1 /* drivemap_int13h.S - interrupt handler for the BIOS drive remapper */
3 * GRUB -- GRand Unified Bootloader
4 * Copyright (C) 2008, 2009 Free Software Foundation, Inc.
6 * GRUB is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
11 * GRUB is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
20 #include <grub/symbol.h>
22 #define INT13H_OFFSET(x) ((x) - LOCAL (base))
26 /* Copy starts here. When deployed, this code must be segment-aligned. */
28 /* The replacement int13 handler. Preserve all registers. */
29 FUNCTION(grub_drivemap_handler)
31 /* Save %dx for future restore. */
33 /* Push flags. Used to simulate interrupt with original flags. */
36 /* Map the drive number (always in DL). */
40 LOCAL(mapstart_offset) = INT13H_OFFSET(LOCAL (mapstart))
41 movw $LOCAL(mapstart_offset), %bx
43 movw $INT13H_OFFSET(LOCAL (mapstart)), %bx
49 jz not_found /* DRV=DST => map end - drive not remapped, keep DL. */
53 jnz more_remaining /* Not found, but more remaining, loop. */
54 movb %ah, %dl /* Found - drive remapped, modify DL. */
60 /* If the call isn't ah=0x8 or ah=0x15 we must restore %dx. */
71 LOCAL(oldhandler_offset) = INT13H_OFFSET (LOCAL (oldhandler))
72 lcall *%cs:LOCAL(oldhandler_offset)
74 lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler))
81 /* Save new flags below %esp so the caller will recieve new flags. */
99 lcall *%cs:LOCAL(oldhandler_offset)
101 lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler))
107 /* Save %dx. So it won't be restored to original value. */
112 /* Far pointer to the old handler. Stored as a CS:IP in the style of real-mode
113 IVT entries (thus PI:SC in mem). */
114 VARIABLE(grub_drivemap_oldhandler)
118 /* This label MUST be at the end of the copied block, since the installer code
119 reserves additional space for mappings at runtime and copies them over it. */
122 VARIABLE(grub_drivemap_mapstart)