runtime/quick_exception_handler.cc - LeafOS-Project/android_art - Gitiles

 /*
  * 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 "quick_exception_handler.h"

 #include "arch/context.h"
 #include "art_method-inl.h"
 #include "dex_instruction.h"
 #include "entrypoints/entrypoint_utils.h"
 #include "entrypoints/runtime_asm_entrypoints.h"
 #include "handle_scope-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/class_loader.h"
 #include "mirror/throwable.h"
 #include "verifier/method_verifier.h"

 namespace art {

 static constexpr bool kDebugExceptionDelivery = false;
 static constexpr size_t kInvalidFrameDepth = 0xffffffff;

 QuickExceptionHandler::QuickExceptionHandler(Thread* self, bool is_deoptimization)
   : self_(self), context_(self->GetLongJumpContext()), is_deoptimization_(is_deoptimization),
     method_tracing_active_(is_deoptimization ||
                            Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled()),
     handler_quick_frame_(nullptr), handler_quick_frame_pc_(0), handler_method_(nullptr),
     handler_dex_pc_(0), clear_exception_(false), handler_frame_depth_(kInvalidFrameDepth) {
 }

 // Finds catch handler or prepares for deoptimization.
 class CatchBlockStackVisitor FINAL : public StackVisitor {
  public:
   CatchBlockStackVisitor(Thread* self, Context* context, Handle<mirror::Throwable>* exception,
                          QuickExceptionHandler* exception_handler)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
       : StackVisitor(self, context, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
         self_(self),
         exception_(exception),
         exception_handler_(exception_handler) {
   }

   bool VisitFrame() OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     ArtMethod* method = GetMethod();
     exception_handler_->SetHandlerFrameDepth(GetFrameDepth());
     if (method == nullptr) {
       // This is the upcall, we remember the frame and last pc so that we may long jump to them.
       exception_handler_->SetHandlerQuickFramePc(GetCurrentQuickFramePc());
       exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
       uint32_t next_dex_pc;
       ArtMethod* next_art_method;
       bool has_next = GetNextMethodAndDexPc(&next_art_method, &next_dex_pc);
       // Report the method that did the down call as the handler.
       exception_handler_->SetHandlerDexPc(next_dex_pc);
       exception_handler_->SetHandlerMethod(next_art_method);
       if (!has_next) {
         // No next method? Check exception handler is set up for the unhandled exception handler
         // case.
         DCHECK_EQ(0U, exception_handler_->GetHandlerDexPc());
         DCHECK(nullptr == exception_handler_->GetHandlerMethod());
       }
       return false;  // End stack walk.
     }
     if (method->IsRuntimeMethod()) {
       // Ignore callee save method.
       DCHECK(method->IsCalleeSaveMethod());
       return true;
     }
     return HandleTryItems(method);
   }

  private:
   bool HandleTryItems(ArtMethod* method)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     uint32_t dex_pc = DexFile::kDexNoIndex;
     if (!method->IsNative()) {
       dex_pc = GetDexPc();
     }
     if (dex_pc != DexFile::kDexNoIndex) {
       bool clear_exception = false;
       StackHandleScope<1> hs(self_);
       Handle<mirror::Class> to_find(hs.NewHandle((*exception_)->GetClass()));
       uint32_t found_dex_pc = method->FindCatchBlock(to_find, dex_pc, &clear_exception);
       exception_handler_->SetClearException(clear_exception);
       if (found_dex_pc != DexFile::kDexNoIndex) {
         exception_handler_->SetHandlerMethod(method);
         exception_handler_->SetHandlerDexPc(found_dex_pc);
         exception_handler_->SetHandlerQuickFramePc(method->ToNativeQuickPc(found_dex_pc));
         exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
         return false;  // End stack walk.
       }
     }
     return true;  // Continue stack walk.
   }

   Thread* const self_;
   // The exception we're looking for the catch block of.
   Handle<mirror::Throwable>* exception_;
   // The quick exception handler we're visiting for.
   QuickExceptionHandler* const exception_handler_;

   DISALLOW_COPY_AND_ASSIGN(CatchBlockStackVisitor);
 };

 void QuickExceptionHandler::FindCatch(mirror::Throwable* exception) {
   DCHECK(!is_deoptimization_);
   if (kDebugExceptionDelivery) {
     mirror::String* msg = exception->GetDetailMessage();
     std::string str_msg(msg != nullptr ? msg->ToModifiedUtf8() : "");
     self_->DumpStack(LOG(INFO) << "Delivering exception: " << PrettyTypeOf(exception)
                      << ": " << str_msg << "\n");
   }
   StackHandleScope<1> hs(self_);
   Handle<mirror::Throwable> exception_ref(hs.NewHandle(exception));

   // Walk the stack to find catch handler or prepare for deoptimization.
   CatchBlockStackVisitor visitor(self_, context_, &exception_ref, this);
   visitor.WalkStack(true);

   if (kDebugExceptionDelivery) {
     if (*handler_quick_frame_ == nullptr) {
       LOG(INFO) << "Handler is upcall";
     }
     if (handler_method_ != nullptr) {
       const DexFile& dex_file = *handler_method_->GetDeclaringClass()->GetDexCache()->GetDexFile();
       int line_number = dex_file.GetLineNumFromPC(handler_method_, handler_dex_pc_);
       LOG(INFO) << "Handler: " << PrettyMethod(handler_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(exception_ref.Get());
   }
   // The debugger may suspend this thread and walk its stack. Let's do this before popping
   // instrumentation frames.
   instrumentation::Instrumentation* instrumentation = Runtime::Current()->GetInstrumentation();
   if (instrumentation->HasExceptionCaughtListeners()
       && self_->IsExceptionThrownByCurrentMethod(exception)) {
     instrumentation->ExceptionCaughtEvent(self_, exception_ref.Get());
   }
 }

 // Prepares deoptimization.
 class DeoptimizeStackVisitor FINAL : public StackVisitor {
  public:
   DeoptimizeStackVisitor(Thread* self, Context* context, QuickExceptionHandler* exception_handler)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
       : StackVisitor(self, context, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
         self_(self),
         exception_handler_(exception_handler),
         prev_shadow_frame_(nullptr),
         stacked_shadow_frame_pushed_(false) {
   }

   bool VisitFrame() OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     exception_handler_->SetHandlerFrameDepth(GetFrameDepth());
     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.
       exception_handler_->SetHandlerQuickFramePc(GetCurrentQuickFramePc());
       exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
       if (!stacked_shadow_frame_pushed_) {
         // In case there is no deoptimized shadow frame for this upcall, we still
         // need to push a nullptr to the stack since there is always a matching pop after
         // the long jump.
         self_->PushStackedShadowFrame(nullptr, StackedShadowFrameType::kDeoptimizationShadowFrame);
         stacked_shadow_frame_pushed_ = true;
       }
       return false;  // End stack walk.
     } else if (method->IsRuntimeMethod()) {
       // Ignore callee save method.
       DCHECK(method->IsCalleeSaveMethod());
       return true;
     } else {
       return HandleDeoptimization(method);
     }
   }

  private:
   static VRegKind GetVRegKind(uint16_t reg, const std::vector<int32_t>& kinds) {
     return static_cast<VRegKind>(kinds.at(reg * 2));
   }

   bool HandleDeoptimization(ArtMethod* m) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     const DexFile::CodeItem* code_item = m->GetCodeItem();
     CHECK(code_item != nullptr);
     uint16_t num_regs = code_item->registers_size_;
     uint32_t dex_pc = GetDexPc();
     StackHandleScope<2> hs(self_);  // Dex cache, class loader and method.
     mirror::Class* declaring_class = m->GetDeclaringClass();
     Handle<mirror::DexCache> h_dex_cache(hs.NewHandle(declaring_class->GetDexCache()));
     Handle<mirror::ClassLoader> h_class_loader(hs.NewHandle(declaring_class->GetClassLoader()));
     verifier::MethodVerifier verifier(self_, h_dex_cache->GetDexFile(), h_dex_cache, h_class_loader,
                                       &m->GetClassDef(), code_item, m->GetDexMethodIndex(),
                                       m, m->GetAccessFlags(), true, true, true, true);
     bool verifier_success = verifier.Verify();
     CHECK(verifier_success) << PrettyMethod(m);
     ShadowFrame* new_frame = ShadowFrame::CreateDeoptimizedFrame(num_regs, nullptr, m, dex_pc);
     {
       ScopedStackedShadowFramePusher pusher(self_, new_frame,
                                             StackedShadowFrameType::kShadowFrameUnderConstruction);
       const std::vector<int32_t> kinds(verifier.DescribeVRegs(dex_pc));

       // Markers for dead values, used when the verifier knows a Dex register is undefined,
       // or when the compiler knows the register has not been initialized, or is not used
       // anymore in the method.
       static constexpr uint32_t kDeadValue = 0xEBADDE09;
       static constexpr uint64_t kLongDeadValue = 0xEBADDE09EBADDE09;
       for (uint16_t reg = 0; reg < num_regs; ++reg) {
         VRegKind kind = GetVRegKind(reg, kinds);
         switch (kind) {
           case kUndefined:
             new_frame->SetVReg(reg, kDeadValue);
             break;
           case kConstant:
             new_frame->SetVReg(reg, kinds.at((reg * 2) + 1));
             break;
           case kReferenceVReg: {
             uint32_t value = 0;
             // Check IsReferenceVReg in case the compiled GC map doesn't agree with the verifier.
             // We don't want to copy a stale reference into the shadow frame as a reference.
             // b/20736048
             if (GetVReg(m, reg, kind, &value) && IsReferenceVReg(m, reg)) {
               new_frame->SetVRegReference(reg, reinterpret_cast<mirror::Object*>(value));
             } else {
               new_frame->SetVReg(reg, kDeadValue);
             }
             break;
           }
           case kLongLoVReg:
             if (GetVRegKind(reg + 1, kinds) == kLongHiVReg) {
               // Treat it as a "long" register pair.
               uint64_t value = 0;
               if (GetVRegPair(m, reg, kLongLoVReg, kLongHiVReg, &value)) {
                 new_frame->SetVRegLong(reg, value);
               } else {
                 new_frame->SetVRegLong(reg, kLongDeadValue);
               }
             } else {
               uint32_t value = 0;
               if (GetVReg(m, reg, kind, &value)) {
                 new_frame->SetVReg(reg, value);
               } else {
                 new_frame->SetVReg(reg, kDeadValue);
               }
             }
             break;
           case kLongHiVReg:
             if (GetVRegKind(reg - 1, kinds) == kLongLoVReg) {
               // Nothing to do: we treated it as a "long" register pair.
             } else {
               uint32_t value = 0;
               if (GetVReg(m, reg, kind, &value)) {
                 new_frame->SetVReg(reg, value);
               } else {
                 new_frame->SetVReg(reg, kDeadValue);
               }
             }
             break;
           case kDoubleLoVReg:
             if (GetVRegKind(reg + 1, kinds) == kDoubleHiVReg) {
               uint64_t value = 0;
               if (GetVRegPair(m, reg, kDoubleLoVReg, kDoubleHiVReg, &value)) {
                 // Treat it as a "double" register pair.
                 new_frame->SetVRegLong(reg, value);
               } else {
                 new_frame->SetVRegLong(reg, kLongDeadValue);
               }
             } else {
               uint32_t value = 0;
               if (GetVReg(m, reg, kind, &value)) {
                 new_frame->SetVReg(reg, value);
               } else {
                 new_frame->SetVReg(reg, kDeadValue);
               }
             }
             break;
           case kDoubleHiVReg:
             if (GetVRegKind(reg - 1, kinds) == kDoubleLoVReg) {
               // Nothing to do: we treated it as a "double" register pair.
             } else {
               uint32_t value = 0;
               if (GetVReg(m, reg, kind, &value)) {
                 new_frame->SetVReg(reg, value);
               } else {
                 new_frame->SetVReg(reg, kDeadValue);
               }
             }
             break;
           default:
             uint32_t value = 0;
             if (GetVReg(m, reg, kind, &value)) {
               new_frame->SetVReg(reg, value);
             } else {
               new_frame->SetVReg(reg, kDeadValue);
             }
             break;
         }
       }
     }
     if (prev_shadow_frame_ != nullptr) {
       prev_shadow_frame_->SetLink(new_frame);
     } else {
       // Will be popped after the long jump after DeoptimizeStack(),
       // right before interpreter::EnterInterpreterFromDeoptimize().
       stacked_shadow_frame_pushed_ = true;
       self_->PushStackedShadowFrame(new_frame, StackedShadowFrameType::kDeoptimizationShadowFrame);
     }
     prev_shadow_frame_ = new_frame;
     return true;
   }

   Thread* const self_;
   QuickExceptionHandler* const exception_handler_;
   ShadowFrame* prev_shadow_frame_;
   bool stacked_shadow_frame_pushed_;

   DISALLOW_COPY_AND_ASSIGN(DeoptimizeStackVisitor);
 };

 void QuickExceptionHandler::DeoptimizeStack() {
   DCHECK(is_deoptimization_);
   if (kDebugExceptionDelivery) {
     self_->DumpStack(LOG(INFO) << "Deoptimizing: ");
   }

   DeoptimizeStackVisitor visitor(self_, context_, this);
   visitor.WalkStack(true);

   // Restore deoptimization exception
   self_->SetException(Thread::GetDeoptimizationException());
 }

 // Unwinds all instrumentation stack frame prior to catch handler or upcall.
 class InstrumentationStackVisitor : public StackVisitor {
  public:
   InstrumentationStackVisitor(Thread* self, size_t frame_depth)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
       : StackVisitor(self, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
         frame_depth_(frame_depth),
         instrumentation_frames_to_pop_(0) {
     CHECK_NE(frame_depth_, kInvalidFrameDepth);
   }

   bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     size_t current_frame_depth = GetFrameDepth();
     if (current_frame_depth < frame_depth_) {
       CHECK(GetMethod() != nullptr);
       if (UNLIKELY(reinterpret_cast<uintptr_t>(GetQuickInstrumentationExitPc()) == GetReturnPc())) {
         if (!IsInInlinedFrame()) {
           // We do not count inlined frames, because we do not instrument them. The reason we
           // include them in the stack walking is the check against `frame_depth_`, which is
           // given to us by a visitor that visits inlined frames.
           ++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:
   const size_t frame_depth_;
   size_t instrumentation_frames_to_pop_;

   DISALLOW_COPY_AND_ASSIGN(InstrumentationStackVisitor);
 };

 void QuickExceptionHandler::UpdateInstrumentationStack() {
   if (method_tracing_active_) {
     InstrumentationStackVisitor visitor(self_, handler_frame_depth_);
     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 QuickExceptionHandler::DoLongJump() {
   // 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();
   UNREACHABLE();
 }

 }  // namespace art
	/*
	* 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 "quick_exception_handler.h"

	#include "arch/context.h"
	#include "art_method-inl.h"
	#include "dex_instruction.h"
	#include "entrypoints/entrypoint_utils.h"
	#include "entrypoints/runtime_asm_entrypoints.h"
	#include "handle_scope-inl.h"
	#include "mirror/class-inl.h"
	#include "mirror/class_loader.h"
	#include "mirror/throwable.h"
	#include "verifier/method_verifier.h"

	namespace art {

	static constexpr bool kDebugExceptionDelivery = false;
	static constexpr size_t kInvalidFrameDepth = 0xffffffff;

	QuickExceptionHandler::QuickExceptionHandler(Thread* self, bool is_deoptimization)
	: self_(self), context_(self->GetLongJumpContext()), is_deoptimization_(is_deoptimization),
	method_tracing_active_(is_deoptimization \|\|
	Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled()),
	handler_quick_frame_(nullptr), handler_quick_frame_pc_(0), handler_method_(nullptr),
	handler_dex_pc_(0), clear_exception_(false), handler_frame_depth_(kInvalidFrameDepth) {
	}

	// Finds catch handler or prepares for deoptimization.
	class CatchBlockStackVisitor FINAL : public StackVisitor {
	public:
	CatchBlockStackVisitor(Thread* self, Context* context, Handle<mirror::Throwable>* exception,
	QuickExceptionHandler* exception_handler)
	SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
	: StackVisitor(self, context, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
	self_(self),
	exception_(exception),
	exception_handler_(exception_handler) {
	}

	bool VisitFrame() OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	ArtMethod* method = GetMethod();
	exception_handler_->SetHandlerFrameDepth(GetFrameDepth());
	if (method == nullptr) {
	// This is the upcall, we remember the frame and last pc so that we may long jump to them.
	exception_handler_->SetHandlerQuickFramePc(GetCurrentQuickFramePc());
	exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
	uint32_t next_dex_pc;
	ArtMethod* next_art_method;
	bool has_next = GetNextMethodAndDexPc(&next_art_method, &next_dex_pc);
	// Report the method that did the down call as the handler.
	exception_handler_->SetHandlerDexPc(next_dex_pc);
	exception_handler_->SetHandlerMethod(next_art_method);
	if (!has_next) {
	// No next method? Check exception handler is set up for the unhandled exception handler
	// case.
	DCHECK_EQ(0U, exception_handler_->GetHandlerDexPc());
	DCHECK(nullptr == exception_handler_->GetHandlerMethod());
	}
	return false; // End stack walk.
	}
	if (method->IsRuntimeMethod()) {
	// Ignore callee save method.
	DCHECK(method->IsCalleeSaveMethod());
	return true;
	}
	return HandleTryItems(method);
	}

	private:
	bool HandleTryItems(ArtMethod* method)
	SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	uint32_t dex_pc = DexFile::kDexNoIndex;
	if (!method->IsNative()) {
	dex_pc = GetDexPc();
	}
	if (dex_pc != DexFile::kDexNoIndex) {
	bool clear_exception = false;
	StackHandleScope<1> hs(self_);
	Handle<mirror::Class> to_find(hs.NewHandle((*exception_)->GetClass()));
	uint32_t found_dex_pc = method->FindCatchBlock(to_find, dex_pc, &clear_exception);
	exception_handler_->SetClearException(clear_exception);
	if (found_dex_pc != DexFile::kDexNoIndex) {
	exception_handler_->SetHandlerMethod(method);
	exception_handler_->SetHandlerDexPc(found_dex_pc);
	exception_handler_->SetHandlerQuickFramePc(method->ToNativeQuickPc(found_dex_pc));
	exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
	return false; // End stack walk.
	}
	}
	return true; // Continue stack walk.
	}

	Thread* const self_;
	// The exception we're looking for the catch block of.
	Handle<mirror::Throwable>* exception_;
	// The quick exception handler we're visiting for.
	QuickExceptionHandler* const exception_handler_;

	DISALLOW_COPY_AND_ASSIGN(CatchBlockStackVisitor);
	};

	void QuickExceptionHandler::FindCatch(mirror::Throwable* exception) {
	DCHECK(!is_deoptimization_);
	if (kDebugExceptionDelivery) {
	mirror::String* msg = exception->GetDetailMessage();
	std::string str_msg(msg != nullptr ? msg->ToModifiedUtf8() : "");
	self_->DumpStack(LOG(INFO) << "Delivering exception: " << PrettyTypeOf(exception)
	<< ": " << str_msg << "\n");
	}
	StackHandleScope<1> hs(self_);
	Handle<mirror::Throwable> exception_ref(hs.NewHandle(exception));

	// Walk the stack to find catch handler or prepare for deoptimization.
	CatchBlockStackVisitor visitor(self_, context_, &exception_ref, this);
	visitor.WalkStack(true);

	if (kDebugExceptionDelivery) {
	if (*handler_quick_frame_ == nullptr) {
	LOG(INFO) << "Handler is upcall";
	}
	if (handler_method_ != nullptr) {
	const DexFile& dex_file = *handler_method_->GetDeclaringClass()->GetDexCache()->GetDexFile();
	int line_number = dex_file.GetLineNumFromPC(handler_method_, handler_dex_pc_);
	LOG(INFO) << "Handler: " << PrettyMethod(handler_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(exception_ref.Get());
	}
	// The debugger may suspend this thread and walk its stack. Let's do this before popping
	// instrumentation frames.
	instrumentation::Instrumentation* instrumentation = Runtime::Current()->GetInstrumentation();
	if (instrumentation->HasExceptionCaughtListeners()
	&& self_->IsExceptionThrownByCurrentMethod(exception)) {
	instrumentation->ExceptionCaughtEvent(self_, exception_ref.Get());
	}
	}

	// Prepares deoptimization.
	class DeoptimizeStackVisitor FINAL : public StackVisitor {
	public:
	DeoptimizeStackVisitor(Thread* self, Context* context, QuickExceptionHandler* exception_handler)
	SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
	: StackVisitor(self, context, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
	self_(self),
	exception_handler_(exception_handler),
	prev_shadow_frame_(nullptr),
	stacked_shadow_frame_pushed_(false) {
	}

	bool VisitFrame() OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	exception_handler_->SetHandlerFrameDepth(GetFrameDepth());
	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.
	exception_handler_->SetHandlerQuickFramePc(GetCurrentQuickFramePc());
	exception_handler_->SetHandlerQuickFrame(GetCurrentQuickFrame());
	if (!stacked_shadow_frame_pushed_) {
	// In case there is no deoptimized shadow frame for this upcall, we still
	// need to push a nullptr to the stack since there is always a matching pop after
	// the long jump.
	self_->PushStackedShadowFrame(nullptr, StackedShadowFrameType::kDeoptimizationShadowFrame);
	stacked_shadow_frame_pushed_ = true;
	}
	return false; // End stack walk.
	} else if (method->IsRuntimeMethod()) {
	// Ignore callee save method.
	DCHECK(method->IsCalleeSaveMethod());
	return true;
	} else {
	return HandleDeoptimization(method);
	}
	}

	private:
	static VRegKind GetVRegKind(uint16_t reg, const std::vector<int32_t>& kinds) {
	return static_cast<VRegKind>(kinds.at(reg * 2));
	}

	bool HandleDeoptimization(ArtMethod* m) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	const DexFile::CodeItem* code_item = m->GetCodeItem();
	CHECK(code_item != nullptr);
	uint16_t num_regs = code_item->registers_size_;
	uint32_t dex_pc = GetDexPc();
	StackHandleScope<2> hs(self_); // Dex cache, class loader and method.
	mirror::Class* declaring_class = m->GetDeclaringClass();
	Handle<mirror::DexCache> h_dex_cache(hs.NewHandle(declaring_class->GetDexCache()));
	Handle<mirror::ClassLoader> h_class_loader(hs.NewHandle(declaring_class->GetClassLoader()));
	verifier::MethodVerifier verifier(self_, h_dex_cache->GetDexFile(), h_dex_cache, h_class_loader,
	&m->GetClassDef(), code_item, m->GetDexMethodIndex(),
	m, m->GetAccessFlags(), true, true, true, true);
	bool verifier_success = verifier.Verify();
	CHECK(verifier_success) << PrettyMethod(m);
	ShadowFrame* new_frame = ShadowFrame::CreateDeoptimizedFrame(num_regs, nullptr, m, dex_pc);
	{
	ScopedStackedShadowFramePusher pusher(self_, new_frame,
	StackedShadowFrameType::kShadowFrameUnderConstruction);
	const std::vector<int32_t> kinds(verifier.DescribeVRegs(dex_pc));

	// Markers for dead values, used when the verifier knows a Dex register is undefined,
	// or when the compiler knows the register has not been initialized, or is not used
	// anymore in the method.
	static constexpr uint32_t kDeadValue = 0xEBADDE09;
	static constexpr uint64_t kLongDeadValue = 0xEBADDE09EBADDE09;
	for (uint16_t reg = 0; reg < num_regs; ++reg) {
	VRegKind kind = GetVRegKind(reg, kinds);
	switch (kind) {
	case kUndefined:
	new_frame->SetVReg(reg, kDeadValue);
	break;
	case kConstant:
	new_frame->SetVReg(reg, kinds.at((reg * 2) + 1));
	break;
	case kReferenceVReg: {
	uint32_t value = 0;
	// Check IsReferenceVReg in case the compiled GC map doesn't agree with the verifier.
	// We don't want to copy a stale reference into the shadow frame as a reference.
	// b/20736048
	if (GetVReg(m, reg, kind, &value) && IsReferenceVReg(m, reg)) {
	new_frame->SetVRegReference(reg, reinterpret_cast<mirror::Object*>(value));
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	break;
	}
	case kLongLoVReg:
	if (GetVRegKind(reg + 1, kinds) == kLongHiVReg) {
	// Treat it as a "long" register pair.
	uint64_t value = 0;
	if (GetVRegPair(m, reg, kLongLoVReg, kLongHiVReg, &value)) {
	new_frame->SetVRegLong(reg, value);
	} else {
	new_frame->SetVRegLong(reg, kLongDeadValue);
	}
	} else {
	uint32_t value = 0;
	if (GetVReg(m, reg, kind, &value)) {
	new_frame->SetVReg(reg, value);
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	}
	break;
	case kLongHiVReg:
	if (GetVRegKind(reg - 1, kinds) == kLongLoVReg) {
	// Nothing to do: we treated it as a "long" register pair.
	} else {
	uint32_t value = 0;
	if (GetVReg(m, reg, kind, &value)) {
	new_frame->SetVReg(reg, value);
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	}
	break;
	case kDoubleLoVReg:
	if (GetVRegKind(reg + 1, kinds) == kDoubleHiVReg) {
	uint64_t value = 0;
	if (GetVRegPair(m, reg, kDoubleLoVReg, kDoubleHiVReg, &value)) {
	// Treat it as a "double" register pair.
	new_frame->SetVRegLong(reg, value);
	} else {
	new_frame->SetVRegLong(reg, kLongDeadValue);
	}
	} else {
	uint32_t value = 0;
	if (GetVReg(m, reg, kind, &value)) {
	new_frame->SetVReg(reg, value);
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	}
	break;
	case kDoubleHiVReg:
	if (GetVRegKind(reg - 1, kinds) == kDoubleLoVReg) {
	// Nothing to do: we treated it as a "double" register pair.
	} else {
	uint32_t value = 0;
	if (GetVReg(m, reg, kind, &value)) {
	new_frame->SetVReg(reg, value);
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	}
	break;
	default:
	uint32_t value = 0;
	if (GetVReg(m, reg, kind, &value)) {
	new_frame->SetVReg(reg, value);
	} else {
	new_frame->SetVReg(reg, kDeadValue);
	}
	break;
	}
	}
	}
	if (prev_shadow_frame_ != nullptr) {
	prev_shadow_frame_->SetLink(new_frame);
	} else {
	// Will be popped after the long jump after DeoptimizeStack(),
	// right before interpreter::EnterInterpreterFromDeoptimize().
	stacked_shadow_frame_pushed_ = true;
	self_->PushStackedShadowFrame(new_frame, StackedShadowFrameType::kDeoptimizationShadowFrame);
	}
	prev_shadow_frame_ = new_frame;
	return true;
	}

	Thread* const self_;
	QuickExceptionHandler* const exception_handler_;
	ShadowFrame* prev_shadow_frame_;
	bool stacked_shadow_frame_pushed_;

	DISALLOW_COPY_AND_ASSIGN(DeoptimizeStackVisitor);
	};

	void QuickExceptionHandler::DeoptimizeStack() {
	DCHECK(is_deoptimization_);
	if (kDebugExceptionDelivery) {
	self_->DumpStack(LOG(INFO) << "Deoptimizing: ");
	}

	DeoptimizeStackVisitor visitor(self_, context_, this);
	visitor.WalkStack(true);

	// Restore deoptimization exception
	self_->SetException(Thread::GetDeoptimizationException());
	}

	// Unwinds all instrumentation stack frame prior to catch handler or upcall.
	class InstrumentationStackVisitor : public StackVisitor {
	public:
	InstrumentationStackVisitor(Thread* self, size_t frame_depth)
	SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
	: StackVisitor(self, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
	frame_depth_(frame_depth),
	instrumentation_frames_to_pop_(0) {
	CHECK_NE(frame_depth_, kInvalidFrameDepth);
	}

	bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	size_t current_frame_depth = GetFrameDepth();
	if (current_frame_depth < frame_depth_) {
	CHECK(GetMethod() != nullptr);
	if (UNLIKELY(reinterpret_cast<uintptr_t>(GetQuickInstrumentationExitPc()) == GetReturnPc())) {
	if (!IsInInlinedFrame()) {
	// We do not count inlined frames, because we do not instrument them. The reason we
	// include them in the stack walking is the check against `frame_depth_`, which is
	// given to us by a visitor that visits inlined frames.
	++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:
	const size_t frame_depth_;
	size_t instrumentation_frames_to_pop_;

	DISALLOW_COPY_AND_ASSIGN(InstrumentationStackVisitor);
	};

	void QuickExceptionHandler::UpdateInstrumentationStack() {
	if (method_tracing_active_) {
	InstrumentationStackVisitor visitor(self_, handler_frame_depth_);
	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 QuickExceptionHandler::DoLongJump() {
	// 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();
	UNREACHABLE();
	}

	} // namespace art