Binder.cpp revision 3bdc5b826803dca10d3625c56de38d6c55d869c8 
1/*
2 * Copyright (C) 2005 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 <binder/Binder.h>
18
19#include <stdatomic.h>
20#include <utils/misc.h>
21#include <binder/BpBinder.h>
22#include <binder/IInterface.h>
23#include <binder/Parcel.h>
24
25#include <stdio.h>
26
27namespace android {
28
29// ---------------------------------------------------------------------------
30
31IBinder::IBinder()
32    : RefBase()
33{
34}
35
36IBinder::~IBinder()
37{
38}
39
40// ---------------------------------------------------------------------------
41
42sp<IInterface>  IBinder::queryLocalInterface(const String16& /*descriptor*/)
43{
44    return NULL;
45}
46
47BBinder* IBinder::localBinder()
48{
49    return NULL;
50}
51
52BpBinder* IBinder::remoteBinder()
53{
54    return NULL;
55}
56
57bool IBinder::checkSubclass(const void* /*subclassID*/) const
58{
59    return false;
60}
61
62// ---------------------------------------------------------------------------
63
64class BBinder::Extras
65{
66public:
67    Mutex mLock;
68    BpBinder::ObjectManager mObjects;
69};
70
71// ---------------------------------------------------------------------------
72
73BBinder::BBinder()
74{
75  atomic_init(&mExtras, static_cast<uintptr_t>(0));
76}
77
78bool BBinder::isBinderAlive() const
79{
80    return true;
81}
82
83status_t BBinder::pingBinder()
84{
85    return NO_ERROR;
86}
87
88const String16& BBinder::getInterfaceDescriptor() const
89{
90    // This is a local static rather than a global static,
91    // to avoid static initializer ordering issues.
92    static String16 sEmptyDescriptor;
93    ALOGW("reached BBinder::getInterfaceDescriptor (this=%p)", this);
94    return sEmptyDescriptor;
95}
96
97status_t BBinder::transact(
98    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
99{
100    data.setDataPosition(0);
101
102    status_t err = NO_ERROR;
103    switch (code) {
104        case PING_TRANSACTION:
105            reply->writeInt32(pingBinder());
106            break;
107        default:
108            err = onTransact(code, data, reply, flags);
109            break;
110    }
111
112    if (reply != NULL) {
113        reply->setDataPosition(0);
114    }
115
116    return err;
117}
118
119status_t BBinder::linkToDeath(
120    const sp<DeathRecipient>& /*recipient*/, void* /*cookie*/,
121    uint32_t /*flags*/)
122{
123    return INVALID_OPERATION;
124}
125
126status_t BBinder::unlinkToDeath(
127    const wp<DeathRecipient>& /*recipient*/, void* /*cookie*/,
128    uint32_t /*flags*/, wp<DeathRecipient>* /*outRecipient*/)
129{
130    return INVALID_OPERATION;
131}
132
133    status_t BBinder::dump(int /*fd*/, const Vector<String16>& /*args*/)
134{
135    return NO_ERROR;
136}
137
138void BBinder::attachObject(
139    const void* objectID, void* object, void* cleanupCookie,
140    object_cleanup_func func)
141{
142    Extras* e = reinterpret_cast<Extras*>(
143                    atomic_load_explicit(&mExtras, memory_order_acquire));
144
145    if (!e) {
146        e = new Extras;
147        uintptr_t expected = 0;
148        if (!atomic_compare_exchange_strong_explicit(
149                                        &mExtras, &expected,
150                                        reinterpret_cast<uintptr_t>(e),
151                                        memory_order_release,
152                                        memory_order_acquire)) {
153            delete e;
154            e = reinterpret_cast<Extras*>(expected);  // Filled in by CAS
155        }
156        if (e == 0) return; // out of memory
157    }
158
159    AutoMutex _l(e->mLock);
160    e->mObjects.attach(objectID, object, cleanupCookie, func);
161}
162
163// The C11 standard doesn't allow atomic loads from const fields,
164// though C++11 does.  Fudge it until standards get straightened out.
165static inline uintptr_t load_const_atomic(const atomic_uintptr_t* p,
166                                          memory_order mo) {
167    atomic_uintptr_t* non_const_p = const_cast<atomic_uintptr_t*>(p);
168    return atomic_load_explicit(non_const_p, mo);
169}
170
171void* BBinder::findObject(const void* objectID) const
172{
173    Extras* e = reinterpret_cast<Extras*>(
174                    load_const_atomic(&mExtras, memory_order_acquire));
175    if (!e) return NULL;
176
177    AutoMutex _l(e->mLock);
178    return e->mObjects.find(objectID);
179}
180
181void BBinder::detachObject(const void* objectID)
182{
183    Extras* e = reinterpret_cast<Extras*>(
184                    atomic_load_explicit(&mExtras, memory_order_acquire));
185    if (!e) return;
186
187    AutoMutex _l(e->mLock);
188    e->mObjects.detach(objectID);
189}
190
191BBinder* BBinder::localBinder()
192{
193    return this;
194}
195
196BBinder::~BBinder()
197{
198    Extras* e = reinterpret_cast<Extras*>(
199                    atomic_load_explicit(&mExtras, memory_order_relaxed));
200    if (e) delete e;
201}
202
203
204status_t BBinder::onTransact(
205    uint32_t code, const Parcel& data, Parcel* reply, uint32_t /*flags*/)
206{
207    switch (code) {
208        case INTERFACE_TRANSACTION:
209            reply->writeString16(getInterfaceDescriptor());
210            return NO_ERROR;
211
212        case DUMP_TRANSACTION: {
213            int fd = data.readFileDescriptor();
214            int argc = data.readInt32();
215            Vector<String16> args;
216            for (int i = 0; i < argc && data.dataAvail() > 0; i++) {
217               args.add(data.readString16());
218            }
219            return dump(fd, args);
220        }
221
222        case SYSPROPS_TRANSACTION: {
223            report_sysprop_change();
224            return NO_ERROR;
225        }
226
227        default:
228            return UNKNOWN_TRANSACTION;
229    }
230}
231
232// ---------------------------------------------------------------------------
233
234enum {
235    // This is used to transfer ownership of the remote binder from
236    // the BpRefBase object holding it (when it is constructed), to the
237    // owner of the BpRefBase object when it first acquires that BpRefBase.
238    kRemoteAcquired = 0x00000001
239};
240
241BpRefBase::BpRefBase(const sp<IBinder>& o)
242    : mRemote(o.get()), mRefs(NULL), mState(0)
243{
244    extendObjectLifetime(OBJECT_LIFETIME_WEAK);
245
246    if (mRemote) {
247        mRemote->incStrong(this);           // Removed on first IncStrong().
248        mRefs = mRemote->createWeak(this);  // Held for our entire lifetime.
249    }
250}
251
252BpRefBase::~BpRefBase()
253{
254    if (mRemote) {
255        if (!(mState&kRemoteAcquired)) {
256            mRemote->decStrong(this);
257        }
258        mRefs->decWeak(this);
259    }
260}
261
262void BpRefBase::onFirstRef()
263{
264    android_atomic_or(kRemoteAcquired, &mState);
265}
266
267void BpRefBase::onLastStrongRef(const void* /*id*/)
268{
269    if (mRemote) {
270        mRemote->decStrong(this);
271    }
272}
273
274bool BpRefBase::onIncStrongAttempted(uint32_t /*flags*/, const void* /*id*/)
275{
276    return mRemote ? mRefs->attemptIncStrong(this) : false;
277}
278
279// ---------------------------------------------------------------------------
280
281}; // namespace android
282