Linux debugging

Check our new training course

Linux debugging, tracing, profiling & perf. analysis

Check our new training course
with Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

  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
/* vi: set sw=4 ts=4: */
/*
 * Mini mount implementation for busybox
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 * Copyright (C) 2005-2006 by Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* todo:
 * bb_getopt_ulflags();
 */

/* Design notes: There is no spec for this.  Remind me to write one.

   mount_main() calls singlemount() which calls mount_it_now().

   mount_main() can loop through /etc/fstab for mount -a
   singlemount() can loop through /etc/filesystems for fstype detection.
   mount_it_now() does the actual mount.
*/

#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <mntent.h>
#include <ctype.h>
#include <sys/mount.h>
#include <fcntl.h>		// for CONFIG_FEATURE_MOUNT_LOOP
#include <sys/ioctl.h>  // for CONFIG_FEATURE_MOUNT_LOOP
#include "busybox.h"

// These two aren't always defined in old headers
#ifndef MS_BIND
#define MS_BIND		4096
#endif
#ifndef MS_MOVE
#define MS_MOVE		8192
#endif
#ifndef MS_SILENT
#define MS_SILENT	32768
#endif

// Not real flags, but we want to be able to check for this.
#define MOUNT_NOAUTO    (1<<29)
#define MOUNT_SWAP      (1<<30)
/* Standard mount options (from -o options or --options), with corresponding
 * flags */

struct {
	const char *name;
	long flags;
} static const mount_options[] = {
	// NOP flags.

	{"loop", 0},
	{"defaults", 0},
	{"quiet", 0},

	// vfs flags

	{"ro", MS_RDONLY},
	{"rw", ~MS_RDONLY},
	{"nosuid", MS_NOSUID},
	{"suid", ~MS_NOSUID},
	{"dev", ~MS_NODEV},
	{"nodev", MS_NODEV},
	{"exec", ~MS_NOEXEC},
	{"noexec", MS_NOEXEC},
	{"sync", MS_SYNCHRONOUS},
	{"async", ~MS_SYNCHRONOUS},
	{"atime", ~MS_NOATIME},
	{"noatime", MS_NOATIME},
	{"diratime", ~MS_NODIRATIME},
	{"nodiratime", MS_NODIRATIME},
	{"loud", ~MS_SILENT},

	// action flags

	{"remount", MS_REMOUNT},
	{"bind", MS_BIND},
	{"move", MS_MOVE},
	{"noauto",MOUNT_NOAUTO},
	{"swap",MOUNT_SWAP}
};

/* Append mount options to string */
static void append_mount_options(char **oldopts, char *newopts)
{
	if(*oldopts && **oldopts) {
		char *temp=bb_xasprintf("%s,%s",*oldopts,newopts);
		free(*oldopts);
		*oldopts=temp;
	} else {
		if (ENABLE_FEATURE_CLEAN_UP) free(*oldopts);
		*oldopts = bb_xstrdup(newopts);
	}
}

/* Use the mount_options list to parse options into flags.
 * Return list of unrecognized options in *strflags if strflags!=NULL */
static int parse_mount_options(char *options, char **unrecognized)
{
	int flags = MS_SILENT;

	// Loop through options
	for (;;) {
		int i;
		char *comma = strchr(options, ',');

		if (comma) *comma = 0;

		// Find this option in mount_options
		for (i = 0; i < (sizeof(mount_options) / sizeof(*mount_options)); i++) {
			if (!strcasecmp(mount_options[i].name, options)) {
				long fl = mount_options[i].flags;
				if(fl < 0) flags &= fl;
				else flags |= fl;
				break;
			}
		}
		// If unrecognized not NULL, append unrecognized mount options */
		if (unrecognized
				&& i == (sizeof(mount_options) / sizeof(*mount_options)))
		{
			// Add it to strflags, to pass on to kernel
			i = *unrecognized ? strlen(*unrecognized) : 0;
			*unrecognized = xrealloc(*unrecognized, i+strlen(options)+2);

			// Comma separated if it's not the first one
			if (i) (*unrecognized)[i++] = ',';
			strcpy((*unrecognized)+i, options);
		}

		// Advance to next option, or finish
		if(comma) {
			*comma = ',';
			options = ++comma;
		} else break;
	}

	return flags;
}

// Return a list of all block device backed filesystems

static llist_t *get_block_backed_filesystems(void)
{
	char *fs, *buf,
		 *filesystems[] = {"/etc/filesystems", "/proc/filesystems", 0};
	llist_t *list = 0;
	int i;
	FILE *f;

	for(i = 0; filesystems[i]; i++) {
		if(!(f = fopen(filesystems[i], "r"))) continue;

		for(fs = buf = 0; (fs = buf = bb_get_chomped_line_from_file(f));
			free(buf))
		{
			if(!strncmp(buf,"nodev",5) && isspace(buf[5])) continue;

			while(isspace(*fs)) fs++;
			if(*fs=='#' || *fs=='*') continue;
			if(!*fs) continue;

			list=llist_add_to_end(list,bb_xstrdup(fs));
		}
		if (ENABLE_FEATURE_CLEAN_UP) fclose(f);
	}

	return list;
}

llist_t *fslist = 0;

#if ENABLE_FEATURE_CLEAN_UP
static void delete_block_backed_filesystems(void)
{
	llist_free(fslist);
}
#else
void delete_block_backed_filesystems(void);
#endif

#if ENABLE_FEATURE_MTAB_SUPPORT
static int useMtab;
static int fakeIt;
#else
#define useMtab 0
#define fakeIt 0
#endif

// Perform actual mount of specific filesystem at specific location.

static int mount_it_now(struct mntent *mp, int vfsflags, char *filteropts)
{
	int rc;

	if (fakeIt) { return 0; }

	// Mount, with fallback to read-only if necessary.

	for(;;) {
		rc = mount(mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
				vfsflags, filteropts);
		if(!rc || (vfsflags&MS_RDONLY) || (errno!=EACCES && errno!=EROFS))
			break;
		bb_error_msg("%s is write-protected, mounting read-only",
				mp->mnt_fsname);
		vfsflags |= MS_RDONLY;
	}

	// Abort entirely if permission denied.

	if (rc && errno == EPERM)
		bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);

	/* If the mount was successful, and we're maintaining an old-style
	 * mtab file by hand, add the new entry to it now. */

	if(ENABLE_FEATURE_MTAB_SUPPORT && useMtab && !rc) {
		FILE *mountTable = setmntent(bb_path_mtab_file, "a+");
		int i;

		if(!mountTable)
			bb_error_msg("No %s\n",bb_path_mtab_file);

		// Add vfs string flags

		for(i=0; mount_options[i].flags != MS_REMOUNT; i++)
			if (mount_options[i].flags > 0)
				append_mount_options(&(mp->mnt_opts),
// Shut up about the darn const.  It's not important.  I don't care.
						(char *)mount_options[i].name);

		// Remove trailing / (if any) from directory we mounted on

		i = strlen(mp->mnt_dir);
		if(i>1 && mp->mnt_dir[i-1] == '/') mp->mnt_dir[i-1] = 0;

		// Write and close.

		if(!mp->mnt_type || !*mp->mnt_type) mp->mnt_type="--bind";
		addmntent(mountTable, mp);
		endmntent(mountTable);
		if (ENABLE_FEATURE_CLEAN_UP)
			if(strcmp(mp->mnt_type,"--bind")) mp->mnt_type = 0;
	}

	return rc;
}


// Mount one directory.  Handles NFS, loopback, autobind, and filesystem type
// detection.  Returns 0 for success, nonzero for failure.

static int singlemount(struct mntent *mp)
{
	int rc = 1, vfsflags;
	char *loopFile = 0, *filteropts = 0;
	llist_t *fl = 0;
	struct stat st;

	vfsflags = parse_mount_options(mp->mnt_opts, &filteropts);

	// Treat fstype "auto" as unspecified.

	if (mp->mnt_type && !strcmp(mp->mnt_type,"auto")) mp->mnt_type = 0;

	// Might this be an NFS filesystem?

	if (ENABLE_FEATURE_MOUNT_NFS &&
		(!mp->mnt_type || !strcmp(mp->mnt_type,"nfs")) &&
		strchr(mp->mnt_fsname, ':') != NULL)
	{
		if (nfsmount(mp->mnt_fsname, mp->mnt_dir, &vfsflags, &filteropts, 1)) {
			bb_perror_msg("nfsmount failed");
			return 1;
		} else {
			// Strangely enough, nfsmount() doesn't actually mount() anything.
			rc = mount_it_now(mp, vfsflags, filteropts);
			if (ENABLE_FEATURE_CLEAN_UP) free(filteropts);
			
			return rc;
		}
	}

	// Look at the file.  (Not found isn't a failure for remount.)

	if (lstat(mp->mnt_fsname, &st));

	if (!(vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))) {
		// Do we need to allocate a loopback device for it?

		if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
			loopFile = bb_simplify_path(mp->mnt_fsname);
			mp->mnt_fsname = 0;
			switch(set_loop(&(mp->mnt_fsname), loopFile, 0)) {
				case 0:
				case 1:
					break;
				default:
					bb_error_msg( errno == EPERM || errno == EACCES
						? bb_msg_perm_denied_are_you_root
					   	: "Couldn't setup loop device");
					return errno;
			}

		// Autodetect bind mounts

		} else if (S_ISDIR(st.st_mode) && !mp->mnt_type) vfsflags |= MS_BIND;
	}

	/* If we know the fstype (or don't need to), jump straight
	 * to the actual mount. */

	if (mp->mnt_type || (vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE)))
		rc = mount_it_now(mp, vfsflags, filteropts);

	// Loop through filesystem types until mount succeeds or we run out

	else {

		/* Initialize list of block backed filesystems.  This has to be
		 * done here so that during "mount -a", mounts after /proc shows up
		 * can autodetect. */

		if (!fslist) {
			fslist = get_block_backed_filesystems();
			if (ENABLE_FEATURE_CLEAN_UP && fslist)
				atexit(delete_block_backed_filesystems);
		}

		for (fl = fslist; fl; fl = fl->link) {
			mp->mnt_type = fl->data;

			if (!(rc = mount_it_now(mp,vfsflags, filteropts))) break;

			mp->mnt_type = 0;
		}
	}

	if (ENABLE_FEATURE_CLEAN_UP) free(filteropts);

	// If mount failed, clean up loop file (if any).

	if (rc && loopFile) {
		del_loop(mp->mnt_fsname);
		if (ENABLE_FEATURE_CLEAN_UP) {
			free(loopFile);
			free(mp->mnt_fsname);
		}
	}
	return rc;
}


// Parse options, if necessary parse fstab/mtab, and call singlemount for
// each directory to be mounted.

int mount_main(int argc, char **argv)
{
	char *cmdopts = bb_xstrdup(""), *fstabname, *fstype=0, *storage_path=0;
	FILE *fstab;
	int i, opt, all = FALSE, rc = 1;
	struct mntent mtpair[2], *mtcur = mtpair;

	/* parse long options, like --bind and --move.  Note that -o option
	 * and --option are synonymous.  Yes, this means --remount,rw works. */

	for (i = opt = 0; i < argc; i++) {
		if (argv[i][0] == '-' && argv[i][1] == '-') {
			append_mount_options(&cmdopts,argv[i]+2);
		} else argv[opt++] = argv[i];
	}
	argc = opt;

	// Parse remaining options

	while ((opt = getopt(argc, argv, "o:t:rwavnf")) > 0) {
		switch (opt) {
			case 'o':
				append_mount_options(&cmdopts, optarg);
				break;
			case 't':
				fstype = optarg;
				break;
			case 'r':
				append_mount_options(&cmdopts, "ro");
				break;
			case 'w':
				append_mount_options(&cmdopts, "rw");
				break;
			case 'a':
				all = TRUE;
				break;
			case 'n':
				USE_FEATURE_MTAB_SUPPORT(useMtab = FALSE;)
				break;
			case 'f':
				USE_FEATURE_MTAB_SUPPORT(fakeIt = FALSE;)
				break;
			case 'v':
				break;		// ignore -v
			default:
				bb_show_usage();
		}
	}

	// Three or more non-option arguments?  Die with a usage message.

	if (optind-argc>2) bb_show_usage();

	// If we have no arguments, show currently mounted filesystems

	if (optind == argc) {
		if (!all) {
			FILE *mountTable = setmntent(bb_path_mtab_file, "r");

			if(!mountTable) bb_error_msg_and_die("No %s",bb_path_mtab_file);

			while (getmntent_r(mountTable,mtpair,bb_common_bufsiz1,
								sizeof(bb_common_bufsiz1)))
			{
				// Don't show rootfs.
				if (!strcmp(mtpair->mnt_fsname, "rootfs")) continue;

				if (!fstype || !strcmp(mtpair->mnt_type, fstype))
					printf("%s on %s type %s (%s)\n", mtpair->mnt_fsname,
							mtpair->mnt_dir, mtpair->mnt_type,
							mtpair->mnt_opts);
			}
			if (ENABLE_FEATURE_CLEAN_UP) endmntent(mountTable);
			return EXIT_SUCCESS;
		}
	}

	// When we have two arguments, the second is the directory and we can
	// skip looking at fstab entirely.  We can always abspath() the directory
	// argument when we get it.

	if (optind+2 == argc) {
		mtpair->mnt_fsname = argv[optind];
		mtpair->mnt_dir = argv[optind+1];
		mtpair->mnt_type = fstype;
		mtpair->mnt_opts = cmdopts;
		rc = singlemount(mtpair);
		goto clean_up;
	}

	// If we have at least one argument, it's the storage location

	if (optind < argc) storage_path = bb_simplify_path(argv[optind]);

	// Open either fstab or mtab

	if (parse_mount_options(cmdopts,0) & MS_REMOUNT)
		fstabname = (char *)bb_path_mtab_file;  // Again with the evil const.
	else fstabname="/etc/fstab";

	if (!(fstab=setmntent(fstabname,"r")))
		bb_perror_msg_and_die("Cannot read %s",fstabname);

	// Loop through entries until we find what we're looking for.

	memset(mtpair,0,sizeof(mtpair));
	for (;;) {
		struct mntent *mtnext = mtpair + (mtcur==mtpair ? 1 : 0);

		// Get next fstab entry

		if (!getmntent_r(fstab, mtcur, bb_common_bufsiz1,
					sizeof(bb_common_bufsiz1)))
		{
			// Were we looking for something specific?

			if (optind != argc) {

				// If we didn't find anything, complain.

				if (!mtnext->mnt_fsname)
					bb_error_msg_and_die("Can't find %s in %s",
						argv[optind], fstabname);

				// Mount the last thing we found.

				mtcur = mtnext;
				mtcur->mnt_opts=bb_xstrdup(mtcur->mnt_opts);
				append_mount_options(&(mtcur->mnt_opts),cmdopts);
				rc = singlemount(mtcur);
				free(mtcur->mnt_opts);
			}
			break;
		}

		/* If we're trying to mount something specific and this isn't it,
		 * skip it.  Note we must match both the exact text in fstab (ala
		 * "proc") or a full path from root */

		if (optind != argc) {

			// Is this what we're looking for?

			if(strcmp(argv[optind],mtcur->mnt_fsname) &&
			   strcmp(storage_path,mtcur->mnt_fsname) &&
			   strcmp(argv[optind],mtcur->mnt_dir) &&
			   strcmp(storage_path,mtcur->mnt_dir)) continue;

			// Remember this entry.  Something later may have overmounted
			// it, and we want the _last_ match.

			mtcur = mtnext;

		// If we're mounting all.

		} else {

			// Do we need to match a filesystem type?
			if (fstype && strcmp(mtcur->mnt_type,fstype)) continue;

			// Skip noauto and swap anyway.

			if (parse_mount_options(mtcur->mnt_opts,0)
				& (MOUNT_NOAUTO | MOUNT_SWAP)) continue;

			// Mount this thing.

			rc = singlemount(mtcur);
			if (rc) {
				// Don't whine about already mounted fs when mounting all.
				if (errno == EBUSY) rc = 0;
				else break;
			}
		}
	}
	if (ENABLE_FEATURE_CLEAN_UP) endmntent(fstab);

clean_up:

	if (ENABLE_FEATURE_CLEAN_UP) {
		free(storage_path);
		free(cmdopts);
	}

	if(rc)
		bb_perror_msg("Mounting %s on %s failed",
				mtcur->mnt_fsname, mtcur->mnt_dir);

	return rc;
}