2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (C) 1995, 1997 Wolfgang Solfrank
5 * Copyright (c) 1995 Martin Husemann
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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.
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.
29 #include <sys/cdefs.h>
31 __RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp ");
32 static const char rcsid[] =
45 readboot(int dosfs, struct bootblock *boot)
47 u_char block[DOSBOOTBLOCKSIZE];
48 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
49 u_char backup[DOSBOOTBLOCKSIZE];
53 if ((size_t)read(dosfs, block, sizeof block) != sizeof block) {
54 perr("could not read boot block");
58 if (block[510] != 0x55 || block[511] != 0xaa) {
59 pfatal("Invalid signature in boot block: %02x%02x",
60 block[511], block[510]);
64 memset(boot, 0, sizeof *boot);
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);
83 boot->FATsecs = boot->bpbFATsmall;
85 if (!boot->bpbRootDirEnts)
87 if (boot->flags & FAT32) {
88 boot->FATsecs = block[36] + (block[37] << 8)
89 + (block[38] << 16) + (block[39] << 24);
91 boot->ValidFat = block[40] & 0x0f;
93 /* check version number: */
94 if (block[42] || block[43]) {
96 pfatal("Unknown file system version: %x.%x",
97 block[43], block[42]);
100 boot->bpbRootClust = block[44] + (block[45] << 8)
101 + (block[46] << 16) + (block[47] << 24);
102 boot->bpbFSInfo = block[48] + (block[49] << 8);
103 boot->bpbBackup = block[50] + (block[51] << 8);
105 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
106 SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
107 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
108 perr("could not read fsinfo block");
111 if (memcmp(fsinfo, "RRaA", 4)
112 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
115 || fsinfo[0x1fe] != 0x55
116 || fsinfo[0x1ff] != 0xaa
119 || fsinfo[0x3fe] != 0x55
120 || fsinfo[0x3ff] != 0xaa) {
121 pwarn("Invalid signature in fsinfo block\n");
123 memcpy(fsinfo, "RRaA", 4);
124 memcpy(fsinfo + 0x1e4, "rrAa", 4);
125 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
126 fsinfo[0x1fe] = 0x55;
127 fsinfo[0x1ff] = 0xaa;
128 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
129 fsinfo[0x3fe] = 0x55;
130 fsinfo[0x3ff] = 0xaa;
131 if (lseek(dosfs, boot->bpbFSInfo *
132 boot->bpbBytesPerSec, SEEK_SET)
133 != boot->bpbFSInfo * boot->bpbBytesPerSec
134 || write(dosfs, fsinfo, sizeof fsinfo)
136 perr("Unable to write bpbFSInfo");
143 if (boot->bpbFSInfo) {
144 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
145 + (fsinfo[0x1ea] << 16)
146 + (fsinfo[0x1eb] << 24);
147 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
148 + (fsinfo[0x1ee] << 16)
149 + (fsinfo[0x1ef] << 24);
152 if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec,
154 != boot->bpbBackup * boot->bpbBytesPerSec
155 || read(dosfs, backup, sizeof backup) != sizeof backup) {
156 perr("could not read backup bootblock");
159 backup[65] = block[65]; /* XXX */
160 if (memcmp(block + 11, backup + 11, 79)) {
162 * XXX We require a reference that explains
163 * that these bytes need to match, or should
164 * drop the check. gdt@NetBSD has observed
165 * filesystems that work fine under Windows XP
166 * and NetBSD that do not match, so the
167 * requirement is suspect. For now, just
168 * print out useful information and continue.
170 pwarn("backup (block %d) mismatch with primary bootblock:\n",
172 for (i = 11; i < 11 + 90; i++) {
173 if (block[i] != backup[i])
174 pwarn("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
175 i, block[i], backup[i]);
178 /* Check backup bpbFSInfo? XXX */
181 boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
182 boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
183 boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
184 CLUST_FIRST * boot->bpbSecPerClust;
186 if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0) {
187 pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
190 if (boot->bpbSecPerClust == 0) {
191 pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
194 if (boot->bpbSectors) {
195 boot->bpbHugeSectors = 0;
196 boot->NumSectors = boot->bpbSectors;
198 boot->NumSectors = boot->bpbHugeSectors;
199 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
200 boot->bpbSecPerClust;
202 if (boot->flags&FAT32)
203 boot->ClustMask = CLUST32_MASK;
204 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
205 boot->ClustMask = CLUST12_MASK;
206 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
207 boot->ClustMask = CLUST16_MASK;
209 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
214 switch (boot->ClustMask) {
216 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
219 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
222 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
226 if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) {
227 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
228 boot->NumClusters, boot->FATsecs);
231 boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
240 writefsinfo(int dosfs, struct bootblock *boot)
242 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
244 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
245 != boot->bpbFSInfo * boot->bpbBytesPerSec
246 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
247 perr("could not read fsinfo block");
250 fsinfo[0x1e8] = (u_char)boot->FSFree;
251 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
252 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
253 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
254 fsinfo[0x1ec] = (u_char)boot->FSNext;
255 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
256 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
257 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
258 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
259 != boot->bpbFSInfo * boot->bpbBytesPerSec
260 || write(dosfs, fsinfo, sizeof fsinfo)
262 perr("Unable to write bpbFSInfo");
266 * Technically, we should return FSBOOTMOD here.
268 * However, since Win95 OSR2 (the first M$ OS that has
269 * support for FAT32) doesn't maintain the FSINFO block
270 * correctly, it has to be fixed pretty often.
272 * Therefor, we handle the FSINFO block only informally,
273 * fixing it if necessary, but otherwise ignoring the
274 * fact that it was incorrect.