mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
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494 lines
18 KiB
NASM
494 lines
18 KiB
NASM
;/** @file
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; Low leve IA32 specific debug support functions.
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;
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; Copyright (c) 2006 - 2011, Intel Corporation. All rights reserved.<BR>
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;
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;**/
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%define EXCPT32_DIVIDE_ERROR 0
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%define EXCPT32_DEBUG 1
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%define EXCPT32_NMI 2
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%define EXCPT32_BREAKPOINT 3
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%define EXCPT32_OVERFLOW 4
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%define EXCPT32_BOUND 5
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%define EXCPT32_INVALID_OPCODE 6
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%define EXCPT32_DOUBLE_FAULT 8
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%define EXCPT32_INVALID_TSS 10
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%define EXCPT32_SEG_NOT_PRESENT 11
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%define EXCPT32_STACK_FAULT 12
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%define EXCPT32_GP_FAULT 13
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%define EXCPT32_PAGE_FAULT 14
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%define EXCPT32_FP_ERROR 16
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%define EXCPT32_ALIGNMENT_CHECK 17
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%define EXCPT32_MACHINE_CHECK 18
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%define EXCPT32_SIMD 19
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%define FXSTOR_FLAG 0x1000000 ; bit cpuid 24 of feature flags
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;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
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;; MMX, SSE, SSE2, etc registers. The initialization of the debugsupport driver
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;; MUST check the CPUID feature flags to see that these instructions are available
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;; and fail to init if they are not.
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;; fxstor [edi]
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%macro FXSTOR_EDI 0
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db 0xf, 0xae, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [edi]
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%endmacro
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;; fxrstor [esi]
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%macro FXRSTOR_ESI 0
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db 0xf, 0xae, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [esi]
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%endmacro
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SECTION .data
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global ASM_PFX(OrigVector)
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global ASM_PFX(InterruptEntryStub)
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global ASM_PFX(StubSize)
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global ASM_PFX(CommonIdtEntry)
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global ASM_PFX(FxStorSupport)
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extern ASM_PFX(InterruptDistrubutionHub)
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ASM_PFX(StubSize): dd InterruptEntryStubEnd - ASM_PFX(InterruptEntryStub)
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AppEsp: dd 0x11111111 ; ?
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DebugEsp: dd 0x22222222 ; ?
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ExtraPush: dd 0x33333333 ; ?
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ExceptData: dd 0x44444444 ; ?
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Eflags: dd 0x55555555 ; ?
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ASM_PFX(OrigVector): dd 0x66666666 ; ?
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;; The declarations below define the memory region that will be used for the debug stack.
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;; The context record will be built by pushing register values onto this stack.
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;; It is imparitive that alignment be carefully managed, since the FXSTOR and
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;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
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;;
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;; The stub will switch stacks from the application stack to the debuger stack
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;; and pushes the exception number.
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;;
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;; Then we building the context record on the stack. Since the stack grows down,
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;; we push the fields of the context record from the back to the front. There
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;; are 132 bytes of stack used prior allocating the 512 bytes of stack to be
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;; used as the memory buffer for the fxstor instruction. Therefore address of
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;; the buffer used for the FXSTOR instruction is &Eax - 132 - 512, which
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;; must be 16 byte aligned.
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;;
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;; We carefully locate the stack to make this happen.
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;;
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;; For reference, the context structure looks like this:
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;; struct {
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;; UINT32 ExceptionData;
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;; FX_SAVE_STATE_IA32 FxSaveState; // 512 bytes, must be 16 byte aligned
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;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
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;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
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;; UINT32 EFlags;
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;; UINT32 Ldtr, Tr;
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;; UINT32 Gdtr[2], Idtr[2];
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;; UINT32 Eip;
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;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
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;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
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;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
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align 16
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DebugStackEnd: db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
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times 0x1ffc dd 0x0 ;; 32K should be enough stack
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;; This allocation is coocked to insure
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;; that the the buffer for the FXSTORE instruction
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;; will be 16 byte aligned also.
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;;
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ExceptionNumber: dd 0 ;; first entry will be the vector number pushed by the stub
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DebugStackBegin: db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
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SECTION .text
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;------------------------------------------------------------------------------
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; BOOLEAN
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; FxStorSupport (
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; void
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; )
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;
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; Abstract: Returns TRUE if FxStor instructions are supported
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;
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global ASM_PFX(FxStorSupport)
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ASM_PFX(FxStorSupport):
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;
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; cpuid corrupts ebx which must be preserved per the C calling convention
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;
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push ebx
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mov eax, 1
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cpuid
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mov eax, edx
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and eax, FXSTOR_FLAG
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shr eax, 24
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pop ebx
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ret
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;------------------------------------------------------------------------------
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; void
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; Vect2Desc (
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; DESCRIPTOR * DestDesc,
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; void (*Vector) (void)
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; )
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;
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; Abstract: Encodes an IDT descriptor with the given physical address
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;
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global ASM_PFX(Vect2Desc)
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ASM_PFX(Vect2Desc):
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push ebp
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mov ebp, esp
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mov eax, [ebp + 0xC]
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mov ecx, [ebp + 0x8]
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mov word [ecx], ax ; write bits 15..0 of offset
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mov dx, cs
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mov word [ecx+2], dx ; SYS_CODE_SEL from GDT
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mov word [ecx+4], 0xe00 | 0x8000 ; type = 386 interrupt gate, present
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shr eax, 16
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mov word [ecx+6], ax ; write bits 31..16 of offset
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leave
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ret
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;------------------------------------------------------------------------------
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; InterruptEntryStub
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;
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; Abstract: This code is not a function, but is a small piece of code that is
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; copied and fixed up once for each IDT entry that is hooked.
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;
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ASM_PFX(InterruptEntryStub):
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mov [AppEsp], esp ; save stack top
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mov esp, DebugStackBegin ; switch to debugger stack
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push 0 ; push vector number - will be modified before installed
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db 0xe9 ; jump rel32
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dd 0 ; fixed up to relative address of CommonIdtEntry
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InterruptEntryStubEnd:
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;------------------------------------------------------------------------------
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; CommonIdtEntry
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;
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; Abstract: This code is not a function, but is the common part for all IDT
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; vectors.
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;
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ASM_PFX(CommonIdtEntry):
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;;
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;; At this point, the stub has saved the current application stack esp into AppEsp
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;; and switched stacks to the debug stack, where it pushed the vector number
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;;
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;; The application stack looks like this:
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;;
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;; ...
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;; (last application stack entry)
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;; eflags from interrupted task
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;; CS from interrupted task
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;; EIP from interrupted task
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;; Error code <-------------------- Only present for some exeption types
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;;
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;;
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;; The stub switched us to the debug stack and pushed the interrupt number.
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;;
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;; Next, construct the context record. It will be build on the debug stack by
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;; pushing the registers in the correct order so as to create the context structure
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;; on the debug stack. The context record must be built from the end back to the
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;; beginning because the stack grows down...
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;
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;; For reference, the context record looks like this:
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;;
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;; typedef
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;; struct {
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;; UINT32 ExceptionData;
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;; FX_SAVE_STATE_IA32 FxSaveState;
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;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
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;; UINT32 Cr0, Cr2, Cr3, Cr4;
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;; UINT32 EFlags;
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;; UINT32 Ldtr, Tr;
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;; UINT32 Gdtr[2], Idtr[2];
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;; UINT32 Eip;
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;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
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;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
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;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
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;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
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pushad
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;; Save interrupt state eflags register...
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pushfd
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pop eax
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mov [Eflags], eax
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;; We need to determine if any extra data was pushed by the exception, and if so, save it
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;; To do this, we check the exception number pushed by the stub, and cache the
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;; result in a variable since we'll need this again.
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cmp dword [ExceptionNumber], EXCPT32_DOUBLE_FAULT
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_INVALID_TSS
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_SEG_NOT_PRESENT
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_STACK_FAULT
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_GP_FAULT
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_PAGE_FAULT
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jz ExtraPushOne
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cmp dword [ExceptionNumber], EXCPT32_ALIGNMENT_CHECK
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jz ExtraPushOne
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mov dword [ExtraPush], 0
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mov dword [ExceptData], 0
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jmp ExtraPushDone
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ExtraPushOne:
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mov dword [ExtraPush], 1
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;; If there's some extra data, save it also, and modify the saved AppEsp to effectively
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;; pop this value off the application's stack.
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mov eax, [AppEsp]
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mov ebx, [eax]
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mov [ExceptData], ebx
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add eax, 4
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mov [AppEsp], eax
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ExtraPushDone:
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;; The "pushad" above pushed the debug stack esp. Since what we're actually doing
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;; is building the context record on the debug stack, we need to save the pushed
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;; debug ESP, and replace it with the application's last stack entry...
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mov eax, [esp + 12]
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mov [DebugEsp], eax
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mov eax, [AppEsp]
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add eax, 12
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; application stack has eflags, cs, & eip, so
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; last actual application stack entry is
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; 12 bytes into the application stack.
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mov [esp + 12], eax
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;; continue building context record
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;; UINT32 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
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mov eax, ss
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push eax
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; CS from application is one entry back in application stack
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mov eax, [AppEsp]
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movzx eax, word [eax + 4]
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push eax
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mov eax, ds
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push eax
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mov eax, es
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push eax
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mov eax, fs
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push eax
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mov eax, gs
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push eax
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;; UINT32 Eip;
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; Eip from application is on top of application stack
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mov eax, [AppEsp]
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push dword [eax]
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;; UINT32 Gdtr[2], Idtr[2];
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push 0
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push 0
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sidt [esp]
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push 0
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push 0
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sgdt [esp]
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;; UINT32 Ldtr, Tr;
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xor eax, eax
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str ax
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push eax
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sldt ax
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push eax
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;; UINT32 EFlags;
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;; Eflags from application is two entries back in application stack
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mov eax, [AppEsp]
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push dword [eax + 8]
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;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
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;; insure FXSAVE/FXRSTOR is enabled in CR4...
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;; ... while we're at it, make sure DE is also enabled...
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mov eax, cr4
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or eax, 0x208
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mov cr4, eax
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push eax
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mov eax, cr3
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push eax
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mov eax, cr2
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push eax
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push 0
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mov eax, cr0
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push eax
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;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
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mov eax, dr7
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push eax
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;; clear Dr7 while executing debugger itself
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xor eax, eax
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mov dr7, eax
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mov eax, dr6
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push eax
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;; insure all status bits in dr6 are clear...
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xor eax, eax
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mov dr6, eax
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mov eax, dr3
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push eax
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mov eax, dr2
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push eax
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mov eax, dr1
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push eax
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mov eax, dr0
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push eax
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;; FX_SAVE_STATE_IA32 FxSaveState;
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sub esp, 512
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mov edi, esp
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; IMPORTANT!! The debug stack has been carefully constructed to
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; insure that esp and edi are 16 byte aligned when we get here.
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; They MUST be. If they are not, a GP fault will occur.
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FXSTOR_EDI
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;; UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
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cld
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;; UINT32 ExceptionData;
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mov eax, [ExceptData]
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push eax
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; call to C code which will in turn call registered handler
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; pass in the vector number
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mov eax, esp
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push eax
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mov eax, [ExceptionNumber]
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push eax
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call ASM_PFX(InterruptDistrubutionHub)
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add esp, 8
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; restore context...
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;; UINT32 ExceptionData;
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add esp, 4
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;; FX_SAVE_STATE_IA32 FxSaveState;
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mov esi, esp
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FXRSTOR_ESI
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add esp, 512
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;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
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pop eax
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mov dr0, eax
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pop eax
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mov dr1, eax
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pop eax
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mov dr2, eax
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pop eax
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mov dr3, eax
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;; skip restore of dr6. We cleared dr6 during the context save.
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add esp, 4
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pop eax
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mov dr7, eax
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;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
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pop eax
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mov cr0, eax
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add esp, 4
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pop eax
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mov cr2, eax
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pop eax
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mov cr3, eax
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pop eax
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mov cr4, eax
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;; UINT32 EFlags;
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mov eax, [AppEsp]
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pop dword [eax + 8]
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;; UINT32 Ldtr, Tr;
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;; UINT32 Gdtr[2], Idtr[2];
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;; Best not let anyone mess with these particular registers...
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add esp, 24
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;; UINT32 Eip;
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pop dword [eax]
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;; UINT32 SegGs, SegFs, SegEs, SegDs, SegCs, SegSs;
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;; NOTE - modified segment registers could hang the debugger... We
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;; could attempt to insulate ourselves against this possibility,
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;; but that poses risks as well.
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;;
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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 dword [eax + 4]
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pop ss
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;; The next stuff to restore is the general purpose registers that were pushed
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;; using the "pushad" instruction.
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;;
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;; The value of ESP as stored in the context record is the application ESP
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;; including the 3 entries on the application stack caused by the exception
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;; itself. It may have been modified by the debug agent, so we need to
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;; determine if we need to relocate the application stack.
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mov ebx, [esp + 12] ; move the potentially modified AppEsp into ebx
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mov eax, [AppEsp]
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add eax, 12
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cmp ebx, eax
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je NoAppStackMove
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mov eax, [AppEsp]
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mov ecx, [eax] ; EIP
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mov [ebx], ecx
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mov ecx, [eax + 4] ; CS
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mov [ebx + 4], ecx
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mov ecx, [eax + 8] ; EFLAGS
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mov [ebx + 8], ecx
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mov eax, ebx ; modify the saved AppEsp to the new AppEsp
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mov [AppEsp], eax
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NoAppStackMove:
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mov eax, [DebugEsp] ; restore the DebugEsp on the debug stack
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; so our "popad" will not cause a stack switch
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mov [esp + 12], eax
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cmp dword [ExceptionNumber], 0x68
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jne NoChain
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Chain:
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;; Restore eflags so when we chain, the flags will be exactly as if we were never here.
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;; We gin up the stack to do an iretd so we can get ALL the flags.
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mov eax, [AppEsp]
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mov ebx, [eax + 8]
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and ebx, ~ 0x300 ; special handling for IF and TF
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push ebx
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push cs
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push PhonyIretd
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iretd
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PhonyIretd:
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;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
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popad
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;; Switch back to application stack
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mov esp, [AppEsp]
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;; Jump to original handler
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jmp [ASM_PFX(OrigVector)]
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NoChain:
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;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
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popad
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;; Switch back to application stack
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mov esp, [AppEsp]
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;; We're outa here...
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iretd
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