tty_io.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 2,610 行 · 第 1/5 页

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

	/*
	 * We've decremented tty->count, so we need to remove this file
	 * descriptor off the tty->tty_files list; this serves two
	 * purposes:
	 *  - check_tty_count sees the correct number of file descriptors
	 *    associated with this tty.
	 *  - do_tty_hangup no longer sees this file descriptor as
	 *    something that needs to be handled for hangups.
	 */
	file_kill(filp);
	filp->private_data = NULL;

	/*
	 * 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.
	 */
	if (tty_closing || o_tty_closing) {
		struct task_struct *p;

		read_lock(&tasklist_lock);
		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
			p->signal->tty = NULL;
		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
		if (o_tty)
			do_each_task_pid(o_tty->session, PIDTYPE_SID, p) {
				p->signal->tty = NULL;
			} while_each_task_pid(o_tty->session, PIDTYPE_SID, p);
		read_unlock(&tasklist_lock);
	}

	/* check whether both sides are closing ... */
	if (!tty_closing || (o_tty && !o_tty_closing))
		return;
	
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "freeing tty structure...");
#endif
	/*
	 * Prevent flush_to_ldisc() from rescheduling the work for later.  Then
	 * kill any delayed work. As this is the final close it does not
	 * race with the set_ldisc code path.
	 */
	clear_bit(TTY_LDISC, &tty->flags);
	clear_bit(TTY_DONT_FLIP, &tty->flags);
	cancel_delayed_work(&tty->flip.work);

	/*
	 * Wait for ->hangup_work and ->flip.work handlers to terminate
	 */
	 
	flush_scheduled_work();
	
	/*
	 * Wait for any short term users (we know they are just driver
	 * side waiters as the file is closing so user count on the file
	 * side is zero.
	 */
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	while(tty->ldisc.refcount)
	{
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
		spin_lock_irqsave(&tty_ldisc_lock, flags);
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 * N.B. why reset ldisc when we're releasing the memory??
	 *
	 * FIXME: this MUST get fixed for the new reflocking
	 */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);
	tty_ldisc_put(tty->ldisc.num);
	
	/*
	 *	Switch the line discipline back
	 */
	tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
	tty_set_termios_ldisc(tty,N_TTY); 
	if (o_tty) {
		/* FIXME: could o_tty be in setldisc here ? */
		clear_bit(TTY_LDISC, &o_tty->flags);
		if (o_tty->ldisc.close)
			(o_tty->ldisc.close)(o_tty);
		tty_ldisc_put(o_tty->ldisc.num);
		tty_ldisc_assign(o_tty, tty_ldisc_get(N_TTY));
		tty_set_termios_ldisc(o_tty,N_TTY); 
	}
	/*
	 * The release_mem function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	release_mem(tty, idx);

#ifdef CONFIG_UNIX98_PTYS
	/* Make this pty number available for reallocation */
	if (devpts) {
		down(&allocated_ptys_lock);
		idr_remove(&allocated_ptys, idx);
		up(&allocated_ptys_lock);
	}
#endif

}

/*
 * 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 noctty, retval;
	struct tty_driver *driver;
	int index;
	dev_t device = inode->i_rdev;
	unsigned short saved_flags = filp->f_flags;

	nonseekable_open(inode, filp);
	
retry_open:
	noctty = filp->f_flags & O_NOCTTY;
	index  = -1;
	retval = 0;

	if (device == MKDEV(TTYAUX_MAJOR,0)) {
		if (!current->signal->tty)
			return -ENXIO;
		driver = current->signal->tty->driver;
		index = current->signal->tty->index;
		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
		/* noctty = 1; */
		goto got_driver;
	}
#ifdef CONFIG_VT
	if (device == MKDEV(TTY_MAJOR,0)) {
		extern int fg_console;
		extern struct tty_driver *console_driver;
		driver = console_driver;
		index = fg_console;
		noctty = 1;
		goto got_driver;
	}
#endif
	if (device == MKDEV(TTYAUX_MAJOR,1)) {
		driver = console_device(&index);
		if (driver) {
			/* Don't let /dev/console block */
			filp->f_flags |= O_NONBLOCK;
			noctty = 1;
			goto got_driver;
		}
		return -ENODEV;
	}

	driver = get_tty_driver(device, &index);
	if (!driver)
		return -ENODEV;
got_driver:
	retval = init_dev(driver, index, &tty);
	if (retval)
		return retval;

	filp->private_data = tty;
	file_move(filp, &tty->tty_files);
	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(KERN_DEBUG "opening %s...", tty->name);
#endif
	if (!retval) {
		if (tty->driver->open)
			retval = tty->driver->open(tty, filp);
		else
			retval = -ENODEV;
	}
	filp->f_flags = saved_flags;

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

	if (retval) {
#ifdef TTY_DEBUG_HANGUP
		printk(KERN_DEBUG "error %d in opening %s...", retval,
		       tty->name);
#endif
		release_dev(filp);
		if (retval != -ERESTARTSYS)
			return retval;
		if (signal_pending(current))
			return retval;
		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		if (filp->f_op == &hung_up_tty_fops)
			filp->f_op = &tty_fops;
		goto retry_open;
	}
	if (!noctty &&
	    current->signal->leader &&
	    !current->signal->tty &&
	    tty->session == 0) {
	    	task_lock(current);
		current->signal->tty = tty;
		task_unlock(current);
		current->signal->tty_old_pgrp = 0;
		tty->session = current->signal->session;
		tty->pgrp = process_group(current);
	}
	return 0;
}

#ifdef CONFIG_UNIX98_PTYS
static int ptmx_open(struct inode * inode, struct file * filp)
{
	struct tty_struct *tty;
	int retval;
	int index;
	int idr_ret;

	nonseekable_open(inode, filp);

	/* find a device that is not in use. */
	down(&allocated_ptys_lock);
	if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
		up(&allocated_ptys_lock);
		return -ENOMEM;
	}
	idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
	if (idr_ret < 0) {
		up(&allocated_ptys_lock);
		if (idr_ret == -EAGAIN)
			return -ENOMEM;
		return -EIO;
	}
	if (index >= pty_limit) {
		idr_remove(&allocated_ptys, index);
		up(&allocated_ptys_lock);
		return -EIO;
	}
	up(&allocated_ptys_lock);

	retval = init_dev(ptm_driver, index, &tty);
	if (retval)
		goto out;

	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
	filp->private_data = tty;
	file_move(filp, &tty->tty_files);

	retval = -ENOMEM;
	if (devpts_pty_new(tty->link))
		goto out1;

	check_tty_count(tty, "tty_open");
	retval = ptm_driver->open(tty, filp);
	if (!retval)
		return 0;
out1:
	release_dev(filp);
out:
	down(&allocated_ptys_lock);
	idr_remove(&allocated_ptys, index);
	up(&allocated_ptys_lock);
	return retval;
}
#endif

static int tty_release(struct inode * inode, struct file * filp)
{
	lock_kernel();
	release_dev(filp);
	unlock_kernel();
	return 0;
}

/* No kernel lock held - fine */
static unsigned int tty_poll(struct file * filp, poll_table * wait)
{
	struct tty_struct * tty;
	struct tty_ldisc *ld;
	int ret = 0;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "tty_poll"))
		return 0;
		
	ld = tty_ldisc_ref_wait(tty);
	if (ld->poll)
		ret = (ld->poll)(tty, filp, wait);
	tty_ldisc_deref(ld);
	return ret;
}

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

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

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

static int tiocsti(struct tty_struct *tty, char __user *p)
{
	char ch, mbz = 0;
	struct tty_ldisc *ld;
	
	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (get_user(ch, p))
		return -EFAULT;
	ld = tty_ldisc_ref_wait(tty);
	ld->receive_buf(tty, &ch, &mbz, 1);
	tty_ldisc_deref(ld);
	return 0;
}

static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
{
	if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
		return -EFAULT;
	return 0;
}

static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
	struct winsize __user * arg)
{
	struct winsize tmp_ws;

	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
		return -EFAULT;
	if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
		return 0;
#ifdef CONFIG_VT
	if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
		unsigned int currcons = tty->index;
		int rc;

		acquire_console_sem();
		rc = vc_resize(currcons, tmp_ws.ws_col, tmp_ws.ws_row);
		release_console_sem();
		if (rc)
			return -ENXIO;
	}
#endif
	if (tty->pgrp > 0)
		kill_pg(tty->pgrp, SIGWINCH, 1);
	if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
		kill_pg(real_tty->pgrp, SIGWINCH, 1);
	tty->winsize = tmp_ws;
	real_tty->winsize = tmp_ws;
	return 0;
}

static int tioccons(struct file *file)
{
	if (file->f_op->write == redirected_tty_write) {
		struct file *f;
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		spin_lock(&redirect_lock);
		f = redirect;
		redirect = NULL;
		spin_unlock(&redirect_lock);
		if (f)
			fput(f);
		return 0;
	}
	spin_lock(&redirect_lock);
	if (redirect) {
		spin_unlock(&redirect_lock);
		return -EBUSY;
	}
	get_file(file);
	redirect = file;
	spin_unlock(&redirect_lock);
	return 0;
}


static int fionbio(struct file *file, int __user *p)
{
	int nonblock;

	if (get_user(nonblock, p))
		return -EFAULT;

	if (nonblock)
		file->f_flags |= O_NONBLOCK;
	else
		file->f_flags &= ~O_NONBLOCK;
	return 0;
}

static int tiocsctty(struct tty_struct *tty, int arg)
{
	task_t *p;

	if (current->signal->leader &&
	    (current->signal->session == tty->session))
		return 0;
	/*
	 * The process must be a session leader and
	 * not have a controlling tty already.
	 */
	if (!current->signal->leader || current->signal->tty)
		return -EPERM;
	if (tty->session > 0) {
		/*
		 * This tty is already the controlling
		 * tty for another session group!
		 */
		if ((arg == 1) && capable(CAP_SYS_ADMIN)) {
			/*
			 * Steal it away
			 */

			read_lock(&tasklist_lock);
			do_each_task_pid(tty->session, PIDTYPE_SID, p) {
				p->signal->tty = NULL;
			} while_each_task_pid(tty->session, PIDTYPE_SID, p);
			read_unlock(&tasklist_lock);
		} else
			return -EPERM;
	}
	task_lock(current);
	current->signal->tty = tty;
	task_unlock(current);
	current->signal->tty_old_pgrp = 0;
	tty->session = current->signal->session;
	tty->pgrp = process_group(current);
	return 0;
}

static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	 */
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	return put_user(real_tty->pgrp, p);
}

static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	pid_t pgrp;
	int retval = tty_check_change(real_tty);

	if (retval == -EIO)
		return -ENOTTY;
	if (retval)
		return retval;
	if (!current->signal->tty ||
	    (current->signal->tty != real_tty) ||
	    (real_tty->session != current->signal->session))
		return -ENOTTY;
	if (get_user(pgrp, p))
		return -EFAULT;
	if (pgrp < 0)