1 /*
   2  * Copyright (c) 2003, 2024, 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/classLoaderDataGraph.hpp"
  27 #include "classfile/javaClasses.inline.hpp"
  28 #include "classfile/moduleEntry.hpp"
  29 #include "classfile/symbolTable.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "jvmtifiles/jvmtiEnv.hpp"
  32 #include "memory/iterator.hpp"
  33 #include "memory/resourceArea.hpp"
  34 #include "oops/klass.inline.hpp"
  35 #include "oops/objArrayKlass.hpp"
  36 #include "oops/objArrayOop.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "oops/oopHandle.inline.hpp"
  39 #include "prims/jvmtiEnvBase.hpp"
  40 #include "prims/jvmtiEventController.inline.hpp"
  41 #include "prims/jvmtiExtensions.hpp"
  42 #include "prims/jvmtiImpl.hpp"
  43 #include "prims/jvmtiManageCapabilities.hpp"
  44 #include "prims/jvmtiTagMap.hpp"
  45 #include "prims/jvmtiThreadState.inline.hpp"
  46 #include "runtime/continuationEntry.inline.hpp"
  47 #include "runtime/deoptimization.hpp"
  48 #include "runtime/frame.inline.hpp"
  49 #include "runtime/handles.inline.hpp"
  50 #include "runtime/interfaceSupport.inline.hpp"
  51 #include "runtime/javaCalls.hpp"
  52 #include "runtime/javaThread.inline.hpp"
  53 #include "runtime/jfieldIDWorkaround.hpp"
  54 #include "runtime/jniHandles.inline.hpp"
  55 #include "runtime/objectMonitor.inline.hpp"
  56 #include "runtime/osThread.hpp"
  57 #include "runtime/signature.hpp"
  58 #include "runtime/stackWatermarkSet.inline.hpp"
  59 #include "runtime/threads.hpp"
  60 #include "runtime/threadSMR.inline.hpp"
  61 #include "runtime/vframe.inline.hpp"
  62 #include "runtime/vframe_hp.hpp"
  63 #include "runtime/vmThread.hpp"
  64 #include "runtime/vmOperations.hpp"
  65 #include "services/threadService.hpp"
  66 
  67 
  68 ///////////////////////////////////////////////////////////////
  69 //
  70 // JvmtiEnvBase
  71 //
  72 
  73 JvmtiEnvBase* JvmtiEnvBase::_head_environment = nullptr;
  74 
  75 bool JvmtiEnvBase::_globally_initialized = false;
  76 volatile bool JvmtiEnvBase::_needs_clean_up = false;
  77 
  78 jvmtiPhase JvmtiEnvBase::_phase = JVMTI_PHASE_PRIMORDIAL;
  79 
  80 volatile int JvmtiEnvBase::_dying_thread_env_iteration_count = 0;
  81 
  82 extern jvmtiInterface_1_ jvmti_Interface;
  83 extern jvmtiInterface_1_ jvmtiTrace_Interface;
  84 
  85 
  86 // perform initializations that must occur before any JVMTI environments
  87 // are released but which should only be initialized once (no matter
  88 // how many environments are created).
  89 void
  90 JvmtiEnvBase::globally_initialize() {
  91   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
  92   assert(_globally_initialized == false, "bad call");
  93 
  94   JvmtiManageCapabilities::initialize();
  95 
  96   // register extension functions and events
  97   JvmtiExtensions::register_extensions();
  98 
  99 #ifdef JVMTI_TRACE
 100   JvmtiTrace::initialize();
 101 #endif
 102 
 103   _globally_initialized = true;
 104 }
 105 
 106 
 107 void
 108 JvmtiEnvBase::initialize() {
 109   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
 110 
 111   // Add this environment to the end of the environment list (order is important)
 112   {
 113     // This block of code must not contain any safepoints, as list deallocation
 114     // (which occurs at a safepoint) cannot occur simultaneously with this list
 115     // addition.  Note: NoSafepointVerifier cannot, currently, be used before
 116     // threads exist.
 117     JvmtiEnvIterator it;
 118     JvmtiEnvBase *previous_env = nullptr;
 119     for (JvmtiEnvBase* env = it.first(); env != nullptr; env = it.next(env)) {
 120       previous_env = env;
 121     }
 122     if (previous_env == nullptr) {
 123       _head_environment = this;
 124     } else {
 125       previous_env->set_next_environment(this);
 126     }
 127   }
 128 
 129   if (_globally_initialized == false) {
 130     globally_initialize();
 131   }
 132 }
 133 
 134 jvmtiPhase
 135 JvmtiEnvBase::phase() {
 136   // For the JVMTI environments possessed the can_generate_early_vmstart:
 137   //   replace JVMTI_PHASE_PRIMORDIAL with JVMTI_PHASE_START
 138   if (_phase == JVMTI_PHASE_PRIMORDIAL &&
 139       JvmtiExport::early_vmstart_recorded() &&
 140       early_vmstart_env()) {
 141     return JVMTI_PHASE_START;
 142   }
 143   return _phase; // Normal case
 144 }
 145 
 146 bool
 147 JvmtiEnvBase::is_valid() {
 148   jlong value = 0;
 149 
 150   // This object might not be a JvmtiEnvBase so we can't assume
 151   // the _magic field is properly aligned. Get the value in a safe
 152   // way and then check against JVMTI_MAGIC.
 153 
 154   switch (sizeof(_magic)) {
 155   case 2:
 156     value = Bytes::get_native_u2((address)&_magic);
 157     break;
 158 
 159   case 4:
 160     value = Bytes::get_native_u4((address)&_magic);
 161     break;
 162 
 163   case 8:
 164     value = Bytes::get_native_u8((address)&_magic);
 165     break;
 166 
 167   default:
 168     guarantee(false, "_magic field is an unexpected size");
 169   }
 170 
 171   return value == JVMTI_MAGIC;
 172 }
 173 
 174 
 175 bool
 176 JvmtiEnvBase::use_version_1_0_semantics() {
 177   int major, minor, micro;
 178 
 179   JvmtiExport::decode_version_values(_version, &major, &minor, &micro);
 180   return major == 1 && minor == 0;  // micro version doesn't matter here
 181 }
 182 
 183 
 184 bool
 185 JvmtiEnvBase::use_version_1_1_semantics() {
 186   int major, minor, micro;
 187 
 188   JvmtiExport::decode_version_values(_version, &major, &minor, &micro);
 189   return major == 1 && minor == 1;  // micro version doesn't matter here
 190 }
 191 
 192 bool
 193 JvmtiEnvBase::use_version_1_2_semantics() {
 194   int major, minor, micro;
 195 
 196   JvmtiExport::decode_version_values(_version, &major, &minor, &micro);
 197   return major == 1 && minor == 2;  // micro version doesn't matter here
 198 }
 199 
 200 
 201 JvmtiEnvBase::JvmtiEnvBase(jint version) : _env_event_enable() {
 202   _version = version;
 203   _env_local_storage = nullptr;
 204   _tag_map = nullptr;
 205   _native_method_prefix_count = 0;
 206   _native_method_prefixes = nullptr;
 207   _next = nullptr;
 208   _class_file_load_hook_ever_enabled = false;
 209 
 210   // Moot since ClassFileLoadHook not yet enabled.
 211   // But "true" will give a more predictable ClassFileLoadHook behavior
 212   // for environment creation during ClassFileLoadHook.
 213   _is_retransformable = true;
 214 
 215   // all callbacks initially null
 216   memset(&_event_callbacks, 0, sizeof(jvmtiEventCallbacks));
 217   memset(&_ext_event_callbacks, 0, sizeof(jvmtiExtEventCallbacks));
 218 
 219   // all capabilities initially off
 220   memset(&_current_capabilities, 0, sizeof(_current_capabilities));
 221 
 222   // all prohibited capabilities initially off
 223   memset(&_prohibited_capabilities, 0, sizeof(_prohibited_capabilities));
 224 
 225   _magic = JVMTI_MAGIC;
 226 
 227   JvmtiEventController::env_initialize((JvmtiEnv*)this);
 228 
 229 #ifdef JVMTI_TRACE
 230   _jvmti_external.functions = TraceJVMTI != nullptr ? &jvmtiTrace_Interface : &jvmti_Interface;
 231 #else
 232   _jvmti_external.functions = &jvmti_Interface;
 233 #endif
 234 }
 235 
 236 
 237 void
 238 JvmtiEnvBase::dispose() {
 239 
 240 #ifdef JVMTI_TRACE
 241   JvmtiTrace::shutdown();
 242 #endif
 243 
 244   // Dispose of event info and let the event controller call us back
 245   // in a locked state (env_dispose, below)
 246   JvmtiEventController::env_dispose(this);
 247 }
 248 
 249 void
 250 JvmtiEnvBase::env_dispose() {
 251   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
 252 
 253   // We have been entered with all events disabled on this environment.
 254   // A race to re-enable events (by setting callbacks) is prevented by
 255   // checking for a valid environment when setting callbacks (while
 256   // holding the JvmtiThreadState_lock).
 257 
 258   // Mark as invalid.
 259   _magic = DISPOSED_MAGIC;
 260 
 261   // Relinquish all capabilities.
 262   jvmtiCapabilities *caps = get_capabilities();
 263   JvmtiManageCapabilities::relinquish_capabilities(caps, caps, caps);
 264 
 265   // Same situation as with events (see above)
 266   set_native_method_prefixes(0, nullptr);
 267 
 268   JvmtiTagMap* tag_map_to_clear = tag_map_acquire();
 269   // A tag map can be big, clear it now to save memory until
 270   // the destructor runs.
 271   if (tag_map_to_clear != nullptr) {
 272     tag_map_to_clear->clear();
 273   }
 274 
 275   _needs_clean_up = true;
 276 }
 277 
 278 
 279 JvmtiEnvBase::~JvmtiEnvBase() {
 280   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
 281 
 282   // There is a small window of time during which the tag map of a
 283   // disposed environment could have been reallocated.
 284   // Make sure it is gone.
 285   JvmtiTagMap* tag_map_to_deallocate = _tag_map;
 286   set_tag_map(nullptr);
 287   // A tag map can be big, deallocate it now
 288   if (tag_map_to_deallocate != nullptr) {
 289     delete tag_map_to_deallocate;
 290   }
 291 
 292   _magic = BAD_MAGIC;
 293 }
 294 
 295 
 296 void
 297 JvmtiEnvBase::periodic_clean_up() {
 298   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
 299 
 300   // JvmtiEnvBase reference is saved in JvmtiEnvThreadState. So
 301   // clean up JvmtiThreadState before deleting JvmtiEnv pointer.
 302   JvmtiThreadState::periodic_clean_up();
 303 
 304   // Unlink all invalid environments from the list of environments
 305   // and deallocate them
 306   JvmtiEnvIterator it;
 307   JvmtiEnvBase* previous_env = nullptr;
 308   JvmtiEnvBase* env = it.first();
 309   while (env != nullptr) {
 310     if (env->is_valid()) {
 311       previous_env = env;
 312       env = it.next(env);
 313     } else {
 314       // This one isn't valid, remove it from the list and deallocate it
 315       JvmtiEnvBase* defunct_env = env;
 316       env = it.next(env);
 317       if (previous_env == nullptr) {
 318         _head_environment = env;
 319       } else {
 320         previous_env->set_next_environment(env);
 321       }
 322       delete defunct_env;
 323     }
 324   }
 325 
 326 }
 327 
 328 
 329 void
 330 JvmtiEnvBase::check_for_periodic_clean_up() {
 331   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
 332 
 333   class ThreadInsideIterationClosure: public ThreadClosure {
 334    private:
 335     bool _inside;
 336    public:
 337     ThreadInsideIterationClosure() : _inside(false) {};
 338 
 339     void do_thread(Thread* thread) {
 340       _inside |= thread->is_inside_jvmti_env_iteration();
 341     }
 342 
 343     bool is_inside_jvmti_env_iteration() {
 344       return _inside;
 345     }
 346   };
 347 
 348   if (_needs_clean_up) {
 349     // Check if we are currently iterating environment,
 350     // deallocation should not occur if we are
 351     ThreadInsideIterationClosure tiic;
 352     Threads::threads_do(&tiic);
 353     if (!tiic.is_inside_jvmti_env_iteration() &&
 354              !is_inside_dying_thread_env_iteration()) {
 355       _needs_clean_up = false;
 356       JvmtiEnvBase::periodic_clean_up();
 357     }
 358   }
 359 }
 360 
 361 
 362 void
 363 JvmtiEnvBase::record_first_time_class_file_load_hook_enabled() {
 364   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(),
 365          "sanity check");
 366 
 367   if (!_class_file_load_hook_ever_enabled) {
 368     _class_file_load_hook_ever_enabled = true;
 369 
 370     if (get_capabilities()->can_retransform_classes) {
 371       _is_retransformable = true;
 372     } else {
 373       _is_retransformable = false;
 374 
 375       // cannot add retransform capability after ClassFileLoadHook has been enabled
 376       get_prohibited_capabilities()->can_retransform_classes = 1;
 377     }
 378   }
 379 }
 380 
 381 
 382 void
 383 JvmtiEnvBase::record_class_file_load_hook_enabled() {
 384   if (!_class_file_load_hook_ever_enabled) {
 385     if (Threads::number_of_threads() == 0) {
 386       record_first_time_class_file_load_hook_enabled();
 387     } else {
 388       MutexLocker mu(JvmtiThreadState_lock);
 389       record_first_time_class_file_load_hook_enabled();
 390     }
 391   }
 392 }
 393 
 394 
 395 jvmtiError
 396 JvmtiEnvBase::set_native_method_prefixes(jint prefix_count, char** prefixes) {
 397   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(),
 398          "sanity check");
 399 
 400   int old_prefix_count = get_native_method_prefix_count();
 401   char **old_prefixes = get_native_method_prefixes();
 402 
 403   // allocate and install the new prefixex
 404   if (prefix_count == 0 || !is_valid()) {
 405     _native_method_prefix_count = 0;
 406     _native_method_prefixes = nullptr;
 407   } else {
 408     // there are prefixes, allocate an array to hold them, and fill it
 409     char** new_prefixes = (char**)os::malloc((prefix_count) * sizeof(char*), mtInternal);
 410     if (new_prefixes == nullptr) {
 411       return JVMTI_ERROR_OUT_OF_MEMORY;
 412     }
 413     for (int i = 0; i < prefix_count; i++) {
 414       char* prefix = prefixes[i];
 415       if (prefix == nullptr) {
 416         for (int j = 0; j < (i-1); j++) {
 417           os::free(new_prefixes[j]);
 418         }
 419         os::free(new_prefixes);
 420         return JVMTI_ERROR_NULL_POINTER;
 421       }
 422       prefix = os::strdup(prefixes[i]);
 423       if (prefix == nullptr) {
 424         for (int j = 0; j < (i-1); j++) {
 425           os::free(new_prefixes[j]);
 426         }
 427         os::free(new_prefixes);
 428         return JVMTI_ERROR_OUT_OF_MEMORY;
 429       }
 430       new_prefixes[i] = prefix;
 431     }
 432     _native_method_prefix_count = prefix_count;
 433     _native_method_prefixes = new_prefixes;
 434   }
 435 
 436   // now that we know the new prefixes have been successfully installed we can
 437   // safely remove the old ones
 438   if (old_prefix_count != 0) {
 439     for (int i = 0; i < old_prefix_count; i++) {
 440       os::free(old_prefixes[i]);
 441     }
 442     os::free(old_prefixes);
 443   }
 444 
 445   return JVMTI_ERROR_NONE;
 446 }
 447 
 448 
 449 // Collect all the prefixes which have been set in any JVM TI environments
 450 // by the SetNativeMethodPrefix(es) functions.  Be sure to maintain the
 451 // order of environments and the order of prefixes within each environment.
 452 // Return in a resource allocated array.
 453 char**
 454 JvmtiEnvBase::get_all_native_method_prefixes(int* count_ptr) {
 455   assert(Threads::number_of_threads() == 0 ||
 456          SafepointSynchronize::is_at_safepoint() ||
 457          JvmtiThreadState_lock->is_locked(),
 458          "sanity check");
 459 
 460   int total_count = 0;
 461   GrowableArray<char*>* prefix_array =new GrowableArray<char*>(5);
 462 
 463   JvmtiEnvIterator it;
 464   for (JvmtiEnvBase* env = it.first(); env != nullptr; env = it.next(env)) {
 465     int prefix_count = env->get_native_method_prefix_count();
 466     char** prefixes = env->get_native_method_prefixes();
 467     for (int j = 0; j < prefix_count; j++) {
 468       // retrieve a prefix and so that it is safe against asynchronous changes
 469       // copy it into the resource area
 470       char* prefix = prefixes[j];
 471       char* prefix_copy = NEW_RESOURCE_ARRAY(char, strlen(prefix)+1);
 472       strcpy(prefix_copy, prefix);
 473       prefix_array->at_put_grow(total_count++, prefix_copy);
 474     }
 475   }
 476 
 477   char** all_prefixes = NEW_RESOURCE_ARRAY(char*, total_count);
 478   char** p = all_prefixes;
 479   for (int i = 0; i < total_count; ++i) {
 480     *p++ = prefix_array->at(i);
 481   }
 482   *count_ptr = total_count;
 483   return all_prefixes;
 484 }
 485 
 486 void
 487 JvmtiEnvBase::set_event_callbacks(const jvmtiEventCallbacks* callbacks,
 488                                                jint size_of_callbacks) {
 489   assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
 490 
 491   size_t byte_cnt = sizeof(jvmtiEventCallbacks);
 492 
 493   // clear in either case to be sure we got any gap between sizes
 494   memset(&_event_callbacks, 0, byte_cnt);
 495 
 496   // Now that JvmtiThreadState_lock is held, prevent a possible race condition where events
 497   // are re-enabled by a call to set event callbacks where the DisposeEnvironment
 498   // occurs after the boiler-plate environment check and before the lock is acquired.
 499   if (callbacks != nullptr && is_valid()) {
 500     if (size_of_callbacks < (jint)byte_cnt) {
 501       byte_cnt = size_of_callbacks;
 502     }
 503     memcpy(&_event_callbacks, callbacks, byte_cnt);
 504   }
 505 }
 506 
 507 
 508 // In the fullness of time, all users of the method should instead
 509 // directly use allocate, besides being cleaner and faster, this will
 510 // mean much better out of memory handling
 511 unsigned char *
 512 JvmtiEnvBase::jvmtiMalloc(jlong size) {
 513   unsigned char* mem = nullptr;
 514   jvmtiError result = allocate(size, &mem);
 515   assert(result == JVMTI_ERROR_NONE, "Allocate failed");
 516   return mem;
 517 }
 518 
 519 
 520 // Handle management
 521 
 522 jobject JvmtiEnvBase::jni_reference(Handle hndl) {
 523   return JNIHandles::make_local(hndl());
 524 }
 525 
 526 jobject JvmtiEnvBase::jni_reference(JavaThread *thread, Handle hndl) {
 527   return JNIHandles::make_local(thread, hndl());
 528 }
 529 
 530 void JvmtiEnvBase::destroy_jni_reference(jobject jobj) {
 531   JNIHandles::destroy_local(jobj);
 532 }
 533 
 534 void JvmtiEnvBase::destroy_jni_reference(JavaThread *thread, jobject jobj) {
 535   JNIHandles::destroy_local(jobj); // thread is unused.
 536 }
 537 
 538 //
 539 // Threads
 540 //
 541 
 542 jthread *
 543 JvmtiEnvBase::new_jthreadArray(int length, Handle *handles) {
 544   if (length == 0) {
 545     return nullptr;
 546   }
 547 
 548   jthread* objArray = (jthread *) jvmtiMalloc(sizeof(jthread) * length);
 549   NULL_CHECK(objArray, nullptr);
 550 
 551   for (int i = 0; i < length; i++) {
 552     objArray[i] = (jthread)jni_reference(handles[i]);
 553   }
 554   return objArray;
 555 }
 556 
 557 jthreadGroup *
 558 JvmtiEnvBase::new_jthreadGroupArray(int length, objArrayHandle groups) {
 559   if (length == 0) {
 560     return nullptr;
 561   }
 562 
 563   jthreadGroup* objArray = (jthreadGroup *) jvmtiMalloc(sizeof(jthreadGroup) * length);
 564   NULL_CHECK(objArray, nullptr);
 565 
 566   for (int i = 0; i < length; i++) {
 567     objArray[i] = (jthreadGroup)JNIHandles::make_local(groups->obj_at(i));
 568   }
 569   return objArray;
 570 }
 571 
 572 // Return the vframe on the specified thread and depth, null if no such frame.
 573 // The thread and the oops in the returned vframe might not have been processed.
 574 javaVFrame*
 575 JvmtiEnvBase::jvf_for_thread_and_depth(JavaThread* java_thread, jint depth) {
 576   if (!java_thread->has_last_Java_frame()) {
 577     return nullptr;
 578   }
 579   RegisterMap reg_map(java_thread,
 580                       RegisterMap::UpdateMap::include,
 581                       RegisterMap::ProcessFrames::skip,
 582                       RegisterMap::WalkContinuation::include);
 583   javaVFrame *jvf = java_thread->last_java_vframe(&reg_map);
 584 
 585   jvf = JvmtiEnvBase::check_and_skip_hidden_frames(java_thread, jvf);
 586 
 587   for (int d = 0; jvf != nullptr && d < depth; d++) {
 588     jvf = jvf->java_sender();
 589   }
 590   return jvf;
 591 }
 592 
 593 //
 594 // utilities: JNI objects
 595 //
 596 
 597 
 598 jclass
 599 JvmtiEnvBase::get_jni_class_non_null(Klass* k) {
 600   assert(k != nullptr, "k != null");
 601   Thread *thread = Thread::current();
 602   return (jclass)jni_reference(Handle(thread, k->java_mirror()));
 603 }
 604 
 605 //
 606 // Field Information
 607 //
 608 
 609 bool
 610 JvmtiEnvBase::get_field_descriptor(Klass* k, jfieldID field, fieldDescriptor* fd) {
 611   if (!jfieldIDWorkaround::is_valid_jfieldID(k, field)) {
 612     return false;
 613   }
 614   bool found = false;
 615   if (jfieldIDWorkaround::is_static_jfieldID(field)) {
 616     JNIid* id = jfieldIDWorkaround::from_static_jfieldID(field);
 617     found = id->find_local_field(fd);
 618   } else {
 619     // Non-static field. The fieldID is really the offset of the field within the object.
 620     int offset = jfieldIDWorkaround::from_instance_jfieldID(k, field);
 621     found = InstanceKlass::cast(k)->find_field_from_offset(offset, false, fd);
 622   }
 623   return found;
 624 }
 625 
 626 bool
 627 JvmtiEnvBase::is_vthread_alive(oop vt) {
 628   oop cont = java_lang_VirtualThread::continuation(vt);
 629   return !jdk_internal_vm_Continuation::done(cont) &&
 630          java_lang_VirtualThread::state(vt) != java_lang_VirtualThread::NEW;
 631 }
 632 
 633 // Return JavaThread if virtual thread is mounted, null otherwise.
 634 JavaThread* JvmtiEnvBase::get_JavaThread_or_null(oop vthread) {
 635   oop carrier_thread = java_lang_VirtualThread::carrier_thread(vthread);
 636   if (carrier_thread == nullptr) {
 637     return nullptr;
 638   }
 639 
 640   JavaThread* java_thread = java_lang_Thread::thread(carrier_thread);
 641 
 642   // This could be a different thread to the current one. So we need to ensure that
 643   // processing has started before we are allowed to read the continuation oop of
 644   // another thread, as it is a direct root of that other thread.
 645   StackWatermarkSet::start_processing(java_thread, StackWatermarkKind::gc);
 646 
 647   oop cont = java_lang_VirtualThread::continuation(vthread);
 648   assert(cont != nullptr, "must be");
 649   assert(Continuation::continuation_scope(cont) == java_lang_VirtualThread::vthread_scope(), "must be");
 650   return Continuation::is_continuation_mounted(java_thread, cont) ? java_thread : nullptr;
 651 }
 652 
 653 javaVFrame*
 654 JvmtiEnvBase::check_and_skip_hidden_frames(bool is_in_VTMS_transition, javaVFrame* jvf) {
 655   // The second condition is needed to hide notification methods.
 656   if (!is_in_VTMS_transition && (jvf == nullptr || !jvf->method()->jvmti_mount_transition())) {
 657     return jvf;  // No frames to skip.
 658   }
 659   // Find jvf with a method annotated with @JvmtiMountTransition.
 660   for ( ; jvf != nullptr; jvf = jvf->java_sender()) {
 661     if (jvf->method()->jvmti_mount_transition()) {  // Cannot actually appear in an unmounted continuation; they're never frozen.
 662       jvf = jvf->java_sender();  // Skip annotated method.
 663       break;
 664     }
 665     if (jvf->method()->changes_current_thread()) {
 666       break;
 667     }
 668     // Skip frame above annotated method.
 669   }
 670   return jvf;
 671 }
 672 
 673 javaVFrame*
 674 JvmtiEnvBase::check_and_skip_hidden_frames(JavaThread* jt, javaVFrame* jvf) {
 675   jvf = check_and_skip_hidden_frames(jt->is_in_VTMS_transition(), jvf);
 676   return jvf;
 677 }
 678 
 679 javaVFrame*
 680 JvmtiEnvBase::check_and_skip_hidden_frames(oop vthread, javaVFrame* jvf) {
 681   JvmtiThreadState* state = java_lang_Thread::jvmti_thread_state(vthread);
 682   if (state == nullptr) {
 683     // nothing to skip
 684     return jvf;
 685   }
 686   jvf = check_and_skip_hidden_frames(java_lang_Thread::is_in_VTMS_transition(vthread), jvf);
 687   return jvf;
 688 }
 689 
 690 javaVFrame*
 691 JvmtiEnvBase::get_vthread_jvf(oop vthread) {
 692   assert(java_lang_VirtualThread::state(vthread) != java_lang_VirtualThread::NEW, "sanity check");
 693   assert(java_lang_VirtualThread::state(vthread) != java_lang_VirtualThread::TERMINATED, "sanity check");
 694 
 695   Thread* cur_thread = Thread::current();
 696   oop cont = java_lang_VirtualThread::continuation(vthread);
 697   javaVFrame* jvf = nullptr;
 698 
 699   JavaThread* java_thread = get_JavaThread_or_null(vthread);
 700   if (java_thread != nullptr) {
 701     if (!java_thread->has_last_Java_frame()) {
 702       // TBD: This is a temporary work around to avoid a guarantee caused by
 703       // the native enterSpecial frame on the top. No frames will be found
 704       // by the JVMTI functions such as GetStackTrace.
 705       return nullptr;
 706     }
 707     vframeStream vfs(java_thread);
 708     jvf = vfs.at_end() ? nullptr : vfs.asJavaVFrame();
 709     jvf = check_and_skip_hidden_frames(java_thread, jvf);
 710   } else {
 711     vframeStream vfs(cont);
 712     jvf = vfs.at_end() ? nullptr : vfs.asJavaVFrame();
 713     jvf = check_and_skip_hidden_frames(vthread, jvf);
 714   }
 715   return jvf;
 716 }
 717 
 718 // Return correct javaVFrame for a carrier (non-virtual) thread.
 719 // It strips vthread frames at the top if there are any.
 720 javaVFrame*
 721 JvmtiEnvBase::get_cthread_last_java_vframe(JavaThread* jt, RegisterMap* reg_map_p) {
 722   // Strip vthread frames in case of carrier thread with mounted continuation.
 723   bool cthread_with_cont = JvmtiEnvBase::is_cthread_with_continuation(jt);
 724   javaVFrame *jvf = cthread_with_cont ? jt->carrier_last_java_vframe(reg_map_p)
 725                                       : jt->last_java_vframe(reg_map_p);
 726   // Skip hidden frames only for carrier threads
 727   // which are in non-temporary VTMS transition.
 728   if (jt->is_in_VTMS_transition()) {
 729     jvf = check_and_skip_hidden_frames(jt, jvf);
 730   }
 731   return jvf;
 732 }
 733 
 734 jint
 735 JvmtiEnvBase::get_thread_state_base(oop thread_oop, JavaThread* jt) {
 736   jint state = 0;
 737 
 738   if (thread_oop != nullptr) {
 739     // Get most state bits.
 740     state = (jint)java_lang_Thread::get_thread_status(thread_oop);
 741   }
 742   if (jt != nullptr) {
 743     // We have a JavaThread* so add more state bits.
 744     JavaThreadState jts = jt->thread_state();
 745 
 746     if (jt->is_carrier_thread_suspended() ||
 747         ((jt->jvmti_vthread() == nullptr || jt->jvmti_vthread() == thread_oop) && jt->is_suspended())) {
 748       // Suspended non-virtual thread.
 749       state |= JVMTI_THREAD_STATE_SUSPENDED;
 750     }
 751     if (jts == _thread_in_native) {
 752       state |= JVMTI_THREAD_STATE_IN_NATIVE;
 753     }
 754     if (jt->is_interrupted(false)) {
 755       state |= JVMTI_THREAD_STATE_INTERRUPTED;
 756     }
 757   }
 758   return state;
 759 }
 760 
 761 jint
 762 JvmtiEnvBase::get_thread_state(oop thread_oop, JavaThread* jt) {
 763   jint state = 0;
 764 
 765   if (is_thread_carrying_vthread(jt, thread_oop)) {
 766     state = (jint)java_lang_Thread::get_thread_status(thread_oop);
 767 
 768     // This is for extra safety. Other bits are not expected nor needed.
 769     state &= (JVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_INTERRUPTED);
 770 
 771     if (jt->is_carrier_thread_suspended()) {
 772       state |= JVMTI_THREAD_STATE_SUSPENDED;
 773     }
 774     // It's okay for the JVMTI state to be reported as WAITING when waiting
 775     // for something other than an Object.wait. So, we treat a thread carrying
 776     // a virtual thread as waiting indefinitely which is not runnable.
 777     // It is why the RUNNABLE bit is not needed and the WAITING bits are added.
 778     state |= JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_INDEFINITELY;
 779   } else {
 780     state = get_thread_state_base(thread_oop, jt);
 781   }
 782   return state;
 783 }
 784 
 785 jint
 786 JvmtiEnvBase::get_vthread_state(oop thread_oop, JavaThread* java_thread) {
 787   jint state = 0;
 788   bool ext_suspended = JvmtiVTSuspender::is_vthread_suspended(thread_oop);
 789   jint interrupted = java_lang_Thread::interrupted(thread_oop);
 790 
 791   if (java_thread != nullptr) {
 792     // If virtual thread is blocked on a monitor enter the BLOCKED_ON_MONITOR_ENTER bit
 793     // is set for carrier thread instead of virtual.
 794     // Other state bits except filtered ones are expected to be the same.
 795     oop ct_oop = java_lang_VirtualThread::carrier_thread(thread_oop);
 796     jint filtered_bits = JVMTI_THREAD_STATE_SUSPENDED | JVMTI_THREAD_STATE_INTERRUPTED;
 797 
 798     // This call can trigger a safepoint, so thread_oop must not be used after it.
 799     state = get_thread_state_base(ct_oop, java_thread) & ~filtered_bits;
 800   } else {
 801     int vt_state = java_lang_VirtualThread::state(thread_oop);
 802     state = (jint)java_lang_VirtualThread::map_state_to_thread_status(vt_state);
 803   }
 804   // Ensure the thread has not exited after retrieving suspended/interrupted values.
 805   if ((state & JVMTI_THREAD_STATE_ALIVE) != 0) {
 806     if (ext_suspended) {
 807       state |= JVMTI_THREAD_STATE_SUSPENDED;
 808     }
 809     if (interrupted) {
 810       state |= JVMTI_THREAD_STATE_INTERRUPTED;
 811     }
 812   }
 813   return state;
 814 }
 815 
 816 jvmtiError
 817 JvmtiEnvBase::get_live_threads(JavaThread* current_thread, Handle group_hdl, jint *count_ptr, Handle **thread_objs_p) {
 818   jint count = 0;
 819   Handle *thread_objs = nullptr;
 820   ThreadsListEnumerator tle(current_thread, /* include_jvmti_agent_threads */ true);
 821   int nthreads = tle.num_threads();
 822   if (nthreads > 0) {
 823     thread_objs = NEW_RESOURCE_ARRAY_RETURN_NULL(Handle, nthreads);
 824     NULL_CHECK(thread_objs, JVMTI_ERROR_OUT_OF_MEMORY);
 825     for (int i = 0; i < nthreads; i++) {
 826       Handle thread = tle.get_threadObj(i);
 827       if (thread()->is_a(vmClasses::Thread_klass()) && java_lang_Thread::threadGroup(thread()) == group_hdl()) {
 828         thread_objs[count++] = thread;
 829       }
 830     }
 831   }
 832   *thread_objs_p = thread_objs;
 833   *count_ptr = count;
 834   return JVMTI_ERROR_NONE;
 835 }
 836 
 837 jvmtiError
 838 JvmtiEnvBase::get_subgroups(JavaThread* current_thread, Handle group_hdl, jint *count_ptr, objArrayHandle *group_objs_p) {
 839 
 840   // This call collects the strong and weak groups
 841   JavaThread* THREAD = current_thread;
 842   JavaValue result(T_OBJECT);
 843   JavaCalls::call_virtual(&result,
 844                           group_hdl,
 845                           vmClasses::ThreadGroup_klass(),
 846                           SymbolTable::new_permanent_symbol("subgroupsAsArray"),
 847                           vmSymbols::void_threadgroup_array_signature(),
 848                           THREAD);
 849   if (HAS_PENDING_EXCEPTION) {
 850     Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
 851     CLEAR_PENDING_EXCEPTION;
 852     if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
 853       return JVMTI_ERROR_OUT_OF_MEMORY;
 854     } else {
 855       return JVMTI_ERROR_INTERNAL;
 856     }
 857   }
 858 
 859   assert(result.get_type() == T_OBJECT, "just checking");
 860   objArrayOop groups = (objArrayOop)result.get_oop();
 861 
 862   *count_ptr = groups == nullptr ? 0 : groups->length();
 863   *group_objs_p = objArrayHandle(current_thread, groups);
 864 
 865   return JVMTI_ERROR_NONE;
 866 }
 867 
 868 //
 869 // Object Monitor Information
 870 //
 871 
 872 //
 873 // Count the number of objects for a lightweight monitor. The hobj
 874 // parameter is object that owns the monitor so this routine will
 875 // count the number of times the same object was locked by frames
 876 // in java_thread.
 877 //
 878 jint
 879 JvmtiEnvBase::count_locked_objects(JavaThread *java_thread, Handle hobj) {
 880   jint ret = 0;
 881   if (!java_thread->has_last_Java_frame()) {
 882     return ret;  // no Java frames so no monitors
 883   }
 884 
 885   Thread* current_thread = Thread::current();
 886   ResourceMark rm(current_thread);
 887   HandleMark   hm(current_thread);
 888   RegisterMap  reg_map(java_thread,
 889                        RegisterMap::UpdateMap::include,
 890                        RegisterMap::ProcessFrames::include,
 891                        RegisterMap::WalkContinuation::skip);
 892 
 893   for (javaVFrame *jvf = java_thread->last_java_vframe(&reg_map); jvf != nullptr;
 894        jvf = jvf->java_sender()) {
 895     GrowableArray<MonitorInfo*>* mons = jvf->monitors();
 896     if (!mons->is_empty()) {
 897       for (int i = 0; i < mons->length(); i++) {
 898         MonitorInfo *mi = mons->at(i);
 899         if (mi->owner_is_scalar_replaced()) continue;
 900 
 901         // see if owner of the monitor is our object
 902         if (mi->owner() != nullptr && mi->owner() == hobj()) {
 903           ret++;
 904         }
 905       }
 906     }
 907   }
 908   return ret;
 909 }
 910 
 911 jvmtiError
 912 JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThread *java_thread,
 913                                             jobject *monitor_ptr, bool is_virtual) {
 914   Thread *current_thread = Thread::current();
 915   assert(java_thread->is_handshake_safe_for(current_thread),
 916          "call by myself or at handshake");
 917   if (!is_virtual && JvmtiEnvBase::is_cthread_with_continuation(java_thread)) {
 918     // Carrier thread with a mounted continuation case.
 919     // No contended monitor can be owned by carrier thread in this case.
 920     *monitor_ptr = nullptr;
 921     return JVMTI_ERROR_NONE;
 922   }
 923   oop obj = nullptr;
 924   // The ObjectMonitor* can't be async deflated since we are either
 925   // at a safepoint or the calling thread is operating on itself so
 926   // it cannot leave the underlying wait()/enter() call.
 927   ObjectMonitor *mon = java_thread->current_waiting_monitor();
 928   if (mon == nullptr) {
 929     // thread is not doing an Object.wait() call
 930     mon = java_thread->current_pending_monitor();
 931     if (mon != nullptr) {
 932       // The thread is trying to enter() an ObjectMonitor.
 933       obj = mon->object();
 934       assert(obj != nullptr, "ObjectMonitor should have a valid object!");
 935     }
 936     // implied else: no contended ObjectMonitor
 937   } else {
 938     // thread is doing an Object.wait() call
 939     obj = mon->object();
 940     assert(obj != nullptr, "Object.wait() should have an object");
 941   }
 942 
 943   if (obj == nullptr) {
 944     *monitor_ptr = nullptr;
 945   } else {
 946     HandleMark hm(current_thread);
 947     Handle     hobj(current_thread, obj);
 948     *monitor_ptr = jni_reference(calling_thread, hobj);
 949   }
 950   return JVMTI_ERROR_NONE;
 951 }
 952 
 953 jvmtiError
 954 JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
 955                                  GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
 956   // Note:
 957   // calling_thread is the thread that requested the list of monitors for java_thread.
 958   // java_thread is the thread owning the monitors.
 959   // current_thread is the thread executing this code, can be a non-JavaThread (e.g. VM Thread).
 960   // And they all may be different threads.
 961   jvmtiError err = JVMTI_ERROR_NONE;
 962   Thread *current_thread = Thread::current();
 963   assert(java_thread->is_handshake_safe_for(current_thread),
 964          "call by myself or at handshake");
 965 
 966   if (JvmtiEnvBase::is_cthread_with_continuation(java_thread)) {
 967     // Carrier thread with a mounted continuation case.
 968     // No contended monitor can be owned by carrier thread in this case.
 969     return JVMTI_ERROR_NONE;
 970   }
 971   if (java_thread->has_last_Java_frame()) {
 972     ResourceMark rm(current_thread);
 973     HandleMark   hm(current_thread);
 974     RegisterMap  reg_map(java_thread,
 975                          RegisterMap::UpdateMap::include,
 976                          RegisterMap::ProcessFrames::include,
 977                          RegisterMap::WalkContinuation::skip);
 978 
 979     int depth = 0;
 980     for (javaVFrame *jvf = get_cthread_last_java_vframe(java_thread, &reg_map);
 981          jvf != nullptr; jvf = jvf->java_sender()) {
 982       if (MaxJavaStackTraceDepth == 0 || depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
 983         // add locked objects for this frame into list
 984         err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth-1);
 985         if (err != JVMTI_ERROR_NONE) {
 986           return err;
 987         }
 988       }
 989     }
 990   }
 991 
 992   // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
 993   JvmtiMonitorClosure jmc(calling_thread, owned_monitors_list, this);
 994   ObjectSynchronizer::owned_monitors_iterate(&jmc, java_thread);
 995   err = jmc.error();
 996 
 997   return err;
 998 }
 999 
1000 jvmtiError
1001 JvmtiEnvBase::get_owned_monitors(JavaThread* calling_thread, JavaThread* java_thread, javaVFrame* jvf,
1002                                  GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
1003   jvmtiError err = JVMTI_ERROR_NONE;
1004   Thread *current_thread = Thread::current();
1005   assert(java_thread->is_handshake_safe_for(current_thread),
1006          "call by myself or at handshake");
1007 
1008   int depth = 0;
1009   for ( ; jvf != nullptr; jvf = jvf->java_sender()) {
1010     if (MaxJavaStackTraceDepth == 0 || depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
1011       // Add locked objects for this frame into list.
1012       err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth - 1);
1013       if (err != JVMTI_ERROR_NONE) {
1014         return err;
1015       }
1016     }
1017   }
1018 
1019   // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
1020   JvmtiMonitorClosure jmc(calling_thread, owned_monitors_list, this);
1021   ObjectSynchronizer::owned_monitors_iterate(&jmc, java_thread);
1022   err = jmc.error();
1023 
1024   return err;
1025 }
1026 
1027 // Save JNI local handles for any objects that this frame owns.
1028 jvmtiError
1029 JvmtiEnvBase::get_locked_objects_in_frame(JavaThread* calling_thread, JavaThread* java_thread,
1030                                  javaVFrame *jvf, GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list, jint stack_depth) {
1031   jvmtiError err = JVMTI_ERROR_NONE;
1032   Thread* current_thread = Thread::current();
1033   ResourceMark rm(current_thread);
1034   HandleMark   hm(current_thread);
1035 
1036   GrowableArray<MonitorInfo*>* mons = jvf->monitors();
1037   if (mons->is_empty()) {
1038     return err;  // this javaVFrame holds no monitors
1039   }
1040 
1041   oop wait_obj = nullptr;
1042   {
1043     // The ObjectMonitor* can't be async deflated since we are either
1044     // at a safepoint or the calling thread is operating on itself so
1045     // it cannot leave the underlying wait() call.
1046     // Save object of current wait() call (if any) for later comparison.
1047     ObjectMonitor *mon = java_thread->current_waiting_monitor();
1048     if (mon != nullptr) {
1049       wait_obj = mon->object();
1050     }
1051   }
1052   oop pending_obj = nullptr;
1053   {
1054     // The ObjectMonitor* can't be async deflated since we are either
1055     // at a safepoint or the calling thread is operating on itself so
1056     // it cannot leave the underlying enter() call.
1057     // Save object of current enter() call (if any) for later comparison.
1058     ObjectMonitor *mon = java_thread->current_pending_monitor();
1059     if (mon != nullptr) {
1060       pending_obj = mon->object();
1061     }
1062   }
1063 
1064   for (int i = 0; i < mons->length(); i++) {
1065     MonitorInfo *mi = mons->at(i);
1066 
1067     if (mi->owner_is_scalar_replaced()) continue;
1068 
1069     oop obj = mi->owner();
1070     if (obj == nullptr) {
1071       // this monitor doesn't have an owning object so skip it
1072       continue;
1073     }
1074 
1075     if (wait_obj == obj) {
1076       // the thread is waiting on this monitor so it isn't really owned
1077       continue;
1078     }
1079 
1080     if (pending_obj == obj) {
1081       // the thread is pending on this monitor so it isn't really owned
1082       continue;
1083     }
1084 
1085     if (owned_monitors_list->length() > 0) {
1086       // Our list has at least one object on it so we have to check
1087       // for recursive object locking
1088       bool found = false;
1089       for (int j = 0; j < owned_monitors_list->length(); j++) {
1090         jobject jobj = ((jvmtiMonitorStackDepthInfo*)owned_monitors_list->at(j))->monitor;
1091         oop check = JNIHandles::resolve(jobj);
1092         if (check == obj) {
1093           found = true;  // we found the object
1094           break;
1095         }
1096       }
1097 
1098       if (found) {
1099         // already have this object so don't include it
1100         continue;
1101       }
1102     }
1103 
1104     // add the owning object to our list
1105     jvmtiMonitorStackDepthInfo *jmsdi;
1106     err = allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
1107     if (err != JVMTI_ERROR_NONE) {
1108         return err;
1109     }
1110     Handle hobj(Thread::current(), obj);
1111     jmsdi->monitor = jni_reference(calling_thread, hobj);
1112     jmsdi->stack_depth = stack_depth;
1113     owned_monitors_list->append(jmsdi);
1114   }
1115 
1116   return err;
1117 }
1118 
1119 jvmtiError
1120 JvmtiEnvBase::get_stack_trace(javaVFrame *jvf,
1121                               jint start_depth, jint max_count,
1122                               jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
1123   Thread *current_thread = Thread::current();
1124   ResourceMark rm(current_thread);
1125   HandleMark hm(current_thread);
1126   int count = 0;
1127 
1128   if (start_depth != 0) {
1129     if (start_depth > 0) {
1130       for (int j = 0; j < start_depth && jvf != nullptr; j++) {
1131         jvf = jvf->java_sender();
1132       }
1133       if (jvf == nullptr) {
1134         // start_depth is deeper than the stack depth.
1135         return JVMTI_ERROR_ILLEGAL_ARGUMENT;
1136       }
1137     } else { // start_depth < 0
1138       // We are referencing the starting depth based on the oldest
1139       // part of the stack.
1140       // Optimize to limit the number of times that java_sender() is called.
1141       javaVFrame *jvf_cursor = jvf;
1142       javaVFrame *jvf_prev = nullptr;
1143       javaVFrame *jvf_prev_prev = nullptr;
1144       int j = 0;
1145       while (jvf_cursor != nullptr) {
1146         jvf_prev_prev = jvf_prev;
1147         jvf_prev = jvf_cursor;
1148         for (j = 0; j > start_depth && jvf_cursor != nullptr; j--) {
1149           jvf_cursor = jvf_cursor->java_sender();
1150         }
1151       }
1152       if (j == start_depth) {
1153         // Previous pointer is exactly where we want to start.
1154         jvf = jvf_prev;
1155       } else {
1156         // We need to back up further to get to the right place.
1157         if (jvf_prev_prev == nullptr) {
1158           // The -start_depth is greater than the stack depth.
1159           return JVMTI_ERROR_ILLEGAL_ARGUMENT;
1160         }
1161         // j is now the number of frames on the stack starting with
1162         // jvf_prev, we start from jvf_prev_prev and move older on
1163         // the stack that many, and the result is -start_depth frames
1164         // remaining.
1165         jvf = jvf_prev_prev;
1166         for (; j < 0; j++) {
1167           jvf = jvf->java_sender();
1168         }
1169       }
1170     }
1171   }
1172   for (; count < max_count && jvf != nullptr; count++) {
1173     frame_buffer[count].method = jvf->method()->jmethod_id();
1174     frame_buffer[count].location = (jvf->method()->is_native() ? -1 : jvf->bci());
1175     jvf = jvf->java_sender();
1176   }
1177   *count_ptr = count;
1178   return JVMTI_ERROR_NONE;
1179 }
1180 
1181 jvmtiError
1182 JvmtiEnvBase::get_stack_trace(JavaThread *java_thread,
1183                               jint start_depth, jint max_count,
1184                               jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
1185   Thread *current_thread = Thread::current();
1186   assert(SafepointSynchronize::is_at_safepoint() ||
1187          java_thread->is_handshake_safe_for(current_thread),
1188          "call by myself / at safepoint / at handshake");
1189   int count = 0;
1190   jvmtiError err = JVMTI_ERROR_NONE;
1191 
1192   if (java_thread->has_last_Java_frame()) {
1193     RegisterMap reg_map(java_thread,
1194                         RegisterMap::UpdateMap::include,
1195                         RegisterMap::ProcessFrames::skip,
1196                         RegisterMap::WalkContinuation::skip);
1197     ResourceMark rm(current_thread);
1198     javaVFrame *jvf = get_cthread_last_java_vframe(java_thread, &reg_map);
1199 
1200     err = get_stack_trace(jvf, start_depth, max_count, frame_buffer, count_ptr);
1201   } else {
1202     *count_ptr = 0;
1203     if (start_depth != 0) {
1204       // no frames and there is a starting depth
1205       err = JVMTI_ERROR_ILLEGAL_ARGUMENT;
1206     }
1207   }
1208   return err;
1209 }
1210 
1211 jint
1212 JvmtiEnvBase::get_frame_count(javaVFrame *jvf) {
1213   int count = 0;
1214 
1215   while (jvf != nullptr) {
1216     jvf = jvf->java_sender();
1217     count++;
1218   }
1219   return count;
1220 }
1221 
1222 jvmtiError
1223 JvmtiEnvBase::get_frame_count(JavaThread* jt, jint *count_ptr) {
1224   Thread *current_thread = Thread::current();
1225   assert(current_thread == jt ||
1226          SafepointSynchronize::is_at_safepoint() ||
1227          jt->is_handshake_safe_for(current_thread),
1228          "call by myself / at safepoint / at handshake");
1229 
1230   if (!jt->has_last_Java_frame()) { // no Java frames
1231     *count_ptr = 0;
1232   } else {
1233     ResourceMark rm(current_thread);
1234     RegisterMap reg_map(jt,
1235                         RegisterMap::UpdateMap::include,
1236                         RegisterMap::ProcessFrames::include,
1237                         RegisterMap::WalkContinuation::skip);
1238     javaVFrame *jvf = get_cthread_last_java_vframe(jt, &reg_map);
1239 
1240     *count_ptr = get_frame_count(jvf);
1241   }
1242   return JVMTI_ERROR_NONE;
1243 }
1244 
1245 jvmtiError
1246 JvmtiEnvBase::get_frame_count(oop vthread_oop, jint *count_ptr) {
1247   Thread *current_thread = Thread::current();
1248   ResourceMark rm(current_thread);
1249   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(vthread_oop);
1250 
1251   *count_ptr = get_frame_count(jvf);
1252   return JVMTI_ERROR_NONE;
1253 }
1254 
1255 jvmtiError
1256 JvmtiEnvBase::get_frame_location(javaVFrame* jvf, jint depth,
1257                                  jmethodID* method_ptr, jlocation* location_ptr) {
1258   int cur_depth = 0;
1259 
1260   while (jvf != nullptr && cur_depth < depth) {
1261     jvf = jvf->java_sender();
1262     cur_depth++;
1263   }
1264   assert(depth >= cur_depth, "ran out of frames too soon");
1265   if (jvf == nullptr) {
1266     return JVMTI_ERROR_NO_MORE_FRAMES;
1267   }
1268   Method* method = jvf->method();
1269   if (method->is_native()) {
1270     *location_ptr = -1;
1271   } else {
1272     *location_ptr = jvf->bci();
1273   }
1274   *method_ptr = method->jmethod_id();
1275   return JVMTI_ERROR_NONE;
1276 }
1277 
1278 jvmtiError
1279 JvmtiEnvBase::get_frame_location(JavaThread *java_thread, jint depth,
1280                                  jmethodID* method_ptr, jlocation* location_ptr) {
1281   Thread* current = Thread::current();
1282   assert(java_thread->is_handshake_safe_for(current),
1283          "call by myself or at handshake");
1284   if (!java_thread->has_last_Java_frame()) {
1285     return JVMTI_ERROR_NO_MORE_FRAMES;
1286   }
1287   ResourceMark rm(current);
1288   HandleMark hm(current);
1289   RegisterMap reg_map(java_thread,
1290                       RegisterMap::UpdateMap::include,
1291                       RegisterMap::ProcessFrames::skip,
1292                       RegisterMap::WalkContinuation::include);
1293   javaVFrame* jvf = JvmtiEnvBase::get_cthread_last_java_vframe(java_thread, &reg_map);
1294 
1295   return get_frame_location(jvf, depth, method_ptr, location_ptr);
1296 }
1297 
1298 jvmtiError
1299 JvmtiEnvBase::get_frame_location(oop vthread_oop, jint depth,
1300                                  jmethodID* method_ptr, jlocation* location_ptr) {
1301   Thread* current = Thread::current();
1302   ResourceMark rm(current);
1303   HandleMark hm(current);
1304   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(vthread_oop);
1305 
1306   return get_frame_location(jvf, depth, method_ptr, location_ptr);
1307 }
1308 
1309 jvmtiError
1310 JvmtiEnvBase::set_frame_pop(JvmtiThreadState* state, javaVFrame* jvf, jint depth) {
1311   for (int d = 0; jvf != nullptr && d < depth; d++) {
1312     jvf = jvf->java_sender();
1313   }
1314   if (jvf == nullptr) {
1315     return JVMTI_ERROR_NO_MORE_FRAMES;
1316   }
1317   if (jvf->method()->is_native()) {
1318     return JVMTI_ERROR_OPAQUE_FRAME;
1319   }
1320   assert(jvf->frame_pointer() != nullptr, "frame pointer mustn't be null");
1321   int frame_number = (int)get_frame_count(jvf);
1322   state->env_thread_state((JvmtiEnvBase*)this)->set_frame_pop(frame_number);
1323   return JVMTI_ERROR_NONE;
1324 }
1325 
1326 bool
1327 JvmtiEnvBase::is_cthread_with_mounted_vthread(JavaThread* jt) {
1328   oop thread_oop = jt->threadObj();
1329   assert(thread_oop != nullptr, "sanity check");
1330   oop mounted_vt = jt->jvmti_vthread();
1331 
1332   return mounted_vt != nullptr && mounted_vt != thread_oop;
1333 }
1334 
1335 bool
1336 JvmtiEnvBase::is_cthread_with_continuation(JavaThread* jt) {
1337   const ContinuationEntry* cont_entry = nullptr;
1338   if (jt->has_last_Java_frame()) {
1339     cont_entry = jt->vthread_continuation();
1340   }
1341   return cont_entry != nullptr && is_cthread_with_mounted_vthread(jt);
1342 }
1343 
1344 // Check if VirtualThread or BoundVirtualThread is suspended.
1345 bool
1346 JvmtiEnvBase::is_vthread_suspended(oop vt_oop, JavaThread* jt) {
1347   bool suspended = false;
1348   if (java_lang_VirtualThread::is_instance(vt_oop)) {
1349     suspended = JvmtiVTSuspender::is_vthread_suspended(vt_oop);
1350   }
1351   if (vt_oop->is_a(vmClasses::BoundVirtualThread_klass())) {
1352     suspended = jt->is_suspended();
1353   }
1354   return suspended;
1355 }
1356 
1357 // If (thread == null) then return current thread object.
1358 // Otherwise return JNIHandles::resolve_external_guard(thread).
1359 oop
1360 JvmtiEnvBase::current_thread_obj_or_resolve_external_guard(jthread thread) {
1361   oop thread_obj = JNIHandles::resolve_external_guard(thread);
1362   if (thread == nullptr) {
1363     thread_obj = get_vthread_or_thread_oop(JavaThread::current());
1364   }
1365   return thread_obj;
1366 }
1367 
1368 jvmtiError
1369 JvmtiEnvBase::get_threadOop_and_JavaThread(ThreadsList* t_list, jthread thread, JavaThread* cur_thread,
1370                                            JavaThread** jt_pp, oop* thread_oop_p) {
1371   JavaThread* java_thread = nullptr;
1372   oop thread_oop = nullptr;
1373 
1374   if (thread == nullptr) {
1375     if (cur_thread == nullptr) { // cur_thread can be null when called from a VM_op
1376       return JVMTI_ERROR_INVALID_THREAD;
1377     }
1378     java_thread = cur_thread;
1379     thread_oop = get_vthread_or_thread_oop(java_thread);
1380     if (thread_oop == nullptr || !thread_oop->is_a(vmClasses::Thread_klass())) {
1381       return JVMTI_ERROR_INVALID_THREAD;
1382     }
1383   } else {
1384     jvmtiError err = JvmtiExport::cv_external_thread_to_JavaThread(t_list, thread, &java_thread, &thread_oop);
1385     if (err != JVMTI_ERROR_NONE) {
1386       // We got an error code so we don't have a JavaThread*, but only return
1387       // an error from here if we didn't get a valid thread_oop. In a vthread case
1388       // the cv_external_thread_to_JavaThread is expected to correctly set the
1389       // thread_oop and return JVMTI_ERROR_INVALID_THREAD which we ignore here.
1390       if (thread_oop == nullptr || err != JVMTI_ERROR_INVALID_THREAD) {
1391         *thread_oop_p = thread_oop;
1392         return err;
1393       }
1394     }
1395     if (java_thread == nullptr && java_lang_VirtualThread::is_instance(thread_oop)) {
1396       java_thread = get_JavaThread_or_null(thread_oop);
1397     }
1398   }
1399   *jt_pp = java_thread;
1400   *thread_oop_p = thread_oop;
1401   if (java_lang_VirtualThread::is_instance(thread_oop) &&
1402       !JvmtiEnvBase::is_vthread_alive(thread_oop)) {
1403     return JVMTI_ERROR_THREAD_NOT_ALIVE;
1404   }
1405   return JVMTI_ERROR_NONE;
1406 }
1407 
1408 jvmtiError
1409 JvmtiEnvBase::get_threadOop_and_JavaThread(ThreadsList* t_list, jthread thread,
1410                                            JavaThread** jt_pp, oop* thread_oop_p) {
1411   JavaThread* cur_thread = JavaThread::current();
1412   jvmtiError err = get_threadOop_and_JavaThread(t_list, thread, cur_thread, jt_pp, thread_oop_p);
1413   return err;
1414 }
1415 
1416 // Check for JVMTI_ERROR_NOT_SUSPENDED and JVMTI_ERROR_OPAQUE_FRAME errors.
1417 // Used in PopFrame and ForceEarlyReturn implementations.
1418 jvmtiError
1419 JvmtiEnvBase::check_non_suspended_or_opaque_frame(JavaThread* jt, oop thr_obj, bool self) {
1420   bool is_virtual = thr_obj != nullptr && thr_obj->is_a(vmClasses::BaseVirtualThread_klass());
1421 
1422   if (is_virtual) {
1423     if (!is_JavaThread_current(jt, thr_obj)) {
1424       if (!is_vthread_suspended(thr_obj, jt)) {
1425         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1426       }
1427       if (jt == nullptr) { // unmounted virtual thread
1428         return JVMTI_ERROR_OPAQUE_FRAME;
1429       }
1430     }
1431   } else { // platform thread
1432     if (!self && !jt->is_suspended() &&
1433         !jt->is_carrier_thread_suspended()) {
1434       return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1435     }
1436   }
1437   return JVMTI_ERROR_NONE;
1438 }
1439 
1440 jvmtiError
1441 JvmtiEnvBase::get_object_monitor_usage(JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
1442   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
1443   Thread* current_thread = VMThread::vm_thread();
1444   assert(current_thread == Thread::current(), "must be");
1445 
1446   HandleMark hm(current_thread);
1447   Handle hobj;
1448 
1449   // Check arguments
1450   {
1451     oop mirror = JNIHandles::resolve_external_guard(object);
1452     NULL_CHECK(mirror, JVMTI_ERROR_INVALID_OBJECT);
1453     NULL_CHECK(info_ptr, JVMTI_ERROR_NULL_POINTER);
1454 
1455     hobj = Handle(current_thread, mirror);
1456   }
1457 
1458   ThreadsListHandle tlh(current_thread);
1459   JavaThread *owning_thread = nullptr;
1460   ObjectMonitor *mon = nullptr;
1461   jvmtiMonitorUsage ret = {
1462       nullptr, 0, 0, nullptr, 0, nullptr
1463   };
1464 
1465   uint32_t debug_bits = 0;
1466   // first derive the object's owner and entry_count (if any)
1467   owning_thread = ObjectSynchronizer::get_lock_owner(tlh.list(), hobj);
1468   if (owning_thread != nullptr) {
1469     Handle th(current_thread, get_vthread_or_thread_oop(owning_thread));
1470     ret.owner = (jthread)jni_reference(calling_thread, th);
1471 
1472     // The recursions field of a monitor does not reflect recursions
1473     // as lightweight locks before inflating the monitor are not included.
1474     // We have to count the number of recursive monitor entries the hard way.
1475     // We pass a handle to survive any GCs along the way.
1476     ret.entry_count = count_locked_objects(owning_thread, hobj);
1477   }
1478   // implied else: entry_count == 0
1479 
1480   jint nWant = 0, nWait = 0;
1481   markWord mark = hobj->mark();
1482   if (mark.has_monitor()) {
1483     mon = mark.monitor();
1484     assert(mon != nullptr, "must have monitor");
1485     // this object has a heavyweight monitor
1486     nWant = mon->contentions(); // # of threads contending for monitor
1487     nWait = mon->waiters();     // # of threads in Object.wait()
1488     ret.waiter_count = nWant + nWait;
1489     ret.notify_waiter_count = nWait;
1490   } else {
1491     // this object has a lightweight monitor
1492     ret.waiter_count = 0;
1493     ret.notify_waiter_count = 0;
1494   }
1495 
1496   // Allocate memory for heavyweight and lightweight monitor.
1497   jvmtiError err;
1498   err = allocate(ret.waiter_count * sizeof(jthread *), (unsigned char**)&ret.waiters);
1499   if (err != JVMTI_ERROR_NONE) {
1500     return err;
1501   }
1502   err = allocate(ret.notify_waiter_count * sizeof(jthread *),
1503                  (unsigned char**)&ret.notify_waiters);
1504   if (err != JVMTI_ERROR_NONE) {
1505     deallocate((unsigned char*)ret.waiters);
1506     return err;
1507   }
1508 
1509   // now derive the rest of the fields
1510   if (mon != nullptr) {
1511     // this object has a heavyweight monitor
1512 
1513     // Number of waiters may actually be less than the waiter count.
1514     // So null out memory so that unused memory will be null.
1515     memset(ret.waiters, 0, ret.waiter_count * sizeof(jthread *));
1516     memset(ret.notify_waiters, 0, ret.notify_waiter_count * sizeof(jthread *));
1517 
1518     if (ret.waiter_count > 0) {
1519       // we have contending and/or waiting threads
1520       if (nWant > 0) {
1521         // we have contending threads
1522         ResourceMark rm(current_thread);
1523         // get_pending_threads returns only java thread so we do not need to
1524         // check for non java threads.
1525         GrowableArray<JavaThread*>* wantList = Threads::get_pending_threads(tlh.list(), nWant, (address)mon);
1526         if (wantList->length() < nWant) {
1527           // robustness: the pending list has gotten smaller
1528           nWant = wantList->length();
1529         }
1530         for (int i = 0; i < nWant; i++) {
1531           JavaThread *pending_thread = wantList->at(i);
1532           Handle th(current_thread, get_vthread_or_thread_oop(pending_thread));
1533           ret.waiters[i] = (jthread)jni_reference(calling_thread, th);
1534         }
1535       }
1536       if (nWait > 0) {
1537         // we have threads in Object.wait()
1538         int offset = nWant;  // add after any contending threads
1539         ObjectWaiter *waiter = mon->first_waiter();
1540         for (int i = 0, j = 0; i < nWait; i++) {
1541           if (waiter == nullptr) {
1542             // robustness: the waiting list has gotten smaller
1543             nWait = j;
1544             break;
1545           }
1546           JavaThread *w = mon->thread_of_waiter(waiter);
1547           if (w != nullptr) {
1548             // If the thread was found on the ObjectWaiter list, then
1549             // it has not been notified. This thread can't change the
1550             // state of the monitor so it doesn't need to be suspended.
1551             Handle th(current_thread, get_vthread_or_thread_oop(w));
1552             ret.waiters[offset + j] = (jthread)jni_reference(calling_thread, th);
1553             ret.notify_waiters[j++] = (jthread)jni_reference(calling_thread, th);
1554           }
1555           waiter = mon->next_waiter(waiter);
1556         }
1557       }
1558     } // ThreadsListHandle is destroyed here.
1559 
1560     // Adjust count. nWant and nWait count values may be less than original.
1561     ret.waiter_count = nWant + nWait;
1562     ret.notify_waiter_count = nWait;
1563   } else {
1564     // this object has a lightweight monitor and we have nothing more
1565     // to do here because the defaults are just fine.
1566   }
1567 
1568   // we don't update return parameter unless everything worked
1569   *info_ptr = ret;
1570 
1571   return JVMTI_ERROR_NONE;
1572 }
1573 
1574 jvmtiError
1575 JvmtiEnvBase::check_thread_list(jint count, const jthread* list) {
1576   if (list == nullptr && count != 0) {
1577     return JVMTI_ERROR_NULL_POINTER;
1578   }
1579   for (int i = 0; i < count; i++) {
1580     jthread thread = list[i];
1581     oop thread_oop = JNIHandles::resolve_external_guard(thread);
1582     if (thread_oop == nullptr || !thread_oop->is_a(vmClasses::BaseVirtualThread_klass())) {
1583       return JVMTI_ERROR_INVALID_THREAD;
1584     }
1585   }
1586   return JVMTI_ERROR_NONE;
1587 }
1588 
1589 bool
1590 JvmtiEnvBase::is_in_thread_list(jint count, const jthread* list, oop jt_oop) {
1591   for (int idx = 0; idx < count; idx++) {
1592     jthread thread = list[idx];
1593     oop thread_oop = JNIHandles::resolve_external_guard(thread);
1594     if (thread_oop == jt_oop) {
1595       return true;
1596     }
1597   }
1598   return false;
1599 }
1600 
1601 class VM_SetNotifyJvmtiEventsMode : public VM_Operation {
1602 private:
1603   bool _enable;
1604 
1605   static void correct_jvmti_thread_state(JavaThread* jt) {
1606     oop  ct_oop = jt->threadObj();
1607     oop  vt_oop = jt->vthread();
1608     JvmtiThreadState* jt_state = jt->jvmti_thread_state();
1609     JvmtiThreadState* ct_state = java_lang_Thread::jvmti_thread_state(jt->threadObj());
1610     JvmtiThreadState* vt_state = vt_oop != nullptr ? java_lang_Thread::jvmti_thread_state(vt_oop) : nullptr;
1611     bool virt = vt_oop != nullptr && java_lang_VirtualThread::is_instance(vt_oop);
1612 
1613     // Correct jt->jvmti_thread_state() and jt->jvmti_vthread().
1614     // It was not maintained while notifyJvmti was disabled.
1615     if (virt) {
1616       jt->set_jvmti_thread_state(nullptr);  // reset jt->jvmti_thread_state()
1617       jt->set_jvmti_vthread(vt_oop);        // restore jt->jvmti_vthread()
1618     } else {
1619       jt->set_jvmti_thread_state(ct_state); // restore jt->jvmti_thread_state()
1620       jt->set_jvmti_vthread(ct_oop);        // restore jt->jvmti_vthread()
1621     }
1622   }
1623 
1624   // This function is called only if _enable == true.
1625   // Iterates over all JavaThread's, counts VTMS transitions and restores
1626   // jt->jvmti_thread_state() and jt->jvmti_vthread() for VTMS transition protocol.
1627   int count_transitions_and_correct_jvmti_thread_states() {
1628     int count = 0;
1629 
1630     for (JavaThread* jt : ThreadsListHandle()) {
1631       if (jt->is_in_VTMS_transition()) {
1632         count++;
1633         continue; // no need in JvmtiThreadState correction below if in transition
1634       }
1635       correct_jvmti_thread_state(jt);
1636     }
1637     return count;
1638   }
1639 
1640 public:
1641   VMOp_Type type() const { return VMOp_SetNotifyJvmtiEventsMode; }
1642   bool allow_nested_vm_operations() const { return false; }
1643   VM_SetNotifyJvmtiEventsMode(bool enable) : _enable(enable) {
1644   }
1645 
1646   void doit() {
1647     int count = _enable ? count_transitions_and_correct_jvmti_thread_states() : 0;
1648 
1649     JvmtiVTMSTransitionDisabler::set_VTMS_transition_count(count);
1650     JvmtiVTMSTransitionDisabler::set_VTMS_notify_jvmti_events(_enable);
1651   }
1652 };
1653 
1654 // This function is to support agents loaded into running VM.
1655 // Must be called in thread-in-native mode.
1656 bool
1657 JvmtiEnvBase::enable_virtual_threads_notify_jvmti() {
1658   if (!Continuations::enabled()) {
1659     return false;
1660   }
1661   if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
1662     return false; // already enabled
1663   }
1664   VM_SetNotifyJvmtiEventsMode op(true);
1665   VMThread::execute(&op);
1666   return true;
1667 }
1668 
1669 // This function is used in WhiteBox, only needed to test the function above.
1670 // It is unsafe to use this function when virtual threads are executed.
1671 // Must be called in thread-in-native mode.
1672 bool
1673 JvmtiEnvBase::disable_virtual_threads_notify_jvmti() {
1674   if (!Continuations::enabled()) {
1675     return false;
1676   }
1677   if (!JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
1678     return false; // already disabled
1679   }
1680   JvmtiVTMSTransitionDisabler disabler(true); // ensure there are no other disablers
1681   VM_SetNotifyJvmtiEventsMode op(false);
1682   VMThread::execute(&op);
1683   return true;
1684 }
1685 
1686 // java_thread - protected by ThreadsListHandle
1687 jvmtiError
1688 JvmtiEnvBase::suspend_thread(oop thread_oop, JavaThread* java_thread, bool single_suspend,
1689                              int* need_safepoint_p) {
1690   JavaThread* current = JavaThread::current();
1691   HandleMark hm(current);
1692   Handle thread_h(current, thread_oop);
1693   bool is_virtual = java_lang_VirtualThread::is_instance(thread_h());
1694 
1695   if (is_virtual) {
1696     if (single_suspend) {
1697       if (JvmtiVTSuspender::is_vthread_suspended(thread_h())) {
1698         return JVMTI_ERROR_THREAD_SUSPENDED;
1699       }
1700       JvmtiVTSuspender::register_vthread_suspend(thread_h());
1701       // Check if virtual thread is mounted and there is a java_thread.
1702       // A non-null java_thread is always passed in the !single_suspend case.
1703       oop carrier_thread = java_lang_VirtualThread::carrier_thread(thread_h());
1704       java_thread = carrier_thread == nullptr ? nullptr : java_lang_Thread::thread(carrier_thread);
1705     }
1706     // The java_thread can be still blocked in VTMS transition after a previous JVMTI resume call.
1707     // There is no need to suspend the java_thread in this case. After vthread unblocking,
1708     // it will check for ext_suspend request and suspend itself if necessary.
1709     if (java_thread == nullptr || java_thread->is_suspended()) {
1710       // We are done if the virtual thread is unmounted or
1711       // the java_thread is externally suspended.
1712       return JVMTI_ERROR_NONE;
1713     }
1714     // The virtual thread is mounted: suspend the java_thread.
1715   }
1716   // Don't allow hidden thread suspend request.
1717   if (java_thread->is_hidden_from_external_view()) {
1718     return JVMTI_ERROR_NONE;
1719   }
1720   bool is_thread_carrying = is_thread_carrying_vthread(java_thread, thread_h());
1721 
1722   // A case of non-virtual thread.
1723   if (!is_virtual) {
1724     // Thread.suspend() is used in some tests. It sets jt->is_suspended() only.
1725     if (java_thread->is_carrier_thread_suspended() ||
1726         (!is_thread_carrying && java_thread->is_suspended())) {
1727       return JVMTI_ERROR_THREAD_SUSPENDED;
1728     }
1729     java_thread->set_carrier_thread_suspended();
1730   }
1731   assert(!java_thread->is_in_VTMS_transition(), "sanity check");
1732 
1733   assert(!single_suspend || (!is_virtual && java_thread->is_carrier_thread_suspended()) ||
1734           (is_virtual && JvmtiVTSuspender::is_vthread_suspended(thread_h())),
1735          "sanity check");
1736 
1737   // An attempt to handshake-suspend a thread carrying a virtual thread will result in
1738   // suspension of mounted virtual thread. So, we just mark it as suspended
1739   // and it will be actually suspended at virtual thread unmount transition.
1740   if (!is_thread_carrying) {
1741     assert(thread_h() != nullptr, "sanity check");
1742     assert(single_suspend || thread_h()->is_a(vmClasses::BaseVirtualThread_klass()),
1743            "SuspendAllVirtualThreads should never suspend non-virtual threads");
1744     // Case of mounted virtual or attached carrier thread.
1745     if (!JvmtiSuspendControl::suspend(java_thread)) {
1746       // Thread is already suspended or in process of exiting.
1747       if (java_thread->is_exiting()) {
1748         // The thread was in the process of exiting.
1749         return JVMTI_ERROR_THREAD_NOT_ALIVE;
1750       }
1751       return JVMTI_ERROR_THREAD_SUSPENDED;
1752     }
1753   }
1754   return JVMTI_ERROR_NONE;
1755 }
1756 
1757 // java_thread - protected by ThreadsListHandle
1758 jvmtiError
1759 JvmtiEnvBase::resume_thread(oop thread_oop, JavaThread* java_thread, bool single_resume) {
1760   JavaThread* current = JavaThread::current();
1761   HandleMark hm(current);
1762   Handle thread_h(current, thread_oop);
1763   bool is_virtual = java_lang_VirtualThread::is_instance(thread_h());
1764 
1765   if (is_virtual) {
1766     if (single_resume) {
1767       if (!JvmtiVTSuspender::is_vthread_suspended(thread_h())) {
1768         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1769       }
1770       JvmtiVTSuspender::register_vthread_resume(thread_h());
1771       // Check if virtual thread is mounted and there is a java_thread.
1772       // A non-null java_thread is always passed in the !single_resume case.
1773       oop carrier_thread = java_lang_VirtualThread::carrier_thread(thread_h());
1774       java_thread = carrier_thread == nullptr ? nullptr : java_lang_Thread::thread(carrier_thread);
1775     }
1776     // The java_thread can be still blocked in VTMS transition after a previous JVMTI suspend call.
1777     // There is no need to resume the java_thread in this case. After vthread unblocking,
1778     // it will check for is_vthread_suspended request and remain resumed if necessary.
1779     if (java_thread == nullptr || !java_thread->is_suspended()) {
1780       // We are done if the virtual thread is unmounted or
1781       // the java_thread is not externally suspended.
1782       return JVMTI_ERROR_NONE;
1783     }
1784     // The virtual thread is mounted and java_thread is supended: resume the java_thread.
1785   }
1786   // Don't allow hidden thread resume request.
1787   if (java_thread->is_hidden_from_external_view()) {
1788     return JVMTI_ERROR_NONE;
1789   }
1790   bool is_thread_carrying = is_thread_carrying_vthread(java_thread, thread_h());
1791 
1792   // A case of a non-virtual thread.
1793   if (!is_virtual) {
1794     if (!java_thread->is_carrier_thread_suspended() &&
1795         (is_thread_carrying || !java_thread->is_suspended())) {
1796       return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1797     }
1798     java_thread->clear_carrier_thread_suspended();
1799   }
1800   assert(!java_thread->is_in_VTMS_transition(), "sanity check");
1801 
1802   if (!is_thread_carrying) {
1803     assert(thread_h() != nullptr, "sanity check");
1804     assert(single_resume || thread_h()->is_a(vmClasses::BaseVirtualThread_klass()),
1805            "ResumeAllVirtualThreads should never resume non-virtual threads");
1806     if (java_thread->is_suspended()) {
1807       if (!JvmtiSuspendControl::resume(java_thread)) {
1808         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1809       }
1810     }
1811   }
1812   return JVMTI_ERROR_NONE;
1813 }
1814 
1815 ResourceTracker::ResourceTracker(JvmtiEnv* env) {
1816   _env = env;
1817   _allocations = new (mtServiceability) GrowableArray<unsigned char*>(20, mtServiceability);
1818   _failed = false;
1819 }
1820 ResourceTracker::~ResourceTracker() {
1821   if (_failed) {
1822     for (int i=0; i<_allocations->length(); i++) {
1823       _env->deallocate(_allocations->at(i));
1824     }
1825   }
1826   delete _allocations;
1827 }
1828 
1829 jvmtiError ResourceTracker::allocate(jlong size, unsigned char** mem_ptr) {
1830   unsigned char *ptr;
1831   jvmtiError err = _env->allocate(size, &ptr);
1832   if (err == JVMTI_ERROR_NONE) {
1833     _allocations->append(ptr);
1834     *mem_ptr = ptr;
1835   } else {
1836     *mem_ptr = nullptr;
1837     _failed = true;
1838   }
1839   return err;
1840  }
1841 
1842 unsigned char* ResourceTracker::allocate(jlong size) {
1843   unsigned char* ptr;
1844   allocate(size, &ptr);
1845   return ptr;
1846 }
1847 
1848 char* ResourceTracker::strdup(const char* str) {
1849   char *dup_str = (char*)allocate(strlen(str)+1);
1850   if (dup_str != nullptr) {
1851     strcpy(dup_str, str);
1852   }
1853   return dup_str;
1854 }
1855 
1856 struct StackInfoNode {
1857   struct StackInfoNode *next;
1858   jvmtiStackInfo info;
1859 };
1860 
1861 // Create a jvmtiStackInfo inside a linked list node and create a
1862 // buffer for the frame information, both allocated as resource objects.
1863 // Fill in both the jvmtiStackInfo and the jvmtiFrameInfo.
1864 // Note that either or both of thr and thread_oop
1865 // may be null if the thread is new or has exited.
1866 void
1867 MultipleStackTracesCollector::fill_frames(jthread jt, JavaThread *thr, oop thread_oop) {
1868 #ifdef ASSERT
1869   Thread *current_thread = Thread::current();
1870   assert(SafepointSynchronize::is_at_safepoint() ||
1871          thr == nullptr ||
1872          thr->is_handshake_safe_for(current_thread),
1873          "unmounted virtual thread / call by myself / at safepoint / at handshake");
1874 #endif
1875 
1876   jint state = 0;
1877   struct StackInfoNode *node = NEW_RESOURCE_OBJ(struct StackInfoNode);
1878   jvmtiStackInfo *infop = &(node->info);
1879 
1880   node->next = head();
1881   set_head(node);
1882   infop->frame_count = 0;
1883   infop->frame_buffer = nullptr;
1884   infop->thread = jt;
1885 
1886   if (java_lang_VirtualThread::is_instance(thread_oop)) {
1887     state = JvmtiEnvBase::get_vthread_state(thread_oop, thr);
1888 
1889     if ((state & JVMTI_THREAD_STATE_ALIVE) != 0) {
1890       javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(thread_oop);
1891       infop->frame_buffer = NEW_RESOURCE_ARRAY(jvmtiFrameInfo, max_frame_count());
1892       _result = env()->get_stack_trace(jvf, 0, max_frame_count(),
1893                                        infop->frame_buffer, &(infop->frame_count));
1894     }
1895   } else {
1896     state = JvmtiEnvBase::get_thread_state(thread_oop, thr);
1897     if (thr != nullptr && (state & JVMTI_THREAD_STATE_ALIVE) != 0) {
1898       infop->frame_buffer = NEW_RESOURCE_ARRAY(jvmtiFrameInfo, max_frame_count());
1899       _result = env()->get_stack_trace(thr, 0, max_frame_count(),
1900                                        infop->frame_buffer, &(infop->frame_count));
1901     }
1902   }
1903   _frame_count_total += infop->frame_count;
1904   infop->state = state;
1905 }
1906 
1907 // Based on the stack information in the linked list, allocate memory
1908 // block to return and fill it from the info in the linked list.
1909 void
1910 MultipleStackTracesCollector::allocate_and_fill_stacks(jint thread_count) {
1911   // do I need to worry about alignment issues?
1912   jlong alloc_size =  thread_count       * sizeof(jvmtiStackInfo)
1913                     + _frame_count_total * sizeof(jvmtiFrameInfo);
1914   env()->allocate(alloc_size, (unsigned char **)&_stack_info);
1915 
1916   // pointers to move through the newly allocated space as it is filled in
1917   jvmtiStackInfo *si = _stack_info + thread_count;      // bottom of stack info
1918   jvmtiFrameInfo *fi = (jvmtiFrameInfo *)si;            // is the top of frame info
1919 
1920   // copy information in resource area into allocated buffer
1921   // insert stack info backwards since linked list is backwards
1922   // insert frame info forwards
1923   // walk the StackInfoNodes
1924   for (struct StackInfoNode *sin = head(); sin != nullptr; sin = sin->next) {
1925     jint frame_count = sin->info.frame_count;
1926     size_t frames_size = frame_count * sizeof(jvmtiFrameInfo);
1927     --si;
1928     memcpy(si, &(sin->info), sizeof(jvmtiStackInfo));
1929     if (frames_size == 0) {
1930       si->frame_buffer = nullptr;
1931     } else {
1932       memcpy(fi, sin->info.frame_buffer, frames_size);
1933       si->frame_buffer = fi;  // point to the new allocated copy of the frames
1934       fi += frame_count;
1935     }
1936   }
1937   assert(si == _stack_info, "the last copied stack info must be the first record");
1938   assert((unsigned char *)fi == ((unsigned char *)_stack_info) + alloc_size,
1939          "the last copied frame info must be the last record");
1940 }
1941 
1942 // AdapterClosure is to make use of JvmtiUnitedHandshakeClosure objects from
1943 // Handshake::execute() which is unaware of the do_vthread() member functions.
1944 class AdapterClosure : public HandshakeClosure {
1945   JvmtiUnitedHandshakeClosure* _hs_cl;
1946   Handle _target_h;
1947 
1948  public:
1949   AdapterClosure(JvmtiUnitedHandshakeClosure* hs_cl, Handle target_h)
1950       : HandshakeClosure(hs_cl->name()), _hs_cl(hs_cl), _target_h(target_h) {}
1951 
1952   virtual void do_thread(Thread* target) {
1953     if (java_lang_VirtualThread::is_instance(_target_h())) {
1954       _hs_cl->do_vthread(_target_h); // virtual thread
1955     } else {
1956       _hs_cl->do_thread(target);     // platform thread
1957     }
1958   }
1959 };
1960 
1961 // Supports platform and virtual threads.
1962 // JvmtiVTMSTransitionDisabler is always set by this function.
1963 void
1964 JvmtiHandshake::execute(JvmtiUnitedHandshakeClosure* hs_cl, jthread target) {
1965   JavaThread* current = JavaThread::current();
1966   HandleMark hm(current);
1967 
1968   JvmtiVTMSTransitionDisabler disabler(target);
1969   ThreadsListHandle tlh(current);
1970   JavaThread* java_thread = nullptr;
1971   oop thread_obj = nullptr;
1972 
1973   jvmtiError err = JvmtiEnvBase::get_threadOop_and_JavaThread(tlh.list(), target, &java_thread, &thread_obj);
1974   if (err != JVMTI_ERROR_NONE) {
1975     hs_cl->set_result(err);
1976     return;
1977   }
1978   Handle target_h(current, thread_obj);
1979   execute(hs_cl, &tlh, java_thread, target_h);
1980 }
1981 
1982 // Supports platform and virtual threads.
1983 // A virtual thread is always identified by the target_h oop handle.
1984 // The target_jt is always nullptr for an unmounted virtual thread.
1985 // JvmtiVTMSTransitionDisabler has to be set before call to this function.
1986 void
1987 JvmtiHandshake::execute(JvmtiUnitedHandshakeClosure* hs_cl, ThreadsListHandle* tlh,
1988                         JavaThread* target_jt, Handle target_h) {
1989   bool self = target_jt == JavaThread::current();
1990 
1991   hs_cl->set_self(self);           // needed when suspend is required for non-current target thread
1992 
1993   if (java_lang_VirtualThread::is_instance(target_h())) { // virtual thread
1994     if (!JvmtiEnvBase::is_vthread_alive(target_h())) {
1995       return;
1996     }
1997     if (target_jt == nullptr) {    // unmounted virtual thread
1998       hs_cl->do_vthread(target_h); // execute handshake closure callback on current thread directly
1999     }
2000   }
2001   if (target_jt != nullptr) {      // mounted virtual or platform thread
2002     AdapterClosure acl(hs_cl, target_h);
2003     if (self) {                    // target platform thread is current
2004       acl.do_thread(target_jt);    // execute handshake closure callback on current thread directly
2005     } else {
2006       Handshake::execute(&acl, tlh, target_jt); // delegate to Handshake implementation
2007     }
2008   }
2009 }
2010 
2011 void
2012 VM_GetThreadListStackTraces::doit() {
2013   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
2014 
2015   ResourceMark rm;
2016   ThreadsListHandle tlh;
2017   for (int i = 0; i < _thread_count; ++i) {
2018     jthread jt = _thread_list[i];
2019     JavaThread* java_thread = nullptr;
2020     oop thread_oop = nullptr;
2021     jvmtiError err = JvmtiEnvBase::get_threadOop_and_JavaThread(tlh.list(), jt, nullptr, &java_thread, &thread_oop);
2022 
2023     if (err != JVMTI_ERROR_NONE) {
2024       // We got an error code so we don't have a JavaThread *, but
2025       // only return an error from here if we didn't get a valid
2026       // thread_oop.
2027       // In the virtual thread case the get_threadOop_and_JavaThread is expected to correctly set
2028       // the thread_oop and return JVMTI_ERROR_THREAD_NOT_ALIVE which we ignore here.
2029       // The corresponding thread state will be recorded in the jvmtiStackInfo.state.
2030       if (thread_oop == nullptr) {
2031         _collector.set_result(err);
2032         return;
2033       }
2034       // We have a valid thread_oop.
2035     }
2036     _collector.fill_frames(jt, java_thread, thread_oop);
2037   }
2038   _collector.allocate_and_fill_stacks(_thread_count);
2039 }
2040 
2041 void
2042 GetSingleStackTraceClosure::do_thread(Thread *target) {
2043   JavaThread *jt = JavaThread::cast(target);
2044   oop thread_oop = JNIHandles::resolve_external_guard(_jthread);
2045 
2046   if (!jt->is_exiting() && thread_oop != nullptr) {
2047     ResourceMark rm;
2048     _collector.fill_frames(_jthread, jt, thread_oop);
2049     _collector.allocate_and_fill_stacks(1);
2050   }
2051 }
2052 
2053 void
2054 VM_GetAllStackTraces::doit() {
2055   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
2056 
2057   ResourceMark rm;
2058   _final_thread_count = 0;
2059   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
2060     oop thread_oop = jt->threadObj();
2061     if (thread_oop != nullptr &&
2062         !jt->is_exiting() &&
2063         java_lang_Thread::is_alive(thread_oop) &&
2064         !jt->is_hidden_from_external_view() &&
2065         !thread_oop->is_a(vmClasses::BoundVirtualThread_klass())) {
2066       ++_final_thread_count;
2067       // Handle block of the calling thread is used to create local refs.
2068       _collector.fill_frames((jthread)JNIHandles::make_local(_calling_thread, thread_oop),
2069                              jt, thread_oop);
2070     }
2071   }
2072   _collector.allocate_and_fill_stacks(_final_thread_count);
2073 }
2074 
2075 // Verifies that the top frame is a java frame in an expected state.
2076 // Deoptimizes frame if needed.
2077 // Checks that the frame method signature matches the return type (tos).
2078 // HandleMark must be defined in the caller only.
2079 // It is to keep a ret_ob_h handle alive after return to the caller.
2080 jvmtiError
2081 JvmtiEnvBase::check_top_frame(Thread* current_thread, JavaThread* java_thread,
2082                               jvalue value, TosState tos, Handle* ret_ob_h) {
2083   ResourceMark rm(current_thread);
2084 
2085   javaVFrame* jvf = jvf_for_thread_and_depth(java_thread, 0);
2086   NULL_CHECK(jvf, JVMTI_ERROR_NO_MORE_FRAMES);
2087 
2088   if (jvf->method()->is_native()) {
2089     return JVMTI_ERROR_OPAQUE_FRAME;
2090   }
2091 
2092   // If the frame is a compiled one, need to deoptimize it.
2093   if (jvf->is_compiled_frame()) {
2094     if (!jvf->fr().can_be_deoptimized()) {
2095       return JVMTI_ERROR_OPAQUE_FRAME;
2096     }
2097     Deoptimization::deoptimize_frame(java_thread, jvf->fr().id());
2098   }
2099 
2100   // Get information about method return type
2101   Symbol* signature = jvf->method()->signature();
2102 
2103   ResultTypeFinder rtf(signature);
2104   TosState fr_tos = as_TosState(rtf.type());
2105   if (fr_tos != tos) {
2106     if (tos != itos || (fr_tos != btos && fr_tos != ztos && fr_tos != ctos && fr_tos != stos)) {
2107       return JVMTI_ERROR_TYPE_MISMATCH;
2108     }
2109   }
2110 
2111   // Check that the jobject class matches the return type signature.
2112   jobject jobj = value.l;
2113   if (tos == atos && jobj != nullptr) { // null reference is allowed
2114     Handle ob_h(current_thread, JNIHandles::resolve_external_guard(jobj));
2115     NULL_CHECK(ob_h, JVMTI_ERROR_INVALID_OBJECT);
2116     Klass* ob_k = ob_h()->klass();
2117     NULL_CHECK(ob_k, JVMTI_ERROR_INVALID_OBJECT);
2118 
2119     // Method return type signature.
2120     char* ty_sign = 1 + strchr(signature->as_C_string(), JVM_SIGNATURE_ENDFUNC);
2121 
2122     if (!VM_GetOrSetLocal::is_assignable(ty_sign, ob_k, current_thread)) {
2123       return JVMTI_ERROR_TYPE_MISMATCH;
2124     }
2125     *ret_ob_h = ob_h;
2126   }
2127   return JVMTI_ERROR_NONE;
2128 } /* end check_top_frame */
2129 
2130 
2131 // ForceEarlyReturn<type> follows the PopFrame approach in many aspects.
2132 // Main difference is on the last stage in the interpreter.
2133 // The PopFrame stops method execution to continue execution
2134 // from the same method call instruction.
2135 // The ForceEarlyReturn forces return from method so the execution
2136 // continues at the bytecode following the method call.
2137 
2138 // thread - NOT protected by ThreadsListHandle and NOT pre-checked
2139 
2140 jvmtiError
2141 JvmtiEnvBase::force_early_return(jthread thread, jvalue value, TosState tos) {
2142   JavaThread* current_thread = JavaThread::current();
2143   HandleMark hm(current_thread);
2144 
2145   JvmtiVTMSTransitionDisabler disabler(thread);
2146   ThreadsListHandle tlh(current_thread);
2147 
2148   JavaThread* java_thread = nullptr;
2149   oop thread_obj = nullptr;
2150   jvmtiError err = get_threadOop_and_JavaThread(tlh.list(), thread, &java_thread, &thread_obj);
2151 
2152   if (err != JVMTI_ERROR_NONE) {
2153     return err;
2154   }
2155   bool self = java_thread == current_thread;
2156 
2157   err = check_non_suspended_or_opaque_frame(java_thread, thread_obj, self);
2158   if (err != JVMTI_ERROR_NONE) {
2159     return err;
2160   }
2161 
2162   // retrieve or create the state
2163   JvmtiThreadState* state = JvmtiThreadState::state_for(java_thread);
2164   if (state == nullptr) {
2165     return JVMTI_ERROR_THREAD_NOT_ALIVE;
2166   }
2167 
2168   // Eagerly reallocate scalar replaced objects.
2169   EscapeBarrier eb(true, current_thread, java_thread);
2170   if (!eb.deoptimize_objects(0)) {
2171     // Reallocation of scalar replaced objects failed -> return with error
2172     return JVMTI_ERROR_OUT_OF_MEMORY;
2173   }
2174 
2175   SetForceEarlyReturn op(state, value, tos);
2176   if (self) {
2177     op.doit(java_thread, self);
2178   } else {
2179     Handshake::execute(&op, java_thread);
2180   }
2181   return op.result();
2182 }
2183 
2184 void
2185 SetForceEarlyReturn::doit(Thread *target, bool self) {
2186   JavaThread* java_thread = JavaThread::cast(target);
2187   Thread* current_thread = Thread::current();
2188   HandleMark   hm(current_thread);
2189 
2190   if (java_thread->is_exiting()) {
2191     return; /* JVMTI_ERROR_THREAD_NOT_ALIVE (default) */
2192   }
2193 
2194   // Check to see if a ForceEarlyReturn was already in progress
2195   if (_state->is_earlyret_pending()) {
2196     // Probably possible for JVMTI clients to trigger this, but the
2197     // JPDA backend shouldn't allow this to happen
2198     _result = JVMTI_ERROR_INTERNAL;
2199     return;
2200   }
2201   {
2202     // The same as for PopFrame. Workaround bug:
2203     //  4812902: popFrame hangs if the method is waiting at a synchronize
2204     // Catch this condition and return an error to avoid hanging.
2205     // Now JVMTI spec allows an implementation to bail out with an opaque
2206     // frame error.
2207     OSThread* osThread = java_thread->osthread();
2208     if (osThread->get_state() == MONITOR_WAIT) {
2209       _result = JVMTI_ERROR_OPAQUE_FRAME;
2210       return;
2211     }
2212   }
2213 
2214   Handle ret_ob_h;
2215   _result = JvmtiEnvBase::check_top_frame(current_thread, java_thread, _value, _tos, &ret_ob_h);
2216   if (_result != JVMTI_ERROR_NONE) {
2217     return;
2218   }
2219   assert(_tos != atos || _value.l == nullptr || ret_ob_h() != nullptr,
2220          "return object oop must not be null if jobject is not null");
2221 
2222   // Update the thread state to reflect that the top frame must be
2223   // forced to return.
2224   // The current frame will be returned later when the suspended
2225   // thread is resumed and right before returning from VM to Java.
2226   // (see call_VM_base() in assembler_<cpu>.cpp).
2227 
2228   _state->set_earlyret_pending();
2229   _state->set_earlyret_oop(ret_ob_h());
2230   _state->set_earlyret_value(_value, _tos);
2231 
2232   // Set pending step flag for this early return.
2233   // It is cleared when next step event is posted.
2234   _state->set_pending_step_for_earlyret();
2235 }
2236 
2237 void
2238 JvmtiMonitorClosure::do_monitor(ObjectMonitor* mon) {
2239   if ( _error != JVMTI_ERROR_NONE) {
2240     // Error occurred in previous iteration so no need to add
2241     // to the list.
2242     return;
2243   }
2244   // Filter out on stack monitors collected during stack walk.
2245   oop obj = mon->object();
2246 
2247   if (obj == nullptr) {
2248     // This can happen if JNI code drops all references to the
2249     // owning object.
2250     return;
2251   }
2252 
2253   bool found = false;
2254   for (int j = 0; j < _owned_monitors_list->length(); j++) {
2255     jobject jobj = ((jvmtiMonitorStackDepthInfo*)_owned_monitors_list->at(j))->monitor;
2256     oop check = JNIHandles::resolve(jobj);
2257     if (check == obj) {
2258       // On stack monitor already collected during the stack walk.
2259       found = true;
2260       break;
2261     }
2262   }
2263   if (found == false) {
2264     // This is off stack monitor (e.g. acquired via jni MonitorEnter).
2265     jvmtiError err;
2266     jvmtiMonitorStackDepthInfo *jmsdi;
2267     err = _env->allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
2268     if (err != JVMTI_ERROR_NONE) {
2269       _error = err;
2270       return;
2271     }
2272     Handle hobj(Thread::current(), obj);
2273     jmsdi->monitor = _env->jni_reference(_calling_thread, hobj);
2274     // stack depth is unknown for this monitor.
2275     jmsdi->stack_depth = -1;
2276     _owned_monitors_list->append(jmsdi);
2277   }
2278 }
2279 
2280 GrowableArray<OopHandle>* JvmtiModuleClosure::_tbl = nullptr;
2281 
2282 void JvmtiModuleClosure::do_module(ModuleEntry* entry) {
2283   assert_locked_or_safepoint(Module_lock);
2284   OopHandle module = entry->module_handle();
2285   guarantee(module.resolve() != nullptr, "module object is null");
2286   _tbl->push(module);
2287 }
2288 
2289 jvmtiError
2290 JvmtiModuleClosure::get_all_modules(JvmtiEnv* env, jint* module_count_ptr, jobject** modules_ptr) {
2291   ResourceMark rm;
2292   MutexLocker mcld(ClassLoaderDataGraph_lock);
2293   MutexLocker ml(Module_lock);
2294 
2295   _tbl = new GrowableArray<OopHandle>(77);
2296   if (_tbl == nullptr) {
2297     return JVMTI_ERROR_OUT_OF_MEMORY;
2298   }
2299 
2300   // Iterate over all the modules loaded to the system.
2301   ClassLoaderDataGraph::modules_do(&do_module);
2302 
2303   jint len = _tbl->length();
2304   guarantee(len > 0, "at least one module must be present");
2305 
2306   jobject* array = (jobject*)env->jvmtiMalloc((jlong)(len * sizeof(jobject)));
2307   if (array == nullptr) {
2308     return JVMTI_ERROR_OUT_OF_MEMORY;
2309   }
2310   for (jint idx = 0; idx < len; idx++) {
2311     array[idx] = JNIHandles::make_local(_tbl->at(idx).resolve());
2312   }
2313   _tbl = nullptr;
2314   *modules_ptr = array;
2315   *module_count_ptr = len;
2316   return JVMTI_ERROR_NONE;
2317 }
2318 
2319 void
2320 UpdateForPopTopFrameClosure::doit(Thread *target, bool self) {
2321   Thread* current_thread  = Thread::current();
2322   HandleMark hm(current_thread);
2323   JavaThread* java_thread = JavaThread::cast(target);
2324 
2325   if (java_thread->is_exiting()) {
2326     return; /* JVMTI_ERROR_THREAD_NOT_ALIVE (default) */
2327   }
2328   assert(java_thread == _state->get_thread(), "Must be");
2329 
2330   // Check to see if a PopFrame was already in progress
2331   if (java_thread->popframe_condition() != JavaThread::popframe_inactive) {
2332     // Probably possible for JVMTI clients to trigger this, but the
2333     // JPDA backend shouldn't allow this to happen
2334     _result = JVMTI_ERROR_INTERNAL;
2335     return;
2336   }
2337 
2338   // Was workaround bug
2339   //    4812902: popFrame hangs if the method is waiting at a synchronize
2340   // Catch this condition and return an error to avoid hanging.
2341   // Now JVMTI spec allows an implementation to bail out with an opaque frame error.
2342   OSThread* osThread = java_thread->osthread();
2343   if (osThread->get_state() == MONITOR_WAIT) {
2344     _result = JVMTI_ERROR_OPAQUE_FRAME;
2345     return;
2346   }
2347 
2348   ResourceMark rm(current_thread);
2349   // Check if there is more than one Java frame in this thread, that the top two frames
2350   // are Java (not native) frames, and that there is no intervening VM frame
2351   int frame_count = 0;
2352   bool is_interpreted[2];
2353   intptr_t *frame_sp[2];
2354   // The 2-nd arg of constructor is needed to stop iterating at java entry frame.
2355   for (vframeStream vfs(java_thread, true, false /* process_frames */); !vfs.at_end(); vfs.next()) {
2356     methodHandle mh(current_thread, vfs.method());
2357     if (mh->is_native()) {
2358       _result = JVMTI_ERROR_OPAQUE_FRAME;
2359       return;
2360     }
2361     is_interpreted[frame_count] = vfs.is_interpreted_frame();
2362     frame_sp[frame_count] = vfs.frame_id();
2363     if (++frame_count > 1) break;
2364   }
2365   if (frame_count < 2)  {
2366     // We haven't found two adjacent non-native Java frames on the top.
2367     // There can be two situations here:
2368     //  1. There are no more java frames
2369     //  2. Two top java frames are separated by non-java native frames
2370     if (JvmtiEnvBase::jvf_for_thread_and_depth(java_thread, 1) == nullptr) {
2371       _result = JVMTI_ERROR_NO_MORE_FRAMES;
2372       return;
2373     } else {
2374       // Intervening non-java native or VM frames separate java frames.
2375       // Current implementation does not support this. See bug #5031735.
2376       // In theory it is possible to pop frames in such cases.
2377       _result = JVMTI_ERROR_OPAQUE_FRAME;
2378       return;
2379     }
2380   }
2381 
2382   // If any of the top 2 frames is a compiled one, need to deoptimize it
2383   for (int i = 0; i < 2; i++) {
2384     if (!is_interpreted[i]) {
2385       Deoptimization::deoptimize_frame(java_thread, frame_sp[i]);
2386     }
2387   }
2388 
2389   // Update the thread state to reflect that the top frame is popped
2390   // so that cur_stack_depth is maintained properly and all frameIDs
2391   // are invalidated.
2392   // The current frame will be popped later when the suspended thread
2393   // is resumed and right before returning from VM to Java.
2394   // (see call_VM_base() in assembler_<cpu>.cpp).
2395 
2396   // It's fine to update the thread state here because no JVMTI events
2397   // shall be posted for this PopFrame.
2398 
2399   _state->update_for_pop_top_frame();
2400   java_thread->set_popframe_condition(JavaThread::popframe_pending_bit);
2401   // Set pending step flag for this popframe and it is cleared when next
2402   // step event is posted.
2403   _state->set_pending_step_for_popframe();
2404   _result = JVMTI_ERROR_NONE;
2405 }
2406 
2407 void
2408 SetFramePopClosure::do_thread(Thread *target) {
2409   Thread* current = Thread::current();
2410   ResourceMark rm(current); // vframes are resource allocated
2411   JavaThread* java_thread = JavaThread::cast(target);
2412 
2413   if (java_thread->is_exiting()) {
2414     return; // JVMTI_ERROR_THREAD_NOT_ALIVE (default)
2415   }
2416 
2417   if (!_self && !java_thread->is_suspended()) {
2418     _result = JVMTI_ERROR_THREAD_NOT_SUSPENDED;
2419     return;
2420   }
2421   if (!java_thread->has_last_Java_frame()) {
2422     _result = JVMTI_ERROR_NO_MORE_FRAMES;
2423     return;
2424   }
2425   assert(_state->get_thread_or_saved() == java_thread, "Must be");
2426 
2427   RegisterMap reg_map(java_thread,
2428                       RegisterMap::UpdateMap::include,
2429                       RegisterMap::ProcessFrames::skip,
2430                       RegisterMap::WalkContinuation::include);
2431   javaVFrame* jvf = JvmtiEnvBase::get_cthread_last_java_vframe(java_thread, &reg_map);
2432   _result = ((JvmtiEnvBase*)_env)->set_frame_pop(_state, jvf, _depth);
2433 }
2434 
2435 void
2436 SetFramePopClosure::do_vthread(Handle target_h) {
2437   Thread* current = Thread::current();
2438   ResourceMark rm(current); // vframes are resource allocated
2439 
2440   if (!_self && !JvmtiVTSuspender::is_vthread_suspended(target_h())) {
2441     _result = JVMTI_ERROR_THREAD_NOT_SUSPENDED;
2442     return;
2443   }
2444   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(target_h());
2445   _result = ((JvmtiEnvBase*)_env)->set_frame_pop(_state, jvf, _depth);
2446 }
2447 
2448 void
2449 GetOwnedMonitorInfoClosure::do_thread(Thread *target) {
2450   JavaThread *jt = JavaThread::cast(target);
2451   if (!jt->is_exiting() && (jt->threadObj() != nullptr)) {
2452     _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(_calling_thread,
2453                                                          jt,
2454                                                          _owned_monitors_list);
2455   }
2456 }
2457 
2458 void
2459 GetCurrentContendedMonitorClosure::do_thread(Thread *target) {
2460   JavaThread *jt = JavaThread::cast(target);
2461   if (!jt->is_exiting() && (jt->threadObj() != nullptr)) {
2462     _result = ((JvmtiEnvBase *)_env)->get_current_contended_monitor(_calling_thread,
2463                                                                     jt,
2464                                                                     _owned_monitor_ptr,
2465                                                                     _is_virtual);
2466   }
2467 }
2468 
2469 void
2470 GetStackTraceClosure::do_thread(Thread *target) {
2471   Thread* current = Thread::current();
2472   ResourceMark rm(current);
2473 
2474   JavaThread *jt = JavaThread::cast(target);
2475   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2476     _result = ((JvmtiEnvBase *)_env)->get_stack_trace(jt,
2477                                                       _start_depth, _max_count,
2478                                                       _frame_buffer, _count_ptr);
2479   }
2480 }
2481 
2482 void
2483 GetStackTraceClosure::do_vthread(Handle target_h) {
2484   Thread* current = Thread::current();
2485   ResourceMark rm(current);
2486 
2487   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(target_h());
2488   _result = ((JvmtiEnvBase *)_env)->get_stack_trace(jvf,
2489                                                     _start_depth, _max_count,
2490                                                     _frame_buffer, _count_ptr);
2491 }
2492 
2493 #ifdef ASSERT
2494 void
2495 PrintStackTraceClosure::do_thread_impl(Thread *target) {
2496   JavaThread *java_thread = JavaThread::cast(target);
2497   Thread *current_thread = Thread::current();
2498 
2499   ResourceMark rm (current_thread);
2500   const char* tname = JvmtiTrace::safe_get_thread_name(java_thread);
2501   oop t_oop = java_thread->jvmti_vthread();
2502   t_oop = t_oop == nullptr ? java_thread->threadObj() : t_oop;
2503   bool is_vt_suspended = java_lang_VirtualThread::is_instance(t_oop) && JvmtiVTSuspender::is_vthread_suspended(t_oop);
2504 
2505   log_error(jvmti)("%s(%s) exiting: %d is_susp: %d is_thread_susp: %d is_vthread_susp: %d "
2506                    "is_VTMS_transition_disabler: %d, is_in_VTMS_transition = %d\n",
2507                    tname, java_thread->name(), java_thread->is_exiting(),
2508                    java_thread->is_suspended(), java_thread->is_carrier_thread_suspended(), is_vt_suspended,
2509                    java_thread->is_VTMS_transition_disabler(), java_thread->is_in_VTMS_transition());
2510 
2511   if (java_thread->has_last_Java_frame()) {
2512     RegisterMap reg_map(java_thread,
2513                         RegisterMap::UpdateMap::include,
2514                         RegisterMap::ProcessFrames::include,
2515                         RegisterMap::WalkContinuation::skip);
2516     ResourceMark rm(current_thread);
2517     HandleMark hm(current_thread);
2518     javaVFrame *jvf = java_thread->last_java_vframe(&reg_map);
2519     while (jvf != nullptr) {
2520       log_error(jvmti)("  %s:%d",
2521                        jvf->method()->external_name(),
2522                        jvf->method()->line_number_from_bci(jvf->bci()));
2523       jvf = jvf->java_sender();
2524     }
2525   }
2526   log_error(jvmti)("\n");
2527 }
2528 
2529 void
2530 PrintStackTraceClosure::do_thread(Thread *target) {
2531   JavaThread *java_thread = JavaThread::cast(target);
2532   Thread *current_thread = Thread::current();
2533 
2534   assert(SafepointSynchronize::is_at_safepoint() ||
2535          java_thread->is_handshake_safe_for(current_thread),
2536          "call by myself / at safepoint / at handshake");
2537 
2538   PrintStackTraceClosure::do_thread_impl(target);
2539 }
2540 #endif
2541 
2542 void
2543 GetFrameCountClosure::do_thread(Thread *target) {
2544   JavaThread* jt = JavaThread::cast(target);
2545   assert(target == jt, "just checking");
2546 
2547   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2548     _result = ((JvmtiEnvBase*)_env)->get_frame_count(jt, _count_ptr);
2549   }
2550 }
2551 
2552 void
2553 GetFrameCountClosure::do_vthread(Handle target_h) {
2554   _result = ((JvmtiEnvBase*)_env)->get_frame_count(target_h(), _count_ptr);
2555 }
2556 
2557 void
2558 GetFrameLocationClosure::do_thread(Thread *target) {
2559   JavaThread *jt = JavaThread::cast(target);
2560   assert(target == jt, "just checking");
2561 
2562   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2563     _result = ((JvmtiEnvBase*)_env)->get_frame_location(jt, _depth,
2564                                                         _method_ptr, _location_ptr);
2565   }
2566 }
2567 
2568 void
2569 GetFrameLocationClosure::do_vthread(Handle target_h) {
2570   _result = ((JvmtiEnvBase*)_env)->get_frame_location(target_h(), _depth,
2571                                                       _method_ptr, _location_ptr);
2572 }
2573 
2574 void
2575 VirtualThreadGetOwnedMonitorInfoClosure::do_thread(Thread *target) {
2576   if (!JvmtiEnvBase::is_vthread_alive(_vthread_h())) {
2577     _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
2578     return;
2579   }
2580   JavaThread* java_thread = JavaThread::cast(target);
2581   Thread* cur_thread = Thread::current();
2582   ResourceMark rm(cur_thread);
2583   HandleMark hm(cur_thread);
2584 
2585   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(_vthread_h());
2586 
2587   if (!java_thread->is_exiting() && java_thread->threadObj() != nullptr) {
2588     _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(java_thread,
2589                                                          java_thread,
2590                                                          jvf,
2591                                                          _owned_monitors_list);
2592   }
2593 }
2594 
2595 void
2596 VirtualThreadGetThreadClosure::do_thread(Thread *target) {
2597   assert(target->is_Java_thread(), "just checking");
2598   JavaThread *jt = JavaThread::cast(target);
2599   oop carrier_thread = java_lang_VirtualThread::carrier_thread(_vthread_h());
2600   *_carrier_thread_ptr = (jthread)JNIHandles::make_local(jt, carrier_thread);
2601 }
2602 
2603 void
2604 VirtualThreadGetThreadStateClosure::do_thread(Thread *target) {
2605   assert(target->is_Java_thread(), "just checking");
2606   int vthread_state = java_lang_VirtualThread::state(_vthread_h());
2607   oop carrier_thread_oop = java_lang_VirtualThread::carrier_thread(_vthread_h());
2608   jint state;
2609 
2610   if (vthread_state == java_lang_VirtualThread::RUNNING && carrier_thread_oop != nullptr) {
2611     state = (jint) java_lang_Thread::get_thread_status(carrier_thread_oop);
2612     JavaThread* java_thread = java_lang_Thread::thread(carrier_thread_oop);
2613     if (java_thread->is_suspended()) {
2614       state |= JVMTI_THREAD_STATE_SUSPENDED;
2615     }
2616   } else {
2617     state = (jint) java_lang_VirtualThread::map_state_to_thread_status(vthread_state);
2618   }
2619   if (java_lang_Thread::interrupted(_vthread_h())) {
2620     state |= JVMTI_THREAD_STATE_INTERRUPTED;
2621   }
2622   *_state_ptr = state;
2623   _result = JVMTI_ERROR_NONE;
2624 }