Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage

Josh Poimboeuf
2021-11-16T00:16:04Z

On Mon, Nov 15, 2021 at 08:01:13AM -0500, Joe Lawrence wrote:
> > This reminded me... one of the things I have on my todo list for a long
> > time is to add an option for a live patch creator to specify functions
> > which are not contained in the live patch but their presence on stacks
> > should be checked for. It could save some space in the final live patch
> > when one would add functions (callers) just because the consistency
> > requires it.
> >
>
> Yea, I've used this technique once (adding a nop to a function so
> kpatch-build would detect and include in klp_funcs[]) to make a set of
> changes safer with respect to the consistency model. Making it simpler
> to for the livepatch author to say, "I'm not changing foo(), but I don't
> want it doing anything while patching a task" sounds reasonable.
>
> > I took as a convenience feature with a low priority and forgot about it.
> > The problem above changes it. So should we take the opportunity and
> > implement both in one step? I wanted to include a list of functions in
> > on a patch level (klp_patch structure) and klp_check_stack() would just
> > have more to check.
> >
>
> As far as I read the original problem, I think it would solve for that,
> too, so I would say go for it.

Sounds good to me.

Miroslav, do I understand correctly that you're volunteering to make
this change? ;-)

--
Josh