1 /*
   2  * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_PRIMS_JVMTIENVBASE_HPP
  26 #define SHARE_PRIMS_JVMTIENVBASE_HPP
  27 
  28 #include "classfile/classLoader.hpp"
  29 #include "prims/jvmtiEnvThreadState.hpp"
  30 #include "prims/jvmtiEventController.hpp"
  31 #include "prims/jvmtiThreadState.hpp"
  32 #include "oops/oopHandle.hpp"
  33 #include "runtime/fieldDescriptor.hpp"
  34 #include "runtime/frame.hpp"
  35 #include "runtime/orderAccess.hpp"
  36 #include "runtime/thread.hpp"
  37 #include "runtime/vmOperations.hpp"
  38 #include "utilities/growableArray.hpp"
  39 #include "utilities/macros.hpp"
  40 
  41 //
  42 // Forward Declarations
  43 //
  44 
  45 class JvmtiEnv;
  46 class JvmtiThreadState;
  47 class JvmtiRawMonitor; // for jvmtiEnv.hpp
  48 class JvmtiEventControllerPrivate;
  49 class JvmtiTagMap;
  50 
  51 
  52 
  53 // One JvmtiEnv object is created per jvmti attachment;
  54 // done via JNI GetEnv() call. Multiple attachments are
  55 // allowed in jvmti.
  56 
  57 class JvmtiEnvBase : public CHeapObj<mtInternal> {
  58 
  59  private:
  60 
  61 #if INCLUDE_JVMTI
  62   static JvmtiEnvBase*     _head_environment;  // head of environment list
  63 #endif // INCLUDE_JVMTI
  64 
  65   static bool              _globally_initialized;
  66   static jvmtiPhase        _phase;
  67   static volatile int      _dying_thread_env_iteration_count;
  68 
  69  public:
  70 
  71   enum {
  72     JDK15_JVMTI_VERSION = JVMTI_VERSION_1_0 +  33,  /* version: 1.0.33  */
  73     JDK16_JVMTI_VERSION = JVMTI_VERSION_1_1 + 102,  /* version: 1.1.102 */
  74     JDK17_JVMTI_VERSION = JVMTI_VERSION_1_2 +   2   /* version: 1.2.2   */
  75   };
  76 
  77   static jvmtiPhase  get_phase()                    { return _phase; }
  78   static jvmtiPhase  get_phase(jvmtiEnv* env)       { return ((JvmtiEnvBase*)JvmtiEnv_from_jvmti_env(env))->phase(); }
  79   static void  set_phase(jvmtiPhase phase)          { _phase = phase; }
  80   static bool is_vm_live()                          { return _phase == JVMTI_PHASE_LIVE; }
  81 
  82   static void entering_dying_thread_env_iteration() { ++_dying_thread_env_iteration_count; }
  83   static void leaving_dying_thread_env_iteration()  { --_dying_thread_env_iteration_count; }
  84   static bool is_inside_dying_thread_env_iteration(){ return _dying_thread_env_iteration_count > 0; }
  85 
  86  private:
  87 
  88   enum {
  89       JVMTI_MAGIC    = 0x71EE,
  90       DISPOSED_MAGIC = 0xDEFC,
  91       BAD_MAGIC      = 0xDEAD
  92   };
  93 
  94   jvmtiEnv _jvmti_external;
  95   jint _magic;
  96   jint _version;  // version value passed to JNI GetEnv()
  97   JvmtiEnvBase* _next;
  98   bool _is_retransformable;
  99   const void *_env_local_storage;     // per env agent allocated data.
 100   jvmtiEventCallbacks _event_callbacks;
 101   jvmtiExtEventCallbacks _ext_event_callbacks;
 102   JvmtiTagMap* volatile _tag_map;
 103   JvmtiEnvEventEnable _env_event_enable;
 104   jvmtiCapabilities _current_capabilities;
 105   jvmtiCapabilities _prohibited_capabilities;
 106   volatile bool _class_file_load_hook_ever_enabled;
 107   static volatile bool _needs_clean_up;
 108   char** _native_method_prefixes;
 109   int    _native_method_prefix_count;
 110 
 111  protected:
 112   JvmtiEnvBase(jint version);
 113   ~JvmtiEnvBase();
 114   void dispose();
 115   void env_dispose();
 116 
 117   void set_env_local_storage(const void* data)     { _env_local_storage = data; }
 118   const void* get_env_local_storage()              { return _env_local_storage; }
 119 
 120   void record_class_file_load_hook_enabled();
 121   void record_first_time_class_file_load_hook_enabled();
 122 
 123   char** get_native_method_prefixes()              { return _native_method_prefixes; }
 124   int    get_native_method_prefix_count()          { return _native_method_prefix_count; }
 125   jvmtiError set_native_method_prefixes(jint prefix_count, char** prefixes);
 126 
 127  private:
 128   friend class JvmtiEventControllerPrivate;
 129   void initialize();
 130   void set_event_callbacks(const jvmtiEventCallbacks* callbacks, jint size_of_callbacks);
 131   static void globally_initialize();
 132   static void periodic_clean_up();
 133 
 134   friend class JvmtiEnvIterator;
 135   JvmtiEnv* next_environment()                     { return (JvmtiEnv*)_next; }
 136   void set_next_environment(JvmtiEnvBase* env)     { _next = env; }
 137   static JvmtiEnv* head_environment()              {
 138     JVMTI_ONLY(return (JvmtiEnv*)_head_environment);
 139     NOT_JVMTI(return NULL);
 140   }
 141 
 142  public:
 143 
 144   jvmtiPhase  phase();
 145   bool is_valid();
 146 
 147   bool use_version_1_0_semantics();  // agent asked for version 1.0
 148   bool use_version_1_1_semantics();  // agent asked for version 1.1
 149   bool use_version_1_2_semantics();  // agent asked for version 1.2
 150 
 151   bool is_retransformable()                        { return _is_retransformable; }
 152 
 153   static ByteSize jvmti_external_offset() {
 154     return byte_offset_of(JvmtiEnvBase, _jvmti_external);
 155   };
 156 
 157   static JvmtiEnv* JvmtiEnv_from_jvmti_env(jvmtiEnv *env) {
 158     return (JvmtiEnv*)((intptr_t)env - in_bytes(jvmti_external_offset()));
 159   };
 160 
 161   jvmtiCapabilities *get_capabilities()             { return &_current_capabilities; }
 162 
 163   jvmtiCapabilities *get_prohibited_capabilities()  { return &_prohibited_capabilities; }
 164 
 165   bool early_class_hook_env() {
 166     return get_capabilities()->can_generate_early_class_hook_events != 0
 167         && get_capabilities()->can_generate_all_class_hook_events != 0;
 168   }
 169 
 170   bool early_vmstart_env() {
 171     return get_capabilities()->can_generate_early_vmstart != 0;
 172   }
 173 
 174   static char** get_all_native_method_prefixes(int* count_ptr);
 175 
 176   // This test will answer true when all environments have been disposed and some have
 177   // not yet been deallocated.  As a result, this test should only be used as an
 178   // optimization for the no environment case.
 179   static bool environments_might_exist() {
 180     return head_environment() != NULL;
 181   }
 182 
 183   static void check_for_periodic_clean_up();
 184 
 185   JvmtiEnvEventEnable *env_event_enable() {
 186     return &_env_event_enable;
 187   }
 188 
 189   jvmtiError allocate(jlong size, unsigned char** mem_ptr) {
 190     if (size < 0) {
 191       return JVMTI_ERROR_ILLEGAL_ARGUMENT;
 192     }
 193     if (size == 0) {
 194       *mem_ptr = NULL;
 195     } else {
 196       *mem_ptr = (unsigned char *)os::malloc((size_t)size, mtInternal);
 197       if (*mem_ptr == NULL) {
 198         return JVMTI_ERROR_OUT_OF_MEMORY;
 199       }
 200     }
 201     return JVMTI_ERROR_NONE;
 202   }
 203 
 204   jvmtiError deallocate(unsigned char* mem) {
 205     if (mem != NULL) {
 206       os::free(mem);
 207     }
 208     return JVMTI_ERROR_NONE;
 209   }
 210 
 211 
 212   // Memory functions
 213   unsigned char* jvmtiMalloc(jlong size);  // don't use this - call allocate
 214 
 215   // method to create a local handle
 216   jobject jni_reference(Handle hndl);
 217 
 218   // method to create a local handle.
 219   // This function allows caller to specify which
 220   // threads local handle table to use.
 221   jobject jni_reference(JavaThread *thread, Handle hndl);
 222 
 223   // method to destroy a local handle
 224   void destroy_jni_reference(jobject jobj);
 225 
 226   // method to destroy a local handle.
 227   // This function allows caller to specify which
 228   // threads local handle table to use.
 229   void destroy_jni_reference(JavaThread *thread, jobject jobj);
 230 
 231   jvmtiEnv* jvmti_external() { return &_jvmti_external; };
 232 
 233 // Event Dispatch
 234 
 235   bool has_callback(jvmtiEvent event_type) {
 236     assert(event_type >= JVMTI_MIN_EVENT_TYPE_VAL &&
 237            event_type <= JVMTI_MAX_EVENT_TYPE_VAL, "checking");
 238     return ((void**)&_event_callbacks)[event_type-JVMTI_MIN_EVENT_TYPE_VAL] != NULL;
 239   }
 240 
 241   jvmtiEventCallbacks* callbacks() {
 242     return &_event_callbacks;
 243   }
 244 
 245   jvmtiExtEventCallbacks* ext_callbacks() {
 246     return &_ext_event_callbacks;
 247   }
 248 
 249   void set_tag_map(JvmtiTagMap* tag_map) {
 250     _tag_map = tag_map;
 251   }
 252 
 253   JvmtiTagMap* tag_map() {
 254     return _tag_map;
 255   }
 256 
 257   JvmtiTagMap* tag_map_acquire() {
 258     return OrderAccess::load_acquire(&_tag_map);
 259   }
 260 
 261   void release_set_tag_map(JvmtiTagMap* tag_map) {
 262     OrderAccess::release_store(&_tag_map, tag_map);
 263   }
 264 
 265   // return true if event is enabled globally or for any thread
 266   // True only if there is a callback for it.
 267   bool is_enabled(jvmtiEvent event_type) {
 268     return _env_event_enable.is_enabled(event_type);
 269   }
 270 
 271 // Random Utilities
 272 
 273  protected:
 274   // helper methods for creating arrays of global JNI Handles from local Handles
 275   // allocated into environment specific storage
 276   jobject * new_jobjectArray(int length, Handle *handles);
 277   jthread * new_jthreadArray(int length, Handle *handles);
 278   jthreadGroup * new_jthreadGroupArray(int length, Handle *handles);
 279 
 280   // convert to a jni jclass from a non-null Klass*
 281   jclass get_jni_class_non_null(Klass* k);
 282 
 283   jint count_locked_objects(JavaThread *java_thread, Handle hobj);
 284   jvmtiError get_locked_objects_in_frame(JavaThread *calling_thread,
 285                                    JavaThread* java_thread,
 286                                    javaVFrame *jvf,
 287                                    GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list,
 288                                    jint depth);
 289   vframe* vframeFor(JavaThread* java_thread, jint depth);
 290 
 291  public:
 292   // get a field descriptor for the specified class and field
 293   static bool get_field_descriptor(Klass* k, jfieldID field, fieldDescriptor* fd);
 294 
 295   // JVMTI API helper functions which are called at safepoint or thread is suspended.
 296   jvmtiError get_frame_count(JvmtiThreadState *state, jint *count_ptr);
 297   jvmtiError get_frame_location(JavaThread* java_thread, jint depth,
 298                                               jmethodID* method_ptr, jlocation* location_ptr);
 299   jvmtiError get_object_monitor_usage(JavaThread *calling_thread,
 300                                                     jobject object, jvmtiMonitorUsage* info_ptr);
 301   jvmtiError get_stack_trace(JavaThread *java_thread,
 302                                            jint stack_depth, jint max_count,
 303                                            jvmtiFrameInfo* frame_buffer, jint* count_ptr);
 304   jvmtiError get_current_contended_monitor(JavaThread *calling_thread,
 305                                                          JavaThread *java_thread,
 306                                                          jobject *monitor_ptr);
 307   jvmtiError get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
 308                           GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list);
 309   jvmtiError check_top_frame(JavaThread* current_thread, JavaThread* java_thread,
 310                              jvalue value, TosState tos, Handle* ret_ob_h);
 311   jvmtiError force_early_return(JavaThread* java_thread, jvalue value, TosState tos);
 312 };
 313 
 314 // This class is the only safe means of iterating through environments.
 315 // Note that this iteratation includes invalid environments pending
 316 // deallocation -- in fact, some uses depend on this behavior.
 317 
 318 class JvmtiEnvIterator : public StackObj {
 319  private:
 320   bool _entry_was_marked;
 321  public:
 322   JvmtiEnvIterator() {
 323     if (Threads::number_of_threads() == 0) {
 324       _entry_was_marked = false; // we are single-threaded, no need
 325     } else {
 326       Thread::current()->entering_jvmti_env_iteration();
 327       _entry_was_marked = true;
 328     }
 329   }
 330   ~JvmtiEnvIterator() {
 331     if (_entry_was_marked) {
 332       Thread::current()->leaving_jvmti_env_iteration();
 333     }
 334   }
 335   JvmtiEnv* first()                 { return JvmtiEnvBase::head_environment(); }
 336   JvmtiEnv* next(JvmtiEnvBase* env) { return env->next_environment(); }
 337 };
 338 
 339 // VM operation to update for pop top frame.
 340 class VM_UpdateForPopTopFrame : public VM_Operation {
 341 private:
 342   JvmtiThreadState* _state;
 343   jvmtiError _result;
 344 
 345 public:
 346   VM_UpdateForPopTopFrame(JvmtiThreadState* state) {
 347     _state = state;
 348     _result = JVMTI_ERROR_NONE;
 349   }
 350   VMOp_Type type() const { return VMOp_UpdateForPopTopFrame; }
 351   jvmtiError result() { return _result; }
 352   void doit();
 353 };
 354 
 355 // VM operation to set frame pop.
 356 class VM_SetFramePop : public VM_Operation {
 357 private:
 358   JvmtiEnv *_env;
 359   JvmtiThreadState* _state;
 360   jint _depth;
 361   jvmtiError _result;
 362 
 363 public:
 364   VM_SetFramePop(JvmtiEnv *env, JvmtiThreadState* state, jint depth) {
 365     _env = env;
 366     _state = state;
 367     _depth = depth;
 368     _result = JVMTI_ERROR_NONE;
 369   }
 370   // Nested operation must be allowed for the VM_EnterInterpOnlyMode that is
 371   // called from the JvmtiEventControllerPrivate::recompute_thread_enabled.
 372   bool allow_nested_vm_operations() const { return true; }
 373   VMOp_Type type() const { return VMOp_SetFramePop; }
 374   jvmtiError result() { return _result; }
 375   void doit();
 376 };
 377 
 378 
 379 // VM operation to get monitor information with stack depth.
 380 class VM_GetOwnedMonitorInfo : public VM_Operation {
 381 private:
 382   JvmtiEnv *_env;
 383   JavaThread* _calling_thread;
 384   JavaThread *_java_thread;
 385   jvmtiError _result;
 386   GrowableArray<jvmtiMonitorStackDepthInfo*> *_owned_monitors_list;
 387 
 388 public:
 389   VM_GetOwnedMonitorInfo(JvmtiEnv* env, JavaThread* calling_thread,
 390                                    JavaThread* java_thread,
 391                                    GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitor_list) {
 392     _env = env;
 393     _calling_thread = calling_thread;
 394     _java_thread = java_thread;
 395     _owned_monitors_list = owned_monitor_list;
 396     _result = JVMTI_ERROR_NONE;
 397   }
 398   VMOp_Type type() const { return VMOp_GetOwnedMonitorInfo; }
 399   void doit();
 400   jvmtiError result() { return _result; }
 401 };
 402 
 403 
 404 // VM operation to get object monitor usage.
 405 class VM_GetObjectMonitorUsage : public VM_Operation {
 406 private:
 407   JvmtiEnv *_env;
 408   jobject _object;
 409   JavaThread* _calling_thread;
 410   jvmtiMonitorUsage* _info_ptr;
 411   jvmtiError _result;
 412 
 413 public:
 414   VM_GetObjectMonitorUsage(JvmtiEnv *env, JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
 415     _env = env;
 416     _object = object;
 417     _calling_thread = calling_thread;
 418     _info_ptr = info_ptr;
 419   }
 420   VMOp_Type type() const { return VMOp_GetObjectMonitorUsage; }
 421   jvmtiError result() { return _result; }
 422   void doit() {
 423     _result = ((JvmtiEnvBase*) _env)->get_object_monitor_usage(_calling_thread, _object, _info_ptr);
 424   }
 425 
 426 };
 427 
 428 // VM operation to get current contended monitor.
 429 class VM_GetCurrentContendedMonitor : public VM_Operation {
 430 private:
 431   JvmtiEnv *_env;
 432   JavaThread *_calling_thread;
 433   JavaThread *_java_thread;
 434   jobject *_owned_monitor_ptr;
 435   jvmtiError _result;
 436 
 437 public:
 438   VM_GetCurrentContendedMonitor(JvmtiEnv *env, JavaThread *calling_thread, JavaThread *java_thread, jobject *mon_ptr) {
 439     _env = env;
 440     _calling_thread = calling_thread;
 441     _java_thread = java_thread;
 442     _owned_monitor_ptr = mon_ptr;
 443   }
 444   VMOp_Type type() const { return VMOp_GetCurrentContendedMonitor; }
 445   jvmtiError result() { return _result; }
 446   void doit();
 447 };
 448 
 449 // VM operation to get stack trace at safepoint.
 450 class VM_GetStackTrace : public VM_Operation {
 451 private:
 452   JvmtiEnv *_env;
 453   JavaThread *_java_thread;
 454   jint _start_depth;
 455   jint _max_count;
 456   jvmtiFrameInfo *_frame_buffer;
 457   jint *_count_ptr;
 458   jvmtiError _result;
 459 
 460 public:
 461   VM_GetStackTrace(JvmtiEnv *env, JavaThread *java_thread,
 462                    jint start_depth, jint max_count,
 463                    jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
 464     _env = env;
 465     _java_thread = java_thread;
 466     _start_depth = start_depth;
 467     _max_count = max_count;
 468     _frame_buffer = frame_buffer;
 469     _count_ptr = count_ptr;
 470   }
 471   jvmtiError result() { return _result; }
 472   VMOp_Type type() const { return VMOp_GetStackTrace; }
 473   void doit();
 474 };
 475 
 476 // forward declaration
 477 struct StackInfoNode;
 478 
 479 // VM operation to get stack trace at safepoint.
 480 class VM_GetMultipleStackTraces : public VM_Operation {
 481 private:
 482   JvmtiEnv *_env;
 483   jint _max_frame_count;
 484   jvmtiStackInfo *_stack_info;
 485   jvmtiError _result;
 486   int _frame_count_total;
 487   struct StackInfoNode *_head;
 488 
 489   JvmtiEnvBase *env()                 { return (JvmtiEnvBase *)_env; }
 490   jint max_frame_count()              { return _max_frame_count; }
 491   struct StackInfoNode *head()        { return _head; }
 492   void set_head(StackInfoNode *head)  { _head = head; }
 493 
 494 protected:
 495   void set_result(jvmtiError result)  { _result = result; }
 496   void fill_frames(jthread jt, JavaThread *thr, oop thread_oop);
 497   void allocate_and_fill_stacks(jint thread_count);
 498 
 499 public:
 500   VM_GetMultipleStackTraces(JvmtiEnv *env, jint max_frame_count) {
 501     _env = env;
 502     _max_frame_count = max_frame_count;
 503     _frame_count_total = 0;
 504     _head = NULL;
 505     _result = JVMTI_ERROR_NONE;
 506   }
 507   VMOp_Type type() const             { return VMOp_GetMultipleStackTraces; }
 508   jvmtiStackInfo *stack_info()       { return _stack_info; }
 509   jvmtiError result()                { return _result; }
 510 };
 511 
 512 
 513 // VM operation to get stack trace at safepoint.
 514 class VM_GetAllStackTraces : public VM_GetMultipleStackTraces {
 515 private:
 516   JavaThread *_calling_thread;
 517   jint _final_thread_count;
 518 
 519 public:
 520   VM_GetAllStackTraces(JvmtiEnv *env, JavaThread *calling_thread,
 521                        jint max_frame_count)
 522       : VM_GetMultipleStackTraces(env, max_frame_count) {
 523     _calling_thread = calling_thread;
 524   }
 525   VMOp_Type type() const          { return VMOp_GetAllStackTraces; }
 526   void doit();
 527   jint final_thread_count()       { return _final_thread_count; }
 528 };
 529 
 530 // VM operation to get stack trace at safepoint.
 531 class VM_GetThreadListStackTraces : public VM_GetMultipleStackTraces {
 532 private:
 533   jint _thread_count;
 534   const jthread* _thread_list;
 535 
 536 public:
 537   VM_GetThreadListStackTraces(JvmtiEnv *env, jint thread_count, const jthread* thread_list, jint max_frame_count)
 538       : VM_GetMultipleStackTraces(env, max_frame_count) {
 539     _thread_count = thread_count;
 540     _thread_list = thread_list;
 541   }
 542   VMOp_Type type() const { return VMOp_GetThreadListStackTraces; }
 543   void doit();
 544 };
 545 
 546 
 547 // VM operation to count stack frames at safepoint.
 548 class VM_GetFrameCount : public VM_Operation {
 549 private:
 550   JvmtiEnv *_env;
 551   JvmtiThreadState *_state;
 552   jint *_count_ptr;
 553   jvmtiError _result;
 554 
 555 public:
 556   VM_GetFrameCount(JvmtiEnv *env, JvmtiThreadState *state, jint *count_ptr) {
 557     _env = env;
 558     _state = state;
 559     _count_ptr = count_ptr;
 560   }
 561   VMOp_Type type() const { return VMOp_GetFrameCount; }
 562   jvmtiError result()    { return _result; }
 563   void doit();
 564 };
 565 
 566 // VM operation to frame location at safepoint.
 567 class VM_GetFrameLocation : public VM_Operation {
 568 private:
 569   JvmtiEnv *_env;
 570   JavaThread* _java_thread;
 571   jint _depth;
 572   jmethodID* _method_ptr;
 573   jlocation* _location_ptr;
 574   jvmtiError _result;
 575 
 576 public:
 577   VM_GetFrameLocation(JvmtiEnv *env, JavaThread* java_thread, jint depth,
 578                       jmethodID* method_ptr, jlocation* location_ptr) {
 579     _env = env;
 580     _java_thread = java_thread;
 581     _depth = depth;
 582     _method_ptr = method_ptr;
 583     _location_ptr = location_ptr;
 584   }
 585   VMOp_Type type() const { return VMOp_GetFrameLocation; }
 586   jvmtiError result()    { return _result; }
 587   void doit();
 588 };
 589 
 590 
 591 // ResourceTracker
 592 //
 593 // ResourceTracker works a little like a ResourceMark. All allocates
 594 // using the resource tracker are recorded. If an allocate using the
 595 // resource tracker fails the destructor will free any resources
 596 // that were allocated using the tracker.
 597 // The motive for this class is to avoid messy error recovery code
 598 // in situations where multiple allocations are done in sequence. If
 599 // the second or subsequent allocation fails it avoids any code to
 600 // release memory allocated in the previous calls.
 601 //
 602 // Usage :-
 603 //   ResourceTracker rt(env);
 604 //   :
 605 //   err = rt.allocate(1024, &ptr);
 606 
 607 class ResourceTracker : public StackObj {
 608  private:
 609   JvmtiEnv* _env;
 610   GrowableArray<unsigned char*> *_allocations;
 611   bool _failed;
 612  public:
 613   ResourceTracker(JvmtiEnv* env);
 614   ~ResourceTracker();
 615   jvmtiError allocate(jlong size, unsigned char** mem_ptr);
 616   unsigned char* allocate(jlong size);
 617   char* strdup(const char* str);
 618 };
 619 
 620 
 621 // Jvmti monitor closure to collect off stack monitors.
 622 class JvmtiMonitorClosure: public MonitorClosure {
 623  private:
 624   JavaThread *_java_thread;
 625   JavaThread *_calling_thread;
 626   GrowableArray<jvmtiMonitorStackDepthInfo*> *_owned_monitors_list;
 627   jvmtiError _error;
 628   JvmtiEnvBase *_env;
 629 
 630  public:
 631   JvmtiMonitorClosure(JavaThread* thread, JavaThread *calling_thread,
 632                       GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors,
 633                       JvmtiEnvBase *env) {
 634     _java_thread = thread;
 635     _calling_thread = calling_thread;
 636     _owned_monitors_list = owned_monitors;
 637     _error = JVMTI_ERROR_NONE;
 638     _env = env;
 639   }
 640   void do_monitor(ObjectMonitor* mon);
 641   jvmtiError error() { return _error;}
 642 };
 643 
 644 
 645 // Jvmti module closure to collect all modules loaded to the system.
 646 class JvmtiModuleClosure : public StackObj {
 647 private:
 648   static GrowableArray<OopHandle> *_tbl; // Protected with Module_lock
 649 
 650   static void do_module(ModuleEntry* entry);
 651 public:
 652   jvmtiError get_all_modules(JvmtiEnv* env, jint* module_count_ptr, jobject** modules_ptr);
 653 };
 654 
 655 #endif // SHARE_PRIMS_JVMTIENVBASE_HPP