Port thunk16 code from MSFT to GCC assembly.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@999 6f19259b-4bc3-4df7-8a09-765794883524
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qhuang8
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@ -11,7 +11,7 @@
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#
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#
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# Module Name:
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# Module Name:
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#
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#
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# Thunk.asm
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# Thunk16.S
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#
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#
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# Abstract:
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# Abstract:
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#
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#
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@ -19,26 +19,189 @@
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#
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#
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#------------------------------------------------------------------------------
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#------------------------------------------------------------------------------
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.global _m16Start, _m16Size, _mThunk16Attr, _m16GdtBase, _m16Gdt, _m16GdtrBase, _mTransition
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.global _m16Start, _m16Size, _mThunk16Attr, _m16GdtrBase, _m16Gdt, _m16GdtrBase, _mTransition
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##########
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# FIXME! #
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##########
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# The following data are INVALID!!
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# They just follow GAS syntax.
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_m16Start: .byte 0x00
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_m16Size: .word 0x00
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_mThunk16Attr: .word 0x00
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_m16Gdt: .word 0x00
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_m16GdtrBase: .word 0x00
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_mTransition: .word 0x00
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.global _InternalAsmThunk16
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.global _InternalAsmThunk16
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#THUNK_ATTRIBUTE_BIG_REAL_MODE EQU 1
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#THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 EQU 2
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#THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL EQU 4
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.code:
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_m16Start:
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SavedGdt: .space 6
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_BackFromUserCode:
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push %ss
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push %cs
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.byte 0x66
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call @Base1 # push eip
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@Base1:
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pushfw # 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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push %es
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push %ds
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pushaw # pushad actually
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.byte 0x66,0xba # mov edx, imm32
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_ThunkAttr: .space 4
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testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15, %dl
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jz @1
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movl $0x15cd2401, %eax # 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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testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL, %dl
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jz @2
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inb $0x92, %al
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orb $2, %al
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outb %al, $0x92 # deactivate A20M#
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@2:
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movl %ss, %eax
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.byte 0x67, 0x66, 0x8d, 0x6c, 0x24, 0x34, 0x66
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mov %ebp,0xffffffd8(%esi)
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mov 0xfffffff8(%esi),%ebx
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shlw $4, %ax # shl eax, 4
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addw %ax, %bp # add ebp, eax
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.byte 0x66,0xb8 # mov eax, imm32
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SavedCr4: .space 4
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movl %eax, %cr4
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lgdtw %cs:0xfffffff2(%edi)
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.byte 0x66,0xb8 # mov eax, imm32
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SavedCr0: .space 4
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movl %eax, %cr0
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.byte 0xb8 # mov ax, imm16
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SavedSs: .space 2
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movl %eax, %ss
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.byte 0x66,0xbc # mov esp, imm32
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SavedEsp: .space 4
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.byte 0x66
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lret # return to protected mode
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_EntryPoint: .long _ToUserCode - _m16Start
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.word 0x8
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_16Idtr: .word 0x3ff
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.long 0
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_16Gdtr: .word GdtEnd - _NullSegDesc - 1
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_16GdtrBase: .long _NullSegDesc
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_ToUserCode:
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movl %ss, %edx
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movl %ecx, %ss # set new segment selectors
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movl %ecx, %ds
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movl %ecx, %es
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movl %ecx, %fs
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movl %ecx, %gs
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movl %eax, %cr0
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movl %ebp, %cr4 # real mode starts at next instruction
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movl %esi, %ss # set up 16-bit stack segment
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xchgw %bx, %sp # set up 16-bit stack pointer
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.byte 0x66
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call @Base # push eip
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@Base:
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popw %bp # ebp <- offset @Base
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addr16 pushl 36(%si)
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.byte 0x36
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lea 0xc(%esi),%eax
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pushl %eax
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lret
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@RealMode:
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mov %edx,%cs:0xffffffc5(%esi)
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mov %bx,%cs:0xffffffcb(%esi)
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lidtw %cs:0xffffffd7(%esi)
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popaw # popad actually
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popl %ds
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popl %es
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popl %fs
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popl %gs
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popfw # popfd
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lretw # transfer control to user code
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_NullSegDesc: .quad 0
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_16CsDesc:
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.word -1
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.word 0
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.byte 0
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.byte 0x9b
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.byte 0x8f # 16-bit segment, 4GB limit
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.byte 0
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_16DsDesc:
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.word -1
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.word 0
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.byte 0
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.byte 0x93
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.byte 0x8f # 16-bit segment, 4GB limit
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.byte 0
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GdtEnd:
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#
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# @param RegSet Pointer to a IA32_DWORD_REGS structure
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# @param Transition Pointer to the transition code
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# @return The address of the 16-bit stack after returning from user code
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#
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_InternalAsmThunk16:
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_InternalAsmThunk16:
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push %ebp
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push %ebx
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push %esi
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push %edi
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push %ds
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push %es
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push %fs
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push %gs
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movl 36(%esp), %esi # esi <- RegSet
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movzwl 0x32(%esi),%edx
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mov 0xc(%esi),%edi
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add $0xffffffc8,%edi
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movl %edi, %ebx # ebx <- stack offset
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imul $0x10,%edx,%eax
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push $0xd
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addl %eax, %edi # edi <- linear address of 16-bit stack
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popl %ecx
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rep
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movsl # copy RegSet
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movl 40(%esp), %eax # eax <- address of transition code
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movl %edx, %esi # esi <- 16-bit stack segment
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lea 0x5e(%eax),%edx
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movl %eax, %ecx
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andl $0xf, %ecx
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shll $12, %eax
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lea 0x6(%ecx),%ecx
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movw %cx, %ax
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stosl # [edi] <- return address of user code
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sgdtl 0xffffffa2(%edx)
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sidtl 0x24(%esp)
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movl %cr0, %eax
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movl %eax, (%edx) # save CR0 in SavedCr0
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andl $0x7ffffffe, %eax # clear PE, PG bits
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movl %cr4, %ebp
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mov %ebp,0xfffffff1(%edx)
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andl $0x300, %ebp # clear all but PCE and OSFXSR bits
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pushl $0x10
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popl %ecx # ecx <- selector for data segments
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lgdtl 0x20(%edx)
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pushfl
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lcall *0x14(%edx)
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popfl
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lidtl 0x24(%esp)
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lea 0xffffffcc(%ebp),%eax
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pop %gs
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pop %fs
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pop %es
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pop %ds
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pop %edi
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pop %esi
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pop %ebx
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pop %ebp
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ret
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##########
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.const:
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# FIXME! #
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##########
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_m16Size: .word _InternalAsmThunk16 - _m16Start
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# This function won't work for now.
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_mThunk16Attr: .word _ThunkAttr - _m16Start
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# it will directly enter dead loop.
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_m16Gdt: .word _NullSegDesc - _m16Start
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jmp .
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_m16GdtrBase: .word _16GdtrBase - _m16Start
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_mTransition: .word _EntryPoint - _m16Start
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