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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS,URIBL_BLOCKED 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 52FBDC43381 for ; Tue, 26 Mar 2019 21:03:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C6A620700 for ; Tue, 26 Mar 2019 21:03:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732779AbfCZVDG (ORCPT ); Tue, 26 Mar 2019 17:03:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727997AbfCZVDF (ORCPT ); Tue, 26 Mar 2019 17:03:05 -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 B089488ACB; Tue, 26 Mar 2019 21:03:04 +0000 (UTC) Received: from [10.18.17.208] (dhcp-17-208.bos.redhat.com [10.18.17.208]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 52D871975D; Tue, 26 Mar 2019 21:03:03 +0000 (UTC) Subject: Re: [PATCH v2 0/8] klp-convert 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 References: <20190301141313.15057-1-jmoreira@suse.de> <20190318191843.GA22702@redhat.com> <3423e586-5ae7-1dd2-8e5f-3930f168143b@suse.de> From: Joe Lawrence Message-ID: <0580fe97-7882-68c1-54f2-5778f47c5564@redhat.com> Date: Tue, 26 Mar 2019 17:03:02 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <3423e586-5ae7-1dd2-8e5f-3930f168143b@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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 [10.5.110.26]); Tue, 26 Mar 2019 21:03:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/26/19 4:18 PM, Joao Moreira wrote: > > > On 3/18/19 4:18 PM, Joe Lawrence wrote: >> 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. >> > > Hi Joe, again thanks a lot for the review. To the things which I had > something to say, I already replied to the respective messages. If none > has issues with the fix for the ppc64le .TOC. symbols issue (on patch > 5/8) and with the fix for the multi-used-m Makefile (on patch 2/8), I > guess we are good for moving forward to a v3. >> If you don't mind, this is fine by me that you squash the changes and > post the newer version. In fact, I can't figure out why my patch > submissions did not appear in lkml (if someone knows what could be the > reason, please, let me know), so I guess it would be nice to have it > reachable this time. I can do that... what I will do is collate all the comments, squash revisions, and update logs accordingly. I'll post it up on github to let the 0-day lkp bot run through it and you can take a look to double check the series, attributions, etc before I post it here. BTW, something I *just* noticed when putting together that toy out-of-tree module to test out multi-object livepatch modules is that we aren't considering out-of-tree symbols in Symbols.list. Perhaps we can save that for v4 or beyond, but maybe we want to re-arrange the klp-convert arguments to "klp-convert [Symbols.list ...]" where we treat everything after as a symbol list file? (This would assume we would generate a separate out-of-tree module Symbols.list file.) /thinking-out-loud -- Joe