How to Build Android Kernel from source (Part 1)

Hi 🙂 This is my first attempt building an android kernel source. I just thought of sharing my experiences so far. This will be useful for a beginner. 🙂

Prerequisites:

Linux installed on a PC or on a Virtual Box
Android Kernel Source
A Toolchain

I have installed Ubuntu on Oracle VM VirtualBox.

Getting Android Kernel Source

I am using the kernel source of “omap” project. According to the android official web page the project is used for PandaBoard and Galaxy Nexus, and can be used as a starting point for work on TI OMAP chipsets.

1. Download the “omap.git-android-omap-3.0.tar.gz” from Google repository https://android.googlesource.com/

Goto ->https://android.googlesource.com/kernel/omap.git
Select android-omap-3.0

2. Extract source:

Open a new Terminal and enter following command.

Create a directory structure as follows and move the downloaded omap.git-android-omap-3.0.tar.gz file into that folder

:~$mkdir -p ~/android/kernel

Extract it:

:~/android/kernel$tar xvf omap.git-android-omap-3.0.tar.gz

Once you extracted the source: Goto ->android–>kernel–>arch–>arm–>configs folder. You can find the panda_defconfig file there.

Getting prebuilt toolchain

You can get prebuilt toolchain from the same Google repository.

1. Goto –> https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6

2. Download the master branch and extract the source in to a new folder call toolchain, following the same steps as above.

:~$mkdir -p ~/android/toolchain

:~/android/toolchain$tar xvf arm-eabi-4.6-master.tar.gz

3. Extract source:

Set the path to toolchain

Here in my example the path to toolchain is : /home/tharaka/android/toolchain/bin. You can check the folder where it contains arm-linux-androideabi-gcc

Open Terminal and enter command: gedit ~/.bashrc

It will open up the text editor:

export PATH=$PATH:/home/tharaka/android/toolchain/bin

CROSS_COMPILE kernel

Kernels are compiled with a program called gcc. The gcc comes with toolchain is an optimized version of gcc. Therefore here we do a cross-compile.

1. Go inside the kernel source folder and enter following command

make ARCH=arm CROSS_COMPILE=arm-linux-androideabi- panda_defconfig

Build the Kernel

Command: make

Compiling….

While compiling it gives messages and warnings. We can ignore warnings but when there are errors compilation stops and terminate and we will have to fix the issuses.