Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261151AbVCQU3f (ORCPT ); Thu, 17 Mar 2005 15:29:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261156AbVCQU3e (ORCPT ); Thu, 17 Mar 2005 15:29:34 -0500 Received: from caramon.arm.linux.org.uk ([212.18.232.186]:35080 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S261151AbVCQU3X (ORCPT ); Thu, 17 Mar 2005 15:29:23 -0500 Date: Thu, 17 Mar 2005 20:28:49 +0000 From: Russell King To: Albert Cahalan Cc: Christoph Lameter , Albert Cahalan , Matt Mackall , john stultz , lkml , Tim Schmielau , George Anzinger , Ulrich Windl , Dominik Brodowski , David Mosberger , Andi Kleen , paulus@samba.org, schwidefsky@de.ibm.com, keith maanthey , Patricia Gaughen , Chris McDermott , Max Asbock , mahuja@us.ibm.com, Nishanth Aravamudan , Darren Hart , "Darrick J. Wong" , Anton Blanchard , donf@us.ibm.com Subject: Re: [RFC][PATCH] new timeofday core subsystem (v. A3) Message-ID: <20050317202848.A15653@flint.arm.linux.org.uk> Mail-Followup-To: Albert Cahalan , Christoph Lameter , Albert Cahalan , Matt Mackall , john stultz , lkml , Tim Schmielau , George Anzinger , Ulrich Windl , Dominik Brodowski , David Mosberger , Andi Kleen , paulus@samba.org, schwidefsky@de.ibm.com, keith maanthey , Patricia Gaughen , Chris McDermott , Max Asbock , mahuja@us.ibm.com, Nishanth Aravamudan , Darren Hart , "Darrick J. Wong" , Anton Blanchard , donf@us.ibm.com References: <20050314192918.GC32638@waste.org> <1110829401.30498.383.camel@cog.beaverton.ibm.com> <20050314195110.GD32638@waste.org> <1110830647.30498.388.camel@cog.beaverton.ibm.com> <20050314202702.GF32638@waste.org> <1110852973.1967.180.camel@cube> <1110900235.7893.207.camel@cube> <20050317165534.B12344@flint.arm.linux.org.uk> <1111088697.1930.6.camel@cube> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <1111088697.1930.6.camel@cube>; from albert@users.sf.net on Thu, Mar 17, 2005 at 02:44:57PM -0500 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 33 On Thu, Mar 17, 2005 at 02:44:57PM -0500, Albert Cahalan wrote: > Does the ARM kernel provide a special page of code for > apps to execute? If not, then ARM is irrelevant. No. However, I was responding to your suggestion that supporting self modifying code in the kernel is trivial. > Doesn't ARM always have an MMU? If you have an MMU, then > it is no problem to have one single page of non-XIP code > for this purpose. No. You also have a big misconception about how we map system memory. We have 1MB mappings, and replacing 1MB of code/data (which would equate to half a kernel) would completely negate the whole point of XIP. > Supposing that you do support the vsyscall hack and you don't > have an MMU, you can just place the tiny code fragment on the > stack (or anywhere else) when an exec is performed. > > So, as far as I can see, ARM is fully capable of supporting this. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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/