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 /*

  * Copyright (c) 2003, 2018, 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.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/symbolTable.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "jvmtifiles/jvmtiEnv.hpp"

 #include "oops/instanceMirrorKlass.hpp"

 #include "oops/objArrayKlass.hpp"

 #include "oops/oop.inline2.hpp"

 #include "prims/jvmtiEventController.hpp"

 #include "prims/jvmtiEventController.inline.hpp"

 #include "prims/jvmtiExport.hpp"

 #include "prims/jvmtiImpl.hpp"

 #include "prims/jvmtiTagMap.hpp"

 #include "runtime/biasedLocking.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/jniHandles.hpp"

 #include "runtime/mutex.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/reflectionUtils.hpp"

 #include "runtime/vframe.hpp"

 #include "runtime/vmThread.hpp"

 #include "runtime/vm_operations.hpp"

 #include "services/serviceUtil.hpp"

 #include "utilities/macros.hpp"

 #if INCLUDE_ALL_GCS

 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"

 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"

 #endif // INCLUDE_ALL_GCS

 // JvmtiTagHashmapEntry

 //

 // Each entry encapsulates a reference to the tagged object

 // and the tag value. In addition an entry includes a next pointer which

 // is used to chain entries together.

 class JvmtiTagHashmapEntry : public CHeapObj<mtInternal> {

  private:

   friend class JvmtiTagMap;

   oop _object;                          // tagged object

   jlong _tag;                           // the tag

   JvmtiTagHashmapEntry* _next;          // next on the list

   inline void init(oop object, jlong tag) {

     _object = object;

     _tag = tag;

     _next = NULL;

   }

   // constructor

   JvmtiTagHashmapEntry(oop object, jlong tag)         { init(object, tag); }

  public:

   // accessor methods

   inline oop object() const                           { return _object; }

   inline oop* object_addr()                           { return &_object; }

   inline jlong tag() const                            { return _tag; }

   inline void set_tag(jlong tag) {

     assert(tag != 0, "can't be zero");

     _tag = tag;

   }

   inline JvmtiTagHashmapEntry* next() const             { return _next; }

   inline void set_next(JvmtiTagHashmapEntry* next)      { _next = next; }

 };

 // JvmtiTagHashmap

 //

 // A hashmap is essentially a table of pointers to entries. Entries

 // are hashed to a location, or position in the table, and then

 // chained from that location. The "key" for hashing is address of

 // the object, or oop. The "value" is the tag value.

 //

 // A hashmap maintains a count of the number entries in the hashmap

 // and resizes if the number of entries exceeds a given threshold.

 // The threshold is specified as a percentage of the size - for

 // example a threshold of 0.75 will trigger the hashmap to resize

 // if the number of entries is >75% of table size.

 //

 // A hashmap provides functions for adding, removing, and finding

 // entries. It also provides a function to iterate over all entries

 // in the hashmap.

 class JvmtiTagHashmap : public CHeapObj<mtInternal> {

  private:

   friend class JvmtiTagMap;

   enum {

     small_trace_threshold  = 10000,                  // threshold for tracing

     medium_trace_threshold = 100000,

     large_trace_threshold  = 1000000,

     initial_trace_threshold = small_trace_threshold

   };

   static int _sizes[];                  // array of possible hashmap sizes

   int _size;                            // actual size of the table

   int _size_index;                      // index into size table

   int _entry_count;                     // number of entries in the hashmap

   float _load_factor;                   // load factor as a % of the size

   int _resize_threshold;                // computed threshold to trigger resizing.

   bool _resizing_enabled;               // indicates if hashmap can resize

   int _trace_threshold;                 // threshold for trace messages

   JvmtiTagHashmapEntry** _table;        // the table of entries.

   // private accessors

   int resize_threshold() const                  { return _resize_threshold; }

   int trace_threshold() const                   { return _trace_threshold; }

   // initialize the hashmap

   void init(int size_index=0, float load_factor=4.0f) {

     int initial_size =  _sizes[size_index];

     _size_index = size_index;

     _size = initial_size;

     _entry_count = 0;

     if (TraceJVMTIObjectTagging) {

       _trace_threshold = initial_trace_threshold;

     } else {

       _trace_threshold = -1;

     }

     _load_factor = load_factor;

     _resize_threshold = (int)(_load_factor * _size);

     _resizing_enabled = true;

     size_t s = initial_size * sizeof(JvmtiTagHashmapEntry*);

     _table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);

     if (_table == NULL) {

       vm_exit_out_of_memory(s, OOM_MALLOC_ERROR,

         "unable to allocate initial hashtable for jvmti object tags");

     }

     for (int i=0; i<initial_size; i++) {

       _table[i] = NULL;

     }

   }

   // hash a given key (oop) with the specified size

   static unsigned int hash(oop key, int size) {

     // shift right to get better distribution (as these bits will be zero

     // with aligned addresses)

     unsigned int addr = (unsigned int)(cast_from_oop<intptr_t>(key));

 #ifdef _LP64

     return (addr >> 3) % size;

 #else

     return (addr >> 2) % size;

 #endif

   }

   // hash a given key (oop)

   unsigned int hash(oop key) {

     return hash(key, _size);

   }

   // resize the hashmap - allocates a large table and re-hashes

   // all entries into the new table.

   void resize() {

     int new_size_index = _size_index+1;

     int new_size = _sizes[new_size_index];

     if (new_size < 0) {

       // hashmap already at maximum capacity

       return;

     }

     // allocate new table

     size_t s = new_size * sizeof(JvmtiTagHashmapEntry*);

     JvmtiTagHashmapEntry** new_table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);

     if (new_table == NULL) {

       warning("unable to allocate larger hashtable for jvmti object tags");

       set_resizing_enabled(false);

       return;

     }

     // initialize new table

     int i;

     for (i=0; i<new_size; i++) {

       new_table[i] = NULL;

     }

     // rehash all entries into the new table

     for (i=0; i<_size; i++) {

       JvmtiTagHashmapEntry* entry = _table[i];

       while (entry != NULL) {

         JvmtiTagHashmapEntry* next = entry->next();

         oop key = entry->object();

         assert(key != NULL, "jni weak reference cleared!!");

         unsigned int h = hash(key, new_size);

         JvmtiTagHashmapEntry* anchor = new_table[h];

         if (anchor == NULL) {

           new_table[h] = entry;

           entry->set_next(NULL);

         } else {

           entry->set_next(anchor);

           new_table[h] = entry;

         }

         entry = next;

       }

     }

     // free old table and update settings.

     os::free((void*)_table);

     _table = new_table;

     _size_index = new_size_index;

     _size = new_size;

     // compute new resize threshold

     _resize_threshold = (int)(_load_factor * _size);

   }

   // internal remove function - remove an entry at a given position in the

   // table.

   inline void remove(JvmtiTagHashmapEntry* prev, int pos, JvmtiTagHashmapEntry* entry) {

     assert(pos >= 0 && pos < _size, "out of range");

     if (prev == NULL) {

       _table[pos] = entry->next();

     } else {

       prev->set_next(entry->next());

     }

     assert(_entry_count > 0, "checking");

     _entry_count--;

   }

   // resizing switch

   bool is_resizing_enabled() const          { return _resizing_enabled; }

   void set_resizing_enabled(bool enable)    { _resizing_enabled = enable; }

   // debugging

   void print_memory_usage();

   void compute_next_trace_threshold();

  public:

   // create a JvmtiTagHashmap of a preferred size and optionally a load factor.

   // The preferred size is rounded down to an actual size.

   JvmtiTagHashmap(int size, float load_factor=0.0f) {

     int i=0;

     while (_sizes[i] < size) {

       if (_sizes[i] < 0) {

         assert(i > 0, "sanity check");

         i--;

         break;

       }

       i++;

     }

     // if a load factor is specified then use it, otherwise use default

     if (load_factor > 0.01f) {

       init(i, load_factor);

     } else {

       init(i);

     }

   }

   // create a JvmtiTagHashmap with default settings

   JvmtiTagHashmap() {

     init();

   }

   // release table when JvmtiTagHashmap destroyed

   ~JvmtiTagHashmap() {

     if (_table != NULL) {

       os::free((void*)_table);

       _table = NULL;

     }

   }

   // accessors

   int size() const                              { return _size; }

   JvmtiTagHashmapEntry** table() const          { return _table; }

   int entry_count() const                       { return _entry_count; }

   // find an entry in the hashmap, returns NULL if not found.

   inline JvmtiTagHashmapEntry* find(oop key) {

     unsigned int h = hash(key);

     JvmtiTagHashmapEntry* entry = _table[h];

     while (entry != NULL) {

       if (entry->object() == key) {

          return entry;

       }

       entry = entry->next();

     }

     return NULL;

   }

   // add a new entry to hashmap

   inline void add(oop key, JvmtiTagHashmapEntry* entry) {

     assert(key != NULL, "checking");

     assert(find(key) == NULL, "duplicate detected");

     unsigned int h = hash(key);

     JvmtiTagHashmapEntry* anchor = _table[h];

     if (anchor == NULL) {

       _table[h] = entry;

       entry->set_next(NULL);

     } else {

       entry->set_next(anchor);

       _table[h] = entry;

     }

     _entry_count++;

     if (trace_threshold() > 0 && entry_count() >= trace_threshold()) {

       assert(TraceJVMTIObjectTagging, "should only get here when tracing");

       print_memory_usage();

       compute_next_trace_threshold();

     }

     // if the number of entries exceed the threshold then resize

     if (entry_count() > resize_threshold() && is_resizing_enabled()) {

       resize();

     }

   }

   // remove an entry with the given key.

   inline JvmtiTagHashmapEntry* remove(oop key) {

     unsigned int h = hash(key);

     JvmtiTagHashmapEntry* entry = _table[h];

     JvmtiTagHashmapEntry* prev = NULL;

     while (entry != NULL) {

       if (key == entry->object()) {

         break;

       }

       prev = entry;

       entry = entry->next();

     }

     if (entry != NULL) {

       remove(prev, h, entry);

     }

     return entry;

   }

   // iterate over all entries in the hashmap

   void entry_iterate(JvmtiTagHashmapEntryClosure* closure);

 };

 // possible hashmap sizes - odd primes that roughly double in size.

 // To avoid excessive resizing the odd primes from 4801-76831 and

 // 76831-307261 have been removed. The list must be terminated by -1.

 int JvmtiTagHashmap::_sizes[] =  { 4801, 76831, 307261, 614563, 1228891,

     2457733, 4915219, 9830479, 19660831, 39321619, 78643219, -1 };

 // A supporting class for iterating over all entries in Hashmap

 class JvmtiTagHashmapEntryClosure {

  public:

   virtual void do_entry(JvmtiTagHashmapEntry* entry) = 0;

 };

 // iterate over all entries in the hashmap

 void JvmtiTagHashmap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {

   for (int i=0; i<_size; i++) {

     JvmtiTagHashmapEntry* entry = _table[i];

     JvmtiTagHashmapEntry* prev = NULL;

     while (entry != NULL) {

       // obtain the next entry before invoking do_entry - this is

       // necessary because do_entry may remove the entry from the

       // hashmap.

       JvmtiTagHashmapEntry* next = entry->next();

       closure->do_entry(entry);

       entry = next;

      }

   }

 }

 // debugging

 void JvmtiTagHashmap::print_memory_usage() {

   intptr_t p = (intptr_t)this;

   tty->print("[JvmtiTagHashmap @ " INTPTR_FORMAT, p);

   // table + entries in KB

   int hashmap_usage = (size()*sizeof(JvmtiTagHashmapEntry*) +

     entry_count()*sizeof(JvmtiTagHashmapEntry))/K;

   int weak_globals_usage = (int)(JNIHandles::weak_global_handle_memory_usage()/K);

   tty->print_cr(", %d entries (%d KB) <JNI weak globals: %d KB>]",

     entry_count(), hashmap_usage, weak_globals_usage);

 }

 // compute threshold for the next trace message

 void JvmtiTagHashmap::compute_next_trace_threshold() {

   if (trace_threshold() < medium_trace_threshold) {

     _trace_threshold += small_trace_threshold;

   } else {

     if (trace_threshold() < large_trace_threshold) {

       _trace_threshold += medium_trace_threshold;

     } else {

       _trace_threshold += large_trace_threshold;

     }

   }

 }

 // create a JvmtiTagMap

 JvmtiTagMap::JvmtiTagMap(JvmtiEnv* env) :

   _env(env),

   _lock(Mutex::nonleaf+2, "JvmtiTagMap._lock", false),

   _free_entries(NULL),

   _free_entries_count(0)

 {

   assert(JvmtiThreadState_lock->is_locked(), "sanity check");

   assert(((JvmtiEnvBase *)env)->tag_map() == NULL, "tag map already exists for environment");

   _hashmap = new JvmtiTagHashmap();

   // finally add us to the environment

   ((JvmtiEnvBase *)env)->set_tag_map(this);

 }

 // destroy a JvmtiTagMap

 JvmtiTagMap::~JvmtiTagMap() {

   // no lock acquired as we assume the enclosing environment is

   // also being destroryed.

   ((JvmtiEnvBase *)_env)->set_tag_map(NULL);

   JvmtiTagHashmapEntry** table = _hashmap->table();

   for (int j = 0; j < _hashmap->size(); j++) {

     JvmtiTagHashmapEntry* entry = table[j];

     while (entry != NULL) {

       JvmtiTagHashmapEntry* next = entry->next();

       delete entry;

       entry = next;

     }

   }

   // finally destroy the hashmap

   delete _hashmap;

   _hashmap = NULL;

   // remove any entries on the free list

   JvmtiTagHashmapEntry* entry = _free_entries;

   while (entry != NULL) {

     JvmtiTagHashmapEntry* next = entry->next();

     delete entry;

     entry = next;

   }

   _free_entries = NULL;

 }

 // create a hashmap entry

 // - if there's an entry on the (per-environment) free list then this

 // is returned. Otherwise an new entry is allocated.

 JvmtiTagHashmapEntry* JvmtiTagMap::create_entry(oop ref, jlong tag) {

   assert(Thread::current()->is_VM_thread() || is_locked(), "checking");

   JvmtiTagHashmapEntry* entry;

   if (_free_entries == NULL) {

     entry = new JvmtiTagHashmapEntry(ref, tag);

   } else {

     assert(_free_entries_count > 0, "mismatched _free_entries_count");

     _free_entries_count--;

     entry = _free_entries;

     _free_entries = entry->next();

     entry->init(ref, tag);

   }

   return entry;

 }

 // destroy an entry by returning it to the free list

 void JvmtiTagMap::destroy_entry(JvmtiTagHashmapEntry* entry) {

   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");

   // limit the size of the free list

   if (_free_entries_count >= max_free_entries) {

     delete entry;

   } else {

     entry->set_next(_free_entries);

     _free_entries = entry;

     _free_entries_count++;

   }

 }

 // returns the tag map for the given environments. If the tag map

 // doesn't exist then it is created.

 JvmtiTagMap* JvmtiTagMap::tag_map_for(JvmtiEnv* env) {

   JvmtiTagMap* tag_map = ((JvmtiEnvBase*)env)->tag_map();

   if (tag_map == NULL) {

     MutexLocker mu(JvmtiThreadState_lock);

     tag_map = ((JvmtiEnvBase*)env)->tag_map();

     if (tag_map == NULL) {

       tag_map = new JvmtiTagMap(env);

     }

   } else {

     CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());

   }

   return tag_map;

 }

 // iterate over all entries in the tag map.

 void JvmtiTagMap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {

   hashmap()->entry_iterate(closure);

 }

 // returns true if the hashmaps are empty

 bool JvmtiTagMap::is_empty() {

   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");

   return hashmap()->entry_count() == 0;

 }

 // Return the tag value for an object, or 0 if the object is

 // not tagged

 //

 static inline jlong tag_for(JvmtiTagMap* tag_map, oop o) {

   JvmtiTagHashmapEntry* entry = tag_map->hashmap()->find(o);

   if (entry == NULL) {

     return 0;

   } else {

     return entry->tag();

   }

 }

 // A CallbackWrapper is a support class for querying and tagging an object

 // around a callback to a profiler. The constructor does pre-callback

 // work to get the tag value, klass tag value, ... and the destructor

 // does the post-callback work of tagging or untagging the object.

 //

 // {

 //   CallbackWrapper wrapper(tag_map, o);

 //

 //   (*callback)(wrapper.klass_tag(), wrapper.obj_size(), wrapper.obj_tag_p(), ...)

 //

 // } // wrapper goes out of scope here which results in the destructor

 //      checking to see if the object has been tagged, untagged, or the

 //      tag value has changed.

 //

 class CallbackWrapper : public StackObj {

  private:

   JvmtiTagMap* _tag_map;

   JvmtiTagHashmap* _hashmap;

   JvmtiTagHashmapEntry* _entry;

   oop _o;

   jlong _obj_size;

   jlong _obj_tag;

   jlong _klass_tag;

  protected:

   JvmtiTagMap* tag_map() const      { return _tag_map; }

   // invoked post-callback to tag, untag, or update the tag of an object

   void inline post_callback_tag_update(oop o, JvmtiTagHashmap* hashmap,

                                        JvmtiTagHashmapEntry* entry, jlong obj_tag);

  public:

   CallbackWrapper(JvmtiTagMap* tag_map, oop o) {

     assert(Thread::current()->is_VM_thread() || tag_map->is_locked(),

            "MT unsafe or must be VM thread");

     // object to tag

     _o = o;

     // object size

     _obj_size = (jlong)_o->size() * wordSize;

     // record the context

     _tag_map = tag_map;

     _hashmap = tag_map->hashmap();

     _entry = _hashmap->find(_o);

     // get object tag

     _obj_tag = (_entry == NULL) ? 0 : _entry->tag();

     // get the class and the class's tag value

     assert(SystemDictionary::Class_klass()->oop_is_instanceMirror(), "Is not?");

     _klass_tag = tag_for(tag_map, _o->klass()->java_mirror());

   }

   ~CallbackWrapper() {

     post_callback_tag_update(_o, _hashmap, _entry, _obj_tag);

   }

   inline jlong* obj_tag_p()                     { return &_obj_tag; }

   inline jlong obj_size() const                 { return _obj_size; }

   inline jlong obj_tag() const                  { return _obj_tag; }

   inline jlong klass_tag() const                { return _klass_tag; }

 };

 // callback post-callback to tag, untag, or update the tag of an object

 void inline CallbackWrapper::post_callback_tag_update(oop o,

                                                       JvmtiTagHashmap* hashmap,

                                                       JvmtiTagHashmapEntry* entry,

                                                       jlong obj_tag) {

   if (entry == NULL) {

     if (obj_tag != 0) {

       // callback has tagged the object

       assert(Thread::current()->is_VM_thread(), "must be VMThread");

       entry = tag_map()->create_entry(o, obj_tag);

       hashmap->add(o, entry);

     }

   } else {

     // object was previously tagged - the callback may have untagged

     // the object or changed the tag value

     if (obj_tag == 0) {

       JvmtiTagHashmapEntry* entry_removed = hashmap->remove(o);

       assert(entry_removed == entry, "checking");

       tag_map()->destroy_entry(entry);

     } else {

       if (obj_tag != entry->tag()) {

          entry->set_tag(obj_tag);

       }

     }

   }

 }

 // An extended CallbackWrapper used when reporting an object reference

 // to the agent.

 //

 // {

 //   TwoOopCallbackWrapper wrapper(tag_map, referrer, o);

 //

 //   (*callback)(wrapper.klass_tag(),

 //               wrapper.obj_size(),

 //               wrapper.obj_tag_p()

 //               wrapper.referrer_tag_p(), ...)

 //

 // } // wrapper goes out of scope here which results in the destructor

 //      checking to see if the referrer object has been tagged, untagged,

 //      or the tag value has changed.

 //

 class TwoOopCallbackWrapper : public CallbackWrapper {

  private:

   bool _is_reference_to_self;

   JvmtiTagHashmap* _referrer_hashmap;

   JvmtiTagHashmapEntry* _referrer_entry;

   oop _referrer;

   jlong _referrer_obj_tag;

   jlong _referrer_klass_tag;

   jlong* _referrer_tag_p;

   bool is_reference_to_self() const             { return _is_reference_to_self; }

  public:

   TwoOopCallbackWrapper(JvmtiTagMap* tag_map, oop referrer, oop o) :

     CallbackWrapper(tag_map, o)

   {

     // self reference needs to be handled in a special way

     _is_reference_to_self = (referrer == o);

     if (_is_reference_to_self) {

       _referrer_klass_tag = klass_tag();

       _referrer_tag_p = obj_tag_p();

     } else {

       _referrer = referrer;

       // record the context

       _referrer_hashmap = tag_map->hashmap();

       _referrer_entry = _referrer_hashmap->find(_referrer);

       // get object tag

       _referrer_obj_tag = (_referrer_entry == NULL) ? 0 : _referrer_entry->tag();

       _referrer_tag_p = &_referrer_obj_tag;

       // get referrer class tag.

       _referrer_klass_tag = tag_for(tag_map, _referrer->klass()->java_mirror());

     }

   }

   ~TwoOopCallbackWrapper() {

     if (!is_reference_to_self()){

       post_callback_tag_update(_referrer,

                                _referrer_hashmap,

                                _referrer_entry,

                                _referrer_obj_tag);

     }

   }

   // address of referrer tag

   // (for a self reference this will return the same thing as obj_tag_p())

   inline jlong* referrer_tag_p()        { return _referrer_tag_p; }

   // referrer's class tag

   inline jlong referrer_klass_tag()     { return _referrer_klass_tag; }

 };

 // tag an object

 //

 // This function is performance critical. If many threads attempt to tag objects

 // around the same time then it's possible that the Mutex associated with the

 // tag map will be a hot lock.

 void JvmtiTagMap::set_tag(jobject object, jlong tag) {

   MutexLocker ml(lock());

   // resolve the object

   oop o = JNIHandles::resolve_non_null(object);

   // see if the object is already tagged

   JvmtiTagHashmap* hashmap = _hashmap;

   JvmtiTagHashmapEntry* entry = hashmap->find(o);

   // if the object is not already tagged then we tag it

   if (entry == NULL) {

     if (tag != 0) {

       entry = create_entry(o, tag);

       hashmap->add(o, entry);

     } else {

       // no-op

     }

   } else {

     // if the object is already tagged then we either update

     // the tag (if a new tag value has been provided)

     // or remove the object if the new tag value is 0.

     if (tag == 0) {

       hashmap->remove(o);

       destroy_entry(entry);

     } else {

       entry->set_tag(tag);

     }

   }

 }

 // get the tag for an object

 jlong JvmtiTagMap::get_tag(jobject object) {

   MutexLocker ml(lock());

   // resolve the object

   oop o = JNIHandles::resolve_non_null(object);

   return tag_for(this, o);

 }

 // Helper class used to describe the static or instance fields of a class.

 // For each field it holds the field index (as defined by the JVMTI specification),

 // the field type, and the offset.

 class ClassFieldDescriptor: public CHeapObj<mtInternal> {

  private:

   int _field_index;

   int _field_offset;

   char _field_type;

  public:

   ClassFieldDescriptor(int index, char type, int offset) :

     _field_index(index), _field_type(type), _field_offset(offset) {

   }

   int field_index()  const  { return _field_index; }

   char field_type()  const  { return _field_type; }

   int field_offset() const  { return _field_offset; }

 };

 class ClassFieldMap: public CHeapObj<mtInternal> {

  private:

   enum {

     initial_field_count = 5

   };

   // list of field descriptors

   GrowableArray<ClassFieldDescriptor*>* _fields;

   // constructor

   ClassFieldMap();

   // add a field

   void add(int index, char type, int offset);

   // returns the field count for the given class

   static int compute_field_count(instanceKlassHandle ikh);

  public:

   ~ClassFieldMap();

   // access

   int field_count()                     { return _fields->length(); }

   ClassFieldDescriptor* field_at(int i) { return _fields->at(i); }

   // functions to create maps of static or instance fields

   static ClassFieldMap* create_map_of_static_fields(Klass* k);

   static ClassFieldMap* create_map_of_instance_fields(oop obj);

 };

 ClassFieldMap::ClassFieldMap() {

   _fields = new (ResourceObj::C_HEAP, mtInternal)

     GrowableArray<ClassFieldDescriptor*>(initial_field_count, true);

 }

 ClassFieldMap::~ClassFieldMap() {

   for (int i=0; i<_fields->length(); i++) {

     delete _fields->at(i);

   }

   delete _fields;

 }

 void ClassFieldMap::add(int index, char type, int offset) {

   ClassFieldDescriptor* field = new ClassFieldDescriptor(index, type, offset);

   _fields->append(field);

 }

 // Returns a heap allocated ClassFieldMap to describe the static fields

 // of the given class.

 //

 ClassFieldMap* ClassFieldMap::create_map_of_static_fields(Klass* k) {

   HandleMark hm;

   instanceKlassHandle ikh = instanceKlassHandle(Thread::current(), k);

   // create the field map

   ClassFieldMap* field_map = new ClassFieldMap();

   FilteredFieldStream f(ikh, false, false);

   int max_field_index = f.field_count()-1;

   int index = 0;

   for (FilteredFieldStream fld(ikh, true, true); !fld.eos(); fld.next(), index++) {

     // ignore instance fields

     if (!fld.access_flags().is_static()) {

       continue;

     }

     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());

   }

   return field_map;

 }

 // Returns a heap allocated ClassFieldMap to describe the instance fields

 // of the given class. All instance fields are included (this means public

 // and private fields declared in superclasses and superinterfaces too).

 //

 ClassFieldMap* ClassFieldMap::create_map_of_instance_fields(oop obj) {

   HandleMark hm;

   instanceKlassHandle ikh = instanceKlassHandle(Thread::current(), obj->klass());

   // create the field map

   ClassFieldMap* field_map = new ClassFieldMap();

   FilteredFieldStream f(ikh, false, false);

   int max_field_index = f.field_count()-1;

   int index = 0;

   for (FilteredFieldStream fld(ikh, false, false); !fld.eos(); fld.next(), index++) {

     // ignore static fields

     if (fld.access_flags().is_static()) {

       continue;

     }

     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());

   }

   return field_map;

 }

 // Helper class used to cache a ClassFileMap for the instance fields of

 // a cache. A JvmtiCachedClassFieldMap can be cached by an InstanceKlass during

 // heap iteration and avoid creating a field map for each object in the heap

 // (only need to create the map when the first instance of a class is encountered).

 //

 class JvmtiCachedClassFieldMap : public CHeapObj<mtInternal> {

  private:

    enum {

      initial_class_count = 200

    };

   ClassFieldMap* _field_map;

   ClassFieldMap* field_map() const          { return _field_map; }

   JvmtiCachedClassFieldMap(ClassFieldMap* field_map);

   ~JvmtiCachedClassFieldMap();

   static GrowableArray<InstanceKlass*>* _class_list;

   static void add_to_class_list(InstanceKlass* ik);

  public:

   // returns the field map for a given object (returning map cached

   // by InstanceKlass if possible

   static ClassFieldMap* get_map_of_instance_fields(oop obj);

   // removes the field map from all instanceKlasses - should be

   // called before VM operation completes

   static void clear_cache();

   // returns the number of ClassFieldMap cached by instanceKlasses

   static int cached_field_map_count();

 };

 GrowableArray<InstanceKlass*>* JvmtiCachedClassFieldMap::_class_list;

 JvmtiCachedClassFieldMap::JvmtiCachedClassFieldMap(ClassFieldMap* field_map) {

   _field_map = field_map;

 }

 JvmtiCachedClassFieldMap::~JvmtiCachedClassFieldMap() {

   if (_field_map != NULL) {

     delete _field_map;

   }

 }

 // Marker class to ensure that the class file map cache is only used in a defined

 // scope.

 class ClassFieldMapCacheMark : public StackObj {

  private:

    static bool _is_active;

  public:

    ClassFieldMapCacheMark() {

      assert(Thread::current()->is_VM_thread(), "must be VMThread");

      assert(JvmtiCachedClassFieldMap::cached_field_map_count() == 0, "cache not empty");

      assert(!_is_active, "ClassFieldMapCacheMark cannot be nested");

      _is_active = true;

    }

    ~ClassFieldMapCacheMark() {

      JvmtiCachedClassFieldMap::clear_cache();

      _is_active = false;

    }

    static bool is_active() { return _is_active; }

 };

 bool ClassFieldMapCacheMark::_is_active;

 // record that the given InstanceKlass is caching a field map

 void JvmtiCachedClassFieldMap::add_to_class_list(InstanceKlass* ik) {

   if (_class_list == NULL) {

     _class_list = new (ResourceObj::C_HEAP, mtInternal)

       GrowableArray<InstanceKlass*>(initial_class_count, true);

   }

   _class_list->push(ik);

 }

 // returns the instance field map for the given object

 // (returns field map cached by the InstanceKlass if possible)

 ClassFieldMap* JvmtiCachedClassFieldMap::get_map_of_instance_fields(oop obj) {

   assert(Thread::current()->is_VM_thread(), "must be VMThread");

   assert(ClassFieldMapCacheMark::is_active(), "ClassFieldMapCacheMark not active");

   Klass* k = obj->klass();

   InstanceKlass* ik = InstanceKlass::cast(k);

   // return cached map if possible

   JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();

   if (cached_map != NULL) {

     assert(cached_map->field_map() != NULL, "missing field list");

     return cached_map->field_map();

   } else {

     ClassFieldMap* field_map = ClassFieldMap::create_map_of_instance_fields(obj);

     cached_map = new JvmtiCachedClassFieldMap(field_map);

     ik->set_jvmti_cached_class_field_map(cached_map);

     add_to_class_list(ik);

     return field_map;

   }

 }

 // remove the fields maps cached from all instanceKlasses

 void JvmtiCachedClassFieldMap::clear_cache() {

   assert(Thread::current()->is_VM_thread(), "must be VMThread");

   if (_class_list != NULL) {

     for (int i = 0; i < _class_list->length(); i++) {

       InstanceKlass* ik = _class_list->at(i);

       JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();

       assert(cached_map != NULL, "should not be NULL");

       ik->set_jvmti_cached_class_field_map(NULL);

       delete cached_map;  // deletes the encapsulated field map

     }

     delete _class_list;

     _class_list = NULL;

   }

 }

 // returns the number of ClassFieldMap cached by instanceKlasses

 int JvmtiCachedClassFieldMap::cached_field_map_count() {

   return (_class_list == NULL) ? 0 : _class_list->length();

 }

 // helper function to indicate if an object is filtered by its tag or class tag

 static inline bool is_filtered_by_heap_filter(jlong obj_tag,

                                               jlong klass_tag,

                                               int heap_filter) {

   // apply the heap filter

   if (obj_tag != 0) {

     // filter out tagged objects

     if (heap_filter & JVMTI_HEAP_FILTER_TAGGED) return true;

   } else {

     // filter out untagged objects

     if (heap_filter & JVMTI_HEAP_FILTER_UNTAGGED) return true;

   }

   if (klass_tag != 0) {

     // filter out objects with tagged classes

     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_TAGGED) return true;

   } else {

     // filter out objects with untagged classes.

     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_UNTAGGED) return true;

   }

   return false;

 }

 // helper function to indicate if an object is filtered by a klass filter

 static inline bool is_filtered_by_klass_filter(oop obj, KlassHandle klass_filter) {

   if (!klass_filter.is_null()) {

     if (obj->klass() != klass_filter()) {

       return true;

     }

   }

   return false;

 }

 // helper function to tell if a field is a primitive field or not

 static inline bool is_primitive_field_type(char type) {

   return (type != 'L' && type != '[');

 }

 // helper function to copy the value from location addr to jvalue.

 static inline void copy_to_jvalue(jvalue *v, address addr, jvmtiPrimitiveType value_type) {

   switch (value_type) {

     case JVMTI_PRIMITIVE_TYPE_BOOLEAN : { v->z = *(jboolean*)addr; break; }

     case JVMTI_PRIMITIVE_TYPE_BYTE    : { v->b = *(jbyte*)addr;    break; }

     case JVMTI_PRIMITIVE_TYPE_CHAR    : { v->c = *(jchar*)addr;    break; }

     case JVMTI_PRIMITIVE_TYPE_SHORT   : { v->s = *(jshort*)addr;   break; }

     case JVMTI_PRIMITIVE_TYPE_INT     : { v->i = *(jint*)addr;     break; }

     case JVMTI_PRIMITIVE_TYPE_LONG    : { v->j = *(jlong*)addr;    break; }

     case JVMTI_PRIMITIVE_TYPE_FLOAT   : { v->f = *(jfloat*)addr;   break; }

     case JVMTI_PRIMITIVE_TYPE_DOUBLE  : { v->d = *(jdouble*)addr;  break; }

     default: ShouldNotReachHere();

   }

 }

 // helper function to invoke string primitive value callback

 // returns visit control flags

 static jint invoke_string_value_callback(jvmtiStringPrimitiveValueCallback cb,

                                          CallbackWrapper* wrapper,

                                          oop str,

                                          void* user_data)

 {

   assert(str->klass() == SystemDictionary::String_klass(), "not a string");

   typeArrayOop s_value = java_lang_String::value(str);

   // JDK-6584008: the value field may be null if a String instance is

   // partially constructed.

   if (s_value == NULL) {

     return 0;

   }

   // get the string value and length

   // (string value may be offset from the base)

   int s_len = java_lang_String::length(str);

   int s_offset = java_lang_String::offset(str);

   jchar* value;

   if (s_len > 0) {

     value = s_value->char_at_addr(s_offset);

   } else {

     value = (jchar*) s_value->base(T_CHAR);

   }

   // invoke the callback

   return (*cb)(wrapper->klass_tag(),

                wrapper->obj_size(),

                wrapper->obj_tag_p(),

                value,

                (jint)s_len,

                user_data);

 }

 // helper function to invoke string primitive value callback

 // returns visit control flags

 static jint invoke_array_primitive_value_callback(jvmtiArrayPrimitiveValueCallback cb,

                                                   CallbackWrapper* wrapper,

                                                   oop obj,

                                                   void* user_data)

 {

   assert(obj->is_typeArray(), "not a primitive array");

   // get base address of first element

   typeArrayOop array = typeArrayOop(obj);

   BasicType type = TypeArrayKlass::cast(array->klass())->element_type();

   void* elements = array->base(type);

   // jvmtiPrimitiveType is defined so this mapping is always correct

   jvmtiPrimitiveType elem_type = (jvmtiPrimitiveType)type2char(type);

   return (*cb)(wrapper->klass_tag(),

                wrapper->obj_size(),

                wrapper->obj_tag_p(),

                (jint)array->length(),

                elem_type,

                elements,

                user_data);

 }

 // helper function to invoke the primitive field callback for all static fields

 // of a given class

 static jint invoke_primitive_field_callback_for_static_fields

   (CallbackWrapper* wrapper,

    oop obj,

    jvmtiPrimitiveFieldCallback cb,

    void* user_data)

 {

   // for static fields only the index will be set

   static jvmtiHeapReferenceInfo reference_info = { 0 };

   assert(obj->klass() == SystemDictionary::Class_klass(), "not a class");

   if (java_lang_Class::is_primitive(obj)) {

     return 0;

   }

   Klass* klass = java_lang_Class::as_Klass(obj);

   // ignore classes for object and type arrays

   if (!klass->oop_is_instance()) {

     return 0;

   }

   // ignore classes which aren't linked yet

   InstanceKlass* ik = InstanceKlass::cast(klass);

   if (!ik->is_linked()) {

     return 0;

   }

   // get the field map

   ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);

   // invoke the callback for each static primitive field

   for (int i=0; i<field_map->field_count(); i++) {

     ClassFieldDescriptor* field = field_map->field_at(i);

     // ignore non-primitive fields

     char type = field->field_type();

     if (!is_primitive_field_type(type)) {

       continue;

     }

     // one-to-one mapping

     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;

     // get offset and field value

     int offset = field->field_offset();

     address addr = (address)klass->java_mirror() + offset;

     jvalue value;

     copy_to_jvalue(&value, addr, value_type);

     // field index

     reference_info.field.index = field->field_index();

     // invoke the callback

     jint res = (*cb)(JVMTI_HEAP_REFERENCE_STATIC_FIELD,

                      &reference_info,

                      wrapper->klass_tag(),

                      wrapper->obj_tag_p(),

                      value,

                      value_type,

                      user_data);

     if (res & JVMTI_VISIT_ABORT) {

       delete field_map;

       return res;

     }

   }

   delete field_map;

   return 0;

 }

 // helper function to invoke the primitive field callback for all instance fields

 // of a given object

 static jint invoke_primitive_field_callback_for_instance_fields(

   CallbackWrapper* wrapper,

   oop obj,

   jvmtiPrimitiveFieldCallback cb,

   void* user_data)

 {

   // for instance fields only the index will be set

   static jvmtiHeapReferenceInfo reference_info = { 0 };

   // get the map of the instance fields

   ClassFieldMap* fields = JvmtiCachedClassFieldMap::get_map_of_instance_fields(obj);

   // invoke the callback for each instance primitive field

   for (int i=0; i<fields->field_count(); i++) {

     ClassFieldDescriptor* field = fields->field_at(i);

     // ignore non-primitive fields

     char type = field->field_type();

     if (!is_primitive_field_type(type)) {

       continue;

     }

     // one-to-one mapping

     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;

     // get offset and field value

     int offset = field->field_offset();

     address addr = (address)obj + offset;

     jvalue value;

     copy_to_jvalue(&value, addr, value_type);

     // field index

     reference_info.field.index = field->field_index();

     // invoke the callback

     jint res = (*cb)(JVMTI_HEAP_REFERENCE_FIELD,

                      &reference_info,

                      wrapper->klass_tag(),

                      wrapper->obj_tag_p(),

                      value,

                      value_type,

                      user_data);

     if (res & JVMTI_VISIT_ABORT) {

       return res;

     }

   }

   return 0;

 }

 // VM operation to iterate over all objects in the heap (both reachable

 // and unreachable)

 class VM_HeapIterateOperation: public VM_Operation {

  private:

   ObjectClosure* _blk;

  public:

   VM_HeapIterateOperation(ObjectClosure* blk) { _blk = blk; }

   VMOp_Type type() const { return VMOp_HeapIterateOperation; }

   void doit() {

     // allows class files maps to be cached during iteration

     ClassFieldMapCacheMark cm;

     // make sure that heap is parsable (fills TLABs with filler objects)

     Universe::heap()->ensure_parsability(false);  // no need to retire TLABs

     // Verify heap before iteration - if the heap gets corrupted then

     // JVMTI's IterateOverHeap will crash.

     if (VerifyBeforeIteration) {

       Universe::verify();

     }

     // do the iteration

     // If this operation encounters a bad object when using CMS,

     // consider using safe_object_iterate() which avoids perm gen

     // objects that may contain bad references.

     Universe::heap()->object_iterate(_blk);

   }

 };

 // An ObjectClosure used to support the deprecated IterateOverHeap and

 // IterateOverInstancesOfClass functions

 class IterateOverHeapObjectClosure: public ObjectClosure {

  private:

   JvmtiTagMap* _tag_map;

   KlassHandle _klass;

   jvmtiHeapObjectFilter _object_filter;

   jvmtiHeapObjectCallback _heap_object_callback;

   const void* _user_data;

   // accessors

   JvmtiTagMap* tag_map() const                    { return _tag_map; }

   jvmtiHeapObjectFilter object_filter() const     { return _object_filter; }

   jvmtiHeapObjectCallback object_callback() const { return _heap_object_callback; }

   KlassHandle klass() const                       { return _klass; }

   const void* user_data() const                   { return _user_data; }

   // indicates if iteration has been aborted

   bool _iteration_aborted;

   bool is_iteration_aborted() const               { return _iteration_aborted; }

   void set_iteration_aborted(bool aborted)        { _iteration_aborted = aborted; }

  public:

   IterateOverHeapObjectClosure(JvmtiTagMap* tag_map,

                                KlassHandle klass,

                                jvmtiHeapObjectFilter object_filter,

                                jvmtiHeapObjectCallback heap_object_callback,

                                const void* user_data) :

     _tag_map(tag_map),

     _klass(klass),

     _object_filter(object_filter),

     _heap_object_callback(heap_object_callback),

     _user_data(user_data),

     _iteration_aborted(false)

   {

   }

   void do_object(oop o);

 };

 // invoked for each object in the heap

 void IterateOverHeapObjectClosure::do_object(oop o) {

   // check if iteration has been halted

   if (is_iteration_aborted()) return;

   // ignore any objects that aren't visible to profiler

   if (!ServiceUtil::visible_oop(o)) return;

   // instanceof check when filtering by klass

   if (!klass().is_null() && !o->is_a(klass()())) {

     return;

   }

   // prepare for the calllback

   CallbackWrapper wrapper(tag_map(), o);

   // if the object is tagged and we're only interested in untagged objects

   // then don't invoke the callback. Similiarly, if the object is untagged

   // and we're only interested in tagged objects we skip the callback.

   if (wrapper.obj_tag() != 0) {

     if (object_filter() == JVMTI_HEAP_OBJECT_UNTAGGED) return;

   } else {

     if (object_filter() == JVMTI_HEAP_OBJECT_TAGGED) return;

   }

   // invoke the agent's callback

   jvmtiIterationControl control = (*object_callback())(wrapper.klass_tag(),

                                                        wrapper.obj_size(),

                                                        wrapper.obj_tag_p(),

                                                        (void*)user_data());

   if (control == JVMTI_ITERATION_ABORT) {

     set_iteration_aborted(true);

   }

 }

 // An ObjectClosure used to support the IterateThroughHeap function

 class IterateThroughHeapObjectClosure: public ObjectClosure {

  private:

   JvmtiTagMap* _tag_map;

   KlassHandle _klass;

   int _heap_filter;

   const jvmtiHeapCallbacks* _callbacks;

   const void* _user_data;

   // accessor functions

   JvmtiTagMap* tag_map() const                     { return _tag_map; }

   int heap_filter() const                          { return _heap_filter; }

   const jvmtiHeapCallbacks* callbacks() const      { return _callbacks; }

   KlassHandle klass() const                        { return _klass; }

   const void* user_data() const                    { return _user_data; }

   // indicates if the iteration has been aborted

   bool _iteration_aborted;

   bool is_iteration_aborted() const                { return _iteration_aborted; }

   // used to check the visit control flags. If the abort flag is set

   // then we set the iteration aborted flag so that the iteration completes

   // without processing any further objects

   bool check_flags_for_abort(jint flags) {

     bool is_abort = (flags & JVMTI_VISIT_ABORT) != 0;

     if (is_abort) {

       _iteration_aborted = true;

     }

     return is_abort;

   }

  public:

   IterateThroughHeapObjectClosure(JvmtiTagMap* tag_map,

                                   KlassHandle klass,

                                   int heap_filter,

                                   const jvmtiHeapCallbacks* heap_callbacks,

                                   const void* user_data) :

     _tag_map(tag_map),

     _klass(klass),

     _heap_filter(heap_filter),

     _callbacks(heap_callbacks),

     _user_data(user_data),

     _iteration_aborted(false)

   {

   }

   void do_object(oop o);

 };

 // invoked for each object in the heap

 void IterateThroughHeapObjectClosure::do_object(oop obj) {

   // check if iteration has been halted

   if (is_iteration_aborted()) return;

   // ignore any objects that aren't visible to profiler

   if (!ServiceUtil::visible_oop(obj)) return;

   // apply class filter

   if (is_filtered_by_klass_filter(obj, klass())) return;

   // prepare for callback

   CallbackWrapper wrapper(tag_map(), obj);

   // check if filtered by the heap filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(), wrapper.klass_tag(), heap_filter())) {

     return;

   }

   // for arrays we need the length, otherwise -1

   bool is_array = obj->is_array();

   int len = is_array ? arrayOop(obj)->length() : -1;

   // invoke the object callback (if callback is provided)

   if (callbacks()->heap_iteration_callback != NULL) {

     jvmtiHeapIterationCallback cb = callbacks()->heap_iteration_callback;

     jint res = (*cb)(wrapper.klass_tag(),

                      wrapper.obj_size(),

                      wrapper.obj_tag_p(),

                      (jint)len,

                      (void*)user_data());

     if (check_flags_for_abort(res)) return;

   }

   // for objects and classes we report primitive fields if callback provided

   if (callbacks()->primitive_field_callback != NULL && obj->is_instance()) {

     jint res;

     jvmtiPrimitiveFieldCallback cb = callbacks()->primitive_field_callback;

     if (obj->klass() == SystemDictionary::Class_klass()) {

       res = invoke_primitive_field_callback_for_static_fields(&wrapper,

                                                                     obj,

                                                                     cb,

                                                                     (void*)user_data());

     } else {

       res = invoke_primitive_field_callback_for_instance_fields(&wrapper,

                                                                       obj,

                                                                       cb,

                                                                       (void*)user_data());

     }

     if (check_flags_for_abort(res)) return;

   }

   // string callback

   if (!is_array &&

       callbacks()->string_primitive_value_callback != NULL &&

       obj->klass() == SystemDictionary::String_klass()) {

     jint res = invoke_string_value_callback(

                 callbacks()->string_primitive_value_callback,

                 &wrapper,

                 obj,

                 (void*)user_data() );

     if (check_flags_for_abort(res)) return;

   }

   // array callback

   if (is_array &&

       callbacks()->array_primitive_value_callback != NULL &&

       obj->is_typeArray()) {

     jint res = invoke_array_primitive_value_callback(

                callbacks()->array_primitive_value_callback,

                &wrapper,

                obj,

                (void*)user_data() );

     if (check_flags_for_abort(res)) return;

   }

 };

 // Deprecated function to iterate over all objects in the heap

 void JvmtiTagMap::iterate_over_heap(jvmtiHeapObjectFilter object_filter,

                                     KlassHandle klass,

                                     jvmtiHeapObjectCallback heap_object_callback,

                                     const void* user_data)

 {

   MutexLocker ml(Heap_lock);

   IterateOverHeapObjectClosure blk(this,

                                    klass,

                                    object_filter,

                                    heap_object_callback,

                                    user_data);

   VM_HeapIterateOperation op(&blk);

   VMThread::execute(&op);

 }

 // Iterates over all objects in the heap

 void JvmtiTagMap::iterate_through_heap(jint heap_filter,

                                        KlassHandle klass,

                                        const jvmtiHeapCallbacks* callbacks,

                                        const void* user_data)

 {

   MutexLocker ml(Heap_lock);

   IterateThroughHeapObjectClosure blk(this,

                                       klass,

                                       heap_filter,

                                       callbacks,

                                       user_data);

   VM_HeapIterateOperation op(&blk);

   VMThread::execute(&op);

 }

 // support class for get_objects_with_tags

 class TagObjectCollector : public JvmtiTagHashmapEntryClosure {

  private:

   JvmtiEnv* _env;

   jlong* _tags;

   jint _tag_count;

   GrowableArray<jobject>* _object_results;  // collected objects (JNI weak refs)

   GrowableArray<uint64_t>* _tag_results;    // collected tags

  public:

   TagObjectCollector(JvmtiEnv* env, const jlong* tags, jint tag_count) {

     _env = env;

     _tags = (jlong*)tags;

     _tag_count = tag_count;

     _object_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jobject>(1,true);

     _tag_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<uint64_t>(1,true);

   }

   ~TagObjectCollector() {

     delete _object_results;

     delete _tag_results;

   }

   // for each tagged object check if the tag value matches

   // - if it matches then we create a JNI local reference to the object

   // and record the reference and tag value.

   //

   void do_entry(JvmtiTagHashmapEntry* entry) {

     for (int i=0; i<_tag_count; i++) {

       if (_tags[i] == entry->tag()) {

         oop o = entry->object();

         assert(o != NULL && Universe::heap()->is_in_reserved(o), "sanity check");

 #if INCLUDE_ALL_GCS

         if (UseG1GC) {

           // The reference in this tag map could be the only (implicitly weak)

           // reference to that object. If we hand it out, we need to keep it live wrt

           // SATB marking similar to other j.l.ref.Reference referents.

           G1SATBCardTableModRefBS::enqueue(o);

         }

 #endif

         jobject ref = JNIHandles::make_local(JavaThread::current(), o);

         _object_results->append(ref);

         _tag_results->append((uint64_t)entry->tag());

       }

     }

   }

   // return the results from the collection

   //

   jvmtiError result(jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {

     jvmtiError error;

     int count = _object_results->length();

     assert(count >= 0, "sanity check");

     // if object_result_ptr is not NULL then allocate the result and copy

     // in the object references.

     if (object_result_ptr != NULL) {

       error = _env->Allocate(count * sizeof(jobject), (unsigned char**)object_result_ptr);

       if (error != JVMTI_ERROR_NONE) {

         return error;

       }

       for (int i=0; i<count; i++) {

         (*object_result_ptr)[i] = _object_results->at(i);

       }

     }

     // if tag_result_ptr is not NULL then allocate the result and copy

     // in the tag values.

     if (tag_result_ptr != NULL) {

       error = _env->Allocate(count * sizeof(jlong), (unsigned char**)tag_result_ptr);

       if (error != JVMTI_ERROR_NONE) {

         if (object_result_ptr != NULL) {

           _env->Deallocate((unsigned char*)object_result_ptr);

         }

         return error;

       }

       for (int i=0; i<count; i++) {

         (*tag_result_ptr)[i] = (jlong)_tag_results->at(i);

       }

     }

     *count_ptr = count;

     return JVMTI_ERROR_NONE;

   }

 };

 // return the list of objects with the specified tags

 jvmtiError JvmtiTagMap::get_objects_with_tags(const jlong* tags,

   jint count, jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {

   TagObjectCollector collector(env(), tags, count);

   {

     // iterate over all tagged objects

     MutexLocker ml(lock());

     entry_iterate(&collector);

   }

   return collector.result(count_ptr, object_result_ptr, tag_result_ptr);

 }

 // ObjectMarker is used to support the marking objects when walking the

 // heap.

 //

 // This implementation uses the existing mark bits in an object for

 // marking. Objects that are marked must later have their headers restored.

 // As most objects are unlocked and don't have their identity hash computed

 // we don't have to save their headers. Instead we save the headers that

 // are "interesting". Later when the headers are restored this implementation

 // restores all headers to their initial value and then restores the few

 // objects that had interesting headers.

 //

 // Future work: This implementation currently uses growable arrays to save

 // the oop and header of interesting objects. As an optimization we could

 // use the same technique as the GC and make use of the unused area

 // between top() and end().

 //

 // An ObjectClosure used to restore the mark bits of an object

 class RestoreMarksClosure : public ObjectClosure {

  public:

   void do_object(oop o) {

     if (o != NULL) {

       markOop mark = o->mark();

       if (mark->is_marked()) {

         o->init_mark();

       }

     }

   }

 };

 // ObjectMarker provides the mark and visited functions

 class ObjectMarker : AllStatic {

  private:

   // saved headers

   static GrowableArray<oop>* _saved_oop_stack;

   static GrowableArray<markOop>* _saved_mark_stack;

   static bool _needs_reset;                  // do we need to reset mark bits?

  public:

   static void init();                       // initialize

   static void done();                       // clean-up

   static inline void mark(oop o);           // mark an object

   static inline bool visited(oop o);        // check if object has been visited

   static inline bool needs_reset()            { return _needs_reset; }

   static inline void set_needs_reset(bool v)  { _needs_reset = v; }

 };

 GrowableArray<oop>* ObjectMarker::_saved_oop_stack = NULL;

 GrowableArray<markOop>* ObjectMarker::_saved_mark_stack = NULL;

 bool ObjectMarker::_needs_reset = true;  // need to reset mark bits by default

 // initialize ObjectMarker - prepares for object marking

 void ObjectMarker::init() {

   assert(Thread::current()->is_VM_thread(), "must be VMThread");

   // prepare heap for iteration

   Universe::heap()->ensure_parsability(false);  // no need to retire TLABs

   // create stacks for interesting headers

   _saved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(4000, true);

   _saved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(4000, true);

   if (UseBiasedLocking) {

     BiasedLocking::preserve_marks();

   }

 }

 // Object marking is done so restore object headers

 void ObjectMarker::done() {

   // iterate over all objects and restore the mark bits to

   // their initial value

   RestoreMarksClosure blk;

   if (needs_reset()) {

     Universe::heap()->object_iterate(&blk);

   } else {

     // We don't need to reset mark bits on this call, but reset the

     // flag to the default for the next call.

     set_needs_reset(true);

   }

   // now restore the interesting headers

   for (int i = 0; i < _saved_oop_stack->length(); i++) {

     oop o = _saved_oop_stack->at(i);

     markOop mark = _saved_mark_stack->at(i);

     o->set_mark(mark);

   }

   if (UseBiasedLocking) {

     BiasedLocking::restore_marks();

   }

   // free the stacks

   delete _saved_oop_stack;

   delete _saved_mark_stack;

 }

 // mark an object

 inline void ObjectMarker::mark(oop o) {

   assert(Universe::heap()->is_in(o), "sanity check");

   assert(!o->mark()->is_marked(), "should only mark an object once");

   // object's mark word

   markOop mark = o->mark();

   if (mark->must_be_preserved(o)) {

     _saved_mark_stack->push(mark);

     _saved_oop_stack->push(o);

   }

   // mark the object

   o->set_mark(markOopDesc::prototype()->set_marked());

 }

 // return true if object is marked

 inline bool ObjectMarker::visited(oop o) {

   return o->mark()->is_marked();

 }

 // Stack allocated class to help ensure that ObjectMarker is used

 // correctly. Constructor initializes ObjectMarker, destructor calls

 // ObjectMarker's done() function to restore object headers.

 class ObjectMarkerController : public StackObj {

  public:

   ObjectMarkerController() {

     ObjectMarker::init();

   }

   ~ObjectMarkerController() {

     ObjectMarker::done();

   }

 };

 // helper to map a jvmtiHeapReferenceKind to an old style jvmtiHeapRootKind

 // (not performance critical as only used for roots)

 static jvmtiHeapRootKind toJvmtiHeapRootKind(jvmtiHeapReferenceKind kind) {

   switch (kind) {

     case JVMTI_HEAP_REFERENCE_JNI_GLOBAL:   return JVMTI_HEAP_ROOT_JNI_GLOBAL;

     case JVMTI_HEAP_REFERENCE_SYSTEM_CLASS: return JVMTI_HEAP_ROOT_SYSTEM_CLASS;

     case JVMTI_HEAP_REFERENCE_MONITOR:      return JVMTI_HEAP_ROOT_MONITOR;

     case JVMTI_HEAP_REFERENCE_STACK_LOCAL:  return JVMTI_HEAP_ROOT_STACK_LOCAL;

     case JVMTI_HEAP_REFERENCE_JNI_LOCAL:    return JVMTI_HEAP_ROOT_JNI_LOCAL;

     case JVMTI_HEAP_REFERENCE_THREAD:       return JVMTI_HEAP_ROOT_THREAD;

     case JVMTI_HEAP_REFERENCE_OTHER:        return JVMTI_HEAP_ROOT_OTHER;

     default: ShouldNotReachHere();          return JVMTI_HEAP_ROOT_OTHER;

   }

 }

 // Base class for all heap walk contexts. The base class maintains a flag

 // to indicate if the context is valid or not.

 class HeapWalkContext VALUE_OBJ_CLASS_SPEC {

  private:

   bool _valid;

  public:

   HeapWalkContext(bool valid)                   { _valid = valid; }

   void invalidate()                             { _valid = false; }

   bool is_valid() const                         { return _valid; }

 };

 // A basic heap walk context for the deprecated heap walking functions.

 // The context for a basic heap walk are the callbacks and fields used by

 // the referrer caching scheme.

 class BasicHeapWalkContext: public HeapWalkContext {

  private:

   jvmtiHeapRootCallback _heap_root_callback;

   jvmtiStackReferenceCallback _stack_ref_callback;

   jvmtiObjectReferenceCallback _object_ref_callback;

   // used for caching

   oop _last_referrer;

   jlong _last_referrer_tag;

  public:

   BasicHeapWalkContext() : HeapWalkContext(false) { }

   BasicHeapWalkContext(jvmtiHeapRootCallback heap_root_callback,

                        jvmtiStackReferenceCallback stack_ref_callback,

                        jvmtiObjectReferenceCallback object_ref_callback) :

     HeapWalkContext(true),

     _heap_root_callback(heap_root_callback),

     _stack_ref_callback(stack_ref_callback),

     _object_ref_callback(object_ref_callback),

     _last_referrer(NULL),

     _last_referrer_tag(0) {

   }

   // accessors

   jvmtiHeapRootCallback heap_root_callback() const         { return _heap_root_callback; }

   jvmtiStackReferenceCallback stack_ref_callback() const   { return _stack_ref_callback; }

   jvmtiObjectReferenceCallback object_ref_callback() const { return _object_ref_callback;  }

   oop last_referrer() const               { return _last_referrer; }

   void set_last_referrer(oop referrer)    { _last_referrer = referrer; }

   jlong last_referrer_tag() const         { return _last_referrer_tag; }

   void set_last_referrer_tag(jlong value) { _last_referrer_tag = value; }

 };

 // The advanced heap walk context for the FollowReferences functions.

 // The context is the callbacks, and the fields used for filtering.

 class AdvancedHeapWalkContext: public HeapWalkContext {

  private:

   jint _heap_filter;

   KlassHandle _klass_filter;

   const jvmtiHeapCallbacks* _heap_callbacks;

  public:

   AdvancedHeapWalkContext() : HeapWalkContext(false) { }

   AdvancedHeapWalkContext(jint heap_filter,

                            KlassHandle klass_filter,

                            const jvmtiHeapCallbacks* heap_callbacks) :

     HeapWalkContext(true),

     _heap_filter(heap_filter),

     _klass_filter(klass_filter),

     _heap_callbacks(heap_callbacks) {

   }

   // accessors

   jint heap_filter() const         { return _heap_filter; }

   KlassHandle klass_filter() const { return _klass_filter; }

   const jvmtiHeapReferenceCallback heap_reference_callback() const {

     return _heap_callbacks->heap_reference_callback;

   };

   const jvmtiPrimitiveFieldCallback primitive_field_callback() const {

     return _heap_callbacks->primitive_field_callback;

   }

   const jvmtiArrayPrimitiveValueCallback array_primitive_value_callback() const {

     return _heap_callbacks->array_primitive_value_callback;

   }

   const jvmtiStringPrimitiveValueCallback string_primitive_value_callback() const {

     return _heap_callbacks->string_primitive_value_callback;

   }

 };

 // The CallbackInvoker is a class with static functions that the heap walk can call

 // into to invoke callbacks. It works in one of two modes. The "basic" mode is

 // used for the deprecated IterateOverReachableObjects functions. The "advanced"

 // mode is for the newer FollowReferences function which supports a lot of

 // additional callbacks.

 class CallbackInvoker : AllStatic {

  private:

   // heap walk styles

   enum { basic, advanced };

   static int _heap_walk_type;

   static bool is_basic_heap_walk()           { return _heap_walk_type == basic; }

   static bool is_advanced_heap_walk()        { return _heap_walk_type == advanced; }

   // context for basic style heap walk

   static BasicHeapWalkContext _basic_context;

   static BasicHeapWalkContext* basic_context() {

     assert(_basic_context.is_valid(), "invalid");

     return &_basic_context;

   }

   // context for advanced style heap walk

   static AdvancedHeapWalkContext _advanced_context;

   static AdvancedHeapWalkContext* advanced_context() {

     assert(_advanced_context.is_valid(), "invalid");

     return &_advanced_context;

   }

   // context needed for all heap walks

   static JvmtiTagMap* _tag_map;

   static const void* _user_data;

   static GrowableArray<oop>* _visit_stack;

   // accessors

   static JvmtiTagMap* tag_map()                        { return _tag_map; }

   static const void* user_data()                       { return _user_data; }

   static GrowableArray<oop>* visit_stack()             { return _visit_stack; }

   // if the object hasn't been visited then push it onto the visit stack

   // so that it will be visited later

   static inline bool check_for_visit(oop obj) {

     if (!ObjectMarker::visited(obj)) visit_stack()->push(obj);

     return true;

   }

   // invoke basic style callbacks

   static inline bool invoke_basic_heap_root_callback

     (jvmtiHeapRootKind root_kind, oop obj);

   static inline bool invoke_basic_stack_ref_callback

     (jvmtiHeapRootKind root_kind, jlong thread_tag, jint depth, jmethodID method,

      int slot, oop obj);

   static inline bool invoke_basic_object_reference_callback

     (jvmtiObjectReferenceKind ref_kind, oop referrer, oop referree, jint index);

   // invoke advanced style callbacks

   static inline bool invoke_advanced_heap_root_callback

     (jvmtiHeapReferenceKind ref_kind, oop obj);

   static inline bool invoke_advanced_stack_ref_callback

     (jvmtiHeapReferenceKind ref_kind, jlong thread_tag, jlong tid, int depth,

      jmethodID method, jlocation bci, jint slot, oop obj);

   static inline bool invoke_advanced_object_reference_callback

     (jvmtiHeapReferenceKind ref_kind, oop referrer, oop referree, jint index);

   // used to report the value of primitive fields

   static inline bool report_primitive_field

     (jvmtiHeapReferenceKind ref_kind, oop obj, jint index, address addr, char type);

  public:

   // initialize for basic mode

   static void initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,

                                              GrowableArray<oop>* visit_stack,

                                              const void* user_data,

                                              BasicHeapWalkContext context);

   // initialize for advanced mode

   static void initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,

                                                 GrowableArray<oop>* visit_stack,

                                                 const void* user_data,

                                                 AdvancedHeapWalkContext context);

    // functions to report roots

   static inline bool report_simple_root(jvmtiHeapReferenceKind kind, oop o);

   static inline bool report_jni_local_root(jlong thread_tag, jlong tid, jint depth,

     jmethodID m, oop o);

   static inline bool report_stack_ref_root(jlong thread_tag, jlong tid, jint depth,

     jmethodID method, jlocation bci, jint slot, oop o);

   // functions to report references

   static inline bool report_array_element_reference(oop referrer, oop referree, jint index);

   static inline bool report_class_reference(oop referrer, oop referree);

   static inline bool report_class_loader_reference(oop referrer, oop referree);

   static inline bool report_signers_reference(oop referrer, oop referree);

   static inline bool report_protection_domain_reference(oop referrer, oop referree);

   static inline bool report_superclass_reference(oop referrer, oop referree);

   static inline bool report_interface_reference(oop referrer, oop referree);

   static inline bool report_static_field_reference(oop referrer, oop referree, jint slot);

   static inline bool report_field_reference(oop referrer, oop referree, jint slot);

   static inline bool report_constant_pool_reference(oop referrer, oop referree, jint index);

   static inline bool report_primitive_array_values(oop array);

   static inline bool report_string_value(oop str);

   static inline bool report_primitive_instance_field(oop o, jint index, address value, char type);

   static inline bool report_primitive_static_field(oop o, jint index, address value, char type);

 };

 // statics

 int CallbackInvoker::_heap_walk_type;

 BasicHeapWalkContext CallbackInvoker::_basic_context;

 AdvancedHeapWalkContext CallbackInvoker::_advanced_context;

 JvmtiTagMap* CallbackInvoker::_tag_map;

 const void* CallbackInvoker::_user_data;

 GrowableArray<oop>* CallbackInvoker::_visit_stack;

 // initialize for basic heap walk (IterateOverReachableObjects et al)

 void CallbackInvoker::initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,

                                                      GrowableArray<oop>* visit_stack,

                                                      const void* user_data,

                                                      BasicHeapWalkContext context) {

   _tag_map = tag_map;

   _visit_stack = visit_stack;

   _user_data = user_data;

   _basic_context = context;

   _advanced_context.invalidate();       // will trigger assertion if used

   _heap_walk_type = basic;

 }

 // initialize for advanced heap walk (FollowReferences)

 void CallbackInvoker::initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,

                                                         GrowableArray<oop>* visit_stack,

                                                         const void* user_data,

                                                         AdvancedHeapWalkContext context) {

   _tag_map = tag_map;

   _visit_stack = visit_stack;

   _user_data = user_data;

   _advanced_context = context;

   _basic_context.invalidate();      // will trigger assertion if used

   _heap_walk_type = advanced;

 }

 // invoke basic style heap root callback

 inline bool CallbackInvoker::invoke_basic_heap_root_callback(jvmtiHeapRootKind root_kind, oop obj) {

   assert(ServiceUtil::visible_oop(obj), "checking");

   // if we heap roots should be reported

   jvmtiHeapRootCallback cb = basic_context()->heap_root_callback();

   if (cb == NULL) {

     return check_for_visit(obj);

   }

   CallbackWrapper wrapper(tag_map(), obj);

   jvmtiIterationControl control = (*cb)(root_kind,

                                         wrapper.klass_tag(),

                                         wrapper.obj_size(),

                                         wrapper.obj_tag_p(),

                                         (void*)user_data());

   // push root to visit stack when following references

   if (control == JVMTI_ITERATION_CONTINUE &&

       basic_context()->object_ref_callback() != NULL) {

     visit_stack()->push(obj);

   }

   return control != JVMTI_ITERATION_ABORT;

 }

 // invoke basic style stack ref callback

 inline bool CallbackInvoker::invoke_basic_stack_ref_callback(jvmtiHeapRootKind root_kind,

                                                              jlong thread_tag,

                                                              jint depth,

                                                              jmethodID method,

                                                              jint slot,

                                                              oop obj) {

   assert(ServiceUtil::visible_oop(obj), "checking");

   // if we stack refs should be reported

   jvmtiStackReferenceCallback cb = basic_context()->stack_ref_callback();

   if (cb == NULL) {

     return check_for_visit(obj);

   }

   CallbackWrapper wrapper(tag_map(), obj);

   jvmtiIterationControl control = (*cb)(root_kind,

                                         wrapper.klass_tag(),

                                         wrapper.obj_size(),

                                         wrapper.obj_tag_p(),

                                         thread_tag,

                                         depth,

                                         method,

                                         slot,

                                         (void*)user_data());

   // push root to visit stack when following references

   if (control == JVMTI_ITERATION_CONTINUE &&

       basic_context()->object_ref_callback() != NULL) {

     visit_stack()->push(obj);

   }

   return control != JVMTI_ITERATION_ABORT;

 }

 // invoke basic style object reference callback

 inline bool CallbackInvoker::invoke_basic_object_reference_callback(jvmtiObjectReferenceKind ref_kind,

                                                                     oop referrer,

                                                                     oop referree,

                                                                     jint index) {

   assert(ServiceUtil::visible_oop(referrer), "checking");

   assert(ServiceUtil::visible_oop(referree), "checking");

   BasicHeapWalkContext* context = basic_context();

   // callback requires the referrer's tag. If it's the same referrer

   // as the last call then we use the cached value.

   jlong referrer_tag;

   if (referrer == context->last_referrer()) {

     referrer_tag = context->last_referrer_tag();

   } else {

     referrer_tag = tag_for(tag_map(), referrer);

   }

   // do the callback

   CallbackWrapper wrapper(tag_map(), referree);

   jvmtiObjectReferenceCallback cb = context->object_ref_callback();

   jvmtiIterationControl control = (*cb)(ref_kind,

                                         wrapper.klass_tag(),

                                         wrapper.obj_size(),

                                         wrapper.obj_tag_p(),

                                         referrer_tag,

                                         index,

                                         (void*)user_data());

   // record referrer and referrer tag. For self-references record the

   // tag value from the callback as this might differ from referrer_tag.

   context->set_last_referrer(referrer);

   if (referrer == referree) {

     context->set_last_referrer_tag(*wrapper.obj_tag_p());

   } else {

     context->set_last_referrer_tag(referrer_tag);

   }

   if (control == JVMTI_ITERATION_CONTINUE) {

     return check_for_visit(referree);

   } else {

     return control != JVMTI_ITERATION_ABORT;

   }

 }

 // invoke advanced style heap root callback

 inline bool CallbackInvoker::invoke_advanced_heap_root_callback(jvmtiHeapReferenceKind ref_kind,

                                                                 oop obj) {

   assert(ServiceUtil::visible_oop(obj), "checking");

   AdvancedHeapWalkContext* context = advanced_context();

   // check that callback is provided

   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();

   if (cb == NULL) {

     return check_for_visit(obj);

   }

   // apply class filter

   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {

     return check_for_visit(obj);

   }

   // setup the callback wrapper

   CallbackWrapper wrapper(tag_map(), obj);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return check_for_visit(obj);

   }

   // for arrays we need the length, otherwise -1

   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);

   // invoke the callback

   jint res  = (*cb)(ref_kind,

                     NULL, // referrer info

                     wrapper.klass_tag(),

                     0,    // referrer_class_tag is 0 for heap root

                     wrapper.obj_size(),

                     wrapper.obj_tag_p(),

                     NULL, // referrer_tag_p

                     len,

                     (void*)user_data());

   if (res & JVMTI_VISIT_ABORT) {

     return false;// referrer class tag

   }

   if (res & JVMTI_VISIT_OBJECTS) {

     check_for_visit(obj);

   }

   return true;

 }

 // report a reference from a thread stack to an object

 inline bool CallbackInvoker::invoke_advanced_stack_ref_callback(jvmtiHeapReferenceKind ref_kind,

                                                                 jlong thread_tag,

                                                                 jlong tid,

                                                                 int depth,

                                                                 jmethodID method,

                                                                 jlocation bci,

                                                                 jint slot,

                                                                 oop obj) {

   assert(ServiceUtil::visible_oop(obj), "checking");

   AdvancedHeapWalkContext* context = advanced_context();

   // check that callback is provider

   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();

   if (cb == NULL) {

     return check_for_visit(obj);

   }

   // apply class filter

   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {

     return check_for_visit(obj);

   }

   // setup the callback wrapper

   CallbackWrapper wrapper(tag_map(), obj);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return check_for_visit(obj);

   }

   // setup the referrer info

   jvmtiHeapReferenceInfo reference_info;

   reference_info.stack_local.thread_tag = thread_tag;

   reference_info.stack_local.thread_id = tid;

   reference_info.stack_local.depth = depth;

   reference_info.stack_local.method = method;

   reference_info.stack_local.location = bci;

   reference_info.stack_local.slot = slot;

   // for arrays we need the length, otherwise -1

   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);

   // call into the agent

   int res = (*cb)(ref_kind,

                   &reference_info,

                   wrapper.klass_tag(),

                   0,    // referrer_class_tag is 0 for heap root (stack)

                   wrapper.obj_size(),

                   wrapper.obj_tag_p(),

                   NULL, // referrer_tag is 0 for root

                   len,

                   (void*)user_data());

   if (res & JVMTI_VISIT_ABORT) {

     return false;

   }

   if (res & JVMTI_VISIT_OBJECTS) {

     check_for_visit(obj);

   }

   return true;

 }

 // This mask is used to pass reference_info to a jvmtiHeapReferenceCallback

 // only for ref_kinds defined by the JVM TI spec. Otherwise, NULL is passed.

 #define REF_INFO_MASK  ((1 << JVMTI_HEAP_REFERENCE_FIELD)         \

                       | (1 << JVMTI_HEAP_REFERENCE_STATIC_FIELD)  \

                       | (1 << JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT) \

                       | (1 << JVMTI_HEAP_REFERENCE_CONSTANT_POOL) \

                       | (1 << JVMTI_HEAP_REFERENCE_STACK_LOCAL)   \

                       | (1 << JVMTI_HEAP_REFERENCE_JNI_LOCAL))

 // invoke the object reference callback to report a reference

 inline bool CallbackInvoker::invoke_advanced_object_reference_callback(jvmtiHeapReferenceKind ref_kind,

                                                                        oop referrer,

                                                                        oop obj,

                                                                        jint index)

 {

   // field index is only valid field in reference_info

   static jvmtiHeapReferenceInfo reference_info = { 0 };

   assert(ServiceUtil::visible_oop(referrer), "checking");

   assert(ServiceUtil::visible_oop(obj), "checking");

   AdvancedHeapWalkContext* context = advanced_context();

   // check that callback is provider

   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();

   if (cb == NULL) {

     return check_for_visit(obj);

   }

   // apply class filter

   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {

     return check_for_visit(obj);

   }

   // setup the callback wrapper

   TwoOopCallbackWrapper wrapper(tag_map(), referrer, obj);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return check_for_visit(obj);

   }

   // field index is only valid field in reference_info

   reference_info.field.index = index;

   // for arrays we need the length, otherwise -1

   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);

   // invoke the callback

   int res = (*cb)(ref_kind,

                   (REF_INFO_MASK & (1 << ref_kind)) ? &reference_info : NULL,

                   wrapper.klass_tag(),

                   wrapper.referrer_klass_tag(),

                   wrapper.obj_size(),

                   wrapper.obj_tag_p(),

                   wrapper.referrer_tag_p(),

                   len,

                   (void*)user_data());

   if (res & JVMTI_VISIT_ABORT) {

     return false;

   }

   if (res & JVMTI_VISIT_OBJECTS) {

     check_for_visit(obj);

   }

   return true;

 }

 // report a "simple root"

 inline bool CallbackInvoker::report_simple_root(jvmtiHeapReferenceKind kind, oop obj) {

   assert(kind != JVMTI_HEAP_REFERENCE_STACK_LOCAL &&

          kind != JVMTI_HEAP_REFERENCE_JNI_LOCAL, "not a simple root");

   assert(ServiceUtil::visible_oop(obj), "checking");

   if (is_basic_heap_walk()) {

     // map to old style root kind

     jvmtiHeapRootKind root_kind = toJvmtiHeapRootKind(kind);

     return invoke_basic_heap_root_callback(root_kind, obj);

   } else {

     assert(is_advanced_heap_walk(), "wrong heap walk type");

     return invoke_advanced_heap_root_callback(kind, obj);

   }

 }

 // invoke the primitive array values

 inline bool CallbackInvoker::report_primitive_array_values(oop obj) {

   assert(obj->is_typeArray(), "not a primitive array");

   AdvancedHeapWalkContext* context = advanced_context();

   assert(context->array_primitive_value_callback() != NULL, "no callback");

   // apply class filter

   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {

     return true;

   }

   CallbackWrapper wrapper(tag_map(), obj);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return true;

   }

   // invoke the callback

   int res = invoke_array_primitive_value_callback(context->array_primitive_value_callback(),

                                                   &wrapper,

                                                   obj,

                                                   (void*)user_data());

   return (!(res & JVMTI_VISIT_ABORT));

 }

 // invoke the string value callback

 inline bool CallbackInvoker::report_string_value(oop str) {

   assert(str->klass() == SystemDictionary::String_klass(), "not a string");

   AdvancedHeapWalkContext* context = advanced_context();

   assert(context->string_primitive_value_callback() != NULL, "no callback");

   // apply class filter

   if (is_filtered_by_klass_filter(str, context->klass_filter())) {

     return true;

   }

   CallbackWrapper wrapper(tag_map(), str);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return true;

   }

   // invoke the callback

   int res = invoke_string_value_callback(context->string_primitive_value_callback(),

                                          &wrapper,

                                          str,

                                          (void*)user_data());

   return (!(res & JVMTI_VISIT_ABORT));

 }

 // invoke the primitive field callback

 inline bool CallbackInvoker::report_primitive_field(jvmtiHeapReferenceKind ref_kind,

                                                     oop obj,

                                                     jint index,

                                                     address addr,

                                                     char type)

 {

   // for primitive fields only the index will be set

   static jvmtiHeapReferenceInfo reference_info = { 0 };

   AdvancedHeapWalkContext* context = advanced_context();

   assert(context->primitive_field_callback() != NULL, "no callback");

   // apply class filter

   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {

     return true;

   }

   CallbackWrapper wrapper(tag_map(), obj);

   // apply tag filter

   if (is_filtered_by_heap_filter(wrapper.obj_tag(),

                                  wrapper.klass_tag(),

                                  context->heap_filter())) {

     return true;

   }

   // the field index in the referrer

   reference_info.field.index = index;

   // map the type

   jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;

   // setup the jvalue

   jvalue value;

   copy_to_jvalue(&value, addr, value_type);

   jvmtiPrimitiveFieldCallback cb = context->primitive_field_callback();

   int res = (*cb)(ref_kind,

                   &reference_info,

                   wrapper.klass_tag(),

                   wrapper.obj_tag_p(),

                   value,

                   value_type,

                   (void*)user_data());

   return (!(res & JVMTI_VISIT_ABORT));

 }

 // instance field

 inline bool CallbackInvoker::report_primitive_instance_field(oop obj,

                                                              jint index,

                                                              address value,

                                                              char type) {

   return report_primitive_field(JVMTI_HEAP_REFERENCE_FIELD,

                                 obj,

                                 index,

                                 value,

                                 type);

 }

 // static field

 inline bool CallbackInvoker::report_primitive_static_field(oop obj,

                                                            jint index,

                                                            address value,

                                                            char type) {

   return report_primitive_field(JVMTI_HEAP_REFERENCE_STATIC_FIELD,

                                 obj,

                                 index,

                                 value,

                                 type);

 }

 // report a JNI local (root object) to the profiler

 inline bool CallbackInvoker::report_jni_local_root(jlong thread_tag, jlong tid, jint depth, jmethodID m, oop obj) {

   if (is_basic_heap_walk()) {

     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_JNI_LOCAL,

                                            thread_tag,

                                            depth,

                                            m,

                                            -1,

                                            obj);

   } else {

     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_JNI_LOCAL,

                                               thread_tag, tid,

                                               depth,

                                               m,

                                               (jlocation)-1,

                                               -1,

                                               obj);

   }

 }

 // report a local (stack reference, root object)

 inline bool CallbackInvoker::report_stack_ref_root(jlong thread_tag,

                                                    jlong tid,

                                                    jint depth,

                                                    jmethodID method,

                                                    jlocation bci,

                                                    jint slot,

                                                    oop obj) {

   if (is_basic_heap_walk()) {

     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_STACK_LOCAL,

                                            thread_tag,

                                            depth,

                                            method,

                                            slot,

                                            obj);

   } else {

     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_STACK_LOCAL,

                                               thread_tag,

                                               tid,

                                               depth,

                                               method,

                                               bci,

                                               slot,

                                               obj);

   }

 }

 // report an object referencing a class.

 inline bool CallbackInvoker::report_class_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS, referrer, referree, -1);

   }

 }

 // report a class referencing its class loader.

 inline bool CallbackInvoker::report_class_loader_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS_LOADER, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS_LOADER, referrer, referree, -1);

   }

 }

 // report a class referencing its signers.

 inline bool CallbackInvoker::report_signers_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_SIGNERS, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SIGNERS, referrer, referree, -1);

   }

 }

 // report a class referencing its protection domain..

 inline bool CallbackInvoker::report_protection_domain_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);

   }

 }

 // report a class referencing its superclass.

 inline bool CallbackInvoker::report_superclass_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     // Send this to be consistent with past implementation

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SUPERCLASS, referrer, referree, -1);

   }

 }

 // report a class referencing one of its interfaces.

 inline bool CallbackInvoker::report_interface_reference(oop referrer, oop referree) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_INTERFACE, referrer, referree, -1);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_INTERFACE, referrer, referree, -1);

   }

 }

 // report a class referencing one of its static fields.

 inline bool CallbackInvoker::report_static_field_reference(oop referrer, oop referree, jint slot) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_STATIC_FIELD, referrer, referree, slot);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_STATIC_FIELD, referrer, referree, slot);

   }

 }

 // report an array referencing an element object

 inline bool CallbackInvoker::report_array_element_reference(oop referrer, oop referree, jint index) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);

   }

 }

 // report an object referencing an instance field object

 inline bool CallbackInvoker::report_field_reference(oop referrer, oop referree, jint slot) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_FIELD, referrer, referree, slot);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_FIELD, referrer, referree, slot);

   }

 }

 // report an array referencing an element object

 inline bool CallbackInvoker::report_constant_pool_reference(oop referrer, oop referree, jint index) {

   if (is_basic_heap_walk()) {

     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CONSTANT_POOL, referrer, referree, index);

   } else {

     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CONSTANT_POOL, referrer, referree, index);

   }

 }

 // A supporting closure used to process simple roots

 class SimpleRootsClosure : public OopClosure {

  private:

   jvmtiHeapReferenceKind _kind;

   bool _continue;

   jvmtiHeapReferenceKind root_kind()    { return _kind; }

  public:

   void set_kind(jvmtiHeapReferenceKind kind) {

     _kind = kind;

     _continue = true;

   }

   inline bool stopped() {

     return !_continue;

   }

   void do_oop(oop* obj_p) {

     // iteration has terminated

     if (stopped()) {

       return;

     }

     // ignore null or deleted handles

     oop o = *obj_p;

     if (o == NULL || o == JNIHandles::deleted_handle()) {

       return;

     }

     assert(Universe::heap()->is_in_reserved(o), "should be impossible");

     jvmtiHeapReferenceKind kind = root_kind();

     if (kind == JVMTI_HEAP_REFERENCE_SYSTEM_CLASS) {

       // SystemDictionary::always_strong_oops_do reports the application

       // class loader as a root. We want this root to be reported as

       // a root kind of "OTHER" rather than "SYSTEM_CLASS".

       if (!o->is_instanceMirror()) {

         kind = JVMTI_HEAP_REFERENCE_OTHER;

       }

     }

     // some objects are ignored - in the case of simple

     // roots it's mostly Symbol*s that we are skipping

     // here.

     if (!ServiceUtil::visible_oop(o)) {

       return;

     }

     // invoke the callback

     _continue = CallbackInvoker::report_simple_root(kind, o);

   }

   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }

 };

 // A supporting closure used to process JNI locals

 class JNILocalRootsClosure : public OopClosure {

  private:

   jlong _thread_tag;

   jlong _tid;

   jint _depth;

   jmethodID _method;

   bool _continue;

  public:

   void set_context(jlong thread_tag, jlong tid, jint depth, jmethodID method) {

     _thread_tag = thread_tag;

     _tid = tid;

     _depth = depth;

     _method = method;

     _continue = true;

   }

   inline bool stopped() {

     return !_continue;

   }

   void do_oop(oop* obj_p) {

     // iteration has terminated

     if (stopped()) {

       return;

     }

     // ignore null or deleted handles

     oop o = *obj_p;

     if (o == NULL || o == JNIHandles::deleted_handle()) {

       return;

     }

     if (!ServiceUtil::visible_oop(o)) {

       return;

     }

     // invoke the callback

     _continue = CallbackInvoker::report_jni_local_root(_thread_tag, _tid, _depth, _method, o);

   }

   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }

 };

 // A VM operation to iterate over objects that are reachable from

 // a set of roots or an initial object.

 //

 // For VM_HeapWalkOperation the set of roots used is :-