grub/partmap/msdos.c
Vladimir 'phcoder' Serbinenko c9ea504d25 merge mainline into nestpart
2010-03-26 15:44:13 +01:00

152 lines
4.1 KiB
C
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/* pc.c - Read PC style partition tables. */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2002,2004,2005,2006,2007,2008,2009 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/partition.h>
#include <grub/msdos_partition.h>
#include <grub/disk.h>
#include <grub/mm.h>
#include <grub/misc.h>
#include <grub/dl.h>
static struct grub_partition_map grub_msdos_partition_map;
static grub_err_t
pc_partition_map_iterate (grub_disk_t disk,
int (*hook) (grub_disk_t disk,
const grub_partition_t partition))
{
struct grub_partition p;
struct grub_msdos_partition_mbr mbr;
int labeln = 0;
grub_disk_addr_t lastaddr;
grub_disk_addr_t ext_offset;
p.offset = 0;
ext_offset = 0;
p.number = -1;
p.partmap = &grub_msdos_partition_map;
/* Any value different than `p.offset' will satisfy the check during
first loop. */
lastaddr = !p.offset;
while (1)
{
int i;
struct grub_msdos_partition_entry *e;
/* Read the MBR. */
if (grub_disk_read (disk, p.offset, 0, sizeof (mbr), &mbr))
goto finish;
/* This is our loop-detection algorithm. It works the following way:
It saves last position which was a power of two. Then it compares the
saved value with a current one. This way it's guaranteed that the loop
will be broken by at most third walk.
*/
if (labeln && lastaddr == p.offset)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");
labeln++;
if ((labeln & (labeln - 1)) == 0)
lastaddr = p.offset;
/* Check if it is valid. */
if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");
for (i = 0; i < 4; i++)
if (mbr.entries[i].flag & 0x7f)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");
/* Analyze DOS partitions. */
for (p.index = 0; p.index < 4; p.index++)
{
e = mbr.entries + p.index;
p.start = p.offset + grub_le_to_cpu32 (e->start);
p.len = grub_le_to_cpu32 (e->length);
grub_dprintf ("partition",
"partition %d: flag 0x%x, type 0x%x, start 0x%llx, len 0x%llx\n",
p.index, e->flag, e->type,
(unsigned long long) p.start,
(unsigned long long) p.len);
/* If this is a GPT partition, this MBR is just a dummy. */
if (e->type == GRUB_PC_PARTITION_TYPE_GPT_DISK && p.index == 0)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "dummy mbr");
/* If this partition is a normal one, call the hook. */
if (! grub_msdos_partition_is_empty (e->type)
&& ! grub_msdos_partition_is_extended (e->type))
{
p.number++;
if (hook (disk, &p))
return grub_errno;
}
else if (p.number < 4)
/* If this partition is a logical one, shouldn't increase the
partition number. */
p.number++;
}
/* Find an extended partition. */
for (i = 0; i < 4; i++)
{
e = mbr.entries + i;
if (grub_msdos_partition_is_extended (e->type))
{
p.offset = ext_offset + grub_le_to_cpu32 (e->start);
if (! ext_offset)
ext_offset = p.offset;
break;
}
}
/* If no extended partition, the end. */
if (i == 4)
break;
}
finish:
return grub_errno;
}
/* Partition map type. */
static struct grub_partition_map grub_msdos_partition_map =
{
.name = "msdos",
.iterate = pc_partition_map_iterate,
};
GRUB_MOD_INIT(part_msdos)
{
grub_partition_map_register (&grub_msdos_partition_map);
}
GRUB_MOD_FINI(part_msdos)
{
grub_partition_map_unregister (&grub_msdos_partition_map);
}