2 * Copyright (C) 1995, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 #include <sys/cdefs.h>
29 __RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp ");
30 static const char rcsid[] =
43 readboot(int dosfs, struct bootblock *boot)
45 u_char block[DOSBOOTBLOCKSIZE];
46 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
47 u_char backup[DOSBOOTBLOCKSIZE];
51 if ((size_t)read(dosfs, block, sizeof block) != sizeof block) {
52 perr("could not read boot block");
56 if (block[510] != 0x55 || block[511] != 0xaa) {
57 pfatal("Invalid signature in boot block: %02x%02x",
58 block[511], block[510]);
62 memset(boot, 0, sizeof *boot);
65 /* decode bios parameter block */
66 boot->bpbBytesPerSec = block[11] + (block[12] << 8);
67 boot->bpbSecPerClust = block[13];
68 boot->bpbResSectors = block[14] + (block[15] << 8);
69 boot->bpbFATs = block[16];
70 boot->bpbRootDirEnts = block[17] + (block[18] << 8);
71 boot->bpbSectors = block[19] + (block[20] << 8);
72 boot->bpbMedia = block[21];
73 boot->bpbFATsmall = block[22] + (block[23] << 8);
74 boot->SecPerTrack = block[24] + (block[25] << 8);
75 boot->bpbHeads = block[26] + (block[27] << 8);
76 boot->bpbHiddenSecs = block[28] + (block[29] << 8) +
77 (block[30] << 16) + (block[31] << 24);
78 boot->bpbHugeSectors = block[32] + (block[33] << 8) +
79 (block[34] << 16) + (block[35] << 24);
81 boot->FATsecs = boot->bpbFATsmall;
83 if (!boot->bpbRootDirEnts)
85 if (boot->flags & FAT32) {
86 boot->FATsecs = block[36] + (block[37] << 8)
87 + (block[38] << 16) + (block[39] << 24);
89 boot->ValidFat = block[40] & 0x0f;
91 /* check version number: */
92 if (block[42] || block[43]) {
94 pfatal("Unknown file system version: %x.%x",
95 block[43], block[42]);
98 boot->bpbRootClust = block[44] + (block[45] << 8)
99 + (block[46] << 16) + (block[47] << 24);
100 boot->bpbFSInfo = block[48] + (block[49] << 8);
101 boot->bpbBackup = block[50] + (block[51] << 8);
103 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
104 SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
105 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
106 perr("could not read fsinfo block");
109 if (memcmp(fsinfo, "RRaA", 4)
110 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
113 || fsinfo[0x1fe] != 0x55
114 || fsinfo[0x1ff] != 0xaa
117 || fsinfo[0x3fe] != 0x55
118 || fsinfo[0x3ff] != 0xaa) {
119 pwarn("Invalid signature in fsinfo block\n");
121 memcpy(fsinfo, "RRaA", 4);
122 memcpy(fsinfo + 0x1e4, "rrAa", 4);
123 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
124 fsinfo[0x1fe] = 0x55;
125 fsinfo[0x1ff] = 0xaa;
126 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
127 fsinfo[0x3fe] = 0x55;
128 fsinfo[0x3ff] = 0xaa;
129 if (lseek(dosfs, boot->bpbFSInfo *
130 boot->bpbBytesPerSec, SEEK_SET)
131 != boot->bpbFSInfo * boot->bpbBytesPerSec
132 || write(dosfs, fsinfo, sizeof fsinfo)
134 perr("Unable to write bpbFSInfo");
141 if (boot->bpbFSInfo) {
142 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
143 + (fsinfo[0x1ea] << 16)
144 + (fsinfo[0x1eb] << 24);
145 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
146 + (fsinfo[0x1ee] << 16)
147 + (fsinfo[0x1ef] << 24);
150 if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec,
152 != boot->bpbBackup * boot->bpbBytesPerSec
153 || read(dosfs, backup, sizeof backup) != sizeof backup) {
154 perr("could not read backup bootblock");
157 backup[65] = block[65]; /* XXX */
158 if (memcmp(block + 11, backup + 11, 79)) {
160 * XXX We require a reference that explains
161 * that these bytes need to match, or should
162 * drop the check. gdt@NetBSD has observed
163 * filesystems that work fine under Windows XP
164 * and NetBSD that do not match, so the
165 * requirement is suspect. For now, just
166 * print out useful information and continue.
168 pfatal("backup (block %d) mismatch with primary bootblock:\n",
170 for (i = 11; i < 11 + 90; i++) {
171 if (block[i] != backup[i])
172 pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
173 i, block[i], backup[i]);
176 /* Check backup bpbFSInfo? XXX */
179 boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
180 boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
181 boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
182 CLUST_FIRST * boot->bpbSecPerClust;
184 if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE != 0) {
185 pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
188 if (boot->bpbSecPerClust == 0) {
189 pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
192 if (boot->bpbSectors) {
193 boot->bpbHugeSectors = 0;
194 boot->NumSectors = boot->bpbSectors;
196 boot->NumSectors = boot->bpbHugeSectors;
197 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
198 boot->bpbSecPerClust;
200 if (boot->flags&FAT32)
201 boot->ClustMask = CLUST32_MASK;
202 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
203 boot->ClustMask = CLUST12_MASK;
204 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
205 boot->ClustMask = CLUST16_MASK;
207 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
212 switch (boot->ClustMask) {
214 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
217 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
220 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
224 if (boot->NumFatEntries < boot->NumClusters) {
225 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
226 boot->NumClusters, boot->FATsecs);
229 boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
238 writefsinfo(int dosfs, struct bootblock *boot)
240 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
242 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
243 != boot->bpbFSInfo * boot->bpbBytesPerSec
244 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
245 perr("could not read fsinfo block");
248 fsinfo[0x1e8] = (u_char)boot->FSFree;
249 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
250 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
251 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
252 fsinfo[0x1ec] = (u_char)boot->FSNext;
253 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
254 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
255 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
256 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
257 != boot->bpbFSInfo * boot->bpbBytesPerSec
258 || write(dosfs, fsinfo, sizeof fsinfo)
260 perr("Unable to write bpbFSInfo");
264 * Technically, we should return FSBOOTMOD here.
266 * However, since Win95 OSR2 (the first M$ OS that has
267 * support for FAT32) doesn't maintain the FSINFO block
268 * correctly, it has to be fixed pretty often.
270 * Therefor, we handle the FSINFO block only informally,
271 * fixing it if necessary, but otherwise ignoring the
272 * fact that it was incorrect.