extras/volume_id/volume_id/msdos.c

   1 /*
   2  * volume_id - reads filesystem label and uuid
   3  *
   4  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
   5  *
   6  *      This library is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU Lesser General Public
   8  *      License as published by the Free Software Foundation; either
   9  *      version 2.1 of the License, or (at your option) any later version.
  10  *
  11  *      This library 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 GNU
  14  *      Lesser General Public License for more details.
  15  *
  16  *      You should have received a copy of the GNU Lesser General Public
  17  *      License along with this library; if not, write to the Free Software
  18  *      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  19  */
  20
  21 #ifndef _GNU_SOURCE
  22 #define _GNU_SOURCE 1
  23 #endif
  24
  25 #ifdef HAVE_CONFIG_H
  26 #  include <config.h>
  27 #endif
  28
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <unistd.h>
  32 #include <string.h>
  33 #include <errno.h>
  34 #include <ctype.h>
  35 #include <asm/types.h>
  36
  37 #include "volume_id.h"
  38 #include "logging.h"
  39 #include "util.h"
  40 #include "msdos.h"
  41
  42 struct msdos_partition_entry {
  43         __u8    boot_ind;
  44         __u8    head;
  45         __u8    sector;
  46         __u8    cyl;
  47         __u8    sys_ind;
  48         __u8    end_head;
  49         __u8    end_sector;
  50         __u8    end_cyl;
  51         __u32   start_sect;
  52         __u32   nr_sects;
  53 } __attribute__((packed));
  54
  55 #define MSDOS_MAGIC                     "\x55\xaa"
  56 #define MSDOS_PARTTABLE_OFFSET          0x1be
  57 #define MSDOS_SIG_OFF                   0x1fe
  58 #define BSIZE                           0x200
  59 #define DOS_EXTENDED_PARTITION          0x05
  60 #define LINUX_EXTENDED_PARTITION        0x85
  61 #define WIN98_EXTENDED_PARTITION        0x0f
  62 #define LINUX_RAID_PARTITION            0xfd
  63 #define is_extended(type) \
  64         (type == DOS_EXTENDED_PARTITION ||      \
  65          type == WIN98_EXTENDED_PARTITION ||    \
  66          type == LINUX_EXTENDED_PARTITION)
  67 #define is_raid(type) \
  68         (type == LINUX_RAID_PARTITION)
  69
  70 int volume_id_probe_msdos_part_table(struct volume_id *id, __u64 off)
  71 {
  72         const __u8 *buf;
  73         int i;
  74         __u64 poff;
  75         __u64 plen;
  76         __u64 extended = 0;
  77         __u64 current;
  78         __u64 next;
  79         int limit;
  80         int empty = 1;
  81         struct msdos_partition_entry *part;
  82         struct volume_id_partition *p;
  83
  84         dbg("probing at offset %llu", off);
  85
  86         buf = volume_id_get_buffer(id, off, 0x200);
  87         if (buf == NULL)
  88                 return -1;
  89
  90         if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
  91                 return -1;
  92
  93         /* check flags on all entries for a valid partition table */
  94         part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
  95         for (i = 0; i < 4; i++) {
  96                 if (part[i].boot_ind != 0 &&
  97                     part[i].boot_ind != 0x80)
  98                         return -1;
  99
 100                 if (le32_to_cpu(part[i].nr_sects) != 0)
 101                         empty = 0;
 102         }
 103         if (empty == 1)
 104                 return -1;
 105
 106         if (id->partitions != NULL)
 107                 free(id->partitions);
 108         id->partitions = malloc(VOLUME_ID_PARTITIONS_MAX *
 109                                 sizeof(struct volume_id_partition));
 110         if (id->partitions == NULL)
 111                 return -1;
 112         memset(id->partitions, 0x00,
 113                VOLUME_ID_PARTITIONS_MAX * sizeof(struct volume_id_partition));
 114
 115         for (i = 0; i < 4; i++) {
 116                 poff = (__u64) le32_to_cpu(part[i].start_sect) * BSIZE;
 117                 plen = (__u64) le32_to_cpu(part[i].nr_sects) * BSIZE;
 118
 119                 if (plen == 0)
 120                         continue;
 121
 122                 p = &id->partitions[i];
 123
 124                 p->partition_type_raw = part[i].sys_ind;
 125
 126                 if (is_extended(part[i].sys_ind)) {
 127                         dbg("found extended partition at 0x%llx", poff);
 128                         volume_id_set_usage_part(p, VOLUME_ID_PARTITIONTABLE);
 129                         p->type = "msdos_extended_partition";
 130                         if (extended == 0)
 131                                 extended = off + poff;
 132                 } else {
 133                         dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 134                             part[i].sys_ind, poff, plen);
 135
 136                         if (is_raid(part[i].sys_ind))
 137                                 volume_id_set_usage_part(p, VOLUME_ID_RAID);
 138                         else
 139                                 volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 140                 }
 141
 142                 p->off = off + poff;
 143                 p->len = plen;
 144                 id->partition_count = i+1;
 145         }
 146
 147         next = extended;
 148         current = extended;
 149         limit = 50;
 150
 151         /* follow extended partition chain and add data partitions */
 152         while (next != 0) {
 153                 if (limit-- == 0) {
 154                         dbg("extended chain limit reached");
 155                         break;
 156                 }
 157
 158                 buf = volume_id_get_buffer(id, current, 0x200);
 159                 if (buf == NULL)
 160                         break;
 161
 162                 part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
 163
 164                 if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
 165                         break;
 166
 167                 next = 0;
 168
 169                 for (i = 0; i < 4; i++) {
 170                         poff = (__u64) le32_to_cpu(part[i].start_sect) * BSIZE;
 171                         plen = (__u64) le32_to_cpu(part[i].nr_sects) * BSIZE;
 172
 173                         if (plen == 0)
 174                                 continue;
 175
 176                         if (is_extended(part[i].sys_ind)) {
 177                                 dbg("found extended partition at 0x%llx", poff);
 178                                 if (next == 0)
 179                                         next = extended + poff;
 180                         } else {
 181                                 dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 182                                         part[i].sys_ind, poff, plen);
 183
 184                                 /* we always start at the 5th entry */
 185                                 while (id->partition_count < 4)
 186                                         volume_id_set_usage_part(&id->partitions[id->partition_count++], VOLUME_ID_UNUSED);
 187
 188                                 p = &id->partitions[id->partition_count];
 189
 190                                 if (is_raid(part[i].sys_ind))
 191                                         volume_id_set_usage_part(p, VOLUME_ID_RAID);
 192                                 else
 193                                         volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 194
 195                                 p->off = current + poff;
 196                                 p->len = plen;
 197                                 id->partition_count++;
 198
 199                                 p->partition_type_raw = part[i].sys_ind;
 200
 201                                 if (id->partition_count >= VOLUME_ID_PARTITIONS_MAX) {
 202                                         dbg("too many partitions");
 203                                         next = 0;
 204                                 }
 205                         }
 206                 }
 207
 208                 current = next;
 209         }
 210
 211         volume_id_set_usage(id, VOLUME_ID_PARTITIONTABLE);
 212         id->type = "msdos_partition_table";
 213
 214         return 0;
 215 }