From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752833AbZHHSTc (ORCPT ); Sat, 8 Aug 2009 14:19:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752722AbZHHSTb (ORCPT ); Sat, 8 Aug 2009 14:19:31 -0400 Received: from mail.atlantis.sk ([80.94.52.35]:43488 "EHLO mail.atlantis.sk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752707AbZHHSTb (ORCPT ); Sat, 8 Aug 2009 14:19:31 -0400 From: Ondrej Zary To: Ingo Molnar Subject: Re: [PATCH] OOPS in identify_cpu() on CPUs without CPUID Date: Sat, 8 Aug 2009 20:19:20 +0200 User-Agent: KMail/1.9.10 Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org References: <200908081908.12240.linux@rainbow-software.org> <20090808175344.GA8099@elte.hu> In-Reply-To: <20090808175344.GA8099@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200908082019.23574.linux@rainbow-software.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 08 August 2009 19:53:44 Ingo Molnar wrote: > * Ondrej Zary wrote: > > Kernel is broken for x86 CPUs without CPUID since 2.6.28. It > > crashes with NULL pointer dereference in identify_cpu(): > > > > 766 generic_identify(c); > > 767 > > 768--> if (this_cpu->c_identify) > > 769 this_cpu->c_identify(c); > > > > this_cpu is NULL. This is because it's only initialized in > > get_cpu_vendor() function, which is not called if the CPU has no > > CPUID instruction. > > indeed ... > > > Signed-off-by: Ondrej Zary > > > > --- linux-2.6.30.4-orig/arch/x86/kernel/cpu/common.c 2009-06-10 > > 05:05:27.000000000 +0200 +++ > > linux-2.6.30.4-router/arch/x86/kernel/cpu/common.c 2009-08-08 > > 18:00:21.000000000 +0200 @@ -699,6 +699,7 @@ > > > > static void __cpuinit generic_identify(struct cpuinfo_x86 *c) > > { > > + this_cpu = &default_cpu; > > c->extended_cpuid_level = 0; > > > > if (!have_cpuid_p()) > > How about initializing this_cpu instead, via: > > static const struct cpu_dev *this_cpu __cpuinitdata = &default_cpu; > > ? That might be even better - looks cleaner. I can't test it right now as I don't have the hardware here. I'll test it tomorrow (unless someone will be faster). -- Ondrej Zary