This does not work on native EFI grub (i.e. when grub platform is
x86_64-efi or i386-efi). You can use EFI chainloading to start Mac OS
X
bootloader instead of trying to load kernel directly. Somehing like
To load OSX, use the following section in grub.cfg:
menuentry "MacOSX" {
# Search the root device for Mac OS X's loader.
search --file --no-floppy --set=root /usr/standalone/i386/boot.efi
# chainload the loader, pass parameters like -v directly
chainloader (${root})/usr/standalone/i386/boot.efi #-v
}
I think boot.efi is also present under some other path, I forgot. The
above is from Ubuntu page.