linux-kernel - Re: [PATCH] x86: Implement _

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Message-ID: <20170225202902.roif2sxdvronwbsl@pd.tnic>
Date:   Sat, 25 Feb 2017 21:29:02 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     hpa@...or.com
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        jpoimboe@...hat.com, richard.weinberger@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86: Implement __WARN using UD0

On Sat, Feb 25, 2017 at 12:04:18PM -0800, hpa@...or.com wrote:
> Note that once you have a trap you can create an immediate yourself,
> the CPU doesn't need to do it for you, unless you really care about
> latency (reading the instruction steam can be kind of expensive,
> although it is quite a bit simpler if we know we come from kernel
> space.)

You mean, put it after the INT 9 opcode?

CD 09 immed8

Yeah, that could be one way to pass callsite-specific info, if needed.

-- 
Regards/Gruss,
    Boris.

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