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.
34 #include <sys/cdefs.h>
36 __RCSID("$NetBSD: boot.c,v 1.5 1997/10/17 11:19:23 ws Exp $");
37 static const char rcsid[] =
53 struct bootblock *boot;
55 u_char block[DOSBOOTBLOCKSIZE];
56 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
57 u_char backup[DOSBOOTBLOCKSIZE];
60 if (read(dosfs, block, sizeof block) < sizeof block) {
61 perror("could not read boot block");
65 if (block[510] != 0x55 || block[511] != 0xaa) {
66 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
70 memset(boot, 0, sizeof *boot);
73 /* decode bios parameter block */
74 boot->BytesPerSec = block[11] + (block[12] << 8);
75 boot->SecPerClust = block[13];
76 boot->ResSectors = block[14] + (block[15] << 8);
77 boot->FATs = block[16];
78 boot->RootDirEnts = block[17] + (block[18] << 8);
79 boot->Sectors = block[19] + (block[20] << 8);
80 boot->Media = block[21];
81 boot->FATsmall = block[22] + (block[23] << 8);
82 boot->SecPerTrack = block[24] + (block[25] << 8);
83 boot->Heads = block[26] + (block[27] << 8);
84 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
85 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
87 boot->FATsecs = boot->FATsmall;
89 if (!boot->RootDirEnts)
91 if (boot->flags & FAT32) {
92 boot->FATsecs = block[36] + (block[37] << 8)
93 + (block[38] << 16) + (block[39] << 24);
95 boot->ValidFat = block[40] & 0x0f;
97 /* check version number: */
98 if (block[42] || block[43]) {
100 pfatal("Unknown filesystem version: %x.%x",
101 block[43], block[42]);
104 boot->RootCl = block[44] + (block[45] << 8)
105 + (block[46] << 16) + (block[47] << 24);
106 boot->FSInfo = block[48] + (block[49] << 8);
107 boot->Backup = block[50] + (block[51] << 8);
109 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
110 != boot->FSInfo * boot->BytesPerSec
111 || read(dosfs, fsinfo, sizeof fsinfo)
113 perror("could not read fsinfo block");
116 if (memcmp(fsinfo, "RRaA", 4)
117 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
120 || fsinfo[0x1fe] != 0x55
121 || fsinfo[0x1ff] != 0xaa
124 || fsinfo[0x3fe] != 0x55
125 || fsinfo[0x3ff] != 0xaa) {
126 pwarn("Invalid signature in fsinfo block");
128 memcpy(fsinfo, "RRaA", 4);
129 memcpy(fsinfo + 0x1e4, "rrAa", 4);
130 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
131 fsinfo[0x1fe] = 0x55;
132 fsinfo[0x1ff] = 0xaa;
133 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
134 fsinfo[0x3fe] = 0x55;
135 fsinfo[0x3ff] = 0xaa;
136 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
137 != boot->FSInfo * boot->BytesPerSec
138 || write(dosfs, fsinfo, sizeof fsinfo)
140 perror("Unable to write FSInfo");
148 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
149 + (fsinfo[0x1ea] << 16)
150 + (fsinfo[0x1eb] << 24);
151 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
152 + (fsinfo[0x1ee] << 16)
153 + (fsinfo[0x1ef] << 24);
156 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
157 != boot->Backup * boot->BytesPerSec
158 || read(dosfs, backup, sizeof backup) != sizeof backup) {
159 perror("could not read backup bootblock");
162 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) {
164 pfatal("backup doesn't compare to primary bootblock");
167 /* Check backup FSInfo? XXX */
170 boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
173 + boot->FATs * boot->FATsecs
174 - CLUST_FIRST * boot->SecPerClust;
176 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
177 pfatal("Invalid sector size: %u", boot->BytesPerSec);
180 if (boot->SecPerClust == 0) {
181 pfatal("Invalid cluster size: %u", boot->SecPerClust);
185 boot->HugeSectors = 0;
186 boot->NumSectors = boot->Sectors;
188 boot->NumSectors = boot->HugeSectors;
189 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
191 if (boot->flags&FAT32)
192 boot->ClustMask = CLUST32_MASK;
193 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
194 boot->ClustMask = CLUST12_MASK;
195 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
196 boot->ClustMask = CLUST16_MASK;
198 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
203 switch (boot->ClustMask) {
205 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
208 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
211 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
215 if (boot->NumFatEntries < boot->NumClusters) {
216 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
217 boot->NumClusters, boot->FATsecs);
220 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
229 writefsinfo(dosfs, boot)
231 struct bootblock *boot;
233 u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
235 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
236 != boot->FSInfo * boot->BytesPerSec
237 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
238 perror("could not read fsinfo block");
241 fsinfo[0x1e8] = (u_char)boot->FSFree;
242 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
243 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
244 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
245 fsinfo[0x1ec] = (u_char)boot->FSNext;
246 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
247 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
248 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
249 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
250 != boot->FSInfo * boot->BytesPerSec
251 || write(dosfs, fsinfo, sizeof fsinfo)
253 perror("Unable to write FSInfo");
257 * Technically, we should return FSBOOTMOD here.
259 * However, since Win95 OSR2 (the first M$ OS that has
260 * support for FAT32) doesn't maintain the FSINFO block
261 * correctly, it has to be fixed pretty often.
263 * Therefor, we handle the FSINFO block only informally,
264 * fixing it if neccessary, but otherwise ignoring the
265 * fact that it was incorrect.