Avoid instrumentation stack corruption.
While debugging a throwing exception, we may end up updating instrumentation
stack frame after having already walked the native stack. This leads to not pop
instrumentation frames prior to catch handler (or upcall if exception is not
caught) and get it desynchronized with the native stack.
To solve this issue, we need to walk the stack again after having reporting the
exception to the instrumentation listener (for example: the debugger) which
may push new instrumentation stack frames. However we do it only when we know
instrumentation is enabled to not slow down exception delivery when executing
code without instrumentation.
Here are the main changes:
- Creates InstrumentationStackVisitor to compute the number of instrumentation
frames to pop (previously done in CatchBlockStackVisitor). We only count frames
prior to catch handler (or upcall). Popping instrumentation frames is done
after having reported the exception to the instrumentation listener.
- Updates the CatchBlockStackVisitor to remove instrumentation frame handling
and focus only on finding the catch handler and prepare deoptimization.
- Creates CatchFinder class to control both visitors and do the long jump.
Change-Id: I29b3871403f297bfb8c087e27f1330b002f5d56d
diff --git a/runtime/catch_finder.cc b/runtime/catch_finder.cc
new file mode 100644
index 0000000..f0293d7
--- /dev/null
+++ b/runtime/catch_finder.cc
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "catch_finder.h"
+#include "catch_block_stack_visitor.h"
+
+namespace art {
+
+CatchFinder::CatchFinder(Thread* self, const ThrowLocation& throw_location,
+ mirror::Throwable* exception, bool is_deoptimization)
+ : self_(self), context_(self->GetLongJumpContext()),
+ exception_(exception), is_deoptimization_(is_deoptimization), throw_location_(throw_location),
+ method_tracing_active_(is_deoptimization ||
+ Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled()),
+ handler_quick_frame_(nullptr), handler_quick_frame_pc_(0),
+ handler_dex_pc_(0), clear_exception_(false), top_shadow_frame_(nullptr),
+ handler_frame_id_(kInvalidFrameId) {
+ // Exception not in root sets, can't allow GC.
+ last_no_assert_suspension_cause_ = self->StartAssertNoThreadSuspension("Finding catch block");
+}
+
+void CatchFinder::FindCatch() {
+ // Walk the stack to find catch handler or prepare for deoptimization.
+ CatchBlockStackVisitor visitor(self_, context_, exception_, is_deoptimization_, this);
+ visitor.WalkStack(true);
+
+ mirror::ArtMethod* catch_method = *handler_quick_frame_;
+ if (catch_method == nullptr) {
+ if (kDebugExceptionDelivery) {
+ LOG(INFO) << "Handler is upcall";
+ }
+ } else {
+ CHECK(!is_deoptimization_);
+ if (kDebugExceptionDelivery) {
+ const DexFile& dex_file = *catch_method->GetDeclaringClass()->GetDexCache()->GetDexFile();
+ int line_number = dex_file.GetLineNumFromPC(catch_method, handler_dex_pc_);
+ LOG(INFO) << "Handler: " << PrettyMethod(catch_method) << " (line: " << line_number << ")";
+ }
+ }
+ if (clear_exception_) {
+ // Exception was cleared as part of delivery.
+ DCHECK(!self_->IsExceptionPending());
+ } else {
+ // Put exception back in root set with clear throw location.
+ self_->SetException(ThrowLocation(), exception_);
+ }
+ self_->EndAssertNoThreadSuspension(last_no_assert_suspension_cause_);
+ // Do instrumentation events after allowing thread suspension again.
+ if (!is_deoptimization_) {
+ // The debugger may suspend this thread and walk its stack. Let's do this before popping
+ // instrumentation frames.
+ instrumentation::Instrumentation* instrumentation = Runtime::Current()->GetInstrumentation();
+ instrumentation->ExceptionCaughtEvent(self_, throw_location_, catch_method, handler_dex_pc_,
+ exception_);
+ }
+}
+
+// Unwinds all instrumentation stack frame prior to catch handler or upcall.
+class InstrumentationStackVisitor : public StackVisitor {
+ public:
+ InstrumentationStackVisitor(Thread* self, bool is_deoptimization, size_t frame_id)
+ SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
+ : StackVisitor(self, nullptr),
+ self_(self), frame_id_(frame_id),
+ instrumentation_frames_to_pop_(0) {
+ CHECK_NE(frame_id_, kInvalidFrameId);
+ }
+
+ bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+ size_t current_frame_id = GetFrameId();
+ if (current_frame_id > frame_id_) {
+ CHECK(GetMethod() != nullptr);
+ if (UNLIKELY(GetQuickInstrumentationExitPc() == GetReturnPc())) {
+ ++instrumentation_frames_to_pop_;
+ }
+ return true;
+ } else {
+ // We reached the frame of the catch handler or the upcall.
+ return false;
+ }
+ }
+
+ size_t GetInstrumentationFramesToPop() const {
+ return instrumentation_frames_to_pop_;
+ }
+
+ private:
+ Thread* const self_;
+ const size_t frame_id_;
+ size_t instrumentation_frames_to_pop_;
+
+ DISALLOW_COPY_AND_ASSIGN(InstrumentationStackVisitor);
+};
+
+void CatchFinder::UpdateInstrumentationStack() {
+ if (method_tracing_active_) {
+ InstrumentationStackVisitor visitor(self_, is_deoptimization_, handler_frame_id_);
+ visitor.WalkStack(true);
+
+ size_t instrumentation_frames_to_pop = visitor.GetInstrumentationFramesToPop();
+ instrumentation::Instrumentation* instrumentation = Runtime::Current()->GetInstrumentation();
+ for (size_t i = 0; i < instrumentation_frames_to_pop; ++i) {
+ instrumentation->PopMethodForUnwind(self_, is_deoptimization_);
+ }
+ }
+}
+
+void CatchFinder::DoLongJump() {
+ if (is_deoptimization_) {
+ // TODO: proper return value.
+ self_->SetDeoptimizationShadowFrame(top_shadow_frame_);
+ }
+ // Place context back on thread so it will be available when we continue.
+ self_->ReleaseLongJumpContext(context_);
+ context_->SetSP(reinterpret_cast<uintptr_t>(handler_quick_frame_));
+ CHECK_NE(handler_quick_frame_pc_, 0u);
+ context_->SetPC(handler_quick_frame_pc_);
+ context_->SmashCallerSaves();
+ context_->DoLongJump();
+}
+
+} // namespace art