linux-kernel - Re: [PATCH 1/4] x86/cpufeature: Add User-Mode Instruction Prevention definitions

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Message-ID: <20161110085833.zw6qgd7pshbni656@pd.tnic>
Date:   Thu, 10 Nov 2016 09:58:34 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chen Yucong <slaoub@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH 1/4] x86/cpufeature: Add User-Mode Instruction Prevention
 definitions

On Wed, Nov 09, 2016 at 07:24:43PM -0800, Ricardo Neri wrote:
> I intended this feature to be configurable at build time in case someone
> wants to build a kernel without it; similar to other features such as
> SMAP. Is this not needed? Should Linux be built with this feature always
> enabled?
> 
> This feature could always be disabled via a kernel parameter, though;
> even if Linux is built with it.

It probably is a good idea to have it build-time configurable for the
embedded folks. But you can do a before and after build and look at
the vmlinux size and see how much it has grown. If it is only a couple
of KBs I guess we can drop the config option even but I know there are
people who still care about KBs too...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--