Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 1 | /*- |
| 2 | * SPDX-License-Identifier: BSD-2-Clause-FreeBSD |
| 3 | * |
| 4 | * Copyright (C) 1995, 1997 Wolfgang Solfrank |
| 5 | * Copyright (c) 1995 Martin Husemann |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions |
| 9 | * are met: |
| 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. |
| 15 | * |
| 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. |
| 26 | */ |
| 27 | |
| 28 | |
| 29 | #include <sys/cdefs.h> |
| 30 | #ifndef lint |
Xin Li | ad1ac48 | 2020-04-27 08:59:19 -0700 | [diff] [blame] | 31 | __RCSID("$NetBSD: boot.c,v 1.22 2020/01/11 16:29:07 christos Exp $"); |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 32 | static const char rcsid[] = |
| 33 | "$FreeBSD$"; |
| 34 | #endif /* not lint */ |
| 35 | |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 36 | #include <sys/param.h> |
| 37 | |
| 38 | #include <stdint.h> |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 39 | #include <stdlib.h> |
| 40 | #include <string.h> |
| 41 | #include <stdio.h> |
| 42 | #include <unistd.h> |
| 43 | |
| 44 | #include "ext.h" |
| 45 | #include "fsutil.h" |
| 46 | |
| 47 | int |
| 48 | readboot(int dosfs, struct bootblock *boot) |
| 49 | { |
| 50 | u_char block[DOSBOOTBLOCKSIZE]; |
| 51 | u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 52 | int ret = FSOK; |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 53 | |
| 54 | if ((size_t)read(dosfs, block, sizeof block) != sizeof block) { |
| 55 | perr("could not read boot block"); |
| 56 | return FSFATAL; |
| 57 | } |
| 58 | |
| 59 | if (block[510] != 0x55 || block[511] != 0xaa) { |
| 60 | pfatal("Invalid signature in boot block: %02x%02x", |
| 61 | block[511], block[510]); |
| 62 | return FSFATAL; |
| 63 | } |
| 64 | |
| 65 | memset(boot, 0, sizeof *boot); |
| 66 | boot->ValidFat = -1; |
| 67 | |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 68 | /* Decode BIOS Parameter Block */ |
| 69 | |
| 70 | /* Bytes per sector: can only be 512, 1024, 2048 and 4096. */ |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 71 | boot->bpbBytesPerSec = block[11] + (block[12] << 8); |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 72 | if (boot->bpbBytesPerSec < DOSBOOTBLOCKSIZE_REAL || |
| 73 | boot->bpbBytesPerSec > DOSBOOTBLOCKSIZE || |
| 74 | !powerof2(boot->bpbBytesPerSec)) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 75 | pfatal("Invalid sector size: %u", boot->bpbBytesPerSec); |
| 76 | return FSFATAL; |
| 77 | } |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 78 | |
| 79 | /* Sectors per cluster: can only be: 1, 2, 4, 8, 16, 32, 64, 128. */ |
| 80 | boot->bpbSecPerClust = block[13]; |
| 81 | if (boot->bpbSecPerClust == 0 || !powerof2(boot->bpbSecPerClust)) { |
| 82 | pfatal("Invalid cluster size: %u", boot->bpbSecPerClust); |
| 83 | return FSFATAL; |
| 84 | } |
| 85 | |
| 86 | /* Reserved sectors: must be non-zero */ |
| 87 | boot->bpbResSectors = block[14] + (block[15] << 8); |
| 88 | if (boot->bpbResSectors < 1) { |
| 89 | pfatal("Invalid reserved sectors: %u", |
| 90 | boot->bpbResSectors); |
| 91 | return FSFATAL; |
| 92 | } |
| 93 | |
| 94 | /* Number of FATs */ |
| 95 | boot->bpbFATs = block[16]; |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 96 | if (boot->bpbFATs == 0) { |
| 97 | pfatal("Invalid number of FATs: %u", boot->bpbFATs); |
| 98 | return FSFATAL; |
| 99 | } |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 100 | |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 101 | /* Root directory entries for FAT12 and FAT16 */ |
| 102 | boot->bpbRootDirEnts = block[17] + (block[18] << 8); |
| 103 | if (!boot->bpbRootDirEnts) { |
| 104 | /* bpbRootDirEnts = 0 suggests that we are FAT32 */ |
| 105 | boot->flags |= FAT32; |
| 106 | } |
| 107 | |
| 108 | /* Total sectors (16 bits) */ |
| 109 | boot->bpbSectors = block[19] + (block[20] << 8); |
| 110 | if (boot->bpbSectors != 0 && (boot->flags & FAT32)) { |
| 111 | pfatal("Invalid 16-bit total sector count on FAT32: %u", |
| 112 | boot->bpbSectors); |
| 113 | return FSFATAL; |
| 114 | } |
| 115 | |
| 116 | /* Media type: ignored */ |
| 117 | boot->bpbMedia = block[21]; |
| 118 | |
| 119 | /* FAT12/FAT16: 16-bit count of sectors per FAT */ |
| 120 | boot->bpbFATsmall = block[22] + (block[23] << 8); |
| 121 | if (boot->bpbFATsmall != 0 && (boot->flags & FAT32)) { |
| 122 | pfatal("Invalid 16-bit FAT sector count on FAT32: %u", |
| 123 | boot->bpbFATsmall); |
| 124 | return FSFATAL; |
| 125 | } |
| 126 | |
| 127 | /* Legacy CHS geometry numbers: ignored */ |
| 128 | boot->SecPerTrack = block[24] + (block[25] << 8); |
| 129 | boot->bpbHeads = block[26] + (block[27] << 8); |
| 130 | |
| 131 | /* Hidden sectors: ignored */ |
| 132 | boot->bpbHiddenSecs = block[28] + (block[29] << 8) + |
| 133 | (block[30] << 16) + (block[31] << 24); |
| 134 | |
| 135 | /* Total sectors (32 bits) */ |
| 136 | boot->bpbHugeSectors = block[32] + (block[33] << 8) + |
| 137 | (block[34] << 16) + (block[35] << 24); |
| 138 | if (boot->bpbHugeSectors == 0) { |
| 139 | if (boot->flags & FAT32) { |
| 140 | pfatal("FAT32 with sector count of zero"); |
| 141 | return FSFATAL; |
| 142 | } else if (boot->bpbSectors == 0) { |
| 143 | pfatal("FAT with sector count of zero"); |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 144 | return FSFATAL; |
| 145 | } |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 146 | boot->NumSectors = boot->bpbSectors; |
| 147 | } else { |
| 148 | if (boot->bpbSectors != 0) { |
| 149 | pfatal("Invalid FAT sector count"); |
| 150 | return FSFATAL; |
| 151 | } |
| 152 | boot->NumSectors = boot->bpbHugeSectors; |
| 153 | } |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 154 | |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 155 | if (boot->flags & FAT32) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 156 | /* If the OEM Name field is EXFAT, it's not FAT32, so bail */ |
| 157 | if (!memcmp(&block[3], "EXFAT ", 8)) { |
| 158 | pfatal("exFAT filesystem is not supported."); |
| 159 | return FSFATAL; |
| 160 | } |
| 161 | |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 162 | /* 32-bit count of sectors per FAT */ |
| 163 | boot->FATsecs = block[36] + (block[37] << 8) |
| 164 | + (block[38] << 16) + (block[39] << 24); |
| 165 | |
| 166 | if (block[40] & 0x80) |
| 167 | boot->ValidFat = block[40] & 0x0f; |
| 168 | |
| 169 | /* FAT32 version, bail out if not 0.0 */ |
| 170 | if (block[42] || block[43]) { |
| 171 | pfatal("Unknown file system version: %x.%x", |
| 172 | block[43], block[42]); |
| 173 | return FSFATAL; |
| 174 | } |
| 175 | |
| 176 | /* |
| 177 | * Cluster number of the first cluster of root directory. |
| 178 | * |
| 179 | * Should be 2 but do not require it. |
| 180 | */ |
| 181 | boot->bpbRootClust = block[44] + (block[45] << 8) |
| 182 | + (block[46] << 16) + (block[47] << 24); |
| 183 | |
| 184 | /* Sector number of the FSInfo structure, usually 1 */ |
| 185 | boot->bpbFSInfo = block[48] + (block[49] << 8); |
| 186 | |
| 187 | /* Sector number of the backup boot block, ignored */ |
| 188 | boot->bpbBackup = block[50] + (block[51] << 8); |
| 189 | |
| 190 | /* Check basic parameters */ |
| 191 | if (boot->bpbFSInfo == 0) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 192 | /* |
| 193 | * Either the BIOS Parameter Block has been corrupted, |
| 194 | * or this is not a FAT32 filesystem, most likely an |
| 195 | * exFAT filesystem. |
| 196 | */ |
| 197 | pfatal("Invalid FAT32 Extended BIOS Parameter Block"); |
| 198 | return FSFATAL; |
| 199 | } |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 200 | |
| 201 | /* Read in and verify the FSInfo block */ |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 202 | if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, |
| 203 | SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec |
| 204 | || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { |
| 205 | perr("could not read fsinfo block"); |
| 206 | return FSFATAL; |
| 207 | } |
| 208 | if (memcmp(fsinfo, "RRaA", 4) |
| 209 | || memcmp(fsinfo + 0x1e4, "rrAa", 4) |
| 210 | || fsinfo[0x1fc] |
| 211 | || fsinfo[0x1fd] |
| 212 | || fsinfo[0x1fe] != 0x55 |
| 213 | || fsinfo[0x1ff] != 0xaa |
| 214 | || fsinfo[0x3fc] |
| 215 | || fsinfo[0x3fd] |
| 216 | || fsinfo[0x3fe] != 0x55 |
| 217 | || fsinfo[0x3ff] != 0xaa) { |
| 218 | pwarn("Invalid signature in fsinfo block\n"); |
| 219 | if (ask(0, "Fix")) { |
| 220 | memcpy(fsinfo, "RRaA", 4); |
| 221 | memcpy(fsinfo + 0x1e4, "rrAa", 4); |
| 222 | fsinfo[0x1fc] = fsinfo[0x1fd] = 0; |
| 223 | fsinfo[0x1fe] = 0x55; |
| 224 | fsinfo[0x1ff] = 0xaa; |
| 225 | fsinfo[0x3fc] = fsinfo[0x3fd] = 0; |
| 226 | fsinfo[0x3fe] = 0x55; |
| 227 | fsinfo[0x3ff] = 0xaa; |
| 228 | if (lseek(dosfs, boot->bpbFSInfo * |
| 229 | boot->bpbBytesPerSec, SEEK_SET) |
| 230 | != boot->bpbFSInfo * boot->bpbBytesPerSec |
| 231 | || write(dosfs, fsinfo, sizeof fsinfo) |
| 232 | != sizeof fsinfo) { |
| 233 | perr("Unable to write bpbFSInfo"); |
| 234 | return FSFATAL; |
| 235 | } |
| 236 | ret = FSBOOTMOD; |
| 237 | } else |
| 238 | boot->bpbFSInfo = 0; |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 239 | } else { |
| 240 | /* We appear to have a valid FSInfo block, decode */ |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 241 | boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8) |
| 242 | + (fsinfo[0x1ea] << 16) |
| 243 | + (fsinfo[0x1eb] << 24); |
| 244 | boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8) |
| 245 | + (fsinfo[0x1ee] << 16) |
| 246 | + (fsinfo[0x1ef] << 24); |
| 247 | } |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 248 | } else { |
| 249 | /* !FAT32: FAT12/FAT16 */ |
| 250 | boot->FATsecs = boot->bpbFATsmall; |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 251 | } |
| 252 | |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 253 | if (boot->FATsecs < 1 || boot->FATsecs > UINT32_MAX / boot->bpbFATs) { |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 254 | pfatal("Invalid FATs(%u) with FATsecs(%zu)", |
| 255 | boot->bpbFATs, (size_t)boot->FATsecs); |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 256 | return FSFATAL; |
| 257 | } |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 258 | |
| 259 | boot->FirstCluster = (boot->bpbRootDirEnts * 32 + |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 260 | boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + |
Xin Li | a4cbc88 | 2019-10-01 15:09:31 -0700 | [diff] [blame] | 261 | boot->bpbResSectors + boot->bpbFATs * boot->FATsecs; |
| 262 | |
| 263 | if (boot->FirstCluster + boot->bpbSecPerClust > boot->NumSectors) { |
| 264 | pfatal("Cluster offset too large (%u clusters)\n", |
| 265 | boot->FirstCluster); |
| 266 | return FSFATAL; |
| 267 | } |
| 268 | |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 269 | /* |
Xin Li | ad1ac48 | 2020-04-27 08:59:19 -0700 | [diff] [blame] | 270 | * The number of clusters is derived from available data sectors, |
| 271 | * divided by sectors per cluster. |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 272 | */ |
Xin Li | ad1ac48 | 2020-04-27 08:59:19 -0700 | [diff] [blame] | 273 | boot->NumClusters = |
| 274 | (boot->NumSectors - boot->FirstCluster) / boot->bpbSecPerClust; |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 275 | |
Xin Li | 21386e0 | 2020-01-03 09:22:03 -0800 | [diff] [blame] | 276 | if (boot->flags & FAT32) { |
| 277 | if (boot->NumClusters > (CLUST_RSRVD & CLUST32_MASK)) { |
| 278 | pfatal("Filesystem too big (%u clusters) for FAT32 partition", |
| 279 | boot->NumClusters); |
| 280 | return FSFATAL; |
| 281 | } |
| 282 | if (boot->NumClusters < (CLUST_RSRVD & CLUST16_MASK)) { |
| 283 | pfatal("Filesystem too small (%u clusters) for FAT32 partition", |
| 284 | boot->NumClusters); |
| 285 | return FSFATAL; |
| 286 | } |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 287 | boot->ClustMask = CLUST32_MASK; |
Xin Li | 21386e0 | 2020-01-03 09:22:03 -0800 | [diff] [blame] | 288 | |
| 289 | if (boot->bpbRootClust < CLUST_FIRST || |
| 290 | boot->bpbRootClust >= boot->NumClusters) { |
| 291 | pfatal("Root directory starts with cluster out of range(%u)", |
| 292 | boot->bpbRootClust); |
| 293 | return FSFATAL; |
| 294 | } |
| 295 | } else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 296 | boot->ClustMask = CLUST12_MASK; |
Xin Li | 21386e0 | 2020-01-03 09:22:03 -0800 | [diff] [blame] | 297 | } else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 298 | boot->ClustMask = CLUST16_MASK; |
Xin Li | 21386e0 | 2020-01-03 09:22:03 -0800 | [diff] [blame] | 299 | } else { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 300 | pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", |
| 301 | boot->NumClusters); |
| 302 | return FSFATAL; |
| 303 | } |
| 304 | |
| 305 | switch (boot->ClustMask) { |
| 306 | case CLUST32_MASK: |
| 307 | boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4; |
| 308 | break; |
| 309 | case CLUST16_MASK: |
| 310 | boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2; |
| 311 | break; |
| 312 | default: |
| 313 | boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3; |
| 314 | break; |
| 315 | } |
| 316 | |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 317 | if (boot->NumFatEntries < boot->NumClusters) { |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 318 | pfatal("FAT size too small, %u entries won't fit into %u sectors\n", |
| 319 | boot->NumClusters, boot->FATsecs); |
| 320 | return FSFATAL; |
| 321 | } |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 322 | |
| 323 | /* |
Xin Li | ad1ac48 | 2020-04-27 08:59:19 -0700 | [diff] [blame] | 324 | * There are two reserved clusters. To avoid adding CLUST_FIRST every |
| 325 | * time we perform boundary checks, we increment the NumClusters by 2, |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 326 | * which is CLUST_FIRST to denote the first out-of-range cluster number. |
| 327 | */ |
| 328 | boot->NumClusters += CLUST_FIRST; |
| 329 | |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 330 | boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust; |
| 331 | |
| 332 | boot->NumFiles = 1; |
| 333 | boot->NumFree = 0; |
| 334 | |
| 335 | return ret; |
| 336 | } |
| 337 | |
| 338 | int |
| 339 | writefsinfo(int dosfs, struct bootblock *boot) |
| 340 | { |
| 341 | u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; |
| 342 | |
| 343 | if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) |
| 344 | != boot->bpbFSInfo * boot->bpbBytesPerSec |
| 345 | || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { |
| 346 | perr("could not read fsinfo block"); |
| 347 | return FSFATAL; |
| 348 | } |
| 349 | fsinfo[0x1e8] = (u_char)boot->FSFree; |
| 350 | fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); |
| 351 | fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); |
| 352 | fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); |
| 353 | fsinfo[0x1ec] = (u_char)boot->FSNext; |
| 354 | fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); |
| 355 | fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); |
| 356 | fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); |
| 357 | if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) |
| 358 | != boot->bpbFSInfo * boot->bpbBytesPerSec |
| 359 | || write(dosfs, fsinfo, sizeof fsinfo) |
| 360 | != sizeof fsinfo) { |
| 361 | perr("Unable to write bpbFSInfo"); |
| 362 | return FSFATAL; |
| 363 | } |
| 364 | /* |
| 365 | * Technically, we should return FSBOOTMOD here. |
| 366 | * |
| 367 | * However, since Win95 OSR2 (the first M$ OS that has |
| 368 | * support for FAT32) doesn't maintain the FSINFO block |
| 369 | * correctly, it has to be fixed pretty often. |
| 370 | * |
The Android Open Source Project | 9721450 | 2020-01-13 15:31:29 -0800 | [diff] [blame] | 371 | * Therefore, we handle the FSINFO block only informally, |
Xin Li | 1e1dad6 | 2019-04-10 13:38:23 -0700 | [diff] [blame] | 372 | * fixing it if necessary, but otherwise ignoring the |
| 373 | * fact that it was incorrect. |
| 374 | */ |
| 375 | return 0; |
| 376 | } |