sbin/fsck_msdosfs/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  * $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  * $DragonFly: src/sbin/fsck_msdosfs/boot.c,v 1.2 2003/06/17 04:27:32 dillon Exp $
  35  */
  36
  37
  38 #include <sys/cdefs.h>
  39
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <ctype.h>
  43 #include <stdio.h>
  44 #include <unistd.h>
  45
  46 #include "ext.h"
  47 #include "fsutil.h"
  48
  49 int
  50 readboot(dosfs, boot)
  51         int dosfs;
  52         struct bootblock *boot;
  53 {
  54         u_char block[DOSBOOTBLOCKSIZE];
  55         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
  56         u_char backup[DOSBOOTBLOCKSIZE];
  57         int ret = FSOK;
  58
  59         if (read(dosfs, block, sizeof block) < sizeof block) {
  60                 perror("could not read boot block");
  61                 return FSFATAL;
  62         }
  63
  64         if (block[510] != 0x55 || block[511] != 0xaa) {
  65                 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
  66                 return FSFATAL;
  67         }
  68
  69         memset(boot, 0, sizeof *boot);
  70         boot->ValidFat = -1;
  71
  72         /* decode bios parameter block */
  73         boot->BytesPerSec = block[11] + (block[12] << 8);
  74         boot->SecPerClust = block[13];
  75         boot->ResSectors = block[14] + (block[15] << 8);
  76         boot->FATs = block[16];
  77         boot->RootDirEnts = block[17] + (block[18] << 8);
  78         boot->Sectors = block[19] + (block[20] << 8);
  79         boot->Media = block[21];
  80         boot->FATsmall = block[22] + (block[23] << 8);
  81         boot->SecPerTrack = block[24] + (block[25] << 8);
  82         boot->Heads = block[26] + (block[27] << 8);
  83         boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
  84         boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
  85
  86         boot->FATsecs = boot->FATsmall;
  87
  88         if (!boot->RootDirEnts)
  89                 boot->flags |= FAT32;
  90         if (boot->flags & FAT32) {
  91                 boot->FATsecs = block[36] + (block[37] << 8)
  92                                 + (block[38] << 16) + (block[39] << 24);
  93                 if (block[40] & 0x80)
  94                         boot->ValidFat = block[40] & 0x0f;
  95
  96                 /* check version number: */
  97                 if (block[42] || block[43]) {
  98                         /* Correct?                             XXX */
  99                         pfatal("Unknown filesystem version: %x.%x",
 100                                block[43], block[42]);
 101                         return FSFATAL;
 102                 }
 103                 boot->RootCl = block[44] + (block[45] << 8)
 104                                + (block[46] << 16) + (block[47] << 24);
 105                 boot->FSInfo = block[48] + (block[49] << 8);
 106                 boot->Backup = block[50] + (block[51] << 8);
 107
 108                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 109                     != boot->FSInfo * boot->BytesPerSec
 110                     || read(dosfs, fsinfo, sizeof fsinfo)
 111                     != sizeof fsinfo) {
 112                         perror("could not read fsinfo block");
 113                         return FSFATAL;
 114                 }
 115                 if (memcmp(fsinfo, "RRaA", 4)
 116                     || memcmp(fsinfo + 0x1e4, "rrAa", 4)
 117                     || fsinfo[0x1fc]
 118                     || fsinfo[0x1fd]
 119                     || fsinfo[0x1fe] != 0x55
 120                     || fsinfo[0x1ff] != 0xaa
 121                     || fsinfo[0x3fc]
 122                     || fsinfo[0x3fd]
 123                     || fsinfo[0x3fe] != 0x55
 124                     || fsinfo[0x3ff] != 0xaa) {
 125                         pwarn("Invalid signature in fsinfo block");
 126                         if (ask(0, "fix")) {
 127                                 memcpy(fsinfo, "RRaA", 4);
 128                                 memcpy(fsinfo + 0x1e4, "rrAa", 4);
 129                                 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
 130                                 fsinfo[0x1fe] = 0x55;
 131                                 fsinfo[0x1ff] = 0xaa;
 132                                 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
 133                                 fsinfo[0x3fe] = 0x55;
 134                                 fsinfo[0x3ff] = 0xaa;
 135                                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 136                                     != boot->FSInfo * boot->BytesPerSec
 137                                     || write(dosfs, fsinfo, sizeof fsinfo)
 138                                     != sizeof fsinfo) {
 139                                         perror("Unable to write FSInfo");
 140                                         return FSFATAL;
 141                                 }
 142                                 ret = FSBOOTMOD;
 143                         } else
 144                                 boot->FSInfo = 0;
 145                 }
 146                 if (boot->FSInfo) {
 147                         boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
 148                                        + (fsinfo[0x1ea] << 16)
 149                                        + (fsinfo[0x1eb] << 24);
 150                         boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
 151                                        + (fsinfo[0x1ee] << 16)
 152                                        + (fsinfo[0x1ef] << 24);
 153                 }
 154
 155                 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
 156                     != boot->Backup * boot->BytesPerSec
 157                     || read(dosfs, backup, sizeof backup) != sizeof  backup) {
 158                         perror("could not read backup bootblock");
 159                         return FSFATAL;
 160                 }
 161                 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) {
 162                         /* Correct?                                     XXX */
 163                         pfatal("backup doesn't compare to primary bootblock");
 164                         return FSFATAL;
 165                 }
 166                 /* Check backup FSInfo?                                 XXX */
 167         }
 168
 169         boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
 170             / boot->BytesPerSec
 171             + boot->ResSectors
 172             + boot->FATs * boot->FATsecs
 173             - CLUST_FIRST * boot->SecPerClust;
 174
 175         if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
 176                 pfatal("Invalid sector size: %u", boot->BytesPerSec);
 177                 return FSFATAL;
 178         }
 179         if (boot->SecPerClust == 0) {
 180                 pfatal("Invalid cluster size: %u", boot->SecPerClust);
 181                 return FSFATAL;
 182         }
 183         if (boot->Sectors) {
 184                 boot->HugeSectors = 0;
 185                 boot->NumSectors = boot->Sectors;
 186         } else
 187                 boot->NumSectors = boot->HugeSectors;
 188         boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
 189
 190         if (boot->flags&FAT32)
 191                 boot->ClustMask = CLUST32_MASK;
 192         else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
 193                 boot->ClustMask = CLUST12_MASK;
 194         else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
 195                 boot->ClustMask = CLUST16_MASK;
 196         else {
 197                 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
 198                        boot->NumClusters);
 199                 return FSFATAL;
 200         }
 201
 202         switch (boot->ClustMask) {
 203         case CLUST32_MASK:
 204                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
 205                 break;
 206         case CLUST16_MASK:
 207                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
 208                 break;
 209         default:
 210                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
 211                 break;
 212         }
 213
 214         if (boot->NumFatEntries < boot->NumClusters) {
 215                 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
 216                        boot->NumClusters, boot->FATsecs);
 217                 return FSFATAL;
 218         }
 219         boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
 220
 221         boot->NumFiles = 1;
 222         boot->NumFree = 0;
 223
 224         return ret;
 225 }
 226
 227 int
 228 writefsinfo(dosfs, boot)
 229         int dosfs;
 230         struct bootblock *boot;
 231 {
 232         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
 233
 234         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 235             != boot->FSInfo * boot->BytesPerSec
 236             || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
 237                 perror("could not read fsinfo block");
 238                 return FSFATAL;
 239         }
 240         fsinfo[0x1e8] = (u_char)boot->FSFree;
 241         fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
 242         fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
 243         fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
 244         fsinfo[0x1ec] = (u_char)boot->FSNext;
 245         fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
 246         fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
 247         fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
 248         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 249             != boot->FSInfo * boot->BytesPerSec
 250             || write(dosfs, fsinfo, sizeof fsinfo)
 251             != sizeof fsinfo) {
 252                 perror("Unable to write FSInfo");
 253                 return FSFATAL;
 254         }
 255         /*
 256          * Technically, we should return FSBOOTMOD here.
 257          *
 258          * However, since Win95 OSR2 (the first M$ OS that has
 259          * support for FAT32) doesn't maintain the FSINFO block
 260          * correctly, it has to be fixed pretty often.
 261          *
 262          * Therefor, we handle the FSINFO block only informally,
 263          * fixing it if neccessary, but otherwise ignoring the
 264          * fact that it was incorrect.
 265          */
 266         return 0;
 267 }