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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 | |
97d92bda | 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 | |
878ddf1f | 28 | \r |
97d92bda | 29 | THUNK_ATTRIBUTE_BIG_REAL_MODE EQU 1\r |
30 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2\r | |
31 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4\r | |
878ddf1f | 32 | \r |
33 | IA32_REGS STRUC 4t\r | |
34 | _EDI DD ?\r | |
35 | _ESI DD ?\r | |
36 | _EBP DD ?\r | |
37 | _ESP DD ?\r | |
38 | _EBX DD ?\r | |
39 | _EDX DD ?\r | |
40 | _ECX DD ?\r | |
41 | _EAX DD ?\r | |
42 | _DS DW ?\r | |
43 | _ES DW ?\r | |
44 | _FS DW ?\r | |
45 | _GS DW ?\r | |
97d92bda | 46 | _EFLAGS DQ ?\r |
878ddf1f | 47 | _EIP DD ?\r |
48 | _CS DW ?\r | |
49 | _SS DW ?\r | |
50 | IA32_REGS ENDS\r | |
51 | \r | |
97d92bda | 52 | .const\r |
53 | \r | |
54 | m16Size DW offset InternalAsmThunk16 - offset m16Start\r | |
55 | mThunk16Attr DW offset _ThunkAttr - offset m16Start\r | |
56 | m16Gdt DW offset _NullSegDesc - offset m16Start\r | |
57 | m16GdtrBase DW offset _16GdtrBase - offset m16Start\r | |
58 | mTransition DW offset _EntryPoint - offset m16Start\r | |
59 | \r | |
60 | .code\r | |
61 | \r | |
62 | m16Start LABEL BYTE\r | |
63 | \r | |
64 | SavedGdt LABEL FWORD\r | |
65 | DW ?\r | |
66 | DQ ?\r | |
67 | \r | |
68 | _BackFromUserCode PROC\r | |
69 | DB 16h ; push ss\r | |
70 | DB 0eh ; push cs\r | |
878ddf1f | 71 | DB 66h\r |
97d92bda | 72 | call @Base ; push eip\r |
73 | @Base:\r | |
878ddf1f | 74 | DB 66h\r |
97d92bda | 75 | push 0 ; reserved high order 32 bits of EFlags\r |
878ddf1f | 76 | pushf ; pushfd actually\r |
97d92bda | 77 | cli ; disable interrupts\r |
878ddf1f | 78 | push gs\r |
79 | push fs\r | |
80 | DB 6 ; push es\r | |
81 | DB 1eh ; push ds\r | |
82 | DB 66h, 60h ; pushad\r | |
97d92bda | 83 | DB 66h, 0bah ; mov edx, imm32\r |
84 | _ThunkAttr DD ?\r | |
85 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r | |
86 | jz @1\r | |
87 | mov eax, 15cd2401h ; mov ax, 2401h & int 15h\r | |
88 | cli ; disable interrupts\r | |
89 | jnc @2\r | |
90 | @1:\r | |
91 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r | |
92 | jz @2\r | |
93 | in al, 92h\r | |
94 | or al, 2\r | |
95 | out 92h, al ; deactivate A20M#\r | |
96 | @2:\r | |
97 | mov eax, ss\r | |
98 | lea bp, [esp + sizeof (IA32_REGS)]\r | |
99 | mov word ptr (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._ESP, bp\r | |
100 | mov ebx, (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._EIP\r | |
101 | shl ax, 4 ; shl eax, 4\r | |
102 | add bp, ax ; add ebp, eax\r | |
103 | DB 66h, 0b8h ; mov eax, imm32\r | |
104 | SavedCr4 DD ?\r | |
105 | mov cr4, rax\r | |
106 | DB 66h, 2eh\r | |
107 | lgdt fword ptr [rdi + (offset SavedGdt - offset @Base)]\r | |
878ddf1f | 108 | DB 66h\r |
109 | mov ecx, 0c0000080h\r | |
110 | rdmsr\r | |
97d92bda | 111 | or ah, 1\r |
878ddf1f | 112 | wrmsr\r |
97d92bda | 113 | DB 66h, 0b8h ; mov eax, imm32\r |
114 | SavedCr0 DD ?\r | |
115 | mov cr0, rax\r | |
116 | DB 0b8h ; mov ax, imm16\r | |
117 | SavedSs DW ?\r | |
118 | mov ss, eax\r | |
119 | DB 66h, 0bch ; mov esp, imm32\r | |
120 | SavedEsp DD ?\r | |
878ddf1f | 121 | DB 66h\r |
97d92bda | 122 | retf ; return to protected mode\r |
123 | _BackFromUserCode ENDP\r | |
124 | \r | |
125 | _EntryPoint DD offset _ToUserCode - offset m16Start\r | |
126 | DW 8h\r | |
127 | _16Gdtr LABEL FWORD\r | |
128 | DW offset GdtEnd - offset _NullSegDesc - 1\r | |
129 | _16GdtrBase DQ offset _NullSegDesc\r | |
130 | _16Idtr FWORD (1 SHL 10) - 1\r | |
131 | \r | |
132 | _ToUserCode PROC\r | |
133 | mov edi, ss\r | |
134 | mov ss, edx ; set new segment selectors\r | |
135 | mov ds, edx\r | |
136 | mov es, edx\r | |
137 | mov fs, edx\r | |
138 | mov gs, edx\r | |
878ddf1f | 139 | DB 66h\r |
97d92bda | 140 | mov ecx, 0c0000080h\r |
141 | mov cr0, rax ; real mode starts at next instruction\r | |
142 | rdmsr\r | |
143 | and ah, NOT 1\r | |
144 | wrmsr\r | |
145 | mov cr4, rbp\r | |
146 | mov ss, esi ; set up 16-bit stack segment\r | |
147 | xchg sp, bx ; set up 16-bit stack pointer\r | |
878ddf1f | 148 | DB 66h\r |
97d92bda | 149 | call @Base ; push eip\r |
150 | @Base:\r | |
151 | pop bp ; ebp <- offset @Base\r | |
18c319ae | 152 | push [esp + sizeof (IA32_REGS) + 2]\r |
153 | lea eax, [rsi + (offset @RealMode - offset @Base)]\r | |
154 | push rax\r | |
155 | retf\r | |
156 | @RealMode:\r | |
97d92bda | 157 | DB 2eh ; cs:\r |
158 | mov [rsi + (offset SavedSs - offset @Base)], edi\r | |
159 | DB 2eh ; cs:\r | |
160 | mov [rsi + (offset SavedEsp - offset @Base)], bx\r | |
161 | DB 66h, 2eh ; CS and operand size override\r | |
162 | lidt fword ptr [rsi + (offset _16Idtr - offset @Base)]\r | |
163 | DB 66h, 61h ; popad\r | |
164 | DB 1fh ; pop ds\r | |
165 | DB 07h ; pop es\r | |
166 | pop fs\r | |
167 | pop gs\r | |
168 | popf ; popfd\r | |
169 | lea sp, [esp + 4] ; skip high order 32 bits of EFlags\r | |
878ddf1f | 170 | DB 66h\r |
97d92bda | 171 | retf ; transfer control to user code\r |
172 | _ToUserCode ENDP\r | |
173 | \r | |
174 | _NullSegDesc DQ 0\r | |
175 | _16CsDesc LABEL QWORD\r | |
176 | DW -1\r | |
177 | DW 0\r | |
178 | DB 0\r | |
179 | DB 9bh\r | |
180 | DB 8fh ; 16-bit segment, 4GB limit\r | |
181 | DB 0\r | |
182 | _16DsDesc LABEL QWORD\r | |
183 | DW -1\r | |
184 | DW 0\r | |
185 | DB 0\r | |
186 | DB 93h\r | |
187 | DB 8fh ; 16-bit segment, 4GB limit\r | |
188 | DB 0\r | |
189 | GdtEnd LABEL QWORD\r | |
190 | \r | |
191 | ;\r | |
192 | ; @param RegSet Pointer to a IA32_DWORD_REGS structure\r | |
193 | ; @param Transition Pointer to the transition code\r | |
194 | ; @return The address of the 16-bit stack after returning from user code\r | |
195 | ;\r | |
196 | InternalAsmThunk16 PROC USES rbp rbx rsi rdi\r | |
197 | mov r10d, ds\r | |
198 | mov r11d, es\r | |
199 | push fs\r | |
200 | push gs\r | |
201 | mov rsi, rcx\r | |
202 | movzx r8d, (IA32_REGS ptr [rsi])._SS\r | |
203 | mov edi, (IA32_REGS ptr [rsi])._ESP\r | |
204 | lea rdi, [edi - (sizeof (IA32_REGS) + 4)]\r | |
205 | imul eax, r8d, 16 ; eax <- r8d(stack segment) * 16\r | |
206 | mov ebx, edi ; ebx <- stack offset for 16-bit code\r | |
207 | push sizeof (IA32_REGS) / 4\r | |
208 | add edi, eax ; edi <- linear address of 16-bit stack\r | |
209 | pop rcx\r | |
210 | rep movsd ; copy RegSet\r | |
211 | lea ecx, [rdx + (offset SavedCr4 - offset m16Start)]\r | |
212 | mov eax, edx ; eax <- transition code address\r | |
213 | and edx, 0fh\r | |
214 | shl eax, 12\r | |
215 | lea edx, [rdx + (offset _BackFromUserCode - offset m16Start)]\r | |
216 | mov ax, dx\r | |
217 | stosd ; [edi] <- return address of user code\r | |
218 | sgdt fword ptr [rcx + (offset SavedGdt - offset SavedCr4)]\r | |
219 | sidt fword ptr [rsp + 38h] ; save IDT stack in argument space\r | |
220 | mov rax, cr0\r | |
221 | mov [rcx + (offset SavedCr0 - offset SavedCr4)], eax\r | |
222 | and eax, 7ffffffeh ; clear PE, PG bits\r | |
223 | mov rbp, cr4\r | |
224 | mov [rcx], ebp ; save CR4 in SavedCr4\r | |
225 | and ebp, 300h ; clear all but PCE and OSFXSR bits\r | |
226 | mov esi, r8d ; esi <- 16-bit stack segment\r | |
227 | push 10h\r | |
228 | pop rdx ; rdx <- selector for data segments\r | |
229 | lgdt fword ptr [rcx + (offset _16Gdtr - offset SavedCr4)]\r | |
18c319ae | 230 | pushfq\r |
97d92bda | 231 | call fword ptr [rcx + (offset _EntryPoint - offset SavedCr4)]\r |
18c319ae | 232 | popfq\r |
97d92bda | 233 | lidt fword ptr [rsp + 38h] ; restore protected mode IDTR\r |
234 | lea eax, [rbp - sizeof (IA32_REGS)]\r | |
878ddf1f | 235 | pop gs\r |
236 | pop fs\r | |
97d92bda | 237 | mov es, r11d\r |
238 | mov ds, r10d\r | |
878ddf1f | 239 | ret\r |
240 | InternalAsmThunk16 ENDP\r | |
241 | \r | |
242 | END\r |