diff options
| -rw-r--r-- | shell/cttyhack.c | 79 |
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); } |