Pileus Git - mkinit/blob - src/gettyd.c

   1 #define _GNU_SOURCE
   2
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <stdarg.h>
   6 #include <string.h>
   7 #include <errno.h>
   8 #include <unistd.h>
   9 #include <termios.h>
  10 #include <fcntl.h>
  11
  12 #include <sys/types.h>
  13 #include <sys/stat.h>
  14 #include <sys/ioctl.h>
  15 #include <sys/wait.h>
  16 #include <sys/epoll.h>
  17 #include <sys/signalfd.h>
  18
  19 /* TTY data */
  20 typedef struct tty_t {
  21         char         *path;
  22         int           fd;
  23         int           pid;
  24         struct tty_t *next;
  25 } tty_t;
  26
  27 /* Local Data */
  28 static int running;
  29 static int epoll;
  30 static int sigs;
  31 static tty_t *ttys;
  32
  33 /* Helper functions */
  34 void error(const char *fmt, ...)
  35 {
  36         va_list ap;
  37         va_start(ap, fmt);
  38         fprintf(stderr, "Error ");
  39         vfprintf(stderr, fmt, ap);
  40         fprintf(stderr, ": %s\n", strerror(errno));
  41         va_end(ap);
  42         if (!running)
  43                 exit(1);
  44 }
  45
  46 int add_poll(int fd, void *ptr)
  47 {
  48         struct epoll_event ctl = {
  49                 .events = EPOLLIN,
  50                 .data.ptr = ptr,
  51         };
  52         return epoll_ctl(epoll, EPOLL_CTL_ADD, fd, &ctl);
  53 }
  54
  55 int del_poll(int fd)
  56 {
  57         return epoll_ctl(epoll, EPOLL_CTL_DEL, fd, NULL);
  58 }
  59
  60 static int start_tty(tty_t *tty)
  61 {
  62         const char *prompt = "[Press enter to login]";
  63         struct termios attr;
  64
  65         if (chown(tty->path, 0, 0) < 0)
  66                 return -1;
  67         if (chmod(tty->path, 0600) < 0)
  68                 return -1;
  69         if ((tty->fd = open(tty->path, O_RDWR|O_NOCTTY|O_NONBLOCK|O_CLOEXEC, 0)) < 0)
  70                 return -1;
  71         if (add_poll(tty->fd, tty) < 0)
  72                 return -1;
  73
  74         tcgetattr(tty->fd, &attr);
  75         attr.c_lflag &= ~ECHO;
  76         tcsetattr(tty->fd, TCSANOW, &attr);
  77
  78         write(tty->fd, "\033c", 2);
  79         write(tty->fd, "\033[?1c", 5);
  80         write(tty->fd, prompt, strlen(prompt));
  81
  82         return 0;
  83 }
  84
  85 static void read_tty(tty_t *tty)
  86 {
  87         int flags;
  88         char ch, login;
  89         while (read(tty->fd, &ch, 1) == 1)
  90                 if (ch == '\n' || ch == '\r')
  91                         login = 1;
  92         if (!login)
  93                 return;
  94         if ((tty->pid = fork()) < 0)
  95                 return;
  96         if (tty->pid == 0) {
  97                 if (putenv("TERM=linux"))
  98                         error("setting environment");
  99                 if (setsid() < 0)
 100                         error("setting sid");
 101                 if (write(tty->fd, "\033c", 2) < 0)
 102                         error("resetting tty");
 103                 if ((flags = fcntl(tty->fd, F_GETFL)) < 0)
 104                         error("getting fd flags");
 105                 if (fcntl(tty->fd, F_SETFL, flags&~O_NONBLOCK) < 0)
 106                         error("setting blocking flags");
 107                 if (ioctl(tty->fd, TIOCSCTTY, 0) < 0)
 108                         error("setting ctty");
 109                 if (dup2(tty->fd, 0) != 0)
 110                         error("setting stdin");
 111                 if (dup2(tty->fd, 1) != 1)
 112                         error("setting stdout");
 113                 if (dup2(tty->fd, 2) != 2)
 114                         error("setting stderr");
 115                 if (execl("/bin/login", "login", NULL) < 0)
 116                         error("execing login program");
 117         }
 118         del_poll(tty->fd);
 119         close(tty->fd);
 120 }
 121
 122 void on_child(void)
 123 {
 124         struct signalfd_siginfo info;
 125         if (read(sigs, &info, sizeof(info)) != sizeof(info))
 126                 return;
 127         if (info.ssi_signo != SIGCHLD)
 128                 return;
 129
 130         int status;
 131         pid_t pid;
 132         tty_t *tty;
 133         while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
 134                 for (tty = ttys; tty; tty = tty->next) {
 135                         if (pid == tty->pid) {
 136                                 tty->pid = 0;
 137                                 start_tty(tty);
 138                         }
 139                 }
 140         }
 141 }
 142
 143 /* Main */
 144 int main(int argc, char **argv)
 145 {
 146         int i, count;
 147         tty_t *tty;
 148         sigset_t mask;
 149
 150         /* Check arguments */
 151         if (argc <= 1) {
 152                 printf("usage: gettyd <tty> ...\n");
 153                 return 0;
 154         }
 155
 156         /* Setup */
 157         sigemptyset(&mask);
 158         sigaddset(&mask, SIGCHLD);
 159         sigaddset(&mask, SIGHUP);
 160         if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0)
 161                 error("blocking signals");
 162         if ((sigs = signalfd(-1, &mask, SFD_CLOEXEC)) < 0)
 163                 error("creating signal fd");
 164         if ((epoll = epoll_create1(EPOLL_CLOEXEC)) < 0)
 165                 error("creating epoll");
 166         if (add_poll(sigs, &sigs) < 0)
 167                 error("adding signal epoll");
 168
 169         /* Open TTYs */
 170         for (i = 1; i < argc; i++) {
 171                 if (!(tty = malloc(sizeof(tty_t))))
 172                         error("allocating memory");
 173                 if (asprintf(&tty->path, "/dev/%s", argv[i]) < 0)
 174                         error("allocating path name");
 175                 if (start_tty(tty) < 0)
 176                         error("starting tty '%s'", tty->path);
 177                 tty->next = ttys;
 178                 ttys = tty;
 179         }
 180
 181         /* Main loop */
 182         running = 1;
 183         while (1) {
 184                 struct epoll_event event;
 185                 errno = 0;
 186                 count = epoll_wait(epoll, &event, 1, -1);
 187                 if (errno == EINTR)
 188                         continue;
 189                 if (count < 0)
 190                         continue;
 191                 if (event.data.ptr == &sigs)
 192                         on_child();
 193                 else
 194                         read_tty(event.data.ptr);
 195         }
 196
 197         return 0;
 198 }