[Nottingham] [Talk] Wednesday 07/04/2010 Install-fest & fix-it evening (Change of event!)

[Martin]

TJ wrote:
> I've been following the list recently and considering coming along to
> the meetings. My main motivation would be to meet like-minded people
> that love a bit of intense hacking on challenging bugs and code.

Welcome to the group!


> Seeing mention of the install/fix-it topic made me wonder if there's any
> interest in group examination/playing in the interests of enlightenment,
> with a bug [1] I'm currently working on.
> 
> It's very simple: GRUB2 [2] boot-strap code in the MBR is reporting
> "Geom Error" because the BIOS of the PC in question, an Acer Travelmate
> C100, is passing incorrect boot-device values. GRUB1 never had this
> problem. Affected users are replacing GRUB2 with Lilo to work around it,
> which is rather extreme.
> 
> The fix is simple: over-ride BIOS and force drive 0x80 (first hard disk)
> in the boot-strap code.
> 
> Achieving that fix is intense since:
> 
> 1) it is machine code/assembly language
> 2) there are less than 300 bytes for the complete boot-strap code

Now that is quite an intense squeeze...


Errr... Is there no BIOS update to fix the source BIOS problem?

And quite a naive question:

Can you not use (GRUB ?) boot-strap code to then boot-strap the patched
GRUB2 boot-strap located elsewhere?


Also note that usually, after the first two sectors, the remainder of
the first cylinder is left unused due to partitions normally starting on
cylinder boundaries only. Just watch out for some versions of RAID that
might also make use of that area...

That'll give you a lot more than just 300 bytes to play with.


Interesting but rather deep!!

You'll be very welcome along on Wed,

Cheers,
Martin