linux-kernel - Re: [PATCH v3 5/6] x86/ftrace: Use text

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Message-ID: <7e9c7dd1-809e-f130-26a3-3d3328477437@redhat.com>
Date:   Tue, 15 Oct 2019 18:17:43 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

On 10/15/19 11:31 AM, Jessica Yu wrote:
> +++ Joe Lawrence [15/10/19 11:06 -0400]:
>> On 10/15/19 10:13 AM, Miroslav Benes wrote:
>>> Yes, it does. klp_module_coming() calls module_disable_ro() on all
>>> patching modules which patch the coming module in order to call
>>> apply_relocate_add(). New (patching) code for a module can be relocated
>>> only when the relevant module is loaded.
>>
>> FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @
>> plumber's where livepatches only patch a single object and updates are
>> kept on disk to handle coming module updates as they are loaded)
>> eliminate those outstanding relocations and the need to perform this
>> late permission flipping?
> 
> I wasn't at Plumbers sadly, was this idea documented/talked about in
> detail somewhere? (recording, slides, etherpad, etc?). What do you
> mean by updates are kept on disk? Maybe someone can explain it more
> in detail? :)
> 

Livepatching folks -- I don't have the LPC summary link (etherpad?) that 
Jiri put together.  Does someone have that handy for Jessica?

Thanks,

-- Joe