linux-kernel - Re: [PATCH v7 00/10] livepatch: klp-convert tool

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Message-ID: <5ee478c9-efa2-60e5-fee5-ed9d5cbceb01@redhat.com>
Date:   Mon, 20 Mar 2023 15:23:58 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Marcos Paulo de Souza <mpdesouza@...e.de>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kbuild@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Marcos Paulo de Souza <mpdesouza@...e.com>
Subject: Re: [PATCH v7 00/10] livepatch: klp-convert tool

On 3/17/23 19:20, Josh Poimboeuf wrote:
> On Fri, Mar 17, 2023 at 04:29:48PM -0400, Joe Lawrence wrote:
>> Have you tried retrofitting klp-convert into any real-world livepatch?
>> I'm curious as to your observations on the overall experience, or
>> thoughts on the sympos annotation style noted above.
> 
> On a related note, the patch creation process (of which klp-convert
> would be part of) needs to be documented.
> 
> If I remember correctly, the proper safe usage of klp-convert requires a
> kernel built with -flive-patching, plus some scripting and/or manual
> processes.
> 
> If nobody knows how to safely use it then there wouldn't be much value
> in merging it.
> 

I took a trip though my inbox and dug up a 2020 discussion on
documenting livepatch and compiler considerations [1].  This led to the
suggestion of a greater, end-to-end livepatch author guide, for which
everyone agreed, but has since remained unwritten :/

If we have a miniconf @ LPC this year, maybe we can volunteer to write
sections, decide on an outline, or even better, have a rough draft to
review and discuss?

Aside: technically klp-convert doesn't require -flive-patching, but it's
probably strongly recommended in order to use it safely.  And fwiw,
kpatch-build could leverage the tool should it desire one day.  In the
meantime, if kpatch-build doesn't need/want to use it, perhaps
klp-convert should have its own CONFIG option?  (Or something in modinfo
to key on.)

[1]
https://lore.kernel.org/live-patching/20200721161407.26806-1-joe.lawrence@redhat.com/

-- 
Joe