Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755825Ab2BUTlD (ORCPT ); Tue, 21 Feb 2012 14:41:03 -0500 Received: from mail-gy0-f174.google.com ([209.85.160.174]:60105 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754088Ab2BUTk6 convert rfc822-to-8bit (ORCPT ); Tue, 21 Feb 2012 14:40:58 -0500 MIME-Version: 1.0 In-Reply-To: <4F43F25E.3030004@zytor.com> 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> <4F43F25E.3030004@zytor.com> From: Andrew Lutomirski Date: Tue, 21 Feb 2012 11:40:38 -0800 X-Google-Sender-Auth: DkPD2s2A-CAGoIz6wjaMpGGT8qU Message-ID: Subject: Re: [PATCH 30/30] x32: Add x32 VDSO support To: "H. Peter Anvin" 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 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1286 Lines: 33 On Tue, Feb 21, 2012 at 11:37 AM, H. Peter Anvin wrote: > 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. I'd like to do that, too, and I'd also like to have a per-cpu kernel-only page in there, but that's even worse. If we had a separate cr3-like register for negative addresses, life would be good :) --Andy -- 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/