1
2 /*
3 * Copyright (C) 1995, 1997 Wolfgang Solfrank
4 * Copyright (c) 1995 Martin Husemann
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27
28 #include <sys/cdefs.h>
29 #ifndef lint
30 __RCSID("$NetBSD: boot.c,v 1.27 2022/08/28 11:32:19 mlelstv Exp $");
31 #endif /* not lint */
32
33 #include <stdlib.h>
34 #include <string.h>
35 #include <strings.h>
36 #include <inttypes.h>
37 #include <stdio.h>
38 #include <unistd.h>
39 #include <sys/ioctl.h>
40 #include <sys/dkio.h>
41
42 #include "ext.h"
43 #include "fsutil.h"
44
45 int
readboot(int dosfs,struct bootblock * boot)46 readboot(int dosfs, struct bootblock *boot)
47 {
48 u_char *block;
49 u_char *fsinfo;
50 u_char *backup;
51 int ret = FSOK;
52 int i, err;
53 u_int secsize;
54
55 secsize = 0;
56 err = ioctl(dosfs, DIOCGSECTORSIZE, &secsize);
57 if (err != 0 || secsize == 0)
58 secsize = DOSBOOTBLOCKSIZE;
59
60 if (secsize < DOSBOOTBLOCKSIZE)
61 pfatal("Invalid sector size %u\n", secsize);
62
63 block = calloc(1, secsize);
64 if (block == NULL)
65 pfatal("Out of memory");
66
67 if ((size_t)read(dosfs, block, secsize) != secsize) {
68 perr("could not read boot block");
69 free(block);
70 return FSFATAL;
71 }
72
73 if (block[510] != 0x55 || block[511] != 0xaa) {
74 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
75 free(block);
76 return FSFATAL;
77 }
78
79 memset(boot, 0, sizeof *boot);
80 boot->ValidFat = -1;
81
82 /* decode bios parameter block */
83 boot->BytesPerSec = block[11] + (block[12] << 8);
84 boot->SecPerClust = block[13];
85 if (boot->SecPerClust == 0 || popcount(boot->SecPerClust) != 1) {
86 pfatal("Invalid cluster size: %u\n", boot->SecPerClust);
87 return FSFATAL;
88 }
89 boot->ResSectors = block[14] + (block[15] << 8);
90 boot->FATs = block[16];
91 if (boot->FATs == 0) {
92 pfatal("Invalid number of FATs: %u\n", boot->FATs);
93 return FSFATAL;
94 }
95 boot->RootDirEnts = block[17] + (block[18] << 8);
96 boot->Sectors = block[19] + (block[20] << 8);
97 boot->Media = block[21];
98 boot->FATsmall = block[22] + (block[23] << 8);
99 boot->SecPerTrack = block[24] + (block[25] << 8);
100 boot->Heads = block[26] + (block[27] << 8);
101 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + ((uint32_t)block[31] << 24);
102 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + ((uint32_t)block[35] << 24);
103
104 boot->FATsecs = boot->FATsmall;
105
106 fsinfo = calloc(2, secsize);
107 if (fsinfo == NULL)
108 pfatal("Out of memory");
109 backup = calloc(1, secsize);
110 if (backup == NULL)
111 pfatal("Out of memory");
112
113 if (!boot->RootDirEnts)
114 boot->flags |= FAT32;
115 if (boot->flags & FAT32) {
116 boot->FATsecs = block[36] + (block[37] << 8)
117 + (block[38] << 16) + ((uint32_t)block[39] << 24);
118 if (block[40] & 0x80)
119 boot->ValidFat = block[40] & 0x0f;
120
121 /* check version number: */
122 if (block[42] || block[43]) {
123 /* Correct? XXX */
124 pfatal("Unknown filesystem version: %x.%x",
125 block[43], block[42]);
126 return FSFATAL;
127 }
128 boot->RootCl = block[44] + (block[45] << 8)
129 + (block[46] << 16) + ((uint32_t)block[47] << 24);
130 boot->FSInfo = block[48] + (block[49] << 8);
131 boot->Backup = block[50] + (block[51] << 8);
132
133 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
134 != boot->FSInfo * boot->BytesPerSec
135 || (size_t)read(dosfs, fsinfo, 2 * secsize)
136 != 2 * secsize) {
137 perr("could not read fsinfo block");
138 return FSFATAL;
139 }
140 if (memcmp(fsinfo, "RRaA", 4)
141 || memcmp(fsinfo + 0x1e4, "rrAa", 4)
142 || fsinfo[0x1fc]
143 || fsinfo[0x1fd]
144 || fsinfo[0x1fe] != 0x55
145 || fsinfo[0x1ff] != 0xaa
146 || fsinfo[0x3fc]
147 || fsinfo[0x3fd]
148 || fsinfo[0x3fe] != 0x55
149 || fsinfo[0x3ff] != 0xaa) {
150 pwarn("Invalid signature in fsinfo block\n");
151 if (ask(0, "fix")) {
152 memcpy(fsinfo, "RRaA", 4);
153 memcpy(fsinfo + 0x1e4, "rrAa", 4);
154 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
155 fsinfo[0x1fe] = 0x55;
156 fsinfo[0x1ff] = 0xaa;
157 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
158 fsinfo[0x3fe] = 0x55;
159 fsinfo[0x3ff] = 0xaa;
160 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
161 != boot->FSInfo * boot->BytesPerSec
162 || (size_t)write(dosfs, fsinfo, 2 * secsize)
163 != 2 * secsize) {
164 perr("Unable to write FSInfo");
165 free(fsinfo);
166 free(backup);
167 free(block);
168 return FSFATAL;
169 }
170 ret = FSBOOTMOD;
171 } else
172 boot->FSInfo = 0;
173 }
174 if (boot->FSInfo) {
175 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
176 + (fsinfo[0x1ea] << 16)
177 + ((uint32_t)fsinfo[0x1eb] << 24);
178 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
179 + (fsinfo[0x1ee] << 16)
180 + ((uint32_t)fsinfo[0x1ef] << 24);
181 }
182
183 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
184 != boot->Backup * boot->BytesPerSec
185 || (size_t)read(dosfs, backup, secsize) != secsize) {
186 perr("could not read backup bootblock");
187 free(fsinfo);
188 free(backup);
189 free(block);
190 return FSFATAL;
191 }
192 backup[65] = block[65]; /* XXX */
193 if (memcmp(block + 11, backup + 11, 79)) {
194 /*
195 * XXX We require a reference that explains
196 * that these bytes need to match, or should
197 * drop the check. gdt@ has observed
198 * filesystems that work fine under Windows XP
199 * and NetBSD that do not match, so the
200 * requirement is suspect. For now, just
201 * print out useful information and continue.
202 */
203 pfatal("backup (block %d) mismatch with primary bootblock:\n",
204 boot->Backup);
205 for (i = 11; i < 11 + 90; i++) {
206 if (block[i] != backup[i])
207 pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
208 i, block[i], backup[i]);
209 }
210 }
211 /* Check backup FSInfo? XXX */
212 }
213
214 free(fsinfo);
215 free(backup);
216 free(block);
217
218 if (boot->FATsecs == 0) {
219 pfatal("Invalid number of FAT sectors: %u\n", boot->FATsecs);
220 return FSFATAL;
221 }
222
223 boot->FirstCluster = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
224 / boot->BytesPerSec
225 + boot->ResSectors
226 + boot->FATs * boot->FATsecs;
227
228 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
229 pfatal("Invalid sector size: %u", boot->BytesPerSec);
230 return FSFATAL;
231 }
232 if (boot->SecPerClust == 0) {
233 pfatal("Invalid cluster size: %u", boot->SecPerClust);
234 return FSFATAL;
235 }
236 if (boot->Sectors) {
237 boot->HugeSectors = 0;
238 boot->NumSectors = boot->Sectors;
239 } else
240 boot->NumSectors = boot->HugeSectors;
241
242 if (boot->FirstCluster + boot->SecPerClust > boot->NumSectors) {
243 pfatal("Cluster offset too large (%u clusters)\n",
244 boot->FirstCluster);
245 return FSFATAL;
246 }
247
248 /*
249 * The number of clusters is derived from available data sectors,
250 * divided by sectors per cluster.
251 */
252 boot->NumClusters =
253 (boot->NumSectors - boot->FirstCluster) / boot->SecPerClust;
254
255 if (boot->flags&FAT32)
256 boot->ClustMask = CLUST32_MASK;
257 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
258 boot->ClustMask = CLUST12_MASK;
259 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
260 boot->ClustMask = CLUST16_MASK;
261 else {
262 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
263 boot->NumClusters);
264 return FSFATAL;
265 }
266
267 switch (boot->ClustMask) {
268 case CLUST32_MASK:
269 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
270 break;
271 case CLUST16_MASK:
272 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
273 break;
274 default:
275 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
276 break;
277 }
278
279 if (boot->NumFatEntries < boot->NumClusters) {
280 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
281 boot->NumClusters, boot->FATsecs);
282 return FSFATAL;
283 }
284
285 /*
286 * There are two reserved clusters. To avoid adding CLUST_FIRST every
287 * time we perform boundary checks, we increment the NumClusters by 2,
288 * which is CLUST_FIRST to denote the first out-of-range cluster number.
289 */
290 boot->NumClusters += CLUST_FIRST;
291
292 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
293
294 boot->NumFiles = 1;
295 boot->NumFree = 0;
296
297 return ret;
298 }
299
300 int
writefsinfo(int dosfs,struct bootblock * boot)301 writefsinfo(int dosfs, struct bootblock *boot)
302 {
303 u_char *fsinfo;
304
305 fsinfo = calloc(2, boot->BytesPerSec);
306 if (fsinfo == NULL)
307 pfatal("Out of memory");
308
309 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
310 != boot->FSInfo * boot->BytesPerSec
311 || (size_t)read(dosfs, fsinfo, 2 * boot->BytesPerSec)
312 != 2 * boot->BytesPerSec) {
313 perr("could not read fsinfo block");
314 free(fsinfo);
315 return FSFATAL;
316 }
317 fsinfo[0x1e8] = (u_char)boot->FSFree;
318 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
319 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
320 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
321 fsinfo[0x1ec] = (u_char)boot->FSNext;
322 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
323 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
324 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
325 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
326 != boot->FSInfo * boot->BytesPerSec
327 || (size_t)write(dosfs, fsinfo, 2 * boot->BytesPerSec)
328 != 2 * boot->BytesPerSec) {
329 perr("Unable to write FSInfo");
330 free(fsinfo);
331 return FSFATAL;
332 }
333
334 free(fsinfo);
335
336 /*
337 * Technically, we should return FSBOOTMOD here.
338 *
339 * However, since Win95 OSR2 (the first M$ OS that has
340 * support for FAT32) doesn't maintain the FSINFO block
341 * correctly, it has to be fixed pretty often.
342 *
343 * Therefore, we handle the FSINFO block only informally,
344 * fixing it if necessary, but otherwise ignoring the
345 * fact that it was incorrect.
346 */
347 return 0;
348 }
349