2009-05-14 01:23:49 +00:00
|
|
|
/* drivemap_int13h.S - interrupt handler for the BIOS drive remapper */
|
|
|
|
|
/*
|
|
|
|
|
* GRUB -- GRand Unified Bootloader
|
|
|
|
|
* Copyright (C) 2008, 2009 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
|
|
|
|
|
* the Free Software Foundation, either version 3 of the License, or
|
|
|
|
|
* (at your option) any later version.
|
|
|
|
|
*
|
|
|
|
|
* GRUB is distributed in the hope that it will be useful,
|
|
|
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
|
|
|
* GNU General Public License for more details.
|
|
|
|
|
*
|
|
|
|
|
* You should have received a copy of the GNU General Public License
|
|
|
|
|
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#include <grub/symbol.h>
|
|
|
|
|
|
2009-05-14 21:56:46 +00:00
|
|
|
#define INT13H_OFFSET(x) ((x) - EXT_C(grub_drivemap_handler))
|
2009-05-14 01:23:49 +00:00
|
|
|
|
|
|
|
|
.code16
|
|
|
|
|
|
|
|
|
|
/* Copy starts here. When deployed, this code must be segment-aligned. */
|
|
|
|
|
|
|
|
|
|
/* The replacement int13 handler. The code must be position independent.
|
|
|
|
|
Preserve all registers. */
|
|
|
|
|
FUNCTION(grub_drivemap_handler)
|
|
|
|
|
/* Map the drive number (always in DL). */
|
|
|
|
|
push %ax
|
|
|
|
|
push %bx
|
2009-05-14 21:56:46 +00:00
|
|
|
movw $INT13H_OFFSET(EXT_C(grub_drivemap_mapstart)), %bx
|
2009-05-14 01:23:49 +00:00
|
|
|
|
|
|
|
|
more_remaining:
|
|
|
|
|
movw %cs:(%bx), %ax
|
|
|
|
|
cmpb %ah, %al
|
|
|
|
|
jz not_found /* DRV=DST => map end - drive not remapped, keep DL. */
|
|
|
|
|
inc %bx
|
|
|
|
|
inc %bx
|
2009-05-14 13:43:13 +00:00
|
|
|
cmpb %dl, %al
|
|
|
|
|
jnz more_remaining /* Not found, but more remaining, loop. */
|
|
|
|
|
movb %ah, %dl /* Found - drive remapped, modify DL. */
|
2009-05-14 01:23:49 +00:00
|
|
|
|
|
|
|
|
not_found:
|
|
|
|
|
pop %bx
|
|
|
|
|
pop %ax
|
|
|
|
|
|
|
|
|
|
/* Upon arrival to this point the stack must be exactly like at entry.
|
|
|
|
|
This long jump will transfer the caller's stack to the old INT13
|
|
|
|
|
handler, thus making it return directly to the original caller. */
|
|
|
|
|
.byte 0xea
|
|
|
|
|
|
|
|
|
|
/* Far pointer to the old handler. Stored as a CS:IP in the style of real-mode
|
|
|
|
|
IVT entries (thus PI:SC in mem). */
|
|
|
|
|
VARIABLE(grub_drivemap_oldhandler)
|
|
|
|
|
.word 0x0, 0x0
|
|
|
|
|
|
|
|
|
|
/* This label MUST be at the end of the copied block, since the installer code
|
|
|
|
|
reserves additional space for mappings at runtime and copies them over it. */
|
|
|
|
|
.align 2
|
|
|
|
|
VARIABLE(grub_drivemap_mapstart)
|
