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n_tty: Factor canonical mode copy from n_tty_read()

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Simplify n_tty_read(); extract complex copy algorithm
into separate function, canon_copy_to_user().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-06-15 09:14:16 -04:00 committed by Greg Kroah-Hartman
parent 24a89d1cb6
commit 88bb0de389
1 changed files with 57 additions and 38 deletions
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95
drivers/tty/n_tty.c
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@ -1747,6 +1747,62 @@ static int copy_from_read_buf(struct tty_struct *tty,
return retval;
}
/**
* canon_copy_to_user - copy read data in canonical mode
* @tty: terminal device
* @b: user data
* @nr: size of data
*
* Helper function for n_tty_read. It is only called when ICANON is on;
* it copies characters one at a time from the read buffer to the user
* space buffer.
*
* Called under the atomic_read_lock mutex
*/
static int canon_copy_to_user(struct tty_struct *tty,
unsigned char __user **b,
size_t *nr)
{
struct n_tty_data *ldata = tty->disc_data;
unsigned long flags;
int eol, c;
/* N.B. avoid overrun if nr == 0 */
raw_spin_lock_irqsave(&ldata->read_lock, flags);
while (*nr && ldata->read_cnt) {
eol = test_and_clear_bit(ldata->read_tail, ldata->read_flags);
c = ldata->read_buf[ldata->read_tail];
ldata->read_tail = (ldata->read_tail+1) & (N_TTY_BUF_SIZE-1);
ldata->read_cnt--;
if (eol) {
/* this test should be redundant:
* we shouldn't be reading data if
* canon_data is 0
*/
if (--ldata->canon_data < 0)
ldata->canon_data = 0;
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
if (!eol || (c != __DISABLED_CHAR)) {
if (tty_put_user(tty, c, *b))
return -EFAULT;
*b += 1;
*nr -= 1;
}
if (eol) {
tty_audit_push(tty);
return 0;
}
raw_spin_lock_irqsave(&ldata->read_lock, flags);
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
return 0;
}
extern ssize_t redirected_tty_write(struct file *, const char __user *,
size_t, loff_t *);
@ -1916,44 +1972,7 @@ do_it_again:
}
if (ldata->icanon && !L_EXTPROC(tty)) {
/* N.B. avoid overrun if nr == 0 */
raw_spin_lock_irqsave(&ldata->read_lock, flags);
while (nr && ldata->read_cnt) {
int eol;
eol = test_and_clear_bit(ldata->read_tail,
ldata->read_flags);
c = ldata->read_buf[ldata->read_tail];
ldata->read_tail = ((ldata->read_tail+1) &
(N_TTY_BUF_SIZE-1));
ldata->read_cnt--;
if (eol) {
/* this test should be redundant:
* we shouldn't be reading data if
* canon_data is 0
*/
if (--ldata->canon_data < 0)
ldata->canon_data = 0;
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
if (!eol || (c != __DISABLED_CHAR)) {
if (tty_put_user(tty, c, b++)) {
retval = -EFAULT;
b--;
raw_spin_lock_irqsave(&ldata->read_lock, flags);
break;
}
nr--;
}
if (eol) {
tty_audit_push(tty);
raw_spin_lock_irqsave(&ldata->read_lock, flags);
break;
}
raw_spin_lock_irqsave(&ldata->read_lock, flags);
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
retval = canon_copy_to_user(tty, &b, &nr);
if (retval)
break;
} else {