Re: [PATCH] THE LINUX/I386 BOOT PROTOCOL - Breaking the 256 limit (ping)

[John Coffman <johninsd@san.rr.com>]

LILO memory usage:

000600 - 001000 BIOS data check area.  Okay to overwrite.  LILO usage 
suppressed with command line "nobd" option.  There's also a config 
file option to suppress usage.

LILO typically loads at 9000:0000 up to the top of the EBDA.  Top of 
EBDA is determined by "int 12h."  Some BIOS's on add-in cards do not 
properly allocate the EBDA.  Use LILO Makefile option "BUG_SI_EBDA" 
to allocate extra EBDA for the BIOS.  If the BIOS data check area is 
created at boot time by LILO, then:

   >  lilo -T ebda

will tell you where LILO is loaded on your system.

--John


At 02:39 PM  Sunday 8/27/2006, H. Peter Anvin wrote:
> Andi Kleen wrote:
> > On Sunday 27 August 2006 21:32, H. Peter Anvin wrote:
> > > Andi Kleen wrote:
> > > > Just increasing that constant caused various lilo setups to not boot
> > > > anymore. I don't know who is actually to blame, just wanting to
> > > > point out that this "obvious" patch isn't actually that obvious.
> > > How would that even be possible (unless you recompiled LILO with 
> > > the new headers)?  There would be no difference in the memory 
> > > image at the point LILO hands off to the kernel.
> > AFAIK the problem was that some EDD data got overwritten.
> >
> > > In order to reproduce this we need some details about your 
> > > "various LILO setups", or this will remain as a source of cargo 
> > > cult programming.
> > You can search the mailing list archives, it's all in there if you don't
> > belive me.
>
> Found the references.  This seems to imply that EDD overwrites the 
> area used by LILO 22.6.1.  LILO 22.6.1 uses the new boot protocol, 
> with the full pointer, and seems to obey the spec as far as I can 
> read the code.  I'm going to try to run it in simulation and observe 
> the failure that way.
>
> However, something is still seriously out of joint.  The EDD data 
> actually overlays the setup code, not the bootsect code, and thus 
> there "shouldn't" be any way that this could interfere.  My best 
> guess at this time is that either the EDD code or LILO uses memory 
> it's not supposed to use, and the simulation should hopefully reveal that.
>
> Sorry if I seem snarky on this, but if we can't get to the bottom of 
> this we can't ever fix it.
>
>         -hpa


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