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boot.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * "Portions Copyright (c) 2000 Apple Computer, Inc.  All Rights
 * Reserved.  This file contains Original Code and/or Modifications of
 * Original Code as defined in and that are subject to the Apple Public
 * Source License Version 1.1 (the 'License').  You may not use this file
 * except in compliance with the License.  Please obtain a copy of the
 * License at http://www.apple.com/publicsource and read it before using
 * this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License."
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright (C) 1995, 1997 Wolfgang Solfrank
 * Copyright (c) 1995 Martin Husemann
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by Martin Husemann
 *    and Wolfgang Solfrank.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <sys/cdefs.h>

#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>

#include "ext.h"
#include "fsutil.h"

int
readboot(dosfs, boot)
      int dosfs;
      struct bootblock *boot;
{
      u_char block[MAX_SECTOR_SIZE];
      u_char fsinfo[MAX_SECTOR_SIZE];
      int ret = FSOK;
      
        /*
         * [2734381] Some devices have sector sizes greater than 512 bytes.  These devices
         * tend to return errors if you try to read less than a sector, so we try reading
         * the maximum sector size (which may end up reading more than one sector).
         */
      if (read(dosfs, block, MAX_SECTOR_SIZE) != MAX_SECTOR_SIZE) {
            perr("could not read boot block");
            return FSFATAL;
      }

      /* [2699033]
      *
      * The first three bytes are an Intel x86 jump instruction.  It should be one
      * of the following forms:
      *    0xE9 0x?? 0x??
      *    0xEC 0x?? 0x90
      * where 0x?? means any byte value is OK.
      */
      if (block[0] != 0xE9 && (block[0] != 0xEB || block[2] != 0x90))
      {
            pfatal("Invalid BS_jmpBoot in boot block: %02x%02x%02x\n", block[0], block[1], block[2]);
            return FSFATAL;
      }

      memset(boot, 0, sizeof *boot);
      boot->ValidFat = -1;

      /* decode bios parameter block */
      boot->BytesPerSec = block[11] + (block[12] << 8);
      boot->SecPerClust = block[13];
      boot->ResSectors = block[14] + (block[15] << 8);
      boot->FATs = block[16];
      boot->RootDirEnts = block[17] + (block[18] << 8);
      boot->Sectors = block[19] + (block[20] << 8);
      boot->Media = block[21];
      boot->FATsmall = block[22] + (block[23] << 8);
      boot->SecPerTrack = block[24] + (block[25] << 8);
      boot->Heads = block[26] + (block[27] << 8);
      boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24);
      boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24);

      boot->FATsecs = boot->FATsmall;

      if (!boot->RootDirEnts)
            boot->flags |= FAT32;
      if (boot->flags & FAT32) {
            boot->FATsecs = block[36] + (block[37] << 8)
                        + (block[38] << 16) + (block[39] << 24);
            if (block[40] & 0x80)
                  boot->ValidFat = block[40] & 0x0f;

            /* check version number: */
            if (block[42] || block[43]) {
                  /* Correct?                   XXX */
                  pfatal("Unknown filesystem version: %x.%x\n",
                         block[43], block[42]);
                  return FSFATAL;
            }
            boot->RootCl = block[44] + (block[45] << 8)
                         + (block[46] << 16) + (block[47] << 24);
            boot->FSInfo = block[48] + (block[49] << 8);
            boot->Backup = block[50] + (block[51] << 8);

            if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
                != boot->FSInfo * boot->BytesPerSec
                || read(dosfs, fsinfo, boot->BytesPerSec)
                != boot->BytesPerSec) {
                  perr("could not read fsinfo block");
                  return FSFATAL;
            }
            if (memcmp(fsinfo, "RRaA", 4)
                || memcmp(fsinfo + 0x1e4, "rrAa", 4)
                || fsinfo[0x1fc]
                || fsinfo[0x1fd]
                || fsinfo[0x1fe] != 0x55
                || fsinfo[0x1ff] != 0xaa) {
                  pwarn("Invalid signature in fsinfo block");
                  if (ask(0, "fix")) {
                        memcpy(fsinfo, "RRaA", 4);
                        memcpy(fsinfo + 0x1e4, "rrAa", 4);
                        fsinfo[0x1fc] = fsinfo[0x1fd] = 0;
                        fsinfo[0x1fe] = 0x55;
                        fsinfo[0x1ff] = 0xaa;
                        fsinfo[0x3fc] = fsinfo[0x3fd] = 0;
                        fsinfo[0x3fe] = 0x55;
                        fsinfo[0x3ff] = 0xaa;
                        if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
                            != boot->FSInfo * boot->BytesPerSec
                            || write(dosfs, fsinfo, boot->BytesPerSec)
                            != boot->BytesPerSec) {
                              perr("Unable to write FSInfo");
                              return FSFATAL;
                        }
                        ret = FSBOOTMOD;
                  } else
                        boot->FSInfo = 0;
            }
            if (boot->FSInfo) {
                  boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
                               + (fsinfo[0x1ea] << 16)
                               + (fsinfo[0x1eb] << 24);
                  boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
                               + (fsinfo[0x1ee] << 16)
                               + (fsinfo[0x1ef] << 24);
            }
      }

      boot->ClusterOffset = (boot->RootDirEnts * 32 + boot->BytesPerSec - 1)
          / boot->BytesPerSec
          + boot->ResSectors
          + boot->FATs * boot->FATsecs
          - CLUST_FIRST * boot->SecPerClust;

      if (boot->BytesPerSec % DOSBOOTBLOCKSIZE != 0) {
            pfatal("Invalid sector size: %u\n", boot->BytesPerSec);
            return FSFATAL;
      }
      if (boot->SecPerClust == 0) {
            pfatal("Invalid cluster size: %u\n", boot->SecPerClust);
            return FSFATAL;
      }
      if (boot->Sectors) {
            boot->HugeSectors = 0;
            boot->NumSectors = boot->Sectors;
      } else
            boot->NumSectors = boot->HugeSectors;
        
        /*
         * Note: NumClusters isn't actually the *number* (or count) of clusters.  It is really
         * the maximum cluster number plus one (which is the number of clusters plus two;
         * it is also the number of valid FAT entries).  It is meant to be used
         * for looping over cluster numbers, or range checking cluster numbers.
         */
      boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust;

        /* Since NumClusters is off by two, use constants that are off by two also. */
      if (boot->flags&FAT32)
            boot->ClustMask = CLUST32_MASK;
      else if (boot->NumClusters < (4085+2))
            boot->ClustMask = CLUST12_MASK;
      else if (boot->NumClusters < (65526+2))         /* Windows allows 65525 clusters, so we should, too */
            boot->ClustMask = CLUST16_MASK;
      else {
            pfatal("Filesystem too big (%u clusters) for non-FAT32 partition\n",
                   boot->NumClusters-2);
            return FSFATAL;
      }

      switch (boot->ClustMask) {
      case CLUST32_MASK:
            boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 4;
            break;
      case CLUST16_MASK:
            boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec) / 2;
            break;
      default:
            boot->NumFatEntries = (boot->FATsecs * boot->BytesPerSec * 2) / 3;
            break;
      }

      /*
       * Verify that the FAT is large enough to hold the number of clusters
       * that we think the volume has.  Some digital cameras, and our own
       * newfs_msdos, can create volumes whose total sector count is too large.
       */
      if (boot->NumFatEntries < boot->NumClusters) {
            pwarn("FAT size too small, %u entries won't fit into %u sectors\n",
                   boot->NumClusters, boot->FATsecs);
            boot->NumClusters = boot->NumFatEntries;
            if (ask(0, "Fix total sectors")) {
                  /* Need to recompute sectors based on clusters */
                  boot->NumSectors = (boot->NumClusters * boot->SecPerClust) + boot->ClusterOffset;
                  if (boot->Sectors) {
                        boot->Sectors = boot->NumSectors;
                        block[19] = boot->NumSectors & 0xFF;
                        block[20] = (boot->NumSectors >> 8) & 0xFF;
                  } else {
                        boot->HugeSectors = boot->NumSectors;
                        block[32] = boot->NumSectors & 0xFF;
                        block[33] = (boot->NumSectors >> 8) & 0xFF;
                        block[34] = (boot->NumSectors >> 16) & 0xFF;
                        block[35] = (boot->NumSectors >> 24) & 0xFF;
                  }
                  if (lseek(dosfs, 0, SEEK_SET) != 0 ||
                        write(dosfs, block, boot->BytesPerSec) != boot->BytesPerSec)
                  {
                        perr("could not write boot sector");
                        return FSFATAL;
                  }
                  ret |= FSBOOTMOD; /* This flag is currently ignored by checkfilesys() */
            } else {
                  pwarn("Continuing, assuming %u clusters\n", boot->NumFatEntries-2);
                  /*
                   * We don't return an error here, so Mac OS X will automatically
                   * mount the volume without attempting to repair the disk just
                   * because of this problem (though it will end up fixing this
                   * problem if there was some other problem that had to be repaired
                   * before mounting).
                   */
            }
      }
      boot->ClusterSize = boot->BytesPerSec * boot->SecPerClust;

      boot->NumFree = 0;

      return ret;
}

int
writefsinfo(dosfs, boot)
      int dosfs;
      struct bootblock *boot;
{
      u_char fsinfo[MAX_SECTOR_SIZE];

      if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
          != boot->FSInfo * boot->BytesPerSec
          || read(dosfs, fsinfo, boot->BytesPerSec) != boot->BytesPerSec) {
            perr("could not read fsinfo block");
            return FSFATAL;
      }
      fsinfo[0x1e8] = (u_char)boot->FSFree;
      fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
      fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
      fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
      fsinfo[0x1ec] = (u_char)boot->FSNext;
      fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
      fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
      fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
      if (lseek(dosfs, boot->FSInfo * boot->BytesPerSec, SEEK_SET)
          != boot->FSInfo * boot->BytesPerSec
          || write(dosfs, fsinfo, boot->BytesPerSec)
          != boot->BytesPerSec) {
            perr("Unable to write FSInfo");
            return FSFATAL;
      }
      /*
       * Technically, we should return FSBOOTMOD here.
       *
       * However, since Win95 OSR2 (the first M$ OS that has
       * support for FAT32) doesn't maintain the FSINFO block
       * correctly, it has to be fixed pretty often.
       *
       * Therefor, we handle the FSINFO block only informally,
       * fixing it if neccessary, but otherwise ignoring the
       * fact that it was incorrect.
       */
      return 0;
}

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