tty: enable the echoing of ^C in the N_TTY discipline

Turn on INTR/QUIT/SUSP echoing in the N_TTY line discipline (e.g.  ctrl-C
will appear as "^C" if stty echoctl is set and ctrl-C is set as INTR).

Linux seems to be the only unix-like OS (recently I've verified this on
Solaris, BSD, and Mac OS X) that does *not* behave this way, and I really
miss this as a good visual confirmation of the interrupt of a program in
the console or xterm.  I remember this fondly from many Unixs I've used
over the years as well.  Bringing this to Linux also seems like a good way
to make it yet more compliant with standard unix-like behavior.

[akpm@linux-foundation.org: coding-style fixes]
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 596c7173997b..e0e3815f92ba 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -769,7 +769,21 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
                 signal = SIGTSTP;
                 if (c == SUSP_CHAR(tty)) {
 send_signal:
-                        isig(signal, tty, 0);
+                        /*
+                         * Echo character, and then send the signal.
+                         * Note that we do not use isig() here because we want
+                         * the order to be:
+                         * 1) flush, 2) echo, 3) signal
+                         */
+                        if (!L_NOFLSH(tty)) {
+                                n_tty_flush_buffer(tty);
+                                if (tty->driver->flush_buffer)
+                                        tty->driver->flush_buffer(tty);
+                        }
+                        if (L_ECHO(tty))
+                                echo_char(c, tty);
+                        if (tty->pgrp)
+                                kill_pgrp(tty->pgrp, signal, 1);
                         return;
                 }
         }