/* vi: set sw=4 ts=4: */
/*
- * Licensed under GPLv2
- *
* 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))
+//applet:IF_CTTYHACK(APPLET(cttyhack, BB_DIR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_CTTYHACK) += cttyhack.o
//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: 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: Proper solution is to use correct device instead of /dev/console.
+//config: The proper solution is to use the correct device instead of
+//config: /dev/console.
//config:
-//config: cttyhack provides "quick and dirty" solution to this problem.
+//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: 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: 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:
//config: # exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'
//config:
+//config: Starting getty on a controlling tty from a shell script:
+//config:
+//config: # getty 115200 $(cttyhack)
//usage:#define cttyhack_trivial_usage
-//usage: "PROG ARGS"
+//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: "\nStarting interactive shell from boot shell script:"
//usage: "\n setsid cttyhack sh"
-#if !defined(__linux__) && !defined(TIOCGSERIAL)
+#if !defined(__linux__) && !defined(TIOCGSERIAL) && !ENABLE_WERROR
# warning cttyhack will not be able to detect a controlling tty on this system
#endif
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 {
+ if (fd < 0) {
/* 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
+ do {
#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:
+ /* Note that this method does not use _stdin_.
+ * Thus, "cttyhack </dev/something" can't be used.
+ * However, this method is more reliable than
+ * TIOCGSERIAL check, which assumes that all
+ * serial lines follow /dev/ttySn convention -
+ * which is not always the case.
+ * Therefore, we use this method first:
*/
- ioctl(0, TIOCSCTTY, 1);
- }
+ int s = open_read_close("/sys/class/tty/console/active",
+ console + 5, sizeof(console) - 5);
+ if (s > 0) {
+ char *last;
+ /* Found active console via sysfs (Linux 2.6.38+).
+ * It looks like "[tty0 ]ttyS0\n" so zap the newline:
+ */
+ console[4 + s] = '\0';
+ /* If there are multiple consoles,
+ * take the last one:
+ */
+ last = strrchr(console + 5, ' ');
+ if (last)
+ overlapping_strcpy(console + 5, last + 1);
+ break;
+ }
+
+ if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
+ /* this is linux virtual tty */
+ sprintf(console + 8, "S%u" + 1, (int)u.vt.v_active);
+ break;
+ }
+#endif
+#ifdef TIOCGSERIAL
+ if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
+ /* this is a serial console; assuming it is named /dev/ttySn */
+ sprintf(console + 8, "S%u", (int)u.sr.line);
+ break;
+ }
+#endif
+ /* nope, could not find it */
+ console[0] = '\0';
+ } while (0);
}
+ argv++;
+ if (!argv[0]) {
+ if (!console[0])
+ return EXIT_FAILURE;
+ puts(console);
+ return EXIT_SUCCESS;
+ }
+
+ if (fd < 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,
+ * try to steal it from them:
+ */
+ ioctl(0, TIOCSCTTY, 1);
+ ret:
BB_EXECVP_or_die(argv);
}
projects / oweals / busybox.git / blobdiff