1 /*
   2  * Copyright (c) 1998, 2013, 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_VM_PRIMS_JVMTIEXPORT_HPP
  26 #define SHARE_VM_PRIMS_JVMTIEXPORT_HPP
  27 
  28 #include "jvmtifiles/jvmti.h"
  29 #include "memory/allocation.hpp"
  30 #include "memory/iterator.hpp"
  31 #include "oops/oop.hpp"
  32 #include "oops/oopsHierarchy.hpp"
  33 #include "runtime/frame.hpp"
  34 #include "runtime/handles.hpp"
  35 #include "utilities/globalDefinitions.hpp"
  36 #include "utilities/growableArray.hpp"
  37 #include "utilities/macros.hpp"
  38 
  39 // Must be included after jvmti.h.
  40 #include "code/jvmticmlr.h"
  41 
  42 // Forward declarations
  43 
  44 class JvmtiEventControllerPrivate;
  45 class JvmtiManageCapabilities;
  46 class JvmtiEnv;
  47 class JvmtiThreadState;
  48 class AttachOperation;
  49 
  50 #define JVMTI_SUPPORT_FLAG(key)                                           \
  51   private:                                                                \
  52   static bool  _##key;                                                    \
  53   public:                                                                 \
  54   inline static void set_##key(bool on) {                                 \
  55     JVMTI_ONLY(_##key = (on != 0));                                       \
  56     NOT_JVMTI(report_unsupported(on));                                    \
  57   }                                                                       \
  58   inline static bool key() {                                              \
  59     JVMTI_ONLY(return _##key);                                            \
  60     NOT_JVMTI(return false);                                              \
  61   }
  62 
  63 
  64 // This class contains the JVMTI interface for the rest of hotspot.
  65 //
  66 class JvmtiExport : public AllStatic {
  67   friend class VMStructs;
  68   friend class CompileReplay;
  69 
  70  private:
  71 
  72 #if INCLUDE_JVMTI
  73   static int         _field_access_count;
  74   static int         _field_modification_count;
  75 
  76   static bool        _can_access_local_variables;
  77   static bool        _can_hotswap_or_post_breakpoint;
  78   static bool        _can_modify_any_class;
  79   static bool        _can_walk_any_space;
  80 #endif // INCLUDE_JVMTI
  81 
  82   JVMTI_SUPPORT_FLAG(can_get_source_debug_extension)
  83   JVMTI_SUPPORT_FLAG(can_maintain_original_method_order)
  84   JVMTI_SUPPORT_FLAG(can_post_interpreter_events)
  85   JVMTI_SUPPORT_FLAG(can_post_on_exceptions)
  86   JVMTI_SUPPORT_FLAG(can_post_breakpoint)
  87   JVMTI_SUPPORT_FLAG(can_post_field_access)
  88   JVMTI_SUPPORT_FLAG(can_post_field_modification)
  89   JVMTI_SUPPORT_FLAG(can_post_method_entry)
  90   JVMTI_SUPPORT_FLAG(can_post_method_exit)
  91   JVMTI_SUPPORT_FLAG(can_pop_frame)
  92   JVMTI_SUPPORT_FLAG(can_force_early_return)
  93 
  94   friend class JvmtiEventControllerPrivate;  // should only modify these flags
  95   JVMTI_SUPPORT_FLAG(should_post_single_step)
  96   JVMTI_SUPPORT_FLAG(should_post_field_access)
  97   JVMTI_SUPPORT_FLAG(should_post_field_modification)
  98   JVMTI_SUPPORT_FLAG(should_post_class_load)
  99   JVMTI_SUPPORT_FLAG(should_post_class_prepare)
 100   JVMTI_SUPPORT_FLAG(should_post_class_unload)
 101   JVMTI_SUPPORT_FLAG(should_post_native_method_bind)
 102   JVMTI_SUPPORT_FLAG(should_post_compiled_method_load)
 103   JVMTI_SUPPORT_FLAG(should_post_compiled_method_unload)
 104   JVMTI_SUPPORT_FLAG(should_post_dynamic_code_generated)
 105   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_enter)
 106   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_entered)
 107   JVMTI_SUPPORT_FLAG(should_post_monitor_wait)
 108   JVMTI_SUPPORT_FLAG(should_post_monitor_waited)
 109   JVMTI_SUPPORT_FLAG(should_post_data_dump)
 110   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_start)
 111   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_finish)
 112   JVMTI_SUPPORT_FLAG(should_post_on_exceptions)
 113 
 114   // ------ the below maybe don't have to be (but are for now)
 115   // fixed conditions here ------------
 116   // any events can be enabled
 117   JVMTI_SUPPORT_FLAG(should_post_thread_life)
 118   JVMTI_SUPPORT_FLAG(should_post_object_free)
 119   JVMTI_SUPPORT_FLAG(should_post_resource_exhausted)
 120 
 121   // we are holding objects on the heap - need to talk to GC - e.g.
 122   // breakpoint info
 123   JVMTI_SUPPORT_FLAG(should_clean_up_heap_objects)
 124   JVMTI_SUPPORT_FLAG(should_post_vm_object_alloc)
 125 
 126   // If flag cannot be implemented, give an error if on=true
 127   static void report_unsupported(bool on);
 128 
 129   // these should only be called by the friend class
 130   friend class JvmtiManageCapabilities;
 131   inline static void set_can_modify_any_class(bool on) {
 132     JVMTI_ONLY(_can_modify_any_class = (on != 0);)
 133   }
 134   inline static void set_can_access_local_variables(bool on) {
 135     JVMTI_ONLY(_can_access_local_variables = (on != 0);)
 136   }
 137   inline static void set_can_hotswap_or_post_breakpoint(bool on) {
 138     JVMTI_ONLY(_can_hotswap_or_post_breakpoint = (on != 0);)
 139   }
 140   inline static void set_can_walk_any_space(bool on) {
 141     JVMTI_ONLY(_can_walk_any_space = (on != 0);)
 142   }
 143 
 144   enum {
 145     JVMTI_VERSION_MASK   = 0x70000000,
 146     JVMTI_VERSION_VALUE  = 0x30000000,
 147     JVMDI_VERSION_VALUE  = 0x20000000
 148   };
 149 
 150   static void post_field_modification(JavaThread *thread, Method* method, address location,
 151                                       KlassHandle field_klass, Handle object, jfieldID field,
 152                                       char sig_type, jvalue *value);
 153 
 154 
 155   // posts a DynamicCodeGenerated event (internal/private implementation).
 156   // The public post_dynamic_code_generated* functions make use of the
 157   // internal implementation.  Also called from JvmtiDeferredEvent::post()
 158   static void post_dynamic_code_generated_internal(const char *name, const void *code_begin, const void *code_end) NOT_JVMTI_RETURN;
 159 
 160  private:
 161 
 162   // GenerateEvents support to allow posting of CompiledMethodLoad and
 163   // DynamicCodeGenerated events for a given environment.
 164   friend class JvmtiCodeBlobEvents;
 165 
 166   static void post_compiled_method_load(JvmtiEnv* env, const jmethodID method, const jint length,
 167                                         const void *code_begin, const jint map_length,
 168                                         const jvmtiAddrLocationMap* map) NOT_JVMTI_RETURN;
 169   static void post_dynamic_code_generated(JvmtiEnv* env, const char *name, const void *code_begin,
 170                                           const void *code_end) NOT_JVMTI_RETURN;
 171 
 172   // The RedefineClasses() API breaks some invariants in the "regular"
 173   // system. For example, there are sanity checks when GC'ing nmethods
 174   // that require the containing class to be unloading. However, when a
 175   // method is redefined, the old method and nmethod can become GC'able
 176   // without the containing class unloading. The state of becoming
 177   // GC'able can be asynchronous to the RedefineClasses() call since
 178   // the old method may still be running and cannot be GC'ed until
 179   // after all old invocations have finished. Additionally, a method
 180   // that has not been redefined may have an nmethod that depends on
 181   // the redefined method. The dependent nmethod will get deopted in
 182   // this case and may also be GC'able without the containing class
 183   // being unloaded.
 184   //
 185   // This flag indicates whether RedefineClasses() has ever redefined
 186   // one or more classes during the lifetime of the VM. The flag should
 187   // only be set by the friend class and can be queried by other sub
 188   // systems as needed to relax invariant checks.
 189   static bool _has_redefined_a_class;
 190   friend class VM_RedefineClasses;
 191   inline static void set_has_redefined_a_class() {
 192     JVMTI_ONLY(_has_redefined_a_class = true;)
 193   }
 194   // Flag to indicate if the compiler has recorded all dependencies. When the
 195   // can_redefine_classes capability is enabled in the OnLoad phase then the compiler
 196   // records all dependencies from startup. However if the capability is first
 197   // enabled some time later then the dependencies recorded by the compiler
 198   // are incomplete. This flag is used by RedefineClasses to know if the
 199   // dependency information is complete or not.
 200   static bool _all_dependencies_are_recorded;
 201 
 202  public:
 203   inline static bool has_redefined_a_class() {
 204     JVMTI_ONLY(return _has_redefined_a_class);
 205     NOT_JVMTI(return false);
 206   }
 207 
 208   inline static bool all_dependencies_are_recorded() {
 209     return _all_dependencies_are_recorded;
 210   }
 211 
 212   inline static void set_all_dependencies_are_recorded(bool on) {
 213     _all_dependencies_are_recorded = (on != 0);
 214   }
 215 
 216 
 217   // let JVMTI know that the JVM_OnLoad code is running
 218   static void enter_onload_phase() NOT_JVMTI_RETURN;
 219 
 220   // let JVMTI know that the VM isn't up yet (and JVM_OnLoad code isn't running)
 221   static void enter_primordial_phase() NOT_JVMTI_RETURN;
 222 
 223   // let JVMTI know that the VM isn't up yet but JNI is live
 224   static void enter_start_phase() NOT_JVMTI_RETURN;
 225 
 226   // let JVMTI know that the VM is fully up and running now
 227   static void enter_live_phase() NOT_JVMTI_RETURN;
 228 
 229   // ------ can_* conditions (below) are set at OnLoad and never changed ------------
 230   inline static bool can_modify_any_class()                       {
 231     JVMTI_ONLY(return _can_modify_any_class);
 232     NOT_JVMTI(return false);
 233   }
 234   inline static bool can_access_local_variables()                 {
 235     JVMTI_ONLY(return _can_access_local_variables);
 236     NOT_JVMTI(return false);
 237   }
 238   inline static bool can_hotswap_or_post_breakpoint()             {
 239     JVMTI_ONLY(return _can_hotswap_or_post_breakpoint);
 240     NOT_JVMTI(return false);
 241   }
 242   inline static bool can_walk_any_space()                         {
 243     JVMTI_ONLY(return _can_walk_any_space);
 244     NOT_JVMTI(return false);
 245   }
 246 
 247   // field access management
 248   static address  get_field_access_count_addr() NOT_JVMTI_RETURN_(0);
 249 
 250   // field modification management
 251   static address  get_field_modification_count_addr() NOT_JVMTI_RETURN_(0);
 252 
 253   // -----------------
 254 
 255   static bool is_jvmti_version(jint version)                      {
 256     JVMTI_ONLY(return (version & JVMTI_VERSION_MASK) == JVMTI_VERSION_VALUE);
 257     NOT_JVMTI(return false);
 258   }
 259   static bool is_jvmdi_version(jint version)                      {
 260     JVMTI_ONLY(return (version & JVMTI_VERSION_MASK) == JVMDI_VERSION_VALUE);
 261     NOT_JVMTI(return false);
 262   }
 263   static jint get_jvmti_interface(JavaVM *jvm, void **penv, jint version) NOT_JVMTI_RETURN_(0);
 264   static void decode_version_values(jint version, int * major, int * minor,
 265                                     int * micro) NOT_JVMTI_RETURN;
 266 
 267   // single stepping management methods
 268   static void at_single_stepping_point(JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
 269   static void expose_single_stepping(JavaThread *thread) NOT_JVMTI_RETURN;
 270   static bool hide_single_stepping(JavaThread *thread) NOT_JVMTI_RETURN_(false);
 271 
 272   // Methods that notify the debugger that something interesting has happened in the VM.
 273   static void post_vm_start              () NOT_JVMTI_RETURN;
 274   static void post_vm_initialized        () NOT_JVMTI_RETURN;
 275   static void post_vm_death              () NOT_JVMTI_RETURN;
 276 
 277   static void post_single_step           (JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
 278   static void post_raw_breakpoint        (JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
 279 
 280   static void post_exception_throw       (JavaThread *thread, Method* method, address location, oop exception) NOT_JVMTI_RETURN;
 281   static void notice_unwind_due_to_exception (JavaThread *thread, Method* method, address location, oop exception, bool in_handler_frame) NOT_JVMTI_RETURN;
 282 
 283   static oop jni_GetField_probe          (JavaThread *thread, jobject jobj,
 284     oop obj, Klass* klass, jfieldID fieldID, bool is_static)
 285     NOT_JVMTI_RETURN_(NULL);
 286   static oop jni_GetField_probe_nh       (JavaThread *thread, jobject jobj,
 287     oop obj, Klass* klass, jfieldID fieldID, bool is_static)
 288     NOT_JVMTI_RETURN_(NULL);
 289   static void post_field_access_by_jni   (JavaThread *thread, oop obj,
 290     Klass* klass, jfieldID fieldID, bool is_static) NOT_JVMTI_RETURN;
 291   static void post_field_access          (JavaThread *thread, Method* method,
 292     address location, KlassHandle field_klass, Handle object, jfieldID field) NOT_JVMTI_RETURN;
 293   static oop jni_SetField_probe          (JavaThread *thread, jobject jobj,
 294     oop obj, Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
 295     jvalue *value) NOT_JVMTI_RETURN_(NULL);
 296   static oop jni_SetField_probe_nh       (JavaThread *thread, jobject jobj,
 297     oop obj, Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
 298     jvalue *value) NOT_JVMTI_RETURN_(NULL);
 299   static void post_field_modification_by_jni(JavaThread *thread, oop obj,
 300     Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
 301     jvalue *value);
 302   static void post_raw_field_modification(JavaThread *thread, Method* method,
 303     address location, KlassHandle field_klass, Handle object, jfieldID field,
 304     char sig_type, jvalue *value) NOT_JVMTI_RETURN;
 305 
 306   static void post_method_entry          (JavaThread *thread, Method* method, frame current_frame) NOT_JVMTI_RETURN;
 307   static void post_method_exit           (JavaThread *thread, Method* method, frame current_frame) NOT_JVMTI_RETURN;
 308 
 309   static void post_class_load            (JavaThread *thread, Klass* klass) NOT_JVMTI_RETURN;
 310   static void post_class_unload          (Klass* klass) NOT_JVMTI_RETURN;
 311   static void post_class_prepare         (JavaThread *thread, Klass* klass) NOT_JVMTI_RETURN;
 312 
 313   static void post_thread_start          (JavaThread *thread) NOT_JVMTI_RETURN;
 314   static void post_thread_end            (JavaThread *thread) NOT_JVMTI_RETURN;
 315 
 316   // Support for java.lang.instrument agent loading.
 317   static bool _should_post_class_file_load_hook;
 318   inline static void set_should_post_class_file_load_hook(bool on)     { _should_post_class_file_load_hook = on;  }
 319   inline static bool should_post_class_file_load_hook()           {
 320     JVMTI_ONLY(return _should_post_class_file_load_hook);
 321     NOT_JVMTI(return false;)
 322   }
 323   static void post_class_file_load_hook(Symbol* h_name, Handle class_loader,
 324                                         Handle h_protection_domain,
 325                                         unsigned char **data_ptr, unsigned char **end_ptr,
 326                                         JvmtiCachedClassFileData **cache_ptr) NOT_JVMTI_RETURN;
 327   static void post_native_method_bind(Method* method, address* function_ptr) NOT_JVMTI_RETURN;
 328   static void post_compiled_method_load(nmethod *nm) NOT_JVMTI_RETURN;
 329   static void post_dynamic_code_generated(const char *name, const void *code_begin, const void *code_end) NOT_JVMTI_RETURN;
 330 
 331   // used to post a CompiledMethodUnload event
 332   static void post_compiled_method_unload(jmethodID mid, const void *code_begin) NOT_JVMTI_RETURN;
 333 
 334   // similiar to post_dynamic_code_generated except that it can be used to
 335   // post a DynamicCodeGenerated event while holding locks in the VM. Any event
 336   // posted using this function is recorded by the enclosing event collector
 337   // -- JvmtiDynamicCodeEventCollector.
 338   static void post_dynamic_code_generated_while_holding_locks(const char* name, address code_begin, address code_end) NOT_JVMTI_RETURN;
 339 
 340   static void post_garbage_collection_finish() NOT_JVMTI_RETURN;
 341   static void post_garbage_collection_start() NOT_JVMTI_RETURN;
 342   static void post_data_dump() NOT_JVMTI_RETURN;
 343   static void post_monitor_contended_enter(JavaThread *thread, ObjectMonitor *obj_mntr) NOT_JVMTI_RETURN;
 344   static void post_monitor_contended_entered(JavaThread *thread, ObjectMonitor *obj_mntr) NOT_JVMTI_RETURN;
 345   static void post_monitor_wait(JavaThread *thread, oop obj, jlong timeout) NOT_JVMTI_RETURN;
 346   static void post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mntr, jboolean timed_out) NOT_JVMTI_RETURN;
 347   static void post_object_free(JvmtiEnv* env, jlong tag) NOT_JVMTI_RETURN;
 348   static void post_resource_exhausted(jint resource_exhausted_flags, const char* detail) NOT_JVMTI_RETURN;
 349   static void record_vm_internal_object_allocation(oop object) NOT_JVMTI_RETURN;
 350   // Post objects collected by vm_object_alloc_event_collector.
 351   static void post_vm_object_alloc(JavaThread *thread, oop object) NOT_JVMTI_RETURN;
 352   // Collects vm internal objects for later event posting.
 353   inline static void vm_object_alloc_event_collector(oop object) {
 354     if (should_post_vm_object_alloc()) {
 355       record_vm_internal_object_allocation(object);
 356     }
 357   }
 358   inline static void post_array_size_exhausted() {
 359     if (should_post_resource_exhausted()) {
 360       post_resource_exhausted(JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR,
 361                               "Requested array size exceeds VM limit");
 362     }
 363   }
 364 
 365   static void cleanup_thread             (JavaThread* thread) NOT_JVMTI_RETURN;
 366   static void clear_detected_exception   (JavaThread* thread) NOT_JVMTI_RETURN;
 367 
 368   static void oops_do(OopClosure* f) NOT_JVMTI_RETURN;
 369   static void weak_oops_do(BoolObjectClosure* b, OopClosure* f) NOT_JVMTI_RETURN;
 370   static void gc_epilogue() NOT_JVMTI_RETURN;
 371 
 372   static void transition_pending_onload_raw_monitors() NOT_JVMTI_RETURN;
 373 
 374   // attach support
 375   static jint load_agent_library(const char *agent, const char *absParam, const char *options, outputStream* out) NOT_JVMTI_RETURN_(JNI_ERR);
 376   static jint load_agent_library(AttachOperation* op, outputStream* out) NOT_JVMTI_RETURN_(JNI_ERR);
 377 
 378   // SetNativeMethodPrefix support
 379   static char** get_all_native_method_prefixes(int* count_ptr) NOT_JVMTI_RETURN_(NULL);
 380 };
 381 
 382 // Support class used by JvmtiDynamicCodeEventCollector and others. It
 383 // describes a single code blob by name and address range.
 384 class JvmtiCodeBlobDesc : public CHeapObj<mtInternal> {
 385  private:
 386   char _name[64];
 387   address _code_begin;
 388   address _code_end;
 389 
 390  public:
 391   JvmtiCodeBlobDesc(const char *name, address code_begin, address code_end) {
 392     assert(name != NULL, "all code blobs must be named");
 393     strncpy(_name, name, sizeof(_name));
 394     _name[sizeof(_name)-1] = '\0';
 395     _code_begin = code_begin;
 396     _code_end = code_end;
 397   }
 398   char* name()                  { return _name; }
 399   address code_begin()          { return _code_begin; }
 400   address code_end()            { return _code_end; }
 401 };
 402 
 403 // JvmtiEventCollector is a helper class to setup thread for
 404 // event collection.
 405 class JvmtiEventCollector : public StackObj {
 406  private:
 407   JvmtiEventCollector* _prev;  // Save previous one to support nested event collector.
 408 
 409  public:
 410   void setup_jvmti_thread_state(); // Set this collector in current thread.
 411   void unset_jvmti_thread_state(); // Reset previous collector in current thread.
 412   virtual bool is_dynamic_code_event()   { return false; }
 413   virtual bool is_vm_object_alloc_event(){ return false; }
 414   JvmtiEventCollector *get_prev()        { return _prev; }
 415 };
 416 
 417 // A JvmtiDynamicCodeEventCollector is a helper class for the JvmtiExport
 418 // interface. It collects "dynamic code generated" events that are posted
 419 // while holding locks. When the event collector goes out of scope the
 420 // events will be posted.
 421 //
 422 // Usage :-
 423 //
 424 // {
 425 //   JvmtiDynamicCodeEventCollector event_collector;
 426 //   :
 427 //   { MutexLocker ml(...)
 428 //     :
 429 //     JvmtiExport::post_dynamic_code_generated_while_holding_locks(...)
 430 //   }
 431 //   // event collector goes out of scope => post events to profiler.
 432 // }
 433 
 434 class JvmtiDynamicCodeEventCollector : public JvmtiEventCollector {
 435  private:
 436   GrowableArray<JvmtiCodeBlobDesc*>* _code_blobs;           // collected code blob events
 437 
 438   friend class JvmtiExport;
 439   void register_stub(const char* name, address start, address end);
 440 
 441  public:
 442   JvmtiDynamicCodeEventCollector()  NOT_JVMTI_RETURN;
 443   ~JvmtiDynamicCodeEventCollector() NOT_JVMTI_RETURN;
 444   bool is_dynamic_code_event()   { return true; }
 445 
 446 };
 447 
 448 // Used to record vm internally allocated object oops and post
 449 // vm object alloc event for objects visible to java world.
 450 // Constructor enables JvmtiThreadState flag and all vm allocated
 451 // objects are recorded in a growable array. When destructor is
 452 // called the vm object alloc event is posted for each objects
 453 // visible to java world.
 454 // See jvm.cpp file for its usage.
 455 //
 456 class JvmtiVMObjectAllocEventCollector : public JvmtiEventCollector {
 457  private:
 458   GrowableArray<oop>* _allocated; // field to record vm internally allocated object oop.
 459   bool _enable;                   // This flag is enabled in constructor and disabled
 460                                   // in destructor before posting event. To avoid
 461                                   // collection of objects allocated while running java code inside
 462                                   // agent post_vm_object_alloc() event handler.
 463 
 464   //GC support
 465   void oops_do(OopClosure* f);
 466 
 467   friend class JvmtiExport;
 468   // Record vm allocated object oop.
 469   inline void record_allocation(oop obj);
 470 
 471   //GC support
 472   static void oops_do_for_all_threads(OopClosure* f);
 473 
 474  public:
 475   JvmtiVMObjectAllocEventCollector()  NOT_JVMTI_RETURN;
 476   ~JvmtiVMObjectAllocEventCollector() NOT_JVMTI_RETURN;
 477   bool is_vm_object_alloc_event()   { return true; }
 478 
 479   bool is_enabled()                 { return _enable; }
 480   void set_enabled(bool on)         { _enable = on; }
 481 };
 482 
 483 
 484 
 485 // Marker class to disable the posting of VMObjectAlloc events
 486 // within its scope.
 487 //
 488 // Usage :-
 489 //
 490 // {
 491 //   NoJvmtiVMObjectAllocMark njm;
 492 //   :
 493 //   // VMObjAlloc event will not be posted
 494 //   JvmtiExport::vm_object_alloc_event_collector(obj);
 495 //   :
 496 // }
 497 
 498 class NoJvmtiVMObjectAllocMark : public StackObj {
 499  private:
 500   // enclosing collector if enabled, NULL otherwise
 501   JvmtiVMObjectAllocEventCollector *_collector;
 502 
 503   bool was_enabled()    { return _collector != NULL; }
 504 
 505  public:
 506   NoJvmtiVMObjectAllocMark() NOT_JVMTI_RETURN;
 507   ~NoJvmtiVMObjectAllocMark() NOT_JVMTI_RETURN;
 508 };
 509 
 510 
 511 // Base class for reporting GC events to JVMTI.
 512 class JvmtiGCMarker : public StackObj {
 513  public:
 514   JvmtiGCMarker() NOT_JVMTI_RETURN;
 515   ~JvmtiGCMarker() NOT_JVMTI_RETURN;
 516 };
 517 
 518 // JvmtiHideSingleStepping is a helper class for hiding
 519 // internal single step events.
 520 class JvmtiHideSingleStepping : public StackObj {
 521  private:
 522   bool         _single_step_hidden;
 523   JavaThread * _thread;
 524 
 525  public:
 526   JvmtiHideSingleStepping(JavaThread * thread) {
 527     assert(thread != NULL, "sanity check");
 528 
 529     _single_step_hidden = false;
 530     _thread = thread;
 531     if (JvmtiExport::should_post_single_step()) {
 532       _single_step_hidden = JvmtiExport::hide_single_stepping(_thread);
 533     }
 534   }
 535 
 536   ~JvmtiHideSingleStepping() {
 537     if (_single_step_hidden) {
 538       JvmtiExport::expose_single_stepping(_thread);
 539     }
 540   }
 541 };
 542 
 543 #endif // SHARE_VM_PRIMS_JVMTIEXPORT_HPP