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OpenCloudOS-Kernel/drivers/tty/n_tty.c

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// 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/bitmap.h>
#include <linux/bitops.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/jiffies.h>
#include <linux/math.h>
#include <linux/poll.h>
#include <linux/ratelimit.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/tty.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
#include "tty.h"
/*
* Until this number of characters is queued in the xmit buffer, select will
* return "we have room for writes".
*/
#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...) no_printk(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;
/* # of chars looked ahead (to find software flow control chars) */
size_t lookahead_count;
/* 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 void tty_copy(struct tty_struct *tty, void *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);
if (n > size) {
tty_audit_add_data(tty, from, size);
memcpy(to, from, size);
zero_buffer(tty, from, size);
to += size;
n -= size;
from = ldata->read_buf;
}
tty_audit_add_data(tty, from, n);
memcpy(to, from, n);
zero_buffer(tty, from, n);
}
/**
* n_tty_kick_worker - start input worker (if required)
* @tty: terminal
*
* Re-schedules the flip buffer work if it may have stopped.
*
* Locking:
* * 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(READ_ONCE(ldata->no_room))) {
WRITE_ONCE(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.
*
* Locking:
* * 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
* @ldata: line disc data 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;
ldata->lookahead_count = 0;
}
static void n_tty_packet_mode_flush(struct tty_struct *tty)
{
unsigned long flags;
if (tty->link->ctrl.packet) {
spin_lock_irqsave(&tty->ctrl.lock, flags);
tty->ctrl.pktstatus |= 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
* @tty: terminal device
*
* 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.
*
* 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.
*
* Returns: the number of characters output.
*
* 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 <= 0) {
mutex_unlock(&ldata->output_lock);
return space;
}
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;
bool space_left = true;
/*
* 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) {
case ECHO_OP_ERASE_TAB: {
unsigned int num_chars, num_bs;
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) {
space_left = false;
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) {
space_left = false;
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) {
space_left = false;
break;
}
tty_put_char(tty, '^');
tty_put_char(tty, op ^ 0100);
ldata->column += 2;
space -= 2;
tail += 2;
}
if (!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
* @ldata: line disc data
*
* Echo user input back onto the screen. This must be called only when
* L_ECHO(tty) is true. Called from the &tty_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 &tty_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.
*
* Locking: 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);
}
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);
}
}
/**
* isig - handle the ISIG optio
* @sig: signal
* @tty: terminal
*
* Called when a signal is being sent due to terminal input. Called from the
* &tty_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 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.
*
* Locking: 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.
*
* Locking: 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);
}
static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
{
return c == START_CHAR(tty) || c == STOP_CHAR(tty);
}
/**
* n_tty_receive_char_flow_ctrl - receive flow control chars
* @tty: terminal device
* @c: character
* @lookahead_done: lookahead has processed this character already
*
* Receive and process flow control character actions.
*
* In case lookahead for flow control chars already handled the character in
* advance to the normal receive, the actions are skipped during normal
* receive.
*
* Returns true if @c is consumed as flow-control character, the character
* must not be treated as normal character.
*/
static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c,
bool lookahead_done)
{
if (!n_tty_is_char_flow_ctrl(tty, c))
return false;
if (lookahead_done)
return true;
if (c == START_CHAR(tty)) {
start_tty(tty);
process_echoes(tty);
return true;
}
/* STOP_CHAR */
stop_tty(tty);
return true;
}
static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c,
bool lookahead_done)
{
struct n_tty_data *ldata = tty->disc_data;
if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
return;
if (L_ISIG(tty)) {
if (c == INTR_CHAR(tty)) {
n_tty_receive_signal_char(tty, SIGINT, c);
return;
} else if (c == QUIT_CHAR(tty)) {
n_tty_receive_signal_char(tty, SIGQUIT, c);
return;
} else if (c == SUSP_CHAR(tty)) {
n_tty_receive_signal_char(tty, SIGTSTP, c);
return;
}
}
if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
start_tty(tty);
process_echoes(tty);
}
if (c == '\r') {
if (I_IGNCR(tty))
return;
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;
}
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;
}
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;
}
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 | EPOLLRDNORM);
return;
}
}
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);
}
/**
* 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.
*
* Locking: n_tty_receive_buf()/producer path:
* caller holds non-exclusive %termios_rwsem
* publishes canon_head if canonical mode is active
*/
static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
{
struct n_tty_data *ldata = tty->disc_data;
if (tty->flow.stopped && !tty->flow.tco_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_closing(struct tty_struct *tty, unsigned char c,
bool lookahead_done)
{
if (I_ISTRIP(tty))
c &= 0x7f;
if (I_IUCLC(tty) && L_IEXTEN(tty))
c = tolower(c);
if (I_IXON(tty)) {
if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
tty->flow.stopped && !tty->flow.tco_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);
}
/* Caller must ensure count > 0 */
static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const unsigned char *cp,
const unsigned char *fp, unsigned int count)
{
struct n_tty_data *ldata = tty->disc_data;
unsigned char flag = TTY_NORMAL;
ldata->lookahead_count += count;
if (!I_IXON(tty))
return;
while (count--) {
if (fp)
flag = *fp++;
if (likely(flag == TTY_NORMAL))
n_tty_receive_char_flow_ctrl(tty, *cp, false);
cp++;
}
}
static void
n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
const 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,
const 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,
const char *fp, int count, bool lookahead_done)
{
char flag = TTY_NORMAL;
while (count--) {
if (fp)
flag = *fp++;
if (likely(flag == TTY_NORMAL))
n_tty_receive_char_closing(tty, *cp++, lookahead_done);
}
}
static void n_tty_receive_buf_standard(struct tty_struct *tty,
const unsigned char *cp, const char *fp, int count, bool lookahead_done)
{
struct n_tty_data *ldata = tty->disc_data;
char flag = TTY_NORMAL;
while (count--) {
unsigned char c = *cp++;
if (fp)
flag = *fp++;
if (ldata->lnext) {
n_tty_receive_char_lnext(tty, c, flag);
continue;
}
if (unlikely(flag != TTY_NORMAL)) {
n_tty_receive_char_flagged(tty, c, flag);
continue;
}
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_special(tty, c, lookahead_done);
else
n_tty_receive_char(tty, c);
}
}
static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
const char *fp, int count)
{
struct n_tty_data *ldata = tty->disc_data;
bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
size_t la_count = min_t(size_t, ldata->lookahead_count, count);
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)) {
if (la_count > 0)
n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
if (count > la_count)
n_tty_receive_buf_closing(tty, cp, fp, count - la_count, false);
} else {
if (la_count > 0)
n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
if (count > la_count)
n_tty_receive_buf_standard(tty, cp, fp, count - la_count, false);
flush_echoes(tty);
if (tty->ops->flush_chars)
tty->ops->flush_chars(tty);
}
ldata->lookahead_count -= la_count;
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 | EPOLLRDNORM);
}
}
/**
* 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
* @flow: enable flow control
*
* 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.
*
* Locking: 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,
const 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);
do {
/*
* 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 = DIV_ROUND_UP(room, 3);
room--;
if (room <= 0) {
overflow = ldata->icanon && ldata->canon_head == tail;
if (overflow && room < 0)
ldata->read_head--;
room = overflow;
WRITE_ONCE(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;
} while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
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);
if (unlikely(ldata->no_room)) {
/*
* Barrier here is to ensure to read the latest read_tail in
* chars_in_buffer() and to make sure that read_tail is not loaded
* before ldata->no_room is set.
*/
smp_mb();
if (!chars_in_buffer(tty))
n_tty_kick_worker(tty);
}
up_read(&tty->termios_rwsem);
return rcvd;
}
static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
const 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,
const 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, const 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.tco_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);
down_write(&tty->termios_rwsem);
vfree(ldata);
tty->disc_data = NULL;
up_write(&tty->termios_rwsem);
}
/**
* 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
* @kbp: 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.
*
* Returns: true if it successfully copied data, but there is still more data
* to be had.
*
* Locking:
* * called under the @ldata->atomic_read_lock sem
* * n_tty_read()/consumer path:
* caller holds non-exclusive %termios_rwsem;
* read_tail published
*/
static bool copy_from_read_buf(struct tty_struct *tty,
unsigned char **kbp,
size_t *nr)
{
struct n_tty_data *ldata = tty->disc_data;
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);
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);
memcpy(*kbp, from, n);
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))
return false;
*kbp += n;
*nr -= n;
/* If we have more to copy, let the caller know */
return head != ldata->read_tail;
}
return false;
}
/**
* canon_copy_from_read_buf - copy read data in canonical mode
* @tty: terminal device
* @kbp: 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 result buffer.
*
* Note: 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.
*
* Locking:
* * called under the %atomic_read_lock mutex
* * n_tty_read()/consumer path:
* caller holds non-exclusive %termios_rwsem;
* read_tail published
*/
static bool canon_copy_from_read_buf(struct tty_struct *tty,
unsigned char **kbp,
size_t *nr)
{
struct n_tty_data *ldata = tty->disc_data;
size_t n, size, more, c;
size_t eol;
size_t tail, canon_head;
int found = 0;
/* N.B. avoid overrun if nr == 0 */
if (!*nr)
return false;
canon_head = smp_load_acquire(&ldata->canon_head);
n = min(*nr, 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_first_bit(ldata->read_flags, more);
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)
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);
tty_copy(tty, *kbp, tail, n);
*kbp += 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 false;
}
/* No EOL found - do a continuation retry if there is more data */
return ldata->read_tail != canon_head;
}
/*
* If we finished a read at the exact location of an
* EOF (special EOL character that's a __DISABLED_CHAR)
* in the stream, silently eat the EOF.
*/
static void canon_skip_eof(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
size_t tail, canon_head;
canon_head = smp_load_acquire(&ldata->canon_head);
tail = ldata->read_tail;
// No data?
if (tail == canon_head)
return;
// See if the tail position is EOF in the circular buffer
tail &= (N_TTY_BUF_SIZE - 1);
if (!test_bit(tail, ldata->read_flags))
return;
if (read_buf(ldata, tail) != __DISABLED_CHAR)
return;
// Clear the EOL bit, skip the EOF char.
clear_bit(tail, ldata->read_flags);
smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
}
/**
* 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->ctrl.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_iter == redirected_tty_write)
return 0;
return __tty_check_change(tty, SIGTTIN);
}
/**
* n_tty_read - read function for tty
* @tty: tty device
* @file: file object
* @kbuf: kernelspace buffer pointer
* @nr: size of I/O
* @cookie: if non-%NULL, this is a continuation read
* @offset: where to continue reading from (unused in n_tty)
*
* 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.
*
* Locking: 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 *kbuf, size_t nr,
void **cookie, unsigned long offset)
{
struct n_tty_data *ldata = tty->disc_data;
unsigned char *kb = kbuf;
DEFINE_WAIT_FUNC(wait, woken_wake_function);
int c;
int minimum, time;
ssize_t retval = 0;
long timeout;
bool packet;
size_t old_tail;
/*
* Is this a continuation of a read started earler?
*
* If so, we still hold the atomic_read_lock and the
* termios_rwsem, and can just continue to copy data.
*/
if (*cookie) {
if (ldata->icanon && !L_EXTPROC(tty)) {
/*
* If we have filled the user buffer, see
* if we should skip an EOF character before
* releasing the lock and returning done.
*/
if (!nr)
canon_skip_eof(tty);
else if (canon_copy_from_read_buf(tty, &kb, &nr))
return kb - kbuf;
} else {
if (copy_from_read_buf(tty, &kb, &nr))
return kb - kbuf;
}
/* No more data - release locks and stop retries */
n_tty_kick_worker(tty);
n_tty_check_unthrottle(tty);
up_read(&tty->termios_rwsem);
mutex_unlock(&ldata->atomic_read_lock);
*cookie = NULL;
return kb - kbuf;
}
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->ctrl.packet;
old_tail = ldata->read_tail;
add_wait_queue(&tty->read_wait, &wait);
while (nr) {
/* First test for status change. */
if (packet && tty->link->ctrl.pktstatus) {
unsigned char cs;
if (kb != kbuf)
break;
spin_lock_irq(&tty->link->ctrl.lock);
cs = tty->link->ctrl.pktstatus;
tty->link->ctrl.pktstatus = 0;
spin_unlock_irq(&tty->link->ctrl.lock);
*kb++ = cs;
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 (tty_io_nonblock(tty, file)) {
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)) {
if (canon_copy_from_read_buf(tty, &kb, &nr))
goto more_to_be_read;
} else {
/* Deal with packet mode. */
if (packet && kb == kbuf) {
*kb++ = TIOCPKT_DATA;
nr--;
}
/*
* Copy data, and if there is more to be had
* and we have nothing more to wait for, then
* let's mark us for retries.
*
* NOTE! We return here with both the termios_sem
* and atomic_read_lock still held, the retries
* will release them when done.
*/
if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
more_to_be_read:
remove_wait_queue(&tty->read_wait, &wait);
*cookie = cookie;
return kb - kbuf;
}
}
n_tty_check_unthrottle(tty);
if (kb - kbuf >= minimum)
break;
if (time)
timeout = time;
}
if (old_tail != ldata->read_tail) {
/*
* Make sure no_room is not read in n_tty_kick_worker()
* before setting ldata->read_tail in copy_from_read_buf().
*/
smp_mb();
n_tty_kick_worker(tty);
}
up_read(&tty->termios_rwsem);
remove_wait_queue(&tty->read_wait, &wait);
mutex_unlock(&ldata->atomic_read_lock);
if (kb - kbuf)
retval = kb - kbuf;
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_iter != 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 (tty_io_nonblock(tty, file)) {
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.
*
* Locking: 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->ctrl.packet && tty->link->ctrl.pktstatus)
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, 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, cmd, arg);
}
}
static struct tty_ldisc_ops n_tty_ops = {
.owner = THIS_MODULE,
.num = N_TTY,
.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,
.lookahead_buf = n_tty_lookahead_flow_ctrl,
};
/**
* 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;
}
EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
void __init n_tty_init(void)
{
tty_register_ldisc(&n_tty_ops);
}
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