linux-kernel - Re: [RFC][PATCH 6/6] objtool,x86: Rewrite retpoline thunk calls

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Message-ID: <20210220223221.GB4746@worktop.programming.kicks-ass.net>
Date:   Sat, 20 Feb 2021 23:32:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        pjt@...gle.com, mbenes@...e.cz, jgross@...e.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 6/6] objtool,x86: Rewrite retpoline thunk calls

On Sat, Feb 20, 2021 at 06:41:01PM +0100, Borislav Petkov wrote:
> >  - if we had negative alternatives objtool doesn't need to actually
> >    rewrite code in this case. It could simply emit alternative entries
> >    and call it a day.
> 
> I don't mind the negative alt per se - I mind the implementation I saw.
> I'm sure we can come up with something nicer, like, for example, struct
> alt_instr.flags to denote that this feature is a NOT feature. 

So you don't like the ~ or - on cpuid? ISTR we talked about
alt_instr::flags before, but Google isn't playing ball today so I can't
seem to find it.

I can certainly look at adding the flags thing.