Re: [PATCH v13 bpf-next 0/1] fprobe: Introduce fprobe function entry/exit probe

Mark Rutland
2022-03-23T14:19:19Z

On Wed, Mar 23, 2022 at 11:34:46AM +0900, Masami Hiramatsu wrote:
> Hi,

Hi Masami,

> Here is the 13th version of rethook x86 port. This is developed for a part
> of fprobe series [1] for hooking function return. But since I forgot to send
> it to arch maintainers, that caused conflict with IBT and SLS mitigation series.
> Now I picked the x86 rethook part and send it to x86 maintainers to be
> reviewed.
>
> [1] https://lore.kernel.org/all/164735281449.1084943.12438881786173547153.stgit@devnote2/T/#u

As mentioned elsewhere, I have similar (though not identical) concerns
to Peter for the arm64 patch, which was equally unreviewed by
maintainers, and the overall structure.

> Note that this patch is still for the bpf-next since the rethook itself
> is on the bpf-next tree. But since this also uses the ANNOTATE_NOENDBR
> macro which has been introduced by IBT/ENDBR patch, to build this series
> you need to merge the tip/master branch with the bpf-next.
> (hopefully, it is rebased soon)

I thought we were going to drop the series from the bpf-next tree so
that this could all go through review it had missed thusfar.

Is that still the plan? What's going on?

> The fprobe itself is for providing the function entry/exit probe
> with multiple probe point. The rethook is a sub-feature to hook the
> function return as same as kretprobe does. Eventually, I would like
> to replace the kretprobe's trampoline with this rethook.

Can we please start by converting each architecture to rethook?

Ideally we'd unify things such that each architecture only needs *one*
return trampoline that both ftrace and krpboes can use, which'd be
significantly easier to get right and manage.

Thanks,
Mark.