1 /*
   2  * Copyright (c) 1997, 2025, 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 "cds/aotClassLocation.hpp"
  26 #include "cds/cdsConfig.hpp"
  27 #include "cds/heapShared.hpp"
  28 #include "classfile/classFileParser.hpp"
  29 #include "classfile/classFileStream.hpp"
  30 #include "classfile/classLoader.hpp"
  31 #include "classfile/classLoaderData.inline.hpp"
  32 #include "classfile/classLoaderDataGraph.inline.hpp"
  33 #include "classfile/classLoadInfo.hpp"
  34 #include "classfile/dictionary.hpp"
  35 #include "classfile/javaClasses.inline.hpp"
  36 #include "classfile/klassFactory.hpp"
  37 #include "classfile/loaderConstraints.hpp"
  38 #include "classfile/modules.hpp"
  39 #include "classfile/packageEntry.hpp"
  40 #include "classfile/placeholders.hpp"
  41 #include "classfile/resolutionErrors.hpp"
  42 #include "classfile/stringTable.hpp"
  43 #include "classfile/symbolTable.hpp"
  44 #include "classfile/systemDictionary.hpp"
  45 #include "classfile/vmClasses.hpp"
  46 #include "classfile/vmSymbols.hpp"
  47 #include "gc/shared/gcTraceTime.inline.hpp"
  48 #include "interpreter/bootstrapInfo.hpp"
  49 #include "jfr/jfrEvents.hpp"
  50 #include "jvm.h"
  51 #include "logging/log.hpp"
  52 #include "logging/logStream.hpp"
  53 #include "memory/metaspaceClosure.hpp"
  54 #include "memory/oopFactory.hpp"
  55 #include "memory/resourceArea.hpp"
  56 #include "memory/universe.hpp"
  57 #include "oops/access.inline.hpp"
  58 #include "oops/instanceKlass.hpp"
  59 #include "oops/klass.inline.hpp"
  60 #include "oops/method.inline.hpp"
  61 #include "oops/objArrayKlass.hpp"
  62 #include "oops/objArrayOop.inline.hpp"
  63 #include "oops/oop.inline.hpp"
  64 #include "oops/oopHandle.inline.hpp"
  65 #include "oops/symbol.hpp"
  66 #include "oops/typeArrayKlass.hpp"
  67 #include "prims/jvmtiExport.hpp"
  68 #include "prims/methodHandles.hpp"
  69 #include "runtime/arguments.hpp"
  70 #include "runtime/atomicAccess.hpp"
  71 #include "runtime/handles.inline.hpp"
  72 #include "runtime/java.hpp"
  73 #include "runtime/javaCalls.hpp"
  74 #include "runtime/mutexLocker.hpp"
  75 #include "runtime/sharedRuntime.hpp"
  76 #include "runtime/signature.hpp"
  77 #include "runtime/synchronizer.hpp"
  78 #include "services/classLoadingService.hpp"
  79 #include "services/diagnosticCommand.hpp"
  80 #include "services/finalizerService.hpp"
  81 #include "services/threadService.hpp"
  82 #include "utilities/growableArray.hpp"
  83 #include "utilities/macros.hpp"
  84 #include "utilities/utf8.hpp"
  85 #if INCLUDE_CDS
  86 #include "classfile/systemDictionaryShared.hpp"
  87 #endif
  88 #if INCLUDE_JFR
  89 #include "jfr/jfr.hpp"
  90 #endif
  91 
  92 class InvokeMethodKey : public StackObj {
  93   private:
  94     Symbol* _symbol;
  95     intptr_t _iid;
  96 
  97   public:
  98     InvokeMethodKey(Symbol* symbol, intptr_t iid) :
  99         _symbol(symbol),
 100         _iid(iid) {}
 101 
 102     static bool key_comparison(InvokeMethodKey const &k1, InvokeMethodKey const &k2){
 103         return k1._symbol == k2._symbol && k1._iid == k2._iid;
 104     }
 105 
 106     static unsigned int compute_hash(const InvokeMethodKey &k) {
 107         Symbol* sym = k._symbol;
 108         intptr_t iid = k._iid;
 109         unsigned int hash = (unsigned int) sym -> identity_hash();
 110         return (unsigned int) (hash ^ iid);
 111     }
 112 
 113 };
 114 
 115 using InvokeMethodIntrinsicTable = HashTable<InvokeMethodKey, Method*, 139, AnyObj::C_HEAP, mtClass,
 116                   InvokeMethodKey::compute_hash, InvokeMethodKey::key_comparison>;
 117 static InvokeMethodIntrinsicTable* _invoke_method_intrinsic_table;
 118 using InvokeMethodTypeTable = HashTable<SymbolHandle, OopHandle, 139, AnyObj::C_HEAP, mtClass, SymbolHandle::compute_hash>;
 119 static InvokeMethodTypeTable* _invoke_method_type_table;
 120 
 121 OopHandle   SystemDictionary::_java_system_loader;
 122 OopHandle   SystemDictionary::_java_platform_loader;
 123 
 124 // ----------------------------------------------------------------------------
 125 // Java-level SystemLoader and PlatformLoader
 126 oop SystemDictionary::java_system_loader() {
 127   return _java_system_loader.resolve();
 128 }
 129 
 130 oop SystemDictionary::java_platform_loader() {
 131   return _java_platform_loader.resolve();
 132 }
 133 
 134 void SystemDictionary::compute_java_loaders(TRAPS) {
 135   if (_java_platform_loader.is_empty()) {
 136     oop platform_loader = get_platform_class_loader_impl(CHECK);
 137     _java_platform_loader = OopHandle(Universe::vm_global(), platform_loader);
 138   } else {
 139     // It must have been restored from the archived module graph
 140     assert(CDSConfig::is_using_archive(), "must be");
 141     assert(CDSConfig::is_using_full_module_graph(), "must be");
 142     DEBUG_ONLY(
 143       oop platform_loader = get_platform_class_loader_impl(CHECK);
 144       assert(_java_platform_loader.resolve() == platform_loader, "must be");
 145     )
 146  }
 147 
 148   if (_java_system_loader.is_empty()) {
 149     oop system_loader = get_system_class_loader_impl(CHECK);
 150     _java_system_loader = OopHandle(Universe::vm_global(), system_loader);
 151   } else {
 152     // It must have been restored from the archived module graph
 153     assert(CDSConfig::is_using_archive(), "must be");
 154     assert(CDSConfig::is_using_full_module_graph(), "must be");
 155     DEBUG_ONLY(
 156       oop system_loader = get_system_class_loader_impl(CHECK);
 157       assert(_java_system_loader.resolve() == system_loader, "must be");
 158     )
 159   }
 160 }
 161 
 162 oop SystemDictionary::get_system_class_loader_impl(TRAPS) {
 163   JavaValue result(T_OBJECT);
 164   InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass();
 165   JavaCalls::call_static(&result,
 166                          class_loader_klass,
 167                          vmSymbols::getSystemClassLoader_name(),
 168                          vmSymbols::void_classloader_signature(),
 169                          CHECK_NULL);
 170   return result.get_oop();
 171 }
 172 
 173 oop SystemDictionary::get_platform_class_loader_impl(TRAPS) {
 174   JavaValue result(T_OBJECT);
 175   InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass();
 176   JavaCalls::call_static(&result,
 177                          class_loader_klass,
 178                          vmSymbols::getPlatformClassLoader_name(),
 179                          vmSymbols::void_classloader_signature(),
 180                          CHECK_NULL);
 181   return result.get_oop();
 182 }
 183 
 184 // Helper function
 185 inline ClassLoaderData* class_loader_data(Handle class_loader) {
 186   return ClassLoaderData::class_loader_data(class_loader());
 187 }
 188 
 189 ClassLoaderData* SystemDictionary::register_loader(Handle class_loader, bool create_mirror_cld) {
 190   if (create_mirror_cld) {
 191     // Add a new class loader data to the graph.
 192     return ClassLoaderDataGraph::add(class_loader, true);
 193   } else {
 194     return (class_loader() == nullptr) ? ClassLoaderData::the_null_class_loader_data() :
 195                                       ClassLoaderDataGraph::find_or_create(class_loader);
 196   }
 197 }
 198 
 199 void SystemDictionary::set_system_loader(ClassLoaderData *cld) {
 200   if (_java_system_loader.is_empty()) {
 201     _java_system_loader = cld->class_loader_handle();
 202   } else {
 203     assert(_java_system_loader.resolve() == cld->class_loader(), "sanity");
 204   }
 205 }
 206 
 207 void SystemDictionary::set_platform_loader(ClassLoaderData *cld) {
 208   if (_java_platform_loader.is_empty()) {
 209     _java_platform_loader = cld->class_loader_handle();
 210   } else {
 211     assert(_java_platform_loader.resolve() == cld->class_loader(), "sanity");
 212   }
 213 }
 214 
 215 // ----------------------------------------------------------------------------
 216 // Parallel class loading check
 217 
 218 static bool is_parallelCapable(Handle class_loader) {
 219   if (class_loader.is_null()) return true;
 220   return java_lang_ClassLoader::parallelCapable(class_loader());
 221 }
 222 // ----------------------------------------------------------------------------
 223 // ParallelDefineClass flag does not apply to bootclass loader
 224 static bool is_parallelDefine(Handle class_loader) {
 225    if (class_loader.is_null()) return false;
 226    if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) {
 227      return true;
 228    }
 229    return false;
 230 }
 231 
 232 // Returns true if the passed class loader is the builtin application class loader
 233 // or a custom system class loader. A customer system class loader can be
 234 // specified via -Djava.system.class.loader.
 235 bool SystemDictionary::is_system_class_loader(oop class_loader) {
 236   if (class_loader == nullptr) {
 237     return false;
 238   }
 239   return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() ||
 240          class_loader == _java_system_loader.peek());
 241 }
 242 
 243 // Returns true if the passed class loader is the platform class loader.
 244 bool SystemDictionary::is_platform_class_loader(oop class_loader) {
 245   if (class_loader == nullptr) {
 246     return false;
 247   }
 248   return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass());
 249 }
 250 
 251 Handle SystemDictionary::get_loader_lock_or_null(Handle class_loader) {
 252   // If class_loader is null or parallelCapable, the JVM doesn't acquire a lock while loading.
 253   if (is_parallelCapable(class_loader)) {
 254     return Handle();
 255   } else {
 256     return class_loader;
 257   }
 258 }
 259 
 260 // ----------------------------------------------------------------------------
 261 // Resolving of classes
 262 
 263 Symbol* SystemDictionary::class_name_symbol(const char* name, Symbol* exception, TRAPS) {
 264   if (name == nullptr) {
 265     THROW_MSG_NULL(exception, "No class name given");
 266   }
 267   size_t name_len = strlen(name);
 268   if (name_len > static_cast<size_t>(Symbol::max_length())) {
 269     // It's impossible to create this class;  the name cannot fit
 270     // into the constant pool. If necessary report an abridged name
 271     // in the exception message.
 272     if (name_len > static_cast<size_t>(MaxStringPrintSize)) {
 273       Exceptions::fthrow(THREAD_AND_LOCATION, exception,
 274                          "Class name exceeds maximum length of %d: %.*s ... (%zu characters omitted) ... %.*s",
 275                          Symbol::max_length(),
 276                          MaxStringPrintSize / 2,
 277                          name,
 278                          name_len - 2 * (MaxStringPrintSize / 2), // allows for odd value
 279                          MaxStringPrintSize / 2,
 280                          name + name_len - MaxStringPrintSize / 2);
 281     }
 282     else {
 283       Exceptions::fthrow(THREAD_AND_LOCATION, exception,
 284                          "Class name exceeds maximum length of %d: %s",
 285                          Symbol::max_length(),
 286                          name);
 287     }
 288     return nullptr;
 289   }
 290   // Callers should ensure that the name is never an illegal UTF8 string.
 291   assert(UTF8::is_legal_utf8((const unsigned char*)name, name_len, false),
 292          "Class name is not a valid utf8 string.");
 293 
 294   // Make a new symbol for the class name.
 295   return SymbolTable::new_symbol(name);
 296 }
 297 
 298 #ifdef ASSERT
 299 // Used to verify that class loading succeeded in adding k to the dictionary.
 300 static void verify_dictionary_entry(Symbol* class_name, InstanceKlass* k) {
 301   MutexLocker mu(SystemDictionary_lock);
 302   ClassLoaderData* loader_data = k->class_loader_data();
 303   Dictionary* dictionary = loader_data->dictionary();
 304   assert(class_name == k->name(), "Must be the same");
 305   InstanceKlass* kk = dictionary->find_class(JavaThread::current(), class_name);
 306   assert(kk == k, "should be present in dictionary");
 307 }
 308 #endif
 309 
 310 static void handle_resolution_exception(Symbol* class_name, bool throw_error, TRAPS) {
 311   if (HAS_PENDING_EXCEPTION) {
 312     // If we have a pending exception we forward it to the caller, unless throw_error is true,
 313     // in which case we have to check whether the pending exception is a ClassNotFoundException,
 314     // and convert it to a NoClassDefFoundError and chain the original ClassNotFoundException.
 315     if (throw_error && PENDING_EXCEPTION->is_a(vmClasses::ClassNotFoundException_klass())) {
 316       ResourceMark rm(THREAD);
 317       Handle e(THREAD, PENDING_EXCEPTION);
 318       CLEAR_PENDING_EXCEPTION;
 319       THROW_MSG_CAUSE(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e);
 320     } else {
 321       return; // the caller will throw the incoming exception
 322     }
 323   }
 324   // If the class is not found, ie, caller has checked that klass is null, throw the appropriate
 325   // error or exception depending on the value of throw_error.
 326   ResourceMark rm(THREAD);
 327   if (throw_error) {
 328     THROW_MSG(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string());
 329   } else {
 330     THROW_MSG(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string());
 331   }
 332 }
 333 
 334 // Forwards to resolve_or_null
 335 
 336 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader,
 337                                          bool throw_error, TRAPS) {
 338   Klass* klass = resolve_or_null(class_name, class_loader, THREAD);
 339   // Check for pending exception or null klass, and throw exception
 340   if (HAS_PENDING_EXCEPTION || klass == nullptr) {
 341     handle_resolution_exception(class_name, throw_error, CHECK_NULL);
 342   }
 343   return klass;
 344 }
 345 
 346 // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null
 347 
 348 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, TRAPS) {
 349   if (Signature::is_array(class_name)) {
 350     return resolve_array_class_or_null(class_name, class_loader, THREAD);
 351   } else {
 352     assert(class_name != nullptr && !Signature::is_array(class_name), "must be");
 353     if (Signature::has_envelope(class_name)) {
 354       ResourceMark rm(THREAD);
 355       // Ignore wrapping L and ;.
 356       TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1,
 357                                                    class_name->utf8_length() - 2);
 358       return resolve_instance_class_or_null(name, class_loader, THREAD);
 359     } else {
 360       return resolve_instance_class_or_null(class_name, class_loader, THREAD);
 361     }
 362   }
 363 }
 364 
 365 // Forwards to resolve_instance_class_or_null
 366 
 367 Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name,
 368                                                      Handle class_loader,
 369                                                      TRAPS) {
 370   assert(Signature::is_array(class_name), "must be array");
 371   ResourceMark rm(THREAD);
 372   SignatureStream ss(class_name, false);
 373   int ndims = ss.skip_array_prefix();  // skip all '['s
 374   Klass* k = nullptr;
 375   BasicType t = ss.type();
 376   if (ss.has_envelope()) {
 377     Symbol* obj_class = ss.as_symbol();
 378     k = SystemDictionary::resolve_instance_class_or_null(obj_class,
 379                                                          class_loader,
 380                                                          CHECK_NULL);
 381     if (k != nullptr) {
 382       k = k->array_klass(ndims, CHECK_NULL);
 383     }
 384   } else {
 385     k = Universe::typeArrayKlass(t);
 386     k = k->array_klass(ndims, CHECK_NULL);
 387   }
 388   return k;
 389 }
 390 
 391 static inline void log_circularity_error(Symbol* name, PlaceholderEntry* probe) {
 392   LogTarget(Debug, class, load, placeholders) lt;
 393   if (lt.is_enabled()) {
 394     ResourceMark rm;
 395     LogStream ls(lt);
 396     ls.print("ClassCircularityError detected for placeholder entry %s", name->as_C_string());
 397     probe->print_on(&ls);
 398     ls.cr();
 399   }
 400 }
 401 
 402 // Must be called for any superclass or superinterface resolution
 403 // during class definition to allow class circularity checking
 404 // superinterface callers:
 405 //    parse_interfaces - from defineClass
 406 // superclass callers:
 407 //   ClassFileParser - from defineClass
 408 //   load_shared_class - while loading a class from shared archive
 409 //   resolve_instance_class_or_null:
 410 //     via: handle_parallel_super_load
 411 //      when resolving a class that has an existing placeholder with
 412 //      a saved superclass [i.e. a defineClass is currently in progress]
 413 //      If another thread is trying to resolve the class, it must do
 414 //      superclass checks on its own thread to catch class circularity and
 415 //      to avoid deadlock.
 416 //
 417 // resolve_with_circularity_detection adds a DETECT_CIRCULARITY placeholder to the placeholder table before calling
 418 // resolve_instance_class_or_null. ClassCircularityError is detected when a DETECT_CIRCULARITY or LOAD_INSTANCE
 419 // placeholder for the same thread, class, classloader is found.
 420 // This can be seen with logging option: -Xlog:class+load+placeholders=debug.
 421 //
 422 InstanceKlass* SystemDictionary::resolve_with_circularity_detection(Symbol* class_name,
 423                                                                     Symbol* next_name,
 424                                                                     Handle class_loader,
 425                                                                     bool is_superclass,
 426                                                                     TRAPS) {
 427 
 428   assert(next_name != nullptr, "null superclass for resolving");
 429   assert(!Signature::is_array(next_name), "invalid superclass name");
 430 
 431   ClassLoaderData* loader_data = class_loader_data(class_loader);
 432 
 433   if (is_superclass) {
 434     InstanceKlass* klassk = loader_data->dictionary()->find_class(THREAD, class_name);
 435     if (klassk != nullptr) {
 436       // We can come here for two reasons:
 437       // (a) RedefineClasses -- the class is already loaded
 438       // (b) Rarely, the class might have been loaded by a parallel thread
 439       // We can do a quick check against the already assigned superclass's name and loader.
 440       InstanceKlass* superk = klassk->super();
 441       if (superk != nullptr &&
 442           superk->name() == next_name &&
 443           superk->class_loader() == class_loader()) {
 444         return superk;
 445       }
 446     }
 447   }
 448 
 449   // can't throw error holding a lock
 450   bool throw_circularity_error = false;
 451   {
 452     MutexLocker mu(THREAD, SystemDictionary_lock);
 453 
 454     // Must check ClassCircularity before resolving next_name (superclass or interface).
 455     PlaceholderEntry* probe = PlaceholderTable::get_entry(class_name, loader_data);
 456     if (probe != nullptr && probe->check_seen_thread(THREAD, PlaceholderTable::DETECT_CIRCULARITY)) {
 457         log_circularity_error(class_name, probe);
 458         throw_circularity_error = true;
 459     }
 460 
 461     // Make sure there's a placeholder for the class_name before resolving.
 462     // This is used as a claim that this thread is currently loading superclass/classloader
 463     // and for ClassCircularity checks.
 464     if (!throw_circularity_error) {
 465       // Be careful not to exit resolve_with_circularity_detection without removing this placeholder.
 466       PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(class_name,
 467                                                                   loader_data,
 468                                                                   PlaceholderTable::DETECT_CIRCULARITY,
 469                                                                   next_name, THREAD);
 470     }
 471   }
 472 
 473   if (throw_circularity_error) {
 474       ResourceMark rm(THREAD);
 475       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), class_name->as_C_string());
 476   }
 477 
 478   // Resolve the superclass or superinterface, check results on return
 479   InstanceKlass* superk =
 480     SystemDictionary::resolve_instance_class_or_null(next_name,
 481                                                      class_loader,
 482                                                      THREAD);
 483 
 484   // Clean up placeholder entry.
 485   {
 486     MutexLocker mu(THREAD, SystemDictionary_lock);
 487     PlaceholderTable::find_and_remove(class_name, loader_data, PlaceholderTable::DETECT_CIRCULARITY, THREAD);
 488     SystemDictionary_lock->notify_all();
 489   }
 490 
 491   // Check for pending exception or null superk, and throw exception
 492   if (HAS_PENDING_EXCEPTION || superk == nullptr) {
 493     handle_resolution_exception(next_name, true, CHECK_NULL);
 494   }
 495 
 496   return superk;
 497 }
 498 
 499 // If the class in is in the placeholder table, class loading is in progress.
 500 // For cases where the application changes threads to load classes, it
 501 // is critical to ClassCircularity detection that we try loading
 502 // the superclass on the new thread internally, so we do parallel
 503 // superclass loading here.  This avoids deadlock for ClassCircularity
 504 // detection for parallelCapable class loaders that lock on a per-class lock.
 505 static void handle_parallel_super_load(Symbol* name,
 506                                        Symbol* superclassname,
 507                                        Handle class_loader,
 508                                        TRAPS) {
 509 
 510   // The result superk is not used; resolve_with_circularity_detection is called for circularity check only.
 511   // This passes false to is_superclass to skip doing the unlikely optimization.
 512   Klass* superk = SystemDictionary::resolve_with_circularity_detection(name,
 513                                                                        superclassname,
 514                                                                        class_loader,
 515                                                                        false,
 516                                                                        CHECK);
 517 }
 518 
 519 // Bootstrap and non-parallel capable class loaders use the LOAD_INSTANCE placeholder to
 520 // wait for parallel class loading and/or to check for circularity error for Xcomp when loading.
 521 static bool needs_load_placeholder(Handle class_loader) {
 522   return class_loader.is_null() || !is_parallelCapable(class_loader);
 523 }
 524 
 525 // Check for other threads loading this class either to throw CCE or wait in the case of the boot loader.
 526 static InstanceKlass* handle_parallel_loading(JavaThread* current,
 527                                               Symbol* name,
 528                                               ClassLoaderData* loader_data,
 529                                               bool must_wait_for_class_loading,
 530                                               bool* throw_circularity_error) {
 531   PlaceholderEntry* oldprobe = PlaceholderTable::get_entry(name, loader_data);
 532   if (oldprobe != nullptr) {
 533     // -Xcomp calls load_signature_classes which might result in loading
 534     // a class that's already in the process of loading, so we detect CCE here also.
 535     // Only need check_seen_thread once, not on each loop
 536     if (oldprobe->check_seen_thread(current, PlaceholderTable::LOAD_INSTANCE)) {
 537       log_circularity_error(name, oldprobe);
 538       *throw_circularity_error = true;
 539       return nullptr;
 540     } else if (must_wait_for_class_loading) {
 541       // Wait until the first thread has finished loading this class. Also wait until all the
 542       // threads trying to load its superclass have removed their placeholders.
 543       while (oldprobe != nullptr &&
 544              (oldprobe->instance_load_in_progress() || oldprobe->circularity_detection_in_progress())) {
 545 
 546         // LOAD_INSTANCE placeholders are used to implement parallel capable class loading
 547         // for the bootclass loader.
 548         SystemDictionary_lock->wait();
 549 
 550         // Check if classloading completed while we were waiting
 551         InstanceKlass* check = loader_data->dictionary()->find_class(current, name);
 552         if (check != nullptr) {
 553           // Klass is already loaded, so just return it
 554           return check;
 555         }
 556         // check if other thread failed to load and cleaned up
 557         oldprobe = PlaceholderTable::get_entry(name, loader_data);
 558       }
 559     }
 560   }
 561   return nullptr;
 562 }
 563 
 564 void SystemDictionary::post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
 565   assert(event != nullptr, "invariant");
 566   assert(k != nullptr, "invariant");
 567   event->set_loadedClass(k);
 568   event->set_definingClassLoader(k->class_loader_data());
 569   event->set_initiatingClassLoader(init_cld);
 570   event->commit();
 571 }
 572 
 573 // SystemDictionary::resolve_instance_class_or_null is the main function for class name resolution.
 574 // After checking if the InstanceKlass already exists, it checks for ClassCircularityError and
 575 // whether the thread must wait for loading in parallel.  It eventually calls load_instance_class,
 576 // which will load the class via the bootstrap loader or call ClassLoader.loadClass().
 577 // This can return null, an exception or an InstanceKlass.
 578 InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name,
 579                                                                 Handle class_loader,
 580                                                                 TRAPS) {
 581   // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;"
 582   DEBUG_ONLY(ResourceMark rm(THREAD));
 583   assert(name != nullptr && !Signature::is_array(name) &&
 584          !Signature::has_envelope(name), "invalid class name: %s", name == nullptr ? "nullptr" : name->as_C_string());
 585 
 586   EventClassLoad class_load_start_event;
 587 
 588   HandleMark hm(THREAD);
 589 
 590   ClassLoaderData* loader_data = register_loader(class_loader);
 591   Dictionary* dictionary = loader_data->dictionary();
 592 
 593   // Do lookup to see if class already exists.
 594   InstanceKlass* probe = dictionary->find_class(THREAD, name);
 595   if (probe != nullptr) return probe;
 596 
 597   // Non-bootstrap class loaders will call out to class loader and
 598   // define via jvm/jni_DefineClass which will acquire the
 599   // class loader object lock to protect against multiple threads
 600   // defining the class in parallel by accident.
 601   // This lock must be acquired here so the waiter will find
 602   // any successful result in the SystemDictionary and not attempt
 603   // the define.
 604   // ParallelCapable class loaders and the bootstrap classloader
 605   // do not acquire lock here.
 606   Handle lockObject = get_loader_lock_or_null(class_loader);
 607   ObjectLocker ol(lockObject, THREAD);
 608 
 609   bool circularity_detection_in_progress  = false;
 610   InstanceKlass* loaded_class = nullptr;
 611   SymbolHandle superclassname; // Keep alive while loading in parallel thread.
 612 
 613   guarantee(THREAD->can_call_java(),
 614          "can not load classes with compiler thread: class=%s, classloader=%s",
 615          name->as_C_string(),
 616          class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string());
 617 
 618   // Check again (after locking) if the class already exists in SystemDictionary
 619   {
 620     MutexLocker mu(THREAD, SystemDictionary_lock);
 621     InstanceKlass* check = dictionary->find_class(THREAD, name);
 622     if (check != nullptr) {
 623       // InstanceKlass is already loaded, but we still need to check protection domain below.
 624       loaded_class = check;
 625     } else {
 626       PlaceholderEntry* placeholder = PlaceholderTable::get_entry(name, loader_data);
 627       if (placeholder != nullptr && placeholder->circularity_detection_in_progress()) {
 628          circularity_detection_in_progress = true;
 629          superclassname = placeholder->next_klass_name();
 630          assert(superclassname != nullptr, "superclass has to have a name");
 631       }
 632     }
 633   }
 634 
 635   // If the class is in the placeholder table with super_class set,
 636   // handle superclass loading in progress.
 637   if (circularity_detection_in_progress) {
 638     handle_parallel_super_load(name, superclassname,
 639                                class_loader,
 640                                CHECK_NULL);
 641   }
 642 
 643   bool throw_circularity_error = false;
 644   if (loaded_class == nullptr) {
 645     bool load_placeholder_added = false;
 646 
 647     // Add placeholder entry to record loading instance class
 648     // case 1. Bootstrap classloader
 649     //    This classloader supports parallelism at the classloader level
 650     //    but only allows a single thread to load a class/classloader pair.
 651     //    The LOAD_INSTANCE placeholder is the mechanism for mutual exclusion.
 652     // case 2. parallelCapable user level classloaders
 653     //    These class loaders lock a per-class object lock when ClassLoader.loadClass()
 654     //    is called. A LOAD_INSTANCE placeholder isn't used for mutual exclusion.
 655     // case 3. traditional classloaders that rely on the classloader object lock
 656     //    There should be no need for need for LOAD_INSTANCE for mutual exclusion,
 657     //    except the LOAD_INSTANCE placeholder is used to detect CCE for -Xcomp.
 658     //    TODO: should also be used to detect CCE for parallel capable class loaders but it's not.
 659     {
 660       MutexLocker mu(THREAD, SystemDictionary_lock);
 661       if (needs_load_placeholder(class_loader)) {
 662         loaded_class = handle_parallel_loading(THREAD,
 663                                                name,
 664                                                loader_data,
 665                                                class_loader.is_null(),
 666                                                &throw_circularity_error);
 667       }
 668 
 669       // Recheck if the class has been loaded for all class loader cases and
 670       // add a LOAD_INSTANCE placeholder while holding the SystemDictionary_lock.
 671       if (!throw_circularity_error && loaded_class == nullptr) {
 672         InstanceKlass* check = dictionary->find_class(THREAD, name);
 673         if (check != nullptr) {
 674           loaded_class = check;
 675         } else if (needs_load_placeholder(class_loader)) {
 676           // Add the LOAD_INSTANCE token. Threads will wait on loading to complete for this thread.
 677           PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(name, loader_data,
 678                                                                       PlaceholderTable::LOAD_INSTANCE,
 679                                                                       nullptr,
 680                                                                       THREAD);
 681           load_placeholder_added = true;
 682         }
 683       }
 684     }
 685 
 686     // Must throw error outside of owning lock
 687     if (throw_circularity_error) {
 688       assert(!HAS_PENDING_EXCEPTION && !load_placeholder_added, "circularity error cleanup");
 689       ResourceMark rm(THREAD);
 690       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string());
 691     }
 692 
 693     // Be careful when modifying this code: once you have run
 694     // PlaceholderTable::find_and_add(PlaceholderTable::LOAD_INSTANCE),
 695     // you need to find_and_remove it before returning.
 696     // So be careful to not exit with a CHECK_ macro between these calls.
 697 
 698     if (loaded_class == nullptr) {
 699       // Do actual loading
 700       loaded_class = load_instance_class(name, class_loader, THREAD);
 701     }
 702 
 703     if (load_placeholder_added) {
 704       // clean up placeholder entries for LOAD_INSTANCE success or error
 705       // This brackets the SystemDictionary updates for both defining
 706       // and initiating loaders
 707       MutexLocker mu(THREAD, SystemDictionary_lock);
 708       PlaceholderTable::find_and_remove(name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD);
 709       SystemDictionary_lock->notify_all();
 710     }
 711   }
 712 
 713   if (HAS_PENDING_EXCEPTION || loaded_class == nullptr) {
 714     return nullptr;
 715   }
 716 
 717   if (class_load_start_event.should_commit()) {
 718     post_class_load_event(&class_load_start_event, loaded_class, loader_data);
 719   }
 720 
 721   // Make sure we have the right class in the dictionary
 722   DEBUG_ONLY(verify_dictionary_entry(name, loaded_class));
 723 
 724   return loaded_class;
 725 }
 726 
 727 
 728 // This routine does not lock the system dictionary.
 729 //
 730 // Since readers don't hold a lock, we must make sure that system
 731 // dictionary entries are added to in a safe way (all links must
 732 // be updated in an MT-safe manner). All entries are removed during class
 733 // unloading, when this class loader is no longer referenced.
 734 //
 735 // Callers should be aware that an entry could be added just after
 736 // Dictionary is read here, so the caller will not see
 737 // the new entry.
 738 
 739 InstanceKlass* SystemDictionary::find_instance_klass(Thread* current,
 740                                                      Symbol* class_name,
 741                                                      Handle class_loader) {
 742 
 743   ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
 744   if (loader_data == nullptr) {
 745     // If the ClassLoaderData has not been setup,
 746     // then the class loader has no entries in the dictionary.
 747     return nullptr;
 748   }
 749 
 750   Dictionary* dictionary = loader_data->dictionary();
 751   return dictionary->find_class(current, class_name);
 752 }
 753 
 754 // Look for a loaded instance or array klass by name.  Do not do any loading.
 755 // return null in case of error.
 756 Klass* SystemDictionary::find_instance_or_array_klass(Thread* current,
 757                                                       Symbol* class_name,
 758                                                       Handle class_loader) {
 759   Klass* k = nullptr;
 760   assert(class_name != nullptr, "class name must be non nullptr");
 761 
 762   if (Signature::is_array(class_name)) {
 763     // The name refers to an array.  Parse the name.
 764     // dimension and object_key in FieldArrayInfo are assigned as a
 765     // side-effect of this call
 766     SignatureStream ss(class_name, false);
 767     int ndims = ss.skip_array_prefix();  // skip all '['s
 768     BasicType t = ss.type();
 769     if (t != T_OBJECT) {
 770       k = Universe::typeArrayKlass(t);
 771     } else {
 772       k = SystemDictionary::find_instance_klass(current, ss.as_symbol(), class_loader);
 773     }
 774     if (k != nullptr) {
 775       k = k->array_klass_or_null(ndims);
 776     }
 777   } else {
 778     k = find_instance_klass(current, class_name, class_loader);
 779   }
 780   return k;
 781 }
 782 
 783 // Note: this method is much like resolve_class_from_stream, but
 784 // does not publish the classes in the SystemDictionary.
 785 // Handles Lookup.defineClass hidden.
 786 InstanceKlass* SystemDictionary::resolve_hidden_class_from_stream(
 787                                                      ClassFileStream* st,
 788                                                      Symbol* class_name,
 789                                                      Handle class_loader,
 790                                                      const ClassLoadInfo& cl_info,
 791                                                      TRAPS) {
 792 
 793   EventClassLoad class_load_start_event;
 794   ClassLoaderData* loader_data;
 795 
 796   // - for hidden classes that are not strong: create a new CLD that has a class holder and
 797   //                                           whose loader is the Lookup class's loader.
 798   // - for hidden class: add the class to the Lookup class's loader's CLD.
 799   assert (cl_info.is_hidden(), "only used for hidden classes");
 800   bool create_mirror_cld = !cl_info.is_strong_hidden();
 801   loader_data = register_loader(class_loader, create_mirror_cld);
 802 
 803   assert(st != nullptr, "invariant");
 804 
 805   // Parse stream and create a klass.
 806   InstanceKlass* k = KlassFactory::create_from_stream(st,
 807                                                       class_name,
 808                                                       loader_data,
 809                                                       cl_info,
 810                                                       CHECK_NULL);
 811   assert(k != nullptr, "no klass created");
 812 
 813   // Hidden classes that are not strong must update ClassLoaderData holder
 814   // so that they can be unloaded when the mirror is no longer referenced.
 815   if (!cl_info.is_strong_hidden()) {
 816     k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror()));
 817   }
 818 
 819   // Add to class hierarchy, and do possible deoptimizations.
 820   k->add_to_hierarchy(THREAD);
 821   // But, do not add to dictionary.
 822 
 823   k->link_class(CHECK_NULL);
 824 
 825   // notify jvmti
 826   if (JvmtiExport::should_post_class_load()) {
 827     JvmtiExport::post_class_load(THREAD, k);
 828   }
 829   if (class_load_start_event.should_commit()) {
 830     post_class_load_event(&class_load_start_event, k, loader_data);
 831   }
 832 
 833   return k;
 834 }
 835 
 836 // Add a klass to the system from a stream (called by jni_DefineClass and
 837 // JVM_DefineClass).
 838 // Note: class_name can be null. In that case we do not know the name of
 839 // the class until we have parsed the stream.
 840 // This function either returns an InstanceKlass or throws an exception.  It does
 841 // not return null without a pending exception.
 842 InstanceKlass* SystemDictionary::resolve_class_from_stream(
 843                                                      ClassFileStream* st,
 844                                                      Symbol* class_name,
 845                                                      Handle class_loader,
 846                                                      const ClassLoadInfo& cl_info,
 847                                                      TRAPS) {
 848 
 849   HandleMark hm(THREAD);
 850 
 851   ClassLoaderData* loader_data = register_loader(class_loader);
 852 
 853   // Classloaders that support parallelism, e.g. bootstrap classloader,
 854   // do not acquire lock here
 855   Handle lockObject = get_loader_lock_or_null(class_loader);
 856   ObjectLocker ol(lockObject, THREAD);
 857 
 858   // Parse the stream and create a klass.
 859   // Note that we do this even though this klass might
 860   // already be present in the SystemDictionary, otherwise we would not
 861   // throw potential ClassFormatErrors.
 862  InstanceKlass* k = nullptr;
 863 
 864 #if INCLUDE_CDS
 865   if (!CDSConfig::is_dumping_static_archive()) {
 866     k = SystemDictionaryShared::lookup_from_stream(class_name,
 867                                                    class_loader,
 868                                                    cl_info.protection_domain(),
 869                                                    st,
 870                                                    CHECK_NULL);
 871   }
 872 #endif
 873 
 874   if (k == nullptr) {
 875     k = KlassFactory::create_from_stream(st, class_name, loader_data, cl_info, CHECK_NULL);
 876   }
 877 
 878   assert(k != nullptr, "no klass created");
 879   Symbol* h_name = k->name();
 880   assert(class_name == nullptr || class_name == h_name, "name mismatch");
 881 
 882   // Add class just loaded
 883   // If a class loader supports parallel classloading, handle parallel define requests.
 884   // find_or_define_instance_class may return a different InstanceKlass,
 885   // in which case the old k would be deallocated
 886   if (is_parallelCapable(class_loader)) {
 887     k = find_or_define_instance_class(h_name, class_loader, k, CHECK_NULL);
 888   } else {
 889     define_instance_class(k, class_loader, THREAD);
 890 
 891     // If defining the class throws an exception register 'k' for cleanup.
 892     if (HAS_PENDING_EXCEPTION) {
 893       assert(k != nullptr, "Must have an instance klass here!");
 894       loader_data->add_to_deallocate_list(k);
 895       return nullptr;
 896     }
 897   }
 898 
 899   // Make sure we have an entry in the SystemDictionary on success
 900   DEBUG_ONLY(verify_dictionary_entry(h_name, k));
 901 
 902   return k;
 903 }
 904 
 905 InstanceKlass* SystemDictionary::resolve_from_stream(ClassFileStream* st,
 906                                                      Symbol* class_name,
 907                                                      Handle class_loader,
 908                                                      const ClassLoadInfo& cl_info,
 909                                                      TRAPS) {
 910   if (cl_info.is_hidden()) {
 911     return resolve_hidden_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL);
 912   } else {
 913     return resolve_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL);
 914   }
 915 }
 916 
 917 
 918 #if INCLUDE_CDS
 919 // Check if a shared class can be loaded by the specific classloader.
 920 bool SystemDictionary::is_shared_class_visible(Symbol* class_name,
 921                                                InstanceKlass* ik,
 922                                                PackageEntry* pkg_entry,
 923                                                Handle class_loader) {
 924   assert(!ModuleEntryTable::javabase_moduleEntry()->is_patched(),
 925          "Cannot use sharing if java.base is patched");
 926 
 927   // (1) Check if we are loading into the same loader as in dump time.
 928 
 929   if (ik->defined_by_boot_loader()) {
 930     if (class_loader() != nullptr) {
 931       return false;
 932     }
 933   } else if (ik->defined_by_platform_loader()) {
 934     if (class_loader() != java_platform_loader()) {
 935       return false;
 936     }
 937   } else if (ik->defined_by_app_loader()) {
 938     if (class_loader() != java_system_loader()) {
 939       return false;
 940     }
 941   } else {
 942     // ik was loaded by a custom loader during dump time
 943     if (class_loader_data(class_loader)->is_builtin_class_loader_data()) {
 944       return false;
 945     } else {
 946       return true;
 947     }
 948   }
 949 
 950   // (2) Check if we are loading into the same module from the same location as in dump time.
 951 
 952   if (CDSConfig::is_using_optimized_module_handling()) {
 953     // Class visibility has not changed between dump time and run time, so a class
 954     // that was visible (and thus archived) during dump time is always visible during runtime.
 955     assert(SystemDictionary::is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader),
 956            "visibility cannot change between dump time and runtime");
 957     return true;
 958   }
 959   return is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader);
 960 }
 961 
 962 bool SystemDictionary::is_shared_class_visible_impl(Symbol* class_name,
 963                                                     InstanceKlass* ik,
 964                                                     PackageEntry* pkg_entry,
 965                                                     Handle class_loader) {
 966   int scp_index = ik->shared_classpath_index();
 967   assert(!ik->defined_by_other_loaders(), "this function should be called for built-in classes only");
 968   assert(scp_index >= 0, "must be");
 969   const AOTClassLocation* cl = AOTClassLocationConfig::runtime()->class_location_at(scp_index);
 970   if (!Universe::is_module_initialized()) {
 971     assert(cl != nullptr, "must be");
 972     // At this point, no modules have been defined yet. KlassSubGraphInfo::check_allowed_klass()
 973     // has restricted the classes can be loaded at this step to be only:
 974     // [1] cs->is_modules_image(): classes in java.base, or,
 975     // [2] HeapShared::is_a_test_class_in_unnamed_module(ik): classes in bootstrap/unnamed module
 976     assert(cl->is_modules_image() || HeapShared::is_a_test_class_in_unnamed_module(ik),
 977            "only these classes can be loaded before the module system is initialized");
 978     assert(class_loader.is_null(), "sanity");
 979     return true;
 980   }
 981 
 982   if (pkg_entry == nullptr) {
 983     // We might have looked up pkg_entry before the module system was initialized.
 984     // Need to reload it now.
 985     TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name);
 986     if (pkg_name != nullptr) {
 987       pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name);
 988     }
 989   }
 990 
 991   ModuleEntry* mod_entry = (pkg_entry == nullptr) ? nullptr : pkg_entry->module();
 992   bool should_be_in_named_module = (mod_entry != nullptr && mod_entry->is_named());
 993   bool was_archived_from_named_module = !cl->has_unnamed_module();
 994   bool visible;
 995 
 996   if (mod_entry != nullptr && mod_entry->location() == nullptr && mod_entry->is_named()) {
 997     // Archived module for dynamic proxies. It's always visible.
 998     assert(Modules::is_dynamic_proxy_module(mod_entry), "must be");
 999     visible = true;
1000   } else if (was_archived_from_named_module) {
1001     if (should_be_in_named_module) {
1002       // Is the module loaded from the same location as during dump time?
1003       visible = mod_entry->shared_path_index() == scp_index;
1004       if (visible) {
1005         assert(!mod_entry->is_patched(), "cannot load archived classes for patched module");
1006       }
1007     } else {
1008       // During dump time, this class was in a named module, but at run time, this class should be
1009       // in an unnamed module.
1010       visible = false;
1011     }
1012   } else {
1013     if (should_be_in_named_module) {
1014       // During dump time, this class was in an unnamed, but at run time, this class should be
1015       // in a named module.
1016       visible = false;
1017     } else {
1018       visible = true;
1019     }
1020   }
1021 
1022   return visible;
1023 }
1024 
1025 bool SystemDictionary::check_shared_class_super_type(InstanceKlass* klass, InstanceKlass* super_type,
1026                                                      Handle class_loader, bool is_superclass, TRAPS) {
1027   assert(super_type->in_aot_cache(), "must be");
1028 
1029   // Quick check if the super type has been already loaded.
1030   // + Don't do it for unregistered classes -- they can be unloaded so
1031   //   super_type->class_loader_data() could be stale.
1032   // + Don't check if loader data is null, ie. the super_type isn't fully loaded.
1033   if (!super_type->defined_by_other_loaders() && super_type->class_loader_data() != nullptr) {
1034     // Check if the superclass is loaded by the current class_loader
1035     Symbol* name = super_type->name();
1036     InstanceKlass* check = find_instance_klass(THREAD, name, class_loader);
1037     if (check == super_type) {
1038       return true;
1039     }
1040   }
1041 
1042   Klass *found = resolve_with_circularity_detection(klass->name(), super_type->name(),
1043                                                     class_loader, is_superclass, CHECK_false);
1044   if (found == super_type) {
1045     return true;
1046   } else {
1047     // The dynamically resolved super type is not the same as the one we used during dump time,
1048     // so we cannot use the class.
1049     return false;
1050   }
1051 }
1052 
1053 bool SystemDictionary::check_shared_class_super_types(InstanceKlass* ik, Handle class_loader, TRAPS) {
1054   // Check the superclass and interfaces. They must be the same
1055   // as in dump time, because the layout of <ik> depends on
1056   // the specific layout of ik->super() and ik->local_interfaces().
1057   //
1058   // If unexpected superclass or interfaces are found, we cannot
1059   // load <ik> from the shared archive.
1060 
1061   if (ik->super() != nullptr) {
1062     bool check_super = check_shared_class_super_type(ik, ik->super(),
1063                                                      class_loader, true,
1064                                                      CHECK_false);
1065     if (!check_super) {
1066       return false;
1067     }
1068   }
1069 
1070   Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1071   int num_interfaces = interfaces->length();
1072   for (int index = 0; index < num_interfaces; index++) {
1073     bool check_interface = check_shared_class_super_type(ik, interfaces->at(index), class_loader, false,
1074                                                          CHECK_false);
1075     if (!check_interface) {
1076       return false;
1077     }
1078   }
1079 
1080   return true;
1081 }
1082 
1083 InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik,
1084                                                    Handle class_loader,
1085                                                    Handle protection_domain,
1086                                                    const ClassFileStream *cfs,
1087                                                    PackageEntry* pkg_entry,
1088                                                    TRAPS) {
1089   assert(ik != nullptr, "sanity");
1090   assert(ik->in_aot_cache(), "sanity");
1091   assert(!ik->is_unshareable_info_restored(), "shared class can be restored only once");
1092   assert(AtomicAccess::add(&ik->_shared_class_load_count, 1) == 1, "shared class loaded more than once");
1093   Symbol* class_name = ik->name();
1094 
1095   if (!is_shared_class_visible(class_name, ik, pkg_entry, class_loader)) {
1096     ik->set_shared_loading_failed();
1097     return nullptr;
1098   }
1099 
1100   bool check = check_shared_class_super_types(ik, class_loader, CHECK_NULL);
1101   if (!check) {
1102     ik->set_shared_loading_failed();
1103     return nullptr;
1104   }
1105 
1106   InstanceKlass* new_ik = nullptr;
1107   // CFLH check is skipped for VM hidden classes (see KlassFactory::create_from_stream).
1108   // It will be skipped for shared VM hidden lambda proxy classes.
1109   if (!ik->is_hidden()) {
1110     new_ik = KlassFactory::check_shared_class_file_load_hook(
1111       ik, class_name, class_loader, protection_domain, cfs, CHECK_NULL);
1112   }
1113   if (new_ik != nullptr) {
1114     // The class is changed by CFLH. Return the new class. The shared class is
1115     // not used.
1116     return new_ik;
1117   }
1118 
1119   // Adjust methods to recover missing data.  They need addresses for
1120   // interpreter entry points and their default native method address
1121   // must be reset.
1122 
1123   // Shared classes are all currently loaded by either the bootstrap or
1124   // internal parallel class loaders, so this will never cause a deadlock
1125   // on a custom class loader lock.
1126   // Since this class is already locked with parallel capable class
1127   // loaders, including the bootstrap loader via the placeholder table,
1128   // this lock is currently a nop.
1129 
1130   ClassLoaderData* loader_data = class_loader_data(class_loader);
1131   {
1132     HandleMark hm(THREAD);
1133     Handle lockObject = get_loader_lock_or_null(class_loader);
1134     ObjectLocker ol(lockObject, THREAD);
1135     // prohibited package check assumes all classes loaded from archive call
1136     // restore_unshareable_info which calls ik->set_package()
1137     ik->restore_unshareable_info(loader_data, protection_domain, pkg_entry, CHECK_NULL);
1138   }
1139 
1140   load_shared_class_misc(ik, loader_data);
1141   return ik;
1142 }
1143 
1144 void SystemDictionary::load_shared_class_misc(InstanceKlass* ik, ClassLoaderData* loader_data) {
1145   ik->print_class_load_logging(loader_data, nullptr, nullptr);
1146 
1147   // For boot loader, ensure that GetSystemPackage knows that a class in this
1148   // package was loaded.
1149   if (loader_data->is_the_null_class_loader_data()) {
1150     s2 path_index = ik->shared_classpath_index();
1151     if (path_index >= 0) { // FIXME ... for lambda form classes
1152       ik->set_classpath_index(path_index);
1153 
1154       if (CDSConfig::is_dumping_final_static_archive()) {
1155         AOTClassLocationConfig::dumptime_update_max_used_index(path_index);
1156       }
1157     }
1158   }
1159 
1160   // notify a class loaded from shared object
1161   ClassLoadingService::notify_class_loaded(ik, true /* shared class */);
1162 
1163   if (CDSConfig::is_dumping_final_static_archive()) {
1164     SystemDictionaryShared::init_dumptime_info_from_preimage(ik);
1165   }
1166 }
1167 
1168 // This is much more lightweight than SystemDictionary::resolve_or_null
1169 // - There's only a single Java thread at this point. No need for placeholder.
1170 // - All supertypes of ik have been loaded
1171 // - There's no circularity (checked in AOT assembly phase)
1172 // - There's no need to call java.lang.ClassLoader::load_class() because the boot/platform/app
1173 //   loaders are well-behaved
1174 void SystemDictionary::preload_class(Handle class_loader, InstanceKlass* ik, TRAPS) {
1175   precond(Universe::is_bootstrapping());
1176   precond(java_platform_loader() != nullptr && java_system_loader() != nullptr);
1177   precond(class_loader() == nullptr || class_loader() == java_platform_loader() ||class_loader() == java_system_loader());
1178   precond(CDSConfig::is_using_aot_linked_classes());
1179   precond(AOTMetaspace::in_aot_cache_static_region((void*)ik));
1180   precond(!ik->is_loaded());
1181 
1182 #ifdef ASSERT
1183   // preload_class() must be called in the correct order -- all super types must have
1184   // already been loaded.
1185   if (ik->java_super() != nullptr) {
1186     assert(ik->java_super()->is_loaded(), "must be");
1187   }
1188 
1189   Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1190   int num_interfaces = interfaces->length();
1191   for (int index = 0; index < num_interfaces; index++) {
1192     assert(interfaces->at(index)->is_loaded(), "must be");
1193   }
1194 #endif
1195 
1196   ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(class_loader());
1197   oop java_mirror = ik->archived_java_mirror();
1198   precond(java_mirror != nullptr);
1199 
1200   Handle pd(THREAD, java_lang_Class::protection_domain(java_mirror));
1201   PackageEntry* pkg_entry = ik->package();
1202   assert(pkg_entry != nullptr || ClassLoader::package_from_class_name(ik->name()) == nullptr,
1203          "non-empty packages must have been archived");
1204 
1205   // TODO: the following assert requires JDK-8365580
1206   // assert(is_shared_class_visible(ik->name(), ik, pkg_entry, class_loader), "must be");
1207 
1208   ik->restore_unshareable_info(loader_data, pd, pkg_entry, CHECK);
1209   load_shared_class_misc(ik, loader_data);
1210   ik->add_to_hierarchy(THREAD);
1211 
1212   if (!ik->is_hidden()) {
1213     update_dictionary(THREAD, ik, loader_data);
1214   }
1215 
1216   assert(java_lang_Class::module(java_mirror) != nullptr, "must have been archived");
1217   assert(ik->is_loaded(), "Must be in at least loaded state");
1218 }
1219 
1220 #endif // INCLUDE_CDS
1221 
1222 InstanceKlass* SystemDictionary::load_instance_class_impl(Symbol* class_name, Handle class_loader, TRAPS) {
1223 
1224   if (class_loader.is_null()) {
1225     ResourceMark rm(THREAD);
1226     PackageEntry* pkg_entry = nullptr;
1227     bool search_only_bootloader_append = false;
1228 
1229     // Find the package in the boot loader's package entry table.
1230     TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name);
1231     if (pkg_name != nullptr) {
1232       pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name);
1233     }
1234 
1235     // Prior to attempting to load the class, enforce the boot loader's
1236     // visibility boundaries.
1237     if (!Universe::is_module_initialized()) {
1238       // During bootstrapping, prior to module initialization, any
1239       // class attempting to be loaded must be checked against the
1240       // java.base packages in the boot loader's PackageEntryTable.
1241       // No class outside of java.base is allowed to be loaded during
1242       // this bootstrapping window.
1243       if (pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1244         // Class is either in the unnamed package or in
1245         // a named package within the unnamed module.  Either
1246         // case is outside of java.base, do not attempt to
1247         // load the class post java.base definition.  If
1248         // java.base has not been defined, let the class load
1249         // and its package will be checked later by
1250         // ModuleEntryTable::verify_javabase_packages.
1251         if (ModuleEntryTable::javabase_defined()) {
1252           return nullptr;
1253         }
1254       } else {
1255         // Check that the class' package is defined within java.base.
1256         ModuleEntry* mod_entry = pkg_entry->module();
1257         Symbol* mod_entry_name = mod_entry->name();
1258         if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) {
1259           return nullptr;
1260         }
1261       }
1262     } else {
1263       // After the module system has been initialized, check if the class'
1264       // package is in a module defined to the boot loader.
1265       if (pkg_name == nullptr || pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1266         // Class is either in the unnamed package, in a named package
1267         // within a module not defined to the boot loader or in a
1268         // a named package within the unnamed module.  In all cases,
1269         // limit visibility to search for the class only in the boot
1270         // loader's append path.
1271         if (!ClassLoader::has_bootclasspath_append()) {
1272            // If there is no bootclasspath append entry, no need to continue
1273            // searching.
1274            return nullptr;
1275         }
1276         search_only_bootloader_append = true;
1277       }
1278     }
1279 
1280     // Prior to bootstrapping's module initialization, never load a class outside
1281     // of the boot loader's module path
1282     assert(Universe::is_module_initialized() ||
1283            !search_only_bootloader_append,
1284            "Attempt to load a class outside of boot loader's module path");
1285 
1286     // Search for classes in the CDS archive.
1287     InstanceKlass* k = nullptr;
1288 
1289 #if INCLUDE_CDS
1290     if (CDSConfig::is_using_archive())
1291     {
1292       PerfTraceElapsedTime vmtimer(ClassLoader::perf_shared_classload_time());
1293       InstanceKlass* ik = SystemDictionaryShared::find_builtin_class(class_name);
1294       if (ik != nullptr && ik->defined_by_boot_loader() && !ik->shared_loading_failed()) {
1295         SharedClassLoadingMark slm(THREAD, ik);
1296         k = load_shared_class(ik, class_loader, Handle(), nullptr,  pkg_entry, CHECK_NULL);
1297       }
1298     }
1299 #endif
1300 
1301     if (k == nullptr) {
1302       // Use VM class loader
1303       PerfTraceElapsedTime vmtimer(ClassLoader::perf_sys_classload_time());
1304       k = ClassLoader::load_class(class_name, pkg_entry, search_only_bootloader_append, CHECK_NULL);
1305     }
1306 
1307     // find_or_define_instance_class may return a different InstanceKlass
1308     if (k != nullptr) {
1309       CDS_ONLY(SharedClassLoadingMark slm(THREAD, k);)
1310       k = find_or_define_instance_class(class_name, class_loader, k, CHECK_NULL);
1311     }
1312     return k;
1313   } else {
1314     // Use user specified class loader to load class. Call loadClass operation on class_loader.
1315     ResourceMark rm(THREAD);
1316 
1317     JavaThread* jt = THREAD;
1318 
1319     PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1320                                ClassLoader::perf_app_classload_selftime(),
1321                                ClassLoader::perf_app_classload_count(),
1322                                jt->get_thread_stat()->perf_recursion_counts_addr(),
1323                                jt->get_thread_stat()->perf_timers_addr(),
1324                                PerfClassTraceTime::CLASS_LOAD);
1325 
1326     // Translate to external class name format, i.e., convert '/' chars to '.'
1327     Handle string = java_lang_String::externalize_classname(class_name, CHECK_NULL);
1328 
1329     JavaValue result(T_OBJECT);
1330 
1331     InstanceKlass* spec_klass = vmClasses::ClassLoader_klass();
1332 
1333     // Call public unsynchronized loadClass(String) directly for all class loaders.
1334     // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1335     // acquire a class-name based lock rather than the class loader object lock.
1336     // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1337     JavaCalls::call_virtual(&result,
1338                             class_loader,
1339                             spec_klass,
1340                             vmSymbols::loadClass_name(),
1341                             vmSymbols::string_class_signature(),
1342                             string,
1343                             CHECK_NULL);
1344 
1345     assert(result.get_type() == T_OBJECT, "just checking");
1346     oop obj = result.get_oop();
1347 
1348     // Primitive classes return null since forName() cannot be
1349     // used to obtain any of the Class objects representing primitives or void
1350     if ((obj != nullptr) && !(java_lang_Class::is_primitive(obj))) {
1351       InstanceKlass* k = java_lang_Class::as_InstanceKlass(obj);
1352       // For user defined Java class loaders, check that the name returned is
1353       // the same as that requested.  This check is done for the bootstrap
1354       // loader when parsing the class file.
1355       if (class_name == k->name()) {
1356         return k;
1357       }
1358     }
1359     // Class is not found or has the wrong name, return null
1360     return nullptr;
1361   }
1362 }
1363 
1364 InstanceKlass* SystemDictionary::load_instance_class(Symbol* name,
1365                                                      Handle class_loader,
1366                                                      TRAPS) {
1367 
1368   InstanceKlass* loaded_class = load_instance_class_impl(name, class_loader, CHECK_NULL);
1369 
1370   // If everything was OK (no exceptions, no null return value), and
1371   // class_loader is NOT the defining loader, do a little more bookkeeping.
1372   if (loaded_class != nullptr &&
1373       loaded_class->class_loader() != class_loader()) {
1374 
1375     ClassLoaderData* loader_data = class_loader_data(class_loader);
1376     check_constraints(loaded_class, loader_data, false, CHECK_NULL);
1377 
1378     // Record dependency for non-parent delegation.
1379     // This recording keeps the defining class loader of the klass (loaded_class) found
1380     // from being unloaded while the initiating class loader is loaded
1381     // even if the reference to the defining class loader is dropped
1382     // before references to the initiating class loader.
1383     loader_data->record_dependency(loaded_class);
1384 
1385     update_dictionary(THREAD, loaded_class, loader_data);
1386 
1387     if (JvmtiExport::should_post_class_load()) {
1388       JvmtiExport::post_class_load(THREAD, loaded_class);
1389     }
1390   }
1391   return loaded_class;
1392 }
1393 
1394 static void post_class_define_event(InstanceKlass* k, const ClassLoaderData* def_cld) {
1395   EventClassDefine event;
1396   if (event.should_commit()) {
1397     event.set_definedClass(k);
1398     event.set_definingClassLoader(def_cld);
1399     event.commit();
1400   }
1401 }
1402 
1403 void SystemDictionary::define_instance_class(InstanceKlass* k, Handle class_loader, TRAPS) {
1404 
1405   ClassLoaderData* loader_data = k->class_loader_data();
1406   assert(loader_data->class_loader() == class_loader(), "they must be the same");
1407 
1408   // Bootstrap and other parallel classloaders don't acquire a lock,
1409   // they use placeholder token.
1410   // If a parallelCapable class loader calls define_instance_class instead of
1411   // find_or_define_instance_class to get here, we have a timing
1412   // hole with systemDictionary updates and check_constraints
1413   if (!is_parallelCapable(class_loader)) {
1414     assert(ObjectSynchronizer::current_thread_holds_lock(THREAD,
1415            get_loader_lock_or_null(class_loader)),
1416            "define called without lock");
1417   }
1418 
1419   // Check class-loading constraints. Throw exception if violation is detected.
1420   // Grabs and releases SystemDictionary_lock
1421   // The check_constraints/find_class call and update_dictionary sequence
1422   // must be "atomic" for a specific class/classloader pair so we never
1423   // define two different instanceKlasses for that class/classloader pair.
1424   // Existing classloaders will call define_instance_class with the
1425   // classloader lock held
1426   // Parallel classloaders will call find_or_define_instance_class
1427   // which will require a token to perform the define class
1428   check_constraints(k, loader_data, true, CHECK);
1429 
1430   // Register class just loaded with class loader (placed in ArrayList)
1431   // Note we do this before updating the dictionary, as this can
1432   // fail with an OutOfMemoryError (if it does, we will *not* put this
1433   // class in the dictionary and will not update the class hierarchy).
1434   // JVMTI FollowReferences needs to find the classes this way.
1435   if (k->class_loader() != nullptr) {
1436     methodHandle m(THREAD, Universe::loader_addClass_method());
1437     JavaValue result(T_VOID);
1438     JavaCallArguments args(class_loader);
1439     args.push_oop(Handle(THREAD, k->java_mirror()));
1440     JavaCalls::call(&result, m, &args, CHECK);
1441   }
1442 
1443   // Add to class hierarchy, and do possible deoptimizations.
1444   k->add_to_hierarchy(THREAD);
1445 
1446   // Add to systemDictionary - so other classes can see it.
1447   // Grabs and releases SystemDictionary_lock
1448   update_dictionary(THREAD, k, loader_data);
1449 
1450   // notify jvmti
1451   if (JvmtiExport::should_post_class_load()) {
1452     JvmtiExport::post_class_load(THREAD, k);
1453   }
1454   post_class_define_event(k, loader_data);
1455 }
1456 
1457 // Support parallel classloading
1458 // All parallel class loaders, including bootstrap classloader
1459 // lock a placeholder entry for this class/class_loader pair
1460 // to allow parallel defines of different classes for this class loader
1461 // With AllowParallelDefine flag==true, in case they do not synchronize around
1462 // FindLoadedClass/DefineClass, calls, we check for parallel
1463 // loading for them, wait if a defineClass is in progress
1464 // and return the initial requestor's results
1465 // This flag does not apply to the bootstrap classloader.
1466 // With AllowParallelDefine flag==false, call through to define_instance_class
1467 // which will throw LinkageError: duplicate class definition.
1468 // False is the requested default.
1469 // For better performance, the class loaders should synchronize
1470 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1471 // potentially waste time reading and parsing the bytestream.
1472 // Note: VM callers should ensure consistency of k/class_name,class_loader
1473 // Be careful when modifying this code: once you have run
1474 // PlaceholderTable::find_and_add(PlaceholderTable::DEFINE_CLASS),
1475 // you need to find_and_remove it before returning.
1476 // So be careful to not exit with a CHECK_ macro between these calls.
1477 InstanceKlass* SystemDictionary::find_or_define_helper(Symbol* class_name, Handle class_loader,
1478                                                        InstanceKlass* k, TRAPS) {
1479 
1480   Symbol* name_h = k->name();
1481   ClassLoaderData* loader_data = class_loader_data(class_loader);
1482   Dictionary* dictionary = loader_data->dictionary();
1483 
1484   // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1485   {
1486     MutexLocker mu(THREAD, SystemDictionary_lock);
1487     // First check if class already defined
1488     if (is_parallelDefine(class_loader)) {
1489       InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1490       if (check != nullptr) {
1491         return check;
1492       }
1493     }
1494 
1495     // Acquire define token for this class/classloader
1496     PlaceholderEntry* probe = PlaceholderTable::find_and_add(name_h, loader_data,
1497                                                              PlaceholderTable::DEFINE_CLASS, nullptr, THREAD);
1498     // Wait if another thread defining in parallel
1499     // All threads wait - even those that will throw duplicate class: otherwise
1500     // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1501     // if other thread has not finished updating dictionary
1502     while (probe->definer() != nullptr) {
1503       SystemDictionary_lock->wait();
1504     }
1505     // Only special cases allow parallel defines and can use other thread's results
1506     // Other cases fall through, and may run into duplicate defines
1507     // caught by finding an entry in the SystemDictionary
1508     if (is_parallelDefine(class_loader) && (probe->instance_klass() != nullptr)) {
1509       InstanceKlass* ik = probe->instance_klass();
1510       PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1511       SystemDictionary_lock->notify_all();
1512 #ifdef ASSERT
1513       InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1514       assert(check != nullptr, "definer missed recording success");
1515 #endif
1516       return ik;
1517     } else {
1518       // This thread will define the class (even if earlier thread tried and had an error)
1519       probe->set_definer(THREAD);
1520     }
1521   }
1522 
1523   define_instance_class(k, class_loader, THREAD);
1524 
1525   // definer must notify any waiting threads
1526   {
1527     MutexLocker mu(THREAD, SystemDictionary_lock);
1528     PlaceholderEntry* probe = PlaceholderTable::get_entry(name_h, loader_data);
1529     assert(probe != nullptr, "DEFINE_CLASS placeholder lost?");
1530     if (!HAS_PENDING_EXCEPTION) {
1531       probe->set_instance_klass(k);
1532     }
1533     probe->set_definer(nullptr);
1534     PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1535     SystemDictionary_lock->notify_all();
1536   }
1537 
1538   return HAS_PENDING_EXCEPTION ? nullptr : k;
1539 }
1540 
1541 // If a class loader supports parallel classloading handle parallel define requests.
1542 // find_or_define_instance_class may return a different InstanceKlass
1543 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1544                                                                InstanceKlass* k, TRAPS) {
1545   InstanceKlass* defined_k = find_or_define_helper(class_name, class_loader, k, THREAD);
1546   // Clean up original InstanceKlass if duplicate or error
1547   if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1548     // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1549     assert(defined_k != nullptr, "Should have a klass if there's no exception");
1550     k->class_loader_data()->add_to_deallocate_list(k);
1551   } else if (HAS_PENDING_EXCEPTION) {
1552     // Remove this InstanceKlass from the LoaderConstraintTable if added.
1553     LoaderConstraintTable::remove_failed_loaded_klass(k, class_loader_data(class_loader));
1554     assert(defined_k == nullptr, "Should not have a klass if there's an exception");
1555     k->class_loader_data()->add_to_deallocate_list(k);
1556   }
1557   return defined_k;
1558 }
1559 
1560 
1561 // ----------------------------------------------------------------------------
1562 // GC support
1563 
1564 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1565 bool SystemDictionary::do_unloading(GCTimer* gc_timer) {
1566 
1567   bool unloading_occurred;
1568   bool is_concurrent = !SafepointSynchronize::is_at_safepoint();
1569   {
1570     GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1571     assert_locked_or_safepoint(ClassLoaderDataGraph_lock);  // caller locks.
1572     // First, mark for unload all ClassLoaderData referencing a dead class loader.
1573     unloading_occurred = ClassLoaderDataGraph::do_unloading();
1574     if (unloading_occurred) {
1575       ConditionalMutexLocker ml2(Module_lock, is_concurrent);
1576       JFR_ONLY(Jfr::on_unloading_classes();)
1577       MANAGEMENT_ONLY(FinalizerService::purge_unloaded();)
1578       ConditionalMutexLocker ml1(SystemDictionary_lock, is_concurrent);
1579       ClassLoaderDataGraph::clean_module_and_package_info();
1580       LoaderConstraintTable::purge_loader_constraints();
1581       ResolutionErrorTable::purge_resolution_errors();
1582     }
1583   }
1584 
1585   GCTraceTime(Debug, gc, phases) t("Trigger cleanups", gc_timer);
1586 
1587   if (unloading_occurred) {
1588     SymbolTable::trigger_cleanup();
1589 
1590     ConditionalMutexLocker ml(ClassInitError_lock, is_concurrent);
1591     InstanceKlass::clean_initialization_error_table();
1592   }
1593 
1594   return unloading_occurred;
1595 }
1596 
1597 void SystemDictionary::methods_do(void f(Method*)) {
1598   // Walk methods in loaded classes
1599 
1600   {
1601     MutexLocker ml(ClassLoaderDataGraph_lock);
1602     ClassLoaderDataGraph::methods_do(f);
1603   }
1604 
1605   auto doit = [&] (InvokeMethodKey key, Method* method) {
1606     if (method != nullptr) {
1607       f(method);
1608     }
1609   };
1610 
1611   {
1612     MutexLocker ml(InvokeMethodIntrinsicTable_lock);
1613     _invoke_method_intrinsic_table->iterate_all(doit);
1614   }
1615 
1616 }
1617 
1618 // ----------------------------------------------------------------------------
1619 // Initialization
1620 
1621 void SystemDictionary::initialize(TRAPS) {
1622   _invoke_method_intrinsic_table = new (mtClass) InvokeMethodIntrinsicTable();
1623   _invoke_method_type_table = new (mtClass) InvokeMethodTypeTable();
1624   ResolutionErrorTable::initialize();
1625   LoaderConstraintTable::initialize();
1626   PlaceholderTable::initialize();
1627 #if INCLUDE_CDS
1628   SystemDictionaryShared::initialize();
1629   if (CDSConfig::is_dumping_archive()) {
1630     AOTClassLocationConfig::dumptime_init(THREAD);
1631   }
1632 #endif
1633   // Resolve basic classes
1634   vmClasses::resolve_all(CHECK);
1635   // Resolve classes used by archived heap objects
1636   if (CDSConfig::is_using_archive()) {
1637     HeapShared::resolve_classes(THREAD);
1638   }
1639 }
1640 
1641 // Constraints on class loaders. The details of the algorithm can be
1642 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
1643 // Virtual Machine" by Sheng Liang and Gilad Bracha.  The basic idea is
1644 // that the dictionary needs to maintain a set of constraints that
1645 // must be satisfied by all classes in the dictionary.
1646 // if defining is true, then LinkageError if already in dictionary
1647 // if initiating loader, then ok if InstanceKlass matches existing entry
1648 
1649 void SystemDictionary::check_constraints(InstanceKlass* k,
1650                                          ClassLoaderData* loader_data,
1651                                          bool defining,
1652                                          TRAPS) {
1653   ResourceMark rm(THREAD);
1654   stringStream ss;
1655   bool throwException = false;
1656 
1657   {
1658     Symbol* name = k->name();
1659 
1660     MutexLocker mu(THREAD, SystemDictionary_lock);
1661 
1662     InstanceKlass* check = loader_data->dictionary()->find_class(THREAD, name);
1663     if (check != nullptr) {
1664       // If different InstanceKlass - duplicate class definition,
1665       // else - ok, class loaded by a different thread in parallel.
1666       // We should only have found it if it was done loading and ok to use.
1667 
1668       if ((defining == true) || (k != check)) {
1669         throwException = true;
1670         ss.print("loader %s", loader_data->loader_name_and_id());
1671         ss.print(" attempted duplicate %s definition for %s. (%s)",
1672                  k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
1673       } else {
1674         return;
1675       }
1676     }
1677 
1678     if (throwException == false) {
1679       if (LoaderConstraintTable::check_or_update(k, loader_data, name) == false) {
1680         throwException = true;
1681         ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
1682         ss.print(" wants to load %s %s.",
1683                  k->external_kind(), k->external_name());
1684         Klass *existing_klass = LoaderConstraintTable::find_constrained_klass(name, loader_data);
1685         if (existing_klass != nullptr && existing_klass->class_loader_data() != loader_data) {
1686           ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
1687                    existing_klass->external_kind(),
1688                    existing_klass->class_loader_data()->loader_name_and_id(),
1689                    existing_klass->class_in_module_of_loader(false, true));
1690         } else {
1691           ss.print(" (%s)", k->class_in_module_of_loader(false, true));
1692         }
1693       }
1694     }
1695   }
1696 
1697   // Throw error now if needed (cannot throw while holding
1698   // SystemDictionary_lock because of rank ordering)
1699   if (throwException == true) {
1700     THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1701   }
1702 }
1703 
1704 // Update class loader data dictionary - done after check_constraint and add_to_hierarchy
1705 // have been called.
1706 void SystemDictionary::update_dictionary(JavaThread* current,
1707                                          InstanceKlass* k,
1708                                          ClassLoaderData* loader_data) {
1709   MonitorLocker mu1(SystemDictionary_lock);
1710 
1711   // Make a new dictionary entry.
1712   Symbol* name  = k->name();
1713   Dictionary* dictionary = loader_data->dictionary();
1714   InstanceKlass* sd_check = dictionary->find_class(current, name);
1715   if (sd_check == nullptr) {
1716     dictionary->add_klass(current, name, k);
1717   }
1718   mu1.notify_all();
1719 }
1720 
1721 #if INCLUDE_CDS
1722 // Indicate that loader_data has initiated the loading of class k, which
1723 // has already been defined by a parent loader.
1724 // This API should be used only by AOTLinkedClassBulkLoader
1725 void SystemDictionary::add_to_initiating_loader(JavaThread* current,
1726                                                 InstanceKlass* k,
1727                                                 ClassLoaderData* loader_data) {
1728   assert(CDSConfig::is_using_aot_linked_classes(), "must be");
1729   assert_locked_or_safepoint(SystemDictionary_lock);
1730   Symbol* name  = k->name();
1731   Dictionary* dictionary = loader_data->dictionary();
1732   assert(k->is_loaded(), "must be");
1733   assert(k->class_loader_data() != loader_data, "only for classes defined by a parent loader");
1734   assert(dictionary->find_class(current, name) == nullptr, "sanity");
1735   dictionary->add_klass(current, name, k);
1736 }
1737 #endif
1738 
1739 // Try to find a class name using the loader constraints.  The
1740 // loader constraints might know about a class that isn't fully loaded
1741 // yet and these will be ignored.
1742 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
1743                     Thread* current, Symbol* class_name, Handle class_loader) {
1744 
1745   // First see if it has been loaded directly.
1746   Klass* klass = find_instance_or_array_klass(current, class_name, class_loader);
1747   if (klass != nullptr)
1748     return klass;
1749 
1750   // Now look to see if it has been loaded elsewhere, and is subject to
1751   // a loader constraint that would require this loader to return the
1752   // klass that is already loaded.
1753   if (Signature::is_array(class_name)) {
1754     // For array classes, their Klass*s are not kept in the
1755     // constraint table. The element Klass*s are.
1756     SignatureStream ss(class_name, false);
1757     int ndims = ss.skip_array_prefix();  // skip all '['s
1758     BasicType t = ss.type();
1759     if (t != T_OBJECT) {
1760       klass = Universe::typeArrayKlass(t);
1761     } else {
1762       MutexLocker mu(current, SystemDictionary_lock);
1763       klass = LoaderConstraintTable::find_constrained_klass(ss.as_symbol(), class_loader_data(class_loader));
1764     }
1765     // If element class already loaded, allocate array klass
1766     if (klass != nullptr) {
1767       klass = klass->array_klass_or_null(ndims);
1768     }
1769   } else {
1770     MutexLocker mu(current, SystemDictionary_lock);
1771     // Non-array classes are easy: simply check the constraint table.
1772     klass = LoaderConstraintTable::find_constrained_klass(class_name, class_loader_data(class_loader));
1773   }
1774 
1775   return klass;
1776 }
1777 
1778 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
1779                                              Klass* klass_being_linked,
1780                                              Handle class_loader1,
1781                                              Handle class_loader2) {
1782   ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
1783   ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
1784 
1785   Symbol* constraint_name = nullptr;
1786 
1787   if (!Signature::is_array(class_name)) {
1788     constraint_name = class_name;
1789   } else {
1790     // For array classes, their Klass*s are not kept in the
1791     // constraint table. The element classes are.
1792     SignatureStream ss(class_name, false);
1793     ss.skip_array_prefix();  // skip all '['s
1794     if (!ss.has_envelope()) {
1795       return true;     // primitive types always pass
1796     }
1797     constraint_name = ss.as_symbol();
1798     // Increment refcount to keep constraint_name alive after
1799     // SignatureStream is destructed. It will be decremented below
1800     // before returning.
1801     constraint_name->increment_refcount();
1802   }
1803 
1804   Dictionary* dictionary1 = loader_data1->dictionary();
1805   Dictionary* dictionary2 = loader_data2->dictionary();
1806 
1807   JavaThread* current = JavaThread::current();
1808   {
1809     MutexLocker mu_s(SystemDictionary_lock);
1810     InstanceKlass* klass1 = dictionary1->find_class(current, constraint_name);
1811     InstanceKlass* klass2 = dictionary2->find_class(current, constraint_name);
1812     bool result = LoaderConstraintTable::add_entry(constraint_name, klass1, loader_data1,
1813                                                    klass2, loader_data2);
1814 #if INCLUDE_CDS
1815     if (CDSConfig::is_dumping_archive() && klass_being_linked != nullptr &&
1816         !klass_being_linked->in_aot_cache()) {
1817          SystemDictionaryShared::record_linking_constraint(constraint_name,
1818                                      InstanceKlass::cast(klass_being_linked),
1819                                      class_loader1, class_loader2);
1820     }
1821 #endif // INCLUDE_CDS
1822     if (Signature::is_array(class_name)) {
1823       constraint_name->decrement_refcount();
1824     }
1825     return result;
1826   }
1827 }
1828 
1829 // Add entry to resolution error table to record the error when the first
1830 // attempt to resolve a reference to a class has failed.
1831 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
1832                                             Symbol* error, const char* message,
1833                                             Symbol* cause, const char* cause_msg) {
1834   {
1835     MutexLocker ml(Thread::current(), SystemDictionary_lock);
1836     ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1837     if (entry == nullptr) {
1838       ResolutionErrorTable::add_entry(pool, which, error, message, cause, cause_msg);
1839     }
1840   }
1841 }
1842 
1843 // Delete a resolution error for RedefineClasses for a constant pool is going away
1844 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
1845   ResolutionErrorTable::delete_entry(pool);
1846 }
1847 
1848 // Lookup resolution error table. Returns error if found, otherwise null.
1849 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
1850                                                 const char** message,
1851                                                 Symbol** cause, const char** cause_msg) {
1852 
1853   {
1854     MutexLocker ml(Thread::current(), SystemDictionary_lock);
1855     ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1856     if (entry != nullptr) {
1857       *message = entry->message();
1858       *cause = entry->cause();
1859       *cause_msg = entry->cause_msg();
1860       return entry->error();
1861     } else {
1862       return nullptr;
1863     }
1864   }
1865 }
1866 
1867 // Add an entry to resolution error table to record an error in resolving or
1868 // validating a nest host. This is used to construct informative error
1869 // messages when IllegalAccessError's occur. If an entry already exists it will
1870 // be updated with the nest host error message.
1871 
1872 void SystemDictionary::add_nest_host_error(const constantPoolHandle& pool,
1873                                            int which,
1874                                            const char* message) {
1875   {
1876     MutexLocker ml(Thread::current(), SystemDictionary_lock);
1877     ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1878     if (entry != nullptr && entry->nest_host_error() == nullptr) {
1879       // An existing entry means we had a true resolution failure (LinkageError) with our nest host, but we
1880       // still want to add the error message for the higher-level access checks to report. We should
1881       // only reach here under the same error condition, so we can ignore the potential race with setting
1882       // the message. If we see it is already set then we can ignore it.
1883       entry->set_nest_host_error(message);
1884     } else {
1885       ResolutionErrorTable::add_entry(pool, which, message);
1886     }
1887   }
1888 }
1889 
1890 // Lookup any nest host error
1891 const char* SystemDictionary::find_nest_host_error(const constantPoolHandle& pool, int which) {
1892   {
1893     MutexLocker ml(Thread::current(), SystemDictionary_lock);
1894     ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1895     if (entry != nullptr) {
1896       return entry->nest_host_error();
1897     } else {
1898       return nullptr;
1899     }
1900   }
1901 }
1902 
1903 // Signature constraints ensure that callers and callees agree about
1904 // the meaning of type names in their signatures.  This routine is the
1905 // intake for constraints.  It collects them from several places:
1906 //
1907 //  * LinkResolver::resolve_method (if check_access is true) requires
1908 //    that the resolving class (the caller) and the defining class of
1909 //    the resolved method (the callee) agree on each type in the
1910 //    method's signature.
1911 //
1912 //  * LinkResolver::resolve_interface_method performs exactly the same
1913 //    checks.
1914 //
1915 //  * LinkResolver::resolve_field requires that the constant pool
1916 //    attempting to link to a field agree with the field's defining
1917 //    class about the type of the field signature.
1918 //
1919 //  * klassVtable::initialize_vtable requires that, when a class
1920 //    overrides a vtable entry allocated by a superclass, that the
1921 //    overriding method (i.e., the callee) agree with the superclass
1922 //    on each type in the method's signature.
1923 //
1924 //  * klassItable::initialize_itable requires that, when a class fills
1925 //    in its itables, for each non-abstract method installed in an
1926 //    itable, the method (i.e., the callee) agree with the interface
1927 //    on each type in the method's signature.
1928 //
1929 // All those methods have a boolean (check_access, checkconstraints)
1930 // which turns off the checks.  This is used from specialized contexts
1931 // such as bootstrapping, dumping, and debugging.
1932 //
1933 // No direct constraint is placed between the class and its
1934 // supertypes.  Constraints are only placed along linked relations
1935 // between callers and callees.  When a method overrides or implements
1936 // an abstract method in a supertype (superclass or interface), the
1937 // constraints are placed as if the supertype were the caller to the
1938 // overriding method.  (This works well, since callers to the
1939 // supertype have already established agreement between themselves and
1940 // the supertype.)  As a result of all this, a class can disagree with
1941 // its supertype about the meaning of a type name, as long as that
1942 // class neither calls a relevant method of the supertype, nor is
1943 // called (perhaps via an override) from the supertype.
1944 //
1945 //
1946 // SystemDictionary::check_signature_loaders(sig, klass_being_linked, l1, l2)
1947 //
1948 // Make sure all class components (including arrays) in the given
1949 // signature will be resolved to the same class in both loaders.
1950 // Returns the name of the type that failed a loader constraint check, or
1951 // null if no constraint failed.  No exception except OOME is thrown.
1952 // Arrays are not added to the loader constraint table, their elements are.
1953 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
1954                                                   Klass* klass_being_linked,
1955                                                   Handle loader1, Handle loader2,
1956                                                   bool is_method)  {
1957   // Nothing to do if loaders are the same.
1958   if (loader1() == loader2()) {
1959     return nullptr;
1960   }
1961 
1962   for (SignatureStream ss(signature, is_method); !ss.is_done(); ss.next()) {
1963     if (ss.is_reference()) {
1964       Symbol* sig = ss.as_symbol();
1965       // Note: In the future, if template-like types can take
1966       // arguments, we will want to recognize them and dig out class
1967       // names hiding inside the argument lists.
1968       if (!add_loader_constraint(sig, klass_being_linked, loader1, loader2)) {
1969         return sig;
1970       }
1971     }
1972   }
1973   return nullptr;
1974 }
1975 
1976 Method* SystemDictionary::find_method_handle_intrinsic(vmIntrinsicID iid,
1977                                                        Symbol* signature,
1978                                                        TRAPS) {
1979 
1980   const int iid_as_int = vmIntrinsics::as_int(iid);
1981   assert(MethodHandles::is_signature_polymorphic(iid) &&
1982          MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
1983          iid != vmIntrinsics::_invokeGeneric,
1984          "must be a known MH intrinsic iid=%d: %s", iid_as_int, vmIntrinsics::name_at(iid));
1985 
1986   InvokeMethodKey key(signature, iid_as_int);
1987   Method** met = nullptr;
1988 
1989   // We only want one entry in the table for this (signature/id, method) pair but the code
1990   // to create the intrinsic method needs to be outside the lock.
1991   // The first thread claims the entry by adding the key and the other threads wait, until the
1992   // Method has been added as the value.
1993   {
1994     MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
1995     while (true) {
1996       bool created;
1997       met = _invoke_method_intrinsic_table->put_if_absent(key, &created);
1998       assert(met != nullptr, "either created or found");
1999       if (*met != nullptr) {
2000         return *met;
2001       } else if (created) {
2002         // The current thread won the race and will try to create the full entry.
2003         break;
2004       } else {
2005         // Another thread beat us to it, so wait for them to complete
2006         // and return *met; or if they hit an error we get another try.
2007         ml.wait();
2008         // Note it is not safe to read *met here as that entry could have
2009         // been deleted, so we must loop and try put_if_absent again.
2010       }
2011     }
2012   }
2013 
2014   methodHandle m = Method::make_method_handle_intrinsic(iid, signature, THREAD);
2015   bool throw_error = HAS_PENDING_EXCEPTION;
2016   if (!throw_error && (!Arguments::is_interpreter_only() || iid == vmIntrinsics::_linkToNative)) {
2017     // Generate a compiled form of the MH intrinsic
2018     // linkToNative doesn't have interpreter-specific implementation, so always has to go through compiled version.
2019     AdapterHandlerLibrary::create_native_wrapper(m);
2020     // Check if have the compiled code.
2021     throw_error = (!m->has_compiled_code());
2022   }
2023 
2024   {
2025     MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
2026     if (throw_error) {
2027       // Remove the entry and let another thread try, or get the same exception.
2028       bool removed = _invoke_method_intrinsic_table->remove(key);
2029       assert(removed, "must be the owner");
2030       ml.notify_all();
2031     } else {
2032       signature->make_permanent(); // The signature is never unloaded.
2033       assert(Arguments::is_interpreter_only() || (m->has_compiled_code() &&
2034              m->code()->entry_point() == m->from_compiled_entry()),
2035              "MH intrinsic invariant");
2036       *met = m(); // insert the element
2037       ml.notify_all();
2038       return m();
2039     }
2040   }
2041 
2042   // Throw OOM or the pending exception in the JavaThread
2043   if (throw_error && !HAS_PENDING_EXCEPTION) {
2044     THROW_MSG_NULL(vmSymbols::java_lang_OutOfMemoryError(),
2045                    "Out of space in CodeCache for method handle intrinsic");
2046   }
2047   return nullptr;
2048 }
2049 
2050 #if INCLUDE_CDS
2051 void SystemDictionary::get_all_method_handle_intrinsics(GrowableArray<Method*>* methods) {
2052   assert(SafepointSynchronize::is_at_safepoint(), "must be");
2053   auto do_method = [&] (InvokeMethodKey& key, Method*& m) {
2054     methods->append(m);
2055   };
2056   _invoke_method_intrinsic_table->iterate_all(do_method);
2057 }
2058 
2059 void SystemDictionary::restore_archived_method_handle_intrinsics() {
2060   if (UseSharedSpaces) {
2061     EXCEPTION_MARK;
2062     restore_archived_method_handle_intrinsics_impl(THREAD);
2063     if (HAS_PENDING_EXCEPTION) {
2064       // This is probably caused by OOM -- other parts of the CDS archive have direct pointers to
2065       // the archived method handle intrinsics, so we can't really recover from this failure.
2066       vm_exit_during_initialization(err_msg("Failed to restore archived method handle intrinsics. Try to increase heap size."));
2067     }
2068   }
2069 }
2070 
2071 void SystemDictionary::restore_archived_method_handle_intrinsics_impl(TRAPS) {
2072   Array<Method*>* list = AOTMetaspace::archived_method_handle_intrinsics();
2073   for (int i = 0; i < list->length(); i++) {
2074     methodHandle m(THREAD, list->at(i));
2075     Method::restore_archived_method_handle_intrinsic(m, CHECK);
2076     m->constants()->restore_unshareable_info(CHECK);
2077     if (!Arguments::is_interpreter_only() || m->intrinsic_id() == vmIntrinsics::_linkToNative) {
2078       AdapterHandlerLibrary::create_native_wrapper(m);
2079       if (!m->has_compiled_code()) {
2080         ResourceMark rm(THREAD);
2081         vm_exit_during_initialization(err_msg("Failed to initialize method %s", m->external_name()));
2082       }
2083     }
2084 
2085     // There's no need to grab the InvokeMethodIntrinsicTable_lock, as we are still very early in
2086     // VM start-up -- in init_globals2() -- so we are still running a single Java thread. It's not
2087     // possible to have a contention.
2088     const int iid_as_int = vmIntrinsics::as_int(m->intrinsic_id());
2089     InvokeMethodKey key(m->signature(), iid_as_int);
2090     bool created = _invoke_method_intrinsic_table->put(key, m());
2091     assert(created, "unexpected contention");
2092   }
2093 }
2094 #endif // INCLUDE_CDS
2095 
2096 // Helper for unpacking the return value from linkMethod and linkCallSite.
2097 static Method* unpack_method_and_appendix(Handle mname,
2098                                           Klass* accessing_klass,
2099                                           objArrayHandle appendix_box,
2100                                           Handle* appendix_result,
2101                                           TRAPS) {
2102   if (mname.not_null()) {
2103     Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2104     if (m != nullptr) {
2105       oop appendix = appendix_box->obj_at(0);
2106       LogTarget(Info, methodhandles) lt;
2107       if (lt.develop_is_enabled()) {
2108         ResourceMark rm(THREAD);
2109         LogStream ls(lt);
2110         ls.print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2111         m->print_on(&ls);
2112         if (appendix != nullptr) { ls.print("appendix = "); appendix->print_on(&ls); }
2113         ls.cr();
2114       }
2115 
2116       (*appendix_result) = Handle(THREAD, appendix);
2117       // the target is stored in the cpCache and if a reference to this
2118       // MemberName is dropped we need a way to make sure the
2119       // class_loader containing this method is kept alive.
2120       methodHandle mh(THREAD, m); // record_dependency can safepoint.
2121       ClassLoaderData* this_key = accessing_klass->class_loader_data();
2122       this_key->record_dependency(m->method_holder());
2123       return mh();
2124     }
2125   }
2126   THROW_MSG_NULL(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives");
2127 }
2128 
2129 Method* SystemDictionary::find_method_handle_invoker(Klass* klass,
2130                                                      Symbol* name,
2131                                                      Symbol* signature,
2132                                                      Klass* accessing_klass,
2133                                                      Handle* appendix_result,
2134                                                      TRAPS) {
2135   guarantee(THREAD->can_call_java(), "");
2136   Handle method_type =
2137     SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_NULL);
2138 
2139   int ref_kind = JVM_REF_invokeVirtual;
2140   oop name_oop = StringTable::intern(name, CHECK_NULL);
2141   Handle name_str (THREAD, name_oop);
2142   objArrayHandle appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK_NULL);
2143   assert(appendix_box->obj_at(0) == nullptr, "");
2144 
2145   // This should not happen.  JDK code should take care of that.
2146   if (accessing_klass == nullptr || method_type.is_null()) {
2147     THROW_MSG_NULL(vmSymbols::java_lang_InternalError(), "bad invokehandle");
2148   }
2149 
2150   // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2151   JavaCallArguments args;
2152   args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2153   args.push_int(ref_kind);
2154   args.push_oop(Handle(THREAD, klass->java_mirror()));
2155   args.push_oop(name_str);
2156   args.push_oop(method_type);
2157   args.push_oop(appendix_box);
2158   JavaValue result(T_OBJECT);
2159   JavaCalls::call_static(&result,
2160                          vmClasses::MethodHandleNatives_klass(),
2161                          vmSymbols::linkMethod_name(),
2162                          vmSymbols::linkMethod_signature(),
2163                          &args, CHECK_NULL);
2164   Handle mname(THREAD, result.get_oop());
2165   return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2166 }
2167 
2168 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2169 // We must ensure that all class loaders everywhere will reach this class, for any client.
2170 // This is a safe bet for public classes in java.lang, such as Object and String.
2171 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2172 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2173 static bool is_always_visible_class(oop mirror) {
2174   Klass* klass = java_lang_Class::as_Klass(mirror);
2175   if (klass->is_objArray_klass()) {
2176     klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2177   }
2178   if (klass->is_typeArray_klass()) {
2179     return true; // primitive array
2180   }
2181   assert(klass->is_instance_klass(), "%s", klass->external_name());
2182   return klass->is_public() &&
2183          (InstanceKlass::cast(klass)->is_same_class_package(vmClasses::Object_klass()) ||       // java.lang
2184           InstanceKlass::cast(klass)->is_same_class_package(vmClasses::MethodHandle_klass()));  // java.lang.invoke
2185 }
2186 
2187 // Find or construct the Java mirror (java.lang.Class instance) for
2188 // the given field type signature, as interpreted relative to the
2189 // given class loader.  Handles primitives, void, references, arrays,
2190 // and all other reflectable types, except method types.
2191 // N.B.  Code in reflection should use this entry point.
2192 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2193                                                    Klass* accessing_klass,
2194                                                    SignatureStream::FailureMode failure_mode,
2195                                                    TRAPS) {
2196 
2197   Handle class_loader;
2198 
2199   // What we have here must be a valid field descriptor,
2200   // and all valid field descriptors are supported.
2201   // Produce the same java.lang.Class that reflection reports.
2202   if (accessing_klass != nullptr) {
2203     class_loader      = Handle(THREAD, accessing_klass->class_loader());
2204   }
2205   ResolvingSignatureStream ss(signature, class_loader, false);
2206   oop mirror_oop = ss.as_java_mirror(failure_mode, CHECK_NH);
2207   if (mirror_oop == nullptr) {
2208     return Handle();  // report failure this way
2209   }
2210   Handle mirror(THREAD, mirror_oop);
2211 
2212   if (accessing_klass != nullptr) {
2213     // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2214     Klass* sel_klass = java_lang_Class::as_Klass(mirror());
2215     if (sel_klass != nullptr) {
2216       LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_NH);
2217     }
2218   }
2219   return mirror;
2220 }
2221 
2222 
2223 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2224 // signature, as interpreted relative to the given class loader.
2225 // Because of class loader constraints, all method handle usage must be
2226 // consistent with this loader.
2227 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2228                                                  Klass* accessing_klass,
2229                                                  TRAPS) {
2230   Handle empty;
2231   OopHandle* o;
2232   {
2233     MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2234     o = _invoke_method_type_table->get(signature);
2235   }
2236 
2237   if (o != nullptr) {
2238     oop mt = o->resolve();
2239     assert(java_lang_invoke_MethodType::is_instance(mt), "");
2240     return Handle(THREAD, mt);
2241   } else if (!THREAD->can_call_java()) {
2242     warning("SystemDictionary::find_method_handle_type called from compiler thread");  // FIXME
2243     return Handle();  // do not attempt from within compiler, unless it was cached
2244   }
2245 
2246   Handle class_loader;
2247   if (accessing_klass != nullptr) {
2248     class_loader      = Handle(THREAD, accessing_klass->class_loader());
2249   }
2250   bool can_be_cached = true;
2251   int npts = ArgumentCount(signature).size();
2252   objArrayHandle pts = oopFactory::new_objArray_handle(vmClasses::Class_klass(), npts, CHECK_(empty));
2253   int arg = 0;
2254   Handle rt; // the return type from the signature
2255   ResourceMark rm(THREAD);
2256   for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2257     oop mirror = nullptr;
2258     if (can_be_cached) {
2259       // Use neutral class loader to lookup candidate classes to be placed in the cache.
2260       mirror = ss.as_java_mirror(Handle(), SignatureStream::ReturnNull, CHECK_(empty));
2261       if (mirror == nullptr || (ss.is_reference() && !is_always_visible_class(mirror))) {
2262         // Fall back to accessing_klass context.
2263         can_be_cached = false;
2264       }
2265     }
2266     if (!can_be_cached) {
2267       // Resolve, throwing a real error if it doesn't work.
2268       mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2269     }
2270     assert(mirror != nullptr, "%s", ss.as_symbol()->as_C_string());
2271     if (ss.at_return_type())
2272       rt = Handle(THREAD, mirror);
2273     else
2274       pts->obj_at_put(arg++, mirror);
2275 
2276     // Check accessibility.
2277     if (!java_lang_Class::is_primitive(mirror) && accessing_klass != nullptr) {
2278       Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2279       mirror = nullptr;  // safety
2280       // Emulate ConstantPool::verify_constant_pool_resolve.
2281       LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_(empty));
2282     }
2283   }
2284   assert(arg == npts, "");
2285 
2286   // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2287   JavaCallArguments args(Handle(THREAD, rt()));
2288   args.push_oop(pts);
2289   JavaValue result(T_OBJECT);
2290   JavaCalls::call_static(&result,
2291                          vmClasses::MethodHandleNatives_klass(),
2292                          vmSymbols::findMethodHandleType_name(),
2293                          vmSymbols::findMethodHandleType_signature(),
2294                          &args, CHECK_(empty));
2295   Handle method_type(THREAD, result.get_oop());
2296 
2297   if (can_be_cached) {
2298     // We can cache this MethodType inside the JVM.
2299     MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2300     bool created = false;
2301     assert(method_type != nullptr, "unexpected null");
2302     OopHandle* h = _invoke_method_type_table->get(signature);
2303     if (h == nullptr) {
2304       signature->make_permanent(); // The signature is never unloaded.
2305       OopHandle elem = OopHandle(Universe::vm_global(), method_type());
2306       bool created = _invoke_method_type_table->put(signature, elem);
2307       assert(created, "better be created");
2308     }
2309   }
2310   // report back to the caller with the MethodType
2311   return method_type;
2312 }
2313 
2314 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2315                                                 Klass* accessing_klass,
2316                                                 TRAPS) {
2317   Handle empty;
2318   ResourceMark rm(THREAD);
2319   SignatureStream ss(signature, /*is_method=*/ false);
2320   if (!ss.is_done()) {
2321     Handle class_loader;
2322     if (accessing_klass != nullptr) {
2323       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2324     }
2325     oop mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2326     ss.next();
2327     if (ss.is_done()) {
2328       return Handle(THREAD, mirror);
2329     }
2330   }
2331   return empty;
2332 }
2333 
2334 // Ask Java code to find or construct a method handle constant.
2335 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2336                                                      int ref_kind, //e.g., JVM_REF_invokeVirtual
2337                                                      Klass* callee,
2338                                                      Symbol* name,
2339                                                      Symbol* signature,
2340                                                      TRAPS) {
2341   Handle empty;
2342   if (caller == nullptr) {
2343     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2344   }
2345   Handle name_str      = java_lang_String::create_from_symbol(name,      CHECK_(empty));
2346   Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2347 
2348   // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2349   Handle mname = vmClasses::MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2350   java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2351   java_lang_invoke_MemberName::set_name (mname(), name_str());
2352   java_lang_invoke_MemberName::set_type (mname(), signature_str());
2353   java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2354 
2355   if (ref_kind == JVM_REF_invokeVirtual &&
2356       MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2357     // Skip resolution for public signature polymorphic methods such as
2358     // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2359     // They require appendix argument which MemberName resolution doesn't handle.
2360     // There's special logic on JDK side to handle them
2361     // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2362   } else {
2363     MethodHandles::resolve_MemberName(mname, caller, 0, false /*speculative_resolve*/, CHECK_(empty));
2364   }
2365 
2366   // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2367   Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2368 
2369   // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2370   JavaCallArguments args;
2371   args.push_oop(Handle(THREAD, caller->java_mirror()));  // the referring class
2372   args.push_int(ref_kind);
2373   args.push_oop(Handle(THREAD, callee->java_mirror()));  // the target class
2374   args.push_oop(name_str);
2375   args.push_oop(type);
2376   JavaValue result(T_OBJECT);
2377   JavaCalls::call_static(&result,
2378                          vmClasses::MethodHandleNatives_klass(),
2379                          vmSymbols::linkMethodHandleConstant_name(),
2380                          vmSymbols::linkMethodHandleConstant_signature(),
2381                          &args, CHECK_(empty));
2382   return Handle(THREAD, result.get_oop());
2383 }
2384 
2385 // Ask Java to run a bootstrap method, in order to create a dynamic call site
2386 // while linking an invokedynamic op, or compute a constant for Dynamic_info CP entry
2387 // with linkage results being stored back into the bootstrap specifier.
2388 void SystemDictionary::invoke_bootstrap_method(BootstrapInfo& bootstrap_specifier, TRAPS) {
2389   // Resolve the bootstrap specifier, its name, type, and static arguments
2390   bootstrap_specifier.resolve_bsm(CHECK);
2391 
2392   // This should not happen.  JDK code should take care of that.
2393   if (bootstrap_specifier.caller() == nullptr || bootstrap_specifier.type_arg().is_null()) {
2394     THROW_MSG(vmSymbols::java_lang_InternalError(), "Invalid bootstrap method invocation with no caller or type argument");
2395   }
2396 
2397   bool is_indy = bootstrap_specifier.is_method_call();
2398   objArrayHandle appendix_box;
2399   if (is_indy) {
2400     // Some method calls may require an appendix argument.  Arrange to receive it.
2401     appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK);
2402     assert(appendix_box->obj_at(0) == nullptr, "");
2403   }
2404 
2405   // call condy: java.lang.invoke.MethodHandleNatives::linkDynamicConstant(caller, bsm, type, info)
2406   //       indy: java.lang.invoke.MethodHandleNatives::linkCallSite(caller, bsm, name, mtype, info, &appendix)
2407   JavaCallArguments args;
2408   args.push_oop(Handle(THREAD, bootstrap_specifier.caller_mirror()));
2409   args.push_oop(bootstrap_specifier.bsm());
2410   args.push_oop(bootstrap_specifier.name_arg());
2411   args.push_oop(bootstrap_specifier.type_arg());
2412   args.push_oop(bootstrap_specifier.arg_values());
2413   if (is_indy) {
2414     args.push_oop(appendix_box);
2415   }
2416   JavaValue result(T_OBJECT);
2417   JavaCalls::call_static(&result,
2418                          vmClasses::MethodHandleNatives_klass(),
2419                          is_indy ? vmSymbols::linkCallSite_name() : vmSymbols::linkDynamicConstant_name(),
2420                          is_indy ? vmSymbols::linkCallSite_signature() : vmSymbols::linkDynamicConstant_signature(),
2421                          &args, CHECK);
2422 
2423   Handle value(THREAD, result.get_oop());
2424   if (is_indy) {
2425     Handle appendix;
2426     Method* method = unpack_method_and_appendix(value,
2427                                                 bootstrap_specifier.caller(),
2428                                                 appendix_box,
2429                                                 &appendix, CHECK);
2430     methodHandle mh(THREAD, method);
2431     bootstrap_specifier.set_resolved_method(mh, appendix);
2432   } else {
2433     bootstrap_specifier.set_resolved_value(value);
2434   }
2435 
2436   // sanity check
2437   assert(bootstrap_specifier.is_resolved() ||
2438          (bootstrap_specifier.is_method_call() &&
2439           bootstrap_specifier.resolved_method().not_null()), "bootstrap method call failed");
2440 }
2441 
2442 
2443 bool SystemDictionary::is_nonpublic_Object_method(Method* m) {
2444   assert(m != nullptr, "Unexpected nullptr Method*");
2445   return !m->is_public() && m->method_holder() == vmClasses::Object_klass();
2446 }
2447 
2448 // ----------------------------------------------------------------------------
2449 
2450 void SystemDictionary::print_on(outputStream *st) {
2451   CDS_ONLY(SystemDictionaryShared::print_on(st));
2452   GCMutexLocker mu(SystemDictionary_lock);
2453 
2454   ClassLoaderDataGraph::print_dictionary(st);
2455 
2456   // Placeholders
2457   PlaceholderTable::print_on(st);
2458   st->cr();
2459 
2460   // loader constraints - print under SD_lock
2461   LoaderConstraintTable::print_on(st);
2462   st->cr();
2463 }
2464 
2465 void SystemDictionary::print() { print_on(tty); }
2466 
2467 void SystemDictionary::verify() {
2468 
2469   GCMutexLocker mu(SystemDictionary_lock);
2470 
2471   // Verify dictionary
2472   ClassLoaderDataGraph::verify_dictionary();
2473 
2474   // Verify constraint table
2475   LoaderConstraintTable::verify();
2476 }
2477 
2478 void SystemDictionary::dump(outputStream *st, bool verbose) {
2479   assert_locked_or_safepoint(SystemDictionary_lock);
2480   if (verbose) {
2481     print_on(st);
2482   } else {
2483     CDS_ONLY(SystemDictionaryShared::print_table_statistics(st));
2484     ClassLoaderDataGraph::print_table_statistics(st);
2485     LoaderConstraintTable::print_table_statistics(st);
2486   }
2487 }
2488 
2489 // Utility for dumping dictionaries.
2490 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
2491                                  DCmdWithParser(output, heap),
2492   _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
2493            "BOOLEAN", false, "false") {
2494   _dcmdparser.add_dcmd_option(&_verbose);
2495 }
2496 
2497 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
2498   VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
2499                          _verbose.value());
2500   VMThread::execute(&dumper);
2501 }