1 /*
   2  * Copyright (c) 2003, 2018, 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/javaClasses.inline.hpp"
  27 #include "classfile/symbolTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "jvmtifiles/jvmtiEnv.hpp"
  32 #include "logging/log.hpp"
  33 #include "memory/allocation.inline.hpp"
  34 #include "memory/resourceArea.hpp"
  35 #include "oops/access.inline.hpp"
  36 #include "oops/arrayOop.inline.hpp"
  37 #include "oops/constantPool.inline.hpp"
  38 #include "oops/instanceMirrorKlass.hpp"
  39 #include "oops/objArrayKlass.hpp"
  40 #include "oops/objArrayOop.inline.hpp"
  41 #include "oops/oop.inline.hpp"
  42 #include "oops/typeArrayOop.inline.hpp"
  43 #include "prims/jvmtiEventController.hpp"
  44 #include "prims/jvmtiEventController.inline.hpp"
  45 #include "prims/jvmtiExport.hpp"
  46 #include "prims/jvmtiImpl.hpp"
  47 #include "prims/jvmtiTagMap.hpp"
  48 #include "runtime/biasedLocking.hpp"
  49 #include "runtime/frame.inline.hpp"
  50 #include "runtime/handles.inline.hpp"
  51 #include "runtime/javaCalls.hpp"
  52 #include "runtime/jniHandles.inline.hpp"
  53 #include "runtime/mutex.hpp"
  54 #include "runtime/mutexLocker.hpp"
  55 #include "runtime/reflectionUtils.hpp"
  56 #include "runtime/thread.inline.hpp"
  57 #include "runtime/threadSMR.hpp"
  58 #include "runtime/vframe.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "runtime/vm_operations.hpp"
  61 #include "utilities/macros.hpp"
  62 #if INCLUDE_ZGC
  63 #include "gc/z/zGlobals.hpp"
  64 #endif
  65 
  66 // JvmtiTagHashmapEntry
  67 //
  68 // Each entry encapsulates a reference to the tagged object
  69 // and the tag value. In addition an entry includes a next pointer which
  70 // is used to chain entries together.
  71 
  72 class JvmtiTagHashmapEntry : public CHeapObj<mtInternal> {
  73  private:
  74   friend class JvmtiTagMap;
  75 
  76   oop _object;                          // tagged object
  77   jlong _tag;                           // the tag
  78   JvmtiTagHashmapEntry* _next;          // next on the list
  79 
  80   inline void init(oop object, jlong tag) {
  81     _object = object;
  82     _tag = tag;
  83     _next = NULL;
  84   }
  85 
  86   // constructor
  87   JvmtiTagHashmapEntry(oop object, jlong tag) { init(object, tag); }
  88 
  89  public:
  90 
  91   // accessor methods
  92   inline oop* object_addr() { return &_object; }
  93   inline oop object()       { return NativeAccess<ON_PHANTOM_OOP_REF>::oop_load(object_addr()); }
  94   // Peek at the object without keeping it alive. The returned object must be
  95   // kept alive using a normal access if it leaks out of a thread transition from VM.
  96   inline oop object_peek()  {
  97     return NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(object_addr());
  98   }
  99   inline jlong tag() const  { return _tag; }
 100 
 101   inline void set_tag(jlong tag) {
 102     assert(tag != 0, "can't be zero");
 103     _tag = tag;
 104   }
 105 
 106   inline bool equals(oop object) {
 107     return oopDesc::equals(object, object_peek());
 108   }
 109 
 110   inline JvmtiTagHashmapEntry* next() const        { return _next; }
 111   inline void set_next(JvmtiTagHashmapEntry* next) { _next = next; }
 112 };
 113 
 114 
 115 // JvmtiTagHashmap
 116 //
 117 // A hashmap is essentially a table of pointers to entries. Entries
 118 // are hashed to a location, or position in the table, and then
 119 // chained from that location. The "key" for hashing is address of
 120 // the object, or oop. The "value" is the tag value.
 121 //
 122 // A hashmap maintains a count of the number entries in the hashmap
 123 // and resizes if the number of entries exceeds a given threshold.
 124 // The threshold is specified as a percentage of the size - for
 125 // example a threshold of 0.75 will trigger the hashmap to resize
 126 // if the number of entries is >75% of table size.
 127 //
 128 // A hashmap provides functions for adding, removing, and finding
 129 // entries. It also provides a function to iterate over all entries
 130 // in the hashmap.
 131 
 132 class JvmtiTagHashmap : public CHeapObj<mtInternal> {
 133  private:
 134   friend class JvmtiTagMap;
 135 
 136   enum {
 137     small_trace_threshold  = 10000,                  // threshold for tracing
 138     medium_trace_threshold = 100000,
 139     large_trace_threshold  = 1000000,
 140     initial_trace_threshold = small_trace_threshold
 141   };
 142 
 143   static int _sizes[];                  // array of possible hashmap sizes
 144   int _size;                            // actual size of the table
 145   int _size_index;                      // index into size table
 146 
 147   int _entry_count;                     // number of entries in the hashmap
 148 
 149   float _load_factor;                   // load factor as a % of the size
 150   int _resize_threshold;                // computed threshold to trigger resizing.
 151   bool _resizing_enabled;               // indicates if hashmap can resize
 152 
 153   int _trace_threshold;                 // threshold for trace messages
 154 
 155   JvmtiTagHashmapEntry** _table;        // the table of entries.
 156 
 157   // private accessors
 158   int resize_threshold() const                  { return _resize_threshold; }
 159   int trace_threshold() const                   { return _trace_threshold; }
 160 
 161   // initialize the hashmap
 162   void init(int size_index=0, float load_factor=4.0f) {
 163     int initial_size =  _sizes[size_index];
 164     _size_index = size_index;
 165     _size = initial_size;
 166     _entry_count = 0;
 167     _trace_threshold = initial_trace_threshold;
 168     _load_factor = load_factor;
 169     _resize_threshold = (int)(_load_factor * _size);
 170     _resizing_enabled = true;
 171     size_t s = initial_size * sizeof(JvmtiTagHashmapEntry*);
 172     _table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 173     if (_table == NULL) {
 174       vm_exit_out_of_memory(s, OOM_MALLOC_ERROR,
 175         "unable to allocate initial hashtable for jvmti object tags");
 176     }
 177     for (int i=0; i<initial_size; i++) {
 178       _table[i] = NULL;
 179     }
 180   }
 181 
 182   // hash a given key (oop) with the specified size
 183   static unsigned int hash(oop key, int size) {
 184     ZGC_ONLY(assert(ZAddressMetadataShift >= sizeof(unsigned int) * BitsPerByte, "cast removes the metadata bits");)
 185 
 186     // shift right to get better distribution (as these bits will be zero
 187     // with aligned addresses)
 188     key = Access<>::resolve(key);
 189     unsigned int addr = (unsigned int)(cast_from_oop<intptr_t>(key));
 190 #ifdef _LP64
 191     return (addr >> 3) % size;
 192 #else
 193     return (addr >> 2) % size;
 194 #endif
 195   }
 196 
 197   // hash a given key (oop)
 198   unsigned int hash(oop key) {
 199     return hash(key, _size);
 200   }
 201 
 202   // resize the hashmap - allocates a large table and re-hashes
 203   // all entries into the new table.
 204   void resize() {
 205     int new_size_index = _size_index+1;
 206     int new_size = _sizes[new_size_index];
 207     if (new_size < 0) {
 208       // hashmap already at maximum capacity
 209       return;
 210     }
 211 
 212     // allocate new table
 213     size_t s = new_size * sizeof(JvmtiTagHashmapEntry*);
 214     JvmtiTagHashmapEntry** new_table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 215     if (new_table == NULL) {
 216       warning("unable to allocate larger hashtable for jvmti object tags");
 217       set_resizing_enabled(false);
 218       return;
 219     }
 220 
 221     // initialize new table
 222     int i;
 223     for (i=0; i<new_size; i++) {
 224       new_table[i] = NULL;
 225     }
 226 
 227     // rehash all entries into the new table
 228     for (i=0; i<_size; i++) {
 229       JvmtiTagHashmapEntry* entry = _table[i];
 230       while (entry != NULL) {
 231         JvmtiTagHashmapEntry* next = entry->next();
 232         oop key = entry->object_peek();
 233         assert(key != NULL, "jni weak reference cleared!!");
 234         unsigned int h = hash(key, new_size);
 235         JvmtiTagHashmapEntry* anchor = new_table[h];
 236         if (anchor == NULL) {
 237           new_table[h] = entry;
 238           entry->set_next(NULL);
 239         } else {
 240           entry->set_next(anchor);
 241           new_table[h] = entry;
 242         }
 243         entry = next;
 244       }
 245     }
 246 
 247     // free old table and update settings.
 248     os::free((void*)_table);
 249     _table = new_table;
 250     _size_index = new_size_index;
 251     _size = new_size;
 252 
 253     // compute new resize threshold
 254     _resize_threshold = (int)(_load_factor * _size);
 255   }
 256 
 257 
 258   // internal remove function - remove an entry at a given position in the
 259   // table.
 260   inline void remove(JvmtiTagHashmapEntry* prev, int pos, JvmtiTagHashmapEntry* entry) {
 261     assert(pos >= 0 && pos < _size, "out of range");
 262     if (prev == NULL) {
 263       _table[pos] = entry->next();
 264     } else {
 265       prev->set_next(entry->next());
 266     }
 267     assert(_entry_count > 0, "checking");
 268     _entry_count--;
 269   }
 270 
 271   // resizing switch
 272   bool is_resizing_enabled() const          { return _resizing_enabled; }
 273   void set_resizing_enabled(bool enable)    { _resizing_enabled = enable; }
 274 
 275   // debugging
 276   void print_memory_usage();
 277   void compute_next_trace_threshold();
 278 
 279  public:
 280 
 281   // create a JvmtiTagHashmap of a preferred size and optionally a load factor.
 282   // The preferred size is rounded down to an actual size.
 283   JvmtiTagHashmap(int size, float load_factor=0.0f) {
 284     int i=0;
 285     while (_sizes[i] < size) {
 286       if (_sizes[i] < 0) {
 287         assert(i > 0, "sanity check");
 288         i--;
 289         break;
 290       }
 291       i++;
 292     }
 293 
 294     // if a load factor is specified then use it, otherwise use default
 295     if (load_factor > 0.01f) {
 296       init(i, load_factor);
 297     } else {
 298       init(i);
 299     }
 300   }
 301 
 302   // create a JvmtiTagHashmap with default settings
 303   JvmtiTagHashmap() {
 304     init();
 305   }
 306 
 307   // release table when JvmtiTagHashmap destroyed
 308   ~JvmtiTagHashmap() {
 309     if (_table != NULL) {
 310       os::free((void*)_table);
 311       _table = NULL;
 312     }
 313   }
 314 
 315   // accessors
 316   int size() const                              { return _size; }
 317   JvmtiTagHashmapEntry** table() const          { return _table; }
 318   int entry_count() const                       { return _entry_count; }
 319 
 320   // find an entry in the hashmap, returns NULL if not found.
 321   inline JvmtiTagHashmapEntry* find(oop key) {
 322     unsigned int h = hash(key);
 323     JvmtiTagHashmapEntry* entry = _table[h];
 324     while (entry != NULL) {
 325       if (entry->equals(key)) {
 326          return entry;
 327       }
 328       entry = entry->next();
 329     }
 330     return NULL;
 331   }
 332 
 333 
 334   // add a new entry to hashmap
 335   inline void add(oop key, JvmtiTagHashmapEntry* entry) {
 336     assert(key != NULL, "checking");
 337     assert(find(key) == NULL, "duplicate detected");
 338     unsigned int h = hash(key);
 339     JvmtiTagHashmapEntry* anchor = _table[h];
 340     if (anchor == NULL) {
 341       _table[h] = entry;
 342       entry->set_next(NULL);
 343     } else {
 344       entry->set_next(anchor);
 345       _table[h] = entry;
 346     }
 347 
 348     _entry_count++;
 349     if (log_is_enabled(Debug, jvmti, objecttagging) && entry_count() >= trace_threshold()) {
 350       print_memory_usage();
 351       compute_next_trace_threshold();
 352     }
 353 
 354     // if the number of entries exceed the threshold then resize
 355     if (entry_count() > resize_threshold() && is_resizing_enabled()) {
 356       resize();
 357     }
 358   }
 359 
 360   // remove an entry with the given key.
 361   inline JvmtiTagHashmapEntry* remove(oop key) {
 362     unsigned int h = hash(key);
 363     JvmtiTagHashmapEntry* entry = _table[h];
 364     JvmtiTagHashmapEntry* prev = NULL;
 365     while (entry != NULL) {
 366       if (entry->equals(key)) {
 367         break;
 368       }
 369       prev = entry;
 370       entry = entry->next();
 371     }
 372     if (entry != NULL) {
 373       remove(prev, h, entry);
 374     }
 375     return entry;
 376   }
 377 
 378   // iterate over all entries in the hashmap
 379   void entry_iterate(JvmtiTagHashmapEntryClosure* closure);
 380 };
 381 
 382 // possible hashmap sizes - odd primes that roughly double in size.
 383 // To avoid excessive resizing the odd primes from 4801-76831 and
 384 // 76831-307261 have been removed. The list must be terminated by -1.
 385 int JvmtiTagHashmap::_sizes[] =  { 4801, 76831, 307261, 614563, 1228891,
 386     2457733, 4915219, 9830479, 19660831, 39321619, 78643219, -1 };
 387 
 388 
 389 // A supporting class for iterating over all entries in Hashmap
 390 class JvmtiTagHashmapEntryClosure {
 391  public:
 392   virtual void do_entry(JvmtiTagHashmapEntry* entry) = 0;
 393 };
 394 
 395 
 396 // iterate over all entries in the hashmap
 397 void JvmtiTagHashmap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 398   for (int i=0; i<_size; i++) {
 399     JvmtiTagHashmapEntry* entry = _table[i];
 400     JvmtiTagHashmapEntry* prev = NULL;
 401     while (entry != NULL) {
 402       // obtain the next entry before invoking do_entry - this is
 403       // necessary because do_entry may remove the entry from the
 404       // hashmap.
 405       JvmtiTagHashmapEntry* next = entry->next();
 406       closure->do_entry(entry);
 407       entry = next;
 408      }
 409   }
 410 }
 411 
 412 // debugging
 413 void JvmtiTagHashmap::print_memory_usage() {
 414   intptr_t p = (intptr_t)this;
 415   tty->print("[JvmtiTagHashmap @ " INTPTR_FORMAT, p);
 416 
 417   // table + entries in KB
 418   int hashmap_usage = (size()*sizeof(JvmtiTagHashmapEntry*) +
 419     entry_count()*sizeof(JvmtiTagHashmapEntry))/K;
 420 
 421   int weak_globals_usage = (int)(JNIHandles::weak_global_handle_memory_usage()/K);
 422   tty->print_cr(", %d entries (%d KB) <JNI weak globals: %d KB>]",
 423     entry_count(), hashmap_usage, weak_globals_usage);
 424 }
 425 
 426 // compute threshold for the next trace message
 427 void JvmtiTagHashmap::compute_next_trace_threshold() {
 428   _trace_threshold = entry_count();
 429   if (trace_threshold() < medium_trace_threshold) {
 430     _trace_threshold += small_trace_threshold;
 431   } else {
 432     if (trace_threshold() < large_trace_threshold) {
 433       _trace_threshold += medium_trace_threshold;
 434     } else {
 435       _trace_threshold += large_trace_threshold;
 436     }
 437   }
 438 }
 439 
 440 // create a JvmtiTagMap
 441 JvmtiTagMap::JvmtiTagMap(JvmtiEnv* env) :
 442   _env(env),
 443   _lock(Mutex::nonleaf+2, "JvmtiTagMap._lock", false),
 444   _free_entries(NULL),
 445   _free_entries_count(0)
 446 {
 447   assert(JvmtiThreadState_lock->is_locked(), "sanity check");
 448   assert(((JvmtiEnvBase *)env)->tag_map() == NULL, "tag map already exists for environment");
 449 
 450   _hashmap = new JvmtiTagHashmap();
 451 
 452   // finally add us to the environment
 453   ((JvmtiEnvBase *)env)->set_tag_map(this);
 454 }
 455 
 456 
 457 // destroy a JvmtiTagMap
 458 JvmtiTagMap::~JvmtiTagMap() {
 459 
 460   // no lock acquired as we assume the enclosing environment is
 461   // also being destroryed.
 462   ((JvmtiEnvBase *)_env)->set_tag_map(NULL);
 463 
 464   JvmtiTagHashmapEntry** table = _hashmap->table();
 465   for (int j = 0; j < _hashmap->size(); j++) {
 466     JvmtiTagHashmapEntry* entry = table[j];
 467     while (entry != NULL) {
 468       JvmtiTagHashmapEntry* next = entry->next();
 469       delete entry;
 470       entry = next;
 471     }
 472   }
 473 
 474   // finally destroy the hashmap
 475   delete _hashmap;
 476   _hashmap = NULL;
 477 
 478   // remove any entries on the free list
 479   JvmtiTagHashmapEntry* entry = _free_entries;
 480   while (entry != NULL) {
 481     JvmtiTagHashmapEntry* next = entry->next();
 482     delete entry;
 483     entry = next;
 484   }
 485   _free_entries = NULL;
 486 }
 487 
 488 // create a hashmap entry
 489 // - if there's an entry on the (per-environment) free list then this
 490 // is returned. Otherwise an new entry is allocated.
 491 JvmtiTagHashmapEntry* JvmtiTagMap::create_entry(oop ref, jlong tag) {
 492   assert(Thread::current()->is_VM_thread() || is_locked(), "checking");
 493   JvmtiTagHashmapEntry* entry;
 494   if (_free_entries == NULL) {
 495     entry = new JvmtiTagHashmapEntry(ref, tag);
 496   } else {
 497     assert(_free_entries_count > 0, "mismatched _free_entries_count");
 498     _free_entries_count--;
 499     entry = _free_entries;
 500     _free_entries = entry->next();
 501     entry->init(ref, tag);
 502   }
 503   return entry;
 504 }
 505 
 506 // destroy an entry by returning it to the free list
 507 void JvmtiTagMap::destroy_entry(JvmtiTagHashmapEntry* entry) {
 508   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 509   // limit the size of the free list
 510   if (_free_entries_count >= max_free_entries) {
 511     delete entry;
 512   } else {
 513     entry->set_next(_free_entries);
 514     _free_entries = entry;
 515     _free_entries_count++;
 516   }
 517 }
 518 
 519 // returns the tag map for the given environments. If the tag map
 520 // doesn't exist then it is created.
 521 JvmtiTagMap* JvmtiTagMap::tag_map_for(JvmtiEnv* env) {
 522   JvmtiTagMap* tag_map = ((JvmtiEnvBase*)env)->tag_map();
 523   if (tag_map == NULL) {
 524     MutexLocker mu(JvmtiThreadState_lock);
 525     tag_map = ((JvmtiEnvBase*)env)->tag_map();
 526     if (tag_map == NULL) {
 527       tag_map = new JvmtiTagMap(env);
 528     }
 529   } else {
 530     CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
 531   }
 532   return tag_map;
 533 }
 534 
 535 // iterate over all entries in the tag map.
 536 void JvmtiTagMap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 537   hashmap()->entry_iterate(closure);
 538 }
 539 
 540 // returns true if the hashmaps are empty
 541 bool JvmtiTagMap::is_empty() {
 542   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 543   return hashmap()->entry_count() == 0;
 544 }
 545 
 546 
 547 // Return the tag value for an object, or 0 if the object is
 548 // not tagged
 549 //
 550 static inline jlong tag_for(JvmtiTagMap* tag_map, oop o) {
 551   JvmtiTagHashmapEntry* entry = tag_map->hashmap()->find(o);
 552   if (entry == NULL) {
 553     return 0;
 554   } else {
 555     return entry->tag();
 556   }
 557 }
 558 
 559 
 560 // A CallbackWrapper is a support class for querying and tagging an object
 561 // around a callback to a profiler. The constructor does pre-callback
 562 // work to get the tag value, klass tag value, ... and the destructor
 563 // does the post-callback work of tagging or untagging the object.
 564 //
 565 // {
 566 //   CallbackWrapper wrapper(tag_map, o);
 567 //
 568 //   (*callback)(wrapper.klass_tag(), wrapper.obj_size(), wrapper.obj_tag_p(), ...)
 569 //
 570 // } // wrapper goes out of scope here which results in the destructor
 571 //      checking to see if the object has been tagged, untagged, or the
 572 //      tag value has changed.
 573 //
 574 class CallbackWrapper : public StackObj {
 575  private:
 576   JvmtiTagMap* _tag_map;
 577   JvmtiTagHashmap* _hashmap;
 578   JvmtiTagHashmapEntry* _entry;
 579   oop _o;
 580   jlong _obj_size;
 581   jlong _obj_tag;
 582   jlong _klass_tag;
 583 
 584  protected:
 585   JvmtiTagMap* tag_map() const      { return _tag_map; }
 586 
 587   // invoked post-callback to tag, untag, or update the tag of an object
 588   void inline post_callback_tag_update(oop o, JvmtiTagHashmap* hashmap,
 589                                        JvmtiTagHashmapEntry* entry, jlong obj_tag);
 590  public:
 591   CallbackWrapper(JvmtiTagMap* tag_map, oop o) {
 592     assert(Thread::current()->is_VM_thread() || tag_map->is_locked(),
 593            "MT unsafe or must be VM thread");
 594 
 595     // object to tag
 596     _o = o;
 597 
 598     // object size
 599     _obj_size = (jlong)_o->size() * wordSize;
 600 
 601     // record the context
 602     _tag_map = tag_map;
 603     _hashmap = tag_map->hashmap();
 604     _entry = _hashmap->find(_o);
 605 
 606     // get object tag
 607     _obj_tag = (_entry == NULL) ? 0 : _entry->tag();
 608 
 609     // get the class and the class's tag value
 610     assert(SystemDictionary::Class_klass()->is_mirror_instance_klass(), "Is not?");
 611 
 612     _klass_tag = tag_for(tag_map, _o->klass()->java_mirror());
 613   }
 614 
 615   ~CallbackWrapper() {
 616     post_callback_tag_update(_o, _hashmap, _entry, _obj_tag);
 617   }
 618 
 619   inline jlong* obj_tag_p()                     { return &_obj_tag; }
 620   inline jlong obj_size() const                 { return _obj_size; }
 621   inline jlong obj_tag() const                  { return _obj_tag; }
 622   inline jlong klass_tag() const                { return _klass_tag; }
 623 };
 624 
 625 
 626 
 627 // callback post-callback to tag, untag, or update the tag of an object
 628 void inline CallbackWrapper::post_callback_tag_update(oop o,
 629                                                       JvmtiTagHashmap* hashmap,
 630                                                       JvmtiTagHashmapEntry* entry,
 631                                                       jlong obj_tag) {
 632   if (entry == NULL) {
 633     if (obj_tag != 0) {
 634       // callback has tagged the object
 635       assert(Thread::current()->is_VM_thread(), "must be VMThread");
 636       entry = tag_map()->create_entry(o, obj_tag);
 637       hashmap->add(o, entry);
 638     }
 639   } else {
 640     // object was previously tagged - the callback may have untagged
 641     // the object or changed the tag value
 642     if (obj_tag == 0) {
 643 
 644       JvmtiTagHashmapEntry* entry_removed = hashmap->remove(o);
 645       assert(entry_removed == entry, "checking");
 646       tag_map()->destroy_entry(entry);
 647 
 648     } else {
 649       if (obj_tag != entry->tag()) {
 650          entry->set_tag(obj_tag);
 651       }
 652     }
 653   }
 654 }
 655 
 656 // An extended CallbackWrapper used when reporting an object reference
 657 // to the agent.
 658 //
 659 // {
 660 //   TwoOopCallbackWrapper wrapper(tag_map, referrer, o);
 661 //
 662 //   (*callback)(wrapper.klass_tag(),
 663 //               wrapper.obj_size(),
 664 //               wrapper.obj_tag_p()
 665 //               wrapper.referrer_tag_p(), ...)
 666 //
 667 // } // wrapper goes out of scope here which results in the destructor
 668 //      checking to see if the referrer object has been tagged, untagged,
 669 //      or the tag value has changed.
 670 //
 671 class TwoOopCallbackWrapper : public CallbackWrapper {
 672  private:
 673   bool _is_reference_to_self;
 674   JvmtiTagHashmap* _referrer_hashmap;
 675   JvmtiTagHashmapEntry* _referrer_entry;
 676   oop _referrer;
 677   jlong _referrer_obj_tag;
 678   jlong _referrer_klass_tag;
 679   jlong* _referrer_tag_p;
 680 
 681   bool is_reference_to_self() const             { return _is_reference_to_self; }
 682 
 683  public:
 684   TwoOopCallbackWrapper(JvmtiTagMap* tag_map, oop referrer, oop o) :
 685     CallbackWrapper(tag_map, o)
 686   {
 687     // self reference needs to be handled in a special way
 688     _is_reference_to_self = (referrer == o);
 689 
 690     if (_is_reference_to_self) {
 691       _referrer_klass_tag = klass_tag();
 692       _referrer_tag_p = obj_tag_p();
 693     } else {
 694       _referrer = referrer;
 695       // record the context
 696       _referrer_hashmap = tag_map->hashmap();
 697       _referrer_entry = _referrer_hashmap->find(_referrer);
 698 
 699       // get object tag
 700       _referrer_obj_tag = (_referrer_entry == NULL) ? 0 : _referrer_entry->tag();
 701       _referrer_tag_p = &_referrer_obj_tag;
 702 
 703       // get referrer class tag.
 704       _referrer_klass_tag = tag_for(tag_map, _referrer->klass()->java_mirror());
 705     }
 706   }
 707 
 708   ~TwoOopCallbackWrapper() {
 709     if (!is_reference_to_self()){
 710       post_callback_tag_update(_referrer,
 711                                _referrer_hashmap,
 712                                _referrer_entry,
 713                                _referrer_obj_tag);
 714     }
 715   }
 716 
 717   // address of referrer tag
 718   // (for a self reference this will return the same thing as obj_tag_p())
 719   inline jlong* referrer_tag_p()        { return _referrer_tag_p; }
 720 
 721   // referrer's class tag
 722   inline jlong referrer_klass_tag()     { return _referrer_klass_tag; }
 723 };
 724 
 725 // tag an object
 726 //
 727 // This function is performance critical. If many threads attempt to tag objects
 728 // around the same time then it's possible that the Mutex associated with the
 729 // tag map will be a hot lock.
 730 void JvmtiTagMap::set_tag(jobject object, jlong tag) {
 731   MutexLocker ml(lock());
 732 
 733   // resolve the object
 734   oop o = JNIHandles::resolve_non_null(object);
 735 
 736   // see if the object is already tagged
 737   JvmtiTagHashmap* hashmap = _hashmap;
 738   JvmtiTagHashmapEntry* entry = hashmap->find(o);
 739 
 740   // if the object is not already tagged then we tag it
 741   if (entry == NULL) {
 742     if (tag != 0) {
 743       entry = create_entry(o, tag);
 744       hashmap->add(o, entry);
 745     } else {
 746       // no-op
 747     }
 748   } else {
 749     // if the object is already tagged then we either update
 750     // the tag (if a new tag value has been provided)
 751     // or remove the object if the new tag value is 0.
 752     if (tag == 0) {
 753       hashmap->remove(o);
 754       destroy_entry(entry);
 755     } else {
 756       entry->set_tag(tag);
 757     }
 758   }
 759 }
 760 
 761 // get the tag for an object
 762 jlong JvmtiTagMap::get_tag(jobject object) {
 763   MutexLocker ml(lock());
 764 
 765   // resolve the object
 766   oop o = JNIHandles::resolve_non_null(object);
 767 
 768   return tag_for(this, o);
 769 }
 770 
 771 
 772 // Helper class used to describe the static or instance fields of a class.
 773 // For each field it holds the field index (as defined by the JVMTI specification),
 774 // the field type, and the offset.
 775 
 776 class ClassFieldDescriptor: public CHeapObj<mtInternal> {
 777  private:
 778   int _field_index;
 779   int _field_offset;
 780   char _field_type;
 781  public:
 782   ClassFieldDescriptor(int index, char type, int offset) :
 783     _field_index(index), _field_type(type), _field_offset(offset) {
 784   }
 785   int field_index()  const  { return _field_index; }
 786   char field_type()  const  { return _field_type; }
 787   int field_offset() const  { return _field_offset; }
 788 };
 789 
 790 class ClassFieldMap: public CHeapObj<mtInternal> {
 791  private:
 792   enum {
 793     initial_field_count = 5
 794   };
 795 
 796   // list of field descriptors
 797   GrowableArray<ClassFieldDescriptor*>* _fields;
 798 
 799   // constructor
 800   ClassFieldMap();
 801 
 802   // add a field
 803   void add(int index, char type, int offset);
 804 
 805   // returns the field count for the given class
 806   static int compute_field_count(InstanceKlass* ik);
 807 
 808  public:
 809   ~ClassFieldMap();
 810 
 811   // access
 812   int field_count()                     { return _fields->length(); }
 813   ClassFieldDescriptor* field_at(int i) { return _fields->at(i); }
 814 
 815   // functions to create maps of static or instance fields
 816   static ClassFieldMap* create_map_of_static_fields(Klass* k);
 817   static ClassFieldMap* create_map_of_instance_fields(oop obj);
 818 };
 819 
 820 ClassFieldMap::ClassFieldMap() {
 821   _fields = new (ResourceObj::C_HEAP, mtInternal)
 822     GrowableArray<ClassFieldDescriptor*>(initial_field_count, true);
 823 }
 824 
 825 ClassFieldMap::~ClassFieldMap() {
 826   for (int i=0; i<_fields->length(); i++) {
 827     delete _fields->at(i);
 828   }
 829   delete _fields;
 830 }
 831 
 832 void ClassFieldMap::add(int index, char type, int offset) {
 833   ClassFieldDescriptor* field = new ClassFieldDescriptor(index, type, offset);
 834   _fields->append(field);
 835 }
 836 
 837 // Returns a heap allocated ClassFieldMap to describe the static fields
 838 // of the given class.
 839 //
 840 ClassFieldMap* ClassFieldMap::create_map_of_static_fields(Klass* k) {
 841   HandleMark hm;
 842   InstanceKlass* ik = InstanceKlass::cast(k);
 843 
 844   // create the field map
 845   ClassFieldMap* field_map = new ClassFieldMap();
 846 
 847   FilteredFieldStream f(ik, false, false);
 848   int max_field_index = f.field_count()-1;
 849 
 850   int index = 0;
 851   for (FilteredFieldStream fld(ik, true, true); !fld.eos(); fld.next(), index++) {
 852     // ignore instance fields
 853     if (!fld.access_flags().is_static()) {
 854       continue;
 855     }
 856     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());
 857   }
 858   return field_map;
 859 }
 860 
 861 // Returns a heap allocated ClassFieldMap to describe the instance fields
 862 // of the given class. All instance fields are included (this means public
 863 // and private fields declared in superclasses and superinterfaces too).
 864 //
 865 ClassFieldMap* ClassFieldMap::create_map_of_instance_fields(oop obj) {
 866   HandleMark hm;
 867   InstanceKlass* ik = InstanceKlass::cast(obj->klass());
 868 
 869   // create the field map
 870   ClassFieldMap* field_map = new ClassFieldMap();
 871 
 872   FilteredFieldStream f(ik, false, false);
 873 
 874   int max_field_index = f.field_count()-1;
 875 
 876   int index = 0;
 877   for (FilteredFieldStream fld(ik, false, false); !fld.eos(); fld.next(), index++) {
 878     // ignore static fields
 879     if (fld.access_flags().is_static()) {
 880       continue;
 881     }
 882     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());
 883   }
 884 
 885   return field_map;
 886 }
 887 
 888 // Helper class used to cache a ClassFileMap for the instance fields of
 889 // a cache. A JvmtiCachedClassFieldMap can be cached by an InstanceKlass during
 890 // heap iteration and avoid creating a field map for each object in the heap
 891 // (only need to create the map when the first instance of a class is encountered).
 892 //
 893 class JvmtiCachedClassFieldMap : public CHeapObj<mtInternal> {
 894  private:
 895    enum {
 896      initial_class_count = 200
 897    };
 898   ClassFieldMap* _field_map;
 899 
 900   ClassFieldMap* field_map() const          { return _field_map; }
 901 
 902   JvmtiCachedClassFieldMap(ClassFieldMap* field_map);
 903   ~JvmtiCachedClassFieldMap();
 904 
 905   static GrowableArray<InstanceKlass*>* _class_list;
 906   static void add_to_class_list(InstanceKlass* ik);
 907 
 908  public:
 909   // returns the field map for a given object (returning map cached
 910   // by InstanceKlass if possible
 911   static ClassFieldMap* get_map_of_instance_fields(oop obj);
 912 
 913   // removes the field map from all instanceKlasses - should be
 914   // called before VM operation completes
 915   static void clear_cache();
 916 
 917   // returns the number of ClassFieldMap cached by instanceKlasses
 918   static int cached_field_map_count();
 919 };
 920 
 921 GrowableArray<InstanceKlass*>* JvmtiCachedClassFieldMap::_class_list;
 922 
 923 JvmtiCachedClassFieldMap::JvmtiCachedClassFieldMap(ClassFieldMap* field_map) {
 924   _field_map = field_map;
 925 }
 926 
 927 JvmtiCachedClassFieldMap::~JvmtiCachedClassFieldMap() {
 928   if (_field_map != NULL) {
 929     delete _field_map;
 930   }
 931 }
 932 
 933 // Marker class to ensure that the class file map cache is only used in a defined
 934 // scope.
 935 class ClassFieldMapCacheMark : public StackObj {
 936  private:
 937    static bool _is_active;
 938  public:
 939    ClassFieldMapCacheMark() {
 940      assert(Thread::current()->is_VM_thread(), "must be VMThread");
 941      assert(JvmtiCachedClassFieldMap::cached_field_map_count() == 0, "cache not empty");
 942      assert(!_is_active, "ClassFieldMapCacheMark cannot be nested");
 943      _is_active = true;
 944    }
 945    ~ClassFieldMapCacheMark() {
 946      JvmtiCachedClassFieldMap::clear_cache();
 947      _is_active = false;
 948    }
 949    static bool is_active() { return _is_active; }
 950 };
 951 
 952 bool ClassFieldMapCacheMark::_is_active;
 953 
 954 
 955 // record that the given InstanceKlass is caching a field map
 956 void JvmtiCachedClassFieldMap::add_to_class_list(InstanceKlass* ik) {
 957   if (_class_list == NULL) {
 958     _class_list = new (ResourceObj::C_HEAP, mtInternal)
 959       GrowableArray<InstanceKlass*>(initial_class_count, true);
 960   }
 961   _class_list->push(ik);
 962 }
 963 
 964 // returns the instance field map for the given object
 965 // (returns field map cached by the InstanceKlass if possible)
 966 ClassFieldMap* JvmtiCachedClassFieldMap::get_map_of_instance_fields(oop obj) {
 967   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 968   assert(ClassFieldMapCacheMark::is_active(), "ClassFieldMapCacheMark not active");
 969 
 970   Klass* k = obj->klass();
 971   InstanceKlass* ik = InstanceKlass::cast(k);
 972 
 973   // return cached map if possible
 974   JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 975   if (cached_map != NULL) {
 976     assert(cached_map->field_map() != NULL, "missing field list");
 977     return cached_map->field_map();
 978   } else {
 979     ClassFieldMap* field_map = ClassFieldMap::create_map_of_instance_fields(obj);
 980     cached_map = new JvmtiCachedClassFieldMap(field_map);
 981     ik->set_jvmti_cached_class_field_map(cached_map);
 982     add_to_class_list(ik);
 983     return field_map;
 984   }
 985 }
 986 
 987 // remove the fields maps cached from all instanceKlasses
 988 void JvmtiCachedClassFieldMap::clear_cache() {
 989   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 990   if (_class_list != NULL) {
 991     for (int i = 0; i < _class_list->length(); i++) {
 992       InstanceKlass* ik = _class_list->at(i);
 993       JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 994       assert(cached_map != NULL, "should not be NULL");
 995       ik->set_jvmti_cached_class_field_map(NULL);
 996       delete cached_map;  // deletes the encapsulated field map
 997     }
 998     delete _class_list;
 999     _class_list = NULL;
1000   }
1001 }
1002 
1003 // returns the number of ClassFieldMap cached by instanceKlasses
1004 int JvmtiCachedClassFieldMap::cached_field_map_count() {
1005   return (_class_list == NULL) ? 0 : _class_list->length();
1006 }
1007 
1008 // helper function to indicate if an object is filtered by its tag or class tag
1009 static inline bool is_filtered_by_heap_filter(jlong obj_tag,
1010                                               jlong klass_tag,
1011                                               int heap_filter) {
1012   // apply the heap filter
1013   if (obj_tag != 0) {
1014     // filter out tagged objects
1015     if (heap_filter & JVMTI_HEAP_FILTER_TAGGED) return true;
1016   } else {
1017     // filter out untagged objects
1018     if (heap_filter & JVMTI_HEAP_FILTER_UNTAGGED) return true;
1019   }
1020   if (klass_tag != 0) {
1021     // filter out objects with tagged classes
1022     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_TAGGED) return true;
1023   } else {
1024     // filter out objects with untagged classes.
1025     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_UNTAGGED) return true;
1026   }
1027   return false;
1028 }
1029 
1030 // helper function to indicate if an object is filtered by a klass filter
1031 static inline bool is_filtered_by_klass_filter(oop obj, Klass* klass_filter) {
1032   if (klass_filter != NULL) {
1033     if (obj->klass() != klass_filter) {
1034       return true;
1035     }
1036   }
1037   return false;
1038 }
1039 
1040 // helper function to tell if a field is a primitive field or not
1041 static inline bool is_primitive_field_type(char type) {
1042   return (type != 'L' && type != '[');
1043 }
1044 
1045 // helper function to copy the value from location addr to jvalue.
1046 static inline void copy_to_jvalue(jvalue *v, address addr, jvmtiPrimitiveType value_type) {
1047   switch (value_type) {
1048     case JVMTI_PRIMITIVE_TYPE_BOOLEAN : { v->z = *(jboolean*)addr; break; }
1049     case JVMTI_PRIMITIVE_TYPE_BYTE    : { v->b = *(jbyte*)addr;    break; }
1050     case JVMTI_PRIMITIVE_TYPE_CHAR    : { v->c = *(jchar*)addr;    break; }
1051     case JVMTI_PRIMITIVE_TYPE_SHORT   : { v->s = *(jshort*)addr;   break; }
1052     case JVMTI_PRIMITIVE_TYPE_INT     : { v->i = *(jint*)addr;     break; }
1053     case JVMTI_PRIMITIVE_TYPE_LONG    : { v->j = *(jlong*)addr;    break; }
1054     case JVMTI_PRIMITIVE_TYPE_FLOAT   : { v->f = *(jfloat*)addr;   break; }
1055     case JVMTI_PRIMITIVE_TYPE_DOUBLE  : { v->d = *(jdouble*)addr;  break; }
1056     default: ShouldNotReachHere();
1057   }
1058 }
1059 
1060 // helper function to invoke string primitive value callback
1061 // returns visit control flags
1062 static jint invoke_string_value_callback(jvmtiStringPrimitiveValueCallback cb,
1063                                          CallbackWrapper* wrapper,
1064                                          oop str,
1065                                          void* user_data)
1066 {
1067   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
1068 
1069   typeArrayOop s_value = java_lang_String::value(str);
1070 
1071   // JDK-6584008: the value field may be null if a String instance is
1072   // partially constructed.
1073   if (s_value == NULL) {
1074     return 0;
1075   }
1076   // get the string value and length
1077   // (string value may be offset from the base)
1078   int s_len = java_lang_String::length(str);
1079   bool is_latin1 = java_lang_String::is_latin1(str);
1080   jchar* value;
1081   if (s_len > 0) {
1082     if (!is_latin1) {
1083       value = s_value->char_at_addr(0);
1084     } else {
1085       // Inflate latin1 encoded string to UTF16
1086       jchar* buf = NEW_C_HEAP_ARRAY(jchar, s_len, mtInternal);
1087       for (int i = 0; i < s_len; i++) {
1088         buf[i] = ((jchar) s_value->byte_at(i)) & 0xff;
1089       }
1090       value = &buf[0];
1091     }
1092   } else {
1093     // Don't use char_at_addr(0) if length is 0
1094     value = (jchar*) s_value->base(T_CHAR);
1095   }
1096 
1097   // invoke the callback
1098   jint res = (*cb)(wrapper->klass_tag(),
1099                    wrapper->obj_size(),
1100                    wrapper->obj_tag_p(),
1101                    value,
1102                    (jint)s_len,
1103                    user_data);
1104 
1105   if (is_latin1 && s_len > 0) {
1106     FREE_C_HEAP_ARRAY(jchar, value);
1107   }
1108   return res;
1109 }
1110 
1111 // helper function to invoke string primitive value callback
1112 // returns visit control flags
1113 static jint invoke_array_primitive_value_callback(jvmtiArrayPrimitiveValueCallback cb,
1114                                                   CallbackWrapper* wrapper,
1115                                                   oop obj,
1116                                                   void* user_data)
1117 {
1118   assert(obj->is_typeArray(), "not a primitive array");
1119 
1120   // get base address of first element
1121   typeArrayOop array = typeArrayOop(obj);
1122   BasicType type = TypeArrayKlass::cast(array->klass())->element_type();
1123   void* elements = array->base(type);
1124 
1125   // jvmtiPrimitiveType is defined so this mapping is always correct
1126   jvmtiPrimitiveType elem_type = (jvmtiPrimitiveType)type2char(type);
1127 
1128   return (*cb)(wrapper->klass_tag(),
1129                wrapper->obj_size(),
1130                wrapper->obj_tag_p(),
1131                (jint)array->length(),
1132                elem_type,
1133                elements,
1134                user_data);
1135 }
1136 
1137 // helper function to invoke the primitive field callback for all static fields
1138 // of a given class
1139 static jint invoke_primitive_field_callback_for_static_fields
1140   (CallbackWrapper* wrapper,
1141    oop obj,
1142    jvmtiPrimitiveFieldCallback cb,
1143    void* user_data)
1144 {
1145   // for static fields only the index will be set
1146   static jvmtiHeapReferenceInfo reference_info = { 0 };
1147 
1148   assert(obj->klass() == SystemDictionary::Class_klass(), "not a class");
1149   if (java_lang_Class::is_primitive(obj)) {
1150     return 0;
1151   }
1152   Klass* klass = java_lang_Class::as_Klass(obj);
1153 
1154   // ignore classes for object and type arrays
1155   if (!klass->is_instance_klass()) {
1156     return 0;
1157   }
1158 
1159   // ignore classes which aren't linked yet
1160   InstanceKlass* ik = InstanceKlass::cast(klass);
1161   if (!ik->is_linked()) {
1162     return 0;
1163   }
1164 
1165   // get the field map
1166   ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
1167 
1168   // invoke the callback for each static primitive field
1169   for (int i=0; i<field_map->field_count(); i++) {
1170     ClassFieldDescriptor* field = field_map->field_at(i);
1171 
1172     // ignore non-primitive fields
1173     char type = field->field_type();
1174     if (!is_primitive_field_type(type)) {
1175       continue;
1176     }
1177     // one-to-one mapping
1178     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1179 
1180     // get offset and field value
1181     int offset = field->field_offset();
1182     address addr = (address)klass->java_mirror() + offset;
1183     jvalue value;
1184     copy_to_jvalue(&value, addr, value_type);
1185 
1186     // field index
1187     reference_info.field.index = field->field_index();
1188 
1189     // invoke the callback
1190     jint res = (*cb)(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
1191                      &reference_info,
1192                      wrapper->klass_tag(),
1193                      wrapper->obj_tag_p(),
1194                      value,
1195                      value_type,
1196                      user_data);
1197     if (res & JVMTI_VISIT_ABORT) {
1198       delete field_map;
1199       return res;
1200     }
1201   }
1202 
1203   delete field_map;
1204   return 0;
1205 }
1206 
1207 // helper function to invoke the primitive field callback for all instance fields
1208 // of a given object
1209 static jint invoke_primitive_field_callback_for_instance_fields(
1210   CallbackWrapper* wrapper,
1211   oop obj,
1212   jvmtiPrimitiveFieldCallback cb,
1213   void* user_data)
1214 {
1215   // for instance fields only the index will be set
1216   static jvmtiHeapReferenceInfo reference_info = { 0 };
1217 
1218   // get the map of the instance fields
1219   ClassFieldMap* fields = JvmtiCachedClassFieldMap::get_map_of_instance_fields(obj);
1220 
1221   // invoke the callback for each instance primitive field
1222   for (int i=0; i<fields->field_count(); i++) {
1223     ClassFieldDescriptor* field = fields->field_at(i);
1224 
1225     // ignore non-primitive fields
1226     char type = field->field_type();
1227     if (!is_primitive_field_type(type)) {
1228       continue;
1229     }
1230     // one-to-one mapping
1231     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1232 
1233     // get offset and field value
1234     int offset = field->field_offset();
1235     address addr = (address)obj + offset;
1236     jvalue value;
1237     copy_to_jvalue(&value, addr, value_type);
1238 
1239     // field index
1240     reference_info.field.index = field->field_index();
1241 
1242     // invoke the callback
1243     jint res = (*cb)(JVMTI_HEAP_REFERENCE_FIELD,
1244                      &reference_info,
1245                      wrapper->klass_tag(),
1246                      wrapper->obj_tag_p(),
1247                      value,
1248                      value_type,
1249                      user_data);
1250     if (res & JVMTI_VISIT_ABORT) {
1251       return res;
1252     }
1253   }
1254   return 0;
1255 }
1256 
1257 
1258 // VM operation to iterate over all objects in the heap (both reachable
1259 // and unreachable)
1260 class VM_HeapIterateOperation: public VM_Operation {
1261  private:
1262   ObjectClosure* _blk;
1263  public:
1264   VM_HeapIterateOperation(ObjectClosure* blk) { _blk = blk; }
1265 
1266   VMOp_Type type() const { return VMOp_HeapIterateOperation; }
1267   void doit() {
1268     // allows class files maps to be cached during iteration
1269     ClassFieldMapCacheMark cm;
1270 
1271     // make sure that heap is parsable (fills TLABs with filler objects)
1272     Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1273 
1274     // Verify heap before iteration - if the heap gets corrupted then
1275     // JVMTI's IterateOverHeap will crash.
1276     if (VerifyBeforeIteration) {
1277       Universe::verify();
1278     }
1279 
1280     // do the iteration
1281     // If this operation encounters a bad object when using CMS,
1282     // consider using safe_object_iterate() which avoids perm gen
1283     // objects that may contain bad references.
1284     Universe::heap()->object_iterate(_blk);
1285   }
1286 
1287 };
1288 
1289 
1290 // An ObjectClosure used to support the deprecated IterateOverHeap and
1291 // IterateOverInstancesOfClass functions
1292 class IterateOverHeapObjectClosure: public ObjectClosure {
1293  private:
1294   JvmtiTagMap* _tag_map;
1295   Klass* _klass;
1296   jvmtiHeapObjectFilter _object_filter;
1297   jvmtiHeapObjectCallback _heap_object_callback;
1298   const void* _user_data;
1299 
1300   // accessors
1301   JvmtiTagMap* tag_map() const                    { return _tag_map; }
1302   jvmtiHeapObjectFilter object_filter() const     { return _object_filter; }
1303   jvmtiHeapObjectCallback object_callback() const { return _heap_object_callback; }
1304   Klass* klass() const                            { return _klass; }
1305   const void* user_data() const                   { return _user_data; }
1306 
1307   // indicates if iteration has been aborted
1308   bool _iteration_aborted;
1309   bool is_iteration_aborted() const               { return _iteration_aborted; }
1310   void set_iteration_aborted(bool aborted)        { _iteration_aborted = aborted; }
1311 
1312  public:
1313   IterateOverHeapObjectClosure(JvmtiTagMap* tag_map,
1314                                Klass* klass,
1315                                jvmtiHeapObjectFilter object_filter,
1316                                jvmtiHeapObjectCallback heap_object_callback,
1317                                const void* user_data) :
1318     _tag_map(tag_map),
1319     _klass(klass),
1320     _object_filter(object_filter),
1321     _heap_object_callback(heap_object_callback),
1322     _user_data(user_data),
1323     _iteration_aborted(false)
1324   {
1325   }
1326 
1327   void do_object(oop o);
1328 };
1329 
1330 // invoked for each object in the heap
1331 void IterateOverHeapObjectClosure::do_object(oop o) {
1332   // check if iteration has been halted
1333   if (is_iteration_aborted()) return;
1334 
1335   // instanceof check when filtering by klass
1336   if (klass() != NULL && !o->is_a(klass())) {
1337     return;
1338   }
1339   // prepare for the calllback
1340   CallbackWrapper wrapper(tag_map(), o);
1341 
1342   // if the object is tagged and we're only interested in untagged objects
1343   // then don't invoke the callback. Similiarly, if the object is untagged
1344   // and we're only interested in tagged objects we skip the callback.
1345   if (wrapper.obj_tag() != 0) {
1346     if (object_filter() == JVMTI_HEAP_OBJECT_UNTAGGED) return;
1347   } else {
1348     if (object_filter() == JVMTI_HEAP_OBJECT_TAGGED) return;
1349   }
1350 
1351   // invoke the agent's callback
1352   jvmtiIterationControl control = (*object_callback())(wrapper.klass_tag(),
1353                                                        wrapper.obj_size(),
1354                                                        wrapper.obj_tag_p(),
1355                                                        (void*)user_data());
1356   if (control == JVMTI_ITERATION_ABORT) {
1357     set_iteration_aborted(true);
1358   }
1359 }
1360 
1361 // An ObjectClosure used to support the IterateThroughHeap function
1362 class IterateThroughHeapObjectClosure: public ObjectClosure {
1363  private:
1364   JvmtiTagMap* _tag_map;
1365   Klass* _klass;
1366   int _heap_filter;
1367   const jvmtiHeapCallbacks* _callbacks;
1368   const void* _user_data;
1369 
1370   // accessor functions
1371   JvmtiTagMap* tag_map() const                     { return _tag_map; }
1372   int heap_filter() const                          { return _heap_filter; }
1373   const jvmtiHeapCallbacks* callbacks() const      { return _callbacks; }
1374   Klass* klass() const                             { return _klass; }
1375   const void* user_data() const                    { return _user_data; }
1376 
1377   // indicates if the iteration has been aborted
1378   bool _iteration_aborted;
1379   bool is_iteration_aborted() const                { return _iteration_aborted; }
1380 
1381   // used to check the visit control flags. If the abort flag is set
1382   // then we set the iteration aborted flag so that the iteration completes
1383   // without processing any further objects
1384   bool check_flags_for_abort(jint flags) {
1385     bool is_abort = (flags & JVMTI_VISIT_ABORT) != 0;
1386     if (is_abort) {
1387       _iteration_aborted = true;
1388     }
1389     return is_abort;
1390   }
1391 
1392  public:
1393   IterateThroughHeapObjectClosure(JvmtiTagMap* tag_map,
1394                                   Klass* klass,
1395                                   int heap_filter,
1396                                   const jvmtiHeapCallbacks* heap_callbacks,
1397                                   const void* user_data) :
1398     _tag_map(tag_map),
1399     _klass(klass),
1400     _heap_filter(heap_filter),
1401     _callbacks(heap_callbacks),
1402     _user_data(user_data),
1403     _iteration_aborted(false)
1404   {
1405   }
1406 
1407   void do_object(oop o);
1408 };
1409 
1410 // invoked for each object in the heap
1411 void IterateThroughHeapObjectClosure::do_object(oop obj) {
1412   // check if iteration has been halted
1413   if (is_iteration_aborted()) return;
1414 
1415   // apply class filter
1416   if (is_filtered_by_klass_filter(obj, klass())) return;
1417 
1418   // prepare for callback
1419   CallbackWrapper wrapper(tag_map(), obj);
1420 
1421   // check if filtered by the heap filter
1422   if (is_filtered_by_heap_filter(wrapper.obj_tag(), wrapper.klass_tag(), heap_filter())) {
1423     return;
1424   }
1425 
1426   // for arrays we need the length, otherwise -1
1427   bool is_array = obj->is_array();
1428   int len = is_array ? arrayOop(obj)->length() : -1;
1429 
1430   // invoke the object callback (if callback is provided)
1431   if (callbacks()->heap_iteration_callback != NULL) {
1432     jvmtiHeapIterationCallback cb = callbacks()->heap_iteration_callback;
1433     jint res = (*cb)(wrapper.klass_tag(),
1434                      wrapper.obj_size(),
1435                      wrapper.obj_tag_p(),
1436                      (jint)len,
1437                      (void*)user_data());
1438     if (check_flags_for_abort(res)) return;
1439   }
1440 
1441   // for objects and classes we report primitive fields if callback provided
1442   if (callbacks()->primitive_field_callback != NULL && obj->is_instance()) {
1443     jint res;
1444     jvmtiPrimitiveFieldCallback cb = callbacks()->primitive_field_callback;
1445     if (obj->klass() == SystemDictionary::Class_klass()) {
1446       res = invoke_primitive_field_callback_for_static_fields(&wrapper,
1447                                                                     obj,
1448                                                                     cb,
1449                                                                     (void*)user_data());
1450     } else {
1451       res = invoke_primitive_field_callback_for_instance_fields(&wrapper,
1452                                                                       obj,
1453                                                                       cb,
1454                                                                       (void*)user_data());
1455     }
1456     if (check_flags_for_abort(res)) return;
1457   }
1458 
1459   // string callback
1460   if (!is_array &&
1461       callbacks()->string_primitive_value_callback != NULL &&
1462       obj->klass() == SystemDictionary::String_klass()) {
1463     jint res = invoke_string_value_callback(
1464                 callbacks()->string_primitive_value_callback,
1465                 &wrapper,
1466                 obj,
1467                 (void*)user_data() );
1468     if (check_flags_for_abort(res)) return;
1469   }
1470 
1471   // array callback
1472   if (is_array &&
1473       callbacks()->array_primitive_value_callback != NULL &&
1474       obj->is_typeArray()) {
1475     jint res = invoke_array_primitive_value_callback(
1476                callbacks()->array_primitive_value_callback,
1477                &wrapper,
1478                obj,
1479                (void*)user_data() );
1480     if (check_flags_for_abort(res)) return;
1481   }
1482 };
1483 
1484 
1485 // Deprecated function to iterate over all objects in the heap
1486 void JvmtiTagMap::iterate_over_heap(jvmtiHeapObjectFilter object_filter,
1487                                     Klass* klass,
1488                                     jvmtiHeapObjectCallback heap_object_callback,
1489                                     const void* user_data)
1490 {
1491   MutexLocker ml(Heap_lock);
1492   IterateOverHeapObjectClosure blk(this,
1493                                    klass,
1494                                    object_filter,
1495                                    heap_object_callback,
1496                                    user_data);
1497   VM_HeapIterateOperation op(&blk);
1498   VMThread::execute(&op);
1499 }
1500 
1501 
1502 // Iterates over all objects in the heap
1503 void JvmtiTagMap::iterate_through_heap(jint heap_filter,
1504                                        Klass* klass,
1505                                        const jvmtiHeapCallbacks* callbacks,
1506                                        const void* user_data)
1507 {
1508   MutexLocker ml(Heap_lock);
1509   IterateThroughHeapObjectClosure blk(this,
1510                                       klass,
1511                                       heap_filter,
1512                                       callbacks,
1513                                       user_data);
1514   VM_HeapIterateOperation op(&blk);
1515   VMThread::execute(&op);
1516 }
1517 
1518 // support class for get_objects_with_tags
1519 
1520 class TagObjectCollector : public JvmtiTagHashmapEntryClosure {
1521  private:
1522   JvmtiEnv* _env;
1523   jlong* _tags;
1524   jint _tag_count;
1525 
1526   GrowableArray<jobject>* _object_results;  // collected objects (JNI weak refs)
1527   GrowableArray<uint64_t>* _tag_results;    // collected tags
1528 
1529  public:
1530   TagObjectCollector(JvmtiEnv* env, const jlong* tags, jint tag_count) {
1531     _env = env;
1532     _tags = (jlong*)tags;
1533     _tag_count = tag_count;
1534     _object_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jobject>(1,true);
1535     _tag_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<uint64_t>(1,true);
1536   }
1537 
1538   ~TagObjectCollector() {
1539     delete _object_results;
1540     delete _tag_results;
1541   }
1542 
1543   // for each tagged object check if the tag value matches
1544   // - if it matches then we create a JNI local reference to the object
1545   // and record the reference and tag value.
1546   //
1547   void do_entry(JvmtiTagHashmapEntry* entry) {
1548     for (int i=0; i<_tag_count; i++) {
1549       if (_tags[i] == entry->tag()) {
1550         // The reference in this tag map could be the only (implicitly weak)
1551         // reference to that object. If we hand it out, we need to keep it live wrt
1552         // SATB marking similar to other j.l.ref.Reference referents. This is
1553         // achieved by using a phantom load in the object() accessor.
1554         oop o = entry->object();
1555         assert(o != NULL && Universe::heap()->is_in_reserved(o), "sanity check");
1556         jobject ref = JNIHandles::make_local(JavaThread::current(), o);
1557         _object_results->append(ref);
1558         _tag_results->append((uint64_t)entry->tag());
1559       }
1560     }
1561   }
1562 
1563   // return the results from the collection
1564   //
1565   jvmtiError result(jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1566     jvmtiError error;
1567     int count = _object_results->length();
1568     assert(count >= 0, "sanity check");
1569 
1570     // if object_result_ptr is not NULL then allocate the result and copy
1571     // in the object references.
1572     if (object_result_ptr != NULL) {
1573       error = _env->Allocate(count * sizeof(jobject), (unsigned char**)object_result_ptr);
1574       if (error != JVMTI_ERROR_NONE) {
1575         return error;
1576       }
1577       for (int i=0; i<count; i++) {
1578         (*object_result_ptr)[i] = _object_results->at(i);
1579       }
1580     }
1581 
1582     // if tag_result_ptr is not NULL then allocate the result and copy
1583     // in the tag values.
1584     if (tag_result_ptr != NULL) {
1585       error = _env->Allocate(count * sizeof(jlong), (unsigned char**)tag_result_ptr);
1586       if (error != JVMTI_ERROR_NONE) {
1587         if (object_result_ptr != NULL) {
1588           _env->Deallocate((unsigned char*)object_result_ptr);
1589         }
1590         return error;
1591       }
1592       for (int i=0; i<count; i++) {
1593         (*tag_result_ptr)[i] = (jlong)_tag_results->at(i);
1594       }
1595     }
1596 
1597     *count_ptr = count;
1598     return JVMTI_ERROR_NONE;
1599   }
1600 };
1601 
1602 // return the list of objects with the specified tags
1603 jvmtiError JvmtiTagMap::get_objects_with_tags(const jlong* tags,
1604   jint count, jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1605 
1606   TagObjectCollector collector(env(), tags, count);
1607   {
1608     // iterate over all tagged objects
1609     MutexLocker ml(lock());
1610     entry_iterate(&collector);
1611   }
1612   return collector.result(count_ptr, object_result_ptr, tag_result_ptr);
1613 }
1614 
1615 
1616 // ObjectMarker is used to support the marking objects when walking the
1617 // heap.
1618 //
1619 // This implementation uses the existing mark bits in an object for
1620 // marking. Objects that are marked must later have their headers restored.
1621 // As most objects are unlocked and don't have their identity hash computed
1622 // we don't have to save their headers. Instead we save the headers that
1623 // are "interesting". Later when the headers are restored this implementation
1624 // restores all headers to their initial value and then restores the few
1625 // objects that had interesting headers.
1626 //
1627 // Future work: This implementation currently uses growable arrays to save
1628 // the oop and header of interesting objects. As an optimization we could
1629 // use the same technique as the GC and make use of the unused area
1630 // between top() and end().
1631 //
1632 
1633 // An ObjectClosure used to restore the mark bits of an object
1634 class RestoreMarksClosure : public ObjectClosure {
1635  public:
1636   void do_object(oop o) {
1637     if (o != NULL) {
1638       markOop mark = o->mark();
1639       if (mark->is_marked()) {
1640         o->init_mark();
1641       }
1642     }
1643   }
1644 };
1645 
1646 // ObjectMarker provides the mark and visited functions
1647 class ObjectMarker : AllStatic {
1648  private:
1649   // saved headers
1650   static GrowableArray<oop>* _saved_oop_stack;
1651   static GrowableArray<markOop>* _saved_mark_stack;
1652   static bool _needs_reset;                  // do we need to reset mark bits?
1653 
1654  public:
1655   static void init();                       // initialize
1656   static void done();                       // clean-up
1657 
1658   static inline void mark(oop o);           // mark an object
1659   static inline bool visited(oop o);        // check if object has been visited
1660 
1661   static inline bool needs_reset()            { return _needs_reset; }
1662   static inline void set_needs_reset(bool v)  { _needs_reset = v; }
1663 };
1664 
1665 GrowableArray<oop>* ObjectMarker::_saved_oop_stack = NULL;
1666 GrowableArray<markOop>* ObjectMarker::_saved_mark_stack = NULL;
1667 bool ObjectMarker::_needs_reset = true;  // need to reset mark bits by default
1668 
1669 // initialize ObjectMarker - prepares for object marking
1670 void ObjectMarker::init() {
1671   assert(Thread::current()->is_VM_thread(), "must be VMThread");
1672 
1673   // prepare heap for iteration
1674   Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1675 
1676   // create stacks for interesting headers
1677   _saved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(4000, true);
1678   _saved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(4000, true);
1679 
1680   if (UseBiasedLocking) {
1681     BiasedLocking::preserve_marks();
1682   }
1683 }
1684 
1685 // Object marking is done so restore object headers
1686 void ObjectMarker::done() {
1687   // iterate over all objects and restore the mark bits to
1688   // their initial value
1689   RestoreMarksClosure blk;
1690   if (needs_reset()) {
1691     Universe::heap()->object_iterate(&blk);
1692   } else {
1693     // We don't need to reset mark bits on this call, but reset the
1694     // flag to the default for the next call.
1695     set_needs_reset(true);
1696   }
1697 
1698   // now restore the interesting headers
1699   for (int i = 0; i < _saved_oop_stack->length(); i++) {
1700     oop o = _saved_oop_stack->at(i);
1701     markOop mark = _saved_mark_stack->at(i);
1702     o->set_mark(mark);
1703   }
1704 
1705   if (UseBiasedLocking) {
1706     BiasedLocking::restore_marks();
1707   }
1708 
1709   // free the stacks
1710   delete _saved_oop_stack;
1711   delete _saved_mark_stack;
1712 }
1713 
1714 // mark an object
1715 inline void ObjectMarker::mark(oop o) {
1716   assert(Universe::heap()->is_in(o), "sanity check");
1717   assert(!o->mark()->is_marked(), "should only mark an object once");
1718 
1719   // object's mark word
1720   markOop mark = o->mark();
1721 
1722   if (mark->must_be_preserved(o)) {
1723     _saved_mark_stack->push(mark);
1724     _saved_oop_stack->push(o);
1725   }
1726 
1727   // mark the object
1728   o->set_mark(markOopDesc::prototype()->set_marked());
1729 }
1730 
1731 // return true if object is marked
1732 inline bool ObjectMarker::visited(oop o) {
1733   return o->mark()->is_marked();
1734 }
1735 
1736 // Stack allocated class to help ensure that ObjectMarker is used
1737 // correctly. Constructor initializes ObjectMarker, destructor calls
1738 // ObjectMarker's done() function to restore object headers.
1739 class ObjectMarkerController : public StackObj {
1740  public:
1741   ObjectMarkerController() {
1742     ObjectMarker::init();
1743   }
1744   ~ObjectMarkerController() {
1745     ObjectMarker::done();
1746   }
1747 };
1748 
1749 
1750 // helper to map a jvmtiHeapReferenceKind to an old style jvmtiHeapRootKind
1751 // (not performance critical as only used for roots)
1752 static jvmtiHeapRootKind toJvmtiHeapRootKind(jvmtiHeapReferenceKind kind) {
1753   switch (kind) {
1754     case JVMTI_HEAP_REFERENCE_JNI_GLOBAL:   return JVMTI_HEAP_ROOT_JNI_GLOBAL;
1755     case JVMTI_HEAP_REFERENCE_SYSTEM_CLASS: return JVMTI_HEAP_ROOT_SYSTEM_CLASS;
1756     case JVMTI_HEAP_REFERENCE_MONITOR:      return JVMTI_HEAP_ROOT_MONITOR;
1757     case JVMTI_HEAP_REFERENCE_STACK_LOCAL:  return JVMTI_HEAP_ROOT_STACK_LOCAL;
1758     case JVMTI_HEAP_REFERENCE_JNI_LOCAL:    return JVMTI_HEAP_ROOT_JNI_LOCAL;
1759     case JVMTI_HEAP_REFERENCE_THREAD:       return JVMTI_HEAP_ROOT_THREAD;
1760     case JVMTI_HEAP_REFERENCE_OTHER:        return JVMTI_HEAP_ROOT_OTHER;
1761     default: ShouldNotReachHere();          return JVMTI_HEAP_ROOT_OTHER;
1762   }
1763 }
1764 
1765 // Base class for all heap walk contexts. The base class maintains a flag
1766 // to indicate if the context is valid or not.
1767 class HeapWalkContext {
1768  private:
1769   bool _valid;
1770  public:
1771   HeapWalkContext(bool valid)                   { _valid = valid; }
1772   void invalidate()                             { _valid = false; }
1773   bool is_valid() const                         { return _valid; }
1774 };
1775 
1776 // A basic heap walk context for the deprecated heap walking functions.
1777 // The context for a basic heap walk are the callbacks and fields used by
1778 // the referrer caching scheme.
1779 class BasicHeapWalkContext: public HeapWalkContext {
1780  private:
1781   jvmtiHeapRootCallback _heap_root_callback;
1782   jvmtiStackReferenceCallback _stack_ref_callback;
1783   jvmtiObjectReferenceCallback _object_ref_callback;
1784 
1785   // used for caching
1786   oop _last_referrer;
1787   jlong _last_referrer_tag;
1788 
1789  public:
1790   BasicHeapWalkContext() : HeapWalkContext(false) { }
1791 
1792   BasicHeapWalkContext(jvmtiHeapRootCallback heap_root_callback,
1793                        jvmtiStackReferenceCallback stack_ref_callback,
1794                        jvmtiObjectReferenceCallback object_ref_callback) :
1795     HeapWalkContext(true),
1796     _heap_root_callback(heap_root_callback),
1797     _stack_ref_callback(stack_ref_callback),
1798     _object_ref_callback(object_ref_callback),
1799     _last_referrer(NULL),
1800     _last_referrer_tag(0) {
1801   }
1802 
1803   // accessors
1804   jvmtiHeapRootCallback heap_root_callback() const         { return _heap_root_callback; }
1805   jvmtiStackReferenceCallback stack_ref_callback() const   { return _stack_ref_callback; }
1806   jvmtiObjectReferenceCallback object_ref_callback() const { return _object_ref_callback;  }
1807 
1808   oop last_referrer() const               { return _last_referrer; }
1809   void set_last_referrer(oop referrer)    { _last_referrer = referrer; }
1810   jlong last_referrer_tag() const         { return _last_referrer_tag; }
1811   void set_last_referrer_tag(jlong value) { _last_referrer_tag = value; }
1812 };
1813 
1814 // The advanced heap walk context for the FollowReferences functions.
1815 // The context is the callbacks, and the fields used for filtering.
1816 class AdvancedHeapWalkContext: public HeapWalkContext {
1817  private:
1818   jint _heap_filter;
1819   Klass* _klass_filter;
1820   const jvmtiHeapCallbacks* _heap_callbacks;
1821 
1822  public:
1823   AdvancedHeapWalkContext() : HeapWalkContext(false) { }
1824 
1825   AdvancedHeapWalkContext(jint heap_filter,
1826                            Klass* klass_filter,
1827                            const jvmtiHeapCallbacks* heap_callbacks) :
1828     HeapWalkContext(true),
1829     _heap_filter(heap_filter),
1830     _klass_filter(klass_filter),
1831     _heap_callbacks(heap_callbacks) {
1832   }
1833 
1834   // accessors
1835   jint heap_filter() const         { return _heap_filter; }
1836   Klass* klass_filter() const      { return _klass_filter; }
1837 
1838   const jvmtiHeapReferenceCallback heap_reference_callback() const {
1839     return _heap_callbacks->heap_reference_callback;
1840   };
1841   const jvmtiPrimitiveFieldCallback primitive_field_callback() const {
1842     return _heap_callbacks->primitive_field_callback;
1843   }
1844   const jvmtiArrayPrimitiveValueCallback array_primitive_value_callback() const {
1845     return _heap_callbacks->array_primitive_value_callback;
1846   }
1847   const jvmtiStringPrimitiveValueCallback string_primitive_value_callback() const {
1848     return _heap_callbacks->string_primitive_value_callback;
1849   }
1850 };
1851 
1852 // The CallbackInvoker is a class with static functions that the heap walk can call
1853 // into to invoke callbacks. It works in one of two modes. The "basic" mode is
1854 // used for the deprecated IterateOverReachableObjects functions. The "advanced"
1855 // mode is for the newer FollowReferences function which supports a lot of
1856 // additional callbacks.
1857 class CallbackInvoker : AllStatic {
1858  private:
1859   // heap walk styles
1860   enum { basic, advanced };
1861   static int _heap_walk_type;
1862   static bool is_basic_heap_walk()           { return _heap_walk_type == basic; }
1863   static bool is_advanced_heap_walk()        { return _heap_walk_type == advanced; }
1864 
1865   // context for basic style heap walk
1866   static BasicHeapWalkContext _basic_context;
1867   static BasicHeapWalkContext* basic_context() {
1868     assert(_basic_context.is_valid(), "invalid");
1869     return &_basic_context;
1870   }
1871 
1872   // context for advanced style heap walk
1873   static AdvancedHeapWalkContext _advanced_context;
1874   static AdvancedHeapWalkContext* advanced_context() {
1875     assert(_advanced_context.is_valid(), "invalid");
1876     return &_advanced_context;
1877   }
1878 
1879   // context needed for all heap walks
1880   static JvmtiTagMap* _tag_map;
1881   static const void* _user_data;
1882   static GrowableArray<oop>* _visit_stack;
1883 
1884   // accessors
1885   static JvmtiTagMap* tag_map()                        { return _tag_map; }
1886   static const void* user_data()                       { return _user_data; }
1887   static GrowableArray<oop>* visit_stack()             { return _visit_stack; }
1888 
1889   // if the object hasn't been visited then push it onto the visit stack
1890   // so that it will be visited later
1891   static inline bool check_for_visit(oop obj) {
1892     if (!ObjectMarker::visited(obj)) visit_stack()->push(obj);
1893     return true;
1894   }
1895 
1896   // invoke basic style callbacks
1897   static inline bool invoke_basic_heap_root_callback
1898     (jvmtiHeapRootKind root_kind, oop obj);
1899   static inline bool invoke_basic_stack_ref_callback
1900     (jvmtiHeapRootKind root_kind, jlong thread_tag, jint depth, jmethodID method,
1901      int slot, oop obj);
1902   static inline bool invoke_basic_object_reference_callback
1903     (jvmtiObjectReferenceKind ref_kind, oop referrer, oop referree, jint index);
1904 
1905   // invoke advanced style callbacks
1906   static inline bool invoke_advanced_heap_root_callback
1907     (jvmtiHeapReferenceKind ref_kind, oop obj);
1908   static inline bool invoke_advanced_stack_ref_callback
1909     (jvmtiHeapReferenceKind ref_kind, jlong thread_tag, jlong tid, int depth,
1910      jmethodID method, jlocation bci, jint slot, oop obj);
1911   static inline bool invoke_advanced_object_reference_callback
1912     (jvmtiHeapReferenceKind ref_kind, oop referrer, oop referree, jint index);
1913 
1914   // used to report the value of primitive fields
1915   static inline bool report_primitive_field
1916     (jvmtiHeapReferenceKind ref_kind, oop obj, jint index, address addr, char type);
1917 
1918  public:
1919   // initialize for basic mode
1920   static void initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1921                                              GrowableArray<oop>* visit_stack,
1922                                              const void* user_data,
1923                                              BasicHeapWalkContext context);
1924 
1925   // initialize for advanced mode
1926   static void initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1927                                                 GrowableArray<oop>* visit_stack,
1928                                                 const void* user_data,
1929                                                 AdvancedHeapWalkContext context);
1930 
1931    // functions to report roots
1932   static inline bool report_simple_root(jvmtiHeapReferenceKind kind, oop o);
1933   static inline bool report_jni_local_root(jlong thread_tag, jlong tid, jint depth,
1934     jmethodID m, oop o);
1935   static inline bool report_stack_ref_root(jlong thread_tag, jlong tid, jint depth,
1936     jmethodID method, jlocation bci, jint slot, oop o);
1937 
1938   // functions to report references
1939   static inline bool report_array_element_reference(oop referrer, oop referree, jint index);
1940   static inline bool report_class_reference(oop referrer, oop referree);
1941   static inline bool report_class_loader_reference(oop referrer, oop referree);
1942   static inline bool report_signers_reference(oop referrer, oop referree);
1943   static inline bool report_protection_domain_reference(oop referrer, oop referree);
1944   static inline bool report_superclass_reference(oop referrer, oop referree);
1945   static inline bool report_interface_reference(oop referrer, oop referree);
1946   static inline bool report_static_field_reference(oop referrer, oop referree, jint slot);
1947   static inline bool report_field_reference(oop referrer, oop referree, jint slot);
1948   static inline bool report_constant_pool_reference(oop referrer, oop referree, jint index);
1949   static inline bool report_primitive_array_values(oop array);
1950   static inline bool report_string_value(oop str);
1951   static inline bool report_primitive_instance_field(oop o, jint index, address value, char type);
1952   static inline bool report_primitive_static_field(oop o, jint index, address value, char type);
1953 };
1954 
1955 // statics
1956 int CallbackInvoker::_heap_walk_type;
1957 BasicHeapWalkContext CallbackInvoker::_basic_context;
1958 AdvancedHeapWalkContext CallbackInvoker::_advanced_context;
1959 JvmtiTagMap* CallbackInvoker::_tag_map;
1960 const void* CallbackInvoker::_user_data;
1961 GrowableArray<oop>* CallbackInvoker::_visit_stack;
1962 
1963 // initialize for basic heap walk (IterateOverReachableObjects et al)
1964 void CallbackInvoker::initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1965                                                      GrowableArray<oop>* visit_stack,
1966                                                      const void* user_data,
1967                                                      BasicHeapWalkContext context) {
1968   _tag_map = tag_map;
1969   _visit_stack = visit_stack;
1970   _user_data = user_data;
1971   _basic_context = context;
1972   _advanced_context.invalidate();       // will trigger assertion if used
1973   _heap_walk_type = basic;
1974 }
1975 
1976 // initialize for advanced heap walk (FollowReferences)
1977 void CallbackInvoker::initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1978                                                         GrowableArray<oop>* visit_stack,
1979                                                         const void* user_data,
1980                                                         AdvancedHeapWalkContext context) {
1981   _tag_map = tag_map;
1982   _visit_stack = visit_stack;
1983   _user_data = user_data;
1984   _advanced_context = context;
1985   _basic_context.invalidate();      // will trigger assertion if used
1986   _heap_walk_type = advanced;
1987 }
1988 
1989 
1990 // invoke basic style heap root callback
1991 inline bool CallbackInvoker::invoke_basic_heap_root_callback(jvmtiHeapRootKind root_kind, oop obj) {
1992   // if we heap roots should be reported
1993   jvmtiHeapRootCallback cb = basic_context()->heap_root_callback();
1994   if (cb == NULL) {
1995     return check_for_visit(obj);
1996   }
1997 
1998   CallbackWrapper wrapper(tag_map(), obj);
1999   jvmtiIterationControl control = (*cb)(root_kind,
2000                                         wrapper.klass_tag(),
2001                                         wrapper.obj_size(),
2002                                         wrapper.obj_tag_p(),
2003                                         (void*)user_data());
2004   // push root to visit stack when following references
2005   if (control == JVMTI_ITERATION_CONTINUE &&
2006       basic_context()->object_ref_callback() != NULL) {
2007     visit_stack()->push(obj);
2008   }
2009   return control != JVMTI_ITERATION_ABORT;
2010 }
2011 
2012 // invoke basic style stack ref callback
2013 inline bool CallbackInvoker::invoke_basic_stack_ref_callback(jvmtiHeapRootKind root_kind,
2014                                                              jlong thread_tag,
2015                                                              jint depth,
2016                                                              jmethodID method,
2017                                                              int slot,
2018                                                              oop obj) {
2019   // if we stack refs should be reported
2020   jvmtiStackReferenceCallback cb = basic_context()->stack_ref_callback();
2021   if (cb == NULL) {
2022     return check_for_visit(obj);
2023   }
2024 
2025   CallbackWrapper wrapper(tag_map(), obj);
2026   jvmtiIterationControl control = (*cb)(root_kind,
2027                                         wrapper.klass_tag(),
2028                                         wrapper.obj_size(),
2029                                         wrapper.obj_tag_p(),
2030                                         thread_tag,
2031                                         depth,
2032                                         method,
2033                                         slot,
2034                                         (void*)user_data());
2035   // push root to visit stack when following references
2036   if (control == JVMTI_ITERATION_CONTINUE &&
2037       basic_context()->object_ref_callback() != NULL) {
2038     visit_stack()->push(obj);
2039   }
2040   return control != JVMTI_ITERATION_ABORT;
2041 }
2042 
2043 // invoke basic style object reference callback
2044 inline bool CallbackInvoker::invoke_basic_object_reference_callback(jvmtiObjectReferenceKind ref_kind,
2045                                                                     oop referrer,
2046                                                                     oop referree,
2047                                                                     jint index) {
2048 
2049   BasicHeapWalkContext* context = basic_context();
2050 
2051   // callback requires the referrer's tag. If it's the same referrer
2052   // as the last call then we use the cached value.
2053   jlong referrer_tag;
2054   if (referrer == context->last_referrer()) {
2055     referrer_tag = context->last_referrer_tag();
2056   } else {
2057     referrer_tag = tag_for(tag_map(), referrer);
2058   }
2059 
2060   // do the callback
2061   CallbackWrapper wrapper(tag_map(), referree);
2062   jvmtiObjectReferenceCallback cb = context->object_ref_callback();
2063   jvmtiIterationControl control = (*cb)(ref_kind,
2064                                         wrapper.klass_tag(),
2065                                         wrapper.obj_size(),
2066                                         wrapper.obj_tag_p(),
2067                                         referrer_tag,
2068                                         index,
2069                                         (void*)user_data());
2070 
2071   // record referrer and referrer tag. For self-references record the
2072   // tag value from the callback as this might differ from referrer_tag.
2073   context->set_last_referrer(referrer);
2074   if (referrer == referree) {
2075     context->set_last_referrer_tag(*wrapper.obj_tag_p());
2076   } else {
2077     context->set_last_referrer_tag(referrer_tag);
2078   }
2079 
2080   if (control == JVMTI_ITERATION_CONTINUE) {
2081     return check_for_visit(referree);
2082   } else {
2083     return control != JVMTI_ITERATION_ABORT;
2084   }
2085 }
2086 
2087 // invoke advanced style heap root callback
2088 inline bool CallbackInvoker::invoke_advanced_heap_root_callback(jvmtiHeapReferenceKind ref_kind,
2089                                                                 oop obj) {
2090   AdvancedHeapWalkContext* context = advanced_context();
2091 
2092   // check that callback is provided
2093   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2094   if (cb == NULL) {
2095     return check_for_visit(obj);
2096   }
2097 
2098   // apply class filter
2099   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2100     return check_for_visit(obj);
2101   }
2102 
2103   // setup the callback wrapper
2104   CallbackWrapper wrapper(tag_map(), obj);
2105 
2106   // apply tag filter
2107   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2108                                  wrapper.klass_tag(),
2109                                  context->heap_filter())) {
2110     return check_for_visit(obj);
2111   }
2112 
2113   // for arrays we need the length, otherwise -1
2114   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2115 
2116   // invoke the callback
2117   jint res  = (*cb)(ref_kind,
2118                     NULL, // referrer info
2119                     wrapper.klass_tag(),
2120                     0,    // referrer_class_tag is 0 for heap root
2121                     wrapper.obj_size(),
2122                     wrapper.obj_tag_p(),
2123                     NULL, // referrer_tag_p
2124                     len,
2125                     (void*)user_data());
2126   if (res & JVMTI_VISIT_ABORT) {
2127     return false;// referrer class tag
2128   }
2129   if (res & JVMTI_VISIT_OBJECTS) {
2130     check_for_visit(obj);
2131   }
2132   return true;
2133 }
2134 
2135 // report a reference from a thread stack to an object
2136 inline bool CallbackInvoker::invoke_advanced_stack_ref_callback(jvmtiHeapReferenceKind ref_kind,
2137                                                                 jlong thread_tag,
2138                                                                 jlong tid,
2139                                                                 int depth,
2140                                                                 jmethodID method,
2141                                                                 jlocation bci,
2142                                                                 jint slot,
2143                                                                 oop obj) {
2144   AdvancedHeapWalkContext* context = advanced_context();
2145 
2146   // check that callback is provider
2147   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2148   if (cb == NULL) {
2149     return check_for_visit(obj);
2150   }
2151 
2152   // apply class filter
2153   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2154     return check_for_visit(obj);
2155   }
2156 
2157   // setup the callback wrapper
2158   CallbackWrapper wrapper(tag_map(), obj);
2159 
2160   // apply tag filter
2161   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2162                                  wrapper.klass_tag(),
2163                                  context->heap_filter())) {
2164     return check_for_visit(obj);
2165   }
2166 
2167   // setup the referrer info
2168   jvmtiHeapReferenceInfo reference_info;
2169   reference_info.stack_local.thread_tag = thread_tag;
2170   reference_info.stack_local.thread_id = tid;
2171   reference_info.stack_local.depth = depth;
2172   reference_info.stack_local.method = method;
2173   reference_info.stack_local.location = bci;
2174   reference_info.stack_local.slot = slot;
2175 
2176   // for arrays we need the length, otherwise -1
2177   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2178 
2179   // call into the agent
2180   int res = (*cb)(ref_kind,
2181                   &reference_info,
2182                   wrapper.klass_tag(),
2183                   0,    // referrer_class_tag is 0 for heap root (stack)
2184                   wrapper.obj_size(),
2185                   wrapper.obj_tag_p(),
2186                   NULL, // referrer_tag is 0 for root
2187                   len,
2188                   (void*)user_data());
2189 
2190   if (res & JVMTI_VISIT_ABORT) {
2191     return false;
2192   }
2193   if (res & JVMTI_VISIT_OBJECTS) {
2194     check_for_visit(obj);
2195   }
2196   return true;
2197 }
2198 
2199 // This mask is used to pass reference_info to a jvmtiHeapReferenceCallback
2200 // only for ref_kinds defined by the JVM TI spec. Otherwise, NULL is passed.
2201 #define REF_INFO_MASK  ((1 << JVMTI_HEAP_REFERENCE_FIELD)         \
2202                       | (1 << JVMTI_HEAP_REFERENCE_STATIC_FIELD)  \
2203                       | (1 << JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT) \
2204                       | (1 << JVMTI_HEAP_REFERENCE_CONSTANT_POOL) \
2205                       | (1 << JVMTI_HEAP_REFERENCE_STACK_LOCAL)   \
2206                       | (1 << JVMTI_HEAP_REFERENCE_JNI_LOCAL))
2207 
2208 // invoke the object reference callback to report a reference
2209 inline bool CallbackInvoker::invoke_advanced_object_reference_callback(jvmtiHeapReferenceKind ref_kind,
2210                                                                        oop referrer,
2211                                                                        oop obj,
2212                                                                        jint index)
2213 {
2214   // field index is only valid field in reference_info
2215   static jvmtiHeapReferenceInfo reference_info = { 0 };
2216 
2217   AdvancedHeapWalkContext* context = advanced_context();
2218 
2219   // check that callback is provider
2220   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2221   if (cb == NULL) {
2222     return check_for_visit(obj);
2223   }
2224 
2225   // apply class filter
2226   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2227     return check_for_visit(obj);
2228   }
2229 
2230   // setup the callback wrapper
2231   TwoOopCallbackWrapper wrapper(tag_map(), referrer, obj);
2232 
2233   // apply tag filter
2234   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2235                                  wrapper.klass_tag(),
2236                                  context->heap_filter())) {
2237     return check_for_visit(obj);
2238   }
2239 
2240   // field index is only valid field in reference_info
2241   reference_info.field.index = index;
2242 
2243   // for arrays we need the length, otherwise -1
2244   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2245 
2246   // invoke the callback
2247   int res = (*cb)(ref_kind,
2248                   (REF_INFO_MASK & (1 << ref_kind)) ? &reference_info : NULL,
2249                   wrapper.klass_tag(),
2250                   wrapper.referrer_klass_tag(),
2251                   wrapper.obj_size(),
2252                   wrapper.obj_tag_p(),
2253                   wrapper.referrer_tag_p(),
2254                   len,
2255                   (void*)user_data());
2256 
2257   if (res & JVMTI_VISIT_ABORT) {
2258     return false;
2259   }
2260   if (res & JVMTI_VISIT_OBJECTS) {
2261     check_for_visit(obj);
2262   }
2263   return true;
2264 }
2265 
2266 // report a "simple root"
2267 inline bool CallbackInvoker::report_simple_root(jvmtiHeapReferenceKind kind, oop obj) {
2268   assert(kind != JVMTI_HEAP_REFERENCE_STACK_LOCAL &&
2269          kind != JVMTI_HEAP_REFERENCE_JNI_LOCAL, "not a simple root");
2270 
2271   if (is_basic_heap_walk()) {
2272     // map to old style root kind
2273     jvmtiHeapRootKind root_kind = toJvmtiHeapRootKind(kind);
2274     return invoke_basic_heap_root_callback(root_kind, obj);
2275   } else {
2276     assert(is_advanced_heap_walk(), "wrong heap walk type");
2277     return invoke_advanced_heap_root_callback(kind, obj);
2278   }
2279 }
2280 
2281 
2282 // invoke the primitive array values
2283 inline bool CallbackInvoker::report_primitive_array_values(oop obj) {
2284   assert(obj->is_typeArray(), "not a primitive array");
2285 
2286   AdvancedHeapWalkContext* context = advanced_context();
2287   assert(context->array_primitive_value_callback() != NULL, "no callback");
2288 
2289   // apply class filter
2290   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2291     return true;
2292   }
2293 
2294   CallbackWrapper wrapper(tag_map(), obj);
2295 
2296   // apply tag filter
2297   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2298                                  wrapper.klass_tag(),
2299                                  context->heap_filter())) {
2300     return true;
2301   }
2302 
2303   // invoke the callback
2304   int res = invoke_array_primitive_value_callback(context->array_primitive_value_callback(),
2305                                                   &wrapper,
2306                                                   obj,
2307                                                   (void*)user_data());
2308   return (!(res & JVMTI_VISIT_ABORT));
2309 }
2310 
2311 // invoke the string value callback
2312 inline bool CallbackInvoker::report_string_value(oop str) {
2313   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
2314 
2315   AdvancedHeapWalkContext* context = advanced_context();
2316   assert(context->string_primitive_value_callback() != NULL, "no callback");
2317 
2318   // apply class filter
2319   if (is_filtered_by_klass_filter(str, context->klass_filter())) {
2320     return true;
2321   }
2322 
2323   CallbackWrapper wrapper(tag_map(), str);
2324 
2325   // apply tag filter
2326   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2327                                  wrapper.klass_tag(),
2328                                  context->heap_filter())) {
2329     return true;
2330   }
2331 
2332   // invoke the callback
2333   int res = invoke_string_value_callback(context->string_primitive_value_callback(),
2334                                          &wrapper,
2335                                          str,
2336                                          (void*)user_data());
2337   return (!(res & JVMTI_VISIT_ABORT));
2338 }
2339 
2340 // invoke the primitive field callback
2341 inline bool CallbackInvoker::report_primitive_field(jvmtiHeapReferenceKind ref_kind,
2342                                                     oop obj,
2343                                                     jint index,
2344                                                     address addr,
2345                                                     char type)
2346 {
2347   // for primitive fields only the index will be set
2348   static jvmtiHeapReferenceInfo reference_info = { 0 };
2349 
2350   AdvancedHeapWalkContext* context = advanced_context();
2351   assert(context->primitive_field_callback() != NULL, "no callback");
2352 
2353   // apply class filter
2354   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2355     return true;
2356   }
2357 
2358   CallbackWrapper wrapper(tag_map(), obj);
2359 
2360   // apply tag filter
2361   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2362                                  wrapper.klass_tag(),
2363                                  context->heap_filter())) {
2364     return true;
2365   }
2366 
2367   // the field index in the referrer
2368   reference_info.field.index = index;
2369 
2370   // map the type
2371   jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
2372 
2373   // setup the jvalue
2374   jvalue value;
2375   copy_to_jvalue(&value, addr, value_type);
2376 
2377   jvmtiPrimitiveFieldCallback cb = context->primitive_field_callback();
2378   int res = (*cb)(ref_kind,
2379                   &reference_info,
2380                   wrapper.klass_tag(),
2381                   wrapper.obj_tag_p(),
2382                   value,
2383                   value_type,
2384                   (void*)user_data());
2385   return (!(res & JVMTI_VISIT_ABORT));
2386 }
2387 
2388 
2389 // instance field
2390 inline bool CallbackInvoker::report_primitive_instance_field(oop obj,
2391                                                              jint index,
2392                                                              address value,
2393                                                              char type) {
2394   return report_primitive_field(JVMTI_HEAP_REFERENCE_FIELD,
2395                                 obj,
2396                                 index,
2397                                 value,
2398                                 type);
2399 }
2400 
2401 // static field
2402 inline bool CallbackInvoker::report_primitive_static_field(oop obj,
2403                                                            jint index,
2404                                                            address value,
2405                                                            char type) {
2406   return report_primitive_field(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
2407                                 obj,
2408                                 index,
2409                                 value,
2410                                 type);
2411 }
2412 
2413 // report a JNI local (root object) to the profiler
2414 inline bool CallbackInvoker::report_jni_local_root(jlong thread_tag, jlong tid, jint depth, jmethodID m, oop obj) {
2415   if (is_basic_heap_walk()) {
2416     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_JNI_LOCAL,
2417                                            thread_tag,
2418                                            depth,
2419                                            m,
2420                                            -1,
2421                                            obj);
2422   } else {
2423     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_JNI_LOCAL,
2424                                               thread_tag, tid,
2425                                               depth,
2426                                               m,
2427                                               (jlocation)-1,
2428                                               -1,
2429                                               obj);
2430   }
2431 }
2432 
2433 
2434 // report a local (stack reference, root object)
2435 inline bool CallbackInvoker::report_stack_ref_root(jlong thread_tag,
2436                                                    jlong tid,
2437                                                    jint depth,
2438                                                    jmethodID method,
2439                                                    jlocation bci,
2440                                                    jint slot,
2441                                                    oop obj) {
2442   if (is_basic_heap_walk()) {
2443     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_STACK_LOCAL,
2444                                            thread_tag,
2445                                            depth,
2446                                            method,
2447                                            slot,
2448                                            obj);
2449   } else {
2450     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_STACK_LOCAL,
2451                                               thread_tag,
2452                                               tid,
2453                                               depth,
2454                                               method,
2455                                               bci,
2456                                               slot,
2457                                               obj);
2458   }
2459 }
2460 
2461 // report an object referencing a class.
2462 inline bool CallbackInvoker::report_class_reference(oop referrer, oop referree) {
2463   if (is_basic_heap_walk()) {
2464     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2465   } else {
2466     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS, referrer, referree, -1);
2467   }
2468 }
2469 
2470 // report a class referencing its class loader.
2471 inline bool CallbackInvoker::report_class_loader_reference(oop referrer, oop referree) {
2472   if (is_basic_heap_walk()) {
2473     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2474   } else {
2475     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2476   }
2477 }
2478 
2479 // report a class referencing its signers.
2480 inline bool CallbackInvoker::report_signers_reference(oop referrer, oop referree) {
2481   if (is_basic_heap_walk()) {
2482     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_SIGNERS, referrer, referree, -1);
2483   } else {
2484     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SIGNERS, referrer, referree, -1);
2485   }
2486 }
2487 
2488 // report a class referencing its protection domain..
2489 inline bool CallbackInvoker::report_protection_domain_reference(oop referrer, oop referree) {
2490   if (is_basic_heap_walk()) {
2491     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2492   } else {
2493     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2494   }
2495 }
2496 
2497 // report a class referencing its superclass.
2498 inline bool CallbackInvoker::report_superclass_reference(oop referrer, oop referree) {
2499   if (is_basic_heap_walk()) {
2500     // Send this to be consistent with past implementation
2501     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2502   } else {
2503     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SUPERCLASS, referrer, referree, -1);
2504   }
2505 }
2506 
2507 // report a class referencing one of its interfaces.
2508 inline bool CallbackInvoker::report_interface_reference(oop referrer, oop referree) {
2509   if (is_basic_heap_walk()) {
2510     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_INTERFACE, referrer, referree, -1);
2511   } else {
2512     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_INTERFACE, referrer, referree, -1);
2513   }
2514 }
2515 
2516 // report a class referencing one of its static fields.
2517 inline bool CallbackInvoker::report_static_field_reference(oop referrer, oop referree, jint slot) {
2518   if (is_basic_heap_walk()) {
2519     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2520   } else {
2521     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2522   }
2523 }
2524 
2525 // report an array referencing an element object
2526 inline bool CallbackInvoker::report_array_element_reference(oop referrer, oop referree, jint index) {
2527   if (is_basic_heap_walk()) {
2528     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2529   } else {
2530     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2531   }
2532 }
2533 
2534 // report an object referencing an instance field object
2535 inline bool CallbackInvoker::report_field_reference(oop referrer, oop referree, jint slot) {
2536   if (is_basic_heap_walk()) {
2537     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_FIELD, referrer, referree, slot);
2538   } else {
2539     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_FIELD, referrer, referree, slot);
2540   }
2541 }
2542 
2543 // report an array referencing an element object
2544 inline bool CallbackInvoker::report_constant_pool_reference(oop referrer, oop referree, jint index) {
2545   if (is_basic_heap_walk()) {
2546     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2547   } else {
2548     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2549   }
2550 }
2551 
2552 // A supporting closure used to process simple roots
2553 class SimpleRootsClosure : public OopClosure {
2554  private:
2555   jvmtiHeapReferenceKind _kind;
2556   bool _continue;
2557 
2558   jvmtiHeapReferenceKind root_kind()    { return _kind; }
2559 
2560  public:
2561   void set_kind(jvmtiHeapReferenceKind kind) {
2562     _kind = kind;
2563     _continue = true;
2564   }
2565 
2566   inline bool stopped() {
2567     return !_continue;
2568   }
2569 
2570   void do_oop(oop* obj_p) {
2571     // iteration has terminated
2572     if (stopped()) {
2573       return;
2574     }
2575 
2576     oop o = *obj_p;
2577     // ignore null
2578     if (o == NULL) {
2579       return;
2580     }
2581 
2582     assert(Universe::heap()->is_in_reserved(o), "should be impossible");
2583 
2584     jvmtiHeapReferenceKind kind = root_kind();
2585     if (kind == JVMTI_HEAP_REFERENCE_SYSTEM_CLASS) {
2586       // SystemDictionary::oops_do reports the application
2587       // class loader as a root. We want this root to be reported as
2588       // a root kind of "OTHER" rather than "SYSTEM_CLASS".
2589       if (!o->is_instance() || !InstanceKlass::cast(o->klass())->is_mirror_instance_klass()) {
2590         kind = JVMTI_HEAP_REFERENCE_OTHER;
2591       }
2592     }
2593 
2594     // invoke the callback
2595     _continue = CallbackInvoker::report_simple_root(kind, o);
2596 
2597   }
2598   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2599 };
2600 
2601 // A supporting closure used to process JNI locals
2602 class JNILocalRootsClosure : public OopClosure {
2603  private:
2604   jlong _thread_tag;
2605   jlong _tid;
2606   jint _depth;
2607   jmethodID _method;
2608   bool _continue;
2609  public:
2610   void set_context(jlong thread_tag, jlong tid, jint depth, jmethodID method) {
2611     _thread_tag = thread_tag;
2612     _tid = tid;
2613     _depth = depth;
2614     _method = method;
2615     _continue = true;
2616   }
2617 
2618   inline bool stopped() {
2619     return !_continue;
2620   }
2621 
2622   void do_oop(oop* obj_p) {
2623     // iteration has terminated
2624     if (stopped()) {
2625       return;
2626     }
2627 
2628     oop o = *obj_p;
2629     // ignore null
2630     if (o == NULL) {
2631       return;
2632     }
2633 
2634     // invoke the callback
2635     _continue = CallbackInvoker::report_jni_local_root(_thread_tag, _tid, _depth, _method, o);
2636   }
2637   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2638 };
2639 
2640 
2641 // A VM operation to iterate over objects that are reachable from
2642 // a set of roots or an initial object.
2643 //
2644 // For VM_HeapWalkOperation the set of roots used is :-
2645 //
2646 // - All JNI global references
2647 // - All inflated monitors
2648 // - All classes loaded by the boot class loader (or all classes
2649 //     in the event that class unloading is disabled)
2650 // - All java threads
2651 // - For each java thread then all locals and JNI local references
2652 //      on the thread's execution stack
2653 // - All visible/explainable objects from Universes::oops_do
2654 //
2655 class VM_HeapWalkOperation: public VM_Operation {
2656  private:
2657   enum {
2658     initial_visit_stack_size = 4000
2659   };
2660 
2661   bool _is_advanced_heap_walk;                      // indicates FollowReferences
2662   JvmtiTagMap* _tag_map;
2663   Handle _initial_object;
2664   GrowableArray<oop>* _visit_stack;                 // the visit stack
2665 
2666   bool _collecting_heap_roots;                      // are we collecting roots
2667   bool _following_object_refs;                      // are we following object references
2668 
2669   bool _reporting_primitive_fields;                 // optional reporting
2670   bool _reporting_primitive_array_values;
2671   bool _reporting_string_values;
2672 
2673   GrowableArray<oop>* create_visit_stack() {
2674     return new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(initial_visit_stack_size, true);
2675   }
2676 
2677   // accessors
2678   bool is_advanced_heap_walk() const               { return _is_advanced_heap_walk; }
2679   JvmtiTagMap* tag_map() const                     { return _tag_map; }
2680   Handle initial_object() const                    { return _initial_object; }
2681 
2682   bool is_following_references() const             { return _following_object_refs; }
2683 
2684   bool is_reporting_primitive_fields()  const      { return _reporting_primitive_fields; }
2685   bool is_reporting_primitive_array_values() const { return _reporting_primitive_array_values; }
2686   bool is_reporting_string_values() const          { return _reporting_string_values; }
2687 
2688   GrowableArray<oop>* visit_stack() const          { return _visit_stack; }
2689 
2690   // iterate over the various object types
2691   inline bool iterate_over_array(oop o);
2692   inline bool iterate_over_type_array(oop o);
2693   inline bool iterate_over_class(oop o);
2694   inline bool iterate_over_object(oop o);
2695 
2696   // root collection
2697   inline bool collect_simple_roots();
2698   inline bool collect_stack_roots();
2699   inline bool collect_stack_roots(JavaThread* java_thread, JNILocalRootsClosure* blk);
2700 
2701   // visit an object
2702   inline bool visit(oop o);
2703 
2704  public:
2705   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2706                        Handle initial_object,
2707                        BasicHeapWalkContext callbacks,
2708                        const void* user_data);
2709 
2710   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2711                        Handle initial_object,
2712                        AdvancedHeapWalkContext callbacks,
2713                        const void* user_data);
2714 
2715   ~VM_HeapWalkOperation();
2716 
2717   VMOp_Type type() const { return VMOp_HeapWalkOperation; }
2718   void doit();
2719 };
2720 
2721 
2722 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2723                                            Handle initial_object,
2724                                            BasicHeapWalkContext callbacks,
2725                                            const void* user_data) {
2726   _is_advanced_heap_walk = false;
2727   _tag_map = tag_map;
2728   _initial_object = initial_object;
2729   _following_object_refs = (callbacks.object_ref_callback() != NULL);
2730   _reporting_primitive_fields = false;
2731   _reporting_primitive_array_values = false;
2732   _reporting_string_values = false;
2733   _visit_stack = create_visit_stack();
2734 
2735 
2736   CallbackInvoker::initialize_for_basic_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2737 }
2738 
2739 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2740                                            Handle initial_object,
2741                                            AdvancedHeapWalkContext callbacks,
2742                                            const void* user_data) {
2743   _is_advanced_heap_walk = true;
2744   _tag_map = tag_map;
2745   _initial_object = initial_object;
2746   _following_object_refs = true;
2747   _reporting_primitive_fields = (callbacks.primitive_field_callback() != NULL);;
2748   _reporting_primitive_array_values = (callbacks.array_primitive_value_callback() != NULL);;
2749   _reporting_string_values = (callbacks.string_primitive_value_callback() != NULL);;
2750   _visit_stack = create_visit_stack();
2751 
2752   CallbackInvoker::initialize_for_advanced_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2753 }
2754 
2755 VM_HeapWalkOperation::~VM_HeapWalkOperation() {
2756   if (_following_object_refs) {
2757     assert(_visit_stack != NULL, "checking");
2758     delete _visit_stack;
2759     _visit_stack = NULL;
2760   }
2761 }
2762 
2763 // an array references its class and has a reference to
2764 // each element in the array
2765 inline bool VM_HeapWalkOperation::iterate_over_array(oop o) {
2766   objArrayOop array = objArrayOop(o);
2767 
2768   // array reference to its class
2769   oop mirror = ObjArrayKlass::cast(array->klass())->java_mirror();
2770   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2771     return false;
2772   }
2773 
2774   // iterate over the array and report each reference to a
2775   // non-null element
2776   for (int index=0; index<array->length(); index++) {
2777     oop elem = array->obj_at(index);
2778     if (elem == NULL) {
2779       continue;
2780     }
2781 
2782     // report the array reference o[index] = elem
2783     if (!CallbackInvoker::report_array_element_reference(o, elem, index)) {
2784       return false;
2785     }
2786   }
2787   return true;
2788 }
2789 
2790 // a type array references its class
2791 inline bool VM_HeapWalkOperation::iterate_over_type_array(oop o) {
2792   Klass* k = o->klass();
2793   oop mirror = k->java_mirror();
2794   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2795     return false;
2796   }
2797 
2798   // report the array contents if required
2799   if (is_reporting_primitive_array_values()) {
2800     if (!CallbackInvoker::report_primitive_array_values(o)) {
2801       return false;
2802     }
2803   }
2804   return true;
2805 }
2806 
2807 #ifdef ASSERT
2808 // verify that a static oop field is in range
2809 static inline bool verify_static_oop(InstanceKlass* ik,
2810                                      oop mirror, int offset) {
2811   address obj_p = (address)mirror + offset;
2812   address start = (address)InstanceMirrorKlass::start_of_static_fields(mirror);
2813   address end = start + (java_lang_Class::static_oop_field_count(mirror) * heapOopSize);
2814   assert(end >= start, "sanity check");
2815 
2816   if (obj_p >= start && obj_p < end) {
2817     return true;
2818   } else {
2819     return false;
2820   }
2821 }
2822 #endif // #ifdef ASSERT
2823 
2824 // a class references its super class, interfaces, class loader, ...
2825 // and finally its static fields
2826 inline bool VM_HeapWalkOperation::iterate_over_class(oop java_class) {
2827   int i;
2828   Klass* klass = java_lang_Class::as_Klass(java_class);
2829 
2830   if (klass->is_instance_klass()) {
2831     InstanceKlass* ik = InstanceKlass::cast(klass);
2832 
2833     // Ignore the class if it hasn't been initialized yet
2834     if (!ik->is_linked()) {
2835       return true;
2836     }
2837 
2838     // get the java mirror
2839     oop mirror = klass->java_mirror();
2840 
2841     // super (only if something more interesting than java.lang.Object)
2842     Klass* java_super = ik->java_super();
2843     if (java_super != NULL && java_super != SystemDictionary::Object_klass()) {
2844       oop super = java_super->java_mirror();
2845       if (!CallbackInvoker::report_superclass_reference(mirror, super)) {
2846         return false;
2847       }
2848     }
2849 
2850     // class loader
2851     oop cl = ik->class_loader();
2852     if (cl != NULL) {
2853       if (!CallbackInvoker::report_class_loader_reference(mirror, cl)) {
2854         return false;
2855       }
2856     }
2857 
2858     // protection domain
2859     oop pd = ik->protection_domain();
2860     if (pd != NULL) {
2861       if (!CallbackInvoker::report_protection_domain_reference(mirror, pd)) {
2862         return false;
2863       }
2864     }
2865 
2866     // signers
2867     oop signers = ik->signers();
2868     if (signers != NULL) {
2869       if (!CallbackInvoker::report_signers_reference(mirror, signers)) {
2870         return false;
2871       }
2872     }
2873 
2874     // references from the constant pool
2875     {
2876       ConstantPool* pool = ik->constants();
2877       for (int i = 1; i < pool->length(); i++) {
2878         constantTag tag = pool->tag_at(i).value();
2879         if (tag.is_string() || tag.is_klass()) {
2880           oop entry;
2881           if (tag.is_string()) {
2882             entry = pool->resolved_string_at(i);
2883             // If the entry is non-null it is resolved.
2884             if (entry == NULL) continue;
2885           } else {
2886             entry = pool->resolved_klass_at(i)->java_mirror();
2887           }
2888           if (!CallbackInvoker::report_constant_pool_reference(mirror, entry, (jint)i)) {
2889             return false;
2890           }
2891         }
2892       }
2893     }
2894 
2895     // interfaces
2896     // (These will already have been reported as references from the constant pool
2897     //  but are specified by IterateOverReachableObjects and must be reported).
2898     Array<Klass*>* interfaces = ik->local_interfaces();
2899     for (i = 0; i < interfaces->length(); i++) {
2900       oop interf = ((Klass*)interfaces->at(i))->java_mirror();
2901       if (interf == NULL) {
2902         continue;
2903       }
2904       if (!CallbackInvoker::report_interface_reference(mirror, interf)) {
2905         return false;
2906       }
2907     }
2908 
2909     // iterate over the static fields
2910 
2911     ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
2912     for (i=0; i<field_map->field_count(); i++) {
2913       ClassFieldDescriptor* field = field_map->field_at(i);
2914       char type = field->field_type();
2915       if (!is_primitive_field_type(type)) {
2916         oop fld_o = mirror->obj_field(field->field_offset());
2917         assert(verify_static_oop(ik, mirror, field->field_offset()), "sanity check");
2918         if (fld_o != NULL) {
2919           int slot = field->field_index();
2920           if (!CallbackInvoker::report_static_field_reference(mirror, fld_o, slot)) {
2921             delete field_map;
2922             return false;
2923           }
2924         }
2925       } else {
2926          if (is_reporting_primitive_fields()) {
2927            address addr = (address)mirror + field->field_offset();
2928            int slot = field->field_index();
2929            if (!CallbackInvoker::report_primitive_static_field(mirror, slot, addr, type)) {
2930              delete field_map;
2931              return false;
2932           }
2933         }
2934       }
2935     }
2936     delete field_map;
2937 
2938     return true;
2939   }
2940 
2941   return true;
2942 }
2943 
2944 // an object references a class and its instance fields
2945 // (static fields are ignored here as we report these as
2946 // references from the class).
2947 inline bool VM_HeapWalkOperation::iterate_over_object(oop o) {
2948   // reference to the class
2949   if (!CallbackInvoker::report_class_reference(o, o->klass()->java_mirror())) {
2950     return false;
2951   }
2952 
2953   // iterate over instance fields
2954   ClassFieldMap* field_map = JvmtiCachedClassFieldMap::get_map_of_instance_fields(o);
2955   for (int i=0; i<field_map->field_count(); i++) {
2956     ClassFieldDescriptor* field = field_map->field_at(i);
2957     char type = field->field_type();
2958     if (!is_primitive_field_type(type)) {
2959       oop fld_o = o->obj_field(field->field_offset());
2960       // ignore any objects that aren't visible to profiler
2961       if (fld_o != NULL) {
2962         assert(Universe::heap()->is_in_reserved(fld_o), "unsafe code should not "
2963                "have references to Klass* anymore");
2964         int slot = field->field_index();
2965         if (!CallbackInvoker::report_field_reference(o, fld_o, slot)) {
2966           return false;
2967         }
2968       }
2969     } else {
2970       if (is_reporting_primitive_fields()) {
2971         // primitive instance field
2972         address addr = (address)o + field->field_offset();
2973         int slot = field->field_index();
2974         if (!CallbackInvoker::report_primitive_instance_field(o, slot, addr, type)) {
2975           return false;
2976         }
2977       }
2978     }
2979   }
2980 
2981   // if the object is a java.lang.String
2982   if (is_reporting_string_values() &&
2983       o->klass() == SystemDictionary::String_klass()) {
2984     if (!CallbackInvoker::report_string_value(o)) {
2985       return false;
2986     }
2987   }
2988   return true;
2989 }
2990 
2991 
2992 // Collects all simple (non-stack) roots except for threads;
2993 // threads are handled in collect_stack_roots() as an optimization.
2994 // if there's a heap root callback provided then the callback is
2995 // invoked for each simple root.
2996 // if an object reference callback is provided then all simple
2997 // roots are pushed onto the marking stack so that they can be
2998 // processed later
2999 //
3000 inline bool VM_HeapWalkOperation::collect_simple_roots() {
3001   SimpleRootsClosure blk;
3002 
3003   // JNI globals
3004   blk.set_kind(JVMTI_HEAP_REFERENCE_JNI_GLOBAL);
3005   JNIHandles::oops_do(&blk);
3006   if (blk.stopped()) {
3007     return false;
3008   }
3009 
3010   // Preloaded classes and loader from the system dictionary
3011   blk.set_kind(JVMTI_HEAP_REFERENCE_SYSTEM_CLASS);
3012   SystemDictionary::oops_do(&blk);
3013   ClassLoaderDataGraph::always_strong_oops_do(&blk, false);
3014   if (blk.stopped()) {
3015     return false;
3016   }
3017 
3018   // Inflated monitors
3019   blk.set_kind(JVMTI_HEAP_REFERENCE_MONITOR);
3020   ObjectSynchronizer::oops_do(&blk);
3021   if (blk.stopped()) {
3022     return false;
3023   }
3024 
3025   // threads are now handled in collect_stack_roots()
3026 
3027   // Other kinds of roots maintained by HotSpot
3028   // Many of these won't be visible but others (such as instances of important
3029   // exceptions) will be visible.
3030   blk.set_kind(JVMTI_HEAP_REFERENCE_OTHER);
3031   Universe::oops_do(&blk);
3032 
3033   // If there are any non-perm roots in the code cache, visit them.
3034   blk.set_kind(JVMTI_HEAP_REFERENCE_OTHER);
3035   CodeBlobToOopClosure look_in_blobs(&blk, !CodeBlobToOopClosure::FixRelocations);
3036   CodeCache::scavenge_root_nmethods_do(&look_in_blobs);
3037 
3038   return true;
3039 }
3040 
3041 // Walk the stack of a given thread and find all references (locals
3042 // and JNI calls) and report these as stack references
3043 inline bool VM_HeapWalkOperation::collect_stack_roots(JavaThread* java_thread,
3044                                                       JNILocalRootsClosure* blk)
3045 {
3046   oop threadObj = java_thread->threadObj();
3047   assert(threadObj != NULL, "sanity check");
3048 
3049   // only need to get the thread's tag once per thread
3050   jlong thread_tag = tag_for(_tag_map, threadObj);
3051 
3052   // also need the thread id
3053   jlong tid = java_lang_Thread::thread_id(threadObj);
3054 
3055 
3056   if (java_thread->has_last_Java_frame()) {
3057 
3058     // vframes are resource allocated
3059     Thread* current_thread = Thread::current();
3060     ResourceMark rm(current_thread);
3061     HandleMark hm(current_thread);
3062 
3063     RegisterMap reg_map(java_thread);
3064     frame f = java_thread->last_frame();
3065     vframe* vf = vframe::new_vframe(&f, &reg_map, java_thread);
3066 
3067     bool is_top_frame = true;
3068     int depth = 0;
3069     frame* last_entry_frame = NULL;
3070 
3071     while (vf != NULL) {
3072       if (vf->is_java_frame()) {
3073 
3074         // java frame (interpreted, compiled, ...)
3075         javaVFrame *jvf = javaVFrame::cast(vf);
3076 
3077         // the jmethodID
3078         jmethodID method = jvf->method()->jmethod_id();
3079 
3080         if (!(jvf->method()->is_native())) {
3081           jlocation bci = (jlocation)jvf->bci();
3082           StackValueCollection* locals = jvf->locals();
3083           for (int slot=0; slot<locals->size(); slot++) {
3084             if (locals->at(slot)->type() == T_OBJECT) {
3085               oop o = locals->obj_at(slot)();
3086               if (o == NULL) {
3087                 continue;
3088               }
3089 
3090               // stack reference
3091               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3092                                                    bci, slot, o)) {
3093                 return false;
3094               }
3095             }
3096           }
3097 
3098           StackValueCollection* exprs = jvf->expressions();
3099           for (int index=0; index < exprs->size(); index++) {
3100             if (exprs->at(index)->type() == T_OBJECT) {
3101               oop o = exprs->obj_at(index)();
3102               if (o == NULL) {
3103                 continue;
3104               }
3105 
3106               // stack reference
3107               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3108                                                    bci, locals->size() + index, o)) {
3109                 return false;
3110               }
3111             }
3112           }
3113 
3114           // Follow oops from compiled nmethod
3115           if (jvf->cb() != NULL && jvf->cb()->is_nmethod()) {
3116             blk->set_context(thread_tag, tid, depth, method);
3117             jvf->cb()->as_nmethod()->oops_do(blk);
3118           }
3119         } else {
3120           blk->set_context(thread_tag, tid, depth, method);
3121           if (is_top_frame) {
3122             // JNI locals for the top frame.
3123             java_thread->active_handles()->oops_do(blk);
3124           } else {
3125             if (last_entry_frame != NULL) {
3126               // JNI locals for the entry frame
3127               assert(last_entry_frame->is_entry_frame(), "checking");
3128               last_entry_frame->entry_frame_call_wrapper()->handles()->oops_do(blk);
3129             }
3130           }
3131         }
3132         last_entry_frame = NULL;
3133         depth++;
3134       } else {
3135         // externalVFrame - for an entry frame then we report the JNI locals
3136         // when we find the corresponding javaVFrame
3137         frame* fr = vf->frame_pointer();
3138         assert(fr != NULL, "sanity check");
3139         if (fr->is_entry_frame()) {
3140           last_entry_frame = fr;
3141         }
3142       }
3143 
3144       vf = vf->sender();
3145       is_top_frame = false;
3146     }
3147   } else {
3148     // no last java frame but there may be JNI locals
3149     blk->set_context(thread_tag, tid, 0, (jmethodID)NULL);
3150     java_thread->active_handles()->oops_do(blk);
3151   }
3152   return true;
3153 }
3154 
3155 
3156 // Collects the simple roots for all threads and collects all
3157 // stack roots - for each thread it walks the execution
3158 // stack to find all references and local JNI refs.
3159 inline bool VM_HeapWalkOperation::collect_stack_roots() {
3160   JNILocalRootsClosure blk;
3161   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
3162     oop threadObj = thread->threadObj();
3163     if (threadObj != NULL && !thread->is_exiting() && !thread->is_hidden_from_external_view()) {
3164       // Collect the simple root for this thread before we
3165       // collect its stack roots
3166       if (!CallbackInvoker::report_simple_root(JVMTI_HEAP_REFERENCE_THREAD,
3167                                                threadObj)) {
3168         return false;
3169       }
3170       if (!collect_stack_roots(thread, &blk)) {
3171         return false;
3172       }
3173     }
3174   }
3175   return true;
3176 }
3177 
3178 // visit an object
3179 // first mark the object as visited
3180 // second get all the outbound references from this object (in other words, all
3181 // the objects referenced by this object).
3182 //
3183 bool VM_HeapWalkOperation::visit(oop o) {
3184   // mark object as visited
3185   assert(!ObjectMarker::visited(o), "can't visit same object more than once");
3186   ObjectMarker::mark(o);
3187 
3188   // instance
3189   if (o->is_instance()) {
3190     if (o->klass() == SystemDictionary::Class_klass()) {
3191       if (!java_lang_Class::is_primitive(o)) {
3192         // a java.lang.Class
3193         return iterate_over_class(o);
3194       }
3195     } else {
3196       return iterate_over_object(o);
3197     }
3198   }
3199 
3200   // object array
3201   if (o->is_objArray()) {
3202     return iterate_over_array(o);
3203   }
3204 
3205   // type array
3206   if (o->is_typeArray()) {
3207     return iterate_over_type_array(o);
3208   }
3209 
3210   return true;
3211 }
3212 
3213 void VM_HeapWalkOperation::doit() {
3214   ResourceMark rm;
3215   ObjectMarkerController marker;
3216   ClassFieldMapCacheMark cm;
3217 
3218   assert(visit_stack()->is_empty(), "visit stack must be empty");
3219 
3220   // the heap walk starts with an initial object or the heap roots
3221   if (initial_object().is_null()) {
3222     // If either collect_stack_roots() or collect_simple_roots()
3223     // returns false at this point, then there are no mark bits
3224     // to reset.
3225     ObjectMarker::set_needs_reset(false);
3226 
3227     // Calling collect_stack_roots() before collect_simple_roots()
3228     // can result in a big performance boost for an agent that is
3229     // focused on analyzing references in the thread stacks.
3230     if (!collect_stack_roots()) return;
3231 
3232     if (!collect_simple_roots()) return;
3233 
3234     // no early return so enable heap traversal to reset the mark bits
3235     ObjectMarker::set_needs_reset(true);
3236   } else {
3237     visit_stack()->push(initial_object()());
3238   }
3239 
3240   // object references required
3241   if (is_following_references()) {
3242 
3243     // visit each object until all reachable objects have been
3244     // visited or the callback asked to terminate the iteration.
3245     while (!visit_stack()->is_empty()) {
3246       oop o = visit_stack()->pop();
3247       if (!ObjectMarker::visited(o)) {
3248         if (!visit(o)) {
3249           break;
3250         }
3251       }
3252     }
3253   }
3254 }
3255 
3256 // iterate over all objects that are reachable from a set of roots
3257 void JvmtiTagMap::iterate_over_reachable_objects(jvmtiHeapRootCallback heap_root_callback,
3258                                                  jvmtiStackReferenceCallback stack_ref_callback,
3259                                                  jvmtiObjectReferenceCallback object_ref_callback,
3260                                                  const void* user_data) {
3261   MutexLocker ml(Heap_lock);
3262   BasicHeapWalkContext context(heap_root_callback, stack_ref_callback, object_ref_callback);
3263   VM_HeapWalkOperation op(this, Handle(), context, user_data);
3264   VMThread::execute(&op);
3265 }
3266 
3267 // iterate over all objects that are reachable from a given object
3268 void JvmtiTagMap::iterate_over_objects_reachable_from_object(jobject object,
3269                                                              jvmtiObjectReferenceCallback object_ref_callback,
3270                                                              const void* user_data) {
3271   oop obj = JNIHandles::resolve(object);
3272   Handle initial_object(Thread::current(), obj);
3273 
3274   MutexLocker ml(Heap_lock);
3275   BasicHeapWalkContext context(NULL, NULL, object_ref_callback);
3276   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3277   VMThread::execute(&op);
3278 }
3279 
3280 // follow references from an initial object or the GC roots
3281 void JvmtiTagMap::follow_references(jint heap_filter,
3282                                     Klass* klass,
3283                                     jobject object,
3284                                     const jvmtiHeapCallbacks* callbacks,
3285                                     const void* user_data)
3286 {
3287   oop obj = JNIHandles::resolve(object);
3288   Handle initial_object(Thread::current(), obj);
3289 
3290   MutexLocker ml(Heap_lock);
3291   AdvancedHeapWalkContext context(heap_filter, klass, callbacks);
3292   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3293   VMThread::execute(&op);
3294 }
3295 
3296 
3297 void JvmtiTagMap::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
3298   // No locks during VM bring-up (0 threads) and no safepoints after main
3299   // thread creation and before VMThread creation (1 thread); initial GC
3300   // verification can happen in that window which gets to here.
3301   assert(Threads::number_of_threads() <= 1 ||
3302          SafepointSynchronize::is_at_safepoint(),
3303          "must be executed at a safepoint");
3304   if (JvmtiEnv::environments_might_exist()) {
3305     JvmtiEnvIterator it;
3306     for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
3307       JvmtiTagMap* tag_map = env->tag_map();
3308       if (tag_map != NULL && !tag_map->is_empty()) {
3309         tag_map->do_weak_oops(is_alive, f);
3310       }
3311     }
3312   }
3313 }
3314 
3315 void JvmtiTagMap::do_weak_oops(BoolObjectClosure* is_alive, OopClosure* f) {
3316 
3317   // does this environment have the OBJECT_FREE event enabled
3318   bool post_object_free = env()->is_enabled(JVMTI_EVENT_OBJECT_FREE);
3319 
3320   // counters used for trace message
3321   int freed = 0;
3322   int moved = 0;
3323 
3324   JvmtiTagHashmap* hashmap = this->hashmap();
3325 
3326   // reenable sizing (if disabled)
3327   hashmap->set_resizing_enabled(true);
3328 
3329   // if the hashmap is empty then we can skip it
3330   if (hashmap->_entry_count == 0) {
3331     return;
3332   }
3333 
3334   // now iterate through each entry in the table
3335 
3336   JvmtiTagHashmapEntry** table = hashmap->table();
3337   int size = hashmap->size();
3338 
3339   JvmtiTagHashmapEntry* delayed_add = NULL;
3340 
3341   for (int pos = 0; pos < size; ++pos) {
3342     JvmtiTagHashmapEntry* entry = table[pos];
3343     JvmtiTagHashmapEntry* prev = NULL;
3344 
3345     while (entry != NULL) {
3346       JvmtiTagHashmapEntry* next = entry->next();
3347 
3348       // has object been GC'ed
3349       if (!is_alive->do_object_b(entry->object_peek())) {
3350         // grab the tag
3351         jlong tag = entry->tag();
3352         guarantee(tag != 0, "checking");
3353 
3354         // remove GC'ed entry from hashmap and return the
3355         // entry to the free list
3356         hashmap->remove(prev, pos, entry);
3357         destroy_entry(entry);
3358 
3359         // post the event to the profiler
3360         if (post_object_free) {
3361           JvmtiExport::post_object_free(env(), tag);
3362         }
3363 
3364         ++freed;
3365       } else {
3366         f->do_oop(entry->object_addr());
3367         oop new_oop = entry->object_peek();
3368 
3369         // if the object has moved then re-hash it and move its
3370         // entry to its new location.
3371         unsigned int new_pos = JvmtiTagHashmap::hash(new_oop, size);
3372         if (new_pos != (unsigned int)pos) {
3373           if (prev == NULL) {
3374             table[pos] = next;
3375           } else {
3376             prev->set_next(next);
3377           }
3378           if (new_pos < (unsigned int)pos) {
3379             entry->set_next(table[new_pos]);
3380             table[new_pos] = entry;
3381           } else {
3382             // Delay adding this entry to it's new position as we'd end up
3383             // hitting it again during this iteration.
3384             entry->set_next(delayed_add);
3385             delayed_add = entry;
3386           }
3387           moved++;
3388         } else {
3389           // object didn't move
3390           prev = entry;
3391         }
3392       }
3393 
3394       entry = next;
3395     }
3396   }
3397 
3398   // Re-add all the entries which were kept aside
3399   while (delayed_add != NULL) {
3400     JvmtiTagHashmapEntry* next = delayed_add->next();
3401     unsigned int pos = JvmtiTagHashmap::hash(delayed_add->object_peek(), size);
3402     delayed_add->set_next(table[pos]);
3403     table[pos] = delayed_add;
3404     delayed_add = next;
3405   }
3406 
3407   log_debug(jvmti, objecttagging)("(%d->%d, %d freed, %d total moves)",
3408                                   hashmap->_entry_count + freed, hashmap->_entry_count, freed, moved);
3409 }