Re: [RFC PATCH 0/4] trace, livepatch: Allow kprobe return overriding for livepatched functions

Song Liu
2026-04-03T16:07:01Z

Hi Yafang,

On Thu, Apr 2, 2026 at 2:26 AM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> Livepatching allows for rapid experimentation with new kernel features
> without interrupting production workloads. However, static livepatches lack
> the flexibility required to tune features based on task-specific attributes,
> such as cgroup membership, which is critical in multi-tenant k8s
> environments. Furthermore, hardcoding logic into a livepatch prevents
> dynamic adjustments based on the runtime environment.
>
> To address this, we propose a hybrid approach using BPF. Our production use
> case involves:
>
> 1. Deploying a Livepatch function to serve as a stable BPF hook.
>
> 2. Utilizing bpf_override_return() to dynamically modify the return value
> of that hook based on the current task's context.

Could you please provide a specific use case that can benefit from this?
AFAICT, livepatch is more flexible but risky (may cause crash); while
BPF is safe, but less flexible. The combination you are proposing seems
to get the worse of the two sides. Maybe it can indeed get the benefit of
both sides in some cases, but I cannot think of such examples.

Thanks,
Song