From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756300Ab2GEXqT (ORCPT ); Thu, 5 Jul 2012 19:46:19 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:41386 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753476Ab2GEXqR (ORCPT ); Thu, 5 Jul 2012 19:46:17 -0400 X-Sasl-enc: V+UvRnn8IrQWrciTSHFas16xvUMYwLuy5ABNTRxCkH85 1341531976 Date: Thu, 5 Jul 2012 20:46:12 -0300 From: Henrique de Moraes Holschuh To: Johannes Goetzfried Cc: Herbert Xu , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Subject: Re: [PATCH] crypto: twofish-avx - remove useless instruction Message-ID: <20120705234612.GD29301@khazad-dum.debian.net> References: <20120705184358.GE2091@kronos.redsun> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120705184358.GE2091@kronos.redsun> X-GPG-Fingerprint: 1024D/1CDB0FE3 5422 5C61 F6B7 06FB 7E04 3738 EE25 DE3F 1CDB 0FE3 User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 05 Jul 2012, Johannes Goetzfried wrote: > The register %rdx is written, but never read till the end of the encryption > routine. Therefore let's delete the useless instruction. Is it useless, or is it there to harden against some side-channel attack? -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh