From owner-freebsd-hackers@FreeBSD.ORG Mon Sep 13 17:13:40 2004 Return-Path: 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 C4E4116A4CE for ; Mon, 13 Sep 2004 17:13:40 +0000 (GMT) Received: from epita.fr (hermes.epita.fr [163.5.255.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id B587A43D58 for ; Mon, 13 Sep 2004 17:13:39 +0000 (GMT) (envelope-from le-hen_j@epita.fr) Received: from garak (garak [10.42.25.5]) by epita.fr id i8DHDSC28453 Mon, 13 Sep 2004 19:13:29 +0200 (CEST) Date: Mon, 13 Sep 2004 19:13:29 +0200 From: Jeremie Le Hen To: Nikita Danilov Message-ID: <20040913171329.GA16110@garak.epita.fr> References: <20040912183437.GF20097@mongers.org> <16708.47393.249768.90818@thebsh.namesys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16708.47393.249768.90818@thebsh.namesys.com> User-Agent: Mutt/1.4i cc: freebsd-hackers@freebsd.org cc: Morten Liebach Subject: Re: FreeBSD on Xserve? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Sep 2004 17:13:40 -0000 > UML (User Mode Linux, user-mode-linux.sf.net) is a port of Linux kernel > to Linux used as an underlying platform. UML kernel is built as a normal > user-level executable, that is run on a "host" machine, providing > "guest" Linux instance. You can log into guest, run processes there, > attach debugger to it, etc. It's more like vmware than jail. I would add that the UML patch applied to the hosted kernel source deeply modifies the ptrace(2) infrastructure. All UML processes are in fact processes on the host kernel, but the UML kernel ptrace's so that it reroutes all invoked syscalls to itself and mmap's processes address space to its own one. There is obviously a major drawback here, since every process may corrupt the address space of other ones, and even the kernel one. This is the reason why the SKAS kernel patch was created : this patch modifies the host kernel so that the MMU can be used to protect addresss spaces, as if processes were on a real kernel ; of course the UML kernel is then also protected. I don't know the internal of this patch, my VM skills are not good enough. > UML is a part of 2.6 mainline. This is correct, but usually patches provided on UML website are newer than those included in the 2.6 source. Sorry for my english, I'm doing my best to improve it :-). -- Jeremie LE HEN aka TtZ jeremie.le-hen@epita.fr ttz@epita.fr Hi! I'm a .signature virus! Copy me into your ~/.signature to help me spread!