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  */
  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 }