Use [UN]INSTALL_MANAGED_EXCEPTION_DISPATCHER_EX to backpatch CallDescrWorkerInternal SEH record on x86/funclets

src/coreclr/vm/exceptionhandling.h

@@ -22,6 +22,12 @@ ProcessCLRException(IN     PEXCEPTION_RECORD     pExceptionRecord,
                     IN OUT PT_CONTEXT            pContextRecord,
                     IN OUT PT_DISPATCHER_CONTEXT pDispatcherContext);
 
+EXTERN_C EXCEPTION_DISPOSITION __cdecl
+CallDescrWorkerUnwindFrameChainHandler(IN     PEXCEPTION_RECORD     pExceptionRecord,
+                                       IN     PVOID                 pEstablisherFrame,
+                                       IN OUT PT_CONTEXT            pContextRecord,
+                                       IN OUT PT_DISPATCHER_CONTEXT pDispatcherContext);
+
 VOID DECLSPEC_NORETURN DispatchManagedException(OBJECTREF throwable, CONTEXT *pExceptionContext, EXCEPTION_RECORD *pExceptionRecord = NULL);
 VOID DECLSPEC_NORETURN DispatchManagedException(OBJECTREF throwable);
 VOID DECLSPEC_NORETURN DispatchManagedException(RuntimeExceptionKind reKind);

src/coreclr/vm/exceptmacros.h

@@ -322,6 +322,41 @@ VOID DECLSPEC_NORETURN DispatchManagedException(PAL_SEHException& ex, bool isHar
             UNREACHABLE();                                                                          \
         }
 
+#elif defined(TARGET_X86) && defined(TARGET_WINDOWS) && defined(FEATURE_EH_FUNCLETS)
+
+#define INSTALL_MANAGED_EXCEPTION_DISPATCHER
+#define UNINSTALL_MANAGED_EXCEPTION_DISPATCHER
+
+#define INSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP
+#define UNINSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP
+
+// We use [UN]INSTALL_MANAGED_EXCEPTION_DISPATCHER_EX to backpatch the SEH record installed
+// in CallDescrWorkerInternal from ProcessCLRException to CallDescrWorkerUnwindFrameChainHandler
+// when throwing an exception. This ensures that class loading exceptions are propagated through
+// unmanaged code before being forwarded to the managed one.
+
+#define INSTALL_MANAGED_EXCEPTION_DISPATCHER_EX \
+        try \
+        {
+
+#define UNINSTALL_MANAGED_EXCEPTION_DISPATCHER_EX(nativeRethrow) \
+        } \
+        catch (...) \
+        { \
+            if (nativeRethrow) \
+            { \
+                PEXCEPTION_REGISTRATION_RECORD pExceptionRecord = GetCurrentSEHRecord(); \
+                _ASSERTE(pExceptionRecord != EXCEPTION_CHAIN_END); \
+                while (pExceptionRecord->Handler != (PEXCEPTION_ROUTINE)ProcessCLRException) \
+                { \
+                    pExceptionRecord = pExceptionRecord->Next; \
+                    _ASSERTE(pExceptionRecord != EXCEPTION_CHAIN_END); \
+                } \
+                pExceptionRecord->Handler = (PEXCEPTION_ROUTINE)CallDescrWorkerUnwindFrameChainHandler; \
+            } \
+            throw; \
+        }
+
 #else // TARGET_UNIX
 
 #define INSTALL_MANAGED_EXCEPTION_DISPATCHER

src/coreclr/vm/i386/asmhelpers.asm

@@ -1215,30 +1215,8 @@ _ThePreStub@0 proc public
 
     push        esi
 
-ifdef FEATURE_EH_FUNCLETS
-    cmp         [esi + 24], CallDescrWorkerInternalReturnAddress
-    jne         NoSEHReplace
-
-    ; If we were called from CallDescrWorkerInternal then swap the last
-    ; SEH registration for _CallDescrWorkerUnwindFrameChainHandler to ensure
-    ; that class loading exceptions are propagated through unmanaged code
-    ; before being forwarded to the managed one.
-    mov         edi, fs:[0]
-    ; mov         esi, [edi]
-    ; mov         fs:[0], esi
-    mov         [edi + 4], _CallDescrWorkerUnwindFrameChainHandler
-    call        _PreStubWorker@8
-    mov         [edi + 4], _ProcessCLRException
-    ; mov         fs:[0], edi
-    jmp         AfterPreStubWorker
-
-NoSEHReplace:
-endif ; FEATURE_EH_FUNCLETS
-
     call        _PreStubWorker@8
 
-AfterPreStubWorker:
-
     ; eax now contains replacement stub. PreStubWorker will never return
     ; NULL (it throws an exception if stub creation fails.)