[PATCH] n_tty: Remove LINEMODE support

[Peter Hurley <peter@hurleysoftware.com>]

Commit 26df6d13406d1 ("tty: Add EXTPROC support for LINEMODE") added
the undocumented EXTPROC input processing mode, which ignores the ICANON
setting and forces pty slave input to be processed in non-canonical
mode.

Although intended to provide a transparent mechanism for local line
edit with telnetd (and other remote shell protocols), the transparency
is limited.

Userspace usage is abandoned; telnetd does not even compile with
LINEMODE support. readline/bash and sshd never supported this.

Cc: Howard Chu <hyc@symas.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/n_tty.c | 22 ++++++----------------
 drivers/tty/pty.c   | 24 +-----------------------
 2 files changed, 7 insertions(+), 39 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index eb9f114..5120d2b 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1562,10 +1562,6 @@ n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
 				c &= 0x7f;
 			if (I_IUCLC(tty) && L_IEXTEN(tty))
 				c = tolower(c);
-			if (L_EXTPROC(tty)) {
-				put_tty_queue(c, ldata);
-				continue;
-			}
 			if (!test_bit(c, ldata->char_map))
 				n_tty_receive_char_inline(tty, c);
 			else if (n_tty_receive_char_special(tty, c) && count) {
@@ -1613,9 +1609,9 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
 
 	if (ldata->real_raw)
 		n_tty_receive_buf_real_raw(tty, cp, fp, count);
-	else if (ldata->raw || (L_EXTPROC(tty) && !preops))
+	else if (ldata->raw)
 		n_tty_receive_buf_raw(tty, cp, fp, count);
-	else if (tty->closing && !L_EXTPROC(tty))
+	else if (tty->closing)
 		n_tty_receive_buf_closing(tty, cp, fp, count);
 	else {
 		if (ldata->lnext) {
@@ -1637,13 +1633,13 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
 			tty->ops->flush_chars(tty);
 	}
 
-	if (ldata->icanon && !L_EXTPROC(tty))
+	if (ldata->icanon)
 		return;
 
 	/* publish read_head to consumer */
 	smp_store_release(&ldata->commit_head, ldata->read_head);
 
-	if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
+	if (read_cnt(ldata) >= ldata->minimum_to_wake) {
 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 		if (waitqueue_active(&tty->read_wait))
 			wake_up_interruptible_poll(&tty->read_wait, POLLIN);
@@ -1939,7 +1935,7 @@ static inline int input_available_p(struct tty_struct *tty, int poll)
 	struct n_tty_data *ldata = tty->disc_data;
 	int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
 
-	if (ldata->icanon && !L_EXTPROC(tty))
+	if (ldata->icanon)
 		return ldata->canon_head != ldata->read_tail;
 	else
 		return ldata->commit_head - ldata->read_tail >= amt;
@@ -1973,7 +1969,6 @@ static int copy_from_read_buf(struct tty_struct *tty,
 	struct n_tty_data *ldata = tty->disc_data;
 	int retval;
 	size_t n;
-	bool is_eof;
 	size_t head = smp_load_acquire(&ldata->commit_head);
 	size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
 
@@ -1983,14 +1978,9 @@ static int copy_from_read_buf(struct tty_struct *tty,
 	if (n) {
 		retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
 		n -= retval;
-		is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
 		tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
 				ldata->icanon);
 		smp_store_release(&ldata->read_tail, ldata->read_tail + n);
-		/* Turn single EOF into zero-length read */
-		if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
-		    (head == ldata->read_tail))
-			n = 0;
 		*b += n;
 		*nr -= n;
 	}
@@ -2257,7 +2247,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 			continue;
 		}
 
-		if (ldata->icanon && !L_EXTPROC(tty)) {
+		if (ldata->icanon) {
 			retval = canon_copy_from_read_buf(tty, &b, &nr);
 			if (retval == -EAGAIN) {
 				retval = 0;
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index ee06b77..01ac182 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -192,20 +192,6 @@ static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 	return put_user(pktmode, arg);
 }
 
-/* Send a signal to the slave */
-static int pty_signal(struct tty_struct *tty, int sig)
-{
-	struct pid *pgrp;
-
-	if (tty->link) {
-		pgrp = tty_get_pgrp(tty->link);
-		if (pgrp)
-			kill_pgrp(pgrp, sig, 1);
-		put_pid(pgrp);
-	}
-	return 0;
-}
-
 static void pty_flush_buffer(struct tty_struct *tty)
 {
 	struct tty_struct *to = tty->link;
@@ -254,15 +240,13 @@ static void pty_set_termios(struct tty_struct *tty,
 {
 	/* See if packet mode change of state. */
 	if (tty->link && tty->link->packet) {
-		int extproc = (old_termios->c_lflag & EXTPROC) |
-				(tty->termios.c_lflag & EXTPROC);
 		int old_flow = ((old_termios->c_iflag & IXON) &&
 				(old_termios->c_cc[VSTOP] == '\023') &&
 				(old_termios->c_cc[VSTART] == '\021'));
 		int new_flow = (I_IXON(tty) &&
 				STOP_CHAR(tty) == '\023' &&
 				START_CHAR(tty) == '\021');
-		if ((old_flow != new_flow) || extproc) {
+		if (old_flow != new_flow) {
 			spin_lock_irq(&tty->ctrl_lock);
 			if (old_flow != new_flow) {
 				tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
@@ -271,8 +255,6 @@ static void pty_set_termios(struct tty_struct *tty,
 				else
 					tty->ctrl_status |= TIOCPKT_NOSTOP;
 			}
-			if (extproc)
-				tty->ctrl_status |= TIOCPKT_IOCTL;
 			spin_unlock_irq(&tty->ctrl_lock);
 			wake_up_interruptible(&tty->link->read_wait);
 		}
@@ -482,8 +464,6 @@ static int pty_bsd_ioctl(struct tty_struct *tty,
 		return pty_set_pktmode(tty, (int __user *)arg);
 	case TIOCGPKT: /* Get PT packet mode */
 		return pty_get_pktmode(tty, (int __user *)arg);
-	case TIOCSIG:    /* Send signal to other side of pty */
-		return pty_signal(tty, (int) arg);
 	case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 		return -EINVAL;
 	}
@@ -607,8 +587,6 @@ static int pty_unix98_ioctl(struct tty_struct *tty,
 		return pty_get_pktmode(tty, (int __user *)arg);
 	case TIOCGPTN: /* Get PT Number */
 		return put_user(tty->index, (unsigned int __user *)arg);
-	case TIOCSIG:    /* Send signal to other side of pty */
-		return pty_signal(tty, (int) arg);
 	}
 
 	return -ENOIOCTLCMD;
-- 
2.2.2