From owner-freebsd-hackers@FreeBSD.ORG  Tue Jun 14 21:33:15 2005
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
X-Original-To: freebsd-hackers@freebsd.org
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 3850816A41C;
	Tue, 14 Jun 2005 21:33:15 +0000 (GMT)
	(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 DCA7843D1D;
	Tue, 14 Jun 2005 21:33:14 +0000 (GMT)
	(envelope-from scottl@samsco.org)
Received: from [192.168.254.14] (imini.samsco.home [192.168.254.14])
	(authenticated bits=0)
	by pooker.samsco.org (8.13.3/8.13.3) with ESMTP id j5ELbsha013988;
	Tue, 14 Jun 2005 15:37:55 -0600 (MDT)
	(envelope-from scottl@samsco.org)
Message-ID: <42AF4C82.7070306@samsco.org>
Date: Tue, 14 Jun 2005 15:30:42 -0600
From: Scott Long <scottl@samsco.org>
User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US;
	rv:1.7.7) Gecko/20050416
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
References: <37273927050614012154fdb80b@mail.gmail.com>
	<20050614212214.GK742@funkthat.com>
In-Reply-To: <20050614212214.GK742@funkthat.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-Spam-Status: No, score=-2.8 required=3.8 tests=ALL_TRUSTED autolearn=failed 
	version=3.0.2
X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on pooker.samsco.org
Cc: freebsd-hackers <freebsd-hackers@freebsd.org>,
	Aziz Kezzou <french.linuxian@gmail.com>,
	freebsd-net <freebsd-net@freebsd.org>
Subject: Re: FreeBSD Memory Management questions ?
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 14 Jun 2005 21:33:15 -0000

John-Mark Gurney wrote:

> Aziz Kezzou wrote this message on Tue, Jun 14, 2005 at 04:21 -0400:
> 
>>I have two questions concerning FreeBSD Memory management :
>>
>>1 - Right now to access the memory address space of a user process
>>from kernel mode, I only have to set, on x86 systems, the register CR3
>>to the right value.  How can I do that on other architectures ? is
>>there an architecture-independant way of doing that ?
>>
>>2- I have noticed that while in kernel mode the value of CR3 is equal
>>to that of the user process beeing interrupted. Doesn't the kernel
>>supposed to have its "own" page-directory, i.e it's own CR3  value ?
>>or is kernel virtual address resolution does  not go through CR3 at
>>all ?
> 
> 
> You should be using copyin(9)/copyout(9) instead of playing around with
> CR3 directly...  or fuword(9)/suword(9)...  This provides a platform
> independant way of accessing user's memory (for the current running
> process)...
> 

Not to mention that setting CR3, or whatever on other platforms, doesn't
handle accessing pages that have been swapped out.  That's the real
magic that copyin/copyout does.

Scott