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
  36 #include "volume_id.h"
  37 #include "logging.h"
  38 #include "util.h"
  39 #include "msdos.h"
  40
  41 struct msdos_partition_entry {
  42         uint8_t         boot_ind;
  43         uint8_t         head;
  44         uint8_t         sector;
  45         uint8_t         cyl;
  46         uint8_t         sys_ind;
  47         uint8_t         end_head;
  48         uint8_t         end_sector;
  49         uint8_t         end_cyl;
  50         uint32_t        start_sect;
  51         uint32_t        nr_sects;
  52 } __attribute__((packed));
  53
  54 #define MSDOS_MAGIC                     "\x55\xaa"
  55 #define MSDOS_PARTTABLE_OFFSET          0x1be
  56 #define MSDOS_SIG_OFF                   0x1fe
  57 #define BSIZE                           0x200
  58 #define DOS_EXTENDED_PARTITION          0x05
  59 #define LINUX_EXTENDED_PARTITION        0x85
  60 #define WIN98_EXTENDED_PARTITION        0x0f
  61 #define LINUX_RAID_PARTITION            0xfd
  62 #define is_extended(type) \
  63         (type == DOS_EXTENDED_PARTITION ||      \
  64          type == WIN98_EXTENDED_PARTITION ||    \
  65          type == LINUX_EXTENDED_PARTITION)
  66 #define is_raid(type) \
  67         (type == LINUX_RAID_PARTITION)
  68
  69 int volume_id_probe_msdos_part_table(struct volume_id *id, uint64_t off)
  70 {
  71         const uint8_t *buf;
  72         int i;
  73         uint64_t poff;
  74         uint64_t plen;
  75         uint64_t extended = 0;
  76         uint64_t current;
  77         uint64_t next;
  78         int limit;
  79         int empty = 1;
  80         struct msdos_partition_entry *part;
  81         struct volume_id_partition *p;
  82
  83         dbg("probing at offset 0x%llx", (unsigned long long) off);
  84
  85         buf = volume_id_get_buffer(id, off, 0x200);
  86         if (buf == NULL)
  87                 return -1;
  88
  89         if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
  90                 return -1;
  91
  92         /* check flags on all entries for a valid partition table */
  93         part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
  94         for (i = 0; i < 4; i++) {
  95                 if (part[i].boot_ind != 0 &&
  96                     part[i].boot_ind != 0x80)
  97                         return -1;
  98
  99                 if (le32_to_cpu(part[i].nr_sects) != 0)
 100                         empty = 0;
 101         }
 102         if (empty == 1)
 103                 return -1;
 104
 105         if (id->partitions != NULL)
 106                 free(id->partitions);
 107         id->partitions = malloc(VOLUME_ID_PARTITIONS_MAX *
 108                                 sizeof(struct volume_id_partition));
 109         if (id->partitions == NULL)
 110                 return -1;
 111         memset(id->partitions, 0x00,
 112                VOLUME_ID_PARTITIONS_MAX * sizeof(struct volume_id_partition));
 113
 114         for (i = 0; i < 4; i++) {
 115                 poff = (uint64_t) le32_to_cpu(part[i].start_sect) * BSIZE;
 116                 plen = (uint64_t) le32_to_cpu(part[i].nr_sects) * BSIZE;
 117
 118                 if (plen == 0)
 119                         continue;
 120
 121                 p = &id->partitions[i];
 122
 123                 p->partition_type_raw = part[i].sys_ind;
 124
 125                 if (is_extended(part[i].sys_ind)) {
 126                         dbg("found extended partition at 0x%llx", (unsigned long long) poff);
 127                         volume_id_set_usage_part(p, VOLUME_ID_PARTITIONTABLE);
 128                         p->type = "msdos_extended_partition";
 129                         if (extended == 0)
 130                                 extended = off + poff;
 131                 } else {
 132                         dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 133                             part[i].sys_ind, (unsigned long long) poff, (unsigned long long) plen);
 134
 135                         if (is_raid(part[i].sys_ind))
 136                                 volume_id_set_usage_part(p, VOLUME_ID_RAID);
 137                         else
 138                                 volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 139                 }
 140
 141                 p->off = off + poff;
 142                 p->len = plen;
 143                 id->partition_count = i+1;
 144         }
 145
 146         next = extended;
 147         current = extended;
 148         limit = 50;
 149
 150         /* follow extended partition chain and add data partitions */
 151         while (next != 0) {
 152                 if (limit-- == 0) {
 153                         dbg("extended chain limit reached");
 154                         break;
 155                 }
 156
 157                 buf = volume_id_get_buffer(id, current, 0x200);
 158                 if (buf == NULL)
 159                         break;
 160
 161                 part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
 162
 163                 if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
 164                         break;
 165
 166                 next = 0;
 167
 168                 for (i = 0; i < 4; i++) {
 169                         poff = (uint64_t) le32_to_cpu(part[i].start_sect) * BSIZE;
 170                         plen = (uint64_t) le32_to_cpu(part[i].nr_sects) * BSIZE;
 171
 172                         if (plen == 0)
 173                                 continue;
 174
 175                         if (is_extended(part[i].sys_ind)) {
 176                                 dbg("found extended partition at 0x%llx", (unsigned long long) poff);
 177                                 if (next == 0)
 178                                         next = extended + poff;
 179                         } else {
 180                                 dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 181                                         part[i].sys_ind, (unsigned long long) poff, (unsigned long long) plen);
 182
 183                                 /* we always start at the 5th entry */
 184                                 while (id->partition_count < 4)
 185                                         volume_id_set_usage_part(&id->partitions[id->partition_count++], VOLUME_ID_UNUSED);
 186
 187                                 p = &id->partitions[id->partition_count];
 188
 189                                 if (is_raid(part[i].sys_ind))
 190                                         volume_id_set_usage_part(p, VOLUME_ID_RAID);
 191                                 else
 192                                         volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 193
 194                                 p->off = current + poff;
 195                                 p->len = plen;
 196                                 id->partition_count++;
 197
 198                                 p->partition_type_raw = part[i].sys_ind;
 199
 200                                 if (id->partition_count >= VOLUME_ID_PARTITIONS_MAX) {
 201                                         dbg("too many partitions");
 202                                         next = 0;
 203                                 }
 204                         }
 205                 }
 206
 207                 current = next;
 208         }
 209
 210         volume_id_set_usage(id, VOLUME_ID_PARTITIONTABLE);
 211         id->type = "msdos_partition_table";
 212
 213         return 0;
 214 }