libs/binder/include/binder/IPCThreadState.h

/*
 * 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.
 */

#pragma once

#include <utils/Errors.h>
#include <binder/Parcel.h>
#include <binder/ProcessState.h>
#include <utils/Vector.h>

#if defined(_WIN32)
typedef  int  uid_t;
#endif

// ---------------------------------------------------------------------------
namespace android {

class IPCThreadState
{
public:
    using CallRestriction = ProcessState::CallRestriction;

    static  IPCThreadState*     self();
    static  IPCThreadState*     selfOrNull();  // self(), but won't instantiate

    // Freeze or unfreeze the binder interface to a specific process. When freezing, this method
    // will block up to timeout_ms to process pending transactions directed to pid. Unfreeze
    // is immediate. Transactions to processes frozen via this method won't be delivered and the
    // driver will return BR_FROZEN_REPLY to the client sending them. After unfreeze,
    // transactions will be delivered normally.
    //
    // pid: id for the process for which the binder interface is to be frozen
    // enable: freeze (true) or unfreeze (false)
    // timeout_ms: maximum time this function is allowed to block the caller waiting for pending
    // binder transactions to be processed.
    //
    // returns: 0 in case of success, a value < 0 in case of error
    static  status_t            freeze(pid_t pid, bool enabled, uint32_t timeout_ms);

    // Provide information about the state of a frozen process
    static  status_t            getProcessFreezeInfo(pid_t pid, bool *sync_received,
                                                    bool *async_received);
            sp<ProcessState>    process();
            
            status_t            clearLastError();

            /**
             * Returns the PID of the process which has made the current binder
             * call. If not in a binder call, this will return getpid. If the
             * call is oneway, this will return 0.
             */
            pid_t               getCallingPid() const;

            /**
             * Returns the SELinux security identifier of the process which has
             * made the current binder call. If not in a binder call this will
             * return nullptr. If this isn't requested with
             * Binder::setRequestingSid, it will also return nullptr.
             *
             * This can't be restored once it's cleared, and it does not return the
             * context of the current process when not in a binder call.
             */
            const char*         getCallingSid() const;

            /**
             * Returns the UID of the process which has made the current binder
             * call. If not in a binder call, this will return 0.
             */
            uid_t               getCallingUid() const;

            void                setStrictModePolicy(int32_t policy);
            int32_t             getStrictModePolicy() const;

            // See Binder#setCallingWorkSourceUid in Binder.java.
            int64_t             setCallingWorkSourceUid(uid_t uid);
            // Internal only. Use setCallingWorkSourceUid(uid) instead.
            int64_t             setCallingWorkSourceUidWithoutPropagation(uid_t uid);
            // See Binder#getCallingWorkSourceUid in Binder.java.
            uid_t               getCallingWorkSourceUid() const;
            // See Binder#clearCallingWorkSource in Binder.java.
            int64_t             clearCallingWorkSource();
            // See Binder#restoreCallingWorkSource in Binder.java.
            void                restoreCallingWorkSource(int64_t token);
            void                clearPropagateWorkSource();
            bool                shouldPropagateWorkSource() const;

            void                setLastTransactionBinderFlags(int32_t flags);
            int32_t             getLastTransactionBinderFlags() const;

            void                setCallRestriction(CallRestriction restriction);
            CallRestriction     getCallRestriction() const;

            int64_t             clearCallingIdentity();
            // Restores PID/UID (not SID)
            void                restoreCallingIdentity(int64_t token);

            status_t            setupPolling(int* fd);
            status_t            handlePolledCommands();
            void                flushCommands();
            bool                flushIfNeeded();

            void                joinThreadPool(bool isMain = true);
            
            // Stop the local process.
            void                stopProcess(bool immediate = true);
            
            status_t            transact(int32_t handle,
                                         uint32_t code, const Parcel& data,
                                         Parcel* reply, uint32_t flags);

            void                incStrongHandle(int32_t handle, BpBinder *proxy);
            void                decStrongHandle(int32_t handle);
            void                incWeakHandle(int32_t handle, BpBinder *proxy);
            void                decWeakHandle(int32_t handle);
            status_t            attemptIncStrongHandle(int32_t handle);
    static  void                expungeHandle(int32_t handle, IBinder* binder);
            status_t            requestDeathNotification(   int32_t handle,
                                                            BpBinder* proxy); 
            status_t            clearDeathNotification( int32_t handle,
                                                        BpBinder* proxy); 

    static  void                shutdown();

    // Call this to disable switching threads to background scheduling when
    // receiving incoming IPC calls.  This is specifically here for the
    // Android system process, since it expects to have background apps calling
    // in to it but doesn't want to acquire locks in its services while in
    // the background.
    static  void                disableBackgroundScheduling(bool disable);
            bool                backgroundSchedulingDisabled();

            // Call blocks until the number of executing binder threads is less than
            // the maximum number of binder threads threads allowed for this process.
            void                blockUntilThreadAvailable();

            // Service manager registration
            void                setTheContextObject(const sp<BBinder>& obj);

            // WARNING: DO NOT USE THIS API
            //
            // Returns a pointer to the stack from the last time a transaction
            // was initiated by the kernel. Used to compare when making nested
            // calls between multiple different transports.
            const void*         getServingStackPointer() const;

            // The work source represents the UID of the process we should attribute the transaction
            // to. We use -1 to specify that the work source was not set using #setWorkSource.
            //
            // This constant needs to be kept in sync with Binder.UNSET_WORKSOURCE from the Java
            // side.
            static const int32_t kUnsetWorkSource = -1;

            // Create a temp reference until commands in queue flushed to driver
            // Internal only.
            // @internal
            void                 createTransactionReference(RefBase* ref);

private:
                                IPCThreadState();
                                ~IPCThreadState();

            status_t            sendReply(const Parcel& reply, uint32_t flags);
            status_t            waitForResponse(Parcel *reply,
                                                status_t *acquireResult=nullptr);
            status_t            talkWithDriver(bool doReceive=true);
            status_t            writeTransactionData(int32_t cmd,
                                                     uint32_t binderFlags,
                                                     int32_t handle,
                                                     uint32_t code,
                                                     const Parcel& data,
                                                     status_t* statusBuffer);
            status_t            getAndExecuteCommand();
            status_t            executeCommand(int32_t command);
            void                processPendingDerefs();
            void                processPostWriteDerefs();

            void                clearCaller();

    static  void                threadDestructor(void *st);
    static  void                freeBuffer(Parcel* parcel,
                                           const uint8_t* data, size_t dataSize,
                                           const binder_size_t* objects, size_t objectsSize);

    const   sp<ProcessState>    mProcess;
            Vector<BBinder*>    mPendingStrongDerefs;
            Vector<RefBase::weakref_type*> mPendingWeakDerefs;
            Vector<RefBase*>    mPostWriteStrongDerefs;
            Vector<RefBase::weakref_type*> mPostWriteWeakDerefs;
            Parcel              mIn;
            Parcel              mOut;
            status_t            mLastError;
            const void*         mServingStackPointer;
            pid_t               mCallingPid;
            const char*         mCallingSid;
            uid_t               mCallingUid;
            // The UID of the process who is responsible for this transaction.
            // This is used for resource attribution.
            int32_t             mWorkSource;
            // Whether the work source should be propagated.
            bool                mPropagateWorkSource;
            bool                mIsLooper;
            bool mIsFlushing;
            int32_t             mStrictModePolicy;
            int32_t             mLastTransactionBinderFlags;
            CallRestriction     mCallRestriction;
};

} // namespace android

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