linux-kernel - Re: [PATCH 1/2] x86: Simplify Retpoline thunk

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Message-ID: <20220420155116.GH2731@worktop.programming.kicks-ass.net>
Date:   Wed, 20 Apr 2022 17:51:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, brgerst@...il.com, jiangshanlai@...il.com,
        Andrew.Cooper3@...rix.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86: Simplify Retpoline thunk

On Wed, Apr 20, 2022 at 08:27:36AM -0700, Josh Poimboeuf wrote:
> On Tue, Apr 19, 2022 at 10:41:10PM +0200, Peter Zijlstra wrote:
> > Now that we rewrite all the indirect call sites, per commit:
> > 
> >   750850090081 ("x86/alternative: Implement .retpoline_sites support")
> > 
> > it doesn't make sense to have the retpoline thunks be an ALTERNATIVE_2
> > that still includes a 'naked' indirect jump.
> > 
> > (this accidentally 'defunnels' i386 by going back to full retpolines)
> 
> So mitigations=off no longer works on i386?

Also true I suppose... does anybody care? /me runs like heck.

I'd hate to make all this more complicated just because i386 tho :/