From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750992Ab0HLEX3 (ORCPT ); Thu, 12 Aug 2010 00:23:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60719 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750846Ab0HLEX1 (ORCPT ); Thu, 12 Aug 2010 00:23:27 -0400 Message-ID: <4C63771B.6030005@zytor.com> Date: Wed, 11 Aug 2010 21:22:51 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.7) Gecko/20100720 Fedora/3.1.1-1.fc13 Thunderbird/3.1.1 MIME-Version: 1.0 To: Andrew Morton CC: Randy Dunlap , linux-kernel@vger.kernel.org, gcosta@redhat.com, lenb@kernel.org, mingo@elte.hu, tglx@linutronix.de, ying.huang@intel.com, Linux Arch Mailing List , Linus Torvalds Subject: Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree References: <201008112336.o7BNaNEj020805@imap1.linux-foundation.org> <20100811164310.a4790773.randy.dunlap@oracle.com> <20100811173327.3ae325ff.akpm@linux-foundation.org> In-Reply-To: <20100811173327.3ae325ff.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Adding Linux and linux-arch. The context is that get_user/put_user don't work on 64 bit values on i386.] On 08/11/2010 05:33 PM, Andrew Morton wrote: > > Anyway, this should be fixed in x86 core, I suspect. After looking at it -- and suffering a bad case of déjà vu -- I'm reluctant to change it, as get/put_user are specified to work only on locally atomic data: * This macro copies a single simple variable from user space to kernel * space. It supports simple types like char and int, but not larger * data types like structures or arrays. Given that u64 is not a simple type on 32 bits, it would appear that the behavior is intentional. A user might very well find that supporting u64 and/or structure types would be beneficial, but it would a) be a semantic change, and b) would introduce the possibility of a partially completed transfer. That is a semantic change to the interface. However, it may very well be nicer to have a generally available get_user()/put_user() for the cases which would just kick an EFAULT up the stack when they fail anyway. If there is consensus for making get_user/put_user a general interface, I'm more than willing to do the x86 changes, but I don't want to do them a) unilaterally and b) for 2.6.36. This seems like .37 material at this point. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.