From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932312AbbKCQJz (ORCPT ); Tue, 3 Nov 2015 11:09:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:49260 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754206AbbKCQJu (ORCPT ); Tue, 3 Nov 2015 11:09:50 -0500 Date: Tue, 3 Nov 2015 17:09:48 +0100 (CET) From: Miroslav Benes To: Josh Poimboeuf cc: Chris J Arges , live-patching@vger.kernel.org, jeyu@redhat.com, Seth Jennings , Jiri Kosina , Vojtech Pavlik , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs directory In-Reply-To: <20151103145843.GH27488@treble.redhat.com> Message-ID: References: <20151102203241.GF27488@treble.redhat.com> <1446505187-28970-1-git-send-email-chris.j.arges@canonical.com> <20151103145843.GH27488@treble.redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 3 Nov 2015, Josh Poimboeuf wrote: > On Tue, Nov 03, 2015 at 11:52:08AM +0100, Miroslav Benes wrote: > > On Mon, 2 Nov 2015, Chris J Arges wrote: > > > > [...] > > > > > +static int klp_get_func_pos_callback(void *data, const char *name, > > > + struct module *mod, unsigned long addr) > > > +{ > > > + struct klp_find_arg *args = data; > > > + > > > + if ((mod && !args->objname) || (!mod && args->objname)) > > > + return 0; > > > + > > > + if (strcmp(args->name, name)) > > > + return 0; > > > + > > > + if (args->objname && strcmp(args->objname, mod->name)) > > > + return 0; > > > + > > > + /* on address match, return 1 to break kallsyms_on_each_symbol loop */ > > > + if (args->addr == addr) > > > + return 1; > > > + > > > + /* if we don't match addr, count instance of named symbol */ > > > + args->count++; > > > + > > > + return 0; > > > +} > > > + > > > +static int klp_get_func_pos(struct klp_object *obj, struct klp_func *func) > > > +{ > > > + struct klp_find_arg args = { > > > + .objname = obj->name, > > > + .name = func->old_name, > > > + .addr = func->old_addr, > > > + .count = 0, > > > + }; > > > + > > > + mutex_lock(&module_mutex); > > > + kallsyms_on_each_symbol(klp_get_func_pos_callback, &args); > > > + mutex_unlock(&module_mutex); > > > + > > > + return args.count; > > > +} > > > + > > > static int klp_init_func(struct klp_object *obj, struct klp_func *func) > > > { > > > INIT_LIST_HEAD(&func->stack_node); > > > func->state = KLP_DISABLED; > > > > > > return kobject_init_and_add(&func->kobj, &klp_ktype_func, > > > - &obj->kobj, "%s", func->old_name); > > > + &obj->kobj, "%s,%d", func->old_name, > > > + klp_get_func_pos(obj, func)); > > > } > > > > There is a problem which I missed before. klp_init_func() is called before > > klp_find_verify_func_addr() in klp_init_object(). This means that > > func->old_addr is either not verified yet or worse it is still 0. This > > means that klp_get_func_pos_callback() never returns 1 and is thus called > > on each symbol. So if you for example patched cmdline_proc_show the > > resulting directory in sysfs would be called cmdline_proc_show,1 because > > addr is never matched. Had old_addr been specified the name would have > > been probably correct, but not for sure. > > > > This should be fixed as well. > > Even worse, klp_init_func() can be called even if the object hasn't been > loaded. In that case there's no way to know what the value of n is, and > therefore no way to reliably create the sysfs entry. Ah, right. > Should we create "func,n" in klp_init_object_loaded() instead of > klp_init_func()? So that the function entries in sysfs would be created only when the object is loaded? Well, why not, but in that case it could easily confuse the user. Object entry would be empty for not loaded object. I would not dare to propose to remove such object entries. It would make things worse. So maybe we could introduce an attribute in sysfs object entry which would say if the object is loaded or not. Or something like that. Hm, we can easily mess this up :) Miroslav