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 <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>hifive-unleashed-5.1
Peter Hurley
Greg Kroah-Hartman
parent
88bb0de389
commit
32f13521ca
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@ -74,6 +74,13 @@
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#define ECHO_OP_SET_CANON_COL 0x81
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#define ECHO_OP_ERASE_TAB 0x82
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#undef N_TTY_TRACE
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#ifdef N_TTY_TRACE
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# define n_tty_trace(f, args...) trace_printk(f, ##args)
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#else
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# define n_tty_trace(f, args...)
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#endif
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struct n_tty_data {
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unsigned int column;
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unsigned long overrun_time;
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@ -1748,58 +1755,95 @@ static int copy_from_read_buf(struct tty_struct *tty,
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}
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/**
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* canon_copy_to_user - copy read data in canonical mode
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* canon_copy_from_read_buf - copy read data in canonical mode
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* @tty: terminal device
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* @b: user data
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* @nr: size of data
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*
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* Helper function for n_tty_read. It is only called when ICANON is on;
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* it copies characters one at a time from the read buffer to the user
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* space buffer.
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* it copies one line of input up to and including the line-delimiting
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* character into the user-space buffer.
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*
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* Called under the atomic_read_lock mutex
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*/
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static int canon_copy_to_user(struct tty_struct *tty,
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unsigned char __user **b,
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size_t *nr)
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static int canon_copy_from_read_buf(struct tty_struct *tty,
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unsigned char __user **b,
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size_t *nr)
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{
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struct n_tty_data *ldata = tty->disc_data;
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unsigned long flags;
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int eol, c;
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size_t n, size, more, c;
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unsigned long eol;
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int ret, tail, found = 0;
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/* N.B. avoid overrun if nr == 0 */
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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while (*nr && ldata->read_cnt) {
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eol = test_and_clear_bit(ldata->read_tail, ldata->read_flags);
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c = ldata->read_buf[ldata->read_tail];
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ldata->read_tail = (ldata->read_tail+1) & (N_TTY_BUF_SIZE-1);
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ldata->read_cnt--;
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if (eol) {
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/* this test should be redundant:
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* we shouldn't be reading data if
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* canon_data is 0
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*/
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if (--ldata->canon_data < 0)
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ldata->canon_data = 0;
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}
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n = min_t(size_t, *nr, ldata->read_cnt);
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if (!n) {
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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return 0;
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}
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if (!eol || (c != __DISABLED_CHAR)) {
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if (tty_put_user(tty, c, *b))
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return -EFAULT;
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*b += 1;
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*nr -= 1;
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}
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if (eol) {
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tty_audit_push(tty);
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return 0;
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}
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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tail = ldata->read_tail;
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size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
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n_tty_trace("%s: nr:%zu tail:%d n:%zu size:%zu\n",
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__func__, *nr, tail, n, size);
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eol = find_next_bit(ldata->read_flags, size, tail);
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more = n - (size - tail);
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if (eol == N_TTY_BUF_SIZE && more) {
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/* scan wrapped without finding set bit */
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eol = find_next_bit(ldata->read_flags, more, 0);
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if (eol != more)
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found = 1;
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} else if (eol != size)
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found = 1;
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size = N_TTY_BUF_SIZE - tail;
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n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
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c = n;
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if (found && ldata->read_buf[eol] == __DISABLED_CHAR)
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n--;
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n_tty_trace("%s: eol:%lu found:%d n:%zu c:%zu size:%zu more:%zu\n",
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__func__, eol, found, n, c, size, more);
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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if (n > size) {
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ret = copy_to_user(*b, &ldata->read_buf[tail], size);
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if (ret)
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return -EFAULT;
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ret = copy_to_user(*b + size, ldata->read_buf, n - size);
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} else
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ret = copy_to_user(*b, &ldata->read_buf[tail], n);
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if (ret)
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return -EFAULT;
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*b += n;
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*nr -= n;
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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ldata->read_tail = (ldata->read_tail + c) & (N_TTY_BUF_SIZE - 1);
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ldata->read_cnt -= c;
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if (found) {
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__clear_bit(eol, ldata->read_flags);
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/* this test should be redundant:
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* we shouldn't be reading data if
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* canon_data is 0
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*/
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if (--ldata->canon_data < 0)
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ldata->canon_data = 0;
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}
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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if (found)
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tty_audit_push(tty);
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return 0;
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}
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@ -1972,7 +2016,7 @@ do_it_again:
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}
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if (ldata->icanon && !L_EXTPROC(tty)) {
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retval = canon_copy_to_user(tty, &b, &nr);
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retval = canon_copy_from_read_buf(tty, &b, &nr);
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if (retval)
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break;
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} else {
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