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 //config:config OPENVT
  11 //config:       bool "openvt (7.4 kb)"
  12 //config:       default y
  13 //config:       help
  14 //config:       This program is used to start a command on an unused
  15 //config:       virtual terminal.
  16
  17 //applet:IF_OPENVT(APPLET(openvt, BB_DIR_USR_BIN, BB_SUID_DROP))
  18
  19 //kbuild:lib-$(CONFIG_OPENVT) += openvt.o
  20
  21 //usage:#define openvt_trivial_usage
  22 //usage:       "[-c N] [-sw] [PROG ARGS]"
  23 //usage:#define openvt_full_usage "\n\n"
  24 //usage:       "Start PROG on a new virtual terminal\n"
  25 //usage:     "\n        -c N    Use specified VT"
  26 //usage:     "\n        -s      Switch to the VT"
  27 /* //usage:     "\n     -l      Run PROG as login shell (by prepending '-')" */
  28 //usage:     "\n        -w      Wait for PROG to exit"
  29 //usage:
  30 //usage:#define openvt_example_usage
  31 //usage:       "openvt 2 /bin/ash\n"
  32
  33 #include <linux/vt.h>
  34 #include "libbb.h"
  35
  36 /* "Standard" openvt's man page (we do not support all of this):
  37
  38 openvt [-c NUM] [-fsulv] [--] [command [args]]
  39
  40 Find the first available VT, and run command on it. Stdio is directed
  41 to that VT. If no command is specified then $SHELL is used.
  42
  43 -c NUM
  44     Use the given VT number, not the first free one.
  45 -f
  46     Force opening a VT: don't try to check if VT is already in use.
  47 -s
  48     Switch to the new VT when starting the command.
  49     The VT of the new command will be made the new current VT.
  50 -u
  51     Figure out the owner of the current VT, and run login as that user.
  52     Suitable to be called by init. Shouldn't be used with -c or -l.
  53 -l
  54     Make the command a login shell: a "-" is prepended to the argv[0]
  55     when command is executed.
  56 -v
  57     Verbose.
  58 -w
  59     Wait for command to complete. If -w and -s are used together,
  60     switch back to the controlling terminal when the command completes.
  61
  62 bbox:
  63 -u: not implemented
  64 -f: always in effect
  65 -l: not implemented, ignored
  66 -v: ignored
  67 -ws: does NOT switch back
  68 */
  69
  70 /* Helper: does this fd understand VT_xxx? */
  71 static int not_vt_fd(int fd)
  72 {
  73         struct vt_stat vtstat;
  74         return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
  75 }
  76
  77 /* Helper: get a fd suitable for VT_xxx */
  78 static int get_vt_fd(void)
  79 {
  80         int fd;
  81
  82         /* Do we, by chance, already have it? */
  83         for (fd = 0; fd < 3; fd++)
  84                 if (!not_vt_fd(fd))
  85                         return fd;
  86         fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
  87         if (fd >= 0 && !not_vt_fd(fd))
  88                 return fd;
  89         bb_simple_error_msg_and_die("can't find open VT");
  90 }
  91
  92 static int find_free_vtno(void)
  93 {
  94         int vtno;
  95         int fd = get_vt_fd();
  96
  97         errno = 0;
  98         /*xfunc_error_retval = 3; - do we need compat? */
  99         if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
 100                 bb_simple_perror_msg_and_die("can't find open VT");
 101 // Not really needed, grep for DAEMON_CLOSE_EXTRA_FDS
 102 //      if (fd > 2)
 103 //              close(fd);
 104         return vtno;
 105 }
 106
 107 /* vfork scares gcc, it generates bigger code.
 108  * Keep it away from main program.
 109  * TODO: move to libbb; or adapt existing libbb's spawn().
 110  */
 111 static NOINLINE void vfork_child(char **argv)
 112 {
 113         if (vfork() == 0) {
 114                 /* CHILD */
 115                 /* Try to make this VT our controlling tty */
 116                 setsid(); /* lose old ctty */
 117                 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
 118                 //bb_error_msg("our sid %d", getsid(0));
 119                 //bb_error_msg("our pgrp %d", getpgrp());
 120                 //bb_error_msg("VT's sid %d", tcgetsid(0));
 121                 //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
 122                 BB_EXECVP_or_die(argv);
 123         }
 124 }
 125
 126 int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 127 int openvt_main(int argc UNUSED_PARAM, char **argv)
 128 {
 129         char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
 130         struct vt_stat vtstat;
 131         char *str_c;
 132         int vtno;
 133         int flags;
 134         enum {
 135                 OPT_c = (1 << 0),
 136                 OPT_w = (1 << 1),
 137                 OPT_s = (1 << 2),
 138                 OPT_l = (1 << 3),
 139                 OPT_f = (1 << 4),
 140                 OPT_v = (1 << 5),
 141         };
 142
 143         /* "+" - stop on first non-option */
 144         flags = getopt32(argv, "+c:wslfv", &str_c);
 145         argv += optind;
 146
 147         if (flags & OPT_c) {
 148                 /* Check for illegal vt number: < 1 or > 63 */
 149                 vtno = xatou_range(str_c, 1, 63);
 150         } else {
 151                 vtno = find_free_vtno();
 152         }
 153
 154         /* Grab new VT */
 155         sprintf(vtname, VC_FORMAT, vtno);
 156         /* (Try to) clean up stray open fds above fd 2 */
 157         bb_daemon_helper(DAEMON_CLOSE_EXTRA_FDS);
 158         close(STDIN_FILENO);
 159         /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
 160         xopen(vtname, O_RDWR);
 161         xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);
 162
 163         if (flags & OPT_s) {
 164                 console_make_active(STDIN_FILENO, vtno);
 165         }
 166
 167         if (!argv[0]) {
 168                 argv--;
 169                 argv[0] = (char *) get_shell_name();
 170                 /*argv[1] = NULL; - already is */
 171         }
 172
 173         xdup2(STDIN_FILENO, STDOUT_FILENO);
 174         xdup2(STDIN_FILENO, STDERR_FILENO);
 175
 176 #ifdef BLOAT
 177         {
 178         /* Handle -l (login shell) option */
 179         const char *prog = argv[0];
 180         if (flags & OPT_l)
 181                 argv[0] = xasprintf("-%s", argv[0]);
 182         }
 183 #endif
 184
 185         vfork_child(argv);
 186         if (flags & OPT_w) {
 187                 /* We have only one child, wait for it */
 188                 safe_waitpid(-1, NULL, 0); /* loops on EINTR */
 189                 if (flags & OPT_s) {
 190                         console_make_active(STDIN_FILENO, vtstat.v_active);
 191                         // Compat: even with -c N (try to) disallocate:
 192                         // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
 193                         // openvt: could not deallocate console 9
 194                         xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
 195                 }
 196         }
 197         return EXIT_SUCCESS;
 198 }