1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (C) 1995, 1997 Wolfgang Solfrank
5 * Copyright (c) 1995 Martin Husemann
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28
29 #include <sys/cdefs.h>
30 #ifndef lint
31 __RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp ");
32 static const char rcsid[] =
33 "$FreeBSD$";
34 #endif /* not lint */
35
36 #include <stdlib.h>
37 #include <string.h>
38 #include <stdio.h>
39 #include <unistd.h>
40
41 #include "ext.h"
42 #include "fsutil.h"
43
44 int
readboot(int dosfs,struct bootblock * boot)45 readboot(int dosfs, struct bootblock *boot)
46 {
47 u_char block[DOSBOOTBLOCKSIZE];
48 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
49 u_char backup[DOSBOOTBLOCKSIZE];
50 int ret = FSOK;
51 int i;
52
53 if ((size_t)read(dosfs, block, sizeof block) != sizeof block) {
54 perr("could not read boot block");
55 return FSFATAL;
56 }
57
58 if (block[510] != 0x55 || block[511] != 0xaa) {
59 pfatal("Invalid signature in boot block: %02x%02x",
60 block[511], block[510]);
61 return FSFATAL;
62 }
63
64 memset(boot, 0, sizeof *boot);
65 boot->ValidFat = -1;
66
67 /* decode bios parameter block */
68 boot->bpbBytesPerSec = block[11] + (block[12] << 8);
69 boot->bpbSecPerClust = block[13];
70 boot->bpbResSectors = block[14] + (block[15] << 8);
71 boot->bpbFATs = block[16];
72 boot->bpbRootDirEnts = block[17] + (block[18] << 8);
73 boot->bpbSectors = block[19] + (block[20] << 8);
74 boot->bpbMedia = block[21];
75 boot->bpbFATsmall = block[22] + (block[23] << 8);
76 boot->SecPerTrack = block[24] + (block[25] << 8);
77 boot->bpbHeads = block[26] + (block[27] << 8);
78 boot->bpbHiddenSecs = block[28] + (block[29] << 8) +
79 (block[30] << 16) + (block[31] << 24);
80 boot->bpbHugeSectors = block[32] + (block[33] << 8) +
81 (block[34] << 16) + (block[35] << 24);
82
83 boot->FATsecs = boot->bpbFATsmall;
84
85 if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0 ||
86 boot->bpbBytesPerSec / DOSBOOTBLOCKSIZE_REAL == 0) {
87 pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
88 return FSFATAL;
89 }
90 if (boot->bpbFATs == 0) {
91 pfatal("Invalid number of FATs: %u", boot->bpbFATs);
92 return FSFATAL;
93 }
94 if (!boot->bpbRootDirEnts)
95 boot->flags |= FAT32;
96 if (boot->flags & FAT32) {
97 boot->FATsecs = block[36] + (block[37] << 8)
98 + (block[38] << 16) + (block[39] << 24);
99 if (block[40] & 0x80)
100 boot->ValidFat = block[40] & 0x0f;
101
102 /* check version number: */
103 if (block[42] || block[43]) {
104 /* Correct? XXX */
105 pfatal("Unknown file system version: %x.%x",
106 block[43], block[42]);
107 return FSFATAL;
108 }
109 boot->bpbRootClust = block[44] + (block[45] << 8)
110 + (block[46] << 16) + (block[47] << 24);
111 boot->bpbFSInfo = block[48] + (block[49] << 8);
112 boot->bpbBackup = block[50] + (block[51] << 8);
113
114 /* If the OEM Name field is EXFAT, it's not FAT32, so bail */
115 if (!memcmp(&block[3], "EXFAT ", 8)) {
116 pfatal("exFAT filesystem is not supported.");
117 return FSFATAL;
118 }
119
120 /* check basic parameters */
121 if ((boot->bpbFSInfo == 0) || (boot->bpbSecPerClust == 0)) {
122 /*
123 * Either the BIOS Parameter Block has been corrupted,
124 * or this is not a FAT32 filesystem, most likely an
125 * exFAT filesystem.
126 */
127 pfatal("Invalid FAT32 Extended BIOS Parameter Block");
128 return FSFATAL;
129 }
130 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
131 SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
132 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
133 perr("could not read fsinfo block");
134 return FSFATAL;
135 }
136 if (memcmp(fsinfo, "RRaA", 4)
137 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
138 || fsinfo[0x1fc]
139 || fsinfo[0x1fd]
140 || fsinfo[0x1fe] != 0x55
141 || fsinfo[0x1ff] != 0xaa
142 || fsinfo[0x3fc]
143 || fsinfo[0x3fd]
144 || fsinfo[0x3fe] != 0x55
145 || fsinfo[0x3ff] != 0xaa) {
146 pwarn("Invalid signature in fsinfo block\n");
147 if (ask(0, "Fix")) {
148 memcpy(fsinfo, "RRaA", 4);
149 memcpy(fsinfo + 0x1e4, "rrAa", 4);
150 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
151 fsinfo[0x1fe] = 0x55;
152 fsinfo[0x1ff] = 0xaa;
153 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
154 fsinfo[0x3fe] = 0x55;
155 fsinfo[0x3ff] = 0xaa;
156 if (lseek(dosfs, boot->bpbFSInfo *
157 boot->bpbBytesPerSec, SEEK_SET)
158 != boot->bpbFSInfo * boot->bpbBytesPerSec
159 || write(dosfs, fsinfo, sizeof fsinfo)
160 != sizeof fsinfo) {
161 perr("Unable to write bpbFSInfo");
162 return FSFATAL;
163 }
164 ret = FSBOOTMOD;
165 } else
166 boot->bpbFSInfo = 0;
167 }
168 if (boot->bpbFSInfo) {
169 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
170 + (fsinfo[0x1ea] << 16)
171 + (fsinfo[0x1eb] << 24);
172 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
173 + (fsinfo[0x1ee] << 16)
174 + (fsinfo[0x1ef] << 24);
175 }
176
177 if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec,
178 SEEK_SET)
179 != boot->bpbBackup * boot->bpbBytesPerSec
180 || read(dosfs, backup, sizeof backup) != sizeof backup) {
181 perr("could not read backup bootblock");
182 return FSFATAL;
183 }
184 backup[65] = block[65]; /* XXX */
185 if (memcmp(block + 11, backup + 11, 79)) {
186 /*
187 * XXX We require a reference that explains
188 * that these bytes need to match, or should
189 * drop the check. gdt@NetBSD has observed
190 * filesystems that work fine under Windows XP
191 * and NetBSD that do not match, so the
192 * requirement is suspect. For now, just
193 * print out useful information and continue.
194 */
195 pwarn("backup (block %d) mismatch with primary bootblock:\n",
196 boot->bpbBackup);
197 for (i = 11; i < 11 + 90; i++) {
198 if (block[i] != backup[i])
199 pwarn("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
200 i, block[i], backup[i]);
201 }
202 }
203 /* Check backup bpbFSInfo? XXX */
204 }
205
206 if (boot->bpbSecPerClust == 0) {
207 pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
208 return FSFATAL;
209 }
210 if (boot->bpbSectors) {
211 boot->bpbHugeSectors = 0;
212 boot->NumSectors = boot->bpbSectors;
213 } else
214 boot->NumSectors = boot->bpbHugeSectors;
215 boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
216 boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
217 boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
218 CLUST_FIRST * boot->bpbSecPerClust;
219 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
220 boot->bpbSecPerClust;
221
222 if (boot->flags&FAT32)
223 boot->ClustMask = CLUST32_MASK;
224 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
225 boot->ClustMask = CLUST12_MASK;
226 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
227 boot->ClustMask = CLUST16_MASK;
228 else {
229 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
230 boot->NumClusters);
231 return FSFATAL;
232 }
233
234 switch (boot->ClustMask) {
235 case CLUST32_MASK:
236 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
237 break;
238 case CLUST16_MASK:
239 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
240 break;
241 default:
242 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
243 break;
244 }
245
246 if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) {
247 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
248 boot->NumClusters, boot->FATsecs);
249 return FSFATAL;
250 }
251 boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
252
253 boot->NumFiles = 1;
254 boot->NumFree = 0;
255
256 return ret;
257 }
258
259 int
writefsinfo(int dosfs,struct bootblock * boot)260 writefsinfo(int dosfs, struct bootblock *boot)
261 {
262 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
263
264 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
265 != boot->bpbFSInfo * boot->bpbBytesPerSec
266 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
267 perr("could not read fsinfo block");
268 return FSFATAL;
269 }
270 fsinfo[0x1e8] = (u_char)boot->FSFree;
271 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
272 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
273 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
274 fsinfo[0x1ec] = (u_char)boot->FSNext;
275 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
276 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
277 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
278 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
279 != boot->bpbFSInfo * boot->bpbBytesPerSec
280 || write(dosfs, fsinfo, sizeof fsinfo)
281 != sizeof fsinfo) {
282 perr("Unable to write bpbFSInfo");
283 return FSFATAL;
284 }
285 /*
286 * Technically, we should return FSBOOTMOD here.
287 *
288 * However, since Win95 OSR2 (the first M$ OS that has
289 * support for FAT32) doesn't maintain the FSINFO block
290 * correctly, it has to be fixed pretty often.
291 *
292 * Therefor, we handle the FSINFO block only informally,
293 * fixing it if necessary, but otherwise ignoring the
294 * fact that it was incorrect.
295 */
296 return 0;
297 }
298