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 G_LABEL_MSDOSFS_DIR     "msdosfs"
  44 #define LABEL_NO_NAME           "NO NAME    "
  45
  46 static void
  47 g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
  48 {
  49         struct g_provider *pp;
  50         FAT_BSBPB *pfat_bsbpb;
  51         FAT32_BSBPB *pfat32_bsbpb;
  52         FAT_DES *pfat_entry;
  53         uint8_t *sector0, *sector;
  54
  55         g_topology_assert_not();
  56         pp = cp->provider;
  57         sector0 = NULL;
  58         sector = NULL;
  59         bzero(label, size);
  60
  61         /* Check if the sector size of the medium is a valid FAT sector size. */
  62         switch(pp->sectorsize) {
  63         case 512:
  64         case 1024:
  65         case 2048:
  66         case 4096:
  67                 break;
  68         default:
  69                 G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
  70                     pp->name, pp->sectorsize);
  71                 return;
  72         }
  73
  74         /* Load 1st sector with boot sector and boot parameter block. */
  75         sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
  76         if (sector0 == NULL)
  77                 return;
  78
  79         /* Check for the FAT boot sector signature. */
  80         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  81                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
  82                     pp->name);
  83                 goto error;
  84         }
  85
  86
  87         /*
  88          * Test if this is really a FAT volume and determine the FAT type.
  89          */
  90
  91         pfat_bsbpb = (FAT_BSBPB *)sector0;
  92         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  93
  94         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  95                 /*
  96                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  97                  * at the right place, this should be a FAT12 or FAT16 volume.
  98                  */
  99                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
 100                         G_LABEL_DEBUG(1,
 101                             "MSDOSFS: %s: FAT12/16 volume not valid.",
 102                             pp->name);
 103                         goto error;
 104                 }
 105                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
 106                     pp->name);
 107
 108                 /* A volume with no name should have "NO NAME    " as label. */
 109                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
 110                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
 111                         G_LABEL_DEBUG(1,
 112                             "MSDOSFS: %s: FAT12/16 volume has no name.",
 113                             pp->name);
 114                         goto error;
 115                 }
 116                 strlcpy(label, pfat_bsbpb->BS_VolLab,
 117                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
 118         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
 119                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
 120
 121                 /*
 122                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
 123                  * at the right place, this should be a FAT32 volume.
 124                  */
 125                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
 126                         G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
 127                             pp->name);
 128                         goto error;
 129                 }
 130                 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
 131                     pp->name);
 132
 133                 /*
 134                  * If the volume label is not "NO NAME    " we're done.
 135                  */
 136                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 137                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 138                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 139                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 140                         goto endofchecks;
 141                 }
 142
 143                 /*
 144                  * If the volume label "NO NAME    " is in the boot sector, the
 145                  * label of FAT32 volumes may be stored as a special entry in
 146                  * the root directory.
 147                  */
 148                 fat_FirstDataSector =
 149                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 150                     (pfat32_bsbpb->BPB_NumFATs *
 151                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 152                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 153
 154                 G_LABEL_DEBUG(2,
 155                     "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
 156                     fat_FirstDataSector, fat_BytesPerSector);
 157
 158                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 159                     offset += fat_BytesPerSector) {
 160                         sector = (uint8_t *)g_read_data(cp, offset,
 161                             fat_BytesPerSector, NULL);
 162                         if (sector == NULL)
 163                                 goto error;
 164
 165                         pfat_entry = (FAT_DES *)sector;
 166                         do {
 167                                 /* No more entries available. */
 168                                 if (pfat_entry->DIR_Name[0] == 0) {
 169                                         G_LABEL_DEBUG(1, "MSDOSFS: %s: "
 170                                             "FAT32 volume has no name.",
 171                                             pp->name);
 172                                         goto error;
 173                                 }
 174
 175                                 /* Skip empty or long name entries. */
 176                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 177                                     (pfat_entry->DIR_Attr &
 178                                      FAT_DES_ATTR_LONG_NAME) ==
 179                                     FAT_DES_ATTR_LONG_NAME) {
 180                                         continue;
 181                                 }
 182
 183                                 /*
 184                                  * The name of the entry is the volume label if
 185                                  * ATTR_VOLUME_ID is set.
 186                                  */
 187                                 if (pfat_entry->DIR_Attr &
 188                                     FAT_DES_ATTR_VOLUME_ID) {
 189                                         strlcpy(label, pfat_entry->DIR_Name,
 190                                             MIN(size,
 191                                             sizeof(pfat_entry->DIR_Name) + 1));
 192                                         goto endofchecks;
 193                                 }
 194                         } while((uint8_t *)(++pfat_entry) <
 195                             (uint8_t *)(sector + fat_BytesPerSector));
 196                         g_free(sector);
 197                 }
 198         } else {
 199                 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
 200                     pp->name);
 201                 goto error;
 202         }
 203
 204 endofchecks:
 205         g_label_rtrim(label, size);
 206
 207 error:
 208         if (sector0 != NULL)
 209                 g_free(sector0);
 210         if (sector != NULL)
 211                 g_free(sector);
 212 }
 213
 214 struct g_label_desc g_label_msdosfs = {
 215         .ld_taste = g_label_msdosfs_taste,
 216         .ld_dir = G_LABEL_MSDOSFS_DIR,
 217         .ld_enabled = 1
 218 };
 219
 220 G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");