tools/jvmti-agents/simple-profile/simple_profile.cc - platform/art - Git at Google

 // Copyright (C) 2020 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 <android-base/logging.h>
 #include <fcntl.h>
 #include <jni.h>
 #include <jvmti.h>

 #include <atomic>
 #include <cstring>
 #include <iomanip>
 #include <iostream>
 #include <memory>
 #include <sstream>
 #include <string>
 #include <unordered_map>
 #include <vector>

 #include "android-base/unique_fd.h"
 #include "nativehelper/scoped_local_ref.h"

 namespace simple_profile {

 static constexpr jint kArtTiVersion = JVMTI_VERSION_1_2 | 0x40000000;

 #define CHECK_JVMTI(a) CHECK_EQ(JVMTI_ERROR_NONE, a)

 struct DataDefinition {
   std::string_view class_name;
   std::string_view method_name;
   std::string_view method_descriptor;
   uint64_t count;
 };

 std::ostream& operator<<(std::ostream& os, const DataDefinition& dd) {
   return os << "{\"class_name\":\"" << dd.class_name << "\",\"method_name\":\"" << dd.method_name
             << "\",\"method_descriptor\":\"" << dd.method_descriptor << "\",\"count\":" << dd.count
             << "}";
 }

 class SimpleProfileData {
  public:
   SimpleProfileData(
       jvmtiEnv* env, std::string out_fd_name, int fd, bool dump_on_shutdown, bool dump_on_main_stop)
       : dump_id_(0),
         out_fd_name_(out_fd_name),
         out_fd_(fd),
         shutdown_(false),
         dump_on_shutdown_(dump_on_shutdown || dump_on_main_stop),
         dump_on_main_stop_(dump_on_main_stop) {
     CHECK_JVMTI(env->CreateRawMonitor("simple_profile_mon", &mon_));
     method_counts_.reserve(10000);
   }

   void Dump(jvmtiEnv* jvmti);
   void Enter(jvmtiEnv* jvmti, JNIEnv* env, jmethodID meth);

   void RunDumpLoop(jvmtiEnv* jvmti, JNIEnv* env);

   static SimpleProfileData* GetProfileData(jvmtiEnv* env) {
     void* data;
     CHECK_JVMTI(env->GetEnvironmentLocalStorage(&data));
     return static_cast<SimpleProfileData*>(data);
   }

   void FinishInitialization(jvmtiEnv* jvmti, JNIEnv* jni, jthread cur);
   void Shutdown(jvmtiEnv* jvmti, JNIEnv* jni);

  private:
   void DoDump(jvmtiEnv* jvmti, JNIEnv* jni, std::unordered_map<jmethodID, uint64_t> copy);

   jlong dump_id_;
   jrawMonitorID mon_;
   std::string out_fd_name_;
   int out_fd_;
   std::unordered_map<jmethodID, uint64_t> method_counts_;
   bool shutdown_;
   bool dump_on_shutdown_;
   bool dump_on_main_stop_;
 };

 struct ScopedJvmtiMonitor {
  public:
   ScopedJvmtiMonitor(jvmtiEnv* env, jrawMonitorID mon) : jvmti_(env), mon_(mon) {
     CHECK_JVMTI(jvmti_->RawMonitorEnter(mon_));
   }

   ~ScopedJvmtiMonitor() {
     CHECK_JVMTI(jvmti_->RawMonitorExit(mon_));
   }

   void Notify() {
     CHECK_JVMTI(jvmti_->RawMonitorNotifyAll(mon_));
   }

   void Wait() {
     CHECK_JVMTI(jvmti_->RawMonitorWait(mon_, 0));
   }

  private:
   jvmtiEnv* jvmti_;
   jrawMonitorID mon_;
 };

 void SimpleProfileData::Enter(jvmtiEnv* jvmti, JNIEnv* env, jmethodID meth) {
   ScopedJvmtiMonitor sjm(jvmti, mon_);
   // Keep all classes from being unloaded to allow us to know we can get the method info later.
   jclass tmp;
   CHECK_JVMTI(jvmti->GetMethodDeclaringClass(meth, &tmp));
   ScopedLocalRef<jclass> klass(env, tmp);
   jlong tag;
   CHECK_JVMTI(jvmti->GetTag(klass.get(), &tag));
   if (tag == 0) {
     CHECK_JVMTI(jvmti->SetTag(klass.get(), 1u));
     env->NewGlobalRef(klass.get());
   }
   method_counts_.insert({ meth, 0u }).first->second++;
 }

 void SimpleProfileData::Dump(jvmtiEnv* jvmti) {
   ScopedJvmtiMonitor sjm(jvmti, mon_);
   dump_id_++;
   sjm.Notify();
 }

 void SimpleProfileData::RunDumpLoop(jvmtiEnv* jvmti, JNIEnv* env) {
   jlong current_id = 0;
   do {
     std::unordered_map<jmethodID, uint64_t> copy;
     {
       ScopedJvmtiMonitor sjm(jvmti, mon_);
       while (!shutdown_ && current_id == dump_id_) {
         sjm.Wait();
       }
       if (shutdown_) {
         break;
       }
       current_id = dump_id_;
       copy = method_counts_;
     }
     DoDump(jvmti, env, std::move(copy));
   } while (true);
 }

 void SimpleProfileData::Shutdown(jvmtiEnv* jvmti, JNIEnv* jni) {
   std::unordered_map<jmethodID, uint64_t> copy;
   {
     ScopedJvmtiMonitor sjm(jvmti, mon_);
     if (shutdown_) {
       return;
     }
     shutdown_ = true;
     copy = method_counts_;
     sjm.Notify();
   }
   if (dump_on_shutdown_) {
     DoDump(jvmti, jni, std::move(copy));
   }
 }

 void SimpleProfileData::FinishInitialization(jvmtiEnv* jvmti, JNIEnv* env, jthread cur) {
   // Finish up startup.
   // Create a Thread object.
   std::string name = std::string("profile dump Thread: ") + this->out_fd_name_;
   ScopedLocalRef<jobject> thread_name(env, env->NewStringUTF(name.c_str()));
   CHECK_NE(thread_name.get(), nullptr);

   ScopedLocalRef<jclass> thread_klass(env, env->FindClass("java/lang/Thread"));
   CHECK_NE(thread_klass.get(), nullptr);
   ScopedLocalRef<jobject> thread(env, env->AllocObject(thread_klass.get()));
   CHECK_NE(thread.get(), nullptr);
   jmethodID initID = env->GetMethodID(thread_klass.get(), "<init>", "(Ljava/lang/String;)V");
   jmethodID setDaemonId = env->GetMethodID(thread_klass.get(), "setDaemon", "(Z)V");
   CHECK_NE(initID, nullptr);
   CHECK_NE(setDaemonId, nullptr);
   env->CallNonvirtualVoidMethod(thread.get(), thread_klass.get(), initID, thread_name.get());
   env->CallVoidMethod(thread.get(), setDaemonId, JNI_TRUE);
   CHECK(!env->ExceptionCheck());

   CHECK_JVMTI(jvmti->RunAgentThread(
       thread.get(),
       [](jvmtiEnv* jvmti, JNIEnv* jni, void* unused_data ATTRIBUTE_UNUSED) {
         SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
         data->RunDumpLoop(jvmti, jni);
       },
       nullptr,
       JVMTI_THREAD_NORM_PRIORITY));

   CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_METHOD_ENTRY, nullptr));
   CHECK_JVMTI(
       jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_DATA_DUMP_REQUEST, nullptr));
   if (dump_on_main_stop_) {
     CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_THREAD_END, cur));
   }
   CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_DEATH, nullptr));
 }

 class ScopedClassInfo {
  public:
   ScopedClassInfo(jvmtiEnv* jvmti_env, jclass c)
       : jvmti_env_(jvmti_env), class_(c), name_(nullptr), generic_(nullptr) {}

   ~ScopedClassInfo() {
     if (class_ != nullptr) {
       jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(name_));
       jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(generic_));
     }
   }

   bool Init() {
     if (class_ == nullptr) {
       name_ = const_cast<char*>("<NONE>");
       generic_ = const_cast<char*>("<NONE>");
       return true;
     } else {
       return jvmti_env_->GetClassSignature(class_, &name_, &generic_) == JVMTI_ERROR_NONE;
     }
   }

   jclass GetClass() const {
     return class_;
   }
   const char* GetName() const {
     return name_;
   }
   // Generic type parameters, whatever is in the <> for a class
   const char* GetGeneric() const {
     return generic_;
   }

  private:
   jvmtiEnv* jvmti_env_;
   jclass class_;
   char* name_;
   char* generic_;
 };

 class ScopedMethodInfo {
  public:
   ScopedMethodInfo(jvmtiEnv* jvmti_env, JNIEnv* env, jmethodID method)
       : jvmti_env_(jvmti_env),
         env_(env),
         method_(method),
         declaring_class_(nullptr),
         class_info_(nullptr),
         name_(nullptr),
         signature_(nullptr),
         generic_(nullptr) {}

   ~ScopedMethodInfo() {
     env_->DeleteLocalRef(declaring_class_);
     jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(name_));
     jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(signature_));
     jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(generic_));
   }

   bool Init() {
     if (jvmti_env_->GetMethodDeclaringClass(method_, &declaring_class_) != JVMTI_ERROR_NONE) {
       LOG(INFO) << "No decl";
       return false;
     }
     class_info_.reset(new ScopedClassInfo(jvmti_env_, declaring_class_));
     return class_info_->Init() &&
            (jvmti_env_->GetMethodName(method_, &name_, &signature_, &generic_) == JVMTI_ERROR_NONE);
   }

   const ScopedClassInfo& GetDeclaringClassInfo() const {
     return *class_info_;
   }

   jclass GetDeclaringClass() const {
     return declaring_class_;
   }

   const char* GetName() const {
     return name_;
   }

   const char* GetSignature() const {
     return signature_;
   }

   const char* GetGeneric() const {
     return generic_;
   }

  private:
   jvmtiEnv* jvmti_env_;
   JNIEnv* env_;
   jmethodID method_;
   jclass declaring_class_;
   std::unique_ptr<ScopedClassInfo> class_info_;
   char* name_;
   char* signature_;
   char* generic_;

   friend std::ostream& operator<<(std::ostream& os, ScopedMethodInfo const& method);
 };

 std::ostream& operator<<(std::ostream& os, const ScopedMethodInfo* method) {
   return os << *method;
 }

 std::ostream& operator<<(std::ostream& os, ScopedMethodInfo const& method) {
   return os << method.GetDeclaringClassInfo().GetName() << "->" << method.GetName()
             << method.GetSignature();
 }

 void SimpleProfileData::DoDump(jvmtiEnv* jvmti,
                                JNIEnv* jni,
                                std::unordered_map<jmethodID, uint64_t> copy) {
   std::ostringstream oss;
   oss << "[";
   bool is_first = true;
   for (auto [meth, cnt] : copy) {
     ScopedMethodInfo smi(jvmti, jni, meth);
     if (!smi.Init()) {
       continue;
     }
     if (!is_first) {
       oss << "," << std::endl;
     }
     is_first = false;
     oss << DataDefinition {
       .class_name = smi.GetDeclaringClassInfo().GetName(),
       .method_name = smi.GetName(),
       .method_descriptor = smi.GetSignature(),
       .count = cnt,
     };
   }
   oss << "]";
   CHECK_GE(TEMP_FAILURE_RETRY(write(out_fd_, oss.str().c_str(), oss.str().size())), 0)
       << strerror(errno) << out_fd_ << " " << out_fd_name_;
   fsync(out_fd_);
 }

 static void DataDumpCb(jvmtiEnv* jvmti_env) {
   SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti_env);
   data->Dump(jvmti_env);
 }

 static void MethodEntryCB(jvmtiEnv* jvmti_env,
                           JNIEnv* env,
                           jthread thread ATTRIBUTE_UNUSED,
                           jmethodID method) {
   SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti_env);
   data->Enter(jvmti_env, env, method);
 }

 static void VMInitCB(jvmtiEnv* jvmti, JNIEnv* env, jthread thr) {
   SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
   data->FinishInitialization(jvmti, env, thr);
 }
 static void VMDeathCB(jvmtiEnv* jvmti, JNIEnv* env) {
   SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
   data->Shutdown(jvmti, env);
 }

 // Fills targets with the breakpoints to add.
 // Lname/of/Klass;->methodName(Lsig/of/Method)Lreturn/Type;@location,<...>
 static bool ParseArgs(const std::string& start_options,
                       /*out*/ std::string* fd_name,
                       /*out*/ int* fd,
                       /*out*/ bool* dump_on_shutdown,
                       /*out*/ bool* dump_on_main_stop) {
   std::istringstream iss(start_options);
   std::string item;
   *dump_on_main_stop = false;
   *dump_on_shutdown = false;
   bool has_fd = false;
   while (std::getline(iss, item, ',')) {
     if (item == "dump_on_shutdown") {
       *dump_on_shutdown = true;
     } else if (item == "dump_on_main_stop") {
       *dump_on_main_stop = true;
     } else if (has_fd) {
       LOG(ERROR) << "Too many args!";
       return false;
     } else {
       has_fd = true;
       *fd_name = item;
       *fd = TEMP_FAILURE_RETRY(open(fd_name->c_str(), O_WRONLY | O_CLOEXEC | O_CREAT, 00666));
       CHECK_GE(*fd, 0) << strerror(errno);
     }
   }
   return has_fd;
 }

 enum class StartType {
   OnAttach,
   OnLoad,
 };

 static jint SetupJvmtiEnv(JavaVM* vm, jvmtiEnv** jvmti) {
   jint res = 0;
   res = vm->GetEnv(reinterpret_cast<void**>(jvmti), JVMTI_VERSION_1_1);

   if (res != JNI_OK || *jvmti == nullptr) {
     LOG(ERROR) << "Unable to access JVMTI, error code " << res;
     return vm->GetEnv(reinterpret_cast<void**>(jvmti), kArtTiVersion);
   }
   return res;
 }

 static jint AgentStart(StartType start,
                        JavaVM* vm,
                        const char* options,
                        void* reserved ATTRIBUTE_UNUSED) {
   if (options == nullptr) {
     options = "";
   }
   jvmtiEnv* jvmti = nullptr;
   jvmtiError error = JVMTI_ERROR_NONE;
   {
     jint res = 0;
     res = SetupJvmtiEnv(vm, &jvmti);

     if (res != JNI_OK || jvmti == nullptr) {
       LOG(ERROR) << "Unable to access JVMTI, error code " << res;
       return JNI_ERR;
     }
   }

   int fd;
   std::string fd_name;
   bool dump_on_shutdown;
   bool dump_on_main_stop;
   if (!ParseArgs(options,
                  /*out*/ &fd_name,
                  /*out*/ &fd,
                  /*out*/ &dump_on_shutdown,
                  /*out*/ &dump_on_main_stop)) {
     LOG(ERROR) << "failed to get output file from " << options << "!";
     return JNI_ERR;
   }

   void* data_mem = nullptr;
   error = jvmti->Allocate(sizeof(SimpleProfileData), reinterpret_cast<unsigned char**>(&data_mem));
   if (error != JVMTI_ERROR_NONE) {
     LOG(ERROR) << "Unable to alloc memory for breakpoint target data";
     return JNI_ERR;
   }

   SimpleProfileData* data =
       new (data_mem) SimpleProfileData(jvmti, fd_name, fd, dump_on_shutdown, dump_on_main_stop);
   error = jvmti->SetEnvironmentLocalStorage(data);
   if (error != JVMTI_ERROR_NONE) {
     LOG(ERROR) << "Unable to set local storage";
     return JNI_ERR;
   }

   jvmtiCapabilities caps {};
   caps.can_generate_method_entry_events = JNI_TRUE;
   caps.can_tag_objects = JNI_TRUE;
   error = jvmti->AddCapabilities(&caps);
   if (error != JVMTI_ERROR_NONE) {
     LOG(ERROR) << "Unable to set caps";
     return JNI_ERR;
   }

   jvmtiEventCallbacks callbacks {};
   callbacks.MethodEntry = &MethodEntryCB;
   callbacks.VMInit = &VMInitCB;
   callbacks.DataDumpRequest = &DataDumpCb;
   callbacks.VMDeath = &VMDeathCB;
   callbacks.ThreadEnd = [](jvmtiEnv* env, JNIEnv* jni, jthread thr ATTRIBUTE_UNUSED) {
     VMDeathCB(env, jni);
   };

   error = jvmti->SetEventCallbacks(&callbacks, static_cast<jint>(sizeof(callbacks)));

   if (error != JVMTI_ERROR_NONE) {
     LOG(ERROR) << "Unable to set event callbacks.";
     return JNI_ERR;
   }

   if (start == StartType::OnAttach) {
     JNIEnv* env = nullptr;
     jint res = 0;
     res = vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_2);
     if (res != JNI_OK || env == nullptr) {
       LOG(ERROR) << "Unable to get jnienv";
       return JNI_ERR;
     }
     jthread temp;
     ScopedLocalRef<jthread> cur(env, nullptr);
     CHECK_JVMTI(jvmti->GetCurrentThread(&temp));
     cur.reset(temp);
     VMInitCB(jvmti, env, cur.get());
   } else {
     error = jvmti->SetEventNotificationMode(
         JVMTI_ENABLE, JVMTI_EVENT_VM_INIT, nullptr /* all threads */);
     if (error != JVMTI_ERROR_NONE) {
       LOG(ERROR) << "Unable to set event vminit";
       return JNI_ERR;
     }
   }
   return JNI_OK;
 }

 // Late attachment (e.g. 'am attach-agent').
 extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
   return AgentStart(StartType::OnAttach, vm, options, reserved);
 }

 // Early attachment
 extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
   return AgentStart(StartType::OnLoad, jvm, options, reserved);
 }

 }  // namespace simple_profile
	// Copyright (C) 2020 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 <android-base/logging.h>
	#include <fcntl.h>
	#include <jni.h>
	#include <jvmti.h>

	#include <atomic>
	#include <cstring>
	#include <iomanip>
	#include <iostream>
	#include <memory>
	#include <sstream>
	#include <string>
	#include <unordered_map>
	#include <vector>

	#include "android-base/unique_fd.h"
	#include "nativehelper/scoped_local_ref.h"

	namespace simple_profile {

	static constexpr jint kArtTiVersion = JVMTI_VERSION_1_2 \| 0x40000000;

	#define CHECK_JVMTI(a) CHECK_EQ(JVMTI_ERROR_NONE, a)

	struct DataDefinition {
	std::string_view class_name;
	std::string_view method_name;
	std::string_view method_descriptor;
	uint64_t count;
	};

	std::ostream& operator<<(std::ostream& os, const DataDefinition& dd) {
	return os << "{\"class_name\":\"" << dd.class_name << "\",\"method_name\":\"" << dd.method_name
	<< "\",\"method_descriptor\":\"" << dd.method_descriptor << "\",\"count\":" << dd.count
	<< "}";
	}

	class SimpleProfileData {
	public:
	SimpleProfileData(
	jvmtiEnv* env, std::string out_fd_name, int fd, bool dump_on_shutdown, bool dump_on_main_stop)
	: dump_id_(0),
	out_fd_name_(out_fd_name),
	out_fd_(fd),
	shutdown_(false),
	dump_on_shutdown_(dump_on_shutdown \|\| dump_on_main_stop),
	dump_on_main_stop_(dump_on_main_stop) {
	CHECK_JVMTI(env->CreateRawMonitor("simple_profile_mon", &mon_));
	method_counts_.reserve(10000);
	}

	void Dump(jvmtiEnv* jvmti);
	void Enter(jvmtiEnv* jvmti, JNIEnv* env, jmethodID meth);

	void RunDumpLoop(jvmtiEnv* jvmti, JNIEnv* env);

	static SimpleProfileData* GetProfileData(jvmtiEnv* env) {
	void* data;
	CHECK_JVMTI(env->GetEnvironmentLocalStorage(&data));
	return static_cast<SimpleProfileData*>(data);
	}

	void FinishInitialization(jvmtiEnv* jvmti, JNIEnv* jni, jthread cur);
	void Shutdown(jvmtiEnv* jvmti, JNIEnv* jni);

	private:
	void DoDump(jvmtiEnv* jvmti, JNIEnv* jni, std::unordered_map<jmethodID, uint64_t> copy);

	jlong dump_id_;
	jrawMonitorID mon_;
	std::string out_fd_name_;
	int out_fd_;
	std::unordered_map<jmethodID, uint64_t> method_counts_;
	bool shutdown_;
	bool dump_on_shutdown_;
	bool dump_on_main_stop_;
	};

	struct ScopedJvmtiMonitor {
	public:
	ScopedJvmtiMonitor(jvmtiEnv* env, jrawMonitorID mon) : jvmti_(env), mon_(mon) {
	CHECK_JVMTI(jvmti_->RawMonitorEnter(mon_));
	}

	~ScopedJvmtiMonitor() {
	CHECK_JVMTI(jvmti_->RawMonitorExit(mon_));
	}

	void Notify() {
	CHECK_JVMTI(jvmti_->RawMonitorNotifyAll(mon_));
	}

	void Wait() {
	CHECK_JVMTI(jvmti_->RawMonitorWait(mon_, 0));
	}

	private:
	jvmtiEnv* jvmti_;
	jrawMonitorID mon_;
	};

	void SimpleProfileData::Enter(jvmtiEnv* jvmti, JNIEnv* env, jmethodID meth) {
	ScopedJvmtiMonitor sjm(jvmti, mon_);
	// Keep all classes from being unloaded to allow us to know we can get the method info later.
	jclass tmp;
	CHECK_JVMTI(jvmti->GetMethodDeclaringClass(meth, &tmp));
	ScopedLocalRef<jclass> klass(env, tmp);
	jlong tag;
	CHECK_JVMTI(jvmti->GetTag(klass.get(), &tag));
	if (tag == 0) {
	CHECK_JVMTI(jvmti->SetTag(klass.get(), 1u));
	env->NewGlobalRef(klass.get());
	}
	method_counts_.insert({ meth, 0u }).first->second++;
	}

	void SimpleProfileData::Dump(jvmtiEnv* jvmti) {
	ScopedJvmtiMonitor sjm(jvmti, mon_);
	dump_id_++;
	sjm.Notify();
	}

	void SimpleProfileData::RunDumpLoop(jvmtiEnv* jvmti, JNIEnv* env) {
	jlong current_id = 0;
	do {
	std::unordered_map<jmethodID, uint64_t> copy;
	{
	ScopedJvmtiMonitor sjm(jvmti, mon_);
	while (!shutdown_ && current_id == dump_id_) {
	sjm.Wait();
	}
	if (shutdown_) {
	break;
	}
	current_id = dump_id_;
	copy = method_counts_;
	}
	DoDump(jvmti, env, std::move(copy));
	} while (true);
	}

	void SimpleProfileData::Shutdown(jvmtiEnv* jvmti, JNIEnv* jni) {
	std::unordered_map<jmethodID, uint64_t> copy;
	{
	ScopedJvmtiMonitor sjm(jvmti, mon_);
	if (shutdown_) {
	return;
	}
	shutdown_ = true;
	copy = method_counts_;
	sjm.Notify();
	}
	if (dump_on_shutdown_) {
	DoDump(jvmti, jni, std::move(copy));
	}
	}

	void SimpleProfileData::FinishInitialization(jvmtiEnv* jvmti, JNIEnv* env, jthread cur) {
	// Finish up startup.
	// Create a Thread object.
	std::string name = std::string("profile dump Thread: ") + this->out_fd_name_;
	ScopedLocalRef<jobject> thread_name(env, env->NewStringUTF(name.c_str()));
	CHECK_NE(thread_name.get(), nullptr);

	ScopedLocalRef<jclass> thread_klass(env, env->FindClass("java/lang/Thread"));
	CHECK_NE(thread_klass.get(), nullptr);
	ScopedLocalRef<jobject> thread(env, env->AllocObject(thread_klass.get()));
	CHECK_NE(thread.get(), nullptr);
	jmethodID initID = env->GetMethodID(thread_klass.get(), "<init>", "(Ljava/lang/String;)V");
	jmethodID setDaemonId = env->GetMethodID(thread_klass.get(), "setDaemon", "(Z)V");
	CHECK_NE(initID, nullptr);
	CHECK_NE(setDaemonId, nullptr);
	env->CallNonvirtualVoidMethod(thread.get(), thread_klass.get(), initID, thread_name.get());
	env->CallVoidMethod(thread.get(), setDaemonId, JNI_TRUE);
	CHECK(!env->ExceptionCheck());

	CHECK_JVMTI(jvmti->RunAgentThread(
	thread.get(),
	[](jvmtiEnv* jvmti, JNIEnv* jni, void* unused_data ATTRIBUTE_UNUSED) {
	SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
	data->RunDumpLoop(jvmti, jni);
	},
	nullptr,
	JVMTI_THREAD_NORM_PRIORITY));

	CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_METHOD_ENTRY, nullptr));
	CHECK_JVMTI(
	jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_DATA_DUMP_REQUEST, nullptr));
	if (dump_on_main_stop_) {
	CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_THREAD_END, cur));
	}
	CHECK_JVMTI(jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_DEATH, nullptr));
	}

	class ScopedClassInfo {
	public:
	ScopedClassInfo(jvmtiEnv* jvmti_env, jclass c)
	: jvmti_env_(jvmti_env), class_(c), name_(nullptr), generic_(nullptr) {}

	~ScopedClassInfo() {
	if (class_ != nullptr) {
	jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(name_));
	jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(generic_));
	}
	}

	bool Init() {
	if (class_ == nullptr) {
	name_ = const_cast<char*>("<NONE>");
	generic_ = const_cast<char*>("<NONE>");
	return true;
	} else {
	return jvmti_env_->GetClassSignature(class_, &name_, &generic_) == JVMTI_ERROR_NONE;
	}
	}

	jclass GetClass() const {
	return class_;
	}
	const char* GetName() const {
	return name_;
	}
	// Generic type parameters, whatever is in the <> for a class
	const char* GetGeneric() const {
	return generic_;
	}

	private:
	jvmtiEnv* jvmti_env_;
	jclass class_;
	char* name_;
	char* generic_;
	};

	class ScopedMethodInfo {
	public:
	ScopedMethodInfo(jvmtiEnv* jvmti_env, JNIEnv* env, jmethodID method)
	: jvmti_env_(jvmti_env),
	env_(env),
	method_(method),
	declaring_class_(nullptr),
	class_info_(nullptr),
	name_(nullptr),
	signature_(nullptr),
	generic_(nullptr) {}

	~ScopedMethodInfo() {
	env_->DeleteLocalRef(declaring_class_);
	jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(name_));
	jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(signature_));
	jvmti_env_->Deallocate(reinterpret_cast<unsigned char*>(generic_));
	}

	bool Init() {
	if (jvmti_env_->GetMethodDeclaringClass(method_, &declaring_class_) != JVMTI_ERROR_NONE) {
	LOG(INFO) << "No decl";
	return false;
	}
	class_info_.reset(new ScopedClassInfo(jvmti_env_, declaring_class_));
	return class_info_->Init() &&
	(jvmti_env_->GetMethodName(method_, &name_, &signature_, &generic_) == JVMTI_ERROR_NONE);
	}

	const ScopedClassInfo& GetDeclaringClassInfo() const {
	return *class_info_;
	}

	jclass GetDeclaringClass() const {
	return declaring_class_;
	}

	const char* GetName() const {
	return name_;
	}

	const char* GetSignature() const {
	return signature_;
	}

	const char* GetGeneric() const {
	return generic_;
	}

	private:
	jvmtiEnv* jvmti_env_;
	JNIEnv* env_;
	jmethodID method_;
	jclass declaring_class_;
	std::unique_ptr<ScopedClassInfo> class_info_;
	char* name_;
	char* signature_;
	char* generic_;

	friend std::ostream& operator<<(std::ostream& os, ScopedMethodInfo const& method);
	};

	std::ostream& operator<<(std::ostream& os, const ScopedMethodInfo* method) {
	return os << *method;
	}

	std::ostream& operator<<(std::ostream& os, ScopedMethodInfo const& method) {
	return os << method.GetDeclaringClassInfo().GetName() << "->" << method.GetName()
	<< method.GetSignature();
	}

	void SimpleProfileData::DoDump(jvmtiEnv* jvmti,
	JNIEnv* jni,
	std::unordered_map<jmethodID, uint64_t> copy) {
	std::ostringstream oss;
	oss << "[";
	bool is_first = true;
	for (auto [meth, cnt] : copy) {
	ScopedMethodInfo smi(jvmti, jni, meth);
	if (!smi.Init()) {
	continue;
	}
	if (!is_first) {
	oss << "," << std::endl;
	}
	is_first = false;
	oss << DataDefinition {
	.class_name = smi.GetDeclaringClassInfo().GetName(),
	.method_name = smi.GetName(),
	.method_descriptor = smi.GetSignature(),
	.count = cnt,
	};
	}
	oss << "]";
	CHECK_GE(TEMP_FAILURE_RETRY(write(out_fd_, oss.str().c_str(), oss.str().size())), 0)
	<< strerror(errno) << out_fd_ << " " << out_fd_name_;
	fsync(out_fd_);
	}

	static void DataDumpCb(jvmtiEnv* jvmti_env) {
	SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti_env);
	data->Dump(jvmti_env);
	}

	static void MethodEntryCB(jvmtiEnv* jvmti_env,
	JNIEnv* env,
	jthread thread ATTRIBUTE_UNUSED,
	jmethodID method) {
	SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti_env);
	data->Enter(jvmti_env, env, method);
	}

	static void VMInitCB(jvmtiEnv* jvmti, JNIEnv* env, jthread thr) {
	SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
	data->FinishInitialization(jvmti, env, thr);
	}
	static void VMDeathCB(jvmtiEnv* jvmti, JNIEnv* env) {
	SimpleProfileData* data = SimpleProfileData::GetProfileData(jvmti);
	data->Shutdown(jvmti, env);
	}

	// Fills targets with the breakpoints to add.
	// Lname/of/Klass;->methodName(Lsig/of/Method)Lreturn/Type;@location,<...>
	static bool ParseArgs(const std::string& start_options,
	/out/ std::string* fd_name,
	/out/ int* fd,
	/out/ bool* dump_on_shutdown,
	/out/ bool* dump_on_main_stop) {
	std::istringstream iss(start_options);
	std::string item;
	*dump_on_main_stop = false;
	*dump_on_shutdown = false;
	bool has_fd = false;
	while (std::getline(iss, item, ',')) {
	if (item == "dump_on_shutdown") {
	*dump_on_shutdown = true;
	} else if (item == "dump_on_main_stop") {
	*dump_on_main_stop = true;
	} else if (has_fd) {
	LOG(ERROR) << "Too many args!";
	return false;
	} else {
	has_fd = true;
	*fd_name = item;
	*fd = TEMP_FAILURE_RETRY(open(fd_name->c_str(), O_WRONLY \| O_CLOEXEC \| O_CREAT, 00666));
	CHECK_GE(*fd, 0) << strerror(errno);
	}
	}
	return has_fd;
	}

	enum class StartType {
	OnAttach,
	OnLoad,
	};

	static jint SetupJvmtiEnv(JavaVM* vm, jvmtiEnv** jvmti) {
	jint res = 0;
	res = vm->GetEnv(reinterpret_cast<void**>(jvmti), JVMTI_VERSION_1_1);

	if (res != JNI_OK \|\| *jvmti == nullptr) {
	LOG(ERROR) << "Unable to access JVMTI, error code " << res;
	return vm->GetEnv(reinterpret_cast<void**>(jvmti), kArtTiVersion);
	}
	return res;
	}

	static jint AgentStart(StartType start,
	JavaVM* vm,
	const char* options,
	void* reserved ATTRIBUTE_UNUSED) {
	if (options == nullptr) {
	options = "";
	}
	jvmtiEnv* jvmti = nullptr;
	jvmtiError error = JVMTI_ERROR_NONE;
	{
	jint res = 0;
	res = SetupJvmtiEnv(vm, &jvmti);

	if (res != JNI_OK \|\| jvmti == nullptr) {
	LOG(ERROR) << "Unable to access JVMTI, error code " << res;
	return JNI_ERR;
	}
	}

	int fd;
	std::string fd_name;
	bool dump_on_shutdown;
	bool dump_on_main_stop;
	if (!ParseArgs(options,
	/out/ &fd_name,
	/out/ &fd,
	/out/ &dump_on_shutdown,
	/out/ &dump_on_main_stop)) {
	LOG(ERROR) << "failed to get output file from " << options << "!";
	return JNI_ERR;
	}

	void* data_mem = nullptr;
	error = jvmti->Allocate(sizeof(SimpleProfileData), reinterpret_cast<unsigned char**>(&data_mem));
	if (error != JVMTI_ERROR_NONE) {
	LOG(ERROR) << "Unable to alloc memory for breakpoint target data";
	return JNI_ERR;
	}

	SimpleProfileData* data =
	new (data_mem) SimpleProfileData(jvmti, fd_name, fd, dump_on_shutdown, dump_on_main_stop);
	error = jvmti->SetEnvironmentLocalStorage(data);
	if (error != JVMTI_ERROR_NONE) {
	LOG(ERROR) << "Unable to set local storage";
	return JNI_ERR;
	}

	jvmtiCapabilities caps {};
	caps.can_generate_method_entry_events = JNI_TRUE;
	caps.can_tag_objects = JNI_TRUE;
	error = jvmti->AddCapabilities(&caps);
	if (error != JVMTI_ERROR_NONE) {
	LOG(ERROR) << "Unable to set caps";
	return JNI_ERR;
	}

	jvmtiEventCallbacks callbacks {};
	callbacks.MethodEntry = &MethodEntryCB;
	callbacks.VMInit = &VMInitCB;
	callbacks.DataDumpRequest = &DataDumpCb;
	callbacks.VMDeath = &VMDeathCB;
	callbacks.ThreadEnd = [](jvmtiEnv* env, JNIEnv* jni, jthread thr ATTRIBUTE_UNUSED) {
	VMDeathCB(env, jni);
	};

	error = jvmti->SetEventCallbacks(&callbacks, static_cast<jint>(sizeof(callbacks)));

	if (error != JVMTI_ERROR_NONE) {
	LOG(ERROR) << "Unable to set event callbacks.";
	return JNI_ERR;
	}

	if (start == StartType::OnAttach) {
	JNIEnv* env = nullptr;
	jint res = 0;
	res = vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_2);
	if (res != JNI_OK \|\| env == nullptr) {
	LOG(ERROR) << "Unable to get jnienv";
	return JNI_ERR;
	}
	jthread temp;
	ScopedLocalRef<jthread> cur(env, nullptr);
	CHECK_JVMTI(jvmti->GetCurrentThread(&temp));
	cur.reset(temp);
	VMInitCB(jvmti, env, cur.get());
	} else {
	error = jvmti->SetEventNotificationMode(
	JVMTI_ENABLE, JVMTI_EVENT_VM_INIT, nullptr /* all threads */);
	if (error != JVMTI_ERROR_NONE) {
	LOG(ERROR) << "Unable to set event vminit";
	return JNI_ERR;
	}
	}
	return JNI_OK;
	}

	// Late attachment (e.g. 'am attach-agent').
	extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
	return AgentStart(StartType::OnAttach, vm, options, reserved);
	}

	// Early attachment
	extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
	return AgentStart(StartType::OnLoad, jvm, options, reserved);
	}

	} // namespace simple_profile