From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933264Ab1JGWDv (ORCPT ); Fri, 7 Oct 2011 18:03:51 -0400 Received: from terminus.zytor.com ([198.137.202.10]:59597 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755662Ab1JGWDt (ORCPT ); Fri, 7 Oct 2011 18:03:49 -0400 Message-ID: <4E8F772D.20408@zytor.com> Date: Fri, 07 Oct 2011 15:03:25 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 MIME-Version: 1.0 To: Steven Rostedt CC: Jason Baron , Jeremy Fitzhardinge , Richard Henderson , "David S. Miller" , David Daney , Michael Ellerman , Jan Glauber , the arch/x86 maintainers , Xen Devel , Linux Kernel Mailing List , Jeremy Fitzhardinge , peterz@infradead.org Subject: Re: [PATCH][RFC] jump_labels/x86: Use either 5 byte or 2 byte jumps References: <4E8CF385.2080804@zytor.com> <4E8DEB19.1050509@goop.org> <20111006181055.GA2505@redhat.com> <1317925615.4729.14.camel@gandalf.stny.rr.com> <4E8DF870.6010000@redhat.com> <1317929321.4729.17.camel@gandalf.stny.rr.com> <4E8E20CD.5030207@goop.org> <1317938775.4729.29.camel@gandalf.stny.rr.com> <4E8E275F.6010801@goop.org> <1318007374.4729.58.camel@gandalf.stny.rr.com> <20111007185214.GD2978@redhat.com> <1318015311.4729.69.camel@gandalf.stny.rr.com> <4E8F73A3.5080904@zytor.com> <1318024853.4729.88.camel@gandalf.stny.rr.com> In-Reply-To: <1318024853.4729.88.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/2011 03:00 PM, Steven Rostedt wrote: > > Ouch, quite shaken by k.org? I guess I should have substituted go blind > with being hacked. > Well, yes, but I would have said exactly the same thing before. > The thing is, it may be as simple as an out of tree module screwing up > the jump table. Or worse, gcc not doing things that we did not expect. > If this is the case, jump labels can be disabled from modifying code. > > But if we just want to do the BUG() case, this will be a big hammer to > the code and we just prevent any further progress until the issue is > addressed. Which may be tell people to disable jump labels in their > code, or use a different compiler. That is EXACTLY what should happen. Something is wrong to the point of the kernel is *known* to be executing the wrong code. That is an extremely serious condition and should be treated as such. If you want, you could have a debug option to demote this to WARN, but I really don't want to see it by default. -hpa