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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 443B8C4360F for ; Thu, 4 Apr 2019 09:23:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F76A20657 for ; Thu, 4 Apr 2019 09:23:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733074AbfDDJXz (ORCPT ); Thu, 4 Apr 2019 05:23:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:35374 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387593AbfDDJO5 (ORCPT ); Thu, 4 Apr 2019 05:14:57 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 88A78ACA8; Thu, 4 Apr 2019 09:14:53 +0000 (UTC) Date: Thu, 4 Apr 2019 11:14:51 +0200 (CEST) From: Miroslav Benes To: Joe Lawrence cc: Joao Moreira , live-patching@vger.kernel.org, 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 2/8] kbuild: Support for Symbols.list creation In-Reply-To: <651eb328-b13a-9f31-d4da-9d2e965914e3@redhat.com> Message-ID: References: <20190301141313.15057-1-jmoreira@suse.de> <20190301141313.15057-3-jmoreira@suse.de> <20190318191926.GA23138@redhat.com> <5f615af5-ced7-2361-5b71-71fece8b43c5@suse.de> <699e78da-36ba-8217-c509-2e9b443bd380@suse.de> <1b6ee81b-5699-a1cc-9a85-02df0eeaed12@redhat.com> <20190328201703.GA8658@redhat.com> <20190401193529.GA26375@redhat.com> <651eb328-b13a-9f31-d4da-9d2e965914e3@redhat.com> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 3 Apr 2019, Joe Lawrence wrote: > On 4/3/19 8:48 AM, Miroslav Benes wrote: > > > >> and it looks like the combined KLP_MODULE_RELOC still contains the two > >> unique symbol position values (2 and 3): > >> > >> % objcopy -O binary --only-section=.klp.module_relocs.vmlinux lib/livepatch/test_klp_convert.klp.o >(hexdump -C) > >> 00000000 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 |................| > >> 00000010 00 00 00 00 00 00 00 00 03 00 00 00 |............| > >> 0000001c > > > > Nice :/ > > > >> Maybe we can work around this by modifying the annotation macros and/or > >> klp-convert, or live with this for now. > > > > The question is (and I'll check later. I cannot wrap my head around it > > now) if it at least works if there are two references of the same symbol > > in two different .o. It would be same state_show in this case and not two > > different ones. If it works then I think we can live with it for a while, > > because after all duplicate symbols are quite rare in the kernel. > > Possibly, but in testing that scenario I found another issue. Check out what > happens to the combined .klp.module_relocs.vmlinux section for: > > test_klp_convert_a.c > KLP_MODULE_RELOC(vmlinux) vmlinux_relocs_a[] = { > KLP_SYMPOS(state_show, 2) > KLP_SYMPOS(joe, 10) > KLP_SYMPOS(joe2, 11) > }; > > test_klp_convert_b.c > KLP_MODULE_RELOC(vmlinux) vmlinux_relocs_b[] = { > KLP_SYMPOS(state_show, 2) > }; > > The second file's klp_module_reloc are not aligned with the first, > so I think there is additional padding to push the second set to a > word boundary: > > % objcopy -O binary --only-section=.klp.module_relocs.vmlinux lib/livepatch/test_klp_convert.klp.o >(hexdump -C) > 00000000 00 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00 > |-*sym----------------| |--sympos-| |-*sym----- > > 00000010 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00 00 > ----------| |--sympos-| |-*sym----------------| > > 00000020 0b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |-sympos--| |-*sym----------------| > > ^^^^^^^^^^^ > padding > 00000030 02 00 00 00 > |-sympos--| > > > in this case, klp-convert thought the last symbol's sympos was > incorrectly 0 and not 2. Ugh. It's getting better and better. > If the packed attribute is merely a space optimization, can we > simply pull that (or can we specify slightly looser alignment to > account for the padding)? I think so. > I'll continue working on putting together v3 and add this new item > to the TODO list. Great job btw. Thanks. Miroslav