xref: /freebsd/sbin/mdmfs/mdmfs.c (revision b89a7cc2ed6e4398d5be502f5bb5885d1ec6ff0f)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2001 Dima Dorfman.
5  * All rights reserved.
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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 /*
30  * mdmfs (md/MFS) is a wrapper around mdconfig(8),
31  * newfs(8), and mount(8) that mimics the command line option set of
32  * the deprecated mount_mfs(8).
33  */
34 
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37 
38 #include <sys/param.h>
39 #include <sys/linker.h>
40 #include <sys/mdioctl.h>
41 #include <sys/module.h>
42 #include <sys/mount.h>
43 #include <sys/stat.h>
44 #include <sys/wait.h>
45 
46 #include <assert.h>
47 #include <err.h>
48 #include <errno.h>
49 #include <fcntl.h>
50 #include <grp.h>
51 #include <inttypes.h>
52 #include <paths.h>
53 #include <pwd.h>
54 #include <stdarg.h>
55 #include <stdio.h>
56 #include <stdlib.h>
57 #include <string.h>
58 #include <ctype.h>
59 #include <unistd.h>
60 
61 typedef enum { false, true } bool;
62 
63 struct mtpt_info {
64 	uid_t		 mi_uid;
65 	bool		 mi_have_uid;
66 	gid_t		 mi_gid;
67 	bool		 mi_have_gid;
68 	mode_t		 mi_mode;
69 	bool		 mi_have_mode;
70 	bool		 mi_forced_pw;
71 };
72 
73 static	bool debug;		/* Emit debugging information? */
74 static	bool loudsubs;		/* Suppress output from helper programs? */
75 static	bool norun;		/* Actually run the helper programs? */
76 static	int unit;      		/* The unit we're working with. */
77 static	const char *mdname;	/* Name of memory disk device (e.g., "md"). */
78 static	const char *mdsuffix;	/* Suffix of memory disk device (e.g., ".uzip"). */
79 static	size_t mdnamelen;	/* Length of mdname. */
80 static	const char *path_mdconfig =_PATH_MDCONFIG;
81 
82 static void	 argappend(char **, const char *, ...) __printflike(2, 3);
83 static void	 debugprintf(const char *, ...) __printflike(1, 2);
84 static void	 do_mdconfig_attach(const char *, const enum md_types);
85 static void	 do_mdconfig_attach_au(const char *, const enum md_types);
86 static void	 do_mdconfig_detach(void);
87 static void	 do_mount_md(const char *, const char *);
88 static void	 do_mount_tmpfs(const char *, const char *);
89 static void	 do_mtptsetup(const char *, struct mtpt_info *);
90 static void	 do_newfs(const char *);
91 static void	 extract_ugid(const char *, struct mtpt_info *);
92 static int	 run(int *, const char *, ...) __printflike(2, 3);
93 static const char *run_exitstr(int);
94 static int	 run_exitnumber(int);
95 static void	 usage(void);
96 
97 int
98 main(int argc, char **argv)
99 {
100 	struct mtpt_info mi;		/* Mountpoint info. */
101 	intmax_t mdsize;
102 	char *mdconfig_arg, *newfs_arg,	/* Args to helper programs. */
103 	    *mount_arg;
104 	enum md_types mdtype;		/* The type of our memory disk. */
105 	bool have_mdtype, mlmac;
106 	bool detach, softdep, autounit, newfs;
107 	const char *mtpoint, *size_arg, *unitstr;
108 	char *p;
109 	int ch, idx;
110 	void *set;
111 	unsigned long ul;
112 
113 	/* Misc. initialization. */
114 	(void)memset(&mi, '\0', sizeof(mi));
115 	detach = true;
116 	softdep = true;
117 	autounit = false;
118 	mlmac = false;
119 	newfs = true;
120 	have_mdtype = false;
121 	mdtype = MD_SWAP;
122 	mdname = MD_NAME;
123 	mdnamelen = strlen(mdname);
124 	mdsize = 0;
125 	/*
126 	 * Can't set these to NULL.  They may be passed to the
127 	 * respective programs without modification.  I.e., we may not
128 	 * receive any command-line options which will caused them to
129 	 * be modified.
130 	 */
131 	mdconfig_arg = strdup("");
132 	newfs_arg = strdup("");
133 	mount_arg = strdup("");
134 	size_arg = NULL;
135 
136 	/* If we were started as mount_mfs or mfs, imply -C. */
137 	if (strcmp(getprogname(), "mount_mfs") == 0 ||
138 	    strcmp(getprogname(), "mfs") == 0) {
139 		/* Make compatibility assumptions. */
140 		mi.mi_mode = 01777;
141 		mi.mi_have_mode = true;
142 	}
143 
144 	while ((ch = getopt(argc, argv,
145 	    "a:b:Cc:Dd:E:e:F:f:hi:LlMm:NnO:o:Pp:Ss:tT:Uv:w:X")) != -1)
146 		switch (ch) {
147 		case 'a':
148 			argappend(&newfs_arg, "-a %s", optarg);
149 			break;
150 		case 'b':
151 			argappend(&newfs_arg, "-b %s", optarg);
152 			break;
153 		case 'C':
154 			/* Ignored for compatibility. */
155 			break;
156 		case 'c':
157 			argappend(&newfs_arg, "-c %s", optarg);
158 			break;
159 		case 'D':
160 			detach = false;
161 			break;
162 		case 'd':
163 			argappend(&newfs_arg, "-d %s", optarg);
164 			break;
165 		case 'E':
166 			path_mdconfig = optarg;
167 			break;
168 		case 'e':
169 			argappend(&newfs_arg, "-e %s", optarg);
170 			break;
171 		case 'F':
172 			if (have_mdtype)
173 				usage();
174 			mdtype = MD_VNODE;
175 			have_mdtype = true;
176 			argappend(&mdconfig_arg, "-f %s", optarg);
177 			break;
178 		case 'f':
179 			argappend(&newfs_arg, "-f %s", optarg);
180 			break;
181 		case 'h':
182 			usage();
183 			break;
184 		case 'i':
185 			argappend(&newfs_arg, "-i %s", optarg);
186 			break;
187 		case 'L':
188 			loudsubs = true;
189 			break;
190 		case 'l':
191 			mlmac = true;
192 			argappend(&newfs_arg, "-l");
193 			break;
194 		case 'M':
195 			if (have_mdtype)
196 				usage();
197 			mdtype = MD_MALLOC;
198 			have_mdtype = true;
199 			break;
200 		case 'm':
201 			argappend(&newfs_arg, "-m %s", optarg);
202 			break;
203 		case 'N':
204 			norun = true;
205 			break;
206 		case 'n':
207 			argappend(&newfs_arg, "-n");
208 			break;
209 		case 'O':
210 			argappend(&newfs_arg, "-o %s", optarg);
211 			break;
212 		case 'o':
213 			argappend(&mount_arg, "-o %s", optarg);
214 			break;
215 		case 'P':
216 			newfs = false;
217 			break;
218 		case 'p':
219 			if ((set = setmode(optarg)) == NULL)
220 				usage();
221 			mi.mi_mode = getmode(set, S_IRWXU | S_IRWXG | S_IRWXO);
222 			mi.mi_have_mode = true;
223 			mi.mi_forced_pw = true;
224 			free(set);
225 			break;
226 		case 'S':
227 			softdep = false;
228 			break;
229 		case 's':
230 			size_arg = optarg;
231 			break;
232 		case 't':
233 			argappend(&newfs_arg, "-t");
234 			break;
235 		case 'T':
236 			argappend(&mount_arg, "-t %s", optarg);
237 			break;
238 		case 'U':
239 			softdep = true;
240 			break;
241 		case 'v':
242 			argappend(&newfs_arg, "-O %s", optarg);
243 			break;
244 		case 'w':
245 			extract_ugid(optarg, &mi);
246 			mi.mi_forced_pw = true;
247 			break;
248 		case 'X':
249 			debug = true;
250 			break;
251 		default:
252 			usage();
253 		}
254 	argc -= optind;
255 	argv += optind;
256 	if (argc < 2)
257 		usage();
258 
259 	/*
260 	 * Historically our size arg was passed directly to mdconfig, which
261 	 * treats a number without a suffix as a count of 512-byte sectors;
262 	 * tmpfs would treat it as a count of bytes.  To get predictable
263 	 * behavior for 'auto' we document that the size always uses mdconfig
264 	 * rules.  To make that work, decode the size here so it can be passed
265 	 * to either tmpfs or mdconfig as a count of bytes.
266 	 */
267 	if (size_arg != NULL) {
268 		mdsize = (intmax_t)strtoumax(size_arg, &p, 0);
269 		if (p == size_arg || (p[0] != 0 && p[1] != 0) || mdsize < 0)
270 			errx(1, "invalid size '%s'", size_arg);
271 		switch (*p) {
272 		case 'p':
273 		case 'P':
274 			mdsize *= 1024;
275 		case 't':
276 		case 'T':
277 			mdsize *= 1024;
278 		case 'g':
279 		case 'G':
280 			mdsize *= 1024;
281 		case 'm':
282 		case 'M':
283 			mdsize *= 1024;
284 		case 'k':
285 		case 'K':
286 			mdsize *= 1024;
287 		case 'b':
288 		case 'B':
289 			break;
290 		case '\0':
291 			mdsize *= 512;
292 			break;
293 		default:
294 			errx(1, "invalid size suffix on '%s'", size_arg);
295 		}
296 	}
297 
298 	/*
299 	 * Based on the command line 'md-device' either mount a tmpfs filesystem
300 	 * or configure the md device then format and mount a filesystem on it.
301 	 * If the device is 'auto' use tmpfs if it is available and there is no
302 	 * request for multilabel MAC (which tmpfs does not support).
303 	 */
304 	unitstr = argv[0];
305 	mtpoint = argv[1];
306 
307 	if (strcmp(unitstr, "auto") == 0) {
308 		if (mlmac)
309 			idx = -1; /* Must use md for mlmac. */
310 		else if ((idx = modfind("tmpfs")) == -1)
311 			idx = kldload("tmpfs");
312 		if (idx == -1)
313 			unitstr = "md";
314 		else
315 			unitstr = "tmpfs";
316 	}
317 
318 	if (strcmp(unitstr, "tmpfs") == 0) {
319 		if (size_arg != NULL && mdsize != 0)
320 			argappend(&mount_arg, "-o size=%jd", mdsize);
321 		do_mount_tmpfs(mount_arg, mtpoint);
322 	} else {
323 		if (size_arg != NULL)
324 			argappend(&mdconfig_arg, "-s %jdB", mdsize);
325 		if (strncmp(unitstr, "/dev/", 5) == 0)
326 			unitstr += 5;
327 		if (strncmp(unitstr, mdname, mdnamelen) == 0)
328 			unitstr += mdnamelen;
329 		if (!isdigit(*unitstr)) {
330 			autounit = true;
331 			unit = -1;
332 			mdsuffix = unitstr;
333 		} else {
334 			ul = strtoul(unitstr, &p, 10);
335 			if (ul == ULONG_MAX)
336 				errx(1, "bad device unit: %s", unitstr);
337 			unit = ul;
338 			mdsuffix = p;	/* can be empty */
339 		}
340 
341 		if (!have_mdtype)
342 			mdtype = MD_SWAP;
343 		if (softdep)
344 			argappend(&newfs_arg, "-U");
345 		if (mdtype != MD_VNODE && !newfs)
346 			errx(1, "-P requires a vnode-backed disk");
347 
348 		/* Do the work. */
349 		if (detach && !autounit)
350 			do_mdconfig_detach();
351 		if (autounit)
352 			do_mdconfig_attach_au(mdconfig_arg, mdtype);
353 		else
354 			do_mdconfig_attach(mdconfig_arg, mdtype);
355 		if (newfs)
356 			do_newfs(newfs_arg);
357 		do_mount_md(mount_arg, mtpoint);
358 	}
359 
360 	do_mtptsetup(mtpoint, &mi);
361 
362 	return (0);
363 }
364 
365 /*
366  * Append the expansion of 'fmt' to the buffer pointed to by '*dstp';
367  * reallocate as required.
368  */
369 static void
370 argappend(char **dstp, const char *fmt, ...)
371 {
372 	char *old, *new;
373 	va_list ap;
374 
375 	old = *dstp;
376 	assert(old != NULL);
377 
378 	va_start(ap, fmt);
379 	if (vasprintf(&new, fmt,ap) == -1)
380 		errx(1, "vasprintf");
381 	va_end(ap);
382 
383 	*dstp = new;
384 	if (asprintf(&new, "%s %s", old, new) == -1)
385 		errx(1, "asprintf");
386 	free(*dstp);
387 	free(old);
388 
389 	*dstp = new;
390 }
391 
392 /*
393  * If run-time debugging is enabled, print the expansion of 'fmt'.
394  * Otherwise, do nothing.
395  */
396 static void
397 debugprintf(const char *fmt, ...)
398 {
399 	va_list ap;
400 
401 	if (!debug)
402 		return;
403 	fprintf(stderr, "DEBUG: ");
404 	va_start(ap, fmt);
405 	vfprintf(stderr, fmt, ap);
406 	va_end(ap);
407 	fprintf(stderr, "\n");
408 	fflush(stderr);
409 }
410 
411 /*
412  * Attach a memory disk with a known unit.
413  */
414 static void
415 do_mdconfig_attach(const char *args, const enum md_types mdtype)
416 {
417 	int rv;
418 	const char *ta;		/* Type arg. */
419 
420 	switch (mdtype) {
421 	case MD_SWAP:
422 		ta = "-t swap";
423 		break;
424 	case MD_VNODE:
425 		ta = "-t vnode";
426 		break;
427 	case MD_MALLOC:
428 		ta = "-t malloc";
429 		break;
430 	default:
431 		abort();
432 	}
433 	rv = run(NULL, "%s -a %s%s -u %s%d", path_mdconfig, ta, args,
434 	    mdname, unit);
435 	if (rv)
436 		errx(1, "mdconfig (attach) exited %s %d", run_exitstr(rv),
437 		    run_exitnumber(rv));
438 }
439 
440 /*
441  * Attach a memory disk with an unknown unit; use autounit.
442  */
443 static void
444 do_mdconfig_attach_au(const char *args, const enum md_types mdtype)
445 {
446 	const char *ta;		/* Type arg. */
447 	char *linep;
448 	char linebuf[12];	/* 32-bit unit (10) + '\n' (1) + '\0' (1) */
449 	int fd;			/* Standard output of mdconfig invocation. */
450 	FILE *sfd;
451 	int rv;
452 	char *p;
453 	size_t linelen;
454 	unsigned long ul;
455 
456 	switch (mdtype) {
457 	case MD_SWAP:
458 		ta = "-t swap";
459 		break;
460 	case MD_VNODE:
461 		ta = "-t vnode";
462 		break;
463 	case MD_MALLOC:
464 		ta = "-t malloc";
465 		break;
466 	default:
467 		abort();
468 	}
469 	rv = run(&fd, "%s -a %s%s", path_mdconfig, ta, args);
470 	if (rv)
471 		errx(1, "mdconfig (attach) exited %s %d", run_exitstr(rv),
472 		    run_exitnumber(rv));
473 
474 	/* Receive the unit number. */
475 	if (norun) {	/* Since we didn't run, we can't read.  Fake it. */
476 		unit = 0;
477 		return;
478 	}
479 	sfd = fdopen(fd, "r");
480 	if (sfd == NULL)
481 		err(1, "fdopen");
482 	linep = fgetln(sfd, &linelen);
483 	/* If the output format changes, we want to know about it. */
484 	if (linep == NULL || linelen <= mdnamelen + 1 ||
485 	    linelen - mdnamelen >= sizeof(linebuf) ||
486 	    strncmp(linep, mdname, mdnamelen) != 0)
487 		errx(1, "unexpected output from mdconfig (attach)");
488 	linep += mdnamelen;
489 	linelen -= mdnamelen;
490 	/* Can't use strlcpy because linep is not NULL-terminated. */
491 	strncpy(linebuf, linep, linelen);
492 	linebuf[linelen] = '\0';
493 	ul = strtoul(linebuf, &p, 10);
494 	if (ul == ULONG_MAX || *p != '\n')
495 		errx(1, "unexpected output from mdconfig (attach)");
496 	unit = ul;
497 
498 	fclose(sfd);
499 }
500 
501 /*
502  * Detach a memory disk.
503  */
504 static void
505 do_mdconfig_detach(void)
506 {
507 	int rv;
508 
509 	rv = run(NULL, "%s -d -u %s%d", path_mdconfig, mdname, unit);
510 	if (rv && debug)	/* This is allowed to fail. */
511 		warnx("mdconfig (detach) exited %s %d (ignored)",
512 		    run_exitstr(rv), run_exitnumber(rv));
513 }
514 
515 /*
516  * Mount the configured memory disk.
517  */
518 static void
519 do_mount_md(const char *args, const char *mtpoint)
520 {
521 	int rv;
522 
523 	rv = run(NULL, "%s%s /dev/%s%d%s %s", _PATH_MOUNT, args,
524 	    mdname, unit, mdsuffix, mtpoint);
525 	if (rv)
526 		errx(1, "mount exited %s %d", run_exitstr(rv),
527 		    run_exitnumber(rv));
528 }
529 
530 /*
531  * Mount the configured tmpfs.
532  */
533 static void
534 do_mount_tmpfs(const char *args, const char *mtpoint)
535 {
536 	int rv;
537 
538 	rv = run(NULL, "%s -t tmpfs %s tmp %s", _PATH_MOUNT, args, mtpoint);
539 	if (rv)
540 		errx(1, "tmpfs mount exited %s %d", run_exitstr(rv),
541 		    run_exitnumber(rv));
542 }
543 
544 /*
545  * Various configuration of the mountpoint.  Mostly, enact 'mip'.
546  */
547 static void
548 do_mtptsetup(const char *mtpoint, struct mtpt_info *mip)
549 {
550 	struct statfs sfs;
551 
552 	if (!mip->mi_have_mode && !mip->mi_have_uid && !mip->mi_have_gid)
553 		return;
554 
555 	if (!norun) {
556 		if (statfs(mtpoint, &sfs) == -1) {
557 			warn("statfs: %s", mtpoint);
558 			return;
559 		}
560 		if ((sfs.f_flags & MNT_RDONLY) != 0) {
561 			if (mip->mi_forced_pw) {
562 				warnx(
563 	"Not changing mode/owner of %s since it is read-only",
564 				    mtpoint);
565 			} else {
566 				debugprintf(
567 	"Not changing mode/owner of %s since it is read-only",
568 				    mtpoint);
569 			}
570 			return;
571 		}
572 	}
573 
574 	if (mip->mi_have_mode) {
575 		debugprintf("changing mode of %s to %o.", mtpoint,
576 		    mip->mi_mode);
577 		if (!norun)
578 			if (chmod(mtpoint, mip->mi_mode) == -1)
579 				err(1, "chmod: %s", mtpoint);
580 	}
581 	/*
582 	 * We have to do these separately because the user may have
583 	 * only specified one of them.
584 	 */
585 	if (mip->mi_have_uid) {
586 		debugprintf("changing owner (user) or %s to %u.", mtpoint,
587 		    mip->mi_uid);
588 		if (!norun)
589 			if (chown(mtpoint, mip->mi_uid, -1) == -1)
590 				err(1, "chown %s to %u (user)", mtpoint,
591 				    mip->mi_uid);
592 	}
593 	if (mip->mi_have_gid) {
594 		debugprintf("changing owner (group) or %s to %u.", mtpoint,
595 		    mip->mi_gid);
596 		if (!norun)
597 			if (chown(mtpoint, -1, mip->mi_gid) == -1)
598 				err(1, "chown %s to %u (group)", mtpoint,
599 				    mip->mi_gid);
600 	}
601 }
602 
603 /*
604  * Put a file system on the memory disk.
605  */
606 static void
607 do_newfs(const char *args)
608 {
609 	int rv;
610 
611 	rv = run(NULL, "%s%s /dev/%s%d", _PATH_NEWFS, args, mdname, unit);
612 	if (rv)
613 		errx(1, "newfs exited %s %d", run_exitstr(rv),
614 		    run_exitnumber(rv));
615 }
616 
617 /*
618  * 'str' should be a user and group name similar to the last argument
619  * to chown(1); i.e., a user, followed by a colon, followed by a
620  * group.  The user and group in 'str' may be either a [ug]id or a
621  * name.  Upon return, the uid and gid fields in 'mip' will contain
622  * the uid and gid of the user and group name in 'str', respectively.
623  *
624  * In other words, this derives a user and group id from a string
625  * formatted like the last argument to chown(1).
626  *
627  * Notice: At this point we don't support only a username or only a
628  * group name. do_mtptsetup already does, so when this feature is
629  * desired, this is the only routine that needs to be changed.
630  */
631 static void
632 extract_ugid(const char *str, struct mtpt_info *mip)
633 {
634 	char *ug;			/* Writable 'str'. */
635 	char *user, *group;		/* Result of extracton. */
636 	struct passwd *pw;
637 	struct group *gr;
638 	char *p;
639 	uid_t *uid;
640 	gid_t *gid;
641 
642 	uid = &mip->mi_uid;
643 	gid = &mip->mi_gid;
644 	mip->mi_have_uid = mip->mi_have_gid = false;
645 
646 	/* Extract the user and group from 'str'.  Format above. */
647 	ug = strdup(str);
648 	assert(ug != NULL);
649 	group = ug;
650 	user = strsep(&group, ":");
651 	if (user == NULL || group == NULL || *user == '\0' || *group == '\0')
652 		usage();
653 
654 	/* Derive uid. */
655 	*uid = strtoul(user, &p, 10);
656 	if (*uid == (uid_t)ULONG_MAX)
657 		usage();
658 	if (*p != '\0') {
659 		pw = getpwnam(user);
660 		if (pw == NULL)
661 			errx(1, "invalid user: %s", user);
662 		*uid = pw->pw_uid;
663 	}
664 	mip->mi_have_uid = true;
665 
666 	/* Derive gid. */
667 	*gid = strtoul(group, &p, 10);
668 	if (*gid == (gid_t)ULONG_MAX)
669 		usage();
670 	if (*p != '\0') {
671 		gr = getgrnam(group);
672 		if (gr == NULL)
673 			errx(1, "invalid group: %s", group);
674 		*gid = gr->gr_gid;
675 	}
676 	mip->mi_have_gid = true;
677 
678 	free(ug);
679 }
680 
681 /*
682  * Run a process with command name and arguments pointed to by the
683  * formatted string 'cmdline'.  Since system(3) is not used, the first
684  * space-delimited token of 'cmdline' must be the full pathname of the
685  * program to run.
686  *
687  * The return value is the return code of the process spawned, or a negative
688  * signal number if the process exited due to an uncaught signal.
689  *
690  * If 'ofd' is non-NULL, it is set to the standard output of
691  * the program spawned (i.e., you can read from ofd and get the output
692  * of the program).
693  */
694 static int
695 run(int *ofd, const char *cmdline, ...)
696 {
697 	char **argv, **argvp;		/* Result of splitting 'cmd'. */
698 	int argc;
699 	char *cmd;			/* Expansion of 'cmdline'. */
700 	int pid, status;		/* Child info. */
701 	int pfd[2];			/* Pipe to the child. */
702 	int nfd;			/* Null (/dev/null) file descriptor. */
703 	bool dup2dn;			/* Dup /dev/null to stdout? */
704 	va_list ap;
705 	char *p;
706 	int rv, i;
707 
708 	dup2dn = true;
709 	va_start(ap, cmdline);
710 	rv = vasprintf(&cmd, cmdline, ap);
711 	if (rv == -1)
712 		err(1, "vasprintf");
713 	va_end(ap);
714 
715 	/* Split up 'cmd' into 'argv' for use with execve. */
716 	for (argc = 1, p = cmd; (p = strchr(p, ' ')) != NULL; p++)
717 		argc++;		/* 'argc' generation loop. */
718 	argv = (char **)malloc(sizeof(*argv) * (argc + 1));
719 	assert(argv != NULL);
720 	for (p = cmd, argvp = argv; (*argvp = strsep(&p, " ")) != NULL;)
721 		if (**argvp != '\0')
722 			if (++argvp >= &argv[argc]) {
723 				*argvp = NULL;
724 				break;
725 			}
726 	assert(*argv);
727 	/* The argv array ends up NULL-terminated here. */
728 
729 	/* Make sure the above loop works as expected. */
730 	if (debug) {
731 		/*
732 		 * We can't, but should, use debugprintf here.  First,
733 		 * it appends a trailing newline to the output, and
734 		 * second it prepends "DEBUG: " to the output.  The
735 		 * former is a problem for this would-be first call,
736 		 * and the latter for the would-be call inside the
737 		 * loop.
738 		 */
739 		(void)fprintf(stderr, "DEBUG: running:");
740 		/* Should be equivalent to 'cmd' (before strsep, of course). */
741 		for (i = 0; argv[i] != NULL; i++)
742 			(void)fprintf(stderr, " %s", argv[i]);
743 		(void)fprintf(stderr, "\n");
744 	}
745 
746 	/* Create a pipe if necessary and fork the helper program. */
747 	if (ofd != NULL) {
748 		if (pipe(&pfd[0]) == -1)
749 			err(1, "pipe");
750 		*ofd = pfd[0];
751 		dup2dn = false;
752 	}
753 	pid = fork();
754 	switch (pid) {
755 	case 0:
756 		/* XXX can we call err() in here? */
757 		if (norun)
758 			_exit(0);
759 		if (ofd != NULL)
760 			if (dup2(pfd[1], STDOUT_FILENO) < 0)
761 				err(1, "dup2");
762 		if (!loudsubs) {
763 			nfd = open(_PATH_DEVNULL, O_RDWR);
764 			if (nfd == -1)
765 				err(1, "open: %s", _PATH_DEVNULL);
766 			if (dup2(nfd, STDIN_FILENO) < 0)
767 				err(1, "dup2");
768 			if (dup2dn)
769 				if (dup2(nfd, STDOUT_FILENO) < 0)
770 				   err(1, "dup2");
771 			if (dup2(nfd, STDERR_FILENO) < 0)
772 				err(1, "dup2");
773 		}
774 
775 		(void)execv(argv[0], argv);
776 		warn("exec: %s", argv[0]);
777 		_exit(-1);
778 	case -1:
779 		err(1, "fork");
780 	}
781 
782 	free(cmd);
783 	free(argv);
784 	while (waitpid(pid, &status, 0) != pid)
785 		;
786 	if (WIFEXITED(status))
787 		return (WEXITSTATUS(status));
788 	if (WIFSIGNALED(status))
789 		return (-WTERMSIG(status));
790 	err(1, "unexpected waitpid status: 0x%x", status);
791 }
792 
793 /*
794  * If run() returns non-zero, provide a string explaining why.
795  */
796 static const char *
797 run_exitstr(int rv)
798 {
799 	if (rv > 0)
800 		return ("with error code");
801 	if (rv < 0)
802 		return ("with signal");
803 	return (NULL);
804 }
805 
806 /*
807  * If run returns non-zero, provide a relevant number.
808  */
809 static int
810 run_exitnumber(int rv)
811 {
812 	if (rv < 0)
813 		return (-rv);
814 	return (rv);
815 }
816 
817 static void
818 usage(void)
819 {
820 
821 	fprintf(stderr,
822 "usage: %s [-DLlMNnPStUX] [-a maxcontig] [-b block-size]\n"
823 "\t[-c blocks-per-cylinder-group][-d max-extent-size] [-E path-mdconfig]\n"
824 "\t[-e maxbpg] [-F file] [-f frag-size] [-i bytes] [-m percent-free]\n"
825 "\t[-O optimization] [-o mount-options]\n"
826 "\t[-p permissions] [-s size] [-v version] [-w user:group]\n"
827 "\tmd-device mount-point\n", getprogname());
828 	exit(1);
829 }
830