3.1 KiB
Working with Linux kernel patches for Moby
We may apply patches to the Linux kernel used in Moby, primarily to cherry-pick some upstream patches or to add some additional functionality, not yet accepted upstream. This document outlines the recommended procedure to handle these patches.
Patches are located in alpine/kernel/patches and are maintained in
git am format to keep important meta data such as the provenance of
the patch.
Preparation
Patches are applied to point releases of the linux stable tree. You need an up-to-date copy of that tree:
git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
Throughout we use the following variables:
MOBYSRC: Base directory of Moby Linux repositoryLINUXSRC: Base directory of Linux stable kernel repositoryCURTAG: Release tag patches are currently based onNEWTAG: New release tag to base the patches on e.g.:
MOBYSRC=~/src/docker/moby
LINUXSRC=~/src/docker/linux-stable
CURTAG=v4.4.23
NEWTAG=v4.4.24
Updating the patches to a new kernel version
There are different ways to do this. You can either rebase or try to re-apply the patches. rebase is the recommended way. Once you have the patches in a new branch you need to export them.
Rebase
The simplest way is to create a new branch of the current tag, apply the patches and then rebase to the new tag:
cd $LINUXSRC
git checkout -b ${NEWTAG}-moby ${CURTAG}
git am ${MOBYSRC}/alpine/kernel/patches/*.patch
git rebase ${NEWTAG}-moby ${NEWTAG}
The git am should not have any conflicts and if the rebase has conflicts resolve them, then git add <files> and git rebase --continue.
If you already have a ${CURTAG}-moby branch, you can also do a more complex rebase by creating a new branch from the current branch and then rebase:
cd $LINUXSRC
git checkout ${CURTAG}-moby
git branch ${NEWTAG}-moby ${CURTAG}-moby
git rebase --onto ${NEWTAG} ${NEWTAG} ${NEWTAG}-moby
Again, resolve any conflicts as described above.
Re-apply patches
Create a branch from a tag for the new patches, e.g.:
cd $LINUXSRC
git checkout -b ${NEWTAG}-moby ${NEWTAG}
Import all the existing patches into the new branch:
cd $LINUXSRC
git am --reject ${MOBYSRC}/alpine/kernel/patches/*.patch
If this causes merge conflicts resolve them as they arise and continue as instructed.
Export patches to moby
Irrespective of using the rebase or re-apply method, you should now have a ${NEWTAG}-moby branch. Form this export the patches to moby:
cd $LINUXSRC
rm $MOBYSRC/alpine/kernel/patches/*
git format-patch -o $MOBYSRC/alpine/kernel/patches ${NEWTAG}..HEAD
Create a PR for Moby.
Adding new patches
For patches from upstream Linux kernel versions, use cherry-picking:
git cherry-pick -x <sha of commit>
The -x ensures that the origin of the patch is recorded in the commit.
For patches from the mailing list or patchworks, add a line like:
Origin: https://patchwork.ozlabs.org/patch/622404/
to the patch (after the Signed-off-by and Cc lines.
For patches written from scratch, make sure it has a sensible commit messages as well as a DCO line.