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_PASS,USER_AGENT_MUTT autolearn=ham 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 5175CC43381 for ; Mon, 18 Mar 2019 19:18:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B1FD2133F for ; Mon, 18 Mar 2019 19:18:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727600AbfCRTSr (ORCPT ); Mon, 18 Mar 2019 15:18:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34822 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726953AbfCRTSr (ORCPT ); Mon, 18 Mar 2019 15:18:47 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F1F7C307CDEA; Mon, 18 Mar 2019 19:18:46 +0000 (UTC) Received: from redhat.com (dhcp-17-208.bos.redhat.com [10.18.17.208]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3DE0919C67; Mon, 18 Mar 2019 19:18:45 +0000 (UTC) Date: Mon, 18 Mar 2019 15:18:43 -0400 From: Joe Lawrence To: Joao Moreira Cc: live-patching@vger.kernel.org, mbenes@suse.cz, pmladek@suse.cz, jikos@suse.cz, nstange@suse.de, jpoimboe@redhat.com, khlebnikov@yandex-team.ru, jeyu@kernel.org, matz@suse.de, linux-kernel@vger.kernel.org, yamada.masahiro@socionext.com, linux-kbuild@vger.kernel.org, michal.lkml@markovi.net Subject: Re: [PATCH v2 0/8] klp-convert Message-ID: <20190318191843.GA22702@redhat.com> References: <20190301141313.15057-1-jmoreira@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190301141313.15057-1-jmoreira@suse.de> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 18 Mar 2019 19:18:47 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 01, 2019 at 11:13:05AM -0300, Joao Moreira wrote: > Livepatches may use symbols which are not contained in its own scope, > and, because of that, may end up compiled with relocations that will > only be resolved during module load. Yet, when the referenced symbols are > not exported, solving this relocation requires information on the object > that holds the symbol (either vmlinux or modules) and its position inside > the object, as an object may contain multiple symbols with the same name. > Providing such information must be done accordingly to what is specified > in Documentation/livepatch/module-elf-format.txt. > > Currently, there is no trivial way to embed the required information as > requested in the final livepatch elf object. klp-convert solves this > problem in two different forms: (i) by relying on a symbol map, which is > built during kernel compilation, to automatically infers the relocation > targeted symbol, and, when such inference is not possible (ii) by using > annotations in the elf object to convert the relocation accordingly to > the specification, enabling it to be handled by the livepatch loader. > > Given the above, add support for symbol mapping in the form of > Symbols.list file; add klp-convert tool; integrate klp-convert tool into > kbuild; make livepatch modules discernible during kernel compilation > pipeline; add data-structure and macros to enable users to annotate > livepatch source code; make modpost stage compatible with livepatches; > update livepatch-sample and update documentation. > > The patch was tested under three use-cases: > > use-case 1: There is a relocation in the lp that can be automatically > resolved by klp-convert (tested by removing the annotations from > samples/livepatch/livepatch-annotated-sample.c) > > use-case 2: There is a relocation in the lp that cannot be automatically > resolved, as the name of the respective symbol appears in multiple > objects. The livepatch contains an annotation to enable a correct > relocation - reproducible with this livepatch sample: > www.livewire.com.br/suse/klp/livepatch-sample.1.c > > use-case 3: There is a relocation in the lp that cannot be automatically > resolved similarly as 2, but no annotation was provided in the livepatch, > triggering an error during compilation - reproducible with this livepatch > sample: www.livewire.com.br/suse/klp/livepatch-sample.2.c > > In comparison with v1, this version of the patch-set: > - was rebased to kernel 4.19 > - adds a Symbols.list versioning information > - brings bug fixes and code improvements to klp-convert sources > > This is a patch-set repost, given that a typo in a mail address prevented > the original submission from being posted to lkml. > > [ ... snip ... ] Hi Joao, Apologies for taking so long to get to this patchset, but I finally spent last week reviewing and testing. My goal was to write a klp self-test based on the implementation and your sample module. Along the way I spotted a few minor bugs and other small suggestions. Instead of dumping a bunch of code or patch content in my replies, I posted my rebase and modified branch here: https://github.com/joe-lawrence/linux/tree/klp-convert-v2-rebase-review I added subject line [squash] tags to individual commits that should be considered fixups for patches in this set. Those commit logs also contain [joe: description] tags and my sign-offs for that purpose as well. Hopefully this form of feedback will be easy to digest. I'll reply to the individual patchs here with high-level comments and a pointer to the corresponding github patch. Let me know if there are any questions. If it is easier to simply repost as a v3 with those changes, I can do that as well -- whichever method is easier for you. I'll also take comments on my work-in-progress self-test for klp-convert: [new] livepatch/selftests: add klp-convert https://github.com/torvalds/linux/commit/b0d858b9356d3c909096509a0f18e092b739b44f At the moment, it consists of two livepatch modules (I'd prefer to consolidate, but ran into an issue with klp-convert and multiple object files) and verifies that livepatch can correctly resolve sympos of 0/1, 2 for unique/non-uniquely named strings and functions. -- Joe