libs/binder/Binder.cpp

/*
 * Copyright (C) 2005 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <binder/Binder.h>

#include <stdatomic.h>
#include <utils/misc.h>
#include <binder/BpBinder.h>
#include <binder/IInterface.h>
#include <binder/Parcel.h>

#include <stdio.h>

namespace android {

// ---------------------------------------------------------------------------

IBinder::IBinder()
    : RefBase()
{
}

IBinder::~IBinder()
{
}

// ---------------------------------------------------------------------------

sp<IInterface>  IBinder::queryLocalInterface(const String16& /*descriptor*/)
{
    return NULL;
}

BBinder* IBinder::localBinder()
{
    return NULL;
}

BpBinder* IBinder::remoteBinder()
{
    return NULL;
}

bool IBinder::checkSubclass(const void* /*subclassID*/) const
{
    return false;
}

// ---------------------------------------------------------------------------

class BBinder::Extras
{
public:
    Mutex mLock;
    BpBinder::ObjectManager mObjects;
};

// ---------------------------------------------------------------------------

BBinder::BBinder()
{
  atomic_init(&mExtras, static_cast<uintptr_t>(0));
}

bool BBinder::isBinderAlive() const
{
    return true;
}

status_t BBinder::pingBinder()
{
    return NO_ERROR;
}

const String16& BBinder::getInterfaceDescriptor() const
{
    // This is a local static rather than a global static,
    // to avoid static initializer ordering issues.
    static String16 sEmptyDescriptor;
    ALOGW("reached BBinder::getInterfaceDescriptor (this=%p)", this);
    return sEmptyDescriptor;
}

status_t BBinder::transact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    data.setDataPosition(0);

    status_t err = NO_ERROR;
    switch (code) {
        case PING_TRANSACTION:
            reply->writeInt32(pingBinder());
            break;
        default:
            err = onTransact(code, data, reply, flags);
            break;
    }

    if (reply != NULL) {
        reply->setDataPosition(0);
    }

    return err;
}

status_t BBinder::linkToDeath(
    const sp<DeathRecipient>& /*recipient*/, void* /*cookie*/,
    uint32_t /*flags*/)
{
    return INVALID_OPERATION;
}

status_t BBinder::unlinkToDeath(
    const wp<DeathRecipient>& /*recipient*/, void* /*cookie*/,
    uint32_t /*flags*/, wp<DeathRecipient>* /*outRecipient*/)
{
    return INVALID_OPERATION;
}

    status_t BBinder::dump(int /*fd*/, const Vector<String16>& /*args*/)
{
    return NO_ERROR;
}

void BBinder::attachObject(
    const void* objectID, void* object, void* cleanupCookie,
    object_cleanup_func func)
{
    Extras* e = reinterpret_cast<Extras*>(
                    atomic_load_explicit(&mExtras, memory_order_acquire));

    if (!e) {
        e = new Extras;
        uintptr_t expected = 0;
        if (!atomic_compare_exchange_strong_explicit(
                                        &mExtras, &expected,
                                        reinterpret_cast<uintptr_t>(e),
                                        memory_order_release,
                                        memory_order_acquire)) {
            delete e;
            e = reinterpret_cast<Extras*>(expected);  // Filled in by CAS
        }
        if (e == 0) return; // out of memory
    }

    AutoMutex _l(e->mLock);
    e->mObjects.attach(objectID, object, cleanupCookie, func);
}

// The C11 standard doesn't allow atomic loads from const fields,
// though C++11 does.  Fudge it until standards get straightened out.
static inline uintptr_t load_const_atomic(const atomic_uintptr_t* p,
                                          memory_order mo) {
    atomic_uintptr_t* non_const_p = const_cast<atomic_uintptr_t*>(p);
    return atomic_load_explicit(non_const_p, mo);
}

void* BBinder::findObject(const void* objectID) const
{
    Extras* e = reinterpret_cast<Extras*>(
                    load_const_atomic(&mExtras, memory_order_acquire));
    if (!e) return NULL;

    AutoMutex _l(e->mLock);
    return e->mObjects.find(objectID);
}

void BBinder::detachObject(const void* objectID)
{
    Extras* e = reinterpret_cast<Extras*>(
                    atomic_load_explicit(&mExtras, memory_order_acquire));
    if (!e) return;

    AutoMutex _l(e->mLock);
    e->mObjects.detach(objectID);
}

BBinder* BBinder::localBinder()
{
    return this;
}

BBinder::~BBinder()
{
    Extras* e = reinterpret_cast<Extras*>(
                    atomic_load_explicit(&mExtras, memory_order_relaxed));
    if (e) delete e;
}


status_t BBinder::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t /*flags*/)
{
    switch (code) {
        case INTERFACE_TRANSACTION:
            reply->writeString16(getInterfaceDescriptor());
            return NO_ERROR;

        case DUMP_TRANSACTION: {
            int fd = data.readFileDescriptor();
            int argc = data.readInt32();
            Vector<String16> args;
            for (int i = 0; i < argc && data.dataAvail() > 0; i++) {
               args.add(data.readString16());
            }
            return dump(fd, args);
        }

        case SYSPROPS_TRANSACTION: {
            report_sysprop_change();
            return NO_ERROR;
        }

        default:
            return UNKNOWN_TRANSACTION;
    }
}

// ---------------------------------------------------------------------------

enum {
    // This is used to transfer ownership of the remote binder from
    // the BpRefBase object holding it (when it is constructed), to the
    // owner of the BpRefBase object when it first acquires that BpRefBase.
    kRemoteAcquired = 0x00000001
};

BpRefBase::BpRefBase(const sp<IBinder>& o)
    : mRemote(o.get()), mRefs(NULL), mState(0)
{
    extendObjectLifetime(OBJECT_LIFETIME_WEAK);

    if (mRemote) {
        mRemote->incStrong(this);           // Removed on first IncStrong().
        mRefs = mRemote->createWeak(this);  // Held for our entire lifetime.
    }
}

BpRefBase::~BpRefBase()
{
    if (mRemote) {
        if (!(mState&kRemoteAcquired)) {
            mRemote->decStrong(this);
        }
        mRefs->decWeak(this);
    }
}

void BpRefBase::onFirstRef()
{
    android_atomic_or(kRemoteAcquired, &mState);
}

void BpRefBase::onLastStrongRef(const void* /*id*/)
{
    if (mRemote) {
        mRemote->decStrong(this);
    }
}

bool BpRefBase::onIncStrongAttempted(uint32_t /*flags*/, const void* /*id*/)
{
    return mRemote ? mRefs->attemptIncStrong(this) : false;
}

// ---------------------------------------------------------------------------

}; // namespace android