1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
31 #include <sys/systm.h>
32 #include <sys/kernel.h>
33 #include <sys/malloc.h>
34
35 #include <geom/geom.h>
36 #include <geom/geom_dbg.h>
37 #include <geom/label/g_label.h>
38 #include <geom/label/g_label_msdosfs.h>
39
40 #define LABEL_NO_NAME "NO NAME "
41
42 static void
g_label_msdosfs_taste(struct g_consumer * cp,char * label,size_t size)43 g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
44 {
45 struct g_provider *pp;
46 FAT_BSBPB *pfat_bsbpb;
47 FAT32_BSBPB *pfat32_bsbpb;
48 FAT_DES *pfat_entry;
49 uint8_t *sector0, *sector;
50 size_t copysize;
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 * Test if this is really a FAT volume and determine the FAT type.
85 */
86
87 pfat_bsbpb = (FAT_BSBPB *)sector0;
88 pfat32_bsbpb = (FAT32_BSBPB *)sector0;
89
90 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
91 /*
92 * If the BPB_FATSz16 field is not zero and the string "FAT" is
93 * at the right place, this should be a FAT12 or FAT16 volume.
94 */
95 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
96 G_LABEL_DEBUG(1,
97 "MSDOSFS: %s: FAT12/16 volume not valid.",
98 pp->name);
99 goto error;
100 }
101 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
102 pp->name);
103
104 /* A volume with no name should have "NO NAME " as label. */
105 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
106 sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
107 G_LABEL_DEBUG(1,
108 "MSDOSFS: %s: FAT12/16 volume has no name.",
109 pp->name);
110 goto error;
111 }
112 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
113 memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
114 label[copysize] = '\0';
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 copysize = MIN(size - 1,
136 sizeof(pfat32_bsbpb->BS_VolLab));
137 memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
138 label[copysize] = '\0';
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 if (fat_BytesPerSector == 0 ||
157 fat_BytesPerSector % pp->sectorsize != 0) {
158 G_LABEL_DEBUG(1, "MSDOSFS: %s: corrupted BPB",
159 pp->name);
160 goto error;
161 }
162
163 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
164 offset += fat_BytesPerSector) {
165 sector = (uint8_t *)g_read_data(cp, offset,
166 fat_BytesPerSector, NULL);
167 if (sector == NULL)
168 goto error;
169
170 pfat_entry = (FAT_DES *)sector;
171 do {
172 /* No more entries available. */
173 if (pfat_entry->DIR_Name[0] == 0) {
174 G_LABEL_DEBUG(1, "MSDOSFS: %s: "
175 "FAT32 volume has no name.",
176 pp->name);
177 goto error;
178 }
179
180 /* Skip empty or long name entries. */
181 if (pfat_entry->DIR_Name[0] == 0xe5 ||
182 (pfat_entry->DIR_Attr &
183 FAT_DES_ATTR_LONG_NAME) ==
184 FAT_DES_ATTR_LONG_NAME) {
185 continue;
186 }
187
188 /*
189 * The name of the entry is the volume label if
190 * ATTR_VOLUME_ID is set.
191 */
192 if (pfat_entry->DIR_Attr &
193 FAT_DES_ATTR_VOLUME_ID) {
194 copysize = MIN(size - 1,
195 sizeof(pfat_entry->DIR_Name));
196 memcpy(label, pfat_entry->DIR_Name,
197 copysize);
198 label[copysize] = '\0';
199 goto endofchecks;
200 }
201 } while((uint8_t *)(++pfat_entry) <
202 (uint8_t *)(sector + fat_BytesPerSector));
203 g_free(sector);
204 }
205 } else {
206 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
207 pp->name);
208 goto error;
209 }
210
211 endofchecks:
212 g_label_rtrim(label, size);
213
214 error:
215 g_free(sector0);
216 g_free(sector);
217 }
218
219 struct g_label_desc g_label_msdosfs = {
220 .ld_taste = g_label_msdosfs_taste,
221 .ld_dirprefix = "msdosfs/",
222 .ld_enabled = 1
223 };
224
225 G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes");
226