Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753561AbZGOJZQ (ORCPT ); Wed, 15 Jul 2009 05:25:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753453AbZGOJZQ (ORCPT ); Wed, 15 Jul 2009 05:25:16 -0400 Received: from 124x34x33x190.ap124.ftth.ucom.ne.jp ([124.34.33.190]:51886 "EHLO master.linux-sh.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753001AbZGOJZO (ORCPT ); Wed, 15 Jul 2009 05:25:14 -0400 Date: Wed, 15 Jul 2009 18:24:46 +0900 From: Paul Mundt To: David Howells Cc: Mike Frysinger , linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, Bernd Schmidt , Bryan Wu Subject: Re: [PATCH v2] NOMMU: add support for Memory Protection Units (MPU) Message-ID: <20090715092446.GB1863@linux-sh.org> Mail-Followup-To: Paul Mundt , David Howells , Mike Frysinger , linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, Bernd Schmidt , Bryan Wu References: <1247591665-12000-1-git-send-email-vapier@gentoo.org> <20090714161416.GA19147@cmpxchg.org> <6206.1247592126@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6206.1247592126@redhat.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1208 Lines: 23 On Tue, Jul 14, 2009 at 06:22:06PM +0100, David Howells wrote: > Mike Frysinger wrote: > > > Some architectures (like the Blackfin arch) implement some of the > > "simpler" features that one would expect out of a MMU such as memory > > protection. In our case, we actually get read/write/exec protection > > down to the page boundary so processes can't stomp on each other let > > alone the kernel. There is a performance decrease (which depends greatly > > on the workload) however as the hardware/software interaction was not > > optimized at design time. > > It occurs to me that I could probably test this on FRV by using the MMU in a > limited way. How do you actually keep track of the protections applied? Do > you have a single global page table that is managed by the mmap code on a > per-VMA basis? > SH can do this as well for the single-address-space mode in the MMU, but in that case I would still use a global page table. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/