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