From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932719AbYETQn2 (ORCPT ); Tue, 20 May 2008 12:43:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758165AbYETQnS (ORCPT ); Tue, 20 May 2008 12:43:18 -0400 Received: from rv-out-0506.google.com ([209.85.198.232]:29381 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757802AbYETQnS (ORCPT ); Tue, 20 May 2008 12:43:18 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=EboKalDVt2jEieNiTH+hZ9Hl6JMMFtwfkUY0S88+y/avG482zl0QpTALMJiPj4zGuEyW5v2ryPCoyMxPSD82/EJGodwtqw2WTPfyRnH7ILU7qe8rdx4eX1RZdDZ2eIPsEvnEpv0trlUpmqtT09IYslDZSLt1EaY8GPpR6BG1JAA= Message-ID: <7b9198260805200943x6fb15512o7ba35a40d006b215@mail.gmail.com> Date: Tue, 20 May 2008 17:43:17 +0100 From: "Tom Spink" To: "Jeff Dike" Subject: Re: UML fails to locate address space Cc: LKML In-Reply-To: <20080520161047.GA9598@c2.user-mode-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <7b9198260805200408k1d6b70a8xc7e4c24106e5020f@mail.gmail.com> <20080520135238.GB6990@c2.user-mode-linux.org> <7b9198260805200659p6ed28403t9b0b0ea995f158d5@mail.gmail.com> <20080520161047.GA9598@c2.user-mode-linux.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2008/5/20 Jeff Dike : > On Tue, May 20, 2008 at 02:59:14PM +0100, Tom Spink wrote: >> Attached. I guess the line of interest is: >> >> mmap2(NULL, 4096, PROT_READ|PROT_WRITE, >> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = -1 EACCES (Permission >> denied) > > Yup. > > Can you try three things: > check the maps file for any arbitrary process > (i.e. /proc/$$/maps) and see if there's anything mapped at 0 Nothing. > gdb UML, stop it at that mmap, check its maps file and see if > there's anything mapped at 0 Nope. > send me a pointer to the patches that Ubuntu has applied on > top of the stock kernel - I'm suspicious that they special-cased page > zero in order to ensure that NULL pointer dereferences cause faults. > > You can test this last theory by initializing bottom to 4096 instead > of 0. I suspected this type of foul-play, and tried altering bottom to 1, but this didn't work. So, I took out the page_ok test, and it continued booting. So I went back, put the test back in and incremented bottom until I got to 16. It worked at 16. :-) Is this something that can be fixed, or would a config option be appropriate? I am willing to blame Ubuntu, but unfortunately, I can't find an online resource of their patches. > Jeff > > -- > Work email - jdike at linux dot intel dot com > -- Tom Spink