From owner-freebsd-stable Fri Dec 8 15:29:58 2000 From owner-freebsd-stable@FreeBSD.ORG Fri Dec 8 15:29:53 2000 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from sender.ngi.de (sender.ngi.de [212.79.47.18]) by hub.freebsd.org (Postfix) with ESMTP id 2957A37B400; Fri, 8 Dec 2000 15:29:53 -0800 (PST) Received: from Gatekeeper.FreeBSD.org (koln-3e366334.pool.mediaWays.net [62.54.99.52]) by sender.ngi.de (Postfix) with ESMTP id 48E0F96D39; Sat, 9 Dec 2000 00:22:50 +0100 (CET) Received: from StefanEsser.FreeBSD.org (StefanEsser [10.0.0.1]) by Gatekeeper.FreeBSD.org (Postfix) with ESMTP id 7C4D0C; Fri, 8 Dec 2000 23:40:39 +0100 (CET) Received: by StefanEsser.FreeBSD.org (Postfix, from userid 200) id E8308D93; Fri, 8 Dec 2000 23:41:14 +0100 (CET) Date: Fri, 8 Dec 2000 23:41:14 +0100 From: Stefan Esser To: Mike Silbersack Cc: "Chad R. Larson" , mjacob@feral.com, gallatin@cs.duke.edu, ken@kdm.org, hackers@FreeBSD.ORG, stable@FreeBSD.ORG, Stefan Esser Subject: Re: Re: PCIOCGETCONF/PCIOCREAD requires write permission? Message-ID: <20001208234114.A1638@StefanEsser.FreeBSD.org> Reply-To: Stefan Esser Mail-Followup-To: Stefan Esser , Mike Silbersack , "Chad R. Larson" , mjacob@feral.com, gallatin@cs.duke.edu, ken@kdm.org, hackers@FreeBSD.ORG, stable@FreeBSD.ORG References: <200012080707.AAA12102@freeway.dcfinc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from silby@silby.com on Fri, Dec 08, 2000 at 10:02:44AM -0600 Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 2000-12-08 10:02 -0600, Mike Silbersack wrote: > Seriously, though. There must be some way to abuse such direct access to > the pci configuration registers. Just because nobody has figured it out > how yet doesn't mean that enabling the feature is a good idea. Well, what makes you think, that nobody has figured out why read access to the pci config space registers might not be a good idea ? ;-) The reason is simple: There are a number of PCI devices that fail in a number of ways, if certain config space registers are accessed while the device is active. This is counterintuitive at first, but just try to read a config register beyond 0x80 from an NCR SCSI chip while it is executing SCRIPTS code ... The PCI spec made higher numbered config space registers implementation dependent. Some vendors mapped their devices' operational registers into config space, even though the spec never encouraged that (though I'm not sure that such an (ab)use of config registers was declared forbidden in later revisions of the spec.). Since there are a number of devices that could be severely impacted by read accesses to configuration space registers, we can't safely permit any user such read access. Root hopefully knows what he is doing and only accesses such registers that are meant to be accessed while the device is operating ... Regards, STefan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message