On Wed, Aug 04, 2010 at 10:07:24AM -0500, Anthony Liguori wrote:
> On 08/04/2010 10:01 AM, Gleb Natapov wrote:
> >
> >Hm, may be. I read seabios code differently, but may be I misread it.
>
> The BIOS Boot Specification spells it all out pretty clearly.
>
I have the spec. Isn't this enough to be an expert? Or do you mean I
should read it too?
> >>If a ROM needs memory after the init function, it needs to use the
> >>traditional tricks to allocate long term memory and the most popular
> >>one is modifying the e820 tables.
> >>
> >e820 has no in memory format,
>
> Indeed.
>
> >>See src/arch/i386/firmware/pcbios/e820mangler.S in gPXE.
> >so this ugly code intercepts int15 and mangle result. OMG. How this can
> >even work if more then two ROMs want to do that?
>
> You have to save the old handlers and invoke them. Where do you
> save the old handlers? There's tricks you can do by trying to use
> some unused vectors and also temporarily using the stack.
>
> But basically, yeah, I'm amazed every time I see a PC boot that it
> all actually works :-)
>
Heh.
--
Gleb.
