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 of %s",
1132 name->as_C_string(), ik->name()->as_C_string(),
1133 name->as_C_string());
1134 return false;
1135 }
1136 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1137 "(cause: null-free non-static field) succeeded",
1138 name->as_C_string(), ik->name()->as_C_string());
1139
1140 assert(real_k != nullptr, "Sanity check");
1141 InstanceKlass::check_can_be_annotated_with_NullRestricted(real_k, ik->name(), CHECK_false);
1142
1143 return true;
1144 }
1145
1146 // Tries to pre-load classes referred to in non-static nullable instance fields if they are found in the
1147 // loadable descriptors attribute. If loading fails, we can fail silently.
1148 void SystemDictionary::try_preload_from_loadable_descriptors(InstanceKlass* ik, Handle class_loader, Symbol* sig, int field_index, TRAPS) {
1149 TempNewSymbol name = Signature::strip_envelope(sig);
1150 if (name != ik->name() && ik->is_class_in_loadable_descriptors_attribute(sig)) {
1151 log_info(class, preload)("Preloading of class %s during loading of shared class %s. "
1152 "Cause: field type in LoadableDescriptors attribute",
1153 name->as_C_string(), ik->name()->as_C_string());
1154 InstanceKlass* real_k = SystemDictionary::resolve_with_circularity_detection(ik->name(), name,
1155 class_loader, false, THREAD);
1156 if (HAS_PENDING_EXCEPTION) {
1157 CLEAR_PENDING_EXCEPTION;
1158 }
1159
1160 InstanceKlass* k = ik->get_inline_type_field_klass_or_null(field_index);
1161 if (real_k != k) {
1162 // oops, the app has substituted a different version of k!
1163 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1164 "(cause: field type in LoadableDescriptors attribute) failed : "
1165 "app substituted a different version of %s",
1166 name->as_C_string(), ik->name()->as_C_string(),
1167 k->name()->as_C_string());
1168 return;
1169 } else if (real_k != nullptr) {
1170 log_info(class, preload)("Preloading of class %s during loading of shared class %s "
1171 "(cause: field type in LoadableDescriptors attribute) succeeded",
1172 name->as_C_string(), ik->name()->as_C_string());
1173 }
1174 }
1175 }
1176
1177
1178 InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik,
1179 Handle class_loader,
1180 Handle protection_domain,
1181 const ClassFileStream *cfs,
1182 PackageEntry* pkg_entry,
1183 TRAPS) {
1184 assert(ik != nullptr, "sanity");
1185 assert(ik->in_aot_cache(), "sanity");
1186 assert(!ik->is_unshareable_info_restored(), "shared class can be restored only once");
1187 assert(AtomicAccess::add(&ik->_shared_class_load_count, 1) == 1, "shared class loaded more than once");
1188 Symbol* class_name = ik->name();
1189
1190 if (!is_shared_class_visible(class_name, ik, pkg_entry, class_loader)) {
1191 ik->set_shared_loading_failed();
1192 return nullptr;
1193 }
1194
1195 bool check = check_shared_class_super_types(ik, class_loader, CHECK_NULL);
1196 if (!check) {
1197 ik->set_shared_loading_failed();
1198 return nullptr;
1199 }
1200
1201 if (ik->has_inlined_fields()) {
1202 for (AllFieldStream fs(ik); !fs.done(); fs.next()) {
1203 if (fs.access_flags().is_static()) continue;
1204
1205 Symbol* sig = fs.signature();
1206 int field_index = fs.index();
1207
1208 if (fs.is_null_free_inline_type()) {
1209 // A false return means that the class didn't load for other reasons than an exception.
1210 bool check = preload_from_null_free_field(ik, class_loader, sig, field_index, CHECK_NULL);
1211 if (!check) {
1212 ik->set_shared_loading_failed();
1213 return nullptr;
1214 }
1215 } else if (Signature::has_envelope(sig)) {
1216 // Pending exceptions are cleared so we can fail silently
1217 try_preload_from_loadable_descriptors(ik, class_loader, sig, field_index, CHECK_NULL);
1218 }
1219 }
1220 }
1221
1222 InstanceKlass* new_ik = nullptr;
1223 // CFLH check is skipped for VM hidden classes (see KlassFactory::create_from_stream).
1224 // It will be skipped for shared VM hidden lambda proxy classes.
1225 if (!ik->is_hidden()) {
1226 new_ik = KlassFactory::check_shared_class_file_load_hook(
1227 ik, class_name, class_loader, protection_domain, cfs, CHECK_NULL);
1228 }
1229 if (new_ik != nullptr) {
1230 // The class is changed by CFLH. Return the new class. The shared class is
1231 // not used.
1232 return new_ik;
1233 }
1234
1235 // Adjust methods to recover missing data. They need addresses for
1236 // interpreter entry points and their default native method address
1237 // must be reset.
1238
1239 // Shared classes are all currently loaded by either the bootstrap or
1240 // internal parallel class loaders, so this will never cause a deadlock
1241 // on a custom class loader lock.
1242 // Since this class is already locked with parallel capable class
1243 // loaders, including the bootstrap loader via the placeholder table,
1244 // this lock is currently a nop.
1245
1246 ClassLoaderData* loader_data = class_loader_data(class_loader);
1247 {
1248 HandleMark hm(THREAD);
1249 Handle lockObject = get_loader_lock_or_null(class_loader);
1250 ObjectLocker ol(lockObject, THREAD);
1251 // prohibited package check assumes all classes loaded from archive call
1252 // restore_unshareable_info which calls ik->set_package()
1253 ik->restore_unshareable_info(loader_data, protection_domain, pkg_entry, CHECK_NULL);
1254 }
1255
1256 load_shared_class_misc(ik, loader_data);
1257
1258 return ik;
1259 }
1260
1261 void SystemDictionary::load_shared_class_misc(InstanceKlass* ik, ClassLoaderData* loader_data) {
1262 ik->print_class_load_logging(loader_data, nullptr, nullptr);
1263
1264 // For boot loader, ensure that GetSystemPackage knows that a class in this
1265 // package was loaded.
1266 if (loader_data->is_the_null_class_loader_data()) {
1267 s2 path_index = ik->shared_classpath_index();
1268 ik->set_classpath_index(path_index);
1269 }
1270
1271 // notify a class loaded from shared object
1272 ClassLoadingService::notify_class_loaded(ik, true /* shared class */);
1273
1274 if (CDSConfig::is_dumping_final_static_archive()) {
1275 SystemDictionaryShared::init_dumptime_info_from_preimage(ik);
1276 }
1277 }
1278
1279 // This is much more lightweight than SystemDictionary::resolve_or_null
1280 // - There's only a single Java thread at this point. No need for placeholder.
1281 // - All supertypes of ik have been loaded
1282 // - There's no circularity (checked in AOT assembly phase)
1283 // - There's no need to call java.lang.ClassLoader::load_class() because the boot/platform/app
1284 // loaders are well-behaved
1285 void SystemDictionary::preload_class(Handle class_loader, InstanceKlass* ik, TRAPS) {
1286 precond(Universe::is_bootstrapping());
1287 precond(java_platform_loader() != nullptr && java_system_loader() != nullptr);
1288 precond(class_loader() == nullptr || class_loader() == java_platform_loader() ||class_loader() == java_system_loader());
1289 precond(CDSConfig::is_using_aot_linked_classes());
1290 precond(AOTMetaspace::in_aot_cache_static_region((void*)ik));
1291 precond(!ik->is_loaded());
1292
1293 #ifdef ASSERT
1294 // preload_class() must be called in the correct order -- all super types must have
1295 // already been loaded.
1296 if (ik->java_super() != nullptr) {
1297 assert(ik->java_super()->is_loaded(), "must be");
1298 }
1299
1300 Array<InstanceKlass*>* interfaces = ik->local_interfaces();
1301 int num_interfaces = interfaces->length();
1302 for (int index = 0; index < num_interfaces; index++) {
1303 assert(interfaces->at(index)->is_loaded(), "must be");
1304 }
1305 #endif
1306
1307 EventClassLoad class_load_event;
1308
1309 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(class_loader());
1310 oop java_mirror = ik->archived_java_mirror();
1311 precond(java_mirror != nullptr);
1312 assert(java_lang_Class::module(java_mirror) != nullptr, "must have been archived");
1313
1314 Handle pd(THREAD, java_lang_Class::protection_domain(java_mirror));
1315 PackageEntry* pkg_entry = ik->package();
1316 assert(pkg_entry != nullptr || ClassLoader::package_from_class_name(ik->name()) == nullptr,
1317 "non-empty packages must have been archived");
1318
1319 // TODO: the following assert requires JDK-8365580
1320 // assert(is_shared_class_visible(ik->name(), ik, pkg_entry, class_loader), "must be");
1321
1322 ik->restore_unshareable_info(loader_data, pd, pkg_entry, CHECK);
1323 load_shared_class_misc(ik, loader_data);
1324 ik->add_to_hierarchy(THREAD);
1325
1326 if (!ik->is_hidden()) {
1327 update_dictionary(THREAD, ik, loader_data);
1328 }
1329
1330 if (class_load_event.should_commit()) {
1331 JFR_ONLY(post_class_load_event(&class_load_event, ik, loader_data);)
1332 }
1333
1334 assert(ik->is_loaded(), "Must be in at least loaded state");
1335 }
1336
1337 #endif // INCLUDE_CDS
1338
1339 #if INCLUDE_JFR
1340 void SystemDictionary::post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) {
1341 assert(event != nullptr, "invariant");
1342 assert(k != nullptr, "invariant");
1343 event->set_loadedClass(k);
1344 event->set_definingClassLoader(k->class_loader_data());
1345 event->set_initiatingClassLoader(init_cld);
1346 event->commit();
1347 }
1348 #endif // INCLUDE_JFR
1349
1350 InstanceKlass* SystemDictionary::load_instance_class_impl(Symbol* class_name, Handle class_loader, TRAPS) {
1351
1352 if (class_loader.is_null()) {
1353 ResourceMark rm(THREAD);
1354 PackageEntry* pkg_entry = nullptr;
1355 bool search_only_bootloader_append = false;
1356
1357 // Find the package in the boot loader's package entry table.
1358 TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name);
1359 if (pkg_name != nullptr) {
1360 pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name);
1361 }
1362
1363 // Prior to attempting to load the class, enforce the boot loader's
1364 // visibility boundaries.
1365 if (!Universe::is_module_initialized()) {
1366 // During bootstrapping, prior to module initialization, any
1367 // class attempting to be loaded must be checked against the
1368 // java.base packages in the boot loader's PackageEntryTable.
1369 // No class outside of java.base is allowed to be loaded during
1370 // this bootstrapping window.
1371 if (pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1372 // Class is either in the unnamed package or in
1373 // a named package within the unnamed module. Either
1374 // case is outside of java.base, do not attempt to
1375 // load the class post java.base definition. If
1376 // java.base has not been defined, let the class load
1377 // and its package will be checked later by
1378 // ModuleEntryTable::verify_javabase_packages.
1379 if (ModuleEntryTable::javabase_defined()) {
1380 return nullptr;
1381 }
1382 } else {
1383 // Check that the class' package is defined within java.base.
1384 ModuleEntry* mod_entry = pkg_entry->module();
1385 Symbol* mod_entry_name = mod_entry->name();
1386 if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) {
1387 return nullptr;
1388 }
1389 }
1390 } else {
1391 // After the module system has been initialized, check if the class'
1392 // package is in a module defined to the boot loader.
1393 if (pkg_name == nullptr || pkg_entry == nullptr || pkg_entry->in_unnamed_module()) {
1394 // Class is either in the unnamed package, in a named package
1395 // within a module not defined to the boot loader or in a
1396 // a named package within the unnamed module. In all cases,
1397 // limit visibility to search for the class only in the boot
1398 // loader's append path.
1399 if (!ClassLoader::has_bootclasspath_append()) {
1400 // If there is no bootclasspath append entry, no need to continue
1401 // searching.
1402 return nullptr;
1403 }
1404 search_only_bootloader_append = true;
1405 }
1406 }
1407
1408 // Prior to bootstrapping's module initialization, never load a class outside
1409 // of the boot loader's module path
1410 assert(Universe::is_module_initialized() ||
1411 !search_only_bootloader_append,
1412 "Attempt to load a class outside of boot loader's module path");
1413
1414 // Search for classes in the CDS archive.
1415 InstanceKlass* k = nullptr;
1416
1417 #if INCLUDE_CDS
1418 if (CDSConfig::is_using_archive())
1419 {
1420 PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time());
1421 InstanceKlass* ik = SystemDictionaryShared::find_builtin_class(class_name);
1422 if (ik != nullptr && ik->defined_by_boot_loader() && !ik->shared_loading_failed()) {
1423 SharedClassLoadingMark slm(THREAD, ik);
1424 k = load_shared_class(ik, class_loader, Handle(), nullptr, pkg_entry, CHECK_NULL);
1425 }
1426 }
1427 #endif
1428
1429 if (k == nullptr) {
1430 // Use VM class loader
1431 PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time());
1432 k = ClassLoader::load_class(class_name, pkg_entry, search_only_bootloader_append, CHECK_NULL);
1433 }
1434
1435 // find_or_define_instance_class may return a different InstanceKlass
1436 if (k != nullptr) {
1437 CDS_ONLY(SharedClassLoadingMark slm(THREAD, k);)
1438 k = find_or_define_instance_class(class_name, class_loader, k, CHECK_NULL);
1439 }
1440 return k;
1441 } else {
1442 // Use user specified class loader to load class. Call loadClass operation on class_loader.
1443 ResourceMark rm(THREAD);
1444
1445 JavaThread* jt = THREAD;
1446
1447 PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(),
1448 ClassLoader::perf_app_classload_selftime(),
1449 ClassLoader::perf_app_classload_count(),
1450 jt->get_thread_stat()->perf_recursion_counts_addr(),
1451 jt->get_thread_stat()->perf_timers_addr(),
1452 PerfClassTraceTime::CLASS_LOAD);
1453
1454 // Translate to external class name format, i.e., convert '/' chars to '.'
1455 Handle string = java_lang_String::externalize_classname(class_name, CHECK_NULL);
1456
1457 JavaValue result(T_OBJECT);
1458
1459 InstanceKlass* spec_klass = vmClasses::ClassLoader_klass();
1460
1461 // Call public unsynchronized loadClass(String) directly for all class loaders.
1462 // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will
1463 // acquire a class-name based lock rather than the class loader object lock.
1464 // JDK < 7 already acquire the class loader lock in loadClass(String, boolean).
1465 JavaCalls::call_virtual(&result,
1466 class_loader,
1467 spec_klass,
1468 vmSymbols::loadClass_name(),
1469 vmSymbols::string_class_signature(),
1470 string,
1471 CHECK_NULL);
1472
1473 assert(result.get_type() == T_OBJECT, "just checking");
1474 oop obj = result.get_oop();
1475
1476 // Primitive classes return null since forName() cannot be
1477 // used to obtain any of the Class objects representing primitives or void
1478 if ((obj != nullptr) && !(java_lang_Class::is_primitive(obj))) {
1479 InstanceKlass* k = java_lang_Class::as_InstanceKlass(obj);
1480 // For user defined Java class loaders, check that the name returned is
1481 // the same as that requested. This check is done for the bootstrap
1482 // loader when parsing the class file.
1483 if (class_name == k->name()) {
1484 return k;
1485 }
1486 }
1487 // Class is not found or has the wrong name, return null
1488 return nullptr;
1489 }
1490 }
1491
1492 InstanceKlass* SystemDictionary::load_instance_class(Symbol* name,
1493 Handle class_loader,
1494 TRAPS) {
1495
1496 InstanceKlass* loaded_class = load_instance_class_impl(name, class_loader, CHECK_NULL);
1497
1498 // If everything was OK (no exceptions, no null return value), and
1499 // class_loader is NOT the defining loader, do a little more bookkeeping.
1500 if (loaded_class != nullptr &&
1501 loaded_class->class_loader() != class_loader()) {
1502
1503 ClassLoaderData* loader_data = class_loader_data(class_loader);
1504 check_constraints(loaded_class, loader_data, false, CHECK_NULL);
1505
1506 // Record dependency for non-parent delegation.
1507 // This recording keeps the defining class loader of the klass (loaded_class) found
1508 // from being unloaded while the initiating class loader is loaded
1509 // even if the reference to the defining class loader is dropped
1510 // before references to the initiating class loader.
1511 loader_data->record_dependency(loaded_class);
1512
1513 update_dictionary(THREAD, loaded_class, loader_data);
1514
1515 if (JvmtiExport::should_post_class_load()) {
1516 JvmtiExport::post_class_load(THREAD, loaded_class);
1517 }
1518 }
1519 return loaded_class;
1520 }
1521
1522 void SystemDictionary::define_instance_class(InstanceKlass* k, Handle class_loader, TRAPS) {
1523
1524 ClassLoaderData* loader_data = k->class_loader_data();
1525 assert(loader_data->class_loader() == class_loader(), "they must be the same");
1526
1527 // Bootstrap and other parallel classloaders don't acquire a lock,
1528 // they use placeholder token.
1529 // If a parallelCapable class loader calls define_instance_class instead of
1530 // find_or_define_instance_class to get here, we have a timing
1531 // hole with systemDictionary updates and check_constraints
1532 if (!is_parallelCapable(class_loader)) {
1533 assert(ObjectSynchronizer::current_thread_holds_lock(THREAD,
1534 get_loader_lock_or_null(class_loader)),
1535 "define called without lock");
1536 }
1537
1538 // Check class-loading constraints. Throw exception if violation is detected.
1539 // Grabs and releases SystemDictionary_lock
1540 // The check_constraints/find_class call and update_dictionary sequence
1541 // must be "atomic" for a specific class/classloader pair so we never
1542 // define two different instanceKlasses for that class/classloader pair.
1543 // Existing classloaders will call define_instance_class with the
1544 // classloader lock held
1545 // Parallel classloaders will call find_or_define_instance_class
1546 // which will require a token to perform the define class
1547 check_constraints(k, loader_data, true, CHECK);
1548
1549 // Register class just loaded with class loader (placed in ArrayList)
1550 // Note we do this before updating the dictionary, as this can
1551 // fail with an OutOfMemoryError (if it does, we will *not* put this
1552 // class in the dictionary and will not update the class hierarchy).
1553 // JVMTI FollowReferences needs to find the classes this way.
1554 if (k->class_loader() != nullptr) {
1555 methodHandle m(THREAD, Universe::loader_addClass_method());
1556 JavaValue result(T_VOID);
1557 JavaCallArguments args(class_loader);
1558 args.push_oop(Handle(THREAD, k->java_mirror()));
1559 JavaCalls::call(&result, m, &args, CHECK);
1560 }
1561
1562 // Add to class hierarchy, and do possible deoptimizations.
1563 k->add_to_hierarchy(THREAD);
1564
1565 // Add to systemDictionary - so other classes can see it.
1566 // Grabs and releases SystemDictionary_lock
1567 update_dictionary(THREAD, k, loader_data);
1568
1569 // notify jvmti
1570 if (JvmtiExport::should_post_class_load()) {
1571 JvmtiExport::post_class_load(THREAD, k);
1572 }
1573 }
1574
1575 // Support parallel classloading
1576 // All parallel class loaders, including bootstrap classloader
1577 // lock a placeholder entry for this class/class_loader pair
1578 // to allow parallel defines of different classes for this class loader
1579 // With AllowParallelDefine flag==true, in case they do not synchronize around
1580 // FindLoadedClass/DefineClass, calls, we check for parallel
1581 // loading for them, wait if a defineClass is in progress
1582 // and return the initial requestor's results
1583 // This flag does not apply to the bootstrap classloader.
1584 // With AllowParallelDefine flag==false, call through to define_instance_class
1585 // which will throw LinkageError: duplicate class definition.
1586 // False is the requested default.
1587 // For better performance, the class loaders should synchronize
1588 // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they
1589 // potentially waste time reading and parsing the bytestream.
1590 // Note: VM callers should ensure consistency of k/class_name,class_loader
1591 // Be careful when modifying this code: once you have run
1592 // PlaceholderTable::find_and_add(PlaceholderTable::DEFINE_CLASS),
1593 // you need to find_and_remove it before returning.
1594 // So be careful to not exit with a CHECK_ macro between these calls.
1595 InstanceKlass* SystemDictionary::find_or_define_helper(Symbol* class_name, Handle class_loader,
1596 InstanceKlass* k, TRAPS) {
1597
1598 Symbol* name_h = k->name();
1599 ClassLoaderData* loader_data = class_loader_data(class_loader);
1600 Dictionary* dictionary = loader_data->dictionary();
1601
1602 // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS
1603 {
1604 MutexLocker mu(THREAD, SystemDictionary_lock);
1605 // First check if class already defined
1606 if (is_parallelDefine(class_loader)) {
1607 InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1608 if (check != nullptr) {
1609 return check;
1610 }
1611 }
1612
1613 // Acquire define token for this class/classloader
1614 PlaceholderEntry* probe = PlaceholderTable::find_and_add(name_h, loader_data,
1615 PlaceholderTable::DEFINE_CLASS, nullptr, THREAD);
1616 // Wait if another thread defining in parallel
1617 // All threads wait - even those that will throw duplicate class: otherwise
1618 // caller is surprised by LinkageError: duplicate, but findLoadedClass fails
1619 // if other thread has not finished updating dictionary
1620 while (probe->definer() != nullptr) {
1621 SystemDictionary_lock->wait();
1622 }
1623 // Only special cases allow parallel defines and can use other thread's results
1624 // Other cases fall through, and may run into duplicate defines
1625 // caught by finding an entry in the SystemDictionary
1626 if (is_parallelDefine(class_loader) && (probe->instance_klass() != nullptr)) {
1627 InstanceKlass* ik = probe->instance_klass();
1628 PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1629 SystemDictionary_lock->notify_all();
1630 #ifdef ASSERT
1631 InstanceKlass* check = dictionary->find_class(THREAD, name_h);
1632 assert(check != nullptr, "definer missed recording success");
1633 #endif
1634 return ik;
1635 } else {
1636 // This thread will define the class (even if earlier thread tried and had an error)
1637 probe->set_definer(THREAD);
1638 }
1639 }
1640
1641 define_instance_class(k, class_loader, THREAD);
1642
1643 // definer must notify any waiting threads
1644 {
1645 MutexLocker mu(THREAD, SystemDictionary_lock);
1646 PlaceholderEntry* probe = PlaceholderTable::get_entry(name_h, loader_data);
1647 assert(probe != nullptr, "DEFINE_CLASS placeholder lost?");
1648 if (!HAS_PENDING_EXCEPTION) {
1649 probe->set_instance_klass(k);
1650 }
1651 probe->set_definer(nullptr);
1652 PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD);
1653 SystemDictionary_lock->notify_all();
1654 }
1655
1656 return HAS_PENDING_EXCEPTION ? nullptr : k;
1657 }
1658
1659 // If a class loader supports parallel classloading handle parallel define requests.
1660 // find_or_define_instance_class may return a different InstanceKlass
1661 InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader,
1662 InstanceKlass* k, TRAPS) {
1663 InstanceKlass* defined_k = find_or_define_helper(class_name, class_loader, k, THREAD);
1664 // Clean up original InstanceKlass if duplicate or error
1665 if (!HAS_PENDING_EXCEPTION && defined_k != k) {
1666 // If a parallel capable class loader already defined this class, register 'k' for cleanup.
1667 assert(defined_k != nullptr, "Should have a klass if there's no exception");
1668 k->class_loader_data()->add_to_deallocate_list(k);
1669 } else if (HAS_PENDING_EXCEPTION) {
1670 // Remove this InstanceKlass from the LoaderConstraintTable if added.
1671 LoaderConstraintTable::remove_failed_loaded_klass(k, class_loader_data(class_loader));
1672 assert(defined_k == nullptr, "Should not have a klass if there's an exception");
1673 k->class_loader_data()->add_to_deallocate_list(k);
1674 }
1675 return defined_k;
1676 }
1677
1678
1679 // ----------------------------------------------------------------------------
1680 // GC support
1681
1682 // Assumes classes in the SystemDictionary are only unloaded at a safepoint
1683 bool SystemDictionary::do_unloading(GCTimer* gc_timer) {
1684
1685 bool unloading_occurred;
1686 bool is_concurrent = !SafepointSynchronize::is_at_safepoint();
1687 {
1688 GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer);
1689 assert_locked_or_safepoint(ClassLoaderDataGraph_lock); // caller locks.
1690 // First, mark for unload all ClassLoaderData referencing a dead class loader.
1691 unloading_occurred = ClassLoaderDataGraph::do_unloading();
1692 if (unloading_occurred) {
1693 ConditionalMutexLocker ml2(Module_lock, is_concurrent);
1694 JFR_ONLY(Jfr::on_unloading_classes();)
1695 MANAGEMENT_ONLY(FinalizerService::purge_unloaded();)
1696 ConditionalMutexLocker ml1(SystemDictionary_lock, is_concurrent);
1697 ClassLoaderDataGraph::clean_module_and_package_info();
1698 LoaderConstraintTable::purge_loader_constraints();
1699 ResolutionErrorTable::purge_resolution_errors();
1700 }
1701 }
1702
1703 GCTraceTime(Debug, gc, phases) t("Trigger cleanups", gc_timer);
1704
1705 if (unloading_occurred) {
1706 SymbolTable::trigger_cleanup();
1707
1708 ConditionalMutexLocker ml(ClassInitError_lock, is_concurrent);
1709 InstanceKlass::clean_initialization_error_table();
1710 }
1711
1712 return unloading_occurred;
1713 }
1714
1715 void SystemDictionary::methods_do(void f(Method*)) {
1716 // Walk methods in loaded classes
1717
1718 {
1719 MutexLocker ml(ClassLoaderDataGraph_lock);
1720 ClassLoaderDataGraph::methods_do(f);
1721 }
1722
1723 auto doit = [&] (InvokeMethodKey key, Method* method) {
1724 if (method != nullptr) {
1725 f(method);
1726 }
1727 };
1728
1729 {
1730 MutexLocker ml(InvokeMethodIntrinsicTable_lock);
1731 _invoke_method_intrinsic_table->iterate_all(doit);
1732 }
1733
1734 }
1735
1736 // ----------------------------------------------------------------------------
1737 // Initialization
1738
1739 void SystemDictionary::initialize(TRAPS) {
1740 _invoke_method_intrinsic_table = new (mtClass) InvokeMethodIntrinsicTable();
1741 _invoke_method_type_table = new (mtClass) InvokeMethodTypeTable();
1742 ResolutionErrorTable::initialize();
1743 LoaderConstraintTable::initialize();
1744 PlaceholderTable::initialize();
1745 #if INCLUDE_CDS
1746 SystemDictionaryShared::initialize();
1747 if (CDSConfig::is_dumping_archive()) {
1748 AOTClassLocationConfig::dumptime_init(THREAD);
1749 }
1750 #endif
1751 // Resolve basic classes
1752 vmClasses::resolve_all(CHECK);
1753 // Resolve classes used by archived heap objects
1754 if (CDSConfig::is_using_archive()) {
1755 HeapShared::resolve_classes(THREAD);
1756 }
1757 }
1758
1759 // Constraints on class loaders. The details of the algorithm can be
1760 // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java
1761 // Virtual Machine" by Sheng Liang and Gilad Bracha. The basic idea is
1762 // that the dictionary needs to maintain a set of constraints that
1763 // must be satisfied by all classes in the dictionary.
1764 // if defining is true, then LinkageError if already in dictionary
1765 // if initiating loader, then ok if InstanceKlass matches existing entry
1766
1767 void SystemDictionary::check_constraints(InstanceKlass* k,
1768 ClassLoaderData* loader_data,
1769 bool defining,
1770 TRAPS) {
1771 ResourceMark rm(THREAD);
1772 stringStream ss;
1773 bool throwException = false;
1774
1775 {
1776 Symbol* name = k->name();
1777
1778 MutexLocker mu(THREAD, SystemDictionary_lock);
1779
1780 InstanceKlass* check = loader_data->dictionary()->find_class(THREAD, name);
1781 if (check != nullptr) {
1782 // If different InstanceKlass - duplicate class definition,
1783 // else - ok, class loaded by a different thread in parallel.
1784 // We should only have found it if it was done loading and ok to use.
1785
1786 if ((defining == true) || (k != check)) {
1787 throwException = true;
1788 ss.print("loader %s", loader_data->loader_name_and_id());
1789 ss.print(" attempted duplicate %s definition for %s. (%s)",
1790 k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true));
1791 } else {
1792 return;
1793 }
1794 }
1795
1796 if (throwException == false) {
1797 if (LoaderConstraintTable::check_or_update(k, loader_data, name) == false) {
1798 throwException = true;
1799 ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id());
1800 ss.print(" wants to load %s %s.",
1801 k->external_kind(), k->external_name());
1802 Klass *existing_klass = LoaderConstraintTable::find_constrained_klass(name, loader_data);
1803 if (existing_klass != nullptr && existing_klass->class_loader_data() != loader_data) {
1804 ss.print(" A different %s with the same name was previously loaded by %s. (%s)",
1805 existing_klass->external_kind(),
1806 existing_klass->class_loader_data()->loader_name_and_id(),
1807 existing_klass->class_in_module_of_loader(false, true));
1808 } else {
1809 ss.print(" (%s)", k->class_in_module_of_loader(false, true));
1810 }
1811 }
1812 }
1813 }
1814
1815 // Throw error now if needed (cannot throw while holding
1816 // SystemDictionary_lock because of rank ordering)
1817 if (throwException == true) {
1818 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1819 }
1820 }
1821
1822 // Update class loader data dictionary - done after check_constraint and add_to_hierarchy
1823 // have been called.
1824 void SystemDictionary::update_dictionary(JavaThread* current,
1825 InstanceKlass* k,
1826 ClassLoaderData* loader_data) {
1827 MonitorLocker mu1(SystemDictionary_lock);
1828
1829 // Make a new dictionary entry.
1830 Symbol* name = k->name();
1831 Dictionary* dictionary = loader_data->dictionary();
1832 InstanceKlass* sd_check = dictionary->find_class(current, name);
1833 if (sd_check == nullptr) {
1834 dictionary->add_klass(current, name, k);
1835 }
1836 mu1.notify_all();
1837 }
1838
1839 // Indicate that loader_data has initiated the loading of class k, which
1840 // has already been defined by a parent loader.
1841 // This API is used by AOTLinkedClassBulkLoader and to register boxing
1842 // classes from java.lang in all class loaders to enable more value
1843 // classes optimizations
1844 void SystemDictionary::add_to_initiating_loader(JavaThread* current,
1845 InstanceKlass* k,
1846 ClassLoaderData* loader_data) {
1847 assert_locked_or_safepoint(SystemDictionary_lock);
1848 Symbol* name = k->name();
1849 Dictionary* dictionary = loader_data->dictionary();
1850 assert(k->is_loaded(), "must be");
1851 assert(k->class_loader_data() != loader_data, "only for classes defined by a parent loader");
1852 if (dictionary->find_class(current, name) == nullptr) {
1853 dictionary->add_klass(current, name, k);
1854 }
1855 }
1856
1857 // Try to find a class name using the loader constraints. The
1858 // loader constraints might know about a class that isn't fully loaded
1859 // yet and these will be ignored.
1860 Klass* SystemDictionary::find_constrained_instance_or_array_klass(
1861 Thread* current, Symbol* class_name, Handle class_loader) {
1862
1863 // First see if it has been loaded directly.
1864 Klass* klass = find_instance_or_array_klass(current, class_name, class_loader);
1865 if (klass != nullptr)
1866 return klass;
1867
1868 // Now look to see if it has been loaded elsewhere, and is subject to
1869 // a loader constraint that would require this loader to return the
1870 // klass that is already loaded.
1871 if (Signature::is_array(class_name)) {
1872 // For array classes, their Klass*s are not kept in the
1873 // constraint table. The element Klass*s are.
1874 SignatureStream ss(class_name, false);
1875 int ndims = ss.skip_array_prefix(); // skip all '['s
1876 BasicType t = ss.type();
1877 if (t != T_OBJECT) {
1878 klass = Universe::typeArrayKlass(t);
1879 } else {
1880 MutexLocker mu(current, SystemDictionary_lock);
1881 klass = LoaderConstraintTable::find_constrained_klass(ss.as_symbol(), class_loader_data(class_loader));
1882 }
1883 // If element class already loaded, allocate array klass
1884 if (klass != nullptr) {
1885 klass = klass->array_klass_or_null(ndims);
1886 }
1887 } else {
1888 MutexLocker mu(current, SystemDictionary_lock);
1889 // Non-array classes are easy: simply check the constraint table.
1890 klass = LoaderConstraintTable::find_constrained_klass(class_name, class_loader_data(class_loader));
1891 }
1892
1893 return klass;
1894 }
1895
1896 bool SystemDictionary::add_loader_constraint(Symbol* class_name,
1897 Klass* klass_being_linked,
1898 Handle class_loader1,
1899 Handle class_loader2) {
1900 ClassLoaderData* loader_data1 = class_loader_data(class_loader1);
1901 ClassLoaderData* loader_data2 = class_loader_data(class_loader2);
1902
1903 Symbol* constraint_name = nullptr;
1904
1905 if (!Signature::is_array(class_name)) {
1906 constraint_name = class_name;
1907 } else {
1908 // For array classes, their Klass*s are not kept in the
1909 // constraint table. The element classes are.
1910 SignatureStream ss(class_name, false);
1911 ss.skip_array_prefix(); // skip all '['s
1912 if (!ss.has_envelope()) {
1913 return true; // primitive types always pass
1914 }
1915 constraint_name = ss.as_symbol();
1916 // Increment refcount to keep constraint_name alive after
1917 // SignatureStream is destructed. It will be decremented below
1918 // before returning.
1919 constraint_name->increment_refcount();
1920 }
1921
1922 Dictionary* dictionary1 = loader_data1->dictionary();
1923 Dictionary* dictionary2 = loader_data2->dictionary();
1924
1925 JavaThread* current = JavaThread::current();
1926 {
1927 MutexLocker mu_s(SystemDictionary_lock);
1928 InstanceKlass* klass1 = dictionary1->find_class(current, constraint_name);
1929 InstanceKlass* klass2 = dictionary2->find_class(current, constraint_name);
1930 bool result = LoaderConstraintTable::add_entry(constraint_name, klass1, loader_data1,
1931 klass2, loader_data2);
1932 #if INCLUDE_CDS
1933 if (CDSConfig::is_dumping_archive() && klass_being_linked != nullptr &&
1934 !klass_being_linked->in_aot_cache()) {
1935 SystemDictionaryShared::record_linking_constraint(constraint_name,
1936 InstanceKlass::cast(klass_being_linked),
1937 class_loader1, class_loader2);
1938 }
1939 #endif // INCLUDE_CDS
1940 if (Signature::is_array(class_name)) {
1941 constraint_name->decrement_refcount();
1942 }
1943 return result;
1944 }
1945 }
1946
1947 // Add entry to resolution error table to record the error when the first
1948 // attempt to resolve a reference to a class has failed.
1949 void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which,
1950 Symbol* error, const char* message,
1951 Symbol* cause, const char* cause_msg) {
1952 {
1953 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1954 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1955 if (entry == nullptr) {
1956 ResolutionErrorTable::add_entry(pool, which, error, message, cause, cause_msg);
1957 }
1958 }
1959 }
1960
1961 // Delete a resolution error for RedefineClasses for a constant pool is going away
1962 void SystemDictionary::delete_resolution_error(ConstantPool* pool) {
1963 ResolutionErrorTable::delete_entry(pool);
1964 }
1965
1966 // Lookup resolution error table. Returns error if found, otherwise null.
1967 Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which,
1968 const char** message,
1969 Symbol** cause, const char** cause_msg) {
1970
1971 {
1972 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1973 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1974 if (entry != nullptr) {
1975 *message = entry->message();
1976 *cause = entry->cause();
1977 *cause_msg = entry->cause_msg();
1978 return entry->error();
1979 } else {
1980 return nullptr;
1981 }
1982 }
1983 }
1984
1985 // Add an entry to resolution error table to record an error in resolving or
1986 // validating a nest host. This is used to construct informative error
1987 // messages when IllegalAccessError's occur. If an entry already exists it will
1988 // be updated with the nest host error message.
1989
1990 void SystemDictionary::add_nest_host_error(const constantPoolHandle& pool,
1991 int which,
1992 const stringStream& message) {
1993 {
1994 MutexLocker ml(Thread::current(), SystemDictionary_lock);
1995 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
1996 if (entry == nullptr) {
1997 // Only add a new entry to the resolution error table if one hasn't been found for this
1998 // constant pool index. In this case resolution succeeded but there's an error in this nest host
1999 // that we use the table to record.
2000 assert(pool->resolved_klass_at(which) != nullptr, "klass should be resolved if there is no entry");
2001 ResolutionErrorTable::add_entry(pool, which, message.as_string(true /* on C-heap */));
2002 } else {
2003 // An existing entry means we had a true resolution failure (LinkageError) with our nest host, but we
2004 // still want to add the error message for the higher-level access checks to report. We should
2005 // only reach here under the same error condition, so we can ignore the potential race with setting
2006 // the message.
2007 const char* nhe = entry->nest_host_error();
2008 if (nhe == nullptr) {
2009 entry->set_nest_host_error(message.as_string(true /* on C-heap */));
2010 } else {
2011 DEBUG_ONLY(const char* msg = message.base();)
2012 assert(strcmp(nhe, msg) == 0, "New message %s, differs from original %s", msg, nhe);
2013 }
2014 }
2015 }
2016 }
2017
2018 // Lookup any nest host error
2019 const char* SystemDictionary::find_nest_host_error(const constantPoolHandle& pool, int which) {
2020 {
2021 MutexLocker ml(Thread::current(), SystemDictionary_lock);
2022 ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which);
2023 if (entry != nullptr) {
2024 return entry->nest_host_error();
2025 } else {
2026 return nullptr;
2027 }
2028 }
2029 }
2030
2031 // Signature constraints ensure that callers and callees agree about
2032 // the meaning of type names in their signatures. This routine is the
2033 // intake for constraints. It collects them from several places:
2034 //
2035 // * LinkResolver::resolve_method (if check_access is true) requires
2036 // that the resolving class (the caller) and the defining class of
2037 // the resolved method (the callee) agree on each type in the
2038 // method's signature.
2039 //
2040 // * LinkResolver::resolve_interface_method performs exactly the same
2041 // checks.
2042 //
2043 // * LinkResolver::resolve_field requires that the constant pool
2044 // attempting to link to a field agree with the field's defining
2045 // class about the type of the field signature.
2046 //
2047 // * klassVtable::initialize_vtable requires that, when a class
2048 // overrides a vtable entry allocated by a superclass, that the
2049 // overriding method (i.e., the callee) agree with the superclass
2050 // on each type in the method's signature.
2051 //
2052 // * klassItable::initialize_itable requires that, when a class fills
2053 // in its itables, for each non-abstract method installed in an
2054 // itable, the method (i.e., the callee) agree with the interface
2055 // on each type in the method's signature.
2056 //
2057 // All those methods have a boolean (check_access, checkconstraints)
2058 // which turns off the checks. This is used from specialized contexts
2059 // such as bootstrapping, dumping, and debugging.
2060 //
2061 // No direct constraint is placed between the class and its
2062 // supertypes. Constraints are only placed along linked relations
2063 // between callers and callees. When a method overrides or implements
2064 // an abstract method in a supertype (superclass or interface), the
2065 // constraints are placed as if the supertype were the caller to the
2066 // overriding method. (This works well, since callers to the
2067 // supertype have already established agreement between themselves and
2068 // the supertype.) As a result of all this, a class can disagree with
2069 // its supertype about the meaning of a type name, as long as that
2070 // class neither calls a relevant method of the supertype, nor is
2071 // called (perhaps via an override) from the supertype.
2072 //
2073 //
2074 // SystemDictionary::check_signature_loaders(sig, klass_being_linked, l1, l2)
2075 //
2076 // Make sure all class components (including arrays) in the given
2077 // signature will be resolved to the same class in both loaders.
2078 // Returns the name of the type that failed a loader constraint check, or
2079 // null if no constraint failed. No exception except OOME is thrown.
2080 // Arrays are not added to the loader constraint table, their elements are.
2081 Symbol* SystemDictionary::check_signature_loaders(Symbol* signature,
2082 Klass* klass_being_linked,
2083 Handle loader1, Handle loader2,
2084 bool is_method) {
2085 // Nothing to do if loaders are the same.
2086 if (loader1() == loader2()) {
2087 return nullptr;
2088 }
2089
2090 for (SignatureStream ss(signature, is_method); !ss.is_done(); ss.next()) {
2091 if (ss.is_reference()) {
2092 Symbol* sig = ss.as_symbol();
2093 // Note: In the future, if template-like types can take
2094 // arguments, we will want to recognize them and dig out class
2095 // names hiding inside the argument lists.
2096 if (!add_loader_constraint(sig, klass_being_linked, loader1, loader2)) {
2097 return sig;
2098 }
2099 }
2100 }
2101 return nullptr;
2102 }
2103
2104 Method* SystemDictionary::find_method_handle_intrinsic(vmIntrinsicID iid,
2105 Symbol* signature,
2106 TRAPS) {
2107
2108 const int iid_as_int = vmIntrinsics::as_int(iid);
2109 assert(MethodHandles::is_signature_polymorphic(iid) &&
2110 MethodHandles::is_signature_polymorphic_intrinsic(iid) &&
2111 iid != vmIntrinsics::_invokeGeneric,
2112 "must be a known MH intrinsic iid=%d: %s", iid_as_int, vmIntrinsics::name_at(iid));
2113
2114 InvokeMethodKey key(signature, iid_as_int);
2115 Method** met = nullptr;
2116
2117 // We only want one entry in the table for this (signature/id, method) pair but the code
2118 // to create the intrinsic method needs to be outside the lock.
2119 // The first thread claims the entry by adding the key and the other threads wait, until the
2120 // Method has been added as the value.
2121 {
2122 MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
2123 while (true) {
2124 bool created;
2125 met = _invoke_method_intrinsic_table->put_if_absent(key, &created);
2126 assert(met != nullptr, "either created or found");
2127 if (*met != nullptr) {
2128 return *met;
2129 } else if (created) {
2130 // The current thread won the race and will try to create the full entry.
2131 break;
2132 } else {
2133 // Another thread beat us to it, so wait for them to complete
2134 // and return *met; or if they hit an error we get another try.
2135 ml.wait();
2136 // Note it is not safe to read *met here as that entry could have
2137 // been deleted, so we must loop and try put_if_absent again.
2138 }
2139 }
2140 }
2141
2142 methodHandle m = Method::make_method_handle_intrinsic(iid, signature, THREAD);
2143 bool throw_error = HAS_PENDING_EXCEPTION;
2144 if (!throw_error && (!Arguments::is_interpreter_only() || iid == vmIntrinsics::_linkToNative)) {
2145 // Generate a compiled form of the MH intrinsic
2146 // linkToNative doesn't have interpreter-specific implementation, so always has to go through compiled version.
2147 AdapterHandlerLibrary::create_native_wrapper(m);
2148 // Check if have the compiled code.
2149 throw_error = (!m->has_compiled_code());
2150 }
2151
2152 {
2153 MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock);
2154 if (throw_error) {
2155 // Remove the entry and let another thread try, or get the same exception.
2156 bool removed = _invoke_method_intrinsic_table->remove(key);
2157 assert(removed, "must be the owner");
2158 ml.notify_all();
2159 } else {
2160 signature->make_permanent(); // The signature is never unloaded.
2161 assert(Arguments::is_interpreter_only() || (m->has_compiled_code() &&
2162 m->code()->entry_point() == m->from_compiled_entry()),
2163 "MH intrinsic invariant");
2164 *met = m(); // insert the element
2165 ml.notify_all();
2166 return m();
2167 }
2168 }
2169
2170 // Throw OOM or the pending exception in the JavaThread
2171 if (throw_error && !HAS_PENDING_EXCEPTION) {
2172 THROW_MSG_NULL(vmSymbols::java_lang_OutOfMemoryError(),
2173 "Out of space in CodeCache for method handle intrinsic");
2174 }
2175 return nullptr;
2176 }
2177
2178 #if INCLUDE_CDS
2179 void SystemDictionary::get_all_method_handle_intrinsics(GrowableArray<Method*>* methods) {
2180 assert(SafepointSynchronize::is_at_safepoint(), "must be");
2181 auto do_method = [&] (InvokeMethodKey& key, Method*& m) {
2182 methods->append(m);
2183 };
2184 _invoke_method_intrinsic_table->iterate_all(do_method);
2185 }
2186
2187 void SystemDictionary::restore_archived_method_handle_intrinsics() {
2188 if (UseSharedSpaces) {
2189 EXCEPTION_MARK;
2190 restore_archived_method_handle_intrinsics_impl(THREAD);
2191 if (HAS_PENDING_EXCEPTION) {
2192 // This is probably caused by OOM -- other parts of the CDS archive have direct pointers to
2193 // the archived method handle intrinsics, so we can't really recover from this failure.
2194 vm_exit_during_initialization(err_msg("Failed to restore archived method handle intrinsics. Try to increase heap size."));
2195 }
2196 }
2197 }
2198
2199 void SystemDictionary::restore_archived_method_handle_intrinsics_impl(TRAPS) {
2200 Array<Method*>* list = AOTMetaspace::archived_method_handle_intrinsics();
2201 for (int i = 0; i < list->length(); i++) {
2202 methodHandle m(THREAD, list->at(i));
2203 Method::restore_archived_method_handle_intrinsic(m, CHECK);
2204 m->constants()->restore_unshareable_info(CHECK);
2205 if (!Arguments::is_interpreter_only() || m->intrinsic_id() == vmIntrinsics::_linkToNative) {
2206 AdapterHandlerLibrary::create_native_wrapper(m);
2207 if (!m->has_compiled_code()) {
2208 ResourceMark rm(THREAD);
2209 vm_exit_during_initialization(err_msg("Failed to initialize method %s", m->external_name()));
2210 }
2211 }
2212
2213 // There's no need to grab the InvokeMethodIntrinsicTable_lock, as we are still very early in
2214 // VM start-up -- in init_globals2() -- so we are still running a single Java thread. It's not
2215 // possible to have a contention.
2216 const int iid_as_int = vmIntrinsics::as_int(m->intrinsic_id());
2217 InvokeMethodKey key(m->signature(), iid_as_int);
2218 bool created = _invoke_method_intrinsic_table->put(key, m());
2219 assert(created, "unexpected contention");
2220 }
2221 }
2222 #endif // INCLUDE_CDS
2223
2224 // Helper for unpacking the return value from linkMethod and linkCallSite.
2225 static Method* unpack_method_and_appendix(Handle mname,
2226 Klass* accessing_klass,
2227 objArrayHandle appendix_box,
2228 Handle* appendix_result,
2229 TRAPS) {
2230 if (mname.not_null()) {
2231 Method* m = java_lang_invoke_MemberName::vmtarget(mname());
2232 if (m != nullptr) {
2233 oop appendix = appendix_box->obj_at(0);
2234 LogTarget(Info, methodhandles) lt;
2235 if (lt.develop_is_enabled()) {
2236 ResourceMark rm(THREAD);
2237 LogStream ls(lt);
2238 ls.print("Linked method=" INTPTR_FORMAT ": ", p2i(m));
2239 m->print_on(&ls);
2240 if (appendix != nullptr) { ls.print("appendix = "); appendix->print_on(&ls); }
2241 ls.cr();
2242 }
2243
2244 (*appendix_result) = Handle(THREAD, appendix);
2245 // the target is stored in the cpCache and if a reference to this
2246 // MemberName is dropped we need a way to make sure the
2247 // class_loader containing this method is kept alive.
2248 methodHandle mh(THREAD, m); // record_dependency can safepoint.
2249 ClassLoaderData* this_key = accessing_klass->class_loader_data();
2250 this_key->record_dependency(m->method_holder());
2251 return mh();
2252 }
2253 }
2254 THROW_MSG_NULL(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives");
2255 }
2256
2257 Method* SystemDictionary::find_method_handle_invoker(Klass* klass,
2258 Symbol* name,
2259 Symbol* signature,
2260 Klass* accessing_klass,
2261 Handle* appendix_result,
2262 TRAPS) {
2263 guarantee(THREAD->can_call_java(), "");
2264 Handle method_type =
2265 SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_NULL);
2266
2267 int ref_kind = JVM_REF_invokeVirtual;
2268 oop name_oop = StringTable::intern(name, CHECK_NULL);
2269 Handle name_str (THREAD, name_oop);
2270 objArrayHandle appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK_NULL);
2271 assert(appendix_box->obj_at(0) == nullptr, "");
2272
2273 // This should not happen. JDK code should take care of that.
2274 if (accessing_klass == nullptr || method_type.is_null()) {
2275 THROW_MSG_NULL(vmSymbols::java_lang_InternalError(), "bad invokehandle");
2276 }
2277
2278 // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName
2279 JavaCallArguments args;
2280 args.push_oop(Handle(THREAD, accessing_klass->java_mirror()));
2281 args.push_int(ref_kind);
2282 args.push_oop(Handle(THREAD, klass->java_mirror()));
2283 args.push_oop(name_str);
2284 args.push_oop(method_type);
2285 args.push_oop(appendix_box);
2286 JavaValue result(T_OBJECT);
2287 JavaCalls::call_static(&result,
2288 vmClasses::MethodHandleNatives_klass(),
2289 vmSymbols::linkMethod_name(),
2290 vmSymbols::linkMethod_signature(),
2291 &args, CHECK_NULL);
2292 Handle mname(THREAD, result.get_oop());
2293 return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD);
2294 }
2295
2296 // Decide if we can globally cache a lookup of this class, to be returned to any client that asks.
2297 // We must ensure that all class loaders everywhere will reach this class, for any client.
2298 // This is a safe bet for public classes in java.lang, such as Object and String.
2299 // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types.
2300 // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util.
2301 static bool is_always_visible_class(oop mirror) {
2302 Klass* klass = java_lang_Class::as_Klass(mirror);
2303 if (klass->is_objArray_klass()) {
2304 klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type
2305 }
2306 if (klass->is_typeArray_klass()) {
2307 return true; // primitive array
2308 }
2309 assert(klass->is_instance_klass(), "%s", klass->external_name());
2310 InstanceKlass* ik = InstanceKlass::cast(klass);
2311 return ik->is_public() &&
2312 (ik->is_same_class_package(vmClasses::Object_klass()) || // java.lang
2313 ik->is_same_class_package(vmClasses::MethodHandle_klass())); // java.lang.invoke
2314 }
2315
2316 // Find or construct the Java mirror (java.lang.Class instance) for
2317 // the given field type signature, as interpreted relative to the
2318 // given class loader. Handles primitives, void, references, arrays,
2319 // and all other reflectable types, except method types.
2320 // N.B. Code in reflection should use this entry point.
2321 Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature,
2322 Klass* accessing_klass,
2323 SignatureStream::FailureMode failure_mode,
2324 TRAPS) {
2325
2326 Handle class_loader;
2327
2328 // What we have here must be a valid field descriptor,
2329 // and all valid field descriptors are supported.
2330 // Produce the same java.lang.Class that reflection reports.
2331 if (accessing_klass != nullptr) {
2332 class_loader = Handle(THREAD, accessing_klass->class_loader());
2333 }
2334 ResolvingSignatureStream ss(signature, class_loader, false);
2335 oop mirror_oop = ss.as_java_mirror(failure_mode, CHECK_NH);
2336 if (mirror_oop == nullptr) {
2337 return Handle(); // report failure this way
2338 }
2339 Handle mirror(THREAD, mirror_oop);
2340
2341 if (accessing_klass != nullptr) {
2342 // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve.
2343 Klass* sel_klass = java_lang_Class::as_Klass(mirror());
2344 if (sel_klass != nullptr) {
2345 LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_NH);
2346 }
2347 }
2348 return mirror;
2349 }
2350
2351
2352 // Ask Java code to find or construct a java.lang.invoke.MethodType for the given
2353 // signature, as interpreted relative to the given class loader.
2354 // Because of class loader constraints, all method handle usage must be
2355 // consistent with this loader.
2356 Handle SystemDictionary::find_method_handle_type(Symbol* signature,
2357 Klass* accessing_klass,
2358 TRAPS) {
2359 Handle empty;
2360 OopHandle* o;
2361 {
2362 MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2363 o = _invoke_method_type_table->get(signature);
2364 }
2365
2366 if (o != nullptr) {
2367 oop mt = o->resolve();
2368 assert(java_lang_invoke_MethodType::is_instance(mt), "");
2369 return Handle(THREAD, mt);
2370 } else if (!THREAD->can_call_java()) {
2371 warning("SystemDictionary::find_method_handle_type called from compiler thread"); // FIXME
2372 return Handle(); // do not attempt from within compiler, unless it was cached
2373 }
2374
2375 Handle class_loader;
2376 if (accessing_klass != nullptr) {
2377 class_loader = Handle(THREAD, accessing_klass->class_loader());
2378 }
2379 bool can_be_cached = true;
2380 int npts = ArgumentCount(signature).size();
2381 objArrayHandle pts = oopFactory::new_objArray_handle(vmClasses::Class_klass(), npts, CHECK_(empty));
2382 int arg = 0;
2383 Handle rt; // the return type from the signature
2384 ResourceMark rm(THREAD);
2385 for (SignatureStream ss(signature); !ss.is_done(); ss.next()) {
2386 oop mirror = nullptr;
2387 if (can_be_cached) {
2388 // Use neutral class loader to lookup candidate classes to be placed in the cache.
2389 mirror = ss.as_java_mirror(Handle(), SignatureStream::ReturnNull, CHECK_(empty));
2390 if (mirror == nullptr || (ss.is_reference() && !is_always_visible_class(mirror))) {
2391 // Fall back to accessing_klass context.
2392 can_be_cached = false;
2393 }
2394 }
2395 if (!can_be_cached) {
2396 // Resolve, throwing a real error if it doesn't work.
2397 mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2398 }
2399 assert(mirror != nullptr, "%s", ss.as_symbol()->as_C_string());
2400 if (ss.at_return_type())
2401 rt = Handle(THREAD, mirror);
2402 else
2403 pts->obj_at_put(arg++, mirror);
2404
2405 // Check accessibility.
2406 if (!java_lang_Class::is_primitive(mirror) && accessing_klass != nullptr) {
2407 Klass* sel_klass = java_lang_Class::as_Klass(mirror);
2408 mirror = nullptr; // safety
2409 // Emulate ConstantPool::verify_constant_pool_resolve.
2410 LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_(empty));
2411 }
2412 }
2413 assert(arg == npts, "");
2414
2415 // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType
2416 JavaCallArguments args(Handle(THREAD, rt()));
2417 args.push_oop(pts);
2418 JavaValue result(T_OBJECT);
2419 JavaCalls::call_static(&result,
2420 vmClasses::MethodHandleNatives_klass(),
2421 vmSymbols::findMethodHandleType_name(),
2422 vmSymbols::findMethodHandleType_signature(),
2423 &args, CHECK_(empty));
2424 Handle method_type(THREAD, result.get_oop());
2425
2426 if (can_be_cached) {
2427 // We can cache this MethodType inside the JVM.
2428 MutexLocker ml(THREAD, InvokeMethodTypeTable_lock);
2429 bool created = false;
2430 assert(method_type != nullptr, "unexpected null");
2431 OopHandle* h = _invoke_method_type_table->get(signature);
2432 if (h == nullptr) {
2433 signature->make_permanent(); // The signature is never unloaded.
2434 OopHandle elem = OopHandle(Universe::vm_global(), method_type());
2435 bool created = _invoke_method_type_table->put(signature, elem);
2436 assert(created, "better be created");
2437 }
2438 }
2439 // report back to the caller with the MethodType
2440 return method_type;
2441 }
2442
2443 Handle SystemDictionary::find_field_handle_type(Symbol* signature,
2444 Klass* accessing_klass,
2445 TRAPS) {
2446 Handle empty;
2447 ResourceMark rm(THREAD);
2448 SignatureStream ss(signature, /*is_method=*/ false);
2449 if (!ss.is_done()) {
2450 Handle class_loader;
2451 if (accessing_klass != nullptr) {
2452 class_loader = Handle(THREAD, accessing_klass->class_loader());
2453 }
2454 oop mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty));
2455 ss.next();
2456 if (ss.is_done()) {
2457 return Handle(THREAD, mirror);
2458 }
2459 }
2460 return empty;
2461 }
2462
2463 // Ask Java code to find or construct a method handle constant.
2464 Handle SystemDictionary::link_method_handle_constant(Klass* caller,
2465 int ref_kind, //e.g., JVM_REF_invokeVirtual
2466 Klass* callee,
2467 Symbol* name,
2468 Symbol* signature,
2469 TRAPS) {
2470 Handle empty;
2471 if (caller == nullptr) {
2472 THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty);
2473 }
2474 Handle name_str = java_lang_String::create_from_symbol(name, CHECK_(empty));
2475 Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty));
2476
2477 // Put symbolic info from the MH constant into freshly created MemberName and resolve it.
2478 Handle mname = vmClasses::MemberName_klass()->allocate_instance_handle(CHECK_(empty));
2479 java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror());
2480 java_lang_invoke_MemberName::set_name (mname(), name_str());
2481 java_lang_invoke_MemberName::set_type (mname(), signature_str());
2482 java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind));
2483
2484 if (ref_kind == JVM_REF_invokeVirtual &&
2485 MethodHandles::is_signature_polymorphic_public_name(callee, name)) {
2486 // Skip resolution for public signature polymorphic methods such as
2487 // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle
2488 // They require appendix argument which MemberName resolution doesn't handle.
2489 // There's special logic on JDK side to handle them
2490 // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()).
2491 } else {
2492 MethodHandles::resolve_MemberName(mname, caller, 0, false /*speculative_resolve*/, CHECK_(empty));
2493 }
2494
2495 // After method/field resolution succeeded, it's safe to resolve MH signature as well.
2496 Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty));
2497
2498 // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle
2499 JavaCallArguments args;
2500 args.push_oop(Handle(THREAD, caller->java_mirror())); // the referring class
2501 args.push_int(ref_kind);
2502 args.push_oop(Handle(THREAD, callee->java_mirror())); // the target class
2503 args.push_oop(name_str);
2504 args.push_oop(type);
2505 JavaValue result(T_OBJECT);
2506 JavaCalls::call_static(&result,
2507 vmClasses::MethodHandleNatives_klass(),
2508 vmSymbols::linkMethodHandleConstant_name(),
2509 vmSymbols::linkMethodHandleConstant_signature(),
2510 &args, CHECK_(empty));
2511 return Handle(THREAD, result.get_oop());
2512 }
2513
2514 // Ask Java to run a bootstrap method, in order to create a dynamic call site
2515 // while linking an invokedynamic op, or compute a constant for Dynamic_info CP entry
2516 // with linkage results being stored back into the bootstrap specifier.
2517 void SystemDictionary::invoke_bootstrap_method(BootstrapInfo& bootstrap_specifier, TRAPS) {
2518 // Resolve the bootstrap specifier, its name, type, and static arguments
2519 bootstrap_specifier.resolve_bsm(CHECK);
2520
2521 // This should not happen. JDK code should take care of that.
2522 if (bootstrap_specifier.caller() == nullptr || bootstrap_specifier.type_arg().is_null()) {
2523 THROW_MSG(vmSymbols::java_lang_InternalError(), "Invalid bootstrap method invocation with no caller or type argument");
2524 }
2525
2526 bool is_indy = bootstrap_specifier.is_method_call();
2527 objArrayHandle appendix_box;
2528 if (is_indy) {
2529 // Some method calls may require an appendix argument. Arrange to receive it.
2530 appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK);
2531 assert(appendix_box->obj_at(0) == nullptr, "");
2532 }
2533
2534 // call condy: java.lang.invoke.MethodHandleNatives::linkDynamicConstant(caller, bsm, type, info)
2535 // indy: java.lang.invoke.MethodHandleNatives::linkCallSite(caller, bsm, name, mtype, info, &appendix)
2536 JavaCallArguments args;
2537 args.push_oop(Handle(THREAD, bootstrap_specifier.caller_mirror()));
2538 args.push_oop(bootstrap_specifier.bsm());
2539 args.push_oop(bootstrap_specifier.name_arg());
2540 args.push_oop(bootstrap_specifier.type_arg());
2541 args.push_oop(bootstrap_specifier.arg_values());
2542 if (is_indy) {
2543 args.push_oop(appendix_box);
2544 }
2545 JavaValue result(T_OBJECT);
2546 JavaCalls::call_static(&result,
2547 vmClasses::MethodHandleNatives_klass(),
2548 is_indy ? vmSymbols::linkCallSite_name() : vmSymbols::linkDynamicConstant_name(),
2549 is_indy ? vmSymbols::linkCallSite_signature() : vmSymbols::linkDynamicConstant_signature(),
2550 &args, CHECK);
2551
2552 Handle value(THREAD, result.get_oop());
2553 if (is_indy) {
2554 Handle appendix;
2555 Method* method = unpack_method_and_appendix(value,
2556 bootstrap_specifier.caller(),
2557 appendix_box,
2558 &appendix, CHECK);
2559 methodHandle mh(THREAD, method);
2560 bootstrap_specifier.set_resolved_method(mh, appendix);
2561 } else {
2562 bootstrap_specifier.set_resolved_value(value);
2563 }
2564
2565 // sanity check
2566 assert(bootstrap_specifier.is_resolved() ||
2567 (bootstrap_specifier.is_method_call() &&
2568 bootstrap_specifier.resolved_method().not_null()), "bootstrap method call failed");
2569 }
2570
2571
2572 bool SystemDictionary::is_nonpublic_Object_method(Method* m) {
2573 assert(m != nullptr, "Unexpected nullptr Method*");
2574 return !m->is_public() && m->method_holder() == vmClasses::Object_klass();
2575 }
2576
2577 // ----------------------------------------------------------------------------
2578
2579 void SystemDictionary::print_on(outputStream *st) {
2580 CDS_ONLY(SystemDictionaryShared::print_on(st));
2581 GCMutexLocker mu(SystemDictionary_lock);
2582
2583 ClassLoaderDataGraph::print_dictionary(st);
2584
2585 // Placeholders
2586 PlaceholderTable::print_on(st);
2587 st->cr();
2588
2589 // loader constraints - print under SD_lock
2590 LoaderConstraintTable::print_on(st);
2591 st->cr();
2592 }
2593
2594 void SystemDictionary::print() { print_on(tty); }
2595
2596 void SystemDictionary::verify() {
2597
2598 GCMutexLocker mu(SystemDictionary_lock);
2599
2600 // Verify dictionary
2601 ClassLoaderDataGraph::verify_dictionary();
2602
2603 // Verify constraint table
2604 LoaderConstraintTable::verify();
2605 }
2606
2607 void SystemDictionary::dump(outputStream *st, bool verbose) {
2608 assert_locked_or_safepoint(SystemDictionary_lock);
2609 if (verbose) {
2610 print_on(st);
2611 } else {
2612 CDS_ONLY(SystemDictionaryShared::print_table_statistics(st));
2613 ClassLoaderDataGraph::print_table_statistics(st);
2614 LoaderConstraintTable::print_table_statistics(st);
2615 }
2616 }
2617
2618 // Utility for dumping dictionaries.
2619 SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) :
2620 DCmdWithParser(output, heap),
2621 _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders",
2622 "BOOLEAN", false, "false") {
2623 _dcmdparser.add_dcmd_option(&_verbose);
2624 }
2625
2626 void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) {
2627 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict,
2628 _verbose.value());
2629 VMThread::execute(&dumper);
2630 }