]>
Commit | Line | Data |
---|---|---|
6dab5c8a JJ |
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 | |
9344f092 | 7 | ; SPDX-License-Identifier: BSD-2-Clause-Patent\r |
6dab5c8a JJ |
8 | ;\r |
9 | ; Module Name:\r | |
10 | ;\r | |
11 | ; Thunk.asm\r | |
12 | ;\r | |
13 | ; Abstract:\r | |
14 | ;\r | |
15 | ; Real mode thunk\r | |
16 | ;\r | |
17 | ;------------------------------------------------------------------------------\r | |
18 | \r | |
19 | global ASM_PFX(m16Size)\r | |
20 | global ASM_PFX(mThunk16Attr)\r | |
21 | global ASM_PFX(m16Gdt)\r | |
22 | global ASM_PFX(m16GdtrBase)\r | |
23 | global ASM_PFX(mTransition)\r | |
24 | global ASM_PFX(m16Start)\r | |
25 | \r | |
26 | struc IA32_REGS\r | |
27 | \r | |
28 | ._EDI: resd 1\r | |
29 | ._ESI: resd 1\r | |
30 | ._EBP: resd 1\r | |
31 | ._ESP: resd 1\r | |
32 | ._EBX: resd 1\r | |
33 | ._EDX: resd 1\r | |
34 | ._ECX: resd 1\r | |
35 | ._EAX: resd 1\r | |
36 | ._DS: resw 1\r | |
37 | ._ES: resw 1\r | |
38 | ._FS: resw 1\r | |
39 | ._GS: resw 1\r | |
40 | ._EFLAGS: resd 1\r | |
41 | ._EIP: resd 1\r | |
42 | ._CS: resw 1\r | |
43 | ._SS: resw 1\r | |
44 | .size:\r | |
45 | \r | |
46 | endstruc\r | |
47 | \r | |
48 | ;; .const\r | |
49 | \r | |
50 | SECTION .data\r | |
51 | \r | |
52 | ;\r | |
53 | ; These are global constant to convey information to C code.\r | |
54 | ;\r | |
15f8eef7 | 55 | ASM_PFX(m16Size) DW ASM_PFX(InternalAsmThunk16) - ASM_PFX(m16Start)\r |
7458df40 | 56 | ASM_PFX(mThunk16Attr) DW _BackFromUserCode.ThunkAttrEnd - 4 - ASM_PFX(m16Start)\r |
6dab5c8a JJ |
57 | ASM_PFX(m16Gdt) DW _NullSegDesc - ASM_PFX(m16Start)\r |
58 | ASM_PFX(m16GdtrBase) DW _16GdtrBase - ASM_PFX(m16Start)\r | |
59 | ASM_PFX(mTransition) DW _EntryPoint - ASM_PFX(m16Start)\r | |
60 | \r | |
61 | SECTION .text\r | |
62 | \r | |
63 | ASM_PFX(m16Start):\r | |
64 | \r | |
65 | SavedGdt:\r | |
66 | dw 0\r | |
67 | dd 0\r | |
68 | \r | |
69 | ;------------------------------------------------------------------------------\r | |
70 | ; _BackFromUserCode() takes control in real mode after 'retf' has been executed\r | |
71 | ; by user code. It will be shadowed to somewhere in memory below 1MB.\r | |
72 | ;------------------------------------------------------------------------------\r | |
73 | _BackFromUserCode:\r | |
74 | ;\r | |
75 | ; The order of saved registers on the stack matches the order they appears\r | |
76 | ; in IA32_REGS structure. This facilitates wrapper function to extract them\r | |
77 | ; into that structure.\r | |
78 | ;\r | |
f6888eea | 79 | BITS 16\r |
6dab5c8a JJ |
80 | push ss\r |
81 | push cs\r | |
eabcdf3a JJ |
82 | ;\r |
83 | ; Note: We can't use o32 on the next instruction because of a bug\r | |
84 | ; in NASM 2.09.04 through 2.10rc1.\r | |
85 | ;\r | |
86 | call dword .Base ; push eip\r | |
a8458d6c | 87 | .Base:\r |
f6888eea | 88 | pushfd\r |
6dab5c8a JJ |
89 | cli ; disable interrupts\r |
90 | push gs\r | |
91 | push fs\r | |
92 | push es\r | |
93 | push ds\r | |
f6888eea | 94 | pushad\r |
7458df40 JJ |
95 | mov edx, strict dword 0\r |
96 | .ThunkAttrEnd:\r | |
6dab5c8a | 97 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15\r |
a8458d6c | 98 | jz .1\r |
f6888eea JJ |
99 | mov ax, 2401h\r |
100 | int 15h\r | |
6dab5c8a | 101 | cli ; disable interrupts\r |
a8458d6c JJ |
102 | jnc .2\r |
103 | .1:\r | |
6dab5c8a | 104 | test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL\r |
a8458d6c | 105 | jz .2\r |
6dab5c8a JJ |
106 | in al, 92h\r |
107 | or al, 2\r | |
108 | out 92h, al ; deactivate A20M#\r | |
a8458d6c | 109 | .2:\r |
f6888eea JJ |
110 | xor eax, eax\r |
111 | mov ax, ss\r | |
112 | lea ebp, [esp + IA32_REGS.size]\r | |
113 | mov [bp - IA32_REGS.size + IA32_REGS._ESP], ebp\r | |
114 | mov bx, [bp - IA32_REGS.size + IA32_REGS._EIP]\r | |
115 | shl eax, 4 ; shl eax, 4\r | |
116 | add ebp, eax ; add ebp, eax\r | |
7458df40 JJ |
117 | mov eax, strict dword 0\r |
118 | .SavedCr4End:\r | |
6dab5c8a | 119 | mov cr4, eax\r |
f6888eea | 120 | o32 lgdt [cs:bx + (SavedGdt - .Base)]\r |
7458df40 JJ |
121 | mov eax, strict dword 0\r |
122 | .SavedCr0End:\r | |
6dab5c8a | 123 | mov cr0, eax\r |
7458df40 JJ |
124 | mov ax, strict word 0\r |
125 | .SavedSsEnd:\r | |
6dab5c8a | 126 | mov ss, eax\r |
7458df40 JJ |
127 | mov esp, strict dword 0\r |
128 | .SavedEspEnd:\r | |
f6888eea | 129 | o32 retf ; return to protected mode\r |
6dab5c8a JJ |
130 | \r |
131 | _EntryPoint:\r | |
132 | DD _ToUserCode - ASM_PFX(m16Start)\r | |
133 | DW 8h\r | |
134 | _16Idtr:\r | |
135 | DW (1 << 10) - 1\r | |
136 | DD 0\r | |
137 | _16Gdtr:\r | |
138 | DW GdtEnd - _NullSegDesc - 1\r | |
139 | _16GdtrBase:\r | |
03e9db15 | 140 | DD 0\r |
6dab5c8a JJ |
141 | \r |
142 | ;------------------------------------------------------------------------------\r | |
143 | ; _ToUserCode() takes control in real mode before passing control to user code.\r | |
144 | ; It will be shadowed to somewhere in memory below 1MB.\r | |
145 | ;------------------------------------------------------------------------------\r | |
146 | _ToUserCode:\r | |
f6888eea JJ |
147 | BITS 16\r |
148 | mov dx, ss\r | |
149 | mov ss, cx ; set new segment selectors\r | |
150 | mov ds, cx\r | |
151 | mov es, cx\r | |
152 | mov fs, cx\r | |
153 | mov gs, cx\r | |
6dab5c8a JJ |
154 | mov cr0, eax ; real mode starts at next instruction\r |
155 | ; which (per SDM) *must* be a far JMP.\r | |
7458df40 JJ |
156 | jmp 0:strict word 0\r |
157 | .RealAddrEnd:\r | |
6dab5c8a | 158 | mov cr4, ebp\r |
f6888eea JJ |
159 | mov ss, si ; set up 16-bit stack segment\r |
160 | xchg esp, ebx ; set up 16-bit stack pointer\r | |
161 | mov bp, [esp + IA32_REGS.size]\r | |
7458df40 JJ |
162 | mov [cs:bp + (_BackFromUserCode.SavedSsEnd - 2 - _BackFromUserCode)], dx\r |
163 | mov [cs:bp + (_BackFromUserCode.SavedEspEnd - 4 - _BackFromUserCode)], ebx\r | |
f6888eea JJ |
164 | lidt [cs:bp + (_16Idtr - _BackFromUserCode)]\r |
165 | \r | |
166 | popad\r | |
6dab5c8a JJ |
167 | pop ds\r |
168 | pop es\r | |
169 | pop fs\r | |
170 | pop gs\r | |
f6888eea | 171 | popfd\r |
6dab5c8a | 172 | \r |
f6888eea | 173 | o32 retf ; transfer control to user code\r |
6dab5c8a JJ |
174 | \r |
175 | ALIGN 16\r | |
176 | _NullSegDesc DQ 0\r | |
177 | _16CsDesc:\r | |
178 | DW -1\r | |
179 | DW 0\r | |
180 | DB 0\r | |
181 | DB 9bh\r | |
182 | DB 8fh ; 16-bit segment, 4GB limit\r | |
183 | DB 0\r | |
184 | _16DsDesc:\r | |
185 | DW -1\r | |
186 | DW 0\r | |
187 | DB 0\r | |
188 | DB 93h\r | |
189 | DB 8fh ; 16-bit segment, 4GB limit\r | |
190 | DB 0\r | |
191 | GdtEnd:\r | |
192 | \r | |
193 | ;------------------------------------------------------------------------------\r | |
194 | ; IA32_REGISTER_SET *\r | |
195 | ; EFIAPI\r | |
196 | ; InternalAsmThunk16 (\r | |
197 | ; IN IA32_REGISTER_SET *RegisterSet,\r | |
198 | ; IN OUT VOID *Transition\r | |
199 | ; );\r | |
200 | ;------------------------------------------------------------------------------\r | |
201 | global ASM_PFX(InternalAsmThunk16)\r | |
202 | ASM_PFX(InternalAsmThunk16):\r | |
f6888eea | 203 | BITS 32\r |
6dab5c8a JJ |
204 | push ebp\r |
205 | push ebx\r | |
206 | push esi\r | |
207 | push edi\r | |
208 | push ds\r | |
209 | push es\r | |
210 | push fs\r | |
211 | push gs\r | |
212 | mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter\r | |
213 | movzx edx, word [esi + IA32_REGS._SS]\r | |
214 | mov edi, [esi + IA32_REGS._ESP]\r | |
215 | add edi, - (IA32_REGS.size + 4) ; reserve stack space\r | |
216 | mov ebx, edi ; ebx <- stack offset\r | |
217 | imul eax, edx, 16 ; eax <- edx * 16\r | |
218 | push IA32_REGS.size / 4\r | |
219 | add edi, eax ; edi <- linear address of 16-bit stack\r | |
220 | pop ecx\r | |
221 | rep movsd ; copy RegSet\r | |
222 | mov eax, [esp + 40] ; eax <- address of transition code\r | |
223 | mov esi, edx ; esi <- 16-bit stack segment\r | |
7458df40 | 224 | lea edx, [eax + (_BackFromUserCode.SavedCr0End - ASM_PFX(m16Start))]\r |
6dab5c8a JJ |
225 | mov ecx, eax\r |
226 | and ecx, 0fh\r | |
227 | shl eax, 12\r | |
228 | lea ecx, [ecx + (_BackFromUserCode - ASM_PFX(m16Start))]\r | |
229 | mov ax, cx\r | |
230 | stosd ; [edi] <- return address of user code\r | |
7458df40 JJ |
231 | add eax, _ToUserCode.RealAddrEnd - _BackFromUserCode\r |
232 | mov [edx + (_ToUserCode.RealAddrEnd - 4 - _BackFromUserCode.SavedCr0End)], eax\r | |
233 | sgdt [edx + (SavedGdt - _BackFromUserCode.SavedCr0End)]\r | |
6dab5c8a JJ |
234 | sidt [esp + 36] ; save IDT stack in argument space\r |
235 | mov eax, cr0\r | |
7458df40 | 236 | mov [edx - 4], eax ; save CR0 in _BackFromUserCode.SavedCr0End - 4\r |
6dab5c8a JJ |
237 | and eax, 7ffffffeh ; clear PE, PG bits\r |
238 | mov ebp, cr4\r | |
7458df40 | 239 | mov [edx + (_BackFromUserCode.SavedCr4End - 4 - _BackFromUserCode.SavedCr0End)], ebp\r |
6dab5c8a JJ |
240 | and ebp, ~30h ; clear PAE, PSE bits\r |
241 | push 10h\r | |
242 | pop ecx ; ecx <- selector for data segments\r | |
7458df40 | 243 | lgdt [edx + (_16Gdtr - _BackFromUserCode.SavedCr0End)]\r |
6dab5c8a | 244 | pushfd ; Save df/if indeed\r |
7458df40 | 245 | call dword far [edx + (_EntryPoint - _BackFromUserCode.SavedCr0End)]\r |
6dab5c8a JJ |
246 | popfd\r |
247 | lidt [esp + 36] ; restore protected mode IDTR\r | |
248 | lea eax, [ebp - IA32_REGS.size] ; eax <- the address of IA32_REGS\r | |
249 | pop gs\r | |
250 | pop fs\r | |
251 | pop es\r | |
252 | pop ds\r | |
253 | pop edi\r | |
254 | pop esi\r | |
255 | pop ebx\r | |
256 | pop ebp\r | |
257 | ret\r |