From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751339Ab2DTEud (ORCPT ); Fri, 20 Apr 2012 00:50:33 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54650 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923Ab2DTEuc (ORCPT ); Fri, 20 Apr 2012 00:50:32 -0400 Message-ID: <4F90EAC1.6070508@zytor.com> Date: Thu, 19 Apr 2012 21:49:05 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-Version: 1.0 To: Linus Torvalds CC: David Daney , David Daney , Ralf Baechle , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Michal Marek , linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, Andrew Morton , David Daney Subject: Re: [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's exception table. References: <1334872799-14589-1-git-send-email-ddaney.cavm@gmail.com> <1334872799-14589-2-git-send-email-ddaney.cavm@gmail.com> <4F90BF8D.7030209@zytor.com> <4F90D564.3090508@gmail.com> <4F90DB37.9080702@zytor.com> In-Reply-To: <4F90DB37.9080702@zytor.com> X-Enigmail-Version: 1.4 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/2012 08:42 PM, H. Peter Anvin wrote: > > I don't think we can get _ASM_EXTABLE() to do that work for us, because > we'd need to subtract symbols from two different sections. We would > need the postprocessing tool to take care this, but guess what, we can > do exactly that (and then, as I mentioned, just zero out the relocation > section.) > Ah, apparently it is possible to generate relocations relative to the start of the current section: # define _ASM_EXTABLE(from,to) \ __ASM_EX_SEC ; \ _ASM_ALIGN ; \ .long (from)-__ex_table,(to)-__ex_table ; \ .previous Then all the postprocessor would have to do is to zero out the relocation section, and we would always just add the base of the particular __ex_table section. We need to make sure the module loader works, too, and not to break the __{get,put}_user_ex macros (which would need to use a new variant of _ASM_EXTABLE()). There is still a disturbing number of open-coded __ex_table instances too; those all need to be converted. Looks like a worthwhile project but not for tonight. All of this is for x86... other architectures would need to be converted in whatever way is appropriate. -hpa