From: Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: x86-64: Maintain 16-byte stack alignment
Date: Thu, 12 Jan 2017 15:05:34 +0800
Message-ID: <20170112070534.GA14016@gondor.apana.org.au>
References: <20170110143340.GA3787@gondor.apana.org.au>
 <20170110143913.GA3822@gondor.apana.org.au>
 <CA+55aFyuUCr3aUBhFt6T3vKyZOskLyH8Kd_2jeFkPYxxvEaXEg@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <CA+55aFyuUCr3aUBhFt6T3vKyZOskLyH8Kd_2jeFkPYxxvEaXEg@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-crypto.vger.kernel.org

On Tue, Jan 10, 2017 at 09:05:28AM -0800, Linus Torvalds wrote:
>
> I'm pretty sure we have random asm code that may not maintain a
> 16-byte stack alignment when it calls other code (including, in some
> cases, calling C code).
> 
> So I'm not at all convinced that this is a good idea. We shouldn't
> expect 16-byte alignment to be something trustworthy.

So what if we audited all the x86 assembly code to fix this? Would
it then be acceptable to do a 16-byte aligned stack?

On the face of it it doesn't seem to be a huge amount of code
assuming they mostly live under arch/x86.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt