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

On Mon, 15 Nov 2021, Josh Poimboeuf wrote:

On Mon, Nov 15, 2021 at 08:01:13AM -0500, Joe Lawrence wrote:

quoted

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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.

quoted

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