[RFC PATCH bpf-next 0/7] bpf: Implement BPF_LINK_UPDATE for tracing links

[Alexei Starovoitov]

On Mon, Nov 17, 2025 at 4:53 PM Jordan Rife <jordan at jrife.io> wrote:
>
> Implement update_prog for bpf_tracing_link_lops to enable
> BPF_LINK_UPDATE for fentry, fexit, fmod_ret, freplace, etc. links.
>
> My initial motivation for this was to enable a use case where one
> process creates and owns links pointing to "hooks" within a tc, xdp, ...
> attachment and an external "plugin" loads freplace programs and updates
> links to these hooks. Aside from that though, it seemed like it could
> be useful to be able to atomically swap out the program associated with
> an freplace/fentry/fexit/fmod_ret link more generally.

I don't think we should burden the kernel with link_update for fentry/fexit.
bpf trampoline is already complex enough. I don't feel that
additional complexity is justified.