sbin/fsck_msdos/boot.c

   1 /*      $NetBSD: boot.c,v 1.14 2008/06/13 20:46:09 martin Exp $ */
   2
   3 /*
   4  * Copyright (C) 1995, 1997 Wolfgang Solfrank
   5  * Copyright (c) 1995 Martin Husemann
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  19  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28
  29 #include <sys/cdefs.h>
  30 #ifndef lint
  31 __RCSID("$NetBSD: boot.c,v 1.14 2008/06/13 20:46:09 martin Exp $");
  32 #endif /* not lint */
  33
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <stdio.h>
  37 #include <unistd.h>
  38
  39 #include "ext.h"
  40 #include "fsutil.h"
  41
  42 int
  43 readboot(int dosfs, struct bootblock *boot)
  44 {
  45         u_char block[DOSBOOTBLOCKSIZE];
  46         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
  47         u_char backup[DOSBOOTBLOCKSIZE];
  48         int ret = FSOK;
  49         int i;
  50
  51         if ((size_t)read(dosfs, block, sizeof block) != sizeof block) {
  52                 perr("could not read boot block");
  53                 return FSFATAL;
  54         }
  55
  56         if (block[510] != 0x55 || block[511] != 0xaa) {
  57                 pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]);
  58                 return FSFATAL;
  59         }
  60
  61         memset(boot, 0, sizeof *boot);
  62         boot->ValidFat = -1;
  63
  64         /* decode bios parameter block */
  65         boot->BytesPerSec = block[11] + (block[12] << 8);
  66         boot->SecPerClust = block[13];
  67         boot->ResSectors = block[14] + (block[15] << 8);
  68         boot->FATs = block[16];
  69         boot->RootDirEnts = block[17] + (block[18] << 8);
  70         boot->Sectors = block[19] + (block[20] << 8);
  71         boot->Media = block[21];
  72         boot->FATsmall = block[22] + (block[23] << 8);
  73         boot->SecPerTrack = block[24] + (block[25] << 8);
  74         boot->Heads = block[26] + (block[27] << 8);
  75         boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
  76         boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);
  77
  78         boot->FATsecs = boot->FATsmall;
  79
  80         if (!boot->RootDirEnts)
  81                 boot->flags |= FAT32;
  82         if (boot->flags & FAT32) {
  83                 boot->FATsecs = block[36] + (block[37] << 8)
  84                                 + (block[38] << 16) + (block[39] << 24);
  85                 if (block[40] & 0x80)
  86                         boot->ValidFat = block[40] & 0x0f;
  87
  88                 /* check version number: */
  89                 if (block[42] || block[43]) {
  90                         /* Correct?                             XXX */
  91                         pfatal("Unknown filesystem version: %x.%x",
  92                                block[43], block[42]);
  93                         return FSFATAL;
  94                 }
  95                 boot->RootCl = block[44] + (block[45] << 8)
  96                                + (block[46] << 16) + (block[47] << 24);
  97                 boot->FSInfo = block[48] + (block[49] << 8);
  98                 boot->Backup = block[50] + (block[51] << 8);
  99
 100                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 101                     != boot->FSInfo * boot->BytesPerSec
 102                     || read(dosfs, fsinfo, sizeof fsinfo)
 103                     != sizeof fsinfo) {
 104                         perr("could not read fsinfo block");
 105                         return FSFATAL;
 106                 }
 107                 if (memcmp(fsinfo, "RRaA", 4)
 108                     || memcmp(fsinfo + 0x1e4, "rrAa", 4)
 109                     || fsinfo[0x1fc]
 110                     || fsinfo[0x1fd]
 111                     || fsinfo[0x1fe] != 0x55
 112                     || fsinfo[0x1ff] != 0xaa
 113                     || fsinfo[0x3fc]
 114                     || fsinfo[0x3fd]
 115                     || fsinfo[0x3fe] != 0x55
 116                     || fsinfo[0x3ff] != 0xaa) {
 117                         pwarn("Invalid signature in fsinfo block");
 118                         if (ask(0, "fix")) {
 119                                 memcpy(fsinfo, "RRaA", 4);
 120                                 memcpy(fsinfo + 0x1e4, "rrAa", 4);
 121                                 fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
 122                                 fsinfo[0x1fe] = 0x55;
 123                                 fsinfo[0x1ff] = 0xaa;
 124                                 fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
 125                                 fsinfo[0x3fe] = 0x55;
 126                                 fsinfo[0x3ff] = 0xaa;
 127                                 if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 128                                     != boot->FSInfo * boot->BytesPerSec
 129                                     || write(dosfs, fsinfo, sizeof fsinfo)
 130                                     != sizeof fsinfo) {
 131                                         perr("Unable to write FSInfo");
 132                                         return FSFATAL;
 133                                 }
 134                                 ret = FSBOOTMOD;
 135                         } else
 136                                 boot->FSInfo = 0;
 137                 }
 138                 if (boot->FSInfo) {
 139                         boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
 140                                        + (fsinfo[0x1ea] << 16)
 141                                        + (fsinfo[0x1eb] << 24);
 142                         boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
 143                                        + (fsinfo[0x1ee] << 16)
 144                                        + (fsinfo[0x1ef] << 24);
 145                 }
 146
 147                 if (lseek(dosfs, boot->Backup * boot->BytesPerSec, SEEK_SET)
 148                     != boot->Backup * boot->BytesPerSec
 149                     || read(dosfs, backup, sizeof backup) != sizeof  backup) {
 150                         perr("could not read backup bootblock");
 151                         return FSFATAL;
 152                 }
 153                 backup[65] = block[65];                         /* XXX */
 154                 if (memcmp(block + 11, backup + 11, 79)) {
 155                         /*
 156                          * XXX We require a reference that explains
 157                          * that these bytes need to match, or should
 158                          * drop the check.  gdt@ has observed
 159                          * filesystems that work fine under Windows XP
 160                          * and NetBSD that do not match, so the
 161                          * requirement is suspect.  For now, just
 162                          * print out useful information and continue.
 163                          */
 164                         pfatal("backup (block %d) mismatch with primary bootblock:\n",
 165                                 boot->Backup);
 166                         for (i = 11; i < 11 + 90; i++) {
 167                                 if (block[i] != backup[i])
 168                                         pfatal("\ti=%d\tprimary 0x%02x\tbackup 0x%02x\n",
 169                                                i, block[i], backup[i]);
 170                         }
 171                 }
 172                 /* Check backup FSInfo?                                 XXX */
 173         }
 174
 175         boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
 176             / boot->BytesPerSec
 177             + boot->ResSectors
 178             + boot->FATs * boot->FATsecs
 179             - CLUST_FIRST * boot->SecPerClust;
 180
 181         if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
 182                 pfatal("Invalid sector size: %u", boot->BytesPerSec);
 183                 return FSFATAL;
 184         }
 185         if (boot->SecPerClust == 0) {
 186                 pfatal("Invalid cluster size: %u", boot->SecPerClust);
 187                 return FSFATAL;
 188         }
 189         if (boot->Sectors) {
 190                 boot->HugeSectors = 0;
 191                 boot->NumSectors = boot->Sectors;
 192         } else
 193                 boot->NumSectors = boot->HugeSectors;
 194         boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;
 195
 196         if (boot->flags&FAT32)
 197                 boot->ClustMask = CLUST32_MASK;
 198         else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
 199                 boot->ClustMask = CLUST12_MASK;
 200         else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
 201                 boot->ClustMask = CLUST16_MASK;
 202         else {
 203                 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition",
 204                        boot->NumClusters);
 205                 return FSFATAL;
 206         }
 207
 208         switch (boot->ClustMask) {
 209         case CLUST32_MASK:
 210                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
 211                 break;
 212         case CLUST16_MASK:
 213                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
 214                 break;
 215         default:
 216                 boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
 217                 break;
 218         }
 219
 220         if (boot->NumFatEntries < boot->NumClusters) {
 221                 pfatal("FAT size too small, %u entries won't fit into %u sectors\n",
 222                        boot->NumClusters, boot->FATsecs);
 223                 return FSFATAL;
 224         }
 225         boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;
 226
 227         boot->NumFiles = 1;
 228         boot->NumFree = 0;
 229
 230         return ret;
 231 }
 232
 233 int
 234 writefsinfo(int dosfs, struct bootblock *boot)
 235 {
 236         u_char fsinfo[2 * DOSBOOTBLOCKSIZE];
 237
 238         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 239             != boot->FSInfo * boot->BytesPerSec
 240             || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) {
 241                 perr("could not read fsinfo block");
 242                 return FSFATAL;
 243         }
 244         fsinfo[0x1e8] = (u_char)boot->FSFree;
 245         fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
 246         fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
 247         fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
 248         fsinfo[0x1ec] = (u_char)boot->FSNext;
 249         fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
 250         fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
 251         fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
 252         if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
 253             != boot->FSInfo * boot->BytesPerSec
 254             || write(dosfs, fsinfo, sizeof fsinfo)
 255             != sizeof fsinfo) {
 256                 perr("Unable to write FSInfo");
 257                 return FSFATAL;
 258         }
 259         /*
 260          * Technically, we should return FSBOOTMOD here.
 261          *
 262          * However, since Win95 OSR2 (the first M$ OS that has
 263          * support for FAT32) doesn't maintain the FSINFO block
 264          * correctly, it has to be fixed pretty often.
 265          *
 266          * Therefor, we handle the FSINFO block only informally,
 267          * fixing it if necessary, but otherwise ignoring the
 268          * fact that it was incorrect.
 269          */
 270         return 0;
 271 }