1 /*
2 * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "cds/aotClassLocation.hpp"
26 #include "cds/cdsConfig.hpp"
27 #include "cds/heapShared.hpp"
28 #include "classfile/classFileParser.hpp"
29 #include "classfile/classFileStream.hpp"
30 #include "classfile/classLoader.hpp"
31 #include "classfile/classLoaderData.inline.hpp"
32 #include "classfile/classLoaderDataGraph.inline.hpp"
33 #include "classfile/classLoadInfo.hpp"
34 #include "classfile/dictionary.hpp"
35 #include "classfile/javaClasses.inline.hpp"
36 #include "classfile/klassFactory.hpp"
37 #include "classfile/loaderConstraints.hpp"
38 #include "classfile/packageEntry.hpp"
39 #include "classfile/placeholders.hpp"
40 #include "classfile/resolutionErrors.hpp"
41 #include "classfile/stringTable.hpp"
42 #include "classfile/symbolTable.hpp"
43 #include "classfile/systemDictionary.hpp"
44 #include "classfile/vmClasses.hpp"
45 #include "classfile/vmSymbols.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "interpreter/bootstrapInfo.hpp"
48 #include "jfr/jfrEvents.hpp"
49 #include "jvm.h"
50 #include "logging/log.hpp"
51 #include "logging/logStream.hpp"
52 #include "memory/metaspaceClosure.hpp"
53 #include "memory/oopFactory.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "memory/universe.hpp"
56 #include "oops/access.inline.hpp"
57 #include "oops/constantPool.inline.hpp"
58 #include "oops/fieldStreams.inline.hpp"
59 #include "oops/inlineKlass.inline.hpp"
60 #include "oops/instanceKlass.hpp"
61 #include "oops/klass.inline.hpp"
62 #include "oops/method.inline.hpp"
63 #include "oops/objArrayKlass.hpp"
64 #include "oops/objArrayOop.inline.hpp"
65 #include "oops/oop.inline.hpp"
66 #include "oops/oopHandle.inline.hpp"
67 #include "oops/symbol.hpp"
68 #include "oops/typeArrayKlass.hpp"
69 #include "prims/jvmtiExport.hpp"
70 #include "prims/methodHandles.hpp"
71 #include "runtime/arguments.hpp"
72 #include "runtime/atomicAccess.hpp"
73 #include "runtime/handles.inline.hpp"
74 #include "runtime/java.hpp"
75 #include "runtime/javaCalls.hpp"
76 #include "runtime/mutexLocker.hpp"
77 #include "runtime/os.hpp"
78 #include "runtime/sharedRuntime.hpp"
79 #include "runtime/signature.hpp"
80 #include "runtime/synchronizer.hpp"
81 #include "services/classLoadingService.hpp"
82 #include "services/diagnosticCommand.hpp"
83 #include "services/finalizerService.hpp"
84 #include "services/threadService.hpp"
85 #include "utilities/growableArray.hpp"
86 #include "utilities/macros.hpp"
87 #include "utilities/utf8.hpp"
88 #if INCLUDE_CDS
89 #include "classfile/systemDictionaryShared.hpp"
90 #endif
91 #if INCLUDE_JFR
92 #include "jfr/jfr.hpp"
93 #endif
94
95 class InvokeMethodKey : public StackObj {
96 private:
97 Symbol* _symbol;
98 intptr_t _iid;
99
100 public:
101 InvokeMethodKey(Symbol* symbol, intptr_t iid) :
102 _symbol(symbol),
103 _iid(iid) {}
104
105 static bool key_comparison(InvokeMethodKey const &k1, InvokeMethodKey const &k2){
106 return k1._symbol == k2._symbol && k1._iid == k2._iid;
107 }
108
109 static unsigned int compute_hash(const InvokeMethodKey &k) {
110 Symbol* sym = k._symbol;
111 intptr_t iid = k._iid;
112 unsigned int hash = (unsigned int) sym -> identity_hash();
113 return (unsigned int) (hash ^ iid);
114 }
115
116 };
117
118 using InvokeMethodIntrinsicTable = HashTable<InvokeMethodKey, Method*, 139, AnyObj::C_HEAP, mtClass,
119 InvokeMethodKey::compute_hash, InvokeMethodKey::key_comparison>;
120 static InvokeMethodIntrinsicTable* _invoke_method_intrinsic_table;
121 using InvokeMethodTypeTable = HashTable<SymbolHandle, OopHandle, 139, AnyObj::C_HEAP, mtClass, SymbolHandle::compute_hash>;
122 static InvokeMethodTypeTable* _invoke_method_type_table;
123
124 OopHandle SystemDictionary::_java_system_loader;
125 OopHandle SystemDictionary::_java_platform_loader;
126
127 // ----------------------------------------------------------------------------
128 // Java-level SystemLoader and PlatformLoader
129 oop SystemDictionary::java_system_loader() {
130 return _java_system_loader.resolve();
131 }
132
133 oop SystemDictionary::java_platform_loader() {
134 return _java_platform_loader.resolve();
135 }
136
137 void SystemDictionary::compute_java_loaders(TRAPS) {
138 if (_java_platform_loader.is_empty()) {
139 oop platform_loader = get_platform_class_loader_impl(CHECK);
140 _java_platform_loader = OopHandle(Universe::vm_global(), platform_loader);
141 } else {
142 // It must have been restored from the archived module graph
143 assert(CDSConfig::is_using_archive(), "must be");
144 assert(CDSConfig::is_using_full_module_graph(), "must be");
145 DEBUG_ONLY(
146 oop platform_loader = get_platform_class_loader_impl(CHECK);
147 assert(_java_platform_loader.resolve() == platform_loader, "must be");
148 )
149 }
150
151 if (_java_system_loader.is_empty()) {
152 oop system_loader = get_system_class_loader_impl(CHECK);
153 _java_system_loader = OopHandle(Universe::vm_global(), system_loader);
154 } else {
155 // It must have been restored from the archived module graph
156 assert(CDSConfig::is_using_archive(), "must be");
157 assert(CDSConfig::is_using_full_module_graph(), "must be");
158 DEBUG_ONLY(
159 oop system_loader = get_system_class_loader_impl(CHECK);
160 assert(_java_system_loader.resolve() == system_loader, "must be");
161 )
162 }
163 }
164
165 oop SystemDictionary::get_system_class_loader_impl(TRAPS) {
166 JavaValue result(T_OBJECT);
167 InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass();
168 JavaCalls::call_static(&result,
169 class_loader_klass,
170 vmSymbols::getSystemClassLoader_name(),
171 vmSymbols::void_classloader_signature(),
172 CHECK_NULL);
173 return result.get_oop();
174 }
175
176 oop SystemDictionary::get_platform_class_loader_impl(TRAPS) {
177 JavaValue result(T_OBJECT);
178 InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass();
179 JavaCalls::call_static(&result,
180 class_loader_klass,
181 vmSymbols::getPlatformClassLoader_name(),
182 vmSymbols::void_classloader_signature(),
183 CHECK_NULL);
184 return result.get_oop();
185 }
186
187 // Helper function
188 inline ClassLoaderData* class_loader_data(Handle class_loader) {
189 return ClassLoaderData::class_loader_data(class_loader());
190 }
191
192 // These migrated value classes are loaded by the bootstrap class loader but are added to the initiating
193 // loaders automatically so that fields of these types can be found and potentially flattened during
194 // field layout.
195 static void add_migrated_value_classes(ClassLoaderData* cld) {
196 JavaThread* current = JavaThread::current();
197 auto add_klass = [&] (Symbol* classname) {
198 InstanceKlass* ik = SystemDictionary::find_instance_klass(current, classname, Handle(current, nullptr));
199 assert(ik != nullptr, "Must exist");
200 SystemDictionary::add_to_initiating_loader(current, ik, cld);
201 };
202
203 MonitorLocker mu1(SystemDictionary_lock);
204 vmSymbols::migrated_class_names_do(add_klass);
205 }
206
207 ClassLoaderData* SystemDictionary::register_loader(Handle class_loader, bool create_mirror_cld) {
208 if (create_mirror_cld) {
209 // Add a new class loader data to the graph.
210 return ClassLoaderDataGraph::add(class_loader, true);
211 } else {
212 if (class_loader() == nullptr) {
213 return ClassLoaderData::the_null_class_loader_data();
214 } else {
215 bool created = false;
216 ClassLoaderData* cld = ClassLoaderDataGraph::find_or_create(class_loader, created);
217 if (created && Arguments::enable_preview()) {
218 if (CDSConfig::is_using_aot_linked_classes() && java_system_loader() == nullptr) {
219 // We are inside AOTLinkedClassBulkLoader::preload_classes().
220 //
221 // AOTLinkedClassBulkLoader will automatically initiate the loading of all archived
222 // public classes from the boot loader into platform/system loaders, so there's
223 // no need to call add_migrated_value_classes().
224 } else {
225 add_migrated_value_classes(cld);
226 }
227 }
228 return cld;
229 }
230 }
231 }
232
233 void SystemDictionary::set_system_loader(ClassLoaderData *cld) {
234 if (_java_system_loader.is_empty()) {
235 _java_system_loader = cld->class_loader_handle();
236 } else {
237 assert(_java_system_loader.resolve() == cld->class_loader(), "sanity");
238 }
239 }
240
241 void SystemDictionary::set_platform_loader(ClassLoaderData *cld) {
242 if (_java_platform_loader.is_empty()) {
243 _java_platform_loader = cld->class_loader_handle();
244 } else {
245 assert(_java_platform_loader.resolve() == cld->class_loader(), "sanity");
246 }
247 }
248
249 // ----------------------------------------------------------------------------
250 // Parallel class loading check
251
252 static bool is_parallelCapable(Handle class_loader) {
253 if (class_loader.is_null()) return true;
254 return java_lang_ClassLoader::parallelCapable(class_loader());
255 }
256 // ----------------------------------------------------------------------------
257 // ParallelDefineClass flag does not apply to bootclass loader
258 static bool is_parallelDefine(Handle class_loader) {
259 if (class_loader.is_null()) return false;
260 if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) {
261 return true;
262 }
263 return false;
264 }
265
266 // Returns true if the passed class loader is the builtin application class loader
267 // or a custom system class loader. A customer system class loader can be
268 // specified via -Djava.system.class.loader.
269 bool SystemDictionary::is_system_class_loader(oop class_loader) {
270 if (class_loader == nullptr) {
271 return false;
272 }
273 return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() ||
274 class_loader == _java_system_loader.peek());
275 }
276
277 // Returns true if the passed class loader is the platform class loader.
278 bool SystemDictionary::is_platform_class_loader(oop class_loader) {
279 if (class_loader == nullptr) {
280 return false;
281 }
282 return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass());
283 }
284
285 Handle SystemDictionary::get_loader_lock_or_null(Handle class_loader) {
286 // If class_loader is null or parallelCapable, the JVM doesn't acquire a lock while loading.
287 if (is_parallelCapable(class_loader)) {
288 return Handle();
289 } else {
290 return class_loader;
291 }
292 }
293
294 // ----------------------------------------------------------------------------
295 // Resolving of classes
296
297 Symbol* SystemDictionary::class_name_symbol(const char* name, Symbol* exception, TRAPS) {
298 if (name == nullptr) {
299 THROW_MSG_NULL(exception, "No class name given");
300 }
301 size_t name_len = strlen(name);
302 if (name_len > static_cast<size_t>(Symbol::max_length())) {
303 // It's impossible to create this class; the name cannot fit
304 // into the constant pool. If necessary report an abridged name
305 // in the exception message.
306 if (name_len > static_cast<size_t>(MaxStringPrintSize)) {
307 Exceptions::fthrow(THREAD_AND_LOCATION, exception,
308 "Class name exceeds maximum length of %d: %.*s ... (%zu characters omitted) ... %.*s",
309 Symbol::max_length(),
310 MaxStringPrintSize / 2,
311 name,
312 name_len - 2 * (MaxStringPrintSize / 2), // allows for odd value
313 MaxStringPrintSize / 2,
314 name + name_len - MaxStringPrintSize / 2);
315 }
316 else {
317 Exceptions::fthrow(THREAD_AND_LOCATION, exception,
318 "Class name exceeds maximum length of %d: %s",
319 Symbol::max_length(),
320 name);
321 }
322 return nullptr;
323 }
324 // Callers should ensure that the name is never an illegal UTF8 string.
325 assert(UTF8::is_legal_utf8((const unsigned char*)name, name_len, false),
326 "Class name is not a valid utf8 string.");
327
328 // Make a new symbol for the class name.
329 return SymbolTable::new_symbol(name);
330 }
331
332 #ifdef ASSERT
333 // Used to verify that class loading succeeded in adding k to the dictionary.
334 static void verify_dictionary_entry(Symbol* class_name, InstanceKlass* k) {
335 MutexLocker mu(SystemDictionary_lock);
336 ClassLoaderData* loader_data = k->class_loader_data();
337 Dictionary* dictionary = loader_data->dictionary();
338 assert(class_name == k->name(), "Must be the same");
339 InstanceKlass* kk = dictionary->find_class(JavaThread::current(), class_name);
340 assert(kk == k, "should be present in dictionary");
341 }
342 #endif
343
344 static void handle_resolution_exception(Symbol* class_name, bool throw_error, TRAPS) {
345 if (HAS_PENDING_EXCEPTION) {
346 // If we have a pending exception we forward it to the caller, unless throw_error is true,
347 // in which case we have to check whether the pending exception is a ClassNotFoundException,
348 // and convert it to a NoClassDefFoundError and chain the original ClassNotFoundException.
349 if (throw_error && PENDING_EXCEPTION->is_a(vmClasses::ClassNotFoundException_klass())) {
350 ResourceMark rm(THREAD);
351 Handle e(THREAD, PENDING_EXCEPTION);
352 CLEAR_PENDING_EXCEPTION;
353 THROW_MSG_CAUSE(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e);
354 } else {
355 return; // the caller will throw the incoming exception
356 }
357 }
358 // If the class is not found, ie, caller has checked that klass is null, throw the appropriate
359 // error or exception depending on the value of throw_error.
360 ResourceMark rm(THREAD);
361 if (throw_error) {
362 THROW_MSG(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string());
363 } else {
364 THROW_MSG(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string());
365 }
366 }
367
368 // Forwards to resolve_or_null
369
370 Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader,
371 bool throw_error, TRAPS) {
372 Klass* klass = resolve_or_null(class_name, class_loader, THREAD);
373 // Check for pending exception or null klass, and throw exception
374 if (HAS_PENDING_EXCEPTION || klass == nullptr) {
375 handle_resolution_exception(class_name, throw_error, CHECK_NULL);
376 }
377 return klass;
378 }
379
380 // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null
381
382 Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, TRAPS) {
383 if (Signature::is_array(class_name)) {
384 return resolve_array_class_or_null(class_name, class_loader, THREAD);
385 } else {
386 assert(class_name != nullptr && !Signature::is_array(class_name), "must be");
387 if (Signature::has_envelope(class_name)) {
388 ResourceMark rm(THREAD);
389 // Ignore wrapping L and ;.
390 TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1,
391 class_name->utf8_length() - 2);
392 return resolve_instance_class_or_null(name, class_loader, THREAD);
393 } else {
394 return resolve_instance_class_or_null(class_name, class_loader, THREAD);
395 }
396 }
397 }
398
399 // Forwards to resolve_instance_class_or_null
400
401 Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name,
402 Handle class_loader,
403 TRAPS) {
404 assert(Signature::is_array(class_name), "must be array");
405 ResourceMark rm(THREAD);
406 SignatureStream ss(class_name, false);
407 int ndims = ss.skip_array_prefix(); // skip all '['s
408 Klass* k = nullptr;
409 BasicType t = ss.type();
410 if (ss.has_envelope()) {
411 Symbol* obj_class = ss.as_symbol();
412 k = SystemDictionary::resolve_instance_class_or_null(obj_class,
413 class_loader,
414 CHECK_NULL);
415 if (k != nullptr) {
416 k = k->array_klass(ndims, CHECK_NULL);
417 }
418 } else {
419 k = Universe::typeArrayKlass(t);
420 k = k->array_klass(ndims, CHECK_NULL);
421 }
422 return k;
423 }
424
425 static inline void log_circularity_error(Symbol* name, PlaceholderEntry* probe) {
426 LogTarget(Debug, class, load, placeholders) lt;
427 if (lt.is_enabled()) {
428 ResourceMark rm;
429 LogStream ls(lt);
430 ls.print("ClassCircularityError detected for placeholder entry %s", name->as_C_string());
431 probe->print_on(&ls);
432 ls.cr();
433 }
434 }
435
436 // Must be called for any superclass or superinterface resolution
437 // during class definition, or may be called for inline field layout processing
438 // to detect class circularity errors.
439 // superinterface callers:
440 // parse_interfaces - from defineClass
441 // superclass callers:
442 // ClassFileParser - from defineClass
443 // load_shared_class - while loading a class from shared archive
444 // resolve_instance_class_or_null:
445 // via: handle_parallel_super_load
446 // when resolving a class that has an existing placeholder with
447 // a saved superclass [i.e. a defineClass is currently in progress]
448 // If another thread is trying to resolve the class, it must do
449 // superclass checks on its own thread to catch class circularity and
450 // to avoid deadlock.
451 // inline field layout callers:
452 // The field's class must be loaded to determine layout.
453 //
454 // resolve_with_circularity_detection adds a DETECT_CIRCULARITY placeholder to the placeholder table before calling
455 // resolve_instance_class_or_null. ClassCircularityError is detected when a DETECT_CIRCULARITY or LOAD_INSTANCE
456 // placeholder for the same thread, class, and classloader is found.
457 // This can be seen with logging option: -Xlog:class+load+placeholders=debug.
458 //
459 InstanceKlass* SystemDictionary::resolve_with_circularity_detection(Symbol* class_name,
460 Symbol* next_name,
461 Handle class_loader,
462 bool is_superclass,
463 TRAPS) {
464
465 assert(next_name != nullptr, "null superclass for resolving");
466 assert(!Signature::is_array(next_name), "invalid superclass name");
467
468 ClassLoaderData* loader_data = class_loader_data(class_loader);
469
470 if (is_superclass) {
471 InstanceKlass* klassk = loader_data->dictionary()->find_class(THREAD, class_name);
472 if (klassk != nullptr) {
473 // We can come here for two reasons:
474 // (a) RedefineClasses -- the class is already loaded
475 // (b) Rarely, the class might have been loaded by a parallel thread
476 // We can do a quick check against the already assigned superclass's name and loader.
477 InstanceKlass* superk = klassk->super();
478 if (superk != nullptr &&
479 superk->name() == next_name &&
480 superk->class_loader() == class_loader()) {
481 return superk;
482 }
483 }
484 }
485
486 // can't throw error holding a lock
487 bool throw_circularity_error = false;
488 {
489 MutexLocker mu(THREAD, SystemDictionary_lock);
490
491 // Must check ClassCircularity before resolving next_name (superclass, interface, field types or speculatively preloaded argument types).
492 PlaceholderEntry* probe = PlaceholderTable::get_entry(class_name, loader_data);
493 if (probe != nullptr && probe->check_seen_thread(THREAD, PlaceholderTable::DETECT_CIRCULARITY)) {
494 log_circularity_error(class_name, probe);
495 throw_circularity_error = true;
496 }
497
498 // Make sure there's a placeholder for the class_name before resolving.
499 // This is used as a claim that this thread is currently loading superclass/classloader
500 // and for ClassCircularity checks.
501 if (!throw_circularity_error) {
502 // Be careful not to exit resolve_with_circularity_detection without removing this placeholder.
503 PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(class_name,
504 loader_data,
505 PlaceholderTable::DETECT_CIRCULARITY,
506 next_name, THREAD);
507 }
508 }
509
510 if (throw_circularity_error) {
511 ResourceMark rm(THREAD);
512 THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), class_name->as_C_string());
513 }
514
515 // Resolve the superclass, superinterface, field type or speculatively preloaded argument types and check results on return.
516 InstanceKlass* superk =
517 SystemDictionary::resolve_instance_class_or_null(next_name,
518 class_loader,
519 THREAD);
520
521 // Clean up placeholder entry.
522 {
523 MutexLocker mu(THREAD, SystemDictionary_lock);
524 PlaceholderTable::find_and_remove(class_name, loader_data, PlaceholderTable::DETECT_CIRCULARITY, THREAD);
525 SystemDictionary_lock->notify_all();
526 }
527
528 // Check for pending exception or null superk, and throw exception
529 if (HAS_PENDING_EXCEPTION || superk == nullptr) {
530 handle_resolution_exception(next_name, true, CHECK_NULL);
531 }
532
533 return superk;
534 }
535
536 // If the class in is in the placeholder table, class loading is in progress.
537 // For cases where the application changes threads to load classes, it
538 // is critical to ClassCircularity detection that we try loading
539 // the superclass on the new thread internally, so we do parallel
540 // superclass loading here. This avoids deadlock for ClassCircularity
541 // detection for parallelCapable class loaders that lock on a per-class lock.
542 static void handle_parallel_super_load(Symbol* name,
543 Symbol* superclassname,
544 Handle class_loader,
545 TRAPS) {
546
547 // The result superk is not used; resolve_with_circularity_detection is called for circularity check only.
548 // This passes false to is_superclass to skip doing the unlikely optimization.
549 Klass* superk = SystemDictionary::resolve_with_circularity_detection(name,
550 superclassname,
551 class_loader,
552 false,
553 CHECK);
554 }
555
556 // Bootstrap and non-parallel capable class loaders use the LOAD_INSTANCE placeholder to
557 // wait for parallel class loading and/or to check for circularity error for Xcomp when loading.
558 static bool needs_load_placeholder(Handle class_loader) {
559 return class_loader.is_null() || !is_parallelCapable(class_loader);
560 }
561
562 // Check for other threads loading this class either to throw CCE or wait in the case of the boot loader.
563 static InstanceKlass* handle_parallel_loading(JavaThread* current,
564 Symbol* name,
565 ClassLoaderData* loader_data,
566 bool must_wait_for_class_loading,
567 bool* throw_circularity_error) {
568 PlaceholderEntry* oldprobe = PlaceholderTable::get_entry(name, loader_data);
569 if (oldprobe != nullptr) {
570 // -Xcomp calls load_signature_classes which might result in loading
571 // a class that's already in the process of loading, so we detect CCE here also.
572 // Only need check_seen_thread once, not on each loop
573 if (oldprobe->check_seen_thread(current, PlaceholderTable::LOAD_INSTANCE)) {
574 log_circularity_error(name, oldprobe);
575 *throw_circularity_error = true;
576 return nullptr;
577 } else if (must_wait_for_class_loading) {
578 // Wait until the first thread has finished loading this class. Also wait until all the
579 // threads trying to load its superclass have removed their placeholders.
580 while (oldprobe != nullptr &&
581 (oldprobe->instance_load_in_progress() || oldprobe->circularity_detection_in_progress())) {
582
583 // LOAD_INSTANCE placeholders are used to implement parallel capable class loading
584 // for the bootclass loader.
585 SystemDictionary_lock->wait();
586
587 // Check if classloading completed while we were waiting
588 InstanceKlass* check = loader_data->dictionary()->find_class(current, name);
589 if (check != nullptr) {
590 // Klass is already loaded, so just return it
591 return check;
592 }
593 // check if other thread failed to load and cleaned up
594 oldprobe = PlaceholderTable::get_entry(name, loader_data);
595 }
596 }
597 }
598 return nullptr;
599 }
600
601 // SystemDictionary::resolve_instance_class_or_null is the main function for class name resolution.
602 // After checking if the InstanceKlass already exists, it checks for ClassCircularityError and
603 // whether the thread must wait for loading in parallel. It eventually calls load_instance_class,
604 // which will load the class via the bootstrap loader or call ClassLoader.loadClass().
605 // This can return null, an exception or an InstanceKlass.
606 InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name,
607 Handle class_loader,
608 TRAPS) {
609 // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;"
610 DEBUG_ONLY(ResourceMark rm(THREAD));
611 assert(name != nullptr && !Signature::is_array(name) &&
612 !Signature::has_envelope(name), "invalid class name: %s", name == nullptr ? "nullptr" : name->as_C_string());
613
614 EventClassLoad class_load_event;
615
616 HandleMark hm(THREAD);
617
618 ClassLoaderData* loader_data = register_loader(class_loader);
619 Dictionary* dictionary = loader_data->dictionary();
620
621 // Do lookup to see if class already exists.
622 InstanceKlass* probe = dictionary->find_class(THREAD, name);
623 if (probe != nullptr) return probe;
624
625 // Non-bootstrap class loaders will call out to class loader and
626 // define via jvm/jni_DefineClass which will acquire the
627 // class loader object lock to protect against multiple threads
628 // defining the class in parallel by accident.
629 // This lock must be acquired here so the waiter will find
630 // any successful result in the SystemDictionary and not attempt
631 // the define.
632 // ParallelCapable class loaders and the bootstrap classloader
633 // do not acquire lock here.
634 Handle lockObject = get_loader_lock_or_null(class_loader);
635 ObjectLocker ol(lockObject, THREAD);
636
637 bool circularity_detection_in_progress = false;
638 InstanceKlass* loaded_class = nullptr;
639 SymbolHandle superclassname; // Keep alive while loading in parallel thread.
640
641 guarantee(THREAD->can_call_java(),
642 "can not load classes with compiler thread: class=%s, classloader=%s",
643 name->as_C_string(),
644 class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string());
645
646 // Check again (after locking) if the class already exists in SystemDictionary
647 {
648 MutexLocker mu(THREAD, SystemDictionary_lock);
649 InstanceKlass* check = dictionary->find_class(THREAD, name);
650 if (check != nullptr) {
651 // InstanceKlass is already loaded, but we still need to check protection domain below.
652 loaded_class = check;
653 } else {
654 PlaceholderEntry* placeholder = PlaceholderTable::get_entry(name, loader_data);
655 if (placeholder != nullptr && placeholder->circularity_detection_in_progress()) {
656 circularity_detection_in_progress = true;
657 superclassname = placeholder->next_klass_name();
658 assert(superclassname != nullptr, "superclass has to have a name");
659 }
660 }
661 }
662
663 // If the class is in the placeholder table with super_class set,
664 // handle superclass loading in progress.
665 if (circularity_detection_in_progress) {
666 handle_parallel_super_load(name, superclassname,
667 class_loader,
668 CHECK_NULL);
669 }
670
671 bool throw_circularity_error = false;
672 if (loaded_class == nullptr) {
673 bool load_placeholder_added = false;
674
675 // Add placeholder entry to record loading instance class
676 // case 1. Bootstrap classloader
677 // This classloader supports parallelism at the classloader level
678 // but only allows a single thread to load a class/classloader pair.
679 // The LOAD_INSTANCE placeholder is the mechanism for mutual exclusion.
680 // case 2. parallelCapable user level classloaders
681 // These class loaders lock a per-class object lock when ClassLoader.loadClass()
682 // is called. A LOAD_INSTANCE placeholder isn't used for mutual exclusion.
683 // case 3. traditional classloaders that rely on the classloader object lock
684 // There should be no need for need for LOAD_INSTANCE for mutual exclusion,
685 // except the LOAD_INSTANCE placeholder is used to detect CCE for -Xcomp.
686 // TODO: should also be used to detect CCE for parallel capable class loaders but it's not.
687 {
688 MutexLocker mu(THREAD, SystemDictionary_lock);
689 if (needs_load_placeholder(class_loader)) {
690 loaded_class = handle_parallel_loading(THREAD,
691 name,
692 loader_data,
693 class_loader.is_null(),
694 &throw_circularity_error);
695 }
696
697 // Recheck if the class has been loaded for all class loader cases and
698 // add a LOAD_INSTANCE placeholder while holding the SystemDictionary_lock.
699 if (!throw_circularity_error && loaded_class == nullptr) {
700 InstanceKlass* check = dictionary->find_class(THREAD, name);
701 if (check != nullptr) {
702 loaded_class = check;
703 } else if (needs_load_placeholder(class_loader)) {
704 // Add the LOAD_INSTANCE token. Threads will wait on loading to complete for this thread.
705 PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(name, loader_data,
706 PlaceholderTable::LOAD_INSTANCE,
707 nullptr,
708 THREAD);
709 load_placeholder_added = true;
710 }
711 }
712 }
713
714 // Must throw error outside of owning lock
715 if (throw_circularity_error) {
716 assert(!HAS_PENDING_EXCEPTION && !load_placeholder_added, "circularity error cleanup");
717 ResourceMark rm(THREAD);
718 THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string());
719 }
720
721 // Be careful when modifying this code: once you have run
722 // PlaceholderTable::find_and_add(PlaceholderTable::LOAD_INSTANCE),
723 // you need to find_and_remove it before returning.
724 // So be careful to not exit with a CHECK_ macro between these calls.
725
726 if (loaded_class == nullptr) {
727 // Do actual loading
728 loaded_class = load_instance_class(name, class_loader, THREAD);
729 }
730
731 if (load_placeholder_added) {
732 // clean up placeholder entries for LOAD_INSTANCE success or error
733 // This brackets the SystemDictionary updates for both defining
734 // and initiating loaders
735 MutexLocker mu(THREAD, SystemDictionary_lock);
736 PlaceholderTable::find_and_remove(name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD);
737 SystemDictionary_lock->notify_all();
738 }
739 }
740
741 if (HAS_PENDING_EXCEPTION || loaded_class == nullptr) {
742 return nullptr;
743 }
744
745 if (class_load_event.should_commit()) {
746 JFR_ONLY(post_class_load_event(&class_load_event, loaded_class, loader_data);)
747 }
748
749 // Make sure we have the right class in the dictionary
750 DEBUG_ONLY(verify_dictionary_entry(name, loaded_class));
751
752 return loaded_class;
753 }
754
755
756 // This routine does not lock the system dictionary.
757 //
758 // Since readers don't hold a lock, we must make sure that system
759 // dictionary entries are added to in a safe way (all links must
760 // be updated in an MT-safe manner). All entries are removed during class
761 // unloading, when this class loader is no longer referenced.
762 //
763 // Callers should be aware that an entry could be added just after
764 // Dictionary is read here, so the caller will not see
765 // the new entry.
766
767 InstanceKlass* SystemDictionary::find_instance_klass(Thread* current,
768 Symbol* class_name,
769 Handle class_loader) {
770
771 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader());
772 if (loader_data == nullptr) {
773 // If the ClassLoaderData has not been setup,
774 // then the class loader has no entries in the dictionary.
775 return nullptr;
776 }
777
778 Dictionary* dictionary = loader_data->dictionary();
779 return dictionary->find_class(current, class_name);
780 }
781
782 // Look for a loaded instance or array klass by name. Do not do any loading.
783 // return null in case of error.
784 Klass* SystemDictionary::find_instance_or_array_klass(Thread* current,
785 Symbol* class_name,
786 Handle class_loader) {
787 Klass* k = nullptr;
788 assert(class_name != nullptr, "class name must be non nullptr");
789
790 if (Signature::is_array(class_name)) {
791 // The name refers to an array. Parse the name.
792 // dimension and object_key in FieldArrayInfo are assigned as a
793 // side-effect of this call
794 SignatureStream ss(class_name, false);
795 int ndims = ss.skip_array_prefix(); // skip all '['s
796 BasicType t = ss.type();
797 if (t != T_OBJECT) {
798 k = Universe::typeArrayKlass(t);
799 } else {
800 k = SystemDictionary::find_instance_klass(current, ss.as_symbol(), class_loader);
801 }
802 if (k != nullptr) {
803 k = k->array_klass_or_null(ndims);
804 }
805 } else {
806 k = find_instance_klass(current, class_name, class_loader);
807 }
808 return k;
809 }
810
811 // Note: this method is much like resolve_class_from_stream, but
812 // does not publish the classes in the SystemDictionary.
813 // Handles Lookup.defineClass hidden.
814 InstanceKlass* SystemDictionary::resolve_hidden_class_from_stream(
815 ClassFileStream* st,
816 Symbol* class_name,
817 Handle class_loader,
818 const ClassLoadInfo& cl_info,
819 TRAPS) {
820
821 EventClassLoad class_load_event;
822 ClassLoaderData* loader_data;
823
824 // - for hidden classes that are not strong: create a new CLD that has a class holder and
825 // whose loader is the Lookup class's loader.
826 // - for hidden class: add the class to the Lookup class's loader's CLD.
827 assert (cl_info.is_hidden(), "only used for hidden classes");
828 bool create_mirror_cld = !cl_info.is_strong_hidden();
829 loader_data = register_loader(class_loader, create_mirror_cld);
830
831 assert(st != nullptr, "invariant");
832
833 // Parse stream and create a klass.
834 InstanceKlass* k = KlassFactory::create_from_stream(st,
835 class_name,
836 loader_data,
837 cl_info,
838 CHECK_NULL);
839 assert(k != nullptr, "no klass created");
840
841 // Hidden classes that are not strong must update ClassLoaderData holder
842 // so that they can be unloaded when the mirror is no longer referenced.
843 if (!cl_info.is_strong_hidden()) {
844 k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror()));
845 }
846
847 // Add to class hierarchy, and do possible deoptimizations.
848 k->add_to_hierarchy(THREAD);
849 // But, do not add to dictionary.
850
851 if (class_load_event.should_commit()) {
852 JFR_ONLY(post_class_load_event(&class_load_event, k, loader_data);)
853 }
854
855 k->link_class(CHECK_NULL);
856
857 // notify jvmti
858 if (JvmtiExport::should_post_class_load()) {
859 JvmtiExport::post_class_load(THREAD, k);
860 }
861
862 return k;
863 }
864
865 // Add a klass to the system from a stream (called by jni_DefineClass and
866 // JVM_DefineClass).
867 // Note: class_name can be null. In that case we do not know the name of
868 // the class until we have parsed the stream.
869 // This function either returns an InstanceKlass or throws an exception. It does
870 // not return null without a pending exception.
871 InstanceKlass* SystemDictionary::resolve_class_from_stream(
872 ClassFileStream* st,
873 Symbol* class_name,
874 Handle class_loader,
875 const ClassLoadInfo& cl_info,
876 TRAPS) {
877
878 HandleMark hm(THREAD);
879
880 ClassLoaderData* loader_data = register_loader(class_loader);
881
882 // Classloaders that support parallelism, e.g. bootstrap classloader,
883 // do not acquire lock here
884 Handle lockObject = get_loader_lock_or_null(class_loader);
885 ObjectLocker ol(lockObject, THREAD);
886
887 // Parse the stream and create a klass.
888 // Note that we do this even though this klass might
889 // already be present in the SystemDictionary, otherwise we would not
890 // throw potential ClassFormatErrors.
891 InstanceKlass* k = nullptr;
892
893 #if INCLUDE_CDS
894 if (!CDSConfig::is_dumping_static_archive()) {
895 k = SystemDictionaryShared::lookup_from_stream(class_name,
896 class_loader,
897 cl_info.protection_domain(),
898 st,
899 CHECK_NULL);
900 }
901 #endif
902
903 if (k == nullptr) {
904 k = KlassFactory::create_from_stream(st, class_name, loader_data, cl_info, CHECK_NULL);
905 }
906
907 assert(k != nullptr, "no klass created");
908 Symbol* h_name = k->name();
909 assert(class_name == nullptr || class_name == h_name, "name mismatch");
910
911 // Add class just loaded
912 // If a class loader supports parallel classloading, handle parallel define requests.
913 // find_or_define_instance_class may return a different InstanceKlass,
914 // in which case the old k would be deallocated
915 if (is_parallelCapable(class_loader)) {
916 k = find_or_define_instance_class(h_name, class_loader, k, CHECK_NULL);
917 } else {
918 define_instance_class(k, class_loader, THREAD);
919
920 // If defining the class throws an exception register 'k' for cleanup.
921 if (HAS_PENDING_EXCEPTION) {
922 assert(k != nullptr, "Must have an instance klass here!");
923 loader_data->add_to_deallocate_list(k);
924 return nullptr;
925 }
926 }
927
928 // Make sure we have an entry in the SystemDictionary on success
929 DEBUG_ONLY(verify_dictionary_entry(h_name, k));
930
931 return k;
932 }
933
934 InstanceKlass* SystemDictionary::resolve_from_stream(ClassFileStream* st,
935 Symbol* class_name,
936 Handle class_loader,
937 const ClassLoadInfo& cl_info,
938 TRAPS) {
939 if (cl_info.is_hidden()) {
940 return resolve_hidden_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL);
941 } else {
942 return resolve_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL);
943 }
944 }
945
946
947 #if INCLUDE_CDS
948 // Check if a shared class can be loaded by the specific classloader.
949 bool SystemDictionary::is_shared_class_visible(Symbol* class_name,
950 InstanceKlass* ik,
951 PackageEntry* pkg_entry,
952 Handle class_loader) {
953
954 assert(!ModuleEntryTable::javabase_moduleEntry()->is_patched(),
955 "Cannot use sharing if java.base is patched");
956
957 // (1) Check if we are loading into the same loader as in dump time.
958
959 if (ik->defined_by_boot_loader()) {
960 if (class_loader() != nullptr) {
961 return false;
962 }
963 } else if (ik->defined_by_platform_loader()) {
964 if (class_loader() != java_platform_loader()) {
965 return false;
966 }
967 } else if (ik->defined_by_app_loader()) {
968 if (class_loader() != java_system_loader()) {
969 return false;
970 }
971 } else {
972 // ik was loaded by a custom loader during dump time
973 if (class_loader_data(class_loader)->is_builtin_class_loader_data()) {
974 return false;
975 } else {
976 return true;
977 }
978 }
979
980 // (2) Check if we are loading into the same module from the same location as in dump time.
981
982 if (CDSConfig::is_using_optimized_module_handling()) {
983 // Class visibility has not changed between dump time and run time, so a class
984 // that was visible (and thus archived) during dump time is always visible during runtime.
985 assert(SystemDictionary::is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader),
986 "visibility cannot change between dump time and runtime");
987 return true;
988 }
989 return is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader);
990 }
991
992 bool SystemDictionary::is_shared_class_visible_impl(Symbol* class_name,
993 InstanceKlass* ik,
994 PackageEntry* pkg_entry,
995 Handle class_loader) {
996 int scp_index = ik->shared_classpath_index();
997 assert(!ik->defined_by_other_loaders(), "this function should be called for built-in classes only");
998 assert(scp_index >= 0, "must be");
999 const AOTClassLocation* cl = AOTClassLocationConfig::runtime()->class_location_at(scp_index);
1000 if (!Universe::is_module_initialized()) {
1001 assert(cl != nullptr, "must be");
1002 // At this point, no modules have been defined yet. KlassSubGraphInfo::check_allowed_klass()
1003 // has restricted the classes can be loaded at this step to be only:
1004 // [1] cs->is_modules_image(): classes in java.base, or,
1005 // [2] HeapShared::is_a_test_class_in_unnamed_module(ik): classes in bootstrap/unnamed module
1006 assert(cl->is_modules_image() || HeapShared::is_a_test_class_in_unnamed_module(ik),
1007 "only these classes can be loaded before the module system is initialized");
1008 assert(class_loader.is_null(), "sanity");
1009 return true;
1010 }
1011
1012 if (pkg_entry == nullptr) {
1013 // We might have looked up pkg_entry before the module system was initialized.
1014 // Need to reload it now.
1015 TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name);
1016 if (pkg_name != nullptr) {
1017 pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name);
1018 }
1019 }
1020
1021 ModuleEntry* mod_entry = (pkg_entry == nullptr) ? nullptr : pkg_entry->module();
1022 bool should_be_in_named_module = (mod_entry != nullptr && mod_entry->is_named());
1023 bool was_archived_from_named_module = !cl->has_unnamed_module();
1024 bool visible;
1025
1026 if (was_archived_from_named_module) {
1027 if (should_be_in_named_module) {
1028 // Is the module loaded from the same location as during dump time?
1029 visible = mod_entry->shared_path_index() == scp_index;
1030 if (visible) {
1031 assert(!mod_entry->is_patched(), "cannot load archived classes for patched module");
1032 }
1033 } else {
1034 // During dump time, this class was in a named module, but at run time, this class should be
1035 // in an unnamed module.
1036 visible = false;
1037 }
1038 } else {
1039 if (should_be_in_named_module) {
1040 // During dump time, this class was in an unnamed, but at run time, this class should be
1041 // in a named module.
1042 visible = false;
1043 } else {
1044 visible = true;
1045 }
1046 }
1047
1048 return visible;
1049 }
1050
1051 bool SystemDictionary::check_shared_class_super_type(InstanceKlass* klass, InstanceKlass* super_type,
1052 Handle class_loader, bool is_superclass, TRAPS) {
1053 assert(super_type->in_aot_cache(), "must be");
1054
1055 // Quick check if the super type has been already loaded.
1056 // + Don't do it for unregistered classes -- they can be unloaded so
1057 // super_type->class_loader_data() could be stale.
1058 // + Don't check if loader data is null, ie. the super_type isn't fully loaded.
1059 if (!super_type->defined_by_other_loaders() && super_type->class_loader_data() != nullptr) {
1060 // Check if the superclass is loaded by the current class_loader
1061 Symbol* name = super_type->name();
1062 InstanceKlass* check = find_instance_klass(THREAD, name, class_loader);
1063 if (check == super_type) {
1064 return true;
1065 }
1066 }
1067
1068 Klass *found = resolve_with_circularity_detection(klass->name(), super_type->name(),
1069 class_loader, is_superclass, CHECK_false);
1070 if (found == super_type) {
1071 return true;
1072 } else {
1073 // The dynamically resolved super type is not the same as the one we used during dump time,
1074 // so we cannot use the class.
1075 return false;
1076 }
1077 }
1078
1079 bool SystemDictionary::check_shared_class_super_types(InstanceKlass* ik, Handle class_loader, TRAPS) {
1080 // Check the superclass and interfaces. They must be the same
1081 // as in dump time, because the layout of <ik> depends on
1082 // the specific layout of ik->super() and ik->local_interfaces().
1083 //
1084 // If unexpected superclass or interfaces are found, we cannot
1085 // load <ik> from the shared archive.
1086
1087 if (ik->super() != nullptr) {
1088 bool check_super = check_shared_class_super_type(ik, ik->super(),
1089 class_loader, true,
1090 CHECK_false);
1091 if (!check_super) {
1092 return false;
1093 }
1094 }
1095
1096 Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1097 int num_interfaces = interfaces->length();
1098 for (int index = 0; index < num_interfaces; index++) {
1099 bool check_interface = check_shared_class_super_type(ik, interfaces->at(index), class_loader, false,
1100 CHECK_false);
1101 if (!check_interface) {
1102 return false;
1103 }
1104 }
1105
1106 return true;
1107 }
1108
1109 // Pre-load class referred to in non-static null-free instance field. These fields trigger MANDATORY loading.
1110 // Some pre-loading does not fail fatally
1111 bool SystemDictionary::preload_from_null_free_field(InstanceKlass* ik, Handle class_loader, Symbol* sig, int field_index, TRAPS) {
1112 TempNewSymbol name = Signature::strip_envelope(sig);
1113 log_info(class, preload)("Preloading of class %s during loading of shared class %s. "
1114 "Cause: a null-free non-static field is declared with this type",
1115 name->as_C_string(), ik->name()->as_C_string());
1116 InstanceKlass* real_k = SystemDictionary::resolve_with_circularity_detection(ik->name(), name,
1117 class_loader, false, CHECK_false);
1118 if (HAS_PENDING_EXCEPTION) {
1119 log_info(class, preload)("Preloading of class %s during loading of class %s "
1120 "(cause: null-free non-static field) failed: %s",
1121 name->as_C_string(), ik->name()->as_C_string(),
1122 PENDING_EXCEPTION->klass()->name()->as_C_string());
1123 return false; // Exception is still pending
1124 }
1125
1126 InstanceKlass* k = ik->get_inline_type_field_klass_or_null(field_index);
1127 if (real_k != k) {
1128 // oops, the app has substituted a different version of k! Does not fail fatally
1129 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1130 "(cause: null-free non-static field) failed : "
1131 "app substituted a different version",
1132 name->as_C_string(), ik->name()->as_C_string());
1133 return false;
1134 }
1135 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1136 "(cause: null-free non-static field) succeeded",
1137 name->as_C_string(), ik->name()->as_C_string());
1138
1139 assert(real_k != nullptr, "Sanity check");
1140 InstanceKlass::check_can_be_annotated_with_NullRestricted(real_k, ik->name(), CHECK_false);
1141
1142 return true;
1143 }
1144
1145 // Tries to pre-load classes referred to in non-static nullable instance fields if they are found in the
1146 // loadable descriptors attribute. If loading fails, we can fail silently.
1147 void SystemDictionary::try_preload_from_loadable_descriptors(InstanceKlass* ik, Handle class_loader, Symbol* sig, int field_index, TRAPS) {
1148 TempNewSymbol name = Signature::strip_envelope(sig);
1149 if (name != ik->name() && ik->is_class_in_loadable_descriptors_attribute(sig)) {
1150 log_info(class, preload)("Preloading of class %s during loading of shared class %s. "
1151 "Cause: field type in LoadableDescriptors attribute",
1152 name->as_C_string(), ik->name()->as_C_string());
1153 InstanceKlass* real_k = SystemDictionary::resolve_with_circularity_detection(ik->name(), name,
1154 class_loader, false, THREAD);
1155 if (HAS_PENDING_EXCEPTION) {
1156 CLEAR_PENDING_EXCEPTION;
1157 }
1158
1159 InstanceKlass* k = ik->get_inline_type_field_klass_or_null(field_index);
1160 if (real_k != k) {
1161 // oops, the app has substituted a different version of k!
1162 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1163 "(cause: field type in LoadableDescriptors attribute) failed : "
1164 "app substituted a different version",
1165 name->as_C_string(), ik->name()->as_C_string());
1166 return;
1167 } else if (real_k != nullptr) {
1168 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1169 "(cause: field type in LoadableDescriptors attribute) succeeded",
1170 name->as_C_string(), ik->name()->as_C_string());
1171 }
1172 }
1173 }
1174
1175
1176 InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik,
1177 Handle class_loader,
1178 Handle protection_domain,
1179 const ClassFileStream *cfs,
1180 PackageEntry* pkg_entry,
1181 TRAPS) {
1182 assert(ik != nullptr, "sanity");
1183 assert(ik->in_aot_cache(), "sanity");
1184 assert(!ik->is_unshareable_info_restored(), "shared class can be restored only once");
1185 assert(AtomicAccess::add(&ik->_shared_class_load_count, 1) == 1, "shared class loaded more than once");
1186 Symbol* class_name = ik->name();
1187
1188 if (!is_shared_class_visible(class_name, ik, pkg_entry, class_loader)) {
1189 ik->set_shared_loading_failed();
1190 return nullptr;
1191 }
1192
1193 bool check = check_shared_class_super_types(ik, class_loader, CHECK_NULL);
1194 if (!check) {
1195 ik->set_shared_loading_failed();
1196 return nullptr;
1197 }
1198
1199 if (ik->has_inlined_fields()) {
1200 for (AllFieldStream fs(ik); !fs.done(); fs.next()) {
1201 if (fs.access_flags().is_static()) continue;
1202
1203 Symbol* sig = fs.signature();
1204 int field_index = fs.index();
1205
1206 if (fs.is_null_free_inline_type()) {
1207 // A false return means that the class didn't load for other reasons than an exception.
1208 bool check = preload_from_null_free_field(ik, class_loader, sig, field_index, CHECK_NULL);
1209 if (!check) {
1210 ik->set_shared_loading_failed();
1211 return nullptr;
1212 }
1213 } else if (Signature::has_envelope(sig)) {
1214 // Pending exceptions are cleared so we can fail silently
1215 try_preload_from_loadable_descriptors(ik, class_loader, sig, field_index, CHECK_NULL);
1216 }
1217 }
1218 }
1219
1220 InstanceKlass* new_ik = nullptr;
1221 // CFLH check is skipped for VM hidden classes (see KlassFactory::create_from_stream).
1222 // It will be skipped for shared VM hidden lambda proxy classes.
1223 if (!ik->is_hidden()) {
1224 new_ik = KlassFactory::check_shared_class_file_load_hook(
1225 ik, class_name, class_loader, protection_domain, cfs, CHECK_NULL);
1226 }
1227 if (new_ik != nullptr) {
1228 // The class is changed by CFLH. Return the new class. The shared class is
1229 // not used.
1230 return new_ik;
1231 }
1232
1233 // Adjust methods to recover missing data. They need addresses for
1234 // interpreter entry points and their default native method address
1235 // must be reset.
1236
1237 // Shared classes are all currently loaded by either the bootstrap or
1238 // internal parallel class loaders, so this will never cause a deadlock
1239 // on a custom class loader lock.
1240 // Since this class is already locked with parallel capable class
1241 // loaders, including the bootstrap loader via the placeholder table,
1242 // this lock is currently a nop.
1243
1244 ClassLoaderData* loader_data = class_loader_data(class_loader);
1245 {
1246 HandleMark hm(THREAD);
1247 Handle lockObject = get_loader_lock_or_null(class_loader);
1248 ObjectLocker ol(lockObject, THREAD);
1249 // prohibited package check assumes all classes loaded from archive call
1250 // restore_unshareable_info which calls ik->set_package()
1251 ik->restore_unshareable_info(loader_data, protection_domain, pkg_entry, CHECK_NULL);
1252 }
1253
1254 load_shared_class_misc(ik, loader_data);
1255 return ik;
1256 }
1257
1258 void SystemDictionary::load_shared_class_misc(InstanceKlass* ik, ClassLoaderData* loader_data) {
1259 ik->print_class_load_logging(loader_data, nullptr, nullptr);
1260
1261 // For boot loader, ensure that GetSystemPackage knows that a class in this
1262 // package was loaded.
1263 if (loader_data->is_the_null_class_loader_data()) {
1264 s2 path_index = ik->shared_classpath_index();
1265 ik->set_classpath_index(path_index);
1266 }
1267
1268 // notify a class loaded from shared object
1269 ClassLoadingService::notify_class_loaded(ik, true /* shared class */);
1270
1271 if (CDSConfig::is_dumping_final_static_archive()) {
1272 SystemDictionaryShared::init_dumptime_info_from_preimage(ik);
1273 }
1274 }
1275
1276 // This is much more lightweight than SystemDictionary::resolve_or_null
1277 // - There's only a single Java thread at this point. No need for placeholder.
1278 // - All supertypes of ik have been loaded
1279 // - There's no circularity (checked in AOT assembly phase)
1280 // - There's no need to call java.lang.ClassLoader::load_class() because the boot/platform/app
1281 // loaders are well-behaved
1282 void SystemDictionary::preload_class(Handle class_loader, InstanceKlass* ik, TRAPS) {
1283 precond(Universe::is_bootstrapping());
1284 precond(java_platform_loader() != nullptr && java_system_loader() != nullptr);
1285 precond(class_loader() == nullptr || class_loader() == java_platform_loader() ||class_loader() == java_system_loader());
1286 precond(CDSConfig::is_using_aot_linked_classes());
1287 precond(AOTMetaspace::in_aot_cache_static_region((void*)ik));
1288 precond(!ik->is_loaded());
1289
1290 #ifdef ASSERT
1291 // preload_class() must be called in the correct order -- all super types must have
1292 // already been loaded.
1293 if (ik->java_super() != nullptr) {
1294 assert(ik->java_super()->is_loaded(), "must be");
1295 }
1296
1297 Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1298 int num_interfaces = interfaces->length();
1299 for (int index = 0; index < num_interfaces; index++) {
1300 assert(interfaces->at(index)->is_loaded(), "must be");
1301 }
1302 #endif
1303
1304 EventClassLoad class_load_event;
1305
1306 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(class_loader());
1307 oop java_mirror = ik->archived_java_mirror();
1308 precond(java_mirror != nullptr);
1309 assert(java_lang_Class::module(java_mirror) != nullptr, "must have been archived");
1310
1311 Handle pd(THREAD, java_lang_Class::protection_domain(java_mirror));
1312 PackageEntry* pkg_entry = ik->package();
1313 assert(pkg_entry != nullptr || ClassLoader::package_from_class_name(ik->name()) == nullptr,
1314 "non-empty packages must have been archived");
1315
1316 // TODO: the following assert requires JDK-8365580
1317 // assert(is_shared_class_visible(ik->name(), ik, pkg_entry, class_loader), "must be");
1318
1319 ik->restore_unshareable_info(loader_data, pd, pkg_entry, CHECK);
1320 load_shared_class_misc(ik, loader_data);
1321 ik->add_to_hierarchy(THREAD);
1322
1323 if (!ik->is_hidden()) {
1324 update_dictionary(THREAD, ik, loader_data);
1325 }
1326
1327 if (class_load_event.should_commit()) {
1328 JFR_ONLY(post_class_load_event(&class_load_event, ik, loader_data);)
1329 }
1330
1331 assert(ik->is_loaded(), "Must be in at least loaded state");
1332 }
1333
1334 #endif // INCLUDE_CDS
1335
1336 #if INCLUDE_JFR
1337 void SystemDictionary::post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
1338 assert(event != nullptr, "invariant");
1339 assert(k != nullptr, "invariant");
1340 event->set_loadedClass(k);
1341 event->set_definingClassLoader(k->class_loader_data());
1342 event->set_initiatingClassLoader(init_cld);
1343 event->commit();
1344 }
1345 #endif // INCLUDE_JFR
1346
1347 InstanceKlass* SystemDictionary::load_instance_class_impl(Symbol* class_name, Handle class_loader, TRAPS) {
1348
1349 if (class_loader.is_null()) {
1350 ResourceMark rm(THREAD);
1351 PackageEntry* pkg_entry = nullptr;
1352 bool search_only_bootloader_append = false;
1353
1354 // Find the package in the boot loader's package entry table.
1355 TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name);
1356 if (pkg_name != nullptr) {
1357 pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name);
1358 }
1359
1360 // Prior to attempting to load the class, enforce the boot loader's
1361 // visibility boundaries.
1362 if (!Universe::is_module_initialized()) {
1363 // During bootstrapping, prior to module initialization, any
1364 // class attempting to be loaded must be checked against the
1365 // java.base packages in the boot loader's PackageEntryTable.
1366 // No class outside of java.base is allowed to be loaded during
1367 // this bootstrapping window.
1368 if (pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1369 // Class is either in the unnamed package or in
1370 // a named package within the unnamed module. Either
1371 // case is outside of java.base, do not attempt to
1372 // load the class post java.base definition. If
1373 // java.base has not been defined, let the class load
1374 // and its package will be checked later by
1375 // ModuleEntryTable::verify_javabase_packages.
1376 if (ModuleEntryTable::javabase_defined()) {
1377 return nullptr;
1378 }
1379 } else {
1380 // Check that the class' package is defined within java.base.
1381 ModuleEntry* mod_entry = pkg_entry->module();
1382 Symbol* mod_entry_name = mod_entry->name();
1383 if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) {
1384 return nullptr;
1385 }
1386 }
1387 } else {
1388 // After the module system has been initialized, check if the class'
1389 // package is in a module defined to the boot loader.
1390 if (pkg_name == nullptr || pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1391 // Class is either in the unnamed package, in a named package
1392 // within a module not defined to the boot loader or in a
1393 // a named package within the unnamed module. In all cases,
1394 // limit visibility to search for the class only in the boot
1395 // loader's append path.
1396 if (!ClassLoader::has_bootclasspath_append()) {
1397 // If there is no bootclasspath append entry, no need to continue
1398 // searching.
1399 return nullptr;
1400 }
1401 search_only_bootloader_append = true;
1402 }
1403 }
1404
1405 // Prior to bootstrapping's module initialization, never load a class outside
1406 // of the boot loader's module path
1407 assert(Universe::is_module_initialized() ||
1408 !search_only_bootloader_append,
1409 "Attempt to load a class outside of boot loader's module path");
1410
1411 // Search for classes in the CDS archive.
1412 InstanceKlass* k = nullptr;
1413
1414 #if INCLUDE_CDS
1415 if (CDSConfig::is_using_archive())
1416 {
1417 PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time());
1418 InstanceKlass* ik = SystemDictionaryShared::find_builtin_class(class_name);
1419 if (ik != nullptr && ik->defined_by_boot_loader() && !ik->shared_loading_failed()) {
1420 SharedClassLoadingMark slm(THREAD, ik);
1421 k = load_shared_class(ik, class_loader, Handle(), nullptr, pkg_entry, CHECK_NULL);
1422 }
1423 }
1424 #endif
1425
1426 if (k == nullptr) {
1427 // Use VM class loader
1428 PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time());
1429 k = ClassLoader::load_class(class_name, pkg_entry, search_only_bootloader_append, CHECK_NULL);
1430 }
1431
1432 // find_or_define_instance_class may return a different InstanceKlass
1433 if (k != nullptr) {
1434 CDS_ONLY(SharedClassLoadingMark slm(THREAD, k);)
1435 k = find_or_define_instance_class(class_name, class_loader, k, CHECK_NULL);
1436 }
1437 return k;
1438 } else {
1439 // Use user specified class loader to load class. Call loadClass operation on class_loader.
1440 ResourceMark rm(THREAD);
1441
1442 JavaThread* jt = THREAD;
1443
1444 PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1445 ClassLoader::perf_app_classload_selftime(),
1446 ClassLoader::perf_app_classload_count(),
1447 jt->get_thread_stat()->perf_recursion_counts_addr(),
1448 jt->get_thread_stat()->perf_timers_addr(),
1449 PerfClassTraceTime::CLASS_LOAD);
1450
1451 // Translate to external class name format, i.e., convert '/' chars to '.'
1452 Handle string = java_lang_String::externalize_classname(class_name, CHECK_NULL);
1453
1454 JavaValue result(T_OBJECT);
1455
1456 InstanceKlass* spec_klass = vmClasses::ClassLoader_klass();
1457
1458 // Call public unsynchronized loadClass(String) directly for all class loaders.
1459 // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1460 // acquire a class-name based lock rather than the class loader object lock.
1461 // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1462 JavaCalls::call_virtual(&result,
1463 class_loader,
1464 spec_klass,
1465 vmSymbols::loadClass_name(),
1466 vmSymbols::string_class_signature(),
1467 string,
1468 CHECK_NULL);
1469
1470 assert(result.get_type() == T_OBJECT, "just checking");
1471 oop obj = result.get_oop();
1472
1473 // Primitive classes return null since forName() cannot be
1474 // used to obtain any of the Class objects representing primitives or void
1475 if ((obj != nullptr) && !(java_lang_Class::is_primitive(obj))) {
1476 InstanceKlass* k = java_lang_Class::as_InstanceKlass(obj);
1477 // For user defined Java class loaders, check that the name returned is
1478 // the same as that requested. This check is done for the bootstrap
1479 // loader when parsing the class file.
1480 if (class_name == k->name()) {
1481 return k;
1482 }
1483 }
1484 // Class is not found or has the wrong name, return null
1485 return nullptr;
1486 }
1487 }
1488
1489 InstanceKlass* SystemDictionary::load_instance_class(Symbol* name,
1490 Handle class_loader,
1491 TRAPS) {
1492
1493 InstanceKlass* loaded_class = load_instance_class_impl(name, class_loader, CHECK_NULL);
1494
1495 // If everything was OK (no exceptions, no null return value), and
1496 // class_loader is NOT the defining loader, do a little more bookkeeping.
1497 if (loaded_class != nullptr &&
1498 loaded_class->class_loader() != class_loader()) {
1499
1500 ClassLoaderData* loader_data = class_loader_data(class_loader);
1501 check_constraints(loaded_class, loader_data, false, CHECK_NULL);
1502
1503 // Record dependency for non-parent delegation.
1504 // This recording keeps the defining class loader of the klass (loaded_class) found
1505 // from being unloaded while the initiating class loader is loaded
1506 // even if the reference to the defining class loader is dropped
1507 // before references to the initiating class loader.
1508 loader_data->record_dependency(loaded_class);
1509
1510 update_dictionary(THREAD, loaded_class, loader_data);
1511
1512 if (JvmtiExport::should_post_class_load()) {
1513 JvmtiExport::post_class_load(THREAD, loaded_class);
1514 }
1515 }
1516 return loaded_class;
1517 }
1518
1519 void SystemDictionary::define_instance_class(InstanceKlass* k, Handle class_loader, TRAPS) {
1520
1521 ClassLoaderData* loader_data = k->class_loader_data();
1522 assert(loader_data->class_loader() == class_loader(), "they must be the same");
1523
1524 // Bootstrap and other parallel classloaders don't acquire a lock,
1525 // they use placeholder token.
1526 // If a parallelCapable class loader calls define_instance_class instead of
1527 // find_or_define_instance_class to get here, we have a timing
1528 // hole with systemDictionary updates and check_constraints
1529 if (!is_parallelCapable(class_loader)) {
1530 assert(ObjectSynchronizer::current_thread_holds_lock(THREAD,
1531 get_loader_lock_or_null(class_loader)),
1532 "define called without lock");
1533 }
1534
1535 // Check class-loading constraints. Throw exception if violation is detected.
1536 // Grabs and releases SystemDictionary_lock
1537 // The check_constraints/find_class call and update_dictionary sequence
1538 // must be "atomic" for a specific class/classloader pair so we never
1539 // define two different instanceKlasses for that class/classloader pair.
1540 // Existing classloaders will call define_instance_class with the
1541 // classloader lock held
1542 // Parallel classloaders will call find_or_define_instance_class
1543 // which will require a token to perform the define class
1544 check_constraints(k, loader_data, true, CHECK);
1545
1546 // Register class just loaded with class loader (placed in ArrayList)
1547 // Note we do this before updating the dictionary, as this can
1548 // fail with an OutOfMemoryError (if it does, we will *not* put this
1549 // class in the dictionary and will not update the class hierarchy).
1550 // JVMTI FollowReferences needs to find the classes this way.
1551 if (k->class_loader() != nullptr) {
1552 methodHandle m(THREAD, Universe::loader_addClass_method());
1553 JavaValue result(T_VOID);
1554 JavaCallArguments args(class_loader);
1555 args.push_oop(Handle(THREAD, k->java_mirror()));
1556 JavaCalls::call(&result, m, &args, CHECK);
1557 }
1558
1559 // Add to class hierarchy, and do possible deoptimizations.
1560 k->add_to_hierarchy(THREAD);
1561
1562 // Add to systemDictionary - so other classes can see it.
1563 // Grabs and releases SystemDictionary_lock
1564 update_dictionary(THREAD, k, loader_data);
1565
1566 // notify jvmti
1567 if (JvmtiExport::should_post_class_load()) {
1568 JvmtiExport::post_class_load(THREAD, k);
1569 }
1570 }
1571
1572 // Support parallel classloading
1573 // All parallel class loaders, including bootstrap classloader
1574 // lock a placeholder entry for this class/class_loader pair
1575 // to allow parallel defines of different classes for this class loader
1576 // With AllowParallelDefine flag==true, in case they do not synchronize around
1577 // FindLoadedClass/DefineClass, calls, we check for parallel
1578 // loading for them, wait if a defineClass is in progress
1579 // and return the initial requestor's results
1580 // This flag does not apply to the bootstrap classloader.
1581 // With AllowParallelDefine flag==false, call through to define_instance_class
1582 // which will throw LinkageError: duplicate class definition.
1583 // False is the requested default.
1584 // For better performance, the class loaders should synchronize
1585 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1586 // potentially waste time reading and parsing the bytestream.
1587 // Note: VM callers should ensure consistency of k/class_name,class_loader
1588 // Be careful when modifying this code: once you have run
1589 // PlaceholderTable::find_and_add(PlaceholderTable::DEFINE_CLASS),
1590 // you need to find_and_remove it before returning.
1591 // So be careful to not exit with a CHECK_ macro between these calls.
1592 InstanceKlass* SystemDictionary::find_or_define_helper(Symbol* class_name, Handle class_loader,
1593 InstanceKlass* k, TRAPS) {
1594
1595 Symbol* name_h = k->name();
1596 ClassLoaderData* loader_data = class_loader_data(class_loader);
1597 Dictionary* dictionary = loader_data->dictionary();
1598
1599 // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1600 {
1601 MutexLocker mu(THREAD, SystemDictionary_lock);
1602 // First check if class already defined
1603 if (is_parallelDefine(class_loader)) {
1604 InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1605 if (check != nullptr) {
1606 return check;
1607 }
1608 }
1609
1610 // Acquire define token for this class/classloader
1611 PlaceholderEntry* probe = PlaceholderTable::find_and_add(name_h, loader_data,
1612 PlaceholderTable::DEFINE_CLASS, nullptr, THREAD);
1613 // Wait if another thread defining in parallel
1614 // All threads wait - even those that will throw duplicate class: otherwise
1615 // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1616 // if other thread has not finished updating dictionary
1617 while (probe->definer() != nullptr) {
1618 SystemDictionary_lock->wait();
1619 }
1620 // Only special cases allow parallel defines and can use other thread's results
1621 // Other cases fall through, and may run into duplicate defines
1622 // caught by finding an entry in the SystemDictionary
1623 if (is_parallelDefine(class_loader) && (probe->instance_klass() != nullptr)) {
1624 InstanceKlass* ik = probe->instance_klass();
1625 PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1626 SystemDictionary_lock->notify_all();
1627 #ifdef ASSERT
1628 InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1629 assert(check != nullptr, "definer missed recording success");
1630 #endif
1631 return ik;
1632 } else {
1633 // This thread will define the class (even if earlier thread tried and had an error)
1634 probe->set_definer(THREAD);
1635 }
1636 }
1637
1638 define_instance_class(k, class_loader, THREAD);
1639
1640 // definer must notify any waiting threads
1641 {
1642 MutexLocker mu(THREAD, SystemDictionary_lock);
1643 PlaceholderEntry* probe = PlaceholderTable::get_entry(name_h, loader_data);
1644 assert(probe != nullptr, "DEFINE_CLASS placeholder lost?");
1645 if (!HAS_PENDING_EXCEPTION) {
1646 probe->set_instance_klass(k);
1647 }
1648 probe->set_definer(nullptr);
1649 PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1650 SystemDictionary_lock->notify_all();
1651 }
1652
1653 return HAS_PENDING_EXCEPTION ? nullptr : k;
1654 }
1655
1656 // If a class loader supports parallel classloading handle parallel define requests.
1657 // find_or_define_instance_class may return a different InstanceKlass
1658 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1659 InstanceKlass* k, TRAPS) {
1660 InstanceKlass* defined_k = find_or_define_helper(class_name, class_loader, k, THREAD);
1661 // Clean up original InstanceKlass if duplicate or error
1662 if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1663 // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1664 assert(defined_k != nullptr, "Should have a klass if there's no exception");
1665 k->class_loader_data()->add_to_deallocate_list(k);
1666 } else if (HAS_PENDING_EXCEPTION) {
1667 // Remove this InstanceKlass from the LoaderConstraintTable if added.
1668 LoaderConstraintTable::remove_failed_loaded_klass(k, class_loader_data(class_loader));
1669 assert(defined_k == nullptr, "Should not have a klass if there's an exception");
1670 k->class_loader_data()->add_to_deallocate_list(k);
1671 }
1672 return defined_k;
1673 }
1674
1675
1676 // ----------------------------------------------------------------------------
1677 // GC support
1678
1679 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1680 bool SystemDictionary::do_unloading(GCTimer* gc_timer) {
1681
1682 bool unloading_occurred;
1683 bool is_concurrent = !SafepointSynchronize::is_at_safepoint();
1684 {
1685 GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1686 assert_locked_or_safepoint(ClassLoaderDataGraph_lock); // caller locks.
1687 // First, mark for unload all ClassLoaderData referencing a dead class loader.
1688 unloading_occurred = ClassLoaderDataGraph::do_unloading();
1689 if (unloading_occurred) {
1690 ConditionalMutexLocker ml2(Module_lock, is_concurrent);
1691 JFR_ONLY(Jfr::on_unloading_classes();)
1692 MANAGEMENT_ONLY(FinalizerService::purge_unloaded();)
1693 ConditionalMutexLocker ml1(SystemDictionary_lock, is_concurrent);
1694 ClassLoaderDataGraph::clean_module_and_package_info();
1695 LoaderConstraintTable::purge_loader_constraints();
1696 ResolutionErrorTable::purge_resolution_errors();
1697 }
1698 }
1699
1700 GCTraceTime(Debug, gc, phases) t("Trigger cleanups", gc_timer);
1701
1702 if (unloading_occurred) {
1703 SymbolTable::trigger_cleanup();
1704
1705 ConditionalMutexLocker ml(ClassInitError_lock, is_concurrent);
1706 InstanceKlass::clean_initialization_error_table();
1707 }
1708
1709 return unloading_occurred;
1710 }
1711
1712 void SystemDictionary::methods_do(void f(Method*)) {
1713 // Walk methods in loaded classes
1714
1715 {
1716 MutexLocker ml(ClassLoaderDataGraph_lock);
1717 ClassLoaderDataGraph::methods_do(f);
1718 }
1719
1720 auto doit = [&] (InvokeMethodKey key, Method* method) {
1721 if (method != nullptr) {
1722 f(method);
1723 }
1724 };
1725
1726 {
1727 MutexLocker ml(InvokeMethodIntrinsicTable_lock);
1728 _invoke_method_intrinsic_table->iterate_all(doit);
1729 }
1730
1731 }
1732
1733 // ----------------------------------------------------------------------------
1734 // Initialization
1735
1736 void SystemDictionary::initialize(TRAPS) {
1737 _invoke_method_intrinsic_table = new (mtClass) InvokeMethodIntrinsicTable();
1738 _invoke_method_type_table = new (mtClass) InvokeMethodTypeTable();
1739 ResolutionErrorTable::initialize();
1740 LoaderConstraintTable::initialize();
1741 PlaceholderTable::initialize();
1742 #if INCLUDE_CDS
1743 SystemDictionaryShared::initialize();
1744 if (CDSConfig::is_dumping_archive()) {
1745 AOTClassLocationConfig::dumptime_init(THREAD);
1746 }
1747 #endif
1748 // Resolve basic classes
1749 vmClasses::resolve_all(CHECK);
1750 // Resolve classes used by archived heap objects
1751 if (CDSConfig::is_using_archive()) {
1752 HeapShared::resolve_classes(THREAD);
1753 }
1754 }
1755
1756 // Constraints on class loaders. The details of the algorithm can be
1757 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
1758 // Virtual Machine" by Sheng Liang and Gilad Bracha. The basic idea is
1759 // that the dictionary needs to maintain a set of constraints that
1760 // must be satisfied by all classes in the dictionary.
1761 // if defining is true, then LinkageError if already in dictionary
1762 // if initiating loader, then ok if InstanceKlass matches existing entry
1763
1764 void SystemDictionary::check_constraints(InstanceKlass* k,
1765 ClassLoaderData* loader_data,
1766 bool defining,
1767 TRAPS) {
1768 ResourceMark rm(THREAD);
1769 stringStream ss;
1770 bool throwException = false;
1771
1772 {
1773 Symbol* name = k->name();
1774
1775 MutexLocker mu(THREAD, SystemDictionary_lock);
1776
1777 InstanceKlass* check = loader_data->dictionary()->find_class(THREAD, name);
1778 if (check != nullptr) {
1779 // If different InstanceKlass - duplicate class definition,
1780 // else - ok, class loaded by a different thread in parallel.
1781 // We should only have found it if it was done loading and ok to use.
1782
1783 if ((defining == true) || (k != check)) {
1784 throwException = true;
1785 ss.print("loader %s", loader_data->loader_name_and_id());
1786 ss.print(" attempted duplicate %s definition for %s. (%s)",
1787 k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
1788 } else {
1789 return;
1790 }
1791 }
1792
1793 if (throwException == false) {
1794 if (LoaderConstraintTable::check_or_update(k, loader_data, name) == false) {
1795 throwException = true;
1796 ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
1797 ss.print(" wants to load %s %s.",
1798 k->external_kind(), k->external_name());
1799 Klass *existing_klass = LoaderConstraintTable::find_constrained_klass(name, loader_data);
1800 if (existing_klass != nullptr && existing_klass->class_loader_data() != loader_data) {
1801 ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
1802 existing_klass->external_kind(),
1803 existing_klass->class_loader_data()->loader_name_and_id(),
1804 existing_klass->class_in_module_of_loader(false, true));
1805 } else {
1806 ss.print(" (%s)", k->class_in_module_of_loader(false, true));
1807 }
1808 }
1809 }
1810 }
1811
1812 // Throw error now if needed (cannot throw while holding
1813 // SystemDictionary_lock because of rank ordering)
1814 if (throwException == true) {
1815 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1816 }
1817 }
1818
1819 // Update class loader data dictionary - done after check_constraint and add_to_hierarchy
1820 // have been called.
1821 void SystemDictionary::update_dictionary(JavaThread* current,
1822 InstanceKlass* k,
1823 ClassLoaderData* loader_data) {
1824 MonitorLocker mu1(SystemDictionary_lock);
1825
1826 // Make a new dictionary entry.
1827 Symbol* name = k->name();
1828 Dictionary* dictionary = loader_data->dictionary();
1829 InstanceKlass* sd_check = dictionary->find_class(current, name);
1830 if (sd_check == nullptr) {
1831 dictionary->add_klass(current, name, k);
1832 }
1833 mu1.notify_all();
1834 }
1835
1836 // Indicate that loader_data has initiated the loading of class k, which
1837 // has already been defined by a parent loader.
1838 // This API is used by AOTLinkedClassBulkLoader and to register boxing
1839 // classes from java.lang in all class loaders to enable more value
1840 // classes optimizations
1841 void SystemDictionary::add_to_initiating_loader(JavaThread* current,
1842 InstanceKlass* k,
1843 ClassLoaderData* loader_data) {
1844 assert_locked_or_safepoint(SystemDictionary_lock);
1845 Symbol* name = k->name();
1846 Dictionary* dictionary = loader_data->dictionary();
1847 assert(k->is_loaded(), "must be");
1848 assert(k->class_loader_data() != loader_data, "only for classes defined by a parent loader");
1849 if (dictionary->find_class(current, name) == nullptr) {
1850 dictionary->add_klass(current, name, k);
1851 }
1852 }
1853
1854 // Try to find a class name using the loader constraints. The
1855 // loader constraints might know about a class that isn't fully loaded
1856 // yet and these will be ignored.
1857 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
1858 Thread* current, Symbol* class_name, Handle class_loader) {
1859
1860 // First see if it has been loaded directly.
1861 Klass* klass = find_instance_or_array_klass(current, class_name, class_loader);
1862 if (klass != nullptr)
1863 return klass;
1864
1865 // Now look to see if it has been loaded elsewhere, and is subject to
1866 // a loader constraint that would require this loader to return the
1867 // klass that is already loaded.
1868 if (Signature::is_array(class_name)) {
1869 // For array classes, their Klass*s are not kept in the
1870 // constraint table. The element Klass*s are.
1871 SignatureStream ss(class_name, false);
1872 int ndims = ss.skip_array_prefix(); // skip all '['s
1873 BasicType t = ss.type();
1874 if (t != T_OBJECT) {
1875 klass = Universe::typeArrayKlass(t);
1876 } else {
1877 MutexLocker mu(current, SystemDictionary_lock);
1878 klass = LoaderConstraintTable::find_constrained_klass(ss.as_symbol(), class_loader_data(class_loader));
1879 }
1880 // If element class already loaded, allocate array klass
1881 if (klass != nullptr) {
1882 klass = klass->array_klass_or_null(ndims);
1883 }
1884 } else {
1885 MutexLocker mu(current, SystemDictionary_lock);
1886 // Non-array classes are easy: simply check the constraint table.
1887 klass = LoaderConstraintTable::find_constrained_klass(class_name, class_loader_data(class_loader));
1888 }
1889
1890 return klass;
1891 }
1892
1893 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
1894 Klass* klass_being_linked,
1895 Handle class_loader1,
1896 Handle class_loader2) {
1897 ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
1898 ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
1899
1900 Symbol* constraint_name = nullptr;
1901
1902 if (!Signature::is_array(class_name)) {
1903 constraint_name = class_name;
1904 } else {
1905 // For array classes, their Klass*s are not kept in the
1906 // constraint table. The element classes are.
1907 SignatureStream ss(class_name, false);
1908 ss.skip_array_prefix(); // skip all '['s
1909 if (!ss.has_envelope()) {
1910 return true; // primitive types always pass
1911 }
1912 constraint_name = ss.as_symbol();
1913 // Increment refcount to keep constraint_name alive after
1914 // SignatureStream is destructed. It will be decremented below
1915 // before returning.
1916 constraint_name->increment_refcount();
1917 }
1918
1919 Dictionary* dictionary1 = loader_data1->dictionary();
1920 Dictionary* dictionary2 = loader_data2->dictionary();
1921
1922 JavaThread* current = JavaThread::current();
1923 {
1924 MutexLocker mu_s(SystemDictionary_lock);
1925 InstanceKlass* klass1 = dictionary1->find_class(current, constraint_name);
1926 InstanceKlass* klass2 = dictionary2->find_class(current, constraint_name);
1927 bool result = LoaderConstraintTable::add_entry(constraint_name, klass1, loader_data1,
1928 klass2, loader_data2);
1929 #if INCLUDE_CDS
1930 if (CDSConfig::is_dumping_archive() && klass_being_linked != nullptr &&
1931 !klass_being_linked->in_aot_cache()) {
1932 SystemDictionaryShared::record_linking_constraint(constraint_name,
1933 InstanceKlass::cast(klass_being_linked),
1934 class_loader1, class_loader2);
1935 }
1936 #endif // INCLUDE_CDS
1937 if (Signature::is_array(class_name)) {
1938 constraint_name->decrement_refcount();
1939 }
1940 return result;
1941 }
1942 }
1943
1944 // Add entry to resolution error table to record the error when the first
1945 // attempt to resolve a reference to a class has failed.
1946 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
1947 Symbol* error, const char* message,
1948 Symbol* cause, const char* cause_msg) {
1949 {
1950 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1951 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1952 if (entry == nullptr) {
1953 ResolutionErrorTable::add_entry(pool, which, error, message, cause, cause_msg);
1954 }
1955 }
1956 }
1957
1958 // Delete a resolution error for RedefineClasses for a constant pool is going away
1959 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
1960 ResolutionErrorTable::delete_entry(pool);
1961 }
1962
1963 // Lookup resolution error table. Returns error if found, otherwise null.
1964 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
1965 const char** message,
1966 Symbol** cause, const char** cause_msg) {
1967
1968 {
1969 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1970 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1971 if (entry != nullptr) {
1972 *message = entry->message();
1973 *cause = entry->cause();
1974 *cause_msg = entry->cause_msg();
1975 return entry->error();
1976 } else {
1977 return nullptr;
1978 }
1979 }
1980 }
1981
1982 // Add an entry to resolution error table to record an error in resolving or
1983 // validating a nest host. This is used to construct informative error
1984 // messages when IllegalAccessError's occur. If an entry already exists it will
1985 // be updated with the nest host error message.
1986
1987 void SystemDictionary::add_nest_host_error(const constantPoolHandle& pool,
1988 int which,
1989 const stringStream& message) {
1990 {
1991 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1992 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1993 if (entry == nullptr) {
1994 // Only add a new entry to the resolution error table if one hasn't been found for this
1995 // constant pool index. In this case resolution succeeded but there's an error in this nest host
1996 // that we use the table to record.
1997 assert(pool->resolved_klass_at(which) != nullptr, "klass should be resolved if there is no entry");
1998 ResolutionErrorTable::add_entry(pool, which, message.as_string(true /* on C-heap */));
1999 } else {
2000 // An existing entry means we had a true resolution failure (LinkageError) with our nest host, but we
2001 // still want to add the error message for the higher-level access checks to report. We should
2002 // only reach here under the same error condition, so we can ignore the potential race with setting
2003 // the message.
2004 const char* nhe = entry->nest_host_error();
2005 if (nhe == nullptr) {
2006 entry->set_nest_host_error(message.as_string(true /* on C-heap */));
2007 } else {
2008 DEBUG_ONLY(const char* msg = message.base();)
2009 assert(strcmp(nhe, msg) == 0, "New message %s, differs from original %s", msg, nhe);
2010 }
2011 }
2012 }
2013 }
2014
2015 // Lookup any nest host error
2016 const char* SystemDictionary::find_nest_host_error(const constantPoolHandle& pool, int which) {
2017 {
2018 MutexLocker ml(Thread::current(), SystemDictionary_lock);
2019 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
2020 if (entry != nullptr) {
2021 return entry->nest_host_error();
2022 } else {
2023 return nullptr;
2024 }
2025 }
2026 }
2027
2028 // Signature constraints ensure that callers and callees agree about
2029 // the meaning of type names in their signatures. This routine is the
2030 // intake for constraints. It collects them from several places:
2031 //
2032 // * LinkResolver::resolve_method (if check_access is true) requires
2033 // that the resolving class (the caller) and the defining class of
2034 // the resolved method (the callee) agree on each type in the
2035 // method's signature.
2036 //
2037 // * LinkResolver::resolve_interface_method performs exactly the same
2038 // checks.
2039 //
2040 // * LinkResolver::resolve_field requires that the constant pool
2041 // attempting to link to a field agree with the field's defining
2042 // class about the type of the field signature.
2043 //
2044 // * klassVtable::initialize_vtable requires that, when a class
2045 // overrides a vtable entry allocated by a superclass, that the
2046 // overriding method (i.e., the callee) agree with the superclass
2047 // on each type in the method's signature.
2048 //
2049 // * klassItable::initialize_itable requires that, when a class fills
2050 // in its itables, for each non-abstract method installed in an
2051 // itable, the method (i.e., the callee) agree with the interface
2052 // on each type in the method's signature.
2053 //
2054 // All those methods have a boolean (check_access, checkconstraints)
2055 // which turns off the checks. This is used from specialized contexts
2056 // such as bootstrapping, dumping, and debugging.
2057 //
2058 // No direct constraint is placed between the class and its
2059 // supertypes. Constraints are only placed along linked relations
2060 // between callers and callees. When a method overrides or implements
2061 // an abstract method in a supertype (superclass or interface), the
2062 // constraints are placed as if the supertype were the caller to the
2063 // overriding method. (This works well, since callers to the
2064 // supertype have already established agreement between themselves and
2065 // the supertype.) As a result of all this, a class can disagree with
2066 // its supertype about the meaning of a type name, as long as that
2067 // class neither calls a relevant method of the supertype, nor is
2068 // called (perhaps via an override) from the supertype.
2069 //
2070 //
2071 // SystemDictionary::check_signature_loaders(sig, klass_being_linked, l1, l2)
2072 //
2073 // Make sure all class components (including arrays) in the given
2074 // signature will be resolved to the same class in both loaders.
2075 // Returns the name of the type that failed a loader constraint check, or
2076 // null if no constraint failed. No exception except OOME is thrown.
2077 // Arrays are not added to the loader constraint table, their elements are.
2078 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
2079 Klass* klass_being_linked,
2080 Handle loader1, Handle loader2,
2081 bool is_method) {
2082 // Nothing to do if loaders are the same.
2083 if (loader1() == loader2()) {
2084 return nullptr;
2085 }
2086
2087 for (SignatureStream ss(signature, is_method); !ss.is_done(); ss.next()) {
2088 if (ss.is_reference()) {
2089 Symbol* sig = ss.as_symbol();
2090 // Note: In the future, if template-like types can take
2091 // arguments, we will want to recognize them and dig out class
2092 // names hiding inside the argument lists.
2093 if (!add_loader_constraint(sig, klass_being_linked, loader1, loader2)) {
2094 return sig;
2095 }
2096 }
2097 }
2098 return nullptr;
2099 }
2100
2101 Method* SystemDictionary::find_method_handle_intrinsic(vmIntrinsicID iid,
2102 Symbol* signature,
2103 TRAPS) {
2104
2105 const int iid_as_int = vmIntrinsics::as_int(iid);
2106 assert(MethodHandles::is_signature_polymorphic(iid) &&
2107 MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
2108 iid != vmIntrinsics::_invokeGeneric,
2109 "must be a known MH intrinsic iid=%d: %s", iid_as_int, vmIntrinsics::name_at(iid));
2110
2111 InvokeMethodKey key(signature, iid_as_int);
2112 Method** met = nullptr;
2113
2114 // We only want one entry in the table for this (signature/id, method) pair but the code
2115 // to create the intrinsic method needs to be outside the lock.
2116 // The first thread claims the entry by adding the key and the other threads wait, until the
2117 // Method has been added as the value.
2118 {
2119 MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
2120 while (true) {
2121 bool created;
2122 met = _invoke_method_intrinsic_table->put_if_absent(key, &created);
2123 assert(met != nullptr, "either created or found");
2124 if (*met != nullptr) {
2125 return *met;
2126 } else if (created) {
2127 // The current thread won the race and will try to create the full entry.
2128 break;
2129 } else {
2130 // Another thread beat us to it, so wait for them to complete
2131 // and return *met; or if they hit an error we get another try.
2132 ml.wait();
2133 // Note it is not safe to read *met here as that entry could have
2134 // been deleted, so we must loop and try put_if_absent again.
2135 }
2136 }
2137 }
2138
2139 methodHandle m = Method::make_method_handle_intrinsic(iid, signature, THREAD);
2140 bool throw_error = HAS_PENDING_EXCEPTION;
2141 if (!throw_error && (!Arguments::is_interpreter_only() || iid == vmIntrinsics::_linkToNative)) {
2142 // Generate a compiled form of the MH intrinsic
2143 // linkToNative doesn't have interpreter-specific implementation, so always has to go through compiled version.
2144 AdapterHandlerLibrary::create_native_wrapper(m);
2145 // Check if have the compiled code.
2146 throw_error = (!m->has_compiled_code());
2147 }
2148
2149 {
2150 MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
2151 if (throw_error) {
2152 // Remove the entry and let another thread try, or get the same exception.
2153 bool removed = _invoke_method_intrinsic_table->remove(key);
2154 assert(removed, "must be the owner");
2155 ml.notify_all();
2156 } else {
2157 signature->make_permanent(); // The signature is never unloaded.
2158 assert(Arguments::is_interpreter_only() || (m->has_compiled_code() &&
2159 m->code()->entry_point() == m->from_compiled_entry()),
2160 "MH intrinsic invariant");
2161 *met = m(); // insert the element
2162 ml.notify_all();
2163 return m();
2164 }
2165 }
2166
2167 // Throw OOM or the pending exception in the JavaThread
2168 if (throw_error && !HAS_PENDING_EXCEPTION) {
2169 THROW_MSG_NULL(vmSymbols::java_lang_OutOfMemoryError(),
2170 "Out of space in CodeCache for method handle intrinsic");
2171 }
2172 return nullptr;
2173 }
2174
2175 #if INCLUDE_CDS
2176 void SystemDictionary::get_all_method_handle_intrinsics(GrowableArray<Method*>* methods) {
2177 assert(SafepointSynchronize::is_at_safepoint(), "must be");
2178 auto do_method = [&] (InvokeMethodKey& key, Method*& m) {
2179 methods->append(m);
2180 };
2181 _invoke_method_intrinsic_table->iterate_all(do_method);
2182 }
2183
2184 void SystemDictionary::restore_archived_method_handle_intrinsics() {
2185 if (UseSharedSpaces) {
2186 EXCEPTION_MARK;
2187 restore_archived_method_handle_intrinsics_impl(THREAD);
2188 if (HAS_PENDING_EXCEPTION) {
2189 // This is probably caused by OOM -- other parts of the CDS archive have direct pointers to
2190 // the archived method handle intrinsics, so we can't really recover from this failure.
2191 vm_exit_during_initialization(err_msg("Failed to restore archived method handle intrinsics. Try to increase heap size."));
2192 }
2193 }
2194 }
2195
2196 void SystemDictionary::restore_archived_method_handle_intrinsics_impl(TRAPS) {
2197 Array<Method*>* list = AOTMetaspace::archived_method_handle_intrinsics();
2198 for (int i = 0; i < list->length(); i++) {
2199 methodHandle m(THREAD, list->at(i));
2200 Method::restore_archived_method_handle_intrinsic(m, CHECK);
2201 m->constants()->restore_unshareable_info(CHECK);
2202 if (!Arguments::is_interpreter_only() || m->intrinsic_id() == vmIntrinsics::_linkToNative) {
2203 AdapterHandlerLibrary::create_native_wrapper(m);
2204 if (!m->has_compiled_code()) {
2205 ResourceMark rm(THREAD);
2206 vm_exit_during_initialization(err_msg("Failed to initialize method %s", m->external_name()));
2207 }
2208 }
2209
2210 // There's no need to grab the InvokeMethodIntrinsicTable_lock, as we are still very early in
2211 // VM start-up -- in init_globals2() -- so we are still running a single Java thread. It's not
2212 // possible to have a contention.
2213 const int iid_as_int = vmIntrinsics::as_int(m->intrinsic_id());
2214 InvokeMethodKey key(m->signature(), iid_as_int);
2215 bool created = _invoke_method_intrinsic_table->put(key, m());
2216 assert(created, "unexpected contention");
2217 }
2218 }
2219 #endif // INCLUDE_CDS
2220
2221 // Helper for unpacking the return value from linkMethod and linkCallSite.
2222 static Method* unpack_method_and_appendix(Handle mname,
2223 Klass* accessing_klass,
2224 refArrayHandle appendix_box,
2225 Handle* appendix_result,
2226 TRAPS) {
2227 if (mname.not_null()) {
2228 Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2229 if (m != nullptr) {
2230 oop appendix = appendix_box->obj_at(0);
2231 LogTarget(Info, methodhandles) lt;
2232 if (lt.develop_is_enabled()) {
2233 ResourceMark rm(THREAD);
2234 LogStream ls(lt);
2235 ls.print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2236 m->print_on(&ls);
2237 if (appendix != nullptr) { ls.print("appendix = "); appendix->print_on(&ls); }
2238 ls.cr();
2239 }
2240
2241 (*appendix_result) = Handle(THREAD, appendix);
2242 // the target is stored in the cpCache and if a reference to this
2243 // MemberName is dropped we need a way to make sure the
2244 // class_loader containing this method is kept alive.
2245 methodHandle mh(THREAD, m); // record_dependency can safepoint.
2246 ClassLoaderData* this_key = accessing_klass->class_loader_data();
2247 this_key->record_dependency(m->method_holder());
2248 return mh();
2249 }
2250 }
2251 THROW_MSG_NULL(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives");
2252 }
2253
2254 Method* SystemDictionary::find_method_handle_invoker(Klass* klass,
2255 Symbol* name,
2256 Symbol* signature,
2257 Klass* accessing_klass,
2258 Handle* appendix_result,
2259 TRAPS) {
2260 guarantee(THREAD->can_call_java(), "");
2261 Handle method_type =
2262 SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_NULL);
2263
2264 int ref_kind = JVM_REF_invokeVirtual;
2265 oop name_oop = StringTable::intern(name, CHECK_NULL);
2266 Handle name_str (THREAD, name_oop);
2267 refArrayHandle appendix_box = oopFactory::new_refArray_handle(vmClasses::Object_klass(), 1, CHECK_NULL);
2268 assert(appendix_box->obj_at(0) == nullptr, "");
2269
2270 // This should not happen. JDK code should take care of that.
2271 if (accessing_klass == nullptr || method_type.is_null()) {
2272 THROW_MSG_NULL(vmSymbols::java_lang_InternalError(), "bad invokehandle");
2273 }
2274
2275 // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2276 JavaCallArguments args;
2277 args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2278 args.push_int(ref_kind);
2279 args.push_oop(Handle(THREAD, klass->java_mirror()));
2280 args.push_oop(name_str);
2281 args.push_oop(method_type);
2282 args.push_oop(appendix_box);
2283 JavaValue result(T_OBJECT);
2284 JavaCalls::call_static(&result,
2285 vmClasses::MethodHandleNatives_klass(),
2286 vmSymbols::linkMethod_name(),
2287 vmSymbols::linkMethod_signature(),
2288 &args, CHECK_NULL);
2289 Handle mname(THREAD, result.get_oop());
2290 return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2291 }
2292
2293 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2294 // We must ensure that all class loaders everywhere will reach this class, for any client.
2295 // This is a safe bet for public classes in java.lang, such as Object and String.
2296 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2297 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2298 static bool is_always_visible_class(oop mirror) {
2299 Klass* klass = java_lang_Class::as_Klass(mirror);
2300 if (klass->is_objArray_klass()) {
2301 klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2302 }
2303 if (klass->is_typeArray_klass()) {
2304 return true; // primitive array
2305 }
2306 assert(klass->is_instance_klass(), "%s", klass->external_name());
2307 InstanceKlass* ik = InstanceKlass::cast(klass);
2308 return ik->is_public() &&
2309 (ik->is_same_class_package(vmClasses::Object_klass()) || // java.lang
2310 ik->is_same_class_package(vmClasses::MethodHandle_klass())); // java.lang.invoke
2311 }
2312
2313 // Find or construct the Java mirror (java.lang.Class instance) for
2314 // the given field type signature, as interpreted relative to the
2315 // given class loader. Handles primitives, void, references, arrays,
2316 // and all other reflectable types, except method types.
2317 // N.B. Code in reflection should use this entry point.
2318 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2319 Klass* accessing_klass,
2320 SignatureStream::FailureMode failure_mode,
2321 TRAPS) {
2322
2323 Handle class_loader;
2324
2325 // What we have here must be a valid field descriptor,
2326 // and all valid field descriptors are supported.
2327 // Produce the same java.lang.Class that reflection reports.
2328 if (accessing_klass != nullptr) {
2329 class_loader = Handle(THREAD, accessing_klass->class_loader());
2330 }
2331 ResolvingSignatureStream ss(signature, class_loader, false);
2332 oop mirror_oop = ss.as_java_mirror(failure_mode, CHECK_NH);
2333 if (mirror_oop == nullptr) {
2334 return Handle(); // report failure this way
2335 }
2336 Handle mirror(THREAD, mirror_oop);
2337
2338 if (accessing_klass != nullptr) {
2339 // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2340 Klass* sel_klass = java_lang_Class::as_Klass(mirror());
2341 if (sel_klass != nullptr) {
2342 LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_NH);
2343 }
2344 }
2345 return mirror;
2346 }
2347
2348
2349 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2350 // signature, as interpreted relative to the given class loader.
2351 // Because of class loader constraints, all method handle usage must be
2352 // consistent with this loader.
2353 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2354 Klass* accessing_klass,
2355 TRAPS) {
2356 Handle empty;
2357 OopHandle* o;
2358 {
2359 MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2360 o = _invoke_method_type_table->get(signature);
2361 }
2362
2363 if (o != nullptr) {
2364 oop mt = o->resolve();
2365 assert(java_lang_invoke_MethodType::is_instance(mt), "");
2366 return Handle(THREAD, mt);
2367 } else if (!THREAD->can_call_java()) {
2368 warning("SystemDictionary::find_method_handle_type called from compiler thread"); // FIXME
2369 return Handle(); // do not attempt from within compiler, unless it was cached
2370 }
2371
2372 Handle class_loader;
2373 if (accessing_klass != nullptr) {
2374 class_loader = Handle(THREAD, accessing_klass->class_loader());
2375 }
2376 bool can_be_cached = true;
2377 int npts = ArgumentCount(signature).size();
2378 refArrayHandle pts = oopFactory::new_refArray_handle(vmClasses::Class_klass(), npts, CHECK_(empty));
2379 int arg = 0;
2380 Handle rt; // the return type from the signature
2381 ResourceMark rm(THREAD);
2382 for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2383 oop mirror = nullptr;
2384 if (can_be_cached) {
2385 // Use neutral class loader to lookup candidate classes to be placed in the cache.
2386 mirror = ss.as_java_mirror(Handle(), SignatureStream::ReturnNull, CHECK_(empty));
2387 if (mirror == nullptr || (ss.is_reference() && !is_always_visible_class(mirror))) {
2388 // Fall back to accessing_klass context.
2389 can_be_cached = false;
2390 }
2391 }
2392 if (!can_be_cached) {
2393 // Resolve, throwing a real error if it doesn't work.
2394 mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2395 }
2396 assert(mirror != nullptr, "%s", ss.as_symbol()->as_C_string());
2397 if (ss.at_return_type())
2398 rt = Handle(THREAD, mirror);
2399 else
2400 pts->obj_at_put(arg++, mirror);
2401
2402 // Check accessibility.
2403 if (!java_lang_Class::is_primitive(mirror) && accessing_klass != nullptr) {
2404 Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2405 mirror = nullptr; // safety
2406 // Emulate ConstantPool::verify_constant_pool_resolve.
2407 LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_(empty));
2408 }
2409 }
2410 assert(arg == npts, "");
2411
2412 // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2413 JavaCallArguments args(Handle(THREAD, rt()));
2414 args.push_oop(pts);
2415 JavaValue result(T_OBJECT);
2416 JavaCalls::call_static(&result,
2417 vmClasses::MethodHandleNatives_klass(),
2418 vmSymbols::findMethodHandleType_name(),
2419 vmSymbols::findMethodHandleType_signature(),
2420 &args, CHECK_(empty));
2421 Handle method_type(THREAD, result.get_oop());
2422
2423 if (can_be_cached) {
2424 // We can cache this MethodType inside the JVM.
2425 MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2426 bool created = false;
2427 assert(method_type != nullptr, "unexpected null");
2428 OopHandle* h = _invoke_method_type_table->get(signature);
2429 if (h == nullptr) {
2430 signature->make_permanent(); // The signature is never unloaded.
2431 OopHandle elem = OopHandle(Universe::vm_global(), method_type());
2432 bool created = _invoke_method_type_table->put(signature, elem);
2433 assert(created, "better be created");
2434 }
2435 }
2436 // report back to the caller with the MethodType
2437 return method_type;
2438 }
2439
2440 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2441 Klass* accessing_klass,
2442 TRAPS) {
2443 Handle empty;
2444 ResourceMark rm(THREAD);
2445 SignatureStream ss(signature, /*is_method=*/ false);
2446 if (!ss.is_done()) {
2447 Handle class_loader;
2448 if (accessing_klass != nullptr) {
2449 class_loader = Handle(THREAD, accessing_klass->class_loader());
2450 }
2451 oop mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2452 ss.next();
2453 if (ss.is_done()) {
2454 return Handle(THREAD, mirror);
2455 }
2456 }
2457 return empty;
2458 }
2459
2460 // Ask Java code to find or construct a method handle constant.
2461 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2462 int ref_kind, //e.g., JVM_REF_invokeVirtual
2463 Klass* callee,
2464 Symbol* name,
2465 Symbol* signature,
2466 TRAPS) {
2467 Handle empty;
2468 if (caller == nullptr) {
2469 THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2470 }
2471 Handle name_str = java_lang_String::create_from_symbol(name, CHECK_(empty));
2472 Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2473
2474 // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2475 Handle mname = vmClasses::MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2476 java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2477 java_lang_invoke_MemberName::set_name (mname(), name_str());
2478 java_lang_invoke_MemberName::set_type (mname(), signature_str());
2479 java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2480
2481 if (ref_kind == JVM_REF_invokeVirtual &&
2482 MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2483 // Skip resolution for public signature polymorphic methods such as
2484 // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2485 // They require appendix argument which MemberName resolution doesn't handle.
2486 // There's special logic on JDK side to handle them
2487 // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2488 } else {
2489 MethodHandles::resolve_MemberName(mname, caller, 0, false /*speculative_resolve*/, CHECK_(empty));
2490 }
2491
2492 // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2493 Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2494
2495 // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2496 JavaCallArguments args;
2497 args.push_oop(Handle(THREAD, caller->java_mirror())); // the referring class
2498 args.push_int(ref_kind);
2499 args.push_oop(Handle(THREAD, callee->java_mirror())); // the target class
2500 args.push_oop(name_str);
2501 args.push_oop(type);
2502 JavaValue result(T_OBJECT);
2503 JavaCalls::call_static(&result,
2504 vmClasses::MethodHandleNatives_klass(),
2505 vmSymbols::linkMethodHandleConstant_name(),
2506 vmSymbols::linkMethodHandleConstant_signature(),
2507 &args, CHECK_(empty));
2508 return Handle(THREAD, result.get_oop());
2509 }
2510
2511 // Ask Java to run a bootstrap method, in order to create a dynamic call site
2512 // while linking an invokedynamic op, or compute a constant for Dynamic_info CP entry
2513 // with linkage results being stored back into the bootstrap specifier.
2514 void SystemDictionary::invoke_bootstrap_method(BootstrapInfo& bootstrap_specifier, TRAPS) {
2515 // Resolve the bootstrap specifier, its name, type, and static arguments
2516 bootstrap_specifier.resolve_bsm(CHECK);
2517
2518 // This should not happen. JDK code should take care of that.
2519 if (bootstrap_specifier.caller() == nullptr || bootstrap_specifier.type_arg().is_null()) {
2520 THROW_MSG(vmSymbols::java_lang_InternalError(), "Invalid bootstrap method invocation with no caller or type argument");
2521 }
2522
2523 bool is_indy = bootstrap_specifier.is_method_call();
2524 refArrayHandle appendix_box;
2525 if (is_indy) {
2526 // Some method calls may require an appendix argument. Arrange to receive it.
2527 appendix_box = oopFactory::new_refArray_handle(vmClasses::Object_klass(), 1, CHECK);
2528 assert(appendix_box->obj_at(0) == nullptr, "");
2529 }
2530
2531 // call condy: java.lang.invoke.MethodHandleNatives::linkDynamicConstant(caller, bsm, type, info)
2532 // indy: java.lang.invoke.MethodHandleNatives::linkCallSite(caller, bsm, name, mtype, info, &appendix)
2533 JavaCallArguments args;
2534 args.push_oop(Handle(THREAD, bootstrap_specifier.caller_mirror()));
2535 args.push_oop(bootstrap_specifier.bsm());
2536 args.push_oop(bootstrap_specifier.name_arg());
2537 args.push_oop(bootstrap_specifier.type_arg());
2538 args.push_oop(bootstrap_specifier.arg_values());
2539 if (is_indy) {
2540 args.push_oop(appendix_box);
2541 }
2542 JavaValue result(T_OBJECT);
2543 JavaCalls::call_static(&result,
2544 vmClasses::MethodHandleNatives_klass(),
2545 is_indy ? vmSymbols::linkCallSite_name() : vmSymbols::linkDynamicConstant_name(),
2546 is_indy ? vmSymbols::linkCallSite_signature() : vmSymbols::linkDynamicConstant_signature(),
2547 &args, CHECK);
2548
2549 Handle value(THREAD, result.get_oop());
2550 if (is_indy) {
2551 Handle appendix;
2552 Method* method = unpack_method_and_appendix(value,
2553 bootstrap_specifier.caller(),
2554 appendix_box,
2555 &appendix, CHECK);
2556 methodHandle mh(THREAD, method);
2557 bootstrap_specifier.set_resolved_method(mh, appendix);
2558 } else {
2559 bootstrap_specifier.set_resolved_value(value);
2560 }
2561
2562 // sanity check
2563 assert(bootstrap_specifier.is_resolved() ||
2564 (bootstrap_specifier.is_method_call() &&
2565 bootstrap_specifier.resolved_method().not_null()), "bootstrap method call failed");
2566 }
2567
2568
2569 bool SystemDictionary::is_nonpublic_Object_method(Method* m) {
2570 assert(m != nullptr, "Unexpected nullptr Method*");
2571 return !m->is_public() && m->method_holder() == vmClasses::Object_klass();
2572 }
2573
2574 // ----------------------------------------------------------------------------
2575
2576 void SystemDictionary::print_on(outputStream *st) {
2577 CDS_ONLY(SystemDictionaryShared::print_on(st));
2578 GCMutexLocker mu(SystemDictionary_lock);
2579
2580 ClassLoaderDataGraph::print_dictionary(st);
2581
2582 // Placeholders
2583 PlaceholderTable::print_on(st);
2584 st->cr();
2585
2586 // loader constraints - print under SD_lock
2587 LoaderConstraintTable::print_on(st);
2588 st->cr();
2589 }
2590
2591 void SystemDictionary::print() { print_on(tty); }
2592
2593 void SystemDictionary::verify() {
2594
2595 GCMutexLocker mu(SystemDictionary_lock);
2596
2597 // Verify dictionary
2598 ClassLoaderDataGraph::verify_dictionary();
2599
2600 // Verify constraint table
2601 LoaderConstraintTable::verify();
2602 }
2603
2604 void SystemDictionary::dump(outputStream *st, bool verbose) {
2605 assert_locked_or_safepoint(SystemDictionary_lock);
2606 if (verbose) {
2607 print_on(st);
2608 } else {
2609 CDS_ONLY(SystemDictionaryShared::print_table_statistics(st));
2610 ClassLoaderDataGraph::print_table_statistics(st);
2611 LoaderConstraintTable::print_table_statistics(st);
2612 }
2613 }
2614
2615 // Utility for dumping dictionaries.
2616 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
2617 DCmdWithParser(output, heap),
2618 _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
2619 "BOOLEAN", false, "false") {
2620 _dcmdparser.add_dcmd_option(&_verbose);
2621 }
2622
2623 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
2624 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
2625 _verbose.value());
2626 VMThread::execute(&dumper);
2627 }