From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752016Ab0IVPn7 (ORCPT ); Wed, 22 Sep 2010 11:43:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39423 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751240Ab0IVPn6 (ORCPT ); Wed, 22 Sep 2010 11:43:58 -0400 Date: Wed, 22 Sep 2010 11:43:10 -0400 From: Jason Baron To: Mathieu Desnoyers Cc: Andi Kleen , rusty@rustcorp.co.au, rostedt@goodmis.com, linux-kernel@vger.kernel.org, mingo@elte.hu, hpa@zytor.com, tglx@linutronix.de, roland@redhat.com, rth@redhat.com, mhiramat@redhat.com, fweisbec@gmail.com, avi@redhat.com, davem@davemloft.net, vgoyal@redhat.com, sam@ravnborg.org, tony@bakeyournoodle.com, Andi Kleen Subject: Re: [PATCH 2/2] Rewrite jump_label.c to use binary search Message-ID: <20100922154310.GE2816@redhat.com> References: <1285150102-5506-1-git-send-email-andi@firstfloor.org> <1285150102-5506-2-git-send-email-andi@firstfloor.org> <20100922113114.GA14179@Krystal> <4a8f3ad8416ed61cba1746883da1f839.squirrel@www.firstfloor.org> <589c3dd38437c80704d8224523efbccc.squirrel@www.firstfloor.org> <20100922150250.GB4897@Krystal> <20100922150743.GA6272@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100922150743.GA6272@Krystal> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2010 at 11:07:43AM -0400, Mathieu Desnoyers wrote: > * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote: > > * Andi Kleen (andi@firstfloor.org) wrote: > > > > > > > > > > >>> + for (; entry < stop && entry->key == key; entry++) > > > >>> + if (kernel_text_address(entry->code)) > > > >> > > > >> This does not work for modules I'm afraid, only for the core kernel. You > > > >> should test for __module_text_address() somewhere. > > > > > > > > I thought it was shared now, but ok. > > > > > > Double checked. This is ok because kernel_text_address() > > > already checks for modules. You were probably thinking > > > of __kernel_text_address() > > > > Ah right, > > > > Although we have another problem: > > > > __module_text_address() includes module init text, which defeats the > > purpose of the check put in there by Jason. > > > > So the check works for the core kernel, but not for modules. > > So, we have this issue, but I also have a question for Jason: what > happens if someone puts static jump in a function declared in the __init > section of the core kernel/module ? Can we enable them at early boot ? > > Thanks, > > Mathieu > Hi Mathieu, Yes, we should be able to enable these. Look at the definition for core_kernel_text(): int core_kernel_text(unsigned long addr) { if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) return 1; if (system_state == SYSTEM_BOOTING && init_kernel_text(addr)) return 1; return 0; } If the system is in the SYSTEM_BOOTING state we allow the text to be updated. same for modules, the check will allow module __init text modifications. At very early init there could be some issue text_poke_smp() working on x86, I'm not sure. In any case, we could always fall back to text_poke_early(), if needed. So I don't see any fundamental issues with this case. thanks, -Jason