From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932668Ab0JAPWa (ORCPT ); Fri, 1 Oct 2010 11:22:30 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50153 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932400Ab0JAPW3 (ORCPT ); Fri, 1 Oct 2010 11:22:29 -0400 Message-ID: <4CA5FC96.1030300@zytor.com> Date: Fri, 01 Oct 2010 08:21:58 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Thunderbird/3.1.4 MIME-Version: 1.0 To: Jan Beulich CC: Ingo Molnar , heukelum@fastmail.fm, tglx@linutronix.de, akpm@linux-foundation.org, LKML Subject: Re: gas 2.16 and assembly macros -- entry_64.S build failure References: <201009152110.o8FLAJeJ015584@imap1.linux-foundation.org> <4C91F07E0200007800016B50@vpn.id2.novell.com> <20100916082816.GA25681@elte.hu> <4C91F3A30200007800016B64@vpn.id2.novell.com> <20100916101355.GA31458@elte.hu> <4C9219BC0200007800016C53@vpn.id2.novell.com> <4CA52AA5.5040402@zytor.com> <4CA5B7910200007800019F50@vpn.id2.novell.com> In-Reply-To: <4CA5B7910200007800019F50@vpn.id2.novell.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/01/2010 01:27 AM, Jan Beulich wrote: >>>> On 01.10.10 at 02:26, "H. Peter Anvin" wrote: >> ... but that doesn't work with the macros like movq_cfi. On those, we > > Is that only because of the register names used as operands to > movq_cfi etc not having the % specified right away? I don't think > that is really needed, i.e. the % could go there rather than being > added in the macro body - the .cfi_* directives are perfectly happy > with having the prefix there (and I don't know why it was coded > this way in the first place, as this made it less similar to the plain > movq while I thought the goal was to keep the differences to a > minimum). > No, and in fact the problem that spurred this discussion was in the use of immediates, not registers: pushq_cfi $(USER_DS) Obviously we can't add the % register prefix, since pushq can take either a register or an immediate (or, for that matter, a memory operand). >> could argue that at least people won't put $ on them, but cpp will still >> split them apart with spaces; this apparently causes problems at least >> as soon as there is an expression more complicated than addition >> involved (apparently plus signs are okay, but minus signs aren't!) >> >> I'm completely lost about how to deal with this. We can't simply >> defang the macros -- at least not in a way that is likely to *stay* >> working -- and dropping the macros is seriously going to impact the >> debuggability of the kernel. One way, of course, is to simply declare >> binutils 2.16 and 2.15.9x (which is apparently included in >> RHEL/CentOS 4) to be broken beyond repair unless distros backport a fix, >> and in many ways I think that is the preferred option, but I don't know >> if that makes sense to others... > > The other alternative, albeit disliked by Ingo, continues to be to use > __stringify() on all non-trivial operands, which then wouldn't require > suppressing CONFIG_AS_CFI for pre-2.17 binutils. You should be taken out and shot for even thinking that, never mind putting it in writing... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.