From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D482C3A5A9 for ; Thu, 5 Sep 2019 02:32:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E362206BA for ; Thu, 5 Sep 2019 02:32:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729848AbfIECcK (ORCPT ); Wed, 4 Sep 2019 22:32:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727156AbfIECcK (ORCPT ); Wed, 4 Sep 2019 22:32:10 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F0A062D1CE; Thu, 5 Sep 2019 02:32:09 +0000 (UTC) Received: from treble (ovpn-121-98.rdu2.redhat.com [10.10.121.98]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4EE5260852; Thu, 5 Sep 2019 02:32:03 +0000 (UTC) Date: Wed, 4 Sep 2019 21:32:02 -0500 From: Josh Poimboeuf To: Miroslav Benes Cc: Joe Lawrence , Petr Mladek , jikos@kernel.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal Message-ID: <20190905023202.ed7fecc22xze4pwj@treble> References: <20190728200427.dbrojgu7hafphia7@treble> <20190814151244.5xoaxib5iya2qjco@treble> <20190816094608.3p2z73oxcoqavnm4@pathway.suse.cz> <20190822223649.ptg6e7qyvosrljqx@treble> <20190823081306.kbkm7b4deqrare2v@pathway.suse.cz> <20190826145449.wyo7avwpqyriem46@treble> <5c649320-a9bf-ae7f-5102-483bc34d219f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 05 Sep 2019 02:32:10 +0000 (UTC) Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Tue, Sep 03, 2019 at 03:02:34PM +0200, Miroslav Benes wrote: > On Mon, 2 Sep 2019, Joe Lawrence wrote: > > > On 9/2/19 12:13 PM, Miroslav Benes wrote: > > >> I can easily foresee more problems like those in the future. Going > > >> forward we have to always keep track of which special sections are > > >> needed for which architectures. Those special sections can change over > > >> time, or can simply be overlooked for a given architecture. It's > > >> fragile. > > > > > > Indeed. It bothers me a lot. Even x86 "port" is not feature complete in > > > this regard (jump labels, alternatives,...) and who knows what lurks in > > > the corners of the other architectures we support. > > > > > > So it is in itself reason enough to do something about late module > > > patching. > > > > > > > Hi Miroslav, > > > > I was tinkering with the "blue-sky" ideas that I mentioned to Josh the other > > day. > > > I dunno if you had a chance to look at what removing that code looks > > like, but I can continue to flesh out that idea if it looks interesting: > > Unfortunately no and I don't think I'll come up with something useful > before LPC, so anything is really welcome. > > > > > https://github.com/joe-lawrence/linux/tree/blue-sky I like this a lot. > > A full demo would require packaging up replacement .ko's with a livepatch, as > > well as "blacklisting" those deprecated .kos, etc. But that's all I had time > > to cook up last week before our holiday weekend here. > > Frankly, I'm not sure about this approach. I'm kind of torn. The current > solution is far from ideal, but I'm not excited about the other options > either. It seems like the choice is basically between "general but > technically complicated fragile solution with nontrivial maintenance > burden", or "something safer and maybe cleaner, but limiting for > users/distros". Of course it depends on whether the limitation is even > real and how big it is. Unfortunately we cannot quantify it much and that > is probably why our opinions (in the email thread) differ. How would this option be "limiting for users/distros"? If the packaging part of the solution is done correctly then I don't see how it would be limiting. -- Josh