Build vanilla kernel for Raspberry Pi

Check this post if you're looking for the build instructions.
Check this post if you're looking for the git main commands.


Raspberry Pi's official kernel git repository :

https://github.com/raspberrypi/linux.git

We could have cloned this repository, built it and ran a linux on our Pi.... yes we could, but we are a bit sadistic and as they say in my fitness club : "No pain, no gain". So let's try something fun : cloning the mainline kernel ( the latest stable version ) and adapt it for the Pi.

Our repository is hosted on bitbucket - which is free by the way - and is a clone of the mainline kernel 3.8.9 :

https://linux389pi@bitbucket.org/linux389pi/linux389pi.git

What we need to do first is grabbing the raspberry Pi's defconfig file. Manually configuring the build would take too much time and requires strong technical skills. This method will be experimented later...
Now we got the file, copy it to arch/arm/configs, and run :

make bcmrpi_defconfig

(ARCH and CROSS_COMPILE must be defined)

First build attempt will fail with :

ERROR: "v7wbi_flush_kern_tlb_range" [drivers/staging/zsmalloc/zsmalloc.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

Not surprising, otherwise a git repository dedicated to the Pi would certainly not exist. The next step is to modify our sources to make them build for the Pi.

Generate a patch to merge the vanilla sources with the rpi ones

The following method is not really the best way for the patch generation, you should consider using git format-patch instead, but, if like me you're living in a building with a poor internet connection, you may want to do it like this :

1. Download the official linux rpi-3.8.y archive from github (about 100 MB, not a big deal compared to GBs of data that you have to download using git fetch command with the rpi remote repo)
2. Create a local git repo with your rpi sources :

# Create a directory where you'll store the rpi linux sources

mkdir rpi-3.8.y

cd rpi-3.8.y

# Move the archive to the current directory

mv /Downloads/linux-rpi-3.8.y.tar.gz .

# Extract it

tar -xf linux-rpi-3.8.y.tar.gz

# Initialize the repository

git init

# Add all elements

git add .

# Commit them

git commit -m "added : rpi-3.8.y sources"

3. Let's assume that your vanilla kernel sources are in a directory named linux_vanilla_kernel :

# Add the vanilla kernel git repo 

git remote add vanilla ../linux_vanilla_kernel/

# Fetch the vanilla kernel repo

git fetch vanilla

After a while, you should obtain an output saying that a branch has been created with vanilla kernel sources :

master --> master/vanilla

4. Generate the patch

git diff --no-prefix master/vanilla HEAD > patchfile

5. You can now apply the patch to your vanilla kernel sources

# Move the patch to your vanilla kernel working directory

mv patchfile ../linux_vanilla_kernel/

cd ../linux_vanilla_kernel

# Apply the patch

patch -p0 < patchfile

6.Build again

make bcmrpi_defconfig

make -j8

The build process should end successfully now.

Cem SOYDING

Author & Editor

Senior software engineer with 12 years of experience in both embedded systems and C# .NET