From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755253AbZHCPTP (ORCPT ); Mon, 3 Aug 2009 11:19:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755096AbZHCPTO (ORCPT ); Mon, 3 Aug 2009 11:19:14 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51513 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755187AbZHCPTN (ORCPT ); Mon, 3 Aug 2009 11:19:13 -0400 Message-ID: <4A76FF8E.80507@zytor.com> Date: Mon, 03 Aug 2009 08:17:34 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Thunderbird/3.0b2 MIME-Version: 1.0 To: Akinobu Mita CC: Ingo Molnar , mingo@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/asm] x86: Introduce GDT_ENTRY_INIT() References: <20090718151219.GD11294@localhost.localdomain> <20090803062024.GA22365@elte.hu> <4A768339.9060904@zytor.com> <961aa3350908030811n6467b2d7hf42dfd58e3a438e7@mail.gmail.com> In-Reply-To: <961aa3350908030811n6467b2d7hf42dfd58e3a438e7@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03/2009 08:11 AM, Akinobu Mita wrote: >>>> >> OK, I spotted the following error, which certainly would explain a crash on >> an APM machine: >> >> /* data */ >> - [GDT_ENTRY_APMBIOS_BASE+2] = { { { 0x0000ffff, 0x00409200 } } >> }, >> + [GDT_ENTRY_APMBIOS_BASE+2] = GDT_ENTRY_INIT(0x409a, 0, 0xffff), > > Oops, I really should have checked the binary because the compiler should > generate same code with this patch. > Well, it doesn't even on the best of days, because the last hunk changes a dynamic initializer to a strange mix between static and dynamic: -static struct desc_struct bad_bios_desc; +static struct desc_struct bad_bios_desc = GDT_ENTRY_INIT(0x4092, 0, 0); /* * At some point we want to use this stack frame pointer to unwind @@ -476,9 +476,6 @@ void pnpbios_calls_init(union pnp_bios_install_struct *header) pnp_bios_callpoint.offset = header->fields.pm16offset; pnp_bios_callpoint.segment = PNP_CS16; - bad_bios_desc.a = 0; - bad_bios_desc.b = 0x00409200; - set_desc_base(&bad_bios_desc, (unsigned long)__va(0x40UL << 4)); set_desc_limit(&bad_bios_desc, 4095 - (0x40 << 4)); This is about at strange as it comes; I think we could simply do: GDT_ENTRY_INIT(0x4092, (unsigned long)__va(0x400UL), 4095-0x400); Although perhaps the 4095 should really be PAGE_SIZE-1... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.