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 <atomic>
#include <binder/BpBinder.h>
#include <binder/IInterface.h>
#include <binder/IPCThreadState.h>
#include <binder/IResultReceiver.h>
#include <binder/IShellCallback.h>
#include <binder/Parcel.h>
#include <cutils/android_filesystem_config.h>
#include <cutils/compiler.h>
#include <utils/misc.h>

#include <stdio.h>

namespace android {

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

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

IBinder::~IBinder()
{
}

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

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

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

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

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


status_t IBinder::shellCommand(const sp<IBinder>& target, int in, int out, int err,
    Vector<String16>& args, const sp<IShellCallback>& callback,
    const sp<IResultReceiver>& resultReceiver)
{
    Parcel send;
    Parcel reply;
    send.writeFileDescriptor(in);
    send.writeFileDescriptor(out);
    send.writeFileDescriptor(err);
    const size_t numArgs = args.size();
    send.writeInt32(numArgs);
    for (size_t i = 0; i < numArgs; i++) {
        send.writeString16(args[i]);
    }
    send.writeStrongBinder(callback != nullptr ? IInterface::asBinder(callback) : nullptr);
    send.writeStrongBinder(resultReceiver != nullptr ? IInterface::asBinder(resultReceiver) : nullptr);
    return target->transact(SHELL_COMMAND_TRANSACTION, send, &reply);
}

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

class BBinder::Extras
{
public:
    // unlocked objects
    bool mRequestingSid = false;

    // for below objects
    Mutex mLock;
    BpBinder::ObjectManager mObjects;
};

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

BBinder::BBinder() : mExtras(nullptr)
{
}

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;
}

// NOLINTNEXTLINE(google-default-arguments)
status_t BBinder::transact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    data.setDataPosition(0);

    // Shell command transaction is conventionally implemented by
    // overriding onTransact by copy/pasting the parceling code from
    // this file. So, we must check permissions for it before we call
    // onTransact. This check is here because shell APIs aren't
    // guaranteed to be stable, and so they should only be used by
    // developers.
    if (CC_UNLIKELY(code == SHELL_COMMAND_TRANSACTION)) {
        uid_t uid = IPCThreadState::self()->getCallingUid();
        if (uid != AID_SHELL && uid != AID_ROOT) {
            return PERMISSION_DENIED;
        }
    }

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

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

    return err;
}

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

// NOLINTNEXTLINE(google-default-arguments)
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 = getOrCreateExtras();
    if (!e) return; // out of memory

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

void* BBinder::findObject(const void* objectID) const
{
    Extras* e = mExtras.load(std::memory_order_acquire);
    if (!e) return nullptr;

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

void BBinder::detachObject(const void* objectID)
{
    Extras* e = mExtras.load(std::memory_order_acquire);
    if (!e) return;

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

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

bool BBinder::isRequestingSid()
{
    Extras* e = mExtras.load(std::memory_order_acquire);

    return e && e->mRequestingSid;
}

void BBinder::setRequestingSid(bool requestingSid)
{
    Extras* e = mExtras.load(std::memory_order_acquire);

    if (!e) {
        // default is false. Most things don't need sids, so avoiding allocations when possible.
        if (!requestingSid) {
            return;
        }

        e = getOrCreateExtras();
        if (!e) return; // out of memory
    }

    e->mRequestingSid = true;
}

BBinder::~BBinder()
{
    Extras* e = mExtras.load(std::memory_order_relaxed);
    if (e) delete e;
}


// NOLINTNEXTLINE(google-default-arguments)
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 SHELL_COMMAND_TRANSACTION: {
            int in = data.readFileDescriptor();
            int out = data.readFileDescriptor();
            int err = data.readFileDescriptor();
            int argc = data.readInt32();
            Vector<String16> args;
            for (int i = 0; i < argc && data.dataAvail() > 0; i++) {
               args.add(data.readString16());
            }
            sp<IShellCallback> shellCallback = IShellCallback::asInterface(
                    data.readStrongBinder());
            sp<IResultReceiver> resultReceiver = IResultReceiver::asInterface(
                    data.readStrongBinder());

            // XXX can't add virtuals until binaries are updated.
            //return shellCommand(in, out, err, args, resultReceiver);
            (void)in;
            (void)out;
            (void)err;

            if (resultReceiver != nullptr) {
                resultReceiver->send(INVALID_OPERATION);
            }

            return NO_ERROR;
        }

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

        default:
            return UNKNOWN_TRANSACTION;
    }
}

BBinder::Extras* BBinder::getOrCreateExtras()
{
    Extras* e = mExtras.load(std::memory_order_acquire);

    if (!e) {
        e = new Extras;
        Extras* expected = nullptr;
        if (!mExtras.compare_exchange_strong(expected, e,
                                             std::memory_order_release,
                                             std::memory_order_acquire)) {
            delete e;
            e = expected;  // Filled in by CAS
        }
        if (e == nullptr) return nullptr; // out of memory
    }

    return e;
}

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

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(nullptr), 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.load(std::memory_order_relaxed)&kRemoteAcquired)) {
            mRemote->decStrong(this);
        }
        mRefs->decWeak(this);
    }
}

void BpRefBase::onFirstRef()
{
    mState.fetch_or(kRemoteAcquired, std::memory_order_relaxed);
}

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