mirror of https://github.com/acidanthera/audk.git
217 lines
6.2 KiB
NASM
217 lines
6.2 KiB
NASM
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;*****************************************************************************
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;*
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;* Copyright (c) 2006, Intel Corporation
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;* All rights reserved. This program and the accompanying materials
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;* are licensed and made available under the terms and conditions of the BSD License
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;* which accompanies this distribution. The full text of the license may be found at
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;* http://opensource.org/licenses/bsd-license.php
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;*
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;* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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;* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;*
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;* Module Name:
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;*
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;* Thunk.asm
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;*
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;* Abstract:
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;*
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;* Real mode thunk
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;*
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;*****************************************************************************
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EXTERNDEF mCode16Size:QWORD
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.const
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mCode16Size DQ _Code16End - _Code16Addr
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.data
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NullSegSel DQ 0
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_16CsSegSel LABEL QWORD
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DW -1
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DW 0
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DB 0
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DB 9bh
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DB 8fh ; 16-bit segment
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DB 0
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_16DsSegSel LABEL QWORD
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DW -1
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DW 0
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DB 0
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DB 93h
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DB 8fh ; 16-bit segment
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DB 0
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_16Gdtr LABEL FWORD
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DW $ - offset NullSegSel - 1
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DQ offset NullSegSel
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.code
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IA32_REGS STRUC 4t
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_EDI DD ?
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_ESI DD ?
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_EBP DD ?
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_ESP DD ?
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_EBX DD ?
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_EDX DD ?
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_ECX DD ?
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_EAX DD ?
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_DS DW ?
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_ES DW ?
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_FS DW ?
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_GS DW ?
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_RFLAGS DQ ?
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_EIP DD ?
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_CS DW ?
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_SS DW ?
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IA32_REGS ENDS
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_STK16 STRUC 1t
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RetEip DD ?
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RetCs DW ?
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ThunkFlags DW ?
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SavedGdtr FWORD ?
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Resvd1 DW ?
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SavedCr0 DD ?
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SavedCr4 DD ?
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_STK16 ENDS
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_Thunk16 PROC USES rbp rbx rsi rdi r12 r13 r14 r15
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push fs
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push gs
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mov r12d, ds
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mov r13d, es
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mov r14d, ss
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mov r15, rsp
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mov rsi, rcx
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movzx r10, (IA32_REGS ptr [rsi])._SS
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xor rdi, rdi
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mov edi, (IA32_REGS ptr [rsi])._ESP
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add rdi, - sizeof (IA32_REGS) - sizeof (_STK16)
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push rdi
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imul rax, r10, 16
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add rdi, rax
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push sizeof (IA32_REGS) / 4
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pop rcx
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rep movsd
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pop rbx ; rbx <- 16-bit stack offset
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lea eax, @F ; return offset
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stosd
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mov eax, cs ; return segment
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stosw
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mov eax, edx ; THUNK Flags
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stosw
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sgdt fword ptr [rsp + 58h] ; save GDTR
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mov rax, [rsp + 58h]
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stosq
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mov rax, cr0 ; save CR0
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mov esi, eax ; esi <- CR0 to set
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stosd
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mov rax, cr4 ; save CR4
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stosd
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sidt fword ptr [rsp + 58h] ; save IDTR
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and esi, 07ffffffeh ; clear PE & PG bits
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mov rdi, r10 ; rdi <- 16-bit stack segment
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shl r8, 16
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push r8 ; far jmp address
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lea eax, @16Bit
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push rax
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mov word ptr [rsp + 4], 8
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lgdt _16Gdtr
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retf
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@16Bit:
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DB 66h
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mov ecx, 0c0000080h
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mov cr0, rsi ; disable PE & PG
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rdmsr
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and ah, NOT 1
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wrmsr ; clear LME bit
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mov rax, cr4
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and al, NOT 30h ; clear PAE & PSE
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mov cr4, rax
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retf
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@@:
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xor rax, rax
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mov eax, ss
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shl eax, 4
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add eax, esp ; rax <- address of 16-bit stack
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mov rsp, r15
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lidt fword ptr [rsp + 58h] ; restore IDTR
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mov ds, r12d
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mov es, r13d
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mov ss, r14d
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pop gs
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pop fs
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ret
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_Thunk16 ENDP
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ALIGN 10h
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_Code16Addr PROC
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_Code16Addr ENDP
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RealMode PROC
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mov ss, edi
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mov sp, bx ; set up 16-bit stack
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DB 2eh, 0fh, 1, 1eh
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DW _16Idtr - _Code16Addr ; lidt _16Idtr
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DB 66h, 61h ; popad
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DB 1fh ; pop ds
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DB 7 ; pop es
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pop fs
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pop gs
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add esp, 8 ; skip RFLAGS
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DB 67h, 0f7h, 44h, 24h, 0eh, 1, 0 ; test [esp + 0eh], 1
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jz @F
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pushfq ; pushf, actually
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@@:
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DB 0eh ; push cs
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DB 68h ; push /iw
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DW @FarCallRet - _Code16Addr
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jz @F
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DB 66h
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jmp fword ptr [esp + 6]
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@@:
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DB 66h
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jmp fword ptr [esp + 4]
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@FarCallRet:
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DB 66h
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push 0 ; push a dword of zero
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pushf ; pushfd, actually
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push gs
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push fs
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DB 6 ; push es
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DB 1eh ; push ds
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DB 66h, 60h ; pushad
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cli
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DB 66h
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lgdt (_STK16 ptr [esp + sizeof(IA32_REGS)]).SavedGdtr
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DB 66h
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mov eax, (_STK16 ptr [esp + sizeof(IA32_REGS)]).SavedCr4
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mov cr4, rax
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DB 66h
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mov ecx, 0c0000080h
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rdmsr
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or ah, 1
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wrmsr ; set LME
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DB 66h
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mov eax, (_STK16 ptr [esp + sizeof(IA32_REGS)]).SavedCr0
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mov cr0, rax
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DB 66h
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jmp fword ptr (_STK16 ptr [esp + sizeof(IA32_REGS)]).RetEip
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RealMode ENDP
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_16Idtr FWORD (1 SHL 10) - 1
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_Code16End:
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END
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