/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2001 Dima Dorfman.
 * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

/*
 * mdmfs (md/MFS) is a wrapper around mdconfig(8),
 * newfs(8), and mount(8) that mimics the command line option set of
 * the deprecated mount_mfs(8).
 */

#include <sys/param.h>
#include <sys/linker.h>
#include <sys/mdioctl.h>
#include <sys/module.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include <assert.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <inttypes.h>
#include <paths.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>

typedef enum { false, true } bool;

struct mtpt_info {
        uid_t            mi_uid;
        bool             mi_have_uid;
        gid_t            mi_gid;
        bool             mi_have_gid;
        mode_t           mi_mode;
        bool             mi_have_mode;
        bool             mi_forced_pw;
};

static  bool debug;             /* Emit debugging information? */
static  bool loudsubs;          /* Suppress output from helper programs? */
static  bool norun;             /* Actually run the helper programs? */
static  int unit;               /* The unit we're working with. */
static  const char *mdname;     /* Name of memory disk device (e.g., "md"). */
static  const char *mdsuffix;   /* Suffix of memory disk device (e.g., ".uzip"). */
static  size_t mdnamelen;       /* Length of mdname. */
static  const char *path_mdconfig =_PATH_MDCONFIG;

static void      argappend(char **, const char *, ...) __printflike(2, 3);
static void      debugprintf(const char *, ...) __printflike(1, 2);
static void      do_mdconfig_attach(const char *, const enum md_types);
static void      do_mdconfig_attach_au(const char *, const enum md_types);
static void      do_mdconfig_detach(void);
static void      do_mount_md(const char *, const char *);
static void      do_mount_tmpfs(const char *, const char *);
static void      do_mtptsetup(const char *, struct mtpt_info *);
static void      do_newfs(const char *);
static void      do_copy(const char *, const char *);
static void      extract_ugid(const char *, struct mtpt_info *);
static int       run(int *, const char *, ...) __printflike(2, 3);
static const char *run_exitstr(int);
static int       run_exitnumber(int);
static void      usage(void);

int
main(int argc, char **argv)
{
        struct mtpt_info mi;            /* Mountpoint info. */
        intmax_t mdsize;
        char *mdconfig_arg, *newfs_arg, /* Args to helper programs. */
            *mount_arg;
        enum md_types mdtype;           /* The type of our memory disk. */
        bool have_mdtype, mlmac;
        bool detach, softdep, autounit, newfs;
        const char *mtpoint, *size_arg, *skel, *unitstr;
        char *p;
        int ch, idx;
        void *set;
        unsigned long ul;

        /* Misc. initialization. */
        (void)memset(&mi, '\0', sizeof(mi));
        detach = true;
        softdep = true;
        autounit = false;
        mlmac = false;
        newfs = true;
        have_mdtype = false;
        skel = NULL;
        mdtype = MD_SWAP;
        mdname = MD_NAME;
        mdnamelen = strlen(mdname);
        mdsize = 0;
        /*
         * Can't set these to NULL.  They may be passed to the
         * respective programs without modification.  I.e., we may not
         * receive any command-line options which will caused them to
         * be modified.
         */
        mdconfig_arg = strdup("");
        newfs_arg = strdup("");
        mount_arg = strdup("");
        size_arg = NULL;

        /* If we were started as mount_mfs or mfs, imply -C. */
        if (strcmp(getprogname(), "mount_mfs") == 0 ||
            strcmp(getprogname(), "mfs") == 0) {
                /* Make compatibility assumptions. */
                mi.mi_mode = 01777;
                mi.mi_have_mode = true;
        }

        while ((ch = getopt(argc, argv,
            "a:b:Cc:Dd:E:e:F:f:hi:k:LlMm:NnO:o:Pp:Ss:tT:Uv:w:X")) != -1)
                switch (ch) {
                case 'a':
                        argappend(&newfs_arg, "-a %s", optarg);
                        break;
                case 'b':
                        argappend(&newfs_arg, "-b %s", optarg);
                        break;
                case 'C':
                        /* Ignored for compatibility. */
                        break;
                case 'c':
                        argappend(&newfs_arg, "-c %s", optarg);
                        break;
                case 'D':
                        detach = false;
                        break;
                case 'd':
                        argappend(&newfs_arg, "-d %s", optarg);
                        break;
                case 'E':
                        path_mdconfig = optarg;
                        break;
                case 'e':
                        argappend(&newfs_arg, "-e %s", optarg);
                        break;
                case 'F':
                        if (have_mdtype)
                                usage();
                        mdtype = MD_VNODE;
                        have_mdtype = true;
                        argappend(&mdconfig_arg, "-f %s", optarg);
                        break;
                case 'f':
                        argappend(&newfs_arg, "-f %s", optarg);
                        break;
                case 'h':
                        usage();
                        break;
                case 'i':
                        argappend(&newfs_arg, "-i %s", optarg);
                        break;
                case 'k':
                        skel = optarg;
                        break;
                case 'L':
                        loudsubs = true;
                        break;
                case 'l':
                        mlmac = true;
                        argappend(&newfs_arg, "-l");
                        break;
                case 'M':
                        if (have_mdtype)
                                usage();
                        mdtype = MD_MALLOC;
                        have_mdtype = true;
                        argappend(&mdconfig_arg, "-o reserve");
                        break;
                case 'm':
                        argappend(&newfs_arg, "-m %s", optarg);
                        break;
                case 'N':
                        norun = true;
                        break;
                case 'n':
                        argappend(&newfs_arg, "-n");
                        break;
                case 'O':
                        argappend(&newfs_arg, "-o %s", optarg);
                        break;
                case 'o':
                        argappend(&mount_arg, "-o %s", optarg);
                        break;
                case 'P':
                        newfs = false;
                        break;
                case 'p':
                        if ((set = setmode(optarg)) == NULL)
                                usage();
                        mi.mi_mode = getmode(set, S_IRWXU | S_IRWXG | S_IRWXO);
                        mi.mi_have_mode = true;
                        mi.mi_forced_pw = true;
                        free(set);
                        break;
                case 'S':
                        softdep = false;
                        break;
                case 's':
                        size_arg = optarg;
                        break;
                case 't':
                        argappend(&newfs_arg, "-t");
                        break;
                case 'T':
                        argappend(&mount_arg, "-t %s", optarg);
                        break;
                case 'U':
                        softdep = true;
                        break;
                case 'v':
                        argappend(&newfs_arg, "-O %s", optarg);
                        break;
                case 'w':
                        extract_ugid(optarg, &mi);
                        mi.mi_forced_pw = true;
                        break;
                case 'X':
                        debug = true;
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;
        if (argc < 2)
                usage();

        /*
         * Historically our size arg was passed directly to mdconfig, which
         * treats a number without a suffix as a count of 512-byte sectors;
         * tmpfs would treat it as a count of bytes.  To get predictable
         * behavior for 'auto' we document that the size always uses mdconfig
         * rules.  To make that work, decode the size here so it can be passed
         * to either tmpfs or mdconfig as a count of bytes.
         */
        if (size_arg != NULL) {
                mdsize = (intmax_t)strtoumax(size_arg, &p, 0);
                if (p == size_arg || (p[0] != 0 && p[1] != 0) || mdsize < 0)
                        errx(1, "invalid size '%s'", size_arg);
                switch (*p) {
                case 'p':
                case 'P':
                        mdsize *= 1024;
                case 't':
                case 'T':
                        mdsize *= 1024;
                case 'g':
                case 'G':
                        mdsize *= 1024;
                case 'm':
                case 'M':
                        mdsize *= 1024;
                case 'k':
                case 'K':
                        mdsize *= 1024;
                case 'b':
                case 'B':
                        break;
                case '\0':
                        mdsize *= 512;
                        break;
                default:
                        errx(1, "invalid size suffix on '%s'", size_arg);
                }
        }

        /*
         * Based on the command line 'md-device' either mount a tmpfs filesystem
         * or configure the md device then format and mount a filesystem on it.
         * If the device is 'auto' use tmpfs if it is available and there is no
         * request for multilabel MAC (which tmpfs does not support).
         */
        unitstr = argv[0];
        mtpoint = argv[1];

        if (strcmp(unitstr, "auto") == 0) {
                if (mlmac)
                        idx = -1; /* Must use md for mlmac. */
                else if ((idx = modfind("tmpfs")) == -1)
                        idx = kldload("tmpfs");
                if (idx == -1)
                        unitstr = "md";
                else
                        unitstr = "tmpfs";
        }

        if (strcmp(unitstr, "tmpfs") == 0) {
                if (size_arg != NULL && mdsize != 0)
                        argappend(&mount_arg, "-o size=%jd", mdsize);
                do_mount_tmpfs(mount_arg, mtpoint); 
        } else {
                if (size_arg != NULL)
                        argappend(&mdconfig_arg, "-s %jdB", mdsize);
                if (strncmp(unitstr, "/dev/", 5) == 0)
                        unitstr += 5;
                if (strncmp(unitstr, mdname, mdnamelen) == 0)
                        unitstr += mdnamelen;
                if (!isdigit(*unitstr)) {
                        autounit = true;
                        unit = -1;
                        mdsuffix = unitstr;
                } else {
                        ul = strtoul(unitstr, &p, 10);
                        if (ul == ULONG_MAX)
                                errx(1, "bad device unit: %s", unitstr);
                        unit = ul;
                        mdsuffix = p;   /* can be empty */
                }
        
                if (!have_mdtype)
                        mdtype = MD_SWAP;
                argappend(&newfs_arg, softdep ? "-U" : "-u");
                if (mdtype != MD_VNODE && !newfs)
                        errx(1, "-P requires a vnode-backed disk");
        
                /* Do the work. */
                if (detach && !autounit)
                        do_mdconfig_detach();
                if (autounit)
                        do_mdconfig_attach_au(mdconfig_arg, mdtype);
                else
                        do_mdconfig_attach(mdconfig_arg, mdtype);
                if (newfs)
                        do_newfs(newfs_arg);
                do_mount_md(mount_arg, mtpoint);
        }

        do_mtptsetup(mtpoint, &mi);
        if (skel != NULL)
                do_copy(mtpoint, skel);

        return (0);
}

/*
 * Append the expansion of 'fmt' to the buffer pointed to by '*dstp';
 * reallocate as required.
 */
static void
argappend(char **dstp, const char *fmt, ...)
{
        char *old, *new;
        va_list ap;

        old = *dstp;
        assert(old != NULL);

        va_start(ap, fmt);
        if (vasprintf(&new, fmt,ap) == -1)
                errx(1, "vasprintf");
        va_end(ap);

        *dstp = new;
        if (asprintf(&new, "%s %s", old, new) == -1)
                errx(1, "asprintf");
        free(*dstp);
        free(old);

        *dstp = new;
}

/*
 * If run-time debugging is enabled, print the expansion of 'fmt'.
 * Otherwise, do nothing.
 */
static void
debugprintf(const char *fmt, ...)
{
        va_list ap;

        if (!debug)
                return;
        fprintf(stderr, "DEBUG: ");
        va_start(ap, fmt);
        vfprintf(stderr, fmt, ap);
        va_end(ap);
        fprintf(stderr, "\n");
        fflush(stderr);
}

/*
 * Attach a memory disk with a known unit.
 */
static void
do_mdconfig_attach(const char *args, const enum md_types mdtype)
{
        int rv;
        const char *ta;         /* Type arg. */

        switch (mdtype) {
        case MD_SWAP:
                ta = "-t swap";
                break;
        case MD_VNODE:
                ta = "-t vnode";
                break;
        case MD_MALLOC:
                ta = "-t malloc";
                break;
        default:
                abort();
        }
        rv = run(NULL, "%s -a %s%s -u %s%d", path_mdconfig, ta, args,
            mdname, unit);
        if (rv)
                errx(1, "mdconfig (attach) exited %s %d", run_exitstr(rv),
                    run_exitnumber(rv));
}

/*
 * Attach a memory disk with an unknown unit; use autounit.
 */
static void
do_mdconfig_attach_au(const char *args, const enum md_types mdtype)
{
        const char *ta;         /* Type arg. */
        char *linep;
        char linebuf[12];       /* 32-bit unit (10) + '\n' (1) + '\0' (1) */
        int fd;                 /* Standard output of mdconfig invocation. */
        FILE *sfd;
        int rv;
        char *p;
        size_t linelen;
        unsigned long ul;

        switch (mdtype) {
        case MD_SWAP:
                ta = "-t swap";
                break;
        case MD_VNODE:
                ta = "-t vnode";
                break;
        case MD_MALLOC:
                ta = "-t malloc";
                break;
        default:
                abort();
        }
        rv = run(&fd, "%s -a %s%s", path_mdconfig, ta, args);
        if (rv)
                errx(1, "mdconfig (attach) exited %s %d", run_exitstr(rv),
                    run_exitnumber(rv));

        /* Receive the unit number. */
        if (norun) {    /* Since we didn't run, we can't read.  Fake it. */
                unit = 0;
                return;
        }
        sfd = fdopen(fd, "r");
        if (sfd == NULL)
                err(1, "fdopen");
        linep = fgetln(sfd, &linelen);
        /* If the output format changes, we want to know about it. */
        if (linep == NULL || linelen <= mdnamelen + 1 ||
            linelen - mdnamelen >= sizeof(linebuf) ||
            strncmp(linep, mdname, mdnamelen) != 0)
                errx(1, "unexpected output from mdconfig (attach)");
        linep += mdnamelen;
        linelen -= mdnamelen;
        /* Can't use strlcpy because linep is not NULL-terminated. */
        strncpy(linebuf, linep, linelen);
        linebuf[linelen] = '\0';
        ul = strtoul(linebuf, &p, 10);
        if (ul == ULONG_MAX || *p != '\n')
                errx(1, "unexpected output from mdconfig (attach)");
        unit = ul;

        fclose(sfd);
}

/*
 * Detach a memory disk.
 */
static void
do_mdconfig_detach(void)
{
        int rv;

        rv = run(NULL, "%s -d -u %s%d", path_mdconfig, mdname, unit);
        if (rv && debug)        /* This is allowed to fail. */
                warnx("mdconfig (detach) exited %s %d (ignored)",
                    run_exitstr(rv), run_exitnumber(rv));
}

/*
 * Mount the configured memory disk.
 */
static void
do_mount_md(const char *args, const char *mtpoint)
{
        int rv;

        rv = run(NULL, "%s%s /dev/%s%d%s %s", _PATH_MOUNT, args,
            mdname, unit, mdsuffix, mtpoint);
        if (rv)
                errx(1, "mount exited %s %d", run_exitstr(rv),
                    run_exitnumber(rv));
}

/*
 * Mount the configured tmpfs.
 */
static void
do_mount_tmpfs(const char *args, const char *mtpoint)
{
        int rv;

        rv = run(NULL, "%s -t tmpfs %s tmp %s", _PATH_MOUNT, args, mtpoint);
        if (rv)
                errx(1, "tmpfs mount exited %s %d", run_exitstr(rv),
                    run_exitnumber(rv));
}

/*
 * Various configuration of the mountpoint.  Mostly, enact 'mip'.
 */
static void
do_mtptsetup(const char *mtpoint, struct mtpt_info *mip)
{
        struct statfs sfs;

        if (!mip->mi_have_mode && !mip->mi_have_uid && !mip->mi_have_gid)
                return;

        if (!norun) {
                if (statfs(mtpoint, &sfs) == -1) {
                        warn("statfs: %s", mtpoint);
                        return;
                }
                if ((sfs.f_flags & MNT_RDONLY) != 0) {
                        if (mip->mi_forced_pw) {
                                warnx(
        "Not changing mode/owner of %s since it is read-only",
                                    mtpoint);
                        } else {
                                debugprintf(
        "Not changing mode/owner of %s since it is read-only",
                                    mtpoint);
                        }
                        return;
                }
        }

        if (mip->mi_have_mode) {
                debugprintf("changing mode of %s to %o.", mtpoint,
                    mip->mi_mode);
                if (!norun)
                        if (chmod(mtpoint, mip->mi_mode) == -1)
                                err(1, "chmod: %s", mtpoint);
        }
        /*
         * We have to do these separately because the user may have
         * only specified one of them.
         */
        if (mip->mi_have_uid) {
                debugprintf("changing owner (user) or %s to %u.", mtpoint,
                    mip->mi_uid);
                if (!norun)
                        if (chown(mtpoint, mip->mi_uid, -1) == -1)
                                err(1, "chown %s to %u (user)", mtpoint,
                                    mip->mi_uid);
        }
        if (mip->mi_have_gid) {
                debugprintf("changing owner (group) or %s to %u.", mtpoint,
                    mip->mi_gid);
                if (!norun)
                        if (chown(mtpoint, -1, mip->mi_gid) == -1)
                                err(1, "chown %s to %u (group)", mtpoint,
                                    mip->mi_gid);
        }
}

/*
 * Put a file system on the memory disk.
 */
static void
do_newfs(const char *args)
{
        int rv;

        rv = run(NULL, "%s%s /dev/%s%d", _PATH_NEWFS, args, mdname, unit);
        if (rv)
                errx(1, "newfs exited %s %d", run_exitstr(rv),
                    run_exitnumber(rv));
}


/*
 * Copy skel into the mountpoint.
 */
static void
do_copy(const char *mtpoint, const char *skel)
{
        int rv;

        rv = chdir(skel);
        if (rv != 0)
                err(1, "chdir to %s", skel);
        rv = run(NULL, "/bin/pax -rw -pe . %s", mtpoint);
        if (rv != 0)
                errx(1, "skel copy failed");
}

/*
 * 'str' should be a user and group name similar to the last argument
 * to chown(1); i.e., a user, followed by a colon, followed by a
 * group.  The user and group in 'str' may be either a [ug]id or a
 * name.  Upon return, the uid and gid fields in 'mip' will contain
 * the uid and gid of the user and group name in 'str', respectively.
 *
 * In other words, this derives a user and group id from a string
 * formatted like the last argument to chown(1).
 *
 * Notice: At this point we don't support only a username or only a
 * group name. do_mtptsetup already does, so when this feature is
 * desired, this is the only routine that needs to be changed.
 */
static void
extract_ugid(const char *str, struct mtpt_info *mip)
{
        char *ug;                       /* Writable 'str'. */
        char *user, *group;             /* Result of extracton. */
        struct passwd *pw;
        struct group *gr;
        char *p;
        uid_t *uid;
        gid_t *gid;

        uid = &mip->mi_uid;
        gid = &mip->mi_gid;
        mip->mi_have_uid = mip->mi_have_gid = false;

        /* Extract the user and group from 'str'.  Format above. */
        ug = strdup(str);
        assert(ug != NULL);
        group = ug;
        user = strsep(&group, ":");
        if (user == NULL || group == NULL || *user == '\0' || *group == '\0')
                usage();

        /* Derive uid. */
        *uid = strtoul(user, &p, 10);
        if (*uid == (uid_t)ULONG_MAX)
                usage();
        if (*p != '\0') {
                pw = getpwnam(user);
                if (pw == NULL)
                        errx(1, "invalid user: %s", user);
                *uid = pw->pw_uid;
        }
        mip->mi_have_uid = true;

        /* Derive gid. */
        *gid = strtoul(group, &p, 10);
        if (*gid == (gid_t)ULONG_MAX)
                usage();
        if (*p != '\0') {
                gr = getgrnam(group);
                if (gr == NULL)
                        errx(1, "invalid group: %s", group);
                *gid = gr->gr_gid;
        }
        mip->mi_have_gid = true;

        free(ug);
}

/*
 * Run a process with command name and arguments pointed to by the
 * formatted string 'cmdline'.  Since system(3) is not used, the first
 * space-delimited token of 'cmdline' must be the full pathname of the
 * program to run.
 *
 * The return value is the return code of the process spawned, or a negative
 * signal number if the process exited due to an uncaught signal.
 *
 * If 'ofd' is non-NULL, it is set to the standard output of
 * the program spawned (i.e., you can read from ofd and get the output
 * of the program).
 */
static int
run(int *ofd, const char *cmdline, ...)
{
        char **argv, **argvp;           /* Result of splitting 'cmd'. */
        int argc;
        char *cmd;                      /* Expansion of 'cmdline'. */
        int pid, status;                /* Child info. */
        int pfd[2];                     /* Pipe to the child. */
        int nfd;                        /* Null (/dev/null) file descriptor. */
        bool dup2dn;                    /* Dup /dev/null to stdout? */
        va_list ap;
        char *p;
        int rv, i;

        dup2dn = true;
        va_start(ap, cmdline);
        rv = vasprintf(&cmd, cmdline, ap);
        if (rv == -1)
                err(1, "vasprintf");
        va_end(ap);

        /* Split up 'cmd' into 'argv' for use with execve. */
        for (argc = 1, p = cmd; (p = strchr(p, ' ')) != NULL; p++)
                argc++;         /* 'argc' generation loop. */
        argv = (char **)malloc(sizeof(*argv) * (argc + 1));
        assert(argv != NULL);
        for (p = cmd, argvp = argv; (*argvp = strsep(&p, " ")) != NULL;)
                if (**argvp != '\0')
                        if (++argvp >= &argv[argc]) {
                                *argvp = NULL;
                                break;
                        }
        assert(*argv);
        /* The argv array ends up NULL-terminated here. */

        /* Make sure the above loop works as expected. */
        if (debug) {
                /*
                 * We can't, but should, use debugprintf here.  First,
                 * it appends a trailing newline to the output, and
                 * second it prepends "DEBUG: " to the output.  The
                 * former is a problem for this would-be first call,
                 * and the latter for the would-be call inside the
                 * loop.
                 */
                (void)fprintf(stderr, "DEBUG: running:");
                /* Should be equivalent to 'cmd' (before strsep, of course). */
                for (i = 0; argv[i] != NULL; i++)
                        (void)fprintf(stderr, " %s", argv[i]);
                (void)fprintf(stderr, "\n");
        }

        /* Create a pipe if necessary and fork the helper program. */
        if (ofd != NULL) {
                if (pipe(&pfd[0]) == -1)
                        err(1, "pipe");
                *ofd = pfd[0];
                dup2dn = false;
        }
        pid = fork();
        switch (pid) {
        case 0:
                /* XXX can we call err() in here? */
                if (norun)
                        _exit(0);
                if (ofd != NULL)
                        if (dup2(pfd[1], STDOUT_FILENO) < 0)
                                err(1, "dup2");
                if (!loudsubs) {
                        nfd = open(_PATH_DEVNULL, O_RDWR);
                        if (nfd == -1)
                                err(1, "open: %s", _PATH_DEVNULL);
                        if (dup2(nfd, STDIN_FILENO) < 0)
                                err(1, "dup2");
                        if (dup2dn)
                                if (dup2(nfd, STDOUT_FILENO) < 0)
                                   err(1, "dup2");
                        if (dup2(nfd, STDERR_FILENO) < 0)
                                err(1, "dup2");
                }

                (void)execv(argv[0], argv);
                warn("exec: %s", argv[0]);
                _exit(-1);
        case -1:
                err(1, "fork");
        }

        free(cmd);
        free(argv);
        while (waitpid(pid, &status, 0) != pid)
                ;
        if (WIFEXITED(status))
                return (WEXITSTATUS(status));
        if (WIFSIGNALED(status))
                return (-WTERMSIG(status));
        err(1, "unexpected waitpid status: 0x%x", status);
}

/*
 * If run() returns non-zero, provide a string explaining why.
 */
static const char *
run_exitstr(int rv)
{
        if (rv > 0)
                return ("with error code");
        if (rv < 0)
                return ("with signal");
        return (NULL);
}

/*
 * If run returns non-zero, provide a relevant number.
 */
static int
run_exitnumber(int rv)
{
        if (rv < 0)
                return (-rv);
        return (rv);
}

static void
usage(void)
{

        fprintf(stderr,
"usage: %s [-DLlMNnPStUX] [-a maxcontig] [-b block-size]\n"
"\t[-c blocks-per-cylinder-group][-d max-extent-size] [-E path-mdconfig]\n"
"\t[-e maxbpg] [-F file] [-f frag-size] [-i bytes] [-k skel]\n"
"\t[-m percent-free] [-O optimization] [-o mount-options]\n"
"\t[-p permissions] [-s size] [-v version] [-w user:group]\n"
"\tmd-device mount-point\n", getprogname());
        exit(1);
}