More minor IPI work.

[dragonfly/vkernel-mp.git] / sbin / init / init.c

/*-
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
 * @(#)init.c   8.1 (Berkeley) 7/15/93
 * $FreeBSD: src/sbin/init/init.c,v 1.38.2.8 2001/10/22 11:27:32 des Exp $
 * $DragonFly: src/sbin/init/init.c,v 1.9 2005/11/06 13:23:40 swildner Exp $
 */

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

#include <db.h>
#include <errno.h>
#include <fcntl.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>

#ifdef __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

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

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

#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"

/*
 * 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);

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

static void     setctty(const char *);

typedef struct init_session {
        int     se_index;               /* index of entry in ttys file */
        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 */
        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      handle(sig_t, ...);
static void      delset(sigset_t *, ...);

static void      stall(const char *, ...);
static void      warning(const char *, ...);
static void      emergency(const char *, ...);
static void      disaster(int);
static void      badsys(int);
static int       runshutdown(void);
static char     *strk(char *);

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 void transition(state_t);

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

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 char     *get_chroot(void);
static int      setupargv(session_t *, struct ttyent *);
#ifdef LOGIN_CAP
static void     setprocresources(const char *);
#endif

static void     clear_session_logs(session_t *);

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 int Reboot = FALSE;
static int howto = RB_AUTOBOOT;

static DB *session_db;
static volatile sig_atomic_t clang;
static session_t *sessions;
state_t requested_transition = runcom;

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


        /* 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;
                                        default:
                                                goto invalid;
                                }
                                kill(1, sig);
                                _exit(0);
                        } else
invalid:
                                errx(1, "invalid run-level ``%s''", argv[1]);
                } else
#endif
                        errx(1, "already running");
        }
        /*
         * Note that this does NOT open a file...
         * Does 'init' deserve its own facility number?
         */
        openlog("init", LOG_CONS|LOG_ODELAY, LOG_AUTH);

        /*
         * If chroot has been requested by the boot loader,
         * do it now.  Try to be robust:  If the directory
         * doesn't exist, continue anyway.
         */
        init_chroot = get_chroot();
        if (init_chroot != NULL) {
                if (chdir(init_chroot) == -1 || chroot(".") == -1)
                        warning("can't chroot to %s: %m", init_chroot);
                free(init_chroot);
        }

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

        if (stat("/dev/null", &sts) < 0) {
                warning("/dev MAY BE CORRUPT! /dev/null is missing!\n");
                sleep(5);
        }

        /*
         * This code assumes that we always get arguments through flags,
         * never through bits set in some random machine register.
         */
        while ((c = getopt(argc, argv, "dsf")) != -1)
                switch (c) {
                case 'd':
                        /* We don't support DEVFS. */
                        break;
                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");

        /*
         * 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, SIGINT, SIGTERM, SIGTSTP,
                SIGUSR1, SIGUSR2, 0);
        handle(alrm_handler, SIGALRM, 0);
        sigfillset(&mask);
        delset(&mask, SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGSYS,
                SIGXCPU, SIGXFSZ, SIGHUP, SIGINT, SIGTERM, SIGTSTP, SIGALRM, 
                SIGUSR1, SIGUSR2, 0);
        sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        sa.sa_handler = SIG_IGN;
        sigaction(SIGTTIN, &sa, (struct sigaction *)0);
        sigaction(SIGTTOU, &sa, (struct sigaction *)0);

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

        /*
         * 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;
        sigfillset(&mask_everything);

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

/*
 * Get the value of the "init_chroot" variable from the
 * kernel environment (or NULL if not set).
 */

static char *
get_chroot(void)
{
        static const char ichname[] = "init_chroot=";   /* includes '=' */
        const int ichlen = strlen(ichname);
        int real_oid[CTL_MAXNAME];
        char sbuf[1024];
        size_t oidlen;
        char *res;
        int slen;
        int i;

        oidlen = __arysize(real_oid);
        if (sysctlnametomib("kern.environment", real_oid, &oidlen)) {
                warning("cannot find kern.environment base sysctl OID");
                return NULL;
        }
        if (oidlen + 1 >= __arysize(real_oid)) {
                warning("kern.environment OID is too large!");
                return NULL;
        }
        res = NULL;
        real_oid[oidlen] = 0;

        for (i = 0; ; i++) {
                real_oid[oidlen + 1] = i;
                slen = sizeof(sbuf);
                if (sysctl(real_oid, oidlen + 2, sbuf, &slen, NULL, 0) < 0) {
                        if (errno != ENOENT)
                                warning("sysctl kern.environment.%d: %m", i);
                        break;
                }

                /*
                 * slen includes the terminating \0, but do a few sanity
                 * checks anyway.
                 */
                if (slen == 0)
                        continue;
                sbuf[slen - 1] = 0;
                if (strncmp(sbuf, ichname, ichlen) != 0)
                        continue;
                if (sbuf[ichlen])
                        res = strdup(sbuf + ichlen);
                break;
        }
        return (res);
}

/*
 * 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)
{
        for (;;)
                s = (state_t) (*s)();
}

/*
 * 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)
{
        char *line = sp->se_device + sizeof(_PATH_DEV) - 1;

        if (logout(line))
                logwtmp(line, "", "");
}

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

        revoke(name);
        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(1);
        }
}

/*
 * 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 = _PATH_BSHELL;
        const char *argv[2];
#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();
                alarm(2);
                pause();
                reboot(howto);
                _exit(0);
        }

        if ((pid = fork()) == 0) {
                /*
                 * Start the single user session.
                 */
                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 && (typ->ty_status & TTY_SECURE) == 0 &&
                    pp && *pp->pw_passwd) {
                        write(2, banner, sizeof banner - 1);
                        for (;;) {
                                clear = getpass("Password:");
                                if (clear == 0 || *clear == '\0')
                                        _exit(0);
                                password = crypt(clear, pp->pw_passwd);
                                bzero(clear, _PASSWORD_LEN);
                                if (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 " _PATH_BSHELL ": "
                        write(STDERR_FILENO, SHREQUEST, sizeof(SHREQUEST) - 1);
                        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, (sigset_t *) 0);

                /*
                 * Fire off a shell.
                 * If the default one doesn't work, try the Bourne shell.
                 */
                argv[0] = "-sh";
                argv[1] = 0;
                execv(shell, __DECONST(char **, argv));
                emergency("can't exec %s for single user: %m", shell);
                execv(_PATH_BSHELL, __DECONST(char **, 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.");
                        sleep(STALL_TIMEOUT);
                        _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)
{
        pid_t pid, wpid;
        int status;
        const char *argv[4];
        struct sigaction sa;

        if ((pid = fork()) == 0) {
                sigemptyset(&sa.sa_mask);
                sa.sa_flags = 0;
                sa.sa_handler = SIG_IGN;
                sigaction(SIGTSTP, &sa, (struct sigaction *)0);
                sigaction(SIGHUP, &sa, (struct sigaction *)0);

                setctty(_PATH_CONSOLE);

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

                sigprocmask(SIG_SETMASK, &sa.sa_mask, (sigset_t *) 0);

#ifdef LOGIN_CAP
                setprocresources(RESOURCE_RC);
#endif
                execv(_PATH_BSHELL, __DECONST(char **, argv));
                stall("can't exec %s for %s: %m", _PATH_BSHELL, _PATH_RUNCOM);
                _exit(1);       /* force single user mode */
        }

        if (pid == -1) {
                emergency("can't fork for %s on %s: %m",
                        _PATH_BSHELL, _PATH_RUNCOM);
                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)
                                return (state_func_t) death;
                        if (errno == EINTR)
                                continue;
                        warning("wait for %s on %s failed: %m; going to single user mode",
                                _PATH_BSHELL, _PATH_RUNCOM);
                        return (state_func_t) single_user;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("init: %s on %s stopped, restarting\n",
                                _PATH_BSHELL, _PATH_RUNCOM);
                        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",
                        _PATH_BSHELL, _PATH_RUNCOM);
                return (state_func_t) single_user;
        }

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

        runcom_mode = AUTOBOOT;         /* the default */
        /* NB: should send a message to the session logger to avoid blocking. */
        logwtmp("~", "reboot", "");
        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: %s", strerror(errno));
        if ((session_db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == 0) {
                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 = malloc(((strlen(command) + 1) / 2 + 1)
                                                * sizeof (char *));

        if ((argv[argc++] = strk(command)) == 0) {
                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, int session_index, struct ttyent *typ)
{
        session_t *sp;
        int fd;

        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_index = session_index;
        sp->se_flags |= SE_PRESENT;

        sp->se_device = malloc(sizeof(_PATH_DEV) + strlen(typ->ty_name));
        sprintf(sp->se_device, "%s%s", _PATH_DEV, typ->ty_name);

        /*
         * Attempt to open the device, if we get "device not configured"
         * then don't add the device to the session list.
         */
        if ((fd = open(sp->se_device, O_RDONLY | O_NONBLOCK, 0)) < 0) {
                if (errno == ENXIO) {
                        free_session(sp);
                        return (0);
                }
        } else
                close(fd);

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

        sp->se_next = 0;
        if (sprev == 0) {
                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);
        }
        sp->se_getty = malloc(strlen(typ->ty_getty) + strlen(typ->ty_name) + 2);
        sprintf(sp->se_getty, "%s %s", typ->ty_getty, typ->ty_name);
        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 == 0) {
                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 == 0) {
                        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)
{
        int session_index = 0;
        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) {
                if (sp->se_process)
                        clear_session_logs(sp);
                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, ++session_index, 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];

        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;

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

        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=");
                strncat(term, sp->se_type, sizeof(term) - 6);
                env[0] = term;
                env[1] = 0;
        }
        else
                env[0] = 0;
        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, (sigset_t *) 0);

#ifdef LOGIN_CAP
        setprocresources(RESOURCE_GETTY);
#endif
        if (sp->se_type) {
                /* Don't use malloc after fork */
                strcpy(term, "TERM=");
                strncat(term, sp->se_type, sizeof(term) - 6);
                env[0] = term;
                env[1] = 0;
        }
        else
                env[0] = 0;
        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);
}

/*
 * 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;

        clear_session_logs(sp);
        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;
        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:
                requested_transition = clean_ttys;
                break;
        case SIGUSR2:
                howto = RB_POWEROFF;
        case SIGUSR1:
                howto |= RB_HALT;
        case SIGINT:
                Reboot = TRUE;
        case SIGTERM:
                requested_transition = death;
                break;
        case SIGTSTP:
                requested_transition = catatonia;
                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 ((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 session_index = 0;
        int devlen;
        char *old_getty, *old_window, *old_type;

        if (! sessions)
                return (state_func_t) multi_user;

        /* 
         * 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) {
                ++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) {
                        /* we want this one to live */
                        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;
                                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, session_index, 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 __unused)
{
        clang = 1;
}

/*
 * Bring the system down to single user.
 */
static state_func_t
death(void)
{
        session_t *sp;
        int i;
        pid_t pid;
        static const int death_sigs[2] = { SIGTERM, SIGKILL };

        /* NB: should send a message to the session logger to avoid blocking. */
        logwtmp("~", "shutdown", "");

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

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

/*
 * 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;
        const char *argv[4];
        struct sigaction sa;
        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) {
                int     fd;

                /* Assume that init already grab console as ctty before */

                sigemptyset(&sa.sa_mask);
                sa.sa_flags = 0;
                sa.sa_handler = SIG_IGN;
                sigaction(SIGTSTP, &sa, (struct sigaction *)0);
                sigaction(SIGHUP, &sa, (struct sigaction *)0);

                if ((fd = open(_PATH_CONSOLE, O_RDWR)) == -1)
                    warning("can't open %s: %m", _PATH_CONSOLE);
                else {
                    dup2(fd, 0);
                    dup2(fd, 1);
                    dup2(fd, 2);
                    if (fd > 2)
                        close(fd);
                }

                /*
                 * Run the shutdown script.
                 */
                argv[0] = "sh";
                argv[1] = _PATH_RUNDOWN;
                if (Reboot)
                        argv[2] = "reboot";
                else
                        argv[2] = "single";
                argv[3] = 0;

                sigprocmask(SIG_SETMASK, &sa.sa_mask, (sigset_t *) 0);

#ifdef LOGIN_CAP
                setprocresources(RESOURCE_RC);
#endif
                execv(_PATH_BSHELL, __DECONST(char **, argv));
                warning("can't exec %s for %s: %m", _PATH_BSHELL, _PATH_RUNDOWN);
                _exit(1);       /* force single user mode */
        }

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

        len = sizeof(shutdowntimeout);
        if (sysctlbyname("kern.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 on %s: %m; going to single user mode",
                                _PATH_BSHELL, _PATH_RUNDOWN);
                        return -1;
                }
                if (wpid == -1) {
                        if (errno == EINTR)
                                continue;
                        warning("wait for %s on %s failed: %m; going to single user mode",
                                _PATH_BSHELL, _PATH_RUNDOWN);
                        return -1;
                }
                if (wpid == pid && WIFSTOPPED(status)) {
                        warning("init: %s on %s stopped, restarting\n",
                                _PATH_BSHELL, _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 on %s terminated abnormally, going to single user mode",
                        _PATH_BSHELL, _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_SETPRIORITY|LOGIN_SETRESOURCES);
                login_close(lc);
        }
}
#endif