From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759023AbXIGWkF (ORCPT ); Fri, 7 Sep 2007 18:40:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758681AbXIGWjy (ORCPT ); Fri, 7 Sep 2007 18:39:54 -0400 Received: from one.firstfloor.org ([213.235.205.2]:52753 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758666AbXIGWjw (ORCPT ); Fri, 7 Sep 2007 18:39:52 -0400 Date: Sat, 8 Sep 2007 00:39:50 +0200 From: Andi Kleen To: Mathieu Desnoyers Cc: Andi Kleen , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Adrian Bunk , Alexey Dobriyan , Christoph Hellwig Subject: Re: [patch 3/8] Immediate Values - Kconfig menu in EMBEDDED Message-ID: <20070907223950.GB22646@one.firstfloor.org> References: <20070906200228.086651361@polymtl.ca> <20070906200314.692565803@polymtl.ca> <20070907064908.GG31880@one.firstfloor.org> <20070907124648.GC9735@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070907124648.GC9735@Krystal> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 07, 2007 at 08:46:48AM -0400, Mathieu Desnoyers wrote: > * Andi Kleen (andi@firstfloor.org) wrote: > > > +config IMMEDIATE > > > + default y if !DISABLE_IMMEDIATE > > > > It's still unclear to me why DISABLE_IMMEDIATE is needed. It would > > be better to make it just the default. > > > > It is actually the default on any non embedded configuration. Do you > think we should make it default to on on embedded configs too ? I would prefer to not have any config options at all and let the non converted architectures always use a asm-generic fallback. > The idea here is to give embedded system developers incentives to > create an optimized immediate value header for their architecture. I Sounds like a quite bogus way to do this. > fear that if it is not trivial to disable when they need to use ROM to > put the kernel code (as kprobes is, meaning, with a single config > option), they will refuse to event think about including an optimized > immediate value header for their architecture. #ifdef CONFIG_ARCH_SPECIFIC_READONLY #include #else /* optimized implementation */ #endif That's trivial. > And yes, having a CONFIG_READ_ONLY_TEXT makes sense, but it implies > menu dependencies with not only immediate values but also kprobes, > paravirt, alternatives, (am I missing others ?) paravirt and alternatives are x86 only. I don't think CONFIG_READ_ONLY_TEXT on x86 makes sense. On other architectures they have to deal with kprobes, but they presumably do this already. Not really your problem I suspect. > As long as we find a way for people to disable _all_ code patching in > their kernel, I'm happy with that. But since every existing code > patching mechanism can currently be disabled one by one, it makes sense > to do the same for the immediate values. Having a global > CONFIG_READ_ONLY_TEXT should IMHO come in a separate effort. You're clearly deep into overdesign territory here. -Andi