Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755966AbbDNQ1h (ORCPT ); Tue, 14 Apr 2015 12:27:37 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43385 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755889AbbDNQ1Y (ORCPT ); Tue, 14 Apr 2015 12:27:24 -0400 Date: Tue, 14 Apr 2015 18:27:18 +0200 From: Petr Mladek To: Minfei Huang Cc: 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 Message-ID: <20150414162718.GC21044@dhcp128.suse.cz> References: <20150413231305.GD4412@treble.hsd1.ky.comcast.net> <20150414045739.GG4412@treble.hsd1.ky.comcast.net> <20150414051113.GH4412@treble.hsd1.ky.comcast.net> <20150414053247.GI4412@treble.hsd1.ky.comcast.net> <20150414151110.GL4412@treble.hsd1.ky.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 2681 Lines: 67 On Tue 2015-04-14 23:55:36, Minfei Huang wrote: > On 04/14/15 at 10:11P, Josh Poimboeuf wrote: > > On Tue, Apr 14, 2015 at 01:45:49PM +0800, Minfei Huang wrote: > > > On 04/14/15 at 12:32P, Josh Poimboeuf wrote: > > > > On Tue, Apr 14, 2015 at 01:29:50PM +0800, Minfei Huang wrote: > > > > > > > > > > For end user, they may know litter about restriction of kallsyms and > > > > > livepatch. How can they know the restriction that function name is > > > > > limited to 127? > > > > > > > > As I mentioned above, I think kallsyms.c should fail the build if it > > > > encounters a symbol longer than KSYM_NAME_LEN. > > > > > > > > > > I dont think it is a good idea to handle this case like that. The > > > function name is only for human recognization. Why the compiler fails > > > to build it? > > > > Well, the function name isn't only for human recognition. kpatch-build > > generates patch modules automatically. It assumes that the compiled > > function name matches the kallsyms name. And I'd guess that a lot of > > other code (both in-kernel and user space tools) make the same > > assumption. > > > > Not to mention that most humans would also make the same assumption... > > Yes. The assumption is correct for most case. > > It is significance for livepatch to support extra module, because in my > opinion kernel is more stable than the third module. > > So it is more important, if the livepatch can patch all sorts of patch. > For dynamic function name, I think it is simple to avoid it. Do you have some really existing module with such a crazy long function names or is this debate pure theoretical, please? Also have you tested your patch and tried to apply livepatch for some really exiting module, please? I ask because it won't be trivial to create such a patch. Also the patch would work only for the one running system. Best Regards, Petr > Usually, we will use ominity to handle a bunch of machines. So it is > simple, if we use script to get the function address and build the patch. > > Josh, is there any chance to accept my patches? It may be important > somewhile that system can not restart without schedule to reload the > fixed-module. > > Thanks > Minfei > > > > > -- > > Josh > -- > To unsubscribe from this list: send the line "unsubscribe live-patching" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/