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