Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262462AbVA0FTF (ORCPT ); Thu, 27 Jan 2005 00:19:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262463AbVA0FTF (ORCPT ); Thu, 27 Jan 2005 00:19:05 -0500 Received: from mx1.redhat.com ([66.187.233.31]:2467 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S262462AbVA0FTA (ORCPT ); Thu, 27 Jan 2005 00:19:00 -0500 Date: Thu, 27 Jan 2005 00:18:56 -0500 From: Dave Jones To: William Lee Irwin III Cc: Rik van Riel , Andrew Morton , linux-kernel@vger.kernel.org, James Antill , Bryn Reeves Subject: Re: don't let mmap allocate down to zero Message-ID: <20050127051855.GB24107@redhat.com> Mail-Followup-To: Dave Jones , William Lee Irwin III , Rik van Riel , Andrew Morton , linux-kernel@vger.kernel.org, James Antill , Bryn Reeves References: <20050126172538.GN10843@holomorphy.com> <20050127050927.GR10843@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050127050927.GR10843@holomorphy.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1571 Lines: 32 On Wed, Jan 26, 2005 at 09:09:27PM -0800, William Lee Irwin III wrote: > On Wed, Jan 26, 2005 at 11:18:08AM -0500, Rik van Riel wrote: > >> With some programs the 2.6 kernel can end up allocating memory > >> at address zero, for a non-MAP_FIXED mmap call! This causes > >> problems with some programs and is generally rude to do. This > >> simple patch fixes the problem in my tests. > >> Make sure that we don't allocate memory all the way down to zero, > >> so the NULL pointer never gets covered up with anonymous memory > >> and we don't end up violating the C standard. > >> Signed-off-by: Rik van Riel > > On Wed, Jan 26, 2005 at 09:25:38AM -0800, William Lee Irwin III wrote: > > SHLIB_BASE does not appear to be present in 2.6.9; perhaps something > > else is going on. > > I think we are better off: > > (a) checking for hitting zero explicitly as opposed to > > enforcing a randomly-chosen lower limit for addresses > > (b) enforcing vma allocation above FIRST_USER_PGD_NR*PGDIR_SIZE, > > to which SHLIB_BASE bears no relation. > > There's a long discussion here, in which no one appears to have noticed > that SHLIB_BASE does not exist in mainline. Is anyone else awake here? It's an exec-shield'ism. Rik likely was working off a Red Hat/Fedora kernel tree. Dave - 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/