Speaker
Description
Kernel livepatches are kernel modules which are able to modify the kernel behavior by redirecting kernel functions, calling pre/post patch callbacks, and allocating shadow variables.
The interface between the kernel and the kernel livepatch module is defined in include/linux/livepatch.h.
The API has evolved over the years. But it has stayed backward compatible since the commit 958ef1e39d24d6cb8bf ("livepatch: Simplify API by removing registration step") which was added in v5.1-rc1 back in Jan 2019. This change was part of a patchset adding an atomic replace feature.
There are two patchsets which would want to break the backward compatibility again:
It has been acceptable to break the API back in 2019. But the kernel livepatching has been a pretty new feature and had only few users back then.
It might be more acceptable when the tools for creating livepatches can deal with it. But is it enough?
Question for discussion:
- Is is possible to break the kernel livepatching API in 2026?
- Is it enough to update tools for creating livepatches?
- Is it needed and enough to update klp-build?
- How many old code streams people still support?
- Should selftests stay backward compatible?