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