Allow structural redefinition on non-final classes.

This adds support for structurally redefining non-final,
non-finalizable classes. The only restriction is that one cannot
redefine a class at the same time as any of its supertypes, if a
structural redefinition is occurring. The structural redefinition may
not remove any fields or methods, change the superclass or change the
implemented interfaces. Adding new methods or fields, both static or
non-static, public, private, protected, or package-private, is
supported.

Test: ./test.py --host
Bug: 134162467
Bug: 144168550
Change-Id: I32e9e854b3e56270170b10e8f5aba9de8f6bfdfa

1 files changed, 19 insertions, 0 deletions

diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 438d5cb709..d4f98afe84 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -3359,12 +3359,31 @@ static bool IsReservedBootClassPathDescriptor(const char* descriptor) {
       StartsWith(descriptor_sv, "Landroid/media/");
 }
 
+// Helper for maintaining DefineClass counting. We need to notify callbacks when we start/end a
+// define-class and how many recursive DefineClasses we are at in order to allow for doing  things
+// like pausing class definition.
+struct ScopedDefiningClass {
+ public:
+  explicit ScopedDefiningClass(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) : self_(self) {
+    Runtime::Current()->GetRuntimeCallbacks()->BeginDefineClass();
+    self_->IncrDefineClassCount();
+  }
+  ~ScopedDefiningClass() REQUIRES_SHARED(Locks::mutator_lock_) {
+    self_->DecrDefineClassCount();
+    Runtime::Current()->GetRuntimeCallbacks()->EndDefineClass();
+  }
+
+ private:
+  Thread* self_;
+};
+
 ObjPtr<mirror::Class> ClassLinker::DefineClass(Thread* self,
                                                const char* descriptor,
                                                size_t hash,
                                                Handle<mirror::ClassLoader> class_loader,
                                                const DexFile& dex_file,
                                                const dex::ClassDef& dex_class_def) {
+  ScopedDefiningClass sdc(self);
   StackHandleScope<3> hs(self);
   auto klass = hs.NewHandle<mirror::Class>(nullptr);