[llvm-branch-commits] [llvm] dbe9c3a - [Support] Don't modify the current EH context during stack unwinding

[Hans Wennborg via llvm-branch-commits]

Author: Reid Kleckner
Date: 2020-02-11T11:03:58+01:00
New Revision: dbe9c3a82dd7db8e50acb008f21a273c55fa5c82

URL: https://github.com/llvm/llvm-project/commit/dbe9c3a82dd7db8e50acb008f21a273c55fa5c82
DIFF: https://github.com/llvm/llvm-project/commit/dbe9c3a82dd7db8e50acb008f21a273c55fa5c82.diff

LOG: [Support] Don't modify the current EH context during stack unwinding

Copy it instead. Otherwise, key registers (such as RBP) may get zeroed
out by the stack unwinder.

Fixes CrashRecoveryTest.DumpStackCleanup with MSVC in release builds.

Reviewed By: stella.stamenova

Differential Revision: https://reviews.llvm.org/D73809

(cherry picked from commit b074acb82f7e75a189fa7933b09627241b166121)

Added: 
    

Modified: 
    llvm/lib/Support/Windows/Signals.inc

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Support/Windows/Signals.inc b/llvm/lib/Support/Windows/Signals.inc
index 8b525f1bd4ac..09e19ae41f1a 100644
--- a/llvm/lib/Support/Windows/Signals.inc
+++ b/llvm/lib/Support/Windows/Signals.inc
@@ -820,7 +820,13 @@ static LONG WINAPI LLVMUnhandledExceptionFilter(LPEXCEPTION_POINTERS ep) {
                    << "\n";
   }
 
-  LocalPrintStackTrace(llvm::errs(), ep ? ep->ContextRecord : nullptr);
+  // Stack unwinding appears to modify the context. Copy it to preserve the
+  // caller's context.
+  CONTEXT ContextCopy;
+  if (ep)
+    memcpy(&ContextCopy, ep->ContextRecord, sizeof(ContextCopy));
+
+  LocalPrintStackTrace(llvm::errs(), ep ? &ContextCopy : nullptr);
 
   return EXCEPTION_EXECUTE_HANDLER;
 }