Re: Kernels > 1M

Mirian Crzig Lennox (lennox@alcita.com)
22 Aug 1999 18:59:18 -0400


Zack Weinberg <zack@bitmover.com> writes:
> >
> > The 16-bit setup code *has* to run in real mode... that's the only
> > reason it's 16 bit. As far as the APM BIOS, I'm sure you're aware of
> > the number of problems caused by APM BIOSes that don't like to be called
> > the way Linux calls them?
>
> I'll defer to you since you know more about x86 than me, but I don't
> see why it's necessary to do any of the setup.S sequence in real
> mode. Especially since the BSDs seem to manage it in protected mode
> fine.

BSD uses a two-stage bootloader. The second stage is usually a file
called "boot" in the root directory of the root partition which is
"tied" to the real-mode bootstrap by a utility program in the same way
that vmlinuz'es are tied to the lilo bootstrap via the lilo program.
This allows more flexibility because the second stage boot loader only
needs to be installed once (since it knows how to walk the filesystem
to load whatever kernel you want) HOWEVER it can't do all of the
advanced things that linux needs, like initial ramdisk loading.

-- 
Mirian Crzig Lennox                                Systems Anarchist
              Invest in America -- buy a Congressman!

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