From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263633AbTJQWXZ (ORCPT ); Fri, 17 Oct 2003 18:23:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263630AbTJQWXY (ORCPT ); Fri, 17 Oct 2003 18:23:24 -0400 Received: from waste.org ([209.173.204.2]:63438 "EHLO waste.org") by vger.kernel.org with ESMTP id S263628AbTJQWXX (ORCPT ); Fri, 17 Oct 2003 18:23:23 -0400 Date: Fri, 17 Oct 2003 17:23:13 -0500 From: Matt Mackall To: Bjorn Helgaas Cc: linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] prevent "dd if=/dev/mem" crash Message-ID: <20031017222313.GF5725@waste.org> References: <200310171610.36569.bjorn.helgaas@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200310171610.36569.bjorn.helgaas@hp.com> User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 17, 2003 at 04:10:36PM -0600, Bjorn Helgaas wrote: > I expect there are probably different opinions about the idea > that "dd if=/dev/mem" exits without doing anything. Sparc and > 68K have nearby code that bit-buckets writes and returns zeroes > for reads of page zero. We could do that, too, but it seems like > kind of a hack, and holes on ia64 can be BIG (on the order of > 256GB for one box). I don't see any reason not to returns zeros. A hole in a file does the same thing, after all. The fact that the hole is big makes no difference. -- Matt Mackall : http://www.selenic.com : Linux development and consulting