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.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by Martin Husemann
16 * and Wolfgang Solfrank.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 * $NetBSD: boot.c,v 1.5 1997/10/17 11:19:23 ws Exp $
33 * $FreeBSD: src/sbin/fsck_msdosfs/boot.c,v 1.1.2.1 2001/08/01 05:47:55 obrien Exp $
46 readboot(int dosfs, struct bootblock *boot)
48 u_char block[DOSBOOTBLOCKSIZE];
49 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
50 u_char backup[DOSBOOTBLOCKSIZE];
53 if (read(dosfs, block, sizeof block) < sizeof block) {
54 perror("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->BytesPerSec = block[11] + (block[12] << 8);
69 boot->SecPerClust = block[13];
70 boot->ResSectors = block[14] + (block[15] << 8);
71 boot->FATs = block[16];
72 boot->RootDirEnts = block[17] + (block[18] << 8);
73 boot->Sectors = block[19] + (block[20] << 8);
74 boot->Media = block[21];
75 boot->FATsmall = block[22] + (block[23] << 8);
76 boot->SecPerTrack = block[24] + (block[25] << 8);
77 boot->Heads = block[26] + (block[27] << 8);
78 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
79 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
81 boot->FATsecs = boot->FATsmall;
83 if (!boot->RootDirEnts)
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 filesystem version: %x.%x",
95 block[43], block[42]);
98 boot->RootCl = block[44] + (block[45] << 8)
99 + (block[46] << 16) + (block[47] << 24);
100 boot->FSInfo = block[48] + (block[49] << 8);
101 boot->Backup = block[50] + (block[51] << 8);
103 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
104 != boot->FSInfo * boot->BytesPerSec
105 || read(dosfs, fsinfo, sizeof fsinfo)
107 perror("could not read fsinfo block");
110 if (memcmp(fsinfo, "RRaA", 4)
111 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
114 || fsinfo[0x1fe] != 0x55
115 || fsinfo[0x1ff] != 0xaa
118 || fsinfo[0x3fe] != 0x55
119 || fsinfo[0x3ff] != 0xaa) {
120 pwarn("Invalid signature in fsinfo block");
122 memcpy(fsinfo, "RRaA", 4);
123 memcpy(fsinfo + 0x1e4, "rrAa", 4);
124 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
125 fsinfo[0x1fe] = 0x55;
126 fsinfo[0x1ff] = 0xaa;
127 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
128 fsinfo[0x3fe] = 0x55;
129 fsinfo[0x3ff] = 0xaa;
130 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
131 != boot->FSInfo * boot->BytesPerSec
132 || write(dosfs, fsinfo, sizeof fsinfo)
134 perror("Unable to write FSInfo");
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->Backup * boot->BytesPerSec, SEEK_SET)
151 != boot->Backup * boot->BytesPerSec
152 || read(dosfs, backup, sizeof backup) != sizeof backup) {
153 perror("could not read backup bootblock");
156 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) {
158 pfatal("backup doesn't compare to primary bootblock");
161 /* Check backup FSInfo? XXX */
164 boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
167 + boot->FATs * boot->FATsecs
168 - CLUST_FIRST * boot->SecPerClust;
170 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
171 pfatal("Invalid sector size: %u", boot->BytesPerSec);
174 if (boot->SecPerClust == 0) {
175 pfatal("Invalid cluster size: %u", boot->SecPerClust);
179 boot->HugeSectors = 0;
180 boot->NumSectors = boot->Sectors;
182 boot->NumSectors = boot->HugeSectors;
183 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
185 if (boot->flags&FAT32)
186 boot->ClustMask = CLUST32_MASK;
187 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
188 boot->ClustMask = CLUST12_MASK;
189 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
190 boot->ClustMask = CLUST16_MASK;
192 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
197 switch (boot->ClustMask) {
199 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
202 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
205 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
209 if (boot->NumFatEntries < boot->NumClusters) {
210 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
211 boot->NumClusters, boot->FATsecs);
214 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
223 writefsinfo(int dosfs, struct bootblock *boot)
225 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
227 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
228 != boot->FSInfo * boot->BytesPerSec
229 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
230 perror("could not read fsinfo block");
233 fsinfo[0x1e8] = (u_char)boot->FSFree;
234 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
235 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
236 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
237 fsinfo[0x1ec] = (u_char)boot->FSNext;
238 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
239 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
240 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
241 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
242 != boot->FSInfo * boot->BytesPerSec
243 || write(dosfs, fsinfo, sizeof fsinfo)
245 perror("Unable to write FSInfo");
249 * Technically, we should return FSBOOTMOD here.
251 * However, since Win95 OSR2 (the first M$ OS that has
252 * support for FAT32) doesn't maintain the FSINFO block
253 * correctly, it has to be fixed pretty often.
255 * Therefor, we handle the FSINFO block only informally,
256 * fixing it if neccessary, but otherwise ignoring the
257 * fact that it was incorrect.