1 /*
2 * Copyright (c) 2003, 2018, 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/systemDictionary.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "memory/universe.hpp"
29 #include "prims/jvmtiGetLoadedClasses.hpp"
30 #include "runtime/handles.inline.hpp"
31 #include "runtime/jniHandles.inline.hpp"
32 #include "runtime/thread.hpp"
33 #include "utilities/stack.inline.hpp"
34 #if INCLUDE_ALL_GCS
35 #include "gc/g1/g1BarrierSet.hpp"
36 #endif
37
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
46 // Tell the GC to keep this klass alive
47 static void ensure_klass_alive(oop o) {
48 // A klass that was previously considered dead can be looked up in the
49 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
50 // or a reachable object making it alive again. The SATB part of G1 needs
51 // to get notified about this potential resurrection, otherwise the marking
52 // might not find the object.
53 #if INCLUDE_ALL_GCS
54 if (UseG1GC && o != NULL) {
55 G1BarrierSet::enqueue(o);
56 }
57 #endif
58 }
59
60 public:
61 LoadedClassesClosure(Thread* thread, JvmtiEnv* env) : _cur_thread(thread), _env(env) {
62 assert(_cur_thread == Thread::current(), "must be current thread");
63 }
64
65 void do_klass(Klass* k) {
66 // Collect all jclasses
67 _classStack.push((jclass) _env->jni_reference(Handle(_cur_thread, k->java_mirror())));
68 ensure_klass_alive(k->java_mirror());
69 }
70
71 int extract(jclass* result_list) {
72 // The size of the Stack will be 0 after extract, so get it here
73 int count = (int)_classStack.size();
74 int i = count;
75
76 // Pop all jclasses, fill backwards
77 while (!_classStack.is_empty()) {
78 result_list[--i] = _classStack.pop();
79 }
80
81 // Return the number of elements written
82 return count;
83 }
84
85 // Return current size of the Stack
86 int get_count() {
87 return (int)_classStack.size();
88 }
89 };
90
91 // The closure for GetClassLoaderClasses
92 class JvmtiGetLoadedClassesClosure : public StackObj {
93 // Since the ClassLoaderDataGraph::dictionary_all_entries_do callback
94 // doesn't pass a closureData pointer,
95 // we use a thread-local slot to hold a pointer to
96 // a stack allocated instance of this structure.
97 private:
98 jobject _initiatingLoader;
99 int _count;
100 Handle* _list;
101 int _index;
102
103 private:
104 // Getting and setting the thread local pointer
105 static JvmtiGetLoadedClassesClosure* get_this() {
106 JvmtiGetLoadedClassesClosure* result = NULL;
107 JavaThread* thread = JavaThread::current();
108 result = thread->get_jvmti_get_loaded_classes_closure();
109 return result;
110 }
111 static void set_this(JvmtiGetLoadedClassesClosure* that) {
112 JavaThread* thread = JavaThread::current();
113 thread->set_jvmti_get_loaded_classes_closure(that);
114 }
115
116 public:
117 // Constructor/Destructor
118 JvmtiGetLoadedClassesClosure() {
119 JvmtiGetLoadedClassesClosure* that = get_this();
120 assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");
121 _initiatingLoader = NULL;
122 _count = 0;
123 _list = NULL;
124 _index = 0;
125 set_this(this);
126 }
127
128 JvmtiGetLoadedClassesClosure(jobject initiatingLoader) {
129 JvmtiGetLoadedClassesClosure* that = get_this();
130 assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");
131 _initiatingLoader = initiatingLoader;
132 _count = 0;
133 _list = NULL;
134 _index = 0;
135 set_this(this);
136 }
137
138 ~JvmtiGetLoadedClassesClosure() {
139 JvmtiGetLoadedClassesClosure* that = get_this();
140 assert(that != NULL, "JvmtiGetLoadedClassesClosure not found");
141 set_this(NULL);
142 _initiatingLoader = NULL;
143 _count = 0;
144 if (_list != NULL) {
145 FreeHeap(_list);
146 _list = NULL;
147 }
148 _index = 0;
149 }
150
151 // Accessors.
152 jobject get_initiatingLoader() {
153 return _initiatingLoader;
154 }
155
156 int get_count() {
157 return _count;
158 }
159
160 void set_count(int value) {
161 _count = value;
162 }
163
164 Handle* get_list() {
165 return _list;
166 }
167
168 void set_list(Handle* value) {
169 _list = value;
170 }
171
172 int get_index() {
173 return _index;
174 }
175
176 void set_index(int value) {
177 _index = value;
178 }
179
180 Handle get_element(int index) {
181 if ((_list != NULL) && (index < _count)) {
182 return _list[index];
183 } else {
184 assert(false, "empty get_element");
185 return Handle();
186 }
187 }
188
189 void set_element(int index, Handle value) {
190 if ((_list != NULL) && (index < _count)) {
191 _list[index] = value;
192 } else {
193 assert(false, "bad set_element");
194 }
195 }
196
197 // Other predicates
198 bool available() {
199 return (_list != NULL);
200 }
201
202 #ifdef ASSERT
203 // For debugging.
204 void check(int limit) {
205 for (int i = 0; i < limit; i += 1) {
206 assert(Universe::heap()->is_in(get_element(i)()), "check fails");
207 }
208 }
209 #endif
210
211 // Public methods that get called within the scope of the closure
212 void allocate() {
213 _list = NEW_C_HEAP_ARRAY(Handle, _count, mtInternal);
214 assert(_list != NULL, "Out of memory");
215 if (_list == NULL) {
216 _count = 0;
217 }
218 }
219
220 void extract(JvmtiEnv *env, jclass* result) {
221 for (int index = 0; index < _count; index += 1) {
222 result[index] = (jclass) env->jni_reference(get_element(index));
223 }
224 }
225
226 static void increment_with_loader(InstanceKlass* k, ClassLoaderData* loader_data) {
227 JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
228 oop class_loader = loader_data->class_loader();
229 if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {
230 for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
231 that->set_count(that->get_count() + 1);
232 }
233 }
234 }
235
236 static void add_with_loader(InstanceKlass* k, ClassLoaderData* loader_data) {
237 JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
238 if (that->available()) {
239 oop class_loader = loader_data->class_loader();
240 if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {
241 Thread *thread = Thread::current();
242 for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
243 Handle mirror(thread, l->java_mirror());
244 that->set_element(that->get_index(), mirror);
245 that->set_index(that->get_index() + 1);
246 }
247 }
248 }
249 }
250
251 // increment the count for the given basic type array class (and any
252 // multi-dimensional arrays). For example, for [B we check for
253 // [[B, [[[B, .. and the count is incremented for each one that exists.
254 static void increment_for_basic_type_arrays(Klass* k) {
255 JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
256 assert(that != NULL, "no JvmtiGetLoadedClassesClosure");
257 for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
258 that->set_count(that->get_count() + 1);
259 }
260 }
261
262 // add the basic type array class and its multi-dimensional array classes to the list
263 static void add_for_basic_type_arrays(Klass* k) {
264 JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
265 assert(that != NULL, "no JvmtiGetLoadedClassesClosure");
266 assert(that->available(), "no list");
267 Thread *thread = Thread::current();
268 for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
269 Handle mirror(thread, l->java_mirror());
270 that->set_element(that->get_index(), mirror);
271 that->set_index(that->get_index() + 1);
272 }
273 }
274 };
275
276
277 jvmtiError
278 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
279
280 LoadedClassesClosure closure(Thread::current(), env);
281 {
282 // To get a consistent list of classes we need MultiArray_lock to ensure
283 // array classes aren't created.
284 MutexLocker ma(MultiArray_lock);
285
286 // Iterate through all classes in ClassLoaderDataGraph
287 // and collect them using the LoadedClassesClosure
288 ClassLoaderDataGraph::loaded_classes_do(&closure);
289 }
290
291 // Return results by extracting the collected contents into a list
292 // allocated via JvmtiEnv
293 jclass* result_list;
294 jvmtiError error = env->Allocate(closure.get_count() * sizeof(jclass),
295 (unsigned char**)&result_list);
296
297 if (error == JVMTI_ERROR_NONE) {
298 int count = closure.extract(result_list);
299 *classCountPtr = count;
300 *classesPtr = result_list;
301 }
302 return error;
303 }
304
305 jvmtiError
306 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
307 jint* classCountPtr, jclass** classesPtr) {
308 // Since ClassLoaderDataGraph::dictionary_all_entries_do only takes a function pointer
309 // and doesn't call back with a closure data pointer,
310 // we can only pass static methods.
311 JvmtiGetLoadedClassesClosure closure(initiatingLoader);
312 {
313 // To get a consistent list of classes we need MultiArray_lock to ensure
314 // array classes aren't created, and SystemDictionary_lock to ensure that
315 // classes aren't added to the class loader data dictionaries.
316 MutexLocker ma(MultiArray_lock);
317 MutexLocker sd(SystemDictionary_lock);
318 // First, count the classes in the class loader data dictionaries which have this loader recorded
319 // as an initiating loader. For basic type arrays this information is not recorded
320 // so GetClassLoaderClasses will return all of the basic type arrays. This is okay
321 // because the defining loader for basic type arrays is always the boot class loader
322 // and these classes are "visible" to all loaders.
323 ClassLoaderDataGraph::dictionary_all_entries_do(&JvmtiGetLoadedClassesClosure::increment_with_loader);
324 Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::increment_for_basic_type_arrays);
325 // Next, fill in the classes
326 closure.allocate();
327 ClassLoaderDataGraph::dictionary_all_entries_do(&JvmtiGetLoadedClassesClosure::add_with_loader);
328 Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::add_for_basic_type_arrays);
329 // Drop the SystemDictionary_lock, so the results could be wrong from here,
330 // but we still have a snapshot.
331 }
332 // Post results
333 jclass* result_list;
334 jvmtiError err = env->Allocate(closure.get_count() * sizeof(jclass),
335 (unsigned char**)&result_list);
336 if (err != JVMTI_ERROR_NONE) {
337 return err;
338 }
339 closure.extract(env, result_list);
340 *classCountPtr = closure.get_count();
341 *classesPtr = result_list;
342 return JVMTI_ERROR_NONE;
343 }