[cfi] Safe handling of unaddressable vtable pointers (clang).

Avoid crashing when printing diagnostics for vtable-related CFI
errors. In diagnostic mode, the frontend does an additional check of
the vtable pointer against the set of all known vtable addresses and
lets the runtime handler know if it is safe to inspect the vtable.

http://reviews.llvm.org/D16823

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259716 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 3 deletions

diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index 0853d6aa1f..2adb74aa0f 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -2607,10 +2607,22 @@ void CodeGenFunction::EmitVTablePtrCheck(const CXXRecordDecl *RD,
   auto TypeId = CGM.CreateCfiIdForTypeMetadata(MD);
   if (CGM.getCodeGenOpts().SanitizeCfiCrossDso && TypeId) {
     EmitCfiSlowPathCheck(M, BitSetTest, TypeId, CastedVTable, StaticData);
-  } else {
-    EmitCheck(std::make_pair(BitSetTest, M), "cfi_check_fail", StaticData,
-              CastedVTable);
+    return;
   }
+
+  if (CGM.getCodeGenOpts().SanitizeTrap.has(M)) {
+    EmitTrapCheck(BitSetTest);
+    return;
+  }
+
+  llvm::Value *AllVtables = llvm::MetadataAsValue::get(
+      CGM.getLLVMContext(),
+      llvm::MDString::get(CGM.getLLVMContext(), "all-vtables"));
+  llvm::Value *ValidVtable =
+      Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::bitset_test),
+                         {CastedVTable, AllVtables});
+  EmitCheck(std::make_pair(BitSetTest, M), "cfi_check_fail", StaticData,
+            {CastedVTable, ValidVtable});
 }
 
 // FIXME: Ideally Expr::IgnoreParenNoopCasts should do this, but it doesn't do