linux-kernel - Re: [PATCH 2/4] objtool: Implement jump_assert for _static_cpu

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Message-ID: <20180115203032.rykendkdrxtjrtf7@treble>
Date:   Mon, 15 Jan 2018 14:30:32 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw2@...radead.org>,
        linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>
Subject: Re: [PATCH 2/4] objtool: Implement jump_assert for _static_cpu_has()

On Mon, Jan 15, 2018 at 09:15:45PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 15, 2018 at 01:11:51PM -0600, Josh Poimboeuf wrote:
> > Well, to clarify, it would solve _some_ of the problem.  Maybe even most
> > of the problem.  We'd still need to special-case jump labels in objtool
> > (like in 1/4), but that's probably not a big deal.
> > 
> > So, contradicting my previous answer here... yes, it would help.
> 
> OK, saves me from having to argue otherwise. My argument would've been
> that jump labels are fully described and don't need further annotation.
> 
> Yes, Boris' proposal would certainly help with the alternative stuff.

Fair enough.  So either annotating _static_cpu_has() or adding an
alt_instr flag works for me.

-- 
Josh