/* * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "cds/aotClassLocation.hpp" #include "cds/cdsConfig.hpp" #include "cds/heapShared.hpp" #include "classfile/classFileParser.hpp" #include "classfile/classFileStream.hpp" #include "classfile/classLoader.hpp" #include "classfile/classLoaderData.inline.hpp" #include "classfile/classLoaderDataGraph.inline.hpp" #include "classfile/classLoaderExt.hpp" #include "classfile/classLoadInfo.hpp" #include "classfile/dictionary.hpp" #include "classfile/javaClasses.inline.hpp" #include "classfile/klassFactory.hpp" #include "classfile/loaderConstraints.hpp" #include "classfile/packageEntry.hpp" #include "classfile/placeholders.hpp" #include "classfile/resolutionErrors.hpp" #include "classfile/stringTable.hpp" #include "classfile/symbolTable.hpp" #include "classfile/systemDictionary.hpp" #include "classfile/vmClasses.hpp" #include "classfile/vmSymbols.hpp" #include "gc/shared/gcTraceTime.inline.hpp" #include "interpreter/bootstrapInfo.hpp" #include "jfr/jfrEvents.hpp" #include "jvm.h" #include "logging/log.hpp" #include "logging/logStream.hpp" #include "memory/metaspaceClosure.hpp" #include "memory/oopFactory.hpp" #include "memory/resourceArea.hpp" #include "memory/universe.hpp" #include "oops/access.inline.hpp" #include "oops/instanceKlass.hpp" #include "oops/klass.inline.hpp" #include "oops/method.inline.hpp" #include "oops/objArrayKlass.hpp" #include "oops/objArrayOop.inline.hpp" #include "oops/oop.inline.hpp" #include "oops/oop.hpp" #include "oops/oopHandle.hpp" #include "oops/oopHandle.inline.hpp" #include "oops/symbol.hpp" #include "oops/typeArrayKlass.hpp" #include "prims/jvmtiExport.hpp" #include "prims/methodHandles.hpp" #include "runtime/arguments.hpp" #include "runtime/atomic.hpp" #include "runtime/handles.inline.hpp" #include "runtime/java.hpp" #include "runtime/javaCalls.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/sharedRuntime.hpp" #include "runtime/signature.hpp" #include "runtime/synchronizer.hpp" #include "services/classLoadingService.hpp" #include "services/diagnosticCommand.hpp" #include "services/finalizerService.hpp" #include "services/threadService.hpp" #include "utilities/growableArray.hpp" #include "utilities/macros.hpp" #include "utilities/utf8.hpp" #if INCLUDE_CDS #include "classfile/systemDictionaryShared.hpp" #endif #if INCLUDE_JFR #include "jfr/jfr.hpp" #endif class InvokeMethodKey : public StackObj { private: Symbol* _symbol; intptr_t _iid; public: InvokeMethodKey(Symbol* symbol, intptr_t iid) : _symbol(symbol), _iid(iid) {} static bool key_comparison(InvokeMethodKey const &k1, InvokeMethodKey const &k2){ return k1._symbol == k2._symbol && k1._iid == k2._iid; } static unsigned int compute_hash(const InvokeMethodKey &k) { Symbol* sym = k._symbol; intptr_t iid = k._iid; unsigned int hash = (unsigned int) sym -> identity_hash(); return (unsigned int) (hash ^ iid); } }; using InvokeMethodIntrinsicTable = ResourceHashtable; static InvokeMethodIntrinsicTable* _invoke_method_intrinsic_table; using InvokeMethodTypeTable = ResourceHashtable; static InvokeMethodTypeTable* _invoke_method_type_table; OopHandle SystemDictionary::_java_system_loader; OopHandle SystemDictionary::_java_platform_loader; // ---------------------------------------------------------------------------- // Java-level SystemLoader and PlatformLoader oop SystemDictionary::java_system_loader() { return _java_system_loader.resolve(); } oop SystemDictionary::java_platform_loader() { return _java_platform_loader.resolve(); } void SystemDictionary::compute_java_loaders(TRAPS) { if (_java_platform_loader.is_empty()) { oop platform_loader = get_platform_class_loader_impl(CHECK); _java_platform_loader = OopHandle(Universe::vm_global(), platform_loader); } else { // It must have been restored from the archived module graph assert(CDSConfig::is_using_archive(), "must be"); assert(CDSConfig::is_using_full_module_graph(), "must be"); DEBUG_ONLY( oop platform_loader = get_platform_class_loader_impl(CHECK); assert(_java_platform_loader.resolve() == platform_loader, "must be"); ) } if (_java_system_loader.is_empty()) { oop system_loader = get_system_class_loader_impl(CHECK); _java_system_loader = OopHandle(Universe::vm_global(), system_loader); } else { // It must have been restored from the archived module graph assert(CDSConfig::is_using_archive(), "must be"); assert(CDSConfig::is_using_full_module_graph(), "must be"); DEBUG_ONLY( oop system_loader = get_system_class_loader_impl(CHECK); assert(_java_system_loader.resolve() == system_loader, "must be"); ) } } oop SystemDictionary::get_system_class_loader_impl(TRAPS) { JavaValue result(T_OBJECT); InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass(); JavaCalls::call_static(&result, class_loader_klass, vmSymbols::getSystemClassLoader_name(), vmSymbols::void_classloader_signature(), CHECK_NULL); return result.get_oop(); } oop SystemDictionary::get_platform_class_loader_impl(TRAPS) { JavaValue result(T_OBJECT); InstanceKlass* class_loader_klass = vmClasses::ClassLoader_klass(); JavaCalls::call_static(&result, class_loader_klass, vmSymbols::getPlatformClassLoader_name(), vmSymbols::void_classloader_signature(), CHECK_NULL); return result.get_oop(); } // Helper function inline ClassLoaderData* class_loader_data(Handle class_loader) { return ClassLoaderData::class_loader_data(class_loader()); } ClassLoaderData* SystemDictionary::register_loader(Handle class_loader, bool create_mirror_cld) { if (create_mirror_cld) { // Add a new class loader data to the graph. return ClassLoaderDataGraph::add(class_loader, true); } else { return (class_loader() == nullptr) ? ClassLoaderData::the_null_class_loader_data() : ClassLoaderDataGraph::find_or_create(class_loader); } } void SystemDictionary::set_system_loader(ClassLoaderData *cld) { assert(_java_system_loader.is_empty(), "already set!"); _java_system_loader = cld->class_loader_handle(); } void SystemDictionary::set_platform_loader(ClassLoaderData *cld) { assert(_java_platform_loader.is_empty(), "already set!"); _java_platform_loader = cld->class_loader_handle(); } // ---------------------------------------------------------------------------- // Parallel class loading check static bool is_parallelCapable(Handle class_loader) { if (class_loader.is_null()) return true; return java_lang_ClassLoader::parallelCapable(class_loader()); } // ---------------------------------------------------------------------------- // ParallelDefineClass flag does not apply to bootclass loader static bool is_parallelDefine(Handle class_loader) { if (class_loader.is_null()) return false; if (AllowParallelDefineClass && java_lang_ClassLoader::parallelCapable(class_loader())) { return true; } return false; } // Returns true if the passed class loader is the builtin application class loader // or a custom system class loader. A customer system class loader can be // specified via -Djava.system.class.loader. bool SystemDictionary::is_system_class_loader(oop class_loader) { if (class_loader == nullptr) { return false; } return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_AppClassLoader_klass() || class_loader == _java_system_loader.peek()); } // Returns true if the passed class loader is the platform class loader. bool SystemDictionary::is_platform_class_loader(oop class_loader) { if (class_loader == nullptr) { return false; } return (class_loader->klass() == vmClasses::jdk_internal_loader_ClassLoaders_PlatformClassLoader_klass()); } Handle SystemDictionary::get_loader_lock_or_null(Handle class_loader) { // If class_loader is null or parallelCapable, the JVM doesn't acquire a lock while loading. if (is_parallelCapable(class_loader)) { return Handle(); } else { return class_loader; } } // ---------------------------------------------------------------------------- // Resolving of classes Symbol* SystemDictionary::class_name_symbol(const char* name, Symbol* exception, TRAPS) { if (name == nullptr) { THROW_MSG_NULL(exception, "No class name given"); } size_t name_len = strlen(name); if (name_len > static_cast(Symbol::max_length())) { // It's impossible to create this class; the name cannot fit // into the constant pool. If necessary report an abridged name // in the exception message. if (name_len > static_cast(MaxStringPrintSize)) { Exceptions::fthrow(THREAD_AND_LOCATION, exception, "Class name exceeds maximum length of %d: %.*s ... (%zu characters omitted) ... %.*s", Symbol::max_length(), MaxStringPrintSize / 2, name, name_len - 2 * (MaxStringPrintSize / 2), // allows for odd value MaxStringPrintSize / 2, name + name_len - MaxStringPrintSize / 2); } else { Exceptions::fthrow(THREAD_AND_LOCATION, exception, "Class name exceeds maximum length of %d: %s", Symbol::max_length(), name); } return nullptr; } // Callers should ensure that the name is never an illegal UTF8 string. assert(UTF8::is_legal_utf8((const unsigned char*)name, name_len, false), "Class name is not a valid utf8 string."); // Make a new symbol for the class name. return SymbolTable::new_symbol(name); } #ifdef ASSERT // Used to verify that class loading succeeded in adding k to the dictionary. static void verify_dictionary_entry(Symbol* class_name, InstanceKlass* k) { MutexLocker mu(SystemDictionary_lock); ClassLoaderData* loader_data = k->class_loader_data(); Dictionary* dictionary = loader_data->dictionary(); assert(class_name == k->name(), "Must be the same"); InstanceKlass* kk = dictionary->find_class(JavaThread::current(), class_name); assert(kk == k, "should be present in dictionary"); } #endif static void handle_resolution_exception(Symbol* class_name, bool throw_error, TRAPS) { if (HAS_PENDING_EXCEPTION) { // If we have a pending exception we forward it to the caller, unless throw_error is true, // in which case we have to check whether the pending exception is a ClassNotFoundException, // and convert it to a NoClassDefFoundError and chain the original ClassNotFoundException. if (throw_error && PENDING_EXCEPTION->is_a(vmClasses::ClassNotFoundException_klass())) { ResourceMark rm(THREAD); Handle e(THREAD, PENDING_EXCEPTION); CLEAR_PENDING_EXCEPTION; THROW_MSG_CAUSE(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e); } else { return; // the caller will throw the incoming exception } } // If the class is not found, ie, caller has checked that klass is null, throw the appropriate // error or exception depending on the value of throw_error. ResourceMark rm(THREAD); if (throw_error) { THROW_MSG(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string()); } else { THROW_MSG(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string()); } } // Forwards to resolve_or_null Klass* SystemDictionary::resolve_or_fail(Symbol* class_name, Handle class_loader, bool throw_error, TRAPS) { Klass* klass = resolve_or_null(class_name, class_loader, THREAD); // Check for pending exception or null klass, and throw exception if (HAS_PENDING_EXCEPTION || klass == nullptr) { handle_resolution_exception(class_name, throw_error, CHECK_NULL); } return klass; } // Forwards to resolve_array_class_or_null or resolve_instance_class_or_null Klass* SystemDictionary::resolve_or_null(Symbol* class_name, Handle class_loader, TRAPS) { if (Signature::is_array(class_name)) { return resolve_array_class_or_null(class_name, class_loader, THREAD); } else { assert(class_name != nullptr && !Signature::is_array(class_name), "must be"); if (Signature::has_envelope(class_name)) { ResourceMark rm(THREAD); // Ignore wrapping L and ;. TempNewSymbol name = SymbolTable::new_symbol(class_name->as_C_string() + 1, class_name->utf8_length() - 2); return resolve_instance_class_or_null(name, class_loader, THREAD); } else { return resolve_instance_class_or_null(class_name, class_loader, THREAD); } } } // Forwards to resolve_instance_class_or_null Klass* SystemDictionary::resolve_array_class_or_null(Symbol* class_name, Handle class_loader, TRAPS) { assert(Signature::is_array(class_name), "must be array"); ResourceMark rm(THREAD); SignatureStream ss(class_name, false); int ndims = ss.skip_array_prefix(); // skip all '['s Klass* k = nullptr; BasicType t = ss.type(); if (ss.has_envelope()) { Symbol* obj_class = ss.as_symbol(); k = SystemDictionary::resolve_instance_class_or_null(obj_class, class_loader, CHECK_NULL); if (k != nullptr) { k = k->array_klass(ndims, CHECK_NULL); } } else { k = Universe::typeArrayKlass(t); k = k->array_klass(ndims, CHECK_NULL); } return k; } static inline void log_circularity_error(Symbol* name, PlaceholderEntry* probe) { LogTarget(Debug, class, load, placeholders) lt; if (lt.is_enabled()) { ResourceMark rm; LogStream ls(lt); ls.print("ClassCircularityError detected for placeholder entry %s", name->as_C_string()); probe->print_on(&ls); ls.cr(); } } // Must be called for any superclass or superinterface resolution // during class definition to allow class circularity checking // superinterface callers: // parse_interfaces - from defineClass // superclass callers: // ClassFileParser - from defineClass // load_shared_class - while loading a class from shared archive // resolve_instance_class_or_null: // via: handle_parallel_super_load // when resolving a class that has an existing placeholder with // a saved superclass [i.e. a defineClass is currently in progress] // If another thread is trying to resolve the class, it must do // superclass checks on its own thread to catch class circularity and // to avoid deadlock. // // resolve_with_circularity_detection adds a DETECT_CIRCULARITY placeholder to the placeholder table before calling // resolve_instance_class_or_null. ClassCircularityError is detected when a DETECT_CIRCULARITY or LOAD_INSTANCE // placeholder for the same thread, class, classloader is found. // This can be seen with logging option: -Xlog:class+load+placeholders=debug. // InstanceKlass* SystemDictionary::resolve_with_circularity_detection(Symbol* class_name, Symbol* next_name, Handle class_loader, bool is_superclass, TRAPS) { assert(next_name != nullptr, "null superclass for resolving"); assert(!Signature::is_array(next_name), "invalid superclass name"); ClassLoaderData* loader_data = class_loader_data(class_loader); if (is_superclass) { InstanceKlass* klassk = loader_data->dictionary()->find_class(THREAD, class_name); if (klassk != nullptr) { // We can come here for two reasons: // (a) RedefineClasses -- the class is already loaded // (b) Rarely, the class might have been loaded by a parallel thread // We can do a quick check against the already assigned superclass's name and loader. InstanceKlass* superk = klassk->java_super(); if (superk != nullptr && superk->name() == next_name && superk->class_loader() == class_loader()) { return superk; } } } // can't throw error holding a lock bool throw_circularity_error = false; { MutexLocker mu(THREAD, SystemDictionary_lock); // Must check ClassCircularity before resolving next_name (superclass or interface). PlaceholderEntry* probe = PlaceholderTable::get_entry(class_name, loader_data); if (probe != nullptr && probe->check_seen_thread(THREAD, PlaceholderTable::DETECT_CIRCULARITY)) { log_circularity_error(class_name, probe); throw_circularity_error = true; } // Make sure there's a placeholder for the class_name before resolving. // This is used as a claim that this thread is currently loading superclass/classloader // and for ClassCircularity checks. if (!throw_circularity_error) { // Be careful not to exit resolve_with_circularity_detection without removing this placeholder. PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(class_name, loader_data, PlaceholderTable::DETECT_CIRCULARITY, next_name, THREAD); } } if (throw_circularity_error) { ResourceMark rm(THREAD); THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), class_name->as_C_string()); } // Resolve the superclass or superinterface, check results on return InstanceKlass* superk = SystemDictionary::resolve_instance_class_or_null(next_name, class_loader, THREAD); // Clean up placeholder entry. { MutexLocker mu(THREAD, SystemDictionary_lock); PlaceholderTable::find_and_remove(class_name, loader_data, PlaceholderTable::DETECT_CIRCULARITY, THREAD); SystemDictionary_lock->notify_all(); } // Check for pending exception or null superk, and throw exception if (HAS_PENDING_EXCEPTION || superk == nullptr) { handle_resolution_exception(next_name, true, CHECK_NULL); } return superk; } // If the class in is in the placeholder table, class loading is in progress. // For cases where the application changes threads to load classes, it // is critical to ClassCircularity detection that we try loading // the superclass on the new thread internally, so we do parallel // superclass loading here. This avoids deadlock for ClassCircularity // detection for parallelCapable class loaders that lock on a per-class lock. static void handle_parallel_super_load(Symbol* name, Symbol* superclassname, Handle class_loader, TRAPS) { // The result superk is not used; resolve_with_circularity_detection is called for circularity check only. // This passes false to is_superclass to skip doing the unlikely optimization. Klass* superk = SystemDictionary::resolve_with_circularity_detection(name, superclassname, class_loader, false, CHECK); } // Bootstrap and non-parallel capable class loaders use the LOAD_INSTANCE placeholder to // wait for parallel class loading and/or to check for circularity error for Xcomp when loading. static bool needs_load_placeholder(Handle class_loader) { return class_loader.is_null() || !is_parallelCapable(class_loader); } // Check for other threads loading this class either to throw CCE or wait in the case of the boot loader. static InstanceKlass* handle_parallel_loading(JavaThread* current, Symbol* name, ClassLoaderData* loader_data, bool must_wait_for_class_loading, bool* throw_circularity_error) { PlaceholderEntry* oldprobe = PlaceholderTable::get_entry(name, loader_data); if (oldprobe != nullptr) { // -Xcomp calls load_signature_classes which might result in loading // a class that's already in the process of loading, so we detect CCE here also. // Only need check_seen_thread once, not on each loop if (oldprobe->check_seen_thread(current, PlaceholderTable::LOAD_INSTANCE)) { log_circularity_error(name, oldprobe); *throw_circularity_error = true; return nullptr; } else if (must_wait_for_class_loading) { // Wait until the first thread has finished loading this class. Also wait until all the // threads trying to load its superclass have removed their placeholders. while (oldprobe != nullptr && (oldprobe->instance_load_in_progress() || oldprobe->circularity_detection_in_progress())) { // LOAD_INSTANCE placeholders are used to implement parallel capable class loading // for the bootclass loader. SystemDictionary_lock->wait(); // Check if classloading completed while we were waiting InstanceKlass* check = loader_data->dictionary()->find_class(current, name); if (check != nullptr) { // Klass is already loaded, so just return it return check; } // check if other thread failed to load and cleaned up oldprobe = PlaceholderTable::get_entry(name, loader_data); } } } return nullptr; } void SystemDictionary::post_class_load_event(EventClassLoad* event, const InstanceKlass* k, const ClassLoaderData* init_cld) { assert(event != nullptr, "invariant"); assert(k != nullptr, "invariant"); event->set_loadedClass(k); event->set_definingClassLoader(k->class_loader_data()); event->set_initiatingClassLoader(init_cld); event->commit(); } // SystemDictionary::resolve_instance_class_or_null is the main function for class name resolution. // After checking if the InstanceKlass already exists, it checks for ClassCircularityError and // whether the thread must wait for loading in parallel. It eventually calls load_instance_class, // which will load the class via the bootstrap loader or call ClassLoader.loadClass(). // This can return null, an exception or an InstanceKlass. InstanceKlass* SystemDictionary::resolve_instance_class_or_null(Symbol* name, Handle class_loader, TRAPS) { // name must be in the form of "java/lang/Object" -- cannot be "Ljava/lang/Object;" DEBUG_ONLY(ResourceMark rm(THREAD)); assert(name != nullptr && !Signature::is_array(name) && !Signature::has_envelope(name), "invalid class name: %s", name == nullptr ? "nullptr" : name->as_C_string()); EventClassLoad class_load_start_event; HandleMark hm(THREAD); ClassLoaderData* loader_data = register_loader(class_loader); Dictionary* dictionary = loader_data->dictionary(); // Do lookup to see if class already exists. InstanceKlass* probe = dictionary->find_class(THREAD, name); if (probe != nullptr) return probe; // Non-bootstrap class loaders will call out to class loader and // define via jvm/jni_DefineClass which will acquire the // class loader object lock to protect against multiple threads // defining the class in parallel by accident. // This lock must be acquired here so the waiter will find // any successful result in the SystemDictionary and not attempt // the define. // ParallelCapable class loaders and the bootstrap classloader // do not acquire lock here. Handle lockObject = get_loader_lock_or_null(class_loader); ObjectLocker ol(lockObject, THREAD); bool circularity_detection_in_progress = false; InstanceKlass* loaded_class = nullptr; SymbolHandle superclassname; // Keep alive while loading in parallel thread. guarantee(THREAD->can_call_java(), "can not load classes with compiler thread: class=%s, classloader=%s", name->as_C_string(), class_loader.is_null() ? "null" : class_loader->klass()->name()->as_C_string()); // Check again (after locking) if the class already exists in SystemDictionary { MutexLocker mu(THREAD, SystemDictionary_lock); InstanceKlass* check = dictionary->find_class(THREAD, name); if (check != nullptr) { // InstanceKlass is already loaded, but we still need to check protection domain below. loaded_class = check; } else { PlaceholderEntry* placeholder = PlaceholderTable::get_entry(name, loader_data); if (placeholder != nullptr && placeholder->circularity_detection_in_progress()) { circularity_detection_in_progress = true; superclassname = placeholder->next_klass_name(); assert(superclassname != nullptr, "superclass has to have a name"); } } } // If the class is in the placeholder table with super_class set, // handle superclass loading in progress. if (circularity_detection_in_progress) { handle_parallel_super_load(name, superclassname, class_loader, CHECK_NULL); } bool throw_circularity_error = false; if (loaded_class == nullptr) { bool load_placeholder_added = false; // Add placeholder entry to record loading instance class // case 1. Bootstrap classloader // This classloader supports parallelism at the classloader level // but only allows a single thread to load a class/classloader pair. // The LOAD_INSTANCE placeholder is the mechanism for mutual exclusion. // case 2. parallelCapable user level classloaders // These class loaders lock a per-class object lock when ClassLoader.loadClass() // is called. A LOAD_INSTANCE placeholder isn't used for mutual exclusion. // case 3. traditional classloaders that rely on the classloader object lock // There should be no need for need for LOAD_INSTANCE for mutual exclusion, // except the LOAD_INSTANCE placeholder is used to detect CCE for -Xcomp. // TODO: should also be used to detect CCE for parallel capable class loaders but it's not. { MutexLocker mu(THREAD, SystemDictionary_lock); if (needs_load_placeholder(class_loader)) { loaded_class = handle_parallel_loading(THREAD, name, loader_data, class_loader.is_null(), &throw_circularity_error); } // Recheck if the class has been loaded for all class loader cases and // add a LOAD_INSTANCE placeholder while holding the SystemDictionary_lock. if (!throw_circularity_error && loaded_class == nullptr) { InstanceKlass* check = dictionary->find_class(THREAD, name); if (check != nullptr) { loaded_class = check; } else if (needs_load_placeholder(class_loader)) { // Add the LOAD_INSTANCE token. Threads will wait on loading to complete for this thread. PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(name, loader_data, PlaceholderTable::LOAD_INSTANCE, nullptr, THREAD); load_placeholder_added = true; } } } // Must throw error outside of owning lock if (throw_circularity_error) { assert(!HAS_PENDING_EXCEPTION && !load_placeholder_added, "circularity error cleanup"); ResourceMark rm(THREAD); THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string()); } // Be careful when modifying this code: once you have run // PlaceholderTable::find_and_add(PlaceholderTable::LOAD_INSTANCE), // you need to find_and_remove it before returning. // So be careful to not exit with a CHECK_ macro between these calls. if (loaded_class == nullptr) { // Do actual loading loaded_class = load_instance_class(name, class_loader, THREAD); } if (load_placeholder_added) { // clean up placeholder entries for LOAD_INSTANCE success or error // This brackets the SystemDictionary updates for both defining // and initiating loaders MutexLocker mu(THREAD, SystemDictionary_lock); PlaceholderTable::find_and_remove(name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD); SystemDictionary_lock->notify_all(); } } if (HAS_PENDING_EXCEPTION || loaded_class == nullptr) { return nullptr; } if (class_load_start_event.should_commit()) { post_class_load_event(&class_load_start_event, loaded_class, loader_data); } // Make sure we have the right class in the dictionary DEBUG_ONLY(verify_dictionary_entry(name, loaded_class)); return loaded_class; } // This routine does not lock the system dictionary. // // Since readers don't hold a lock, we must make sure that system // dictionary entries are added to in a safe way (all links must // be updated in an MT-safe manner). All entries are removed during class // unloading, when this class loader is no longer referenced. // // Callers should be aware that an entry could be added just after // Dictionary is read here, so the caller will not see // the new entry. InstanceKlass* SystemDictionary::find_instance_klass(Thread* current, Symbol* class_name, Handle class_loader) { ClassLoaderData* loader_data = ClassLoaderData::class_loader_data_or_null(class_loader()); if (loader_data == nullptr) { // If the ClassLoaderData has not been setup, // then the class loader has no entries in the dictionary. return nullptr; } Dictionary* dictionary = loader_data->dictionary(); return dictionary->find_class(current, class_name); } // Look for a loaded instance or array klass by name. Do not do any loading. // return null in case of error. Klass* SystemDictionary::find_instance_or_array_klass(Thread* current, Symbol* class_name, Handle class_loader) { Klass* k = nullptr; assert(class_name != nullptr, "class name must be non nullptr"); if (Signature::is_array(class_name)) { // The name refers to an array. Parse the name. // dimension and object_key in FieldArrayInfo are assigned as a // side-effect of this call SignatureStream ss(class_name, false); int ndims = ss.skip_array_prefix(); // skip all '['s BasicType t = ss.type(); if (t != T_OBJECT) { k = Universe::typeArrayKlass(t); } else { k = SystemDictionary::find_instance_klass(current, ss.as_symbol(), class_loader); } if (k != nullptr) { k = k->array_klass_or_null(ndims); } } else { k = find_instance_klass(current, class_name, class_loader); } return k; } // Note: this method is much like resolve_class_from_stream, but // does not publish the classes in the SystemDictionary. // Handles Lookup.defineClass hidden. InstanceKlass* SystemDictionary::resolve_hidden_class_from_stream( ClassFileStream* st, Symbol* class_name, Handle class_loader, const ClassLoadInfo& cl_info, TRAPS) { EventClassLoad class_load_start_event; ClassLoaderData* loader_data; // - for hidden classes that are not strong: create a new CLD that has a class holder and // whose loader is the Lookup class's loader. // - for hidden class: add the class to the Lookup class's loader's CLD. assert (cl_info.is_hidden(), "only used for hidden classes"); bool create_mirror_cld = !cl_info.is_strong_hidden(); loader_data = register_loader(class_loader, create_mirror_cld); assert(st != nullptr, "invariant"); // Parse stream and create a klass. InstanceKlass* k = KlassFactory::create_from_stream(st, class_name, loader_data, cl_info, CHECK_NULL); assert(k != nullptr, "no klass created"); // Hidden classes that are not strong must update ClassLoaderData holder // so that they can be unloaded when the mirror is no longer referenced. if (!cl_info.is_strong_hidden()) { k->class_loader_data()->initialize_holder(Handle(THREAD, k->java_mirror())); } // Add to class hierarchy, and do possible deoptimizations. k->add_to_hierarchy(THREAD); // But, do not add to dictionary. k->link_class(CHECK_NULL); // notify jvmti if (JvmtiExport::should_post_class_load()) { JvmtiExport::post_class_load(THREAD, k); } if (class_load_start_event.should_commit()) { post_class_load_event(&class_load_start_event, k, loader_data); } return k; } // Add a klass to the system from a stream (called by jni_DefineClass and // JVM_DefineClass). // Note: class_name can be null. In that case we do not know the name of // the class until we have parsed the stream. // This function either returns an InstanceKlass or throws an exception. It does // not return null without a pending exception. InstanceKlass* SystemDictionary::resolve_class_from_stream( ClassFileStream* st, Symbol* class_name, Handle class_loader, const ClassLoadInfo& cl_info, TRAPS) { HandleMark hm(THREAD); ClassLoaderData* loader_data = register_loader(class_loader); // Classloaders that support parallelism, e.g. bootstrap classloader, // do not acquire lock here Handle lockObject = get_loader_lock_or_null(class_loader); ObjectLocker ol(lockObject, THREAD); // Parse the stream and create a klass. // Note that we do this even though this klass might // already be present in the SystemDictionary, otherwise we would not // throw potential ClassFormatErrors. InstanceKlass* k = nullptr; #if INCLUDE_CDS if (!CDSConfig::is_dumping_static_archive()) { k = SystemDictionaryShared::lookup_from_stream(class_name, class_loader, cl_info.protection_domain(), st, CHECK_NULL); } #endif if (k == nullptr) { k = KlassFactory::create_from_stream(st, class_name, loader_data, cl_info, CHECK_NULL); } assert(k != nullptr, "no klass created"); Symbol* h_name = k->name(); assert(class_name == nullptr || class_name == h_name, "name mismatch"); // Add class just loaded // If a class loader supports parallel classloading, handle parallel define requests. // find_or_define_instance_class may return a different InstanceKlass, // in which case the old k would be deallocated if (is_parallelCapable(class_loader)) { k = find_or_define_instance_class(h_name, class_loader, k, CHECK_NULL); } else { define_instance_class(k, class_loader, THREAD); // If defining the class throws an exception register 'k' for cleanup. if (HAS_PENDING_EXCEPTION) { assert(k != nullptr, "Must have an instance klass here!"); loader_data->add_to_deallocate_list(k); return nullptr; } } // Make sure we have an entry in the SystemDictionary on success DEBUG_ONLY(verify_dictionary_entry(h_name, k)); return k; } InstanceKlass* SystemDictionary::resolve_from_stream(ClassFileStream* st, Symbol* class_name, Handle class_loader, const ClassLoadInfo& cl_info, TRAPS) { if (cl_info.is_hidden()) { return resolve_hidden_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL); } else { return resolve_class_from_stream(st, class_name, class_loader, cl_info, CHECK_NULL); } } #if INCLUDE_CDS // Check if a shared class can be loaded by the specific classloader. bool SystemDictionary::is_shared_class_visible(Symbol* class_name, InstanceKlass* ik, PackageEntry* pkg_entry, Handle class_loader) { assert(!ModuleEntryTable::javabase_moduleEntry()->is_patched(), "Cannot use sharing if java.base is patched"); // (1) Check if we are loading into the same loader as in dump time. if (ik->defined_by_boot_loader()) { if (class_loader() != nullptr) { return false; } } else if (ik->defined_by_platform_loader()) { if (class_loader() != java_platform_loader()) { return false; } } else if (ik->defined_by_app_loader()) { if (class_loader() != java_system_loader()) { return false; } } else { // ik was loaded by a custom loader during dump time if (class_loader_data(class_loader)->is_builtin_class_loader_data()) { return false; } else { return true; } } // (2) Check if we are loading into the same module from the same location as in dump time. if (CDSConfig::is_using_optimized_module_handling()) { // Class visibility has not changed between dump time and run time, so a class // that was visible (and thus archived) during dump time is always visible during runtime. assert(SystemDictionary::is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader), "visibility cannot change between dump time and runtime"); return true; } return is_shared_class_visible_impl(class_name, ik, pkg_entry, class_loader); } bool SystemDictionary::is_shared_class_visible_impl(Symbol* class_name, InstanceKlass* ik, PackageEntry* pkg_entry, Handle class_loader) { int scp_index = ik->shared_classpath_index(); assert(!ik->defined_by_other_loaders(), "this function should be called for built-in classes only"); assert(scp_index >= 0, "must be"); const AOTClassLocation* cl = AOTClassLocationConfig::runtime()->class_location_at(scp_index); if (!Universe::is_module_initialized()) { assert(cl != nullptr, "must be"); // At this point, no modules have been defined yet. KlassSubGraphInfo::check_allowed_klass() // has restricted the classes can be loaded at this step to be only: // [1] cs->is_modules_image(): classes in java.base, or, // [2] HeapShared::is_a_test_class_in_unnamed_module(ik): classes in bootstrap/unnamed module assert(cl->is_modules_image() || HeapShared::is_a_test_class_in_unnamed_module(ik), "only these classes can be loaded before the module system is initialized"); assert(class_loader.is_null(), "sanity"); return true; } if (pkg_entry == nullptr) { // We might have looked up pkg_entry before the module system was initialized. // Need to reload it now. TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name); if (pkg_name != nullptr) { pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name); } } ModuleEntry* mod_entry = (pkg_entry == nullptr) ? nullptr : pkg_entry->module(); bool should_be_in_named_module = (mod_entry != nullptr && mod_entry->is_named()); bool was_archived_from_named_module = !cl->has_unnamed_module(); bool visible; if (was_archived_from_named_module) { if (should_be_in_named_module) { // Is the module loaded from the same location as during dump time? visible = mod_entry->shared_path_index() == scp_index; if (visible) { assert(!mod_entry->is_patched(), "cannot load archived classes for patched module"); } } else { // During dump time, this class was in a named module, but at run time, this class should be // in an unnamed module. visible = false; } } else { if (should_be_in_named_module) { // During dump time, this class was in an unnamed, but at run time, this class should be // in a named module. visible = false; } else { visible = true; } } return visible; } bool SystemDictionary::check_shared_class_super_type(InstanceKlass* klass, InstanceKlass* super_type, Handle class_loader, bool is_superclass, TRAPS) { assert(super_type->is_shared(), "must be"); // Quick check if the super type has been already loaded. // + Don't do it for unregistered classes -- they can be unloaded so // super_type->class_loader_data() could be stale. // + Don't check if loader data is null, ie. the super_type isn't fully loaded. if (!super_type->defined_by_other_loaders() && super_type->class_loader_data() != nullptr) { // Check if the superclass is loaded by the current class_loader Symbol* name = super_type->name(); InstanceKlass* check = find_instance_klass(THREAD, name, class_loader); if (check == super_type) { return true; } } Klass *found = resolve_with_circularity_detection(klass->name(), super_type->name(), class_loader, is_superclass, CHECK_false); if (found == super_type) { return true; } else { // The dynamically resolved super type is not the same as the one we used during dump time, // so we cannot use the class. return false; } } bool SystemDictionary::check_shared_class_super_types(InstanceKlass* ik, Handle class_loader, TRAPS) { // Check the superclass and interfaces. They must be the same // as in dump time, because the layout of depends on // the specific layout of ik->super() and ik->local_interfaces(). // // If unexpected superclass or interfaces are found, we cannot // load from the shared archive. if (ik->super() != nullptr) { bool check_super = check_shared_class_super_type(ik, InstanceKlass::cast(ik->super()), class_loader, true, CHECK_false); if (!check_super) { return false; } } Array* interfaces = ik->local_interfaces(); int num_interfaces = interfaces->length(); for (int index = 0; index < num_interfaces; index++) { bool check_interface = check_shared_class_super_type(ik, interfaces->at(index), class_loader, false, CHECK_false); if (!check_interface) { return false; } } return true; } InstanceKlass* SystemDictionary::load_shared_class(InstanceKlass* ik, Handle class_loader, Handle protection_domain, const ClassFileStream *cfs, PackageEntry* pkg_entry, TRAPS) { assert(ik != nullptr, "sanity"); assert(ik->is_shared(), "sanity"); assert(!ik->is_unshareable_info_restored(), "shared class can be restored only once"); assert(Atomic::add(&ik->_shared_class_load_count, 1) == 1, "shared class loaded more than once"); Symbol* class_name = ik->name(); if (!is_shared_class_visible(class_name, ik, pkg_entry, class_loader)) { ik->set_shared_loading_failed(); return nullptr; } bool check = check_shared_class_super_types(ik, class_loader, CHECK_NULL); if (!check) { ik->set_shared_loading_failed(); return nullptr; } InstanceKlass* new_ik = nullptr; // CFLH check is skipped for VM hidden classes (see KlassFactory::create_from_stream). // It will be skipped for shared VM hidden lambda proxy classes. if (!ik->is_hidden()) { new_ik = KlassFactory::check_shared_class_file_load_hook( ik, class_name, class_loader, protection_domain, cfs, CHECK_NULL); } if (new_ik != nullptr) { // The class is changed by CFLH. Return the new class. The shared class is // not used. return new_ik; } // Adjust methods to recover missing data. They need addresses for // interpreter entry points and their default native method address // must be reset. // Shared classes are all currently loaded by either the bootstrap or // internal parallel class loaders, so this will never cause a deadlock // on a custom class loader lock. // Since this class is already locked with parallel capable class // loaders, including the bootstrap loader via the placeholder table, // this lock is currently a nop. ClassLoaderData* loader_data = class_loader_data(class_loader); { HandleMark hm(THREAD); Handle lockObject = get_loader_lock_or_null(class_loader); ObjectLocker ol(lockObject, THREAD); // prohibited package check assumes all classes loaded from archive call // restore_unshareable_info which calls ik->set_package() ik->restore_unshareable_info(loader_data, protection_domain, pkg_entry, CHECK_NULL); } load_shared_class_misc(ik, loader_data); return ik; } void SystemDictionary::load_shared_class_misc(InstanceKlass* ik, ClassLoaderData* loader_data) { ik->print_class_load_logging(loader_data, nullptr, nullptr); // For boot loader, ensure that GetSystemPackage knows that a class in this // package was loaded. if (loader_data->is_the_null_class_loader_data()) { s2 path_index = ik->shared_classpath_index(); ik->set_classpath_index(path_index); } // notify a class loaded from shared object ClassLoadingService::notify_class_loaded(ik, true /* shared class */); if (CDSConfig::is_dumping_final_static_archive()) { SystemDictionaryShared::init_dumptime_info_from_preimage(ik); } } #endif // INCLUDE_CDS InstanceKlass* SystemDictionary::load_instance_class_impl(Symbol* class_name, Handle class_loader, TRAPS) { if (class_loader.is_null()) { ResourceMark rm(THREAD); PackageEntry* pkg_entry = nullptr; bool search_only_bootloader_append = false; // Find the package in the boot loader's package entry table. TempNewSymbol pkg_name = ClassLoader::package_from_class_name(class_name); if (pkg_name != nullptr) { pkg_entry = class_loader_data(class_loader)->packages()->lookup_only(pkg_name); } // Prior to attempting to load the class, enforce the boot loader's // visibility boundaries. if (!Universe::is_module_initialized()) { // During bootstrapping, prior to module initialization, any // class attempting to be loaded must be checked against the // java.base packages in the boot loader's PackageEntryTable. // No class outside of java.base is allowed to be loaded during // this bootstrapping window. if (pkg_entry == nullptr || pkg_entry->in_unnamed_module()) { // Class is either in the unnamed package or in // a named package within the unnamed module. Either // case is outside of java.base, do not attempt to // load the class post java.base definition. If // java.base has not been defined, let the class load // and its package will be checked later by // ModuleEntryTable::verify_javabase_packages. if (ModuleEntryTable::javabase_defined()) { return nullptr; } } else { // Check that the class' package is defined within java.base. ModuleEntry* mod_entry = pkg_entry->module(); Symbol* mod_entry_name = mod_entry->name(); if (mod_entry_name->fast_compare(vmSymbols::java_base()) != 0) { return nullptr; } } } else { // After the module system has been initialized, check if the class' // package is in a module defined to the boot loader. if (pkg_name == nullptr || pkg_entry == nullptr || pkg_entry->in_unnamed_module()) { // Class is either in the unnamed package, in a named package // within a module not defined to the boot loader or in a // a named package within the unnamed module. In all cases, // limit visibility to search for the class only in the boot // loader's append path. if (!ClassLoader::has_bootclasspath_append()) { // If there is no bootclasspath append entry, no need to continue // searching. return nullptr; } search_only_bootloader_append = true; } } // Prior to bootstrapping's module initialization, never load a class outside // of the boot loader's module path assert(Universe::is_module_initialized() || !search_only_bootloader_append, "Attempt to load a class outside of boot loader's module path"); // Search for classes in the CDS archive. InstanceKlass* k = nullptr; #if INCLUDE_CDS if (CDSConfig::is_using_archive()) { PerfTraceTime vmtimer(ClassLoader::perf_shared_classload_time()); InstanceKlass* ik = SystemDictionaryShared::find_builtin_class(class_name); if (ik != nullptr && ik->defined_by_boot_loader() && !ik->shared_loading_failed()) { SharedClassLoadingMark slm(THREAD, ik); k = load_shared_class(ik, class_loader, Handle(), nullptr, pkg_entry, CHECK_NULL); } } #endif if (k == nullptr) { // Use VM class loader PerfTraceTime vmtimer(ClassLoader::perf_sys_classload_time()); k = ClassLoader::load_class(class_name, pkg_entry, search_only_bootloader_append, CHECK_NULL); } // find_or_define_instance_class may return a different InstanceKlass if (k != nullptr) { CDS_ONLY(SharedClassLoadingMark slm(THREAD, k);) k = find_or_define_instance_class(class_name, class_loader, k, CHECK_NULL); } return k; } else { // Use user specified class loader to load class. Call loadClass operation on class_loader. ResourceMark rm(THREAD); JavaThread* jt = THREAD; PerfClassTraceTime vmtimer(ClassLoader::perf_app_classload_time(), ClassLoader::perf_app_classload_selftime(), ClassLoader::perf_app_classload_count(), jt->get_thread_stat()->perf_recursion_counts_addr(), jt->get_thread_stat()->perf_timers_addr(), PerfClassTraceTime::CLASS_LOAD); // Translate to external class name format, i.e., convert '/' chars to '.' Handle string = java_lang_String::externalize_classname(class_name, CHECK_NULL); JavaValue result(T_OBJECT); InstanceKlass* spec_klass = vmClasses::ClassLoader_klass(); // Call public unsynchronized loadClass(String) directly for all class loaders. // For parallelCapable class loaders, JDK >=7, loadClass(String, boolean) will // acquire a class-name based lock rather than the class loader object lock. // JDK < 7 already acquire the class loader lock in loadClass(String, boolean). JavaCalls::call_virtual(&result, class_loader, spec_klass, vmSymbols::loadClass_name(), vmSymbols::string_class_signature(), string, CHECK_NULL); assert(result.get_type() == T_OBJECT, "just checking"); oop obj = result.get_oop(); // Primitive classes return null since forName() can not be // used to obtain any of the Class objects representing primitives or void if ((obj != nullptr) && !(java_lang_Class::is_primitive(obj))) { InstanceKlass* k = InstanceKlass::cast(java_lang_Class::as_Klass(obj)); // For user defined Java class loaders, check that the name returned is // the same as that requested. This check is done for the bootstrap // loader when parsing the class file. if (class_name == k->name()) { return k; } } // Class is not found or has the wrong name, return null return nullptr; } } InstanceKlass* SystemDictionary::load_instance_class(Symbol* name, Handle class_loader, TRAPS) { InstanceKlass* loaded_class = load_instance_class_impl(name, class_loader, CHECK_NULL); // If everything was OK (no exceptions, no null return value), and // class_loader is NOT the defining loader, do a little more bookkeeping. if (loaded_class != nullptr && loaded_class->class_loader() != class_loader()) { ClassLoaderData* loader_data = class_loader_data(class_loader); check_constraints(loaded_class, loader_data, false, CHECK_NULL); // Record dependency for non-parent delegation. // This recording keeps the defining class loader of the klass (loaded_class) found // from being unloaded while the initiating class loader is loaded // even if the reference to the defining class loader is dropped // before references to the initiating class loader. loader_data->record_dependency(loaded_class); update_dictionary(THREAD, loaded_class, loader_data); if (JvmtiExport::should_post_class_load()) { JvmtiExport::post_class_load(THREAD, loaded_class); } } return loaded_class; } static void post_class_define_event(InstanceKlass* k, const ClassLoaderData* def_cld) { EventClassDefine event; if (event.should_commit()) { event.set_definedClass(k); event.set_definingClassLoader(def_cld); event.commit(); } } void SystemDictionary::define_instance_class(InstanceKlass* k, Handle class_loader, TRAPS) { ClassLoaderData* loader_data = k->class_loader_data(); assert(loader_data->class_loader() == class_loader(), "they must be the same"); // Bootstrap and other parallel classloaders don't acquire a lock, // they use placeholder token. // If a parallelCapable class loader calls define_instance_class instead of // find_or_define_instance_class to get here, we have a timing // hole with systemDictionary updates and check_constraints if (!is_parallelCapable(class_loader)) { assert(ObjectSynchronizer::current_thread_holds_lock(THREAD, get_loader_lock_or_null(class_loader)), "define called without lock"); } // Check class-loading constraints. Throw exception if violation is detected. // Grabs and releases SystemDictionary_lock // The check_constraints/find_class call and update_dictionary sequence // must be "atomic" for a specific class/classloader pair so we never // define two different instanceKlasses for that class/classloader pair. // Existing classloaders will call define_instance_class with the // classloader lock held // Parallel classloaders will call find_or_define_instance_class // which will require a token to perform the define class check_constraints(k, loader_data, true, CHECK); // Register class just loaded with class loader (placed in ArrayList) // Note we do this before updating the dictionary, as this can // fail with an OutOfMemoryError (if it does, we will *not* put this // class in the dictionary and will not update the class hierarchy). // JVMTI FollowReferences needs to find the classes this way. if (k->class_loader() != nullptr) { methodHandle m(THREAD, Universe::loader_addClass_method()); JavaValue result(T_VOID); JavaCallArguments args(class_loader); args.push_oop(Handle(THREAD, k->java_mirror())); JavaCalls::call(&result, m, &args, CHECK); } // Add to class hierarchy, and do possible deoptimizations. k->add_to_hierarchy(THREAD); // Add to systemDictionary - so other classes can see it. // Grabs and releases SystemDictionary_lock update_dictionary(THREAD, k, loader_data); // notify jvmti if (JvmtiExport::should_post_class_load()) { JvmtiExport::post_class_load(THREAD, k); } post_class_define_event(k, loader_data); } // Support parallel classloading // All parallel class loaders, including bootstrap classloader // lock a placeholder entry for this class/class_loader pair // to allow parallel defines of different classes for this class loader // With AllowParallelDefine flag==true, in case they do not synchronize around // FindLoadedClass/DefineClass, calls, we check for parallel // loading for them, wait if a defineClass is in progress // and return the initial requestor's results // This flag does not apply to the bootstrap classloader. // With AllowParallelDefine flag==false, call through to define_instance_class // which will throw LinkageError: duplicate class definition. // False is the requested default. // For better performance, the class loaders should synchronize // findClass(), i.e. FindLoadedClass/DefineClassIfAbsent or they // potentially waste time reading and parsing the bytestream. // Note: VM callers should ensure consistency of k/class_name,class_loader // Be careful when modifying this code: once you have run // PlaceholderTable::find_and_add(PlaceholderTable::DEFINE_CLASS), // you need to find_and_remove it before returning. // So be careful to not exit with a CHECK_ macro between these calls. InstanceKlass* SystemDictionary::find_or_define_helper(Symbol* class_name, Handle class_loader, InstanceKlass* k, TRAPS) { Symbol* name_h = k->name(); ClassLoaderData* loader_data = class_loader_data(class_loader); Dictionary* dictionary = loader_data->dictionary(); // Hold SD lock around find_class and placeholder creation for DEFINE_CLASS { MutexLocker mu(THREAD, SystemDictionary_lock); // First check if class already defined if (is_parallelDefine(class_loader)) { InstanceKlass* check = dictionary->find_class(THREAD, name_h); if (check != nullptr) { return check; } } // Acquire define token for this class/classloader PlaceholderEntry* probe = PlaceholderTable::find_and_add(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, nullptr, THREAD); // Wait if another thread defining in parallel // All threads wait - even those that will throw duplicate class: otherwise // caller is surprised by LinkageError: duplicate, but findLoadedClass fails // if other thread has not finished updating dictionary while (probe->definer() != nullptr) { SystemDictionary_lock->wait(); } // Only special cases allow parallel defines and can use other thread's results // Other cases fall through, and may run into duplicate defines // caught by finding an entry in the SystemDictionary if (is_parallelDefine(class_loader) && (probe->instance_klass() != nullptr)) { InstanceKlass* ik = probe->instance_klass(); PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD); SystemDictionary_lock->notify_all(); #ifdef ASSERT InstanceKlass* check = dictionary->find_class(THREAD, name_h); assert(check != nullptr, "definer missed recording success"); #endif return ik; } else { // This thread will define the class (even if earlier thread tried and had an error) probe->set_definer(THREAD); } } define_instance_class(k, class_loader, THREAD); // definer must notify any waiting threads { MutexLocker mu(THREAD, SystemDictionary_lock); PlaceholderEntry* probe = PlaceholderTable::get_entry(name_h, loader_data); assert(probe != nullptr, "DEFINE_CLASS placeholder lost?"); if (!HAS_PENDING_EXCEPTION) { probe->set_instance_klass(k); } probe->set_definer(nullptr); PlaceholderTable::find_and_remove(name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD); SystemDictionary_lock->notify_all(); } return HAS_PENDING_EXCEPTION ? nullptr : k; } // If a class loader supports parallel classloading handle parallel define requests. // find_or_define_instance_class may return a different InstanceKlass InstanceKlass* SystemDictionary::find_or_define_instance_class(Symbol* class_name, Handle class_loader, InstanceKlass* k, TRAPS) { InstanceKlass* defined_k = find_or_define_helper(class_name, class_loader, k, THREAD); // Clean up original InstanceKlass if duplicate or error if (!HAS_PENDING_EXCEPTION && defined_k != k) { // If a parallel capable class loader already defined this class, register 'k' for cleanup. assert(defined_k != nullptr, "Should have a klass if there's no exception"); k->class_loader_data()->add_to_deallocate_list(k); } else if (HAS_PENDING_EXCEPTION) { // Remove this InstanceKlass from the LoaderConstraintTable if added. LoaderConstraintTable::remove_failed_loaded_klass(k, class_loader_data(class_loader)); assert(defined_k == nullptr, "Should not have a klass if there's an exception"); k->class_loader_data()->add_to_deallocate_list(k); } return defined_k; } // ---------------------------------------------------------------------------- // GC support // Assumes classes in the SystemDictionary are only unloaded at a safepoint bool SystemDictionary::do_unloading(GCTimer* gc_timer) { bool unloading_occurred; bool is_concurrent = !SafepointSynchronize::is_at_safepoint(); { GCTraceTime(Debug, gc, phases) t("ClassLoaderData", gc_timer); assert_locked_or_safepoint(ClassLoaderDataGraph_lock); // caller locks. // First, mark for unload all ClassLoaderData referencing a dead class loader. unloading_occurred = ClassLoaderDataGraph::do_unloading(); if (unloading_occurred) { ConditionalMutexLocker ml2(Module_lock, is_concurrent); JFR_ONLY(Jfr::on_unloading_classes();) MANAGEMENT_ONLY(FinalizerService::purge_unloaded();) ConditionalMutexLocker ml1(SystemDictionary_lock, is_concurrent); ClassLoaderDataGraph::clean_module_and_package_info(); LoaderConstraintTable::purge_loader_constraints(); ResolutionErrorTable::purge_resolution_errors(); } } GCTraceTime(Debug, gc, phases) t("Trigger cleanups", gc_timer); if (unloading_occurred) { SymbolTable::trigger_cleanup(); ConditionalMutexLocker ml(ClassInitError_lock, is_concurrent); InstanceKlass::clean_initialization_error_table(); } return unloading_occurred; } void SystemDictionary::methods_do(void f(Method*)) { // Walk methods in loaded classes { MutexLocker ml(ClassLoaderDataGraph_lock); ClassLoaderDataGraph::methods_do(f); } auto doit = [&] (InvokeMethodKey key, Method* method) { if (method != nullptr) { f(method); } }; { MutexLocker ml(InvokeMethodIntrinsicTable_lock); _invoke_method_intrinsic_table->iterate_all(doit); } } // ---------------------------------------------------------------------------- // Initialization void SystemDictionary::initialize(TRAPS) { _invoke_method_intrinsic_table = new (mtClass) InvokeMethodIntrinsicTable(); _invoke_method_type_table = new (mtClass) InvokeMethodTypeTable(); ResolutionErrorTable::initialize(); LoaderConstraintTable::initialize(); PlaceholderTable::initialize(); #if INCLUDE_CDS SystemDictionaryShared::initialize(); if (CDSConfig::is_dumping_archive()) { AOTClassLocationConfig::dumptime_init(THREAD); } #endif // Resolve basic classes vmClasses::resolve_all(CHECK); // Resolve classes used by archived heap objects if (CDSConfig::is_using_archive()) { HeapShared::resolve_classes(THREAD); } } // Constraints on class loaders. The details of the algorithm can be // found in the OOPSLA'98 paper "Dynamic Class Loading in the Java // Virtual Machine" by Sheng Liang and Gilad Bracha. The basic idea is // that the dictionary needs to maintain a set of constraints that // must be satisfied by all classes in the dictionary. // if defining is true, then LinkageError if already in dictionary // if initiating loader, then ok if InstanceKlass matches existing entry void SystemDictionary::check_constraints(InstanceKlass* k, ClassLoaderData* loader_data, bool defining, TRAPS) { ResourceMark rm(THREAD); stringStream ss; bool throwException = false; { Symbol* name = k->name(); MutexLocker mu(THREAD, SystemDictionary_lock); InstanceKlass* check = loader_data->dictionary()->find_class(THREAD, name); if (check != nullptr) { // If different InstanceKlass - duplicate class definition, // else - ok, class loaded by a different thread in parallel. // We should only have found it if it was done loading and ok to use. if ((defining == true) || (k != check)) { throwException = true; ss.print("loader %s", loader_data->loader_name_and_id()); ss.print(" attempted duplicate %s definition for %s. (%s)", k->external_kind(), k->external_name(), k->class_in_module_of_loader(false, true)); } else { return; } } if (throwException == false) { if (LoaderConstraintTable::check_or_update(k, loader_data, name) == false) { throwException = true; ss.print("loader constraint violation: loader %s", loader_data->loader_name_and_id()); ss.print(" wants to load %s %s.", k->external_kind(), k->external_name()); Klass *existing_klass = LoaderConstraintTable::find_constrained_klass(name, loader_data); if (existing_klass != nullptr && existing_klass->class_loader_data() != loader_data) { ss.print(" A different %s with the same name was previously loaded by %s. (%s)", existing_klass->external_kind(), existing_klass->class_loader_data()->loader_name_and_id(), existing_klass->class_in_module_of_loader(false, true)); } else { ss.print(" (%s)", k->class_in_module_of_loader(false, true)); } } } } // Throw error now if needed (cannot throw while holding // SystemDictionary_lock because of rank ordering) if (throwException == true) { THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string()); } } // Update class loader data dictionary - done after check_constraint and add_to_hierarchy // have been called. void SystemDictionary::update_dictionary(JavaThread* current, InstanceKlass* k, ClassLoaderData* loader_data) { MonitorLocker mu1(SystemDictionary_lock); // Make a new dictionary entry. Symbol* name = k->name(); Dictionary* dictionary = loader_data->dictionary(); InstanceKlass* sd_check = dictionary->find_class(current, name); if (sd_check == nullptr) { dictionary->add_klass(current, name, k); } mu1.notify_all(); } #if INCLUDE_CDS // Indicate that loader_data has initiated the loading of class k, which // has already been defined by a parent loader. // This API should be used only by AOTLinkedClassBulkLoader void SystemDictionary::add_to_initiating_loader(JavaThread* current, InstanceKlass* k, ClassLoaderData* loader_data) { assert(CDSConfig::is_using_aot_linked_classes(), "must be"); assert_locked_or_safepoint(SystemDictionary_lock); Symbol* name = k->name(); Dictionary* dictionary = loader_data->dictionary(); assert(k->is_loaded(), "must be"); assert(k->class_loader_data() != loader_data, "only for classes defined by a parent loader"); assert(dictionary->find_class(current, name) == nullptr, "sanity"); dictionary->add_klass(current, name, k); } #endif // Try to find a class name using the loader constraints. The // loader constraints might know about a class that isn't fully loaded // yet and these will be ignored. Klass* SystemDictionary::find_constrained_instance_or_array_klass( Thread* current, Symbol* class_name, Handle class_loader) { // First see if it has been loaded directly. Klass* klass = find_instance_or_array_klass(current, class_name, class_loader); if (klass != nullptr) return klass; // Now look to see if it has been loaded elsewhere, and is subject to // a loader constraint that would require this loader to return the // klass that is already loaded. if (Signature::is_array(class_name)) { // For array classes, their Klass*s are not kept in the // constraint table. The element Klass*s are. SignatureStream ss(class_name, false); int ndims = ss.skip_array_prefix(); // skip all '['s BasicType t = ss.type(); if (t != T_OBJECT) { klass = Universe::typeArrayKlass(t); } else { MutexLocker mu(current, SystemDictionary_lock); klass = LoaderConstraintTable::find_constrained_klass(ss.as_symbol(), class_loader_data(class_loader)); } // If element class already loaded, allocate array klass if (klass != nullptr) { klass = klass->array_klass_or_null(ndims); } } else { MutexLocker mu(current, SystemDictionary_lock); // Non-array classes are easy: simply check the constraint table. klass = LoaderConstraintTable::find_constrained_klass(class_name, class_loader_data(class_loader)); } return klass; } bool SystemDictionary::add_loader_constraint(Symbol* class_name, Klass* klass_being_linked, Handle class_loader1, Handle class_loader2) { ClassLoaderData* loader_data1 = class_loader_data(class_loader1); ClassLoaderData* loader_data2 = class_loader_data(class_loader2); Symbol* constraint_name = nullptr; if (!Signature::is_array(class_name)) { constraint_name = class_name; } else { // For array classes, their Klass*s are not kept in the // constraint table. The element classes are. SignatureStream ss(class_name, false); ss.skip_array_prefix(); // skip all '['s if (!ss.has_envelope()) { return true; // primitive types always pass } constraint_name = ss.as_symbol(); // Increment refcount to keep constraint_name alive after // SignatureStream is destructed. It will be decremented below // before returning. constraint_name->increment_refcount(); } Dictionary* dictionary1 = loader_data1->dictionary(); Dictionary* dictionary2 = loader_data2->dictionary(); JavaThread* current = JavaThread::current(); { MutexLocker mu_s(SystemDictionary_lock); InstanceKlass* klass1 = dictionary1->find_class(current, constraint_name); InstanceKlass* klass2 = dictionary2->find_class(current, constraint_name); bool result = LoaderConstraintTable::add_entry(constraint_name, klass1, loader_data1, klass2, loader_data2); #if INCLUDE_CDS if (CDSConfig::is_dumping_archive() && klass_being_linked != nullptr && !klass_being_linked->is_shared()) { SystemDictionaryShared::record_linking_constraint(constraint_name, InstanceKlass::cast(klass_being_linked), class_loader1, class_loader2); } #endif // INCLUDE_CDS if (Signature::is_array(class_name)) { constraint_name->decrement_refcount(); } return result; } } // Add entry to resolution error table to record the error when the first // attempt to resolve a reference to a class has failed. void SystemDictionary::add_resolution_error(const constantPoolHandle& pool, int which, Symbol* error, const char* message, Symbol* cause, const char* cause_msg) { { MutexLocker ml(Thread::current(), SystemDictionary_lock); ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which); if (entry == nullptr) { ResolutionErrorTable::add_entry(pool, which, error, message, cause, cause_msg); } } } // Delete a resolution error for RedefineClasses for a constant pool is going away void SystemDictionary::delete_resolution_error(ConstantPool* pool) { ResolutionErrorTable::delete_entry(pool); } // Lookup resolution error table. Returns error if found, otherwise null. Symbol* SystemDictionary::find_resolution_error(const constantPoolHandle& pool, int which, const char** message, Symbol** cause, const char** cause_msg) { { MutexLocker ml(Thread::current(), SystemDictionary_lock); ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which); if (entry != nullptr) { *message = entry->message(); *cause = entry->cause(); *cause_msg = entry->cause_msg(); return entry->error(); } else { return nullptr; } } } // Add an entry to resolution error table to record an error in resolving or // validating a nest host. This is used to construct informative error // messages when IllegalAccessError's occur. If an entry already exists it will // be updated with the nest host error message. void SystemDictionary::add_nest_host_error(const constantPoolHandle& pool, int which, const char* message) { { MutexLocker ml(Thread::current(), SystemDictionary_lock); ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which); if (entry != nullptr && entry->nest_host_error() == nullptr) { // An existing entry means we had a true resolution failure (LinkageError) with our nest host, but we // still want to add the error message for the higher-level access checks to report. We should // only reach here under the same error condition, so we can ignore the potential race with setting // the message. If we see it is already set then we can ignore it. entry->set_nest_host_error(message); } else { ResolutionErrorTable::add_entry(pool, which, message); } } } // Lookup any nest host error const char* SystemDictionary::find_nest_host_error(const constantPoolHandle& pool, int which) { { MutexLocker ml(Thread::current(), SystemDictionary_lock); ResolutionErrorEntry* entry = ResolutionErrorTable::find_entry(pool, which); if (entry != nullptr) { return entry->nest_host_error(); } else { return nullptr; } } } // Signature constraints ensure that callers and callees agree about // the meaning of type names in their signatures. This routine is the // intake for constraints. It collects them from several places: // // * LinkResolver::resolve_method (if check_access is true) requires // that the resolving class (the caller) and the defining class of // the resolved method (the callee) agree on each type in the // method's signature. // // * LinkResolver::resolve_interface_method performs exactly the same // checks. // // * LinkResolver::resolve_field requires that the constant pool // attempting to link to a field agree with the field's defining // class about the type of the field signature. // // * klassVtable::initialize_vtable requires that, when a class // overrides a vtable entry allocated by a superclass, that the // overriding method (i.e., the callee) agree with the superclass // on each type in the method's signature. // // * klassItable::initialize_itable requires that, when a class fills // in its itables, for each non-abstract method installed in an // itable, the method (i.e., the callee) agree with the interface // on each type in the method's signature. // // All those methods have a boolean (check_access, checkconstraints) // which turns off the checks. This is used from specialized contexts // such as bootstrapping, dumping, and debugging. // // No direct constraint is placed between the class and its // supertypes. Constraints are only placed along linked relations // between callers and callees. When a method overrides or implements // an abstract method in a supertype (superclass or interface), the // constraints are placed as if the supertype were the caller to the // overriding method. (This works well, since callers to the // supertype have already established agreement between themselves and // the supertype.) As a result of all this, a class can disagree with // its supertype about the meaning of a type name, as long as that // class neither calls a relevant method of the supertype, nor is // called (perhaps via an override) from the supertype. // // // SystemDictionary::check_signature_loaders(sig, klass_being_linked, l1, l2) // // Make sure all class components (including arrays) in the given // signature will be resolved to the same class in both loaders. // Returns the name of the type that failed a loader constraint check, or // null if no constraint failed. No exception except OOME is thrown. // Arrays are not added to the loader constraint table, their elements are. Symbol* SystemDictionary::check_signature_loaders(Symbol* signature, Klass* klass_being_linked, Handle loader1, Handle loader2, bool is_method) { // Nothing to do if loaders are the same. if (loader1() == loader2()) { return nullptr; } for (SignatureStream ss(signature, is_method); !ss.is_done(); ss.next()) { if (ss.is_reference()) { Symbol* sig = ss.as_symbol(); // Note: In the future, if template-like types can take // arguments, we will want to recognize them and dig out class // names hiding inside the argument lists. if (!add_loader_constraint(sig, klass_being_linked, loader1, loader2)) { return sig; } } } return nullptr; } Method* SystemDictionary::find_method_handle_intrinsic(vmIntrinsicID iid, Symbol* signature, TRAPS) { const int iid_as_int = vmIntrinsics::as_int(iid); assert(MethodHandles::is_signature_polymorphic(iid) && MethodHandles::is_signature_polymorphic_intrinsic(iid) && iid != vmIntrinsics::_invokeGeneric, "must be a known MH intrinsic iid=%d: %s", iid_as_int, vmIntrinsics::name_at(iid)); InvokeMethodKey key(signature, iid_as_int); Method** met = nullptr; // We only want one entry in the table for this (signature/id, method) pair but the code // to create the intrinsic method needs to be outside the lock. // The first thread claims the entry by adding the key and the other threads wait, until the // Method has been added as the value. { MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock); while (true) { bool created; met = _invoke_method_intrinsic_table->put_if_absent(key, &created); assert(met != nullptr, "either created or found"); if (*met != nullptr) { return *met; } else if (created) { // The current thread won the race and will try to create the full entry. break; } else { // Another thread beat us to it, so wait for them to complete // and return *met; or if they hit an error we get another try. ml.wait(); // Note it is not safe to read *met here as that entry could have // been deleted, so we must loop and try put_if_absent again. } } } methodHandle m = Method::make_method_handle_intrinsic(iid, signature, THREAD); bool throw_error = HAS_PENDING_EXCEPTION; if (!throw_error && (!Arguments::is_interpreter_only() || iid == vmIntrinsics::_linkToNative)) { // Generate a compiled form of the MH intrinsic // linkToNative doesn't have interpreter-specific implementation, so always has to go through compiled version. AdapterHandlerLibrary::create_native_wrapper(m); // Check if have the compiled code. throw_error = (!m->has_compiled_code()); } { MonitorLocker ml(THREAD, InvokeMethodIntrinsicTable_lock); if (throw_error) { // Remove the entry and let another thread try, or get the same exception. bool removed = _invoke_method_intrinsic_table->remove(key); assert(removed, "must be the owner"); ml.notify_all(); } else { signature->make_permanent(); // The signature is never unloaded. assert(Arguments::is_interpreter_only() || (m->has_compiled_code() && m->code()->entry_point() == m->from_compiled_entry()), "MH intrinsic invariant"); *met = m(); // insert the element ml.notify_all(); return m(); } } // Throw OOM or the pending exception in the JavaThread if (throw_error && !HAS_PENDING_EXCEPTION) { THROW_MSG_NULL(vmSymbols::java_lang_OutOfMemoryError(), "Out of space in CodeCache for method handle intrinsic"); } return nullptr; } #if INCLUDE_CDS void SystemDictionary::get_all_method_handle_intrinsics(GrowableArray* methods) { assert(SafepointSynchronize::is_at_safepoint(), "must be"); auto do_method = [&] (InvokeMethodKey& key, Method*& m) { methods->append(m); }; _invoke_method_intrinsic_table->iterate_all(do_method); } void SystemDictionary::restore_archived_method_handle_intrinsics() { if (UseSharedSpaces) { EXCEPTION_MARK; restore_archived_method_handle_intrinsics_impl(THREAD); if (HAS_PENDING_EXCEPTION) { // This is probably caused by OOM -- other parts of the CDS archive have direct pointers to // the archived method handle intrinsics, so we can't really recover from this failure. vm_exit_during_initialization(err_msg("Failed to restore archived method handle intrinsics. Try to increase heap size.")); } } } void SystemDictionary::restore_archived_method_handle_intrinsics_impl(TRAPS) { Array* list = MetaspaceShared::archived_method_handle_intrinsics(); for (int i = 0; i < list->length(); i++) { methodHandle m(THREAD, list->at(i)); Method::restore_archived_method_handle_intrinsic(m, CHECK); m->constants()->restore_unshareable_info(CHECK); if (!Arguments::is_interpreter_only() || m->intrinsic_id() == vmIntrinsics::_linkToNative) { AdapterHandlerLibrary::create_native_wrapper(m); if (!m->has_compiled_code()) { ResourceMark rm(THREAD); vm_exit_during_initialization(err_msg("Failed to initialize method %s", m->external_name())); } } // There's no need to grab the InvokeMethodIntrinsicTable_lock, as we are still very early in // VM start-up -- in init_globals2() -- so we are still running a single Java thread. It's not // possible to have a contention. const int iid_as_int = vmIntrinsics::as_int(m->intrinsic_id()); InvokeMethodKey key(m->signature(), iid_as_int); bool created = _invoke_method_intrinsic_table->put(key, m()); assert(created, "unexpected contention"); } } #endif // INCLUDE_CDS // Helper for unpacking the return value from linkMethod and linkCallSite. static Method* unpack_method_and_appendix(Handle mname, Klass* accessing_klass, objArrayHandle appendix_box, Handle* appendix_result, TRAPS) { if (mname.not_null()) { Method* m = java_lang_invoke_MemberName::vmtarget(mname()); if (m != nullptr) { oop appendix = appendix_box->obj_at(0); LogTarget(Info, methodhandles) lt; if (lt.develop_is_enabled()) { ResourceMark rm(THREAD); LogStream ls(lt); ls.print("Linked method=" INTPTR_FORMAT ": ", p2i(m)); m->print_on(&ls); if (appendix != nullptr) { ls.print("appendix = "); appendix->print_on(&ls); } ls.cr(); } (*appendix_result) = Handle(THREAD, appendix); // the target is stored in the cpCache and if a reference to this // MemberName is dropped we need a way to make sure the // class_loader containing this method is kept alive. methodHandle mh(THREAD, m); // record_dependency can safepoint. ClassLoaderData* this_key = accessing_klass->class_loader_data(); this_key->record_dependency(m->method_holder()); return mh(); } } THROW_MSG_NULL(vmSymbols::java_lang_LinkageError(), "bad value from MethodHandleNatives"); } Method* SystemDictionary::find_method_handle_invoker(Klass* klass, Symbol* name, Symbol* signature, Klass* accessing_klass, Handle* appendix_result, TRAPS) { guarantee(THREAD->can_call_java(), ""); Handle method_type = SystemDictionary::find_method_handle_type(signature, accessing_klass, CHECK_NULL); int ref_kind = JVM_REF_invokeVirtual; oop name_oop = StringTable::intern(name, CHECK_NULL); Handle name_str (THREAD, name_oop); objArrayHandle appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK_NULL); assert(appendix_box->obj_at(0) == nullptr, ""); // This should not happen. JDK code should take care of that. if (accessing_klass == nullptr || method_type.is_null()) { THROW_MSG_NULL(vmSymbols::java_lang_InternalError(), "bad invokehandle"); } // call java.lang.invoke.MethodHandleNatives::linkMethod(... String, MethodType) -> MemberName JavaCallArguments args; args.push_oop(Handle(THREAD, accessing_klass->java_mirror())); args.push_int(ref_kind); args.push_oop(Handle(THREAD, klass->java_mirror())); args.push_oop(name_str); args.push_oop(method_type); args.push_oop(appendix_box); JavaValue result(T_OBJECT); JavaCalls::call_static(&result, vmClasses::MethodHandleNatives_klass(), vmSymbols::linkMethod_name(), vmSymbols::linkMethod_signature(), &args, CHECK_NULL); Handle mname(THREAD, result.get_oop()); return unpack_method_and_appendix(mname, accessing_klass, appendix_box, appendix_result, THREAD); } // Decide if we can globally cache a lookup of this class, to be returned to any client that asks. // We must ensure that all class loaders everywhere will reach this class, for any client. // This is a safe bet for public classes in java.lang, such as Object and String. // We also include public classes in java.lang.invoke, because they appear frequently in system-level method types. // Out of an abundance of caution, we do not include any other classes, not even for packages like java.util. static bool is_always_visible_class(oop mirror) { Klass* klass = java_lang_Class::as_Klass(mirror); if (klass->is_objArray_klass()) { klass = ObjArrayKlass::cast(klass)->bottom_klass(); // check element type } if (klass->is_typeArray_klass()) { return true; // primitive array } assert(klass->is_instance_klass(), "%s", klass->external_name()); return klass->is_public() && (InstanceKlass::cast(klass)->is_same_class_package(vmClasses::Object_klass()) || // java.lang InstanceKlass::cast(klass)->is_same_class_package(vmClasses::MethodHandle_klass())); // java.lang.invoke } // Find or construct the Java mirror (java.lang.Class instance) for // the given field type signature, as interpreted relative to the // given class loader. Handles primitives, void, references, arrays, // and all other reflectable types, except method types. // N.B. Code in reflection should use this entry point. Handle SystemDictionary::find_java_mirror_for_type(Symbol* signature, Klass* accessing_klass, SignatureStream::FailureMode failure_mode, TRAPS) { Handle class_loader; // What we have here must be a valid field descriptor, // and all valid field descriptors are supported. // Produce the same java.lang.Class that reflection reports. if (accessing_klass != nullptr) { class_loader = Handle(THREAD, accessing_klass->class_loader()); } ResolvingSignatureStream ss(signature, class_loader, false); oop mirror_oop = ss.as_java_mirror(failure_mode, CHECK_NH); if (mirror_oop == nullptr) { return Handle(); // report failure this way } Handle mirror(THREAD, mirror_oop); if (accessing_klass != nullptr) { // Check accessibility, emulating ConstantPool::verify_constant_pool_resolve. Klass* sel_klass = java_lang_Class::as_Klass(mirror()); if (sel_klass != nullptr) { LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_NH); } } return mirror; } // Ask Java code to find or construct a java.lang.invoke.MethodType for the given // signature, as interpreted relative to the given class loader. // Because of class loader constraints, all method handle usage must be // consistent with this loader. Handle SystemDictionary::find_method_handle_type(Symbol* signature, Klass* accessing_klass, TRAPS) { Handle empty; OopHandle* o; { MutexLocker ml(THREAD, InvokeMethodTypeTable_lock); o = _invoke_method_type_table->get(signature); } if (o != nullptr) { oop mt = o->resolve(); assert(java_lang_invoke_MethodType::is_instance(mt), ""); return Handle(THREAD, mt); } else if (!THREAD->can_call_java()) { warning("SystemDictionary::find_method_handle_type called from compiler thread"); // FIXME return Handle(); // do not attempt from within compiler, unless it was cached } Handle class_loader; if (accessing_klass != nullptr) { class_loader = Handle(THREAD, accessing_klass->class_loader()); } bool can_be_cached = true; int npts = ArgumentCount(signature).size(); objArrayHandle pts = oopFactory::new_objArray_handle(vmClasses::Class_klass(), npts, CHECK_(empty)); int arg = 0; Handle rt; // the return type from the signature ResourceMark rm(THREAD); for (SignatureStream ss(signature); !ss.is_done(); ss.next()) { oop mirror = nullptr; if (can_be_cached) { // Use neutral class loader to lookup candidate classes to be placed in the cache. mirror = ss.as_java_mirror(Handle(), SignatureStream::ReturnNull, CHECK_(empty)); if (mirror == nullptr || (ss.is_reference() && !is_always_visible_class(mirror))) { // Fall back to accessing_klass context. can_be_cached = false; } } if (!can_be_cached) { // Resolve, throwing a real error if it doesn't work. mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty)); } assert(mirror != nullptr, "%s", ss.as_symbol()->as_C_string()); if (ss.at_return_type()) rt = Handle(THREAD, mirror); else pts->obj_at_put(arg++, mirror); // Check accessibility. if (!java_lang_Class::is_primitive(mirror) && accessing_klass != nullptr) { Klass* sel_klass = java_lang_Class::as_Klass(mirror); mirror = nullptr; // safety // Emulate ConstantPool::verify_constant_pool_resolve. LinkResolver::check_klass_accessibility(accessing_klass, sel_klass, CHECK_(empty)); } } assert(arg == npts, ""); // call java.lang.invoke.MethodHandleNatives::findMethodHandleType(Class rt, Class[] pts) -> MethodType JavaCallArguments args(Handle(THREAD, rt())); args.push_oop(pts); JavaValue result(T_OBJECT); JavaCalls::call_static(&result, vmClasses::MethodHandleNatives_klass(), vmSymbols::findMethodHandleType_name(), vmSymbols::findMethodHandleType_signature(), &args, CHECK_(empty)); Handle method_type(THREAD, result.get_oop()); if (can_be_cached) { // We can cache this MethodType inside the JVM. MutexLocker ml(THREAD, InvokeMethodTypeTable_lock); bool created = false; assert(method_type != nullptr, "unexpected null"); OopHandle* h = _invoke_method_type_table->get(signature); if (h == nullptr) { signature->make_permanent(); // The signature is never unloaded. OopHandle elem = OopHandle(Universe::vm_global(), method_type()); bool created = _invoke_method_type_table->put(signature, elem); assert(created, "better be created"); } } // report back to the caller with the MethodType return method_type; } Handle SystemDictionary::find_field_handle_type(Symbol* signature, Klass* accessing_klass, TRAPS) { Handle empty; ResourceMark rm(THREAD); SignatureStream ss(signature, /*is_method=*/ false); if (!ss.is_done()) { Handle class_loader; if (accessing_klass != nullptr) { class_loader = Handle(THREAD, accessing_klass->class_loader()); } oop mirror = ss.as_java_mirror(class_loader, SignatureStream::NCDFError, CHECK_(empty)); ss.next(); if (ss.is_done()) { return Handle(THREAD, mirror); } } return empty; } // Ask Java code to find or construct a method handle constant. Handle SystemDictionary::link_method_handle_constant(Klass* caller, int ref_kind, //e.g., JVM_REF_invokeVirtual Klass* callee, Symbol* name, Symbol* signature, TRAPS) { Handle empty; if (caller == nullptr) { THROW_MSG_(vmSymbols::java_lang_InternalError(), "bad MH constant", empty); } Handle name_str = java_lang_String::create_from_symbol(name, CHECK_(empty)); Handle signature_str = java_lang_String::create_from_symbol(signature, CHECK_(empty)); // Put symbolic info from the MH constant into freshly created MemberName and resolve it. Handle mname = vmClasses::MemberName_klass()->allocate_instance_handle(CHECK_(empty)); java_lang_invoke_MemberName::set_clazz(mname(), callee->java_mirror()); java_lang_invoke_MemberName::set_name (mname(), name_str()); java_lang_invoke_MemberName::set_type (mname(), signature_str()); java_lang_invoke_MemberName::set_flags(mname(), MethodHandles::ref_kind_to_flags(ref_kind)); if (ref_kind == JVM_REF_invokeVirtual && MethodHandles::is_signature_polymorphic_public_name(callee, name)) { // Skip resolution for public signature polymorphic methods such as // j.l.i.MethodHandle.invoke()/invokeExact() and those on VarHandle // They require appendix argument which MemberName resolution doesn't handle. // There's special logic on JDK side to handle them // (see MethodHandles.linkMethodHandleConstant() and MethodHandles.findVirtualForMH()). } else { MethodHandles::resolve_MemberName(mname, caller, 0, false /*speculative_resolve*/, CHECK_(empty)); } // After method/field resolution succeeded, it's safe to resolve MH signature as well. Handle type = MethodHandles::resolve_MemberName_type(mname, caller, CHECK_(empty)); // call java.lang.invoke.MethodHandleNatives::linkMethodHandleConstant(Class caller, int refKind, Class callee, String name, Object type) -> MethodHandle JavaCallArguments args; args.push_oop(Handle(THREAD, caller->java_mirror())); // the referring class args.push_int(ref_kind); args.push_oop(Handle(THREAD, callee->java_mirror())); // the target class args.push_oop(name_str); args.push_oop(type); JavaValue result(T_OBJECT); JavaCalls::call_static(&result, vmClasses::MethodHandleNatives_klass(), vmSymbols::linkMethodHandleConstant_name(), vmSymbols::linkMethodHandleConstant_signature(), &args, CHECK_(empty)); return Handle(THREAD, result.get_oop()); } // Ask Java to run a bootstrap method, in order to create a dynamic call site // while linking an invokedynamic op, or compute a constant for Dynamic_info CP entry // with linkage results being stored back into the bootstrap specifier. void SystemDictionary::invoke_bootstrap_method(BootstrapInfo& bootstrap_specifier, TRAPS) { // Resolve the bootstrap specifier, its name, type, and static arguments bootstrap_specifier.resolve_bsm(CHECK); // This should not happen. JDK code should take care of that. if (bootstrap_specifier.caller() == nullptr || bootstrap_specifier.type_arg().is_null()) { THROW_MSG(vmSymbols::java_lang_InternalError(), "Invalid bootstrap method invocation with no caller or type argument"); } bool is_indy = bootstrap_specifier.is_method_call(); objArrayHandle appendix_box; if (is_indy) { // Some method calls may require an appendix argument. Arrange to receive it. appendix_box = oopFactory::new_objArray_handle(vmClasses::Object_klass(), 1, CHECK); assert(appendix_box->obj_at(0) == nullptr, ""); } // call condy: java.lang.invoke.MethodHandleNatives::linkDynamicConstant(caller, bsm, type, info) // indy: java.lang.invoke.MethodHandleNatives::linkCallSite(caller, bsm, name, mtype, info, &appendix) JavaCallArguments args; args.push_oop(Handle(THREAD, bootstrap_specifier.caller_mirror())); args.push_oop(bootstrap_specifier.bsm()); args.push_oop(bootstrap_specifier.name_arg()); args.push_oop(bootstrap_specifier.type_arg()); args.push_oop(bootstrap_specifier.arg_values()); if (is_indy) { args.push_oop(appendix_box); } JavaValue result(T_OBJECT); JavaCalls::call_static(&result, vmClasses::MethodHandleNatives_klass(), is_indy ? vmSymbols::linkCallSite_name() : vmSymbols::linkDynamicConstant_name(), is_indy ? vmSymbols::linkCallSite_signature() : vmSymbols::linkDynamicConstant_signature(), &args, CHECK); Handle value(THREAD, result.get_oop()); if (is_indy) { Handle appendix; Method* method = unpack_method_and_appendix(value, bootstrap_specifier.caller(), appendix_box, &appendix, CHECK); methodHandle mh(THREAD, method); bootstrap_specifier.set_resolved_method(mh, appendix); } else { bootstrap_specifier.set_resolved_value(value); } // sanity check assert(bootstrap_specifier.is_resolved() || (bootstrap_specifier.is_method_call() && bootstrap_specifier.resolved_method().not_null()), "bootstrap method call failed"); } bool SystemDictionary::is_nonpublic_Object_method(Method* m) { assert(m != nullptr, "Unexpected nullptr Method*"); return !m->is_public() && m->method_holder() == vmClasses::Object_klass(); } // ---------------------------------------------------------------------------- void SystemDictionary::print_on(outputStream *st) { CDS_ONLY(SystemDictionaryShared::print_on(st)); GCMutexLocker mu(SystemDictionary_lock); ClassLoaderDataGraph::print_dictionary(st); // Placeholders PlaceholderTable::print_on(st); st->cr(); // loader constraints - print under SD_lock LoaderConstraintTable::print_on(st); st->cr(); } void SystemDictionary::print() { print_on(tty); } void SystemDictionary::verify() { GCMutexLocker mu(SystemDictionary_lock); // Verify dictionary ClassLoaderDataGraph::verify_dictionary(); // Verify constraint table LoaderConstraintTable::verify(); } void SystemDictionary::dump(outputStream *st, bool verbose) { assert_locked_or_safepoint(SystemDictionary_lock); if (verbose) { print_on(st); } else { CDS_ONLY(SystemDictionaryShared::print_table_statistics(st)); ClassLoaderDataGraph::print_table_statistics(st); LoaderConstraintTable::print_table_statistics(st); } } // Utility for dumping dictionaries. SystemDictionaryDCmd::SystemDictionaryDCmd(outputStream* output, bool heap) : DCmdWithParser(output, heap), _verbose("-verbose", "Dump the content of each dictionary entry for all class loaders", "BOOLEAN", false, "false") { _dcmdparser.add_dcmd_option(&_verbose); } void SystemDictionaryDCmd::execute(DCmdSource source, TRAPS) { VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSysDict, _verbose.value()); VMThread::execute(&dumper); }