;/** @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
; 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.
;
;**/
%define EXCPT32_DIVIDE_ERROR 0
%define EXCPT32_DEBUG 1
%define EXCPT32_NMI 2
%define EXCPT32_BREAKPOINT 3
%define EXCPT32_OVERFLOW 4
%define EXCPT32_BOUND 5
%define EXCPT32_INVALID_OPCODE 6
%define EXCPT32_DOUBLE_FAULT 8
%define EXCPT32_INVALID_TSS 10
%define EXCPT32_SEG_NOT_PRESENT 11
%define EXCPT32_STACK_FAULT 12
%define EXCPT32_GP_FAULT 13
%define EXCPT32_PAGE_FAULT 14
%define EXCPT32_FP_ERROR 16
%define EXCPT32_ALIGNMENT_CHECK 17
%define EXCPT32_MACHINE_CHECK 18
%define EXCPT32_SIMD 19
%define FXSTOR_FLAG 0x1000000 ; 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]
%macro FXSTOR_EDI 0
db 0xf, 0xae, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [edi]
%endmacro
;; fxrstor [esi]
%macro FXRSTOR_ESI 0
db 0xf, 0xae, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [esi]
%endmacro
SECTION .data
global ASM_PFX(OrigVector)
global ASM_PFX(InterruptEntryStub)
global ASM_PFX(StubSize)
global ASM_PFX(CommonIdtEntry)
global ASM_PFX(FxStorSupport)
extern ASM_PFX(InterruptDistrubutionHub)
ASM_PFX(StubSize): dd InterruptEntryStubEnd - ASM_PFX(InterruptEntryStub)
AppEsp: dd 0x11111111 ; ?
DebugEsp: dd 0x22222222 ; ?
ExtraPush: dd 0x33333333 ; ?
ExceptData: dd 0x44444444 ; ?
Eflags: dd 0x55555555 ; ?
ASM_PFX(OrigVector): dd 0x66666666 ; ?
;; 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
times 0x1ffc dd 0x0 ;; 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 0 ;; first entry will be the vector number pushed by the stub
DebugStackBegin: db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
SECTION .text
;------------------------------------------------------------------------------
; BOOLEAN
; FxStorSupport (
; void
; )
;
; Abstract: Returns TRUE if FxStor instructions are supported
;
global ASM_PFX(FxStorSupport)
ASM_PFX(FxStorSupport):
;
; 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
;------------------------------------------------------------------------------
; void
; Vect2Desc (
; DESCRIPTOR * DestDesc,
; void (*Vector) (void)
; )
;
; Abstract: Encodes an IDT descriptor with the given physical address
;
global ASM_PFX(Vect2Desc)
ASM_PFX(Vect2Desc):
push ebp
mov ebp, esp
mov eax, [ebp + 0xC]
mov ecx, [ebp + 0x8]
mov word [ecx], ax ; write bits 15..0 of offset
mov dx, cs
mov word [ecx+2], dx ; SYS_CODE_SEL from GDT
mov word [ecx+4], 0xe00 | 0x8000 ; type = 386 interrupt gate, present
shr eax, 16
mov word [ecx+6], ax ; write bits 31..16 of offset
leave
ret
;------------------------------------------------------------------------------
; 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.
;
ASM_PFX(InterruptEntryStub):
mov [AppEsp], esp ; save stack top
mov esp, DebugStackBegin ; switch to debugger stack
push 0 ; push vector number - will be modified before installed
db 0xe9 ; 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.
;
ASM_PFX(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 [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.
cmp dword [ExceptionNumber], EXCPT32_DOUBLE_FAULT
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_INVALID_TSS
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_SEG_NOT_PRESENT
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_STACK_FAULT
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_GP_FAULT
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_PAGE_FAULT
jz ExtraPushOne
cmp dword [ExceptionNumber], EXCPT32_ALIGNMENT_CHECK
jz ExtraPushOne
mov dword [ExtraPush], 0
mov dword [ExceptData], 0
jmp ExtraPushDone
ExtraPushOne:
mov dword [ExtraPush], 1
;; If there's some extra data, save it also, and modify the saved AppEsp to effectively
;; pop this value off the application's stack.
mov eax, [AppEsp]
mov ebx, [eax]
mov [ExceptData], ebx
add eax, 4
mov [AppEsp], eax
ExtraPushDone:
;; 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 [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 [eax]
;; UINT32 Gdtr[2], Idtr[2];
push 0
push 0
sidt [esp]
push 0
push 0
sgdt [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 [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, 0x208
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 ASM_PFX(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 [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 [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 dword [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 dword [ExceptionNumber], 0x68
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, ~ 0x300 ; 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 [ASM_PFX(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