From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946361AbcHRMs2 (ORCPT ); Thu, 18 Aug 2016 08:48:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:60130 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752898AbcHRMsZ (ORCPT ); Thu, 18 Aug 2016 08:48:25 -0400 Date: Thu, 18 Aug 2016 14:48:21 +0200 (CEST) From: Miroslav Benes To: Jessica Yu cc: Josh Poimboeuf , Petr Mladek , Jiri Kosina , Chris J Arges , Eugene Shatokhin , live-patching@vger.kernel.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/3] Fix issue with alternatives/paravirt patches In-Reply-To: <1471481911-5003-1-git-send-email-jeyu@redhat.com> Message-ID: References: <1471481911-5003-1-git-send-email-jeyu@redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 17 Aug 2016, Jessica Yu wrote: > Hi, > > A few months ago, Chris Arges reported a bug involving alternatives/paravirt > patching that was discussed here [1] and here [2]. To briefly summarize the > bug, patch modules that contained .altinstructions or .parainstructions > sections would break because these alternative/paravirt patches would be > applied first by the module loader (see x86 module_finalize()), then > livepatch would later clobber these patches when applying per-object > relocations. This lead to crashes and unpredictable behavior. > > One conclusion we reached from our last discussion was that we will > need to introduce some arch-specific code to address this problem. > This patchset presents a possible fix for the bug by adding a new > arch-specific arch_klp_init_object_loaded() function that by default > does nothing but can be overridden by different arches. > > To fix this issue for x86, since we can access a patch module's Elf > sections through mod->klp_info, we can simply delay the calls to > apply_paravirt() and apply_alternatives() to arch_klp_init_object_loaded(), > which is called after relocations have been written for an object. > In addition, for patch modules, .parainstructions and .altinstructions are > prefixed by ".klp.arch.${objname}" so that the module loader ignores them > and livepatch can apply them manually. > > Currently for kpatch, we don't support including jump table sections in > the patch module, and supporting .smp_locks is currently broken, so we > don't consider those sections (for now). > > I did some light testing with some patches to kvm and verified that the > original issue reported in [2] was fixed. > > Based on linux-next. For the whole patch set Acked-by: Miroslav Benes Thanks Miroslav