The document discusses debugging and profiling approaches for Android. It describes popular techniques like logging with logcat, using gdb for debugging, tracing with tools like DDMS and LTTng. It also discusses profiling CPU and memory usage with tools like smem and oprofile. Finally, it provides an overview of WiFi, Bluetooth, and radio interface layer subsystems in Android.

1. Android internals
Egor Elizarov
SPbSU 2012

2. Legal info
 Android internals by Egor Elizarov is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
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 Under the following conditions
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 All pictures and trademarks are the property of their respective owners. Use of
these trademarks and pictures is subject to owners permissions.
 Corrections, suggestions, contributions and translations are welcome!
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3. Lecture 10
Debugging / profiling
WiFi / Bluetooth / RIL
yegor.yelizarov(at)gmail.com
Rev: 1.1 http://vk.com/android_internals
Last update: 06/01/2012
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4. Previous time
 Suspend/Resume process
 Android PM main components
 Android Input subsystem
 *.kl, *.kcm, *.idc configuration files
 Sensor subsystem
 Input noise reduction approaches
 Android data storage
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5. Useful host/target configuration
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6. Debugging/profiling agenda

Very good presentation about debugging &
profiling by Tim Bird

Most popular approaches

Tools covered by Tim in brief

Few words about not covered approaches
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7. Debugging approaches
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8. Logging

logcat – obtaining android log
– For both C/C++ (LOGE) & Java (Log.e) code
– Have rich formatting options

dmesg – obtatining kernel log
– printk()
– Extra logs from userspace through /dev/kmsg

Stdio redirection
– For both Java (log.redirect-stdio) & Native (xargs) code
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9. GNU debugger (gdb)

DDD can be used as graphic backend

On target

$ gdbserver :1234 --attach pid

Or $gdbserver :1234 /system/bin/app
●
On host

$ adb forward tcp:1234 tcp:1234 && gdbclient app :1234 app

Or $ arm-eabi-gdb

# file ./out/target/product/generic/symbols/system/bin/app_process

# set solib-search-path
./out/target/product/generic/symbols/system/lib

# target remote target_ip:1234
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10. Google debuggers

Fastboot
– Protocol & tool to communicate with host over USB
– Install images, erase partitions, booting from host
– Supported in UBoot

ADB
– Remote shell, install, file copy, etc.
– Work over Network/USB
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11. Tracing & dumping

Strace
– Shows system calls for a process (or set of processes)

Dalvik Debug Monitor Servic (DDMS)
– Integrated into Eclipse
– Provides port-forwarding services, screen capture on the device,
thread and heap information on the device, logcat and much more

Dumpsys / Dumpstate
– Dumps huge amounts of information about the system, including
status, counts and statistics
– Dumpsys show status information from Android service
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12. Virtual Network Computing

VNC - Graphical desktop sharing system

Transmits input events from host to target

Transmits screen updates from target to host

On target
– androidvncserver &

On host
– vncviewer target_ip:5901
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13. Profiling approaches
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14. CPU and memory statistics

Common profiling workflow

Smem
– Analyze of system-wide memory usage

OProfile
– CPU usage statistic for both kernel & userspace
– Monitors execution point periodically
– Should be enabled in kernel
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15. Tracing

Bootchart
– Analyze system booting process
– init should be recompiled to add Bootchart support

TraceView
– Java methods tracing
– Can be used with DDMS
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16. Benchmarks

Rowboat bench
– Set of benchmarks for CPU, 2D, 3D, etc.
– Developed by Rowboat team

0xbench
– Another set of benchmarks
– Developed by 0xlab team

Lots of benchmarks in Google Play
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17. Linux Trace Toolkit next generation

Work for both kernel and userspace

Useful to debug threads and processes

Allow to trace only some events

Allow userspace events (/mnt/debugfs/ltt/write_event)

Kernel patches + ltt-control + ltt-viewer
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18. Add LTTng support to Android
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19. Different tricks

Activity Manager - control applications
– am start -a android.intent.action.MAIN -n
com.android.camera/com.android.camera.Camera &

input keyevent X – send keyboard events

sendevent – send touch events

setprop/getprop - control system properties

sqlite - access database

start/stop - restart whole system
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20. WiFi in Android

Supports IEEE 802.11 abgn

Supports both IPv4 and IPv6

Based on customized wpa_supplicant

Wifi drivers compiled as modules (Wifi HAL
can changed to support built-in drivers)
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21. Wifi subsystem
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22. Porting Wifi driver
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23. Bluetooth in Android

Bluetooth is covered by IEEE 802.15.1

Android BT is based on the BlueZ stack

Android provides subset of BlueZ functionality

Android supports point-to-point and multiple-
point connections

Supports maximum 9 simultaneous connections
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24. Bluetooth workflow
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25. Bluetooth subsystem
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26. RIL in Android

Most devices have separate Radio Frequency
module for signal strength measurement etc.

Modem often have own CPU with running OS
(Ex: Mentor Nucleus)

Usually have firmware

Often kernel interface to these devices is PPP
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27. RIL subsystem
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28. Next Time

Exam
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29. Useful links

http://vk.com/android_internals

http://elinux.org/images/c/c9/Android-tips-and-tricks-2010-10.pdf

http://developer.android.com/guide/developing/debugging/index.html

http://source.android.com/tech/debugging/native-memory.html

http://developer.android.com/guide/developing/debugging/ddms.
html
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30. Useful links (2)

http://code.google.com/p/android-vnc-server/wiki/README

http://softteco.blogspot.com/2011/03/android-low-level-shell-
click-on-screen.html

http://lttng.org/

http://softteco.blogspot.com/2011/03/android-low-level-shell-
click-on-screen.html

http://www.kandroid.org/online-pdk/guide/telephony.html
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31. Thanks to

Sergey Matyukevich for review and advices
(www.linkedin.com/pub/sergey-
matyukevich/31/889/769)

Nikolay F. Fominykh for review and advices

Vladimir Barinov for review and advices
(http://www.linkedin.com/pub/vladimir-
barinov/2a/18a/bab)
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