busybox: update to 1.25.0

[tomato.git] / release / src / router / busybox / loginutils / getty.c

/* 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.
 */
//config:config GETTY
//config:       bool "getty"
//config:       default y
//config:       select FEATURE_SYSLOG
//config:       help
//config:         getty lets you log in on a tty. It is normally invoked by init.
//config:
//config:         Note that you can save a few bytes by disabling it and
//config:         using login applet directly.
//config:         If you need to reset tty attributes before calling login,
//config:         this script approximates getty:
//config:
//config:         exec </dev/$1 >/dev/$1 2>&1 || exit 1
//config:         reset
//config:         stty sane; stty ispeed 38400; stty ospeed 38400
//config:         printf "%s login: " "`hostname`"
//config:         read -r login
//config:         exec /bin/login "$login"

//applet:IF_GETTY(APPLET(getty, BB_DIR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_GETTY) += getty.o

#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
         */

        /* ICANON  line buffered input (NL or EOL or EOF chars end a line);
         * ISIG    recognize INT/QUIT/SUSP chars;
         * ECHO    echo input chars;
         * ECHOE   echo BS-SP-BS on erase character;
         * ECHOK   echo kill char specially, not as ^c (ECHOKE controls how exactly);
         * ECHOKE  erase all input via BS-SP-BS on kill char (else go to next line)
         * ECHOCTL Echo ctrl chars as ^c (else echo verbatim:
         *         e.g. up arrow emits "ESC-something" and thus moves cursor up!)
         */
        G.tty_attrs.c_lflag |= ICANON | ISIG | ECHO | ECHOE | ECHOK | ECHOKE | ECHOCTL;
        /* Other bits in c_lflag:
         * XCASE   Map uppercase to \lowercase [tried, doesn't work]
         * ECHONL  Echo NL even if ECHO is not set
         * 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);
}

static void sleep10(void)
{
        sleep(10);
}

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");
                        /*
                         * When we can end up here?
                         * Example: setsid() fails when run alone in interactive shell:
                         *  # getty 115200 /dev/tty2
                         * because shell's child (getty) is put in a new process group.
                         * But doesn't fail if shell is not interactive
                         * (and therefore doesn't create process groups for pipes),
                         * or if getty is not the first process in the process group:
                         *  # true | getty 115200 /dev/tty2
                         */
                }
                /* 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_func = sleep10;
        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, (char *)0);
        bb_error_msg_and_die("can't execute '%s'", G.login);
}