From owner-freebsd-current@FreeBSD.ORG  Thu Jun 16 00:59:01 2011
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: current@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 77E09106566B;
	Thu, 16 Jun 2011 00:59:01 +0000 (UTC)
	(envelope-from scottl@samsco.org)
Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57])
	by mx1.freebsd.org (Postfix) with ESMTP id 1F9838FC1A;
	Thu, 16 Jun 2011 00:59:00 +0000 (UTC)
Received: from [127.0.0.1] (pooker.samsco.org [168.103.85.57])
	(authenticated bits=0)
	by pooker.samsco.org (8.14.4/8.14.4) with ESMTP id p5G0wtX0003294;
	Wed, 15 Jun 2011 18:58:56 -0600 (MDT)
	(envelope-from scottl@samsco.org)
Mime-Version: 1.0 (Apple Message framework v1084)
Content-Type: text/plain; charset=us-ascii
From: Scott Long <scottl@samsco.org>
In-Reply-To: <4DF951E3.7010209@freebsd.org>
Date: Wed, 15 Jun 2011 18:58:55 -0600
Content-Transfer-Encoding: quoted-printable
Message-Id: <FA098515-E1C8-4514-81BA-C361DE248D84@samsco.org>
References: <20110614161105.GA17306@onelab2.iet.unipi.it>	<BANLkTinOq73nGQT88NByuOgH3ByuA=ZLJA@mail.gmail.com>
	<4A46AC77-BEE5-4401-8896-4E4F1A5304B0@samsco.org>
	<4DF951E3.7010209@freebsd.org>
To: Julian Elischer <julian@FreeBSD.org>
X-Mailer: Apple Mail (2.1084)
X-Spam-Status: No, score=-50.0 required=3.8 tests=ALL_TRUSTED,
	T_RP_MATCHES_RCVD autolearn=unavailable version=3.3.0
X-Spam-Checker-Version: SpamAssassin 3.3.0 (2010-01-18) on pooker.samsco.org
Cc: Luigi Rizzo <rizzo@iet.unipi.it>, "K. Macy" <kmacy@FreeBSD.org>,
	current@FreeBSD.org
Subject: Re: fast/syscall-free gettimeofday ?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 16 Jun 2011 00:59:01 -0000

On Jun 15, 2011, at 6:44 PM, Julian Elischer wrote:
>> If this was to be extended with cached global syscall information =
like gettimeofday, would we want that to be in a separate page that is =
marked non-executable?  Is there any way to trick the kernel into =
leaking arbitrary (and thus executable) code?  Also, would it matter for =
jails?  Per-process info like getpid would obviously have to be a =
separate per-process page.
>>=20
>> Scott
>>=20
> In the talk about this sort of topic  I have seen mention at various =
times
> of a page per system, a page per jail, a page per process and a page =
per thread.
>=20
> I'm not saying we want this all just that I've seen it mentionned..
>=20
> The per-thread one is the most intersting to do challenge wise.

I guess that per-thread would be done via a pointer off of the TLS data, =
or would it be yet another bumping of the stack?  It would be =
interesting to see how expensive it is to go that direction.

Scott