tty_io.c

unix/linux 编程实践一书的所有源代码

		kfree_s(o_tp, sizeof(struct termios));
	if (o_tty)
		free_page((unsigned long) o_tty);
	if (ltp)
		kfree_s(ltp, sizeof(struct termios));
	if (tp)
		kfree_s(tp, sizeof(struct termios));
	free_page((unsigned long) tty);

fail_no_mem:
	retval = -ENOMEM;
	goto end_init;

	/* call the tty release_mem routine to clean out this slot */
release_mem_out:
	printk("init_dev: ldisc open failed, clearing slot %d\n", idx);
	release_mem(tty, idx);
	goto end_init;
}

/*
 * Releases memory associated with a tty structure, and clears out the
 * driver table slots.
 */
static void release_mem(struct tty_struct *tty, int idx)
{
	struct tty_struct *o_tty;
	struct termios *tp;

	if ((o_tty = tty->link) != NULL) {
		o_tty->driver.table[idx] = NULL;
		if (o_tty->driver.flags & TTY_DRIVER_RESET_TERMIOS) {
			tp = o_tty->driver.termios[idx];
			o_tty->driver.termios[idx] = NULL;
			kfree_s(tp, sizeof(struct termios));
		}
		o_tty->magic = 0;
		(*o_tty->driver.refcount)--;
		free_page((unsigned long) o_tty);
	}

	tty->driver.table[idx] = NULL;
	if (tty->driver.flags & TTY_DRIVER_RESET_TERMIOS) {
		tp = tty->driver.termios[idx];
		tty->driver.termios[idx] = NULL;
		kfree_s(tp, sizeof(struct termios));
	}
	tty->magic = 0;
	(*tty->driver.refcount)--;
	free_page((unsigned long) tty);
}

/*
 * Even releasing the tty structures is a tricky business.. We have
 * to be very careful that the structures are all released at the
 * same time, as interrupts might otherwise get the wrong pointers.
 */
static void release_dev(struct file * filp)
{
	struct tty_struct *tty, *o_tty;
	int	pty_master, tty_closing, o_tty_closing, do_sleep;
	int	idx;
	
	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_inode->i_rdev, "release_dev"))
		return;

	check_tty_count(tty, "release_dev");

	tty_fasync(filp->f_inode, filp, 0);

	idx = MINOR(tty->device) - tty->driver.minor_start;
	pty_master = (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
		      tty->driver.subtype == PTY_TYPE_MASTER);
	o_tty = tty->link;

#ifdef TTY_PARANOIA_CHECK
	if (idx < 0 || idx >= tty->driver.num) {
		printk("release_dev: bad idx when trying to free (%s)\n",
		       kdevname(tty->device));
		return;
	}
	if (tty != tty->driver.table[idx]) {
		printk("release_dev: driver.table[%d] not tty for (%s)\n",
		       idx, kdevname(tty->device));
		return;
	}
	if (tty->termios != tty->driver.termios[idx]) {
		printk("release_dev: driver.termios[%d] not termios "
		       "for (%s)\n",
		       idx, kdevname(tty->device));
		return;
	}
	if (tty->termios_locked != tty->driver.termios_locked[idx]) {
		printk("release_dev: driver.termios_locked[%d] not "
		       "termios_locked for (%s)\n",
		       idx, kdevname(tty->device));
		return;
	}
#endif

#ifdef TTY_DEBUG_HANGUP
	printk("release_dev of %s (tty count=%d)...", tty_name(tty),
	       tty->count);
#endif

#ifdef TTY_PARANOIA_CHECK
	if (tty->driver.other) {
		if (o_tty != tty->driver.other->table[idx]) {
			printk("release_dev: other->table[%d] not o_tty for ("
			       "%s)\n",
			       idx, kdevname(tty->device));
			return;
		}
		if (o_tty->termios != tty->driver.other->termios[idx]) {
			printk("release_dev: other->termios[%d] not o_termios "
			       "for (%s)\n",
			       idx, kdevname(tty->device));
			return;
		}
		if (o_tty->termios_locked != 
		      tty->driver.other->termios_locked[idx]) {
			printk("release_dev: other->termios_locked[%d] not "
			       "o_termios_locked for (%s)\n",
			       idx, kdevname(tty->device));
			return;
		}
		if (o_tty->link != tty) {
			printk("release_dev: bad pty pointers\n");
			return;
		}
	}
#endif
	/*
	 * Sanity check: if tty->count is going to zero, there shouldn't be
	 * any waiters on tty->read_wait or tty->write_wait.  We test the
	 * wait queues and kick everyone out _before_ actually starting to
	 * close.  This ensures that we won't block while releasing the tty
	 * structure.
	 *
	 * The test for the o_tty closing is necessary, since the master and
	 * slave sides may close in any order.  If the slave side closes out
	 * first, its count will be one, since the master side holds an open.
	 * Thus this test wouldn't be triggered at the time the slave closes,
	 * so we do it now.
	 *
	 * Note that it's possible for the tty to be opened again while we're
	 * flushing out waiters.  By recalculating the closing flags before
	 * each iteration we avoid any problems.
	 */
	while (1) {
		tty_closing = tty->count <= 1;
		o_tty_closing = o_tty &&
			(o_tty->count <= (pty_master ? 1 : 0));
		do_sleep = 0;

		if (tty_closing) {
			if (waitqueue_active(&tty->read_wait)) {
				wake_up(&tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&tty->write_wait)) {
				wake_up(&tty->write_wait);
				do_sleep++;
			}
		}
		if (o_tty_closing) {
			if (waitqueue_active(&o_tty->read_wait)) {
				wake_up(&o_tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&o_tty->write_wait)) {
				wake_up(&o_tty->write_wait);
				do_sleep++;
			}
		}
		if (!do_sleep)
			break;

		printk("release_dev: %s: read/write wait queue active!\n",
		       tty_name(tty));
		schedule();
	}	

	/*
	 * The closing flags are now consistent with the open counts on 
	 * both sides, and we've completed the last operation that could 
	 * block, so it's safe to proceed with closing.
	 */

	if (tty->driver.close)
		tty->driver.close(tty, filp);

	if (pty_master) {
		if (--o_tty->count < 0) {
			printk("release_dev: bad pty slave count (%d) for %s\n",
			       o_tty->count, tty_name(o_tty));
			o_tty->count = 0;
		}
	}
	if (--tty->count < 0) {
		printk("release_dev: bad tty->count (%d) for %s\n",
		       tty->count, tty_name(tty));
		tty->count = 0;
	}

	/*
	 * Perform some housekeeping before deciding whether to return.
	 *
	 * Set the TTY_CLOSING flag if this was the last open.  In the
	 * case of a pty we may have to wait around for the other side
	 * to close, and TTY_CLOSING makes sure we can't be reopened.
	 */
	if(tty_closing)
		set_bit(TTY_CLOSING, &tty->flags);
	if(o_tty_closing)
		set_bit(TTY_CLOSING, &o_tty->flags);

	/*
	 * If _either_ side is closing, make sure there aren't any
	 * processes that still think tty or o_tty is their controlling
	 * tty.  Also, clear redirect if it points to either tty.
	 */
	if (tty_closing || o_tty_closing) {
		struct task_struct *p;

		for_each_task(p) {
			if (p->tty == tty || (o_tty && p->tty == o_tty))
				p->tty = NULL;
		}

		if (redirect == tty || (o_tty && redirect == o_tty))
			redirect = NULL;
	}

	/* check whether both sides are closing ... */
	if (!tty_closing || (o_tty && !o_tty_closing))
		return;
	filp->private_data = 0;
	
#ifdef TTY_DEBUG_HANGUP
	printk("freeing tty structure...");
#endif

	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 * N.B. why reset ldisc when we're releasing the memory??
	 */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);
	tty->ldisc = ldiscs[N_TTY];
	tty->termios->c_line = N_TTY;
	if (o_tty) {
		if (o_tty->ldisc.close)
			(o_tty->ldisc.close)(o_tty);
		o_tty->ldisc = ldiscs[N_TTY];
	}
	
	/*
	 * Make sure that the tty's task queue isn't activated.  If it
	 * is, take it out of the linked list.  The tqueue isn't used by
	 * pty's, so skip the test for them.
	 */
	if (tty->driver.type != TTY_DRIVER_TYPE_PTY) {
		cli();
		if (tty->flip.tqueue.sync) {
			struct tq_struct *tq, *prev;

			for (tq=tq_timer, prev=0; tq; prev=tq, tq=tq->next) {
				if (tq == &tty->flip.tqueue) {
					if (prev)
						prev->next = tq->next;
					else
						tq_timer = tq->next;
					break;
				}
			}
		}
		sti();
	}

	/* 
	 * The release_mem function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	release_mem(tty, idx);
}

/*
 * tty_open and tty_release keep up the tty count that contains the
 * number of opens done on a tty. We cannot use the inode-count, as
 * different inodes might point to the same tty.
 *
 * Open-counting is needed for pty masters, as well as for keeping
 * track of serial lines: DTR is dropped when the last close happens.
 * (This is not done solely through tty->count, now.  - Ted 1/27/92)
 *
 * The termios state of a pty is reset on first open so that
 * settings don't persist across reuse.
 */
static int tty_open(struct inode * inode, struct file * filp)
{
	struct tty_struct *tty;
	int minor;
	int noctty, retval;
	kdev_t device;

retry_open:
	noctty = filp->f_flags & O_NOCTTY;
	device = inode->i_rdev;
	if (device == TTY_DEV) {
		if (!current->tty)
			return -ENXIO;
		device = current->tty->device;
		/* noctty = 1; */
	}
	if (device == CONSOLE_DEV) {
		device = MKDEV(TTY_MAJOR, fg_console+1);
		noctty = 1;
	}
	minor = MINOR(device);
	
	retval = init_dev(device, &tty);
	if (retval)
		return retval;
	filp->private_data = tty;
	check_tty_count(tty, "tty_open");
	if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver.subtype == PTY_TYPE_MASTER)
		noctty = 1;
#ifdef TTY_DEBUG_HANGUP
	printk("opening %s...", tty_name(tty));
#endif
	if (tty->driver.open)
		retval = tty->driver.open(tty, filp);
	else
		retval = -ENODEV;

	if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) && !suser())
		retval = -EBUSY;

	if (retval) {
#ifdef TTY_DEBUG_HANGUP
		printk("error %d in opening %s...", retval, tty_name(tty));
#endif

		release_dev(filp);
		if (retval != -ERESTARTSYS)
			return retval;
		if (current->signal & ~current->blocked)
			return retval;
		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		filp->f_op = &tty_fops;
		goto retry_open;
	}
	if (!noctty &&
	    current->leader &&
	    !current->tty &&
	    tty->session == 0) {
		current->tty = tty;
		current->tty_old_pgrp = 0;
		tty->session = current->session;
		tty->pgrp = current->pgrp;
	}
	return 0;
}

static void tty_release(struct inode * inode, struct file * filp)
{
	release_dev(filp);
}

static int tty_select(struct inode * inode, struct file * filp, int sel_type, select_table * wait)
{
	struct tty_struct * tty;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, inode->i_rdev, "tty_select"))
		return 0;

	if (tty->ldisc.select)
		return (tty->ldisc.select)(tty, inode, filp, sel_type, wait);
	return 0;
}

/*
 * fasync_helper() is used by some character device drivers (mainly mice)
 * to set up the fasync queue. It returns negative on error, 0 if it did
 * no changes and positive if it added/deleted the entry.
 */
int fasync_helper(struct inode * inode, struct file * filp, int on, struct fasync_struct **fapp)
{
	struct fasync_struct *fa, **fp;
	unsigned long flags;

	for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
		if (fa->fa_file == filp)
			break;
	}

	if (on) {
		if (fa)
			return 0;
		fa = (struct fasync_struct *)kmalloc(sizeof(struct fasync_struct), GFP_KERNEL);
		if (!fa)
			return -ENOMEM;
		fa->magic = FASYNC_MAGIC;
		fa->fa_file = filp;
		save_flags(flags);
		cli();
		fa->fa_next = *fapp;
		*fapp = fa;
		restore_flags(flags);
		return 1;
	}
	if (!fa)
		return 0;
	save_flags(flags);
	cli();
	*fp = fa->fa_next;
	restore_flags(flags);
	kfree(fa);
	return 1;
}

static int tty_fasync(struct inode * inode, struct file * filp, int on)
{
	struct tty_struct * tty;
	int retval;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, inode->i_rdev, "tty_fasync"))
		return 0;
	
	retval = fasync_helper(inode, filp, on, &tty->fasync);
	if (retval <= 0)
		return retval;

	if (on) {
		if (!waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = 1;
		if (filp->f_owner.pid == 0) {
			filp->f_owner.pid = (-tty->pgrp) ? : current->pid;
			filp->f_owner.uid = current->uid;
			filp->f_owner.euid = current->euid;
		}
	} else {
		if (!tty->fasync && !waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = N_TTY_BUF_SIZE;
	}
	return 0;
}

#if 0
/*
 * XXX does anyone use this anymore?!?
 */
static int do_get_ps_info(unsigned long arg)
{
	struct tstruct {
		int flag;
		int present[NR_TASKS];
		struct task_struct tasks[NR_TASKS];
	};
	struct tstruct *ts = (struct tstruct *)arg;
	struct task_struct **p;
	char *c, *d;
	int i, n = 0;
	
	i = verify_area(VERIFY_WRITE, (void *)arg, sizeof(struct tstruct));
	if (i)
		return i;
	for (p = &FIRST_TASK ; p <= &LAST_TASK ; p++, n++)
		if (*p)
		{
			c = (char *)(*p);
			d = (char *)(ts->tasks+n);
			for (i=0 ; i<sizeof(struct task_struct) ; i++)
				put_user(*c++, d++);
			put_user(1, ts->present+n);
		}
		else	
			put_user(0, ts->present+n);
	return(0);			
}
#endif

static int tty_ioctl(struct inode * inode, struct file * file,
		     unsigned int cmd, unsigned long arg)
{
	int	retval;
	struct tty_struct * tty;
	struct tty_struct * real_tty;
	struct winsize tmp_ws;
	pid_t pgrp;
	unsigned char	ch;
	char	mbz = 0;
	
	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode->i_rdev, "tty_ioctl"))
		return -EINVAL;

	if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver.subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;
	else
		real_tty = tty;

	switch (cmd) {
		case TIOCSTI:
			if ((current->tty != tty) && !suser())
				return -EPERM;
			retval = verify_area(VERIFY_READ, (void *) arg, 1);