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1 | \r |
2 | #include "BaseLibInternals.h"\r | |
3 | \r | |
4 | ;------------------------------------------------------------------------------\r | |
5 | ;\r | |
6 | ; Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>\r | |
7 | ; This program and the accompanying materials\r | |
8 | ; are licensed and made available under the terms and conditions of the BSD License\r | |
9 | ; which accompanies this distribution. The full text of the license may be found at\r | |
10 | ; http://opensource.org/licenses/bsd-license.php.\r | |
11 | ;\r | |
12 | ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r | |
13 | ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r | |
14 | ;\r | |
15 | ; Module Name:\r | |
16 | ;\r | |
17 | ; Thunk.asm\r | |
18 | ;\r | |
19 | ; Abstract:\r | |
20 | ;\r | |
21 | ; Real mode thunk\r | |
22 | ;\r | |
23 | ;------------------------------------------------------------------------------\r | |
24 | \r | |
25 | global ASM_PFX(m16Size)\r | |
26 | global ASM_PFX(mThunk16Attr)\r | |
27 | global ASM_PFX(m16Gdt)\r | |
28 | global ASM_PFX(m16GdtrBase)\r | |
29 | global ASM_PFX(mTransition)\r | |
30 | global ASM_PFX(m16Start)\r | |
31 | \r | |
32 | struc IA32_REGS\r | |
33 | \r | |
34 | ._EDI: resd 1\r | |
35 | ._ESI: resd 1\r | |
36 | ._EBP: resd 1\r | |
37 | ._ESP: resd 1\r | |
38 | ._EBX: resd 1\r | |
39 | ._EDX: resd 1\r | |
40 | ._ECX: resd 1\r | |
41 | ._EAX: resd 1\r | |
42 | ._DS: resw 1\r | |
43 | ._ES: resw 1\r | |
44 | ._FS: resw 1\r | |
45 | ._GS: resw 1\r | |
46 | ._EFLAGS: resd 1\r | |
47 | ._EIP: resd 1\r | |
48 | ._CS: resw 1\r | |
49 | ._SS: resw 1\r | |
50 | .size:\r | |
51 | \r | |
52 | endstruc\r | |
53 | \r | |
54 | ;; .const\r | |
55 | \r | |
56 | SECTION .data\r | |
57 | \r | |
58 | ;\r | |
59 | ; These are global constant to convey information to C code.\r | |
60 | ;\r | |
61 | ASM_PFX(m16Size) DW InternalAsmThunk16 - ASM_PFX(m16Start)\r | |
62 | ASM_PFX(mThunk16Attr) DW _ThunkAttr - ASM_PFX(m16Start)\r | |
63 | ASM_PFX(m16Gdt) DW _NullSegDesc - ASM_PFX(m16Start)\r | |
64 | ASM_PFX(m16GdtrBase) DW _16GdtrBase - ASM_PFX(m16Start)\r | |
65 | ASM_PFX(mTransition) DW _EntryPoint - ASM_PFX(m16Start)\r | |
66 | \r | |
67 | SECTION .text\r | |
68 | \r | |
69 | ASM_PFX(m16Start):\r | |
70 | \r | |
71 | SavedGdt:\r | |
72 | dw 0\r | |
73 | dd 0\r | |
74 | \r | |
75 | ;------------------------------------------------------------------------------\r | |
76 | ; _BackFromUserCode() takes control in real mode after 'retf' has been executed\r | |
77 | ; by user code. It will be shadowed to somewhere in memory below 1MB.\r | |
78 | ;------------------------------------------------------------------------------\r | |
79 | _BackFromUserCode:\r | |
80 | ;\r | |
81 | ; The order of saved registers on the stack matches the order they appears\r | |
82 | ; in IA32_REGS structure. This facilitates wrapper function to extract them\r | |
83 | ; into that structure.\r | |
84 | ;\r | |
85 | push ss\r | |
86 | push cs\r | |
87 | DB 66h\r | |
88 | call @Base ; push eip\r | |
89 | @Base:\r | |
90 | pushfw ; pushfd actually\r | |
91 | cli ; disable interrupts\r | |
92 | push gs\r | |
93 | push fs\r | |
94 | push es\r | |
95 | push ds\r | |
96 | pushaw ; pushad actually\r | |
97 | DB 66h, 0bah ; mov edx, imm32\r | |
98 | _ThunkAttr: dd 0\r | |
99 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r | |
100 | jz @1\r | |
101 | mov eax, 15cd2401h ; mov ax, 2401h & int 15h\r | |
102 | cli ; disable interrupts\r | |
103 | jnc @2\r | |
104 | @1:\r | |
105 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r | |
106 | jz @2\r | |
107 | in al, 92h\r | |
108 | or al, 2\r | |
109 | out 92h, al ; deactivate A20M#\r | |
110 | @2:\r | |
111 | xor ax, ax ; xor eax, eax\r | |
112 | mov eax, ss ; mov ax, ss\r | |
113 | DB 67h\r | |
114 | lea bp, [esp + IA32_REGS.size]\r | |
115 | ;\r | |
116 | ; esi's in the following 2 instructions are indeed bp in 16-bit code. Fact\r | |
117 | ; is "esi" in 32-bit addressing mode has the same encoding of "bp" in 16-\r | |
118 | ; bit addressing mode.\r | |
119 | ;\r | |
120 | mov [esi - IA32_REGS.size + IA32_REGS._ESP], bp\r | |
121 | mov ebx, [esi - IA32_REGS.size + IA32_REGS._EIP]\r | |
122 | shl ax, 4 ; shl eax, 4\r | |
123 | add bp, ax ; add ebp, eax\r | |
124 | DB 66h, 0b8h ; mov eax, imm32\r | |
125 | SavedCr4: DD 0\r | |
126 | mov cr4, eax\r | |
127 | DB 66h\r | |
128 | lgdt [cs:edi + (SavedGdt - @Base)]\r | |
129 | DB 66h, 0b8h ; mov eax, imm32\r | |
130 | SavedCr0: DD 0\r | |
131 | mov cr0, eax\r | |
132 | DB 0b8h ; mov ax, imm16\r | |
133 | SavedSs DW 0\r | |
134 | mov ss, eax\r | |
135 | DB 66h, 0bch ; mov esp, imm32\r | |
136 | SavedEsp DD 0\r | |
137 | DB 66h\r | |
138 | retf ; return to protected mode\r | |
139 | \r | |
140 | _EntryPoint:\r | |
141 | DD _ToUserCode - ASM_PFX(m16Start)\r | |
142 | DW 8h\r | |
143 | _16Idtr:\r | |
144 | DW (1 << 10) - 1\r | |
145 | DD 0\r | |
146 | _16Gdtr:\r | |
147 | DW GdtEnd - _NullSegDesc - 1\r | |
148 | _16GdtrBase:\r | |
149 | DD _NullSegDesc\r | |
150 | \r | |
151 | ;------------------------------------------------------------------------------\r | |
152 | ; _ToUserCode() takes control in real mode before passing control to user code.\r | |
153 | ; It will be shadowed to somewhere in memory below 1MB.\r | |
154 | ;------------------------------------------------------------------------------\r | |
155 | _ToUserCode:\r | |
156 | mov edx, ss\r | |
157 | mov ss, ecx ; set new segment selectors\r | |
158 | mov ds, ecx\r | |
159 | mov es, ecx\r | |
160 | mov fs, ecx\r | |
161 | mov gs, ecx\r | |
162 | mov cr0, eax ; real mode starts at next instruction\r | |
163 | ; which (per SDM) *must* be a far JMP.\r | |
164 | DB 0eah\r | |
165 | _RealAddr: DW 0, 0\r | |
166 | \r | |
167 | mov cr4, ebp\r | |
168 | mov ss, esi ; set up 16-bit stack segment\r | |
169 | xchg sp, bx ; set up 16-bit stack pointer\r | |
170 | \r | |
171 | ; mov bp, [esp + sizeof(IA32_REGS)\r | |
172 | DB 67h\r | |
173 | mov ebp, [esp + IA32_REGS.size] ; BackFromUserCode address from stack\r | |
174 | \r | |
175 | ; mov cs:[bp + (SavedSs - _BackFromUserCode)], dx\r | |
176 | mov [cs:esi + (SavedSs - _BackFromUserCode)], edx\r | |
177 | \r | |
178 | ; mov cs:[bp + (SavedEsp - _BackFromUserCode)], ebx\r | |
179 | DB 2eh, 66h, 89h, 9eh\r | |
180 | DW SavedEsp - _BackFromUserCode\r | |
181 | \r | |
182 | ; lidt cs:[bp + (_16Idtr - _BackFromUserCode)]\r | |
183 | DB 2eh, 66h, 0fh, 01h, 9eh\r | |
184 | DW _16Idtr - _BackFromUserCode\r | |
185 | \r | |
186 | popaw ; popad actually\r | |
187 | pop ds\r | |
188 | pop es\r | |
189 | pop fs\r | |
190 | pop gs\r | |
191 | popfw ; popfd\r | |
192 | \r | |
193 | DB 66h ; Use 32-bit addressing for "retf" below\r | |
194 | retf ; transfer control to user code\r | |
195 | \r | |
196 | ALIGN 16\r | |
197 | _NullSegDesc DQ 0\r | |
198 | _16CsDesc:\r | |
199 | DW -1\r | |
200 | DW 0\r | |
201 | DB 0\r | |
202 | DB 9bh\r | |
203 | DB 8fh ; 16-bit segment, 4GB limit\r | |
204 | DB 0\r | |
205 | _16DsDesc:\r | |
206 | DW -1\r | |
207 | DW 0\r | |
208 | DB 0\r | |
209 | DB 93h\r | |
210 | DB 8fh ; 16-bit segment, 4GB limit\r | |
211 | DB 0\r | |
212 | GdtEnd:\r | |
213 | \r | |
214 | ;------------------------------------------------------------------------------\r | |
215 | ; IA32_REGISTER_SET *\r | |
216 | ; EFIAPI\r | |
217 | ; InternalAsmThunk16 (\r | |
218 | ; IN IA32_REGISTER_SET *RegisterSet,\r | |
219 | ; IN OUT VOID *Transition\r | |
220 | ; );\r | |
221 | ;------------------------------------------------------------------------------\r | |
222 | global ASM_PFX(InternalAsmThunk16)\r | |
223 | ASM_PFX(InternalAsmThunk16):\r | |
224 | push ebp\r | |
225 | push ebx\r | |
226 | push esi\r | |
227 | push edi\r | |
228 | push ds\r | |
229 | push es\r | |
230 | push fs\r | |
231 | push gs\r | |
232 | mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter\r | |
233 | movzx edx, word [esi + IA32_REGS._SS]\r | |
234 | mov edi, [esi + IA32_REGS._ESP]\r | |
235 | add edi, - (IA32_REGS.size + 4) ; reserve stack space\r | |
236 | mov ebx, edi ; ebx <- stack offset\r | |
237 | imul eax, edx, 16 ; eax <- edx * 16\r | |
238 | push IA32_REGS.size / 4\r | |
239 | add edi, eax ; edi <- linear address of 16-bit stack\r | |
240 | pop ecx\r | |
241 | rep movsd ; copy RegSet\r | |
242 | mov eax, [esp + 40] ; eax <- address of transition code\r | |
243 | mov esi, edx ; esi <- 16-bit stack segment\r | |
244 | lea edx, [eax + (SavedCr0 - ASM_PFX(m16Start))]\r | |
245 | mov ecx, eax\r | |
246 | and ecx, 0fh\r | |
247 | shl eax, 12\r | |
248 | lea ecx, [ecx + (_BackFromUserCode - ASM_PFX(m16Start))]\r | |
249 | mov ax, cx\r | |
250 | stosd ; [edi] <- return address of user code\r | |
251 | add eax, _RealAddr + 4 - _BackFromUserCode\r | |
252 | mov [edx + (_RealAddr - SavedCr0)], eax\r | |
253 | sgdt [edx + (SavedGdt - SavedCr0)]\r | |
254 | sidt [esp + 36] ; save IDT stack in argument space\r | |
255 | mov eax, cr0\r | |
256 | mov [edx], eax ; save CR0 in SavedCr0\r | |
257 | and eax, 7ffffffeh ; clear PE, PG bits\r | |
258 | mov ebp, cr4\r | |
259 | mov [edx + (SavedCr4 - SavedCr0)], ebp\r | |
260 | and ebp, ~30h ; clear PAE, PSE bits\r | |
261 | push 10h\r | |
262 | pop ecx ; ecx <- selector for data segments\r | |
263 | lgdt [edx + (_16Gdtr - SavedCr0)]\r | |
264 | pushfd ; Save df/if indeed\r | |
265 | call dword far [edx + (_EntryPoint - SavedCr0)]\r | |
266 | popfd\r | |
267 | lidt [esp + 36] ; restore protected mode IDTR\r | |
268 | lea eax, [ebp - IA32_REGS.size] ; eax <- the address of IA32_REGS\r | |
269 | pop gs\r | |
270 | pop fs\r | |
271 | pop es\r | |
272 | pop ds\r | |
273 | pop edi\r | |
274 | pop esi\r | |
275 | pop ebx\r | |
276 | pop ebp\r | |
277 | ret\r |