Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755603Ab2BUThW (ORCPT ); Tue, 21 Feb 2012 14:37:22 -0500 Received: from terminus.zytor.com ([198.137.202.10]:45068 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752438Ab2BUThU (ORCPT ); Tue, 21 Feb 2012 14:37:20 -0500 Message-ID: <4F43F25E.3030004@zytor.com> Date: Tue, 21 Feb 2012 11:37:02 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20120131 Thunderbird/10.0 MIME-Version: 1.0 To: Andrew Lutomirski CC: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, hjl.tools@gmail.com Subject: Re: [PATCH 30/30] x32: Add x32 VDSO support References: <1329696488-16970-1-git-send-email-hpa@zytor.com> <1329696488-16970-31-git-send-email-hpa@zytor.com> <4F42E171.9080005@mit.edu> <4F431665.3010004@zytor.com> <4F43D98D.1020406@zytor.com> <4F43EA83.6020203@zytor.com> In-Reply-To: X-Enigmail-Version: 1.3.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 990 Lines: 27 On 02/21/2012 11:29 AM, Andrew Lutomirski wrote: >> >> The vsyscall page shouldn't be mapped for x32 tasks... > > How is that possible? It lives in the fixmap and is presumably > visible from any 64-bit code. > > Admittedly, x32 tasks are probably somewhat difficult to trick into > calling addresses with high bits set, but it's not necessarily > impossible. > Fair enough, and it's not necessarily all that hard either. And it's visible even in a 32-bit task, although a 32-bit task has to switch into 64-bit mode. Yet another reason the vsyscall page needs to die. I was having delusions that we could have a task-owned PDT in negative space, but that would require unsharing the third level, too, which is just way too messy. -hpa -- 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/