2 ; Low leve IA32 specific debug support functions.
4 ; Copyright (c) 2006, Intel Corporation. <BR>
5 ; All rights reserved. This program and the accompanying materials
6 ; are licensed and made available under the terms and conditions of the BSD License
7 ; which accompanies this distribution. The full text of the license may be found at
8 ; http://opensource.org/licenses/bsd-license.php
10 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
11 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
18 EXCPT32_DIVIDE_ERROR EQU 0
21 EXCPT32_BREAKPOINT EQU 3
22 EXCPT32_OVERFLOW EQU 4
24 EXCPT32_INVALID_OPCODE EQU 6
25 EXCPT32_DOUBLE_FAULT EQU 8
26 EXCPT32_INVALID_TSS EQU 10
27 EXCPT32_SEG_NOT_PRESENT EQU 11
28 EXCPT32_STACK_FAULT EQU 12
29 EXCPT32_GP_FAULT EQU 13
30 EXCPT32_PAGE_FAULT EQU 14
31 EXCPT32_FP_ERROR EQU 16
32 EXCPT32_ALIGNMENT_CHECK EQU 17
33 EXCPT32_MACHINE_CHECK EQU 18
36 FXSTOR_FLAG EQU 01000000h ; bit cpuid 24 of feature flags
38 ;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
39 ;; MMX, SSE, SSE2, etc registers. The initialization of the debugsupport driver
40 ;; MUST check the CPUID feature flags to see that these instructions are available
41 ;; and fail to init if they are not.
45 db 0fh, 0aeh, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [edi]
50 db 0fh, 0aeh, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [esi]
54 public OrigVector, InterruptEntryStub, StubSize, CommonIdtEntry, FxStorSupport
56 StubSize dd InterruptEntryStubEnd - InterruptEntryStub
57 AppEsp dd 11111111h ; ?
58 DebugEsp dd 22222222h ; ?
59 ExtraPush dd 33333333h ; ?
60 ExceptData dd 44444444h ; ?
61 Eflags dd 55555555h ; ?
62 OrigVector dd 66666666h ; ?
64 ;; The declarations below define the memory region that will be used for the debug stack.
65 ;; The context record will be built by pushing register values onto this stack.
66 ;; It is imparitive that alignment be carefully managed, since the FXSTOR and
67 ;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
69 ;; The stub will switch stacks from the application stack to the debuger stack
70 ;; and pushes the exception number.
72 ;; Then we building the context record on the stack. Since the stack grows down,
73 ;; we push the fields of the context record from the back to the front. There
74 ;; are 132 bytes of stack used prior allocating the 512 bytes of stack to be
75 ;; used as the memory buffer for the fxstor instruction. Therefore address of
76 ;; the buffer used for the FXSTOR instruction is &Eax - 132 - 512, which
77 ;; must be 16 byte aligned.
79 ;; We carefully locate the stack to make this happen.
81 ;; For reference, the context structure looks like this:
83 ;; UINT32 ExceptionData;
84 ;; FX_SAVE_STATE_IA32 FxSaveState; // 512 bytes, must be 16 byte aligned
85 ;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
86 ;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
89 ;; UINT32 Gdtr[2], Idtr[2];
91 ;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
92 ;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
93 ;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
97 DebugStackEnd db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
98 dd 1ffdh dup (000000000h) ;; 32K should be enough stack
99 ;; This allocation is coocked to insure
100 ;; that the the buffer for the FXSTORE instruction
101 ;; will be 16 byte aligned also.
103 ExceptionNumber dd ? ;; first entry will be the vector number pushed by the stub
105 DebugStackBegin db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
109 externdef InterruptDistrubutionHub:near
111 ;------------------------------------------------------------------------------
117 ; Abstract: Returns TRUE if FxStor instructions are supported
119 FxStorSupport PROC C PUBLIC
122 ; cpuid corrupts ebx which must be preserved per the C calling convention
135 ;------------------------------------------------------------------------------
141 ; Abstract: Returns physical address of IDTR
143 GetIdtr PROC C PUBLIC
147 mov eax, DWORD PTR IdtrBuf + 2
152 ;------------------------------------------------------------------------------
154 ; WriteInterruptFlag (
158 ; Abstract: Programs interrupt flag to the requested state and returns previous
161 WriteInterruptFlag PROC C PUBLIC State:DWORD
175 WriteInterruptFlag ENDP
179 ;------------------------------------------------------------------------------
182 ; DESCRIPTOR * DestDesc,
183 ; void (*Vector) (void)
186 ; Abstract: Encodes an IDT descriptor with the given physical address
188 Vect2Desc PROC C PUBLIC DestPtr:DWORD, Vector:DWORD
192 mov word ptr [ecx], ax ; write bits 15..0 of offset
194 mov word ptr [ecx+2], dx ; SYS_CODE_SEL from GDT
195 mov word ptr [ecx+4], 0e00h OR 8000h ; type = 386 interrupt gate, present
197 mov word ptr [ecx+6], ax ; write bits 31..16 of offset
205 ;------------------------------------------------------------------------------
208 ; Abstract: This code is not a function, but is a small piece of code that is
209 ; copied and fixed up once for each IDT entry that is hooked.
212 mov AppEsp, esp ; save stack top
213 mov esp, offset DebugStackBegin ; switch to debugger stack
214 push 0 ; push vector number - will be modified before installed
216 dd 0 ; fixed up to relative address of CommonIdtEntry
217 InterruptEntryStubEnd:
221 ;------------------------------------------------------------------------------
224 ; Abstract: This code is not a function, but is the common part for all IDT
229 ;; At this point, the stub has saved the current application stack esp into AppEsp
230 ;; and switched stacks to the debug stack, where it pushed the vector number
232 ;; The application stack looks like this:
235 ;; (last application stack entry)
236 ;; eflags from interrupted task
237 ;; CS from interrupted task
238 ;; EIP from interrupted task
239 ;; Error code <-------------------- Only present for some exeption types
244 ;; The stub switched us to the debug stack and pushed the interrupt number.
246 ;; Next, construct the context record. It will be build on the debug stack by
247 ;; pushing the registers in the correct order so as to create the context structure
248 ;; on the debug stack. The context record must be built from the end back to the
249 ;; beginning because the stack grows down...
251 ;; For reference, the context record looks like this:
255 ;; UINT32 ExceptionData;
256 ;; FX_SAVE_STATE_IA32 FxSaveState;
257 ;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
258 ;; UINT32 Cr0, Cr2, Cr3, Cr4;
261 ;; UINT32 Gdtr[2], Idtr[2];
263 ;; UINT32 Gs, Fs, Es, Ds, Cs, Ss;
264 ;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
265 ;; } SYSTEM_CONTEXT_IA32; // 32 bit system context record
267 ;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
270 ;; Save interrupt state eflags register...
273 mov dword ptr Eflags, eax
275 ;; We need to determine if any extra data was pushed by the exception, and if so, save it
276 ;; To do this, we check the exception number pushed by the stub, and cache the
277 ;; result in a variable since we'll need this again.
278 .IF ExceptionNumber == EXCPT32_DOUBLE_FAULT
280 .ELSEIF ExceptionNumber == EXCPT32_INVALID_TSS
282 .ELSEIF ExceptionNumber == EXCPT32_SEG_NOT_PRESENT
284 .ELSEIF ExceptionNumber == EXCPT32_STACK_FAULT
286 .ELSEIF ExceptionNumber == EXCPT32_GP_FAULT
288 .ELSEIF ExceptionNumber == EXCPT32_PAGE_FAULT
290 .ELSEIF ExceptionNumber == EXCPT32_ALIGNMENT_CHECK
296 ;; If there's some extra data, save it also, and modify the saved AppEsp to effectively
297 ;; pop this value off the application's stack.
308 ;; The "pushad" above pushed the debug stack esp. Since what we're actually doing
309 ;; is building the context record on the debug stack, we need to save the pushed
310 ;; debug ESP, and replace it with the application's last stack entry...
315 ; application stack has eflags, cs, & eip, so
316 ; last actual application stack entry is
317 ; 12 bytes into the application stack.
320 ;; continue building context record
321 ;; UINT32 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
325 ; CS from application is one entry back in application stack
327 movzx eax, word ptr [eax + 4]
340 ; Eip from application is on top of application stack
344 ;; UINT32 Gdtr[2], Idtr[2];
360 ;; Eflags from application is two entries back in application stack
362 push dword ptr [eax + 8]
364 ;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
365 ;; insure FXSAVE/FXRSTOR is enabled in CR4...
366 ;; ... while we're at it, make sure DE is also enabled...
379 ;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
382 ;; clear Dr7 while executing debugger itself
388 ;; insure all status bits in dr6 are clear...
401 ;; FX_SAVE_STATE_IA32 FxSaveState;
404 ; IMPORTANT!! The debug stack has been carefully constructed to
405 ; insure that esp and edi are 16 byte aligned when we get here.
406 ; They MUST be. If they are not, a GP fault will occur.
409 ;; UINT32 ExceptionData;
413 ; call to C code which will in turn call registered handler
414 ; pass in the vector number
417 mov eax, ExceptionNumber
419 call InterruptDistrubutionHub
423 ;; UINT32 ExceptionData;
426 ;; FX_SAVE_STATE_IA32 FxSaveState;
431 ;; UINT32 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
440 ;; skip restore of dr6. We cleared dr6 during the context save.
445 ;; UINT32 Cr0, Cr1, Cr2, Cr3, Cr4;
458 pop dword ptr [eax + 8]
461 ;; UINT32 Gdtr[2], Idtr[2];
462 ;; Best not let anyone mess with these particular registers...
468 ;; UINT32 SegGs, SegFs, SegEs, SegDs, SegCs, SegSs;
469 ;; NOTE - modified segment registers could hang the debugger... We
470 ;; could attempt to insulate ourselves against this possibility,
471 ;; but that poses risks as well.
481 ;; The next stuff to restore is the general purpose registers that were pushed
482 ;; using the "pushad" instruction.
484 ;; The value of ESP as stored in the context record is the application ESP
485 ;; including the 3 entries on the application stack caused by the exception
486 ;; itself. It may have been modified by the debug agent, so we need to
487 ;; determine if we need to relocate the application stack.
489 mov ebx, [esp + 12] ; move the potentially modified AppEsp into ebx
499 mov ecx, [eax + 4] ; CS
502 mov ecx, [eax + 8] ; EFLAGS
505 mov eax, ebx ; modify the saved AppEsp to the new AppEsp
508 mov eax, DebugEsp ; restore the DebugEsp on the debug stack
509 ; so our "popad" will not cause a stack switch
512 cmp ExceptionNumber, 068h
517 ;; Restore eflags so when we chain, the flags will be exactly as if we were never here.
518 ;; We gin up the stack to do an iretd so we can get ALL the flags.
521 and ebx, NOT 300h ; special handling for IF and TF
528 ;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
531 ;; Switch back to application stack
534 ;; Jump to original handler
538 ;; UINT32 Edi, Esi, Ebp, Esp, Ebx, Edx, Ecx, Eax;
541 ;; Switch back to application stack
544 ;; We're outa here...