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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 |
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22 | EXTERNDEF m16Start:BYTE\r |
23 | EXTERNDEF m16Size:WORD\r |
24 | EXTERNDEF mThunk16Attr:WORD\r |
25 | EXTERNDEF m16Gdt:WORD\r |
26 | EXTERNDEF m16GdtrBase:WORD\r |
27 | EXTERNDEF mTransition:WORD\r |
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28 | \r |
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29 | ;THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2\r |
30 | ;THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4\r |
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31 | \r |
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32 | IA32_REGS STRUC 4t\r |
33 | _EDI DD ?\r |
34 | _ESI DD ?\r |
35 | _EBP DD ?\r |
36 | _ESP DD ?\r |
37 | _EBX DD ?\r |
38 | _EDX DD ?\r |
39 | _ECX DD ?\r |
40 | _EAX DD ?\r |
41 | _DS DW ?\r |
42 | _ES DW ?\r |
43 | _FS DW ?\r |
44 | _GS DW ?\r |
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45 | _EFLAGS DQ ?\r |
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46 | _EIP DD ?\r |
47 | _CS DW ?\r |
48 | _SS DW ?\r |
49 | IA32_REGS ENDS\r |
50 | \r |
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51 | .const\r |
52 | \r |
53 | m16Size DW offset InternalAsmThunk16 - offset m16Start\r |
54 | mThunk16Attr DW offset _ThunkAttr - offset m16Start\r |
55 | m16Gdt DW offset _NullSegDesc - offset m16Start\r |
56 | m16GdtrBase DW offset _16GdtrBase - offset m16Start\r |
57 | mTransition DW offset _EntryPoint - offset m16Start\r |
58 | \r |
59 | .code\r |
60 | \r |
61 | m16Start LABEL BYTE\r |
62 | \r |
63 | SavedGdt LABEL FWORD\r |
64 | DW ?\r |
65 | DQ ?\r |
66 | \r |
67 | _BackFromUserCode PROC\r |
68 | DB 16h ; push ss\r |
69 | DB 0eh ; push cs\r |
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70 | DB 66h\r |
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71 | call @Base ; push eip\r |
72 | @Base:\r |
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73 | DB 66h\r |
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74 | push 0 ; reserved high order 32 bits of EFlags\r |
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75 | pushf ; pushfd actually\r |
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76 | cli ; disable interrupts\r |
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77 | push gs\r |
78 | push fs\r |
79 | DB 6 ; push es\r |
80 | DB 1eh ; push ds\r |
81 | DB 66h, 60h ; pushad\r |
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82 | DB 66h, 0bah ; mov edx, imm32\r |
83 | _ThunkAttr DD ?\r |
84 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r |
85 | jz @1\r |
86 | mov eax, 15cd2401h ; mov ax, 2401h & int 15h\r |
87 | cli ; disable interrupts\r |
88 | jnc @2\r |
89 | @1:\r |
90 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r |
91 | jz @2\r |
92 | in al, 92h\r |
93 | or al, 2\r |
94 | out 92h, al ; deactivate A20M#\r |
95 | @2:\r |
96 | mov eax, ss\r |
97 | lea bp, [esp + sizeof (IA32_REGS)]\r |
98 | mov word ptr (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._ESP, bp\r |
99 | mov ebx, (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._EIP\r |
100 | shl ax, 4 ; shl eax, 4\r |
101 | add bp, ax ; add ebp, eax\r |
102 | DB 66h, 0b8h ; mov eax, imm32\r |
103 | SavedCr4 DD ?\r |
104 | mov cr4, rax\r |
105 | DB 66h, 2eh\r |
106 | lgdt fword ptr [rdi + (offset SavedGdt - offset @Base)]\r |
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107 | DB 66h\r |
108 | mov ecx, 0c0000080h\r |
109 | rdmsr\r |
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110 | or ah, 1\r |
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111 | wrmsr\r |
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112 | DB 66h, 0b8h ; mov eax, imm32\r |
113 | SavedCr0 DD ?\r |
114 | mov cr0, rax\r |
115 | DB 0b8h ; mov ax, imm16\r |
116 | SavedSs DW ?\r |
117 | mov ss, eax\r |
118 | DB 66h, 0bch ; mov esp, imm32\r |
119 | SavedEsp DD ?\r |
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120 | DB 66h\r |
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121 | retf ; return to protected mode\r |
122 | _BackFromUserCode ENDP\r |
123 | \r |
124 | _EntryPoint DD offset _ToUserCode - offset m16Start\r |
125 | DW 8h\r |
126 | _16Gdtr LABEL FWORD\r |
127 | DW offset GdtEnd - offset _NullSegDesc - 1\r |
128 | _16GdtrBase DQ offset _NullSegDesc\r |
129 | _16Idtr FWORD (1 SHL 10) - 1\r |
130 | \r |
131 | _ToUserCode PROC\r |
132 | mov edi, ss\r |
133 | mov ss, edx ; set new segment selectors\r |
134 | mov ds, edx\r |
135 | mov es, edx\r |
136 | mov fs, edx\r |
137 | mov gs, edx\r |
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138 | DB 66h\r |
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139 | mov ecx, 0c0000080h\r |
140 | mov cr0, rax ; real mode starts at next instruction\r |
141 | rdmsr\r |
142 | and ah, NOT 1\r |
143 | wrmsr\r |
144 | mov cr4, rbp\r |
145 | mov ss, esi ; set up 16-bit stack segment\r |
146 | xchg sp, bx ; set up 16-bit stack pointer\r |
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147 | DB 66h\r |
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148 | call @Base ; push eip\r |
149 | @Base:\r |
150 | pop bp ; ebp <- offset @Base\r |
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151 | push [esp + sizeof (IA32_REGS) + 2]\r |
152 | lea eax, [rsi + (offset @RealMode - offset @Base)]\r |
153 | push rax\r |
154 | retf\r |
155 | @RealMode:\r |
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156 | DB 2eh ; cs:\r |
157 | mov [rsi + (offset SavedSs - offset @Base)], edi\r |
158 | DB 2eh ; cs:\r |
159 | mov [rsi + (offset SavedEsp - offset @Base)], bx\r |
160 | DB 66h, 2eh ; CS and operand size override\r |
161 | lidt fword ptr [rsi + (offset _16Idtr - offset @Base)]\r |
162 | DB 66h, 61h ; popad\r |
163 | DB 1fh ; pop ds\r |
164 | DB 07h ; pop es\r |
165 | pop fs\r |
166 | pop gs\r |
167 | popf ; popfd\r |
168 | lea sp, [esp + 4] ; skip high order 32 bits of EFlags\r |
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169 | DB 66h\r |
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170 | retf ; transfer control to user code\r |
171 | _ToUserCode ENDP\r |
172 | \r |
173 | _NullSegDesc DQ 0\r |
174 | _16CsDesc LABEL QWORD\r |
175 | DW -1\r |
176 | DW 0\r |
177 | DB 0\r |
178 | DB 9bh\r |
179 | DB 8fh ; 16-bit segment, 4GB limit\r |
180 | DB 0\r |
181 | _16DsDesc LABEL QWORD\r |
182 | DW -1\r |
183 | DW 0\r |
184 | DB 0\r |
185 | DB 93h\r |
186 | DB 8fh ; 16-bit segment, 4GB limit\r |
187 | DB 0\r |
188 | GdtEnd LABEL QWORD\r |
189 | \r |
190 | ;\r |
191 | ; @param RegSet Pointer to a IA32_DWORD_REGS structure\r |
192 | ; @param Transition Pointer to the transition code\r |
193 | ; @return The address of the 16-bit stack after returning from user code\r |
194 | ;\r |
195 | InternalAsmThunk16 PROC USES rbp rbx rsi rdi\r |
196 | mov r10d, ds\r |
197 | mov r11d, es\r |
198 | push fs\r |
199 | push gs\r |
200 | mov rsi, rcx\r |
201 | movzx r8d, (IA32_REGS ptr [rsi])._SS\r |
202 | mov edi, (IA32_REGS ptr [rsi])._ESP\r |
203 | lea rdi, [edi - (sizeof (IA32_REGS) + 4)]\r |
204 | imul eax, r8d, 16 ; eax <- r8d(stack segment) * 16\r |
205 | mov ebx, edi ; ebx <- stack offset for 16-bit code\r |
206 | push sizeof (IA32_REGS) / 4\r |
207 | add edi, eax ; edi <- linear address of 16-bit stack\r |
208 | pop rcx\r |
209 | rep movsd ; copy RegSet\r |
210 | lea ecx, [rdx + (offset SavedCr4 - offset m16Start)]\r |
211 | mov eax, edx ; eax <- transition code address\r |
212 | and edx, 0fh\r |
213 | shl eax, 12\r |
214 | lea edx, [rdx + (offset _BackFromUserCode - offset m16Start)]\r |
215 | mov ax, dx\r |
216 | stosd ; [edi] <- return address of user code\r |
217 | sgdt fword ptr [rcx + (offset SavedGdt - offset SavedCr4)]\r |
218 | sidt fword ptr [rsp + 38h] ; save IDT stack in argument space\r |
219 | mov rax, cr0\r |
220 | mov [rcx + (offset SavedCr0 - offset SavedCr4)], eax\r |
221 | and eax, 7ffffffeh ; clear PE, PG bits\r |
222 | mov rbp, cr4\r |
223 | mov [rcx], ebp ; save CR4 in SavedCr4\r |
224 | and ebp, 300h ; clear all but PCE and OSFXSR bits\r |
225 | mov esi, r8d ; esi <- 16-bit stack segment\r |
226 | push 10h\r |
227 | pop rdx ; rdx <- selector for data segments\r |
228 | lgdt fword ptr [rcx + (offset _16Gdtr - offset SavedCr4)]\r |
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229 | pushfq\r |
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230 | call fword ptr [rcx + (offset _EntryPoint - offset SavedCr4)]\r |
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231 | popfq\r |
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232 | lidt fword ptr [rsp + 38h] ; restore protected mode IDTR\r |
233 | lea eax, [rbp - sizeof (IA32_REGS)]\r |
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234 | pop gs\r |
235 | pop fs\r |
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236 | mov es, r11d\r |
237 | mov ds, r10d\r |
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238 | ret\r |
239 | InternalAsmThunk16 ENDP\r |
240 | \r |
241 | END\r |