1 2 /* 3 * Copyright (C) 1995, 1997 Wolfgang Solfrank 4 * Copyright (c) 1995 Martin Husemann 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 28 #include <sys/cdefs.h> 29 #ifndef lint 30 __RCSID("$NetBSD: boot.c,v 1.23 2020/02/22 09:59:22 kamil Exp $"); 31 #endif /* not lint */ 32 33 #include <stdlib.h> 34 #include <string.h> 35 #include <strings.h> 36 #include <inttypes.h> 37 #include <stdio.h> 38 #include <unistd.h> 39 40 #include "ext.h" 41 #include "fsutil.h" 42 43 int 44 readboot(int dosfs, struct bootblock *boot) 45 { 46 u_char block[DOSBOOTBLOCKSIZE]; 47 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 48 u_char backup[DOSBOOTBLOCKSIZE]; 49 int ret = FSOK; 50 int i; 51 52 if ((size_t)read(dosfs, block, sizeof block) != sizeof block) { 53 perr("could not read boot block"); 54 return FSFATAL; 55 } 56 57 if (block[510] != 0x55 || block[511] != 0xaa) { 58 pfatal("Invalid signature in boot block: %02x%02x", 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->BytesPerSec = block[11] + (block[12] << 8); 67 boot->SecPerClust = block[13]; 68 if (boot->SecPerClust == 0 || popcount(boot->SecPerClust) != 1) { 69 pfatal("Invalid cluster size: %u\n", boot->SecPerClust); 70 return FSFATAL; 71 } 72 boot->ResSectors = block[14] + (block[15] << 8); 73 boot->FATs = block[16]; 74 if (boot->FATs == 0) { 75 pfatal("Invalid number of FATs: %u\n", boot->FATs); 76 return FSFATAL; 77 } 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) + ((uint32_t)block[31] << 24); 85 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + ((uint32_t)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) + ((uint32_t)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 filesystem version: %x.%x", 101 block[43], block[42]); 102 return FSFATAL; 103 } 104 boot->RootCl = block[44] + (block[45] << 8) 105 + (block[46] << 16) + ((uint32_t)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 perr("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"); 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 perr("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 + ((uint32_t)fsinfo[0x1eb] << 24); 151 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8) 152 + (fsinfo[0x1ee] << 16) 153 + ((uint32_t)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 perr("could not read backup bootblock"); 160 return FSFATAL; 161 } 162 backup[65] = block[65]; /* XXX */ 163 if (memcmp(block + 11, backup + 11, 79)) { 164 /* 165 * XXX We require a reference that explains 166 * that these bytes need to match, or should 167 * drop the check. gdt@ has observed 168 * filesystems that work fine under Windows XP 169 * and NetBSD that do not match, so the 170 * requirement is suspect. For now, just 171 * print out useful information and continue. 172 */ 173 pfatal("backup (block %d) mismatch with primary bootblock:\n", 174 boot->Backup); 175 for (i = 11; i < 11 + 90; i++) { 176 if (block[i] != backup[i]) 177 pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n", 178 i, block[i], backup[i]); 179 } 180 } 181 /* Check backup FSInfo? XXX */ 182 } 183 if (boot->FATsecs == 0) { 184 pfatal("Invalid number of FAT sectors: %u\n", boot->FATsecs); 185 return FSFATAL; 186 } 187 188 boot->FirstCluster = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1) 189 / boot->BytesPerSec 190 + boot->ResSectors 191 + boot->FATs * boot->FATsecs; 192 193 if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) { 194 pfatal("Invalid sector size: %u", boot->BytesPerSec); 195 return FSFATAL; 196 } 197 if (boot->SecPerClust == 0) { 198 pfatal("Invalid cluster size: %u", boot->SecPerClust); 199 return FSFATAL; 200 } 201 if (boot->Sectors) { 202 boot->HugeSectors = 0; 203 boot->NumSectors = boot->Sectors; 204 } else 205 boot->NumSectors = boot->HugeSectors; 206 207 if (boot->FirstCluster + boot->SecPerClust > boot->NumSectors) { 208 pfatal("Cluster offset too large (%u clusters)\n", 209 boot->FirstCluster); 210 return FSFATAL; 211 } 212 213 /* 214 * The number of clusters is derived from available data sectors, 215 * divided by sectors per cluster. 216 */ 217 boot->NumClusters = 218 (boot->NumSectors - boot->FirstCluster) / boot->SecPerClust; 219 220 if (boot->flags&FAT32) 221 boot->ClustMask = CLUST32_MASK; 222 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 223 boot->ClustMask = CLUST12_MASK; 224 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 225 boot->ClustMask = CLUST16_MASK; 226 else { 227 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", 228 boot->NumClusters); 229 return FSFATAL; 230 } 231 232 switch (boot->ClustMask) { 233 case CLUST32_MASK: 234 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4; 235 break; 236 case CLUST16_MASK: 237 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2; 238 break; 239 default: 240 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3; 241 break; 242 } 243 244 if (boot->NumFatEntries < boot->NumClusters) { 245 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 246 boot->NumClusters, boot->FATsecs); 247 return FSFATAL; 248 } 249 250 /* 251 * There are two reserved clusters. To avoid adding CLUST_FIRST every 252 * time we perform boundary checks, we increment the NumClusters by 2, 253 * which is CLUST_FIRST to denote the first out-of-range cluster number. 254 */ 255 boot->NumClusters += CLUST_FIRST; 256 257 boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust; 258 259 boot->NumFiles = 1; 260 boot->NumFree = 0; 261 262 return ret; 263 } 264 265 int 266 writefsinfo(int dosfs, struct bootblock *boot) 267 { 268 u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; 269 270 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 271 != boot->FSInfo * boot->BytesPerSec 272 || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { 273 perr("could not read fsinfo block"); 274 return FSFATAL; 275 } 276 fsinfo[0x1e8] = (u_char)boot->FSFree; 277 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 278 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 279 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 280 fsinfo[0x1ec] = (u_char)boot->FSNext; 281 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 282 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 283 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 284 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET) 285 != boot->FSInfo * boot->BytesPerSec 286 || write(dosfs, fsinfo, sizeof fsinfo) 287 != sizeof fsinfo) { 288 perr("Unable to write FSInfo"); 289 return FSFATAL; 290 } 291 /* 292 * Technically, we should return FSBOOTMOD here. 293 * 294 * However, since Win95 OSR2 (the first M$ OS that has 295 * support for FAT32) doesn't maintain the FSINFO block 296 * correctly, it has to be fixed pretty often. 297 * 298 * Therefore, we handle the FSINFO block only informally, 299 * fixing it if necessary, but otherwise ignoring the 300 * fact that it was incorrect. 301 */ 302 return 0; 303 } 304