| /* |
| * Copyright (c) 1998, 2013, 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. |
| */ |
| |
| #if defined(_ALLBSD_SOURCE) |
| #include <stdint.h> /* for uintptr_t */ |
| #endif |
| |
| #include "util.h" |
| #include "commonRef.h" |
| |
| /* |
| * ANDROID-CHANGED: This was modified for android to avoid any use of weak |
| * global (jweak) references. On Android hosts the number of jweak |
| * references active at any one time is limited. By using jweaks to keep |
| * track of objects here we could hit the jweak limit on some very large |
| * apps. The implementation is compatible with any JVMTI implementation |
| * that provides the 'can_tag_objects' and |
| * 'can_generate_object_free_events' capabilities. This works by watching |
| * for the ObjectFree events on tagged objects and storing them in a list |
| * of things that have been deleted. |
| * |
| * Each object sent to the front end is tracked with the RefNode struct |
| * (see util.h). |
| * External to this module, objects are identified by a jlong id which is |
| * simply the sequence number. A JVMTI tag is usually used so that |
| * the presence of a debugger-tracked object will not prevent |
| * its collection. Once an object is collected, its RefNode may be |
| * deleted (these may happen in * either order). Using the sequence number |
| * as the object id prevents ambiguity in the object id when the weak ref |
| * is reused. The RefNode* is stored with the object as it's JVMTI Tag. |
| * This tag also provides the weak-reference behavior. |
| * |
| * The ref member is changed from weak to strong when gc of the object is |
| * to be prevented. Whether or not it is strong, it is never exported |
| * from this module. |
| * |
| * A reference count of each jobject is also maintained here. It tracks |
| * the number times an object has been referenced through |
| * commonRef_refToID. A RefNode is freed once the reference |
| * count is decremented to 0 (with commonRef_release*), even if the |
| * corresponding object has not been collected. |
| * |
| * One hash table is maintained. The mapping of ID to RefNode* is handled |
| * with one hash table that will re-size itself as the number of RefNode's |
| * grow. |
| */ |
| |
| /* Initial hash table size (must be power of 2) */ |
| #define HASH_INIT_SIZE 512 |
| /* If element count exceeds HASH_EXPAND_SCALE*hash_size we expand & re-hash */ |
| #define HASH_EXPAND_SCALE 8 |
| /* Maximum hash table size (must be power of 2) */ |
| #define HASH_MAX_SIZE (1024*HASH_INIT_SIZE) |
| |
| /* Map a key (ID) to a hash bucket */ |
| static jint |
| hashBucket(jlong key) |
| { |
| /* Size should always be a power of 2, use mask instead of mod operator */ |
| /*LINTED*/ |
| return ((jint)key) & (gdata->objectsByIDsize-1); |
| } |
| |
| /* Generate a new ID */ |
| static jlong |
| newSeqNum(void) |
| { |
| return gdata->nextSeqNum++; |
| } |
| |
| /* ANDROID-CHANGED: This helper function is unique to android. |
| * This function gets a local-ref to object the node is pointing to. If the node's object has been |
| * collected it will return NULL. The caller is responsible for calling env->DeleteLocalRef or |
| * env->PopLocalFrame to clean up the reference. This function makes no changes to the passed in |
| * node. |
| */ |
| static jobject |
| getLocalRef(JNIEnv *env, const RefNode* node) { |
| if (node->isStrong) { |
| return JNI_FUNC_PTR(env,NewLocalRef)(env, node->ref); |
| } |
| jint count = -1; |
| jobject *objects = NULL; |
| jlong tag = ptr_to_jlong(node); |
| jvmtiError error = JVMTI_FUNC_PTR(gdata->jvmti,GetObjectsWithTags) |
| (gdata->jvmti, 1, &tag, &count, &objects, NULL); |
| if (error != JVMTI_ERROR_NONE) { |
| EXIT_ERROR(error,"GetObjectsWithTags"); |
| } |
| if (count != 1 && count != 0) { |
| EXIT_ERROR(AGENT_ERROR_INTERNAL, |
| "GetObjectsWithTags returned multiple objects unexpectedly"); |
| } |
| jobject res = (count == 0) ? NULL : objects[0]; |
| JVMTI_FUNC_PTR(gdata->jvmti,Deallocate)(gdata->jvmti,(unsigned char*)objects); |
| return res; |
| } |
| |
| /* ANDROID-CHANGED: Handler function for objects being freed. */ |
| void commonRef_handleFreedObject(jlong tag) { |
| RefNode* node = (RefNode*)jlong_to_ptr(tag); |
| debugMonitorEnterNoSuspend(gdata->refLock); { |
| // Delete the node and remove it from the hashmap. |
| // If we raced with a deleteNode call and lost the next and prev will be null but we will |
| // not be at the start of the bucket. This is fine. |
| jint slot = hashBucket(node->seqNum); |
| if (node->next != NULL || |
| node->prev != NULL || |
| gdata->objectsByID[slot] == node) { |
| /* Detach from id hash table */ |
| if (node->prev == NULL) { |
| gdata->objectsByID[slot] = node->next; |
| } else { |
| node->prev->next = node->next; |
| } |
| /* Also fixup back links. */ |
| if (node->next != NULL) { |
| node->next->prev = node->prev; |
| } |
| gdata->objectsByIDcount--; |
| } |
| jvmtiDeallocate(node); |
| } debugMonitorExit(gdata->refLock); |
| } |
| |
| /* Create a fresh RefNode structure, and tag the object (creating a weak-ref to it). |
| * ANDROID-CHANGED: The definition of RefNode was changed slightly so that node->ref is only for |
| * a strong reference. For weak references we use the node as a tag on the object to keep track if |
| * it. |
| * ANDROID-CHANGED: ref must be a local-reference held live for the duration of this method until it |
| * is fully in the objectByID map. |
| */ |
| static RefNode * |
| createNode(JNIEnv *env, jobject ref) |
| { |
| RefNode *node; |
| jvmtiError error; |
| |
| if (ref == NULL) { |
| return NULL; |
| } |
| |
| /* Could allocate RefNode's in blocks, not sure it would help much */ |
| node = (RefNode*)jvmtiAllocate((int)sizeof(RefNode)); |
| if (node == NULL) { |
| return NULL; |
| } |
| |
| /* ANDROID-CHANGED: Use local reference to make sure we have a reference. We will use this |
| * reference to set a tag to the node to use as a weak-reference and keep track of the ref. |
| * ANDROID-CHANGED: Set node tag on the ref. This tag now functions as the weak-reference to the |
| * object. |
| */ |
| error = JVMTI_FUNC_PTR(gdata->jvmti, SetTag)(gdata->jvmti, ref, ptr_to_jlong(node)); |
| if ( error != JVMTI_ERROR_NONE ) { |
| jvmtiDeallocate(node); |
| return NULL; |
| } |
| |
| /* Fill in RefNode */ |
| node->ref = NULL; |
| node->isStrong = JNI_FALSE; |
| node->count = 1; |
| node->seqNum = newSeqNum(); |
| |
| /* Count RefNode's created */ |
| gdata->objectsByIDcount++; |
| return node; |
| } |
| |
| /* Delete a RefNode allocation, delete weak/global ref and clear tag */ |
| static void |
| deleteNode(JNIEnv *env, RefNode *node) |
| { |
| /* ANDROID-CHANGED: use getLocalRef to get a local reference to the node. */ |
| WITH_LOCAL_REFS(env, 1) { |
| jobject localRef = getLocalRef(env, node); |
| LOG_MISC(("Freeing %d\n", (int)node->seqNum)); |
| |
| /* Detach from id hash table */ |
| if (node->prev == NULL) { |
| gdata->objectsByID[hashBucket(node->seqNum)] = node->next; |
| } else { |
| node->prev->next = node->next; |
| } |
| /* Also fixup back links. */ |
| if (node->next != NULL) { |
| node->next->prev = node->prev; |
| } |
| |
| // If we don't get the localref that means the ObjectFree event is being called and the |
| // node will be deleted there. |
| if ( localRef != NULL ) { |
| /* Clear tag */ |
| (void)JVMTI_FUNC_PTR(gdata->jvmti,SetTag) |
| (gdata->jvmti, localRef, NULL_OBJECT_ID); |
| if (node->isStrong) { |
| JNI_FUNC_PTR(env,DeleteGlobalRef)(env, node->ref); |
| } |
| |
| jvmtiDeallocate(node); |
| } else { |
| // We are going to let the object-free do the final work. Mark this node as not in the |
| // list with both null links but not in the bucket. |
| node->prev = NULL; |
| node->next = NULL; |
| } |
| gdata->objectsByIDcount--; |
| } END_WITH_LOCAL_REFS(env); |
| } |
| |
| /* Change a RefNode to have a strong reference */ |
| static jobject |
| strengthenNode(JNIEnv *env, RefNode *node) |
| { |
| if (!node->isStrong) { |
| /* ANDROID-CHANGED: We need to find and fill in the node->ref when we strengthen a node. */ |
| WITH_LOCAL_REFS(env, 1) { |
| /* getLocalRef will return NULL if the referent has been collected. */ |
| jobject localRef = getLocalRef(env, node); |
| if (localRef != NULL) { |
| node->ref = JNI_FUNC_PTR(env,NewGlobalRef)(env, localRef); |
| if (node->ref == NULL) { |
| EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"NewGlobalRef"); |
| } |
| node->isStrong = JNI_TRUE; |
| } |
| } END_WITH_LOCAL_REFS(env); |
| } |
| return node->ref; |
| } |
| |
| /* Change a RefNode to have a weak reference |
| * ANDROID-CHANGED: This is done by deleting the strong reference. We already have a tag in |
| * to the node from when we created the node. Since this is never removed we can simply delete the |
| * global ref, reset node->isStrong & node->ref, and return. Since no part of this can fail we can |
| * change this function to be void too. |
| */ |
| static void |
| weakenNode(JNIEnv *env, RefNode *node) |
| { |
| if (node->isStrong) { |
| JNI_FUNC_PTR(env,DeleteGlobalRef)(env, node->ref); |
| node->ref = NULL; |
| node->isStrong = JNI_FALSE; |
| } |
| } |
| |
| /* |
| * Returns the node which contains the common reference for the |
| * given object. The passed reference should not be a weak reference |
| * managed in the object hash table (i.e. returned by commonRef_idToRef) |
| * because no sequence number checking is done. |
| */ |
| static RefNode * |
| findNodeByRef(JNIEnv *env, jobject ref) |
| { |
| jvmtiError error; |
| jlong tag; |
| |
| tag = NULL_OBJECT_ID; |
| error = JVMTI_FUNC_PTR(gdata->jvmti,GetTag)(gdata->jvmti, ref, &tag); |
| if ( error == JVMTI_ERROR_NONE ) { |
| RefNode *node; |
| |
| node = (RefNode*)jlong_to_ptr(tag); |
| return node; |
| } |
| return NULL; |
| } |
| |
| /* Locate and delete a node based on ID */ |
| static void |
| deleteNodeByID(JNIEnv *env, jlong id, jint refCount) |
| { |
| /* ANDROID-CHANGED: Rewrite for double-linked list. Also remove ALL_REFS since it's not needed |
| * since the free-callback will do the work of cleaning up when an object gets collected. */ |
| jint slot; |
| RefNode *node; |
| |
| slot = hashBucket(id); |
| node = gdata->objectsByID[slot]; |
| |
| while (node != NULL) { |
| if (id == node->seqNum) { |
| node->count -= refCount; |
| if (node->count <= 0) { |
| if ( node->count < 0 ) { |
| EXIT_ERROR(AGENT_ERROR_INTERNAL,"RefNode count < 0"); |
| } |
| deleteNode(env, node); |
| } |
| break; |
| } |
| node = node->next; |
| } |
| } |
| |
| /* |
| * Returns the node stored in the object hash table for the given object |
| * id. The id should be a value previously returned by |
| * commonRef_refToID. |
| * |
| * NOTE: It is possible that a match is found here, but that the object |
| * is garbage collected by the time the caller inspects node->ref. |
| * Callers should take care using the node->ref object returned here. |
| * |
| */ |
| static RefNode * |
| findNodeByID(JNIEnv *env, jlong id) |
| { |
| /* ANDROID-CHANGED: Rewrite for double-linked list */ |
| jint slot; |
| RefNode *node; |
| |
| slot = hashBucket(id); |
| node = gdata->objectsByID[slot]; |
| |
| while (node != NULL) { |
| if ( id == node->seqNum ) { |
| if ( node->prev != NULL ) { |
| /* Re-order hash list so this one is up front */ |
| node->prev->next = node->next; |
| node->prev->prev = node->prev; |
| node->next = gdata->objectsByID[slot]; |
| node->next->prev = node; |
| node->prev = NULL; |
| gdata->objectsByID[slot] = node; |
| } |
| break; |
| } |
| node = node->next; |
| } |
| return node; |
| } |
| |
| /* Initialize the hash table stored in gdata area */ |
| static void |
| initializeObjectsByID(int size) |
| { |
| /* Size should always be a power of 2 */ |
| if ( size > HASH_MAX_SIZE ) size = HASH_MAX_SIZE; |
| gdata->objectsByIDsize = size; |
| gdata->objectsByIDcount = 0; |
| gdata->objectsByID = (RefNode**)jvmtiAllocate((int)sizeof(RefNode*)*size); |
| (void)memset(gdata->objectsByID, 0, (int)sizeof(RefNode*)*size); |
| } |
| |
| /* hash in a RefNode */ |
| static void |
| hashIn(RefNode *node) |
| { |
| /* ANDROID-CHANGED: Modify for double-linked list */ |
| jint slot; |
| |
| /* Add to id hashtable */ |
| slot = hashBucket(node->seqNum); |
| node->next = gdata->objectsByID[slot]; |
| node->prev = NULL; |
| if (node->next != NULL) { |
| node->next->prev = node; |
| } |
| gdata->objectsByID[slot] = node; |
| } |
| |
| /* Allocate and add RefNode to hash table |
| * ANDROID-CHANGED: Requires that ref be a held-live local ref.*/ |
| static RefNode * |
| newCommonRef(JNIEnv *env, jobject ref) |
| { |
| RefNode *node; |
| |
| /* Allocate the node and set it up */ |
| node = createNode(env, ref); |
| if ( node == NULL ) { |
| return NULL; |
| } |
| |
| /* See if hash table needs expansion */ |
| if ( gdata->objectsByIDcount > gdata->objectsByIDsize*HASH_EXPAND_SCALE && |
| gdata->objectsByIDsize < HASH_MAX_SIZE ) { |
| RefNode **old; |
| int oldsize; |
| int newsize; |
| int i; |
| |
| /* Save old information */ |
| old = gdata->objectsByID; |
| oldsize = gdata->objectsByIDsize; |
| /* Allocate new hash table */ |
| gdata->objectsByID = NULL; |
| newsize = oldsize*HASH_EXPAND_SCALE; |
| if ( newsize > HASH_MAX_SIZE ) newsize = HASH_MAX_SIZE; |
| initializeObjectsByID(newsize); |
| /* Walk over old one and hash in all the RefNodes */ |
| for ( i = 0 ; i < oldsize ; i++ ) { |
| RefNode *onode; |
| |
| onode = old[i]; |
| while (onode != NULL) { |
| RefNode *next; |
| |
| next = onode->next; |
| hashIn(onode); |
| onode = next; |
| } |
| } |
| jvmtiDeallocate(old); |
| } |
| |
| /* Add to id hashtable */ |
| hashIn(node); |
| return node; |
| } |
| |
| /* Initialize the commonRefs usage */ |
| void |
| commonRef_initialize(void) |
| { |
| gdata->refLock = debugMonitorCreate("JDWP Reference Table Monitor"); |
| gdata->nextSeqNum = 1; /* 0 used for error indication */ |
| initializeObjectsByID(HASH_INIT_SIZE); |
| } |
| |
| /* Reset the commonRefs usage */ |
| void |
| commonRef_reset(JNIEnv *env) |
| { |
| debugMonitorEnter(gdata->refLock); { |
| int i; |
| |
| for (i = 0; i < gdata->objectsByIDsize; i++) { |
| RefNode *node; |
| |
| for (node = gdata->objectsByID[i]; node != NULL; node = gdata->objectsByID[i]) { |
| deleteNode(env, node); |
| } |
| gdata->objectsByID[i] = NULL; |
| } |
| |
| /* Toss entire hash table and re-create a new one */ |
| jvmtiDeallocate(gdata->objectsByID); |
| gdata->objectsByID = NULL; |
| gdata->nextSeqNum = 1; /* 0 used for error indication */ |
| initializeObjectsByID(HASH_INIT_SIZE); |
| |
| } debugMonitorExit(gdata->refLock); |
| } |
| |
| /* |
| * Given a reference obtained from JNI or JVMTI, return an object |
| * id suitable for sending to the debugger front end. |
| */ |
| jlong |
| commonRef_refToID(JNIEnv *env, jobject ref) |
| { |
| jlong id; |
| |
| if (ref == NULL) { |
| return NULL_OBJECT_ID; |
| } |
| |
| id = NULL_OBJECT_ID; |
| debugMonitorEnter(gdata->refLock); { |
| RefNode *node; |
| |
| node = findNodeByRef(env, ref); |
| if (node == NULL) { |
| WITH_LOCAL_REFS(env, 1) { |
| node = newCommonRef(env, JNI_FUNC_PTR(env,NewLocalRef)(env, ref)); |
| if ( node != NULL ) { |
| id = node->seqNum; |
| } |
| } END_WITH_LOCAL_REFS(env); |
| } else { |
| id = node->seqNum; |
| node->count++; |
| } |
| } debugMonitorExit(gdata->refLock); |
| return id; |
| } |
| |
| /* |
| * Given an object ID obtained from the debugger front end, return a |
| * strong, global reference to that object (or NULL if the object |
| * has been collected). The reference can then be used for JNI and |
| * JVMTI calls. Caller is resposible for deleting the returned reference. |
| */ |
| jobject |
| commonRef_idToRef(JNIEnv *env, jlong id) |
| { |
| jobject ref; |
| |
| ref = NULL; |
| debugMonitorEnter(gdata->refLock); { |
| RefNode *node; |
| |
| node = findNodeByID(env, id); |
| if (node != NULL) { |
| if (node->isStrong) { |
| saveGlobalRef(env, node->ref, &ref); |
| } else { |
| jobject lref; |
| |
| /* ANDROID-CHANGED: Use getLocalRef helper to get a local-reference to the object |
| * this node weakly points to. It will return NULL if the object has been GCd |
| */ |
| lref = getLocalRef(env, node); |
| if ( lref != NULL ) { |
| /* ANDROID-CHANGED: Use lref to save the global ref since that is the only real |
| * jobject we have. |
| */ |
| saveGlobalRef(env, lref, &ref); |
| JNI_FUNC_PTR(env,DeleteLocalRef)(env, lref); |
| } |
| /* ANDROID-CHANGED: Otherwise the object was GC'd shortly after we found the node. |
| * The free callback will deal with cleanup once we return. |
| */ |
| } |
| } |
| } debugMonitorExit(gdata->refLock); |
| return ref; |
| } |
| |
| /* Deletes the global reference that commonRef_idToRef() created */ |
| void |
| commonRef_idToRef_delete(JNIEnv *env, jobject ref) |
| { |
| if ( ref==NULL ) { |
| return; |
| } |
| tossGlobalRef(env, &ref); |
| } |
| |
| |
| /* Prevent garbage collection of an object */ |
| jvmtiError |
| commonRef_pin(jlong id) |
| { |
| jvmtiError error; |
| |
| error = JVMTI_ERROR_NONE; |
| if (id == NULL_OBJECT_ID) { |
| return error; |
| } |
| debugMonitorEnter(gdata->refLock); { |
| JNIEnv *env; |
| RefNode *node; |
| |
| env = getEnv(); |
| node = findNodeByID(env, id); |
| if (node == NULL) { |
| error = AGENT_ERROR_INVALID_OBJECT; |
| } else { |
| jobject strongRef; |
| |
| strongRef = strengthenNode(env, node); |
| if (strongRef == NULL) { |
| /* |
| * Referent has been collected, clean up now. |
| * ANDROID-CHANGED: The node will be cleaned up by the object-free callback. |
| */ |
| error = AGENT_ERROR_INVALID_OBJECT; |
| } |
| } |
| } debugMonitorExit(gdata->refLock); |
| return error; |
| } |
| |
| /* Permit garbage collection of an object */ |
| jvmtiError |
| commonRef_unpin(jlong id) |
| { |
| jvmtiError error; |
| |
| error = JVMTI_ERROR_NONE; |
| debugMonitorEnter(gdata->refLock); { |
| JNIEnv *env; |
| RefNode *node; |
| |
| env = getEnv(); |
| node = findNodeByID(env, id); |
| if (node != NULL) { |
| // ANDROID-CHANGED: weakenNode was changed to never fail. |
| weakenNode(env, node); |
| } |
| } debugMonitorExit(gdata->refLock); |
| return error; |
| } |
| |
| /* Release tracking of an object by ID */ |
| void |
| commonRef_release(JNIEnv *env, jlong id) |
| { |
| debugMonitorEnter(gdata->refLock); { |
| deleteNodeByID(env, id, 1); |
| } debugMonitorExit(gdata->refLock); |
| } |
| |
| void |
| commonRef_releaseMultiple(JNIEnv *env, jlong id, jint refCount) |
| { |
| debugMonitorEnter(gdata->refLock); { |
| deleteNodeByID(env, id, refCount); |
| } debugMonitorExit(gdata->refLock); |
| } |
| |
| /* Get rid of RefNodes for objects that no longer exist */ |
| void |
| commonRef_compact(void) |
| { |
| // NO-OP. |
| } |
| |
| /* Lock the commonRef tables */ |
| void |
| commonRef_lock(void) |
| { |
| debugMonitorEnter(gdata->refLock); |
| } |
| |
| /* Unlock the commonRef tables */ |
| void |
| commonRef_unlock(void) |
| { |
| debugMonitorExit(gdata->refLock); |
| } |
