sys/geom/label/g_label_msdosfs.c

   1 /*-
   2  * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   3  * Copyright (c) 2006 Tobias Reifenberger
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  */
  27
  28 #include <sys/cdefs.h>
  29 __FBSDID("$FreeBSD$");
  30
  31 #include <sys/param.h>
  32 #include <sys/systm.h>
  33 #include <sys/kernel.h>
  34 #include <sys/malloc.h>
  35
  36 #include <geom/geom.h>
  37 #include <geom/label/g_label.h>
  38 #include <geom/label/g_label_msdosfs.h>
  39
  40 #define G_LABEL_MSDOSFS_DIR     "msdosfs"
  41 #define LABEL_NO_NAME           "NO NAME    "
  42
  43 static void
  44 g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
  45 {
  46         struct g_provider *pp;
  47         FAT_BSBPB *pfat_bsbpb;
  48         FAT32_BSBPB *pfat32_bsbpb;
  49         FAT_DES *pfat_entry;
  50         uint8_t *sector0, *sector;
  51
  52         g_topology_assert_not();
  53         pp = cp->provider;
  54         sector0 = NULL;
  55         sector = NULL;
  56         bzero(label, size);
  57
  58         /* Check if the sector size of the medium is a valid FAT sector size. */
  59         switch(pp->sectorsize) {
  60         case 512:
  61         case 1024:
  62         case 2048:
  63         case 4096:
  64                 break;
  65         default:
  66                 G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
  67                     pp->name, pp->sectorsize);
  68                 return;
  69         }
  70
  71         /* Load 1st sector with boot sector and boot parameter block. */
  72         sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
  73         if (sector0 == NULL)
  74                 return;
  75
  76         /* Check for the FAT boot sector signature. */
  77         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  78                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
  79                     pp->name);
  80                 goto error;
  81         }
  82
  83
  84         /*
  85          * Test if this is really a FAT volume and determine the FAT type.
  86          */
  87
  88         pfat_bsbpb = (FAT_BSBPB *)sector0;
  89         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  90
  91         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  92                 /*
  93                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  94                  * at the right place, this should be a FAT12 or FAT16 volume.
  95                  */
  96                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  97                         G_LABEL_DEBUG(1,
  98                             "MSDOSFS: %s: FAT12/16 volume not valid.",
  99                             pp->name);
 100                         goto error;
 101                 }
 102                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
 103                     pp->name);
 104
 105                 /* A volume with no name should have "NO NAME    " as label. */
 106                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
 107                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
 108                         G_LABEL_DEBUG(1,
 109                             "MSDOSFS: %s: FAT12/16 volume has no name.",
 110                             pp->name);
 111                         goto error;
 112                 }
 113                 strlcpy(label, pfat_bsbpb->BS_VolLab,
 114                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
 115         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
 116                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
 117
 118                 /*
 119                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
 120                  * at the right place, this should be a FAT32 volume.
 121                  */
 122                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
 123                         G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
 124                             pp->name);
 125                         goto error;
 126                 }
 127                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
 128                     pp->name);
 129
 130                 /*
 131                  * If the volume label is not "NO NAME    " we're done.
 132                  */
 133                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 134                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 135                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 136                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 137                         goto endofchecks;
 138                 }
 139
 140                 /*
 141                  * If the volume label "NO NAME    " is in the boot sector, the
 142                  * label of FAT32 volumes may be stored as a special entry in
 143                  * the root directory.
 144                  */
 145                 fat_FirstDataSector =
 146                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 147                     (pfat32_bsbpb->BPB_NumFATs *
 148                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 149                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 150
 151                 G_LABEL_DEBUG(2,
 152                     "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
 153                     fat_FirstDataSector, fat_BytesPerSector);
 154
 155                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 156                     offset += fat_BytesPerSector) {
 157                         sector = (uint8_t *)g_read_data(cp, offset,
 158                             fat_BytesPerSector, NULL);
 159                         if (sector == NULL)
 160                                 goto error;
 161
 162                         pfat_entry = (FAT_DES *)sector;
 163                         do {
 164                                 /* No more entries available. */
 165                                 if (pfat_entry->DIR_Name[0] == 0) {
 166                                         G_LABEL_DEBUG(1, "MSDOSFS: %s: "
 167                                             "FAT32 volume has no name.",
 168                                             pp->name);
 169                                         goto error;
 170                                 }
 171
 172                                 /* Skip empty or long name entries. */
 173                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 174                                     (pfat_entry->DIR_Attr &
 175                                      FAT_DES_ATTR_LONG_NAME) ==
 176                                     FAT_DES_ATTR_LONG_NAME) {
 177                                         continue;
 178                                 }
 179
 180                                 /*
 181                                  * The name of the entry is the volume label if
 182                                  * ATTR_VOLUME_ID is set.
 183                                  */
 184                                 if (pfat_entry->DIR_Attr &
 185                                     FAT_DES_ATTR_VOLUME_ID) {
 186                                         strlcpy(label, pfat_entry->DIR_Name,
 187                                             MIN(size,
 188                                             sizeof(pfat_entry->DIR_Name) + 1));
 189                                         goto endofchecks;
 190                                 }
 191                         } while((uint8_t *)(++pfat_entry) <
 192                             (uint8_t *)(sector + fat_BytesPerSector));
 193                         g_free(sector);
 194                 }
 195         } else {
 196                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
 197                     pp->name);
 198                 goto error;
 199         }
 200
 201 endofchecks:
 202         g_label_rtrim(label, size);
 203
 204 error:
 205         if (sector0 != NULL)
 206                 g_free(sector0);
 207         if (sector != NULL)
 208                 g_free(sector);
 209 }
 210
 211 struct g_label_desc g_label_msdosfs = {
 212         .ld_taste = g_label_msdosfs_taste,
 213         .ld_dir = G_LABEL_MSDOSFS_DIR,
 214         .ld_enabled = 1
 215 };
 216
 217 G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");