Linux/VAX boot protocol

[Pekka Enberg]

Hello Maciej,

On Sat, Nov 24, 2012 at 10:26 PM, Maciej W. Rozycki
<macro at linux-mips.org> wrote:
>  The all-zeroes image parameters are probably accepted by client's
> bootstrap firmware for backwards compatibility only and I have used the
> daemon and the protocol with non-VAX devices (e.g. a terminal server or a
> DECstation workstation) in a more sophisticated manner, where actual load
> addresses (that need not be contiguous, BTW, as all Memory Load MOP data
> transfer packets have an individual load address included in the packet
> header) and entry point had meaningful values.
>
>  Beyond the note quoted I don't know if there has been any proper
> documentation written up for these internals, perhaps someone else could
> speak up.  I hope this helps regardless -- what do you need this
> information for anyway?  Perhaps I could look into further details.
>
>  In the past I did some work on our `mopd' implementation (added ELF file
> format support among others -- to support plain "vmlinux" images on the
> DECstation), so perhaps I could dust off some old knowledge in that area
> if that helped you.  OTOH I have never had a real need to look into our
> early bootstrap code outlined in the note above, so unless someone else
> steps in we'd have to explore that area from scratch.

I'm trying to understand the boot process so that I can emulate the
relevant parts in QEMU.

Thanks for clearing up a lot of the details! I wonder what
specifications the people who wrote mopchk were looking at. Or maybe
they reverse engineered the proprietary image format?

                        Pekka