v4.19.13 snapshot.
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
new file mode 100644
index 0000000..3ad4602
--- /dev/null
+++ b/drivers/tty/n_tty.c
@@ -0,0 +1,2502 @@
+// SPDX-License-Identifier: GPL-1.0+
+/*
+ * 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.
+ *
+ * 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 <linux/ratelimit.h>
+#include <linux/vmalloc.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
+
+#define ECHO_COMMIT_WATERMARK 256
+#define ECHO_BLOCK 256
+#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
+
+
+#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 {
+ /* producer-published */
+ size_t read_head;
+ size_t commit_head;
+ size_t canon_head;
+ size_t echo_head;
+ size_t echo_commit;
+ size_t echo_mark;
+ DECLARE_BITMAP(char_map, 256);
+
+ /* private to n_tty_receive_overrun (single-threaded) */
+ unsigned long overrun_time;
+ int num_overrun;
+
+ /* non-atomic */
+ bool no_room;
+
+ /* must hold exclusive termios_rwsem to reset these */
+ unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
+ unsigned char push:1;
+
+ /* shared by producer and consumer */
+ char read_buf[N_TTY_BUF_SIZE];
+ DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
+ unsigned char echo_buf[N_TTY_BUF_SIZE];
+
+ /* consumer-published */
+ size_t read_tail;
+ size_t line_start;
+
+ /* protected by output lock */
+ unsigned int column;
+ unsigned int canon_column;
+ size_t echo_tail;
+
+ struct mutex atomic_read_lock;
+ struct mutex output_lock;
+};
+
+#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
+
+static inline size_t read_cnt(struct n_tty_data *ldata)
+{
+ return ldata->read_head - ldata->read_tail;
+}
+
+static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
+{
+ return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
+}
+
+static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
+{
+ return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
+}
+
+static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
+{
+ smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
+ return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
+}
+
+static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
+{
+ return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
+}
+
+/* If we are not echoing the data, perhaps this is a secret so erase it */
+static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
+{
+ bool icanon = !!L_ICANON(tty);
+ bool no_echo = !L_ECHO(tty);
+
+ if (icanon && no_echo)
+ memset(buffer, 0x00, size);
+}
+
+static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
+ size_t tail, size_t n)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ size_t size = N_TTY_BUF_SIZE - tail;
+ void *from = read_buf_addr(ldata, tail);
+ int uncopied;
+
+ if (n > size) {
+ tty_audit_add_data(tty, from, size);
+ uncopied = copy_to_user(to, from, size);
+ zero_buffer(tty, from, size - uncopied);
+ if (uncopied)
+ return uncopied;
+ to += size;
+ n -= size;
+ from = ldata->read_buf;
+ }
+
+ tty_audit_add_data(tty, from, n);
+ uncopied = copy_to_user(to, from, n);
+ zero_buffer(tty, from, n - uncopied);
+ return uncopied;
+}
+
+/**
+ * n_tty_kick_worker - start input worker (if required)
+ * @tty: terminal
+ *
+ * Re-schedules the flip buffer work if it may have stopped
+ *
+ * Caller holds exclusive termios_rwsem
+ * or
+ * n_tty_read()/consumer path:
+ * holds non-exclusive termios_rwsem
+ */
+
+static void n_tty_kick_worker(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ /* Did the input worker stop? Restart it */
+ if (unlikely(ldata->no_room)) {
+ ldata->no_room = 0;
+
+ WARN_RATELIMIT(tty->port->itty == NULL,
+ "scheduling with invalid itty\n");
+ /* see if ldisc has been killed - if so, this means that
+ * even though the ldisc has been halted and ->buf.work
+ * cancelled, ->buf.work is about to be rescheduled
+ */
+ WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
+ "scheduling buffer work for halted ldisc\n");
+ tty_buffer_restart_work(tty->port);
+ }
+}
+
+static ssize_t chars_in_buffer(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ ssize_t n = 0;
+
+ if (!ldata->icanon)
+ n = ldata->commit_head - ldata->read_tail;
+ else
+ n = ldata->canon_head - ldata->read_tail;
+ return n;
+}
+
+/**
+ * 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)
+{
+ clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+ kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
+}
+
+static void n_tty_check_throttle(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ /*
+ * 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 (ldata->icanon && ldata->canon_head == ldata->read_tail)
+ return;
+
+ while (1) {
+ int throttled;
+ tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
+ if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
+ break;
+ throttled = tty_throttle_safe(tty);
+ if (!throttled)
+ break;
+ }
+ __tty_set_flow_change(tty, 0);
+}
+
+static void n_tty_check_unthrottle(struct tty_struct *tty)
+{
+ if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
+ if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
+ return;
+ n_tty_kick_worker(tty);
+ tty_wakeup(tty->link);
+ return;
+ }
+
+ /* If there is enough space in the read buffer now, let the
+ * low-level driver know. We use 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.
+ */
+
+ while (1) {
+ int unthrottled;
+ tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
+ if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
+ break;
+ n_tty_kick_worker(tty);
+ unthrottled = tty_unthrottle_safe(tty);
+ if (!unthrottled)
+ break;
+ }
+ __tty_set_flow_change(tty, 0);
+}
+
+/**
+ * put_tty_queue - add character to tty
+ * @c: character
+ * @ldata: n_tty data
+ *
+ * Add a character to the tty read_buf queue.
+ *
+ * n_tty_receive_buf()/producer path:
+ * caller holds non-exclusive termios_rwsem
+ */
+
+static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
+{
+ *read_buf_addr(ldata, ldata->read_head) = c;
+ ldata->read_head++;
+}
+
+/**
+ * reset_buffer_flags - reset buffer state
+ * @tty: terminal to reset
+ *
+ * Reset the read buffer counters and clear the flags.
+ * Called from n_tty_open() and n_tty_flush_buffer().
+ *
+ * Locking: caller holds exclusive termios_rwsem
+ * (or locking is not required)
+ */
+
+static void reset_buffer_flags(struct n_tty_data *ldata)
+{
+ ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
+ ldata->commit_head = 0;
+ ldata->line_start = 0;
+
+ ldata->erasing = 0;
+ bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
+ ldata->push = 0;
+}
+
+static void n_tty_packet_mode_flush(struct tty_struct *tty)
+{
+ unsigned long flags;
+
+ if (tty->link->packet) {
+ spin_lock_irqsave(&tty->ctrl_lock, flags);
+ tty->ctrl_status |= TIOCPKT_FLUSHREAD;
+ spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+ wake_up_interruptible(&tty->link->read_wait);
+ }
+}
+
+/**
+ * n_tty_flush_buffer - clean input queue
+ * @tty: terminal device
+ *
+ * Flush the input buffer. Called 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).
+ *
+ * Holds termios_rwsem to exclude producer/consumer while
+ * buffer indices are reset.
+ *
+ * Locking: ctrl_lock, exclusive termios_rwsem
+ */
+
+static void n_tty_flush_buffer(struct tty_struct *tty)
+{
+ down_write(&tty->termios_rwsem);
+ reset_buffer_flags(tty->disc_data);
+ n_tty_kick_worker(tty);
+
+ if (tty->link)
+ n_tty_packet_mode_flush(tty);
+ up_write(&tty->termios_rwsem);
+}
+
+/**
+ * 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)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int spaces;
+
+ if (!space)
+ return -1;
+
+ switch (c) {
+ case '\n':
+ if (O_ONLRET(tty))
+ ldata->column = 0;
+ if (O_ONLCR(tty)) {
+ if (space < 2)
+ return -1;
+ ldata->canon_column = ldata->column = 0;
+ tty->ops->write(tty, "\r\n", 2);
+ return 2;
+ }
+ ldata->canon_column = ldata->column;
+ break;
+ case '\r':
+ if (O_ONOCR(tty) && ldata->column == 0)
+ return 0;
+ if (O_OCRNL(tty)) {
+ c = '\n';
+ if (O_ONLRET(tty))
+ ldata->canon_column = ldata->column = 0;
+ break;
+ }
+ ldata->canon_column = ldata->column = 0;
+ break;
+ case '\t':
+ spaces = 8 - (ldata->column & 7);
+ if (O_TABDLY(tty) == XTABS) {
+ if (space < spaces)
+ return -1;
+ ldata->column += spaces;
+ tty->ops->write(tty, " ", spaces);
+ return spaces;
+ }
+ ldata->column += spaces;
+ break;
+ case '\b':
+ if (ldata->column > 0)
+ ldata->column--;
+ break;
+ default:
+ if (!iscntrl(c)) {
+ if (O_OLCUC(tty))
+ c = toupper(c);
+ if (!is_continuation(c, tty))
+ ldata->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)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int space, retval;
+
+ mutex_lock(&ldata->output_lock);
+
+ space = tty_write_room(tty);
+ retval = do_output_char(c, tty, space);
+
+ mutex_unlock(&ldata->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)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int space;
+ int i;
+ const unsigned char *cp;
+
+ mutex_lock(&ldata->output_lock);
+
+ space = tty_write_room(tty);
+ if (!space) {
+ mutex_unlock(&ldata->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))
+ ldata->column = 0;
+ if (O_ONLCR(tty))
+ goto break_out;
+ ldata->canon_column = ldata->column;
+ break;
+ case '\r':
+ if (O_ONOCR(tty) && ldata->column == 0)
+ goto break_out;
+ if (O_OCRNL(tty))
+ goto break_out;
+ ldata->canon_column = ldata->column = 0;
+ break;
+ case '\t':
+ goto break_out;
+ case '\b':
+ if (ldata->column > 0)
+ ldata->column--;
+ break;
+ default:
+ if (!iscntrl(c)) {
+ if (O_OLCUC(tty))
+ goto break_out;
+ if (!is_continuation(c, tty))
+ ldata->column++;
+ }
+ break;
+ }
+ }
+break_out:
+ i = tty->ops->write(tty, buf, i);
+
+ mutex_unlock(&ldata->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: callers must hold output_lock
+ */
+
+static size_t __process_echoes(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int space, old_space;
+ size_t tail;
+ unsigned char c;
+
+ old_space = space = tty_write_room(tty);
+
+ tail = ldata->echo_tail;
+ while (MASK(ldata->echo_commit) != MASK(tail)) {
+ c = echo_buf(ldata, tail);
+ if (c == ECHO_OP_START) {
+ unsigned char op;
+ int no_space_left = 0;
+
+ /*
+ * Since add_echo_byte() is called without holding
+ * output_lock, we might see only portion of multi-byte
+ * operation.
+ */
+ if (MASK(ldata->echo_commit) == MASK(tail + 1))
+ goto not_yet_stored;
+ /*
+ * 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.
+ */
+ op = echo_buf(ldata, tail + 1);
+
+ switch (op) {
+ unsigned int num_chars, num_bs;
+
+ case ECHO_OP_ERASE_TAB:
+ if (MASK(ldata->echo_commit) == MASK(tail + 2))
+ goto not_yet_stored;
+ num_chars = echo_buf(ldata, tail + 2);
+
+ /*
+ * 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 += ldata->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 (ldata->column > 0)
+ ldata->column--;
+ }
+ tail += 3;
+ break;
+
+ case ECHO_OP_SET_CANON_COL:
+ ldata->canon_column = ldata->column;
+ tail += 2;
+ break;
+
+ case ECHO_OP_MOVE_BACK_COL:
+ if (ldata->column > 0)
+ ldata->column--;
+ tail += 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);
+ ldata->column++;
+ space--;
+ tail += 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);
+ ldata->column += 2;
+ space -= 2;
+ tail += 2;
+ }
+
+ if (no_space_left)
+ break;
+ } else {
+ if (O_OPOST(tty)) {
+ 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;
+ }
+ tail += 1;
+ }
+ }
+
+ /* If the echo buffer is nearly full (so that the possibility exists
+ * of echo overrun before the next commit), then discard enough
+ * data at the tail to prevent a subsequent overrun */
+ while (ldata->echo_commit > tail &&
+ ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
+ if (echo_buf(ldata, tail) == ECHO_OP_START) {
+ if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
+ tail += 3;
+ else
+ tail += 2;
+ } else
+ tail++;
+ }
+
+ not_yet_stored:
+ ldata->echo_tail = tail;
+ return old_space - space;
+}
+
+static void commit_echoes(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ size_t nr, old, echoed;
+ size_t head;
+
+ mutex_lock(&ldata->output_lock);
+ head = ldata->echo_head;
+ ldata->echo_mark = head;
+ old = ldata->echo_commit - ldata->echo_tail;
+
+ /* Process committed echoes if the accumulated # of bytes
+ * is over the threshold (and try again each time another
+ * block is accumulated) */
+ nr = head - ldata->echo_tail;
+ if (nr < ECHO_COMMIT_WATERMARK ||
+ (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
+ mutex_unlock(&ldata->output_lock);
+ return;
+ }
+
+ ldata->echo_commit = head;
+ echoed = __process_echoes(tty);
+ mutex_unlock(&ldata->output_lock);
+
+ if (echoed && tty->ops->flush_chars)
+ tty->ops->flush_chars(tty);
+}
+
+static void process_echoes(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ size_t echoed;
+
+ if (ldata->echo_mark == ldata->echo_tail)
+ return;
+
+ mutex_lock(&ldata->output_lock);
+ ldata->echo_commit = ldata->echo_mark;
+ echoed = __process_echoes(tty);
+ mutex_unlock(&ldata->output_lock);
+
+ if (echoed && tty->ops->flush_chars)
+ tty->ops->flush_chars(tty);
+}
+
+/* NB: echo_mark and echo_head should be equivalent here */
+static void flush_echoes(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
+ ldata->echo_commit == ldata->echo_head)
+ return;
+
+ mutex_lock(&ldata->output_lock);
+ ldata->echo_commit = ldata->echo_head;
+ __process_echoes(tty);
+ mutex_unlock(&ldata->output_lock);
+}
+
+/**
+ * add_echo_byte - add a byte to the echo buffer
+ * @c: unicode byte to echo
+ * @ldata: n_tty data
+ *
+ * Add a character or operation byte to the echo buffer.
+ */
+
+static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
+{
+ *echo_buf_addr(ldata, ldata->echo_head) = c;
+ smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
+ ldata->echo_head++;
+}
+
+/**
+ * echo_move_back_col - add operation to move back a column
+ * @ldata: n_tty data
+ *
+ * Add an operation to the echo buffer to move back one column.
+ */
+
+static void echo_move_back_col(struct n_tty_data *ldata)
+{
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
+}
+
+/**
+ * echo_set_canon_col - add operation to set the canon column
+ * @ldata: n_tty data
+ *
+ * Add an operation to the echo buffer to set the canon column
+ * to the current column.
+ */
+
+static void echo_set_canon_col(struct n_tty_data *ldata)
+{
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
+}
+
+/**
+ * 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
+ * @ldata: n_tty data
+ *
+ * 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.
+ */
+
+static void echo_erase_tab(unsigned int num_chars, int after_tab,
+ struct n_tty_data *ldata)
+{
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
+
+ /* 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, ldata);
+}
+
+/**
+ * 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.
+ */
+
+static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
+{
+ if (c == ECHO_OP_START) {
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(ECHO_OP_START, ldata);
+ } else {
+ add_echo_byte(c, ldata);
+ }
+}
+
+/**
+ * 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).
+ */
+
+static void echo_char(unsigned char c, struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (c == ECHO_OP_START) {
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(ECHO_OP_START, ldata);
+ } else {
+ if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
+ add_echo_byte(ECHO_OP_START, ldata);
+ add_echo_byte(c, ldata);
+ }
+}
+
+/**
+ * finish_erasing - complete erase
+ * @ldata: n_tty data
+ */
+
+static inline void finish_erasing(struct n_tty_data *ldata)
+{
+ if (ldata->erasing) {
+ echo_char_raw('/', ldata);
+ ldata->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.
+ *
+ * n_tty_receive_buf()/producer path:
+ * caller holds non-exclusive termios_rwsem
+ */
+
+static void eraser(unsigned char c, struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ enum { ERASE, WERASE, KILL } kill_type;
+ size_t head;
+ size_t cnt;
+ int seen_alnums;
+
+ if (ldata->read_head == ldata->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)) {
+ ldata->read_head = ldata->canon_head;
+ return;
+ }
+ if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
+ ldata->read_head = ldata->canon_head;
+ finish_erasing(ldata);
+ 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', ldata);
+ return;
+ }
+ kill_type = KILL;
+ }
+
+ seen_alnums = 0;
+ while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
+ head = ldata->read_head;
+
+ /* erase a single possibly multibyte character */
+ do {
+ head--;
+ c = read_buf(ldata, head);
+ } while (is_continuation(c, tty) &&
+ MASK(head) != MASK(ldata->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 = ldata->read_head - head;
+ ldata->read_head = head;
+ if (L_ECHO(tty)) {
+ if (L_ECHOPRT(tty)) {
+ if (!ldata->erasing) {
+ echo_char_raw('\\', ldata);
+ ldata->erasing = 1;
+ }
+ /* if cnt > 1, output a multi-byte character */
+ echo_char(c, tty);
+ while (--cnt > 0) {
+ head++;
+ echo_char_raw(read_buf(ldata, head), ldata);
+ echo_move_back_col(ldata);
+ }
+ } 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;
+ size_t tail = ldata->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 (MASK(tail) != MASK(ldata->canon_head)) {
+ tail--;
+ c = read_buf(ldata, 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, ldata);
+ } else {
+ if (iscntrl(c) && L_ECHOCTL(tty)) {
+ echo_char_raw('\b', ldata);
+ echo_char_raw(' ', ldata);
+ echo_char_raw('\b', ldata);
+ }
+ if (!iscntrl(c) || L_ECHOCTL(tty)) {
+ echo_char_raw('\b', ldata);
+ echo_char_raw(' ', ldata);
+ echo_char_raw('\b', ldata);
+ }
+ }
+ }
+ if (kill_type == ERASE)
+ break;
+ }
+ if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
+ finish_erasing(ldata);
+}
+
+/**
+ * isig - handle the ISIG optio
+ * @sig: signal
+ * @tty: terminal
+ *
+ * Called when a signal is being sent due to terminal input.
+ * Called from the driver receive_buf path so serialized.
+ *
+ * Performs input and output flush if !NOFLSH. In this context, the echo
+ * buffer is 'output'. The signal is processed first to alert any current
+ * readers or writers to discontinue and exit their i/o loops.
+ *
+ * Locking: ctrl_lock
+ */
+
+static void __isig(int sig, struct tty_struct *tty)
+{
+ struct pid *tty_pgrp = tty_get_pgrp(tty);
+ if (tty_pgrp) {
+ kill_pgrp(tty_pgrp, sig, 1);
+ put_pid(tty_pgrp);
+ }
+}
+
+static void isig(int sig, struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (L_NOFLSH(tty)) {
+ /* signal only */
+ __isig(sig, tty);
+
+ } else { /* signal and flush */
+ up_read(&tty->termios_rwsem);
+ down_write(&tty->termios_rwsem);
+
+ __isig(sig, tty);
+
+ /* clear echo buffer */
+ mutex_lock(&ldata->output_lock);
+ ldata->echo_head = ldata->echo_tail = 0;
+ ldata->echo_mark = ldata->echo_commit = 0;
+ mutex_unlock(&ldata->output_lock);
+
+ /* clear output buffer */
+ tty_driver_flush_buffer(tty);
+
+ /* clear input buffer */
+ reset_buffer_flags(tty->disc_data);
+
+ /* notify pty master of flush */
+ if (tty->link)
+ n_tty_packet_mode_flush(tty);
+
+ up_write(&tty->termios_rwsem);
+ down_read(&tty->termios_rwsem);
+ }
+}
+
+/**
+ * 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.
+ *
+ * n_tty_receive_buf()/producer path:
+ * caller holds non-exclusive termios_rwsem
+ *
+ * Note: may get exclusive termios_rwsem if flushing input buffer
+ */
+
+static void n_tty_receive_break(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (I_IGNBRK(tty))
+ return;
+ if (I_BRKINT(tty)) {
+ isig(SIGINT, tty);
+ return;
+ }
+ if (I_PARMRK(tty)) {
+ put_tty_queue('\377', ldata);
+ put_tty_queue('\0', ldata);
+ }
+ put_tty_queue('\0', ldata);
+}
+
+/**
+ * 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 void n_tty_receive_overrun(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ ldata->num_overrun++;
+ if (time_after(jiffies, ldata->overrun_time + HZ) ||
+ time_after(ldata->overrun_time, jiffies)) {
+ tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
+ ldata->overrun_time = jiffies;
+ ldata->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.
+ *
+ * n_tty_receive_buf()/producer path:
+ * caller holds non-exclusive termios_rwsem
+ */
+static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (I_INPCK(tty)) {
+ if (I_IGNPAR(tty))
+ return;
+ if (I_PARMRK(tty)) {
+ put_tty_queue('\377', ldata);
+ put_tty_queue('\0', ldata);
+ put_tty_queue(c, ldata);
+ } else
+ put_tty_queue('\0', ldata);
+ } else
+ put_tty_queue(c, ldata);
+}
+
+static void
+n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
+{
+ isig(signal, tty);
+ if (I_IXON(tty))
+ start_tty(tty);
+ if (L_ECHO(tty)) {
+ echo_char(c, tty);
+ commit_echoes(tty);
+ } else
+ process_echoes(tty);
+ return;
+}
+
+/**
+ * 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.
+ *
+ * n_tty_receive_buf()/producer path:
+ * caller holds non-exclusive termios_rwsem
+ * publishes canon_head if canonical mode is active
+ *
+ * Returns 1 if LNEXT was received, else returns 0
+ */
+
+static int
+n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (I_IXON(tty)) {
+ if (c == START_CHAR(tty)) {
+ start_tty(tty);
+ process_echoes(tty);
+ return 0;
+ }
+ if (c == STOP_CHAR(tty)) {
+ stop_tty(tty);
+ return 0;
+ }
+ }
+
+ if (L_ISIG(tty)) {
+ if (c == INTR_CHAR(tty)) {
+ n_tty_receive_signal_char(tty, SIGINT, c);
+ return 0;
+ } else if (c == QUIT_CHAR(tty)) {
+ n_tty_receive_signal_char(tty, SIGQUIT, c);
+ return 0;
+ } else if (c == SUSP_CHAR(tty)) {
+ n_tty_receive_signal_char(tty, SIGTSTP, c);
+ return 0;
+ }
+ }
+
+ if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
+ start_tty(tty);
+ process_echoes(tty);
+ }
+
+ if (c == '\r') {
+ if (I_IGNCR(tty))
+ return 0;
+ if (I_ICRNL(tty))
+ c = '\n';
+ } else if (c == '\n' && I_INLCR(tty))
+ c = '\r';
+
+ if (ldata->icanon) {
+ if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
+ (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
+ eraser(c, tty);
+ commit_echoes(tty);
+ return 0;
+ }
+ if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
+ ldata->lnext = 1;
+ if (L_ECHO(tty)) {
+ finish_erasing(ldata);
+ if (L_ECHOCTL(tty)) {
+ echo_char_raw('^', ldata);
+ echo_char_raw('\b', ldata);
+ commit_echoes(tty);
+ }
+ }
+ return 1;
+ }
+ if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
+ size_t tail = ldata->canon_head;
+
+ finish_erasing(ldata);
+ echo_char(c, tty);
+ echo_char_raw('\n', ldata);
+ while (MASK(tail) != MASK(ldata->read_head)) {
+ echo_char(read_buf(ldata, tail), tty);
+ tail++;
+ }
+ commit_echoes(tty);
+ return 0;
+ }
+ if (c == '\n') {
+ if (L_ECHO(tty) || L_ECHONL(tty)) {
+ echo_char_raw('\n', ldata);
+ commit_echoes(tty);
+ }
+ goto handle_newline;
+ }
+ if (c == EOF_CHAR(tty)) {
+ c = __DISABLED_CHAR;
+ goto handle_newline;
+ }
+ if ((c == EOL_CHAR(tty)) ||
+ (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
+ /*
+ * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
+ */
+ if (L_ECHO(tty)) {
+ /* Record the column of first canon char. */
+ if (ldata->canon_head == ldata->read_head)
+ echo_set_canon_col(ldata);
+ echo_char(c, tty);
+ commit_echoes(tty);
+ }
+ /*
+ * XXX does PARMRK doubling happen for
+ * EOL_CHAR and EOL2_CHAR?
+ */
+ if (c == (unsigned char) '\377' && I_PARMRK(tty))
+ put_tty_queue(c, ldata);
+
+handle_newline:
+ set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
+ put_tty_queue(c, ldata);
+ smp_store_release(&ldata->canon_head, ldata->read_head);
+ kill_fasync(&tty->fasync, SIGIO, POLL_IN);
+ wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
+ return 0;
+ }
+ }
+
+ if (L_ECHO(tty)) {
+ finish_erasing(ldata);
+ if (c == '\n')
+ echo_char_raw('\n', ldata);
+ else {
+ /* Record the column of first canon char. */
+ if (ldata->canon_head == ldata->read_head)
+ echo_set_canon_col(ldata);
+ echo_char(c, tty);
+ }
+ commit_echoes(tty);
+ }
+
+ /* PARMRK doubling check */
+ if (c == (unsigned char) '\377' && I_PARMRK(tty))
+ put_tty_queue(c, ldata);
+
+ put_tty_queue(c, ldata);
+ return 0;
+}
+
+static inline void
+n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
+ start_tty(tty);
+ process_echoes(tty);
+ }
+ if (L_ECHO(tty)) {
+ finish_erasing(ldata);
+ /* Record the column of first canon char. */
+ if (ldata->canon_head == ldata->read_head)
+ echo_set_canon_col(ldata);
+ echo_char(c, tty);
+ commit_echoes(tty);
+ }
+ /* PARMRK doubling check */
+ if (c == (unsigned char) '\377' && I_PARMRK(tty))
+ put_tty_queue(c, ldata);
+ put_tty_queue(c, ldata);
+}
+
+static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
+{
+ n_tty_receive_char_inline(tty, c);
+}
+
+static inline void
+n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
+ start_tty(tty);
+ process_echoes(tty);
+ }
+ if (L_ECHO(tty)) {
+ finish_erasing(ldata);
+ /* Record the column of first canon char. */
+ if (ldata->canon_head == ldata->read_head)
+ echo_set_canon_col(ldata);
+ echo_char(c, tty);
+ commit_echoes(tty);
+ }
+ put_tty_queue(c, ldata);
+}
+
+static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
+{
+ if (I_ISTRIP(tty))
+ c &= 0x7f;
+ if (I_IUCLC(tty) && L_IEXTEN(tty))
+ c = tolower(c);
+
+ if (I_IXON(tty)) {
+ if (c == STOP_CHAR(tty))
+ stop_tty(tty);
+ else if (c == START_CHAR(tty) ||
+ (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
+ c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
+ c != SUSP_CHAR(tty))) {
+ start_tty(tty);
+ process_echoes(tty);
+ }
+ }
+}
+
+static void
+n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
+{
+ switch (flag) {
+ case TTY_BREAK:
+ n_tty_receive_break(tty);
+ break;
+ case TTY_PARITY:
+ case TTY_FRAME:
+ n_tty_receive_parity_error(tty, c);
+ break;
+ case TTY_OVERRUN:
+ n_tty_receive_overrun(tty);
+ break;
+ default:
+ tty_err(tty, "unknown flag %d\n", flag);
+ break;
+ }
+}
+
+static void
+n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ ldata->lnext = 0;
+ if (likely(flag == TTY_NORMAL)) {
+ if (I_ISTRIP(tty))
+ c &= 0x7f;
+ if (I_IUCLC(tty) && L_IEXTEN(tty))
+ c = tolower(c);
+ n_tty_receive_char(tty, c);
+ } else
+ n_tty_receive_char_flagged(tty, c, flag);
+}
+
+static void
+n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ size_t n, head;
+
+ head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
+ n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
+ memcpy(read_buf_addr(ldata, head), cp, n);
+ ldata->read_head += n;
+ cp += n;
+ count -= n;
+
+ head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
+ n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
+ memcpy(read_buf_addr(ldata, head), cp, n);
+ ldata->read_head += n;
+}
+
+static void
+n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ char flag = TTY_NORMAL;
+
+ while (count--) {
+ if (fp)
+ flag = *fp++;
+ if (likely(flag == TTY_NORMAL))
+ put_tty_queue(*cp++, ldata);
+ else
+ n_tty_receive_char_flagged(tty, *cp++, flag);
+ }
+}
+
+static void
+n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ char flag = TTY_NORMAL;
+
+ while (count--) {
+ if (fp)
+ flag = *fp++;
+ if (likely(flag == TTY_NORMAL))
+ n_tty_receive_char_closing(tty, *cp++);
+ }
+}
+
+static void
+n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ char flag = TTY_NORMAL;
+
+ while (count--) {
+ if (fp)
+ flag = *fp++;
+ if (likely(flag == TTY_NORMAL)) {
+ unsigned char c = *cp++;
+
+ if (I_ISTRIP(tty))
+ c &= 0x7f;
+ if (I_IUCLC(tty) && L_IEXTEN(tty))
+ c = tolower(c);
+ if (L_EXTPROC(tty)) {
+ put_tty_queue(c, ldata);
+ continue;
+ }
+ if (!test_bit(c, ldata->char_map))
+ n_tty_receive_char_inline(tty, c);
+ else if (n_tty_receive_char_special(tty, c) && count) {
+ if (fp)
+ flag = *fp++;
+ n_tty_receive_char_lnext(tty, *cp++, flag);
+ count--;
+ }
+ } else
+ n_tty_receive_char_flagged(tty, *cp++, flag);
+ }
+}
+
+static void
+n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ char flag = TTY_NORMAL;
+
+ while (count--) {
+ if (fp)
+ flag = *fp++;
+ if (likely(flag == TTY_NORMAL)) {
+ unsigned char c = *cp++;
+
+ if (!test_bit(c, ldata->char_map))
+ n_tty_receive_char_fast(tty, c);
+ else if (n_tty_receive_char_special(tty, c) && count) {
+ if (fp)
+ flag = *fp++;
+ n_tty_receive_char_lnext(tty, *cp++, flag);
+ count--;
+ }
+ } else
+ n_tty_receive_char_flagged(tty, *cp++, flag);
+ }
+}
+
+static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
+
+ if (ldata->real_raw)
+ n_tty_receive_buf_real_raw(tty, cp, fp, count);
+ else if (ldata->raw || (L_EXTPROC(tty) && !preops))
+ n_tty_receive_buf_raw(tty, cp, fp, count);
+ else if (tty->closing && !L_EXTPROC(tty))
+ n_tty_receive_buf_closing(tty, cp, fp, count);
+ else {
+ if (ldata->lnext) {
+ char flag = TTY_NORMAL;
+
+ if (fp)
+ flag = *fp++;
+ n_tty_receive_char_lnext(tty, *cp++, flag);
+ count--;
+ }
+
+ if (!preops && !I_PARMRK(tty))
+ n_tty_receive_buf_fast(tty, cp, fp, count);
+ else
+ n_tty_receive_buf_standard(tty, cp, fp, count);
+
+ flush_echoes(tty);
+ if (tty->ops->flush_chars)
+ tty->ops->flush_chars(tty);
+ }
+
+ if (ldata->icanon && !L_EXTPROC(tty))
+ return;
+
+ /* publish read_head to consumer */
+ smp_store_release(&ldata->commit_head, ldata->read_head);
+
+ if (read_cnt(ldata)) {
+ kill_fasync(&tty->fasync, SIGIO, POLL_IN);
+ wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
+ }
+}
+
+/**
+ * n_tty_receive_buf_common - process input
+ * @tty: device to receive input
+ * @cp: input chars
+ * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
+ * @count: number of input chars in @cp
+ *
+ * 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)
+ *
+ * Returns the # of input chars from @cp which were processed.
+ *
+ * In canonical mode, the maximum line length is 4096 chars (including
+ * the line termination char); lines longer than 4096 chars are
+ * truncated. After 4095 chars, input data is still processed but
+ * not stored. Overflow processing ensures the tty can always
+ * receive more input until at least one line can be read.
+ *
+ * In non-canonical mode, the read buffer will only accept 4095 chars;
+ * this provides the necessary space for a newline char if the input
+ * mode is switched to canonical.
+ *
+ * Note it is possible for the read buffer to _contain_ 4096 chars
+ * in non-canonical mode: the read buffer could already contain the
+ * maximum canon line of 4096 chars when the mode is switched to
+ * non-canonical.
+ *
+ * n_tty_receive_buf()/producer path:
+ * claims non-exclusive termios_rwsem
+ * publishes commit_head or canon_head
+ */
+static int
+n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count, int flow)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int room, n, rcvd = 0, overflow;
+
+ down_read(&tty->termios_rwsem);
+
+ while (1) {
+ /*
+ * When PARMRK is set, each input char may take up to 3 chars
+ * in the read buf; reduce the buffer space avail by 3x
+ *
+ * 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.
+ *
+ * paired with store in *_copy_from_read_buf() -- guarantees
+ * the consumer has loaded the data in read_buf up to the new
+ * read_tail (so this producer will not overwrite unread data)
+ */
+ size_t tail = smp_load_acquire(&ldata->read_tail);
+
+ room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
+ if (I_PARMRK(tty))
+ room = (room + 2) / 3;
+ room--;
+ if (room <= 0) {
+ overflow = ldata->icanon && ldata->canon_head == tail;
+ if (overflow && room < 0)
+ ldata->read_head--;
+ room = overflow;
+ ldata->no_room = flow && !room;
+ } else
+ overflow = 0;
+
+ n = min(count, room);
+ if (!n)
+ break;
+
+ /* ignore parity errors if handling overflow */
+ if (!overflow || !fp || *fp != TTY_PARITY)
+ __receive_buf(tty, cp, fp, n);
+
+ cp += n;
+ if (fp)
+ fp += n;
+ count -= n;
+ rcvd += n;
+ }
+
+ tty->receive_room = room;
+
+ /* Unthrottle if handling overflow on pty */
+ if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
+ if (overflow) {
+ tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
+ tty_unthrottle_safe(tty);
+ __tty_set_flow_change(tty, 0);
+ }
+ } else
+ n_tty_check_throttle(tty);
+
+ up_read(&tty->termios_rwsem);
+
+ return rcvd;
+}
+
+static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ n_tty_receive_buf_common(tty, cp, fp, count, 0);
+}
+
+static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
+ char *fp, int count)
+{
+ return n_tty_receive_buf_common(tty, cp, fp, count, 1);
+}
+
+/**
+ * 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_rwsem
+ */
+
+static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
+ bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
+ ldata->line_start = ldata->read_tail;
+ if (!L_ICANON(tty) || !read_cnt(ldata)) {
+ ldata->canon_head = ldata->read_tail;
+ ldata->push = 0;
+ } else {
+ set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
+ ldata->read_flags);
+ ldata->canon_head = ldata->read_head;
+ ldata->push = 1;
+ }
+ ldata->commit_head = ldata->read_head;
+ ldata->erasing = 0;
+ ldata->lnext = 0;
+ }
+
+ ldata->icanon = (L_ICANON(tty) != 0);
+
+ 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)) {
+ bitmap_zero(ldata->char_map, 256);
+
+ if (I_IGNCR(tty) || I_ICRNL(tty))
+ set_bit('\r', ldata->char_map);
+ if (I_INLCR(tty))
+ set_bit('\n', ldata->char_map);
+
+ if (L_ICANON(tty)) {
+ set_bit(ERASE_CHAR(tty), ldata->char_map);
+ set_bit(KILL_CHAR(tty), ldata->char_map);
+ set_bit(EOF_CHAR(tty), ldata->char_map);
+ set_bit('\n', ldata->char_map);
+ set_bit(EOL_CHAR(tty), ldata->char_map);
+ if (L_IEXTEN(tty)) {
+ set_bit(WERASE_CHAR(tty), ldata->char_map);
+ set_bit(LNEXT_CHAR(tty), ldata->char_map);
+ set_bit(EOL2_CHAR(tty), ldata->char_map);
+ if (L_ECHO(tty))
+ set_bit(REPRINT_CHAR(tty),
+ ldata->char_map);
+ }
+ }
+ if (I_IXON(tty)) {
+ set_bit(START_CHAR(tty), ldata->char_map);
+ set_bit(STOP_CHAR(tty), ldata->char_map);
+ }
+ if (L_ISIG(tty)) {
+ set_bit(INTR_CHAR(tty), ldata->char_map);
+ set_bit(QUIT_CHAR(tty), ldata->char_map);
+ set_bit(SUSP_CHAR(tty), ldata->char_map);
+ }
+ clear_bit(__DISABLED_CHAR, ldata->char_map);
+ ldata->raw = 0;
+ ldata->real_raw = 0;
+ } else {
+ ldata->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))
+ ldata->real_raw = 1;
+ else
+ ldata->real_raw = 0;
+ }
+ /*
+ * Fix tty hang when I_IXON(tty) is cleared, but the tty
+ * been stopped by STOP_CHAR(tty) before it.
+ */
+ if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
+ start_tty(tty);
+ process_echoes(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)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (tty->link)
+ n_tty_packet_mode_flush(tty);
+
+ vfree(ldata);
+ tty->disc_data = 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)
+{
+ struct n_tty_data *ldata;
+
+ /* Currently a malloc failure here can panic */
+ ldata = vzalloc(sizeof(*ldata));
+ if (!ldata)
+ return -ENOMEM;
+
+ ldata->overrun_time = jiffies;
+ mutex_init(&ldata->atomic_read_lock);
+ mutex_init(&ldata->output_lock);
+
+ tty->disc_data = ldata;
+ tty->closing = 0;
+ /* indicate buffer work may resume */
+ clear_bit(TTY_LDISC_HALTED, &tty->flags);
+ n_tty_set_termios(tty, NULL);
+ tty_unthrottle(tty);
+ return 0;
+}
+
+static inline int input_available_p(struct tty_struct *tty, int poll)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
+
+ if (ldata->icanon && !L_EXTPROC(tty))
+ return ldata->canon_head != ldata->read_tail;
+ else
+ return ldata->commit_head - ldata->read_tail >= amt;
+}
+
+/**
+ * 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 ldata->atomic_read_lock sem
+ *
+ * n_tty_read()/consumer path:
+ * caller holds non-exclusive termios_rwsem
+ * read_tail published
+ */
+
+static int copy_from_read_buf(struct tty_struct *tty,
+ unsigned char __user **b,
+ size_t *nr)
+
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int retval;
+ size_t n;
+ bool is_eof;
+ size_t head = smp_load_acquire(&ldata->commit_head);
+ size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
+
+ retval = 0;
+ n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
+ n = min(*nr, n);
+ if (n) {
+ unsigned char *from = read_buf_addr(ldata, tail);
+ retval = copy_to_user(*b, from, n);
+ n -= retval;
+ is_eof = n == 1 && *from == EOF_CHAR(tty);
+ tty_audit_add_data(tty, from, n);
+ zero_buffer(tty, from, n);
+ smp_store_release(&ldata->read_tail, ldata->read_tail + n);
+ /* Turn single EOF into zero-length read */
+ if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
+ (head == ldata->read_tail))
+ n = 0;
+ *b += n;
+ *nr -= n;
+ }
+ return retval;
+}
+
+/**
+ * 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 one line of input up to and including the line-delimiting
+ * character into the user-space buffer.
+ *
+ * NB: When termios is changed from non-canonical to canonical mode and
+ * the read buffer contains data, n_tty_set_termios() simulates an EOF
+ * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
+ * This causes data already processed as input to be immediately available
+ * as input although a newline has not been received.
+ *
+ * Called under the atomic_read_lock mutex
+ *
+ * n_tty_read()/consumer path:
+ * caller holds non-exclusive termios_rwsem
+ * read_tail published
+ */
+
+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;
+ size_t n, size, more, c;
+ size_t eol;
+ size_t tail;
+ int ret, found = 0;
+
+ /* N.B. avoid overrun if nr == 0 */
+ if (!*nr)
+ return 0;
+
+ n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
+
+ tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
+ size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
+
+ n_tty_trace("%s: nr:%zu tail:%zu 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);
+ found = eol != more;
+ } else
+ found = eol != size;
+
+ n = eol - tail;
+ if (n > N_TTY_BUF_SIZE)
+ n += N_TTY_BUF_SIZE;
+ c = n + found;
+
+ if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
+ c = min(*nr, c);
+ n = c;
+ }
+
+ n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
+ __func__, eol, found, n, c, tail, more);
+
+ ret = tty_copy_to_user(tty, *b, tail, n);
+ if (ret)
+ return -EFAULT;
+ *b += n;
+ *nr -= n;
+
+ if (found)
+ clear_bit(eol, ldata->read_flags);
+ smp_store_release(&ldata->read_tail, ldata->read_tail + c);
+
+ if (found) {
+ if (!ldata->push)
+ ldata->line_start = ldata->read_tail;
+ else
+ ldata->push = 0;
+ tty_audit_push();
+ }
+ return 0;
+}
+
+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.
+ *
+ * Locking: redirected write test is safe
+ * current->signal->tty check is safe
+ * ctrl_lock to safely reference tty->pgrp
+ */
+
+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)
+ return 0;
+
+ return __tty_check_change(tty, SIGTTIN);
+}
+
+
+/**
+ * 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.
+ *
+ * n_tty_read()/consumer path:
+ * claims non-exclusive termios_rwsem
+ * publishes read_tail
+ */
+
+static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
+ unsigned char __user *buf, size_t nr)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ unsigned char __user *b = buf;
+ DEFINE_WAIT_FUNC(wait, woken_wake_function);
+ int c;
+ int minimum, time;
+ ssize_t retval = 0;
+ long timeout;
+ int packet;
+ size_t tail;
+
+ c = job_control(tty, file);
+ if (c < 0)
+ return c;
+
+ /*
+ * Internal serialization of reads.
+ */
+ if (file->f_flags & O_NONBLOCK) {
+ if (!mutex_trylock(&ldata->atomic_read_lock))
+ return -EAGAIN;
+ } else {
+ if (mutex_lock_interruptible(&ldata->atomic_read_lock))
+ return -ERESTARTSYS;
+ }
+
+ down_read(&tty->termios_rwsem);
+
+ minimum = time = 0;
+ timeout = MAX_SCHEDULE_TIMEOUT;
+ if (!ldata->icanon) {
+ minimum = MIN_CHAR(tty);
+ if (minimum) {
+ time = (HZ / 10) * TIME_CHAR(tty);
+ } else {
+ timeout = (HZ / 10) * TIME_CHAR(tty);
+ minimum = 1;
+ }
+ }
+
+ packet = tty->packet;
+ tail = ldata->read_tail;
+
+ 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_irq(&tty->link->ctrl_lock);
+ cs = tty->link->ctrl_status;
+ tty->link->ctrl_status = 0;
+ spin_unlock_irq(&tty->link->ctrl_lock);
+ if (put_user(cs, b)) {
+ retval = -EFAULT;
+ break;
+ }
+ b++;
+ nr--;
+ break;
+ }
+
+ if (!input_available_p(tty, 0)) {
+ up_read(&tty->termios_rwsem);
+ tty_buffer_flush_work(tty->port);
+ down_read(&tty->termios_rwsem);
+ if (!input_available_p(tty, 0)) {
+ if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
+ retval = -EIO;
+ break;
+ }
+ if (tty_hung_up_p(file))
+ break;
+ /*
+ * Abort readers for ttys which never actually
+ * get hung up. See __tty_hangup().
+ */
+ if (test_bit(TTY_HUPPING, &tty->flags))
+ break;
+ if (!timeout)
+ break;
+ if (file->f_flags & O_NONBLOCK) {
+ retval = -EAGAIN;
+ break;
+ }
+ if (signal_pending(current)) {
+ retval = -ERESTARTSYS;
+ break;
+ }
+ up_read(&tty->termios_rwsem);
+
+ timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
+ timeout);
+
+ down_read(&tty->termios_rwsem);
+ continue;
+ }
+ }
+
+ if (ldata->icanon && !L_EXTPROC(tty)) {
+ retval = canon_copy_from_read_buf(tty, &b, &nr);
+ if (retval)
+ break;
+ } else {
+ int uncopied;
+
+ /* Deal with packet mode. */
+ if (packet && b == buf) {
+ if (put_user(TIOCPKT_DATA, b)) {
+ retval = -EFAULT;
+ break;
+ }
+ b++;
+ nr--;
+ }
+
+ uncopied = copy_from_read_buf(tty, &b, &nr);
+ uncopied += copy_from_read_buf(tty, &b, &nr);
+ if (uncopied) {
+ retval = -EFAULT;
+ break;
+ }
+ }
+
+ n_tty_check_unthrottle(tty);
+
+ if (b - buf >= minimum)
+ break;
+ if (time)
+ timeout = time;
+ }
+ if (tail != ldata->read_tail)
+ n_tty_kick_worker(tty);
+ up_read(&tty->termios_rwsem);
+
+ remove_wait_queue(&tty->read_wait, &wait);
+ mutex_unlock(&ldata->atomic_read_lock);
+
+ if (b - buf)
+ retval = b - buf;
+
+ 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;
+ DEFINE_WAIT_FUNC(wait, woken_wake_function);
+ 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;
+ }
+
+ down_read(&tty->termios_rwsem);
+
+ /* Write out any echoed characters that are still pending */
+ process_echoes(tty);
+
+ add_wait_queue(&tty->write_wait, &wait);
+ while (1) {
+ 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)) {
+ 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 {
+ struct n_tty_data *ldata = tty->disc_data;
+
+ while (nr > 0) {
+ mutex_lock(&ldata->output_lock);
+ c = tty->ops->write(tty, b, nr);
+ mutex_unlock(&ldata->output_lock);
+ 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;
+ }
+ up_read(&tty->termios_rwsem);
+
+ wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
+
+ down_read(&tty->termios_rwsem);
+ }
+break_out:
+ remove_wait_queue(&tty->write_wait, &wait);
+ if (nr && tty->fasync)
+ set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+ up_read(&tty->termios_rwsem);
+ 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 __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
+ poll_table *wait)
+{
+ __poll_t mask = 0;
+
+ poll_wait(file, &tty->read_wait, wait);
+ poll_wait(file, &tty->write_wait, wait);
+ if (input_available_p(tty, 1))
+ mask |= EPOLLIN | EPOLLRDNORM;
+ else {
+ tty_buffer_flush_work(tty->port);
+ if (input_available_p(tty, 1))
+ mask |= EPOLLIN | EPOLLRDNORM;
+ }
+ if (tty->packet && tty->link->ctrl_status)
+ mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
+ if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+ mask |= EPOLLHUP;
+ if (tty_hung_up_p(file))
+ mask |= EPOLLHUP;
+ if (tty->ops->write && !tty_is_writelocked(tty) &&
+ tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
+ tty_write_room(tty) > 0)
+ mask |= EPOLLOUT | EPOLLWRNORM;
+ return mask;
+}
+
+static unsigned long inq_canon(struct n_tty_data *ldata)
+{
+ size_t nr, head, tail;
+
+ if (ldata->canon_head == ldata->read_tail)
+ return 0;
+ head = ldata->canon_head;
+ tail = ldata->read_tail;
+ nr = head - tail;
+ /* Skip EOF-chars.. */
+ while (MASK(head) != MASK(tail)) {
+ if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
+ read_buf(ldata, tail) == __DISABLED_CHAR)
+ nr--;
+ tail++;
+ }
+ return nr;
+}
+
+static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+ int retval;
+
+ switch (cmd) {
+ case TIOCOUTQ:
+ return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
+ case TIOCINQ:
+ down_write(&tty->termios_rwsem);
+ if (L_ICANON(tty) && !L_EXTPROC(tty))
+ retval = inq_canon(ldata);
+ else
+ retval = read_cnt(ldata);
+ up_write(&tty->termios_rwsem);
+ return put_user(retval, (unsigned int __user *) arg);
+ default:
+ return n_tty_ioctl_helper(tty, file, cmd, arg);
+ }
+}
+
+static struct tty_ldisc_ops n_tty_ops = {
+ .magic = TTY_LDISC_MAGIC,
+ .name = "n_tty",
+ .open = n_tty_open,
+ .close = n_tty_close,
+ .flush_buffer = n_tty_flush_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,
+ .receive_buf2 = n_tty_receive_buf2,
+};
+
+/**
+ * n_tty_inherit_ops - inherit N_TTY methods
+ * @ops: struct tty_ldisc_ops where to save N_TTY methods
+ *
+ * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
+ */
+
+void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
+{
+ *ops = n_tty_ops;
+ ops->owner = NULL;
+ ops->refcount = ops->flags = 0;
+}
+EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
+
+void __init n_tty_init(void)
+{
+ tty_register_ldisc(N_TTY, &n_tty_ops);
+}