src/fsck-msdos/boot.c

   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
  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(dosfs, boot)
  47         int dosfs;
  48         struct bootblock *boot;
  49 {
  50         u_char block[DOSBOOTBLOCKSIZE];
  51         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
  52         u_char backup[DOSBOOTBLOCKSIZE];
  53         int ret = FSOK;
  54
  55         if (read(dosfs, block, sizeof block) < sizeof block) {
  56                 perror("could not read boot block");
  57                 exit(2);
  58         }
  59
  60         if (block[510] != 0x55 || block[511] != 0xaa) {
  61                 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
  62                 exit(2);
  63         }
  64
  65         memset(boot, 0, sizeof *boot);
  66         boot->ValidFat = -1;
  67
  68         /* decode bios parameter block */
  69         boot->BytesPerSec = block[11] + (block[12] << 8);
  70         boot->SecPerClust = block[13];
  71         boot->ResSectors = block[14] + (block[15] << 8);
  72         boot->FATs = block[16];
  73         boot->RootDirEnts = block[17] + (block[18] << 8);
  74         boot->Sectors = block[19] + (block[20] << 8);
  75         boot->Media = block[21];
  76         boot->FATsmall = block[22] + (block[23] << 8);
  77         boot->SecPerTrack = block[24] + (block[25] << 8);
  78         boot->Heads = block[26] + (block[27] << 8);
  79         boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
  80         boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
  81
  82         boot->FATsecs = boot->FATsmall;
  83
  84         if (!boot->RootDirEnts)
  85                 boot->flags |= FAT32;
  86         if (boot->flags & FAT32) {
  87                 boot->FATsecs = block[36] + (block[37] << 8)
  88                                 + (block[38] << 16) + (block[39] << 24);
  89                 if (block[40] & 0x80)
  90                         boot->ValidFat = block[40] & 0x0f;
  91
  92                 /* check version number: */
  93                 if (block[42] || block[43]) {
  94                         /* Correct?                             XXX */
  95                         pfatal("Unknown file system version: %x.%x",
  96                                block[43], block[42]);
  97                         exit(2);
  98                 }
  99                 boot->RootCl = block[44] + (block[45] << 8)
 100                                + (block[46] << 16) + (block[47] << 24);
 101                 boot->FSInfo = block[48] + (block[49] << 8);
 102                 boot->Backup = block[50] + (block[51] << 8);
 103
 104                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 105                     != boot->FSInfo * boot->BytesPerSec
 106                     || read(dosfs, fsinfo, sizeof fsinfo)
 107                     != sizeof fsinfo) {
 108                         perror("could not read fsinfo block");
 109                         return FSFATAL;
 110                 }
 111                 if (memcmp(fsinfo, "RRaA", 4)
 112                     || memcmp(fsinfo + 0x1e4, "rrAa", 4)
 113                     || fsinfo[0x1fc]
 114                     || fsinfo[0x1fd]
 115                     || fsinfo[0x1fe] != 0x55
 116                     || fsinfo[0x1ff] != 0xaa
 117                     || fsinfo[0x3fc]
 118                     || fsinfo[0x3fd]
 119                     || fsinfo[0x3fe] != 0x55
 120                     || fsinfo[0x3ff] != 0xaa) {
 121                         pwarn("Invalid signature in fsinfo block\n");
 122                         if (ask(1, "fix")) {
 123                                 memcpy(fsinfo, "RRaA", 4);
 124                                 memcpy(fsinfo + 0x1e4, "rrAa", 4);
 125                                 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
 126                                 fsinfo[0x1fe] = 0x55;
 127                                 fsinfo[0x1ff] = 0xaa;
 128                                 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
 129                                 fsinfo[0x3fe] = 0x55;
 130                                 fsinfo[0x3ff] = 0xaa;
 131                                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 132                                     != boot->FSInfo * boot->BytesPerSec
 133                                     || write(dosfs, fsinfo, sizeof fsinfo)
 134                                     != sizeof fsinfo) {
 135                                         perror("Unable to write FSInfo");
 136                                         return FSFATAL;
 137                                 }
 138                                 ret = FSBOOTMOD;
 139                         } else
 140                                 boot->FSInfo = 0;
 141                 }
 142                 if (boot->FSInfo) {
 143                         boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
 144                                        + (fsinfo[0x1ea] << 16)
 145                                        + (fsinfo[0x1eb] << 24);
 146                         boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
 147                                        + (fsinfo[0x1ee] << 16)
 148                                        + (fsinfo[0x1ef] << 24);
 149                 }
 150
 151                 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
 152                     != boot->Backup * boot->BytesPerSec
 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                         char tmp[255];
 160                         int i;
 161
 162                         /*
 163                          * For now, lets not bail out if they don't match
 164                          * It seems a lot of sdcards are formatted with
 165                          * the backup either empty or containing garbage.
 166                          */
 167
 168                         pwarn("Primary/Backup bootblock miscompare\n");
 169
 170                         strcpy(tmp, "");
 171                         pwarn("Primary:\n");
 172                         for (i = 0; i < 79; i++) {
 173                                 char tmp2[16];
 174                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", block[11 + i]);
 175                                 strcat(tmp, tmp2);
 176                         }
 177                         pwarn("%s\n", tmp);
 178
 179                         strcpy(tmp, "");
 180                         pwarn("Backup:\n");
 181                         for (i = 0; i < 79; i++) {
 182                                 char tmp2[16];
 183                                 snprintf(tmp2, sizeof(tmp2), "%.2x ", backup[11 + i]);
 184                                 strcat(tmp, tmp2);
 185                         }
 186                         pwarn("%s\n", tmp);
 187                 }
 188                 /* Check backup FSInfo?                                 XXX */
 189         }
 190
 191         if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
 192                 pfatal("Invalid sector size: %u", boot->BytesPerSec);
 193                 return FSFATAL;
 194         }
 195         if (boot->SecPerClust == 0) {
 196                 pfatal("Invalid cluster size: %u", boot->SecPerClust);
 197                 return FSFATAL;
 198         }
 199         if (boot->BytesPerSec == 0) {
 200                 pfatal("Invalid sector size: %u", boot->BytesPerSec);
 201                 return FSFATAL;
 202         }
 203         if (boot->FATs == 0) {
 204                 pfatal("Invalid number of FATs: %u", boot->FATs);
 205                 return FSFATAL;
 206         }
 207         if (boot->Sectors) {
 208                 boot->HugeSectors = 0;
 209                 boot->NumSectors = boot->Sectors;
 210         } else
 211                 boot->NumSectors = boot->HugeSectors;
 212
 213         boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
 214             / boot->BytesPerSec
 215             + boot->ResSectors
 216             + boot->FATs * boot->FATsecs
 217             - CLUST_FIRST * boot->SecPerClust;
 218
 219         boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
 220
 221         if (boot->flags&FAT32)
 222                 boot->ClustMask = CLUST32_MASK;
 223         else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
 224                 boot->ClustMask = CLUST12_MASK;
 225         else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
 226                 boot->ClustMask = CLUST16_MASK;
 227         else {
 228                 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
 229                        boot->NumClusters);
 230                 return FSFATAL;
 231         }
 232
 233         switch (boot->ClustMask) {
 234         case CLUST32_MASK:
 235                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
 236                 break;
 237         case CLUST16_MASK:
 238                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
 239                 break;
 240         default:
 241                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
 242                 break;
 243         }
 244
 245         if (boot->NumFatEntries < boot->NumClusters) {
 246                 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
 247                        boot->NumClusters, boot->FATsecs);
 248                 return FSFATAL;
 249         }
 250         boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
 251
 252         boot->NumFiles = 1;
 253         boot->NumFree = 0;
 254
 255         return ret;
 256 }
 257
 258 int
 259 writefsinfo(dosfs, boot)
 260         int dosfs;
 261         struct bootblock *boot;
 262 {
 263         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
 264
 265         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 266             != boot->FSInfo * boot->BytesPerSec
 267             || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
 268                 perror("could not read fsinfo block");
 269                 return FSFATAL;
 270         }
 271         fsinfo[0x1e8] = (u_char)boot->FSFree;
 272         fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
 273         fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
 274         fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
 275         fsinfo[0x1ec] = (u_char)boot->FSNext;
 276         fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
 277         fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
 278         fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
 279         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 280             != boot->FSInfo * boot->BytesPerSec
 281             || write(dosfs, fsinfo, sizeof fsinfo)
 282             != sizeof fsinfo) {
 283                 perror("Unable to write FSInfo");
 284                 return FSFATAL;
 285         }
 286         /*
 287          * Technically, we should return FSBOOTMOD here.
 288          *
 289          * However, since Win95 OSR2 (the first M$ OS that has
 290          * support for FAT32) doesn't maintain the FSINFO block
 291          * correctly, it has to be fixed pretty often.
 292          *
 293          * Therefor, we handle the FSINFO block only informally,
 294          * fixing it if necessary, but otherwise ignoring the
 295          * fact that it was incorrect.
 296          */
 297         return 0;
 298 }