source: MondoRescue/branches/2.2.9/mindi-busybox/util-linux/volume_id/fat.c@ 3320

Last change on this file since 3320 was 3320, checked in by Bruno Cornec, 9 years ago
  • Re-add (thanks git BTW) the 2.2.9 branch which had been destroyed in the move to 3.0
  • Property svn:eol-style set to native
File size: 9.0 KB
Line 
1/*
2 * volume_id - reads filesystem label and uuid
3 *
4 * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 */
20
21#include "volume_id_internal.h"
22
23/* linux/msdos_fs.h says: */
24#define FAT12_MAX 0xff4
25#define FAT16_MAX 0xfff4
26#define FAT32_MAX 0x0ffffff6
27
28#define FAT_ATTR_VOLUME_ID 0x08
29#define FAT_ATTR_DIR 0x10
30#define FAT_ATTR_LONG_NAME 0x0f
31#define FAT_ATTR_MASK 0x3f
32#define FAT_ENTRY_FREE 0xe5
33
34struct vfat_super_block {
35 uint8_t boot_jump[3];
36 uint8_t sysid[8];
37 uint16_t sector_size_bytes;
38 uint8_t sectors_per_cluster;
39 uint16_t reserved_sct;
40 uint8_t fats;
41 uint16_t dir_entries;
42 uint16_t sectors;
43 uint8_t media;
44 uint16_t fat_length;
45 uint16_t secs_track;
46 uint16_t heads;
47 uint32_t hidden;
48 uint32_t total_sect;
49 union {
50 struct fat_super_block {
51 uint8_t unknown[3];
52 uint8_t serno[4];
53 uint8_t label[11];
54 uint8_t magic[8];
55 uint8_t dummy2[192];
56 uint8_t pmagic[2];
57 } PACKED fat;
58 struct fat32_super_block {
59 uint32_t fat32_length;
60 uint16_t flags;
61 uint8_t version[2];
62 uint32_t root_cluster;
63 uint16_t insfo_sector;
64 uint16_t backup_boot;
65 uint16_t reserved2[6];
66 uint8_t unknown[3];
67 uint8_t serno[4];
68 uint8_t label[11];
69 uint8_t magic[8];
70 uint8_t dummy2[164];
71 uint8_t pmagic[2];
72 } PACKED fat32;
73 } PACKED type;
74} PACKED;
75
76struct vfat_dir_entry {
77 uint8_t name[11];
78 uint8_t attr;
79 uint16_t time_creat;
80 uint16_t date_creat;
81 uint16_t time_acc;
82 uint16_t date_acc;
83 uint16_t cluster_high;
84 uint16_t time_write;
85 uint16_t date_write;
86 uint16_t cluster_low;
87 uint32_t size;
88} PACKED;
89
90static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
91{
92 for (;--count >= 0; dir++) {
93 /* end marker */
94 if (dir->name[0] == 0x00) {
95 dbg("end of dir");
96 break;
97 }
98
99 /* empty entry */
100 if (dir->name[0] == FAT_ENTRY_FREE)
101 continue;
102
103 /* long name */
104 if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
105 continue;
106
107 if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
108 /* labels do not have file data */
109 if (dir->cluster_high != 0 || dir->cluster_low != 0)
110 continue;
111
112 dbg("found ATTR_VOLUME_ID id in root dir");
113 return dir->name;
114 }
115
116 dbg("skip dir entry");
117 }
118
119 return NULL;
120}
121
122int FAST_FUNC volume_id_probe_vfat(struct volume_id *id /*,uint64_t fat_partition_off*/)
123{
124#define fat_partition_off ((uint64_t)0)
125 struct vfat_super_block *vs;
126 struct vfat_dir_entry *dir;
127 uint16_t sector_size_bytes;
128 uint16_t dir_entries;
129 uint32_t sect_count;
130 uint16_t reserved_sct;
131 uint32_t fat_size_sct;
132 uint32_t root_cluster;
133 uint32_t dir_size_sct;
134 uint32_t cluster_count;
135 uint64_t root_start_off;
136 uint32_t start_data_sct;
137 uint8_t *buf;
138 uint32_t buf_size;
139 uint8_t *label = NULL;
140 uint32_t next_cluster;
141 int maxloop;
142
143 dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
144
145 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
146 if (vs == NULL)
147 return -1;
148
149 /* believe only that's fat, don't trust the version
150 * the cluster_count will tell us
151 */
152 if (memcmp(vs->sysid, "NTFS", 4) == 0)
153 return -1;
154
155 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
156 goto valid;
157
158 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
159 goto valid;
160
161 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
162 goto valid;
163
164 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
165 goto valid;
166
167 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
168 goto valid;
169
170 /*
171 * There are old floppies out there without a magic, so we check
172 * for well known values and guess if it's a fat volume
173 */
174
175 /* boot jump address check */
176 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90)
177 && vs->boot_jump[0] != 0xe9
178 ) {
179 return -1;
180 }
181
182 /* heads check */
183 if (vs->heads == 0)
184 return -1;
185
186 /* cluster size check */
187 if (vs->sectors_per_cluster == 0
188 || (vs->sectors_per_cluster & (vs->sectors_per_cluster-1))
189 ) {
190 return -1;
191 }
192
193 /* media check */
194 if (vs->media < 0xf8 && vs->media != 0xf0)
195 return -1;
196
197 /* fat count*/
198 if (vs->fats != 2)
199 return -1;
200
201 valid:
202 /* sector size check */
203 sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
204 if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400
205 && sector_size_bytes != 0x800 && sector_size_bytes != 0x1000
206 ) {
207 return -1;
208 }
209
210 dbg("sector_size_bytes 0x%x", sector_size_bytes);
211 dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
212
213 reserved_sct = le16_to_cpu(vs->reserved_sct);
214 dbg("reserved_sct 0x%x", reserved_sct);
215
216 sect_count = le16_to_cpu(vs->sectors);
217 if (sect_count == 0)
218 sect_count = le32_to_cpu(vs->total_sect);
219 dbg("sect_count 0x%x", sect_count);
220
221 fat_size_sct = le16_to_cpu(vs->fat_length);
222 if (fat_size_sct == 0)
223 fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
224 fat_size_sct *= vs->fats;
225 dbg("fat_size_sct 0x%x", fat_size_sct);
226
227 dir_entries = le16_to_cpu(vs->dir_entries);
228 dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
229 (sector_size_bytes-1)) / sector_size_bytes;
230 dbg("dir_size_sct 0x%x", dir_size_sct);
231
232 cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
233 cluster_count /= vs->sectors_per_cluster;
234 dbg("cluster_count 0x%x", cluster_count);
235
236// if (cluster_count < FAT12_MAX) {
237// strcpy(id->type_version, "FAT12");
238// } else if (cluster_count < FAT16_MAX) {
239// strcpy(id->type_version, "FAT16");
240// } else {
241// strcpy(id->type_version, "FAT32");
242// goto fat32;
243// }
244 if (cluster_count >= FAT16_MAX)
245 goto fat32;
246
247 /* the label may be an attribute in the root directory */
248 root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
249 dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
250 dbg("expected entries 0x%x", dir_entries);
251
252 buf_size = dir_entries * sizeof(struct vfat_dir_entry);
253 buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
254 if (buf == NULL)
255 goto ret;
256
257 label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
258
259 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
260 if (vs == NULL)
261 return -1;
262
263 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
264// volume_id_set_label_raw(id, label, 11);
265 volume_id_set_label_string(id, label, 11);
266 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
267// volume_id_set_label_raw(id, vs->type.fat.label, 11);
268 volume_id_set_label_string(id, vs->type.fat.label, 11);
269 }
270 volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
271 goto ret;
272
273 fat32:
274 /* FAT32 root dir is a cluster chain like any other directory */
275 buf_size = vs->sectors_per_cluster * sector_size_bytes;
276 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
277 start_data_sct = reserved_sct + fat_size_sct;
278
279 next_cluster = root_cluster;
280 maxloop = 100;
281 while (--maxloop) {
282 uint64_t next_off_sct;
283 uint64_t next_off;
284 uint64_t fat_entry_off;
285 int count;
286
287 dbg("next_cluster 0x%x", (unsigned)next_cluster);
288 next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
289 next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
290 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
291
292 /* get cluster */
293 buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
294 if (buf == NULL)
295 goto ret;
296
297 dir = (struct vfat_dir_entry*) buf;
298 count = buf_size / sizeof(struct vfat_dir_entry);
299 dbg("expected entries 0x%x", count);
300
301 label = get_attr_volume_id(dir, count);
302 if (label)
303 break;
304
305 /* get FAT entry */
306 fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
307 dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
308 buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
309 if (buf == NULL)
310 goto ret;
311
312 /* set next cluster */
313 next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
314 if (next_cluster < 2 || next_cluster > FAT32_MAX)
315 break;
316 }
317 if (maxloop == 0)
318 dbg("reached maximum follow count of root cluster chain, give up");
319
320 vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
321 if (vs == NULL)
322 return -1;
323
324 if (label != NULL && memcmp(label, "NO NAME ", 11) != 0) {
325// volume_id_set_label_raw(id, label, 11);
326 volume_id_set_label_string(id, label, 11);
327 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
328// volume_id_set_label_raw(id, vs->type.fat32.label, 11);
329 volume_id_set_label_string(id, vs->type.fat32.label, 11);
330 }
331 volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
332
333 ret:
334// volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
335// id->type = "vfat";
336
337 return 0;
338}
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