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2008-06-22, 00:46 上午 skyworth 注册: 2008-06-07 发 贴: 55 关于《软件调试》 3.3.3 示例 手工输入程序源代码: #include #include #define VAR_WATCH() printf("nDividend=%d, nDivisor=%d, nResult=%d.\n", nDividend, nDivisor, nResult) int main(int argc, char* argv[]) { int nDividend = 22; int nDivisor = 0; int nResult = 100; __try { printf("Before div in __try block:\n"); VAR_WATCH(); nResult = nDividend / nDivisor; printf("After div in __try block:\n"); VAR_WATCH(); } __except(printf("In __except block\n"), VAR_WATCH(), GetExceptionCode() == EXCEPTION_INT_DIVIDE_BY_ZERO ? (nDivisor = 1, printf("Devide by zero exception detected.\n"), VAR_WATCH(), EXCEPTION_CONTINUE_EXECUTION) : EXCEPTION_CONTINUE_SEARCH ) { printf("In handler block\n"); } getchar(); return 0; } 仔细检查无误，保存为fault.c。 用命令行编译：cl fault.c /Zi 生成fault.exe 执行，输出： Before div in __try block: nDividend=22, nDivisor=0, nResult=100. In __except block nDividend=22, nDivisor=1, nResult=100. Devide by zero exception detected. nDividend=22, nDivisor=1, nResult=100. In __except block nDividend=22, nDivisor=1, nResult=100. Devide by zero exception detected. nDividend=22, nDivisor=1, nResult=100. In __except block nDividend=22, nDivisor=1, nResult=100. Devide by zero exception detected. nDividend=22, nDivisor=1, nResult=100. In __except block nDividend=22, nDivisor=1, nResult=100. Devide by zero exception detected. nDividend=22, nDivisor=1, nResult=100. In __except block nDividend=22, nDivisor=1, nResult=100. Devide by zero exception detected. nDividend=22, nDivisor=1, nResult=100. .................................. 怀疑是编译器优化的原因。 禁用优化，重新编译: cl fault.c /Od /Zi 重新执行，结果和上面一样。 IP 地址: 已记录   报告

2008-06-22, 00:46 上午 skyworth 注册: 2008-06-07 发 贴: 55 Re: 关于《软件调试》 3.3.3 示例 无奈，让编译器生成汇编源程序，如下。 ; Listing generated by Microsoft (R) Optimizing Compiler Version 15.00.21022.08 TITLE C:\TSource\fault.c .686P .XMM include listing.inc .model flat INCLUDELIB LIBCMT INCLUDELIB OLDNAMES _DATA SEGMENT $SG78567 DB 'Before div in __try block:', 0aH, 00H $SG78568 DB 'nDividend=%d, nDivisor=%d, nResult=%d.', 0aH, 00H $SG78569 DB 'After div in __try block:', 0aH, 00H ORG $+1 $SG78570 DB 'nDividend=%d, nDivisor=%d, nResult=%d.', 0aH, 00H $SG78572 DB 'In __except block', 0aH, 00H ORG $+1 $SG78573 DB 'nDividend=%d, nDivisor=%d, nResult=%d.', 0aH, 00H $SG78574 DB 'Devide by zero exception detected.', 0aH, 00H $SG78575 DB 'nDividend=%d, nDivisor=%d, nResult=%d.', 0aH, 00H $SG78576 DB 'In handler block', 0aH, 00H _DATA ENDS PUBLIC _main EXTRN _getchar:PROC EXTRN _printf:PROC EXTRN ___security_cookie:DWORD EXTRN __except_handler4:PROC xdata$x SEGMENT __sehtable$_main DD 0fffffffeH DD 00H DD 0ffffffc4H DD 00H DD 0fffffffeH DD FLAT:$LN7@main DD FLAT:$LN8@main ; Function compile flags: /Odtp ; File c:\tsource\fault.c xdata$x ENDS _TEXT SEGMENT tv85 = -44 ; size = 4 $T78597 = -40 ; size = 4 _nResult$ = -36 ; size = 4 _nDividend$ = -32 ; size = 4 _nDivisor$ = -28 ; size = 4 __$SEHRec$ = -24 ; size = 24 _argc$ = 8 ; size = 4 _argv$ = 12 ; size = 4 _main PROC ; 7 : { push ebp mov ebp, esp push -2 ; fffffffeH push OFFSET __sehtable$_main push OFFSET __except_handler4 mov eax, DWORD PTR fs:0 push eax add esp, -28 ; ffffffe4H push ebx push esi push edi mov eax, DWORD PTR ___security_cookie xor DWORD PTR __$SEHRec$[ebp+16], eax xor eax, ebp push eax lea eax, DWORD PTR __$SEHRec$[ebp+8] mov DWORD PTR fs:0, eax mov DWORD PTR __$SEHRec$[ebp], esp ; 8 : int nDividend = 22; mov DWORD PTR _nDividend$[ebp], 22 ; 00000016H ; 9 : int nDivisor = 0; mov DWORD PTR _nDivisor$[ebp], 0 ; 10 : int nResult = 100; mov DWORD PTR _nResult$[ebp], 100 ; 00000064H ; 11 : ; 12 : __try mov DWORD PTR __$SEHRec$[ebp+20], 0 ; 13 : { ; 14 : printf("Before div in __try block:\n"); push OFFSET $SG78567 call _printf add esp, 4 ; 15 : VAR_WATCH(); mov eax, DWORD PTR _nResult$[ebp] push eax mov ecx, DWORD PTR _nDivisor$[ebp] push ecx mov edx, DWORD PTR _nDividend$[ebp] push edx push OFFSET $SG78568 call _printf add esp, 16 ; 00000010H mov ecx, DWORD PTR _nDivisor$[ebp] ; 16 : ; 17 : nResult = nDividend / nDivisor; mov eax, DWORD PTR _nDividend$[ebp] cdq idiv ecx mov DWORD PTR _nResult$[ebp], eax ; 18 : ; 19 : printf("After div in __try block:\n"); push OFFSET $SG78569 call _printf add esp, 4 ; 20 : VAR_WATCH(); mov edx, DWORD PTR _nResult$[ebp] push edx mov eax, DWORD PTR _nDivisor$[ebp] push eax mov ecx, DWORD PTR _nDividend$[ebp] push ecx push OFFSET $SG78570 call _printf add esp, 16 ; 00000010H ; 21 : } mov DWORD PTR __$SEHRec$[ebp+20], -2 ; fffffffeH jmp $LN10@main $LN7@main: $LN12@main: ; 22 : __except(printf("In __except block\n"), ; 23 : VAR_WATCH(), ; 24 : GetExceptionCode() == EXCEPTION_INT_DIVIDE_BY_ZERO ; 25 : ? (nDivisor = 1, ; 26 : printf("Devide by zero exception detected.\n"), ; 27 : VAR_WATCH(), EXCEPTION_CONTINUE_EXECUTION) ; 28 : : EXCEPTION_CONTINUE_SEARCH ; 29 : ) mov edx, DWORD PTR __$SEHRec$[ebp+4] mov eax, DWORD PTR [edx] mov ecx, DWORD PTR [eax] mov DWORD PTR $T78597[ebp], ecx push OFFSET $SG78572 call _printf add esp, 4 mov edx, DWORD PTR _nResult$[ebp] push edx mov eax, DWORD PTR _nDivisor$[ebp] push eax mov ecx, DWORD PTR _nDividend$[ebp] push ecx push OFFSET $SG78573 call _printf add esp, 16 ; 00000010H cmp DWORD PTR $T78597[ebp], -1073741676 ; c0000094H jne SHORT $LN4@main mov DWORD PTR _nDivisor$[ebp], 1 push OFFSET $SG78574 call _printf add esp, 4 mov edx, DWORD PTR _nResult$[ebp] push edx mov eax, DWORD PTR _nDivisor$[ebp] push eax mov ecx, DWORD PTR _nDividend$[ebp] push ecx push OFFSET $SG78575 call _printf add esp, 16 ; 00000010H mov DWORD PTR tv85[ebp], -1 jmp SHORT $LN5@main $LN4@main: mov DWORD PTR tv85[ebp], 0 $LN5@main: mov eax, DWORD PTR tv85[ebp] $LN9@main: $LN11@main: ret 0 $LN8@main: mov esp, DWORD PTR __$SEHRec$[ebp] ; 30 : { ; 31 : printf("In handler block\n"); push OFFSET $SG78576 call _printf add esp, 4 ; 32 : } mov DWORD PTR __$SEHRec$[ebp+20], -2 ; fffffffeH $LN10@main: ; 33 : ; 34 : getchar(); call _getchar ; 35 : ; 36 : return 0; xor eax, eax $LN6@main: ; 37 : } mov ecx, DWORD PTR __$SEHRec$[ebp+8] mov DWORD PTR fs:0, ecx pop ecx pop edi pop esi pop ebx mov esp, ebp pop ebp ret 0 _main ENDP _TEXT ENDS END IP 地址: 已记录   报告

2008-06-22, 00:56 上午 skyworth 注册: 2008-06-07 发 贴: 55 Re: 关于《软件调试》 3.3.3 示例 观察汇编源程序 line 108 mov ecx, DWORD PTR _nDivisor$[ebp] ; 16 : ; 17 : nResult = nDividend / nDivisor; mov eax, DWORD PTR _nDividend$[ebp] cdq idiv ecx mov DWORD PTR _nResult$[ebp], eax 可以知道除数保存在寄存器ecx中。 观察汇编源程序 line 171 mov DWORD PTR _nDivisor$[ebp], 1 push OFFSET $SG78574 可以知道，在异常块中只是把内存中的nDivisor变量的值变成了1，而寄存器ecx的值不变。 再次执行fault.exe,用WinDBG attach到fault.exe，并单步执行，输出如下： Microsoft (R) Windows Debugger Version 6.9.0003.113 X86 Copyright (c) Microsoft Corporation. All rights reserved. *** wait with pending attach Symbol search path is: srv*D:\SymbolsCache*http://msdl.microsoft.com/download/symbols Executable search path is: ModLoad: 00400000 00427000 C:\TSource\fault.exe ModLoad: 7c930000 7ca00000 C:\WINDOWS\system32\ntdll.dll ModLoad: 7c800000 7c92b000 C:\WINDOWS\system32\kernel32.dll (be0.ab4): Break instruction exception - code 80000003 (first chance) eax=7ffdc000 ebx=00000001 ecx=00000002 edx=00000003 esi=00000004 edi=00000005 eip=7c94a3e1 esp=0039ffcc ebp=0039fff4 iopl=0 nv up ei pl zr na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=0038 gs=0000 efl=00000246 ntdll!DbgBreakPoint: 7c94a3e1 cc int 3 0:001> kb ChildEBP RetAddr Args to Child 0039ffc8 7c96fdd8 00000005 00000004 00000001 ntdll!DbgBreakPoint 0039fff4 00000000 00000000 00000000 00000000 ntdll!DbgUiRemoteBreakin+0x36 0:001> g (be0.acc): Integer divide-by-zero - code c0000094 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=00000016 ebx=7ffdc000 ecx=00000000 edx=00000000 esi=00000000 edi=00000000 eip=0040108c esp=0012ff3c ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010206 *** WARNING: Unable to verify checksum for C:\TSource\fault.exe fault!main+0x7c: 0040108c f7f9 idiv eax,ecx 0:000> p eax=00000016 ebx=7ffdc000 ecx=0012fc70 edx=00000000 esi=00000000 edi=00000000 eip=7c958554 esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 ntdll!KiUserExceptionDispatcher+0x4: 7c958554 8b1c24 mov ebx,dword ptr [esp] ss:0023:0012fc54=0012fc5c 0:000> eax=00000016 ebx=0012fc5c ecx=0012fc70 edx=00000000 esi=00000000 edi=00000000 eip=7c958557 esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 ntdll!KiUserExceptionDispatcher+0x7: 7c958557 51 push ecx 0:000> eax=00000016 ebx=0012fc5c ecx=0012fc70 edx=00000000 esi=00000000 edi=00000000 eip=7c958558 esp=0012fc50 ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 ntdll!KiUserExceptionDispatcher+0x8: 7c958558 53 push ebx 0:000> eax=00000016 ebx=0012fc5c ecx=0012fc70 edx=00000000 esi=00000000 edi=00000000 eip=7c958559 esp=0012fc4c ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 ntdll!KiUserExceptionDispatcher+0x9: 7c958559 e8d88f0000 call ntdll!RtlDispatchException (7c961536) 0:000> eax=00000001 ebx=0012fc5c ecx=00000000 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c95855e esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl zr na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000246 ntdll!KiUserExceptionDispatcher+0xe: 7c95855e 0ac0 or al,al 0:000> eax=00000001 ebx=0012fc5c ecx=00000000 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958560 esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x10: 7c958560 740c je ntdll!KiUserExceptionDispatcher+0x1e (7c95856e) [br=0] 0:000> eax=00000001 ebx=0012fc5c ecx=00000000 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958562 esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x12: 7c958562 5b pop ebx 0:000> eax=00000001 ebx=0012fc5c ecx=00000000 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958563 esp=0012fc58 ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x13: 7c958563 59 pop ecx 0:000> eax=00000001 ebx=0012fc5c ecx=0012fc70 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958564 esp=0012fc5c ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x14: 7c958564 6a00 push 0 0:000> eax=00000001 ebx=0012fc5c ecx=0012fc70 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958566 esp=0012fc58 ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x16: 7c958566 51 push ecx 0:000> eax=00000001 ebx=0012fc5c ecx=0012fc70 edx=ffffffc4 esi=00000000 edi=00000000 eip=7c958567 esp=0012fc54 ebp=0012ff78 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000202 ntdll!KiUserExceptionDispatcher+0x17: 7c958567 e823e8ffff call ntdll!NtContinue (7c956d8f) 0:000> (be0.acc): Integer divide-by-zero - code c0000094 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=00000016 ebx=7ffdc000 ecx=00000000 edx=00000000 esi=00000000 edi=00000000 eip=0040108c esp=0012ff3c ebp=0012ff78 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010206 fault!main+0x7c: 0040108c f7f9 idiv eax,ecx 0:000> x fault!nDivisor 0:000> .detach Detached 可以看出，异常处理后，会再次试图执行触发异常的指令。而此时ecx仍然为零，从而再次触发异常，如此往复，从而得到最开始的输出结果。 不知我的分析对否。现在正在想如何修正这个例子。 IP 地址: 已记录   报告

2008-06-22, 09:21 上午 格蠹老雷 注册: 2005-12-19 发 贴: 1,303 Re: 关于《软件调试》 3.3.3 示例 因为编译器（VC6，与VC7/VC8）的差异，产生的代码不一样，注意《软件调试》71页中部产生的汇编代码。 这个例子只是用来演示异常处理的过程和恢复执行的可能性。事实上，由于实际的异常情况大多很复杂，所以尝试恢复执行的难度也更大，主要是难以有通用的做法。 阅读24.4.1节的SehRaw示例，你可以知道如何绕过这个问题。 因为VC6轻便灵活，编译C/C++程序足够强大，所以建议你安装一个VC6环境，这样对于有DSW项目文件的示例就可以直接用VC6来编译。 IP 地址: 已记录   报告

2008-06-25, 22:35 下午 skyworth 注册: 2008-06-07 发 贴: 55 Re: 关于《软件调试》 3.3.3 示例 嗯，看过了书上的相关代码，的确是那样的。 谢谢你的建议^_^。 IP 地址: 已记录   报告

高端调试 » 软件调试 » Windows内核调试 » Re: 关于《软件调试》 3.3.3 示例

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