Android internalsEgor ElizarovSPbSU 2012

Egor Elizarov SPbSU 20122

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Egor Elizarov SPbSU 20123

Lecture 6

Android IPC

Typical Android subsystem

yegor.yelizarov(at)gmail.com

http://vk.com/android_internalsRev: 1.1Last update: 06/01/2012

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Previous time

VM types

Virtualization approaches

Dalvik VM features

Interpreter core types

JIT algorithm

Android application start up process

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IPC Approaches

Classic

– System V IPC

– Posix IPC

Modern

– Binder

– Cross Memory Attach (CMA)

– KNEM

– Kdbus

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Linux IPC

Pipe

Socket

Signal

Semaphore

Message queue

Shared memory

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Binder

Lightweight IPC/RPC

Customized re-implementation of Open Binder

BeOS -> ACCESS/PalmOS -> Open Binder

Per process thread pool for processing requests

Synchronous calls between processes

Zero copy message transmission

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Socket vs Binder

Socket

Associated with FD

Network transparency

Stream IO read/write

Binder

Associated with PID

Local only

Communication via IOCTL

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Binder facilities

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Parcels and marshalling

Parcel is a message to be send through Binder

Different types of data can be marshalled (packed) in parcels

To make remote procedure call binder marshalles function arguments and meta data, sends it to remote process and unpacks the results

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RPC main idea

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OOP patterns used in Binder

Bridge

Mediator

Proxy

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Application layer

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Application layer transaction

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Android Interface Definition Language

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AIDL example

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Application layer internals

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Service Manager

Special Binder node with known address

Provide information about existing services

All services should be registered in Service Manager (name & binder token)

Command line tool: adb service

sp<IBinder> binder = defaultServiceManager() ->getService(String16("media.player"));

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Service Manager workflow

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Middleware layer

Provide binder facilities to java framework

Marshalling/unmarshalling Parcels

Interaction with kernel

Managing threads

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Middleware layer internals

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Kernel layer

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Binder in action

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Typical subsytem

Main logic is implemented in frameworks

C++ layer contains some servers (Ex: mediaserver) connected to java framework via Binder

Use standard external libraries (Ex: libBluez)

HAL as interface for HW vendors

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Typical subsystem scheme

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Next Time

Graphic subsystem

HW acceleration

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Useful links

http://vk.com/android_internals

http://0xlab.org/~jserv/android-binder-ipc.pdf

http://cs736-android.pbworks.com/w/page/5834468/IPC%20Binder

http://www.angryredplanet.com/~hackbod/openbinder/docs/html/BinderIPCMechanism.html

http://mylifewithandroid.blogspot.com/2008/01/about-binders.html

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Useful links (2)

http://free-electrons.com/doc/posix-api.pdf

http://lwn.net/Articles/466304/

http://www.slideshare.net/opersys/android-internals

https://github.com/keesj/gomo/wiki/AndroidNativeBinder

http://lwn.net/Articles/472984/

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Thanks to

Sergey Matyukevich for review and advices (www.linkedin.com/pub/sergey-matyukevich/31/889/769)

Nikolay F. Fominykh for review and advices

Nikita Shulga for advices and notes (http://www.linkedin.com/pub/nikita-shulga/8/582/287)

Grigory Tolstolytkin for advices and notes (http://www.linkedin.com/pub/grigory-tolstolytkin/2a/b41/74)