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 program is free software; you can redistribute it and/or modify it
   7  *      under the terms of the GNU General Public License as published by the
   8  *      Free Software Foundation version 2 of the License.
   9  */
  10
  11 #ifndef _GNU_SOURCE
  12 #define _GNU_SOURCE 1
  13 #endif
  14
  15 #ifdef HAVE_CONFIG_H
  16 #  include <config.h>
  17 #endif
  18
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23 #include <errno.h>
  24 #include <ctype.h>
  25
  26 #include "volume_id.h"
  27 #include "logging.h"
  28 #include "util.h"
  29 #include "msdos.h"
  30
  31 struct msdos_partition_entry {
  32         uint8_t         boot_ind;
  33         uint8_t         head;
  34         uint8_t         sector;
  35         uint8_t         cyl;
  36         uint8_t         sys_ind;
  37         uint8_t         end_head;
  38         uint8_t         end_sector;
  39         uint8_t         end_cyl;
  40         uint32_t        start_sect;
  41         uint32_t        nr_sects;
  42 } __attribute__((packed));
  43
  44 #define MSDOS_MAGIC                     "\x55\xaa"
  45 #define MSDOS_PARTTABLE_OFFSET          0x1be
  46 #define MSDOS_SIG_OFF                   0x1fe
  47 #define BSIZE                           0x200
  48 #define DOS_EXTENDED_PARTITION          0x05
  49 #define LINUX_EXTENDED_PARTITION        0x85
  50 #define WIN98_EXTENDED_PARTITION        0x0f
  51 #define LINUX_RAID_PARTITION            0xfd
  52 #define is_extended(type) \
  53         (type == DOS_EXTENDED_PARTITION ||      \
  54          type == WIN98_EXTENDED_PARTITION ||    \
  55          type == LINUX_EXTENDED_PARTITION)
  56 #define is_raid(type) \
  57         (type == LINUX_RAID_PARTITION)
  58
  59 int volume_id_probe_msdos_part_table(struct volume_id *id, uint64_t off)
  60 {
  61         const uint8_t *buf;
  62         int i;
  63         uint64_t poff;
  64         uint64_t plen;
  65         uint64_t extended = 0;
  66         uint64_t current;
  67         uint64_t next;
  68         int limit;
  69         int empty = 1;
  70         struct msdos_partition_entry *part;
  71         struct volume_id_partition *p;
  72
  73         dbg("probing at offset 0x%llx", (unsigned long long) off);
  74
  75         buf = volume_id_get_buffer(id, off, 0x200);
  76         if (buf == NULL)
  77                 return -1;
  78
  79         if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
  80                 return -1;
  81
  82         /* check flags on all entries for a valid partition table */
  83         part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
  84         for (i = 0; i < 4; i++) {
  85                 if (part[i].boot_ind != 0 &&
  86                     part[i].boot_ind != 0x80)
  87                         return -1;
  88
  89                 if (le32_to_cpu(part[i].nr_sects) != 0)
  90                         empty = 0;
  91         }
  92         if (empty == 1)
  93                 return -1;
  94
  95         if (id->partitions != NULL)
  96                 free(id->partitions);
  97         id->partitions = malloc(VOLUME_ID_PARTITIONS_MAX *
  98                                 sizeof(struct volume_id_partition));
  99         if (id->partitions == NULL)
 100                 return -1;
 101         memset(id->partitions, 0x00,
 102                VOLUME_ID_PARTITIONS_MAX * sizeof(struct volume_id_partition));
 103
 104         for (i = 0; i < 4; i++) {
 105                 poff = (uint64_t) le32_to_cpu(part[i].start_sect) * BSIZE;
 106                 plen = (uint64_t) le32_to_cpu(part[i].nr_sects) * BSIZE;
 107
 108                 if (plen == 0)
 109                         continue;
 110
 111                 p = &id->partitions[i];
 112
 113                 p->partition_type_raw = part[i].sys_ind;
 114
 115                 if (is_extended(part[i].sys_ind)) {
 116                         dbg("found extended partition at 0x%llx", (unsigned long long) poff);
 117                         volume_id_set_usage_part(p, VOLUME_ID_PARTITIONTABLE);
 118                         p->type = "msdos_extended_partition";
 119                         if (extended == 0)
 120                                 extended = off + poff;
 121                 } else {
 122                         dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 123                             part[i].sys_ind, (unsigned long long) poff, (unsigned long long) plen);
 124
 125                         if (is_raid(part[i].sys_ind))
 126                                 volume_id_set_usage_part(p, VOLUME_ID_RAID);
 127                         else
 128                                 volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 129                 }
 130
 131                 p->off = off + poff;
 132                 p->len = plen;
 133                 id->partition_count = i+1;
 134         }
 135
 136         next = extended;
 137         current = extended;
 138         limit = 50;
 139
 140         /* follow extended partition chain and add data partitions */
 141         while (next != 0) {
 142                 if (limit-- == 0) {
 143                         dbg("extended chain limit reached");
 144                         break;
 145                 }
 146
 147                 buf = volume_id_get_buffer(id, current, 0x200);
 148                 if (buf == NULL)
 149                         break;
 150
 151                 part = (struct msdos_partition_entry*) &buf[MSDOS_PARTTABLE_OFFSET];
 152
 153                 if (memcmp(&buf[MSDOS_SIG_OFF], MSDOS_MAGIC, 2) != 0)
 154                         break;
 155
 156                 next = 0;
 157
 158                 for (i = 0; i < 4; i++) {
 159                         poff = (uint64_t) le32_to_cpu(part[i].start_sect) * BSIZE;
 160                         plen = (uint64_t) le32_to_cpu(part[i].nr_sects) * BSIZE;
 161
 162                         if (plen == 0)
 163                                 continue;
 164
 165                         if (is_extended(part[i].sys_ind)) {
 166                                 dbg("found extended partition at 0x%llx", (unsigned long long) poff);
 167                                 if (next == 0)
 168                                         next = extended + poff;
 169                         } else {
 170                                 dbg("found 0x%x data partition at 0x%llx, len 0x%llx",
 171                                         part[i].sys_ind, (unsigned long long) poff, (unsigned long long) plen);
 172
 173                                 /* we always start at the 5th entry */
 174                                 while (id->partition_count < 4)
 175                                         volume_id_set_usage_part(&id->partitions[id->partition_count++], VOLUME_ID_UNUSED);
 176
 177                                 p = &id->partitions[id->partition_count];
 178
 179                                 if (is_raid(part[i].sys_ind))
 180                                         volume_id_set_usage_part(p, VOLUME_ID_RAID);
 181                                 else
 182                                         volume_id_set_usage_part(p, VOLUME_ID_UNPROBED);
 183
 184                                 p->off = current + poff;
 185                                 p->len = plen;
 186                                 id->partition_count++;
 187
 188                                 p->partition_type_raw = part[i].sys_ind;
 189
 190                                 if (id->partition_count >= VOLUME_ID_PARTITIONS_MAX) {
 191                                         dbg("too many partitions");
 192                                         next = 0;
 193                                 }
 194                         }
 195                 }
 196
 197                 current = next;
 198         }
 199
 200         volume_id_set_usage(id, VOLUME_ID_PARTITIONTABLE);
 201         id->type = "msdos_partition_table";
 202
 203         return 0;
 204 }