1.1 development release targets.

Eric W. Biederman ebiederman at lnxi.com
Thu Apr 17 01:27:01 CEST 2003

Steve Gehlbach <steve at nexpath.com> writes:

> >
> >>Does linuxbios in the current version support elfboot images from ide/floppy
> >>(directly, without etherboot)?  I guess if it does I don't see it.
> >  Yes.  The switch on the ``rom loader'' is the same on code, for
> > either the elf loader or the other one.
> >
> Thanks, I guess I never tried it since I needed to fiddle with the
> zero page parameters.

I have found that most of the time it is enough to simply tell the
kernel it has a VGA adapter.  And the rest it seems to handle
properly.  That is what I currently do in mkelfImage.

> >>One issue I have with elfboot images is the inability to dynamically pass
> >>parameters to the zero page (specifically the vga cursor location). I
> understand
> >>the idea of not locking the boot mechanism into the bios, but there are pros
> and
> >>cons.
> > As ron mentioned putting enough information in the LinuxBIOS table so
> > the code in mkelfImage can properly position the vga cursor location is
> > straight forward.
> >
> I don't understand.  Which linuxbios table are you referring to?  Is
> this a proposal or currently implemented?

Currently implemented. 

see src/include/boot/linuxbios_tables.h

The LinuxBIOS table on x86 is located near address 0, or around
0xF0000 - 0x100000.  It is a binary table of tagged data so it can be
grown and expanded while still retaining backwards compatibility.  It
is at a fixed address so we don't need to pass it explicitly to
anyone, but the data in it is position independent in case the table
needs to be moved.  In addition the table is composed of fixed size
data types so it can be used on dual 32/64 bit platforms without
surprises.  This is how we currently pass memory size information.

We have mptables and irq tables setup separately mostly for
historical reasons.  As we rework things in 1.1. for LinuxBIOS
to assign irqs I want to get those in there as well and generate
the other tables from the LinuxBIOS table.

Any binary loaded under LinuxBIOS can go out look for and
find the LinuxBIOS table.  We tried passing parameters explicitly
but the LinuxBIOS table is much more stable, for large vary amounts of
data.  Especially when you interpose something like etherboot in
between your BIOS and your loaded kernel.


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