cttyhack: new applet.

3 files changed, 95 insertions, 0 deletions

diff --git a/shell/Config.in b/shell/Config.in
index 027993483..253752bc3 100644
--- a/shell/Config.in
+++ b/shell/Config.in
@@ -270,4 +270,24 @@ config FEATURE_SH_STANDALONE
 #	  that exact location with that exact name, this option will not work at
 #	  all.
 
+config CTTYHACK
+	bool "cttyhack"
+	default n
+	help
+	  One common problem reported on the mailing list is "can't access tty;
+	  job control turned off" error message which typically appears when
+	  one tries to use shell with stdin/stdout opened to /dev/console.
+	  This device is special - it cannot be a controlling tty.
+
+	  Proper solution is to use correct device instead of /dev/console.
+
+	  cttyhack provides "quick and dirty" solution to this problem.
+	  It analyzes stdin with various ioctls, trying to determine whether
+	  it is a /dev/ttyN or /dev/ttySN (virtual terminal or serial line).
+	  If it detects one, it closes stdin/out/err and reopens that device.
+	  Then it executes given program. Usage example for /etc/inittab
+	  (for busybox init):
+
+	  ::respawn:/bin/cttyhack /bin/sh
+
 endmenu
diff --git a/shell/Kbuild b/shell/Kbuild
index 6b58040fc..944eaff51 100644
--- a/shell/Kbuild
+++ b/shell/Kbuild
@@ -9,3 +9,5 @@ lib-$(CONFIG_ASH)  += ash.o
 lib-$(CONFIG_HUSH) += hush.o
 lib-$(CONFIG_LASH) += lash.o
 lib-$(CONFIG_MSH)  += msh.o
+
+lib-$(CONFIG_CTTYHACK) += cttyhack.o
diff --git a/shell/cttyhack.c b/shell/cttyhack.c
new file mode 100644
index 000000000..cdd0ed1d6
--- /dev/null
+++ b/shell/cttyhack.c
@@ -0,0 +1,73 @@
+/* This code is adapted from busybox project
+ *
+ * Licensed under GPLv2
+ */
+#include "libbb.h"
+
+/* From <linux/vt.h> */
+struct vt_stat {
+	unsigned short v_active;	/* active vt */
+	unsigned short v_signal;	/* signal to send */
+	unsigned short v_state;	/* vt bitmask */
+};
+enum { VT_GETSTATE = 0x5603 };	/* get global vt state info */
+
+/* From <linux/serial.h> */
+struct serial_struct {
+	int	type;
+	int	line;
+	unsigned int	port;
+	int	irq;
+	int	flags;
+	int	xmit_fifo_size;
+	int	custom_divisor;
+	int	baud_base;
+	unsigned short	close_delay;
+	char	io_type;
+	char	reserved_char[1];
+	int	hub6;
+	unsigned short	closing_wait; /* time to wait before closing */
+	unsigned short	closing_wait2; /* no longer used... */
+	unsigned char	*iomem_base;
+	unsigned short	iomem_reg_shift;
+	unsigned int	port_high;
+	unsigned long	iomap_base;	/* cookie passed into ioremap */
+	int	reserved[1];
+};
+
+int cttyhack_main(int argc, char **argv) ATTRIBUTE_NORETURN;
+int cttyhack_main(int argc, char **argv)
+{
+	int fd;
+	char console[sizeof(int)*3 + 16];
+	union {
+		struct vt_stat vt;
+		struct serial_struct sr;
+		char paranoia[sizeof(struct serial_struct) * 3];
+	} u;
+
+	if (!*++argv) {
+		bb_show_usage();
+	}
+
+	strcpy(console, "/dev/tty");
+	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) {
+		/* this is linux virtual tty */
+		sprintf(console + 8, "S%d" + 1, u.vt.v_active);
+	}
+
+	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--);
+	}
+
+	execvp(argv[0], argv);
+	bb_perror_msg_and_die("cannot exec '%s'", argv[0]);
+}