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Re: grub-probe fails to find PC partition due to Apple disklabel

From: Robert Millan
Subject: Re: grub-probe fails to find PC partition due to Apple disklabel
Date: Tue, 15 Apr 2008 15:15:47 +0200
User-agent: Mutt/1.5.13 (2006-08-11)

On Mon, Apr 14, 2008 at 01:20:49PM -0400, Pavel Roskin wrote:
> On Mon, 2008-04-14 at 10:21 -0400, Chris Knadle wrote:
> >    Instead of probing for partmaps in a particular order, it seems that
> > solving for this might best be done by probing for all of the possible
> > partmaps for the architecture and trying to figure out which one best fits. 
> > grub2's grub-probe is clearly already doing this; _however_, somehow the PC
> > partmap probe is subtly different depending on whether partmap/apple.c is
> > included in the search.
> Apple and PC partition maps can coexist.  The place occupied by the PC
> partition and the PC magic is not used by the Apple partition.
> The way to differentiate them would be to check at the first sector.  If
> it starts with 0x45 0x52, then it's an Apple partition.  A PC partition
> would have an executable entry there.  The Apple magic would decode to:
> inc    %bp
> push   %dx
> It's highly unlikely to be used in the first two instructions of the PC
> boot code.
> partmap/apple.c starts reading with the second sector (unsigned pos =
> GRUB_DISK_SECTOR_SIZE).  Perhaps it should read the first sector to
> check the magic.

Are you sure checking for the code part would be a good idea?  One could be
using i8088 bootstrap code in an Apple first sector, or vice-versa.

Btw, how does Linux handle this?  Maybe this issue has been beaten to death

Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call… if you are unable to speak?
(as seen on /.)

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