From owner-freebsd-arch@FreeBSD.ORG  Fri Sep 15 15:21:48 2006
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
X-Original-To: freebsd-arch@freebsd.org
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 8B05A16A403;
	Fri, 15 Sep 2006 15:21:48 +0000 (UTC)
	(envelope-from delphij@delphij.net)
Received: from tarsier.geekcn.org (tarsier.geekcn.org [210.51.165.229])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 1234A43D4C;
	Fri, 15 Sep 2006 15:21:47 +0000 (GMT)
	(envelope-from delphij@delphij.net)
Received: from localhost (tarsier.geekcn.org [210.51.165.229])
	by tarsier.geekcn.org (Postfix) with ESMTP id 675ABEB3198;
	Fri, 15 Sep 2006 23:21:43 +0800 (CST)
X-Virus-Scanned: amavisd-new at geekcn.org
Received: from tarsier.geekcn.org ([210.51.165.229])
	by localhost (mail.geekcn.org [210.51.165.229]) (amavisd-new,
	port 10024)
	with ESMTP id 09pp2GK66bDq; Fri, 15 Sep 2006 23:21:38 +0800 (CST)
Received: from [192.168.1.32] (unknown [221.216.126.47])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by tarsier.geekcn.org (Postfix) with ESMTP id 57A68EB1BE1;
	Fri, 15 Sep 2006 23:21:38 +0800 (CST)
DomainKey-Signature: a=rsa-sha1; s=default; d=delphij.net; c=nofws; q=dns;
	h=message-id:date:from:organization:user-agent:mime-version:to:cc:
	subject:references:in-reply-to:content-type:content-transfer-encoding; 
	b=FEOv/iV8eBzB/wU/U/XWKJC6HCrPHSLTJXcYmc64B4K8ns6Dogv04WeHzC0dwhsmD
	tv/TvymDAJfYAiwz7UjEA==
Message-ID: <450AC4FE.6070303@delphij.net>
Date: Fri, 15 Sep 2006 23:21:34 +0800
From: LI Xin <delphij@delphij.net>
Organization: The FreeBSD Project
User-Agent: Thunderbird 1.5.0.7 (Macintosh/20060909)
MIME-Version: 1.0
To: John Baldwin <jhb@freebsd.org>
References: <450AB80B.1050100@delphij.net> <200609151035.12069.jhb@freebsd.org>
In-Reply-To: <200609151035.12069.jhb@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: freebsd-arch@freebsd.org
Subject: Re: How to map a page with userland program?
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 15 Sep 2006 15:21:48 -0000

John Baldwin wrote:
> On Friday 15 September 2006 10:26, LI Xin wrote:
>> Dear folks,
>>
>> Is there a continent and MI way to map a kernel page into userland 
>> address space under the same virtual address?  It seems that this can be 
>> implemented through some routines in MD part of pmap, but is it possible 
>> to use higher level VM routines to do the job?
> 
> Not to the same userland virtual address.  Why do you need the same
> virtual address anyway?  If it's for pointers use offsets relative to
> the start of the page instead.

That would make it easier to implement some sort of VSYSCALL, which is 
in fact executed in userland.  Or, is there any better way? :-)

Cheers,
-- 
Xin LI <delphij@delphij.net>	http://www.delphij.net/
FreeBSD - The Power to Serve!