From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932314AbbEHQ2d (ORCPT <rfc822;w@1wt.eu>);
	Fri, 8 May 2015 12:28:33 -0400
Received: from terminus.zytor.com ([198.137.202.10]:51001 "EHLO mail.zytor.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932288AbbEHQ21 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 8 May 2015 12:28:27 -0400
User-Agent: K-9 Mail for Android
In-Reply-To: <87mw1fkpgn.fsf@rasmusvillemoes.dk>
References: <1431092553-12914-1-git-send-email-linux@rasmusvillemoes.dk> <20150508142453.GC4137@pd.tnic> <87mw1fkpgn.fsf@rasmusvillemoes.dk>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain;
 charset=UTF-8
Subject: Re: [PATCH] x86: tell the world boot_params is 16-byte aligned
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Fri, 08 May 2015 09:26:49 -0700
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Borislav Petkov <bp@alien8.de>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org
Message-ID: <853B4FF2-FAC4-4FE3-90F5-D1CFD18B10F7@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

NAK.  This could break in the case of careless bootloaders...

On May 8, 2015 9:23:52 AM PDT, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
>On Fri, May 08 2015, Borislav Petkov <bp@alien8.de> wrote:
>
>> On Fri, May 08, 2015 at 03:42:33PM +0200, Rasmus Villemoes wrote:
>>> It doesn't matter much, but this disassembly makes me cry a little
>bit:
>>> 
>>> ffffffff81f21223 <copy_bootdata>:
>>> ffffffff81f21223:       55                      push   %rbp
>>> ffffffff81f21224:       48 c7 c0 40 c2 02 82    mov   
>$0xffffffff8202c240,%rax
>>> ffffffff81f2122b:       48 89 fe                mov    %rdi,%rsi
>>> ffffffff81f2122e:       a8 01                   test   $0x1,%al
>>> 
>>> The reason is that boot_params is defined with
>>> __attribute__((aligned(16))) in boot/main.c, but other translation
>>> units only see the packed attribute on the definition of struct
>>> boot_params, so assume the worst. Making the de facto alignment
>public
>>
>> Wouldn't it be better if we put both attributes together, i.e.:
>
>Sure, putting it on the type works as well. Either way is fine with me.
>
>Rasmus

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.