1 /* 2 * Copyright 1998-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 #ifndef _JAVA_JVMTIEXPORT_H_ 26 #define _JAVA_JVMTIEXPORT_H_ 27 28 // Forward declarations 29 30 class JvmtiEventControllerPrivate; 31 class JvmtiManageCapabilities; 32 class JvmtiEnv; 33 class JvmtiThreadState; 34 class AttachOperation; 35 36 #ifndef JVMTI_KERNEL 37 #define JVMTI_SUPPORT_FLAG(key) \ 38 private: \ 39 static bool _##key; \ 40 public: \ 41 inline static void set_##key(bool on) { _##key = (on != 0); } \ 42 inline static bool key() { return _##key; } 43 #else // JVMTI_KERNEL 44 #define JVMTI_SUPPORT_FLAG(key) \ 45 private: \ 46 const static bool _##key = false; \ 47 public: \ 48 inline static void set_##key(bool on) { report_unsupported(on); } \ 49 inline static bool key() { return _##key; } 50 #endif // JVMTI_KERNEL 51 52 53 // This class contains the JVMTI interface for the rest of hotspot. 54 // 55 class JvmtiExport : public AllStatic { 56 private: 57 static int _field_access_count; 58 static int _field_modification_count; 59 60 static bool _can_access_local_variables; 61 static bool _can_examine_or_deopt_anywhere; 62 static bool _can_hotswap_or_post_breakpoint; 63 static bool _can_modify_any_class; 64 static bool _can_walk_any_space; 65 66 JVMTI_SUPPORT_FLAG(can_get_source_debug_extension) 67 JVMTI_SUPPORT_FLAG(can_maintain_original_method_order) 68 JVMTI_SUPPORT_FLAG(can_post_interpreter_events) 69 JVMTI_SUPPORT_FLAG(can_post_exceptions) 70 JVMTI_SUPPORT_FLAG(can_post_breakpoint) 71 JVMTI_SUPPORT_FLAG(can_post_field_access) 72 JVMTI_SUPPORT_FLAG(can_post_field_modification) 73 JVMTI_SUPPORT_FLAG(can_post_method_entry) 74 JVMTI_SUPPORT_FLAG(can_post_method_exit) 75 JVMTI_SUPPORT_FLAG(can_pop_frame) 76 JVMTI_SUPPORT_FLAG(can_force_early_return) 77 78 friend class JvmtiEventControllerPrivate; // should only modify these flags 79 JVMTI_SUPPORT_FLAG(should_post_single_step) 80 JVMTI_SUPPORT_FLAG(should_post_field_access) 81 JVMTI_SUPPORT_FLAG(should_post_field_modification) 82 JVMTI_SUPPORT_FLAG(should_post_class_load) 83 JVMTI_SUPPORT_FLAG(should_post_class_prepare) 84 JVMTI_SUPPORT_FLAG(should_post_class_unload) 85 JVMTI_SUPPORT_FLAG(should_post_native_method_bind) 86 JVMTI_SUPPORT_FLAG(should_post_compiled_method_load) 87 JVMTI_SUPPORT_FLAG(should_post_compiled_method_unload) 88 JVMTI_SUPPORT_FLAG(should_post_dynamic_code_generated) 89 JVMTI_SUPPORT_FLAG(should_post_monitor_contended_enter) 90 JVMTI_SUPPORT_FLAG(should_post_monitor_contended_entered) 91 JVMTI_SUPPORT_FLAG(should_post_monitor_wait) 92 JVMTI_SUPPORT_FLAG(should_post_monitor_waited) 93 JVMTI_SUPPORT_FLAG(should_post_data_dump) 94 JVMTI_SUPPORT_FLAG(should_post_garbage_collection_start) 95 JVMTI_SUPPORT_FLAG(should_post_garbage_collection_finish) 96 97 // ------ the below maybe don't have to be (but are for now) 98 // fixed conditions here ------------ 99 // any events can be enabled 100 JVMTI_SUPPORT_FLAG(should_post_thread_life) 101 JVMTI_SUPPORT_FLAG(should_post_object_free) 102 JVMTI_SUPPORT_FLAG(should_post_resource_exhausted) 103 104 // we are holding objects on the heap - need to talk to GC - e.g. 105 // breakpoint info 106 JVMTI_SUPPORT_FLAG(should_clean_up_heap_objects) 107 JVMTI_SUPPORT_FLAG(should_post_vm_object_alloc) 108 109 // If flag cannot be implemented, give an error if on=true 110 static void report_unsupported(bool on); 111 112 // these should only be called by the friend class 113 friend class JvmtiManageCapabilities; 114 inline static void set_can_examine_or_deopt_anywhere(bool on) { _can_examine_or_deopt_anywhere = (on != 0); } 115 inline static void set_can_modify_any_class(bool on) { _can_modify_any_class = (on != 0); } 116 inline static void set_can_access_local_variables(bool on) { _can_access_local_variables = (on != 0); } 117 inline static void set_can_hotswap_or_post_breakpoint(bool on) { _can_hotswap_or_post_breakpoint = (on != 0); } 118 inline static void set_can_walk_any_space(bool on) { _can_walk_any_space = (on != 0); } 119 120 enum { 121 JVMTI_VERSION_MASK = 0x70000000, 122 JVMTI_VERSION_VALUE = 0x30000000, 123 JVMDI_VERSION_VALUE = 0x20000000 124 }; 125 126 static void post_field_modification(JavaThread *thread, methodOop method, address location, 127 KlassHandle field_klass, Handle object, jfieldID field, 128 char sig_type, jvalue *value); 129 130 131 private: 132 // CompiledMethodUnload events are reported from the VM thread so they 133 // are collected in lists (of jmethodID/addresses) and the events are posted later 134 // from threads posting CompieldMethodLoad or DynamicCodeGenerated events. 135 static bool _have_pending_compiled_method_unload_events; 136 static GrowableArray<jmethodID>* _pending_compiled_method_unload_method_ids; 137 static GrowableArray<const void *>* _pending_compiled_method_unload_code_begins; 138 static JavaThread* _current_poster; 139 140 // tests if there are CompiledMethodUnload events pending 141 inline static bool have_pending_compiled_method_unload_events() { 142 return _have_pending_compiled_method_unload_events; 143 } 144 145 // posts any pending CompiledMethodUnload events. 146 static void post_pending_compiled_method_unload_events(); 147 148 // posts a DynamicCodeGenerated event (internal/private implementation). 149 // The public post_dynamic_code_generated* functions make use of the 150 // internal implementation. 151 static void post_dynamic_code_generated_internal(const char *name, const void *code_begin, const void *code_end) KERNEL_RETURN; 152 153 154 // GenerateEvents support to allow posting of CompiledMethodLoad and 155 // DynamicCodeGenerated events for a given environment. 156 friend class JvmtiCodeBlobEvents; 157 158 static void post_compiled_method_load(JvmtiEnv* env, const jmethodID method, const jint length, 159 const void *code_begin, const jint map_length, 160 const jvmtiAddrLocationMap* map) KERNEL_RETURN; 161 static void post_dynamic_code_generated(JvmtiEnv* env, const char *name, const void *code_begin, 162 const void *code_end) KERNEL_RETURN; 163 164 // The RedefineClasses() API breaks some invariants in the "regular" 165 // system. For example, there are sanity checks when GC'ing nmethods 166 // that require the containing class to be unloading. However, when a 167 // method is redefined, the old method and nmethod can become GC'able 168 // without the containing class unloading. The state of becoming 169 // GC'able can be asynchronous to the RedefineClasses() call since 170 // the old method may still be running and cannot be GC'ed until 171 // after all old invocations have finished. Additionally, a method 172 // that has not been redefined may have an nmethod that depends on 173 // the redefined method. The dependent nmethod will get deopted in 174 // this case and may also be GC'able without the containing class 175 // being unloaded. 176 // 177 // This flag indicates whether RedefineClasses() has ever redefined 178 // one or more classes during the lifetime of the VM. The flag should 179 // only be set by the friend class and can be queried by other sub 180 // systems as needed to relax invariant checks. 181 static bool _has_redefined_a_class; 182 friend class VM_RedefineClasses; 183 inline static void set_has_redefined_a_class() { 184 _has_redefined_a_class = true; 185 } 186 187 // Flag to indicate if the compiler has recorded all dependencies. When the 188 // can_redefine_classes capability is enabled in the OnLoad phase then the compiler 189 // records all dependencies from startup. However if the capability is first 190 // enabled some time later then the dependencies recorded by the compiler 191 // are incomplete. This flag is used by RedefineClasses to know if the 192 // dependency information is complete or not. 193 static bool _all_dependencies_are_recorded; 194 195 public: 196 inline static bool has_redefined_a_class() { 197 return _has_redefined_a_class; 198 } 199 200 inline static bool all_dependencies_are_recorded() { 201 return _all_dependencies_are_recorded; 202 } 203 204 inline static void set_all_dependencies_are_recorded(bool on) { 205 _all_dependencies_are_recorded = (on != 0); 206 } 207 208 209 // let JVMTI know that the JVM_OnLoad code is running 210 static void enter_onload_phase(); 211 212 // let JVMTI know that the VM isn't up yet (and JVM_OnLoad code isn't running) 213 static void enter_primordial_phase(); 214 215 // let JVMTI know that the VM isn't up yet but JNI is live 216 static void enter_start_phase(); 217 218 // let JVMTI know that the VM is fully up and running now 219 static void enter_live_phase(); 220 221 // ------ can_* conditions (below) are set at OnLoad and never changed ------------ 222 inline static bool can_examine_or_deopt_anywhere() { return _can_examine_or_deopt_anywhere; } 223 inline static bool can_modify_any_class() { return _can_modify_any_class; } 224 inline static bool can_access_local_variables() { return _can_access_local_variables; } 225 inline static bool can_hotswap_or_post_breakpoint() { return _can_hotswap_or_post_breakpoint; } 226 inline static bool can_walk_any_space() { return _can_walk_any_space; } 227 228 // field access management 229 static address get_field_access_count_addr(); 230 231 // field modification management 232 static address get_field_modification_count_addr(); 233 234 // ----------------- 235 236 static bool is_jvmti_version(jint version) { return (version & JVMTI_VERSION_MASK) == JVMTI_VERSION_VALUE; } 237 static bool is_jvmdi_version(jint version) { return (version & JVMTI_VERSION_MASK) == JVMDI_VERSION_VALUE; } 238 static jint get_jvmti_interface(JavaVM *jvm, void **penv, jint version); 239 240 // single stepping management methods 241 static void at_single_stepping_point(JavaThread *thread, methodOop method, address location) KERNEL_RETURN; 242 static void expose_single_stepping(JavaThread *thread) KERNEL_RETURN; 243 static bool hide_single_stepping(JavaThread *thread) KERNEL_RETURN_(return false;); 244 245 // Methods that notify the debugger that something interesting has happened in the VM. 246 static void post_vm_start (); 247 static void post_vm_initialized (); 248 static void post_vm_death (); 249 250 static void post_single_step (JavaThread *thread, methodOop method, address location) KERNEL_RETURN; 251 static void post_raw_breakpoint (JavaThread *thread, methodOop method, address location) KERNEL_RETURN; 252 253 static void post_exception_throw (JavaThread *thread, methodOop method, address location, oop exception) KERNEL_RETURN; 254 static void notice_unwind_due_to_exception (JavaThread *thread, methodOop method, address location, oop exception, bool in_handler_frame) KERNEL_RETURN; 255 static jint must_post_exception_events_jrt_leaf(); 256 static jint must_post_exception_events(); 257 258 static oop jni_GetField_probe (JavaThread *thread, jobject jobj, 259 oop obj, klassOop klass, jfieldID fieldID, bool is_static) 260 KERNEL_RETURN_(return NULL;); 261 static oop jni_GetField_probe_nh (JavaThread *thread, jobject jobj, 262 oop obj, klassOop klass, jfieldID fieldID, bool is_static) 263 KERNEL_RETURN_(return NULL;); 264 static void post_field_access_by_jni (JavaThread *thread, oop obj, 265 klassOop klass, jfieldID fieldID, bool is_static) KERNEL_RETURN; 266 static void post_field_access (JavaThread *thread, methodOop method, 267 address location, KlassHandle field_klass, Handle object, jfieldID field) KERNEL_RETURN; 268 static oop jni_SetField_probe (JavaThread *thread, jobject jobj, 269 oop obj, klassOop klass, jfieldID fieldID, bool is_static, char sig_type, 270 jvalue *value) KERNEL_RETURN_(return NULL;); 271 static oop jni_SetField_probe_nh (JavaThread *thread, jobject jobj, 272 oop obj, klassOop klass, jfieldID fieldID, bool is_static, char sig_type, 273 jvalue *value) KERNEL_RETURN_(return NULL;); 274 static void post_field_modification_by_jni(JavaThread *thread, oop obj, 275 klassOop klass, jfieldID fieldID, bool is_static, char sig_type, 276 jvalue *value); 277 static void post_raw_field_modification(JavaThread *thread, methodOop method, 278 address location, KlassHandle field_klass, Handle object, jfieldID field, 279 char sig_type, jvalue *value) KERNEL_RETURN; 280 281 static void post_method_entry (JavaThread *thread, methodOop method, frame current_frame) KERNEL_RETURN; 282 static void post_method_exit (JavaThread *thread, methodOop method, frame current_frame) KERNEL_RETURN; 283 284 static void post_class_load (JavaThread *thread, klassOop klass) KERNEL_RETURN; 285 static void post_class_unload (klassOop klass) KERNEL_RETURN; 286 static void post_class_prepare (JavaThread *thread, klassOop klass) KERNEL_RETURN; 287 288 static void post_thread_start (JavaThread *thread) KERNEL_RETURN; 289 static void post_thread_end (JavaThread *thread) KERNEL_RETURN; 290 291 // Support for java.lang.instrument agent loading. 292 static bool _should_post_class_file_load_hook; 293 inline static void set_should_post_class_file_load_hook(bool on) { _should_post_class_file_load_hook = on; } 294 inline static bool should_post_class_file_load_hook() { return _should_post_class_file_load_hook; } 295 static void post_class_file_load_hook(symbolHandle h_name, Handle class_loader, 296 Handle h_protection_domain, 297 unsigned char **data_ptr, unsigned char **end_ptr, 298 unsigned char **cached_data_ptr, 299 jint *cached_length_ptr); 300 static void post_native_method_bind(methodOop method, address* function_ptr) KERNEL_RETURN; 301 static void post_compiled_method_load(nmethod *nm) KERNEL_RETURN; 302 static void post_dynamic_code_generated(const char *name, const void *code_begin, const void *code_end) KERNEL_RETURN; 303 304 // used at a safepoint to post a CompiledMethodUnload event 305 static void post_compiled_method_unload_at_safepoint(jmethodID mid, const void *code_begin) KERNEL_RETURN; 306 307 // similiar to post_dynamic_code_generated except that it can be used to 308 // post a DynamicCodeGenerated event while holding locks in the VM. Any event 309 // posted using this function is recorded by the enclosing event collector 310 // -- JvmtiDynamicCodeEventCollector. 311 static void post_dynamic_code_generated_while_holding_locks(const char* name, address code_begin, address code_end) KERNEL_RETURN; 312 313 static void post_garbage_collection_finish() KERNEL_RETURN; 314 static void post_garbage_collection_start() KERNEL_RETURN; 315 static void post_data_dump() KERNEL_RETURN; 316 static void post_monitor_contended_enter(JavaThread *thread, ObjectMonitor *obj_mntr) KERNEL_RETURN; 317 static void post_monitor_contended_entered(JavaThread *thread, ObjectMonitor *obj_mntr) KERNEL_RETURN; 318 static void post_monitor_wait(JavaThread *thread, oop obj, jlong timeout) KERNEL_RETURN; 319 static void post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mntr, jboolean timed_out) KERNEL_RETURN; 320 static void post_object_free(JvmtiEnv* env, jlong tag) KERNEL_RETURN; 321 static void post_resource_exhausted(jint resource_exhausted_flags, const char* detail) KERNEL_RETURN; 322 static void record_vm_internal_object_allocation(oop object) KERNEL_RETURN; 323 // Post objects collected by vm_object_alloc_event_collector. 324 static void post_vm_object_alloc(JavaThread *thread, oop object) KERNEL_RETURN; 325 // Collects vm internal objects for later event posting. 326 inline static void vm_object_alloc_event_collector(oop object) { 327 if (should_post_vm_object_alloc()) { 328 record_vm_internal_object_allocation(object); 329 } 330 } 331 332 static void cleanup_thread (JavaThread* thread) KERNEL_RETURN; 333 334 static void oops_do(OopClosure* f) KERNEL_RETURN; 335 336 static void transition_pending_onload_raw_monitors() KERNEL_RETURN; 337 338 #ifndef SERVICES_KERNEL 339 // attach support 340 static jint load_agent_library(AttachOperation* op, outputStream* out); 341 #endif // SERVICES_KERNEL 342 343 // SetNativeMethodPrefix support 344 static char** get_all_native_method_prefixes(int* count_ptr); 345 346 // call after CMS has completed referencing processing 347 static void cms_ref_processing_epilogue() KERNEL_RETURN; 348 }; 349 350 // Support class used by JvmtiDynamicCodeEventCollector and others. It 351 // describes a single code blob by name and address range. 352 class JvmtiCodeBlobDesc : public CHeapObj { 353 private: 354 char _name[64]; 355 address _code_begin; 356 address _code_end; 357 358 public: 359 JvmtiCodeBlobDesc(const char *name, address code_begin, address code_end) { 360 assert(name != NULL, "all code blobs must be named"); 361 strncpy(_name, name, sizeof(_name)); 362 _name[sizeof(_name)-1] = '\0'; 363 _code_begin = code_begin; 364 _code_end = code_end; 365 } 366 char* name() { return _name; } 367 address code_begin() { return _code_begin; } 368 address code_end() { return _code_end; } 369 }; 370 371 // JvmtiEventCollector is a helper class to setup thread for 372 // event collection. 373 class JvmtiEventCollector : public StackObj { 374 private: 375 JvmtiEventCollector* _prev; // Save previous one to support nested event collector. 376 377 public: 378 void setup_jvmti_thread_state(); // Set this collector in current thread. 379 void unset_jvmti_thread_state(); // Reset previous collector in current thread. 380 virtual bool is_dynamic_code_event() { return false; } 381 virtual bool is_vm_object_alloc_event(){ return false; } 382 JvmtiEventCollector *get_prev() { return _prev; } 383 }; 384 385 // A JvmtiDynamicCodeEventCollector is a helper class for the JvmtiExport 386 // interface. It collects "dynamic code generated" events that are posted 387 // while holding locks. When the event collector goes out of scope the 388 // events will be posted. 389 // 390 // Usage :- 391 // 392 // { 393 // JvmtiDynamicCodeEventCollector event_collector; 394 // : 395 // { MutexLocker ml(...) 396 // : 397 // JvmtiExport::post_dynamic_code_generated_while_holding_locks(...) 398 // } 399 // // event collector goes out of scope => post events to profiler. 400 // } 401 402 class JvmtiDynamicCodeEventCollector : public JvmtiEventCollector { 403 private: 404 GrowableArray<JvmtiCodeBlobDesc*>* _code_blobs; // collected code blob events 405 406 friend class JvmtiExport; 407 void register_stub(const char* name, address start, address end); 408 409 public: 410 JvmtiDynamicCodeEventCollector() KERNEL_RETURN; 411 ~JvmtiDynamicCodeEventCollector() KERNEL_RETURN; 412 bool is_dynamic_code_event() { return true; } 413 414 }; 415 416 // Used to record vm internally allocated object oops and post 417 // vm object alloc event for objects visible to java world. 418 // Constructor enables JvmtiThreadState flag and all vm allocated 419 // objects are recorded in a growable array. When destructor is 420 // called the vm object alloc event is posted for each objects 421 // visible to java world. 422 // See jvm.cpp file for its usage. 423 // 424 class JvmtiVMObjectAllocEventCollector : public JvmtiEventCollector { 425 private: 426 GrowableArray<oop>* _allocated; // field to record vm internally allocated object oop. 427 bool _enable; // This flag is enabled in constructor and disabled 428 // in destructor before posting event. To avoid 429 // collection of objects allocated while running java code inside 430 // agent post_vm_object_alloc() event handler. 431 432 //GC support 433 void oops_do(OopClosure* f); 434 435 friend class JvmtiExport; 436 // Record vm allocated object oop. 437 inline void record_allocation(oop obj); 438 439 //GC support 440 static void oops_do_for_all_threads(OopClosure* f); 441 442 public: 443 JvmtiVMObjectAllocEventCollector() KERNEL_RETURN; 444 ~JvmtiVMObjectAllocEventCollector() KERNEL_RETURN; 445 bool is_vm_object_alloc_event() { return true; } 446 447 bool is_enabled() { return _enable; } 448 void set_enabled(bool on) { _enable = on; } 449 }; 450 451 452 453 // Marker class to disable the posting of VMObjectAlloc events 454 // within its scope. 455 // 456 // Usage :- 457 // 458 // { 459 // NoJvmtiVMObjectAllocMark njm; 460 // : 461 // // VMObjAlloc event will not be posted 462 // JvmtiExport::vm_object_alloc_event_collector(obj); 463 // : 464 // } 465 466 class NoJvmtiVMObjectAllocMark : public StackObj { 467 private: 468 // enclosing collector if enabled, NULL otherwise 469 JvmtiVMObjectAllocEventCollector *_collector; 470 471 bool was_enabled() { return _collector != NULL; } 472 473 public: 474 NoJvmtiVMObjectAllocMark() KERNEL_RETURN; 475 ~NoJvmtiVMObjectAllocMark() KERNEL_RETURN; 476 }; 477 478 479 // Base class for reporting GC events to JVMTI. 480 class JvmtiGCMarker : public StackObj { 481 private: 482 bool _full; // marks a "full" GC 483 unsigned int _invocation_count; // GC invocation count 484 protected: 485 JvmtiGCMarker(bool full) KERNEL_RETURN; // protected 486 ~JvmtiGCMarker() KERNEL_RETURN; // protected 487 }; 488 489 490 // Support class used to report GC events to JVMTI. The class is stack 491 // allocated and should be placed in the doit() implementation of all 492 // vm operations that do a stop-the-world GC for failed allocation. 493 // 494 // Usage :- 495 // 496 // void VM_GenCollectForAllocation::doit() { 497 // JvmtiGCForAllocationMarker jgcm; 498 // : 499 // } 500 // 501 // If jvmti is not enabled the constructor and destructor is essentially 502 // a no-op (no overhead). 503 // 504 class JvmtiGCForAllocationMarker : public JvmtiGCMarker { 505 public: 506 JvmtiGCForAllocationMarker() : JvmtiGCMarker(false) { 507 } 508 }; 509 510 // Support class used to report GC events to JVMTI. The class is stack 511 // allocated and should be placed in the doit() implementation of all 512 // vm operations that do a "full" stop-the-world GC. This class differs 513 // from JvmtiGCForAllocationMarker in that this class assumes that a 514 // "full" GC will happen. 515 // 516 // Usage :- 517 // 518 // void VM_GenCollectFull::doit() { 519 // JvmtiGCFullMarker jgcm; 520 // : 521 // } 522 // 523 class JvmtiGCFullMarker : public JvmtiGCMarker { 524 public: 525 JvmtiGCFullMarker() : JvmtiGCMarker(true) { 526 } 527 }; 528 529 530 // JvmtiHideSingleStepping is a helper class for hiding 531 // internal single step events. 532 class JvmtiHideSingleStepping : public StackObj { 533 private: 534 bool _single_step_hidden; 535 JavaThread * _thread; 536 537 public: 538 JvmtiHideSingleStepping(JavaThread * thread) { 539 assert(thread != NULL, "sanity check"); 540 541 _single_step_hidden = false; 542 _thread = thread; 543 if (JvmtiExport::should_post_single_step()) { 544 _single_step_hidden = JvmtiExport::hide_single_stepping(_thread); 545 } 546 } 547 548 ~JvmtiHideSingleStepping() { 549 if (_single_step_hidden) { 550 JvmtiExport::expose_single_stepping(_thread); 551 } 552 } 553 }; 554 555 #endif /* _JAVA_JVMTIEXPORT_H_ */