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

	 
	work = cancel_delayed_work(&tty->flip.work);
	/*
	 * Wait for ->hangup_work and ->flip.work handlers to terminate
	 */
	 
	flush_scheduled_work();
	/* Shutdown the current discipline. */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);

	/* Now set up the new line discipline. */
	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, ldisc);
	if (tty->ldisc.open)
		retval = (tty->ldisc.open)(tty);
	if (retval < 0) {
		tty_ldisc_put(ldisc);
		/* There is an outstanding reference here so this is safe */
		tty_ldisc_assign(tty, tty_ldisc_get(o_ldisc.num));
		tty_set_termios_ldisc(tty, tty->ldisc.num);
		if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
			tty_ldisc_put(o_ldisc.num);
			/* This driver is always present */
			tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
			tty_set_termios_ldisc(tty, N_TTY);
			if (tty->ldisc.open) {
				int r = tty->ldisc.open(tty);

				if (r < 0)
					panic("Couldn't open N_TTY ldisc for "
					      "%s --- error %d.",
					      tty_name(tty, buf), r);
			}
		}
	}
	/* At this point we hold a reference to the new ldisc and a
	   a reference to the old ldisc. If we ended up flipping back
	   to the existing ldisc we have two references to it */
	
	if (tty->ldisc.num != o_ldisc.num && tty->driver->set_ldisc)
		tty->driver->set_ldisc(tty);
		
	tty_ldisc_put(o_ldisc.num);
	
	/*
	 *	Allow ldisc referencing to occur as soon as the driver
	 *	ldisc callback completes.
	 */
	 
	tty_ldisc_enable(tty);
	
	/* Restart it in case no characters kick it off. Safe if
	   already running */
	if(work)
		schedule_delayed_work(&tty->flip.work, 1);
	return retval;
}

/*
 * This routine returns a tty driver structure, given a device number
 */
struct tty_driver *get_tty_driver(dev_t device, int *index)
{
	struct tty_driver *p;

	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		dev_t base = MKDEV(p->major, p->minor_start);
		if (device < base || device >= base + p->num)
			continue;
		*index = device - base;
		return p;
	}
	return NULL;
}

/*
 * If we try to write to, or set the state of, a terminal and we're
 * not in the foreground, send a SIGTTOU.  If the signal is blocked or
 * ignored, go ahead and perform the operation.  (POSIX 7.2)
 */
int tty_check_change(struct tty_struct * tty)
{
	if (current->signal->tty != tty)
		return 0;
	if (tty->pgrp <= 0) {
		printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
		return 0;
	}
	if (process_group(current) == tty->pgrp)
		return 0;
	if (is_ignored(SIGTTOU))
		return 0;
	if (is_orphaned_pgrp(process_group(current)))
		return -EIO;
	(void) kill_pg(process_group(current), SIGTTOU, 1);
	return -ERESTARTSYS;
}

EXPORT_SYMBOL(tty_check_change);

static ssize_t hung_up_tty_read(struct file * file, char __user * buf,
				size_t count, loff_t *ppos)
{
	return 0;
}

static ssize_t hung_up_tty_write(struct file * file, const char __user * buf,
				 size_t count, loff_t *ppos)
{
	return -EIO;
}

/* No kernel lock held - none needed ;) */
static unsigned int hung_up_tty_poll(struct file * filp, poll_table * wait)
{
	return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
}

static int hung_up_tty_ioctl(struct inode * inode, struct file * file,
			     unsigned int cmd, unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

#ifdef CONFIG_UNIX98_PTYS
static struct file_operations ptmx_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= ptmx_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};
#endif

static struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.ioctl		= hung_up_tty_ioctl,
	.release	= tty_release,
};

static spinlock_t redirect_lock = SPIN_LOCK_UNLOCKED;
static struct file *redirect;

/**
 *	tty_wakeup	-	request more data
 *	@tty: terminal
 *
 *	Internal and external helper for wakeups of tty. This function
 *	informs the line discipline if present that the driver is ready
 *	to receive more output data.
 */
 
void tty_wakeup(struct tty_struct *tty)
{
	struct tty_ldisc *ld;
	
	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
		ld = tty_ldisc_ref(tty);
		if(ld) {
			if(ld->write_wakeup)
				ld->write_wakeup(tty);
			tty_ldisc_deref(ld);
		}
	}
	wake_up_interruptible(&tty->write_wait);
}

EXPORT_SYMBOL_GPL(tty_wakeup);

/**
 *	tty_ldisc_flush	-	flush line discipline queue
 *	@tty: tty
 *
 *	Flush the line discipline queue (if any) for this tty. If there
 *	is no line discipline active this is a no-op.
 */
 
void tty_ldisc_flush(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_ref(tty);
	if(ld) {
		if(ld->flush_buffer)
			ld->flush_buffer(tty);
		tty_ldisc_deref(ld);
	}
}

EXPORT_SYMBOL_GPL(tty_ldisc_flush);
	
/*
 * This can be called by the "eventd" kernel thread.  That is process synchronous,
 * but doesn't hold any locks, so we need to make sure we have the appropriate
 * locks for what we're doing..
 */
void do_tty_hangup(void *data)
{
	struct tty_struct *tty = (struct tty_struct *) data;
	struct file * cons_filp = NULL;
	struct file *filp, *f = NULL;
	struct task_struct *p;
	struct tty_ldisc *ld;
	int    closecount = 0, n;

	if (!tty)
		return;

	/* inuse_filps is protected by the single kernel lock */
	lock_kernel();

	spin_lock(&redirect_lock);
	if (redirect && redirect->private_data == tty) {
		f = redirect;
		redirect = NULL;
	}
	spin_unlock(&redirect_lock);
	
	check_tty_count(tty, "do_tty_hangup");
	file_list_lock();
	/* This breaks for file handles being sent over AF_UNIX sockets ? */
	list_for_each_entry(filp, &tty->tty_files, f_list) {
		if (filp->f_op->write == redirected_tty_write)
			cons_filp = filp;
		if (filp->f_op->write != tty_write)
			continue;
		closecount++;
		tty_fasync(-1, filp, 0);	/* can't block */
		filp->f_op = &hung_up_tty_fops;
	}
	file_list_unlock();
	
	/* FIXME! What are the locking issues here? This may me overdoing things..
	 * this question is especially important now that we've removed the irqlock. */

	ld = tty_ldisc_ref(tty);
	if(ld != NULL)	/* We may have no line discipline at this point */
	{
		if (ld->flush_buffer)
			ld->flush_buffer(tty);
		if (tty->driver->flush_buffer)
			tty->driver->flush_buffer(tty);
		if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
		    ld->write_wakeup)
			ld->write_wakeup(tty);
		if (ld->hangup)
			ld->hangup(tty);
	}

	/* FIXME: Once we trust the LDISC code better we can wait here for
	   ldisc completion and fix the driver call race */
	   
	wake_up_interruptible(&tty->write_wait);
	wake_up_interruptible(&tty->read_wait);

	/*
	 * Shutdown the current line discipline, and reset it to
	 * N_TTY.
	 */
	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
	{
		down(&tty->termios_sem);
		*tty->termios = tty->driver->init_termios;
		up(&tty->termios_sem);
	}
	
	/* Defer ldisc switch */
	/* tty_deferred_ldisc_switch(N_TTY);
	
	  This should get done automatically when the port closes and
	  tty_release is called */
	
	read_lock(&tasklist_lock);
	if (tty->session > 0) {
		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
			if (p->signal->tty == tty)
				p->signal->tty = NULL;
			if (!p->signal->leader)
				continue;
			send_group_sig_info(SIGHUP, SEND_SIG_PRIV, p);
			send_group_sig_info(SIGCONT, SEND_SIG_PRIV, p);
			if (tty->pgrp > 0)
				p->signal->tty_old_pgrp = tty->pgrp;
		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
	}
	read_unlock(&tasklist_lock);

	tty->flags = 0;
	tty->session = 0;
	tty->pgrp = -1;
	tty->ctrl_status = 0;
	/*
	 *	If one of the devices matches a console pointer, we
	 *	cannot just call hangup() because that will cause
	 *	tty->count and state->count to go out of sync.
	 *	So we just call close() the right number of times.
	 */
	if (cons_filp) {
		if (tty->driver->close)
			for (n = 0; n < closecount; n++)
				tty->driver->close(tty, cons_filp);
	} else if (tty->driver->hangup)
		(tty->driver->hangup)(tty);
		
	/* We don't want to have driver/ldisc interactions beyond
	   the ones we did here. The driver layer expects no
	   calls after ->hangup() from the ldisc side. However we
	   can't yet guarantee all that */

	set_bit(TTY_HUPPED, &tty->flags);
	if (ld) {
		tty_ldisc_enable(tty);
		tty_ldisc_deref(ld);
	}
	unlock_kernel();
	if (f)
		fput(f);
}

void tty_hangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];
	
	printk(KERN_DEBUG "%s hangup...\n", tty_name(tty, buf));
#endif
	schedule_work(&tty->hangup_work);
}

EXPORT_SYMBOL(tty_hangup);

void tty_vhangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];

	printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
#endif
	do_tty_hangup((void *) tty);
}
EXPORT_SYMBOL(tty_vhangup);

int tty_hung_up_p(struct file * filp)
{
	return (filp->f_op == &hung_up_tty_fops);
}

EXPORT_SYMBOL(tty_hung_up_p);

/*
 * This function is typically called only by the session leader, when
 * it wants to disassociate itself from its controlling tty.
 *
 * It performs the following functions:
 * 	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
 * 	(2)  Clears the tty from being controlling the session
 * 	(3)  Clears the controlling tty for all processes in the
 * 		session group.
 *
 * The argument on_exit is set to 1 if called when a process is
 * exiting; it is 0 if called by the ioctl TIOCNOTTY.
 */
void disassociate_ctty(int on_exit)
{
	struct tty_struct *tty;
	struct task_struct *p;
	int tty_pgrp = -1;

	lock_kernel();

	tty = current->signal->tty;
	if (tty) {
		tty_pgrp = tty->pgrp;
		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
			tty_vhangup(tty);
	} else {
		if (current->signal->tty_old_pgrp) {
			kill_pg(current->signal->tty_old_pgrp, SIGHUP, on_exit);
			kill_pg(current->signal->tty_old_pgrp, SIGCONT, on_exit);
		}
		unlock_kernel();	
		return;
	}
	if (tty_pgrp > 0) {
		kill_pg(tty_pgrp, SIGHUP, on_exit);
		if (!on_exit)
			kill_pg(tty_pgrp, SIGCONT, on_exit);
	}

	current->signal->tty_old_pgrp = 0;
	tty->session = 0;
	tty->pgrp = -1;

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

void stop_tty(struct tty_struct *tty)
{
	if (tty->stopped)
		return;
	tty->stopped = 1;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_START;
		tty->ctrl_status |= TIOCPKT_STOP;
		wake_up_interruptible(&tty->link->read_wait);
	}
	if (tty->driver->stop)
		(tty->driver->stop)(tty);
}

EXPORT_SYMBOL(stop_tty);

void start_tty(struct tty_struct *tty)
{
	if (!tty->stopped || tty->flow_stopped)
		return;
	tty->stopped = 0;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_STOP;
		tty->ctrl_status |= TIOCPKT_START;
		wake_up_interruptible(&tty->link->read_wait);
	}
	if (tty->driver->start)
		(tty->driver->start)(tty);

	/* If we have a running line discipline it may need kicking */
	tty_wakeup(tty);
	wake_up_interruptible(&tty->write_wait);
}

EXPORT_SYMBOL(start_tty);

static ssize_t tty_read(struct file * file, char __user * buf, size_t count, 
			loff_t *ppos)
{
	int i;
	struct tty_struct * tty;
	struct inode *inode;
	struct tty_ldisc *ld;

	tty = (struct tty_struct *)file->private_data;
	inode = file->f_dentry->d_inode;
	if (tty_paranoia_check(tty, inode, "tty_read"))
		return -EIO;
	if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
		return -EIO;

	/* We want to wait for the line discipline to sort out in this
	   situation */
	ld = tty_ldisc_ref_wait(tty);
	lock_kernel();
	if (ld->read)
		i = (ld->read)(tty,file,buf,count);
	else
		i = -EIO;
	tty_ldisc_deref(ld);
	unlock_kernel();
	if (i > 0)
		inode->i_atime = CURRENT_TIME;
	return i;
}

/*
 * Split writes up in sane blocksizes to avoid
 * denial-of-service type attacks
 */
static inline ssize_t do_tty_write(
	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char __user *, size_t),
	struct tty_struct *tty,
	struct file *file,
	const unsigned char __user *buf,
	size_t count)
{
	ssize_t ret = 0, written = 0;
	
	if (down_interruptible(&tty->atomic_write)) {
		return -ERESTARTSYS;
	}
	if ( test_bit(TTY_NO_WRITE_SPLIT, &tty->flags) ) {
		lock_kernel();
		written = write(tty, file, buf, count);
		unlock_kernel();
	} else {
		for (;;) {
			unsigned long size = max((unsigned long)PAGE_SIZE*2, 16384UL);
			if (size > count)
				size = count;
			lock_kernel();
			ret = write(tty, file, buf, size);
			unlock_kernel();