Date: Fri, 30 Aug 2002 11:11:22 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: RE: cvs commit: src/sys/boot/i386/loader Makefile Message-ID: <XFMail.20020830111122.jhb@FreeBSD.org> In-Reply-To: <200208301459.g7UExl7N064859@freefall.freebsd.org>
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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 parts: > At the front is btxldr, in the middle is BTX itself (our mini-kernel), and > 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 being > 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 utilities > 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. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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