Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932136AbaKXNbw (ORCPT ); Mon, 24 Nov 2014 08:31:52 -0500 Received: from cantor2.suse.de ([195.135.220.15]:44783 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754038AbaKXNbu (ORCPT ); Mon, 24 Nov 2014 08:31:50 -0500 Date: Mon, 24 Nov 2014 14:31:58 +0100 (CET) From: Jiri Kosina To: Thomas Gleixner cc: Seth Jennings , Josh Poimboeuf , Vojtech Pavlik , Steven Rostedt , Petr Mladek , Miroslav Benes , Christoph Hellwig , Greg KH , Andy Lutomirski , Masami Hiramatsu , live-patching@vger.kernel.org, x86@kernel.org, kpatch@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 2/3] kernel: add support for live patching In-Reply-To: Message-ID: References: <1416522580-5593-1-git-send-email-sjenning@redhat.com> <1416522580-5593-3-git-send-email-sjenning@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 Mon, 24 Nov 2014, Thomas Gleixner wrote: > > The person writing the patch would always need to understand what he is > > doing to be able to pick correct consistency model to be used. I > > personally think this is a good thing -- this is nothing where we should > > be relying on any kinds of tools. > > But why want we to provide a mechanism which has no consistency > enforcement at all? "No consistency model needed" is also a consistency model in a sense that there is a (large) group of patches that can be applied that way. We've done some very rough analysis, and vast majority patches for CVE bugs with severity 6+ (which is in some sense the main motivation for all this) are applicable without any need of extra consistency model. The "add bounds checking to syscall entry" is a prime example of that. > Surely you can argue that the person who is doing that is supposed to > know what he's doing, but what's the downside of enforcing consistency > mechanisms on all live code changes? The implementation of the consistency models (the ones that kgraft and kpatch have at least) is not really super-trivial and it's sometimes tricky to get it right and cover all the corner cases. So the agreement was to do cover "no consistency model needed" group of live patches first, and design the API and data structures in such way that more sophisticated consistency models can be added on top as needed in the future. -- Jiri Kosina SUSE Labs -- 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/