Visit.cpp revision c1a4ab9c313d8a3d12007f2dbef7b5a6fa4ac2ef 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "Dalvik.h"
18#include "alloc/HeapInternal.h"
19#include "alloc/Visit.h"
20#include "alloc/VisitInlines.h"
21
22/*
23 * Visits all of the reference locations in an object.
24 */
25void dvmVisitObject(Visitor *visitor, Object *obj, void *arg)
26{
27    assert(visitor != NULL);
28    assert(obj != NULL);
29    assert(obj->clazz != NULL);
30    visitObject(visitor, obj, arg);
31}
32
33/*
34 * Applies a verification function to all present values in the hash table.
35 */
36static void visitHashTable(RootVisitor *visitor, HashTable *table,
37                           RootType type, void *arg)
38{
39    assert(visitor != NULL);
40    assert(table != NULL);
41    dvmHashTableLock(table);
42    for (int i = 0; i < table->tableSize; ++i) {
43        HashEntry *entry = &table->pEntries[i];
44        if (entry->data != NULL && entry->data != HASH_TOMBSTONE) {
45            (*visitor)(&entry->data, 0, type, arg);
46        }
47    }
48    dvmHashTableUnlock(table);
49}
50
51/*
52 * Visits all entries in the reference table.
53 */
54static void visitReferenceTable(RootVisitor *visitor, ReferenceTable *table,
55                                u4 threadId, RootType type, void *arg)
56{
57    assert(visitor != NULL);
58    assert(table != NULL);
59    for (Object **entry = table->table; entry < table->nextEntry; ++entry) {
60        assert(entry != NULL);
61        (*visitor)(entry, threadId, type, arg);
62    }
63}
64
65/*
66 * Visits all entries in the indirect reference table.
67 */
68static void visitIndirectRefTable(RootVisitor *visitor, IndirectRefTable *table,
69                                  u4 threadId, RootType type, void *arg)
70{
71    assert(visitor != NULL);
72    assert(table != NULL);
73    typedef IndirectRefTable::iterator It; // TODO: C++0x auto
74    for (It it = table->begin(), end = table->end(); it != end; ++it) {
75        (*visitor)(*it, threadId, type, arg);
76    }
77}
78
79/*
80 * Visits all stack slots except those belonging to native method
81 * arguments.
82 */
83static void visitThreadStack(RootVisitor *visitor, Thread *thread, void *arg)
84{
85    assert(visitor != NULL);
86    assert(thread != NULL);
87    u4 threadId = thread->threadId;
88    const StackSaveArea *saveArea;
89    for (u4 *fp = (u4 *)thread->interpSave.curFrame;
90         fp != NULL;
91         fp = (u4 *)saveArea->prevFrame) {
92        Method *method;
93        saveArea = SAVEAREA_FROM_FP(fp);
94        method = (Method *)saveArea->method;
95        if (method != NULL && !dvmIsNativeMethod(method)) {
96            const RegisterMap* pMap = dvmGetExpandedRegisterMap(method);
97            const u1* regVector = NULL;
98            if (pMap != NULL) {
99                /* found map, get registers for this address */
100                int addr = saveArea->xtra.currentPc - method->insns;
101                regVector = dvmRegisterMapGetLine(pMap, addr);
102            }
103            if (regVector == NULL) {
104                /*
105                 * Either there was no register map or there is no
106                 * info for the current PC.  Perform a conservative
107                 * scan.
108                 */
109                for (size_t i = 0; i < method->registersSize; ++i) {
110                    if (dvmIsValidObject((Object *)fp[i])) {
111                        (*visitor)(&fp[i], threadId, ROOT_JAVA_FRAME, arg);
112                    }
113                }
114            } else {
115                /*
116                 * Precise scan.  v0 is at the lowest address on the
117                 * interpreted stack, and is the first bit in the
118                 * register vector, so we can walk through the
119                 * register map and memory in the same direction.
120                 *
121                 * A '1' bit indicates a live reference.
122                 */
123                u2 bits = 1 << 1;
124                for (size_t i = 0; i < method->registersSize; ++i) {
125                    bits >>= 1;
126                    if (bits == 1) {
127                        /* set bit 9 so we can tell when we're empty */
128                        bits = *regVector++ | 0x0100;
129                    }
130                    if ((bits & 0x1) != 0) {
131                        /*
132                         * Register is marked as live, it's a valid root.
133                         */
134#if WITH_EXTRA_GC_CHECKS
135                        if (fp[i] != 0 && !dvmIsValidObject((Object *)fp[i])) {
136                            /* this is very bad */
137                            ALOGE("PGC: invalid ref in reg %d: %#x",
138                                 method->registersSize - 1 - i, fp[i]);
139                            ALOGE("PGC: %s.%s addr %#x",
140                                 method->clazz->descriptor, method->name,
141                                 saveArea->xtra.currentPc - method->insns);
142                            continue;
143                        }
144#endif
145                        (*visitor)(&fp[i], threadId, ROOT_JAVA_FRAME, arg);
146                    }
147                }
148                dvmReleaseRegisterMapLine(pMap, regVector);
149            }
150        }
151        /*
152         * Don't fall into an infinite loop if things get corrupted.
153         */
154        assert((uintptr_t)saveArea->prevFrame > (uintptr_t)fp ||
155               saveArea->prevFrame == NULL);
156    }
157}
158
159/*
160 * Visits all roots associated with a thread.
161 */
162static void visitThread(RootVisitor *visitor, Thread *thread, void *arg)
163{
164    u4 threadId;
165
166    assert(visitor != NULL);
167    assert(thread != NULL);
168    threadId = thread->threadId;
169    (*visitor)(&thread->threadObj, threadId, ROOT_THREAD_OBJECT, arg);
170    (*visitor)(&thread->exception, threadId, ROOT_NATIVE_STACK, arg);
171    visitReferenceTable(visitor, &thread->internalLocalRefTable, threadId, ROOT_NATIVE_STACK, arg);
172    visitIndirectRefTable(visitor, &thread->jniLocalRefTable, threadId, ROOT_JNI_LOCAL, arg);
173    if (thread->jniMonitorRefTable.table != NULL) {
174        visitReferenceTable(visitor, &thread->jniMonitorRefTable, threadId, ROOT_JNI_MONITOR, arg);
175    }
176    visitThreadStack(visitor, thread, arg);
177}
178
179/*
180 * Visits all threads on the thread list.
181 */
182static void visitThreads(RootVisitor *visitor, void *arg)
183{
184    Thread *thread;
185
186    assert(visitor != NULL);
187    dvmLockThreadList(dvmThreadSelf());
188    thread = gDvm.threadList;
189    while (thread) {
190        visitThread(visitor, thread, arg);
191        thread = thread->next;
192    }
193    dvmUnlockThreadList();
194}
195
196static void visitPrimitiveTypes(RootVisitor *visitor, void *arg)
197{
198    (*visitor)(&gDvm.typeVoid, 0, ROOT_STICKY_CLASS, arg);
199    (*visitor)(&gDvm.typeBoolean, 0, ROOT_STICKY_CLASS, arg);
200    (*visitor)(&gDvm.typeByte, 0, ROOT_STICKY_CLASS, arg);
201    (*visitor)(&gDvm.typeShort, 0, ROOT_STICKY_CLASS, arg);
202    (*visitor)(&gDvm.typeChar, 0, ROOT_STICKY_CLASS, arg);
203    (*visitor)(&gDvm.typeInt, 0, ROOT_STICKY_CLASS, arg);
204    (*visitor)(&gDvm.typeLong, 0, ROOT_STICKY_CLASS, arg);
205    (*visitor)(&gDvm.typeFloat, 0, ROOT_STICKY_CLASS, arg);
206    (*visitor)(&gDvm.typeDouble, 0, ROOT_STICKY_CLASS, arg);
207}
208
209/*
210 * Visits roots.  TODO: visit cached global references.
211 */
212void dvmVisitRoots(RootVisitor *visitor, void *arg)
213{
214    assert(visitor != NULL);
215    visitHashTable(visitor, gDvm.loadedClasses, ROOT_STICKY_CLASS, arg);
216    visitPrimitiveTypes(visitor, arg);
217    if (gDvm.dbgRegistry != NULL) {
218        visitHashTable(visitor, gDvm.dbgRegistry, ROOT_DEBUGGER, arg);
219    }
220    if (gDvm.literalStrings != NULL) {
221        visitHashTable(visitor, gDvm.literalStrings, ROOT_INTERNED_STRING, arg);
222    }
223    dvmLockMutex(&gDvm.jniGlobalRefLock);
224    visitIndirectRefTable(visitor, &gDvm.jniGlobalRefTable, 0, ROOT_JNI_GLOBAL, arg);
225    dvmUnlockMutex(&gDvm.jniGlobalRefLock);
226    dvmLockMutex(&gDvm.jniPinRefLock);
227    visitReferenceTable(visitor, &gDvm.jniPinRefTable, 0, ROOT_VM_INTERNAL, arg);
228    dvmUnlockMutex(&gDvm.jniPinRefLock);
229    visitThreads(visitor, arg);
230    (*visitor)(&gDvm.outOfMemoryObj, 0, ROOT_VM_INTERNAL, arg);
231    (*visitor)(&gDvm.internalErrorObj, 0, ROOT_VM_INTERNAL, arg);
232    (*visitor)(&gDvm.noClassDefFoundErrorObj, 0, ROOT_VM_INTERNAL, arg);
233}
234