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/thread.cc b/runtime/thread.cc
index 7a09818..621e350 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -32,6 +32,7 @@
#include "arch/context.h"
#include "base/mutex.h"
+#include "catch_finder.h"
#include "class_linker.h"
#include "class_linker-inl.h"
#include "cutils/atomic.h"
@@ -65,7 +66,6 @@
#include "thread_list.h"
#include "utils.h"
#include "verifier/dex_gc_map.h"
-#include "verifier/method_verifier.h"
#include "vmap_table.h"
#include "well_known_classes.h"
@@ -1740,194 +1740,6 @@
os << offset;
}
-static const bool kDebugExceptionDelivery = false;
-class CatchBlockStackVisitor : public StackVisitor {
- public:
- CatchBlockStackVisitor(Thread* self, const ThrowLocation& throw_location,
- mirror::Throwable* exception, bool is_deoptimization)
- SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
- : StackVisitor(self, self->GetLongJumpContext()),
- self_(self), exception_(exception), is_deoptimization_(is_deoptimization),
- to_find_(is_deoptimization ? nullptr : exception->GetClass()), throw_location_(throw_location),
- handler_quick_frame_(nullptr), handler_quick_frame_pc_(0), handler_dex_pc_(0),
- native_method_count_(0), clear_exception_(false),
- method_tracing_active_(is_deoptimization ||
- Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled()),
- instrumentation_frames_to_pop_(0), top_shadow_frame_(nullptr), prev_shadow_frame_(nullptr) {
- // Exception not in root sets, can't allow GC.
- last_no_assert_suspension_cause_ = self->StartAssertNoThreadSuspension("Finding catch block");
- }
-
- ~CatchBlockStackVisitor() {
- LOG(FATAL) << "UNREACHABLE"; // Expected to take long jump.
- }
-
- bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- mirror::ArtMethod* method = GetMethod();
- if (method == nullptr) {
- // This is the upcall, we remember the frame and last pc so that we may long jump to them.
- handler_quick_frame_pc_ = GetCurrentQuickFramePc();
- handler_quick_frame_ = GetCurrentQuickFrame();
- return false; // End stack walk.
- } else {
- if (UNLIKELY(method_tracing_active_ &&
- GetQuickInstrumentationExitPc() == GetReturnPc())) {
- // Keep count of the number of unwinds during instrumentation.
- ++instrumentation_frames_to_pop_;
- }
- if (method->IsRuntimeMethod()) {
- // Ignore callee save method.
- DCHECK(method->IsCalleeSaveMethod());
- return true;
- } else if (is_deoptimization_) {
- return HandleDeoptimization(method);
- } else {
- return HandleTryItems(method);
- }
- }
- }
-
- bool HandleTryItems(mirror::ArtMethod* method) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- uint32_t dex_pc = DexFile::kDexNoIndex;
- if (method->IsNative()) {
- ++native_method_count_;
- } else {
- dex_pc = GetDexPc();
- }
- if (dex_pc != DexFile::kDexNoIndex) {
- uint32_t found_dex_pc = method->FindCatchBlock(to_find_, dex_pc, &clear_exception_);
- if (found_dex_pc != DexFile::kDexNoIndex) {
- handler_dex_pc_ = found_dex_pc;
- handler_quick_frame_pc_ = method->ToNativePc(found_dex_pc);
- handler_quick_frame_ = GetCurrentQuickFrame();
- return false; // End stack walk.
- }
- }
- return true; // Continue stack walk.
- }
-
- bool HandleDeoptimization(mirror::ArtMethod* m)
- SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- MethodHelper mh(m);
- const DexFile::CodeItem* code_item = mh.GetCodeItem();
- CHECK(code_item != nullptr);
- uint16_t num_regs = code_item->registers_size_;
- uint32_t dex_pc = GetDexPc();
- const Instruction* inst = Instruction::At(code_item->insns_ + dex_pc);
- uint32_t new_dex_pc = dex_pc + inst->SizeInCodeUnits();
- ShadowFrame* new_frame = ShadowFrame::Create(num_regs, nullptr, m, new_dex_pc);
- SirtRef<mirror::DexCache> dex_cache(self_, mh.GetDexCache());
- SirtRef<mirror::ClassLoader> class_loader(self_, mh.GetClassLoader());
- verifier::MethodVerifier verifier(&mh.GetDexFile(), &dex_cache, &class_loader,
- &mh.GetClassDef(), code_item, m->GetDexMethodIndex(), m,
- m->GetAccessFlags(), false, true);
- verifier.Verify();
- std::vector<int32_t> kinds = verifier.DescribeVRegs(dex_pc);
- for (uint16_t reg = 0; reg < num_regs; ++reg) {
- VRegKind kind = static_cast<VRegKind>(kinds.at(reg * 2));
- switch (kind) {
- case kUndefined:
- new_frame->SetVReg(reg, 0xEBADDE09);
- break;
- case kConstant:
- new_frame->SetVReg(reg, kinds.at((reg * 2) + 1));
- break;
- case kReferenceVReg:
- new_frame->SetVRegReference(reg,
- reinterpret_cast<mirror::Object*>(GetVReg(m, reg, kind)));
- break;
- default:
- new_frame->SetVReg(reg, GetVReg(m, reg, kind));
- break;
- }
- }
- if (prev_shadow_frame_ != nullptr) {
- prev_shadow_frame_->SetLink(new_frame);
- } else {
- top_shadow_frame_ = new_frame;
- }
- prev_shadow_frame_ = new_frame;
- return true;
- }
-
- void DoLongJump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
- 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.
- instrumentation::Instrumentation* instrumentation = Runtime::Current()->GetInstrumentation();
- if (!is_deoptimization_) {
- // The debugger may suspend this thread and walk its stack. Let's do this before popping
- // instrumentation frames.
- instrumentation->ExceptionCaughtEvent(self_, throw_location_, catch_method, handler_dex_pc_,
- exception_);
- }
- for (size_t i = 0; i < instrumentation_frames_to_pop_; ++i) {
- // We pop the instrumentation stack here so as not to corrupt it during the stack walk.
- if (i != instrumentation_frames_to_pop_ - 1 || self_->GetInstrumentationStack()->front().method_ != catch_method) {
- // Don't pop the instrumentation frame of the catch handler.
- instrumentation->PopMethodForUnwind(self_, is_deoptimization_);
- }
- }
- 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();
- }
-
- private:
- Thread* const self_;
- mirror::Throwable* const exception_;
- const bool is_deoptimization_;
- // The type of the exception catch block to find.
- mirror::Class* const to_find_;
- // Location of the throw.
- const ThrowLocation& throw_location_;
- // Quick frame with found handler or last frame if no handler found.
- mirror::ArtMethod** handler_quick_frame_;
- // PC to branch to for the handler.
- uintptr_t handler_quick_frame_pc_;
- // Associated dex PC.
- uint32_t handler_dex_pc_;
- // Number of native methods passed in crawl (equates to number of SIRTs to pop)
- uint32_t native_method_count_;
- // Should the exception be cleared as the catch block has no move-exception?
- bool clear_exception_;
- // Is method tracing active?
- const bool method_tracing_active_;
- // Support for nesting no thread suspension checks.
- const char* last_no_assert_suspension_cause_;
- // Number of frames to pop in long jump.
- size_t instrumentation_frames_to_pop_;
- ShadowFrame* top_shadow_frame_;
- ShadowFrame* prev_shadow_frame_;
-};
-
void Thread::QuickDeliverException() {
// Get exception from thread.
ThrowLocation throw_location;
@@ -1947,8 +1759,9 @@
DumpStack(LOG(INFO) << "Deoptimizing: ");
}
}
- CatchBlockStackVisitor catch_finder(this, throw_location, exception, is_deoptimization);
- catch_finder.WalkStack(true);
+ CatchFinder catch_finder(this, throw_location, exception, is_deoptimization);
+ catch_finder.FindCatch();
+ catch_finder.UpdateInstrumentationStack();
catch_finder.DoLongJump();
LOG(FATAL) << "UNREACHABLE";
}