From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956AbaCJPBK (ORCPT ); Mon, 10 Mar 2014 11:01:10 -0400 Received: from mga02.intel.com ([134.134.136.20]:52712 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753290AbaCJPBI (ORCPT ); Mon, 10 Mar 2014 11:01:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,624,1389772800"; d="scan'208";a="469610586" Message-ID: <531DD35A.5060202@linux.intel.com> Date: Mon, 10 Mar 2014 07:59:38 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Andy Lutomirski CC: Stefani Seibold , "linux-kernel@vger.kernel.org" , Martin Runge , Andreas Brief , Linus Torvalds Subject: Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000 References: <20140307013833.GD8427@localhost> <1394176888.1018.3.camel@wall-e.seibold.net> <1394229220.20013.13.camel@wall-e.seibold.net> <1394354848.1002.37.camel@wall-e.seibold.net> <531D044C.2090303@linux.intel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/09/2014 09:46 PM, Andy Lutomirski wrote: > On Sun, Mar 9, 2014 at 8:18 PM, Andy Lutomirski wrote: >> (Of course, I haven't the faintest idea what l_addr in glibc means. >> If there was a way to arrange for l_addr to be zero, then maybe none >> of this would matter. Hmm, I wonder if just not relocating the vdso >> at all would have the desired effect. Anyone out there understand >> glibc?) > > No, that won't work. The bug is that glibc expects PT_DYNAMIC's vaddr > to be the virtual address of the dynamic table. This can only be true > if the vdso is mapped at the address that the kernel relocated it to. > > I also learned that glibc's code is really hideous. Wow. > At the same time it does mean we have more flexibility than having a hard-coded address... we can at least allocate more than one page in the fixmap; for a really "full service" solution the kernel could adjust the vdso for whatever address the "fixmap" is at. I have mentioned in the past wanting to move the fixmap to the low part of the kernel space, because the top isn't really fixed... -hpa