LXR busybox/util-linux/volume

   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/* linux/msdos_fs.h says: */
  24#define FAT12_MAX                       0xff4
  25#define FAT16_MAX                       0xfff4
  26#define FAT32_MAX                       0x0ffffff6
  27
  28#define FAT_ATTR_VOLUME_ID              0x08
  29#define FAT_ATTR_DIR                    0x10
  30#define FAT_ATTR_LONG_NAME              0x0f
  31#define FAT_ATTR_MASK                   0x3f
  32#define FAT_ENTRY_FREE                  0xe5
  33
  34struct vfat_super_block {
  35        uint8_t         boot_jump[3];
  36        uint8_t         sysid[8];
  37        uint16_t        sector_size_bytes;
  38        uint8_t         sectors_per_cluster;
  39        uint16_t        reserved_sct;
  40        uint8_t         fats;
  41        uint16_t        dir_entries;
  42        uint16_t        sectors;
  43        uint8_t         media;
  44        uint16_t        fat_length;
  45        uint16_t        secs_track;
  46        uint16_t        heads;
  47        uint32_t        hidden;
  48        uint32_t        total_sect;
  49        union {
  50                struct fat_super_block {
  51                        uint8_t         unknown[3];
  52                        uint8_t         serno[4];
  53                        uint8_t         label[11];
  54                        uint8_t         magic[8];
  55                        uint8_t         dummy2[192];
  56                        uint8_t         pmagic[2];
  57                } __attribute__((__packed__)) fat;
  58                struct fat32_super_block {
  59                        uint32_t        fat32_length;
  60                        uint16_t        flags;
  61                        uint8_t         version[2];
  62                        uint32_t        root_cluster;
  63                        uint16_t        insfo_sector;
  64                        uint16_t        backup_boot;
  65                        uint16_t        reserved2[6];
  66                        uint8_t         unknown[3];
  67                        uint8_t         serno[4];
  68                        uint8_t         label[11];
  69                        uint8_t         magic[8];
  70                        uint8_t         dummy2[164];
  71                        uint8_t         pmagic[2];
  72                } __attribute__((__packed__)) fat32;
  73        } __attribute__((__packed__)) type;
  74} __attribute__((__packed__));
  75
  76struct vfat_dir_entry {
  77        uint8_t         name[11];
  78        uint8_t         attr;
  79        uint16_t        time_creat;
  80        uint16_t        date_creat;
  81        uint16_t        time_acc;
  82        uint16_t        date_acc;
  83        uint16_t        cluster_high;
  84        uint16_t        time_write;
  85        uint16_t        date_write;
  86        uint16_t        cluster_low;
  87        uint32_t        size;
  88} __attribute__((__packed__));
  89
  90static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
  91{
  92        for (;--count >= 0; dir++) {
  93                /* end marker */
  94                if (dir->name[0] == 0x00) {
  95                        dbg("end of dir");
  96                        break;
  97                }
  98
  99                /* empty entry */
 100                if (dir->name[0] == FAT_ENTRY_FREE)
 101                        continue;
 102
 103                /* long name */
 104                if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
 105                        continue;
 106
 107                if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
 108                        /* labels do not have file data */
 109                        if (dir->cluster_high != 0 || dir->cluster_low != 0)
 110                                continue;
 111
 112                        dbg("found ATTR_VOLUME_ID id in root dir");
 113                        return dir->name;
 114                }
 115
 116                dbg("skip dir entry");
 117        }
 118
 119        return NULL;
 120}
 121
 122int volume_id_probe_vfat(struct volume_id *id /*,uint64_t fat_partition_off*/)
 123{
 124#define fat_partition_off ((uint64_t)0)
 125        struct vfat_super_block *vs;
 126        struct vfat_dir_entry *dir;
 127        uint16_t sector_size_bytes;
 128        uint16_t dir_entries;
 129        uint32_t sect_count;
 130        uint16_t reserved_sct;
 131        uint32_t fat_size_sct;
 132        uint32_t root_cluster;
 133        uint32_t dir_size_sct;
 134        uint32_t cluster_count;
 135        uint64_t root_start_off;
 136        uint32_t start_data_sct;
 137        uint8_t *buf;
 138        uint32_t buf_size;
 139        uint8_t *label = NULL;
 140        uint32_t next_cluster;
 141        int maxloop;
 142
 143        dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
 144
 145        vs = volume_id_get_buffer(id, fat_partition_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_bytes = le16_to_cpu(vs->sector_size_bytes);
 200        if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 &&
 201            sector_size_bytes != 0x800 && sector_size_bytes != 0x1000)
 202                return -1;
 203
 204        dbg("sector_size_bytes 0x%x", sector_size_bytes);
 205        dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
 206
 207        reserved_sct = le16_to_cpu(vs->reserved_sct);
 208        dbg("reserved_sct 0x%x", reserved_sct);
 209
 210        sect_count = le16_to_cpu(vs->sectors);
 211        if (sect_count == 0)
 212                sect_count = le32_to_cpu(vs->total_sect);
 213        dbg("sect_count 0x%x", sect_count);
 214
 215        fat_size_sct = le16_to_cpu(vs->fat_length);
 216        if (fat_size_sct == 0)
 217                fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
 218        fat_size_sct *= vs->fats;
 219        dbg("fat_size_sct 0x%x", fat_size_sct);
 220
 221        dir_entries = le16_to_cpu(vs->dir_entries);
 222        dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
 223                        (sector_size_bytes-1)) / sector_size_bytes;
 224        dbg("dir_size_sct 0x%x", dir_size_sct);
 225
 226        cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
 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_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
 243        dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
 244        dbg("expected entries 0x%x", dir_entries);
 245
 246        buf_size = dir_entries * sizeof(struct vfat_dir_entry);
 247        buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
 248        if (buf == NULL)
 249                goto ret;
 250
 251        label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
 252
 253        vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
 254        if (vs == NULL)
 255                return -1;
 256
 257        if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
 258//              volume_id_set_label_raw(id, label, 11);
 259                volume_id_set_label_string(id, label, 11);
 260        } else if (memcmp(vs->type.fat.label, "NO NAME    ", 11) != 0) {
 261//              volume_id_set_label_raw(id, vs->type.fat.label, 11);
 262                volume_id_set_label_string(id, vs->type.fat.label, 11);
 263        }
 264        volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
 265        goto ret;
 266
 267 fat32:
 268        /* FAT32 root dir is a cluster chain like any other directory */
 269        buf_size = vs->sectors_per_cluster * sector_size_bytes;
 270        root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
 271        start_data_sct = reserved_sct + fat_size_sct;
 272
 273        next_cluster = root_cluster;
 274        maxloop = 100;
 275        while (--maxloop) {
 276                uint64_t next_off_sct;
 277                uint64_t next_off;
 278                uint64_t fat_entry_off;
 279                int count;
 280
 281                dbg("next_cluster 0x%x", (unsigned)next_cluster);
 282                next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
 283                next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
 284                dbg("cluster offset 0x%llx", (unsigned long long) next_off);
 285
 286                /* get cluster */
 287                buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
 288                if (buf == NULL)
 289                        goto ret;
 290
 291                dir = (struct vfat_dir_entry*) buf;
 292                count = buf_size / sizeof(struct vfat_dir_entry);
 293                dbg("expected entries 0x%x", count);
 294
 295                label = get_attr_volume_id(dir, count);
 296                if (label)
 297                        break;
 298
 299                /* get FAT entry */
 300                fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
 301                dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
 302                buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
 303                if (buf == NULL)
 304                        goto ret;
 305
 306                /* set next cluster */
 307                next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
 308                if (next_cluster < 2 || next_cluster > FAT32_MAX)
 309                        break;
 310        }
 311        if (maxloop == 0)
 312                dbg("reached maximum follow count of root cluster chain, give up");
 313
 314        vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
 315        if (vs == NULL)
 316                return -1;
 317
 318        if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
 319//              volume_id_set_label_raw(id, label, 11);
 320                volume_id_set_label_string(id, label, 11);
 321        } else if (memcmp(vs->type.fat32.label, "NO NAME    ", 11) != 0) {
 322//              volume_id_set_label_raw(id, vs->type.fat32.label, 11);
 323                volume_id_set_label_string(id, vs->type.fat32.label, 11);
 324        }
 325        volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
 326
 327 ret:
 328//      volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
 329//      id->type = "vfat";
 330
 331        return 0;
 332}
 333