Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424343AbWKJEAN (ORCPT ); Thu, 9 Nov 2006 23:00:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1424344AbWKJEAN (ORCPT ); Thu, 9 Nov 2006 23:00:13 -0500 Received: from nf-out-0910.google.com ([64.233.182.188]:24916 "EHLO nf-out-0910.google.com") by vger.kernel.org with ESMTP id S1424343AbWKJEAL (ORCPT ); Thu, 9 Nov 2006 23:00:11 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=JhF+gvNn1Wj7lxLiwEG5yhejRAs6ilNhfttKjZGmMYheqzd5EcvVag6KSNdzaQa1t1Vw8b5TtBWybNQbD2Bdp8Ial0rarcJ0AIk+TeNCCWY2CH9KzGIN1vmhFIlm+Gi6+FykNMfxIUQutPjvbxcQCjFAuS6jajipCHYXPmdPLA4= Message-ID: Date: Fri, 10 Nov 2006 13:00:09 +0900 From: "Magnus Damm" To: Horms Subject: Re: [PATCH 02/02] Elf: Align elf notes properly Cc: "Eric W. Biederman" , "Magnus Damm" , linux-kernel@vger.kernel.org, "Vivek Goyal" , "Andi Kleen" , fastboot@lists.osdl.org, "Dave Anderson" In-Reply-To: <20061110005051.GB4107@verge.net.au> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20061102101942.452.73192.sendpatchset@localhost> <20061102101949.452.23441.sendpatchset@localhost> <20061110005051.GB4107@verge.net.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2500 Lines: 52 On 11/10/06, Horms wrote: > On Thu, Nov 09, 2006 at 07:00:22AM -0700, Eric W. Biederman wrote: > > Magnus Damm writes: > > > > > elf: Align elf notes properly > > > > > > The kernel currently contains several elf note aligment implementations. Most > > > implementations follow the spec on 32-bit platforms, but none current aligns > > > the notes correctly on 64-bit platforms. This patch tries to fix this by > > > interpreting the 64-bit and 32-bit elf specs as the following: > > > > > > offset bytes name > > > 0 4 n_namesz -+ -+ > > > 4 4 n_descsz | elf note header | > > > 8 4 n_type -+ | elf note entry size - N4 > > > 12 N1 name | > > > N2 N3 desc -+ > > > > > > WS = word size in bytes (4 for 32 bit, 8 for 64 bit) > > > N1 = roundup(n_namesz + sizeof(elf note header), WS) - sizeof(elf note header) > > > N2 = sizeof(elf note header) + N1 > > > N3 = roundup(n_descsz, WS) > > > N4 = sizeof(elf note header) + N1 + N2 > > > > > > The elf note header contains three 32-bit values on 32-bit and 64-bit systems. > > > The header is followed by name and desc data together with padding. The > > > alignment and padding varies depending on the word size. > > > > I see your point and I disagree. The notes in a kernel generated > > core dump do not vary in size. Find me some implementation evidence that > > anyone ever added the extra 4 bytes of alignment to the description and the > > padding fields and I will be ready to consider this. Currently this > > just appears to be reading a draft spec that doesn't match reality. > > Or perhaps a spec that hasn't been implemented correctly. > I guess that the real question is, what padding is correct? I see no point in aligning to 32-bit boundaries on 64-bit platforms. Their intention was most likely to align to the word size IMO, so this is most likely a "thinko" left over from whoever ported the code from 32-bit to 64-bit. How we chose to align on 64-bit platforms is another issue, either we fix it soon or live with the fact that we are not following the 64-bit draft spec. Either way is fine with me. / magnus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/