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newfs_msdos.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) 1998 Robert Nordier
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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 AUTHOR(S) 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/param.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/disklabel.h>
#include <sys/mount.h>

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

int dkdisklabel __P((int fd, struct disklabel * lp));

#define MAXU16      0xffff    /* maximum unsigned 16-bit quantity */
#define BPN   4         /* bits per nibble */
#define NPB   2         /* nibbles per byte */

#define DOSMAGIC  0xaa55      /* DOS magic number */
#define MINBPS      128       /* minimum bytes per sector */
#define MAXSPC      128       /* maximum sectors per cluster */
#define MAXNFT      16        /* maximum number of FATs */
#define DEFBLK      4096            /* default block size */
#define DEFBLK16  2048        /* default block size FAT16 */
#define DEFRDE      512       /* default root directory entries */
#define RESFTE      2         /* reserved FAT entries */

/*
 * [2873845]  FAT12 volumes can have 1..4084 clusters.  FAT16 can have
 * 4085..65524 clusters.  FAT32 is 65525 clusters or more.
 * Since many other implementations are off by 1, 2, 4, 8, 10, or 16,
 * Microsoft recommends staying at least 16 clusters away from these
 * boundary points.  They also recommend that FAT32 volumes avoid
 * making the bad cluster mark an allocatable cluster number.
 *
 * So, the minimum and maximum values listed below aren't the strict
 * limits (smaller or larger values may work on more robust implementations).
 * The limits below are safe limits that should be compatible with a
 * wide variety of implementations.
 */
#define MINCLS12  1           /* minimum FAT12 clusters */
#define MINCLS16  4085        /* minimum FAT16 clusters */
#define MINCLS32  65525       /* minimum FAT32 clusters */
#define MAXCLS12  4084        /* maximum FAT12 clusters */
#define MAXCLS16  65524       /* maximum FAT16 clusters */
#define MAXCLS32  0x0FFFFFF5  /* maximum FAT32 clusters */

#define BACKUP_BOOT_SECTOR 6  /* Default location for backup boot sector on FAT32 */
#define FAT32_RESERVED_SECTORS 32

#define mincls(fat)  ((fat) == 12 ? MINCLS12 :  \
                  (fat) == 16 ? MINCLS16 :      \
                            MINCLS32)

#define maxcls(fat)  ((fat) == 12 ? MAXCLS12 :  \
                  (fat) == 16 ? MAXCLS16 :      \
                            MAXCLS32)

#define mk1(p, x)                   \
    (p) = (u_int8_t)(x)

#define mk2(p, x)                   \
    (p)[0] = (u_int8_t)(x),               \
    (p)[1] = (u_int8_t)((x) >> 010)

#define mk4(p, x)                   \
    (p)[0] = (u_int8_t)(x),               \
    (p)[1] = (u_int8_t)((x) >> 010),            \
    (p)[2] = (u_int8_t)((x) >> 020),            \
    (p)[3] = (u_int8_t)((x) >> 030)

#define argto1(arg, lo, msg)  argtou(arg, lo, 0xff, msg)
#define argto2(arg, lo, msg)  argtou(arg, lo, 0xffff, msg)
#define argto4(arg, lo, msg)  argtou(arg, lo, 0xffffffff, msg)
#define argtox(arg, lo, msg)  argtou(arg, lo, UINT_MAX, msg)

struct bs {
    u_int8_t jmp[3];          /* bootstrap entry point */
    u_int8_t oem[8];          /* OEM name and version */
};

struct bsbpb {
    u_int8_t bps[2];          /* bytes per sector */
    u_int8_t spc;       /* sectors per cluster */
    u_int8_t res[2];          /* reserved sectors */
    u_int8_t nft;       /* number of FATs */
    u_int8_t rde[2];          /* root directory entries */
    u_int8_t sec[2];          /* total sectors */
    u_int8_t mid;       /* media descriptor */
    u_int8_t spf[2];          /* sectors per FAT */
    u_int8_t spt[2];          /* sectors per track */
    u_int8_t hds[2];          /* drive heads */
    u_int8_t hid[4];          /* hidden sectors */
    u_int8_t bsec[4];         /* big total sectors */
};

struct bsxbpb {
    u_int8_t bspf[4];         /* big sectors per FAT */
    u_int8_t xflg[2];         /* FAT control flags */
    u_int8_t vers[2];         /* file system version */
    u_int8_t rdcl[4];         /* root directory start cluster */
    u_int8_t infs[2];         /* file system info sector */
    u_int8_t bkbs[2];         /* backup boot sector */
    u_int8_t rsvd[12];        /* reserved */
};

struct bsx {
    u_int8_t drv;       /* drive number */
    u_int8_t rsvd;            /* reserved */
    u_int8_t sig;       /* extended boot signature */
    u_int8_t volid[4];        /* volume ID number */
    u_int8_t label[11];       /* volume label */
    u_int8_t type[8];         /* file system type */
};

struct de {
    u_int8_t namext[11];      /* name and extension */
    u_int8_t attr;            /* attributes */
    u_int8_t rsvd[10];        /* reserved */
    u_int8_t time[2];         /* creation time */
    u_int8_t date[2];         /* creation date */
    u_int8_t clus[2];         /* starting cluster */
    u_int8_t size[4];         /* size */
};

struct bpb {
    u_int bps;                /* bytes per sector */
    u_int spc;                /* sectors per cluster */
    u_int res;                /* reserved sectors */
    u_int nft;                /* number of FATs */
    u_int rde;                /* root directory entries */
    u_int sec;                /* total sectors */
    u_int mid;                /* media descriptor */
    u_int spf;                /* sectors per FAT */
    u_int spt;                /* sectors per track */
    u_int hds;                /* drive heads */
    u_int hid;                /* hidden sectors */
    u_int bsec;         /* big total sectors */
    u_int bspf;         /* big sectors per FAT */
    u_int rdcl;         /* root directory start cluster */
    u_int infs;         /* file system info sector */
    u_int bkbs;         /* backup boot sector */
};

static struct {
    const char *name;
    struct bpb bpb;
} stdfmt[] = {
    {"160",  {512, 1, 1, 2,  64,  320, 0xfe, 1,  8, 1}},
    {"180",  {512, 1, 1, 2,  64,  360, 0xfc, 2,  9, 1}},
    {"320",  {512, 2, 1, 2, 112,  640, 0xff, 1,  8, 2}},
    {"360",  {512, 2, 1, 2, 112,  720, 0xfd, 2,  9, 2}},
    {"640",  {512, 2, 1, 2, 112, 1280, 0xfb, 2,  8, 2}},    
    {"720",  {512, 2, 1, 2, 112, 1440, 0xf9, 3,  9, 2}},
    {"1200", {512, 1, 1, 2, 224, 2400, 0xf9, 7, 15, 2}},
    {"1232", {1024,1, 1, 2, 192, 1232, 0xfe, 2,  8, 2}},    
    {"1440", {512, 1, 1, 2, 224, 2880, 0xf0, 9, 18, 2}},
    {"2880", {512, 2, 1, 2, 240, 5760, 0xf0, 9, 36, 2}}
};

static u_int8_t bootcode[] = {
    0xfa,               /* cli                */
    0x31, 0xc0,         /* xor         ax,ax    */
    0x8e, 0xd0,         /* mov         ss,ax    */
    0xbc, 0x00, 0x7c,         /* mov         sp,7c00h */
    0xfb,               /* sti                */
    0x8e, 0xd8,         /* mov         ds,ax    */
    0xe8, 0x00, 0x00,         /* call    $ + 3    */
    0x5e,               /* pop         si     */
    0x83, 0xc6, 0x19,         /* add         si,+19h  */
    0xbb, 0x07, 0x00,         /* mov         bx,0007h */
    0xfc,               /* cld                */
    0xac,               /* lodsb        */
    0x84, 0xc0,         /* test    al,al    */
    0x74, 0x06,         /* jz    $ + 8    */
    0xb4, 0x0e,         /* mov         ah,0eh   */
    0xcd, 0x10,         /* int         10h          */
    0xeb, 0xf5,         /* jmp         $ - 9    */
    0x30, 0xe4,         /* xor         ah,ah    */
    0xcd, 0x16,         /* int         16h          */
    0xcd, 0x19,         /* int         19h          */
    0x0d, 0x0a,
    'N', 'o', 'n', '-', 's', 'y', 's', 't',
    'e', 'm', ' ', 'd', 'i', 's', 'k',
    0x0d, 0x0a,
    'P', 'r', 'e', 's', 's', ' ', 'a', 'n',
    'y', ' ', 'k', 'e', 'y', ' ', 't', 'o',
    ' ', 'r', 'e', 'b', 'o', 'o', 't',
    0x0d, 0x0a,
    0
};

/*
 * [2873851] Tables of default cluster sizes for FAT16 and FAT32.
 * These constants come from Microsoft's documentation.
 */

#define MAX_SEC_FAT12 8400    /* (4 MB) Maximum number of sectors to default to FAT12 */
#define MAX_SEC_FAT16 1048576 /* (512 MB) Maximum number of sectors t odefault to FAT16 */

struct DiskSizeToClusterSize {
    u_int diskSectors;        /* input: maximum bpb.bsec */
    u_int sectorsPerCluster;  /* output: desired bpb.spc */
};

struct DiskSizeToClusterSize fat16Sizes[] = {
    {   8400,  0},      /* Disks up to 4.1 MB; the 0 triggers an error */
    {  32680,  2},      /* Disks up to  16 MB => 1 KB cluster */
    { 262144,  4},      /* Disks up to 128 MB => 2 KB cluster */
    { 524288,  8},      /* Disks up to 256 MB => 4 KB cluster */
    {1048576, 16},      /* Disks up to 512 MB => 8 KB cluster */
    /* The following entries are used only if FAT16 is forced */
    {2097152, 32},      /* Disks up to 1 GB => 16 KB cluster */
    {0xFFFFFFFF, 64}    /* Disks over 2 GB => 32KB cluster (total size may be limited) */
};
struct DiskSizeToClusterSize fat32Sizes[] = {
    {   66600,  0},     /* Disks up to 32.5 MB; the 0 triggers an error */
    {  532480,  1},     /* Disks up to 260 MB => 512 byte cluster; not used unles FAT32 forced */
    {16777216,  8},     /* Disks up to   8 GB =>  4 KB cluster */
    {33554432, 16},     /* Disks up to  16 GB =>  8 KB cluster */
    {67108864, 32},     /* Disks up to  32 GB => 16 KB cluster */
    {0xFFFFFFFF, 64}    /* Disks over 32 GB => 32 KB cluster */
};

static void check_mounted(const char *, mode_t);
static void getstdfmt(const char *, struct bpb *);
static void getdiskinfo(int, const char *, const char *, int,
                  struct bpb *);
static void print_bpb(struct bpb *);
static u_int ckgeom(const char *, u_int, const char *);
static u_int argtou(const char *, u_int, u_int, const char *);
static int oklabel(const char *);
static void mklabel(u_int8_t *, const char *);
static void setstr(u_int8_t *, const char *, size_t);
static void usage(void);

/*
 * Construct a FAT12, FAT16, or FAT32 file system.
 */
int
main(int argc, char *argv[])
{
    static char opts[] = "NB:F:I:O:S:a:b:c:e:f:h:i:k:m:n:o:r:s:u:v:";
    static const char *opt_B, *opt_v, *opt_O, *opt_f;
    static u_int opt_F, opt_I, opt_S, opt_a, opt_b, opt_c, opt_e;
    static u_int opt_h, opt_i, opt_k, opt_m, opt_n, opt_o, opt_r;
    static u_int opt_s, opt_u;
    static int opt_N;
    static int Iflag, mflag, oflag;
    char buf[MAXPATHLEN];
    struct stat sb;
    struct timeval tv;
    struct bpb bpb;
    struct tm *tm;
    struct bs *bs;
    struct bsbpb *bsbpb;
    struct bsxbpb *bsxbpb;
    struct bsx *bsx;
    struct de *de;
    u_int8_t *img;
    const char *fname, *dtype, *bname;
    ssize_t n;
    time_t now;
    u_int fat, bss, rds, cls, dir, lsn, x, x1, x2;
    int ch, fd, fd1;

    while ((ch = getopt(argc, argv, opts)) != -1)
      switch (ch) {
      case 'N':
          opt_N = 1;
          break;
      case 'B':
          opt_B = optarg;
          break;
      case 'F':
          if (strcmp(optarg, "12") &&
            strcmp(optarg, "16") &&
            strcmp(optarg, "32"))
            errx(1, "%s: bad FAT type", optarg);
          opt_F = atoi(optarg);
          break;
      case 'I':
          opt_I = argto4(optarg, 0, "volume ID");
          Iflag = 1;
          break;
      case 'O':
          if (strlen(optarg) > 8)
            errx(1, "%s: bad OEM string", optarg);
          opt_O = optarg;
          break;
      case 'S':
          opt_S = argto2(optarg, 1, "bytes/sector");
          break;
      case 'a':
          opt_a = argto4(optarg, 1, "sectors/FAT");
          break;
      case 'b':
          opt_b = argtox(optarg, 1, "block size");
          opt_c = 0;
          break;
      case 'c':
          opt_c = argto1(optarg, 1, "sectors/cluster");
          opt_b = 0;
          break;
      case 'e':
          opt_e = argto2(optarg, 1, "directory entries");
          break;
      case 'f':
          opt_f = optarg;
          break;
      case 'h':
          opt_h = argto2(optarg, 1, "drive heads");
          break;
      case 'i':
          opt_i = argto2(optarg, 1, "info sector");
          break;
      case 'k':
          opt_k = argto2(optarg, 1, "backup sector");
          break;
      case 'm':
          opt_m = argto1(optarg, 0, "media descriptor");
          mflag = 1;
          break;
      case 'n':
          opt_n = argto1(optarg, 1, "number of FATs");
          break;
      case 'o':
          opt_o = argto4(optarg, 0, "hidden sectors");
          oflag = 1;
          break;
      case 'r':
          opt_r = argto2(optarg, 1, "reserved sectors");
          break;
      case 's':
          opt_s = argto4(optarg, 1, "file system size");
          break;
      case 'u':
          opt_u = argto2(optarg, 1, "sectors/track");
          break;
      case 'v':
          if (!oklabel(optarg))
            errx(1, "%s: bad volume name", optarg);
          opt_v = optarg;
          break;
      default:
          usage();
      }
    argc -= optind;
    argv += optind;
    if (argc < 1 || argc > 2)
      usage();
    fname = *argv++;
    if (!strchr(fname, '/')) {
      snprintf(buf, sizeof(buf), "%sr%s", _PATH_DEV, fname);
      if (stat(buf, &sb))
          snprintf(buf, sizeof(buf), "%s%s", _PATH_DEV, fname);
      if (!(fname = strdup(buf)))
          err(1, NULL);
    }
    dtype = *argv;
    if ((fd = open(fname, opt_N ? O_RDONLY : O_RDWR)) == -1 ||
      fstat(fd, &sb))
      err(1, "%s", fname);
    if (!opt_N)
      check_mounted(fname, sb.st_mode);
    if (!S_ISCHR(sb.st_mode))
      warnx("warning: %s is not a character device", fname);
    memset(&bpb, 0, sizeof(bpb));
    if (opt_f) {
      getstdfmt(opt_f, &bpb);
      bpb.bsec = bpb.sec;
      bpb.sec = 0;
      bpb.bspf = bpb.spf;
      bpb.spf = 0;
    }
    if (opt_h)
      bpb.hds = opt_h;
    if (opt_u)
      bpb.spt = opt_u;
    if (opt_S)
      bpb.bps = opt_S;
    if (opt_s)
      bpb.bsec = opt_s;
    if (oflag)
      bpb.hid = opt_o;
    if (!(opt_f || (opt_h && opt_u && opt_S && opt_s && oflag)))
      getdiskinfo(fd, fname, dtype, oflag, &bpb);
    if (!powerof2(bpb.bps))
      errx(1, "bytes/sector (%u) is not a power of 2", bpb.bps);
    if (bpb.bps < MINBPS)
      errx(1, "bytes/sector (%u) is too small; minimum is %u",
           bpb.bps, MINBPS);
    if (!(fat = opt_F)) {
      if (opt_f)
          fat = 12;
      else if (!opt_e && (opt_i || opt_k))
          fat = 32;
    }
    if ((fat == 32 && opt_e) || (fat != 32 && (opt_i || opt_k)))
      errx(1, "-%c is not a legal FAT%s option",
           fat == 32 ? 'e' : opt_i ? 'i' : 'k',
           fat == 32 ? "32" : "12/16");
    if (opt_f && fat == 32)
      bpb.rde = 0;
    if (opt_b) {
      if (!powerof2(opt_b))
          errx(1, "block size (%u) is not a power of 2", opt_b);
      if (opt_b < bpb.bps)
          errx(1, "block size (%u) is too small; minimum is %u",
             opt_b, bpb.bps);
      if (opt_b > bpb.bps * MAXSPC)
          errx(1, "block size (%u) is too large; maximum is %u",
             opt_b, bpb.bps * MAXSPC);
      bpb.spc = opt_b / bpb.bps;
    }
    if (opt_c) {
      if (!powerof2(opt_c))
          errx(1, "sectors/cluster (%u) is not a power of 2", opt_c);
      bpb.spc = opt_c;
    }
    if (opt_r)
      bpb.res = opt_r;
    if (opt_n) {
      if (opt_n > MAXNFT)
          errx(1, "number of FATs (%u) is too large; maximum is %u",
             opt_n, MAXNFT);
      bpb.nft = opt_n;
    }
    if (opt_e)
      bpb.rde = opt_e;
    if (mflag) {
      if (opt_m < 0xf0)
          errx(1, "illegal media descriptor (%#x)", opt_m);
      bpb.mid = opt_m;
    }
    if (opt_a)
      bpb.bspf = opt_a;
    if (opt_i)
      bpb.infs = opt_i;
    if (opt_k)
      bpb.bkbs = opt_k;
    bss = 1;
    bname = NULL;
    fd1 = -1;
    if (opt_B) {
      bname = opt_B;
      if (!strchr(bname, '/')) {
          snprintf(buf, sizeof(buf), "/boot/%s", bname);
          if (!(bname = strdup(buf)))
            err(1, NULL);
      }
      if ((fd1 = open(bname, O_RDONLY)) == -1 || fstat(fd1, &sb))
          err(1, "%s", bname);
      if (!S_ISREG(sb.st_mode) || sb.st_size % bpb.bps ||
          sb.st_size < bpb.bps || sb.st_size > bpb.bps * MAXU16)
          errx(1, "%s: inappropriate file type or format", bname);
      bss = sb.st_size / bpb.bps;
    }
    if (!bpb.nft)
      bpb.nft = 2;

    /*
     * [2873851] If the FAT type or sectors per cluster were not explicitly specified,
     * set them to default values.
     */
    if (!bpb.spc)
    {
      /*
       * If the user didn't specify the FAT type, then pick a default based on the
       * number of sectors on the volume.
       */
      if (!fat)
      {
          if (bpb.bsec <= MAX_SEC_FAT12)
            fat = 12;
          else if (bpb.bsec <= MAX_SEC_FAT16)
            fat = 16;
          else
            fat = 32;
      }

      switch (fat)
      {
      case 12:
          /*
           * There is no general table for FAT12, so try all possible
           * sector-per-cluster values until it all fits, or we try the
           * maximum cluster size.
           */
          for (bpb.spc=1; bpb.spc<64; bpb.spc*=2)
          {
            /* Start with number of reserved sectors */
            x = bpb.res ? bpb.res : bss;
            /* Plus number of sectors used by FAT */
            x = howmany((RESFTE+MAXCLS12+1)*(12/BPN), bpb.bps*NPB) * bpb.nft;
            /* Plus root directory */
            x += howmany(bpb.rde ? bpb.rde : DEFRDE, bpb.bps / sizeof(struct de));
            /* Plus data clusters */
            x += (MAXCLS12+1) * bpb.spc;

            /*
             * We now know how many sectors the volume would occupy with the given
             * sectors per cluster, and the maximum number of FAT12 clusters.  If
             * this is as big as or bigger than the actual volume, we've found the
             * minimum sectors per cluster.
             */
            if (x >= bpb.bsec)
                break;
          }
          break;
      case 16:
          for (x=0; bpb.bsec > fat16Sizes[x].diskSectors; ++x)
            ;
          bpb.spc = fat16Sizes[x].sectorsPerCluster;
          break;
      case 32:
          for (x=0; bpb.bsec > fat32Sizes[x].diskSectors; ++x)
            ;
          bpb.spc = fat32Sizes[x].sectorsPerCluster;
          break;
      default:
          errx(1, "Invalid FAT type: %d", fat);
          break;
      }
      
      if (bpb.spc == 0)
          errx(1, "FAT%d is impossible with %lu sectors", fat, bpb.bsec);
    }
    else
    {
      /*
       * User explicitly specified sectors per cluster.  If they didn't
       * specify the FAT type, pick one that uses up the available sectors.
       */
      if (!fat)
      {
          /* See if a maximum number of FAT clusters would fill it up. */
          if (bpb.bsec < (bpb.res ? bpb.res : bss) +
            howmany((RESFTE+MAXCLS12+1) * (12/BPN), bpb.bps * BPN) * bpb.nft +
            howmany(bpb.rde ? bpb.rde : DEFRDE, bpb.bps / sizeof(struct de)) +
            (MAXCLS12+1) * bpb.spc)
          {
            fat = 12;
          }
          else if (bpb.bsec < (bpb.res ? bpb.res : bss) +
            howmany((RESFTE+MAXCLS16) * 2, bpb.bps) * bpb.nft +
            howmany(bpb.rde ? bpb.rde : DEFRDE, bpb.bps / sizeof(struct de)) +
            (MAXCLS16+1) * bpb.spc)
          {
            fat = 16;
          }
          else
          {
            fat = 32;
          }
      }
    }
    
    x = bss;
    if (fat == 32) {
      if (!bpb.infs) {
          if (x == MAXU16 || x == bpb.bkbs)
            errx(1, "no room for info sector");
          bpb.infs = x;
      }
      if (bpb.infs != MAXU16 && x <= bpb.infs)
          x = bpb.infs + 1;
      if (!bpb.bkbs) {
          if (x == MAXU16)
            errx(1, "no room for backup sector");
          if (x <= BACKUP_BOOT_SECTOR)
            bpb.bkbs = BACKUP_BOOT_SECTOR;
          else
            bpb.bkbs = x;
      } else if (bpb.bkbs != MAXU16 && bpb.bkbs == bpb.infs)
          errx(1, "backup sector would overwrite info sector");
      if (bpb.bkbs != MAXU16 && x <= bpb.bkbs)
          x = bpb.bkbs + 1;
    }
    if (!bpb.res)
      bpb.res = fat == 32 ? MAX(x, FAT32_RESERVED_SECTORS) : x;
    else if (bpb.res < x)
      errx(1, "too few reserved sectors");
    if (fat != 32 && !bpb.rde)
      bpb.rde = DEFRDE;
    rds = howmany(bpb.rde, bpb.bps / sizeof(struct de));
    if (fat != 32 && bpb.bspf > MAXU16)
      errx(1, "too many sectors/FAT for FAT12/16");
    x1 = bpb.res + rds;
    x = bpb.bspf ? bpb.bspf : 1;
    if (x1 + (u_int64_t)x * bpb.nft > bpb.bsec)
      errx(1, "meta data exceeds file system size");
    x1 += x * bpb.nft;
    x = (u_int64_t)(bpb.bsec - x1) * bpb.bps * NPB /
      (bpb.spc * bpb.bps * NPB + fat / BPN * bpb.nft);
    x2 = howmany((RESFTE + MIN(x, maxcls(fat))) * (fat / BPN),
             bpb.bps * NPB);
    if (!bpb.bspf) {
      bpb.bspf = x2;
      x1 += (bpb.bspf - 1) * bpb.nft;
    }
    cls = (bpb.bsec - x1) / bpb.spc;
    x = (u_int64_t)bpb.bspf * bpb.bps * NPB / (fat / BPN) - RESFTE;
    if (cls > x)
    {
      /* 
       * This indicates that there are more sectors available
       * for data clusters than there are usable entries in the
       * FAT.  In this case, we need to limit the number of
       * clusters, and also reduce the number of sectors.
       */
      bpb.bsec = bpb.res + bpb.bspf*bpb.nft + rds + x*bpb.spc;
      warnx("warning: sectors/FAT limits sectors to %u, clusters to %u", bpb.bsec, x);
      cls = x;
    }
    if (bpb.bspf < x2)
      warnx("warning: sectors/FAT limits file system to %u clusters",
            cls);
    if (cls < mincls(fat))
      errx(1, "%u clusters too few clusters for FAT%u, need %u", cls, fat,
          mincls(fat));
    if (cls > maxcls(fat)) {
      cls = maxcls(fat);
      bpb.bsec = x1 + (cls + 1) * bpb.spc - 1;
      warnx("warning: FAT type limits file system to %u sectors",
            bpb.bsec);
    }
    printf("%s: %u sector%s in %u FAT%u cluster%s "
         "(%u bytes/cluster)\n", fname, cls * bpb.spc,
         cls * bpb.spc == 1 ? "" : "s", cls, fat,
         cls == 1 ? "" : "s", bpb.bps * bpb.spc);
    if (!bpb.mid)
        bpb.mid = !bpb.hid ? 0xf0 : 0xf8;
    if (fat == 32)
        bpb.rdcl = RESFTE;
    if (bpb.hid + bpb.bsec <= MAXU16) {
        bpb.sec = bpb.bsec;
        bpb.bsec = 0;
    }
    if (fat != 32) {
        bpb.spf = bpb.bspf;
        bpb.bspf = 0;
    } else {
        if (bpb.bsec == 0)
            bpb.bsec = bpb.sec;
        bpb.spf = 0;
        bpb.sec = 0;
    }
    print_bpb(&bpb);
    if (!opt_N) {
        gettimeofday(&tv, NULL);
        now = tv.tv_sec;
        tm = localtime(&now);
        if (!(img = malloc(bpb.bps)))
            err(1, NULL);
        dir = bpb.res + (bpb.spf ? bpb.spf : bpb.bspf) * bpb.nft;
      for (lsn = 0; lsn < dir + (fat == 32 ? bpb.spc : rds); lsn++) {
          x = lsn;
          if (opt_B &&
            fat == 32 && bpb.bkbs != MAXU16 &&
            bss <= bpb.bkbs && x >= bpb.bkbs) {
            x -= bpb.bkbs;
            if (!x && lseek(fd1, 0, SEEK_SET))
                err(1, "%s", bname);
          }
          if (opt_B && x < bss) {
            if ((n = read(fd1, img, bpb.bps)) == -1)
                err(1, "%s", bname);
            if (n != bpb.bps)
                errx(1, "%s: can't read sector %u", bname, x);
          } else
            memset(img, 0, bpb.bps);
          if (!lsn ||
            (fat == 32 && bpb.bkbs != MAXU16 && lsn == bpb.bkbs)) {
            x1 = sizeof(struct bs);
            bsbpb = (struct bsbpb *)(img + x1);
            mk2(bsbpb->bps, bpb.bps);
            mk1(bsbpb->spc, bpb.spc);
            mk2(bsbpb->res, bpb.res);
            mk1(bsbpb->nft, bpb.nft);
            mk2(bsbpb->rde, bpb.rde);
            mk2(bsbpb->sec, bpb.sec);
            mk1(bsbpb->mid, bpb.mid);
            mk2(bsbpb->spf, bpb.spf);
            mk2(bsbpb->spt, bpb.spt);
            mk2(bsbpb->hds, bpb.hds);
            mk4(bsbpb->hid, bpb.hid);
            mk4(bsbpb->bsec, bpb.bsec);
            x1 += sizeof(struct bsbpb);
            if (fat == 32) {
                bsxbpb = (struct bsxbpb *)(img + x1);
                mk4(bsxbpb->bspf, bpb.bspf);
                mk2(bsxbpb->xflg, 0);
                mk2(bsxbpb->vers, 0);
                mk4(bsxbpb->rdcl, bpb.rdcl);
                mk2(bsxbpb->infs, bpb.infs);
                mk2(bsxbpb->bkbs, bpb.bkbs);
                x1 += sizeof(struct bsxbpb);
            }
            bsx = (struct bsx *)(img + x1);
            mk1(bsx->sig, 0x29);
            if (Iflag)
                x = opt_I;
            else
                x = (((u_int)(1 + tm->tm_mon) << 8 |
                    (u_int)tm->tm_mday) +
                   ((u_int)tm->tm_sec << 8 |
                    (u_int)(tv.tv_usec / 10))) << 16 |
                  ((u_int)(1900 + tm->tm_year) +
                   ((u_int)tm->tm_hour << 8 |
                    (u_int)tm->tm_min));
            mk4(bsx->volid, x);
            mklabel(bsx->label, opt_v ? opt_v : "NO NAME");
            sprintf(buf, "FAT%u", fat);
            setstr(bsx->type, buf, sizeof(bsx->type));
            if (!opt_B) {
                x1 += sizeof(struct bsx);
                bs = (struct bs *)img;
                mk1(bs->jmp[0], 0xeb);
                mk1(bs->jmp[1], x1 - 2);
                mk1(bs->jmp[2], 0x90);
                setstr(bs->oem, opt_O ? opt_O : "BSD  4.4",
                     sizeof(bs->oem));
                memcpy(img + x1, bootcode, sizeof(bootcode));
                mk2(img + bpb.bps - 2, DOSMAGIC);
            }
          } else if (fat == 32 && bpb.infs != MAXU16 &&
                   (lsn == bpb.infs ||
                  (bpb.bkbs != MAXU16 &&
                   lsn == bpb.bkbs + bpb.infs))) {
            mk4(img, 0x41615252);
            mk4(img + 484, 0x61417272);
            mk4(img + 488, 0xffffffff);
            mk4(img + 492, bpb.rdcl+1);
            /* Offsets 508-509 remain zero */
            mk2(img + 510, DOSMAGIC);
          } else if (lsn >= bpb.res && lsn < dir &&
                   !((lsn - bpb.res) %
                   (bpb.spf ? bpb.spf : bpb.bspf))) {
            mk1(img[0], bpb.mid);
            for (x = 1; x < fat * (fat == 32 ? 3 : 2) / 8; x++)
                mk1(img[x], fat == 32 && x % 4 == 3 ? 0x0f : 0xff);
          } else if (lsn == dir && opt_v && *opt_v) {
            de = (struct de *)img;
            mklabel(de->namext, opt_v);
            mk1(de->attr, 050);
            x = (u_int)tm->tm_hour << 11 |
                (u_int)tm->tm_min << 5 |
                (u_int)tm->tm_sec >> 1;
            mk2(de->time, x);
            x = (u_int)(tm->tm_year - 80) << 9 |
                (u_int)(tm->tm_mon + 1) << 5 |
                (u_int)tm->tm_mday;
            mk2(de->date, x);
          }
          if ((n = write(fd, img, bpb.bps)) == -1)
            err(1, "%s", fname);
          if (n != bpb.bps)
            errx(1, "%s: can't write sector %u", fname, lsn);
      }
    }
    return 0;
}

/*
 * Exit with error if file system is mounted.
 */
static void
check_mounted(const char *fname, mode_t mode)
{
    struct statfs *mp;
    const char *s1, *s2;
    size_t len;
    int n, r;

    if (!(n = getmntinfo(&mp, MNT_NOWAIT)))
      err(1, "getmntinfo");
    len = strlen(_PATH_DEV);
    s1 = fname;
    if (!strncmp(s1, _PATH_DEV, len))
      s1 += len;
    r = S_ISCHR(mode) && s1 != fname && *s1 == 'r';
    for (; n--; mp++) {
      s2 = mp->f_mntfromname;
      if (!strncmp(s2, _PATH_DEV, len))
          s2 += len;
      if ((r && s2 != mp->f_mntfromname && !strcmp(s1 + 1, s2)) ||
          !strcmp(s1, s2))
          errx(1, "%s is mounted on %s", fname, mp->f_mntonname);
    }
}

/*
 * Get a standard format.
 */
static void
getstdfmt(const char *fmt, struct bpb *bpb)
{
    u_int x, i;

    x = sizeof(stdfmt) / sizeof(stdfmt[0]);
    for (i = 0; i < x && strcmp(fmt, stdfmt[i].name); i++);
    if (i == x)
      errx(1, "%s: unknown standard format", fmt);
    *bpb = stdfmt[i].bpb;
}

/*
 * Get disk partition, and geometry information.
 */
static void
getdiskinfo(int fd, const char *fname, const char *dtype, int oflag,
          struct bpb *bpb)
{
      struct disklabel lab;

      if (dkdisklabel(fd, &lab) < 0) {
            warn("ioctl (GDINFO)");
            errx(1, "%s: can't figure out partition info", fname);
      }

      if (!oflag)
            bpb->hid = lab.d_partitions[0].p_offset;
      if (!bpb->bsec)
            bpb->bsec = lab.d_partitions[0].p_size;

      if (!bpb->bps)
            bpb->bps = ckgeom(fname, lab.d_secsize, "bytes/sector");
      if (!bpb->spt)
            bpb->spt = ckgeom(fname, lab.d_nsectors, "sectors/track");
      if (!bpb->hds)
            bpb->hds = ckgeom(fname, lab.d_ntracks, "drive heads");
}

/*
 * Print out BPB values.
 */
static void
print_bpb(struct bpb *bpb)
{
    printf("bps=%u spc=%u res=%u nft=%u", bpb->bps, bpb->spc, bpb->res,
         bpb->nft);
    if (bpb->rde)
      printf(" rde=%u", bpb->rde);
    if (bpb->sec)
      printf(" sec=%u", bpb->sec);
    printf(" mid=%#x", bpb->mid);
    if (bpb->spf)
      printf(" spf=%u", bpb->spf);
    printf(" spt=%u hds=%u hid=%u", bpb->spt, bpb->hds, bpb->hid);
    if (bpb->bsec)
      printf(" bsec=%u", bpb->bsec);
    if (!bpb->spf) {
      printf(" bspf=%u rdcl=%u", bpb->bspf, bpb->rdcl);
      printf(" infs=");
      printf(bpb->infs == MAXU16 ? "%#x" : "%u", bpb->infs);
      printf(" bkbs=");
      printf(bpb->bkbs == MAXU16 ? "%#x" : "%u", bpb->bkbs);
    }
    printf("\n");
}

/*
 * Check a disk geometry value.
 */
static u_int
ckgeom(const char *fname, u_int val, const char *msg)
{
    if (!val)
      errx(1, "%s: no default %s", fname, msg);
    if (val > MAXU16)
      errx(1, "%s: illegal %s", fname, msg);
    return val;
}

/*
 * Convert and check a numeric option argument.
 */
static u_int
argtou(const char *arg, u_int lo, u_int hi, const char *msg)
{
    char *s;
    u_long x;

    errno = 0;
    x = strtoul(arg, &s, 0);
    if (errno || !*arg || *s || x < lo || x > hi)
      errx(1, "%s: bad %s", arg, msg);
    return x;
}

/*
 * Check a volume label.
 */
static int
oklabel(const char *src)
{
    int c, i;

    for (i = 0; i <= 11; i++) {
      c = (u_char)*src++;
      if (c < ' ' + !i || strchr("\"*+,./:;<=>?[\\]|", c))
          break;
    }
    return !c;
}

/*
 * Make a volume label.
 */
static void
mklabel(u_int8_t *dest, const char *src)
{
    int c, i;

    for (i = 0; i < 11; i++) {
      c = *src ? toupper(*src++) : ' ';
      *dest++ = !i && c == '\xe5' ? 5 : c;
    }
}

/*
 * Copy string, padding with spaces.
 */
static void
setstr(u_int8_t *dest, const char *src, size_t len)
{
    while (len--)
      *dest++ = *src ? *src++ : ' ';
}

/*
 * Print usage message.
 */
static void
usage(void)
{
    fprintf(stderr,
          "usage: newfs_msdos [ -options ] special [disktype]\n");
    fprintf(stderr, "where the options are:\n");
    fprintf(stderr, "\t-N don't create file system: "
          "just print out parameters\n");
    fprintf(stderr, "\t-B get bootstrap from file\n");
    fprintf(stderr, "\t-F FAT type (12, 16, or 32)\n");
    fprintf(stderr, "\t-I volume ID\n");
    fprintf(stderr, "\t-O OEM string\n");
    fprintf(stderr, "\t-S bytes/sector\n");
    fprintf(stderr, "\t-a sectors/FAT\n");
    fprintf(stderr, "\t-b block size\n");
    fprintf(stderr, "\t-c sectors/cluster\n");
    fprintf(stderr, "\t-e root directory entries\n");
    fprintf(stderr, "\t-f standard format\n");
    fprintf(stderr, "\t-h drive heads\n");
    fprintf(stderr, "\t-i file system info sector\n");
    fprintf(stderr, "\t-k backup boot sector\n");
    fprintf(stderr, "\t-m media descriptor\n");
    fprintf(stderr, "\t-n number of FATs\n");
    fprintf(stderr, "\t-o hidden sectors\n");
    fprintf(stderr, "\t-r reserved sectors\n");
    fprintf(stderr, "\t-s file system size (sectors)\n");
    fprintf(stderr, "\t-u sectors/track\n");
    fprintf(stderr, "\t-v filesystem/volume name\n");
    exit(1);
}

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