[libFuzzer] Properly handle exceptions with UnhandledExceptionFilter.

Use SetUnhandledExceptionFilter instead of AddVectoredExceptionHandler.

According to the documentation on Structured Exception Handling, this is the
order for the Exception Dispatching:
+ If the process is being debugged, the system notifies the debugger.
+ The Vectored Exception Handler is called.
+ The system attempts to locate a frame-based exception handler by searching the
 stack frames of the thread in which the exception occurred.
+ If no frame-based handler can be found, the UnhandledExceptionFilter filter is
 called.
+ Default handling based on the exception type.

So, similar to what we do for asan, we should use SetUnhandledExceptionFilter
instead of AddVectoredExceptionHandler, so user's code that is being fuzzed can
execute frame-based exception handlers before we catch them . We want to catch
unhandled exceptions, not all the exceptions.

Differential Revision: https://reviews.llvm.org/D29462

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293920 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Fuzzer/FuzzerUtilWindows.cpp b/lib/Fuzzer/FuzzerUtilWindows.cpp
index 7fd09e0ed1bc735b661811e4ab5aaf511627a9e0..08bb3cf3be157b3a98055f751d4f3ed412f0433f 100644 (file)
--- a/lib/Fuzzer/FuzzerUtilWindows.cpp
+++ b/lib/Fuzzer/FuzzerUtilWindows.cpp
@@ -28,7 +28,7 @@ namespace fuzzer {
 
 static const FuzzingOptions* HandlerOpt = nullptr;
 
-LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ExceptionInfo) {
+static LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ExceptionInfo) {
   switch (ExceptionInfo->ExceptionRecord->ExceptionCode) {
     case EXCEPTION_ACCESS_VIOLATION:
     case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
@@ -126,10 +126,7 @@ void SetSignalHandler(const FuzzingOptions& Options) {
 
   if (Options.HandleSegv || Options.HandleBus || Options.HandleIll ||
       Options.HandleFpe)
-    if (!AddVectoredExceptionHandler(1, ExceptionHandler)) {
-      Printf("libFuzzer: AddVectoredExceptionHandler failed.\n");
-      exit(1);
-    }
+    SetUnhandledExceptionFilter(ExceptionHandler);
 
   if (Options.HandleAbrt)
     if (SIG_ERR == signal(SIGABRT, CrashHandler)) {