编译Android源码

Android Build System

In this document

Understanding the makefile
Layers
Building the Android Platform
Building the Android Kernel
Build Variants

Android uses a custom build system to generate tools, binaries, and documentation. This document provides an overview of Android's build system and instructions for doing a simple build.

Android's build system is make based and requires a recent version of GNU Make (note that Android uses advanced features of GNU Make that may not yet appear on the GNU Make web site). Before continuing, check your version of make by running % make -v. If you don't have version 3.80 or greater, you need to upgrade your version of make.

Understanding the makefile

A makefile defines how to build a particular application. Makefiles typically include all of the following elements:

Name: Give your build a name (LOCAL_MODULE := <build_name>).
Local Variables: Clear local variables with CLEAR_VARS (include $(CLEAR_VARS)).
Files: Determine which files your application depends upon (LOCAL_SRC_FILES := main.c).
Tags: Define tags, as necessary (LOCAL_MODULE_TAGS := eng development).
Libraries: Define whether your application links with other libraries (LOCAL_SHARED_LIBRARIES := cutils).
Template file: Include a template file to define underlining make tools for a particular target (include $(BUILD_EXECUTABLE)).

The following snippet illustrates a typical makefile.

LOCAL_PATH := $(my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := <buil_name>
LOCAL_SRC_FILES := main.c
LOCAL_MODULE_TAGS := eng development
LOCAL_SHARED_LIBRARIES := cutils
include $(BUILD_EXECUTABLE)
(HOST_)EXECUTABLE, (HOST_)JAVA_LIBRARY, (HOST_)PREBUILT, (HOST_)SHARED_LIBRARY,
(HOST_)STATIC_LIBRARY, PACKAGE, JAVADOC, RAW_EXECUTABLE, RAW_STATIC_LIBRARY,
COPY_HEADERS, KEY_CHAR_MAP

The snippet above includes artificial line breaks to maintain a print-friendly document.

Layers

The build hierarchy includes the abstraction layers described in the table below.

Each layer relates to the one above it in a one-to-many relationship. For example, an arch can have more than one board and each board can have more than one device. You may define an element in a given layer as a specialization of an element in the same layer, thus eliminating copying and simplifying maintenance.

Layer	Example	Description
Product	myProduct, myProduct_eu, myProduct_eu_fr, j2, sdk	The product layer defines a complete specification of a shipping product, defining which modules to build and how to configure them. You might offer a device in several different versions based on locale, for example, or on features such as a camera.
Device	myDevice, myDevice_eu, myDevice_eu_lite	The device layer represents the physical layer of plastic on the device. For example, North American devices probably include QWERTY keyboards whereas devices sold in France probably include AZERTY keyboards. Peripherals typically connect to the device layer.
Board	sardine, trout, goldfish	The board layer represents the bare schematics of a product. You may still connect peripherals to the board layer.
Arch	arm (arm5te) (arm6), x86, 68k	The arch layer describes the processor running on your board.

Building the Android Platform

This section describes how to build the default version of Android. Once you are comfortable with a generic build, then you can begin to modify Android for your own target device.

Device Code

To do a generic build of android, source build/envsetup.sh, which contains necessary variable and function definitions, as described below.

% cd $TOP
% . build/envsetup.sh
# pick a configuration using choosecombo
% choosecombo
% make -j4 PRODUCT-generic-user

You can also replace user with eng for a debug engineering build:

% make -j4 PRODUCT-generic-eng

These Build Variants differ in terms of debug options and packages installed.

Cleaning Up

Execute % m clean to clean up the binaries you just created. You can also execute % m clobber to get rid of the binaries of all combos. % m clobber is equivalent to removing the //out/ directory where all generated files are stored.

Speeding Up Rebuilds

The binaries of each combo are stored as distinct sub-directories of //out/, making it possible to quickly switch between combos without having to recompile all sources each time.

However, performing a clean rebuild is necessary if the build system doesn't catch changes to environment variables or makefiles. If this happens often, you should define the USE_CCACHE environment variable as shown below:

% export USE_CCACHE=1

Doing so will force the build system to use the ccache compiler cache tool, which reduces recompiling all sources.

ccache binaries are provided in //prebuilt/... and don't need to get installed on your system.

Troubleshooting

The following error is likely caused by running an outdated version of Java.

device Dex: core  UNEXPECTED TOP-LEVEL ERROR:
java.lang.NoSuchMethodError: method java.util.Arrays.hashCode with
signature ([Ljava.lang.Object;)I was not found.
at com.google.util.FixedSizeList.hashCode(FixedSizeList.java:66)
at com.google.rop.code.Rop.hashCode(Rop.java:245)
at java.util.HashMap.hash(libgcj.so.7)
[...]

dx is a Java program that uses facilities first made available in Java version 1.5. Check your version of Java by executing % java -version in the shell you use to build. You should see something like:

java version "1.5.0_07"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_07-164)
Java HotSpot(TM) Client VM (build 1.5.0_07-87, mixed mode, sharing)

If you do have Java 1.5 or later and your receive this error, verify that you have properly updated your PATH variable.

Building the Android Kernel

This section describes how to build Android's default kernel. Once you are comfortable with a generic build, then you can begin to modify Android drivers for your own target device.

To build the kernel base, switch to the device directory (/home/joe/android/device) in order to establish variables and run:

% . build/envsetup.sh
% partner_setup generic

Then switch to the kernel directory /home/joe/android/kernel.

Checking Out a Branch

The default branch is always android. To check out a different branch, execute the following:

% git checkout --track -b android-mydevice origin/android-mydevice
//Branch android-mydevice set up to track remote branch
% refs/remotes/origin/android-mydevice.
//Switched to a new branch "android-mydevice"

To simplify code management, give your local branch the same name as the remote branch it is tracking (as illustrated in the snippet above). Switch between branches by executing % git checkout <branchname>.

Verifying Location

Find out which branches exist (both locally and remotely) and which one is active (marked with an asterisk) by executing the following:

% git branch -a
android
* android-mydevice
origin/HEAD
origin/android
origin/android-mydevice
origin/android-mychipset

To only see local branches, omit the -a flag.

Building the Kernel

To build the kernel, execute:

% make -j4

Build Variants

When building for a particular product, it's often useful to have minor variations on what is ultimately the final release build. These are the currently-defined build variants:

eng

This is the default flavor. A plain make is the same as make eng.

Installs modules tagged with: eng, debug, user, and/or development.
Installs non-APK modules that have no tags specified.
Installs APKs according to the product definition files, in addition to tagged APKs.
ro.secure=0
ro.debuggable=1
ro.kernel.android.checkjni=1
adb is enabled by default.

user

make user

This is the flavor intended to be the final release bits.

Installs modules tagged with user.
Installs non-APK modules that have no tags specified.
Installs APKs according to the product definition files; tags are ignored for APK modules.
ro.secure=1
ro.debuggable=0
adb is disabled by default.

userdebug

make userdebug

The same as user, except:

Also installs modules tagged with debug.
ro.debuggable=1
adb is enabled by default.

If you build one flavor and then want to build another, you should run make installclean between the two makes to guarantee that you don't pick up files installed by the previous flavor. make clean will also suffice, but it takes a lot longer.

从 http://android.git.kernel.org/ 查看各个分支及其TAG

下载源码

mkdir /android; cd /android

curl http://android.git.kernel.org/repo > repo
# repo上android的下载源码脚本
mkdir -p /android/donut_release; cd /android/donut_release
../repo init -u git://android.git.kernel.org/platform/manifest.git -b donut
../repo sync

下载内核

mkdir /android/donut_kernel; cd /android/donut_kernel
git clone git://android.git.kernel.org/kernel/common.git
cd common;
git branch -a; 查看分支
git checkout origin/android-goldfish-2.6.29 -b goldfish
vi Makefile : 设置 ARCH和CROSS_COMPILE为 arm/ arm-eabi-
make 尝试编译。

设置编译环境

sudo apt-get -y install git-core gnupg sun-java5-jdk flex bison gperf libsdl-dev libesd0-dev libwxgtk2.6-dev build-essential zip curl libncurses5-dev zlib1g-dev valgrind g++ sun-javadb-javadoc
export JAVA_HOME=/usr/lib/jvm/java-5-sun
export JRE_HOME=${JAVA_HOME}/jre
export ANDROID_JAVA_HOME=$JAVA_HOME
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:${JAVA_HOME}/lib:$JRE_HOME/lib:$CLASSPATH
export ANDROID_HOME=/android/donut_release
export ANDROID_PRODUCT_OUT=$ANDROID_HOME/out/target/product/generic
export PATH=$PATH:$JAVA_HOME/bin:${JRE_HOME}/bin:$ANDROID_HOME/out/host/linux-x86/bin:$ANDROID_HOME:/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin
sudo update-alternatives --config javac [java/javadoc]
＃配置使用 java-5-sun的配置。(ubuntu 9.10中舍弃了jdk5，可以自己安装 jdk1.5.bin

编译make (make sdk)

cd $ANDROID_HOME; make #修改做部分修改，详情看最后
编译完成后，使用模拟器进行测试。

模拟器

./android list targets ; 查看当前的支持的target

./android create avd --name avd-donut --target 1 ./androld list avd ./emulator -avd avd-donut
调试桥 ./adb remount ./adb shell 根文件系统目录在 out/target/product/generic/ 下

从模拟器中获取默认配置文件 adb pull /proc/config.gz /tmp; cd /tmp

gunzip config.gz

mv config /android/donut_kernel/.config

测试配置文件

cd /android/donut_kernel

make ARCH=arm menuconfig

make CROSS_COMPILE=arm-eabi-

初始化完成，进行第二步，内核的移植，搭载idea 6410 自带的rootfs

==== 编译android时需要改动的源码地方 BEGIN===
E: ‘EAI_NODATA’ undeclared
S: vi external/qemu/Makefile.android
     ifeq ($(HOST_OS)-$(HOST_ARCH),linux-x86)
     - MY_CFLAGS += -Wa,--32
     + MY_CFLAGS += -Wa,--32 -D_GNU_SOURCE
     endif

E: cupcake battery bug
S: vi frameworks/base/services/java/com/android/server/BatteryService.java
     private final void sendIntent() {
         // Pack up the values and broadcast them to everyone
        +    mBatteryLevel = 100;

E: Build error message:
frameworks/policies/base/PolicyConfig.mk:22: *** No module defined for the given PRODUCT_POLICY (android.policy_phone).

S: modify codes at line 89 in build/tools/findleaves.sh
#find "${@:0:$nargs}" $findargs -type f -name "$filename" -print |
find "${@:1:$nargs-1}" $findargs -type f -name "$filename" -print |

E: frameworks/base/tools/aidl/AST.cpp:10: error: 'fprintf' was not declared in this scope的错误

S:下载gcc-4.3和g++-4.3

　　apt-get install gcc-4.3 g++-4.3

cd /usr/bin

　　ln -s gcc-4.3 gcc

　　ln -s g++-4.3 g++

==== 编译android时需要改动的源码地方 END ===

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