| /* 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 the "can't |
| //config: access tty; job control turned off" error message, which typically |
| //config: appears when one tries to use a shell with stdin/stdout on |
| //config: /dev/console. |
| //config: This device is special - it cannot be a controlling tty. |
| //config: |
| //config: The proper solution is to use the correct device instead of |
| //config: /dev/console. |
| //config: |
| //config: cttyhack provides a "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: On Linux it also checks sysfs for a pointer to the active console. |
| //config: If cttyhack is able to find the real console device, it closes |
| //config: stdin/out/err and reopens that device. |
| //config: Then it executes the 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...) */ |
| do { |
| #ifdef __linux__ |
| int s = open_read_close("/sys/class/tty/console/active", |
| console + 5, sizeof(console) - 5); |
| if (s > 0) { |
| /* found active console via sysfs (Linux 2.6.38+) |
| * sysfs string looks like "ttyS0\n" so zap the newline: |
| */ |
| console[4 + s] = '\0'; |
| break; |
| } |
| |
| if (ioctl(0, VT_GETSTATE, &u.vt) == 0) { |
| /* this is linux virtual tty */ |
| sprintf(console + 8, "S%d" + 1, u.vt.v_active); |
| break; |
| } |
| #endif |
| #ifdef TIOCGSERIAL |
| if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) { |
| /* this is a serial console, asuming it is named /dev/ttySn */ |
| sprintf(console + 8, "S%d", u.sr.line); |
| break; |
| } |
| #endif |
| /* nope, could not find it */ |
| goto ret; |
| } while (0); |
| |
| fd = open_or_warn(console, O_RDWR); |
| if (fd < 0) |
| goto ret; |
| //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); |
| } |
| |
| ret: |
| BB_EXECVP_or_die(argv); |
| } |