openjdkjvmti/events.h - platform/art - Gitiles

 /*
  * Copyright (C) 2016 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.
  */

 #ifndef ART_OPENJDKJVMTI_EVENTS_H_
 #define ART_OPENJDKJVMTI_EVENTS_H_

 #include <bitset>
 #include <vector>

 #include <android-base/logging.h>

 #include "base/macros.h"
 #include "base/mutex.h"
 #include "jvmti.h"
 #include "thread.h"

 namespace openjdkjvmti {

 struct ArtJvmTiEnv;
 class JvmtiAllocationListener;
 class JvmtiDdmChunkListener;
 class JvmtiGcPauseListener;
 class JvmtiMethodTraceListener;
 class JvmtiMonitorListener;
 class JvmtiParkListener;

 // an enum for ArtEvents. This differs from the JVMTI events only in that we distinguish between
 // retransformation capable and incapable loading
 enum class ArtJvmtiEvent : jint {
     kMinEventTypeVal = JVMTI_MIN_EVENT_TYPE_VAL,
     kVmInit = JVMTI_EVENT_VM_INIT,
     kVmDeath = JVMTI_EVENT_VM_DEATH,
     kThreadStart = JVMTI_EVENT_THREAD_START,
     kThreadEnd = JVMTI_EVENT_THREAD_END,
     kClassFileLoadHookNonRetransformable = JVMTI_EVENT_CLASS_FILE_LOAD_HOOK,
     kClassLoad = JVMTI_EVENT_CLASS_LOAD,
     kClassPrepare = JVMTI_EVENT_CLASS_PREPARE,
     kVmStart = JVMTI_EVENT_VM_START,
     kException = JVMTI_EVENT_EXCEPTION,
     kExceptionCatch = JVMTI_EVENT_EXCEPTION_CATCH,
     kSingleStep = JVMTI_EVENT_SINGLE_STEP,
     kFramePop = JVMTI_EVENT_FRAME_POP,
     kBreakpoint = JVMTI_EVENT_BREAKPOINT,
     kFieldAccess = JVMTI_EVENT_FIELD_ACCESS,
     kFieldModification = JVMTI_EVENT_FIELD_MODIFICATION,
     kMethodEntry = JVMTI_EVENT_METHOD_ENTRY,
     kMethodExit = JVMTI_EVENT_METHOD_EXIT,
     kNativeMethodBind = JVMTI_EVENT_NATIVE_METHOD_BIND,
     kCompiledMethodLoad = JVMTI_EVENT_COMPILED_METHOD_LOAD,
     kCompiledMethodUnload = JVMTI_EVENT_COMPILED_METHOD_UNLOAD,
     kDynamicCodeGenerated = JVMTI_EVENT_DYNAMIC_CODE_GENERATED,
     kDataDumpRequest = JVMTI_EVENT_DATA_DUMP_REQUEST,
     kMonitorWait = JVMTI_EVENT_MONITOR_WAIT,
     kMonitorWaited = JVMTI_EVENT_MONITOR_WAITED,
     kMonitorContendedEnter = JVMTI_EVENT_MONITOR_CONTENDED_ENTER,
     kMonitorContendedEntered = JVMTI_EVENT_MONITOR_CONTENDED_ENTERED,
     kResourceExhausted = JVMTI_EVENT_RESOURCE_EXHAUSTED,
     kGarbageCollectionStart = JVMTI_EVENT_GARBAGE_COLLECTION_START,
     kGarbageCollectionFinish = JVMTI_EVENT_GARBAGE_COLLECTION_FINISH,
     kObjectFree = JVMTI_EVENT_OBJECT_FREE,
     kVmObjectAlloc = JVMTI_EVENT_VM_OBJECT_ALLOC,
     kClassFileLoadHookRetransformable = JVMTI_MAX_EVENT_TYPE_VAL + 1,
     kDdmPublishChunk = JVMTI_MAX_EVENT_TYPE_VAL + 2,
     kMaxEventTypeVal = kDdmPublishChunk,
 };

 using ArtJvmtiEventDdmPublishChunk = void (*)(jvmtiEnv *jvmti_env,
                                               JNIEnv* jni_env,
                                               jint data_type,
                                               jint data_len,
                                               const jbyte* data);

 struct ArtJvmtiEventCallbacks : jvmtiEventCallbacks {
   ArtJvmtiEventCallbacks() : DdmPublishChunk(nullptr) {
     memset(this, 0, sizeof(jvmtiEventCallbacks));
   }

   // Copies extension functions from other callback struct if it exists. There must not have been
   // any modifications to this struct when it is called.
   void CopyExtensionsFrom(const ArtJvmtiEventCallbacks* cb);

   jvmtiError Set(jint index, jvmtiExtensionEvent cb);

   ArtJvmtiEventDdmPublishChunk DdmPublishChunk;
 };

 bool IsExtensionEvent(jint e);
 bool IsExtensionEvent(ArtJvmtiEvent e);

 // Convert a jvmtiEvent into a ArtJvmtiEvent
 ALWAYS_INLINE static inline ArtJvmtiEvent GetArtJvmtiEvent(ArtJvmTiEnv* env, jvmtiEvent e);

 static inline jvmtiEvent GetJvmtiEvent(ArtJvmtiEvent e) {
   if (UNLIKELY(e == ArtJvmtiEvent::kClassFileLoadHookRetransformable)) {
     return JVMTI_EVENT_CLASS_FILE_LOAD_HOOK;
   } else {
     return static_cast<jvmtiEvent>(e);
   }
 }

 struct EventMask {
   static constexpr size_t kEventsSize =
       static_cast<size_t>(ArtJvmtiEvent::kMaxEventTypeVal) -
       static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal) + 1;
   std::bitset<kEventsSize> bit_set;

   static bool EventIsInRange(ArtJvmtiEvent event) {
     return event >= ArtJvmtiEvent::kMinEventTypeVal && event <= ArtJvmtiEvent::kMaxEventTypeVal;
   }

   void Set(ArtJvmtiEvent event, bool value = true) {
     DCHECK(EventIsInRange(event));
     bit_set.set(static_cast<size_t>(event) - static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal),
                 value);
   }

   bool Test(ArtJvmtiEvent event) const {
     DCHECK(EventIsInRange(event));
     return bit_set.test(
         static_cast<size_t>(event) - static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal));
   }
 };

 struct EventMasks {
   // The globally enabled events.
   EventMask global_event_mask;

   // The per-thread enabled events.

   // It is not enough to store a Thread pointer, as these may be reused. Use the pointer and the
   // thread id.
   // Note: We could just use the tid like tracing does.
   using UniqueThread = std::pair<art::Thread*, uint32_t>;
   // TODO: Native thread objects are immovable, so we can use them as keys in an (unordered) map,
   //       if necessary.
   std::vector<std::pair<UniqueThread, EventMask>> thread_event_masks;

   // A union of the per-thread events, for fast-pathing.
   EventMask unioned_thread_event_mask;

   EventMask& GetEventMask(art::Thread* thread);
   EventMask* GetEventMaskOrNull(art::Thread* thread);
   // Circular dependencies mean we cannot see the definition of ArtJvmTiEnv so the mutex is simply
   // asserted in the function.
   // Note that the 'env' passed in must be the same env this EventMasks is associated with.
   void EnableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event);
       // REQUIRES(env->event_info_mutex_);
   // Circular dependencies mean we cannot see the definition of ArtJvmTiEnv so the mutex is simply
   // asserted in the function.
   // Note that the 'env' passed in must be the same env this EventMasks is associated with.
   void DisableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event);
       // REQUIRES(env->event_info_mutex_);
   bool IsEnabledAnywhere(ArtJvmtiEvent event);
   // Make any changes to event masks needed for the given capability changes. If caps_added is true
   // then caps is all the newly set capabilities of the jvmtiEnv. If it is false then caps is the
   // set of all capabilities that were removed from the jvmtiEnv.
   void HandleChangedCapabilities(const jvmtiCapabilities& caps, bool caps_added);
 };

 namespace impl {
 template <ArtJvmtiEvent kEvent> struct EventHandlerFunc { };
 }  // namespace impl

 // Helper class for event handling.
 class EventHandler {
  public:
   EventHandler();
   ~EventHandler();

   // do cleanup for the event handler.
   void Shutdown();

   // Register an env. It is assumed that this happens on env creation, that is, no events are
   // enabled, yet.
   void RegisterArtJvmTiEnv(ArtJvmTiEnv* env) REQUIRES(!envs_lock_);

   // Remove an env.
   void RemoveArtJvmTiEnv(ArtJvmTiEnv* env) REQUIRES(!envs_lock_);

   bool IsEventEnabledAnywhere(ArtJvmtiEvent event) const {
     if (!EventMask::EventIsInRange(event)) {
       return false;
     }
     return global_mask.Test(event);
   }

   jvmtiError SetEvent(ArtJvmTiEnv* env,
                       art::Thread* thread,
                       ArtJvmtiEvent event,
                       jvmtiEventMode mode)
       REQUIRES(!envs_lock_);

   // Dispatch event to all registered environments. Since this one doesn't have a JNIEnv* it doesn't
   // matter if it has the mutator_lock.
   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline void DispatchEvent(art::Thread* thread, Args... args) const
       REQUIRES(!envs_lock_);

   // Dispatch event to all registered environments stashing exceptions as needed. This works since
   // JNIEnv* is always the second argument if it is passed to an event. Needed since C++ does not
   // allow partial template function specialization.
   //
   // We need both of these since we want to make sure to push a stack frame when it is possible for
   // the event to allocate local references.
   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline void DispatchEvent(art::Thread* thread, JNIEnv* jnienv, Args... args) const
       REQUIRES(!envs_lock_);

   // Tell the event handler capabilities were added/lost so it can adjust the sent events.If
   // caps_added is true then caps is all the newly set capabilities of the jvmtiEnv. If it is false
   // then caps is the set of all capabilities that were removed from the jvmtiEnv.
   ALWAYS_INLINE
   inline void HandleChangedCapabilities(ArtJvmTiEnv* env,
                                         const jvmtiCapabilities& caps,
                                         bool added)
       REQUIRES(!envs_lock_);

   // Dispatch event to the given environment, only.
   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline void DispatchEventOnEnv(ArtJvmTiEnv* env,
                                  art::Thread* thread,
                                  JNIEnv* jnienv,
                                  Args... args) const
       REQUIRES(!envs_lock_);

   // Dispatch event to the given environment, only.
   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline void DispatchEventOnEnv(ArtJvmTiEnv* env, art::Thread* thread, Args... args) const
       REQUIRES(!envs_lock_);

  private:
   void SetupTraceListener(JvmtiMethodTraceListener* listener, ArtJvmtiEvent event, bool enable);

   // Specifically handle the FramePop event which it might not always be possible to turn off.
   void SetupFramePopTraceListener(bool enable);

   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline std::vector<impl::EventHandlerFunc<kEvent>> CollectEvents(art::Thread* thread,
                                                                    Args... args) const
       REQUIRES(!envs_lock_);

   template <ArtJvmtiEvent kEvent>
   ALWAYS_INLINE
   inline bool ShouldDispatchOnThread(ArtJvmTiEnv* env, art::Thread* thread) const;

   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   static inline void ExecuteCallback(impl::EventHandlerFunc<kEvent> handler,
                                      JNIEnv* env,
                                      Args... args)
       REQUIRES(!envs_lock_);

   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   static inline void ExecuteCallback(impl::EventHandlerFunc<kEvent> handler, Args... args)
       REQUIRES(!envs_lock_);

   // Public for use to collect dispatches
   template <ArtJvmtiEvent kEvent, typename ...Args>
   ALWAYS_INLINE
   inline bool ShouldDispatch(ArtJvmTiEnv* env, art::Thread* thread, Args... args) const;

   ALWAYS_INLINE
   inline bool NeedsEventUpdate(ArtJvmTiEnv* env,
                                const jvmtiCapabilities& caps,
                                bool added);

   // Recalculates the event mask for the given event.
   ALWAYS_INLINE
   inline void RecalculateGlobalEventMask(ArtJvmtiEvent event) REQUIRES(!envs_lock_);
   ALWAYS_INLINE
   inline void RecalculateGlobalEventMaskLocked(ArtJvmtiEvent event) REQUIRES_SHARED(envs_lock_);

   template <ArtJvmtiEvent kEvent>
   ALWAYS_INLINE inline void DispatchClassFileLoadHookEvent(art::Thread* thread,
                                                            JNIEnv* jnienv,
                                                            jclass class_being_redefined,
                                                            jobject loader,
                                                            const char* name,
                                                            jobject protection_domain,
                                                            jint class_data_len,
                                                            const unsigned char* class_data,
                                                            jint* new_class_data_len,
                                                            unsigned char** new_class_data) const
       REQUIRES(!envs_lock_);

   template <ArtJvmtiEvent kEvent>
   ALWAYS_INLINE inline void DispatchClassLoadOrPrepareEvent(art::Thread* thread,
                                                             JNIEnv* jnienv,
                                                             jthread jni_thread,
                                                             jclass klass) const
       REQUIRES(!envs_lock_);

   void HandleEventType(ArtJvmtiEvent event, bool enable);
   void HandleLocalAccessCapabilityAdded();
   void HandleBreakpointEventsChanged(bool enable);

   bool OtherMonitorEventsEnabledAnywhere(ArtJvmtiEvent event);

   // List of all JvmTiEnv objects that have been created, in their creation order. It is a std::list
   // since we mostly access it by iterating over the entire thing, only ever append to the end, and
   // need to be able to remove arbitrary elements from it.
   std::list<ArtJvmTiEnv*> envs GUARDED_BY(envs_lock_);

   // Top level lock. Nothing at all should be held when we lock this.
   mutable art::ReaderWriterMutex envs_lock_
       ACQUIRED_BEFORE(art::Locks::instrument_entrypoints_lock_);

   // A union of all enabled events, anywhere.
   EventMask global_mask;

   std::unique_ptr<JvmtiAllocationListener> alloc_listener_;
   std::unique_ptr<JvmtiDdmChunkListener> ddm_listener_;
   std::unique_ptr<JvmtiGcPauseListener> gc_pause_listener_;
   std::unique_ptr<JvmtiMethodTraceListener> method_trace_listener_;
   std::unique_ptr<JvmtiMonitorListener> monitor_listener_;
   std::unique_ptr<JvmtiParkListener> park_listener_;

   // True if frame pop has ever been enabled. Since we store pointers to stack frames we need to
   // continue to listen to this event even if it has been disabled.
   // TODO We could remove the listeners once all jvmtiEnvs have drained their shadow-frame vectors.
   bool frame_pop_enabled;
 };

 }  // namespace openjdkjvmti

 #endif  // ART_OPENJDKJVMTI_EVENTS_H_
	/*
	* Copyright (C) 2016 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.
	*/

	#ifndef ART_OPENJDKJVMTI_EVENTS_H_
	#define ART_OPENJDKJVMTI_EVENTS_H_

	#include <bitset>
	#include <vector>

	#include <android-base/logging.h>

	#include "base/macros.h"
	#include "base/mutex.h"
	#include "jvmti.h"
	#include "thread.h"

	namespace openjdkjvmti {

	struct ArtJvmTiEnv;
	class JvmtiAllocationListener;
	class JvmtiDdmChunkListener;
	class JvmtiGcPauseListener;
	class JvmtiMethodTraceListener;
	class JvmtiMonitorListener;
	class JvmtiParkListener;

	// an enum for ArtEvents. This differs from the JVMTI events only in that we distinguish between
	// retransformation capable and incapable loading
	enum class ArtJvmtiEvent : jint {
	kMinEventTypeVal = JVMTI_MIN_EVENT_TYPE_VAL,
	kVmInit = JVMTI_EVENT_VM_INIT,
	kVmDeath = JVMTI_EVENT_VM_DEATH,
	kThreadStart = JVMTI_EVENT_THREAD_START,
	kThreadEnd = JVMTI_EVENT_THREAD_END,
	kClassFileLoadHookNonRetransformable = JVMTI_EVENT_CLASS_FILE_LOAD_HOOK,
	kClassLoad = JVMTI_EVENT_CLASS_LOAD,
	kClassPrepare = JVMTI_EVENT_CLASS_PREPARE,
	kVmStart = JVMTI_EVENT_VM_START,
	kException = JVMTI_EVENT_EXCEPTION,
	kExceptionCatch = JVMTI_EVENT_EXCEPTION_CATCH,
	kSingleStep = JVMTI_EVENT_SINGLE_STEP,
	kFramePop = JVMTI_EVENT_FRAME_POP,
	kBreakpoint = JVMTI_EVENT_BREAKPOINT,
	kFieldAccess = JVMTI_EVENT_FIELD_ACCESS,
	kFieldModification = JVMTI_EVENT_FIELD_MODIFICATION,
	kMethodEntry = JVMTI_EVENT_METHOD_ENTRY,
	kMethodExit = JVMTI_EVENT_METHOD_EXIT,
	kNativeMethodBind = JVMTI_EVENT_NATIVE_METHOD_BIND,
	kCompiledMethodLoad = JVMTI_EVENT_COMPILED_METHOD_LOAD,
	kCompiledMethodUnload = JVMTI_EVENT_COMPILED_METHOD_UNLOAD,
	kDynamicCodeGenerated = JVMTI_EVENT_DYNAMIC_CODE_GENERATED,
	kDataDumpRequest = JVMTI_EVENT_DATA_DUMP_REQUEST,
	kMonitorWait = JVMTI_EVENT_MONITOR_WAIT,
	kMonitorWaited = JVMTI_EVENT_MONITOR_WAITED,
	kMonitorContendedEnter = JVMTI_EVENT_MONITOR_CONTENDED_ENTER,
	kMonitorContendedEntered = JVMTI_EVENT_MONITOR_CONTENDED_ENTERED,
	kResourceExhausted = JVMTI_EVENT_RESOURCE_EXHAUSTED,
	kGarbageCollectionStart = JVMTI_EVENT_GARBAGE_COLLECTION_START,
	kGarbageCollectionFinish = JVMTI_EVENT_GARBAGE_COLLECTION_FINISH,
	kObjectFree = JVMTI_EVENT_OBJECT_FREE,
	kVmObjectAlloc = JVMTI_EVENT_VM_OBJECT_ALLOC,
	kClassFileLoadHookRetransformable = JVMTI_MAX_EVENT_TYPE_VAL + 1,
	kDdmPublishChunk = JVMTI_MAX_EVENT_TYPE_VAL + 2,
	kMaxEventTypeVal = kDdmPublishChunk,
	};

	using ArtJvmtiEventDdmPublishChunk = void ()(jvmtiEnv jvmti_env,
	JNIEnv* jni_env,
	jint data_type,
	jint data_len,
	const jbyte* data);

	struct ArtJvmtiEventCallbacks : jvmtiEventCallbacks {
	ArtJvmtiEventCallbacks() : DdmPublishChunk(nullptr) {
	memset(this, 0, sizeof(jvmtiEventCallbacks));
	}

	// Copies extension functions from other callback struct if it exists. There must not have been
	// any modifications to this struct when it is called.
	void CopyExtensionsFrom(const ArtJvmtiEventCallbacks* cb);

	jvmtiError Set(jint index, jvmtiExtensionEvent cb);

	ArtJvmtiEventDdmPublishChunk DdmPublishChunk;
	};

	bool IsExtensionEvent(jint e);
	bool IsExtensionEvent(ArtJvmtiEvent e);

	// Convert a jvmtiEvent into a ArtJvmtiEvent
	ALWAYS_INLINE static inline ArtJvmtiEvent GetArtJvmtiEvent(ArtJvmTiEnv* env, jvmtiEvent e);

	static inline jvmtiEvent GetJvmtiEvent(ArtJvmtiEvent e) {
	if (UNLIKELY(e == ArtJvmtiEvent::kClassFileLoadHookRetransformable)) {
	return JVMTI_EVENT_CLASS_FILE_LOAD_HOOK;
	} else {
	return static_cast<jvmtiEvent>(e);
	}
	}

	struct EventMask {
	static constexpr size_t kEventsSize =
	static_cast<size_t>(ArtJvmtiEvent::kMaxEventTypeVal) -
	static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal) + 1;
	std::bitset<kEventsSize> bit_set;

	static bool EventIsInRange(ArtJvmtiEvent event) {
	return event >= ArtJvmtiEvent::kMinEventTypeVal && event <= ArtJvmtiEvent::kMaxEventTypeVal;
	}

	void Set(ArtJvmtiEvent event, bool value = true) {
	DCHECK(EventIsInRange(event));
	bit_set.set(static_cast<size_t>(event) - static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal),
	value);
	}

	bool Test(ArtJvmtiEvent event) const {
	DCHECK(EventIsInRange(event));
	return bit_set.test(
	static_cast<size_t>(event) - static_cast<size_t>(ArtJvmtiEvent::kMinEventTypeVal));
	}
	};

	struct EventMasks {
	// The globally enabled events.
	EventMask global_event_mask;

	// The per-thread enabled events.

	// It is not enough to store a Thread pointer, as these may be reused. Use the pointer and the
	// thread id.
	// Note: We could just use the tid like tracing does.
	using UniqueThread = std::pair<art::Thread*, uint32_t>;
	// TODO: Native thread objects are immovable, so we can use them as keys in an (unordered) map,
	// if necessary.
	std::vector<std::pair<UniqueThread, EventMask>> thread_event_masks;

	// A union of the per-thread events, for fast-pathing.
	EventMask unioned_thread_event_mask;

	EventMask& GetEventMask(art::Thread* thread);
	EventMask* GetEventMaskOrNull(art::Thread* thread);
	// Circular dependencies mean we cannot see the definition of ArtJvmTiEnv so the mutex is simply
	// asserted in the function.
	// Note that the 'env' passed in must be the same env this EventMasks is associated with.
	void EnableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event);
	// REQUIRES(env->event_info_mutex_);
	// Circular dependencies mean we cannot see the definition of ArtJvmTiEnv so the mutex is simply
	// asserted in the function.
	// Note that the 'env' passed in must be the same env this EventMasks is associated with.
	void DisableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event);
	// REQUIRES(env->event_info_mutex_);
	bool IsEnabledAnywhere(ArtJvmtiEvent event);
	// Make any changes to event masks needed for the given capability changes. If caps_added is true
	// then caps is all the newly set capabilities of the jvmtiEnv. If it is false then caps is the
	// set of all capabilities that were removed from the jvmtiEnv.
	void HandleChangedCapabilities(const jvmtiCapabilities& caps, bool caps_added);
	};

	namespace impl {
	template <ArtJvmtiEvent kEvent> struct EventHandlerFunc { };
	} // namespace impl

	// Helper class for event handling.
	class EventHandler {
	public:
	EventHandler();
	~EventHandler();

	// do cleanup for the event handler.
	void Shutdown();

	// Register an env. It is assumed that this happens on env creation, that is, no events are
	// enabled, yet.
	void RegisterArtJvmTiEnv(ArtJvmTiEnv* env) REQUIRES(!envs_lock_);

	// Remove an env.
	void RemoveArtJvmTiEnv(ArtJvmTiEnv* env) REQUIRES(!envs_lock_);

	bool IsEventEnabledAnywhere(ArtJvmtiEvent event) const {
	if (!EventMask::EventIsInRange(event)) {
	return false;
	}
	return global_mask.Test(event);
	}

	jvmtiError SetEvent(ArtJvmTiEnv* env,
	art::Thread* thread,
	ArtJvmtiEvent event,
	jvmtiEventMode mode)
	REQUIRES(!envs_lock_);

	// Dispatch event to all registered environments. Since this one doesn't have a JNIEnv* it doesn't
	// matter if it has the mutator_lock.
	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline void DispatchEvent(art::Thread* thread, Args... args) const
	REQUIRES(!envs_lock_);

	// Dispatch event to all registered environments stashing exceptions as needed. This works since
	// JNIEnv* is always the second argument if it is passed to an event. Needed since C++ does not
	// allow partial template function specialization.
	//
	// We need both of these since we want to make sure to push a stack frame when it is possible for
	// the event to allocate local references.
	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline void DispatchEvent(art::Thread* thread, JNIEnv* jnienv, Args... args) const
	REQUIRES(!envs_lock_);

	// Tell the event handler capabilities were added/lost so it can adjust the sent events.If
	// caps_added is true then caps is all the newly set capabilities of the jvmtiEnv. If it is false
	// then caps is the set of all capabilities that were removed from the jvmtiEnv.
	ALWAYS_INLINE
	inline void HandleChangedCapabilities(ArtJvmTiEnv* env,
	const jvmtiCapabilities& caps,
	bool added)
	REQUIRES(!envs_lock_);

	// Dispatch event to the given environment, only.
	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline void DispatchEventOnEnv(ArtJvmTiEnv* env,
	art::Thread* thread,
	JNIEnv* jnienv,
	Args... args) const
	REQUIRES(!envs_lock_);

	// Dispatch event to the given environment, only.
	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline void DispatchEventOnEnv(ArtJvmTiEnv* env, art::Thread* thread, Args... args) const
	REQUIRES(!envs_lock_);

	private:
	void SetupTraceListener(JvmtiMethodTraceListener* listener, ArtJvmtiEvent event, bool enable);

	// Specifically handle the FramePop event which it might not always be possible to turn off.
	void SetupFramePopTraceListener(bool enable);

	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline std::vector<impl::EventHandlerFunc<kEvent>> CollectEvents(art::Thread* thread,
	Args... args) const
	REQUIRES(!envs_lock_);

	template <ArtJvmtiEvent kEvent>
	ALWAYS_INLINE
	inline bool ShouldDispatchOnThread(ArtJvmTiEnv* env, art::Thread* thread) const;

	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	static inline void ExecuteCallback(impl::EventHandlerFunc<kEvent> handler,
	JNIEnv* env,
	Args... args)
	REQUIRES(!envs_lock_);

	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	static inline void ExecuteCallback(impl::EventHandlerFunc<kEvent> handler, Args... args)
	REQUIRES(!envs_lock_);

	// Public for use to collect dispatches
	template <ArtJvmtiEvent kEvent, typename ...Args>
	ALWAYS_INLINE
	inline bool ShouldDispatch(ArtJvmTiEnv* env, art::Thread* thread, Args... args) const;

	ALWAYS_INLINE
	inline bool NeedsEventUpdate(ArtJvmTiEnv* env,
	const jvmtiCapabilities& caps,
	bool added);

	// Recalculates the event mask for the given event.
	ALWAYS_INLINE
	inline void RecalculateGlobalEventMask(ArtJvmtiEvent event) REQUIRES(!envs_lock_);
	ALWAYS_INLINE
	inline void RecalculateGlobalEventMaskLocked(ArtJvmtiEvent event) REQUIRES_SHARED(envs_lock_);

	template <ArtJvmtiEvent kEvent>
	ALWAYS_INLINE inline void DispatchClassFileLoadHookEvent(art::Thread* thread,
	JNIEnv* jnienv,
	jclass class_being_redefined,
	jobject loader,
	const char* name,
	jobject protection_domain,
	jint class_data_len,
	const unsigned char* class_data,
	jint* new_class_data_len,
	unsigned char** new_class_data) const
	REQUIRES(!envs_lock_);

	template <ArtJvmtiEvent kEvent>
	ALWAYS_INLINE inline void DispatchClassLoadOrPrepareEvent(art::Thread* thread,
	JNIEnv* jnienv,
	jthread jni_thread,
	jclass klass) const
	REQUIRES(!envs_lock_);

	void HandleEventType(ArtJvmtiEvent event, bool enable);
	void HandleLocalAccessCapabilityAdded();
	void HandleBreakpointEventsChanged(bool enable);

	bool OtherMonitorEventsEnabledAnywhere(ArtJvmtiEvent event);

	// List of all JvmTiEnv objects that have been created, in their creation order. It is a std::list
	// since we mostly access it by iterating over the entire thing, only ever append to the end, and
	// need to be able to remove arbitrary elements from it.
	std::list<ArtJvmTiEnv*> envs GUARDED_BY(envs_lock_);

	// Top level lock. Nothing at all should be held when we lock this.
	mutable art::ReaderWriterMutex envs_lock_
	ACQUIRED_BEFORE(art::Locks::instrument_entrypoints_lock_);

	// A union of all enabled events, anywhere.
	EventMask global_mask;

	std::unique_ptr<JvmtiAllocationListener> alloc_listener_;
	std::unique_ptr<JvmtiDdmChunkListener> ddm_listener_;
	std::unique_ptr<JvmtiGcPauseListener> gc_pause_listener_;
	std::unique_ptr<JvmtiMethodTraceListener> method_trace_listener_;
	std::unique_ptr<JvmtiMonitorListener> monitor_listener_;
	std::unique_ptr<JvmtiParkListener> park_listener_;

	// True if frame pop has ever been enabled. Since we store pointers to stack frames we need to
	// continue to listen to this event even if it has been disabled.
	// TODO We could remove the listeners once all jvmtiEnvs have drained their shadow-frame vectors.
	bool frame_pop_enabled;
	};

	} // namespace openjdkjvmti

	#endif // ART_OPENJDKJVMTI_EVENTS_H_