g_label_msdosfs.c revision 161246 
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: head/sys/geom/label/g_label_msdosfs.c 161246 2006-08-12 15:34:15Z pjd $");
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
43static void
44g_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	uint32_t i;
52
53	g_topology_assert_not();
54	pp = cp->provider;
55	sector0 = NULL;
56	sector = NULL;
57	bzero(label, size);
58
59	/* Check if the sector size of the medium is a valid FAT sector size. */
60	switch(pp->sectorsize) {
61	case 512:
62	case 1024:
63	case 2048:
64	case 4096:
65		break;
66	default:
67		G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.",
68		    pp->name, pp->sectorsize);
69		return;
70	}
71
72	/* Load 1st sector with boot sector and boot parameter block. */
73	sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL);
74	if (sector0 == NULL)
75		return;
76
77	/* Check for the FAT boot sector signature. */
78	if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
79		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.",
80		    pp->name);
81		goto error;
82	}
83
84
85	/*
86	 * Test if this is really a FAT volume and determine the FAT type.
87	 */
88
89	pfat_bsbpb = (FAT_BSBPB *)sector0;
90	pfat32_bsbpb = (FAT32_BSBPB *)sector0;
91
92	if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
93		/*
94		 * If the BPB_FATSz16 field is not zero and the string "FAT" is
95		 * at the right place, this should be a FAT12 or FAT16 volume.
96		 */
97		if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
98			G_LABEL_DEBUG(1,
99			    "MSDOSFS: %s: FAT12/16 volume not valid.",
100			    pp->name);
101			goto error;
102		}
103		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.",
104		    pp->name);
105
106		/* A volume with no name should have "NO NAME    " as label. */
107		if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
108		    sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
109			G_LABEL_DEBUG(1,
110			    "MSDOSFS: %s: FAT12/16 volume has no name.",
111			    pp->name);
112			goto error;
113		}
114		strlcpy(label, pfat_bsbpb->BS_VolLab,
115		    MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
116	} else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
117		uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
118
119		/*
120		 * If the BPB_FATSz32 field is not zero and the string "FAT" is
121		 * at the right place, this should be a FAT32 volume.
122		 */
123		if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
124			G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.",
125			    pp->name);
126			goto error;
127		}
128		G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.",
129		    pp->name);
130
131		/*
132		 * If the volume label is not "NO NAME    " we're done.
133		 */
134		if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
135		    sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
136			strlcpy(label, pfat32_bsbpb->BS_VolLab,
137			    MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
138			goto endofchecks;
139		}
140
141		/*
142		 * If the volume label "NO NAME    " is in the boot sector, the
143		 * label of FAT32 volumes may be stored as a special entry in
144		 * the root directory.
145		 */
146		fat_FirstDataSector =
147		    UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
148		    (pfat32_bsbpb->BPB_NumFATs *
149		     UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
150		fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
151
152		G_LABEL_DEBUG(2,
153		    "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
154		    fat_FirstDataSector, fat_BytesPerSector);
155
156		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
157		    offset += fat_BytesPerSector) {
158			sector = (uint8_t *)g_read_data(cp, offset,
159			    fat_BytesPerSector, NULL);
160			if (sector == NULL)
161				goto error;
162
163			pfat_entry = (FAT_DES *)sector;
164			do {
165				/* No more entries available. */
166				if (pfat_entry->DIR_Name[0] == 0) {
167					G_LABEL_DEBUG(1, "MSDOSFS: %s: "
168					    "FAT32 volume has no name.",
169					    pp->name);
170					goto error;
171				}
172
173				/* Skip empty or long name entries. */
174				if (pfat_entry->DIR_Name[0] == 0xe5 ||
175				    (pfat_entry->DIR_Attr &
176				     FAT_DES_ATTR_LONG_NAME) ==
177				    FAT_DES_ATTR_LONG_NAME) {
178					continue;
179				}
180
181				/*
182				 * The name of the entry is the volume label if
183				 * ATTR_VOLUME_ID is set.
184				 */
185				if (pfat_entry->DIR_Attr &
186				    FAT_DES_ATTR_VOLUME_ID) {
187					strlcpy(label, pfat_entry->DIR_Name,
188					    MIN(size,
189					    sizeof(pfat_bsbpb->BS_VolLab) + 1));
190					goto endofchecks;
191				}
192			} while((uint8_t *)(++pfat_entry) <
193			    (uint8_t *)(sector + fat_BytesPerSector));
194			g_free(sector);
195		}
196	} else {
197		G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.",
198		    pp->name);
199		goto error;
200	}
201
202endofchecks:
203	for (i = size - 1; i > 0; i--) {
204		if (label[i] == '\0')
205			continue;
206		else if (label[i] == ' ')
207			label[i] = '\0';
208		else
209			break;
210	}
211
212error:
213	if (sector0 != NULL)
214		g_free(sector0);
215	if (sector != NULL)
216		g_free(sector);
217}
218
219const struct g_label_desc g_label_msdosfs = {
220	.ld_taste = g_label_msdosfs_taste,
221	.ld_dir = G_LABEL_MSDOSFS_DIR
222};
223