Re: [PATCH bpf-next 1/2] bpf, x86: patch tail-call fentry slot on non-IBT JITs

[Alexei Starovoitov]

On Fri, Mar 27, 2026 at 8:45 AM Takeru Hayasaka <hayatake396@xxxxxxxxx> wrote:
>
> Understood. I was a bit surprised to read that this area ended up taking
> months of follow-up work....
>
> One thing I am still trying to understand is what the preferred
> debuggability/observability direction would be for existing
> tailcall-heavy BPF/XDP deployments.
>
> Tail calls are already used in practice as a program decomposition
> mechanism, especially in XDP pipelines, and that leaves tail-called leaf
> programs harder to observe today.
>
> If fentry on tail-called programs is not something you'd want upstream,
> is there another direction you would recommend for improving
> observability/debuggability of such existing deployments?

You don't need fentry to debug.
perf works just fine on all bpf progs whether tailcall or not.

Also pls don't top post.