From owner-cvs-all Fri Aug 30 17:36:49 2002 Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 46BA337B401; Fri, 30 Aug 2002 17:36:37 -0700 (PDT) Received: from canning.wemm.org (canning.wemm.org [192.203.228.65]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0AB1F43E42; Fri, 30 Aug 2002 17:36:37 -0700 (PDT) (envelope-from peter@wemm.org) Received: from wemm.org (localhost [127.0.0.1]) by canning.wemm.org (Postfix) with ESMTP id 90ED52A7D6; Fri, 30 Aug 2002 17:36:36 -0700 (PDT) (envelope-from peter@wemm.org) X-Mailer: exmh version 2.5 07/13/2001 with nmh-1.0.4 To: John Baldwin Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: Re: cvs commit: src/sys/boot/i386/loader Makefile In-Reply-To: Date: Fri, 30 Aug 2002 17:36:36 -0700 From: Peter Wemm Message-Id: <20020831003636.90ED52A7D6@canning.wemm.org> Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG John Baldwin wrote: > > On 30-Aug-2002 John Baldwin wrote: > > jhb 2002/08/30 07:59:47 PDT > > > > Modified files: > > sys/boot/i386/loader Makefile > > Log: > > Revert previous untested revision. The i386 loader consists of three par ts: > > At the front is btxldr, in the middle is BTX itself (our mini-kernel), an d > > then the 'client' (loader.bin) which is the actual loader itself. boot2 > > just executes a raw ELF or a.out binary with the only setup provided bein g > > that a bootinfo structure is passed on the stack. Now, since loader.bin > > is a BTX client, the loader needs to be able to locate a BTX kernel for > > the client to execute in the context. Thus, just like pxelder, btxldr > > uses the a.out header on the loader binary to find the BTX kernel stored > > in the loader and set it up. It does _not_ just reuse the BTX kernel > > that boot2 invoked it with. This is because it can't assume that it will > > _have_ a "spare" BTX kernel lying around. For example, when cdboot > > loads the loader there isn't an existing BTX kernel. In fact, cdboot > > will only work with an a.out loader as well since it also "borrows" the > > BTX kernel in the loader binary (which it finds by parsing the a.out > > header) just as pxeldr does. The only difference between cdboot and > > pxeldr is where they get /boot/loader from. > > > > If we wanted to make /boot/loader be an actual ELF binary we would need > > to change the following utilites to handle that (and they all have to be > > able to handle locating the BTX kernel inside of an ELF binary somehow): > > - btxldr > > - pxeldr > > - cdboot > > > > If we didn't want to require a flag day but make the transition smooth > > then we need to be able to support both a.out and ELF versions of > > /boot/loader which isn't exactly trivial since all three of these utiliti es > > are written in assembly. > > > > Pointy-hat to: peter > > Hmm, in hindsight this message is perhaps a bit harsh. Sorry, Peter. I > don't see how you could have succesfully tested it though, the loader just > won't work in any case if /boot/loader isn't a.out atm. If it is any consolation, I had to recover my laptop with a hosed /boot/loader and /boot/loader.old today. :-] Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message