Add support for having a grub directory in a different drive. This
is still only the data handling part.
* kern/i386/pc/startup.S (multiboot_trampoline): Set %dh to 0xFF.
(codestart): Save %dh in GRUB_ROOT_DRIVE.
(grub_root_drive): New variable.
* kern/i386/pc/init.c (make_install_device): Use GRUB_ROOT_DRIVE
instead of GRUB_BOOT_DRIVE to construct a device name. Set
GRUB_ROOT_DRIVE to GRUB_BOOT_DRIVE if it is 0xFF, otherwise use it
as it was.
* include/grub/i386/pc/kernel.h (grub_root_drive): New prototype.
* include/grub/i386/pc/boot.h (GRUB_BOOT_MACHINE_ROOT_DRIVE): New
macro.
(GRUB_BOOT_MACHINE_DRIVE_CHECK): Set to 0x4f.
* boot/i386/pc/pxeboot.S (_start): Set %dh to 0xFF. For now, this
is bogus, because PXE booting does not specify any drive
correctly.
* boot/i386/pc/lnxboot.S (reg_edx): Set the second byte to 0xFF. I
am not sure if this is really correct.
* boot/i386/pc/cdboot.S: Set %dh to 0xFF, because the root drive
is always identical to the boot drive when booting from a CD.
* boot/i386/pc/boot.S (MOV_MEM_TO_AL): Removed. Not needed any
longer.
(root_drive): New variable.
(real_start): Unconditionally set %dh to ROOT_DRIVE.
(setup_sectors): Push %dx right after popping it, because %dh will
be modified later.
(copy_buffer): Restore %dx.
9be6b98b6f