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copied!<p>If you are following <a href="http://www.rohitab.com/structured-exception-handling-in-assembly-language" rel="nofollow">this article</a>, which it seems you are, then why aren't you properly restoring the stack as shown in the code there?</p> <p>The code in the article:</p> <pre><code>18 NoException&;Handler: ;;No Exception Occured 19 pop dword ptr fs:[0] ;;Restore Old Exception Handler 20 add esp, 32 + 4 ;;ESP value before SEH was set. 32 for pushad and ... 21 ExceptionHandled&;Handler: ;;...4 for push offset Handler. (No Restore State) 22 ;;Exception has been handled, or no exception occured </code></pre> <p>Your code:</p> <pre><code>NoException: pop dword ptr fs:[0] add esp, 8 ExceptionHandled: </code></pre> <p>32 in that code is to undo <code>pushad</code>, 4 is to undo <code>push esi</code>. Why do you have 8? 32 + 4 ≠ 8.</p> <p>If that's how you want to remove <code>u32Param</code> from the stack (in case <code>pFunc</code> doesn't do it for you), then you should do it between these two lines:</p> <pre><code> call pFunc; add esp, 4 jmp NoException </code></pre> <p>My version:</p> <pre><code>// file: tst.c // compile with Open Watcom C/C++ 1.9: wcl386.exe /q /we /wx tst.c // ditto with debug info: wcl386.exe /q /we /wx /d2 tst.c #include <stdio.h> unsigned __stdcall func(volatile unsigned* p) { return *p; } unsigned blah(unsigned (__stdcall *pFunc)(volatile unsigned*), volatile unsigned* u32Param) { unsigned result = 0; __asm { pushad // mov esi, offset Handler // Open Watcom C/C++ says Handler is undefined // push esi // lea eax, blah // add eax, Handler - blah // this difference doesn't come out correct with Open Watcom C/C++ // add eax, 78 // 78 is Handler - blah // this is unreliable // push eax push 0xFDCB4321 jmp GetHandlerAddr GotHandlerAddr: pop eax add esp, 4 push eax push dword ptr fs:[0] mov dword ptr fs:[0], esp push u32Param call dword ptr [pFunc] jmp NoException GetHandlerAddr: call Handler // this will place &Handler on the stack Handler: cmp dword ptr [esp + 4], 0xFDCB4321 je GotHandlerAddr mov esp, [esp + 8] pop dword ptr fs:[0] add esp, 4 popad mov eax, 0x80000000 jmp ExceptionHandled NoException: pop dword ptr fs:[0] add esp, 32 + 4 ExceptionHandled: mov result, eax } return result; } int main(void) { volatile unsigned n = 0x113355AA; printf("%08X\n", func(&n)); printf("%08X\n", blah(&func, &n)); printf("%08X\n", blah(&func, (volatile unsigned*)0)); printf("%08X\n", blah(&func, (volatile unsigned*)0)); return 0; } </code></pre> <p>Output:</p> <pre><code>113355AA 113355AA 80000000 80000000 </code></pre>

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