Changeset 67136 in vbox for trunk/src

Timestamp:

May 30, 2017 7:58:21 AM (8 years ago)

Author:

vboxsync

Message:

HostDrivers/Support, VMM: bugref:8864: On Linux 4.12 the GDT is mapped read-only. The writable-mapped GDT is available and is used for clearing the TSS BUSY descriptor bit and for LTR.

Location:

trunk/src/VBox

Files:

• HostDrivers/Support/SUPDrv.cpp (modified) (2 diffs)
• HostDrivers/Support/SUPDrvInternal.h (modified) (1 diff)
• HostDrivers/Support/linux/SUPDrv-linux.c (modified) (3 diffs)
• VMM/VMMR0/HMR0A.asm (modified) (2 diffs)
• VMM/VMMR0/HMVMXR0.cpp (modified) (2 diffs)

trunk/src/VBox/HostDrivers/Support/SUPDrv.cpp

@@ -199 +199 @@
     { "SUPR0SuspendVTxOnCpu",                   (void *)(uintptr_t)SUPR0SuspendVTxOnCpu },
     { "SUPR0ResumeVTxOnCpu",                    (void *)(uintptr_t)SUPR0ResumeVTxOnCpu },
+    { "SUPR0GetCurrentGdtRw",                   (void *)(uintptr_t)SUPR0GetCurrentGdtRw },
     { "SUPR0GetKernelFeatures",                 (void *)(uintptr_t)SUPR0GetKernelFeatures },
     { "SUPR0GetPagingMode",                     (void *)(uintptr_t)SUPR0GetPagingMode },
@@ -3877 +3878 @@
 
 
+SUPR0DECL(int) SUPR0GetCurrentGdtRw(RTHCUINTPTR *pGdtRw)
+{
+#ifdef RT_OS_LINUX
+    return supdrvOSetCurrentGdtRw(pGdtRw);
+#else
+    return VERR_NOT_IMPLEMENTED;
+#endif
+}
+
+
 /**
  * Checks if Intel VT-x feature is usable on this CPU.

trunk/src/VBox/HostDrivers/Support/SUPDrvInternal.h

@@ -842 +842 @@
 bool VBOXCALL   supdrvOSSuspendVTxOnCpu(void);
 void VBOXCALL   supdrvOSResumeVTxOnCpu(bool fSuspended);
+int  VBOXCALL   supdrvOSetCurrentGdtRw(RTHCUINTPTR *pGdtRw);
 
 /**

trunk/src/VBox/HostDrivers/Support/linux/SUPDrv-linux.c

@@ -61 +61 @@
 # include <asm/msr.h>
 #endif
+
+#include <asm/desc.h>
 
 #include <iprt/asm-amd64-x86.h>
@@ -1401 +1403 @@
     fFlags |= SUPKERNELFEATURES_GDT_READ_ONLY;
 #endif
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0)
+    fFlags |= SUPKERNELFEATURES_GDT_NEED_WRITABLE;
+#endif
 #if defined(VBOX_STRICT) || defined(VBOX_WITH_EFLAGS_AC_SET_IN_VBOXDRV)
     fFlags |= SUPKERNELFEATURES_SMAP;
@@ -1411 +1416 @@
 
 
+int supdrvOSetCurrentGdtRw(RTHCUINTPTR *pGdtRw)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 12, 0)
+    *pGdtRw = (RTHCUINTPTR)get_current_gdt_rw();
+    return VINF_SUCCESS;
+#else
+    return VERR_NOT_IMPLEMENTED;
+#endif
+}
+
+
 module_init(VBoxDrvLinuxInit);
 module_exit(VBoxDrvLinuxUnload);

trunk/src/VBox/VMM/VMMR0/HMR0A.asm

@@ -285 +285 @@
     mov         ax, dx
     and         eax, X86_SEL_MASK_OFF_RPL                       ; Mask away TI and RPL bits leaving only the descriptor offset.
+    test        edi, VMX_RESTORE_HOST_GDT_READ_ONLY | VMX_RESTORE_HOST_GDT_NEED_WRITABLE
+    jnz         .gdt_readonly
     add         rax, qword [rsi + VMXRESTOREHOST.HostGdtr + 2]  ; xAX <- descriptor offset + GDTR.pGdt.
-    test        edi, VMX_RESTORE_HOST_GDT_READ_ONLY
-    jnz         .gdt_readonly
     and         dword [rax + 4], ~RT_BIT(9)                     ; Clear the busy flag in TSS desc (bits 0-7=base, bit 9=busy bit).
     ltr         dx
     jmp short   .test_fs
 .gdt_readonly:
+    test        edi, VMX_RESTORE_HOST_GDT_NEED_WRITABLE
+    jnz         .gdt_readonly_need_writable
     mov         rcx, cr0
     mov         r9, rcx
+    add         rax, qword [rsi + VMXRESTOREHOST.HostGdtr + 2]  ; xAX <- descriptor offset + GDTR.pGdt.
     and         rcx, ~X86_CR0_WP
     mov         cr0, rcx
@@ -299 +302 @@
     ltr         dx
     mov         cr0, r9
+    jmp short   .test_fs
+.gdt_readonly_need_writable:
+    add         rax, qword [rsi + VMXRESTOREHOST.HostGdtrRw + 2]  ; xAX <- descriptor offset + GDTR.pGdtRw.
+    and         dword [rax + 4], ~RT_BIT(9)                     ; Clear the busy flag in TSS desc (bits 0-7=base, bit 9=busy bit).
+    lgdt        [rsi + VMXRESTOREHOST.HostGdtrRw]
+    ltr         dx
+    lgdt        [rsi + VMXRESTOREHOST.HostGdtr]                 ; Load the original GDT
 
 .test_fs:

trunk/src/VBox/VMM/VMMR0/HMVMXR0.cpp

@@ -3038 +3038 @@
      */
     if (Gdtr.cbGdt != 0xffff)
-    {
         pVCpu->hm.s.vmx.fRestoreHostFlags |= VMX_RESTORE_HOST_GDTR;
-        AssertCompile(sizeof(Gdtr) == sizeof(X86XDTR64));
-        memcpy(&pVCpu->hm.s.vmx.RestoreHost.HostGdtr, &Gdtr, sizeof(X86XDTR64));
-    }
 
     /*
@@ -3094 +3090 @@
             pVCpu->hm.s.vmx.fRestoreHostFlags |= VMX_RESTORE_HOST_GDT_READ_ONLY;
         pVCpu->hm.s.vmx.RestoreHost.uHostSelTR = uSelTR;
-
-        /* Store the GDTR here as we need it while restoring TR. */
+    }
+
+    /*
+     * Store the GDTR as we need it when restoring the GDT and while restoring the TR.
+     */
+    if (pVCpu->hm.s.vmx.fRestoreHostFlags & (VMX_RESTORE_HOST_GDTR | VMX_RESTORE_HOST_SEL_TR))
+    {
+        AssertCompile(sizeof(Gdtr) == sizeof(X86XDTR64));
         memcpy(&pVCpu->hm.s.vmx.RestoreHost.HostGdtr, &Gdtr, sizeof(X86XDTR64));
+        if (pVM->hm.s.fHostKernelFeatures & SUPKERNELFEATURES_GDT_NEED_WRITABLE)
+        {
+            /* The GDT is read-only but the writable GDT is available. */
+            pVCpu->hm.s.vmx.fRestoreHostFlags |= VMX_RESTORE_HOST_GDT_NEED_WRITABLE;
+            pVCpu->hm.s.vmx.RestoreHost.HostGdtrRw.cb = Gdtr.cbGdt;
+            rc = SUPR0GetCurrentGdtRw(&pVCpu->hm.s.vmx.RestoreHost.HostGdtrRw.uAddr);
+            AssertRCReturn(rc, rc);
+        }
     }
 #else