boot.c revision 330449
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 31__RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp "); 32static const char rcsid[] = 33 "$FreeBSD: stable/11/sbin/fsck_msdosfs/boot.c 330449 2018-03-05 07:26:05Z eadler $"; 34#endif /* not lint */ 35 36#include <stdlib.h> 37#include <string.h> 38#include <stdio.h> 39#include <unistd.h> 40 41#include "ext.h" 42#include "fsutil.h" 43 44int 45readboot(int dosfs, struct bootblock *boot) 46{ 47 u_char block[DOSBOOTBLOCKSIZE]; 48 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 49 u_char backup[DOSBOOTBLOCKSIZE]; 50 int ret = FSOK; 51 int i; 52 53 if ((size_t)read(dosfs, block, sizeof block) != sizeof block) { 54 perr("could not read boot block"); 55 return FSFATAL; 56 } 57 58 if (block[510] != 0x55 || block[511] != 0xaa) { 59 pfatal("Invalid signature in boot block: %02x%02x", 60 block[511], block[510]); 61 return FSFATAL; 62 } 63 64 memset(boot, 0, sizeof *boot); 65 boot->ValidFat = -1; 66 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); 82 83 boot->FATsecs = boot->bpbFATsmall; 84 85 if (!boot->bpbRootDirEnts) 86 boot->flags |= FAT32; 87 if (boot->flags & FAT32) { 88 boot->FATsecs = block[36] + (block[37] << 8) 89 + (block[38] << 16) + (block[39] << 24); 90 if (block[40] & 0x80) 91 boot->ValidFat = block[40] & 0x0f; 92 93 /* check version number: */ 94 if (block[42] || block[43]) { 95 /* Correct? XXX */ 96 pfatal("Unknown file system version: %x.%x", 97 block[43], block[42]); 98 return FSFATAL; 99 } 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); 104 105 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"); 109 return FSFATAL; 110 } 111 if (memcmp(fsinfo, "RRaA", 4) 112 || memcmp(fsinfo + 0x1e4, "rrAa", 4) 113 || fsinfo[0x1fc] 114 || fsinfo[0x1fd] 115 || fsinfo[0x1fe] != 0x55 116 || fsinfo[0x1ff] != 0xaa 117 || fsinfo[0x3fc] 118 || fsinfo[0x3fd] 119 || fsinfo[0x3fe] != 0x55 120 || fsinfo[0x3ff] != 0xaa) { 121 pwarn("Invalid signature in fsinfo block\n"); 122 if (ask(0, "Fix")) { 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) 135 != sizeof fsinfo) { 136 perr("Unable to write bpbFSInfo"); 137 return FSFATAL; 138 } 139 ret = FSBOOTMOD; 140 } else 141 boot->bpbFSInfo = 0; 142 } 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); 150 } 151 152 if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec, 153 SEEK_SET) 154 != boot->bpbBackup * boot->bpbBytesPerSec 155 || read(dosfs, backup, sizeof backup) != sizeof backup) { 156 perr("could not read backup bootblock"); 157 return FSFATAL; 158 } 159 backup[65] = block[65]; /* XXX */ 160 if (memcmp(block + 11, backup + 11, 79)) { 161 /* 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. 169 */ 170 pfatal("backup (block %d) mismatch with primary bootblock:\n", 171 boot->bpbBackup); 172 for (i = 11; i < 11 + 90; i++) { 173 if (block[i] != backup[i]) 174 pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n", 175 i, block[i], backup[i]); 176 } 177 } 178 /* Check backup bpbFSInfo? XXX */ 179 } 180 181 boot->ClusterOffset = (boot->bpbRootDirEnts * 32 + 182 boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + 183 boot->bpbResSectors + boot->bpbFATs * boot->FATsecs - 184 CLUST_FIRST * boot->bpbSecPerClust; 185 186 if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0) { 187 pfatal("Invalid sector size: %u", boot->bpbBytesPerSec); 188 return FSFATAL; 189 } 190 if (boot->bpbSecPerClust == 0) { 191 pfatal("Invalid cluster size: %u", boot->bpbSecPerClust); 192 return FSFATAL; 193 } 194 if (boot->bpbSectors) { 195 boot->bpbHugeSectors = 0; 196 boot->NumSectors = boot->bpbSectors; 197 } else 198 boot->NumSectors = boot->bpbHugeSectors; 199 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / 200 boot->bpbSecPerClust; 201 202 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; 208 else { 209 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 210 boot->NumClusters); 211 return FSFATAL; 212 } 213 214 switch (boot->ClustMask) { 215 case CLUST32_MASK: 216 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4; 217 break; 218 case CLUST16_MASK: 219 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2; 220 break; 221 default: 222 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3; 223 break; 224 } 225 226 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); 229 return FSFATAL; 230 } 231 boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust; 232 233 boot->NumFiles = 1; 234 boot->NumFree = 0; 235 236 return ret; 237} 238 239int 240writefsinfo(int dosfs, struct bootblock *boot) 241{ 242 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 243 244 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"); 248 return FSFATAL; 249 } 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) 261 != sizeof fsinfo) { 262 perr("Unable to write bpbFSInfo"); 263 return FSFATAL; 264 } 265 /* 266 * Technically, we should return FSBOOTMOD here. 267 * 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. 271 * 272 * Therefor, we handle the FSINFO block only informally, 273 * fixing it if necessary, but otherwise ignoring the 274 * fact that it was incorrect. 275 */ 276 return 0; 277} 278