; $Id: bs3-mode-SwitchToRM.asm 64694 2016-11-17 17:10:47Z vboxsync $ ;; @file ; BS3Kit - Bs3SwitchToRM ; ; ; Copyright (C) 2007-2016 Oracle Corporation ; ; This file is part of VirtualBox Open Source Edition (OSE), as ; available from http://www.virtualbox.org. This file is free software; ; you can redistribute it and/or modify it under the terms of the GNU ; General Public License (GPL) as published by the Free Software ; Foundation, in version 2 as it comes in the "COPYING" file of the ; VirtualBox OSE distribution. VirtualBox OSE is distributed in the ; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. ; ; The contents of this file may alternatively be used under the terms ; of the Common Development and Distribution License Version 1.0 ; (CDDL) only, as it comes in the "COPYING.CDDL" file of the ; VirtualBox OSE distribution, in which case the provisions of the ; CDDL are applicable instead of those of the GPL. ; ; You may elect to license modified versions of this file under the ; terms and conditions of either the GPL or the CDDL or both. ; %include "bs3kit-template-header.mac" BS3_EXTERN_SYSTEM16 Bs3Gdt %if TMPL_MODE == BS3_MODE_PE16 BS3_EXTERN_DATA16 g_uBs3CpuDetected BS3_EXTERN_CMN Bs3KbdWrite BS3_EXTERN_CMN Bs3KbdWait %endif ;********************************************************************************************************************************* ;* Global Variables * ;********************************************************************************************************************************* %if TMPL_MODE == BS3_MODE_PE16 BS3_BEGIN_DATA16 ;; Where to start restoring stack. g_ResumeSp: dw 0xfeed ;; Where to start restoring stack. g_ResumeSs: dw 0xface %endif TMPL_BEGIN_TEXT ;; ; Switch to real mode from any other mode. ; ; @cproto BS3_DECL(void) Bs3SwitchToRM(void); ; ; @uses GPRs and EFLAGS are unchanged (except high 32-bit register (AMD64) parts). ; CS is loaded with CGROUP16. ; SS:[RE]SP is converted to real mode address. ; DS and ES are loaded with BS3DATA16_GROUP. ; FS and GS are loaded with zero if present. ; ; @remarks Obviously returns to 16-bit mode, even if the caller was ; in 32-bit or 64-bit mode. ; ; @remarks Does not require 20h of parameter scratch space in 64-bit mode. ; %if TMPL_BITS == 16 BS3_GLOBAL_NAME_EX TMPL_NM(Bs3SwitchToRM_Safe), function , 0 %endif BS3_PROC_BEGIN_MODE Bs3SwitchToRM, BS3_PBC_NEAR %ifdef TMPL_RM push ax mov ax, BS3_SEL_DATA16 mov ds, ax mov es, ax pop ax ret %elif BS3_MODE_IS_V86(TMPL_MODE) ; ; V8086 - Switch to 16-bit ring-0 and call worker for that mode. ; extern BS3_CMN_NM(Bs3SwitchToRing0) call BS3_CMN_NM(Bs3SwitchToRing0) extern %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToRM) jmp %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToRM) %else ; ; Protected mode. ; 80286 requirements for PE16 clutters the code a little. ; %if TMPL_MODE == BS3_MODE_PE16 cmp byte [BS3_DATA16_WRT(g_uBs3CpuDetected)], BS3CPU_80286 ja .do_386_prologue push ax push bx pushf push word 1 jmp .done_prologue %endif .do_386_prologue: push sAX push sBX sPUSHF %if TMPL_MODE == BS3_MODE_PE16 push word 0 %elif BS3_MODE_IS_64BIT_SYS(TMPL_MODE) push sDX push sCX %endif .done_prologue: ; ; Get to 16-bit ring-0 and disable interrupts. ; extern BS3_CMN_NM(Bs3SwitchToRing0) call BS3_CMN_NM(Bs3SwitchToRing0) cli %if TMPL_MODE == BS3_MODE_PE16 ; ; On 80286 we must reset the CPU to get back to real mode. ; CPU 286 pop ax push ax test ax, ax jz .is_386_or_better ; Save registers and flags, storing SS:SP in at a known global address. %ifdef BS3_STRICT mov ax, 0feedh mov bx, 0faceh %endif push di push si push bp push bx push dx push cx push ax pushf ; Convert ss:sp to real mode address. BS3_EXTERN_CMN Bs3SelProtFar32ToFlat32 mov ax, sp push ss push 0 push ax call Bs3SelProtFar32ToFlat32 add sp, 6 mov [g_ResumeSp], ax shl dx, 12 mov [g_ResumeSs], dx ; Setup resume vector. mov bx, BS3_SEL_R0_SS16 mov es, bx mov word [es:467h], .resume mov word [es:467h+2], BS3_SEL_TEXT16 mov al, 0fh | 80h out 70h, al ; set register index in al, 80h mov al, 0ah ; shutdown action command - no EOI, no 287 reset. out 71h, al ; set cmos[f] = al - invoke testResume as early as possible. in al, 71h ; flush %if 0 ; for testing in VM CPU 386 mov ax, BS3_SEL_R0_DS16 mov ds, ax mov es, ax mov fs, ax mov gs, ax mov eax, cr0 and ax, ~X86_CR0_PE mov cr0, eax jmp BS3_SEL_TEXT16:.resume %endif ; Port A reset. (FYI: tripple fault does not do the trick) in al, 92h or al, 1 out 92h, al in al, 80h ; flush mov cx, 0ffffh .reset_delay: loop .reset_delay ; Keyboard controller reset. call Bs3KbdWait push 0 ; zero data (whatever. push 0fh ; KBD_CCMD_RESET call Bs3KbdWrite .forever: jmp .forever ; This is the resume point. We should be in real mode now, at least in theory. .resume: mov ax, BS3_SEL_DATA16 mov ds, ax mov es, ax mov ax, [g_ResumeSp] mov ss, [g_ResumeSs] mov sp, ax popf pop ax pop cx pop dx pop bx pop bp pop si pop di %ifdef BS3_STRICT cmp ax, 0feedh jne .bad_286_rm_switch cmp bx, 0faceh jne .bad_286_rm_switch %endif jmp .enter_mode %ifdef BS3_STRICT .bad_286_rm_switch: mov ax, 0e00h + 'Q' mov bx, 0ff00h int 10h jmp .bad_286_rm_switch %endif CPU 386 %elif TMPL_BITS != 16 ; ; Must be in 16-bit segment when calling Bs3SwitchTo16Bit. ; jmp .sixteen_bit_segment wrt FLAT BS3_BEGIN_TEXT16 BS3_SET_BITS TMPL_BITS BS3_GLOBAL_LOCAL_LABEL .sixteen_bit_segment extern BS3_CMN_NM(Bs3SwitchTo16Bit) call BS3_CMN_NM(Bs3SwitchTo16Bit) BS3_SET_BITS 16 %endif ; ; Before exiting to real mode we must load sensible selectors into the ; segment registers so the hidden parts (which doesn't get reloaded in ; real mode) are real mode compatible. ; .is_386_or_better: ;; @todo Testcase: Experiment leaving weird stuff in the hidden segment registers. mov ax, BS3_SEL_R0_DS16 mov ds, ax mov es, ax mov fs, ax mov gs, ax ; ; Exit to real mode. ; mov eax, cr0 and eax, X86_CR0_NO_PE_NO_PG mov cr0, eax jmp CGROUP16:.reload_cs .reload_cs: ; ; Convert the stack (now 16-bit prot) to real mode. ; mov ax, BS3_SEL_SYSTEM16 mov ds, ax mov bx, ss and bx, X86_SEL_MASK ; ASSUMES GDT stack selector mov al, [bx + 4 + Bs3Gdt] mov ah, [bx + 7 + Bs3Gdt] add sp, [bx + 2 + Bs3Gdt] ; ASSUMES not expand down segment. adc ax, 0 %ifdef BS3_STRICT test ax, 0fff0h jz .stack_conv_ok int3 .stack_conv_ok: %endif shl ax, 12 mov ss, ax %if TMPL_BITS != 16 and esp, 0ffffh %endif %if BS3_MODE_IS_64BIT_SYS(TMPL_MODE) ; ; Clear the long mode enable bit. ; mov ecx, MSR_K6_EFER rdmsr and eax, ~MSR_K6_EFER_LME wrmsr %endif ; ; Call routine for doing mode specific setups. ; .enter_mode: extern NAME(Bs3EnteredMode_rm) call NAME(Bs3EnteredMode_rm) %if TMPL_MODE == BS3_MODE_PE16 pop ax test ax, ax jz .do_386_epilogue popf pop bx pop ax ret %endif .do_386_epilogue: %if BS3_MODE_IS_64BIT_SYS(TMPL_MODE) pop ecx TONLY64 pop eax pop edx TONLY64 pop eax %endif popfd TONLY64 pop eax pop ebx TONLY64 pop eax pop eax TONLY64 add sp, 4 retn (TMPL_BITS - 16) / 8 %if TMPL_BITS != 16 TMPL_BEGIN_TEXT %endif %endif BS3_PROC_END_MODE Bs3SwitchToRM %if TMPL_BITS == 16 ;; ; Custom far stub. BS3_BEGIN_TEXT16_FARSTUBS BS3_PROC_BEGIN_MODE Bs3SwitchToRM, BS3_PBC_FAR inc bp push bp mov bp, sp ; Call the real thing. call TMPL_NM(Bs3SwitchToRM) %if !BS3_MODE_IS_RM_OR_V86(TMPL_MODE) ; Jmp to common code for the tedious conversion. BS3_EXTERN_CMN Bs3SwitchHlpConvProtModeRetfPopBpDecBpAndReturn jmp Bs3SwitchHlpConvProtModeRetfPopBpDecBpAndReturn %else pop bp dec bp retf %endif BS3_PROC_END_MODE Bs3SwitchToRM %else ;; ; Safe far return to non-BS3TEXT16 code. BS3_EXTERN_CMN Bs3SelFlatCodeToRealMode BS3_BEGIN_TEXT16 BS3_SET_BITS TMPL_BITS BS3_PROC_BEGIN_MODE Bs3SwitchToRM_Safe, BS3_PBC_NEAR %if TMPL_BITS == 64 push xAX push xCX sub xSP, 20h mov xCX, [xSP + xCB*2 + 20h] call Bs3SelFlatCodeToRealMode ; well behaved assembly function, only clobbers ecx mov [xSP + xCB*2 + 20h + 4], eax add xSP, 20h pop xCX pop xAX add xSP, 4 %else xchg eax, [xSP] push xAX call Bs3SelFlatCodeToRealMode ; well behaved assembly function, only clobbers eax add xSP, 4 xchg [xSP], eax %endif call TMPL_NM(Bs3SwitchToRM) BS3_SET_BITS 16 retf BS3_PROC_END_MODE Bs3SwitchToRM_Safe %endif