boot.c revision 267654
1/* 2 * Copyright (C) 1995, 1997 Wolfgang Solfrank 3 * Copyright (c) 1995 Martin Husemann 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 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 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 27#include <sys/cdefs.h> 28#ifndef lint 29__RCSID("$NetBSD: boot.c,v 1.9 2003/07/24 19:25:46 ws Exp $"); 30static const char rcsid[] = 31 "$FreeBSD: releng/9.3/sbin/fsck_msdosfs/boot.c 209364 2010-06-20 09:40:54Z brian $"; 32#endif /* not lint */ 33 34#include <stdlib.h> 35#include <string.h> 36#include <stdio.h> 37#include <unistd.h> 38 39#include "ext.h" 40#include "fsutil.h" 41 42int 43readboot(int dosfs, struct bootblock *boot) 44{ 45 u_char block[DOSBOOTBLOCKSIZE]; 46 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 47 u_char backup[DOSBOOTBLOCKSIZE]; 48 int ret = FSOK; 49 int i; 50 51 if (read(dosfs, block, sizeof block) != sizeof block) { 52 perror("could not read boot block"); 53 return FSFATAL; 54 } 55 56 if (block[510] != 0x55 || block[511] != 0xaa) { 57 pfatal("Invalid signature in boot block: %02x%02x", 58 block[511], block[510]); 59 return FSFATAL; 60 } 61 62 memset(boot, 0, sizeof *boot); 63 boot->ValidFat = -1; 64 65 /* decode bios parameter block */ 66 boot->bpbBytesPerSec = block[11] + (block[12] << 8); 67 boot->bpbSecPerClust = block[13]; 68 boot->bpbResSectors = block[14] + (block[15] << 8); 69 boot->bpbFATs = block[16]; 70 boot->bpbRootDirEnts = block[17] + (block[18] << 8); 71 boot->bpbSectors = block[19] + (block[20] << 8); 72 boot->bpbMedia = block[21]; 73 boot->bpbFATsmall = block[22] + (block[23] << 8); 74 boot->SecPerTrack = block[24] + (block[25] << 8); 75 boot->bpbHeads = block[26] + (block[27] << 8); 76 boot->bpbHiddenSecs = block[28] + (block[29] << 8) + 77 (block[30] << 16) + (block[31] << 24); 78 boot->bpbHugeSectors = block[32] + (block[33] << 8) + 79 (block[34] << 16) + (block[35] << 24); 80 81 boot->FATsecs = boot->bpbFATsmall; 82 83 if (!boot->bpbRootDirEnts) 84 boot->flags |= FAT32; 85 if (boot->flags & FAT32) { 86 boot->FATsecs = block[36] + (block[37] << 8) 87 + (block[38] << 16) + (block[39] << 24); 88 if (block[40] & 0x80) 89 boot->ValidFat = block[40] & 0x0f; 90 91 /* check version number: */ 92 if (block[42] || block[43]) { 93 /* Correct? XXX */ 94 pfatal("Unknown file system version: %x.%x", 95 block[43], block[42]); 96 return FSFATAL; 97 } 98 boot->bpbRootClust = block[44] + (block[45] << 8) 99 + (block[46] << 16) + (block[47] << 24); 100 boot->bpbFSInfo = block[48] + (block[49] << 8); 101 boot->bpbBackup = block[50] + (block[51] << 8); 102 103 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, 104 SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec 105 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 106 perror("could not read fsinfo block"); 107 return FSFATAL; 108 } 109 if (memcmp(fsinfo, "RRaA", 4) 110 || memcmp(fsinfo + 0x1e4, "rrAa", 4) 111 || fsinfo[0x1fc] 112 || fsinfo[0x1fd] 113 || fsinfo[0x1fe] != 0x55 114 || fsinfo[0x1ff] != 0xaa 115 || fsinfo[0x3fc] 116 || fsinfo[0x3fd] 117 || fsinfo[0x3fe] != 0x55 118 || fsinfo[0x3ff] != 0xaa) { 119 pwarn("Invalid signature in fsinfo block\n"); 120 if (ask(0, "Fix")) { 121 memcpy(fsinfo, "RRaA", 4); 122 memcpy(fsinfo + 0x1e4, "rrAa", 4); 123 fsinfo[0x1fc] = fsinfo[0x1fd] = 0; 124 fsinfo[0x1fe] = 0x55; 125 fsinfo[0x1ff] = 0xaa; 126 fsinfo[0x3fc] = fsinfo[0x3fd] = 0; 127 fsinfo[0x3fe] = 0x55; 128 fsinfo[0x3ff] = 0xaa; 129 if (lseek(dosfs, boot->bpbFSInfo * 130 boot->bpbBytesPerSec, SEEK_SET) 131 != boot->bpbFSInfo * boot->bpbBytesPerSec 132 || write(dosfs, fsinfo, sizeof fsinfo) 133 != sizeof fsinfo) { 134 perror("Unable to write bpbFSInfo"); 135 return FSFATAL; 136 } 137 ret = FSBOOTMOD; 138 } else 139 boot->bpbFSInfo = 0; 140 } 141 if (boot->bpbFSInfo) { 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); 148 } 149 150 if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec, 151 SEEK_SET) 152 != boot->bpbBackup * boot->bpbBytesPerSec 153 || read(dosfs, backup, sizeof backup) != sizeof backup) { 154 perror("could not read backup bootblock"); 155 return FSFATAL; 156 } 157 backup[65] = block[65]; /* XXX */ 158 if (memcmp(block + 11, backup + 11, 79)) { 159 /* 160 * XXX We require a reference that explains 161 * that these bytes need to match, or should 162 * drop the check. gdt@NetBSD has observed 163 * filesystems that work fine under Windows XP 164 * and NetBSD that do not match, so the 165 * requirement is suspect. For now, just 166 * print out useful information and continue. 167 */ 168 pfatal("backup (block %d) mismatch with primary bootblock:\n", 169 boot->bpbBackup); 170 for (i = 11; i < 11 + 90; i++) { 171 if (block[i] != backup[i]) 172 pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n", 173 i, block[i], backup[i]); 174 } 175 } 176 /* Check backup bpbFSInfo? XXX */ 177 } 178 179 boot->ClusterOffset = (boot->bpbRootDirEnts * 32 + 180 boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + 181 boot->bpbResSectors + boot->bpbFATs * boot->FATsecs - 182 CLUST_FIRST * boot->bpbSecPerClust; 183 184 if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE != 0) { 185 pfatal("Invalid sector size: %u", boot->bpbBytesPerSec); 186 return FSFATAL; 187 } 188 if (boot->bpbSecPerClust == 0) { 189 pfatal("Invalid cluster size: %u", boot->bpbSecPerClust); 190 return FSFATAL; 191 } 192 if (boot->bpbSectors) { 193 boot->bpbHugeSectors = 0; 194 boot->NumSectors = boot->bpbSectors; 195 } else 196 boot->NumSectors = boot->bpbHugeSectors; 197 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / 198 boot->bpbSecPerClust; 199 200 if (boot->flags&FAT32) 201 boot->ClustMask = CLUST32_MASK; 202 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 203 boot->ClustMask = CLUST12_MASK; 204 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 205 boot->ClustMask = CLUST16_MASK; 206 else { 207 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 208 boot->NumClusters); 209 return FSFATAL; 210 } 211 212 switch (boot->ClustMask) { 213 case CLUST32_MASK: 214 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4; 215 break; 216 case CLUST16_MASK: 217 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2; 218 break; 219 default: 220 boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3; 221 break; 222 } 223 224 if (boot->NumFatEntries < boot->NumClusters) { 225 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 226 boot->NumClusters, boot->FATsecs); 227 return FSFATAL; 228 } 229 boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust; 230 231 boot->NumFiles = 1; 232 boot->NumFree = 0; 233 234 return ret; 235} 236 237int 238writefsinfo(int dosfs, struct bootblock *boot) 239{ 240 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 241 242 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) 243 != boot->bpbFSInfo * boot->bpbBytesPerSec 244 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 245 perror("could not read fsinfo block"); 246 return FSFATAL; 247 } 248 fsinfo[0x1e8] = (u_char)boot->FSFree; 249 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 250 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 251 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 252 fsinfo[0x1ec] = (u_char)boot->FSNext; 253 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 254 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 255 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 256 if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) 257 != boot->bpbFSInfo * boot->bpbBytesPerSec 258 || write(dosfs, fsinfo, sizeof fsinfo) 259 != sizeof fsinfo) { 260 perror("Unable to write bpbFSInfo"); 261 return FSFATAL; 262 } 263 /* 264 * Technically, we should return FSBOOTMOD here. 265 * 266 * However, since Win95 OSR2 (the first M$ OS that has 267 * support for FAT32) doesn't maintain the FSINFO block 268 * correctly, it has to be fixed pretty often. 269 * 270 * Therefor, we handle the FSINFO block only informally, 271 * fixing it if necessary, but otherwise ignoring the 272 * fact that it was incorrect. 273 */ 274 return 0; 275} 276