jdk

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/*
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 * Copyright (c) 2003, 2024, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "classfile/classLoaderDataGraph.hpp"
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#include "classfile/dictionary.hpp"
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#include "classfile/javaClasses.hpp"
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#include "gc/shared/collectedHeap.hpp"
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#include "memory/universe.hpp"
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#include "oops/klass.inline.hpp"
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#include "prims/jvmtiGetLoadedClasses.hpp"
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#include "runtime/handles.inline.hpp"
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#include "runtime/javaThread.hpp"
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#include "runtime/jniHandles.inline.hpp"
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#include "utilities/stack.inline.hpp"
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// The closure for GetLoadedClasses
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class LoadedClassesClosure : public KlassClosure {
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private:
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  Stack<jclass, mtInternal> _classStack;
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  JvmtiEnv* _env;
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  Thread*   _cur_thread;
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  bool      _dictionary_walk;
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  int extract(jclass* result_list) {
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    // The size of the Stack will be 0 after extract, so get it here
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    int count = (int)_classStack.size();
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    int i = count;
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    // Pop all jclasses, fill backwards
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    while (!_classStack.is_empty()) {
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      result_list[--i] = _classStack.pop();
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    }
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    // Return the number of elements written
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    return count;
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  }
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  // Return current size of the Stack
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  int get_count() {
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    return (int)_classStack.size();
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  }
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public:
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  LoadedClassesClosure(JvmtiEnv* env, bool dictionary_walk) :
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      _env(env),
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      _cur_thread(Thread::current()),
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      _dictionary_walk(dictionary_walk) {
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  }
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  void do_klass(Klass* k) {
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    // Collect all jclasses
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    _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
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    if (_dictionary_walk) {
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      // Collect array classes this way when walking the dictionary (because array classes are
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      // not in the dictionary).
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      for (Klass* l = k->array_klass_or_null(); l != nullptr; l = l->array_klass_or_null()) {
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        _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, l->java_mirror())));
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      }
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    }
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  }
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  jvmtiError get_result(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
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    // Return results by extracting the collected contents into a list
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    // allocated via JvmtiEnv
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    jclass* result_list;
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    jvmtiError error = env->Allocate(get_count() * sizeof(jclass),
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                               (unsigned char**)&result_list);
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    if (error == JVMTI_ERROR_NONE) {
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      int count = extract(result_list);
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      *classCountPtr = count;
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      *classesPtr = result_list;
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    }
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    return error;
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  }
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};
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jvmtiError
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JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
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  LoadedClassesClosure closure(env, false);
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  {
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    // Iterate through all classes in ClassLoaderDataGraph
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    // and collect them using the LoadedClassesClosure
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    MutexLocker mcld(ClassLoaderDataGraph_lock);
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    ClassLoaderDataGraph::loaded_classes_do_keepalive(&closure);
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  }
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  return closure.get_result(env, classCountPtr, classesPtr);
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}
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jvmtiError
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JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
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                                             jint* classCountPtr, jclass** classesPtr) {
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  LoadedClassesClosure closure(env, true);
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  {
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    // To get a consistent list of classes we need MultiArray_lock to ensure
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    // array classes aren't created by another thread during this walk. This walks through the
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    // InstanceKlass::_array_klasses links.
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    RecursiveLocker ma(MultiArray_lock, Thread::current());
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    MutexLocker sd(SystemDictionary_lock);
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    oop loader = JNIHandles::resolve(initiatingLoader);
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    // All classes loaded from this loader as initiating loader are
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    // requested, so only need to walk this loader's ClassLoaderData
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    // dictionary, or the null ClassLoaderData dictionary for bootstrap loader.
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    if (loader != nullptr) {
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      ClassLoaderData* data = java_lang_ClassLoader::loader_data_acquire(loader);
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      // ClassLoader may not be used yet for loading.
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      if (data != nullptr && data->dictionary() != nullptr) {
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        data->dictionary()->all_entries_do(&closure);
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      }
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    } else {
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      ClassLoaderData::the_null_class_loader_data()->dictionary()->all_entries_do(&closure);
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    }
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    // Get basic arrays for all loaders.
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    Universe::basic_type_classes_do(&closure);
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  }
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  return closure.get_result(env, classCountPtr, classesPtr);
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}
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