From owner-freebsd-hackers@FreeBSD.ORG  Tue Jun 14 21:22:15 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 A297216A41C;
	Tue, 14 Jun 2005 21:22:15 +0000 (GMT)
	(envelope-from jmg@hydrogen.funkthat.com)
Received: from hydrogen.funkthat.com (gate.funkthat.com [69.17.45.168])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 7179443D49;
	Tue, 14 Jun 2005 21:22:15 +0000 (GMT)
	(envelope-from jmg@hydrogen.funkthat.com)
Received: from hydrogen.funkthat.com (nprxrc@localhost.funkthat.com
	[127.0.0.1])
	by hydrogen.funkthat.com (8.13.3/8.13.3) with ESMTP id j5ELMEes079099; 
	Tue, 14 Jun 2005 14:22:14 -0700 (PDT)
	(envelope-from jmg@hydrogen.funkthat.com)
Received: (from jmg@localhost)
	by hydrogen.funkthat.com (8.13.3/8.13.3/Submit) id j5ELMEVU079098;
	Tue, 14 Jun 2005 14:22:14 -0700 (PDT) (envelope-from jmg)
Date: Tue, 14 Jun 2005 14:22:14 -0700
From: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
To: Aziz Kezzou <french.linuxian@gmail.com>
Message-ID: <20050614212214.GK742@funkthat.com>
Mail-Followup-To: Aziz Kezzou <french.linuxian@gmail.com>,
	freebsd-hackers <freebsd-hackers@freebsd.org>,
	freebsd-net <freebsd-net@freebsd.org>
References: <37273927050614012154fdb80b@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <37273927050614012154fdb80b@mail.gmail.com>
User-Agent: Mutt/1.4.2.1i
X-Operating-System: FreeBSD 5.4-RELEASE-p1 i386
X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31  96 7A 22 B3 D8 56 36 F4
X-Files: The truth is out there
X-URL: http://resnet.uoregon.edu/~gurney_j/
X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html
Cc: freebsd-hackers <freebsd-hackers@freebsd.org>,
	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
Reply-To: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
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 21:22:15 -0000

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)...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."