release/src/router/busybox/console-tools/openvt.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  *  openvt.c - open a vt to run a command.
   4  *
   5  *  busyboxed by Quy Tonthat <quy@signal3.com>
   6  *  hacked by Tito <farmatito@tiscali.it>
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9  */
  10
  11 #include <linux/vt.h>
  12 #include "libbb.h"
  13
  14 /* "Standard" openvt's man page (we do not support all of this):
  15
  16 openvt [-c NUM] [-fsulv] [--] [command [args]]
  17
  18 Find the first available VT, and run command on it. Stdio is directed
  19 to that VT. If no command is specified then $SHELL is used.
  20
  21 -c NUM
  22     Use the given VT number, not the first free one.
  23 -f
  24     Force opening a VT: don't try to check if VT is already in use.
  25 -s
  26     Switch to the new VT when starting the command.
  27     The VT of the new command will be made the new current VT.
  28 -u
  29     Figure out the owner of the current VT, and run login as that user.
  30     Suitable to be called by init. Shouldn't be used with -c or -l.
  31 -l
  32     Make the command a login shell: a "-" is prepended to the argv[0]
  33     when command is executed.
  34 -v
  35     Verbose.
  36 -w
  37     Wait for command to complete. If -w and -s are used together,
  38     switch back to the controlling terminal when the command completes.
  39
  40 bbox:
  41 -u: not implemented
  42 -f: always in effect
  43 -l: not implemented, ignored
  44 -v: ignored
  45 -ws: does NOT switch back
  46 */
  47
  48 /* Helper: does this fd understand VT_xxx? */
  49 static int not_vt_fd(int fd)
  50 {
  51         struct vt_stat vtstat;
  52         return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
  53 }
  54
  55 /* Helper: get a fd suitable for VT_xxx */
  56 static int get_vt_fd(void)
  57 {
  58         int fd;
  59
  60         /* Do we, by chance, already have it? */
  61         for (fd = 0; fd < 3; fd++)
  62                 if (!not_vt_fd(fd))
  63                         return fd;
  64         fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
  65         if (fd >= 0 && !not_vt_fd(fd))
  66                 return fd;
  67         bb_error_msg_and_die("can't find open VT");
  68 }
  69
  70 static int find_free_vtno(void)
  71 {
  72         int vtno;
  73         int fd = get_vt_fd();
  74
  75         errno = 0;
  76         /*xfunc_error_retval = 3; - do we need compat? */
  77         if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
  78                 bb_perror_msg_and_die("can't find open VT");
  79 // Not really needed, grep for DAEMON_ONLY_SANITIZE
  80 //      if (fd > 2)
  81 //              close(fd);
  82         return vtno;
  83 }
  84
  85 /* vfork scares gcc, it generates bigger code.
  86  * Keep it away from main program.
  87  * TODO: move to libbb; or adapt existing libbb's spawn().
  88  */
  89 static NOINLINE void vfork_child(char **argv)
  90 {
  91         if (vfork() == 0) {
  92                 /* CHILD */
  93                 /* Try to make this VT our controlling tty */
  94                 setsid(); /* lose old ctty */
  95                 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
  96                 //bb_error_msg("our sid %d", getsid(0));
  97                 //bb_error_msg("our pgrp %d", getpgrp());
  98                 //bb_error_msg("VT's sid %d", tcgetsid(0));
  99                 //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
 100                 BB_EXECVP_or_die(argv);
 101         }
 102 }
 103
 104 int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 105 int openvt_main(int argc UNUSED_PARAM, char **argv)
 106 {
 107         char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
 108         struct vt_stat vtstat;
 109         char *str_c;
 110         int vtno;
 111         int flags;
 112         enum {
 113                 OPT_c = (1 << 0),
 114                 OPT_w = (1 << 1),
 115                 OPT_s = (1 << 2),
 116                 OPT_l = (1 << 3),
 117                 OPT_f = (1 << 4),
 118                 OPT_v = (1 << 5),
 119         };
 120
 121         /* "+" - stop on first non-option */
 122         flags = getopt32(argv, "+c:wslfv", &str_c);
 123         argv += optind;
 124
 125         if (flags & OPT_c) {
 126                 /* Check for illegal vt number: < 1 or > 63 */
 127                 vtno = xatou_range(str_c, 1, 63);
 128         } else {
 129                 vtno = find_free_vtno();
 130         }
 131
 132         /* Grab new VT */
 133         sprintf(vtname, VC_FORMAT, vtno);
 134         /* (Try to) clean up stray open fds above fd 2 */
 135         bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS | DAEMON_ONLY_SANITIZE, NULL);
 136         close(STDIN_FILENO);
 137         /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
 138         xopen(vtname, O_RDWR);
 139         xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);
 140
 141         if (flags & OPT_s) {
 142                 console_make_active(STDIN_FILENO, vtno);
 143         }
 144
 145         if (!argv[0]) {
 146                 argv--;
 147                 argv[0] = getenv("SHELL");
 148                 if (!argv[0])
 149                         argv[0] = (char *) DEFAULT_SHELL;
 150                 /*argv[1] = NULL; - already is */
 151         }
 152
 153         xdup2(STDIN_FILENO, STDOUT_FILENO);
 154         xdup2(STDIN_FILENO, STDERR_FILENO);
 155
 156 #ifdef BLOAT
 157         {
 158         /* Handle -l (login shell) option */
 159         const char *prog = argv[0];
 160         if (flags & OPT_l)
 161                 argv[0] = xasprintf("-%s", argv[0]);
 162         }
 163 #endif
 164
 165         vfork_child(argv);
 166         if (flags & OPT_w) {
 167                 /* We have only one child, wait for it */
 168                 safe_waitpid(-1, NULL, 0); /* loops on EINTR */
 169                 if (flags & OPT_s) {
 170                         console_make_active(STDIN_FILENO, vtstat.v_active);
 171                         // Compat: even with -c N (try to) disallocate:
 172                         // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
 173                         // openvt: could not deallocate console 9
 174                         xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
 175                 }
 176         }
 177         return EXIT_SUCCESS;
 178 }