1 /*
2 * Copyright (c) 2001, 2005, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * This module tracks classes that have been prepared, so as to
28 * be able to report which have been unloaded. On VM start-up
29 * and whenever new classes are loaded, all prepared classes'
30 * signatures are attached as JVMTI tag to the class object.
31 * Class unloading is tracked by registering
32 * ObjectFree callback on class objects. When this happens, we find
33 * the signature of the unloaded class(es) and report them back
34 * to the event handler to synthesize class-unload-events.
35 */
36
37 #include "util.h"
38 #include "bag.h"
39 #include "classTrack.h"
40
41 /*
42 * The JVMTI tracking env to keep track of klass tags for class-unloads
43 */
44 static jvmtiEnv* trackingEnv;
45
46 /*
47 * A bag containing all the deleted classes' signatures. Must be accessed under
48 * classTrackLock.
49 */
50 struct bag* deletedSignatures;
51
52 /*
53 * Lock to keep integrity of deletedSignatures.
54 */
55 static jrawMonitorID classTrackLock;
56
57 /*
58 * Invoke the callback when classes are freed, find and record the signature
59 * in deletedSignatures. Those are only used in addPreparedClass() by the
60 * same thread.
61 */
62 static void JNICALL
63 cbTrackingObjectFree(jvmtiEnv* jvmti_env, jlong tag)
64 {
65 debugMonitorEnter(classTrackLock);
66 if (deletedSignatures == NULL) {
67 debugMonitorExit(classTrackLock);
68 return;
69 }
70 *(char**)bagAdd(deletedSignatures) = (char*)tag;
71
72 debugMonitorExit(classTrackLock);
73 }
74
75 /*
76 * Called after class unloads have occurred.
77 * The signatures of classes which were unloaded are returned.
78 */
79 struct bag *
80 classTrack_processUnloads(JNIEnv *env)
81 {
82 debugMonitorEnter(classTrackLock);
83 if (deletedSignatures == NULL) {
84 // Class tracking not initialized, nobody's interested.
85 debugMonitorExit(classTrackLock);
86 return NULL;
87 }
88 struct bag* deleted = deletedSignatures;
89 deletedSignatures = bagCreateBag(sizeof(char*), 10);
90 debugMonitorExit(classTrackLock);
91 return deleted;
92 }
93
94 /*
95 * Add a class to the prepared class table.
96 */
97 void
98 classTrack_addPreparedClass(JNIEnv *env_unused, jclass klass)
99 {
100 jvmtiError error;
101
102 jvmtiEnv* env = trackingEnv;
103
104 // Check this is not already tagged.
105 jlong tag;
106 error = JVMTI_FUNC_PTR(trackingEnv, GetTag)(env, klass, &tag);
107 if (error != JVMTI_ERROR_NONE) {
108 EXIT_ERROR(error, "Unable to GetTag with class trackingEnv");
109 }
110 if (tag != 0l) {
111 return; // Already added
112 }
113
114 char* signature;
115 error = classSignature(klass, &signature, NULL);
116 if (error != JVMTI_ERROR_NONE) {
117 EXIT_ERROR(error,"signature");
118 }
119 error = JVMTI_FUNC_PTR(trackingEnv, SetTag)(env, klass, (jlong)signature);
120 if (error != JVMTI_ERROR_NONE) {
121 jvmtiDeallocate(signature);
122 EXIT_ERROR(error,"SetTag");
123 }
124
125 }
126
127 static jboolean
128 setupEvents()
129 {
130 jvmtiCapabilities caps;
131 memset(&caps, 0, sizeof(caps));
132 caps.can_generate_object_free_events = 1;
133 jvmtiError error = JVMTI_FUNC_PTR(trackingEnv, AddCapabilities)(trackingEnv, &caps);
134 if (error != JVMTI_ERROR_NONE) {
135 return JNI_FALSE;
136 }
137 jvmtiEventCallbacks cb;
138 memset(&cb, 0, sizeof(cb));
139 cb.ObjectFree = cbTrackingObjectFree;
140 error = JVMTI_FUNC_PTR(trackingEnv, SetEventCallbacks)(trackingEnv, &cb, sizeof(cb));
141 if (error != JVMTI_ERROR_NONE) {
142 return JNI_FALSE;
143 }
144 error = JVMTI_FUNC_PTR(trackingEnv, SetEventNotificationMode)(trackingEnv, JVMTI_ENABLE, JVMTI_EVENT_OBJECT_FREE, NULL);
145 if (error != JVMTI_ERROR_NONE) {
146 return JNI_FALSE;
147 }
148 return JNI_TRUE;
149 }
150
151 /*
152 * Called once to initialize class-tracking.
153 */
154 void
155 classTrack_initialize(JNIEnv *env)
156 {
157 deletedSignatures = NULL;
158 classTrackLock = debugMonitorCreate("Deleted class tag lock");
159 trackingEnv = getSpecialJvmti();
160 if (trackingEnv == NULL) {
161 EXIT_ERROR(AGENT_ERROR_INTERNAL, "Failed to allocate tag-tracking jvmtiEnv");
162 }
163
164
165 if (!setupEvents()) {
166 EXIT_ERROR(AGENT_ERROR_INTERNAL, "Unable to setup ObjectFree tracking");
167 }
168
169 jint classCount;
170 jclass *classes;
171 jvmtiError error;
172 jint i;
173
174 error = allLoadedClasses(&classes, &classCount);
175 if ( error == JVMTI_ERROR_NONE ) {
176 for (i = 0; i < classCount; i++) {
177 jclass klass = classes[i];
178 jint status;
179 jint wanted = JVMTI_CLASS_STATUS_PREPARED | JVMTI_CLASS_STATUS_ARRAY;
180 status = classStatus(klass);
181 if ((status & wanted) != 0) {
182 classTrack_addPreparedClass(env, klass);
183 }
184 }
185 jvmtiDeallocate(classes);
186 } else {
187 EXIT_ERROR(error,"loaded classes array");
188 }
189 }
190
191 /*
192 * Called to activate class-tracking when a listener registers for EI_GC_FINISH.
193 */
194 void
195 classTrack_activate(JNIEnv *env)
196 {
197 debugMonitorEnter(classTrackLock);
198 deletedSignatures = bagCreateBag(sizeof(char*), 1000);
199 debugMonitorExit(classTrackLock);
200 }
201
202 static jboolean
203 cleanDeleted(void *signatureVoid, void *arg)
204 {
205 char* sig = *(char**)signatureVoid;
206 jvmtiDeallocate(sig);
207 return JNI_TRUE;
208 }
209
210 /*
211 * Called when agent detaches.
212 */
213 void
214 classTrack_reset(void)
215 {
216 debugMonitorEnter(classTrackLock);
217
218 bagEnumerateOver(deletedSignatures, cleanDeleted, NULL);
219 bagDestroyBag(deletedSignatures);
220 deletedSignatures = NULL;
221
222 debugMonitorExit(classTrackLock);
223 }