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878ddf1f | 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 | |
97d92bda | 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 | |
878ddf1f | 31 | \r |
92b34fde LG |
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 | |
35 | \r | |
878ddf1f | 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 | |
97d92bda | 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 | |
878ddf1f | 74 | DB 66h\r |
97d92bda | 75 | call @Base ; push eip\r |
76 | @Base:\r | |
878ddf1f | 77 | pushf ; pushfd actually\r |
97d92bda | 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 | |
97d92bda | 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 | |
878ddf1f | 98 | mov eax, ss\r |
99 | DB 67h\r | |
97d92bda | 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 | |
878ddf1f | 118 | DB 66h\r |
97d92bda | 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 | |
18c319ae | 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 | |
97d92bda | 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 | |
18c319ae | 217 | pushfd\r |
97d92bda | 218 | call fword ptr [edx + (offset _EntryPoint - offset SavedCr0)]\r |
18c319ae | 219 | popfd\r |
878ddf1f | 220 | lidt fword ptr [esp + 36] ; restore protected mode IDTR\r |
97d92bda | 221 | lea eax, [ebp - sizeof (IA32_REGS)]\r |
878ddf1f | 222 | ret\r |
223 | InternalAsmThunk16 ENDP\r | |
224 | \r | |
225 | END\r |