From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::228]) by sourceware.org (Postfix) with ESMTPS id 4A77A382EF00 for ; Thu, 17 Nov 2022 10:14:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4A77A382EF00 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=seketeli.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=seketeli.org Received: (Authenticated sender: dodji@seketeli.org) by mail.gandi.net (Postfix) with ESMTPSA id A27AA1BF20B; Thu, 17 Nov 2022 10:13:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=seketeli.org; s=gm1; t=1668680040; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kdtH3+XetrgTIPlM/NNX2Cozs2Xphu1adXjinqdDj6Q=; b=W+aNp2CWPJhVWAqt8LblorjZGosyqhblj1kmN9CszBIxk/LDgPBBPp4pEMGWxqoBG47X/C 2FoA0YmZGyZSIRupHkq8A2pOnqMHN54jVoQdj+I3i6XGMaIg1JGidk2wcqoTAnfzvmipqI JcHYVFozU0B5EiHp7zMDDLLW0eXhsfZDtpKfR4LYGcX0EbAAKDi8XTDd6neEGZbyQklJ+8 urSX+G80sRrOgL0S/0FPUKNp6EI30053qJfK4IZZwjiX4/cvR9iZGdeESNN97/QEaWTWDF OkCYe+HQkoPRlKJXcbKwOvEAwM4hUO43T9Co6z1CLLDJop3srmdVkUXBgwi9Zg== Received: by localhost (Postfix, from userid 1000) id C02191800CDA; Thu, 17 Nov 2022 11:13:57 +0100 (CET) From: Dodji Seketeli To: Giuliano Procida Cc: libabigail@sourceware.org, kernel-team@android.com, maennich@google.com, sidnayyar@google.com, vvvvvv@google.com Subject: Re: [PATCH] Narrow Linux symbol CRCs to 32 bits Organization: Me, myself and I References: <20221027140928.1480353-1-gprocida@google.com> <875yg4ugk4.fsf@seketeli.org> X-Operating-System: Red Hat Enterprise Linux Workstation 7.9 X-URL: http://www.seketeli.net/~dodji Date: Thu, 17 Nov 2022 11:13:57 +0100 In-Reply-To: (Giuliano Procida's message of "Fri, 28 Oct 2022 17:08:48 +0100") Message-ID: <871qq1q462.fsf@seketeli.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-3.3 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,JMQ_SPF_NEUTRAL,RCVD_IN_DNSWL_LOW,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hello, [...] On Fri, 28 Oct 2022 at 16:13, Dodji Seketeli wrote: >> The changes look good to me. Do you want me to apply it right now, or >> do you prefer to send a subsequent patch that addresses the new way how >> CRCs are emitted in kernel object? Giuliano Procida a =C3=A9crit: > I'm happy for the change to go in. However, the commit message text > should be updated. I would make it: > > -- > > MODVERSIONS CRCs are 32-bit hashes of strings representing C type > elements or typed symbols. The hashes are calculated using a 32-bit CRC, > hence the name. The kernel module loading code (implicitly) truncates > any provided CRC value to 32 bits before comparing it with anything. > > When support was added to libabigail, values up to 64 bits wide were > supported. This change narrows libabigail's concept of Linux CRC to 32 > bits. No tests are affected. > > -- > > I'm not sure when we'll get around to updating the symtab reader. It'll > probably not be done by me. As I understand things, there are > something like 3 or 4 different encodings of CRCs depending on the > kernel version and architecture (and that's ignoring endianness issues). > > Matthias has even suggested it might be better (more reliable) just readi= ng > CRCs from Modules.symvers instead. However, that would require more > integration into build scripts etc. This felt through the cracks on my end, sorry about that. I have just applied the v2 of the patch that you've sent 5 days ago. Thank you for that. [...] Cheers, --=20 Dodji