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). */
39
movw $INT13H_OFFSET(LOCAL (mapstart)), %bx
44
jz not_found /* DRV=DST => map end - drive not remapped, keep DL. */
48
jnz more_remaining /* Not found, but more remaining, loop. */
49
movb %ah, %dl /* Found - drive remapped, modify DL. */
55
/* If the call isn't ah=0x8 or ah=0x15 we must restore %dx. */
65
lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler))
71
/* Save new flags below %esp so the caller will recieve new flags. */
88
lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler))
93
/* Save %dx. So it won't be restored to original value. */
98
/* Far pointer to the old handler. Stored as a CS:IP in the style of real-mode
99
IVT entries (thus PI:SC in mem). */
100
VARIABLE(grub_drivemap_oldhandler)
104
/* This label MUST be at the end of the copied block, since the installer code
105
reserves additional space for mappings at runtime and copies them over it. */
108
VARIABLE(grub_drivemap_mapstart)