/*      $NetBSD: init.c,v 1.109 2021/10/11 20:23:25 jmcneill Exp $      */

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Donn Seeley at Berkeley Software Design, Inc.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1991, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)init.c      8.2 (Berkeley) 4/28/95";
#else
__RCSID("$NetBSD: init.c,v 1.109 2021/10/11 20:23:25 jmcneill Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <machine/cpu.h>

#include <db.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <ttyent.h>
#include <unistd.h>
#include <util.h>
#include <paths.h>
#include <err.h>
#ifdef SUPPORT_UTMP
#include <utmp.h>
#endif
#ifdef SUPPORT_UTMPX
#include <utmpx.h>
#endif

#include <stdarg.h>

#ifdef SECURE
#include <pwd.h>
#endif

#include "pathnames.h"

#define XSTR(x) #x
#define STR(x) XSTR(x)

/*
 * Sleep times; used to prevent thrashing.
 */
#define GETTY_SPACING            5      /* N secs minimum getty spacing */
#define GETTY_SLEEP             30      /* sleep N secs after spacing problem */
#define GETTY_NSPACE             5      /* N retries before spacing problem */
#define WINDOW_WAIT              3      /* wait N secs after starting window */
#define STALL_TIMEOUT           30      /* wait N secs after warning */
#define DEATH_WATCH             10      /* wait N secs for procs to die */

static const struct timespec dtrtime = {.tv_sec = 0, .tv_nsec = 250000};

#if defined(RESCUEDIR)
#define INIT_BSHELL     RESCUEDIR "/sh"
#define INIT_MOUNT_MFS  RESCUEDIR "/mount_mfs"
#define INIT_PATH       RESCUEDIR ":" _PATH_STDPATH
#else
#define INIT_BSHELL     _PATH_BSHELL
#define INIT_MOUNT_MFS  "/sbin/mount_mfs"
#define INIT_PATH       _PATH_STDPATH
#endif

static void handle(sig_t, ...);
static void delset(sigset_t *, ...);

static void stall(const char *, ...) __sysloglike(1, 2);
static void warning(const char *, ...) __sysloglike(1, 2);
static void emergency(const char *, ...) __sysloglike(1, 2);
__dead static void disaster(int);
static void badsys(int);

/*
 * We really need a recursive typedef...
 * The following at least guarantees that the return type of (*state_t)()
 * is sufficiently wide to hold a function pointer.
 */
typedef long (*state_func_t)(void);
typedef state_func_t (*state_t)(void);

#define DEATH           'd'
#define SINGLE_USER     's'
#define RUNCOM          'r'
#define READ_TTYS       't'
#define MULTI_USER      'm'
#define CLEAN_TTYS      'T'
#define CATATONIA       'c'

static state_func_t single_user(void);
#ifndef LETS_GET_SMALL
static state_func_t runcom(void);
static state_func_t read_ttys(void);
static state_func_t multi_user(void);
static state_func_t clean_ttys(void);
static state_func_t catatonia(void);
static state_func_t death(void);
#endif

static enum { AUTOBOOT, FASTBOOT } runcom_mode = AUTOBOOT;

static void transition(state_t);
static void setctty(const char *);

typedef struct init_session {
        int     se_index;               /* index of entry in ttys file */
        pid_t   se_process;             /* controlling process */
        struct timeval  se_started;     /* used to avoid thrashing */
        int     se_nspace;              /* spacing count */
        int     se_flags;               /* status of session */
#define SE_SHUTDOWN     0x1             /* session won't be restarted */
#define SE_PRESENT      0x2             /* session is in /etc/ttys */
        char    *se_device;             /* filename of port */
        char    *se_getty;              /* what to run on that port */
        char    **se_getty_argv;        /* pre-parsed argument array */
        char    *se_window;             /* window system (started only once) */
        char    **se_window_argv;       /* pre-parsed argument array */
        struct  init_session *se_prev;
        struct  init_session *se_next;
} session_t;

static void collect_child(pid_t, int);
static int clang;
static void transition_handler(int);
static void alrm_handler(int);
static int has_securelevel(void);
static int securelevel_present;

#ifndef LETS_GET_SMALL
static int do_setttyent(void);
static void start_window_system(session_t *);
static char **construct_argv(char *);
static int setupargv(session_t *, struct ttyent *);
static pid_t start_getty(session_t *);
static void free_session(session_t *);
static session_t *new_session(session_t *, int, struct ttyent *);
static session_t *sessions;
static void setsecuritylevel(int);
static int getsecuritylevel(void);
static int start_session_db(void);
static void add_session(session_t *);
static void del_session(session_t *);
static session_t *find_session(pid_t);
static DB *session_db;
static state_t requested_transition = runcom;

static void clear_session_logs(session_t *, int);
static state_func_t runetcrc(int);
#ifdef SUPPORT_UTMPX
static struct timeval boot_time;
static state_t current_state = death;
static void session_utmpx(const session_t *, int);
static void make_utmpx(const char *, const char *, int, pid_t,
    const struct timeval *, int);
static char get_runlevel(const state_t);
static void utmpx_set_runlevel(char, char);
#endif

#ifdef CHROOT
static int did_multiuser_chroot = 0;
static char rootdir[PATH_MAX];
static int shouldchroot(void);
static int createsysctlnode(void);
#endif /* CHROOT */

#else /* LETS_GET_SMALL */
static state_t requested_transition = single_user;
#endif /* !LETS_GET_SMALL */

#ifdef MFS_DEV_IF_NO_CONSOLE

static int mfs_dev(void);

#endif

/*
 * The mother of all processes.
 */
int
main(int argc, char **argv)
{
        struct sigaction sa;
        sigset_t mask;
#ifndef LETS_GET_SMALL
        int c;

#ifdef SUPPORT_UTMPX
        (void)gettimeofday(&boot_time, NULL);
#endif /* SUPPORT_UTMPX */

        /* Dispose of random users. */
        if (getuid() != 0) {
                errno = EPERM;
                err(1, NULL);
        }

        /* System V users like to reexec init. */
        if (getpid() != 1)
                errx(1, "already running");
#endif

        /*
         * Create an initial session.
         */
        if (setsid() < 0)
                warn("initial setsid() failed");

        /*
         * Establish an initial user so that programs running
         * single user do not freak out and die (like passwd).
         */
        if (setlogin("root") < 0)
                warn("setlogin() failed");


#ifdef MFS_DEV_IF_NO_CONSOLE
        if (mfs_dev() == -1)
                requested_transition = single_user;
#endif

#ifndef LETS_GET_SMALL
        /*
         * Note that this does NOT open a file...
         * Does 'init' deserve its own facility number?
         */
        openlog("init", LOG_CONS, LOG_AUTH);
#endif /* LETS_GET_SMALL */


#ifndef LETS_GET_SMALL
        /*
         * This code assumes that we always get arguments through flags,
         * never through bits set in some random machine register.
         */
        while ((c = getopt(argc, argv, "sf")) != -1)
                switch (c) {
                case 's':
                        requested_transition = single_user;
                        break;
                case 'f':
                        runcom_mode = FASTBOOT;
                        break;
                default:
                        warning("unrecognized flag `%c'", c);
                        break;
                }

        if (optind != argc)
                warning("ignoring excess arguments");
#else /* LETS_GET_SMALL */
        requested_transition = single_user;
#endif /* LETS_GET_SMALL */

        /*
         * We catch or block signals rather than ignore them,
         * so that they get reset on exec.
         */
        handle(badsys, SIGSYS, 0);
        handle(disaster, SIGABRT, SIGFPE, SIGILL, SIGSEGV,
               SIGBUS, SIGXCPU, SIGXFSZ, 0);
        handle(transition_handler, SIGHUP, SIGTERM, SIGTSTP, 0);
        handle(alrm_handler, SIGALRM, 0);
        (void)sigfillset(&mask);
        delset(&mask, SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGSYS,
            SIGXCPU, SIGXFSZ, SIGHUP, SIGTERM, SIGTSTP, SIGALRM, 0);
        (void)sigprocmask(SIG_SETMASK, &mask, NULL);
        (void)sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        sa.sa_handler = SIG_IGN;
        (void)sigaction(SIGTTIN, &sa, NULL);
        (void)sigaction(SIGTTOU, &sa, NULL);

        /*
         * Paranoia.
         */
        (void)close(0);
        (void)close(1);
        (void)close(2);

#if !defined(LETS_GET_SMALL) && defined(CHROOT)
        /* Create "init.root" sysctl node. */
        (void)createsysctlnode();
#endif /* !LETS_GET_SMALL && CHROOT*/

        /*
         * Securelevel might not be supported by the kernel. Query for it, and
         * set a variable indicating whether we should attempt anything with it
         * or not.
         */
        securelevel_present = has_securelevel();

        /*
         * Start the state machine.
         */
        transition(requested_transition);

        /*
         * Should never reach here.
         */
        return 1;
}

/*
 * Associate a function with a signal handler.
 */
static void
handle(sig_t handler, ...)
{
        int sig;
        struct sigaction sa;
        sigset_t mask_everything;
        va_list ap;

        va_start(ap, handler);

        sa.sa_handler = handler;
        (void)sigfillset(&mask_everything);

        while ((sig = va_arg(ap, int)) != 0) {
                sa.sa_mask = mask_everything;
                /* XXX SA_RESTART? */
                sa.sa_flags = sig == SIGCHLD ? SA_NOCLDSTOP : 0;
                (void)sigaction(sig, &sa, NULL);
        }
        va_end(ap);
}

/*
 * Delete a set of signals from a mask.
 */
static void
delset(sigset_t *maskp, ...)
{
        int sig;
        va_list ap;

        va_start(ap, maskp);

        while ((sig = va_arg(ap, int)) != 0)
                (void)sigdelset(maskp, sig);
        va_end(ap);
}

#if 0   /* Enable to get error messages from init ! */
#define vsyslog(level, fmt, ap) print_console(level, fmt, ap)
#define closelog()

static void
print_console(int level, const char *message, va_list ap)
{
        /*
         * XXX: syslog seems to just plain not work in console-only
         * XXX: situation... that should be fixed.  Let's leave this
         * XXX: note + code here in case someone gets in trouble and
         * XXX: wants to debug. -- Jachym Holecek <freza@liberouter.org>
         */
        char errbuf[1024];
        int fd, len;

        /* We can't do anything on errors, anyway... */
        fd = open(_PATH_CONSOLE, O_WRONLY);
        if (fd == -1)
                return ;

        /* %m will get lost... */
        len = vsnprintf(errbuf, sizeof(errbuf), message, ap);
        (void)write(fd, (void *)errbuf, len);
        (void)close(fd);
}
#endif

/*
 * Log a message and sleep for a while (to give someone an opportunity
 * to read it and to save log or hardcopy output if the problem is chronic).
 * NB: should send a message to the session logger to avoid blocking.
 */
static void
stall(const char *message, ...)
{
        va_list ap;

        va_start(ap, message);
        vsyslog(LOG_ALERT, message, ap);
        va_end(ap);
        closelog();
        (void)sleep(STALL_TIMEOUT);
}

/*
 * Like stall(), but doesn't sleep.
 * If cpp had variadic macros, the two functions could be #defines for another.
 * NB: should send a message to the session logger to avoid blocking.
 */
static void
warning(const char *message, ...)
{
        va_list ap;

        va_start(ap, message);
        vsyslog(LOG_ALERT, message, ap);
        va_end(ap);
        closelog();
}

/*
 * Log an emergency message.
 * NB: should send a message to the session logger to avoid blocking.
 */
static void
emergency(const char *message, ...)
{
        va_list ap;

        va_start(ap, message);
        vsyslog(LOG_EMERG, message, ap);
        va_end(ap);
        closelog();
}

/*
 * Catch a SIGSYS signal.
 *
 * These may arise if a system does not support sysctl.
 * We tolerate up to 25 of these, then throw in the towel.
 */
static void
badsys(int sig)
{
        static int badcount = 0;

        if (badcount++ < 25)
                return;
        disaster(sig);
}

/*
 * Catch an unexpected signal.
 */
static void
disaster(int sig)
{

        emergency("fatal signal: %s", strsignal(sig));
        (void)sleep(STALL_TIMEOUT);
        _exit(sig);             /* reboot */
}

/*
 * Check if securelevel is present.
 */
static int
has_securelevel(void)
{
#ifdef KERN_SECURELVL
        int name[2], curlevel;
        size_t len;

        name[0] = CTL_KERN;
        name[1] = KERN_SECURELVL;
        len = sizeof curlevel;
        if (sysctl(name, 2, &curlevel, &len, NULL, 0) == -1) {
                /* If it doesn't exist, it's okay. */
                if (errno == ENOENT) 
                        return 0;
        }
        return 1;
#else
        return 0;
#endif
}

/*
 * Get the security level of the kernel.
 */
static int
getsecuritylevel(void)
{
#ifdef KERN_SECURELVL
        int name[2], curlevel;
        size_t len;

        if (!securelevel_present)
                return -1;

        name[0] = CTL_KERN;
        name[1] = KERN_SECURELVL;
        len = sizeof curlevel;
        if (sysctl(name, 2, &curlevel, &len, NULL, 0) == -1) {
                emergency("cannot get kernel security level: %m");
                return -1;
        }
        return curlevel;
#else
        return -1;
#endif
}

/*
 * Set the security level of the kernel.
 */
static void
setsecuritylevel(int newlevel)
{
#ifdef KERN_SECURELVL
        int name[2], curlevel;

        if (!securelevel_present)
                return;

        curlevel = getsecuritylevel();
        if (newlevel == curlevel)
                return;
        name[0] = CTL_KERN;
        name[1] = KERN_SECURELVL;
        if (sysctl(name, 2, NULL, NULL, &newlevel, sizeof newlevel) == -1) {
                emergency("cannot change kernel security level from"
                    " %d to %d: %m", curlevel, newlevel);
                return;
        }
#ifdef SECURE
        warning("kernel security level changed from %d to %d",
            curlevel, newlevel);
#endif
#endif
}

/*
 * Change states in the finite state machine.
 * The initial state is passed as an argument.
 */
static void
transition(state_t s)
{

        if (s == NULL)
                return;
        for (;;) {
#ifdef SUPPORT_UTMPX
#ifndef LETS_GET_SMALL
                utmpx_set_runlevel(get_runlevel(current_state),
                    get_runlevel(s));
                current_state = s;
#endif
#endif
                s = (state_t)(*s)();
        }
}

#ifndef LETS_GET_SMALL
/*
 * Close out the accounting files for a login session.
 * NB: should send a message to the session logger to avoid blocking.
 */
static void
clear_session_logs(session_t *sp, int status)
{
#if defined(SUPPORT_UTMP) || defined(SUPPORT_UTMPX)
        char *line = sp->se_device + sizeof(_PATH_DEV) - 1;
#endif

#ifdef SUPPORT_UTMPX
        if (logoutx(line, status, DEAD_PROCESS))
                logwtmpx(line, "", "", status, DEAD_PROCESS);
#endif
#ifdef SUPPORT_UTMP
        if (logout(line))
                logwtmp(line, "", "");
#endif
}
#endif

/*
 * Start a session and allocate a controlling terminal.
 * Only called by children of init after forking.
 */
static void
setctty(const char *name)
{
        int fd;

        (void)revoke(name);
        (void)nanosleep(&dtrtime, NULL);        /* leave DTR low for a bit */
        if ((fd = open(name, O_RDWR)) == -1) {
                stall("can't open %s: %m", name);
                _exit(1);
        }
        if (login_tty(fd) == -1) {
                stall("can't get %s for controlling terminal: %m", name);
                _exit(2);
        }
}

/*
 * Bring the system up single user.
 */
static state_func_t
single_user(void)
{
        pid_t pid, wpid;
        int status;
        int from_securitylevel;
        sigset_t mask;
        struct sigaction sa, satstp, sahup;
#ifdef ALTSHELL
        const char *shell = INIT_BSHELL;
#endif
        const char *argv[2];
#ifdef SECURE
        struct ttyent *typ;
        struct passwd *pp;
        char *clear, *password;
#endif
#ifdef ALTSHELL
        char altshell[128];
#endif /* ALTSHELL */

#if !defined(LETS_GET_SMALL) && defined(CHROOT)
        /* Clear previous idea, just in case. */
        did_multiuser_chroot = 0;
#endif /* !LETS_GET_SMALL && CHROOT */

        /*
         * If the kernel is in secure mode, downgrade it to insecure mode.
         */
        from_securitylevel = getsecuritylevel();
        if (from_securitylevel > 0)
                setsecuritylevel(0);

        (void)sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        sa.sa_handler = SIG_IGN;
        (void)sigaction(SIGTSTP, &sa, &satstp);
        (void)sigaction(SIGHUP, &sa, &sahup);
        if ((pid = fork()) == 0) {
                /*
                 * Start the single user session.
                 */
                if (access(_PATH_CONSTTY, F_OK) == 0)
                        setctty(_PATH_CONSTTY);
                else
                        setctty(_PATH_CONSOLE);

#ifdef SECURE
                /*
                 * Check the root password.
                 * We don't care if the console is 'on' by default;
                 * it's the only tty that can be 'off' and 'secure'.
                 */
                typ = getttynam("console");
                pp = getpwnam("root");
                if (typ && (from_securitylevel >=2 || (typ->ty_status
                    & TTY_SECURE) == 0) && pp && *pp->pw_passwd != '\0') {
                        (void)fprintf(stderr,
                            "Enter root password, or ^D to go multi-user\n");
                        for (;;) {
                                clear = getpass("Password:");
                                if (clear == 0 || *clear == '\0')
                                        _exit(0);
                                password = crypt(clear, pp->pw_passwd);
                                (void)memset(clear, 0, _PASSWORD_LEN);
                                if (strcmp(password, pp->pw_passwd) == 0)
                                        break;
                                warning("single-user login failed");
                        }
                }
                (void)endttyent();
                endpwent();
#endif /* SECURE */

#ifdef ALTSHELL
                (void)fprintf(stderr,
                    "Enter pathname of shell or RETURN for %s: ", shell);
                if (fgets(altshell, sizeof(altshell), stdin) == NULL) {
                        altshell[0] = '\0';
                } else {
                        /* nuke \n */
                        char *p;

                        if ((p = strchr(altshell, '\n')) != NULL)
                                *p = '\0';
                }

                if (altshell[0])
                        shell = altshell;
#endif /* ALTSHELL */

                /*
                 * Unblock signals.
                 * We catch all the interesting ones,
                 * and those are reset to SIG_DFL on exec.
                 */
                (void)sigemptyset(&mask);
                (void)sigprocmask(SIG_SETMASK, &mask, NULL);

                /*
                 * Fire off a shell.
                 * If the default one doesn't work, try the Bourne shell.
                 */
                argv[0] = "-sh";
                argv[1] = 0;
                (void)setenv("PATH", INIT_PATH, 1);
#ifdef ALTSHELL
                if (altshell[0])
                        argv[0] = altshell;
                (void)execv(shell, __UNCONST(argv));
                emergency("can't exec `%s' for single user: %m", shell);
                argv[0] = "-sh";
#endif /* ALTSHELL */
                (void)execv(INIT_BSHELL, __UNCONST(argv));
                emergency("can't exec `%s' for single user: %m", INIT_BSHELL);
                (void)sleep(STALL_TIMEOUT);
                _exit(3);
        }

        if (pid == -1) {
                /*
                 * We are seriously hosed.  Do our best.
                 */
                emergency("can't fork single-user shell: %m, trying again");
                while (waitpid(-1, NULL, WNOHANG) > 0)
                        continue;
                (void)sigaction(SIGTSTP, &satstp, NULL);
                (void)sigaction(SIGHUP, &sahup, NULL);
                return (state_func_t)single_user;
        }

        requested_transition = 0;
        do {
                if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
                        collect_child(wpid, status);
                if (wpid == -1) {
                        if (errno == EINTR)
                                continue;
                        warning("wait for single-user shell failed: %m; "
                            "restarting");
                        return (state_func_t)single_user;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("shell stopped, restarting");
                        (void)kill(pid, SIGCONT);
                        wpid = -1;
                }
        } while (wpid != pid && !requested_transition);

        if (requested_transition) {
                (void)sigaction(SIGTSTP, &satstp, NULL);
                (void)sigaction(SIGHUP, &sahup, NULL);
                return (state_func_t)requested_transition;
        }

        if (WIFSIGNALED(status)) {
                if (WTERMSIG(status) == SIGKILL) {
                        /* executed /sbin/reboot; wait for the end quietly */
                        sigset_t s;
        
                        (void)sigfillset(&s);
                        for (;;)
                                (void)sigsuspend(&s);
                } else {        
                        warning("single user shell terminated (%x), restarting",
                                status);
                        (void)sigaction(SIGTSTP, &satstp, NULL);
                        (void)sigaction(SIGHUP, &sahup, NULL);
                        return (state_func_t)single_user;
                }
        }

        runcom_mode = FASTBOOT;
        (void)sigaction(SIGTSTP, &satstp, NULL);
        (void)sigaction(SIGHUP, &sahup, NULL);
#ifndef LETS_GET_SMALL
        return (state_func_t)runcom;
#else /* LETS_GET_SMALL */
        return (state_func_t)single_user;
#endif /* LETS_GET_SMALL */
}

#ifndef LETS_GET_SMALL

/* ARGSUSED */
static state_func_t
runetcrc(int trychroot)
{
        pid_t pid, wpid;
        int status;
        const char *argv[4];
        struct sigaction sa;

        switch ((pid = fork())) {
        case 0:
                (void)sigemptyset(&sa.sa_mask);
                sa.sa_flags = 0;
                sa.sa_handler = SIG_IGN;
                (void)sigaction(SIGTSTP, &sa, NULL);
                (void)sigaction(SIGHUP, &sa, NULL);

                setctty(_PATH_CONSOLE);

                argv[0] = "sh";
                argv[1] = _PATH_RUNCOM;
                argv[2] = (runcom_mode == AUTOBOOT ? "autoboot" : 0);
                argv[3] = 0;

                (void)sigprocmask(SIG_SETMASK, &sa.sa_mask, NULL);

#ifdef CHROOT
                if (trychroot)
                        if (chroot(rootdir) != 0) {
                                warning("failed to chroot to `%s': %m",
                                    rootdir);
                                _exit(4);       /* force single user mode */
                        }
#endif /* CHROOT */

                (void)execv(INIT_BSHELL, __UNCONST(argv));
                stall("can't exec `%s' for `%s': %m", INIT_BSHELL, _PATH_RUNCOM);
                _exit(5);       /* force single user mode */
                /*NOTREACHED*/
        case -1:
                emergency("can't fork for `%s' on `%s': %m", INIT_BSHELL,
                    _PATH_RUNCOM);
                while (waitpid(-1, NULL, WNOHANG) > 0)
                        continue;
                (void)sleep(STALL_TIMEOUT);
                return (state_func_t)single_user;
        default:
                break;
        }

        /*
         * Copied from single_user().  This is a bit paranoid.
         */
        do {
                if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
                        collect_child(wpid, status);
                if (wpid == -1) {
                        if (errno == EINTR)
                                continue;
                        warning("wait for `%s' on `%s' failed: %m; going to "
                            "single user mode", INIT_BSHELL, _PATH_RUNCOM);
                        return (state_func_t)single_user;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("`%s' on `%s' stopped, restarting",
                            INIT_BSHELL, _PATH_RUNCOM);
                        (void)kill(pid, SIGCONT);
                        wpid = -1;
                }
        } while (wpid != pid);

        if (WIFSIGNALED(status) && WTERMSIG(status) == SIGTERM &&
            requested_transition == catatonia) {
                /* /etc/rc executed /sbin/reboot; wait for the end quietly */
                sigset_t s;

                (void)sigfillset(&s);
                for (;;)
                        (void)sigsuspend(&s);
        }

        if (!WIFEXITED(status)) {
                warning("`%s' on `%s' terminated abnormally, going to "
                    "single user mode", INIT_BSHELL, _PATH_RUNCOM);
                return (state_func_t)single_user;
        }

        if (WEXITSTATUS(status))
                return (state_func_t)single_user;

        return (state_func_t)read_ttys;
}

/*
 * Run the system startup script.
 */
static state_func_t
runcom(void)
{
        state_func_t next_step;

        /* Run /etc/rc and choose next state depending on the result. */
        next_step = runetcrc(0);
        if (next_step != (state_func_t)read_ttys)
                return (state_func_t)next_step;

#ifdef CHROOT
        /*
         * If init.root sysctl does not point to "/", we'll chroot and run
         * The Real(tm) /etc/rc now.  Global variable rootdir will tell us
         * where to go.
         */
        if (shouldchroot()) {
                next_step = runetcrc(1);
                if (next_step != (state_func_t)read_ttys)
                        return (state_func_t)next_step;

                did_multiuser_chroot = 1;
        } else {
                did_multiuser_chroot = 0;
        }
#endif /* CHROOT */

        /*
         * Regardless of whether in chroot or not, we booted successfully.
         * It's time to spawn gettys (ie. next_step's value at this point).
         */
        runcom_mode = AUTOBOOT;         /* the default */
        /* NB: should send a message to the session logger to avoid blocking. */
#ifdef SUPPORT_UTMPX
        logwtmpx("~", "reboot", "", 0, INIT_PROCESS);
#endif
#ifdef SUPPORT_UTMP
        logwtmp("~", "reboot", "");
#endif
        return (state_func_t)read_ttys;
}

/*
 * Open the session database.
 *
 * NB: We could pass in the size here; is it necessary?
 */
static int
start_session_db(void)
{

        if (session_db && (*session_db->close)(session_db))
                emergency("session database close: %m");
        if ((session_db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == 0) {
                emergency("session database open: %m");
                return 1;
        }
        return 0;
                
}

/*
 * Add a new login session.
 */
static void
add_session(session_t *sp)
{
        DBT key;
        DBT data;

        if (session_db == NULL)
                return;

        key.data = &sp->se_process;
        key.size = sizeof sp->se_process;
        data.data = &sp;
        data.size = sizeof sp;

        if ((*session_db->put)(session_db, &key, &data, 0))
                emergency("insert %d: %m", sp->se_process);
#ifdef SUPPORT_UTMPX
        session_utmpx(sp, 1);
#endif
}

/*
 * Delete an old login session.
 */
static void
del_session(session_t *sp)
{
        DBT key;

        key.data = &sp->se_process;
        key.size = sizeof sp->se_process;

        if ((*session_db->del)(session_db, &key, 0))
                emergency("delete %d: %m", sp->se_process);
#ifdef SUPPORT_UTMPX
        session_utmpx(sp, 0);
#endif
}

/*
 * Look up a login session by pid.
 */
static session_t *
find_session(pid_t pid)
{
        DBT key;
        DBT data;
        session_t *ret;

        if (session_db == NULL)
                return NULL;

        key.data = &pid;
        key.size = sizeof pid;
        if ((*session_db->get)(session_db, &key, &data, 0) != 0)
                return 0;
        (void)memmove(&ret, data.data, sizeof(ret));
        return ret;
}

/*
 * Construct an argument vector from a command line.
 */
static char **
construct_argv(char *command)
{
        int argc = 0;
        char **argv = malloc(((strlen(command) + 1) / 2 + 1) * sizeof (char *));
        static const char separators[] = " \t";

        if (argv == NULL)
                return NULL;

        if ((argv[argc++] = strtok(command, separators)) == 0) {
                free(argv);
                return NULL;
        }
        while ((argv[argc++] = strtok(NULL, separators)) != NULL)
                continue;
        return argv;
}

/*
 * Deallocate a session descriptor.
 */
static void
free_session(session_t *sp)
{

        free(sp->se_device);
        if (sp->se_getty) {
                free(sp->se_getty);
                free(sp->se_getty_argv);
        }
        if (sp->se_window) {
                free(sp->se_window);
                free(sp->se_window_argv);
        }
        free(sp);
}

/*
 * Allocate a new session descriptor.
 */
static session_t *
new_session(session_t *sprev, int session_index, struct ttyent *typ)
{
        session_t *sp;

        if ((typ->ty_status & TTY_ON) == 0 || typ->ty_name == NULL ||
            typ->ty_getty == NULL)
                return NULL;

        sp = malloc(sizeof (session_t));
        if (sp == NULL)
                return NULL;
        (void)memset(sp, 0, sizeof *sp);

        sp->se_flags = SE_PRESENT;
        sp->se_index = session_index;

        (void)asprintf(&sp->se_device, "%s%s", _PATH_DEV, typ->ty_name);
        if (!sp->se_device) {
                free(sp);
                return NULL;
        }

        if (setupargv(sp, typ) == 0) {
                free_session(sp);
                return NULL;
        }

        sp->se_next = NULL;
        if (sprev == NULL) {
                sessions = sp;
                sp->se_prev = NULL;
        } else {
                sprev->se_next = sp;
                sp->se_prev = sprev;
        }

        return sp;
}

/*
 * Calculate getty and if useful window argv vectors.
 */
static int
setupargv(session_t *sp, struct ttyent *typ)
{

        if (sp->se_getty) {
                free(sp->se_getty);
                free(sp->se_getty_argv);
        }
        (void)asprintf(&sp->se_getty, "%s %s", typ->ty_getty, typ->ty_name);
        if (!sp->se_getty)
                return 0;
        sp->se_getty_argv = construct_argv(sp->se_getty);
        if (sp->se_getty_argv == NULL) {
                warning("can't parse getty for port `%s'", sp->se_device);
                free(sp->se_getty);
                sp->se_getty = NULL;
                return 0;
        }
        if (typ->ty_window) {
                if (sp->se_window)
                        free(sp->se_window);
                sp->se_window = strdup(typ->ty_window);
                sp->se_window_argv = construct_argv(sp->se_window);
                if (sp->se_window_argv == NULL) {
                        warning("can't parse window for port `%s'",
                            sp->se_device);
                        free(sp->se_window);
                        sp->se_window = NULL;
                        return 0;
                }
        }
        return 1;
}

/*
 * Walk the list of ttys and create sessions for each active line.
 */
static state_func_t
read_ttys(void)
{
        int session_index = 0;
        session_t *sp, *snext;
        struct ttyent *typ;

#ifdef SUPPORT_UTMPX
        if (sessions == NULL) {
                struct stat st;

                make_utmpx("", BOOT_MSG, BOOT_TIME, 0, &boot_time, 0);

                /*
                 * If wtmpx is not empty, pick the down time from there
                 */
                if (stat(_PATH_WTMPX, &st) != -1 && st.st_size != 0) {
                        struct timeval down_time;

                        TIMESPEC_TO_TIMEVAL(&down_time, 
                            st.st_atime > st.st_mtime ?
                            &st.st_atimespec : &st.st_mtimespec);
                        make_utmpx("", DOWN_MSG, DOWN_TIME, 0, &down_time, 0);
                }
        }
#endif
        /*
         * Destroy any previous session state.
         * There shouldn't be any, but just in case...
         */
        for (sp = sessions; sp; sp = snext) {
#ifndef LETS_GET_SMALL
                if (sp->se_process)
                        clear_session_logs(sp, 0);
#endif
                snext = sp->se_next;
                free_session(sp);
        }
        sessions = NULL;

        if (start_session_db()) {
                warning("start_session_db failed, death");
#ifdef CHROOT
                /* If /etc/rc ran in chroot, we want to kill any survivors. */
                if (did_multiuser_chroot)
                        return (state_func_t)death;
                else
#endif /* CHROOT */
                        return (state_func_t)single_user;
        }

        (void)do_setttyent();

        /*
         * Allocate a session entry for each active port.
         * Note that sp starts at 0.
         */
        while ((typ = getttyent()) != NULL)
                if ((snext = new_session(sp, ++session_index, typ)) != NULL)
                        sp = snext;
        (void)endttyent();

        return (state_func_t)multi_user;
}

/*
 * Start a window system running.
 */
static void
start_window_system(session_t *sp)
{
        pid_t pid;
        sigset_t mask;

        if ((pid = fork()) == -1) {
                emergency("can't fork for window system on port `%s': %m",
                    sp->se_device);
                /* hope that getty fails and we can try again */
                return;
        }

        if (pid)
                return;

        (void)sigemptyset(&mask);
        (void)sigprocmask(SIG_SETMASK, &mask, NULL);

        if (setsid() < 0)
                emergency("setsid failed (window): %m");

        (void)execv(sp->se_window_argv[0], sp->se_window_argv);
        stall("can't exec window system `%s' for port `%s': %m",
            sp->se_window_argv[0], sp->se_device);
        _exit(6);
}

/*
 * Start a login session running.
 */
static pid_t
start_getty(session_t *sp)
{
        pid_t pid;
        sigset_t mask;
        time_t current_time = time(NULL);
        bool do_sleep = false;

        if (current_time >= sp->se_started.tv_sec &&
            current_time - sp->se_started.tv_sec < GETTY_SPACING) {
                if (++sp->se_nspace > GETTY_NSPACE) {
                        sp->se_nspace = 0;
                        do_sleep = true;
                }
        } else {
                sp->se_nspace = 0;
        }

        /*
         * fork(), not vfork() -- we can't afford to block.
         */
        if ((pid = fork()) == -1) {
                emergency("can't fork for getty on port `%s': %m",
                    sp->se_device);
                return -1;
        }

        if (pid)
                return pid;

#ifdef CHROOT
        /* If /etc/rc did proceed inside chroot, we have to try as well. */
        if (did_multiuser_chroot)
                if (chroot(rootdir) != 0) {
                        stall("can't chroot getty `%s' inside `%s': %m",
                            sp->se_getty_argv[0], rootdir);
                        _exit(7);
                }
#endif /* CHROOT */

        if (do_sleep) {
                warning("getty repeating too quickly on port `%s', sleeping",
                    sp->se_device);
                (void)sleep(GETTY_SLEEP);
        }

        if (sp->se_window) {
                start_window_system(sp);
                (void)sleep(WINDOW_WAIT);
        }

        (void)sigemptyset(&mask);
        (void)sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);

        (void)execv(sp->se_getty_argv[0], sp->se_getty_argv);
        stall("can't exec getty `%s' for port `%s': %m",
            sp->se_getty_argv[0], sp->se_device);
        _exit(8);
        /*NOTREACHED*/
}
#ifdef SUPPORT_UTMPX
static void
session_utmpx(const session_t *sp, int add)
{
        const char *name = sp->se_getty ? sp->se_getty :
            (sp->se_window ? sp->se_window : "");
        const char *line = sp->se_device + sizeof(_PATH_DEV) - 1;

        make_utmpx(name, line, add ? LOGIN_PROCESS : DEAD_PROCESS,
            sp->se_process, &sp->se_started, sp->se_index);
}

static void
make_utmpx(const char *name, const char *line, int type, pid_t pid,
    const struct timeval *tv, int session)
{
        struct utmpx ut;
        const char *eline;

        (void)memset(&ut, 0, sizeof(ut));
        (void)strlcpy(ut.ut_name, name, sizeof(ut.ut_name));
        ut.ut_type = type;
        (void)strlcpy(ut.ut_line, line, sizeof(ut.ut_line));
        ut.ut_pid = pid;
        if (tv)
                ut.ut_tv = *tv;
        else
                (void)gettimeofday(&ut.ut_tv, NULL);
        ut.ut_session = session;

        eline = line + strlen(line);
        if ((size_t)(eline - line) >= sizeof(ut.ut_id))
                line = eline - sizeof(ut.ut_id);
        (void)strncpy(ut.ut_id, line, sizeof(ut.ut_id));

        if (pututxline(&ut) == NULL)
                warning("can't add utmpx record for `%s': %m", ut.ut_line);
        endutxent();
}

static char
get_runlevel(const state_t s)
{
        if (s == (state_t)single_user)
                return SINGLE_USER;
        if (s == (state_t)runcom)
                return RUNCOM;
        if (s == (state_t)read_ttys)
                return READ_TTYS;
        if (s == (state_t)multi_user)
                return MULTI_USER;
        if (s == (state_t)clean_ttys)
                return CLEAN_TTYS;
        if (s == (state_t)catatonia)
                return CATATONIA;
        return DEATH;
}

static void
utmpx_set_runlevel(char old, char new)
{
        struct utmpx ut;

        /*
         * Don't record any transitions until we did the first transition
         * to read ttys, which is when we are guaranteed to have a read-write
         * /var. Perhaps use a different variable for this?
         */
        if (sessions == NULL)
                return;

        (void)memset(&ut, 0, sizeof(ut));
        (void)snprintf(ut.ut_line, sizeof(ut.ut_line), RUNLVL_MSG, new);
        ut.ut_type = RUN_LVL;
        (void)gettimeofday(&ut.ut_tv, NULL);
        ut.ut_exit.e_exit = old;
        ut.ut_exit.e_termination = new;
        if (pututxline(&ut) == NULL)
                warning("can't add utmpx record for `runlevel': %m");
        endutxent();
}
#endif /* SUPPORT_UTMPX */

#endif /* LETS_GET_SMALL */

/*
 * Collect exit status for a child.
 * If an exiting login, start a new login running.
 */
static void
collect_child(pid_t pid, int status)
{
#ifndef LETS_GET_SMALL
        session_t *sp, *sprev, *snext;

        if (! sessions)
                return;

        if ((sp = find_session(pid)) == NULL)
                return;

        clear_session_logs(sp, status);
        del_session(sp);
        sp->se_process = 0;

        if (sp->se_flags & SE_SHUTDOWN) {
                if ((sprev = sp->se_prev) != NULL)
                        sprev->se_next = sp->se_next;
                else
                        sessions = sp->se_next;
                if ((snext = sp->se_next) != NULL)
                        snext->se_prev = sp->se_prev;
                free_session(sp);
                return;
        }

        if ((pid = start_getty(sp)) == -1) {
                /* serious trouble */
                requested_transition = clean_ttys;
                return;
        }

        sp->se_process = pid;
        (void)gettimeofday(&sp->se_started, NULL);
        add_session(sp);
#endif /* LETS_GET_SMALL */
}

/*
 * Catch a signal and request a state transition.
 */
static void
transition_handler(int sig)
{

        switch (sig) {
#ifndef LETS_GET_SMALL
        case SIGHUP:
                requested_transition = clean_ttys;
                break;
        case SIGTERM:
                requested_transition = death;
                break;
        case SIGTSTP:
                requested_transition = catatonia;
                break;
#endif /* LETS_GET_SMALL */
        default:
                requested_transition = 0;
                break;
        }
}

#ifndef LETS_GET_SMALL
/*
 * Take the system multiuser.
 */
static state_func_t
multi_user(void)
{
        pid_t pid;
        int status;
        session_t *sp;

        requested_transition = 0;

        /*
         * If the administrator has not set the security level to -1
         * to indicate that the kernel should not run multiuser in secure
         * mode, and the run script has not set a higher level of security 
         * than level 1, then put the kernel into secure mode.
         */
        if (getsecuritylevel() == 0)
                setsecuritylevel(1);

        for (sp = sessions; sp; sp = sp->se_next) {
                if (sp->se_process)
                        continue;
                if ((pid = start_getty(sp)) == -1) {
                        /* serious trouble */
                        requested_transition = clean_ttys;
                        break;
                }
                sp->se_process = pid;
                (void)gettimeofday(&sp->se_started, NULL);
                add_session(sp);
        }

        while (!requested_transition)
                if ((pid = waitpid(-1, &status, 0)) != -1)
                        collect_child(pid, status);

        return (state_func_t)requested_transition;
}

/*
 * This is an n-squared algorithm.  We hope it isn't run often...
 */
static state_func_t
clean_ttys(void)
{
        session_t *sp, *sprev;
        struct ttyent *typ;
        int session_index = 0;
        int devlen;

        for (sp = sessions; sp; sp = sp->se_next)
                sp->se_flags &= ~SE_PRESENT;

        (void)do_setttyent();

        devlen = sizeof(_PATH_DEV) - 1;
        while ((typ = getttyent()) != NULL) {
                ++session_index;

                for (sprev = 0, sp = sessions; sp; sprev = sp, sp = sp->se_next)
                        if (strcmp(typ->ty_name, sp->se_device + devlen) == 0)
                                break;

                if (sp) {
                        sp->se_flags |= SE_PRESENT;
                        if (sp->se_index != session_index) {
                                warning("port `%s' changed utmp index from "
                                    "%d to %d", sp->se_device, sp->se_index,
                                    session_index);
                                sp->se_index = session_index;
                        }
                        if ((typ->ty_status & TTY_ON) == 0 ||
                            typ->ty_getty == 0) {
                                sp->se_flags |= SE_SHUTDOWN;
                                if (sp->se_process != 0)
                                        (void)kill(sp->se_process, SIGHUP);
                                continue;
                        }
                        sp->se_flags &= ~SE_SHUTDOWN;
                        if (setupargv(sp, typ) == 0) {
                                warning("can't parse getty for port `%s'",
                                    sp->se_device);
                                sp->se_flags |= SE_SHUTDOWN;
                                if (sp->se_process != 0)
                                        (void)kill(sp->se_process, SIGHUP);
                        } else {
                                sp->se_nspace = 0;
                        }
                        continue;
                }

                (void)new_session(sprev, session_index, typ);
        }

        (void)endttyent();

        for (sp = sessions; sp; sp = sp->se_next)
                if ((sp->se_flags & SE_PRESENT) == 0) {
                        sp->se_flags |= SE_SHUTDOWN;
                        if (sp->se_process != 0)
                                (void)kill(sp->se_process, SIGHUP);
                }

        return (state_func_t)multi_user;
}

/*
 * Block further logins.
 */
static state_func_t
catatonia(void)
{
        session_t *sp;

        for (sp = sessions; sp; sp = sp->se_next)
                sp->se_flags |= SE_SHUTDOWN;

        return (state_func_t)multi_user;
}
#endif /* LETS_GET_SMALL */

/*
 * Note SIGALRM.
 */
static void
/*ARGSUSED*/
alrm_handler(int sig)
{

        clang = 1;
}

#ifndef LETS_GET_SMALL
/*
 * Bring the system down to single user.
 */
static state_func_t
death(void)
{
        session_t *sp;
        int i, status;
        pid_t pid;
        static const int death_sigs[3] = { SIGHUP, SIGTERM, SIGKILL };

        for (sp = sessions; sp; sp = sp->se_next)
                sp->se_flags |= SE_SHUTDOWN;

        /* NB: should send a message to the session logger to avoid blocking. */
#ifdef SUPPORT_UTMPX
        logwtmpx("~", "shutdown", "", 0, INIT_PROCESS);
#endif
#ifdef SUPPORT_UTMP
        logwtmp("~", "shutdown", "");
#endif

        for (i = 0; i < 3; ++i) {
                if (kill(-1, death_sigs[i]) == -1 && errno == ESRCH)
                        return (state_func_t)single_user;

                clang = 0;
                (void)alarm(DEATH_WATCH);
                do
                        if ((pid = waitpid(-1, &status, 0)) != -1)
                                collect_child(pid, status);
                while (clang == 0 && errno != ECHILD);

                if (errno == ECHILD)
                        return (state_func_t)single_user;
        }

        warning("some processes would not die; ps axl advised");

        return (state_func_t)single_user;
}
#endif /* LETS_GET_SMALL */

#ifdef MFS_DEV_IF_NO_CONSOLE

static int
mfs_dev(void)
{
        /*
         * We cannot print errors so we bail out silently...
         */
        pid_t pid;
        int status;

        /* If we have /dev/console, assume all is OK  */
        if (access(_PATH_CONSOLE, F_OK) == 0)
                return 0;

#if 0   /* Useful for testing MAKEDEV */
        /* Mount an mfs over /mnt so we can create a console entry */
        switch ((pid = fork())) {
        case 0:
                (void)execl(INIT_MOUNT_MFS, "mount_mfs",
                    "-b", "4096", "-f", "512",
                    "-s", 64, "-n", 10,
                    "-p", "0755",
                    "swap", "/mnt", NULL);
                _exit(9);
                /*NOTREACHED*/

        case -1:
                return(-1);

        default:
                if (waitpid(pid, &status, 0) == -1)
                        return(-1);
                if (status != 0)
                        return(-1);
                break;
        }

        {
                dev_t dev;
#ifdef CPU_CONSDEV
                static int name[2] = { CTL_MACHDEP, CPU_CONSDEV };
                size_t olen;
                olen = sizeof(dev);
                if (sysctl(name, sizeof(name) / sizeof(name[0]), &dev, &olen,
                    NULL, 0) == -1)
#endif
                        dev = makedev(0, 0);

                /* Make a console for us, so we can see things happening */
                if (mknod("/mnt/console", 0666 | S_IFCHR, dev) == -1)
                        return(-1);
                (void)freopen("/mnt/console", "a", stderr);
        }

#endif

        /* Run the makedev script to create devices */
        switch ((pid = fork())) {
        case 0:
                (void)dup2(2, 1);       /* Give the script stdout */
                if (chdir("/dev") == 0)
                        (void)execl(INIT_BSHELL, "sh",
                            access("./MAKEDEV", X_OK) == 0
                                ? "./MAKEDEV" : "/etc/MAKEDEV",
                            "-MM", "init", NULL); 
                _exit(10);
                /* NOTREACHED */

        case -1:
                break;

        default:
                if (waitpid(pid, &status, 0) == -1)
                        break;
                if (status != 0)
                        warn("MAKEDEV exit status %d", status);
                /*
                 * If /dev/console got created, then return 0
                 * regardless of MAKEDEV exit status.
                 */
                if (access(_PATH_CONSOLE, F_OK) == 0)
                        return 0;
                _exit(11);
        }
        warn("Unable to run MAKEDEV");
        _exit(12);
}
#endif

#ifndef LETS_GET_SMALL
static int
do_setttyent(void)
{
        (void)endttyent();
#ifdef CHROOT
        if (did_multiuser_chroot) {
                char path[PATH_MAX];

                (void)snprintf(path, sizeof(path), "%s/%s", rootdir, _PATH_TTYS);

                return setttyentpath(path);
        } else
#endif /* CHROOT */
                return setttyent();
}
#endif

#if !defined(LETS_GET_SMALL) && defined(CHROOT)

static int
createsysctlnode(void)
{
        struct sysctlnode node;
        int mib[2];
        size_t len;

        /*
         * Create top-level dynamic sysctl node.  Its child nodes will only
         * be readable by the superuser, since regular mortals should not
         * care ("Sssh, it's a secret!").
         */
        len = sizeof(struct sysctlnode);
        mib[0] = CTL_CREATE;

        (void)memset(&node, 0, len);
        node.sysctl_flags = SYSCTL_VERSION | CTLFLAG_READWRITE |
            CTLFLAG_PRIVATE | CTLTYPE_NODE;
        node.sysctl_num = CTL_CREATE;
        (void)snprintf(node.sysctl_name, SYSCTL_NAMELEN, "init");
        if (sysctl(&mib[0], 1, &node, &len, &node, len) == -1) {
                warning("could not create init node: %m");
                return -1;
        }

        /*
         * Create second level dynamic node capable of holding pathname.
         * Provide "/" as the default value.
         */
        len = sizeof(struct sysctlnode);
        mib[0] = node.sysctl_num;
        mib[1] = CTL_CREATE;

        (void)memset(&node, 0, len);
        node.sysctl_flags = SYSCTL_VERSION | CTLFLAG_READWRITE |
            CTLTYPE_STRING | CTLFLAG_OWNDATA;
        node.sysctl_size = _POSIX_PATH_MAX;
        node.sysctl_data = __UNCONST("/");
        node.sysctl_num = CTL_CREATE;
        (void)snprintf(node.sysctl_name, SYSCTL_NAMELEN, "root");
        if (sysctl(&mib[0], 2, NULL, NULL, &node, len) == -1) {
                warning("could not create init.root node: %m");
                return -1;
        }

        return 0;
}

static int
shouldchroot(void)
{
        struct sysctlnode node;
        size_t len, cnt;
        int mib;

        len = sizeof(struct sysctlnode);

        if (sysctlbyname("init.root", rootdir, &len, NULL, 0) == -1) {
                warning("could not read init.root: %m");

                /* Child killed our node. Recreate it. */
                if (errno == ENOENT) {
                        /* Destroy whatever is left, recreate from scratch. */
                        if (sysctlnametomib("init", &mib, &cnt) != -1) {
                                (void)memset(&node, 0, sizeof(node));
                                node.sysctl_flags = SYSCTL_VERSION;
                                node.sysctl_num = mib;
                                mib = CTL_DESTROY;

                                (void)sysctl(&mib, 1, NULL, NULL, &node,
                                    sizeof(node));
                        }

                        (void)createsysctlnode();
                }

                /* We certainly won't chroot. */
                return 0;
        }

        if (rootdir[len] != '\0' || strlen(rootdir) != len - 1) {
                warning("init.root is not a string");
                return 0;
        }

        if (strcmp(rootdir, "/") == 0)
                return 0;

        return 1;
}

#endif /* !LETS_GET_SMALL && CHROOT */