Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030187AbVKHPQm (ORCPT ); Tue, 8 Nov 2005 10:16:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030201AbVKHPQm (ORCPT ); Tue, 8 Nov 2005 10:16:42 -0500 Received: from terminus.zytor.com ([192.83.249.54]:42175 "EHLO terminus.zytor.com") by vger.kernel.org with ESMTP id S1030187AbVKHPQm (ORCPT ); Tue, 8 Nov 2005 10:16:42 -0500 Message-ID: <4370C141.6010508@zytor.com> Date: Tue, 08 Nov 2005 07:16:17 -0800 From: "H. Peter Anvin" User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Linus Torvalds CC: Zachary Amsden , Andrew Morton , Chris Wright , Linux Kernel Mailing List , Virtualization Mailing List , Zwane Mwaikambo , Martin Bligh , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [PATCH 4/21] i386 Broken bios common References: <200511080422.jA84MQxK009859@zach-dev.vmware.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1426 Lines: 32 Linus Torvalds wrote: > > On Mon, 7 Nov 2005, Zachary Amsden wrote: > >>Both the APM BIOS and PnP BIOS code use a segment hack to simulate real >>mode selector 0x40 (which points to the BIOS data area at 0x00400 in >>real mode). Several broken BIOSen use selector 0x40 as if they were >>running in real mode, which we make work by faking up selector 0x40 in >>the GDT to point to physical memory starting at 0x400. We limit the >>access to the remainder of this physical page using a byte granular >>limit. Rather than have this tricky code in multiple places, it makes >>sense to define it in one place, and the GDT makes a very convenient >>place for it. Use GDT entry 4 as the BAD_BIOS_CACHE segment. > > I'd much rather use entry 8 instead, which should just automatically mean > that selector 0x40 _always_ points to virtual address 0x400. No switching > etc.. > > Isn't this what Wine already has to work around, or something? > > Ingo, can we move the TLS selectors upwards, or does user space perhaps > know about the current TLS layout? Wine in particular may well know ;( > I thought the point was that Wine needs to point GDT entry 8 into userspace. -hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/