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 * $NetBSD: boot.c,v 1.5 1997/10/17 11:19:23 ws Exp $ 33 * $FreeBSD: src/sbin/fsck_msdosfs/boot.c,v 1.1.2.1 2001/08/01 05:47:55 obrien Exp $ 34 */ 35 36 #include <stdlib.h> 37 #include <string.h> 38 #include <ctype.h> 39 #include <stdio.h> 40 #include <unistd.h> 41 42 #include "ext.h" 43 #include "fsutil.h" 44 45 int 46 readboot(int dosfs, struct bootblock *boot) 47 { 48 u_char block[DOSBOOTBLOCKSIZE]; 49 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 50 u_char backup[DOSBOOTBLOCKSIZE]; 51 int ret = FSOK; 52 53 if (read(dosfs, block, sizeof block) < sizeof block) { 54 perror("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->BytesPerSec = block[11] + (block[12] << 8); 69 boot->SecPerClust = block[13]; 70 boot->ResSectors = block[14] + (block[15] << 8); 71 boot->FATs = block[16]; 72 boot->RootDirEnts = block[17] + (block[18] << 8); 73 boot->Sectors = block[19] + (block[20] << 8); 74 boot->Media = block[21]; 75 boot->FATsmall = block[22] + (block[23] << 8); 76 boot->SecPerTrack = block[24] + (block[25] << 8); 77 boot->Heads = block[26] + (block[27] << 8); 78 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24); 79 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24); 80 81 boot->FATsecs = boot->FATsmall; 82 83 if (!boot->RootDirEnts) 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 filesystem version: %x.%x", 95 block[43], block[42]); 96 return FSFATAL; 97 } 98 boot->RootCl = block[44] + (block[45] << 8) 99 + (block[46] << 16) + (block[47] << 24); 100 boot->FSInfo = block[48] + (block[49] << 8); 101 boot->Backup = block[50] + (block[51] << 8); 102 103 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 104 != boot->FSInfo * boot->BytesPerSec 105 || read(dosfs, fsinfo, sizeof fsinfo) 106 != sizeof fsinfo) { 107 perror("could not read fsinfo block"); 108 return FSFATAL; 109 } 110 if (memcmp(fsinfo, "RRaA", 4) 111 || memcmp(fsinfo + 0x1e4, "rrAa", 4) 112 || fsinfo[0x1fc] 113 || fsinfo[0x1fd] 114 || fsinfo[0x1fe] != 0x55 115 || fsinfo[0x1ff] != 0xaa 116 || fsinfo[0x3fc] 117 || fsinfo[0x3fd] 118 || fsinfo[0x3fe] != 0x55 119 || fsinfo[0x3ff] != 0xaa) { 120 pwarn("Invalid signature in fsinfo block"); 121 if (ask(0, "fix")) { 122 memcpy(fsinfo, "RRaA", 4); 123 memcpy(fsinfo + 0x1e4, "rrAa", 4); 124 fsinfo[0x1fc] = fsinfo[0x1fd] = 0; 125 fsinfo[0x1fe] = 0x55; 126 fsinfo[0x1ff] = 0xaa; 127 fsinfo[0x3fc] = fsinfo[0x3fd] = 0; 128 fsinfo[0x3fe] = 0x55; 129 fsinfo[0x3ff] = 0xaa; 130 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 131 != boot->FSInfo * boot->BytesPerSec 132 || write(dosfs, fsinfo, sizeof fsinfo) 133 != sizeof fsinfo) { 134 perror("Unable to write FSInfo"); 135 return FSFATAL; 136 } 137 ret = FSBOOTMOD; 138 } else 139 boot->FSInfo = 0; 140 } 141 if (boot->FSInfo) { 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->Backup * boot->BytesPerSec, SEEK_SET) 151 != boot->Backup * boot->BytesPerSec 152 || read(dosfs, backup, sizeof backup) != sizeof backup) { 153 perror("could not read backup bootblock"); 154 return FSFATAL; 155 } 156 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) { 157 /* Correct? XXX */ 158 pfatal("backup doesn't compare to primary bootblock"); 159 return FSFATAL; 160 } 161 /* Check backup FSInfo? XXX */ 162 } 163 164 boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1) 165 / boot->BytesPerSec 166 + boot->ResSectors 167 + boot->FATs * boot->FATsecs 168 - CLUST_FIRST * boot->SecPerClust; 169 170 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) { 171 pfatal("Invalid sector size: %u", boot->BytesPerSec); 172 return FSFATAL; 173 } 174 if (boot->SecPerClust == 0) { 175 pfatal("Invalid cluster size: %u", boot->SecPerClust); 176 return FSFATAL; 177 } 178 if (boot->Sectors) { 179 boot->HugeSectors = 0; 180 boot->NumSectors = boot->Sectors; 181 } else 182 boot->NumSectors = boot->HugeSectors; 183 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust; 184 185 if (boot->flags&FAT32) 186 boot->ClustMask = CLUST32_MASK; 187 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 188 boot->ClustMask = CLUST12_MASK; 189 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 190 boot->ClustMask = CLUST16_MASK; 191 else { 192 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 193 boot->NumClusters); 194 return FSFATAL; 195 } 196 197 switch (boot->ClustMask) { 198 case CLUST32_MASK: 199 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4; 200 break; 201 case CLUST16_MASK: 202 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2; 203 break; 204 default: 205 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3; 206 break; 207 } 208 209 if (boot->NumFatEntries < boot->NumClusters) { 210 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 211 boot->NumClusters, boot->FATsecs); 212 return FSFATAL; 213 } 214 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust; 215 216 boot->NumFiles = 1; 217 boot->NumFree = 0; 218 219 return ret; 220 } 221 222 int 223 writefsinfo(int dosfs, struct bootblock *boot) 224 { 225 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 226 227 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 228 != boot->FSInfo * boot->BytesPerSec 229 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 230 perror("could not read fsinfo block"); 231 return FSFATAL; 232 } 233 fsinfo[0x1e8] = (u_char)boot->FSFree; 234 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 235 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 236 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 237 fsinfo[0x1ec] = (u_char)boot->FSNext; 238 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 239 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 240 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 241 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 242 != boot->FSInfo * boot->BytesPerSec 243 || write(dosfs, fsinfo, sizeof fsinfo) 244 != sizeof fsinfo) { 245 perror("Unable to write FSInfo"); 246 return FSFATAL; 247 } 248 /* 249 * Technically, we should return FSBOOTMOD here. 250 * 251 * However, since Win95 OSR2 (the first M$ OS that has 252 * support for FAT32) doesn't maintain the FSINFO block 253 * correctly, it has to be fixed pretty often. 254 * 255 * Therefor, we handle the FSINFO block only informally, 256 * fixing it if neccessary, but otherwise ignoring the 257 * fact that it was incorrect. 258 */ 259 return 0; 260 } 261