Notify attached debugger of NAOT exception (dotnet#115678)

Native AOT does not use C++ or SEH exceptions, meaning that debuggers do
not recognize the exception throw/catch sequence and cannot break on
first-chance exceptions. On Windows, we can use OS functionality to
throw and catch an SEH exception when a Native AOT exception is thrown
and a debugger is attached, effectively acting as a notification to
debuggers that an exception is in flight. The exception code used here
is the same one as CoreCLR, so the WinDbg command `sxe clr` would also
be sufficient to catch Native AOT exceptions.

Fixes dotnet#115514

Author: agocke

src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/ExceptionHandling.cs

@@ -649,11 +649,18 @@ public static void RhThrowHwEx(uint exceptionCode, ref ExInfo exInfo)
         public static void RhThrowEx(object exceptionObj, ref ExInfo exInfo)
         {
 #if NATIVEAOT
+
+#if TARGET_WINDOWS
+            // Alert the debugger that we threw an exception.
+            InternalCalls.RhpFirstChanceExceptionNotification();
+#endif // TARGET_WINDOWS
+
             // trigger a GC (only if gcstress) to ensure we can stackwalk at this point
             GCStress.TriggerGC();
 
             InternalCalls.RhpValidateExInfoStack();
-#endif
+#endif // NATIVEAOT
+
             // Transform attempted throws of null to a throw of NullReferenceException.
             if (exceptionObj == null)
             {
@@ -665,6 +672,7 @@ public static void RhThrowEx(object exceptionObj, ref ExInfo exInfo)
             DispatchEx(ref exInfo._frameIter, ref exInfo);
             FallbackFailFast(RhFailFastReason.InternalError, null);
         }
+
 #if !NATIVEAOT
         public static void RhUnwindAndIntercept(ref ExInfo exInfo, UIntPtr interceptStackFrameSP)
         {

src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/InternalCalls.cs

@@ -247,6 +247,12 @@ internal static extern unsafe IntPtr RhpCallPropagateExceptionCallback(
         [MethodImpl(MethodImplOptions.InternalCall)]
         internal static extern void RhpValidateExInfoStack();
 
+#if TARGET_WINDOWS
+        [RuntimeImport(Redhawk.BaseName, "RhpFirstChanceExceptionNotification")]
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern void RhpFirstChanceExceptionNotification();
+#endif
+
 #if TARGET_WINDOWS
         [RuntimeImport(Redhawk.BaseName, "RhpCopyContextFromExInfo")]
         [MethodImpl(MethodImplOptions.InternalCall)]

src/coreclr/nativeaot/Runtime/EHHelpers.cpp

@@ -31,6 +31,8 @@
 #include "MethodTable.inl"
 #include "CommonMacros.inl"
 #include "NativeContext.h"
+#include <minipal/debugger.h>
+#include "corexcep.h"
 
 struct MethodRegionInfo
 {
@@ -85,6 +87,26 @@ FCIMPL0(void, RhpValidateExInfoStack)
 }
 FCIMPLEND
 
+#ifdef TARGET_WINDOWS
+FCIMPL0(void, RhpFirstChanceExceptionNotification)
+{
+    // Throw an SEH exception and immediately catch it. This is used to notify debuggers and other tools
+    // that an exception has been thrown.
+    if (minipal_is_native_debugger_present())
+    {
+        __try
+        {
+            RaiseException(EXCEPTION_COMPLUS, 0, 0, NULL);
+        }
+        __except (EXCEPTION_EXECUTE_HANDLER)
+        {
+            // Do nothing, we just want to notify the debugger.
+        }
+    }
+}
+FCIMPLEND
+#endif // TARGET_WINDOWS
+
 FCIMPL0(void, RhpClearThreadDoNotTriggerGC)
 {
     Thread * pThisThread = ThreadStore::GetCurrentThread();

src/coreclr/nativeaot/Runtime/corexcep.h

@@ -0,0 +1,4 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#include "../../inc/corexcep.h"

src/coreclr/vm/exceptionhandling.cpp

@@ -605,7 +605,7 @@ ProcessCLRException(IN     PEXCEPTION_RECORD   pExceptionRecord,
                 // The 3rd argument passes to PopExplicitFrame is normally the parent SP to correctly handle InlinedCallFrame embbeded
                 // in parent managed frame. But at this point there are no further managed frames are on the stack, so we can pass NULL.
                 // Also don't pop the GC frames, their destructor will pop them as the exception propagates.
-                // NOTE: this needs to be popped in the 2nd pass to ensure that crash dumps and Watson get the dump with these still 
+                // NOTE: this needs to be popped in the 2nd pass to ensure that crash dumps and Watson get the dump with these still
                 // present.
                 ExInfo *pExInfo = (ExInfo*)pThread->GetExceptionState()->GetCurrentExceptionTracker();
                 void *sp = (void*)GetRegdisplaySP(pExInfo->m_frameIter.m_crawl.GetRegisterSet());
@@ -637,7 +637,7 @@ ProcessCLRException(IN     PEXCEPTION_RECORD   pExceptionRecord,
 
 #ifdef TARGET_X86
         CallRtlUnwind((PEXCEPTION_REGISTRATION_RECORD)pEstablisherFrame, NULL, pExceptionRecord, 0);
-#else        
+#else
         ClrUnwindEx(pExceptionRecord,
                     (UINT_PTR)pThread,
                     INVALID_RESUME_ADDRESS,
@@ -1578,19 +1578,21 @@ BOOL HandleHardwareException(PAL_SEHException* ex)
 
 void FirstChanceExceptionNotification()
 {
-#ifndef TARGET_UNIX
+#ifdef TARGET_WINDOWS
+    // Throw an SEH exception and immediately catch it. This is used to notify debuggers and other tools
+    // that an exception has been thrown.
     if (minipal_is_native_debugger_present())
     {
-        PAL_TRY(VOID *, unused, NULL)
+        __try
         {
             RaiseException(EXCEPTION_COMPLUS, 0, 0, NULL);
         }
-        PAL_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
+        __except (EXCEPTION_EXECUTE_HANDLER)
         {
+            // Do nothing, we just want to notify the debugger.
         }
-        PAL_ENDTRY;
     }
-#endif // TARGET_UNIX
+#endif // TARGET_WINDOWS
 }
 
 VOID DECLSPEC_NORETURN DispatchManagedException(OBJECTREF throwable, CONTEXT* pExceptionContext, EXCEPTION_RECORD* pExceptionRecord)
@@ -3347,7 +3349,7 @@ extern "C" void QCALLTYPE ResumeAtInterceptionLocation(REGDISPLAY* pvRegDisplay)
     uResumePC = codeInfo.GetJitManager()->GetCodeAddressForRelOffset(codeInfo.GetMethodToken(), static_cast<DWORD>(ulRelOffset));
 
     SetIP(pvRegDisplay->pCurrentContext, uResumePC);
-    
+
     STRESS_LOG2(LF_EH, LL_INFO100, "Resuming at interception location at IP=%p, SP=%p\n", uResumePC, GetSP(pvRegDisplay->pCurrentContext));
     ClrRestoreNonvolatileContext(pvRegDisplay->pCurrentContext, targetSSP);
 }
@@ -3442,7 +3444,7 @@ extern "C" CLR_BOOL QCALLTYPE EHEnumInitFromStackFrameIterator(StackFrameIterato
     IJitManager* pJitMan = pFrameIter->m_crawl.GetJitManager();
     const METHODTOKEN& MethToken = pFrameIter->m_crawl.GetMethodToken();
     pExtendedEHEnum->EHCount = pJitMan->InitializeEHEnumeration(MethToken, pEHEnum);
-    EH_LOG((LL_INFO100, "Initialized EH enumeration, %d clauses found\n", pExtendedEHEnum->EHCount));    
+    EH_LOG((LL_INFO100, "Initialized EH enumeration, %d clauses found\n", pExtendedEHEnum->EHCount));
 
     if (pExtendedEHEnum->EHCount == 0)
     {
@@ -4071,7 +4073,7 @@ extern "C" CLR_BOOL QCALLTYPE SfiNext(StackFrameIterator* pThis, uint* uExCollid
 
                             // Unwind to the frame of the prevExInfo
                             ExInfo* pPrevExInfo = pThis->GetNextExInfo();
-                            EH_LOG((LL_INFO100, "SfiNext: collided with previous exception handling, skipping from IP=%p, SP=%p to IP=%p, SP=%p\n", 
+                            EH_LOG((LL_INFO100, "SfiNext: collided with previous exception handling, skipping from IP=%p, SP=%p to IP=%p, SP=%p\n",
                                     GetControlPC(&pTopExInfo->m_regDisplay), GetRegdisplaySP(&pTopExInfo->m_regDisplay),
                                     GetControlPC(&pPrevExInfo->m_regDisplay), GetRegdisplaySP(&pPrevExInfo->m_regDisplay)));