2008-02-03 Yoshinori K. Okuji <okuji@enbug.org>

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.

kern/i386/pc/startup.S

@@ -1,6 +1,6 @@
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 1999,2000,2001,2002,2003,2005,2006,2007 Free Software Foundation, Inc.
+ *  Copyright (C) 1999,2000,2001,2002,2003,2005,2006,2007,2008 Free Software Foundation, Inc.
  *
  *  GRUB is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -162,6 +162,7 @@ multiboot_trampoline:
 	movl	%ebx, EXT_C(grub_install_bsd_part)
 2:
 	shrl	$24, %edx
+        movb    $0xFF, %dh
 	/* enter the usual booting */
 	call	prot_to_real
 	.code16
@@ -182,8 +183,9 @@ codestart:
 
 	sti		/* we're safe again */
 
-	/* save boot drive reference */
+	/* save boot and root drive references */
 	ADDR32	movb	%dl, EXT_C(grub_boot_drive)
+	ADDR32	movb	%dh, EXT_C(grub_root_drive)
 
 	/* reset disk system (%ah = 0) */
 	int	$0x13
@@ -255,6 +257,9 @@ codestart:
 VARIABLE(grub_boot_drive)
 	.long	0
 
+VARIABLE(grub_root_drive)
+	.long	0
+
 VARIABLE(grub_start_addr)
 	.long	START_SYMBOL