AudioTrack: Prevent server from reading client data after stop (1d3556d6) · Commits · e / devices / smdk4412 / android_frameworks_av

include/private/media/AudioTrackShared.h

+32 −0

Original line number	Diff line number	Diff line
		@@ -60,6 +60,8 @@ struct AudioTrackSharedStreaming {
		volatile int32_t mRear; // written by producer (output: client, input: server)
		volatile int32_t mFlush; // incremented by client to indicate a request to flush;
		// server notices and discards all data between mFront and mRear
		volatile int32_t mStop; // set by client to indicate a stop frame position; server
		// will not read beyond this position until start is called.
		volatile uint32_t mUnderrunFrames; // server increments for each unavailable but desired frame
		volatile uint32_t mUnderrunCount; // server increments for each underrun occurrence
		};
		@@ -335,6 +337,8 @@ public:
		mTimestamp.clear();
		}

		virtual void stop() { }; // called by client in AudioTrack::stop()

		private:
		// This is a copy of mCblk->mBufferSizeInFrames
		uint32_t mBufferSizeInFrames; // effective size of the buffer
		@@ -383,8 +387,14 @@ public:
		mPlaybackRateMutator.push(playbackRate);
		}

		// Sends flush and stop position information from the client to the server,
		// used by streaming AudioTrack flush() or stop().
		void sendStreamingFlushStop(bool flush);

		virtual void flush();

		void stop() override;

		virtual uint32_t getUnderrunFrames() const {
		return mCblk->u.mStreaming.mUnderrunFrames;
		}
		@@ -410,6 +420,8 @@ public:

		virtual void flush();

		void stop() override;

		#define MIN_LOOP 16 // minimum length of each loop iteration in frames

		// setLoop(), setBufferPosition(), and setBufferPositionAndLoop() set the
		@@ -532,6 +544,10 @@ public:
		// client will be notified via Futex
		virtual void flushBufferIfNeeded();

		// Returns the rear position of the AudioTrack shared ring buffer, limited by
		// the stop frame position level.
		virtual int32_t getRear() const = 0;

		// Total count of the number of flushed frames since creation (never reset).
		virtual int64_t framesFlushed() const { return mFlushed; }

		@@ -607,10 +623,18 @@ public:
		return mDrained.load();
		}

		int32_t getRear() const override;

		// Called on server side track start().
		virtual void start();

		private:
		AudioPlaybackRate mPlaybackRate; // last observed playback rate
		PlaybackRateQueue::Observer mPlaybackRateObserver;

		// Last client stop-at position when start() was called. Used for streaming AudioTracks.
		std::atomic<int32_t> mStopLast{0};

		// The server keeps a copy here where it is safe from the client.
		uint32_t mUnderrunCount; // echoed to mCblk
		bool mUnderrunning; // used to detect edge of underrun
		@@ -634,6 +658,10 @@ public:
		virtual void tallyUnderrunFrames(uint32_t frameCount);
		virtual uint32_t getUnderrunFrames() const { return 0; }

		int32_t getRear() const override;

		void start() override { } // ignore for static tracks

		private:
		status_t updateStateWithLoop(StaticAudioTrackState *localState,
		const StaticAudioTrackState &update) const;
		@@ -661,6 +689,10 @@ public:
		size_t frameSize, bool clientInServer)
		: ServerProxy(cblk, buffers, frameCount, frameSize, false /isOut/, clientInServer) { }

		int32_t getRear() const override {
		return mCblk->u.mStreaming.mRear; // For completeness only; mRear written by server.
		}

		protected:
		virtual ~AudioRecordServerProxy() { }
		};

media/libaudioclient/AudioTrack.cpp

+1 −0

Original line number	Diff line number	Diff line
		@@ -770,6 +770,7 @@ void AudioTrack::stop()
		mReleased = 0;
		}

		mProxy->stop(); // notify server not to read beyond current client position until start().
		mProxy->interrupt();
		mAudioTrack->stop();

media/libaudioclient/AudioTrackShared.cpp

+92 −11

Original line number	Diff line number	Diff line
		@@ -393,19 +393,50 @@ size_t ClientProxy::getMisalignment()

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

		__attribute__((no_sanitize("integer")))
		void AudioTrackClientProxy::flush()
		{
		sendStreamingFlushStop(true /* flush */);
		}

		void AudioTrackClientProxy::stop()
		{
		sendStreamingFlushStop(false /* flush */);
		}

		// Sets the client-written mFlush and mStop positions, which control server behavior.
		//
		// @param flush indicates whether the operation is a flush or stop.
		// A client stop sets mStop to the current write position;
		// the server will not read past this point until start() or subsequent flush().
		// A client flush sets both mStop and mFlush to the current write position.
		// This advances the server read limit (if previously set) and on the next
		// server read advances the server read position to this limit.
		//
		void AudioTrackClientProxy::sendStreamingFlushStop(bool flush)
		{
		// TODO: Replace this by 64 bit counters - avoids wrap complication.
		// This works for mFrameCountP2 <= 2^30
		size_t increment = mFrameCountP2 << 1;
		size_t mask = increment - 1;
		audio_track_cblk_t* cblk = mCblk;
		// mFlush is 32 bits concatenated as [ flush_counter ] [ newfront_offset ]
		// Should newFlush = cblk->u.mStreaming.mRear? Only problem is
		// if you want to flush twice to the same rear location after a 32 bit wrap.
		int32_t newFlush = (cblk->u.mStreaming.mRear & mask) \|
		((cblk->u.mStreaming.mFlush & ~mask) + increment);
		android_atomic_release_store(newFlush, &cblk->u.mStreaming.mFlush);

		const size_t increment = mFrameCountP2 << 1;
		const size_t mask = increment - 1;
		// No need for client atomic synchronization on mRear, mStop, mFlush
		// as AudioTrack client only read/writes to them under client lock. Server only reads.
		const int32_t rearMasked = mCblk->u.mStreaming.mRear & mask;

		// update stop before flush so that the server front
		// never advances beyond a (potential) previous stop's rear limit.
		int32_t stopBits; // the following add can overflow
		__builtin_add_overflow(mCblk->u.mStreaming.mStop & ~mask, increment, &stopBits);
		android_atomic_release_store(rearMasked \| stopBits, &mCblk->u.mStreaming.mStop);

		if (flush) {
		int32_t flushBits; // the following add can overflow
		__builtin_add_overflow(mCblk->u.mStreaming.mFlush & ~mask, increment, &flushBits);
		android_atomic_release_store(rearMasked \| flushBits, &mCblk->u.mStreaming.mFlush);
		}
		}

		bool AudioTrackClientProxy::clearStreamEndDone() {
		@@ -540,6 +571,11 @@ void StaticAudioTrackClientProxy::flush()
		LOG_ALWAYS_FATAL("static flush");
		}

		void StaticAudioTrackClientProxy::stop()
		{
		; // no special handling required for static tracks.
		}

		void StaticAudioTrackClientProxy::setLoop(size_t loopStart, size_t loopEnd, int loopCount)
		{
		// This can only happen on a 64-bit client
		@@ -638,6 +674,7 @@ void ServerProxy::flushBufferIfNeeded()
		if (flush != mFlush) {
		ALOGV("ServerProxy::flushBufferIfNeeded() mStreaming.mFlush = 0x%x, mFlush = 0x%0x",
		flush, mFlush);
		// shouldn't matter, but for range safety use mRear instead of getRear().
		int32_t rear = android_atomic_acquire_load(&cblk->u.mStreaming.mRear);
		int32_t front = cblk->u.mStreaming.mFront;

		@@ -676,6 +713,45 @@ void ServerProxy::flushBufferIfNeeded()
		}
		}

		__attribute__((no_sanitize("integer")))
		int32_t AudioTrackServerProxy::getRear() const
		{
		const int32_t stop = android_atomic_acquire_load(&mCblk->u.mStreaming.mStop);
		const int32_t rear = android_atomic_acquire_load(&mCblk->u.mStreaming.mRear);
		const int32_t stopLast = mStopLast.load(std::memory_order_acquire);
		if (stop != stopLast) {
		const int32_t front = mCblk->u.mStreaming.mFront;
		const size_t overflowBit = mFrameCountP2 << 1;
		const size_t mask = overflowBit - 1;
		int32_t newRear = (rear & ~mask) \| (stop & mask);
		ssize_t filled = newRear - front;
		if (filled < 0) {
		// front and rear offsets span the overflow bit of the p2 mask
		// so rebasing newrear.
		ALOGV("stop wrap: filled %zx >= overflowBit %zx", filled, overflowBit);
		newRear += overflowBit;
		filled += overflowBit;
		}
		if (0 <= filled && (size_t) filled <= mFrameCount) {
		// we're stopped, return the stop level as newRear
		return newRear;
		}

		// A corrupt stop. Log error and ignore.
		ALOGE("mStopLast %#x -> stop %#x, front %#x, rear %#x, mask %#x, newRear %#x, "
		"filled %zd=%#x",
		stopLast, stop, front, rear,
		(unsigned)mask, newRear, filled, (unsigned)filled);
		// Don't reset mStopLast as this is const.
		}
		return rear;
		}

		void AudioTrackServerProxy::start()
		{
		mStopLast = android_atomic_acquire_load(&mCblk->u.mStreaming.mStop);
		}

		__attribute__((no_sanitize("integer")))
		status_t ServerProxy::obtainBuffer(Buffer* buffer, bool ackFlush)
		{
		@@ -693,7 +769,7 @@ status_t ServerProxy::obtainBuffer(Buffer* buffer, bool ackFlush)
		// See notes on barriers at ClientProxy::obtainBuffer()
		if (mIsOut) {
		flushBufferIfNeeded(); // might modify mFront
		rear = android_atomic_acquire_load(&cblk->u.mStreaming.mRear);
		rear = getRear();
		front = cblk->u.mStreaming.mFront;
		} else {
		front = android_atomic_acquire_load(&cblk->u.mStreaming.mFront);
		@@ -825,8 +901,7 @@ size_t AudioTrackServerProxy::framesReady()
		// FIXME should return an accurate value, but over-estimate is better than under-estimate
		return mFrameCount;
		}
		// the acquire might not be necessary since not doing a subsequent read
		int32_t rear = android_atomic_acquire_load(&cblk->u.mStreaming.mRear);
		const int32_t rear = getRear();
		ssize_t filled = rear - cblk->u.mStreaming.mFront;
		// pipe should not already be overfull
		if (!(0 <= filled && (size_t) filled <= mFrameCount)) {
		@@ -852,7 +927,7 @@ size_t AudioTrackServerProxy::framesReadySafe() const
		if (flush != mFlush) {
		return mFrameCount;
		}
		const int32_t rear = android_atomic_acquire_load(&cblk->u.mStreaming.mRear);
		const int32_t rear = getRear();
		const ssize_t filled = rear - cblk->u.mStreaming.mFront;
		if (!(0 <= filled && (size_t) filled <= mFrameCount)) {
		return 0; // error condition, silently return 0.
		@@ -1149,6 +1224,12 @@ void StaticAudioTrackServerProxy::tallyUnderrunFrames(uint32_t frameCount)
		}
		}

		int32_t StaticAudioTrackServerProxy::getRear() const
		{
		LOG_ALWAYS_FATAL("getRear() not permitted for static tracks");
		return 0;
		}

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

		} // namespace android

media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp

+1 −8

Original line number	Diff line number	Diff line
		@@ -1617,14 +1617,7 @@ void NuPlayer::Renderer::onFlush(const sp<AMessage> &msg) {
		// internal buffer before resuming playback.
		// FIXME: this is ignored after flush().
		mAudioSink->stop();
		if (mPaused) {
		// Race condition: if renderer is paused and audio sink is stopped,
		// we need to make sure that the audio track buffer fully drains
		// before delivering data.
		// FIXME: remove this if we can detect if stop() is complete.
		const int delayUs = 2 * 50 * 1000; // (2 full mixer thread cycles at 50ms)
		mPauseDrainAudioAllowedUs = ALooper::GetNowUs() + delayUs;
		} else {
		if (!mPaused) {
		mAudioSink->start();
		}
		mNumFramesWritten = 0;

services/audioflinger/Tracks.cpp

+6 −0

Original line number	Diff line number	Diff line
		@@ -761,6 +761,12 @@ status_t AudioFlinger::PlaybackThread::Track::start(AudioSystem::sync_event_t ev
		mState = state;
		}
		}

		if (status == NO_ERROR \|\| status == ALREADY_EXISTS) {
		// for streaming tracks, remove the buffer read stop limit.
		mAudioTrackServerProxy->start();
		}

		// track was already in the active list, not a problem
		if (status == ALREADY_EXISTS) {
		status = NO_ERROR;