Date: Mon, 30 Oct 1995 17:14:37 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, msmith@atrad.adelaide.edu.au Cc: hackers@freebsd.org, lenzi@cwbone.bsi.com.br, terry@lambert.org Subject: Re: boot disk.... Message-ID: <199510300614.RAA08870@godzilla.zeta.org.au>
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>> >Stage 2 boostrap ... >> >... should perform MBR fixup to >> >guarantee that the absolute offset field in the MBR matches the c/h/s >> >values for the slice under the BIOS geometry. >> >> Only for its own benefit. Drivers don't want to know about yet another >> translation. >It's actually intended to remove the need for any driver to need to know >about any translation. There are issues related to disks not covered by >a BIOS, but from the point of view of the 'panic: can't mount root' problem >experienced when an unwitting installer gets the geometry wrong. Drivers only need to know about the BIOS translation so that they can report it to fdisk so installers can get the geometry right. This is remarkably complicated, especially for handling of disks not covered by the BIOS, and still not handled right. The stage 2 bootstrap shouldn't have to duplicate the complications. Anyway, the stage 2 bootstrap is far too late to fix the values. The previous stage (stage 1 of 0, 1, 2, ...) is written at the absolute offset but loaded using the c/h/s values. Only stage 0 (the MBR) can fix them. >> >It should also be buildable >> >as a DOS program, to allow it to work with Ontrack's Disk Mangler. The >> >> Nothing should require DOS utilitites to build. >Nothing would. "It should be buildable as a DOS program"; in other words, >it should fit into the fbsdboot tool, to cover all booting scenarios. fbsdboot should _be_ a DOS program and be built as a FreeBSD program. Then it would be easier to add extensions to it. The new stage should also be buildable as an extension for netboot. Bruce
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