runtime/debugger.cc

/*
 * Copyright (C) 2008 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 "debugger.h"

#include <sys/uio.h>

#include <set>

#include "arch/context.h"
#include "class_linker.h"
#include "class_linker-inl.h"
#include "dex_file-inl.h"
#include "dex_instruction.h"
#include "gc/accounting/card_table-inl.h"
#include "gc/space/large_object_space.h"
#include "gc/space/space-inl.h"
#include "handle_scope.h"
#include "jdwp/object_registry.h"
#include "mirror/art_field-inl.h"
#include "mirror/art_method-inl.h"
#include "mirror/class.h"
#include "mirror/class-inl.h"
#include "mirror/class_loader.h"
#include "mirror/object-inl.h"
#include "mirror/object_array-inl.h"
#include "mirror/string-inl.h"
#include "mirror/throwable.h"
#include "quick/inline_method_analyser.h"
#include "reflection.h"
#include "safe_map.h"
#include "scoped_thread_state_change.h"
#include "ScopedLocalRef.h"
#include "ScopedPrimitiveArray.h"
#include "handle_scope-inl.h"
#include "thread_list.h"
#include "utf.h"
#include "verifier/method_verifier-inl.h"
#include "well_known_classes.h"

#ifdef HAVE_ANDROID_OS
#include "cutils/properties.h"
#endif

namespace art {

static const size_t kMaxAllocRecordStackDepth = 16;  // Max 255.
static const size_t kDefaultNumAllocRecords = 64*1024;  // Must be a power of 2. 2BE can hold 64k-1.

// Limit alloc_record_count to the 2BE value that is the limit of the current protocol.
static uint16_t CappedAllocRecordCount(size_t alloc_record_count) {
  if (alloc_record_count > 0xffff) {
    return 0xffff;
  }
  return alloc_record_count;
}

class AllocRecordStackTraceElement {
 public:
  AllocRecordStackTraceElement() : method_(nullptr), dex_pc_(0) {
  }

  int32_t LineNumber() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    mirror::ArtMethod* method = Method();
    DCHECK(method != nullptr);
    return method->GetLineNumFromDexPC(DexPc());
  }

  mirror::ArtMethod* Method() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    return soa.DecodeMethod(method_);
  }

  void SetMethod(mirror::ArtMethod* m) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    method_ = soa.EncodeMethod(m);
  }

  uint32_t DexPc() const {
    return dex_pc_;
  }

  void SetDexPc(uint32_t pc) {
    dex_pc_ = pc;
  }

 private:
  jmethodID method_;
  uint32_t dex_pc_;
};

jobject Dbg::TypeCache::Add(mirror::Class* t) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JNIEnv* const env = soa.Env();
  ScopedLocalRef<jobject> local_ref(soa.Env(), soa.AddLocalReference<jobject>(t));
  const int32_t hash_code = soa.Decode<mirror::Class*>(local_ref.get())->IdentityHashCode();
  auto range = objects_.equal_range(hash_code);
  for (auto it = range.first; it != range.second; ++it) {
    if (soa.Decode<mirror::Class*>(it->second) == soa.Decode<mirror::Class*>(local_ref.get())) {
      // Found a matching weak global, return it.
      return it->second;
    }
  }
  const jobject weak_global = env->NewWeakGlobalRef(local_ref.get());
  objects_.insert(std::make_pair(hash_code, weak_global));
  return weak_global;
}

void Dbg::TypeCache::Clear() {
  JavaVMExt* vm = Runtime::Current()->GetJavaVM();
  Thread* self = Thread::Current();
  for (const auto& p : objects_) {
    vm->DeleteWeakGlobalRef(self, p.second);
  }
  objects_.clear();
}

class AllocRecord {
 public:
  AllocRecord() : type_(nullptr), byte_count_(0), thin_lock_id_(0) {}

  mirror::Class* Type() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    return down_cast<mirror::Class*>(Thread::Current()->DecodeJObject(type_));
  }

  void SetType(mirror::Class* t) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_,
                                                       Locks::alloc_tracker_lock_) {
    type_ = Dbg::type_cache_.Add(t);
  }

  size_t GetDepth() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    size_t depth = 0;
    while (depth < kMaxAllocRecordStackDepth && stack_[depth].Method() != nullptr) {
      ++depth;
    }
    return depth;
  }

  size_t ByteCount() const {
    return byte_count_;
  }

  void SetByteCount(size_t count) {
    byte_count_ = count;
  }

  uint16_t ThinLockId() const {
    return thin_lock_id_;
  }

  void SetThinLockId(uint16_t id) {
    thin_lock_id_ = id;
  }

  AllocRecordStackTraceElement* StackElement(size_t index) {
    DCHECK_LT(index, kMaxAllocRecordStackDepth);
    return &stack_[index];
  }

 private:
  jobject type_;  // This is a weak global.
  size_t byte_count_;
  uint16_t thin_lock_id_;
  AllocRecordStackTraceElement stack_[kMaxAllocRecordStackDepth];  // Unused entries have nullptr method.
};

class Breakpoint {
 public:
  Breakpoint(mirror::ArtMethod* method, uint32_t dex_pc,
             DeoptimizationRequest::Kind deoptimization_kind)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
    : method_(nullptr), dex_pc_(dex_pc), deoptimization_kind_(deoptimization_kind) {
    CHECK(deoptimization_kind_ == DeoptimizationRequest::kNothing ||
          deoptimization_kind_ == DeoptimizationRequest::kSelectiveDeoptimization ||
          deoptimization_kind_ == DeoptimizationRequest::kFullDeoptimization);
    ScopedObjectAccessUnchecked soa(Thread::Current());
    method_ = soa.EncodeMethod(method);
  }

  Breakpoint(const Breakpoint& other) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
    : method_(nullptr), dex_pc_(other.dex_pc_),
      deoptimization_kind_(other.deoptimization_kind_) {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    method_ = soa.EncodeMethod(other.Method());
  }

  mirror::ArtMethod* Method() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    return soa.DecodeMethod(method_);
  }

  uint32_t DexPc() const {
    return dex_pc_;
  }

  DeoptimizationRequest::Kind GetDeoptimizationKind() const {
    return deoptimization_kind_;
  }

 private:
  // The location of this breakpoint.
  jmethodID method_;
  uint32_t dex_pc_;

  // Indicates whether breakpoint needs full deoptimization or selective deoptimization.
  DeoptimizationRequest::Kind deoptimization_kind_;
};

static std::ostream& operator<<(std::ostream& os, const Breakpoint& rhs)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  os << StringPrintf("Breakpoint[%s @%#x]", PrettyMethod(rhs.Method()).c_str(), rhs.DexPc());
  return os;
}

class DebugInstrumentationListener FINAL : public instrumentation::InstrumentationListener {
 public:
  DebugInstrumentationListener() {}
  virtual ~DebugInstrumentationListener() {}

  void MethodEntered(Thread* thread, mirror::Object* this_object, mirror::ArtMethod* method,
                     uint32_t dex_pc ATTRIBUTE_UNUSED)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    if (method->IsNative()) {
      // TODO: post location events is a suspension point and native method entry stubs aren't.
      return;
    }
    Dbg::UpdateDebugger(thread, this_object, method, 0, Dbg::kMethodEntry, nullptr);
  }

  void MethodExited(Thread* thread, mirror::Object* this_object, mirror::ArtMethod* method,
                    uint32_t dex_pc, const JValue& return_value)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    if (method->IsNative()) {
      // TODO: post location events is a suspension point and native method entry stubs aren't.
      return;
    }
    Dbg::UpdateDebugger(thread, this_object, method, dex_pc, Dbg::kMethodExit, &return_value);
  }

  void MethodUnwind(Thread* thread, mirror::Object* this_object, mirror::ArtMethod* method,
                    uint32_t dex_pc)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    // We're not recorded to listen to this kind of event, so complain.
    UNUSED(thread, this_object, method, dex_pc);
    LOG(ERROR) << "Unexpected method unwind event in debugger " << PrettyMethod(method)
               << " " << dex_pc;
  }

  void DexPcMoved(Thread* thread, mirror::Object* this_object, mirror::ArtMethod* method,
                  uint32_t new_dex_pc)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    Dbg::UpdateDebugger(thread, this_object, method, new_dex_pc, 0, nullptr);
  }

  void FieldRead(Thread* thread, mirror::Object* this_object, mirror::ArtMethod* method,
                 uint32_t dex_pc, mirror::ArtField* field)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    UNUSED(thread);
    Dbg::PostFieldAccessEvent(method, dex_pc, this_object, field);
  }

  void FieldWritten(Thread* thread ATTRIBUTE_UNUSED, mirror::Object* this_object,
                    mirror::ArtMethod* method, uint32_t dex_pc, mirror::ArtField* field,
                    const JValue& field_value)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    Dbg::PostFieldModificationEvent(method, dex_pc, this_object, field, &field_value);
  }

  void ExceptionCaught(Thread* thread ATTRIBUTE_UNUSED, mirror::Throwable* exception_object)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    Dbg::PostException(exception_object);
  }

  // We only care about how many backward branches were executed in the Jit.
  void BackwardBranch(Thread* /*thread*/, mirror::ArtMethod* method, int32_t dex_pc_offset)
      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    LOG(ERROR) << "Unexpected backward branch event in debugger " << PrettyMethod(method)
               << " " << dex_pc_offset;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(DebugInstrumentationListener);
} gDebugInstrumentationListener;

// JDWP is allowed unless the Zygote forbids it.
static bool gJdwpAllowed = true;

// Was there a -Xrunjdwp or -agentlib:jdwp= argument on the command line?
static bool gJdwpConfigured = false;

// JDWP options for debugging. Only valid if IsJdwpConfigured() is true.
static JDWP::JdwpOptions gJdwpOptions;

// Runtime JDWP state.
static JDWP::JdwpState* gJdwpState = nullptr;
static bool gDebuggerConnected;  // debugger or DDMS is connected.
static bool gDebuggerActive;     // debugger is making requests.
static bool gDisposed;           // debugger called VirtualMachine.Dispose, so we should drop the connection.

static bool gDdmThreadNotification = false;

// DDMS GC-related settings.
static Dbg::HpifWhen gDdmHpifWhen = Dbg::HPIF_WHEN_NEVER;
static Dbg::HpsgWhen gDdmHpsgWhen = Dbg::HPSG_WHEN_NEVER;
static Dbg::HpsgWhat gDdmHpsgWhat;
static Dbg::HpsgWhen gDdmNhsgWhen = Dbg::HPSG_WHEN_NEVER;
static Dbg::HpsgWhat gDdmNhsgWhat;

ObjectRegistry* Dbg::gRegistry = nullptr;

// Recent allocation tracking.
AllocRecord* Dbg::recent_allocation_records_ = nullptr;  // TODO: CircularBuffer<AllocRecord>
size_t Dbg::alloc_record_max_ = 0;
size_t Dbg::alloc_record_head_ = 0;
size_t Dbg::alloc_record_count_ = 0;
Dbg::TypeCache Dbg::type_cache_;

// Deoptimization support.
std::vector<DeoptimizationRequest> Dbg::deoptimization_requests_;
size_t Dbg::full_deoptimization_event_count_ = 0;
size_t Dbg::delayed_full_undeoptimization_count_ = 0;

// Instrumentation event reference counters.
size_t Dbg::dex_pc_change_event_ref_count_ = 0;
size_t Dbg::method_enter_event_ref_count_ = 0;
size_t Dbg::method_exit_event_ref_count_ = 0;
size_t Dbg::field_read_event_ref_count_ = 0;
size_t Dbg::field_write_event_ref_count_ = 0;
size_t Dbg::exception_catch_event_ref_count_ = 0;
uint32_t Dbg::instrumentation_events_ = 0;

// Breakpoints.
static std::vector<Breakpoint> gBreakpoints GUARDED_BY(Locks::breakpoint_lock_);

void DebugInvokeReq::VisitRoots(RootCallback* callback, void* arg, const RootInfo& root_info) {
  receiver.VisitRootIfNonNull(callback, arg, root_info);  // null for static method call.
  klass.VisitRoot(callback, arg, root_info);
  method.VisitRoot(callback, arg, root_info);
}

void SingleStepControl::VisitRoots(RootCallback* callback, void* arg, const RootInfo& root_info) {
  if (method_ != nullptr) {
    callback(reinterpret_cast<mirror::Object**>(&method_), arg, root_info);
  }
}

void SingleStepControl::AddDexPc(uint32_t dex_pc) {
  dex_pcs_.insert(dex_pc);
}

bool SingleStepControl::ContainsDexPc(uint32_t dex_pc) const {
  return dex_pcs_.find(dex_pc) == dex_pcs_.end();
}

static bool IsBreakpoint(const mirror::ArtMethod* m, uint32_t dex_pc)
    LOCKS_EXCLUDED(Locks::breakpoint_lock_)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  ReaderMutexLock mu(Thread::Current(), *Locks::breakpoint_lock_);
  for (size_t i = 0, e = gBreakpoints.size(); i < e; ++i) {
    if (gBreakpoints[i].DexPc() == dex_pc && gBreakpoints[i].Method() == m) {
      VLOG(jdwp) << "Hit breakpoint #" << i << ": " << gBreakpoints[i];
      return true;
    }
  }
  return false;
}

static bool IsSuspendedForDebugger(ScopedObjectAccessUnchecked& soa, Thread* thread)
    LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) {
  MutexLock mu(soa.Self(), *Locks::thread_suspend_count_lock_);
  // A thread may be suspended for GC; in this code, we really want to know whether
  // there's a debugger suspension active.
  return thread->IsSuspended() && thread->GetDebugSuspendCount() > 0;
}

static mirror::Array* DecodeNonNullArray(JDWP::RefTypeId id, JDWP::JdwpError* error)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  mirror::Object* o = Dbg::GetObjectRegistry()->Get<mirror::Object*>(id, error);
  if (o == nullptr) {
    *error = JDWP::ERR_INVALID_OBJECT;
    return nullptr;
  }
  if (!o->IsArrayInstance()) {
    *error = JDWP::ERR_INVALID_ARRAY;
    return nullptr;
  }
  *error = JDWP::ERR_NONE;
  return o->AsArray();
}

static mirror::Class* DecodeClass(JDWP::RefTypeId id, JDWP::JdwpError* error)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  mirror::Object* o = Dbg::GetObjectRegistry()->Get<mirror::Object*>(id, error);
  if (o == nullptr) {
    *error = JDWP::ERR_INVALID_OBJECT;
    return nullptr;
  }
  if (!o->IsClass()) {
    *error = JDWP::ERR_INVALID_CLASS;
    return nullptr;
  }
  *error = JDWP::ERR_NONE;
  return o->AsClass();
}

static Thread* DecodeThread(ScopedObjectAccessUnchecked& soa, JDWP::ObjectId thread_id,
                            JDWP::JdwpError* error)
    EXCLUSIVE_LOCKS_REQUIRED(Locks::thread_list_lock_)
    LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  mirror::Object* thread_peer = Dbg::GetObjectRegistry()->Get<mirror::Object*>(thread_id, error);
  if (thread_peer == nullptr) {
    // This isn't even an object.
    *error = JDWP::ERR_INVALID_OBJECT;
    return nullptr;
  }

  mirror::Class* java_lang_Thread = soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_Thread);
  if (!java_lang_Thread->IsAssignableFrom(thread_peer->GetClass())) {
    // This isn't a thread.
    *error = JDWP::ERR_INVALID_THREAD;
    return nullptr;
  }

  Thread* thread = Thread::FromManagedThread(soa, thread_peer);
  // If thread is null then this a java.lang.Thread without a Thread*. Must be a un-started or a
  // zombie.
  *error = (thread == nullptr) ? JDWP::ERR_THREAD_NOT_ALIVE : JDWP::ERR_NONE;
  return thread;
}

static JDWP::JdwpTag BasicTagFromDescriptor(const char* descriptor) {
  // JDWP deliberately uses the descriptor characters' ASCII values for its enum.
  // Note that by "basic" we mean that we don't get more specific than JT_OBJECT.
  return static_cast<JDWP::JdwpTag>(descriptor[0]);
}

static JDWP::JdwpTag BasicTagFromClass(mirror::Class* klass)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  std::string temp;
  const char* descriptor = klass->GetDescriptor(&temp);
  return BasicTagFromDescriptor(descriptor);
}

static JDWP::JdwpTag TagFromClass(const ScopedObjectAccessUnchecked& soa, mirror::Class* c)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  CHECK(c != nullptr);
  if (c->IsArrayClass()) {
    return JDWP::JT_ARRAY;
  }
  if (c->IsStringClass()) {
    return JDWP::JT_STRING;
  }
  if (c->IsClassClass()) {
    return JDWP::JT_CLASS_OBJECT;
  }
  {
    mirror::Class* thread_class = soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_Thread);
    if (thread_class->IsAssignableFrom(c)) {
      return JDWP::JT_THREAD;
    }
  }
  {
    mirror::Class* thread_group_class =
        soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_ThreadGroup);
    if (thread_group_class->IsAssignableFrom(c)) {
      return JDWP::JT_THREAD_GROUP;
    }
  }
  {
    mirror::Class* class_loader_class =
        soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_ClassLoader);
    if (class_loader_class->IsAssignableFrom(c)) {
      return JDWP::JT_CLASS_LOADER;
    }
  }
  return JDWP::JT_OBJECT;
}

/*
 * Objects declared to hold Object might actually hold a more specific
 * type.  The debugger may take a special interest in these (e.g. it
 * wants to display the contents of Strings), so we want to return an
 * appropriate tag.
 *
 * Null objects are tagged JT_OBJECT.
 */
JDWP::JdwpTag Dbg::TagFromObject(const ScopedObjectAccessUnchecked& soa, mirror::Object* o) {
  return (o == nullptr) ? JDWP::JT_OBJECT : TagFromClass(soa, o->GetClass());
}

static bool IsPrimitiveTag(JDWP::JdwpTag tag) {
  switch (tag) {
  case JDWP::JT_BOOLEAN:
  case JDWP::JT_BYTE:
  case JDWP::JT_CHAR:
  case JDWP::JT_FLOAT:
  case JDWP::JT_DOUBLE:
  case JDWP::JT_INT:
  case JDWP::JT_LONG:
  case JDWP::JT_SHORT:
  case JDWP::JT_VOID:
    return true;
  default:
    return false;
  }
}

void Dbg::StartJdwp() {
  if (!gJdwpAllowed || !IsJdwpConfigured()) {
    // No JDWP for you!
    return;
  }

  CHECK(gRegistry == nullptr);
  gRegistry = new ObjectRegistry;

  // Init JDWP if the debugger is enabled. This may connect out to a
  // debugger, passively listen for a debugger, or block waiting for a
  // debugger.
  gJdwpState = JDWP::JdwpState::Create(&gJdwpOptions);
  if (gJdwpState == nullptr) {
    // We probably failed because some other process has the port already, which means that
    // if we don't abort the user is likely to think they're talking to us when they're actually
    // talking to that other process.
    LOG(FATAL) << "Debugger thread failed to initialize";
  }

  // If a debugger has already attached, send the "welcome" message.
  // This may cause us to suspend all threads.
  if (gJdwpState->IsActive()) {
    ScopedObjectAccess soa(Thread::Current());
    gJdwpState->PostVMStart();
  }
}

void Dbg::StopJdwp() {
  // Post VM_DEATH event before the JDWP connection is closed (either by the JDWP thread or the
  // destruction of gJdwpState).
  if (gJdwpState != nullptr && gJdwpState->IsActive()) {
    gJdwpState->PostVMDeath();
  }
  // Prevent the JDWP thread from processing JDWP incoming packets after we close the connection.
  Disposed();
  delete gJdwpState;
  gJdwpState = nullptr;
  delete gRegistry;
  gRegistry = nullptr;
}

void Dbg::GcDidFinish() {
  if (gDdmHpifWhen != HPIF_WHEN_NEVER) {
    ScopedObjectAccess soa(Thread::Current());
    VLOG(jdwp) << "Sending heap info to DDM";
    DdmSendHeapInfo(gDdmHpifWhen);
  }
  if (gDdmHpsgWhen != HPSG_WHEN_NEVER) {
    ScopedObjectAccess soa(Thread::Current());
    VLOG(jdwp) << "Dumping heap to DDM";
    DdmSendHeapSegments(false);
  }
  if (gDdmNhsgWhen != HPSG_WHEN_NEVER) {
    ScopedObjectAccess soa(Thread::Current());
    VLOG(jdwp) << "Dumping native heap to DDM";
    DdmSendHeapSegments(true);
  }
}

void Dbg::SetJdwpAllowed(bool allowed) {
  gJdwpAllowed = allowed;
}

DebugInvokeReq* Dbg::GetInvokeReq() {
  return Thread::Current()->GetInvokeReq();
}

Thread* Dbg::GetDebugThread() {
  return (gJdwpState != nullptr) ? gJdwpState->GetDebugThread() : nullptr;
}

void Dbg::ClearWaitForEventThread() {
  gJdwpState->ReleaseJdwpTokenForEvent();
}

void Dbg::Connected() {
  CHECK(!gDebuggerConnected);
  VLOG(jdwp) << "JDWP has attached";
  gDebuggerConnected = true;
  gDisposed = false;
}

void Dbg::Disposed() {
  gDisposed = true;
}

bool Dbg::IsDisposed() {
  return gDisposed;
}

bool Dbg::RequiresDeoptimization() {
  // We don't need deoptimization if everything runs with interpreter after
  // enabling -Xint mode.
  return !Runtime::Current()->GetInstrumentation()->IsForcedInterpretOnly();
}

void Dbg::GoActive() {
  // Enable all debugging features, including scans for breakpoints.
  // This is a no-op if we're already active.
  // Only called from the JDWP handler thread.
  if (gDebuggerActive) {
    return;
  }

  {
    // TODO: dalvik only warned if there were breakpoints left over. clear in Dbg::Disconnected?
    ReaderMutexLock mu(Thread::Current(), *Locks::breakpoint_lock_);
    CHECK_EQ(gBreakpoints.size(), 0U);
  }

  {
    MutexLock mu(Thread::Current(), *Locks::deoptimization_lock_);
    CHECK_EQ(deoptimization_requests_.size(), 0U);
    CHECK_EQ(full_deoptimization_event_count_, 0U);
    CHECK_EQ(delayed_full_undeoptimization_count_, 0U);
    CHECK_EQ(dex_pc_change_event_ref_count_, 0U);
    CHECK_EQ(method_enter_event_ref_count_, 0U);
    CHECK_EQ(method_exit_event_ref_count_, 0U);
    CHECK_EQ(field_read_event_ref_count_, 0U);
    CHECK_EQ(field_write_event_ref_count_, 0U);
    CHECK_EQ(exception_catch_event_ref_count_, 0U);
  }

  Runtime* runtime = Runtime::Current();
  runtime->GetThreadList()->SuspendAll(__FUNCTION__);
  Thread* self = Thread::Current();
  ThreadState old_state = self->SetStateUnsafe(kRunnable);
  CHECK_NE(old_state, kRunnable);
  if (RequiresDeoptimization()) {
    runtime->GetInstrumentation()->EnableDeoptimization();
  }
  instrumentation_events_ = 0;
  gDebuggerActive = true;
  CHECK_EQ(self->SetStateUnsafe(old_state), kRunnable);
  runtime->GetThreadList()->ResumeAll();

  LOG(INFO) << "Debugger is active";
}

void Dbg::Disconnected() {
  CHECK(gDebuggerConnected);

  LOG(INFO) << "Debugger is no longer active";

  // Suspend all threads and exclusively acquire the mutator lock. Set the state of the thread
  // to kRunnable to avoid scoped object access transitions. Remove the debugger as a listener
  // and clear the object registry.
  Runtime* runtime = Runtime::Current();
  runtime->GetThreadList()->SuspendAll(__FUNCTION__);
  Thread* self = Thread::Current();
  ThreadState old_state = self->SetStateUnsafe(kRunnable);

  // Debugger may not be active at this point.
  if (gDebuggerActive) {
    {
      // Since we're going to disable deoptimization, we clear the deoptimization requests queue.
      // This prevents us from having any pending deoptimization request when the debugger attaches
      // to us again while no event has been requested yet.
      MutexLock mu(Thread::Current(), *Locks::deoptimization_lock_);
      deoptimization_requests_.clear();
      full_deoptimization_event_count_ = 0U;
      delayed_full_undeoptimization_count_ = 0U;
    }
    if (instrumentation_events_ != 0) {
      runtime->GetInstrumentation()->RemoveListener(&gDebugInstrumentationListener,
                                                    instrumentation_events_);
      instrumentation_events_ = 0;
    }
    if (RequiresDeoptimization()) {
      runtime->GetInstrumentation()->DisableDeoptimization();
    }
    gDebuggerActive = false;
  }
  CHECK_EQ(self->SetStateUnsafe(old_state), kRunnable);
  runtime->GetThreadList()->ResumeAll();

  {
    ScopedObjectAccess soa(self);
    gRegistry->Clear();
  }

  gDebuggerConnected = false;
}

bool Dbg::IsDebuggerActive() {
  return gDebuggerActive;
}

void Dbg::ConfigureJdwp(const JDWP::JdwpOptions& jdwp_options) {
  CHECK_NE(jdwp_options.transport, JDWP::kJdwpTransportUnknown);
  gJdwpOptions = jdwp_options;
  gJdwpConfigured = true;
}

bool Dbg::IsJdwpConfigured() {
  return gJdwpConfigured;
}

int64_t Dbg::LastDebuggerActivity() {
  return gJdwpState->LastDebuggerActivity();
}

void Dbg::UndoDebuggerSuspensions() {
  Runtime::Current()->GetThreadList()->UndoDebuggerSuspensions();
}

std::string Dbg::GetClassName(JDWP::RefTypeId class_id) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(class_id, &error);
  if (o == nullptr) {
    if (error == JDWP::ERR_NONE) {
      return "NULL";
    } else {
      return StringPrintf("invalid object %p", reinterpret_cast<void*>(class_id));
    }
  }
  if (!o->IsClass()) {
    return StringPrintf("non-class %p", o);  // This is only used for debugging output anyway.
  }
  return GetClassName(o->AsClass());
}

std::string Dbg::GetClassName(mirror::Class* klass) {
  if (klass == nullptr) {
    return "NULL";
  }
  std::string temp;
  return DescriptorToName(klass->GetDescriptor(&temp));
}

JDWP::JdwpError Dbg::GetClassObject(JDWP::RefTypeId id, JDWP::ObjectId* class_object_id) {
  JDWP::JdwpError status;
  mirror::Class* c = DecodeClass(id, &status);
  if (c == nullptr) {
    *class_object_id = 0;
    return status;
  }
  *class_object_id = gRegistry->Add(c);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetSuperclass(JDWP::RefTypeId id, JDWP::RefTypeId* superclass_id) {
  JDWP::JdwpError status;
  mirror::Class* c = DecodeClass(id, &status);
  if (c == nullptr) {
    *superclass_id = 0;
    return status;
  }
  if (c->IsInterface()) {
    // http://code.google.com/p/android/issues/detail?id=20856
    *superclass_id = 0;
  } else {
    *superclass_id = gRegistry->Add(c->GetSuperClass());
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetClassLoader(JDWP::RefTypeId id, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(id, &error);
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  expandBufAddObjectId(pReply, gRegistry->Add(o->GetClass()->GetClassLoader()));
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetModifiers(JDWP::RefTypeId id, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(id, &error);
  if (c == nullptr) {
    return error;
  }

  uint32_t access_flags = c->GetAccessFlags() & kAccJavaFlagsMask;

  // Set ACC_SUPER. Dex files don't contain this flag but only classes are supposed to have it set,
  // not interfaces.
  // Class.getModifiers doesn't return it, but JDWP does, so we set it here.
  if ((access_flags & kAccInterface) == 0) {
    access_flags |= kAccSuper;
  }

  expandBufAdd4BE(pReply, access_flags);

  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetMonitorInfo(JDWP::ObjectId object_id, JDWP::ExpandBuf* reply) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }

  // Ensure all threads are suspended while we read objects' lock words.
  Thread* self = Thread::Current();
  CHECK_EQ(self->GetState(), kRunnable);
  self->TransitionFromRunnableToSuspended(kSuspended);
  Runtime::Current()->GetThreadList()->SuspendAll(__FUNCTION__);

  MonitorInfo monitor_info(o);

  Runtime::Current()->GetThreadList()->ResumeAll();
  self->TransitionFromSuspendedToRunnable();

  if (monitor_info.owner_ != nullptr) {
    expandBufAddObjectId(reply, gRegistry->Add(monitor_info.owner_->GetPeer()));
  } else {
    expandBufAddObjectId(reply, gRegistry->Add(nullptr));
  }
  expandBufAdd4BE(reply, monitor_info.entry_count_);
  expandBufAdd4BE(reply, monitor_info.waiters_.size());
  for (size_t i = 0; i < monitor_info.waiters_.size(); ++i) {
    expandBufAddObjectId(reply, gRegistry->Add(monitor_info.waiters_[i]->GetPeer()));
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetOwnedMonitors(JDWP::ObjectId thread_id,
                                      std::vector<JDWP::ObjectId>* monitors,
                                      std::vector<uint32_t>* stack_depths) {
  struct OwnedMonitorVisitor : public StackVisitor {
    OwnedMonitorVisitor(Thread* thread, Context* context,
                        std::vector<JDWP::ObjectId>* monitor_vector,
                        std::vector<uint32_t>* stack_depth_vector)
        SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
      : StackVisitor(thread, context), current_stack_depth(0),
        monitors(monitor_vector), stack_depths(stack_depth_vector) {}

    // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
    // annotalysis.
    bool VisitFrame() NO_THREAD_SAFETY_ANALYSIS {
      if (!GetMethod()->IsRuntimeMethod()) {
        Monitor::VisitLocks(this, AppendOwnedMonitors, this);
        ++current_stack_depth;
      }
      return true;
    }

    static void AppendOwnedMonitors(mirror::Object* owned_monitor, void* arg)
        SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
      OwnedMonitorVisitor* visitor = reinterpret_cast<OwnedMonitorVisitor*>(arg);
      visitor->monitors->push_back(gRegistry->Add(owned_monitor));
      visitor->stack_depths->push_back(visitor->current_stack_depth);
    }

    size_t current_stack_depth;
    std::vector<JDWP::ObjectId>* const monitors;
    std::vector<uint32_t>* const stack_depths;
  };

  ScopedObjectAccessUnchecked soa(Thread::Current());
  Thread* thread;
  {
    MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
    JDWP::JdwpError error;
    thread = DecodeThread(soa, thread_id, &error);
    if (thread == nullptr) {
      return error;
    }
    if (!IsSuspendedForDebugger(soa, thread)) {
      return JDWP::ERR_THREAD_NOT_SUSPENDED;
    }
  }
  std::unique_ptr<Context> context(Context::Create());
  OwnedMonitorVisitor visitor(thread, context.get(), monitors, stack_depths);
  visitor.WalkStack();
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetContendedMonitor(JDWP::ObjectId thread_id,
                                         JDWP::ObjectId* contended_monitor) {
  mirror::Object* contended_monitor_obj;
  ScopedObjectAccessUnchecked soa(Thread::Current());
  *contended_monitor = 0;
  {
    MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
    JDWP::JdwpError error;
    Thread* thread = DecodeThread(soa, thread_id, &error);
    if (thread == nullptr) {
      return error;
    }
    if (!IsSuspendedForDebugger(soa, thread)) {
      return JDWP::ERR_THREAD_NOT_SUSPENDED;
    }
    contended_monitor_obj = Monitor::GetContendedMonitor(thread);
  }
  // Add() requires the thread_list_lock_ not held to avoid the lock
  // level violation.
  *contended_monitor = gRegistry->Add(contended_monitor_obj);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetInstanceCounts(const std::vector<JDWP::RefTypeId>& class_ids,
                                       std::vector<uint64_t>* counts) {
  gc::Heap* heap = Runtime::Current()->GetHeap();
  heap->CollectGarbage(false);
  std::vector<mirror::Class*> classes;
  counts->clear();
  for (size_t i = 0; i < class_ids.size(); ++i) {
    JDWP::JdwpError error;
    mirror::Class* c = DecodeClass(class_ids[i], &error);
    if (c == nullptr) {
      return error;
    }
    classes.push_back(c);
    counts->push_back(0);
  }
  heap->CountInstances(classes, false, &(*counts)[0]);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetInstances(JDWP::RefTypeId class_id, int32_t max_count,
                                  std::vector<JDWP::ObjectId>* instances) {
  gc::Heap* heap = Runtime::Current()->GetHeap();
  // We only want reachable instances, so do a GC.
  heap->CollectGarbage(false);
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }
  std::vector<mirror::Object*> raw_instances;
  Runtime::Current()->GetHeap()->GetInstances(c, max_count, raw_instances);
  for (size_t i = 0; i < raw_instances.size(); ++i) {
    instances->push_back(gRegistry->Add(raw_instances[i]));
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetReferringObjects(JDWP::ObjectId object_id, int32_t max_count,
                                         std::vector<JDWP::ObjectId>* referring_objects) {
  gc::Heap* heap = Runtime::Current()->GetHeap();
  heap->CollectGarbage(false);
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  std::vector<mirror::Object*> raw_instances;
  heap->GetReferringObjects(o, max_count, raw_instances);
  for (size_t i = 0; i < raw_instances.size(); ++i) {
    referring_objects->push_back(gRegistry->Add(raw_instances[i]));
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::DisableCollection(JDWP::ObjectId object_id) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  gRegistry->DisableCollection(object_id);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::EnableCollection(JDWP::ObjectId object_id) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  // Unlike DisableCollection, JDWP specs do not state an invalid object causes an error. The RI
  // also ignores these cases and never return an error. However it's not obvious why this command
  // should behave differently from DisableCollection and IsCollected commands. So let's be more
  // strict and return an error if this happens.
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  gRegistry->EnableCollection(object_id);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::IsCollected(JDWP::ObjectId object_id, bool* is_collected) {
  *is_collected = true;
  if (object_id == 0) {
    // Null object id is invalid.
    return JDWP::ERR_INVALID_OBJECT;
  }
  // JDWP specs state an INVALID_OBJECT error is returned if the object ID is not valid. However
  // the RI seems to ignore this and assume object has been collected.
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (o != nullptr) {
    *is_collected = gRegistry->IsCollected(object_id);
  }
  return JDWP::ERR_NONE;
}

void Dbg::DisposeObject(JDWP::ObjectId object_id, uint32_t reference_count) {
  gRegistry->DisposeObject(object_id, reference_count);
}

JDWP::JdwpTypeTag Dbg::GetTypeTag(mirror::Class* klass) {
  DCHECK(klass != nullptr);
  if (klass->IsArrayClass()) {
    return JDWP::TT_ARRAY;
  } else if (klass->IsInterface()) {
    return JDWP::TT_INTERFACE;
  } else {
    return JDWP::TT_CLASS;
  }
}

JDWP::JdwpError Dbg::GetReflectedType(JDWP::RefTypeId class_id, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }

  JDWP::JdwpTypeTag type_tag = GetTypeTag(c);
  expandBufAdd1(pReply, type_tag);
  expandBufAddRefTypeId(pReply, class_id);
  return JDWP::ERR_NONE;
}

void Dbg::GetClassList(std::vector<JDWP::RefTypeId>* classes) {
  // Get the complete list of reference classes (i.e. all classes except
  // the primitive types).
  // Returns a newly-allocated buffer full of RefTypeId values.
  struct ClassListCreator {
    explicit ClassListCreator(std::vector<JDWP::RefTypeId>* classes_in) : classes(classes_in) {
    }

    static bool Visit(mirror::Class* c, void* arg) {
      return reinterpret_cast<ClassListCreator*>(arg)->Visit(c);
    }

    // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
    // annotalysis.
    bool Visit(mirror::Class* c) NO_THREAD_SAFETY_ANALYSIS {
      if (!c->IsPrimitive()) {
        classes->push_back(gRegistry->AddRefType(c));
      }
      return true;
    }

    std::vector<JDWP::RefTypeId>* const classes;
  };

  ClassListCreator clc(classes);
  Runtime::Current()->GetClassLinker()->VisitClassesWithoutClassesLock(ClassListCreator::Visit,
                                                                       &clc);
}

JDWP::JdwpError Dbg::GetClassInfo(JDWP::RefTypeId class_id, JDWP::JdwpTypeTag* pTypeTag,
                                  uint32_t* pStatus, std::string* pDescriptor) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }

  if (c->IsArrayClass()) {
    *pStatus = JDWP::CS_VERIFIED | JDWP::CS_PREPARED;
    *pTypeTag = JDWP::TT_ARRAY;
  } else {
    if (c->IsErroneous()) {
      *pStatus = JDWP::CS_ERROR;
    } else {
      *pStatus = JDWP::CS_VERIFIED | JDWP::CS_PREPARED | JDWP::CS_INITIALIZED;
    }
    *pTypeTag = c->IsInterface() ? JDWP::TT_INTERFACE : JDWP::TT_CLASS;
  }

  if (pDescriptor != nullptr) {
    std::string temp;
    *pDescriptor = c->GetDescriptor(&temp);
  }
  return JDWP::ERR_NONE;
}

void Dbg::FindLoadedClassBySignature(const char* descriptor, std::vector<JDWP::RefTypeId>* ids) {
  std::vector<mirror::Class*> classes;
  Runtime::Current()->GetClassLinker()->LookupClasses(descriptor, classes);
  ids->clear();
  for (size_t i = 0; i < classes.size(); ++i) {
    ids->push_back(gRegistry->Add(classes[i]));
  }
}

JDWP::JdwpError Dbg::GetReferenceType(JDWP::ObjectId object_id, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (o == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }

  JDWP::JdwpTypeTag type_tag = GetTypeTag(o->GetClass());
  JDWP::RefTypeId type_id = gRegistry->AddRefType(o->GetClass());

  expandBufAdd1(pReply, type_tag);
  expandBufAddRefTypeId(pReply, type_id);

  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetSignature(JDWP::RefTypeId class_id, std::string* signature) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }
  std::string temp;
  *signature = c->GetDescriptor(&temp);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetSourceFile(JDWP::RefTypeId class_id, std::string* result) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }
  const char* source_file = c->GetSourceFile();
  if (source_file == nullptr) {
    return JDWP::ERR_ABSENT_INFORMATION;
  }
  *result = source_file;
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetObjectTag(JDWP::ObjectId object_id, uint8_t* tag) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* o = gRegistry->Get<mirror::Object*>(object_id, &error);
  if (error != JDWP::ERR_NONE) {
    *tag = JDWP::JT_VOID;
    return error;
  }
  *tag = TagFromObject(soa, o);
  return JDWP::ERR_NONE;
}

size_t Dbg::GetTagWidth(JDWP::JdwpTag tag) {
  switch (tag) {
  case JDWP::JT_VOID:
    return 0;
  case JDWP::JT_BYTE:
  case JDWP::JT_BOOLEAN:
    return 1;
  case JDWP::JT_CHAR:
  case JDWP::JT_SHORT:
    return 2;
  case JDWP::JT_FLOAT:
  case JDWP::JT_INT:
    return 4;
  case JDWP::JT_ARRAY:
  case JDWP::JT_OBJECT:
  case JDWP::JT_STRING:
  case JDWP::JT_THREAD:
  case JDWP::JT_THREAD_GROUP:
  case JDWP::JT_CLASS_LOADER:
  case JDWP::JT_CLASS_OBJECT:
    return sizeof(JDWP::ObjectId);
  case JDWP::JT_DOUBLE:
  case JDWP::JT_LONG:
    return 8;
  default:
    LOG(FATAL) << "Unknown tag " << tag;
    return -1;
  }
}

JDWP::JdwpError Dbg::GetArrayLength(JDWP::ObjectId array_id, int32_t* length) {
  JDWP::JdwpError error;
  mirror::Array* a = DecodeNonNullArray(array_id, &error);
  if (a == nullptr) {
    return error;
  }
  *length = a->GetLength();
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::OutputArray(JDWP::ObjectId array_id, int offset, int count, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Array* a = DecodeNonNullArray(array_id, &error);
  if (a == nullptr) {
    return error;
  }

  if (offset < 0 || count < 0 || offset > a->GetLength() || a->GetLength() - offset < count) {
    LOG(WARNING) << __FUNCTION__ << " access out of bounds: offset=" << offset << "; count=" << count;
    return JDWP::ERR_INVALID_LENGTH;
  }
  JDWP::JdwpTag element_tag = BasicTagFromClass(a->GetClass()->GetComponentType());
  expandBufAdd1(pReply, element_tag);
  expandBufAdd4BE(pReply, count);

  if (IsPrimitiveTag(element_tag)) {
    size_t width = GetTagWidth(element_tag);
    uint8_t* dst = expandBufAddSpace(pReply, count * width);
    if (width == 8) {
      const uint64_t* src8 = reinterpret_cast<uint64_t*>(a->GetRawData(sizeof(uint64_t), 0));
      for (int i = 0; i < count; ++i) JDWP::Write8BE(&dst, src8[offset + i]);
    } else if (width == 4) {
      const uint32_t* src4 = reinterpret_cast<uint32_t*>(a->GetRawData(sizeof(uint32_t), 0));
      for (int i = 0; i < count; ++i) JDWP::Write4BE(&dst, src4[offset + i]);
    } else if (width == 2) {
      const uint16_t* src2 = reinterpret_cast<uint16_t*>(a->GetRawData(sizeof(uint16_t), 0));
      for (int i = 0; i < count; ++i) JDWP::Write2BE(&dst, src2[offset + i]);
    } else {
      const uint8_t* src = reinterpret_cast<uint8_t*>(a->GetRawData(sizeof(uint8_t), 0));
      memcpy(dst, &src[offset * width], count * width);
    }
  } else {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    mirror::ObjectArray<mirror::Object>* oa = a->AsObjectArray<mirror::Object>();
    for (int i = 0; i < count; ++i) {
      mirror::Object* element = oa->Get(offset + i);
      JDWP::JdwpTag specific_tag = (element != nullptr) ? TagFromObject(soa, element)
                                                        : element_tag;
      expandBufAdd1(pReply, specific_tag);
      expandBufAddObjectId(pReply, gRegistry->Add(element));
    }
  }

  return JDWP::ERR_NONE;
}

template <typename T>
static void CopyArrayData(mirror::Array* a, JDWP::Request* src, int offset, int count)
    NO_THREAD_SAFETY_ANALYSIS {
  // TODO: fix when annotalysis correctly handles non-member functions.
  DCHECK(a->GetClass()->IsPrimitiveArray());

  T* dst = reinterpret_cast<T*>(a->GetRawData(sizeof(T), offset));
  for (int i = 0; i < count; ++i) {
    *dst++ = src->ReadValue(sizeof(T));
  }
}

JDWP::JdwpError Dbg::SetArrayElements(JDWP::ObjectId array_id, int offset, int count,
                                      JDWP::Request* request) {
  JDWP::JdwpError error;
  mirror::Array* dst = DecodeNonNullArray(array_id, &error);
  if (dst == nullptr) {
    return error;
  }

  if (offset < 0 || count < 0 || offset > dst->GetLength() || dst->GetLength() - offset < count) {
    LOG(WARNING) << __FUNCTION__ << " access out of bounds: offset=" << offset << "; count=" << count;
    return JDWP::ERR_INVALID_LENGTH;
  }
  JDWP::JdwpTag element_tag = BasicTagFromClass(dst->GetClass()->GetComponentType());

  if (IsPrimitiveTag(element_tag)) {
    size_t width = GetTagWidth(element_tag);
    if (width == 8) {
      CopyArrayData<uint64_t>(dst, request, offset, count);
    } else if (width == 4) {
      CopyArrayData<uint32_t>(dst, request, offset, count);
    } else if (width == 2) {
      CopyArrayData<uint16_t>(dst, request, offset, count);
    } else {
      CopyArrayData<uint8_t>(dst, request, offset, count);
    }
  } else {
    mirror::ObjectArray<mirror::Object>* oa = dst->AsObjectArray<mirror::Object>();
    for (int i = 0; i < count; ++i) {
      JDWP::ObjectId id = request->ReadObjectId();
      mirror::Object* o = gRegistry->Get<mirror::Object*>(id, &error);
      if (error != JDWP::ERR_NONE) {
        return error;
      }
      oa->Set<false>(offset + i, o);
    }
  }

  return JDWP::ERR_NONE;
}

JDWP::ObjectId Dbg::CreateString(const std::string& str) {
  return gRegistry->Add(mirror::String::AllocFromModifiedUtf8(Thread::Current(), str.c_str()));
}

JDWP::JdwpError Dbg::CreateObject(JDWP::RefTypeId class_id, JDWP::ObjectId* new_object) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    *new_object = 0;
    return error;
  }
  *new_object = gRegistry->Add(c->AllocObject(Thread::Current()));
  return JDWP::ERR_NONE;
}

/*
 * Used by Eclipse's "Display" view to evaluate "new byte[5]" to get "(byte[]) [0, 0, 0, 0, 0]".
 */
JDWP::JdwpError Dbg::CreateArrayObject(JDWP::RefTypeId array_class_id, uint32_t length,
                                       JDWP::ObjectId* new_array) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(array_class_id, &error);
  if (c == nullptr) {
    *new_array = 0;
    return error;
  }
  *new_array = gRegistry->Add(mirror::Array::Alloc<true>(Thread::Current(), c, length,
                                                         c->GetComponentSizeShift(),
                                                         Runtime::Current()->GetHeap()->GetCurrentAllocator()));
  return JDWP::ERR_NONE;
}

JDWP::FieldId Dbg::ToFieldId(const mirror::ArtField* f) {
  CHECK(!kMovingFields);
  return static_cast<JDWP::FieldId>(reinterpret_cast<uintptr_t>(f));
}

static JDWP::MethodId ToMethodId(const mirror::ArtMethod* m)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  CHECK(!kMovingMethods);
  return static_cast<JDWP::MethodId>(reinterpret_cast<uintptr_t>(m));
}

static mirror::ArtField* FromFieldId(JDWP::FieldId fid)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  CHECK(!kMovingFields);
  return reinterpret_cast<mirror::ArtField*>(static_cast<uintptr_t>(fid));
}

static mirror::ArtMethod* FromMethodId(JDWP::MethodId mid)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  CHECK(!kMovingMethods);
  return reinterpret_cast<mirror::ArtMethod*>(static_cast<uintptr_t>(mid));
}

bool Dbg::MatchThread(JDWP::ObjectId expected_thread_id, Thread* event_thread) {
  CHECK(event_thread != nullptr);
  JDWP::JdwpError error;
  mirror::Object* expected_thread_peer = gRegistry->Get<mirror::Object*>(expected_thread_id,
                                                                         &error);
  return expected_thread_peer == event_thread->GetPeer();
}

bool Dbg::MatchLocation(const JDWP::JdwpLocation& expected_location,
                        const JDWP::EventLocation& event_location) {
  if (expected_location.dex_pc != event_location.dex_pc) {
    return false;
  }
  mirror::ArtMethod* m = FromMethodId(expected_location.method_id);
  return m == event_location.method;
}

bool Dbg::MatchType(mirror::Class* event_class, JDWP::RefTypeId class_id) {
  if (event_class == nullptr) {
    return false;
  }
  JDWP::JdwpError error;
  mirror::Class* expected_class = DecodeClass(class_id, &error);
  CHECK(expected_class != nullptr);
  return expected_class->IsAssignableFrom(event_class);
}

bool Dbg::MatchField(JDWP::RefTypeId expected_type_id, JDWP::FieldId expected_field_id,
                     mirror::ArtField* event_field) {
  mirror::ArtField* expected_field = FromFieldId(expected_field_id);
  if (expected_field != event_field) {
    return false;
  }
  return Dbg::MatchType(event_field->GetDeclaringClass(), expected_type_id);
}

bool Dbg::MatchInstance(JDWP::ObjectId expected_instance_id, mirror::Object* event_instance) {
  JDWP::JdwpError error;
  mirror::Object* modifier_instance = gRegistry->Get<mirror::Object*>(expected_instance_id, &error);
  return modifier_instance == event_instance;
}

void Dbg::SetJdwpLocation(JDWP::JdwpLocation* location, mirror::ArtMethod* m, uint32_t dex_pc)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  if (m == nullptr) {
    memset(location, 0, sizeof(*location));
  } else {
    mirror::Class* c = m->GetDeclaringClass();
    location->type_tag = GetTypeTag(c);
    location->class_id = gRegistry->AddRefType(c);
    location->method_id = ToMethodId(m);
    location->dex_pc = (m->IsNative() || m->IsProxyMethod()) ? static_cast<uint64_t>(-1) : dex_pc;
  }
}

std::string Dbg::GetMethodName(JDWP::MethodId method_id) {
  mirror::ArtMethod* m = FromMethodId(method_id);
  if (m == nullptr) {
    return "NULL";
  }
  return m->GetName();
}

std::string Dbg::GetFieldName(JDWP::FieldId field_id) {
  mirror::ArtField* f = FromFieldId(field_id);
  if (f == nullptr) {
    return "NULL";
  }
  return f->GetName();
}

/*
 * Augment the access flags for synthetic methods and fields by setting
 * the (as described by the spec) "0xf0000000 bit".  Also, strip out any
 * flags not specified by the Java programming language.
 */
static uint32_t MangleAccessFlags(uint32_t accessFlags) {
  accessFlags &= kAccJavaFlagsMask;
  if ((accessFlags & kAccSynthetic) != 0) {
    accessFlags |= 0xf0000000;
  }
  return accessFlags;
}

/*
 * Circularly shifts registers so that arguments come first. Debuggers
 * expect slots to begin with arguments, but dex code places them at
 * the end.
 */
static uint16_t MangleSlot(uint16_t slot, mirror::ArtMethod* m)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  const DexFile::CodeItem* code_item = m->GetCodeItem();
  if (code_item == nullptr) {
    // We should not get here for a method without code (native, proxy or abstract). Log it and
    // return the slot as is since all registers are arguments.
    LOG(WARNING) << "Trying to mangle slot for method without code " << PrettyMethod(m);
    return slot;
  }
  uint16_t ins_size = code_item->ins_size_;
  uint16_t locals_size = code_item->registers_size_ - ins_size;
  if (slot >= locals_size) {
    return slot - locals_size;
  } else {
    return slot + ins_size;
  }
}

/*
 * Circularly shifts registers so that arguments come last. Reverts
 * slots to dex style argument placement.
 */
static uint16_t DemangleSlot(uint16_t slot, mirror::ArtMethod* m)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  const DexFile::CodeItem* code_item = m->GetCodeItem();
  if (code_item == nullptr) {
    // We should not get here for a method without code (native, proxy or abstract). Log it and
    // return the slot as is since all registers are arguments.
    LOG(WARNING) << "Trying to demangle slot for method without code " << PrettyMethod(m);
    return slot;
  }
  uint16_t ins_size = code_item->ins_size_;
  uint16_t locals_size = code_item->registers_size_ - ins_size;
  if (slot < ins_size) {
    return slot + locals_size;
  } else {
    return slot - ins_size;
  }
}

JDWP::JdwpError Dbg::OutputDeclaredFields(JDWP::RefTypeId class_id, bool with_generic, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }

  size_t instance_field_count = c->NumInstanceFields();
  size_t static_field_count = c->NumStaticFields();

  expandBufAdd4BE(pReply, instance_field_count + static_field_count);

  for (size_t i = 0; i < instance_field_count + static_field_count; ++i) {
    mirror::ArtField* f = (i < instance_field_count) ? c->GetInstanceField(i) : c->GetStaticField(i - instance_field_count);
    expandBufAddFieldId(pReply, ToFieldId(f));
    expandBufAddUtf8String(pReply, f->GetName());
    expandBufAddUtf8String(pReply, f->GetTypeDescriptor());
    if (with_generic) {
      static const char genericSignature[1] = "";
      expandBufAddUtf8String(pReply, genericSignature);
    }
    expandBufAdd4BE(pReply, MangleAccessFlags(f->GetAccessFlags()));
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::OutputDeclaredMethods(JDWP::RefTypeId class_id, bool with_generic,
                                           JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(class_id, &error);
  if (c == nullptr) {
    return error;
  }

  size_t direct_method_count = c->NumDirectMethods();
  size_t virtual_method_count = c->NumVirtualMethods();

  expandBufAdd4BE(pReply, direct_method_count + virtual_method_count);

  for (size_t i = 0; i < direct_method_count + virtual_method_count; ++i) {
    mirror::ArtMethod* m = (i < direct_method_count) ? c->GetDirectMethod(i) : c->GetVirtualMethod(i - direct_method_count);
    expandBufAddMethodId(pReply, ToMethodId(m));
    expandBufAddUtf8String(pReply, m->GetName());
    expandBufAddUtf8String(pReply, m->GetSignature().ToString());
    if (with_generic) {
      static const char genericSignature[1] = "";
      expandBufAddUtf8String(pReply, genericSignature);
    }
    expandBufAdd4BE(pReply, MangleAccessFlags(m->GetAccessFlags()));
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::OutputDeclaredInterfaces(JDWP::RefTypeId class_id, JDWP::ExpandBuf* pReply) {
  JDWP::JdwpError error;
  Thread* self = Thread::Current();
  StackHandleScope<1> hs(self);
  Handle<mirror::Class> c(hs.NewHandle(DecodeClass(class_id, &error)));
  if (c.Get() == nullptr) {
    return error;
  }
  size_t interface_count = c->NumDirectInterfaces();
  expandBufAdd4BE(pReply, interface_count);
  for (size_t i = 0; i < interface_count; ++i) {
    expandBufAddRefTypeId(pReply,
                          gRegistry->AddRefType(mirror::Class::GetDirectInterface(self, c, i)));
  }
  return JDWP::ERR_NONE;
}

void Dbg::OutputLineTable(JDWP::RefTypeId, JDWP::MethodId method_id, JDWP::ExpandBuf* pReply) {
  struct DebugCallbackContext {
    int numItems;
    JDWP::ExpandBuf* pReply;

    static bool Callback(void* context, uint32_t address, uint32_t line_number) {
      DebugCallbackContext* pContext = reinterpret_cast<DebugCallbackContext*>(context);
      expandBufAdd8BE(pContext->pReply, address);
      expandBufAdd4BE(pContext->pReply, line_number);
      pContext->numItems++;
      return false;
    }
  };
  mirror::ArtMethod* m = FromMethodId(method_id);
  const DexFile::CodeItem* code_item = m->GetCodeItem();
  uint64_t start, end;
  if (code_item == nullptr) {
    DCHECK(m->IsNative() || m->IsProxyMethod());
    start = -1;
    end = -1;
  } else {
    start = 0;
    // Return the index of the last instruction
    end = code_item->insns_size_in_code_units_ - 1;
  }

  expandBufAdd8BE(pReply, start);
  expandBufAdd8BE(pReply, end);

  // Add numLines later
  size_t numLinesOffset = expandBufGetLength(pReply);
  expandBufAdd4BE(pReply, 0);

  DebugCallbackContext context;
  context.numItems = 0;
  context.pReply = pReply;

  if (code_item != nullptr) {
    m->GetDexFile()->DecodeDebugInfo(code_item, m->IsStatic(), m->GetDexMethodIndex(),
                                     DebugCallbackContext::Callback, nullptr, &context);
  }

  JDWP::Set4BE(expandBufGetBuffer(pReply) + numLinesOffset, context.numItems);
}

void Dbg::OutputVariableTable(JDWP::RefTypeId, JDWP::MethodId method_id, bool with_generic,
                              JDWP::ExpandBuf* pReply) {
  struct DebugCallbackContext {
    mirror::ArtMethod* method;
    JDWP::ExpandBuf* pReply;
    size_t variable_count;
    bool with_generic;

    static void Callback(void* context, uint16_t slot, uint32_t startAddress, uint32_t endAddress,
                         const char* name, const char* descriptor, const char* signature)
        SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
      DebugCallbackContext* pContext = reinterpret_cast<DebugCallbackContext*>(context);

      VLOG(jdwp) << StringPrintf("    %2zd: %d(%d) '%s' '%s' '%s' actual slot=%d mangled slot=%d",
                                 pContext->variable_count, startAddress, endAddress - startAddress,
                                 name, descriptor, signature, slot,
                                 MangleSlot(slot, pContext->method));

      slot = MangleSlot(slot, pContext->method);

      expandBufAdd8BE(pContext->pReply, startAddress);
      expandBufAddUtf8String(pContext->pReply, name);
      expandBufAddUtf8String(pContext->pReply, descriptor);
      if (pContext->with_generic) {
        expandBufAddUtf8String(pContext->pReply, signature);
      }
      expandBufAdd4BE(pContext->pReply, endAddress - startAddress);
      expandBufAdd4BE(pContext->pReply, slot);

      ++pContext->variable_count;
    }
  };
  mirror::ArtMethod* m = FromMethodId(method_id);

  // arg_count considers doubles and longs to take 2 units.
  // variable_count considers everything to take 1 unit.
  std::string shorty(m->GetShorty());
  expandBufAdd4BE(pReply, mirror::ArtMethod::NumArgRegisters(shorty));

  // We don't know the total number of variables yet, so leave a blank and update it later.
  size_t variable_count_offset = expandBufGetLength(pReply);
  expandBufAdd4BE(pReply, 0);

  DebugCallbackContext context;
  context.method = m;
  context.pReply = pReply;
  context.variable_count = 0;
  context.with_generic = with_generic;

  const DexFile::CodeItem* code_item = m->GetCodeItem();
  if (code_item != nullptr) {
    m->GetDexFile()->DecodeDebugInfo(
        code_item, m->IsStatic(), m->GetDexMethodIndex(), nullptr, DebugCallbackContext::Callback,
        &context);
  }

  JDWP::Set4BE(expandBufGetBuffer(pReply) + variable_count_offset, context.variable_count);
}

void Dbg::OutputMethodReturnValue(JDWP::MethodId method_id, const JValue* return_value,
                                  JDWP::ExpandBuf* pReply) {
  mirror::ArtMethod* m = FromMethodId(method_id);
  JDWP::JdwpTag tag = BasicTagFromDescriptor(m->GetShorty());
  OutputJValue(tag, return_value, pReply);
}

void Dbg::OutputFieldValue(JDWP::FieldId field_id, const JValue* field_value,
                           JDWP::ExpandBuf* pReply) {
  mirror::ArtField* f = FromFieldId(field_id);
  JDWP::JdwpTag tag = BasicTagFromDescriptor(f->GetTypeDescriptor());
  OutputJValue(tag, field_value, pReply);
}

JDWP::JdwpError Dbg::GetBytecodes(JDWP::RefTypeId, JDWP::MethodId method_id,
                                  std::vector<uint8_t>* bytecodes) {
  mirror::ArtMethod* m = FromMethodId(method_id);
  if (m == nullptr) {
    return JDWP::ERR_INVALID_METHODID;
  }
  const DexFile::CodeItem* code_item = m->GetCodeItem();
  size_t byte_count = code_item->insns_size_in_code_units_ * 2;
  const uint8_t* begin = reinterpret_cast<const uint8_t*>(code_item->insns_);
  const uint8_t* end = begin + byte_count;
  for (const uint8_t* p = begin; p != end; ++p) {
    bytecodes->push_back(*p);
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpTag Dbg::GetFieldBasicTag(JDWP::FieldId field_id) {
  return BasicTagFromDescriptor(FromFieldId(field_id)->GetTypeDescriptor());
}

JDWP::JdwpTag Dbg::GetStaticFieldBasicTag(JDWP::FieldId field_id) {
  return BasicTagFromDescriptor(FromFieldId(field_id)->GetTypeDescriptor());
}

static JDWP::JdwpError GetFieldValueImpl(JDWP::RefTypeId ref_type_id, JDWP::ObjectId object_id,
                                         JDWP::FieldId field_id, JDWP::ExpandBuf* pReply,
                                         bool is_static)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  JDWP::JdwpError error;
  mirror::Class* c = DecodeClass(ref_type_id, &error);
  if (ref_type_id != 0 && c == nullptr) {
    return error;
  }

  mirror::Object* o = Dbg::GetObjectRegistry()->Get<mirror::Object*>(object_id, &error);
  if ((!is_static && o == nullptr) || error != JDWP::ERR_NONE) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  mirror::ArtField* f = FromFieldId(field_id);

  mirror::Class* receiver_class = c;
  if (receiver_class == nullptr && o != nullptr) {
    receiver_class = o->GetClass();
  }
  // TODO: should we give up now if receiver_class is nullptr?
  if (receiver_class != nullptr && !f->GetDeclaringClass()->IsAssignableFrom(receiver_class)) {
    LOG(INFO) << "ERR_INVALID_FIELDID: " << PrettyField(f) << " " << PrettyClass(receiver_class);
    return JDWP::ERR_INVALID_FIELDID;
  }

  // The RI only enforces the static/non-static mismatch in one direction.
  // TODO: should we change the tests and check both?
  if (is_static) {
    if (!f->IsStatic()) {
      return JDWP::ERR_INVALID_FIELDID;
    }
  } else {
    if (f->IsStatic()) {
      LOG(WARNING) << "Ignoring non-nullptr receiver for ObjectReference.SetValues on static field "
          << PrettyField(f);
    }
  }
  if (f->IsStatic()) {
    o = f->GetDeclaringClass();
  }

  JDWP::JdwpTag tag = BasicTagFromDescriptor(f->GetTypeDescriptor());
  JValue field_value;
  if (tag == JDWP::JT_VOID) {
    LOG(FATAL) << "Unknown tag: " << tag;
  } else if (!IsPrimitiveTag(tag)) {
    field_value.SetL(f->GetObject(o));
  } else if (tag == JDWP::JT_DOUBLE || tag == JDWP::JT_LONG) {
    field_value.SetJ(f->Get64(o));
  } else {
    field_value.SetI(f->Get32(o));
  }
  Dbg::OutputJValue(tag, &field_value, pReply);

  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetFieldValue(JDWP::ObjectId object_id, JDWP::FieldId field_id,
                                   JDWP::ExpandBuf* pReply) {
  return GetFieldValueImpl(0, object_id, field_id, pReply, false);
}

JDWP::JdwpError Dbg::GetStaticFieldValue(JDWP::RefTypeId ref_type_id, JDWP::FieldId field_id,
                                         JDWP::ExpandBuf* pReply) {
  return GetFieldValueImpl(ref_type_id, 0, field_id, pReply, true);
}

static JDWP::JdwpError SetFieldValueImpl(JDWP::ObjectId object_id, JDWP::FieldId field_id,
                                         uint64_t value, int width, bool is_static)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  JDWP::JdwpError error;
  mirror::Object* o = Dbg::GetObjectRegistry()->Get<mirror::Object*>(object_id, &error);
  if ((!is_static && o == nullptr) || error != JDWP::ERR_NONE) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  mirror::ArtField* f = FromFieldId(field_id);

  // The RI only enforces the static/non-static mismatch in one direction.
  // TODO: should we change the tests and check both?
  if (is_static) {
    if (!f->IsStatic()) {
      return JDWP::ERR_INVALID_FIELDID;
    }
  } else {
    if (f->IsStatic()) {
      LOG(WARNING) << "Ignoring non-nullptr receiver for ObjectReference.SetValues on static field " << PrettyField(f);
    }
  }
  if (f->IsStatic()) {
    o = f->GetDeclaringClass();
  }

  JDWP::JdwpTag tag = BasicTagFromDescriptor(f->GetTypeDescriptor());

  if (IsPrimitiveTag(tag)) {
    if (tag == JDWP::JT_DOUBLE || tag == JDWP::JT_LONG) {
      CHECK_EQ(width, 8);
      // Debugging can't use transactional mode (runtime only).
      f->Set64<false>(o, value);
    } else {
      CHECK_LE(width, 4);
      // Debugging can't use transactional mode (runtime only).
      f->Set32<false>(o, value);
    }
  } else {
    mirror::Object* v = Dbg::GetObjectRegistry()->Get<mirror::Object*>(value, &error);
    if (error != JDWP::ERR_NONE) {
      return JDWP::ERR_INVALID_OBJECT;
    }
    if (v != nullptr) {
      mirror::Class* field_type;
      {
        StackHandleScope<3> hs(Thread::Current());
        HandleWrapper<mirror::Object> h_v(hs.NewHandleWrapper(&v));
        HandleWrapper<mirror::ArtField> h_f(hs.NewHandleWrapper(&f));
        HandleWrapper<mirror::Object> h_o(hs.NewHandleWrapper(&o));
        field_type = h_f->GetType(true);
      }
      if (!field_type->IsAssignableFrom(v->GetClass())) {
        return JDWP::ERR_INVALID_OBJECT;
      }
    }
    // Debugging can't use transactional mode (runtime only).
    f->SetObject<false>(o, v);
  }

  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::SetFieldValue(JDWP::ObjectId object_id, JDWP::FieldId field_id, uint64_t value,
                                   int width) {
  return SetFieldValueImpl(object_id, field_id, value, width, false);
}

JDWP::JdwpError Dbg::SetStaticFieldValue(JDWP::FieldId field_id, uint64_t value, int width) {
  return SetFieldValueImpl(0, field_id, value, width, true);
}

JDWP::JdwpError Dbg::StringToUtf8(JDWP::ObjectId string_id, std::string* str) {
  JDWP::JdwpError error;
  mirror::Object* obj = gRegistry->Get<mirror::Object*>(string_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  if (obj == nullptr) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    mirror::Class* java_lang_String = soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_String);
    if (!java_lang_String->IsAssignableFrom(obj->GetClass())) {
      // This isn't a string.
      return JDWP::ERR_INVALID_STRING;
    }
  }
  *str = obj->AsString()->ToModifiedUtf8();
  return JDWP::ERR_NONE;
}

void Dbg::OutputJValue(JDWP::JdwpTag tag, const JValue* return_value, JDWP::ExpandBuf* pReply) {
  if (IsPrimitiveTag(tag)) {
    expandBufAdd1(pReply, tag);
    if (tag == JDWP::JT_BOOLEAN || tag == JDWP::JT_BYTE) {
      expandBufAdd1(pReply, return_value->GetI());
    } else if (tag == JDWP::JT_CHAR || tag == JDWP::JT_SHORT) {
      expandBufAdd2BE(pReply, return_value->GetI());
    } else if (tag == JDWP::JT_FLOAT || tag == JDWP::JT_INT) {
      expandBufAdd4BE(pReply, return_value->GetI());
    } else if (tag == JDWP::JT_DOUBLE || tag == JDWP::JT_LONG) {
      expandBufAdd8BE(pReply, return_value->GetJ());
    } else {
      CHECK_EQ(tag, JDWP::JT_VOID);
    }
  } else {
    ScopedObjectAccessUnchecked soa(Thread::Current());
    mirror::Object* value = return_value->GetL();
    expandBufAdd1(pReply, TagFromObject(soa, value));
    expandBufAddObjectId(pReply, gRegistry->Add(value));
  }
}

JDWP::JdwpError Dbg::GetThreadName(JDWP::ObjectId thread_id, std::string* name) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  UNUSED(thread);
  if (error != JDWP::ERR_NONE && error != JDWP::ERR_THREAD_NOT_ALIVE) {
    return error;
  }

  // We still need to report the zombie threads' names, so we can't just call Thread::GetThreadName.
  mirror::Object* thread_object = gRegistry->Get<mirror::Object*>(thread_id, &error);
  CHECK(thread_object != nullptr) << error;
  mirror::ArtField* java_lang_Thread_name_field =
      soa.DecodeField(WellKnownClasses::java_lang_Thread_name);
  mirror::String* s =
      reinterpret_cast<mirror::String*>(java_lang_Thread_name_field->GetObject(thread_object));
  if (s != nullptr) {
    *name = s->ToModifiedUtf8();
  }
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetThreadGroup(JDWP::ObjectId thread_id, JDWP::ExpandBuf* pReply) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* thread_object = gRegistry->Get<mirror::Object*>(thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    return JDWP::ERR_INVALID_OBJECT;
  }
  ScopedAssertNoThreadSuspension ants(soa.Self(), "Debugger: GetThreadGroup");
  // Okay, so it's an object, but is it actually a thread?
  {
    MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
    Thread* thread = DecodeThread(soa, thread_id, &error);
    UNUSED(thread);
  }
  if (error == JDWP::ERR_THREAD_NOT_ALIVE) {
    // Zombie threads are in the null group.
    expandBufAddObjectId(pReply, JDWP::ObjectId(0));
    error = JDWP::ERR_NONE;
  } else if (error == JDWP::ERR_NONE) {
    mirror::Class* c = soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_Thread);
    CHECK(c != nullptr);
    mirror::ArtField* f = soa.DecodeField(WellKnownClasses::java_lang_Thread_group);
    CHECK(f != nullptr);
    mirror::Object* group = f->GetObject(thread_object);
    CHECK(group != nullptr);
    JDWP::ObjectId thread_group_id = gRegistry->Add(group);
    expandBufAddObjectId(pReply, thread_group_id);
  }
  return error;
}

static mirror::Object* DecodeThreadGroup(ScopedObjectAccessUnchecked& soa,
                                         JDWP::ObjectId thread_group_id, JDWP::JdwpError* error)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  mirror::Object* thread_group = Dbg::GetObjectRegistry()->Get<mirror::Object*>(thread_group_id,
                                                                                error);
  if (*error != JDWP::ERR_NONE) {
    return nullptr;
  }
  if (thread_group == nullptr) {
    *error = JDWP::ERR_INVALID_OBJECT;
    return nullptr;
  }
  mirror::Class* c = soa.Decode<mirror::Class*>(WellKnownClasses::java_lang_ThreadGroup);
  CHECK(c != nullptr);
  if (!c->IsAssignableFrom(thread_group->GetClass())) {
    // This is not a java.lang.ThreadGroup.
    *error = JDWP::ERR_INVALID_THREAD_GROUP;
    return nullptr;
  }
  *error = JDWP::ERR_NONE;
  return thread_group;
}

JDWP::JdwpError Dbg::GetThreadGroupName(JDWP::ObjectId thread_group_id, JDWP::ExpandBuf* pReply) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* thread_group = DecodeThreadGroup(soa, thread_group_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  ScopedAssertNoThreadSuspension ants(soa.Self(), "Debugger: GetThreadGroupName");
  mirror::ArtField* f = soa.DecodeField(WellKnownClasses::java_lang_ThreadGroup_name);
  CHECK(f != nullptr);
  mirror::String* s = reinterpret_cast<mirror::String*>(f->GetObject(thread_group));

  std::string thread_group_name(s->ToModifiedUtf8());
  expandBufAddUtf8String(pReply, thread_group_name);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetThreadGroupParent(JDWP::ObjectId thread_group_id, JDWP::ExpandBuf* pReply) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* thread_group = DecodeThreadGroup(soa, thread_group_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  mirror::Object* parent;
  {
    ScopedAssertNoThreadSuspension ants(soa.Self(), "Debugger: GetThreadGroupParent");
    mirror::ArtField* f = soa.DecodeField(WellKnownClasses::java_lang_ThreadGroup_parent);
    CHECK(f != nullptr);
    parent = f->GetObject(thread_group);
  }
  JDWP::ObjectId parent_group_id = gRegistry->Add(parent);
  expandBufAddObjectId(pReply, parent_group_id);
  return JDWP::ERR_NONE;
}

static void GetChildThreadGroups(ScopedObjectAccessUnchecked& soa, mirror::Object* thread_group,
                                 std::vector<JDWP::ObjectId>* child_thread_group_ids)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  CHECK(thread_group != nullptr);

  // Get the ArrayList<ThreadGroup> "groups" out of this thread group...
  mirror::ArtField* groups_field = soa.DecodeField(WellKnownClasses::java_lang_ThreadGroup_groups);
  mirror::Object* groups_array_list = groups_field->GetObject(thread_group);
  {
    // The "groups" field is declared as a java.util.List: check it really is
    // an instance of java.util.ArrayList.
    CHECK(groups_array_list != nullptr);
    mirror::Class* java_util_ArrayList_class =
        soa.Decode<mirror::Class*>(WellKnownClasses::java_util_ArrayList);
    CHECK(groups_array_list->InstanceOf(java_util_ArrayList_class));
  }

  // Get the array and size out of the ArrayList<ThreadGroup>...
  mirror::ArtField* array_field = soa.DecodeField(WellKnownClasses::java_util_ArrayList_array);
  mirror::ArtField* size_field = soa.DecodeField(WellKnownClasses::java_util_ArrayList_size);
  mirror::ObjectArray<mirror::Object>* groups_array =
      array_field->GetObject(groups_array_list)->AsObjectArray<mirror::Object>();
  const int32_t size = size_field->GetInt(groups_array_list);

  // Copy the first 'size' elements out of the array into the result.
  ObjectRegistry* registry = Dbg::GetObjectRegistry();
  for (int32_t i = 0; i < size; ++i) {
    child_thread_group_ids->push_back(registry->Add(groups_array->Get(i)));
  }
}

JDWP::JdwpError Dbg::GetThreadGroupChildren(JDWP::ObjectId thread_group_id,
                                            JDWP::ExpandBuf* pReply) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* thread_group = DecodeThreadGroup(soa, thread_group_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }

  // Add child threads.
  {
    std::vector<JDWP::ObjectId> child_thread_ids;
    GetThreads(thread_group, &child_thread_ids);
    expandBufAdd4BE(pReply, child_thread_ids.size());
    for (JDWP::ObjectId child_thread_id : child_thread_ids) {
      expandBufAddObjectId(pReply, child_thread_id);
    }
  }

  // Add child thread groups.
  {
    std::vector<JDWP::ObjectId> child_thread_groups_ids;
    GetChildThreadGroups(soa, thread_group, &child_thread_groups_ids);
    expandBufAdd4BE(pReply, child_thread_groups_ids.size());
    for (JDWP::ObjectId child_thread_group_id : child_thread_groups_ids) {
      expandBufAddObjectId(pReply, child_thread_group_id);
    }
  }

  return JDWP::ERR_NONE;
}

JDWP::ObjectId Dbg::GetSystemThreadGroupId() {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  mirror::ArtField* f = soa.DecodeField(WellKnownClasses::java_lang_ThreadGroup_systemThreadGroup);
  mirror::Object* group = f->GetObject(f->GetDeclaringClass());
  return gRegistry->Add(group);
}

JDWP::JdwpThreadStatus Dbg::ToJdwpThreadStatus(ThreadState state) {
  switch (state) {
    case kBlocked:
      return JDWP::TS_MONITOR;
    case kNative:
    case kRunnable:
    case kSuspended:
      return JDWP::TS_RUNNING;
    case kSleeping:
      return JDWP::TS_SLEEPING;
    case kStarting:
    case kTerminated:
      return JDWP::TS_ZOMBIE;
    case kTimedWaiting:
    case kWaitingForCheckPointsToRun:
    case kWaitingForDebuggerSend:
    case kWaitingForDebuggerSuspension:
    case kWaitingForDebuggerToAttach:
    case kWaitingForDeoptimization:
    case kWaitingForGcToComplete:
    case kWaitingForJniOnLoad:
    case kWaitingForMethodTracingStart:
    case kWaitingForSignalCatcherOutput:
    case kWaitingForVisitObjects:
    case kWaitingInMainDebuggerLoop:
    case kWaitingInMainSignalCatcherLoop:
    case kWaitingPerformingGc:
    case kWaiting:
      return JDWP::TS_WAIT;
      // Don't add a 'default' here so the compiler can spot incompatible enum changes.
  }
  LOG(FATAL) << "Unknown thread state: " << state;
  return JDWP::TS_ZOMBIE;
}

JDWP::JdwpError Dbg::GetThreadStatus(JDWP::ObjectId thread_id, JDWP::JdwpThreadStatus* pThreadStatus,
                                     JDWP::JdwpSuspendStatus* pSuspendStatus) {
  ScopedObjectAccess soa(Thread::Current());

  *pSuspendStatus = JDWP::SUSPEND_STATUS_NOT_SUSPENDED;

  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    if (error == JDWP::ERR_THREAD_NOT_ALIVE) {
      *pThreadStatus = JDWP::TS_ZOMBIE;
      return JDWP::ERR_NONE;
    }
    return error;
  }

  if (IsSuspendedForDebugger(soa, thread)) {
    *pSuspendStatus = JDWP::SUSPEND_STATUS_SUSPENDED;
  }

  *pThreadStatus = ToJdwpThreadStatus(thread->GetState());
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetThreadDebugSuspendCount(JDWP::ObjectId thread_id, JDWP::ExpandBuf* pReply) {
  ScopedObjectAccess soa(Thread::Current());
  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  MutexLock mu2(soa.Self(), *Locks::thread_suspend_count_lock_);
  expandBufAdd4BE(pReply, thread->GetDebugSuspendCount());
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::Interrupt(JDWP::ObjectId thread_id) {
  ScopedObjectAccess soa(Thread::Current());
  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  thread->Interrupt(soa.Self());
  return JDWP::ERR_NONE;
}

static bool IsInDesiredThreadGroup(ScopedObjectAccessUnchecked& soa,
                                   mirror::Object* desired_thread_group, mirror::Object* peer)
    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  // Do we want threads from all thread groups?
  if (desired_thread_group == nullptr) {
    return true;
  }
  mirror::ArtField* thread_group_field = soa.DecodeField(WellKnownClasses::java_lang_Thread_group);
  DCHECK(thread_group_field != nullptr);
  mirror::Object* group = thread_group_field->GetObject(peer);
  return (group == desired_thread_group);
}

void Dbg::GetThreads(mirror::Object* thread_group, std::vector<JDWP::ObjectId>* thread_ids) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  std::list<Thread*> all_threads_list;
  {
    MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
    all_threads_list = Runtime::Current()->GetThreadList()->GetList();
  }
  for (Thread* t : all_threads_list) {
    if (t == Dbg::GetDebugThread()) {
      // Skip the JDWP thread. Some debuggers get bent out of shape when they can't suspend and
      // query all threads, so it's easier if we just don't tell them about this thread.
      continue;
    }
    if (t->IsStillStarting()) {
      // This thread is being started (and has been registered in the thread list). However, it is
      // not completely started yet so we must ignore it.
      continue;
    }
    mirror::Object* peer = t->GetPeer();
    if (peer == nullptr) {
      // peer might be NULL if the thread is still starting up. We can't tell the debugger about
      // this thread yet.
      // TODO: if we identified threads to the debugger by their Thread*
      // rather than their peer's mirror::Object*, we could fix this.
      // Doing so might help us report ZOMBIE threads too.
      continue;
    }
    if (IsInDesiredThreadGroup(soa, thread_group, peer)) {
      thread_ids->push_back(gRegistry->Add(peer));
    }
  }
}

static int GetStackDepth(Thread* thread) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
  struct CountStackDepthVisitor : public StackVisitor {
    explicit CountStackDepthVisitor(Thread* thread_in)
        : StackVisitor(thread_in, nullptr), depth(0) {}

    // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
    // annotalysis.
    bool VisitFrame() NO_THREAD_SAFETY_ANALYSIS {
      if (!GetMethod()->IsRuntimeMethod()) {
        ++depth;
      }
      return true;
    }
    size_t depth;
  };

  CountStackDepthVisitor visitor(thread);
  visitor.WalkStack();
  return visitor.depth;
}

JDWP::JdwpError Dbg::GetThreadFrameCount(JDWP::ObjectId thread_id, size_t* result) {
  ScopedObjectAccess soa(Thread::Current());
  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  *result = 0;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  if (!IsSuspendedForDebugger(soa, thread)) {
    return JDWP::ERR_THREAD_NOT_SUSPENDED;
  }
  *result = GetStackDepth(thread);
  return JDWP::ERR_NONE;
}

JDWP::JdwpError Dbg::GetThreadFrames(JDWP::ObjectId thread_id, size_t start_frame,
                                     size_t frame_count, JDWP::ExpandBuf* buf) {
  class GetFrameVisitor : public StackVisitor {
   public:
    GetFrameVisitor(Thread* thread, size_t start_frame_in, size_t frame_count_in,
                    JDWP::ExpandBuf* buf_in)
        SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
        : StackVisitor(thread, nullptr), depth_(0),
          start_frame_(start_frame_in), frame_count_(frame_count_in), buf_(buf_in) {
      expandBufAdd4BE(buf_, frame_count_);
    }

    // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
    // annotalysis.
    virtual bool VisitFrame() NO_THREAD_SAFETY_ANALYSIS {
      if (GetMethod()->IsRuntimeMethod()) {
        return true;  // The debugger can't do anything useful with a frame that has no Method*.
      }
      if (depth_ >= start_frame_ + frame_count_) {
        return false;
      }
      if (depth_ >= start_frame_) {
        JDWP::FrameId frame_id(GetFrameId());
        JDWP::JdwpLocation location;
        SetJdwpLocation(&location, GetMethod(), GetDexPc());
        VLOG(jdwp) << StringPrintf("    Frame %3zd: id=%3" PRIu64 " ", depth_, frame_id) << location;
        expandBufAdd8BE(buf_, frame_id);
        expandBufAddLocation(buf_, location);
      }
      ++depth_;
      return true;
    }

   private:
    size_t depth_;
    const size_t start_frame_;
    const size_t frame_count_;
    JDWP::ExpandBuf* buf_;
  };

  ScopedObjectAccessUnchecked soa(Thread::Current());
  MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
  JDWP::JdwpError error;
  Thread* thread = DecodeThread(soa, thread_id, &error);
  if (error != JDWP::ERR_NONE) {
    return error;
  }
  if (!IsSuspendedForDebugger(soa, thread)) {
    return JDWP::ERR_THREAD_NOT_SUSPENDED;
  }
  GetFrameVisitor visitor(thread, start_frame, frame_count, buf);
  visitor.WalkStack();
  return JDWP::ERR_NONE;
}

JDWP::ObjectId Dbg::GetThreadSelfId() {
  return GetThreadId(Thread::Current());
}

JDWP::ObjectId Dbg::GetThreadId(Thread* thread) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  return gRegistry->Add(thread->GetPeer());
}

void Dbg::SuspendVM() {
  Runtime::Current()->GetThreadList()->SuspendAllForDebugger();
}

void Dbg::ResumeVM() {
  Runtime::Current()->GetThreadList()->ResumeAllForDebugger();
}

JDWP::JdwpError Dbg::SuspendThread(JDWP::ObjectId thread_id, bool request_suspension) {
  Thread* self = Thread::Current();
  ScopedLocalRef<jobject> peer(self->GetJniEnv(), nullptr);
  {
    ScopedObjectAccess soa(self);
    JDWP::JdwpError error;
    peer.reset(soa.AddLocalReference<jobject>(gRegistry->Get<mirror::Object*>(thread_id, &error)));
  }
  if (peer.get() == nullptr) {
    return JDWP::ERR_THREAD_NOT_ALIVE;
  }
  // Suspend thread to build stack trace.
  bool timed_out;
  ThreadList* thread_list = Runtime::Current()->GetThreadList();
  Thread* thread = thread_list->SuspendThreadByPeer(peer.get(), request_suspension, true,
                                                    &timed_out);
  if (thread != nullptr) {
    return JDWP::ERR_NONE;
  } else if (timed_out) {
    return JDWP::ERR_INTERNAL;
  } else {
    return JDWP::ERR_THREAD_NOT_ALIVE;
  }
}

void Dbg::ResumeThread(JDWP::ObjectId thread_id) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  JDWP::JdwpError error;
  mirror::Object* peer = gRegistry->Get<mirror::Object*>(thread_id, &error);
  CHECK(peer != nullptr) << error;
  Thread* thread;
  {
    MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
    thread = Thread::FromManagedThread(soa, peer);
  }
  if (thread == nullptr) {
    LOG(WARNING) << "No such thread for resume: " << peer;
    return;
  }
  bool needs_resume;
  {
    MutexLock mu2(soa.Self(), *Locks::thread_suspend_count_lock_);
    needs_resume = thread->GetSuspendCount() > 0;
  }
  if (needs_resume) {
    Runtime::Current()->GetThreadList()->Resume(thread, true);
  }
}

void Dbg::SuspendSelf() {
  Runtime::Current()->GetThreadList()->SuspendSelfForDebugger();
}

struct GetThisVisitor : public StackVisitor {
  GetThisVisitor(Thread* thread, Context* context, JDWP::FrameId frame_id_in)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
      : StackVisitor(thread, context), this_object(nullptr), frame_id(frame_id_in) {}

  // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
  // annotalysis.
  virtual bool VisitFrame() NO_THREAD_SAFETY_ANALYSIS {
    if (frame_id != GetFrameId()) {
      return true;  // continue
    } else {
      this_object = GetThisObject();
      return false;
    }
  }

  mirror::Object* this_object;
  JDWP::FrameId frame_id;
};

JDWP::JdwpError Dbg::GetThisObject(JDWP::ObjectId thread_id, JDWP::FrameId frame_id,
                                   JDWP::ObjectId* result) {
  ScopedObjectAccessUnchecked soa(Thread::Current());
  Thread* thread;
  {
    MutexLock mu(soa.Self(), *Locks::thread_list_lock_);
    JDWP::JdwpError error;
    thread = DecodeThread(soa, thread_id, &error);
    if (error != JDWP::ERR_NONE) {
      return error;
    }
    if (!IsSuspendedForDebugger(soa, thread)) {
      return JDWP::ERR_THREAD_NOT_SUSPENDED;
    }
  }
  std::unique_ptr<Context> context(Context::Create());
  GetThisVisitor visitor(thread, context.get(), frame_id);
  visitor.WalkStack();
  *result = gRegistry->Add(visitor.this_object);
  return JDWP::ERR_NONE;
}

// Walks the stack until we find the frame with the given FrameId.
class FindFrameVisitor FINAL : public StackVisitor {
 public:
  FindFrameVisitor(Thread* thread, Context* context, JDWP::FrameId frame_id)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
      : StackVisitor(thread, context), frame_id_(frame_id), error_(JDWP::ERR_INVALID_FRAMEID) {}

  // TODO: Enable annotalysis. We know lock is held in constructor, but abstraction confuses
  // annotalysis.
  bool VisitFrame() NO_THREAD_SAFETY_ANALYSIS {
    if (GetFrameId() != frame_id_) {
      return true;  // Not our frame, carry on.
    }
    mirror::ArtMethod* m = GetMethod();
    if (m->IsNative()) {
      // We can't read/write local value from/into native method.
      error_ = JDWP::ERR_OPAQUE_FRAME;
    } else {
      // We found our frame.
      error_ = JDWP::ERR_NONE;
    }
    return false;
  }

  JDWP::JdwpError GetError() const {
    return error_;
  }

 private:
  const JDWP::FrameId frame_id_;
  JDWP::JdwpError error_;
};

JDWP::JdwpError Dbg::GetLocalValues(JDWP::Request* request, JDWP::ExpandBuf* pReply) {
  JDWP