extern "C" EXCEPTION_DISPOSITION __cdecl _CatchGuardHandler(
EHExceptionRecord *pExcept, // Information for this exception
CatchGuardRN *pRN, // The special marker frame
void *pContext, // Context info (we don't care what's in it)
void * // (ignored)
) {
#if defined(ENABLE_EHTRACE)
EHTracePushLevel(pRN->trace_level);
#endif
EHTRACE_ENTER_FMT1("pRN = 0x%p", pRN);
__asm cld; // Our code-gen assumes this
//
// Validate our registration record, to secure against hacker attacks.
//
__security_check_cookie(pRN->RandomCookie ^ (UINT_PTR)pRN);
EXCEPTION_DISPOSITION result =
__InternalCxxFrameHandler( pExcept,
pRN->pRN,
pContext,
nullptr,
pRN->pFuncInfo,
pRN->CatchDepth,
(EHRegistrationNode*)pRN,
FALSE );
EHTRACE_HANDLER_EXIT(result);
EHTRACE_RESTORE_LEVEL(true);
return result;
}
// If an exception happen as doing a local unwind, this function is the nested exception handler.
// The call convention is __cdecl, but in fact it could be __stdcall too.
// The EstablishFrame would be
// ebp
// CookiePointer
// PrevEstablishFrame
// EnclosingLevel
// Cookie
// _unwind_handler4
// next
EXCEPTION_DISPOSITION __cdecl
_unwind_handler4(PEXCEPTION_RECORD ExceptionRecord,
PVOID EstablishFrame,
PCONTEXT ContextRecord,
PVOID DispatchContext)
{
if ( (ExceptionRecord->ExceptionFlags & (EXCEPTION_UNWINDING | EXCEPTION_EXIT_UNWIND)) == 0) {
return ExceptionContinueSearch;
}
// first check is the establishframe cookie is overwritten.
DWORD cookie = *(DWORD*)((DWORD)EstablishFrame + 8);
cookie ^= (DWORD)EstablishFrame;
__security_check_cookie(cookie);
__asm {
mov eax, EstablishFrame
push ebp
mov ebp, eax
push [eax+0x0c] // EstablishFrame.EnclosingLevel
push [eax+0x10] // EstablishFrame.PrevEstablishFrame
push [eax+0x14] // EstablishFrame.CookiePointer
call __local_unwind4
add esp, 0x0c
pop ebp
}
*(DWORD*)DispatchContext = (DWORD)EstablishFrame;
return ExceptionCollidedUnwind;
}
