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1 | ;------------------------------------------------------------------------------\r |
| 2 | ;\r |
| 3 | ; Copyright (c) 2006, Intel Corporation\r |
| 4 | ; All rights reserved. This program and the accompanying materials\r |
| 5 | ; are licensed and made available under the terms and conditions of the BSD License\r |
| 6 | ; which accompanies this distribution. The full text of the license may be found at\r |
| 7 | ; http://opensource.org/licenses/bsd-license.php\r |
| 8 | ;\r |
| 9 | ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r |
| 10 | ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r |
| 11 | ;\r |
| 12 | ; Module Name:\r |
| 13 | ;\r |
| 14 | ; Thunk.asm\r |
| 15 | ;\r |
| 16 | ; Abstract:\r |
| 17 | ;\r |
| 18 | ; Real mode thunk\r |
| 19 | ;\r |
| 20 | ;------------------------------------------------------------------------------\r |
| 21 | \r |
| 22 | .686p\r |
| 23 | .model flat,C\r |
| 24 | \r |
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25 | EXTERNDEF C m16Start:BYTE\r |
| 26 | EXTERNDEF C m16Size:WORD\r |
| 27 | EXTERNDEF C mThunk16Attr:WORD\r |
| 28 | EXTERNDEF C m16Gdt:WORD\r |
| 29 | EXTERNDEF C m16GdtrBase:WORD\r |
| 30 | EXTERNDEF C mTransition:WORD\r |
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31 | \r |
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32 | ;THUNK_ATTRIBUTE_BIG_REAL_MODE EQU 1\r |
| 33 | ;THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2\r |
| 34 | ;THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4\r |
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35 | \r |
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36 | IA32_REGS STRUC 4t\r |
| 37 | _EDI DD ?\r |
| 38 | _ESI DD ?\r |
| 39 | _EBP DD ?\r |
| 40 | _ESP DD ?\r |
| 41 | _EBX DD ?\r |
| 42 | _EDX DD ?\r |
| 43 | _ECX DD ?\r |
| 44 | _EAX DD ?\r |
| 45 | _DS DW ?\r |
| 46 | _ES DW ?\r |
| 47 | _FS DW ?\r |
| 48 | _GS DW ?\r |
| 49 | _EFLAGS DD ?\r |
| 50 | _EIP DD ?\r |
| 51 | _CS DW ?\r |
| 52 | _SS DW ?\r |
| 53 | IA32_REGS ENDS\r |
| 54 | \r |
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55 | .const\r |
| 56 | \r |
| 57 | m16Size DW offset InternalAsmThunk16 - offset m16Start\r |
| 58 | mThunk16Attr DW offset _ThunkAttr - offset m16Start\r |
| 59 | m16Gdt DW offset _NullSegDesc - offset m16Start\r |
| 60 | m16GdtrBase DW offset _16GdtrBase - offset m16Start\r |
| 61 | mTransition DW offset _EntryPoint - offset m16Start\r |
| 62 | \r |
| 63 | .code\r |
| 64 | \r |
| 65 | m16Start LABEL BYTE\r |
| 66 | \r |
| 67 | SavedGdt LABEL FWORD\r |
| 68 | DW ?\r |
| 69 | DD ?\r |
| 70 | \r |
| 71 | _BackFromUserCode PROC\r |
| 72 | push ss\r |
| 73 | push cs\r |
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74 | DB 66h\r |
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75 | call @Base ; push eip\r |
| 76 | @Base:\r |
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77 | pushf ; pushfd actually\r |
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78 | cli ; disable interrupts\r |
| 878ddf1f |
79 | push gs\r |
| 80 | push fs\r |
| 81 | push es\r |
| 82 | push ds\r |
| 83 | pushaw ; pushad actually\r |
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84 | DB 66h, 0bah ; mov edx, imm32\r |
| 85 | _ThunkAttr DD ?\r |
| 86 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r |
| 87 | jz @1\r |
| 88 | mov eax, 15cd2401h ; mov ax, 2401h & int 15h\r |
| 89 | cli ; disable interrupts\r |
| 90 | jnc @2\r |
| 91 | @1:\r |
| 92 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r |
| 93 | jz @2\r |
| 94 | in al, 92h\r |
| 95 | or al, 2\r |
| 96 | out 92h, al ; deactivate A20M#\r |
| 97 | @2:\r |
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98 | mov eax, ss\r |
| 99 | DB 67h\r |
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100 | lea bp, [esp + sizeof (IA32_REGS)]\r |
| 101 | mov word ptr (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._ESP, bp\r |
| 102 | mov ebx, (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._EIP\r |
| 103 | shl ax, 4 ; shl eax, 4\r |
| 104 | add bp, ax ; add ebp, eax\r |
| 105 | DB 66h, 0b8h ; mov eax, imm32\r |
| 106 | SavedCr4 DD ?\r |
| 107 | mov cr4, eax\r |
| 108 | DB 66h\r |
| 109 | lgdt fword ptr cs:[edi + (offset SavedGdt - offset @Base)]\r |
| 110 | DB 66h, 0b8h ; mov eax, imm32\r |
| 111 | SavedCr0 DD ?\r |
| 112 | mov cr0, eax\r |
| 113 | DB 0b8h ; mov ax, imm16\r |
| 114 | SavedSs DW ?\r |
| 115 | mov ss, eax\r |
| 116 | DB 66h, 0bch ; mov esp, imm32\r |
| 117 | SavedEsp DD ?\r |
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118 | DB 66h\r |
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119 | retf ; return to protected mode\r |
| 120 | _BackFromUserCode ENDP\r |
| 121 | \r |
| 122 | _EntryPoint DD offset _ToUserCode - offset m16Start\r |
| 123 | DW 8h\r |
| 124 | _16Idtr FWORD (1 SHL 10) - 1\r |
| 125 | _16Gdtr LABEL FWORD\r |
| 126 | DW offset GdtEnd - offset _NullSegDesc - 1\r |
| 127 | _16GdtrBase DD offset _NullSegDesc\r |
| 128 | \r |
| 129 | _ToUserCode PROC\r |
| 130 | mov edx, ss\r |
| 131 | mov ss, ecx ; set new segment selectors\r |
| 132 | mov ds, ecx\r |
| 133 | mov es, ecx\r |
| 134 | mov fs, ecx\r |
| 135 | mov gs, ecx\r |
| 136 | mov cr0, eax\r |
| 137 | mov cr4, ebp ; real mode starts at next instruction\r |
| 138 | mov ss, esi ; set up 16-bit stack segment\r |
| 139 | xchg sp, bx ; set up 16-bit stack pointer\r |
| 140 | DB 66h\r |
| 141 | call @Base ; push eip\r |
| 142 | @Base:\r |
| 143 | pop bp ; ebp <- offset @Base\r |
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144 | DB 67h ; address size override\r |
| 145 | push [esp + sizeof (IA32_REGS) + 2]\r |
| 146 | lea eax, [esi + (offset @RealMode - offset @Base)]\r |
| 147 | push eax\r |
| 148 | retf\r |
| 149 | @RealMode:\r |
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150 | mov cs:[esi + (offset SavedSs - offset @Base)], edx\r |
| 151 | mov cs:[esi + (offset SavedEsp - offset @Base)], bx\r |
| 152 | DB 66h\r |
| 153 | lidt fword ptr cs:[esi + (offset _16Idtr - offset @Base)]\r |
| 154 | popaw ; popad actually\r |
| 155 | pop ds\r |
| 156 | pop es\r |
| 157 | pop fs\r |
| 158 | pop gs\r |
| 159 | popf ; popfd\r |
| 160 | DB 66h\r |
| 161 | retf ; transfer control to user code\r |
| 162 | _ToUserCode ENDP\r |
| 163 | \r |
| 164 | _NullSegDesc DQ 0\r |
| 165 | _16CsDesc LABEL QWORD\r |
| 166 | DW -1\r |
| 167 | DW 0\r |
| 168 | DB 0\r |
| 169 | DB 9bh\r |
| 170 | DB 8fh ; 16-bit segment, 4GB limit\r |
| 171 | DB 0\r |
| 172 | _16DsDesc LABEL QWORD\r |
| 173 | DW -1\r |
| 174 | DW 0\r |
| 175 | DB 0\r |
| 176 | DB 93h\r |
| 177 | DB 8fh ; 16-bit segment, 4GB limit\r |
| 178 | DB 0\r |
| 179 | GdtEnd LABEL QWORD\r |
| 180 | \r |
| 181 | ;\r |
| 182 | ; @param RegSet Pointer to a IA32_DWORD_REGS structure\r |
| 183 | ; @param Transition Pointer to the transition code\r |
| 184 | ; @return The address of the 16-bit stack after returning from user code\r |
| 185 | ;\r |
| 186 | InternalAsmThunk16 PROC USES ebp ebx esi edi ds es fs gs\r |
| 187 | mov esi, [esp + 36] ; esi <- RegSet\r |
| 188 | movzx edx, (IA32_REGS ptr [esi])._SS\r |
| 189 | mov edi, (IA32_REGS ptr [esi])._ESP\r |
| 190 | add edi, - (sizeof (IA32_REGS) + 4) ; reserve stack space\r |
| 191 | mov ebx, edi ; ebx <- stack offset\r |
| 192 | imul eax, edx, 16 ; eax <- edx * 16\r |
| 193 | push sizeof (IA32_REGS) / 4\r |
| 194 | add edi, eax ; edi <- linear address of 16-bit stack\r |
| 195 | pop ecx\r |
| 196 | rep movsd ; copy RegSet\r |
| 197 | mov eax, [esp + 40] ; eax <- address of transition code\r |
| 198 | mov esi, edx ; esi <- 16-bit stack segment\r |
| 199 | lea edx, [eax + (offset SavedCr0 - offset m16Start)]\r |
| 200 | mov ecx, eax\r |
| 201 | and ecx, 0fh\r |
| 202 | shl eax, 12\r |
| 203 | lea ecx, [ecx + (offset _BackFromUserCode - offset m16Start)]\r |
| 204 | mov ax, cx\r |
| 205 | stosd ; [edi] <- return address of user code\r |
| 206 | sgdt fword ptr [edx + (offset SavedGdt - offset SavedCr0)]\r |
| 207 | sidt fword ptr [esp + 36] ; save IDT stack in argument space\r |
| 208 | mov eax, cr0\r |
| 209 | mov [edx], eax ; save CR0 in SavedCr0\r |
| 210 | and eax, 7ffffffeh ; clear PE, PG bits\r |
| 211 | mov ebp, cr4\r |
| 212 | mov [edx + (offset SavedCr4 - offset SavedCr0)], ebp\r |
| 213 | and ebp, 300h ; clear all but PCE and OSFXSR bits\r |
| 214 | push 10h\r |
| 215 | pop ecx ; ecx <- selector for data segments\r |
| 216 | lgdt fword ptr [edx + (offset _16Gdtr - offset SavedCr0)]\r |
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217 | pushfd\r |
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218 | call fword ptr [edx + (offset _EntryPoint - offset SavedCr0)]\r |
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219 | popfd\r |
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220 | lidt fword ptr [esp + 36] ; restore protected mode IDTR\r |
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221 | lea eax, [ebp - sizeof (IA32_REGS)]\r |
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222 | ret\r |
| 223 | InternalAsmThunk16 ENDP\r |
| 224 | \r |
| 225 | END\r |
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