Course: Android Internals Lecture 6: Binder, Typical subsystem

1. Android internals
Egor Elizarov
SPbSU 2012

2. Legal info
 Android internals by Egor Elizarov is licensed under a
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 All pictures and trademarks are the property of their respective owners. Use of
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 Corrections, suggestions, contributions and translations are welcome!
2 Egor Elizarov SPbSU 2012

3. Lecture 6
Android IPC
Typical Android subsystem
yegor.yelizarov(at)gmail.com
Rev: 1.1
Last update: 06/01/2012 http://vk.com/android_internals
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4. Previous time

VM types

Virtualization approaches

Dalvik VM features

Interpreter core types

JIT algorithm

Android application start up process
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5. IPC Approaches

Classic
– System V IPC
– Posix IPC

Modern
– Binder
– Cross Memory Attach (CMA)
– KNEM
– Kdbus
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6. Linux IPC

Pipe

Socket

Signal

Semaphore

Message queue

Shared memory
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7. 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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8. Socket vs Binder
Binder
Socket

Associated with PID

Associated with FD

Local only

Network transparency

Communication via

Stream IO read/write
IOCTL
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9. Binder facilities
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10. 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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11. RPC main idea
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12. OOP patterns used in Binder

Bridge

Mediator

Proxy
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13. Application layer
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14. Application layer transaction
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15. Android Interface Definition Language
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16. AIDL example
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17. Application layer internals
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18. 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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19. Service Manager workflow
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20. Middleware layer

Provide binder facilities to java framework

Marshalling/unmarshalling Parcels

Interaction with kernel

Managing threads
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21. Middleware layer internals
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22. Kernel layer
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23. Binder in action
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24. 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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25. Typical subsystem scheme
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26. Next Time

Graphic subsystem

HW acceleration
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27. 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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28. 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/AndroidNati
veBinder

http://lwn.net/Articles/472984/
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29. 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)
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