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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 02A85C56202 for ; Tue, 24 Nov 2020 18:13:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96A80206D8 for ; Tue, 24 Nov 2020 18:13:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="tLy8IsjZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404294AbgKXSMo (ORCPT ); Tue, 24 Nov 2020 13:12:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:35184 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729291AbgKXSMo (ORCPT ); Tue, 24 Nov 2020 13:12:44 -0500 Received: from localhost (82-217-20-185.cable.dynamic.v4.ziggo.nl [82.217.20.185]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D86A420684; Tue, 24 Nov 2020 18:12:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1606241563; bh=6ueb6PQc/kg1g7WGD1geVPCHnT05IVlvxmtC1abRplI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tLy8IsjZVJ9Ah+G1T/xIxZLVB3SeDio4nhXvlWYyPAQy4GxEFFe2qb8tYSOnmmjpi S2N84jZexq5SWpWWrBw916LNvMRMYlvNwRlODPhydxa9d/NJdCiV7bY4Uwhjajc56g Nd3hY8hwZXFHuukoPhrTjf1sGuZMPLhKTihwFY+k= Date: Tue, 24 Nov 2020 19:12:40 +0100 From: Greg Kroah-Hartman To: William Mcvicker Cc: Jessica Yu , Christoph Hellwig , Masahiro Yamada , Michal Marek , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, kernel-team@android.com, Saravana Kannan Subject: Re: [PATCH v1 0/2] Add support to capture external module's SCM version Message-ID: References: <20201121011652.2006613-1-willmcvicker@google.com> <20201123090257.GB6334@infradead.org> <20201123221338.GA2726675@google.com> <20201124093117.GA21089@linux-8ccs> <20201124180516.GA737971@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201124180516.GA737971@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 24, 2020 at 10:05:16AM -0800, William Mcvicker wrote: > On Tue, Nov 24, 2020 at 10:31:18AM +0100, Jessica Yu wrote: > > +++ William Mcvicker [23/11/20 14:13 -0800]: > > > On Mon, Nov 23, 2020 at 09:02:57AM +0000, Christoph Hellwig wrote: > > > > On Sat, Nov 21, 2020 at 01:16:49AM +0000, Will McVicker wrote: > > > > > These two patches add module support to capture an external module's SCM > > > > > version as a MODULE_INFO() attribute. This allows users to identity the SCM > > > > > version of a given kernel module by using the modinfo tool or on the device > > > > > via sysfs: > > > > > > > > As this obviously is of no use for in-tree modules it falls under the we > > > > don't add code to support things that are not in tree rule and has no > > > > business in the kernel. > > > > > > Hi Christoph, > > > > > > Ah sorry, I didn't intend this to come across as only for external modules. > > > That just seemed like the easiest way to explain how the scmversion attribute > > > can be different from the vermagic. We mainly need this for in-tree kernel > > > modules since that's where most our drivers are. Let me re-phrase this with > > > that in mind. Basically, I like to look at this as an improved version of the > > > existing srcversion module attribute since it allows you to easily identify the > > > module version with a quick SCM version string check instead of doing a full > > > checksum on the module source. > > > > > > For example, we have a setup to test kernel changes on the hikey and db845c > > > devices without updating the kernel modules. Without this scmversion module > > > attribute, you can't identify the original module version using `uname > > > -r`. And for kernel modules in the initramfs, you can't even use modinfo to get > > > the module vermagic. With this patch, you are able to get the SCM version for > > > *all* kernel modules (on disk and in the initramfs) via the sysfs node: > > > /sys/module//scmversion. This also works the other way around when > > > developers update their kernel modules to fix some bug (like a security > > > vulnerability) but don't need to update the full kernel. > > > > Hi Will, > > > > If this were also intended for in-tree kernel modules, then why do > > intree modules only get the UTS_RELEASE string in their scmversion > > field, which basically already exists in the vermagic? Or do you plan > > to change that? > > > > Jessica > > Hi Jessica, > > Thanks for asking! The reason in-tree kernel modules get the UTS_RELEASE string > is for a few reasons: > > (1) It contains the SCM version (since UTS_RELEASE has that). > (2) It allows you to get the SCM version via the sysfs node (useful for modules > in the initramfs). > (3) It helps identify that that particular kernel module was in-tree when > originally compiled. > (4) Using UTS_RELEASE also allows us to respect the privacy of kernels with > "# CONFIG_LOCALVERSION_AUTO is not set" by not including the SCM version in the > module scmversion attribute. > > Now, if we don't care about knowing if a module was in-tree or not (since > we only care about in-tree modules here anyway), I can update the patch to have > a consistent format regardless of in-tree or external. Personally, I like the > UTS_RELEASE version better because it gives me more information from the sysfs > node which is useful when debugging issues related to modules loaded in > initramfs. We already know if a module was built in-or-out of tree, the "O" taint flag is set, so that information is already in the module today, right? Can't that be used somehow here? thanks, greg k-h