source: MondoRescue/branches/3.2/mindi-busybox/loginutils/getty.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * Based on agetty - another getty program for Linux. By W. Z. Venema 1989
 * Ported to Linux by Peter Orbaek <poe@daimi.aau.dk>
 * This program is freely distributable.
 *
 * option added by Eric Rasmussen <ear@usfirst.org> - 12/28/95
 *
 * 1999-02-22 Arkadiusz Mickiewicz <misiek@misiek.eu.org>
 * - Added Native Language Support
 *
 * 1999-05-05 Thorsten Kranzkowski <dl8bcu@gmx.net>
 * - Enabled hardware flow control before displaying /etc/issue
 *
 * 2011-01 Venys Vlasenko
 * - Removed parity detection code. It can't work reliably:
 * if all chars received have bit 7 cleared and odd (or even) parity,
 * it is impossible to determine whether other side is 8-bit,no-parity
 * or 7-bit,odd(even)-parity. It also interferes with non-ASCII usernames.
 * - From now on, we assume that parity is correctly set.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"
#include <syslog.h>
#ifndef IUCLC
# define IUCLC 0
#endif

#ifndef LOGIN_PROCESS
# undef ENABLE_FEATURE_UTMP
# undef ENABLE_FEATURE_WTMP
# define ENABLE_FEATURE_UTMP 0
# define ENABLE_FEATURE_WTMP 0
#endif


/* The following is used for understandable diagnostics */
#ifdef DEBUGGING
static FILE *dbf;
# define DEBUGTERM "/dev/ttyp0"
# define debug(...) do { fprintf(dbf, __VA_ARGS__); fflush(dbf); } while (0)
#else
# define debug(...) ((void)0)
#endif


/*
 * Things you may want to modify.
 *
 * You may disagree with the default line-editing etc. characters defined
 * below. Note, however, that DEL cannot be used for interrupt generation
 * and for line editing at the same time.
 */
#undef  _PATH_LOGIN
#define _PATH_LOGIN "/bin/login"

/* Displayed before the login prompt.
 * If ISSUE is not defined, getty will never display the contents of the
 * /etc/issue file. You will not want to spit out large "issue" files at the
 * wrong baud rate.
 */
#define ISSUE "/etc/issue"

/* Macro to build Ctrl-LETTER. Assumes ASCII dialect */
#define CTL(x)          ((x) ^ 0100)

/*
 * When multiple baud rates are specified on the command line,
 * the first one we will try is the first one specified.
 */
#define MAX_SPEED       10              /* max. nr. of baud rates */

struct globals {
    unsigned timeout;
    const char *login;              /* login program */
    const char *fakehost;
    const char *tty_name;
    char *initstring;               /* modem init string */
    const char *issue;              /* alternative issue file */
    int numspeed;                   /* number of baud rates to try */
    int speeds[MAX_SPEED];          /* baud rates to be tried */
    unsigned char eol;              /* end-of-line char seen (CR or NL) */
    struct termios tty_attrs;
    char line_buf[128];
};

#define G (*ptr_to_globals)
#define INIT_G() do { \
    SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
} while (0)

//usage:#define getty_trivial_usage
//usage:       "[OPTIONS] BAUD_RATE[,BAUD_RATE]... TTY [TERMTYPE]"
//usage:#define getty_full_usage "\n\n"
//usage:       "Open TTY, prompt for login name, then invoke /bin/login\n"
//usage:     "\n    -h      Enable hardware RTS/CTS flow control"
//usage:     "\n    -L      Set CLOCAL (ignore Carrier Detect state)"
//usage:     "\n    -m      Get baud rate from modem's CONNECT status message"
//usage:     "\n    -n      Don't prompt for login name"
//usage:     "\n    -w      Wait for CR or LF before sending /etc/issue"
//usage:     "\n    -i      Don't display /etc/issue"
//usage:     "\n    -f ISSUE_FILE   Display ISSUE_FILE instead of /etc/issue"
//usage:     "\n    -l LOGIN    Invoke LOGIN instead of /bin/login"
//usage:     "\n    -t SEC      Terminate after SEC if no login name is read"
//usage:     "\n    -I INITSTR  Send INITSTR before anything else"
//usage:     "\n    -H HOST     Log HOST into the utmp file as the hostname"
//usage:     "\n"
//usage:     "\nBAUD_RATE of 0 leaves it unchanged"

static const char opt_string[] ALIGN1 = "I:LH:f:hil:mt:wn";
#define F_INITSTRING    (1 << 0)   /* -I */
#define F_LOCAL         (1 << 1)   /* -L */
#define F_FAKEHOST      (1 << 2)   /* -H */
#define F_CUSTISSUE     (1 << 3)   /* -f */
#define F_RTSCTS        (1 << 4)   /* -h */
#define F_NOISSUE       (1 << 5)   /* -i */
#define F_LOGIN         (1 << 6)   /* -l */
#define F_PARSE         (1 << 7)   /* -m */
#define F_TIMEOUT       (1 << 8)   /* -t */
#define F_WAITCRLF      (1 << 9)   /* -w */
#define F_NOPROMPT      (1 << 10)  /* -n */


/* convert speed string to speed code; return <= 0 on failure */
static int bcode(const char *s)
{
    int value = bb_strtou(s, NULL, 10); /* yes, int is intended! */
    if (value < 0) /* bad terminating char, overflow, etc */
        return value;
    return tty_value_to_baud(value);
}

/* parse alternate baud rates */
static void parse_speeds(char *arg)
{
    char *cp;

    /* NB: at least one iteration is always done */
    debug("entered parse_speeds\n");
    while ((cp = strsep(&arg, ",")) != NULL) {
        G.speeds[G.numspeed] = bcode(cp);
        if (G.speeds[G.numspeed] < 0)
            bb_error_msg_and_die("bad speed: %s", cp);
        /* note: arg "0" turns into speed B0 */
        G.numspeed++;
        if (G.numspeed > MAX_SPEED)
            bb_error_msg_and_die("too many alternate speeds");
    }
    debug("exiting parse_speeds\n");
}

/* parse command-line arguments */
static void parse_args(char **argv)
{
    char *ts;
    int flags;

    opt_complementary = "-2:t+"; /* at least 2 args; -t N */
    flags = getopt32(argv, opt_string,
        &G.initstring, &G.fakehost, &G.issue,
        &G.login, &G.timeout
    );
    if (flags & F_INITSTRING) {
        G.initstring = xstrdup(G.initstring);
        /* decode \ddd octal codes into chars */
        strcpy_and_process_escape_sequences(G.initstring, G.initstring);
    }
    argv += optind;
    debug("after getopt\n");

    /* We loosen up a bit and accept both "baudrate tty" and "tty baudrate" */
    G.tty_name = argv[0];
    ts = argv[1];            /* baud rate(s) */
    if (isdigit(argv[0][0])) {
        /* A number first, assume it's a speed (BSD style) */
        G.tty_name = ts; /* tty name is in argv[1] */
        ts = argv[0];    /* baud rate(s) */
    }
    parse_speeds(ts);

    if (argv[2])
        xsetenv("TERM", argv[2]);

    debug("exiting parse_args\n");
}

/* set up tty as standard input, output, error */
static void open_tty(void)
{
    /* Set up new standard input, unless we are given an already opened port */
    if (NOT_LONE_DASH(G.tty_name)) {
        if (G.tty_name[0] != '/')
            G.tty_name = xasprintf("/dev/%s", G.tty_name); /* will leak it */

        /* Open the tty as standard input */
        debug("open(2)\n");
        close(0);
        xopen(G.tty_name, O_RDWR | O_NONBLOCK); /* uses fd 0 */

        /* Set proper protections and ownership */
        fchown(0, 0, 0);        /* 0:0 */
        fchmod(0, 0620);        /* crw--w---- */
    } else {
        char *n;
        /*
         * Standard input should already be connected to an open port.
         * Make sure it is open for read/write.
         */
        if ((fcntl(0, F_GETFL) & (O_RDWR|O_RDONLY|O_WRONLY)) != O_RDWR)
            bb_error_msg_and_die("stdin is not open for read/write");

        /* Try to get real tty name instead of "-" */
        n = xmalloc_ttyname(0);
        if (n)
            G.tty_name = n;
    }
    applet_name = xasprintf("getty: %s", skip_dev_pfx(G.tty_name));
}

static void set_tty_attrs(void)
{
    if (tcsetattr_stdin_TCSANOW(&G.tty_attrs) < 0)
        bb_perror_msg_and_die("tcsetattr");
}

/* We manipulate tty_attrs this way:
 * - first, we read existing tty_attrs
 * - init_tty_attrs modifies some parts and sets it
 * - auto_baud and/or BREAK processing can set different speed and set tty attrs
 * - finalize_tty_attrs again modifies some parts and sets tty attrs before
 *   execing login
 */
static void init_tty_attrs(int speed)
{
    /* Try to drain output buffer, with 5 sec timeout.
     * Added on request from users of ~600 baud serial interface
     * with biggish buffer on a 90MHz CPU.
     * They were losing hundreds of bytes of buffered output
     * on tcflush.
     */
    signal_no_SA_RESTART_empty_mask(SIGALRM, record_signo);
    alarm(5);
    tcdrain(STDIN_FILENO);
    alarm(0);

    /* Flush input and output queues, important for modems! */
    tcflush(STDIN_FILENO, TCIOFLUSH);

    /* Set speed if it wasn't specified as "0" on command line */
    if (speed != B0)
        cfsetspeed(&G.tty_attrs, speed);

    /* Initial settings: 8-bit characters, raw mode, blocking i/o.
     * Special characters are set after we have read the login name; all
     * reads will be done in raw mode anyway.
     */
    /* Clear all bits except: */
    G.tty_attrs.c_cflag &= (0
        /* 2 stop bits (1 otherwise)
         * Enable parity bit (both on input and output)
         * Odd parity (else even)
         */
        | CSTOPB | PARENB | PARODD
#ifdef CMSPAR
        | CMSPAR  /* mark or space parity */
#endif
#ifdef CBAUD
        | CBAUD   /* (output) baud rate */
#endif
#ifdef CBAUDEX
        | CBAUDEX /* (output) baud rate */
#endif
#ifdef CIBAUD
        | CIBAUD   /* input baud rate */
#endif
    );
    /* Set: 8 bits; hang up (drop DTR) on last close; enable receive */
    G.tty_attrs.c_cflag |= CS8 | HUPCL | CREAD;
    if (option_mask32 & F_LOCAL) {
        /* ignore Carrier Detect pin:
         * opens don't block when CD is low,
         * losing CD doesn't hang up processes whose ctty is this tty
         */
        G.tty_attrs.c_cflag |= CLOCAL;
    }
#ifdef CRTSCTS
    if (option_mask32 & F_RTSCTS)
        G.tty_attrs.c_cflag |= CRTSCTS; /* flow control using RTS/CTS pins */
#endif
    G.tty_attrs.c_iflag = 0;
    G.tty_attrs.c_lflag = 0;
    /* non-raw output; add CR to each NL */
    G.tty_attrs.c_oflag = OPOST | ONLCR;

    /* reads would block only if < 1 char is available */
    G.tty_attrs.c_cc[VMIN] = 1;
    /* no timeout (reads block forever) */
    G.tty_attrs.c_cc[VTIME] = 0;
#ifdef __linux__
    G.tty_attrs.c_line = 0;
#endif

    set_tty_attrs();

    debug("term_io 2\n");
}

static void finalize_tty_attrs(void)
{
    /* software flow control on output (stop sending if XOFF is recvd);
     * and on input (send XOFF when buffer is full)
     */
    G.tty_attrs.c_iflag |= IXON | IXOFF;
    if (G.eol == '\r') {
        G.tty_attrs.c_iflag |= ICRNL; /* map CR on input to NL */
    }
    /* Other bits in c_iflag:
     * IXANY   Any recvd char enables output (any char is also a XON)
     * INPCK   Enable parity check
     * IGNPAR  Ignore parity errors (drop bad bytes)
     * PARMRK  Mark parity errors with 0xff, 0x00 prefix
     *         (else bad byte is received as 0x00)
     * ISTRIP  Strip parity bit
     * IGNBRK  Ignore break condition
     * BRKINT  Send SIGINT on break - maybe set this?
     * INLCR   Map NL to CR
     * IGNCR   Ignore CR
     * ICRNL   Map CR to NL
     * IUCLC   Map uppercase to lowercase
     * IMAXBEL Echo BEL on input line too long
     * IUTF8   Appears to affect tty's idea of char widths,
     *         observed to improve backspacing through Unicode chars
     */

    /* line buffered input (NL or EOL or EOF chars end a line);
     * recognize INT/QUIT/SUSP chars;
     * echo input chars;
     * echo BS-SP-BS on erase character;
     * echo kill char specially, not as ^c (ECHOKE controls how exactly);
     * erase all input via BS-SP-BS on kill char (else go to next line)
     */
    G.tty_attrs.c_lflag |= ICANON | ISIG | ECHO | ECHOE | ECHOK | ECHOKE;
    /* Other bits in c_lflag:
     * XCASE   Map uppercase to \lowercase [tried, doesn't work]
     * ECHONL  Echo NL even if ECHO is not set
     * ECHOCTL Echo ctrl chars as ^c (else don't echo) - maybe set this?
     * ECHOPRT On erase, echo erased chars
     *         [qwe<BS><BS><BS> input looks like "qwe\ewq/" on screen]
     * NOFLSH  Don't flush input buffer after interrupt or quit chars
     * IEXTEN  Enable extended functions (??)
     *         [glibc says it enables c_cc[LNEXT] "enter literal char"
     *         and c_cc[VDISCARD] "toggle discard buffered output" chars]
     * FLUSHO  Output being flushed (c_cc[VDISCARD] is in effect)
     * PENDIN  Retype pending input at next read or input char
     *         (c_cc[VREPRINT] is being processed)
     * TOSTOP  Send SIGTTOU for background output
     *         (why "stty sane" unsets this bit?)
     */

    G.tty_attrs.c_cc[VINTR] = CTL('C');
    G.tty_attrs.c_cc[VQUIT] = CTL('\\');
    G.tty_attrs.c_cc[VEOF] = CTL('D');
    G.tty_attrs.c_cc[VEOL] = '\n';
#ifdef VSWTC
    G.tty_attrs.c_cc[VSWTC] = 0;
#endif
#ifdef VSWTCH
    G.tty_attrs.c_cc[VSWTCH] = 0;
#endif
    G.tty_attrs.c_cc[VKILL] = CTL('U');
    /* Other control chars:
     * VEOL2
     * VERASE, VWERASE - (word) erase. we may set VERASE in get_logname
     * VREPRINT - reprint current input buffer
     * VLNEXT, VDISCARD, VSTATUS
     * VSUSP, VDSUSP - send (delayed) SIGTSTP
     * VSTART, VSTOP - chars used for IXON/IXOFF
     */

    set_tty_attrs();

    /* Now the newline character should be properly written */
    full_write(STDOUT_FILENO, "\n", 1);
}

/* extract baud rate from modem status message */
static void auto_baud(void)
{
    int nread;

    /*
     * This works only if the modem produces its status code AFTER raising
     * the DCD line, and if the computer is fast enough to set the proper
     * baud rate before the message has gone by. We expect a message of the
     * following format:
     *
     * <junk><number><junk>
     *
     * The number is interpreted as the baud rate of the incoming call. If the
     * modem does not tell us the baud rate within one second, we will keep
     * using the current baud rate. It is advisable to enable BREAK
     * processing (comma-separated list of baud rates) if the processing of
     * modem status messages is enabled.
     */

    G.tty_attrs.c_cc[VMIN] = 0; /* don't block reads (min read is 0 chars) */
    set_tty_attrs();

    /*
     * Wait for a while, then read everything the modem has said so far and
     * try to extract the speed of the dial-in call.
     */
    sleep(1);
    nread = safe_read(STDIN_FILENO, G.line_buf, sizeof(G.line_buf) - 1);
    if (nread > 0) {
        int speed;
        char *bp;
        G.line_buf[nread] = '\0';
        for (bp = G.line_buf; bp < G.line_buf + nread; bp++) {
            if (isdigit(*bp)) {
                speed = bcode(bp);
                if (speed > 0)
                    cfsetspeed(&G.tty_attrs, speed);
                break;
            }
        }
    }

    /* Restore terminal settings */
    G.tty_attrs.c_cc[VMIN] = 1; /* restore to value set by init_tty_attrs */
    set_tty_attrs();
}

/* get user name, establish parity, speed, erase, kill, eol;
 * return NULL on BREAK, logname on success
 */
static char *get_logname(void)
{
    char *bp;
    char c;

    /* Flush pending input (esp. after parsing or switching the baud rate) */
    usleep(100*1000); /* 0.1 sec */
    tcflush(STDIN_FILENO, TCIFLUSH);

    /* Prompt for and read a login name */
    do {
        /* Write issue file and prompt */
#ifdef ISSUE
        if (!(option_mask32 & F_NOISSUE))
            print_login_issue(G.issue, G.tty_name);
#endif
        print_login_prompt();

        /* Read name, watch for break, erase, kill, end-of-line */
        bp = G.line_buf;
        while (1) {
            /* Do not report trivial EINTR/EIO errors */
            errno = EINTR; /* make read of 0 bytes be silent too */
            if (read(STDIN_FILENO, &c, 1) < 1) {
                finalize_tty_attrs();
                if (errno == EINTR || errno == EIO)
                    exit(EXIT_SUCCESS);
                bb_perror_msg_and_die(bb_msg_read_error);
            }

            switch (c) {
            case '\r':
            case '\n':
                *bp = '\0';
                G.eol = c;
                goto got_logname;
            case CTL('H'):
            case 0x7f:
                G.tty_attrs.c_cc[VERASE] = c;
                if (bp > G.line_buf) {
                    full_write(STDOUT_FILENO, "\010 \010", 3);
                    bp--;
                }
                break;
            case CTL('U'):
                while (bp > G.line_buf) {
                    full_write(STDOUT_FILENO, "\010 \010", 3);
                    bp--;
                }
                break;
            case CTL('C'):
            case CTL('D'):
                finalize_tty_attrs();
                exit(EXIT_SUCCESS);
            case '\0':
                /* BREAK. If we have speeds to try,
                 * return NULL (will switch speeds and return here) */
                if (G.numspeed > 1)
                    return NULL;
                /* fall through and ignore it */
            default:
                if ((unsigned char)c < ' ') {
                    /* ignore garbage characters */
                } else if ((int)(bp - G.line_buf) < sizeof(G.line_buf) - 1) {
                    /* echo and store the character */
                    full_write(STDOUT_FILENO, &c, 1);
                    *bp++ = c;
                }
                break;
            }
        } /* end of get char loop */
 got_logname: ;
    } while (G.line_buf[0] == '\0');  /* while logname is empty */

    return G.line_buf;
}

static void alarm_handler(int sig UNUSED_PARAM)
{
    finalize_tty_attrs();
    _exit(EXIT_SUCCESS);
}

int getty_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int getty_main(int argc UNUSED_PARAM, char **argv)
{
    int n;
    pid_t pid, tsid;
    char *logname;

    INIT_G();
    G.login = _PATH_LOGIN;    /* default login program */
#ifdef ISSUE
    G.issue = ISSUE;          /* default issue file */
#endif
    G.eol = '\r';

    /* Parse command-line arguments */
    parse_args(argv);

    /* Create new session and pgrp, lose controlling tty */
    pid = setsid();  /* this also gives us our pid :) */
    if (pid < 0) {
        int fd;
        /* :(
         * docs/ctty.htm says:
         * "This is allowed only when the current process
         *  is not a process group leader".
         * Thus, setsid() will fail if we _already_ are
         * a session leader - which is quite possible for getty!
         */
        pid = getpid();
        if (getsid(0) != pid) {
            //for debugging:
            //bb_perror_msg_and_die("setsid failed:"
            //  " pid %d ppid %d"
            //  " sid %d pgid %d",
            //  pid, getppid(),
            //  getsid(0), getpgid(0));
            bb_perror_msg_and_die("setsid");
        }
        /* Looks like we are already a session leader.
         * In this case (setsid failed) we may still have ctty,
         * and it may be different from tty we need to control!
         * If we still have ctty, on Linux ioctl(TIOCSCTTY)
         * (which we are going to use a bit later) always fails -
         * even if we try to take ctty which is already ours!
         * Try to drop old ctty now to prevent that.
         * Use O_NONBLOCK: old ctty may be a serial line.
         */
        fd = open("/dev/tty", O_RDWR | O_NONBLOCK);
        if (fd >= 0) {
            /* TIOCNOTTY sends SIGHUP to the foreground
             * process group - which may include us!
             * Make sure to not die on it:
             */
            sighandler_t old = signal(SIGHUP, SIG_IGN);
            ioctl(fd, TIOCNOTTY);
            close(fd);
            signal(SIGHUP, old);
        }
    }

    /* Close stdio, and stray descriptors, just in case */
    n = xopen(bb_dev_null, O_RDWR);
    /* dup2(n, 0); - no, we need to handle "getty - 9600" too */
    xdup2(n, 1);
    xdup2(n, 2);
    while (n > 2)
        close(n--);

    /* Logging. We want special flavor of error_msg_and_die */
    die_sleep = 10;
    msg_eol = "\r\n";
    /* most likely will internally use fd #3 in CLOEXEC mode: */
    openlog(applet_name, LOG_PID, LOG_AUTH);
    logmode = LOGMODE_BOTH;

#ifdef DEBUGGING
    dbf = xfopen_for_write(DEBUGTERM);
    for (n = 1; argv[n]; n++) {
        debug(argv[n]);
        debug("\n");
    }
#endif

    /* Open the tty as standard input, if it is not "-" */
    debug("calling open_tty\n");
    open_tty();
    ndelay_off(STDIN_FILENO);
    debug("duping\n");
    xdup2(STDIN_FILENO, 1);
    xdup2(STDIN_FILENO, 2);

    /* Steal ctty if we don't have it yet */
    tsid = tcgetsid(STDIN_FILENO);
    if (tsid < 0 || pid != tsid) {
        if (ioctl(STDIN_FILENO, TIOCSCTTY, /*force:*/ (long)1) < 0)
            bb_perror_msg_and_die("TIOCSCTTY");
    }

#ifdef __linux__
    /* Make ourself a foreground process group within our session */
    if (tcsetpgrp(STDIN_FILENO, pid) < 0)
        bb_perror_msg_and_die("tcsetpgrp");
#endif

    /*
     * The following ioctl will fail if stdin is not a tty, but also when
     * there is noise on the modem control lines. In the latter case, the
     * common course of action is (1) fix your cables (2) give the modem more
     * time to properly reset after hanging up. SunOS users can achieve (2)
     * by patching the SunOS kernel variable "zsadtrlow" to a larger value;
     * 5 seconds seems to be a good value.
     */
    if (tcgetattr(STDIN_FILENO, &G.tty_attrs) < 0)
        bb_perror_msg_and_die("tcgetattr");

    /* Update the utmp file. This tty is ours now! */
    update_utmp(pid, LOGIN_PROCESS, G.tty_name, "LOGIN", G.fakehost);

    /* Initialize tty attrs (raw mode, eight-bit, blocking i/o) */
    debug("calling init_tty_attrs\n");
    init_tty_attrs(G.speeds[0]);

    /* Write the modem init string and DON'T flush the buffers */
    if (option_mask32 & F_INITSTRING) {
        debug("writing init string\n");
        full_write1_str(G.initstring);
    }

    /* Optionally detect the baud rate from the modem status message */
    debug("before autobaud\n");
    if (option_mask32 & F_PARSE)
        auto_baud();

    /* Set the optional timer */
    signal(SIGALRM, alarm_handler);
    alarm(G.timeout); /* if 0, alarm is not set */

    /* Optionally wait for CR or LF before writing /etc/issue */
    if (option_mask32 & F_WAITCRLF) {
        char ch;
        debug("waiting for cr-lf\n");
        while (safe_read(STDIN_FILENO, &ch, 1) == 1) {
            debug("read %x\n", (unsigned char)ch);
            if (ch == '\n' || ch == '\r')
                break;
        }
    }

    logname = NULL;
    if (!(option_mask32 & F_NOPROMPT)) {
        /* NB: init_tty_attrs already set line speed
         * to G.speeds[0] */
        int baud_index = 0;

        while (1) {
            /* Read the login name */
            debug("reading login name\n");
            logname = get_logname();
            if (logname)
                break;
            /* We are here only if G.numspeed > 1 */
            baud_index = (baud_index + 1) % G.numspeed;
            cfsetspeed(&G.tty_attrs, G.speeds[baud_index]);
            set_tty_attrs();
        }
    }

    /* Disable timer */
    alarm(0);

    finalize_tty_attrs();

    /* Let the login program take care of password validation */
    /* We use PATH because we trust that root doesn't set "bad" PATH,
     * and getty is not suid-root applet */
    /* With -n, logname == NULL, and login will ask for username instead */
    BB_EXECLP(G.login, G.login, "--", logname, NULL);
    bb_error_msg_and_die("can't execute '%s'", G.login);
}