Resume TTY on SUSP and fix CRNL order in N_TTY line discipline

Refine these behaviors in the N_TTY line discipline:

1) Handle the signal characters consistently when received in a stopped TTY
   so that SUSP (typically ctrl-Z) behaves like INTR and QUIT in resuming a
   stopped TTY.

2) Adjust the order in which the IGNCR/ICRNL/INLCR processing is applied to
   be more logical and consistent with the behavior of other Unix systems.

Signed-off-by: Joe Peterson <joe@skyrush.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 001d9d875387..e1518e17e09d 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -708,7 +708,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 
         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
             ((I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty)) ||
-             c == INTR_CHAR(tty) || c == QUIT_CHAR(tty)))
+             c == INTR_CHAR(tty) || c == QUIT_CHAR(tty) || c == SUSP_CHAR(tty)))
                 start_tty(tty);
 
         if (tty->closing) {
@@ -746,13 +746,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
                 return;
         }
 
-        if (c == '\r') {
-                if (I_IGNCR(tty))
-                        return;
-                if (I_ICRNL(tty))
-                        c = '\n';
-        } else if (c == '\n' && I_INLCR(tty))
-                c = '\r';
         if (I_IXON(tty)) {
                 if (c == START_CHAR(tty)) {
                         start_tty(tty);
@@ -763,6 +756,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
                         return;
                 }
         }
+
         if (L_ISIG(tty)) {
                 int signal;
                 signal = SIGINT;
@@ -792,6 +786,15 @@ send_signal:
                         return;
                 }
         }
+
+        if (c == '\r') {
+                if (I_IGNCR(tty))
+                        return;
+                if (I_ICRNL(tty))
+                        c = '\n';
+        } else if (c == '\n' && I_INLCR(tty))
+                c = '\r';
+
         if (tty->icanon) {
                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {