src/source/building-kernels.md

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# Building Kernels #

If you are only interested in the kernel, you may use this guide
to download and build the appropriate kernel.

The following instructions assume that you have not downloaded all
of AOSP.  If you have downloaded all of AOSP, you may skip the git
clone steps other than the step to download the actual kernel sources.

We will use the Pandaboard kernel in all the following examples.


## Figuring out which kernel to build ##

You will want to look at the git log for the kernel in the device project that
you are interested in.
Device projects are of the form device/&lt;vendor&gt;/&lt;name&gt;.

    $ git clone https://android.googlesource.com/device/ti/panda
    $ cd panda
    $ git log kernel

The log should contain notes of the commit SHA1 for the appropriate
kernel project.  Keep this value at hand so that you can use it in
a later step.

## Downloading sources ##

Depending on which kernel you want,

    $ git clone https://android.googlesource.com/kernel/common.git
    $ git clone https://android.googlesource.com/kernel/exynos.git
    $ git clone https://android.googlesource.com/kernel/goldfish.git
    $ git clone https://android.googlesource.com/kernel/msm.git
    $ git clone https://android.googlesource.com/kernel/omap.git
    $ git clone https://android.googlesource.com/kernel/samsung.git
    $ git clone https://android.googlesource.com/kernel/tegra.git

The goldfish project contains the kernel sources for the emulated
platforms. The msm project has the sources for ADP1, ADP2 and
Nexus One. The omap project is used for PandaBoard and Galaxy Nexus,
the samsung project for Nexus S, and the tegra project for Xoom.

## Downloading a prebuilt gcc ##

Ensure that the prebuilt toolchain is in your path.

    $ git clone https://android.googlesource.com/platform/prebuilt
    $ export PATH=$(pwd)/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin:$PATH


## Building ##

As an example, we would build the panda kernel using the following commands:

    $ export ARCH=arm
    $ export SUBARCH=arm
    $ export CROSS_COMPILE=arm-eabi-
    $ cd omap
    $ git checkout <commit_from_first_step>
    $ make panda_defconfig
    $ make

To build the tuna kernel, you may run the previous commands replacing all
instances of "panda" with "tuna".

The image is output as arch/arm/boot/zImage.  You may copy it as
device/<vendor>/<name>/kernel or device/ti/panda/kernel in the case of this
example.