2008-09-17 09:46:17 +02:00
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2008-10-31 05:32:02 +01:00
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#include "BaseLibInternals.h"
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2007-07-02 11:34:25 +02:00
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;------------------------------------------------------------------------------
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;
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2008-12-29 15:07:07 +01:00
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; Copyright (c) 2006 - 2008, Intel Corporation
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2007-07-02 11:34:25 +02:00
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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 m16Start:BYTE
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EXTERNDEF m16Size:WORD
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EXTERNDEF mThunk16Attr:WORD
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EXTERNDEF m16Gdt:WORD
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EXTERNDEF m16GdtrBase:WORD
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EXTERNDEF mTransition:WORD
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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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_EFLAGS 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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.const
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m16Size DW InternalAsmThunk16 - m16Start
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mThunk16Attr DW _ThunkAttr - m16Start
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m16Gdt DW _NullSeg - m16Start
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m16GdtrBase DW _16GdtrBase - m16Start
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mTransition DW _EntryPoint - m16Start
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.code
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m16Start LABEL BYTE
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SavedGdt LABEL FWORD
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DW ?
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DQ ?
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;------------------------------------------------------------------------------
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; _BackFromUserCode() takes control in real mode after 'retf' has been executed
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; by user code. It will be shadowed to somewhere in memory below 1MB.
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;------------------------------------------------------------------------------
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_BackFromUserCode PROC
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;
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; The order of saved registers on the stack matches the order they appears
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; in IA32_REGS structure. This facilitates wrapper function to extract them
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; into that structure.
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;
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; Some instructions for manipulation of segment registers have to be written
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; in opcode since 64-bit MASM prevents accesses to those registers.
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;
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DB 16h ; push ss
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DB 0eh ; push cs
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DB 66h
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call @Base ; push eip
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@Base:
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DB 66h
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push 0 ; reserved high order 32 bits of EFlags
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pushf ; pushfd actually
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cli ; disable interrupts
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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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DB 66h, 0bah ; mov edx, imm32
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_ThunkAttr DD ?
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test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15
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jz @1
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mov eax, 15cd2401h ; mov ax, 2401h & int 15h
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cli ; disable interrupts
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jnc @2
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@1:
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test dl, THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL
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jz @2
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in al, 92h
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or al, 2
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out 92h, al ; deactivate A20M#
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@2:
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mov eax, ss
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lea bp, [esp + sizeof (IA32_REGS)]
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;
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; rsi in the following 2 instructions is indeed bp in 16-bit code
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;
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mov word ptr (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._ESP, bp
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DB 66h
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mov ebx, (IA32_REGS ptr [rsi - sizeof (IA32_REGS)])._EIP
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shl ax, 4 ; shl eax, 4
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add bp, ax ; add ebp, eax
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mov ax, cs
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shl ax, 4
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lea ax, [eax + ebx + (@64BitCode - @Base)]
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DB 66h, 2eh, 89h, 87h ; mov cs:[bx + (@64Eip - @Base)], eax
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DW @64Eip - @Base
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DB 66h, 0b8h ; mov eax, imm32
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SavedCr4 DD ?
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mov cr4, rax
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;
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; rdi in the instruction below is indeed bx in 16-bit code
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;
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DB 66h, 2eh ; 2eh is "cs:" segment override
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lgdt fword ptr [rdi + (SavedGdt - @Base)]
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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
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DB 66h, 0b8h ; mov eax, imm32
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SavedCr0 DD ?
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mov cr0, rax
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DB 66h, 0eah ; jmp far cs:@64Bit
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@64Eip DD ?
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SavedCs DW ?
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@64BitCode:
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mov rsp, r8 ; restore stack
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ret
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_BackFromUserCode ENDP
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_EntryPoint DD _ToUserCode - m16Start
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DW CODE16
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_16Gdtr LABEL FWORD
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DW GDT_SIZE - 1
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_16GdtrBase DQ _NullSeg
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_16Idtr FWORD (1 SHL 10) - 1
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;------------------------------------------------------------------------------
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; _ToUserCode() takes control in real mode before passing control to user code.
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; It will be shadowed to somewhere in memory below 1MB.
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;------------------------------------------------------------------------------
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_ToUserCode PROC
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mov ss, edx ; set new segment selectors
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mov ds, edx
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mov es, edx
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mov fs, edx
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mov gs, edx
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DB 66h
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mov ecx, 0c0000080h
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mov cr0, rax ; real mode starts at next instruction
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rdmsr
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and ah, NOT 1
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wrmsr
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mov cr4, rbp
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mov ss, esi ; set up 16-bit stack segment
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mov sp, bx ; set up 16-bit stack pointer
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DB 66h ; make the following call 32-bit
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call @Base ; push eip
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@Base:
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pop bp ; ebp <- address of @Base
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push [esp + sizeof (IA32_REGS) + 2]
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lea eax, [rsi + (@RealMode - @Base)] ; rsi is "bp" in 16-bit code
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push rax
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retf ; execution begins at next instruction
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@RealMode:
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DB 66h, 2eh ; CS and operand size override
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lidt fword ptr [rsi + (_16Idtr - @Base)]
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DB 66h, 61h ; popad
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DB 1fh ; pop ds
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DB 07h ; pop es
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pop fs
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pop gs
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popf ; popfd
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lea sp, [esp + 4] ; skip high order 32 bits of EFlags
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DB 66h ; make the following retf 32-bit
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retf ; transfer control to user code
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_ToUserCode ENDP
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CODE16 = _16Code - $
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DATA16 = _16Data - $
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DATA32 = _32Data - $
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_NullSeg DQ 0
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_16Code 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, 4GB limit
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DB 0
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_16Data 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, 4GB limit
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DB 0
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_32Data 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 0cfh ; 16-bit segment, 4GB limit
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DB 0
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GDT_SIZE = $ - _NullSeg
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;------------------------------------------------------------------------------
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; IA32_REGISTER_SET *
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; EFIAPI
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; InternalAsmThunk16 (
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; IN IA32_REGISTER_SET *RegisterSet,
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; IN OUT VOID *Transition
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; );
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;------------------------------------------------------------------------------
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InternalAsmThunk16 PROC USES rbp rbx rsi rdi
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mov r10d, ds ; r9 ~ r11 are not accessible in 16-bit
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mov r11d, es ; so use them for saving seg registers
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mov r9d, ss
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push fs
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push gs
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mov rsi, rcx
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movzx r8d, (IA32_REGS ptr [rsi])._SS
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mov edi, (IA32_REGS ptr [rsi])._ESP
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lea rdi, [edi - (sizeof (IA32_REGS) + 4)]
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imul eax, r8d, 16 ; eax <- r8d(stack segment) * 16
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mov ebx, edi ; ebx <- stack for 16-bit code
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push sizeof (IA32_REGS) / 4
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add edi, eax ; edi <- linear address of 16-bit stack
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pop rcx
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rep movsd ; copy RegSet
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lea ecx, [rdx + (SavedCr4 - m16Start)]
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mov eax, edx ; eax <- transition code address
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and edx, 0fh
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shl eax, 12 ; segment address in high order 16 bits
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lea ax, [rdx + (_BackFromUserCode - m16Start)] ; offset address
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stosd ; [edi] <- return address of user code
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sgdt fword ptr [rcx + (SavedGdt - SavedCr4)]
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sidt fword ptr [rsp + 38h] ; save IDT stack in argument space
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mov rax, cr0
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mov [rcx + (SavedCr0 - SavedCr4)], eax
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and eax, 7ffffffeh ; clear PE, PG bits
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mov rbp, cr4
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mov [rcx], ebp ; save CR4 in SavedCr4
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and ebp, 300h ; clear all but PCE and OSFXSR bits
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mov esi, r8d ; esi <- 16-bit stack segment
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DB 6ah, DATA32 ; push DATA32
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pop rdx ; rdx <- 32-bit data segment selector
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lgdt fword ptr [rcx + (_16Gdtr - SavedCr4)]
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mov ss, edx
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pushfq
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lea edx, [rdx + DATA16 - DATA32]
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lea r8, @RetFromRealMode
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push r8
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mov r8d, cs
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mov [rcx + (SavedCs - SavedCr4)], r8w
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mov r8, rsp
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jmp fword ptr [rcx + (_EntryPoint - SavedCr4)]
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@RetFromRealMode:
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popfq
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lidt fword ptr [rsp + 38h] ; restore protected mode IDTR
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lea eax, [rbp - sizeof (IA32_REGS)]
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pop gs
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pop fs
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mov ss, r9d
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mov es, r11d
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mov ds, r10d
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ret
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InternalAsmThunk16 ENDP
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END
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