From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755476AbYGNPEQ (ORCPT ); Mon, 14 Jul 2008 11:04:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753851AbYGNPED (ORCPT ); Mon, 14 Jul 2008 11:04:03 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:56450 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753466AbYGNPEB (ORCPT ); Mon, 14 Jul 2008 11:04:01 -0400 Date: Mon, 14 Jul 2008 08:03:16 -0700 (PDT) From: Linus Torvalds To: Ingo Molnar cc: Linux Kernel Mailing List , Andrew Morton , Avi Kivity Subject: Re: [git pull] core, x86: make LIST_POISON less deadly In-Reply-To: <20080714144828.GA22666@elte.hu> Message-ID: References: <20080714144828.GA22666@elte.hu> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 14 Jul 2008, Ingo Molnar wrote: > > +config ILLEGAL_POINTER_VALUE > + hex > + default 0 if X86_32 > + default 0xffffc10000000000 if X86_64 This looks like a singularly bad pointer value on x86-64. Why not pick something that is *guaranteed* to fault? The above looks like any future setup that supports 41 bits of addressing and has extended the page tables (yes, it will happen eventually) will find that to be a perfectly valid address? It's also visually confusing, since it's visually very close to a real kernel pointer too. Grr. Why not use something sane like 0xdead000000000000, which has the high bit set but very fundamentally isn't a valid pointer, and never will be? And which is a *lot* more visually obvious too! Linus