From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Wed, 10 Oct 2012 10:08:07 +0200 (CEST) Received: from localhost.localdomain ([127.0.0.1]:47506 "EHLO linux-mips.org" rhost-flags-OK-OK-OK-FAIL) by eddie.linux-mips.org with ESMTP id S6870520Ab2JJIH6mF0w5 (ORCPT ); Wed, 10 Oct 2012 10:07:58 +0200 Received: from scotty.linux-mips.net (localhost.localdomain [127.0.0.1]) by scotty.linux-mips.net (8.14.5/8.14.4) with ESMTP id q9A87uBI007344; Wed, 10 Oct 2012 10:07:56 +0200 Received: (from ralf@localhost) by scotty.linux-mips.net (8.14.5/8.14.5/Submit) id q9A87u8n007343; Wed, 10 Oct 2012 10:07:56 +0200 Date: Wed, 10 Oct 2012 10:07:56 +0200 From: Ralf Baechle To: Ronny Meeus Cc: linux-mips@linux-mips.org Subject: Re: 2GB userspace limitation in ABI N32 Message-ID: <20121010080756.GC6740@linux-mips.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-archive-position: 34666 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips Return-Path: On Wed, Oct 10, 2012 at 08:32:47AM +0200, Ronny Meeus wrote: > I have a legacy application that we want to port to a MIPS (Cavium) > architecture from a PPC based one. > The board has 4GB memory of which we actually need almost 3GB in > application space. On the PPC this is no issue since the split > user/kernel is 3GB/1GB. > We have to use the N32 ABI Initial tests on MIPS showed me the > user-space limit of 2GB. > We do not want to port the application to a 64bit > > Now the question is: are there any workarounds, tricks existing to get > around this limitation? > I found some mailthreads on this subject (n32-big ABI - > http://gcc.gnu.org/ml/gcc/2011-02/msg00278.html, > http://elinux.org/images/1/1f/New-tricks-mips-linux.pdf) but is looks > like this is not accepted by the community. Is there any process > planned or made in this area? I think limited time and gain killed the propoosed ABI rather than theoretical issues raised. Other architectures such as i386 - well, IIRC any 32-bit ABI with more than 2GB userspace and a signed ptrdiff_t - are suffering from them as well. Also there's limited gain and even more limited time to implement things ... Ralf