Commit d7fe75cb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

tty: teach the n_tty ICANON case about the new "cookie continuations" too 



The ICANON case is a bit messy, since it has to look for the line
ending, and has special code to then suppress line ending characters if
they match the __DISABLED_CHAR.  So it actually looks up the line ending
even past the point where it knows it won't copy it to the result
buffer.

That said, apart from all those odd legacy N_TTY ICANON cases, the
actual "should we continue copying" logic isn't really all that
complicated or different from the non-canon case.  In fact, the lack of
"wait for at least N characters" arguably makes the repeat case slightly
simpler.  It really just boils down to "there's more of the line to be
copied".

So add the necessarily trivial logic, and now the N_TTY case will give
long result lines even when in canon mode.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 15ea8ae8

drivers/tty/n_tty.c

+19 −7
Original line number Diff line number Diff line
@@ -2009,21 +2009,22 @@ static bool copy_from_read_buf(struct tty_struct *tty, 
 *		read_tail published

 */



static void canon_copy_from_read_buf(struct tty_struct *tty,

static bool canon_copy_from_read_buf(struct tty_struct *tty,

				     unsigned char **kbp,

				     size_t *nr)

{

	struct n_tty_data *ldata = tty->disc_data;

	size_t n, size, more, c;

	size_t eol;

	size_t tail;

	size_t tail, canon_head;

	int found = 0;



	/* N.B. avoid overrun if nr == 0 */

	if (!*nr)

		return;

		return false;



	n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);

	canon_head = smp_load_acquire(&ldata->canon_head);

	n = min(*nr + 1, canon_head - ldata->read_tail);



	tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);

	size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
@@ -2067,7 +2068,11 @@ static void canon_copy_from_read_buf(struct tty_struct *tty, 
		else

			ldata->push = 0;

		tty_audit_push();

		return false;

	}



	/* No EOL found - do a continuation retry if there is more data */

	return ldata->read_tail != canon_head;

}



extern ssize_t redirected_tty_write(struct file *, const char __user *,
@@ -2141,8 +2146,13 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
	 * termios_rwsem, and can just continue to copy data.

	 */

	if (*cookie) {

		if (ldata->icanon && !L_EXTPROC(tty)) {

			if (canon_copy_from_read_buf(tty, &kb, &nr))

				return kb - kbuf;

		} else {

			if (copy_from_read_buf(tty, &kb, &nr))

				return kb - kbuf;

		}



		/* No more data - release locks and stop retries */

		n_tty_kick_worker(tty);
@@ -2239,7 +2249,8 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
		}



		if (ldata->icanon && !L_EXTPROC(tty)) {

			canon_copy_from_read_buf(tty, &kb, &nr);

			if (canon_copy_from_read_buf(tty, &kb, &nr))

				goto more_to_be_read;

		} else {

			/* Deal with packet mode. */

			if (packet && kb == kbuf) {
@@ -2257,6 +2268,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
			 * will release them when done.

			 */

			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {

more_to_be_read:

				remove_wait_queue(&tty->read_wait, &wait);

				*cookie = cookie;

				return kb - kbuf;