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

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Message-ID: <20190905134239.fmoknq3z422tflst@treble>
Date:   Thu, 5 Sep 2019 08:42:39 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Petr Mladek <pmladek@...e.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, Sep 05, 2019 at 03:31:56PM +0200, Jiri Kosina wrote:
> On Thu, 5 Sep 2019, Josh Poimboeuf wrote:
> 
> > > All the indirect jumps are turned into alternatives when retpolines 
> > > are in place.
> > 
> > Actually in C code those are done by the compiler as calls/jumps to
> > __x86_indirect_thunk_*.
> 
> Sure, and the thunks do the redirection via JMP_NOSPEC / CALL_NOSPEC, 
> which has alternative in it.

But the thunks are isolated to arch/x86/lib/retpoline.S.  We can't patch
that code anyway.

-- 
Josh