[x86/Linux] Adds Dummy Exception Handler (#8613)

This commit adds a dummy exeption handler to enable x86/Linux build.

This commit also reverts 7b92136d5ee to make it easy to enable
WIN64EXCEPTIONS in x86/Linux.

3 files changed, 59 insertions, 7 deletions

diff --git a/src/vm/exceptmacros.h b/src/vm/exceptmacros.h
index 9b6c5549f7..2af064c96d 100644
--- a/src/vm/exceptmacros.h
+++ b/src/vm/exceptmacros.h
@@ -296,7 +296,7 @@ VOID DECLSPEC_NORETURN RaiseTheExceptionInternalOnly(OBJECTREF throwable, BOOL r
 void UnwindAndContinueRethrowHelperInsideCatch(Frame* pEntryFrame, Exception* pException);
 VOID DECLSPEC_NORETURN UnwindAndContinueRethrowHelperAfterCatch(Frame* pEntryFrame, Exception* pException);
 
-#if defined(FEATURE_PAL) && defined(WIN64EXCEPTIONS)
+#ifdef FEATURE_PAL
 VOID DECLSPEC_NORETURN DispatchManagedException(PAL_SEHException& ex, bool isHardwareException);
 
 #define INSTALL_MANAGED_EXCEPTION_DISPATCHER        \
@@ -334,14 +334,14 @@ VOID DECLSPEC_NORETURN DispatchManagedException(PAL_SEHException& ex, bool isHar
             UNREACHABLE();                                                                          \
         }
 
-#else // FEATURE_PAL && WIN64EXCEPTIONS
+#else // FEATURE_PAL
 
 #define INSTALL_MANAGED_EXCEPTION_DISPATCHER
 #define UNINSTALL_MANAGED_EXCEPTION_DISPATCHER
 #define INSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP
 #define UNINSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP
 
-#endif // FEATURE_PAL && WIN64EXCEPTIONS
+#endif // FEATURE_PAL
 
 #define INSTALL_UNWIND_AND_CONTINUE_HANDLER_NO_PROBE                                        \
     {                                                                                       \
diff --git a/src/vm/i386/excepcpu.h b/src/vm/i386/excepcpu.h
index 3f2f0810a7..ff540e784b 100644
--- a/src/vm/i386/excepcpu.h
+++ b/src/vm/i386/excepcpu.h
@@ -28,12 +28,37 @@ class Thread;
                               // Actually, the handler getting set is properly registered
 #endif
 
+#ifdef FEATURE_PAL
+
+extern VOID SetSEHRecord(PEXCEPTION_REGISTRATION_RECORD record);
+extern VOID ResetSEHRecord(PEXCEPTION_REGISTRATION_RECORD record);
+
+#define INSTALL_SEH_RECORD(record)                                        \
+    SetSEHRecord(record);                                                 \
+
+#define UNINSTALL_SEH_RECORD(record)                                      \
+    ResetSEHRecord(record);
+
+#else  // FEATURE_PAL
+
+#define INSTALL_SEH_RECORD(record)                                        \
+    {                                                                     \
+       (record)->Next = (PEXCEPTION_REGISTRATION_RECORD)__readfsdword(0); \
+       __writefsdword(0, (DWORD) (record));                               \
+    }
+
+#define UNINSTALL_SEH_RECORD(record)                                      \
+    {                                                                     \
+        __writefsdword(0, (DWORD) ((record)->Next));                      \
+    }
+
+#endif // FEATURE_PAL
+
 #define INSTALL_EXCEPTION_HANDLING_RECORD(record)               \
     {                                                           \
         PEXCEPTION_REGISTRATION_RECORD __record = (record);     \
         _ASSERTE(__record < GetCurrentSEHRecord());             \
-        __record->Next = (PEXCEPTION_REGISTRATION_RECORD)__readfsdword(0); \
-        __writefsdword(0, (DWORD)__record);                     \
+        INSTALL_SEH_RECORD(record);                             \
     }
 
 //
@@ -44,7 +69,7 @@ class Thread;
     {                                                           \
         PEXCEPTION_REGISTRATION_RECORD __record = (record);     \
         _ASSERTE(__record == GetCurrentSEHRecord());            \
-        __writefsdword(0, (DWORD)__record->Next);               \
+        UNINSTALL_SEH_RECORD(record);                           \
     }
 
 // stackOverwriteBarrier is used to detect overwriting of stack which will mess up handler registration
diff --git a/src/vm/i386/excepx86.cpp b/src/vm/i386/excepx86.cpp
index 025098c3ad..71200f671f 100644
--- a/src/vm/i386/excepx86.cpp
+++ b/src/vm/i386/excepx86.cpp
@@ -1971,11 +1971,17 @@ PTR_CONTEXT GetCONTEXTFromRedirectedStubStackFrame(CONTEXT * pContext)
 }
 
 #if !defined(DACCESS_COMPILE)
+#ifdef FEATURE_PAL
+static PEXCEPTION_REGISTRATION_RECORD CurrentSEHRecord = EXCEPTION_CHAIN_END;
+#endif
 
 PEXCEPTION_REGISTRATION_RECORD GetCurrentSEHRecord()
 {
     WRAPPER_NO_CONTRACT;
 
+#ifdef FEATURE_PAL
+    LPVOID fs0 = CurrentSEHRecord;
+#else  // FEATURE_PAL
     LPVOID fs0 = (LPVOID)__readfsdword(0);
 
 #if 0  // This walk is too expensive considering we hit it every time we a CONTRACT(NOTHROW)
@@ -2006,11 +2012,26 @@ PEXCEPTION_REGISTRATION_RECORD GetCurrentSEHRecord()
         pEHR = pEHR->Next;
     }
 #endif
-#endif
+#endif // 0
+#endif // FEATURE_PAL
 
     return (EXCEPTION_REGISTRATION_RECORD*) fs0;
 }
 
+#ifdef FEATURE_PAL
+VOID SetSEHRecord(PEXCEPTION_REGISTRATION_RECORD record)
+{
+    WRAPPER_NO_CONTRACT;
+    record->Next = CurrentSEHRecord;
+    CurrentSEHRecord = record;
+}
+
+VOID ResetSEHRecord(PEXCEPTION_REGISTRATION_RECORD record)
+{
+    CurrentSEHRecord = record->Next;
+}
+#endif // FEATURE_PAL
+
 PEXCEPTION_REGISTRATION_RECORD GetFirstCOMPlusSEHRecord(Thread *pThread) {
     WRAPPER_NO_CONTRACT;
 #ifndef FEATURE_PAL
@@ -3748,4 +3769,10 @@ AdjustContextForVirtualStub(
     return TRUE;
 }
 
+#ifdef FEATURE_PAL
+VOID DECLSPEC_NORETURN DispatchManagedException(PAL_SEHException& ex, bool isHardwareException)
+{
+    UNREACHABLE();
+}
+#endif
 #endif // !DACCESS_COMPILE