Linux-kernel mailing list archive 1999-34,: Re: Kernels > 1M

# Re: Kernels > 1M

Zack Weinberg (zack@bitmover.com)
Sun, 22 Aug 1999 16:09:58 -0700

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Mirian Crzig Lennox wrote:
> 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.

I know - and /boot does do a lot of the work that our setup.S does.
But it's written mostly in C and it does everything from protected
mode. Look at /usr/src/sys/i386/boot/biosboot - my copy is from
FreeBSD 3.2, but the code hasn't changed much since 1992.

They do it, we can do it too.

zw

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