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 jint
 817 JvmtiEnvBase::get_thread_or_vthread_state(oop thread_oop, JavaThread* java_thread) {
 818   jint state = 0;
 819   if (java_lang_VirtualThread::is_instance(thread_oop)) {
 820     state = JvmtiEnvBase::get_vthread_state(thread_oop, java_thread);
 821   } else {
 822     state = JvmtiEnvBase::get_thread_state(thread_oop, java_thread);
 823   }
 824   return state;
 825 }
 826 
 827 jvmtiError
 828 JvmtiEnvBase::get_live_threads(JavaThread* current_thread, Handle group_hdl, jint *count_ptr, Handle **thread_objs_p) {
 829   jint count = 0;
 830   Handle *thread_objs = nullptr;
 831   ThreadsListEnumerator tle(current_thread, /* include_jvmti_agent_threads */ true);
 832   int nthreads = tle.num_threads();
 833   if (nthreads > 0) {
 834     thread_objs = NEW_RESOURCE_ARRAY_RETURN_NULL(Handle, nthreads);
 835     NULL_CHECK(thread_objs, JVMTI_ERROR_OUT_OF_MEMORY);
 836     for (int i = 0; i < nthreads; i++) {
 837       Handle thread = tle.get_threadObj(i);
 838       if (thread()->is_a(vmClasses::Thread_klass()) && java_lang_Thread::threadGroup(thread()) == group_hdl()) {
 839         thread_objs[count++] = thread;
 840       }
 841     }
 842   }
 843   *thread_objs_p = thread_objs;
 844   *count_ptr = count;
 845   return JVMTI_ERROR_NONE;
 846 }
 847 
 848 jvmtiError
 849 JvmtiEnvBase::get_subgroups(JavaThread* current_thread, Handle group_hdl, jint *count_ptr, objArrayHandle *group_objs_p) {
 850 
 851   // This call collects the strong and weak groups
 852   JavaThread* THREAD = current_thread;
 853   JavaValue result(T_OBJECT);
 854   JavaCalls::call_virtual(&result,
 855                           group_hdl,
 856                           vmClasses::ThreadGroup_klass(),
 857                           SymbolTable::new_permanent_symbol("subgroupsAsArray"),
 858                           vmSymbols::void_threadgroup_array_signature(),
 859                           THREAD);
 860   if (HAS_PENDING_EXCEPTION) {
 861     Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
 862     CLEAR_PENDING_EXCEPTION;
 863     if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
 864       return JVMTI_ERROR_OUT_OF_MEMORY;
 865     } else {
 866       return JVMTI_ERROR_INTERNAL;
 867     }
 868   }
 869 
 870   assert(result.get_type() == T_OBJECT, "just checking");
 871   objArrayOop groups = (objArrayOop)result.get_oop();
 872 
 873   *count_ptr = groups == nullptr ? 0 : groups->length();
 874   *group_objs_p = objArrayHandle(current_thread, groups);
 875 
 876   return JVMTI_ERROR_NONE;
 877 }
 878 
 879 //
 880 // Object Monitor Information
 881 //
 882 
 883 //
 884 // Count the number of objects for a lightweight monitor. The hobj
 885 // parameter is object that owns the monitor so this routine will
 886 // count the number of times the same object was locked by frames
 887 // in java_thread.
 888 //
 889 jint
 890 JvmtiEnvBase::count_locked_objects(JavaThread *java_thread, Handle hobj) {
 891   jint ret = 0;
 892   if (!java_thread->has_last_Java_frame()) {
 893     return ret;  // no Java frames so no monitors
 894   }
 895 
 896   Thread* current_thread = Thread::current();
 897   ResourceMark rm(current_thread);
 898   HandleMark   hm(current_thread);
 899   RegisterMap  reg_map(java_thread,
 900                        RegisterMap::UpdateMap::include,
 901                        RegisterMap::ProcessFrames::include,
 902                        RegisterMap::WalkContinuation::skip);
 903 
 904   for (javaVFrame *jvf = java_thread->last_java_vframe(&reg_map); jvf != nullptr;
 905        jvf = jvf->java_sender()) {
 906     GrowableArray<MonitorInfo*>* mons = jvf->monitors();
 907     if (!mons->is_empty()) {
 908       for (int i = 0; i < mons->length(); i++) {
 909         MonitorInfo *mi = mons->at(i);
 910         if (mi->owner_is_scalar_replaced()) continue;
 911 
 912         // see if owner of the monitor is our object
 913         if (mi->owner() != nullptr && mi->owner() == hobj()) {
 914           ret++;
 915         }
 916       }
 917     }
 918   }
 919   return ret;
 920 }
 921 
 922 jvmtiError
 923 JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThread *java_thread,
 924                                             jobject *monitor_ptr, bool is_virtual) {
 925   Thread *current_thread = Thread::current();
 926   assert(java_thread->is_handshake_safe_for(current_thread),
 927          "call by myself or at handshake");
 928   if (!is_virtual && JvmtiEnvBase::is_cthread_with_continuation(java_thread)) {
 929     // Carrier thread with a mounted continuation case.
 930     // No contended monitor can be owned by carrier thread in this case.
 931     *monitor_ptr = nullptr;
 932     return JVMTI_ERROR_NONE;
 933   }
 934   oop obj = nullptr;
 935   // The ObjectMonitor* can't be async deflated since we are either
 936   // at a safepoint or the calling thread is operating on itself so
 937   // it cannot leave the underlying wait()/enter() call.
 938   ObjectMonitor *mon = java_thread->current_waiting_monitor();
 939   if (mon == nullptr) {
 940     // thread is not doing an Object.wait() call
 941     mon = java_thread->current_pending_monitor();
 942     if (mon != nullptr) {
 943       // The thread is trying to enter() an ObjectMonitor.
 944       obj = mon->object();
 945       assert(obj != nullptr, "ObjectMonitor should have a valid object!");
 946     }
 947   } else {
 948     // thread is doing an Object.wait() call
 949     oop thread_oop = get_vthread_or_thread_oop(java_thread);
 950     jint state = get_thread_or_vthread_state(thread_oop, java_thread);
 951 
 952     if (state & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) {
 953       // thread is re-entering the monitor in an Object.wait() call
 954       obj = mon->object();
 955       assert(obj != nullptr, "Object.wait() should have an object");
 956     }
 957   }
 958 
 959   if (obj == nullptr) {
 960     *monitor_ptr = nullptr;
 961   } else {
 962     HandleMark hm(current_thread);
 963     Handle     hobj(current_thread, obj);
 964     *monitor_ptr = jni_reference(calling_thread, hobj);
 965   }
 966   return JVMTI_ERROR_NONE;
 967 }
 968 
 969 jvmtiError
 970 JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
 971                                  GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
 972   // Note:
 973   // calling_thread is the thread that requested the list of monitors for java_thread.
 974   // java_thread is the thread owning the monitors.
 975   // current_thread is the thread executing this code, can be a non-JavaThread (e.g. VM Thread).
 976   // And they all may be different threads.
 977   jvmtiError err = JVMTI_ERROR_NONE;
 978   Thread *current_thread = Thread::current();
 979   assert(java_thread->is_handshake_safe_for(current_thread),
 980          "call by myself or at handshake");
 981 
 982   if (JvmtiEnvBase::is_cthread_with_continuation(java_thread)) {
 983     // Carrier thread with a mounted continuation case.
 984     // No contended monitor can be owned by carrier thread in this case.
 985     return JVMTI_ERROR_NONE;
 986   }
 987   if (java_thread->has_last_Java_frame()) {
 988     ResourceMark rm(current_thread);
 989     HandleMark   hm(current_thread);
 990     RegisterMap  reg_map(java_thread,
 991                          RegisterMap::UpdateMap::include,
 992                          RegisterMap::ProcessFrames::include,
 993                          RegisterMap::WalkContinuation::skip);
 994 
 995     int depth = 0;
 996     for (javaVFrame *jvf = get_cthread_last_java_vframe(java_thread, &reg_map);
 997          jvf != nullptr; jvf = jvf->java_sender()) {
 998       if (MaxJavaStackTraceDepth == 0 || depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
 999         // add locked objects for this frame into list
1000         err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth-1);
1001         if (err != JVMTI_ERROR_NONE) {
1002           return err;
1003         }
1004       }
1005     }
1006   }
1007 
1008   // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
1009   JvmtiMonitorClosure jmc(calling_thread, owned_monitors_list, this);
1010   ObjectSynchronizer::owned_monitors_iterate(&jmc, java_thread);
1011   err = jmc.error();
1012 
1013   return err;
1014 }
1015 
1016 jvmtiError
1017 JvmtiEnvBase::get_owned_monitors(JavaThread* calling_thread, JavaThread* java_thread, javaVFrame* jvf,
1018                                  GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
1019   jvmtiError err = JVMTI_ERROR_NONE;
1020   Thread *current_thread = Thread::current();
1021   assert(java_thread->is_handshake_safe_for(current_thread),
1022          "call by myself or at handshake");
1023 
1024   int depth = 0;
1025   for ( ; jvf != nullptr; jvf = jvf->java_sender()) {
1026     if (MaxJavaStackTraceDepth == 0 || depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
1027       // Add locked objects for this frame into list.
1028       err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth - 1);
1029       if (err != JVMTI_ERROR_NONE) {
1030         return err;
1031       }
1032     }
1033   }
1034 
1035   // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
1036   JvmtiMonitorClosure jmc(calling_thread, owned_monitors_list, this);
1037   ObjectSynchronizer::owned_monitors_iterate(&jmc, java_thread);
1038   err = jmc.error();
1039 
1040   return err;
1041 }
1042 
1043 // Save JNI local handles for any objects that this frame owns.
1044 jvmtiError
1045 JvmtiEnvBase::get_locked_objects_in_frame(JavaThread* calling_thread, JavaThread* java_thread,
1046                                  javaVFrame *jvf, GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list, jint stack_depth) {
1047   jvmtiError err = JVMTI_ERROR_NONE;
1048   Thread* current_thread = Thread::current();
1049   ResourceMark rm(current_thread);
1050   HandleMark   hm(current_thread);
1051 
1052   GrowableArray<MonitorInfo*>* mons = jvf->monitors();
1053   if (mons->is_empty()) {
1054     return err;  // this javaVFrame holds no monitors
1055   }
1056 
1057   oop wait_obj = nullptr;
1058   {
1059     // The ObjectMonitor* can't be async deflated since we are either
1060     // at a safepoint or the calling thread is operating on itself so
1061     // it cannot leave the underlying wait() call.
1062     // Save object of current wait() call (if any) for later comparison.
1063     ObjectMonitor *mon = java_thread->current_waiting_monitor();
1064     if (mon != nullptr) {
1065       wait_obj = mon->object();
1066     }
1067   }
1068   oop pending_obj = nullptr;
1069   {
1070     // The ObjectMonitor* can't be async deflated since we are either
1071     // at a safepoint or the calling thread is operating on itself so
1072     // it cannot leave the underlying enter() call.
1073     // Save object of current enter() call (if any) for later comparison.
1074     ObjectMonitor *mon = java_thread->current_pending_monitor();
1075     if (mon != nullptr) {
1076       pending_obj = mon->object();
1077     }
1078   }
1079 
1080   for (int i = 0; i < mons->length(); i++) {
1081     MonitorInfo *mi = mons->at(i);
1082 
1083     if (mi->owner_is_scalar_replaced()) continue;
1084 
1085     oop obj = mi->owner();
1086     if (obj == nullptr) {
1087       // this monitor doesn't have an owning object so skip it
1088       continue;
1089     }
1090 
1091     if (wait_obj == obj) {
1092       // the thread is waiting on this monitor so it isn't really owned
1093       continue;
1094     }
1095 
1096     if (pending_obj == obj) {
1097       // the thread is pending on this monitor so it isn't really owned
1098       continue;
1099     }
1100 
1101     if (owned_monitors_list->length() > 0) {
1102       // Our list has at least one object on it so we have to check
1103       // for recursive object locking
1104       bool found = false;
1105       for (int j = 0; j < owned_monitors_list->length(); j++) {
1106         jobject jobj = ((jvmtiMonitorStackDepthInfo*)owned_monitors_list->at(j))->monitor;
1107         oop check = JNIHandles::resolve(jobj);
1108         if (check == obj) {
1109           found = true;  // we found the object
1110           break;
1111         }
1112       }
1113 
1114       if (found) {
1115         // already have this object so don't include it
1116         continue;
1117       }
1118     }
1119 
1120     // add the owning object to our list
1121     jvmtiMonitorStackDepthInfo *jmsdi;
1122     err = allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
1123     if (err != JVMTI_ERROR_NONE) {
1124         return err;
1125     }
1126     Handle hobj(Thread::current(), obj);
1127     jmsdi->monitor = jni_reference(calling_thread, hobj);
1128     jmsdi->stack_depth = stack_depth;
1129     owned_monitors_list->append(jmsdi);
1130   }
1131 
1132   return err;
1133 }
1134 
1135 jvmtiError
1136 JvmtiEnvBase::get_stack_trace(javaVFrame *jvf,
1137                               jint start_depth, jint max_count,
1138                               jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
1139   Thread *current_thread = Thread::current();
1140   ResourceMark rm(current_thread);
1141   HandleMark hm(current_thread);
1142   int count = 0;
1143 
1144   if (start_depth != 0) {
1145     if (start_depth > 0) {
1146       for (int j = 0; j < start_depth && jvf != nullptr; j++) {
1147         jvf = jvf->java_sender();
1148       }
1149       if (jvf == nullptr) {
1150         // start_depth is deeper than the stack depth.
1151         return JVMTI_ERROR_ILLEGAL_ARGUMENT;
1152       }
1153     } else { // start_depth < 0
1154       // We are referencing the starting depth based on the oldest
1155       // part of the stack.
1156       // Optimize to limit the number of times that java_sender() is called.
1157       javaVFrame *jvf_cursor = jvf;
1158       javaVFrame *jvf_prev = nullptr;
1159       javaVFrame *jvf_prev_prev = nullptr;
1160       int j = 0;
1161       while (jvf_cursor != nullptr) {
1162         jvf_prev_prev = jvf_prev;
1163         jvf_prev = jvf_cursor;
1164         for (j = 0; j > start_depth && jvf_cursor != nullptr; j--) {
1165           jvf_cursor = jvf_cursor->java_sender();
1166         }
1167       }
1168       if (j == start_depth) {
1169         // Previous pointer is exactly where we want to start.
1170         jvf = jvf_prev;
1171       } else {
1172         // We need to back up further to get to the right place.
1173         if (jvf_prev_prev == nullptr) {
1174           // The -start_depth is greater than the stack depth.
1175           return JVMTI_ERROR_ILLEGAL_ARGUMENT;
1176         }
1177         // j is now the number of frames on the stack starting with
1178         // jvf_prev, we start from jvf_prev_prev and move older on
1179         // the stack that many, and the result is -start_depth frames
1180         // remaining.
1181         jvf = jvf_prev_prev;
1182         for (; j < 0; j++) {
1183           jvf = jvf->java_sender();
1184         }
1185       }
1186     }
1187   }
1188   for (; count < max_count && jvf != nullptr; count++) {
1189     frame_buffer[count].method = jvf->method()->jmethod_id();
1190     frame_buffer[count].location = (jvf->method()->is_native() ? -1 : jvf->bci());
1191     jvf = jvf->java_sender();
1192   }
1193   *count_ptr = count;
1194   return JVMTI_ERROR_NONE;
1195 }
1196 
1197 jvmtiError
1198 JvmtiEnvBase::get_stack_trace(JavaThread *java_thread,
1199                               jint start_depth, jint max_count,
1200                               jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
1201   Thread *current_thread = Thread::current();
1202   assert(SafepointSynchronize::is_at_safepoint() ||
1203          java_thread->is_handshake_safe_for(current_thread),
1204          "call by myself / at safepoint / at handshake");
1205   int count = 0;
1206   jvmtiError err = JVMTI_ERROR_NONE;
1207 
1208   if (java_thread->has_last_Java_frame()) {
1209     RegisterMap reg_map(java_thread,
1210                         RegisterMap::UpdateMap::include,
1211                         RegisterMap::ProcessFrames::skip,
1212                         RegisterMap::WalkContinuation::skip);
1213     ResourceMark rm(current_thread);
1214     javaVFrame *jvf = get_cthread_last_java_vframe(java_thread, &reg_map);
1215 
1216     err = get_stack_trace(jvf, start_depth, max_count, frame_buffer, count_ptr);
1217   } else {
1218     *count_ptr = 0;
1219     if (start_depth != 0) {
1220       // no frames and there is a starting depth
1221       err = JVMTI_ERROR_ILLEGAL_ARGUMENT;
1222     }
1223   }
1224   return err;
1225 }
1226 
1227 jint
1228 JvmtiEnvBase::get_frame_count(javaVFrame *jvf) {
1229   int count = 0;
1230 
1231   while (jvf != nullptr) {
1232     jvf = jvf->java_sender();
1233     count++;
1234   }
1235   return count;
1236 }
1237 
1238 jvmtiError
1239 JvmtiEnvBase::get_frame_count(JavaThread* jt, jint *count_ptr) {
1240   Thread *current_thread = Thread::current();
1241   assert(current_thread == jt ||
1242          SafepointSynchronize::is_at_safepoint() ||
1243          jt->is_handshake_safe_for(current_thread),
1244          "call by myself / at safepoint / at handshake");
1245 
1246   if (!jt->has_last_Java_frame()) { // no Java frames
1247     *count_ptr = 0;
1248   } else {
1249     ResourceMark rm(current_thread);
1250     RegisterMap reg_map(jt,
1251                         RegisterMap::UpdateMap::include,
1252                         RegisterMap::ProcessFrames::include,
1253                         RegisterMap::WalkContinuation::skip);
1254     javaVFrame *jvf = get_cthread_last_java_vframe(jt, &reg_map);
1255 
1256     *count_ptr = get_frame_count(jvf);
1257   }
1258   return JVMTI_ERROR_NONE;
1259 }
1260 
1261 jvmtiError
1262 JvmtiEnvBase::get_frame_count(oop vthread_oop, jint *count_ptr) {
1263   Thread *current_thread = Thread::current();
1264   ResourceMark rm(current_thread);
1265   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(vthread_oop);
1266 
1267   *count_ptr = get_frame_count(jvf);
1268   return JVMTI_ERROR_NONE;
1269 }
1270 
1271 jvmtiError
1272 JvmtiEnvBase::get_frame_location(javaVFrame* jvf, jint depth,
1273                                  jmethodID* method_ptr, jlocation* location_ptr) {
1274   int cur_depth = 0;
1275 
1276   while (jvf != nullptr && cur_depth < depth) {
1277     jvf = jvf->java_sender();
1278     cur_depth++;
1279   }
1280   assert(depth >= cur_depth, "ran out of frames too soon");
1281   if (jvf == nullptr) {
1282     return JVMTI_ERROR_NO_MORE_FRAMES;
1283   }
1284   Method* method = jvf->method();
1285   if (method->is_native()) {
1286     *location_ptr = -1;
1287   } else {
1288     *location_ptr = jvf->bci();
1289   }
1290   *method_ptr = method->jmethod_id();
1291   return JVMTI_ERROR_NONE;
1292 }
1293 
1294 jvmtiError
1295 JvmtiEnvBase::get_frame_location(JavaThread *java_thread, jint depth,
1296                                  jmethodID* method_ptr, jlocation* location_ptr) {
1297   Thread* current = Thread::current();
1298   assert(java_thread->is_handshake_safe_for(current),
1299          "call by myself or at handshake");
1300   if (!java_thread->has_last_Java_frame()) {
1301     return JVMTI_ERROR_NO_MORE_FRAMES;
1302   }
1303   ResourceMark rm(current);
1304   HandleMark hm(current);
1305   RegisterMap reg_map(java_thread,
1306                       RegisterMap::UpdateMap::include,
1307                       RegisterMap::ProcessFrames::skip,
1308                       RegisterMap::WalkContinuation::include);
1309   javaVFrame* jvf = JvmtiEnvBase::get_cthread_last_java_vframe(java_thread, &reg_map);
1310 
1311   return get_frame_location(jvf, depth, method_ptr, location_ptr);
1312 }
1313 
1314 jvmtiError
1315 JvmtiEnvBase::get_frame_location(oop vthread_oop, jint depth,
1316                                  jmethodID* method_ptr, jlocation* location_ptr) {
1317   Thread* current = Thread::current();
1318   ResourceMark rm(current);
1319   HandleMark hm(current);
1320   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(vthread_oop);
1321 
1322   return get_frame_location(jvf, depth, method_ptr, location_ptr);
1323 }
1324 
1325 jvmtiError
1326 JvmtiEnvBase::set_frame_pop(JvmtiThreadState* state, javaVFrame* jvf, jint depth) {
1327   for (int d = 0; jvf != nullptr && d < depth; d++) {
1328     jvf = jvf->java_sender();
1329   }
1330   if (jvf == nullptr) {
1331     return JVMTI_ERROR_NO_MORE_FRAMES;
1332   }
1333   if (jvf->method()->is_native()) {
1334     return JVMTI_ERROR_OPAQUE_FRAME;
1335   }
1336   assert(jvf->frame_pointer() != nullptr, "frame pointer mustn't be null");
1337   int frame_number = (int)get_frame_count(jvf);
1338   state->env_thread_state((JvmtiEnvBase*)this)->set_frame_pop(frame_number);
1339   return JVMTI_ERROR_NONE;
1340 }
1341 
1342 bool
1343 JvmtiEnvBase::is_cthread_with_mounted_vthread(JavaThread* jt) {
1344   oop thread_oop = jt->threadObj();
1345   assert(thread_oop != nullptr, "sanity check");
1346   oop mounted_vt = jt->jvmti_vthread();
1347 
1348   return mounted_vt != nullptr && mounted_vt != thread_oop;
1349 }
1350 
1351 bool
1352 JvmtiEnvBase::is_cthread_with_continuation(JavaThread* jt) {
1353   const ContinuationEntry* cont_entry = nullptr;
1354   if (jt->has_last_Java_frame()) {
1355     cont_entry = jt->vthread_continuation();
1356   }
1357   return cont_entry != nullptr && is_cthread_with_mounted_vthread(jt);
1358 }
1359 
1360 // Check if VirtualThread or BoundVirtualThread is suspended.
1361 bool
1362 JvmtiEnvBase::is_vthread_suspended(oop vt_oop, JavaThread* jt) {
1363   bool suspended = false;
1364   if (java_lang_VirtualThread::is_instance(vt_oop)) {
1365     suspended = JvmtiVTSuspender::is_vthread_suspended(vt_oop);
1366   }
1367   if (vt_oop->is_a(vmClasses::BoundVirtualThread_klass())) {
1368     suspended = jt->is_suspended();
1369   }
1370   return suspended;
1371 }
1372 
1373 // If (thread == null) then return current thread object.
1374 // Otherwise return JNIHandles::resolve_external_guard(thread).
1375 oop
1376 JvmtiEnvBase::current_thread_obj_or_resolve_external_guard(jthread thread) {
1377   oop thread_obj = JNIHandles::resolve_external_guard(thread);
1378   if (thread == nullptr) {
1379     thread_obj = get_vthread_or_thread_oop(JavaThread::current());
1380   }
1381   return thread_obj;
1382 }
1383 
1384 jvmtiError
1385 JvmtiEnvBase::get_threadOop_and_JavaThread(ThreadsList* t_list, jthread thread, JavaThread* cur_thread,
1386                                            JavaThread** jt_pp, oop* thread_oop_p) {
1387   JavaThread* java_thread = nullptr;
1388   oop thread_oop = nullptr;
1389 
1390   if (thread == nullptr) {
1391     if (cur_thread == nullptr) { // cur_thread can be null when called from a VM_op
1392       return JVMTI_ERROR_INVALID_THREAD;
1393     }
1394     java_thread = cur_thread;
1395     thread_oop = get_vthread_or_thread_oop(java_thread);
1396     if (thread_oop == nullptr || !thread_oop->is_a(vmClasses::Thread_klass())) {
1397       return JVMTI_ERROR_INVALID_THREAD;
1398     }
1399   } else {
1400     jvmtiError err = JvmtiExport::cv_external_thread_to_JavaThread(t_list, thread, &java_thread, &thread_oop);
1401     if (err != JVMTI_ERROR_NONE) {
1402       // We got an error code so we don't have a JavaThread*, but only return
1403       // an error from here if we didn't get a valid thread_oop. In a vthread case
1404       // the cv_external_thread_to_JavaThread is expected to correctly set the
1405       // thread_oop and return JVMTI_ERROR_INVALID_THREAD which we ignore here.
1406       if (thread_oop == nullptr || err != JVMTI_ERROR_INVALID_THREAD) {
1407         *thread_oop_p = thread_oop;
1408         return err;
1409       }
1410     }
1411     if (java_thread == nullptr && java_lang_VirtualThread::is_instance(thread_oop)) {
1412       java_thread = get_JavaThread_or_null(thread_oop);
1413     }
1414   }
1415   *jt_pp = java_thread;
1416   *thread_oop_p = thread_oop;
1417   if (java_lang_VirtualThread::is_instance(thread_oop) &&
1418       !JvmtiEnvBase::is_vthread_alive(thread_oop)) {
1419     return JVMTI_ERROR_THREAD_NOT_ALIVE;
1420   }
1421   return JVMTI_ERROR_NONE;
1422 }
1423 
1424 // Check for JVMTI_ERROR_NOT_SUSPENDED and JVMTI_ERROR_OPAQUE_FRAME errors.
1425 // Used in PopFrame and ForceEarlyReturn implementations.
1426 jvmtiError
1427 JvmtiEnvBase::check_non_suspended_or_opaque_frame(JavaThread* jt, oop thr_obj, bool self) {
1428   bool is_virtual = thr_obj != nullptr && thr_obj->is_a(vmClasses::BaseVirtualThread_klass());
1429 
1430   if (is_virtual) {
1431     if (!is_JavaThread_current(jt, thr_obj)) {
1432       if (!is_vthread_suspended(thr_obj, jt)) {
1433         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1434       }
1435       if (jt == nullptr) { // unmounted virtual thread
1436         return JVMTI_ERROR_OPAQUE_FRAME;
1437       }
1438     }
1439   } else { // platform thread
1440     if (!self && !jt->is_suspended() &&
1441         !jt->is_carrier_thread_suspended()) {
1442       return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1443     }
1444   }
1445   return JVMTI_ERROR_NONE;
1446 }
1447 
1448 jvmtiError
1449 JvmtiEnvBase::get_object_monitor_usage(JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
1450   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
1451   Thread* current_thread = VMThread::vm_thread();
1452   assert(current_thread == Thread::current(), "must be");
1453 
1454   HandleMark hm(current_thread);
1455   Handle hobj;
1456 
1457   // Check arguments
1458   {
1459     oop mirror = JNIHandles::resolve_external_guard(object);
1460     NULL_CHECK(mirror, JVMTI_ERROR_INVALID_OBJECT);
1461     NULL_CHECK(info_ptr, JVMTI_ERROR_NULL_POINTER);
1462 
1463     hobj = Handle(current_thread, mirror);
1464   }
1465 
1466   ThreadsListHandle tlh(current_thread);
1467   JavaThread *owning_thread = nullptr;
1468   ObjectMonitor *mon = nullptr;
1469   jvmtiMonitorUsage ret = {
1470       nullptr, 0, 0, nullptr, 0, nullptr
1471   };
1472 
1473   uint32_t debug_bits = 0;
1474   // first derive the object's owner and entry_count (if any)
1475   owning_thread = ObjectSynchronizer::get_lock_owner(tlh.list(), hobj);
1476   if (owning_thread != nullptr) {
1477     oop thread_oop = get_vthread_or_thread_oop(owning_thread);
1478     bool is_virtual = thread_oop->is_a(vmClasses::BaseVirtualThread_klass());
1479     if (is_virtual) {
1480       thread_oop = nullptr;
1481     }
1482     Handle th(current_thread, thread_oop);
1483     ret.owner = (jthread)jni_reference(calling_thread, th);
1484 
1485     // The recursions field of a monitor does not reflect recursions
1486     // as lightweight locks before inflating the monitor are not included.
1487     // We have to count the number of recursive monitor entries the hard way.
1488     // We pass a handle to survive any GCs along the way.
1489     ret.entry_count = is_virtual ? 0 : count_locked_objects(owning_thread, hobj);
1490   }
1491   // implied else: entry_count == 0
1492 
1493   jint nWant = 0, nWait = 0;
1494   markWord mark = hobj->mark();
1495   ResourceMark rm(current_thread);
1496   GrowableArray<JavaThread*>* wantList = nullptr;
1497 
1498   if (mark.has_monitor()) {
1499     mon = mark.monitor();
1500     assert(mon != nullptr, "must have monitor");
1501     // this object has a heavyweight monitor
1502     nWant = mon->contentions(); // # of threads contending for monitor entry, but not re-entry
1503     nWait = mon->waiters();     // # of threads waiting for notification,
1504                                 // or to re-enter monitor, in Object.wait()
1505 
1506     // Get the actual set of threads trying to enter, or re-enter, the monitor.
1507     wantList = Threads::get_pending_threads(tlh.list(), nWant + nWait, (address)mon);
1508     nWant = wantList->length();
1509   } else {
1510     // this object has a lightweight monitor
1511   }
1512 
1513   jint skipped = 0;
1514   if (mon != nullptr) {
1515     // Robustness: the actual waiting list can be smaller.
1516     // The nWait count we got from the mon->waiters() may include the re-entering
1517     // the monitor threads after being notified. Here we are correcting the actual
1518     // number of the waiting threads by excluding those re-entering the monitor.
1519     nWait = 0;
1520     for (ObjectWaiter* waiter = mon->first_waiter();
1521          waiter != nullptr && (nWait == 0 || waiter != mon->first_waiter());
1522          waiter = mon->next_waiter(waiter)) {
1523       JavaThread *w = mon->thread_of_waiter(waiter);
1524       oop thread_oop = get_vthread_or_thread_oop(w);
1525       if (thread_oop->is_a(vmClasses::BaseVirtualThread_klass())) {
1526         skipped++;
1527       }
1528       nWait++;
1529     }
1530   }
1531   ret.waiter_count = nWant;
1532   ret.notify_waiter_count = nWait - skipped;
1533 
1534   // Allocate memory for heavyweight and lightweight monitor.
1535   jvmtiError err;
1536   err = allocate(ret.waiter_count * sizeof(jthread *), (unsigned char**)&ret.waiters);
1537   if (err != JVMTI_ERROR_NONE) {
1538     return err;
1539   }
1540   err = allocate(ret.notify_waiter_count * sizeof(jthread *),
1541                  (unsigned char**)&ret.notify_waiters);
1542   if (err != JVMTI_ERROR_NONE) {
1543     deallocate((unsigned char*)ret.waiters);
1544     return err;
1545   }
1546 
1547   // now derive the rest of the fields
1548   if (mon != nullptr) {
1549     // this object has a heavyweight monitor
1550 
1551     // null out memory for robustness
1552     if (ret.waiters != nullptr) {
1553       memset(ret.waiters, 0, ret.waiter_count * sizeof(jthread *));
1554     }
1555     if (ret.notify_waiters != nullptr) {
1556       memset(ret.notify_waiters, 0, ret.notify_waiter_count * sizeof(jthread *));
1557     }
1558 
1559     if (ret.waiter_count > 0) { // we have contending threads waiting to enter/re-enter the monitor
1560       // identify threads waiting to enter and re-enter the monitor
1561       // get_pending_threads returns only java thread so we do not need to
1562       // check for non java threads.
1563       for (int i = 0; i < nWant; i++) {
1564         JavaThread *pending_thread = wantList->at(i);
1565         Handle th(current_thread, get_vthread_or_thread_oop(pending_thread));
1566         ret.waiters[i] = (jthread)jni_reference(calling_thread, th);
1567       }
1568     }
1569     if (ret.notify_waiter_count > 0) { // we have threads waiting to be notified in Object.wait()
1570       ObjectWaiter *waiter = mon->first_waiter();
1571       jint skipped = 0;
1572       for (int i = 0; i < nWait; i++) {
1573         JavaThread *w = mon->thread_of_waiter(waiter);
1574         oop thread_oop = get_vthread_or_thread_oop(w);
1575         bool is_virtual = thread_oop->is_a(vmClasses::BaseVirtualThread_klass());
1576         assert(w != nullptr, "sanity check");
1577         if (is_virtual) {
1578           skipped++;
1579         } else {
1580           // If the thread was found on the ObjectWaiter list, then
1581           // it has not been notified.
1582           Handle th(current_thread, get_vthread_or_thread_oop(w));
1583           ret.notify_waiters[i - skipped] = (jthread)jni_reference(calling_thread, th);
1584         }
1585         waiter = mon->next_waiter(waiter);
1586       }
1587     }
1588   } else {
1589     // this object has a lightweight monitor and we have nothing more
1590     // to do here because the defaults are just fine.
1591   }
1592 
1593   // we don't update return parameter unless everything worked
1594   *info_ptr = ret;
1595 
1596   return JVMTI_ERROR_NONE;
1597 }
1598 
1599 jvmtiError
1600 JvmtiEnvBase::check_thread_list(jint count, const jthread* list) {
1601   if (list == nullptr && count != 0) {
1602     return JVMTI_ERROR_NULL_POINTER;
1603   }
1604   for (int i = 0; i < count; i++) {
1605     jthread thread = list[i];
1606     oop thread_oop = JNIHandles::resolve_external_guard(thread);
1607     if (thread_oop == nullptr || !thread_oop->is_a(vmClasses::BaseVirtualThread_klass())) {
1608       return JVMTI_ERROR_INVALID_THREAD;
1609     }
1610   }
1611   return JVMTI_ERROR_NONE;
1612 }
1613 
1614 bool
1615 JvmtiEnvBase::is_in_thread_list(jint count, const jthread* list, oop jt_oop) {
1616   for (int idx = 0; idx < count; idx++) {
1617     jthread thread = list[idx];
1618     oop thread_oop = JNIHandles::resolve_external_guard(thread);
1619     if (thread_oop == jt_oop) {
1620       return true;
1621     }
1622   }
1623   return false;
1624 }
1625 
1626 class VM_SetNotifyJvmtiEventsMode : public VM_Operation {
1627 private:
1628   bool _enable;
1629 
1630   static void correct_jvmti_thread_state(JavaThread* jt) {
1631     oop  ct_oop = jt->threadObj();
1632     oop  vt_oop = jt->vthread();
1633     JvmtiThreadState* jt_state = jt->jvmti_thread_state();
1634     JvmtiThreadState* ct_state = java_lang_Thread::jvmti_thread_state(jt->threadObj());
1635     JvmtiThreadState* vt_state = vt_oop != nullptr ? java_lang_Thread::jvmti_thread_state(vt_oop) : nullptr;
1636     bool virt = vt_oop != nullptr && java_lang_VirtualThread::is_instance(vt_oop);
1637 
1638     // Correct jt->jvmti_thread_state() and jt->jvmti_vthread().
1639     // It was not maintained while notifyJvmti was disabled.
1640     if (virt) {
1641       jt->set_jvmti_thread_state(nullptr);  // reset jt->jvmti_thread_state()
1642       jt->set_jvmti_vthread(vt_oop);        // restore jt->jvmti_vthread()
1643     } else {
1644       jt->set_jvmti_thread_state(ct_state); // restore jt->jvmti_thread_state()
1645       jt->set_jvmti_vthread(ct_oop);        // restore jt->jvmti_vthread()
1646     }
1647   }
1648 
1649   // This function is called only if _enable == true.
1650   // Iterates over all JavaThread's, restores jt->jvmti_thread_state() and
1651   // jt->jvmti_vthread() for VTMS transition protocol.
1652   void correct_jvmti_thread_states() {
1653     for (JavaThread* jt : ThreadsListHandle()) {
1654       if (jt->is_in_VTMS_transition()) {
1655         jt->set_VTMS_transition_mark(true);
1656         continue; // no need in JvmtiThreadState correction below if in transition
1657       }
1658       correct_jvmti_thread_state(jt);
1659     }
1660   }
1661 
1662 public:
1663   VMOp_Type type() const { return VMOp_SetNotifyJvmtiEventsMode; }
1664   bool allow_nested_vm_operations() const { return false; }
1665   VM_SetNotifyJvmtiEventsMode(bool enable) : _enable(enable) {
1666   }
1667 
1668   void doit() {
1669     if (_enable) {
1670       correct_jvmti_thread_states();
1671     }
1672     JvmtiVTMSTransitionDisabler::set_VTMS_notify_jvmti_events(_enable);
1673   }
1674 };
1675 
1676 // This function is to support agents loaded into running VM.
1677 // Must be called in thread-in-native mode.
1678 bool
1679 JvmtiEnvBase::enable_virtual_threads_notify_jvmti() {
1680   if (!Continuations::enabled()) {
1681     return false;
1682   }
1683   if (JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
1684     return false; // already enabled
1685   }
1686   VM_SetNotifyJvmtiEventsMode op(true);
1687   VMThread::execute(&op);
1688   return true;
1689 }
1690 
1691 // This function is used in WhiteBox, only needed to test the function above.
1692 // It is unsafe to use this function when virtual threads are executed.
1693 // Must be called in thread-in-native mode.
1694 bool
1695 JvmtiEnvBase::disable_virtual_threads_notify_jvmti() {
1696   if (!Continuations::enabled()) {
1697     return false;
1698   }
1699   if (!JvmtiVTMSTransitionDisabler::VTMS_notify_jvmti_events()) {
1700     return false; // already disabled
1701   }
1702   JvmtiVTMSTransitionDisabler disabler(true); // ensure there are no other disablers
1703   VM_SetNotifyJvmtiEventsMode op(false);
1704   VMThread::execute(&op);
1705   return true;
1706 }
1707 
1708 // java_thread - protected by ThreadsListHandle
1709 jvmtiError
1710 JvmtiEnvBase::suspend_thread(oop thread_oop, JavaThread* java_thread, bool single_suspend,
1711                              int* need_safepoint_p) {
1712   JavaThread* current = JavaThread::current();
1713   HandleMark hm(current);
1714   Handle thread_h(current, thread_oop);
1715   bool is_virtual = java_lang_VirtualThread::is_instance(thread_h());
1716 
1717   if (is_virtual) {
1718     if (single_suspend) {
1719       if (JvmtiVTSuspender::is_vthread_suspended(thread_h())) {
1720         return JVMTI_ERROR_THREAD_SUSPENDED;
1721       }
1722       JvmtiVTSuspender::register_vthread_suspend(thread_h());
1723       // Check if virtual thread is mounted and there is a java_thread.
1724       // A non-null java_thread is always passed in the !single_suspend case.
1725       oop carrier_thread = java_lang_VirtualThread::carrier_thread(thread_h());
1726       java_thread = carrier_thread == nullptr ? nullptr : java_lang_Thread::thread(carrier_thread);
1727     }
1728     // The java_thread can be still blocked in VTMS transition after a previous JVMTI resume call.
1729     // There is no need to suspend the java_thread in this case. After vthread unblocking,
1730     // it will check for ext_suspend request and suspend itself if necessary.
1731     if (java_thread == nullptr || java_thread->is_suspended()) {
1732       // We are done if the virtual thread is unmounted or
1733       // the java_thread is externally suspended.
1734       return JVMTI_ERROR_NONE;
1735     }
1736     // The virtual thread is mounted: suspend the java_thread.
1737   }
1738   // Don't allow hidden thread suspend request.
1739   if (java_thread->is_hidden_from_external_view()) {
1740     return JVMTI_ERROR_NONE;
1741   }
1742   bool is_thread_carrying = is_thread_carrying_vthread(java_thread, thread_h());
1743 
1744   // A case of non-virtual thread.
1745   if (!is_virtual) {
1746     // Thread.suspend() is used in some tests. It sets jt->is_suspended() only.
1747     if (java_thread->is_carrier_thread_suspended() ||
1748         (!is_thread_carrying && java_thread->is_suspended())) {
1749       return JVMTI_ERROR_THREAD_SUSPENDED;
1750     }
1751     java_thread->set_carrier_thread_suspended();
1752   }
1753   assert(!java_thread->is_in_VTMS_transition(), "sanity check");
1754 
1755   assert(!single_suspend || (!is_virtual && java_thread->is_carrier_thread_suspended()) ||
1756           (is_virtual && JvmtiVTSuspender::is_vthread_suspended(thread_h())),
1757          "sanity check");
1758 
1759   // An attempt to handshake-suspend a thread carrying a virtual thread will result in
1760   // suspension of mounted virtual thread. So, we just mark it as suspended
1761   // and it will be actually suspended at virtual thread unmount transition.
1762   if (!is_thread_carrying) {
1763     assert(thread_h() != nullptr, "sanity check");
1764     assert(single_suspend || thread_h()->is_a(vmClasses::BaseVirtualThread_klass()),
1765            "SuspendAllVirtualThreads should never suspend non-virtual threads");
1766     // Case of mounted virtual or attached carrier thread.
1767     if (!JvmtiSuspendControl::suspend(java_thread)) {
1768       // Thread is already suspended or in process of exiting.
1769       if (java_thread->is_exiting()) {
1770         // The thread was in the process of exiting.
1771         return JVMTI_ERROR_THREAD_NOT_ALIVE;
1772       }
1773       return JVMTI_ERROR_THREAD_SUSPENDED;
1774     }
1775   }
1776   return JVMTI_ERROR_NONE;
1777 }
1778 
1779 // java_thread - protected by ThreadsListHandle
1780 jvmtiError
1781 JvmtiEnvBase::resume_thread(oop thread_oop, JavaThread* java_thread, bool single_resume) {
1782   JavaThread* current = JavaThread::current();
1783   HandleMark hm(current);
1784   Handle thread_h(current, thread_oop);
1785   bool is_virtual = java_lang_VirtualThread::is_instance(thread_h());
1786 
1787   if (is_virtual) {
1788     if (single_resume) {
1789       if (!JvmtiVTSuspender::is_vthread_suspended(thread_h())) {
1790         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1791       }
1792       JvmtiVTSuspender::register_vthread_resume(thread_h());
1793       // Check if virtual thread is mounted and there is a java_thread.
1794       // A non-null java_thread is always passed in the !single_resume case.
1795       oop carrier_thread = java_lang_VirtualThread::carrier_thread(thread_h());
1796       java_thread = carrier_thread == nullptr ? nullptr : java_lang_Thread::thread(carrier_thread);
1797     }
1798     // The java_thread can be still blocked in VTMS transition after a previous JVMTI suspend call.
1799     // There is no need to resume the java_thread in this case. After vthread unblocking,
1800     // it will check for is_vthread_suspended request and remain resumed if necessary.
1801     if (java_thread == nullptr || !java_thread->is_suspended()) {
1802       // We are done if the virtual thread is unmounted or
1803       // the java_thread is not externally suspended.
1804       return JVMTI_ERROR_NONE;
1805     }
1806     // The virtual thread is mounted and java_thread is supended: resume the java_thread.
1807   }
1808   // Don't allow hidden thread resume request.
1809   if (java_thread->is_hidden_from_external_view()) {
1810     return JVMTI_ERROR_NONE;
1811   }
1812   bool is_thread_carrying = is_thread_carrying_vthread(java_thread, thread_h());
1813 
1814   // A case of a non-virtual thread.
1815   if (!is_virtual) {
1816     if (!java_thread->is_carrier_thread_suspended() &&
1817         (is_thread_carrying || !java_thread->is_suspended())) {
1818       return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1819     }
1820     java_thread->clear_carrier_thread_suspended();
1821   }
1822   assert(!java_thread->is_in_VTMS_transition(), "sanity check");
1823 
1824   if (!is_thread_carrying) {
1825     assert(thread_h() != nullptr, "sanity check");
1826     assert(single_resume || thread_h()->is_a(vmClasses::BaseVirtualThread_klass()),
1827            "ResumeAllVirtualThreads should never resume non-virtual threads");
1828     if (java_thread->is_suspended()) {
1829       if (!JvmtiSuspendControl::resume(java_thread)) {
1830         return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
1831       }
1832     }
1833   }
1834   return JVMTI_ERROR_NONE;
1835 }
1836 
1837 ResourceTracker::ResourceTracker(JvmtiEnv* env) {
1838   _env = env;
1839   _allocations = new (mtServiceability) GrowableArray<unsigned char*>(20, mtServiceability);
1840   _failed = false;
1841 }
1842 ResourceTracker::~ResourceTracker() {
1843   if (_failed) {
1844     for (int i=0; i<_allocations->length(); i++) {
1845       _env->deallocate(_allocations->at(i));
1846     }
1847   }
1848   delete _allocations;
1849 }
1850 
1851 jvmtiError ResourceTracker::allocate(jlong size, unsigned char** mem_ptr) {
1852   unsigned char *ptr;
1853   jvmtiError err = _env->allocate(size, &ptr);
1854   if (err == JVMTI_ERROR_NONE) {
1855     _allocations->append(ptr);
1856     *mem_ptr = ptr;
1857   } else {
1858     *mem_ptr = nullptr;
1859     _failed = true;
1860   }
1861   return err;
1862  }
1863 
1864 unsigned char* ResourceTracker::allocate(jlong size) {
1865   unsigned char* ptr;
1866   allocate(size, &ptr);
1867   return ptr;
1868 }
1869 
1870 char* ResourceTracker::strdup(const char* str) {
1871   char *dup_str = (char*)allocate(strlen(str)+1);
1872   if (dup_str != nullptr) {
1873     strcpy(dup_str, str);
1874   }
1875   return dup_str;
1876 }
1877 
1878 struct StackInfoNode {
1879   struct StackInfoNode *next;
1880   jvmtiStackInfo info;
1881 };
1882 
1883 // Create a jvmtiStackInfo inside a linked list node and create a
1884 // buffer for the frame information, both allocated as resource objects.
1885 // Fill in both the jvmtiStackInfo and the jvmtiFrameInfo.
1886 // Note that either or both of thr and thread_oop
1887 // may be null if the thread is new or has exited.
1888 void
1889 MultipleStackTracesCollector::fill_frames(jthread jt, JavaThread *thr, oop thread_oop) {
1890 #ifdef ASSERT
1891   Thread *current_thread = Thread::current();
1892   assert(SafepointSynchronize::is_at_safepoint() ||
1893          thr == nullptr ||
1894          thr->is_handshake_safe_for(current_thread),
1895          "unmounted virtual thread / call by myself / at safepoint / at handshake");
1896 #endif
1897 
1898   jint state = 0;
1899   struct StackInfoNode *node = NEW_RESOURCE_OBJ(struct StackInfoNode);
1900   jvmtiStackInfo *infop = &(node->info);
1901 
1902   node->next = head();
1903   set_head(node);
1904   infop->frame_count = 0;
1905   infop->frame_buffer = nullptr;
1906   infop->thread = jt;
1907 
1908   if (java_lang_VirtualThread::is_instance(thread_oop)) {
1909     state = JvmtiEnvBase::get_vthread_state(thread_oop, thr);
1910 
1911     if ((state & JVMTI_THREAD_STATE_ALIVE) != 0) {
1912       javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(thread_oop);
1913       infop->frame_buffer = NEW_RESOURCE_ARRAY(jvmtiFrameInfo, max_frame_count());
1914       _result = env()->get_stack_trace(jvf, 0, max_frame_count(),
1915                                        infop->frame_buffer, &(infop->frame_count));
1916     }
1917   } else {
1918     state = JvmtiEnvBase::get_thread_state(thread_oop, thr);
1919     if (thr != nullptr && (state & JVMTI_THREAD_STATE_ALIVE) != 0) {
1920       infop->frame_buffer = NEW_RESOURCE_ARRAY(jvmtiFrameInfo, max_frame_count());
1921       _result = env()->get_stack_trace(thr, 0, max_frame_count(),
1922                                        infop->frame_buffer, &(infop->frame_count));
1923     }
1924   }
1925   _frame_count_total += infop->frame_count;
1926   infop->state = state;
1927 }
1928 
1929 // Based on the stack information in the linked list, allocate memory
1930 // block to return and fill it from the info in the linked list.
1931 void
1932 MultipleStackTracesCollector::allocate_and_fill_stacks(jint thread_count) {
1933   // do I need to worry about alignment issues?
1934   jlong alloc_size =  thread_count       * sizeof(jvmtiStackInfo)
1935                     + _frame_count_total * sizeof(jvmtiFrameInfo);
1936   env()->allocate(alloc_size, (unsigned char **)&_stack_info);
1937 
1938   // pointers to move through the newly allocated space as it is filled in
1939   jvmtiStackInfo *si = _stack_info + thread_count;      // bottom of stack info
1940   jvmtiFrameInfo *fi = (jvmtiFrameInfo *)si;            // is the top of frame info
1941 
1942   // copy information in resource area into allocated buffer
1943   // insert stack info backwards since linked list is backwards
1944   // insert frame info forwards
1945   // walk the StackInfoNodes
1946   for (struct StackInfoNode *sin = head(); sin != nullptr; sin = sin->next) {
1947     jint frame_count = sin->info.frame_count;
1948     size_t frames_size = frame_count * sizeof(jvmtiFrameInfo);
1949     --si;
1950     memcpy(si, &(sin->info), sizeof(jvmtiStackInfo));
1951     if (frames_size == 0) {
1952       si->frame_buffer = nullptr;
1953     } else {
1954       memcpy(fi, sin->info.frame_buffer, frames_size);
1955       si->frame_buffer = fi;  // point to the new allocated copy of the frames
1956       fi += frame_count;
1957     }
1958   }
1959   assert(si == _stack_info, "the last copied stack info must be the first record");
1960   assert((unsigned char *)fi == ((unsigned char *)_stack_info) + alloc_size,
1961          "the last copied frame info must be the last record");
1962 }
1963 
1964 // AdapterClosure is to make use of JvmtiUnitedHandshakeClosure objects from
1965 // Handshake::execute() which is unaware of the do_vthread() member functions.
1966 class AdapterClosure : public HandshakeClosure {
1967   JvmtiUnitedHandshakeClosure* _hs_cl;
1968   Handle _target_h;
1969 
1970  public:
1971   AdapterClosure(JvmtiUnitedHandshakeClosure* hs_cl, Handle target_h)
1972       : HandshakeClosure(hs_cl->name()), _hs_cl(hs_cl), _target_h(target_h) {}
1973 
1974   virtual void do_thread(Thread* target) {
1975     if (java_lang_VirtualThread::is_instance(_target_h())) {
1976       _hs_cl->do_vthread(_target_h); // virtual thread
1977     } else {
1978       _hs_cl->do_thread(target);     // platform thread
1979     }
1980   }
1981 };
1982 
1983 // Supports platform and virtual threads.
1984 // JvmtiVTMSTransitionDisabler is always set by this function.
1985 void
1986 JvmtiHandshake::execute(JvmtiUnitedHandshakeClosure* hs_cl, jthread target) {
1987   JavaThread* current = JavaThread::current();
1988   HandleMark hm(current);
1989 
1990   JvmtiVTMSTransitionDisabler disabler(target);
1991   ThreadsListHandle tlh(current);
1992   JavaThread* java_thread = nullptr;
1993   oop thread_obj = nullptr;
1994 
1995   jvmtiError err = JvmtiEnvBase::get_threadOop_and_JavaThread(tlh.list(), target, current, &java_thread, &thread_obj);
1996   if (err != JVMTI_ERROR_NONE) {
1997     hs_cl->set_result(err);
1998     return;
1999   }
2000   Handle target_h(current, thread_obj);
2001   execute(hs_cl, &tlh, java_thread, target_h);
2002 }
2003 
2004 // Supports platform and virtual threads.
2005 // A virtual thread is always identified by the target_h oop handle.
2006 // The target_jt is always nullptr for an unmounted virtual thread.
2007 // JvmtiVTMSTransitionDisabler has to be set before call to this function.
2008 void
2009 JvmtiHandshake::execute(JvmtiUnitedHandshakeClosure* hs_cl, ThreadsListHandle* tlh,
2010                         JavaThread* target_jt, Handle target_h) {
2011   JavaThread* current = JavaThread::current();
2012   bool is_virtual = java_lang_VirtualThread::is_instance(target_h());
2013   bool self = target_jt == current;
2014 
2015   assert(!Continuations::enabled() || self || !is_virtual || current->is_VTMS_transition_disabler(), "sanity check");
2016 
2017   hs_cl->set_target_jt(target_jt);   // can be needed in the virtual thread case
2018   hs_cl->set_is_virtual(is_virtual); // can be needed in the virtual thread case
2019   hs_cl->set_self(self);             // needed when suspend is required for non-current target thread
2020 
2021   if (is_virtual) {                // virtual thread
2022     if (!JvmtiEnvBase::is_vthread_alive(target_h())) {
2023       return;
2024     }
2025     if (target_jt == nullptr) {    // unmounted virtual thread
2026       hs_cl->do_vthread(target_h); // execute handshake closure callback on current thread directly
2027     }
2028   }
2029   if (target_jt != nullptr) {      // mounted virtual or platform thread
2030     AdapterClosure acl(hs_cl, target_h);
2031     if (self) {                    // target platform thread is current
2032       acl.do_thread(target_jt);    // execute handshake closure callback on current thread directly
2033     } else {
2034       Handshake::execute(&acl, tlh, target_jt); // delegate to Handshake implementation
2035     }
2036   }
2037 }
2038 
2039 void
2040 VM_GetThreadListStackTraces::doit() {
2041   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
2042 
2043   ResourceMark rm;
2044   ThreadsListHandle tlh;
2045   for (int i = 0; i < _thread_count; ++i) {
2046     jthread jt = _thread_list[i];
2047     JavaThread* java_thread = nullptr;
2048     oop thread_oop = nullptr;
2049     jvmtiError err = JvmtiEnvBase::get_threadOop_and_JavaThread(tlh.list(), jt, nullptr, &java_thread, &thread_oop);
2050 
2051     if (err != JVMTI_ERROR_NONE) {
2052       // We got an error code so we don't have a JavaThread *, but
2053       // only return an error from here if we didn't get a valid
2054       // thread_oop.
2055       // In the virtual thread case the get_threadOop_and_JavaThread is expected to correctly set
2056       // the thread_oop and return JVMTI_ERROR_THREAD_NOT_ALIVE which we ignore here.
2057       // The corresponding thread state will be recorded in the jvmtiStackInfo.state.
2058       if (thread_oop == nullptr) {
2059         _collector.set_result(err);
2060         return;
2061       }
2062       // We have a valid thread_oop.
2063     }
2064     _collector.fill_frames(jt, java_thread, thread_oop);
2065   }
2066   _collector.allocate_and_fill_stacks(_thread_count);
2067 }
2068 
2069 void
2070 GetSingleStackTraceClosure::doit() {
2071   JavaThread *jt = _target_jt;
2072   oop thread_oop = JNIHandles::resolve_external_guard(_jthread);
2073 
2074   if ((jt == nullptr || !jt->is_exiting()) && thread_oop != nullptr) {
2075     ResourceMark rm;
2076     _collector.fill_frames(_jthread, jt, thread_oop);
2077     _collector.allocate_and_fill_stacks(1);
2078     set_result(_collector.result());
2079   }
2080 }
2081 
2082 void
2083 GetSingleStackTraceClosure::do_thread(Thread *target) {
2084   assert(_target_jt == JavaThread::cast(target), "sanity check");
2085   doit();
2086 }
2087 
2088 void
2089 GetSingleStackTraceClosure::do_vthread(Handle target_h) {
2090   // Use jvmti_vthread() instead of vthread() as target could have temporarily changed
2091   // identity to carrier thread (see VirtualThread.switchToCarrierThread).
2092   assert(_target_jt == nullptr || _target_jt->jvmti_vthread() == target_h(), "sanity check");
2093   doit();
2094 }
2095 
2096 void
2097 VM_GetAllStackTraces::doit() {
2098   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
2099 
2100   ResourceMark rm;
2101   _final_thread_count = 0;
2102   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
2103     oop thread_oop = jt->threadObj();
2104     if (thread_oop != nullptr &&
2105         !jt->is_exiting() &&
2106         java_lang_Thread::is_alive(thread_oop) &&
2107         !jt->is_hidden_from_external_view() &&
2108         !thread_oop->is_a(vmClasses::BoundVirtualThread_klass())) {
2109       ++_final_thread_count;
2110       // Handle block of the calling thread is used to create local refs.
2111       _collector.fill_frames((jthread)JNIHandles::make_local(_calling_thread, thread_oop),
2112                              jt, thread_oop);
2113     }
2114   }
2115   _collector.allocate_and_fill_stacks(_final_thread_count);
2116 }
2117 
2118 // Verifies that the top frame is a java frame in an expected state.
2119 // Deoptimizes frame if needed.
2120 // Checks that the frame method signature matches the return type (tos).
2121 // HandleMark must be defined in the caller only.
2122 // It is to keep a ret_ob_h handle alive after return to the caller.
2123 jvmtiError
2124 JvmtiEnvBase::check_top_frame(Thread* current_thread, JavaThread* java_thread,
2125                               jvalue value, TosState tos, Handle* ret_ob_h) {
2126   ResourceMark rm(current_thread);
2127 
2128   javaVFrame* jvf = jvf_for_thread_and_depth(java_thread, 0);
2129   NULL_CHECK(jvf, JVMTI_ERROR_NO_MORE_FRAMES);
2130 
2131   if (jvf->method()->is_native()) {
2132     return JVMTI_ERROR_OPAQUE_FRAME;
2133   }
2134 
2135   // If the frame is a compiled one, need to deoptimize it.
2136   if (jvf->is_compiled_frame()) {
2137     if (!jvf->fr().can_be_deoptimized()) {
2138       return JVMTI_ERROR_OPAQUE_FRAME;
2139     }
2140     Deoptimization::deoptimize_frame(java_thread, jvf->fr().id());
2141   }
2142 
2143   // Get information about method return type
2144   Symbol* signature = jvf->method()->signature();
2145 
2146   ResultTypeFinder rtf(signature);
2147   TosState fr_tos = as_TosState(rtf.type());
2148   if (fr_tos != tos) {
2149     if (tos != itos || (fr_tos != btos && fr_tos != ztos && fr_tos != ctos && fr_tos != stos)) {
2150       return JVMTI_ERROR_TYPE_MISMATCH;
2151     }
2152   }
2153 
2154   // Check that the jobject class matches the return type signature.
2155   jobject jobj = value.l;
2156   if (tos == atos && jobj != nullptr) { // null reference is allowed
2157     Handle ob_h(current_thread, JNIHandles::resolve_external_guard(jobj));
2158     NULL_CHECK(ob_h, JVMTI_ERROR_INVALID_OBJECT);
2159     Klass* ob_k = ob_h()->klass();
2160     NULL_CHECK(ob_k, JVMTI_ERROR_INVALID_OBJECT);
2161 
2162     // Method return type signature.
2163     char* ty_sign = 1 + strchr(signature->as_C_string(), JVM_SIGNATURE_ENDFUNC);
2164 
2165     if (!VM_GetOrSetLocal::is_assignable(ty_sign, ob_k, current_thread)) {
2166       return JVMTI_ERROR_TYPE_MISMATCH;
2167     }
2168     *ret_ob_h = ob_h;
2169   }
2170   return JVMTI_ERROR_NONE;
2171 } /* end check_top_frame */
2172 
2173 
2174 // ForceEarlyReturn<type> follows the PopFrame approach in many aspects.
2175 // Main difference is on the last stage in the interpreter.
2176 // The PopFrame stops method execution to continue execution
2177 // from the same method call instruction.
2178 // The ForceEarlyReturn forces return from method so the execution
2179 // continues at the bytecode following the method call.
2180 
2181 // thread - NOT protected by ThreadsListHandle and NOT pre-checked
2182 
2183 jvmtiError
2184 JvmtiEnvBase::force_early_return(jthread thread, jvalue value, TosState tos) {
2185   JavaThread* current_thread = JavaThread::current();
2186   HandleMark hm(current_thread);
2187 
2188   JvmtiVTMSTransitionDisabler disabler(thread);
2189   ThreadsListHandle tlh(current_thread);
2190 
2191   JavaThread* java_thread = nullptr;
2192   oop thread_obj = nullptr;
2193   jvmtiError err = get_threadOop_and_JavaThread(tlh.list(), thread, current_thread, &java_thread, &thread_obj);
2194 
2195   if (err != JVMTI_ERROR_NONE) {
2196     return err;
2197   }
2198   Handle thread_handle(current_thread, thread_obj);
2199   bool self = java_thread == current_thread;
2200 
2201   err = check_non_suspended_or_opaque_frame(java_thread, thread_obj, self);
2202   if (err != JVMTI_ERROR_NONE) {
2203     return err;
2204   }
2205 
2206   // retrieve or create the state
2207   JvmtiThreadState* state = JvmtiThreadState::state_for(java_thread);
2208   if (state == nullptr) {
2209     return JVMTI_ERROR_THREAD_NOT_ALIVE;
2210   }
2211 
2212   // Eagerly reallocate scalar replaced objects.
2213   EscapeBarrier eb(true, current_thread, java_thread);
2214   if (!eb.deoptimize_objects(0)) {
2215     // Reallocation of scalar replaced objects failed -> return with error
2216     return JVMTI_ERROR_OUT_OF_MEMORY;
2217   }
2218 
2219   MutexLocker mu(JvmtiThreadState_lock);
2220   SetForceEarlyReturn op(state, value, tos);
2221   JvmtiHandshake::execute(&op, &tlh, java_thread, thread_handle);
2222   return op.result();
2223 }
2224 
2225 void
2226 SetForceEarlyReturn::doit(Thread *target) {
2227   JavaThread* java_thread = JavaThread::cast(target);
2228   Thread* current_thread = Thread::current();
2229   HandleMark   hm(current_thread);
2230 
2231   if (java_thread->is_exiting()) {
2232     return; /* JVMTI_ERROR_THREAD_NOT_ALIVE (default) */
2233   }
2234 
2235   // Check to see if a ForceEarlyReturn was already in progress
2236   if (_state->is_earlyret_pending()) {
2237     // Probably possible for JVMTI clients to trigger this, but the
2238     // JPDA backend shouldn't allow this to happen
2239     _result = JVMTI_ERROR_INTERNAL;
2240     return;
2241   }
2242   {
2243     // The same as for PopFrame. Workaround bug:
2244     //  4812902: popFrame hangs if the method is waiting at a synchronize
2245     // Catch this condition and return an error to avoid hanging.
2246     // Now JVMTI spec allows an implementation to bail out with an opaque
2247     // frame error.
2248     OSThread* osThread = java_thread->osthread();
2249     if (osThread->get_state() == MONITOR_WAIT) {
2250       _result = JVMTI_ERROR_OPAQUE_FRAME;
2251       return;
2252     }
2253   }
2254 
2255   Handle ret_ob_h;
2256   _result = JvmtiEnvBase::check_top_frame(current_thread, java_thread, _value, _tos, &ret_ob_h);
2257   if (_result != JVMTI_ERROR_NONE) {
2258     return;
2259   }
2260   assert(_tos != atos || _value.l == nullptr || ret_ob_h() != nullptr,
2261          "return object oop must not be null if jobject is not null");
2262 
2263   // Update the thread state to reflect that the top frame must be
2264   // forced to return.
2265   // The current frame will be returned later when the suspended
2266   // thread is resumed and right before returning from VM to Java.
2267   // (see call_VM_base() in assembler_<cpu>.cpp).
2268 
2269   _state->set_earlyret_pending();
2270   _state->set_earlyret_oop(ret_ob_h());
2271   _state->set_earlyret_value(_value, _tos);
2272 
2273   // Set pending step flag for this early return.
2274   // It is cleared when next step event is posted.
2275   _state->set_pending_step_for_earlyret();
2276 }
2277 
2278 void
2279 JvmtiMonitorClosure::do_monitor(ObjectMonitor* mon) {
2280   if ( _error != JVMTI_ERROR_NONE) {
2281     // Error occurred in previous iteration so no need to add
2282     // to the list.
2283     return;
2284   }
2285   // Filter out on stack monitors collected during stack walk.
2286   oop obj = mon->object();
2287 
2288   if (obj == nullptr) {
2289     // This can happen if JNI code drops all references to the
2290     // owning object.
2291     return;
2292   }
2293 
2294   bool found = false;
2295   for (int j = 0; j < _owned_monitors_list->length(); j++) {
2296     jobject jobj = ((jvmtiMonitorStackDepthInfo*)_owned_monitors_list->at(j))->monitor;
2297     oop check = JNIHandles::resolve(jobj);
2298     if (check == obj) {
2299       // On stack monitor already collected during the stack walk.
2300       found = true;
2301       break;
2302     }
2303   }
2304   if (found == false) {
2305     // This is off stack monitor (e.g. acquired via jni MonitorEnter).
2306     jvmtiError err;
2307     jvmtiMonitorStackDepthInfo *jmsdi;
2308     err = _env->allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
2309     if (err != JVMTI_ERROR_NONE) {
2310       _error = err;
2311       return;
2312     }
2313     Handle hobj(Thread::current(), obj);
2314     jmsdi->monitor = _env->jni_reference(_calling_thread, hobj);
2315     // stack depth is unknown for this monitor.
2316     jmsdi->stack_depth = -1;
2317     _owned_monitors_list->append(jmsdi);
2318   }
2319 }
2320 
2321 GrowableArray<OopHandle>* JvmtiModuleClosure::_tbl = nullptr;
2322 
2323 void JvmtiModuleClosure::do_module(ModuleEntry* entry) {
2324   assert_locked_or_safepoint(Module_lock);
2325   OopHandle module = entry->module_handle();
2326   guarantee(module.resolve() != nullptr, "module object is null");
2327   _tbl->push(module);
2328 }
2329 
2330 jvmtiError
2331 JvmtiModuleClosure::get_all_modules(JvmtiEnv* env, jint* module_count_ptr, jobject** modules_ptr) {
2332   ResourceMark rm;
2333   MutexLocker mcld(ClassLoaderDataGraph_lock);
2334   MutexLocker ml(Module_lock);
2335 
2336   _tbl = new GrowableArray<OopHandle>(77);
2337   if (_tbl == nullptr) {
2338     return JVMTI_ERROR_OUT_OF_MEMORY;
2339   }
2340 
2341   // Iterate over all the modules loaded to the system.
2342   ClassLoaderDataGraph::modules_do(&do_module);
2343 
2344   jint len = _tbl->length();
2345   guarantee(len > 0, "at least one module must be present");
2346 
2347   jobject* array = (jobject*)env->jvmtiMalloc((jlong)(len * sizeof(jobject)));
2348   if (array == nullptr) {
2349     return JVMTI_ERROR_OUT_OF_MEMORY;
2350   }
2351   for (jint idx = 0; idx < len; idx++) {
2352     array[idx] = JNIHandles::make_local(_tbl->at(idx).resolve());
2353   }
2354   _tbl = nullptr;
2355   *modules_ptr = array;
2356   *module_count_ptr = len;
2357   return JVMTI_ERROR_NONE;
2358 }
2359 
2360 void
2361 UpdateForPopTopFrameClosure::doit(Thread *target) {
2362   Thread* current_thread  = Thread::current();
2363   HandleMark hm(current_thread);
2364   JavaThread* java_thread = JavaThread::cast(target);
2365 
2366   if (java_thread->is_exiting()) {
2367     return; /* JVMTI_ERROR_THREAD_NOT_ALIVE (default) */
2368   }
2369   assert(java_thread == _state->get_thread(), "Must be");
2370 
2371   // Check to see if a PopFrame was already in progress
2372   if (java_thread->popframe_condition() != JavaThread::popframe_inactive) {
2373     // Probably possible for JVMTI clients to trigger this, but the
2374     // JPDA backend shouldn't allow this to happen
2375     _result = JVMTI_ERROR_INTERNAL;
2376     return;
2377   }
2378 
2379   // Was workaround bug
2380   //    4812902: popFrame hangs if the method is waiting at a synchronize
2381   // Catch this condition and return an error to avoid hanging.
2382   // Now JVMTI spec allows an implementation to bail out with an opaque frame error.
2383   OSThread* osThread = java_thread->osthread();
2384   if (osThread->get_state() == MONITOR_WAIT) {
2385     _result = JVMTI_ERROR_OPAQUE_FRAME;
2386     return;
2387   }
2388 
2389   ResourceMark rm(current_thread);
2390   // Check if there is more than one Java frame in this thread, that the top two frames
2391   // are Java (not native) frames, and that there is no intervening VM frame
2392   int frame_count = 0;
2393   bool is_interpreted[2];
2394   intptr_t *frame_sp[2];
2395   // The 2-nd arg of constructor is needed to stop iterating at java entry frame.
2396   for (vframeStream vfs(java_thread, true, false /* process_frames */); !vfs.at_end(); vfs.next()) {
2397     methodHandle mh(current_thread, vfs.method());
2398     if (mh->is_native()) {
2399       _result = JVMTI_ERROR_OPAQUE_FRAME;
2400       return;
2401     }
2402     is_interpreted[frame_count] = vfs.is_interpreted_frame();
2403     frame_sp[frame_count] = vfs.frame_id();
2404     if (++frame_count > 1) break;
2405   }
2406   if (frame_count < 2)  {
2407     // We haven't found two adjacent non-native Java frames on the top.
2408     // There can be two situations here:
2409     //  1. There are no more java frames
2410     //  2. Two top java frames are separated by non-java native frames
2411     if (JvmtiEnvBase::jvf_for_thread_and_depth(java_thread, 1) == nullptr) {
2412       _result = JVMTI_ERROR_NO_MORE_FRAMES;
2413       return;
2414     } else {
2415       // Intervening non-java native or VM frames separate java frames.
2416       // Current implementation does not support this. See bug #5031735.
2417       // In theory it is possible to pop frames in such cases.
2418       _result = JVMTI_ERROR_OPAQUE_FRAME;
2419       return;
2420     }
2421   }
2422 
2423   // If any of the top 2 frames is a compiled one, need to deoptimize it
2424   for (int i = 0; i < 2; i++) {
2425     if (!is_interpreted[i]) {
2426       Deoptimization::deoptimize_frame(java_thread, frame_sp[i]);
2427     }
2428   }
2429 
2430   // Update the thread state to reflect that the top frame is popped
2431   // so that cur_stack_depth is maintained properly and all frameIDs
2432   // are invalidated.
2433   // The current frame will be popped later when the suspended thread
2434   // is resumed and right before returning from VM to Java.
2435   // (see call_VM_base() in assembler_<cpu>.cpp).
2436 
2437   // It's fine to update the thread state here because no JVMTI events
2438   // shall be posted for this PopFrame.
2439 
2440   _state->update_for_pop_top_frame();
2441   java_thread->set_popframe_condition(JavaThread::popframe_pending_bit);
2442   // Set pending step flag for this popframe and it is cleared when next
2443   // step event is posted.
2444   _state->set_pending_step_for_popframe();
2445   _result = JVMTI_ERROR_NONE;
2446 }
2447 
2448 void
2449 SetFramePopClosure::do_thread(Thread *target) {
2450   Thread* current = Thread::current();
2451   ResourceMark rm(current); // vframes are resource allocated
2452   JavaThread* java_thread = JavaThread::cast(target);
2453 
2454   if (java_thread->is_exiting()) {
2455     return; // JVMTI_ERROR_THREAD_NOT_ALIVE (default)
2456   }
2457 
2458   if (!_self && !java_thread->is_suspended()) {
2459     _result = JVMTI_ERROR_THREAD_NOT_SUSPENDED;
2460     return;
2461   }
2462   if (!java_thread->has_last_Java_frame()) {
2463     _result = JVMTI_ERROR_NO_MORE_FRAMES;
2464     return;
2465   }
2466   assert(_state->get_thread_or_saved() == java_thread, "Must be");
2467 
2468   RegisterMap reg_map(java_thread,
2469                       RegisterMap::UpdateMap::include,
2470                       RegisterMap::ProcessFrames::skip,
2471                       RegisterMap::WalkContinuation::include);
2472   javaVFrame* jvf = JvmtiEnvBase::get_cthread_last_java_vframe(java_thread, &reg_map);
2473   _result = ((JvmtiEnvBase*)_env)->set_frame_pop(_state, jvf, _depth);
2474 }
2475 
2476 void
2477 SetFramePopClosure::do_vthread(Handle target_h) {
2478   Thread* current = Thread::current();
2479   ResourceMark rm(current); // vframes are resource allocated
2480 
2481   if (!_self && !JvmtiVTSuspender::is_vthread_suspended(target_h())) {
2482     _result = JVMTI_ERROR_THREAD_NOT_SUSPENDED;
2483     return;
2484   }
2485   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(target_h());
2486   _result = ((JvmtiEnvBase*)_env)->set_frame_pop(_state, jvf, _depth);
2487 }
2488 
2489 void
2490 GetOwnedMonitorInfoClosure::do_thread(Thread *target) {
2491   JavaThread *jt = JavaThread::cast(target);
2492   if (!jt->is_exiting() && (jt->threadObj() != nullptr)) {
2493     _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(_calling_thread,
2494                                                          jt,
2495                                                          _owned_monitors_list);
2496   }
2497 }
2498 
2499 void
2500 GetOwnedMonitorInfoClosure::do_vthread(Handle target_h) {
2501   assert(_target_jt != nullptr, "sanity check");
2502   Thread* current = Thread::current();
2503   ResourceMark rm(current); // vframes are resource allocated
2504   HandleMark hm(current);
2505 
2506   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(target_h());
2507 
2508   if (!_target_jt->is_exiting() && _target_jt->threadObj() != nullptr) {
2509     _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(_calling_thread,
2510                                                          _target_jt,
2511                                                          jvf,
2512                                                          _owned_monitors_list);
2513   }
2514 }
2515 
2516 void
2517 GetCurrentContendedMonitorClosure::do_thread(Thread *target) {
2518   JavaThread *jt = JavaThread::cast(target);
2519   if (!jt->is_exiting() && (jt->threadObj() != nullptr)) {
2520     _result = ((JvmtiEnvBase *)_env)->get_current_contended_monitor(_calling_thread,
2521                                                                     jt,
2522                                                                     _owned_monitor_ptr,
2523                                                                     _is_virtual);
2524   }
2525 }
2526 
2527 void
2528 GetCurrentContendedMonitorClosure::do_vthread(Handle target_h) {
2529   if (_target_jt == nullptr) {
2530     _result = JVMTI_ERROR_NONE; // target virtual thread is unmounted
2531     return;
2532   }
2533   // mounted virtual thread case
2534   do_thread(_target_jt);
2535 }
2536 
2537 void
2538 GetStackTraceClosure::do_thread(Thread *target) {
2539   Thread* current = Thread::current();
2540   ResourceMark rm(current);
2541 
2542   JavaThread *jt = JavaThread::cast(target);
2543   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2544     _result = ((JvmtiEnvBase *)_env)->get_stack_trace(jt,
2545                                                       _start_depth, _max_count,
2546                                                       _frame_buffer, _count_ptr);
2547   }
2548 }
2549 
2550 void
2551 GetStackTraceClosure::do_vthread(Handle target_h) {
2552   Thread* current = Thread::current();
2553   ResourceMark rm(current);
2554 
2555   javaVFrame *jvf = JvmtiEnvBase::get_vthread_jvf(target_h());
2556   _result = ((JvmtiEnvBase *)_env)->get_stack_trace(jvf,
2557                                                     _start_depth, _max_count,
2558                                                     _frame_buffer, _count_ptr);
2559 }
2560 
2561 #ifdef ASSERT
2562 void
2563 PrintStackTraceClosure::do_thread_impl(Thread *target) {
2564   JavaThread *java_thread = JavaThread::cast(target);
2565   Thread *current_thread = Thread::current();
2566 
2567   ResourceMark rm (current_thread);
2568   const char* tname = JvmtiTrace::safe_get_thread_name(java_thread);
2569   oop t_oop = java_thread->jvmti_vthread();
2570   t_oop = t_oop == nullptr ? java_thread->threadObj() : t_oop;
2571   bool is_vt_suspended = java_lang_VirtualThread::is_instance(t_oop) && JvmtiVTSuspender::is_vthread_suspended(t_oop);
2572 
2573   log_error(jvmti)("%s(%s) exiting: %d is_susp: %d is_thread_susp: %d is_vthread_susp: %d "
2574                    "is_VTMS_transition_disabler: %d, is_in_VTMS_transition = %d\n",
2575                    tname, java_thread->name(), java_thread->is_exiting(),
2576                    java_thread->is_suspended(), java_thread->is_carrier_thread_suspended(), is_vt_suspended,
2577                    java_thread->is_VTMS_transition_disabler(), java_thread->is_in_VTMS_transition());
2578 
2579   if (java_thread->has_last_Java_frame()) {
2580     RegisterMap reg_map(java_thread,
2581                         RegisterMap::UpdateMap::include,
2582                         RegisterMap::ProcessFrames::include,
2583                         RegisterMap::WalkContinuation::skip);
2584     ResourceMark rm(current_thread);
2585     HandleMark hm(current_thread);
2586     javaVFrame *jvf = java_thread->last_java_vframe(&reg_map);
2587     while (jvf != nullptr) {
2588       log_error(jvmti)("  %s:%d",
2589                        jvf->method()->external_name(),
2590                        jvf->method()->line_number_from_bci(jvf->bci()));
2591       jvf = jvf->java_sender();
2592     }
2593   }
2594   log_error(jvmti)("\n");
2595 }
2596 
2597 void
2598 PrintStackTraceClosure::do_thread(Thread *target) {
2599   JavaThread *java_thread = JavaThread::cast(target);
2600   Thread *current_thread = Thread::current();
2601 
2602   assert(SafepointSynchronize::is_at_safepoint() ||
2603          java_thread->is_handshake_safe_for(current_thread),
2604          "call by myself / at safepoint / at handshake");
2605 
2606   PrintStackTraceClosure::do_thread_impl(target);
2607 }
2608 #endif
2609 
2610 void
2611 GetFrameCountClosure::do_thread(Thread *target) {
2612   JavaThread* jt = JavaThread::cast(target);
2613   assert(target == jt, "just checking");
2614 
2615   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2616     _result = ((JvmtiEnvBase*)_env)->get_frame_count(jt, _count_ptr);
2617   }
2618 }
2619 
2620 void
2621 GetFrameCountClosure::do_vthread(Handle target_h) {
2622   _result = ((JvmtiEnvBase*)_env)->get_frame_count(target_h(), _count_ptr);
2623 }
2624 
2625 void
2626 GetFrameLocationClosure::do_thread(Thread *target) {
2627   JavaThread *jt = JavaThread::cast(target);
2628   assert(target == jt, "just checking");
2629 
2630   if (!jt->is_exiting() && jt->threadObj() != nullptr) {
2631     _result = ((JvmtiEnvBase*)_env)->get_frame_location(jt, _depth,
2632                                                         _method_ptr, _location_ptr);
2633   }
2634 }
2635 
2636 void
2637 GetFrameLocationClosure::do_vthread(Handle target_h) {
2638   _result = ((JvmtiEnvBase*)_env)->get_frame_location(target_h(), _depth,
2639                                                       _method_ptr, _location_ptr);
2640 }