064e99646
Kevin Cernekee
2011-07-13
Subject
cttyhack: check sysfs for the name of the active console
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shell/cttyhack.c+48 -31
| @@ -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); | |
| } | |