Commit 32f13521 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

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: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 88bb0de3

drivers/tty/n_tty.c

+77 −33
Original line number Diff line number Diff line
@@ -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;
@@ -1748,35 +1755,84 @@ 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,

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) {

	n = min_t(size_t, *nr, ldata->read_cnt);

	if (!n) {

		raw_spin_unlock_irqrestore(&ldata->read_lock, flags);

		return 0;

	}



	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
@@ -1786,22 +1842,10 @@ static int canon_copy_to_user(struct tty_struct *tty, 
	}

	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) {

	if (found)

		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 *);
@@ -1972,7 +2016,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
		}



		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 {