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

Miroslav Benes
2021-11-16T07:26:10Z

On Mon, 15 Nov 2021, Josh Poimboeuf wrote:

> 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? ;-)

Yes, you do. I am not superfast peterz, so it will take some time, but
I'll be happy to do it :).

Miroslav