Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753561AbbDNSle (ORCPT ); Tue, 14 Apr 2015 14:41:34 -0400 Received: from cantor2.suse.de ([195.135.220.15]:36601 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751422AbbDNSl1 (ORCPT ); Tue, 14 Apr 2015 14:41:27 -0400 Date: Tue, 14 Apr 2015 20:41:21 +0200 From: Petr Mladek To: Minfei Huang Cc: Minfei Huang , 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: <20150414184121.GD21044@dhcp128.suse.cz> References: <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> <20150414162718.GC21044@dhcp128.suse.cz> <20150414170139.GA30740@dhcp-128-1.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150414170139.GA30740@dhcp-128-1.nay.redhat.com> 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: 2704 Lines: 60 On Wed 2015-04-15 01:01:39, Minfei Huang wrote: > On 04/14/15 at 06:27pm, Petr Mladek wrote: > > 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? > > > > No, I do not have such running module which function name is exceed to > 127. > > Again, we can not predict what end user do to name the function name. I > think the overlength function name is valid for linux kernel, if the > module can be installed. My position on this is that using >127 length function names is insane. I would be scared to use such a module on a production system. If we refuse patching, we actually do a favor for the user. Instead of fixing live patch for such a scenario, we should suggest the user to use more trustful modules. Best Regards, Petr -- 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/