Re: booting a ELF binary

[Ton Biegstraaten <a.w.w.m.biegstraaten@twi.tudelft.nl>]

Hi Markus, and others of course
markus@infoscape.com wrote:
> 
> Hi Ton,
> 
>  > Net/etherboot can easily boot MSDOS and linux images that are build with
>  > the mknbi programs. Now I have `a' self contained ELF binary I like to
>                                       ^^^^^^^^^^^^^^

It's actually an operating system. The boot system is based on a PC
based SVR4 system. The boot loader sets up some tables in low mem,
before starting the OS it first updates those tables, so I think the OS
uses them. As these tables depend on the SVR4 system I haven't here
there are some more problems to solve, but that's not for this list.
allthough I appreciate any help on info on this subject (:-).

Assume I know how to setup those tables in low mem, I should still do
that somehow next to loading the OS. The mknbi programs do that for
Linux and DOS so I should write one myself. Well, what should be the
structure of the resulting image made by mknbi that's loaded by the
bootrom?
Do I need to change the bootrom itself? Is there some magic word for
each type of mknbi program that the bootrom should be aware of? I prefer
to keep as much of the stuff the same (read: working)
The bootrom should start a program within the image, where should the
image be placed?, what memory locations are used?
The program to be started should setup those low mem tables, then
loading the OS and start it, the priciple is easy,as usual.
I have a bootflop(SVR4 of course :-(), is it easy to change it into a
ramdisk?
> 
> On the other hand, if you cannot run the application from within
> Linux, you will have to write your own loader. In all likelyhood, your
> image file uses only one very small subset of the ELF format. You can
> probably take a look at the ELF loader in the Linux kernel and use
> this as a template for writing your own customized mknbi-ELF loader. I
> do not expect this to be very difficult and an experienced programmer
> will probably be able to come up with a running prototype within a
> time-frame of one to three days.
That's sounds hopefull. 
I have the source code (licenced, so I may not show it) for the
bootflop, but it's very very dependent on the SVR4 system, so I can only
look at it and have to combine the relevant parts with the relevant
parts of the bootrom and mknbi stuff. And apart from my zillions of
questions that's what I like to know, where should I start, what do I
need to know before hand

Well, I hope this gives some more info on my questions and I hope (some
of) you get me on my way.

Ton
> --
> Markus Gutschke                         Internet: markus@infoscape.com
> Infoscape, Inc                          Phone:    +1-415-537-3778
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> 
> Disclaimer: The above message represents my personal opinion; It does
>             not constitute an offical statement by Infoscape!
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-- 
Name: Ton Biegstraaten              Tel : +31152782467
Org.: TU Delft, Faculty ITS         Fax : +31152787141
      Zuidplantsoen 4               Mail: A.Biegstraaten@twi.tudelft.nl
      2628 BZ Delft, The Netherlands