From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262074AbUKKBUu (ORCPT ); Wed, 10 Nov 2004 20:20:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262130AbUKKBUu (ORCPT ); Wed, 10 Nov 2004 20:20:50 -0500 Received: from canuck.infradead.org ([205.233.218.70]:11026 "EHLO canuck.infradead.org") by vger.kernel.org with ESMTP id S262074AbUKKBUo (ORCPT ); Wed, 10 Nov 2004 20:20:44 -0500 Subject: Re: [PATCH] VM routine fixes From: David Woodhouse To: Andrew Morton Cc: dhowells , hch@infradead.org, torvalds@osdl.org, davidm@snapgear.com, linux-kernel@vger.kernel.org, uclinux-dev@uclinux.org In-Reply-To: <20041110110145.3751ae17.akpm@osdl.org> References: <20041109140122.GA5388@infradead.org> <20041109125539.GA4867@infradead.org> <200411081432.iA8EWfmh023432@warthog.cambridge.redhat.com> <15068.1100008386@redhat.com> <4530.1100093877@redhat.com> <20041110110145.3751ae17.akpm@osdl.org> Content-Type: text/plain Date: Thu, 11 Nov 2004 01:17:13 +0000 Message-Id: <1100135833.4631.10.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-3.dwmw2.1) Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) X-SRS-Rewrite: SMTP reverse-path rewritten from by canuck.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2004-11-10 at 11:01 -0800, Andrew Morton wrote: > Why _does_ !CONFIG_MMU futz around with page counts in such weird ways > anyway? Why does it have requirements for higher-order pages which differ > from !CONFIG_MMU? Because in the absence of an MMU, an mmap of a large region (like an executable) has to be satisfied by a large enough allocation followed by a read. > If someone could explain the reasoning behind the current code, and the FRV > enhancements then perhaps we could work something out. I think these parts aren't FRV-specific; they're the fixes required to do proper shared readable mmap with !CONFIG_MMU. That was a prerequisite for the ELF-FDPIC executable format, which allows real shared libraries on uClinux. -- dwmw2