git.maemo.org Git - busybox4maemo/blob - util-linux/volume_id/fat.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 #include "volume_id_internal.h"
  22
  23 #define FAT12_MAX                       0xff5
  24 #define FAT16_MAX                       0xfff5
  25 #define FAT_ATTR_VOLUME_ID              0x08
  26 #define FAT_ATTR_DIR                    0x10
  27 #define FAT_ATTR_LONG_NAME              0x0f
  28 #define FAT_ATTR_MASK                   0x3f
  29 #define FAT_ENTRY_FREE                  0xe5
  30
  31 struct vfat_super_block {
  32         uint8_t         boot_jump[3];
  33         uint8_t         sysid[8];
  34         uint16_t        sector_size;
  35         uint8_t         sectors_per_cluster;
  36         uint16_t        reserved;
  37         uint8_t         fats;
  38         uint16_t        dir_entries;
  39         uint16_t        sectors;
  40         uint8_t         media;
  41         uint16_t        fat_length;
  42         uint16_t        secs_track;
  43         uint16_t        heads;
  44         uint32_t        hidden;
  45         uint32_t        total_sect;
  46         union {
  47                 struct fat_super_block {
  48                         uint8_t         unknown[3];
  49                         uint8_t         serno[4];
  50                         uint8_t         label[11];
  51                         uint8_t         magic[8];
  52                         uint8_t         dummy2[192];
  53                         uint8_t         pmagic[2];
  54                 } __attribute__((__packed__)) fat;
  55                 struct fat32_super_block {
  56                         uint32_t        fat32_length;
  57                         uint16_t        flags;
  58                         uint8_t         version[2];
  59                         uint32_t        root_cluster;
  60                         uint16_t        insfo_sector;
  61                         uint16_t        backup_boot;
  62                         uint16_t        reserved2[6];
  63                         uint8_t         unknown[3];
  64                         uint8_t         serno[4];
  65                         uint8_t         label[11];
  66                         uint8_t         magic[8];
  67                         uint8_t         dummy2[164];
  68                         uint8_t         pmagic[2];
  69                 } __attribute__((__packed__)) fat32;
  70         } __attribute__((__packed__)) type;
  71 } __attribute__((__packed__));
  72
  73 struct vfat_dir_entry {
  74         uint8_t         name[11];
  75         uint8_t         attr;
  76         uint16_t        time_creat;
  77         uint16_t        date_creat;
  78         uint16_t        time_acc;
  79         uint16_t        date_acc;
  80         uint16_t        cluster_high;
  81         uint16_t        time_write;
  82         uint16_t        date_write;
  83         uint16_t        cluster_low;
  84         uint32_t        size;
  85 } __attribute__((__packed__));
  86
  87 static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
  88 {
  89         unsigned i;
  90
  91         for (i = 0; i < count; i++) {
  92                 /* end marker */
  93                 if (dir[i].name[0] == 0x00) {
  94                         dbg("end of dir");
  95                         break;
  96                 }
  97
  98                 /* empty entry */
  99                 if (dir[i].name[0] == FAT_ENTRY_FREE)
 100                         continue;
 101
 102                 /* long name */
 103                 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
 104                         continue;
 105
 106                 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
 107                         /* labels do not have file data */
 108                         if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
 109                                 continue;
 110
 111                         dbg("found ATTR_VOLUME_ID id in root dir");
 112                         return dir[i].name;
 113                 }
 114
 115                 dbg("skip dir entry");
 116         }
 117
 118         return NULL;
 119 }
 120
 121 int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
 122 {
 123         struct vfat_super_block *vs;
 124         struct vfat_dir_entry *dir;
 125         uint16_t sector_size;
 126         uint16_t dir_entries;
 127         uint32_t sect_count;
 128         uint16_t reserved;
 129         uint32_t fat_size;
 130         uint32_t root_cluster;
 131         uint32_t dir_size;
 132         uint32_t cluster_count;
 133         uint32_t fat_length;
 134         uint64_t root_start;
 135         uint32_t start_data_sect;
 136         uint16_t root_dir_entries;
 137         uint8_t *buf;
 138         uint32_t buf_size;
 139         uint8_t *label = NULL;
 140         uint32_t next;
 141         int maxloop;
 142
 143         dbg("probing at offset 0x%llx", (unsigned long long) off);
 144
 145         vs = volume_id_get_buffer(id, off, 0x200);
 146         if (vs == NULL)
 147                 return -1;
 148
 149         /* believe only that's fat, don't trust the version
 150          * the cluster_count will tell us
 151          */
 152         if (memcmp(vs->sysid, "NTFS", 4) == 0)
 153                 return -1;
 154
 155         if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
 156                 goto valid;
 157
 158         if (memcmp(vs->type.fat32.magic, "FAT32   ", 8) == 0)
 159                 goto valid;
 160
 161         if (memcmp(vs->type.fat.magic, "FAT16   ", 8) == 0)
 162                 goto valid;
 163
 164         if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
 165                 goto valid;
 166
 167         if (memcmp(vs->type.fat.magic, "FAT12   ", 8) == 0)
 168                 goto valid;
 169
 170         /*
 171          * There are old floppies out there without a magic, so we check
 172          * for well known values and guess if it's a fat volume
 173          */
 174
 175         /* boot jump address check */
 176         if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
 177              vs->boot_jump[0] != 0xe9)
 178                 return -1;
 179
 180         /* heads check */
 181         if (vs->heads == 0)
 182                 return -1;
 183
 184         /* cluster size check*/
 185         if (vs->sectors_per_cluster == 0 ||
 186             (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
 187                 return -1;
 188
 189         /* media check */
 190         if (vs->media < 0xf8 && vs->media != 0xf0)
 191                 return -1;
 192
 193         /* fat count*/
 194         if (vs->fats != 2)
 195                 return -1;
 196
 197  valid:
 198         /* sector size check */
 199         sector_size = le16_to_cpu(vs->sector_size);
 200         if (sector_size != 0x200 && sector_size != 0x400 &&
 201             sector_size != 0x800 && sector_size != 0x1000)
 202                 return -1;
 203
 204         dbg("sector_size 0x%x", sector_size);
 205         dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
 206
 207         dir_entries = le16_to_cpu(vs->dir_entries);
 208         reserved = le16_to_cpu(vs->reserved);
 209         dbg("reserved 0x%x", reserved);
 210
 211         sect_count = le16_to_cpu(vs->sectors);
 212         if (sect_count == 0)
 213                 sect_count = le32_to_cpu(vs->total_sect);
 214         dbg("sect_count 0x%x", sect_count);
 215
 216         fat_length = le16_to_cpu(vs->fat_length);
 217         if (fat_length == 0)
 218                 fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
 219         dbg("fat_length 0x%x", fat_length);
 220
 221         fat_size = fat_length * vs->fats;
 222         dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
 223                         (sector_size-1)) / sector_size;
 224         dbg("dir_size 0x%x", dir_size);
 225
 226         cluster_count = sect_count - (reserved + fat_size + dir_size);
 227         cluster_count /= vs->sectors_per_cluster;
 228         dbg("cluster_count 0x%x", cluster_count);
 229
 230 //      if (cluster_count < FAT12_MAX) {
 231 //              strcpy(id->type_version, "FAT12");
 232 //      } else if (cluster_count < FAT16_MAX) {
 233 //              strcpy(id->type_version, "FAT16");
 234 //      } else {
 235 //              strcpy(id->type_version, "FAT32");
 236 //              goto fat32;
 237 //      }
 238         if (cluster_count >= FAT16_MAX)
 239                 goto fat32;
 240
 241         /* the label may be an attribute in the root directory */
 242         root_start = (reserved + fat_size) * sector_size;
 243         dbg("root dir start 0x%llx", (unsigned long long) root_start);
 244         root_dir_entries = le16_to_cpu(vs->dir_entries);
 245         dbg("expected entries 0x%x", root_dir_entries);
 246
 247         buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
 248         buf = volume_id_get_buffer(id, off + root_start, buf_size);
 249         if (buf == NULL)
 250                 goto found;
 251
 252         dir = (struct vfat_dir_entry*) buf;
 253
 254         label = get_attr_volume_id(dir, root_dir_entries);
 255
 256         vs = volume_id_get_buffer(id, off, 0x200);
 257         if (vs == NULL)
 258                 return -1;
 259
 260         if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
 261 //              volume_id_set_label_raw(id, label, 11);
 262                 volume_id_set_label_string(id, label, 11);
 263         } else if (memcmp(vs->type.fat.label, "NO NAME    ", 11) != 0) {
 264 //              volume_id_set_label_raw(id, vs->type.fat.label, 11);
 265                 volume_id_set_label_string(id, vs->type.fat.label, 11);
 266         }
 267         volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
 268         goto found;
 269
 270  fat32:
 271         /* FAT32 root dir is a cluster chain like any other directory */
 272         buf_size = vs->sectors_per_cluster * sector_size;
 273         root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
 274         dbg("root dir cluster %u", root_cluster);
 275         start_data_sect = reserved + fat_size;
 276
 277         next = root_cluster;
 278         maxloop = 100;
 279         while (--maxloop) {
 280                 uint32_t next_sect_off;
 281                 uint64_t next_off;
 282                 uint64_t fat_entry_off;
 283                 int count;
 284
 285                 dbg("next cluster %u", next);
 286                 next_sect_off = (next - 2) * vs->sectors_per_cluster;
 287                 next_off = (start_data_sect + next_sect_off) * sector_size;
 288                 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
 289
 290                 /* get cluster */
 291                 buf = volume_id_get_buffer(id, off + next_off, buf_size);
 292                 if (buf == NULL)
 293                         goto found;
 294
 295                 dir = (struct vfat_dir_entry*) buf;
 296                 count = buf_size / sizeof(struct vfat_dir_entry);
 297                 dbg("expected entries 0x%x", count);
 298
 299                 label = get_attr_volume_id(dir, count);
 300                 if (label)
 301                         break;
 302
 303                 /* get FAT entry */
 304                 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
 305                 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
 306                 if (buf == NULL)
 307                         goto found;
 308
 309                 /* set next cluster */
 310                 next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
 311                 if (next == 0)
 312                         break;
 313         }
 314         if (maxloop == 0)
 315                 dbg("reached maximum follow count of root cluster chain, give up");
 316
 317         vs = volume_id_get_buffer(id, off, 0x200);
 318         if (vs == NULL)
 319                 return -1;
 320
 321         if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
 322 //              volume_id_set_label_raw(id, label, 11);
 323                 volume_id_set_label_string(id, label, 11);
 324         } else if (memcmp(vs->type.fat32.label, "NO NAME    ", 11) != 0) {
 325 //              volume_id_set_label_raw(id, vs->type.fat32.label, 11);
 326                 volume_id_set_label_string(id, vs->type.fat32.label, 11);
 327         }
 328         volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
 329
 330  found:
 331 //      volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
 332 //      id->type = "vfat";
 333
 334         return 0;
 335 }