sbin/init/init.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 */

#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1991, 1993\n\
        The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)init.c      8.1 (Berkeley) 7/15/93";
#endif
static const char rcsid[] =
  "$FreeBSD$";
#endif /* not lint */

#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/uio.h>

#include <db.h>
#include <errno.h>
#include <fcntl.h>
#include <kenv.h>
#include <libutil.h>
#include <paths.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 <sys/reboot.h>
#include <err.h>

#include <stdarg.h>

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

#ifdef LOGIN_CAP
#include <login_cap.h>
#endif

#include "mntopts.h"
#include "pathnames.h"

/*
 * 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             3      /* max. spacing count to bring reaction */
#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 */
#define DEATH_SCRIPT            120     /* wait for 2min for /etc/rc.shutdown */
#define RESOURCE_RC             "daemon"
#define RESOURCE_WINDOW         "default"
#define RESOURCE_GETTY          "default"

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

static void stall(const char *, ...) __printflike(1, 2);
static void warning(const char *, ...) __printflike(1, 2);
static void emergency(const char *, ...) __printflike(1, 2);
static void disaster(int);
static void revoke_ttys(void);
static int  runshutdown(void);
static char *strk(char *);

/*
 * 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);

static state_func_t single_user(void);
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);
static state_func_t death_single(void);
static state_func_t reroot(void);
static state_func_t reroot_phase_two(void);

static state_func_t run_script(const char *);

static enum { AUTOBOOT, FASTBOOT } runcom_mode = AUTOBOOT;
#define FALSE   0
#define TRUE    1

static int Reboot = FALSE;
static int howto = RB_AUTOBOOT;

static int devfs;
static char *init_path_argv0;

static void transition(state_t);
static state_t requested_transition;
static state_t current_state = death_single;

static void execute_script(char *argv[]);
static void open_console(void);
static const char *get_shell(void);
static void replace_init(char *path);
static void write_stderr(const char *message);

typedef struct init_session {
        pid_t   se_process;             /* controlling process */
        time_t  se_started;             /* used to avoid thrashing */
        int     se_flags;               /* status of session */
#define SE_SHUTDOWN     0x1             /* session won't be restarted */
#define SE_PRESENT      0x2             /* session is in /etc/ttys */
#define SE_IFEXISTS     0x4             /* session defined as "onifexists" */
#define SE_IFCONSOLE    0x8             /* session defined as "onifconsole" */
        int     se_nspace;              /* spacing count */
        char    *se_device;             /* filename of port */
        char    *se_getty;              /* what to run on that port */
        char    *se_getty_argv_space;   /* pre-parsed argument array space */
        char    **se_getty_argv;        /* pre-parsed argument array */
        char    *se_window;             /* window system (started only once) */
        char    *se_window_argv_space;  /* pre-parsed argument array space */
        char    **se_window_argv;       /* pre-parsed argument array */
        char    *se_type;               /* default terminal type */
        struct  init_session *se_prev;
        struct  init_session *se_next;
} session_t;

static void free_session(session_t *);
static session_t *new_session(session_t *, struct ttyent *);
static session_t *sessions;

static char **construct_argv(char *);
static void start_window_system(session_t *);
static void collect_child(pid_t);
static pid_t start_getty(session_t *);
static void transition_handler(int);
static void alrm_handler(int);
static void setsecuritylevel(int);
static int getsecuritylevel(void);
static int setupargv(session_t *, struct ttyent *);
#ifdef LOGIN_CAP
static void setprocresources(const char *);
#endif
static int clang;

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;

/*
 * The mother of all processes.
 */
int
main(int argc, char *argv[])
{
        state_t initial_transition = runcom;
        char kenv_value[PATH_MAX];
        int c, error;
        struct sigaction sa;
        sigset_t mask;

        /* Dispose of random users. */
        if (getuid() != 0)
                errx(1, "%s", strerror(EPERM));

        /* System V users like to reexec init. */
        if (getpid() != 1) {
#ifdef COMPAT_SYSV_INIT
                /* So give them what they want */
                if (argc > 1) {
                        if (strlen(argv[1]) == 1) {
                                char runlevel = *argv[1];
                                int sig;

                                switch (runlevel) {
                                case '0': /* halt + poweroff */
                                        sig = SIGUSR2;
                                        break;
                                case '1': /* single-user */
                                        sig = SIGTERM;
                                        break;
                                case '6': /* reboot */
                                        sig = SIGINT;
                                        break;
                                case 'c': /* block further logins */
                                        sig = SIGTSTP;
                                        break;
                                case 'q': /* rescan /etc/ttys */
                                        sig = SIGHUP;
                                        break;
                                case 'r': /* remount root */
                                        sig = SIGEMT;
                                        break;
                                default:
                                        goto invalid;
                                }
                                kill(1, sig);
                                _exit(0);
                        } else
invalid:
                                errx(1, "invalid run-level ``%s''", argv[1]);
                } else
#endif
                        errx(1, "already running");
        }

        init_path_argv0 = strdup(argv[0]);
        if (init_path_argv0 == NULL)
                err(1, "strdup");

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

        /*
         * Create an initial session.
         */
        if (setsid() < 0 && (errno != EPERM || getsid(0) != 1))
                warning("initial setsid() failed: %m");

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

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

        if (optind != argc)
                warning("ignoring excess arguments");

        /*
         * We catch or block signals rather than ignore them,
         * so that they get reset on exec.
         */
        handle(disaster, SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGSYS,
            SIGXCPU, SIGXFSZ, 0);
        handle(transition_handler, SIGHUP, SIGINT, SIGEMT, SIGTERM, SIGTSTP,
            SIGUSR1, SIGUSR2, SIGWINCH, 0);
        handle(alrm_handler, SIGALRM, 0);
        sigfillset(&mask);
        delset(&mask, SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGSYS,
            SIGXCPU, SIGXFSZ, SIGHUP, SIGINT, SIGEMT, SIGTERM, SIGTSTP,
            SIGALRM, SIGUSR1, SIGUSR2, SIGWINCH, 0);
        sigprocmask(SIG_SETMASK, &mask, NULL);
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        sa.sa_handler = SIG_IGN;
        sigaction(SIGTTIN, &sa, NULL);
        sigaction(SIGTTOU, &sa, NULL);

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

        if (kenv(KENV_GET, "init_exec", kenv_value, sizeof(kenv_value)) > 0) {
                replace_init(kenv_value);
                _exit(0); /* reboot */
        }

        if (kenv(KENV_GET, "init_script", kenv_value, sizeof(kenv_value)) > 0) {
                state_func_t next_transition;

                if ((next_transition = run_script(kenv_value)) != NULL)
                        initial_transition = (state_t) next_transition;
        }

        if (kenv(KENV_GET, "init_chroot", kenv_value, sizeof(kenv_value)) > 0) {
                if (chdir(kenv_value) != 0 || chroot(".") != 0)
                        warning("Can't chroot to %s: %m", kenv_value);
        }

        /*
         * Additional check if devfs needs to be mounted:
         * If "/" and "/dev" have the same device number,
         * then it hasn't been mounted yet.
         */
        if (!devfs) {
                struct stat stst;
                dev_t root_devno;

                stat("/", &stst);
                root_devno = stst.st_dev;
                if (stat("/dev", &stst) != 0)
                        warning("Can't stat /dev: %m");
                else if (stst.st_dev == root_devno)
                        devfs++;
        }

        if (devfs) {
                struct iovec iov[4];
                char *s;
                int i;

                char _fstype[]  = "fstype";
                char _devfs[]   = "devfs";
                char _fspath[]  = "fspath";
                char _path_dev[]= _PATH_DEV;

                iov[0].iov_base = _fstype;
                iov[0].iov_len = sizeof(_fstype);
                iov[1].iov_base = _devfs;
                iov[1].iov_len = sizeof(_devfs);
                iov[2].iov_base = _fspath;
                iov[2].iov_len = sizeof(_fspath);
                /*
                 * Try to avoid the trailing slash in _PATH_DEV.
                 * Be *very* defensive.
                 */
                s = strdup(_PATH_DEV);
                if (s != NULL) {
                        i = strlen(s);
                        if (i > 0 && s[i - 1] == '/')
                                s[i - 1] = '\0';
                        iov[3].iov_base = s;
                        iov[3].iov_len = strlen(s) + 1;
                } else {
                        iov[3].iov_base = _path_dev;
                        iov[3].iov_len = sizeof(_path_dev);
                }
                nmount(iov, 4, 0);
                if (s != NULL)
                        free(s);
        }

        if (initial_transition != reroot_phase_two) {
                /*
                 * Unmount reroot leftovers.  This runs after init(8)
                 * gets reexecuted after reroot_phase_two() is done.
                 */
                error = unmount(_PATH_REROOT, MNT_FORCE);
                if (error != 0 && errno != EINVAL)
                        warning("Cannot unmount %s: %m", _PATH_REROOT);
        }

        /*
         * Start the state machine.
         */
        transition(initial_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;
        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;
                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)
                sigdelset(maskp, sig);
        va_end(ap);
}

/*
 * 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);
        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);
}

/*
 * 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);
}

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

        emergency("fatal signal: %s",
            (unsigned)sig < NSIG ? sys_siglist[sig] : "unknown signal");

        sleep(STALL_TIMEOUT);
        _exit(sig);             /* reboot */
}

/*
 * Get the security level of the kernel.
 */
static int
getsecuritylevel(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) {
                emergency("cannot get kernel security level: %s",
                    strerror(errno));
                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;

        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: %s",
                    curlevel, newlevel, strerror(errno));
                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)
{

        current_state = s;
        for (;;)
                current_state = (state_t) (*current_state)();
}

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

        /*
         * Try to open /dev/console.  Open the device with O_NONBLOCK to
         * prevent potential blocking on a carrier.
         */
        revoke(_PATH_CONSOLE);
        if ((fd = open(_PATH_CONSOLE, O_RDWR | O_NONBLOCK)) != -1) {
                (void)fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) & ~O_NONBLOCK);
                if (login_tty(fd) == 0)
                        return;
                close(fd);
        }

        /* No luck.  Log output to file if possible. */
        if ((fd = open(_PATH_DEVNULL, O_RDWR)) == -1) {
                stall("cannot open null device.");
                _exit(1);
        }
        if (fd != STDIN_FILENO) {
                dup2(fd, STDIN_FILENO);
                close(fd);
        }
        fd = open(_PATH_INITLOG, O_WRONLY | O_APPEND | O_CREAT, 0644);
        if (fd == -1)
                dup2(STDIN_FILENO, STDOUT_FILENO);
        else if (fd != STDOUT_FILENO) {
                dup2(fd, STDOUT_FILENO);
                close(fd);
        }
        dup2(STDOUT_FILENO, STDERR_FILENO);
}

static const char *
get_shell(void)
{
        static char kenv_value[PATH_MAX];

        if (kenv(KENV_GET, "init_shell", kenv_value, sizeof(kenv_value)) > 0)
                return kenv_value;
        else
                return _PATH_BSHELL;
}

static void
write_stderr(const char *message)
{

        write(STDERR_FILENO, message, strlen(message));
}

static int
read_file(const char *path, void **bufp, size_t *bufsizep)
{
        struct stat sb;
        size_t bufsize;
        void *buf;
        ssize_t nbytes;
        int error, fd;

        fd = open(path, O_RDONLY);
        if (fd < 0) {
                emergency("%s: %s", path, strerror(errno));
                return (-1);
        }

        error = fstat(fd, &sb);
        if (error != 0) {
                emergency("fstat: %s", strerror(errno));
                close(fd);
                return (error);
        }

        bufsize = sb.st_size;
        buf = malloc(bufsize);
        if (buf == NULL) {
                emergency("malloc: %s", strerror(errno));
                close(fd);
                return (error);
        }

        nbytes = read(fd, buf, bufsize);
        if (nbytes != (ssize_t)bufsize) {
                emergency("read: %s", strerror(errno));
                close(fd);
                free(buf);
                return (error);
        }

        error = close(fd);
        if (error != 0) {
                emergency("close: %s", strerror(errno));
                free(buf);
                return (error);
        }

        *bufp = buf;
        *bufsizep = bufsize;

        return (0);
}

static int
create_file(const char *path, const void *buf, size_t bufsize)
{
        ssize_t nbytes;
        int error, fd;

        fd = open(path, O_WRONLY | O_CREAT | O_EXCL, 0700);
        if (fd < 0) {
                emergency("%s: %s", path, strerror(errno));
                return (-1);
        }

        nbytes = write(fd, buf, bufsize);
        if (nbytes != (ssize_t)bufsize) {
                emergency("write: %s", strerror(errno));
                close(fd);
                return (-1);
        }

        error = close(fd);
        if (error != 0) {
                emergency("close: %s", strerror(errno));
                return (-1);
        }

        return (0);
}

static int
mount_tmpfs(const char *fspath)
{
        struct iovec *iov;
        char errmsg[255];
        int error, iovlen;

        iov = NULL;
        iovlen = 0;
        memset(errmsg, 0, sizeof(errmsg));
        build_iovec(&iov, &iovlen, "fstype",
            __DECONST(void *, "tmpfs"), (size_t)-1);
        build_iovec(&iov, &iovlen, "fspath",
            __DECONST(void *, fspath), (size_t)-1);
        build_iovec(&iov, &iovlen, "errmsg",
            errmsg, sizeof(errmsg));

        error = nmount(iov, iovlen, 0);
        if (error != 0) {
                if (*errmsg != '\0') {
                        emergency("cannot mount tmpfs on %s: %s: %s",
                            fspath, errmsg, strerror(errno));
                } else {
                        emergency("cannot mount tmpfs on %s: %s",
                            fspath, strerror(errno));
                }
                return (error);
        }
        return (0);
}

static state_func_t
reroot(void)
{
        void *buf;
        size_t bufsize;
        int error;

        buf = NULL;
        bufsize = 0;

        revoke_ttys();
        runshutdown();

        /*
         * Make sure nobody can interfere with our scheme.
         * Ignore ESRCH, which can apparently happen when
         * there are no processes to kill.
         */
        error = kill(-1, SIGKILL);
        if (error != 0 && errno != ESRCH) {
                emergency("kill(2) failed: %s", strerror(errno));
                goto out;
        }

        /*
         * Copy the init binary into tmpfs, so that we can unmount
         * the old rootfs without committing suicide.
         */
        error = read_file(init_path_argv0, &buf, &bufsize);
        if (error != 0)
                goto out;
        error = mount_tmpfs(_PATH_REROOT);
        if (error != 0)
                goto out;
        error = create_file(_PATH_REROOT_INIT, buf, bufsize);
        if (error != 0)
                goto out;

        /*
         * Execute the temporary init.
         */
        execl(_PATH_REROOT_INIT, _PATH_REROOT_INIT, "-r", NULL);
        emergency("cannot exec %s: %s", _PATH_REROOT_INIT, strerror(errno));

out:
        emergency("reroot failed; going to single user mode");
        free(buf);
        return (state_func_t) single_user;
}

static state_func_t
reroot_phase_two(void)
{
        char init_path[PATH_MAX], *path, *path_component;
        size_t init_path_len;
        int nbytes, error;

        /*
         * Ask the kernel to mount the new rootfs.
         */
        error = reboot(RB_REROOT);
        if (error != 0) {
                emergency("RB_REBOOT failed: %s", strerror(errno));
                goto out;
        }

        /*
         * Figure out where the destination init(8) binary is.  Note that
         * the path could be different than what we've started with.  Use
         * the value from kenv, if set, or the one from sysctl otherwise.
         * The latter defaults to a hardcoded value, but can be overridden
         * by a build time option.
         */
        nbytes = kenv(KENV_GET, "init_path", init_path, sizeof(init_path));
        if (nbytes <= 0) {
                init_path_len = sizeof(init_path);
                error = sysctlbyname("kern.init_path",
                    init_path, &init_path_len, NULL, 0);
                if (error != 0) {
                        emergency("failed to retrieve kern.init_path: %s",
                            strerror(errno));
                        goto out;
                }
        }

        /*
         * Repeat the init search logic from sys/kern/init_path.c
         */
        path_component = init_path;
        while ((path = strsep(&path_component, ":")) != NULL) {
                /*
                 * Execute init(8) from the new rootfs.
                 */
                execl(path, path, NULL);
        }
        emergency("cannot exec init from %s: %s", init_path, strerror(errno));

out:
        emergency("reroot failed; going to single user mode");
        return (state_func_t) single_user;
}

/*
 * Bring the system up single user.
 */
static state_func_t
single_user(void)
{
        pid_t pid, wpid;
        int status;
        sigset_t mask;
        const char *shell;
        char *argv[2];
        struct timeval tv, tn;
#ifdef SECURE
        struct ttyent *typ;
        struct passwd *pp;
        static const char banner[] =
                "Enter root password, or ^D to go multi-user\n";
        char *clear, *password;
#endif
#ifdef DEBUGSHELL
        char altshell[128];
#endif

        if (Reboot) {
                /* Instead of going single user, let's reboot the machine */
                sync();
                if (reboot(howto) == -1) {
                        emergency("reboot(%#x) failed, %s", howto,
                            strerror(errno));
                        _exit(1); /* panic and reboot */
                }
                warning("reboot(%#x) returned", howto);
                _exit(0); /* panic as well */
        }

        shell = get_shell();

        if ((pid = fork()) == 0) {
                /*
                 * Start the single user session.
                 */
                open_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 && (typ->ty_status & TTY_SECURE) == 0 &&
                    pp && *pp->pw_passwd) {
                        write_stderr(banner);
                        for (;;) {
                                clear = getpass("Password:");
                                if (clear == NULL || *clear == '\0')
                                        _exit(0);
                                password = crypt(clear, pp->pw_passwd);
                                bzero(clear, _PASSWORD_LEN);
                                if (password != NULL &&
                                    strcmp(password, pp->pw_passwd) == 0)
                                        break;
                                warning("single-user login failed\n");
                        }
                }
                endttyent();
                endpwent();
#endif /* SECURE */

#ifdef DEBUGSHELL
                {
                        char *cp = altshell;
                        int num;

#define SHREQUEST "Enter full pathname of shell or RETURN for "
                        write_stderr(SHREQUEST);
                        write_stderr(shell);
                        write_stderr(": ");
                        while ((num = read(STDIN_FILENO, cp, 1)) != -1 &&
                            num != 0 && *cp != '\n' && cp < &altshell[127])
                                cp++;
                        *cp = '\0';
                        if (altshell[0] != '\0')
                                shell = altshell;
                }
#endif /* DEBUGSHELL */

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

                /*
                 * Fire off a shell.
                 * If the default one doesn't work, try the Bourne shell.
                 */

                char name[] = "-sh";

                argv[0] = name;
                argv[1] = NULL;
                execv(shell, argv);
                emergency("can't exec %s for single user: %m", shell);
                execv(_PATH_BSHELL, argv);
                emergency("can't exec %s for single user: %m", _PATH_BSHELL);
                sleep(STALL_TIMEOUT);
                _exit(1);
        }

        if (pid == -1) {
                /*
                 * We are seriously hosed.  Do our best.
                 */
                emergency("can't fork single-user shell, trying again");
                while (waitpid(-1, (int *) 0, WNOHANG) > 0)
                        continue;
                return (state_func_t) single_user;
        }

        requested_transition = 0;
        do {
                if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
                        collect_child(wpid);
                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("init: shell stopped, restarting\n");
                        kill(pid, SIGCONT);
                        wpid = -1;
                }
        } while (wpid != pid && !requested_transition);

        if (requested_transition)
                return (state_func_t) requested_transition;

        if (!WIFEXITED(status)) {
                if (WTERMSIG(status) == SIGKILL) {
                        /*
                         *  reboot(8) killed shell?
                         */
                        warning("single user shell terminated.");
                        gettimeofday(&tv, NULL);
                        tn = tv;
                        tv.tv_sec += STALL_TIMEOUT;
                        while (tv.tv_sec > tn.tv_sec || (tv.tv_sec ==
                            tn.tv_sec && tv.tv_usec > tn.tv_usec)) {
                                sleep(1);
                                gettimeofday(&tn, NULL);
                        }
                        _exit(0);
                } else {
                        warning("single user shell terminated, restarting");
                        return (state_func_t) single_user;
                }
        }

        runcom_mode = FASTBOOT;
        return (state_func_t) runcom;
}

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

        if ((next_transition = run_script(_PATH_RUNCOM)) != NULL)
                return next_transition;

        runcom_mode = AUTOBOOT;         /* the default */
        return (state_func_t) read_ttys;
}

static void
execute_script(char *argv[])
{
        struct sigaction sa;
        const char *shell, *script;
        int error;

        bzero(&sa, sizeof(sa));
        sigemptyset(&sa.sa_mask);
        sa.sa_handler = SIG_IGN;
        sigaction(SIGTSTP, &sa, NULL);
        sigaction(SIGHUP, &sa, NULL);

        open_console();

        sigprocmask(SIG_SETMASK, &sa.sa_mask, NULL);
#ifdef LOGIN_CAP
        setprocresources(RESOURCE_RC);
#endif

        /*
         * Try to directly execute the script first.  If it
         * fails, try the old method of passing the script path
         * to sh(1).  Don't complain if it fails because of
         * the missing execute bit.
         */
        script = argv[1];
        error = access(script, X_OK);
        if (error == 0) {
                execv(script, argv + 1);
                warning("can't directly exec %s: %m", script);
        } else if (errno != EACCES) {
                warning("can't access %s: %m", script);
        }

        shell = get_shell();
        execv(shell, argv);
        stall("can't exec %s for %s: %m", shell, script);
}

/*
 * Execute binary, replacing init(8) as PID 1.
 */
static void
replace_init(char *path)
{
        char *argv[3];
        char sh[] = "sh";

        argv[0] = sh;
        argv[1] = path;
        argv[2] = NULL;

        execute_script(argv);
}

/*
 * Run a shell script.
 * Returns 0 on success, otherwise the next transition to enter:
 *  - single_user if fork/execv/waitpid failed, or if the script
 *    terminated with a signal or exit code != 0.
 *  - death_single if a SIGTERM was delivered to init(8).
 */
static state_func_t
run_script(const char *script)
{
        pid_t pid, wpid;
        int status;
        char *argv[4];
        const char *shell;

        shell = get_shell();

        if ((pid = fork()) == 0) {

                char _sh[]              = "sh";
                char _autoboot[]        = "autoboot";

                argv[0] = _sh;
                argv[1] = __DECONST(char *, script);
                argv[2] = runcom_mode == AUTOBOOT ? _autoboot : 0;
                argv[3] = NULL;

                execute_script(argv);
                sleep(STALL_TIMEOUT);
                _exit(1);       /* force single user mode */
        }

        if (pid == -1) {
                emergency("can't fork for %s on %s: %m", shell, script);
                while (waitpid(-1, (int *) 0, WNOHANG) > 0)
                        continue;
                sleep(STALL_TIMEOUT);
                return (state_func_t) single_user;
        }

        /*
         * Copied from single_user().  This is a bit paranoid.
         */
        requested_transition = 0;
        do {
                if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
                        collect_child(wpid);
                if (wpid == -1) {
                        if (requested_transition == death_single ||
                            requested_transition == reroot)
                                return (state_func_t) requested_transition;
                        if (errno == EINTR)
                                continue;
                        warning("wait for %s on %s failed: %m; going to "
                            "single user mode", shell, script);
                        return (state_func_t) single_user;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("init: %s on %s stopped, restarting\n",
                            shell, script);
                        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;

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

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

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

        return (state_func_t) 0;
}

/*
 * 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: %s", strerror(errno));
        if ((session_db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == NULL) {
                emergency("session database open: %s", strerror(errno));
                return (1);
        }
        return (0);

}

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

        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: %s", sp->se_process, strerror(errno));
}

/*
 * 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: %s", sp->se_process, strerror(errno));
}

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

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

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

        if ((argv[argc++] = strk(command)) == NULL) {
                free(argv);
                return (NULL);
        }
        while ((argv[argc++] = strk((char *) 0)) != 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_space);
                free(sp->se_getty_argv);
        }
        if (sp->se_window) {
                free(sp->se_window);
                free(sp->se_window_argv_space);
                free(sp->se_window_argv);
        }
        if (sp->se_type)
                free(sp->se_type);
        free(sp);
}

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

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

        sp = (session_t *) calloc(1, sizeof (session_t));

        sp->se_flags |= SE_PRESENT;

        if ((typ->ty_status & TTY_IFEXISTS) != 0)
                sp->se_flags |= SE_IFEXISTS;

        if ((typ->ty_status & TTY_IFCONSOLE) != 0)
                sp->se_flags |= SE_IFCONSOLE;

        if (asprintf(&sp->se_device, "%s%s", _PATH_DEV, typ->ty_name) < 0)
                err(1, "asprintf");

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

        sp->se_next = 0;
        if (sprev == NULL) {
                sessions = sp;
                sp->se_prev = 0;
        } 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_space);
                free(sp->se_getty_argv);
        }
        if (asprintf(&sp->se_getty, "%s %s", typ->ty_getty, typ->ty_name) < 0)
                err(1, "asprintf");
        sp->se_getty_argv_space = strdup(sp->se_getty);
        sp->se_getty_argv = construct_argv(sp->se_getty_argv_space);
        if (sp->se_getty_argv == NULL) {
                warning("can't parse getty for port %s", sp->se_device);
                free(sp->se_getty);
                free(sp->se_getty_argv_space);
                sp->se_getty = sp->se_getty_argv_space = 0;
                return (0);
        }
        if (sp->se_window) {
                free(sp->se_window);
                free(sp->se_window_argv_space);
                free(sp->se_window_argv);
        }
        sp->se_window = sp->se_window_argv_space = 0;
        sp->se_window_argv = 0;
        if (typ->ty_window) {
                sp->se_window = strdup(typ->ty_window);
                sp->se_window_argv_space = strdup(sp->se_window);
                sp->se_window_argv = construct_argv(sp->se_window_argv_space);
                if (sp->se_window_argv == NULL) {
                        warning("can't parse window for port %s",
                            sp->se_device);
                        free(sp->se_window_argv_space);
                        free(sp->se_window);
                        sp->se_window = sp->se_window_argv_space = 0;
                        return (0);
                }
        }
        if (sp->se_type)
                free(sp->se_type);
        sp->se_type = typ->ty_type ? strdup(typ->ty_type) : 0;
        return (1);
}

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

        /*
         * Destroy any previous session state.
         * There shouldn't be any, but just in case...
         */
        for (sp = sessions; sp; sp = snext) {
                snext = sp->se_next;
                free_session(sp);
        }
        sessions = 0;
        if (start_session_db())
                return (state_func_t) single_user;

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

        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;
        char term[64], *env[2];
        int status;

        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) {
                waitpid(-1, &status, 0);
                return;
        }

        /* reparent window process to the init to not make a zombie on exit */
        if ((pid = fork()) == -1) {
                emergency("can't fork for window system on port %s: %m",
                    sp->se_device);
                _exit(1);
        }
        if (pid)
                _exit(0);

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

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

#ifdef LOGIN_CAP
        setprocresources(RESOURCE_WINDOW);
#endif
        if (sp->se_type) {
                /* Don't use malloc after fork */
                strcpy(term, "TERM=");
                strlcat(term, sp->se_type, sizeof(term));
                env[0] = term;
                env[1] = NULL;
        }
        else
                env[0] = NULL;
        execve(sp->se_window_argv[0], sp->se_window_argv, env);
        stall("can't exec window system '%s' for port %s: %m",
                sp->se_window_argv[0], sp->se_device);
        _exit(1);
}

/*
 * Start a login session running.
 */
static pid_t
start_getty(session_t *sp)
{
        pid_t pid;
        sigset_t mask;
        time_t current_time = time((time_t *) 0);
        int too_quick = 0;
        char term[64], *env[2];

        if (current_time >= sp->se_started &&
            current_time - sp->se_started < GETTY_SPACING) {
                if (++sp->se_nspace > GETTY_NSPACE) {
                        sp->se_nspace = 0;
                        too_quick = 1;
                }
        } 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;

        if (too_quick) {
                warning("getty repeating too quickly on port %s, sleeping %d secs",
                    sp->se_device, GETTY_SLEEP);
                sleep((unsigned) GETTY_SLEEP);
        }

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

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

#ifdef LOGIN_CAP
        setprocresources(RESOURCE_GETTY);
#endif
        if (sp->se_type) {
                /* Don't use malloc after fork */
                strcpy(term, "TERM=");
                strlcat(term, sp->se_type, sizeof(term));
                env[0] = term;
                env[1] = NULL;
        } else
                env[0] = NULL;
        execve(sp->se_getty_argv[0], sp->se_getty_argv, env);
        stall("can't exec getty '%s' for port %s: %m",
                sp->se_getty_argv[0], sp->se_device);
        _exit(1);
}

/*
 * Return 1 if the session is defined as "onifexists"
 * or "onifconsole" and the device node does not exist.
 */
static int
session_has_no_tty(session_t *sp)
{
        int fd;

        if ((sp->se_flags & SE_IFEXISTS) == 0 &&
            (sp->se_flags & SE_IFCONSOLE) == 0)
                return (0);

        fd = open(sp->se_device, O_RDONLY | O_NONBLOCK, 0);
        if (fd < 0) {
                if (errno == ENOENT)
                        return (1);
                return (0);
        }

        close(fd);
        return (0);
}

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

        if (! sessions)
                return;

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

        del_session(sp);
        sp->se_process = 0;

        if (sp->se_flags & SE_SHUTDOWN ||
            session_has_no_tty(sp)) {
                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;
        sp->se_started = time((time_t *) 0);
        add_session(sp);
}

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

        switch (sig) {
        case SIGHUP:
                if (current_state == read_ttys || current_state == multi_user ||
                    current_state == clean_ttys || current_state == catatonia)
                        requested_transition = clean_ttys;
                break;
        case SIGUSR2:
                howto = RB_POWEROFF;
        case SIGUSR1:
                howto |= RB_HALT;
        case SIGWINCH:
        case SIGINT:
                if (sig == SIGWINCH)
                        howto |= RB_POWERCYCLE;
                Reboot = TRUE;
        case SIGTERM:
                if (current_state == read_ttys || current_state == multi_user ||
                    current_state == clean_ttys || current_state == catatonia)
                        requested_transition = death;
                else
                        requested_transition = death_single;
                break;
        case SIGTSTP:
                if (current_state == runcom || current_state == read_ttys ||
                    current_state == clean_ttys ||
                    current_state == multi_user || current_state == catatonia)
                        requested_transition = catatonia;
                break;
        case SIGEMT:
                requested_transition = reroot;
                break;
        default:
                requested_transition = 0;
                break;
        }
}

/*
 * Take the system multiuser.
 */
static state_func_t
multi_user(void)
{
        pid_t pid;
        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 (session_has_no_tty(sp))
                        continue;
                if ((pid = start_getty(sp)) == -1) {
                        /* serious trouble */
                        requested_transition = clean_ttys;
                        break;
                }
                sp->se_process = pid;
                sp->se_started = time((time_t *) 0);
                add_session(sp);
        }

        while (!requested_transition)
                if ((pid = waitpid(-1, (int *) 0, 0)) != -1)
                        collect_child(pid);

        return (state_func_t) requested_transition;
}

/*
 * This is an (n*2)+(n^2) algorithm.  We hope it isn't run often...
 */
static state_func_t
clean_ttys(void)
{
        session_t *sp, *sprev;
        struct ttyent *typ;
        int devlen;
        char *old_getty, *old_window, *old_type;

        /*
         * mark all sessions for death, (!SE_PRESENT)
         * as we find or create new ones they'll be marked as keepers,
         * we'll later nuke all the ones not found in /etc/ttys
         */
        for (sp = sessions; sp != NULL; sp = sp->se_next)
                sp->se_flags &= ~SE_PRESENT;

        devlen = sizeof(_PATH_DEV) - 1;
        while ((typ = getttyent()) != NULL) {
                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) {
                        /* we want this one to live */
                        sp->se_flags |= SE_PRESENT;
                        if ((typ->ty_status & TTY_ON) == 0 ||
                            typ->ty_getty == 0) {
                                sp->se_flags |= SE_SHUTDOWN;
                                kill(sp->se_process, SIGHUP);
                                continue;
                        }
                        sp->se_flags &= ~SE_SHUTDOWN;
                        old_getty = sp->se_getty ? strdup(sp->se_getty) : 0;
                        old_window = sp->se_window ? strdup(sp->se_window) : 0;
                        old_type = sp->se_type ? strdup(sp->se_type) : 0;
                        if (setupargv(sp, typ) == 0) {
                                warning("can't parse getty for port %s",
                                        sp->se_device);
                                sp->se_flags |= SE_SHUTDOWN;
                                kill(sp->se_process, SIGHUP);
                        }
                        else if (   !old_getty
                                 || (!old_type && sp->se_type)
                                 || (old_type && !sp->se_type)
                                 || (!old_window && sp->se_window)
                                 || (old_window && !sp->se_window)
                                 || (strcmp(old_getty, sp->se_getty) != 0)
                                 || (old_window && strcmp(old_window, sp->se_window) != 0)
                                 || (old_type && strcmp(old_type, sp->se_type) != 0)
                                ) {
                                /* Don't set SE_SHUTDOWN here */
                                sp->se_nspace = 0;
                                sp->se_started = 0;
                                kill(sp->se_process, SIGHUP);
                        }
                        if (old_getty)
                                free(old_getty);
                        if (old_window)
                                free(old_window);
                        if (old_type)
                                free(old_type);
                        continue;
                }

                new_session(sprev, typ);
        }

        endttyent();

        /*
         * sweep through and kill all deleted sessions
         * ones who's /etc/ttys line was deleted (SE_PRESENT unset)
         */
        for (sp = sessions; sp != NULL; sp = sp->se_next) {
                if ((sp->se_flags & SE_PRESENT) == 0) {
                        sp->se_flags |= SE_SHUTDOWN;
                        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;
}

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

        (void)sig;
        clang = 1;
}

/*
 * Bring the system down to single user.
 */
static state_func_t
death(void)
{
        int block, blocked;
        size_t len;

        /* Temporarily block suspend. */
        len = sizeof(blocked);
        block = 1;
        if (sysctlbyname("kern.suspend_blocked", &blocked, &len,
            &block, sizeof(block)) == -1)
                blocked = 0;

        /*
         * Also revoke the TTY here.  Because runshutdown() may reopen
         * the TTY whose getty we're killing here, there is no guarantee
         * runshutdown() will perform the initial open() call, causing
         * the terminal attributes to be misconfigured.
         */
        revoke_ttys();

        /* Try to run the rc.shutdown script within a period of time */
        runshutdown();

        /* Unblock suspend if we blocked it. */
        if (!blocked)
                sysctlbyname("kern.suspend_blocked", NULL, NULL,
                    &blocked, sizeof(blocked));

        return (state_func_t) death_single;
}

/*
 * Do what is necessary to reinitialize single user mode or reboot
 * from an incomplete state.
 */
static state_func_t
death_single(void)
{
        int i;
        pid_t pid;
        static const int death_sigs[2] = { SIGTERM, SIGKILL };

        revoke(_PATH_CONSOLE);

        for (i = 0; i < 2; ++i) {
                if (kill(-1, death_sigs[i]) == -1 && errno == ESRCH)
                        return (state_func_t) single_user;

                clang = 0;
                alarm(DEATH_WATCH);
                do
                        if ((pid = waitpid(-1, (int *)0, 0)) != -1)
                                collect_child(pid);
                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;
}

static void
revoke_ttys(void)
{
        session_t *sp;

        for (sp = sessions; sp; sp = sp->se_next) {
                sp->se_flags |= SE_SHUTDOWN;
                kill(sp->se_process, SIGHUP);
                revoke(sp->se_device);
        }
}

/*
 * Run the system shutdown script.
 *
 * Exit codes:      XXX I should document more
 * -2       shutdown script terminated abnormally
 * -1       fatal error - can't run script
 * 0        good.
 * >0       some error (exit code)
 */
static int
runshutdown(void)
{
        pid_t pid, wpid;
        int status;
        int shutdowntimeout;
        size_t len;
        char *argv[4];
        struct stat sb;

        /*
         * rc.shutdown is optional, so to prevent any unnecessary
         * complaints from the shell we simply don't run it if the
         * file does not exist. If the stat() here fails for other
         * reasons, we'll let the shell complain.
         */
        if (stat(_PATH_RUNDOWN, &sb) == -1 && errno == ENOENT)
                return 0;

        if ((pid = fork()) == 0) {
                char _sh[]      = "sh";
                char _reboot[]  = "reboot";
                char _single[]  = "single";
                char _path_rundown[] = _PATH_RUNDOWN;

                argv[0] = _sh;
                argv[1] = _path_rundown;
                argv[2] = Reboot ? _reboot : _single;
                argv[3] = NULL;
                
                execute_script(argv);
                _exit(1);       /* force single user mode */
        }

        if (pid == -1) {
                emergency("can't fork for %s: %m", _PATH_RUNDOWN);
                while (waitpid(-1, (int *) 0, WNOHANG) > 0)
                        continue;
                sleep(STALL_TIMEOUT);
                return -1;
        }

        len = sizeof(shutdowntimeout);
        if (sysctlbyname("kern.init_shutdown_timeout", &shutdowntimeout, &len,
            NULL, 0) == -1 || shutdowntimeout < 2)
                shutdowntimeout = DEATH_SCRIPT;
        alarm(shutdowntimeout);
        clang = 0;
        /*
         * Copied from single_user().  This is a bit paranoid.
         * Use the same ALRM handler.
         */
        do {
                if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
                        collect_child(wpid);
                if (clang == 1) {
                        /* we were waiting for the sub-shell */
                        kill(wpid, SIGTERM);
                        warning("timeout expired for %s: %m; going to "
                            "single user mode", _PATH_RUNDOWN);
                        return -1;
                }
                if (wpid == -1) {
                        if (errno == EINTR)
                                continue;
                        warning("wait for %s failed: %m; going to "
                            "single user mode", _PATH_RUNDOWN);
                        return -1;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("init: %s stopped, restarting\n",
                            _PATH_RUNDOWN);
                        kill(pid, SIGCONT);
                        wpid = -1;
                }
        } while (wpid != pid && !clang);

        /* Turn off the alarm */
        alarm(0);

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

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

        if (!WIFEXITED(status)) {
                warning("%s terminated abnormally, going to "
                    "single user mode", _PATH_RUNDOWN);
                return -2;
        }

        if ((status = WEXITSTATUS(status)) != 0)
                warning("%s returned status %d", _PATH_RUNDOWN, status);

        return status;
}

static char *
strk(char *p)
{
        static char *t;
        char *q;
        int c;

        if (p)
                t = p;
        if (!t)
                return 0;

        c = *t;
        while (c == ' ' || c == '\t' )
                c = *++t;
        if (!c) {
                t = 0;
                return 0;
        }
        q = t;
        if (c == '\'') {
                c = *++t;
                q = t;
                while (c && c != '\'')
                        c = *++t;
                if (!c)  /* unterminated string */
                        q = t = 0;
                else
                        *t++ = 0;
        } else {
                while (c && c != ' ' && c != '\t' )
                        c = *++t;
                *t++ = 0;
                if (!c)
                        t = 0;
        }
        return q;
}

#ifdef LOGIN_CAP
static void
setprocresources(const char *cname)
{
        login_cap_t *lc;
        if ((lc = login_getclassbyname(cname, NULL)) != NULL) {
                setusercontext(lc, (struct passwd*)NULL, 0,
                    LOGIN_SETENV |
                    LOGIN_SETPRIORITY | LOGIN_SETRESOURCES |
                    LOGIN_SETLOGINCLASS | LOGIN_SETCPUMASK);
                login_close(lc);
        }
}
#endif