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/jfr.hpp"
  51 #include "jfr/jfrEvents.hpp"
  52 #include "logging/log.hpp"
  53 #include "logging/logStream.hpp"
  54 #include "memory/filemap.hpp"
  55 #include "memory/metaspaceClosure.hpp"
  56 #include "memory/oopFactory.hpp"
  57 #include "memory/resourceArea.hpp"
  58 #include "oops/access.inline.hpp"
  59 #include "oops/instanceKlass.hpp"
  60 #include "oops/instanceRefKlass.hpp"
  61 #include "oops/klass.inline.hpp"
  62 #include "oops/method.inline.hpp"
  63 #include "oops/methodData.hpp"
  64 #include "oops/objArrayKlass.hpp"
  65 #include "oops/objArrayOop.inline.hpp"
  66 #include "oops/oop.inline.hpp"
  67 #include "oops/symbol.hpp"
  68 #include "oops/typeArrayKlass.hpp"
  69 #include "prims/jvmtiEnvBase.hpp"
  70 #include "prims/resolvedMethodTable.hpp"
  71 #include "prims/methodHandles.hpp"
  72 #include "runtime/arguments.hpp"
  73 #include "runtime/arguments_ext.hpp"
  74 #include "runtime/biasedLocking.hpp"
  75 #include "runtime/fieldType.hpp"
  76 #include "runtime/handles.inline.hpp"
  77 #include "runtime/java.hpp"
  78 #include "runtime/javaCalls.hpp"
  79 #include "runtime/mutexLocker.hpp"
  80 #include "runtime/orderAccess.hpp"
  81 #include "runtime/sharedRuntime.hpp"
  82 #include "runtime/signature.hpp"
  83 #include "services/classLoadingService.hpp"
  84 #include "services/diagnosticCommand.hpp"
  85 #include "services/threadService.hpp"
  86 #include "utilities/macros.hpp"
  87 #include "utilities/ticks.hpp"
  88 #if INCLUDE_CDS
  89 #include "classfile/systemDictionaryShared.hpp"
  90 #endif
  91 #if INCLUDE_JVMCI
  92 #include "jvmci/jvmciRuntime.hpp"
  93 #endif
  94 
  95 PlaceholderTable*      SystemDictionary::_placeholders        = NULL;
  96 Dictionary*            SystemDictionary::_shared_dictionary   = NULL;
  97 LoaderConstraintTable* SystemDictionary::_loader_constraints  = NULL;
  98 ResolutionErrorTable*  SystemDictionary::_resolution_errors   = NULL;
  99 SymbolPropertyTable*   SystemDictionary::_invoke_method_table = NULL;
 100 ProtectionDomainCacheTable*   SystemDictionary::_pd_cache_table = NULL;
 101 
 102 int         SystemDictionary::_number_of_modifications = 0;
 103 oop         SystemDictionary::_system_loader_lock_obj     =  NULL;
 104 
 105 InstanceKlass*      SystemDictionary::_well_known_klasses[SystemDictionary::WKID_LIMIT]
 106                                                           =  { NULL /*, NULL...*/ };
 107 
 108 InstanceKlass*      SystemDictionary::_box_klasses[T_VOID+1]      =  { NULL /*, NULL...*/ };
 109 
 110 oop         SystemDictionary::_java_system_loader         =  NULL;
 111 oop         SystemDictionary::_java_platform_loader       =  NULL;
 112 
 113 bool        SystemDictionary::_has_checkPackageAccess     =  false;
 114 
 115 // Default ProtectionDomainCacheSize value
 116 
 117 const int defaultProtectionDomainCacheSize = 1009;
 118 
 119 OopStorage* SystemDictionary::_vm_weak_oop_storage = NULL;
 120 
 121 
 122 // ----------------------------------------------------------------------------
 123 // Java-level SystemLoader and PlatformLoader
 124 
 125 oop SystemDictionary::java_system_loader() {
 126   return _java_system_loader;
 127 }
 128 
 129 oop SystemDictionary::java_platform_loader() {
 130   return _java_platform_loader;
 131 }
 132 
 133 void SystemDictionary::compute_java_loaders(TRAPS) {
 134   JavaValue result(T_OBJECT);
 135   InstanceKlass* class_loader_klass = SystemDictionary::ClassLoader_klass();
 136   JavaCalls::call_static(&result,
 137                          class_loader_klass,
 138                          vmSymbols::getSystemClassLoader_name(),
 139                          vmSymbols::void_classloader_signature(),
 140                          CHECK);
 141 
 142   _java_system_loader = (oop)result.get_jobject();
 143 
 144   JavaCalls::call_static(&result,
 145                          class_loader_klass,
 146                          vmSymbols::getPlatformClassLoader_name(),
 147                          vmSymbols::void_classloader_signature(),
 148                          CHECK);
 149 
 150   _java_platform_loader = (oop)result.get_jobject();
 151 }
 152 
 153 ClassLoaderData* SystemDictionary::register_loader(Handle class_loader) {
 154   if (class_loader() == NULL) return ClassLoaderData::the_null_class_loader_data();
 155   return ClassLoaderDataGraph::find_or_create(class_loader);
 156 }
 157 
 158 // ----------------------------------------------------------------------------
 159 // Parallel class loading check
 160 
 161 bool SystemDictionary::is_parallelCapable(Handle class_loader) {
 162   if (class_loader.is_null()) return true;
 163   if (AlwaysLockClassLoader) return false;
 164   return java_lang_ClassLoader::parallelCapable(class_loader());
 165 }
 166 // ----------------------------------------------------------------------------
 167 // ParallelDefineClass flag does not apply to bootclass loader
 168 bool SystemDictionary::is_parallelDefine(Handle class_loader) {
 169    if (class_loader.is_null()) return false;
 170    if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) {
 171      return true;
 172    }
 173    return false;
 174 }
 175 
 176 // Returns true if the passed class loader is the builtin application class loader
 177 // or a custom system class loader. A customer system class loader can be
 178 // specified via -Djava.system.class.loader.
 179 bool SystemDictionary::is_system_class_loader(oop class_loader) {
 180   if (class_loader == NULL) {
 181     return false;
 182   }
 183   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() ||
 184          oopDesc::equals(class_loader, _java_system_loader));
 185 }
 186 
 187 // Returns true if the passed class loader is the platform class loader.
 188 bool SystemDictionary::is_platform_class_loader(oop class_loader) {
 189   if (class_loader == NULL) {
 190     return false;
 191   }
 192   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass());
 193 }
 194 
 195 // ----------------------------------------------------------------------------
 196 // Resolving of classes
 197 
 198 // Forwards to resolve_or_null
 199 
 200 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader, Handle protection_domain, bool throw_error, TRAPS) {
 201   Klass* klass = resolve_or_null(class_name, class_loader, protection_domain, THREAD);
 202   if (HAS_PENDING_EXCEPTION || klass == NULL) {
 203     // can return a null klass
 204     klass = handle_resolution_exception(class_name, throw_error, klass, THREAD);
 205   }
 206   return klass;
 207 }
 208 
 209 Klass* SystemDictionary::handle_resolution_exception(Symbol* class_name,
 210                                                      bool throw_error,
 211                                                      Klass* klass, TRAPS) {
 212   if (HAS_PENDING_EXCEPTION) {
 213     // If we have a pending exception we forward it to the caller, unless throw_error is true,
 214     // in which case we have to check whether the pending exception is a ClassNotFoundException,
 215     // and if so convert it to a NoClassDefFoundError
 216     // And chain the original ClassNotFoundException
 217     if (throw_error && PENDING_EXCEPTION->is_a(SystemDictionary::ClassNotFoundException_klass())) {
 218       ResourceMark rm(THREAD);
 219       assert(klass == NULL, "Should not have result with exception pending");
 220       Handle e(THREAD, PENDING_EXCEPTION);
 221       CLEAR_PENDING_EXCEPTION;
 222       THROW_MSG_CAUSE_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e);
 223     } else {
 224       return NULL;
 225     }
 226   }
 227   // Class not found, throw appropriate error or exception depending on value of throw_error
 228   if (klass == NULL) {
 229     ResourceMark rm(THREAD);
 230     if (throw_error) {
 231       THROW_MSG_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string());
 232     } else {
 233       THROW_MSG_NULL(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string());
 234     }
 235   }
 236   return klass;
 237 }
 238 
 239 
 240 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name,
 241                                            bool throw_error, TRAPS)
 242 {
 243   return resolve_or_fail(class_name, Handle(), Handle(), throw_error, THREAD);
 244 }
 245 
 246 
 247 // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null
 248 
 249 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, Handle protection_domain, TRAPS) {
 250   if (FieldType::is_array(class_name)) {
 251     return resolve_array_class_or_null(class_name, class_loader, protection_domain, THREAD);
 252   } else {
 253     return resolve_instance_class_or_null_helper(class_name, class_loader, protection_domain, THREAD);
 254   }
 255 }
 256 
 257 // name may be in the form of "java/lang/Object" or "Ljava/lang/Object;"
 258 InstanceKlass* SystemDictionary::resolve_instance_class_or_null_helper(Symbol* class_name,
 259                                                                        Handle class_loader,
 260                                                                        Handle protection_domain,
 261                                                                        TRAPS) {
 262   assert(class_name != NULL && !FieldType::is_array(class_name), "must be");
 263   if (FieldType::is_obj(class_name)) {
 264     ResourceMark rm(THREAD);
 265     // Ignore wrapping L and ;.
 266     TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1,
 267                                    class_name->utf8_length() - 2, CHECK_NULL);
 268     return resolve_instance_class_or_null(name, class_loader, protection_domain, THREAD);
 269   } else {
 270     return resolve_instance_class_or_null(class_name, class_loader, protection_domain, THREAD);
 271   }
 272 }
 273 
 274 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, TRAPS) {
 275   return resolve_or_null(class_name, Handle(), Handle(), THREAD);
 276 }
 277 
 278 // Forwards to resolve_instance_class_or_null
 279 
 280 Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name,
 281                                                      Handle class_loader,
 282                                                      Handle protection_domain,
 283                                                      TRAPS) {
 284   assert(FieldType::is_array(class_name), "must be array");
 285   Klass* k = NULL;
 286   FieldArrayInfo fd;
 287   // dimension and object_key in FieldArrayInfo are assigned as a side-effect
 288   // of this call
 289   BasicType t = FieldType::get_array_info(class_name, fd, CHECK_NULL);
 290   if (t == T_OBJECT) {
 291     // naked oop "k" is OK here -- we assign back into it
 292     k = SystemDictionary::resolve_instance_class_or_null(fd.object_key(),
 293                                                          class_loader,
 294                                                          protection_domain,
 295                                                          CHECK_NULL);
 296     if (k != NULL) {
 297       k = k->array_klass(fd.dimension(), CHECK_NULL);
 298     }
 299   } else {
 300     k = Universe::typeArrayKlassObj(t);
 301     k = TypeArrayKlass::cast(k)->array_klass(fd.dimension(), CHECK_NULL);
 302   }
 303   return k;
 304 }
 305 
 306 
 307 // Must be called for any super-class or super-interface resolution
 308 // during class definition to allow class circularity checking
 309 // super-interface callers:
 310 //    parse_interfaces - for defineClass & jvmtiRedefineClasses
 311 // super-class callers:
 312 //   ClassFileParser - for defineClass & jvmtiRedefineClasses
 313 //   load_shared_class - while loading a class from shared archive
 314 //   resolve_instance_class_or_null:
 315 //     via: handle_parallel_super_load
 316 //      when resolving a class that has an existing placeholder with
 317 //      a saved superclass [i.e. a defineClass is currently in progress]
 318 //      if another thread is trying to resolve the class, it must do
 319 //      super-class checks on its own thread to catch class circularity
 320 // This last call is critical in class circularity checking for cases
 321 // where classloading is delegated to different threads and the
 322 // classloader lock is released.
 323 // Take the case: Base->Super->Base
 324 //   1. If thread T1 tries to do a defineClass of class Base
 325 //    resolve_super_or_fail creates placeholder: T1, Base (super Super)
 326 //   2. resolve_instance_class_or_null does not find SD or placeholder for Super
 327 //    so it tries to load Super
 328 //   3. If we load the class internally, or user classloader uses same thread
 329 //      loadClassFromxxx or defineClass via parseClassFile Super ...
 330 //      3.1 resolve_super_or_fail creates placeholder: T1, Super (super Base)
 331 //      3.3 resolve_instance_class_or_null Base, finds placeholder for Base
 332 //      3.4 calls resolve_super_or_fail Base
 333 //      3.5 finds T1,Base -> throws class circularity
 334 //OR 4. If T2 tries to resolve Super via defineClass Super ...
 335 //      4.1 resolve_super_or_fail creates placeholder: T2, Super (super Base)
 336 //      4.2 resolve_instance_class_or_null Base, finds placeholder for Base (super Super)
 337 //      4.3 calls resolve_super_or_fail Super in parallel on own thread T2
 338 //      4.4 finds T2, Super -> throws class circularity
 339 // Must be called, even if superclass is null, since this is
 340 // where the placeholder entry is created which claims this
 341 // thread is loading this class/classloader.
 342 // Be careful when modifying this code: once you have run
 343 // placeholders()->find_and_add(PlaceholderTable::LOAD_SUPER),
 344 // you need to find_and_remove it before returning.
 345 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 346 InstanceKlass* SystemDictionary::resolve_super_or_fail(Symbol* child_name,
 347                                                        Symbol* super_name,
 348                                                        Handle class_loader,
 349                                                        Handle protection_domain,
 350                                                        bool is_superclass,
 351                                                        TRAPS) {
 352   assert(!FieldType::is_array(super_name), "invalid super class name");
 353 #if INCLUDE_CDS
 354   if (DumpSharedSpaces) {
 355     // Special processing for CDS dump time.
 356     InstanceKlass* k = SystemDictionaryShared::dump_time_resolve_super_or_fail(child_name,
 357         super_name, class_loader, protection_domain, is_superclass, CHECK_NULL);
 358     if (k) {
 359       return k;
 360     }
 361   }
 362 #endif // INCLUDE_CDS
 363 
 364   // Double-check, if child class is already loaded, just return super-class,interface
 365   // Don't add a placedholder if already loaded, i.e. already in appropriate class loader
 366   // dictionary.
 367   // Make sure there's a placeholder for the *child* before resolving.
 368   // Used as a claim that this thread is currently loading superclass/classloader
 369   // Used here for ClassCircularity checks and also for heap verification
 370   // (every InstanceKlass needs to be in its class loader dictionary or have a placeholder).
 371   // Must check ClassCircularity before checking if super class is already loaded.
 372   //
 373   // We might not already have a placeholder if this child_name was
 374   // first seen via resolve_from_stream (jni_DefineClass or JVM_DefineClass);
 375   // the name of the class might not be known until the stream is actually
 376   // parsed.
 377   // Bugs 4643874, 4715493
 378 
 379   ClassLoaderData* loader_data = class_loader_data(class_loader);
 380   Dictionary* dictionary = loader_data->dictionary();
 381   unsigned int d_hash = dictionary->compute_hash(child_name);
 382   unsigned int p_hash = placeholders()->compute_hash(child_name);
 383   int p_index = placeholders()->hash_to_index(p_hash);
 384   // can't throw error holding a lock
 385   bool child_already_loaded = false;
 386   bool throw_circularity_error = false;
 387   {
 388     MutexLocker mu(SystemDictionary_lock, THREAD);
 389     InstanceKlass* childk = find_class(d_hash, child_name, dictionary);
 390     InstanceKlass* quicksuperk;
 391     // to support // loading: if child done loading, just return superclass
 392     // if super_name, & class_loader don't match:
 393     // if initial define, SD update will give LinkageError
 394     // if redefine: compare_class_versions will give HIERARCHY_CHANGED
 395     // so we don't throw an exception here.
 396     // see: nsk redefclass014 & java.lang.instrument Instrument032
 397     if ((childk != NULL ) && (is_superclass) &&
 398         ((quicksuperk = childk->java_super()) != NULL) &&
 399          ((quicksuperk->name() == super_name) &&
 400             (oopDesc::equals(quicksuperk->class_loader(), class_loader())))) {
 401            return quicksuperk;
 402     } else {
 403       PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, child_name, loader_data);
 404       if (probe && probe->check_seen_thread(THREAD, PlaceholderTable::LOAD_SUPER)) {
 405           throw_circularity_error = true;
 406       }
 407     }
 408     if (!throw_circularity_error) {
 409       // Be careful not to exit resolve_super
 410       PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, super_name, THREAD);
 411     }
 412   }
 413   if (throw_circularity_error) {
 414       ResourceMark rm(THREAD);
 415       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), child_name->as_C_string());
 416   }
 417 
 418 // java.lang.Object should have been found above
 419   assert(super_name != NULL, "null super class for resolving");
 420   // Resolve the super class or interface, check results on return
 421   InstanceKlass* superk =
 422     SystemDictionary::resolve_instance_class_or_null_helper(super_name,
 423                                                             class_loader,
 424                                                             protection_domain,
 425                                                             THREAD);
 426 
 427   // Clean up of placeholders moved so that each classloadAction registrar self-cleans up
 428   // It is no longer necessary to keep the placeholder table alive until update_dictionary
 429   // or error. GC used to walk the placeholder table as strong roots.
 430   // The instanceKlass is kept alive because the class loader is on the stack,
 431   // which keeps the loader_data alive, as well as all instanceKlasses in
 432   // the loader_data. parseClassFile adds the instanceKlass to loader_data.
 433   {
 434     MutexLocker mu(SystemDictionary_lock, THREAD);
 435     placeholders()->find_and_remove(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, THREAD);
 436     SystemDictionary_lock->notify_all();
 437   }
 438   if (HAS_PENDING_EXCEPTION || superk == NULL) {
 439     // can null superk
 440     Klass* k = handle_resolution_exception(super_name, true, superk, THREAD);
 441     assert(k == NULL || k == superk, "must be");
 442     if (k == NULL) {
 443       superk = NULL;
 444     }
 445   }
 446 
 447   return superk;
 448 }
 449 
 450 void SystemDictionary::validate_protection_domain(InstanceKlass* klass,
 451                                                   Handle class_loader,
 452                                                   Handle protection_domain,
 453                                                   TRAPS) {
 454   if(!has_checkPackageAccess()) return;
 455 
 456   // Now we have to call back to java to check if the initating class has access
 457   JavaValue result(T_VOID);
 458   LogTarget(Debug, protectiondomain) lt;
 459   if (lt.is_enabled()) {
 460     ResourceMark rm;
 461     // Print out trace information
 462     LogStream ls(lt);
 463     ls.print_cr("Checking package access");
 464     if (class_loader() != NULL) {
 465       ls.print("class loader: ");
 466       class_loader()->print_value_on(&ls);
 467     } else {
 468       ls.print_cr("class loader: NULL");
 469     }
 470     if (protection_domain() != NULL) {
 471       ls.print(" protection domain: ");
 472       protection_domain()->print_value_on(&ls);
 473     } else {
 474       ls.print_cr(" protection domain: NULL");
 475     }
 476     ls.print(" loading: "); klass->print_value_on(&ls);
 477     ls.cr();
 478   }
 479 
 480   // This handle and the class_loader handle passed in keeps this class from
 481   // being unloaded through several GC points.
 482   // The class_loader handle passed in is the initiating loader.
 483   Handle mirror(THREAD, klass->java_mirror());
 484 
 485   InstanceKlass* system_loader = SystemDictionary::ClassLoader_klass();
 486   JavaCalls::call_special(&result,
 487                          class_loader,
 488                          system_loader,
 489                          vmSymbols::checkPackageAccess_name(),
 490                          vmSymbols::class_protectiondomain_signature(),
 491                          mirror,
 492                          protection_domain,
 493                          THREAD);
 494 
 495   if (HAS_PENDING_EXCEPTION) {
 496     log_debug(protectiondomain)("DENIED !!!!!!!!!!!!!!!!!!!!!");
 497   } else {
 498    log_debug(protectiondomain)("granted");
 499   }
 500 
 501   if (HAS_PENDING_EXCEPTION) return;
 502 
 503   // If no exception has been thrown, we have validated the protection domain
 504   // Insert the protection domain of the initiating class into the set.
 505   {
 506     ClassLoaderData* loader_data = class_loader_data(class_loader);
 507     Dictionary* dictionary = loader_data->dictionary();
 508 
 509     Symbol*  kn = klass->name();
 510     unsigned int d_hash = dictionary->compute_hash(kn);
 511 
 512     MutexLocker mu(SystemDictionary_lock, THREAD);
 513     int d_index = dictionary->hash_to_index(d_hash);
 514     dictionary->add_protection_domain(d_index, d_hash, klass,
 515                                       protection_domain, THREAD);
 516   }
 517 }
 518 
 519 // We only get here if this thread finds that another thread
 520 // has already claimed the placeholder token for the current operation,
 521 // but that other thread either never owned or gave up the
 522 // object lock
 523 // Waits on SystemDictionary_lock to indicate placeholder table updated
 524 // On return, caller must recheck placeholder table state
 525 //
 526 // We only get here if
 527 //  1) custom classLoader, i.e. not bootstrap classloader
 528 //  2) custom classLoader has broken the class loader objectLock
 529 //     so another thread got here in parallel
 530 //
 531 // lockObject must be held.
 532 // Complicated dance due to lock ordering:
 533 // Must first release the classloader object lock to
 534 // allow initial definer to complete the class definition
 535 // and to avoid deadlock
 536 // Reclaim classloader lock object with same original recursion count
 537 // Must release SystemDictionary_lock after notify, since
 538 // class loader lock must be claimed before SystemDictionary_lock
 539 // to prevent deadlocks
 540 //
 541 // The notify allows applications that did an untimed wait() on
 542 // the classloader object lock to not hang.
 543 void SystemDictionary::double_lock_wait(Handle lockObject, TRAPS) {
 544   assert_lock_strong(SystemDictionary_lock);
 545 
 546   bool calledholdinglock
 547       = ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD, lockObject);
 548   assert(calledholdinglock,"must hold lock for notify");
 549   assert((!oopDesc::equals(lockObject(), _system_loader_lock_obj) && !is_parallelCapable(lockObject)), "unexpected double_lock_wait");
 550   ObjectSynchronizer::notifyall(lockObject, THREAD);
 551   intptr_t recursions =  ObjectSynchronizer::complete_exit(lockObject, THREAD);
 552   SystemDictionary_lock->wait();
 553   SystemDictionary_lock->unlock();
 554   ObjectSynchronizer::reenter(lockObject, recursions, THREAD);
 555   SystemDictionary_lock->lock();
 556 }
 557 
 558 // If the class in is in the placeholder table, class loading is in progress
 559 // For cases where the application changes threads to load classes, it
 560 // is critical to ClassCircularity detection that we try loading
 561 // the superclass on the same thread internally, so we do parallel
 562 // super class loading here.
 563 // This also is critical in cases where the original thread gets stalled
 564 // even in non-circularity situations.
 565 // Note: must call resolve_super_or_fail even if null super -
 566 // to force placeholder entry creation for this class for circularity detection
 567 // Caller must check for pending exception
 568 // Returns non-null Klass* if other thread has completed load
 569 // and we are done,
 570 // If return null Klass* and no pending exception, the caller must load the class
 571 InstanceKlass* SystemDictionary::handle_parallel_super_load(
 572     Symbol* name, Symbol* superclassname, Handle class_loader,
 573     Handle protection_domain, Handle lockObject, TRAPS) {
 574 
 575   ClassLoaderData* loader_data = class_loader_data(class_loader);
 576   Dictionary* dictionary = loader_data->dictionary();
 577   unsigned int d_hash = dictionary->compute_hash(name);
 578   unsigned int p_hash = placeholders()->compute_hash(name);
 579   int p_index = placeholders()->hash_to_index(p_hash);
 580 
 581   // superk is not used, resolve_super called for circularity check only
 582   // This code is reached in two situations. One if this thread
 583   // is loading the same class twice (e.g. ClassCircularity, or
 584   // java.lang.instrument).
 585   // The second is if another thread started the resolve_super first
 586   // and has not yet finished.
 587   // In both cases the original caller will clean up the placeholder
 588   // entry on error.
 589   Klass* superk = SystemDictionary::resolve_super_or_fail(name,
 590                                                           superclassname,
 591                                                           class_loader,
 592                                                           protection_domain,
 593                                                           true,
 594                                                           CHECK_NULL);
 595 
 596   // parallelCapable class loaders do NOT wait for parallel superclass loads to complete
 597   // Serial class loaders and bootstrap classloader do wait for superclass loads
 598  if (!class_loader.is_null() && is_parallelCapable(class_loader)) {
 599     MutexLocker mu(SystemDictionary_lock, THREAD);
 600     // Check if classloading completed while we were loading superclass or waiting
 601     return find_class(d_hash, name, dictionary);
 602   }
 603 
 604   // must loop to both handle other placeholder updates
 605   // and spurious notifications
 606   bool super_load_in_progress = true;
 607   PlaceholderEntry* placeholder;
 608   while (super_load_in_progress) {
 609     MutexLocker mu(SystemDictionary_lock, THREAD);
 610     // Check if classloading completed while we were loading superclass or waiting
 611     InstanceKlass* check = find_class(d_hash, name, dictionary);
 612     if (check != NULL) {
 613       // Klass is already loaded, so just return it
 614       return check;
 615     } else {
 616       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 617       if (placeholder && placeholder->super_load_in_progress() ){
 618         // We only get here if the application has released the
 619         // classloader lock when another thread was in the middle of loading a
 620         // superclass/superinterface for this class, and now
 621         // this thread is also trying to load this class.
 622         // To minimize surprises, the first thread that started to
 623         // load a class should be the one to complete the loading
 624         // with the classfile it initially expected.
 625         // This logic has the current thread wait once it has done
 626         // all the superclass/superinterface loading it can, until
 627         // the original thread completes the class loading or fails
 628         // If it completes we will use the resulting InstanceKlass
 629         // which we will find below in the systemDictionary.
 630         // We also get here for parallel bootstrap classloader
 631         if (class_loader.is_null()) {
 632           SystemDictionary_lock->wait();
 633         } else {
 634           double_lock_wait(lockObject, THREAD);
 635         }
 636       } else {
 637         // If not in SD and not in PH, other thread's load must have failed
 638         super_load_in_progress = false;
 639       }
 640     }
 641   }
 642   return NULL;
 643 }
 644 
 645 static void post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
 646   assert(event != NULL, "invariant");
 647   assert(k != NULL, "invariant");
 648   assert(event->should_commit(), "invariant");
 649   event->set_loadedClass(k);
 650   event->set_definingClassLoader(k->class_loader_data());
 651   event->set_initiatingClassLoader(init_cld);
 652   event->commit();
 653 }
 654 
 655 
 656 // Be careful when modifying this code: once you have run
 657 // placeholders()->find_and_add(PlaceholderTable::LOAD_INSTANCE),
 658 // you need to find_and_remove it before returning.
 659 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 660 //
 661 // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;"
 662 InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name,
 663                                                                 Handle class_loader,
 664                                                                 Handle protection_domain,
 665                                                                 TRAPS) {
 666   assert(name != NULL && !FieldType::is_array(name) &&
 667          !FieldType::is_obj(name), "invalid class name");
 668 
 669   EventClassLoad class_load_start_event;
 670 
 671   HandleMark hm(THREAD);
 672 
 673   // Fix for 4474172; see evaluation for more details
 674   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 675   ClassLoaderData* loader_data = register_loader(class_loader);
 676   Dictionary* dictionary = loader_data->dictionary();
 677   unsigned int d_hash = dictionary->compute_hash(name);
 678 
 679   // Do lookup to see if class already exist and the protection domain
 680   // has the right access
 681   // This call uses find which checks protection domain already matches
 682   // All subsequent calls use find_class, and set has_loaded_class so that
 683   // before we return a result we call out to java to check for valid protection domain
 684   // to allow returning the Klass* and add it to the pd_set if it is valid
 685   {
 686     InstanceKlass* probe = dictionary->find(d_hash, name, protection_domain);
 687     if (probe != NULL) return probe;
 688   }
 689 
 690   // Non-bootstrap class loaders will call out to class loader and
 691   // define via jvm/jni_DefineClass which will acquire the
 692   // class loader object lock to protect against multiple threads
 693   // defining the class in parallel by accident.
 694   // This lock must be acquired here so the waiter will find
 695   // any successful result in the SystemDictionary and not attempt
 696   // the define.
 697   // ParallelCapable Classloaders and the bootstrap classloader
 698   // do not acquire lock here.
 699   bool DoObjectLock = true;
 700   if (is_parallelCapable(class_loader)) {
 701     DoObjectLock = false;
 702   }
 703 
 704   unsigned int p_hash = placeholders()->compute_hash(name);
 705   int p_index = placeholders()->hash_to_index(p_hash);
 706 
 707   // Class is not in SystemDictionary so we have to do loading.
 708   // Make sure we are synchronized on the class loader before we proceed
 709   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
 710   check_loader_lock_contention(lockObject, THREAD);
 711   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
 712 
 713   // Check again (after locking) if class already exist in SystemDictionary
 714   bool class_has_been_loaded   = false;
 715   bool super_load_in_progress  = false;
 716   bool havesupername = false;
 717   InstanceKlass* k = NULL;
 718   PlaceholderEntry* placeholder;
 719   Symbol* superclassname = NULL;
 720 
 721   assert(THREAD->can_call_java(),
 722          "can not load classes with compiler thread: class=%s, classloader=%s",
 723          name->as_C_string(),
 724          class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string());
 725   {
 726     MutexLocker mu(SystemDictionary_lock, THREAD);
 727     InstanceKlass* check = find_class(d_hash, name, dictionary);
 728     if (check != NULL) {
 729       // InstanceKlass is already loaded, so just return it
 730       class_has_been_loaded = true;
 731       k = check;
 732     } else {
 733       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 734       if (placeholder && placeholder->super_load_in_progress()) {
 735          super_load_in_progress = true;
 736          if (placeholder->havesupername() == true) {
 737            superclassname = placeholder->supername();
 738            havesupername = true;
 739          }
 740       }
 741     }
 742   }
 743 
 744   // If the class is in the placeholder table, class loading is in progress
 745   if (super_load_in_progress && havesupername==true) {
 746     k = handle_parallel_super_load(name,
 747                                    superclassname,
 748                                    class_loader,
 749                                    protection_domain,
 750                                    lockObject, THREAD);
 751     if (HAS_PENDING_EXCEPTION) {
 752       return NULL;
 753     }
 754     if (k != NULL) {
 755       class_has_been_loaded = true;
 756     }
 757   }
 758 
 759   bool throw_circularity_error = false;
 760   if (!class_has_been_loaded) {
 761     bool load_instance_added = false;
 762 
 763     // add placeholder entry to record loading instance class
 764     // Five cases:
 765     // All cases need to prevent modifying bootclasssearchpath
 766     // in parallel with a classload of same classname
 767     // Redefineclasses uses existence of the placeholder for the duration
 768     // of the class load to prevent concurrent redefinition of not completely
 769     // defined classes.
 770     // case 1. traditional classloaders that rely on the classloader object lock
 771     //   - no other need for LOAD_INSTANCE
 772     // case 2. traditional classloaders that break the classloader object lock
 773     //    as a deadlock workaround. Detection of this case requires that
 774     //    this check is done while holding the classloader object lock,
 775     //    and that lock is still held when calling classloader's loadClass.
 776     //    For these classloaders, we ensure that the first requestor
 777     //    completes the load and other requestors wait for completion.
 778     // case 3. Bootstrap classloader - don't own objectLocker
 779     //    This classloader supports parallelism at the classloader level,
 780     //    but only allows a single load of a class/classloader pair.
 781     //    No performance benefit and no deadlock issues.
 782     // case 4. parallelCapable user level classloaders - without objectLocker
 783     //    Allow parallel classloading of a class/classloader pair
 784 
 785     {
 786       MutexLocker mu(SystemDictionary_lock, THREAD);
 787       if (class_loader.is_null() || !is_parallelCapable(class_loader)) {
 788         PlaceholderEntry* oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 789         if (oldprobe) {
 790           // only need check_seen_thread once, not on each loop
 791           // 6341374 java/lang/Instrument with -Xcomp
 792           if (oldprobe->check_seen_thread(THREAD, PlaceholderTable::LOAD_INSTANCE)) {
 793             throw_circularity_error = true;
 794           } else {
 795             // case 1: traditional: should never see load_in_progress.
 796             while (!class_has_been_loaded && oldprobe && oldprobe->instance_load_in_progress()) {
 797 
 798               // case 3: bootstrap classloader: prevent futile classloading,
 799               // wait on first requestor
 800               if (class_loader.is_null()) {
 801                 SystemDictionary_lock->wait();
 802               } else {
 803               // case 2: traditional with broken classloader lock. wait on first
 804               // requestor.
 805                 double_lock_wait(lockObject, THREAD);
 806               }
 807               // Check if classloading completed while we were waiting
 808               InstanceKlass* check = find_class(d_hash, name, dictionary);
 809               if (check != NULL) {
 810                 // Klass is already loaded, so just return it
 811                 k = check;
 812                 class_has_been_loaded = true;
 813               }
 814               // check if other thread failed to load and cleaned up
 815               oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 816             }
 817           }
 818         }
 819       }
 820       // All cases: add LOAD_INSTANCE holding SystemDictionary_lock
 821       // case 4: parallelCapable: allow competing threads to try
 822       // LOAD_INSTANCE in parallel
 823 
 824       if (!throw_circularity_error && !class_has_been_loaded) {
 825         PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, NULL, THREAD);
 826         load_instance_added = true;
 827         // For class loaders that do not acquire the classloader object lock,
 828         // if they did not catch another thread holding LOAD_INSTANCE,
 829         // need a check analogous to the acquire ObjectLocker/find_class
 830         // i.e. now that we hold the LOAD_INSTANCE token on loading this class/CL
 831         // one final check if the load has already completed
 832         // class loaders holding the ObjectLock shouldn't find the class here
 833         InstanceKlass* check = find_class(d_hash, name, dictionary);
 834         if (check != NULL) {
 835         // Klass is already loaded, so return it after checking/adding protection domain
 836           k = check;
 837           class_has_been_loaded = true;
 838         }
 839       }
 840     }
 841 
 842     // must throw error outside of owning lock
 843     if (throw_circularity_error) {
 844       assert(!HAS_PENDING_EXCEPTION && load_instance_added == false,"circularity error cleanup");
 845       ResourceMark rm(THREAD);
 846       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string());
 847     }
 848 
 849     if (!class_has_been_loaded) {
 850 
 851       // Do actual loading
 852       k = load_instance_class(name, class_loader, THREAD);
 853 
 854       // If everything was OK (no exceptions, no null return value), and
 855       // class_loader is NOT the defining loader, do a little more bookkeeping.
 856       if (!HAS_PENDING_EXCEPTION && k != NULL &&
 857         !oopDesc::equals(k->class_loader(), class_loader())) {
 858 
 859         check_constraints(d_hash, k, class_loader, false, THREAD);
 860 
 861         // Need to check for a PENDING_EXCEPTION again; check_constraints
 862         // can throw and doesn't use the CHECK macro.
 863         if (!HAS_PENDING_EXCEPTION) {
 864           { // Grabbing the Compile_lock prevents systemDictionary updates
 865             // during compilations.
 866             MutexLocker mu(Compile_lock, THREAD);
 867             update_dictionary(d_hash, p_index, p_hash,
 868               k, class_loader, THREAD);
 869           }
 870 
 871           if (JvmtiExport::should_post_class_load()) {
 872             Thread *thread = THREAD;
 873             assert(thread->is_Java_thread(), "thread->is_Java_thread()");
 874             JvmtiExport::post_class_load((JavaThread *) thread, k);
 875           }
 876         }
 877       }
 878     } // load_instance_class
 879 
 880     if (load_instance_added == true) {
 881       // clean up placeholder entries for LOAD_INSTANCE success or error
 882       // This brackets the SystemDictionary updates for both defining
 883       // and initiating loaders
 884       MutexLocker mu(SystemDictionary_lock, THREAD);
 885       placeholders()->find_and_remove(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD);
 886       SystemDictionary_lock->notify_all();
 887     }
 888   }
 889 
 890   if (HAS_PENDING_EXCEPTION || k == NULL) {
 891     return NULL;
 892   }
 893   if (class_load_start_event.should_commit()) {
 894     post_class_load_event(&class_load_start_event, k, loader_data);
 895   }
 896 #ifdef ASSERT
 897   {
 898     ClassLoaderData* loader_data = k->class_loader_data();
 899     MutexLocker mu(SystemDictionary_lock, THREAD);
 900     InstanceKlass* kk = find_class(name, loader_data);
 901     assert(kk == k, "should be present in dictionary");
 902   }
 903 #endif
 904 
 905   // return if the protection domain in NULL
 906   if (protection_domain() == NULL) return k;
 907 
 908   // Check the protection domain has the right access
 909   if (dictionary->is_valid_protection_domain(d_hash, name,
 910                                              protection_domain)) {
 911     return k;
 912   }
 913 
 914   // Verify protection domain. If it fails an exception is thrown
 915   validate_protection_domain(k, class_loader, protection_domain, CHECK_NULL);
 916 
 917   return k;
 918 }
 919 
 920 
 921 // This routine does not lock the system dictionary.
 922 //
 923 // Since readers don't hold a lock, we must make sure that system
 924 // dictionary entries are only removed at a safepoint (when only one
 925 // thread is running), and are added to in a safe way (all links must
 926 // be updated in an MT-safe manner).
 927 //
 928 // Callers should be aware that an entry could be added just after
 929 // _dictionary->bucket(index) is read here, so the caller will not see
 930 // the new entry.
 931 
 932 Klass* SystemDictionary::find(Symbol* class_name,
 933                               Handle class_loader,
 934                               Handle protection_domain,
 935                               TRAPS) {
 936 
 937   // The result of this call should be consistent with the result
 938   // of the call to resolve_instance_class_or_null().
 939   // See evaluation 6790209 and 4474172 for more details.
 940   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 941   ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
 942 
 943   if (loader_data == NULL) {
 944     // If the ClassLoaderData has not been setup,
 945     // then the class loader has no entries in the dictionary.
 946     return NULL;
 947   }
 948 
 949   Dictionary* dictionary = loader_data->dictionary();
 950   unsigned int d_hash = dictionary->compute_hash(class_name);
 951   return dictionary->find(d_hash, class_name,
 952                           protection_domain);
 953 }
 954 
 955 
 956 // Look for a loaded instance or array klass by name.  Do not do any loading.
 957 // return NULL in case of error.
 958 Klass* SystemDictionary::find_instance_or_array_klass(Symbol* class_name,
 959                                                       Handle class_loader,
 960                                                       Handle protection_domain,
 961                                                       TRAPS) {
 962   Klass* k = NULL;
 963   assert(class_name != NULL, "class name must be non NULL");
 964 
 965   if (FieldType::is_array(class_name)) {
 966     // The name refers to an array.  Parse the name.
 967     // dimension and object_key in FieldArrayInfo are assigned as a
 968     // side-effect of this call
 969     FieldArrayInfo fd;
 970     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
 971     if (t != T_OBJECT) {
 972       k = Universe::typeArrayKlassObj(t);
 973     } else {
 974       k = SystemDictionary::find(fd.object_key(), class_loader, protection_domain, THREAD);
 975     }
 976     if (k != NULL) {
 977       k = k->array_klass_or_null(fd.dimension());
 978     }
 979   } else {
 980     k = find(class_name, class_loader, protection_domain, THREAD);
 981   }
 982   return k;
 983 }
 984 
 985 // Note: this method is much like resolve_from_stream, but
 986 // does not publish the classes via the SystemDictionary.
 987 // Handles unsafe_DefineAnonymousClass and redefineclasses
 988 // RedefinedClasses do not add to the class hierarchy
 989 InstanceKlass* SystemDictionary::parse_stream(Symbol* class_name,
 990                                               Handle class_loader,
 991                                               Handle protection_domain,
 992                                               ClassFileStream* st,
 993                                               const InstanceKlass* unsafe_anonymous_host,
 994                                               GrowableArray<Handle>* cp_patches,
 995                                               TRAPS) {
 996 
 997   EventClassLoad class_load_start_event;
 998 
 999   ClassLoaderData* loader_data;
1000   if (unsafe_anonymous_host != NULL) {
1001     // Create a new CLD for an unsafe anonymous class, that uses the same class loader
1002     // as the unsafe_anonymous_host
1003     guarantee(oopDesc::equals(unsafe_anonymous_host->class_loader(), class_loader()), "should be the same");
1004     loader_data = ClassLoaderData::unsafe_anonymous_class_loader_data(class_loader);
1005   } else {
1006     loader_data = ClassLoaderData::class_loader_data(class_loader());
1007   }
1008 
1009   assert(st != NULL, "invariant");
1010   assert(st->need_verify(), "invariant");
1011 
1012   // Parse stream and create a klass.
1013   // Note that we do this even though this klass might
1014   // already be present in the SystemDictionary, otherwise we would not
1015   // throw potential ClassFormatErrors.
1016 
1017   InstanceKlass* k = KlassFactory::create_from_stream(st,
1018                                                       class_name,
1019                                                       loader_data,
1020                                                       protection_domain,
1021                                                       unsafe_anonymous_host,
1022                                                       cp_patches,
1023                                                       CHECK_NULL);
1024 
1025   if (unsafe_anonymous_host != NULL && k != NULL) {
1026     // Unsafe anonymous classes must update ClassLoaderData holder (was unsafe_anonymous_host loader)
1027     // so that they can be unloaded when the mirror is no longer referenced.
1028     k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror()));
1029 
1030     {
1031       MutexLocker mu_r(Compile_lock, THREAD);
1032 
1033       // Add to class hierarchy, initialize vtables, and do possible
1034       // deoptimizations.
1035       add_to_hierarchy(k, CHECK_NULL); // No exception, but can block
1036 
1037       // But, do not add to dictionary.
1038 
1039       // compiled code dependencies need to be validated anyway
1040       notice_modification();
1041     }
1042 
1043     // Rewrite and patch constant pool here.
1044     k->link_class(CHECK_NULL);
1045     if (cp_patches != NULL) {
1046       k->constants()->patch_resolved_references(cp_patches);
1047     }
1048 
1049     // If it's anonymous, initialize it now, since nobody else will.
1050     k->eager_initialize(CHECK_NULL);
1051 
1052     // notify jvmti
1053     if (JvmtiExport::should_post_class_load()) {
1054         assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1055         JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1056     }
1057     if (class_load_start_event.should_commit()) {
1058       post_class_load_event(&class_load_start_event, k, loader_data);
1059     }
1060   }
1061   assert(unsafe_anonymous_host != NULL || NULL == cp_patches,
1062          "cp_patches only found with unsafe_anonymous_host");
1063 
1064   return k;
1065 }
1066 
1067 // Add a klass to the system from a stream (called by jni_DefineClass and
1068 // JVM_DefineClass).
1069 // Note: class_name can be NULL. In that case we do not know the name of
1070 // the class until we have parsed the stream.
1071 
1072 InstanceKlass* SystemDictionary::resolve_from_stream(Symbol* class_name,
1073                                                      Handle class_loader,
1074                                                      Handle protection_domain,
1075                                                      ClassFileStream* st,
1076                                                      TRAPS) {
1077 
1078   HandleMark hm(THREAD);
1079 
1080   // Classloaders that support parallelism, e.g. bootstrap classloader,
1081   // do not acquire lock here
1082   bool DoObjectLock = true;
1083   if (is_parallelCapable(class_loader)) {
1084     DoObjectLock = false;
1085   }
1086 
1087   ClassLoaderData* loader_data = register_loader(class_loader);
1088 
1089   // Make sure we are synchronized on the class loader before we proceed
1090   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
1091   check_loader_lock_contention(lockObject, THREAD);
1092   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
1093 
1094   assert(st != NULL, "invariant");
1095 
1096   // Parse the stream and create a klass.
1097   // Note that we do this even though this klass might
1098   // already be present in the SystemDictionary, otherwise we would not
1099   // throw potential ClassFormatErrors.
1100  InstanceKlass* k = NULL;
1101 
1102 #if INCLUDE_CDS
1103   if (!DumpSharedSpaces) {
1104     k = SystemDictionaryShared::lookup_from_stream(class_name,
1105                                                    class_loader,
1106                                                    protection_domain,
1107                                                    st,
1108                                                    CHECK_NULL);
1109   }
1110 #endif
1111 
1112   if (k == NULL) {
1113     if (st->buffer() == NULL) {
1114       return NULL;
1115     }
1116     k = KlassFactory::create_from_stream(st,
1117                                          class_name,
1118                                          loader_data,
1119                                          protection_domain,
1120                                          NULL, // unsafe_anonymous_host
1121                                          NULL, // cp_patches
1122                                          CHECK_NULL);
1123   }
1124 
1125   assert(k != NULL, "no klass created");
1126   Symbol* h_name = k->name();
1127   assert(class_name == NULL || class_name == h_name, "name mismatch");
1128 
1129   // Add class just loaded
1130   // If a class loader supports parallel classloading handle parallel define requests
1131   // find_or_define_instance_class may return a different InstanceKlass
1132   if (is_parallelCapable(class_loader)) {
1133     InstanceKlass* defined_k = find_or_define_instance_class(h_name, class_loader, k, THREAD);
1134     if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1135       // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1136       assert(defined_k != NULL, "Should have a klass if there's no exception");
1137       loader_data->add_to_deallocate_list(k);
1138       k = defined_k;
1139     }
1140   } else {
1141     define_instance_class(k, THREAD);
1142   }
1143 
1144   // If defining the class throws an exception register 'k' for cleanup.
1145   if (HAS_PENDING_EXCEPTION) {
1146     assert(k != NULL, "Must have an instance klass here!");
1147     loader_data->add_to_deallocate_list(k);
1148     return NULL;
1149   }
1150 
1151   // Make sure we have an entry in the SystemDictionary on success
1152   debug_only( {
1153     MutexLocker mu(SystemDictionary_lock, THREAD);
1154 
1155     Klass* check = find_class(h_name, k->class_loader_data());
1156     assert(check == k, "should be present in the dictionary");
1157   } );
1158 
1159   return k;
1160 }
1161 
1162 #if INCLUDE_CDS
1163 void SystemDictionary::set_shared_dictionary(HashtableBucket<mtClass>* t, int length,
1164                                              int number_of_entries) {
1165   assert(length == _shared_dictionary_size * sizeof(HashtableBucket<mtClass>),
1166          "bad shared dictionary size.");
1167   _shared_dictionary = new Dictionary(ClassLoaderData::the_null_class_loader_data(),
1168                                       _shared_dictionary_size, t, number_of_entries);
1169 }
1170 
1171 
1172 // If there is a shared dictionary, then find the entry for the
1173 // given shared system class, if any.
1174 
1175 InstanceKlass* SystemDictionary::find_shared_class(Symbol* class_name) {
1176   if (shared_dictionary() != NULL) {
1177     unsigned int d_hash = shared_dictionary()->compute_hash(class_name);
1178     int d_index = shared_dictionary()->hash_to_index(d_hash);
1179 
1180     return shared_dictionary()->find_shared_class(d_index, d_hash, class_name);
1181   } else {
1182     return NULL;
1183   }
1184 }
1185 
1186 
1187 // Load a class from the shared spaces (found through the shared system
1188 // dictionary).  Force the superclass and all interfaces to be loaded.
1189 // Update the class definition to include sibling classes and no
1190 // subclasses (yet).  [Classes in the shared space are not part of the
1191 // object hierarchy until loaded.]
1192 
1193 InstanceKlass* SystemDictionary::load_shared_class(
1194                  Symbol* class_name, Handle class_loader, TRAPS) {
1195   InstanceKlass* ik = find_shared_class(class_name);
1196   // Make sure we only return the boot class for the NULL classloader.
1197   if (ik != NULL &&
1198       ik->is_shared_boot_class() && class_loader.is_null()) {
1199     Handle protection_domain;
1200     return load_shared_class(ik, class_loader, protection_domain, THREAD);
1201   }
1202   return NULL;
1203 }
1204 
1205 // Check if a shared class can be loaded by the specific classloader:
1206 //
1207 // NULL classloader:
1208 //   - Module class from "modules" jimage. ModuleEntry must be defined in the classloader.
1209 //   - Class from -Xbootclasspath/a. The class has no defined PackageEntry, or must
1210 //     be defined in an unnamed module.
1211 bool SystemDictionary::is_shared_class_visible(Symbol* class_name,
1212                                                InstanceKlass* ik,
1213                                                Handle class_loader, TRAPS) {
1214   assert(!ModuleEntryTable::javabase_moduleEntry()->is_patched(),
1215          "Cannot use sharing if java.base is patched");
1216   ResourceMark rm;
1217   int path_index = ik->shared_classpath_index();
1218   ClassLoaderData* loader_data = class_loader_data(class_loader);
1219   if (path_index < 0) {
1220     // path_index < 0 indicates that the class is intended for a custom loader
1221     // and should not be loaded by boot/platform/app loaders
1222     if (loader_data->is_builtin_class_loader_data()) {
1223       return false;
1224     } else {
1225       return true;
1226     }
1227   }
1228   SharedClassPathEntry* ent =
1229             (SharedClassPathEntry*)FileMapInfo::shared_path(path_index);
1230   if (!Universe::is_module_initialized()) {
1231     assert(ent != NULL && ent->is_modules_image(),
1232            "Loading non-bootstrap classes before the module system is initialized");
1233     assert(class_loader.is_null(), "sanity");
1234     return true;
1235   }
1236   // Get the pkg_entry from the classloader
1237   TempNewSymbol pkg_name = NULL;
1238   PackageEntry* pkg_entry = NULL;
1239   ModuleEntry* mod_entry = NULL;
1240   const char* pkg_string = NULL;
1241   pkg_name = InstanceKlass::package_from_name(class_name, CHECK_false);
1242   if (pkg_name != NULL) {
1243     pkg_string = pkg_name->as_C_string();
1244     if (loader_data != NULL) {
1245       pkg_entry = loader_data->packages()->lookup_only(pkg_name);
1246     }
1247     if (pkg_entry != NULL) {
1248       mod_entry = pkg_entry->module();
1249     }
1250   }
1251 
1252   // If the archived class is from a module that has been patched at runtime,
1253   // the class cannot be loaded from the archive.
1254   if (mod_entry != NULL && mod_entry->is_patched()) {
1255     return false;
1256   }
1257 
1258   if (class_loader.is_null()) {
1259     assert(ent != NULL, "Shared class for NULL classloader must have valid SharedClassPathEntry");
1260     // The NULL classloader can load archived class originated from the
1261     // "modules" jimage and the -Xbootclasspath/a. For class from the
1262     // "modules" jimage, the PackageEntry/ModuleEntry must be defined
1263     // by the NULL classloader.
1264     if (mod_entry != NULL) {
1265       // PackageEntry/ModuleEntry is found in the classloader. Check if the
1266       // ModuleEntry's location agrees with the archived class' origination.
1267       if (ent->is_modules_image() && mod_entry->location()->starts_with("jrt:")) {
1268         return true; // Module class from the "module" jimage
1269       }
1270     }
1271 
1272     // If the archived class is not from the "module" jimage, the class can be
1273     // loaded by the NULL classloader if
1274     //
1275     // 1. the class is from the unamed package
1276     // 2. or, the class is not from a module defined in the NULL classloader
1277     // 3. or, the class is from an unamed module
1278     if (!ent->is_modules_image() && ik->is_shared_boot_class()) {
1279       // the class is from the -Xbootclasspath/a
1280       if (pkg_string == NULL ||
1281           pkg_entry == NULL ||
1282           pkg_entry->in_unnamed_module()) {
1283         assert(mod_entry == NULL ||
1284                mod_entry == loader_data->unnamed_module(),
1285                "the unnamed module is not defined in the classloader");
1286         return true;
1287       }
1288     }
1289     return false;
1290   } else {
1291     bool res = SystemDictionaryShared::is_shared_class_visible_for_classloader(
1292               ik, class_loader, pkg_string, pkg_name,
1293               pkg_entry, mod_entry, CHECK_(false));
1294     return res;
1295   }
1296 }
1297 
1298 InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik,
1299                                                    Handle class_loader,
1300                                                    Handle protection_domain, TRAPS) {
1301 
1302   if (ik != NULL) {
1303     Symbol* class_name = ik->name();
1304 
1305     bool visible = is_shared_class_visible(
1306                             class_name, ik, class_loader, CHECK_NULL);
1307     if (!visible) {
1308       return NULL;
1309     }
1310 
1311     // Resolve the superclass and interfaces. They must be the same
1312     // as in dump time, because the layout of <ik> depends on
1313     // the specific layout of ik->super() and ik->local_interfaces().
1314     //
1315     // If unexpected superclass or interfaces are found, we cannot
1316     // load <ik> from the shared archive.
1317 
1318     if (ik->super() != NULL) {
1319       Symbol*  cn = ik->super()->name();
1320       Klass *s = resolve_super_or_fail(class_name, cn,
1321                                        class_loader, protection_domain, true, CHECK_NULL);
1322       if (s != ik->super()) {
1323         // The dynamically resolved super class is not the same as the one we used during dump time,
1324         // so we cannot use ik.
1325         return NULL;
1326       } else {
1327         assert(s->is_shared(), "must be");
1328       }
1329     }
1330 
1331     Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1332     int num_interfaces = interfaces->length();
1333     for (int index = 0; index < num_interfaces; index++) {
1334       InstanceKlass* k = interfaces->at(index);
1335       Symbol* name  = k->name();
1336       Klass* i = resolve_super_or_fail(class_name, name, class_loader, protection_domain, false, CHECK_NULL);
1337       if (k != i) {
1338         // The dynamically resolved interface class is not the same as the one we used during dump time,
1339         // so we cannot use ik.
1340         return NULL;
1341       } else {
1342         assert(i->is_shared(), "must be");
1343       }
1344     }
1345 
1346     InstanceKlass* new_ik = KlassFactory::check_shared_class_file_load_hook(
1347         ik, class_name, class_loader, protection_domain, CHECK_NULL);
1348     if (new_ik != NULL) {
1349       // The class is changed by CFLH. Return the new class. The shared class is
1350       // not used.
1351       return new_ik;
1352     }
1353 
1354     // Adjust methods to recover missing data.  They need addresses for
1355     // interpreter entry points and their default native method address
1356     // must be reset.
1357 
1358     // Updating methods must be done under a lock so multiple
1359     // threads don't update these in parallel
1360     //
1361     // Shared classes are all currently loaded by either the bootstrap or
1362     // internal parallel class loaders, so this will never cause a deadlock
1363     // on a custom class loader lock.
1364 
1365     ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(class_loader());
1366     {
1367       HandleMark hm(THREAD);
1368       Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
1369       check_loader_lock_contention(lockObject, THREAD);
1370       ObjectLocker ol(lockObject, THREAD, true);
1371       // prohibited package check assumes all classes loaded from archive call
1372       // restore_unshareable_info which calls ik->set_package()
1373       ik->restore_unshareable_info(loader_data, protection_domain, CHECK_NULL);
1374     }
1375 
1376     ik->print_class_load_logging(loader_data, NULL, NULL);
1377 
1378     // For boot loader, ensure that GetSystemPackage knows that a class in this
1379     // package was loaded.
1380     if (class_loader.is_null()) {
1381       int path_index = ik->shared_classpath_index();
1382       ResourceMark rm;
1383       ClassLoader::add_package(ik->name()->as_C_string(), path_index, THREAD);
1384     }
1385 
1386     if (DumpLoadedClassList != NULL && classlist_file->is_open()) {
1387       // Only dump the classes that can be stored into CDS archive
1388       if (SystemDictionaryShared::is_sharing_possible(loader_data)) {
1389         ResourceMark rm(THREAD);
1390         classlist_file->print_cr("%s", ik->name()->as_C_string());
1391         classlist_file->flush();
1392       }
1393     }
1394 
1395     // notify a class loaded from shared object
1396     ClassLoadingService::notify_class_loaded(ik, true /* shared class */);
1397 
1398     ik->set_has_passed_fingerprint_check(false);
1399     if (UseAOT && ik->supers_have_passed_fingerprint_checks()) {
1400       uint64_t aot_fp = AOTLoader::get_saved_fingerprint(ik);
1401       uint64_t cds_fp = ik->get_stored_fingerprint();
1402       if (aot_fp != 0 && aot_fp == cds_fp) {
1403         // This class matches with a class saved in an AOT library
1404         ik->set_has_passed_fingerprint_check(true);
1405       } else {
1406         ResourceMark rm;
1407         log_info(class, fingerprint)("%s :  expected = " PTR64_FORMAT " actual = " PTR64_FORMAT, ik->external_name(), aot_fp, cds_fp);
1408       }
1409     }
1410   }
1411   return ik;
1412 }
1413 
1414 void SystemDictionary::clear_invoke_method_table() {
1415   SymbolPropertyEntry* spe = NULL;
1416   for (int index = 0; index < _invoke_method_table->table_size(); index++) {
1417     SymbolPropertyEntry* p = _invoke_method_table->bucket(index);
1418     while (p != NULL) {
1419       spe = p;
1420       p = p->next();
1421       _invoke_method_table->free_entry(spe);
1422     }
1423   }
1424 }
1425 #endif // INCLUDE_CDS
1426 
1427 InstanceKlass* SystemDictionary::load_instance_class(Symbol* class_name, Handle class_loader, TRAPS) {
1428 
1429   if (class_loader.is_null()) {
1430     ResourceMark rm;
1431     PackageEntry* pkg_entry = NULL;
1432     bool search_only_bootloader_append = false;
1433     ClassLoaderData *loader_data = class_loader_data(class_loader);
1434 
1435     // Find the package in the boot loader's package entry table.
1436     TempNewSymbol pkg_name = InstanceKlass::package_from_name(class_name, CHECK_NULL);
1437     if (pkg_name != NULL) {
1438       pkg_entry = loader_data->packages()->lookup_only(pkg_name);
1439     }
1440 
1441     // Prior to attempting to load the class, enforce the boot loader's
1442     // visibility boundaries.
1443     if (!Universe::is_module_initialized()) {
1444       // During bootstrapping, prior to module initialization, any
1445       // class attempting to be loaded must be checked against the
1446       // java.base packages in the boot loader's PackageEntryTable.
1447       // No class outside of java.base is allowed to be loaded during
1448       // this bootstrapping window.
1449       if (pkg_entry == NULL || pkg_entry->in_unnamed_module()) {
1450         // Class is either in the unnamed package or in
1451         // a named package within the unnamed module.  Either
1452         // case is outside of java.base, do not attempt to
1453         // load the class post java.base definition.  If
1454         // java.base has not been defined, let the class load
1455         // and its package will be checked later by
1456         // ModuleEntryTable::verify_javabase_packages.
1457         if (ModuleEntryTable::javabase_defined()) {
1458           return NULL;
1459         }
1460       } else {
1461         // Check that the class' package is defined within java.base.
1462         ModuleEntry* mod_entry = pkg_entry->module();
1463         Symbol* mod_entry_name = mod_entry->name();
1464         if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) {
1465           return NULL;
1466         }
1467       }
1468     } else {
1469       // After the module system has been initialized, check if the class'
1470       // package is in a module defined to the boot loader.
1471       if (pkg_name == NULL || pkg_entry == NULL || pkg_entry->in_unnamed_module()) {
1472         // Class is either in the unnamed package, in a named package
1473         // within a module not defined to the boot loader or in a
1474         // a named package within the unnamed module.  In all cases,
1475         // limit visibility to search for the class only in the boot
1476         // loader's append path.
1477         search_only_bootloader_append = true;
1478       }
1479     }
1480 
1481     // Prior to bootstrapping's module initialization, never load a class outside
1482     // of the boot loader's module path
1483     assert(Universe::is_module_initialized() ||
1484            !search_only_bootloader_append,
1485            "Attempt to load a class outside of boot loader's module path");
1486 
1487     // Search the shared system dictionary for classes preloaded into the
1488     // shared spaces.
1489     InstanceKlass* k = NULL;
1490     {
1491 #if INCLUDE_CDS
1492       PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time());
1493       k = load_shared_class(class_name, class_loader, THREAD);
1494 #endif
1495     }
1496 
1497     if (k == NULL) {
1498       // Use VM class loader
1499       PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time());
1500       k = ClassLoader::load_class(class_name, search_only_bootloader_append, CHECK_NULL);
1501     }
1502 
1503     // find_or_define_instance_class may return a different InstanceKlass
1504     if (k != NULL) {
1505       InstanceKlass* defined_k =
1506         find_or_define_instance_class(class_name, class_loader, k, THREAD);
1507       if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1508         // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1509         assert(defined_k != NULL, "Should have a klass if there's no exception");
1510         loader_data->add_to_deallocate_list(k);
1511         k = defined_k;
1512       } else if (HAS_PENDING_EXCEPTION) {
1513         loader_data->add_to_deallocate_list(k);
1514         return NULL;
1515       }
1516     }
1517     return k;
1518   } else {
1519     // Use user specified class loader to load class. Call loadClass operation on class_loader.
1520     ResourceMark rm(THREAD);
1521 
1522     assert(THREAD->is_Java_thread(), "must be a JavaThread");
1523     JavaThread* jt = (JavaThread*) THREAD;
1524 
1525     PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1526                                ClassLoader::perf_app_classload_selftime(),
1527                                ClassLoader::perf_app_classload_count(),
1528                                jt->get_thread_stat()->perf_recursion_counts_addr(),
1529                                jt->get_thread_stat()->perf_timers_addr(),
1530                                PerfClassTraceTime::CLASS_LOAD);
1531 
1532     Handle s = java_lang_String::create_from_symbol(class_name, CHECK_NULL);
1533     // Translate to external class name format, i.e., convert '/' chars to '.'
1534     Handle string = java_lang_String::externalize_classname(s, CHECK_NULL);
1535 
1536     JavaValue result(T_OBJECT);
1537 
1538     InstanceKlass* spec_klass = SystemDictionary::ClassLoader_klass();
1539 
1540     // Call public unsynchronized loadClass(String) directly for all class loaders.
1541     // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1542     // acquire a class-name based lock rather than the class loader object lock.
1543     // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1544     JavaCalls::call_virtual(&result,
1545                             class_loader,
1546                             spec_klass,
1547                             vmSymbols::loadClass_name(),
1548                             vmSymbols::string_class_signature(),
1549                             string,
1550                             CHECK_NULL);
1551 
1552     assert(result.get_type() == T_OBJECT, "just checking");
1553     oop obj = (oop) result.get_jobject();
1554 
1555     // Primitive classes return null since forName() can not be
1556     // used to obtain any of the Class objects representing primitives or void
1557     if ((obj != NULL) && !(java_lang_Class::is_primitive(obj))) {
1558       InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(obj));
1559       // For user defined Java class loaders, check that the name returned is
1560       // the same as that requested.  This check is done for the bootstrap
1561       // loader when parsing the class file.
1562       if (class_name == k->name()) {
1563         return k;
1564       }
1565     }
1566     // Class is not found or has the wrong name, return NULL
1567     return NULL;
1568   }
1569 }
1570 
1571 static void post_class_define_event(InstanceKlass* k, const ClassLoaderData* def_cld) {
1572   EventClassDefine event;
1573   if (event.should_commit()) {
1574     event.set_definedClass(k);
1575     event.set_definingClassLoader(def_cld);
1576     event.commit();
1577   }
1578 }
1579 
1580 void SystemDictionary::define_instance_class(InstanceKlass* k, TRAPS) {
1581 
1582   HandleMark hm(THREAD);
1583   ClassLoaderData* loader_data = k->class_loader_data();
1584   Handle class_loader_h(THREAD, loader_data->class_loader());
1585 
1586  // for bootstrap and other parallel classloaders don't acquire lock,
1587  // use placeholder token
1588  // If a parallelCapable class loader calls define_instance_class instead of
1589  // find_or_define_instance_class to get here, we have a timing
1590  // hole with systemDictionary updates and check_constraints
1591  if (!class_loader_h.is_null() && !is_parallelCapable(class_loader_h)) {
1592     assert(ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD,
1593          compute_loader_lock_object(class_loader_h, THREAD)),
1594          "define called without lock");
1595   }
1596 
1597   // Check class-loading constraints. Throw exception if violation is detected.
1598   // Grabs and releases SystemDictionary_lock
1599   // The check_constraints/find_class call and update_dictionary sequence
1600   // must be "atomic" for a specific class/classloader pair so we never
1601   // define two different instanceKlasses for that class/classloader pair.
1602   // Existing classloaders will call define_instance_class with the
1603   // classloader lock held
1604   // Parallel classloaders will call find_or_define_instance_class
1605   // which will require a token to perform the define class
1606   Symbol*  name_h = k->name();
1607   Dictionary* dictionary = loader_data->dictionary();
1608   unsigned int d_hash = dictionary->compute_hash(name_h);
1609   check_constraints(d_hash, k, class_loader_h, true, CHECK);
1610 
1611   // Register class just loaded with class loader (placed in Vector)
1612   // Note we do this before updating the dictionary, as this can
1613   // fail with an OutOfMemoryError (if it does, we will *not* put this
1614   // class in the dictionary and will not update the class hierarchy).
1615   // JVMTI FollowReferences needs to find the classes this way.
1616   if (k->class_loader() != NULL) {
1617     methodHandle m(THREAD, Universe::loader_addClass_method());
1618     JavaValue result(T_VOID);
1619     JavaCallArguments args(class_loader_h);
1620     args.push_oop(Handle(THREAD, k->java_mirror()));
1621     JavaCalls::call(&result, m, &args, CHECK);
1622   }
1623 
1624   // Add the new class. We need recompile lock during update of CHA.
1625   {
1626     unsigned int p_hash = placeholders()->compute_hash(name_h);
1627     int p_index = placeholders()->hash_to_index(p_hash);
1628 
1629     MutexLocker mu_r(Compile_lock, THREAD);
1630 
1631     // Add to class hierarchy, initialize vtables, and do possible
1632     // deoptimizations.
1633     add_to_hierarchy(k, CHECK); // No exception, but can block
1634 
1635     // Add to systemDictionary - so other classes can see it.
1636     // Grabs and releases SystemDictionary_lock
1637     update_dictionary(d_hash, p_index, p_hash,
1638                       k, class_loader_h, THREAD);
1639   }
1640   k->eager_initialize(THREAD);
1641 
1642   // notify jvmti
1643   if (JvmtiExport::should_post_class_load()) {
1644       assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1645       JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1646 
1647   }
1648   post_class_define_event(k, loader_data);
1649 }
1650 
1651 // Support parallel classloading
1652 // All parallel class loaders, including bootstrap classloader
1653 // lock a placeholder entry for this class/class_loader pair
1654 // to allow parallel defines of different classes for this class loader
1655 // With AllowParallelDefine flag==true, in case they do not synchronize around
1656 // FindLoadedClass/DefineClass, calls, we check for parallel
1657 // loading for them, wait if a defineClass is in progress
1658 // and return the initial requestor's results
1659 // This flag does not apply to the bootstrap classloader.
1660 // With AllowParallelDefine flag==false, call through to define_instance_class
1661 // which will throw LinkageError: duplicate class definition.
1662 // False is the requested default.
1663 // For better performance, the class loaders should synchronize
1664 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1665 // potentially waste time reading and parsing the bytestream.
1666 // Note: VM callers should ensure consistency of k/class_name,class_loader
1667 // Be careful when modifying this code: once you have run
1668 // placeholders()->find_and_add(PlaceholderTable::DEFINE_CLASS),
1669 // you need to find_and_remove it before returning.
1670 // So be careful to not exit with a CHECK_ macro betweeen these calls.
1671 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1672                                                                InstanceKlass* k, TRAPS) {
1673 
1674   Symbol*  name_h = k->name(); // passed in class_name may be null
1675   ClassLoaderData* loader_data = class_loader_data(class_loader);
1676   Dictionary* dictionary = loader_data->dictionary();
1677 
1678   unsigned int d_hash = dictionary->compute_hash(name_h);
1679 
1680   // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1681   unsigned int p_hash = placeholders()->compute_hash(name_h);
1682   int p_index = placeholders()->hash_to_index(p_hash);
1683   PlaceholderEntry* probe;
1684 
1685   {
1686     MutexLocker mu(SystemDictionary_lock, THREAD);
1687     // First check if class already defined
1688     if (is_parallelDefine(class_loader)) {
1689       InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1690       if (check != NULL) {
1691         return check;
1692       }
1693     }
1694 
1695     // Acquire define token for this class/classloader
1696     probe = placeholders()->find_and_add(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, NULL, THREAD);
1697     // Wait if another thread defining in parallel
1698     // All threads wait - even those that will throw duplicate class: otherwise
1699     // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1700     // if other thread has not finished updating dictionary
1701     while (probe->definer() != NULL) {
1702       SystemDictionary_lock->wait();
1703     }
1704     // Only special cases allow parallel defines and can use other thread's results
1705     // Other cases fall through, and may run into duplicate defines
1706     // caught by finding an entry in the SystemDictionary
1707     if (is_parallelDefine(class_loader) && (probe->instance_klass() != NULL)) {
1708         placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1709         SystemDictionary_lock->notify_all();
1710 #ifdef ASSERT
1711         InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1712         assert(check != NULL, "definer missed recording success");
1713 #endif
1714         return probe->instance_klass();
1715     } else {
1716       // This thread will define the class (even if earlier thread tried and had an error)
1717       probe->set_definer(THREAD);
1718     }
1719   }
1720 
1721   define_instance_class(k, THREAD);
1722 
1723   Handle linkage_exception = Handle(); // null handle
1724 
1725   // definer must notify any waiting threads
1726   {
1727     MutexLocker mu(SystemDictionary_lock, THREAD);
1728     PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, name_h, loader_data);
1729     assert(probe != NULL, "DEFINE_CLASS placeholder lost?");
1730     if (probe != NULL) {
1731       if (HAS_PENDING_EXCEPTION) {
1732         linkage_exception = Handle(THREAD,PENDING_EXCEPTION);
1733         CLEAR_PENDING_EXCEPTION;
1734       } else {
1735         probe->set_instance_klass(k);
1736       }
1737       probe->set_definer(NULL);
1738       placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1739       SystemDictionary_lock->notify_all();
1740     }
1741   }
1742 
1743   // Can't throw exception while holding lock due to rank ordering
1744   if (linkage_exception() != NULL) {
1745     THROW_OOP_(linkage_exception(), NULL); // throws exception and returns
1746   }
1747 
1748   return k;
1749 }
1750 
1751 Handle SystemDictionary::compute_loader_lock_object(Handle class_loader, TRAPS) {
1752   // If class_loader is NULL we synchronize on _system_loader_lock_obj
1753   if (class_loader.is_null()) {
1754     return Handle(THREAD, _system_loader_lock_obj);
1755   } else {
1756     return class_loader;
1757   }
1758 }
1759 
1760 // This method is added to check how often we have to wait to grab loader
1761 // lock. The results are being recorded in the performance counters defined in
1762 // ClassLoader::_sync_systemLoaderLockContentionRate and
1763 // ClassLoader::_sync_nonSystemLoaderLockConteionRate.
1764 void SystemDictionary::check_loader_lock_contention(Handle loader_lock, TRAPS) {
1765   if (!UsePerfData) {
1766     return;
1767   }
1768 
1769   assert(!loader_lock.is_null(), "NULL lock object");
1770 
1771   if (ObjectSynchronizer::query_lock_ownership((JavaThread*)THREAD, loader_lock)
1772       == ObjectSynchronizer::owner_other) {
1773     // contention will likely happen, so increment the corresponding
1774     // contention counter.
1775     if (oopDesc::equals(loader_lock(), _system_loader_lock_obj)) {
1776       ClassLoader::sync_systemLoaderLockContentionRate()->inc();
1777     } else {
1778       ClassLoader::sync_nonSystemLoaderLockContentionRate()->inc();
1779     }
1780   }
1781 }
1782 
1783 // ----------------------------------------------------------------------------
1784 // Lookup
1785 
1786 InstanceKlass* SystemDictionary::find_class(unsigned int hash,
1787                                             Symbol* class_name,
1788                                             Dictionary* dictionary) {
1789   assert_locked_or_safepoint(SystemDictionary_lock);
1790   int index = dictionary->hash_to_index(hash);
1791   return dictionary->find_class(index, hash, class_name);
1792 }
1793 
1794 
1795 // Basic find on classes in the midst of being loaded
1796 Symbol* SystemDictionary::find_placeholder(Symbol* class_name,
1797                                            ClassLoaderData* loader_data) {
1798   assert_locked_or_safepoint(SystemDictionary_lock);
1799   unsigned int p_hash = placeholders()->compute_hash(class_name);
1800   int p_index = placeholders()->hash_to_index(p_hash);
1801   return placeholders()->find_entry(p_index, p_hash, class_name, loader_data);
1802 }
1803 
1804 
1805 // Used for assertions and verification only
1806 // Precalculating the hash and index is an optimization because there are many lookups
1807 // before adding the class.
1808 InstanceKlass* SystemDictionary::find_class(Symbol* class_name, ClassLoaderData* loader_data) {
1809   assert_locked_or_safepoint(SystemDictionary_lock);
1810   #ifndef ASSERT
1811   guarantee(VerifyBeforeGC      ||
1812             VerifyDuringGC      ||
1813             VerifyBeforeExit    ||
1814             VerifyDuringStartup ||
1815             VerifyAfterGC, "too expensive");
1816   #endif
1817 
1818   Dictionary* dictionary = loader_data->dictionary();
1819   unsigned int d_hash = dictionary->compute_hash(class_name);
1820   return find_class(d_hash, class_name, dictionary);
1821 }
1822 
1823 
1824 // ----------------------------------------------------------------------------
1825 // Update hierachy. This is done before the new klass has been added to the SystemDictionary. The Recompile_lock
1826 // is held, to ensure that the compiler is not using the class hierachy, and that deoptimization will kick in
1827 // before a new class is used.
1828 
1829 void SystemDictionary::add_to_hierarchy(InstanceKlass* k, TRAPS) {
1830   assert(k != NULL, "just checking");
1831   assert_locked_or_safepoint(Compile_lock);
1832 
1833   // Link into hierachy. Make sure the vtables are initialized before linking into
1834   k->append_to_sibling_list();                    // add to superklass/sibling list
1835   k->process_interfaces(THREAD);                  // handle all "implements" declarations
1836   k->set_init_state(InstanceKlass::loaded);
1837   // Now flush all code that depended on old class hierarchy.
1838   // Note: must be done *after* linking k into the hierarchy (was bug 12/9/97)
1839   // Also, first reinitialize vtable because it may have gotten out of synch
1840   // while the new class wasn't connected to the class hierarchy.
1841   CodeCache::flush_dependents_on(k);
1842 }
1843 
1844 // ----------------------------------------------------------------------------
1845 // GC support
1846 
1847 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1848 // Note: anonymous classes are not in the SD.
1849 bool SystemDictionary::do_unloading(GCTimer* gc_timer,
1850                                     bool do_cleaning) {
1851 
1852   bool unloading_occurred;
1853   {
1854     GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1855 
1856 #if INCLUDE_JFR
1857     // If unloading occurs, make sure time stamp is consistent.
1858     if (Jfr::is_enabled()) {
1859       InstanceKlass::set_class_unload_time(Ticks::now());
1860     }
1861 #endif
1862 
1863     // First, mark for unload all ClassLoaderData referencing a dead class loader.
1864     unloading_occurred = ClassLoaderDataGraph::do_unloading(do_cleaning);
1865     if (unloading_occurred) {
1866       ClassLoaderDataGraph::clean_module_and_package_info();
1867 #if INCLUDE_JFR
1868       if (Jfr::is_enabled()) {
1869         Jfr::on_unloading_classes();
1870       }
1871 #endif
1872     }
1873   }
1874 
1875   // TODO: just return if !unloading_occurred.
1876   if (unloading_occurred) {
1877     {
1878       GCTraceTime(Debug, gc, phases) t("SymbolTable", gc_timer);
1879       // Check if there's work to do in the SymbolTable
1880       SymbolTable::do_check_concurrent_work();
1881     }
1882 
1883     {
1884       GCTraceTime(Debug, gc, phases) t("Dictionary", gc_timer);
1885       constraints()->purge_loader_constraints();
1886       resolution_errors()->purge_resolution_errors();
1887     }
1888   }
1889 
1890   {
1891     GCTraceTime(Debug, gc, phases) t("ProtectionDomainCacheTable", gc_timer);
1892     // Oops referenced by the protection domain cache table may get unreachable independently
1893     // of the class loader (eg. cached protection domain oops). So we need to
1894     // explicitly unlink them here.
1895     _pd_cache_table->unlink();
1896   }
1897 
1898   if (do_cleaning) {
1899     GCTraceTime(Debug, gc, phases) t("ResolvedMethodTable", gc_timer);
1900     ResolvedMethodTable::trigger_cleanup();
1901   }
1902 
1903   return unloading_occurred;
1904 }
1905 
1906 void SystemDictionary::oops_do(OopClosure* f) {
1907   f->do_oop(&_java_system_loader);
1908   f->do_oop(&_java_platform_loader);
1909   f->do_oop(&_system_loader_lock_obj);
1910   CDS_ONLY(SystemDictionaryShared::oops_do(f);)
1911 
1912   // Visit extra methods
1913   invoke_method_table()->oops_do(f);
1914 }
1915 
1916 // CDS: scan and relocate all classes in the system dictionary.
1917 void SystemDictionary::classes_do(MetaspaceClosure* it) {
1918   ClassLoaderData::the_null_class_loader_data()->dictionary()->classes_do(it);
1919 }
1920 
1921 // CDS: scan and relocate all classes referenced by _well_known_klasses[].
1922 void SystemDictionary::well_known_klasses_do(MetaspaceClosure* it) {
1923   for (int id = FIRST_WKID; id < WKID_LIMIT; id++) {
1924     it->push(well_known_klass_addr((WKID)id));
1925   }
1926 }
1927 
1928 void SystemDictionary::methods_do(void f(Method*)) {
1929   // Walk methods in loaded classes
1930   ClassLoaderDataGraph::methods_do(f);
1931   // Walk method handle intrinsics
1932   invoke_method_table()->methods_do(f);
1933 }
1934 
1935 class RemoveClassesClosure : public CLDClosure {
1936   public:
1937     void do_cld(ClassLoaderData* cld) {
1938       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
1939         cld->dictionary()->remove_classes_in_error_state();
1940       }
1941     }
1942 };
1943 
1944 void SystemDictionary::remove_classes_in_error_state() {
1945   ClassLoaderData::the_null_class_loader_data()->dictionary()->remove_classes_in_error_state();
1946   RemoveClassesClosure rcc;
1947   ClassLoaderDataGraph::cld_do(&rcc);
1948 }
1949 
1950 // ----------------------------------------------------------------------------
1951 // Initialization
1952 
1953 void SystemDictionary::initialize(TRAPS) {
1954   // Allocate arrays
1955   _placeholders        = new PlaceholderTable(_placeholder_table_size);
1956   _number_of_modifications = 0;
1957   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
1958   _resolution_errors   = new ResolutionErrorTable(_resolution_error_size);
1959   _invoke_method_table = new SymbolPropertyTable(_invoke_method_size);
1960   _pd_cache_table = new ProtectionDomainCacheTable(defaultProtectionDomainCacheSize);
1961 
1962   // Allocate private object used as system class loader lock
1963   _system_loader_lock_obj = oopFactory::new_intArray(0, CHECK);
1964   // Initialize basic classes
1965   resolve_preloaded_classes(CHECK);
1966 }
1967 
1968 // Compact table of directions on the initialization of klasses:
1969 static const short wk_init_info[] = {
1970   #define WK_KLASS_INIT_INFO(name, symbol, option) \
1971     ( ((int)vmSymbols::VM_SYMBOL_ENUM_NAME(symbol) \
1972           << SystemDictionary::CEIL_LG_OPTION_LIMIT) \
1973       | (int)SystemDictionary::option ),
1974   WK_KLASSES_DO(WK_KLASS_INIT_INFO)
1975   #undef WK_KLASS_INIT_INFO
1976   0
1977 };
1978 
1979 bool SystemDictionary::resolve_wk_klass(WKID id, int init_opt, TRAPS) {
1980   assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
1981   int  info = wk_init_info[id - FIRST_WKID];
1982   int  sid  = (info >> CEIL_LG_OPTION_LIMIT);
1983   Symbol* symbol = vmSymbols::symbol_at((vmSymbols::SID)sid);
1984   InstanceKlass** klassp = &_well_known_klasses[id];
1985 
1986   bool must_load;
1987 #if INCLUDE_JVMCI
1988   if (EnableJVMCI) {
1989     // If JVMCI is enabled we require its classes to be found.
1990     must_load = (init_opt < SystemDictionary::Opt) || (init_opt == SystemDictionary::Jvmci);
1991   } else
1992 #endif
1993   {
1994     must_load = (init_opt < SystemDictionary::Opt);
1995   }
1996 
1997   if ((*klassp) == NULL) {
1998     Klass* k;
1999     if (must_load) {
2000       k = resolve_or_fail(symbol, true, CHECK_0); // load required class
2001     } else {
2002       k = resolve_or_null(symbol,       CHECK_0); // load optional klass
2003     }
2004     (*klassp) = (k == NULL) ? NULL : InstanceKlass::cast(k);
2005   }
2006   return ((*klassp) != NULL);
2007 }
2008 
2009 void SystemDictionary::resolve_wk_klasses_until(WKID limit_id, WKID &start_id, TRAPS) {
2010   assert((int)start_id <= (int)limit_id, "IDs are out of order!");
2011   for (int id = (int)start_id; id < (int)limit_id; id++) {
2012     assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
2013     int info = wk_init_info[id - FIRST_WKID];
2014     int sid  = (info >> CEIL_LG_OPTION_LIMIT);
2015     int opt  = (info & right_n_bits(CEIL_LG_OPTION_LIMIT));
2016 
2017     resolve_wk_klass((WKID)id, opt, CHECK);
2018   }
2019 
2020   // move the starting value forward to the limit:
2021   start_id = limit_id;
2022 }
2023 
2024 void SystemDictionary::resolve_preloaded_classes(TRAPS) {
2025   assert(WK_KLASS(Object_klass) == NULL, "preloaded classes should only be initialized once");
2026 
2027   // Create the ModuleEntry for java.base.  This call needs to be done here,
2028   // after vmSymbols::initialize() is called but before any classes are pre-loaded.
2029   ClassLoader::classLoader_init2(CHECK);
2030 
2031   // Preload commonly used klasses
2032   WKID scan = FIRST_WKID;
2033   // first do Object, then String, Class
2034 #if INCLUDE_CDS
2035   if (UseSharedSpaces) {
2036     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Object_klass), scan, CHECK);
2037     // Initialize the constant pool for the Object_class
2038     Object_klass()->constants()->restore_unshareable_info(CHECK);
2039     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2040   } else
2041 #endif
2042   {
2043     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2044   }
2045 
2046   // Calculate offsets for String and Class classes since they are loaded and
2047   // can be used after this point.
2048   java_lang_String::compute_offsets();
2049   java_lang_Class::compute_offsets();
2050 
2051   // Fixup mirrors for classes loaded before java.lang.Class.
2052   // These calls iterate over the objects currently in the perm gen
2053   // so calling them at this point is matters (not before when there
2054   // are fewer objects and not later after there are more objects
2055   // in the perm gen.
2056   Universe::initialize_basic_type_mirrors(CHECK);
2057   Universe::fixup_mirrors(CHECK);
2058 
2059   // do a bunch more:
2060   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Reference_klass), scan, CHECK);
2061 
2062   // Preload ref klasses and set reference types
2063   InstanceKlass::cast(WK_KLASS(Reference_klass))->set_reference_type(REF_OTHER);
2064   InstanceRefKlass::update_nonstatic_oop_maps(WK_KLASS(Reference_klass));
2065 
2066   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(PhantomReference_klass), scan, CHECK);
2067   InstanceKlass::cast(WK_KLASS(SoftReference_klass))->set_reference_type(REF_SOFT);
2068   InstanceKlass::cast(WK_KLASS(WeakReference_klass))->set_reference_type(REF_WEAK);
2069   InstanceKlass::cast(WK_KLASS(FinalReference_klass))->set_reference_type(REF_FINAL);
2070   InstanceKlass::cast(WK_KLASS(PhantomReference_klass))->set_reference_type(REF_PHANTOM);
2071 
2072   // JSR 292 classes
2073   WKID jsr292_group_start = WK_KLASS_ENUM_NAME(MethodHandle_klass);
2074   WKID jsr292_group_end   = WK_KLASS_ENUM_NAME(VolatileCallSite_klass);
2075   resolve_wk_klasses_until(jsr292_group_start, scan, CHECK);
2076   resolve_wk_klasses_through(jsr292_group_end, scan, CHECK);
2077   resolve_wk_klasses_until(NOT_JVMCI(WKID_LIMIT) JVMCI_ONLY(FIRST_JVMCI_WKID), scan, CHECK);
2078 
2079   _box_klasses[T_BOOLEAN] = WK_KLASS(Boolean_klass);
2080   _box_klasses[T_CHAR]    = WK_KLASS(Character_klass);
2081   _box_klasses[T_FLOAT]   = WK_KLASS(Float_klass);
2082   _box_klasses[T_DOUBLE]  = WK_KLASS(Double_klass);
2083   _box_klasses[T_BYTE]    = WK_KLASS(Byte_klass);
2084   _box_klasses[T_SHORT]   = WK_KLASS(Short_klass);
2085   _box_klasses[T_INT]     = WK_KLASS(Integer_klass);
2086   _box_klasses[T_LONG]    = WK_KLASS(Long_klass);
2087   //_box_klasses[T_OBJECT]  = WK_KLASS(object_klass);
2088   //_box_klasses[T_ARRAY]   = WK_KLASS(object_klass);
2089 
2090   { // Compute whether we should use checkPackageAccess or NOT
2091     Method* method = InstanceKlass::cast(ClassLoader_klass())->find_method(vmSymbols::checkPackageAccess_name(), vmSymbols::class_protectiondomain_signature());
2092     _has_checkPackageAccess = (method != NULL);
2093   }
2094 }
2095 
2096 // Tells if a given klass is a box (wrapper class, such as java.lang.Integer).
2097 // If so, returns the basic type it holds.  If not, returns T_OBJECT.
2098 BasicType SystemDictionary::box_klass_type(Klass* k) {
2099   assert(k != NULL, "");
2100   for (int i = T_BOOLEAN; i < T_VOID+1; i++) {
2101     if (_box_klasses[i] == k)
2102       return (BasicType)i;
2103   }
2104   return T_OBJECT;
2105 }
2106 
2107 // Constraints on class loaders. The details of the algorithm can be
2108 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
2109 // Virtual Machine" by Sheng Liang and Gilad Bracha.  The basic idea is
2110 // that the dictionary needs to maintain a set of contraints that
2111 // must be satisfied by all classes in the dictionary.
2112 // if defining is true, then LinkageError if already in dictionary
2113 // if initiating loader, then ok if InstanceKlass matches existing entry
2114 
2115 void SystemDictionary::check_constraints(unsigned int d_hash,
2116                                          InstanceKlass* k,
2117                                          Handle class_loader,
2118                                          bool defining,
2119                                          TRAPS) {
2120   ResourceMark rm(THREAD);
2121   stringStream ss;
2122   bool throwException = false;
2123 
2124   {
2125     Symbol *name = k->name();
2126     ClassLoaderData *loader_data = class_loader_data(class_loader);
2127 
2128     MutexLocker mu(SystemDictionary_lock, THREAD);
2129 
2130     InstanceKlass* check = find_class(d_hash, name, loader_data->dictionary());
2131     if (check != NULL) {
2132       // If different InstanceKlass - duplicate class definition,
2133       // else - ok, class loaded by a different thread in parallel.
2134       // We should only have found it if it was done loading and ok to use.
2135       // The dictionary only holds instance classes, placeholders
2136       // also hold array classes.
2137 
2138       assert(check->is_instance_klass(), "noninstance in systemdictionary");
2139       if ((defining == true) || (k != check)) {
2140         throwException = true;
2141         ss.print("loader %s", loader_data->loader_name_and_id());
2142         ss.print(" attempted duplicate %s definition for %s. (%s)",
2143                  k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
2144       } else {
2145         return;
2146       }
2147     }
2148 
2149 #ifdef ASSERT
2150     Symbol* ph_check = find_placeholder(name, loader_data);
2151     assert(ph_check == NULL || ph_check == name, "invalid symbol");
2152 #endif
2153 
2154     if (throwException == false) {
2155       if (constraints()->check_or_update(k, class_loader, name) == false) {
2156         throwException = true;
2157         ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
2158         ss.print(" wants to load %s %s.",
2159                  k->external_kind(), k->external_name());
2160         Klass *existing_klass = constraints()->find_constrained_klass(name, class_loader);
2161         if (existing_klass->class_loader() != class_loader()) {
2162           ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
2163                    existing_klass->external_kind(),
2164                    existing_klass->class_loader_data()->loader_name_and_id(),
2165                    existing_klass->class_in_module_of_loader(false, true));
2166         } else {
2167           ss.print(" (%s)", k->class_in_module_of_loader(false, true));
2168         }
2169       }
2170     }
2171   }
2172 
2173   // Throw error now if needed (cannot throw while holding
2174   // SystemDictionary_lock because of rank ordering)
2175   if (throwException == true) {
2176     THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
2177   }
2178 }
2179 
2180 // Update class loader data dictionary - done after check_constraint and add_to_hierachy
2181 // have been called.
2182 void SystemDictionary::update_dictionary(unsigned int d_hash,
2183                                          int p_index, unsigned int p_hash,
2184                                          InstanceKlass* k,
2185                                          Handle class_loader,
2186                                          TRAPS) {
2187   // Compile_lock prevents systemDictionary updates during compilations
2188   assert_locked_or_safepoint(Compile_lock);
2189   Symbol*  name  = k->name();
2190   ClassLoaderData *loader_data = class_loader_data(class_loader);
2191 
2192   {
2193     MutexLocker mu1(SystemDictionary_lock, THREAD);
2194 
2195     // See whether biased locking is enabled and if so set it for this
2196     // klass.
2197     // Note that this must be done past the last potential blocking
2198     // point / safepoint. We enable biased locking lazily using a
2199     // VM_Operation to iterate the SystemDictionary and installing the
2200     // biasable mark word into each InstanceKlass's prototype header.
2201     // To avoid race conditions where we accidentally miss enabling the
2202     // optimization for one class in the process of being added to the
2203     // dictionary, we must not safepoint after the test of
2204     // BiasedLocking::enabled().
2205     if (UseBiasedLocking && BiasedLocking::enabled()) {
2206       // Set biased locking bit for all loaded classes; it will be
2207       // cleared if revocation occurs too often for this type
2208       // NOTE that we must only do this when the class is initally
2209       // defined, not each time it is referenced from a new class loader
2210       if (oopDesc::equals(k->class_loader(), class_loader())) {
2211         k->set_prototype_header(markOopDesc::biased_locking_prototype());
2212       }
2213     }
2214 
2215     // Make a new dictionary entry.
2216     Dictionary* dictionary = loader_data->dictionary();
2217     InstanceKlass* sd_check = find_class(d_hash, name, dictionary);
2218     if (sd_check == NULL) {
2219       dictionary->add_klass(d_hash, name, k);
2220       notice_modification();
2221     }
2222   #ifdef ASSERT
2223     sd_check = find_class(d_hash, name, dictionary);
2224     assert (sd_check != NULL, "should have entry in dictionary");
2225     // Note: there may be a placeholder entry: for circularity testing
2226     // or for parallel defines
2227   #endif
2228     SystemDictionary_lock->notify_all();
2229   }
2230 }
2231 
2232 
2233 // Try to find a class name using the loader constraints.  The
2234 // loader constraints might know about a class that isn't fully loaded
2235 // yet and these will be ignored.
2236 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
2237                     Symbol* class_name, Handle class_loader, TRAPS) {
2238 
2239   // First see if it has been loaded directly.
2240   // Force the protection domain to be null.  (This removes protection checks.)
2241   Handle no_protection_domain;
2242   Klass* klass = find_instance_or_array_klass(class_name, class_loader,
2243                                               no_protection_domain, CHECK_NULL);
2244   if (klass != NULL)
2245     return klass;
2246 
2247   // Now look to see if it has been loaded elsewhere, and is subject to
2248   // a loader constraint that would require this loader to return the
2249   // klass that is already loaded.
2250   if (FieldType::is_array(class_name)) {
2251     // For array classes, their Klass*s are not kept in the
2252     // constraint table. The element Klass*s are.
2253     FieldArrayInfo fd;
2254     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
2255     if (t != T_OBJECT) {
2256       klass = Universe::typeArrayKlassObj(t);
2257     } else {
2258       MutexLocker mu(SystemDictionary_lock, THREAD);
2259       klass = constraints()->find_constrained_klass(fd.object_key(), class_loader);
2260     }
2261     // If element class already loaded, allocate array klass
2262     if (klass != NULL) {
2263       klass = klass->array_klass_or_null(fd.dimension());
2264     }
2265   } else {
2266     MutexLocker mu(SystemDictionary_lock, THREAD);
2267     // Non-array classes are easy: simply check the constraint table.
2268     klass = constraints()->find_constrained_klass(class_name, class_loader);
2269   }
2270 
2271   return klass;
2272 }
2273 
2274 
2275 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
2276                                              Handle class_loader1,
2277                                              Handle class_loader2,
2278                                              Thread* THREAD) {
2279   ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
2280   ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
2281 
2282   Symbol* constraint_name = NULL;
2283   // Needs to be in same scope as constraint_name in case a Symbol is created and
2284   // assigned to constraint_name.
2285   FieldArrayInfo fd;
2286   if (!FieldType::is_array(class_name)) {
2287     constraint_name = class_name;
2288   } else {
2289     // For array classes, their Klass*s are not kept in the
2290     // constraint table. The element classes are.
2291     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(false));
2292     // primitive types always pass
2293     if (t != T_OBJECT) {
2294       return true;
2295     } else {
2296       constraint_name = fd.object_key();
2297     }
2298   }
2299 
2300   Dictionary* dictionary1 = loader_data1->dictionary();
2301   unsigned int d_hash1 = dictionary1->compute_hash(constraint_name);
2302 
2303   Dictionary* dictionary2 = loader_data2->dictionary();
2304   unsigned int d_hash2 = dictionary2->compute_hash(constraint_name);
2305 
2306   {
2307     MutexLocker mu_s(SystemDictionary_lock, THREAD);
2308     InstanceKlass* klass1 = find_class(d_hash1, constraint_name, dictionary1);
2309     InstanceKlass* klass2 = find_class(d_hash2, constraint_name, dictionary2);
2310     return constraints()->add_entry(constraint_name, klass1, class_loader1,
2311                                     klass2, class_loader2);
2312   }
2313 }
2314 
2315 // Add entry to resolution error table to record the error when the first
2316 // attempt to resolve a reference to a class has failed.
2317 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
2318                                             Symbol* error, Symbol* message) {
2319   unsigned int hash = resolution_errors()->compute_hash(pool, which);
2320   int index = resolution_errors()->hash_to_index(hash);
2321   {
2322     MutexLocker ml(SystemDictionary_lock, Thread::current());
2323     resolution_errors()->add_entry(index, hash, pool, which, error, message);
2324   }
2325 }
2326 
2327 // Delete a resolution error for RedefineClasses for a constant pool is going away
2328 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
2329   resolution_errors()->delete_entry(pool);
2330 }
2331 
2332 // Lookup resolution error table. Returns error if found, otherwise NULL.
2333 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
2334                                                 Symbol** message) {
2335   unsigned int hash = resolution_errors()->compute_hash(pool, which);
2336   int index = resolution_errors()->hash_to_index(hash);
2337   {
2338     MutexLocker ml(SystemDictionary_lock, Thread::current());
2339     ResolutionErrorEntry* entry = resolution_errors()->find_entry(index, hash, pool, which);
2340     if (entry != NULL) {
2341       *message = entry->message();
2342       return entry->error();
2343     } else {
2344       return NULL;
2345     }
2346   }
2347 }
2348 
2349 
2350 // Signature constraints ensure that callers and callees agree about
2351 // the meaning of type names in their signatures.  This routine is the
2352 // intake for constraints.  It collects them from several places:
2353 //
2354 //  * LinkResolver::resolve_method (if check_access is true) requires
2355 //    that the resolving class (the caller) and the defining class of
2356 //    the resolved method (the callee) agree on each type in the
2357 //    method's signature.
2358 //
2359 //  * LinkResolver::resolve_interface_method performs exactly the same
2360 //    checks.
2361 //
2362 //  * LinkResolver::resolve_field requires that the constant pool
2363 //    attempting to link to a field agree with the field's defining
2364 //    class about the type of the field signature.
2365 //
2366 //  * klassVtable::initialize_vtable requires that, when a class
2367 //    overrides a vtable entry allocated by a superclass, that the
2368 //    overriding method (i.e., the callee) agree with the superclass
2369 //    on each type in the method's signature.
2370 //
2371 //  * klassItable::initialize_itable requires that, when a class fills
2372 //    in its itables, for each non-abstract method installed in an
2373 //    itable, the method (i.e., the callee) agree with the interface
2374 //    on each type in the method's signature.
2375 //
2376 // All those methods have a boolean (check_access, checkconstraints)
2377 // which turns off the checks.  This is used from specialized contexts
2378 // such as bootstrapping, dumping, and debugging.
2379 //
2380 // No direct constraint is placed between the class and its
2381 // supertypes.  Constraints are only placed along linked relations
2382 // between callers and callees.  When a method overrides or implements
2383 // an abstract method in a supertype (superclass or interface), the
2384 // constraints are placed as if the supertype were the caller to the
2385 // overriding method.  (This works well, since callers to the
2386 // supertype have already established agreement between themselves and
2387 // the supertype.)  As a result of all this, a class can disagree with
2388 // its supertype about the meaning of a type name, as long as that
2389 // class neither calls a relevant method of the supertype, nor is
2390 // called (perhaps via an override) from the supertype.
2391 //
2392 //
2393 // SystemDictionary::check_signature_loaders(sig, l1, l2)
2394 //
2395 // Make sure all class components (including arrays) in the given
2396 // signature will be resolved to the same class in both loaders.
2397 // Returns the name of the type that failed a loader constraint check, or
2398 // NULL if no constraint failed.  No exception except OOME is thrown.
2399 // Arrays are not added to the loader constraint table, their elements are.
2400 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
2401                                                Handle loader1, Handle loader2,
2402                                                bool is_method, TRAPS)  {
2403   // Nothing to do if loaders are the same.
2404   if (oopDesc::equals(loader1(), loader2())) {
2405     return NULL;
2406   }
2407 
2408   SignatureStream sig_strm(signature, is_method);
2409   while (!sig_strm.is_done()) {
2410     if (sig_strm.is_object()) {
2411       Symbol* sig = sig_strm.as_symbol(CHECK_NULL);
2412       if (!add_loader_constraint(sig, loader1, loader2, THREAD)) {
2413         return sig;
2414       }
2415     }
2416     sig_strm.next();
2417   }
2418   return NULL;
2419 }
2420 
2421 
2422 methodHandle SystemDictionary::find_method_handle_intrinsic(vmIntrinsics::ID iid,
2423                                                             Symbol* signature,
2424                                                             TRAPS) {
2425   methodHandle empty;
2426   assert(MethodHandles::is_signature_polymorphic(iid) &&
2427          MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
2428          iid != vmIntrinsics::_invokeGeneric,
2429          "must be a known MH intrinsic iid=%d: %s", iid, vmIntrinsics::name_at(iid));
2430 
2431   unsigned int hash  = invoke_method_table()->compute_hash(signature, iid);
2432   int          index = invoke_method_table()->hash_to_index(hash);
2433   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2434   methodHandle m;
2435   if (spe == NULL || spe->method() == NULL) {
2436     spe = NULL;
2437     // Must create lots of stuff here, but outside of the SystemDictionary lock.
2438     m = Method::make_method_handle_intrinsic(iid, signature, CHECK_(empty));
2439     if (!Arguments::is_interpreter_only()) {
2440       // Generate a compiled form of the MH intrinsic.
2441       AdapterHandlerLibrary::create_native_wrapper(m);
2442       // Check if have the compiled code.
2443       if (!m->has_compiled_code()) {
2444         THROW_MSG_(vmSymbols::java_lang_VirtualMachineError(),
2445                    "Out of space in CodeCache for method handle intrinsic", empty);
2446       }
2447     }
2448     // Now grab the lock.  We might have to throw away the new method,
2449     // if a racing thread has managed to install one at the same time.
2450     {
2451       MutexLocker ml(SystemDictionary_lock, THREAD);
2452       spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2453       if (spe == NULL)
2454         spe = invoke_method_table()->add_entry(index, hash, signature, iid);
2455       if (spe->method() == NULL)
2456         spe->set_method(m());
2457     }
2458   }
2459 
2460   assert(spe != NULL && spe->method() != NULL, "");
2461   assert(Arguments::is_interpreter_only() || (spe->method()->has_compiled_code() &&
2462          spe->method()->code()->entry_point() == spe->method()->from_compiled_entry()),
2463          "MH intrinsic invariant");
2464   return spe->method();
2465 }
2466 
2467 // Helper for unpacking the return value from linkMethod and linkCallSite.
2468 static methodHandle unpack_method_and_appendix(Handle mname,
2469                                                Klass* accessing_klass,
2470                                                objArrayHandle appendix_box,
2471                                                Handle* appendix_result,
2472                                                TRAPS) {
2473   methodHandle empty;
2474   if (mname.not_null()) {
2475     Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2476     if (m != NULL) {
2477       oop appendix = appendix_box->obj_at(0);
2478       if (TraceMethodHandles) {
2479     #ifndef PRODUCT
2480         ttyLocker ttyl;
2481         tty->print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2482         m->print();
2483         if (appendix != NULL) { tty->print("appendix = "); appendix->print(); }
2484         tty->cr();
2485     #endif //PRODUCT
2486       }
2487       (*appendix_result) = Handle(THREAD, appendix);
2488       // the target is stored in the cpCache and if a reference to this
2489       // MemberName is dropped we need a way to make sure the
2490       // class_loader containing this method is kept alive.
2491       ClassLoaderData* this_key = accessing_klass->class_loader_data();
2492       this_key->record_dependency(m->method_holder());
2493       return methodHandle(THREAD, m);
2494     }
2495   }
2496   THROW_MSG_(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives", empty);
2497   return empty;
2498 }
2499 
2500 methodHandle SystemDictionary::find_method_handle_invoker(Klass* klass,
2501                                                           Symbol* name,
2502                                                           Symbol* signature,
2503                                                           Klass* accessing_klass,
2504                                                           Handle *appendix_result,
2505                                                           Handle *method_type_result,
2506                                                           TRAPS) {
2507   methodHandle empty;
2508   assert(THREAD->can_call_java() ,"");
2509   Handle method_type =
2510     SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_(empty));
2511 
2512   int ref_kind = JVM_REF_invokeVirtual;
2513   oop name_oop = StringTable::intern(name, CHECK_(empty));
2514   Handle name_str (THREAD, name_oop);
2515   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2516   assert(appendix_box->obj_at(0) == NULL, "");
2517 
2518   // This should not happen.  JDK code should take care of that.
2519   if (accessing_klass == NULL || method_type.is_null()) {
2520     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokehandle", empty);
2521   }
2522 
2523   // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2524   JavaCallArguments args;
2525   args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2526   args.push_int(ref_kind);
2527   args.push_oop(Handle(THREAD, klass->java_mirror()));
2528   args.push_oop(name_str);
2529   args.push_oop(method_type);
2530   args.push_oop(appendix_box);
2531   JavaValue result(T_OBJECT);
2532   JavaCalls::call_static(&result,
2533                          SystemDictionary::MethodHandleNatives_klass(),
2534                          vmSymbols::linkMethod_name(),
2535                          vmSymbols::linkMethod_signature(),
2536                          &args, CHECK_(empty));
2537   Handle mname(THREAD, (oop) result.get_jobject());
2538   (*method_type_result) = method_type;
2539   return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2540 }
2541 
2542 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2543 // We must ensure that all class loaders everywhere will reach this class, for any client.
2544 // This is a safe bet for public classes in java.lang, such as Object and String.
2545 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2546 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2547 static bool is_always_visible_class(oop mirror) {
2548   Klass* klass = java_lang_Class::as_Klass(mirror);
2549   if (klass->is_objArray_klass()) {
2550     klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2551   }
2552   if (klass->is_typeArray_klass()) {
2553     return true; // primitive array
2554   }
2555   assert(klass->is_instance_klass(), "%s", klass->external_name());
2556   return klass->is_public() &&
2557          (InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::Object_klass()) ||       // java.lang
2558           InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::MethodHandle_klass()));  // java.lang.invoke
2559 }
2560 
2561 
2562 // Return the Java mirror (java.lang.Class instance) for a single-character
2563 // descriptor.  This result, when available, is the same as produced by the
2564 // heavier API point of the same name that takes a Symbol.
2565 oop SystemDictionary::find_java_mirror_for_type(char signature_char) {
2566   return java_lang_Class::primitive_mirror(char2type(signature_char));
2567 }
2568 
2569 // Find or construct the Java mirror (java.lang.Class instance) for a
2570 // for the given field type signature, as interpreted relative to the
2571 // given class loader.  Handles primitives, void, references, arrays,
2572 // and all other reflectable types, except method types.
2573 // N.B.  Code in reflection should use this entry point.
2574 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2575                                                    Klass* accessing_klass,
2576                                                    Handle class_loader,
2577                                                    Handle protection_domain,
2578                                                    SignatureStream::FailureMode failure_mode,
2579                                                    TRAPS) {
2580   Handle empty;
2581 
2582   assert(accessing_klass == NULL || (class_loader.is_null() && protection_domain.is_null()),
2583          "one or the other, or perhaps neither");
2584 
2585   Symbol* type = signature;
2586 
2587   // What we have here must be a valid field descriptor,
2588   // and all valid field descriptors are supported.
2589   // Produce the same java.lang.Class that reflection reports.
2590   if (type->utf8_length() == 1) {
2591 
2592     // It's a primitive.  (Void has a primitive mirror too.)
2593     char ch = (char) type->byte_at(0);
2594     assert(is_java_primitive(char2type(ch)) || ch == 'V', "");
2595     return Handle(THREAD, find_java_mirror_for_type(ch));
2596 
2597   } else if (FieldType::is_obj(type) || FieldType::is_array(type)) {
2598 
2599     // It's a reference type.
2600     if (accessing_klass != NULL) {
2601       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2602       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2603     }
2604     Klass* constant_type_klass;
2605     if (failure_mode == SignatureStream::ReturnNull) {
2606       constant_type_klass = resolve_or_null(type, class_loader, protection_domain,
2607                                             CHECK_(empty));
2608     } else {
2609       bool throw_error = (failure_mode == SignatureStream::NCDFError);
2610       constant_type_klass = resolve_or_fail(type, class_loader, protection_domain,
2611                                             throw_error, CHECK_(empty));
2612     }
2613     if (constant_type_klass == NULL) {
2614       return Handle();  // report failure this way
2615     }
2616     Handle mirror(THREAD, constant_type_klass->java_mirror());
2617 
2618     // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2619     if (accessing_klass != NULL) {
2620       Klass* sel_klass = constant_type_klass;
2621       bool fold_type_to_class = true;
2622       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2623                                               fold_type_to_class, CHECK_(empty));
2624     }
2625 
2626     return mirror;
2627 
2628   }
2629 
2630   // Fall through to an error.
2631   assert(false, "unsupported mirror syntax");
2632   THROW_MSG_(vmSymbols::java_lang_InternalError(), "unsupported mirror syntax", empty);
2633 }
2634 
2635 
2636 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2637 // signature, as interpreted relative to the given class loader.
2638 // Because of class loader constraints, all method handle usage must be
2639 // consistent with this loader.
2640 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2641                                                  Klass* accessing_klass,
2642                                                  TRAPS) {
2643   Handle empty;
2644   vmIntrinsics::ID null_iid = vmIntrinsics::_none;  // distinct from all method handle invoker intrinsics
2645   unsigned int hash  = invoke_method_table()->compute_hash(signature, null_iid);
2646   int          index = invoke_method_table()->hash_to_index(hash);
2647   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2648   if (spe != NULL && spe->method_type() != NULL) {
2649     assert(java_lang_invoke_MethodType::is_instance(spe->method_type()), "");
2650     return Handle(THREAD, spe->method_type());
2651   } else if (!THREAD->can_call_java()) {
2652     warning("SystemDictionary::find_method_handle_type called from compiler thread");  // FIXME
2653     return Handle();  // do not attempt from within compiler, unless it was cached
2654   }
2655 
2656   Handle class_loader, protection_domain;
2657   if (accessing_klass != NULL) {
2658     class_loader      = Handle(THREAD, accessing_klass->class_loader());
2659     protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2660   }
2661   bool can_be_cached = true;
2662   int npts = ArgumentCount(signature).size();
2663   objArrayHandle pts = oopFactory::new_objArray_handle(SystemDictionary::Class_klass(), npts, CHECK_(empty));
2664   int arg = 0;
2665   Handle rt; // the return type from the signature
2666   ResourceMark rm(THREAD);
2667   for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2668     oop mirror = NULL;
2669     if (can_be_cached) {
2670       // Use neutral class loader to lookup candidate classes to be placed in the cache.
2671       mirror = ss.as_java_mirror(Handle(), Handle(),
2672                                  SignatureStream::ReturnNull, CHECK_(empty));
2673       if (mirror == NULL || (ss.is_object() && !is_always_visible_class(mirror))) {
2674         // Fall back to accessing_klass context.
2675         can_be_cached = false;
2676       }
2677     }
2678     if (!can_be_cached) {
2679       // Resolve, throwing a real error if it doesn't work.
2680       mirror = ss.as_java_mirror(class_loader, protection_domain,
2681                                  SignatureStream::NCDFError, CHECK_(empty));
2682     }
2683     assert(mirror != NULL, "%s", ss.as_symbol(THREAD)->as_C_string());
2684     if (ss.at_return_type())
2685       rt = Handle(THREAD, mirror);
2686     else
2687       pts->obj_at_put(arg++, mirror);
2688 
2689     // Check accessibility.
2690     if (!java_lang_Class::is_primitive(mirror) && accessing_klass != NULL) {
2691       Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2692       mirror = NULL;  // safety
2693       // Emulate ConstantPool::verify_constant_pool_resolve.
2694       bool fold_type_to_class = true;
2695       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2696                                               fold_type_to_class, CHECK_(empty));
2697     }
2698   }
2699   assert(arg == npts, "");
2700 
2701   // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2702   JavaCallArguments args(Handle(THREAD, rt()));
2703   args.push_oop(pts);
2704   JavaValue result(T_OBJECT);
2705   JavaCalls::call_static(&result,
2706                          SystemDictionary::MethodHandleNatives_klass(),
2707                          vmSymbols::findMethodHandleType_name(),
2708                          vmSymbols::findMethodHandleType_signature(),
2709                          &args, CHECK_(empty));
2710   Handle method_type(THREAD, (oop) result.get_jobject());
2711 
2712   if (can_be_cached) {
2713     // We can cache this MethodType inside the JVM.
2714     MutexLocker ml(SystemDictionary_lock, THREAD);
2715     spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2716     if (spe == NULL)
2717       spe = invoke_method_table()->add_entry(index, hash, signature, null_iid);
2718     if (spe->method_type() == NULL) {
2719       spe->set_method_type(method_type());
2720     }
2721   }
2722 
2723   // report back to the caller with the MethodType
2724   return method_type;
2725 }
2726 
2727 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2728                                                 Klass* accessing_klass,
2729                                                 TRAPS) {
2730   Handle empty;
2731   ResourceMark rm(THREAD);
2732   SignatureStream ss(signature, /*is_method=*/ false);
2733   if (!ss.is_done()) {
2734     Handle class_loader, protection_domain;
2735     if (accessing_klass != NULL) {
2736       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2737       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2738     }
2739     oop mirror = ss.as_java_mirror(class_loader, protection_domain, SignatureStream::NCDFError, CHECK_(empty));
2740     ss.next();
2741     if (ss.is_done()) {
2742       return Handle(THREAD, mirror);
2743     }
2744   }
2745   return empty;
2746 }
2747 
2748 // Ask Java code to find or construct a method handle constant.
2749 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2750                                                      int ref_kind, //e.g., JVM_REF_invokeVirtual
2751                                                      Klass* callee,
2752                                                      Symbol* name,
2753                                                      Symbol* signature,
2754                                                      TRAPS) {
2755   Handle empty;
2756   if (caller == NULL) {
2757     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2758   }
2759   Handle name_str      = java_lang_String::create_from_symbol(name,      CHECK_(empty));
2760   Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2761 
2762   // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2763   Handle mname = MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2764   java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2765   java_lang_invoke_MemberName::set_name (mname(), name_str());
2766   java_lang_invoke_MemberName::set_type (mname(), signature_str());
2767   java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2768 
2769   if (ref_kind == JVM_REF_invokeVirtual &&
2770       MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2771     // Skip resolution for public signature polymorphic methods such as
2772     // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2773     // They require appendix argument which MemberName resolution doesn't handle.
2774     // There's special logic on JDK side to handle them
2775     // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2776   } else {
2777     MethodHandles::resolve_MemberName(mname, caller, /*speculative_resolve*/false, CHECK_(empty));
2778   }
2779 
2780   // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2781   Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2782 
2783   // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2784   JavaCallArguments args;
2785   args.push_oop(Handle(THREAD, caller->java_mirror()));  // the referring class
2786   args.push_int(ref_kind);
2787   args.push_oop(Handle(THREAD, callee->java_mirror()));  // the target class
2788   args.push_oop(name_str);
2789   args.push_oop(type);
2790   JavaValue result(T_OBJECT);
2791   JavaCalls::call_static(&result,
2792                          SystemDictionary::MethodHandleNatives_klass(),
2793                          vmSymbols::linkMethodHandleConstant_name(),
2794                          vmSymbols::linkMethodHandleConstant_signature(),
2795                          &args, CHECK_(empty));
2796   return Handle(THREAD, (oop) result.get_jobject());
2797 }
2798 
2799 // Ask Java to compute a constant by invoking a BSM given a Dynamic_info CP entry
2800 Handle SystemDictionary::link_dynamic_constant(Klass* caller,
2801                                                int condy_index,
2802                                                Handle bootstrap_specifier,
2803                                                Symbol* name,
2804                                                Symbol* type,
2805                                                TRAPS) {
2806   Handle empty;
2807   Handle bsm, info;
2808   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2809     bsm = bootstrap_specifier;
2810   } else {
2811     assert(bootstrap_specifier->is_objArray(), "");
2812     objArrayOop args = (objArrayOop) bootstrap_specifier();
2813     assert(args->length() == 2, "");
2814     bsm  = Handle(THREAD, args->obj_at(0));
2815     info = Handle(THREAD, args->obj_at(1));
2816   }
2817   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2818             "caller must supply a valid BSM");
2819 
2820   // This should not happen.  JDK code should take care of that.
2821   if (caller == NULL) {
2822     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad dynamic constant", empty);
2823   }
2824 
2825   Handle constant_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2826 
2827   // Resolve the constant type in the context of the caller class
2828   Handle type_mirror = find_java_mirror_for_type(type, caller, SignatureStream::NCDFError,
2829                                                  CHECK_(empty));
2830 
2831   // call java.lang.invoke.MethodHandleNatives::linkConstantDyanmic(caller, condy_index, bsm, type, info)
2832   JavaCallArguments args;
2833   args.push_oop(Handle(THREAD, caller->java_mirror()));
2834   args.push_int(condy_index);
2835   args.push_oop(bsm);
2836   args.push_oop(constant_name);
2837   args.push_oop(type_mirror);
2838   args.push_oop(info);
2839   JavaValue result(T_OBJECT);
2840   JavaCalls::call_static(&result,
2841                          SystemDictionary::MethodHandleNatives_klass(),
2842                          vmSymbols::linkDynamicConstant_name(),
2843                          vmSymbols::linkDynamicConstant_signature(),
2844                          &args, CHECK_(empty));
2845 
2846   return Handle(THREAD, (oop) result.get_jobject());
2847 }
2848 
2849 // Ask Java code to find or construct a java.lang.invoke.CallSite for the given
2850 // name and signature, as interpreted relative to the given class loader.
2851 methodHandle SystemDictionary::find_dynamic_call_site_invoker(Klass* caller,
2852                                                               int indy_index,
2853                                                               Handle bootstrap_specifier,
2854                                                               Symbol* name,
2855                                                               Symbol* type,
2856                                                               Handle *appendix_result,
2857                                                               Handle *method_type_result,
2858                                                               TRAPS) {
2859   methodHandle empty;
2860   Handle bsm, info;
2861   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2862     bsm = bootstrap_specifier;
2863   } else {
2864     objArrayOop args = (objArrayOop) bootstrap_specifier();
2865     assert(args->length() == 2, "");
2866     bsm  = Handle(THREAD, args->obj_at(0));
2867     info = Handle(THREAD, args->obj_at(1));
2868   }
2869   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2870             "caller must supply a valid BSM");
2871 
2872   Handle method_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2873   Handle method_type = find_method_handle_type(type, caller, CHECK_(empty));
2874 
2875   // This should not happen.  JDK code should take care of that.
2876   if (caller == NULL || method_type.is_null()) {
2877     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokedynamic", empty);
2878   }
2879 
2880   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2881   assert(appendix_box->obj_at(0) == NULL, "");
2882 
2883   // call java.lang.invoke.MethodHandleNatives::linkCallSite(caller, indy_index, bsm, name, mtype, info, &appendix)
2884   JavaCallArguments args;
2885   args.push_oop(Handle(THREAD, caller->java_mirror()));
2886   args.push_int(indy_index);
2887   args.push_oop(bsm);
2888   args.push_oop(method_name);
2889   args.push_oop(method_type);
2890   args.push_oop(info);
2891   args.push_oop(appendix_box);
2892   JavaValue result(T_OBJECT);
2893   JavaCalls::call_static(&result,
2894                          SystemDictionary::MethodHandleNatives_klass(),
2895                          vmSymbols::linkCallSite_name(),
2896                          vmSymbols::linkCallSite_signature(),
2897                          &args, CHECK_(empty));
2898   Handle mname(THREAD, (oop) result.get_jobject());
2899   (*method_type_result) = method_type;
2900   return unpack_method_and_appendix(mname, caller, appendix_box, appendix_result, THREAD);
2901 }
2902 
2903 // Protection domain cache table handling
2904 
2905 ProtectionDomainCacheEntry* SystemDictionary::cache_get(Handle protection_domain) {
2906   return _pd_cache_table->get(protection_domain);
2907 }
2908 
2909 #if INCLUDE_CDS
2910 void SystemDictionary::reorder_dictionary_for_sharing() {
2911   ClassLoaderData::the_null_class_loader_data()->dictionary()->reorder_dictionary_for_sharing();
2912 }
2913 #endif
2914 
2915 size_t SystemDictionary::count_bytes_for_buckets() {
2916   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_buckets();
2917 }
2918 
2919 size_t SystemDictionary::count_bytes_for_table() {
2920   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_table();
2921 }
2922 
2923 void SystemDictionary::copy_buckets(char* top, char* end) {
2924   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_buckets(top, end);
2925 }
2926 
2927 void SystemDictionary::copy_table(char* top, char* end) {
2928   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_table(top, end);
2929 }
2930 
2931 // ----------------------------------------------------------------------------
2932 void SystemDictionary::print_shared(outputStream *st) {
2933   shared_dictionary()->print_on(st);
2934 }
2935 
2936 void SystemDictionary::print_on(outputStream *st) {
2937   if (shared_dictionary() != NULL) {
2938     st->print_cr("Shared Dictionary");
2939     shared_dictionary()->print_on(st);
2940     st->cr();
2941   }
2942 
2943   GCMutexLocker mu(SystemDictionary_lock);
2944 
2945   ClassLoaderDataGraph::print_dictionary(st);
2946 
2947   // Placeholders
2948   placeholders()->print_on(st);
2949   st->cr();
2950 
2951   // loader constraints - print under SD_lock
2952   constraints()->print_on(st);
2953   st->cr();
2954 
2955   _pd_cache_table->print_on(st);
2956   st->cr();
2957 }
2958 
2959 void SystemDictionary::verify() {
2960   guarantee(constraints() != NULL,
2961             "Verify of loader constraints failed");
2962   guarantee(placeholders()->number_of_entries() >= 0,
2963             "Verify of placeholders failed");
2964 
2965   GCMutexLocker mu(SystemDictionary_lock);
2966 
2967   // Verify dictionary
2968   ClassLoaderDataGraph::verify_dictionary();
2969 
2970   placeholders()->verify();
2971 
2972   // Verify constraint table
2973   guarantee(constraints() != NULL, "Verify of loader constraints failed");
2974   constraints()->verify(placeholders());
2975 
2976   _pd_cache_table->verify();
2977 }
2978 
2979 void SystemDictionary::dump(outputStream *st, bool verbose) {
2980   assert_locked_or_safepoint(SystemDictionary_lock);
2981   if (verbose) {
2982     print_on(st);
2983   } else {
2984     if (shared_dictionary() != NULL) {
2985       shared_dictionary()->print_table_statistics(st, "Shared Dictionary");
2986     }
2987     ClassLoaderDataGraph::print_dictionary_statistics(st);
2988     placeholders()->print_table_statistics(st, "Placeholder Table");
2989     constraints()->print_table_statistics(st, "LoaderConstraints Table");
2990     _pd_cache_table->print_table_statistics(st, "ProtectionDomainCache Table");
2991   }
2992 }
2993 
2994 // Utility for dumping dictionaries.
2995 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
2996                                  DCmdWithParser(output, heap),
2997   _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
2998            "BOOLEAN", false, "false") {
2999   _dcmdparser.add_dcmd_option(&_verbose);
3000 }
3001 
3002 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
3003   VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
3004                          _verbose.value());
3005   VMThread::execute(&dumper);
3006 }
3007 
3008 int SystemDictionaryDCmd::num_arguments() {
3009   ResourceMark rm;
3010   SystemDictionaryDCmd* dcmd = new SystemDictionaryDCmd(NULL, false);
3011   if (dcmd != NULL) {
3012     DCmdMark mark(dcmd);
3013     return dcmd->_dcmdparser.num_arguments();
3014   } else {
3015     return 0;
3016   }
3017 }
3018 
3019 class CombineDictionariesClosure : public CLDClosure {
3020   private:
3021     Dictionary* _master_dictionary;
3022   public:
3023     CombineDictionariesClosure(Dictionary* master_dictionary) :
3024       _master_dictionary(master_dictionary) {}
3025     void do_cld(ClassLoaderData* cld) {
3026       ResourceMark rm;
3027       if (cld->is_unsafe_anonymous()) {
3028         return;
3029       }
3030       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
3031         for (int i = 0; i < cld->dictionary()->table_size(); ++i) {
3032           Dictionary* curr_dictionary = cld->dictionary();
3033           DictionaryEntry* p = curr_dictionary->bucket(i);
3034           while (p != NULL) {
3035             Symbol* name = p->instance_klass()->name();
3036             unsigned int d_hash = _master_dictionary->compute_hash(name);
3037             int d_index = _master_dictionary->hash_to_index(d_hash);
3038             DictionaryEntry* next = p->next();
3039             if (p->literal()->class_loader_data() != cld) {
3040               // This is an initiating class loader entry; don't use it
3041               log_trace(cds)("Skipping initiating cl entry: %s", name->as_C_string());
3042               curr_dictionary->free_entry(p);
3043             } else {
3044               log_trace(cds)("Moved to boot dictionary: %s", name->as_C_string());
3045               curr_dictionary->unlink_entry(p);
3046               p->set_pd_set(NULL); // pd_set is runtime only information and will be reconstructed.
3047               _master_dictionary->add_entry(d_index, p);
3048             }
3049             p = next;
3050           }
3051           *curr_dictionary->bucket_addr(i) = NULL;
3052         }
3053       }
3054     }
3055 };
3056 
3057 // Combining platform and system loader dictionaries into boot loader dictionary.
3058 // During run time, we only have one shared dictionary.
3059 void SystemDictionary::combine_shared_dictionaries() {
3060   assert(DumpSharedSpaces, "dump time only");
3061   Dictionary* master_dictionary = ClassLoaderData::the_null_class_loader_data()->dictionary();
3062   CombineDictionariesClosure cdc(master_dictionary);
3063   ClassLoaderDataGraph::cld_do(&cdc);
3064 
3065   // These tables are no longer valid or necessary. Keeping them around will
3066   // cause SystemDictionary::verify() to fail. Let's empty them.
3067   _placeholders        = new PlaceholderTable(_placeholder_table_size);
3068   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
3069 
3070   NOT_PRODUCT(SystemDictionary::verify());
3071 }
3072 
3073 void SystemDictionary::initialize_oop_storage() {
3074   _vm_weak_oop_storage =
3075     new OopStorage("VM Weak Oop Handles",
3076                    VMWeakAlloc_lock,
3077                    VMWeakActive_lock);
3078 }
3079 
3080 OopStorage* SystemDictionary::vm_weak_oop_storage() {
3081   assert(_vm_weak_oop_storage != NULL, "Uninitialized");
3082   return _vm_weak_oop_storage;
3083 }