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x86/funclets: Handle longjmp #115932

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merged 2 commits into from
May 24, 2025
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x86/funclets: Handle longjmp #115932

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x86: Implement basic support for unwinding longjmp across managed fra…
filipnavara May 23, 2025
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filipnavara May 23, 2025
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55 changes: 53 additions & 2 deletions src/coreclr/vm/exceptionhandling.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -521,6 +521,40 @@ static void PopExplicitFrames(Thread *pThread, void *targetSp, void *targetCalle
}
}

#if defined(HOST_WINDOWS) && defined(HOST_X86)
static void DispatchLongJmp(IN PEXCEPTION_RECORD pExceptionRecord,
IN PVOID pEstablisherFrame,
IN OUT PCONTEXT pContextRecord)
{
// Pop all the SEH frames including the one that is currently called
// to prevent setjmp from trying to unwind it again when we inject our
// longjmp.
SetCurrentSEHRecord(((PEXCEPTION_REGISTRATION_RECORD)pEstablisherFrame)->Next);

#pragma warning(push)
#pragma warning(disable:4611) // interaction between 'function' and C++ object destruction is non-portable
jmp_buf jumpBuffer;
if (setjmp(jumpBuffer))
{
// We reach this point after the finally handlers were called and
// the unwinding should continue below the managed frame.
return;
}
#pragma warning(pop)

// Emulate the parameters that are passed on 64-bit systems and expected by
// DispatchManagedException.
EXCEPTION_RECORD newExceptionRecord = *pExceptionRecord;
newExceptionRecord.NumberParameters = 2;
newExceptionRecord.ExceptionInformation[0] = (DWORD_PTR)&jumpBuffer;
newExceptionRecord.ExceptionInformation[1] = 1;

OBJECTREF oref = ExInfo::CreateThrowable(&newExceptionRecord, FALSE);
DispatchManagedException(oref, pContextRecord, &newExceptionRecord);
UNREACHABLE();
}
#endif

EXTERN_C EXCEPTION_DISPOSITION __cdecl
ProcessCLRException(IN PEXCEPTION_RECORD pExceptionRecord,
IN PVOID pEstablisherFrame,
Expand Down Expand Up @@ -613,14 +647,22 @@ ProcessCLRException(IN PEXCEPTION_RECORD pExceptionRecord,
}

// Second pass (unwinding)
GCX_COOP();
GCX_COOP_NO_DTOR();
ThreadExceptionState* pExState = pThread->GetExceptionState();
ExInfo *pPrevExInfo = (ExInfo*)pExState->GetCurrentExceptionTracker();
if (pPrevExInfo != NULL && pPrevExInfo->m_DebuggerExState.GetDebuggerInterceptContext() != NULL)
{
ContinueExceptionInterceptionUnwind();
UNREACHABLE();
}
#if defined(HOST_WINDOWS) && defined(HOST_X86)
else if (pExceptionRecord->ExceptionCode == STATUS_LONGJUMP)
{
DispatchLongJmp(pExceptionRecord, pEstablisherFrame, pContextRecord);
GCX_COOP_NO_DTOR_END();
return ExceptionContinueSearch;
}
#endif
else
{
OBJECTREF oref = ExInfo::CreateThrowable(pExceptionRecord, FALSE);
Expand Down Expand Up @@ -3030,10 +3072,12 @@ void ExecuteFunctionBelowContext(PCODE functionPtr, CONTEXT *pContext, size_t ta
}

#ifdef HOST_WINDOWS
VOID DECLSPEC_NORETURN PropagateLongJmpThroughNativeFrames(jmp_buf *pJmpBuf, int retVal)
VOID DECLSPEC_NORETURN __fastcall PropagateLongJmpThroughNativeFrames(jmp_buf *pJmpBuf, int retVal)
{
WRAPPER_NO_CONTRACT;
GCX_PREEMP_NO_DTOR();
longjmp(*pJmpBuf, retVal);
UNREACHABLE();
}

// This is a personality routine that the RtlRestoreContext calls when it is called with
Expand Down Expand Up @@ -3235,7 +3279,14 @@ extern "C" void * QCALLTYPE CallCatchFunclet(QCall::ObjectHandleOnStack exceptio
if (pLongJmpBuf != NULL)
{
STRESS_LOG2(LF_EH, LL_INFO100, "Resuming propagation of longjmp through native frames at IP=%p, SP=%p\n", GetIP(pvRegDisplay->pCurrentContext), GetSP(pvRegDisplay->pCurrentContext));
#ifdef HOST_X86
// On x86 we don't jump to the original longjmp target. Instead we return to DispatchLongJmp called
// from ProcessCLRException which in turn return ExceptionContinueSearch to continue unwinding the
// original longjmp call.
longjmp(*pLongJmpBuf, longJmpReturnValue);
#else
ExecuteFunctionBelowContext((PCODE)PropagateLongJmpThroughNativeFrames, pvRegDisplay->pCurrentContext, targetSSP, (size_t)pLongJmpBuf, longJmpReturnValue);
#endif
}
else
#endif
Expand Down
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