linux-kernel - Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal

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Message-ID: <nycvar.YFH.7.76.1909051317550.31470@cbobk.fhfr.pm>
Date:   Thu, 5 Sep 2019 13:19:06 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Petr Mladek <pmladek@...e.com>
cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module
 removal

On Thu, 5 Sep 2019, Petr Mladek wrote:

> > I don't have a number, but it's very common to patch a function which 
> > uses jump labels or alternatives.
> 
> Really? My impression is that both alternatives and jump_labels
> are used in hot paths. I would expect them mostly in core code
> that is always loaded.
> 
> Alternatives are often used in assembly that we are not able
> to livepatch anyway.
> 
> Or are they spread widely via some macros or inlined functions?

All the indirect jumps are turned into alternatives when retpolines are in 
place.

-- 
Jiri Kosina
SUSE Labs