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 //usage:#define openvt_trivial_usage
  12 //usage:       "[-c N] [-sw] [PROG ARGS]"
  13 //usage:#define openvt_full_usage "\n\n"
  14 //usage:       "Start PROG on a new virtual terminal\n"
  15 //usage:     "\n        -c N    Use specified VT"
  16 //usage:     "\n        -s      Switch to the VT"
  17 /* //usage:     "\n     -l      Run PROG as login shell (by prepending '-')" */
  18 //usage:     "\n        -w      Wait for PROG to exit"
  19 //usage:
  20 //usage:#define openvt_example_usage
  21 //usage:       "openvt 2 /bin/ash\n"
  22
  23 #include <linux/vt.h>
  24 #include "libbb.h"
  25
  26 /* "Standard" openvt's man page (we do not support all of this):
  27
  28 openvt [-c NUM] [-fsulv] [--] [command [args]]
  29
  30 Find the first available VT, and run command on it. Stdio is directed
  31 to that VT. If no command is specified then $SHELL is used.
  32
  33 -c NUM
  34     Use the given VT number, not the first free one.
  35 -f
  36     Force opening a VT: don't try to check if VT is already in use.
  37 -s
  38     Switch to the new VT when starting the command.
  39     The VT of the new command will be made the new current VT.
  40 -u
  41     Figure out the owner of the current VT, and run login as that user.
  42     Suitable to be called by init. Shouldn't be used with -c or -l.
  43 -l
  44     Make the command a login shell: a "-" is prepended to the argv[0]
  45     when command is executed.
  46 -v
  47     Verbose.
  48 -w
  49     Wait for command to complete. If -w and -s are used together,
  50     switch back to the controlling terminal when the command completes.
  51
  52 bbox:
  53 -u: not implemented
  54 -f: always in effect
  55 -l: not implemented, ignored
  56 -v: ignored
  57 -ws: does NOT switch back
  58 */
  59
  60 /* Helper: does this fd understand VT_xxx? */
  61 static int not_vt_fd(int fd)
  62 {
  63         struct vt_stat vtstat;
  64         return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
  65 }
  66
  67 /* Helper: get a fd suitable for VT_xxx */
  68 static int get_vt_fd(void)
  69 {
  70         int fd;
  71
  72         /* Do we, by chance, already have it? */
  73         for (fd = 0; fd < 3; fd++)
  74                 if (!not_vt_fd(fd))
  75                         return fd;
  76         fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
  77         if (fd >= 0 && !not_vt_fd(fd))
  78                 return fd;
  79         bb_error_msg_and_die("can't find open VT");
  80 }
  81
  82 static int find_free_vtno(void)
  83 {
  84         int vtno;
  85         int fd = get_vt_fd();
  86
  87         errno = 0;
  88         /*xfunc_error_retval = 3; - do we need compat? */
  89         if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
  90                 bb_perror_msg_and_die("can't find open VT");
  91 // Not really needed, grep for DAEMON_ONLY_SANITIZE
  92 //      if (fd > 2)
  93 //              close(fd);
  94         return vtno;
  95 }
  96
  97 /* vfork scares gcc, it generates bigger code.
  98  * Keep it away from main program.
  99  * TODO: move to libbb; or adapt existing libbb's spawn().
 100  */
 101 static NOINLINE void vfork_child(char **argv)
 102 {
 103         if (vfork() == 0) {
 104                 /* CHILD */
 105                 /* Try to make this VT our controlling tty */
 106                 setsid(); /* lose old ctty */
 107                 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
 108                 //bb_error_msg("our sid %d", getsid(0));
 109                 //bb_error_msg("our pgrp %d", getpgrp());
 110                 //bb_error_msg("VT's sid %d", tcgetsid(0));
 111                 //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
 112                 BB_EXECVP_or_die(argv);
 113         }
 114 }
 115
 116 int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 117 int openvt_main(int argc UNUSED_PARAM, char **argv)
 118 {
 119         char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
 120         struct vt_stat vtstat;
 121         char *str_c;
 122         int vtno;
 123         int flags;
 124         enum {
 125                 OPT_c = (1 << 0),
 126                 OPT_w = (1 << 1),
 127                 OPT_s = (1 << 2),
 128                 OPT_l = (1 << 3),
 129                 OPT_f = (1 << 4),
 130                 OPT_v = (1 << 5),
 131         };
 132
 133         /* "+" - stop on first non-option */
 134         flags = getopt32(argv, "+c:wslfv", &str_c);
 135         argv += optind;
 136
 137         if (flags & OPT_c) {
 138                 /* Check for illegal vt number: < 1 or > 63 */
 139                 vtno = xatou_range(str_c, 1, 63);
 140         } else {
 141                 vtno = find_free_vtno();
 142         }
 143
 144         /* Grab new VT */
 145         sprintf(vtname, VC_FORMAT, vtno);
 146         /* (Try to) clean up stray open fds above fd 2 */
 147         bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS | DAEMON_ONLY_SANITIZE, NULL);
 148         close(STDIN_FILENO);
 149         /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
 150         xopen(vtname, O_RDWR);
 151         xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);
 152
 153         if (flags & OPT_s) {
 154                 console_make_active(STDIN_FILENO, vtno);
 155         }
 156
 157         if (!argv[0]) {
 158                 argv--;
 159                 argv[0] = (char *) get_shell_name();
 160                 /*argv[1] = NULL; - already is */
 161         }
 162
 163         xdup2(STDIN_FILENO, STDOUT_FILENO);
 164         xdup2(STDIN_FILENO, STDERR_FILENO);
 165
 166 #ifdef BLOAT
 167         {
 168         /* Handle -l (login shell) option */
 169         const char *prog = argv[0];
 170         if (flags & OPT_l)
 171                 argv[0] = xasprintf("-%s", argv[0]);
 172         }
 173 #endif
 174
 175         vfork_child(argv);
 176         if (flags & OPT_w) {
 177                 /* We have only one child, wait for it */
 178                 safe_waitpid(-1, NULL, 0); /* loops on EINTR */
 179                 if (flags & OPT_s) {
 180                         console_make_active(STDIN_FILENO, vtstat.v_active);
 181                         // Compat: even with -c N (try to) disallocate:
 182                         // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
 183                         // openvt: could not deallocate console 9
 184                         xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
 185                 }
 186         }
 187         return EXIT_SUCCESS;
 188 }