AsmFuncs.asm revision 4fd606d1f5abe38e1f42c38de1d2e895166bd0f4
;/** @file
; Low leve IA32 specific debug support functions.
;
; Copyright (c) 2006 - 2011, 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
;
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
;**/
.586p
.MODEL FLAT, C
EXCPT32_DIVIDE_ERROR EQU 0
EXCPT32_DEBUG EQU 1
EXCPT32_NMI EQU 2
EXCPT32_BREAKPOINT EQU 3
EXCPT32_OVERFLOW EQU 4
EXCPT32_BOUND EQU 5
EXCPT32_INVALID_OPCODE EQU 6
EXCPT32_DOUBLE_FAULT EQU 8
EXCPT32_INVALID_TSS EQU 10
EXCPT32_SEG_NOT_PRESENT EQU 11
EXCPT32_STACK_FAULT EQU 12
EXCPT32_GP_FAULT EQU 13
EXCPT32_PAGE_FAULT EQU 14
EXCPT32_FP_ERROR EQU 16
EXCPT32_ALIGNMENT_CHECK EQU 17
EXCPT32_MACHINE_CHECK EQU 18
EXCPT32_SIMD EQU 19
FXSTOR_FLAG EQU 01000000h ; bit cpuid 24 of feature flags
;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
;; MMX, SSE, SSE2, etc registers. The initialization of the debugsupport driver
;; MUST check the CPUID feature flags to see that these instructions are available
;; and fail to init if they are not.
;; fxstor [edi]
FXSTOR_EDI MACRO
db 0fh, 0aeh, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [edi]
ENDM
;; fxrstor [esi]
FXRSTOR_ESI MACRO
db 0fh, 0aeh, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [esi]
ENDM
.DATA
public OrigVector, InterruptEntryStub, StubSize, CommonIdtEntry, FxStorSupport
StubSize dd InterruptEntryStubEnd - InterruptEntryStub
AppEsp dd 11111111h ; ?
DebugEsp dd 22222222h ; ?
ExtraPush dd 33333333h ; ?
ExceptData dd 44444444h ; ?
Eflags dd 55555555h ; ?
OrigVector dd 66666666h ; ?
;; The declarations below define the memory region that will be used for the debug stack.
;; The context record will be built by pushing register values onto this stack.
;; It is imparitive that alignment be carefully managed, since the FXSTOR and
;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
;;
;; The stub will switch stacks from the application stack to the debuger stack
;; and pushes the exception number.
;;
;; Then we building the context record on the stack. Since the stack grows down,
;; we push the fields of the context record from the back to the front. There
;; are 132 bytes of stack used prior allocating the 512 bytes of stack to be
;; used as the memory buffer for the fxstor instruction. Therefore address of
;; the buffer used for the FXSTOR instruction is &Eax - 132 - 512, which
;; must be 16 byte aligned.
;;
;; We carefully locate the stack to make this happen.
;;
;; For reference, the context structure looks like this:
;; struct {
;; UINT32 ExceptionData;
;; FX_SAVE_STATE_IA32 FxSaveState; // 512 bytes, must be 16 byte aligned
;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
;; UINT32 EFlags;
;; UINT32 Ldtr, Tr;
;; UINT32 Gdtr[2], Idtr[2];
;; UINT32 Eip;
;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
align 16
DebugStackEnd db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
dd 1ffdh dup (000000000h) ;; 32K should be enough stack
;; This allocation is coocked to insure
;; that the the buffer for the FXSTORE instruction
;; will be 16 byte aligned also.
;;
ExceptionNumber dd ? ;; first entry will be the vector number pushed by the stub
DebugStackBegin db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
.CODE
externdef InterruptDistrubutionHub:near
;------------------------------------------------------------------------------
; BOOLEAN
; FxStorSupport (
; void
; )
;
; Abstract: Returns TRUE if FxStor instructions are supported
;
FxStorSupport PROC C PUBLIC
;
; cpuid corrupts ebx which must be preserved per the C calling convention
;
push ebx
mov eax, 1
cpuid
mov eax, edx
and eax, FXSTOR_FLAG
shr eax, 24
pop ebx
ret
FxStorSupport ENDP
;------------------------------------------------------------------------------
; void
; Vect2Desc (
; DESCRIPTOR * DestDesc,
; void (*Vector) (void)
; )
;
; Abstract: Encodes an IDT descriptor with the given physical address
;
Vect2Desc PROC C PUBLIC DestPtr:DWORD, Vector:DWORD
mov eax, Vector
mov ecx, DestPtr
mov word ptr [ecx], ax ; write bits 15..0 of offset
mov dx, cs
mov word ptr [ecx+2], dx ; SYS_CODE_SEL from GDT
mov word ptr [ecx+4], 0e00h OR 8000h ; type = 386 interrupt gate, present
shr eax, 16
mov word ptr [ecx+6], ax ; write bits 31..16 of offset
ret
Vect2Desc ENDP
;------------------------------------------------------------------------------
; InterruptEntryStub
;
; Abstract: This code is not a function, but is a small piece of code that is
; copied and fixed up once for each IDT entry that is hooked.
;
InterruptEntryStub::
mov AppEsp, esp ; save stack top
mov esp, offset DebugStackBegin ; switch to debugger stack
push 0 ; push vector number - will be modified before installed
db 0e9h ; jump rel32
dd 0 ; fixed up to relative address of CommonIdtEntry
InterruptEntryStubEnd:
;------------------------------------------------------------------------------
; CommonIdtEntry
;
; Abstract: This code is not a function, but is the common part for all IDT
; vectors.
;
CommonIdtEntry::
;;
;; At this point, the stub has saved the current application stack esp into AppEsp
;; and switched stacks to the debug stack, where it pushed the vector number
;;
;; The application stack looks like this:
;;
;; ...
;; (last application stack entry)
;; eflags from interrupted task
;; CS from interrupted task
;; EIP from interrupted task
;; Error code <-------------------- Only present for some exeption types
;;
;;
;; The stub switched us to the debug stack and pushed the interrupt number.
;;
;; Next, construct the context record. It will be build on the debug stack by
;; pushing the registers in the correct order so as to create the context structure
;; on the debug stack. The context record must be built from the end back to the
;; beginning because the stack grows down...
;
;; For reference, the context record looks like this:
;;
;; typedef
;; struct {
;; UINT32 ExceptionData;
;; FX_SAVE_STATE_IA32 FxSaveState;
;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
;; UINT32 Cr0, Cr2, Cr3, Cr4;
;; UINT32 EFlags;
;; UINT32 Ldtr, Tr;
;; UINT32 Gdtr[2], Idtr[2];
;; UINT32 Eip;
;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
pushad
;; Save interrupt state eflags register...
pushfd
pop eax
mov dword ptr Eflags, eax
;; We need to determine if any extra data was pushed by the exception, and if so, save it
;; To do this, we check the exception number pushed by the stub, and cache the
;; result in a variable since we'll need this again.
.IF ExceptionNumber == EXCPT32_DOUBLE_FAULT
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_INVALID_TSS
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_SEG_NOT_PRESENT
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_STACK_FAULT
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_GP_FAULT
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_PAGE_FAULT
mov ExtraPush, 1
.ELSEIF ExceptionNumber == EXCPT32_ALIGNMENT_CHECK
mov ExtraPush, 1
.ELSE
mov ExtraPush, 0
.ENDIF
;; If there's some extra data, save it also, and modify the saved AppEsp to effectively
;; pop this value off the application's stack.
.IF ExtraPush == 1
mov eax, AppEsp
mov ebx, [eax]
mov ExceptData, ebx
add eax, 4
mov AppEsp, eax
.ELSE
mov ExceptData, 0
.ENDIF
;; The "pushad" above pushed the debug stack esp. Since what we're actually doing
;; is building the context record on the debug stack, we need to save the pushed
;; debug ESP, and replace it with the application's last stack entry...
mov eax, [esp + 12]
mov DebugEsp, eax
mov eax, AppEsp
add eax, 12
; application stack has eflags, cs, & eip, so
; last actual application stack entry is
; 12 bytes into the application stack.
mov [esp + 12], eax
;; continue building context record
;; UINT32 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
mov eax, ss
push eax
; CS from application is one entry back in application stack
mov eax, AppEsp
movzx eax, word ptr [eax + 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;
; Eip from application is on top of application stack
mov eax, AppEsp
push dword ptr [eax]
;; UINT32 Gdtr[2], Idtr[2];
push 0
push 0
sidt fword ptr [esp]
push 0
push 0
sgdt fword ptr [esp]
;; UINT32 Ldtr, Tr;
xor eax, eax
str ax
push eax
sldt ax
push eax
;; UINT32 EFlags;
;; Eflags from application is two entries back in application stack
mov eax, AppEsp
push dword ptr [eax + 8]
;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
;; insure FXSAVE/FXRSTOR is enabled in CR4...
;; ... while we're at it, make sure DE is also enabled...
mov eax, cr4
or eax, 208h
mov cr4, eax
push eax
mov eax, cr3
push eax
mov eax, cr2
push eax
push 0
mov eax, cr0
push eax
;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
mov eax, dr7
push eax
;; clear Dr7 while executing debugger itself
xor eax, eax
mov dr7, eax
mov eax, dr6
push eax
;; insure all status bits in dr6 are clear...
xor eax, eax
mov dr6, 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
; IMPORTANT!! The debug stack has been carefully constructed to
; insure that esp and edi are 16 byte aligned when we get here.
; They MUST be. If they are not, a GP fault will occur.
FXSTOR_EDI
;; UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
cld
;; UINT32 ExceptionData;
mov eax, ExceptData
push eax
; call to C code which will in turn call registered handler
; pass in the vector number
mov eax, esp
push eax
mov eax, ExceptionNumber
push eax
call InterruptDistrubutionHub
add esp, 8
; restore context...
;; UINT32 ExceptionData;
add esp, 4
;; FX_SAVE_STATE_IA32 FxSaveState;
mov esi, esp
FXRSTOR_ESI
add esp, 512
;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
pop eax
mov dr0, eax
pop eax
mov dr1, eax
pop eax
mov dr2, eax
pop eax
mov dr3, eax
;; skip restore of dr6. We cleared dr6 during the context save.
add esp, 4
pop eax
mov dr7, eax
;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
pop eax
mov cr0, eax
add esp, 4
pop eax
mov cr2, eax
pop eax
mov cr3, eax
pop eax
mov cr4, eax
;; UINT32 EFlags;
mov eax, AppEsp
pop dword ptr [eax + 8]
;; UINT32 Ldtr, Tr;
;; UINT32 Gdtr[2], Idtr[2];
;; Best not let anyone mess with these particular registers...
add esp, 24
;; UINT32 Eip;
pop dword ptr [eax]
;; UINT32 SegGs, SegFs, SegEs, SegDs, SegCs, SegSs;
;; 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 [eax + 4]
pop ss
;; The next stuff to restore is the general purpose registers that were pushed
;; using the "pushad" instruction.
;;
;; The value of ESP as stored in the context record is the application ESP
;; including the 3 entries on the application stack caused by the exception
;; itself. It may have been modified by the debug agent, so we need to
;; determine if we need to relocate the application stack.
mov ebx, [esp + 12] ; move the potentially modified AppEsp into ebx
mov eax, AppEsp
add eax, 12
cmp ebx, eax
je NoAppStackMove
mov eax, AppEsp
mov ecx, [eax] ; EIP
mov [ebx], ecx
mov ecx, [eax + 4] ; CS
mov [ebx + 4], ecx
mov ecx, [eax + 8] ; EFLAGS
mov [ebx + 8], ecx
mov eax, ebx ; modify the saved AppEsp to the new AppEsp
mov AppEsp, eax
NoAppStackMove:
mov eax, DebugEsp ; restore the DebugEsp on the debug stack
; so our "popad" will not cause a stack switch
mov [esp + 12], eax
cmp ExceptionNumber, 068h
jne NoChain
Chain:
;; Restore eflags so when we chain, the flags will be exactly as if we were never here.
;; We gin up the stack to do an iretd so we can get ALL the flags.
mov eax, AppEsp
mov ebx, [eax + 8]
and ebx, NOT 300h ; special handling for IF and TF
push ebx
push cs
push PhonyIretd
iretd
PhonyIretd:
;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
popad
;; Switch back to application stack
mov esp, AppEsp
;; Jump to original handler
jmp OrigVector
NoChain:
;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
popad
;; Switch back to application stack
mov esp, AppEsp
;; We're outa here...
iretd
END