From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757502Ab2BXPpi (ORCPT ); Fri, 24 Feb 2012 10:45:38 -0500 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:42752 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754567Ab2BXPph (ORCPT ); Fri, 24 Feb 2012 10:45:37 -0500 X-Sasl-enc: 0+2bO/ZvWLxBhBrbrc/AslpmsmCQ1clSu/7E/DZWTX3L 1330098336 Date: Fri, 24 Feb 2012 07:38:11 -0800 From: Greg KH To: Jidong Xiao Cc: Kernel development list Subject: Re: Can we move device drivers into user-space? Message-ID: <20120224153811.GA16535@kroah.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 24, 2012 at 10:19:36AM -0500, Jidong Xiao wrote: > On Wed, Feb 22, 2012 at 11:56 PM, Jidong Xiao wrote: > > Hi, > > > > I am just curious. Since the concept user-space device drivers has > > been proposed for several years, and some related projects and > > research papers have demonstrated the feasibility of of moving device > > drivers into use space. In particular, this paper: > > > > Tolerating Malicious Device Drivers in Linux. > > http://pdos.csail.mit.edu/papers/sud:usenix10.pdf > > > > In this paper, existing device driver code need not to be changed, > > which should help the idea to be applied in practice. > > > > The advantage and disadvantage of move device drivers into use space > > of both obvious: > > > > Advantage: Since most of kernel bugs are caused by device drivers > > issues, moving device drivers into user space can reduce the impact of > > device driver bugs. From security perspective, the system can be more > > secure and robust if most device drivers are working in user space. > > Disadvantage: At least, existing techniques as well as the above paper > > showed a relatively high overhead. > > > > So is it mainly because the high overhead that prevents the user-space > > device drivers ideas being accepted in Linux? > > > > Actually, my major concern is, since UIO has been accepted, then why > don't we move all the rest device drivers into user space as well. As > I understand, currently, some of device drivers are running on user > space, while the other (or say the majority of) device drivers are > running on kernel space, so why don't we maintain a consistent device > drivers infrastructure, say, either all in user space, or all in > kernel space. (Sure some critical device drivers still need to be kept > in kernel space.) Feel free to create patches to do so, and handle all of the userspace changes needed in order to implement this. I think you haven't thought through the true reason we have device drivers, and why Linux isn't a microkernel... And I'd take exception to your "advantage:" line above, I don't believe that is true at all. Best of luck with your work, greg k-h