Reflection: Support reading the remote process's isaMask

Also, use the instance layout entry point in swift-reflection-test,
so that we can dump the layout of a class instance and not the
lowering of the reference value.

Author: slavapestov

include/swift/Reflection/ReflectionContext.h

@@ -65,6 +65,10 @@ class ReflectionContext
     getBuilder().addReflectionInfo(I);
   }
 
+  std::pair<bool, StoredPointer> readerIsaMask() {
+    return getReader().readIsaMask();
+  }
+
   /// Return a description of the layout of a heap object having the given
   /// metadata as its isa pointer.
   const TypeInfo *getInstanceTypeInfo(StoredPointer MetadataAddress) {

include/swift/Remote/MetadataReader.h

@@ -425,6 +425,10 @@ class MetadataReader {
   using OwnedCaptureDescriptor =
     std::unique_ptr<const CaptureDescriptor, delete_with_free>;
 
+  /// Cached isa mask.
+  StoredPointer isaMask;
+  bool hasIsaMask = false;
+
 public:
   BuilderType Builder;
 
@@ -456,6 +460,19 @@ class MetadataReader {
     return swift::remote::decodeMangledType(Builder, Node);
   }
 
+  /// Get the remote process's swift_isaMask.
+  std::pair<bool, StoredPointer> readIsaMask() {
+    auto address = Reader->getSymbolAddress("swift_isaMask");
+    if (!address)
+      return {false, 0};
+
+    if (!Reader->readInteger(address, &isaMask))
+      return {false, 0};
+
+    hasIsaMask = true;
+    return {true, isaMask};
+  }
+
   /// Given a remote pointer to metadata, attempt to discover its MetadataKind.
   std::pair<bool, MetadataKind>
   readKindFromMetadata(StoredPointer MetadataAddress) {

include/swift/SwiftRemoteMirror/SwiftRemoteMirror.h

@@ -59,6 +59,12 @@ swift_reflection_addReflectionInfo(SwiftReflectionContextRef ContextRef,
                                    swift_reflection_section_t reflstr);
 
 
+/// Returns a boolean indicating if the isa mask was successfully
+/// read, in which case it is stored in the isaMask out parameter.
+int
+swift_reflection_readIsaMask(SwiftReflectionContextRef ContextRef,
+                             uintptr_t *outIsaMask);
+
 /// Returns an opaque type reference for a metadata pointer, or
 /// NULL if one can't be constructed.
 swift_typeref_t

stdlib/public/SwiftRemoteMirror/SwiftRemoteMirror.cpp

@@ -69,6 +69,15 @@ swift_reflection_addReflectionInfo(SwiftReflectionContextRef ContextRef,
   Context->addReflectionInfo(Info);
 }
 
+int
+swift_reflection_readIsaMask(SwiftReflectionContextRef ContextRef,
+                             uintptr_t *outIsaMask) {
+  auto Context = reinterpret_cast<NativeReflectionContext *>(ContextRef);
+  auto isaMask = Context->readIsaMask();
+  *outIsaMask = isaMask.second;
+  return isaMask.first;
+}
+
 swift_typeref_t
 swift_reflection_typeRefForMetadata(SwiftReflectionContextRef ContextRef,
                                     uintptr_t metadata) {

tools/swift-reflection-test/swift-reflection-test.c

@@ -410,12 +410,19 @@ int doDumpHeapInstance(const char *BinaryFilename) {
                                            Info.reflstr);
       }
 
+      uintptr_t isaMask;
+      if (!swift_reflection_readIsaMask(RC, &isaMask))
+        errorAndExit("Couldn't read isa mask");
+      printf("Parent: isa mask in child address space: 0x%lx\n", isaMask);
+
+      isa &= isaMask;
+
       printf("Parent: metadata pointer in child address space: 0x%lx\n", isa);
       printf("Decoding type reference ...\n");
 
       swift_typeref_t TR = swift_reflection_typeRefForMetadata(RC, isa);
       swift_reflection_dumpTypeRef(TR);
-      swift_reflection_dumpInfoForTypeRef(RC, TR);
+      swift_reflection_dumpInfoForMetadata(RC, isa);
     }
   }