How To Debug

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how to debug buffer overrun 最近开发一套基于InfiniBand的网络通讯组件，在使用InfiniBand通讯前，我使用socket来进行同步，在服务端开发中遇到这样的一个问题：A buffer overrun has occurred in IBConnection.exe which has corrupted the program's internal state. Press Break to debug th 阅读详情

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How To Debug

These are my debugging notes.

The magic symbol path is SRV*c:/websymbols*http://msdl.microsoft.com/download/symbols

Given a crashed process:

0:001> kb
ChildEBP RetAddr  Args to Child              
44fedb5c 77f7f49f 77e74bd8 00000002 44fedba8 SharedUserData+0x304
44fedb60 77e74bd8 00000002 44fedba8 00000001 ntdll!ZwWaitForMultipleObjects+0xc
44fedbfc 77e74c70 00000002 44fedcd0 00000000 kernel32!WaitForMultipleObjectsEx+0x12c
44fedc14 69455a73 00000002 44fedcd0 00000000 kernel32!WaitForMultipleObjects+0x17
44fee398 69456ba3 44fef96c ffffffff 00008310 faultrep!StartDWException+0x575
44fef400 77eb9d66 44fef96c ffffffff c0000005 faultrep!ReportFault+0x488
44fef924 77c313c8 44fef96c 77c140c8 00000000 kernel32!UnhandledExceptionFilter+0x2e2
44fef940 77c37fde 00000000 44fef96c 77c33efb MSVCRT!_XcptFilter+0x15f
44feffb4 77e802ed 00862e60 0006f96c 77f519f3 MSVCRT!_endthreadex+0xc6
44feffec 00000000 77c37f49 00862e60 00000000 kernel32!BaseThreadStart+0x37

The first param to kernel32!UnhandledExceptionFilter (44fef96c) is a pointer to an EXCEPTION_POINTERS struct.

0:001> dd 44fef96c
44fef96c  44fefa5c 44fefa78 44fef998 77f833a0
44fef97c  44fefa5c 44feffa4 44fefa78 44fefa34
44fef98c  44feffa4 77f833b4 44feffa4 44fefa44

The second pointer in the struct is the pointer to the CONTEXT_RECORD. Use .cxr addr to reset the debuggers context to the thread as it was when it faulted. (Use ~s to return to the thread's current context.)

0:001> .cxr 44fefa78
eax=00000000 ebx=00000001 ecx=00000841 edx=44b9c1d8 esi=493dfad8 edi=44fefde4
eip=6d476a25 esp=44fefd44 ebp=44fefd74 iopl=0         nv up ei pl zr na po nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010246
jvm!JVM_FindSignal+1ef27:
6d476a25 837cc21400 cmp dword ptr [edx+eax*8+0x14],0x0 ds:0023:44b9c1ec=????????

The first pointer in the struct is the pointer to the EXCEPTION_RECORD. Use .exr addr to dump the struct.

0:001> .exr 44fefa5c
ExceptionAddress: 6d476a25 (jvm!JVM_FindSignal+0x0001ef27)
   ExceptionCode: c0000005
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 44b9c1ec
Attempt to read from address 44b9c1ec

More useful command examples:

`x kernel32!Ctrl`	search for symbol
`~*kb`	dump stack of all threads
`bp 77e9658d "r eax=0;g"`	create breakpoint that executes command when hit
`bl`	list breakpoints
`u kernel32!CreateEventA`	disassemble

Stack Frame Layout

Push moves the stack pointer backward in memory (ie, esp -= 4) and then writes the given value to location pointed at by the stack pointer.

Stack frame layout (no frame pointer optimization)

this function's ebp
points here ------------/
    ebp-0x8   ebp-0x4   ebp+0x0   ebp+0x4   ebp+0x8   ebp+0xC
                        caller's  return 
    local1    local0    ebp       addr      param0    param1
... 00000000  00000000  00000000  00000000  00000000  00000000 ...

Calling Conventions

All arguments are widened to 32 bits when they are passed. Return values are also widened to 32 bits and returned in the eax register, except for 8-byte structures, which are returned in the edx:eax register pair. Larger structures are returned in the eax register as pointers to hidden return structures. Parameters are pushed onto the stack from right to left.

The compiler generates prolog and epilog code to save and restore the esi, edi, ebx, and ebp registers, if they are used in the function.

name	argument passing	stack cleanup	name decoration	`int func(int a, double b)`
cdecl	on stack, reverse order / right to left (`ebp+0x8` is param0, `ebp+0xC` is param1 ...)	caller	prefix: "_"	`_func`
stdcall	on stack, reverse order / right to left (`ebp+0x8` is param0, `ebp+0xC` is param1 ...)	callee	prefix: "_"; suffix: "@" followed by the number of bytes (in decimal) in the argument list.	`_func@12`
fastcall	The first two `DWORD` or smaller arguments are passed in `ecx` and `edx` registers; all other arguments are passed on stack, reverse order / right to left (`ebp+0x8` is param2, `ebp+0xC` is param3 ...)	callee	prefix: "@"; suffix: "@" followed by the number of bytes (in decimal) in the argument list.	`@func@12`
thiscall	`this` in `ecx`; all other arbuments are passed on stack, reverse order / right to left (`ebp+0x8` is param0, `ebp+0xC` is param1 ...);	callee	(C++ mangling)

Inline Assembler

__asm { int 3 }	hardcoded debug breakpoint
#define TEB_OFFSET 4 void ** ppvStackBase; __asm { mov eax, fs:[TEB_OFFSET] } __asm { mov ppvStackBase, eax }	stack base from TEB
void ** ppvFrame; _asm { mov ppvFrame, ebp }	frame pointer

C o m m e n t s : updated: 2006-01-19 (99 days ago)

This is a great start. Can you point me to some good references - online or offline which can help me getting more info about debugging. Thanks Blake

Edit

Louis K. Thomas <louiNØSP@Msth@hotmÑOSP@Mail.coNÕSP@Mm> Fight Spam!

Auth

2006-03-15 (44 days ago)

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