aboutsummaryrefslogtreecommitdiffstats
path: root/linux/syslinux.c
blob: 10c089c09bcc8a6d2410e66abe45818684eb3bab (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
/* ----------------------------------------------------------------------- *
 *
 *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * syslinux.c - Linux installer program for SYSLINUX
 *
 * This is Linux-specific by now.
 *
 * This is an alternate version of the installer which doesn't require
 * mtools, but requires root privilege.
 */

/*
 * If DO_DIRECT_MOUNT is 0, call mount(8)
 * If DO_DIRECT_MOUNT is 1, call mount(2)
 */
#ifdef __KLIBC__
# define DO_DIRECT_MOUNT 1
#else
# define DO_DIRECT_MOUNT 0	/* glibc has broken losetup ioctls */
#endif

#define _GNU_SOURCE
#define _XOPEN_SOURCE 500	/* For pread() pwrite() */
#define _FILE_OFFSET_BITS 64
#include <alloca.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/mount.h>

#include <sys/ioctl.h>
#include <linux/fs.h>		/* FIGETBSZ, FIBMAP */
#include <linux/msdos_fs.h>	/* FAT_IOCTL_SET_ATTRIBUTES */
#ifndef FAT_IOCTL_SET_ATTRIBUTES
# define FAT_IOCTL_SET_ATTRIBUTES _IOW('r', 0x11, uint32_t)
#endif
#undef SECTOR_SIZE
#undef SECTOR_SHIFT

#include <paths.h>
#ifndef _PATH_MOUNT
# define _PATH_MOUNT "/bin/mount"
#endif
#ifndef _PATH_UMOUNT
# define _PATH_UMOUNT "/bin/umount"
#endif
#ifndef _PATH_TMP
# define _PATH_TMP "/tmp/"
#endif

#include "syslinux.h"

#if DO_DIRECT_MOUNT
# include <linux/loop.h>
#endif

const char *program;		/* Name of program */
const char *device;		/* Device to install to */
pid_t mypid;
char *mntpath = NULL;		/* Path on which to mount */
off_t filesystem_offset = 0;	/* Filesystem offset */
#if DO_DIRECT_MOUNT
int loop_fd = -1;		/* Loop device */
#endif

void __attribute__((noreturn)) usage(void)
{
  fprintf(stderr, "Usage: %s [-sfr][-d directory][-o offset] device\n", program);
  exit(1);
}

void __attribute__((noreturn)) die(const char *msg)
{
  fprintf(stderr, "%s: %s\n", program, msg);

#if DO_DIRECT_MOUNT
  if ( loop_fd != -1 ) {
    ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
    close(loop_fd);
    loop_fd = -1;
  }
#endif

  if ( mntpath )
    unlink(mntpath);

  exit(1);
}

/*
 * read/write wrapper functions
 */
ssize_t xpread(int fd, void *buf, size_t count, off_t offset)
{
  char *bufp = (char *)buf;
  ssize_t rv;
  ssize_t done = 0;

  while ( count ) {
    rv = pread(fd, bufp, count, offset);
    if ( rv == 0 ) {
      die("short read");
    } else if ( rv == -1 ) {
      if ( errno == EINTR ) {
	continue;
      } else {
	die(strerror(errno));
      }
    } else {
      bufp += rv;
      offset += rv;
      done += rv;
      count -= rv;
    }
  }

  return done;
}

ssize_t xpwrite(int fd, const void *buf, size_t count, off_t offset)
{
  const char *bufp = (const char *)buf;
  ssize_t rv;
  ssize_t done = 0;

  while ( count ) {
    rv = pwrite(fd, bufp, count, offset);
    if ( rv == 0 ) {
      die("short write");
    } else if ( rv == -1 ) {
      if ( errno == EINTR ) {
	continue;
      } else {
	die(strerror(errno));
      }
    } else {
      bufp += rv;
      offset += rv;
      done += rv;
      count -= rv;
    }
  }

  return done;
}

/*
 * Create a block map for ldlinux.sys
 */
int make_block_map(uint32_t *sectors, int len, int dev_fd, int fd)
{
  int nsectors = 0;
  int blocksize, nblock, block;
  int i;

  (void)dev_fd;

  if (ioctl(fd, FIGETBSZ, &blocksize) < 0)
    die("ioctl FIGETBSZ failed");

  blocksize >>= SECTOR_SHIFT;	/* sectors/block */

  nblock = 0;
  while (len > 0) {
    block = nblock++;
    if (ioctl(fd, FIBMAP, &block) < 0)
      die("ioctl FIBMAP failed");

    for (i = 0; i < blocksize; i++) {
      if (len <= 0)
	break;

      *sectors++ = (block*blocksize)+i;
      nsectors++;
      len -= (1 << SECTOR_SHIFT);
    }
  }

  return nsectors;
}

/*
 * Mount routine
 */
int do_mount(int dev_fd, int *cookie, const char *mntpath, const char *fstype)
{
  struct stat st;

  (void)cookie;

  if (fstat(dev_fd, &st) < 0)
    return errno;

#if DO_DIRECT_MOUNT
  {
    if ( !S_ISBLK(st.st_mode) ) {
      /* It's file, need to mount it loopback */
      unsigned int n = 0;
      struct loop_info64 loopinfo;
      int loop_fd;

      for ( n = 0 ; loop_fd < 0 ; n++ ) {
	snprintf(devfdname, sizeof devfdname, "/dev/loop%u", n);
	loop_fd = open(devfdname, O_RDWR);
	if ( loop_fd < 0 && errno == ENOENT ) {
	  die("no available loopback device!");
	}
	if ( ioctl(loop_fd, LOOP_SET_FD, (void *)dev_fd) ) {
	  close(loop_fd); loop_fd = -1;
	  if ( errno != EBUSY )
	    die("cannot set up loopback device");
	  else
	    continue;
	}

	if ( ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo) ||
	     (loopinfo.lo_offset = filesystem_offset,
	      ioctl(loop_fd, LOOP_SET_STATUS64, &loopinfo)) )
	  die("cannot set up loopback device");
      }

      *cookie = loop_fd;
    } else {
      snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
	       (unsigned long)mypid, dev_fd);
      *cookie = -1;
    }

    return mount(devfdname, mntpath, fstype,
		 MS_NOEXEC|MS_NOSUID, "umask=077,quiet");
  }
#else
  {
    char devfdname[128], mnt_opts[128];
    pid_t f, w;
    int status;

    snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
	     (unsigned long)mypid, dev_fd);

    f = fork();
    if ( f < 0 ) {
      return -1;
    } else if ( f == 0 ) {
      if ( !S_ISBLK(st.st_mode) ) {
	snprintf(mnt_opts, sizeof mnt_opts,
		 "rw,nodev,noexec,loop,offset=%llu,umask=077,quiet",
		 (unsigned long long)filesystem_offset);
      } else {
	snprintf(mnt_opts, sizeof mnt_opts, "rw,nodev,noexec,umask=077,quiet");
      }
      execl(_PATH_MOUNT, _PATH_MOUNT, "-t", fstype, "-o", mnt_opts,	\
	    devfdname, mntpath, NULL);
      _exit(255);		/* execl failed */
    }

    w = waitpid(f, &status, 0);
    return ( w != f || status ) ? -1 : 0;
  }
#endif
}

/*
 * umount routine
 */
void do_umount(const char *mntpath, int cookie)
{
#if DO_DIRECT_MOUNT
  int loop_fd = cookie;

  if ( umount2(mntpath, 0) )
    die("could not umount path");

  if ( loop_fd != -1 ) {
    ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
    close(loop_fd);
    loop_fd = -1;
  }

#else
  pid_t f = fork();
  pid_t w;
  int status;
  (void)cookie;

  if ( f < 0 ) {
    perror("fork");
    exit(1);
  } else if ( f == 0 ) {
    execl(_PATH_UMOUNT, _PATH_UMOUNT, mntpath, NULL);
  }

  w = waitpid(f, &status, 0);
  if ( w != f || status ) {
    exit(1);
  }
#endif
}

int main(int argc, char *argv[])
{
  static unsigned char sectbuf[SECTOR_SIZE];
  unsigned char *dp;
  const unsigned char *cdp;
  int dev_fd, fd;
  struct stat st;
  int nb, left;
  int err = 0;
  char mntname[128];
  char *ldlinux_name, **argp, *opt;
  const char *subdir = NULL;
  uint32_t *sectors;
  int ldlinux_sectors;
  int nsectors = 0;
  const char *errmsg;
  int mnt_cookie;
  int patch_sectors;
  int i;

  int force = 0;		/* -f (force) option */
  int stupid = 0;		/* -s (stupid) option */
  int raid_mode = 0;		/* -r (RAID) option */

  (void)argc;			/* Unused */

  program = argv[0];
  mypid = getpid();

  device = NULL;

  umask(077);

  for ( argp = argv+1 ; *argp ; argp++ ) {
    if ( **argp == '-' ) {
      opt = *argp + 1;
      if ( !*opt )
	usage();

      while ( *opt ) {
	if ( *opt == 's' ) {
	  stupid = 1;
	} else if ( *opt == 'r' ) {
	  raid_mode = 1;
	} else if ( *opt == 'f' ) {
	  force = 1;		/* Force install */
	} else if ( *opt == 'd' && argp[1] ) {
	  subdir = *++argp;
	} else if ( *opt == 'o' && argp[1] ) {
	  /* Byte offset */
	  filesystem_offset = (off_t)strtoull(*++argp, NULL, 0);
	} else {
	  usage();
	}
	opt++;
      }
    } else {
      if ( device )
	usage();
      device = *argp;
    }
  }

  if ( !device )
    usage();

  /*
   * First make sure we can open the device at all, and that we have
   * read/write permission.
   */
  dev_fd = open(device, O_RDWR);
  if ( dev_fd < 0 || fstat(dev_fd, &st) < 0 ) {
    perror(device);
    exit(1);
  }

  if ( !S_ISBLK(st.st_mode) && !S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode) ) {
    die("not a device or regular file");
  }

  if ( filesystem_offset && S_ISBLK(st.st_mode) ) {
    die("can't combine an offset with a block device");
  }

  xpread(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);
  fsync(dev_fd);

  /*
   * Check to see that what we got was indeed an MS-DOS boot sector/superblock
   */
  if( (errmsg = syslinux_check_bootsect(sectbuf)) ) {
    fprintf(stderr, "%s: %s\n", device, errmsg);
    exit(1);
  }

  /*
   * Now mount the device.
   */
  if ( geteuid() ) {
    die("This program needs root privilege");
  } else {
    int i = 0;
    struct stat dst;
    int rv;

    /* We're root or at least setuid.
       Make a temp dir and pass all the gunky options to mount. */

    if ( chdir(_PATH_TMP) ) {
      perror(program);
      exit(1);
    }

#define TMP_MODE (S_IXUSR|S_IWUSR|S_IXGRP|S_IWGRP|S_IWOTH|S_IXOTH|S_ISVTX)

    if ( stat(".", &dst) || !S_ISDIR(dst.st_mode) ||
	 (dst.st_mode & TMP_MODE) != TMP_MODE ) {
      die("possibly unsafe " _PATH_TMP " permissions");
    }

    for ( i = 0 ; ; i++ ) {
      snprintf(mntname, sizeof mntname, "syslinux.mnt.%lu.%d",
	       (unsigned long)mypid, i);

      if ( lstat(mntname, &dst) != -1 || errno != ENOENT )
	continue;

      rv = mkdir(mntname, 0000);

      if ( rv == -1 ) {
	if ( errno == EEXIST || errno == EINTR )
	  continue;
	perror(program);
	exit(1);
      }

      if ( lstat(mntname, &dst) || dst.st_mode != (S_IFDIR|0000) ||
	   dst.st_uid != 0 ) {
	die("someone is trying to symlink race us!");
      }
      break;			/* OK, got something... */
    }

    mntpath = mntname;
  }

  if (do_mount(dev_fd, &mnt_cookie, mntpath, "vfat") &&
      do_mount(dev_fd, &mnt_cookie, mntpath, "msdos")) {
    rmdir(mntpath);
    die("mount failed");
  }

  ldlinux_name = alloca(strlen(mntpath)+14+
			(subdir ? strlen(subdir)+2 : 0));
  if ( !ldlinux_name ) {
    perror(program);
    err = 1;
    goto umount;
  }
  sprintf(ldlinux_name, "%s%s%s//ldlinux.sys",
	  mntpath, subdir ? "//" : "", subdir ? subdir : "");

  if ((fd = open(ldlinux_name, O_RDONLY)) >= 0) {
    uint32_t zero_attr = 0;
    ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &zero_attr);
    close(fd);
  }

  unlink(ldlinux_name);
  fd = open(ldlinux_name, O_WRONLY|O_CREAT|O_TRUNC, 0444);
  if ( fd < 0 ) {
    perror(device);
    err = 1;
    goto umount;
  }

  cdp = syslinux_ldlinux;
  left = syslinux_ldlinux_len;
  while ( left ) {
    nb = write(fd, cdp, left);
    if ( nb == -1 && errno == EINTR )
      continue;
    else if ( nb <= 0 ) {
      perror(device);
      err = 1;
      goto umount;
    }

    dp += nb;
    left -= nb;
  }

  fsync(fd);
  /*
   * Set the attributes
   */
  {
    uint32_t attr = 0x07;	/* Hidden+System+Readonly */
    ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr);
  }

  /*
   * Create a block map.
   */
  ldlinux_sectors = (syslinux_ldlinux_len+SECTOR_SIZE-1) >> SECTOR_SHIFT;
  sectors = calloc(ldlinux_sectors, sizeof *sectors);
  nsectors = make_block_map(sectors, syslinux_ldlinux_len, dev_fd, fd);

  close(fd);
  sync();

umount:
  do_umount(mntpath, mnt_cookie);
  sync();
  rmdir(mntpath);

  if ( err )
    exit(err);

  /*
   * Patch ldlinux.sys and the boot sector
   */
  i = syslinux_patch(sectors, nsectors, stupid, raid_mode);
  patch_sectors = (i + SECTOR_SIZE - 1) >> SECTOR_SHIFT;

  /*
   * Write the now-patched first sectors of ldlinux.sys
   */
  for (i = 0; i < patch_sectors; i++) {
    xpwrite(dev_fd, syslinux_ldlinux + i*SECTOR_SIZE, SECTOR_SIZE,
	    filesystem_offset+((off_t)sectors[i] << SECTOR_SHIFT));
  }

  /*
   * To finish up, write the boot sector
   */

  /* Read the superblock again since it might have changed while mounted */
  xpread(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);

  /* Copy the syslinux code into the boot sector */
  syslinux_make_bootsect(sectbuf);

  /* Write new boot sector */
  xpwrite(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);

  close(dev_fd);
  sync();

  /* Done! */

  return 0;
}