1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "jvm.h"
  27 #include "aot/aotLoader.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/classLoaderExt.hpp"
  33 #include "classfile/dictionary.hpp"
  34 #include "classfile/javaClasses.inline.hpp"
  35 #include "classfile/klassFactory.hpp"
  36 #include "classfile/loaderConstraints.hpp"
  37 #include "classfile/packageEntry.hpp"
  38 #include "classfile/placeholders.hpp"
  39 #include "classfile/protectionDomainCache.hpp"
  40 #include "classfile/resolutionErrors.hpp"
  41 #include "classfile/stringTable.hpp"
  42 #include "classfile/systemDictionary.hpp"
  43 #include "classfile/vmSymbols.hpp"
  44 #include "code/codeCache.hpp"
  45 #include "compiler/compileBroker.hpp"
  46 #include "gc/shared/gcTraceTime.inline.hpp"
  47 #include "gc/shared/oopStorage.inline.hpp"
  48 #include "interpreter/bytecodeStream.hpp"
  49 #include "interpreter/interpreter.hpp"
  50 #include "jfr/jfrEvents.hpp"
  51 #include "logging/log.hpp"
  52 #include "logging/logStream.hpp"
  53 #include "memory/filemap.hpp"
  54 #include "memory/metaspaceClosure.hpp"
  55 #include "memory/oopFactory.hpp"
  56 #include "memory/resourceArea.hpp"
  57 #include "oops/access.inline.hpp"
  58 #include "oops/instanceKlass.hpp"
  59 #include "oops/instanceRefKlass.hpp"
  60 #include "oops/klass.inline.hpp"
  61 #include "oops/method.inline.hpp"
  62 #include "oops/methodData.hpp"
  63 #include "oops/objArrayKlass.hpp"
  64 #include "oops/objArrayOop.inline.hpp"
  65 #include "oops/oop.inline.hpp"
  66 #include "oops/symbol.hpp"
  67 #include "oops/typeArrayKlass.hpp"
  68 #include "prims/jvmtiEnvBase.hpp"
  69 #include "prims/resolvedMethodTable.hpp"
  70 #include "prims/methodHandles.hpp"
  71 #include "runtime/arguments.hpp"
  72 #include "runtime/arguments_ext.hpp"
  73 #include "runtime/biasedLocking.hpp"
  74 #include "runtime/fieldType.hpp"
  75 #include "runtime/handles.inline.hpp"
  76 #include "runtime/java.hpp"
  77 #include "runtime/javaCalls.hpp"
  78 #include "runtime/mutexLocker.hpp"
  79 #include "runtime/orderAccess.hpp"
  80 #include "runtime/sharedRuntime.hpp"
  81 #include "runtime/signature.hpp"
  82 #include "services/classLoadingService.hpp"
  83 #include "services/diagnosticCommand.hpp"
  84 #include "services/threadService.hpp"
  85 #include "utilities/macros.hpp"
  86 #if INCLUDE_CDS
  87 #include "classfile/systemDictionaryShared.hpp"
  88 #endif
  89 #if INCLUDE_JVMCI
  90 #include "jvmci/jvmciRuntime.hpp"
  91 #endif
  92 
  93 PlaceholderTable*      SystemDictionary::_placeholders        = NULL;
  94 Dictionary*            SystemDictionary::_shared_dictionary   = NULL;
  95 LoaderConstraintTable* SystemDictionary::_loader_constraints  = NULL;
  96 ResolutionErrorTable*  SystemDictionary::_resolution_errors   = NULL;
  97 SymbolPropertyTable*   SystemDictionary::_invoke_method_table = NULL;
  98 ProtectionDomainCacheTable*   SystemDictionary::_pd_cache_table = NULL;
  99 
 100 int         SystemDictionary::_number_of_modifications = 0;
 101 oop         SystemDictionary::_system_loader_lock_obj     =  NULL;
 102 
 103 InstanceKlass*      SystemDictionary::_well_known_klasses[SystemDictionary::WKID_LIMIT]
 104                                                           =  { NULL /*, NULL...*/ };
 105 
 106 InstanceKlass*      SystemDictionary::_box_klasses[T_VOID+1]      =  { NULL /*, NULL...*/ };
 107 
 108 oop         SystemDictionary::_java_system_loader         =  NULL;
 109 oop         SystemDictionary::_java_platform_loader       =  NULL;
 110 
 111 bool        SystemDictionary::_has_checkPackageAccess     =  false;
 112 
 113 // Default ProtectionDomainCacheSize value
 114 
 115 const int defaultProtectionDomainCacheSize = 1009;
 116 
 117 OopStorage* SystemDictionary::_vm_weak_oop_storage = NULL;
 118 
 119 
 120 // ----------------------------------------------------------------------------
 121 // Java-level SystemLoader and PlatformLoader
 122 
 123 oop SystemDictionary::java_system_loader() {
 124   return _java_system_loader;
 125 }
 126 
 127 oop SystemDictionary::java_platform_loader() {
 128   return _java_platform_loader;
 129 }
 130 
 131 void SystemDictionary::compute_java_loaders(TRAPS) {
 132   JavaValue result(T_OBJECT);
 133   InstanceKlass* class_loader_klass = SystemDictionary::ClassLoader_klass();
 134   JavaCalls::call_static(&result,
 135                          class_loader_klass,
 136                          vmSymbols::getSystemClassLoader_name(),
 137                          vmSymbols::void_classloader_signature(),
 138                          CHECK);
 139 
 140   _java_system_loader = (oop)result.get_jobject();
 141 
 142   JavaCalls::call_static(&result,
 143                          class_loader_klass,
 144                          vmSymbols::getPlatformClassLoader_name(),
 145                          vmSymbols::void_classloader_signature(),
 146                          CHECK);
 147 
 148   _java_platform_loader = (oop)result.get_jobject();
 149 }
 150 
 151 ClassLoaderData* SystemDictionary::register_loader(Handle class_loader) {
 152   if (class_loader() == NULL) return ClassLoaderData::the_null_class_loader_data();
 153   return ClassLoaderDataGraph::find_or_create(class_loader);
 154 }
 155 
 156 // ----------------------------------------------------------------------------
 157 // Parallel class loading check
 158 
 159 bool SystemDictionary::is_parallelCapable(Handle class_loader) {
 160   if (class_loader.is_null()) return true;
 161   if (AlwaysLockClassLoader) return false;
 162   return java_lang_ClassLoader::parallelCapable(class_loader());
 163 }
 164 // ----------------------------------------------------------------------------
 165 // ParallelDefineClass flag does not apply to bootclass loader
 166 bool SystemDictionary::is_parallelDefine(Handle class_loader) {
 167    if (class_loader.is_null()) return false;
 168    if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) {
 169      return true;
 170    }
 171    return false;
 172 }
 173 
 174 // Returns true if the passed class loader is the builtin application class loader
 175 // or a custom system class loader. A customer system class loader can be
 176 // specified via -Djava.system.class.loader.
 177 bool SystemDictionary::is_system_class_loader(oop class_loader) {
 178   if (class_loader == NULL) {
 179     return false;
 180   }
 181   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() ||
 182          oopDesc::equals(class_loader, _java_system_loader));
 183 }
 184 
 185 // Returns true if the passed class loader is the platform class loader.
 186 bool SystemDictionary::is_platform_class_loader(oop class_loader) {
 187   if (class_loader == NULL) {
 188     return false;
 189   }
 190   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass());
 191 }
 192 
 193 // ----------------------------------------------------------------------------
 194 // Resolving of classes
 195 
 196 // Forwards to resolve_or_null
 197 
 198 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader, Handle protection_domain, bool throw_error, TRAPS) {
 199   Klass* klass = resolve_or_null(class_name, class_loader, protection_domain, THREAD);
 200   if (HAS_PENDING_EXCEPTION || klass == NULL) {
 201     // can return a null klass
 202     klass = handle_resolution_exception(class_name, throw_error, klass, THREAD);
 203   }
 204   return klass;
 205 }
 206 
 207 Klass* SystemDictionary::handle_resolution_exception(Symbol* class_name,
 208                                                      bool throw_error,
 209                                                      Klass* klass, TRAPS) {
 210   if (HAS_PENDING_EXCEPTION) {
 211     // If we have a pending exception we forward it to the caller, unless throw_error is true,
 212     // in which case we have to check whether the pending exception is a ClassNotFoundException,
 213     // and if so convert it to a NoClassDefFoundError
 214     // And chain the original ClassNotFoundException
 215     if (throw_error && PENDING_EXCEPTION->is_a(SystemDictionary::ClassNotFoundException_klass())) {
 216       ResourceMark rm(THREAD);
 217       assert(klass == NULL, "Should not have result with exception pending");
 218       Handle e(THREAD, PENDING_EXCEPTION);
 219       CLEAR_PENDING_EXCEPTION;
 220       THROW_MSG_CAUSE_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e);
 221     } else {
 222       return NULL;
 223     }
 224   }
 225   // Class not found, throw appropriate error or exception depending on value of throw_error
 226   if (klass == NULL) {
 227     ResourceMark rm(THREAD);
 228     if (throw_error) {
 229       THROW_MSG_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string());
 230     } else {
 231       THROW_MSG_NULL(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string());
 232     }
 233   }
 234   return klass;
 235 }
 236 
 237 
 238 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name,
 239                                            bool throw_error, TRAPS)
 240 {
 241   return resolve_or_fail(class_name, Handle(), Handle(), throw_error, THREAD);
 242 }
 243 
 244 
 245 // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null
 246 
 247 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, Handle protection_domain, TRAPS) {
 248   if (FieldType::is_array(class_name)) {
 249     return resolve_array_class_or_null(class_name, class_loader, protection_domain, THREAD);
 250   } else {
 251     return resolve_instance_class_or_null_helper(class_name, class_loader, protection_domain, THREAD);
 252   }
 253 }
 254 
 255 // name may be in the form of "java/lang/Object" or "Ljava/lang/Object;"
 256 InstanceKlass* SystemDictionary::resolve_instance_class_or_null_helper(Symbol* class_name,
 257                                                                        Handle class_loader,
 258                                                                        Handle protection_domain,
 259                                                                        TRAPS) {
 260   assert(class_name != NULL && !FieldType::is_array(class_name), "must be");
 261   if (FieldType::is_obj(class_name)) {
 262     ResourceMark rm(THREAD);
 263     // Ignore wrapping L and ;.
 264     TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1,
 265                                    class_name->utf8_length() - 2, CHECK_NULL);
 266     return resolve_instance_class_or_null(name, class_loader, protection_domain, THREAD);
 267   } else {
 268     return resolve_instance_class_or_null(class_name, class_loader, protection_domain, THREAD);
 269   }
 270 }
 271 
 272 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, TRAPS) {
 273   return resolve_or_null(class_name, Handle(), Handle(), THREAD);
 274 }
 275 
 276 // Forwards to resolve_instance_class_or_null
 277 
 278 Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name,
 279                                                      Handle class_loader,
 280                                                      Handle protection_domain,
 281                                                      TRAPS) {
 282   assert(FieldType::is_array(class_name), "must be array");
 283   Klass* k = NULL;
 284   FieldArrayInfo fd;
 285   // dimension and object_key in FieldArrayInfo are assigned as a side-effect
 286   // of this call
 287   BasicType t = FieldType::get_array_info(class_name, fd, CHECK_NULL);
 288   if (t == T_OBJECT) {
 289     // naked oop "k" is OK here -- we assign back into it
 290     k = SystemDictionary::resolve_instance_class_or_null(fd.object_key(),
 291                                                          class_loader,
 292                                                          protection_domain,
 293                                                          CHECK_NULL);
 294     if (k != NULL) {
 295       k = k->array_klass(fd.dimension(), CHECK_NULL);
 296     }
 297   } else {
 298     k = Universe::typeArrayKlassObj(t);
 299     k = TypeArrayKlass::cast(k)->array_klass(fd.dimension(), CHECK_NULL);
 300   }
 301   return k;
 302 }
 303 
 304 
 305 // Must be called for any super-class or super-interface resolution
 306 // during class definition to allow class circularity checking
 307 // super-interface callers:
 308 //    parse_interfaces - for defineClass & jvmtiRedefineClasses
 309 // super-class callers:
 310 //   ClassFileParser - for defineClass & jvmtiRedefineClasses
 311 //   load_shared_class - while loading a class from shared archive
 312 //   resolve_instance_class_or_null:
 313 //     via: handle_parallel_super_load
 314 //      when resolving a class that has an existing placeholder with
 315 //      a saved superclass [i.e. a defineClass is currently in progress]
 316 //      if another thread is trying to resolve the class, it must do
 317 //      super-class checks on its own thread to catch class circularity
 318 // This last call is critical in class circularity checking for cases
 319 // where classloading is delegated to different threads and the
 320 // classloader lock is released.
 321 // Take the case: Base->Super->Base
 322 //   1. If thread T1 tries to do a defineClass of class Base
 323 //    resolve_super_or_fail creates placeholder: T1, Base (super Super)
 324 //   2. resolve_instance_class_or_null does not find SD or placeholder for Super
 325 //    so it tries to load Super
 326 //   3. If we load the class internally, or user classloader uses same thread
 327 //      loadClassFromxxx or defineClass via parseClassFile Super ...
 328 //      3.1 resolve_super_or_fail creates placeholder: T1, Super (super Base)
 329 //      3.3 resolve_instance_class_or_null Base, finds placeholder for Base
 330 //      3.4 calls resolve_super_or_fail Base
 331 //      3.5 finds T1,Base -> throws class circularity
 332 //OR 4. If T2 tries to resolve Super via defineClass Super ...
 333 //      4.1 resolve_super_or_fail creates placeholder: T2, Super (super Base)
 334 //      4.2 resolve_instance_class_or_null Base, finds placeholder for Base (super Super)
 335 //      4.3 calls resolve_super_or_fail Super in parallel on own thread T2
 336 //      4.4 finds T2, Super -> throws class circularity
 337 // Must be called, even if superclass is null, since this is
 338 // where the placeholder entry is created which claims this
 339 // thread is loading this class/classloader.
 340 // Be careful when modifying this code: once you have run
 341 // placeholders()->find_and_add(PlaceholderTable::LOAD_SUPER),
 342 // you need to find_and_remove it before returning.
 343 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 344 InstanceKlass* SystemDictionary::resolve_super_or_fail(Symbol* child_name,
 345                                                        Symbol* super_name,
 346                                                        Handle class_loader,
 347                                                        Handle protection_domain,
 348                                                        bool is_superclass,
 349                                                        TRAPS) {
 350   assert(!FieldType::is_array(super_name), "invalid super class name");
 351 #if INCLUDE_CDS
 352   if (DumpSharedSpaces) {
 353     // Special processing for CDS dump time.
 354     InstanceKlass* k = SystemDictionaryShared::dump_time_resolve_super_or_fail(child_name,
 355         super_name, class_loader, protection_domain, is_superclass, CHECK_NULL);
 356     if (k) {
 357       return k;
 358     }
 359   }
 360 #endif // INCLUDE_CDS
 361 
 362   // Double-check, if child class is already loaded, just return super-class,interface
 363   // Don't add a placedholder if already loaded, i.e. already in appropriate class loader
 364   // dictionary.
 365   // Make sure there's a placeholder for the *child* before resolving.
 366   // Used as a claim that this thread is currently loading superclass/classloader
 367   // Used here for ClassCircularity checks and also for heap verification
 368   // (every InstanceKlass needs to be in its class loader dictionary or have a placeholder).
 369   // Must check ClassCircularity before checking if super class is already loaded.
 370   //
 371   // We might not already have a placeholder if this child_name was
 372   // first seen via resolve_from_stream (jni_DefineClass or JVM_DefineClass);
 373   // the name of the class might not be known until the stream is actually
 374   // parsed.
 375   // Bugs 4643874, 4715493
 376 
 377   ClassLoaderData* loader_data = class_loader_data(class_loader);
 378   Dictionary* dictionary = loader_data->dictionary();
 379   unsigned int d_hash = dictionary->compute_hash(child_name);
 380   unsigned int p_hash = placeholders()->compute_hash(child_name);
 381   int p_index = placeholders()->hash_to_index(p_hash);
 382   // can't throw error holding a lock
 383   bool child_already_loaded = false;
 384   bool throw_circularity_error = false;
 385   {
 386     MutexLocker mu(SystemDictionary_lock, THREAD);
 387     InstanceKlass* childk = find_class(d_hash, child_name, dictionary);
 388     InstanceKlass* quicksuperk;
 389     // to support // loading: if child done loading, just return superclass
 390     // if super_name, & class_loader don't match:
 391     // if initial define, SD update will give LinkageError
 392     // if redefine: compare_class_versions will give HIERARCHY_CHANGED
 393     // so we don't throw an exception here.
 394     // see: nsk redefclass014 & java.lang.instrument Instrument032
 395     if ((childk != NULL ) && (is_superclass) &&
 396         ((quicksuperk = childk->java_super()) != NULL) &&
 397          ((quicksuperk->name() == super_name) &&
 398             (oopDesc::equals(quicksuperk->class_loader(), class_loader())))) {
 399            return quicksuperk;
 400     } else {
 401       PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, child_name, loader_data);
 402       if (probe && probe->check_seen_thread(THREAD, PlaceholderTable::LOAD_SUPER)) {
 403           throw_circularity_error = true;
 404       }
 405     }
 406     if (!throw_circularity_error) {
 407       // Be careful not to exit resolve_super
 408       PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, super_name, THREAD);
 409     }
 410   }
 411   if (throw_circularity_error) {
 412       ResourceMark rm(THREAD);
 413       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), child_name->as_C_string());
 414   }
 415 
 416 // java.lang.Object should have been found above
 417   assert(super_name != NULL, "null super class for resolving");
 418   // Resolve the super class or interface, check results on return
 419   InstanceKlass* superk =
 420     SystemDictionary::resolve_instance_class_or_null_helper(super_name,
 421                                                             class_loader,
 422                                                             protection_domain,
 423                                                             THREAD);
 424 
 425   // Clean up of placeholders moved so that each classloadAction registrar self-cleans up
 426   // It is no longer necessary to keep the placeholder table alive until update_dictionary
 427   // or error. GC used to walk the placeholder table as strong roots.
 428   // The instanceKlass is kept alive because the class loader is on the stack,
 429   // which keeps the loader_data alive, as well as all instanceKlasses in
 430   // the loader_data. parseClassFile adds the instanceKlass to loader_data.
 431   {
 432     MutexLocker mu(SystemDictionary_lock, THREAD);
 433     placeholders()->find_and_remove(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, THREAD);
 434     SystemDictionary_lock->notify_all();
 435   }
 436   if (HAS_PENDING_EXCEPTION || superk == NULL) {
 437     // can null superk
 438     Klass* k = handle_resolution_exception(super_name, true, superk, THREAD);
 439     assert(k == NULL || k == superk, "must be");
 440     if (k == NULL) {
 441       superk = NULL;
 442     }
 443   }
 444 
 445   return superk;
 446 }
 447 
 448 void SystemDictionary::validate_protection_domain(InstanceKlass* klass,
 449                                                   Handle class_loader,
 450                                                   Handle protection_domain,
 451                                                   TRAPS) {
 452   if(!has_checkPackageAccess()) return;
 453 
 454   // Now we have to call back to java to check if the initating class has access
 455   JavaValue result(T_VOID);
 456   LogTarget(Debug, protectiondomain) lt;
 457   if (lt.is_enabled()) {
 458     ResourceMark rm;
 459     // Print out trace information
 460     LogStream ls(lt);
 461     ls.print_cr("Checking package access");
 462     if (class_loader() != NULL) {
 463       ls.print("class loader: ");
 464       class_loader()->print_value_on(&ls);
 465     } else {
 466       ls.print_cr("class loader: NULL");
 467     }
 468     if (protection_domain() != NULL) {
 469       ls.print(" protection domain: ");
 470       protection_domain()->print_value_on(&ls);
 471     } else {
 472       ls.print_cr(" protection domain: NULL");
 473     }
 474     ls.print(" loading: "); klass->print_value_on(&ls);
 475     ls.cr();
 476   }
 477 
 478   // This handle and the class_loader handle passed in keeps this class from
 479   // being unloaded through several GC points.
 480   // The class_loader handle passed in is the initiating loader.
 481   Handle mirror(THREAD, klass->java_mirror());
 482 
 483   InstanceKlass* system_loader = SystemDictionary::ClassLoader_klass();
 484   JavaCalls::call_special(&result,
 485                          class_loader,
 486                          system_loader,
 487                          vmSymbols::checkPackageAccess_name(),
 488                          vmSymbols::class_protectiondomain_signature(),
 489                          mirror,
 490                          protection_domain,
 491                          THREAD);
 492 
 493   if (HAS_PENDING_EXCEPTION) {
 494     log_debug(protectiondomain)("DENIED !!!!!!!!!!!!!!!!!!!!!");
 495   } else {
 496    log_debug(protectiondomain)("granted");
 497   }
 498 
 499   if (HAS_PENDING_EXCEPTION) return;
 500 
 501   // If no exception has been thrown, we have validated the protection domain
 502   // Insert the protection domain of the initiating class into the set.
 503   {
 504     ClassLoaderData* loader_data = class_loader_data(class_loader);
 505     Dictionary* dictionary = loader_data->dictionary();
 506 
 507     Symbol*  kn = klass->name();
 508     unsigned int d_hash = dictionary->compute_hash(kn);
 509 
 510     MutexLocker mu(SystemDictionary_lock, THREAD);
 511     int d_index = dictionary->hash_to_index(d_hash);
 512     dictionary->add_protection_domain(d_index, d_hash, klass,
 513                                       protection_domain, THREAD);
 514   }
 515 }
 516 
 517 // We only get here if this thread finds that another thread
 518 // has already claimed the placeholder token for the current operation,
 519 // but that other thread either never owned or gave up the
 520 // object lock
 521 // Waits on SystemDictionary_lock to indicate placeholder table updated
 522 // On return, caller must recheck placeholder table state
 523 //
 524 // We only get here if
 525 //  1) custom classLoader, i.e. not bootstrap classloader
 526 //  2) custom classLoader has broken the class loader objectLock
 527 //     so another thread got here in parallel
 528 //
 529 // lockObject must be held.
 530 // Complicated dance due to lock ordering:
 531 // Must first release the classloader object lock to
 532 // allow initial definer to complete the class definition
 533 // and to avoid deadlock
 534 // Reclaim classloader lock object with same original recursion count
 535 // Must release SystemDictionary_lock after notify, since
 536 // class loader lock must be claimed before SystemDictionary_lock
 537 // to prevent deadlocks
 538 //
 539 // The notify allows applications that did an untimed wait() on
 540 // the classloader object lock to not hang.
 541 void SystemDictionary::double_lock_wait(Handle lockObject, TRAPS) {
 542   assert_lock_strong(SystemDictionary_lock);
 543 
 544   bool calledholdinglock
 545       = ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD, lockObject);
 546   assert(calledholdinglock,"must hold lock for notify");
 547   assert((!oopDesc::equals(lockObject(), _system_loader_lock_obj) && !is_parallelCapable(lockObject)), "unexpected double_lock_wait");
 548   ObjectSynchronizer::notifyall(lockObject, THREAD);
 549   intptr_t recursions =  ObjectSynchronizer::complete_exit(lockObject, THREAD);
 550   SystemDictionary_lock->wait();
 551   SystemDictionary_lock->unlock();
 552   ObjectSynchronizer::reenter(lockObject, recursions, THREAD);
 553   SystemDictionary_lock->lock();
 554 }
 555 
 556 // If the class in is in the placeholder table, class loading is in progress
 557 // For cases where the application changes threads to load classes, it
 558 // is critical to ClassCircularity detection that we try loading
 559 // the superclass on the same thread internally, so we do parallel
 560 // super class loading here.
 561 // This also is critical in cases where the original thread gets stalled
 562 // even in non-circularity situations.
 563 // Note: must call resolve_super_or_fail even if null super -
 564 // to force placeholder entry creation for this class for circularity detection
 565 // Caller must check for pending exception
 566 // Returns non-null Klass* if other thread has completed load
 567 // and we are done,
 568 // If return null Klass* and no pending exception, the caller must load the class
 569 InstanceKlass* SystemDictionary::handle_parallel_super_load(
 570     Symbol* name, Symbol* superclassname, Handle class_loader,
 571     Handle protection_domain, Handle lockObject, TRAPS) {
 572 
 573   ClassLoaderData* loader_data = class_loader_data(class_loader);
 574   Dictionary* dictionary = loader_data->dictionary();
 575   unsigned int d_hash = dictionary->compute_hash(name);
 576   unsigned int p_hash = placeholders()->compute_hash(name);
 577   int p_index = placeholders()->hash_to_index(p_hash);
 578 
 579   // superk is not used, resolve_super called for circularity check only
 580   // This code is reached in two situations. One if this thread
 581   // is loading the same class twice (e.g. ClassCircularity, or
 582   // java.lang.instrument).
 583   // The second is if another thread started the resolve_super first
 584   // and has not yet finished.
 585   // In both cases the original caller will clean up the placeholder
 586   // entry on error.
 587   Klass* superk = SystemDictionary::resolve_super_or_fail(name,
 588                                                           superclassname,
 589                                                           class_loader,
 590                                                           protection_domain,
 591                                                           true,
 592                                                           CHECK_NULL);
 593 
 594   // parallelCapable class loaders do NOT wait for parallel superclass loads to complete
 595   // Serial class loaders and bootstrap classloader do wait for superclass loads
 596  if (!class_loader.is_null() && is_parallelCapable(class_loader)) {
 597     MutexLocker mu(SystemDictionary_lock, THREAD);
 598     // Check if classloading completed while we were loading superclass or waiting
 599     return find_class(d_hash, name, dictionary);
 600   }
 601 
 602   // must loop to both handle other placeholder updates
 603   // and spurious notifications
 604   bool super_load_in_progress = true;
 605   PlaceholderEntry* placeholder;
 606   while (super_load_in_progress) {
 607     MutexLocker mu(SystemDictionary_lock, THREAD);
 608     // Check if classloading completed while we were loading superclass or waiting
 609     InstanceKlass* check = find_class(d_hash, name, dictionary);
 610     if (check != NULL) {
 611       // Klass is already loaded, so just return it
 612       return check;
 613     } else {
 614       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 615       if (placeholder && placeholder->super_load_in_progress() ){
 616         // We only get here if the application has released the
 617         // classloader lock when another thread was in the middle of loading a
 618         // superclass/superinterface for this class, and now
 619         // this thread is also trying to load this class.
 620         // To minimize surprises, the first thread that started to
 621         // load a class should be the one to complete the loading
 622         // with the classfile it initially expected.
 623         // This logic has the current thread wait once it has done
 624         // all the superclass/superinterface loading it can, until
 625         // the original thread completes the class loading or fails
 626         // If it completes we will use the resulting InstanceKlass
 627         // which we will find below in the systemDictionary.
 628         // We also get here for parallel bootstrap classloader
 629         if (class_loader.is_null()) {
 630           SystemDictionary_lock->wait();
 631         } else {
 632           double_lock_wait(lockObject, THREAD);
 633         }
 634       } else {
 635         // If not in SD and not in PH, other thread's load must have failed
 636         super_load_in_progress = false;
 637       }
 638     }
 639   }
 640   return NULL;
 641 }
 642 
 643 static void post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
 644   assert(event != NULL, "invariant");
 645   assert(k != NULL, "invariant");
 646   assert(event->should_commit(), "invariant");
 647   event->set_loadedClass(k);
 648   event->set_definingClassLoader(k->class_loader_data());
 649   event->set_initiatingClassLoader(init_cld);
 650   event->commit();
 651 }
 652 
 653 
 654 // Be careful when modifying this code: once you have run
 655 // placeholders()->find_and_add(PlaceholderTable::LOAD_INSTANCE),
 656 // you need to find_and_remove it before returning.
 657 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 658 //
 659 // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;"
 660 InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name,
 661                                                                 Handle class_loader,
 662                                                                 Handle protection_domain,
 663                                                                 TRAPS) {
 664   assert(name != NULL && !FieldType::is_array(name) &&
 665          !FieldType::is_obj(name), "invalid class name");
 666 
 667   EventClassLoad class_load_start_event;
 668 
 669   HandleMark hm(THREAD);
 670 
 671   // Fix for 4474172; see evaluation for more details
 672   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 673   ClassLoaderData* loader_data = register_loader(class_loader);
 674   Dictionary* dictionary = loader_data->dictionary();
 675   unsigned int d_hash = dictionary->compute_hash(name);
 676 
 677   // Do lookup to see if class already exist and the protection domain
 678   // has the right access
 679   // This call uses find which checks protection domain already matches
 680   // All subsequent calls use find_class, and set has_loaded_class so that
 681   // before we return a result we call out to java to check for valid protection domain
 682   // to allow returning the Klass* and add it to the pd_set if it is valid
 683   {
 684     InstanceKlass* probe = dictionary->find(d_hash, name, protection_domain);
 685     if (probe != NULL) return probe;
 686   }
 687 
 688   // Non-bootstrap class loaders will call out to class loader and
 689   // define via jvm/jni_DefineClass which will acquire the
 690   // class loader object lock to protect against multiple threads
 691   // defining the class in parallel by accident.
 692   // This lock must be acquired here so the waiter will find
 693   // any successful result in the SystemDictionary and not attempt
 694   // the define.
 695   // ParallelCapable Classloaders and the bootstrap classloader
 696   // do not acquire lock here.
 697   bool DoObjectLock = true;
 698   if (is_parallelCapable(class_loader)) {
 699     DoObjectLock = false;
 700   }
 701 
 702   unsigned int p_hash = placeholders()->compute_hash(name);
 703   int p_index = placeholders()->hash_to_index(p_hash);
 704 
 705   // Class is not in SystemDictionary so we have to do loading.
 706   // Make sure we are synchronized on the class loader before we proceed
 707   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
 708   check_loader_lock_contention(lockObject, THREAD);
 709   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
 710 
 711   // Check again (after locking) if class already exist in SystemDictionary
 712   bool class_has_been_loaded   = false;
 713   bool super_load_in_progress  = false;
 714   bool havesupername = false;
 715   InstanceKlass* k = NULL;
 716   PlaceholderEntry* placeholder;
 717   Symbol* superclassname = NULL;
 718 
 719   assert(THREAD->can_call_java(),
 720          "can not load classes with compiler thread: class=%s, classloader=%s",
 721          name->as_C_string(),
 722          class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string());
 723   {
 724     MutexLocker mu(SystemDictionary_lock, THREAD);
 725     InstanceKlass* check = find_class(d_hash, name, dictionary);
 726     if (check != NULL) {
 727       // InstanceKlass is already loaded, so just return it
 728       class_has_been_loaded = true;
 729       k = check;
 730     } else {
 731       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 732       if (placeholder && placeholder->super_load_in_progress()) {
 733          super_load_in_progress = true;
 734          if (placeholder->havesupername() == true) {
 735            superclassname = placeholder->supername();
 736            havesupername = true;
 737          }
 738       }
 739     }
 740   }
 741 
 742   // If the class is in the placeholder table, class loading is in progress
 743   if (super_load_in_progress && havesupername==true) {
 744     k = handle_parallel_super_load(name,
 745                                    superclassname,
 746                                    class_loader,
 747                                    protection_domain,
 748                                    lockObject, THREAD);
 749     if (HAS_PENDING_EXCEPTION) {
 750       return NULL;
 751     }
 752     if (k != NULL) {
 753       class_has_been_loaded = true;
 754     }
 755   }
 756 
 757   bool throw_circularity_error = false;
 758   if (!class_has_been_loaded) {
 759     bool load_instance_added = false;
 760 
 761     // add placeholder entry to record loading instance class
 762     // Five cases:
 763     // All cases need to prevent modifying bootclasssearchpath
 764     // in parallel with a classload of same classname
 765     // Redefineclasses uses existence of the placeholder for the duration
 766     // of the class load to prevent concurrent redefinition of not completely
 767     // defined classes.
 768     // case 1. traditional classloaders that rely on the classloader object lock
 769     //   - no other need for LOAD_INSTANCE
 770     // case 2. traditional classloaders that break the classloader object lock
 771     //    as a deadlock workaround. Detection of this case requires that
 772     //    this check is done while holding the classloader object lock,
 773     //    and that lock is still held when calling classloader's loadClass.
 774     //    For these classloaders, we ensure that the first requestor
 775     //    completes the load and other requestors wait for completion.
 776     // case 3. Bootstrap classloader - don't own objectLocker
 777     //    This classloader supports parallelism at the classloader level,
 778     //    but only allows a single load of a class/classloader pair.
 779     //    No performance benefit and no deadlock issues.
 780     // case 4. parallelCapable user level classloaders - without objectLocker
 781     //    Allow parallel classloading of a class/classloader pair
 782 
 783     {
 784       MutexLocker mu(SystemDictionary_lock, THREAD);
 785       if (class_loader.is_null() || !is_parallelCapable(class_loader)) {
 786         PlaceholderEntry* oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 787         if (oldprobe) {
 788           // only need check_seen_thread once, not on each loop
 789           // 6341374 java/lang/Instrument with -Xcomp
 790           if (oldprobe->check_seen_thread(THREAD, PlaceholderTable::LOAD_INSTANCE)) {
 791             throw_circularity_error = true;
 792           } else {
 793             // case 1: traditional: should never see load_in_progress.
 794             while (!class_has_been_loaded && oldprobe && oldprobe->instance_load_in_progress()) {
 795 
 796               // case 3: bootstrap classloader: prevent futile classloading,
 797               // wait on first requestor
 798               if (class_loader.is_null()) {
 799                 SystemDictionary_lock->wait();
 800               } else {
 801               // case 2: traditional with broken classloader lock. wait on first
 802               // requestor.
 803                 double_lock_wait(lockObject, THREAD);
 804               }
 805               // Check if classloading completed while we were waiting
 806               InstanceKlass* check = find_class(d_hash, name, dictionary);
 807               if (check != NULL) {
 808                 // Klass is already loaded, so just return it
 809                 k = check;
 810                 class_has_been_loaded = true;
 811               }
 812               // check if other thread failed to load and cleaned up
 813               oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 814             }
 815           }
 816         }
 817       }
 818       // All cases: add LOAD_INSTANCE holding SystemDictionary_lock
 819       // case 4: parallelCapable: allow competing threads to try
 820       // LOAD_INSTANCE in parallel
 821 
 822       if (!throw_circularity_error && !class_has_been_loaded) {
 823         PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, NULL, THREAD);
 824         load_instance_added = true;
 825         // For class loaders that do not acquire the classloader object lock,
 826         // if they did not catch another thread holding LOAD_INSTANCE,
 827         // need a check analogous to the acquire ObjectLocker/find_class
 828         // i.e. now that we hold the LOAD_INSTANCE token on loading this class/CL
 829         // one final check if the load has already completed
 830         // class loaders holding the ObjectLock shouldn't find the class here
 831         InstanceKlass* check = find_class(d_hash, name, dictionary);
 832         if (check != NULL) {
 833         // Klass is already loaded, so return it after checking/adding protection domain
 834           k = check;
 835           class_has_been_loaded = true;
 836         }
 837       }
 838     }
 839 
 840     // must throw error outside of owning lock
 841     if (throw_circularity_error) {
 842       assert(!HAS_PENDING_EXCEPTION && load_instance_added == false,"circularity error cleanup");
 843       ResourceMark rm(THREAD);
 844       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string());
 845     }
 846 
 847     if (!class_has_been_loaded) {
 848 
 849       // Do actual loading
 850       k = load_instance_class(name, class_loader, THREAD);
 851 
 852       // If everything was OK (no exceptions, no null return value), and
 853       // class_loader is NOT the defining loader, do a little more bookkeeping.
 854       if (!HAS_PENDING_EXCEPTION && k != NULL &&
 855         !oopDesc::equals(k->class_loader(), class_loader())) {
 856 
 857         check_constraints(d_hash, k, class_loader, false, THREAD);
 858 
 859         // Need to check for a PENDING_EXCEPTION again; check_constraints
 860         // can throw and doesn't use the CHECK macro.
 861         if (!HAS_PENDING_EXCEPTION) {
 862           { // Grabbing the Compile_lock prevents systemDictionary updates
 863             // during compilations.
 864             MutexLocker mu(Compile_lock, THREAD);
 865             update_dictionary(d_hash, p_index, p_hash,
 866               k, class_loader, THREAD);
 867           }
 868 
 869           if (JvmtiExport::should_post_class_load()) {
 870             Thread *thread = THREAD;
 871             assert(thread->is_Java_thread(), "thread->is_Java_thread()");
 872             JvmtiExport::post_class_load((JavaThread *) thread, k);
 873           }
 874         }
 875       }
 876     } // load_instance_class
 877 
 878     if (load_instance_added == true) {
 879       // clean up placeholder entries for LOAD_INSTANCE success or error
 880       // This brackets the SystemDictionary updates for both defining
 881       // and initiating loaders
 882       MutexLocker mu(SystemDictionary_lock, THREAD);
 883       placeholders()->find_and_remove(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD);
 884       SystemDictionary_lock->notify_all();
 885     }
 886   }
 887 
 888   if (HAS_PENDING_EXCEPTION || k == NULL) {
 889     return NULL;
 890   }
 891   if (class_load_start_event.should_commit()) {
 892     post_class_load_event(&class_load_start_event, k, loader_data);
 893   }
 894 #ifdef ASSERT
 895   {
 896     ClassLoaderData* loader_data = k->class_loader_data();
 897     MutexLocker mu(SystemDictionary_lock, THREAD);
 898     InstanceKlass* kk = find_class(name, loader_data);
 899     assert(kk == k, "should be present in dictionary");
 900   }
 901 #endif
 902 
 903   // return if the protection domain in NULL
 904   if (protection_domain() == NULL) return k;
 905 
 906   // Check the protection domain has the right access
 907   if (dictionary->is_valid_protection_domain(d_hash, name,
 908                                              protection_domain)) {
 909     return k;
 910   }
 911 
 912   // Verify protection domain. If it fails an exception is thrown
 913   validate_protection_domain(k, class_loader, protection_domain, CHECK_NULL);
 914 
 915   return k;
 916 }
 917 
 918 
 919 // This routine does not lock the system dictionary.
 920 //
 921 // Since readers don't hold a lock, we must make sure that system
 922 // dictionary entries are only removed at a safepoint (when only one
 923 // thread is running), and are added to in a safe way (all links must
 924 // be updated in an MT-safe manner).
 925 //
 926 // Callers should be aware that an entry could be added just after
 927 // _dictionary->bucket(index) is read here, so the caller will not see
 928 // the new entry.
 929 
 930 Klass* SystemDictionary::find(Symbol* class_name,
 931                               Handle class_loader,
 932                               Handle protection_domain,
 933                               TRAPS) {
 934 
 935   // The result of this call should be consistent with the result
 936   // of the call to resolve_instance_class_or_null().
 937   // See evaluation 6790209 and 4474172 for more details.
 938   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 939   ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
 940 
 941   if (loader_data == NULL) {
 942     // If the ClassLoaderData has not been setup,
 943     // then the class loader has no entries in the dictionary.
 944     return NULL;
 945   }
 946 
 947   Dictionary* dictionary = loader_data->dictionary();
 948   unsigned int d_hash = dictionary->compute_hash(class_name);
 949   return dictionary->find(d_hash, class_name,
 950                           protection_domain);
 951 }
 952 
 953 
 954 // Look for a loaded instance or array klass by name.  Do not do any loading.
 955 // return NULL in case of error.
 956 Klass* SystemDictionary::find_instance_or_array_klass(Symbol* class_name,
 957                                                       Handle class_loader,
 958                                                       Handle protection_domain,
 959                                                       TRAPS) {
 960   Klass* k = NULL;
 961   assert(class_name != NULL, "class name must be non NULL");
 962 
 963   if (FieldType::is_array(class_name)) {
 964     // The name refers to an array.  Parse the name.
 965     // dimension and object_key in FieldArrayInfo are assigned as a
 966     // side-effect of this call
 967     FieldArrayInfo fd;
 968     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
 969     if (t != T_OBJECT) {
 970       k = Universe::typeArrayKlassObj(t);
 971     } else {
 972       k = SystemDictionary::find(fd.object_key(), class_loader, protection_domain, THREAD);
 973     }
 974     if (k != NULL) {
 975       k = k->array_klass_or_null(fd.dimension());
 976     }
 977   } else {
 978     k = find(class_name, class_loader, protection_domain, THREAD);
 979   }
 980   return k;
 981 }
 982 
 983 // Note: this method is much like resolve_from_stream, but
 984 // does not publish the classes via the SystemDictionary.
 985 // Handles unsafe_DefineAnonymousClass and redefineclasses
 986 // RedefinedClasses do not add to the class hierarchy
 987 InstanceKlass* SystemDictionary::parse_stream(Symbol* class_name,
 988                                               Handle class_loader,
 989                                               Handle protection_domain,
 990                                               ClassFileStream* st,
 991                                               const InstanceKlass* unsafe_anonymous_host,
 992                                               GrowableArray<Handle>* cp_patches,
 993                                               TRAPS) {
 994 
 995   EventClassLoad class_load_start_event;
 996 
 997   ClassLoaderData* loader_data;
 998   if (unsafe_anonymous_host != NULL) {
 999     // Create a new CLD for an unsafe anonymous class, that uses the same class loader
1000     // as the unsafe_anonymous_host
1001     guarantee(oopDesc::equals(unsafe_anonymous_host->class_loader(), class_loader()), "should be the same");
1002     loader_data = ClassLoaderData::unsafe_anonymous_class_loader_data(class_loader);
1003   } else {
1004     loader_data = ClassLoaderData::class_loader_data(class_loader());
1005   }
1006 
1007   assert(st != NULL, "invariant");
1008   assert(st->need_verify(), "invariant");
1009 
1010   // Parse stream and create a klass.
1011   // Note that we do this even though this klass might
1012   // already be present in the SystemDictionary, otherwise we would not
1013   // throw potential ClassFormatErrors.
1014 
1015   InstanceKlass* k = KlassFactory::create_from_stream(st,
1016                                                       class_name,
1017                                                       loader_data,
1018                                                       protection_domain,
1019                                                       unsafe_anonymous_host,
1020                                                       cp_patches,
1021                                                       CHECK_NULL);
1022 
1023   if (unsafe_anonymous_host != NULL && k != NULL) {
1024     // Unsafe anonymous classes must update ClassLoaderData holder (was unsafe_anonymous_host loader)
1025     // so that they can be unloaded when the mirror is no longer referenced.
1026     k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror()));
1027 
1028     {
1029       MutexLocker mu_r(Compile_lock, THREAD);
1030 
1031       // Add to class hierarchy, initialize vtables, and do possible
1032       // deoptimizations.
1033       add_to_hierarchy(k, CHECK_NULL); // No exception, but can block
1034 
1035       // But, do not add to dictionary.
1036 
1037       // compiled code dependencies need to be validated anyway
1038       notice_modification();
1039     }
1040 
1041     // Rewrite and patch constant pool here.
1042     k->link_class(CHECK_NULL);
1043     if (cp_patches != NULL) {
1044       k->constants()->patch_resolved_references(cp_patches);
1045     }
1046 
1047     // If it's anonymous, initialize it now, since nobody else will.
1048     k->eager_initialize(CHECK_NULL);
1049 
1050     // notify jvmti
1051     if (JvmtiExport::should_post_class_load()) {
1052         assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1053         JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1054     }
1055     if (class_load_start_event.should_commit()) {
1056       post_class_load_event(&class_load_start_event, k, loader_data);
1057     }
1058   }
1059   assert(unsafe_anonymous_host != NULL || NULL == cp_patches,
1060          "cp_patches only found with unsafe_anonymous_host");
1061 
1062   return k;
1063 }
1064 
1065 // Add a klass to the system from a stream (called by jni_DefineClass and
1066 // JVM_DefineClass).
1067 // Note: class_name can be NULL. In that case we do not know the name of
1068 // the class until we have parsed the stream.
1069 
1070 InstanceKlass* SystemDictionary::resolve_from_stream(Symbol* class_name,
1071                                                      Handle class_loader,
1072                                                      Handle protection_domain,
1073                                                      ClassFileStream* st,
1074                                                      TRAPS) {
1075 
1076   HandleMark hm(THREAD);
1077 
1078   // Classloaders that support parallelism, e.g. bootstrap classloader,
1079   // do not acquire lock here
1080   bool DoObjectLock = true;
1081   if (is_parallelCapable(class_loader)) {
1082     DoObjectLock = false;
1083   }
1084 
1085   ClassLoaderData* loader_data = register_loader(class_loader);
1086 
1087   // Make sure we are synchronized on the class loader before we proceed
1088   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
1089   check_loader_lock_contention(lockObject, THREAD);
1090   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
1091 
1092   assert(st != NULL, "invariant");
1093 
1094   // Parse the stream and create a klass.
1095   // Note that we do this even though this klass might
1096   // already be present in the SystemDictionary, otherwise we would not
1097   // throw potential ClassFormatErrors.
1098  InstanceKlass* k = NULL;
1099 
1100 #if INCLUDE_CDS
1101   if (!DumpSharedSpaces) {
1102     k = SystemDictionaryShared::lookup_from_stream(class_name,
1103                                                    class_loader,
1104                                                    protection_domain,
1105                                                    st,
1106                                                    CHECK_NULL);
1107   }
1108 #endif
1109 
1110   if (k == NULL) {
1111     if (st->buffer() == NULL) {
1112       return NULL;
1113     }
1114     k = KlassFactory::create_from_stream(st,
1115                                          class_name,
1116                                          loader_data,
1117                                          protection_domain,
1118                                          NULL, // unsafe_anonymous_host
1119                                          NULL, // cp_patches
1120                                          CHECK_NULL);
1121   }
1122 
1123   assert(k != NULL, "no klass created");
1124   Symbol* h_name = k->name();
1125   assert(class_name == NULL || class_name == h_name, "name mismatch");
1126 
1127   // Add class just loaded
1128   // If a class loader supports parallel classloading handle parallel define requests
1129   // find_or_define_instance_class may return a different InstanceKlass
1130   if (is_parallelCapable(class_loader)) {
1131     InstanceKlass* defined_k = find_or_define_instance_class(h_name, class_loader, k, THREAD);
1132     if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1133       // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1134       assert(defined_k != NULL, "Should have a klass if there's no exception");
1135       loader_data->add_to_deallocate_list(k);
1136       k = defined_k;
1137     }
1138   } else {
1139     define_instance_class(k, THREAD);
1140   }
1141 
1142   // If defining the class throws an exception register 'k' for cleanup.
1143   if (HAS_PENDING_EXCEPTION) {
1144     assert(k != NULL, "Must have an instance klass here!");
1145     loader_data->add_to_deallocate_list(k);
1146     return NULL;
1147   }
1148 
1149   // Make sure we have an entry in the SystemDictionary on success
1150   debug_only( {
1151     MutexLocker mu(SystemDictionary_lock, THREAD);
1152 
1153     Klass* check = find_class(h_name, k->class_loader_data());
1154     assert(check == k, "should be present in the dictionary");
1155   } );
1156 
1157   return k;
1158 }
1159 
1160 #if INCLUDE_CDS
1161 void SystemDictionary::set_shared_dictionary(HashtableBucket<mtClass>* t, int length,
1162                                              int number_of_entries) {
1163   assert(length == _shared_dictionary_size * sizeof(HashtableBucket<mtClass>),
1164          "bad shared dictionary size.");
1165   _shared_dictionary = new Dictionary(ClassLoaderData::the_null_class_loader_data(),
1166                                       _shared_dictionary_size, t, number_of_entries);
1167 }
1168 
1169 
1170 // If there is a shared dictionary, then find the entry for the
1171 // given shared system class, if any.
1172 
1173 InstanceKlass* SystemDictionary::find_shared_class(Symbol* class_name) {
1174   if (shared_dictionary() != NULL) {
1175     unsigned int d_hash = shared_dictionary()->compute_hash(class_name);
1176     int d_index = shared_dictionary()->hash_to_index(d_hash);
1177 
1178     return shared_dictionary()->find_shared_class(d_index, d_hash, class_name);
1179   } else {
1180     return NULL;
1181   }
1182 }
1183 
1184 
1185 // Load a class from the shared spaces (found through the shared system
1186 // dictionary).  Force the superclass and all interfaces to be loaded.
1187 // Update the class definition to include sibling classes and no
1188 // subclasses (yet).  [Classes in the shared space are not part of the
1189 // object hierarchy until loaded.]
1190 
1191 InstanceKlass* SystemDictionary::load_shared_class(
1192                  Symbol* class_name, Handle class_loader, TRAPS) {
1193   InstanceKlass* ik = find_shared_class(class_name);
1194   // Make sure we only return the boot class for the NULL classloader.
1195   if (ik != NULL &&
1196       ik->is_shared_boot_class() && class_loader.is_null()) {
1197     Handle protection_domain;
1198     return load_shared_class(ik, class_loader, protection_domain, THREAD);
1199   }
1200   return NULL;
1201 }
1202 
1203 // Check if a shared class can be loaded by the specific classloader:
1204 //
1205 // NULL classloader:
1206 //   - Module class from "modules" jimage. ModuleEntry must be defined in the classloader.
1207 //   - Class from -Xbootclasspath/a. The class has no defined PackageEntry, or must
1208 //     be defined in an unnamed module.
1209 bool SystemDictionary::is_shared_class_visible(Symbol* class_name,
1210                                                InstanceKlass* ik,
1211                                                Handle class_loader, TRAPS) {
1212   assert(!ModuleEntryTable::javabase_moduleEntry()->is_patched(),
1213          "Cannot use sharing if java.base is patched");
1214   ResourceMark rm;
1215   int path_index = ik->shared_classpath_index();
1216   ClassLoaderData* loader_data = class_loader_data(class_loader);
1217   if (path_index < 0) {
1218     // path_index < 0 indicates that the class is intended for a custom loader
1219     // and should not be loaded by boot/platform/app loaders
1220     if (loader_data->is_builtin_class_loader_data()) {
1221       return false;
1222     } else {
1223       return true;
1224     }
1225   }
1226   SharedClassPathEntry* ent =
1227             (SharedClassPathEntry*)FileMapInfo::shared_path(path_index);
1228   if (!Universe::is_module_initialized()) {
1229     assert(ent != NULL && ent->is_modules_image(),
1230            "Loading non-bootstrap classes before the module system is initialized");
1231     assert(class_loader.is_null(), "sanity");
1232     return true;
1233   }
1234   // Get the pkg_entry from the classloader
1235   TempNewSymbol pkg_name = NULL;
1236   PackageEntry* pkg_entry = NULL;
1237   ModuleEntry* mod_entry = NULL;
1238   const char* pkg_string = NULL;
1239   pkg_name = InstanceKlass::package_from_name(class_name, CHECK_false);
1240   if (pkg_name != NULL) {
1241     pkg_string = pkg_name->as_C_string();
1242     if (loader_data != NULL) {
1243       pkg_entry = loader_data->packages()->lookup_only(pkg_name);
1244     }
1245     if (pkg_entry != NULL) {
1246       mod_entry = pkg_entry->module();
1247     }
1248   }
1249 
1250   // If the archived class is from a module that has been patched at runtime,
1251   // the class cannot be loaded from the archive.
1252   if (mod_entry != NULL && mod_entry->is_patched()) {
1253     return false;
1254   }
1255 
1256   if (class_loader.is_null()) {
1257     assert(ent != NULL, "Shared class for NULL classloader must have valid SharedClassPathEntry");
1258     // The NULL classloader can load archived class originated from the
1259     // "modules" jimage and the -Xbootclasspath/a. For class from the
1260     // "modules" jimage, the PackageEntry/ModuleEntry must be defined
1261     // by the NULL classloader.
1262     if (mod_entry != NULL) {
1263       // PackageEntry/ModuleEntry is found in the classloader. Check if the
1264       // ModuleEntry's location agrees with the archived class' origination.
1265       if (ent->is_modules_image() && mod_entry->location()->starts_with("jrt:")) {
1266         return true; // Module class from the "module" jimage
1267       }
1268     }
1269 
1270     // If the archived class is not from the "module" jimage, the class can be
1271     // loaded by the NULL classloader if
1272     //
1273     // 1. the class is from the unamed package
1274     // 2. or, the class is not from a module defined in the NULL classloader
1275     // 3. or, the class is from an unamed module
1276     if (!ent->is_modules_image() && ik->is_shared_boot_class()) {
1277       // the class is from the -Xbootclasspath/a
1278       if (pkg_string == NULL ||
1279           pkg_entry == NULL ||
1280           pkg_entry->in_unnamed_module()) {
1281         assert(mod_entry == NULL ||
1282                mod_entry == loader_data->unnamed_module(),
1283                "the unnamed module is not defined in the classloader");
1284         return true;
1285       }
1286     }
1287     return false;
1288   } else {
1289     bool res = SystemDictionaryShared::is_shared_class_visible_for_classloader(
1290               ik, class_loader, pkg_string, pkg_name,
1291               pkg_entry, mod_entry, CHECK_(false));
1292     return res;
1293   }
1294 }
1295 
1296 InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik,
1297                                                    Handle class_loader,
1298                                                    Handle protection_domain, TRAPS) {
1299 
1300   if (ik != NULL) {
1301     Symbol* class_name = ik->name();
1302 
1303     bool visible = is_shared_class_visible(
1304                             class_name, ik, class_loader, CHECK_NULL);
1305     if (!visible) {
1306       return NULL;
1307     }
1308 
1309     // Resolve the superclass and interfaces. They must be the same
1310     // as in dump time, because the layout of <ik> depends on
1311     // the specific layout of ik->super() and ik->local_interfaces().
1312     //
1313     // If unexpected superclass or interfaces are found, we cannot
1314     // load <ik> from the shared archive.
1315 
1316     if (ik->super() != NULL) {
1317       Symbol*  cn = ik->super()->name();
1318       Klass *s = resolve_super_or_fail(class_name, cn,
1319                                        class_loader, protection_domain, true, CHECK_NULL);
1320       if (s != ik->super()) {
1321         // The dynamically resolved super class is not the same as the one we used during dump time,
1322         // so we cannot use ik.
1323         return NULL;
1324       } else {
1325         assert(s->is_shared(), "must be");
1326       }
1327     }
1328 
1329     Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1330     int num_interfaces = interfaces->length();
1331     for (int index = 0; index < num_interfaces; index++) {
1332       InstanceKlass* k = interfaces->at(index);
1333       Symbol* name  = k->name();
1334       Klass* i = resolve_super_or_fail(class_name, name, class_loader, protection_domain, false, CHECK_NULL);
1335       if (k != i) {
1336         // The dynamically resolved interface class is not the same as the one we used during dump time,
1337         // so we cannot use ik.
1338         return NULL;
1339       } else {
1340         assert(i->is_shared(), "must be");
1341       }
1342     }
1343 
1344     InstanceKlass* new_ik = KlassFactory::check_shared_class_file_load_hook(
1345         ik, class_name, class_loader, protection_domain, CHECK_NULL);
1346     if (new_ik != NULL) {
1347       // The class is changed by CFLH. Return the new class. The shared class is
1348       // not used.
1349       return new_ik;
1350     }
1351 
1352     // Adjust methods to recover missing data.  They need addresses for
1353     // interpreter entry points and their default native method address
1354     // must be reset.
1355 
1356     // Updating methods must be done under a lock so multiple
1357     // threads don't update these in parallel
1358     //
1359     // Shared classes are all currently loaded by either the bootstrap or
1360     // internal parallel class loaders, so this will never cause a deadlock
1361     // on a custom class loader lock.
1362 
1363     ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(class_loader());
1364     {
1365       HandleMark hm(THREAD);
1366       Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
1367       check_loader_lock_contention(lockObject, THREAD);
1368       ObjectLocker ol(lockObject, THREAD, true);
1369       // prohibited package check assumes all classes loaded from archive call
1370       // restore_unshareable_info which calls ik->set_package()
1371       ik->restore_unshareable_info(loader_data, protection_domain, CHECK_NULL);
1372     }
1373 
1374     ik->print_class_load_logging(loader_data, NULL, NULL);
1375 
1376     // For boot loader, ensure that GetSystemPackage knows that a class in this
1377     // package was loaded.
1378     if (class_loader.is_null()) {
1379       int path_index = ik->shared_classpath_index();
1380       ResourceMark rm;
1381       ClassLoader::add_package(ik->name()->as_C_string(), path_index, THREAD);
1382     }
1383 
1384     if (DumpLoadedClassList != NULL && classlist_file->is_open()) {
1385       // Only dump the classes that can be stored into CDS archive
1386       if (SystemDictionaryShared::is_sharing_possible(loader_data)) {
1387         ResourceMark rm(THREAD);
1388         classlist_file->print_cr("%s", ik->name()->as_C_string());
1389         classlist_file->flush();
1390       }
1391     }
1392 
1393     // notify a class loaded from shared object
1394     ClassLoadingService::notify_class_loaded(ik, true /* shared class */);
1395 
1396     ik->set_has_passed_fingerprint_check(false);
1397     if (UseAOT && ik->supers_have_passed_fingerprint_checks()) {
1398       uint64_t aot_fp = AOTLoader::get_saved_fingerprint(ik);
1399       uint64_t cds_fp = ik->get_stored_fingerprint();
1400       if (aot_fp != 0 && aot_fp == cds_fp) {
1401         // This class matches with a class saved in an AOT library
1402         ik->set_has_passed_fingerprint_check(true);
1403       } else {
1404         ResourceMark rm;
1405         log_info(class, fingerprint)("%s :  expected = " PTR64_FORMAT " actual = " PTR64_FORMAT, ik->external_name(), aot_fp, cds_fp);
1406       }
1407     }
1408   }
1409   return ik;
1410 }
1411 
1412 void SystemDictionary::clear_invoke_method_table() {
1413   SymbolPropertyEntry* spe = NULL;
1414   for (int index = 0; index < _invoke_method_table->table_size(); index++) {
1415     SymbolPropertyEntry* p = _invoke_method_table->bucket(index);
1416     while (p != NULL) {
1417       spe = p;
1418       p = p->next();
1419       _invoke_method_table->free_entry(spe);
1420     }
1421   }
1422 }
1423 #endif // INCLUDE_CDS
1424 
1425 InstanceKlass* SystemDictionary::load_instance_class(Symbol* class_name, Handle class_loader, TRAPS) {
1426 
1427   if (class_loader.is_null()) {
1428     ResourceMark rm;
1429     PackageEntry* pkg_entry = NULL;
1430     bool search_only_bootloader_append = false;
1431     ClassLoaderData *loader_data = class_loader_data(class_loader);
1432 
1433     // Find the package in the boot loader's package entry table.
1434     TempNewSymbol pkg_name = InstanceKlass::package_from_name(class_name, CHECK_NULL);
1435     if (pkg_name != NULL) {
1436       pkg_entry = loader_data->packages()->lookup_only(pkg_name);
1437     }
1438 
1439     // Prior to attempting to load the class, enforce the boot loader's
1440     // visibility boundaries.
1441     if (!Universe::is_module_initialized()) {
1442       // During bootstrapping, prior to module initialization, any
1443       // class attempting to be loaded must be checked against the
1444       // java.base packages in the boot loader's PackageEntryTable.
1445       // No class outside of java.base is allowed to be loaded during
1446       // this bootstrapping window.
1447       if (pkg_entry == NULL || pkg_entry->in_unnamed_module()) {
1448         // Class is either in the unnamed package or in
1449         // a named package within the unnamed module.  Either
1450         // case is outside of java.base, do not attempt to
1451         // load the class post java.base definition.  If
1452         // java.base has not been defined, let the class load
1453         // and its package will be checked later by
1454         // ModuleEntryTable::verify_javabase_packages.
1455         if (ModuleEntryTable::javabase_defined()) {
1456           return NULL;
1457         }
1458       } else {
1459         // Check that the class' package is defined within java.base.
1460         ModuleEntry* mod_entry = pkg_entry->module();
1461         Symbol* mod_entry_name = mod_entry->name();
1462         if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) {
1463           return NULL;
1464         }
1465       }
1466     } else {
1467       // After the module system has been initialized, check if the class'
1468       // package is in a module defined to the boot loader.
1469       if (pkg_name == NULL || pkg_entry == NULL || pkg_entry->in_unnamed_module()) {
1470         // Class is either in the unnamed package, in a named package
1471         // within a module not defined to the boot loader or in a
1472         // a named package within the unnamed module.  In all cases,
1473         // limit visibility to search for the class only in the boot
1474         // loader's append path.
1475         search_only_bootloader_append = true;
1476       }
1477     }
1478 
1479     // Prior to bootstrapping's module initialization, never load a class outside
1480     // of the boot loader's module path
1481     assert(Universe::is_module_initialized() ||
1482            !search_only_bootloader_append,
1483            "Attempt to load a class outside of boot loader's module path");
1484 
1485     // Search the shared system dictionary for classes preloaded into the
1486     // shared spaces.
1487     InstanceKlass* k = NULL;
1488     {
1489 #if INCLUDE_CDS
1490       PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time());
1491       k = load_shared_class(class_name, class_loader, THREAD);
1492 #endif
1493     }
1494 
1495     if (k == NULL) {
1496       // Use VM class loader
1497       PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time());
1498       k = ClassLoader::load_class(class_name, search_only_bootloader_append, CHECK_NULL);
1499     }
1500 
1501     // find_or_define_instance_class may return a different InstanceKlass
1502     if (k != NULL) {
1503       InstanceKlass* defined_k =
1504         find_or_define_instance_class(class_name, class_loader, k, THREAD);
1505       if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1506         // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1507         assert(defined_k != NULL, "Should have a klass if there's no exception");
1508         loader_data->add_to_deallocate_list(k);
1509         k = defined_k;
1510       } else if (HAS_PENDING_EXCEPTION) {
1511         loader_data->add_to_deallocate_list(k);
1512         return NULL;
1513       }
1514     }
1515     return k;
1516   } else {
1517     // Use user specified class loader to load class. Call loadClass operation on class_loader.
1518     ResourceMark rm(THREAD);
1519 
1520     assert(THREAD->is_Java_thread(), "must be a JavaThread");
1521     JavaThread* jt = (JavaThread*) THREAD;
1522 
1523     PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1524                                ClassLoader::perf_app_classload_selftime(),
1525                                ClassLoader::perf_app_classload_count(),
1526                                jt->get_thread_stat()->perf_recursion_counts_addr(),
1527                                jt->get_thread_stat()->perf_timers_addr(),
1528                                PerfClassTraceTime::CLASS_LOAD);
1529 
1530     Handle s = java_lang_String::create_from_symbol(class_name, CHECK_NULL);
1531     // Translate to external class name format, i.e., convert '/' chars to '.'
1532     Handle string = java_lang_String::externalize_classname(s, CHECK_NULL);
1533 
1534     JavaValue result(T_OBJECT);
1535 
1536     InstanceKlass* spec_klass = SystemDictionary::ClassLoader_klass();
1537 
1538     // Call public unsynchronized loadClass(String) directly for all class loaders.
1539     // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1540     // acquire a class-name based lock rather than the class loader object lock.
1541     // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1542     JavaCalls::call_virtual(&result,
1543                             class_loader,
1544                             spec_klass,
1545                             vmSymbols::loadClass_name(),
1546                             vmSymbols::string_class_signature(),
1547                             string,
1548                             CHECK_NULL);
1549 
1550     assert(result.get_type() == T_OBJECT, "just checking");
1551     oop obj = (oop) result.get_jobject();
1552 
1553     // Primitive classes return null since forName() can not be
1554     // used to obtain any of the Class objects representing primitives or void
1555     if ((obj != NULL) && !(java_lang_Class::is_primitive(obj))) {
1556       InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(obj));
1557       // For user defined Java class loaders, check that the name returned is
1558       // the same as that requested.  This check is done for the bootstrap
1559       // loader when parsing the class file.
1560       if (class_name == k->name()) {
1561         return k;
1562       }
1563     }
1564     // Class is not found or has the wrong name, return NULL
1565     return NULL;
1566   }
1567 }
1568 
1569 static void post_class_define_event(InstanceKlass* k, const ClassLoaderData* def_cld) {
1570   EventClassDefine event;
1571   if (event.should_commit()) {
1572     event.set_definedClass(k);
1573     event.set_definingClassLoader(def_cld);
1574     event.commit();
1575   }
1576 }
1577 
1578 void SystemDictionary::define_instance_class(InstanceKlass* k, TRAPS) {
1579 
1580   HandleMark hm(THREAD);
1581   ClassLoaderData* loader_data = k->class_loader_data();
1582   Handle class_loader_h(THREAD, loader_data->class_loader());
1583 
1584  // for bootstrap and other parallel classloaders don't acquire lock,
1585  // use placeholder token
1586  // If a parallelCapable class loader calls define_instance_class instead of
1587  // find_or_define_instance_class to get here, we have a timing
1588  // hole with systemDictionary updates and check_constraints
1589  if (!class_loader_h.is_null() && !is_parallelCapable(class_loader_h)) {
1590     assert(ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD,
1591          compute_loader_lock_object(class_loader_h, THREAD)),
1592          "define called without lock");
1593   }
1594 
1595   // Check class-loading constraints. Throw exception if violation is detected.
1596   // Grabs and releases SystemDictionary_lock
1597   // The check_constraints/find_class call and update_dictionary sequence
1598   // must be "atomic" for a specific class/classloader pair so we never
1599   // define two different instanceKlasses for that class/classloader pair.
1600   // Existing classloaders will call define_instance_class with the
1601   // classloader lock held
1602   // Parallel classloaders will call find_or_define_instance_class
1603   // which will require a token to perform the define class
1604   Symbol*  name_h = k->name();
1605   Dictionary* dictionary = loader_data->dictionary();
1606   unsigned int d_hash = dictionary->compute_hash(name_h);
1607   check_constraints(d_hash, k, class_loader_h, true, CHECK);
1608 
1609   // Register class just loaded with class loader (placed in Vector)
1610   // Note we do this before updating the dictionary, as this can
1611   // fail with an OutOfMemoryError (if it does, we will *not* put this
1612   // class in the dictionary and will not update the class hierarchy).
1613   // JVMTI FollowReferences needs to find the classes this way.
1614   if (k->class_loader() != NULL) {
1615     methodHandle m(THREAD, Universe::loader_addClass_method());
1616     JavaValue result(T_VOID);
1617     JavaCallArguments args(class_loader_h);
1618     args.push_oop(Handle(THREAD, k->java_mirror()));
1619     JavaCalls::call(&result, m, &args, CHECK);
1620   }
1621 
1622   // Add the new class. We need recompile lock during update of CHA.
1623   {
1624     unsigned int p_hash = placeholders()->compute_hash(name_h);
1625     int p_index = placeholders()->hash_to_index(p_hash);
1626 
1627     MutexLocker mu_r(Compile_lock, THREAD);
1628 
1629     // Add to class hierarchy, initialize vtables, and do possible
1630     // deoptimizations.
1631     add_to_hierarchy(k, CHECK); // No exception, but can block
1632 
1633     // Add to systemDictionary - so other classes can see it.
1634     // Grabs and releases SystemDictionary_lock
1635     update_dictionary(d_hash, p_index, p_hash,
1636                       k, class_loader_h, THREAD);
1637   }
1638   k->eager_initialize(THREAD);
1639 
1640   // notify jvmti
1641   if (JvmtiExport::should_post_class_load()) {
1642       assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1643       JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1644 
1645   }
1646   post_class_define_event(k, loader_data);
1647 }
1648 
1649 // Support parallel classloading
1650 // All parallel class loaders, including bootstrap classloader
1651 // lock a placeholder entry for this class/class_loader pair
1652 // to allow parallel defines of different classes for this class loader
1653 // With AllowParallelDefine flag==true, in case they do not synchronize around
1654 // FindLoadedClass/DefineClass, calls, we check for parallel
1655 // loading for them, wait if a defineClass is in progress
1656 // and return the initial requestor's results
1657 // This flag does not apply to the bootstrap classloader.
1658 // With AllowParallelDefine flag==false, call through to define_instance_class
1659 // which will throw LinkageError: duplicate class definition.
1660 // False is the requested default.
1661 // For better performance, the class loaders should synchronize
1662 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1663 // potentially waste time reading and parsing the bytestream.
1664 // Note: VM callers should ensure consistency of k/class_name,class_loader
1665 // Be careful when modifying this code: once you have run
1666 // placeholders()->find_and_add(PlaceholderTable::DEFINE_CLASS),
1667 // you need to find_and_remove it before returning.
1668 // So be careful to not exit with a CHECK_ macro betweeen these calls.
1669 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1670                                                                InstanceKlass* k, TRAPS) {
1671 
1672   Symbol*  name_h = k->name(); // passed in class_name may be null
1673   ClassLoaderData* loader_data = class_loader_data(class_loader);
1674   Dictionary* dictionary = loader_data->dictionary();
1675 
1676   unsigned int d_hash = dictionary->compute_hash(name_h);
1677 
1678   // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1679   unsigned int p_hash = placeholders()->compute_hash(name_h);
1680   int p_index = placeholders()->hash_to_index(p_hash);
1681   PlaceholderEntry* probe;
1682 
1683   {
1684     MutexLocker mu(SystemDictionary_lock, THREAD);
1685     // First check if class already defined
1686     if (is_parallelDefine(class_loader)) {
1687       InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1688       if (check != NULL) {
1689         return check;
1690       }
1691     }
1692 
1693     // Acquire define token for this class/classloader
1694     probe = placeholders()->find_and_add(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, NULL, THREAD);
1695     // Wait if another thread defining in parallel
1696     // All threads wait - even those that will throw duplicate class: otherwise
1697     // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1698     // if other thread has not finished updating dictionary
1699     while (probe->definer() != NULL) {
1700       SystemDictionary_lock->wait();
1701     }
1702     // Only special cases allow parallel defines and can use other thread's results
1703     // Other cases fall through, and may run into duplicate defines
1704     // caught by finding an entry in the SystemDictionary
1705     if (is_parallelDefine(class_loader) && (probe->instance_klass() != NULL)) {
1706         placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1707         SystemDictionary_lock->notify_all();
1708 #ifdef ASSERT
1709         InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1710         assert(check != NULL, "definer missed recording success");
1711 #endif
1712         return probe->instance_klass();
1713     } else {
1714       // This thread will define the class (even if earlier thread tried and had an error)
1715       probe->set_definer(THREAD);
1716     }
1717   }
1718 
1719   define_instance_class(k, THREAD);
1720 
1721   Handle linkage_exception = Handle(); // null handle
1722 
1723   // definer must notify any waiting threads
1724   {
1725     MutexLocker mu(SystemDictionary_lock, THREAD);
1726     PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, name_h, loader_data);
1727     assert(probe != NULL, "DEFINE_CLASS placeholder lost?");
1728     if (probe != NULL) {
1729       if (HAS_PENDING_EXCEPTION) {
1730         linkage_exception = Handle(THREAD,PENDING_EXCEPTION);
1731         CLEAR_PENDING_EXCEPTION;
1732       } else {
1733         probe->set_instance_klass(k);
1734       }
1735       probe->set_definer(NULL);
1736       placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1737       SystemDictionary_lock->notify_all();
1738     }
1739   }
1740 
1741   // Can't throw exception while holding lock due to rank ordering
1742   if (linkage_exception() != NULL) {
1743     THROW_OOP_(linkage_exception(), NULL); // throws exception and returns
1744   }
1745 
1746   return k;
1747 }
1748 
1749 Handle SystemDictionary::compute_loader_lock_object(Handle class_loader, TRAPS) {
1750   // If class_loader is NULL we synchronize on _system_loader_lock_obj
1751   if (class_loader.is_null()) {
1752     return Handle(THREAD, _system_loader_lock_obj);
1753   } else {
1754     return class_loader;
1755   }
1756 }
1757 
1758 // This method is added to check how often we have to wait to grab loader
1759 // lock. The results are being recorded in the performance counters defined in
1760 // ClassLoader::_sync_systemLoaderLockContentionRate and
1761 // ClassLoader::_sync_nonSystemLoaderLockConteionRate.
1762 void SystemDictionary::check_loader_lock_contention(Handle loader_lock, TRAPS) {
1763   if (!UsePerfData) {
1764     return;
1765   }
1766 
1767   assert(!loader_lock.is_null(), "NULL lock object");
1768 
1769   if (ObjectSynchronizer::query_lock_ownership((JavaThread*)THREAD, loader_lock)
1770       == ObjectSynchronizer::owner_other) {
1771     // contention will likely happen, so increment the corresponding
1772     // contention counter.
1773     if (oopDesc::equals(loader_lock(), _system_loader_lock_obj)) {
1774       ClassLoader::sync_systemLoaderLockContentionRate()->inc();
1775     } else {
1776       ClassLoader::sync_nonSystemLoaderLockContentionRate()->inc();
1777     }
1778   }
1779 }
1780 
1781 // ----------------------------------------------------------------------------
1782 // Lookup
1783 
1784 InstanceKlass* SystemDictionary::find_class(unsigned int hash,
1785                                             Symbol* class_name,
1786                                             Dictionary* dictionary) {
1787   assert_locked_or_safepoint(SystemDictionary_lock);
1788   int index = dictionary->hash_to_index(hash);
1789   return dictionary->find_class(index, hash, class_name);
1790 }
1791 
1792 
1793 // Basic find on classes in the midst of being loaded
1794 Symbol* SystemDictionary::find_placeholder(Symbol* class_name,
1795                                            ClassLoaderData* loader_data) {
1796   assert_locked_or_safepoint(SystemDictionary_lock);
1797   unsigned int p_hash = placeholders()->compute_hash(class_name);
1798   int p_index = placeholders()->hash_to_index(p_hash);
1799   return placeholders()->find_entry(p_index, p_hash, class_name, loader_data);
1800 }
1801 
1802 
1803 // Used for assertions and verification only
1804 // Precalculating the hash and index is an optimization because there are many lookups
1805 // before adding the class.
1806 InstanceKlass* SystemDictionary::find_class(Symbol* class_name, ClassLoaderData* loader_data) {
1807   assert_locked_or_safepoint(SystemDictionary_lock);
1808   #ifndef ASSERT
1809   guarantee(VerifyBeforeGC      ||
1810             VerifyDuringGC      ||
1811             VerifyBeforeExit    ||
1812             VerifyDuringStartup ||
1813             VerifyAfterGC, "too expensive");
1814   #endif
1815 
1816   Dictionary* dictionary = loader_data->dictionary();
1817   unsigned int d_hash = dictionary->compute_hash(class_name);
1818   return find_class(d_hash, class_name, dictionary);
1819 }
1820 
1821 
1822 // ----------------------------------------------------------------------------
1823 // Update hierachy. This is done before the new klass has been added to the SystemDictionary. The Recompile_lock
1824 // is held, to ensure that the compiler is not using the class hierachy, and that deoptimization will kick in
1825 // before a new class is used.
1826 
1827 void SystemDictionary::add_to_hierarchy(InstanceKlass* k, TRAPS) {
1828   assert(k != NULL, "just checking");
1829   assert_locked_or_safepoint(Compile_lock);
1830 
1831   // Link into hierachy. Make sure the vtables are initialized before linking into
1832   k->append_to_sibling_list();                    // add to superklass/sibling list
1833   k->process_interfaces(THREAD);                  // handle all "implements" declarations
1834   k->set_init_state(InstanceKlass::loaded);
1835   // Now flush all code that depended on old class hierarchy.
1836   // Note: must be done *after* linking k into the hierarchy (was bug 12/9/97)
1837   // Also, first reinitialize vtable because it may have gotten out of synch
1838   // while the new class wasn't connected to the class hierarchy.
1839   CodeCache::flush_dependents_on(k);
1840 }
1841 
1842 // ----------------------------------------------------------------------------
1843 // GC support
1844 
1845 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1846 // Note: anonymous classes are not in the SD.
1847 bool SystemDictionary::do_unloading(GCTimer* gc_timer,
1848                                     bool do_cleaning) {
1849 
1850   bool unloading_occurred;
1851   {
1852     GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1853 
1854     // First, mark for unload all ClassLoaderData referencing a dead class loader.
1855     unloading_occurred = ClassLoaderDataGraph::do_unloading(do_cleaning);
1856     if (unloading_occurred) {
1857       ClassLoaderDataGraph::clean_module_and_package_info();
1858     }
1859   }
1860 
1861   // TODO: just return if !unloading_occurred.
1862   if (unloading_occurred) {
1863     {
1864       GCTraceTime(Debug, gc, phases) t("SymbolTable", gc_timer);
1865       // Check if there's work to do in the SymbolTable
1866       SymbolTable::do_check_concurrent_work();
1867     }
1868 
1869     {
1870       GCTraceTime(Debug, gc, phases) t("Dictionary", gc_timer);
1871       constraints()->purge_loader_constraints();
1872       resolution_errors()->purge_resolution_errors();
1873     }
1874   }
1875 
1876   {
1877     GCTraceTime(Debug, gc, phases) t("ProtectionDomainCacheTable", gc_timer);
1878     // Oops referenced by the protection domain cache table may get unreachable independently
1879     // of the class loader (eg. cached protection domain oops). So we need to
1880     // explicitly unlink them here.
1881     _pd_cache_table->trigger_cleanup();
1882   }
1883 
1884   if (do_cleaning) {
1885     GCTraceTime(Debug, gc, phases) t("ResolvedMethodTable", gc_timer);
1886     ResolvedMethodTable::trigger_cleanup();
1887   }
1888 
1889   return unloading_occurred;
1890 }
1891 
1892 void SystemDictionary::oops_do(OopClosure* f) {
1893   f->do_oop(&_java_system_loader);
1894   f->do_oop(&_java_platform_loader);
1895   f->do_oop(&_system_loader_lock_obj);
1896   CDS_ONLY(SystemDictionaryShared::oops_do(f);)
1897 
1898   // Visit extra methods
1899   invoke_method_table()->oops_do(f);
1900 }
1901 
1902 // CDS: scan and relocate all classes in the system dictionary.
1903 void SystemDictionary::classes_do(MetaspaceClosure* it) {
1904   ClassLoaderData::the_null_class_loader_data()->dictionary()->classes_do(it);
1905 }
1906 
1907 // CDS: scan and relocate all classes referenced by _well_known_klasses[].
1908 void SystemDictionary::well_known_klasses_do(MetaspaceClosure* it) {
1909   for (int id = FIRST_WKID; id < WKID_LIMIT; id++) {
1910     it->push(well_known_klass_addr((WKID)id));
1911   }
1912 }
1913 
1914 void SystemDictionary::methods_do(void f(Method*)) {
1915   // Walk methods in loaded classes
1916   ClassLoaderDataGraph::methods_do(f);
1917   // Walk method handle intrinsics
1918   invoke_method_table()->methods_do(f);
1919 }
1920 
1921 class RemoveClassesClosure : public CLDClosure {
1922   public:
1923     void do_cld(ClassLoaderData* cld) {
1924       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
1925         cld->dictionary()->remove_classes_in_error_state();
1926       }
1927     }
1928 };
1929 
1930 void SystemDictionary::remove_classes_in_error_state() {
1931   ClassLoaderData::the_null_class_loader_data()->dictionary()->remove_classes_in_error_state();
1932   RemoveClassesClosure rcc;
1933   ClassLoaderDataGraph::cld_do(&rcc);
1934 }
1935 
1936 // ----------------------------------------------------------------------------
1937 // Initialization
1938 
1939 void SystemDictionary::initialize(TRAPS) {
1940   // Allocate arrays
1941   _placeholders        = new PlaceholderTable(_placeholder_table_size);
1942   _number_of_modifications = 0;
1943   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
1944   _resolution_errors   = new ResolutionErrorTable(_resolution_error_size);
1945   _invoke_method_table = new SymbolPropertyTable(_invoke_method_size);
1946   _pd_cache_table = new ProtectionDomainCacheTable(defaultProtectionDomainCacheSize);
1947 
1948   // Allocate private object used as system class loader lock
1949   _system_loader_lock_obj = oopFactory::new_intArray(0, CHECK);
1950   // Initialize basic classes
1951   resolve_preloaded_classes(CHECK);
1952 }
1953 
1954 // Compact table of directions on the initialization of klasses:
1955 static const short wk_init_info[] = {
1956   #define WK_KLASS_INIT_INFO(name, symbol, option) \
1957     ( ((int)vmSymbols::VM_SYMBOL_ENUM_NAME(symbol) \
1958           << SystemDictionary::CEIL_LG_OPTION_LIMIT) \
1959       | (int)SystemDictionary::option ),
1960   WK_KLASSES_DO(WK_KLASS_INIT_INFO)
1961   #undef WK_KLASS_INIT_INFO
1962   0
1963 };
1964 
1965 bool SystemDictionary::resolve_wk_klass(WKID id, int init_opt, TRAPS) {
1966   assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
1967   int  info = wk_init_info[id - FIRST_WKID];
1968   int  sid  = (info >> CEIL_LG_OPTION_LIMIT);
1969   Symbol* symbol = vmSymbols::symbol_at((vmSymbols::SID)sid);
1970   InstanceKlass** klassp = &_well_known_klasses[id];
1971 
1972   bool must_load;
1973 #if INCLUDE_JVMCI
1974   if (EnableJVMCI) {
1975     // If JVMCI is enabled we require its classes to be found.
1976     must_load = (init_opt < SystemDictionary::Opt) || (init_opt == SystemDictionary::Jvmci);
1977   } else
1978 #endif
1979   {
1980     must_load = (init_opt < SystemDictionary::Opt);
1981   }
1982 
1983   if ((*klassp) == NULL) {
1984     Klass* k;
1985     if (must_load) {
1986       k = resolve_or_fail(symbol, true, CHECK_0); // load required class
1987     } else {
1988       k = resolve_or_null(symbol,       CHECK_0); // load optional klass
1989     }
1990     (*klassp) = (k == NULL) ? NULL : InstanceKlass::cast(k);
1991   }
1992   return ((*klassp) != NULL);
1993 }
1994 
1995 void SystemDictionary::resolve_wk_klasses_until(WKID limit_id, WKID &start_id, TRAPS) {
1996   assert((int)start_id <= (int)limit_id, "IDs are out of order!");
1997   for (int id = (int)start_id; id < (int)limit_id; id++) {
1998     assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
1999     int info = wk_init_info[id - FIRST_WKID];
2000     int sid  = (info >> CEIL_LG_OPTION_LIMIT);
2001     int opt  = (info & right_n_bits(CEIL_LG_OPTION_LIMIT));
2002 
2003     resolve_wk_klass((WKID)id, opt, CHECK);
2004   }
2005 
2006   // move the starting value forward to the limit:
2007   start_id = limit_id;
2008 }
2009 
2010 void SystemDictionary::resolve_preloaded_classes(TRAPS) {
2011   assert(WK_KLASS(Object_klass) == NULL, "preloaded classes should only be initialized once");
2012 
2013   // Create the ModuleEntry for java.base.  This call needs to be done here,
2014   // after vmSymbols::initialize() is called but before any classes are pre-loaded.
2015   ClassLoader::classLoader_init2(CHECK);
2016 
2017   // Preload commonly used klasses
2018   WKID scan = FIRST_WKID;
2019   // first do Object, then String, Class
2020 #if INCLUDE_CDS
2021   if (UseSharedSpaces) {
2022     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Object_klass), scan, CHECK);
2023     // Initialize the constant pool for the Object_class
2024     Object_klass()->constants()->restore_unshareable_info(CHECK);
2025     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2026   } else
2027 #endif
2028   {
2029     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2030   }
2031 
2032   // Calculate offsets for String and Class classes since they are loaded and
2033   // can be used after this point.
2034   java_lang_String::compute_offsets();
2035   java_lang_Class::compute_offsets();
2036 
2037   // Fixup mirrors for classes loaded before java.lang.Class.
2038   // These calls iterate over the objects currently in the perm gen
2039   // so calling them at this point is matters (not before when there
2040   // are fewer objects and not later after there are more objects
2041   // in the perm gen.
2042   Universe::initialize_basic_type_mirrors(CHECK);
2043   Universe::fixup_mirrors(CHECK);
2044 
2045   // do a bunch more:
2046   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Reference_klass), scan, CHECK);
2047 
2048   // Preload ref klasses and set reference types
2049   InstanceKlass::cast(WK_KLASS(Reference_klass))->set_reference_type(REF_OTHER);
2050   InstanceRefKlass::update_nonstatic_oop_maps(WK_KLASS(Reference_klass));
2051 
2052   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(PhantomReference_klass), scan, CHECK);
2053   InstanceKlass::cast(WK_KLASS(SoftReference_klass))->set_reference_type(REF_SOFT);
2054   InstanceKlass::cast(WK_KLASS(WeakReference_klass))->set_reference_type(REF_WEAK);
2055   InstanceKlass::cast(WK_KLASS(FinalReference_klass))->set_reference_type(REF_FINAL);
2056   InstanceKlass::cast(WK_KLASS(PhantomReference_klass))->set_reference_type(REF_PHANTOM);
2057 
2058   // JSR 292 classes
2059   WKID jsr292_group_start = WK_KLASS_ENUM_NAME(MethodHandle_klass);
2060   WKID jsr292_group_end   = WK_KLASS_ENUM_NAME(VolatileCallSite_klass);
2061   resolve_wk_klasses_until(jsr292_group_start, scan, CHECK);
2062   resolve_wk_klasses_through(jsr292_group_end, scan, CHECK);
2063   resolve_wk_klasses_until(NOT_JVMCI(WKID_LIMIT) JVMCI_ONLY(FIRST_JVMCI_WKID), scan, CHECK);
2064 
2065   _box_klasses[T_BOOLEAN] = WK_KLASS(Boolean_klass);
2066   _box_klasses[T_CHAR]    = WK_KLASS(Character_klass);
2067   _box_klasses[T_FLOAT]   = WK_KLASS(Float_klass);
2068   _box_klasses[T_DOUBLE]  = WK_KLASS(Double_klass);
2069   _box_klasses[T_BYTE]    = WK_KLASS(Byte_klass);
2070   _box_klasses[T_SHORT]   = WK_KLASS(Short_klass);
2071   _box_klasses[T_INT]     = WK_KLASS(Integer_klass);
2072   _box_klasses[T_LONG]    = WK_KLASS(Long_klass);
2073   //_box_klasses[T_OBJECT]  = WK_KLASS(object_klass);
2074   //_box_klasses[T_ARRAY]   = WK_KLASS(object_klass);
2075 
2076   { // Compute whether we should use checkPackageAccess or NOT
2077     Method* method = InstanceKlass::cast(ClassLoader_klass())->find_method(vmSymbols::checkPackageAccess_name(), vmSymbols::class_protectiondomain_signature());
2078     _has_checkPackageAccess = (method != NULL);
2079   }
2080 }
2081 
2082 // Tells if a given klass is a box (wrapper class, such as java.lang.Integer).
2083 // If so, returns the basic type it holds.  If not, returns T_OBJECT.
2084 BasicType SystemDictionary::box_klass_type(Klass* k) {
2085   assert(k != NULL, "");
2086   for (int i = T_BOOLEAN; i < T_VOID+1; i++) {
2087     if (_box_klasses[i] == k)
2088       return (BasicType)i;
2089   }
2090   return T_OBJECT;
2091 }
2092 
2093 // Constraints on class loaders. The details of the algorithm can be
2094 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
2095 // Virtual Machine" by Sheng Liang and Gilad Bracha.  The basic idea is
2096 // that the dictionary needs to maintain a set of contraints that
2097 // must be satisfied by all classes in the dictionary.
2098 // if defining is true, then LinkageError if already in dictionary
2099 // if initiating loader, then ok if InstanceKlass matches existing entry
2100 
2101 void SystemDictionary::check_constraints(unsigned int d_hash,
2102                                          InstanceKlass* k,
2103                                          Handle class_loader,
2104                                          bool defining,
2105                                          TRAPS) {
2106   ResourceMark rm(THREAD);
2107   stringStream ss;
2108   bool throwException = false;
2109 
2110   {
2111     Symbol *name = k->name();
2112     ClassLoaderData *loader_data = class_loader_data(class_loader);
2113 
2114     MutexLocker mu(SystemDictionary_lock, THREAD);
2115 
2116     InstanceKlass* check = find_class(d_hash, name, loader_data->dictionary());
2117     if (check != NULL) {
2118       // If different InstanceKlass - duplicate class definition,
2119       // else - ok, class loaded by a different thread in parallel.
2120       // We should only have found it if it was done loading and ok to use.
2121       // The dictionary only holds instance classes, placeholders
2122       // also hold array classes.
2123 
2124       assert(check->is_instance_klass(), "noninstance in systemdictionary");
2125       if ((defining == true) || (k != check)) {
2126         throwException = true;
2127         ss.print("loader %s", loader_data->loader_name_and_id());
2128         ss.print(" attempted duplicate %s definition for %s. (%s)",
2129                  k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
2130       } else {
2131         return;
2132       }
2133     }
2134 
2135 #ifdef ASSERT
2136     Symbol* ph_check = find_placeholder(name, loader_data);
2137     assert(ph_check == NULL || ph_check == name, "invalid symbol");
2138 #endif
2139 
2140     if (throwException == false) {
2141       if (constraints()->check_or_update(k, class_loader, name) == false) {
2142         throwException = true;
2143         ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
2144         ss.print(" wants to load %s %s.",
2145                  k->external_kind(), k->external_name());
2146         Klass *existing_klass = constraints()->find_constrained_klass(name, class_loader);
2147         if (existing_klass->class_loader() != class_loader()) {
2148           ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
2149                    existing_klass->external_kind(),
2150                    existing_klass->class_loader_data()->loader_name_and_id(),
2151                    existing_klass->class_in_module_of_loader(false, true));
2152         } else {
2153           ss.print(" (%s)", k->class_in_module_of_loader(false, true));
2154         }
2155       }
2156     }
2157   }
2158 
2159   // Throw error now if needed (cannot throw while holding
2160   // SystemDictionary_lock because of rank ordering)
2161   if (throwException == true) {
2162     THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
2163   }
2164 }
2165 
2166 // Update class loader data dictionary - done after check_constraint and add_to_hierachy
2167 // have been called.
2168 void SystemDictionary::update_dictionary(unsigned int d_hash,
2169                                          int p_index, unsigned int p_hash,
2170                                          InstanceKlass* k,
2171                                          Handle class_loader,
2172                                          TRAPS) {
2173   // Compile_lock prevents systemDictionary updates during compilations
2174   assert_locked_or_safepoint(Compile_lock);
2175   Symbol*  name  = k->name();
2176   ClassLoaderData *loader_data = class_loader_data(class_loader);
2177 
2178   {
2179     MutexLocker mu1(SystemDictionary_lock, THREAD);
2180 
2181     // See whether biased locking is enabled and if so set it for this
2182     // klass.
2183     // Note that this must be done past the last potential blocking
2184     // point / safepoint. We enable biased locking lazily using a
2185     // VM_Operation to iterate the SystemDictionary and installing the
2186     // biasable mark word into each InstanceKlass's prototype header.
2187     // To avoid race conditions where we accidentally miss enabling the
2188     // optimization for one class in the process of being added to the
2189     // dictionary, we must not safepoint after the test of
2190     // BiasedLocking::enabled().
2191     if (UseBiasedLocking && BiasedLocking::enabled()) {
2192       // Set biased locking bit for all loaded classes; it will be
2193       // cleared if revocation occurs too often for this type
2194       // NOTE that we must only do this when the class is initally
2195       // defined, not each time it is referenced from a new class loader
2196       if (oopDesc::equals(k->class_loader(), class_loader())) {
2197         k->set_prototype_header(markOopDesc::biased_locking_prototype());
2198       }
2199     }
2200 
2201     // Make a new dictionary entry.
2202     Dictionary* dictionary = loader_data->dictionary();
2203     InstanceKlass* sd_check = find_class(d_hash, name, dictionary);
2204     if (sd_check == NULL) {
2205       dictionary->add_klass(d_hash, name, k);
2206       notice_modification();
2207     }
2208   #ifdef ASSERT
2209     sd_check = find_class(d_hash, name, dictionary);
2210     assert (sd_check != NULL, "should have entry in dictionary");
2211     // Note: there may be a placeholder entry: for circularity testing
2212     // or for parallel defines
2213   #endif
2214     SystemDictionary_lock->notify_all();
2215   }
2216 }
2217 
2218 
2219 // Try to find a class name using the loader constraints.  The
2220 // loader constraints might know about a class that isn't fully loaded
2221 // yet and these will be ignored.
2222 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
2223                     Symbol* class_name, Handle class_loader, TRAPS) {
2224 
2225   // First see if it has been loaded directly.
2226   // Force the protection domain to be null.  (This removes protection checks.)
2227   Handle no_protection_domain;
2228   Klass* klass = find_instance_or_array_klass(class_name, class_loader,
2229                                               no_protection_domain, CHECK_NULL);
2230   if (klass != NULL)
2231     return klass;
2232 
2233   // Now look to see if it has been loaded elsewhere, and is subject to
2234   // a loader constraint that would require this loader to return the
2235   // klass that is already loaded.
2236   if (FieldType::is_array(class_name)) {
2237     // For array classes, their Klass*s are not kept in the
2238     // constraint table. The element Klass*s are.
2239     FieldArrayInfo fd;
2240     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
2241     if (t != T_OBJECT) {
2242       klass = Universe::typeArrayKlassObj(t);
2243     } else {
2244       MutexLocker mu(SystemDictionary_lock, THREAD);
2245       klass = constraints()->find_constrained_klass(fd.object_key(), class_loader);
2246     }
2247     // If element class already loaded, allocate array klass
2248     if (klass != NULL) {
2249       klass = klass->array_klass_or_null(fd.dimension());
2250     }
2251   } else {
2252     MutexLocker mu(SystemDictionary_lock, THREAD);
2253     // Non-array classes are easy: simply check the constraint table.
2254     klass = constraints()->find_constrained_klass(class_name, class_loader);
2255   }
2256 
2257   return klass;
2258 }
2259 
2260 
2261 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
2262                                              Handle class_loader1,
2263                                              Handle class_loader2,
2264                                              Thread* THREAD) {
2265   ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
2266   ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
2267 
2268   Symbol* constraint_name = NULL;
2269   // Needs to be in same scope as constraint_name in case a Symbol is created and
2270   // assigned to constraint_name.
2271   FieldArrayInfo fd;
2272   if (!FieldType::is_array(class_name)) {
2273     constraint_name = class_name;
2274   } else {
2275     // For array classes, their Klass*s are not kept in the
2276     // constraint table. The element classes are.
2277     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(false));
2278     // primitive types always pass
2279     if (t != T_OBJECT) {
2280       return true;
2281     } else {
2282       constraint_name = fd.object_key();
2283     }
2284   }
2285 
2286   Dictionary* dictionary1 = loader_data1->dictionary();
2287   unsigned int d_hash1 = dictionary1->compute_hash(constraint_name);
2288 
2289   Dictionary* dictionary2 = loader_data2->dictionary();
2290   unsigned int d_hash2 = dictionary2->compute_hash(constraint_name);
2291 
2292   {
2293     MutexLocker mu_s(SystemDictionary_lock, THREAD);
2294     InstanceKlass* klass1 = find_class(d_hash1, constraint_name, dictionary1);
2295     InstanceKlass* klass2 = find_class(d_hash2, constraint_name, dictionary2);
2296     return constraints()->add_entry(constraint_name, klass1, class_loader1,
2297                                     klass2, class_loader2);
2298   }
2299 }
2300 
2301 // Add entry to resolution error table to record the error when the first
2302 // attempt to resolve a reference to a class has failed.
2303 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
2304                                             Symbol* error, Symbol* message) {
2305   unsigned int hash = resolution_errors()->compute_hash(pool, which);
2306   int index = resolution_errors()->hash_to_index(hash);
2307   {
2308     MutexLocker ml(SystemDictionary_lock, Thread::current());
2309     resolution_errors()->add_entry(index, hash, pool, which, error, message);
2310   }
2311 }
2312 
2313 // Delete a resolution error for RedefineClasses for a constant pool is going away
2314 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
2315   resolution_errors()->delete_entry(pool);
2316 }
2317 
2318 // Lookup resolution error table. Returns error if found, otherwise NULL.
2319 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
2320                                                 Symbol** message) {
2321   unsigned int hash = resolution_errors()->compute_hash(pool, which);
2322   int index = resolution_errors()->hash_to_index(hash);
2323   {
2324     MutexLocker ml(SystemDictionary_lock, Thread::current());
2325     ResolutionErrorEntry* entry = resolution_errors()->find_entry(index, hash, pool, which);
2326     if (entry != NULL) {
2327       *message = entry->message();
2328       return entry->error();
2329     } else {
2330       return NULL;
2331     }
2332   }
2333 }
2334 
2335 
2336 // Signature constraints ensure that callers and callees agree about
2337 // the meaning of type names in their signatures.  This routine is the
2338 // intake for constraints.  It collects them from several places:
2339 //
2340 //  * LinkResolver::resolve_method (if check_access is true) requires
2341 //    that the resolving class (the caller) and the defining class of
2342 //    the resolved method (the callee) agree on each type in the
2343 //    method's signature.
2344 //
2345 //  * LinkResolver::resolve_interface_method performs exactly the same
2346 //    checks.
2347 //
2348 //  * LinkResolver::resolve_field requires that the constant pool
2349 //    attempting to link to a field agree with the field's defining
2350 //    class about the type of the field signature.
2351 //
2352 //  * klassVtable::initialize_vtable requires that, when a class
2353 //    overrides a vtable entry allocated by a superclass, that the
2354 //    overriding method (i.e., the callee) agree with the superclass
2355 //    on each type in the method's signature.
2356 //
2357 //  * klassItable::initialize_itable requires that, when a class fills
2358 //    in its itables, for each non-abstract method installed in an
2359 //    itable, the method (i.e., the callee) agree with the interface
2360 //    on each type in the method's signature.
2361 //
2362 // All those methods have a boolean (check_access, checkconstraints)
2363 // which turns off the checks.  This is used from specialized contexts
2364 // such as bootstrapping, dumping, and debugging.
2365 //
2366 // No direct constraint is placed between the class and its
2367 // supertypes.  Constraints are only placed along linked relations
2368 // between callers and callees.  When a method overrides or implements
2369 // an abstract method in a supertype (superclass or interface), the
2370 // constraints are placed as if the supertype were the caller to the
2371 // overriding method.  (This works well, since callers to the
2372 // supertype have already established agreement between themselves and
2373 // the supertype.)  As a result of all this, a class can disagree with
2374 // its supertype about the meaning of a type name, as long as that
2375 // class neither calls a relevant method of the supertype, nor is
2376 // called (perhaps via an override) from the supertype.
2377 //
2378 //
2379 // SystemDictionary::check_signature_loaders(sig, l1, l2)
2380 //
2381 // Make sure all class components (including arrays) in the given
2382 // signature will be resolved to the same class in both loaders.
2383 // Returns the name of the type that failed a loader constraint check, or
2384 // NULL if no constraint failed.  No exception except OOME is thrown.
2385 // Arrays are not added to the loader constraint table, their elements are.
2386 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
2387                                                Handle loader1, Handle loader2,
2388                                                bool is_method, TRAPS)  {
2389   // Nothing to do if loaders are the same.
2390   if (oopDesc::equals(loader1(), loader2())) {
2391     return NULL;
2392   }
2393 
2394   SignatureStream sig_strm(signature, is_method);
2395   while (!sig_strm.is_done()) {
2396     if (sig_strm.is_object()) {
2397       Symbol* sig = sig_strm.as_symbol(CHECK_NULL);
2398       if (!add_loader_constraint(sig, loader1, loader2, THREAD)) {
2399         return sig;
2400       }
2401     }
2402     sig_strm.next();
2403   }
2404   return NULL;
2405 }
2406 
2407 
2408 methodHandle SystemDictionary::find_method_handle_intrinsic(vmIntrinsics::ID iid,
2409                                                             Symbol* signature,
2410                                                             TRAPS) {
2411   methodHandle empty;
2412   assert(MethodHandles::is_signature_polymorphic(iid) &&
2413          MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
2414          iid != vmIntrinsics::_invokeGeneric,
2415          "must be a known MH intrinsic iid=%d: %s", iid, vmIntrinsics::name_at(iid));
2416 
2417   unsigned int hash  = invoke_method_table()->compute_hash(signature, iid);
2418   int          index = invoke_method_table()->hash_to_index(hash);
2419   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2420   methodHandle m;
2421   if (spe == NULL || spe->method() == NULL) {
2422     spe = NULL;
2423     // Must create lots of stuff here, but outside of the SystemDictionary lock.
2424     m = Method::make_method_handle_intrinsic(iid, signature, CHECK_(empty));
2425     if (!Arguments::is_interpreter_only()) {
2426       // Generate a compiled form of the MH intrinsic.
2427       AdapterHandlerLibrary::create_native_wrapper(m);
2428       // Check if have the compiled code.
2429       if (!m->has_compiled_code()) {
2430         THROW_MSG_(vmSymbols::java_lang_VirtualMachineError(),
2431                    "Out of space in CodeCache for method handle intrinsic", empty);
2432       }
2433     }
2434     // Now grab the lock.  We might have to throw away the new method,
2435     // if a racing thread has managed to install one at the same time.
2436     {
2437       MutexLocker ml(SystemDictionary_lock, THREAD);
2438       spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2439       if (spe == NULL)
2440         spe = invoke_method_table()->add_entry(index, hash, signature, iid);
2441       if (spe->method() == NULL)
2442         spe->set_method(m());
2443     }
2444   }
2445 
2446   assert(spe != NULL && spe->method() != NULL, "");
2447   assert(Arguments::is_interpreter_only() || (spe->method()->has_compiled_code() &&
2448          spe->method()->code()->entry_point() == spe->method()->from_compiled_entry()),
2449          "MH intrinsic invariant");
2450   return spe->method();
2451 }
2452 
2453 // Helper for unpacking the return value from linkMethod and linkCallSite.
2454 static methodHandle unpack_method_and_appendix(Handle mname,
2455                                                Klass* accessing_klass,
2456                                                objArrayHandle appendix_box,
2457                                                Handle* appendix_result,
2458                                                TRAPS) {
2459   methodHandle empty;
2460   if (mname.not_null()) {
2461     Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2462     if (m != NULL) {
2463       oop appendix = appendix_box->obj_at(0);
2464       if (TraceMethodHandles) {
2465     #ifndef PRODUCT
2466         ttyLocker ttyl;
2467         tty->print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2468         m->print();
2469         if (appendix != NULL) { tty->print("appendix = "); appendix->print(); }
2470         tty->cr();
2471     #endif //PRODUCT
2472       }
2473       (*appendix_result) = Handle(THREAD, appendix);
2474       // the target is stored in the cpCache and if a reference to this
2475       // MemberName is dropped we need a way to make sure the
2476       // class_loader containing this method is kept alive.
2477       ClassLoaderData* this_key = accessing_klass->class_loader_data();
2478       this_key->record_dependency(m->method_holder());
2479       return methodHandle(THREAD, m);
2480     }
2481   }
2482   THROW_MSG_(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives", empty);
2483   return empty;
2484 }
2485 
2486 methodHandle SystemDictionary::find_method_handle_invoker(Klass* klass,
2487                                                           Symbol* name,
2488                                                           Symbol* signature,
2489                                                           Klass* accessing_klass,
2490                                                           Handle *appendix_result,
2491                                                           Handle *method_type_result,
2492                                                           TRAPS) {
2493   methodHandle empty;
2494   assert(THREAD->can_call_java() ,"");
2495   Handle method_type =
2496     SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_(empty));
2497 
2498   int ref_kind = JVM_REF_invokeVirtual;
2499   oop name_oop = StringTable::intern(name, CHECK_(empty));
2500   Handle name_str (THREAD, name_oop);
2501   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2502   assert(appendix_box->obj_at(0) == NULL, "");
2503 
2504   // This should not happen.  JDK code should take care of that.
2505   if (accessing_klass == NULL || method_type.is_null()) {
2506     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokehandle", empty);
2507   }
2508 
2509   // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2510   JavaCallArguments args;
2511   args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2512   args.push_int(ref_kind);
2513   args.push_oop(Handle(THREAD, klass->java_mirror()));
2514   args.push_oop(name_str);
2515   args.push_oop(method_type);
2516   args.push_oop(appendix_box);
2517   JavaValue result(T_OBJECT);
2518   JavaCalls::call_static(&result,
2519                          SystemDictionary::MethodHandleNatives_klass(),
2520                          vmSymbols::linkMethod_name(),
2521                          vmSymbols::linkMethod_signature(),
2522                          &args, CHECK_(empty));
2523   Handle mname(THREAD, (oop) result.get_jobject());
2524   (*method_type_result) = method_type;
2525   return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2526 }
2527 
2528 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2529 // We must ensure that all class loaders everywhere will reach this class, for any client.
2530 // This is a safe bet for public classes in java.lang, such as Object and String.
2531 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2532 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2533 static bool is_always_visible_class(oop mirror) {
2534   Klass* klass = java_lang_Class::as_Klass(mirror);
2535   if (klass->is_objArray_klass()) {
2536     klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2537   }
2538   if (klass->is_typeArray_klass()) {
2539     return true; // primitive array
2540   }
2541   assert(klass->is_instance_klass(), "%s", klass->external_name());
2542   return klass->is_public() &&
2543          (InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::Object_klass()) ||       // java.lang
2544           InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::MethodHandle_klass()));  // java.lang.invoke
2545 }
2546 
2547 
2548 // Return the Java mirror (java.lang.Class instance) for a single-character
2549 // descriptor.  This result, when available, is the same as produced by the
2550 // heavier API point of the same name that takes a Symbol.
2551 oop SystemDictionary::find_java_mirror_for_type(char signature_char) {
2552   return java_lang_Class::primitive_mirror(char2type(signature_char));
2553 }
2554 
2555 // Find or construct the Java mirror (java.lang.Class instance) for a
2556 // for the given field type signature, as interpreted relative to the
2557 // given class loader.  Handles primitives, void, references, arrays,
2558 // and all other reflectable types, except method types.
2559 // N.B.  Code in reflection should use this entry point.
2560 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2561                                                    Klass* accessing_klass,
2562                                                    Handle class_loader,
2563                                                    Handle protection_domain,
2564                                                    SignatureStream::FailureMode failure_mode,
2565                                                    TRAPS) {
2566   Handle empty;
2567 
2568   assert(accessing_klass == NULL || (class_loader.is_null() && protection_domain.is_null()),
2569          "one or the other, or perhaps neither");
2570 
2571   Symbol* type = signature;
2572 
2573   // What we have here must be a valid field descriptor,
2574   // and all valid field descriptors are supported.
2575   // Produce the same java.lang.Class that reflection reports.
2576   if (type->utf8_length() == 1) {
2577 
2578     // It's a primitive.  (Void has a primitive mirror too.)
2579     char ch = (char) type->byte_at(0);
2580     assert(is_java_primitive(char2type(ch)) || ch == 'V', "");
2581     return Handle(THREAD, find_java_mirror_for_type(ch));
2582 
2583   } else if (FieldType::is_obj(type) || FieldType::is_array(type)) {
2584 
2585     // It's a reference type.
2586     if (accessing_klass != NULL) {
2587       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2588       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2589     }
2590     Klass* constant_type_klass;
2591     if (failure_mode == SignatureStream::ReturnNull) {
2592       constant_type_klass = resolve_or_null(type, class_loader, protection_domain,
2593                                             CHECK_(empty));
2594     } else {
2595       bool throw_error = (failure_mode == SignatureStream::NCDFError);
2596       constant_type_klass = resolve_or_fail(type, class_loader, protection_domain,
2597                                             throw_error, CHECK_(empty));
2598     }
2599     if (constant_type_klass == NULL) {
2600       return Handle();  // report failure this way
2601     }
2602     Handle mirror(THREAD, constant_type_klass->java_mirror());
2603 
2604     // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2605     if (accessing_klass != NULL) {
2606       Klass* sel_klass = constant_type_klass;
2607       bool fold_type_to_class = true;
2608       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2609                                               fold_type_to_class, CHECK_(empty));
2610     }
2611 
2612     return mirror;
2613 
2614   }
2615 
2616   // Fall through to an error.
2617   assert(false, "unsupported mirror syntax");
2618   THROW_MSG_(vmSymbols::java_lang_InternalError(), "unsupported mirror syntax", empty);
2619 }
2620 
2621 
2622 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2623 // signature, as interpreted relative to the given class loader.
2624 // Because of class loader constraints, all method handle usage must be
2625 // consistent with this loader.
2626 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2627                                                  Klass* accessing_klass,
2628                                                  TRAPS) {
2629   Handle empty;
2630   vmIntrinsics::ID null_iid = vmIntrinsics::_none;  // distinct from all method handle invoker intrinsics
2631   unsigned int hash  = invoke_method_table()->compute_hash(signature, null_iid);
2632   int          index = invoke_method_table()->hash_to_index(hash);
2633   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2634   if (spe != NULL && spe->method_type() != NULL) {
2635     assert(java_lang_invoke_MethodType::is_instance(spe->method_type()), "");
2636     return Handle(THREAD, spe->method_type());
2637   } else if (!THREAD->can_call_java()) {
2638     warning("SystemDictionary::find_method_handle_type called from compiler thread");  // FIXME
2639     return Handle();  // do not attempt from within compiler, unless it was cached
2640   }
2641 
2642   Handle class_loader, protection_domain;
2643   if (accessing_klass != NULL) {
2644     class_loader      = Handle(THREAD, accessing_klass->class_loader());
2645     protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2646   }
2647   bool can_be_cached = true;
2648   int npts = ArgumentCount(signature).size();
2649   objArrayHandle pts = oopFactory::new_objArray_handle(SystemDictionary::Class_klass(), npts, CHECK_(empty));
2650   int arg = 0;
2651   Handle rt; // the return type from the signature
2652   ResourceMark rm(THREAD);
2653   for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2654     oop mirror = NULL;
2655     if (can_be_cached) {
2656       // Use neutral class loader to lookup candidate classes to be placed in the cache.
2657       mirror = ss.as_java_mirror(Handle(), Handle(),
2658                                  SignatureStream::ReturnNull, CHECK_(empty));
2659       if (mirror == NULL || (ss.is_object() && !is_always_visible_class(mirror))) {
2660         // Fall back to accessing_klass context.
2661         can_be_cached = false;
2662       }
2663     }
2664     if (!can_be_cached) {
2665       // Resolve, throwing a real error if it doesn't work.
2666       mirror = ss.as_java_mirror(class_loader, protection_domain,
2667                                  SignatureStream::NCDFError, CHECK_(empty));
2668     }
2669     assert(mirror != NULL, "%s", ss.as_symbol(THREAD)->as_C_string());
2670     if (ss.at_return_type())
2671       rt = Handle(THREAD, mirror);
2672     else
2673       pts->obj_at_put(arg++, mirror);
2674 
2675     // Check accessibility.
2676     if (!java_lang_Class::is_primitive(mirror) && accessing_klass != NULL) {
2677       Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2678       mirror = NULL;  // safety
2679       // Emulate ConstantPool::verify_constant_pool_resolve.
2680       bool fold_type_to_class = true;
2681       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2682                                               fold_type_to_class, CHECK_(empty));
2683     }
2684   }
2685   assert(arg == npts, "");
2686 
2687   // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2688   JavaCallArguments args(Handle(THREAD, rt()));
2689   args.push_oop(pts);
2690   JavaValue result(T_OBJECT);
2691   JavaCalls::call_static(&result,
2692                          SystemDictionary::MethodHandleNatives_klass(),
2693                          vmSymbols::findMethodHandleType_name(),
2694                          vmSymbols::findMethodHandleType_signature(),
2695                          &args, CHECK_(empty));
2696   Handle method_type(THREAD, (oop) result.get_jobject());
2697 
2698   if (can_be_cached) {
2699     // We can cache this MethodType inside the JVM.
2700     MutexLocker ml(SystemDictionary_lock, THREAD);
2701     spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2702     if (spe == NULL)
2703       spe = invoke_method_table()->add_entry(index, hash, signature, null_iid);
2704     if (spe->method_type() == NULL) {
2705       spe->set_method_type(method_type());
2706     }
2707   }
2708 
2709   // report back to the caller with the MethodType
2710   return method_type;
2711 }
2712 
2713 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2714                                                 Klass* accessing_klass,
2715                                                 TRAPS) {
2716   Handle empty;
2717   ResourceMark rm(THREAD);
2718   SignatureStream ss(signature, /*is_method=*/ false);
2719   if (!ss.is_done()) {
2720     Handle class_loader, protection_domain;
2721     if (accessing_klass != NULL) {
2722       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2723       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2724     }
2725     oop mirror = ss.as_java_mirror(class_loader, protection_domain, SignatureStream::NCDFError, CHECK_(empty));
2726     ss.next();
2727     if (ss.is_done()) {
2728       return Handle(THREAD, mirror);
2729     }
2730   }
2731   return empty;
2732 }
2733 
2734 // Ask Java code to find or construct a method handle constant.
2735 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2736                                                      int ref_kind, //e.g., JVM_REF_invokeVirtual
2737                                                      Klass* callee,
2738                                                      Symbol* name,
2739                                                      Symbol* signature,
2740                                                      TRAPS) {
2741   Handle empty;
2742   if (caller == NULL) {
2743     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2744   }
2745   Handle name_str      = java_lang_String::create_from_symbol(name,      CHECK_(empty));
2746   Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2747 
2748   // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2749   Handle mname = MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2750   java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2751   java_lang_invoke_MemberName::set_name (mname(), name_str());
2752   java_lang_invoke_MemberName::set_type (mname(), signature_str());
2753   java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2754 
2755   if (ref_kind == JVM_REF_invokeVirtual &&
2756       MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2757     // Skip resolution for public signature polymorphic methods such as
2758     // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2759     // They require appendix argument which MemberName resolution doesn't handle.
2760     // There's special logic on JDK side to handle them
2761     // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2762   } else {
2763     MethodHandles::resolve_MemberName(mname, caller, /*speculative_resolve*/false, CHECK_(empty));
2764   }
2765 
2766   // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2767   Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2768 
2769   // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2770   JavaCallArguments args;
2771   args.push_oop(Handle(THREAD, caller->java_mirror()));  // the referring class
2772   args.push_int(ref_kind);
2773   args.push_oop(Handle(THREAD, callee->java_mirror()));  // the target class
2774   args.push_oop(name_str);
2775   args.push_oop(type);
2776   JavaValue result(T_OBJECT);
2777   JavaCalls::call_static(&result,
2778                          SystemDictionary::MethodHandleNatives_klass(),
2779                          vmSymbols::linkMethodHandleConstant_name(),
2780                          vmSymbols::linkMethodHandleConstant_signature(),
2781                          &args, CHECK_(empty));
2782   return Handle(THREAD, (oop) result.get_jobject());
2783 }
2784 
2785 // Ask Java to compute a constant by invoking a BSM given a Dynamic_info CP entry
2786 Handle SystemDictionary::link_dynamic_constant(Klass* caller,
2787                                                int condy_index,
2788                                                Handle bootstrap_specifier,
2789                                                Symbol* name,
2790                                                Symbol* type,
2791                                                TRAPS) {
2792   Handle empty;
2793   Handle bsm, info;
2794   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2795     bsm = bootstrap_specifier;
2796   } else {
2797     assert(bootstrap_specifier->is_objArray(), "");
2798     objArrayOop args = (objArrayOop) bootstrap_specifier();
2799     assert(args->length() == 2, "");
2800     bsm  = Handle(THREAD, args->obj_at(0));
2801     info = Handle(THREAD, args->obj_at(1));
2802   }
2803   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2804             "caller must supply a valid BSM");
2805 
2806   // This should not happen.  JDK code should take care of that.
2807   if (caller == NULL) {
2808     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad dynamic constant", empty);
2809   }
2810 
2811   Handle constant_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2812 
2813   // Resolve the constant type in the context of the caller class
2814   Handle type_mirror = find_java_mirror_for_type(type, caller, SignatureStream::NCDFError,
2815                                                  CHECK_(empty));
2816 
2817   // call java.lang.invoke.MethodHandleNatives::linkConstantDyanmic(caller, condy_index, bsm, type, info)
2818   JavaCallArguments args;
2819   args.push_oop(Handle(THREAD, caller->java_mirror()));
2820   args.push_int(condy_index);
2821   args.push_oop(bsm);
2822   args.push_oop(constant_name);
2823   args.push_oop(type_mirror);
2824   args.push_oop(info);
2825   JavaValue result(T_OBJECT);
2826   JavaCalls::call_static(&result,
2827                          SystemDictionary::MethodHandleNatives_klass(),
2828                          vmSymbols::linkDynamicConstant_name(),
2829                          vmSymbols::linkDynamicConstant_signature(),
2830                          &args, CHECK_(empty));
2831 
2832   return Handle(THREAD, (oop) result.get_jobject());
2833 }
2834 
2835 // Ask Java code to find or construct a java.lang.invoke.CallSite for the given
2836 // name and signature, as interpreted relative to the given class loader.
2837 methodHandle SystemDictionary::find_dynamic_call_site_invoker(Klass* caller,
2838                                                               int indy_index,
2839                                                               Handle bootstrap_specifier,
2840                                                               Symbol* name,
2841                                                               Symbol* type,
2842                                                               Handle *appendix_result,
2843                                                               Handle *method_type_result,
2844                                                               TRAPS) {
2845   methodHandle empty;
2846   Handle bsm, info;
2847   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2848     bsm = bootstrap_specifier;
2849   } else {
2850     objArrayOop args = (objArrayOop) bootstrap_specifier();
2851     assert(args->length() == 2, "");
2852     bsm  = Handle(THREAD, args->obj_at(0));
2853     info = Handle(THREAD, args->obj_at(1));
2854   }
2855   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2856             "caller must supply a valid BSM");
2857 
2858   Handle method_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2859   Handle method_type = find_method_handle_type(type, caller, CHECK_(empty));
2860 
2861   // This should not happen.  JDK code should take care of that.
2862   if (caller == NULL || method_type.is_null()) {
2863     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokedynamic", empty);
2864   }
2865 
2866   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2867   assert(appendix_box->obj_at(0) == NULL, "");
2868 
2869   // call java.lang.invoke.MethodHandleNatives::linkCallSite(caller, indy_index, bsm, name, mtype, info, &appendix)
2870   JavaCallArguments args;
2871   args.push_oop(Handle(THREAD, caller->java_mirror()));
2872   args.push_int(indy_index);
2873   args.push_oop(bsm);
2874   args.push_oop(method_name);
2875   args.push_oop(method_type);
2876   args.push_oop(info);
2877   args.push_oop(appendix_box);
2878   JavaValue result(T_OBJECT);
2879   JavaCalls::call_static(&result,
2880                          SystemDictionary::MethodHandleNatives_klass(),
2881                          vmSymbols::linkCallSite_name(),
2882                          vmSymbols::linkCallSite_signature(),
2883                          &args, CHECK_(empty));
2884   Handle mname(THREAD, (oop) result.get_jobject());
2885   (*method_type_result) = method_type;
2886   return unpack_method_and_appendix(mname, caller, appendix_box, appendix_result, THREAD);
2887 }
2888 
2889 // Protection domain cache table handling
2890 
2891 ProtectionDomainCacheEntry* SystemDictionary::cache_get(Handle protection_domain) {
2892   return _pd_cache_table->get(protection_domain);
2893 }
2894 
2895 #if INCLUDE_CDS
2896 void SystemDictionary::reorder_dictionary_for_sharing() {
2897   ClassLoaderData::the_null_class_loader_data()->dictionary()->reorder_dictionary_for_sharing();
2898 }
2899 #endif
2900 
2901 size_t SystemDictionary::count_bytes_for_buckets() {
2902   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_buckets();
2903 }
2904 
2905 size_t SystemDictionary::count_bytes_for_table() {
2906   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_table();
2907 }
2908 
2909 void SystemDictionary::copy_buckets(char* top, char* end) {
2910   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_buckets(top, end);
2911 }
2912 
2913 void SystemDictionary::copy_table(char* top, char* end) {
2914   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_table(top, end);
2915 }
2916 
2917 // ----------------------------------------------------------------------------
2918 void SystemDictionary::print_shared(outputStream *st) {
2919   shared_dictionary()->print_on(st);
2920 }
2921 
2922 void SystemDictionary::print_on(outputStream *st) {
2923   if (shared_dictionary() != NULL) {
2924     st->print_cr("Shared Dictionary");
2925     shared_dictionary()->print_on(st);
2926     st->cr();
2927   }
2928 
2929   GCMutexLocker mu(SystemDictionary_lock);
2930 
2931   ClassLoaderDataGraph::print_dictionary(st);
2932 
2933   // Placeholders
2934   placeholders()->print_on(st);
2935   st->cr();
2936 
2937   // loader constraints - print under SD_lock
2938   constraints()->print_on(st);
2939   st->cr();
2940 
2941   _pd_cache_table->print_on(st);
2942   st->cr();
2943 }
2944 
2945 void SystemDictionary::verify() {
2946   guarantee(constraints() != NULL,
2947             "Verify of loader constraints failed");
2948   guarantee(placeholders()->number_of_entries() >= 0,
2949             "Verify of placeholders failed");
2950 
2951   GCMutexLocker mu(SystemDictionary_lock);
2952 
2953   // Verify dictionary
2954   ClassLoaderDataGraph::verify_dictionary();
2955 
2956   placeholders()->verify();
2957 
2958   // Verify constraint table
2959   guarantee(constraints() != NULL, "Verify of loader constraints failed");
2960   constraints()->verify(placeholders());
2961 
2962   _pd_cache_table->verify();
2963 }
2964 
2965 void SystemDictionary::dump(outputStream *st, bool verbose) {
2966   assert_locked_or_safepoint(SystemDictionary_lock);
2967   if (verbose) {
2968     print_on(st);
2969   } else {
2970     if (shared_dictionary() != NULL) {
2971       shared_dictionary()->print_table_statistics(st, "Shared Dictionary");
2972     }
2973     ClassLoaderDataGraph::print_dictionary_statistics(st);
2974     placeholders()->print_table_statistics(st, "Placeholder Table");
2975     constraints()->print_table_statistics(st, "LoaderConstraints Table");
2976     _pd_cache_table->print_table_statistics(st, "ProtectionDomainCache Table");
2977   }
2978 }
2979 
2980 // Utility for dumping dictionaries.
2981 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
2982                                  DCmdWithParser(output, heap),
2983   _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
2984            "BOOLEAN", false, "false") {
2985   _dcmdparser.add_dcmd_option(&_verbose);
2986 }
2987 
2988 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
2989   VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
2990                          _verbose.value());
2991   VMThread::execute(&dumper);
2992 }
2993 
2994 int SystemDictionaryDCmd::num_arguments() {
2995   ResourceMark rm;
2996   SystemDictionaryDCmd* dcmd = new SystemDictionaryDCmd(NULL, false);
2997   if (dcmd != NULL) {
2998     DCmdMark mark(dcmd);
2999     return dcmd->_dcmdparser.num_arguments();
3000   } else {
3001     return 0;
3002   }
3003 }
3004 
3005 class CombineDictionariesClosure : public CLDClosure {
3006   private:
3007     Dictionary* _master_dictionary;
3008   public:
3009     CombineDictionariesClosure(Dictionary* master_dictionary) :
3010       _master_dictionary(master_dictionary) {}
3011     void do_cld(ClassLoaderData* cld) {
3012       ResourceMark rm;
3013       if (cld->is_unsafe_anonymous()) {
3014         return;
3015       }
3016       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
3017         for (int i = 0; i < cld->dictionary()->table_size(); ++i) {
3018           Dictionary* curr_dictionary = cld->dictionary();
3019           DictionaryEntry* p = curr_dictionary->bucket(i);
3020           while (p != NULL) {
3021             Symbol* name = p->instance_klass()->name();
3022             unsigned int d_hash = _master_dictionary->compute_hash(name);
3023             int d_index = _master_dictionary->hash_to_index(d_hash);
3024             DictionaryEntry* next = p->next();
3025             if (p->literal()->class_loader_data() != cld) {
3026               // This is an initiating class loader entry; don't use it
3027               log_trace(cds)("Skipping initiating cl entry: %s", name->as_C_string());
3028               curr_dictionary->free_entry(p);
3029             } else {
3030               log_trace(cds)("Moved to boot dictionary: %s", name->as_C_string());
3031               curr_dictionary->unlink_entry(p);
3032               p->set_pd_set(NULL); // pd_set is runtime only information and will be reconstructed.
3033               _master_dictionary->add_entry(d_index, p);
3034             }
3035             p = next;
3036           }
3037           *curr_dictionary->bucket_addr(i) = NULL;
3038         }
3039       }
3040     }
3041 };
3042 
3043 // Combining platform and system loader dictionaries into boot loader dictionary.
3044 // During run time, we only have one shared dictionary.
3045 void SystemDictionary::combine_shared_dictionaries() {
3046   assert(DumpSharedSpaces, "dump time only");
3047   Dictionary* master_dictionary = ClassLoaderData::the_null_class_loader_data()->dictionary();
3048   CombineDictionariesClosure cdc(master_dictionary);
3049   ClassLoaderDataGraph::cld_do(&cdc);
3050 
3051   // These tables are no longer valid or necessary. Keeping them around will
3052   // cause SystemDictionary::verify() to fail. Let's empty them.
3053   _placeholders        = new PlaceholderTable(_placeholder_table_size);
3054   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
3055 
3056   NOT_PRODUCT(SystemDictionary::verify());
3057 }
3058 
3059 void SystemDictionary::initialize_oop_storage() {
3060   _vm_weak_oop_storage =
3061     new OopStorage("VM Weak Oop Handles",
3062                    VMWeakAlloc_lock,
3063                    VMWeakActive_lock);
3064 }
3065 
3066 OopStorage* SystemDictionary::vm_weak_oop_storage() {
3067   assert(_vm_weak_oop_storage != NULL, "Uninitialized");
3068   return _vm_weak_oop_storage;
3069 }