From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20096 invoked by alias); 17 Dec 2009 19:14:22 -0000 Received: (qmail 20084 invoked by uid 22791); 17 Dec 2009 19:14:20 -0000 X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from us02smtp2.synopsys.com (HELO alvesta.synopsys.com) (198.182.60.77) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 17 Dec 2009 19:14:15 +0000 Received: from maiden.synopsys.com (maiden.synopsys.com [146.225.100.170]) by alvesta.synopsys.com (Postfix) with ESMTP id 20AE52CB9B; Thu, 17 Dec 2009 11:14:14 -0800 (PST) Received: from atgmv5.synopsys.com (localhost [127.0.0.1]) by maiden.synopsys.com (8.9.1/8.9.1) with ESMTP id LAA15085; Thu, 17 Dec 2009 11:14:13 -0800 (PST) Received: from atgmv5.synopsys.com (localhost [127.0.0.1]) by atgmv5.synopsys.com (8.13.1/8.12.3) with ESMTP id nBHJE6HM031216; Thu, 17 Dec 2009 11:14:06 -0800 Received: (from jbuck@localhost) by atgmv5.synopsys.com (8.13.1/8.13.1/Submit) id nBHJE1HK031210; Thu, 17 Dec 2009 11:14:01 -0800 Date: Thu, 17 Dec 2009 19:14:00 -0000 From: Joe Buck To: Russell King - ARM Linux Cc: Richard Guenther , David Daney , "gcc@gcc.gnu.org" , Jamie Lokier , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH] ARM: Convert BUG() to use unreachable() Message-ID: <20091217191401.GD10707@synopsys.com> References: <1260266138-17684-1-git-send-email-u.kleine-koenig@pengutronix.de> <20091217150120.GD24967@shareable.org> <4B2A65C6.7080009@caviumnetworks.com> <84fc9c000912170917y4b2772d0n47bb4dabc74b91ef@mail.gmail.com> <20091217181718.GA4440@n2100.arm.linux.org.uk> <20091217183517.GC10707@synopsys.com> <20091217190613.GB4440@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091217190613.GB4440@n2100.arm.linux.org.uk> User-Agent: Mutt/1.4.1i Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2009-12/txt/msg00261.txt.bz2 On Thu, Dec 17, 2009 at 11:06:13AM -0800, Russell King - ARM Linux wrote: > On Thu, Dec 17, 2009 at 10:35:17AM -0800, Joe Buck wrote: > > Besides, didn't I see a whole bunch of kernel security patches related > > to null pointer dereferences lately? If page 0 can be mapped, you > > suddenly won't get your trap. > > Page 0 can not be mapped on ARM kernels since the late 1990s, and this > protection is independent of the generic kernel. > > Milage may vary on other architectures, but that's not a concern here. I don't understand, though, why you would want to implement a generally useful facility (make the kernel trap so you can do a post-mortem analysis) in a way that's only safe for the ARM port.