shell/cttyhack.c

   1 /* This code is adapted from busybox project
   2  *
   3  * Licensed under GPLv2
   4  */
   5 #include "libbb.h"
   6
   7 /* From <linux/vt.h> */
   8 struct vt_stat {
   9         unsigned short v_active;        /* active vt */
  10         unsigned short v_signal;        /* signal to send */
  11         unsigned short v_state; /* vt bitmask */
  12 };
  13 enum { VT_GETSTATE = 0x5603 };  /* get global vt state info */
  14
  15 /* From <linux/serial.h> */
  16 struct serial_struct {
  17         int     type;
  18         int     line;
  19         unsigned int    port;
  20         int     irq;
  21         int     flags;
  22         int     xmit_fifo_size;
  23         int     custom_divisor;
  24         int     baud_base;
  25         unsigned short  close_delay;
  26         char    io_type;
  27         char    reserved_char[1];
  28         int     hub6;
  29         unsigned short  closing_wait; /* time to wait before closing */
  30         unsigned short  closing_wait2; /* no longer used... */
  31         unsigned char   *iomem_base;
  32         unsigned short  iomem_reg_shift;
  33         unsigned int    port_high;
  34         unsigned long   iomap_base;     /* cookie passed into ioremap */
  35         int     reserved[1];
  36 };
  37
  38 int cttyhack_main(int argc, char **argv) ATTRIBUTE_NORETURN;
  39 int cttyhack_main(int argc, char **argv)
  40 {
  41         int fd;
  42         char console[sizeof(int)*3 + 16];
  43         union {
  44                 struct vt_stat vt;
  45                 struct serial_struct sr;
  46                 char paranoia[sizeof(struct serial_struct) * 3];
  47         } u;
  48
  49         if (!*++argv) {
  50                 bb_show_usage();
  51         }
  52
  53         strcpy(console, "/dev/tty");
  54         if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
  55                 /* this is a serial console */
  56                 sprintf(console + 8, "S%d", u.sr.line);
  57         } else if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
  58                 /* this is linux virtual tty */
  59                 sprintf(console + 8, "S%d" + 1, u.vt.v_active);
  60         }
  61
  62         if (console[8]) {
  63                 fd = xopen(console, O_RDWR);
  64                 //bb_error_msg("switching to '%s'", console);
  65                 dup2(fd, 0);
  66                 dup2(fd, 1);
  67                 dup2(fd, 2);
  68                 while (fd > 2) close(fd--);
  69         }
  70
  71         execvp(argv[0], argv);
  72         bb_perror_msg_and_die("cannot exec '%s'", argv[0]);
  73 }