Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/geom/label/g_label_msdosfs.c
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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: releng/11.0/sys/geom/label/g_label_msdosfs.c 284582 2015-06-18 21:55:55Z trasz $"); 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");
Cache object: 4b7d602484aaeb811da9e5d86f0e2169
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