Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261392AbTEKTHL (ORCPT ); Sun, 11 May 2003 15:07:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261399AbTEKTHL (ORCPT ); Sun, 11 May 2003 15:07:11 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:34127 "EHLO frodo.biederman.org") by vger.kernel.org with ESMTP id S261392AbTEKTHL (ORCPT ); Sun, 11 May 2003 15:07:11 -0400 To: Matt Mackall Cc: Linus Torvalds , Davide Libenzi , Jamie Lokier , Jos Hulzink , Andi Kleen , Linux Kernel Mailing List Subject: Re: [PATCH] Use correct x86 reboot vector References: <20030511190023.GC9173@waste.org> From: ebiederm@xmission.com (Eric W. Biederman) Date: 11 May 2003 13:16:26 -0600 In-Reply-To: <20030511190023.GC9173@waste.org> 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: 956 Lines: 17 Matt Mackall writes: > There's a missing piece of behavior here that's probably fatal. > Namely, the next time the CS descriptor is loaded, even with the same > value, the high bits are lost. So, for example, if you're running BIOS > out of ROM, decompressing it into the top of 20-bit address space, > then long jumping to your uncompressed code, you don't want to find > yourself back in ROM. > > Perhaps there's a trick that can be played with loading the descriptor > into CS and then clearing the descriptor table without flushing, but it > sounds rather dubious.. If PE is really disabled that should bit should come for free. And it is why it is so hard to fake this behavior. 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/