Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751491AbdFZJkI (ORCPT ); Mon, 26 Jun 2017 05:40:08 -0400 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:22889 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbdFZJkC (ORCPT ); Mon, 26 Jun 2017 05:40:02 -0400 X-IronPort-AV: E=Sophos;i="5.39,395,1493676000"; d="scan'208";a="280605222" Date: Mon, 26 Jun 2017 05:39:56 -0400 (EDT) From: Julia Lawall X-X-Sender: jll@hadrien To: Frans Klaver cc: Julia Lawall , Joe Perches , Greg Kroah-Hartman , kernel-janitors , Guenter Roeck , Yueyao Zhu , Rui Miguel Silva , Guru Das Srinagesh , Javier Martinez Canillas , devel@driverdev.osuosl.org, "linux-kernel@vger.kernel.org" Subject: Re: endian bitshift defects [ was: staging: fusb302: don't bitshift __le16 type ] In-Reply-To: Message-ID: References: <20170616174556.2358-1-fransklaver@gmail.com> <1497653077.10546.23.camel@perches.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1669 Lines: 41 On Mon, 26 Jun 2017, Frans Klaver wrote: > On Sat, Jun 24, 2017 at 1:37 AM, Julia Lawall wrote: > > > > > > On Sat, 24 Jun 2017, Frans Klaver wrote: > > > >> Hm. For some reason the great mail filtering scheme decided to push > >> this past my inbox :-/ > >> > >> On Sat, Jun 17, 2017 at 12:44 AM, Joe Perches wrote: > >> > On Fri, 2017-06-16 at 19:45 +0200, Frans Klaver wrote: > >> >> The header field in struct pd_message is declared as an __le16 type. The > >> >> data in the message is supposed to be little endian. This means we don't > >> >> have to go and shift the individual bytes into position when we're > >> >> filling the buffer, we can just copy the contents right away. As an > >> >> added benefit we don't get fishy results on big endian systems anymore. > >> > > >> > Thanks for pointing this out. > >> > > >> > There are several instances of this class of error. > >> > >> There are other smells around __(le|be) types that show up in staging > >> that might be worth checking in the rest of the kernel as well. e.g. > >> converting to cpu and storing it back into itself (possibly with its > >> bytes reversed), direct assignments without conversion and what else > >> you might have. sparse obviously already flags anything fishy going on > >> with these types, but cannot distinguish between the classes of > >> errors. I'll need to acquaint myself with spatch a bit more to be able > >> to track that down. > > > > If you have concrete code examples, even fake ones, illustrating a class > > of problem, then that would be great. > > I'll see if I can produce some somewhere this week. Thanks. julia