source: branches/3.2/mindi-busybox/util-linux/volume_id/fat.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
  • 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    IF_FEATURE_BLKID_TYPE(id->type = "vfat";)
336
337    return 0;
338}
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