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