From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992542AbcB0TQs (ORCPT ); Sat, 27 Feb 2016 14:16:48 -0500 Received: from www.sr71.net ([198.145.64.142]:39672 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751389AbcB0TQq (ORCPT ); Sat, 27 Feb 2016 14:16:46 -0500 Subject: Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field To: Ingo Molnar , Stephen Rothwell References: <20160226173427.54A6949F@viggo.jf.intel.com> <6C5C3B9B-CAD6-4010-9A3E-AFFF7E13FAE3@zytor.com> <20160227091013.6e0606d1@canb.auug.org.au> <20160227114154.GA16200@gmail.com> Cc: "H. Peter Anvin" , linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, akpm@linux-foundation.org, tglx@linutronix.de, mingo@elte.hu, peterz@infradead.org, linux-next@vger.kernel.org, deller@gmx.de From: Dave Hansen Message-ID: <56D1F61C.5050308@sr71.net> Date: Sat, 27 Feb 2016 11:16:44 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160227114154.GA16200@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/27/2016 03:41 AM, Ingo Molnar wrote: > * Stephen Rothwell wrote: >> > On Fri, 26 Feb 2016 09:44:00 -0800 "H. Peter Anvin" wrote: >>> > > __u64 is okay, "unsigned long" is really messy in the presence of 32-on-64 bit ABIs... >> > >> > Yeah, but unfortunately, any 64 bit scalar type here will change the >> > alignment of the enclosing unions on (some) 32 bit platforms and thus >> > break the ABI. > Then a different solution has to be found. I've acked Stephen's initial patch changing the 'u64' to an 'int'. x86 only needs 4 bits, and in the remote chance that a future implementation needed more space, we could easily add a second 32-bit field "_pkey_hi" or something that wouldn't have the alignment issues of a true 64-bit type. How should we get Stephen's patch in to the tip tree?