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