From owner-freebsd-stable@FreeBSD.ORG Thu Oct 26 14:28:31 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3E6AE16A407; Thu, 26 Oct 2006 14:28:31 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (66-23-211-162.clients.speedfactory.net [66.23.211.162]) by mx1.FreeBSD.org (Postfix) with ESMTP id 491F243D5F; Thu, 26 Oct 2006 14:28:27 +0000 (GMT) (envelope-from jhb@freebsd.org) Received: from zion.baldwin.cx (zion.baldwin.cx [192.168.0.7]) (authenticated bits=0) by server.baldwin.cx (8.13.6/8.13.6) with ESMTP id k9QESE00027778; Thu, 26 Oct 2006 10:28:20 -0400 (EDT) (envelope-from jhb@freebsd.org) From: John Baldwin To: Ruslan Ermilov Date: Thu, 26 Oct 2006 10:28:09 -0400 User-Agent: KMail/1.9.1 References: <3A8131D4-881E-4873-A682-543A1A88C063@lassitu.de> <20061026222234.P2553@epsplex.bde.org> <20061026141830.GA790@rambler-co.ru> In-Reply-To: <20061026141830.GA790@rambler-co.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200610261028.10680.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [192.168.0.1]); Thu, 26 Oct 2006 10:28:22 -0400 (EDT) X-Virus-Scanned: ClamAV 0.88.3/2106/Thu Oct 26 09:18:05 2006 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: freebsd-stable@freebsd.org, Stefan Bethke , Bruce Evans , Bruce Evans Subject: Re: Still possible to directly boot without loader? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Oct 2006 14:28:31 -0000 On Thursday 26 October 2006 10:18, Ruslan Ermilov wrote: > On Thu, Oct 26, 2006 at 10:52:30PM +1000, Bruce Evans wrote: > > On Thu, 26 Oct 2006, Ruslan Ermilov wrote: > > >3) It's currently broken even on i386; backing out > > > rev. 1.71 of boot2.c by jhb@ fixes this for me. > > > > > >: revision 1.71 > > >: date: 2004/09/18 02:07:00; author: jhb; state: Exp; lines: +3 -3 > > >: A long, long time ago in a CVS branch far away (specifically, HEAD prior > > >: to 4.0 and RELENG_3), the BTX mini-kernel used paging rather than flat > > >: mode and clients were limited to a virtual address space of 16 megabytes. > > >: Because of this limitation, boot2 silently masked all physical addresses > > >: in any binaries it loaded so that they were always loaded into the first > > >: 16 Meg. Since BTX no longer has this limitation (and hasn't for a long > > >: time), remove the masking from boot2. This allows boot2 to load kernels > > >: larger than about 12 to 14 meg (12 for non-PAE, 14 for PAE). > > >: > > >: Submitted by: Sergey Lyubka devnull at uptsoft dot com > > >: MFC after: 1 month > > > > The kernel is linked at 0xc0000000 but loade din low memory, so the high > > bits must be masked off like they used to be for the kernel to boot at all. > > This has nothing to do with paging AFAIK. Rev.1.71 makes no sense, since > > BTX isn't large, and large kernels are more unbootable than before with > > 1.71. > > > The real purpose of this commit was to allow to directly "load kernels > larger than about 12 to 14 meg (12 for non-PAE, 14 for PAE)". (Old > version masked high 8 bits, leaving only 2^24=16MB for the kernel.) > > I have compiled GENERIC and PAE kernels; objdump(1) reports that GENERIC > kernel has virtual "start address 0xc0449cb0", and PAE has virtual "start > address 0xc02458f0". Yes, KERNLOAD for PAE is 2MB and for non-PAE is 4MB (to skip PSE page 0). > What happens here is that BTX now uses flat memory model, and by not > masking higher bits at all, BTX attempts to load kernels at above 3G, > which silently fails, and then jumps to the entry point located in > "no memory" unless the machine has enough memory. > > If the machine has enough physical memory, e.g. 4G, then it works (I > think that was the case on the machine John tested this change), but > on my test machine I only have 3G of memory, so it fails. Actually, it should never work, as the kernel assumes it is loaded at KERNLOAD. > My interim solution to the problem that would still allow booting > larger than 16MB kernels is to mask some of the higher bits. > Currently, I mask 28 bits that gives possible 256MB which is probably > practical. boot2 should do whatever loader does. -- John Baldwin