1 /*
2 * Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/dictionary.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "gc/shared/collectedHeap.hpp"
29 #include "memory/universe.hpp"
30 #include "oops/klass.inline.hpp"
31 #include "prims/jvmtiGetLoadedClasses.hpp"
32 #include "runtime/handles.inline.hpp"
33 #include "runtime/javaThread.hpp"
34 #include "runtime/jniHandles.inline.hpp"
35 #include "utilities/stack.inline.hpp"
36
37 // The closure for GetLoadedClasses
38 class LoadedClassesClosure : public KlassClosure {
39 private:
40 Stack<jclass, mtInternal> _classStack;
41 JvmtiEnv* _env;
42 Thread* _cur_thread;
43 bool _dictionary_walk;
44
45 int extract(jclass* result_list) {
46 // The size of the Stack will be 0 after extract, so get it here
47 int count = (int)_classStack.size();
48 int i = count;
49
50 // Pop all jclasses, fill backwards
51 while (!_classStack.is_empty()) {
52 result_list[--i] = _classStack.pop();
53 }
54
55 // Return the number of elements written
56 return count;
57 }
58
59 // Return current size of the Stack
60 int get_count() {
61 return (int)_classStack.size();
62 }
63
64 public:
65 LoadedClassesClosure(JvmtiEnv* env, bool dictionary_walk) :
66 _env(env),
67 _cur_thread(Thread::current()),
68 _dictionary_walk(dictionary_walk) {
69 }
70
71 void do_klass(Klass* k) {
72 // Collect all jclasses
73 _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
74 if (_dictionary_walk) {
75 // Collect array classes this way when walking the dictionary (because array classes are
76 // not in the dictionary).
77 for (Klass* l = k->array_klass_or_null(); l != nullptr; l = l->array_klass_or_null()) {
78 _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, l->java_mirror())));
79 }
80 }
81 }
82
83 jvmtiError get_result(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
84 // Return results by extracting the collected contents into a list
85 // allocated via JvmtiEnv
86 jclass* result_list;
87 jvmtiError error = env->Allocate(get_count() * sizeof(jclass),
88 (unsigned char**)&result_list);
89
90 if (error == JVMTI_ERROR_NONE) {
91 int count = extract(result_list);
92 *classCountPtr = count;
93 *classesPtr = result_list;
94 }
95 return error;
96 }
97 };
98
99 jvmtiError
100 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
101
102 LoadedClassesClosure closure(env, false);
103 {
104 // Iterate through all classes in ClassLoaderDataGraph
105 // and collect them using the LoadedClassesClosure
106 MutexLocker mcld(ClassLoaderDataGraph_lock);
107 ClassLoaderDataGraph::loaded_classes_do_keepalive(&closure);
108 }
109
110 return closure.get_result(env, classCountPtr, classesPtr);
111 }
112
113 jvmtiError
114 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
115 jint* classCountPtr, jclass** classesPtr) {
116
117 LoadedClassesClosure closure(env, true);
118 {
119 // To get a consistent list of classes we need MultiArray_lock to ensure
120 // array classes aren't created by another thread during this walk. This walks through the
121 // InstanceKlass::_array_klasses links.
122 RecursiveLocker ma(MultiArray_lock, Thread::current());
123 MutexLocker sd(SystemDictionary_lock);
124 oop loader = JNIHandles::resolve(initiatingLoader);
125 // All classes loaded from this loader as initiating loader are
126 // requested, so only need to walk this loader's ClassLoaderData
127 // dictionary, or the null ClassLoaderData dictionary for bootstrap loader.
128 if (loader != nullptr) {
129 ClassLoaderData* data = java_lang_ClassLoader::loader_data_acquire(loader);
130 // ClassLoader may not be used yet for loading.
131 if (data != nullptr && data->dictionary() != nullptr) {
132 data->dictionary()->all_entries_do(&closure);
133 }
134 } else {
135 ClassLoaderData::the_null_class_loader_data()->dictionary()->all_entries_do(&closure);
136 }
137 // Get basic arrays for all loaders.
138 Universe::basic_type_classes_do(&closure);
139 }
140
141 return closure.get_result(env, classCountPtr, classesPtr);
142 }