1 /*
  2  * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "classfile/classLoaderDataGraph.hpp"
 27 #include "classfile/dictionary.hpp"
 28 #include "classfile/javaClasses.hpp"
 29 #include "gc/shared/collectedHeap.hpp"
 30 #include "memory/universe.hpp"
 31 #include "oops/klass.inline.hpp"
 32 #include "prims/jvmtiGetLoadedClasses.hpp"
 33 #include "runtime/handles.inline.hpp"
 34 #include "runtime/jniHandles.inline.hpp"
 35 #include "runtime/thread.hpp"
 36 #include "utilities/stack.inline.hpp"
 37 
 38 // The closure for GetLoadedClasses
 39 class LoadedClassesClosure : public KlassClosure {
 40 private:
 41   Stack<jclass, mtInternal> _classStack;
 42   JvmtiEnv* _env;
 43   Thread*   _cur_thread;
 44   bool      _dictionary_walk;
 45 
 46   int extract(jclass* result_list) {
 47     // The size of the Stack will be 0 after extract, so get it here
 48     int count = (int)_classStack.size();
 49     int i = count;
 50 
 51     // Pop all jclasses, fill backwards
 52     while (!_classStack.is_empty()) {
 53       result_list[--i] = _classStack.pop();
 54     }
 55 
 56     // Return the number of elements written
 57     return count;
 58   }
 59 
 60   // Return current size of the Stack
 61   int get_count() {
 62     return (int)_classStack.size();
 63   }
 64 
 65 public:
 66   LoadedClassesClosure(JvmtiEnv* env, bool dictionary_walk) :
 67       _env(env),
 68       _cur_thread(Thread::current()),
 69       _dictionary_walk(dictionary_walk) {
 70   }
 71 
 72   void do_klass(Klass* k) {
 73     // Collect all jclasses
 74     _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
 75     if (_dictionary_walk) {
 76       // Collect array classes this way when walking the dictionary (because array classes are
 77       // not in the dictionary).
 78       for (Klass* l = k->array_klass_or_null(); l != NULL; l = l->array_klass_or_null()) {
 79         _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, l->java_mirror())));
 80       }
 81     }
 82   }
 83 
 84   jvmtiError get_result(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
 85     // Return results by extracting the collected contents into a list
 86     // allocated via JvmtiEnv
 87     jclass* result_list;
 88     jvmtiError error = env->Allocate(get_count() * sizeof(jclass),
 89                                (unsigned char**)&result_list);
 90 
 91     if (error == JVMTI_ERROR_NONE) {
 92       int count = extract(result_list);
 93       *classCountPtr = count;
 94       *classesPtr = result_list;
 95     }
 96     return error;
 97   }
 98 };
 99 
100 jvmtiError
101 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
102 
103   LoadedClassesClosure closure(env, false);
104   {
105     // To get a consistent list of classes we need MultiArray_lock to ensure
106     // array classes aren't created.
107     MutexLocker ma(MultiArray_lock);
108 
109     // Iterate through all classes in ClassLoaderDataGraph
110     // and collect them using the LoadedClassesClosure
111     MutexLocker mcld(ClassLoaderDataGraph_lock);
112     ClassLoaderDataGraph::loaded_classes_do(&closure);
113   }
114 
115   return closure.get_result(env, classCountPtr, classesPtr);
116 }
117 
118 jvmtiError
119 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
120                                              jint* classCountPtr, jclass** classesPtr) {
121 
122   LoadedClassesClosure closure(env, true);
123   {
124     // To get a consistent list of classes we need MultiArray_lock to ensure
125     // array classes aren't created during this walk.
126     MutexLocker ma(MultiArray_lock);
127     MutexLocker sd(SystemDictionary_lock);
128     oop loader = JNIHandles::resolve(initiatingLoader);
129     // All classes loaded from this loader as initiating loader are
130     // requested, so only need to walk this loader's ClassLoaderData
131     // dictionary, or the NULL ClassLoaderData dictionary for bootstrap loader.
132     if (loader != NULL) {
133       ClassLoaderData* data = java_lang_ClassLoader::loader_data_acquire(loader);
134       // ClassLoader may not be used yet for loading.
135       if (data != NULL && data->dictionary() != NULL) {
136         data->dictionary()->all_entries_do(&closure);
137       }
138     } else {
139       ClassLoaderData::the_null_class_loader_data()->dictionary()->all_entries_do(&closure);
140     }
141     // Get basic arrays for all loaders.
142     Universe::basic_type_classes_do(&closure);
143   }
144 
145   return closure.get_result(env, classCountPtr, classesPtr);
146 }