From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261312AbVDMMAJ (ORCPT ); Wed, 13 Apr 2005 08:00:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261315AbVDMMAJ (ORCPT ); Wed, 13 Apr 2005 08:00:09 -0400 Received: from hacksaw.org ([66.92.70.107]:19670 "EHLO hacksaw.org") by vger.kernel.org with ESMTP id S261312AbVDMMAE (ORCPT ); Wed, 13 Apr 2005 08:00:04 -0400 Message-Id: <200504131159.j3DBxsoa010918@hacksaw.org> X-Mailer: exmh version 2.7.0 06/18/2004 with nmh-1.0.4 To: Benjamin Herrenschmidt cc: Tomko , Linux Kernel list Subject: Re: Why system call need to copy the date from the userspace before using it In-reply-to: Your message of "Wed, 13 Apr 2005 21:33:27 +1000." <1113392007.5516.26.camel@gaston> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 13 Apr 2005 07:59:54 -0400 From: Hacksaw Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >>Why not use it directly >Some of these reasons are: It seems like you gave reason why userland pointers shouldn't be trusted, not why userland data should be copied into kernel land. All the problems you mentioned would have to be solved by the kernel regardless of copying the data around. Ummm... Except for the who's mapped now problem. That's pretty weird. I guess that's something that comes with trying to use tons of RAM in a 32 bit system. I thought the big issue was the need to lock the page(s) during the call, and maybe some tricky races which made the idea difficult. -- The key is realizing the whole world is stupid and being happy anyway http://www.hacksaw.org -- http://www.privatecircus.com -- KB1FVD