diff options
Diffstat (limited to 'EdkCompatibilityPkg/Foundation/Library/Thunk16/Ia32/Thunk16.asm')
| -rw-r--r-- | EdkCompatibilityPkg/Foundation/Library/Thunk16/Ia32/Thunk16.asm | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/EdkCompatibilityPkg/Foundation/Library/Thunk16/Ia32/Thunk16.asm b/EdkCompatibilityPkg/Foundation/Library/Thunk16/Ia32/Thunk16.asm new file mode 100644 index 0000000000..b59583effd --- /dev/null +++ b/EdkCompatibilityPkg/Foundation/Library/Thunk16/Ia32/Thunk16.asm @@ -0,0 +1,199 @@ +;*****************************************************************************
+;*
+;* Copyright (c) 2006 - 2007, Intel Corporation
+;* All rights reserved. This program and the accompanying materials
+;* are licensed and made available under the terms and conditions of the BSD License
+;* which accompanies this distribution. The full text of the license may be found at
+;* http://opensource.org/licenses/bsd-license.php
+;*
+;* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+;* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;*
+;* Module Name:
+;*
+;* Thunk.asm
+;*
+;* Abstract:
+;*
+;* Real mode thunk
+;*
+;*****************************************************************************
+
+ .686p
+
+EXTERNDEF C mCode16Size:DWORD
+
+CONST SEGMENT FLAT "DATA" READONLY
+
+mCode16Size DD _TEXT16SIZE
+
+CONST ENDS
+
+_DATA SEGMENT FLAT "DATA"
+
+NullSegSel DQ 0
+_16BitCsSel LABEL QWORD
+ DW -1
+ DW 0
+ DB 0
+ DB 9bh
+ DB 8fh ; 16-bit segment
+ DB 0
+_16BitSsSel LABEL QWORD
+ DW -1
+ DW 0
+ DB 0
+ DB 93h
+ DB 8fh ; 16-bit segment
+ DB 0
+
+_16Gdtr LABEL FWORD
+ DW $ - offset NullSegSel - 1
+ DD offset NullSegSel
+
+_DATA ENDS
+
+_TEXT SEGMENT FLAT "CODE" PARA
+
+IA32_REGS STRUC 4t
+_EDI DD ?
+_ESI DD ?
+_EBP DD ?
+_ESP DD ?
+_EBX DD ?
+_EDX DD ?
+_ECX DD ?
+_EAX DD ?
+_DS DW ?
+_ES DW ?
+_FS DW ?
+_GS DW ?
+_EFLAGS DD ?
+_EIP DD ?
+_CS DW ?
+_SS DW ?
+IA32_REGS ENDS
+
+_STK16 STRUC 1t
+RetEip DD ?
+RetCs DW ?
+ThunkFlags DW ?
+SavedEsp DD ?
+SavedSs DW ?
+SavedGdtr FWORD ?
+SavedCr0 DD ?
+SavedCr4 DD ?
+_STK16 ENDS
+
+ ASSUME ds:_DATA
+
+__Thunk16 PROC USES ebp ebx esi edi ds es fs gs
+ ASSUME esi:PTR IA32_REGS
+ mov esi, [esp + 36]
+ movzx edx, [esi]._SS
+ mov edi, [esi]._ESP
+ add edi, - sizeof (_STK16) - sizeof (IA32_REGS)
+ push edi ; save stack offset
+ imul eax, edx, 16 ; eax <- edx*16
+ add edi, eax ; edi <- linear address of 16-bit stack
+ push sizeof (IA32_REGS) / 4
+ pop ecx
+ rep movsd ; copy context to 16-bit stack
+ pop ebx ; ebx <- 16-bit stack offset
+ mov eax, offset @F ; return offset
+ stosd
+ mov eax, cs ; return segment
+ stosw
+ mov eax, [esp + 40] ; THUNK flags
+ stosw
+ mov eax, esp
+ stosd ; save esp
+ mov eax, ss ; save ss
+ stosw
+ sgdt fword ptr [edi] ; save GDTR
+ sidt fword ptr [esp + 36] ; save IDTR
+ mov esi, cr0
+ mov [edi + 6], esi ; save CR0
+ and esi, NOT 80000001h ; esi <- CR0 to set
+ mov eax, cr4
+ mov [edi + 10], eax ; save CR4
+ and al, NOT 30h ; clear PAE & PSE
+ mov edi, edx ; edi <- 16-bit stack segment
+ mov edx, [esp + 44]
+ shl edx, 16
+ push edx
+ pop edx
+ mov dx, _16BitSsSel - NullSegSel
+ lgdt _16Gdtr ; load 16-bit GDTR
+ DB 0eah
+ DD offset @16Bit
+ DW _16BitCsSel - NullSegSel ; jmp far 8:@16Bit
+@16Bit:
+ mov ss, dx
+ mov cr0, esi ; disable protected mode
+ mov cr4, eax ; disable PAE & PSE
+ db 67h, 0FFh, 06Ch, 024h, 0FCh ; jmp dword ptr [esp-4]
+@@:
+ mov eax, ss
+ shl eax, 4
+ add eax, esp ; eax <- address of 16-bit stack
+ lss esp, fword ptr (_STK16 ptr [esp + sizeof (IA32_REGS)]).SavedEsp
+ lidt fword ptr [esp + 36] ; restore IDTR
+ ret
+__Thunk16 ENDP
+
+_TEXT ENDS
+
+_TEXT16 SEGMENT USE16 "CODE" PARA
+
+_Code16Addr PROC C
+_Code16Addr ENDP
+
+RealMode PROC
+ mov ss, di ; set up stack
+ mov esp, ebx
+ lidt fword ptr cs:[_16Idtr - _Code16Addr]
+ popad
+ pop ds
+ pop es
+ pop fs
+ pop gs
+ add sp, 4 ; skip EFlags
+ test (_STK16 ptr [esp + 8]).ThunkFlags, 1
+ jz @F
+ pushf
+@@:
+ push cs
+; push @FarCallRet - _Code16Addr
+ DB 68h ; push /iw
+ DW @FarCallRet - _Code16Addr
+ jz @F
+ jmp fword ptr [esp + 6]
+@@:
+ jmp fword ptr [esp + 4]
+@FarCallRet:
+ pushfd
+ push gs
+ push fs
+ push es
+ push ds
+ pushad
+ cli
+ DB 66h
+ lgdt (_STK16 ptr [esp + sizeof (IA32_REGS)]).SavedGdtr
+ mov eax, (_STK16 ptr [esp + sizeof (IA32_REGS)]).SavedCr4
+ mov cr4, eax
+ mov eax, (_STK16 ptr [esp + sizeof (IA32_REGS)]).SavedCr0
+ mov cr0, eax ; restore CR0
+ jmp fword ptr (_STK16 ptr [esp + sizeof (IA32_REGS)]).RetEip
+RealMode ENDP
+
+_16Idtr FWORD (1 SHL 10) - 1
+
+_TEXT16END:
+
+_TEXT16SIZE = _TEXT16END - _Code16Addr
+
+_TEXT16 ENDS
+
+ END
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