Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753320Ab2BUT3X (ORCPT ); Tue, 21 Feb 2012 14:29:23 -0500 Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:32805 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752600Ab2BUT3V convert rfc822-to-8bit (ORCPT ); Tue, 21 Feb 2012 14:29:21 -0500 MIME-Version: 1.0 In-Reply-To: <4F43EA83.6020203@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> From: Andrew Lutomirski Date: Tue, 21 Feb 2012 11:29:00 -0800 X-Google-Sender-Auth: M9d8TY9nVF72GNUOINuYqZJW3f8 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: 1026 Lines: 25 On Tue, Feb 21, 2012 at 11:03 AM, H. Peter Anvin wrote: > On 02/21/2012 10:54 AM, Andrew Lutomirski wrote: >> >> uclibc hardcodes a call to the vsyscall gettimeofday implementation in >> its locking primitives, which probably gives terrible performance, but >> that's a separate issue. ?I think do_emulate_vsyscall should send a >> segfault if called by an x32 task -- there's some security benefit to >> doing so, and there's unlikely to be any downside. >> > > 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. --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/