Re: Bug#584846: Detects only 64MB and fails to boot on Intel GreenCity board if e820 hooked by GRUB2

From: Josh Triplett
Date: Sat Jun 12 2010 - 20:08:17 EST

On Sat, Jun 12, 2010 at 04:02:44PM -0700, H. Peter Anvin wrote:
> On 06/12/2010 03:26 PM, Josh Triplett wrote:
> >
> > Everything looks identical except for the region GRUB hooked right below
> > the first reserved region; the unhooked version has available memory
> > from 0-0x9cbf0, and the hooked version has available memory from
> > 0-0x9cba0, then reserved from 0x9cba0-0x9cbec, then 4 bytes of available
> > memory, and then the same reserved region as before.
> Actually... are both these done by chainloading Grub (with and without
> mapping), or is the unhooked done without chainloading Grub at all?
> To me it looks like something is chaining INT 15h even in the
> "unchained" case...

The "unhooked" case still chainloaded from GRUB, just without calling
drivemap and thus without hooking anything. I can test without
chainloading from GRUB, though to the best of my knowledge GRUB doesn't
hook int 15 unless it needs to intercept e820 (and e801 and 88).

- Josh Triplett
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