From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752400AbZHIRph (ORCPT ); Sun, 9 Aug 2009 13:45:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751576AbZHIRpg (ORCPT ); Sun, 9 Aug 2009 13:45:36 -0400 Received: from mail.atlantis.sk ([80.94.52.35]:54558 "EHLO mail.atlantis.sk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751227AbZHIRpg convert rfc822-to-8bit (ORCPT ); Sun, 9 Aug 2009 13:45:36 -0400 From: Ondrej Zary To: Ingo Molnar Subject: [PATCH v2] OOPS in identify_cpu() on CPUs without CPUID Date: Sun, 9 Aug 2009 19:45:25 +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: 8BIT Content-Disposition: inline Message-Id: <200908091945.29233.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; > > ? > Ingo The new patch is not very nice as default_cpu has to be moved. Works fine. 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. 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 2009-08-09 13:33:04.000000000 +0200 @@ -58,7 +58,30 @@ alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask); } -static const struct cpu_dev *this_cpu __cpuinitdata; +static void __cpuinit default_init(struct cpuinfo_x86 *c) +{ +#ifdef CONFIG_X86_64 + display_cacheinfo(c); +#else + /* Not much we can do here... */ + /* Check if at least it has cpuid */ + if (c->cpuid_level == -1) { + /* No cpuid. It must be an ancient CPU */ + if (c->x86 == 4) + strcpy(c->x86_model_id, "486"); + else if (c->x86 == 3) + strcpy(c->x86_model_id, "386"); + } +#endif +} + +static const struct cpu_dev __cpuinitconst default_cpu = { + .c_init = default_init, + .c_vendor = "Unknown", + .c_x86_vendor = X86_VENDOR_UNKNOWN, +}; + +static const struct cpu_dev *this_cpu __cpuinitdata = &default_cpu; DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = { #ifdef CONFIG_X86_64 @@ -330,29 +353,6 @@ static const struct cpu_dev *__cpuinitdata cpu_devs[X86_VENDOR_NUM] = {}; -static void __cpuinit default_init(struct cpuinfo_x86 *c) -{ -#ifdef CONFIG_X86_64 - display_cacheinfo(c); -#else - /* Not much we can do here... */ - /* Check if at least it has cpuid */ - if (c->cpuid_level == -1) { - /* No cpuid. It must be an ancient CPU */ - if (c->x86 == 4) - strcpy(c->x86_model_id, "486"); - else if (c->x86 == 3) - strcpy(c->x86_model_id, "386"); - } -#endif -} - -static const struct cpu_dev __cpuinitconst default_cpu = { - .c_init = default_init, - .c_vendor = "Unknown", - .c_x86_vendor = X86_VENDOR_UNKNOWN, -}; - static void __cpuinit get_model_name(struct cpuinfo_x86 *c) { unsigned int *v; -- Ondrej Zary