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 <oops/inlineKlass.hpp>
 26 #include "precompiled.hpp"
 27 #include "classfile/classLoaderDataGraph.hpp"
 28 #include "classfile/dictionary.hpp"
 29 #include "classfile/javaClasses.hpp"
 30 #include "gc/shared/collectedHeap.hpp"
 31 #include "memory/universe.hpp"
 32 #include "oops/klass.inline.hpp"
 33 #include "prims/jvmtiGetLoadedClasses.hpp"
 34 #include "runtime/handles.inline.hpp"
 35 #include "runtime/jniHandles.inline.hpp"
 36 #include "runtime/thread.hpp"
 37 #include "utilities/stack.inline.hpp"
 38 
 39 // The closure for GetLoadedClasses
 40 class LoadedClassesClosure : public KlassClosure {
 41 private:
 42   Stack<jclass, mtInternal> _classStack;
 43   JvmtiEnv* _env;
 44   Thread*   _cur_thread;
 45   bool      _dictionary_walk;
 46 
 47   int extract(jclass* result_list) {
 48     // The size of the Stack will be 0 after extract, so get it here
 49     int count = (int)_classStack.size();
 50     int i = count;
 51 
 52     // Pop all jclasses, fill backwards
 53     while (!_classStack.is_empty()) {
 54       result_list[--i] = _classStack.pop();
 55     }
 56 
 57     // Return the number of elements written
 58     return count;
 59   }
 60 
 61   // Return current size of the Stack
 62   int get_count() {
 63     return (int)_classStack.size();
 64   }
 65 
 66 public:
 67   LoadedClassesClosure(JvmtiEnv* env, bool dictionary_walk) :
 68       _env(env),
 69       _cur_thread(Thread::current()),
 70       _dictionary_walk(dictionary_walk) {
 71   }
 72 
 73   void do_klass(Klass* k) {
 74     // Collect all jclasses
 75     _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
 76     if (_dictionary_walk) {
 77       // Collect array classes this way when walking the dictionary (because array classes are
 78       // not in the dictionary).
 79       for (Klass* l = k->array_klass_or_null(); l != NULL; l = l->array_klass_or_null()) {
 80         _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, l->java_mirror())));
 81       }
 82       // CMH flat arrays (InlineKlass)
 83     }
 84   }
 85 
 86   jvmtiError get_result(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
 87     // Return results by extracting the collected contents into a list
 88     // allocated via JvmtiEnv
 89     jclass* result_list;
 90     jvmtiError error = env->Allocate(get_count() * sizeof(jclass),
 91                                (unsigned char**)&result_list);
 92 
 93     if (error == JVMTI_ERROR_NONE) {
 94       int count = extract(result_list);
 95       *classCountPtr = count;
 96       *classesPtr = result_list;
 97     }
 98     return error;
 99   }
100 };
101 
102 jvmtiError
103 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
104 
105   LoadedClassesClosure closure(env, false);
106   {
107     // To get a consistent list of classes we need MultiArray_lock to ensure
108     // array classes aren't created.
109     MutexLocker ma(MultiArray_lock);
110 
111     // Iterate through all classes in ClassLoaderDataGraph
112     // and collect them using the LoadedClassesClosure
113     MutexLocker mcld(ClassLoaderDataGraph_lock);
114     ClassLoaderDataGraph::loaded_classes_do(&closure);
115   }
116 
117   return closure.get_result(env, classCountPtr, classesPtr);
118 }
119 
120 jvmtiError
121 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
122                                              jint* classCountPtr, jclass** classesPtr) {
123 
124   LoadedClassesClosure closure(env, true);
125   {
126     // To get a consistent list of classes we need MultiArray_lock to ensure
127     // array classes aren't created during this walk.
128     MutexLocker ma(MultiArray_lock);
129     MutexLocker sd(SystemDictionary_lock);
130     oop loader = JNIHandles::resolve(initiatingLoader);
131     // All classes loaded from this loader as initiating loader are
132     // requested, so only need to walk this loader's ClassLoaderData
133     // dictionary, or the NULL ClassLoaderData dictionary for bootstrap loader.
134     if (loader != NULL) {
135       ClassLoaderData* data = java_lang_ClassLoader::loader_data_acquire(loader);
136       // ClassLoader may not be used yet for loading.
137       if (data != NULL && data->dictionary() != NULL) {
138         data->dictionary()->all_entries_do(&closure);
139       }
140     } else {
141       ClassLoaderData::the_null_class_loader_data()->dictionary()->all_entries_do(&closure);
142     }
143     // Get basic arrays for all loaders.
144     Universe::basic_type_classes_do(&closure);
145   }
146 
147   return closure.get_result(env, classCountPtr, classesPtr);
148 }