Course: Android Internals Lecture 3: Build system, emulator

1. Android internals
Egor Elizarov
SPbSU 2012

2. Legal info
 Android internals by Egor Elizarov is licensed under a
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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!
2 Egor Elizarov SPbSU 2012

3. Lecture 3
Android build system,
Emulator
yegor.yelizarov(at)gmail.com
Rev: 1.1
Last update: 05/30/2012 http://vk.com/android_internals
3 Egor Elizarov SPbSU 2012

4. Previous time

AOSP

High level architecture

Android OS bring up

CTS & CDD

repo / git / gerrit

Code layout
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5. Android build system

Based on GNU Make

Build system code is in “build” directory
(./build/core/main.mk - start point)

Android.mk files

All output and temporary files are in “out”
directory
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6. Makefile structure

Structure:
Target: depenencies
List of commands

Usage:
make target
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7. Interesting files

Android.mk — build scenario for module

buildspec.mk — variable defenitions for build
system

envsetup.sh — setup environment, add some
helper functions
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8. Sample Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := list_of_sources
LOCAL_C_INCLUDES := list_of_directories_with_header_files
LOCAL_SHARED_LIBRARIES := list_of_shared_libraries
LOCAL_STATIC_LABRARIES := list_of_static_libraries
LOCAL_MODULE_TAGS := debug
LOCAL_MODULE := module_name
include $(BUILD_EXECUTABLE)
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9. More variables

LOCAL_MODULE_PATH := install_path

LOCAL_CFLAGS := flags_for_compiler

LOCAL_LDFLAGS := flags_for_linker

LOCAL_OVERRIDES_PACKAGES :=
packages_to_be_dropped

Etc.
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10. Target hierarchy
CPU type
Bare schematics
Fixed peripherals
Fixed applications
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11. buildspec.mk

TARGER_PRODUCT = product_name

TARGET_BUILD_TYPE = debug

SHOW_COMMANDS = true

USE_CCACHE = 1

BUILD_TINY_ANDROID = true (board bring
up/ low level debugging)
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12. Some make targets

make droid (default target)

make update-api (update current API)

make sdk (build SDK)

make help (prints more targets)
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13. Build process
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14. Building AOSP

cd AOSP

. build/envsetup.sh

lunch

Select generic-eng version

make -j4
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15. Add new program
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16. Board specific files

BoardConfig.mk (Target configuration)

Board_name.mk (board related defenitions, list
of packages)

Device.mk (list of files to be copied, list of
packages, etc.)
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17. Android emulator

Based on Qemu VM

Goldfish – codename for emulator

Code in development/tools/emulator &
external/qemu

Provided as part of SDK
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18. Emulator features

Runs full Android stack down to the kernel level

ARM v5 CPU and correcponding MMU

LCD with different resolutions

GSM modem

Simulates application interrupts, data channel
lost, etc.
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19. Qemu

Single loop for each core

Worker threads for long term tasks

Tiny Code Generator (TCG)

Kernel Virtual Machine (KVM)
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20. Emulator window
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21. Tools

android — control AVD, update SDK, manage
android projects

emulator — launches emulator

adb — remote debug console

mksdcard — create SD card image
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22. Android Debug Bridge

adb kill-server

adb devices

adb logcat

adb shell

adb push what where

adb pull what where
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23. ADB internals
USB or TCP/IP
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24. Launch emulator

$ out/host/linux-x86/bin/emulator &

$ adb kill-server

$ adb shell
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25. Target filesystem layout

/system — main system directory

/data — main data directory

/cache — Dalvik cache

/sdcard — SD card mount point

/etc; /sys; /proc; /dev; /sbin; /root; /mnt —
derived from linux
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26. Next time

“Androdized” kernel

Bionic standard C library

Logging system
Source: http://androidcommunity.com
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27. Useful links
 http://vk.com/android_internals
 http://mrbook.org/tutorials/make/
 http://elinux.org/Android_Build_System
 K. Yaghmour. Embedded Android. Early Release, O'Reilly, October 2011
 http://developer.android.com/guide/developing/tools/emulator.html
 http://developer.android.com/guide/developing/devices/emulator.html
 http://blog.vmsplice.net/2011/03/qemu-internals-overall-architecture-and.html
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28. 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)
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