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Fix the issue to clear the high 16-bit of EAX before use it Thunk code.
[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / Thunk16.asm
1
2 #include "BaseLibInternals.h"
3
4 ;------------------------------------------------------------------------------
5 ;
6 ; Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
7 ; This program and the accompanying materials
8 ; are licensed and made available under the terms and conditions of the BSD License
9 ; which accompanies this distribution. The full text of the license may be found at
10 ; http://opensource.org/licenses/bsd-license.php.
11 ;
12 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
13 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
14 ;
15 ; Module Name:
16 ;
17 ; Thunk.asm
18 ;
19 ; Abstract:
20 ;
21 ; Real mode thunk
22 ;
23 ;------------------------------------------------------------------------------
24
25 .686p
26 .model flat,C
27
28 EXTERNDEF C m16Start:BYTE
29 EXTERNDEF C m16Size:WORD
30 EXTERNDEF C mThunk16Attr:WORD
31 EXTERNDEF C m16Gdt:WORD
32 EXTERNDEF C m16GdtrBase:WORD
33 EXTERNDEF C mTransition:WORD
34
35 ;
36 ; Here is the layout of the real mode stack. _ToUserCode() is responsible for
37 ; loading all these registers from real mode stack.
38 ;
39 IA32_REGS STRUC 4t
40 _EDI DD ?
41 _ESI DD ?
42 _EBP DD ?
43 _ESP DD ?
44 _EBX DD ?
45 _EDX DD ?
46 _ECX DD ?
47 _EAX DD ?
48 _DS DW ?
49 _ES DW ?
50 _FS DW ?
51 _GS DW ?
52 _EFLAGS DD ?
53 _EIP DD ?
54 _CS DW ?
55 _SS DW ?
56 IA32_REGS ENDS
57
58 .const
59
60 ;
61 ; These are global constant to convey information to C code.
62 ;
63 m16Size DW InternalAsmThunk16 - m16Start
64 mThunk16Attr DW _ThunkAttr - m16Start
65 m16Gdt DW _NullSegDesc - m16Start
66 m16GdtrBase DW _16GdtrBase - m16Start
67 mTransition DW _EntryPoint - m16Start
68
69 .code
70
71 m16Start LABEL BYTE
72
73 SavedGdt LABEL FWORD
74 DW ?
75 DD ?
76 ;------------------------------------------------------------------------------
77 ; _BackFromUserCode() takes control in real mode after 'retf' has been executed
78 ; by user code. It will be shadowed to somewhere in memory below 1MB.
79 ;------------------------------------------------------------------------------
80 _BackFromUserCode PROC
81 ;
82 ; The order of saved registers on the stack matches the order they appears
83 ; in IA32_REGS structure. This facilitates wrapper function to extract them
84 ; into that structure.
85 ;
86 push ss
87 push cs
88 DB 66h
89 call @Base ; push eip
90 @Base:
91 pushf ; pushfd actually
92 cli ; disable interrupts
93 push gs
94 push fs
95 push es
96 push ds
97 pushaw ; pushad actually
98 DB 66h, 0bah ; mov edx, imm32
99 _ThunkAttr DD ?
100 test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15
101 jz @1
102 mov eax, 15cd2401h ; mov ax, 2401h & int 15h
103 cli ; disable interrupts
104 jnc @2
105 @1:
106 test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL
107 jz @2
108 in al, 92h
109 or al, 2
110 out 92h, al ; deactivate A20M#
111 @2:
112 xor ax, ax ; xor eax, eax
113 mov eax, ss ; mov ax, ss
114 DB 67h
115 lea bp, [esp + sizeof (IA32_REGS)]
116 ;
117 ; esi's in the following 2 instructions are indeed bp in 16-bit code. Fact
118 ; is "esi" in 32-bit addressing mode has the same encoding of "bp" in 16-
119 ; bit addressing mode.
120 ;
121 mov word ptr (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._ESP, bp
122 mov ebx, (IA32_REGS ptr [esi - sizeof (IA32_REGS)])._EIP
123 shl ax, 4 ; shl eax, 4
124 add bp, ax ; add ebp, eax
125 DB 66h, 0b8h ; mov eax, imm32
126 SavedCr4 DD ?
127 mov cr4, eax
128 DB 66h
129 lgdt fword ptr cs:[edi + (SavedGdt - @Base)]
130 DB 66h, 0b8h ; mov eax, imm32
131 SavedCr0 DD ?
132 mov cr0, eax
133 DB 0b8h ; mov ax, imm16
134 SavedSs DW ?
135 mov ss, eax
136 DB 66h, 0bch ; mov esp, imm32
137 SavedEsp DD ?
138 DB 66h
139 retf ; return to protected mode
140 _BackFromUserCode ENDP
141
142 _EntryPoint DD _ToUserCode - m16Start
143 DW 8h
144 _16Idtr FWORD (1 SHL 10) - 1
145 _16Gdtr LABEL FWORD
146 DW GdtEnd - _NullSegDesc - 1
147 _16GdtrBase DD _NullSegDesc
148
149 ;------------------------------------------------------------------------------
150 ; _ToUserCode() takes control in real mode before passing control to user code.
151 ; It will be shadowed to somewhere in memory below 1MB.
152 ;------------------------------------------------------------------------------
153 _ToUserCode PROC
154 mov edx, ss
155 mov ss, ecx ; set new segment selectors
156 mov ds, ecx
157 mov es, ecx
158 mov fs, ecx
159 mov gs, ecx
160 mov cr0, eax
161 mov cr4, ebp ; real mode starts at next instruction
162 mov ss, esi ; set up 16-bit stack segment
163 xchg sp, bx ; set up 16-bit stack pointer
164 DB 66h
165 call @Base ; push eip
166 @Base:
167 pop bp ; ebp <- address of @Base
168 DB 67h ; address size override
169 push [esp + sizeof (IA32_REGS) + 2]
170 lea eax, [esi + (@RealMode - @Base)]
171 push eax
172 retf
173 @RealMode:
174 mov cs:[esi + (SavedSs - @Base)], edx
175 mov cs:[esi + (SavedEsp - @Base)], bx
176 DB 66h
177 lidt fword ptr cs:[esi + (_16Idtr - @Base)]
178 popaw ; popad actually
179 pop ds
180 pop es
181 pop fs
182 pop gs
183 popf ; popfd
184 DB 66h ; Use 32-bit addressing for "retf" below
185 retf ; transfer control to user code
186 _ToUserCode ENDP
187
188 _NullSegDesc DQ 0
189 _16CsDesc LABEL QWORD
190 DW -1
191 DW 0
192 DB 0
193 DB 9bh
194 DB 8fh ; 16-bit segment, 4GB limit
195 DB 0
196 _16DsDesc LABEL QWORD
197 DW -1
198 DW 0
199 DB 0
200 DB 93h
201 DB 8fh ; 16-bit segment, 4GB limit
202 DB 0
203 GdtEnd LABEL QWORD
204
205 ;------------------------------------------------------------------------------
206 ; IA32_REGISTER_SET *
207 ; EFIAPI
208 ; InternalAsmThunk16 (
209 ; IN IA32_REGISTER_SET *RegisterSet,
210 ; IN OUT VOID *Transition
211 ; );
212 ;------------------------------------------------------------------------------
213 InternalAsmThunk16 PROC USES ebp ebx esi edi ds es fs gs
214 mov esi, [esp + 36] ; esi <- RegSet, the 1st parameter
215 movzx edx, (IA32_REGS ptr [esi])._SS
216 mov edi, (IA32_REGS ptr [esi])._ESP
217 add edi, - (sizeof (IA32_REGS) + 4) ; reserve stack space
218 mov ebx, edi ; ebx <- stack offset
219 imul eax, edx, 16 ; eax <- edx * 16
220 push sizeof (IA32_REGS) / 4
221 add edi, eax ; edi <- linear address of 16-bit stack
222 pop ecx
223 rep movsd ; copy RegSet
224 mov eax, [esp + 40] ; eax <- address of transition code
225 mov esi, edx ; esi <- 16-bit stack segment
226 lea edx, [eax + (SavedCr0 - m16Start)]
227 mov ecx, eax
228 and ecx, 0fh
229 shl eax, 12
230 lea ecx, [ecx + (_BackFromUserCode - m16Start)]
231 mov ax, cx
232 stosd ; [edi] <- return address of user code
233 sgdt fword ptr [edx + (SavedGdt - SavedCr0)]
234 sidt fword ptr [esp + 36] ; save IDT stack in argument space
235 mov eax, cr0
236 mov [edx], eax ; save CR0 in SavedCr0
237 and eax, 7ffffffeh ; clear PE, PG bits
238 mov ebp, cr4
239 mov [edx + (SavedCr4 - SavedCr0)], ebp
240 and ebp, 300h ; clear all but PCE and OSFXSR bits
241 push 10h
242 pop ecx ; ecx <- selector for data segments
243 lgdt fword ptr [edx + (_16Gdtr - SavedCr0)]
244 pushfd ; Save df/if indeed
245 call fword ptr [edx + (_EntryPoint - SavedCr0)]
246 popfd
247 lidt fword ptr [esp + 36] ; restore protected mode IDTR
248 lea eax, [ebp - sizeof (IA32_REGS)] ; eax <- the address of IA32_REGS
249 ret
250 InternalAsmThunk16 ENDP
251
252 END