Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261807AbTEKRo5 (ORCPT ); Sun, 11 May 2003 13:44:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261821AbTEKRo5 (ORCPT ); Sun, 11 May 2003 13:44:57 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:57166 "EHLO frodo.biederman.org") by vger.kernel.org with ESMTP id S261807AbTEKRo4 (ORCPT ); Sun, 11 May 2003 13:44:56 -0400 To: Linus Torvalds Cc: Jamie Lokier , Jos Hulzink , Andi Kleen , Subject: Re: [PATCH] Use correct x86 reboot vector References: From: ebiederm@xmission.com (Eric W. Biederman) Date: 11 May 2003 11:54:20 -0600 In-Reply-To: Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.1 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1431 Lines: 30 Linus Torvalds writes: > On Sat, 10 May 2003, Jamie Lokier wrote: > > Jos Hulzink wrote: > > > For the sake of bad behaving BIOSes however, I'd vote for the f000:fff0 > > > vector, unless someone can hand me a paper that says it is wrong. > > > > I agree, for the simple reason that it is what the chip does on a > > hardware reset signal. > > Hmm.. Doesnt' a _real_ hardware reset actually use a magic segment that > isn't even really true real mode? I have this memory that the reset value > for a i386 has CS=0xf000, but the shadow base register actually contains > 0xffff0000. In other words, the CPU actually starts up in "unreal" mode, > and will fetch the first instruction from physical address 0xfffffff0. > > At least that was true on an original 386. It's something that could > easily have changed since. Correct. And no one has changed it since. I use that all of the time. > In other words, you're all wrong. Nyaah, nyaah. However 0xf000:fff0 is as close as you can get, and since that is usually RAM it can do something different on a reset vs a reboot if it wants to. Using 0xf000 is just polite as it allows relative jumps. Eric - 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/