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/* vi: set sw=4 ts=4: */
/*
* Copyright (c) 2007 Denys Vlasenko <vda.linux@googlemail.com>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "libbb.h"
//applet:IF_CTTYHACK(APPLET(cttyhack, BB_DIR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_CTTYHACK) += cttyhack.o
//config:config CTTYHACK
//config: bool "cttyhack"
//config: default y
//config: help
//config: One common problem reported on the mailing list is "can't access tty;
//config: job control turned off" error message which typically appears when
//config: one tries to use shell with stdin/stdout opened to /dev/console.
//config: This device is special - it cannot be a controlling tty.
//config:
//config: Proper solution is to use correct device instead of /dev/console.
//config:
//config: cttyhack provides "quick and dirty" solution to this problem.
//config: It analyzes stdin with various ioctls, trying to determine whether
//config: it is a /dev/ttyN or /dev/ttySN (virtual terminal or serial line).
//config: If it detects one, it closes stdin/out/err and reopens that device.
//config: Then it executes given program. Opening the device will make
//config: that device a controlling tty. This may require cttyhack
//config: to be a session leader.
//config:
//config: Example for /etc/inittab (for busybox init):
//config:
//config: ::respawn:/bin/cttyhack /bin/sh
//config:
//config: Starting an interactive shell from boot shell script:
//config:
//config: setsid cttyhack sh
//config:
//config: Giving controlling tty to shell running with PID 1:
//config:
//config: # exec cttyhack sh
//config:
//config: Without cttyhack, you need to know exact tty name,
//config: and do something like this:
//config:
//config: # exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'
//config:
//usage:#define cttyhack_trivial_usage
//usage: "PROG ARGS"
//usage:#define cttyhack_full_usage "\n\n"
//usage: "Give PROG a controlling tty if possible."
//usage: "\nExample for /etc/inittab (for busybox init):"
//usage: "\n ::respawn:/bin/cttyhack /bin/sh"
//usage: "\nGiving controlling tty to shell running with PID 1:"
//usage: "\n $ exec cttyhack sh"
//usage: "\nStarting interactive shell from boot shell script:"
//usage: "\n setsid cttyhack sh"
#if !defined(__linux__) && !defined(TIOCGSERIAL) && !ENABLE_WERROR
# warning cttyhack will not be able to detect a controlling tty on this system
#endif
/* From <linux/vt.h> */
struct vt_stat {
unsigned short v_active; /* active vt */
unsigned short v_signal; /* signal to send */
unsigned short v_state; /* vt bitmask */
};
enum { VT_GETSTATE = 0x5603 }; /* get global vt state info */
/* From <linux/serial.h> */
struct serial_struct {
int type;
int line;
unsigned int port;
int irq;
int flags;
int xmit_fifo_size;
int custom_divisor;
int baud_base;
unsigned short close_delay;
char io_type;
char reserved_char[1];
int hub6;
unsigned short closing_wait; /* time to wait before closing */
unsigned short closing_wait2; /* no longer used... */
unsigned char *iomem_base;
unsigned short iomem_reg_shift;
unsigned int port_high;
unsigned long iomap_base; /* cookie passed into ioremap */
int reserved[1];
};
int cttyhack_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int cttyhack_main(int argc UNUSED_PARAM, char **argv)
{
int fd;
char console[sizeof(int)*3 + 16];
union {
struct vt_stat vt;
struct serial_struct sr;
char paranoia[sizeof(struct serial_struct) * 3];
} u;
if (!*++argv) {
bb_show_usage();
}
strcpy(console, "/dev/tty");
fd = open(console, O_RDWR);
if (fd >= 0) {
/* We already have ctty, nothing to do */
close(fd);
} else {
/* We don't have ctty (or don't have "/dev/tty" node...) */
if (0) {}
#ifdef TIOCGSERIAL
else if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
/* this is a serial console */
sprintf(console + 8, "S%d", u.sr.line);
}
#endif
#ifdef __linux__
else if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
/* this is linux virtual tty */
sprintf(console + 8, "S%d" + 1, u.vt.v_active);
}
#endif
if (console[8]) {
fd = xopen(console, O_RDWR);
//bb_error_msg("switching to '%s'", console);
dup2(fd, 0);
dup2(fd, 1);
dup2(fd, 2);
while (fd > 2)
close(fd--);
/* Some other session may have it as ctty,
* steal it from them:
*/
ioctl(0, TIOCSCTTY, 1);
}
}
BB_EXECVP_or_die(argv);
}
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