Improve windows hardware exception handling performance (#74426)

* Improve windows hardware exception handling performance

With my recent change that modified hardware exception handling so that
the related managed exception is thrown directly from the vectored
exception handler, the performance of handling such exceptions have
regressed. Several exception handling dotnet/performance microbenchmarks
have regressed upto 15%.
The reason for the regression was the larger number of stack frames
between the exception raising and the actual handler frame. With a
recent change that @AntonLapounov has made to fix process corrupting
exceptions handling, the regression went down to 8%. This change moves
the location where we raise the exception down to the
ClrVectoredExceptionHandlerShim, which means to the closest possible
frame to the managed code.
This gets rid of the regression completely.

src/coreclr/vm/excep.cpp

@@ -6723,27 +6723,16 @@ bool ShouldHandleManagedFault(
 
 #ifndef TARGET_UNIX
 
-LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo);
-
-enum VEH_ACTION
-{
-    VEH_NO_ACTION = 0,
-    VEH_EXECUTE_HANDLE_MANAGED_EXCEPTION,
-    VEH_CONTINUE_EXECUTION,
-    VEH_CONTINUE_SEARCH,
-    VEH_EXECUTE_HANDLER
-};
-
-
+VEH_ACTION WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo);
 VEH_ACTION WINAPI CLRVectoredExceptionHandlerPhase3(PEXCEPTION_POINTERS pExceptionInfo);
 
-LONG WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo)
+VEH_ACTION WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo)
 {
     // It is not safe to execute code inside VM after we shutdown EE.  One example is DisablePreemptiveGC
     // will block forever.
     if (g_fForbidEnterEE)
     {
-        return EXCEPTION_CONTINUE_SEARCH;
+        return VEH_CONTINUE_SEARCH;
     }
 
 
@@ -6833,7 +6822,7 @@ LONG WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo)
             pExceptionInfo->ContextRecord->Rip = hijackArgs.ReturnAddress;
         }
 
-        return EXCEPTION_CONTINUE_EXECUTION;
+        return VEH_CONTINUE_EXECUTION;
     }
 #endif
 
@@ -6857,11 +6846,9 @@ LONG WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo)
         //
         // Not an Out-of-memory situation, so no need for a forbid fault region here
         //
-        return EXCEPTION_CONTINUE_SEARCH;
+        return VEH_CONTINUE_SEARCH;
     }
 
-    LONG retVal = 0;
-
     // We can't probe here, because we won't return from the CLRVectoredExceptionHandlerPhase2
     // on WIN64
     //
@@ -6872,15 +6859,10 @@ LONG WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo)
         CantAllocHolder caHolder;
     }
 
-    retVal = CLRVectoredExceptionHandlerPhase2(pExceptionInfo);
-
-    //
-        //END_ENTRYPOINT_VOIDRET;
-    //
-    return retVal;
+    return CLRVectoredExceptionHandlerPhase2(pExceptionInfo);
 }
 
-LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo)
+VEH_ACTION WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo)
 {
     //
     // DO NOT USE CONTRACTS HERE AS THIS ROUTINE MAY NEVER RETURN.  You can use
@@ -6914,27 +6896,16 @@ LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo
         action = CLRVectoredExceptionHandlerPhase3(pExceptionInfo);
     }
 
-    if (action == VEH_CONTINUE_EXECUTION)
+    if ((action == VEH_CONTINUE_EXECUTION) || (action == VEH_CONTINUE_SEARCH) || (action == VEH_EXECUTE_HANDLER))
     {
-        return EXCEPTION_CONTINUE_EXECUTION;
-    }
-
-    if (action == VEH_CONTINUE_SEARCH)
-    {
-        return EXCEPTION_CONTINUE_SEARCH;
-    }
-
-    if (action == VEH_EXECUTE_HANDLER)
-    {
-        return EXCEPTION_EXECUTE_HANDLER;
+        return action;
     }
 
 #if defined(FEATURE_EH_FUNCLETS)
 
     if (action == VEH_EXECUTE_HANDLE_MANAGED_EXCEPTION)
     {
-        HandleManagedFault(pExceptionInfo->ExceptionRecord, pExceptionInfo->ContextRecord);
-        return EXCEPTION_CONTINUE_EXECUTION;
+        return action;
     }
 
 #endif // defined(FEATURE_EH_FUNCLETS)
@@ -6954,7 +6925,7 @@ LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo
         // the choice to break the no-trigger region after taking all necessary precautions.
         if (IsDebuggerFault(pExceptionRecord, pExceptionInfo->ContextRecord, pExceptionRecord->ExceptionCode, GetThreadNULLOk()))
         {
-            return EXCEPTION_CONTINUE_EXECUTION;
+            return VEH_CONTINUE_EXECUTION;
         }
     }
 
@@ -6986,11 +6957,11 @@ LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo
         {
             // The breakpoint was not ours.  Someone else can handle it.  (Or if not, we'll get it again as
             //  an unhandled exception.)
-            return EXCEPTION_CONTINUE_SEARCH;
+            return VEH_CONTINUE_SEARCH;
         }
 
         // The breakpoint was from managed or the runtime.  Handle it.
-        return UserBreakpointFilter(pExceptionInfo);
+        return (VEH_ACTION)UserBreakpointFilter(pExceptionInfo);
     }
 
 #if defined(FEATURE_EH_FUNCLETS)
@@ -7008,15 +6979,11 @@ LONG WINAPI CLRVectoredExceptionHandlerPhase2(PEXCEPTION_POINTERS pExceptionInfo
 
     if (fShouldHandleManagedFault)
     {
-        //
-        // HandleManagedFault may never return, so we cannot use a forbid fault region around it.
-        //
-        HandleManagedFault(pExceptionInfo->ExceptionRecord, pExceptionInfo->ContextRecord);
-        return EXCEPTION_CONTINUE_EXECUTION;
-}
+        return VEH_EXECUTE_HANDLE_MANAGED_EXCEPTION;
+    }
 #endif // defined(FEATURE_EH_FUNCLETS)
 
-    return EXCEPTION_EXECUTE_HANDLER;
+    return VEH_EXECUTE_HANDLER;
 }
 
 /*
@@ -7583,13 +7550,34 @@ LONG WINAPI CLRVectoredExceptionHandlerShim(PEXCEPTION_POINTERS pExceptionInfo)
     if (pThread || fExceptionInEE)
     {
         if (!bIsGCMarker)
-            result = CLRVectoredExceptionHandler(pExceptionInfo);
-        else
-            result = EXCEPTION_CONTINUE_EXECUTION;
+        {
+            VEH_ACTION action = CLRVectoredExceptionHandler(pExceptionInfo);
+
+#ifdef FEATURE_EH_FUNCLETS
+            if (VEH_EXECUTE_HANDLE_MANAGED_EXCEPTION == action)
+            {
+                //
+                // HandleManagedFault may never return, so we cannot use a forbid fault region around it.
+                //
+                HandleManagedFault(pExceptionInfo->ExceptionRecord, pExceptionInfo->ContextRecord);
+                return EXCEPTION_CONTINUE_EXECUTION;
+            }
+#endif // FEATURE_EH_FUNCLETS
 
-        if (EXCEPTION_EXECUTE_HANDLER == result)
+            if (VEH_EXECUTE_HANDLER == action)
+            {
+                result = EXCEPTION_CONTINUE_SEARCH;
+            }
+            else
+            {
+                _ASSERTE((action == VEH_CONTINUE_EXECUTION) || (action == VEH_CONTINUE_SEARCH));
+                result = (LONG)action;
+            }
+
+        }
+        else
         {
-            result = EXCEPTION_CONTINUE_SEARCH;
+            result = EXCEPTION_CONTINUE_EXECUTION;
         }
 
 #ifdef _DEBUG

src/coreclr/vm/exceptmacros.h

@@ -240,7 +240,16 @@ VOID DECLSPEC_NORETURN RealCOMPlusThrowOM();
 
 #endif // !defined(FEATURE_EH_FUNCLETS)
 
-LONG WINAPI CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo);
+enum VEH_ACTION
+{
+    VEH_NO_ACTION = -3,
+    VEH_EXECUTE_HANDLE_MANAGED_EXCEPTION = -2,
+    VEH_CONTINUE_EXECUTION = EXCEPTION_CONTINUE_EXECUTION,
+    VEH_CONTINUE_SEARCH = EXCEPTION_CONTINUE_SEARCH,
+    VEH_EXECUTE_HANDLER = EXCEPTION_EXECUTE_HANDLER
+};
+
+VEH_ACTION CLRVectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo);
 
 // Actual UEF worker prototype for use by GCUnhandledExceptionFilter.
 extern LONG InternalUnhandledExceptionFilter_Worker(PEXCEPTION_POINTERS pExceptionInfo);

src/coreclr/vm/i386/excepx86.cpp

@@ -1255,13 +1255,13 @@ CPFH_FirstPassHandler(EXCEPTION_RECORD *pExceptionRecord,
     // Call to the vectored handler to give other parts of the Runtime a chance to jump in and take over an
     // exception before we do too much with it. The most important point in the vectored handler is not to toggle
     // the GC mode.
-    DWORD filter = CLRVectoredExceptionHandler(&ptrs);
+    VEH_ACTION filter = CLRVectoredExceptionHandler(&ptrs);
 
-    if (filter == (DWORD) EXCEPTION_CONTINUE_EXECUTION)
+    if (filter == VEH_CONTINUE_EXECUTION)
     {
         return ExceptionContinueExecution;
     }
-    else if (filter == EXCEPTION_CONTINUE_SEARCH)
+    else if (filter == VEH_CONTINUE_SEARCH)
     {
         return ExceptionContinueSearch;
     }