Android internalsEgor ElizarovSPbSU 2012

Egor Elizarov SPbSU 20122

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Egor Elizarov SPbSU 20123

Lecture 3

Android build system,

Emulator

yegor.yelizarov(at)gmail.com

http://vk.com/android_internalsRev: 1.1Last update: 05/30/2012

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Previous time

AOSP

High level architecture

Android OS bring up

CTS & CDD

repo / git / gerrit

Code layout

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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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Makefile structure

Structure:

Target: depenencies List of commands

Usage:

make target

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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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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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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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Target hierarchyCPU type

Bare schematics

Fixed peripherals

Fixed applications

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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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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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Build process

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Building AOSP

cd AOSP

. build/envsetup.sh

lunch

Select generic-eng version

make -j4

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Add new program

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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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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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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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Qemu

Single loop for each core

Worker threads for long term tasks

Tiny Code Generator (TCG)

Kernel Virtual Machine (KVM)

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Emulator window

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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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Android Debug Bridge

adb kill-server

adb devices

adb logcat

adb shell

adb push what where

adb pull what where

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ADB internals

USB or TCP/IP

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Launch emulator

$ out/host/linux-x86/bin/emulator &

$ adb kill-server

$ adb shell

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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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Next time

“Androdized” kernel

Bionic standard C library

Logging system

Source: http://androidcommunity.com

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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

Egor Elizarov SPbSU 201228

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)