sys/geom/label/g_label_msdosfs.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   5  * Copyright (c) 2006 Tobias Reifenberger
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <sys/cdefs.h>
  31 __FBSDID("$FreeBSD$");
  32
  33 #include <sys/param.h>
  34 #include <sys/systm.h>
  35 #include <sys/kernel.h>
  36 #include <sys/malloc.h>
  37
  38 #include <geom/geom.h>
  39 #include <geom/geom_dbg.h>
  40 #include <geom/label/g_label.h>
  41 #include <geom/label/g_label_msdosfs.h>
  42
  43 #define LABEL_NO_NAME           "NO NAME    "
  44
  45 static void
  46 g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
  47 {
  48         struct g_provider *pp;
  49         FAT_BSBPB *pfat_bsbpb;
  50         FAT32_BSBPB *pfat32_bsbpb;
  51         FAT_DES *pfat_entry;
  52         uint8_t *sector0, *sector;
  53
  54         g_topology_assert_not();
  55         pp = cp->provider;
  56         sector0 = NULL;
  57         sector = NULL;
  58         bzero(label, size);
  59
  60         /* Check if the sector size of the medium is a valid FAT sector size. */
  61         switch(pp->sectorsize) {
  62         case 512:
  63         case 1024:
  64         case 2048:
  65         case 4096:
  66                 break;
  67         default:
  68                 G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
  69                     pp->name, pp->sectorsize);
  70                 return;
  71         }
  72
  73         /* Load 1st sector with boot sector and boot parameter block. */
  74         sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
  75         if (sector0 == NULL)
  76                 return;
  77
  78         /* Check for the FAT boot sector signature. */
  79         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  80                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
  81                     pp->name);
  82                 goto error;
  83         }
  84
  85
  86         /*
  87          * Test if this is really a FAT volume and determine the FAT type.
  88          */
  89
  90         pfat_bsbpb = (FAT_BSBPB *)sector0;
  91         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  92
  93         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  94                 /*
  95                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  96                  * at the right place, this should be a FAT12 or FAT16 volume.
  97                  */
  98                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  99                         G_LABEL_DEBUG(1,
 100                             "MSDOSFS: %s: FAT12/16 volume not valid.",
 101                             pp->name);
 102                         goto error;
 103                 }
 104                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
 105                     pp->name);
 106
 107                 /* A volume with no name should have "NO NAME    " as label. */
 108                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
 109                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
 110                         G_LABEL_DEBUG(1,
 111                             "MSDOSFS: %s: FAT12/16 volume has no name.",
 112                             pp->name);
 113                         goto error;
 114                 }
 115                 strlcpy(label, pfat_bsbpb->BS_VolLab,
 116                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
 117         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
 118                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
 119
 120                 /*
 121                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
 122                  * at the right place, this should be a FAT32 volume.
 123                  */
 124                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
 125                         G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
 126                             pp->name);
 127                         goto error;
 128                 }
 129                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
 130                     pp->name);
 131
 132                 /*
 133                  * If the volume label is not "NO NAME    " we're done.
 134                  */
 135                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 136                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 137                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 138                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 139                         goto endofchecks;
 140                 }
 141
 142                 /*
 143                  * If the volume label "NO NAME    " is in the boot sector, the
 144                  * label of FAT32 volumes may be stored as a special entry in
 145                  * the root directory.
 146                  */
 147                 fat_FirstDataSector =
 148                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 149                     (pfat32_bsbpb->BPB_NumFATs *
 150                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 151                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 152
 153                 G_LABEL_DEBUG(2,
 154                     "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
 155                     fat_FirstDataSector, fat_BytesPerSector);
 156
 157                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 158                     offset += fat_BytesPerSector) {
 159                         sector = (uint8_t *)g_read_data(cp, offset,
 160                             fat_BytesPerSector, NULL);
 161                         if (sector == NULL)
 162                                 goto error;
 163
 164                         pfat_entry = (FAT_DES *)sector;
 165                         do {
 166                                 /* No more entries available. */
 167                                 if (pfat_entry->DIR_Name[0] == 0) {
 168                                         G_LABEL_DEBUG(1, "MSDOSFS: %s: "
 169                                             "FAT32 volume has no name.",
 170                                             pp->name);
 171                                         goto error;
 172                                 }
 173
 174                                 /* Skip empty or long name entries. */
 175                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 176                                     (pfat_entry->DIR_Attr &
 177                                      FAT_DES_ATTR_LONG_NAME) ==
 178                                     FAT_DES_ATTR_LONG_NAME) {
 179                                         continue;
 180                                 }
 181
 182                                 /*
 183                                  * The name of the entry is the volume label if
 184                                  * ATTR_VOLUME_ID is set.
 185                                  */
 186                                 if (pfat_entry->DIR_Attr &
 187                                     FAT_DES_ATTR_VOLUME_ID) {
 188                                         strlcpy(label, pfat_entry->DIR_Name,
 189                                             MIN(size,
 190                                             sizeof(pfat_entry->DIR_Name) + 1));
 191                                         goto endofchecks;
 192                                 }
 193                         } while((uint8_t *)(++pfat_entry) <
 194                             (uint8_t *)(sector + fat_BytesPerSector));
 195                         g_free(sector);
 196                 }
 197         } else {
 198                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
 199                     pp->name);
 200                 goto error;
 201         }
 202
 203 endofchecks:
 204         g_label_rtrim(label, size);
 205
 206 error:
 207         if (sector0 != NULL)
 208                 g_free(sector0);
 209         if (sector != NULL)
 210                 g_free(sector);
 211 }
 212
 213 struct g_label_desc g_label_msdosfs = {
 214         .ld_taste = g_label_msdosfs_taste,
 215         .ld_dirprefix = "msdosfs/",
 216         .ld_enabled = 1
 217 };
 218
 219 G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");