[Runtime] Use ptrauth qualifiers on metadata and superclass fields.

Author: mikeash

include/swift/ABI/Metadata.h

@@ -1035,7 +1035,9 @@ struct TargetAnyClassMetadata : public TargetHeapMetadata<Runtime> {
   // Note that ObjC classes do not have a metadata header.
 
   /// The metadata for the superclass.  This is null for the root class.
-  ConstTargetMetadataPointer<Runtime, swift::TargetClassMetadata> Superclass;
+  TargetSignedPointer<Runtime, const TargetClassMetadata<Runtime> *
+                                   __ptrauth_swift_objc_superclass>
+      Superclass;
 
 #if SWIFT_OBJC_INTEROP
   /// The cache data is used for certain dynamic lookups; it is owned

include/swift/ABI/MetadataValues.h

@@ -1209,6 +1209,10 @@ namespace SpecialPointerAuthDiscriminators {
   const uint16_t OpaqueReadResumeFunction = 56769;
   const uint16_t OpaqueModifyResumeFunction = 3909;
 
+  /// ObjC class pointers.
+  const uint16_t ObjCISA = 0x6AE1;
+  const uint16_t ObjCSuperclass = 0xB5AB;
+
   /// Resilient class stub initializer callback
   const uint16_t ResilientClassStubInitCallback = 0xC671;
 

include/swift/Remote/MetadataReader.h

@@ -500,7 +500,7 @@ class MetadataReader {
       return StoredPointer();
 
     auto classMeta = cast<TargetClassMetadata<Runtime>>(meta);
-    return classMeta->Superclass;
+    return stripSignedPointer(classMeta->Superclass);
   }
 
   /// Given a remote pointer to class metadata, attempt to discover its class
@@ -534,9 +534,9 @@ class MetadataReader {
     size_t start = isaAndRetainCountSize;
 
     auto classMeta = cast<TargetClassMetadata<Runtime>>(meta);
-    while (classMeta->Superclass) {
+    while (stripSignedPointer(classMeta->Superclass)) {
       classMeta = cast<TargetClassMetadata<Runtime>>(
-          readMetadata(classMeta->Superclass));
+          readMetadata(stripSignedPointer(classMeta->Superclass)));
 
       // Subtract the size contribution of the isa and retain counts from 
       // the super class.
@@ -1751,7 +1751,8 @@ class MetadataReader {
         if (descriptorAddress || !skipArtificialSubclasses)
           return static_cast<StoredPointer>(descriptorAddress);
 
-        auto superclassMetadataAddress = classMeta->Superclass;
+        auto superclassMetadataAddress =
+            stripSignedPointer(classMeta->Superclass);
         if (!superclassMetadataAddress)
           return 0;
 
@@ -2661,11 +2662,11 @@ class MetadataReader {
     BuiltType BuiltObjCClass = Builder.createObjCClassType(std::move(className));
     if (!BuiltObjCClass) {
       // Try the superclass.
-      if (!classMeta->Superclass)
+      if (!stripSignedPointer(classMeta->Superclass))
         return BuiltType();
 
-      BuiltObjCClass = readTypeFromMetadata(classMeta->Superclass,
-                                            skipArtificialSubclasses);
+      BuiltObjCClass = readTypeFromMetadata(
+          stripSignedPointer(classMeta->Superclass), skipArtificialSubclasses);
     }
 
     TypeCache[origMetadataPtr] = BuiltObjCClass;

include/swift/Runtime/Config.h

@@ -250,6 +250,9 @@ extern uintptr_t __COMPATIBILITY_LIBRARIES_CANNOT_CHECK_THE_IS_SWIFT_BIT_DIRECTL
 #define __ptrauth_swift_dispatch_invoke_function                               \
   __ptrauth(ptrauth_key_process_independent_code, 1,                           \
             SpecialPointerAuthDiscriminators::DispatchInvokeFunction)
+#define __ptrauth_swift_objc_superclass                                        \
+  __ptrauth(ptrauth_key_process_independent_data, 1,                           \
+            swift::SpecialPointerAuthDiscriminators::ObjCSuperclass)
 #define swift_ptrauth_sign_opaque_read_resume_function(__fn, __buffer)         \
   ptrauth_auth_and_resign(__fn, ptrauth_key_function_pointer, 0,               \
                           ptrauth_key_process_independent_code,                \
@@ -276,6 +279,7 @@ extern uintptr_t __COMPATIBILITY_LIBRARIES_CANNOT_CHECK_THE_IS_SWIFT_BIT_DIRECTL
 #define __ptrauth_swift_cancellation_notification_function
 #define __ptrauth_swift_escalation_notification_function
 #define __ptrauth_swift_dispatch_invoke_function
+#define __ptrauth_swift_objc_superclass
 #define __ptrauth_swift_runtime_function_entry
 #define __ptrauth_swift_runtime_function_entry_with_key(__key)
 #define __ptrauth_swift_runtime_function_entry_strip(__fn) (__fn)

stdlib/public/SwiftShims/HeapObject.h

@@ -35,6 +35,13 @@ typedef struct HeapMetadata HeapMetadata;
 typedef struct HeapObject HeapObject;
 #endif
 
+#if !defined(__swift__) && __has_feature(ptrauth_calls)
+#include <ptrauth.h>
+#endif
+#ifndef __ptrauth_objc_isa_pointer
+#define __ptrauth_objc_isa_pointer
+#endif
+
 // The members of the HeapObject header that are not shared by a
 // standard Objective-C instance
 #define SWIFT_HEAPOBJECT_NON_OBJC_MEMBERS       \
@@ -44,7 +51,7 @@ typedef struct HeapObject HeapObject;
 /// This must match RefCountedStructTy in IRGen.
 struct HeapObject {
   /// This is always a valid pointer to a metadata object.
-  HeapMetadata const *metadata;
+  HeapMetadata const *__ptrauth_objc_isa_pointer metadata;
 
   SWIFT_HEAPOBJECT_NON_OBJC_MEMBERS;