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authorLinus Torvalds <torvalds@linux-foundation.org>2021-01-20 15:43:38 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-01-20 16:48:49 -0800
commitd7fe75cbc23c7d225eee2ef04def239b6603dce7 (patch)
tree65456a12f4b83aac3852431f167ee1466a024097
parent15ea8ae8e03fdb845ed3ff5d9f11dd5f4f60252c (diff)
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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: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/tty/n_tty.c26
1 files changed, 19 insertions, 7 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index b89308d52ade..9e546d0cc55c 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -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 (copy_from_read_buf(tty, &kb, &nr))
- return kb - kbuf;
+ 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;