linux-kernel - Re: [PATCH 1/7] livepatch: Apply vmlinux-specific KLP relocations early

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Date:   Tue, 14 Apr 2020 13:01:09 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH 1/7] livepatch: Apply vmlinux-specific KLP relocations
 early

On Tue, Apr 14, 2020 at 07:44:06PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 14, 2020 at 11:28:37AM -0500, Josh Poimboeuf wrote:
> > KLP relocations are livepatch-specific relocations which are applied to
> >   1) vmlinux-specific KLP relocation sections
> > 
> >      .klp.rela.vmlinux.{sec}
> > 
> >      These are relocations (applied to the KLP module) which reference
> >      unexported vmlinux symbols.
> > 
> >   2) module-specific KLP relocation sections
> > 
> >      .klp.rela.{module}.{sec}:
> > 
> >      These are relocations (applied to the KLP module) which reference
> >      unexported or exported module symbols.
> 
> Is there something that disallows a module from being called 'vmlinux' ?
> If not, we might want to enforce this somewhere.

I'm pretty sure we don't have a check for that anywhere, though the KLP
module would almost certainly fail during the module load when it
couldn't find the vmlinux.ko symbols it needed.

It wouldn't hurt to add a check somewhere though.  Maybe in
klp_module_coming() since the restriction only applies to
CONFIG_LIVEPATCH...

-- 
Josh