diff options
| author | Liming Gao <liming.gao@intel.com> | 2016-06-14 16:29:11 +0800 |
|---|---|---|
| committer | Liming Gao <liming.gao@intel.com> | 2016-06-28 09:52:15 +0800 |
| commit | 28ee5816465b16aa14cc656a6bb9aab1aaa07244 (patch) | |
| tree | 752b30d5731c1b197ae6f44fe55d3d5b37e1170e /UefiCpuPkg/PiSmmCpuDxeSmm | |
| parent | 63a4f4607681947037b4609c63d1bb36e1c2c689 (diff) | |
| download | edk2-platforms-28ee5816465b16aa14cc656a6bb9aab1aaa07244.tar.xz | |
UefiCpuPkg PiSmmCpuDxeSmm: Convert Ia32/SmiException.asm to NASM
Manually convert Ia32/SmiException.asm to Ia32/SmiException.nasm
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Diffstat (limited to 'UefiCpuPkg/PiSmmCpuDxeSmm')
| -rw-r--r-- | UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiException.nasm | 737 |
1 files changed, 737 insertions, 0 deletions
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiException.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiException.nasm new file mode 100644 index 0000000000..f9f3986ea1 --- /dev/null +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiException.nasm @@ -0,0 +1,737 @@ +;------------------------------------------------------------------------------ ;
+; Copyright (c) 2009 - 2015, Intel Corporation. All rights reserved.<BR>
+; 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:
+;
+; SmiException.nasm
+;
+; Abstract:
+;
+; Exception handlers used in SM mode
+;
+;-------------------------------------------------------------------------------
+
+extern ASM_PFX(FeaturePcdGet (PcdCpuSmmProfileEnable))
+extern ASM_PFX(gSmiMtrrs)
+extern ASM_PFX(SmiPFHandler)
+
+global ASM_PFX(gcSmiIdtr)
+global ASM_PFX(gcSmiGdtr)
+global ASM_PFX(gcPsd)
+
+ SECTION .data
+
+NullSeg: DQ 0 ; reserved by architecture
+CodeSeg32:
+ DW -1 ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x9b
+ DB 0xcf ; LimitHigh
+ DB 0 ; BaseHigh
+ProtModeCodeSeg32:
+ DW -1 ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x9b
+ DB 0xcf ; LimitHigh
+ DB 0 ; BaseHigh
+ProtModeSsSeg32:
+ DW -1 ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x93
+ DB 0xcf ; LimitHigh
+ DB 0 ; BaseHigh
+DataSeg32:
+ DW -1 ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x93
+ DB 0xcf ; LimitHigh
+ DB 0 ; BaseHigh
+CodeSeg16:
+ DW -1
+ DW 0
+ DB 0
+ DB 0x9b
+ DB 0x8f
+ DB 0
+DataSeg16:
+ DW -1
+ DW 0
+ DB 0
+ DB 0x93
+ DB 0x8f
+ DB 0
+CodeSeg64:
+ DW -1 ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x9b
+ DB 0xaf ; LimitHigh
+ DB 0 ; BaseHigh
+GDT_SIZE equ $ - NullSeg
+
+TssSeg:
+ DW TSS_DESC_SIZE ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x89
+ DB 0x80 ; LimitHigh
+ DB 0 ; BaseHigh
+ExceptionTssSeg:
+ DW TSS_DESC_SIZE ; LimitLow
+ DW 0 ; BaseLow
+ DB 0 ; BaseMid
+ DB 0x89
+ DB 0x80 ; LimitHigh
+ DB 0 ; BaseHigh
+
+CODE_SEL equ CodeSeg32 - NullSeg
+DATA_SEL equ DataSeg32 - NullSeg
+TSS_SEL equ TssSeg - NullSeg
+EXCEPTION_TSS_SEL equ ExceptionTssSeg - NullSeg
+
+struc IA32_TSS
+ resw 1
+ resw 1
+ .ESP0: resd 1
+ .SS0: resw 1
+ resw 1
+ .ESP1: resd 1
+ .SS1: resw 1
+ resw 1
+ .ESP2: resd 1
+ .SS2: resw 1
+ resw 1
+ ._CR3: resd 1
+ .EIP: resd 1
+ .EFLAGS: resd 1
+ ._EAX: resd 1
+ ._ECX: resd 1
+ ._EDX: resd 1
+ ._EBX: resd 1
+ ._ESP: resd 1
+ ._EBP: resd 1
+ ._ESI: resd 1
+ ._EDI: resd 1
+ ._ES: resw 1
+ resw 1
+ ._CS: resw 1
+ resw 1
+ ._SS: resw 1
+ resw 1
+ ._DS: resw 1
+ resw 1
+ ._FS: resw 1
+ resw 1
+ ._GS: resw 1
+ resw 1
+ .LDT: resw 1
+ resw 1
+ resw 1
+ resw 1
+endstruc
+
+; Create 2 TSS segments just after GDT
+TssDescriptor:
+ DW 0 ; PreviousTaskLink
+ DW 0 ; Reserved
+ DD 0 ; ESP0
+ DW 0 ; SS0
+ DW 0 ; Reserved
+ DD 0 ; ESP1
+ DW 0 ; SS1
+ DW 0 ; Reserved
+ DD 0 ; ESP2
+ DW 0 ; SS2
+ DW 0 ; Reserved
+ DD 0 ; CR3
+ DD 0 ; EIP
+ DD 0 ; EFLAGS
+ DD 0 ; EAX
+ DD 0 ; ECX
+ DD 0 ; EDX
+ DD 0 ; EBX
+ DD 0 ; ESP
+ DD 0 ; EBP
+ DD 0 ; ESI
+ DD 0 ; EDI
+ DW 0 ; ES
+ DW 0 ; Reserved
+ DW 0 ; CS
+ DW 0 ; Reserved
+ DW 0 ; SS
+ DW 0 ; Reserved
+ DW 0 ; DS
+ DW 0 ; Reserved
+ DW 0 ; FS
+ DW 0 ; Reserved
+ DW 0 ; GS
+ DW 0 ; Reserved
+ DW 0 ; LDT Selector
+ DW 0 ; Reserved
+ DW 0 ; T
+ DW 0 ; I/O Map Base
+TSS_DESC_SIZE equ $ - TssDescriptor
+
+ExceptionTssDescriptor:
+ DW 0 ; PreviousTaskLink
+ DW 0 ; Reserved
+ DD 0 ; ESP0
+ DW 0 ; SS0
+ DW 0 ; Reserved
+ DD 0 ; ESP1
+ DW 0 ; SS1
+ DW 0 ; Reserved
+ DD 0 ; ESP2
+ DW 0 ; SS2
+ DW 0 ; Reserved
+ DD 0 ; CR3
+ DD PFHandlerEntry ; EIP
+ DD 00000002 ; EFLAGS
+ DD 0 ; EAX
+ DD 0 ; ECX
+ DD 0 ; EDX
+ DD 0 ; EBX
+ DD 0 ; ESP
+ DD 0 ; EBP
+ DD 0 ; ESI
+ DD 0 ; EDI
+ DW DATA_SEL ; ES
+ DW 0 ; Reserved
+ DW CODE_SEL ; CS
+ DW 0 ; Reserved
+ DW DATA_SEL ; SS
+ DW 0 ; Reserved
+ DW DATA_SEL ; DS
+ DW 0 ; Reserved
+ DW DATA_SEL ; FS
+ DW 0 ; Reserved
+ DW DATA_SEL ; GS
+ DW 0 ; Reserved
+ DW 0 ; LDT Selector
+ DW 0 ; Reserved
+ DW 0 ; T
+ DW 0 ; I/O Map Base
+
+ASM_PFX(gcPsd):
+ DB 'PSDSIG '
+ DW PSD_SIZE
+ DW 2
+ DW 1 << 2
+ DW CODE_SEL
+ DW DATA_SEL
+ DW DATA_SEL
+ DW DATA_SEL
+ DW 0
+ DQ 0
+ DQ 0
+ DQ 0
+ DD 0
+ DD NullSeg
+ DD GDT_SIZE
+ DD 0
+ times 24 DB 0
+ DD 0
+ DD ASM_PFX(gSmiMtrrs)
+PSD_SIZE equ $ - ASM_PFX(gcPsd)
+
+ASM_PFX(gcSmiGdtr):
+ DW GDT_SIZE - 1
+ DD NullSeg
+
+ASM_PFX(gcSmiIdtr):
+ DW IDT_SIZE - 1
+ DD _SmiIDT
+
+_SmiIDT:
+%rep 32
+ DW 0 ; Offset 0:15
+ DW CODE_SEL ; Segment selector
+ DB 0 ; Unused
+ DB 0x8e ; Interrupt Gate, Present
+ DW 0 ; Offset 16:31
+%endrep
+
+IDT_SIZE equ $ - _SmiIDT
+
+TaskGateDescriptor:
+ DW 0 ; Reserved
+ DW EXCEPTION_TSS_SEL ; TSS Segment selector
+ DB 0 ; Reserved
+ DB 0x85 ; Task Gate, present, DPL = 0
+ DW 0 ; Reserved
+
+ SECTION .text
+;------------------------------------------------------------------------------
+; PageFaultIdtHandlerSmmProfile is the entry point page fault only
+;
+;
+; Stack:
+; +---------------------+
+; + EFlags +
+; +---------------------+
+; + CS +
+; +---------------------+
+; + EIP +
+; +---------------------+
+; + Error Code +
+; +---------------------+
+; + Vector Number +
+; +---------------------+
+; + EBP +
+; +---------------------+ <-- EBP
+;
+;
+;------------------------------------------------------------------------------
+global ASM_PFX(PageFaultIdtHandlerSmmProfile)
+ASM_PFX(PageFaultIdtHandlerSmmProfile):
+ push 0xe ; Page Fault
+
+ push ebp
+ mov ebp, esp
+
+ ;
+ ; Align stack to make sure that EFI_FX_SAVE_STATE_IA32 of EFI_SYSTEM_CONTEXT_IA32
+ ; is 16-byte aligned
+ ;
+ and esp, 0xfffffff0
+ sub esp, 12
+
+;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
+ push eax
+ push ecx
+ push edx
+ push ebx
+ lea ecx, [ebp + 6 * 4]
+ push ecx ; ESP
+ push dword [ebp] ; EBP
+ push esi
+ push edi
+
+;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
+ mov eax, ss
+ push eax
+ movzx eax, word [ebp + 4 * 4]
+ push eax
+ mov eax, ds
+ push eax
+ mov eax, es
+ push eax
+ mov eax, fs
+ push eax
+ mov eax, gs
+ push eax
+
+;; UINT32 Eip;
+ mov eax, [ebp + 3 * 4]
+ push eax
+
+;; UINT32 Gdtr[2], Idtr[2];
+ sub esp, 8
+ sidt [esp]
+ mov eax, [esp + 2]
+ xchg eax, [esp]
+ and eax, 0xFFFF
+ mov [esp+4], eax
+
+ sub esp, 8
+ sgdt [esp]
+ mov eax, [esp + 2]
+ xchg eax, [esp]
+ and eax, 0xFFFF
+ mov [esp+4], eax
+
+;; UINT32 Ldtr, Tr;
+ xor eax, eax
+ str ax
+ push eax
+ sldt ax
+ push eax
+
+;; UINT32 EFlags;
+ mov eax, [ebp + 5 * 4]
+ push eax
+
+;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
+ mov eax, cr4
+ or eax, 0x208
+ mov cr4, eax
+ push eax
+ mov eax, cr3
+ push eax
+ mov eax, cr2
+ push eax
+ xor eax, eax
+ push eax
+ mov eax, cr0
+ push eax
+
+;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+ mov eax, dr7
+ push eax
+ mov eax, dr6
+ push eax
+ mov eax, dr3
+ push eax
+ mov eax, dr2
+ push eax
+ mov eax, dr1
+ push eax
+ mov eax, dr0
+ push eax
+
+;; FX_SAVE_STATE_IA32 FxSaveState;
+ sub esp, 512
+ mov edi, esp
+ db 0xf, 0xae, 0x7 ;fxsave [edi]
+
+; UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
+ cld
+
+;; UINT32 ExceptionData;
+ push dword [ebp + 2 * 4]
+
+;; call into exception handler
+
+;; Prepare parameter and call
+ mov edx, esp
+ push edx
+ mov edx, dword [ebp + 1 * 4]
+ push edx
+
+ ;
+ ; Call External Exception Handler
+ ;
+ mov eax, ASM_PFX(SmiPFHandler)
+ call eax
+ add esp, 8
+
+;; UINT32 ExceptionData;
+ add esp, 4
+
+;; FX_SAVE_STATE_IA32 FxSaveState;
+ mov esi, esp
+ db 0xf, 0xae, 0xe ; fxrstor [esi]
+ add esp, 512
+
+;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+;; Skip restoration of DRx registers to support debuggers
+;; that set breakpoint in interrupt/exception context
+ add esp, 4 * 6
+
+;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
+ pop eax
+ mov cr0, eax
+ add esp, 4 ; not for Cr1
+ pop eax
+ mov cr2, eax
+ pop eax
+ mov cr3, eax
+ pop eax
+ mov cr4, eax
+
+;; UINT32 EFlags;
+ pop dword [ebp + 5 * 4]
+
+;; UINT32 Ldtr, Tr;
+;; UINT32 Gdtr[2], Idtr[2];
+;; Best not let anyone mess with these particular registers...
+ add esp, 24
+
+;; UINT32 Eip;
+ pop dword [ebp + 3 * 4]
+
+;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
+;; NOTE - modified segment registers could hang the debugger... We
+;; could attempt to insulate ourselves against this possibility,
+;; but that poses risks as well.
+;;
+ pop gs
+ pop fs
+ pop es
+ pop ds
+ pop dword [ebp + 4 * 4]
+ pop ss
+
+;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
+ pop edi
+ pop esi
+ add esp, 4 ; not for ebp
+ add esp, 4 ; not for esp
+ pop ebx
+ pop edx
+ pop ecx
+ pop eax
+
+ mov esp, ebp
+ pop ebp
+
+; Enable TF bit after page fault handler runs
+ bts dword [esp + 16], 8 ; EFLAGS
+
+ add esp, 8 ; skip INT# & ErrCode
+Return:
+ iretd
+;
+; Page Fault Exception Handler entry when SMM Stack Guard is enabled
+; Executiot starts here after a task switch
+;
+PFHandlerEntry:
+;
+; Get this processor's TSS
+;
+ sub esp, 8
+ sgdt [esp + 2]
+ mov eax, [esp + 4] ; GDT base
+ add esp, 8
+ mov ecx, [eax + TSS_SEL + 2]
+ shl ecx, 8
+ mov cl, [eax + TSS_SEL + 7]
+ ror ecx, 8 ; ecx = TSS base
+
+ mov ebp, esp
+
+ ;
+ ; Align stack to make sure that EFI_FX_SAVE_STATE_IA32 of EFI_SYSTEM_CONTEXT_IA32
+ ; is 16-byte aligned
+ ;
+ and esp, 0xfffffff0
+ sub esp, 12
+
+;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
+ push dword [ecx + IA32_TSS._EAX]
+ push dword [ecx + IA32_TSS._ECX]
+ push dword [ecx + IA32_TSS._EDX]
+ push dword [ecx + IA32_TSS._EBX]
+ push dword [ecx + IA32_TSS._ESP]
+ push dword [ecx + IA32_TSS._EBP]
+ push dword [ecx + IA32_TSS._ESI]
+ push dword [ecx + IA32_TSS._EDI]
+
+;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
+ movzx eax, word [ecx + IA32_TSS._SS]
+ push eax
+ movzx eax, word [ecx + IA32_TSS._CS]
+ push eax
+ movzx eax, word [ecx + IA32_TSS._DS]
+ push eax
+ movzx eax, word [ecx + IA32_TSS._ES]
+ push eax
+ movzx eax, word [ecx + IA32_TSS._FS]
+ push eax
+ movzx eax, word [ecx + IA32_TSS._GS]
+ push eax
+
+;; UINT32 Eip;
+ push dword [ecx + IA32_TSS.EIP]
+
+;; UINT32 Gdtr[2], Idtr[2];
+ sub esp, 8
+ sidt [esp]
+ mov eax, [esp + 2]
+ xchg eax, [esp]
+ and eax, 0xFFFF
+ mov [esp+4], eax
+
+ sub esp, 8
+ sgdt [esp]
+ mov eax, [esp + 2]
+ xchg eax, [esp]
+ and eax, 0xFFFF
+ mov [esp+4], eax
+
+;; UINT32 Ldtr, Tr;
+ mov eax, TSS_SEL
+ push eax
+ movzx eax, word [ecx + IA32_TSS.LDT]
+ push eax
+
+;; UINT32 EFlags;
+ push dword [ecx + IA32_TSS.EFLAGS]
+
+;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
+ mov eax, cr4
+ or eax, 0x208
+ mov cr4, eax
+ push eax
+ mov eax, cr3
+ push eax
+ mov eax, cr2
+ push eax
+ xor eax, eax
+ push eax
+ mov eax, cr0
+ push eax
+
+;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+ mov eax, dr7
+ push eax
+ mov eax, dr6
+ push eax
+ mov eax, dr3
+ push eax
+ mov eax, dr2
+ push eax
+ mov eax, dr1
+ push eax
+ mov eax, dr0
+ push eax
+
+;; FX_SAVE_STATE_IA32 FxSaveState;
+;; Clear TS bit in CR0 to avoid Device Not Available Exception (#NM)
+;; when executing fxsave/fxrstor instruction
+ clts
+ sub esp, 512
+ mov edi, esp
+ db 0xf, 0xae, 0x7 ;fxsave [edi]
+
+; UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
+ cld
+
+;; UINT32 ExceptionData;
+ push dword [ebp]
+
+;; call into exception handler
+ mov ebx, ecx
+ mov eax, ASM_PFX(SmiPFHandler)
+
+;; Prepare parameter and call
+ mov edx, esp
+ push edx
+ mov edx, 14
+ push edx
+
+ ;
+ ; Call External Exception Handler
+ ;
+ call eax
+ add esp, 8
+
+ mov ecx, ebx
+;; UINT32 ExceptionData;
+ add esp, 4
+
+;; FX_SAVE_STATE_IA32 FxSaveState;
+ mov esi, esp
+ db 0xf, 0xae, 0xe ; fxrstor [esi]
+ add esp, 512
+
+;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+;; Skip restoration of DRx registers to support debuggers
+;; that set breakpoints in interrupt/exception context
+ add esp, 4 * 6
+
+;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
+ pop eax
+ mov cr0, eax
+ add esp, 4 ; not for Cr1
+ pop eax
+ mov cr2, eax
+ pop eax
+ mov dword [ecx + IA32_TSS._CR3], eax
+ pop eax
+ mov cr4, eax
+
+;; UINT32 EFlags;
+ pop dword [ecx + IA32_TSS.EFLAGS]
+
+;; UINT32 Ldtr, Tr;
+;; UINT32 Gdtr[2], Idtr[2];
+;; Best not let anyone mess with these particular registers...
+ add esp, 24
+
+;; UINT32 Eip;
+ pop dword [ecx + IA32_TSS.EIP]
+
+;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
+;; NOTE - modified segment registers could hang the debugger... We
+;; could attempt to insulate ourselves against this possibility,
+;; but that poses risks as well.
+;;
+ pop eax
+o16 mov [ecx + IA32_TSS._GS], ax
+ pop eax
+o16 mov [ecx + IA32_TSS._FS], ax
+ pop eax
+o16 mov [ecx + IA32_TSS._ES], ax
+ pop eax
+o16 mov [ecx + IA32_TSS._DS], ax
+ pop eax
+o16 mov [ecx + IA32_TSS._CS], ax
+ pop eax
+o16 mov [ecx + IA32_TSS._SS], ax
+
+;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
+ pop dword [ecx + IA32_TSS._EDI]
+ pop dword [ecx + IA32_TSS._ESI]
+ add esp, 4 ; not for ebp
+ add esp, 4 ; not for esp
+ pop dword [ecx + IA32_TSS._EBX]
+ pop dword [ecx + IA32_TSS._EDX]
+ pop dword [ecx + IA32_TSS._ECX]
+ pop dword [ecx + IA32_TSS._EAX]
+
+ mov esp, ebp
+
+; Set single step DB# if SMM profile is enabled and page fault exception happens
+ cmp byte [dword ASM_PFX(FeaturePcdGet (PcdCpuSmmProfileEnable))], 0
+ jz @Done2
+
+; Create return context for iretd in stub function
+ mov eax, dword [ecx + IA32_TSS._ESP] ; Get old stack pointer
+ mov ebx, dword [ecx + IA32_TSS.EIP]
+ mov [eax - 0xc], ebx ; create EIP in old stack
+ movzx ebx, word [ecx + IA32_TSS._CS]
+ mov [eax - 0x8], ebx ; create CS in old stack
+ mov ebx, dword [ecx + IA32_TSS.EFLAGS]
+ bts ebx, 8
+ mov [eax - 0x4], ebx ; create eflags in old stack
+ mov eax, dword [ecx + IA32_TSS._ESP] ; Get old stack pointer
+ sub eax, 0xc ; minus 12 byte
+ mov dword [ecx + IA32_TSS._ESP], eax ; Set new stack pointer
+; Replace the EIP of interrupted task with stub function
+ mov eax, ASM_PFX(PageFaultStubFunction)
+ mov dword [ecx + IA32_TSS.EIP], eax
+; Jump to the iretd so next page fault handler as a task will start again after iretd.
+@Done2:
+ add esp, 4 ; skip ErrCode
+
+ jmp Return
+
+global ASM_PFX(PageFaultStubFunction)
+ASM_PFX(PageFaultStubFunction):
+;
+; we need clean TS bit in CR0 to execute
+; x87 FPU/MMX/SSE/SSE2/SSE3/SSSE3/SSE4 instructions.
+;
+ clts
+ iretd
+
+global ASM_PFX(InitializeIDTSmmStackGuard)
+ASM_PFX(InitializeIDTSmmStackGuard):
+ push ebx
+;
+; If SMM Stack Guard feature is enabled, the Page Fault Exception entry in IDT
+; is a Task Gate Descriptor so that when a Page Fault Exception occurrs,
+; the processors can use a known good stack in case stack is ran out.
+;
+ lea ebx, [_SmiIDT + 14 * 8]
+ lea edx, [TaskGateDescriptor]
+ mov eax, [edx]
+ mov [ebx], eax
+ mov eax, [edx + 4]
+ mov [ebx + 4], eax
+ pop ebx
+ ret
+
+ END
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