| 1 | ; $Id: bs3-mode-SwitchToRM.asm 59950 2016-03-08 07:50:19Z vboxsync $
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| 2 | ;; @file
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| 3 | ; BS3Kit - Bs3SwitchToRM
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| 4 | ;
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| 5 |
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| 6 | ;
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| 7 | ; Copyright (C) 2007-2015 Oracle Corporation
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| 8 | ;
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| 9 | ; This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | ; available from http://www.virtualbox.org. This file is free software;
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| 11 | ; you can redistribute it and/or modify it under the terms of the GNU
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| 12 | ; General Public License (GPL) as published by the Free Software
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| 13 | ; Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | ; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | ; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | ;
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| 17 | ; The contents of this file may alternatively be used under the terms
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| 18 | ; of the Common Development and Distribution License Version 1.0
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| 19 | ; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | ; VirtualBox OSE distribution, in which case the provisions of the
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| 21 | ; CDDL are applicable instead of those of the GPL.
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| 22 | ;
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| 23 | ; You may elect to license modified versions of this file under the
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| 24 | ; terms and conditions of either the GPL or the CDDL or both.
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| 25 | ;
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| 26 |
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| 27 | %include "bs3kit-template-header.mac"
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| 28 |
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| 29 | BS3_EXTERN_SYSTEM16 Bs3Gdt
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| 30 | %if TMPL_MODE == BS3_MODE_PE16
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| 31 | BS3_EXTERN_DATA16 g_uBs3CpuDetected
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| 32 | %endif
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| 33 |
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| 34 | TMPL_BEGIN_TEXT
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| 35 |
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| 36 |
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| 37 | ;;
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| 38 | ; Switch to real mode from any other mode.
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| 39 | ;
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| 40 | ; @cproto BS3_DECL(void) Bs3SwitchToRM(void);
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| 41 | ;
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| 42 | ; @uses Nothing (except high 32-bit register parts).
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| 43 | ;
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| 44 | ; @remarks Obviously returns to 16-bit mode, even if the caller was
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| 45 | ; in 32-bit or 64-bit mode.
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| 46 | ;
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| 47 | ; @remarks Does not require 20h of parameter scratch space in 64-bit mode.
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| 48 | ;
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| 49 | BS3_PROC_BEGIN_MODE Bs3SwitchToRM
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| 50 | %ifdef TMPL_RM
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| 51 | ret
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| 52 |
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| 53 | %elif BS3_MODE_IS_V86(TMPL_MODE)
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| 54 | ;
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| 55 | ; V8086 - Switch to 16-bit ring-0 and call worker for that mode.
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| 56 | ;
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| 57 | extern BS3_CMN_NM(Bs3SwitchToRing0)
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| 58 | call BS3_CMN_NM(Bs3SwitchToRing0)
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| 59 | extern %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToRM)
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| 60 | jmp %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToRM)
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| 61 |
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| 62 | %else
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| 63 | ;
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| 64 | ; Protected mode.
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| 65 | ;
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| 66 | push sAX
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| 67 | push sBX
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| 68 | sPUSHF
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| 69 |
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| 70 | ;
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| 71 | ; Get to 16-bit ring-0 and disable interrupts.
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| 72 | ;
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| 73 | extern BS3_CMN_NM(Bs3SwitchToRing0)
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| 74 | call BS3_CMN_NM(Bs3SwitchToRing0)
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| 75 |
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| 76 | cli
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| 77 |
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| 78 | %if TMPL_MODE == BS3_MODE_PE16
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| 79 | ;
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| 80 | ; On 80286 we must reset the CPU to get back to real mode.
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| 81 | ;
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| 82 | mov ax, BS3_SEL_DATA16
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| 83 | mov ds, ax
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| 84 | cmp byte [BS3_DATA16_WRT(g_uBs3CpuDetected)], BS3CPU_80286
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| 85 | jne .is_386_or_better
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| 86 | .implement_this_later:
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| 87 | int3
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| 88 | jmp .implement_this_later
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| 89 |
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| 90 | jmp .reload_cs
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| 91 |
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| 92 | %elif TMPL_BITS != 16
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| 93 | ;
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| 94 | ; Must be in 16-bit segment when calling Bs3SwitchTo16Bit.
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| 95 | ;
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| 96 | jmp .sixteen_bit_segment wrt FLAT
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| 97 | BS3_BEGIN_TEXT16
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| 98 | BS3_SET_BITS TMPL_BITS
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| 99 | .sixteen_bit_segment:
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| 100 |
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| 101 | extern BS3_CMN_NM(Bs3SwitchTo16Bit)
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| 102 | call BS3_CMN_NM(Bs3SwitchTo16Bit)
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| 103 | BS3_SET_BITS 16
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| 104 | %endif
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| 105 |
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| 106 | ;
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| 107 | ; Exit to real mode.
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| 108 | ;
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| 109 | .is_386_or_better:
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| 110 | mov eax, cr0
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| 111 | and eax, X86_CR0_NO_PE_NO_PG
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| 112 | mov cr0, eax
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| 113 | jmp BS3TEXT16:.reload_cs
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| 114 | .reload_cs:
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| 115 |
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| 116 | ;
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| 117 | ; Convert the stack (now 16-bit prot) to real mode.
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| 118 | ;
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| 119 | mov ax, BS3_SEL_SYSTEM16
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| 120 | mov ds, ax
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| 121 | mov bx, ss
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| 122 | and bx, X86_SEL_MASK ; ASSUMES GDT stack selector
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| 123 | mov al, [bx + 4 + Bs3Gdt]
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| 124 | mov ah, [bx + 7 + Bs3Gdt]
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| 125 | add sp, [bx + 2 + Bs3Gdt] ; ASSUMES not expand down segment.
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| 126 | adc ax, 0
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| 127 | %ifdef BS3_STRICT
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| 128 | test ax, 0fff0h
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| 129 | jz .stack_conv_ok
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| 130 | int3
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| 131 | .stack_conv_ok:
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| 132 | %endif
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| 133 | shl ax, 12
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| 134 | mov ss, ax
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| 135 | %if TMPL_BITS != 16
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| 136 | and esp, 0ffffh
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| 137 | %endif
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| 138 |
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| 139 | ;
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| 140 | ; Call routine for doing mode specific setups.
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| 141 | ;
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| 142 | extern NAME(Bs3EnteredMode_rm)
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| 143 | call NAME(Bs3EnteredMode_rm)
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| 144 |
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| 145 | %if TMPL_BITS == 64
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| 146 | pop eax
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| 147 | popfd
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| 148 | pop ebx
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| 149 | pop ebx
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| 150 | pop eax
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| 151 | pop eax
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| 152 | %else
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| 153 | popfd
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| 154 | pop ebx
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| 155 | pop eax
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| 156 | %endif
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| 157 | retn BS3_IF_16_32_64BIT(0, 2, 6)
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| 158 |
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| 159 | %if TMPL_BITS != 16
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| 160 | TMPL_BEGIN_TEXT
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| 161 | %endif
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| 162 | %endif
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| 163 | BS3_PROC_END_MODE Bs3SwitchToRM
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| 164 |
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