Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755588AbXFOMrZ (ORCPT ); Fri, 15 Jun 2007 08:47:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753304AbXFOMrR (ORCPT ); Fri, 15 Jun 2007 08:47:17 -0400 Received: from canuck.infradead.org ([209.217.80.40]:41683 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752299AbXFOMrP (ORCPT ); Fri, 15 Jun 2007 08:47:15 -0400 Subject: Re: [PATCH] Introduce compat_u64 and compat_s64 types From: David Woodhouse To: Andi Kleen Cc: Arnd Bergmann , Benjamin Herrenschmidt , Linux Kernel Mailing List , Dave Airlie , linux-arch@vger.kernel.org, Andrew Morton In-Reply-To: <200706151440.10273.ak@suse.de> References: <200706150159.l5F1xNgM000459@hera.kernel.org> <200706151355.57464.ak@suse.de> <200706151403.53855.arnd@arndb.de> <200706151440.10273.ak@suse.de> Content-Type: text/plain Date: Fri, 15 Jun 2007 13:47:08 +0100 Message-Id: <1181911628.25228.483.camel@pmac.infradead.org> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 (2.10.1-17.fc7.dwmw2.1) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by canuck.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1095 Lines: 28 On Fri, 2007-06-15 at 14:40 +0200, Andi Kleen wrote: > > That is broken on all non-x86 architectures, > It cannot be broken, it just might be somewhat slower No, Andi. It's broken. We're speaking of a 32-bit ioctl compat routine. I would say it's more than 'convention' that the structure used by the compat_ioctl routine actually matches the 'real' structure as it gets laid out on the 32-bit architecture. The 'real' structure as used by the 32-bit userspace does not have the 'packed' attribute. Thus the u64 member of the structure is aligned to 8 bytes on _all_ relevant 32-bit architectures except for i386. By adding 'packed' in the compat_ioctl routine, you cause it to expect a structure which does not match what userspace is using, for all non-x86 architectures. That's kind of not very compatible. I call that 'broken'. -- dwmw2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/