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authorKevin Cernekee <cernekee@gmail.com>2011-07-13 07:26:58 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2011-07-13 07:26:58 (GMT)
commit064e99646a233240e91f453ba49f6baeab7c2c70 (patch)
treeb4dabf5fe257da0a51f199fe4fbc1daf2a0e02c7
parent80856b37e888612c054158b9fa8a0021dbf8dadf (diff)
downloadbusybox-064e99646a233240e91f453ba49f6baeab7c2c70.tar.gz
busybox-064e99646a233240e91f453ba49f6baeab7c2c70.tar.bz2
cttyhack: check sysfs for the name of the active console
Signed-off-by: Kevin Cernekee <cernekee@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--shell/cttyhack.c79
1 files changed, 48 insertions, 31 deletions
diff --git a/shell/cttyhack.c b/shell/cttyhack.c
index d1ac2cd..522a1ba 100644
--- a/shell/cttyhack.c
+++ b/shell/cttyhack.c
@@ -14,18 +14,22 @@
//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:
@@ -115,33 +119,46 @@ 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 (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);
- }
+ int s = open_read_close("/sys/class/tty/console/active",
+ console + 5, sizeof(console) - 5 - 1);
+ if (s > 0) {
+ /* found active console via sysfs (Linux 2.6.38+) */
+ console[5 + 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
- 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);
- }
+#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 = 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);
}
+ret:
BB_EXECVP_or_die(argv);
}