vm/prims/jvmtiEnvBase.hpp

/*
 * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_PRIMS_JVMTIENVBASE_HPP
#define SHARE_VM_PRIMS_JVMTIENVBASE_HPP

#include "classfile/classLoader.hpp"
#include "prims/jvmtiEnvThreadState.hpp"
#include "prims/jvmtiEventController.hpp"
#include "prims/jvmtiThreadState.hpp"
#include "prims/jvmtiThreadState.inline.hpp"
#include "oops/oopHandle.hpp"
#include "runtime/fieldDescriptor.hpp"
#include "runtime/frame.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/thread.hpp"
#include "runtime/vm_operations.hpp"
#include "utilities/growableArray.hpp"
#include "utilities/macros.hpp"

//
// Forward Declarations
//

class JvmtiEnv;
class JvmtiThreadState;
class JvmtiRawMonitor; // for jvmtiEnv.hpp
class JvmtiEventControllerPrivate;
class JvmtiTagMap;


// One JvmtiEnv object is created per jvmti attachment;
// done via JNI GetEnv() call. Multiple attachments are
// allowed in jvmti.

class JvmtiEnvBase : public CHeapObj<mtInternal> {

 private:

#if INCLUDE_JVMTI
  static JvmtiEnvBase*     _head_environment;  // head of environment list
#endif // INCLUDE_JVMTI

  static bool              _globally_initialized;
  static jvmtiPhase        _phase;
  static volatile int      _dying_thread_env_iteration_count;

 public:

  enum {
    JDK15_JVMTI_VERSION = JVMTI_VERSION_1_0 +  33,  /* version: 1.0.33  */
    JDK16_JVMTI_VERSION = JVMTI_VERSION_1_1 + 102,  /* version: 1.1.102 */
    JDK17_JVMTI_VERSION = JVMTI_VERSION_1_2 +   2   /* version: 1.2.2   */
  };

  static jvmtiPhase  get_phase()                    { return _phase; }
  static jvmtiPhase  get_phase(jvmtiEnv* env)       { return ((JvmtiEnvBase*)JvmtiEnv_from_jvmti_env(env))->phase(); }
  static void  set_phase(jvmtiPhase phase)          { _phase = phase; }
  static bool is_vm_live()                          { return _phase == JVMTI_PHASE_LIVE; }

  static void entering_dying_thread_env_iteration() { ++_dying_thread_env_iteration_count; }
  static void leaving_dying_thread_env_iteration()  { --_dying_thread_env_iteration_count; }
  static bool is_inside_dying_thread_env_iteration(){ return _dying_thread_env_iteration_count > 0; }

 private:

  enum {
      JVMTI_MAGIC    = 0x71EE,
      DISPOSED_MAGIC = 0xDEFC,
      BAD_MAGIC      = 0xDEAD
  };

  jvmtiEnv _jvmti_external;
  jint _magic;
  jint _version;  // version value passed to JNI GetEnv()
  JvmtiEnvBase* _next;
  bool _is_retransformable;
  const void *_env_local_storage;     // per env agent allocated data.
  jvmtiEventCallbacks _event_callbacks;
  jvmtiExtEventCallbacks _ext_event_callbacks;
  JvmtiTagMap* _tag_map;
  JvmtiEnvEventEnable _env_event_enable;
  jvmtiCapabilities _current_capabilities;
  jvmtiCapabilities _prohibited_capabilities;
  volatile bool _class_file_load_hook_ever_enabled;
  static volatile bool _needs_clean_up;
  char** _native_method_prefixes;
  int    _native_method_prefix_count;

 protected:
  JvmtiEnvBase(jint version);
  ~JvmtiEnvBase();
  void dispose();
  void env_dispose();

  void set_env_local_storage(const void* data)     { _env_local_storage = data; }
  const void* get_env_local_storage()              { return _env_local_storage; }

  void record_class_file_load_hook_enabled();
  void record_first_time_class_file_load_hook_enabled();

  char** get_native_method_prefixes()              { return _native_method_prefixes; }
  int    get_native_method_prefix_count()          { return _native_method_prefix_count; }
  jvmtiError set_native_method_prefixes(jint prefix_count, char** prefixes);

 private:
  friend class JvmtiEventControllerPrivate;
  void initialize();
  void set_event_callbacks(const jvmtiEventCallbacks* callbacks, jint size_of_callbacks);
  static void globally_initialize();
  static void periodic_clean_up();

  friend class JvmtiEnvIterator;
  JvmtiEnv* next_environment()                     { return (JvmtiEnv*)_next; }
  void set_next_environment(JvmtiEnvBase* env)     { _next = env; }
  static JvmtiEnv* head_environment()              {
    JVMTI_ONLY(return (JvmtiEnv*)_head_environment);
    NOT_JVMTI(return NULL);
  }

 public:

  jvmtiPhase  phase();
  bool is_valid();

  bool use_version_1_0_semantics();  // agent asked for version 1.0
  bool use_version_1_1_semantics();  // agent asked for version 1.1
  bool use_version_1_2_semantics();  // agent asked for version 1.2

  bool is_retransformable()                        { return _is_retransformable; }

  static ByteSize jvmti_external_offset() {
    return byte_offset_of(JvmtiEnvBase, _jvmti_external);
  };

  static JvmtiEnv* JvmtiEnv_from_jvmti_env(jvmtiEnv *env) {
    return (JvmtiEnv*)((intptr_t)env - in_bytes(jvmti_external_offset()));
  };

  jvmtiCapabilities *get_capabilities()             { return &_current_capabilities; }

  jvmtiCapabilities *get_prohibited_capabilities()  { return &_prohibited_capabilities; }

  bool early_class_hook_env() {
    return get_capabilities()->can_generate_early_class_hook_events != 0
        && get_capabilities()->can_generate_all_class_hook_events != 0;
  }

  bool early_vmstart_env() {
    return get_capabilities()->can_generate_early_vmstart != 0;
  }

  static char** get_all_native_method_prefixes(int* count_ptr);

  // This test will answer true when all environments have been disposed and some have
  // not yet been deallocated.  As a result, this test should only be used as an
  // optimization for the no environment case.
  static bool environments_might_exist() {
    return head_environment() != NULL;
  }

  static void check_for_periodic_clean_up();

  JvmtiEnvEventEnable *env_event_enable() {
    return &_env_event_enable;
  }

  jvmtiError allocate(jlong size, unsigned char** mem_ptr) {
    if (size < 0) {
      return JVMTI_ERROR_ILLEGAL_ARGUMENT;
    }
    if (size == 0) {
      *mem_ptr = NULL;
    } else {
      *mem_ptr = (unsigned char *)os::malloc((size_t)size, mtInternal);
      if (*mem_ptr == NULL) {
        return JVMTI_ERROR_OUT_OF_MEMORY;
      }
    }
    return JVMTI_ERROR_NONE;
  }

  jvmtiError deallocate(unsigned char* mem) {
    if (mem != NULL) {
      os::free(mem);
    }
    return JVMTI_ERROR_NONE;
  }


  // Memory functions
  unsigned char* jvmtiMalloc(jlong size);  // don't use this - call allocate

  // method to create a local handle
  jobject jni_reference(Handle hndl) {
    return JNIHandles::make_local(hndl());
  }

  // method to create a local handle.
  // This function allows caller to specify which
  // threads local handle table to use.
  jobject jni_reference(JavaThread *thread, Handle hndl) {
    return JNIHandles::make_local(thread, hndl());
  }

  // method to destroy a local handle
  void destroy_jni_reference(jobject jobj) {
    JNIHandles::destroy_local(jobj);
  }

  // method to destroy a local handle.
  // This function allows caller to specify which
  // threads local handle table to use although currently it is
  // not used.
  void destroy_jni_reference(JavaThread *thread, jobject jobj) {
    destroy_jni_reference(jobj);
  }

  jvmtiEnv* jvmti_external() { return &_jvmti_external; };

// Event Dispatch

  bool has_callback(jvmtiEvent event_type) {
    assert(event_type >= JVMTI_MIN_EVENT_TYPE_VAL &&
           event_type <= JVMTI_MAX_EVENT_TYPE_VAL, "checking");
    return ((void**)&_event_callbacks)[event_type-JVMTI_MIN_EVENT_TYPE_VAL] != NULL;
  }

  jvmtiEventCallbacks* callbacks() {
    return &_event_callbacks;
  }

  jvmtiExtEventCallbacks* ext_callbacks() {
    return &_ext_event_callbacks;
  }

  void set_tag_map(JvmtiTagMap* tag_map) {
    _tag_map = tag_map;
  }

  JvmtiTagMap* tag_map() {
    return _tag_map;
  }


  // return true if event is enabled globally or for any thread
  // True only if there is a callback for it.
  bool is_enabled(jvmtiEvent event_type) {
    return _env_event_enable.is_enabled(event_type);
  }

// Random Utilities

 protected:
  // helper methods for creating arrays of global JNI Handles from local Handles
  // allocated into environment specific storage
  jobject * new_jobjectArray(int length, Handle *handles);
  jthread * new_jthreadArray(int length, Handle *handles);
  jthreadGroup * new_jthreadGroupArray(int length, Handle *handles);

  // convert from JNIHandle to JavaThread *
  JavaThread  * get_JavaThread(jthread jni_thread);

  // convert to a jni jclass from a non-null Klass*
  jclass get_jni_class_non_null(Klass* k);

  jint count_locked_objects(JavaThread *java_thread, Handle hobj);
  jvmtiError get_locked_objects_in_frame(JavaThread *calling_thread,
                                   JavaThread* java_thread,
                                   javaVFrame *jvf,
                                   GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list,
                                   jint depth);
  vframe* vframeFor(JavaThread* java_thread, jint depth);

 public:
  // get a field descriptor for the specified class and field
  static bool get_field_descriptor(Klass* k, jfieldID field, fieldDescriptor* fd);
  // test for suspend - most (all?) of these should go away
  static bool is_thread_fully_suspended(JavaThread *thread,
                                        bool wait_for_suspend,
                                        uint32_t *bits);


  // JVMTI API helper functions which are called at safepoint or thread is suspended.
  jvmtiError get_frame_count(JvmtiThreadState *state, jint *count_ptr);
  jvmtiError get_frame_location(JavaThread* java_thread, jint depth,
                                              jmethodID* method_ptr, jlocation* location_ptr);
  jvmtiError get_object_monitor_usage(JavaThread *calling_thread,
                                                    jobject object, jvmtiMonitorUsage* info_ptr);
  jvmtiError get_stack_trace(JavaThread *java_thread,
                                           jint stack_depth, jint max_count,
                                           jvmtiFrameInfo* frame_buffer, jint* count_ptr);
  jvmtiError get_current_contended_monitor(JavaThread *calling_thread,
                                                         JavaThread *java_thread,
                                                         jobject *monitor_ptr);
  jvmtiError get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
                          GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list);
  jvmtiError check_top_frame(JavaThread* current_thread, JavaThread* java_thread,
                             jvalue value, TosState tos, Handle* ret_ob_h);
  jvmtiError force_early_return(JavaThread* java_thread, jvalue value, TosState tos);
};

// This class is the only safe means of iterating through environments.
// Note that this iteratation includes invalid environments pending
// deallocation -- in fact, some uses depend on this behavior.

class JvmtiEnvIterator : public StackObj {
 private:
  bool _entry_was_marked;
 public:
  JvmtiEnvIterator() {
    if (Threads::number_of_threads() == 0) {
      _entry_was_marked = false; // we are single-threaded, no need
    } else {
      Thread::current()->entering_jvmti_env_iteration();
      _entry_was_marked = true;
    }
  }
  ~JvmtiEnvIterator() {
    if (_entry_was_marked) {
      Thread::current()->leaving_jvmti_env_iteration();
    }
  }
  JvmtiEnv* first()                 { return JvmtiEnvBase::head_environment(); }
  JvmtiEnv* next(JvmtiEnvBase* env) { return env->next_environment(); }
};

// VM operation to update for pop top frame.
class VM_UpdateForPopTopFrame : public VM_Operation {
private:
  JvmtiThreadState* _state;
  jvmtiError _result;

public:
  VM_UpdateForPopTopFrame(JvmtiThreadState* state) {
    _state = state;
    _result = JVMTI_ERROR_NONE;
  }
  VMOp_Type type() const { return VMOp_UpdateForPopTopFrame; }
  jvmtiError result() { return _result; }
  void doit() {
    JavaThread* jt = _state->get_thread();
    if (Threads::includes(jt) && !jt->is_exiting() && jt->threadObj() != NULL) {
      _state->update_for_pop_top_frame();
    } else {
      _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    }
  }
};

// VM operation to set frame pop.
class VM_SetFramePop : public VM_Operation {
private:
  JvmtiEnv *_env;
  JvmtiThreadState* _state;
  jint _depth;
  jvmtiError _result;

public:
  VM_SetFramePop(JvmtiEnv *env, JvmtiThreadState* state, jint depth) {
    _env = env;
    _state = state;
    _depth = depth;
    _result = JVMTI_ERROR_NONE;
  }
  // Nested operation must be allowed for the VM_EnterInterpOnlyMode that is
  // called from the JvmtiEventControllerPrivate::recompute_thread_enabled.
  bool allow_nested_vm_operations() const { return true; }
  VMOp_Type type() const { return VMOp_SetFramePop; }
  jvmtiError result() { return _result; }
  void doit() {
    JavaThread* jt = _state->get_thread();
    if (Threads::includes(jt) && !jt->is_exiting() && jt->threadObj() != NULL) {
      int frame_number = _state->count_frames() - _depth;
      _state->env_thread_state((JvmtiEnvBase*)_env)->set_frame_pop(frame_number);
    } else {
      _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    }
  }
};


// VM operation to get monitor information with stack depth.
class VM_GetOwnedMonitorInfo : public VM_Operation {
private:
  JvmtiEnv *_env;
  JavaThread* _calling_thread;
  JavaThread *_java_thread;
  jvmtiError _result;
  GrowableArray<jvmtiMonitorStackDepthInfo*> *_owned_monitors_list;

public:
  VM_GetOwnedMonitorInfo(JvmtiEnv* env, JavaThread* calling_thread,
                                   JavaThread* java_thread,
                                   GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitor_list) {
    _env = env;
    _calling_thread = calling_thread;
    _java_thread = java_thread;
    _owned_monitors_list = owned_monitor_list;
    _result = JVMTI_ERROR_NONE;
  }
  VMOp_Type type() const { return VMOp_GetOwnedMonitorInfo; }
  void doit() {
    _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    if (Threads::includes(_java_thread) && !_java_thread->is_exiting()
                                        && _java_thread->threadObj() != NULL) {
      _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(_calling_thread, _java_thread,
                                                            _owned_monitors_list);
    }
  }
  jvmtiError result() { return _result; }
};


// VM operation to get object monitor usage.
class VM_GetObjectMonitorUsage : public VM_Operation {
private:
  JvmtiEnv *_env;
  jobject _object;
  JavaThread* _calling_thread;
  jvmtiMonitorUsage* _info_ptr;
  jvmtiError _result;

public:
  VM_GetObjectMonitorUsage(JvmtiEnv *env, JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
    _env = env;
    _object = object;
    _calling_thread = calling_thread;
    _info_ptr = info_ptr;
  }
  VMOp_Type type() const { return VMOp_GetObjectMonitorUsage; }
  jvmtiError result() { return _result; }
  void doit() {
    _result = ((JvmtiEnvBase*) _env)->get_object_monitor_usage(_calling_thread, _object, _info_ptr);
  }

};

// VM operation to get current contended monitor.
class VM_GetCurrentContendedMonitor : public VM_Operation {
private:
  JvmtiEnv *_env;
  JavaThread *_calling_thread;
  JavaThread *_java_thread;
  jobject *_owned_monitor_ptr;
  jvmtiError _result;

public:
  VM_GetCurrentContendedMonitor(JvmtiEnv *env, JavaThread *calling_thread, JavaThread *java_thread, jobject *mon_ptr) {
    _env = env;
    _calling_thread = calling_thread;
    _java_thread = java_thread;
    _owned_monitor_ptr = mon_ptr;
  }
  VMOp_Type type() const { return VMOp_GetCurrentContendedMonitor; }
  jvmtiError result() { return _result; }
  void doit() {
    _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    if (Threads::includes(_java_thread) && !_java_thread->is_exiting() &&
        _java_thread->threadObj() != NULL) {
      _result = ((JvmtiEnvBase *)_env)->get_current_contended_monitor(_calling_thread,_java_thread,_owned_monitor_ptr);
    }
  }
};

// VM operation to get stack trace at safepoint.
class VM_GetStackTrace : public VM_Operation {
private:
  JvmtiEnv *_env;
  JavaThread *_java_thread;
  jint _start_depth;
  jint _max_count;
  jvmtiFrameInfo *_frame_buffer;
  jint *_count_ptr;
  jvmtiError _result;

public:
  VM_GetStackTrace(JvmtiEnv *env, JavaThread *java_thread,
                   jint start_depth, jint max_count,
                   jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
    _env = env;
    _java_thread = java_thread;
    _start_depth = start_depth;
    _max_count = max_count;
    _frame_buffer = frame_buffer;
    _count_ptr = count_ptr;
  }
  jvmtiError result() { return _result; }
  VMOp_Type type() const { return VMOp_GetStackTrace; }
  void doit() {
    _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    if (Threads::includes(_java_thread) && !_java_thread->is_exiting()
                                        && _java_thread->threadObj() != NULL) {
      _result = ((JvmtiEnvBase *)_env)->get_stack_trace(_java_thread,
                                                        _start_depth, _max_count,
                                                        _frame_buffer, _count_ptr);
    }
  }
};

// forward declaration
struct StackInfoNode;

// VM operation to get stack trace at safepoint.
class VM_GetMultipleStackTraces : public VM_Operation {
private:
  JvmtiEnv *_env;
  jint _max_frame_count;
  jvmtiStackInfo *_stack_info;
  jvmtiError _result;
  int _frame_count_total;
  struct StackInfoNode *_head;

  JvmtiEnvBase *env()                 { return (JvmtiEnvBase *)_env; }
  jint max_frame_count()              { return _max_frame_count; }
  struct StackInfoNode *head()        { return _head; }
  void set_head(StackInfoNode *head)  { _head = head; }

protected:
  void set_result(jvmtiError result)  { _result = result; }
  void fill_frames(jthread jt, JavaThread *thr, oop thread_oop);
  void allocate_and_fill_stacks(jint thread_count);

public:
  VM_GetMultipleStackTraces(JvmtiEnv *env, jint max_frame_count) {
    _env = env;
    _max_frame_count = max_frame_count;
    _frame_count_total = 0;
    _head = NULL;
    _result = JVMTI_ERROR_NONE;
  }
  VMOp_Type type() const             { return VMOp_GetMultipleStackTraces; }
  jvmtiStackInfo *stack_info()       { return _stack_info; }
  jvmtiError result()                { return _result; }
};


// VM operation to get stack trace at safepoint.
class VM_GetAllStackTraces : public VM_GetMultipleStackTraces {
private:
  JavaThread *_calling_thread;
  jint _final_thread_count;

public:
  VM_GetAllStackTraces(JvmtiEnv *env, JavaThread *calling_thread,
                       jint max_frame_count)
      : VM_GetMultipleStackTraces(env, max_frame_count) {
    _calling_thread = calling_thread;
  }
  VMOp_Type type() const          { return VMOp_GetAllStackTraces; }
  void doit();
  jint final_thread_count()       { return _final_thread_count; }
};

// VM operation to get stack trace at safepoint.
class VM_GetThreadListStackTraces : public VM_GetMultipleStackTraces {
private:
  jint _thread_count;
  const jthread* _thread_list;

public:
  VM_GetThreadListStackTraces(JvmtiEnv *env, jint thread_count, const jthread* thread_list, jint max_frame_count)
      : VM_GetMultipleStackTraces(env, max_frame_count) {
    _thread_count = thread_count;
    _thread_list = thread_list;
  }
  VMOp_Type type() const { return VMOp_GetThreadListStackTraces; }
  void doit();
};


// VM operation to count stack frames at safepoint.
class VM_GetFrameCount : public VM_Operation {
private:
  JvmtiEnv *_env;
  JvmtiThreadState *_state;
  jint *_count_ptr;
  jvmtiError _result;

public:
  VM_GetFrameCount(JvmtiEnv *env, JvmtiThreadState *state, jint *count_ptr) {
    _env = env;
    _state = state;
    _count_ptr = count_ptr;
  }
  VMOp_Type type() const { return VMOp_GetFrameCount; }
  jvmtiError result()    { return _result; }
  void doit() {
    _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    JavaThread* jt = _state->get_thread();
    if (Threads::includes(jt) && !jt->is_exiting() && jt->threadObj() != NULL) {
      _result = ((JvmtiEnvBase*)_env)->get_frame_count(_state, _count_ptr);
    }
  }
};

// VM operation to frame location at safepoint.
class VM_GetFrameLocation : public VM_Operation {
private:
  JvmtiEnv *_env;
  JavaThread* _java_thread;
  jint _depth;
  jmethodID* _method_ptr;
  jlocation* _location_ptr;
  jvmtiError _result;

public:
  VM_GetFrameLocation(JvmtiEnv *env, JavaThread* java_thread, jint depth,
                      jmethodID* method_ptr, jlocation* location_ptr) {
    _env = env;
    _java_thread = java_thread;
    _depth = depth;
    _method_ptr = method_ptr;
    _location_ptr = location_ptr;
  }
  VMOp_Type type() const { return VMOp_GetFrameLocation; }
  jvmtiError result()    { return _result; }
  void doit() {
    _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
    if (Threads::includes(_java_thread) && !_java_thread->is_exiting() &&
        _java_thread->threadObj() != NULL) {
      _result = ((JvmtiEnvBase*)_env)->get_frame_location(_java_thread, _depth,
                                                          _method_ptr, _location_ptr);
    }
  }
};


// ResourceTracker
//
// ResourceTracker works a little like a ResourceMark. All allocates
// using the resource tracker are recorded. If an allocate using the
// resource tracker fails the destructor will free any resources
// that were allocated using the tracker.
// The motive for this class is to avoid messy error recovery code
// in situations where multiple allocations are done in sequence. If
// the second or subsequent allocation fails it avoids any code to
// release memory allocated in the previous calls.
//
// Usage :-
//   ResourceTracker rt(env);
//   :
//   err = rt.allocate(1024, &ptr);

class ResourceTracker : public StackObj {
 private:
  JvmtiEnv* _env;
  GrowableArray<unsigned char*> *_allocations;
  bool _failed;
 public:
  ResourceTracker(JvmtiEnv* env);
  ~ResourceTracker();
  jvmtiError allocate(jlong size, unsigned char** mem_ptr);
  unsigned char* allocate(jlong size);
  char* strdup(const char* str);
};


// Jvmti monitor closure to collect off stack monitors.
class JvmtiMonitorClosure: public MonitorClosure {
 private:
  JavaThread *_java_thread;
  JavaThread *_calling_thread;
  GrowableArray<jvmtiMonitorStackDepthInfo*> *_owned_monitors_list;
  jvmtiError _error;
  JvmtiEnvBase *_env;

 public:
  JvmtiMonitorClosure(JavaThread* thread, JavaThread *calling_thread,
                      GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors,
                      JvmtiEnvBase *env) {
    _java_thread = thread;
    _calling_thread = calling_thread;
    _owned_monitors_list = owned_monitors;
    _error = JVMTI_ERROR_NONE;
    _env = env;
  }
  void do_monitor(ObjectMonitor* mon);
  jvmtiError error() { return _error;}
};


// Jvmti module closure to collect all modules loaded to the system.
class JvmtiModuleClosure : public StackObj {
private:
  static GrowableArray<OopHandle> *_tbl; // Protected with Module_lock

  static void do_module(ModuleEntry* entry) {
    assert_locked_or_safepoint(Module_lock);
    OopHandle module = entry->module_handle();
    guarantee(module.resolve() != NULL, "module object is NULL");
    _tbl->push(module);
  }

public:
  jvmtiError get_all_modules(JvmtiEnv* env, jint* module_count_ptr, jobject** modules_ptr);
};

#endif // SHARE_VM_PRIMS_JVMTIENVBASE_HPP