Build a custom kernel

From Android Wiki

0. Install an Ubuntu linux system

1. Install packages

 $ sudo apt-get install git-core gnupg sun-java6-jdk flex bison gperf libsdl-dev libesd0-dev libwxgtk2.6-dev build-essential zip curl libncurses5-dev zlib1g-dev

2. Make an A688 directory, and download the cross compiler tools

 $ mkdir ~/A688
 $ cd A688
 $ git clone git://android.git.kernel.org/platform/frameworks/base.git
 $ git clone git://android.git.kernel.org/platform/hardware/libhardware.git
 $ git clone git://android.git.kernel.org/platform/hardware/libhardware_legacy.git
 $ git clone git://android.git.kernel.org/platform/hardware/msm7k.git
 $ git clone git://android.git.kernel.org/platform/prebuilt.git

3. Download Motorola Xt5 source code, and put into ~/A688 directory

https://opensource.motorola.com/sf/frs/do/viewRelease/projects.quenchxt/frs.xt5.xt502

4. Unpack source code

 $ cd A688
 $ tar –zxvf bionic.tar.gz
 $ tar –zxvf dalvik.tar.gz
 $ tar –zxvf external.tar.gz
 $ tar –zxvf kernel.tar.gz

5. Grab kernel.gz from mobile, and put the config into ~/A688/Kernel/ direcotry

(1) connect your mobile to your computer

(2) cd ~/A688/Kernel/

(3) adb pull /proc/config.gz config.gz

(4) gunzip config.gz

(5) mv config .config

6. Setup environment variable

 $ export PLATFORM_DIR=~/A688
 $ export ARCH=arm
 $ export CROSS_COMPILE=arm-eabi-
 $ export PATH=~/A688/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin:$PATH

7. Modify Makefile

 $ vi Makefile

find

 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                    -fno-strict-aliasing -fno-common \
                    -Werror \
                    -Werror-implicit-function-declaration

and replace with

 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                    -fno-strict-aliasing -fno-common
 #                  -Werror \
 #                  -Werror-implicit-function-declaration

8. Start to make your kernel

 $ make ANDROID_BUILD_TOP=

You will find your kernel image at ~/A688/kernel/arch/arm/boot/zImage

9. Unpack boot.img, and replace the kernel with new one

 $ cd ~/RomRepackTools_Linux
 $ cp ~/A688/kernel/arch/arm/boot/zImage .
 $ ./unpack-bootimg.pl boot.img
 $ ./repack-bootimg.pl zImage boot.img-ramdisk boot_newkernel.img

10. Flash the boot partition on your mobile

 $ fastboot flash boot boot_newkernel.img