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]);
+}