[patch] rough Mac OS X loader

[Hollis Blanchard]

I've been working on a Mac OS X loader for GRUB. During the usual OS X 
boot process, the firmware loads the BootX bootloader (which is a 
hybrid CHRP script and XCOFF binary), which has a Mach-O loader and 
loads the OS X Mach kernel.

Rather than trying to load and run the Mach kernel directly, I chose to 
focus on the BootX bootloader, since it seems to do a fair amount of 
setup work that I would rather not duplicate in GRUB. Also important: 
if OS X is ever updated (for example, the parameter-passing mechanism 
between BootX and the kernel), we would need to track those changes, 
which is a lot more long-term maintenance.

Unfortunately, BootX attempts to claim all memory from 0 to 96MiB, 
which conflicts with GRUB running in this area. To get around that 
problem, I install a trampoline just above 96MiB which releases all of 
GRUB's memory and jumps into BootX. It's a bit of a hack, and for 
example if the code being copied exceeds some fixed size (currently 
0x200 bytes) things will fail mysteriously. I'm open to suggestions on 
that problem.

I'm afraid I don't know if this code works yet. Because the current 
HFS+ driver doesn't support the HFS wrapper found on all Apple 
filesystems, I can't boot from an HFS+ installation. I've copied BootX 
to a plain HFS partition, and that works somewhat (I expect it fails 
when it cannot find /mach_kernel). I'm relatively optimistic, and I'm 
working on the HFS wrapper support now.

There are a few rough edges still, but if there are no comments I will 
be checking this patch in largely unchanged some day.

-Hollis

macosx.txt
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