Merge branch 'master' into for-linus

1 files changed, 2121 insertions, 0 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
new file mode 100644
index 0000000..428f4fe
--- /dev/null
+++ b/drivers/tty/n_tty.c
@@ -0,0 +1,2121 @@
+/*
+ * n_tty.c --- implements the N_TTY line discipline.
+ *
+ * This code used to be in tty_io.c, but things are getting hairy
+ * enough that it made sense to split things off.  (The N_TTY
+ * processing has changed so much that it's hardly recognizable,
+ * anyway...)
+ *
+ * Note that the open routine for N_TTY is guaranteed never to return
+ * an error.  This is because Linux will fall back to setting a line
+ * to N_TTY if it can not switch to any other line discipline.
+ *
+ * Written by Theodore Ts'o, Copyright 1994.
+ *
+ * This file also contains code originally written by Linus Torvalds,
+ * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
+ *
+ * This file may be redistributed under the terms of the GNU General Public
+ * License.
+ *
+ * Reduced memory usage for older ARM systems  - Russell King.
+ *
+ * 2000/01/20   Fixed SMP locking on put_tty_queue using bits of
+ *		the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
+ *		who actually finally proved there really was a race.
+ *
+ * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
+ *		waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
+ *		Also fixed a bug in BLOCKING mode where n_tty_write returns
+ *		EAGAIN
+ */
+
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/fcntl.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/bitops.h>
+#include <linux/audit.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+
+#include <asm/system.h>
+
+/* number of characters left in xmit buffer before select has we have room */
+#define WAKEUP_CHARS 256
+
+/*
+ * This defines the low- and high-watermarks for throttling and
+ * unthrottling the TTY driver.  These watermarks are used for
+ * controlling the space in the read buffer.
+ */
+#define TTY_THRESHOLD_THROTTLE		128 /* now based on remaining room */
+#define TTY_THRESHOLD_UNTHROTTLE 	128
+
+/*
+ * Special byte codes used in the echo buffer to represent operations
+ * or special handling of characters.  Bytes in the echo buffer that
+ * are not part of such special blocks are treated as normal character
+ * codes.
+ */
+#define ECHO_OP_START 0xff
+#define ECHO_OP_MOVE_BACK_COL 0x80
+#define ECHO_OP_SET_CANON_COL 0x81
+#define ECHO_OP_ERASE_TAB 0x82
+
+static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
+			       unsigned char __user *ptr)
+{
+	tty_audit_add_data(tty, &x, 1);
+	return put_user(x, ptr);
+}
+
+/**
+ *	n_tty_set__room	-	receive space
+ *	@tty: terminal
+ *
+ *	Called by the driver to find out how much data it is
+ *	permitted to feed to the line discipline without any being lost
+ *	and thus to manage flow control. Not serialized. Answers for the
+ *	"instant".
+ */
+
+static void n_tty_set_room(struct tty_struct *tty)
+{
+	/* tty->read_cnt is not read locked ? */
+	int	left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
+
+	/*
+	 * If we are doing input canonicalization, and there are no
+	 * pending newlines, let characters through without limit, so
+	 * that erase characters will be handled.  Other excess
+	 * characters will be beeped.
+	 */
+	if (left <= 0)
+		left = tty->icanon && !tty->canon_data;
+	tty->receive_room = left;
+}
+
+static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
+{
+	if (tty->read_cnt < N_TTY_BUF_SIZE) {
+		tty->read_buf[tty->read_head] = c;
+		tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
+		tty->read_cnt++;
+	}
+}
+
+/**
+ *	put_tty_queue		-	add character to tty
+ *	@c: character
+ *	@tty: tty device
+ *
+ *	Add a character to the tty read_buf queue. This is done under the
+ *	read_lock to serialize character addition and also to protect us
+ *	against parallel reads or flushes
+ */
+
+static void put_tty_queue(unsigned char c, struct tty_struct *tty)
+{
+	unsigned long flags;
+	/*
+	 *	The problem of stomping on the buffers ends here.
+	 *	Why didn't anyone see this one coming? --AJK
+	*/
+	spin_lock_irqsave(&tty->read_lock, flags);
+	put_tty_queue_nolock(c, tty);
+	spin_unlock_irqrestore(&tty->read_lock, flags);
+}
+
+/**
+ *	check_unthrottle	-	allow new receive data
+ *	@tty; tty device
+ *
+ *	Check whether to call the driver unthrottle functions
+ *
+ *	Can sleep, may be called under the atomic_read_lock mutex but
+ *	this is not guaranteed.
+ */
+static void check_unthrottle(struct tty_struct *tty)
+{
+	if (tty->count)
+		tty_unthrottle(tty);
+}
+
+/**
+ *	reset_buffer_flags	-	reset buffer state
+ *	@tty: terminal to reset
+ *
+ *	Reset the read buffer counters, clear the flags,
+ *	and make sure the driver is unthrottled. Called
+ *	from n_tty_open() and n_tty_flush_buffer().
+ *
+ *	Locking: tty_read_lock for read fields.
+ */
+
+static void reset_buffer_flags(struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->read_lock, flags);
+	tty->read_head = tty->read_tail = tty->read_cnt = 0;
+	spin_unlock_irqrestore(&tty->read_lock, flags);
+
+	mutex_lock(&tty->echo_lock);
+	tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
+	mutex_unlock(&tty->echo_lock);
+
+	tty->canon_head = tty->canon_data = tty->erasing = 0;
+	memset(&tty->read_flags, 0, sizeof tty->read_flags);
+	n_tty_set_room(tty);
+	check_unthrottle(tty);
+}
+
+/**
+ *	n_tty_flush_buffer	-	clean input queue
+ *	@tty:	terminal device
+ *
+ *	Flush the input buffer. Called when the line discipline is
+ *	being closed, when the tty layer wants the buffer flushed (eg
+ *	at hangup) or when the N_TTY line discipline internally has to
+ *	clean the pending queue (for example some signals).
+ *
+ *	Locking: ctrl_lock, read_lock.
+ */
+
+static void n_tty_flush_buffer(struct tty_struct *tty)
+{
+	unsigned long flags;
+	/* clear everything and unthrottle the driver */
+	reset_buffer_flags(tty);
+
+	if (!tty->link)
+		return;
+
+	spin_lock_irqsave(&tty->ctrl_lock, flags);
+	if (tty->link->packet) {
+		tty->ctrl_status |= TIOCPKT_FLUSHREAD;
+		wake_up_interruptible(&tty->link->read_wait);
+	}
+	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+}
+
+/**
+ *	n_tty_chars_in_buffer	-	report available bytes
+ *	@tty: tty device
+ *
+ *	Report the number of characters buffered to be delivered to user
+ *	at this instant in time.
+ *
+ *	Locking: read_lock
+ */
+
+static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
+{
+	unsigned long flags;
+	ssize_t n = 0;
+
+	spin_lock_irqsave(&tty->read_lock, flags);
+	if (!tty->icanon) {
+		n = tty->read_cnt;
+	} else if (tty->canon_data) {
+		n = (tty->canon_head > tty->read_tail) ?
+			tty->canon_head - tty->read_tail :
+			tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
+	}
+	spin_unlock_irqrestore(&tty->read_lock, flags);
+	return n;
+}
+
+/**
+ *	is_utf8_continuation	-	utf8 multibyte check
+ *	@c: byte to check
+ *
+ *	Returns true if the utf8 character 'c' is a multibyte continuation
+ *	character. We use this to correctly compute the on screen size
+ *	of the character when printing
+ */
+
+static inline int is_utf8_continuation(unsigned char c)
+{
+	return (c & 0xc0) == 0x80;
+}
+
+/**
+ *	is_continuation		-	multibyte check
+ *	@c: byte to check
+ *
+ *	Returns true if the utf8 character 'c' is a multibyte continuation
+ *	character and the terminal is in unicode mode.
+ */
+
+static inline int is_continuation(unsigned char c, struct tty_struct *tty)
+{
+	return I_IUTF8(tty) && is_utf8_continuation(c);
+}
+
+/**
+ *	do_output_char			-	output one character
+ *	@c: character (or partial unicode symbol)
+ *	@tty: terminal device
+ *	@space: space available in tty driver write buffer
+ *
+ *	This is a helper function that handles one output character
+ *	(including special characters like TAB, CR, LF, etc.),
+ *	doing OPOST processing and putting the results in the
+ *	tty driver's write buffer.
+ *
+ *	Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
+ *	and NLDLY.  They simply aren't relevant in the world today.
+ *	If you ever need them, add them here.
+ *
+ *	Returns the number of bytes of buffer space used or -1 if
+ *	no space left.
+ *
+ *	Locking: should be called under the output_lock to protect
+ *		 the column state and space left in the buffer
+ */
+
+static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
+{
+	int	spaces;
+
+	if (!space)
+		return -1;
+
+	switch (c) {
+	case '\n':
+		if (O_ONLRET(tty))
+			tty->column = 0;
+		if (O_ONLCR(tty)) {
+			if (space < 2)
+				return -1;
+			tty->canon_column = tty->column = 0;
+			tty->ops->write(tty, "\r\n", 2);
+			return 2;
+		}
+		tty->canon_column = tty->column;
+		break;
+	case '\r':
+		if (O_ONOCR(tty) && tty->column == 0)
+			return 0;
+		if (O_OCRNL(tty)) {
+			c = '\n';
+			if (O_ONLRET(tty))
+				tty->canon_column = tty->column = 0;
+			break;
+		}
+		tty->canon_column = tty->column = 0;
+		break;
+	case '\t':
+		spaces = 8 - (tty->column & 7);
+		if (O_TABDLY(tty) == XTABS) {
+			if (space < spaces)
+				return -1;
+			tty->column += spaces;
+			tty->ops->write(tty, "        ", spaces);
+			return spaces;
+		}
+		tty->column += spaces;
+		break;
+	case '\b':
+		if (tty->column > 0)
+			tty->column--;
+		break;
+	default:
+		if (!iscntrl(c)) {
+			if (O_OLCUC(tty))
+				c = toupper(c);
+			if (!is_continuation(c, tty))
+				tty->column++;
+		}
+		break;
+	}
+
+	tty_put_char(tty, c);
+	return 1;
+}
+
+/**
+ *	process_output			-	output post processor
+ *	@c: character (or partial unicode symbol)
+ *	@tty: terminal device
+ *
+ *	Output one character with OPOST processing.
+ *	Returns -1 when the output device is full and the character
+ *	must be retried.
+ *
+ *	Locking: output_lock to protect column state and space left
+ *		 (also, this is called from n_tty_write under the
+ *		  tty layer write lock)
+ */
+
+static int process_output(unsigned char c, struct tty_struct *tty)
+{
+	int	space, retval;
+
+	mutex_lock(&tty->output_lock);
+
+	space = tty_write_room(tty);
+	retval = do_output_char(c, tty, space);
+
+	mutex_unlock(&tty->output_lock);
+	if (retval < 0)
+		return -1;
+	else
+		return 0;
+}
+
+/**
+ *	process_output_block		-	block post processor
+ *	@tty: terminal device
+ *	@buf: character buffer
+ *	@nr: number of bytes to output
+ *
+ *	Output a block of characters with OPOST processing.
+ *	Returns the number of characters output.
+ *
+ *	This path is used to speed up block console writes, among other
+ *	things when processing blocks of output data. It handles only
+ *	the simple cases normally found and helps to generate blocks of
+ *	symbols for the console driver and thus improve performance.
+ *
+ *	Locking: output_lock to protect column state and space left
+ *		 (also, this is called from n_tty_write under the
+ *		  tty layer write lock)
+ */
+
+static ssize_t process_output_block(struct tty_struct *tty,
+				    const unsigned char *buf, unsigned int nr)
+{
+	int	space;
+	int 	i;
+	const unsigned char *cp;
+
+	mutex_lock(&tty->output_lock);
+
+	space = tty_write_room(tty);
+	if (!space) {
+		mutex_unlock(&tty->output_lock);
+		return 0;
+	}
+	if (nr > space)
+		nr = space;
+
+	for (i = 0, cp = buf; i < nr; i++, cp++) {
+		unsigned char c = *cp;
+
+		switch (c) {
+		case '\n':
+			if (O_ONLRET(tty))
+				tty->column = 0;
+			if (O_ONLCR(tty))
+				goto break_out;
+			tty->canon_column = tty->column;
+			break;
+		case '\r':
+			if (O_ONOCR(tty) && tty->column == 0)
+				goto break_out;
+			if (O_OCRNL(tty))
+				goto break_out;
+			tty->canon_column = tty->column = 0;
+			break;
+		case '\t':
+			goto break_out;
+		case '\b':
+			if (tty->column > 0)
+				tty->column--;
+			break;
+		default:
+			if (!iscntrl(c)) {
+				if (O_OLCUC(tty))
+					goto break_out;
+				if (!is_continuation(c, tty))
+					tty->column++;
+			}
+			break;
+		}
+	}
+break_out:
+	i = tty->ops->write(tty, buf, i);
+
+	mutex_unlock(&tty->output_lock);
+	return i;
+}
+
+/**
+ *	process_echoes	-	write pending echo characters
+ *	@tty: terminal device
+ *
+ *	Write previously buffered echo (and other ldisc-generated)
+ *	characters to the tty.
+ *
+ *	Characters generated by the ldisc (including echoes) need to
+ *	be buffered because the driver's write buffer can fill during
+ *	heavy program output.  Echoing straight to the driver will
+ *	often fail under these conditions, causing lost characters and
+ *	resulting mismatches of ldisc state information.
+ *
+ *	Since the ldisc state must represent the characters actually sent
+ *	to the driver at the time of the write, operations like certain
+ *	changes in column state are also saved in the buffer and executed
+ *	here.
+ *
+ *	A circular fifo buffer is used so that the most recent characters
+ *	are prioritized.  Also, when control characters are echoed with a
+ *	prefixed "^", the pair is treated atomically and thus not separated.
+ *
+ *	Locking: output_lock to protect column state and space left,
+ *		 echo_lock to protect the echo buffer
+ */
+
+static void process_echoes(struct tty_struct *tty)
+{
+	int	space, nr;
+	unsigned char c;
+	unsigned char *cp, *buf_end;
+
+	if (!tty->echo_cnt)
+		return;
+
+	mutex_lock(&tty->output_lock);
+	mutex_lock(&tty->echo_lock);
+
+	space = tty_write_room(tty);
+
+	buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
+	cp = tty->echo_buf + tty->echo_pos;
+	nr = tty->echo_cnt;
+	while (nr > 0) {
+		c = *cp;
+		if (c == ECHO_OP_START) {
+			unsigned char op;
+			unsigned char *opp;
+			int no_space_left = 0;
+
+			/*
+			 * If the buffer byte is the start of a multi-byte
+			 * operation, get the next byte, which is either the
+			 * op code or a control character value.
+			 */
+			opp = cp + 1;
+			if (opp == buf_end)
+				opp -= N_TTY_BUF_SIZE;
+			op = *opp;
+
+			switch (op) {
+				unsigned int num_chars, num_bs;
+
+			case ECHO_OP_ERASE_TAB:
+				if (++opp == buf_end)
+					opp -= N_TTY_BUF_SIZE;
+				num_chars = *opp;
+
+				/*
+				 * Determine how many columns to go back
+				 * in order to erase the tab.
+				 * This depends on the number of columns
+				 * used by other characters within the tab
+				 * area.  If this (modulo 8) count is from
+				 * the start of input rather than from a
+				 * previous tab, we offset by canon column.
+				 * Otherwise, tab spacing is normal.
+				 */
+				if (!(num_chars & 0x80))
+					num_chars += tty->canon_column;
+				num_bs = 8 - (num_chars & 7);
+
+				if (num_bs > space) {
+					no_space_left = 1;
+					break;
+				}
+				space -= num_bs;
+				while (num_bs--) {
+					tty_put_char(tty, '\b');
+					if (tty->column > 0)
+						tty->column--;
+				}
+				cp += 3;
+				nr -= 3;
+				break;
+
+			case ECHO_OP_SET_CANON_COL:
+				tty->canon_column = tty->column;
+				cp += 2;
+				nr -= 2;
+				break;
+
+			case ECHO_OP_MOVE_BACK_COL:
+				if (tty->column > 0)
+					tty->column--;
+				cp += 2;
+				nr -= 2;
+				break;
+
+			case ECHO_OP_START:
+				/* This is an escaped echo op start code */
+				if (!space) {
+					no_space_left = 1;
+					break;
+				}
+				tty_put_char(tty, ECHO_OP_START);
+				tty->column++;
+				space--;
+				cp += 2;
+				nr -= 2;
+				break;
+
+			default:
+				/*
+				 * If the op is not a special byte code,
+				 * it is a ctrl char tagged to be echoed
+				 * as "^X" (where X is the letter
+				 * representing the control char).
+				 * Note that we must ensure there is
+				 * enough space for the whole ctrl pair.
+				 *
+				 */
+				if (space < 2) {
+					no_space_left = 1;
+					break;
+				}
+				tty_put_char(tty, '^');
+				tty_put_char(tty, op ^ 0100);
+				tty->column += 2;
+				space -= 2;
+				cp += 2;
+				nr -= 2;
+			}
+
+			if (no_space_left)
+				break;
+		} else {
+			if (O_OPOST(tty) &&
+			    !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
+				int retval = do_output_char(c, tty, space);
+				if (retval < 0)
+					break;
+				space -= retval;
+			} else {
+				if (!space)
+					break;
+				tty_put_char(tty, c);
+				space -= 1;
+			}
+			cp += 1;
+			nr -= 1;
+		}
+
+		/* When end of circular buffer reached, wrap around */
+		if (cp >= buf_end)
+			cp -= N_TTY_BUF_SIZE;
+	}
+
+	if (nr == 0) {
+		tty->echo_pos = 0;
+		tty->echo_cnt = 0;
+		tty->echo_overrun = 0;
+	} else {
+		int num_processed = tty->echo_cnt - nr;
+		tty->echo_pos += num_processed;
+		tty->echo_pos &= N_TTY_BUF_SIZE - 1;
+		tty->echo_cnt = nr;
+		if (num_processed > 0)
+			tty->echo_overrun = 0;
+	}
+
+	mutex_unlock(&tty->echo_lock);
+	mutex_unlock(&tty->output_lock);
+
+	if (tty->ops->flush_chars)
+		tty->ops->flush_chars(tty);
+}
+
+/**
+ *	add_echo_byte	-	add a byte to the echo buffer
+ *	@c: unicode byte to echo
+ *	@tty: terminal device
+ *
+ *	Add a character or operation byte to the echo buffer.
+ *
+ *	Should be called under the echo lock to protect the echo buffer.
+ */
+
+static void add_echo_byte(unsigned char c, struct tty_struct *tty)
+{
+	int	new_byte_pos;
+
+	if (tty->echo_cnt == N_TTY_BUF_SIZE) {
+		/* Circular buffer is already at capacity */
+		new_byte_pos = tty->echo_pos;
+
+		/*
+		 * Since the buffer start position needs to be advanced,
+		 * be sure to step by a whole operation byte group.
+		 */
+		if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
+			if (tty->echo_buf[(tty->echo_pos + 1) &
+					  (N_TTY_BUF_SIZE - 1)] ==
+						ECHO_OP_ERASE_TAB) {
+				tty->echo_pos += 3;
+				tty->echo_cnt -= 2;
+			} else {
+				tty->echo_pos += 2;
+				tty->echo_cnt -= 1;
+			}
+		} else {
+			tty->echo_pos++;
+		}
+		tty->echo_pos &= N_TTY_BUF_SIZE - 1;
+
+		tty->echo_overrun = 1;
+	} else {
+		new_byte_pos = tty->echo_pos + tty->echo_cnt;
+		new_byte_pos &= N_TTY_BUF_SIZE - 1;
+		tty->echo_cnt++;
+	}
+
+	tty->echo_buf[new_byte_pos] = c;
+}
+
+/**
+ *	echo_move_back_col	-	add operation to move back a column
+ *	@tty: terminal device
+ *
+ *	Add an operation to the echo buffer to move back one column.
+ *
+ *	Locking: echo_lock to protect the echo buffer
+ */
+
+static void echo_move_back_col(struct tty_struct *tty)
+{
+	mutex_lock(&tty->echo_lock);
+
+	add_echo_byte(ECHO_OP_START, tty);
+	add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
+
+	mutex_unlock(&tty->echo_lock);
+}
+
+/**
+ *	echo_set_canon_col	-	add operation to set the canon column
+ *	@tty: terminal device
+ *
+ *	Add an operation to the echo buffer to set the canon column
+ *	to the current column.
+ *
+ *	Locking: echo_lock to protect the echo buffer
+ */
+
+static void echo_set_canon_col(struct tty_struct *tty)
+{
+	mutex_lock(&tty->echo_lock);
+
+	add_echo_byte(ECHO_OP_START, tty);
+	add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
+
+	mutex_unlock(&tty->echo_lock);
+}
+
+/**
+ *	echo_erase_tab	-	add operation to erase a tab
+ *	@num_chars: number of character columns already used
+ *	@after_tab: true if num_chars starts after a previous tab
+ *	@tty: terminal device
+ *
+ *	Add an operation to the echo buffer to erase a tab.
+ *
+ *	Called by the eraser function, which knows how many character
+ *	columns have been used since either a previous tab or the start
+ *	of input.  This information will be used later, along with
+ *	canon column (if applicable), to go back the correct number
+ *	of columns.
+ *
+ *	Locking: echo_lock to protect the echo buffer
+ */
+
+static void echo_erase_tab(unsigned int num_chars, int after_tab,
+			   struct tty_struct *tty)
+{
+	mutex_lock(&tty->echo_lock);
+
+	add_echo_byte(ECHO_OP_START, tty);
+	add_echo_byte(ECHO_OP_ERASE_TAB, tty);
+
+	/* We only need to know this modulo 8 (tab spacing) */
+	num_chars &= 7;
+
+	/* Set the high bit as a flag if num_chars is after a previous tab */
+	if (after_tab)
+		num_chars |= 0x80;
+
+	add_echo_byte(num_chars, tty);
+
+	mutex_unlock(&tty->echo_lock);
+}
+
+/**
+ *	echo_char_raw	-	echo a character raw
+ *	@c: unicode byte to echo
+ *	@tty: terminal device
+ *
+ *	Echo user input back onto the screen. This must be called only when
+ *	L_ECHO(tty) is true. Called from the driver receive_buf path.
+ *
+ *	This variant does not treat control characters specially.
+ *
+ *	Locking: echo_lock to protect the echo buffer
+ */
+
+static void echo_char_raw(unsigned char c, struct tty_struct *tty)
+{
+	mutex_lock(&tty->echo_lock);
+
+	if (c == ECHO_OP_START) {
+		add_echo_byte(ECHO_OP_START, tty);
+		add_echo_byte(ECHO_OP_START, tty);
+	} else {
+		add_echo_byte(c, tty);
+	}
+
+	mutex_unlock(&tty->echo_lock);
+}
+
+/**
+ *	echo_char	-	echo a character
+ *	@c: unicode byte to echo
+ *	@tty: terminal device
+ *
+ *	Echo user input back onto the screen. This must be called only when
+ *	L_ECHO(tty) is true. Called from the driver receive_buf path.
+ *
+ *	This variant tags control characters to be echoed as "^X"
+ *	(where X is the letter representing the control char).
+ *
+ *	Locking: echo_lock to protect the echo buffer
+ */
+
+static void echo_char(unsigned char c, struct tty_struct *tty)
+{
+	mutex_lock(&tty->echo_lock);
+
+	if (c == ECHO_OP_START) {
+		add_echo_byte(ECHO_OP_START, tty);
+		add_echo_byte(ECHO_OP_START, tty);
+	} else {
+		if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
+			add_echo_byte(ECHO_OP_START, tty);
+		add_echo_byte(c, tty);
+	}
+
+	mutex_unlock(&tty->echo_lock);
+}
+
+/**
+ *	finish_erasing		-	complete erase
+ *	@tty: tty doing the erase
+ */
+
+static inline void finish_erasing(struct tty_struct *tty)
+{
+	if (tty->erasing) {
+		echo_char_raw('/', tty);
+		tty->erasing = 0;
+	}
+}
+
+/**
+ *	eraser		-	handle erase function
+ *	@c: character input
+ *	@tty: terminal device
+ *
+ *	Perform erase and necessary output when an erase character is
+ *	present in the stream from the driver layer. Handles the complexities
+ *	of UTF-8 multibyte symbols.
+ *
+ *	Locking: read_lock for tty buffers
+ */
+
+static void eraser(unsigned char c, struct tty_struct *tty)
+{
+	enum { ERASE, WERASE, KILL } kill_type;
+	int head, seen_alnums, cnt;
+	unsigned long flags;
+
+	/* FIXME: locking needed ? */
+	if (tty->read_head == tty->canon_head) {
+		/* process_output('\a', tty); */ /* what do you think? */
+		return;
+	}
+	if (c == ERASE_CHAR(tty))
+		kill_type = ERASE;
+	else if (c == WERASE_CHAR(tty))
+		kill_type = WERASE;
+	else {
+		if (!L_ECHO(tty)) {
+			spin_lock_irqsave(&tty->read_lock, flags);
+			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
+					  (N_TTY_BUF_SIZE - 1));
+			tty->read_head = tty->canon_head;
+			spin_unlock_irqrestore(&tty->read_lock, flags);
+			return;
+		}
+		if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
+			spin_lock_irqsave(&tty->read_lock, flags);
+			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
+					  (N_TTY_BUF_SIZE - 1));
+			tty->read_head = tty->canon_head;
+			spin_unlock_irqrestore(&tty->read_lock, flags);
+			finish_erasing(tty);
+			echo_char(KILL_CHAR(tty), tty);
+			/* Add a newline if ECHOK is on and ECHOKE is off. */
+			if (L_ECHOK(tty))
+				echo_char_raw('\n', tty);
+			return;
+		}
+		kill_type = KILL;
+	}
+
+	seen_alnums = 0;
+	/* FIXME: Locking ?? */
+	while (tty->read_head != tty->canon_head) {
+		head = tty->read_head;
+
+		/* erase a single possibly multibyte character */
+		do {
+			head = (head - 1) & (N_TTY_BUF_SIZE-1);
+			c = tty->read_buf[head];
+		} while (is_continuation(c, tty) && head != tty->canon_head);
+
+		/* do not partially erase */
+		if (is_continuation(c, tty))
+			break;
+
+		if (kill_type == WERASE) {
+			/* Equivalent to BSD's ALTWERASE. */
+			if (isalnum(c) || c == '_')
+				seen_alnums++;
+			else if (seen_alnums)
+				break;
+		}
+		cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
+		spin_lock_irqsave(&tty->read_lock, flags);
+		tty->read_head = head;
+		tty->read_cnt -= cnt;
+		spin_unlock_irqrestore(&tty->read_lock, flags);
+		if (L_ECHO(tty)) {
+			if (L_ECHOPRT(tty)) {
+				if (!tty->erasing) {
+					echo_char_raw('\\', tty);
+					tty->erasing = 1;
+				}
+				/* if cnt > 1, output a multi-byte character */
+				echo_char(c, tty);
+				while (--cnt > 0) {
+					head = (head+1) & (N_TTY_BUF_SIZE-1);
+					echo_char_raw(tty->read_buf[head], tty);
+					echo_move_back_col(tty);
+				}
+			} else if (kill_type == ERASE && !L_ECHOE(tty)) {
+				echo_char(ERASE_CHAR(tty), tty);
+			} else if (c == '\t') {
+				unsigned int num_chars = 0;
+				int after_tab = 0;
+				unsigned long tail = tty->read_head;
+
+				/*
+				 * Count the columns used for characters
+				 * since the start of input or after a
+				 * previous tab.
+				 * This info is used to go back the correct
+				 * number of columns.
+				 */
+				while (tail != tty->canon_head) {
+					tail = (tail-1) & (N_TTY_BUF_SIZE-1);
+					c = tty->read_buf[tail];
+					if (c == '\t') {
+						after_tab = 1;
+						break;
+					} else if (iscntrl(c)) {
+						if (L_ECHOCTL(tty))
+							num_chars += 2;
+					} else if (!is_continuation(c, tty)) {
+						num_chars++;
+					}
+				}
+				echo_erase_tab(num_chars, after_tab, tty);
+			} else {
+				if (iscntrl(c) && L_ECHOCTL(tty)) {
+					echo_char_raw('\b', tty);
+					echo_char_raw(' ', tty);
+					echo_char_raw('\b', tty);
+				}
+				if (!iscntrl(c) || L_ECHOCTL(tty)) {
+					echo_char_raw('\b', tty);
+					echo_char_raw(' ', tty);
+					echo_char_raw('\b', tty);
+				}
+			}
+		}
+		if (kill_type == ERASE)
+			break;
+	}
+	if (tty->read_head == tty->canon_head && L_ECHO(tty))
+		finish_erasing(tty);
+}
+
+/**
+ *	isig		-	handle the ISIG optio
+ *	@sig: signal
+ *	@tty: terminal
+ *	@flush: force flush
+ *
+ *	Called when a signal is being sent due to terminal input. This
+ *	may caus terminal flushing to take place according to the termios
+ *	settings and character used. Called from the driver receive_buf
+ *	path so serialized.
+ *
+ *	Locking: ctrl_lock, read_lock (both via flush buffer)
+ */
+
+static inline void isig(int sig, struct tty_struct *tty, int flush)
+{
+	if (tty->pgrp)
+		kill_pgrp(tty->pgrp, sig, 1);
+	if (flush || !L_NOFLSH(tty)) {
+		n_tty_flush_buffer(tty);
+		tty_driver_flush_buffer(tty);
+	}
+}
+
+/**
+ *	n_tty_receive_break	-	handle break
+ *	@tty: terminal
+ *
+ *	An RS232 break event has been hit in the incoming bitstream. This
+ *	can cause a variety of events depending upon the termios settings.
+ *
+ *	Called from the receive_buf path so single threaded.
+ */
+
+static inline void n_tty_receive_break(struct tty_struct *tty)
+{
+	if (I_IGNBRK(tty))
+		return;
+	if (I_BRKINT(tty)) {
+		isig(SIGINT, tty, 1);
+		return;
+	}
+	if (I_PARMRK(tty)) {
+		put_tty_queue('\377', tty);
+		put_tty_queue('\0', tty);
+	}
+	put_tty_queue('\0', tty);
+	wake_up_interruptible(&tty->read_wait);
+}
+
+/**
+ *	n_tty_receive_overrun	-	handle overrun reporting
+ *	@tty: terminal
+ *
+ *	Data arrived faster than we could process it. While the tty
+ *	driver has flagged this the bits that were missed are gone
+ *	forever.
+ *
+ *	Called from the receive_buf path so single threaded. Does not
+ *	need locking as num_overrun and overrun_time are function
+ *	private.
+ */
+
+static inline void n_tty_receive_overrun(struct tty_struct *tty)
+{
+	char buf[64];
+
+	tty->num_overrun++;
+	if (time_before(tty->overrun_time, jiffies - HZ) ||
+			time_after(tty->overrun_time, jiffies)) {
+		printk(KERN_WARNING "%s: %d input overrun(s)\n",
+			tty_name(tty, buf),
+			tty->num_overrun);
+		tty->overrun_time = jiffies;
+		tty->num_overrun = 0;
+	}
+}
+
+/**
+ *	n_tty_receive_parity_error	-	error notifier
+ *	@tty: terminal device
+ *	@c: character
+ *
+ *	Process a parity error and queue the right data to indicate
+ *	the error case if necessary. Locking as per n_tty_receive_buf.
+ */
+static inline void n_tty_receive_parity_error(struct tty_struct *tty,
+					      unsigned char c)
+{
+	if (I_IGNPAR(tty))
+		return;
+	if (I_PARMRK(tty)) {
+		put_tty_queue('\377', tty);
+		put_tty_queue('\0', tty);
+		put_tty_queue(c, tty);
+	} else	if (I_INPCK(tty))
+		put_tty_queue('\0', tty);
+	else
+		put_tty_queue(c, tty);
+	wake_up_interruptible(&tty->read_wait);
+}
+
+/**
+ *	n_tty_receive_char	-	perform processing
+ *	@tty: terminal device
+ *	@c: character
+ *
+ *	Process an individual character of input received from the driver.
+ *	This is serialized with respect to itself by the rules for the
+ *	driver above.
+ */
+
+static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
+{
+	unsigned long flags;
+	int parmrk;
+
+	if (tty->raw) {
+		put_tty_queue(c, tty);
+		return;
+	}
+
+	if (I_ISTRIP(tty))
+		c &= 0x7f;
+	if (I_IUCLC(tty) && L_IEXTEN(tty))
+		c = tolower(c);
+
+	if (L_EXTPROC(tty)) {
+		put_tty_queue(c, tty);
+		return;
+	}
+
+	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
+	    I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
+	    c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
+		start_tty(tty);
+		process_echoes(tty);
+	}
+
+	if (tty->closing) {
+		if (I_IXON(tty)) {
+			if (c == START_CHAR(tty)) {
+				start_tty(tty);
+				process_echoes(tty);
+			} else if (c == STOP_CHAR(tty))
+				stop_tty(tty);
+		}
+		return;
+	}
+
+	/*
+	 * If the previous character was LNEXT, or we know that this
+	 * character is not one of the characters that we'll have to
+	 * handle specially, do shortcut processing to speed things
+	 * up.
+	 */
+	if (!test_bit(c, tty->process_char_map) || tty->lnext) {
+		tty->lnext = 0;
+		parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
+		if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
+			/* beep if no space */
+			if (L_ECHO(tty))
+				process_output('\a', tty);
+			return;
+		}
+		if (L_ECHO(tty)) {
+			finish_erasing(tty);
+			/* Record the column of first canon char. */
+			if (tty->canon_head == tty->read_head)
+				echo_set_canon_col(tty);
+			echo_char(c, tty);
+			process_echoes(tty);
+		}
+		if (parmrk)
+			put_tty_queue(c, tty);
+		put_tty_queue(c, tty);
+		return;
+	}
+
+	if (I_IXON(tty)) {
+		if (c == START_CHAR(tty)) {
+			start_tty(tty);
+			process_echoes(tty);
+			return;
+		}
+		if (c == STOP_CHAR(tty)) {
+			stop_tty(tty);
+			return;
+		}
+	}
+
+	if (L_ISIG(tty)) {
+		int signal;
+		signal = SIGINT;
+		if (c == INTR_CHAR(tty))
+			goto send_signal;
+		signal = SIGQUIT;
+		if (c == QUIT_CHAR(tty))
+			goto send_signal;
+		signal = SIGTSTP;
+		if (c == SUSP_CHAR(tty)) {
+send_signal:
+			/*
+			 * Note that we do not use isig() here because we want
+			 * the order to be:
+			 * 1) flush, 2) echo, 3) signal
+			 */
+			if (!L_NOFLSH(tty)) {
+				n_tty_flush_buffer(tty);
+				tty_driver_flush_buffer(tty);
+			}
+			if (I_IXON(tty))
+				start_tty(tty);
+			if (L_ECHO(tty)) {
+				echo_char(c, tty);
+				process_echoes(tty);
+			}
+			if (tty->pgrp)
+				kill_pgrp(tty->pgrp, signal, 1);
+			return;
+		}
+	}
+
+	if (c == '\r') {
+		if (I_IGNCR(tty))
+			return;
+		if (I_ICRNL(tty))
+			c = '\n';
+	} else if (c == '\n' && I_INLCR(tty))
+		c = '\r';
+
+	if (tty->icanon) {
+		if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
+		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
+			eraser(c, tty);
+			process_echoes(tty);
+			return;
+		}
+		if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
+			tty->lnext = 1;
+			if (L_ECHO(tty)) {
+				finish_erasing(tty);
+				if (L_ECHOCTL(tty)) {
+					echo_char_raw('^', tty);
+					echo_char_raw('\b', tty);
+					process_echoes(tty);
+				}
+			}
+			return;
+		}
+		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
+		    L_IEXTEN(tty)) {
+			unsigned long tail = tty->canon_head;
+
+			finish_erasing(tty);
+			echo_char(c, tty);
+			echo_char_raw('\n', tty);
+			while (tail != tty->read_head) {
+				echo_char(tty->read_buf[tail], tty);
+				tail = (tail+1) & (N_TTY_BUF_SIZE-1);
+			}
+			process_echoes(tty);
+			return;
+		}
+		if (c == '\n') {
+			if (tty->read_cnt >= N_TTY_BUF_SIZE) {
+				if (L_ECHO(tty))
+					process_output('\a', tty);
+				return;
+			}
+			if (L_ECHO(tty) || L_ECHONL(tty)) {
+				echo_char_raw('\n', tty);
+				process_echoes(tty);
+			}
+			goto handle_newline;
+		}
+		if (c == EOF_CHAR(tty)) {
+			if (tty->read_cnt >= N_TTY_BUF_SIZE)
+				return;
+			if (tty->canon_head != tty->read_head)
+				set_bit(TTY_PUSH, &tty->flags);
+			c = __DISABLED_CHAR;
+			goto handle_newline;
+		}
+		if ((c == EOL_CHAR(tty)) ||
+		    (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
+			parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
+				 ? 1 : 0;
+			if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
+				if (L_ECHO(tty))
+					process_output('\a', tty);
+				return;
+			}
+			/*
+			 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
+			 */
+			if (L_ECHO(tty)) {
+				/* Record the column of first canon char. */
+				if (tty->canon_head == tty->read_head)
+					echo_set_canon_col(tty);
+				echo_char(c, tty);
+				process_echoes(tty);
+			}
+			/*
+			 * XXX does PARMRK doubling happen for
+			 * EOL_CHAR and EOL2_CHAR?
+			 */
+			if (parmrk)
+				put_tty_queue(c, tty);
+
+handle_newline:
+			spin_lock_irqsave(&tty->read_lock, flags);
+			set_bit(tty->read_head, tty->read_flags);
+			put_tty_queue_nolock(c, tty);
+			tty->canon_head = tty->read_head;
+			tty->canon_data++;
+			spin_unlock_irqrestore(&tty->read_lock, flags);
+			kill_fasync(&tty->fasync, SIGIO, POLL_IN);
+			if (waitqueue_active(&tty->read_wait))
+				wake_up_interruptible(&tty->read_wait);
+			return;
+		}
+	}
+
+	parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
+	if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
+		/* beep if no space */
+		if (L_ECHO(tty))
+			process_output('\a', tty);
+		return;
+	}
+	if (L_ECHO(tty)) {
+		finish_erasing(tty);
+		if (c == '\n')
+			echo_char_raw('\n', tty);
+		else {
+			/* Record the column of first canon char. */
+			if (tty->canon_head == tty->read_head)
+				echo_set_canon_col(tty);
+			echo_char(c, tty);
+		}
+		process_echoes(tty);
+	}
+
+	if (parmrk)
+		put_tty_queue(c, tty);
+
+	put_tty_queue(c, tty);
+}
+
+
+/**
+ *	n_tty_write_wakeup	-	asynchronous I/O notifier
+ *	@tty: tty device
+ *
+ *	Required for the ptys, serial driver etc. since processes
+ *	that attach themselves to the master and rely on ASYNC
+ *	IO must be woken up
+ */
+
+static void n_tty_write_wakeup(struct tty_struct *tty)
+{
+	if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
+		kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
+}
+
+/**
+ *	n_tty_receive_buf	-	data receive
+ *	@tty: terminal device
+ *	@cp: buffer
+ *	@fp: flag buffer
+ *	@count: characters
+ *
+ *	Called by the terminal driver when a block of characters has
+ *	been received. This function must be called from soft contexts
+ *	not from interrupt context. The driver is responsible for making
+ *	calls one at a time and in order (or using flush_to_ldisc)
+ */
+
+static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
+			      char *fp, int count)
+{
+	const unsigned char *p;
+	char *f, flags = TTY_NORMAL;
+	int	i;
+	char	buf[64];
+	unsigned long cpuflags;
+
+	if (!tty->read_buf)
+		return;
+
+	if (tty->real_raw) {
+		spin_lock_irqsave(&tty->read_lock, cpuflags);
+		i = min(N_TTY_BUF_SIZE - tty->read_cnt,
+			N_TTY_BUF_SIZE - tty->read_head);
+		i = min(count, i);
+		memcpy(tty->read_buf + tty->read_head, cp, i);
+		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
+		tty->read_cnt += i;
+		cp += i;
+		count -= i;
+
+		i = min(N_TTY_BUF_SIZE - tty->read_cnt,
+			N_TTY_BUF_SIZE - tty->read_head);
+		i = min(count, i);
+		memcpy(tty->read_buf + tty->read_head, cp, i);
+		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
+		tty->read_cnt += i;
+		spin_unlock_irqrestore(&tty->read_lock, cpuflags);
+	} else {
+		for (i = count, p = cp, f = fp; i; i--, p++) {
+			if (f)
+				flags = *f++;
+			switch (flags) {
+			case TTY_NORMAL:
+				n_tty_receive_char(tty, *p);
+				break;
+			case TTY_BREAK:
+				n_tty_receive_break(tty);
+				break;
+			case TTY_PARITY:
+			case TTY_FRAME:
+				n_tty_receive_parity_error(tty, *p);
+				break;
+			case TTY_OVERRUN:
+				n_tty_receive_overrun(tty);
+				break;
+			default:
+				printk(KERN_ERR "%s: unknown flag %d\n",
+				       tty_name(tty, buf), flags);
+				break;
+			}
+		}
+		if (tty->ops->flush_chars)
+			tty->ops->flush_chars(tty);
+	}
+
+	n_tty_set_room(tty);
+
+	if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
+		L_EXTPROC(tty)) {
+		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
+		if (waitqueue_active(&tty->read_wait))
+			wake_up_interruptible(&tty->read_wait);
+	}
+
+	/*
+	 * Check the remaining room for the input canonicalization
+	 * mode.  We don't want to throttle the driver if we're in
+	 * canonical mode and don't have a newline yet!
+	 */
+	if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
+		tty_throttle(tty);
+}
+
+int is_ignored(int sig)
+{
+	return (sigismember(&current->blocked, sig) ||
+		current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
+}
+
+/**
+ *	n_tty_set_termios	-	termios data changed
+ *	@tty: terminal
+ *	@old: previous data
+ *
+ *	Called by the tty layer when the user changes termios flags so
+ *	that the line discipline can plan ahead. This function cannot sleep
+ *	and is protected from re-entry by the tty layer. The user is
+ *	guaranteed that this function will not be re-entered or in progress
+ *	when the ldisc is closed.
+ *
+ *	Locking: Caller holds tty->termios_mutex
+ */
+
+static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
+{
+	int canon_change = 1;
+	BUG_ON(!tty);
+
+	if (old)
+		canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
+	if (canon_change) {
+		memset(&tty->read_flags, 0, sizeof tty->read_flags);
+		tty->canon_head = tty->read_tail;
+		tty->canon_data = 0;
+		tty->erasing = 0;
+	}
+
+	if (canon_change && !L_ICANON(tty) && tty->read_cnt)
+		wake_up_interruptible(&tty->read_wait);
+
+	tty->icanon = (L_ICANON(tty) != 0);
+	if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
+		tty->raw = 1;
+		tty->real_raw = 1;
+		n_tty_set_room(tty);
+		return;
+	}
+	if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
+	    I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
+	    I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
+	    I_PARMRK(tty)) {
+		memset(tty->process_char_map, 0, 256/8);
+
+		if (I_IGNCR(tty) || I_ICRNL(tty))
+			set_bit('\r', tty->process_char_map);
+		if (I_INLCR(tty))
+			set_bit('\n', tty->process_char_map);
+
+		if (L_ICANON(tty)) {
+			set_bit(ERASE_CHAR(tty), tty->process_char_map);
+			set_bit(KILL_CHAR(tty), tty->process_char_map);
+			set_bit(EOF_CHAR(tty), tty->process_char_map);
+			set_bit('\n', tty->process_char_map);
+			set_bit(EOL_CHAR(tty), tty->process_char_map);
+			if (L_IEXTEN(tty)) {
+				set_bit(WERASE_CHAR(tty),
+					tty->process_char_map);
+				set_bit(LNEXT_CHAR(tty),
+					tty->process_char_map);
+				set_bit(EOL2_CHAR(tty),
+					tty->process_char_map);
+				if (L_ECHO(tty))
+					set_bit(REPRINT_CHAR(tty),
+						tty->process_char_map);
+			}
+		}
+		if (I_IXON(tty)) {
+			set_bit(START_CHAR(tty), tty->process_char_map);
+			set_bit(STOP_CHAR(tty), tty->process_char_map);
+		}
+		if (L_ISIG(tty)) {
+			set_bit(INTR_CHAR(tty), tty->process_char_map);
+			set_bit(QUIT_CHAR(tty), tty->process_char_map);
+			set_bit(SUSP_CHAR(tty), tty->process_char_map);
+		}
+		clear_bit(__DISABLED_CHAR, tty->process_char_map);
+		tty->raw = 0;
+		tty->real_raw = 0;
+	} else {
+		tty->raw = 1;
+		if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
+		    (I_IGNPAR(tty) || !I_INPCK(tty)) &&
+		    (tty->driver->flags & TTY_DRIVER_REAL_RAW))
+			tty->real_raw = 1;
+		else
+			tty->real_raw = 0;
+	}
+	n_tty_set_room(tty);
+	/* The termios change make the tty ready for I/O */
+	wake_up_interruptible(&tty->write_wait);
+	wake_up_interruptible(&tty->read_wait);
+}
+
+/**
+ *	n_tty_close		-	close the ldisc for this tty
+ *	@tty: device
+ *
+ *	Called from the terminal layer when this line discipline is
+ *	being shut down, either because of a close or becsuse of a
+ *	discipline change. The function will not be called while other
+ *	ldisc methods are in progress.
+ */
+
+static void n_tty_close(struct tty_struct *tty)
+{
+	n_tty_flush_buffer(tty);
+	if (tty->read_buf) {
+		kfree(tty->read_buf);
+		tty->read_buf = NULL;
+	}
+	if (tty->echo_buf) {
+		kfree(tty->echo_buf);
+		tty->echo_buf = NULL;
+	}
+}
+
+/**
+ *	n_tty_open		-	open an ldisc
+ *	@tty: terminal to open
+ *
+ *	Called when this line discipline is being attached to the
+ *	terminal device. Can sleep. Called serialized so that no
+ *	other events will occur in parallel. No further open will occur
+ *	until a close.
+ */
+
+static int n_tty_open(struct tty_struct *tty)
+{
+	if (!tty)
+		return -EINVAL;
+
+	/* These are ugly. Currently a malloc failure here can panic */
+	if (!tty->read_buf) {
+		tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
+		if (!tty->read_buf)
+			return -ENOMEM;
+	}
+	if (!tty->echo_buf) {
+		tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
+
+		if (!tty->echo_buf)
+			return -ENOMEM;
+	}
+	reset_buffer_flags(tty);
+	tty->column = 0;
+	n_tty_set_termios(tty, NULL);
+	tty->minimum_to_wake = 1;
+	tty->closing = 0;
+	return 0;
+}
+
+static inline int input_available_p(struct tty_struct *tty, int amt)
+{
+	tty_flush_to_ldisc(tty);
+	if (tty->icanon && !L_EXTPROC(tty)) {
+		if (tty->canon_data)
+			return 1;
+	} else if (tty->read_cnt >= (amt ? amt : 1))
+		return 1;
+
+	return 0;
+}
+
+/**
+ * 	copy_from_read_buf	-	copy read data directly
+ *	@tty: terminal device
+ *	@b: user data
+ *	@nr: size of data
+ *
+ *	Helper function to speed up n_tty_read.  It is only called when
+ *	ICANON is off; it copies characters straight from the tty queue to
+ *	user space directly.  It can be profitably called twice; once to
+ *	drain the space from the tail pointer to the (physical) end of the
+ *	buffer, and once to drain the space from the (physical) beginning of
+ *	the buffer to head pointer.
+ *
+ *	Called under the tty->atomic_read_lock sem
+ *
+ */
+
+static int copy_from_read_buf(struct tty_struct *tty,
+				      unsigned char __user **b,
+				      size_t *nr)
+
+{
+	int retval;
+	size_t n;
+	unsigned long flags;
+
+	retval = 0;
+	spin_lock_irqsave(&tty->read_lock, flags);
+	n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
+	n = min(*nr, n);
+	spin_unlock_irqrestore(&tty->read_lock, flags);
+	if (n) {
+		retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
+		n -= retval;
+		tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
+		spin_lock_irqsave(&tty->read_lock, flags);
+		tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
+		tty->read_cnt -= n;
+		/* Turn single EOF into zero-length read */
+		if (L_EXTPROC(tty) && tty->icanon && n == 1) {
+			if (!tty->read_cnt && (*b)[n-1] == EOF_CHAR(tty))
+				n--;
+		}
+		spin_unlock_irqrestore(&tty->read_lock, flags);
+		*b += n;
+		*nr -= n;
+	}
+	return retval;
+}
+
+extern ssize_t redirected_tty_write(struct file *, const char __user *,
+							size_t, loff_t *);
+
+/**
+ *	job_control		-	check job control
+ *	@tty: tty
+ *	@file: file handle
+ *
+ *	Perform job control management checks on this file/tty descriptor
+ *	and if appropriate send any needed signals and return a negative
+ *	error code if action should be taken.
+ *
+ *	FIXME:
+ *	Locking: None - redirected write test is safe, testing
+ *	current->signal should possibly lock current->sighand
+ *	pgrp locking ?
+ */
+
+static int job_control(struct tty_struct *tty, struct file *file)
+{
+	/* Job control check -- must be done at start and after
+	   every sleep (POSIX.1 7.1.1.4). */
+	/* NOTE: not yet done after every sleep pending a thorough
+	   check of the logic of this change. -- jlc */
+	/* don't stop on /dev/console */
+	if (file->f_op->write != redirected_tty_write &&
+	    current->signal->tty == tty) {
+		if (!tty->pgrp)
+			printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
+		else if (task_pgrp(current) != tty->pgrp) {
+			if (is_ignored(SIGTTIN) ||
+			    is_current_pgrp_orphaned())
+				return -EIO;
+			kill_pgrp(task_pgrp(current), SIGTTIN, 1);
+			set_thread_flag(TIF_SIGPENDING);
+			return -ERESTARTSYS;
+		}
+	}
+	return 0;
+}
+
+
+/**
+ *	n_tty_read		-	read function for tty
+ *	@tty: tty device
+ *	@file: file object
+ *	@buf: userspace buffer pointer
+ *	@nr: size of I/O
+ *
+ *	Perform reads for the line discipline. We are guaranteed that the
+ *	line discipline will not be closed under us but we may get multiple
+ *	parallel readers and must handle this ourselves. We may also get
+ *	a hangup. Always called in user context, may sleep.
+ *
+ *	This code must be sure never to sleep through a hangup.
+ */
+
+static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
+			 unsigned char __user *buf, size_t nr)
+{
+	unsigned char __user *b = buf;
+	DECLARE_WAITQUEUE(wait, current);
+	int c;
+	int minimum, time;
+	ssize_t retval = 0;
+	ssize_t size;
+	long timeout;
+	unsigned long flags;
+	int packet;
+
+do_it_again:
+
+	BUG_ON(!tty->read_buf);
+
+	c = job_control(tty, file);
+	if (c < 0)
+		return c;
+
+	minimum = time = 0;
+	timeout = MAX_SCHEDULE_TIMEOUT;
+	if (!tty->icanon) {
+		time = (HZ / 10) * TIME_CHAR(tty);
+		minimum = MIN_CHAR(tty);
+		if (minimum) {
+			if (time)
+				tty->minimum_to_wake = 1;
+			else if (!waitqueue_active(&tty->read_wait) ||
+				 (tty->minimum_to_wake > minimum))
+				tty->minimum_to_wake = minimum;
+		} else {
+			timeout = 0;
+			if (time) {
+				timeout = time;
+				time = 0;
+			}
+			tty->minimum_to_wake = minimum = 1;
+		}
+	}
+
+	/*
+	 *	Internal serialization of reads.
+	 */
+	if (file->f_flags & O_NONBLOCK) {
+		if (!mutex_trylock(&tty->atomic_read_lock))
+			return -EAGAIN;
+	} else {
+		if (mutex_lock_interruptible(&tty->atomic_read_lock))
+			return -ERESTARTSYS;
+	}
+	packet = tty->packet;
+
+	add_wait_queue(&tty->read_wait, &wait);
+	while (nr) {
+		/* First test for status change. */
+		if (packet && tty->link->ctrl_status) {
+			unsigned char cs;
+			if (b != buf)
+				break;
+			spin_lock_irqsave(&tty->link->ctrl_lock, flags);
+			cs = tty->link->ctrl_status;
+			tty->link->ctrl_status = 0;
+			spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
+			if (tty_put_user(tty, cs, b++)) {
+				retval = -EFAULT;
+				b--;
+				break;
+			}
+			nr--;
+			break;
+		}
+		/* This statement must be first before checking for input
+		   so that any interrupt will set the state back to
+		   TASK_RUNNING. */
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
+		    ((minimum - (b - buf)) >= 1))
+			tty->minimum_to_wake = (minimum - (b - buf));
+
+		if (!input_available_p(tty, 0)) {
+			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
+				retval = -EIO;
+				break;
+			}
+			if (tty_hung_up_p(file))
+				break;
+			if (!timeout)
+				break;
+			if (file->f_flags & O_NONBLOCK) {
+				retval = -EAGAIN;
+				break;
+			}
+			if (signal_pending(current)) {
+				retval = -ERESTARTSYS;
+				break;
+			}
+			/* FIXME: does n_tty_set_room need locking ? */
+			n_tty_set_room(tty);
+			timeout = schedule_timeout(timeout);
+			continue;
+		}
+		__set_current_state(TASK_RUNNING);
+
+		/* Deal with packet mode. */
+		if (packet && b == buf) {
+			if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
+				retval = -EFAULT;
+				b--;
+				break;
+			}
+			nr--;
+		}
+
+		if (tty->icanon && !L_EXTPROC(tty)) {
+			/* N.B. avoid overrun if nr == 0 */
+			while (nr && tty->read_cnt) {
+				int eol;
+
+				eol = test_and_clear_bit(tty->read_tail,
+						tty->read_flags);
+				c = tty->read_buf[tty->read_tail];
+				spin_lock_irqsave(&tty->read_lock, flags);
+				tty->read_tail = ((tty->read_tail+1) &
+						  (N_TTY_BUF_SIZE-1));
+				tty->read_cnt--;
+				if (eol) {
+					/* this test should be redundant:
+					 * we shouldn't be reading data if
+					 * canon_data is 0
+					 */
+					if (--tty->canon_data < 0)
+						tty->canon_data = 0;
+				}
+				spin_unlock_irqrestore(&tty->read_lock, flags);
+
+				if (!eol || (c != __DISABLED_CHAR)) {
+					if (tty_put_user(tty, c, b++)) {
+						retval = -EFAULT;
+						b--;
+						break;
+					}
+					nr--;
+				}
+				if (eol) {
+					tty_audit_push(tty);
+					break;
+				}
+			}
+			if (retval)
+				break;
+		} else {
+			int uncopied;
+			/* The copy function takes the read lock and handles
+			   locking internally for this case */
+			uncopied = copy_from_read_buf(tty, &b, &nr);
+			uncopied += copy_from_read_buf(tty, &b, &nr);
+			if (uncopied) {
+				retval = -EFAULT;
+				break;
+			}
+		}
+
+		/* If there is enough space in the read buffer now, let the
+		 * low-level driver know. We use n_tty_chars_in_buffer() to
+		 * check the buffer, as it now knows about canonical mode.
+		 * Otherwise, if the driver is throttled and the line is
+		 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
+		 * we won't get any more characters.
+		 */
+		if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
+			n_tty_set_room(tty);
+			check_unthrottle(tty);
+		}
+
+		if (b - buf >= minimum)
+			break;
+		if (time)
+			timeout = time;
+	}
+	mutex_unlock(&tty->atomic_read_lock);
+	remove_wait_queue(&tty->read_wait, &wait);
+
+	if (!waitqueue_active(&tty->read_wait))
+		tty->minimum_to_wake = minimum;
+
+	__set_current_state(TASK_RUNNING);
+	size = b - buf;
+	if (size) {
+		retval = size;
+		if (nr)
+			clear_bit(TTY_PUSH, &tty->flags);
+	} else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
+		 goto do_it_again;
+
+	n_tty_set_room(tty);
+	return retval;
+}
+
+/**
+ *	n_tty_write		-	write function for tty
+ *	@tty: tty device
+ *	@file: file object
+ *	@buf: userspace buffer pointer
+ *	@nr: size of I/O
+ *
+ *	Write function of the terminal device.  This is serialized with
+ *	respect to other write callers but not to termios changes, reads
+ *	and other such events.  Since the receive code will echo characters,
+ *	thus calling driver write methods, the output_lock is used in
+ *	the output processing functions called here as well as in the
+ *	echo processing function to protect the column state and space
+ *	left in the buffer.
+ *
+ *	This code must be sure never to sleep through a hangup.
+ *
+ *	Locking: output_lock to protect column state and space left
+ *		 (note that the process_output*() functions take this
+ *		  lock themselves)
+ */
+
+static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
+			   const unsigned char *buf, size_t nr)
+{
+	const unsigned char *b = buf;
+	DECLARE_WAITQUEUE(wait, current);
+	int c;
+	ssize_t retval = 0;
+
+	/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
+	if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
+		retval = tty_check_change(tty);
+		if (retval)
+			return retval;
+	}
+
+	/* Write out any echoed characters that are still pending */
+	process_echoes(tty);
+
+	add_wait_queue(&tty->write_wait, &wait);
+	while (1) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (signal_pending(current)) {
+			retval = -ERESTARTSYS;
+			break;
+		}
+		if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
+			retval = -EIO;
+			break;
+		}
+		if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
+			while (nr > 0) {
+				ssize_t num = process_output_block(tty, b, nr);
+				if (num < 0) {
+					if (num == -EAGAIN)
+						break;
+					retval = num;
+					goto break_out;
+				}
+				b += num;
+				nr -= num;
+				if (nr == 0)
+					break;
+				c = *b;
+				if (process_output(c, tty) < 0)
+					break;
+				b++; nr--;
+			}
+			if (tty->ops->flush_chars)
+				tty->ops->flush_chars(tty);
+		} else {
+			while (nr > 0) {
+				c = tty->ops->write(tty, b, nr);
+				if (c < 0) {
+					retval = c;
+					goto break_out;
+				}
+				if (!c)
+					break;
+				b += c;
+				nr -= c;
+			}
+		}
+		if (!nr)
+			break;
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			break;
+		}
+		schedule();
+	}
+break_out:
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(&tty->write_wait, &wait);
+	if (b - buf != nr && tty->fasync)
+		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+	return (b - buf) ? b - buf : retval;
+}
+
+/**
+ *	n_tty_poll		-	poll method for N_TTY
+ *	@tty: terminal device
+ *	@file: file accessing it
+ *	@wait: poll table
+ *
+ *	Called when the line discipline is asked to poll() for data or
+ *	for special events. This code is not serialized with respect to
+ *	other events save open/close.
+ *
+ *	This code must be sure never to sleep through a hangup.
+ *	Called without the kernel lock held - fine
+ */
+
+static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
+							poll_table *wait)
+{
+	unsigned int mask = 0;
+
+	poll_wait(file, &tty->read_wait, wait);
+	poll_wait(file, &tty->write_wait, wait);
+	if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
+		mask |= POLLIN | POLLRDNORM;
+	if (tty->packet && tty->link->ctrl_status)
+		mask |= POLLPRI | POLLIN | POLLRDNORM;
+	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+		mask |= POLLHUP;
+	if (tty_hung_up_p(file))
+		mask |= POLLHUP;
+	if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
+		if (MIN_CHAR(tty) && !TIME_CHAR(tty))
+			tty->minimum_to_wake = MIN_CHAR(tty);
+		else
+			tty->minimum_to_wake = 1;
+	}
+	if (tty->ops->write && !tty_is_writelocked(tty) &&
+			tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
+			tty_write_room(tty) > 0)
+		mask |= POLLOUT | POLLWRNORM;
+	return mask;
+}
+
+static unsigned long inq_canon(struct tty_struct *tty)
+{
+	int nr, head, tail;
+
+	if (!tty->canon_data)
+		return 0;
+	head = tty->canon_head;
+	tail = tty->read_tail;
+	nr = (head - tail) & (N_TTY_BUF_SIZE-1);
+	/* Skip EOF-chars.. */
+	while (head != tail) {
+		if (test_bit(tail, tty->read_flags) &&
+		    tty->read_buf[tail] == __DISABLED_CHAR)
+			nr--;
+		tail = (tail+1) & (N_TTY_BUF_SIZE-1);
+	}
+	return nr;
+}
+
+static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
+		       unsigned int cmd, unsigned long arg)
+{
+	int retval;
+
+	switch (cmd) {
+	case TIOCOUTQ:
+		return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
+	case TIOCINQ:
+		/* FIXME: Locking */
+		retval = tty->read_cnt;
+		if (L_ICANON(tty))
+			retval = inq_canon(tty);
+		return put_user(retval, (unsigned int __user *) arg);
+	default:
+		return n_tty_ioctl_helper(tty, file, cmd, arg);
+	}
+}
+
+struct tty_ldisc_ops tty_ldisc_N_TTY = {
+	.magic           = TTY_LDISC_MAGIC,
+	.name            = "n_tty",
+	.open            = n_tty_open,
+	.close           = n_tty_close,
+	.flush_buffer    = n_tty_flush_buffer,
+	.chars_in_buffer = n_tty_chars_in_buffer,
+	.read            = n_tty_read,
+	.write           = n_tty_write,
+	.ioctl           = n_tty_ioctl,
+	.set_termios     = n_tty_set_termios,
+	.poll            = n_tty_poll,
+	.receive_buf     = n_tty_receive_buf,
+	.write_wakeup    = n_tty_write_wakeup
+};
+
+/**
+ *	n_tty_inherit_ops	-	inherit N_TTY methods
+ *	@ops: struct tty_ldisc_ops where to save N_TTY methods
+ *
+ *	Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
+ *	methods.
+ */
+
+void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
+{
+	*ops = tty_ldisc_N_TTY;
+	ops->owner = NULL;
+	ops->refcount = ops->flags = 0;
+}
+EXPORT_SYMBOL_GPL(n_tty_inherit_ops);