[External] Re: Question - Livepatch/Kprobe Coexistence on Ftrace-enabled Functions (Ubuntu kernel based on Linux stable 5.15.30)

[Song Liu]

On Tue, Oct 21, 2025 at 7:15 AM Andrey Grodzovsky
<andrey.grodzovsky at crowdstrike.com> wrote:
[...]
> > commit a8b9cf62ade1bf17261a979fc97e40c2d7842353
> > Author: Masami Hiramatsu (Google) <mhiramat at kernel.org>
> > Date: 1 year, 9 months ago
> > ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default
> >
> > commit bdbddb109c75365d22ec4826f480c5e75869e1cb
> > Author: Petr Pavlu <petr.pavlu at suse.com>
> > Date:   1 year, 8 months ago
> >
> >      tracing: Fix HAVE_DYNAMIC_FTRACE_WITH_REGS ifdef
> >
> > I tried to cherry-pick 60c8971899f3b34ad24857913c0784dab08962f0
> > and a8b9cf62ade1bf17261a979fc97e40c2d7842353, on top of 6.5.13
> > kernel. Then, fentry and fexit both work with livepatch.
>
>
> I see, thanks for testing! Is the reason it breaks so often is because
> this combination of having BPF
> and llivepatch together on a system with intersection on same functions
> as relatively   rate event and
> so regressions go easily unnoticed ? Isn't there any relevant automated
> testing in upstream that checks for
> those types of breaks ?

This case is not being covered because it is the intersection of tracing
and livepatch. I am thinking about adding a BPF selftest to cover this
case.

Thanks,
Song