Re: UNDI Driver and Grub architecture.

[Christoph Plattner]

Hello !

GRUB is mainly running in protected mode !
But it has functions to switch to realmode and back to call BIOS
interrupts.

I don't know, at the moment, if the kernel is booted from real mode,
but I think the kernel is started from protected mode, as GRUB can
interprete
the linux kernel image and knows, what Linux is. So it could be, that
GRUB
puts the Bios data to a special location (stuff that setup.S of the
linux 
kernel do) and jumps directly to the ELF kernel image.

Again, I don;t this know exactly here, but fact is, except for BIOS
calls,
GRUB runs in protected mode, but with an 1:1 memory mapping between the
physical and the virtual memory (AFAIK).

With friendly regards
        Christoph


Mark Buckaway wrote:
> 
> I'm not expert....so our company has hired a contractor to come up with
> an UNDI driver for GRUB. I know I have a driver a person here on the
> list came up with and apparently has working on a 3COM ethernet card.
> 
> Our contractor has come back to me and suggested an UNDI driver is not
> possible because GRUB uses protected mode for downloading the kernel and
> initrd. I have my doubts on this since what I know of grub, this is not
> true....and the Linux kernel starts up in real mode, does BIOS calls,
> etc. anyways....
> 
> Can someone please clearify for me if this is or is not the case?  Does
> GRUB use some protected mode magic to load the kernel/initrd into high
> ram? Our contractor is craving a custom solution for us which I'd like
> to avoid if possible.
> 
> Mark
> --
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