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/classLoaderDataGraph.inline.hpp"
  33 #include "classfile/classLoaderExt.hpp"
  34 #include "classfile/dictionary.hpp"
  35 #include "classfile/javaClasses.inline.hpp"
  36 #include "classfile/klassFactory.hpp"
  37 #include "classfile/loaderConstraints.hpp"
  38 #include "classfile/packageEntry.hpp"
  39 #include "classfile/placeholders.hpp"
  40 #include "classfile/protectionDomainCache.hpp"
  41 #include "classfile/resolutionErrors.hpp"
  42 #include "classfile/stringTable.hpp"
  43 #include "classfile/systemDictionary.hpp"
  44 #include "classfile/vmSymbols.hpp"
  45 #include "code/codeCache.hpp"
  46 #include "compiler/compileBroker.hpp"
  47 #include "gc/shared/gcTraceTime.inline.hpp"
  48 #include "gc/shared/oopStorage.inline.hpp"
  49 #include "interpreter/bytecodeStream.hpp"
  50 #include "interpreter/interpreter.hpp"
  51 #include "jfr/jfrEvents.hpp"
  52 #include "logging/log.hpp"
  53 #include "logging/logStream.hpp"
  54 #include "memory/filemap.hpp"
  55 #include "memory/heapShared.hpp"
  56 #include "memory/metaspaceClosure.hpp"
  57 #include "memory/oopFactory.hpp"
  58 #include "memory/resourceArea.hpp"
  59 #include "oops/access.inline.hpp"
  60 #include "oops/instanceKlass.hpp"
  61 #include "oops/instanceRefKlass.hpp"
  62 #include "oops/klass.inline.hpp"
  63 #include "oops/method.inline.hpp"
  64 #include "oops/methodData.hpp"
  65 #include "oops/objArrayKlass.hpp"
  66 #include "oops/objArrayOop.inline.hpp"
  67 #include "oops/oop.inline.hpp"
  68 #include "oops/symbol.hpp"
  69 #include "oops/typeArrayKlass.hpp"
  70 #include "prims/jvmtiExport.hpp"
  71 #include "prims/resolvedMethodTable.hpp"
  72 #include "prims/methodHandles.hpp"
  73 #include "runtime/arguments.hpp"
  74 #include "runtime/arguments_ext.hpp"
  75 #include "runtime/biasedLocking.hpp"
  76 #include "runtime/fieldType.hpp"
  77 #include "runtime/handles.inline.hpp"
  78 #include "runtime/java.hpp"
  79 #include "runtime/javaCalls.hpp"
  80 #include "runtime/mutexLocker.hpp"
  81 #include "runtime/orderAccess.hpp"
  82 #include "runtime/sharedRuntime.hpp"
  83 #include "runtime/signature.hpp"
  84 #include "services/classLoadingService.hpp"
  85 #include "services/diagnosticCommand.hpp"
  86 #include "services/threadService.hpp"
  87 #include "utilities/macros.hpp"
  88 #if INCLUDE_CDS
  89 #include "classfile/systemDictionaryShared.hpp"
  90 #endif
  91 #if INCLUDE_JVMCI
  92 #include "jvmci/jvmciRuntime.hpp"
  93 #endif
  94 #if INCLUDE_JFR
  95 #include "jfr/jfr.hpp"
  96 #endif
  97 
  98 PlaceholderTable*      SystemDictionary::_placeholders        = NULL;
  99 Dictionary*            SystemDictionary::_shared_dictionary   = NULL;
 100 LoaderConstraintTable* SystemDictionary::_loader_constraints  = NULL;
 101 ResolutionErrorTable*  SystemDictionary::_resolution_errors   = NULL;
 102 SymbolPropertyTable*   SystemDictionary::_invoke_method_table = NULL;
 103 ProtectionDomainCacheTable*   SystemDictionary::_pd_cache_table = NULL;
 104 
 105 int         SystemDictionary::_number_of_modifications = 0;
 106 oop         SystemDictionary::_system_loader_lock_obj     =  NULL;
 107 
 108 InstanceKlass*      SystemDictionary::_well_known_klasses[SystemDictionary::WKID_LIMIT]
 109                                                           =  { NULL /*, NULL...*/ };
 110 
 111 InstanceKlass*      SystemDictionary::_box_klasses[T_VOID+1]      =  { NULL /*, NULL...*/ };
 112 
 113 oop         SystemDictionary::_java_system_loader         =  NULL;
 114 oop         SystemDictionary::_java_platform_loader       =  NULL;
 115 
 116 bool        SystemDictionary::_has_checkPackageAccess     =  false;
 117 
 118 // Default ProtectionDomainCacheSize value
 119 
 120 const int defaultProtectionDomainCacheSize = 1009;
 121 
 122 OopStorage* SystemDictionary::_vm_weak_oop_storage = NULL;
 123 
 124 
 125 // ----------------------------------------------------------------------------
 126 // Java-level SystemLoader and PlatformLoader
 127 
 128 oop SystemDictionary::java_system_loader() {
 129   return _java_system_loader;
 130 }
 131 
 132 oop SystemDictionary::java_platform_loader() {
 133   return _java_platform_loader;
 134 }
 135 
 136 void SystemDictionary::compute_java_loaders(TRAPS) {
 137   JavaValue result(T_OBJECT);
 138   InstanceKlass* class_loader_klass = SystemDictionary::ClassLoader_klass();
 139   JavaCalls::call_static(&result,
 140                          class_loader_klass,
 141                          vmSymbols::getSystemClassLoader_name(),
 142                          vmSymbols::void_classloader_signature(),
 143                          CHECK);
 144 
 145   _java_system_loader = (oop)result.get_jobject();
 146 
 147   JavaCalls::call_static(&result,
 148                          class_loader_klass,
 149                          vmSymbols::getPlatformClassLoader_name(),
 150                          vmSymbols::void_classloader_signature(),
 151                          CHECK);
 152 
 153   _java_platform_loader = (oop)result.get_jobject();
 154 }
 155 
 156 ClassLoaderData* SystemDictionary::register_loader(Handle class_loader) {
 157   if (class_loader() == NULL) return ClassLoaderData::the_null_class_loader_data();
 158   return ClassLoaderDataGraph::find_or_create(class_loader);
 159 }
 160 
 161 // ----------------------------------------------------------------------------
 162 // Parallel class loading check
 163 
 164 bool SystemDictionary::is_parallelCapable(Handle class_loader) {
 165   if (class_loader.is_null()) return true;
 166   if (AlwaysLockClassLoader) return false;
 167   return java_lang_ClassLoader::parallelCapable(class_loader());
 168 }
 169 // ----------------------------------------------------------------------------
 170 // ParallelDefineClass flag does not apply to bootclass loader
 171 bool SystemDictionary::is_parallelDefine(Handle class_loader) {
 172    if (class_loader.is_null()) return false;
 173    if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) {
 174      return true;
 175    }
 176    return false;
 177 }
 178 
 179 // Returns true if the passed class loader is the builtin application class loader
 180 // or a custom system class loader. A customer system class loader can be
 181 // specified via -Djava.system.class.loader.
 182 bool SystemDictionary::is_system_class_loader(oop class_loader) {
 183   if (class_loader == NULL) {
 184     return false;
 185   }
 186   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() ||
 187          oopDesc::equals(class_loader, _java_system_loader));
 188 }
 189 
 190 // Returns true if the passed class loader is the platform class loader.
 191 bool SystemDictionary::is_platform_class_loader(oop class_loader) {
 192   if (class_loader == NULL) {
 193     return false;
 194   }
 195   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass());
 196 }
 197 
 198 // ----------------------------------------------------------------------------
 199 // Resolving of classes
 200 
 201 // Forwards to resolve_or_null
 202 
 203 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader, Handle protection_domain, bool throw_error, TRAPS) {
 204   Klass* klass = resolve_or_null(class_name, class_loader, protection_domain, THREAD);
 205   if (HAS_PENDING_EXCEPTION || klass == NULL) {
 206     // can return a null klass
 207     klass = handle_resolution_exception(class_name, throw_error, klass, THREAD);
 208   }
 209   return klass;
 210 }
 211 
 212 Klass* SystemDictionary::handle_resolution_exception(Symbol* class_name,
 213                                                      bool throw_error,
 214                                                      Klass* klass, TRAPS) {
 215   if (HAS_PENDING_EXCEPTION) {
 216     // If we have a pending exception we forward it to the caller, unless throw_error is true,
 217     // in which case we have to check whether the pending exception is a ClassNotFoundException,
 218     // and if so convert it to a NoClassDefFoundError
 219     // And chain the original ClassNotFoundException
 220     if (throw_error && PENDING_EXCEPTION->is_a(SystemDictionary::ClassNotFoundException_klass())) {
 221       ResourceMark rm(THREAD);
 222       assert(klass == NULL, "Should not have result with exception pending");
 223       Handle e(THREAD, PENDING_EXCEPTION);
 224       CLEAR_PENDING_EXCEPTION;
 225       THROW_MSG_CAUSE_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e);
 226     } else {
 227       return NULL;
 228     }
 229   }
 230   // Class not found, throw appropriate error or exception depending on value of throw_error
 231   if (klass == NULL) {
 232     ResourceMark rm(THREAD);
 233     if (throw_error) {
 234       THROW_MSG_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string());
 235     } else {
 236       THROW_MSG_NULL(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string());
 237     }
 238   }
 239   return klass;
 240 }
 241 
 242 
 243 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name,
 244                                            bool throw_error, TRAPS)
 245 {
 246   return resolve_or_fail(class_name, Handle(), Handle(), throw_error, THREAD);
 247 }
 248 
 249 
 250 // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null
 251 
 252 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, Handle protection_domain, TRAPS) {
 253   if (FieldType::is_array(class_name)) {
 254     return resolve_array_class_or_null(class_name, class_loader, protection_domain, THREAD);
 255   } else {
 256     return resolve_instance_class_or_null_helper(class_name, class_loader, protection_domain, THREAD);
 257   }
 258 }
 259 
 260 // name may be in the form of "java/lang/Object" or "Ljava/lang/Object;"
 261 InstanceKlass* SystemDictionary::resolve_instance_class_or_null_helper(Symbol* class_name,
 262                                                                        Handle class_loader,
 263                                                                        Handle protection_domain,
 264                                                                        TRAPS) {
 265   assert(class_name != NULL && !FieldType::is_array(class_name), "must be");
 266   if (FieldType::is_obj(class_name)) {
 267     ResourceMark rm(THREAD);
 268     // Ignore wrapping L and ;.
 269     TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1,
 270                                    class_name->utf8_length() - 2, CHECK_NULL);
 271     return resolve_instance_class_or_null(name, class_loader, protection_domain, THREAD);
 272   } else {
 273     return resolve_instance_class_or_null(class_name, class_loader, protection_domain, THREAD);
 274   }
 275 }
 276 
 277 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, TRAPS) {
 278   return resolve_or_null(class_name, Handle(), Handle(), THREAD);
 279 }
 280 
 281 // Forwards to resolve_instance_class_or_null
 282 
 283 Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name,
 284                                                      Handle class_loader,
 285                                                      Handle protection_domain,
 286                                                      TRAPS) {
 287   assert(FieldType::is_array(class_name), "must be array");
 288   Klass* k = NULL;
 289   FieldArrayInfo fd;
 290   // dimension and object_key in FieldArrayInfo are assigned as a side-effect
 291   // of this call
 292   BasicType t = FieldType::get_array_info(class_name, fd, CHECK_NULL);
 293   if (t == T_OBJECT) {
 294     // naked oop "k" is OK here -- we assign back into it
 295     k = SystemDictionary::resolve_instance_class_or_null(fd.object_key(),
 296                                                          class_loader,
 297                                                          protection_domain,
 298                                                          CHECK_NULL);
 299     if (k != NULL) {
 300       k = k->array_klass(fd.dimension(), CHECK_NULL);
 301     }
 302   } else {
 303     k = Universe::typeArrayKlassObj(t);
 304     k = TypeArrayKlass::cast(k)->array_klass(fd.dimension(), CHECK_NULL);
 305   }
 306   return k;
 307 }
 308 
 309 
 310 // Must be called for any super-class or super-interface resolution
 311 // during class definition to allow class circularity checking
 312 // super-interface callers:
 313 //    parse_interfaces - for defineClass & jvmtiRedefineClasses
 314 // super-class callers:
 315 //   ClassFileParser - for defineClass & jvmtiRedefineClasses
 316 //   load_shared_class - while loading a class from shared archive
 317 //   resolve_instance_class_or_null:
 318 //     via: handle_parallel_super_load
 319 //      when resolving a class that has an existing placeholder with
 320 //      a saved superclass [i.e. a defineClass is currently in progress]
 321 //      if another thread is trying to resolve the class, it must do
 322 //      super-class checks on its own thread to catch class circularity
 323 // This last call is critical in class circularity checking for cases
 324 // where classloading is delegated to different threads and the
 325 // classloader lock is released.
 326 // Take the case: Base->Super->Base
 327 //   1. If thread T1 tries to do a defineClass of class Base
 328 //    resolve_super_or_fail creates placeholder: T1, Base (super Super)
 329 //   2. resolve_instance_class_or_null does not find SD or placeholder for Super
 330 //    so it tries to load Super
 331 //   3. If we load the class internally, or user classloader uses same thread
 332 //      loadClassFromxxx or defineClass via parseClassFile Super ...
 333 //      3.1 resolve_super_or_fail creates placeholder: T1, Super (super Base)
 334 //      3.3 resolve_instance_class_or_null Base, finds placeholder for Base
 335 //      3.4 calls resolve_super_or_fail Base
 336 //      3.5 finds T1,Base -> throws class circularity
 337 //OR 4. If T2 tries to resolve Super via defineClass Super ...
 338 //      4.1 resolve_super_or_fail creates placeholder: T2, Super (super Base)
 339 //      4.2 resolve_instance_class_or_null Base, finds placeholder for Base (super Super)
 340 //      4.3 calls resolve_super_or_fail Super in parallel on own thread T2
 341 //      4.4 finds T2, Super -> throws class circularity
 342 // Must be called, even if superclass is null, since this is
 343 // where the placeholder entry is created which claims this
 344 // thread is loading this class/classloader.
 345 // Be careful when modifying this code: once you have run
 346 // placeholders()->find_and_add(PlaceholderTable::LOAD_SUPER),
 347 // you need to find_and_remove it before returning.
 348 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 349 InstanceKlass* SystemDictionary::resolve_super_or_fail(Symbol* child_name,
 350                                                        Symbol* super_name,
 351                                                        Handle class_loader,
 352                                                        Handle protection_domain,
 353                                                        bool is_superclass,
 354                                                        TRAPS) {
 355   assert(!FieldType::is_array(super_name), "invalid super class name");
 356 #if INCLUDE_CDS
 357   if (DumpSharedSpaces) {
 358     // Special processing for CDS dump time.
 359     InstanceKlass* k = SystemDictionaryShared::dump_time_resolve_super_or_fail(child_name,
 360         super_name, class_loader, protection_domain, is_superclass, CHECK_NULL);
 361     if (k) {
 362       return k;
 363     }
 364   }
 365 #endif // INCLUDE_CDS
 366 
 367   // Double-check, if child class is already loaded, just return super-class,interface
 368   // Don't add a placedholder if already loaded, i.e. already in appropriate class loader
 369   // dictionary.
 370   // Make sure there's a placeholder for the *child* before resolving.
 371   // Used as a claim that this thread is currently loading superclass/classloader
 372   // Used here for ClassCircularity checks and also for heap verification
 373   // (every InstanceKlass needs to be in its class loader dictionary or have a placeholder).
 374   // Must check ClassCircularity before checking if super class is already loaded.
 375   //
 376   // We might not already have a placeholder if this child_name was
 377   // first seen via resolve_from_stream (jni_DefineClass or JVM_DefineClass);
 378   // the name of the class might not be known until the stream is actually
 379   // parsed.
 380   // Bugs 4643874, 4715493
 381 
 382   ClassLoaderData* loader_data = class_loader_data(class_loader);
 383   Dictionary* dictionary = loader_data->dictionary();
 384   unsigned int d_hash = dictionary->compute_hash(child_name);
 385   unsigned int p_hash = placeholders()->compute_hash(child_name);
 386   int p_index = placeholders()->hash_to_index(p_hash);
 387   // can't throw error holding a lock
 388   bool child_already_loaded = false;
 389   bool throw_circularity_error = false;
 390   {
 391     MutexLocker mu(SystemDictionary_lock, THREAD);
 392     InstanceKlass* childk = find_class(d_hash, child_name, dictionary);
 393     InstanceKlass* quicksuperk;
 394     // to support // loading: if child done loading, just return superclass
 395     // if super_name, & class_loader don't match:
 396     // if initial define, SD update will give LinkageError
 397     // if redefine: compare_class_versions will give HIERARCHY_CHANGED
 398     // so we don't throw an exception here.
 399     // see: nsk redefclass014 & java.lang.instrument Instrument032
 400     if ((childk != NULL ) && (is_superclass) &&
 401         ((quicksuperk = childk->java_super()) != NULL) &&
 402          ((quicksuperk->name() == super_name) &&
 403             (oopDesc::equals(quicksuperk->class_loader(), class_loader())))) {
 404            return quicksuperk;
 405     } else {
 406       PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, child_name, loader_data);
 407       if (probe && probe->check_seen_thread(THREAD, PlaceholderTable::LOAD_SUPER)) {
 408           throw_circularity_error = true;
 409       }
 410     }
 411     if (!throw_circularity_error) {
 412       // Be careful not to exit resolve_super
 413       PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, super_name, THREAD);
 414     }
 415   }
 416   if (throw_circularity_error) {
 417       ResourceMark rm(THREAD);
 418       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), child_name->as_C_string());
 419   }
 420 
 421 // java.lang.Object should have been found above
 422   assert(super_name != NULL, "null super class for resolving");
 423   // Resolve the super class or interface, check results on return
 424   InstanceKlass* superk =
 425     SystemDictionary::resolve_instance_class_or_null_helper(super_name,
 426                                                             class_loader,
 427                                                             protection_domain,
 428                                                             THREAD);
 429 
 430   // Clean up of placeholders moved so that each classloadAction registrar self-cleans up
 431   // It is no longer necessary to keep the placeholder table alive until update_dictionary
 432   // or error. GC used to walk the placeholder table as strong roots.
 433   // The instanceKlass is kept alive because the class loader is on the stack,
 434   // which keeps the loader_data alive, as well as all instanceKlasses in
 435   // the loader_data. parseClassFile adds the instanceKlass to loader_data.
 436   {
 437     MutexLocker mu(SystemDictionary_lock, THREAD);
 438     placeholders()->find_and_remove(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, THREAD);
 439     SystemDictionary_lock->notify_all();
 440   }
 441   if (HAS_PENDING_EXCEPTION || superk == NULL) {
 442     // can null superk
 443     Klass* k = handle_resolution_exception(super_name, true, superk, THREAD);
 444     assert(k == NULL || k == superk, "must be");
 445     if (k == NULL) {
 446       superk = NULL;
 447     }
 448   }
 449 
 450   return superk;
 451 }
 452 
 453 void SystemDictionary::validate_protection_domain(InstanceKlass* klass,
 454                                                   Handle class_loader,
 455                                                   Handle protection_domain,
 456                                                   TRAPS) {
 457   if(!has_checkPackageAccess()) return;
 458 
 459   // Now we have to call back to java to check if the initating class has access
 460   JavaValue result(T_VOID);
 461   LogTarget(Debug, protectiondomain) lt;
 462   if (lt.is_enabled()) {
 463     ResourceMark rm;
 464     // Print out trace information
 465     LogStream ls(lt);
 466     ls.print_cr("Checking package access");
 467     if (class_loader() != NULL) {
 468       ls.print("class loader: ");
 469       class_loader()->print_value_on(&ls);
 470     } else {
 471       ls.print_cr("class loader: NULL");
 472     }
 473     if (protection_domain() != NULL) {
 474       ls.print(" protection domain: ");
 475       protection_domain()->print_value_on(&ls);
 476     } else {
 477       ls.print_cr(" protection domain: NULL");
 478     }
 479     ls.print(" loading: "); klass->print_value_on(&ls);
 480     ls.cr();
 481   }
 482 
 483   // This handle and the class_loader handle passed in keeps this class from
 484   // being unloaded through several GC points.
 485   // The class_loader handle passed in is the initiating loader.
 486   Handle mirror(THREAD, klass->java_mirror());
 487 
 488   InstanceKlass* system_loader = SystemDictionary::ClassLoader_klass();
 489   JavaCalls::call_special(&result,
 490                          class_loader,
 491                          system_loader,
 492                          vmSymbols::checkPackageAccess_name(),
 493                          vmSymbols::class_protectiondomain_signature(),
 494                          mirror,
 495                          protection_domain,
 496                          THREAD);
 497 
 498   if (HAS_PENDING_EXCEPTION) {
 499     log_debug(protectiondomain)("DENIED !!!!!!!!!!!!!!!!!!!!!");
 500   } else {
 501    log_debug(protectiondomain)("granted");
 502   }
 503 
 504   if (HAS_PENDING_EXCEPTION) return;
 505 
 506   // If no exception has been thrown, we have validated the protection domain
 507   // Insert the protection domain of the initiating class into the set.
 508   {
 509     ClassLoaderData* loader_data = class_loader_data(class_loader);
 510     Dictionary* dictionary = loader_data->dictionary();
 511 
 512     Symbol*  kn = klass->name();
 513     unsigned int d_hash = dictionary->compute_hash(kn);
 514 
 515     MutexLocker mu(SystemDictionary_lock, THREAD);
 516     int d_index = dictionary->hash_to_index(d_hash);
 517     dictionary->add_protection_domain(d_index, d_hash, klass,
 518                                       protection_domain, THREAD);
 519   }
 520 }
 521 
 522 // We only get here if this thread finds that another thread
 523 // has already claimed the placeholder token for the current operation,
 524 // but that other thread either never owned or gave up the
 525 // object lock
 526 // Waits on SystemDictionary_lock to indicate placeholder table updated
 527 // On return, caller must recheck placeholder table state
 528 //
 529 // We only get here if
 530 //  1) custom classLoader, i.e. not bootstrap classloader
 531 //  2) custom classLoader has broken the class loader objectLock
 532 //     so another thread got here in parallel
 533 //
 534 // lockObject must be held.
 535 // Complicated dance due to lock ordering:
 536 // Must first release the classloader object lock to
 537 // allow initial definer to complete the class definition
 538 // and to avoid deadlock
 539 // Reclaim classloader lock object with same original recursion count
 540 // Must release SystemDictionary_lock after notify, since
 541 // class loader lock must be claimed before SystemDictionary_lock
 542 // to prevent deadlocks
 543 //
 544 // The notify allows applications that did an untimed wait() on
 545 // the classloader object lock to not hang.
 546 void SystemDictionary::double_lock_wait(Handle lockObject, TRAPS) {
 547   assert_lock_strong(SystemDictionary_lock);
 548 
 549   bool calledholdinglock
 550       = ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD, lockObject);
 551   assert(calledholdinglock,"must hold lock for notify");
 552   assert((!oopDesc::equals(lockObject(), _system_loader_lock_obj) && !is_parallelCapable(lockObject)), "unexpected double_lock_wait");
 553   ObjectSynchronizer::notifyall(lockObject, THREAD);
 554   intptr_t recursions =  ObjectSynchronizer::complete_exit(lockObject, THREAD);
 555   SystemDictionary_lock->wait();
 556   SystemDictionary_lock->unlock();
 557   ObjectSynchronizer::reenter(lockObject, recursions, THREAD);
 558   SystemDictionary_lock->lock();
 559 }
 560 
 561 // If the class in is in the placeholder table, class loading is in progress
 562 // For cases where the application changes threads to load classes, it
 563 // is critical to ClassCircularity detection that we try loading
 564 // the superclass on the same thread internally, so we do parallel
 565 // super class loading here.
 566 // This also is critical in cases where the original thread gets stalled
 567 // even in non-circularity situations.
 568 // Note: must call resolve_super_or_fail even if null super -
 569 // to force placeholder entry creation for this class for circularity detection
 570 // Caller must check for pending exception
 571 // Returns non-null Klass* if other thread has completed load
 572 // and we are done,
 573 // If return null Klass* and no pending exception, the caller must load the class
 574 InstanceKlass* SystemDictionary::handle_parallel_super_load(
 575     Symbol* name, Symbol* superclassname, Handle class_loader,
 576     Handle protection_domain, Handle lockObject, TRAPS) {
 577 
 578   ClassLoaderData* loader_data = class_loader_data(class_loader);
 579   Dictionary* dictionary = loader_data->dictionary();
 580   unsigned int d_hash = dictionary->compute_hash(name);
 581   unsigned int p_hash = placeholders()->compute_hash(name);
 582   int p_index = placeholders()->hash_to_index(p_hash);
 583 
 584   // superk is not used, resolve_super called for circularity check only
 585   // This code is reached in two situations. One if this thread
 586   // is loading the same class twice (e.g. ClassCircularity, or
 587   // java.lang.instrument).
 588   // The second is if another thread started the resolve_super first
 589   // and has not yet finished.
 590   // In both cases the original caller will clean up the placeholder
 591   // entry on error.
 592   Klass* superk = SystemDictionary::resolve_super_or_fail(name,
 593                                                           superclassname,
 594                                                           class_loader,
 595                                                           protection_domain,
 596                                                           true,
 597                                                           CHECK_NULL);
 598 
 599   // parallelCapable class loaders do NOT wait for parallel superclass loads to complete
 600   // Serial class loaders and bootstrap classloader do wait for superclass loads
 601  if (!class_loader.is_null() && is_parallelCapable(class_loader)) {
 602     MutexLocker mu(SystemDictionary_lock, THREAD);
 603     // Check if classloading completed while we were loading superclass or waiting
 604     return find_class(d_hash, name, dictionary);
 605   }
 606 
 607   // must loop to both handle other placeholder updates
 608   // and spurious notifications
 609   bool super_load_in_progress = true;
 610   PlaceholderEntry* placeholder;
 611   while (super_load_in_progress) {
 612     MutexLocker mu(SystemDictionary_lock, THREAD);
 613     // Check if classloading completed while we were loading superclass or waiting
 614     InstanceKlass* check = find_class(d_hash, name, dictionary);
 615     if (check != NULL) {
 616       // Klass is already loaded, so just return it
 617       return check;
 618     } else {
 619       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 620       if (placeholder && placeholder->super_load_in_progress() ){
 621         // We only get here if the application has released the
 622         // classloader lock when another thread was in the middle of loading a
 623         // superclass/superinterface for this class, and now
 624         // this thread is also trying to load this class.
 625         // To minimize surprises, the first thread that started to
 626         // load a class should be the one to complete the loading
 627         // with the classfile it initially expected.
 628         // This logic has the current thread wait once it has done
 629         // all the superclass/superinterface loading it can, until
 630         // the original thread completes the class loading or fails
 631         // If it completes we will use the resulting InstanceKlass
 632         // which we will find below in the systemDictionary.
 633         // We also get here for parallel bootstrap classloader
 634         if (class_loader.is_null()) {
 635           SystemDictionary_lock->wait();
 636         } else {
 637           double_lock_wait(lockObject, THREAD);
 638         }
 639       } else {
 640         // If not in SD and not in PH, other thread's load must have failed
 641         super_load_in_progress = false;
 642       }
 643     }
 644   }
 645   return NULL;
 646 }
 647 
 648 static void post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
 649   assert(event != NULL, "invariant");
 650   assert(k != NULL, "invariant");
 651   assert(event->should_commit(), "invariant");
 652   event->set_loadedClass(k);
 653   event->set_definingClassLoader(k->class_loader_data());
 654   event->set_initiatingClassLoader(init_cld);
 655   event->commit();
 656 }
 657 
 658 
 659 // Be careful when modifying this code: once you have run
 660 // placeholders()->find_and_add(PlaceholderTable::LOAD_INSTANCE),
 661 // you need to find_and_remove it before returning.
 662 // So be careful to not exit with a CHECK_ macro betweeen these calls.
 663 //
 664 // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;"
 665 InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name,
 666                                                                 Handle class_loader,
 667                                                                 Handle protection_domain,
 668                                                                 TRAPS) {
 669   assert(name != NULL && !FieldType::is_array(name) &&
 670          !FieldType::is_obj(name), "invalid class name");
 671 
 672   EventClassLoad class_load_start_event;
 673 
 674   HandleMark hm(THREAD);
 675 
 676   // Fix for 4474172; see evaluation for more details
 677   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 678   ClassLoaderData* loader_data = register_loader(class_loader);
 679   Dictionary* dictionary = loader_data->dictionary();
 680   unsigned int d_hash = dictionary->compute_hash(name);
 681 
 682   // Do lookup to see if class already exist and the protection domain
 683   // has the right access
 684   // This call uses find which checks protection domain already matches
 685   // All subsequent calls use find_class, and set has_loaded_class so that
 686   // before we return a result we call out to java to check for valid protection domain
 687   // to allow returning the Klass* and add it to the pd_set if it is valid
 688   {
 689     InstanceKlass* probe = dictionary->find(d_hash, name, protection_domain);
 690     if (probe != NULL) return probe;
 691   }
 692 
 693   // Non-bootstrap class loaders will call out to class loader and
 694   // define via jvm/jni_DefineClass which will acquire the
 695   // class loader object lock to protect against multiple threads
 696   // defining the class in parallel by accident.
 697   // This lock must be acquired here so the waiter will find
 698   // any successful result in the SystemDictionary and not attempt
 699   // the define.
 700   // ParallelCapable Classloaders and the bootstrap classloader
 701   // do not acquire lock here.
 702   bool DoObjectLock = true;
 703   if (is_parallelCapable(class_loader)) {
 704     DoObjectLock = false;
 705   }
 706 
 707   unsigned int p_hash = placeholders()->compute_hash(name);
 708   int p_index = placeholders()->hash_to_index(p_hash);
 709 
 710   // Class is not in SystemDictionary so we have to do loading.
 711   // Make sure we are synchronized on the class loader before we proceed
 712   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
 713   check_loader_lock_contention(lockObject, THREAD);
 714   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
 715 
 716   // Check again (after locking) if class already exist in SystemDictionary
 717   bool class_has_been_loaded   = false;
 718   bool super_load_in_progress  = false;
 719   bool havesupername = false;
 720   InstanceKlass* k = NULL;
 721   PlaceholderEntry* placeholder;
 722   Symbol* superclassname = NULL;
 723 
 724   assert(THREAD->can_call_java(),
 725          "can not load classes with compiler thread: class=%s, classloader=%s",
 726          name->as_C_string(),
 727          class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string());
 728   {
 729     MutexLocker mu(SystemDictionary_lock, THREAD);
 730     InstanceKlass* check = find_class(d_hash, name, dictionary);
 731     if (check != NULL) {
 732       // InstanceKlass is already loaded, so just return it
 733       class_has_been_loaded = true;
 734       k = check;
 735     } else {
 736       placeholder = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 737       if (placeholder && placeholder->super_load_in_progress()) {
 738          super_load_in_progress = true;
 739          if (placeholder->havesupername() == true) {
 740            superclassname = placeholder->supername();
 741            havesupername = true;
 742          }
 743       }
 744     }
 745   }
 746 
 747   // If the class is in the placeholder table, class loading is in progress
 748   if (super_load_in_progress && havesupername==true) {
 749     k = handle_parallel_super_load(name,
 750                                    superclassname,
 751                                    class_loader,
 752                                    protection_domain,
 753                                    lockObject, THREAD);
 754     if (HAS_PENDING_EXCEPTION) {
 755       return NULL;
 756     }
 757     if (k != NULL) {
 758       class_has_been_loaded = true;
 759     }
 760   }
 761 
 762   bool throw_circularity_error = false;
 763   if (!class_has_been_loaded) {
 764     bool load_instance_added = false;
 765 
 766     // add placeholder entry to record loading instance class
 767     // Five cases:
 768     // All cases need to prevent modifying bootclasssearchpath
 769     // in parallel with a classload of same classname
 770     // Redefineclasses uses existence of the placeholder for the duration
 771     // of the class load to prevent concurrent redefinition of not completely
 772     // defined classes.
 773     // case 1. traditional classloaders that rely on the classloader object lock
 774     //   - no other need for LOAD_INSTANCE
 775     // case 2. traditional classloaders that break the classloader object lock
 776     //    as a deadlock workaround. Detection of this case requires that
 777     //    this check is done while holding the classloader object lock,
 778     //    and that lock is still held when calling classloader's loadClass.
 779     //    For these classloaders, we ensure that the first requestor
 780     //    completes the load and other requestors wait for completion.
 781     // case 3. Bootstrap classloader - don't own objectLocker
 782     //    This classloader supports parallelism at the classloader level,
 783     //    but only allows a single load of a class/classloader pair.
 784     //    No performance benefit and no deadlock issues.
 785     // case 4. parallelCapable user level classloaders - without objectLocker
 786     //    Allow parallel classloading of a class/classloader pair
 787 
 788     {
 789       MutexLocker mu(SystemDictionary_lock, THREAD);
 790       if (class_loader.is_null() || !is_parallelCapable(class_loader)) {
 791         PlaceholderEntry* oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 792         if (oldprobe) {
 793           // only need check_seen_thread once, not on each loop
 794           // 6341374 java/lang/Instrument with -Xcomp
 795           if (oldprobe->check_seen_thread(THREAD, PlaceholderTable::LOAD_INSTANCE)) {
 796             throw_circularity_error = true;
 797           } else {
 798             // case 1: traditional: should never see load_in_progress.
 799             while (!class_has_been_loaded && oldprobe && oldprobe->instance_load_in_progress()) {
 800 
 801               // case 3: bootstrap classloader: prevent futile classloading,
 802               // wait on first requestor
 803               if (class_loader.is_null()) {
 804                 SystemDictionary_lock->wait();
 805               } else {
 806               // case 2: traditional with broken classloader lock. wait on first
 807               // requestor.
 808                 double_lock_wait(lockObject, THREAD);
 809               }
 810               // Check if classloading completed while we were waiting
 811               InstanceKlass* check = find_class(d_hash, name, dictionary);
 812               if (check != NULL) {
 813                 // Klass is already loaded, so just return it
 814                 k = check;
 815                 class_has_been_loaded = true;
 816               }
 817               // check if other thread failed to load and cleaned up
 818               oldprobe = placeholders()->get_entry(p_index, p_hash, name, loader_data);
 819             }
 820           }
 821         }
 822       }
 823       // All cases: add LOAD_INSTANCE holding SystemDictionary_lock
 824       // case 4: parallelCapable: allow competing threads to try
 825       // LOAD_INSTANCE in parallel
 826 
 827       if (!throw_circularity_error && !class_has_been_loaded) {
 828         PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, NULL, THREAD);
 829         load_instance_added = true;
 830         // For class loaders that do not acquire the classloader object lock,
 831         // if they did not catch another thread holding LOAD_INSTANCE,
 832         // need a check analogous to the acquire ObjectLocker/find_class
 833         // i.e. now that we hold the LOAD_INSTANCE token on loading this class/CL
 834         // one final check if the load has already completed
 835         // class loaders holding the ObjectLock shouldn't find the class here
 836         InstanceKlass* check = find_class(d_hash, name, dictionary);
 837         if (check != NULL) {
 838         // Klass is already loaded, so return it after checking/adding protection domain
 839           k = check;
 840           class_has_been_loaded = true;
 841         }
 842       }
 843     }
 844 
 845     // must throw error outside of owning lock
 846     if (throw_circularity_error) {
 847       assert(!HAS_PENDING_EXCEPTION && load_instance_added == false,"circularity error cleanup");
 848       ResourceMark rm(THREAD);
 849       THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string());
 850     }
 851 
 852     if (!class_has_been_loaded) {
 853 
 854       // Do actual loading
 855       k = load_instance_class(name, class_loader, THREAD);
 856 
 857       // If everything was OK (no exceptions, no null return value), and
 858       // class_loader is NOT the defining loader, do a little more bookkeeping.
 859       if (!HAS_PENDING_EXCEPTION && k != NULL &&
 860         !oopDesc::equals(k->class_loader(), class_loader())) {
 861 
 862         check_constraints(d_hash, k, class_loader, false, THREAD);
 863 
 864         // Need to check for a PENDING_EXCEPTION again; check_constraints
 865         // can throw and doesn't use the CHECK macro.
 866         if (!HAS_PENDING_EXCEPTION) {
 867           { // Grabbing the Compile_lock prevents systemDictionary updates
 868             // during compilations.
 869             MutexLocker mu(Compile_lock, THREAD);
 870             update_dictionary(d_hash, p_index, p_hash,
 871               k, class_loader, THREAD);
 872           }
 873 
 874           if (JvmtiExport::should_post_class_load()) {
 875             Thread *thread = THREAD;
 876             assert(thread->is_Java_thread(), "thread->is_Java_thread()");
 877             JvmtiExport::post_class_load((JavaThread *) thread, k);
 878           }
 879         }
 880       }
 881     } // load_instance_class
 882 
 883     if (load_instance_added == true) {
 884       // clean up placeholder entries for LOAD_INSTANCE success or error
 885       // This brackets the SystemDictionary updates for both defining
 886       // and initiating loaders
 887       MutexLocker mu(SystemDictionary_lock, THREAD);
 888       placeholders()->find_and_remove(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD);
 889       SystemDictionary_lock->notify_all();
 890     }
 891   }
 892 
 893   if (HAS_PENDING_EXCEPTION || k == NULL) {
 894     return NULL;
 895   }
 896   if (class_load_start_event.should_commit()) {
 897     post_class_load_event(&class_load_start_event, k, loader_data);
 898   }
 899 #ifdef ASSERT
 900   {
 901     ClassLoaderData* loader_data = k->class_loader_data();
 902     MutexLocker mu(SystemDictionary_lock, THREAD);
 903     InstanceKlass* kk = find_class(name, loader_data);
 904     assert(kk == k, "should be present in dictionary");
 905   }
 906 #endif
 907 
 908   // return if the protection domain in NULL
 909   if (protection_domain() == NULL) return k;
 910 
 911   // Check the protection domain has the right access
 912   if (dictionary->is_valid_protection_domain(d_hash, name,
 913                                              protection_domain)) {
 914     return k;
 915   }
 916 
 917   // Verify protection domain. If it fails an exception is thrown
 918   validate_protection_domain(k, class_loader, protection_domain, CHECK_NULL);
 919 
 920   return k;
 921 }
 922 
 923 
 924 // This routine does not lock the system dictionary.
 925 //
 926 // Since readers don't hold a lock, we must make sure that system
 927 // dictionary entries are only removed at a safepoint (when only one
 928 // thread is running), and are added to in a safe way (all links must
 929 // be updated in an MT-safe manner).
 930 //
 931 // Callers should be aware that an entry could be added just after
 932 // _dictionary->bucket(index) is read here, so the caller will not see
 933 // the new entry.
 934 
 935 Klass* SystemDictionary::find(Symbol* class_name,
 936                               Handle class_loader,
 937                               Handle protection_domain,
 938                               TRAPS) {
 939 
 940   // The result of this call should be consistent with the result
 941   // of the call to resolve_instance_class_or_null().
 942   // See evaluation 6790209 and 4474172 for more details.
 943   class_loader = Handle(THREAD, java_lang_ClassLoader::non_reflection_class_loader(class_loader()));
 944   ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
 945 
 946   if (loader_data == NULL) {
 947     // If the ClassLoaderData has not been setup,
 948     // then the class loader has no entries in the dictionary.
 949     return NULL;
 950   }
 951 
 952   Dictionary* dictionary = loader_data->dictionary();
 953   unsigned int d_hash = dictionary->compute_hash(class_name);
 954   return dictionary->find(d_hash, class_name,
 955                           protection_domain);
 956 }
 957 
 958 
 959 // Look for a loaded instance or array klass by name.  Do not do any loading.
 960 // return NULL in case of error.
 961 Klass* SystemDictionary::find_instance_or_array_klass(Symbol* class_name,
 962                                                       Handle class_loader,
 963                                                       Handle protection_domain,
 964                                                       TRAPS) {
 965   Klass* k = NULL;
 966   assert(class_name != NULL, "class name must be non NULL");
 967 
 968   if (FieldType::is_array(class_name)) {
 969     // The name refers to an array.  Parse the name.
 970     // dimension and object_key in FieldArrayInfo are assigned as a
 971     // side-effect of this call
 972     FieldArrayInfo fd;
 973     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
 974     if (t != T_OBJECT) {
 975       k = Universe::typeArrayKlassObj(t);
 976     } else {
 977       k = SystemDictionary::find(fd.object_key(), class_loader, protection_domain, THREAD);
 978     }
 979     if (k != NULL) {
 980       k = k->array_klass_or_null(fd.dimension());
 981     }
 982   } else {
 983     k = find(class_name, class_loader, protection_domain, THREAD);
 984   }
 985   return k;
 986 }
 987 
 988 // Note: this method is much like resolve_from_stream, but
 989 // does not publish the classes via the SystemDictionary.
 990 // Handles unsafe_DefineAnonymousClass and redefineclasses
 991 // RedefinedClasses do not add to the class hierarchy
 992 InstanceKlass* SystemDictionary::parse_stream(Symbol* class_name,
 993                                               Handle class_loader,
 994                                               Handle protection_domain,
 995                                               ClassFileStream* st,
 996                                               const InstanceKlass* unsafe_anonymous_host,
 997                                               GrowableArray<Handle>* cp_patches,
 998                                               TRAPS) {
 999 
1000   EventClassLoad class_load_start_event;
1001 
1002   ClassLoaderData* loader_data;
1003   if (unsafe_anonymous_host != NULL) {
1004     // Create a new CLD for an unsafe anonymous class, that uses the same class loader
1005     // as the unsafe_anonymous_host
1006     guarantee(oopDesc::equals(unsafe_anonymous_host->class_loader(), class_loader()), "should be the same");
1007     loader_data = ClassLoaderData::unsafe_anonymous_class_loader_data(class_loader);
1008   } else {
1009     loader_data = ClassLoaderData::class_loader_data(class_loader());
1010   }
1011 
1012   assert(st != NULL, "invariant");
1013   assert(st->need_verify(), "invariant");
1014 
1015   // Parse stream and create a klass.
1016   // Note that we do this even though this klass might
1017   // already be present in the SystemDictionary, otherwise we would not
1018   // throw potential ClassFormatErrors.
1019 
1020   InstanceKlass* k = KlassFactory::create_from_stream(st,
1021                                                       class_name,
1022                                                       loader_data,
1023                                                       protection_domain,
1024                                                       unsafe_anonymous_host,
1025                                                       cp_patches,
1026                                                       CHECK_NULL);
1027 
1028   if (unsafe_anonymous_host != NULL && k != NULL) {
1029     // Unsafe anonymous classes must update ClassLoaderData holder (was unsafe_anonymous_host loader)
1030     // so that they can be unloaded when the mirror is no longer referenced.
1031     k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror()));
1032 
1033     {
1034       MutexLocker mu_r(Compile_lock, THREAD);
1035 
1036       // Add to class hierarchy, initialize vtables, and do possible
1037       // deoptimizations.
1038       add_to_hierarchy(k, CHECK_NULL); // No exception, but can block
1039 
1040       // But, do not add to dictionary.
1041 
1042       // compiled code dependencies need to be validated anyway
1043       notice_modification();
1044     }
1045 
1046     // Rewrite and patch constant pool here.
1047     k->link_class(CHECK_NULL);
1048     if (cp_patches != NULL) {
1049       k->constants()->patch_resolved_references(cp_patches);
1050     }
1051 
1052     // If it's anonymous, initialize it now, since nobody else will.
1053     k->eager_initialize(CHECK_NULL);
1054 
1055     // notify jvmti
1056     if (JvmtiExport::should_post_class_load()) {
1057         assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1058         JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1059     }
1060     if (class_load_start_event.should_commit()) {
1061       post_class_load_event(&class_load_start_event, k, loader_data);
1062     }
1063   }
1064   assert(unsafe_anonymous_host != NULL || NULL == cp_patches,
1065          "cp_patches only found with unsafe_anonymous_host");
1066 
1067   return k;
1068 }
1069 
1070 // Add a klass to the system from a stream (called by jni_DefineClass and
1071 // JVM_DefineClass).
1072 // Note: class_name can be NULL. In that case we do not know the name of
1073 // the class until we have parsed the stream.
1074 
1075 InstanceKlass* SystemDictionary::resolve_from_stream(Symbol* class_name,
1076                                                      Handle class_loader,
1077                                                      Handle protection_domain,
1078                                                      ClassFileStream* st,
1079                                                      TRAPS) {
1080 
1081   HandleMark hm(THREAD);
1082 
1083   // Classloaders that support parallelism, e.g. bootstrap classloader,
1084   // do not acquire lock here
1085   bool DoObjectLock = true;
1086   if (is_parallelCapable(class_loader)) {
1087     DoObjectLock = false;
1088   }
1089 
1090   ClassLoaderData* loader_data = register_loader(class_loader);
1091 
1092   // Make sure we are synchronized on the class loader before we proceed
1093   Handle lockObject = compute_loader_lock_object(class_loader, THREAD);
1094   check_loader_lock_contention(lockObject, THREAD);
1095   ObjectLocker ol(lockObject, THREAD, DoObjectLock);
1096 
1097   assert(st != NULL, "invariant");
1098 
1099   // Parse the stream and create a klass.
1100   // Note that we do this even though this klass might
1101   // already be present in the SystemDictionary, otherwise we would not
1102   // throw potential ClassFormatErrors.
1103  InstanceKlass* k = NULL;
1104 
1105 #if INCLUDE_CDS
1106   if (!DumpSharedSpaces) {
1107     k = SystemDictionaryShared::lookup_from_stream(class_name,
1108                                                    class_loader,
1109                                                    protection_domain,
1110                                                    st,
1111                                                    CHECK_NULL);
1112   }
1113 #endif
1114 
1115   if (k == NULL) {
1116     if (st->buffer() == NULL) {
1117       return NULL;
1118     }
1119     k = KlassFactory::create_from_stream(st,
1120                                          class_name,
1121                                          loader_data,
1122                                          protection_domain,
1123                                          NULL, // unsafe_anonymous_host
1124                                          NULL, // cp_patches
1125                                          CHECK_NULL);
1126   }
1127 
1128   assert(k != NULL, "no klass created");
1129   Symbol* h_name = k->name();
1130   assert(class_name == NULL || class_name == h_name, "name mismatch");
1131 
1132   // Add class just loaded
1133   // If a class loader supports parallel classloading handle parallel define requests
1134   // find_or_define_instance_class may return a different InstanceKlass
1135   if (is_parallelCapable(class_loader)) {
1136     InstanceKlass* defined_k = find_or_define_instance_class(h_name, class_loader, k, THREAD);
1137     if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1138       // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1139       assert(defined_k != NULL, "Should have a klass if there's no exception");
1140       loader_data->add_to_deallocate_list(k);
1141       k = defined_k;
1142     }
1143   } else {
1144     define_instance_class(k, THREAD);
1145   }
1146 
1147   // If defining the class throws an exception register 'k' for cleanup.
1148   if (HAS_PENDING_EXCEPTION) {
1149     assert(k != NULL, "Must have an instance klass here!");
1150     loader_data->add_to_deallocate_list(k);
1151     return NULL;
1152   }
1153 
1154   // Make sure we have an entry in the SystemDictionary on success
1155   debug_only( {
1156     MutexLocker mu(SystemDictionary_lock, THREAD);
1157 
1158     Klass* check = find_class(h_name, k->class_loader_data());
1159     assert(check == k, "should be present in the dictionary");
1160   } );
1161 
1162   return k;
1163 }
1164 
1165 #if INCLUDE_CDS
1166 void SystemDictionary::set_shared_dictionary(HashtableBucket<mtClass>* t, int length,
1167                                              int number_of_entries) {
1168   assert(!DumpSharedSpaces, "Should not be called with DumpSharedSpaces");
1169   assert(length == _shared_dictionary_size * sizeof(HashtableBucket<mtClass>),
1170          "bad shared dictionary size.");
1171   _shared_dictionary = new Dictionary(ClassLoaderData::the_null_class_loader_data(),
1172                                       _shared_dictionary_size, t, number_of_entries,
1173                                       false /* explicitly set _resizable to false */);
1174 }
1175 
1176 
1177 // If there is a shared dictionary, then find the entry for the
1178 // given shared system class, if any.
1179 
1180 InstanceKlass* SystemDictionary::find_shared_class(Symbol* class_name) {
1181   if (shared_dictionary() != NULL) {
1182     unsigned int d_hash = shared_dictionary()->compute_hash(class_name);
1183     int d_index = shared_dictionary()->hash_to_index(d_hash);
1184 
1185     return shared_dictionary()->find_shared_class(d_index, d_hash, class_name);
1186   } else {
1187     return NULL;
1188   }
1189 }
1190 
1191 
1192 // Load a class for boot loader from the shared spaces (found through
1193 // the shared system dictionary). Force the super class and all interfaces
1194 // to be loaded.
1195 InstanceKlass* SystemDictionary::load_shared_boot_class(Symbol* class_name,
1196                                                         TRAPS) {
1197   InstanceKlass* ik = find_shared_class(class_name);
1198   // Make sure we only return the boot class.
1199   if (ik != NULL && ik->is_shared_boot_class()) {
1200     return load_shared_class(ik, Handle(), Handle(), 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 for classes in the CDS archive.
1488     InstanceKlass* k = NULL;
1489     {
1490 #if INCLUDE_CDS
1491       PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time());
1492       k = load_shared_boot_class(class_name, THREAD);
1493 #endif
1494     }
1495 
1496     if (k == NULL) {
1497       // Use VM class loader
1498       PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time());
1499       k = ClassLoader::load_class(class_name, search_only_bootloader_append, CHECK_NULL);
1500     }
1501 
1502     // find_or_define_instance_class may return a different InstanceKlass
1503     if (k != NULL) {
1504       InstanceKlass* defined_k =
1505         find_or_define_instance_class(class_name, class_loader, k, THREAD);
1506       if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1507         // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1508         assert(defined_k != NULL, "Should have a klass if there's no exception");
1509         loader_data->add_to_deallocate_list(k);
1510         k = defined_k;
1511       } else if (HAS_PENDING_EXCEPTION) {
1512         loader_data->add_to_deallocate_list(k);
1513         return NULL;
1514       }
1515     }
1516     return k;
1517   } else {
1518     // Use user specified class loader to load class. Call loadClass operation on class_loader.
1519     ResourceMark rm(THREAD);
1520 
1521     assert(THREAD->is_Java_thread(), "must be a JavaThread");
1522     JavaThread* jt = (JavaThread*) THREAD;
1523 
1524     PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1525                                ClassLoader::perf_app_classload_selftime(),
1526                                ClassLoader::perf_app_classload_count(),
1527                                jt->get_thread_stat()->perf_recursion_counts_addr(),
1528                                jt->get_thread_stat()->perf_timers_addr(),
1529                                PerfClassTraceTime::CLASS_LOAD);
1530 
1531     Handle s = java_lang_String::create_from_symbol(class_name, CHECK_NULL);
1532     // Translate to external class name format, i.e., convert '/' chars to '.'
1533     Handle string = java_lang_String::externalize_classname(s, CHECK_NULL);
1534 
1535     JavaValue result(T_OBJECT);
1536 
1537     InstanceKlass* spec_klass = SystemDictionary::ClassLoader_klass();
1538 
1539     // Call public unsynchronized loadClass(String) directly for all class loaders.
1540     // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1541     // acquire a class-name based lock rather than the class loader object lock.
1542     // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1543     JavaCalls::call_virtual(&result,
1544                             class_loader,
1545                             spec_klass,
1546                             vmSymbols::loadClass_name(),
1547                             vmSymbols::string_class_signature(),
1548                             string,
1549                             CHECK_NULL);
1550 
1551     assert(result.get_type() == T_OBJECT, "just checking");
1552     oop obj = (oop) result.get_jobject();
1553 
1554     // Primitive classes return null since forName() can not be
1555     // used to obtain any of the Class objects representing primitives or void
1556     if ((obj != NULL) && !(java_lang_Class::is_primitive(obj))) {
1557       InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(obj));
1558       // For user defined Java class loaders, check that the name returned is
1559       // the same as that requested.  This check is done for the bootstrap
1560       // loader when parsing the class file.
1561       if (class_name == k->name()) {
1562         return k;
1563       }
1564     }
1565     // Class is not found or has the wrong name, return NULL
1566     return NULL;
1567   }
1568 }
1569 
1570 static void post_class_define_event(InstanceKlass* k, const ClassLoaderData* def_cld) {
1571   EventClassDefine event;
1572   if (event.should_commit()) {
1573     event.set_definedClass(k);
1574     event.set_definingClassLoader(def_cld);
1575     event.commit();
1576   }
1577 }
1578 
1579 void SystemDictionary::define_instance_class(InstanceKlass* k, TRAPS) {
1580 
1581   HandleMark hm(THREAD);
1582   ClassLoaderData* loader_data = k->class_loader_data();
1583   Handle class_loader_h(THREAD, loader_data->class_loader());
1584 
1585  // for bootstrap and other parallel classloaders don't acquire lock,
1586  // use placeholder token
1587  // If a parallelCapable class loader calls define_instance_class instead of
1588  // find_or_define_instance_class to get here, we have a timing
1589  // hole with systemDictionary updates and check_constraints
1590  if (!class_loader_h.is_null() && !is_parallelCapable(class_loader_h)) {
1591     assert(ObjectSynchronizer::current_thread_holds_lock((JavaThread*)THREAD,
1592          compute_loader_lock_object(class_loader_h, THREAD)),
1593          "define called without lock");
1594   }
1595 
1596   // Check class-loading constraints. Throw exception if violation is detected.
1597   // Grabs and releases SystemDictionary_lock
1598   // The check_constraints/find_class call and update_dictionary sequence
1599   // must be "atomic" for a specific class/classloader pair so we never
1600   // define two different instanceKlasses for that class/classloader pair.
1601   // Existing classloaders will call define_instance_class with the
1602   // classloader lock held
1603   // Parallel classloaders will call find_or_define_instance_class
1604   // which will require a token to perform the define class
1605   Symbol*  name_h = k->name();
1606   Dictionary* dictionary = loader_data->dictionary();
1607   unsigned int d_hash = dictionary->compute_hash(name_h);
1608   check_constraints(d_hash, k, class_loader_h, true, CHECK);
1609 
1610   // Register class just loaded with class loader (placed in Vector)
1611   // Note we do this before updating the dictionary, as this can
1612   // fail with an OutOfMemoryError (if it does, we will *not* put this
1613   // class in the dictionary and will not update the class hierarchy).
1614   // JVMTI FollowReferences needs to find the classes this way.
1615   if (k->class_loader() != NULL) {
1616     methodHandle m(THREAD, Universe::loader_addClass_method());
1617     JavaValue result(T_VOID);
1618     JavaCallArguments args(class_loader_h);
1619     args.push_oop(Handle(THREAD, k->java_mirror()));
1620     JavaCalls::call(&result, m, &args, CHECK);
1621   }
1622 
1623   // Add the new class. We need recompile lock during update of CHA.
1624   {
1625     unsigned int p_hash = placeholders()->compute_hash(name_h);
1626     int p_index = placeholders()->hash_to_index(p_hash);
1627 
1628     MutexLocker mu_r(Compile_lock, THREAD);
1629 
1630     // Add to class hierarchy, initialize vtables, and do possible
1631     // deoptimizations.
1632     add_to_hierarchy(k, CHECK); // No exception, but can block
1633 
1634     // Add to systemDictionary - so other classes can see it.
1635     // Grabs and releases SystemDictionary_lock
1636     update_dictionary(d_hash, p_index, p_hash,
1637                       k, class_loader_h, THREAD);
1638   }
1639   k->eager_initialize(THREAD);
1640 
1641   // notify jvmti
1642   if (JvmtiExport::should_post_class_load()) {
1643       assert(THREAD->is_Java_thread(), "thread->is_Java_thread()");
1644       JvmtiExport::post_class_load((JavaThread *) THREAD, k);
1645 
1646   }
1647   post_class_define_event(k, loader_data);
1648 }
1649 
1650 // Support parallel classloading
1651 // All parallel class loaders, including bootstrap classloader
1652 // lock a placeholder entry for this class/class_loader pair
1653 // to allow parallel defines of different classes for this class loader
1654 // With AllowParallelDefine flag==true, in case they do not synchronize around
1655 // FindLoadedClass/DefineClass, calls, we check for parallel
1656 // loading for them, wait if a defineClass is in progress
1657 // and return the initial requestor's results
1658 // This flag does not apply to the bootstrap classloader.
1659 // With AllowParallelDefine flag==false, call through to define_instance_class
1660 // which will throw LinkageError: duplicate class definition.
1661 // False is the requested default.
1662 // For better performance, the class loaders should synchronize
1663 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1664 // potentially waste time reading and parsing the bytestream.
1665 // Note: VM callers should ensure consistency of k/class_name,class_loader
1666 // Be careful when modifying this code: once you have run
1667 // placeholders()->find_and_add(PlaceholderTable::DEFINE_CLASS),
1668 // you need to find_and_remove it before returning.
1669 // So be careful to not exit with a CHECK_ macro betweeen these calls.
1670 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1671                                                                InstanceKlass* k, TRAPS) {
1672 
1673   Symbol*  name_h = k->name(); // passed in class_name may be null
1674   ClassLoaderData* loader_data = class_loader_data(class_loader);
1675   Dictionary* dictionary = loader_data->dictionary();
1676 
1677   unsigned int d_hash = dictionary->compute_hash(name_h);
1678 
1679   // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1680   unsigned int p_hash = placeholders()->compute_hash(name_h);
1681   int p_index = placeholders()->hash_to_index(p_hash);
1682   PlaceholderEntry* probe;
1683 
1684   {
1685     MutexLocker mu(SystemDictionary_lock, THREAD);
1686     // First check if class already defined
1687     if (is_parallelDefine(class_loader)) {
1688       InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1689       if (check != NULL) {
1690         return check;
1691       }
1692     }
1693 
1694     // Acquire define token for this class/classloader
1695     probe = placeholders()->find_and_add(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, NULL, THREAD);
1696     // Wait if another thread defining in parallel
1697     // All threads wait - even those that will throw duplicate class: otherwise
1698     // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1699     // if other thread has not finished updating dictionary
1700     while (probe->definer() != NULL) {
1701       SystemDictionary_lock->wait();
1702     }
1703     // Only special cases allow parallel defines and can use other thread's results
1704     // Other cases fall through, and may run into duplicate defines
1705     // caught by finding an entry in the SystemDictionary
1706     if (is_parallelDefine(class_loader) && (probe->instance_klass() != NULL)) {
1707         placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1708         SystemDictionary_lock->notify_all();
1709 #ifdef ASSERT
1710         InstanceKlass* check = find_class(d_hash, name_h, dictionary);
1711         assert(check != NULL, "definer missed recording success");
1712 #endif
1713         return probe->instance_klass();
1714     } else {
1715       // This thread will define the class (even if earlier thread tried and had an error)
1716       probe->set_definer(THREAD);
1717     }
1718   }
1719 
1720   define_instance_class(k, THREAD);
1721 
1722   Handle linkage_exception = Handle(); // null handle
1723 
1724   // definer must notify any waiting threads
1725   {
1726     MutexLocker mu(SystemDictionary_lock, THREAD);
1727     PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, name_h, loader_data);
1728     assert(probe != NULL, "DEFINE_CLASS placeholder lost?");
1729     if (probe != NULL) {
1730       if (HAS_PENDING_EXCEPTION) {
1731         linkage_exception = Handle(THREAD,PENDING_EXCEPTION);
1732         CLEAR_PENDING_EXCEPTION;
1733       } else {
1734         probe->set_instance_klass(k);
1735       }
1736       probe->set_definer(NULL);
1737       placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1738       SystemDictionary_lock->notify_all();
1739     }
1740   }
1741 
1742   // Can't throw exception while holding lock due to rank ordering
1743   if (linkage_exception() != NULL) {
1744     THROW_OOP_(linkage_exception(), NULL); // throws exception and returns
1745   }
1746 
1747   return k;
1748 }
1749 
1750 Handle SystemDictionary::compute_loader_lock_object(Handle class_loader, TRAPS) {
1751   // If class_loader is NULL we synchronize on _system_loader_lock_obj
1752   if (class_loader.is_null()) {
1753     return Handle(THREAD, _system_loader_lock_obj);
1754   } else {
1755     return class_loader;
1756   }
1757 }
1758 
1759 // This method is added to check how often we have to wait to grab loader
1760 // lock. The results are being recorded in the performance counters defined in
1761 // ClassLoader::_sync_systemLoaderLockContentionRate and
1762 // ClassLoader::_sync_nonSystemLoaderLockConteionRate.
1763 void SystemDictionary::check_loader_lock_contention(Handle loader_lock, TRAPS) {
1764   if (!UsePerfData) {
1765     return;
1766   }
1767 
1768   assert(!loader_lock.is_null(), "NULL lock object");
1769 
1770   if (ObjectSynchronizer::query_lock_ownership((JavaThread*)THREAD, loader_lock)
1771       == ObjectSynchronizer::owner_other) {
1772     // contention will likely happen, so increment the corresponding
1773     // contention counter.
1774     if (oopDesc::equals(loader_lock(), _system_loader_lock_obj)) {
1775       ClassLoader::sync_systemLoaderLockContentionRate()->inc();
1776     } else {
1777       ClassLoader::sync_nonSystemLoaderLockContentionRate()->inc();
1778     }
1779   }
1780 }
1781 
1782 // ----------------------------------------------------------------------------
1783 // Lookup
1784 
1785 InstanceKlass* SystemDictionary::find_class(unsigned int hash,
1786                                             Symbol* class_name,
1787                                             Dictionary* dictionary) {
1788   assert_locked_or_safepoint(SystemDictionary_lock);
1789   int index = dictionary->hash_to_index(hash);
1790   return dictionary->find_class(index, hash, class_name);
1791 }
1792 
1793 
1794 // Basic find on classes in the midst of being loaded
1795 Symbol* SystemDictionary::find_placeholder(Symbol* class_name,
1796                                            ClassLoaderData* loader_data) {
1797   assert_locked_or_safepoint(SystemDictionary_lock);
1798   unsigned int p_hash = placeholders()->compute_hash(class_name);
1799   int p_index = placeholders()->hash_to_index(p_hash);
1800   return placeholders()->find_entry(p_index, p_hash, class_name, loader_data);
1801 }
1802 
1803 
1804 // Used for assertions and verification only
1805 // Precalculating the hash and index is an optimization because there are many lookups
1806 // before adding the class.
1807 InstanceKlass* SystemDictionary::find_class(Symbol* class_name, ClassLoaderData* loader_data) {
1808   assert_locked_or_safepoint(SystemDictionary_lock);
1809   #ifndef ASSERT
1810   guarantee(VerifyBeforeGC      ||
1811             VerifyDuringGC      ||
1812             VerifyBeforeExit    ||
1813             VerifyDuringStartup ||
1814             VerifyAfterGC, "too expensive");
1815   #endif
1816 
1817   Dictionary* dictionary = loader_data->dictionary();
1818   unsigned int d_hash = dictionary->compute_hash(class_name);
1819   return find_class(d_hash, class_name, dictionary);
1820 }
1821 
1822 
1823 // ----------------------------------------------------------------------------
1824 // Update hierachy. This is done before the new klass has been added to the SystemDictionary. The Recompile_lock
1825 // is held, to ensure that the compiler is not using the class hierachy, and that deoptimization will kick in
1826 // before a new class is used.
1827 
1828 void SystemDictionary::add_to_hierarchy(InstanceKlass* k, TRAPS) {
1829   assert(k != NULL, "just checking");
1830   assert_locked_or_safepoint(Compile_lock);
1831 
1832   // Link into hierachy. Make sure the vtables are initialized before linking into
1833   k->append_to_sibling_list();                    // add to superklass/sibling list
1834   k->process_interfaces(THREAD);                  // handle all "implements" declarations
1835   k->set_init_state(InstanceKlass::loaded);
1836   // Now flush all code that depended on old class hierarchy.
1837   // Note: must be done *after* linking k into the hierarchy (was bug 12/9/97)
1838   // Also, first reinitialize vtable because it may have gotten out of synch
1839   // while the new class wasn't connected to the class hierarchy.
1840   CodeCache::flush_dependents_on(k);
1841 }
1842 
1843 // ----------------------------------------------------------------------------
1844 // GC support
1845 
1846 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1847 // Note: anonymous classes are not in the SD.
1848 bool SystemDictionary::do_unloading(GCTimer* gc_timer,
1849                                     bool do_cleaning) {
1850 
1851   bool unloading_occurred;
1852   {
1853     GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1854 
1855     // First, mark for unload all ClassLoaderData referencing a dead class loader.
1856     unloading_occurred = ClassLoaderDataGraph::do_unloading(do_cleaning);
1857     if (unloading_occurred) {
1858       JFR_ONLY(Jfr::on_unloading_classes();)
1859       ClassLoaderDataGraph::clean_module_and_package_info();
1860     }
1861   }
1862 
1863   // TODO: just return if !unloading_occurred.
1864   if (unloading_occurred) {
1865     {
1866       GCTraceTime(Debug, gc, phases) t("SymbolTable", gc_timer);
1867       // Check if there's work to do in the SymbolTable
1868       SymbolTable::do_check_concurrent_work();
1869     }
1870 
1871     {
1872       GCTraceTime(Debug, gc, phases) t("Dictionary", gc_timer);
1873       constraints()->purge_loader_constraints();
1874       resolution_errors()->purge_resolution_errors();
1875     }
1876   }
1877 
1878   {
1879     GCTraceTime(Debug, gc, phases) t("ProtectionDomainCacheTable", gc_timer);
1880     // Oops referenced by the protection domain cache table may get unreachable independently
1881     // of the class loader (eg. cached protection domain oops). So we need to
1882     // explicitly unlink them here.
1883     _pd_cache_table->trigger_cleanup();
1884   }
1885 
1886   if (do_cleaning) {
1887     GCTraceTime(Debug, gc, phases) t("ResolvedMethodTable", gc_timer);
1888     ResolvedMethodTable::trigger_cleanup();
1889   }
1890 
1891   return unloading_occurred;
1892 }
1893 
1894 void SystemDictionary::oops_do(OopClosure* f) {
1895   f->do_oop(&_java_system_loader);
1896   f->do_oop(&_java_platform_loader);
1897   f->do_oop(&_system_loader_lock_obj);
1898   CDS_ONLY(SystemDictionaryShared::oops_do(f);)
1899 
1900   // Visit extra methods
1901   invoke_method_table()->oops_do(f);
1902 }
1903 
1904 // CDS: scan and relocate all classes in the system dictionary.
1905 void SystemDictionary::classes_do(MetaspaceClosure* it) {
1906   ClassLoaderData::the_null_class_loader_data()->dictionary()->classes_do(it);
1907 }
1908 
1909 // CDS: scan and relocate all classes referenced by _well_known_klasses[].
1910 void SystemDictionary::well_known_klasses_do(MetaspaceClosure* it) {
1911   for (int id = FIRST_WKID; id < WKID_LIMIT; id++) {
1912     it->push(well_known_klass_addr((WKID)id));
1913   }
1914 }
1915 
1916 void SystemDictionary::methods_do(void f(Method*)) {
1917   // Walk methods in loaded classes
1918   MutexLocker ml(ClassLoaderDataGraph_lock);
1919   ClassLoaderDataGraph::methods_do(f);
1920   // Walk method handle intrinsics
1921   invoke_method_table()->methods_do(f);
1922 }
1923 
1924 class RemoveClassesClosure : public CLDClosure {
1925   public:
1926     void do_cld(ClassLoaderData* cld) {
1927       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
1928         cld->dictionary()->remove_classes_in_error_state();
1929       }
1930     }
1931 };
1932 
1933 void SystemDictionary::remove_classes_in_error_state() {
1934   ClassLoaderData::the_null_class_loader_data()->dictionary()->remove_classes_in_error_state();
1935   RemoveClassesClosure rcc;
1936   MutexLocker ml(ClassLoaderDataGraph_lock);
1937   ClassLoaderDataGraph::loaded_cld_do(&rcc);
1938 }
1939 
1940 // ----------------------------------------------------------------------------
1941 // Initialization
1942 
1943 void SystemDictionary::initialize(TRAPS) {
1944   // Allocate arrays
1945   _placeholders        = new PlaceholderTable(_placeholder_table_size);
1946   _number_of_modifications = 0;
1947   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
1948   _resolution_errors   = new ResolutionErrorTable(_resolution_error_size);
1949   _invoke_method_table = new SymbolPropertyTable(_invoke_method_size);
1950   _pd_cache_table = new ProtectionDomainCacheTable(defaultProtectionDomainCacheSize);
1951 
1952   // Allocate private object used as system class loader lock
1953   _system_loader_lock_obj = oopFactory::new_intArray(0, CHECK);
1954   // Initialize basic classes
1955   resolve_well_known_classes(CHECK);
1956 }
1957 
1958 // Compact table of directions on the initialization of klasses:
1959 static const short wk_init_info[] = {
1960   #define WK_KLASS_INIT_INFO(name, symbol) \
1961     ((short)vmSymbols::VM_SYMBOL_ENUM_NAME(symbol)),
1962 
1963   WK_KLASSES_DO(WK_KLASS_INIT_INFO)
1964   #undef WK_KLASS_INIT_INFO
1965   0
1966 };
1967 
1968 #ifdef ASSERT
1969 bool SystemDictionary::is_well_known_klass(Symbol* class_name) {
1970   int sid;
1971   for (int i = 0; (sid = wk_init_info[i]) != 0; i++) {
1972     Symbol* symbol = vmSymbols::symbol_at((vmSymbols::SID)sid);
1973     if (class_name == symbol) {
1974       return true;
1975     }
1976   }
1977   return false;
1978 }
1979 #endif
1980 
1981 bool SystemDictionary::resolve_wk_klass(WKID id, TRAPS) {
1982   assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
1983   int sid = wk_init_info[id - FIRST_WKID];
1984   Symbol* symbol = vmSymbols::symbol_at((vmSymbols::SID)sid);
1985   InstanceKlass** klassp = &_well_known_klasses[id];
1986 
1987 
1988 #if INCLUDE_JVMCI
1989   if (id >= FIRST_JVMCI_WKID) {
1990     assert(EnableJVMCI, "resolve JVMCI classes only when EnableJVMCI is true");
1991   }
1992 #endif
1993 
1994   if ((*klassp) == NULL) {
1995     Klass* k = resolve_or_fail(symbol, true, CHECK_0);
1996     (*klassp) = InstanceKlass::cast(k);
1997   }
1998   return ((*klassp) != NULL);
1999 }
2000 
2001 void SystemDictionary::resolve_wk_klasses_until(WKID limit_id, WKID &start_id, TRAPS) {
2002   assert((int)start_id <= (int)limit_id, "IDs are out of order!");
2003   for (int id = (int)start_id; id < (int)limit_id; id++) {
2004     assert(id >= (int)FIRST_WKID && id < (int)WKID_LIMIT, "oob");
2005     resolve_wk_klass((WKID)id, CHECK);
2006   }
2007 
2008   // move the starting value forward to the limit:
2009   start_id = limit_id;
2010 }
2011 
2012 void SystemDictionary::resolve_well_known_classes(TRAPS) {
2013   assert(WK_KLASS(Object_klass) == NULL, "well-known classes should only be initialized once");
2014 
2015   // Create the ModuleEntry for java.base.  This call needs to be done here,
2016   // after vmSymbols::initialize() is called but before any classes are pre-loaded.
2017   ClassLoader::classLoader_init2(CHECK);
2018 
2019   // Preload commonly used klasses
2020   WKID scan = FIRST_WKID;
2021   // first do Object, then String, Class
2022 #if INCLUDE_CDS
2023   if (UseSharedSpaces) {
2024     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Object_klass), scan, CHECK);
2025 
2026     // It's unsafe to access the archived heap regions before they
2027     // are fixed up, so we must do the fixup as early as possible
2028     // before the archived java objects are accessed by functions
2029     // such as java_lang_Class::restore_archived_mirror and
2030     // ConstantPool::restore_unshareable_info (restores the archived
2031     // resolved_references array object).
2032     //
2033     // HeapShared::fixup_mapped_heap_regions() fills the empty
2034     // spaces in the archived heap regions and may use
2035     // SystemDictionary::Object_klass(), so we can do this only after
2036     // Object_klass is resolved. See the above resolve_wk_klasses_through()
2037     // call. No mirror objects are accessed/restored in the above call.
2038     // Mirrors are restored after java.lang.Class is loaded.
2039     HeapShared::fixup_mapped_heap_regions();
2040 
2041     // Initialize the constant pool for the Object_class
2042     Object_klass()->constants()->restore_unshareable_info(CHECK);
2043     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2044   } else
2045 #endif
2046   {
2047     resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Class_klass), scan, CHECK);
2048   }
2049 
2050   // Calculate offsets for String and Class classes since they are loaded and
2051   // can be used after this point.
2052   java_lang_String::compute_offsets();
2053   java_lang_Class::compute_offsets();
2054 
2055   // Fixup mirrors for classes loaded before java.lang.Class.
2056   // These calls iterate over the objects currently in the perm gen
2057   // so calling them at this point is matters (not before when there
2058   // are fewer objects and not later after there are more objects
2059   // in the perm gen.
2060   Universe::initialize_basic_type_mirrors(CHECK);
2061   Universe::fixup_mirrors(CHECK);
2062 
2063   // do a bunch more:
2064   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(Reference_klass), scan, CHECK);
2065 
2066   // Preload ref klasses and set reference types
2067   InstanceKlass::cast(WK_KLASS(Reference_klass))->set_reference_type(REF_OTHER);
2068   InstanceRefKlass::update_nonstatic_oop_maps(WK_KLASS(Reference_klass));
2069 
2070   resolve_wk_klasses_through(WK_KLASS_ENUM_NAME(PhantomReference_klass), scan, CHECK);
2071   InstanceKlass::cast(WK_KLASS(SoftReference_klass))->set_reference_type(REF_SOFT);
2072   InstanceKlass::cast(WK_KLASS(WeakReference_klass))->set_reference_type(REF_WEAK);
2073   InstanceKlass::cast(WK_KLASS(FinalReference_klass))->set_reference_type(REF_FINAL);
2074   InstanceKlass::cast(WK_KLASS(PhantomReference_klass))->set_reference_type(REF_PHANTOM);
2075 
2076   // JSR 292 classes
2077   WKID jsr292_group_start = WK_KLASS_ENUM_NAME(MethodHandle_klass);
2078   WKID jsr292_group_end   = WK_KLASS_ENUM_NAME(VolatileCallSite_klass);
2079   resolve_wk_klasses_until(jsr292_group_start, scan, CHECK);
2080   resolve_wk_klasses_through(jsr292_group_end, scan, CHECK);
2081   WKID last = NOT_JVMCI(WKID_LIMIT) JVMCI_ONLY(FIRST_JVMCI_WKID);
2082   resolve_wk_klasses_until(last, scan, CHECK);
2083 
2084   _box_klasses[T_BOOLEAN] = WK_KLASS(Boolean_klass);
2085   _box_klasses[T_CHAR]    = WK_KLASS(Character_klass);
2086   _box_klasses[T_FLOAT]   = WK_KLASS(Float_klass);
2087   _box_klasses[T_DOUBLE]  = WK_KLASS(Double_klass);
2088   _box_klasses[T_BYTE]    = WK_KLASS(Byte_klass);
2089   _box_klasses[T_SHORT]   = WK_KLASS(Short_klass);
2090   _box_klasses[T_INT]     = WK_KLASS(Integer_klass);
2091   _box_klasses[T_LONG]    = WK_KLASS(Long_klass);
2092   //_box_klasses[T_OBJECT]  = WK_KLASS(object_klass);
2093   //_box_klasses[T_ARRAY]   = WK_KLASS(object_klass);
2094 
2095   { // Compute whether we should use checkPackageAccess or NOT
2096     Method* method = InstanceKlass::cast(ClassLoader_klass())->find_method(vmSymbols::checkPackageAccess_name(), vmSymbols::class_protectiondomain_signature());
2097     _has_checkPackageAccess = (method != NULL);
2098   }
2099 
2100 #ifdef ASSERT
2101   if (UseSharedSpaces) {
2102     assert(JvmtiExport::is_early_phase(),
2103            "All well known classes must be resolved in JVMTI early phase");
2104     for (int i = FIRST_WKID; i < last; i++) {
2105       InstanceKlass* k = _well_known_klasses[i];
2106       assert(k->is_shared(), "must not be replaced by JVMTI class file load hook");
2107     }
2108   }
2109 #endif
2110 }
2111 
2112 // Tells if a given klass is a box (wrapper class, such as java.lang.Integer).
2113 // If so, returns the basic type it holds.  If not, returns T_OBJECT.
2114 BasicType SystemDictionary::box_klass_type(Klass* k) {
2115   assert(k != NULL, "");
2116   for (int i = T_BOOLEAN; i < T_VOID+1; i++) {
2117     if (_box_klasses[i] == k)
2118       return (BasicType)i;
2119   }
2120   return T_OBJECT;
2121 }
2122 
2123 // Constraints on class loaders. The details of the algorithm can be
2124 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
2125 // Virtual Machine" by Sheng Liang and Gilad Bracha.  The basic idea is
2126 // that the dictionary needs to maintain a set of contraints that
2127 // must be satisfied by all classes in the dictionary.
2128 // if defining is true, then LinkageError if already in dictionary
2129 // if initiating loader, then ok if InstanceKlass matches existing entry
2130 
2131 void SystemDictionary::check_constraints(unsigned int d_hash,
2132                                          InstanceKlass* k,
2133                                          Handle class_loader,
2134                                          bool defining,
2135                                          TRAPS) {
2136   ResourceMark rm(THREAD);
2137   stringStream ss;
2138   bool throwException = false;
2139 
2140   {
2141     Symbol *name = k->name();
2142     ClassLoaderData *loader_data = class_loader_data(class_loader);
2143 
2144     MutexLocker mu(SystemDictionary_lock, THREAD);
2145 
2146     InstanceKlass* check = find_class(d_hash, name, loader_data->dictionary());
2147     if (check != NULL) {
2148       // If different InstanceKlass - duplicate class definition,
2149       // else - ok, class loaded by a different thread in parallel.
2150       // We should only have found it if it was done loading and ok to use.
2151       // The dictionary only holds instance classes, placeholders
2152       // also hold array classes.
2153 
2154       assert(check->is_instance_klass(), "noninstance in systemdictionary");
2155       if ((defining == true) || (k != check)) {
2156         throwException = true;
2157         ss.print("loader %s", loader_data->loader_name_and_id());
2158         ss.print(" attempted duplicate %s definition for %s. (%s)",
2159                  k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
2160       } else {
2161         return;
2162       }
2163     }
2164 
2165 #ifdef ASSERT
2166     Symbol* ph_check = find_placeholder(name, loader_data);
2167     assert(ph_check == NULL || ph_check == name, "invalid symbol");
2168 #endif
2169 
2170     if (throwException == false) {
2171       if (constraints()->check_or_update(k, class_loader, name) == false) {
2172         throwException = true;
2173         ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
2174         ss.print(" wants to load %s %s.",
2175                  k->external_kind(), k->external_name());
2176         Klass *existing_klass = constraints()->find_constrained_klass(name, class_loader);
2177         if (existing_klass->class_loader() != class_loader()) {
2178           ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
2179                    existing_klass->external_kind(),
2180                    existing_klass->class_loader_data()->loader_name_and_id(),
2181                    existing_klass->class_in_module_of_loader(false, true));
2182         } else {
2183           ss.print(" (%s)", k->class_in_module_of_loader(false, true));
2184         }
2185       }
2186     }
2187   }
2188 
2189   // Throw error now if needed (cannot throw while holding
2190   // SystemDictionary_lock because of rank ordering)
2191   if (throwException == true) {
2192     THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
2193   }
2194 }
2195 
2196 // Update class loader data dictionary - done after check_constraint and add_to_hierachy
2197 // have been called.
2198 void SystemDictionary::update_dictionary(unsigned int d_hash,
2199                                          int p_index, unsigned int p_hash,
2200                                          InstanceKlass* k,
2201                                          Handle class_loader,
2202                                          TRAPS) {
2203   // Compile_lock prevents systemDictionary updates during compilations
2204   assert_locked_or_safepoint(Compile_lock);
2205   Symbol*  name  = k->name();
2206   ClassLoaderData *loader_data = class_loader_data(class_loader);
2207 
2208   {
2209     MutexLocker mu1(SystemDictionary_lock, THREAD);
2210 
2211     // See whether biased locking is enabled and if so set it for this
2212     // klass.
2213     // Note that this must be done past the last potential blocking
2214     // point / safepoint. We enable biased locking lazily using a
2215     // VM_Operation to iterate the SystemDictionary and installing the
2216     // biasable mark word into each InstanceKlass's prototype header.
2217     // To avoid race conditions where we accidentally miss enabling the
2218     // optimization for one class in the process of being added to the
2219     // dictionary, we must not safepoint after the test of
2220     // BiasedLocking::enabled().
2221     if (UseBiasedLocking && BiasedLocking::enabled()) {
2222       // Set biased locking bit for all loaded classes; it will be
2223       // cleared if revocation occurs too often for this type
2224       // NOTE that we must only do this when the class is initally
2225       // defined, not each time it is referenced from a new class loader
2226       if (oopDesc::equals(k->class_loader(), class_loader())) {
2227         k->set_prototype_header(markOopDesc::biased_locking_prototype());
2228       }
2229     }
2230 
2231     // Make a new dictionary entry.
2232     Dictionary* dictionary = loader_data->dictionary();
2233     InstanceKlass* sd_check = find_class(d_hash, name, dictionary);
2234     if (sd_check == NULL) {
2235       dictionary->add_klass(d_hash, name, k);
2236       notice_modification();
2237     }
2238   #ifdef ASSERT
2239     sd_check = find_class(d_hash, name, dictionary);
2240     assert (sd_check != NULL, "should have entry in dictionary");
2241     // Note: there may be a placeholder entry: for circularity testing
2242     // or for parallel defines
2243   #endif
2244     SystemDictionary_lock->notify_all();
2245   }
2246 }
2247 
2248 
2249 // Try to find a class name using the loader constraints.  The
2250 // loader constraints might know about a class that isn't fully loaded
2251 // yet and these will be ignored.
2252 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
2253                     Symbol* class_name, Handle class_loader, TRAPS) {
2254 
2255   // First see if it has been loaded directly.
2256   // Force the protection domain to be null.  (This removes protection checks.)
2257   Handle no_protection_domain;
2258   Klass* klass = find_instance_or_array_klass(class_name, class_loader,
2259                                               no_protection_domain, CHECK_NULL);
2260   if (klass != NULL)
2261     return klass;
2262 
2263   // Now look to see if it has been loaded elsewhere, and is subject to
2264   // a loader constraint that would require this loader to return the
2265   // klass that is already loaded.
2266   if (FieldType::is_array(class_name)) {
2267     // For array classes, their Klass*s are not kept in the
2268     // constraint table. The element Klass*s are.
2269     FieldArrayInfo fd;
2270     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(NULL));
2271     if (t != T_OBJECT) {
2272       klass = Universe::typeArrayKlassObj(t);
2273     } else {
2274       MutexLocker mu(SystemDictionary_lock, THREAD);
2275       klass = constraints()->find_constrained_klass(fd.object_key(), class_loader);
2276     }
2277     // If element class already loaded, allocate array klass
2278     if (klass != NULL) {
2279       klass = klass->array_klass_or_null(fd.dimension());
2280     }
2281   } else {
2282     MutexLocker mu(SystemDictionary_lock, THREAD);
2283     // Non-array classes are easy: simply check the constraint table.
2284     klass = constraints()->find_constrained_klass(class_name, class_loader);
2285   }
2286 
2287   return klass;
2288 }
2289 
2290 
2291 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
2292                                              Handle class_loader1,
2293                                              Handle class_loader2,
2294                                              Thread* THREAD) {
2295   ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
2296   ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
2297 
2298   Symbol* constraint_name = NULL;
2299   // Needs to be in same scope as constraint_name in case a Symbol is created and
2300   // assigned to constraint_name.
2301   FieldArrayInfo fd;
2302   if (!FieldType::is_array(class_name)) {
2303     constraint_name = class_name;
2304   } else {
2305     // For array classes, their Klass*s are not kept in the
2306     // constraint table. The element classes are.
2307     BasicType t = FieldType::get_array_info(class_name, fd, CHECK_(false));
2308     // primitive types always pass
2309     if (t != T_OBJECT) {
2310       return true;
2311     } else {
2312       constraint_name = fd.object_key();
2313     }
2314   }
2315 
2316   Dictionary* dictionary1 = loader_data1->dictionary();
2317   unsigned int d_hash1 = dictionary1->compute_hash(constraint_name);
2318 
2319   Dictionary* dictionary2 = loader_data2->dictionary();
2320   unsigned int d_hash2 = dictionary2->compute_hash(constraint_name);
2321 
2322   {
2323     MutexLocker mu_s(SystemDictionary_lock, THREAD);
2324     InstanceKlass* klass1 = find_class(d_hash1, constraint_name, dictionary1);
2325     InstanceKlass* klass2 = find_class(d_hash2, constraint_name, dictionary2);
2326     return constraints()->add_entry(constraint_name, klass1, class_loader1,
2327                                     klass2, class_loader2);
2328   }
2329 }
2330 
2331 // Add entry to resolution error table to record the error when the first
2332 // attempt to resolve a reference to a class has failed.
2333 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
2334                                             Symbol* error, 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     resolution_errors()->add_entry(index, hash, pool, which, error, message);
2340   }
2341 }
2342 
2343 // Delete a resolution error for RedefineClasses for a constant pool is going away
2344 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
2345   resolution_errors()->delete_entry(pool);
2346 }
2347 
2348 // Lookup resolution error table. Returns error if found, otherwise NULL.
2349 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
2350                                                 Symbol** message) {
2351   unsigned int hash = resolution_errors()->compute_hash(pool, which);
2352   int index = resolution_errors()->hash_to_index(hash);
2353   {
2354     MutexLocker ml(SystemDictionary_lock, Thread::current());
2355     ResolutionErrorEntry* entry = resolution_errors()->find_entry(index, hash, pool, which);
2356     if (entry != NULL) {
2357       *message = entry->message();
2358       return entry->error();
2359     } else {
2360       return NULL;
2361     }
2362   }
2363 }
2364 
2365 
2366 // Signature constraints ensure that callers and callees agree about
2367 // the meaning of type names in their signatures.  This routine is the
2368 // intake for constraints.  It collects them from several places:
2369 //
2370 //  * LinkResolver::resolve_method (if check_access is true) requires
2371 //    that the resolving class (the caller) and the defining class of
2372 //    the resolved method (the callee) agree on each type in the
2373 //    method's signature.
2374 //
2375 //  * LinkResolver::resolve_interface_method performs exactly the same
2376 //    checks.
2377 //
2378 //  * LinkResolver::resolve_field requires that the constant pool
2379 //    attempting to link to a field agree with the field's defining
2380 //    class about the type of the field signature.
2381 //
2382 //  * klassVtable::initialize_vtable requires that, when a class
2383 //    overrides a vtable entry allocated by a superclass, that the
2384 //    overriding method (i.e., the callee) agree with the superclass
2385 //    on each type in the method's signature.
2386 //
2387 //  * klassItable::initialize_itable requires that, when a class fills
2388 //    in its itables, for each non-abstract method installed in an
2389 //    itable, the method (i.e., the callee) agree with the interface
2390 //    on each type in the method's signature.
2391 //
2392 // All those methods have a boolean (check_access, checkconstraints)
2393 // which turns off the checks.  This is used from specialized contexts
2394 // such as bootstrapping, dumping, and debugging.
2395 //
2396 // No direct constraint is placed between the class and its
2397 // supertypes.  Constraints are only placed along linked relations
2398 // between callers and callees.  When a method overrides or implements
2399 // an abstract method in a supertype (superclass or interface), the
2400 // constraints are placed as if the supertype were the caller to the
2401 // overriding method.  (This works well, since callers to the
2402 // supertype have already established agreement between themselves and
2403 // the supertype.)  As a result of all this, a class can disagree with
2404 // its supertype about the meaning of a type name, as long as that
2405 // class neither calls a relevant method of the supertype, nor is
2406 // called (perhaps via an override) from the supertype.
2407 //
2408 //
2409 // SystemDictionary::check_signature_loaders(sig, l1, l2)
2410 //
2411 // Make sure all class components (including arrays) in the given
2412 // signature will be resolved to the same class in both loaders.
2413 // Returns the name of the type that failed a loader constraint check, or
2414 // NULL if no constraint failed.  No exception except OOME is thrown.
2415 // Arrays are not added to the loader constraint table, their elements are.
2416 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
2417                                                Handle loader1, Handle loader2,
2418                                                bool is_method, TRAPS)  {
2419   // Nothing to do if loaders are the same.
2420   if (oopDesc::equals(loader1(), loader2())) {
2421     return NULL;
2422   }
2423 
2424   SignatureStream sig_strm(signature, is_method);
2425   while (!sig_strm.is_done()) {
2426     if (sig_strm.is_object()) {
2427       Symbol* sig = sig_strm.as_symbol(CHECK_NULL);
2428       if (!add_loader_constraint(sig, loader1, loader2, THREAD)) {
2429         return sig;
2430       }
2431     }
2432     sig_strm.next();
2433   }
2434   return NULL;
2435 }
2436 
2437 
2438 methodHandle SystemDictionary::find_method_handle_intrinsic(vmIntrinsics::ID iid,
2439                                                             Symbol* signature,
2440                                                             TRAPS) {
2441   methodHandle empty;
2442   assert(MethodHandles::is_signature_polymorphic(iid) &&
2443          MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
2444          iid != vmIntrinsics::_invokeGeneric,
2445          "must be a known MH intrinsic iid=%d: %s", iid, vmIntrinsics::name_at(iid));
2446 
2447   unsigned int hash  = invoke_method_table()->compute_hash(signature, iid);
2448   int          index = invoke_method_table()->hash_to_index(hash);
2449   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2450   methodHandle m;
2451   if (spe == NULL || spe->method() == NULL) {
2452     spe = NULL;
2453     // Must create lots of stuff here, but outside of the SystemDictionary lock.
2454     m = Method::make_method_handle_intrinsic(iid, signature, CHECK_(empty));
2455     if (!Arguments::is_interpreter_only()) {
2456       // Generate a compiled form of the MH intrinsic.
2457       AdapterHandlerLibrary::create_native_wrapper(m);
2458       // Check if have the compiled code.
2459       if (!m->has_compiled_code()) {
2460         THROW_MSG_(vmSymbols::java_lang_VirtualMachineError(),
2461                    "Out of space in CodeCache for method handle intrinsic", empty);
2462       }
2463     }
2464     // Now grab the lock.  We might have to throw away the new method,
2465     // if a racing thread has managed to install one at the same time.
2466     {
2467       MutexLocker ml(SystemDictionary_lock, THREAD);
2468       spe = invoke_method_table()->find_entry(index, hash, signature, iid);
2469       if (spe == NULL)
2470         spe = invoke_method_table()->add_entry(index, hash, signature, iid);
2471       if (spe->method() == NULL)
2472         spe->set_method(m());
2473     }
2474   }
2475 
2476   assert(spe != NULL && spe->method() != NULL, "");
2477   assert(Arguments::is_interpreter_only() || (spe->method()->has_compiled_code() &&
2478          spe->method()->code()->entry_point() == spe->method()->from_compiled_entry()),
2479          "MH intrinsic invariant");
2480   return spe->method();
2481 }
2482 
2483 // Helper for unpacking the return value from linkMethod and linkCallSite.
2484 static methodHandle unpack_method_and_appendix(Handle mname,
2485                                                Klass* accessing_klass,
2486                                                objArrayHandle appendix_box,
2487                                                Handle* appendix_result,
2488                                                TRAPS) {
2489   methodHandle empty;
2490   if (mname.not_null()) {
2491     Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2492     if (m != NULL) {
2493       oop appendix = appendix_box->obj_at(0);
2494       if (TraceMethodHandles) {
2495     #ifndef PRODUCT
2496         ttyLocker ttyl;
2497         tty->print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2498         m->print();
2499         if (appendix != NULL) { tty->print("appendix = "); appendix->print(); }
2500         tty->cr();
2501     #endif //PRODUCT
2502       }
2503       (*appendix_result) = Handle(THREAD, appendix);
2504       // the target is stored in the cpCache and if a reference to this
2505       // MemberName is dropped we need a way to make sure the
2506       // class_loader containing this method is kept alive.
2507       ClassLoaderData* this_key = accessing_klass->class_loader_data();
2508       this_key->record_dependency(m->method_holder());
2509       return methodHandle(THREAD, m);
2510     }
2511   }
2512   THROW_MSG_(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives", empty);
2513   return empty;
2514 }
2515 
2516 methodHandle SystemDictionary::find_method_handle_invoker(Klass* klass,
2517                                                           Symbol* name,
2518                                                           Symbol* signature,
2519                                                           Klass* accessing_klass,
2520                                                           Handle *appendix_result,
2521                                                           Handle *method_type_result,
2522                                                           TRAPS) {
2523   methodHandle empty;
2524   assert(THREAD->can_call_java() ,"");
2525   Handle method_type =
2526     SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_(empty));
2527 
2528   int ref_kind = JVM_REF_invokeVirtual;
2529   oop name_oop = StringTable::intern(name, CHECK_(empty));
2530   Handle name_str (THREAD, name_oop);
2531   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2532   assert(appendix_box->obj_at(0) == NULL, "");
2533 
2534   // This should not happen.  JDK code should take care of that.
2535   if (accessing_klass == NULL || method_type.is_null()) {
2536     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokehandle", empty);
2537   }
2538 
2539   // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2540   JavaCallArguments args;
2541   args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2542   args.push_int(ref_kind);
2543   args.push_oop(Handle(THREAD, klass->java_mirror()));
2544   args.push_oop(name_str);
2545   args.push_oop(method_type);
2546   args.push_oop(appendix_box);
2547   JavaValue result(T_OBJECT);
2548   JavaCalls::call_static(&result,
2549                          SystemDictionary::MethodHandleNatives_klass(),
2550                          vmSymbols::linkMethod_name(),
2551                          vmSymbols::linkMethod_signature(),
2552                          &args, CHECK_(empty));
2553   Handle mname(THREAD, (oop) result.get_jobject());
2554   (*method_type_result) = method_type;
2555   return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2556 }
2557 
2558 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2559 // We must ensure that all class loaders everywhere will reach this class, for any client.
2560 // This is a safe bet for public classes in java.lang, such as Object and String.
2561 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2562 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2563 static bool is_always_visible_class(oop mirror) {
2564   Klass* klass = java_lang_Class::as_Klass(mirror);
2565   if (klass->is_objArray_klass()) {
2566     klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2567   }
2568   if (klass->is_typeArray_klass()) {
2569     return true; // primitive array
2570   }
2571   assert(klass->is_instance_klass(), "%s", klass->external_name());
2572   return klass->is_public() &&
2573          (InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::Object_klass()) ||       // java.lang
2574           InstanceKlass::cast(klass)->is_same_class_package(SystemDictionary::MethodHandle_klass()));  // java.lang.invoke
2575 }
2576 
2577 
2578 // Return the Java mirror (java.lang.Class instance) for a single-character
2579 // descriptor.  This result, when available, is the same as produced by the
2580 // heavier API point of the same name that takes a Symbol.
2581 oop SystemDictionary::find_java_mirror_for_type(char signature_char) {
2582   return java_lang_Class::primitive_mirror(char2type(signature_char));
2583 }
2584 
2585 // Find or construct the Java mirror (java.lang.Class instance) for a
2586 // for the given field type signature, as interpreted relative to the
2587 // given class loader.  Handles primitives, void, references, arrays,
2588 // and all other reflectable types, except method types.
2589 // N.B.  Code in reflection should use this entry point.
2590 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2591                                                    Klass* accessing_klass,
2592                                                    Handle class_loader,
2593                                                    Handle protection_domain,
2594                                                    SignatureStream::FailureMode failure_mode,
2595                                                    TRAPS) {
2596   Handle empty;
2597 
2598   assert(accessing_klass == NULL || (class_loader.is_null() && protection_domain.is_null()),
2599          "one or the other, or perhaps neither");
2600 
2601   Symbol* type = signature;
2602 
2603   // What we have here must be a valid field descriptor,
2604   // and all valid field descriptors are supported.
2605   // Produce the same java.lang.Class that reflection reports.
2606   if (type->utf8_length() == 1) {
2607 
2608     // It's a primitive.  (Void has a primitive mirror too.)
2609     char ch = type->char_at(0);
2610     assert(is_java_primitive(char2type(ch)) || ch == 'V', "");
2611     return Handle(THREAD, find_java_mirror_for_type(ch));
2612 
2613   } else if (FieldType::is_obj(type) || FieldType::is_array(type)) {
2614 
2615     // It's a reference type.
2616     if (accessing_klass != NULL) {
2617       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2618       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2619     }
2620     Klass* constant_type_klass;
2621     if (failure_mode == SignatureStream::ReturnNull) {
2622       constant_type_klass = resolve_or_null(type, class_loader, protection_domain,
2623                                             CHECK_(empty));
2624     } else {
2625       bool throw_error = (failure_mode == SignatureStream::NCDFError);
2626       constant_type_klass = resolve_or_fail(type, class_loader, protection_domain,
2627                                             throw_error, CHECK_(empty));
2628     }
2629     if (constant_type_klass == NULL) {
2630       return Handle();  // report failure this way
2631     }
2632     Handle mirror(THREAD, constant_type_klass->java_mirror());
2633 
2634     // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2635     if (accessing_klass != NULL) {
2636       Klass* sel_klass = constant_type_klass;
2637       bool fold_type_to_class = true;
2638       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2639                                               fold_type_to_class, CHECK_(empty));
2640     }
2641 
2642     return mirror;
2643 
2644   }
2645 
2646   // Fall through to an error.
2647   assert(false, "unsupported mirror syntax");
2648   THROW_MSG_(vmSymbols::java_lang_InternalError(), "unsupported mirror syntax", empty);
2649 }
2650 
2651 
2652 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2653 // signature, as interpreted relative to the given class loader.
2654 // Because of class loader constraints, all method handle usage must be
2655 // consistent with this loader.
2656 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2657                                                  Klass* accessing_klass,
2658                                                  TRAPS) {
2659   Handle empty;
2660   vmIntrinsics::ID null_iid = vmIntrinsics::_none;  // distinct from all method handle invoker intrinsics
2661   unsigned int hash  = invoke_method_table()->compute_hash(signature, null_iid);
2662   int          index = invoke_method_table()->hash_to_index(hash);
2663   SymbolPropertyEntry* spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2664   if (spe != NULL && spe->method_type() != NULL) {
2665     assert(java_lang_invoke_MethodType::is_instance(spe->method_type()), "");
2666     return Handle(THREAD, spe->method_type());
2667   } else if (!THREAD->can_call_java()) {
2668     warning("SystemDictionary::find_method_handle_type called from compiler thread");  // FIXME
2669     return Handle();  // do not attempt from within compiler, unless it was cached
2670   }
2671 
2672   Handle class_loader, protection_domain;
2673   if (accessing_klass != NULL) {
2674     class_loader      = Handle(THREAD, accessing_klass->class_loader());
2675     protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2676   }
2677   bool can_be_cached = true;
2678   int npts = ArgumentCount(signature).size();
2679   objArrayHandle pts = oopFactory::new_objArray_handle(SystemDictionary::Class_klass(), npts, CHECK_(empty));
2680   int arg = 0;
2681   Handle rt; // the return type from the signature
2682   ResourceMark rm(THREAD);
2683   for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2684     oop mirror = NULL;
2685     if (can_be_cached) {
2686       // Use neutral class loader to lookup candidate classes to be placed in the cache.
2687       mirror = ss.as_java_mirror(Handle(), Handle(),
2688                                  SignatureStream::ReturnNull, CHECK_(empty));
2689       if (mirror == NULL || (ss.is_object() && !is_always_visible_class(mirror))) {
2690         // Fall back to accessing_klass context.
2691         can_be_cached = false;
2692       }
2693     }
2694     if (!can_be_cached) {
2695       // Resolve, throwing a real error if it doesn't work.
2696       mirror = ss.as_java_mirror(class_loader, protection_domain,
2697                                  SignatureStream::NCDFError, CHECK_(empty));
2698     }
2699     assert(mirror != NULL, "%s", ss.as_symbol(THREAD)->as_C_string());
2700     if (ss.at_return_type())
2701       rt = Handle(THREAD, mirror);
2702     else
2703       pts->obj_at_put(arg++, mirror);
2704 
2705     // Check accessibility.
2706     if (!java_lang_Class::is_primitive(mirror) && accessing_klass != NULL) {
2707       Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2708       mirror = NULL;  // safety
2709       // Emulate ConstantPool::verify_constant_pool_resolve.
2710       bool fold_type_to_class = true;
2711       LinkResolver::check_klass_accessability(accessing_klass, sel_klass,
2712                                               fold_type_to_class, CHECK_(empty));
2713     }
2714   }
2715   assert(arg == npts, "");
2716 
2717   // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2718   JavaCallArguments args(Handle(THREAD, rt()));
2719   args.push_oop(pts);
2720   JavaValue result(T_OBJECT);
2721   JavaCalls::call_static(&result,
2722                          SystemDictionary::MethodHandleNatives_klass(),
2723                          vmSymbols::findMethodHandleType_name(),
2724                          vmSymbols::findMethodHandleType_signature(),
2725                          &args, CHECK_(empty));
2726   Handle method_type(THREAD, (oop) result.get_jobject());
2727 
2728   if (can_be_cached) {
2729     // We can cache this MethodType inside the JVM.
2730     MutexLocker ml(SystemDictionary_lock, THREAD);
2731     spe = invoke_method_table()->find_entry(index, hash, signature, null_iid);
2732     if (spe == NULL)
2733       spe = invoke_method_table()->add_entry(index, hash, signature, null_iid);
2734     if (spe->method_type() == NULL) {
2735       spe->set_method_type(method_type());
2736     }
2737   }
2738 
2739   // report back to the caller with the MethodType
2740   return method_type;
2741 }
2742 
2743 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2744                                                 Klass* accessing_klass,
2745                                                 TRAPS) {
2746   Handle empty;
2747   ResourceMark rm(THREAD);
2748   SignatureStream ss(signature, /*is_method=*/ false);
2749   if (!ss.is_done()) {
2750     Handle class_loader, protection_domain;
2751     if (accessing_klass != NULL) {
2752       class_loader      = Handle(THREAD, accessing_klass->class_loader());
2753       protection_domain = Handle(THREAD, accessing_klass->protection_domain());
2754     }
2755     oop mirror = ss.as_java_mirror(class_loader, protection_domain, SignatureStream::NCDFError, CHECK_(empty));
2756     ss.next();
2757     if (ss.is_done()) {
2758       return Handle(THREAD, mirror);
2759     }
2760   }
2761   return empty;
2762 }
2763 
2764 // Ask Java code to find or construct a method handle constant.
2765 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2766                                                      int ref_kind, //e.g., JVM_REF_invokeVirtual
2767                                                      Klass* callee,
2768                                                      Symbol* name,
2769                                                      Symbol* signature,
2770                                                      TRAPS) {
2771   Handle empty;
2772   if (caller == NULL) {
2773     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2774   }
2775   Handle name_str      = java_lang_String::create_from_symbol(name,      CHECK_(empty));
2776   Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2777 
2778   // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2779   Handle mname = MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2780   java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2781   java_lang_invoke_MemberName::set_name (mname(), name_str());
2782   java_lang_invoke_MemberName::set_type (mname(), signature_str());
2783   java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2784 
2785   if (ref_kind == JVM_REF_invokeVirtual &&
2786       MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2787     // Skip resolution for public signature polymorphic methods such as
2788     // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2789     // They require appendix argument which MemberName resolution doesn't handle.
2790     // There's special logic on JDK side to handle them
2791     // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2792   } else {
2793     MethodHandles::resolve_MemberName(mname, caller, /*speculative_resolve*/false, CHECK_(empty));
2794   }
2795 
2796   // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2797   Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2798 
2799   // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2800   JavaCallArguments args;
2801   args.push_oop(Handle(THREAD, caller->java_mirror()));  // the referring class
2802   args.push_int(ref_kind);
2803   args.push_oop(Handle(THREAD, callee->java_mirror()));  // the target class
2804   args.push_oop(name_str);
2805   args.push_oop(type);
2806   JavaValue result(T_OBJECT);
2807   JavaCalls::call_static(&result,
2808                          SystemDictionary::MethodHandleNatives_klass(),
2809                          vmSymbols::linkMethodHandleConstant_name(),
2810                          vmSymbols::linkMethodHandleConstant_signature(),
2811                          &args, CHECK_(empty));
2812   return Handle(THREAD, (oop) result.get_jobject());
2813 }
2814 
2815 // Ask Java to compute a constant by invoking a BSM given a Dynamic_info CP entry
2816 Handle SystemDictionary::link_dynamic_constant(Klass* caller,
2817                                                int condy_index,
2818                                                Handle bootstrap_specifier,
2819                                                Symbol* name,
2820                                                Symbol* type,
2821                                                TRAPS) {
2822   Handle empty;
2823   Handle bsm, info;
2824   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2825     bsm = bootstrap_specifier;
2826   } else {
2827     assert(bootstrap_specifier->is_objArray(), "");
2828     objArrayOop args = (objArrayOop) bootstrap_specifier();
2829     assert(args->length() == 2, "");
2830     bsm  = Handle(THREAD, args->obj_at(0));
2831     info = Handle(THREAD, args->obj_at(1));
2832   }
2833   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2834             "caller must supply a valid BSM");
2835 
2836   // This should not happen.  JDK code should take care of that.
2837   if (caller == NULL) {
2838     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad dynamic constant", empty);
2839   }
2840 
2841   Handle constant_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2842 
2843   // Resolve the constant type in the context of the caller class
2844   Handle type_mirror = find_java_mirror_for_type(type, caller, SignatureStream::NCDFError,
2845                                                  CHECK_(empty));
2846 
2847   // call java.lang.invoke.MethodHandleNatives::linkConstantDyanmic(caller, condy_index, bsm, type, info)
2848   JavaCallArguments args;
2849   args.push_oop(Handle(THREAD, caller->java_mirror()));
2850   args.push_int(condy_index);
2851   args.push_oop(bsm);
2852   args.push_oop(constant_name);
2853   args.push_oop(type_mirror);
2854   args.push_oop(info);
2855   JavaValue result(T_OBJECT);
2856   JavaCalls::call_static(&result,
2857                          SystemDictionary::MethodHandleNatives_klass(),
2858                          vmSymbols::linkDynamicConstant_name(),
2859                          vmSymbols::linkDynamicConstant_signature(),
2860                          &args, CHECK_(empty));
2861 
2862   return Handle(THREAD, (oop) result.get_jobject());
2863 }
2864 
2865 // Ask Java code to find or construct a java.lang.invoke.CallSite for the given
2866 // name and signature, as interpreted relative to the given class loader.
2867 methodHandle SystemDictionary::find_dynamic_call_site_invoker(Klass* caller,
2868                                                               int indy_index,
2869                                                               Handle bootstrap_specifier,
2870                                                               Symbol* name,
2871                                                               Symbol* type,
2872                                                               Handle *appendix_result,
2873                                                               Handle *method_type_result,
2874                                                               TRAPS) {
2875   methodHandle empty;
2876   Handle bsm, info;
2877   if (java_lang_invoke_MethodHandle::is_instance(bootstrap_specifier())) {
2878     bsm = bootstrap_specifier;
2879   } else {
2880     objArrayOop args = (objArrayOop) bootstrap_specifier();
2881     assert(args->length() == 2, "");
2882     bsm  = Handle(THREAD, args->obj_at(0));
2883     info = Handle(THREAD, args->obj_at(1));
2884   }
2885   guarantee(java_lang_invoke_MethodHandle::is_instance(bsm()),
2886             "caller must supply a valid BSM");
2887 
2888   Handle method_name = java_lang_String::create_from_symbol(name, CHECK_(empty));
2889   Handle method_type = find_method_handle_type(type, caller, CHECK_(empty));
2890 
2891   // This should not happen.  JDK code should take care of that.
2892   if (caller == NULL || method_type.is_null()) {
2893     THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad invokedynamic", empty);
2894   }
2895 
2896   objArrayHandle appendix_box = oopFactory::new_objArray_handle(SystemDictionary::Object_klass(), 1, CHECK_(empty));
2897   assert(appendix_box->obj_at(0) == NULL, "");
2898 
2899   // call java.lang.invoke.MethodHandleNatives::linkCallSite(caller, indy_index, bsm, name, mtype, info, &appendix)
2900   JavaCallArguments args;
2901   args.push_oop(Handle(THREAD, caller->java_mirror()));
2902   args.push_int(indy_index);
2903   args.push_oop(bsm);
2904   args.push_oop(method_name);
2905   args.push_oop(method_type);
2906   args.push_oop(info);
2907   args.push_oop(appendix_box);
2908   JavaValue result(T_OBJECT);
2909   JavaCalls::call_static(&result,
2910                          SystemDictionary::MethodHandleNatives_klass(),
2911                          vmSymbols::linkCallSite_name(),
2912                          vmSymbols::linkCallSite_signature(),
2913                          &args, CHECK_(empty));
2914   Handle mname(THREAD, (oop) result.get_jobject());
2915   (*method_type_result) = method_type;
2916   return unpack_method_and_appendix(mname, caller, appendix_box, appendix_result, THREAD);
2917 }
2918 
2919 // Protection domain cache table handling
2920 
2921 ProtectionDomainCacheEntry* SystemDictionary::cache_get(Handle protection_domain) {
2922   return _pd_cache_table->get(protection_domain);
2923 }
2924 
2925 #if INCLUDE_CDS
2926 void SystemDictionary::reorder_dictionary_for_sharing() {
2927   ClassLoaderData::the_null_class_loader_data()->dictionary()->reorder_dictionary_for_sharing();
2928 }
2929 #endif
2930 
2931 size_t SystemDictionary::count_bytes_for_buckets() {
2932   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_buckets();
2933 }
2934 
2935 size_t SystemDictionary::count_bytes_for_table() {
2936   return ClassLoaderData::the_null_class_loader_data()->dictionary()->count_bytes_for_table();
2937 }
2938 
2939 void SystemDictionary::copy_buckets(char* top, char* end) {
2940   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_buckets(top, end);
2941 }
2942 
2943 void SystemDictionary::copy_table(char* top, char* end) {
2944   ClassLoaderData::the_null_class_loader_data()->dictionary()->copy_table(top, end);
2945 }
2946 
2947 // ----------------------------------------------------------------------------
2948 void SystemDictionary::print_shared(outputStream *st) {
2949   shared_dictionary()->print_on(st);
2950 }
2951 
2952 void SystemDictionary::print_on(outputStream *st) {
2953   if (shared_dictionary() != NULL) {
2954     st->print_cr("Shared Dictionary");
2955     shared_dictionary()->print_on(st);
2956     st->cr();
2957   }
2958 
2959   GCMutexLocker mu(SystemDictionary_lock);
2960 
2961   ClassLoaderDataGraph::print_dictionary(st);
2962 
2963   // Placeholders
2964   placeholders()->print_on(st);
2965   st->cr();
2966 
2967   // loader constraints - print under SD_lock
2968   constraints()->print_on(st);
2969   st->cr();
2970 
2971   _pd_cache_table->print_on(st);
2972   st->cr();
2973 }
2974 
2975 void SystemDictionary::verify() {
2976   guarantee(constraints() != NULL,
2977             "Verify of loader constraints failed");
2978   guarantee(placeholders()->number_of_entries() >= 0,
2979             "Verify of placeholders failed");
2980 
2981   GCMutexLocker mu(SystemDictionary_lock);
2982 
2983   // Verify dictionary
2984   ClassLoaderDataGraph::verify_dictionary();
2985 
2986   placeholders()->verify();
2987 
2988   // Verify constraint table
2989   guarantee(constraints() != NULL, "Verify of loader constraints failed");
2990   constraints()->verify(placeholders());
2991 
2992   _pd_cache_table->verify();
2993 }
2994 
2995 void SystemDictionary::dump(outputStream *st, bool verbose) {
2996   assert_locked_or_safepoint(SystemDictionary_lock);
2997   if (verbose) {
2998     print_on(st);
2999   } else {
3000     if (shared_dictionary() != NULL) {
3001       shared_dictionary()->print_table_statistics(st, "Shared Dictionary");
3002     }
3003     ClassLoaderDataGraph::print_dictionary_statistics(st);
3004     placeholders()->print_table_statistics(st, "Placeholder Table");
3005     constraints()->print_table_statistics(st, "LoaderConstraints Table");
3006     _pd_cache_table->print_table_statistics(st, "ProtectionDomainCache Table");
3007   }
3008 }
3009 
3010 // Utility for dumping dictionaries.
3011 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
3012                                  DCmdWithParser(output, heap),
3013   _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
3014            "BOOLEAN", false, "false") {
3015   _dcmdparser.add_dcmd_option(&_verbose);
3016 }
3017 
3018 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
3019   VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
3020                          _verbose.value());
3021   VMThread::execute(&dumper);
3022 }
3023 
3024 int SystemDictionaryDCmd::num_arguments() {
3025   ResourceMark rm;
3026   SystemDictionaryDCmd* dcmd = new SystemDictionaryDCmd(NULL, false);
3027   if (dcmd != NULL) {
3028     DCmdMark mark(dcmd);
3029     return dcmd->_dcmdparser.num_arguments();
3030   } else {
3031     return 0;
3032   }
3033 }
3034 
3035 class CombineDictionariesClosure : public CLDClosure {
3036   private:
3037     Dictionary* _master_dictionary;
3038   public:
3039     CombineDictionariesClosure(Dictionary* master_dictionary) :
3040       _master_dictionary(master_dictionary) {}
3041     void do_cld(ClassLoaderData* cld) {
3042       ResourceMark rm;
3043       if (cld->is_unsafe_anonymous()) {
3044         return;
3045       }
3046       if (cld->is_system_class_loader_data() || cld->is_platform_class_loader_data()) {
3047         for (int i = 0; i < cld->dictionary()->table_size(); ++i) {
3048           Dictionary* curr_dictionary = cld->dictionary();
3049           DictionaryEntry* p = curr_dictionary->bucket(i);
3050           while (p != NULL) {
3051             Symbol* name = p->instance_klass()->name();
3052             unsigned int d_hash = _master_dictionary->compute_hash(name);
3053             int d_index = _master_dictionary->hash_to_index(d_hash);
3054             DictionaryEntry* next = p->next();
3055             if (p->literal()->class_loader_data() != cld) {
3056               // This is an initiating class loader entry; don't use it
3057               log_trace(cds)("Skipping initiating cl entry: %s", name->as_C_string());
3058               curr_dictionary->free_entry(p);
3059             } else {
3060               log_trace(cds)("Moved to boot dictionary: %s", name->as_C_string());
3061               curr_dictionary->unlink_entry(p);
3062               p->set_pd_set(NULL); // pd_set is runtime only information and will be reconstructed.
3063               _master_dictionary->add_entry(d_index, p);
3064             }
3065             p = next;
3066           }
3067           *curr_dictionary->bucket_addr(i) = NULL;
3068         }
3069       }
3070     }
3071 };
3072 
3073 // Combining platform and system loader dictionaries into boot loader dictionary.
3074 // During run time, we only have one shared dictionary.
3075 void SystemDictionary::combine_shared_dictionaries() {
3076   assert(DumpSharedSpaces, "dump time only");
3077   Dictionary* master_dictionary = ClassLoaderData::the_null_class_loader_data()->dictionary();
3078   CombineDictionariesClosure cdc(master_dictionary);
3079   ClassLoaderDataGraph::loaded_cld_do(&cdc);
3080 
3081   // These tables are no longer valid or necessary. Keeping them around will
3082   // cause SystemDictionary::verify() to fail. Let's empty them.
3083   _placeholders        = new PlaceholderTable(_placeholder_table_size);
3084   _loader_constraints  = new LoaderConstraintTable(_loader_constraint_size);
3085 
3086   NOT_PRODUCT(SystemDictionary::verify());
3087 }
3088 
3089 void SystemDictionary::initialize_oop_storage() {
3090   _vm_weak_oop_storage =
3091     new OopStorage("VM Weak Oop Handles",
3092                    VMWeakAlloc_lock,
3093                    VMWeakActive_lock);
3094 }
3095 
3096 OopStorage* SystemDictionary::vm_weak_oop_storage() {
3097   assert(_vm_weak_oop_storage != NULL, "Uninitialized");
3098   return _vm_weak_oop_storage;
3099 }