boot.c revision 175853
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 * 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. 20 * 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. 31 */ 32 33 34#include <sys/cdefs.h> 35#ifndef lint 36__RCSID("$NetBSD: boot.c,v 1.9 2003/07/24 19:25:46 ws Exp $"); 37static const char rcsid[] = 38 "$FreeBSD: head/sbin/fsck_msdosfs/boot.c 175853 2008-01-31 13:16:29Z yar $"; 39#endif /* not lint */ 40 41#include <stdlib.h> 42#include <string.h> 43#include <ctype.h> 44#include <stdio.h> 45#include <unistd.h> 46 47#include "ext.h" 48#include "fsutil.h" 49 50int 51readboot(dosfs, boot) 52 int dosfs; 53 struct bootblock *boot; 54{ 55 u_char block[DOSBOOTBLOCKSIZE]; 56 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 57 u_char backup[DOSBOOTBLOCKSIZE]; 58 int ret = FSOK; 59 60 if (read(dosfs, block, sizeof block) < sizeof block) { 61 perror("could not read boot block"); 62 return FSFATAL; 63 } 64 65 if (block[510] != 0x55 || block[511] != 0xaa) { 66 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]); 67 return FSFATAL; 68 } 69 70 memset(boot, 0, sizeof *boot); 71 boot->ValidFat = -1; 72 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); 86 87 boot->FATsecs = boot->FATsmall; 88 89 if (!boot->RootDirEnts) 90 boot->flags |= FAT32; 91 if (boot->flags & FAT32) { 92 boot->FATsecs = block[36] + (block[37] << 8) 93 + (block[38] << 16) + (block[39] << 24); 94 if (block[40] & 0x80) 95 boot->ValidFat = block[40] & 0x0f; 96 97 /* check version number: */ 98 if (block[42] || block[43]) { 99 /* Correct? XXX */ 100 pfatal("Unknown file system version: %x.%x", 101 block[43], block[42]); 102 return FSFATAL; 103 } 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); 108 109 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 110 != boot->FSInfo * boot->BytesPerSec 111 || read(dosfs, fsinfo, sizeof fsinfo) 112 != sizeof fsinfo) { 113 perror("could not read fsinfo block"); 114 return FSFATAL; 115 } 116 if (memcmp(fsinfo, "RRaA", 4) 117 || memcmp(fsinfo + 0x1e4, "rrAa", 4) 118 || fsinfo[0x1fc] 119 || fsinfo[0x1fd] 120 || fsinfo[0x1fe] != 0x55 121 || fsinfo[0x1ff] != 0xaa 122 || fsinfo[0x3fc] 123 || fsinfo[0x3fd] 124 || fsinfo[0x3fe] != 0x55 125 || fsinfo[0x3ff] != 0xaa) { 126 pwarn("Invalid signature in fsinfo block\n"); 127 if (ask(0, "Fix")) { 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) 139 != sizeof fsinfo) { 140 perror("Unable to write FSInfo"); 141 return FSFATAL; 142 } 143 ret = FSBOOTMOD; 144 } else 145 boot->FSInfo = 0; 146 } 147 if (boot->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); 154 } 155 156 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"); 160 return FSFATAL; 161 } 162 backup[65] = block[65]; /* XXX */ 163 if (memcmp(block + 11, backup + 11, 79)) { 164 /* Correct? XXX */ 165 pfatal("backup doesn't compare to primary bootblock"); 166 if (alwaysno) 167 pfatal("\n"); 168 else 169 return FSFATAL; 170 } 171 /* Check backup FSInfo? XXX */ 172 } 173 174 boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1) 175 / boot->BytesPerSec 176 + boot->ResSectors 177 + boot->FATs * boot->FATsecs 178 - CLUST_FIRST * boot->SecPerClust; 179 180 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) { 181 pfatal("Invalid sector size: %u", boot->BytesPerSec); 182 return FSFATAL; 183 } 184 if (boot->SecPerClust == 0) { 185 pfatal("Invalid cluster size: %u", boot->SecPerClust); 186 return FSFATAL; 187 } 188 if (boot->Sectors) { 189 boot->HugeSectors = 0; 190 boot->NumSectors = boot->Sectors; 191 } else 192 boot->NumSectors = boot->HugeSectors; 193 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust; 194 195 if (boot->flags&FAT32) 196 boot->ClustMask = CLUST32_MASK; 197 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 198 boot->ClustMask = CLUST12_MASK; 199 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 200 boot->ClustMask = CLUST16_MASK; 201 else { 202 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 203 boot->NumClusters); 204 return FSFATAL; 205 } 206 207 switch (boot->ClustMask) { 208 case CLUST32_MASK: 209 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4; 210 break; 211 case CLUST16_MASK: 212 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2; 213 break; 214 default: 215 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3; 216 break; 217 } 218 219 if (boot->NumFatEntries < boot->NumClusters) { 220 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 221 boot->NumClusters, boot->FATsecs); 222 return FSFATAL; 223 } 224 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust; 225 226 boot->NumFiles = 1; 227 boot->NumFree = 0; 228 229 return ret; 230} 231 232int 233writefsinfo(dosfs, boot) 234 int dosfs; 235 struct bootblock *boot; 236{ 237 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 238 239 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 240 != boot->FSInfo * boot->BytesPerSec 241 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 242 perror("could not read fsinfo block"); 243 return FSFATAL; 244 } 245 fsinfo[0x1e8] = (u_char)boot->FSFree; 246 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 247 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 248 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 249 fsinfo[0x1ec] = (u_char)boot->FSNext; 250 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 251 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 252 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 253 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 254 != boot->FSInfo * boot->BytesPerSec 255 || write(dosfs, fsinfo, sizeof fsinfo) 256 != sizeof fsinfo) { 257 perror("Unable to write FSInfo"); 258 return FSFATAL; 259 } 260 /* 261 * Technically, we should return FSBOOTMOD here. 262 * 263 * However, since Win95 OSR2 (the first M$ OS that has 264 * support for FAT32) doesn't maintain the FSINFO block 265 * correctly, it has to be fixed pretty often. 266 * 267 * Therefor, we handle the FSINFO block only informally, 268 * fixing it if necessary, but otherwise ignoring the 269 * fact that it was incorrect. 270 */ 271 return 0; 272} 273