1 /*
   2  * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/javaClasses.inline.hpp"
  27 #include "classfile/symbolTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "jvmtifiles/jvmtiEnv.hpp"
  32 #include "memory/allocation.inline.hpp"
  33 #include "memory/resourceArea.hpp"
  34 #include "oops/access.inline.hpp"
  35 #include "oops/arrayOop.inline.hpp"
  36 #include "oops/constantPool.inline.hpp"
  37 #include "oops/instanceMirrorKlass.hpp"
  38 #include "oops/objArrayKlass.hpp"
  39 #include "oops/objArrayOop.inline.hpp"
  40 #include "oops/oop.inline.hpp"
  41 #include "oops/typeArrayOop.inline.hpp"
  42 #include "prims/jvmtiEventController.hpp"
  43 #include "prims/jvmtiEventController.inline.hpp"
  44 #include "prims/jvmtiExport.hpp"
  45 #include "prims/jvmtiImpl.hpp"
  46 #include "prims/jvmtiTagMap.hpp"
  47 #include "runtime/biasedLocking.hpp"
  48 #include "runtime/javaCalls.hpp"
  49 #include "runtime/jniHandles.inline.hpp"
  50 #include "runtime/mutex.hpp"
  51 #include "runtime/mutexLocker.hpp"
  52 #include "runtime/reflectionUtils.hpp"
  53 #include "runtime/thread.inline.hpp"
  54 #include "runtime/threadSMR.hpp"
  55 #include "runtime/vframe.hpp"
  56 #include "runtime/vmThread.hpp"
  57 #include "runtime/vm_operations.hpp"
  58 #include "utilities/macros.hpp"
  59 
  60 // JvmtiTagHashmapEntry
  61 //
  62 // Each entry encapsulates a reference to the tagged object
  63 // and the tag value. In addition an entry includes a next pointer which
  64 // is used to chain entries together.
  65 
  66 class JvmtiTagHashmapEntry : public CHeapObj<mtInternal> {
  67  private:
  68   friend class JvmtiTagMap;
  69 
  70   oop _object;                          // tagged object
  71   jlong _tag;                           // the tag
  72   JvmtiTagHashmapEntry* _next;          // next on the list
  73 
  74   inline void init(oop object, jlong tag) {
  75     _object = object;
  76     _tag = tag;
  77     _next = NULL;
  78   }
  79 
  80   // constructor
  81   JvmtiTagHashmapEntry(oop object, jlong tag) { init(object, tag); }
  82 
  83  public:
  84 
  85   // accessor methods
  86   inline oop* object_addr() { return &_object; }
  87   inline oop object()       { return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(object_addr()); }
  88   // Peek at the object without keeping it alive. The returned object must be
  89   // kept alive using a normal access if it leaks out of a thread transition from VM.
  90   inline oop object_peek()  {
  91     return RootAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(object_addr());
  92   }
  93   inline jlong tag() const  { return _tag; }
  94 
  95   inline void set_tag(jlong tag) {
  96     assert(tag != 0, "can't be zero");
  97     _tag = tag;
  98   }
  99 
 100   inline bool equals(oop object) {
 101     return object == object_peek();
 102   }
 103 
 104   inline JvmtiTagHashmapEntry* next() const        { return _next; }
 105   inline void set_next(JvmtiTagHashmapEntry* next) { _next = next; }
 106 };
 107 
 108 
 109 // JvmtiTagHashmap
 110 //
 111 // A hashmap is essentially a table of pointers to entries. Entries
 112 // are hashed to a location, or position in the table, and then
 113 // chained from that location. The "key" for hashing is address of
 114 // the object, or oop. The "value" is the tag value.
 115 //
 116 // A hashmap maintains a count of the number entries in the hashmap
 117 // and resizes if the number of entries exceeds a given threshold.
 118 // The threshold is specified as a percentage of the size - for
 119 // example a threshold of 0.75 will trigger the hashmap to resize
 120 // if the number of entries is >75% of table size.
 121 //
 122 // A hashmap provides functions for adding, removing, and finding
 123 // entries. It also provides a function to iterate over all entries
 124 // in the hashmap.
 125 
 126 class JvmtiTagHashmap : public CHeapObj<mtInternal> {
 127  private:
 128   friend class JvmtiTagMap;
 129 
 130   enum {
 131     small_trace_threshold  = 10000,                  // threshold for tracing
 132     medium_trace_threshold = 100000,
 133     large_trace_threshold  = 1000000,
 134     initial_trace_threshold = small_trace_threshold
 135   };
 136 
 137   static int _sizes[];                  // array of possible hashmap sizes
 138   int _size;                            // actual size of the table
 139   int _size_index;                      // index into size table
 140 
 141   int _entry_count;                     // number of entries in the hashmap
 142 
 143   float _load_factor;                   // load factor as a % of the size
 144   int _resize_threshold;                // computed threshold to trigger resizing.
 145   bool _resizing_enabled;               // indicates if hashmap can resize
 146 
 147   int _trace_threshold;                 // threshold for trace messages
 148 
 149   JvmtiTagHashmapEntry** _table;        // the table of entries.
 150 
 151   // private accessors
 152   int resize_threshold() const                  { return _resize_threshold; }
 153   int trace_threshold() const                   { return _trace_threshold; }
 154 
 155   // initialize the hashmap
 156   void init(int size_index=0, float load_factor=4.0f) {
 157     int initial_size =  _sizes[size_index];
 158     _size_index = size_index;
 159     _size = initial_size;
 160     _entry_count = 0;
 161     _trace_threshold = initial_trace_threshold;
 162     _load_factor = load_factor;
 163     _resize_threshold = (int)(_load_factor * _size);
 164     _resizing_enabled = true;
 165     size_t s = initial_size * sizeof(JvmtiTagHashmapEntry*);
 166     _table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 167     if (_table == NULL) {
 168       vm_exit_out_of_memory(s, OOM_MALLOC_ERROR,
 169         "unable to allocate initial hashtable for jvmti object tags");
 170     }
 171     for (int i=0; i<initial_size; i++) {
 172       _table[i] = NULL;
 173     }
 174   }
 175 
 176   // hash a given key (oop) with the specified size
 177   static unsigned int hash(oop key, int size) {
 178     // shift right to get better distribution (as these bits will be zero
 179     // with aligned addresses)
 180     unsigned int addr = (unsigned int)(cast_from_oop<intptr_t>(key));
 181 #ifdef _LP64
 182     return (addr >> 3) % size;
 183 #else
 184     return (addr >> 2) % size;
 185 #endif
 186   }
 187 
 188   // hash a given key (oop)
 189   unsigned int hash(oop key) {
 190     return hash(key, _size);
 191   }
 192 
 193   // resize the hashmap - allocates a large table and re-hashes
 194   // all entries into the new table.
 195   void resize() {
 196     int new_size_index = _size_index+1;
 197     int new_size = _sizes[new_size_index];
 198     if (new_size < 0) {
 199       // hashmap already at maximum capacity
 200       return;
 201     }
 202 
 203     // allocate new table
 204     size_t s = new_size * sizeof(JvmtiTagHashmapEntry*);
 205     JvmtiTagHashmapEntry** new_table = (JvmtiTagHashmapEntry**)os::malloc(s, mtInternal);
 206     if (new_table == NULL) {
 207       warning("unable to allocate larger hashtable for jvmti object tags");
 208       set_resizing_enabled(false);
 209       return;
 210     }
 211 
 212     // initialize new table
 213     int i;
 214     for (i=0; i<new_size; i++) {
 215       new_table[i] = NULL;
 216     }
 217 
 218     // rehash all entries into the new table
 219     for (i=0; i<_size; i++) {
 220       JvmtiTagHashmapEntry* entry = _table[i];
 221       while (entry != NULL) {
 222         JvmtiTagHashmapEntry* next = entry->next();
 223         oop key = entry->object_peek();
 224         assert(key != NULL, "jni weak reference cleared!!");
 225         unsigned int h = hash(key, new_size);
 226         JvmtiTagHashmapEntry* anchor = new_table[h];
 227         if (anchor == NULL) {
 228           new_table[h] = entry;
 229           entry->set_next(NULL);
 230         } else {
 231           entry->set_next(anchor);
 232           new_table[h] = entry;
 233         }
 234         entry = next;
 235       }
 236     }
 237 
 238     // free old table and update settings.
 239     os::free((void*)_table);
 240     _table = new_table;
 241     _size_index = new_size_index;
 242     _size = new_size;
 243 
 244     // compute new resize threshold
 245     _resize_threshold = (int)(_load_factor * _size);
 246   }
 247 
 248 
 249   // internal remove function - remove an entry at a given position in the
 250   // table.
 251   inline void remove(JvmtiTagHashmapEntry* prev, int pos, JvmtiTagHashmapEntry* entry) {
 252     assert(pos >= 0 && pos < _size, "out of range");
 253     if (prev == NULL) {
 254       _table[pos] = entry->next();
 255     } else {
 256       prev->set_next(entry->next());
 257     }
 258     assert(_entry_count > 0, "checking");
 259     _entry_count--;
 260   }
 261 
 262   // resizing switch
 263   bool is_resizing_enabled() const          { return _resizing_enabled; }
 264   void set_resizing_enabled(bool enable)    { _resizing_enabled = enable; }
 265 
 266   // debugging
 267   void print_memory_usage();
 268   void compute_next_trace_threshold();
 269 
 270  public:
 271 
 272   // create a JvmtiTagHashmap of a preferred size and optionally a load factor.
 273   // The preferred size is rounded down to an actual size.
 274   JvmtiTagHashmap(int size, float load_factor=0.0f) {
 275     int i=0;
 276     while (_sizes[i] < size) {
 277       if (_sizes[i] < 0) {
 278         assert(i > 0, "sanity check");
 279         i--;
 280         break;
 281       }
 282       i++;
 283     }
 284 
 285     // if a load factor is specified then use it, otherwise use default
 286     if (load_factor > 0.01f) {
 287       init(i, load_factor);
 288     } else {
 289       init(i);
 290     }
 291   }
 292 
 293   // create a JvmtiTagHashmap with default settings
 294   JvmtiTagHashmap() {
 295     init();
 296   }
 297 
 298   // release table when JvmtiTagHashmap destroyed
 299   ~JvmtiTagHashmap() {
 300     if (_table != NULL) {
 301       os::free((void*)_table);
 302       _table = NULL;
 303     }
 304   }
 305 
 306   // accessors
 307   int size() const                              { return _size; }
 308   JvmtiTagHashmapEntry** table() const          { return _table; }
 309   int entry_count() const                       { return _entry_count; }
 310 
 311   // find an entry in the hashmap, returns NULL if not found.
 312   inline JvmtiTagHashmapEntry* find(oop key) {
 313     unsigned int h = hash(key);
 314     JvmtiTagHashmapEntry* entry = _table[h];
 315     while (entry != NULL) {
 316       if (entry->equals(key)) {
 317          return entry;
 318       }
 319       entry = entry->next();
 320     }
 321     return NULL;
 322   }
 323 
 324 
 325   // add a new entry to hashmap
 326   inline void add(oop key, JvmtiTagHashmapEntry* entry) {
 327     assert(key != NULL, "checking");
 328     assert(find(key) == NULL, "duplicate detected");
 329     unsigned int h = hash(key);
 330     JvmtiTagHashmapEntry* anchor = _table[h];
 331     if (anchor == NULL) {
 332       _table[h] = entry;
 333       entry->set_next(NULL);
 334     } else {
 335       entry->set_next(anchor);
 336       _table[h] = entry;
 337     }
 338 
 339     _entry_count++;
 340     if (log_is_enabled(Debug, jvmti, objecttagging) && entry_count() >= trace_threshold()) {
 341       print_memory_usage();
 342       compute_next_trace_threshold();
 343     }
 344 
 345     // if the number of entries exceed the threshold then resize
 346     if (entry_count() > resize_threshold() && is_resizing_enabled()) {
 347       resize();
 348     }
 349   }
 350 
 351   // remove an entry with the given key.
 352   inline JvmtiTagHashmapEntry* remove(oop key) {
 353     unsigned int h = hash(key);
 354     JvmtiTagHashmapEntry* entry = _table[h];
 355     JvmtiTagHashmapEntry* prev = NULL;
 356     while (entry != NULL) {
 357       if (entry->equals(key)) {
 358         break;
 359       }
 360       prev = entry;
 361       entry = entry->next();
 362     }
 363     if (entry != NULL) {
 364       remove(prev, h, entry);
 365     }
 366     return entry;
 367   }
 368 
 369   // iterate over all entries in the hashmap
 370   void entry_iterate(JvmtiTagHashmapEntryClosure* closure);
 371 };
 372 
 373 // possible hashmap sizes - odd primes that roughly double in size.
 374 // To avoid excessive resizing the odd primes from 4801-76831 and
 375 // 76831-307261 have been removed. The list must be terminated by -1.
 376 int JvmtiTagHashmap::_sizes[] =  { 4801, 76831, 307261, 614563, 1228891,
 377     2457733, 4915219, 9830479, 19660831, 39321619, 78643219, -1 };
 378 
 379 
 380 // A supporting class for iterating over all entries in Hashmap
 381 class JvmtiTagHashmapEntryClosure {
 382  public:
 383   virtual void do_entry(JvmtiTagHashmapEntry* entry) = 0;
 384 };
 385 
 386 
 387 // iterate over all entries in the hashmap
 388 void JvmtiTagHashmap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 389   for (int i=0; i<_size; i++) {
 390     JvmtiTagHashmapEntry* entry = _table[i];
 391     JvmtiTagHashmapEntry* prev = NULL;
 392     while (entry != NULL) {
 393       // obtain the next entry before invoking do_entry - this is
 394       // necessary because do_entry may remove the entry from the
 395       // hashmap.
 396       JvmtiTagHashmapEntry* next = entry->next();
 397       closure->do_entry(entry);
 398       entry = next;
 399      }
 400   }
 401 }
 402 
 403 // debugging
 404 void JvmtiTagHashmap::print_memory_usage() {
 405   intptr_t p = (intptr_t)this;
 406   tty->print("[JvmtiTagHashmap @ " INTPTR_FORMAT, p);
 407 
 408   // table + entries in KB
 409   int hashmap_usage = (size()*sizeof(JvmtiTagHashmapEntry*) +
 410     entry_count()*sizeof(JvmtiTagHashmapEntry))/K;
 411 
 412   int weak_globals_usage = (int)(JNIHandles::weak_global_handle_memory_usage()/K);
 413   tty->print_cr(", %d entries (%d KB) <JNI weak globals: %d KB>]",
 414     entry_count(), hashmap_usage, weak_globals_usage);
 415 }
 416 
 417 // compute threshold for the next trace message
 418 void JvmtiTagHashmap::compute_next_trace_threshold() {
 419   _trace_threshold = entry_count();
 420   if (trace_threshold() < medium_trace_threshold) {
 421     _trace_threshold += small_trace_threshold;
 422   } else {
 423     if (trace_threshold() < large_trace_threshold) {
 424       _trace_threshold += medium_trace_threshold;
 425     } else {
 426       _trace_threshold += large_trace_threshold;
 427     }
 428   }
 429 }
 430 
 431 // create a JvmtiTagMap
 432 JvmtiTagMap::JvmtiTagMap(JvmtiEnv* env) :
 433   _env(env),
 434   _lock(Mutex::nonleaf+2, "JvmtiTagMap._lock", false),
 435   _free_entries(NULL),
 436   _free_entries_count(0)
 437 {
 438   assert(JvmtiThreadState_lock->is_locked(), "sanity check");
 439   assert(((JvmtiEnvBase *)env)->tag_map() == NULL, "tag map already exists for environment");
 440 
 441   _hashmap = new JvmtiTagHashmap();
 442 
 443   // finally add us to the environment
 444   ((JvmtiEnvBase *)env)->set_tag_map(this);
 445 }
 446 
 447 
 448 // destroy a JvmtiTagMap
 449 JvmtiTagMap::~JvmtiTagMap() {
 450 
 451   // no lock acquired as we assume the enclosing environment is
 452   // also being destroryed.
 453   ((JvmtiEnvBase *)_env)->set_tag_map(NULL);
 454 
 455   JvmtiTagHashmapEntry** table = _hashmap->table();
 456   for (int j = 0; j < _hashmap->size(); j++) {
 457     JvmtiTagHashmapEntry* entry = table[j];
 458     while (entry != NULL) {
 459       JvmtiTagHashmapEntry* next = entry->next();
 460       delete entry;
 461       entry = next;
 462     }
 463   }
 464 
 465   // finally destroy the hashmap
 466   delete _hashmap;
 467   _hashmap = NULL;
 468 
 469   // remove any entries on the free list
 470   JvmtiTagHashmapEntry* entry = _free_entries;
 471   while (entry != NULL) {
 472     JvmtiTagHashmapEntry* next = entry->next();
 473     delete entry;
 474     entry = next;
 475   }
 476   _free_entries = NULL;
 477 }
 478 
 479 // create a hashmap entry
 480 // - if there's an entry on the (per-environment) free list then this
 481 // is returned. Otherwise an new entry is allocated.
 482 JvmtiTagHashmapEntry* JvmtiTagMap::create_entry(oop ref, jlong tag) {
 483   assert(Thread::current()->is_VM_thread() || is_locked(), "checking");
 484   JvmtiTagHashmapEntry* entry;
 485   if (_free_entries == NULL) {
 486     entry = new JvmtiTagHashmapEntry(ref, tag);
 487   } else {
 488     assert(_free_entries_count > 0, "mismatched _free_entries_count");
 489     _free_entries_count--;
 490     entry = _free_entries;
 491     _free_entries = entry->next();
 492     entry->init(ref, tag);
 493   }
 494   return entry;
 495 }
 496 
 497 // destroy an entry by returning it to the free list
 498 void JvmtiTagMap::destroy_entry(JvmtiTagHashmapEntry* entry) {
 499   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 500   // limit the size of the free list
 501   if (_free_entries_count >= max_free_entries) {
 502     delete entry;
 503   } else {
 504     entry->set_next(_free_entries);
 505     _free_entries = entry;
 506     _free_entries_count++;
 507   }
 508 }
 509 
 510 // returns the tag map for the given environments. If the tag map
 511 // doesn't exist then it is created.
 512 JvmtiTagMap* JvmtiTagMap::tag_map_for(JvmtiEnv* env) {
 513   JvmtiTagMap* tag_map = ((JvmtiEnvBase*)env)->tag_map();
 514   if (tag_map == NULL) {
 515     MutexLocker mu(JvmtiThreadState_lock);
 516     tag_map = ((JvmtiEnvBase*)env)->tag_map();
 517     if (tag_map == NULL) {
 518       tag_map = new JvmtiTagMap(env);
 519     }
 520   } else {
 521     CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
 522   }
 523   return tag_map;
 524 }
 525 
 526 // iterate over all entries in the tag map.
 527 void JvmtiTagMap::entry_iterate(JvmtiTagHashmapEntryClosure* closure) {
 528   hashmap()->entry_iterate(closure);
 529 }
 530 
 531 // returns true if the hashmaps are empty
 532 bool JvmtiTagMap::is_empty() {
 533   assert(SafepointSynchronize::is_at_safepoint() || is_locked(), "checking");
 534   return hashmap()->entry_count() == 0;
 535 }
 536 
 537 
 538 // Return the tag value for an object, or 0 if the object is
 539 // not tagged
 540 //
 541 static inline jlong tag_for(JvmtiTagMap* tag_map, oop o) {
 542   JvmtiTagHashmapEntry* entry = tag_map->hashmap()->find(o);
 543   if (entry == NULL) {
 544     return 0;
 545   } else {
 546     return entry->tag();
 547   }
 548 }
 549 
 550 
 551 // A CallbackWrapper is a support class for querying and tagging an object
 552 // around a callback to a profiler. The constructor does pre-callback
 553 // work to get the tag value, klass tag value, ... and the destructor
 554 // does the post-callback work of tagging or untagging the object.
 555 //
 556 // {
 557 //   CallbackWrapper wrapper(tag_map, o);
 558 //
 559 //   (*callback)(wrapper.klass_tag(), wrapper.obj_size(), wrapper.obj_tag_p(), ...)
 560 //
 561 // } // wrapper goes out of scope here which results in the destructor
 562 //      checking to see if the object has been tagged, untagged, or the
 563 //      tag value has changed.
 564 //
 565 class CallbackWrapper : public StackObj {
 566  private:
 567   JvmtiTagMap* _tag_map;
 568   JvmtiTagHashmap* _hashmap;
 569   JvmtiTagHashmapEntry* _entry;
 570   oop _o;
 571   jlong _obj_size;
 572   jlong _obj_tag;
 573   jlong _klass_tag;
 574 
 575  protected:
 576   JvmtiTagMap* tag_map() const      { return _tag_map; }
 577 
 578   // invoked post-callback to tag, untag, or update the tag of an object
 579   void inline post_callback_tag_update(oop o, JvmtiTagHashmap* hashmap,
 580                                        JvmtiTagHashmapEntry* entry, jlong obj_tag);
 581  public:
 582   CallbackWrapper(JvmtiTagMap* tag_map, oop o) {
 583     assert(Thread::current()->is_VM_thread() || tag_map->is_locked(),
 584            "MT unsafe or must be VM thread");
 585 
 586     // object to tag
 587     _o = o;
 588 
 589     // object size
 590     _obj_size = (jlong)_o->size() * wordSize;
 591 
 592     // record the context
 593     _tag_map = tag_map;
 594     _hashmap = tag_map->hashmap();
 595     _entry = _hashmap->find(_o);
 596 
 597     // get object tag
 598     _obj_tag = (_entry == NULL) ? 0 : _entry->tag();
 599 
 600     // get the class and the class's tag value
 601     assert(SystemDictionary::Class_klass()->is_mirror_instance_klass(), "Is not?");
 602 
 603     _klass_tag = tag_for(tag_map, _o->klass()->java_mirror());
 604   }
 605 
 606   ~CallbackWrapper() {
 607     post_callback_tag_update(_o, _hashmap, _entry, _obj_tag);
 608   }
 609 
 610   inline jlong* obj_tag_p()                     { return &_obj_tag; }
 611   inline jlong obj_size() const                 { return _obj_size; }
 612   inline jlong obj_tag() const                  { return _obj_tag; }
 613   inline jlong klass_tag() const                { return _klass_tag; }
 614 };
 615 
 616 
 617 
 618 // callback post-callback to tag, untag, or update the tag of an object
 619 void inline CallbackWrapper::post_callback_tag_update(oop o,
 620                                                       JvmtiTagHashmap* hashmap,
 621                                                       JvmtiTagHashmapEntry* entry,
 622                                                       jlong obj_tag) {
 623   if (entry == NULL) {
 624     if (obj_tag != 0) {
 625       // callback has tagged the object
 626       assert(Thread::current()->is_VM_thread(), "must be VMThread");
 627       entry = tag_map()->create_entry(o, obj_tag);
 628       hashmap->add(o, entry);
 629     }
 630   } else {
 631     // object was previously tagged - the callback may have untagged
 632     // the object or changed the tag value
 633     if (obj_tag == 0) {
 634 
 635       JvmtiTagHashmapEntry* entry_removed = hashmap->remove(o);
 636       assert(entry_removed == entry, "checking");
 637       tag_map()->destroy_entry(entry);
 638 
 639     } else {
 640       if (obj_tag != entry->tag()) {
 641          entry->set_tag(obj_tag);
 642       }
 643     }
 644   }
 645 }
 646 
 647 // An extended CallbackWrapper used when reporting an object reference
 648 // to the agent.
 649 //
 650 // {
 651 //   TwoOopCallbackWrapper wrapper(tag_map, referrer, o);
 652 //
 653 //   (*callback)(wrapper.klass_tag(),
 654 //               wrapper.obj_size(),
 655 //               wrapper.obj_tag_p()
 656 //               wrapper.referrer_tag_p(), ...)
 657 //
 658 // } // wrapper goes out of scope here which results in the destructor
 659 //      checking to see if the referrer object has been tagged, untagged,
 660 //      or the tag value has changed.
 661 //
 662 class TwoOopCallbackWrapper : public CallbackWrapper {
 663  private:
 664   bool _is_reference_to_self;
 665   JvmtiTagHashmap* _referrer_hashmap;
 666   JvmtiTagHashmapEntry* _referrer_entry;
 667   oop _referrer;
 668   jlong _referrer_obj_tag;
 669   jlong _referrer_klass_tag;
 670   jlong* _referrer_tag_p;
 671 
 672   bool is_reference_to_self() const             { return _is_reference_to_self; }
 673 
 674  public:
 675   TwoOopCallbackWrapper(JvmtiTagMap* tag_map, oop referrer, oop o) :
 676     CallbackWrapper(tag_map, o)
 677   {
 678     // self reference needs to be handled in a special way
 679     _is_reference_to_self = (referrer == o);
 680 
 681     if (_is_reference_to_self) {
 682       _referrer_klass_tag = klass_tag();
 683       _referrer_tag_p = obj_tag_p();
 684     } else {
 685       _referrer = referrer;
 686       // record the context
 687       _referrer_hashmap = tag_map->hashmap();
 688       _referrer_entry = _referrer_hashmap->find(_referrer);
 689 
 690       // get object tag
 691       _referrer_obj_tag = (_referrer_entry == NULL) ? 0 : _referrer_entry->tag();
 692       _referrer_tag_p = &_referrer_obj_tag;
 693 
 694       // get referrer class tag.
 695       _referrer_klass_tag = tag_for(tag_map, _referrer->klass()->java_mirror());
 696     }
 697   }
 698 
 699   ~TwoOopCallbackWrapper() {
 700     if (!is_reference_to_self()){
 701       post_callback_tag_update(_referrer,
 702                                _referrer_hashmap,
 703                                _referrer_entry,
 704                                _referrer_obj_tag);
 705     }
 706   }
 707 
 708   // address of referrer tag
 709   // (for a self reference this will return the same thing as obj_tag_p())
 710   inline jlong* referrer_tag_p()        { return _referrer_tag_p; }
 711 
 712   // referrer's class tag
 713   inline jlong referrer_klass_tag()     { return _referrer_klass_tag; }
 714 };
 715 
 716 // tag an object
 717 //
 718 // This function is performance critical. If many threads attempt to tag objects
 719 // around the same time then it's possible that the Mutex associated with the
 720 // tag map will be a hot lock.
 721 void JvmtiTagMap::set_tag(jobject object, jlong tag) {
 722   MutexLocker ml(lock());
 723 
 724   // resolve the object
 725   oop o = JNIHandles::resolve_non_null(object);
 726 
 727   // see if the object is already tagged
 728   JvmtiTagHashmap* hashmap = _hashmap;
 729   JvmtiTagHashmapEntry* entry = hashmap->find(o);
 730 
 731   // if the object is not already tagged then we tag it
 732   if (entry == NULL) {
 733     if (tag != 0) {
 734       entry = create_entry(o, tag);
 735       hashmap->add(o, entry);
 736     } else {
 737       // no-op
 738     }
 739   } else {
 740     // if the object is already tagged then we either update
 741     // the tag (if a new tag value has been provided)
 742     // or remove the object if the new tag value is 0.
 743     if (tag == 0) {
 744       hashmap->remove(o);
 745       destroy_entry(entry);
 746     } else {
 747       entry->set_tag(tag);
 748     }
 749   }
 750 }
 751 
 752 // get the tag for an object
 753 jlong JvmtiTagMap::get_tag(jobject object) {
 754   MutexLocker ml(lock());
 755 
 756   // resolve the object
 757   oop o = JNIHandles::resolve_non_null(object);
 758 
 759   return tag_for(this, o);
 760 }
 761 
 762 
 763 // Helper class used to describe the static or instance fields of a class.
 764 // For each field it holds the field index (as defined by the JVMTI specification),
 765 // the field type, and the offset.
 766 
 767 class ClassFieldDescriptor: public CHeapObj<mtInternal> {
 768  private:
 769   int _field_index;
 770   int _field_offset;
 771   char _field_type;
 772  public:
 773   ClassFieldDescriptor(int index, char type, int offset) :
 774     _field_index(index), _field_type(type), _field_offset(offset) {
 775   }
 776   int field_index()  const  { return _field_index; }
 777   char field_type()  const  { return _field_type; }
 778   int field_offset() const  { return _field_offset; }
 779 };
 780 
 781 class ClassFieldMap: public CHeapObj<mtInternal> {
 782  private:
 783   enum {
 784     initial_field_count = 5
 785   };
 786 
 787   // list of field descriptors
 788   GrowableArray<ClassFieldDescriptor*>* _fields;
 789 
 790   // constructor
 791   ClassFieldMap();
 792 
 793   // add a field
 794   void add(int index, char type, int offset);
 795 
 796   // returns the field count for the given class
 797   static int compute_field_count(InstanceKlass* ik);
 798 
 799  public:
 800   ~ClassFieldMap();
 801 
 802   // access
 803   int field_count()                     { return _fields->length(); }
 804   ClassFieldDescriptor* field_at(int i) { return _fields->at(i); }
 805 
 806   // functions to create maps of static or instance fields
 807   static ClassFieldMap* create_map_of_static_fields(Klass* k);
 808   static ClassFieldMap* create_map_of_instance_fields(oop obj);
 809 };
 810 
 811 ClassFieldMap::ClassFieldMap() {
 812   _fields = new (ResourceObj::C_HEAP, mtInternal)
 813     GrowableArray<ClassFieldDescriptor*>(initial_field_count, true);
 814 }
 815 
 816 ClassFieldMap::~ClassFieldMap() {
 817   for (int i=0; i<_fields->length(); i++) {
 818     delete _fields->at(i);
 819   }
 820   delete _fields;
 821 }
 822 
 823 void ClassFieldMap::add(int index, char type, int offset) {
 824   ClassFieldDescriptor* field = new ClassFieldDescriptor(index, type, offset);
 825   _fields->append(field);
 826 }
 827 
 828 // Returns a heap allocated ClassFieldMap to describe the static fields
 829 // of the given class.
 830 //
 831 ClassFieldMap* ClassFieldMap::create_map_of_static_fields(Klass* k) {
 832   HandleMark hm;
 833   InstanceKlass* ik = InstanceKlass::cast(k);
 834 
 835   // create the field map
 836   ClassFieldMap* field_map = new ClassFieldMap();
 837 
 838   FilteredFieldStream f(ik, false, false);
 839   int max_field_index = f.field_count()-1;
 840 
 841   int index = 0;
 842   for (FilteredFieldStream fld(ik, true, true); !fld.eos(); fld.next(), index++) {
 843     // ignore instance fields
 844     if (!fld.access_flags().is_static()) {
 845       continue;
 846     }
 847     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());
 848   }
 849   return field_map;
 850 }
 851 
 852 // Returns a heap allocated ClassFieldMap to describe the instance fields
 853 // of the given class. All instance fields are included (this means public
 854 // and private fields declared in superclasses and superinterfaces too).
 855 //
 856 ClassFieldMap* ClassFieldMap::create_map_of_instance_fields(oop obj) {
 857   HandleMark hm;
 858   InstanceKlass* ik = InstanceKlass::cast(obj->klass());
 859 
 860   // create the field map
 861   ClassFieldMap* field_map = new ClassFieldMap();
 862 
 863   FilteredFieldStream f(ik, false, false);
 864 
 865   int max_field_index = f.field_count()-1;
 866 
 867   int index = 0;
 868   for (FilteredFieldStream fld(ik, false, false); !fld.eos(); fld.next(), index++) {
 869     // ignore static fields
 870     if (fld.access_flags().is_static()) {
 871       continue;
 872     }
 873     field_map->add(max_field_index - index, fld.signature()->byte_at(0), fld.offset());
 874   }
 875 
 876   return field_map;
 877 }
 878 
 879 // Helper class used to cache a ClassFileMap for the instance fields of
 880 // a cache. A JvmtiCachedClassFieldMap can be cached by an InstanceKlass during
 881 // heap iteration and avoid creating a field map for each object in the heap
 882 // (only need to create the map when the first instance of a class is encountered).
 883 //
 884 class JvmtiCachedClassFieldMap : public CHeapObj<mtInternal> {
 885  private:
 886    enum {
 887      initial_class_count = 200
 888    };
 889   ClassFieldMap* _field_map;
 890 
 891   ClassFieldMap* field_map() const          { return _field_map; }
 892 
 893   JvmtiCachedClassFieldMap(ClassFieldMap* field_map);
 894   ~JvmtiCachedClassFieldMap();
 895 
 896   static GrowableArray<InstanceKlass*>* _class_list;
 897   static void add_to_class_list(InstanceKlass* ik);
 898 
 899  public:
 900   // returns the field map for a given object (returning map cached
 901   // by InstanceKlass if possible
 902   static ClassFieldMap* get_map_of_instance_fields(oop obj);
 903 
 904   // removes the field map from all instanceKlasses - should be
 905   // called before VM operation completes
 906   static void clear_cache();
 907 
 908   // returns the number of ClassFieldMap cached by instanceKlasses
 909   static int cached_field_map_count();
 910 };
 911 
 912 GrowableArray<InstanceKlass*>* JvmtiCachedClassFieldMap::_class_list;
 913 
 914 JvmtiCachedClassFieldMap::JvmtiCachedClassFieldMap(ClassFieldMap* field_map) {
 915   _field_map = field_map;
 916 }
 917 
 918 JvmtiCachedClassFieldMap::~JvmtiCachedClassFieldMap() {
 919   if (_field_map != NULL) {
 920     delete _field_map;
 921   }
 922 }
 923 
 924 // Marker class to ensure that the class file map cache is only used in a defined
 925 // scope.
 926 class ClassFieldMapCacheMark : public StackObj {
 927  private:
 928    static bool _is_active;
 929  public:
 930    ClassFieldMapCacheMark() {
 931      assert(Thread::current()->is_VM_thread(), "must be VMThread");
 932      assert(JvmtiCachedClassFieldMap::cached_field_map_count() == 0, "cache not empty");
 933      assert(!_is_active, "ClassFieldMapCacheMark cannot be nested");
 934      _is_active = true;
 935    }
 936    ~ClassFieldMapCacheMark() {
 937      JvmtiCachedClassFieldMap::clear_cache();
 938      _is_active = false;
 939    }
 940    static bool is_active() { return _is_active; }
 941 };
 942 
 943 bool ClassFieldMapCacheMark::_is_active;
 944 
 945 
 946 // record that the given InstanceKlass is caching a field map
 947 void JvmtiCachedClassFieldMap::add_to_class_list(InstanceKlass* ik) {
 948   if (_class_list == NULL) {
 949     _class_list = new (ResourceObj::C_HEAP, mtInternal)
 950       GrowableArray<InstanceKlass*>(initial_class_count, true);
 951   }
 952   _class_list->push(ik);
 953 }
 954 
 955 // returns the instance field map for the given object
 956 // (returns field map cached by the InstanceKlass if possible)
 957 ClassFieldMap* JvmtiCachedClassFieldMap::get_map_of_instance_fields(oop obj) {
 958   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 959   assert(ClassFieldMapCacheMark::is_active(), "ClassFieldMapCacheMark not active");
 960 
 961   Klass* k = obj->klass();
 962   InstanceKlass* ik = InstanceKlass::cast(k);
 963 
 964   // return cached map if possible
 965   JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 966   if (cached_map != NULL) {
 967     assert(cached_map->field_map() != NULL, "missing field list");
 968     return cached_map->field_map();
 969   } else {
 970     ClassFieldMap* field_map = ClassFieldMap::create_map_of_instance_fields(obj);
 971     cached_map = new JvmtiCachedClassFieldMap(field_map);
 972     ik->set_jvmti_cached_class_field_map(cached_map);
 973     add_to_class_list(ik);
 974     return field_map;
 975   }
 976 }
 977 
 978 // remove the fields maps cached from all instanceKlasses
 979 void JvmtiCachedClassFieldMap::clear_cache() {
 980   assert(Thread::current()->is_VM_thread(), "must be VMThread");
 981   if (_class_list != NULL) {
 982     for (int i = 0; i < _class_list->length(); i++) {
 983       InstanceKlass* ik = _class_list->at(i);
 984       JvmtiCachedClassFieldMap* cached_map = ik->jvmti_cached_class_field_map();
 985       assert(cached_map != NULL, "should not be NULL");
 986       ik->set_jvmti_cached_class_field_map(NULL);
 987       delete cached_map;  // deletes the encapsulated field map
 988     }
 989     delete _class_list;
 990     _class_list = NULL;
 991   }
 992 }
 993 
 994 // returns the number of ClassFieldMap cached by instanceKlasses
 995 int JvmtiCachedClassFieldMap::cached_field_map_count() {
 996   return (_class_list == NULL) ? 0 : _class_list->length();
 997 }
 998 
 999 // helper function to indicate if an object is filtered by its tag or class tag
1000 static inline bool is_filtered_by_heap_filter(jlong obj_tag,
1001                                               jlong klass_tag,
1002                                               int heap_filter) {
1003   // apply the heap filter
1004   if (obj_tag != 0) {
1005     // filter out tagged objects
1006     if (heap_filter & JVMTI_HEAP_FILTER_TAGGED) return true;
1007   } else {
1008     // filter out untagged objects
1009     if (heap_filter & JVMTI_HEAP_FILTER_UNTAGGED) return true;
1010   }
1011   if (klass_tag != 0) {
1012     // filter out objects with tagged classes
1013     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_TAGGED) return true;
1014   } else {
1015     // filter out objects with untagged classes.
1016     if (heap_filter & JVMTI_HEAP_FILTER_CLASS_UNTAGGED) return true;
1017   }
1018   return false;
1019 }
1020 
1021 // helper function to indicate if an object is filtered by a klass filter
1022 static inline bool is_filtered_by_klass_filter(oop obj, Klass* klass_filter) {
1023   if (klass_filter != NULL) {
1024     if (obj->klass() != klass_filter) {
1025       return true;
1026     }
1027   }
1028   return false;
1029 }
1030 
1031 // helper function to tell if a field is a primitive field or not
1032 static inline bool is_primitive_field_type(char type) {
1033   return (type != 'L' && type != '[');
1034 }
1035 
1036 // helper function to copy the value from location addr to jvalue.
1037 static inline void copy_to_jvalue(jvalue *v, address addr, jvmtiPrimitiveType value_type) {
1038   switch (value_type) {
1039     case JVMTI_PRIMITIVE_TYPE_BOOLEAN : { v->z = *(jboolean*)addr; break; }
1040     case JVMTI_PRIMITIVE_TYPE_BYTE    : { v->b = *(jbyte*)addr;    break; }
1041     case JVMTI_PRIMITIVE_TYPE_CHAR    : { v->c = *(jchar*)addr;    break; }
1042     case JVMTI_PRIMITIVE_TYPE_SHORT   : { v->s = *(jshort*)addr;   break; }
1043     case JVMTI_PRIMITIVE_TYPE_INT     : { v->i = *(jint*)addr;     break; }
1044     case JVMTI_PRIMITIVE_TYPE_LONG    : { v->j = *(jlong*)addr;    break; }
1045     case JVMTI_PRIMITIVE_TYPE_FLOAT   : { v->f = *(jfloat*)addr;   break; }
1046     case JVMTI_PRIMITIVE_TYPE_DOUBLE  : { v->d = *(jdouble*)addr;  break; }
1047     default: ShouldNotReachHere();
1048   }
1049 }
1050 
1051 // helper function to invoke string primitive value callback
1052 // returns visit control flags
1053 static jint invoke_string_value_callback(jvmtiStringPrimitiveValueCallback cb,
1054                                          CallbackWrapper* wrapper,
1055                                          oop str,
1056                                          void* user_data)
1057 {
1058   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
1059 
1060   typeArrayOop s_value = java_lang_String::value(str);
1061 
1062   // JDK-6584008: the value field may be null if a String instance is
1063   // partially constructed.
1064   if (s_value == NULL) {
1065     return 0;
1066   }
1067   // get the string value and length
1068   // (string value may be offset from the base)
1069   int s_len = java_lang_String::length(str);
1070   bool is_latin1 = java_lang_String::is_latin1(str);
1071   jchar* value;
1072   if (s_len > 0) {
1073     if (!is_latin1) {
1074       value = s_value->char_at_addr(0);
1075     } else {
1076       // Inflate latin1 encoded string to UTF16
1077       jchar* buf = NEW_C_HEAP_ARRAY(jchar, s_len, mtInternal);
1078       for (int i = 0; i < s_len; i++) {
1079         buf[i] = ((jchar) s_value->byte_at(i)) & 0xff;
1080       }
1081       value = &buf[0];
1082     }
1083   } else {
1084     // Don't use char_at_addr(0) if length is 0
1085     value = (jchar*) s_value->base(T_CHAR);
1086   }
1087 
1088   // invoke the callback
1089   jint res = (*cb)(wrapper->klass_tag(),
1090                    wrapper->obj_size(),
1091                    wrapper->obj_tag_p(),
1092                    value,
1093                    (jint)s_len,
1094                    user_data);
1095 
1096   if (is_latin1 && s_len > 0) {
1097     FREE_C_HEAP_ARRAY(jchar, value);
1098   }
1099   return res;
1100 }
1101 
1102 // helper function to invoke string primitive value callback
1103 // returns visit control flags
1104 static jint invoke_array_primitive_value_callback(jvmtiArrayPrimitiveValueCallback cb,
1105                                                   CallbackWrapper* wrapper,
1106                                                   oop obj,
1107                                                   void* user_data)
1108 {
1109   assert(obj->is_typeArray(), "not a primitive array");
1110 
1111   // get base address of first element
1112   typeArrayOop array = typeArrayOop(obj);
1113   BasicType type = TypeArrayKlass::cast(array->klass())->element_type();
1114   void* elements = array->base(type);
1115 
1116   // jvmtiPrimitiveType is defined so this mapping is always correct
1117   jvmtiPrimitiveType elem_type = (jvmtiPrimitiveType)type2char(type);
1118 
1119   return (*cb)(wrapper->klass_tag(),
1120                wrapper->obj_size(),
1121                wrapper->obj_tag_p(),
1122                (jint)array->length(),
1123                elem_type,
1124                elements,
1125                user_data);
1126 }
1127 
1128 // helper function to invoke the primitive field callback for all static fields
1129 // of a given class
1130 static jint invoke_primitive_field_callback_for_static_fields
1131   (CallbackWrapper* wrapper,
1132    oop obj,
1133    jvmtiPrimitiveFieldCallback cb,
1134    void* user_data)
1135 {
1136   // for static fields only the index will be set
1137   static jvmtiHeapReferenceInfo reference_info = { 0 };
1138 
1139   assert(obj->klass() == SystemDictionary::Class_klass(), "not a class");
1140   if (java_lang_Class::is_primitive(obj)) {
1141     return 0;
1142   }
1143   Klass* klass = java_lang_Class::as_Klass(obj);
1144 
1145   // ignore classes for object and type arrays
1146   if (!klass->is_instance_klass()) {
1147     return 0;
1148   }
1149 
1150   // ignore classes which aren't linked yet
1151   InstanceKlass* ik = InstanceKlass::cast(klass);
1152   if (!ik->is_linked()) {
1153     return 0;
1154   }
1155 
1156   // get the field map
1157   ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
1158 
1159   // invoke the callback for each static primitive field
1160   for (int i=0; i<field_map->field_count(); i++) {
1161     ClassFieldDescriptor* field = field_map->field_at(i);
1162 
1163     // ignore non-primitive fields
1164     char type = field->field_type();
1165     if (!is_primitive_field_type(type)) {
1166       continue;
1167     }
1168     // one-to-one mapping
1169     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1170 
1171     // get offset and field value
1172     int offset = field->field_offset();
1173     address addr = (address)klass->java_mirror() + offset;
1174     jvalue value;
1175     copy_to_jvalue(&value, addr, value_type);
1176 
1177     // field index
1178     reference_info.field.index = field->field_index();
1179 
1180     // invoke the callback
1181     jint res = (*cb)(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
1182                      &reference_info,
1183                      wrapper->klass_tag(),
1184                      wrapper->obj_tag_p(),
1185                      value,
1186                      value_type,
1187                      user_data);
1188     if (res & JVMTI_VISIT_ABORT) {
1189       delete field_map;
1190       return res;
1191     }
1192   }
1193 
1194   delete field_map;
1195   return 0;
1196 }
1197 
1198 // helper function to invoke the primitive field callback for all instance fields
1199 // of a given object
1200 static jint invoke_primitive_field_callback_for_instance_fields(
1201   CallbackWrapper* wrapper,
1202   oop obj,
1203   jvmtiPrimitiveFieldCallback cb,
1204   void* user_data)
1205 {
1206   // for instance fields only the index will be set
1207   static jvmtiHeapReferenceInfo reference_info = { 0 };
1208 
1209   // get the map of the instance fields
1210   ClassFieldMap* fields = JvmtiCachedClassFieldMap::get_map_of_instance_fields(obj);
1211 
1212   // invoke the callback for each instance primitive field
1213   for (int i=0; i<fields->field_count(); i++) {
1214     ClassFieldDescriptor* field = fields->field_at(i);
1215 
1216     // ignore non-primitive fields
1217     char type = field->field_type();
1218     if (!is_primitive_field_type(type)) {
1219       continue;
1220     }
1221     // one-to-one mapping
1222     jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
1223 
1224     // get offset and field value
1225     int offset = field->field_offset();
1226     address addr = (address)obj + offset;
1227     jvalue value;
1228     copy_to_jvalue(&value, addr, value_type);
1229 
1230     // field index
1231     reference_info.field.index = field->field_index();
1232 
1233     // invoke the callback
1234     jint res = (*cb)(JVMTI_HEAP_REFERENCE_FIELD,
1235                      &reference_info,
1236                      wrapper->klass_tag(),
1237                      wrapper->obj_tag_p(),
1238                      value,
1239                      value_type,
1240                      user_data);
1241     if (res & JVMTI_VISIT_ABORT) {
1242       return res;
1243     }
1244   }
1245   return 0;
1246 }
1247 
1248 
1249 // VM operation to iterate over all objects in the heap (both reachable
1250 // and unreachable)
1251 class VM_HeapIterateOperation: public VM_Operation {
1252  private:
1253   ObjectClosure* _blk;
1254  public:
1255   VM_HeapIterateOperation(ObjectClosure* blk) { _blk = blk; }
1256 
1257   VMOp_Type type() const { return VMOp_HeapIterateOperation; }
1258   void doit() {
1259     // allows class files maps to be cached during iteration
1260     ClassFieldMapCacheMark cm;
1261 
1262     // make sure that heap is parsable (fills TLABs with filler objects)
1263     Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1264 
1265     // Verify heap before iteration - if the heap gets corrupted then
1266     // JVMTI's IterateOverHeap will crash.
1267     if (VerifyBeforeIteration) {
1268       Universe::verify();
1269     }
1270 
1271     // do the iteration
1272     // If this operation encounters a bad object when using CMS,
1273     // consider using safe_object_iterate() which avoids perm gen
1274     // objects that may contain bad references.
1275     Universe::heap()->object_iterate(_blk);
1276   }
1277 
1278 };
1279 
1280 
1281 // An ObjectClosure used to support the deprecated IterateOverHeap and
1282 // IterateOverInstancesOfClass functions
1283 class IterateOverHeapObjectClosure: public ObjectClosure {
1284  private:
1285   JvmtiTagMap* _tag_map;
1286   Klass* _klass;
1287   jvmtiHeapObjectFilter _object_filter;
1288   jvmtiHeapObjectCallback _heap_object_callback;
1289   const void* _user_data;
1290 
1291   // accessors
1292   JvmtiTagMap* tag_map() const                    { return _tag_map; }
1293   jvmtiHeapObjectFilter object_filter() const     { return _object_filter; }
1294   jvmtiHeapObjectCallback object_callback() const { return _heap_object_callback; }
1295   Klass* klass() const                            { return _klass; }
1296   const void* user_data() const                   { return _user_data; }
1297 
1298   // indicates if iteration has been aborted
1299   bool _iteration_aborted;
1300   bool is_iteration_aborted() const               { return _iteration_aborted; }
1301   void set_iteration_aborted(bool aborted)        { _iteration_aborted = aborted; }
1302 
1303  public:
1304   IterateOverHeapObjectClosure(JvmtiTagMap* tag_map,
1305                                Klass* klass,
1306                                jvmtiHeapObjectFilter object_filter,
1307                                jvmtiHeapObjectCallback heap_object_callback,
1308                                const void* user_data) :
1309     _tag_map(tag_map),
1310     _klass(klass),
1311     _object_filter(object_filter),
1312     _heap_object_callback(heap_object_callback),
1313     _user_data(user_data),
1314     _iteration_aborted(false)
1315   {
1316   }
1317 
1318   void do_object(oop o);
1319 };
1320 
1321 // invoked for each object in the heap
1322 void IterateOverHeapObjectClosure::do_object(oop o) {
1323   // check if iteration has been halted
1324   if (is_iteration_aborted()) return;
1325 
1326   // instanceof check when filtering by klass
1327   if (klass() != NULL && !o->is_a(klass())) {
1328     return;
1329   }
1330   // prepare for the calllback
1331   CallbackWrapper wrapper(tag_map(), o);
1332 
1333   // if the object is tagged and we're only interested in untagged objects
1334   // then don't invoke the callback. Similiarly, if the object is untagged
1335   // and we're only interested in tagged objects we skip the callback.
1336   if (wrapper.obj_tag() != 0) {
1337     if (object_filter() == JVMTI_HEAP_OBJECT_UNTAGGED) return;
1338   } else {
1339     if (object_filter() == JVMTI_HEAP_OBJECT_TAGGED) return;
1340   }
1341 
1342   // invoke the agent's callback
1343   jvmtiIterationControl control = (*object_callback())(wrapper.klass_tag(),
1344                                                        wrapper.obj_size(),
1345                                                        wrapper.obj_tag_p(),
1346                                                        (void*)user_data());
1347   if (control == JVMTI_ITERATION_ABORT) {
1348     set_iteration_aborted(true);
1349   }
1350 }
1351 
1352 // An ObjectClosure used to support the IterateThroughHeap function
1353 class IterateThroughHeapObjectClosure: public ObjectClosure {
1354  private:
1355   JvmtiTagMap* _tag_map;
1356   Klass* _klass;
1357   int _heap_filter;
1358   const jvmtiHeapCallbacks* _callbacks;
1359   const void* _user_data;
1360 
1361   // accessor functions
1362   JvmtiTagMap* tag_map() const                     { return _tag_map; }
1363   int heap_filter() const                          { return _heap_filter; }
1364   const jvmtiHeapCallbacks* callbacks() const      { return _callbacks; }
1365   Klass* klass() const                             { return _klass; }
1366   const void* user_data() const                    { return _user_data; }
1367 
1368   // indicates if the iteration has been aborted
1369   bool _iteration_aborted;
1370   bool is_iteration_aborted() const                { return _iteration_aborted; }
1371 
1372   // used to check the visit control flags. If the abort flag is set
1373   // then we set the iteration aborted flag so that the iteration completes
1374   // without processing any further objects
1375   bool check_flags_for_abort(jint flags) {
1376     bool is_abort = (flags & JVMTI_VISIT_ABORT) != 0;
1377     if (is_abort) {
1378       _iteration_aborted = true;
1379     }
1380     return is_abort;
1381   }
1382 
1383  public:
1384   IterateThroughHeapObjectClosure(JvmtiTagMap* tag_map,
1385                                   Klass* klass,
1386                                   int heap_filter,
1387                                   const jvmtiHeapCallbacks* heap_callbacks,
1388                                   const void* user_data) :
1389     _tag_map(tag_map),
1390     _klass(klass),
1391     _heap_filter(heap_filter),
1392     _callbacks(heap_callbacks),
1393     _user_data(user_data),
1394     _iteration_aborted(false)
1395   {
1396   }
1397 
1398   void do_object(oop o);
1399 };
1400 
1401 // invoked for each object in the heap
1402 void IterateThroughHeapObjectClosure::do_object(oop obj) {
1403   // check if iteration has been halted
1404   if (is_iteration_aborted()) return;
1405 
1406   // apply class filter
1407   if (is_filtered_by_klass_filter(obj, klass())) return;
1408 
1409   // prepare for callback
1410   CallbackWrapper wrapper(tag_map(), obj);
1411 
1412   // check if filtered by the heap filter
1413   if (is_filtered_by_heap_filter(wrapper.obj_tag(), wrapper.klass_tag(), heap_filter())) {
1414     return;
1415   }
1416 
1417   // for arrays we need the length, otherwise -1
1418   bool is_array = obj->is_array();
1419   int len = is_array ? arrayOop(obj)->length() : -1;
1420 
1421   // invoke the object callback (if callback is provided)
1422   if (callbacks()->heap_iteration_callback != NULL) {
1423     jvmtiHeapIterationCallback cb = callbacks()->heap_iteration_callback;
1424     jint res = (*cb)(wrapper.klass_tag(),
1425                      wrapper.obj_size(),
1426                      wrapper.obj_tag_p(),
1427                      (jint)len,
1428                      (void*)user_data());
1429     if (check_flags_for_abort(res)) return;
1430   }
1431 
1432   // for objects and classes we report primitive fields if callback provided
1433   if (callbacks()->primitive_field_callback != NULL && obj->is_instance()) {
1434     jint res;
1435     jvmtiPrimitiveFieldCallback cb = callbacks()->primitive_field_callback;
1436     if (obj->klass() == SystemDictionary::Class_klass()) {
1437       res = invoke_primitive_field_callback_for_static_fields(&wrapper,
1438                                                                     obj,
1439                                                                     cb,
1440                                                                     (void*)user_data());
1441     } else {
1442       res = invoke_primitive_field_callback_for_instance_fields(&wrapper,
1443                                                                       obj,
1444                                                                       cb,
1445                                                                       (void*)user_data());
1446     }
1447     if (check_flags_for_abort(res)) return;
1448   }
1449 
1450   // string callback
1451   if (!is_array &&
1452       callbacks()->string_primitive_value_callback != NULL &&
1453       obj->klass() == SystemDictionary::String_klass()) {
1454     jint res = invoke_string_value_callback(
1455                 callbacks()->string_primitive_value_callback,
1456                 &wrapper,
1457                 obj,
1458                 (void*)user_data() );
1459     if (check_flags_for_abort(res)) return;
1460   }
1461 
1462   // array callback
1463   if (is_array &&
1464       callbacks()->array_primitive_value_callback != NULL &&
1465       obj->is_typeArray()) {
1466     jint res = invoke_array_primitive_value_callback(
1467                callbacks()->array_primitive_value_callback,
1468                &wrapper,
1469                obj,
1470                (void*)user_data() );
1471     if (check_flags_for_abort(res)) return;
1472   }
1473 };
1474 
1475 
1476 // Deprecated function to iterate over all objects in the heap
1477 void JvmtiTagMap::iterate_over_heap(jvmtiHeapObjectFilter object_filter,
1478                                     Klass* klass,
1479                                     jvmtiHeapObjectCallback heap_object_callback,
1480                                     const void* user_data)
1481 {
1482   MutexLocker ml(Heap_lock);
1483   IterateOverHeapObjectClosure blk(this,
1484                                    klass,
1485                                    object_filter,
1486                                    heap_object_callback,
1487                                    user_data);
1488   VM_HeapIterateOperation op(&blk);
1489   VMThread::execute(&op);
1490 }
1491 
1492 
1493 // Iterates over all objects in the heap
1494 void JvmtiTagMap::iterate_through_heap(jint heap_filter,
1495                                        Klass* klass,
1496                                        const jvmtiHeapCallbacks* callbacks,
1497                                        const void* user_data)
1498 {
1499   MutexLocker ml(Heap_lock);
1500   IterateThroughHeapObjectClosure blk(this,
1501                                       klass,
1502                                       heap_filter,
1503                                       callbacks,
1504                                       user_data);
1505   VM_HeapIterateOperation op(&blk);
1506   VMThread::execute(&op);
1507 }
1508 
1509 // support class for get_objects_with_tags
1510 
1511 class TagObjectCollector : public JvmtiTagHashmapEntryClosure {
1512  private:
1513   JvmtiEnv* _env;
1514   jlong* _tags;
1515   jint _tag_count;
1516 
1517   GrowableArray<jobject>* _object_results;  // collected objects (JNI weak refs)
1518   GrowableArray<uint64_t>* _tag_results;    // collected tags
1519 
1520  public:
1521   TagObjectCollector(JvmtiEnv* env, const jlong* tags, jint tag_count) {
1522     _env = env;
1523     _tags = (jlong*)tags;
1524     _tag_count = tag_count;
1525     _object_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jobject>(1,true);
1526     _tag_results = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<uint64_t>(1,true);
1527   }
1528 
1529   ~TagObjectCollector() {
1530     delete _object_results;
1531     delete _tag_results;
1532   }
1533 
1534   // for each tagged object check if the tag value matches
1535   // - if it matches then we create a JNI local reference to the object
1536   // and record the reference and tag value.
1537   //
1538   void do_entry(JvmtiTagHashmapEntry* entry) {
1539     for (int i=0; i<_tag_count; i++) {
1540       if (_tags[i] == entry->tag()) {
1541         // The reference in this tag map could be the only (implicitly weak)
1542         // reference to that object. If we hand it out, we need to keep it live wrt
1543         // SATB marking similar to other j.l.ref.Reference referents. This is
1544         // achieved by using a phantom load in the object() accessor.
1545         oop o = entry->object();
1546         assert(o != NULL && Universe::heap()->is_in_reserved(o), "sanity check");
1547         jobject ref = JNIHandles::make_local(JavaThread::current(), o);
1548         _object_results->append(ref);
1549         _tag_results->append((uint64_t)entry->tag());
1550       }
1551     }
1552   }
1553 
1554   // return the results from the collection
1555   //
1556   jvmtiError result(jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1557     jvmtiError error;
1558     int count = _object_results->length();
1559     assert(count >= 0, "sanity check");
1560 
1561     // if object_result_ptr is not NULL then allocate the result and copy
1562     // in the object references.
1563     if (object_result_ptr != NULL) {
1564       error = _env->Allocate(count * sizeof(jobject), (unsigned char**)object_result_ptr);
1565       if (error != JVMTI_ERROR_NONE) {
1566         return error;
1567       }
1568       for (int i=0; i<count; i++) {
1569         (*object_result_ptr)[i] = _object_results->at(i);
1570       }
1571     }
1572 
1573     // if tag_result_ptr is not NULL then allocate the result and copy
1574     // in the tag values.
1575     if (tag_result_ptr != NULL) {
1576       error = _env->Allocate(count * sizeof(jlong), (unsigned char**)tag_result_ptr);
1577       if (error != JVMTI_ERROR_NONE) {
1578         if (object_result_ptr != NULL) {
1579           _env->Deallocate((unsigned char*)object_result_ptr);
1580         }
1581         return error;
1582       }
1583       for (int i=0; i<count; i++) {
1584         (*tag_result_ptr)[i] = (jlong)_tag_results->at(i);
1585       }
1586     }
1587 
1588     *count_ptr = count;
1589     return JVMTI_ERROR_NONE;
1590   }
1591 };
1592 
1593 // return the list of objects with the specified tags
1594 jvmtiError JvmtiTagMap::get_objects_with_tags(const jlong* tags,
1595   jint count, jint* count_ptr, jobject** object_result_ptr, jlong** tag_result_ptr) {
1596 
1597   TagObjectCollector collector(env(), tags, count);
1598   {
1599     // iterate over all tagged objects
1600     MutexLocker ml(lock());
1601     entry_iterate(&collector);
1602   }
1603   return collector.result(count_ptr, object_result_ptr, tag_result_ptr);
1604 }
1605 
1606 
1607 // ObjectMarker is used to support the marking objects when walking the
1608 // heap.
1609 //
1610 // This implementation uses the existing mark bits in an object for
1611 // marking. Objects that are marked must later have their headers restored.
1612 // As most objects are unlocked and don't have their identity hash computed
1613 // we don't have to save their headers. Instead we save the headers that
1614 // are "interesting". Later when the headers are restored this implementation
1615 // restores all headers to their initial value and then restores the few
1616 // objects that had interesting headers.
1617 //
1618 // Future work: This implementation currently uses growable arrays to save
1619 // the oop and header of interesting objects. As an optimization we could
1620 // use the same technique as the GC and make use of the unused area
1621 // between top() and end().
1622 //
1623 
1624 // An ObjectClosure used to restore the mark bits of an object
1625 class RestoreMarksClosure : public ObjectClosure {
1626  public:
1627   void do_object(oop o) {
1628     if (o != NULL) {
1629       markOop mark = o->mark();
1630       if (mark->is_marked()) {
1631         o->init_mark();
1632       }
1633     }
1634   }
1635 };
1636 
1637 // ObjectMarker provides the mark and visited functions
1638 class ObjectMarker : AllStatic {
1639  private:
1640   // saved headers
1641   static GrowableArray<oop>* _saved_oop_stack;
1642   static GrowableArray<markOop>* _saved_mark_stack;
1643   static bool _needs_reset;                  // do we need to reset mark bits?
1644 
1645  public:
1646   static void init();                       // initialize
1647   static void done();                       // clean-up
1648 
1649   static inline void mark(oop o);           // mark an object
1650   static inline bool visited(oop o);        // check if object has been visited
1651 
1652   static inline bool needs_reset()            { return _needs_reset; }
1653   static inline void set_needs_reset(bool v)  { _needs_reset = v; }
1654 };
1655 
1656 GrowableArray<oop>* ObjectMarker::_saved_oop_stack = NULL;
1657 GrowableArray<markOop>* ObjectMarker::_saved_mark_stack = NULL;
1658 bool ObjectMarker::_needs_reset = true;  // need to reset mark bits by default
1659 
1660 // initialize ObjectMarker - prepares for object marking
1661 void ObjectMarker::init() {
1662   assert(Thread::current()->is_VM_thread(), "must be VMThread");
1663 
1664   // prepare heap for iteration
1665   Universe::heap()->ensure_parsability(false);  // no need to retire TLABs
1666 
1667   // create stacks for interesting headers
1668   _saved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(4000, true);
1669   _saved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(4000, true);
1670 
1671   if (UseBiasedLocking) {
1672     BiasedLocking::preserve_marks();
1673   }
1674 }
1675 
1676 // Object marking is done so restore object headers
1677 void ObjectMarker::done() {
1678   // iterate over all objects and restore the mark bits to
1679   // their initial value
1680   RestoreMarksClosure blk;
1681   if (needs_reset()) {
1682     Universe::heap()->object_iterate(&blk);
1683   } else {
1684     // We don't need to reset mark bits on this call, but reset the
1685     // flag to the default for the next call.
1686     set_needs_reset(true);
1687   }
1688 
1689   // now restore the interesting headers
1690   for (int i = 0; i < _saved_oop_stack->length(); i++) {
1691     oop o = _saved_oop_stack->at(i);
1692     markOop mark = _saved_mark_stack->at(i);
1693     o->set_mark(mark);
1694   }
1695 
1696   if (UseBiasedLocking) {
1697     BiasedLocking::restore_marks();
1698   }
1699 
1700   // free the stacks
1701   delete _saved_oop_stack;
1702   delete _saved_mark_stack;
1703 }
1704 
1705 // mark an object
1706 inline void ObjectMarker::mark(oop o) {
1707   assert(Universe::heap()->is_in(o), "sanity check");
1708   assert(!o->mark()->is_marked(), "should only mark an object once");
1709 
1710   // object's mark word
1711   markOop mark = o->mark();
1712 
1713   if (mark->must_be_preserved(o)) {
1714     _saved_mark_stack->push(mark);
1715     _saved_oop_stack->push(o);
1716   }
1717 
1718   // mark the object
1719   o->set_mark(markOopDesc::prototype()->set_marked());
1720 }
1721 
1722 // return true if object is marked
1723 inline bool ObjectMarker::visited(oop o) {
1724   return o->mark()->is_marked();
1725 }
1726 
1727 // Stack allocated class to help ensure that ObjectMarker is used
1728 // correctly. Constructor initializes ObjectMarker, destructor calls
1729 // ObjectMarker's done() function to restore object headers.
1730 class ObjectMarkerController : public StackObj {
1731  public:
1732   ObjectMarkerController() {
1733     ObjectMarker::init();
1734   }
1735   ~ObjectMarkerController() {
1736     ObjectMarker::done();
1737   }
1738 };
1739 
1740 
1741 // helper to map a jvmtiHeapReferenceKind to an old style jvmtiHeapRootKind
1742 // (not performance critical as only used for roots)
1743 static jvmtiHeapRootKind toJvmtiHeapRootKind(jvmtiHeapReferenceKind kind) {
1744   switch (kind) {
1745     case JVMTI_HEAP_REFERENCE_JNI_GLOBAL:   return JVMTI_HEAP_ROOT_JNI_GLOBAL;
1746     case JVMTI_HEAP_REFERENCE_SYSTEM_CLASS: return JVMTI_HEAP_ROOT_SYSTEM_CLASS;
1747     case JVMTI_HEAP_REFERENCE_MONITOR:      return JVMTI_HEAP_ROOT_MONITOR;
1748     case JVMTI_HEAP_REFERENCE_STACK_LOCAL:  return JVMTI_HEAP_ROOT_STACK_LOCAL;
1749     case JVMTI_HEAP_REFERENCE_JNI_LOCAL:    return JVMTI_HEAP_ROOT_JNI_LOCAL;
1750     case JVMTI_HEAP_REFERENCE_THREAD:       return JVMTI_HEAP_ROOT_THREAD;
1751     case JVMTI_HEAP_REFERENCE_OTHER:        return JVMTI_HEAP_ROOT_OTHER;
1752     default: ShouldNotReachHere();          return JVMTI_HEAP_ROOT_OTHER;
1753   }
1754 }
1755 
1756 // Base class for all heap walk contexts. The base class maintains a flag
1757 // to indicate if the context is valid or not.
1758 class HeapWalkContext {
1759  private:
1760   bool _valid;
1761  public:
1762   HeapWalkContext(bool valid)                   { _valid = valid; }
1763   void invalidate()                             { _valid = false; }
1764   bool is_valid() const                         { return _valid; }
1765 };
1766 
1767 // A basic heap walk context for the deprecated heap walking functions.
1768 // The context for a basic heap walk are the callbacks and fields used by
1769 // the referrer caching scheme.
1770 class BasicHeapWalkContext: public HeapWalkContext {
1771  private:
1772   jvmtiHeapRootCallback _heap_root_callback;
1773   jvmtiStackReferenceCallback _stack_ref_callback;
1774   jvmtiObjectReferenceCallback _object_ref_callback;
1775 
1776   // used for caching
1777   oop _last_referrer;
1778   jlong _last_referrer_tag;
1779 
1780  public:
1781   BasicHeapWalkContext() : HeapWalkContext(false) { }
1782 
1783   BasicHeapWalkContext(jvmtiHeapRootCallback heap_root_callback,
1784                        jvmtiStackReferenceCallback stack_ref_callback,
1785                        jvmtiObjectReferenceCallback object_ref_callback) :
1786     HeapWalkContext(true),
1787     _heap_root_callback(heap_root_callback),
1788     _stack_ref_callback(stack_ref_callback),
1789     _object_ref_callback(object_ref_callback),
1790     _last_referrer(NULL),
1791     _last_referrer_tag(0) {
1792   }
1793 
1794   // accessors
1795   jvmtiHeapRootCallback heap_root_callback() const         { return _heap_root_callback; }
1796   jvmtiStackReferenceCallback stack_ref_callback() const   { return _stack_ref_callback; }
1797   jvmtiObjectReferenceCallback object_ref_callback() const { return _object_ref_callback;  }
1798 
1799   oop last_referrer() const               { return _last_referrer; }
1800   void set_last_referrer(oop referrer)    { _last_referrer = referrer; }
1801   jlong last_referrer_tag() const         { return _last_referrer_tag; }
1802   void set_last_referrer_tag(jlong value) { _last_referrer_tag = value; }
1803 };
1804 
1805 // The advanced heap walk context for the FollowReferences functions.
1806 // The context is the callbacks, and the fields used for filtering.
1807 class AdvancedHeapWalkContext: public HeapWalkContext {
1808  private:
1809   jint _heap_filter;
1810   Klass* _klass_filter;
1811   const jvmtiHeapCallbacks* _heap_callbacks;
1812 
1813  public:
1814   AdvancedHeapWalkContext() : HeapWalkContext(false) { }
1815 
1816   AdvancedHeapWalkContext(jint heap_filter,
1817                            Klass* klass_filter,
1818                            const jvmtiHeapCallbacks* heap_callbacks) :
1819     HeapWalkContext(true),
1820     _heap_filter(heap_filter),
1821     _klass_filter(klass_filter),
1822     _heap_callbacks(heap_callbacks) {
1823   }
1824 
1825   // accessors
1826   jint heap_filter() const         { return _heap_filter; }
1827   Klass* klass_filter() const      { return _klass_filter; }
1828 
1829   const jvmtiHeapReferenceCallback heap_reference_callback() const {
1830     return _heap_callbacks->heap_reference_callback;
1831   };
1832   const jvmtiPrimitiveFieldCallback primitive_field_callback() const {
1833     return _heap_callbacks->primitive_field_callback;
1834   }
1835   const jvmtiArrayPrimitiveValueCallback array_primitive_value_callback() const {
1836     return _heap_callbacks->array_primitive_value_callback;
1837   }
1838   const jvmtiStringPrimitiveValueCallback string_primitive_value_callback() const {
1839     return _heap_callbacks->string_primitive_value_callback;
1840   }
1841 };
1842 
1843 // The CallbackInvoker is a class with static functions that the heap walk can call
1844 // into to invoke callbacks. It works in one of two modes. The "basic" mode is
1845 // used for the deprecated IterateOverReachableObjects functions. The "advanced"
1846 // mode is for the newer FollowReferences function which supports a lot of
1847 // additional callbacks.
1848 class CallbackInvoker : AllStatic {
1849  private:
1850   // heap walk styles
1851   enum { basic, advanced };
1852   static int _heap_walk_type;
1853   static bool is_basic_heap_walk()           { return _heap_walk_type == basic; }
1854   static bool is_advanced_heap_walk()        { return _heap_walk_type == advanced; }
1855 
1856   // context for basic style heap walk
1857   static BasicHeapWalkContext _basic_context;
1858   static BasicHeapWalkContext* basic_context() {
1859     assert(_basic_context.is_valid(), "invalid");
1860     return &_basic_context;
1861   }
1862 
1863   // context for advanced style heap walk
1864   static AdvancedHeapWalkContext _advanced_context;
1865   static AdvancedHeapWalkContext* advanced_context() {
1866     assert(_advanced_context.is_valid(), "invalid");
1867     return &_advanced_context;
1868   }
1869 
1870   // context needed for all heap walks
1871   static JvmtiTagMap* _tag_map;
1872   static const void* _user_data;
1873   static GrowableArray<oop>* _visit_stack;
1874 
1875   // accessors
1876   static JvmtiTagMap* tag_map()                        { return _tag_map; }
1877   static const void* user_data()                       { return _user_data; }
1878   static GrowableArray<oop>* visit_stack()             { return _visit_stack; }
1879 
1880   // if the object hasn't been visited then push it onto the visit stack
1881   // so that it will be visited later
1882   static inline bool check_for_visit(oop obj) {
1883     if (!ObjectMarker::visited(obj)) visit_stack()->push(obj);
1884     return true;
1885   }
1886 
1887   // invoke basic style callbacks
1888   static inline bool invoke_basic_heap_root_callback
1889     (jvmtiHeapRootKind root_kind, oop obj);
1890   static inline bool invoke_basic_stack_ref_callback
1891     (jvmtiHeapRootKind root_kind, jlong thread_tag, jint depth, jmethodID method,
1892      int slot, oop obj);
1893   static inline bool invoke_basic_object_reference_callback
1894     (jvmtiObjectReferenceKind ref_kind, oop referrer, oop referree, jint index);
1895 
1896   // invoke advanced style callbacks
1897   static inline bool invoke_advanced_heap_root_callback
1898     (jvmtiHeapReferenceKind ref_kind, oop obj);
1899   static inline bool invoke_advanced_stack_ref_callback
1900     (jvmtiHeapReferenceKind ref_kind, jlong thread_tag, jlong tid, int depth,
1901      jmethodID method, jlocation bci, jint slot, oop obj);
1902   static inline bool invoke_advanced_object_reference_callback
1903     (jvmtiHeapReferenceKind ref_kind, oop referrer, oop referree, jint index);
1904 
1905   // used to report the value of primitive fields
1906   static inline bool report_primitive_field
1907     (jvmtiHeapReferenceKind ref_kind, oop obj, jint index, address addr, char type);
1908 
1909  public:
1910   // initialize for basic mode
1911   static void initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1912                                              GrowableArray<oop>* visit_stack,
1913                                              const void* user_data,
1914                                              BasicHeapWalkContext context);
1915 
1916   // initialize for advanced mode
1917   static void initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1918                                                 GrowableArray<oop>* visit_stack,
1919                                                 const void* user_data,
1920                                                 AdvancedHeapWalkContext context);
1921 
1922    // functions to report roots
1923   static inline bool report_simple_root(jvmtiHeapReferenceKind kind, oop o);
1924   static inline bool report_jni_local_root(jlong thread_tag, jlong tid, jint depth,
1925     jmethodID m, oop o);
1926   static inline bool report_stack_ref_root(jlong thread_tag, jlong tid, jint depth,
1927     jmethodID method, jlocation bci, jint slot, oop o);
1928 
1929   // functions to report references
1930   static inline bool report_array_element_reference(oop referrer, oop referree, jint index);
1931   static inline bool report_class_reference(oop referrer, oop referree);
1932   static inline bool report_class_loader_reference(oop referrer, oop referree);
1933   static inline bool report_signers_reference(oop referrer, oop referree);
1934   static inline bool report_protection_domain_reference(oop referrer, oop referree);
1935   static inline bool report_superclass_reference(oop referrer, oop referree);
1936   static inline bool report_interface_reference(oop referrer, oop referree);
1937   static inline bool report_static_field_reference(oop referrer, oop referree, jint slot);
1938   static inline bool report_field_reference(oop referrer, oop referree, jint slot);
1939   static inline bool report_constant_pool_reference(oop referrer, oop referree, jint index);
1940   static inline bool report_primitive_array_values(oop array);
1941   static inline bool report_string_value(oop str);
1942   static inline bool report_primitive_instance_field(oop o, jint index, address value, char type);
1943   static inline bool report_primitive_static_field(oop o, jint index, address value, char type);
1944 };
1945 
1946 // statics
1947 int CallbackInvoker::_heap_walk_type;
1948 BasicHeapWalkContext CallbackInvoker::_basic_context;
1949 AdvancedHeapWalkContext CallbackInvoker::_advanced_context;
1950 JvmtiTagMap* CallbackInvoker::_tag_map;
1951 const void* CallbackInvoker::_user_data;
1952 GrowableArray<oop>* CallbackInvoker::_visit_stack;
1953 
1954 // initialize for basic heap walk (IterateOverReachableObjects et al)
1955 void CallbackInvoker::initialize_for_basic_heap_walk(JvmtiTagMap* tag_map,
1956                                                      GrowableArray<oop>* visit_stack,
1957                                                      const void* user_data,
1958                                                      BasicHeapWalkContext context) {
1959   _tag_map = tag_map;
1960   _visit_stack = visit_stack;
1961   _user_data = user_data;
1962   _basic_context = context;
1963   _advanced_context.invalidate();       // will trigger assertion if used
1964   _heap_walk_type = basic;
1965 }
1966 
1967 // initialize for advanced heap walk (FollowReferences)
1968 void CallbackInvoker::initialize_for_advanced_heap_walk(JvmtiTagMap* tag_map,
1969                                                         GrowableArray<oop>* visit_stack,
1970                                                         const void* user_data,
1971                                                         AdvancedHeapWalkContext context) {
1972   _tag_map = tag_map;
1973   _visit_stack = visit_stack;
1974   _user_data = user_data;
1975   _advanced_context = context;
1976   _basic_context.invalidate();      // will trigger assertion if used
1977   _heap_walk_type = advanced;
1978 }
1979 
1980 
1981 // invoke basic style heap root callback
1982 inline bool CallbackInvoker::invoke_basic_heap_root_callback(jvmtiHeapRootKind root_kind, oop obj) {
1983   // if we heap roots should be reported
1984   jvmtiHeapRootCallback cb = basic_context()->heap_root_callback();
1985   if (cb == NULL) {
1986     return check_for_visit(obj);
1987   }
1988 
1989   CallbackWrapper wrapper(tag_map(), obj);
1990   jvmtiIterationControl control = (*cb)(root_kind,
1991                                         wrapper.klass_tag(),
1992                                         wrapper.obj_size(),
1993                                         wrapper.obj_tag_p(),
1994                                         (void*)user_data());
1995   // push root to visit stack when following references
1996   if (control == JVMTI_ITERATION_CONTINUE &&
1997       basic_context()->object_ref_callback() != NULL) {
1998     visit_stack()->push(obj);
1999   }
2000   return control != JVMTI_ITERATION_ABORT;
2001 }
2002 
2003 // invoke basic style stack ref callback
2004 inline bool CallbackInvoker::invoke_basic_stack_ref_callback(jvmtiHeapRootKind root_kind,
2005                                                              jlong thread_tag,
2006                                                              jint depth,
2007                                                              jmethodID method,
2008                                                              int slot,
2009                                                              oop obj) {
2010   // if we stack refs should be reported
2011   jvmtiStackReferenceCallback cb = basic_context()->stack_ref_callback();
2012   if (cb == NULL) {
2013     return check_for_visit(obj);
2014   }
2015 
2016   CallbackWrapper wrapper(tag_map(), obj);
2017   jvmtiIterationControl control = (*cb)(root_kind,
2018                                         wrapper.klass_tag(),
2019                                         wrapper.obj_size(),
2020                                         wrapper.obj_tag_p(),
2021                                         thread_tag,
2022                                         depth,
2023                                         method,
2024                                         slot,
2025                                         (void*)user_data());
2026   // push root to visit stack when following references
2027   if (control == JVMTI_ITERATION_CONTINUE &&
2028       basic_context()->object_ref_callback() != NULL) {
2029     visit_stack()->push(obj);
2030   }
2031   return control != JVMTI_ITERATION_ABORT;
2032 }
2033 
2034 // invoke basic style object reference callback
2035 inline bool CallbackInvoker::invoke_basic_object_reference_callback(jvmtiObjectReferenceKind ref_kind,
2036                                                                     oop referrer,
2037                                                                     oop referree,
2038                                                                     jint index) {
2039 
2040   BasicHeapWalkContext* context = basic_context();
2041 
2042   // callback requires the referrer's tag. If it's the same referrer
2043   // as the last call then we use the cached value.
2044   jlong referrer_tag;
2045   if (referrer == context->last_referrer()) {
2046     referrer_tag = context->last_referrer_tag();
2047   } else {
2048     referrer_tag = tag_for(tag_map(), referrer);
2049   }
2050 
2051   // do the callback
2052   CallbackWrapper wrapper(tag_map(), referree);
2053   jvmtiObjectReferenceCallback cb = context->object_ref_callback();
2054   jvmtiIterationControl control = (*cb)(ref_kind,
2055                                         wrapper.klass_tag(),
2056                                         wrapper.obj_size(),
2057                                         wrapper.obj_tag_p(),
2058                                         referrer_tag,
2059                                         index,
2060                                         (void*)user_data());
2061 
2062   // record referrer and referrer tag. For self-references record the
2063   // tag value from the callback as this might differ from referrer_tag.
2064   context->set_last_referrer(referrer);
2065   if (referrer == referree) {
2066     context->set_last_referrer_tag(*wrapper.obj_tag_p());
2067   } else {
2068     context->set_last_referrer_tag(referrer_tag);
2069   }
2070 
2071   if (control == JVMTI_ITERATION_CONTINUE) {
2072     return check_for_visit(referree);
2073   } else {
2074     return control != JVMTI_ITERATION_ABORT;
2075   }
2076 }
2077 
2078 // invoke advanced style heap root callback
2079 inline bool CallbackInvoker::invoke_advanced_heap_root_callback(jvmtiHeapReferenceKind ref_kind,
2080                                                                 oop obj) {
2081   AdvancedHeapWalkContext* context = advanced_context();
2082 
2083   // check that callback is provided
2084   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2085   if (cb == NULL) {
2086     return check_for_visit(obj);
2087   }
2088 
2089   // apply class filter
2090   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2091     return check_for_visit(obj);
2092   }
2093 
2094   // setup the callback wrapper
2095   CallbackWrapper wrapper(tag_map(), obj);
2096 
2097   // apply tag filter
2098   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2099                                  wrapper.klass_tag(),
2100                                  context->heap_filter())) {
2101     return check_for_visit(obj);
2102   }
2103 
2104   // for arrays we need the length, otherwise -1
2105   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2106 
2107   // invoke the callback
2108   jint res  = (*cb)(ref_kind,
2109                     NULL, // referrer info
2110                     wrapper.klass_tag(),
2111                     0,    // referrer_class_tag is 0 for heap root
2112                     wrapper.obj_size(),
2113                     wrapper.obj_tag_p(),
2114                     NULL, // referrer_tag_p
2115                     len,
2116                     (void*)user_data());
2117   if (res & JVMTI_VISIT_ABORT) {
2118     return false;// referrer class tag
2119   }
2120   if (res & JVMTI_VISIT_OBJECTS) {
2121     check_for_visit(obj);
2122   }
2123   return true;
2124 }
2125 
2126 // report a reference from a thread stack to an object
2127 inline bool CallbackInvoker::invoke_advanced_stack_ref_callback(jvmtiHeapReferenceKind ref_kind,
2128                                                                 jlong thread_tag,
2129                                                                 jlong tid,
2130                                                                 int depth,
2131                                                                 jmethodID method,
2132                                                                 jlocation bci,
2133                                                                 jint slot,
2134                                                                 oop obj) {
2135   AdvancedHeapWalkContext* context = advanced_context();
2136 
2137   // check that callback is provider
2138   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2139   if (cb == NULL) {
2140     return check_for_visit(obj);
2141   }
2142 
2143   // apply class filter
2144   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2145     return check_for_visit(obj);
2146   }
2147 
2148   // setup the callback wrapper
2149   CallbackWrapper wrapper(tag_map(), obj);
2150 
2151   // apply tag filter
2152   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2153                                  wrapper.klass_tag(),
2154                                  context->heap_filter())) {
2155     return check_for_visit(obj);
2156   }
2157 
2158   // setup the referrer info
2159   jvmtiHeapReferenceInfo reference_info;
2160   reference_info.stack_local.thread_tag = thread_tag;
2161   reference_info.stack_local.thread_id = tid;
2162   reference_info.stack_local.depth = depth;
2163   reference_info.stack_local.method = method;
2164   reference_info.stack_local.location = bci;
2165   reference_info.stack_local.slot = slot;
2166 
2167   // for arrays we need the length, otherwise -1
2168   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2169 
2170   // call into the agent
2171   int res = (*cb)(ref_kind,
2172                   &reference_info,
2173                   wrapper.klass_tag(),
2174                   0,    // referrer_class_tag is 0 for heap root (stack)
2175                   wrapper.obj_size(),
2176                   wrapper.obj_tag_p(),
2177                   NULL, // referrer_tag is 0 for root
2178                   len,
2179                   (void*)user_data());
2180 
2181   if (res & JVMTI_VISIT_ABORT) {
2182     return false;
2183   }
2184   if (res & JVMTI_VISIT_OBJECTS) {
2185     check_for_visit(obj);
2186   }
2187   return true;
2188 }
2189 
2190 // This mask is used to pass reference_info to a jvmtiHeapReferenceCallback
2191 // only for ref_kinds defined by the JVM TI spec. Otherwise, NULL is passed.
2192 #define REF_INFO_MASK  ((1 << JVMTI_HEAP_REFERENCE_FIELD)         \
2193                       | (1 << JVMTI_HEAP_REFERENCE_STATIC_FIELD)  \
2194                       | (1 << JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT) \
2195                       | (1 << JVMTI_HEAP_REFERENCE_CONSTANT_POOL) \
2196                       | (1 << JVMTI_HEAP_REFERENCE_STACK_LOCAL)   \
2197                       | (1 << JVMTI_HEAP_REFERENCE_JNI_LOCAL))
2198 
2199 // invoke the object reference callback to report a reference
2200 inline bool CallbackInvoker::invoke_advanced_object_reference_callback(jvmtiHeapReferenceKind ref_kind,
2201                                                                        oop referrer,
2202                                                                        oop obj,
2203                                                                        jint index)
2204 {
2205   // field index is only valid field in reference_info
2206   static jvmtiHeapReferenceInfo reference_info = { 0 };
2207 
2208   AdvancedHeapWalkContext* context = advanced_context();
2209 
2210   // check that callback is provider
2211   jvmtiHeapReferenceCallback cb = context->heap_reference_callback();
2212   if (cb == NULL) {
2213     return check_for_visit(obj);
2214   }
2215 
2216   // apply class filter
2217   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2218     return check_for_visit(obj);
2219   }
2220 
2221   // setup the callback wrapper
2222   TwoOopCallbackWrapper wrapper(tag_map(), referrer, obj);
2223 
2224   // apply tag filter
2225   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2226                                  wrapper.klass_tag(),
2227                                  context->heap_filter())) {
2228     return check_for_visit(obj);
2229   }
2230 
2231   // field index is only valid field in reference_info
2232   reference_info.field.index = index;
2233 
2234   // for arrays we need the length, otherwise -1
2235   jint len = (jint)(obj->is_array() ? arrayOop(obj)->length() : -1);
2236 
2237   // invoke the callback
2238   int res = (*cb)(ref_kind,
2239                   (REF_INFO_MASK & (1 << ref_kind)) ? &reference_info : NULL,
2240                   wrapper.klass_tag(),
2241                   wrapper.referrer_klass_tag(),
2242                   wrapper.obj_size(),
2243                   wrapper.obj_tag_p(),
2244                   wrapper.referrer_tag_p(),
2245                   len,
2246                   (void*)user_data());
2247 
2248   if (res & JVMTI_VISIT_ABORT) {
2249     return false;
2250   }
2251   if (res & JVMTI_VISIT_OBJECTS) {
2252     check_for_visit(obj);
2253   }
2254   return true;
2255 }
2256 
2257 // report a "simple root"
2258 inline bool CallbackInvoker::report_simple_root(jvmtiHeapReferenceKind kind, oop obj) {
2259   assert(kind != JVMTI_HEAP_REFERENCE_STACK_LOCAL &&
2260          kind != JVMTI_HEAP_REFERENCE_JNI_LOCAL, "not a simple root");
2261 
2262   if (is_basic_heap_walk()) {
2263     // map to old style root kind
2264     jvmtiHeapRootKind root_kind = toJvmtiHeapRootKind(kind);
2265     return invoke_basic_heap_root_callback(root_kind, obj);
2266   } else {
2267     assert(is_advanced_heap_walk(), "wrong heap walk type");
2268     return invoke_advanced_heap_root_callback(kind, obj);
2269   }
2270 }
2271 
2272 
2273 // invoke the primitive array values
2274 inline bool CallbackInvoker::report_primitive_array_values(oop obj) {
2275   assert(obj->is_typeArray(), "not a primitive array");
2276 
2277   AdvancedHeapWalkContext* context = advanced_context();
2278   assert(context->array_primitive_value_callback() != NULL, "no callback");
2279 
2280   // apply class filter
2281   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2282     return true;
2283   }
2284 
2285   CallbackWrapper wrapper(tag_map(), obj);
2286 
2287   // apply tag filter
2288   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2289                                  wrapper.klass_tag(),
2290                                  context->heap_filter())) {
2291     return true;
2292   }
2293 
2294   // invoke the callback
2295   int res = invoke_array_primitive_value_callback(context->array_primitive_value_callback(),
2296                                                   &wrapper,
2297                                                   obj,
2298                                                   (void*)user_data());
2299   return (!(res & JVMTI_VISIT_ABORT));
2300 }
2301 
2302 // invoke the string value callback
2303 inline bool CallbackInvoker::report_string_value(oop str) {
2304   assert(str->klass() == SystemDictionary::String_klass(), "not a string");
2305 
2306   AdvancedHeapWalkContext* context = advanced_context();
2307   assert(context->string_primitive_value_callback() != NULL, "no callback");
2308 
2309   // apply class filter
2310   if (is_filtered_by_klass_filter(str, context->klass_filter())) {
2311     return true;
2312   }
2313 
2314   CallbackWrapper wrapper(tag_map(), str);
2315 
2316   // apply tag filter
2317   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2318                                  wrapper.klass_tag(),
2319                                  context->heap_filter())) {
2320     return true;
2321   }
2322 
2323   // invoke the callback
2324   int res = invoke_string_value_callback(context->string_primitive_value_callback(),
2325                                          &wrapper,
2326                                          str,
2327                                          (void*)user_data());
2328   return (!(res & JVMTI_VISIT_ABORT));
2329 }
2330 
2331 // invoke the primitive field callback
2332 inline bool CallbackInvoker::report_primitive_field(jvmtiHeapReferenceKind ref_kind,
2333                                                     oop obj,
2334                                                     jint index,
2335                                                     address addr,
2336                                                     char type)
2337 {
2338   // for primitive fields only the index will be set
2339   static jvmtiHeapReferenceInfo reference_info = { 0 };
2340 
2341   AdvancedHeapWalkContext* context = advanced_context();
2342   assert(context->primitive_field_callback() != NULL, "no callback");
2343 
2344   // apply class filter
2345   if (is_filtered_by_klass_filter(obj, context->klass_filter())) {
2346     return true;
2347   }
2348 
2349   CallbackWrapper wrapper(tag_map(), obj);
2350 
2351   // apply tag filter
2352   if (is_filtered_by_heap_filter(wrapper.obj_tag(),
2353                                  wrapper.klass_tag(),
2354                                  context->heap_filter())) {
2355     return true;
2356   }
2357 
2358   // the field index in the referrer
2359   reference_info.field.index = index;
2360 
2361   // map the type
2362   jvmtiPrimitiveType value_type = (jvmtiPrimitiveType)type;
2363 
2364   // setup the jvalue
2365   jvalue value;
2366   copy_to_jvalue(&value, addr, value_type);
2367 
2368   jvmtiPrimitiveFieldCallback cb = context->primitive_field_callback();
2369   int res = (*cb)(ref_kind,
2370                   &reference_info,
2371                   wrapper.klass_tag(),
2372                   wrapper.obj_tag_p(),
2373                   value,
2374                   value_type,
2375                   (void*)user_data());
2376   return (!(res & JVMTI_VISIT_ABORT));
2377 }
2378 
2379 
2380 // instance field
2381 inline bool CallbackInvoker::report_primitive_instance_field(oop obj,
2382                                                              jint index,
2383                                                              address value,
2384                                                              char type) {
2385   return report_primitive_field(JVMTI_HEAP_REFERENCE_FIELD,
2386                                 obj,
2387                                 index,
2388                                 value,
2389                                 type);
2390 }
2391 
2392 // static field
2393 inline bool CallbackInvoker::report_primitive_static_field(oop obj,
2394                                                            jint index,
2395                                                            address value,
2396                                                            char type) {
2397   return report_primitive_field(JVMTI_HEAP_REFERENCE_STATIC_FIELD,
2398                                 obj,
2399                                 index,
2400                                 value,
2401                                 type);
2402 }
2403 
2404 // report a JNI local (root object) to the profiler
2405 inline bool CallbackInvoker::report_jni_local_root(jlong thread_tag, jlong tid, jint depth, jmethodID m, oop obj) {
2406   if (is_basic_heap_walk()) {
2407     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_JNI_LOCAL,
2408                                            thread_tag,
2409                                            depth,
2410                                            m,
2411                                            -1,
2412                                            obj);
2413   } else {
2414     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_JNI_LOCAL,
2415                                               thread_tag, tid,
2416                                               depth,
2417                                               m,
2418                                               (jlocation)-1,
2419                                               -1,
2420                                               obj);
2421   }
2422 }
2423 
2424 
2425 // report a local (stack reference, root object)
2426 inline bool CallbackInvoker::report_stack_ref_root(jlong thread_tag,
2427                                                    jlong tid,
2428                                                    jint depth,
2429                                                    jmethodID method,
2430                                                    jlocation bci,
2431                                                    jint slot,
2432                                                    oop obj) {
2433   if (is_basic_heap_walk()) {
2434     return invoke_basic_stack_ref_callback(JVMTI_HEAP_ROOT_STACK_LOCAL,
2435                                            thread_tag,
2436                                            depth,
2437                                            method,
2438                                            slot,
2439                                            obj);
2440   } else {
2441     return invoke_advanced_stack_ref_callback(JVMTI_HEAP_REFERENCE_STACK_LOCAL,
2442                                               thread_tag,
2443                                               tid,
2444                                               depth,
2445                                               method,
2446                                               bci,
2447                                               slot,
2448                                               obj);
2449   }
2450 }
2451 
2452 // report an object referencing a class.
2453 inline bool CallbackInvoker::report_class_reference(oop referrer, oop referree) {
2454   if (is_basic_heap_walk()) {
2455     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2456   } else {
2457     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS, referrer, referree, -1);
2458   }
2459 }
2460 
2461 // report a class referencing its class loader.
2462 inline bool CallbackInvoker::report_class_loader_reference(oop referrer, oop referree) {
2463   if (is_basic_heap_walk()) {
2464     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2465   } else {
2466     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CLASS_LOADER, referrer, referree, -1);
2467   }
2468 }
2469 
2470 // report a class referencing its signers.
2471 inline bool CallbackInvoker::report_signers_reference(oop referrer, oop referree) {
2472   if (is_basic_heap_walk()) {
2473     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_SIGNERS, referrer, referree, -1);
2474   } else {
2475     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SIGNERS, referrer, referree, -1);
2476   }
2477 }
2478 
2479 // report a class referencing its protection domain..
2480 inline bool CallbackInvoker::report_protection_domain_reference(oop referrer, oop referree) {
2481   if (is_basic_heap_walk()) {
2482     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2483   } else {
2484     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_PROTECTION_DOMAIN, referrer, referree, -1);
2485   }
2486 }
2487 
2488 // report a class referencing its superclass.
2489 inline bool CallbackInvoker::report_superclass_reference(oop referrer, oop referree) {
2490   if (is_basic_heap_walk()) {
2491     // Send this to be consistent with past implementation
2492     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CLASS, referrer, referree, -1);
2493   } else {
2494     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_SUPERCLASS, referrer, referree, -1);
2495   }
2496 }
2497 
2498 // report a class referencing one of its interfaces.
2499 inline bool CallbackInvoker::report_interface_reference(oop referrer, oop referree) {
2500   if (is_basic_heap_walk()) {
2501     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_INTERFACE, referrer, referree, -1);
2502   } else {
2503     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_INTERFACE, referrer, referree, -1);
2504   }
2505 }
2506 
2507 // report a class referencing one of its static fields.
2508 inline bool CallbackInvoker::report_static_field_reference(oop referrer, oop referree, jint slot) {
2509   if (is_basic_heap_walk()) {
2510     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2511   } else {
2512     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_STATIC_FIELD, referrer, referree, slot);
2513   }
2514 }
2515 
2516 // report an array referencing an element object
2517 inline bool CallbackInvoker::report_array_element_reference(oop referrer, oop referree, jint index) {
2518   if (is_basic_heap_walk()) {
2519     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2520   } else {
2521     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT, referrer, referree, index);
2522   }
2523 }
2524 
2525 // report an object referencing an instance field object
2526 inline bool CallbackInvoker::report_field_reference(oop referrer, oop referree, jint slot) {
2527   if (is_basic_heap_walk()) {
2528     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_FIELD, referrer, referree, slot);
2529   } else {
2530     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_FIELD, referrer, referree, slot);
2531   }
2532 }
2533 
2534 // report an array referencing an element object
2535 inline bool CallbackInvoker::report_constant_pool_reference(oop referrer, oop referree, jint index) {
2536   if (is_basic_heap_walk()) {
2537     return invoke_basic_object_reference_callback(JVMTI_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2538   } else {
2539     return invoke_advanced_object_reference_callback(JVMTI_HEAP_REFERENCE_CONSTANT_POOL, referrer, referree, index);
2540   }
2541 }
2542 
2543 // A supporting closure used to process simple roots
2544 class SimpleRootsClosure : public OopClosure {
2545  private:
2546   jvmtiHeapReferenceKind _kind;
2547   bool _continue;
2548 
2549   jvmtiHeapReferenceKind root_kind()    { return _kind; }
2550 
2551  public:
2552   void set_kind(jvmtiHeapReferenceKind kind) {
2553     _kind = kind;
2554     _continue = true;
2555   }
2556 
2557   inline bool stopped() {
2558     return !_continue;
2559   }
2560 
2561   void do_oop(oop* obj_p) {
2562     // iteration has terminated
2563     if (stopped()) {
2564       return;
2565     }
2566 
2567     oop o = *obj_p;
2568     // ignore null
2569     if (o == NULL) {
2570       return;
2571     }
2572 
2573     assert(Universe::heap()->is_in_reserved(o), "should be impossible");
2574 
2575     jvmtiHeapReferenceKind kind = root_kind();
2576     if (kind == JVMTI_HEAP_REFERENCE_SYSTEM_CLASS) {
2577       // SystemDictionary::always_strong_oops_do reports the application
2578       // class loader as a root. We want this root to be reported as
2579       // a root kind of "OTHER" rather than "SYSTEM_CLASS".
2580       if (!o->is_instance() || !InstanceKlass::cast(o->klass())->is_mirror_instance_klass()) {
2581         kind = JVMTI_HEAP_REFERENCE_OTHER;
2582       }
2583     }
2584 
2585     // invoke the callback
2586     _continue = CallbackInvoker::report_simple_root(kind, o);
2587 
2588   }
2589   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2590 };
2591 
2592 // A supporting closure used to process JNI locals
2593 class JNILocalRootsClosure : public OopClosure {
2594  private:
2595   jlong _thread_tag;
2596   jlong _tid;
2597   jint _depth;
2598   jmethodID _method;
2599   bool _continue;
2600  public:
2601   void set_context(jlong thread_tag, jlong tid, jint depth, jmethodID method) {
2602     _thread_tag = thread_tag;
2603     _tid = tid;
2604     _depth = depth;
2605     _method = method;
2606     _continue = true;
2607   }
2608 
2609   inline bool stopped() {
2610     return !_continue;
2611   }
2612 
2613   void do_oop(oop* obj_p) {
2614     // iteration has terminated
2615     if (stopped()) {
2616       return;
2617     }
2618 
2619     oop o = *obj_p;
2620     // ignore null
2621     if (o == NULL) {
2622       return;
2623     }
2624 
2625     // invoke the callback
2626     _continue = CallbackInvoker::report_jni_local_root(_thread_tag, _tid, _depth, _method, o);
2627   }
2628   virtual void do_oop(narrowOop* obj_p) { ShouldNotReachHere(); }
2629 };
2630 
2631 
2632 // A VM operation to iterate over objects that are reachable from
2633 // a set of roots or an initial object.
2634 //
2635 // For VM_HeapWalkOperation the set of roots used is :-
2636 //
2637 // - All JNI global references
2638 // - All inflated monitors
2639 // - All classes loaded by the boot class loader (or all classes
2640 //     in the event that class unloading is disabled)
2641 // - All java threads
2642 // - For each java thread then all locals and JNI local references
2643 //      on the thread's execution stack
2644 // - All visible/explainable objects from Universes::oops_do
2645 //
2646 class VM_HeapWalkOperation: public VM_Operation {
2647  private:
2648   enum {
2649     initial_visit_stack_size = 4000
2650   };
2651 
2652   bool _is_advanced_heap_walk;                      // indicates FollowReferences
2653   JvmtiTagMap* _tag_map;
2654   Handle _initial_object;
2655   GrowableArray<oop>* _visit_stack;                 // the visit stack
2656 
2657   bool _collecting_heap_roots;                      // are we collecting roots
2658   bool _following_object_refs;                      // are we following object references
2659 
2660   bool _reporting_primitive_fields;                 // optional reporting
2661   bool _reporting_primitive_array_values;
2662   bool _reporting_string_values;
2663 
2664   GrowableArray<oop>* create_visit_stack() {
2665     return new (ResourceObj::C_HEAP, mtInternal) GrowableArray<oop>(initial_visit_stack_size, true);
2666   }
2667 
2668   // accessors
2669   bool is_advanced_heap_walk() const               { return _is_advanced_heap_walk; }
2670   JvmtiTagMap* tag_map() const                     { return _tag_map; }
2671   Handle initial_object() const                    { return _initial_object; }
2672 
2673   bool is_following_references() const             { return _following_object_refs; }
2674 
2675   bool is_reporting_primitive_fields()  const      { return _reporting_primitive_fields; }
2676   bool is_reporting_primitive_array_values() const { return _reporting_primitive_array_values; }
2677   bool is_reporting_string_values() const          { return _reporting_string_values; }
2678 
2679   GrowableArray<oop>* visit_stack() const          { return _visit_stack; }
2680 
2681   // iterate over the various object types
2682   inline bool iterate_over_array(oop o);
2683   inline bool iterate_over_type_array(oop o);
2684   inline bool iterate_over_class(oop o);
2685   inline bool iterate_over_object(oop o);
2686 
2687   // root collection
2688   inline bool collect_simple_roots();
2689   inline bool collect_stack_roots();
2690   inline bool collect_stack_roots(JavaThread* java_thread, JNILocalRootsClosure* blk);
2691 
2692   // visit an object
2693   inline bool visit(oop o);
2694 
2695  public:
2696   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2697                        Handle initial_object,
2698                        BasicHeapWalkContext callbacks,
2699                        const void* user_data);
2700 
2701   VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2702                        Handle initial_object,
2703                        AdvancedHeapWalkContext callbacks,
2704                        const void* user_data);
2705 
2706   ~VM_HeapWalkOperation();
2707 
2708   VMOp_Type type() const { return VMOp_HeapWalkOperation; }
2709   void doit();
2710 };
2711 
2712 
2713 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2714                                            Handle initial_object,
2715                                            BasicHeapWalkContext callbacks,
2716                                            const void* user_data) {
2717   _is_advanced_heap_walk = false;
2718   _tag_map = tag_map;
2719   _initial_object = initial_object;
2720   _following_object_refs = (callbacks.object_ref_callback() != NULL);
2721   _reporting_primitive_fields = false;
2722   _reporting_primitive_array_values = false;
2723   _reporting_string_values = false;
2724   _visit_stack = create_visit_stack();
2725 
2726 
2727   CallbackInvoker::initialize_for_basic_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2728 }
2729 
2730 VM_HeapWalkOperation::VM_HeapWalkOperation(JvmtiTagMap* tag_map,
2731                                            Handle initial_object,
2732                                            AdvancedHeapWalkContext callbacks,
2733                                            const void* user_data) {
2734   _is_advanced_heap_walk = true;
2735   _tag_map = tag_map;
2736   _initial_object = initial_object;
2737   _following_object_refs = true;
2738   _reporting_primitive_fields = (callbacks.primitive_field_callback() != NULL);;
2739   _reporting_primitive_array_values = (callbacks.array_primitive_value_callback() != NULL);;
2740   _reporting_string_values = (callbacks.string_primitive_value_callback() != NULL);;
2741   _visit_stack = create_visit_stack();
2742 
2743   CallbackInvoker::initialize_for_advanced_heap_walk(tag_map, _visit_stack, user_data, callbacks);
2744 }
2745 
2746 VM_HeapWalkOperation::~VM_HeapWalkOperation() {
2747   if (_following_object_refs) {
2748     assert(_visit_stack != NULL, "checking");
2749     delete _visit_stack;
2750     _visit_stack = NULL;
2751   }
2752 }
2753 
2754 // an array references its class and has a reference to
2755 // each element in the array
2756 inline bool VM_HeapWalkOperation::iterate_over_array(oop o) {
2757   objArrayOop array = objArrayOop(o);
2758 
2759   // array reference to its class
2760   oop mirror = ObjArrayKlass::cast(array->klass())->java_mirror();
2761   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2762     return false;
2763   }
2764 
2765   // iterate over the array and report each reference to a
2766   // non-null element
2767   for (int index=0; index<array->length(); index++) {
2768     oop elem = array->obj_at(index);
2769     if (elem == NULL) {
2770       continue;
2771     }
2772 
2773     // report the array reference o[index] = elem
2774     if (!CallbackInvoker::report_array_element_reference(o, elem, index)) {
2775       return false;
2776     }
2777   }
2778   return true;
2779 }
2780 
2781 // a type array references its class
2782 inline bool VM_HeapWalkOperation::iterate_over_type_array(oop o) {
2783   Klass* k = o->klass();
2784   oop mirror = k->java_mirror();
2785   if (!CallbackInvoker::report_class_reference(o, mirror)) {
2786     return false;
2787   }
2788 
2789   // report the array contents if required
2790   if (is_reporting_primitive_array_values()) {
2791     if (!CallbackInvoker::report_primitive_array_values(o)) {
2792       return false;
2793     }
2794   }
2795   return true;
2796 }
2797 
2798 #ifdef ASSERT
2799 // verify that a static oop field is in range
2800 static inline bool verify_static_oop(InstanceKlass* ik,
2801                                      oop mirror, int offset) {
2802   address obj_p = (address)mirror + offset;
2803   address start = (address)InstanceMirrorKlass::start_of_static_fields(mirror);
2804   address end = start + (java_lang_Class::static_oop_field_count(mirror) * heapOopSize);
2805   assert(end >= start, "sanity check");
2806 
2807   if (obj_p >= start && obj_p < end) {
2808     return true;
2809   } else {
2810     return false;
2811   }
2812 }
2813 #endif // #ifdef ASSERT
2814 
2815 // a class references its super class, interfaces, class loader, ...
2816 // and finally its static fields
2817 inline bool VM_HeapWalkOperation::iterate_over_class(oop java_class) {
2818   int i;
2819   Klass* klass = java_lang_Class::as_Klass(java_class);
2820 
2821   if (klass->is_instance_klass()) {
2822     InstanceKlass* ik = InstanceKlass::cast(klass);
2823 
2824     // Ignore the class if it hasn't been initialized yet
2825     if (!ik->is_linked()) {
2826       return true;
2827     }
2828 
2829     // get the java mirror
2830     oop mirror = klass->java_mirror();
2831 
2832     // super (only if something more interesting than java.lang.Object)
2833     Klass* java_super = ik->java_super();
2834     if (java_super != NULL && java_super != SystemDictionary::Object_klass()) {
2835       oop super = java_super->java_mirror();
2836       if (!CallbackInvoker::report_superclass_reference(mirror, super)) {
2837         return false;
2838       }
2839     }
2840 
2841     // class loader
2842     oop cl = ik->class_loader();
2843     if (cl != NULL) {
2844       if (!CallbackInvoker::report_class_loader_reference(mirror, cl)) {
2845         return false;
2846       }
2847     }
2848 
2849     // protection domain
2850     oop pd = ik->protection_domain();
2851     if (pd != NULL) {
2852       if (!CallbackInvoker::report_protection_domain_reference(mirror, pd)) {
2853         return false;
2854       }
2855     }
2856 
2857     // signers
2858     oop signers = ik->signers();
2859     if (signers != NULL) {
2860       if (!CallbackInvoker::report_signers_reference(mirror, signers)) {
2861         return false;
2862       }
2863     }
2864 
2865     // references from the constant pool
2866     {
2867       ConstantPool* pool = ik->constants();
2868       for (int i = 1; i < pool->length(); i++) {
2869         constantTag tag = pool->tag_at(i).value();
2870         if (tag.is_string() || tag.is_klass()) {
2871           oop entry;
2872           if (tag.is_string()) {
2873             entry = pool->resolved_string_at(i);
2874             // If the entry is non-null it is resolved.
2875             if (entry == NULL) continue;
2876           } else {
2877             entry = pool->resolved_klass_at(i)->java_mirror();
2878           }
2879           if (!CallbackInvoker::report_constant_pool_reference(mirror, entry, (jint)i)) {
2880             return false;
2881           }
2882         }
2883       }
2884     }
2885 
2886     // interfaces
2887     // (These will already have been reported as references from the constant pool
2888     //  but are specified by IterateOverReachableObjects and must be reported).
2889     Array<Klass*>* interfaces = ik->local_interfaces();
2890     for (i = 0; i < interfaces->length(); i++) {
2891       oop interf = ((Klass*)interfaces->at(i))->java_mirror();
2892       if (interf == NULL) {
2893         continue;
2894       }
2895       if (!CallbackInvoker::report_interface_reference(mirror, interf)) {
2896         return false;
2897       }
2898     }
2899 
2900     // iterate over the static fields
2901 
2902     ClassFieldMap* field_map = ClassFieldMap::create_map_of_static_fields(klass);
2903     for (i=0; i<field_map->field_count(); i++) {
2904       ClassFieldDescriptor* field = field_map->field_at(i);
2905       char type = field->field_type();
2906       if (!is_primitive_field_type(type)) {
2907         oop fld_o = mirror->obj_field(field->field_offset());
2908         assert(verify_static_oop(ik, mirror, field->field_offset()), "sanity check");
2909         if (fld_o != NULL) {
2910           int slot = field->field_index();
2911           if (!CallbackInvoker::report_static_field_reference(mirror, fld_o, slot)) {
2912             delete field_map;
2913             return false;
2914           }
2915         }
2916       } else {
2917          if (is_reporting_primitive_fields()) {
2918            address addr = (address)mirror + field->field_offset();
2919            int slot = field->field_index();
2920            if (!CallbackInvoker::report_primitive_static_field(mirror, slot, addr, type)) {
2921              delete field_map;
2922              return false;
2923           }
2924         }
2925       }
2926     }
2927     delete field_map;
2928 
2929     return true;
2930   }
2931 
2932   return true;
2933 }
2934 
2935 // an object references a class and its instance fields
2936 // (static fields are ignored here as we report these as
2937 // references from the class).
2938 inline bool VM_HeapWalkOperation::iterate_over_object(oop o) {
2939   // reference to the class
2940   if (!CallbackInvoker::report_class_reference(o, o->klass()->java_mirror())) {
2941     return false;
2942   }
2943 
2944   // iterate over instance fields
2945   ClassFieldMap* field_map = JvmtiCachedClassFieldMap::get_map_of_instance_fields(o);
2946   for (int i=0; i<field_map->field_count(); i++) {
2947     ClassFieldDescriptor* field = field_map->field_at(i);
2948     char type = field->field_type();
2949     if (!is_primitive_field_type(type)) {
2950       oop fld_o = o->obj_field(field->field_offset());
2951       // ignore any objects that aren't visible to profiler
2952       if (fld_o != NULL) {
2953         assert(Universe::heap()->is_in_reserved(fld_o), "unsafe code should not "
2954                "have references to Klass* anymore");
2955         int slot = field->field_index();
2956         if (!CallbackInvoker::report_field_reference(o, fld_o, slot)) {
2957           return false;
2958         }
2959       }
2960     } else {
2961       if (is_reporting_primitive_fields()) {
2962         // primitive instance field
2963         address addr = (address)o + field->field_offset();
2964         int slot = field->field_index();
2965         if (!CallbackInvoker::report_primitive_instance_field(o, slot, addr, type)) {
2966           return false;
2967         }
2968       }
2969     }
2970   }
2971 
2972   // if the object is a java.lang.String
2973   if (is_reporting_string_values() &&
2974       o->klass() == SystemDictionary::String_klass()) {
2975     if (!CallbackInvoker::report_string_value(o)) {
2976       return false;
2977     }
2978   }
2979   return true;
2980 }
2981 
2982 
2983 // Collects all simple (non-stack) roots except for threads;
2984 // threads are handled in collect_stack_roots() as an optimization.
2985 // if there's a heap root callback provided then the callback is
2986 // invoked for each simple root.
2987 // if an object reference callback is provided then all simple
2988 // roots are pushed onto the marking stack so that they can be
2989 // processed later
2990 //
2991 inline bool VM_HeapWalkOperation::collect_simple_roots() {
2992   SimpleRootsClosure blk;
2993 
2994   // JNI globals
2995   blk.set_kind(JVMTI_HEAP_REFERENCE_JNI_GLOBAL);
2996   JNIHandles::oops_do(&blk);
2997   if (blk.stopped()) {
2998     return false;
2999   }
3000 
3001   // Preloaded classes and loader from the system dictionary
3002   blk.set_kind(JVMTI_HEAP_REFERENCE_SYSTEM_CLASS);
3003   SystemDictionary::always_strong_oops_do(&blk);
3004   ClassLoaderDataGraph::always_strong_oops_do(&blk, false);
3005   if (blk.stopped()) {
3006     return false;
3007   }
3008 
3009   // Inflated monitors
3010   blk.set_kind(JVMTI_HEAP_REFERENCE_MONITOR);
3011   ObjectSynchronizer::oops_do(&blk);
3012   if (blk.stopped()) {
3013     return false;
3014   }
3015 
3016   // threads are now handled in collect_stack_roots()
3017 
3018   // Other kinds of roots maintained by HotSpot
3019   // Many of these won't be visible but others (such as instances of important
3020   // exceptions) will be visible.
3021   blk.set_kind(JVMTI_HEAP_REFERENCE_OTHER);
3022   Universe::oops_do(&blk);
3023 
3024   // If there are any non-perm roots in the code cache, visit them.
3025   blk.set_kind(JVMTI_HEAP_REFERENCE_OTHER);
3026   CodeBlobToOopClosure look_in_blobs(&blk, !CodeBlobToOopClosure::FixRelocations);
3027   CodeCache::scavenge_root_nmethods_do(&look_in_blobs);
3028 
3029   return true;
3030 }
3031 
3032 // Walk the stack of a given thread and find all references (locals
3033 // and JNI calls) and report these as stack references
3034 inline bool VM_HeapWalkOperation::collect_stack_roots(JavaThread* java_thread,
3035                                                       JNILocalRootsClosure* blk)
3036 {
3037   oop threadObj = java_thread->threadObj();
3038   assert(threadObj != NULL, "sanity check");
3039 
3040   // only need to get the thread's tag once per thread
3041   jlong thread_tag = tag_for(_tag_map, threadObj);
3042 
3043   // also need the thread id
3044   jlong tid = java_lang_Thread::thread_id(threadObj);
3045 
3046 
3047   if (java_thread->has_last_Java_frame()) {
3048 
3049     // vframes are resource allocated
3050     Thread* current_thread = Thread::current();
3051     ResourceMark rm(current_thread);
3052     HandleMark hm(current_thread);
3053 
3054     RegisterMap reg_map(java_thread);
3055     frame f = java_thread->last_frame();
3056     vframe* vf = vframe::new_vframe(&f, &reg_map, java_thread);
3057 
3058     bool is_top_frame = true;
3059     int depth = 0;
3060     frame* last_entry_frame = NULL;
3061 
3062     while (vf != NULL) {
3063       if (vf->is_java_frame()) {
3064 
3065         // java frame (interpreted, compiled, ...)
3066         javaVFrame *jvf = javaVFrame::cast(vf);
3067 
3068         // the jmethodID
3069         jmethodID method = jvf->method()->jmethod_id();
3070 
3071         if (!(jvf->method()->is_native())) {
3072           jlocation bci = (jlocation)jvf->bci();
3073           StackValueCollection* locals = jvf->locals();
3074           for (int slot=0; slot<locals->size(); slot++) {
3075             if (locals->at(slot)->type() == T_OBJECT) {
3076               oop o = locals->obj_at(slot)();
3077               if (o == NULL) {
3078                 continue;
3079               }
3080 
3081               // stack reference
3082               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3083                                                    bci, slot, o)) {
3084                 return false;
3085               }
3086             }
3087           }
3088 
3089           StackValueCollection* exprs = jvf->expressions();
3090           for (int index=0; index < exprs->size(); index++) {
3091             if (exprs->at(index)->type() == T_OBJECT) {
3092               oop o = exprs->obj_at(index)();
3093               if (o == NULL) {
3094                 continue;
3095               }
3096 
3097               // stack reference
3098               if (!CallbackInvoker::report_stack_ref_root(thread_tag, tid, depth, method,
3099                                                    bci, locals->size() + index, o)) {
3100                 return false;
3101               }
3102             }
3103           }
3104 
3105           // Follow oops from compiled nmethod
3106           if (jvf->cb() != NULL && jvf->cb()->is_nmethod()) {
3107             blk->set_context(thread_tag, tid, depth, method);
3108             jvf->cb()->as_nmethod()->oops_do(blk);
3109           }
3110         } else {
3111           blk->set_context(thread_tag, tid, depth, method);
3112           if (is_top_frame) {
3113             // JNI locals for the top frame.
3114             java_thread->active_handles()->oops_do(blk);
3115           } else {
3116             if (last_entry_frame != NULL) {
3117               // JNI locals for the entry frame
3118               assert(last_entry_frame->is_entry_frame(), "checking");
3119               last_entry_frame->entry_frame_call_wrapper()->handles()->oops_do(blk);
3120             }
3121           }
3122         }
3123         last_entry_frame = NULL;
3124         depth++;
3125       } else {
3126         // externalVFrame - for an entry frame then we report the JNI locals
3127         // when we find the corresponding javaVFrame
3128         frame* fr = vf->frame_pointer();
3129         assert(fr != NULL, "sanity check");
3130         if (fr->is_entry_frame()) {
3131           last_entry_frame = fr;
3132         }
3133       }
3134 
3135       vf = vf->sender();
3136       is_top_frame = false;
3137     }
3138   } else {
3139     // no last java frame but there may be JNI locals
3140     blk->set_context(thread_tag, tid, 0, (jmethodID)NULL);
3141     java_thread->active_handles()->oops_do(blk);
3142   }
3143   return true;
3144 }
3145 
3146 
3147 // Collects the simple roots for all threads and collects all
3148 // stack roots - for each thread it walks the execution
3149 // stack to find all references and local JNI refs.
3150 inline bool VM_HeapWalkOperation::collect_stack_roots() {
3151   JNILocalRootsClosure blk;
3152   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
3153     oop threadObj = thread->threadObj();
3154     if (threadObj != NULL && !thread->is_exiting() && !thread->is_hidden_from_external_view()) {
3155       // Collect the simple root for this thread before we
3156       // collect its stack roots
3157       if (!CallbackInvoker::report_simple_root(JVMTI_HEAP_REFERENCE_THREAD,
3158                                                threadObj)) {
3159         return false;
3160       }
3161       if (!collect_stack_roots(thread, &blk)) {
3162         return false;
3163       }
3164     }
3165   }
3166   return true;
3167 }
3168 
3169 // visit an object
3170 // first mark the object as visited
3171 // second get all the outbound references from this object (in other words, all
3172 // the objects referenced by this object).
3173 //
3174 bool VM_HeapWalkOperation::visit(oop o) {
3175   // mark object as visited
3176   assert(!ObjectMarker::visited(o), "can't visit same object more than once");
3177   ObjectMarker::mark(o);
3178 
3179   // instance
3180   if (o->is_instance()) {
3181     if (o->klass() == SystemDictionary::Class_klass()) {
3182       if (!java_lang_Class::is_primitive(o)) {
3183         // a java.lang.Class
3184         return iterate_over_class(o);
3185       }
3186     } else {
3187       return iterate_over_object(o);
3188     }
3189   }
3190 
3191   // object array
3192   if (o->is_objArray()) {
3193     return iterate_over_array(o);
3194   }
3195 
3196   // type array
3197   if (o->is_typeArray()) {
3198     return iterate_over_type_array(o);
3199   }
3200 
3201   return true;
3202 }
3203 
3204 void VM_HeapWalkOperation::doit() {
3205   ResourceMark rm;
3206   ObjectMarkerController marker;
3207   ClassFieldMapCacheMark cm;
3208 
3209   assert(visit_stack()->is_empty(), "visit stack must be empty");
3210 
3211   // the heap walk starts with an initial object or the heap roots
3212   if (initial_object().is_null()) {
3213     // If either collect_stack_roots() or collect_simple_roots()
3214     // returns false at this point, then there are no mark bits
3215     // to reset.
3216     ObjectMarker::set_needs_reset(false);
3217 
3218     // Calling collect_stack_roots() before collect_simple_roots()
3219     // can result in a big performance boost for an agent that is
3220     // focused on analyzing references in the thread stacks.
3221     if (!collect_stack_roots()) return;
3222 
3223     if (!collect_simple_roots()) return;
3224 
3225     // no early return so enable heap traversal to reset the mark bits
3226     ObjectMarker::set_needs_reset(true);
3227   } else {
3228     visit_stack()->push(initial_object()());
3229   }
3230 
3231   // object references required
3232   if (is_following_references()) {
3233 
3234     // visit each object until all reachable objects have been
3235     // visited or the callback asked to terminate the iteration.
3236     while (!visit_stack()->is_empty()) {
3237       oop o = visit_stack()->pop();
3238       if (!ObjectMarker::visited(o)) {
3239         if (!visit(o)) {
3240           break;
3241         }
3242       }
3243     }
3244   }
3245 }
3246 
3247 // iterate over all objects that are reachable from a set of roots
3248 void JvmtiTagMap::iterate_over_reachable_objects(jvmtiHeapRootCallback heap_root_callback,
3249                                                  jvmtiStackReferenceCallback stack_ref_callback,
3250                                                  jvmtiObjectReferenceCallback object_ref_callback,
3251                                                  const void* user_data) {
3252   MutexLocker ml(Heap_lock);
3253   BasicHeapWalkContext context(heap_root_callback, stack_ref_callback, object_ref_callback);
3254   VM_HeapWalkOperation op(this, Handle(), context, user_data);
3255   VMThread::execute(&op);
3256 }
3257 
3258 // iterate over all objects that are reachable from a given object
3259 void JvmtiTagMap::iterate_over_objects_reachable_from_object(jobject object,
3260                                                              jvmtiObjectReferenceCallback object_ref_callback,
3261                                                              const void* user_data) {
3262   oop obj = JNIHandles::resolve(object);
3263   Handle initial_object(Thread::current(), obj);
3264 
3265   MutexLocker ml(Heap_lock);
3266   BasicHeapWalkContext context(NULL, NULL, object_ref_callback);
3267   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3268   VMThread::execute(&op);
3269 }
3270 
3271 // follow references from an initial object or the GC roots
3272 void JvmtiTagMap::follow_references(jint heap_filter,
3273                                     Klass* klass,
3274                                     jobject object,
3275                                     const jvmtiHeapCallbacks* callbacks,
3276                                     const void* user_data)
3277 {
3278   oop obj = JNIHandles::resolve(object);
3279   Handle initial_object(Thread::current(), obj);
3280 
3281   MutexLocker ml(Heap_lock);
3282   AdvancedHeapWalkContext context(heap_filter, klass, callbacks);
3283   VM_HeapWalkOperation op(this, initial_object, context, user_data);
3284   VMThread::execute(&op);
3285 }
3286 
3287 
3288 void JvmtiTagMap::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
3289   // No locks during VM bring-up (0 threads) and no safepoints after main
3290   // thread creation and before VMThread creation (1 thread); initial GC
3291   // verification can happen in that window which gets to here.
3292   assert(Threads::number_of_threads() <= 1 ||
3293          SafepointSynchronize::is_at_safepoint(),
3294          "must be executed at a safepoint");
3295   if (JvmtiEnv::environments_might_exist()) {
3296     JvmtiEnvIterator it;
3297     for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
3298       JvmtiTagMap* tag_map = env->tag_map();
3299       if (tag_map != NULL && !tag_map->is_empty()) {
3300         tag_map->do_weak_oops(is_alive, f);
3301       }
3302     }
3303   }
3304 }
3305 
3306 void JvmtiTagMap::do_weak_oops(BoolObjectClosure* is_alive, OopClosure* f) {
3307 
3308   // does this environment have the OBJECT_FREE event enabled
3309   bool post_object_free = env()->is_enabled(JVMTI_EVENT_OBJECT_FREE);
3310 
3311   // counters used for trace message
3312   int freed = 0;
3313   int moved = 0;
3314 
3315   JvmtiTagHashmap* hashmap = this->hashmap();
3316 
3317   // reenable sizing (if disabled)
3318   hashmap->set_resizing_enabled(true);
3319 
3320   // if the hashmap is empty then we can skip it
3321   if (hashmap->_entry_count == 0) {
3322     return;
3323   }
3324 
3325   // now iterate through each entry in the table
3326 
3327   JvmtiTagHashmapEntry** table = hashmap->table();
3328   int size = hashmap->size();
3329 
3330   JvmtiTagHashmapEntry* delayed_add = NULL;
3331 
3332   for (int pos = 0; pos < size; ++pos) {
3333     JvmtiTagHashmapEntry* entry = table[pos];
3334     JvmtiTagHashmapEntry* prev = NULL;
3335 
3336     while (entry != NULL) {
3337       JvmtiTagHashmapEntry* next = entry->next();
3338 
3339       // has object been GC'ed
3340       if (!is_alive->do_object_b(entry->object_peek())) {
3341         // grab the tag
3342         jlong tag = entry->tag();
3343         guarantee(tag != 0, "checking");
3344 
3345         // remove GC'ed entry from hashmap and return the
3346         // entry to the free list
3347         hashmap->remove(prev, pos, entry);
3348         destroy_entry(entry);
3349 
3350         // post the event to the profiler
3351         if (post_object_free) {
3352           JvmtiExport::post_object_free(env(), tag);
3353         }
3354 
3355         ++freed;
3356       } else {
3357         f->do_oop(entry->object_addr());
3358         oop new_oop = entry->object_peek();
3359 
3360         // if the object has moved then re-hash it and move its
3361         // entry to its new location.
3362         unsigned int new_pos = JvmtiTagHashmap::hash(new_oop, size);
3363         if (new_pos != (unsigned int)pos) {
3364           if (prev == NULL) {
3365             table[pos] = next;
3366           } else {
3367             prev->set_next(next);
3368           }
3369           if (new_pos < (unsigned int)pos) {
3370             entry->set_next(table[new_pos]);
3371             table[new_pos] = entry;
3372           } else {
3373             // Delay adding this entry to it's new position as we'd end up
3374             // hitting it again during this iteration.
3375             entry->set_next(delayed_add);
3376             delayed_add = entry;
3377           }
3378           moved++;
3379         } else {
3380           // object didn't move
3381           prev = entry;
3382         }
3383       }
3384 
3385       entry = next;
3386     }
3387   }
3388 
3389   // Re-add all the entries which were kept aside
3390   while (delayed_add != NULL) {
3391     JvmtiTagHashmapEntry* next = delayed_add->next();
3392     unsigned int pos = JvmtiTagHashmap::hash(delayed_add->object_peek(), size);
3393     delayed_add->set_next(table[pos]);
3394     table[pos] = delayed_add;
3395     delayed_add = next;
3396   }
3397 
3398   log_debug(jvmti, objecttagging)("(%d->%d, %d freed, %d total moves)",
3399                                   hashmap->_entry_count + freed, hashmap->_entry_count, freed, moved);
3400 }