From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753100Ab3JJJVv (ORCPT ); Thu, 10 Oct 2013 05:21:51 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:52248 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752024Ab3JJJVt (ORCPT ); Thu, 10 Oct 2013 05:21:49 -0400 Date: Thu, 10 Oct 2013 10:21:46 +0100 From: Will Deacon To: "Wang, Yalin" Cc: "'linux-arm-msm-owner@vger.kernel.org'" , "linux-kernel@vger.kernel.org" , jonathan.austin@arm.com Subject: Re: SDIV / UDIV Question Message-ID: <20131010092146.GC3817@mudshark.cambridge.arm.com> References: <35FD53F367049845BC99AC72306C23D1014D1A0971AC@CNBJMBX05.corpusers.net> <20131009105357.GC6564@mudshark.cambridge.arm.com> <35FD53F367049845BC99AC72306C23D1014D1A0971B0@CNBJMBX05.corpusers.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <35FD53F367049845BC99AC72306C23D1014D1A0971B0@CNBJMBX05.corpusers.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Adding Jonny] On Thu, Oct 10, 2013 at 06:04:41AM +0100, Wang, Yalin wrote: > Oh , I see , > Thanks for your clarification ! > So R-class cores will not run linux ? R-class cores can run Linux, but I don't reckon we touch SCTLR.DZ. I've added Jonny, so he can clarify the behaviour here. (I'm also not sure which cores have these instructions either). Will > -----Original Message----- > From: Will Deacon [mailto:will.deacon@arm.com] > Sent: Wednesday, October 09, 2013 6:54 PM > To: Wang, Yalin > Cc: 'linux-arm-msm-owner@vger.kernel.org'; linux-kernel@vger.kernel.org > Subject: Re: SDIV / UDIV Question > > On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: > > I have a question about sdiv/ udiv instructions : > > In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as > > undefined exception or just return zero (decided by implementation) . > > > > So in kernel , should we need register a undef hook to Get this > > undef exception and send SIGFPE to user space Process ? > > As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. > > Will >