1 files changed, 64 insertions, 2 deletions

diff --git a/shell/cttyhack.c b/shell/cttyhack.c
index 67736ad62..7a5e1ffd2 100644
--- a/shell/cttyhack.c
+++ b/shell/cttyhack.c
@@ -6,6 +6,62 @@
  */
 #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 */
@@ -59,13 +115,19 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
                 close(fd);
         } else {
                 /* We don't have ctty (or don't have "/dev/tty" node...) */
-                if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
+                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);
-                } else if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
+                }
+#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);