX;
                                        break;
                                } else {
                                        *(uint8_t *)a = 0;
                                        a += sizeof (uint64_t);
                                }
                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                    mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    (void *)a, &v->dtdv_type);
                                break;
                        }

                        svar->dtsv_data = regs[rd];
                        break;

                case DIF_OP_LDTA:
                        /*
                         * There are no DTrace built-in thread-local arrays at
                         * present.  This opcode is saved for future work.
                         */
                        *flags |= CPU_DTRACE_ILLOP;
                        regs[rd] = 0;
                        break;

                case DIF_OP_LDLS:
                        id = DIF_INSTR_VAR(instr);

                        if (id < DIF_VAR_OTHER_UBASE) {
                                /*
                                 * For now, this has no meaning.
                                 */
                                regs[rd] = 0;
                                break;
                        }

                        id -= DIF_VAR_OTHER_UBASE;

                        ASSERT(VBDTCAST(int64_t)id < vstate->dtvs_nlocals);
                        ASSERT(vstate->dtvs_locals != NULL);

                        svar = vstate->dtvs_locals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;
                                size_t sz = v->dtdv_type.dtdt_size;

                                sz += sizeof (uint64_t);
                                ASSERT(svar->dtsv_size == NCPU * sz);
                                a += VBDT_GET_CPUID() * sz;

                                if (*(uint8_t *)a == UINT8_MAX) {
                                        /*
                                         * If the 0th byte is set to UINT8_MAX
                                         * then this is to be treated as a
                                         * reference to a NULL variable.
                                         */
                                        regs[rd] = NULL;
                                } else {
                                        regs[rd] = a + sizeof (uint64_t);
                                }

                                break;
                        }

                        ASSERT(svar->dtsv_size == NCPU * sizeof (uint64_t));
                        tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                        regs[rd] = tmp[VBDT_GET_CPUID()];
                        break;

                case DIF_OP_STLS:
                        id = DIF_INSTR_VAR(instr);

                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;
                        ASSERT(VBDTCAST(int64_t)id < vstate->dtvs_nlocals);

                        ASSERT(vstate->dtvs_locals != NULL);
                        svar = vstate->dtvs_locals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;
                                size_t sz = v->dtdv_type.dtdt_size;

                                sz += sizeof (uint64_t);
                                ASSERT(svar->dtsv_size == NCPU * sz);
                                a += VBDT_GET_CPUID() * sz;

                                if (regs[rd] == NULL) {
                                        *(uint8_t *)a = UINT8_MAX;
                                        break;
                                } else {
                                        *(uint8_t *)a = 0;
                                        a += sizeof (uint64_t);
                                }

                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                    mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    (void *)a, &v->dtdv_type);
                                break;
                        }

                        ASSERT(svar->dtsv_size == NCPU * sizeof (uint64_t));
                        tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                        tmp[VBDT_GET_CPUID()] = regs[rd];
                        break;

                case DIF_OP_LDTS: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;
                        v = &vstate->dtvs_tlocals[id];

                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_value = (uint64_t)id;
                        key[0].dttk_size = 0;
                        DTRACE_TLS_THRKEY(key[1].dttk_value);
                        key[1].dttk_size = 0;

                        dvar = dtrace_dynvar(dstate, 2, key,
                            sizeof (uint64_t), DTRACE_DYNVAR_NOALLOC,
                            mstate, vstate);

                        if (dvar == NULL) {
                                regs[rd] = 0;
                                break;
                        }

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                        } else {
                                regs[rd] = *((uint64_t *)dvar->dtdv_data);
                        }

                        break;
                }

                case DIF_OP_STTS: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_value = (uint64_t)id;
                        key[0].dttk_size = 0;
                        DTRACE_TLS_THRKEY(key[1].dttk_value);
                        key[1].dttk_size = 0;
                        v = &vstate->dtvs_tlocals[id];

                        dvar = dtrace_dynvar(dstate, 2, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            regs[rd] ? DTRACE_DYNVAR_ALLOC :
                            DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                        /*
                         * Given that we're storing to thread-local data,
                         * we need to flush our predicate cache.
                         */
                        curthread->t_predcache = NULL;

                        if (dvar == NULL)
                                break;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd],
                                    &v->dtdv_type, mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    dvar->dtdv_data, &v->dtdv_type);
                        } else {
                                *((uint64_t *)dvar->dtdv_data) = regs[rd];
                        }

                        break;
                }

                case DIF_OP_SRA:
                        regs[rd] = (int64_t)regs[r1] >> regs[r2];
                        break;

                case DIF_OP_CALL:
                        dtrace_dif_subr(DIF_INSTR_SUBR(instr), rd,
                            regs, tupregs, ttop, mstate, state);
                        break;

                case DIF_OP_PUSHTR:
                        if (ttop == DIF_DTR_NREGS) {
                                *flags |= CPU_DTRACE_TUPOFLOW;
                                break;
                        }

                        if (r1 == DIF_TYPE_STRING) {
                                /*
                                 * If this is a string type and the size is 0,
                                 * we'll use the system-wide default string
                                 * size.  Note that we are _not_ looking at
                                 * the value of the DTRACEOPT_STRSIZE option;
                                 * had this been set, we would expect to have
                                 * a non-zero size value in the "pushtr".
                                 */
                                tupregs[ttop].dttk_size =
                                    dtrace_strlen((char *)(uintptr_t)regs[rd],
                                    regs[r2] ? regs[r2] :
                                    dtrace_strsize_default) + 1;
                        } else {
                                tupregs[ttop].dttk_size = regs[r2];
                        }

                        tupregs[ttop++].dttk_value = regs[rd];
                        break;

                case DIF_OP_PUSHTV:
                        if (ttop == DIF_DTR_NREGS) {
                                *flags |= CPU_DTRACE_TUPOFLOW;
                                break;
                        }

                        tupregs[ttop].dttk_value = regs[rd];
                        tupregs[ttop++].dttk_size = 0;
                        break;

                case DIF_OP_POPTS:
                        if (ttop != 0)
                                ttop--;
                        break;

                case DIF_OP_FLUSHTS:
                        ttop = 0;
                        break;

                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key = tupregs;
                        uint_t nkeys = ttop;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        key[nkeys].dttk_value = (uint64_t)id;
                        key[nkeys++].dttk_size = 0;

                        if (DIF_INSTR_OP(instr) == DIF_OP_LDTAA) {
                                DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                                key[nkeys++].dttk_size = 0;
                                v = &vstate->dtvs_tlocals[id];
                        } else {
                                v = &vstate->dtvs_globals[id]->dtsv_var;
                        }

                        dvar = dtrace_dynvar(dstate, nkeys, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            DTRACE_DYNVAR_NOALLOC, mstate, vstate);

                        if (dvar == NULL) {
                                regs[rd] = 0;
                                break;
                        }

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                        } else {
                                regs[rd] = *((uint64_t *)dvar->dtdv_data);
                        }

                        break;
                }

                case DIF_OP_STGAA:
                case DIF_OP_STTAA: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key = tupregs;
                        uint_t nkeys = ttop;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        key[nkeys].dttk_value = (uint64_t)id;
                        key[nkeys++].dttk_size = 0;

                        if (DIF_INSTR_OP(instr) == DIF_OP_STTAA) {
                                DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                                key[nkeys++].dttk_size = 0;
                                v = &vstate->dtvs_tlocals[id];
                        } else {
                                v = &vstate->dtvs_globals[id]->dtsv_var;
                        }

                        dvar = dtrace_dynvar(dstate, nkeys, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            regs[rd] ? DTRACE_DYNVAR_ALLOC :
                            DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                        if (dvar == NULL)
                                break;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                    mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    dvar->dtdv_data, &v->dtdv_type);
                        } else {
                                *((uint64_t *)dvar->dtdv_data) = regs[rd];
                        }

                        break;
                }

                case DIF_OP_ALLOCS: {
                        uintptr_t ptr = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
                        size_t size = ptr - mstate->dtms_scratch_ptr + regs[r1];

                        /*
                         * Rounding up the user allocation size could have
                         * overflowed large, bogus allocations (like -1ULL) to
                         * 0.
                         */
                        if (size < regs[r1] ||
                            !DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = NULL;
                                break;
                        }

                        dtrace_bzero((void *) mstate->dtms_scratch_ptr, size);
                        mstate->dtms_scratch_ptr += size;
                        regs[rd] = ptr;
                        break;
                }

                case DIF_OP_COPYS:
                        if (!dtrace_canstore(regs[rd], regs[r2],
                            mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }

                        if (!dtrace_canload(regs[r1], regs[r2], mstate, vstate))
                                break;

                        dtrace_bcopy((void *)(uintptr_t)regs[r1],
                            (void *)(uintptr_t)regs[rd], (size_t)regs[r2]);
                        break;

                case DIF_OP_STB:
                        if (!dtrace_canstore(regs[rd], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint8_t *)(uintptr_t)regs[rd]) = (uint8_t)regs[r1];
                        break;

                case DIF_OP_STH:
                        if (!dtrace_canstore(regs[rd], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        if (regs[rd] & 1) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint16_t *)(uintptr_t)regs[rd]) = (uint16_t)regs[r1];
                        break;

                case DIF_OP_STW:
                        if (!dtrace_canstore(regs[rd], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        if (regs[rd] & 3) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint32_t *)(uintptr_t)regs[rd]) = (uint32_t)regs[r1];
                        break;

                case DIF_OP_STX:
                        if (!dtrace_canstore(regs[rd], 8, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        if (regs[rd] & 7) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint64_t *)(uintptr_t)regs[rd]) = regs[r1];
                        break;
                }
        }

        if (!(*flags & CPU_DTRACE_FAULT))
                return (rval);

        mstate->dtms_fltoffs = opc * sizeof (dif_instr_t);
        mstate->dtms_present |= DTRACE_MSTATE_FLTOFFS;

        return (0);
}

#ifndef VBOX /* no destructive stuff */

static void
dtrace_action_breakpoint(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;
        dtrace_provider_t *prov = probe->dtpr_provider;
        char c[DTRACE_FULLNAMELEN + 80], *str;
        char *msg = "dtrace: breakpoint action at probe ";
        char *ecbmsg = " (ecb ";
        uintptr_t mask = (0xf << (sizeof (uintptr_t) * NBBY / 4));
        uintptr_t val = (uintptr_t)ecb;
        int shift = (sizeof (uintptr_t) * NBBY) - 4, i = 0;

        if (dtrace_destructive_disallow)
                return;

        /*
         * It's impossible to be taking action on the NULL probe.
         */
        ASSERT(probe != NULL);

        /*
         * This is a poor man's (destitute man's?) sprintf():  we want to
         * print the provider name, module name, function name and name of
         * the probe, along with the hex address of the ECB with the breakpoint
         * action -- all of which we must place in the character buffer by
         * hand.
         */
        while (*msg != '\0')
                c[i++] = *msg++;

        for (str = prov->dtpv_name; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_mod; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_func; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_name; *str != '\0'; str++)
                c[i++] = *str;

        while (*ecbmsg != '\0')
                c[i++] = *ecbmsg++;

        while (shift >= 0) {
                mask = (uintptr_t)0xf << shift;

                if (val >= ((uintptr_t)1 << shift))
                        c[i++] = "0123456789abcdef"[(val & mask) >> shift];
                shift -= 4;
        }

        c[i++] = ')';
        c[i] = '\0';

        debug_enter(c);
}

static void
dtrace_action_panic(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;

        /*
         * It's impossible to be taking action on the NULL probe.
         */
        ASSERT(probe != NULL);

        if (dtrace_destructive_disallow)
                return;

        if (dtrace_panicked != NULL)
                return;

        if (dtrace_casptr(&dtrace_panicked, NULL, curthread) != NULL)
                return;

        /*
         * We won the right to panic.  (We want to be sure that only one
         * thread calls panic() from dtrace_probe(), and that panic() is
         * called exactly once.)
         */
        dtrace_panic("dtrace: panic action at probe %s:%s:%s:%s (ecb %p)",
            probe->dtpr_provider->dtpv_name, probe->dtpr_mod,
            probe->dtpr_func, probe->dtpr_name, (void *)ecb);
}

static void
dtrace_action_raise(uint64_t sig)
{
        if (dtrace_destructive_disallow)
                return;

        if (sig >= NSIG) {
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                return;
        }

        /*
         * raise() has a queue depth of 1 -- we ignore all subsequent
         * invocations of the raise() action.
         */
        if (curthread->t_dtrace_sig == 0)
                curthread->t_dtrace_sig = (uint8_t)sig;

        curthread->t_sig_check = 1;
        aston(curthread);
}

static void
dtrace_action_stop(void)
{
        if (dtrace_destructive_disallow)
                return;

        if (!curthread->t_dtrace_stop) {
                curthread->t_dtrace_stop = 1;
                curthread->t_sig_check = 1;
                aston(curthread);
        }
}

static void
dtrace_action_chill(dtrace_mstate_t *mstate, hrtime_t val)
{
        hrtime_t now;
        volatile uint16_t *flags;
        cpu_t *cpu = CPU;

        if (dtrace_destructive_disallow)
                return;

        flags = (volatile uint16_t *)&cpu_core[cpu->cpu_id].cpuc_dtrace_flags;

        now = dtrace_gethrtime();

        if (now - cpu->cpu_dtrace_chillmark > dtrace_chill_interval) {
                /*
                 * We need to advance the mark to the current time.
                 */
                cpu->cpu_dtrace_chillmark = now;
                cpu->cpu_dtrace_chilled = 0;
        }

        /*
         * Now check to see if the requested chill time would take us over
         * the maximum amount of time allowed in the chill interval.  (Or
         * worse, if the calculation itself induces overflow.)
         */
        if (cpu->cpu_dtrace_chilled + val > dtrace_chill_max ||
            cpu->cpu_dtrace_chilled + val < cpu->cpu_dtrace_chilled) {
                *flags |= CPU_DTRACE_ILLOP;
                return;
        }

        while (dtrace_gethrtime() - now < val)
                continue;

        /*
         * Normally, we assure that the value of the variable "timestamp" does
         * not change within an ECB.  The presence of chill() represents an
         * exception to this rule, however.
         */
        mstate->dtms_present &= ~DTRACE_MSTATE_TIMESTAMP;
        cpu->cpu_dtrace_chilled += val;
}

#endif /* !VBOX */

static void
dtrace_action_ustack(dtrace_mstate_t *mstate, dtrace_state_t *state,
    uint64_t *buf, uint64_t arg)
{
        int nframes = DTRACE_USTACK_NFRAMES(arg);
        int strsize = DTRACE_USTACK_STRSIZE(arg);
        uint64_t *pcs = &buf[1], *fps;
        char *str = (char *)&pcs[nframes];
        int size, offs = 0, i, j;
        uintptr_t old = mstate->dtms_scratch_ptr, saved;
#ifndef VBOX
        uint16_t *flags = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;
#else
        uint16_t volatile *flags = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;
#endif
        char *sym;

        /*
         * Should be taking a faster path if string space has not been
         * allocated.
         */
        ASSERT(strsize != 0);

        /*
         * We will first allocate some temporary space for the frame pointers.
         */
        fps = (uint64_t *)P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
        size = (uintptr_t)fps - mstate->dtms_scratch_ptr +
            (nframes * sizeof (uint64_t));

        if (!DTRACE_INSCRATCH(mstate, VBDTCAST(unsigned)size)) {
                /*
                 * Not enough room for our frame pointers -- need to indicate
                 * that we ran out of scratch space.
                 */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                return;
        }

        mstate->dtms_scratch_ptr += size;
        saved = mstate->dtms_scratch_ptr;

        /*
         * Now get a stack with both program counters and frame pointers.
         */
        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
        dtrace_getufpstack(buf, fps, nframes + 1);
        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

        /*
         * If that faulted, we're cooked.
         */
        if (*flags & CPU_DTRACE_FAULT)
                goto out;

        /*
         * Now we want to walk up the stack, calling the USTACK helper.  For
         * each iteration, we restore the scratch pointer.
         */
        for (i = 0; i < nframes; i++) {
                mstate->dtms_scratch_ptr = saved;

                if (offs >= strsize)
                        break;

                sym = (char *)(uintptr_t)dtrace_helper(
                    DTRACE_HELPER_ACTION_USTACK,
                    mstate, state, pcs[i], fps[i]);

                /*
                 * If we faulted while running the helper, we're going to
                 * clear the fault and null out the corresponding string.
                 */
                if (*flags & CPU_DTRACE_FAULT) {
                        *flags &= ~CPU_DTRACE_FAULT;
                        str[offs++] = '\0';
                        continue;
                }

                if (sym == NULL) {
                        str[offs++] = '\0';
                        continue;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

                /*
                 * Now copy in the string that the helper returned to us.
                 */
                for (j = 0; offs + j < strsize; j++) {
                        if ((str[offs + j] = sym[j]) == '\0')
                                break;
                }

                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                offs += j + 1;
        }

        if (offs >= strsize) {
                /*
                 * If we didn't have room for all of the strings, we don't
                 * abort processing -- this needn't be a fatal error -- but we
                 * still want to increment a counter (dts_stkstroverflows) to
                 * allow this condition to be warned about.  (If this is from
                 * a jstack() action, it is easily tuned via jstackstrsize.)
                 */
                dtrace_error(&state->dts_stkstroverflows);
        }

        while (offs < strsize)
                str[offs++] = '\0';

out:
        mstate->dtms_scratch_ptr = old;
}

#ifdef VBOX
extern void dtrace_probe6(dtrace_id_t, uintptr_t arg0, uintptr_t arg1,
                                                  uintptr_t arg2, uintptr_t arg3, uintptr_t arg4, uintptr_t arg5);
# define dtrace_probe_error(a1, a2, a3, a4, a5, a6) \
        dtrace_probe6(dtrace_probeid_error, (uintptr_t)a1, a2, a3, a4, a5, a6)
#endif

/*
 * If you're looking for the epicenter of DTrace, you just found it.  This
 * is the function called by the provider to fire a probe -- from which all
 * subsequent probe-context DTrace activity emanates.
 */
void
dtrace_probe(dtrace_id_t id, uintptr_t arg0, uintptr_t arg1,
    uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
{
        processorid_t cpuid;
        dtrace_icookie_t cookie;
        dtrace_probe_t *probe;
        dtrace_mstate_t mstate;
        dtrace_ecb_t *ecb;
        dtrace_action_t *act;
        intptr_t offs;
        size_t size;
        int vtime, onintr;
        volatile uint16_t *flags;
        hrtime_t now;

#ifndef VBOX
        /*
         * Kick out immediately if this CPU is still being born (in which case
         * curthread will be set to -1) or the current thread can't allow
         * probes in its current context.
         */
        if (((uintptr_t)curthread & 1) || (curthread->t_flag & T_DONTDTRACE))
                return;
#endif

        cookie = dtrace_interrupt_disable();
        probe = dtrace_probes[id - 1];
        cpuid = VBDT_GET_CPUID();
        onintr = CPU_ON_INTR(CPU);

        if (!onintr && probe->dtpr_predcache != DTRACE_CACHEIDNONE &&
            probe->dtpr_predcache == curthread->t_predcache) {
                /*
                 * We have hit in the predicate cache; we know that
                 * this predicate would evaluate to be false.
                 */
                dtrace_interrupt_enable(cookie);
                return;
        }

#ifndef VBOX
        if (panic_quiesce) {
                /*
                 * We don't trace anything if we're panicking.
                 */
                dtrace_interrupt_enable(cookie);
                return;
        }
#endif

        now = dtrace_gethrtime();
        vtime = dtrace_vtime_references != 0;

        if (vtime && curthread->t_dtrace_start)
                curthread->t_dtrace_vtime += now - curthread->t_dtrace_start;

        mstate.dtms_difo = NULL;
        mstate.dtms_probe = probe;
        mstate.dtms_strtok = NULL;
        mstate.dtms_arg[0] = arg0;
        mstate.dtms_arg[1] = arg1;
        mstate.dtms_arg[2] = arg2;
        mstate.dtms_arg[3] = arg3;
        mstate.dtms_arg[4] = arg4;

        flags = (volatile uint16_t *)&cpu_core[cpuid].cpuc_dtrace_flags;

        for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
                dtrace_predicate_t *pred = ecb->dte_predicate;
                dtrace_state_t *state = ecb->dte_state;
                dtrace_buffer_t *buf = &state->dts_buffer[cpuid];
                dtrace_buffer_t *aggbuf = &state->dts_aggbuffer[cpuid];
                dtrace_vstate_t *vstate = &state->dts_vstate;
                dtrace_provider_t *prov = probe->dtpr_provider;
                int committed = 0;
                caddr_t tomax;

                /*
                 * A little subtlety with the following (seemingly innocuous)
                 * declaration of the automatic 'val':  by looking at the
                 * code, you might think that it could be declared in the
                 * action processing loop, below.  (That is, it's only used in
                 * the action processing loop.)  However, it must be declared
                 * out of that scope because in the case of DIF expression
                 * arguments to aggregating actions, one iteration of the
                 * action loop will use the last iteration's value.
                 */
#ifdef lint
                uint64_t val = 0;
#else
                uint64_t val VBDTUNASS(0);
#endif

                mstate.dtms_present = DTRACE_MSTATE_ARGS | DTRACE_MSTATE_PROBE;
                *flags &= ~CPU_DTRACE_ERROR;

                if (prov == dtrace_provider) {
                        /*
                         * If dtrace itself is the provider of this probe,
                         * we're only going to continue processing the ECB if
                         * arg0 (the dtrace_state_t) is equal to the ECB's
                         * creating state.  (This prevents disjoint consumers
                         * from seeing one another's metaprobes.)
                         */
                        if (arg0 != (uint64_t)(uintptr_t)state)
                                continue;
                }

                if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE) {
                        /*
                         * We're not currently active.  If our provider isn't
                         * the dtrace pseudo provider, we're not interested.
                         */
                        if (prov != dtrace_provider)
                                continue;

                        /*
                         * Now we must further check if we are in the BEGIN
                         * probe.  If we are, we will only continue processing
                         * if we're still in WARMUP -- if one BEGIN enabling
                         * has invoked the exit() action, we don't want to
                         * evaluate subsequent BEGIN enablings.
                         */
                        if (probe->dtpr_id == dtrace_probeid_begin &&
                            state->dts_activity != DTRACE_ACTIVITY_WARMUP) {
                                ASSERT(state->dts_activity ==
                                    DTRACE_ACTIVITY_DRAINING);
                                continue;
                        }
                }

                if (ecb->dte_cond) {
                        /*
                         * If the dte_cond bits indicate that this
                         * consumer is only allowed to see user-mode firings
                         * of this probe, call the provider's dtps_usermode()
                         * entry point to check that the probe was fired
                         * while in a user context. Skip this ECB if that's
                         * not the case.
                         */
                        if ((ecb->dte_cond & DTRACE_COND_USERMODE) &&
                            prov->dtpv_pops.dtps_usermode(prov->dtpv_arg,
                            probe->dtpr_id, probe->dtpr_arg) == 0)
                                continue;

                        /*
                         * This is more subtle than it looks. We have to be
                         * absolutely certain that CRED() isn't going to
                         * change out from under us so it's only legit to
                         * examine that structure if we're in constrained
                         * situations. Currently, the only times we'll this
                         * check is if a non-super-user has enabled the
                         * profile or syscall providers -- providers that
                         * allow visibility of all processes. For the
                         * profile case, the check above will ensure that
                         * we're examining a user context.
                         */
                        if (ecb->dte_cond & DTRACE_COND_OWNER) {
                                cred_t *cr;
                                cred_t *s_cr =
                                    ecb->dte_state->dts_cred.dcr_cred;
                                proc_t *proc;

                                ASSERT(s_cr != NULL);

                                if ((cr = CRED()) == NULL ||
                                    s_cr->cr_uid != cr->cr_uid ||
                                    s_cr->cr_uid != cr->cr_ruid ||
                                    s_cr->cr_uid != cr->cr_suid ||
                                    s_cr->cr_gid != cr->cr_gid ||
                                    s_cr->cr_gid != cr->cr_rgid ||
                                    s_cr->cr_gid != cr->cr_sgid ||
                                    (proc = VBDT_GET_PROC()) == NULL ||
                                    (proc->p_flag & SNOCD))
                                        continue;
                        }

#ifndef VBOX
                        if (ecb->dte_cond & DTRACE_COND_ZONEOWNER) {
                                cred_t *cr;
                                cred_t *s_cr =
                                    ecb->dte_state->dts_cred.dcr_cred;

                                ASSERT(s_cr != NULL);

                                if ((cr = CRED()) == NULL ||
                                    s_cr->cr_zone->zone_id !=
                                    cr->cr_zone->zone_id)
                                        continue;
                        }
#endif
                }

                if (now - state->dts_alive > dtrace_deadman_timeout) {
                        /*
                         * We seem to be dead.  Unless we (a) have kernel
                         * destructive permissions (b) have expicitly enabled
                         * destructive actions and (c) destructive actions have
                         * not been disabled, we're going to transition into
                         * the KILLED state, from which no further processing
                         * on this state will be performed.
                         */
                        if (!dtrace_priv_kernel_destructive(state) ||
                            !state->dts_cred.dcr_destructive ||
                            dtrace_destructive_disallow) {
                                void *activity = &state->dts_activity;
                                dtrace_activity_t current;

                                do {
                                        current = state->dts_activity;
                                } while (dtrace_cas32(activity, current,
                                    DTRACE_ACTIVITY_KILLED) != current);

                                continue;
                        }
                }

                if ((offs = dtrace_buffer_reserve(buf, ecb->dte_needed,
                    ecb->dte_alignment, state, &mstate)) < 0)
                        continue;

                tomax = buf->dtb_tomax;
                ASSERT(tomax != NULL);

                if (ecb->dte_size != 0)
                        DTRACE_STORE(uint32_t, tomax, offs, ecb->dte_epid);

                mstate.dtms_epid = ecb->dte_epid;
                mstate.dtms_present |= DTRACE_MSTATE_EPID;

                if (state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL)
                        mstate.dtms_access = DTRACE_ACCESS_KERNEL;
                else
                        mstate.dtms_access = 0;

                if (pred != NULL) {
                        dtrace_difo_t *dp = pred->dtp_difo;
                        int rval;

                        rval = dtrace_dif_emulate(dp, &mstate, vstate, state);

                        if (!(*flags & CPU_DTRACE_ERROR) && !rval) {
                                dtrace_cacheid_t cid = probe->dtpr_predcache;

                                if (cid != DTRACE_CACHEIDNONE && !onintr) {
                                        /*
                                         * Update the predicate cache...
                                         */
                                        ASSERT(cid == pred->dtp_cacheid);
                                        curthread->t_predcache = cid;
                                }

                                continue;
                        }
                }

                for (act = ecb->dte_action; !(*flags & CPU_DTRACE_ERROR) &&
                    act != NULL; act = act->dta_next) {
                        size_t valoffs;
                        dtrace_difo_t *dp;
                        dtrace_recdesc_t *rec = &act->dta_rec;

                        size = rec->dtrd_size;
                        valoffs = offs + rec->dtrd_offset;

                        if (DTRACEACT_ISAGG(act->dta_kind)) {
                                uint64_t v = 0xbad;
                                dtrace_aggregation_t *agg;

                                agg = (dtrace_aggregation_t *)act;

                                if ((dp = act->dta_difo) != NULL)
                                        v = dtrace_dif_emulate(dp,
                                            &mstate, vstate, state);

                                if (*flags & CPU_DTRACE_ERROR)
                                        continue;

                                /*
                                 * Note that we always pass the expression
                                 * value from the previous iteration of the
                                 * action loop.  This value will only be used
                                 * if there is an expression argument to the
                                 * aggregating action, denoted by the
                                 * dtag_hasarg field.
                                 */
                                dtrace_aggregate(agg, buf,
                                    offs, aggbuf, v, val);
                                continue;
                        }

                        switch (act->dta_kind) {
                        case DTRACEACT_STOP:
#ifndef VBOX
                                if (dtrace_priv_proc_destructive(state))
                                        dtrace_action_stop();
#else
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                                continue;

                        case DTRACEACT_BREAKPOINT:
#ifndef VBOX
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_breakpoint(ecb);
#else
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                                continue;

                        case DTRACEACT_PANIC:
#ifndef VBOX
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_panic(ecb);
#endif
                                continue;

                        case DTRACEACT_STACK:
                                if (!dtrace_priv_kernel(state))
                                        continue;

                                dtrace_getpcstack((pc_t *)(tomax + valoffs),
                                    VBDTCAST(int)(size / sizeof (pc_t)), probe->dtpr_aframes,
                                    DTRACE_ANCHORED(probe) ? NULL :
                                    (uint32_t *)arg0);

                                continue;

                        case DTRACEACT_JSTACK:
                        case DTRACEACT_USTACK:
                                if (!dtrace_priv_proc(state))
                                        continue;

                                /*
                                 * See comment in DIF_VAR_PID.
                                 */
                                if (DTRACE_ANCHORED(mstate.dtms_probe) &&
                                    CPU_ON_INTR(CPU)) {
                                        int depth = DTRACE_USTACK_NFRAMES(
                                            rec->dtrd_arg) + 1;

                                        dtrace_bzero((void *)(tomax + valoffs),
                                            DTRACE_USTACK_STRSIZE(rec->dtrd_arg)
                                            + depth * sizeof (uint64_t));

                                        continue;
                                }

                                if (DTRACE_USTACK_STRSIZE(rec->dtrd_arg) != 0 &&
                                    curproc->p_dtrace_helpers != NULL) {
                                        /*
                                         * This is the slow path -- we have
                                         * allocated string space, and we're
                                         * getting the stack of a process that
                                         * has helpers.  Call into a separate
                                         * routine to perform this processing.
                                         */
                                        dtrace_action_ustack(&mstate, state,
                                            (uint64_t *)(tomax + valoffs),
                                            rec->dtrd_arg);
                                        continue;
                                }

                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                dtrace_getupcstack((uint64_t *)
                                    (tomax + valoffs),
                                    DTRACE_USTACK_NFRAMES(rec->dtrd_arg) + 1);
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                                continue;

                        default:
                                break;
                        }

                        dp = act->dta_difo;
                        ASSERT(dp != NULL);

                        val = dtrace_dif_emulate(dp, &mstate, vstate, state);

                        if (*flags & CPU_DTRACE_ERROR)
                                continue;

                        switch (act->dta_kind) {
                        case DTRACEACT_SPECULATE:
                                ASSERT(buf == &state->dts_buffer[cpuid]);
                                buf = dtrace_speculation_buffer(state,
                                    cpuid, val);

                                if (buf == NULL) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                offs = dtrace_buffer_reserve(buf,
                                    ecb->dte_needed, ecb->dte_alignment,
                                    state, NULL);

                                if (offs < 0) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                tomax = buf->dtb_tomax;
                                ASSERT(tomax != NULL);

                                if (ecb->dte_size != 0)
                                        DTRACE_STORE(uint32_t, tomax, offs,
                                            ecb->dte_epid);
                                continue;

                        case DTRACEACT_CHILL:
#ifndef VBOX
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_chill(&mstate, val);
#else
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                                continue;

                        case DTRACEACT_RAISE:
#ifndef VBOX
                                if (dtrace_priv_proc_destructive(state))
                                        dtrace_action_raise(val);
#else
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
#endif
                                continue;

                        case DTRACEACT_COMMIT:
                                ASSERT(!committed);

                                /*
                                 * We need to commit our buffer state.
                                 */
                                if (ecb->dte_size)
                                        buf->dtb_offset = offs + ecb->dte_size;
                                buf = &state->dts_buffer[cpuid];
                                dtrace_speculation_commit(state, cpuid, val);
                                committed = 1;
                                continue;

                        case DTRACEACT_DISCARD:
                                dtrace_speculation_discard(state, cpuid, val);
                                continue;

                        case DTRACEACT_DIFEXPR:
                        case DTRACEACT_LIBACT:
                        case DTRACEACT_PRINTF:
                        case DTRACEACT_PRINTA:
                        case DTRACEACT_SYSTEM:
                        case DTRACEACT_FREOPEN:
                                break;

                        case DTRACEACT_SYM:
                        case DTRACEACT_MOD:
                                if (!dtrace_priv_kernel(state))
                                        continue;
                                break;

                        case DTRACEACT_USYM:
                        case DTRACEACT_UMOD:
                        case DTRACEACT_UADDR: {
#ifndef VBOX
                                struct pid *pid = curthread->t_procp->p_pidp;

                                if (!dtrace_priv_proc(state))
                                        continue;

                                DTRACE_STORE(uint64_t, tomax,
                                    valoffs, (uint64_t)pid->pid_id);
                                DTRACE_STORE(uint64_t, tomax,
                                    valoffs + sizeof (uint64_t), val);
#else
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_UPRIV);
#endif
                                continue;
                        }

                        case DTRACEACT_EXIT: {
                                /*
                                 * For the exit action, we are going to attempt
                                 * to atomically set our activity to be
                                 * draining.  If this fails (either because
                                 * another CPU has beat us to the exit action,
                                 * or because our current activity is something
                                 * other than ACTIVE or WARMUP), we will
                                 * continue.  This assures that the exit action
                                 * can be successfully recorded at most once
                                 * when we're in the ACTIVE state.  If we're
                                 * encountering the exit() action while in
                                 * COOLDOWN, however, we want to honor the new
                                 * status code.  (We know that we're the only
                                 * thread in COOLDOWN, so there is no race.)
                                 */
                                void *activity = &state->dts_activity;
                                dtrace_activity_t current = state->dts_activity;

                                if (current == DTRACE_ACTIVITY_COOLDOWN)
                                        break;

                                if (current != DTRACE_ACTIVITY_WARMUP)
                                        current = DTRACE_ACTIVITY_ACTIVE;

                                if (dtrace_cas32(activity, current,
                                    DTRACE_ACTIVITY_DRAINING) != current) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                break;
                        }

                        default:
#ifndef VBOX
                                ASSERT(0);
#else
                                AssertFatalMsgFailed(("%d\n", act->dta_kind));
#endif
                        }

                        if (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t end = valoffs + size;

                                if (!dtrace_vcanload((void *)(uintptr_t)val,
                                    &dp->dtdo_rtype, &mstate, vstate))
                                        continue;

                                /*
                                 * If this is a string, we're going to only
                                 * load until we find the zero byte -- after
                                 * which we'll store zero bytes.
                                 */
                                if (dp->dtdo_rtype.dtdt_kind ==
                                    DIF_TYPE_STRING) {
                                        char c = '\0' + 1;
                                        int intuple = act->dta_intuple;
                                        size_t s;

                                        for (s = 0; s < size; s++) {
                                                if (c != '\0')
                                                        c = dtrace_load8(val++);

                                                DTRACE_STORE(uint8_t, tomax,
                                                    valoffs++, c);

                                                if (c == '\0' && intuple)
                                                        break;
                                        }

                                        continue;
                                }

                                while (valoffs < end) {
                                        DTRACE_STORE(uint8_t, tomax, valoffs++,
                                            dtrace_load8(val++));
                                }

                                continue;
                        }

                        switch (size) {
                        case 0:
                                break;

                        case sizeof (uint8_t):
                                DTRACE_STORE(uint8_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint16_t):
                                DTRACE_STORE(uint16_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint32_t):
                                DTRACE_STORE(uint32_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint64_t):
                                DTRACE_STORE(uint64_t, tomax, valoffs, val);
                                break;
                        default:
                                /*
                                 * Any other size should have been returned by
                                 * reference, not by value.
                                 */
#ifndef VBOX
                                ASSERT(0);
#else
                                AssertFatalMsgFailed(("%zu\n", size));
#endif
                                break;
                        }
                }

                if (*flags & CPU_DTRACE_DROP)
                        continue;

                if (*flags & CPU_DTRACE_FAULT) {
                        int ndx;
                        dtrace_action_t *err;

                        buf->dtb_errors++;

                        if (probe->dtpr_id == dtrace_probeid_error) {
                                /*
                                 * There's nothing we can do -- we had an
                                 * error on the error probe.  We bump an
                                 * error counter to at least indicate that
                                 * this condition happened.
                                 */
                                dtrace_error(&state->dts_dblerrors);
                                continue;
                        }

                        if (vtime) {
                                /*
                                 * Before recursing on dtrace_probe(), we
                                 * need to explicitly clear out our start
                                 * time to prevent it from being accumulated
                                 * into t_dtrace_vtime.
                                 */
                                curthread->t_dtrace_start = 0;
                        }

                        /*
                         * Iterate over the actions to figure out which action
                         * we were processing when we experienced the error.
                         * Note that act points _past_ the faulting action; if
                         * act is ecb->dte_action, the fault was in the
                         * predicate, if it's ecb->dte_action->dta_next it's
                         * in action #1, and so on.
                         */
                        for (err = ecb->dte_action, ndx = 0;
                            err != act; err = err->dta_next, ndx++)
                                continue;

                        dtrace_probe_error(state, ecb->dte_epid, ndx,
                            (mstate.dtms_present & DTRACE_MSTATE_FLTOFFS) ?
                            mstate.dtms_fltoffs : -1, DTRACE_FLAGS2FLT(*flags),
                            cpu_core[cpuid].cpuc_dtrace_illval);

                        continue;
                }

                if (!committed)
                        buf->dtb_offset = offs + ecb->dte_size;
        }

        if (vtime)
                curthread->t_dtrace_start = dtrace_gethrtime();

        dtrace_interrupt_enable(cookie);
}

/*
 * DTrace Probe Hashing Functions
 *
 * The functions in this section (and indeed, the functions in remaining
 * sections) are not _called_ from probe context.  (Any exceptions to this are
 * marked with a "Note:".)  Rather, they are called from elsewhere in the
 * DTrace framework to look-up probes in, add probes to and remove probes from
 * the DTrace probe hashes.  (Each probe is hashed by each element of the
 * probe tuple -- allowing for fast lookups, regardless of what was
 * specified.)
 */
static uint_t
dtrace_hash_str(char *p)
{
        unsigned int g;
        uint_t hval = 0;

        while (*p) {
                hval = (hval << 4) + *p++;
                if ((g = (hval & 0xf0000000)) != 0)
                        hval ^= g >> 24;
                hval &= ~g;
        }
        return (hval);
}

static dtrace_hash_t *
dtrace_hash_create(uintptr_t stroffs, uintptr_t nextoffs, uintptr_t prevoffs)
{
        dtrace_hash_t *hash = kmem_zalloc(sizeof (dtrace_hash_t), KM_SLEEP);

        hash->dth_stroffs = stroffs;
        hash->dth_nextoffs = nextoffs;
        hash->dth_prevoffs = prevoffs;

        hash->dth_size = 1;
        hash->dth_mask = hash->dth_size - 1;

        hash->dth_tab = kmem_zalloc(hash->dth_size *
            sizeof (dtrace_hashbucket_t *), KM_SLEEP);

        return (hash);
}

static void
dtrace_hash_destroy(dtrace_hash_t *hash)
{
#ifdef DEBUG
        int i;

        for (i = 0; i < hash->dth_size; i++)
                ASSERT(hash->dth_tab[i] == NULL);
#endif

        kmem_free(hash->dth_tab,
            hash->dth_size * sizeof (dtrace_hashbucket_t *));
        kmem_free(hash, sizeof (dtrace_hash_t));
}

static void
dtrace_hash_resize(dtrace_hash_t *hash)
{
        int size = hash->dth_size, i, ndx;
        int new_size = hash->dth_size << 1;
        int new_mask = new_size - 1;
        dtrace_hashbucket_t **new_tab, *bucket, *next;

        ASSERT((new_size & new_mask) == 0);

        new_tab = kmem_zalloc(new_size * sizeof (void *), KM_SLEEP);

        for (i = 0; i < size; i++) {
                for (bucket = hash->dth_tab[i]; bucket != NULL; bucket = next) {
                        dtrace_probe_t *probe = bucket->dthb_chain;

                        ASSERT(probe != NULL);
                        ndx = DTRACE_HASHSTR(hash, probe) & new_mask;

                        next = bucket->dthb_next;
                        bucket->dthb_next = new_tab[ndx];
                        new_tab[ndx] = bucket;
                }
        }

        kmem_free(hash->dth_tab, hash->dth_size * sizeof (void *));
        hash->dth_tab = new_tab;
        hash->dth_size = new_size;
        hash->dth_mask = new_mask;
}

static void
dtrace_hash_add(dtrace_hash_t *hash, dtrace_probe_t *new)
{
        int hashval = DTRACE_HASHSTR(hash, new);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];
        dtrace_probe_t **nextp, **prevp;

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, new))
                        goto add;
        }

        if ((hash->dth_nbuckets >> 1) > hash->dth_size) {
                dtrace_hash_resize(hash);
                dtrace_hash_add(hash, new);
                return;
        }

        bucket = kmem_zalloc(sizeof (dtrace_hashbucket_t), KM_SLEEP);
        bucket->dthb_next = hash->dth_tab[ndx];
        hash->dth_tab[ndx] = bucket;
        hash->dth_nbuckets++;

add:
        nextp = DTRACE_HASHNEXT(hash, new);
        ASSERT(*nextp == NULL && *(DTRACE_HASHPREV(hash, new)) == NULL);
        *nextp = bucket->dthb_chain;

        if (bucket->dthb_chain != NULL) {
                prevp = DTRACE_HASHPREV(hash, bucket->dthb_chain);
                ASSERT(*prevp == NULL);
                *prevp = new;
        }

        bucket->dthb_chain = new;
        bucket->dthb_len++;
}

static dtrace_probe_t *
dtrace_hash_lookup(dtrace_hash_t *hash, dtrace_probe_t *template)
{
        int hashval = DTRACE_HASHSTR(hash, template);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, template))
                        return (bucket->dthb_chain);
        }

        return (NULL);
}

static int
dtrace_hash_collisions(dtrace_hash_t *hash, dtrace_probe_t *template)
{
        int hashval = DTRACE_HASHSTR(hash, template);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, template))
                        return (bucket->dthb_len);
        }

        return (NULL);
}

static void
dtrace_hash_remove(dtrace_hash_t *hash, dtrace_probe_t *probe)
{
        int ndx = DTRACE_HASHSTR(hash, probe) & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        dtrace_probe_t **prevp = DTRACE_HASHPREV(hash, probe);
        dtrace_probe_t **nextp = DTRACE_HASHNEXT(hash, probe);

        /*
         * Find the bucket that we're removing this probe from.
         */
        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, probe))
                        break;
        }

        ASSERT(bucket != NULL);

        if (*prevp == NULL) {
                if (*nextp == NULL) {
                        /*
                         * The removed probe was the only probe on this
                         * bucket; we need to remove the bucket.
                         */
                        dtrace_hashbucket_t *b = hash->dth_tab[ndx];

                        ASSERT(bucket->dthb_chain == probe);
                        ASSERT(b != NULL);

                        if (b == bucket) {
                                hash->dth_tab[ndx] = bucket->dthb_next;
                        } else {
                                while (b->dthb_next != bucket)
                                        b = b->dthb_next;
                                b->dthb_next = bucket->dthb_next;
                        }

                        ASSERT(hash->dth_nbuckets > 0);
                        hash->dth_nbuckets--;
                        kmem_free(bucket, sizeof (dtrace_hashbucket_t));
                        return;
                }

                bucket->dthb_chain = *nextp;
        } else {
                *(DTRACE_HASHNEXT(hash, *prevp)) = *nextp;
        }

        if (*nextp != NULL)
                *(DTRACE_HASHPREV(hash, *nextp)) = *prevp;
}

/*
 * DTrace Utility Functions
 *
 * These are random utility functions that are _not_ called from probe context.
 */
static int
dtrace_badattr(const dtrace_attribute_t *a)
{
        return (a->dtat_name > DTRACE_STABILITY_MAX ||
            a->dtat_data > DTRACE_STABILITY_MAX ||
            a->dtat_class > DTRACE_CLASS_MAX);
}

/*
 * Return a duplicate copy of a string.  If the specified string is NULL,
 * this function returns a zero-length string.
 */
static char *
dtrace_strdup(const char *str)
{
        char *new = kmem_zalloc((str != NULL ? strlen(str) : 0) + 1, KM_SLEEP);

        if (str != NULL)
                (void) strcpy(new, str);

        return (new);
}

#define DTRACE_ISALPHA(c)       \
        (((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z'))

static int
dtrace_badname(const char *s)
{
        char c;

        if (s == NULL || (c = *s++) == '\0')
                return (0);

        if (!DTRACE_ISALPHA(c) && c != '-' && c != '_' && c != '.')
                return (1);

        while ((c = *s++) != '\0') {
                if (!DTRACE_ISALPHA(c) && (c < '0' || c > '9') &&
                    c != '-' && c != '_' && c != '.' && c != '`')
                        return (1);
        }

        return (0);
}

static void
dtrace_cred2priv(cred_t *cr, uint32_t *privp, uid_t *uidp, zoneid_t *zoneidp)
{
        uint32_t priv;

        if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
                /*
                 * For DTRACE_PRIV_ALL, the uid and zoneid don't matter.
                 */
                priv = DTRACE_PRIV_ALL;
#ifdef VBOX
                *uidp = ~0;
                *zoneidp = 0;
#endif
        } else {
                *uidp = crgetuid(cr);
                *zoneidp = crgetzoneid(cr);

                priv = 0;
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE))
                        priv |= DTRACE_PRIV_KERNEL | DTRACE_PRIV_USER;
                else if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE))
                        priv |= DTRACE_PRIV_USER;
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE))
                        priv |= DTRACE_PRIV_PROC;
                if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                        priv |= DTRACE_PRIV_OWNER;
                if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                        priv |= DTRACE_PRIV_ZONEOWNER;
        }

        *privp = priv;
}

#ifdef DTRACE_ERRDEBUG
static void
dtrace_errdebug(const char *str)
{
        int hval = dtrace_hash_str((char *)str) % DTRACE_ERRHASHSZ;
        int occupied = 0;

        mutex_enter(&dtrace_errlock);
        dtrace_errlast = str;
        dtrace_errthread = curthread;

        while (occupied++ < DTRACE_ERRHASHSZ) {
                if (dtrace_errhash[hval].dter_msg == str) {
                        dtrace_errhash[hval].dter_count++;
                        goto out;
                }

                if (dtrace_errhash[hval].dter_msg != NULL) {
                        hval = (hval + 1) % DTRACE_ERRHASHSZ;
                        continue;
                }

                dtrace_errhash[hval].dter_msg = str;
                dtrace_errhash[hval].dter_count = 1;
                goto out;
        }

        panic("dtrace: undersized error hash");
out:
        mutex_exit(&dtrace_errlock);
}
#endif

/*
 * DTrace Matching Functions
 *
 * These functions are used to match groups of probes, given some elements of
 * a probe tuple, or some globbed expressions for elements of a probe tuple.
 */
static int
dtrace_match_priv(const dtrace_probe_t *prp, uint32_t priv, uid_t uid,
    zoneid_t zoneid)
{
        if (priv != DTRACE_PRIV_ALL) {
                uint32_t ppriv = prp->dtpr_provider->dtpv_priv.dtpp_flags;
                uint32_t match = priv & ppriv;

                /*
                 * No PRIV_DTRACE_* privileges...
                 */
                if ((priv & (DTRACE_PRIV_PROC | DTRACE_PRIV_USER |
                    DTRACE_PRIV_KERNEL)) == 0)
                        return (0);

                /*
                 * No matching bits, but there were bits to match...
                 */
                if (match == 0 && ppriv != 0)
                        return (0);

                /*
                 * Need to have permissions to the process, but don't...
                 */
                if (((ppriv & ~match) & DTRACE_PRIV_OWNER) != 0 &&
                    uid != prp->dtpr_provider->dtpv_priv.dtpp_uid) {
                        return (0);
                }

                /*
                 * Need to be in the same zone unless we possess the
                 * privilege to examine all zones.
                 */
                if (((ppriv & ~match) & DTRACE_PRIV_ZONEOWNER) != 0 &&
                    zoneid != prp->dtpr_provider->dtpv_priv.dtpp_zoneid) {
                        return (0);
                }
        }

        return (1);
}

/*
 * dtrace_match_probe compares a dtrace_probe_t to a pre-compiled key, which
 * consists of input pattern strings and an ops-vector to evaluate them.
 * This function returns >0 for match, 0 for no match, and <0 for error.
 */
static int
dtrace_match_probe(const dtrace_probe_t *prp, const dtrace_probekey_t *pkp,
    uint32_t priv, uid_t uid, zoneid_t zoneid)
{
        dtrace_provider_t *pvp = prp->dtpr_provider;
        int rv;

        if (pvp->dtpv_defunct)
                return (0);

        if ((rv = pkp->dtpk_pmatch(pvp->dtpv_name, pkp->dtpk_prov, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_mmatch(prp->dtpr_mod, pkp->dtpk_mod, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_fmatch(prp->dtpr_func, pkp->dtpk_func, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_nmatch(prp->dtpr_name, pkp->dtpk_name, 0)) <= 0)
                return (rv);

        if (dtrace_match_priv(prp, priv, uid, zoneid) == 0)
                return (0);

        return (rv);
}

/*
 * dtrace_match_glob() is a safe kernel implementation of the gmatch(3GEN)
 * interface for matching a glob pattern 'p' to an input string 's'.  Unlike
 * libc's version, the kernel version only applies to 8-bit ASCII strings.
 * In addition, all of the recursion cases except for '*' matching have been
 * unwound.  For '*', we still implement recursive evaluation, but a depth
 * counter is maintained and matching is aborted if we recurse too deep.
 * The function returns 0 if no match, >0 if match, and <0 if recursion error.
 */
static int
dtrace_match_glob(const char *s, const char *p, int depth)
{
        const char *olds;
        char s1, c;
        int gs;

        if (depth > DTRACE_PROBEKEY_MAXDEPTH)
                return (-1);

        if (s == NULL)
                s = ""; /* treat NULL as empty string */

top:
        olds = s;
        s1 = *s++;

        if (p == NULL)
                return (0);

        if ((c = *p++) == '\0')
                return (s1 == '\0');

        switch (c) {
        case '[': {
                int ok = 0, notflag = 0;
                char lc = '\0';

                if (s1 == '\0')
                        return (0);

                if (*p == '!') {
                        notflag = 1;
                        p++;
                }

                if ((c = *p++) == '\0')
                        return (0);

                do {
                        if (c == '-' && lc != '\0' && *p != ']') {
                                if ((c = *p++) == '\0')
                                        return (0);
                                if (c == '\\' && (c = *p++) == '\0')
                                        return (0);

                                if (notflag) {
                                        if (s1 < lc || s1 > c)
                                                ok++;
                                        else
                                                return (0);
                                } else if (lc <= s1 && s1 <= c)
                                        ok++;

                        } else if (c == '\\' && (c = *p++) == '\0')
                                return (0);

                        lc = c; /* save left-hand 'c' for next iteration */

                        if (notflag) {
                                if (s1 != c)
                                        ok++;
                                else
                                        return (0);
                        } else if (s1 == c)
                                ok++;

                        if ((c = *p++) == '\0')
                                return (0);

                } while (c != ']');

                if (ok)
                        goto top;

                return (0);
        }

        case '\\':
                if ((c = *p++) == '\0')
                        return (0);
                /*FALLTHRU*/

        default:
                if (c != s1)
                        return (0);
                /*FALLTHRU*/

        case '?':
                if (s1 != '\0')
                        goto top;
                return (0);

        case '*':
                while (*p == '*')
                        p++; /* consecutive *'s are identical to a single one */

                if (*p == '\0')
                        return (1);

                for (s = olds; *s != '\0'; s++) {
                        if ((gs = dtrace_match_glob(s, p, depth + 1)) != 0)
                                return (gs);
                }

                return (0);
        }
}

/*ARGSUSED*/
static int
dtrace_match_string(const char *s, const char *p, int depth)
{
        return (s != NULL && strcmp(s, p) == 0);
}

/*ARGSUSED*/
static int
dtrace_match_nul(const char *s, const char *p, int depth)
{
        return (1); /* always match the empty pattern */
}

/*ARGSUSED*/
static int
dtrace_match_nonzero(const char *s, const char *p, int depth)
{
        return (s != NULL && s[0] != '\0');
}

static int
dtrace_match(const dtrace_probekey_t *pkp, uint32_t priv, uid_t uid,
    zoneid_t zoneid, int (*matched)(dtrace_probe_t *, void *), void *arg)
{
        dtrace_probe_t template, *probe;
        dtrace_hash_t *hash = NULL;
        int len, rc, best = INT_MAX, nmatched = 0;
        dtrace_id_t i;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        /*
         * If the probe ID is specified in the key, just lookup by ID and
         * invoke the match callback once if a matching probe is found.
         */
        if (pkp->dtpk_id != DTRACE_IDNONE) {
                if ((probe = dtrace_probe_lookup_id(pkp->dtpk_id)) != NULL &&
                    dtrace_match_probe(probe, pkp, priv, uid, zoneid) > 0) {
                        if ((*matched)(probe, arg) == DTRACE_MATCH_FAIL)
                                return (DTRACE_MATCH_FAIL);
                        nmatched++;
                }
                return (nmatched);
        }

        template.dtpr_mod = (char *)pkp->dtpk_mod;
        template.dtpr_func = (char *)pkp->dtpk_func;
        template.dtpr_name = (char *)pkp->dtpk_name;

        /*
         * We want to find the most distinct of the module name, function
         * name, and name.  So for each one that is not a glob pattern or
         * empty string, we perform a lookup in the corresponding hash and
         * use the hash table with the fewest collisions to do our search.
         */
        if (pkp->dtpk_mmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_bymod, &template)) < best) {
                best = len;
                hash = dtrace_bymod;
        }

        if (pkp->dtpk_fmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_byfunc, &template)) < best) {
                best = len;
                hash = dtrace_byfunc;
        }

        if (pkp->dtpk_nmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_byname, &template)) < best) {
                best = len;
                hash = dtrace_byname;
        }

        /*
         * If we did not select a hash table, iterate over every probe and
         * invoke our callback for each one that matches our input probe key.
         */
        if (hash == NULL) {
                for (i = 0; i < VBDTCAST(dtrace_id_t)dtrace_nprobes; i++) {
                        if ((probe = dtrace_probes[i]) == NULL ||
                            dtrace_match_probe(probe, pkp, priv, uid,
                            zoneid) <= 0)
                                continue;

                        nmatched++;

                        if ((rc = (*matched)(probe, arg)) !=
                            DTRACE_MATCH_NEXT) {
                                if (rc == DTRACE_MATCH_FAIL)
                                        return (DTRACE_MATCH_FAIL);
                                break;
                        }
                }

                return (nmatched);
        }

        /*
         * If we selected a hash table, iterate over each probe of the same key
         * name and invoke the callback for every probe that matches the other
         * attributes of our input probe key.
         */
        for (probe = dtrace_hash_lookup(hash, &template); probe != NULL;
            probe = *(DTRACE_HASHNEXT(hash, probe))) {

                if (dtrace_match_probe(probe, pkp, priv, uid, zoneid) <= 0)
                        continue;

                nmatched++;

                if ((rc = (*matched)(probe, arg)) != DTRACE_MATCH_NEXT) {
                        if (rc == DTRACE_MATCH_FAIL)
                                return (DTRACE_MATCH_FAIL);
                        break;
                }
        }

        return (nmatched);
}

/*
 * Return the function pointer dtrace_probecmp() should use to compare the
 * specified pattern with a string.  For NULL or empty patterns, we select
 * dtrace_match_nul().  For glob pattern strings, we use dtrace_match_glob().
 * For non-empty non-glob strings, we use dtrace_match_string().
 */
static dtrace_probekey_f *
dtrace_probekey_func(const char *p)
{
        char c;

        if (p == NULL || *p == '\0')
                return (&dtrace_match_nul);

        while ((c = *p++) != '\0') {
                if (c == '[' || c == '?' || c == '*' || c == '\\')
                        return (&dtrace_match_glob);
        }

        return (&dtrace_match_string);
}

/*
 * Build a probe comparison key for use with dtrace_match_probe() from the
 * given probe description.  By convention, a null key only matches anchored
 * probes: if each field is the empty string, reset dtpk_fmatch to
 * dtrace_match_nonzero().
 */
static void
dtrace_probekey(const dtrace_probedesc_t *pdp, dtrace_probekey_t *pkp)
{
        pkp->dtpk_prov = pdp->dtpd_provider;
        pkp->dtpk_pmatch = dtrace_probekey_func(pdp->dtpd_provider);

        pkp->dtpk_mod = pdp->dtpd_mod;
        pkp->dtpk_mmatch = dtrace_probekey_func(pdp->dtpd_mod);

        pkp->dtpk_func = pdp->dtpd_func;
        pkp->dtpk_fmatch = dtrace_probekey_func(pdp->dtpd_func);

        pkp->dtpk_name = pdp->dtpd_name;
        pkp->dtpk_nmatch = dtrace_probekey_func(pdp->dtpd_name);

        pkp->dtpk_id = pdp->dtpd_id;

        if (pkp->dtpk_id == DTRACE_IDNONE &&
            pkp->dtpk_pmatch == &dtrace_match_nul &&
            pkp->dtpk_mmatch == &dtrace_match_nul &&
            pkp->dtpk_fmatch == &dtrace_match_nul &&
            pkp->dtpk_nmatch == &dtrace_match_nul)
                pkp->dtpk_fmatch = &dtrace_match_nonzero;
}

/*
 * DTrace Provider-to-Framework API Functions
 *
 * These functions implement much of the Provider-to-Framework API, as
 * described in <sys/dtrace.h>.  The parts of the API not in this section are
 * the functions in the API for probe management (found below), and
 * dtrace_probe() itself (found above).
 */

/*
 * Register the calling provider with the DTrace framework.  This should
 * generally be called by DTrace providers in their attach(9E) entry point.
 */
int
dtrace_register(const char *name, const dtrace_pattr_t *pap, uint32_t priv,
    cred_t *cr, const dtrace_pops_t *pops, void *arg, dtrace_provider_id_t *idp)
{
        dtrace_provider_t *provider;

        if (name == NULL || pap == NULL || pops == NULL || idp == NULL) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "arguments", name ? name : "<NULL>");
                return (EINVAL);
        }

        if (name[0] == '\0' || dtrace_badname(name)) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider name", name);
                return (EINVAL);
        }

        if ((pops->dtps_provide == NULL && pops->dtps_provide_module == NULL) ||
            pops->dtps_enable == NULL || pops->dtps_disable == NULL ||
            pops->dtps_destroy == NULL ||
            ((pops->dtps_resume == NULL) != (pops->dtps_suspend == NULL))) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider ops", name);
                return (EINVAL);
        }

        if (dtrace_badattr(&pap->dtpa_provider) ||
            dtrace_badattr(&pap->dtpa_mod) ||
            dtrace_badattr(&pap->dtpa_func) ||
            dtrace_badattr(&pap->dtpa_name) ||
            dtrace_badattr(&pap->dtpa_args)) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider attributes", name);
                return (EINVAL);
        }

        if (priv & ~DTRACE_PRIV_ALL) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "privilege attributes", name);
                return (EINVAL);
        }

        if ((priv & DTRACE_PRIV_KERNEL) &&
            (priv & (DTRACE_PRIV_USER | DTRACE_PRIV_OWNER)) &&
            pops->dtps_usermode == NULL) {
                cmn_err(CE_WARN, "failed to register provider '%s': need "
                    "dtps_usermode() op for given privilege attributes", name);
                return (EINVAL);
        }

        provider = kmem_zalloc(sizeof (dtrace_provider_t), KM_SLEEP);
        provider->dtpv_name = kmem_alloc(strlen(name) + 1, KM_SLEEP);
        (void) strcpy(provider->dtpv_name, name);

        provider->dtpv_attr = *pap;
        provider->dtpv_priv.dtpp_flags = priv;
        if (cr != NULL) {
                provider->dtpv_priv.dtpp_uid = crgetuid(cr);
                provider->dtpv_priv.dtpp_zoneid = crgetzoneid(cr);
        }
        provider->dtpv_pops = *pops;

        if (pops->dtps_provide == NULL) {
                ASSERT(pops->dtps_provide_module != NULL);
                provider->dtpv_pops.dtps_provide =
                    (void (*)(void *, const dtrace_probedesc_t *))dtrace_nullop;
        }

        if (pops->dtps_provide_module == NULL) {
                ASSERT(pops->dtps_provide != NULL);
                provider->dtpv_pops.dtps_provide_module =
                    (void (*)(void *, struct modctl *))dtrace_nullop;
        }

        if (pops->dtps_suspend == NULL) {
                ASSERT(pops->dtps_resume == NULL);
                provider->dtpv_pops.dtps_suspend =
                    (void (*)(void *, dtrace_id_t, void *))dtrace_nullop;
                provider->dtpv_pops.dtps_resume =
                    (void (*)(void *, dtrace_id_t, void *))dtrace_nullop;
        }

        provider->dtpv_arg = arg;
        *idp = (dtrace_provider_id_t)provider;

        if (pops == &dtrace_provider_ops) {
                ASSERT(MUTEX_HELD(&dtrace_provider_lock));
                ASSERT(MUTEX_HELD(&dtrace_lock));
                ASSERT(dtrace_anon.dta_enabling == NULL);

                /*
                 * We make sure that the DTrace provider is at the head of
                 * the provider chain.
                 */
                provider->dtpv_next = dtrace_provider;
                dtrace_provider = provider;
                return (0);
        }

        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&dtrace_lock);

        /*
         * If there is at least one provider registered, we'll add this
         * provider after the first provider.
         */
        if (dtrace_provider != NULL) {
                provider->dtpv_next = dtrace_provider->dtpv_next;
                dtrace_provider->dtpv_next = provider;
        } else {
                dtrace_provider = provider;
        }

        if (dtrace_retained != NULL) {
                dtrace_enabling_provide(provider);

                /*
                 * Now we need to call dtrace_enabling_matchall() -- which
                 * will acquire cpu_lock and dtrace_lock.  We therefore need
                 * to drop all of our locks before calling into it...
                 */
                mutex_exit(&dtrace_lock);
                mutex_exit(&dtrace_provider_lock);
                dtrace_enabling_matchall();

                return (0);
        }

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_provider_lock);

        return (0);
}

/*
 * Unregister the specified provider from the DTrace framework.  This should
 * generally be called by DTrace providers in their detach(9E) entry point.
 */
int
dtrace_unregister(dtrace_provider_id_t id)
{
        dtrace_provider_t *old = (dtrace_provider_t *)id;
        dtrace_provider_t *prev = NULL;
        VBDTTYPE(uint32_t,int) i, self = 0;
        dtrace_probe_t *probe, *first = NULL;

        if (old->dtpv_pops.dtps_enable ==
            (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop) {
                /*
                 * If DTrace itself is the provider, we're called with locks
                 * already held.
                 */
                ASSERT(old == dtrace_provider);
                ASSERT(dtrace_devi != NULL);
                ASSERT(MUTEX_HELD(&dtrace_provider_lock));
                ASSERT(MUTEX_HELD(&dtrace_lock));
                self = 1;

                if (dtrace_provider->dtpv_next != NULL) {
                        /*
                         * There's another provider here; return failure.
                         */
                        return (EBUSY);
                }
        } else {
                mutex_enter(&dtrace_provider_lock);
                mutex_enter(&mod_lock);
                mutex_enter(&dtrace_lock);
        }

        /*
         * If anyone has /dev/dtrace open, or if there are anonymous enabled
         * probes, we refuse to let providers slither away, unless this
         * provider has already been explicitly invalidated.
         */
        if (!old->dtpv_defunct &&
            (dtrace_opens || (dtrace_anon.dta_state != NULL &&
            dtrace_anon.dta_state->dts_necbs > 0))) {
                if (!self) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&mod_lock);
                        mutex_exit(&dtrace_provider_lock);
                }
                return (EBUSY);
        }

        /*
         * Attempt to destroy the probes associated with this provider.
         */
        for (i = 0; i < dtrace_nprobes; i++) {
                if ((probe = dtrace_probes[i]) == NULL)
                        continue;

                if (probe->dtpr_provider != old)
                        continue;

                if (probe->dtpr_ecb == NULL)
                        continue;

                /*
                 * We have at least one ECB; we can't remove this provider.
                 */
                if (!self) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&mod_lock);
                        mutex_exit(&dtrace_provider_lock);
                }
                return (EBUSY);
        }

        /*
         * All of the probes for this provider are disabled; we can safely
         * remove all of them from their hash chains and from the probe array.
         */
        for (i = 0; i < dtrace_nprobes; i++) {
                if ((probe = dtrace_probes[i]) == NULL)
                        continue;

                if (probe->dtpr_provider != old)
                        continue;

                dtrace_probes[i] = NULL;

                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                if (first == NULL) {
                        first = probe;
                        probe->dtpr_nextmod = NULL;
                } else {
                        probe->dtpr_nextmod = first;
                        first = probe;
                }
        }

        /*
         * The provider's probes have been removed from the hash chains and
         * from the probe array.  Now issue a dtrace_sync() to be sure that
         * everyone has cleared out from any probe array processing.
         */
        dtrace_sync();

        for (probe = first; probe != NULL; probe = first) {
                first = probe->dtpr_nextmod;

                old->dtpv_pops.dtps_destroy(old->dtpv_arg, probe->dtpr_id,
                    probe->dtpr_arg);
                kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
                kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
                kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
                vmem_free(dtrace_arena, (void *)(uintptr_t)(probe->dtpr_id), 1);
                kmem_free(probe, sizeof (dtrace_probe_t));
        }

        if ((prev = dtrace_provider) == old) {
                ASSERT(self || dtrace_devi == NULL);
                ASSERT(old->dtpv_next == NULL || dtrace_devi == NULL);
                dtrace_provider = old->dtpv_next;
        } else {
                while (prev != NULL && prev->dtpv_next != old)
                        prev = prev->dtpv_next;

                if (prev == NULL) {
                        panic("attempt to unregister non-existent "
                            "dtrace provider %p\n", (void *)id);
                }

                prev->dtpv_next = old->dtpv_next;
        }

        if (!self) {
                mutex_exit(&dtrace_lock);
                mutex_exit(&mod_lock);
                mutex_exit(&dtrace_provider_lock);
        }

        kmem_free(old->dtpv_name, strlen(old->dtpv_name) + 1);
        kmem_free(old, sizeof (dtrace_provider_t));

        return (0);
}

/*
 * Invalidate the specified provider.  All subsequent probe lookups for the
 * specified provider will fail, but its probes will not be removed.
 */
void
dtrace_invalidate(dtrace_provider_id_t id)
{
        dtrace_provider_t *pvp = (dtrace_provider_t *)id;

        ASSERT(pvp->dtpv_pops.dtps_enable !=
            (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop);

        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&dtrace_lock);

        pvp->dtpv_defunct = 1;

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_provider_lock);
}

/*
 * Indicate whether or not DTrace has attached.
 */
int
dtrace_attached(void)
{
        /*
         * dtrace_provider will be non-NULL iff the DTrace driver has
         * attached.  (It's non-NULL because DTrace is always itself a
         * provider.)
         */
        return (dtrace_provider != NULL);
}

/*
 * Remove all the unenabled probes for the given provider.  This function is
 * not unlike dtrace_unregister(), except that it doesn't remove the provider
 * -- just as many of its associated probes as it can.
 */
int
dtrace_condense(dtrace_provider_id_t id)
{
        dtrace_provider_t *prov = (dtrace_provider_t *)id;
        VBDTTYPE(uint32_t,int) i;
        dtrace_probe_t *probe;

        /*
         * Make sure this isn't the dtrace provider itself.
         */
        ASSERT(prov->dtpv_pops.dtps_enable !=
            (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop);

        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&dtrace_lock);

        /*
         * Attempt to destroy the probes associated with this provider.
         */
        for (i = 0; i < dtrace_nprobes; i++) {
                if ((probe = dtrace_probes[i]) == NULL)
                        continue;

                if (probe->dtpr_provider != prov)
                        continue;

                if (probe->dtpr_ecb != NULL)
                        continue;

                dtrace_probes[i] = NULL;

                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, i + 1,
                    probe->dtpr_arg);
                kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
                kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
                kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
                kmem_free(probe, sizeof (dtrace_probe_t));
                vmem_free(dtrace_arena, (void *)((uintptr_t)i + 1), 1);
        }

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_provider_lock);

        return (0);
}

/*
 * DTrace Probe Management Functions
 *
 * The functions in this section perform the DTrace probe management,
 * including functions to create probes, look-up probes, and call into the
 * providers to request that probes be provided.  Some of these functions are
 * in the Provider-to-Framework API; these functions can be identified by the
 * fact that they are not declared "static".
 */

/*
 * Create a probe with the specified module name, function name, and name.
 */
dtrace_id_t
dtrace_probe_create(dtrace_provider_id_t prov, const char *mod,
    const char *func, const char *name, int aframes, void *arg)
{
        dtrace_probe_t *probe, **probes;
        dtrace_provider_t *provider = (dtrace_provider_t *)prov;
        dtrace_id_t id;

        if (provider == dtrace_provider) {
                ASSERT(MUTEX_HELD(&dtrace_lock));
        } else {
                mutex_enter(&dtrace_lock);
        }

        id = (dtrace_id_t)(uintptr_t)vmem_alloc(dtrace_arena, 1,
            VM_BESTFIT | VM_SLEEP);
        probe = kmem_zalloc(sizeof (dtrace_probe_t), KM_SLEEP);

        probe->dtpr_id = id;
        probe->dtpr_gen = dtrace_probegen++;
        probe->dtpr_mod = dtrace_strdup(mod);
        probe->dtpr_func = dtrace_strdup(func);
        probe->dtpr_name = dtrace_strdup(name);
        probe->dtpr_arg = arg;
        probe->dtpr_aframes = aframes;
        probe->dtpr_provider = provider;

        dtrace_hash_add(dtrace_bymod, probe);
        dtrace_hash_add(dtrace_byfunc, probe);
        dtrace_hash_add(dtrace_byname, probe);

        if (id - 1 >= dtrace_nprobes) {
                size_t osize = dtrace_nprobes * sizeof (dtrace_probe_t *);
                size_t nsize = osize << 1;

                if (nsize == 0) {
                        ASSERT(osize == 0);
                        ASSERT(dtrace_probes == NULL);
                        nsize = sizeof (dtrace_probe_t *);
                }

                probes = kmem_zalloc(nsize, KM_SLEEP);

                if (dtrace_probes == NULL) {
                        ASSERT(osize == 0);
                        dtrace_probes = probes;
                        dtrace_nprobes = 1;
                } else {
                        dtrace_probe_t **oprobes = dtrace_probes;

                        bcopy(oprobes, probes, osize);
                        dtrace_membar_producer();
                        dtrace_probes = probes;

                        dtrace_sync();

                        /*
                         * All CPUs are now seeing the new probes array; we can
                         * safely free the old array.
                         */
                        kmem_free(oprobes, osize);
                        dtrace_nprobes <<= 1;
                }

                ASSERT(id - 1 < dtrace_nprobes);
        }

        ASSERT(dtrace_probes[id - 1] == NULL);
        dtrace_probes[id - 1] = probe;

        if (provider != dtrace_provider)
                mutex_exit(&dtrace_lock);

        return (id);
}

static dtrace_probe_t *
dtrace_probe_lookup_id(dtrace_id_t id)
{
        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (id == 0 || id > dtrace_nprobes)
                return (NULL);

        return (dtrace_probes[id - 1]);
}

static int
dtrace_probe_lookup_match(dtrace_probe_t *probe, void *arg)
{
        *((dtrace_id_t *)arg) = probe->dtpr_id;

        return (DTRACE_MATCH_DONE);
}

/*
 * Look up a probe based on provider and one or more of module name, function
 * name and probe name.
 */
dtrace_id_t
dtrace_probe_lookup(dtrace_provider_id_t prid, const char *mod,
    const char *func, const char *name)
{
        dtrace_probekey_t pkey;
        dtrace_id_t id;
        int match;

        pkey.dtpk_prov = ((dtrace_provider_t *)prid)->dtpv_name;
        pkey.dtpk_pmatch = &dtrace_match_string;
        pkey.dtpk_mod = mod;
        pkey.dtpk_mmatch = mod ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_func = func;
        pkey.dtpk_fmatch = func ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_name = name;
        pkey.dtpk_nmatch = name ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_id = DTRACE_IDNONE;

        mutex_enter(&dtrace_lock);
        match = dtrace_match(&pkey, DTRACE_PRIV_ALL, 0, 0,
            dtrace_probe_lookup_match, &id);
        mutex_exit(&dtrace_lock);

        ASSERT(match == 1 || match == 0);
        return (match ? id : 0);
}

/*
 * Returns the probe argument associated with the specified probe.
 */
void *
dtrace_probe_arg(dtrace_provider_id_t id, dtrace_id_t pid)
{
        dtrace_probe_t *probe;
        void *rval = NULL;

        mutex_enter(&dtrace_lock);

        if ((probe = dtrace_probe_lookup_id(pid)) != NULL &&
            probe->dtpr_provider == (dtrace_provider_t *)id)
                rval = probe->dtpr_arg;

        mutex_exit(&dtrace_lock);

        return (rval);
}

/*
 * Copy a probe into a probe description.
 */
static void
dtrace_probe_description(const dtrace_probe_t *prp, dtrace_probedesc_t *pdp)
{
        bzero(pdp, sizeof (dtrace_probedesc_t));
        pdp->dtpd_id = prp->dtpr_id;

        (void) strncpy(pdp->dtpd_provider,
            prp->dtpr_provider->dtpv_name, DTRACE_PROVNAMELEN - 1);

        (void) strncpy(pdp->dtpd_mod, prp->dtpr_mod, DTRACE_MODNAMELEN - 1);
        (void) strncpy(pdp->dtpd_func, prp->dtpr_func, DTRACE_FUNCNAMELEN - 1);
        (void) strncpy(pdp->dtpd_name, prp->dtpr_name, DTRACE_NAMELEN - 1);
}

/*
 * Called to indicate that a probe -- or probes -- should be provided by a
 * specfied provider.  If the specified description is NULL, the provider will
 * be told to provide all of its probes.  (This is done whenever a new
 * consumer comes along, or whenever a retained enabling is to be matched.) If
 * the specified description is non-NULL, the provider is given the
 * opportunity to dynamically provide the specified probe, allowing providers
 * to support the creation of probes on-the-fly.  (So-called _autocreated_
 * probes.)  If the provider is NULL, the operations will be applied to all
 * providers; if the provider is non-NULL the operations will only be applied
 * to the specified provider.  The dtrace_provider_lock must be held, and the
 * dtrace_lock must _not_ be held -- the provider's dtps_provide() operation
 * will need to grab the dtrace_lock when it reenters the framework through
 * dtrace_probe_lookup(), dtrace_probe_create(), etc.
 */
static void
dtrace_probe_provide(dtrace_probedesc_t *desc, dtrace_provider_t *prv)
{
#ifndef VBOX
        struct modctl *ctl;
#endif
        int all = 0;

        ASSERT(MUTEX_HELD(&dtrace_provider_lock));

        if (prv == NULL) {
                all = 1;
                prv = dtrace_provider;
        }

        do {
                /*
                 * First, call the blanket provide operation.
                 */
                prv->dtpv_pops.dtps_provide(prv->dtpv_arg, desc);

#ifndef VBOX
                /*
                 * Now call the per-module provide operation.  We will grab
                 * mod_lock to prevent the list from being modified.  Note
                 * that this also prevents the mod_busy bits from changing.
                 * (mod_busy can only be changed with mod_lock held.)
                 */
                mutex_enter(&mod_lock);

                ctl = &modules;
                do {
                        if (ctl->mod_busy || ctl->mod_mp == NULL)
                                continue;

                        prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);

                } while ((ctl = ctl->mod_next) != &modules);

                mutex_exit(&mod_lock);
#endif
        } while (all && (prv = prv->dtpv_next) != NULL);
}

/*
 * Iterate over each probe, and call the Framework-to-Provider API function
 * denoted by offs.
 */
static void
dtrace_probe_foreach(uintptr_t offs)
{
        dtrace_provider_t *prov;
        void (*func)(void *, dtrace_id_t, void *);
        dtrace_probe_t *probe;
        dtrace_icookie_t cookie;
        VBDTTYPE(uint32_t,int) i;

        /*
         * We disable interrupts to walk through the probe array.  This is
         * safe -- the dtrace_sync() in dtrace_unregister() assures that we
         * won't see stale data.
         */
        cookie = dtrace_interrupt_disable();

        for (i = 0; i < dtrace_nprobes; i++) {
                if ((probe = dtrace_probes[i]) == NULL)
                        continue;

                if (probe->dtpr_ecb == NULL) {
                        /*
                         * This probe isn't enabled -- don't call the function.
                         */
                        continue;
                }

                prov = probe->dtpr_provider;
                func = *((void(**)(void *, dtrace_id_t, void *))
                    ((uintptr_t)&prov->dtpv_pops + offs));

                func(prov->dtpv_arg, i + 1, probe->dtpr_arg);
        }

        dtrace_interrupt_enable(cookie);
}

static int
dtrace_probe_enable(const dtrace_probedesc_t *desc, dtrace_enabling_t *enab)
{
        dtrace_probekey_t pkey;
        uint32_t priv;
        uid_t uid;
        zoneid_t zoneid;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        dtrace_ecb_create_cache = NULL;

        if (desc == NULL) {
                /*
                 * If we're passed a NULL description, we're being asked to
                 * create an ECB with a NULL probe.
                 */
                (void) dtrace_ecb_create_enable(NULL, enab);
                return (0);
        }

        dtrace_probekey(desc, &pkey);
        dtrace_cred2priv(enab->dten_vstate->dtvs_state->dts_cred.dcr_cred,
            &priv, &uid, &zoneid);

        return (dtrace_match(&pkey, priv, uid, zoneid, dtrace_ecb_create_enable,
            enab));
}

/*
 * DTrace Helper Provider Functions
 */
static void
dtrace_dofattr2attr(dtrace_attribute_t *attr, const dof_attr_t dofattr)
{
        attr->dtat_name = DOF_ATTR_NAME(dofattr);
        attr->dtat_data = DOF_ATTR_DATA(dofattr);
        attr->dtat_class = DOF_ATTR_CLASS(dofattr);
}

static void
dtrace_dofprov2hprov(dtrace_helper_provdesc_t *hprov,
    const dof_provider_t *dofprov, char *strtab)
{
        hprov->dthpv_provname = strtab + dofprov->dofpv_name;
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_provider,
            dofprov->dofpv_provattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_mod,
            dofprov->dofpv_modattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_func,
            dofprov->dofpv_funcattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_name,
            dofprov->dofpv_nameattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_args,
            dofprov->dofpv_argsattr);
}

static void
dtrace_helper_provide_one(dof_helper_t *dhp, dof_sec_t *sec, pid_t pid)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
        dof_provider_t *provider;
        dof_probe_t *probe;
        uint32_t *off, *enoff;
        uint8_t *arg;
        char *strtab;
        uint_t i, nprobes;
        dtrace_helper_provdesc_t dhpv;
        dtrace_helper_probedesc_t dhpb;
        dtrace_meta_t *meta = dtrace_meta_pid;
        dtrace_mops_t *mops = &meta->dtm_mops;
        void *parg;

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_strtab * dof->dofh_secsize);
        prb_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_probes * dof->dofh_secsize);
        arg_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_prargs * dof->dofh_secsize);
        off_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_proffs * dof->dofh_secsize);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);
        off = (uint32_t *)(uintptr_t)(daddr + off_sec->dofs_offset);
        arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);
        enoff = NULL;

        /*
         * See dtrace_helper_provider_validate().
         */
        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
            provider->dofpv_prenoffs != DOF_SECT_NONE) {
                enoff_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
                    provider->dofpv_prenoffs * dof->dofh_secsize);
                enoff = (uint32_t *)(uintptr_t)(daddr + enoff_sec->dofs_offset);
        }

        nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

        /*
         * Create the provider.
         */
        dtrace_dofprov2hprov(&dhpv, provider, strtab);

        if ((parg = mops->dtms_provide_pid(meta->dtm_arg, &dhpv, pid)) == NULL)
                return;

        meta->dtm_count++;

        /*
         * Create the probes.
         */
        for (i = 0; i < nprobes; i++) {
                probe = (dof_probe_t *)(uintptr_t)(daddr +
                    prb_sec->dofs_offset + i * prb_sec->dofs_entsize);

                dhpb.dthpb_mod = dhp->dofhp_mod;
                dhpb.dthpb_func = strtab + probe->dofpr_func;
                dhpb.dthpb_name = strtab + probe->dofpr_name;
                dhpb.dthpb_base = probe->dofpr_addr;
                dhpb.dthpb_offs = off + probe->dofpr_offidx;
                dhpb.dthpb_noffs = probe->dofpr_noffs;
                if (enoff != NULL) {
                        dhpb.dthpb_enoffs = enoff + probe->dofpr_enoffidx;
                        dhpb.dthpb_nenoffs = probe->dofpr_nenoffs;
                } else {
                        dhpb.dthpb_enoffs = NULL;
                        dhpb.dthpb_nenoffs = 0;
                }
                dhpb.dthpb_args = arg + probe->dofpr_argidx;
                dhpb.dthpb_nargc = probe->dofpr_nargc;
                dhpb.dthpb_xargc = probe->dofpr_xargc;
                dhpb.dthpb_ntypes = strtab + probe->dofpr_nargv;
                dhpb.dthpb_xtypes = strtab + probe->dofpr_xargv;

                mops->dtms_create_probe(meta->dtm_arg, parg, &dhpb);
        }
}

static void
dtrace_helper_provide(dof_helper_t *dhp, pid_t pid)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        VBDTTYPE(uint32_t,int) i;

        ASSERT(MUTEX_HELD(&dtrace_meta_lock));

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                    dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_PROVIDER)
                        continue;

                dtrace_helper_provide_one(dhp, sec, pid);
        }

        /*
         * We may have just created probes, so we must now rematch against
         * any retained enablings.  Note that this call will acquire both
         * cpu_lock and dtrace_lock; the fact that we are holding
         * dtrace_meta_lock now is what defines the ordering with respect to
         * these three locks.
         */
        dtrace_enabling_matchall();
}

static void
dtrace_helper_provider_remove_one(dof_helper_t *dhp, dof_sec_t *sec, pid_t pid)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        dof_sec_t *str_sec;
        dof_provider_t *provider;
        char *strtab;
        dtrace_helper_provdesc_t dhpv;
        dtrace_meta_t *meta = dtrace_meta_pid;
        dtrace_mops_t *mops = &meta->dtm_mops;

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_strtab * dof->dofh_secsize);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

        /*
         * Create the provider.
         */
        dtrace_dofprov2hprov(&dhpv, provider, strtab);

        mops->dtms_remove_pid(meta->dtm_arg, &dhpv, pid);

        meta->dtm_count--;
}

static void
dtrace_helper_provider_remove(dof_helper_t *dhp, pid_t pid)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        VBDTTYPE(uint32_t,int) i;

        ASSERT(MUTEX_HELD(&dtrace_meta_lock));

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                    dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_PROVIDER)
                        continue;

                dtrace_helper_provider_remove_one(dhp, sec, pid);
        }
}

/*
 * DTrace Meta Provider-to-Framework API Functions
 *
 * These functions implement the Meta Provider-to-Framework API, as described
 * in <sys/dtrace.h>.
 */
int
dtrace_meta_register(const char *name, const dtrace_mops_t *mops, void *arg,
    dtrace_meta_provider_id_t *idp)
{
        dtrace_meta_t *meta;
        dtrace_helpers_t *help, *next;
        VBDTTYPE(uint32_t,int) i;

        *idp = DTRACE_METAPROVNONE;

        /*
         * We strictly don't need the name, but we hold onto it for
         * debuggability. All hail error queues!
         */
        if (name == NULL) {
                cmn_err(CE_WARN, "failed to register meta-provider: "
                    "invalid name");
                return (EINVAL);
        }

        if (mops == NULL ||
            mops->dtms_create_probe == NULL ||
            mops->dtms_provide_pid == NULL ||
            mops->dtms_remove_pid == NULL) {
                cmn_err(CE_WARN, "failed to register meta-register %s: "
                    "invalid ops", name);
                return (EINVAL);
        }

        meta = kmem_zalloc(sizeof (dtrace_meta_t), KM_SLEEP);
        meta->dtm_mops = *mops;
        meta->dtm_name = kmem_alloc(strlen(name) + 1, KM_SLEEP);
        (void) strcpy(meta->dtm_name, name);
        meta->dtm_arg = arg;

        mutex_enter(&dtrace_meta_lock);
        mutex_enter(&dtrace_lock);

        if (dtrace_meta_pid != NULL) {
                mutex_exit(&dtrace_lock);
                mutex_exit(&dtrace_meta_lock);
                cmn_err(CE_WARN, "failed to register meta-register %s: "
                    "user-land meta-provider exists", name);
                kmem_free(meta->dtm_name, strlen(meta->dtm_name) + 1);
                kmem_free(meta, sizeof (dtrace_meta_t));
                return (EINVAL);
        }

        dtrace_meta_pid = meta;
        *idp = (dtrace_meta_provider_id_t)meta;

        /*
         * If there are providers and probes ready to go, pass them
         * off to the new meta provider now.
         */

        help = dtrace_deferred_pid;
        dtrace_deferred_pid = NULL;

        mutex_exit(&dtrace_lock);

        while (help != NULL) {
                for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                            help->dthps_pid);
                }

                next = help->dthps_next;
                help->dthps_next = NULL;
                help->dthps_prev = NULL;
                help->dthps_deferred = 0;
                help = next;
        }

        mutex_exit(&dtrace_meta_lock);

        return (0);
}

int
dtrace_meta_unregister(dtrace_meta_provider_id_t id)
{
        dtrace_meta_t **pp, *old = (dtrace_meta_t *)id;

        mutex_enter(&dtrace_meta_lock);
        mutex_enter(&dtrace_lock);

        if (old == dtrace_meta_pid) {
                pp = &dtrace_meta_pid;
        } else {
                panic("attempt to unregister non-existent "
                    "dtrace meta-provider %p\n", (void *)old);
#ifdef VBOX
                return EINVAL;
#endif
        }

        if (old->dtm_count != 0) {
                mutex_exit(&dtrace_lock);
                mutex_exit(&dtrace_meta_lock);
                return (EBUSY);
        }

        *pp = NULL;

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_meta_lock);

        kmem_free(old->dtm_name, strlen(old->dtm_name) + 1);
        kmem_free(old, sizeof (dtrace_meta_t));

        return (0);
}


/*
 * DTrace DIF Object Functions
 */
static int
dtrace_difo_err(uint_t pc, const char *format, ...)
{
        if (dtrace_err_verbose) {
                va_list alist;

                (void) uprintf("dtrace DIF object error: [%u]: ", pc);
                va_start(alist, format);
                (void) vuprintf(format, alist);
                va_end(alist);
        }

#ifdef DTRACE_ERRDEBUG
        dtrace_errdebug(format);
#endif
        return (1);
}

/*
 * Validate a DTrace DIF object by checking the IR instructions.  The following
 * rules are currently enforced by dtrace_difo_validate():
 *
 * 1. Each instruction must have a valid opcode
 * 2. Each register, string, variable, or subroutine reference must be valid
 * 3. No instruction can modify register %r0 (must be zero)
 * 4. All instruction reserved bits must be set to zero
 * 5. The last instruction must be a "ret" instruction
 * 6. All branch targets must reference a valid instruction _after_ the branch
 */
static int
dtrace_difo_validate(dtrace_difo_t *dp, dtrace_vstate_t *vstate, uint_t nregs,
    cred_t *cr)
{
#ifndef VBOX
        int err = 0, i;
#else
        int err = 0;
        uint_t i;
#endif
        int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
        int kcheckload;
        uint_t pc;

        kcheckload = cr == NULL ||
            (vstate->dtvs_state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) == 0;

        dp->dtdo_destructive = 0;

        for (pc = 0; pc < dp->dtdo_len && err == 0; pc++) {
                dif_instr_t instr = dp->dtdo_buf[pc];

                uint_t r1 = DIF_INSTR_R1(instr);
                uint_t r2 = DIF_INSTR_R2(instr);
                uint_t rd = DIF_INSTR_RD(instr);
                uint_t rs = DIF_INSTR_RS(instr);
                uint_t label = DIF_INSTR_LABEL(instr);
                uint_t v = DIF_INSTR_VAR(instr);
                uint_t subr = DIF_INSTR_SUBR(instr);
                uint_t type = DIF_INSTR_TYPE(instr);
                uint_t op = DIF_INSTR_OP(instr);

                switch (op) {
                case DIF_OP_OR:
                case DIF_OP_XOR:
                case DIF_OP_AND:
                case DIF_OP_SLL:
                case DIF_OP_SRL:
                case DIF_OP_SRA:
                case DIF_OP_SUB:
                case DIF_OP_ADD:
                case DIF_OP_MUL:
                case DIF_OP_SDIV:
                case DIF_OP_UDIV:
                case DIF_OP_SREM:
                case DIF_OP_UREM:
                case DIF_OP_COPYS:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_NOT:
                case DIF_OP_MOV:
                case DIF_OP_ALLOCS:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_LDSB:
                case DIF_OP_LDSH:
                case DIF_OP_LDSW:
                case DIF_OP_LDUB:
                case DIF_OP_LDUH:
                case DIF_OP_LDUW:
                case DIF_OP_LDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        if (kcheckload)
                                dp->dtdo_buf[pc] = DIF_INSTR_LOAD(op +
                                    DIF_OP_RLDSB - DIF_OP_LDSB, r1, rd);
                        break;
                case DIF_OP_RLDSB:
                case DIF_OP_RLDSH:
                case DIF_OP_RLDSW:
                case DIF_OP_RLDUB:
                case DIF_OP_RLDUH:
                case DIF_OP_RLDUW:
                case DIF_OP_RLDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_ULDSB:
                case DIF_OP_ULDSH:
                case DIF_OP_ULDSW:
                case DIF_OP_ULDUB:
                case DIF_OP_ULDUH:
                case DIF_OP_ULDUW:
                case DIF_OP_ULDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_STB:
                case DIF_OP_STH:
                case DIF_OP_STW:
                case DIF_OP_STX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to 0 address\n");
                        break;
                case DIF_OP_CMP:
                case DIF_OP_SCMP:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_TST:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0 || rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_BA:
                case DIF_OP_BE:
                case DIF_OP_BNE:
                case DIF_OP_BG:
                case DIF_OP_BGU:
                case DIF_OP_BGE:
                case DIF_OP_BGEU:
                case DIF_OP_BL:
                case DIF_OP_BLU:
                case DIF_OP_BLE:
                case DIF_OP_BLEU:
                        if (label >= dp->dtdo_len) {
                                err += efunc(pc, "invalid branch target %u\n",
                                    label);
                        }
                        if (label <= pc) {
                                err += efunc(pc, "backward branch to %u\n",
                                    label);
                        }
                        break;
                case DIF_OP_RET:
                        if (r1 != 0 || r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        break;
                case DIF_OP_NOP:
                case DIF_OP_POPTS:
                case DIF_OP_FLUSHTS:
                        if (r1 != 0 || r2 != 0 || rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_SETX:
                        if (DIF_INSTR_INTEGER(instr) >= dp->dtdo_intlen) {
                                err += efunc(pc, "invalid integer ref %u\n",
                                    DIF_INSTR_INTEGER(instr));
                        }
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_SETS:
                        if (DIF_INSTR_STRING(instr) >= dp->dtdo_strlen) {
                                err += efunc(pc, "invalid string ref %u\n",
                                    DIF_INSTR_STRING(instr));
                        }
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_LDGA:
                case DIF_OP_LDTA:
                        if (r1 > DIF_VAR_ARRAY_MAX)
                                err += efunc(pc, "invalid array %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_LDGS:
                case DIF_OP_LDTS:
                case DIF_OP_LDLS:
                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA:
                        if (v < DIF_VAR_OTHER_MIN || v > DIF_VAR_OTHER_MAX)
                                err += efunc(pc, "invalid variable %u\n", v);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");
                        break;
                case DIF_OP_STGS:
                case DIF_OP_STTS:
                case DIF_OP_STLS:
                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        if (v < DIF_VAR_OTHER_UBASE || v > DIF_VAR_OTHER_MAX)
                                err += efunc(pc, "invalid variable %u\n", v);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        break;
                case DIF_OP_CALL:
                        if (subr > DIF_SUBR_MAX)
                                err += efunc(pc, "invalid subr %u\n", subr);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %r0\n");

                        if (subr == DIF_SUBR_COPYOUT ||
                            subr == DIF_SUBR_COPYOUTSTR) {
                                dp->dtdo_destructive = 1;
                        }
                        break;
                case DIF_OP_PUSHTR:
                        if (type != DIF_TYPE_STRING && type != DIF_TYPE_CTF)
                                err += efunc(pc, "invalid ref type %u\n", type);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rs);
                        break;
                case DIF_OP_PUSHTV:
                        if (type != DIF_TYPE_CTF)
                                err += efunc(pc, "invalid val type %u\n", type);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rs);
                        break;
                default:
                        err += efunc(pc, "invalid opcode %u\n",
                            DIF_INSTR_OP(instr));
                }
        }

        if (dp->dtdo_len != 0 &&
            DIF_INSTR_OP(dp->dtdo_buf[dp->dtdo_len - 1]) != DIF_OP_RET) {
                err += efunc(dp->dtdo_len - 1,
                    "expected 'ret' as last DIF instruction\n");
        }

        if (!(dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF)) {
                /*
                 * If we're not returning by reference, the size must be either
                 * 0 or the size of one of the base types.
                 */
                switch (dp->dtdo_rtype.dtdt_size) {
                case 0:
                case sizeof (uint8_t):
                case sizeof (uint16_t):
                case sizeof (uint32_t):
                case sizeof (uint64_t):
                        break;

                default:
                        err += efunc(dp->dtdo_len - 1, "bad return size\n");
                }
        }

        for (i = 0; i < dp->dtdo_varlen && err == 0; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i], *existing = NULL;
                dtrace_diftype_t *vt, *et;
                uint_t id, ndx;

                if (v->dtdv_scope != DIFV_SCOPE_GLOBAL &&
                    v->dtdv_scope != DIFV_SCOPE_THREAD &&
                    v->dtdv_scope != DIFV_SCOPE_LOCAL) {
                        err += efunc(i, "unrecognized variable scope %d\n",
                            v->dtdv_scope);
                        break;
                }

                if (v->dtdv_kind != DIFV_KIND_ARRAY &&
                    v->dtdv_kind != DIFV_KIND_SCALAR) {
                        err += efunc(i, "unrecognized variable type %d\n",
                            v->dtdv_kind);
                        break;
                }

                if ((id = v->dtdv_id) > DIF_VARIABLE_MAX) {
                        err += efunc(i, "%d exceeds variable id limit\n", id);
                        break;
                }

                if (id < DIF_VAR_OTHER_UBASE)
                        continue;

                /*
                 * For user-defined variables, we need to check that this
                 * definition is identical to any previous definition that we
                 * encountered.
                 */
                ndx = id - DIF_VAR_OTHER_UBASE;

                switch (v->dtdv_scope) {
                case DIFV_SCOPE_GLOBAL:
                        if (VBDTCAST(int64_t)ndx < vstate->dtvs_nglobals) {
                                dtrace_statvar_t *svar;

                                if ((svar = vstate->dtvs_globals[ndx]) != NULL)
                                        existing = &svar->dtsv_var;
                        }

                        break;

                case DIFV_SCOPE_THREAD:
                        if (VBDTCAST(int64_t)ndx < vstate->dtvs_ntlocals)
                                existing = &vstate->dtvs_tlocals[ndx];
                        break;

                case DIFV_SCOPE_LOCAL:
                        if (VBDTCAST(int64_t)ndx < vstate->dtvs_nlocals) {
                                dtrace_statvar_t *svar;

                                if ((svar = vstate->dtvs_locals[ndx]) != NULL)
                                        existing = &svar->dtsv_var;
                        }

                        break;
                }

                vt = &v->dtdv_type;

                if (vt->dtdt_flags & DIF_TF_BYREF) {
                        if (vt->dtdt_size == 0) {
                                err += efunc(i, "zero-sized variable\n");
                                break;
                        }

                        if (v->dtdv_scope == DIFV_SCOPE_GLOBAL &&
                            vt->dtdt_size > dtrace_global_maxsize) {
                                err += efunc(i, "oversized by-ref global\n");
                                break;
                        }
                }

                if (existing == NULL || existing->dtdv_id == 0)
                        continue;

                ASSERT(existing->dtdv_id == v->dtdv_id);
                ASSERT(existing->dtdv_scope == v->dtdv_scope);

                if (existing->dtdv_kind != v->dtdv_kind)
                        err += efunc(i, "%d changed variable kind\n", id);

                et = &existing->dtdv_type;

                if (vt->dtdt_flags != et->dtdt_flags) {
                        err += efunc(i, "%d changed variable type flags\n", id);
                        break;
                }

                if (vt->dtdt_size != 0 && vt->dtdt_size != et->dtdt_size) {
                        err += efunc(i, "%d changed variable type size\n", id);
                        break;
                }
        }

        return (err);
}

/*
 * Validate a DTrace DIF object that it is to be used as a helper.  Helpers
 * are much more constrained than normal DIFOs.  Specifically, they may
 * not:
 *
 * 1. Make calls to subroutines other than copyin(), copyinstr() or
 *    miscellaneous string routines
 * 2. Access DTrace variables other than the args[] array, and the
 *    curthread, pid, ppid, tid, execname, zonename, uid and gid variables.
 * 3. Have thread-local variables.
 * 4. Have dynamic variables.
 */
static int
dtrace_difo_validate_helper(dtrace_difo_t *dp)
{
        int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
        int err = 0;
        uint_t pc;

        for (pc = 0; pc < dp->dtdo_len; pc++) {
                dif_instr_t instr = dp->dtdo_buf[pc];

                uint_t v = DIF_INSTR_VAR(instr);
                uint_t subr = DIF_INSTR_SUBR(instr);
                uint_t op = DIF_INSTR_OP(instr);

                switch (op) {
                case DIF_OP_OR:
                case DIF_OP_XOR:
                case DIF_OP_AND:
                case DIF_OP_SLL:
                case DIF_OP_SRL:
                case DIF_OP_SRA:
                case DIF_OP_SUB:
                case DIF_OP_ADD:
                case DIF_OP_MUL:
                case DIF_OP_SDIV:
                case DIF_OP_UDIV:
                case DIF_OP_SREM:
                case DIF_OP_UREM:
                case DIF_OP_COPYS:
                case DIF_OP_NOT:
                case DIF_OP_MOV:
                case DIF_OP_RLDSB:
                case DIF_OP_RLDSH:
                case DIF_OP_RLDSW:
                case DIF_OP_RLDUB:
                case DIF_OP_RLDUH:
                case DIF_OP_RLDUW:
                case DIF_OP_RLDX:
                case DIF_OP_ULDSB:
                case DIF_OP_ULDSH:
                case DIF_OP_ULDSW:
                case DIF_OP_ULDUB:
                case DIF_OP_ULDUH:
                case DIF_OP_ULDUW:
                case DIF_OP_ULDX:
                case DIF_OP_STB:
                case DIF_OP_STH:
                case DIF_OP_STW:
                case DIF_OP_STX:
                case DIF_OP_ALLOCS:
                case DIF_OP_CMP:
                case DIF_OP_SCMP:
                case DIF_OP_TST:
                case DIF_OP_BA:
                case DIF_OP_BE:
                case DIF_OP_BNE:
                case DIF_OP_BG:
                case DIF_OP_BGU:
                case DIF_OP_BGE:
                case DIF_OP_BGEU:
                case DIF_OP_BL:
                case DIF_OP_BLU:
                case DIF_OP_BLE:
                case DIF_OP_BLEU:
                case DIF_OP_RET:
                case DIF_OP_NOP:
                case DIF_OP_POPTS:
                case DIF_OP_FLUSHTS:
                case DIF_OP_SETX:
                case DIF_OP_SETS:
                case DIF_OP_LDGA:
                case DIF_OP_LDLS:
                case DIF_OP_STGS:
                case DIF_OP_STLS:
                case DIF_OP_PUSHTR:
                case DIF_OP_PUSHTV:
                        break;

                case DIF_OP_LDGS:
                        if (v >= DIF_VAR_OTHER_UBASE)
                                break;

                        if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9)
                                break;

                        if (v == DIF_VAR_CURTHREAD || v == DIF_VAR_PID ||
                            v == DIF_VAR_PPID || v == DIF_VAR_TID ||
                            v == DIF_VAR_EXECNAME || v == DIF_VAR_ZONENAME ||
                            v == DIF_VAR_UID || v == DIF_VAR_GID)
                                break;

                        err += efunc(pc, "illegal variable %u\n", v);
                        break;

                case DIF_OP_LDTA:
                case DIF_OP_LDTS:
                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA:
                        err += efunc(pc, "illegal dynamic variable load\n");
                        break;

                case DIF_OP_STTS:
                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        err += efunc(pc, "illegal dynamic variable store\n");
                        break;

                case DIF_OP_CALL:
                        if (subr == DIF_SUBR_ALLOCA ||
                            subr == DIF_SUBR_BCOPY ||
                            subr == DIF_SUBR_COPYIN ||
                            subr == DIF_SUBR_COPYINTO ||
                            subr == DIF_SUBR_COPYINSTR ||
                            subr == DIF_SUBR_INDEX ||
                            subr == DIF_SUBR_INET_NTOA ||
                            subr == DIF_SUBR_INET_NTOA6 ||
                            subr == DIF_SUBR_INET_NTOP ||
                            subr == DIF_SUBR_LLTOSTR ||
                            subr == DIF_SUBR_RINDEX ||
                            subr == DIF_SUBR_STRCHR ||
                            subr == DIF_SUBR_STRJOIN ||
                            subr == DIF_SUBR_STRRCHR ||
                            subr == DIF_SUBR_STRSTR ||
                            subr == DIF_SUBR_HTONS ||
                            subr == DIF_SUBR_HTONL ||
                            subr == DIF_SUBR_HTONLL ||
                            subr == DIF_SUBR_NTOHS ||
                            subr == DIF_SUBR_NTOHL ||
                            subr == DIF_SUBR_NTOHLL)
                                break;

                        err += efunc(pc, "invalid subr %u\n", subr);
                        break;

                default:
                        err += efunc(pc, "invalid opcode %u\n",
                            DIF_INSTR_OP(instr));
                }
        }

        return (err);
}

/*
 * Returns 1 if the expression in the DIF object can be cached on a per-thread
 * basis; 0 if not.
 */
static int
dtrace_difo_cacheable(dtrace_difo_t *dp)
{
        VBDTTYPE(uint_t,int) i;

        if (dp == NULL)
                return (0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_scope != DIFV_SCOPE_GLOBAL)
                        continue;

                switch (v->dtdv_id) {
                case DIF_VAR_CURTHREAD:
                case DIF_VAR_PID:
                case DIF_VAR_TID:
                case DIF_VAR_EXECNAME:
                case DIF_VAR_ZONENAME:
                        break;

                default:
                        return (0);
                }
        }

        /*
         * This DIF object may be cacheable.  Now we need to look for any
         * array loading instructions, any memory loading instructions, or
         * any stores to thread-local variables.
         */
        for (i = 0; i < dp->dtdo_len; i++) {
                uint_t op = DIF_INSTR_OP(dp->dtdo_buf[i]);

                if ((op >= DIF_OP_LDSB && op <= DIF_OP_LDX) ||
                    (op >= DIF_OP_ULDSB && op <= DIF_OP_ULDX) ||
                    (op >= DIF_OP_RLDSB && op <= DIF_OP_RLDX) ||
                    op == DIF_OP_LDGA || op == DIF_OP_STTS)
                        return (0);
        }

        return (1);
}

static void
dtrace_difo_hold(dtrace_difo_t *dp)
{
#ifndef VBOX
        VBDTTYPE(uint_t,int) i;
#endif

        ASSERT(MUTEX_HELD(&dtrace_lock));

        dp->dtdo_refcnt++;
        ASSERT(dp->dtdo_refcnt != 0);

#ifndef VBOX
        /*
         * We need to check this DIF object for references to the variable
         * DIF_VAR_VTIMESTAMP.
         */
        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                        continue;

                if (dtrace_vtime_references++ == 0)
                        dtrace_vtime_enable();
        }
#endif
}

/*
 * This routine calculates the dynamic variable chunksize for a given DIF
 * object.  The calculation is not fool-proof, and can probably be tricked by
 * malicious DIF -- but it works for all compiler-generated DIF.  Because this
 * calculation is likely imperfect, dtrace_dynvar() is able to gracefully fail
 * if a dynamic variable size exceeds the chunksize.
 */
static void
dtrace_difo_chunksize(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        uint64_t sval;
        dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
        const dif_instr_t *text = dp->dtdo_buf;
        uint_t pc, srd = 0;
        uint_t ttop = 0;
        size_t size, ksize;
        uint_t id, i;

        for (pc = 0; pc < dp->dtdo_len; pc++) {
                dif_instr_t instr = text[pc];
                uint_t op = DIF_INSTR_OP(instr);
                uint_t rd = DIF_INSTR_RD(instr);
                uint_t r1 = DIF_INSTR_R1(instr);
                uint_t nkeys = 0;
                uchar_t scope;

                dtrace_key_t *key = tupregs;

                switch (op) {
                case DIF_OP_SETX:
                        sval = dp->dtdo_inttab[DIF_INSTR_INTEGER(instr)];
                        srd = rd;
                        continue;

                case DIF_OP_STTS:
                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_size = 0;
                        key[1].dttk_size = 0;
                        nkeys = 2;
                        scope = DIFV_SCOPE_THREAD;
                        break;

                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        nkeys = ttop;

                        if (DIF_INSTR_OP(instr) == DIF_OP_STTAA)
                                key[nkeys++].dttk_size = 0;

                        key[nkeys++].dttk_size = 0;

                        if (op == DIF_OP_STTAA) {
                                scope = DIFV_SCOPE_THREAD;
                        } else {
                                scope = DIFV_SCOPE_GLOBAL;
                        }

                        break;

                case DIF_OP_PUSHTR:
                        if (ttop == DIF_DTR_NREGS)
                                return;

                        if ((srd == 0 || sval == 0) && r1 == DIF_TYPE_STRING) {
                                /*
                                 * If the register for the size of the "pushtr"
                                 * is %r0 (or the value is 0) and the type is
                                 * a string, we'll use the system-wide default
                                 * string size.
                                 */
                                tupregs[ttop++].dttk_size =
                                    dtrace_strsize_default;
                        } else {
                                if (srd == 0)
                                        return;

                                tupregs[ttop++].dttk_size = sval;
                        }

                        break;

                case DIF_OP_PUSHTV:
                        if (ttop == DIF_DTR_NREGS)
                                return;

                        tupregs[ttop++].dttk_size = 0;
                        break;

                case DIF_OP_FLUSHTS:
                        ttop = 0;
                        break;

                case DIF_OP_POPTS:
                        if (ttop != 0)
                                ttop--;
                        break;
                }

                sval = 0;
                srd = 0;

                if (nkeys == 0)
                        continue;

                /*
                 * We have a dynamic variable allocation; calculate its size.
                 */
                for (ksize = 0, i = 0; i < nkeys; i++)
                        ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

                size = sizeof (dtrace_dynvar_t);
                size += sizeof (dtrace_key_t) * (nkeys - 1);
                size += ksize;

                /*
                 * Now we need to determine the size of the stored data.
                 */
                id = DIF_INSTR_VAR(instr);

                for (i = 0; i < dp->dtdo_varlen; i++) {
                        dtrace_difv_t *v = &dp->dtdo_vartab[i];

                        if (v->dtdv_id == id && v->dtdv_scope == scope) {
                                size += v->dtdv_type.dtdt_size;
                                break;
                        }
                }

                if (i == dp->dtdo_varlen)
                        return;

                /*
                 * We have the size.  If this is larger than the chunk size
                 * for our dynamic variable state, reset the chunk size.
                 */
                size = P2ROUNDUP(size, sizeof (uint64_t));

                if (size > vstate->dtvs_dynvars.dtds_chunksize)
                        vstate->dtvs_dynvars.dtds_chunksize = size;
        }
}

static void
dtrace_difo_init(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
#ifndef VBOX
        int i, oldsvars, osz, nsz, otlocals, ntlocals;
#else
        int oldsvars, osz, nsz, otlocals, ntlocals;
        uint_t i;
#endif
        uint_t id;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dp->dtdo_buf != NULL && dp->dtdo_len != 0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_statvar_t *svar, ***svarp;
                size_t dsize = 0;
                uint8_t scope = v->dtdv_scope;
                int *np;

                if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                        continue;

                id -= DIF_VAR_OTHER_UBASE;

                switch (scope) {
                case DIFV_SCOPE_THREAD:
                        while (VBDTCAST(int64_t)id >= (otlocals = vstate->dtvs_ntlocals)) {
                                dtrace_difv_t *tlocals;

                                if ((ntlocals = (otlocals << 1)) == 0)
                                        ntlocals = 1;

                                osz = otlocals * sizeof (dtrace_difv_t);
                                nsz = ntlocals * sizeof (dtrace_difv_t);

                                tlocals = kmem_zalloc(nsz, KM_SLEEP);

                                if (osz != 0) {
                                        bcopy(vstate->dtvs_tlocals,
                                            tlocals, osz);
                                        kmem_free(vstate->dtvs_tlocals, osz);
                                }

                                vstate->dtvs_tlocals = tlocals;
                                vstate->dtvs_ntlocals = ntlocals;
                        }

                        vstate->dtvs_tlocals[id] = *v;
                        continue;

                case DIFV_SCOPE_LOCAL:
                        np = &vstate->dtvs_nlocals;
                        svarp = &vstate->dtvs_locals;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                                dsize = NCPU * (v->dtdv_type.dtdt_size +
                                    sizeof (uint64_t));
                        else
                                dsize = NCPU * sizeof (uint64_t);

                        break;

                case DIFV_SCOPE_GLOBAL:
                        np = &vstate->dtvs_nglobals;
                        svarp = &vstate->dtvs_globals;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                                dsize = v->dtdv_type.dtdt_size +
                                    sizeof (uint64_t);

                        break;

                default:
#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalMsgFailed(("%d\n", scope));
#endif
                }

                while (VBDTCAST(int64_t)id >= (oldsvars = *np)) {
                        dtrace_statvar_t **statics;
                        int newsvars, oldsize, newsize;

                        if ((newsvars = (oldsvars << 1)) == 0)
                                newsvars = 1;

                        oldsize = oldsvars * sizeof (dtrace_statvar_t *);
                        newsize = newsvars * sizeof (dtrace_statvar_t *);

                        statics = kmem_zalloc(newsize, KM_SLEEP);

                        if (oldsize != 0) {
                                bcopy(*svarp, statics, oldsize);
                                kmem_free(*svarp, oldsize);
                        }

                        *svarp = statics;
                        *np = newsvars;
                }

                if ((svar = (*svarp)[id]) == NULL) {
                        svar = kmem_zalloc(sizeof (dtrace_statvar_t), KM_SLEEP);
                        svar->dtsv_var = *v;

                        if ((svar->dtsv_size = dsize) != 0) {
                                svar->dtsv_data = (uint64_t)(uintptr_t)
                                    kmem_zalloc(dsize, KM_SLEEP);
                        }

                        (*svarp)[id] = svar;
                }

                svar->dtsv_refcnt++;
        }

        dtrace_difo_chunksize(dp, vstate);
        dtrace_difo_hold(dp);
}

static dtrace_difo_t *
dtrace_difo_duplicate(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        dtrace_difo_t *new;
        size_t sz;

        ASSERT(dp->dtdo_buf != NULL);
        ASSERT(dp->dtdo_refcnt != 0);

        new = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);

        ASSERT(dp->dtdo_buf != NULL);
        sz = dp->dtdo_len * sizeof (dif_instr_t);
        new->dtdo_buf = kmem_alloc(sz, KM_SLEEP);
        bcopy(dp->dtdo_buf, new->dtdo_buf, sz);
        new->dtdo_len = dp->dtdo_len;

        if (dp->dtdo_strtab != NULL) {
                ASSERT(dp->dtdo_strlen != 0);
                new->dtdo_strtab = kmem_alloc(dp->dtdo_strlen, KM_SLEEP);
                bcopy(dp->dtdo_strtab, new->dtdo_strtab, dp->dtdo_strlen);
                new->dtdo_strlen = dp->dtdo_strlen;
        }

        if (dp->dtdo_inttab != NULL) {
                ASSERT(dp->dtdo_intlen != 0);
                sz = dp->dtdo_intlen * sizeof (uint64_t);
                new->dtdo_inttab = kmem_alloc(sz, KM_SLEEP);
                bcopy(dp->dtdo_inttab, new->dtdo_inttab, sz);
                new->dtdo_intlen = dp->dtdo_intlen;
        }

        if (dp->dtdo_vartab != NULL) {
                ASSERT(dp->dtdo_varlen != 0);
                sz = dp->dtdo_varlen * sizeof (dtrace_difv_t);
                new->dtdo_vartab = kmem_alloc(sz, KM_SLEEP);
                bcopy(dp->dtdo_vartab, new->dtdo_vartab, sz);
                new->dtdo_varlen = dp->dtdo_varlen;
        }

        dtrace_difo_init(new, vstate);
        return (new);
}

static void
dtrace_difo_destroy(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        VBDTTYPE(uint_t,int)  i;

        ASSERT(dp->dtdo_refcnt == 0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_statvar_t *svar, **svarp;
                uint_t id;
                uint8_t scope = v->dtdv_scope;
                int *np;

                switch (scope) {
                case DIFV_SCOPE_THREAD:
                        continue;

                case DIFV_SCOPE_LOCAL:
                        np = &vstate->dtvs_nlocals;
                        svarp = vstate->dtvs_locals;
                        break;

                case DIFV_SCOPE_GLOBAL:
                        np = &vstate->dtvs_nglobals;
                        svarp = vstate->dtvs_globals;
                        break;

                default:
#ifndef VBOX
                        ASSERT(0);
#else
                        AssertFatalMsgFailed(("%d\n", scope));
#endif
                }

                if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                        continue;

                id -= DIF_VAR_OTHER_UBASE;
                ASSERT(VBDTCAST(int64_t)id < *np);

                svar = svarp[id];
                ASSERT(svar != NULL);
                ASSERT(svar->dtsv_refcnt > 0);

                if (--svar->dtsv_refcnt > 0)
                        continue;

                if (svar->dtsv_size != 0) {
                        ASSERT(svar->dtsv_data != NULL);
                        kmem_free((void *)(uintptr_t)svar->dtsv_data,
                            svar->dtsv_size);
                }

                kmem_free(svar, sizeof (dtrace_statvar_t));
                svarp[id] = NULL;
        }

        kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
        kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
        kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
        kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

        kmem_free(dp, sizeof (dtrace_difo_t));
}

static void
dtrace_difo_release(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
#ifndef VBOX
        VBDTTYPE(uint_t,int)  i;
#endif

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dp->dtdo_refcnt != 0);

#ifndef VBOX
        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                        continue;

                ASSERT(dtrace_vtime_references > 0);
                if (--dtrace_vtime_references == 0)
                        dtrace_vtime_disable();
        }
#endif

        if (--dp->dtdo_refcnt == 0)
                dtrace_difo_destroy(dp, vstate);
}

/*
 * DTrace Format Functions
 */
static uint16_t
dtrace_format_add(dtrace_state_t *state, char *str)
{
        char *fmt, **new;
        uint16_t ndx, len = VBDTCAST(uint16_t)strlen(str) + 1;

        fmt = kmem_zalloc(len, KM_SLEEP);
        bcopy(str, fmt, len);

        for (ndx = 0; ndx < state->dts_nformats; ndx++) {
                if (state->dts_formats[ndx] == NULL) {
                        state->dts_formats[ndx] = fmt;
                        return (ndx + 1);
                }
        }

        if (state->dts_nformats == USHRT_MAX) {
                /*
                 * This is only likely if a denial-of-service attack is being
                 * attempted.  As such, it's okay to fail silently here.
                 */
                kmem_free(fmt, len);
                return (0);
        }

        /*
         * For simplicity, we always resize the formats array to be exactly the
         * number of formats.
         */
        ndx = state->dts_nformats++;
        new = kmem_alloc((ndx + 1) * sizeof (char *), KM_SLEEP);

        if (state->dts_formats != NULL) {
                ASSERT(ndx != 0);
                bcopy(state->dts_formats, new, ndx * sizeof (char *));
                kmem_free(state->dts_formats, ndx * sizeof (char *));
        }

        state->dts_formats = new;
        state->dts_formats[ndx] = fmt;

        return (ndx + 1);
}

static void
dtrace_format_remove(dtrace_state_t *state, uint16_t format)
{
        char *fmt;

        ASSERT(state->dts_formats != NULL);
        ASSERT(format <= state->dts_nformats);
        ASSERT(state->dts_formats[format - 1] != NULL);

        fmt = state->dts_formats[format - 1];
        kmem_free(fmt, strlen(fmt) + 1);
        state->dts_formats[format - 1] = NULL;
}

static void
dtrace_format_destroy(dtrace_state_t *state)
{
        int i;

        if (state->dts_nformats == 0) {
                ASSERT(state->dts_formats == NULL);
                return;
        }

        ASSERT(state->dts_formats != NULL);

        for (i = 0; i < state->dts_nformats; i++) {
                char *fmt = state->dts_formats[i];

                if (fmt == NULL)
                        continue;

                kmem_free(fmt, strlen(fmt) + 1);
        }

        kmem_free(state->dts_formats, state->dts_nformats * sizeof (char *));
        state->dts_nformats = 0;
        state->dts_formats = NULL;
}

/*
 * DTrace Predicate Functions
 */
static dtrace_predicate_t *
dtrace_predicate_create(dtrace_difo_t *dp)
{
        dtrace_predicate_t *pred;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dp->dtdo_refcnt != 0);

        pred = kmem_zalloc(sizeof (dtrace_predicate_t), KM_SLEEP);
        pred->dtp_difo = dp;
        pred->dtp_refcnt = 1;

        if (!dtrace_difo_cacheable(dp))
                return (pred);

        if (dtrace_predcache_id == DTRACE_CACHEIDNONE) {
                /*
                 * This is only theoretically possible -- we have had 2^32
                 * cacheable predicates on this machine.  We cannot allow any
                 * more predicates to become cacheable:  as unlikely as it is,
                 * there may be a thread caching a (now stale) predicate cache
                 * ID. (N.B.: the temptation is being successfully resisted to
                 * have this cmn_err() "Holy shit -- we executed this code!")
                 */
                return (pred);
        }

        pred->dtp_cacheid = dtrace_predcache_id++;

        return (pred);
}

static void
dtrace_predicate_hold(dtrace_predicate_t *pred)
{
        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(pred->dtp_difo != NULL && pred->dtp_difo->dtdo_refcnt != 0);
        ASSERT(pred->dtp_refcnt > 0);

        pred->dtp_refcnt++;
}

static void
dtrace_predicate_release(dtrace_predicate_t *pred, dtrace_vstate_t *vstate)
{
        dtrace_difo_t *dp = pred->dtp_difo;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dp != NULL && dp->dtdo_refcnt != 0);
        ASSERT(pred->dtp_refcnt > 0);

        if (--pred->dtp_refcnt == 0) {
                dtrace_difo_release(pred->dtp_difo, vstate);
                kmem_free(pred, sizeof (dtrace_predicate_t));
        }
}

/*
 * DTrace Action Description Functions
 */
static dtrace_actdesc_t *
dtrace_actdesc_create(dtrace_actkind_t kind, uint32_t ntuple,
    uint64_t uarg, uint64_t arg)
{
        dtrace_actdesc_t *act;

        ASSERT(!DTRACEACT_ISPRINTFLIKE(kind) || (arg != NULL &&
            arg >= KERNELBASE) || (arg == NULL && kind == DTRACEACT_PRINTA));

        act = kmem_zalloc(sizeof (dtrace_actdesc_t), KM_SLEEP);
        act->dtad_kind = kind;
        act->dtad_ntuple = ntuple;
        act->dtad_uarg = uarg;
        act->dtad_arg = arg;
        act->dtad_refcnt = 1;

        return (act);
}

static void
dtrace_actdesc_hold(dtrace_actdesc_t *act)
{
        ASSERT(act->dtad_refcnt >= 1);
        act->dtad_refcnt++;
}

static void
dtrace_actdesc_release(dtrace_actdesc_t *act, dtrace_vstate_t *vstate)
{
        dtrace_actkind_t kind = act->dtad_kind;
        dtrace_difo_t *dp;

        ASSERT(act->dtad_refcnt >= 1);

        if (--act->dtad_refcnt != 0)
                return;

        if ((dp = act->dtad_difo) != NULL)
                dtrace_difo_release(dp, vstate);

        if (DTRACEACT_ISPRINTFLIKE(kind)) {
                char *str = (char *)(uintptr_t)act->dtad_arg;

                ASSERT((str != NULL && (uintptr_t)str >= KERNELBASE) ||
                    (str == NULL && act->dtad_kind == DTRACEACT_PRINTA));

                if (str != NULL)
                        kmem_free(str, strlen(str) + 1);
        }

        kmem_free(act, sizeof (dtrace_actdesc_t));
}

/*
 * DTrace ECB Functions
 */
static dtrace_ecb_t *
dtrace_ecb_add(dtrace_state_t *state, dtrace_probe_t *probe)
{
        dtrace_ecb_t *ecb;
        dtrace_epid_t epid;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        ecb = kmem_zalloc(sizeof (dtrace_ecb_t), KM_SLEEP);
        ecb->dte_predicate = NULL;
        ecb->dte_probe = probe;

        /*
         * The default size is the size of the default action: recording
         * the epid.
         */
        ecb->dte_size = ecb->dte_needed = sizeof (dtrace_epid_t);
        ecb->dte_alignment = sizeof (dtrace_epid_t);

        epid = state->dts_epid++;

        if (VBDTCAST(int64_t)epid - 1 >= state->dts_necbs) {
                dtrace_ecb_t **oecbs = state->dts_ecbs, **ecbs;
                int necbs = state->dts_necbs << 1;

                ASSERT(epid == VBDTCAST(dtrace_epid_t)state->dts_necbs + 1);

                if (necbs == 0) {
                        ASSERT(oecbs == NULL);
                        necbs = 1;
                }

                ecbs = kmem_zalloc(necbs * sizeof (*ecbs), KM_SLEEP);

                if (oecbs != NULL)
                        bcopy(oecbs, ecbs, state->dts_necbs * sizeof (*ecbs));

                dtrace_membar_producer();
                state->dts_ecbs = ecbs;

                if (oecbs != NULL) {
                        /*
                         * If this state is active, we must dtrace_sync()
                         * before we can free the old dts_ecbs array:  we're
                         * coming in hot, and there may be active ring
                         * buffer processing (which indexes into the dts_ecbs
                         * array) on another CPU.
                         */
                        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                                dtrace_sync();

                        kmem_free(oecbs, state->dts_necbs * sizeof (*ecbs));
                }

                dtrace_membar_producer();
                state->dts_necbs = necbs;
        }

        ecb->dte_state = state;

        ASSERT(state->dts_ecbs[epid - 1] == NULL);
        dtrace_membar_producer();
        state->dts_ecbs[(ecb->dte_epid = epid) - 1] = ecb;

        return (ecb);
}

static int
dtrace_ecb_enable(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;

        ASSERT(MUTEX_HELD(&cpu_lock));
        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(ecb->dte_next == NULL);

        if (probe == NULL) {
                /*
                 * This is the NULL probe -- there's nothing to do.
                 */
                return (0);
        }

        if (probe->dtpr_ecb == NULL) {
                dtrace_provider_t *prov = probe->dtpr_provider;

                /*
                 * We're the first ECB on this probe.
                 */
                probe->dtpr_ecb = probe->dtpr_ecb_last = ecb;

                if (ecb->dte_predicate != NULL)
                        probe->dtpr_predcache = ecb->dte_predicate->dtp_cacheid;

                return (prov->dtpv_pops.dtps_enable(prov->dtpv_arg,
                    probe->dtpr_id, probe->dtpr_arg));
        } else {
                /*
                 * This probe is already active.  Swing the last pointer to
                 * point to the new ECB, and issue a dtrace_sync() to assure
                 * that all CPUs have seen the change.
                 */
                ASSERT(probe->dtpr_ecb_last != NULL);
                probe->dtpr_ecb_last->dte_next = ecb;
                probe->dtpr_ecb_last = ecb;
                probe->dtpr_predcache = 0;

                dtrace_sync();
                return (0);
        }
}

static void
dtrace_ecb_resize(dtrace_ecb_t *ecb)
{
        uint32_t maxalign = sizeof (dtrace_epid_t);
        uint32_t align = sizeof (uint8_t), offs, diff;
        dtrace_action_t *act;
        int wastuple = 0;
        uint32_t aggbase = UINT32_MAX;
        dtrace_state_t *state = ecb->dte_state;

        /*
         * If we record anything, we always record the epid.  (And we always
         * record it first.)
         */
        offs = sizeof (dtrace_epid_t);
        ecb->dte_size = ecb->dte_needed = sizeof (dtrace_epid_t);

        for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                dtrace_recdesc_t *rec = &act->dta_rec;

                if ((align = rec->dtrd_alignment) > maxalign)
                        maxalign = align;

                if (!wastuple && act->dta_intuple) {
                        /*
                         * This is the first record in a tuple.  Align the
                         * offset to be at offset 4 in an 8-byte aligned
                         * block.
                         */
                        diff = offs + sizeof (dtrace_aggid_t);

                        if ((diff = (diff & (sizeof (uint64_t) - 1))))
                                offs += sizeof (uint64_t) - diff;

                        aggbase = offs - sizeof (dtrace_aggid_t);
                        ASSERT(!(aggbase & (sizeof (uint64_t) - 1)));
                }

                /*LINTED*/
                if (rec->dtrd_size != 0 && (diff = (offs & (align - 1)))) {
                        /*
                         * The current offset is not properly aligned; align it.
                         */
                        offs += align - diff;
                }

                rec->dtrd_offset = offs;

                if (offs + rec->dtrd_size > ecb->dte_needed) {
                        ecb->dte_needed = offs + rec->dtrd_size;

                        if (ecb->dte_needed > state->dts_needed)
                                state->dts_needed = ecb->dte_needed;
                }

                if (DTRACEACT_ISAGG(act->dta_kind)) {
                        dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;
                        dtrace_action_t *first = agg->dtag_first, *prev;

                        ASSERT(rec->dtrd_size != 0 && first != NULL);
                        ASSERT(wastuple);
                        ASSERT(aggbase != UINT32_MAX);

                        agg->dtag_base = aggbase;

                        while ((prev = first->dta_prev) != NULL &&
                            DTRACEACT_ISAGG(prev->dta_kind)) {
                                agg = (dtrace_aggregation_t *)prev;
                                first = agg->dtag_first;
                        }

                        if (prev != NULL) {
                                offs = prev->dta_rec.dtrd_offset +
                                    prev->dta_rec.dtrd_size;
                        } else {
                                offs = sizeof (dtrace_epid_t);
                        }
                        wastuple = 0;
                } else {
                        if (!act->dta_intuple)
                                ecb->dte_size = offs + rec->dtrd_size;

                        offs += rec->dtrd_size;
                }

                wastuple = act->dta_intuple;
        }

        if ((act = ecb->dte_action) != NULL &&
            !(act->dta_kind == DTRACEACT_SPECULATE && act->dta_next == NULL) &&
            ecb->dte_size == sizeof (dtrace_epid_t)) {
                /*
                 * If the size is still sizeof (dtrace_epid_t), then all
                 * actions store no data; set the size to 0.
                 */
                ecb->dte_alignment = maxalign;
                ecb->dte_size = 0;

                /*
                 * If the needed space is still sizeof (dtrace_epid_t), then
                 * all actions need no additional space; set the needed
                 * size to 0.
                 */
                if (ecb->dte_needed == sizeof (dtrace_epid_t))
                        ecb->dte_needed = 0;

                return;
        }

        /*
         * Set our alignment, and make sure that the dte_size and dte_needed
         * are aligned to the size of an EPID.
         */
        ecb->dte_alignment = maxalign;
        ecb->dte_size = (ecb->dte_size + (sizeof (dtrace_epid_t) - 1)) &
            ~(sizeof (dtrace_epid_t) - 1);
        ecb->dte_needed = (ecb->dte_needed + (sizeof (dtrace_epid_t) - 1)) &
            ~(sizeof (dtrace_epid_t) - 1);
        ASSERT(ecb->dte_size <= ecb->dte_needed);
}

static dtrace_action_t *
dtrace_ecb_aggregation_create(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
        dtrace_aggregation_t *agg;
        size_t size = sizeof (uint64_t);
        int ntuple = desc->dtad_ntuple;
        dtrace_action_t *act;
        dtrace_recdesc_t *frec;
        dtrace_aggid_t aggid;
        dtrace_state_t *state = ecb->dte_state;

        agg = kmem_zalloc(sizeof (dtrace_aggregation_t), KM_SLEEP);
        agg->dtag_ecb = ecb;

        ASSERT(DTRACEACT_ISAGG(desc->dtad_kind));

        switch (desc->dtad_kind) {
        case DTRACEAGG_MIN:
                agg->dtag_initial = INT64_MAX;
                agg->dtag_aggregate = dtrace_aggregate_min;
                break;

        case DTRACEAGG_MAX:
                agg->dtag_initial = INT64_MIN;
                agg->dtag_aggregate = dtrace_aggregate_max;
                break;

        case DTRACEAGG_COUNT:
                agg->dtag_aggregate = dtrace_aggregate_count;
                break;

        case DTRACEAGG_QUANTIZE:
                agg->dtag_aggregate = dtrace_aggregate_quantize;
                size = (((sizeof (uint64_t) * NBBY) - 1) * 2 + 1) *
                    sizeof (uint64_t);
                break;

        case DTRACEAGG_LQUANTIZE: {
                uint16_t step = DTRACE_LQUANTIZE_STEP(desc->dtad_arg);
                uint16_t levels = DTRACE_LQUANTIZE_LEVELS(desc->dtad_arg);

                agg->dtag_initial = desc->dtad_arg;
                agg->dtag_aggregate = dtrace_aggregate_lquantize;

                if (step == 0 || levels == 0)
                        goto err;

                size = levels * sizeof (uint64_t) + 3 * sizeof (uint64_t);
                break;
        }

        case DTRACEAGG_AVG:
                agg->dtag_aggregate = dtrace_aggregate_avg;
                size = sizeof (uint64_t) * 2;
                break;

        case DTRACEAGG_STDDEV:
                agg->dtag_aggregate = dtrace_aggregate_stddev;
                size = sizeof (uint64_t) * 4;
                break;

        case DTRACEAGG_SUM:
                agg->dtag_aggregate = dtrace_aggregate_sum;
                break;

        default:
                goto err;
        }

        agg->dtag_action.dta_rec.dtrd_size = VBDTCAST(uint32_t)size;

        if (ntuple == 0)
                goto err;

        /*
         * We must make sure that we have enough actions for the n-tuple.
         */
        for (act = ecb->dte_action_last; act != NULL; act = act->dta_prev) {
                if (DTRACEACT_ISAGG(act->dta_kind))
                        break;

                if (--ntuple == 0) {
                        /*
                         * This is the action with which our n-tuple begins.
                         */
                        agg->dtag_first = act;
                        goto success;
                }
        }

        /*
         * This n-tuple is short by ntuple elements.  Return failure.
         */
        ASSERT(ntuple != 0);
err:
        kmem_free(agg, sizeof (dtrace_aggregation_t));
        return (NULL);

success:
        /*
         * If the last action in the tuple has a size of zero, it's actually
         * an expression argument for the aggregating action.
         */
        ASSERT(ecb->dte_action_last != NULL);
        act = ecb->dte_action_last;

        if (act->dta_kind == DTRACEACT_DIFEXPR) {
                ASSERT(act->dta_difo != NULL);

                if (act->dta_difo->dtdo_rtype.dtdt_size == 0)
                        agg->dtag_hasarg = 1;
        }

        /*
         * We need to allocate an id for this aggregation.
         */
        aggid = (dtrace_aggid_t)(uintptr_t)vmem_alloc(state->dts_aggid_arena, 1,
            VM_BESTFIT | VM_SLEEP);

        if (VBDTCAST(int64_t)aggid - 1 >= state->dts_naggregations) {
                dtrace_aggregation_t **oaggs = state->dts_aggregations;
                dtrace_aggregation_t **aggs;
                int naggs = state->dts_naggregations << 1;
                int onaggs = state->dts_naggregations;

                ASSERT(aggid == VBDTCAST(dtrace_aggid_t)state->dts_naggregations + 1);

                if (naggs == 0) {
                        ASSERT(oaggs == NULL);
                        naggs = 1;
                }

                aggs = kmem_zalloc(naggs * sizeof (*aggs), KM_SLEEP);

                if (oaggs != NULL) {
                        bcopy(oaggs, aggs, onaggs * sizeof (*aggs));
                        kmem_free(oaggs, onaggs * sizeof (*aggs));
                }

                state->dts_aggregations = aggs;
                state->dts_naggregations = naggs;
        }

        ASSERT(state->dts_aggregations[aggid - 1] == NULL);
        state->dts_aggregations[(agg->dtag_id = aggid) - 1] = agg;

        frec = &agg->dtag_first->dta_rec;
        if (frec->dtrd_alignment < sizeof (dtrace_aggid_t))
                frec->dtrd_alignment = sizeof (dtrace_aggid_t);

        for (act = agg->dtag_first; act != NULL; act = act->dta_next) {
                ASSERT(!act->dta_intuple);
                act->dta_intuple = 1;
        }

        return (&agg->dtag_action);
}

static void
dtrace_ecb_aggregation_destroy(dtrace_ecb_t *ecb, dtrace_action_t *act)
{
        dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;
        dtrace_state_t *state = ecb->dte_state;
        dtrace_aggid_t aggid = agg->dtag_id;

        ASSERT(DTRACEACT_ISAGG(act->dta_kind));
        vmem_free(state->dts_aggid_arena, (void *)(uintptr_t)aggid, 1);

        ASSERT(state->dts_aggregations[aggid - 1] == agg);
        state->dts_aggregations[aggid - 1] = NULL;

        kmem_free(agg, sizeof (dtrace_aggregation_t));
}

static int
dtrace_ecb_action_add(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
        dtrace_action_t *action, *last;
        dtrace_difo_t *dp = desc->dtad_difo;
        uint32_t size = 0, align = sizeof (uint8_t), mask;
        uint16_t format = 0;
        dtrace_recdesc_t *rec;
        dtrace_state_t *state = ecb->dte_state;
        dtrace_optval_t *opt = state->dts_options, nframes VBDTUNASS(0), strsize;
        uint64_t arg = desc->dtad_arg;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(ecb->dte_action == NULL || ecb->dte_action->dta_refcnt == 1);

        if (DTRACEACT_ISAGG(desc->dtad_kind)) {
                /*
                 * If this is an aggregating action, there must be neither
                 * a speculate nor a commit on the action chain.
                 */
                dtrace_action_t *act;

                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (act->dta_kind == DTRACEACT_COMMIT)
                                return (EINVAL);

                        if (act->dta_kind == DTRACEACT_SPECULATE)
                                return (EINVAL);
                }

                action = dtrace_ecb_aggregation_create(ecb, desc);

                if (action == NULL)
                        return (EINVAL);
        } else {
                if (DTRACEACT_ISDESTRUCTIVE(desc->dtad_kind) ||
                    (desc->dtad_kind == DTRACEACT_DIFEXPR &&
                    dp != NULL && dp->dtdo_destructive)) {
                        state->dts_destructive = 1;
                }

                switch (desc->dtad_kind) {
                case DTRACEACT_PRINTF:
                case DTRACEACT_PRINTA:
                case DTRACEACT_SYSTEM:
                case DTRACEACT_FREOPEN:
                        /*
                         * We know that our arg is a string -- turn it into a
                         * format.
                         */
                        if (arg == NULL) {
                                ASSERT(desc->dtad_kind == DTRACEACT_PRINTA);
                                format = 0;
                        } else {
                                ASSERT(arg != NULL);
                                ASSERT(arg > KERNELBASE);
                                format = dtrace_format_add(state,
                                    (char *)(uintptr_t)arg);
                        }

                        /*FALLTHROUGH*/
                case DTRACEACT_LIBACT:
                case DTRACEACT_DIFEXPR:
                        if (dp == NULL)
                                return (EINVAL);

                        if ((size = dp->dtdo_rtype.dtdt_size) != 0)
                                break;

                        if (dp->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING) {
                                if (!(dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                        return (EINVAL);

                                size = opt[DTRACEOPT_STRSIZE];
                        }

                        break;

                case DTRACEACT_STACK:
                        if ((nframes = arg) == 0) {
                                nframes = opt[DTRACEOPT_STACKFRAMES];
                                ASSERT(nframes > 0);
                                arg = nframes;
                        }

                        size = VBDTCAST(uint32_t)(nframes * sizeof (pc_t));
                        break;

                case DTRACEACT_JSTACK:
                        if ((strsize = DTRACE_USTACK_STRSIZE(arg)) == 0)
                                strsize = opt[DTRACEOPT_JSTACKSTRSIZE];

                        if ((nframes = DTRACE_USTACK_NFRAMES(arg)) == 0)
                                nframes = opt[DTRACEOPT_JSTACKFRAMES];

                        arg = DTRACE_USTACK_ARG(nframes, strsize);

                        /*FALLTHROUGH*/
                case DTRACEACT_USTACK:
                        if (desc->dtad_kind != DTRACEACT_JSTACK &&
                            (nframes = DTRACE_USTACK_NFRAMES(arg)) == 0) {
                                strsize = DTRACE_USTACK_STRSIZE(arg);
                                nframes = opt[DTRACEOPT_USTACKFRAMES];
                                ASSERT(nframes > 0);
                                arg = DTRACE_USTACK_ARG(nframes, strsize);
                        }

                        /*
                         * Save a slot for the pid.
                         */
                        size = VBDTCAST(uint32_t)((nframes + 1) * sizeof (uint64_t));
                        size += DTRACE_USTACK_STRSIZE(arg);
                        size = P2ROUNDUP(size, (uint32_t)(sizeof (uintptr_t)));

                        break;

                case DTRACEACT_SYM:
                case DTRACEACT_MOD:
                        if (dp == NULL || ((size = dp->dtdo_rtype.dtdt_size) !=
                            sizeof (uint64_t)) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);
                        break;

                case DTRACEACT_USYM:
                case DTRACEACT_UMOD:
                case DTRACEACT_UADDR:
                        if (dp == NULL ||
                            (dp->dtdo_rtype.dtdt_size != sizeof (uint64_t)) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);

                        /*
                         * We have a slot for the pid, plus a slot for the
                         * argument.  To keep things simple (aligned with
                         * bitness-neutral sizing), we store each as a 64-bit
                         * quantity.
                         */
                        size = 2 * sizeof (uint64_t);
                        break;

                case DTRACEACT_STOP:
                case DTRACEACT_BREAKPOINT:
                case DTRACEACT_PANIC:
                        break;

                case DTRACEACT_CHILL:
                case DTRACEACT_DISCARD:
                case DTRACEACT_RAISE:
                        if (dp == NULL)
                                return (EINVAL);
                        break;

                case DTRACEACT_EXIT:
                        if (dp == NULL ||
                            (size = dp->dtdo_rtype.dtdt_size) != sizeof (int) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);
                        break;

                case DTRACEACT_SPECULATE:
                        if (ecb->dte_size > sizeof (dtrace_epid_t))
                                return (EINVAL);

                        if (dp == NULL)
                                return (EINVAL);

                        state->dts_speculates = 1;
                        break;

                case DTRACEACT_COMMIT: {
                        dtrace_action_t *act = ecb->dte_action;

                        for (; act != NULL; act = act->dta_next) {
                                if (act->dta_kind == DTRACEACT_COMMIT)
                                        return (EINVAL);
                        }

                        if (dp == NULL)
                                return (EINVAL);
                        break;
                }

                default:
                        return (EINVAL);
                }

                if (size != 0 || desc->dtad_kind == DTRACEACT_SPECULATE) {
                        /*
                         * If this is a data-storing action or a speculate,
                         * we must be sure that there isn't a commit on the
                         * action chain.
                         */
                        dtrace_action_t *act = ecb->dte_action;

                        for (; act != NULL; act = act->dta_next) {
                                if (act->dta_kind == DTRACEACT_COMMIT)
                                        return (EINVAL);
                        }
                }

                action = kmem_zalloc(sizeof (dtrace_action_t), KM_SLEEP);
                action->dta_rec.dtrd_size = size;
        }

        action->dta_refcnt = 1;
        rec = &action->dta_rec;
        size = rec->dtrd_size;

        for (mask = sizeof (uint64_t) - 1; size != 0 && mask > 0; mask >>= 1) {
                if (!(size & mask)) {
                        align = mask + 1;
                        break;
                }
        }

        action->dta_kind = desc->dtad_kind;

        if ((action->dta_difo = dp) != NULL)
                dtrace_difo_hold(dp);

        rec->dtrd_action = action->dta_kind;
        rec->dtrd_arg = arg;
        rec->dtrd_uarg = desc->dtad_uarg;
        rec->dtrd_alignment = (uint16_t)align;
        rec->dtrd_format = format;

        if ((last = ecb->dte_action_last) != NULL) {
                ASSERT(ecb->dte_action != NULL);
                action->dta_prev = last;
                last->dta_next = action;
        } else {
                ASSERT(ecb->dte_action == NULL);
                ecb->dte_action = action;
        }

        ecb->dte_action_last = action;

        return (0);
}

static void
dtrace_ecb_action_remove(dtrace_ecb_t *ecb)
{
        dtrace_action_t *act = ecb->dte_action, *next;
        dtrace_vstate_t *vstate = &ecb->dte_state->dts_vstate;
        dtrace_difo_t *dp;
        uint16_t format;

        if (act != NULL && act->dta_refcnt > 1) {
                ASSERT(act->dta_next == NULL || act->dta_next->dta_refcnt == 1);
                act->dta_refcnt--;
        } else {
                for (; act != NULL; act = next) {
                        next = act->dta_next;
                        ASSERT(next != NULL || act == ecb->dte_action_last);
                        ASSERT(act->dta_refcnt == 1);

                        if ((format = act->dta_rec.dtrd_format) != 0)
                                dtrace_format_remove(ecb->dte_state, format);

                        if ((dp = act->dta_difo) != NULL)
                                dtrace_difo_release(dp, vstate);

                        if (DTRACEACT_ISAGG(act->dta_kind)) {
                                dtrace_ecb_aggregation_destroy(ecb, act);
                        } else {
                                kmem_free(act, sizeof (dtrace_action_t));
                        }
                }
        }

        ecb->dte_action = NULL;
        ecb->dte_action_last = NULL;
        ecb->dte_size = sizeof (dtrace_epid_t);
}

static void
dtrace_ecb_disable(dtrace_ecb_t *ecb)
{
        /*
         * We disable the ECB by removing it from its probe.
         */
        dtrace_ecb_t *pecb, *prev = NULL;
        dtrace_probe_t *probe = ecb->dte_probe;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (probe == NULL) {
                /*
                 * This is the NULL probe; there is nothing to disable.
                 */
                return;
        }

        for (pecb = probe->dtpr_ecb; pecb != NULL; pecb = pecb->dte_next) {
                if (pecb == ecb)
                        break;
                prev = pecb;
        }

        ASSERT(pecb != NULL);

        if (prev == NULL) {
                probe->dtpr_ecb = ecb->dte_next;
        } else {
                prev->dte_next = ecb->dte_next;
        }

        if (ecb == probe->dtpr_ecb_last) {
                ASSERT(ecb->dte_next == NULL);
                probe->dtpr_ecb_last = prev;
        }

        /*
         * The ECB has been disconnected from the probe; now sync to assure
         * that all CPUs have seen the change before returning.
         */
        dtrace_sync();

        if (probe->dtpr_ecb == NULL) {
                /*
                 * That was the last ECB on the probe; clear the predicate
                 * cache ID for the probe, disable it and sync one more time
                 * to assure that we'll never hit it again.
                 */
                dtrace_provider_t *prov = probe->dtpr_provider;

                ASSERT(ecb->dte_next == NULL);
                ASSERT(probe->dtpr_ecb_last == NULL);
                probe->dtpr_predcache = DTRACE_CACHEIDNONE;
                prov->dtpv_pops.dtps_disable(prov->dtpv_arg,
                    probe->dtpr_id, probe->dtpr_arg);
                dtrace_sync();
        } else {
                /*
                 * There is at least one ECB remaining on the probe.  If there
                 * is _exactly_ one, set the probe's predicate cache ID to be
                 * the predicate cache ID of the remaining ECB.
                 */
                ASSERT(probe->dtpr_ecb_last != NULL);
                ASSERT(probe->dtpr_predcache == DTRACE_CACHEIDNONE);

                if (probe->dtpr_ecb == probe->dtpr_ecb_last) {
                        dtrace_predicate_t *p = probe->dtpr_ecb->dte_predicate;

                        ASSERT(probe->dtpr_ecb->dte_next == NULL);

                        if (p != NULL)
                                probe->dtpr_predcache = p->dtp_cacheid;
                }

                ecb->dte_next = NULL;
        }
}

static void
dtrace_ecb_destroy(dtrace_ecb_t *ecb)
{
        dtrace_state_t *state = ecb->dte_state;
        dtrace_vstate_t *vstate = &state->dts_vstate;
        dtrace_predicate_t *pred;
        dtrace_epid_t epid = ecb->dte_epid;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(ecb->dte_next == NULL);
        ASSERT(ecb->dte_probe == NULL || ecb->dte_probe->dtpr_ecb != ecb);

        if ((pred = ecb->dte_predicate) != NULL)
                dtrace_predicate_release(pred, vstate);

        dtrace_ecb_action_remove(ecb);

        ASSERT(state->dts_ecbs[epid - 1] == ecb);
        state->dts_ecbs[epid - 1] = NULL;

        kmem_free(ecb, sizeof (dtrace_ecb_t));
}

static dtrace_ecb_t *
dtrace_ecb_create(dtrace_state_t *state, dtrace_probe_t *probe,
    dtrace_enabling_t *enab)
{
        dtrace_ecb_t *ecb;
        dtrace_predicate_t *pred;
        dtrace_actdesc_t *act;
        dtrace_provider_t *prov;
        dtrace_ecbdesc_t *desc = enab->dten_current;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(state != NULL);

        ecb = dtrace_ecb_add(state, probe);
        ecb->dte_uarg = desc->dted_uarg;

        if ((pred = desc->dted_pred.dtpdd_predicate) != NULL) {
                dtrace_predicate_hold(pred);
                ecb->dte_predicate = pred;
        }

        if (probe != NULL) {
                /*
                 * If the provider shows more leg than the consumer is old
                 * enough to see, we need to enable the appropriate implicit
                 * predicate bits to prevent the ecb from activating at
                 * revealing times.
                 *
                 * Providers specifying DTRACE_PRIV_USER at register time
                 * are stating that they need the /proc-style privilege
                 * model to be enforced, and this is what DTRACE_COND_OWNER
                 * and DTRACE_COND_ZONEOWNER will then do at probe time.
                 */
                prov = probe->dtpr_provider;
                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLPROC) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                        ecb->dte_cond |= DTRACE_COND_OWNER;

                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLZONE) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                        ecb->dte_cond |= DTRACE_COND_ZONEOWNER;

                /*
                 * If the provider shows us kernel innards and the user
                 * is lacking sufficient privilege, enable the
                 * DTRACE_COND_USERMODE implicit predicate.
                 */
                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_KERNEL))
                        ecb->dte_cond |= DTRACE_COND_USERMODE;
        }

        if (dtrace_ecb_create_cache != NULL) {
                /*
                 * If we have a cached ecb, we'll use its action list instead
                 * of creating our own (saving both time and space).
                 */
                dtrace_ecb_t *cached = dtrace_ecb_create_cache;
                dtrace_action_t *act2 = cached->dte_action;

                if (act2 != NULL) {
                        ASSERT(act2->dta_refcnt > 0);
                        act2->dta_refcnt++;
                        ecb->dte_action = act2;
                        ecb->dte_action_last = cached->dte_action_last;
                        ecb->dte_needed = cached->dte_needed;
                        ecb->dte_size = cached->dte_size;
                        ecb->dte_alignment = cached->dte_alignment;
                }

                return (ecb);
        }

        for (act = desc->dted_action; act != NULL; act = act->dtad_next) {
                if ((enab->dten_error = dtrace_ecb_action_add(ecb, act)) != 0) {
                        dtrace_ecb_destroy(ecb);
                        return (NULL);
                }
        }

        dtrace_ecb_resize(ecb);

        return (dtrace_ecb_create_cache = ecb);
}

static int
dtrace_ecb_create_enable(dtrace_probe_t *probe, void *arg)
{
        dtrace_ecb_t *ecb;
        dtrace_enabling_t *enab = arg;
        dtrace_state_t *state = enab->dten_vstate->dtvs_state;

        ASSERT(state != NULL);

        if (probe != NULL && probe->dtpr_gen < enab->dten_probegen) {
                /*
                 * This probe was created in a generation for which this
                 * enabling has previously created ECBs; we don't want to
                 * enable it again, so just kick out.
                 */
                return (DTRACE_MATCH_NEXT);
        }

        if ((ecb = dtrace_ecb_create(state, probe, enab)) == NULL)
                return (DTRACE_MATCH_DONE);

        if (dtrace_ecb_enable(ecb) < 0)
                return (DTRACE_MATCH_FAIL);

        return (DTRACE_MATCH_NEXT);
}

static dtrace_ecb_t *
dtrace_epid2ecb(dtrace_state_t *state, dtrace_epid_t id)
{
        dtrace_ecb_t *ecb;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (id == 0 || VBDTCAST(int64_t)id > state->dts_necbs)
                return (NULL);

        ASSERT(state->dts_necbs > 0 && state->dts_ecbs != NULL);
        ASSERT((ecb = state->dts_ecbs[id - 1]) == NULL || ecb->dte_epid == id);

        return (state->dts_ecbs[id - 1]);
}

static dtrace_aggregation_t *
dtrace_aggid2agg(dtrace_state_t *state, dtrace_aggid_t id)
{
        dtrace_aggregation_t *agg;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (id == 0 || VBDTCAST(int64_t)id > state->dts_naggregations)
                return (NULL);

        ASSERT(state->dts_naggregations > 0 && state->dts_aggregations != NULL);
        ASSERT((agg = state->dts_aggregations[id - 1]) == NULL ||
            agg->dtag_id == id);

        return (state->dts_aggregations[id - 1]);
}

/*
 * DTrace Buffer Functions
 *
 * The following functions manipulate DTrace buffers.  Most of these functions
 * are called in the context of establishing or processing consumer state;
 * exceptions are explicitly noted.
 */

/*
 * Note:  called from cross call context.  This function switches the two
 * buffers on a given CPU.  The atomicity of this operation is assured by
 * disabling interrupts while the actual switch takes place; the disabling of
 * interrupts serializes the execution with any execution of dtrace_probe() on
 * the same CPU.
 */
static void
dtrace_buffer_switch(dtrace_buffer_t *buf)
{
        caddr_t tomax = buf->dtb_tomax;
        caddr_t xamot = buf->dtb_xamot;
        dtrace_icookie_t cookie;

        ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
        ASSERT(!(buf->dtb_flags & DTRACEBUF_RING));

        cookie = dtrace_interrupt_disable();
        buf->dtb_tomax = xamot;
        buf->dtb_xamot = tomax;
        buf->dtb_xamot_drops = buf->dtb_drops;
        buf->dtb_xamot_offset = buf->dtb_offset;
        buf->dtb_xamot_errors = buf->dtb_errors;
        buf->dtb_xamot_flags = buf->dtb_flags;
        buf->dtb_offset = 0;
        buf->dtb_drops = 0;
        buf->dtb_errors = 0;
        buf->dtb_flags &= ~(DTRACEBUF_ERROR | DTRACEBUF_DROPPED);
        dtrace_interrupt_enable(cookie);
}

/*
 * Note:  called from cross call context.  This function activates a buffer
 * on a CPU.  As with dtrace_buffer_switch(), the atomicity of the operation
 * is guaranteed by the disabling of interrupts.
 */
static void
dtrace_buffer_activate(dtrace_state_t *state)
{
        dtrace_buffer_t *buf;
        dtrace_icookie_t cookie = dtrace_interrupt_disable();

        buf = &state->dts_buffer[VBDT_GET_CPUID()];

        if (buf->dtb_tomax != NULL) {
                /*
                 * We might like to assert that the buffer is marked inactive,
                 * but this isn't necessarily true:  the buffer for the CPU
                 * that processes the BEGIN probe has its buffer activated
                 * manually.  In this case, we take the (harmless) action
                 * re-clearing the bit INACTIVE bit.
                 */
                buf->dtb_flags &= ~DTRACEBUF_INACTIVE;
        }

        dtrace_interrupt_enable(cookie);
}

static int
dtrace_buffer_alloc(dtrace_buffer_t *bufs, size_t size, int flags,
    processorid_t cpu)
{
#ifndef VBOX
        cpu_t *cp;
#else
        RTCPUSET CpuSet;
        unsigned iCpu;
#endif
        dtrace_buffer_t *buf;

        ASSERT(MUTEX_HELD(&cpu_lock));
        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (VBDTCAST(int64_t)size > dtrace_nonroot_maxsize
#ifndef VBOX
            && !PRIV_POLICY_CHOICE(CRED(), PRIV_ALL, B_FALSE)
#endif
            )
                return (EFBIG);

#ifndef VBOX
        cp = cpu_list;
#else
        RTMpGetSet(&CpuSet);
#endif

#ifndef VBOX
        do {
                if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                        continue;

                buf = &bufs[cp->cpu_id];
#else
    for (iCpu = 0; iCpu < RTCPUSET_MAX_CPUS; iCpu++) {
                if (   !RTCpuSetIsMember(&CpuSet, iCpu)
                        || (cpu != (processorid_t)DTRACE_CPUALL && cpu != iCpu))
                        continue;

                buf = &bufs[iCpu];
#endif

                /*
                 * If there is already a buffer allocated for this CPU, it
                 * is only possible that this is a DR event.  In this case,
                 * the buffer size must match our specified size.
                 */
                if (buf->dtb_tomax != NULL) {
                        ASSERT(buf->dtb_size == size);
                        continue;
                }

                ASSERT(buf->dtb_xamot == NULL);

                if ((buf->dtb_tomax = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                        goto err;

                buf->dtb_size = size;
                buf->dtb_flags = flags;
                buf->dtb_offset = 0;
                buf->dtb_drops = 0;

                if (flags & DTRACEBUF_NOSWITCH)
                        continue;

                if ((buf->dtb_xamot = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                        goto err;
#ifndef VBOX
        } while ((cp = cp->cpu_next) != cpu_list);
#else
        }
#endif

        return (0);

err:
#ifndef VBOX
        cp = cpu_list;

        do {
                if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                        continue;

                buf = &bufs[cp->cpu_id];
#else
                for (iCpu = 0; iCpu < RTCPUSET_MAX_CPUS; iCpu++) {
                        if (   !RTCpuSetIsMember(&CpuSet, iCpu)
                                || (cpu != (processorid_t)DTRACE_CPUALL && cpu != iCpu))
                                continue;

                        buf = &bufs[iCpu];
#endif

                if (buf->dtb_xamot != NULL) {
                        ASSERT(buf->dtb_tomax != NULL);
                        ASSERT(buf->dtb_size == size);
                        kmem_free(buf->dtb_xamot, size);
                }

                if (buf->dtb_tomax != NULL) {
                        ASSERT(buf->dtb_size == size);
                        kmem_free(buf->dtb_tomax, size);
                }

                buf->dtb_tomax = NULL;
                buf->dtb_xamot = NULL;
                buf->dtb_size = 0;
#ifndef VBOX
        } while ((cp = cp->cpu_next) != cpu_list);
#else
        }
#endif

        return (ENOMEM);
}

/*
 * Note:  called from probe context.  This function just increments the drop
 * count on a buffer.  It has been made a function to allow for the
 * possibility of understanding the source of mysterious drop counts.  (A
 * problem for which one may be particularly disappointed that DTrace cannot
 * be used to understand DTrace.)
 */
static void
dtrace_buffer_drop(dtrace_buffer_t *buf)
{
        buf->dtb_drops++;
}

/*
 * Note:  called from probe context.  This function is called to reserve space
 * in a buffer.  If mstate is non-NULL, sets the scratch base and size in the
 * mstate.  Returns the new offset in the buffer, or a negative value if an
 * error has occurred.
 */
static intptr_t
dtrace_buffer_reserve(dtrace_buffer_t *buf, size_t needed, size_t align,
    dtrace_state_t *state, dtrace_mstate_t *mstate)
{
        intptr_t offs = buf->dtb_offset, soffs;
        intptr_t woffs;
        caddr_t tomax;
        size_t total;

        if (buf->dtb_flags & DTRACEBUF_INACTIVE)
                return (-1);

        if ((tomax = buf->dtb_tomax) == NULL) {
                dtrace_buffer_drop(buf);
                return (-1);
        }

        if (!(buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL))) {
                while (offs & (align - 1)) {
                        /*
                         * Assert that our alignment is off by a number which
                         * is itself sizeof (uint32_t) aligned.
                         */
                        ASSERT(!((align - (offs & (align - 1))) &
                            (sizeof (uint32_t) - 1)));
                        DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
                        offs += sizeof (uint32_t);
                }

                if (VBDTCAST(uintptr_t)(soffs = offs + needed) > buf->dtb_size) {
                        dtrace_buffer_drop(buf);
                        return (-1);
                }

                if (mstate == NULL)
                        return (offs);

                mstate->dtms_scratch_base = (uintptr_t)tomax + soffs;
                mstate->dtms_scratch_size = buf->dtb_size - soffs;
                mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

                return (offs);
        }

        if (buf->dtb_flags & DTRACEBUF_FILL) {
                if (state->dts_activity != DTRACE_ACTIVITY_COOLDOWN &&
                    (buf->dtb_flags & DTRACEBUF_FULL))
                        return (-1);
                goto out;
        }

        total = needed + (offs & (align - 1));

        /*
         * For a ring buffer, life is quite a bit more complicated.  Before
         * we can store any padding, we need to adjust our wrapping offset.
         * (If we've never before wrapped or we're not about to, no adjustment
         * is required.)
         */
        if ((buf->dtb_flags & DTRACEBUF_WRAPPED) ||
            offs + total > buf->dtb_size) {
                woffs = buf->dtb_xamot_offset;

                if (offs + total > buf->dtb_size) {
                        /*
                         * We can't fit in the end of the buffer.  First, a
                         * sanity check that we can fit in the buffer at all.
                         */
                        if (total > buf->dtb_size) {
                                dtrace_buffer_drop(buf);
                                return (-1);
                        }

                        /*
                         * We're going to be storing at the top of the buffer,
                         * so now we need to deal with the wrapped offset.  We
                         * only reset our wrapped offset to 0 if it is
                         * currently greater than the current offset.  If it
                         * is less than the current offset, it is because a
                         * previous allocation induced a wrap -- but the
                         * allocation didn't subsequently take the space due
                         * to an error or false predicate evaluation.  In this
                         * case, we'll just leave the wrapped offset alone: if
                         * the wrapped offset hasn't been advanced far enough
                         * for this allocation, it will be adjusted in the
                         * lower loop.
                         */
                        if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                                if (woffs >= offs)
                                        woffs = 0;
                        } else {
                                woffs = 0;
                        }

                        /*
                         * Now we know that we're going to be storing to the
                         * top of the buffer and that there is room for us
                         * there.  We need to clear the buffer from the current
                         * offset to the end (there may be old gunk there).
                         */
                        while (VBDTCAST(uintptr_t)offs < buf->dtb_size)
                                tomax[offs++] = 0;

                        /*
                         * We need to set our offset to zero.  And because we
                         * are wrapping, we need to set the bit indicating as
                         * much.  We can also adjust our needed space back
                         * down to the space required by the ECB -- we know
                         * that the top of the buffer is aligned.
                         */
                        offs = 0;
                        total = needed;
                        buf->dtb_flags |= DTRACEBUF_WRAPPED;
                } else {
                        /*
                         * There is room for us in the buffer, so we simply
                         * need to check the wrapped offset.
                         */
                        if (woffs < offs) {
                                /*
                                 * The wrapped offset is less than the offset.
                                 * This can happen if we allocated buffer space
                                 * that induced a wrap, but then we didn't
                                 * subsequently take the space due to an error
                                 * or false predicate evaluation.  This is
                                 * okay; we know that _this_ allocation isn't
                                 * going to induce a wrap.  We still can't
                                 * reset the wrapped offset to be zero,
                                 * however: the space may have been trashed in
                                 * the previous failed probe attempt.  But at
                                 * least the wrapped offset doesn't need to
                                 * be adjusted at all...
                                 */
                                goto out;
                        }
                }

                while (VBDTCAST(uintptr_t)offs + total > VBDTCAST(uintptr_t)woffs) {
                        dtrace_epid_t epid = *(uint32_t *)(tomax + woffs);
                        size_t size;

                        if (epid == DTRACE_EPIDNONE) {
                                size = sizeof (uint32_t);
                        } else {
                                ASSERT(VBDTCAST(int64_t)epid <= state->dts_necbs);
                                ASSERT(state->dts_ecbs[epid - 1] != NULL);

                                size = state->dts_ecbs[epid - 1]->dte_size;
                        }

                        ASSERT(woffs + size <= buf->dtb_size);
                        ASSERT(size != 0);

                        if (woffs + size == buf->dtb_size) {
                                /*
                                 * We've reached the end of the buffer; we want
                                 * to set the wrapped offset to 0 and break
                                 * out.  However, if the offs is 0, then we're
                                 * in a strange edge-condition:  the amount of
                                 * space that we want to reserve plus the size
                                 * of the record that we're overwriting is
                                 * greater than the size of the buffer.  This
                                 * is problematic because if we reserve the
                                 * space but subsequently don't consume it (due
                                 * to a failed predicate or error) the wrapped
                                 * offset will be 0 -- yet the EPID at offset 0
                                 * will not be committed.  This situation is
                                 * relatively easy to deal with:  if we're in
                                 * this case, the buffer is indistinguishable
                                 * from one that hasn't wrapped; we need only
                                 * finish the job by clearing the wrapped bit,
                                 * explicitly setting the offset to be 0, and
                                 * zero'ing out the old data in the buffer.
                                 */
                                if (offs == 0) {
                                        buf->dtb_flags &= ~DTRACEBUF_WRAPPED;
                                        buf->dtb_offset = 0;
                                        woffs = total;

                                        while (VBDTCAST(uintptr_t)woffs < buf->dtb_size)
                                                tomax[woffs++] = 0;
                                }

                                woffs = 0;
                                break;
                        }

                        woffs += size;
                }

                /*
                 * We have a wrapped offset.  It may be that the wrapped offset
                 * has become zero -- that's okay.
                 */
                buf->dtb_xamot_offset = woffs;
        }

out:
        /*
         * Now we can plow the buffer with any necessary padding.
         */
        while (offs & (align - 1)) {
                /*
                 * Assert that our alignment is off by a number which
                 * is itself sizeof (uint32_t) aligned.
                 */
                ASSERT(!((align - (offs & (align - 1))) &
                    (sizeof (uint32_t) - 1)));
                DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
                offs += sizeof (uint32_t);
        }

        if (buf->dtb_flags & DTRACEBUF_FILL) {
                if (offs + needed > buf->dtb_size - state->dts_reserve) {
                        buf->dtb_flags |= DTRACEBUF_FULL;
                        return (-1);
                }
        }

        if (mstate == NULL)
                return (offs);

        /*
         * For ring buffers and fill buffers, the scratch space is always
         * the inactive buffer.
         */
        mstate->dtms_scratch_base = (uintptr_t)buf->dtb_xamot;
        mstate->dtms_scratch_size = buf->dtb_size;
        mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

        return (offs);
}

static void
dtrace_buffer_polish(dtrace_buffer_t *buf)
{
        ASSERT(buf->dtb_flags & DTRACEBUF_RING);
        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (!(buf->dtb_flags & DTRACEBUF_WRAPPED))
                return;

        /*
         * We need to polish the ring buffer.  There are three cases:
         *
         * - The first (and presumably most common) is that there is no gap
         *   between the buffer offset and the wrapped offset.  In this case,
         *   there is nothing in the buffer that isn't valid data; we can
         *   mark the buffer as polished and return.
         *
         * - The second (less common than the first but still more common
         *   than the third) is that there is a gap between the buffer offset
         *   and the wrapped offset, and the wrapped offset is larger than the
         *   buffer offset.  This can happen because of an alignment issue, or
         *   can happen because of a call to dtrace_buffer_reserve() that
         *   didn't subsequently consume the buffer space.  In this case,
         *   we need to zero the data from the buffer offset to the wrapped
         *   offset.
         *
         * - The third (and least common) is that there is a gap between the
         *   buffer offset and the wrapped offset, but the wrapped offset is
         *   _less_ than the buffer offset.  This can only happen because a
         *   call to dtrace_buffer_reserve() induced a wrap, but the space
         *   was not subsequently consumed.  In this case, we need to zero the
         *   space from the offset to the end of the buffer _and_ from the
         *   top of the buffer to the wrapped offset.
         */
        if (buf->dtb_offset < buf->dtb_xamot_offset) {
                bzero(buf->dtb_tomax + buf->dtb_offset,
                    buf->dtb_xamot_offset - buf->dtb_offset);
        }

        if (buf->dtb_offset > buf->dtb_xamot_offset) {
                bzero(buf->dtb_tomax + buf->dtb_offset,
                    buf->dtb_size - buf->dtb_offset);
                bzero(buf->dtb_tomax, buf->dtb_xamot_offset);
        }
}

static void
dtrace_buffer_free(dtrace_buffer_t *bufs)
{
        int i;

        for (i = 0; i < NCPU; i++) {
                dtrace_buffer_t *buf = &bufs[i];

                if (buf->dtb_tomax == NULL) {
                        ASSERT(buf->dtb_xamot == NULL);
                        ASSERT(buf->dtb_size == 0);
                        continue;
                }

                if (buf->dtb_xamot != NULL) {
                        ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
                        kmem_free(buf->dtb_xamot, buf->dtb_size);
                }

                kmem_free(buf->dtb_tomax, buf->dtb_size);
                buf->dtb_size = 0;
                buf->dtb_tomax = NULL;
                buf->dtb_xamot = NULL;
        }
}

/*
 * DTrace Enabling Functions
 */
static dtrace_enabling_t *
dtrace_enabling_create(dtrace_vstate_t *vstate)
{
        dtrace_enabling_t *enab;

        enab = kmem_zalloc(sizeof (dtrace_enabling_t), KM_SLEEP);
        enab->dten_vstate = vstate;

        return (enab);
}

static void
dtrace_enabling_add(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb)
{
        dtrace_ecbdesc_t **ndesc;
        size_t osize, nsize;

        /*
         * We can't add to enablings after we've enabled them, or after we've
         * retained them.
         */
        ASSERT(enab->dten_probegen == 0);
        ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);

        if (enab->dten_ndesc < enab->dten_maxdesc) {
                enab->dten_desc[enab->dten_ndesc++] = ecb;
                return;
        }

        osize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);

        if (enab->dten_maxdesc == 0) {
                enab->dten_maxdesc = 1;
        } else {
                enab->dten_maxdesc <<= 1;
        }

        ASSERT(enab->dten_ndesc < enab->dten_maxdesc);

        nsize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);
        ndesc = kmem_zalloc(nsize, KM_SLEEP);
        bcopy(enab->dten_desc, ndesc, osize);
        kmem_free(enab->dten_desc, osize);

        enab->dten_desc = ndesc;
        enab->dten_desc[enab->dten_ndesc++] = ecb;
}

static void
dtrace_enabling_addlike(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb,
    dtrace_probedesc_t *pd)
{
        dtrace_ecbdesc_t *new;
        dtrace_predicate_t *pred;
        dtrace_actdesc_t *act;

        /*
         * We're going to create a new ECB description that matches the
         * specified ECB in every way, but has the specified probe description.
         */
        new = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);

        if ((pred = ecb->dted_pred.dtpdd_predicate) != NULL)
                dtrace_predicate_hold(pred);

        for (act = ecb->dted_action; act != NULL; act = act->dtad_next)
                dtrace_actdesc_hold(act);

        new->dted_action = ecb->dted_action;
        new->dted_pred = ecb->dted_pred;
        new->dted_probe = *pd;
        new->dted_uarg = ecb->dted_uarg;

        dtrace_enabling_add(enab, new);
}

static void
dtrace_enabling_dump(dtrace_enabling_t *enab)
{
        int i;

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_probedesc_t *desc = &enab->dten_desc[i]->dted_probe;

                cmn_err(CE_NOTE, "enabling probe %d (%s:%s:%s:%s)", i,
                    desc->dtpd_provider, desc->dtpd_mod,
                    desc->dtpd_func, desc->dtpd_name);
        }
}

static void
dtrace_enabling_destroy(dtrace_enabling_t *enab)
{
        int i;
        dtrace_ecbdesc_t *ep;
        dtrace_vstate_t *vstate = enab->dten_vstate;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_actdesc_t *act, *next;
                dtrace_predicate_t *pred;

                ep = enab->dten_desc[i];

                if ((pred = ep->dted_pred.dtpdd_predicate) != NULL)
                        dtrace_predicate_release(pred, vstate);

                for (act = ep->dted_action; act != NULL; act = next) {
                        next = act->dtad_next;
                        dtrace_actdesc_release(act, vstate);
                }

                kmem_free(ep, sizeof (dtrace_ecbdesc_t));
        }

        kmem_free(enab->dten_desc,
            enab->dten_maxdesc * sizeof (dtrace_enabling_t *));

        /*
         * If this was a retained enabling, decrement the dts_nretained count
         * and take it off of the dtrace_retained list.
         */
        if (enab->dten_prev != NULL || enab->dten_next != NULL ||
            dtrace_retained == enab) {
                ASSERT(enab->dten_vstate->dtvs_state != NULL);
                ASSERT(enab->dten_vstate->dtvs_state->dts_nretained > 0);
                enab->dten_vstate->dtvs_state->dts_nretained--;
                dtrace_retained_gen++;
        }

        if (enab->dten_prev == NULL) {
                if (dtrace_retained == enab) {
                        dtrace_retained = enab->dten_next;

                        if (dtrace_retained != NULL)
                                dtrace_retained->dten_prev = NULL;
                }
        } else {
                ASSERT(enab != dtrace_retained);
                ASSERT(dtrace_retained != NULL);
                enab->dten_prev->dten_next = enab->dten_next;
        }

        if (enab->dten_next != NULL) {
                ASSERT(dtrace_retained != NULL);
                enab->dten_next->dten_prev = enab->dten_prev;
        }

        kmem_free(enab, sizeof (dtrace_enabling_t));
}

static int
dtrace_enabling_retain(dtrace_enabling_t *enab)
{
        dtrace_state_t *state;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);
        ASSERT(enab->dten_vstate != NULL);

        state = enab->dten_vstate->dtvs_state;
        ASSERT(state != NULL);

        /*
         * We only allow each state to retain dtrace_retain_max enablings.
         */
        if (state->dts_nretained >= dtrace_retain_max)
                return (ENOSPC);

        state->dts_nretained++;
        dtrace_retained_gen++;

        if (dtrace_retained == NULL) {
                dtrace_retained = enab;
                return (0);
        }

        enab->dten_next = dtrace_retained;
        dtrace_retained->dten_prev = enab;
        dtrace_retained = enab;

        return (0);
}

static int
dtrace_enabling_replicate(dtrace_state_t *state, dtrace_probedesc_t *match,
    dtrace_probedesc_t *create)
{
        dtrace_enabling_t *new, *enab;
        int found = 0, err = ENOENT;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(strlen(match->dtpd_provider) < DTRACE_PROVNAMELEN);
        ASSERT(strlen(match->dtpd_mod) < DTRACE_MODNAMELEN);
        ASSERT(strlen(match->dtpd_func) < DTRACE_FUNCNAMELEN);
        ASSERT(strlen(match->dtpd_name) < DTRACE_NAMELEN);

        new = dtrace_enabling_create(&state->dts_vstate);

        /*
         * Iterate over all retained enablings, looking for enablings that
         * match the specified state.
         */
        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                int i;

                /*
                 * dtvs_state can only be NULL for helper enablings -- and
                 * helper enablings can't be retained.
                 */
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state != state)
                        continue;

                /*
                 * Now iterate over each probe description; we're looking for
                 * an exact match to the specified probe description.
                 */
                for (i = 0; i < enab->dten_ndesc; i++) {
                        dtrace_ecbdesc_t *ep = enab->dten_desc[i];
                        dtrace_probedesc_t *pd = &ep->dted_probe;

                        if (strcmp(pd->dtpd_provider, match->dtpd_provider))
                                continue;

                        if (strcmp(pd->dtpd_mod, match->dtpd_mod))
                                continue;

                        if (strcmp(pd->dtpd_func, match->dtpd_func))
                                continue;

                        if (strcmp(pd->dtpd_name, match->dtpd_name))
                                continue;

                        /*
                         * We have a winning probe!  Add it to our growing
                         * enabling.
                         */
                        found = 1;
                        dtrace_enabling_addlike(new, ep, create);
                }
        }

        if (!found || (err = dtrace_enabling_retain(new)) != 0) {
                dtrace_enabling_destroy(new);
                return (err);
        }

        return (0);
}

static void
dtrace_enabling_retract(dtrace_state_t *state)
{
        dtrace_enabling_t *enab, *next;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        /*
         * Iterate over all retained enablings, destroy the enablings retained
         * for the specified state.
         */
        for (enab = dtrace_retained; enab != NULL; enab = next) {
                next = enab->dten_next;

                /*
                 * dtvs_state can only be NULL for helper enablings -- and
                 * helper enablings can't be retained.
                 */
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state == state) {
                        ASSERT(state->dts_nretained > 0);
                        dtrace_enabling_destroy(enab);
                }
        }

        ASSERT(state->dts_nretained == 0);
}

static int
dtrace_enabling_match(dtrace_enabling_t *enab, int *nmatched)
{
        int i = 0;
        int total_matched = 0, matched = 0;

        ASSERT(MUTEX_HELD(&cpu_lock));
        ASSERT(MUTEX_HELD(&dtrace_lock));

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_ecbdesc_t *ep = enab->dten_desc[i];

                enab->dten_current = ep;
                enab->dten_error = 0;

                /*
                 * If a provider failed to enable a probe then get out and
                 * let the consumer know we failed.
                 */
                if ((matched = dtrace_probe_enable(&ep->dted_probe, enab)) < 0)
                        return (EBUSY);

                total_matched += matched;

                if (enab->dten_error != 0) {
                        /*
                         * If we get an error half-way through enabling the
                         * probes, we kick out -- perhaps with some number of
                         * them enabled.  Leaving enabled probes enabled may
                         * be slightly confusing for user-level, but we expect
                         * that no one will attempt to actually drive on in
                         * the face of such errors.  If this is an anonymous
                         * enabling (indicated with a NULL nmatched pointer),
                         * we cmn_err() a message.  We aren't expecting to
                         * get such an error -- such as it can exist at all,
                         * it would be a result of corrupted DOF in the driver
                         * properties.
                         */
                        if (nmatched == NULL) {
                                cmn_err(CE_WARN, "dtrace_enabling_match() "
                                    "error on %p: %d", (void *)ep,
                                    enab->dten_error);
                        }

                        return (enab->dten_error);
                }
        }

        enab->dten_probegen = dtrace_probegen;
        if (nmatched != NULL)
                *nmatched = total_matched;

        return (0);
}

static void
dtrace_enabling_matchall(void)
{
        dtrace_enabling_t *enab;

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_lock);

        /*
         * Iterate over all retained enablings to see if any probes match
         * against them.  We only perform this operation on enablings for which
         * we have sufficient permissions by virtue of being in the global zone
         * or in the same zone as the DTrace client.  Because we can be called
         * after dtrace_detach() has been called, we cannot assert that there
         * are retained enablings.  We can safely load from dtrace_retained,
         * however:  the taskq_destroy() at the end of dtrace_detach() will
         * block pending our completion.
         */
        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                cred_t *cr = enab->dten_vstate->dtvs_state->dts_cred.dcr_cred;

#ifndef VBOX
                if (INGLOBALZONE(curproc) ||
                    cr != NULL && getzoneid() == crgetzoneid(cr))
#endif
                        (void) dtrace_enabling_match(enab, NULL);
        }

        mutex_exit(&dtrace_lock);
        mutex_exit(&cpu_lock);
}

/*
 * If an enabling is to be enabled without having matched probes (that is, if
 * dtrace_state_go() is to be called on the underlying dtrace_state_t), the
 * enabling must be _primed_ by creating an ECB for every ECB description.
 * This must be done to assure that we know the number of speculations, the
 * number of aggregations, the minimum buffer size needed, etc. before we
 * transition out of DTRACE_ACTIVITY_INACTIVE.  To do this without actually
 * enabling any probes, we create ECBs for every ECB decription, but with a
 * NULL probe -- which is exactly what this function does.
 */
static void
dtrace_enabling_prime(dtrace_state_t *state)
{
        dtrace_enabling_t *enab;
        int i;

        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state != state)
                        continue;

                /*
                 * We don't want to prime an enabling more than once, lest
                 * we allow a malicious user to induce resource exhaustion.
                 * (The ECBs that result from priming an enabling aren't
                 * leaked -- but they also aren't deallocated until the
                 * consumer state is destroyed.)
                 */
                if (enab->dten_primed)
                        continue;

                for (i = 0; i < enab->dten_ndesc; i++) {
                        enab->dten_current = enab->dten_desc[i];
                        (void) dtrace_probe_enable(NULL, enab);
                }

                enab->dten_primed = 1;
        }
}

/*
 * Called to indicate that probes should be provided due to retained
 * enablings.  This is implemented in terms of dtrace_probe_provide(), but it
 * must take an initial lap through the enabling calling the dtps_provide()
 * entry point explicitly to allow for autocreated probes.
 */
static void
dtrace_enabling_provide(dtrace_provider_t *prv)
{
        int i, all = 0;
        dtrace_probedesc_t desc;
        dtrace_genid_t gen;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(MUTEX_HELD(&dtrace_provider_lock));

        if (prv == NULL) {
                all = 1;
                prv = dtrace_provider;
        }

        do {
                dtrace_enabling_t *enab;
                void *parg = prv->dtpv_arg;

retry:
                gen = dtrace_retained_gen;
                for (enab = dtrace_retained; enab != NULL;
                    enab = enab->dten_next) {
                        for (i = 0; i < enab->dten_ndesc; i++) {
                                desc = enab->dten_desc[i]->dted_probe;
                                mutex_exit(&dtrace_lock);
                                prv->dtpv_pops.dtps_provide(parg, &desc);
                                mutex_enter(&dtrace_lock);
                                /*
                                 * Process the retained enablings again if
                                 * they have changed while we weren't holding
                                 * dtrace_lock.
                                 */
                                if (gen != dtrace_retained_gen)
                                        goto retry;
                        }
                }
        } while (all && (prv = prv->dtpv_next) != NULL);

        mutex_exit(&dtrace_lock);
        dtrace_probe_provide(NULL, all ? NULL : prv);
        mutex_enter(&dtrace_lock);
}

/*
 * DTrace DOF Functions
 */
/*ARGSUSED*/
static void
dtrace_dof_error(dof_hdr_t *dof, const char *str)
{
        if (dtrace_err_verbose)
                cmn_err(CE_WARN, "failed to process DOF: %s", str);

#ifdef DTRACE_ERRDEBUG
        dtrace_errdebug(str);
#endif
}

/*
 * Create DOF out of a currently enabled state.  Right now, we only create
 * DOF containing the run-time options -- but this could be expanded to create
 * complete DOF representing the enabled state.
 */
static dof_hdr_t *
dtrace_dof_create(dtrace_state_t *state)
{
        dof_hdr_t *dof;
        dof_sec_t *sec;
        dof_optdesc_t *opt;
        int i, len = sizeof (dof_hdr_t) +
            roundup(sizeof (dof_sec_t), sizeof (uint64_t)) +
            sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        dof = kmem_zalloc(len, KM_SLEEP);
        dof->dofh_ident[DOF_ID_MAG0] = DOF_MAG_MAG0;
        dof->dofh_ident[DOF_ID_MAG1] = DOF_MAG_MAG1;
        dof->dofh_ident[DOF_ID_MAG2] = DOF_MAG_MAG2;
        dof->dofh_ident[DOF_ID_MAG3] = DOF_MAG_MAG3;

        dof->dofh_ident[DOF_ID_MODEL] = DOF_MODEL_NATIVE;
        dof->dofh_ident[DOF_ID_ENCODING] = DOF_ENCODE_NATIVE;
        dof->dofh_ident[DOF_ID_VERSION] = DOF_VERSION;
        dof->dofh_ident[DOF_ID_DIFVERS] = DIF_VERSION;
        dof->dofh_ident[DOF_ID_DIFIREG] = DIF_DIR_NREGS;
        dof->dofh_ident[DOF_ID_DIFTREG] = DIF_DTR_NREGS;

        dof->dofh_flags = 0;
        dof->dofh_hdrsize = sizeof (dof_hdr_t);
        dof->dofh_secsize = sizeof (dof_sec_t);
        dof->dofh_secnum = 1;   /* only DOF_SECT_OPTDESC */
        dof->dofh_secoff = sizeof (dof_hdr_t);
        dof->dofh_loadsz = len;
        dof->dofh_filesz = len;
        dof->dofh_pad = 0;

        /*
         * Fill in the option section header...
         */
        sec = (dof_sec_t *)((uintptr_t)dof + sizeof (dof_hdr_t));
        sec->dofs_type = DOF_SECT_OPTDESC;
        sec->dofs_align = sizeof (uint64_t);
        sec->dofs_flags = DOF_SECF_LOAD;
        sec->dofs_entsize = sizeof (dof_optdesc_t);

        opt = (dof_optdesc_t *)((uintptr_t)sec +
            roundup(sizeof (dof_sec_t), sizeof (uint64_t)));

        sec->dofs_offset = (uintptr_t)opt - (uintptr_t)dof;
        sec->dofs_size = sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

        for (i = 0; i < DTRACEOPT_MAX; i++) {
                opt[i].dofo_option = i;
                opt[i].dofo_strtab = DOF_SECIDX_NONE;
                opt[i].dofo_value = state->dts_options[i];
        }

        return (dof);
}

static dof_hdr_t *
dtrace_dof_copyin(uintptr_t uarg, int *errp)
{
        dof_hdr_t hdr, *dof;

        ASSERT(!MUTEX_HELD(&dtrace_lock));

        /*
         * First, we're going to copyin() the sizeof (dof_hdr_t).
         */
        if (copyin((void *)uarg, &hdr, sizeof (hdr)) != 0) {
                dtrace_dof_error(NULL, "failed to copyin DOF header");
                *errp = EFAULT;
                return (NULL);
        }

        /*
         * Now we'll allocate the entire DOF and copy it in -- provided
         * that the length isn't outrageous.
         */
        if (hdr.dofh_loadsz >= VBDTCAST(uint64_t)dtrace_dof_maxsize) {
                dtrace_dof_error(&hdr, "load size exceeds maximum");
                *errp = E2BIG;
                return (NULL);
        }

        if (hdr.dofh_loadsz < sizeof (hdr)) {
                dtrace_dof_error(&hdr, "invalid load size");
                *errp = EINVAL;
                return (NULL);
        }

        dof = kmem_alloc(hdr.dofh_loadsz, KM_SLEEP);

        if (copyin((void *)uarg, dof, hdr.dofh_loadsz) != 0 ||
            dof->dofh_loadsz != hdr.dofh_loadsz) {
                kmem_free(dof, hdr.dofh_loadsz);
                *errp = EFAULT;
                return (NULL);
        }

        return (dof);
}

static dof_hdr_t *
dtrace_dof_property(const char *name)
{
#ifndef VBOX
        uchar_t *buf;
        uint64_t loadsz;
        unsigned int len, i;
        dof_hdr_t *dof;

        /*
         * Unfortunately, array of values in .conf files are always (and
         * only) interpreted to be integer arrays.  We must read our DOF
         * as an integer array, and then squeeze it into a byte array.
         */
        if (ddi_prop_lookup_int_array(DDI_DEV_T_ANY, dtrace_devi, 0,
            (char *)name, (int **)&buf, &len) != DDI_PROP_SUCCESS)
                return (NULL);

        for (i = 0; i < len; i++)
                buf[i] = (uchar_t)(((int *)buf)[i]);

        if (len < sizeof (dof_hdr_t)) {
                ddi_prop_free(buf);
                dtrace_dof_error(NULL, "truncated header");
                return (NULL);
        }

        if (len < (loadsz = ((dof_hdr_t *)buf)->dofh_loadsz)) {
                ddi_prop_free(buf);
                dtrace_dof_error(NULL, "truncated DOF");
                return (NULL);
        }

        if (loadsz >= dtrace_dof_maxsize) {
                ddi_prop_free(buf);
                dtrace_dof_error(NULL, "oversized DOF");
                return (NULL);
        }

        dof = kmem_alloc(loadsz, KM_SLEEP);
        bcopy(buf, dof, loadsz);
        ddi_prop_free(buf);

        return (dof);
#else  /* VBOX */
        return (NULL);
#endif /* VBOX */
}

static void
dtrace_dof_destroy(dof_hdr_t *dof)
{
        kmem_free(dof, dof->dofh_loadsz);
}

/*
 * Return the dof_sec_t pointer corresponding to a given section index.  If the
 * index is not valid, dtrace_dof_error() is called and NULL is returned.  If
 * a type other than DOF_SECT_NONE is specified, the header is checked against
 * this type and NULL is returned if the types do not match.
 */
static dof_sec_t *
dtrace_dof_sect(dof_hdr_t *dof, uint32_t type, dof_secidx_t i)
{
        dof_sec_t *sec = (dof_sec_t *)(uintptr_t)
            ((uintptr_t)dof + dof->dofh_secoff + i * dof->dofh_secsize);

        if (i >= dof->dofh_secnum) {
                dtrace_dof_error(dof, "referenced section index is invalid");
                return (NULL);
        }

        if (!(sec->dofs_flags & DOF_SECF_LOAD)) {
                dtrace_dof_error(dof, "referenced section is not loadable");
                return (NULL);
        }

        if (type != DOF_SECT_NONE && type != sec->dofs_type) {
                dtrace_dof_error(dof, "referenced section is the wrong type");
                return (NULL);
        }

        return (sec);
}

static dtrace_probedesc_t *
dtrace_dof_probedesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_probedesc_t *desc)
{
        dof_probedesc_t *probe;
        dof_sec_t *strtab;
        uintptr_t daddr = (uintptr_t)dof;
        uintptr_t str;
        size_t size;

        if (sec->dofs_type != DOF_SECT_PROBEDESC) {
                dtrace_dof_error(dof, "invalid probe section");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad alignment in probe description");
                return (NULL);
        }

        if (sec->dofs_offset + sizeof (dof_probedesc_t) > dof->dofh_loadsz) {
                dtrace_dof_error(dof, "truncated probe description");
                return (NULL);
        }

        probe = (dof_probedesc_t *)(uintptr_t)(daddr + sec->dofs_offset);
        strtab = dtrace_dof_sect(dof, DOF_SECT_STRTAB, probe->dofp_strtab);

        if (strtab == NULL)
                return (NULL);

        str = daddr + strtab->dofs_offset;
        size = strtab->dofs_size;

        if (probe->dofp_provider >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe provider");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_provider,
            (char *)(str + probe->dofp_provider),
            MIN(DTRACE_PROVNAMELEN - 1, size - probe->dofp_provider));

        if (probe->dofp_mod >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe module");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_mod, (char *)(str + probe->dofp_mod),
            MIN(DTRACE_MODNAMELEN - 1, size - probe->dofp_mod));

        if (probe->dofp_func >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe function");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_func, (char *)(str + probe->dofp_func),
            MIN(DTRACE_FUNCNAMELEN - 1, size - probe->dofp_func));

        if (probe->dofp_name >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe name");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_name, (char *)(str + probe->dofp_name),
            MIN(DTRACE_NAMELEN - 1, size - probe->dofp_name));

        return (desc);
}

static dtrace_difo_t *
dtrace_dof_difo(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_difo_t *dp;
        size_t ttl = 0;
        dof_difohdr_t *dofd;
        uintptr_t daddr = (uintptr_t)dof;
        size_t max = dtrace_difo_maxsize;
        int i, l, n;

        static const struct {
                int section;
                int bufoffs;
                int lenoffs;
                int entsize;
                int align;
                const char *msg;
        } difo[] = {
                { DOF_SECT_DIF, offsetof(dtrace_difo_t, dtdo_buf),
                offsetof(dtrace_difo_t, dtdo_len), sizeof (dif_instr_t),
                sizeof (dif_instr_t), "multiple DIF sections" },

                { DOF_SECT_INTTAB, offsetof(dtrace_difo_t, dtdo_inttab),
                offsetof(dtrace_difo_t, dtdo_intlen), sizeof (uint64_t),
                sizeof (uint64_t), "multiple integer tables" },

                { DOF_SECT_STRTAB, offsetof(dtrace_difo_t, dtdo_strtab),
                offsetof(dtrace_difo_t, dtdo_strlen), 0,
                sizeof (char), "multiple string tables" },

                { DOF_SECT_VARTAB, offsetof(dtrace_difo_t, dtdo_vartab),
                offsetof(dtrace_difo_t, dtdo_varlen), sizeof (dtrace_difv_t),
                sizeof (uint_t), "multiple variable tables" },

                { DOF_SECT_NONE, 0, 0, 0, NULL }
        };

        if (sec->dofs_type != DOF_SECT_DIFOHDR) {
                dtrace_dof_error(dof, "invalid DIFO header section");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad alignment in DIFO header");
                return (NULL);
        }

        if (sec->dofs_size < sizeof (dof_difohdr_t) ||
            sec->dofs_size % sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad size in DIFO header");
                return (NULL);
        }

        dofd = (dof_difohdr_t *)(uintptr_t)(daddr + sec->dofs_offset);
        n = (sec->dofs_size - sizeof (*dofd)) / sizeof (dof_secidx_t) + 1;

        dp = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);
        dp->dtdo_rtype = dofd->dofd_rtype;

        for (l = 0; l < n; l++) {
                dof_sec_t *subsec;
                void **bufp;
                uint32_t *lenp;

                if ((subsec = dtrace_dof_sect(dof, DOF_SECT_NONE,
                    dofd->dofd_links[l])) == NULL)
                        goto err; /* invalid section link */

                if (ttl + subsec->dofs_size > max) {
                        dtrace_dof_error(dof, "exceeds maximum size");
                        goto err;
                }

                ttl += subsec->dofs_size;

                for (i = 0; difo[i].section != DOF_SECT_NONE; i++) {
                        if (subsec->dofs_type != VBDTCAST(uint32_t)difo[i].section)
                                continue;

                        if (!(subsec->dofs_flags & DOF_SECF_LOAD)) {
                                dtrace_dof_error(dof, "section not loaded");
                                goto err;
                        }

                        if (subsec->dofs_align != VBDTCAST(uint32_t)difo[i].align) {
                                dtrace_dof_error(dof, "bad alignment");
                                goto err;
                        }

                        bufp = (void **)((uintptr_t)dp + difo[i].bufoffs);
                        lenp = (uint32_t *)((uintptr_t)dp + difo[i].lenoffs);

                        if (*bufp != NULL) {
                                dtrace_dof_error(dof, difo[i].msg);
                                goto err;
                        }

                        if (VBDTCAST(uint32_t)difo[i].entsize != subsec->dofs_entsize) {
                                dtrace_dof_error(dof, "entry size mismatch");
                                goto err;
                        }

                        if (subsec->dofs_entsize != 0 &&
                            (subsec->dofs_size % subsec->dofs_entsize) != 0) {
                                dtrace_dof_error(dof, "corrupt entry size");
                                goto err;
                        }

                        *lenp = subsec->dofs_size;
                        *bufp = kmem_alloc(subsec->dofs_size, KM_SLEEP);
                        bcopy((char *)(uintptr_t)(daddr + subsec->dofs_offset),
                            *bufp, subsec->dofs_size);

                        if (subsec->dofs_entsize != 0)
                                *lenp /= subsec->dofs_entsize;

                        break;
                }

                /*
                 * If we encounter a loadable DIFO sub-section that is not
                 * known to us, assume this is a broken program and fail.
                 */
                if (difo[i].section == DOF_SECT_NONE &&
                    (subsec->dofs_flags & DOF_SECF_LOAD)) {
                        dtrace_dof_error(dof, "unrecognized DIFO subsection");
                        goto err;
                }
        }

        if (dp->dtdo_buf == NULL) {
                /*
                 * We can't have a DIF object without DIF text.
                 */
                dtrace_dof_error(dof, "missing DIF text");
                goto err;
        }

        /*
         * Before we validate the DIF object, run through the variable table
         * looking for the strings -- if any of their size are under, we'll set
         * their size to be the system-wide default string size.  Note that
         * this should _not_ happen if the "strsize" option has been set --
         * in this case, the compiler should have set the size to reflect the
         * setting of the option.
         */
        for (i = 0; VBDTCAST(unsigned)i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_diftype_t *t = &v->dtdv_type;

                if (v->dtdv_id < DIF_VAR_OTHER_UBASE)
                        continue;

                if (t->dtdt_kind == DIF_TYPE_STRING && t->dtdt_size == 0)
                        t->dtdt_size = VBDTCAST(uint32_t)dtrace_strsize_default;
        }

        if (dtrace_difo_validate(dp, vstate, DIF_DIR_NREGS, cr) != 0)
                goto err;

        dtrace_difo_init(dp, vstate);
        return (dp);

err:
        kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
        kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
        kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
        kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

        kmem_free(dp, sizeof (dtrace_difo_t));
        return (NULL);
}

static dtrace_predicate_t *
dtrace_dof_predicate(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_difo_t *dp;

        if ((dp = dtrace_dof_difo(dof, sec, vstate, cr)) == NULL)
                return (NULL);

        return (dtrace_predicate_create(dp));
}

static dtrace_actdesc_t *
dtrace_dof_actdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_actdesc_t *act, *first = NULL, *last = NULL, *next;
        dof_actdesc_t *desc;
        dof_sec_t *difosec;
        size_t offs;
        uintptr_t daddr = (uintptr_t)dof;
        uint64_t arg;
        dtrace_actkind_t kind;

        if (sec->dofs_type != DOF_SECT_ACTDESC) {
                dtrace_dof_error(dof, "invalid action section");
                return (NULL);
        }

        if (sec->dofs_offset + sizeof (dof_actdesc_t) > dof->dofh_loadsz) {
                dtrace_dof_error(dof, "truncated action description");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (uint64_t)) {
                dtrace_dof_error(dof, "bad alignment in action description");
                return (NULL);
        }

        if (sec->dofs_size < sec->dofs_entsize) {
                dtrace_dof_error(dof, "section entry size exceeds total size");
                return (NULL);
        }

        if (sec->dofs_entsize != sizeof (dof_actdesc_t)) {
                dtrace_dof_error(dof, "bad entry size in action description");
                return (NULL);
        }

        if (sec->dofs_size / sec->dofs_entsize > dtrace_actions_max) {
                dtrace_dof_error(dof, "actions exceed dtrace_actions_max");
                return (NULL);
        }

        for (offs = 0; offs < sec->dofs_size; offs += sec->dofs_entsize) {
                desc = (dof_actdesc_t *)(daddr +
                    (uintptr_t)sec->dofs_offset + offs);
                kind = (dtrace_actkind_t)desc->dofa_kind;

                if (DTRACEACT_ISPRINTFLIKE(kind) &&
                    (kind != DTRACEACT_PRINTA ||
                    desc->dofa_strtab != DOF_SECIDX_NONE)) {
                        dof_sec_t *strtab;
                        char *str, *fmt;
                        uint64_t i;

                        /*
                         * printf()-like actions must have a format string.
                         */
                        if ((strtab = dtrace_dof_sect(dof,
                            DOF_SECT_STRTAB, desc->dofa_strtab)) == NULL)
                                goto err;

                        str = (char *)((uintptr_t)dof +
                            (uintptr_t)strtab->dofs_offset);

                        for (i = desc->dofa_arg; i < strtab->dofs_size; i++) {
                                if (str[i] == '\0')
                                        break;
                        }

                        if (i >= strtab->dofs_size) {
                                dtrace_dof_error(dof, "bogus format string");
                                goto err;
                        }

                        if (i == desc->dofa_arg) {
                                dtrace_dof_error(dof, "empty format string");
                                goto err;
                        }

                        i -= desc->dofa_arg;
                        fmt = kmem_alloc(i + 1, KM_SLEEP);
                        bcopy(&str[desc->dofa_arg], fmt, i + 1);
                        arg = (uint64_t)(uintptr_t)fmt;
                } else {
                        if (kind == DTRACEACT_PRINTA) {
                                ASSERT(desc->dofa_strtab == DOF_SECIDX_NONE);
                                arg = 0;
                        } else {
                                arg = desc->dofa_arg;
                        }
                }

                act = dtrace_actdesc_create(kind, desc->dofa_ntuple,
                    desc->dofa_uarg, arg);

                if (last != NULL) {
                        last->dtad_next = act;
                } else {
                        first = act;
                }

                last = act;

                if (desc->dofa_difo == DOF_SECIDX_NONE)
                        continue;

                if ((difosec = dtrace_dof_sect(dof,
                    DOF_SECT_DIFOHDR, desc->dofa_difo)) == NULL)
                        goto err;

                act->dtad_difo = dtrace_dof_difo(dof, difosec, vstate, cr);

                if (act->dtad_difo == NULL)
                        goto err;
        }

        ASSERT(first != NULL);
        return (first);

err:
        for (act = first; act != NULL; act = next) {
                next = act->dtad_next;
                dtrace_actdesc_release(act, vstate);
        }

        return (NULL);
}

static dtrace_ecbdesc_t *
dtrace_dof_ecbdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_ecbdesc_t *ep;
        dof_ecbdesc_t *ecb;
        dtrace_probedesc_t *desc;
        dtrace_predicate_t *pred = NULL;

        if (sec->dofs_size < sizeof (dof_ecbdesc_t)) {
                dtrace_dof_error(dof, "truncated ECB description");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (uint64_t)) {
                dtrace_dof_error(dof, "bad alignment in ECB description");
                return (NULL);
        }

        ecb = (dof_ecbdesc_t *)((uintptr_t)dof + (uintptr_t)sec->dofs_offset);
        sec = dtrace_dof_sect(dof, DOF_SECT_PROBEDESC, ecb->dofe_probes);

        if (sec == NULL)
                return (NULL);

        ep = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);
        ep->dted_uarg = ecb->dofe_uarg;
        desc = &ep->dted_probe;

        if (dtrace_dof_probedesc(dof, sec, desc) == NULL)
                goto err;

        if (ecb->dofe_pred != DOF_SECIDX_NONE) {
                if ((sec = dtrace_dof_sect(dof,
                    DOF_SECT_DIFOHDR, ecb->dofe_pred)) == NULL)
                        goto err;

                if ((pred = dtrace_dof_predicate(dof, sec, vstate, cr)) == NULL)
                        goto err;

                ep->dted_pred.dtpdd_predicate = pred;
        }

        if (ecb->dofe_actions != DOF_SECIDX_NONE) {
                if ((sec = dtrace_dof_sect(dof,
                    DOF_SECT_ACTDESC, ecb->dofe_actions)) == NULL)
                        goto err;

                ep->dted_action = dtrace_dof_actdesc(dof, sec, vstate, cr);

                if (ep->dted_action == NULL)
                        goto err;
        }

        return (ep);

err:
        if (pred != NULL)
                dtrace_predicate_release(pred, vstate);
        kmem_free(ep, sizeof (dtrace_ecbdesc_t));
        return (NULL);
}

/*
 * Apply the relocations from the specified 'sec' (a DOF_SECT_URELHDR) to the
 * specified DOF.  At present, this amounts to simply adding 'ubase' to the
 * site of any user SETX relocations to account for load object base address.
 * In the future, if we need other relocations, this function can be extended.
 */
static int
dtrace_dof_relocate(dof_hdr_t *dof, dof_sec_t *sec, uint64_t ubase)
{
        uintptr_t daddr = (uintptr_t)dof;
        dof_relohdr_t *dofr =
            (dof_relohdr_t *)(uintptr_t)(daddr + sec->dofs_offset);
        dof_sec_t *ss, *rs, *ts;
        dof_relodesc_t *r;
        uint_t i, n;

        if (sec->dofs_size < sizeof (dof_relohdr_t) ||
            sec->dofs_align != sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "invalid relocation header");
                return (-1);
        }

        ss = dtrace_dof_sect(dof, DOF_SECT_STRTAB, dofr->dofr_strtab);
        rs = dtrace_dof_sect(dof, DOF_SECT_RELTAB, dofr->dofr_relsec);
        ts = dtrace_dof_sect(dof, DOF_SECT_NONE, dofr->dofr_tgtsec);

        if (ss == NULL || rs == NULL || ts == NULL)
                return (-1); /* dtrace_dof_error() has been called already */

        if (rs->dofs_entsize < sizeof (dof_relodesc_t) ||
            rs->dofs_align != sizeof (uint64_t)) {
                dtrace_dof_error(dof, "invalid relocation section");
                return (-1);
        }

        r = (dof_relodesc_t *)(uintptr_t)(daddr + rs->dofs_offset);
        n = rs->dofs_size / rs->dofs_entsize;

        for (i = 0; i < n; i++) {
                uintptr_t taddr = daddr + ts->dofs_offset + r->dofr_offset;

                switch (r->dofr_type) {
                case DOF_RELO_NONE:
                        break;
                case DOF_RELO_SETX:
                        if (r->dofr_offset >= ts->dofs_size || r->dofr_offset +
                            sizeof (uint64_t) > ts->dofs_size) {
                                dtrace_dof_error(dof, "bad relocation offset");
                                return (-1);
                        }

                        if (!IS_P2ALIGNED(taddr, sizeof (uint64_t))) {
                                dtrace_dof_error(dof, "misaligned setx relo");
                                return (-1);
                        }

                        *(uint64_t *)taddr += ubase;
                        break;
                default:
                        dtrace_dof_error(dof, "invalid relocation type");
                        return (-1);
                }

                r = (dof_relodesc_t *)((uintptr_t)r + rs->dofs_entsize);
        }

        return (0);
}

/*
 * The dof_hdr_t passed to dtrace_dof_slurp() should be a partially validated
 * header:  it should be at the front of a memory region that is at least
 * sizeof (dof_hdr_t) in size -- and then at least dof_hdr.dofh_loadsz in
 * size.  It need not be validated in any other way.
 */
static int
dtrace_dof_slurp(dof_hdr_t *dof, dtrace_vstate_t *vstate, cred_t *cr,
    dtrace_enabling_t **enabp, uint64_t ubase, int noprobes)
{
        uint64_t len = dof->dofh_loadsz, seclen;
        uintptr_t daddr = (uintptr_t)dof;
        dtrace_ecbdesc_t *ep;
        dtrace_enabling_t *enab;
        uint_t i;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dof->dofh_loadsz >= sizeof (dof_hdr_t));

        /*
         * Check the DOF header identification bytes.  In addition to checking
         * valid settings, we also verify that unused bits/bytes are zeroed so
         * we can use them later without fear of regressing existing binaries.
         */
        if (bcmp(&dof->dofh_ident[DOF_ID_MAG0],
            DOF_MAG_STRING, DOF_MAG_STRLEN) != 0) {
                dtrace_dof_error(dof, "DOF magic string mismatch");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_ILP32 &&
            dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_LP64) {
                dtrace_dof_error(dof, "DOF has invalid data model");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_ENCODING] != DOF_ENCODE_NATIVE) {
                dtrace_dof_error(dof, "DOF encoding mismatch");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
            dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_2) {
                dtrace_dof_error(dof, "DOF version mismatch");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFVERS] != DIF_VERSION_2) {
                dtrace_dof_error(dof, "DOF uses unsupported instruction set");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFIREG] > DIF_DIR_NREGS) {
                dtrace_dof_error(dof, "DOF uses too many integer registers");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFTREG] > DIF_DTR_NREGS) {
                dtrace_dof_error(dof, "DOF uses too many tuple registers");
                return (-1);
        }

        for (i = DOF_ID_PAD; i < DOF_ID_SIZE; i++) {
                if (dof->dofh_ident[i] != 0) {
                        dtrace_dof_error(dof, "DOF has invalid ident byte set");
                        return (-1);
                }
        }

        if (dof->dofh_flags & ~DOF_FL_VALID) {
                dtrace_dof_error(dof, "DOF has invalid flag bits set");
                return (-1);
        }

        if (dof->dofh_secsize == 0) {
                dtrace_dof_error(dof, "zero section header size");
                return (-1);
        }

        /*
         * Check that the section headers don't exceed the amount of DOF
         * data.  Note that we cast the section size and number of sections
         * to uint64_t's to prevent possible overflow in the multiplication.
         */
        seclen = (uint64_t)dof->dofh_secnum * (uint64_t)dof->dofh_secsize;

        if (dof->dofh_secoff > len || seclen > len ||
            dof->dofh_secoff + seclen > len) {
                dtrace_dof_error(dof, "truncated section headers");
                return (-1);
        }

        if (!IS_P2ALIGNED(dof->dofh_secoff, sizeof (uint64_t))) {
                dtrace_dof_error(dof, "misaligned section headers");
                return (-1);
        }

        if (!IS_P2ALIGNED(dof->dofh_secsize, sizeof (uint64_t))) {
                dtrace_dof_error(dof, "misaligned section size");
                return (-1);
        }

        /*
         * Take an initial pass through the section headers to be sure that
         * the headers don't have stray offsets.  If the 'noprobes' flag is
         * set, do not permit sections relating to providers, probes, or args.
         */
        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(daddr +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (noprobes) {
                        switch (sec->dofs_type) {
                        case DOF_SECT_PROVIDER:
                        case DOF_SECT_PROBES:
                        case DOF_SECT_PRARGS:
                        case DOF_SECT_PROFFS:
                                dtrace_dof_error(dof, "illegal sections "
                                    "for enabling");
                                return (-1);
                        }
                }

                if (DOF_SEC_ISLOADABLE(sec->dofs_type) &&
                    !(sec->dofs_flags & DOF_SECF_LOAD)) {
                        dtrace_dof_error(dof, "loadable section with load "
                            "flag unset");
                        return (-1);
                }

                if (!(sec->dofs_flags & DOF_SECF_LOAD))
                        continue; /* just ignore non-loadable sections */

                if (sec->dofs_align & (sec->dofs_align - 1)) {
                        dtrace_dof_error(dof, "bad section alignment");
                        return (-1);
                }

                if (sec->dofs_offset & (sec->dofs_align - 1)) {
                        dtrace_dof_error(dof, "misaligned section");
                        return (-1);
                }

                if (sec->dofs_offset > len || sec->dofs_size > len ||
                    sec->dofs_offset + sec->dofs_size > len) {
                        dtrace_dof_error(dof, "corrupt section header");
                        return (-1);
                }

                if (sec->dofs_type == DOF_SECT_STRTAB && *((char *)daddr +
                    sec->dofs_offset + sec->dofs_size - 1) != '\0') {
                        dtrace_dof_error(dof, "non-terminating string table");
                        return (-1);
                }
        }

        /*
         * Take a second pass through the sections and locate and perform any
         * relocations that are present.  We do this after the first pass to
         * be sure that all sections have had their headers validated.
         */
        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(daddr +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (!(sec->dofs_flags & DOF_SECF_LOAD))
                        continue; /* skip sections that are not loadable */

                switch (sec->dofs_type) {
                case DOF_SECT_URELHDR:
                        if (dtrace_dof_relocate(dof, sec, ubase) != 0)
                                return (-1);
                        break;
                }
        }

        if ((enab = *enabp) == NULL)
                enab = *enabp = dtrace_enabling_create(vstate);

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(daddr +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_ECBDESC)
                        continue;

                if ((ep = dtrace_dof_ecbdesc(dof, sec, vstate, cr)) == NULL) {
                        dtrace_enabling_destroy(enab);
                        *enabp = NULL;
                        return (-1);
                }

                dtrace_enabling_add(enab, ep);
        }

        return (0);
}

/*
 * Process DOF for any options.  This routine assumes that the DOF has been
 * at least processed by dtrace_dof_slurp().
 */
static int
dtrace_dof_options(dof_hdr_t *dof, dtrace_state_t *state)
{
        int i, rval;
        uint32_t entsize;
        size_t offs;
        dof_optdesc_t *desc;

        for (i = 0; VBDTCAST(unsigned)i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)((uintptr_t)dof +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_OPTDESC)
                        continue;

                if (sec->dofs_align != sizeof (uint64_t)) {
                        dtrace_dof_error(dof, "bad alignment in "
                            "option description");
                        return (EINVAL);
                }

                if ((entsize = sec->dofs_entsize) == 0) {
                        dtrace_dof_error(dof, "zeroed option entry size");
                        return (EINVAL);
                }

                if (entsize < sizeof (dof_optdesc_t)) {
                        dtrace_dof_error(dof, "bad option entry size");
                        return (EINVAL);
                }

                for (offs = 0; offs < sec->dofs_size; offs += entsize) {
                        desc = (dof_optdesc_t *)((uintptr_t)dof +
                            (uintptr_t)sec->dofs_offset + offs);

                        if (desc->dofo_strtab != DOF_SECIDX_NONE) {
                                dtrace_dof_error(dof, "non-zero option string");
                                return (EINVAL);
                        }

                        if (desc->dofo_value == VBDTCAST(uint64_t)DTRACEOPT_UNSET) {
                                dtrace_dof_error(dof, "unset option");
                                return (EINVAL);
                        }

                        if ((rval = dtrace_state_option(state,
                            desc->dofo_option, desc->dofo_value)) != 0) {
                                dtrace_dof_error(dof, "rejected option");
                                return (rval);
                        }
                }
        }

        return (0);
}

/*
 * DTrace Consumer State Functions
 */
VBDTSTATIC int
dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
{
        size_t hashsize, maxper, min, chunksize = dstate->dtds_chunksize;
        void *base;
        uintptr_t limit;
        dtrace_dynvar_t *dvar, *next, *start;
        VBDTTYPE(size_t,int) i;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(dstate->dtds_base == NULL && dstate->dtds_percpu == NULL);

        bzero(dstate, sizeof (dtrace_dstate_t));

        if ((dstate->dtds_chunksize = chunksize) == 0)
                dstate->dtds_chunksize = DTRACE_DYNVAR_CHUNKSIZE;

        if (size < (min = dstate->dtds_chunksize + sizeof (dtrace_dynhash_t)))
                size = min;

        if ((base = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                return (ENOMEM);

        dstate->dtds_size = size;
        dstate->dtds_base = base;
        dstate->dtds_percpu = kmem_cache_alloc(dtrace_state_cache, KM_SLEEP);
        bzero(dstate->dtds_percpu, NCPU * sizeof (dtrace_dstate_percpu_t));

        hashsize = size / (dstate->dtds_chunksize + sizeof (dtrace_dynhash_t));

        if (hashsize != 1 && (hashsize & 1))
                hashsize--;

        dstate->dtds_hashsize = hashsize;
        dstate->dtds_hash = dstate->dtds_base;

        /*
         * Set all of our hash buckets to point to the single sink, and (if
         * it hasn't already been set), set the sink's hash value to be the
         * sink sentinel value.  The sink is needed for dynamic variable
         * lookups to know that they have iterated over an entire, valid hash
         * chain.
         */
        for (i = 0; i < hashsize; i++)
                dstate->dtds_hash[i].dtdh_chain = &dtrace_dynhash_sink;

        if (dtrace_dynhash_sink.dtdv_hashval != DTRACE_DYNHASH_SINK)
                dtrace_dynhash_sink.dtdv_hashval = DTRACE_DYNHASH_SINK;

        /*
         * Determine number of active CPUs.  Divide free list evenly among
         * active CPUs.
         */
        start = (dtrace_dynvar_t *)
            ((uintptr_t)base + hashsize * sizeof (dtrace_dynhash_t));
        limit = (uintptr_t)base + size;

        maxper = (limit - (uintptr_t)start) / NCPU;
        maxper = (maxper / dstate->dtds_chunksize) * dstate->dtds_chunksize;

        for (i = 0; i < NCPU; i++) {
                dstate->dtds_percpu[i].dtdsc_free = dvar = start;

                /*
                 * If we don't even have enough chunks to make it once through
                 * NCPUs, we're just going to allocate everything to the first
                 * CPU.  And if we're on the last CPU, we're going to allocate
                 * whatever is left over.  In either case, we set the limit to
                 * be the limit of the dynamic variable space.
                 */
                if (maxper == 0 || i == NCPU - 1) {
                        limit = (uintptr_t)base + size;
                        start = NULL;
                } else {
                        limit = (uintptr_t)start + maxper;
                        start = (dtrace_dynvar_t *)limit;
                }

                ASSERT(limit <= (uintptr_t)base + size);

                for (;;) {
                        next = (dtrace_dynvar_t *)((uintptr_t)dvar +
                            dstate->dtds_chunksize);

                        if ((uintptr_t)next + dstate->dtds_chunksize >= limit)
                                break;

                        dvar->dtdv_next = next;
                        dvar = next;
                }

                if (maxper == 0)
                        break;
        }

        return (0);
}

VBDTSTATIC void
dtrace_dstate_fini(dtrace_dstate_t *dstate)
{
        ASSERT(MUTEX_HELD(&cpu_lock));

        if (dstate->dtds_base == NULL)
                return;

        kmem_free(dstate->dtds_base, dstate->dtds_size);
        kmem_cache_free(dtrace_state_cache, dstate->dtds_percpu);
}

static void
dtrace_vstate_fini(dtrace_vstate_t *vstate)
{
        /*
         * Logical XOR, where are you?
         */
        ASSERT((vstate->dtvs_nglobals == 0) ^ (vstate->dtvs_globals != NULL));

        if (vstate->dtvs_nglobals > 0) {
                kmem_free(vstate->dtvs_globals, vstate->dtvs_nglobals *
                    sizeof (dtrace_statvar_t *));
        }

        if (vstate->dtvs_ntlocals > 0) {
                kmem_free(vstate->dtvs_tlocals, vstate->dtvs_ntlocals *
                    sizeof (dtrace_difv_t));
        }

        ASSERT((vstate->dtvs_nlocals == 0) ^ (vstate->dtvs_locals != NULL));

        if (vstate->dtvs_nlocals > 0) {
                kmem_free(vstate->dtvs_locals, vstate->dtvs_nlocals *
                    sizeof (dtrace_statvar_t *));
        }
}

static void
dtrace_state_clean(dtrace_state_t *state)
{
        if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE)
                return;

        dtrace_dynvar_clean(&state->dts_vstate.dtvs_dynvars);
        dtrace_speculation_clean(state);
}
#ifdef VBOX
static DECLCALLBACK(void) dtrace_state_clean_timer(PRTTIMER pTimer, void *pvUser, uint64_t iTick)
{
    dtrace_state_clean((dtrace_state_t *)pvUser);
    NOREF(pTimer); NOREF(iTick);
}
#endif

static void
dtrace_state_deadman(dtrace_state_t *state)
{
        hrtime_t now;

        dtrace_sync();

        now = dtrace_gethrtime();

        if (state != dtrace_anon.dta_state &&
            now - state->dts_laststatus >= dtrace_deadman_user)
                return;

        /*
         * We must be sure that dts_alive never appears to be less than the
         * value upon entry to dtrace_state_deadman(), and because we lack a
         * dtrace_cas64(), we cannot store to it atomically.  We thus instead
         * store INT64_MAX to it, followed by a memory barrier, followed by
         * the new value.  This assures that dts_alive never appears to be
         * less than its true value, regardless of the order in which the
         * stores to the underlying storage are issued.
         */
        state->dts_alive = INT64_MAX;
        dtrace_membar_producer();
        state->dts_alive = now;
}

#ifdef VBOX
static DECLCALLBACK(void) dtrace_state_deadman_timer(PRTTIMER pTimer, void *pvUser, uint64_t iTick)
{
    dtrace_state_deadman((dtrace_state_t *)pvUser);
    NOREF(pTimer); NOREF(iTick);
}
#endif

VBDTSTATIC dtrace_state_t *
dtrace_state_create(dev_t *devp, cred_t *cr)
{
        minor_t minor;
        major_t major;
        char c[30];
        dtrace_state_t *state;
        dtrace_optval_t *opt;
        int bufsize = NCPU * sizeof (dtrace_buffer_t), i;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(MUTEX_HELD(&cpu_lock));

        minor = (minor_t)(uintptr_t)vmem_alloc(dtrace_minor, 1,
            VM_BESTFIT | VM_SLEEP);

        if (ddi_soft_state_zalloc(dtrace_softstate, minor) != DDI_SUCCESS) {
                vmem_free(dtrace_minor, (void *)(uintptr_t)minor, 1);
                return (NULL);
        }

        state = ddi_get_soft_state(dtrace_softstate, minor);
        state->dts_epid = DTRACE_EPIDNONE + 1;

        (void) snprintf(c, sizeof (c), "dtrace_aggid_%d", minor);
        state->dts_aggid_arena = vmem_create(c, (void *)1, UINT32_MAX, 1,
            NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);

        if (devp != NULL) {
                major = getemajor(*devp);
        } else {
                major = ddi_driver_major(dtrace_devi);
        }

        state->dts_dev = makedevice(major, minor);

        if (devp != NULL)
                *devp = state->dts_dev;

        /*
         * We allocate NCPU buffers.  On the one hand, this can be quite
         * a bit of memory per instance (nearly 36K on a Starcat).  On the
         * other hand, it saves an additional memory reference in the probe
         * path.
         */
        state->dts_buffer = kmem_zalloc(bufsize, KM_SLEEP);
        state->dts_aggbuffer = kmem_zalloc(bufsize, KM_SLEEP);
        state->dts_cleaner = CYCLIC_NONE;
        state->dts_deadman = CYCLIC_NONE;
        state->dts_vstate.dtvs_state = state;

        for (i = 0; i < DTRACEOPT_MAX; i++)
                state->dts_options[i] = DTRACEOPT_UNSET;

        /*
         * Set the default options.
         */
        opt = state->dts_options;
        opt[DTRACEOPT_BUFPOLICY] = DTRACEOPT_BUFPOLICY_SWITCH;
        opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_AUTO;
        opt[DTRACEOPT_NSPEC] = dtrace_nspec_default;
        opt[DTRACEOPT_SPECSIZE] = dtrace_specsize_default;
        opt[DTRACEOPT_CPU] = (dtrace_optval_t)DTRACE_CPUALL;
        opt[DTRACEOPT_STRSIZE] = dtrace_strsize_default;
        opt[DTRACEOPT_STACKFRAMES] = dtrace_stackframes_default;
        opt[DTRACEOPT_USTACKFRAMES] = dtrace_ustackframes_default;
        opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_default;
        opt[DTRACEOPT_AGGRATE] = dtrace_aggrate_default;
        opt[DTRACEOPT_SWITCHRATE] = dtrace_switchrate_default;
        opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_default;
        opt[DTRACEOPT_JSTACKFRAMES] = dtrace_jstackframes_default;
        opt[DTRACEOPT_JSTACKSTRSIZE] = dtrace_jstackstrsize_default;

        state->dts_activity = DTRACE_ACTIVITY_INACTIVE;

        /*
         * Depending on the user credentials, we set flag bits which alter probe
         * visibility or the amount of destructiveness allowed.  In the case of
         * actual anonymous tracing, or the possession of all privileges, all of
         * the normal checks are bypassed.
         */
        if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
                state->dts_cred.dcr_visible = DTRACE_CRV_ALL;
                state->dts_cred.dcr_action = DTRACE_CRA_ALL;
        } else {
                /*
                 * Set up the credentials for this instantiation.  We take a
                 * hold on the credential to prevent it from disappearing on
                 * us; this in turn prevents the zone_t referenced by this
                 * credential from disappearing.  This means that we can
                 * examine the credential and the zone from probe context.
                 */
                crhold(cr);
                state->dts_cred.dcr_cred = cr;

                /*
                 * CRA_PROC means "we have *some* privilege for dtrace" and
                 * unlocks the use of variables like pid, zonename, etc.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE) ||
                    PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                        state->dts_cred.dcr_action |= DTRACE_CRA_PROC;
                }

                /*
                 * dtrace_user allows use of syscall and profile providers.
                 * If the user also has proc_owner and/or proc_zone, we
                 * extend the scope to include additional visibility and
                 * destructive power.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE)) {
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE)) {
                                state->dts_cred.dcr_visible |=
                                    DTRACE_CRV_ALLPROC;

                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;
                        }

                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE)) {
                                state->dts_cred.dcr_visible |=
                                    DTRACE_CRV_ALLZONE;

                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
                        }

                        /*
                         * If we have all privs in whatever zone this is,
                         * we can do destructive things to processes which
                         * have altered credentials.
                         */
                        if (priv_isequalset(priv_getset(cr, PRIV_EFFECTIVE),
                            cr->cr_zone->zone_privset)) {
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                        }
                }

                /*
                 * Holding the dtrace_kernel privilege also implies that
                 * the user has the dtrace_user privilege from a visibility
                 * perspective.  But without further privileges, some
                 * destructive actions are not available.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE)) {
                        /*
                         * Make all probes in all zones visible.  However,
                         * this doesn't mean that all actions become available
                         * to all zones.
                         */
                        state->dts_cred.dcr_visible |= DTRACE_CRV_KERNEL |
                            DTRACE_CRV_ALLPROC | DTRACE_CRV_ALLZONE;

                        state->dts_cred.dcr_action |= DTRACE_CRA_KERNEL |
                            DTRACE_CRA_PROC;
                        /*
                         * Holding proc_owner means that destructive actions
                         * for *this* zone are allowed.
                         */
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                        /*
                         * Holding proc_zone means that destructive actions
                         * for this user/group ID in all zones is allowed.
                         */
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;

                        /*
                         * If we have all privs in whatever zone this is,
                         * we can do destructive things to processes which
                         * have altered credentials.
                         */
                        if (priv_isequalset(priv_getset(cr, PRIV_EFFECTIVE),
                            cr->cr_zone->zone_privset)) {
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                        }
                }

                /*
                 * Holding the dtrace_proc privilege gives control over fasttrap
                 * and pid providers.  We need to grant wider destructive
                 * privileges in the event that the user has proc_owner and/or
                 * proc_zone.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
                }
        }

        return (state);
}

static int
dtrace_state_buffer(dtrace_state_t *state, dtrace_buffer_t *buf, int which)
{
        dtrace_optval_t *opt = state->dts_options, size;
        processorid_t cpu;
        int flags = 0, rval;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(MUTEX_HELD(&cpu_lock));
        ASSERT(which < DTRACEOPT_MAX);
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_INACTIVE ||
            (state == dtrace_anon.dta_state &&
            state->dts_activity == DTRACE_ACTIVITY_ACTIVE));

        if (opt[which] == DTRACEOPT_UNSET || opt[which] == 0)
                return (0);

        if (opt[DTRACEOPT_CPU] != DTRACEOPT_UNSET)
                cpu = opt[DTRACEOPT_CPU];

        if (which == DTRACEOPT_SPECSIZE)
                flags |= DTRACEBUF_NOSWITCH;

        if (which == DTRACEOPT_BUFSIZE) {
                if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_RING)
                        flags |= DTRACEBUF_RING;

                if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_FILL)
                        flags |= DTRACEBUF_FILL;

                if (state != dtrace_anon.dta_state ||
                    state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                        flags |= DTRACEBUF_INACTIVE;
        }

        for (size = opt[which]; size >= VBDTCAST(dtrace_optval_t)sizeof (uint64_t); size >>= 1) {
                /*
                 * The size must be 8-byte aligned.  If the size is not 8-byte
                 * aligned, drop it down by the difference.
                 */
                if (size & (sizeof (uint64_t) - 1))
                        size -= size & (sizeof (uint64_t) - 1);

                if (size < state->dts_reserve) {
                        /*
                         * Buffers always must be large enough to accommodate
                         * their prereserved space.  We return E2BIG instead
                         * of ENOMEM in this case to allow for user-level
                         * software to differentiate the cases.
                         */
                        return (E2BIG);
                }

                rval = dtrace_buffer_alloc(buf, size, flags, cpu);

                if (rval != ENOMEM) {
                        opt[which] = size;
                        return (rval);
                }

                if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                        return (rval);
        }

        return (ENOMEM);
}

static int
dtrace_state_buffers(dtrace_state_t *state)
{
        dtrace_speculation_t *spec = state->dts_speculations;
        int rval, i;

        if ((rval = dtrace_state_buffer(state, state->dts_buffer,
            DTRACEOPT_BUFSIZE)) != 0)
                return (rval);

        if ((rval = dtrace_state_buffer(state, state->dts_aggbuffer,
            DTRACEOPT_AGGSIZE)) != 0)
                return (rval);

        for (i = 0; i < state->dts_nspeculations; i++) {
                if ((rval = dtrace_state_buffer(state,
                    spec[i].dtsp_buffer, DTRACEOPT_SPECSIZE)) != 0)
                        return (rval);
        }

        return (0);
}

static void
dtrace_state_prereserve(dtrace_state_t *state)
{
        dtrace_ecb_t *ecb;
        dtrace_probe_t *probe;

        state->dts_reserve = 0;

        if (state->dts_options[DTRACEOPT_BUFPOLICY] != DTRACEOPT_BUFPOLICY_FILL)
                return;

        /*
         * If our buffer policy is a "fill" buffer policy, we need to set the
         * prereserved space to be the space required by the END probes.
         */
        probe = dtrace_probes[dtrace_probeid_end - 1];
        ASSERT(probe != NULL);

        for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
                if (ecb->dte_state != state)
                        continue;

                state->dts_reserve += VBDTCAST(uint32_t)ecb->dte_needed + ecb->dte_alignment;
        }
}

static int
dtrace_state_go(dtrace_state_t *state, processorid_t *cpu)
{
        dtrace_optval_t *opt = state->dts_options, sz, nspec;
        dtrace_speculation_t *spec;
        dtrace_buffer_t *buf;
#ifndef VBOX
        cyc_handler_t hdlr;
        cyc_time_t when;
#endif
        int rval = 0, i, bufsize = NCPU * sizeof (dtrace_buffer_t);
        dtrace_icookie_t cookie;

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_lock);

        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
                rval = EBUSY;
                goto out;
        }

        /*
         * Before we can perform any checks, we must prime all of the
         * retained enablings that correspond to this state.
         */
        dtrace_enabling_prime(state);

        if (state->dts_destructive && !state->dts_cred.dcr_destructive) {
                rval = EACCES;
                goto out;
        }

        dtrace_state_prereserve(state);

        /*
         * Now we want to do is try to allocate our speculations.
         * We do not automatically resize the number of speculations; if
         * this fails, we will fail the operation.
         */
        nspec = opt[DTRACEOPT_NSPEC];
        ASSERT(nspec != DTRACEOPT_UNSET);

        if (nspec > INT_MAX) {
                rval = ENOMEM;
                goto out;
        }

        spec = kmem_zalloc(nspec * sizeof (dtrace_speculation_t), KM_NOSLEEP);

        if (spec == NULL) {
                rval = ENOMEM;
                goto out;
        }

        state->dts_speculations = spec;
        state->dts_nspeculations = (int)nspec;

        for (i = 0; i < nspec; i++) {
                if ((buf = kmem_zalloc(bufsize, KM_NOSLEEP)) == NULL) {
                        rval = ENOMEM;
                        goto err;
                }

                spec[i].dtsp_buffer = buf;
        }

        if (opt[DTRACEOPT_GRABANON] != DTRACEOPT_UNSET) {
                if (dtrace_anon.dta_state == NULL) {
                        rval = ENOENT;
                        goto out;
                }

                if (state->dts_necbs != 0) {
                        rval = EALREADY;
                        goto out;
                }

                state->dts_anon = dtrace_anon_grab();
                ASSERT(state->dts_anon != NULL);
                state = state->dts_anon;

                /*
                 * We want "grabanon" to be set in the grabbed state, so we'll
                 * copy that option value from the grabbing state into the
                 * grabbed state.
                 */
                state->dts_options[DTRACEOPT_GRABANON] =
                    opt[DTRACEOPT_GRABANON];

                *cpu = dtrace_anon.dta_beganon;

                /*
                 * If the anonymous state is active (as it almost certainly
                 * is if the anonymous enabling ultimately matched anything),
                 * we don't allow any further option processing -- but we
                 * don't return failure.
                 */
                if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                        goto out;
        }

        if (opt[DTRACEOPT_AGGSIZE] != DTRACEOPT_UNSET &&
            opt[DTRACEOPT_AGGSIZE] != 0) {
                if (state->dts_aggregations == NULL) {
                        /*
                         * We're not going to create an aggregation buffer
                         * because we don't have any ECBs that contain
                         * aggregations -- set this option to 0.
                         */
                        opt[DTRACEOPT_AGGSIZE] = 0;
                } else {
                        /*
                         * If we have an aggregation buffer, we must also have
                         * a buffer to use as scratch.
                         */
                        if (opt[DTRACEOPT_BUFSIZE] == DTRACEOPT_UNSET ||
                            opt[DTRACEOPT_BUFSIZE] < VBDTCAST(dtrace_optval_t)state->dts_needed) {
                                opt[DTRACEOPT_BUFSIZE] = state->dts_needed;
                        }
                }
        }

        if (opt[DTRACEOPT_SPECSIZE] != DTRACEOPT_UNSET &&
            opt[DTRACEOPT_SPECSIZE] != 0) {
                if (!state->dts_speculates) {
                        /*
                         * We're not going to create speculation buffers
                         * because we don't have any ECBs that actually
                         * speculate -- set the speculation size to 0.
                         */
                        opt[DTRACEOPT_SPECSIZE] = 0;
                }
        }

        /*
         * The bare minimum size for any buffer that we're actually going to
         * do anything to is sizeof (uint64_t).
         */
        sz = sizeof (uint64_t);

        if ((state->dts_needed != 0 && opt[DTRACEOPT_BUFSIZE] < sz) ||
            (state->dts_speculates && opt[DTRACEOPT_SPECSIZE] < sz) ||
            (state->dts_aggregations != NULL && opt[DTRACEOPT_AGGSIZE] < sz)) {
                /*
                 * A buffer size has been explicitly set to 0 (or to a size
                 * that will be adjusted to 0) and we need the space -- we
                 * need to return failure.  We return ENOSPC to differentiate
                 * it from failing to allocate a buffer due to failure to meet
                 * the reserve (for which we return E2BIG).
                 */
                rval = ENOSPC;
                goto out;
        }

        if ((rval = dtrace_state_buffers(state)) != 0)
                goto err;

        if ((sz = opt[DTRACEOPT_DYNVARSIZE]) == DTRACEOPT_UNSET)
                sz = dtrace_dstate_defsize;

        do {
                rval = dtrace_dstate_init(&state->dts_vstate.dtvs_dynvars, sz);

                if (rval == 0)
                        break;

                if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                        goto err;
        } while (sz >>= 1);

        opt[DTRACEOPT_DYNVARSIZE] = sz;

        if (rval != 0)
                goto err;

        if (opt[DTRACEOPT_STATUSRATE] > dtrace_statusrate_max)
                opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_max;

        if (opt[DTRACEOPT_CLEANRATE] == 0)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

        if (opt[DTRACEOPT_CLEANRATE] < dtrace_cleanrate_min)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_min;

        if (opt[DTRACEOPT_CLEANRATE] > dtrace_cleanrate_max)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

#ifndef VBOX
        hdlr.cyh_func = (cyc_func_t)dtrace_state_clean;
        hdlr.cyh_arg = state;
        hdlr.cyh_level = CY_LOW_LEVEL;

        when.cyt_when = 0;
        when.cyt_interval = opt[DTRACEOPT_CLEANRATE];

        state->dts_cleaner = cyclic_add(&hdlr, &when);

        hdlr.cyh_func = (cyc_func_t)dtrace_state_deadman;
        hdlr.cyh_arg = state;
        hdlr.cyh_level = CY_LOW_LEVEL;

        when.cyt_when = 0;
        when.cyt_interval = dtrace_deadman_interval;

        state->dts_alive = state->dts_laststatus = dtrace_gethrtime();
        state->dts_deadman = cyclic_add(&hdlr, &when);
#else  /* VBOX */

        rval = RTTimerCreateEx(&state->dts_cleaner, opt[DTRACEOPT_CLEANRATE],
                               RTTIMER_FLAGS_CPU_ANY, dtrace_state_clean_timer, state);
        if (RT_FAILURE(rval)) {
            rval = RTErrConvertToErrno(rval);
            goto err;
        }

        state->dts_alive = state->dts_laststatus = dtrace_gethrtime();
        rval = RTTimerCreateEx(&state->dts_deadman, dtrace_deadman_interval,
                               RTTIMER_FLAGS_CPU_ANY, dtrace_state_deadman_timer, state);
        if (RT_FAILURE(rval)) {
            RTTimerDestroy(state->dts_cleaner);
            state->dts_cleaner = CYCLIC_NONE;
            state->dts_deadman = CYCLIC_NONE;
            rval = RTErrConvertToErrno(rval);
            goto err;
        }
#endif /* VBOX */

        state->dts_activity = DTRACE_ACTIVITY_WARMUP;

        /*
         * Now it's time to actually fire the BEGIN probe.  We need to disable
         * interrupts here both to record the CPU on which we fired the BEGIN
         * probe (the data from this CPU will be processed first at user
         * level) and to manually activate the buffer for this CPU.
         */
        cookie = dtrace_interrupt_disable();
        *cpu = VBDT_GET_CPUID();
        ASSERT(state->dts_buffer[*cpu].dtb_flags & DTRACEBUF_INACTIVE);
        state->dts_buffer[*cpu].dtb_flags &= ~DTRACEBUF_INACTIVE;

        dtrace_probe(dtrace_probeid_begin,
            (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
        dtrace_interrupt_enable(cookie);
        /*
         * We may have had an exit action from a BEGIN probe; only change our
         * state to ACTIVE if we're still in WARMUP.
         */
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_WARMUP ||
            state->dts_activity == DTRACE_ACTIVITY_DRAINING);

        if (state->dts_activity == DTRACE_ACTIVITY_WARMUP)
                state->dts_activity = DTRACE_ACTIVITY_ACTIVE;

        /*
         * Regardless of whether or not now we're in ACTIVE or DRAINING, we
         * want each CPU to transition its principal buffer out of the
         * INACTIVE state.  Doing this assures that no CPU will suddenly begin
         * processing an ECB halfway down a probe's ECB chain; all CPUs will
         * atomically transition from processing none of a state's ECBs to
         * processing all of them.
         */
        dtrace_xcall(DTRACE_CPUALL,
            (dtrace_xcall_t)dtrace_buffer_activate, state);
        goto out;

err:
        dtrace_buffer_free(state->dts_buffer);
        dtrace_buffer_free(state->dts_aggbuffer);

        if ((nspec = state->dts_nspeculations) == 0) {
                ASSERT(state->dts_speculations == NULL);
                goto out;
        }

        spec = state->dts_speculations;
        ASSERT(spec != NULL);

        for (i = 0; i < state->dts_nspeculations; i++) {
                if ((buf = spec[i].dtsp_buffer) == NULL)
                        break;

                dtrace_buffer_free(buf);
                kmem_free(buf, bufsize);
        }

        kmem_free(spec, nspec * sizeof (dtrace_speculation_t));
        state->dts_nspeculations = 0;
        state->dts_speculations = NULL;

out:
        mutex_exit(&dtrace_lock);
        mutex_exit(&cpu_lock);

        return (rval);
}

static int
dtrace_state_stop(dtrace_state_t *state, processorid_t *cpu)
{
        dtrace_icookie_t cookie;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE &&
            state->dts_activity != DTRACE_ACTIVITY_DRAINING)
                return (EINVAL);

        /*
         * We'll set the activity to DTRACE_ACTIVITY_DRAINING, and issue a sync
         * to be sure that every CPU has seen it.  See below for the details
         * on why this is done.
         */
        state->dts_activity = DTRACE_ACTIVITY_DRAINING;
        dtrace_sync();

        /*
         * By this point, it is impossible for any CPU to be still processing
         * with DTRACE_ACTIVITY_ACTIVE.  We can thus set our activity to
         * DTRACE_ACTIVITY_COOLDOWN and know that we're not racing with any
         * other CPU in dtrace_buffer_reserve().  This allows dtrace_probe()
         * and callees to know that the activity is DTRACE_ACTIVITY_COOLDOWN
         * iff we're in the END probe.
         */
        state->dts_activity = DTRACE_ACTIVITY_COOLDOWN;
        dtrace_sync();
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_COOLDOWN);

        /*
         * Finally, we can release the reserve and call the END probe.  We
         * disable interrupts across calling the END probe to allow us to
         * return the CPU on which we actually called the END probe.  This
         * allows user-land to be sure that this CPU's principal buffer is
         * processed last.
         */
        state->dts_reserve = 0;

        cookie = dtrace_interrupt_disable();
        *cpu = VBDT_GET_CPUID();
        dtrace_probe(dtrace_probeid_end,
            (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
        dtrace_interrupt_enable(cookie);

        state->dts_activity = DTRACE_ACTIVITY_STOPPED;
        dtrace_sync();

        return (0);
}

static int
dtrace_state_option(dtrace_state_t *state, dtrace_optid_t option,
    dtrace_optval_t val)
{
        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                return (EBUSY);

        if (option >= DTRACEOPT_MAX)
                return (EINVAL);

        if (option != DTRACEOPT_CPU && val < 0)
                return (EINVAL);

        switch (option) {
        case DTRACEOPT_DESTRUCTIVE:
                if (dtrace_destructive_disallow)
                        return (EACCES);

                state->dts_cred.dcr_destructive = 1;
                break;

        case DTRACEOPT_BUFSIZE:
        case DTRACEOPT_DYNVARSIZE:
        case DTRACEOPT_AGGSIZE:
        case DTRACEOPT_SPECSIZE:
        case DTRACEOPT_STRSIZE:
                if (val < 0)
                        return (EINVAL);

                if (val >= LONG_MAX) {
                        /*
                         * If this is an otherwise negative value, set it to
                         * the highest multiple of 128m less than LONG_MAX.
                         * Technically, we're adjusting the size without
                         * regard to the buffer resizing policy, but in fact,
                         * this has no effect -- if we set the buffer size to
                         * ~LONG_MAX and the buffer policy is ultimately set to
                         * be "manual", the buffer allocation is guaranteed to
                         * fail, if only because the allocation requires two
                         * buffers.  (We set the the size to the highest
                         * multiple of 128m because it ensures that the size
                         * will remain a multiple of a megabyte when
                         * repeatedly halved -- all the way down to 15m.)
                         */
                        val = LONG_MAX - (1 << 27) + 1;
                }
        }

        state->dts_options[option] = val;

        return (0);
}

static void
dtrace_state_destroy(dtrace_state_t *state)
{
        dtrace_ecb_t *ecb;
        dtrace_vstate_t *vstate = &state->dts_vstate;
        minor_t minor = getminor(state->dts_dev);
        int i, bufsize = NCPU * sizeof (dtrace_buffer_t);
        dtrace_speculation_t *spec = state->dts_speculations;
        int nspec = state->dts_nspeculations;
        uint32_t match;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(MUTEX_HELD(&cpu_lock));

        /*
         * First, retract any retained enablings for this state.
         */
        dtrace_enabling_retract(state);
        ASSERT(state->dts_nretained == 0);

        if (state->dts_activity == DTRACE_ACTIVITY_ACTIVE ||
            state->dts_activity == DTRACE_ACTIVITY_DRAINING) {
                /*
                 * We have managed to come into dtrace_state_destroy() on a
                 * hot enabling -- almost certainly because of a disorderly
                 * shutdown of a consumer.  (That is, a consumer that is
                 * exiting without having called dtrace_stop().) In this case,
                 * we're going to set our activity to be KILLED, and then
                 * issue a sync to be sure that everyone is out of probe
                 * context before we start blowing away ECBs.
                 */
                state->dts_activity = DTRACE_ACTIVITY_KILLED;
                dtrace_sync();
        }

        /*
         * Release the credential hold we took in dtrace_state_create().
         */
        if (state->dts_cred.dcr_cred != NULL)
                crfree(state->dts_cred.dcr_cred);

        /*
         * Now we can safely disable and destroy any enabled probes.  Because
         * any DTRACE_PRIV_KERNEL probes may actually be slowing our progress
         * (especially if they're all enabled), we take two passes through the
         * ECBs:  in the first, we disable just DTRACE_PRIV_KERNEL probes, and
         * in the second we disable whatever is left over.
         */
        for (match = DTRACE_PRIV_KERNEL; ; match = 0) {
                for (i = 0; i < state->dts_necbs; i++) {
                        if ((ecb = state->dts_ecbs[i]) == NULL)
                                continue;

                        if (match && ecb->dte_probe != NULL) {
                                dtrace_probe_t *probe = ecb->dte_probe;
                                dtrace_provider_t *prov = probe->dtpr_provider;

                                if (!(prov->dtpv_priv.dtpp_flags & match))
                                        continue;
                        }

                        dtrace_ecb_disable(ecb);
                        dtrace_ecb_destroy(ecb);
                }

                if (!match)
                        break;
        }

        /*
         * Before we free the buffers, perform one more sync to assure that
         * every CPU is out of probe context.
         */
        dtrace_sync();

        dtrace_buffer_free(state->dts_buffer);
        dtrace_buffer_free(state->dts_aggbuffer);

        for (i = 0; i < nspec; i++)
                dtrace_buffer_free(spec[i].dtsp_buffer);

        if (state->dts_cleaner != CYCLIC_NONE)
                cyclic_remove(state->dts_cleaner);

        if (state->dts_deadman != CYCLIC_NONE)
                cyclic_remove(state->dts_deadman);

        dtrace_dstate_fini(&vstate->dtvs_dynvars);
        dtrace_vstate_fini(vstate);
        kmem_free(state->dts_ecbs, state->dts_necbs * sizeof (dtrace_ecb_t *));

        if (state->dts_aggregations != NULL) {
#ifdef DEBUG
                for (i = 0; i < state->dts_naggregations; i++)
                        ASSERT(state->dts_aggregations[i] == NULL);
#endif
                ASSERT(state->dts_naggregations > 0);
                kmem_free(state->dts_aggregations,
                    state->dts_naggregations * sizeof (dtrace_aggregation_t *));
        }

        kmem_free(state->dts_buffer, bufsize);
        kmem_free(state->dts_aggbuffer, bufsize);

        for (i = 0; i < nspec; i++)
                kmem_free(spec[i].dtsp_buffer, bufsize);

        kmem_free(spec, nspec * sizeof (dtrace_speculation_t));

        dtrace_format_destroy(state);

        vmem_destroy(state->dts_aggid_arena);
        ddi_soft_state_free(dtrace_softstate, minor);
        vmem_free(dtrace_minor, (void *)(uintptr_t)minor, 1);
}

/*
 * DTrace Anonymous Enabling Functions
 */
static dtrace_state_t *
dtrace_anon_grab(void)
{
        dtrace_state_t *state;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if ((state = dtrace_anon.dta_state) == NULL) {
                ASSERT(dtrace_anon.dta_enabling == NULL);
                return (NULL);
        }

        ASSERT(dtrace_anon.dta_enabling != NULL);
        ASSERT(dtrace_retained != NULL);

        dtrace_enabling_destroy(dtrace_anon.dta_enabling);
        dtrace_anon.dta_enabling = NULL;
        dtrace_anon.dta_state = NULL;

        return (state);
}

static void
dtrace_anon_property(void)
{
        int i, rv;
        dtrace_state_t *state;
        dof_hdr_t *dof;
        char c[32];             /* enough for "dof-data-" + digits */

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(MUTEX_HELD(&cpu_lock));

        for (i = 0; ; i++) {
                (void) snprintf(c, sizeof (c), "dof-data-%d", i);

                dtrace_err_verbose = 1;

                if ((dof = dtrace_dof_property(c)) == NULL) {
                        dtrace_err_verbose = 0;
                        break;
                }

#ifndef VBOX
                /*
                 * We want to create anonymous state, so we need to transition
                 * the kernel debugger to indicate that DTrace is active.  If
                 * this fails (e.g. because the debugger has modified text in
                 * some way), we won't continue with the processing.
                 */
                if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
                        cmn_err(CE_NOTE, "kernel debugger active; anonymous "
                            "enabling ignored.");
                        dtrace_dof_destroy(dof);
                        break;
                }
#endif

                /*
                 * If we haven't allocated an anonymous state, we'll do so now.
                 */
                if ((state = dtrace_anon.dta_state) == NULL) {
                        state = dtrace_state_create(NULL, NULL);
                        dtrace_anon.dta_state = state;

                        if (state == NULL) {
                                /*
                                 * This basically shouldn't happen:  the only
                                 * failure mode from dtrace_state_create() is a
                                 * failure of ddi_soft_state_zalloc() that
                                 * itself should never happen.  Still, the
                                 * interface allows for a failure mode, and
                                 * we want to fail as gracefully as possible:
                                 * we'll emit an error message and cease
                                 * processing anonymous state in this case.
                                 */
                                cmn_err(CE_WARN, "failed to create "
                                    "anonymous state");
                                dtrace_dof_destroy(dof);
                                break;
                        }
                }

                rv = dtrace_dof_slurp(dof, &state->dts_vstate, CRED(),
                    &dtrace_anon.dta_enabling, 0, B_TRUE);

                if (rv == 0)
                        rv = dtrace_dof_options(dof, state);

                dtrace_err_verbose = 0;
                dtrace_dof_destroy(dof);

                if (rv != 0) {
                        /*
                         * This is malformed DOF; chuck any anonymous state
                         * that we created.
                         */
                        ASSERT(dtrace_anon.dta_enabling == NULL);
                        dtrace_state_destroy(state);
                        dtrace_anon.dta_state = NULL;
                        break;
                }

                ASSERT(dtrace_anon.dta_enabling != NULL);
        }

        if (dtrace_anon.dta_enabling != NULL) {
                int rval;

                /*
                 * dtrace_enabling_retain() can only fail because we are
                 * trying to retain more enablings than are allowed -- but
                 * we only have one anonymous enabling, and we are guaranteed
                 * to be allowed at least one retained enabling; we assert
                 * that dtrace_enabling_retain() returns success.
                 */
                rval = dtrace_enabling_retain(dtrace_anon.dta_enabling);
                ASSERT(rval == 0);

                dtrace_enabling_dump(dtrace_anon.dta_enabling);
        }
}

/*
 * DTrace Helper Functions
 */
static void
dtrace_helper_trace(dtrace_helper_action_t *helper,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate, int where)
{
        uint32_t size, next, nnext, i;
        dtrace_helptrace_t *ent;
        uint16_t flags = cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;

        if (!dtrace_helptrace_enabled)
                return;

        ASSERT(vstate->dtvs_nlocals <= VBDTCAST(int32_t)dtrace_helptrace_nlocals);

        /*
         * What would a tracing framework be without its own tracing
         * framework?  (Well, a hell of a lot simpler, for starters...)
         */
        size = sizeof (dtrace_helptrace_t) + dtrace_helptrace_nlocals *
            sizeof (uint64_t) - sizeof (uint64_t);

        /*
         * Iterate until we can allocate a slot in the trace buffer.
         */
        do {
                next = dtrace_helptrace_next;

                if (next + size < VBDTCAST(unsigned)dtrace_helptrace_bufsize) {
                        nnext = next + size;
                } else {
                        nnext = size;
                }
        } while (dtrace_cas32(&dtrace_helptrace_next, next, nnext) != next);

        /*
         * We have our slot; fill it in.
         */
        if (nnext == size)
                next = 0;

        ent = (dtrace_helptrace_t *)&dtrace_helptrace_buffer[next];
        ent->dtht_helper = helper;
        ent->dtht_where = where;
        ent->dtht_nlocals = vstate->dtvs_nlocals;

        ent->dtht_fltoffs = (mstate->dtms_present & DTRACE_MSTATE_FLTOFFS) ?
            mstate->dtms_fltoffs : -1;
        ent->dtht_fault = DTRACE_FLAGS2FLT(flags);
        ent->dtht_illval = cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_illval;

        for (i = 0; VBDTCAST(int32_t)i < vstate->dtvs_nlocals; i++) {
                dtrace_statvar_t *svar;

                if ((svar = vstate->dtvs_locals[i]) == NULL)
                        continue;

                ASSERT(svar->dtsv_size >= NCPU * sizeof (uint64_t));
                ent->dtht_locals[i] =
                    ((uint64_t *)(uintptr_t)svar->dtsv_data)[VBDT_GET_CPUID()];
        }
}

static uint64_t
dtrace_helper(int which, dtrace_mstate_t *mstate,
    dtrace_state_t *state, uint64_t arg0, uint64_t arg1)
{
        VBDTTYPE(uint16_t volatile *, uint16_t *)flags = &cpu_core[VBDT_GET_CPUID()].cpuc_dtrace_flags;
        uint64_t sarg0 = mstate->dtms_arg[0];
        uint64_t sarg1 = mstate->dtms_arg[1];
        uint64_t rval VBDTUNASS(666);
        dtrace_helpers_t *helpers = curproc->p_dtrace_helpers;
        dtrace_helper_action_t *helper;
        dtrace_vstate_t *vstate;
        dtrace_difo_t *pred;
        int i, trace = dtrace_helptrace_enabled;

        ASSERT(which >= 0 && which < DTRACE_NHELPER_ACTIONS);

        if (helpers == NULL)
                return (0);

        if ((helper = helpers->dthps_actions[which]) == NULL)
                return (0);

        vstate = &helpers->dthps_vstate;
        mstate->dtms_arg[0] = arg0;
        mstate->dtms_arg[1] = arg1;

        /*
         * Now iterate over each helper.  If its predicate evaluates to 'true',
         * we'll call the corresponding actions.  Note that the below calls
         * to dtrace_dif_emulate() may set faults in machine state.  This is
         * okay:  our caller (the outer dtrace_dif_emulate()) will simply plow
         * the stored DIF offset with its own (which is the desired behavior).
         * Also, note the calls to dtrace_dif_emulate() may allocate scratch
         * from machine state; this is okay, too.
         */
        for (; helper != NULL; helper = helper->dtha_next) {
                if ((pred = helper->dtha_predicate) != NULL) {
                        if (trace)
                                dtrace_helper_trace(helper, mstate, vstate, 0);

                        if (!dtrace_dif_emulate(pred, mstate, vstate, state))
                                goto next;

                        if (*flags & CPU_DTRACE_FAULT)
                                goto err;
                }

                for (i = 0; i < helper->dtha_nactions; i++) {
                        if (trace)
                                dtrace_helper_trace(helper,
                                    mstate, vstate, i + 1);

                        rval = dtrace_dif_emulate(helper->dtha_actions[i],
                            mstate, vstate, state);

                        if (*flags & CPU_DTRACE_FAULT)
                                goto err;
                }

next:
                if (trace)
                        dtrace_helper_trace(helper, mstate, vstate,
                            DTRACE_HELPTRACE_NEXT);
        }

        if (trace)
                dtrace_helper_trace(helper, mstate, vstate,
                    DTRACE_HELPTRACE_DONE);

        /*
         * Restore the arg0 that we saved upon entry.
         */
        mstate->dtms_arg[0] = sarg0;
        mstate->dtms_arg[1] = sarg1;

        return (rval);

err:
        if (trace)
                dtrace_helper_trace(helper, mstate, vstate,
                    DTRACE_HELPTRACE_ERR);

        /*
         * Restore the arg0 that we saved upon entry.
         */
        mstate->dtms_arg[0] = sarg0;
        mstate->dtms_arg[1] = sarg1;

        return (NULL);
}

static void
dtrace_helper_action_destroy(dtrace_helper_action_t *helper,
    dtrace_vstate_t *vstate)
{
        int i;

        if (helper->dtha_predicate != NULL)
                dtrace_difo_release(helper->dtha_predicate, vstate);

        for (i = 0; i < helper->dtha_nactions; i++) {
                ASSERT(helper->dtha_actions[i] != NULL);
                dtrace_difo_release(helper->dtha_actions[i], vstate);
        }

        kmem_free(helper->dtha_actions,
            helper->dtha_nactions * sizeof (dtrace_difo_t *));
        kmem_free(helper, sizeof (dtrace_helper_action_t));
}

static int
dtrace_helper_destroygen(int gen)
{
        proc_t *p = curproc;
        dtrace_helpers_t *help = p->p_dtrace_helpers;
        dtrace_vstate_t *vstate;
        VBDTTYPE(uint_t,int) i;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if (help == NULL || gen > help->dthps_generation)
                return (EINVAL);

        vstate = &help->dthps_vstate;

        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                dtrace_helper_action_t *last = NULL, *h, *next;

                for (h = help->dthps_actions[i]; h != NULL; h = next) {
                        next = h->dtha_next;

                        if (h->dtha_generation == gen) {
                                if (last != NULL) {
                                        last->dtha_next = next;
                                } else {
                                        help->dthps_actions[i] = next;
                                }

                                dtrace_helper_action_destroy(h, vstate);
                        } else {
                                last = h;
                        }
                }
        }

        /*
         * Interate until we've cleared out all helper providers with the
         * given generation number.
         */
        for (;;) {
                dtrace_helper_provider_t *prov;

                /*
                 * Look for a helper provider with the right generation. We
                 * have to start back at the beginning of the list each time
                 * because we drop dtrace_lock. It's unlikely that we'll make
                 * more than two passes.
                 */
                for (i = 0; i < help->dthps_nprovs; i++) {
                        prov = help->dthps_provs[i];

                        if (prov->dthp_generation == gen)
                                break;
                }

                /*
                 * If there were no matches, we're done.
                 */
                if (i == help->dthps_nprovs)
                        break;

                /*
                 * Move the last helper provider into this slot.
                 */
                help->dthps_nprovs--;
                help->dthps_provs[i] = help->dthps_provs[help->dthps_nprovs];
                help->dthps_provs[help->dthps_nprovs] = NULL;

                mutex_exit(&dtrace_lock);

                /*
                 * If we have a meta provider, remove this helper provider.
                 */
                mutex_enter(&dtrace_meta_lock);
                if (dtrace_meta_pid != NULL) {
                        ASSERT(dtrace_deferred_pid == NULL);
                        dtrace_helper_provider_remove(&prov->dthp_prov,
                            p->p_pid);
                }
                mutex_exit(&dtrace_meta_lock);

                dtrace_helper_provider_destroy(prov);

                mutex_enter(&dtrace_lock);
        }

        return (0);
}

static int
dtrace_helper_validate(dtrace_helper_action_t *helper)
{
        int err = 0, i;
        dtrace_difo_t *dp;

        if ((dp = helper->dtha_predicate) != NULL)
                err += dtrace_difo_validate_helper(dp);

        for (i = 0; i < helper->dtha_nactions; i++)
                err += dtrace_difo_validate_helper(helper->dtha_actions[i]);

        return (err == 0);
}

static int
dtrace_helper_action_add(int which, dtrace_ecbdesc_t *ep)
{
        dtrace_helpers_t *help;
        dtrace_helper_action_t *helper, *last;
        dtrace_actdesc_t *act;
        dtrace_vstate_t *vstate;
        dtrace_predicate_t *pred;
        int count = 0, nactions = 0, i;

        if (which < 0 || which >= DTRACE_NHELPER_ACTIONS)
                return (EINVAL);

        help = curproc->p_dtrace_helpers;
        last = help->dthps_actions[which];
        vstate = &help->dthps_vstate;

        for (count = 0; last != NULL; last = last->dtha_next) {
                count++;
                if (last->dtha_next == NULL)
                        break;
        }

        /*
         * If we already have dtrace_helper_actions_max helper actions for this
         * helper action type, we'll refuse to add a new one.
         */
        if (count >= dtrace_helper_actions_max)
                return (ENOSPC);

        helper = kmem_zalloc(sizeof (dtrace_helper_action_t), KM_SLEEP);
        helper->dtha_generation = help->dthps_generation;

        if ((pred = ep->dted_pred.dtpdd_predicate) != NULL) {
                ASSERT(pred->dtp_difo != NULL);
                dtrace_difo_hold(pred->dtp_difo);
                helper->dtha_predicate = pred->dtp_difo;
        }

        for (act = ep->dted_action; act != NULL; act = act->dtad_next) {
                if (act->dtad_kind != DTRACEACT_DIFEXPR)
                        goto err;

                if (act->dtad_difo == NULL)
                        goto err;

                nactions++;
        }

        helper->dtha_actions = kmem_zalloc(sizeof (dtrace_difo_t *) *
            (helper->dtha_nactions = nactions), KM_SLEEP);

        for (act = ep->dted_action, i = 0; act != NULL; act = act->dtad_next) {
                dtrace_difo_hold(act->dtad_difo);
                helper->dtha_actions[i++] = act->dtad_difo;
        }

        if (!dtrace_helper_validate(helper))
                goto err;

        if (last == NULL) {
                help->dthps_actions[which] = helper;
        } else {
                last->dtha_next = helper;
        }

        if (vstate->dtvs_nlocals > VBDTCAST(int32_t)dtrace_helptrace_nlocals) {
                dtrace_helptrace_nlocals = vstate->dtvs_nlocals;
                dtrace_helptrace_next = 0;
        }

        return (0);
err:
        dtrace_helper_action_destroy(helper, vstate);
        return (EINVAL);
}

static void
dtrace_helper_provider_register(proc_t *p, dtrace_helpers_t *help,
    dof_helper_t *dofhp)
{
        ASSERT(MUTEX_NOT_HELD(&dtrace_lock));

        mutex_enter(&dtrace_meta_lock);
        mutex_enter(&dtrace_lock);

        if (!dtrace_attached() || dtrace_meta_pid == NULL) {
                /*
                 * If the dtrace module is loaded but not attached, or if
                 * there aren't isn't a meta provider registered to deal with
                 * these provider descriptions, we need to postpone creating
                 * the actual providers until later.
                 */

                if (help->dthps_next == NULL && help->dthps_prev == NULL &&
                    dtrace_deferred_pid != help) {
                        help->dthps_deferred = 1;
                        help->dthps_pid = p->p_pid;
                        help->dthps_next = dtrace_deferred_pid;
                        help->dthps_prev = NULL;
                        if (dtrace_deferred_pid != NULL)
                                dtrace_deferred_pid->dthps_prev = help;
                        dtrace_deferred_pid = help;
                }

                mutex_exit(&dtrace_lock);

        } else if (dofhp != NULL) {
                /*
                 * If the dtrace module is loaded and we have a particular
                 * helper provider description, pass that off to the
                 * meta provider.
                 */

                mutex_exit(&dtrace_lock);

                dtrace_helper_provide(dofhp, p->p_pid);

        } else {
                /*
                 * Otherwise, just pass all the helper provider descriptions
                 * off to the meta provider.
                 */

                VBDTTYPE(uint_t,int) i;
                mutex_exit(&dtrace_lock);

                for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                            p->p_pid);
                }
        }

        mutex_exit(&dtrace_meta_lock);
}

static int
dtrace_helper_provider_add(dof_helper_t *dofhp, int gen)
{
        dtrace_helpers_t *help;
        dtrace_helper_provider_t *hprov, **tmp_provs;
        uint_t tmp_maxprovs, i;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        help = curproc->p_dtrace_helpers;
        ASSERT(help != NULL);

        /*
         * If we already have dtrace_helper_providers_max helper providers,
         * we're refuse to add a new one.
         */
        if (help->dthps_nprovs >= dtrace_helper_providers_max)
                return (ENOSPC);

        /*
         * Check to make sure this isn't a duplicate.
         */
        for (i = 0; i < help->dthps_nprovs; i++) {
                if (dofhp->dofhp_addr ==
                    help->dthps_provs[i]->dthp_prov.dofhp_addr)
                        return (EALREADY);
        }

        hprov = kmem_zalloc(sizeof (dtrace_helper_provider_t), KM_SLEEP);
        hprov->dthp_prov = *dofhp;
        hprov->dthp_ref = 1;
        hprov->dthp_generation = gen;

        /*
         * Allocate a bigger table for helper providers if it's already full.
         */
        if (help->dthps_maxprovs == help->dthps_nprovs) {
                tmp_maxprovs = help->dthps_maxprovs;
                tmp_provs = help->dthps_provs;

                if (help->dthps_maxprovs == 0)
                        help->dthps_maxprovs = 2;
                else
                        help->dthps_maxprovs *= 2;
                if (help->dthps_maxprovs > dtrace_helper_providers_max)
                        help->dthps_maxprovs = dtrace_helper_providers_max;

                ASSERT(tmp_maxprovs < help->dthps_maxprovs);

                help->dthps_provs = kmem_zalloc(help->dthps_maxprovs *
                    sizeof (dtrace_helper_provider_t *), KM_SLEEP);

                if (tmp_provs != NULL) {
                        bcopy(tmp_provs, help->dthps_provs, tmp_maxprovs *
                            sizeof (dtrace_helper_provider_t *));
                        kmem_free(tmp_provs, tmp_maxprovs *
                            sizeof (dtrace_helper_provider_t *));
                }
        }

        help->dthps_provs[help->dthps_nprovs] = hprov;
        help->dthps_nprovs++;

        return (0);
}

static void
dtrace_helper_provider_destroy(dtrace_helper_provider_t *hprov)
{
        mutex_enter(&dtrace_lock);

        if (--hprov->dthp_ref == 0) {
                dof_hdr_t *dof;
                mutex_exit(&dtrace_lock);
                dof = (dof_hdr_t *)(uintptr_t)hprov->dthp_prov.dofhp_dof;
                dtrace_dof_destroy(dof);
                kmem_free(hprov, sizeof (dtrace_helper_provider_t));
        } else {
                mutex_exit(&dtrace_lock);
        }
}

static int
dtrace_helper_provider_validate(dof_hdr_t *dof, dof_sec_t *sec)
{
        uintptr_t daddr = (uintptr_t)dof;
        dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
        dof_provider_t *provider;
        dof_probe_t *probe;
        uint8_t *arg;
        char *strtab, *typestr;
        dof_stridx_t typeidx;
        size_t typesz;
        uint_t nprobes, j, k;

        ASSERT(sec->dofs_type == DOF_SECT_PROVIDER);

        if (sec->dofs_offset & (sizeof (uint_t) - 1)) {
                dtrace_dof_error(dof, "misaligned section offset");
                return (-1);
        }

        /*
         * The section needs to be large enough to contain the DOF provider
         * structure appropriate for the given version.
         */
        if (sec->dofs_size <
            ((dof->dofh_ident[DOF_ID_VERSION] == DOF_VERSION_1) ?
            offsetof(dof_provider_t, dofpv_prenoffs) :
            sizeof (dof_provider_t))) {
                dtrace_dof_error(dof, "provider section too small");
                return (-1);
        }

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = dtrace_dof_sect(dof, DOF_SECT_STRTAB, provider->dofpv_strtab);
        prb_sec = dtrace_dof_sect(dof, DOF_SECT_PROBES, provider->dofpv_probes);
        arg_sec = dtrace_dof_sect(dof, DOF_SECT_PRARGS, provider->dofpv_prargs);
        off_sec = dtrace_dof_sect(dof, DOF_SECT_PROFFS, provider->dofpv_proffs);

        if (str_sec == NULL || prb_sec == NULL ||
            arg_sec == NULL || off_sec == NULL)
                return (-1);

        enoff_sec = NULL;

        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
            provider->dofpv_prenoffs != DOF_SECT_NONE &&
            (enoff_sec = dtrace_dof_sect(dof, DOF_SECT_PRENOFFS,
            provider->dofpv_prenoffs)) == NULL)
                return (-1);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

        if (provider->dofpv_name >= str_sec->dofs_size ||
            strlen(strtab + provider->dofpv_name) >= DTRACE_PROVNAMELEN) {
                dtrace_dof_error(dof, "invalid provider name");
                return (-1);
        }

        if (prb_sec->dofs_entsize == 0 ||
            prb_sec->dofs_entsize > prb_sec->dofs_size) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        if (prb_sec->dofs_entsize & (sizeof (uintptr_t) - 1)) {
                dtrace_dof_error(dof, "misaligned entry size");
                return (-1);
        }

        if (off_sec->dofs_entsize != sizeof (uint32_t)) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        if (off_sec->dofs_offset & (sizeof (uint32_t) - 1)) {
                dtrace_dof_error(dof, "misaligned section offset");
                return (-1);
        }

        if (arg_sec->dofs_entsize != sizeof (uint8_t)) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);

        nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

        /*
         * Take a pass through the probes to check for errors.
         */
        for (j = 0; j < nprobes; j++) {
                probe = (dof_probe_t *)(uintptr_t)(daddr +
                    prb_sec->dofs_offset + j * prb_sec->dofs_entsize);

                if (probe->dofpr_func >= str_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid function name");
                        return (-1);
                }

                if (strlen(strtab + probe->dofpr_func) >= DTRACE_FUNCNAMELEN) {
                        dtrace_dof_error(dof, "function name too long");
                        return (-1);
                }

                if (probe->dofpr_name >= str_sec->dofs_size ||
                    strlen(strtab + probe->dofpr_name) >= DTRACE_NAMELEN) {
                        dtrace_dof_error(dof, "invalid probe name");
                        return (-1);
                }

                /*
                 * The offset count must not wrap the index, and the offsets
                 * must also not overflow the section's data.
                 */
                if (probe->dofpr_offidx + probe->dofpr_noffs <
                    probe->dofpr_offidx ||
                    (probe->dofpr_offidx + probe->dofpr_noffs) *
                    off_sec->dofs_entsize > off_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid probe offset");
                        return (-1);
                }

                if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1) {
                        /*
                         * If there's no is-enabled offset section, make sure
                         * there aren't any is-enabled offsets. Otherwise
                         * perform the same checks as for probe offsets
                         * (immediately above).
                         */
                        if (enoff_sec == NULL) {
                                if (probe->dofpr_enoffidx != 0 ||
                                    probe->dofpr_nenoffs != 0) {
                                        dtrace_dof_error(dof, "is-enabled "
                                            "offsets with null section");
                                        return (-1);
                                }
                        } else if (probe->dofpr_enoffidx +
                            probe->dofpr_nenoffs < probe->dofpr_enoffidx ||
                            (probe->dofpr_enoffidx + probe->dofpr_nenoffs) *
                            enoff_sec->dofs_entsize > enoff_sec->dofs_size) {
                                dtrace_dof_error(dof, "invalid is-enabled "
                                    "offset");
                                return (-1);
                        }

                        if (probe->dofpr_noffs + probe->dofpr_nenoffs == 0) {
                                dtrace_dof_error(dof, "zero probe and "
                                    "is-enabled offsets");
                                return (-1);
                        }
                } else if (probe->dofpr_noffs == 0) {
                        dtrace_dof_error(dof, "zero probe offsets");
                        return (-1);
                }

                if (probe->dofpr_argidx + probe->dofpr_xargc <
                    probe->dofpr_argidx ||
                    (probe->dofpr_argidx + probe->dofpr_xargc) *
                    arg_sec->dofs_entsize > arg_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid args");
                        return (-1);
                }

                typeidx = probe->dofpr_nargv;
                typestr = strtab + probe->dofpr_nargv;
                for (k = 0; k < probe->dofpr_nargc; k++) {
                        if (typeidx >= str_sec->dofs_size) {
                                dtrace_dof_error(dof, "bad "
                                    "native argument type");
                                return (-1);
                        }

                        typesz = strlen(typestr) + 1;
                        if (typesz > DTRACE_ARGTYPELEN) {
                                dtrace_dof_error(dof, "native "
                                    "argument type too long");
                                return (-1);
                        }
                        typeidx += VBDTCAST(dof_stridx_t)typesz;
                        typestr += typesz;
                }

                typeidx = probe->dofpr_xargv;
                typestr = strtab + probe->dofpr_xargv;
                for (k = 0; k < probe->dofpr_xargc; k++) {
                        if (arg[probe->dofpr_argidx + k] > probe->dofpr_nargc) {
                                dtrace_dof_error(dof, "bad "
                                    "native argument index");
                                return (-1);
                        }

                        if (typeidx >= str_sec->dofs_size) {
                                dtrace_dof_error(dof, "bad "
                                    "translated argument type");
                                return (-1);
                        }

                        typesz = strlen(typestr) + 1;
                        if (typesz > DTRACE_ARGTYPELEN) {
                                dtrace_dof_error(dof, "translated argument "
                                    "type too long");
                                return (-1);
                        }

                        typeidx += VBDTCAST(dof_stridx_t)typesz;
                        typestr += typesz;
                }
        }

        return (0);
}

static int
dtrace_helper_slurp(dof_hdr_t *dof, dof_helper_t *dhp)
{
        dtrace_helpers_t *help;
        dtrace_vstate_t *vstate;
        dtrace_enabling_t *enab = NULL;
        int i, gen, rv, nhelpers = 0, nprovs = 0, destroy = 1;
        uintptr_t daddr = (uintptr_t)dof;

        ASSERT(MUTEX_HELD(&dtrace_lock));

        if ((help = curproc->p_dtrace_helpers) == NULL)
                help = dtrace_helpers_create(curproc);

        vstate = &help->dthps_vstate;

        if ((rv = dtrace_dof_slurp(dof, vstate, NULL, &enab,
            dhp != NULL ? dhp->dofhp_addr : 0, B_FALSE)) != 0) {
                dtrace_dof_destroy(dof);
                return (rv);
        }

        /*
         * Look for helper providers and validate their descriptions.
         */
        if (dhp != NULL) {
                for (i = 0; i < VBDTCAST(int)dof->dofh_secnum; i++) {
                        dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                            dof->dofh_secoff + i * dof->dofh_secsize);

                        if (sec->dofs_type != DOF_SECT_PROVIDER)
                                continue;

                        if (dtrace_helper_provider_validate(dof, sec) != 0) {
                                dtrace_enabling_destroy(enab);
                                dtrace_dof_destroy(dof);
                                return (-1);
                        }

                        nprovs++;
                }
        }

        /*
         * Now we need to walk through the ECB descriptions in the enabling.
         */
        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_ecbdesc_t *ep = enab->dten_desc[i];
                dtrace_probedesc_t *desc = &ep->dted_probe;

                if (strcmp(desc->dtpd_provider, "dtrace") != 0)
                        continue;

                if (strcmp(desc->dtpd_mod, "helper") != 0)
                        continue;

                if (strcmp(desc->dtpd_func, "ustack") != 0)
                        continue;

                if ((rv = dtrace_helper_action_add(DTRACE_HELPER_ACTION_USTACK,
                    ep)) != 0) {
                        /*
                         * Adding this helper action failed -- we are now going
                         * to rip out the entire generation and return failure.
                         */
                        (void) dtrace_helper_destroygen(help->dthps_generation);
                        dtrace_enabling_destroy(enab);
                        dtrace_dof_destroy(dof);
                        return (-1);
                }

                nhelpers++;
        }

        if (nhelpers < enab->dten_ndesc)
                dtrace_dof_error(dof, "unmatched helpers");

        gen = help->dthps_generation++;
        dtrace_enabling_destroy(enab);

        if (dhp != NULL && nprovs > 0) {
                dhp->dofhp_dof = (uint64_t)(uintptr_t)dof;
                if (dtrace_helper_provider_add(dhp, gen) == 0) {
                        mutex_exit(&dtrace_lock);
                        dtrace_helper_provider_register(curproc, help, dhp);
                        mutex_enter(&dtrace_lock);

                        destroy = 0;
                }
        }

        if (destroy)
                dtrace_dof_destroy(dof);

        return (gen);
}

static dtrace_helpers_t *
dtrace_helpers_create(proc_t *p)
{
        dtrace_helpers_t *help;

        ASSERT(MUTEX_HELD(&dtrace_lock));
        ASSERT(p->p_dtrace_helpers == NULL);

        help = kmem_zalloc(sizeof (dtrace_helpers_t), KM_SLEEP);
        help->dthps_actions = kmem_zalloc(sizeof (dtrace_helper_action_t *) *
            DTRACE_NHELPER_ACTIONS, KM_SLEEP);

        p->p_dtrace_helpers = help;
        dtrace_helpers++;

        return (help);
}

static void
dtrace_helpers_destroy(void)
{
        dtrace_helpers_t *help;
        dtrace_vstate_t *vstate;
        proc_t *p = curproc;
        VBDTTYPE(uint_t, int) i;

        mutex_enter(&dtrace_lock);

        ASSERT(p->p_dtrace_helpers != NULL);
        ASSERT(dtrace_helpers > 0);

        help = p->p_dtrace_helpers;
        vstate = &help->dthps_vstate;

        /*
         * We're now going to lose the help from this process.
         */
        p->p_dtrace_helpers = NULL;
        dtrace_sync();

        /*
         * Destory the helper actions.
         */
        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                dtrace_helper_action_t *h, *next;

                for (h = help->dthps_actions[i]; h != NULL; h = next) {
                        next = h->dtha_next;
                        dtrace_helper_action_destroy(h, vstate);
                        h = next;
                }
        }

        mutex_exit(&dtrace_lock);

        /*
         * Destroy the helper providers.
         */
        if (help->dthps_maxprovs > 0) {
                mutex_enter(&dtrace_meta_lock);
                if (dtrace_meta_pid != NULL) {
                        ASSERT(dtrace_deferred_pid == NULL);

                        for (i = 0; i < help->dthps_nprovs; i++) {
                                dtrace_helper_provider_remove(
                                    &help->dthps_provs[i]->dthp_prov, p->p_pid);
                        }
                } else {
                        mutex_enter(&dtrace_lock);
                        ASSERT(help->dthps_deferred == 0 ||
                            help->dthps_next != NULL ||
                            help->dthps_prev != NULL ||
                            help == dtrace_deferred_pid);

                        /*
                         * Remove the helper from the deferred list.
                         */
                        if (help->dthps_next != NULL)
                                help->dthps_next->dthps_prev = help->dthps_prev;
                        if (help->dthps_prev != NULL)
                                help->dthps_prev->dthps_next = help->dthps_next;
                        if (dtrace_deferred_pid == help) {
                                dtrace_deferred_pid = help->dthps_next;
                                ASSERT(help->dthps_prev == NULL);
                        }

                        mutex_exit(&dtrace_lock);
                }

                mutex_exit(&dtrace_meta_lock);

                for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provider_destroy(help->dthps_provs[i]);
                }

                kmem_free(help->dthps_provs, help->dthps_maxprovs *
                    sizeof (dtrace_helper_provider_t *));
        }

        mutex_enter(&dtrace_lock);

        dtrace_vstate_fini(&help->dthps_vstate);
        kmem_free(help->dthps_actions,
            sizeof (dtrace_helper_action_t *) * DTRACE_NHELPER_ACTIONS);
        kmem_free(help, sizeof (dtrace_helpers_t));

        --dtrace_helpers;
        mutex_exit(&dtrace_lock);
}

static void
dtrace_helpers_duplicate(proc_t *from, proc_t *to)
{
        dtrace_helpers_t *help, *newhelp;
        dtrace_helper_action_t *helper, *new, *last;
        dtrace_difo_t *dp;
        dtrace_vstate_t *vstate;
        int i, j, sz, hasprovs = 0;

        mutex_enter(&dtrace_lock);
        ASSERT(from->p_dtrace_helpers != NULL);
        ASSERT(dtrace_helpers > 0);

        help = from->p_dtrace_helpers;
        newhelp = dtrace_helpers_create(to);
        ASSERT(to->p_dtrace_helpers != NULL);

        newhelp->dthps_generation = help->dthps_generation;
        vstate = &newhelp->dthps_vstate;

        /*
         * Duplicate the helper actions.
         */
        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                if ((helper = help->dthps_actions[i]) == NULL)
                        continue;

                for (last = NULL; helper != NULL; helper = helper->dtha_next) {
                        new = kmem_zalloc(sizeof (dtrace_helper_action_t),
                            KM_SLEEP);
                        new->dtha_generation = helper->dtha_generation;

                        if ((dp = helper->dtha_predicate) != NULL) {
                                dp = dtrace_difo_duplicate(dp, vstate);
                                new->dtha_predicate = dp;
                        }

                        new->dtha_nactions = helper->dtha_nactions;
                        sz = sizeof (dtrace_difo_t *) * new->dtha_nactions;
                        new->dtha_actions = kmem_alloc(sz, KM_SLEEP);

                        for (j = 0; j < new->dtha_nactions; j++) {
                                dtrace_difo_t *dp2 = helper->dtha_actions[j];

                                ASSERT(dp2 != NULL);
                                dp2 = dtrace_difo_duplicate(dp2, vstate);
                                new->dtha_actions[j] = dp2;
                        }

                        if (last != NULL) {
                                last->dtha_next = new;
                        } else {
                                newhelp->dthps_actions[i] = new;
                        }

                        last = new;
                }
        }

        /*
         * Duplicate the helper providers and register them with the
         * DTrace framework.
         */
        if (help->dthps_nprovs > 0) {
                newhelp->dthps_nprovs = help->dthps_nprovs;
                newhelp->dthps_maxprovs = help->dthps_nprovs;
                newhelp->dthps_provs = kmem_alloc(newhelp->dthps_nprovs *
                    sizeof (dtrace_helper_provider_t *), KM_SLEEP);
                for (i = 0; i < VBDTCAST(int)newhelp->dthps_nprovs; i++) {
                        newhelp->dthps_provs[i] = help->dthps_provs[i];
                        newhelp->dthps_provs[i]->dthp_ref++;
                }

                hasprovs = 1;
        }

        mutex_exit(&dtrace_lock);

        if (hasprovs)
                dtrace_helper_provider_register(to, newhelp, NULL);
}

#ifndef VBOX

/*
 * DTrace Hook Functions
 */
static void
dtrace_module_loaded(struct modctl *ctl)
{
        dtrace_provider_t *prv;

        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&mod_lock);

        ASSERT(ctl->mod_busy);

        /*
         * We're going to call each providers per-module provide operation
         * specifying only this module.
         */
        for (prv = dtrace_provider; prv != NULL; prv = prv->dtpv_next)
                prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);

        mutex_exit(&mod_lock);
        mutex_exit(&dtrace_provider_lock);

        /*
         * If we have any retained enablings, we need to match against them.
         * Enabling probes requires that cpu_lock be held, and we cannot hold
         * cpu_lock here -- it is legal for cpu_lock to be held when loading a
         * module.  (In particular, this happens when loading scheduling
         * classes.)  So if we have any retained enablings, we need to dispatch
         * our task queue to do the match for us.
         */
        mutex_enter(&dtrace_lock);

        if (dtrace_retained == NULL) {
                mutex_exit(&dtrace_lock);
                return;
        }

        (void) taskq_dispatch(dtrace_taskq,
            (task_func_t *)dtrace_enabling_matchall, NULL, TQ_SLEEP);

        mutex_exit(&dtrace_lock);

        /*
         * And now, for a little heuristic sleaze:  in general, we want to
         * match modules as soon as they load.  However, we cannot guarantee
         * this, because it would lead us to the lock ordering violation
         * outlined above.  The common case, of course, is that cpu_lock is
         * _not_ held -- so we delay here for a clock tick, hoping that that's
         * long enough for the task queue to do its work.  If it's not, it's
         * not a serious problem -- it just means that the module that we
         * just loaded may not be immediately instrumentable.
         */
        delay(1);
}

static void
dtrace_module_unloaded(struct modctl *ctl)
{
        dtrace_probe_t template, *probe, *first, *next;
        dtrace_provider_t *prov;

        template.dtpr_mod = ctl->mod_modname;

        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&mod_lock);
        mutex_enter(&dtrace_lock);

        if (dtrace_bymod == NULL) {
                /*
                 * The DTrace module is loaded (obviously) but not attached;
                 * we don't have any work to do.
                 */
                mutex_exit(&dtrace_provider_lock);
                mutex_exit(&mod_lock);
                mutex_exit(&dtrace_lock);
                return;
        }

        for (probe = first = dtrace_hash_lookup(dtrace_bymod, &template);
            probe != NULL; probe = probe->dtpr_nextmod) {
                if (probe->dtpr_ecb != NULL) {
                        mutex_exit(&dtrace_provider_lock);
                        mutex_exit(&mod_lock);
                        mutex_exit(&dtrace_lock);

                        /*
                         * This shouldn't _actually_ be possible -- we're
                         * unloading a module that has an enabled probe in it.
                         * (It's normally up to the provider to make sure that
                         * this can't happen.)  However, because dtps_enable()
                         * doesn't have a failure mode, there can be an
                         * enable/unload race.  Upshot:  we don't want to
                         * assert, but we're not going to disable the
                         * probe, either.
                         */
                        if (dtrace_err_verbose) {
                                cmn_err(CE_WARN, "unloaded module '%s' had "
                                    "enabled probes", ctl->mod_modname);
                        }

                        return;
                }
        }

        probe = first;

        for (first = NULL; probe != NULL; probe = next) {
                ASSERT(dtrace_probes[probe->dtpr_id - 1] == probe);

                dtrace_probes[probe->dtpr_id - 1] = NULL;

                next = probe->dtpr_nextmod;
                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                if (first == NULL) {
                        first = probe;
                        probe->dtpr_nextmod = NULL;
                } else {
                        probe->dtpr_nextmod = first;
                        first = probe;
                }
        }

        /*
         * We've removed all of the module's probes from the hash chains and
         * from the probe array.  Now issue a dtrace_sync() to be sure that
         * everyone has cleared out from any probe array processing.
         */
        dtrace_sync();

        for (probe = first; probe != NULL; probe = first) {
                first = probe->dtpr_nextmod;
                prov = probe->dtpr_provider;
                prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, probe->dtpr_id,
                    probe->dtpr_arg);
                kmem_free(probe->dtpr_mod, strlen(probe->dtpr_mod) + 1);
                kmem_free(probe->dtpr_func, strlen(probe->dtpr_func) + 1);
                kmem_free(probe->dtpr_name, strlen(probe->dtpr_name) + 1);
                vmem_free(dtrace_arena, (void *)(uintptr_t)probe->dtpr_id, 1);
                kmem_free(probe, sizeof (dtrace_probe_t));
        }

        mutex_exit(&dtrace_lock);
        mutex_exit(&mod_lock);
        mutex_exit(&dtrace_provider_lock);
}

#endif /* !VBOX */

VBDTSTATIC void
dtrace_suspend(void)
{
        dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_suspend));
}

VBDTSTATIC void
dtrace_resume(void)
{
        dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_resume));
}

#ifdef VBOX
typedef enum {
    CPU_INVALID,
    CPU_CONFIG,
    CPU_UNCONFIG
} cpu_setup_t;
#endif


static int
dtrace_cpu_setup(cpu_setup_t what, processorid_t cpu)
{
        ASSERT(MUTEX_HELD(&cpu_lock));
        mutex_enter(&dtrace_lock);

        switch (what) {
        case CPU_CONFIG: {
                dtrace_state_t *state;
                dtrace_optval_t *opt, rs, c;

                /*
                 * For now, we only allocate a new buffer for anonymous state.
                 */
                if ((state = dtrace_anon.dta_state) == NULL)
                        break;

                if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                        break;

                opt = state->dts_options;
                c = opt[DTRACEOPT_CPU];

                if (c != DTRACE_CPUALL && c != DTRACEOPT_UNSET && c != cpu)
                        break;

                /*
                 * Regardless of what the actual policy is, we're going to
                 * temporarily set our resize policy to be manual.  We're
                 * also going to temporarily set our CPU option to denote
                 * the newly configured CPU.
                 */
                rs = opt[DTRACEOPT_BUFRESIZE];
                opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_MANUAL;
                opt[DTRACEOPT_CPU] = (dtrace_optval_t)cpu;

                (void) dtrace_state_buffers(state);

                opt[DTRACEOPT_BUFRESIZE] = rs;
                opt[DTRACEOPT_CPU] = c;

                break;
        }

        case CPU_UNCONFIG:
                /*
                 * We don't free the buffer in the CPU_UNCONFIG case.  (The
                 * buffer will be freed when the consumer exits.)
                 */
                break;

        default:
                break;
        }

        mutex_exit(&dtrace_lock);
        return (0);
}

#ifndef VBOX
static void
dtrace_cpu_setup_initial(processorid_t cpu)
{
        (void) dtrace_cpu_setup(CPU_CONFIG, cpu);
}
#endif /* !VBOX */

static void
dtrace_toxrange_add(uintptr_t base, uintptr_t limit)
{
        if (dtrace_toxranges >= dtrace_toxranges_max) {
                int osize, nsize;
                dtrace_toxrange_t *range;

                osize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);

                if (osize == 0) {
                        ASSERT(dtrace_toxrange == NULL);
                        ASSERT(dtrace_toxranges_max == 0);
                        dtrace_toxranges_max = 1;
                } else {
                        dtrace_toxranges_max <<= 1;
                }

                nsize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);
                range = kmem_zalloc(nsize, KM_SLEEP);

                if (dtrace_toxrange != NULL) {
                        ASSERT(osize != 0);
                        bcopy(dtrace_toxrange, range, osize);
                        kmem_free(dtrace_toxrange, osize);
                }

                dtrace_toxrange = range;
        }

        ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_base == NULL);
        ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_limit == NULL);

        dtrace_toxrange[dtrace_toxranges].dtt_base = base;
        dtrace_toxrange[dtrace_toxranges].dtt_limit = limit;
        dtrace_toxranges++;
}

/*
 * DTrace Driver Cookbook Functions
 */
/*ARGSUSED*/
static int
dtrace_attach(dev_info_t *devi, ddi_attach_cmd_t cmd)
{
        dtrace_provider_id_t id;
        dtrace_state_t *state = NULL;
        dtrace_enabling_t *enab;

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&dtrace_lock);

        if (ddi_soft_state_init(&dtrace_softstate,
            sizeof (dtrace_state_t), 0) != 0) {
                cmn_err(CE_NOTE, "/dev/dtrace failed to initialize soft state");
                mutex_exit(&cpu_lock);
                mutex_exit(&dtrace_provider_lock);
                mutex_exit(&dtrace_lock);
                return (DDI_FAILURE);
        }

#ifndef VBOX
        if (ddi_create_minor_node(devi, DTRACEMNR_DTRACE, S_IFCHR,
            DTRACEMNRN_DTRACE, DDI_PSEUDO, NULL) == DDI_FAILURE ||
            ddi_create_minor_node(devi, DTRACEMNR_HELPER, S_IFCHR,
            DTRACEMNRN_HELPER, DDI_PSEUDO, NULL) == DDI_FAILURE) {
                cmn_err(CE_NOTE, "/dev/dtrace couldn't create minor nodes");
                ddi_remove_minor_node(devi, NULL);
                ddi_soft_state_fini(&dtrace_softstate);
                mutex_exit(&cpu_lock);
                mutex_exit(&dtrace_provider_lock);
                mutex_exit(&dtrace_lock);
                return (DDI_FAILURE);
        }
#endif

        ddi_report_dev(devi);
        dtrace_devi = devi;

#ifndef VBOX
        dtrace_modload = dtrace_module_loaded;
        dtrace_modunload = dtrace_module_unloaded;
        dtrace_cpu_init = dtrace_cpu_setup_initial;
        dtrace_helpers_cleanup = dtrace_helpers_destroy;
        dtrace_helpers_fork = dtrace_helpers_duplicate;
        dtrace_cpustart_init = dtrace_suspend;
        dtrace_cpustart_fini = dtrace_resume;
        dtrace_debugger_init = dtrace_suspend;
        dtrace_debugger_fini = dtrace_resume;

        register_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);
#else
        /** @todo some of these hooks needs checking out! */
#endif

        ASSERT(MUTEX_HELD(&cpu_lock));

        dtrace_arena = vmem_create("dtrace", (void *)1, UINT32_MAX, 1,
            NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);
        dtrace_minor = vmem_create("dtrace_minor", (void *)DTRACEMNRN_CLONE,
            UINT32_MAX - DTRACEMNRN_CLONE, 1, NULL, NULL, NULL, 0,
            VM_SLEEP | VMC_IDENTIFIER);
#ifndef VBOX
        dtrace_taskq = taskq_create("dtrace_taskq", 1, maxclsyspri,
            1, INT_MAX, 0);
#endif

        dtrace_state_cache = kmem_cache_create("dtrace_state_cache",
            sizeof (dtrace_dstate_percpu_t) * NCPU, DTRACE_STATE_ALIGN,
            NULL, NULL, NULL, NULL, NULL, 0);

        ASSERT(MUTEX_HELD(&cpu_lock));
        dtrace_bymod = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_mod),
            offsetof(dtrace_probe_t, dtpr_nextmod),
            offsetof(dtrace_probe_t, dtpr_prevmod));

        dtrace_byfunc = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_func),
            offsetof(dtrace_probe_t, dtpr_nextfunc),
            offsetof(dtrace_probe_t, dtpr_prevfunc));

        dtrace_byname = dtrace_hash_create(offsetof(dtrace_probe_t, dtpr_name),
            offsetof(dtrace_probe_t, dtpr_nextname),
            offsetof(dtrace_probe_t, dtpr_prevname));

        if (dtrace_retain_max < 1) {
                cmn_err(CE_WARN, "illegal value (%lu) for dtrace_retain_max; "
                    "setting to 1", dtrace_retain_max);
                dtrace_retain_max = 1;
        }

        /*
         * Now discover our toxic ranges.
         */
        dtrace_toxic_ranges(dtrace_toxrange_add);

        /*
         * Before we register ourselves as a provider to our own framework,
         * we would like to assert that dtrace_provider is NULL -- but that's
         * not true if we were loaded as a dependency of a DTrace provider.
         * Once we've registered, we can assert that dtrace_provider is our
         * pseudo provider.
         */
        (void) dtrace_register("dtrace", &dtrace_provider_attr,
            DTRACE_PRIV_NONE, 0, &dtrace_provider_ops, NULL, &id);

        ASSERT(dtrace_provider != NULL);
        ASSERT((dtrace_provider_id_t)dtrace_provider == id);

        dtrace_probeid_begin = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "BEGIN", 0, NULL);
        dtrace_probeid_end = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "END", 0, NULL);
        dtrace_probeid_error = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "ERROR", 1, NULL);

        dtrace_anon_property();
        mutex_exit(&cpu_lock);

        /*
         * If DTrace helper tracing is enabled, we need to allocate the
         * trace buffer and initialize the values.
         */
        if (dtrace_helptrace_enabled) {
                ASSERT(dtrace_helptrace_buffer == NULL);
                dtrace_helptrace_buffer =
                    kmem_zalloc(dtrace_helptrace_bufsize, KM_SLEEP);
                dtrace_helptrace_next = 0;
        }

        /*
         * If there are already providers, we must ask them to provide their
         * probes, and then match any anonymous enabling against them.  Note
         * that there should be no other retained enablings at this time:
         * the only retained enablings at this time should be the anonymous
         * enabling.
         */
        if (dtrace_anon.dta_enabling != NULL) {
                ASSERT(dtrace_retained == dtrace_anon.dta_enabling);

                dtrace_enabling_provide(NULL);
                state = dtrace_anon.dta_state;

                /*
                 * We couldn't hold cpu_lock across the above call to
                 * dtrace_enabling_provide(), but we must hold it to actually
                 * enable the probes.  We have to drop all of our locks, pick
                 * up cpu_lock, and regain our locks before matching the
                 * retained anonymous enabling.
                 */
                mutex_exit(&dtrace_lock);
                mutex_exit(&dtrace_provider_lock);

                mutex_enter(&cpu_lock);
                mutex_enter(&dtrace_provider_lock);
                mutex_enter(&dtrace_lock);

                if ((enab = dtrace_anon.dta_enabling) != NULL)
                        (void) dtrace_enabling_match(enab, NULL);

                mutex_exit(&cpu_lock);
        }

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_provider_lock);

        if (state != NULL) {
                /*
                 * If we created any anonymous state, set it going now.
                 */
                (void) dtrace_state_go(state, &dtrace_anon.dta_beganon);
        }

        return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
dtrace_open(dev_t *devp, int flag, int otyp, cred_t *cred_p)
{
        dtrace_state_t *state;
        uint32_t priv;
        uid_t uid;
        zoneid_t zoneid;

        if (getminor(*devp) == DTRACEMNRN_HELPER)
                return (0);

        /*
         * If this wasn't an open with the "helper" minor, then it must be
         * the "dtrace" minor.
         */
        if (getminor(*devp) != DTRACEMNRN_DTRACE)
                return (ENXIO);

        /*
         * If no DTRACE_PRIV_* bits are set in the credential, then the
         * caller lacks sufficient permission to do anything with DTrace.
         */
        dtrace_cred2priv(cred_p, &priv, &uid, &zoneid);
        if (priv == DTRACE_PRIV_NONE)
                return (EACCES);

        /*
         * Ask all providers to provide all their probes.
         */
        mutex_enter(&dtrace_provider_lock);
        dtrace_probe_provide(NULL, NULL);
        mutex_exit(&dtrace_provider_lock);

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_lock);
        dtrace_opens++;
        dtrace_membar_producer();

#ifndef VBOX
        /*
         * If the kernel debugger is active (that is, if the kernel debugger
         * modified text in some way), we won't allow the open.
         */
        if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
                dtrace_opens--;
                mutex_exit(&cpu_lock);
                mutex_exit(&dtrace_lock);
                return (EBUSY);
        }
#endif

        state = dtrace_state_create(devp, cred_p);
        mutex_exit(&cpu_lock);

        if (state == NULL) {
#ifndef VBOX
                if (--dtrace_opens == 0 && dtrace_anon.dta_enabling == NULL)
                        (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#endif
                mutex_exit(&dtrace_lock);
                return (EAGAIN);
        }

        mutex_exit(&dtrace_lock);

        return (0);
}

/*ARGSUSED*/
static int
dtrace_close(dev_t dev, int flag, int otyp, cred_t *cred_p)
{
        minor_t minor = getminor(dev);
        dtrace_state_t *state;

        if (minor == DTRACEMNRN_HELPER)
                return (0);

        state = ddi_get_soft_state(dtrace_softstate, minor);

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_lock);

        if (state->dts_anon) {
                /*
                 * There is anonymous state. Destroy that first.
                 */
                ASSERT(dtrace_anon.dta_state == NULL);
                dtrace_state_destroy(state->dts_anon);
        }

        dtrace_state_destroy(state);
        ASSERT(dtrace_opens > 0);

#ifndef VBOX
        /*
         * Only relinquish control of the kernel debugger interface when there
         * are no consumers and no anonymous enablings.
         */
        if (--dtrace_opens == 0 && dtrace_anon.dta_enabling == NULL)
                (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#endif

        mutex_exit(&dtrace_lock);
        mutex_exit(&cpu_lock);

        return (0);
}

/*ARGSUSED*/
static int
dtrace_ioctl_helper(int cmd, intptr_t arg, int *rv)
{
        int rval;
        dof_helper_t help, *dhp = NULL;

        switch (cmd) {
        case DTRACEHIOC_ADDDOF:
                if (copyin((void *)arg, &help, sizeof (help)) != 0) {
                        dtrace_dof_error(NULL, "failed to copyin DOF helper");
                        return (EFAULT);
                }

                dhp = &help;
                arg = (intptr_t)help.dofhp_dof;
                /*FALLTHROUGH*/

        case DTRACEHIOC_ADD: {
                dof_hdr_t *dof = dtrace_dof_copyin(arg, &rval);

                if (dof == NULL)
                        return (rval);

                mutex_enter(&dtrace_lock);

                /*
                 * dtrace_helper_slurp() takes responsibility for the dof --
                 * it may free it now or it may save it and free it later.
                 */
                if ((rval = dtrace_helper_slurp(dof, dhp)) != -1) {
                        *rv = rval;
                        rval = 0;
                } else {
                        rval = EINVAL;
                }

                mutex_exit(&dtrace_lock);
                return (rval);
        }

        case DTRACEHIOC_REMOVE: {
                mutex_enter(&dtrace_lock);
                rval = dtrace_helper_destroygen(arg);
                mutex_exit(&dtrace_lock);

                return (rval);
        }

        default:
                break;
        }

        return (ENOTTY);
}

/*ARGSUSED*/
static int
dtrace_ioctl(dev_t dev, int cmd, intptr_t arg, int md, cred_t *cr, int *rv)
{
        minor_t minor = getminor(dev);
        dtrace_state_t *state;
        int rval;

        if (minor == DTRACEMNRN_HELPER)
                return (dtrace_ioctl_helper(cmd, arg, rv));

        state = ddi_get_soft_state(dtrace_softstate, minor);

        if (state->dts_anon) {
                ASSERT(dtrace_anon.dta_state == NULL);
                state = state->dts_anon;
        }

        switch (cmd) {
        case DTRACEIOC_PROVIDER: {
                dtrace_providerdesc_t pvd;
                dtrace_provider_t *pvp;

                if (copyin((void *)arg, &pvd, sizeof (pvd)) != 0)
                        return (EFAULT);

                pvd.dtvd_name[DTRACE_PROVNAMELEN - 1] = '\0';
                mutex_enter(&dtrace_provider_lock);

                for (pvp = dtrace_provider; pvp != NULL; pvp = pvp->dtpv_next) {
                        if (strcmp(pvp->dtpv_name, pvd.dtvd_name) == 0)
                                break;
                }

                mutex_exit(&dtrace_provider_lock);

                if (pvp == NULL)
                        return (ESRCH);

                bcopy(&pvp->dtpv_priv, &pvd.dtvd_priv, sizeof (dtrace_ppriv_t));
                bcopy(&pvp->dtpv_attr, &pvd.dtvd_attr, sizeof (dtrace_pattr_t));
                if (copyout(&pvd, (void *)arg, sizeof (pvd)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_EPROBE: {
                dtrace_eprobedesc_t epdesc;
                dtrace_ecb_t *ecb;
                dtrace_action_t *act;
                void *buf;
                size_t size;
                uintptr_t dest;
                int nrecs;

                if (copyin((void *)arg, &epdesc, sizeof (epdesc)) != 0)
                        return (EFAULT);

                mutex_enter(&dtrace_lock);

                if ((ecb = dtrace_epid2ecb(state, epdesc.dtepd_epid)) == NULL) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                }

                if (ecb->dte_probe == NULL) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                }

                epdesc.dtepd_probeid = ecb->dte_probe->dtpr_id;
                epdesc.dtepd_uarg = ecb->dte_uarg;
                epdesc.dtepd_size = VBDTCAST(uint32_t)ecb->dte_size;

                nrecs = epdesc.dtepd_nrecs;
                epdesc.dtepd_nrecs = 0;
                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                                continue;

                        epdesc.dtepd_nrecs++;
                }

                /*
                 * Now that we have the size, we need to allocate a temporary
                 * buffer in which to store the complete description.  We need
                 * the temporary buffer to be able to drop dtrace_lock()
                 * across the copyout(), below.
                 */
                size = sizeof (dtrace_eprobedesc_t) +
                    (epdesc.dtepd_nrecs * sizeof (dtrace_recdesc_t));

                buf = kmem_alloc(size, KM_SLEEP);
                dest = (uintptr_t)buf;

                bcopy(&epdesc, (void *)dest, sizeof (epdesc));
                dest += offsetof(dtrace_eprobedesc_t, dtepd_rec[0]);

                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                                continue;

                        if (nrecs-- == 0)
                                break;

                        bcopy(&act->dta_rec, (void *)dest,
                            sizeof (dtrace_recdesc_t));
                        dest += sizeof (dtrace_recdesc_t);
                }

                mutex_exit(&dtrace_lock);

                if (copyout(buf, (void *)arg, dest - (uintptr_t)buf) != 0) {
                        kmem_free(buf, size);
                        return (EFAULT);
                }

                kmem_free(buf, size);
                return (0);
        }

        case DTRACEIOC_AGGDESC: {
                dtrace_aggdesc_t aggdesc;
                dtrace_action_t *act;
                dtrace_aggregation_t *agg;
                int nrecs;
                uint32_t offs;
                dtrace_recdesc_t *lrec;
                void *buf;
                size_t size;
                uintptr_t dest;

                if (copyin((void *)arg, &aggdesc, sizeof (aggdesc)) != 0)
                        return (EFAULT);

                mutex_enter(&dtrace_lock);

                if ((agg = dtrace_aggid2agg(state, aggdesc.dtagd_id)) == NULL) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                }

                aggdesc.dtagd_epid = agg->dtag_ecb->dte_epid;

                nrecs = aggdesc.dtagd_nrecs;
                aggdesc.dtagd_nrecs = 0;

                offs = agg->dtag_base;
                lrec = &agg->dtag_action.dta_rec;
                aggdesc.dtagd_size = lrec->dtrd_offset + lrec->dtrd_size - offs;

                for (act = agg->dtag_first; ; act = act->dta_next) {
                        ASSERT(act->dta_intuple ||
                            DTRACEACT_ISAGG(act->dta_kind));

                        /*
                         * If this action has a record size of zero, it
                         * denotes an argument to the aggregating action.
                         * Because the presence of this record doesn't (or
                         * shouldn't) affect the way the data is interpreted,
                         * we don't copy it out to save user-level the
                         * confusion of dealing with a zero-length record.
                         */
                        if (act->dta_rec.dtrd_size == 0) {
                                ASSERT(agg->dtag_hasarg);
                                continue;
                        }

                        aggdesc.dtagd_nrecs++;

                        if (act == &agg->dtag_action)
                                break;
                }

                /*
                 * Now that we have the size, we need to allocate a temporary
                 * buffer in which to store the complete description.  We need
                 * the temporary buffer to be able to drop dtrace_lock()
                 * across the copyout(), below.
                 */
                size = sizeof (dtrace_aggdesc_t) +
                    (aggdesc.dtagd_nrecs * sizeof (dtrace_recdesc_t));

                buf = kmem_alloc(size, KM_SLEEP);
                dest = (uintptr_t)buf;

                bcopy(&aggdesc, (void *)dest, sizeof (aggdesc));
                dest += offsetof(dtrace_aggdesc_t, dtagd_rec[0]);

                for (act = agg->dtag_first; ; act = act->dta_next) {
                        dtrace_recdesc_t rec = act->dta_rec;

                        /*
                         * See the comment in the above loop for why we pass
                         * over zero-length records.
                         */
                        if (rec.dtrd_size == 0) {
                                ASSERT(agg->dtag_hasarg);
                                continue;
                        }

                        if (nrecs-- == 0)
                                break;

                        rec.dtrd_offset -= offs;
                        bcopy(&rec, (void *)dest, sizeof (rec));
                        dest += sizeof (dtrace_recdesc_t);

                        if (act == &agg->dtag_action)
                                break;
                }

                mutex_exit(&dtrace_lock);

                if (copyout(buf, (void *)arg, dest - (uintptr_t)buf) != 0) {
                        kmem_free(buf, size);
                        return (EFAULT);
                }

                kmem_free(buf, size);
                return (0);
        }

        case DTRACEIOC_ENABLE: {
                dof_hdr_t *dof;
                dtrace_enabling_t *enab = NULL;
                dtrace_vstate_t *vstate;
                int err = 0;

                *rv = 0;

                /*
                 * If a NULL argument has been passed, we take this as our
                 * cue to reevaluate our enablings.
                 */
                if (arg == NULL) {
                        dtrace_enabling_matchall();

                        return (0);
                }

                if ((dof = dtrace_dof_copyin(arg, &rval)) == NULL)
                        return (rval);

                mutex_enter(&cpu_lock);
                mutex_enter(&dtrace_lock);
                vstate = &state->dts_vstate;

                if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (EBUSY);
                }

                if (dtrace_dof_slurp(dof, vstate, cr, &enab, 0, B_TRUE) != 0) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (EINVAL);
                }

                if ((rval = dtrace_dof_options(dof, state)) != 0) {
                        dtrace_enabling_destroy(enab);
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (rval);
                }

                if ((err = dtrace_enabling_match(enab, rv)) == 0) {
                        err = dtrace_enabling_retain(enab);
                } else {
                        dtrace_enabling_destroy(enab);
                }

                mutex_exit(&cpu_lock);
                mutex_exit(&dtrace_lock);
                dtrace_dof_destroy(dof);

                return (err);
        }

        case DTRACEIOC_REPLICATE: {
                dtrace_repldesc_t desc;
                dtrace_probedesc_t *match = &desc.dtrpd_match;
                dtrace_probedesc_t *create = &desc.dtrpd_create;
                int err;

                if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                match->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                match->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                match->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                match->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                create->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                create->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                create->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                create->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                mutex_enter(&dtrace_lock);
                err = dtrace_enabling_replicate(state, match, create);
                mutex_exit(&dtrace_lock);

                return (err);
        }

        case DTRACEIOC_PROBEMATCH:
        case DTRACEIOC_PROBES: {
                dtrace_probe_t *probe = NULL;
                dtrace_probedesc_t desc;
                dtrace_probekey_t pkey;
                dtrace_id_t i;
                int m = 0;
                uint32_t priv;
                uid_t uid;
                zoneid_t zoneid;

                if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                desc.dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                desc.dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                desc.dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                desc.dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                /*
                 * Before we attempt to match this probe, we want to give
                 * all providers the opportunity to provide it.
                 */
                if (desc.dtpd_id == DTRACE_IDNONE) {
                        mutex_enter(&dtrace_provider_lock);
                        dtrace_probe_provide(&desc, NULL);
                        mutex_exit(&dtrace_provider_lock);
                        desc.dtpd_id++;
                }

                if (cmd == DTRACEIOC_PROBEMATCH)  {
                        dtrace_probekey(&desc, &pkey);
                        pkey.dtpk_id = DTRACE_IDNONE;
                }

                dtrace_cred2priv(cr, &priv, &uid, &zoneid);

                mutex_enter(&dtrace_lock);

                if (cmd == DTRACEIOC_PROBEMATCH) {
                        for (i = desc.dtpd_id; i <= dtrace_nprobes; i++) {
                                if ((probe = dtrace_probes[i - 1]) != NULL &&
                                    (m = dtrace_match_probe(probe, &pkey,
                                    priv, uid, zoneid)) != 0)
                                        break;
                        }

                        if (m < 0) {
                                mutex_exit(&dtrace_lock);
                                return (EINVAL);
                        }

                } else {
                        for (i = desc.dtpd_id; i <= dtrace_nprobes; i++) {
                                if ((probe = dtrace_probes[i - 1]) != NULL &&
                                    dtrace_match_priv(probe, priv, uid, zoneid))
                                        break;
                        }
                }

                if (probe == NULL) {
                        mutex_exit(&dtrace_lock);
                        return (ESRCH);
                }

                dtrace_probe_description(probe, &desc);
                mutex_exit(&dtrace_lock);

                if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_PROBEARG: {
                dtrace_argdesc_t desc;
                dtrace_probe_t *probe;
                dtrace_provider_t *prov;

                if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                if (desc.dtargd_id == DTRACE_IDNONE)
                        return (EINVAL);

                if (desc.dtargd_ndx == DTRACE_ARGNONE)
                        return (EINVAL);

                mutex_enter(&dtrace_provider_lock);
                mutex_enter(&mod_lock);
                mutex_enter(&dtrace_lock);

                if (desc.dtargd_id > dtrace_nprobes) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&mod_lock);
                        mutex_exit(&dtrace_provider_lock);
                        return (EINVAL);
                }

                if ((probe = dtrace_probes[desc.dtargd_id - 1]) == NULL) {
                        mutex_exit(&dtrace_lock);
                        mutex_exit(&mod_lock);
                        mutex_exit(&dtrace_provider_lock);
                        return (EINVAL);
                }

                mutex_exit(&dtrace_lock);

                prov = probe->dtpr_provider;

                if (prov->dtpv_pops.dtps_getargdesc == NULL) {
                        /*
                         * There isn't any typed information for this probe.
                         * Set the argument number to DTRACE_ARGNONE.
                         */
                        desc.dtargd_ndx = DTRACE_ARGNONE;
                } else {
                        desc.dtargd_native[0] = '\0';
                        desc.dtargd_xlate[0] = '\0';
                        desc.dtargd_mapping = desc.dtargd_ndx;

                        prov->dtpv_pops.dtps_getargdesc(prov->dtpv_arg,
                            probe->dtpr_id, probe->dtpr_arg, &desc);
                }

                mutex_exit(&mod_lock);
                mutex_exit(&dtrace_provider_lock);

                if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_GO: {
                processorid_t cpuid;
                rval = dtrace_state_go(state, &cpuid);

                if (rval != 0)
                        return (rval);

                if (copyout(&cpuid, (void *)arg, sizeof (cpuid)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_STOP: {
                processorid_t cpuid;

                mutex_enter(&dtrace_lock);
                rval = dtrace_state_stop(state, &cpuid);
                mutex_exit(&dtrace_lock);

                if (rval != 0)
                        return (rval);

                if (copyout(&cpuid, (void *)arg, sizeof (cpuid)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_DOFGET: {
                dof_hdr_t hdr, *dof;
                uint64_t len;

                if (copyin((void *)arg, &hdr, sizeof (hdr)) != 0)
                        return (EFAULT);

                mutex_enter(&dtrace_lock);
                dof = dtrace_dof_create(state);
                mutex_exit(&dtrace_lock);

                len = MIN(hdr.dofh_loadsz, dof->dofh_loadsz);
                rval = copyout(dof, (void *)arg, len);
                dtrace_dof_destroy(dof);

                return (rval == 0 ? 0 : EFAULT);
        }

        case DTRACEIOC_AGGSNAP:
        case DTRACEIOC_BUFSNAP: {
                dtrace_bufdesc_t desc;
                caddr_t cached;
                dtrace_buffer_t *buf;

                if (copyin((void *)arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                if (/*VBox value is is unsigned: desc.dtbd_cpu < 0 ||*/ desc.dtbd_cpu >= NCPU)
                        return (EINVAL);

                mutex_enter(&dtrace_lock);

                if (cmd == DTRACEIOC_BUFSNAP) {
                        buf = &state->dts_buffer[desc.dtbd_cpu];
                } else {
                        buf = &state->dts_aggbuffer[desc.dtbd_cpu];
                }

                if (buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL)) {
                        size_t sz = buf->dtb_offset;

                        if (state->dts_activity != DTRACE_ACTIVITY_STOPPED) {
                                mutex_exit(&dtrace_lock);
                                return (EBUSY);
                        }

                        /*
                         * If this buffer has already been consumed, we're
                         * going to indicate that there's nothing left here
                         * to consume.
                         */
                        if (buf->dtb_flags & DTRACEBUF_CONSUMED) {
                                mutex_exit(&dtrace_lock);

                                desc.dtbd_size = 0;
                                desc.dtbd_drops = 0;
                                desc.dtbd_errors = 0;
                                desc.dtbd_oldest = 0;
                                sz = sizeof (desc);

                                if (copyout(&desc, (void *)arg, sz) != 0)
                                        return (EFAULT);

                                return (0);
                        }

                        /*
                         * If this is a ring buffer that has wrapped, we want
                         * to copy the whole thing out.
                         */
                        if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                                dtrace_buffer_polish(buf);
                                sz = buf->dtb_size;
                        }

                        if (copyout(buf->dtb_tomax, desc.dtbd_data, sz) != 0) {
                                mutex_exit(&dtrace_lock);
                                return (EFAULT);
                        }

                        desc.dtbd_size = sz;
                        desc.dtbd_drops = buf->dtb_drops;
                        desc.dtbd_errors = buf->dtb_errors;
                        desc.dtbd_oldest = buf->dtb_xamot_offset;

                        mutex_exit(&dtrace_lock);

                        if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                                return (EFAULT);

                        buf->dtb_flags |= DTRACEBUF_CONSUMED;

                        return (0);
                }

                if (buf->dtb_tomax == NULL) {
                        ASSERT(buf->dtb_xamot == NULL);
                        mutex_exit(&dtrace_lock);
                        return (ENOENT);
                }

                cached = buf->dtb_tomax;
                ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));

                dtrace_xcall(desc.dtbd_cpu,
                    (dtrace_xcall_t)dtrace_buffer_switch, buf);

                state->dts_errors += buf->dtb_xamot_errors;

                /*
                 * If the buffers did not actually switch, then the cross call
                 * did not take place -- presumably because the given CPU is
                 * not in the ready set.  If this is the case, we'll return
                 * ENOENT.
                 */
                if (buf->dtb_tomax == cached) {
                        ASSERT(buf->dtb_xamot != cached);
                        mutex_exit(&dtrace_lock);
                        return (ENOENT);
                }

                ASSERT(cached == buf->dtb_xamot);

                /*
                 * We have our snapshot; now copy it out.
                 */
                if (copyout(buf->dtb_xamot, desc.dtbd_data,
                    buf->dtb_xamot_offset) != 0) {
                        mutex_exit(&dtrace_lock);
                        return (EFAULT);
                }

                desc.dtbd_size = buf->dtb_xamot_offset;
                desc.dtbd_drops = buf->dtb_xamot_drops;
                desc.dtbd_errors = buf->dtb_xamot_errors;
                desc.dtbd_oldest = 0;

                mutex_exit(&dtrace_lock);

                /*
                 * Finally, copy out the buffer description.
                 */
                if (copyout(&desc, (void *)arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_CONF: {
                dtrace_conf_t conf;

                bzero(&conf, sizeof (conf));
                conf.dtc_difversion = DIF_VERSION;
                conf.dtc_difintregs = DIF_DIR_NREGS;
                conf.dtc_diftupregs = DIF_DTR_NREGS;
                conf.dtc_ctfmodel = CTF_MODEL_NATIVE;

                if (copyout(&conf, (void *)arg, sizeof (conf)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_STATUS: {
                dtrace_status_t stat;
                dtrace_dstate_t *dstate;
                int i, j;
                uint64_t nerrs;

                /*
                 * See the comment in dtrace_state_deadman() for the reason
                 * for setting dts_laststatus to INT64_MAX before setting
                 * it to the correct value.
                 */
                state->dts_laststatus = INT64_MAX;
                dtrace_membar_producer();
                state->dts_laststatus = dtrace_gethrtime();

                bzero(&stat, sizeof (stat));

                mutex_enter(&dtrace_lock);

                if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE) {
                        mutex_exit(&dtrace_lock);
                        return (ENOENT);
                }

                if (state->dts_activity == DTRACE_ACTIVITY_DRAINING)
                        stat.dtst_exiting = 1;

                nerrs = state->dts_errors;
                dstate = &state->dts_vstate.dtvs_dynvars;

                for (i = 0; i < NCPU; i++) {
                        dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[i];

                        stat.dtst_dyndrops += dcpu->dtdsc_drops;
                        stat.dtst_dyndrops_dirty += dcpu->dtdsc_dirty_drops;
                        stat.dtst_dyndrops_rinsing += dcpu->dtdsc_rinsing_drops;

                        if (state->dts_buffer[i].dtb_flags & DTRACEBUF_FULL)
                                stat.dtst_filled++;

                        nerrs += state->dts_buffer[i].dtb_errors;

                        for (j = 0; j < state->dts_nspeculations; j++) {
                                dtrace_speculation_t *spec;
                                dtrace_buffer_t *buf;

                                spec = &state->dts_speculations[j];
                                buf = &spec->dtsp_buffer[i];
                                stat.dtst_specdrops += buf->dtb_xamot_drops;
                        }
                }

                stat.dtst_specdrops_busy = state->dts_speculations_busy;
                stat.dtst_specdrops_unavail = state->dts_speculations_unavail;
                stat.dtst_stkstroverflows = state->dts_stkstroverflows;
                stat.dtst_dblerrors = state->dts_dblerrors;
                stat.dtst_killed =
                    (state->dts_activity == DTRACE_ACTIVITY_KILLED);
                stat.dtst_errors = nerrs;

                mutex_exit(&dtrace_lock);

                if (copyout(&stat, (void *)arg, sizeof (stat)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_FORMAT: {
                dtrace_fmtdesc_t fmt;
                char *str;
                int len;

                if (copyin((void *)arg, &fmt, sizeof (fmt)) != 0)
                        return (EFAULT);

                mutex_enter(&dtrace_lock);

                if (fmt.dtfd_format == 0 ||
                    fmt.dtfd_format > state->dts_nformats) {
                        mutex_exit(&dtrace_lock);
                        return (EINVAL);
                }

                /*
                 * Format strings are allocated contiguously and they are
                 * never freed; if a format index is less than the number
                 * of formats, we can assert that the format map is non-NULL
                 * and that the format for the specified index is non-NULL.
                 */
                ASSERT(state->dts_formats != NULL);
                str = state->dts_formats[fmt.dtfd_format - 1];
                ASSERT(str != NULL);

                len = VBDTCAST(int)strlen(str) + 1;

                if (len > fmt.dtfd_length) {
                        fmt.dtfd_length = len;

                        if (copyout(&fmt, (void *)arg, sizeof (fmt)) != 0) {
                                mutex_exit(&dtrace_lock);
                                return (EINVAL);
                        }
                } else {
                        if (copyout(str, fmt.dtfd_string, len) != 0) {
                                mutex_exit(&dtrace_lock);
                                return (EINVAL);
                        }
                }

                mutex_exit(&dtrace_lock);
                return (0);
        }

        default:
                break;
        }

        return (ENOTTY);
}

/*ARGSUSED*/
static int
dtrace_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        dtrace_state_t *state;

        switch (cmd) {
        case DDI_DETACH:
                break;

        case DDI_SUSPEND:
                return (DDI_SUCCESS);

        default:
                return (DDI_FAILURE);
        }

        mutex_enter(&cpu_lock);
        mutex_enter(&dtrace_provider_lock);
        mutex_enter(&dtrace_lock);

        ASSERT(dtrace_opens == 0);

        if (dtrace_helpers > 0) {
                mutex_exit(&dtrace_provider_lock);
                mutex_exit(&dtrace_lock);
                mutex_exit(&cpu_lock);
                return (DDI_FAILURE);
        }

        if (dtrace_unregister((dtrace_provider_id_t)dtrace_provider) != 0) {
                mutex_exit(&dtrace_provider_lock);
                mutex_exit(&dtrace_lock);
                mutex_exit(&cpu_lock);
                return (DDI_FAILURE);
        }

        dtrace_provider = NULL;

        if ((state = dtrace_anon_grab()) != NULL) {
                /*
                 * If there were ECBs on this state, the provider should
                 * have not been allowed to detach; assert that there is
                 * none.
                 */
                ASSERT(state->dts_necbs == 0);
                dtrace_state_destroy(state);

#ifndef VBOX
                /*
                 * If we're being detached with anonymous state, we need to
                 * indicate to the kernel debugger that DTrace is now inactive.
                 */
                (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#endif
        }

        bzero(&dtrace_anon, sizeof (dtrace_anon_t));
#ifndef VBOX /** @todo CPU hooks */
        unregister_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);
#endif
        dtrace_cpu_init = NULL;
        dtrace_helpers_cleanup = NULL;
        dtrace_helpers_fork = NULL;
        dtrace_cpustart_init = NULL;
        dtrace_cpustart_fini = NULL;
        dtrace_debugger_init = NULL;
        dtrace_debugger_fini = NULL;
        dtrace_modload = NULL;
        dtrace_modunload = NULL;

        mutex_exit(&cpu_lock);

        if (dtrace_helptrace_enabled) {
                kmem_free(dtrace_helptrace_buffer, dtrace_helptrace_bufsize);
                dtrace_helptrace_buffer = NULL;
        }

        kmem_free(dtrace_probes, dtrace_nprobes * sizeof (dtrace_probe_t *));
        dtrace_probes = NULL;
        dtrace_nprobes = 0;

        dtrace_hash_destroy(dtrace_bymod);
        dtrace_hash_destroy(dtrace_byfunc);
        dtrace_hash_destroy(dtrace_byname);
        dtrace_bymod = NULL;
        dtrace_byfunc = NULL;
        dtrace_byname = NULL;

        kmem_cache_destroy(dtrace_state_cache);
        vmem_destroy(dtrace_minor);
        vmem_destroy(dtrace_arena);

        if (dtrace_toxrange != NULL) {
                kmem_free(dtrace_toxrange,
                    dtrace_toxranges_max * sizeof (dtrace_toxrange_t));
                dtrace_toxrange = NULL;
                dtrace_toxranges = 0;
                dtrace_toxranges_max = 0;
        }

#ifndef VBOX
        ddi_remove_minor_node(dtrace_devi, NULL);
#endif
        dtrace_devi = NULL;

        ddi_soft_state_fini(&dtrace_softstate);

        ASSERT(dtrace_vtime_references == 0);
        ASSERT(dtrace_opens == 0);
        ASSERT(dtrace_retained == NULL);

        mutex_exit(&dtrace_lock);
        mutex_exit(&dtrace_provider_lock);

        /*
         * We don't destroy the task queue until after we have dropped our
         * locks (taskq_destroy() may block on running tasks).  To prevent
         * attempting to do work after we have effectively detached but before
         * the task queue has been destroyed, all tasks dispatched via the
         * task queue must check that DTrace is still attached before
         * performing any operation.
         */
#ifndef VBOX
        taskq_destroy(dtrace_taskq);
        dtrace_taskq = NULL;
#endif

        return (DDI_SUCCESS);
}

#ifndef VBOX
/*ARGSUSED*/
static int
dtrace_info(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
{
        int error;

        switch (infocmd) {
        case DDI_INFO_DEVT2DEVINFO:
                *result = (void *)dtrace_devi;
                error = DDI_SUCCESS;
                break;
        case DDI_INFO_DEVT2INSTANCE:
                *result = (void *)0;
                error = DDI_SUCCESS;
                break;
        default:
                error = DDI_FAILURE;
        }
        return (error);
}

static struct cb_ops dtrace_cb_ops = {
        dtrace_open,            /* open */
        dtrace_close,           /* close */
        nulldev,                /* strategy */
        nulldev,                /* print */
        nodev,                  /* dump */
        nodev,                  /* read */
        nodev,                  /* write */
        dtrace_ioctl,           /* ioctl */
        nodev,                  /* devmap */
        nodev,                  /* mmap */
        nodev,                  /* segmap */
        nochpoll,               /* poll */
        ddi_prop_op,            /* cb_prop_op */
        0,                      /* streamtab  */
        D_NEW | D_MP            /* Driver compatibility flag */
};

static struct dev_ops dtrace_ops = {
        DEVO_REV,               /* devo_rev */
        0,                      /* refcnt */
        dtrace_info,            /* get_dev_info */
        nulldev,                /* identify */
        nulldev,                /* probe */
        dtrace_attach,          /* attach */
        dtrace_detach,          /* detach */
        nodev,                  /* reset */
        &dtrace_cb_ops,         /* driver operations */
        NULL,                   /* bus operations */
        nodev,                  /* dev power */
        ddi_quiesce_not_needed,         /* quiesce */
};

static struct modldrv modldrv = {
        &mod_driverops,         /* module type (this is a pseudo driver) */
        "Dynamic Tracing",      /* name of module */
        &dtrace_ops,            /* driver ops */
};

static struct modlinkage modlinkage = {
        MODREV_1,
        (void *)&modldrv,
        NULL
};

int
_init(void)
{
        return (mod_install(&modlinkage));
}

int
_info(struct modinfo *modinfop)
{
        return (mod_info(&modlinkage, modinfop));
}

int
_fini(void)
{
        return (mod_remove(&modlinkage));
}

#endif /* !VBOX */