1 /*
   2  * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "classfile/javaClasses.inline.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "jvmtifiles/jvmtiEnv.hpp"
  32 #include "logging/log.hpp"
  33 #include "memory/allocation.inline.hpp"
  34 #include "memory/resourceArea.hpp"
  35 #include "memory/universe.hpp"
  36 #include "oops/access.inline.hpp"
  37 #include "oops/arrayOop.inline.hpp"
  38 #include "oops/constantPool.inline.hpp"
  39 #include "oops/instanceMirrorKlass.hpp"
  40 #include "oops/objArrayKlass.hpp"
  41 #include "oops/objArrayOop.inline.hpp"
  42 #include "oops/oop.inline.hpp"
  43 #include "oops/typeArrayOop.inline.hpp"
  44 #include "prims/jvmtiEventController.hpp"
  45 #include "prims/jvmtiEventController.inline.hpp"
  46 #include "prims/jvmtiExport.hpp"
  47 #include "prims/jvmtiImpl.hpp"
  48 #include "prims/jvmtiTagMap.hpp"
  49 #include "runtime/biasedLocking.hpp"
  50 #include "runtime/frame.inline.hpp"
  51 #include "runtime/handles.inline.hpp"
  52 #include "runtime/javaCalls.hpp"
  53 #include "runtime/jniHandles.inline.hpp"
  54 #include "runtime/mutex.hpp"
  55 #include "runtime/mutexLocker.hpp"
  56 #include "runtime/reflectionUtils.hpp"
  57 #include "runtime/thread.inline.hpp"
  58 #include "runtime/threadSMR.hpp"
  59 #include "runtime/vframe.hpp"
  60 #include "runtime/vmThread.hpp"
  61 #include "runtime/vmOperations.hpp"
  62 #include "utilities/macros.hpp"
  63 #if INCLUDE_ZGC
  64 #include "gc/z/zGlobals.hpp"
  65 #endif
  66 
  67 // JvmtiTagHashmapEntry
  68 //
  69 // Each entry encapsulates a reference to the tagged object
  70 // and the tag value. In addition an entry includes a next pointer which
  71 // is used to chain entries together.
  72 
  73 class JvmtiTagHashmapEntry : public CHeapObj<mtInternal> {
  74  private:
  75   friend class JvmtiTagMap;
  76 
  77   oop _object;                          // tagged object
  78   jlong _tag;                           // the tag
  79   JvmtiTagHashmapEntry* _next;          // next on the list
  80 
  81   inline void init(oop object, jlong tag) {
  82     _object = object;
  83     _tag = tag;
  84     _next = NULL;
  85   }
  86 
  87   // constructor
  88   JvmtiTagHashmapEntry(oop object, jlong tag) { init(object, tag); }
  89 
  90  public:
  91 
  92   // accessor methods
  93   inline oop* object_addr() { return &_object; }
  94   inline oop object()       { return NativeAccess<ON_PHANTOM_OOP_REF>::oop_load(object_addr()); }
  95   // Peek at the object without keeping it alive. The returned object must be
  96   // kept alive using a normal access if it leaks out of a thread transition from VM.
  97   inline oop object_peek()  {
  98     return NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(object_addr());
  99   }
 100   inline jlong tag() const  { return _tag; }
 101 
 102   inline void set_tag(jlong tag) {
 103     assert(tag != 0, "can't be zero");
 104     _tag = tag;
 105   }
 106 
 107   inline bool equals(oop object) {
 108     return oopDesc::equals(object, object_peek());
 109   }
 110 
 111   inline JvmtiTagHashmapEntry* next() const        { return _next; }
 112   inline void set_next(JvmtiTagHashmapEntry* next) { _next = next; }
 113 };
 114 
 115 
 116 // JvmtiTagHashmap
 117 //
 118 // A hashmap is essentially a table of pointers to entries. Entries
 119 // are hashed to a location, or position in the table, and then
 120 // chained from that location. The "key" for hashing is address of
 121 // the object, or oop. The "value" is the tag value.
 122 //
 123 // A hashmap maintains a count of the number entries in the hashmap
 124 // and resizes if the number of entries exceeds a given threshold.
 125 // The threshold is specified as a percentage of the size - for
 126 // example a threshold of 0.75 will trigger the hashmap to resize
 127 // if the number of entries is >75% of table size.
 128 //
 129 // A hashmap provides functions for adding, removing, and finding
 130 // entries. It also provides a function to iterate over all entries
 131 // in the hashmap.
 132 
 133 class JvmtiTagHashmap : public CHeapObj<mtInternal> {
 134  private:
 135   friend class JvmtiTagMap;
 136 
 137   enum {
 138     small_trace_threshold  = 10000,                  // threshold for tracing
 139     medium_trace_threshold = 100000,
 140     large_trace_threshold  = 1000000,
 141     initial_trace_threshold = small_trace_threshold
 142   };
 143 
 144   static int _sizes[];                  // array of possible hashmap sizes
 145   int _size;                            // actual size of the table
 146   int _size_index;                      // index into size table
 147 
 148   int _entry_count;                     // number of entries in the hashmap
 149 
 150   float _load_factor;                   // load factor as a % of the size
 151   int _resize_threshold;                // computed threshold to trigger resizing.
 152   bool _resizing_enabled;               // indicates if hashmap can resize
 153 
 154   int _trace_threshold;                 // threshold for trace messages
 155 
 156   JvmtiTagHashmapEntry** _table;        // the table of entries.
 157 
 158   // private accessors
 159   int resize_threshold() const                  { return _resize_threshold; }
 160   int trace_threshold() const                   { return _trace_threshold; }
 161 
 162   // initialize the hashmap
 163   void init(int size_index=0, float load_factor=4.0f) {
 164     int initial_size =  _sizes[size_index];
 165     _size_index = size_index;
 166     _size = initial_size;
 167     _entry_count = 0;
 168     _trace_threshold = initial_trace_threshold;
 169     _load_factor = load_factor;
 170     _resize_threshold = (int)(_load_factor * _size);
 171     _resizing_enabled = true;
 172     size_t s = initial_size * sizeof(JvmtiTagHashmapEntry*);
 173     _table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 174     if (_table == NULL) {
 175       vm_exit_out_of_memory(s, OOM_MALLOC_ERROR,
 176         "unable to allocate initial hashtable for jvmti object tags");
 177     }
 178     for (int i=0; i<initial_size; i++) {
 179       _table[i] = NULL;
 180     }
 181   }
 182 
 183   // hash a given key (oop) with the specified size
 184   static unsigned int hash(oop key, int size) {
 185     const oop obj = Access<>::resolve(key);
 186     const unsigned int hash = Universe::heap()->hash_oop(obj);
 187     return hash % size;
 188   }
 189 
 190   // hash a given key (oop)
 191   unsigned int hash(oop key) {
 192     return hash(key, _size);
 193   }
 194 
 195   // resize the hashmap - allocates a large table and re-hashes
 196   // all entries into the new table.
 197   void resize() {
 198     int new_size_index = _size_index+1;
 199     int new_size = _sizes[new_size_index];
 200     if (new_size < 0) {
 201       // hashmap already at maximum capacity
 202       return;
 203     }
 204 
 205     // allocate new table
 206     size_t s = new_size * sizeof(JvmtiTagHashmapEntry*);
 207     JvmtiTagHashmapEntry** new_table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 208     if (new_table == NULL) {
 209       warning("unable to allocate larger hashtable for jvmti object tags");
 210       set_resizing_enabled(false);
 211       return;
 212     }
 213 
 214     // initialize new table
 215     int i;
 216     for (i=0; i<new_size; i++) {
 217       new_table[i] = NULL;
 218     }
 219 
 220     // rehash all entries into the new table
 221     for (i=0; i<_size; i++) {
 222       JvmtiTagHashmapEntry* entry = _table[i];
 223       while (entry != NULL) {
 224         JvmtiTagHashmapEntry* next = entry->next();
 225         oop key = entry->object_peek();
 226         assert(key != NULL, "jni weak reference cleared!!");
 227         unsigned int h = hash(key, new_size);
 228         JvmtiTagHashmapEntry* anchor = new_table[h];
 229         if (anchor == NULL) {
 230           new_table[h] = entry;
 231           entry->set_next(NULL);
 232         } else {
 233           entry->set_next(anchor);
 234           new_table[h] = entry;
 235         }
 236         entry = next;
 237       }
 238     }
 239 
 240     // free old table and update settings.
 241     os::free((void*)_table);
 242     _table = new_table;
 243     _size_index = new_size_index;
 244     _size = new_size;
 245 
 246     // compute new resize threshold
 247     _resize_threshold = (int)(_load_factor * _size);
 248   }
 249 
 250 
 251   // internal remove function - remove an entry at a given position in the
 252   // table.
 253   inline void remove(JvmtiTagHashmapEntry* prev, int pos, JvmtiTagHashmapEntry* entry) {
 254     assert(pos >= 0 && pos < _size, "out of range");
 255     if (prev == NULL) {
 256       _table[pos] = entry->next();
 257     } else {
 258       prev->set_next(entry->next());
 259     }
 260     assert(_entry_count > 0, "checking");
 261     _entry_count--;
 262   }
 263 
 264   // resizing switch
 265   bool is_resizing_enabled() const          { return _resizing_enabled; }
 266   void set_resizing_enabled(bool enable)    { _resizing_enabled = enable; }
 267 
 268   // debugging
 269   void print_memory_usage();
 270   void compute_next_trace_threshold();
 271 
 272  public:
 273 
 274   // create a JvmtiTagHashmap of a preferred size and optionally a load factor.
 275   // The preferred size is rounded down to an actual size.
 276   JvmtiTagHashmap(int size, float load_factor=0.0f) {
 277     int i=0;
 278     while (_sizes[i] < size) {
 279       if (_sizes[i] < 0) {
 280         assert(i > 0, "sanity check");
 281         i--;
 282         break;
 283       }
 284       i++;
 285     }
 286 
 287     // if a load factor is specified then use it, otherwise use default
 288     if (load_factor > 0.01f) {
 289       init(i, load_factor);
 290     } else {
 291       init(i);
 292     }
 293   }
 294 
 295   // create a JvmtiTagHashmap with default settings
 296   JvmtiTagHashmap() {
 297     init();
 298   }
 299 
 300   // release table when JvmtiTagHashmap destroyed
 301   ~JvmtiTagHashmap() {
 302     if (_table != NULL) {
 303       os::free((void*)_table);
 304       _table = NULL;
 305     }
 306   }
 307 
 308   // accessors
 309   int size() const                              { return _size; }
 310   JvmtiTagHashmapEntry** table() const          { return _table; }
 311   int entry_count() const                       { return _entry_count; }
 312 
 313   // find an entry in the hashmap, returns NULL if not found.
 314   inline JvmtiTagHashmapEntry* find(oop key) {
 315     unsigned int h = hash(key);
 316     JvmtiTagHashmapEntry* entry = _table[h];
 317     while (entry != NULL) {
 318       if (entry->equals(key)) {
 319          return entry;
 320       }
 321       entry = entry->next();
 322     }
 323     return NULL;
 324   }
 325 
 326 
 327   // add a new entry to hashmap
 328   inline void add(oop key, JvmtiTagHashmapEntry* entry) {
 329     assert(key != NULL, "checking");
 330     assert(find(key) == NULL, "duplicate detected");
 331     unsigned int h = hash(key);
 332     JvmtiTagHashmapEntry* anchor = _table[h];
 333     if (anchor == NULL) {
 334       _table[h] = entry;
 335       entry->set_next(NULL);
 336     } else {
 337       entry->set_next(anchor);
 338       _table[h] = entry;
 339     }
 340 
 341     _entry_count++;
 342     if (log_is_enabled(Debug, jvmti, objecttagging) && entry_count() >= trace_threshold()) {
 343       print_memory_usage();
 344       compute_next_trace_threshold();
 345     }
 346 
 347     // if the number of entries exceed the threshold then resize
 348     if (entry_count() > resize_threshold() && is_resizing_enabled()) {
 349       resize();
 350     }
 351   }
 352 
 353   // remove an entry with the given key.
 354   inline JvmtiTagHashmapEntry* remove(oop key) {
 355     unsigned int h = hash(key);
 356     JvmtiTagHashmapEntry* entry = _table[h];
 357     JvmtiTagHashmapEntry* prev = NULL;
 358     while (entry != NULL) {
 359       if (entry->equals(key)) {
 360         break;
 361       }
 362       prev = entry;
 363       entry = entry->next();
 364     }
 365     if (entry != NULL) {
 366       remove(prev, h, entry);
 367     }
 368     return entry;
 369   }
 370 
 371   // iterate over all entries in the hashmap
 372   void entry_iterate(JvmtiTagHashmapEntryClosure* closure);
 373 };
 374 
 375 // possible hashmap sizes - odd primes that roughly double in size.
 376 // To avoid excessive resizing the odd primes from 4801-76831 and
 377 // 76831-307261 have been removed. The list must be terminated by -1.
 378 int JvmtiTagHashmap::_sizes[] =  { 4801, 76831, 307261, 614563, 1228891,
 379     2457733, 4915219, 9830479, 19660831, 39321619, 78643219, -1 };
 380 
 381 
 382 // A supporting class for iterating over all entries in Hashmap
 383 class JvmtiTagHashmapEntryClosure {
 384  public:
 385   virtual void do_entry(JvmtiTagHashmapEntry* entry) = 0;
 386 };
 387 
 388 
 389 // iterate over all entries in the hashmap
 390 void JvmtiTagHashmap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 391   for (int i=0; i<_size; i++) {
 392     JvmtiTagHashmapEntry* entry = _table[i];
 393     JvmtiTagHashmapEntry* prev = NULL;
 394     while (entry != NULL) {
 395       // obtain the next entry before invoking do_entry - this is
 396       // necessary because do_entry may remove the entry from the
 397       // hashmap.
 398       JvmtiTagHashmapEntry* next = entry->next();
 399       closure->do_entry(entry);
 400       entry = next;
 401      }
 402   }
 403 }
 404 
 405 // debugging
 406 void JvmtiTagHashmap::print_memory_usage() {
 407   intptr_t p = (intptr_t)this;
 408   tty->print("[JvmtiTagHashmap @ " INTPTR_FORMAT, p);
 409 
 410   // table + entries in KB
 411   int hashmap_usage = (size()*sizeof(JvmtiTagHashmapEntry*) +
 412     entry_count()*sizeof(JvmtiTagHashmapEntry))/K;
 413 
 414   int weak_globals_usage = (int)(JNIHandles::weak_global_handle_memory_usage()/K);
 415   tty->print_cr(", %d entries (%d KB) <JNI weak globals: %d KB>]",
 416     entry_count(), hashmap_usage, weak_globals_usage);
 417 }
 418 
 419 // compute threshold for the next trace message
 420 void JvmtiTagHashmap::compute_next_trace_threshold() {
 421   _trace_threshold = entry_count();
 422   if (trace_threshold() < medium_trace_threshold) {
 423     _trace_threshold += small_trace_threshold;
 424   } else {
 425     if (trace_threshold() < large_trace_threshold) {
 426       _trace_threshold += medium_trace_threshold;
 427     } else {
 428       _trace_threshold += large_trace_threshold;
 429     }
 430   }
 431 }
 432 
 433 // create a JvmtiTagMap
 434 JvmtiTagMap::JvmtiTagMap(JvmtiEnv* env) :
 435   _env(env),
 436   _lock(Mutex::nonleaf+2, "JvmtiTagMap._lock", false),
 437   _free_entries(NULL),
 438   _free_entries_count(0)
 439 {
 440   assert(JvmtiThreadState_lock->is_locked(), "sanity check");
 441   assert(((JvmtiEnvBase *)env)->tag_map() == NULL, "tag map already exists for environment");
 442 
 443   _hashmap = new JvmtiTagHashmap();
 444 
 445   // finally add us to the environment
 446   ((JvmtiEnvBase *)env)->release_set_tag_map(this);
 447 }
 448 
 449 
 450 // destroy a JvmtiTagMap
 451 JvmtiTagMap::~JvmtiTagMap() {
 452 
 453   // no lock acquired as we assume the enclosing environment is
 454   // also being destroryed.
 455   ((JvmtiEnvBase *)_env)->set_tag_map(NULL);
 456 
 457   JvmtiTagHashmapEntry** table = _hashmap->table();
 458   for (int j = 0; j < _hashmap->size(); j++) {
 459     JvmtiTagHashmapEntry* entry = table[j];
 460     while (entry != NULL) {
 461       JvmtiTagHashmapEntry* next = entry->next();
 462       delete entry;
 463       entry = next;
 464     }
 465   }
 466 
 467   // finally destroy the hashmap
 468   delete _hashmap;
 469   _hashmap = NULL;
 470 
 471   // remove any entries on the free list
 472   JvmtiTagHashmapEntry* entry = _free_entries;
 473   while (entry != NULL) {
 474     JvmtiTagHashmapEntry* next = entry->next();
 475     delete entry;
 476     entry = next;
 477   }
 478   _free_entries = NULL;
 479 }
 480 
 481 // create a hashmap entry
 482 // - if there's an entry on the (per-environment) free list then this
 483 // is returned. Otherwise an new entry is allocated.
 484 JvmtiTagHashmapEntry* JvmtiTagMap::create_entry(oop ref, jlong tag) {
 485   assert(Thread::current()->is_VM_thread() || is_locked(), "checking");
 486   JvmtiTagHashmapEntry* entry;
 487   if (_free_entries == NULL) {
 488     entry = new JvmtiTagHashmapEntry(ref, tag);
 489   } else {
 490     assert(_free_entries_count > 0, "mismatched _free_entries_count");
 491     _free_entries_count--;
 492     entry = _free_entries;
 493     _free_entries = entry->next();
 494     entry->init(ref, tag);
 495   }
 496   return entry;
 497 }
 498 
 499 // destroy an entry by returning it to the free list
 500 void JvmtiTagMap::destroy_entry(JvmtiTagHashmapEntry* entry) {
 501   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 502   // limit the size of the free list
 503   if (_free_entries_count >= max_free_entries) {
 504     delete entry;
 505   } else {
 506     entry->set_next(_free_entries);
 507     _free_entries = entry;
 508     _free_entries_count++;
 509   }
 510 }
 511 
 512 // returns the tag map for the given environments. If the tag map
 513 // doesn't exist then it is created.
 514 JvmtiTagMap* JvmtiTagMap::tag_map_for(JvmtiEnv* env) {
 515   JvmtiTagMap* tag_map = ((JvmtiEnvBase*)env)->tag_map_acquire();
 516   if (tag_map == NULL) {
 517     MutexLocker mu(JvmtiThreadState_lock);
 518     tag_map = ((JvmtiEnvBase*)env)->tag_map();
 519     if (tag_map == NULL) {
 520       tag_map = new JvmtiTagMap(env);
 521     }
 522   } else {
 523     DEBUG_ONLY(Thread::current()->check_possible_safepoint());
 524   }
 525   return tag_map;
 526 }
 527 
 528 // iterate over all entries in the tag map.
 529 void JvmtiTagMap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 530   hashmap()->entry_iterate(closure);
 531 }
 532 
 533 // returns true if the hashmaps are empty
 534 bool JvmtiTagMap::is_empty() {
 535   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 536   return hashmap()->entry_count() == 0;
 537 }
 538 
 539 
 540 // Return the tag value for an object, or 0 if the object is
 541 // not tagged
 542 //
 543 static inline jlong tag_for(JvmtiTagMap* tag_map, oop o) {
 544   JvmtiTagHashmapEntry* entry = tag_map->hashmap()->find(o);
 545   if (entry == NULL) {
 546     return 0;
 547   } else {
 548     return entry->tag();
 549   }
 550 }
 551 
 552 
 553 // A CallbackWrapper is a support class for querying and tagging an object
 554 // around a callback to a profiler. The constructor does pre-callback
 555 // work to get the tag value, klass tag value, ... and the destructor
 556 // does the post-callback work of tagging or untagging the object.
 557 //
 558 // {
 559 //   CallbackWrapper wrapper(tag_map, o);
 560 //
 561 //   (*callback)(wrapper.klass_tag(), wrapper.obj_size(), wrapper.obj_tag_p(), ...)
 562 //
 563 // } // wrapper goes out of scope here which results in the destructor
 564 //      checking to see if the object has been tagged, untagged, or the
 565 //      tag value has changed.
 566 //
 567 class CallbackWrapper : public StackObj {
 568  private:
 569   JvmtiTagMap* _tag_map;
 570   JvmtiTagHashmap* _hashmap;
 571   JvmtiTagHashmapEntry* _entry;
 572   oop _o;
 573   jlong _obj_size;
 574   jlong _obj_tag;
 575   jlong _klass_tag;
 576 
 577  protected:
 578   JvmtiTagMap* tag_map() const      { return _tag_map; }
 579 
 580   // invoked post-callback to tag, untag, or update the tag of an object
 581   void inline post_callback_tag_update(oop o, JvmtiTagHashmap* hashmap,
 582                                        JvmtiTagHashmapEntry* entry, jlong obj_tag);
 583  public:
 584   CallbackWrapper(JvmtiTagMap* tag_map, oop o) {
 585     assert(Thread::current()->is_VM_thread() || tag_map->is_locked(),
 586            "MT unsafe or must be VM thread");
 587 
 588     // object to tag
 589     _o = o;
 590 
 591     // object size
 592     _obj_size = (jlong)_o->size() * wordSize;
 593 
 594     // record the context
 595     _tag_map = tag_map;
 596     _hashmap = tag_map->hashmap();
 597     _entry = _hashmap->find(_o);
 598 
 599     // get object tag
 600     _obj_tag = (_entry == NULL) ? 0 : _entry->tag();
 601 
 602     // get the class and the class's tag value
 603     assert(SystemDictionary::Class_klass()->is_mirror_instance_klass(), "Is not?");
 604 
 605     _klass_tag = tag_for(tag_map, _o->klass()->java_mirror());
 606   }
 607 
 608   ~CallbackWrapper() {
 609     post_callback_tag_update(_o, _hashmap, _entry, _obj_tag);
 610   }
 611 
 612   inline jlong* obj_tag_p()                     { return &_obj_tag; }
 613   inline jlong obj_size() const                 { return _obj_size; }
 614   inline jlong obj_tag() const                  { return _obj_tag; }
 615   inline jlong klass_tag() const                { return _klass_tag; }
 616 };
 617 
 618 
 619 
 620 // callback post-callback to tag, untag, or update the tag of an object
 621 void inline CallbackWrapper::post_callback_tag_update(oop o,
 622                                                       JvmtiTagHashmap* hashmap,
 623                                                       JvmtiTagHashmapEntry* entry,
 624                                                       jlong obj_tag) {
 625   if (entry == NULL) {
 626     if (obj_tag != 0) {
 627       // callback has tagged the object
 628       assert(Thread::current()->is_VM_thread(), "must be VMThread");
 629       entry = tag_map()->create_entry(o, obj_tag);
 630       hashmap->add(o, entry);
 631     }
 632   } else {
 633     // object was previously tagged - the callback may have untagged
 634     // the object or changed the tag value
 635     if (obj_tag == 0) {
 636 
 637       JvmtiTagHashmapEntry* entry_removed = hashmap->remove(o);
 638       assert(entry_removed == entry, "checking");
 639       tag_map()->destroy_entry(entry);
 640 
 641     } else {
 642       if (obj_tag != entry->tag()) {
 643          entry->set_tag(obj_tag);
 644       }
 645     }
 646   }
 647 }
 648 
 649 // An extended CallbackWrapper used when reporting an object reference
 650 // to the agent.
 651 //
 652 // {
 653 //   TwoOopCallbackWrapper wrapper(tag_map, referrer, o);
 654 //
 655 //   (*callback)(wrapper.klass_tag(),
 656 //               wrapper.obj_size(),
 657 //               wrapper.obj_tag_p()
 658 //               wrapper.referrer_tag_p(), ...)
 659 //
 660 // } // wrapper goes out of scope here which results in the destructor
 661 //      checking to see if the referrer object has been tagged, untagged,
 662 //      or the tag value has changed.
 663 //
 664 class TwoOopCallbackWrapper : public CallbackWrapper {
 665  private:
 666   bool _is_reference_to_self;
 667   JvmtiTagHashmap* _referrer_hashmap;
 668   JvmtiTagHashmapEntry* _referrer_entry;
 669   oop _referrer;
 670   jlong _referrer_obj_tag;
 671   jlong _referrer_klass_tag;
 672   jlong* _referrer_tag_p;
 673 
 674   bool is_reference_to_self() const             { return _is_reference_to_self; }
 675 
 676  public:
 677   TwoOopCallbackWrapper(JvmtiTagMap* tag_map, oop referrer, oop o) :
 678     CallbackWrapper(tag_map, o)
 679   {
 680     // self reference needs to be handled in a special way
 681     _is_reference_to_self = (referrer == o);
 682 
 683     if (_is_reference_to_self) {
 684       _referrer_klass_tag = klass_tag();
 685       _referrer_tag_p = obj_tag_p();
 686     } else {
 687       _referrer = referrer;
 688       // record the context
 689       _referrer_hashmap = tag_map->hashmap();
 690       _referrer_entry = _referrer_hashmap->find(_referrer);
 691 
 692       // get object tag
 693       _referrer_obj_tag = (_referrer_entry == NULL) ? 0 : _referrer_entry->tag();
 694       _referrer_tag_p = &_referrer_obj_tag;
 695 
 696       // get referrer class tag.
 697       _referrer_klass_tag = tag_for(tag_map, _referrer->klass()->java_mirror());
 698     }
 699   }
 700 
 701   ~TwoOopCallbackWrapper() {
 702     if (!is_reference_to_self()){
 703       post_callback_tag_update(_referrer,
 704                                _referrer_hashmap,
 705                                _referrer_entry,
 706                                _referrer_obj_tag);
 707     }
 708   }
 709 
 710   // address of referrer tag
 711   // (for a self reference this will return the same thing as obj_tag_p())
 712   inline jlong* referrer_tag_p()        { return _referrer_tag_p; }
 713 
 714   // referrer's class tag
 715   inline jlong referrer_klass_tag()     { return _referrer_klass_tag; }
 716 };
 717 
 718 // tag an object
 719 //
 720 // This function is performance critical. If many threads attempt to tag objects
 721 // around the same time then it's possible that the Mutex associated with the
 722 // tag map will be a hot lock.
 723 void JvmtiTagMap::set_tag(jobject object, jlong tag) {
 724   MutexLocker ml(lock());
 725 
 726   // resolve the object
 727   oop o = JNIHandles::resolve_non_null(object);
 728 
 729   // see if the object is already tagged
 730   JvmtiTagHashmap* hashmap = _hashmap;
 731   JvmtiTagHashmapEntry* entry = hashmap->find(o);
 732 
 733   // if the object is not already tagged then we tag it
 734   if (entry == NULL) {
 735     if (tag != 0) {
 736       entry = create_entry(o, tag);
 737       hashmap->add(o, entry);
 738     } else {
 739       // no-op
 740     }
 741   } else {
 742     // if the object is already tagged then we either update
 743     // the tag (if a new tag value has been provided)
 744     // or remove the object if the new tag value is 0.
 745     if (tag == 0) {
 746       hashmap->remove(o);
 747       destroy_entry(entry);
 748     } else {
 749       entry->set_tag(tag);
 750     }
 751   }
 752 }
 753 
 754 // get the tag for an object
 755 jlong JvmtiTagMap::get_tag(jobject object) {
 756   MutexLocker ml(lock());
 757 
 758   // resolve the object
 759   oop o = JNIHandles::resolve_non_null(object);
 760 
 761   return tag_for(this, o);
 762 }
 763 
 764 
 765 // Helper class used to describe the static or instance fields of a class.
 766 // For each field it holds the field index (as defined by the JVMTI specification),
 767 // the field type, and the offset.
 768 
 769 class ClassFieldDescriptor: public CHeapObj<mtInternal> {
 770  private:
 771   int _field_index;
 772   int _field_offset;
 773   char _field_type;
 774  public:
 775   ClassFieldDescriptor(int index, char type, int offset) :
 776     _field_index(index), _field_offset(offset), _field_type(type) {
 777   }
 778   int field_index()  const  { return _field_index; }
 779   char field_type()  const  { return _field_type; }
 780   int field_offset() const  { return _field_offset; }
 781 };
 782 
 783 class ClassFieldMap: public CHeapObj<mtInternal> {
 784  private:
 785   enum {
 786     initial_field_count = 5
 787   };
 788 
 789   // list of field descriptors
 790   GrowableArray<ClassFieldDescriptor*>* _fields;
 791 
 792   // constructor
 793   ClassFieldMap();
 794 
 795   // add a field
 796   void add(int index, char type, int offset);
 797 
 798   // returns the field count for the given class
 799   static int compute_field_count(InstanceKlass* ik);
 800 
 801  public:
 802   ~ClassFieldMap();
 803 
 804   // access
 805   int field_count()                     { return _fields->length(); }
 806   ClassFieldDescriptor* field_at(int i) { return _fields->at(i); }
 807 
 808   // functions to create maps of static or instance fields
 809   static ClassFieldMap* create_map_of_static_fields(Klass* k);
 810   static ClassFieldMap* create_map_of_instance_fields(oop obj);
 811 };
 812 
 813 ClassFieldMap::ClassFieldMap() {
 814   _fields = new (ResourceObj::C_HEAP, mtInternal)
 815     GrowableArray<ClassFieldDescriptor*>(initial_field_count, true);
 816 }
 817 
 818 ClassFieldMap::~ClassFieldMap() {
 819   for (int i=0; i<_fields->length(); i++) {
 820     delete _fields->at(i);
 821   }
 822   delete _fields;
 823 }
 824 
 825 void ClassFieldMap::add(int index, char type, int offset) {
 826   ClassFieldDescriptor* field = new ClassFieldDescriptor(index, type, offset);
 827   _fields->append(field);
 828 }
 829 
 830 // Returns a heap allocated ClassFieldMap to describe the static fields
 831 // of the given class.
 832 //
 833 ClassFieldMap* ClassFieldMap::create_map_of_static_fields(Klass* k) {
 834   HandleMark hm;
 835   InstanceKlass* ik = InstanceKlass::cast(k);
 836 
 837   // create the field map
 838   ClassFieldMap* field_map = new ClassFieldMap();
 839 
 840   FilteredFieldStream f(ik, false, false);
 841   int max_field_index = f.field_count()-1;
 842 
 843   int index = 0;
 844   for (FilteredFieldStream fld(ik, true, true); !fld.eos(); fld.next(), index++) {
 845     // ignore instance fields
 846     if (!fld.access_flags().is_static()) {
 847       continue;
 848     }
 849     field_map->add(max_field_index - index, fld.signature()->char_at(0), fld.offset());
 850   }
 851   return field_map;
 852 }
 853 
 854 // Returns a heap allocated ClassFieldMap to describe the instance fields
 855 // of the given class. All instance fields are included (this means public
 856 // and private fields declared in superclasses and superinterfaces too).
 857 //
 858 ClassFieldMap* ClassFieldMap::create_map_of_instance_fields(oop obj) {
 859   HandleMark hm;
 860   InstanceKlass* ik = InstanceKlass::cast(obj->klass());
 861 
 862   // create the field map
 863   ClassFieldMap* field_map = new ClassFieldMap();
 864 
 865   FilteredFieldStream f(ik, false, false);
 866 
 867   int max_field_index = f.field_count()-1;
 868 
 869   int index = 0;
 870   for (FilteredFieldStream fld(ik, false, false); !fld.eos(); fld.next(), index++) {
 871     // ignore static fields
 872     if (fld.access_flags().is_static()) {
 873       continue;
 874     }
 875     field_map->add(max_field_index - index, fld.signature()->char_at(0), fld.offset());
 876   }
 877 
 878   return field_map;
 879 }
 880 
 881 // Helper class used to cache a ClassFileMap for the instance fields of
 882 // a cache. A JvmtiCachedClassFieldMap can be cached by an InstanceKlass during
 883 // heap iteration and avoid creating a field map for each object in the heap
 884 // (only need to create the map when the first instance of a class is encountered).
 885 //
 886 class JvmtiCachedClassFieldMap : public CHeapObj<mtInternal> {
 887  private:
 888    enum {
 889      initial_class_count = 200
 890    };
 891   ClassFieldMap* _field_map;
 892 
 893   ClassFieldMap* field_map() const          { return _field_map; }
 894 
 895   JvmtiCachedClassFieldMap(ClassFieldMap* field_map);
 896   ~JvmtiCachedClassFieldMap();
 897 
 898   static GrowableArray<InstanceKlass*>* _class_list;
 899   static void add_to_class_list(InstanceKlass* ik);
 900 
 901  public:
 902   // returns the field map for a given object (returning map cached
 903   // by InstanceKlass if possible
 904   static ClassFieldMap* get_map_of_instance_fields(oop obj);
 905 
 906   // removes the field map from all instanceKlasses - should be
 907   // called before VM operation completes
 908   static void clear_cache();
 909 
 910   // returns the number of ClassFieldMap cached by instanceKlasses
 911   static int cached_field_map_count();
 912 };
 913 
 914 GrowableArray<InstanceKlass*>* JvmtiCachedClassFieldMap::_class_list;
 915 
 916 JvmtiCachedClassFieldMap::JvmtiCachedClassFieldMap(ClassFieldMap* field_map) {
 917   _field_map = field_map;
 918 }
 919 
 920 JvmtiCachedClassFieldMap::~JvmtiCachedClassFieldMap() {
 921   if (_field_map != NULL) {
 922     delete _field_map;
 923   }
 924 }
 925 
 926 // Marker class to ensure that the class file map cache is only used in a defined
 927 // scope.
 928 class ClassFieldMapCacheMark : public StackObj {
 929  private:
 930    static bool _is_active;
 931  public:
 932    ClassFieldMapCacheMark() {
 933      assert(Thread::current()->is_VM_thread(), "must be VMThread");
 934      assert(JvmtiCachedClassFieldMap::cached_field_map_count() == 0, "cache not empty");
 935      assert(!_is_active, "ClassFieldMapCacheMark cannot be nested");
 936      _is_active = true;
 937    }
 938    ~ClassFieldMapCacheMark() {
 939      JvmtiCachedClassFieldMap::clear_cache();
 940      _is_active = false;
 941    }
 942    static bool is_active() { return _is_active; }
 943 };
 944 
 945 bool ClassFieldMapCacheMark::_is_active;
 946 
 947 
 948 // record that the given InstanceKlass is caching a field map
 949 void JvmtiCachedClassFieldMap::add_to_class_list(InstanceKlass* ik) {
 950   if (_class_list == NULL) {
 951     _class_list = new (ResourceObj::C_HEAP, mtInternal)
 952       GrowableArray<InstanceKlass*>(initial_class_count, true);
 953   }
 954   _class_list->push(ik);
 955 }
 956 
 957 // returns the instance field map for the given object
 958 // (returns field map cached by the InstanceKlass if possible)
 959 ClassFieldMap* JvmtiCachedClassFieldMap::get_map_of_instance_fields(oop obj) {
 960   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 961   assert(ClassFieldMapCacheMark::is_active(), "ClassFieldMapCacheMark not active");
 962 
 963   Klass* k = obj->klass();
 964   InstanceKlass* ik = InstanceKlass::cast(k);
 965 
 966   // return cached map if possible
 967   JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 968   if (cached_map != NULL) {
 969     assert(cached_map->field_map() != NULL, "missing field list");
 970     return cached_map->field_map();
 971   } else {
 972     ClassFieldMap* field_map = ClassFieldMap::create_map_of_instance_fields(obj);
 973     cached_map = new JvmtiCachedClassFieldMap(field_map);
 974     ik->set_jvmti_cached_class_field_map(cached_map);
 975     add_to_class_list(ik);
 976     return field_map;
 977   }
 978 }
 979 
 980 // remove the fields maps cached from all instanceKlasses
 981 void JvmtiCachedClassFieldMap::clear_cache() {
 982   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 983   if (_class_list != NULL) {
 984     for (int i = 0; i < _class_list->length(); i++) {
 985       InstanceKlass* ik = _class_list->at(i);
 986       JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 987       assert(cached_map != NULL, "should not be NULL");
 988       ik->set_jvmti_cached_class_field_map(NULL);
 989       delete cached_map;  // deletes the encapsulated field map
 990     }
 991     delete _class_list;
 992     _class_list = NULL;
 993   }
 994 }
 995 
 996 // returns the number of ClassFieldMap cached by instanceKlasses
 997 int JvmtiCachedClassFieldMap::cached_field_map_count() {
 998   return (_class_list == NULL) ? 0 : _class_list->length();
 999 }
1000 
1001 // helper function to indicate if an object is filtered by its tag or class tag
1002 static inline bool is_filtered_by_heap_filter(jlong obj_tag,
1003                                               jlong klass_tag,
1004                                               int heap_filter) {
1005   // apply the heap filter
1006   if (obj_tag != 0) {
1007     // filter out tagged objects
1008     if (heap_filter & JVMTI_HEAP_FILTER_TAGGED) return true;
1009   } else {
1010     // filter out untagged objects
1011     if (heap_filter & JVMTI_HEAP_FILTER_UNTAGGED) return true;
1012   }
1013   if (klass_tag != 0) {
1014     // filter out objects with tagged classes
1015     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_TAGGED) return true;
1016   } else {
1017     // filter out objects with untagged classes.
1018     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_UNTAGGED) return true;
1019   }
1020   return false;
1021 }
1022 
1023 // helper function to indicate if an object is filtered by a klass filter
1024 static inline bool is_filtered_by_klass_filter(oop obj, Klass* klass_filter) {
1025   if (klass_filter != NULL) {
1026     if (obj->klass() != klass_filter) {
1027       return true;
1028     }
1029   }
1030   return false;
1031 }
1032 
1033 // helper function to tell if a field is a primitive field or not
1034 static inline bool is_primitive_field_type(char type) {
1035   return (type != 'L' && type != '[');
1036 }
1037 
1038 // helper function to copy the value from location addr to jvalue.
1039 static inline void copy_to_jvalue(jvalue *v, address addr, jvmtiPrimitiveType value_type) {
1040   switch (value_type) {
1041     case JVMTI_PRIMITIVE_TYPE_BOOLEAN : { v->z = *(jboolean*)addr; break; }
1042     case JVMTI_PRIMITIVE_TYPE_BYTE    : { v->b = *(jbyte*)addr;    break; }
1043     case JVMTI_PRIMITIVE_TYPE_CHAR    : { v->c = *(jchar*)addr;    break; }
1044     case JVMTI_PRIMITIVE_TYPE_SHORT   : { v->s = *(jshort*)addr;   break; }
1045     case JVMTI_PRIMITIVE_TYPE_INT     : { v->i = *(jint*)addr;     break; }
1046     case JVMTI_PRIMITIVE_TYPE_LONG    : { v->j = *(jlong*)addr;    break; }
1047     case JVMTI_PRIMITIVE_TYPE_FLOAT   : { v->f = *(jfloat*)addr;   break; }
1048     case JVMTI_PRIMITIVE_TYPE_DOUBLE  : { v->d = *(jdouble*)addr;  break; }
1049     default: ShouldNotReachHere();
1050   }
1051 }
1052 
1053 // helper function to invoke string primitive value callback
1054 // returns visit control flags
1055 static jint invoke_string_value_callback(jvmtiStringPrimitiveValueCallback cb,
1056                                          CallbackWrapper* wrapper,
1057                                          oop str,
1058                                          void* user_data)
1059 {
1060   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
1061 
1062   typeArrayOop s_value = java_lang_String::value(str);
1063 
1064   // JDK-6584008: the value field may be null if a String instance is
1065   // partially constructed.
1066   if (s_value == NULL) {
1067     return 0;
1068   }
1069   // get the string value and length
1070   // (string value may be offset from the base)
1071   int s_len = java_lang_String::length(str);
1072   bool is_latin1 = java_lang_String::is_latin1(str);
1073   jchar* value;
1074   if (s_len > 0) {
1075     if (!is_latin1) {
1076       value = s_value->char_at_addr(0);
1077     } else {
1078       // Inflate latin1 encoded string to UTF16
1079       jchar* buf = NEW_C_HEAP_ARRAY(jchar, s_len, mtInternal);
1080       for (int i = 0; i < s_len; i++) {
1081         buf[i] = ((jchar) s_value->byte_at(i)) & 0xff;
1082       }
1083       value = &buf[0];
1084     }
1085   } else {
1086     // Don't use char_at_addr(0) if length is 0
1087     value = (jchar*) s_value->base(T_CHAR);
1088   }
1089 
1090   // invoke the callback
1091   jint res = (*cb)(wrapper->klass_tag(),
1092                    wrapper->obj_size(),
1093                    wrapper->obj_tag_p(),
1094                    value,
1095                    (jint)s_len,
1096                    user_data);
1097 
1098   if (is_latin1 && s_len > 0) {
1099     FREE_C_HEAP_ARRAY(jchar, value);
1100   }
1101   return res;
1102 }
1103 
1104 // helper function to invoke string primitive value callback
1105 // returns visit control flags
1106 static jint invoke_array_primitive_value_callback(jvmtiArrayPrimitiveValueCallback cb,
1107                                                   CallbackWrapper* wrapper,
1108                                                   oop obj,
1109                                                   void* user_data)
1110 {
1111   assert(obj->is_typeArray(), "not a primitive array");
1112 
1113   // get base address of first element
1114   typeArrayOop array = typeArrayOop(obj);
1115   BasicType type = TypeArrayKlass::cast(array->klass())->element_type();
1116   void* elements = array->base(type);
1117 
1118   // jvmtiPrimitiveType is defined so this mapping is always correct
1119   jvmtiPrimitiveType elem_type = (jvmtiPrimitiveType)type2char(type);
1120 
1121   return (*cb)(wrapper->klass_tag(),
1122                wrapper->obj_size(),
1123                wrapper->obj_tag_p(),
1124                (jint)array->length(),
1125                elem_type,
1126                elements,
1127                user_data);
1128 }
1129 
1130 // helper function to invoke the primitive field callback for all static fields
1131 // of a given class
1132 static jint invoke_primitive_field_callback_for_static_fields
1133   (CallbackWrapper* wrapper,
1134    oop obj,
1135    jvmtiPrimitiveFieldCallback cb,
1136    void* user_data)
1137 {
1138   // for static fields only the index will be set
1139   static jvmtiHeapReferenceInfo reference_info = { 0 };
1140 
1141   assert(obj->klass() == SystemDictionary::Class_klass(), "not a class");
1142   if (java_lang_Class::is_primitive(obj)) {
1143     return 0;
1144   }
1145   Klass* klass = java_lang_Class::as_Klass(obj);
1146 
1147   // ignore classes for object and type arrays
1148   if (!klass->is_instance_klass()) {
1149     return 0;
1150   }
1151 
1152   // ignore classes which aren't linked yet
1153   InstanceKlass* ik = InstanceKlass::cast(klass);
1154   if (!ik->is_linked()) {
1155     return 0;
1156   }
1157 
1158   // get the field map
1159   ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
1160 
1161   // invoke the callback for each static primitive field
1162   for (int i=0; i<field_map->field_count(); i++) {
1163     ClassFieldDescriptor* field = field_map->field_at(i);
1164 
1165     // ignore non-primitive fields
1166     char type = field->field_type();
1167     if (!is_primitive_field_type(type)) {
1168       continue;
1169     }
1170     // one-to-one mapping
1171     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1172 
1173     // get offset and field value
1174     int offset = field->field_offset();
1175     address addr = (address)klass->java_mirror() + offset;
1176     jvalue value;
1177     copy_to_jvalue(&value, addr, value_type);
1178 
1179     // field index
1180     reference_info.field.index = field->field_index();
1181 
1182     // invoke the callback
1183     jint res = (*cb)(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
1184                      &reference_info,
1185                      wrapper->klass_tag(),
1186                      wrapper->obj_tag_p(),
1187                      value,
1188                      value_type,
1189                      user_data);
1190     if (res & JVMTI_VISIT_ABORT) {
1191       delete field_map;
1192       return res;
1193     }
1194   }
1195 
1196   delete field_map;
1197   return 0;
1198 }
1199 
1200 // helper function to invoke the primitive field callback for all instance fields
1201 // of a given object
1202 static jint invoke_primitive_field_callback_for_instance_fields(
1203   CallbackWrapper* wrapper,
1204   oop obj,
1205   jvmtiPrimitiveFieldCallback cb,
1206   void* user_data)
1207 {
1208   // for instance fields only the index will be set
1209   static jvmtiHeapReferenceInfo reference_info = { 0 };
1210 
1211   // get the map of the instance fields
1212   ClassFieldMap* fields = JvmtiCachedClassFieldMap::get_map_of_instance_fields(obj);
1213 
1214   // invoke the callback for each instance primitive field
1215   for (int i=0; i<fields->field_count(); i++) {
1216     ClassFieldDescriptor* field = fields->field_at(i);
1217 
1218     // ignore non-primitive fields
1219     char type = field->field_type();
1220     if (!is_primitive_field_type(type)) {
1221       continue;
1222     }
1223     // one-to-one mapping
1224     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1225 
1226     // get offset and field value
1227     int offset = field->field_offset();
1228     address addr = (address)obj + offset;
1229     jvalue value;
1230     copy_to_jvalue(&value, addr, value_type);
1231 
1232     // field index
1233     reference_info.field.index = field->field_index();
1234 
1235     // invoke the callback
1236     jint res = (*cb)(JVMTI_HEAP_REFERENCE_FIELD,
1237                      &reference_info,
1238                      wrapper->klass_tag(),
1239                      wrapper->obj_tag_p(),
1240                      value,
1241                      value_type,
1242                      user_data);
1243     if (res & JVMTI_VISIT_ABORT) {
1244       return res;
1245     }
1246   }
1247   return 0;
1248 }
1249 
1250 
1251 // VM operation to iterate over all objects in the heap (both reachable
1252 // and unreachable)
1253 class VM_HeapIterateOperation: public VM_Operation {
1254  private:
1255   ObjectClosure* _blk;
1256  public:
1257   VM_HeapIterateOperation(ObjectClosure* blk) { _blk = blk; }
1258 
1259   VMOp_Type type() const { return VMOp_HeapIterateOperation; }
1260   void doit() {
1261     // allows class files maps to be cached during iteration
1262     ClassFieldMapCacheMark cm;
1263 
1264     // make sure that heap is parsable (fills TLABs with filler objects)
1265     Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1266 
1267     // Verify heap before iteration - if the heap gets corrupted then
1268     // JVMTI's IterateOverHeap will crash.
1269     if (VerifyBeforeIteration) {
1270       Universe::verify();
1271     }
1272 
1273     // do the iteration
1274     // If this operation encounters a bad object when using CMS,
1275     // consider using safe_object_iterate() which avoids perm gen
1276     // objects that may contain bad references.
1277     Universe::heap()->object_iterate(_blk);
1278   }
1279 
1280 };
1281 
1282 
1283 // An ObjectClosure used to support the deprecated IterateOverHeap and
1284 // IterateOverInstancesOfClass functions
1285 class IterateOverHeapObjectClosure: public ObjectClosure {
1286  private:
1287   JvmtiTagMap* _tag_map;
1288   Klass* _klass;
1289   jvmtiHeapObjectFilter _object_filter;
1290   jvmtiHeapObjectCallback _heap_object_callback;
1291   const void* _user_data;
1292 
1293   // accessors
1294   JvmtiTagMap* tag_map() const                    { return _tag_map; }
1295   jvmtiHeapObjectFilter object_filter() const     { return _object_filter; }
1296   jvmtiHeapObjectCallback object_callback() const { return _heap_object_callback; }
1297   Klass* klass() const                            { return _klass; }
1298   const void* user_data() const                   { return _user_data; }
1299 
1300   // indicates if iteration has been aborted
1301   bool _iteration_aborted;
1302   bool is_iteration_aborted() const               { return _iteration_aborted; }
1303   void set_iteration_aborted(bool aborted)        { _iteration_aborted = aborted; }
1304 
1305  public:
1306   IterateOverHeapObjectClosure(JvmtiTagMap* tag_map,
1307                                Klass* klass,
1308                                jvmtiHeapObjectFilter object_filter,
1309                                jvmtiHeapObjectCallback heap_object_callback,
1310                                const void* user_data) :
1311     _tag_map(tag_map),
1312     _klass(klass),
1313     _object_filter(object_filter),
1314     _heap_object_callback(heap_object_callback),
1315     _user_data(user_data),
1316     _iteration_aborted(false)
1317   {
1318   }
1319 
1320   void do_object(oop o);
1321 };
1322 
1323 // invoked for each object in the heap
1324 void IterateOverHeapObjectClosure::do_object(oop o) {
1325   // check if iteration has been halted
1326   if (is_iteration_aborted()) return;
1327 
1328   // instanceof check when filtering by klass
1329   if (klass() != NULL && !o->is_a(klass())) {
1330     return;
1331   }
1332   // prepare for the calllback
1333   CallbackWrapper wrapper(tag_map(), o);
1334 
1335   // if the object is tagged and we're only interested in untagged objects
1336   // then don't invoke the callback. Similiarly, if the object is untagged
1337   // and we're only interested in tagged objects we skip the callback.
1338   if (wrapper.obj_tag() != 0) {
1339     if (object_filter() == JVMTI_HEAP_OBJECT_UNTAGGED) return;
1340   } else {
1341     if (object_filter() == JVMTI_HEAP_OBJECT_TAGGED) return;
1342   }
1343 
1344   // invoke the agent's callback
1345   jvmtiIterationControl control = (*object_callback())(wrapper.klass_tag(),
1346                                                        wrapper.obj_size(),
1347                                                        wrapper.obj_tag_p(),
1348                                                        (void*)user_data());
1349   if (control == JVMTI_ITERATION_ABORT) {
1350     set_iteration_aborted(true);
1351   }
1352 }
1353 
1354 // An ObjectClosure used to support the IterateThroughHeap function
1355 class IterateThroughHeapObjectClosure: public ObjectClosure {
1356  private:
1357   JvmtiTagMap* _tag_map;
1358   Klass* _klass;
1359   int _heap_filter;
1360   const jvmtiHeapCallbacks* _callbacks;
1361   const void* _user_data;
1362 
1363   // accessor functions
1364   JvmtiTagMap* tag_map() const                     { return _tag_map; }
1365   int heap_filter() const                          { return _heap_filter; }
1366   const jvmtiHeapCallbacks* callbacks() const      { return _callbacks; }
1367   Klass* klass() const                             { return _klass; }
1368   const void* user_data() const                    { return _user_data; }
1369 
1370   // indicates if the iteration has been aborted
1371   bool _iteration_aborted;
1372   bool is_iteration_aborted() const                { return _iteration_aborted; }
1373 
1374   // used to check the visit control flags. If the abort flag is set
1375   // then we set the iteration aborted flag so that the iteration completes
1376   // without processing any further objects
1377   bool check_flags_for_abort(jint flags) {
1378     bool is_abort = (flags & JVMTI_VISIT_ABORT) != 0;
1379     if (is_abort) {
1380       _iteration_aborted = true;
1381     }
1382     return is_abort;
1383   }
1384 
1385  public:
1386   IterateThroughHeapObjectClosure(JvmtiTagMap* tag_map,
1387                                   Klass* klass,
1388                                   int heap_filter,
1389                                   const jvmtiHeapCallbacks* heap_callbacks,
1390                                   const void* user_data) :
1391     _tag_map(tag_map),
1392     _klass(klass),
1393     _heap_filter(heap_filter),
1394     _callbacks(heap_callbacks),
1395     _user_data(user_data),
1396     _iteration_aborted(false)
1397   {
1398   }
1399 
1400   void do_object(oop o);
1401 };
1402 
1403 // invoked for each object in the heap
1404 void IterateThroughHeapObjectClosure::do_object(oop obj) {
1405   // check if iteration has been halted
1406   if (is_iteration_aborted()) return;
1407 
1408   // apply class filter
1409   if (is_filtered_by_klass_filter(obj, klass())) return;
1410 
1411   // prepare for callback
1412   CallbackWrapper wrapper(tag_map(), obj);
1413 
1414   // check if filtered by the heap filter
1415   if (is_filtered_by_heap_filter(wrapper.obj_tag(), wrapper.klass_tag(), heap_filter())) {
1416     return;
1417   }
1418 
1419   // for arrays we need the length, otherwise -1
1420   bool is_array = obj->is_array();
1421   int len = is_array ? arrayOop(obj)->length() : -1;
1422 
1423   // invoke the object callback (if callback is provided)
1424   if (callbacks()->heap_iteration_callback != NULL) {
1425     jvmtiHeapIterationCallback cb = callbacks()->heap_iteration_callback;
1426     jint res = (*cb)(wrapper.klass_tag(),
1427                      wrapper.obj_size(),
1428                      wrapper.obj_tag_p(),
1429                      (jint)len,
1430                      (void*)user_data());
1431     if (check_flags_for_abort(res)) return;
1432   }
1433 
1434   // for objects and classes we report primitive fields if callback provided
1435   if (callbacks()->primitive_field_callback != NULL && obj->is_instance()) {
1436     jint res;
1437     jvmtiPrimitiveFieldCallback cb = callbacks()->primitive_field_callback;
1438     if (obj->klass() == SystemDictionary::Class_klass()) {
1439       res = invoke_primitive_field_callback_for_static_fields(&wrapper,
1440                                                                     obj,
1441                                                                     cb,
1442                                                                     (void*)user_data());
1443     } else {
1444       res = invoke_primitive_field_callback_for_instance_fields(&wrapper,
1445                                                                       obj,
1446                                                                       cb,
1447                                                                       (void*)user_data());
1448     }
1449     if (check_flags_for_abort(res)) return;
1450   }
1451 
1452   // string callback
1453   if (!is_array &&
1454       callbacks()->string_primitive_value_callback != NULL &&
1455       obj->klass() == SystemDictionary::String_klass()) {
1456     jint res = invoke_string_value_callback(
1457                 callbacks()->string_primitive_value_callback,
1458                 &wrapper,
1459                 obj,
1460                 (void*)user_data() );
1461     if (check_flags_for_abort(res)) return;
1462   }
1463 
1464   // array callback
1465   if (is_array &&
1466       callbacks()->array_primitive_value_callback != NULL &&
1467       obj->is_typeArray()) {
1468     jint res = invoke_array_primitive_value_callback(
1469                callbacks()->array_primitive_value_callback,
1470                &wrapper,
1471                obj,
1472                (void*)user_data() );
1473     if (check_flags_for_abort(res)) return;
1474   }
1475 };
1476 
1477 
1478 // Deprecated function to iterate over all objects in the heap
1479 void JvmtiTagMap::iterate_over_heap(jvmtiHeapObjectFilter object_filter,
1480                                     Klass* klass,
1481                                     jvmtiHeapObjectCallback heap_object_callback,
1482                                     const void* user_data)
1483 {
1484   MutexLocker ml(Heap_lock);
1485   IterateOverHeapObjectClosure blk(this,
1486                                    klass,
1487                                    object_filter,
1488                                    heap_object_callback,
1489                                    user_data);
1490   VM_HeapIterateOperation op(&blk);
1491   VMThread::execute(&op);
1492 }
1493 
1494 
1495 // Iterates over all objects in the heap
1496 void JvmtiTagMap::iterate_through_heap(jint heap_filter,
1497                                        Klass* klass,
1498                                        const jvmtiHeapCallbacks* callbacks,
1499                                        const void* user_data)
1500 {
1501   MutexLocker ml(Heap_lock);
1502   IterateThroughHeapObjectClosure blk(this,
1503                                       klass,
1504                                       heap_filter,
1505                                       callbacks,
1506                                       user_data);
1507   VM_HeapIterateOperation op(&blk);
1508   VMThread::execute(&op);
1509 }
1510 
1511 // support class for get_objects_with_tags
1512 
1513 class TagObjectCollector : public JvmtiTagHashmapEntryClosure {
1514  private:
1515   JvmtiEnv* _env;
1516   jlong* _tags;
1517   jint _tag_count;
1518 
1519   GrowableArray<jobject>* _object_results;  // collected objects (JNI weak refs)
1520   GrowableArray<uint64_t>* _tag_results;    // collected tags
1521 
1522  public:
1523   TagObjectCollector(JvmtiEnv* env, const jlong* tags, jint tag_count) {
1524     _env = env;
1525     _tags = (jlong*)tags;
1526     _tag_count = tag_count;
1527     _object_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jobject>(1,true);
1528     _tag_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<uint64_t>(1,true);
1529   }
1530 
1531   ~TagObjectCollector() {
1532     delete _object_results;
1533     delete _tag_results;
1534   }
1535 
1536   // for each tagged object check if the tag value matches
1537   // - if it matches then we create a JNI local reference to the object
1538   // and record the reference and tag value.
1539   //
1540   void do_entry(JvmtiTagHashmapEntry* entry) {
1541     for (int i=0; i<_tag_count; i++) {
1542       if (_tags[i] == entry->tag()) {
1543         // The reference in this tag map could be the only (implicitly weak)
1544         // reference to that object. If we hand it out, we need to keep it live wrt
1545         // SATB marking similar to other j.l.ref.Reference referents. This is
1546         // achieved by using a phantom load in the object() accessor.
1547         oop o = entry->object();
1548         assert(o != NULL && Universe::heap()->is_in_reserved(o), "sanity check");
1549         jobject ref = JNIHandles::make_local(JavaThread::current(), o);
1550         _object_results->append(ref);
1551         _tag_results->append((uint64_t)entry->tag());
1552       }
1553     }
1554   }
1555 
1556   // return the results from the collection
1557   //
1558   jvmtiError result(jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1559     jvmtiError error;
1560     int count = _object_results->length();
1561     assert(count >= 0, "sanity check");
1562 
1563     // if object_result_ptr is not NULL then allocate the result and copy
1564     // in the object references.
1565     if (object_result_ptr != NULL) {
1566       error = _env->Allocate(count * sizeof(jobject), (unsigned char**)object_result_ptr);
1567       if (error != JVMTI_ERROR_NONE) {
1568         return error;
1569       }
1570       for (int i=0; i<count; i++) {
1571         (*object_result_ptr)[i] = _object_results->at(i);
1572       }
1573     }
1574 
1575     // if tag_result_ptr is not NULL then allocate the result and copy
1576     // in the tag values.
1577     if (tag_result_ptr != NULL) {
1578       error = _env->Allocate(count * sizeof(jlong), (unsigned char**)tag_result_ptr);
1579       if (error != JVMTI_ERROR_NONE) {
1580         if (object_result_ptr != NULL) {
1581           _env->Deallocate((unsigned char*)object_result_ptr);
1582         }
1583         return error;
1584       }
1585       for (int i=0; i<count; i++) {
1586         (*tag_result_ptr)[i] = (jlong)_tag_results->at(i);
1587       }
1588     }
1589 
1590     *count_ptr = count;
1591     return JVMTI_ERROR_NONE;
1592   }
1593 };
1594 
1595 // return the list of objects with the specified tags
1596 jvmtiError JvmtiTagMap::get_objects_with_tags(const jlong* tags,
1597   jint count, jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1598 
1599   TagObjectCollector collector(env(), tags, count);
1600   {
1601     // iterate over all tagged objects
1602     MutexLocker ml(lock());
1603     entry_iterate(&collector);
1604   }
1605   return collector.result(count_ptr, object_result_ptr, tag_result_ptr);
1606 }
1607 
1608 
1609 // ObjectMarker is used to support the marking objects when walking the
1610 // heap.
1611 //
1612 // This implementation uses the existing mark bits in an object for
1613 // marking. Objects that are marked must later have their headers restored.
1614 // As most objects are unlocked and don't have their identity hash computed
1615 // we don't have to save their headers. Instead we save the headers that
1616 // are "interesting". Later when the headers are restored this implementation
1617 // restores all headers to their initial value and then restores the few
1618 // objects that had interesting headers.
1619 //
1620 // Future work: This implementation currently uses growable arrays to save
1621 // the oop and header of interesting objects. As an optimization we could
1622 // use the same technique as the GC and make use of the unused area
1623 // between top() and end().
1624 //
1625 
1626 // An ObjectClosure used to restore the mark bits of an object
1627 class RestoreMarksClosure : public ObjectClosure {
1628  public:
1629   void do_object(oop o) {
1630     if (o != NULL) {
1631       markWord mark = o->mark();
1632       if (mark.is_marked()) {
1633         o->init_mark();
1634       }
1635     }
1636   }
1637 };
1638 
1639 // ObjectMarker provides the mark and visited functions
1640 class ObjectMarker : AllStatic {
1641  private:
1642   // saved headers
1643   static GrowableArray<oop>* _saved_oop_stack;
1644   static GrowableArray<markWord>* _saved_mark_stack;
1645   static bool _needs_reset;                  // do we need to reset mark bits?
1646 
1647  public:
1648   static void init();                       // initialize
1649   static void done();                       // clean-up
1650 
1651   static inline void mark(oop o);           // mark an object
1652   static inline bool visited(oop o);        // check if object has been visited
1653 
1654   static inline bool needs_reset()            { return _needs_reset; }
1655   static inline void set_needs_reset(bool v)  { _needs_reset = v; }
1656 };
1657 
1658 GrowableArray<oop>* ObjectMarker::_saved_oop_stack = NULL;
1659 GrowableArray<markWord>* ObjectMarker::_saved_mark_stack = NULL;
1660 bool ObjectMarker::_needs_reset = true;  // need to reset mark bits by default
1661 
1662 // initialize ObjectMarker - prepares for object marking
1663 void ObjectMarker::init() {
1664   assert(Thread::current()->is_VM_thread(), "must be VMThread");
1665 
1666   // prepare heap for iteration
1667   Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1668 
1669   // create stacks for interesting headers
1670   _saved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markWord>(4000, true);
1671   _saved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(4000, true);
1672 
1673   if (UseBiasedLocking) {
1674     BiasedLocking::preserve_marks();
1675   }
1676 }
1677 
1678 // Object marking is done so restore object headers
1679 void ObjectMarker::done() {
1680   // iterate over all objects and restore the mark bits to
1681   // their initial value
1682   RestoreMarksClosure blk;
1683   if (needs_reset()) {
1684     Universe::heap()->object_iterate(&blk);
1685   } else {
1686     // We don't need to reset mark bits on this call, but reset the
1687     // flag to the default for the next call.
1688     set_needs_reset(true);
1689   }
1690 
1691   // now restore the interesting headers
1692   for (int i = 0; i < _saved_oop_stack->length(); i++) {
1693     oop o = _saved_oop_stack->at(i);
1694     markWord mark = _saved_mark_stack->at(i);
1695     o->set_mark(mark);
1696   }
1697 
1698   if (UseBiasedLocking) {
1699     BiasedLocking::restore_marks();
1700   }
1701 
1702   // free the stacks
1703   delete _saved_oop_stack;
1704   delete _saved_mark_stack;
1705 }
1706 
1707 // mark an object
1708 inline void ObjectMarker::mark(oop o) {
1709   assert(Universe::heap()->is_in(o), "sanity check");
1710   assert(!o->mark().is_marked(), "should only mark an object once");
1711 
1712   // object's mark word
1713   markWord mark = o->mark();
1714 
1715   if (o->mark_must_be_preserved(mark)) {
1716     _saved_mark_stack->push(mark);
1717     _saved_oop_stack->push(o);
1718   }
1719 
1720   // mark the object
1721   o->set_mark(markWord::prototype().set_marked());
1722 }
1723 
1724 // return true if object is marked
1725 inline bool ObjectMarker::visited(oop o) {
1726   return o->mark().is_marked();
1727 }
1728 
1729 // Stack allocated class to help ensure that ObjectMarker is used
1730 // correctly. Constructor initializes ObjectMarker, destructor calls
1731 // ObjectMarker's done() function to restore object headers.
1732 class ObjectMarkerController : public StackObj {
1733  public:
1734   ObjectMarkerController() {
1735     ObjectMarker::init();
1736   }
1737   ~ObjectMarkerController() {
1738     ObjectMarker::done();
1739   }
1740 };
1741 
1742 
1743 // helper to map a jvmtiHeapReferenceKind to an old style jvmtiHeapRootKind
1744 // (not performance critical as only used for roots)
1745 static jvmtiHeapRootKind toJvmtiHeapRootKind(jvmtiHeapReferenceKind kind) {
1746   switch (kind) {
1747     case JVMTI_HEAP_REFERENCE_JNI_GLOBAL:   return JVMTI_HEAP_ROOT_JNI_GLOBAL;
1748     case JVMTI_HEAP_REFERENCE_SYSTEM_CLASS: return JVMTI_HEAP_ROOT_SYSTEM_CLASS;
1749     case JVMTI_HEAP_REFERENCE_MONITOR:      return JVMTI_HEAP_ROOT_MONITOR;
1750     case JVMTI_HEAP_REFERENCE_STACK_LOCAL:  return JVMTI_HEAP_ROOT_STACK_LOCAL;
1751     case JVMTI_HEAP_REFERENCE_JNI_LOCAL:    return JVMTI_HEAP_ROOT_JNI_LOCAL;
1752     case JVMTI_HEAP_REFERENCE_THREAD:       return JVMTI_HEAP_ROOT_THREAD;
1753     case JVMTI_HEAP_REFERENCE_OTHER:        return JVMTI_HEAP_ROOT_OTHER;
1754     default: ShouldNotReachHere();          return JVMTI_HEAP_ROOT_OTHER;
1755   }
1756 }
1757 
1758 // Base class for all heap walk contexts. The base class maintains a flag
1759 // to indicate if the context is valid or not.
1760 class HeapWalkContext {
1761  private:
1762   bool _valid;
1763  public:
1764   HeapWalkContext(bool valid)                   { _valid = valid; }
1765   void invalidate()                             { _valid = false; }
1766   bool is_valid() const                         { return _valid; }
1767 };
1768 
1769 // A basic heap walk context for the deprecated heap walking functions.
1770 // The context for a basic heap walk are the callbacks and fields used by
1771 // the referrer caching scheme.
1772 class BasicHeapWalkContext: public HeapWalkContext {
1773  private:
1774   jvmtiHeapRootCallback _heap_root_callback;
1775   jvmtiStackReferenceCallback _stack_ref_callback;
1776   jvmtiObjectReferenceCallback _object_ref_callback;
1777 
1778   // used for caching
1779   oop _last_referrer;
1780   jlong _last_referrer_tag;
1781 
1782  public:
1783   BasicHeapWalkContext() : HeapWalkContext(false) { }
1784 
1785   BasicHeapWalkContext(jvmtiHeapRootCallback heap_root_callback,
1786                        jvmtiStackReferenceCallback stack_ref_callback,
1787                        jvmtiObjectReferenceCallback object_ref_callback) :
1788     HeapWalkContext(true),
1789     _heap_root_callback(heap_root_callback),
1790     _stack_ref_callback(stack_ref_callback),
1791     _object_ref_callback(object_ref_callback),
1792     _last_referrer(NULL),
1793     _last_referrer_tag(0) {
1794   }
1795 
1796   // accessors
1797   jvmtiHeapRootCallback heap_root_callback() const         { return _heap_root_callback; }
1798   jvmtiStackReferenceCallback stack_ref_callback() const   { return _stack_ref_callback; }
1799   jvmtiObjectReferenceCallback object_ref_callback() const { return _object_ref_callback;  }
1800 
1801   oop last_referrer() const               { return _last_referrer; }
1802   void set_last_referrer(oop referrer)    { _last_referrer = referrer; }
1803   jlong last_referrer_tag() const         { return _last_referrer_tag; }
1804   void set_last_referrer_tag(jlong value) { _last_referrer_tag = value; }
1805 };
1806 
1807 // The advanced heap walk context for the FollowReferences functions.
1808 // The context is the callbacks, and the fields used for filtering.
1809 class AdvancedHeapWalkContext: public HeapWalkContext {
1810  private:
1811   jint _heap_filter;
1812   Klass* _klass_filter;
1813   const jvmtiHeapCallbacks* _heap_callbacks;
1814 
1815  public:
1816   AdvancedHeapWalkContext() : HeapWalkContext(false) { }
1817 
1818   AdvancedHeapWalkContext(jint heap_filter,
1819                            Klass* klass_filter,
1820                            const jvmtiHeapCallbacks* heap_callbacks) :
1821     HeapWalkContext(true),
1822     _heap_filter(heap_filter),
1823     _klass_filter(klass_filter),
1824     _heap_callbacks(heap_callbacks) {
1825   }
1826 
1827   // accessors
1828   jint heap_filter() const         { return _heap_filter; }
1829   Klass* klass_filter() const      { return _klass_filter; }
1830 
1831   const jvmtiHeapReferenceCallback heap_reference_callback() const {
1832     return _heap_callbacks->heap_reference_callback;
1833   };
1834   const jvmtiPrimitiveFieldCallback primitive_field_callback() const {
1835     return _heap_callbacks->primitive_field_callback;
1836   }
1837   const jvmtiArrayPrimitiveValueCallback array_primitive_value_callback() const {
1838     return _heap_callbacks->array_primitive_value_callback;
1839   }
1840   const jvmtiStringPrimitiveValueCallback string_primitive_value_callback() const {
1841     return _heap_callbacks->string_primitive_value_callback;
1842   }
1843 };
1844 
1845 // The CallbackInvoker is a class with static functions that the heap walk can call
1846 // into to invoke callbacks. It works in one of two modes. The "basic" mode is
1847 // used for the deprecated IterateOverReachableObjects functions. The "advanced"
1848 // mode is for the newer FollowReferences function which supports a lot of
1849 // additional callbacks.
1850 class CallbackInvoker : AllStatic {
1851  private:
1852   // heap walk styles
1853   enum { basic, advanced };
1854   static int _heap_walk_type;
1855   static bool is_basic_heap_walk()           { return _heap_walk_type == basic; }
1856   static bool is_advanced_heap_walk()        { return _heap_walk_type == advanced; }
1857 
1858   // context for basic style heap walk
1859   static BasicHeapWalkContext _basic_context;
1860   static BasicHeapWalkContext* basic_context() {
1861     assert(_basic_context.is_valid(), "invalid");
1862     return &_basic_context;
1863   }
1864 
1865   // context for advanced style heap walk
1866   static AdvancedHeapWalkContext _advanced_context;
1867   static AdvancedHeapWalkContext* advanced_context() {
1868     assert(_advanced_context.is_valid(), "invalid");
1869     return &_advanced_context;
1870   }
1871 
1872   // context needed for all heap walks
1873   static JvmtiTagMap* _tag_map;
1874   static const void* _user_data;
1875   static GrowableArray<oop>* _visit_stack;
1876 
1877   // accessors
1878   static JvmtiTagMap* tag_map()                        { return _tag_map; }
1879   static const void* user_data()                       { return _user_data; }
1880   static GrowableArray<oop>* visit_stack()             { return _visit_stack; }
1881 
1882   // if the object hasn't been visited then push it onto the visit stack
1883   // so that it will be visited later
1884   static inline bool check_for_visit(oop obj) {
1885     if (!ObjectMarker::visited(obj)) visit_stack()->push(obj);
1886     return true;
1887   }
1888 
1889   // invoke basic style callbacks
1890   static inline bool invoke_basic_heap_root_callback
1891     (jvmtiHeapRootKind root_kind, oop obj);
1892   static inline bool invoke_basic_stack_ref_callback
1893     (jvmtiHeapRootKind root_kind, jlong thread_tag, jint depth, jmethodID method,
1894      int slot, oop obj);
1895   static inline bool invoke_basic_object_reference_callback
1896     (jvmtiObjectReferenceKind ref_kind, oop referrer, oop referree, jint index);
1897 
1898   // invoke advanced style callbacks
1899   static inline bool invoke_advanced_heap_root_callback
1900     (jvmtiHeapReferenceKind ref_kind, oop obj);
1901   static inline bool invoke_advanced_stack_ref_callback
1902     (jvmtiHeapReferenceKind ref_kind, jlong thread_tag, jlong tid, int depth,
1903      jmethodID method, jlocation bci, jint slot, oop obj);
1904   static inline bool invoke_advanced_object_reference_callback
1905     (jvmtiHeapReferenceKind ref_kind, oop referrer, oop referree, jint index);
1906 
1907   // used to report the value of primitive fields
1908   static inline bool report_primitive_field
1909     (jvmtiHeapReferenceKind ref_kind, oop obj, jint index, address addr, char type);
1910 
1911  public:
1912   // initialize for basic mode
1913   static void initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1914                                              GrowableArray<oop>* visit_stack,
1915                                              const void* user_data,
1916                                              BasicHeapWalkContext context);
1917 
1918   // initialize for advanced mode
1919   static void initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1920                                                 GrowableArray<oop>* visit_stack,
1921                                                 const void* user_data,
1922                                                 AdvancedHeapWalkContext context);
1923 
1924    // functions to report roots
1925   static inline bool report_simple_root(jvmtiHeapReferenceKind kind, oop o);
1926   static inline bool report_jni_local_root(jlong thread_tag, jlong tid, jint depth,
1927     jmethodID m, oop o);
1928   static inline bool report_stack_ref_root(jlong thread_tag, jlong tid, jint depth,
1929     jmethodID method, jlocation bci, jint slot, oop o);
1930 
1931   // functions to report references
1932   static inline bool report_array_element_reference(oop referrer, oop referree, jint index);
1933   static inline bool report_class_reference(oop referrer, oop referree);
1934   static inline bool report_class_loader_reference(oop referrer, oop referree);
1935   static inline bool report_signers_reference(oop referrer, oop referree);
1936   static inline bool report_protection_domain_reference(oop referrer, oop referree);
1937   static inline bool report_superclass_reference(oop referrer, oop referree);
1938   static inline bool report_interface_reference(oop referrer, oop referree);
1939   static inline bool report_static_field_reference(oop referrer, oop referree, jint slot);
1940   static inline bool report_field_reference(oop referrer, oop referree, jint slot);
1941   static inline bool report_constant_pool_reference(oop referrer, oop referree, jint index);
1942   static inline bool report_primitive_array_values(oop array);
1943   static inline bool report_string_value(oop str);
1944   static inline bool report_primitive_instance_field(oop o, jint index, address value, char type);
1945   static inline bool report_primitive_static_field(oop o, jint index, address value, char type);
1946 };
1947 
1948 // statics
1949 int CallbackInvoker::_heap_walk_type;
1950 BasicHeapWalkContext CallbackInvoker::_basic_context;
1951 AdvancedHeapWalkContext CallbackInvoker::_advanced_context;
1952 JvmtiTagMap* CallbackInvoker::_tag_map;
1953 const void* CallbackInvoker::_user_data;
1954 GrowableArray<oop>* CallbackInvoker::_visit_stack;
1955 
1956 // initialize for basic heap walk (IterateOverReachableObjects et al)
1957 void CallbackInvoker::initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1958                                                      GrowableArray<oop>* visit_stack,
1959                                                      const void* user_data,
1960                                                      BasicHeapWalkContext context) {
1961   _tag_map = tag_map;
1962   _visit_stack = visit_stack;
1963   _user_data = user_data;
1964   _basic_context = context;
1965   _advanced_context.invalidate();       // will trigger assertion if used
1966   _heap_walk_type = basic;
1967 }
1968 
1969 // initialize for advanced heap walk (FollowReferences)
1970 void CallbackInvoker::initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1971                                                         GrowableArray<oop>* visit_stack,
1972                                                         const void* user_data,
1973                                                         AdvancedHeapWalkContext context) {
1974   _tag_map = tag_map;
1975   _visit_stack = visit_stack;
1976   _user_data = user_data;
1977   _advanced_context = context;
1978   _basic_context.invalidate();      // will trigger assertion if used
1979   _heap_walk_type = advanced;
1980 }
1981 
1982 
1983 // invoke basic style heap root callback
1984 inline bool CallbackInvoker::invoke_basic_heap_root_callback(jvmtiHeapRootKind root_kind, oop obj) {
1985   // if we heap roots should be reported
1986   jvmtiHeapRootCallback cb = basic_context()->heap_root_callback();
1987   if (cb == NULL) {
1988     return check_for_visit(obj);
1989   }
1990 
1991   CallbackWrapper wrapper(tag_map(), obj);
1992   jvmtiIterationControl control = (*cb)(root_kind,
1993                                         wrapper.klass_tag(),
1994                                         wrapper.obj_size(),
1995                                         wrapper.obj_tag_p(),
1996                                         (void*)user_data());
1997   // push root to visit stack when following references
1998   if (control == JVMTI_ITERATION_CONTINUE &&
1999       basic_context()->object_ref_callback() != NULL) {
2000     visit_stack()->push(obj);
2001   }
2002   return control != JVMTI_ITERATION_ABORT;
2003 }
2004 
2005 // invoke basic style stack ref callback
2006 inline bool CallbackInvoker::invoke_basic_stack_ref_callback(jvmtiHeapRootKind root_kind,
2007                                                              jlong thread_tag,
2008                                                              jint depth,
2009                                                              jmethodID method,
2010                                                              int slot,
2011                                                              oop obj) {
2012   // if we stack refs should be reported
2013   jvmtiStackReferenceCallback cb = basic_context()->stack_ref_callback();
2014   if (cb == NULL) {
2015     return check_for_visit(obj);
2016   }
2017 
2018   CallbackWrapper wrapper(tag_map(), obj);
2019   jvmtiIterationControl control = (*cb)(root_kind,
2020                                         wrapper.klass_tag(),
2021                                         wrapper.obj_size(),
2022                                         wrapper.obj_tag_p(),
2023                                         thread_tag,
2024                                         depth,
2025                                         method,
2026                                         slot,
2027                                         (void*)user_data());
2028   // push root to visit stack when following references
2029   if (control == JVMTI_ITERATION_CONTINUE &&
2030       basic_context()->object_ref_callback() != NULL) {
2031     visit_stack()->push(obj);
2032   }
2033   return control != JVMTI_ITERATION_ABORT;
2034 }
2035 
2036 // invoke basic style object reference callback
2037 inline bool CallbackInvoker::invoke_basic_object_reference_callback(jvmtiObjectReferenceKind ref_kind,
2038                                                                     oop referrer,
2039                                                                     oop referree,
2040                                                                     jint index) {
2041 
2042   BasicHeapWalkContext* context = basic_context();
2043 
2044   // callback requires the referrer's tag. If it's the same referrer
2045   // as the last call then we use the cached value.
2046   jlong referrer_tag;
2047   if (referrer == context->last_referrer()) {
2048     referrer_tag = context->last_referrer_tag();
2049   } else {
2050     referrer_tag = tag_for(tag_map(), referrer);
2051   }
2052 
2053   // do the callback
2054   CallbackWrapper wrapper(tag_map(), referree);
2055   jvmtiObjectReferenceCallback cb = context->object_ref_callback();
2056   jvmtiIterationControl control = (*cb)(ref_kind,
2057                                         wrapper.klass_tag(),
2058                                         wrapper.obj_size(),
2059                                         wrapper.obj_tag_p(),
2060                                         referrer_tag,
2061                                         index,
2062                                         (void*)user_data());
2063 
2064   // record referrer and referrer tag. For self-references record the
2065   // tag value from the callback as this might differ from referrer_tag.
2066   context->set_last_referrer(referrer);
2067   if (referrer == referree) {
2068     context->set_last_referrer_tag(*wrapper.obj_tag_p());
2069   } else {
2070     context->set_last_referrer_tag(referrer_tag);
2071   }
2072 
2073   if (control == JVMTI_ITERATION_CONTINUE) {
2074     return check_for_visit(referree);
2075   } else {
2076     return control != JVMTI_ITERATION_ABORT;
2077   }
2078 }
2079 
2080 // invoke advanced style heap root callback
2081 inline bool CallbackInvoker::invoke_advanced_heap_root_callback(jvmtiHeapReferenceKind ref_kind,
2082                                                                 oop obj) {
2083   AdvancedHeapWalkContext* context = advanced_context();
2084 
2085   // check that callback is provided
2086   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2087   if (cb == NULL) {
2088     return check_for_visit(obj);
2089   }
2090 
2091   // apply class filter
2092   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2093     return check_for_visit(obj);
2094   }
2095 
2096   // setup the callback wrapper
2097   CallbackWrapper wrapper(tag_map(), obj);
2098 
2099   // apply tag filter
2100   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2101                                  wrapper.klass_tag(),
2102                                  context->heap_filter())) {
2103     return check_for_visit(obj);
2104   }
2105 
2106   // for arrays we need the length, otherwise -1
2107   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2108 
2109   // invoke the callback
2110   jint res  = (*cb)(ref_kind,
2111                     NULL, // referrer info
2112                     wrapper.klass_tag(),
2113                     0,    // referrer_class_tag is 0 for heap root
2114                     wrapper.obj_size(),
2115                     wrapper.obj_tag_p(),
2116                     NULL, // referrer_tag_p
2117                     len,
2118                     (void*)user_data());
2119   if (res & JVMTI_VISIT_ABORT) {
2120     return false;// referrer class tag
2121   }
2122   if (res & JVMTI_VISIT_OBJECTS) {
2123     check_for_visit(obj);
2124   }
2125   return true;
2126 }
2127 
2128 // report a reference from a thread stack to an object
2129 inline bool CallbackInvoker::invoke_advanced_stack_ref_callback(jvmtiHeapReferenceKind ref_kind,
2130                                                                 jlong thread_tag,
2131                                                                 jlong tid,
2132                                                                 int depth,
2133                                                                 jmethodID method,
2134                                                                 jlocation bci,
2135                                                                 jint slot,
2136                                                                 oop obj) {
2137   AdvancedHeapWalkContext* context = advanced_context();
2138 
2139   // check that callback is provider
2140   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2141   if (cb == NULL) {
2142     return check_for_visit(obj);
2143   }
2144 
2145   // apply class filter
2146   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2147     return check_for_visit(obj);
2148   }
2149 
2150   // setup the callback wrapper
2151   CallbackWrapper wrapper(tag_map(), obj);
2152 
2153   // apply tag filter
2154   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2155                                  wrapper.klass_tag(),
2156                                  context->heap_filter())) {
2157     return check_for_visit(obj);
2158   }
2159 
2160   // setup the referrer info
2161   jvmtiHeapReferenceInfo reference_info;
2162   reference_info.stack_local.thread_tag = thread_tag;
2163   reference_info.stack_local.thread_id = tid;
2164   reference_info.stack_local.depth = depth;
2165   reference_info.stack_local.method = method;
2166   reference_info.stack_local.location = bci;
2167   reference_info.stack_local.slot = slot;
2168 
2169   // for arrays we need the length, otherwise -1
2170   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2171 
2172   // call into the agent
2173   int res = (*cb)(ref_kind,
2174                   &reference_info,
2175                   wrapper.klass_tag(),
2176                   0,    // referrer_class_tag is 0 for heap root (stack)
2177                   wrapper.obj_size(),
2178                   wrapper.obj_tag_p(),
2179                   NULL, // referrer_tag is 0 for root
2180                   len,
2181                   (void*)user_data());
2182 
2183   if (res & JVMTI_VISIT_ABORT) {
2184     return false;
2185   }
2186   if (res & JVMTI_VISIT_OBJECTS) {
2187     check_for_visit(obj);
2188   }
2189   return true;
2190 }
2191 
2192 // This mask is used to pass reference_info to a jvmtiHeapReferenceCallback
2193 // only for ref_kinds defined by the JVM TI spec. Otherwise, NULL is passed.
2194 #define REF_INFO_MASK  ((1 << JVMTI_HEAP_REFERENCE_FIELD)         \
2195                       | (1 << JVMTI_HEAP_REFERENCE_STATIC_FIELD)  \
2196                       | (1 << JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT) \
2197                       | (1 << JVMTI_HEAP_REFERENCE_CONSTANT_POOL) \
2198                       | (1 << JVMTI_HEAP_REFERENCE_STACK_LOCAL)   \
2199                       | (1 << JVMTI_HEAP_REFERENCE_JNI_LOCAL))
2200 
2201 // invoke the object reference callback to report a reference
2202 inline bool CallbackInvoker::invoke_advanced_object_reference_callback(jvmtiHeapReferenceKind ref_kind,
2203                                                                        oop referrer,
2204                                                                        oop obj,
2205                                                                        jint index)
2206 {
2207   // field index is only valid field in reference_info
2208   static jvmtiHeapReferenceInfo reference_info = { 0 };
2209 
2210   AdvancedHeapWalkContext* context = advanced_context();
2211 
2212   // check that callback is provider
2213   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2214   if (cb == NULL) {
2215     return check_for_visit(obj);
2216   }
2217 
2218   // apply class filter
2219   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2220     return check_for_visit(obj);
2221   }
2222 
2223   // setup the callback wrapper
2224   TwoOopCallbackWrapper wrapper(tag_map(), referrer, obj);
2225 
2226   // apply tag filter
2227   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2228                                  wrapper.klass_tag(),
2229                                  context->heap_filter())) {
2230     return check_for_visit(obj);
2231   }
2232 
2233   // field index is only valid field in reference_info
2234   reference_info.field.index = index;
2235 
2236   // for arrays we need the length, otherwise -1
2237   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2238 
2239   // invoke the callback
2240   int res = (*cb)(ref_kind,
2241                   (REF_INFO_MASK & (1 << ref_kind)) ? &reference_info : NULL,
2242                   wrapper.klass_tag(),
2243                   wrapper.referrer_klass_tag(),
2244                   wrapper.obj_size(),
2245                   wrapper.obj_tag_p(),
2246                   wrapper.referrer_tag_p(),
2247                   len,
2248                   (void*)user_data());
2249 
2250   if (res & JVMTI_VISIT_ABORT) {
2251     return false;
2252   }
2253   if (res & JVMTI_VISIT_OBJECTS) {
2254     check_for_visit(obj);
2255   }
2256   return true;
2257 }
2258 
2259 // report a "simple root"
2260 inline bool CallbackInvoker::report_simple_root(jvmtiHeapReferenceKind kind, oop obj) {
2261   assert(kind != JVMTI_HEAP_REFERENCE_STACK_LOCAL &&
2262          kind != JVMTI_HEAP_REFERENCE_JNI_LOCAL, "not a simple root");
2263 
2264   if (is_basic_heap_walk()) {
2265     // map to old style root kind
2266     jvmtiHeapRootKind root_kind = toJvmtiHeapRootKind(kind);
2267     return invoke_basic_heap_root_callback(root_kind, obj);
2268   } else {
2269     assert(is_advanced_heap_walk(), "wrong heap walk type");
2270     return invoke_advanced_heap_root_callback(kind, obj);
2271   }
2272 }
2273 
2274 
2275 // invoke the primitive array values
2276 inline bool CallbackInvoker::report_primitive_array_values(oop obj) {
2277   assert(obj->is_typeArray(), "not a primitive array");
2278 
2279   AdvancedHeapWalkContext* context = advanced_context();
2280   assert(context->array_primitive_value_callback() != NULL, "no callback");
2281 
2282   // apply class filter
2283   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2284     return true;
2285   }
2286 
2287   CallbackWrapper wrapper(tag_map(), obj);
2288 
2289   // apply tag filter
2290   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2291                                  wrapper.klass_tag(),
2292                                  context->heap_filter())) {
2293     return true;
2294   }
2295 
2296   // invoke the callback
2297   int res = invoke_array_primitive_value_callback(context->array_primitive_value_callback(),
2298                                                   &wrapper,
2299                                                   obj,
2300                                                   (void*)user_data());
2301   return (!(res & JVMTI_VISIT_ABORT));
2302 }
2303 
2304 // invoke the string value callback
2305 inline bool CallbackInvoker::report_string_value(oop str) {
2306   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
2307 
2308   AdvancedHeapWalkContext* context = advanced_context();
2309   assert(context->string_primitive_value_callback() != NULL, "no callback");
2310 
2311   // apply class filter
2312   if (is_filtered_by_klass_filter(str, context->klass_filter())) {
2313     return true;
2314   }
2315 
2316   CallbackWrapper wrapper(tag_map(), str);
2317 
2318   // apply tag filter
2319   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2320                                  wrapper.klass_tag(),
2321                                  context->heap_filter())) {
2322     return true;
2323   }
2324 
2325   // invoke the callback
2326   int res = invoke_string_value_callback(context->string_primitive_value_callback(),
2327                                          &wrapper,
2328                                          str,
2329                                          (void*)user_data());
2330   return (!(res & JVMTI_VISIT_ABORT));
2331 }
2332 
2333 // invoke the primitive field callback
2334 inline bool CallbackInvoker::report_primitive_field(jvmtiHeapReferenceKind ref_kind,
2335                                                     oop obj,
2336                                                     jint index,
2337                                                     address addr,
2338                                                     char type)
2339 {
2340   // for primitive fields only the index will be set
2341   static jvmtiHeapReferenceInfo reference_info = { 0 };
2342 
2343   AdvancedHeapWalkContext* context = advanced_context();
2344   assert(context->primitive_field_callback() != NULL, "no callback");
2345 
2346   // apply class filter
2347   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2348     return true;
2349   }
2350 
2351   CallbackWrapper wrapper(tag_map(), obj);
2352 
2353   // apply tag filter
2354   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2355                                  wrapper.klass_tag(),
2356                                  context->heap_filter())) {
2357     return true;
2358   }
2359 
2360   // the field index in the referrer
2361   reference_info.field.index = index;
2362 
2363   // map the type
2364   jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
2365 
2366   // setup the jvalue
2367   jvalue value;
2368   copy_to_jvalue(&value, addr, value_type);
2369 
2370   jvmtiPrimitiveFieldCallback cb = context->primitive_field_callback();
2371   int res = (*cb)(ref_kind,
2372                   &reference_info,
2373                   wrapper.klass_tag(),
2374                   wrapper.obj_tag_p(),
2375                   value,
2376                   value_type,
2377                   (void*)user_data());
2378   return (!(res & JVMTI_VISIT_ABORT));
2379 }
2380 
2381 
2382 // instance field
2383 inline bool CallbackInvoker::report_primitive_instance_field(oop obj,
2384                                                              jint index,
2385                                                              address value,
2386                                                              char type) {
2387   return report_primitive_field(JVMTI_HEAP_REFERENCE_FIELD,
2388                                 obj,
2389                                 index,
2390                                 value,
2391                                 type);
2392 }
2393 
2394 // static field
2395 inline bool CallbackInvoker::report_primitive_static_field(oop obj,
2396                                                            jint index,
2397                                                            address value,
2398                                                            char type) {
2399   return report_primitive_field(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
2400                                 obj,
2401                                 index,
2402                                 value,
2403                                 type);
2404 }
2405 
2406 // report a JNI local (root object) to the profiler
2407 inline bool CallbackInvoker::report_jni_local_root(jlong thread_tag, jlong tid, jint depth, jmethodID m, oop obj) {
2408   if (is_basic_heap_walk()) {
2409     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_JNI_LOCAL,
2410                                            thread_tag,
2411                                            depth,
2412                                            m,
2413                                            -1,
2414                                            obj);
2415   } else {
2416     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_JNI_LOCAL,
2417                                               thread_tag, tid,
2418                                               depth,
2419                                               m,
2420                                               (jlocation)-1,
2421                                               -1,
2422                                               obj);
2423   }
2424 }
2425 
2426 
2427 // report a local (stack reference, root object)
2428 inline bool CallbackInvoker::report_stack_ref_root(jlong thread_tag,
2429                                                    jlong tid,
2430                                                    jint depth,
2431                                                    jmethodID method,
2432                                                    jlocation bci,
2433                                                    jint slot,
2434                                                    oop obj) {
2435   if (is_basic_heap_walk()) {
2436     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_STACK_LOCAL,
2437                                            thread_tag,
2438                                            depth,
2439                                            method,
2440                                            slot,
2441                                            obj);
2442   } else {
2443     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_STACK_LOCAL,
2444                                               thread_tag,
2445                                               tid,
2446                                               depth,
2447                                               method,
2448                                               bci,
2449                                               slot,
2450                                               obj);
2451   }
2452 }
2453 
2454 // report an object referencing a class.
2455 inline bool CallbackInvoker::report_class_reference(oop referrer, oop referree) {
2456   if (is_basic_heap_walk()) {
2457     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2458   } else {
2459     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS, referrer, referree, -1);
2460   }
2461 }
2462 
2463 // report a class referencing its class loader.
2464 inline bool CallbackInvoker::report_class_loader_reference(oop referrer, oop referree) {
2465   if (is_basic_heap_walk()) {
2466     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2467   } else {
2468     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2469   }
2470 }
2471 
2472 // report a class referencing its signers.
2473 inline bool CallbackInvoker::report_signers_reference(oop referrer, oop referree) {
2474   if (is_basic_heap_walk()) {
2475     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_SIGNERS, referrer, referree, -1);
2476   } else {
2477     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SIGNERS, referrer, referree, -1);
2478   }
2479 }
2480 
2481 // report a class referencing its protection domain..
2482 inline bool CallbackInvoker::report_protection_domain_reference(oop referrer, oop referree) {
2483   if (is_basic_heap_walk()) {
2484     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2485   } else {
2486     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2487   }
2488 }
2489 
2490 // report a class referencing its superclass.
2491 inline bool CallbackInvoker::report_superclass_reference(oop referrer, oop referree) {
2492   if (is_basic_heap_walk()) {
2493     // Send this to be consistent with past implementation
2494     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2495   } else {
2496     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SUPERCLASS, referrer, referree, -1);
2497   }
2498 }
2499 
2500 // report a class referencing one of its interfaces.
2501 inline bool CallbackInvoker::report_interface_reference(oop referrer, oop referree) {
2502   if (is_basic_heap_walk()) {
2503     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_INTERFACE, referrer, referree, -1);
2504   } else {
2505     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_INTERFACE, referrer, referree, -1);
2506   }
2507 }
2508 
2509 // report a class referencing one of its static fields.
2510 inline bool CallbackInvoker::report_static_field_reference(oop referrer, oop referree, jint slot) {
2511   if (is_basic_heap_walk()) {
2512     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2513   } else {
2514     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2515   }
2516 }
2517 
2518 // report an array referencing an element object
2519 inline bool CallbackInvoker::report_array_element_reference(oop referrer, oop referree, jint index) {
2520   if (is_basic_heap_walk()) {
2521     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2522   } else {
2523     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2524   }
2525 }
2526 
2527 // report an object referencing an instance field object
2528 inline bool CallbackInvoker::report_field_reference(oop referrer, oop referree, jint slot) {
2529   if (is_basic_heap_walk()) {
2530     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_FIELD, referrer, referree, slot);
2531   } else {
2532     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_FIELD, referrer, referree, slot);
2533   }
2534 }
2535 
2536 // report an array referencing an element object
2537 inline bool CallbackInvoker::report_constant_pool_reference(oop referrer, oop referree, jint index) {
2538   if (is_basic_heap_walk()) {
2539     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2540   } else {
2541     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2542   }
2543 }
2544 
2545 // A supporting closure used to process simple roots
2546 class SimpleRootsClosure : public OopClosure {
2547  private:
2548   jvmtiHeapReferenceKind _kind;
2549   bool _continue;
2550 
2551   jvmtiHeapReferenceKind root_kind()    { return _kind; }
2552 
2553  public:
2554   void set_kind(jvmtiHeapReferenceKind kind) {
2555     _kind = kind;
2556     _continue = true;
2557   }
2558 
2559   inline bool stopped() {
2560     return !_continue;
2561   }
2562 
2563   void do_oop(oop* obj_p) {
2564     // iteration has terminated
2565     if (stopped()) {
2566       return;
2567     }
2568 
2569     oop o = NativeAccess<AS_NO_KEEPALIVE>::oop_load(obj_p);
2570     // ignore null
2571     if (o == NULL) {
2572       return;
2573     }
2574 
2575     assert(Universe::heap()->is_in_reserved(o), "should be impossible");
2576 
2577     jvmtiHeapReferenceKind kind = root_kind();
2578     if (kind == JVMTI_HEAP_REFERENCE_SYSTEM_CLASS) {
2579       // SystemDictionary::oops_do reports the application
2580       // class loader as a root. We want this root to be reported as
2581       // a root kind of "OTHER" rather than "SYSTEM_CLASS".
2582       if (!o->is_instance() || !InstanceKlass::cast(o->klass())->is_mirror_instance_klass()) {
2583         kind = JVMTI_HEAP_REFERENCE_OTHER;
2584       }
2585     }
2586 
2587     // invoke the callback
2588     _continue = CallbackInvoker::report_simple_root(kind, o);
2589 
2590   }
2591   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2592 };
2593 
2594 // A supporting closure used to process JNI locals
2595 class JNILocalRootsClosure : public OopClosure {
2596  private:
2597   jlong _thread_tag;
2598   jlong _tid;
2599   jint _depth;
2600   jmethodID _method;
2601   bool _continue;
2602  public:
2603   void set_context(jlong thread_tag, jlong tid, jint depth, jmethodID method) {
2604     _thread_tag = thread_tag;
2605     _tid = tid;
2606     _depth = depth;
2607     _method = method;
2608     _continue = true;
2609   }
2610 
2611   inline bool stopped() {
2612     return !_continue;
2613   }
2614 
2615   void do_oop(oop* obj_p) {
2616     // iteration has terminated
2617     if (stopped()) {
2618       return;
2619     }
2620 
2621     oop o = *obj_p;
2622     // ignore null
2623     if (o == NULL) {
2624       return;
2625     }
2626 
2627     // invoke the callback
2628     _continue = CallbackInvoker::report_jni_local_root(_thread_tag, _tid, _depth, _method, o);
2629   }
2630   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2631 };
2632 
2633 
2634 // A VM operation to iterate over objects that are reachable from
2635 // a set of roots or an initial object.
2636 //
2637 // For VM_HeapWalkOperation the set of roots used is :-
2638 //
2639 // - All JNI global references
2640 // - All inflated monitors
2641 // - All classes loaded by the boot class loader (or all classes
2642 //     in the event that class unloading is disabled)
2643 // - All java threads
2644 // - For each java thread then all locals and JNI local references
2645 //      on the thread's execution stack
2646 // - All visible/explainable objects from Universes::oops_do
2647 //
2648 class VM_HeapWalkOperation: public VM_Operation {
2649  private:
2650   enum {
2651     initial_visit_stack_size = 4000
2652   };
2653 
2654   bool _is_advanced_heap_walk;                      // indicates FollowReferences
2655   JvmtiTagMap* _tag_map;
2656   Handle _initial_object;
2657   GrowableArray<oop>* _visit_stack;                 // the visit stack
2658 
2659   bool _collecting_heap_roots;                      // are we collecting roots
2660   bool _following_object_refs;                      // are we following object references
2661 
2662   bool _reporting_primitive_fields;                 // optional reporting
2663   bool _reporting_primitive_array_values;
2664   bool _reporting_string_values;
2665 
2666   GrowableArray<oop>* create_visit_stack() {
2667     return new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(initial_visit_stack_size, true);
2668   }
2669 
2670   // accessors
2671   bool is_advanced_heap_walk() const               { return _is_advanced_heap_walk; }
2672   JvmtiTagMap* tag_map() const                     { return _tag_map; }
2673   Handle initial_object() const                    { return _initial_object; }
2674 
2675   bool is_following_references() const             { return _following_object_refs; }
2676 
2677   bool is_reporting_primitive_fields()  const      { return _reporting_primitive_fields; }
2678   bool is_reporting_primitive_array_values() const { return _reporting_primitive_array_values; }
2679   bool is_reporting_string_values() const          { return _reporting_string_values; }
2680 
2681   GrowableArray<oop>* visit_stack() const          { return _visit_stack; }
2682 
2683   // iterate over the various object types
2684   inline bool iterate_over_array(oop o);
2685   inline bool iterate_over_type_array(oop o);
2686   inline bool iterate_over_class(oop o);
2687   inline bool iterate_over_object(oop o);
2688 
2689   // root collection
2690   inline bool collect_simple_roots();
2691   inline bool collect_stack_roots();
2692   inline bool collect_stack_roots(JavaThread* java_thread, JNILocalRootsClosure* blk);
2693 
2694   // visit an object
2695   inline bool visit(oop o);
2696 
2697  public:
2698   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2699                        Handle initial_object,
2700                        BasicHeapWalkContext callbacks,
2701                        const void* user_data);
2702 
2703   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2704                        Handle initial_object,
2705                        AdvancedHeapWalkContext callbacks,
2706                        const void* user_data);
2707 
2708   ~VM_HeapWalkOperation();
2709 
2710   VMOp_Type type() const { return VMOp_HeapWalkOperation; }
2711   void doit();
2712 };
2713 
2714 
2715 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2716                                            Handle initial_object,
2717                                            BasicHeapWalkContext callbacks,
2718                                            const void* user_data) {
2719   _is_advanced_heap_walk = false;
2720   _tag_map = tag_map;
2721   _initial_object = initial_object;
2722   _following_object_refs = (callbacks.object_ref_callback() != NULL);
2723   _reporting_primitive_fields = false;
2724   _reporting_primitive_array_values = false;
2725   _reporting_string_values = false;
2726   _visit_stack = create_visit_stack();
2727 
2728 
2729   CallbackInvoker::initialize_for_basic_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2730 }
2731 
2732 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2733                                            Handle initial_object,
2734                                            AdvancedHeapWalkContext callbacks,
2735                                            const void* user_data) {
2736   _is_advanced_heap_walk = true;
2737   _tag_map = tag_map;
2738   _initial_object = initial_object;
2739   _following_object_refs = true;
2740   _reporting_primitive_fields = (callbacks.primitive_field_callback() != NULL);;
2741   _reporting_primitive_array_values = (callbacks.array_primitive_value_callback() != NULL);;
2742   _reporting_string_values = (callbacks.string_primitive_value_callback() != NULL);;
2743   _visit_stack = create_visit_stack();
2744 
2745   CallbackInvoker::initialize_for_advanced_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2746 }
2747 
2748 VM_HeapWalkOperation::~VM_HeapWalkOperation() {
2749   if (_following_object_refs) {
2750     assert(_visit_stack != NULL, "checking");
2751     delete _visit_stack;
2752     _visit_stack = NULL;
2753   }
2754 }
2755 
2756 // an array references its class and has a reference to
2757 // each element in the array
2758 inline bool VM_HeapWalkOperation::iterate_over_array(oop o) {
2759   objArrayOop array = objArrayOop(o);
2760 
2761   // array reference to its class
2762   oop mirror = ObjArrayKlass::cast(array->klass())->java_mirror();
2763   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2764     return false;
2765   }
2766 
2767   // iterate over the array and report each reference to a
2768   // non-null element
2769   for (int index=0; index<array->length(); index++) {
2770     oop elem = array->obj_at(index);
2771     if (elem == NULL) {
2772       continue;
2773     }
2774 
2775     // report the array reference o[index] = elem
2776     if (!CallbackInvoker::report_array_element_reference(o, elem, index)) {
2777       return false;
2778     }
2779   }
2780   return true;
2781 }
2782 
2783 // a type array references its class
2784 inline bool VM_HeapWalkOperation::iterate_over_type_array(oop o) {
2785   Klass* k = o->klass();
2786   oop mirror = k->java_mirror();
2787   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2788     return false;
2789   }
2790 
2791   // report the array contents if required
2792   if (is_reporting_primitive_array_values()) {
2793     if (!CallbackInvoker::report_primitive_array_values(o)) {
2794       return false;
2795     }
2796   }
2797   return true;
2798 }
2799 
2800 #ifdef ASSERT
2801 // verify that a static oop field is in range
2802 static inline bool verify_static_oop(InstanceKlass* ik,
2803                                      oop mirror, int offset) {
2804   address obj_p = (address)mirror + offset;
2805   address start = (address)InstanceMirrorKlass::start_of_static_fields(mirror);
2806   address end = start + (java_lang_Class::static_oop_field_count(mirror) * heapOopSize);
2807   assert(end >= start, "sanity check");
2808 
2809   if (obj_p >= start && obj_p < end) {
2810     return true;
2811   } else {
2812     return false;
2813   }
2814 }
2815 #endif // #ifdef ASSERT
2816 
2817 // a class references its super class, interfaces, class loader, ...
2818 // and finally its static fields
2819 inline bool VM_HeapWalkOperation::iterate_over_class(oop java_class) {
2820   int i;
2821   Klass* klass = java_lang_Class::as_Klass(java_class);
2822 
2823   if (klass->is_instance_klass()) {
2824     InstanceKlass* ik = InstanceKlass::cast(klass);
2825 
2826     // Ignore the class if it hasn't been initialized yet
2827     if (!ik->is_linked()) {
2828       return true;
2829     }
2830 
2831     // get the java mirror
2832     oop mirror = klass->java_mirror();
2833 
2834     // super (only if something more interesting than java.lang.Object)
2835     InstanceKlass* java_super = ik->java_super();
2836     if (java_super != NULL && java_super != SystemDictionary::Object_klass()) {
2837       oop super = java_super->java_mirror();
2838       if (!CallbackInvoker::report_superclass_reference(mirror, super)) {
2839         return false;
2840       }
2841     }
2842 
2843     // class loader
2844     oop cl = ik->class_loader();
2845     if (cl != NULL) {
2846       if (!CallbackInvoker::report_class_loader_reference(mirror, cl)) {
2847         return false;
2848       }
2849     }
2850 
2851     // protection domain
2852     oop pd = ik->protection_domain();
2853     if (pd != NULL) {
2854       if (!CallbackInvoker::report_protection_domain_reference(mirror, pd)) {
2855         return false;
2856       }
2857     }
2858 
2859     // signers
2860     oop signers = ik->signers();
2861     if (signers != NULL) {
2862       if (!CallbackInvoker::report_signers_reference(mirror, signers)) {
2863         return false;
2864       }
2865     }
2866 
2867     // references from the constant pool
2868     {
2869       ConstantPool* pool = ik->constants();
2870       for (int i = 1; i < pool->length(); i++) {
2871         constantTag tag = pool->tag_at(i).value();
2872         if (tag.is_string() || tag.is_klass() || tag.is_unresolved_klass()) {
2873           oop entry;
2874           if (tag.is_string()) {
2875             entry = pool->resolved_string_at(i);
2876             // If the entry is non-null it is resolved.
2877             if (entry == NULL) {
2878               continue;
2879             }
2880           } else if (tag.is_klass()) {
2881             entry = pool->resolved_klass_at(i)->java_mirror();
2882           } else {
2883             // Code generated by JIT and AOT compilers might not resolve constant
2884             // pool entries.  Treat them as resolved if they are loaded.
2885             assert(tag.is_unresolved_klass(), "must be");
2886             constantPoolHandle cp(Thread::current(), pool);
2887             Klass* klass = ConstantPool::klass_at_if_loaded(cp, i);
2888             if (klass == NULL) {
2889               continue;
2890             }
2891             entry = klass->java_mirror();
2892           }
2893           if (!CallbackInvoker::report_constant_pool_reference(mirror, entry, (jint)i)) {
2894             return false;
2895           }
2896         }
2897       }
2898     }
2899 
2900     // interfaces
2901     // (These will already have been reported as references from the constant pool
2902     //  but are specified by IterateOverReachableObjects and must be reported).
2903     Array<InstanceKlass*>* interfaces = ik->local_interfaces();
2904     for (i = 0; i < interfaces->length(); i++) {
2905       oop interf = interfaces->at(i)->java_mirror();
2906       if (interf == NULL) {
2907         continue;
2908       }
2909       if (!CallbackInvoker::report_interface_reference(mirror, interf)) {
2910         return false;
2911       }
2912     }
2913 
2914     // iterate over the static fields
2915 
2916     ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
2917     for (i=0; i<field_map->field_count(); i++) {
2918       ClassFieldDescriptor* field = field_map->field_at(i);
2919       char type = field->field_type();
2920       if (!is_primitive_field_type(type)) {
2921         oop fld_o = mirror->obj_field(field->field_offset());
2922         assert(verify_static_oop(ik, mirror, field->field_offset()), "sanity check");
2923         if (fld_o != NULL) {
2924           int slot = field->field_index();
2925           if (!CallbackInvoker::report_static_field_reference(mirror, fld_o, slot)) {
2926             delete field_map;
2927             return false;
2928           }
2929         }
2930       } else {
2931          if (is_reporting_primitive_fields()) {
2932            address addr = (address)mirror + field->field_offset();
2933            int slot = field->field_index();
2934            if (!CallbackInvoker::report_primitive_static_field(mirror, slot, addr, type)) {
2935              delete field_map;
2936              return false;
2937           }
2938         }
2939       }
2940     }
2941     delete field_map;
2942 
2943     return true;
2944   }
2945 
2946   return true;
2947 }
2948 
2949 // an object references a class and its instance fields
2950 // (static fields are ignored here as we report these as
2951 // references from the class).
2952 inline bool VM_HeapWalkOperation::iterate_over_object(oop o) {
2953   // reference to the class
2954   if (!CallbackInvoker::report_class_reference(o, o->klass()->java_mirror())) {
2955     return false;
2956   }
2957 
2958   // iterate over instance fields
2959   ClassFieldMap* field_map = JvmtiCachedClassFieldMap::get_map_of_instance_fields(o);
2960   for (int i=0; i<field_map->field_count(); i++) {
2961     ClassFieldDescriptor* field = field_map->field_at(i);
2962     char type = field->field_type();
2963     if (!is_primitive_field_type(type)) {
2964       oop fld_o = o->obj_field(field->field_offset());
2965       // ignore any objects that aren't visible to profiler
2966       if (fld_o != NULL) {
2967         assert(Universe::heap()->is_in_reserved(fld_o), "unsafe code should not "
2968                "have references to Klass* anymore");
2969         int slot = field->field_index();
2970         if (!CallbackInvoker::report_field_reference(o, fld_o, slot)) {
2971           return false;
2972         }
2973       }
2974     } else {
2975       if (is_reporting_primitive_fields()) {
2976         // primitive instance field
2977         address addr = (address)o + field->field_offset();
2978         int slot = field->field_index();
2979         if (!CallbackInvoker::report_primitive_instance_field(o, slot, addr, type)) {
2980           return false;
2981         }
2982       }
2983     }
2984   }
2985 
2986   // if the object is a java.lang.String
2987   if (is_reporting_string_values() &&
2988       o->klass() == SystemDictionary::String_klass()) {
2989     if (!CallbackInvoker::report_string_value(o)) {
2990       return false;
2991     }
2992   }
2993   return true;
2994 }
2995 
2996 
2997 // Collects all simple (non-stack) roots except for threads;
2998 // threads are handled in collect_stack_roots() as an optimization.
2999 // if there's a heap root callback provided then the callback is
3000 // invoked for each simple root.
3001 // if an object reference callback is provided then all simple
3002 // roots are pushed onto the marking stack so that they can be
3003 // processed later
3004 //
3005 inline bool VM_HeapWalkOperation::collect_simple_roots() {
3006   SimpleRootsClosure blk;
3007 
3008   // JNI globals
3009   blk.set_kind(JVMTI_HEAP_REFERENCE_JNI_GLOBAL);
3010   JNIHandles::oops_do(&blk);
3011   if (blk.stopped()) {
3012     return false;
3013   }
3014 
3015   // Preloaded classes and loader from the system dictionary
3016   blk.set_kind(JVMTI_HEAP_REFERENCE_SYSTEM_CLASS);
3017   SystemDictionary::oops_do(&blk);
3018   CLDToOopClosure cld_closure(&blk, false);
3019   ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
3020   if (blk.stopped()) {
3021     return false;
3022   }
3023 
3024   // Inflated monitors
3025   blk.set_kind(JVMTI_HEAP_REFERENCE_MONITOR);
3026   ObjectSynchronizer::oops_do(&blk);
3027   if (blk.stopped()) {
3028     return false;
3029   }
3030 
3031   // threads are now handled in collect_stack_roots()
3032 
3033   // Other kinds of roots maintained by HotSpot
3034   // Many of these won't be visible but others (such as instances of important
3035   // exceptions) will be visible.
3036   blk.set_kind(JVMTI_HEAP_REFERENCE_OTHER);
3037   Universe::oops_do(&blk);
3038   if (blk.stopped()) {
3039     return false;
3040   }
3041 
3042   return true;
3043 }
3044 
3045 // Walk the stack of a given thread and find all references (locals
3046 // and JNI calls) and report these as stack references
3047 inline bool VM_HeapWalkOperation::collect_stack_roots(JavaThread* java_thread,
3048                                                       JNILocalRootsClosure* blk)
3049 {
3050   oop threadObj = java_thread->threadObj();
3051   assert(threadObj != NULL, "sanity check");
3052 
3053   // only need to get the thread's tag once per thread
3054   jlong thread_tag = tag_for(_tag_map, threadObj);
3055 
3056   // also need the thread id
3057   jlong tid = java_lang_Thread::thread_id(threadObj);
3058 
3059 
3060   if (java_thread->has_last_Java_frame()) {
3061 
3062     // vframes are resource allocated
3063     Thread* current_thread = Thread::current();
3064     ResourceMark rm(current_thread);
3065     HandleMark hm(current_thread);
3066 
3067     RegisterMap reg_map(java_thread);
3068     frame f = java_thread->last_frame();
3069     vframe* vf = vframe::new_vframe(&f, &reg_map, java_thread);
3070 
3071     bool is_top_frame = true;
3072     int depth = 0;
3073     frame* last_entry_frame = NULL;
3074 
3075     while (vf != NULL) {
3076       if (vf->is_java_frame()) {
3077 
3078         // java frame (interpreted, compiled, ...)
3079         javaVFrame *jvf = javaVFrame::cast(vf);
3080 
3081         // the jmethodID
3082         jmethodID method = jvf->method()->jmethod_id();
3083 
3084         if (!(jvf->method()->is_native())) {
3085           jlocation bci = (jlocation)jvf->bci();
3086           StackValueCollection* locals = jvf->locals();
3087           for (int slot=0; slot<locals->size(); slot++) {
3088             if (locals->at(slot)->type() == T_OBJECT) {
3089               oop o = locals->obj_at(slot)();
3090               if (o == NULL) {
3091                 continue;
3092               }
3093 
3094               // stack reference
3095               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3096                                                    bci, slot, o)) {
3097                 return false;
3098               }
3099             }
3100           }
3101 
3102           StackValueCollection* exprs = jvf->expressions();
3103           for (int index=0; index < exprs->size(); index++) {
3104             if (exprs->at(index)->type() == T_OBJECT) {
3105               oop o = exprs->obj_at(index)();
3106               if (o == NULL) {
3107                 continue;
3108               }
3109 
3110               // stack reference
3111               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3112                                                    bci, locals->size() + index, o)) {
3113                 return false;
3114               }
3115             }
3116           }
3117 
3118           // Follow oops from compiled nmethod
3119           if (jvf->cb() != NULL && jvf->cb()->is_nmethod()) {
3120             blk->set_context(thread_tag, tid, depth, method);
3121             jvf->cb()->as_nmethod()->oops_do(blk);
3122           }
3123         } else {
3124           blk->set_context(thread_tag, tid, depth, method);
3125           if (is_top_frame) {
3126             // JNI locals for the top frame.
3127             java_thread->active_handles()->oops_do(blk);
3128           } else {
3129             if (last_entry_frame != NULL) {
3130               // JNI locals for the entry frame
3131               assert(last_entry_frame->is_entry_frame(), "checking");
3132               last_entry_frame->entry_frame_call_wrapper()->handles()->oops_do(blk);
3133             }
3134           }
3135         }
3136         last_entry_frame = NULL;
3137         depth++;
3138       } else {
3139         // externalVFrame - for an entry frame then we report the JNI locals
3140         // when we find the corresponding javaVFrame
3141         frame* fr = vf->frame_pointer();
3142         assert(fr != NULL, "sanity check");
3143         if (fr->is_entry_frame()) {
3144           last_entry_frame = fr;
3145         }
3146       }
3147 
3148       vf = vf->sender();
3149       is_top_frame = false;
3150     }
3151   } else {
3152     // no last java frame but there may be JNI locals
3153     blk->set_context(thread_tag, tid, 0, (jmethodID)NULL);
3154     java_thread->active_handles()->oops_do(blk);
3155   }
3156   return true;
3157 }
3158 
3159 
3160 // Collects the simple roots for all threads and collects all
3161 // stack roots - for each thread it walks the execution
3162 // stack to find all references and local JNI refs.
3163 inline bool VM_HeapWalkOperation::collect_stack_roots() {
3164   JNILocalRootsClosure blk;
3165   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
3166     oop threadObj = thread->threadObj();
3167     if (threadObj != NULL && !thread->is_exiting() && !thread->is_hidden_from_external_view()) {
3168       // Collect the simple root for this thread before we
3169       // collect its stack roots
3170       if (!CallbackInvoker::report_simple_root(JVMTI_HEAP_REFERENCE_THREAD,
3171                                                threadObj)) {
3172         return false;
3173       }
3174       if (!collect_stack_roots(thread, &blk)) {
3175         return false;
3176       }
3177     }
3178   }
3179   return true;
3180 }
3181 
3182 // visit an object
3183 // first mark the object as visited
3184 // second get all the outbound references from this object (in other words, all
3185 // the objects referenced by this object).
3186 //
3187 bool VM_HeapWalkOperation::visit(oop o) {
3188   // mark object as visited
3189   assert(!ObjectMarker::visited(o), "can't visit same object more than once");
3190   ObjectMarker::mark(o);
3191 
3192   // instance
3193   if (o->is_instance()) {
3194     if (o->klass() == SystemDictionary::Class_klass()) {
3195       if (!java_lang_Class::is_primitive(o)) {
3196         // a java.lang.Class
3197         return iterate_over_class(o);
3198       }
3199     } else {
3200       return iterate_over_object(o);
3201     }
3202   }
3203 
3204   // object array
3205   if (o->is_objArray()) {
3206     return iterate_over_array(o);
3207   }
3208 
3209   // type array
3210   if (o->is_typeArray()) {
3211     return iterate_over_type_array(o);
3212   }
3213 
3214   return true;
3215 }
3216 
3217 void VM_HeapWalkOperation::doit() {
3218   ResourceMark rm;
3219   ObjectMarkerController marker;
3220   ClassFieldMapCacheMark cm;
3221 
3222   assert(visit_stack()->is_empty(), "visit stack must be empty");
3223 
3224   // the heap walk starts with an initial object or the heap roots
3225   if (initial_object().is_null()) {
3226     // If either collect_stack_roots() or collect_simple_roots()
3227     // returns false at this point, then there are no mark bits
3228     // to reset.
3229     ObjectMarker::set_needs_reset(false);
3230 
3231     // Calling collect_stack_roots() before collect_simple_roots()
3232     // can result in a big performance boost for an agent that is
3233     // focused on analyzing references in the thread stacks.
3234     if (!collect_stack_roots()) return;
3235 
3236     if (!collect_simple_roots()) return;
3237 
3238     // no early return so enable heap traversal to reset the mark bits
3239     ObjectMarker::set_needs_reset(true);
3240   } else {
3241     visit_stack()->push(initial_object()());
3242   }
3243 
3244   // object references required
3245   if (is_following_references()) {
3246 
3247     // visit each object until all reachable objects have been
3248     // visited or the callback asked to terminate the iteration.
3249     while (!visit_stack()->is_empty()) {
3250       oop o = visit_stack()->pop();
3251       if (!ObjectMarker::visited(o)) {
3252         if (!visit(o)) {
3253           break;
3254         }
3255       }
3256     }
3257   }
3258 }
3259 
3260 // iterate over all objects that are reachable from a set of roots
3261 void JvmtiTagMap::iterate_over_reachable_objects(jvmtiHeapRootCallback heap_root_callback,
3262                                                  jvmtiStackReferenceCallback stack_ref_callback,
3263                                                  jvmtiObjectReferenceCallback object_ref_callback,
3264                                                  const void* user_data) {
3265   MutexLocker ml(Heap_lock);
3266   BasicHeapWalkContext context(heap_root_callback, stack_ref_callback, object_ref_callback);
3267   VM_HeapWalkOperation op(this, Handle(), context, user_data);
3268   VMThread::execute(&op);
3269 }
3270 
3271 // iterate over all objects that are reachable from a given object
3272 void JvmtiTagMap::iterate_over_objects_reachable_from_object(jobject object,
3273                                                              jvmtiObjectReferenceCallback object_ref_callback,
3274                                                              const void* user_data) {
3275   oop obj = JNIHandles::resolve(object);
3276   Handle initial_object(Thread::current(), obj);
3277 
3278   MutexLocker ml(Heap_lock);
3279   BasicHeapWalkContext context(NULL, NULL, object_ref_callback);
3280   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3281   VMThread::execute(&op);
3282 }
3283 
3284 // follow references from an initial object or the GC roots
3285 void JvmtiTagMap::follow_references(jint heap_filter,
3286                                     Klass* klass,
3287                                     jobject object,
3288                                     const jvmtiHeapCallbacks* callbacks,
3289                                     const void* user_data)
3290 {
3291   oop obj = JNIHandles::resolve(object);
3292   Handle initial_object(Thread::current(), obj);
3293 
3294   MutexLocker ml(Heap_lock);
3295   AdvancedHeapWalkContext context(heap_filter, klass, callbacks);
3296   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3297   VMThread::execute(&op);
3298 }
3299 
3300 
3301 void JvmtiTagMap::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
3302   // No locks during VM bring-up (0 threads) and no safepoints after main
3303   // thread creation and before VMThread creation (1 thread); initial GC
3304   // verification can happen in that window which gets to here.
3305   assert(Threads::number_of_threads() <= 1 ||
3306          SafepointSynchronize::is_at_safepoint(),
3307          "must be executed at a safepoint");
3308   if (JvmtiEnv::environments_might_exist()) {
3309     JvmtiEnvIterator it;
3310     for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
3311       JvmtiTagMap* tag_map = env->tag_map_acquire();
3312       if (tag_map != NULL && !tag_map->is_empty()) {
3313         tag_map->do_weak_oops(is_alive, f);
3314       }
3315     }
3316   }
3317 }
3318 
3319 void JvmtiTagMap::do_weak_oops(BoolObjectClosure* is_alive, OopClosure* f) {
3320 
3321   // does this environment have the OBJECT_FREE event enabled
3322   bool post_object_free = env()->is_enabled(JVMTI_EVENT_OBJECT_FREE);
3323 
3324   // counters used for trace message
3325   int freed = 0;
3326   int moved = 0;
3327 
3328   JvmtiTagHashmap* hashmap = this->hashmap();
3329 
3330   // reenable sizing (if disabled)
3331   hashmap->set_resizing_enabled(true);
3332 
3333   // if the hashmap is empty then we can skip it
3334   if (hashmap->_entry_count == 0) {
3335     return;
3336   }
3337 
3338   // now iterate through each entry in the table
3339 
3340   JvmtiTagHashmapEntry** table = hashmap->table();
3341   int size = hashmap->size();
3342 
3343   JvmtiTagHashmapEntry* delayed_add = NULL;
3344 
3345   for (int pos = 0; pos < size; ++pos) {
3346     JvmtiTagHashmapEntry* entry = table[pos];
3347     JvmtiTagHashmapEntry* prev = NULL;
3348 
3349     while (entry != NULL) {
3350       JvmtiTagHashmapEntry* next = entry->next();
3351 
3352       // has object been GC'ed
3353       if (!is_alive->do_object_b(entry->object_peek())) {
3354         // grab the tag
3355         jlong tag = entry->tag();
3356         guarantee(tag != 0, "checking");
3357 
3358         // remove GC'ed entry from hashmap and return the
3359         // entry to the free list
3360         hashmap->remove(prev, pos, entry);
3361         destroy_entry(entry);
3362 
3363         // post the event to the profiler
3364         if (post_object_free) {
3365           JvmtiExport::post_object_free(env(), tag);
3366         }
3367 
3368         ++freed;
3369       } else {
3370         f->do_oop(entry->object_addr());
3371         oop new_oop = entry->object_peek();
3372 
3373         // if the object has moved then re-hash it and move its
3374         // entry to its new location.
3375         unsigned int new_pos = JvmtiTagHashmap::hash(new_oop, size);
3376         if (new_pos != (unsigned int)pos) {
3377           if (prev == NULL) {
3378             table[pos] = next;
3379           } else {
3380             prev->set_next(next);
3381           }
3382           if (new_pos < (unsigned int)pos) {
3383             entry->set_next(table[new_pos]);
3384             table[new_pos] = entry;
3385           } else {
3386             // Delay adding this entry to it's new position as we'd end up
3387             // hitting it again during this iteration.
3388             entry->set_next(delayed_add);
3389             delayed_add = entry;
3390           }
3391           moved++;
3392         } else {
3393           // object didn't move
3394           prev = entry;
3395         }
3396       }
3397 
3398       entry = next;
3399     }
3400   }
3401 
3402   // Re-add all the entries which were kept aside
3403   while (delayed_add != NULL) {
3404     JvmtiTagHashmapEntry* next = delayed_add->next();
3405     unsigned int pos = JvmtiTagHashmap::hash(delayed_add->object_peek(), size);
3406     delayed_add->set_next(table[pos]);
3407     table[pos] = delayed_add;
3408     delayed_add = next;
3409   }
3410 
3411   log_debug(jvmti, objecttagging)("(%d->%d, %d freed, %d total moves)",
3412                                   hashmap->_entry_count + freed, hashmap->_entry_count, freed, moved);
3413 }