From 32f13521ca68bc624ff6effc77f308a52b038bf0 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 15 Jun 2013 09:14:17 -0400 Subject: [PATCH] n_tty: Line copy to user buffer in canonical mode Instead of pushing one char per loop, pre-compute the data length to copy and copy all at once. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 110 +++++++++++++++++++++++++++++++------------- 1 file changed, 77 insertions(+), 33 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 7fd77746f2d0..74dcedd06a8b 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -74,6 +74,13 @@ #define ECHO_OP_SET_CANON_COL 0x81 #define ECHO_OP_ERASE_TAB 0x82 +#undef N_TTY_TRACE +#ifdef N_TTY_TRACE +# define n_tty_trace(f, args...) trace_printk(f, ##args) +#else +# define n_tty_trace(f, args...) +#endif + struct n_tty_data { unsigned int column; unsigned long overrun_time; @@ -1748,58 +1755,95 @@ static int copy_from_read_buf(struct tty_struct *tty, } /** - * canon_copy_to_user - copy read data in canonical mode + * canon_copy_from_read_buf - 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. + * it copies one line of input up to and including the line-delimiting + * character into 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) +static int canon_copy_from_read_buf(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; + size_t n, size, more, c; + unsigned long eol; + int ret, tail, found = 0; /* 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; - } + + n = min_t(size_t, *nr, ldata->read_cnt); + if (!n) { raw_spin_unlock_irqrestore(&ldata->read_lock, flags); + return 0; + } - 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); + tail = ldata->read_tail; + size = min_t(size_t, tail + n, N_TTY_BUF_SIZE); + + n_tty_trace("%s: nr:%zu tail:%d n:%zu size:%zu\n", + __func__, *nr, tail, n, size); + + eol = find_next_bit(ldata->read_flags, size, tail); + more = n - (size - tail); + if (eol == N_TTY_BUF_SIZE && more) { + /* scan wrapped without finding set bit */ + eol = find_next_bit(ldata->read_flags, more, 0); + if (eol != more) + found = 1; + } else if (eol != size) + found = 1; + + size = N_TTY_BUF_SIZE - tail; + n = (found + eol + size) & (N_TTY_BUF_SIZE - 1); + c = n; + + if (found && ldata->read_buf[eol] == __DISABLED_CHAR) + n--; + + n_tty_trace("%s: eol:%lu found:%d n:%zu c:%zu size:%zu more:%zu\n", + __func__, eol, found, n, c, size, more); + + raw_spin_unlock_irqrestore(&ldata->read_lock, flags); + + if (n > size) { + ret = copy_to_user(*b, &ldata->read_buf[tail], size); + if (ret) + return -EFAULT; + ret = copy_to_user(*b + size, ldata->read_buf, n - size); + } else + ret = copy_to_user(*b, &ldata->read_buf[tail], n); + + if (ret) + return -EFAULT; + *b += n; + *nr -= n; + + raw_spin_lock_irqsave(&ldata->read_lock, flags); + ldata->read_tail = (ldata->read_tail + c) & (N_TTY_BUF_SIZE - 1); + ldata->read_cnt -= c; + if (found) { + __clear_bit(eol, ldata->read_flags); + /* 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 (found) + tty_audit_push(tty); return 0; } @@ -1972,7 +2016,7 @@ do_it_again: } if (ldata->icanon && !L_EXTPROC(tty)) { - retval = canon_copy_to_user(tty, &b, &nr); + retval = canon_copy_from_read_buf(tty, &b, &nr); if (retval) break; } else { -- 2.20.1