[clang] Sign the v-table pointer in ObjC exception RTTI.

Author: ahmedbougacha

clang/lib/CodeGen/CGObjCMac.cpp

@@ -7894,11 +7894,26 @@ CGObjCNonFragileABIMac::GetInterfaceEHType(const ObjCInterfaceDecl *ID,
   }
 
   llvm::Value *VTableIdx = llvm::ConstantInt::get(CGM.Int32Ty, 2);
+  llvm::Constant *VTablePtr = llvm::ConstantExpr::getInBoundsGetElementPtr(
+      VTableGV->getValueType(), VTableGV, VTableIdx);
+
   ConstantInitBuilder builder(CGM);
   auto values = builder.beginStruct(ObjCTypes.EHTypeTy);
-  values.add(
-    llvm::ConstantExpr::getInBoundsGetElementPtr(VTableGV->getValueType(),
-                                                 VTableGV, VTableIdx));
+
+  if (auto &Schema =
+          CGM.getCodeGenOpts().PointerAuth.CXXTypeInfoVTablePointer) {
+    uint32_t discrimination = 0;
+    if (Schema.hasOtherDiscrimination()) {
+      assert(Schema.getOtherDiscrimination() ==
+             PointerAuthSchema::Discrimination::Constant);
+      discrimination = Schema.getConstantDiscrimination();
+    }
+    values.addSignedPointer(
+        VTablePtr, Schema.getKey(), Schema.isAddressDiscriminated(),
+        llvm::ConstantInt::get(CGM.IntPtrTy, discrimination));
+  } else {
+    values.add(VTablePtr);
+  }
   values.add(GetClassName(ClassName));
   values.add(GetClassGlobal(ID, /*metaclass*/ false, NotForDefinition));
 

clang/test/CodeGenObjC/ptrauth-attr-exception.m

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -emit-llvm -fexceptions -fobjc-exceptions -o - %s | FileCheck %s
+
+__attribute__((objc_root_class))
+@interface Root {
+  Class isa;
+}
+@end
+
+__attribute__((objc_exception))
+@interface A : Root
+@end
+
+@implementation A
+@end
+
+// CHECK: @objc_ehtype_vtable.ptrauth = private constant { ptr, i32, i64, i64 } { ptr getelementptr inbounds (ptr, ptr @objc_ehtype_vtable, i32 2), i32 2, i64 0, i64 0 }, section "llvm.ptrauth", align 8
+// CHECK: @"OBJC_EHTYPE_$_A" = global {{%.*}} { ptr @objc_ehtype_vtable.ptrauth,