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
  33
  34 #include <sys/cdefs.h>
  35 #ifndef lint
  36 __RCSID("$NetBSD: boot.c,v 1.5 1997/10/17 11:19:23 ws Exp $");
  37 static const char rcsid[] =
  38   "$FreeBSD: src/sbin/fsck_msdosfs/boot.c,v 1.1.2.1 2001/08/01 05:47:55 obrien Exp $";
  39 #endif /* not lint */
  40
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <ctype.h>
  44 #include <stdio.h>
  45 #include <unistd.h>
  46
  47 #include "ext.h"
  48 #include "fsutil.h"
  49
  50 int
  51 readboot(dosfs, boot)
  52         int dosfs;
  53         struct bootblock *boot;
  54 {
  55         u_char block[DOSBOOTBLOCKSIZE];
  56         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
  57         u_char backup[DOSBOOTBLOCKSIZE];
  58         int ret = FSOK;
  59
  60         if (read(dosfs, block, sizeof block) < sizeof block) {
  61                 perror("could not read boot block");
  62                 return FSFATAL;
  63         }
  64
  65         if (block[510] != 0x55 || block[511] != 0xaa) {
  66                 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
  67                 return FSFATAL;
  68         }
  69
  70         memset(boot, 0, sizeof *boot);
  71         boot->ValidFat = -1;
  72
  73         /* decode bios parameter block */
  74         boot->BytesPerSec = block[11] + (block[12] << 8);
  75         boot->SecPerClust = block[13];
  76         boot->ResSectors = block[14] + (block[15] << 8);
  77         boot->FATs = block[16];
  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) + (block[31] << 24);
  85         boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (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) + (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) + (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                         perror("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                                         perror("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                                        + (fsinfo[0x1eb] << 24);
 151                         boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
 152                                        + (fsinfo[0x1ee] << 16)
 153                                        + (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                         perror("could not read backup bootblock");
 160                         return FSFATAL;
 161                 }
 162                 if (memcmp(block, backup, DOSBOOTBLOCKSIZE)) {
 163                         /* Correct?                                     XXX */
 164                         pfatal("backup doesn't compare to primary bootblock");
 165                         return FSFATAL;
 166                 }
 167                 /* Check backup FSInfo?                                 XXX */
 168         }
 169
 170         boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
 171             / boot->BytesPerSec
 172             + boot->ResSectors
 173             + boot->FATs * boot->FATsecs
 174             - CLUST_FIRST * boot->SecPerClust;
 175
 176         if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
 177                 pfatal("Invalid sector size: %u", boot->BytesPerSec);
 178                 return FSFATAL;
 179         }
 180         if (boot->SecPerClust == 0) {
 181                 pfatal("Invalid cluster size: %u", boot->SecPerClust);
 182                 return FSFATAL;
 183         }
 184         if (boot->Sectors) {
 185                 boot->HugeSectors = 0;
 186                 boot->NumSectors = boot->Sectors;
 187         } else
 188                 boot->NumSectors = boot->HugeSectors;
 189         boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
 190
 191         if (boot->flags&FAT32)
 192                 boot->ClustMask = CLUST32_MASK;
 193         else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
 194                 boot->ClustMask = CLUST12_MASK;
 195         else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
 196                 boot->ClustMask = CLUST16_MASK;
 197         else {
 198                 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
 199                        boot->NumClusters);
 200                 return FSFATAL;
 201         }
 202
 203         switch (boot->ClustMask) {
 204         case CLUST32_MASK:
 205                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
 206                 break;
 207         case CLUST16_MASK:
 208                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
 209                 break;
 210         default:
 211                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
 212                 break;
 213         }
 214
 215         if (boot->NumFatEntries < boot->NumClusters) {
 216                 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
 217                        boot->NumClusters, boot->FATsecs);
 218                 return FSFATAL;
 219         }
 220         boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
 221
 222         boot->NumFiles = 1;
 223         boot->NumFree = 0;
 224
 225         return ret;
 226 }
 227
 228 int
 229 writefsinfo(dosfs, boot)
 230         int dosfs;
 231         struct bootblock *boot;
 232 {
 233         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
 234
 235         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 236             != boot->FSInfo * boot->BytesPerSec
 237             || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
 238                 perror("could not read fsinfo block");
 239                 return FSFATAL;
 240         }
 241         fsinfo[0x1e8] = (u_char)boot->FSFree;
 242         fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
 243         fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
 244         fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
 245         fsinfo[0x1ec] = (u_char)boot->FSNext;
 246         fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
 247         fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
 248         fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
 249         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 250             != boot->FSInfo * boot->BytesPerSec
 251             || write(dosfs, fsinfo, sizeof fsinfo)
 252             != sizeof fsinfo) {
 253                 perror("Unable to write FSInfo");
 254                 return FSFATAL;
 255         }
 256         /*
 257          * Technically, we should return FSBOOTMOD here.
 258          *
 259          * However, since Win95 OSR2 (the first M$ OS that has
 260          * support for FAT32) doesn't maintain the FSINFO block
 261          * correctly, it has to be fixed pretty often.
 262          *
 263          * Therefor, we handle the FSINFO block only informally,
 264          * fixing it if neccessary, but otherwise ignoring the
 265          * fact that it was incorrect.
 266          */
 267         return 0;
 268 }