LXR 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
  16openvt [-c NUM] [-fsulv] [--] [command [args]]
  17
  18Find the first available VT, and run command on it. Stdio is directed
  19to 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
  40bbox:
  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? */
  49static 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 */
  56static 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
  70static 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 */
  89static 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
 104int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 105int 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}
 179