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", block[511], block[510]); 60 return FSFATAL; 61 } 62 63 memset(boot, 0, sizeof *boot); 64 boot->ValidFat = -1; 65 66 /* decode bios parameter block */ 67 boot->BytesPerSec = block[11] + (block[12] << 8); 68 boot->SecPerClust = block[13]; 69 boot->ResSectors = block[14] + (block[15] << 8); 70 boot->FATs = block[16]; 71 boot->RootDirEnts = block[17] + (block[18] << 8); 72 boot->Sectors = block[19] + (block[20] << 8); 73 boot->Media = block[21]; 74 boot->FATsmall = block[22] + (block[23] << 8); 75 boot->SecPerTrack = block[24] + (block[25] << 8); 76 boot->Heads = block[26] + (block[27] << 8); 77 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24); 78 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24); 79 80 boot->FATsecs = boot->FATsmall; 81 82 if (!boot->RootDirEnts) 83 boot->flags |= FAT32; 84 if (boot->flags & FAT32) { 85 boot->FATsecs = block[36] + (block[37] << 8) 86 + (block[38] << 16) + (block[39] << 24); 87 if (block[40] & 0x80) 88 boot->ValidFat = block[40] & 0x0f; 89 90 /* check version number: */ 91 if (block[42] || block[43]) { 92 /* Correct? XXX */ 93 pfatal("Unknown filesystem version: %x.%x", 94 block[43], block[42]); 95 return FSFATAL; 96 } 97 boot->RootCl = block[44] + (block[45] << 8) 98 + (block[46] << 16) + (block[47] << 24); 99 boot->FSInfo = block[48] + (block[49] << 8); 100 boot->Backup = block[50] + (block[51] << 8); 101 102 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 103 != boot->FSInfo * boot->BytesPerSec 104 || read(dosfs, fsinfo, sizeof fsinfo) 105 != 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"); 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->FSInfo * boot->BytesPerSec, SEEK_SET) 130 != boot->FSInfo * boot->BytesPerSec 131 || write(dosfs, fsinfo, sizeof fsinfo) 132 != sizeof fsinfo) { 133 perror("Unable to write FSInfo"); 134 return FSFATAL; 135 } 136 ret = FSBOOTMOD; 137 } else 138 boot->FSInfo = 0; 139 } 140 if (boot->FSInfo) { 141 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8) 142 + (fsinfo[0x1ea] << 16) 143 + (fsinfo[0x1eb] << 24); 144 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8) 145 + (fsinfo[0x1ee] << 16) 146 + (fsinfo[0x1ef] << 24); 147 } 148 149 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET) 150 != boot->Backup * boot->BytesPerSec 151 || read(dosfs, backup, sizeof backup) != sizeof backup) { 152 perror("could not read backup bootblock"); 153 return FSFATAL; 154 } 155 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) { 156 /* Correct? XXX */ 157 pfatal("backup doesn't compare to primary bootblock"); 158 return FSFATAL; 159 } 160 /* Check backup FSInfo? XXX */ 161 } 162 163 boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1) 164 / boot->BytesPerSec 165 + boot->ResSectors 166 + boot->FATs * boot->FATsecs 167 - CLUST_FIRST * boot->SecPerClust; 168 169 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) { 170 pfatal("Invalid sector size: %u", boot->BytesPerSec); 171 return FSFATAL; 172 } 173 if (boot->SecPerClust == 0) { 174 pfatal("Invalid cluster size: %u", boot->SecPerClust); 175 return FSFATAL; 176 } 177 if (boot->Sectors) { 178 boot->HugeSectors = 0; 179 boot->NumSectors = boot->Sectors; 180 } else 181 boot->NumSectors = boot->HugeSectors; 182 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust; 183 184 if (boot->flags&FAT32) 185 boot->ClustMask = CLUST32_MASK; 186 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 187 boot->ClustMask = CLUST12_MASK; 188 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 189 boot->ClustMask = CLUST16_MASK; 190 else { 191 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 192 boot->NumClusters); 193 return FSFATAL; 194 } 195 196 switch (boot->ClustMask) { 197 case CLUST32_MASK: 198 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4; 199 break; 200 case CLUST16_MASK: 201 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2; 202 break; 203 default: 204 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3; 205 break; 206 } 207 208 if (boot->NumFatEntries < boot->NumClusters) { 209 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 210 boot->NumClusters, boot->FATsecs); 211 return FSFATAL; 212 } 213 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust; 214 215 boot->NumFiles = 1; 216 boot->NumFree = 0; 217 218 return ret; 219 } 220 221 int 222 writefsinfo(int dosfs, struct bootblock *boot) 223 { 224 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 225 226 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 227 != boot->FSInfo * boot->BytesPerSec 228 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 229 perror("could not read fsinfo block"); 230 return FSFATAL; 231 } 232 fsinfo[0x1e8] = (u_char)boot->FSFree; 233 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 234 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 235 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 236 fsinfo[0x1ec] = (u_char)boot->FSNext; 237 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 238 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 239 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 240 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 241 != boot->FSInfo * boot->BytesPerSec 242 || write(dosfs, fsinfo, sizeof fsinfo) 243 != sizeof fsinfo) { 244 perror("Unable to write FSInfo"); 245 return FSFATAL; 246 } 247 /* 248 * Technically, we should return FSBOOTMOD here. 249 * 250 * However, since Win95 OSR2 (the first M$ OS that has 251 * support for FAT32) doesn't maintain the FSINFO block 252 * correctly, it has to be fixed pretty often. 253 * 254 * Therefor, we handle the FSINFO block only informally, 255 * fixing it if neccessary, but otherwise ignoring the 256 * fact that it was incorrect. 257 */ 258 return 0; 259 } 260