Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755569AbbDOKgJ (ORCPT ); Wed, 15 Apr 2015 06:36:09 -0400 Received: from blu004-omc4s30.hotmail.com ([65.55.111.169]:54304 "EHLO BLU004-OMC4S30.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752202AbbDOKf6 (ORCPT ); Wed, 15 Apr 2015 06:35:58 -0400 X-TMN: [gK+rIsSWN4clz0a+Z6EhRbK8fXfxOk1K] X-Originating-Email: [minfei.huang@hotmail.com] Message-ID: Date: Wed, 15 Apr 2015 18:35:53 +0800 From: Minfei Huang To: Miroslav Benes CC: Minfei Huang , Petr Mladek , Josh Poimboeuf , sjenning@redhat.com, jkosina@suse.cz, vojtech@suse.cz, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] livepatch: Fix the bug if the function name is larger than KSYM_NAME_LEN-1 References: <20150414053247.GI4412@treble.hsd1.ky.comcast.net> <20150414151110.GL4412@treble.hsd1.ky.comcast.net> <20150414162718.GC21044@dhcp128.suse.cz> <20150414170139.GA30740@dhcp-128-1.nay.redhat.com> <20150414184121.GD21044@dhcp128.suse.cz> <20150415021558.GA21518@dhcp-128-1.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-OriginalArrivalTime: 15 Apr 2015 10:35:57.0127 (UTC) FILETIME=[F51B0570:01D07767] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2368 Lines: 59 On 04/15/15 at 10:30P, Miroslav Benes wrote: > On Wed, 15 Apr 2015, Minfei Huang wrote: > > > > > Yes, the function name can be changed, before the extra module is > > installed to the production system. > > > > We discuss around and around, there are still some confusion with it. > > > > 1) How does end user know that livepatch can _not_ support the function > > which length is larger than 127. We can not enforce the end user > > to know the livepatch and kallsyms code in detail. > > 2) How does end user use livepatch to patch running extra module, once > > the module is running in the production system, if the function name > > is insane. > > 3) The error message is ambiguity, if we try to patch the overlength > > function. We can give the error message clearly, once the function > > name is overlength. > > > > I think it is better that we can take more time on the people who will > > use livepatch frequently. > > Just my two cents, even if we admit that such change is worth it (and I > am still not convinced that it is the case), I think it would make sense > to fix it somewhere in kallsyms as Josh proposed. I suspect that when Ohhh... Fixing kallsyms to restrict the function name length maybe is not a good idea. I have no idea how we should do this, except for the coding problems. > function names longer than KSYM_NAME_LEN were common there would be many > similar problems elsewhere in the kernel. > > That is you can prepare a patch to kallsyms and submit it there. Not sure > who is the maintainer but he might have an opinion about this... > > Thanks, > Miroslav Hold on, I get a scenario that livepatch may do fatal error. I am fine that livepatch do not support overlength function name, because it can not corrupt the kernel. Once there is a function name A is larger than 127, and another function name B is as longer as 127, it is disaster that we want to patch function B, if function name of first 127 is same between A and B. Livepatch may find the function of A to patch it. So this patch(2/2) may be needed to fix the issue. Thanks Minfei -- 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/