| /* |
| * Copyright (c) 2001, 2005, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| /* |
| * This module tracks classes that have been prepared, so as to |
| * be able to compute which have been unloaded. On VM start-up |
| * all prepared classes are put in a table. As class prepare |
| * events come in they are added to the table. After an unload |
| * event or series of them, the VM can be asked for the list |
| * of classes; this list is compared against the table keep by |
| * this module, any classes no longer present are known to |
| * have been unloaded. |
| * |
| * ANDROID-CHANGED: This module is almost totally re-written |
| * for android. On android, we have a limited number of jweak |
| * references that can be around at any one time. In order to |
| * preserve this limited resource for user-code use we keep |
| * track of the status of classes using JVMTI tags. |
| * |
| * We keep a linked-list of the signatures of loaded classes |
| * associated with the tag we gave to that class. The tag is |
| * simply incremented every time we add a new class. |
| * |
| * We also request (on the separate tracking jvmtiEnv) an |
| * ObjectFree event be called for each of these classes. This |
| * allows us to keep a running list of all the classes known to |
| * have been collected since the last call to |
| * classTrack_processUnloads. On each call to processUnloads we |
| * iterate through this list and remove from the main list all |
| * the objects that have been collected. We then return a list of |
| * the class-signatures that have been collected. |
| * |
| * For efficiency and simplicity we don't bother retagging or |
| * re-using old tags, instead relying on the fact that no |
| * program will ever be able to exhaust the (2^64 - 1) possible |
| * tag values (which would require that many class-loads). |
| * |
| * This relies on the tagging and ObjectFree implementation being |
| * relatively efficient for performance. It has the advantage of |
| * not requiring any jweaks. |
| * |
| * All calls into any function of this module must be either |
| * done before the event-handler system is setup or done while |
| * holding the event handlerLock. The list of freed classes is |
| * protected by the classTagLock. |
| */ |
| |
| #include "util.h" |
| #include "bag.h" |
| #include "classTrack.h" |
| |
| typedef struct KlassNode { |
| jlong klass_tag; /* Tag the klass has in the tracking-env */ |
| char *signature; /* class signature */ |
| struct KlassNode *next; /* next node in this slot */ |
| } KlassNode; |
| |
| /* |
| * pointer to first node of a linked list of prepared classes KlassNodes. |
| */ |
| static KlassNode *list; |
| |
| /* |
| * The JVMTI env we use to keep track of klass tags which allows us to detect class-unloads. |
| */ |
| static jvmtiEnv *trackingEnv; |
| |
| /* |
| * The current highest tag number in use by the trackingEnv. |
| * |
| * No need for synchronization since everything is done under the handlerLock. |
| */ |
| static jlong currentKlassTag; |
| |
| /* |
| * A lock to protect access to 'deletedTagBag' |
| */ |
| static jrawMonitorID deletedTagLock; |
| |
| /* |
| * A bag containing all the deleted klass_tags ids. This must be accessed under the |
| * deletedTagLock. |
| * |
| * It is cleared each time classTrack_processUnloads is called. |
| */ |
| struct bag* deletedTagBag; |
| |
| /* |
| * The callback for when classes are freed. Only classes are called because this is registered with |
| * the trackingEnv which only tags classes. |
| */ |
| static void JNICALL |
| cbTrackingObjectFree(jvmtiEnv* jvmti_env, jlong tag) |
| { |
| debugMonitorEnter(deletedTagLock); |
| *(jlong*)bagAdd(deletedTagBag) = tag; |
| debugMonitorExit(deletedTagLock); |
| } |
| |
| /* |
| * Returns true (thus continuing the iteration) if the item is not the searched for tag. |
| */ |
| static jboolean |
| isNotTag(void* item, void* needle) |
| { |
| return *(jlong*)item != *(jlong*)needle; |
| } |
| |
| /* |
| * This requires that deletedTagLock and the handlerLock are both held. |
| */ |
| static jboolean |
| isClassUnloaded(jlong tag) |
| { |
| /* bagEnumerateOver returns true if 'func' returns true on all items and aborts early if not. */ |
| return !bagEnumerateOver(deletedTagBag, isNotTag, &tag); |
| } |
| |
| /* |
| * Called after class unloads have occurred. Creates a new hash table |
| * of currently loaded prepared classes. |
| * The signatures of classes which were unloaded (not present in the |
| * new table) are returned. |
| * |
| * NB This relies on addPreparedClass being called for every class loaded after the |
| * classTrack_initialize function is called. We will not request all loaded classes again after |
| * that. It also relies on not being called concurrently with any classTrack_addPreparedClass or |
| * other classTrack_processUnloads calls. |
| */ |
| struct bag * |
| classTrack_processUnloads(JNIEnv *env) |
| { |
| /* We could optimize this somewhat by holding the deletedTagLock for a much shorter time, |
| * replacing it as soon as we enter and then destroying it once we are done with it. This will |
| * cause a lot of memory churn and this function is not expected to be called that often. |
| * Furthermore due to the check for an empty bag (which should be very common) normally this |
| * will finish very quickly. In cases where there is a concurrent GC occuring and a class is |
| * being collected the GC-ing threads could be blocked until we are done but this is expected to |
| * be very rare. |
| */ |
| debugMonitorEnter(deletedTagLock); |
| /* Take and return the deletedTagBag */ |
| struct bag* deleted = bagCreateBag(sizeof(char*), bagSize(deletedTagBag)); |
| /* The deletedTagBag is going to be much shorter than the klassNode list so we should walk the |
| * KlassNode list once and scan the deletedTagBag each time. We only need to this in the rare |
| * case that there was anything deleted though. |
| */ |
| if (bagSize(deletedTagBag) != 0) { |
| KlassNode* node = list; |
| KlassNode** previousNext = &list; |
| |
| while (node != NULL) { |
| if (isClassUnloaded(node->klass_tag)) { |
| /* Update the previous node's next pointer to point after this node. Note that we |
| * update the value pointed to by previousNext but not the value of previousNext |
| * itself. |
| */ |
| *previousNext = node->next; |
| /* Put this nodes signature into the deleted bag */ |
| *(char**)bagAdd(deleted) = node->signature; |
| /* Deallocate the node */ |
| jvmtiDeallocate(node); |
| } else { |
| /* This node will become the previous node so update the previousNext pointer to |
| * this nodes next pointer. |
| */ |
| previousNext = &(node->next); |
| } |
| node = *previousNext; |
| } |
| bagDeleteAll(deletedTagBag); |
| } |
| debugMonitorExit(deletedTagLock); |
| return deleted; |
| } |
| |
| /* |
| * Add a class to the prepared class list. |
| * Assumes no duplicates. |
| */ |
| void |
| classTrack_addPreparedClass(JNIEnv *env, jclass klass) |
| { |
| KlassNode *node; |
| jvmtiError error; |
| |
| if (gdata->assertOn) { |
| /* Check this is not a duplicate */ |
| jlong tag; |
| error = JVMTI_FUNC_PTR(trackingEnv,GetTag)(trackingEnv, klass, &tag); |
| if (error != JVMTI_ERROR_NONE) { |
| EXIT_ERROR(error,"unable to get-tag with class trackingEnv!"); |
| } |
| if (tag != 0l) { |
| JDI_ASSERT_FAILED("Attempting to insert duplicate class"); |
| } |
| } |
| |
| node = jvmtiAllocate(sizeof(KlassNode)); |
| if (node == NULL) { |
| EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"KlassNode"); |
| } |
| error = classSignature(klass, &(node->signature), NULL); |
| if (error != JVMTI_ERROR_NONE) { |
| jvmtiDeallocate(node); |
| EXIT_ERROR(error,"signature"); |
| } |
| node->klass_tag = ++currentKlassTag; |
| error = JVMTI_FUNC_PTR(trackingEnv,SetTag)(trackingEnv, klass, node->klass_tag); |
| if (error != JVMTI_ERROR_NONE) { |
| jvmtiDeallocate(node->signature); |
| jvmtiDeallocate(node); |
| EXIT_ERROR(error,"SetTag"); |
| } |
| |
| /* Insert the new node */ |
| node->next = list; |
| list = node; |
| } |
| |
| static jboolean |
| setupEvents() |
| { |
| jvmtiCapabilities caps; |
| memset(&caps, 0, sizeof(caps)); |
| caps.can_generate_object_free_events = 1; |
| jvmtiError error = JVMTI_FUNC_PTR(trackingEnv,AddCapabilities)(trackingEnv, &caps); |
| if (error != JVMTI_ERROR_NONE) { |
| return JNI_FALSE; |
| } |
| jvmtiEventCallbacks cb; |
| memset(&cb, 0, sizeof(cb)); |
| cb.ObjectFree = cbTrackingObjectFree; |
| error = JVMTI_FUNC_PTR(trackingEnv,SetEventCallbacks)(trackingEnv, &cb, sizeof(cb)); |
| if (error != JVMTI_ERROR_NONE) { |
| return JNI_FALSE; |
| } |
| error = JVMTI_FUNC_PTR(trackingEnv,SetEventNotificationMode) |
| (trackingEnv, JVMTI_ENABLE, JVMTI_EVENT_OBJECT_FREE, NULL); |
| if (error != JVMTI_ERROR_NONE) { |
| return JNI_FALSE; |
| } |
| return JNI_TRUE; |
| } |
| |
| /* |
| * Called once to build the initial prepared class hash table. |
| */ |
| void |
| classTrack_initialize(JNIEnv *env) |
| { |
| /* ANDROID_CHANGED: Setup the tracking env and the currentKlassTag */ |
| trackingEnv = getSpecialJvmti(); |
| if ( trackingEnv == NULL ) { |
| EXIT_ERROR(AGENT_ERROR_INTERNAL,"Failed to allocate tag-tracking jvmtiEnv"); |
| } |
| /* We want to create these before turning on the events or tagging anything. */ |
| deletedTagLock = debugMonitorCreate("Deleted class tag lock"); |
| deletedTagBag = bagCreateBag(sizeof(jlong), 10); |
| /* ANDROID-CHANGED: Setup the trackingEnv's ObjectFree event */ |
| if (!setupEvents()) { |
| /* On android classes are usually not unloaded too often so this is not a huge loss. */ |
| ERROR_MESSAGE(("Unable to setup class ObjectFree tracking! Class unloads will not " |
| "be reported!")); |
| } |
| currentKlassTag = 0l; |
| list = NULL; |
| WITH_LOCAL_REFS(env, 1) { |
| |
| jint classCount; |
| jclass *classes; |
| jvmtiError error; |
| jint i; |
| |
| error = allLoadedClasses(&classes, &classCount); |
| if ( error == JVMTI_ERROR_NONE ) { |
| for (i=0; i<classCount; i++) { |
| jclass klass = classes[i]; |
| jint status; |
| jint wanted = |
| (JVMTI_CLASS_STATUS_PREPARED|JVMTI_CLASS_STATUS_ARRAY); |
| |
| /* We only want prepared classes and arrays */ |
| status = classStatus(klass); |
| if ( (status & wanted) != 0 ) { |
| classTrack_addPreparedClass(env, klass); |
| } |
| } |
| jvmtiDeallocate(classes); |
| } else { |
| EXIT_ERROR(error,"loaded classes array"); |
| } |
| |
| } END_WITH_LOCAL_REFS(env) |
| |
| } |
| |
| void |
| classTrack_reset(void) |
| { |
| } |