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Date:   Wed, 16 Oct 2019 08:51:27 +0200 (CEST)
From:   Miroslav Benes <mbenes@suse.cz>
To:     Joe Lawrence <joe.lawrence@redhat.com>
cc:     Peter Zijlstra <peterz@infradead.org>,
        Jessica Yu <jeyu@kernel.org>,
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Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()
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On Tue, 15 Oct 2019, Joe Lawrence wrote:

> 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?

Yes, it should, but we don't have to wait for it. PeterZ proposed a 
different solution to this specific issue in 
https://lore.kernel.org/lkml/20191015141111.GP2359@hirez.programming.kicks-ass.net/

It should not be a problem to create a live patch module like that and the 
code in kernel/livepatch/ is almost ready. Something like 
module_section_disable_ro(mod, section) (and similar for X protection) 
should be enough. Module reloads would still require juggling with the 
protections, but I think it is all feasible.

Miroslav