n_tty.c

unix/linux 编程实践一书的所有源代码

/*
 * n_tty.c --- implements the N_TTY line discipline.
 * 
 * This code used to be in tty_io.c, but things are getting hairy
 * enough that it made sense to split things off.  (The N_TTY
 * processing has changed so much that it's hardly recognizable,
 * anyway...)
 *
 * Note that the open routine for N_TTY is guaranteed never to return
 * an error.  This is because Linux will fall back to setting a line
 * to N_TTY if it can not switch to any other line discipline.  
 *
 * Written by Theodore Ts'o, Copyright 1994.
 * 
 * This file also contains code originally written by Linus Torvalds,
 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
 * 
 * This file may be redistributed under the terms of the GNU Public
 * License.
 */

#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/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/poll.h>

#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/bitops.h>

#define CONSOLE_DEV MKDEV(TTY_MAJOR,0)
#define SYSCONS_DEV  MKDEV(TTYAUX_MAJOR,1)

#ifndef MIN
#define MIN(a,b)	((a) < (b) ? (a) : (b))
#endif

/* 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

static inline void put_tty_queue(unsigned char c, struct tty_struct *tty)
{
	if (tty->read_cnt < N_TTY_BUF_SIZE) {
		tty->read_buf[tty->read_head] = c;
		tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
		tty->read_cnt++;
	}
}

/* 
 * Check whether to call the driver.unthrottle function.
 * We test the TTY_THROTTLED bit first so that it always
 * indicates the current state.
 */
static void check_unthrottle(struct tty_struct * tty)
{
	if (tty->count &&
	    test_and_clear_bit(TTY_THROTTLED, &tty->flags) && 
	    tty->driver.unthrottle)
		tty->driver.unthrottle(tty);
}

/*
 * Reset the read buffer counters, clear the flags, 
 * and make sure the driver is unthrottled. Called
 * from n_tty_open() and n_tty_flush_buffer().
 */
static void reset_buffer_flags(struct tty_struct *tty)
{
	tty->read_head = tty->read_tail = tty->read_cnt = 0;
	tty->canon_head = tty->canon_data = tty->erasing = 0;
	memset(&tty->read_flags, 0, sizeof tty->read_flags);
	check_unthrottle(tty);
}

/*
 * Flush the input buffer
 */
void n_tty_flush_buffer(struct tty_struct * tty)
{
	/* clear everything and unthrottle the driver */
	reset_buffer_flags(tty);
	
	if (!tty->link)
		return;

	if (tty->link->packet) {
		tty->ctrl_status |= TIOCPKT_FLUSHREAD;
		wake_up_interruptible(&tty->link->read_wait);
	}
}

/*
 * Return number of characters buffered to be delivered to user
 */
ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
{
	if (tty->icanon) {
		if (!tty->canon_data) return 0;

		return (tty->canon_head > tty->read_tail) ?
			tty->canon_head - tty->read_tail :
			tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
	}
	return tty->read_cnt;
}

/*
 * Perform OPOST processing.  Returns -1 when the output device is
 * full and the character must be retried.
 */
static int opost(unsigned char c, struct tty_struct *tty)
{
	int	space, spaces;

	space = tty->driver.write_room(tty);
	if (!space)
		return -1;

	if (O_OPOST(tty)) {
		switch (c) {
		case '\n':
			if (O_ONLRET(tty))
				tty->column = 0;
			if (O_ONLCR(tty)) {
				if (space < 2)
					return -1;
				tty->driver.put_char(tty, '\r');
				tty->column = 0;
			}
			tty->canon_column = tty->column;
			break;
		case '\r':
			if (O_ONOCR(tty) && tty->column == 0)
				return 0;
			if (O_OCRNL(tty)) {
				c = '\n';
				if (O_ONLRET(tty))
					tty->canon_column = tty->column = 0;
				break;
			}
			tty->canon_column = tty->column = 0;
			break;
		case '\t':
			spaces = 8 - (tty->column & 7);
			if (O_TABDLY(tty) == XTABS) {
				if (space < spaces)
					return -1;
				tty->column += spaces;
				tty->driver.write(tty, 0, "        ", spaces);
				return 0;
			}
			tty->column += spaces;
			break;
		case '\b':
			if (tty->column > 0)
				tty->column--;
			break;
		default:
			if (O_OLCUC(tty))
				c = toupper(c);
			if (!iscntrl(c))
				tty->column++;
			break;
		}
	}
	tty->driver.put_char(tty, c);
	return 0;
}

/*
 * opost_block --- to speed up block console writes, among other
 * things.
 */
static ssize_t opost_block(struct tty_struct * tty,
		       const unsigned char * inbuf, unsigned int nr)
{
	char	buf[80];
	int	space;
	int 	i;
	char	*cp;

	space = tty->driver.write_room(tty);
	if (!space)
		return 0;
	if (nr > space)
		nr = space;
	if (nr > sizeof(buf))
	    nr = sizeof(buf);
	nr -= copy_from_user(buf, inbuf, nr);
	if (!nr)
		return 0;
	
	for (i = 0, cp = buf; i < nr; i++, cp++) {
		switch (*cp) {
		case '\n':
			if (O_ONLRET(tty))
				tty->column = 0;
			if (O_ONLCR(tty))
				goto break_out;
			tty->canon_column = tty->column;
			break;
		case '\r':
			if (O_ONOCR(tty) && tty->column == 0)
				goto break_out;
			if (O_OCRNL(tty)) {
				*cp = '\n';
				if (O_ONLRET(tty))
					tty->canon_column = tty->column = 0;
				break;
			}
			tty->canon_column = tty->column = 0;
			break;
		case '\t':
			goto break_out;
		case '\b':
			if (tty->column > 0)
				tty->column--;
			break;
		default:
			if (O_OLCUC(tty))
				*cp = toupper(*cp);
			if (!iscntrl(*cp))
				tty->column++;
			break;
		}
	}
break_out:
	if (tty->driver.flush_chars)
		tty->driver.flush_chars(tty);
	i = tty->driver.write(tty, 0, buf, i);	
	return i;
}



static inline void put_char(unsigned char c, struct tty_struct *tty)
{
	tty->driver.put_char(tty, c);
}

/* Must be called only when L_ECHO(tty) is true. */

static void echo_char(unsigned char c, struct tty_struct *tty)
{
	if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
		put_char('^', tty);
		put_char(c ^ 0100, tty);
		tty->column += 2;
	} else
		opost(c, tty);
}

static inline void finish_erasing(struct tty_struct *tty)
{
	if (tty->erasing) {
		put_char('/', tty);
		tty->column += 2;
		tty->erasing = 0;
	}
}

static void eraser(unsigned char c, struct tty_struct *tty)
{
	enum { ERASE, WERASE, KILL } kill_type;
	int head, seen_alnums;

	if (tty->read_head == tty->canon_head) {
		/* opost('\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)) {
			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
					  (N_TTY_BUF_SIZE - 1));
			tty->read_head = tty->canon_head;
			return;
		}
		if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
					  (N_TTY_BUF_SIZE - 1));
			tty->read_head = tty->canon_head;
			finish_erasing(tty);
			echo_char(KILL_CHAR(tty), tty);
			/* Add a newline if ECHOK is on and ECHOKE is off. */
			if (L_ECHOK(tty))
				opost('\n', tty);
			return;
		}
		kill_type = KILL;
	}

	seen_alnums = 0;
	while (tty->read_head != tty->canon_head) {
		head = (tty->read_head - 1) & (N_TTY_BUF_SIZE-1);
		c = tty->read_buf[head];
		if (kill_type == WERASE) {
			/* Equivalent to BSD's ALTWERASE. */
			if (isalnum(c) || c == '_')
				seen_alnums++;
			else if (seen_alnums)
				break;
		}
		tty->read_head = head;
		tty->read_cnt--;
		if (L_ECHO(tty)) {
			if (L_ECHOPRT(tty)) {
				if (!tty->erasing) {
					put_char('\\', tty);
					tty->column++;
					tty->erasing = 1;
				}
				echo_char(c, tty);
			} else if (kill_type == ERASE && !L_ECHOE(tty)) {
				echo_char(ERASE_CHAR(tty), tty);
			} else if (c == '\t') {
				unsigned int col = tty->canon_column;
				unsigned long tail = tty->canon_head;

				/* Find the column of the last char. */
				while (tail != tty->read_head) {
					c = tty->read_buf[tail];
					if (c == '\t')
						col = (col | 7) + 1;
					else if (iscntrl(c)) {
						if (L_ECHOCTL(tty))
							col += 2;
					} else
						col++;
					tail = (tail+1) & (N_TTY_BUF_SIZE-1);
				}

				/* should never happen */
				if (tty->column > 0x80000000)
					tty->column = 0; 

				/* Now backup to that column. */
				while (tty->column > col) {
					/* Can't use opost here. */
					put_char('\b', tty);
					if (tty->column > 0)
						tty->column--;
				}
			} else {
				if (iscntrl(c) && L_ECHOCTL(tty)) {
					put_char('\b', tty);
					put_char(' ', tty);
					put_char('\b', tty);
					if (tty->column > 0)
						tty->column--;
				}
				if (!iscntrl(c) || L_ECHOCTL(tty)) {
					put_char('\b', tty);
					put_char(' ', tty);
					put_char('\b', tty);
					if (tty->column > 0)
						tty->column--;
				}
			}
		}
		if (kill_type == ERASE)
			break;
	}
	if (tty->read_head == tty->canon_head)
		finish_erasing(tty);
}

static inline void isig(int sig, struct tty_struct *tty, int flush)
{
	if (tty->pgrp > 0)
		kill_pg(tty->pgrp, sig, 1);
	if (flush || !L_NOFLSH(tty)) {
		n_tty_flush_buffer(tty);
		if (tty->driver.flush_buffer)
			tty->driver.flush_buffer(tty);
	}
}

static inline void n_tty_receive_break(struct tty_struct *tty)
{
	if (I_IGNBRK(tty))
		return;
	if (I_BRKINT(tty)) {
		isig(SIGINT, tty, 1);
		return;
	}
	if (I_PARMRK(tty)) {
		put_tty_queue('\377', tty);
		put_tty_queue('\0', tty);
	}
	put_tty_queue('\0', tty);
	wake_up_interruptible(&tty->read_wait);
}

static inline void n_tty_receive_overrun(struct tty_struct *tty)
{
	char buf[64];

	tty->num_overrun++;
	if (time_before(tty->overrun_time, jiffies - HZ)) {
		printk("%s: %d input overrun(s)\n", tty_name(tty, buf),
		       tty->num_overrun);
		tty->overrun_time = jiffies;
		tty->num_overrun = 0;
	}
}

static inline void n_tty_receive_parity_error(struct tty_struct *tty,
					      unsigned char c)
{
	if (I_IGNPAR(tty)) {
		return;
	}
	if (I_PARMRK(tty)) {
		put_tty_queue('\377', tty);
		put_tty_queue('\0', tty);
		put_tty_queue(c, tty);
	} else	if (I_INPCK(tty))
		put_tty_queue('\0', tty);
	else
		put_tty_queue(c, tty);
	wake_up_interruptible(&tty->read_wait);
}

static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
{
	if (tty->raw) {
		put_tty_queue(c, tty);
		return;
	}
	
	if (tty->stopped && !tty->flow_stopped &&
	    I_IXON(tty) && I_IXANY(tty)) {
		start_tty(tty);
		return;
	}
	
	if (I_ISTRIP(tty))
		c &= 0x7f;
	if (I_IUCLC(tty) && L_IEXTEN(tty))
		c=tolower(c);

	if (tty->closing) {
		if (I_IXON(tty)) {
			if (c == START_CHAR(tty))
				start_tty(tty);
			else if (c == STOP_CHAR(tty))
				stop_tty(tty);
		}
		return;
	}

	/*
	 * If the previous character was LNEXT, or we know that this
	 * character is not one of the characters that we'll have to
	 * handle specially, do shortcut processing to speed things
	 * up.
	 */
	if (!test_bit(c, &tty->process_char_map) || tty->lnext) {
		finish_erasing(tty);
		tty->lnext = 0;
		if (L_ECHO(tty)) {
			if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
				put_char('\a', tty); /* beep if no space */
				return;
			}
			/* Record the column of first canon char. */
			if (tty->canon_head == tty->read_head)
				tty->canon_column = tty->column;
			echo_char(c, tty);
		}
		if (I_PARMRK(tty) && c == (unsigned char) '\377')
			put_tty_queue(c, tty);
		put_tty_queue(c, tty);
		return;
	}
		
	if (c == '\r') {
		if (I_IGNCR(tty))
			return;
		if (I_ICRNL(tty))
			c = '\n';
	} else if (c == '\n' && I_INLCR(tty))
		c = '\r';
	if (I_IXON(tty)) {
		if (c == START_CHAR(tty)) {
			start_tty(tty);
			return;
		}
		if (c == STOP_CHAR(tty)) {
			stop_tty(tty);
			return;
		}
	}
	if (L_ISIG(tty)) {
		int signal;
		signal = SIGINT;
		if (c == INTR_CHAR(tty))
			goto send_signal;
		signal = SIGQUIT;
		if (c == QUIT_CHAR(tty))
			goto send_signal;
		signal = SIGTSTP;
		if (c == SUSP_CHAR(tty)) {
send_signal:
			isig(signal, tty, 0);
			return;
		}
	}
	if (tty->icanon) {
		if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
			eraser(c, tty);
			return;
		}
		if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
			tty->lnext = 1;
			if (L_ECHO(tty)) {
				finish_erasing(tty);
				if (L_ECHOCTL(tty)) {
					put_char('^', tty);
					put_char('\b', tty);
				}
			}
			return;
		}
		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
		    L_IEXTEN(tty)) {
			unsigned long tail = tty->canon_head;

			finish_erasing(tty);
			echo_char(c, tty);
			opost('\n', tty);
			while (tail != tty->read_head) {
				echo_char(tty->read_buf[tail], tty);
				tail = (tail+1) & (N_TTY_BUF_SIZE-1);
			}
			return;
		}
		if (c == '\n') {
			if (L_ECHO(tty) || L_ECHONL(tty)) {
				if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
					put_char('\a', tty);
					return;
				}
				opost('\n', tty);
			}
			goto handle_newline;
		}
		if (c == EOF_CHAR(tty)) {
		        if (tty->canon_head != tty->read_head)
			        set_bit(TTY_PUSH, &tty->flags);
			c = __DISABLED_CHAR;
			goto handle_newline;
		}
		if ((c == EOL_CHAR(tty)) ||
		    (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
			/*
			 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
			 */
			if (L_ECHO(tty)) {
				if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
					put_char('\a', tty);
					return;
				}