1 #include <linux/types.h>
2 #include <linux/major.h>
3 #include <linux/errno.h>
4 #include <linux/signal.h>
5 #include <linux/fcntl.h>
6 #include <linux/sched.h>
7 #include <linux/interrupt.h>
9 #include <linux/tty_driver.h>
10 #include <linux/tty_flip.h>
11 #include <linux/devpts_fs.h>
12 #include <linux/file.h>
13 #include <linux/console.h>
14 #include <linux/timer.h>
15 #include <linux/ctype.h>
18 #include <linux/string.h>
19 #include <linux/slab.h>
20 #include <linux/poll.h>
21 #include <linux/proc_fs.h>
22 #include <linux/init.h>
23 #include <linux/module.h>
24 #include <linux/device.h>
25 #include <linux/wait.h>
26 #include <linux/bitops.h>
27 #include <linux/delay.h>
28 #include <linux/seq_file.h>
30 #include <linux/uaccess.h>
31 #include <asm/system.h>
33 #include <linux/kbd_kern.h>
34 #include <linux/vt_kern.h>
35 #include <linux/selection.h>
37 #include <linux/smp_lock.h> /* For the moment */
39 #include <linux/kmod.h>
40 #include <linux/nsproxy.h>
43 * This guards the refcounted line discipline lists. The lock
44 * must be taken with irqs off because there are hangup path
45 * callers who will do ldisc lookups and cannot sleep.
48 static DEFINE_SPINLOCK(tty_ldisc_lock);
49 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
50 /* Line disc dispatch table */
51 static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
53 static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
56 atomic_inc(&ld->users);
60 static void put_ldisc(struct tty_ldisc *ld)
64 if (WARN_ON_ONCE(!ld))
68 * If this is the last user, free the ldisc, and
69 * release the ldisc ops.
71 * We really want an "atomic_dec_and_lock_irqsave()",
72 * but we don't have it, so this does it by hand.
74 local_irq_save(flags);
75 if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
76 struct tty_ldisc_ops *ldo = ld->ops;
79 module_put(ldo->owner);
80 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
85 local_irq_restore(flags);
89 * tty_register_ldisc - install a line discipline
91 * @new_ldisc: pointer to the ldisc object
93 * Installs a new line discipline into the kernel. The discipline
94 * is set up as unreferenced and then made available to the kernel
95 * from this point onwards.
98 * takes tty_ldisc_lock to guard against ldisc races
101 int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
106 if (disc < N_TTY || disc >= NR_LDISCS)
109 spin_lock_irqsave(&tty_ldisc_lock, flags);
110 tty_ldiscs[disc] = new_ldisc;
111 new_ldisc->num = disc;
112 new_ldisc->refcount = 0;
113 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
117 EXPORT_SYMBOL(tty_register_ldisc);
120 * tty_unregister_ldisc - unload a line discipline
121 * @disc: ldisc number
122 * @new_ldisc: pointer to the ldisc object
124 * Remove a line discipline from the kernel providing it is not
128 * takes tty_ldisc_lock to guard against ldisc races
131 int tty_unregister_ldisc(int disc)
136 if (disc < N_TTY || disc >= NR_LDISCS)
139 spin_lock_irqsave(&tty_ldisc_lock, flags);
140 if (tty_ldiscs[disc]->refcount)
143 tty_ldiscs[disc] = NULL;
144 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
148 EXPORT_SYMBOL(tty_unregister_ldisc);
150 static struct tty_ldisc_ops *get_ldops(int disc)
153 struct tty_ldisc_ops *ldops, *ret;
155 spin_lock_irqsave(&tty_ldisc_lock, flags);
156 ret = ERR_PTR(-EINVAL);
157 ldops = tty_ldiscs[disc];
159 ret = ERR_PTR(-EAGAIN);
160 if (try_module_get(ldops->owner)) {
165 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
169 static void put_ldops(struct tty_ldisc_ops *ldops)
173 spin_lock_irqsave(&tty_ldisc_lock, flags);
175 module_put(ldops->owner);
176 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
180 * tty_ldisc_get - take a reference to an ldisc
181 * @disc: ldisc number
183 * Takes a reference to a line discipline. Deals with refcounts and
184 * module locking counts. Returns NULL if the discipline is not available.
185 * Returns a pointer to the discipline and bumps the ref count if it is
189 * takes tty_ldisc_lock to guard against ldisc races
192 static struct tty_ldisc *tty_ldisc_get(int disc)
194 struct tty_ldisc *ld;
195 struct tty_ldisc_ops *ldops;
197 if (disc < N_TTY || disc >= NR_LDISCS)
198 return ERR_PTR(-EINVAL);
201 * Get the ldisc ops - we may need to request them to be loaded
202 * dynamically and try again.
204 ldops = get_ldops(disc);
206 request_module("tty-ldisc-%d", disc);
207 ldops = get_ldops(disc);
209 return ERR_CAST(ldops);
212 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
215 return ERR_PTR(-ENOMEM);
219 atomic_set(&ld->users, 1);
223 static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
225 return (*pos < NR_LDISCS) ? pos : NULL;
228 static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
231 return (*pos < NR_LDISCS) ? pos : NULL;
234 static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
238 static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
240 int i = *(loff_t *)v;
241 struct tty_ldisc_ops *ldops;
243 ldops = get_ldops(i);
246 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
251 static const struct seq_operations tty_ldiscs_seq_ops = {
252 .start = tty_ldiscs_seq_start,
253 .next = tty_ldiscs_seq_next,
254 .stop = tty_ldiscs_seq_stop,
255 .show = tty_ldiscs_seq_show,
258 static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
260 return seq_open(file, &tty_ldiscs_seq_ops);
263 const struct file_operations tty_ldiscs_proc_fops = {
264 .owner = THIS_MODULE,
265 .open = proc_tty_ldiscs_open,
268 .release = seq_release,
272 * tty_ldisc_assign - set ldisc on a tty
273 * @tty: tty to assign
274 * @ld: line discipline
276 * Install an instance of a line discipline into a tty structure. The
277 * ldisc must have a reference count above zero to ensure it remains.
278 * The tty instance refcount starts at zero.
281 * Caller must hold references
284 static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
290 * tty_ldisc_try - internal helper
293 * Make a single attempt to grab and bump the refcount on
294 * the tty ldisc. Return 0 on failure or 1 on success. This is
295 * used to implement both the waiting and non waiting versions
298 * Locking: takes tty_ldisc_lock
301 static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
304 struct tty_ldisc *ld;
306 spin_lock_irqsave(&tty_ldisc_lock, flags);
308 if (test_bit(TTY_LDISC, &tty->flags))
309 ld = get_ldisc(tty->ldisc);
310 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
315 * tty_ldisc_ref_wait - wait for the tty ldisc
318 * Dereference the line discipline for the terminal and take a
319 * reference to it. If the line discipline is in flux then
320 * wait patiently until it changes.
322 * Note: Must not be called from an IRQ/timer context. The caller
323 * must also be careful not to hold other locks that will deadlock
324 * against a discipline change, such as an existing ldisc reference
325 * (which we check for)
327 * Locking: call functions take tty_ldisc_lock
330 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
332 struct tty_ldisc *ld;
334 /* wait_event is a macro */
335 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
338 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
341 * tty_ldisc_ref - get the tty ldisc
344 * Dereference the line discipline for the terminal and take a
345 * reference to it. If the line discipline is in flux then
346 * return NULL. Can be called from IRQ and timer functions.
348 * Locking: called functions take tty_ldisc_lock
351 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
353 return tty_ldisc_try(tty);
355 EXPORT_SYMBOL_GPL(tty_ldisc_ref);
358 * tty_ldisc_deref - free a tty ldisc reference
359 * @ld: reference to free up
361 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
362 * be called in IRQ context.
364 * Locking: takes tty_ldisc_lock
367 void tty_ldisc_deref(struct tty_ldisc *ld)
371 EXPORT_SYMBOL_GPL(tty_ldisc_deref);
373 static inline void tty_ldisc_put(struct tty_ldisc *ld)
379 * tty_ldisc_enable - allow ldisc use
380 * @tty: terminal to activate ldisc on
382 * Set the TTY_LDISC flag when the line discipline can be called
383 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
384 * changing flag to indicate any ldisc change is now over.
386 * Note: nobody should set the TTY_LDISC bit except via this function.
387 * Clearing directly is allowed.
390 void tty_ldisc_enable(struct tty_struct *tty)
392 set_bit(TTY_LDISC, &tty->flags);
393 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
394 wake_up(&tty_ldisc_wait);
398 * tty_ldisc_flush - flush line discipline queue
401 * Flush the line discipline queue (if any) for this tty. If there
402 * is no line discipline active this is a no-op.
405 void tty_ldisc_flush(struct tty_struct *tty)
407 struct tty_ldisc *ld = tty_ldisc_ref(tty);
409 if (ld->ops->flush_buffer)
410 ld->ops->flush_buffer(tty);
413 tty_buffer_flush(tty);
415 EXPORT_SYMBOL_GPL(tty_ldisc_flush);
418 * tty_set_termios_ldisc - set ldisc field
419 * @tty: tty structure
420 * @num: line discipline number
422 * This is probably overkill for real world processors but
423 * they are not on hot paths so a little discipline won't do
426 * Locking: takes termios_mutex
429 static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
431 mutex_lock(&tty->termios_mutex);
432 tty->termios->c_line = num;
433 mutex_unlock(&tty->termios_mutex);
437 * tty_ldisc_open - open a line discipline
438 * @tty: tty we are opening the ldisc on
439 * @ld: discipline to open
441 * A helper opening method. Also a convenient debugging and check
445 static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
447 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
449 return ld->ops->open(tty);
454 * tty_ldisc_close - close a line discipline
455 * @tty: tty we are opening the ldisc on
456 * @ld: discipline to close
458 * A helper close method. Also a convenient debugging and check
462 static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
464 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
465 clear_bit(TTY_LDISC_OPEN, &tty->flags);
471 * tty_ldisc_restore - helper for tty ldisc change
472 * @tty: tty to recover
473 * @old: previous ldisc
475 * Restore the previous line discipline or N_TTY when a line discipline
476 * change fails due to an open error
479 static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
482 struct tty_ldisc *new_ldisc;
485 /* There is an outstanding reference here so this is safe */
486 old = tty_ldisc_get(old->ops->num);
487 WARN_ON(IS_ERR(old));
488 tty_ldisc_assign(tty, old);
489 tty_set_termios_ldisc(tty, old->ops->num);
490 if (tty_ldisc_open(tty, old) < 0) {
492 /* This driver is always present */
493 new_ldisc = tty_ldisc_get(N_TTY);
494 if (IS_ERR(new_ldisc))
496 tty_ldisc_assign(tty, new_ldisc);
497 tty_set_termios_ldisc(tty, N_TTY);
498 r = tty_ldisc_open(tty, new_ldisc);
500 panic("Couldn't open N_TTY ldisc for "
502 tty_name(tty, buf), r);
507 * tty_ldisc_halt - shut down the line discipline
510 * Shut down the line discipline and work queue for this tty device.
511 * The TTY_LDISC flag being cleared ensures no further references can
512 * be obtained while the delayed work queue halt ensures that no more
513 * data is fed to the ldisc.
515 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
516 * in order to make sure any currently executing ldisc work is also
520 static int tty_ldisc_halt(struct tty_struct *tty)
522 clear_bit(TTY_LDISC, &tty->flags);
523 return cancel_delayed_work_sync(&tty->buf.work);
527 * tty_set_ldisc - set line discipline
528 * @tty: the terminal to set
529 * @ldisc: the line discipline
531 * Set the discipline of a tty line. Must be called from a process
532 * context. The ldisc change logic has to protect itself against any
533 * overlapping ldisc change (including on the other end of pty pairs),
534 * the close of one side of a tty/pty pair, and eventually hangup.
536 * Locking: takes tty_ldisc_lock, termios_mutex
539 int tty_set_ldisc(struct tty_struct *tty, int ldisc)
542 struct tty_ldisc *o_ldisc, *new_ldisc;
543 int work, o_work = 0;
544 struct tty_struct *o_tty;
546 new_ldisc = tty_ldisc_get(ldisc);
547 if (IS_ERR(new_ldisc))
548 return PTR_ERR(new_ldisc);
552 * We need to look at the tty locking here for pty/tty pairs
553 * when both sides try to change in parallel.
556 o_tty = tty->link; /* o_tty is the pty side or NULL */
560 * Check the no-op case
563 if (tty->ldisc->ops->num == ldisc) {
565 tty_ldisc_put(new_ldisc);
570 * Problem: What do we do if this blocks ?
571 * We could deadlock here
574 tty_wait_until_sent(tty, 0);
577 mutex_lock(&tty->ldisc_mutex);
580 * We could be midstream of another ldisc change which has
581 * dropped the lock during processing. If so we need to wait.
584 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
585 mutex_unlock(&tty->ldisc_mutex);
586 wait_event(tty_ldisc_wait,
587 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
588 mutex_lock(&tty->ldisc_mutex);
593 set_bit(TTY_LDISC_CHANGING, &tty->flags);
596 * No more input please, we are switching. The new ldisc
597 * will update this value in the ldisc open function
600 tty->receive_room = 0;
602 o_ldisc = tty->ldisc;
606 * Make sure we don't change while someone holds a
607 * reference to the line discipline. The TTY_LDISC bit
608 * prevents anyone taking a reference once it is clear.
609 * We need the lock to avoid racing reference takers.
611 * We must clear the TTY_LDISC bit here to avoid a livelock
612 * with a userspace app continually trying to use the tty in
613 * parallel to the change and re-referencing the tty.
616 work = tty_ldisc_halt(tty);
618 o_work = tty_ldisc_halt(o_tty);
621 * Wait for ->hangup_work and ->buf.work handlers to terminate.
622 * We must drop the mutex here in case a hangup is also in process.
625 mutex_unlock(&tty->ldisc_mutex);
627 flush_scheduled_work();
629 mutex_lock(&tty->ldisc_mutex);
631 if (test_bit(TTY_HUPPED, &tty->flags)) {
632 /* We were raced by the hangup method. It will have stomped
633 the ldisc data and closed the ldisc down */
634 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
635 mutex_unlock(&tty->ldisc_mutex);
636 tty_ldisc_put(new_ldisc);
641 /* Shutdown the current discipline. */
642 tty_ldisc_close(tty, o_ldisc);
644 /* Now set up the new line discipline. */
645 tty_ldisc_assign(tty, new_ldisc);
646 tty_set_termios_ldisc(tty, ldisc);
648 retval = tty_ldisc_open(tty, new_ldisc);
650 /* Back to the old one or N_TTY if we can't */
651 tty_ldisc_put(new_ldisc);
652 tty_ldisc_restore(tty, o_ldisc);
655 /* At this point we hold a reference to the new ldisc and a
656 a reference to the old ldisc. If we ended up flipping back
657 to the existing ldisc we have two references to it */
659 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
660 tty->ops->set_ldisc(tty);
662 tty_ldisc_put(o_ldisc);
665 * Allow ldisc referencing to occur again
668 tty_ldisc_enable(tty);
670 tty_ldisc_enable(o_tty);
672 /* Restart the work queue in case no characters kick it off. Safe if
675 schedule_delayed_work(&tty->buf.work, 1);
677 schedule_delayed_work(&o_tty->buf.work, 1);
678 mutex_unlock(&tty->ldisc_mutex);
684 * tty_reset_termios - reset terminal state
687 * Restore a terminal to the driver default state.
690 static void tty_reset_termios(struct tty_struct *tty)
692 mutex_lock(&tty->termios_mutex);
693 *tty->termios = tty->driver->init_termios;
694 tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
695 tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
696 mutex_unlock(&tty->termios_mutex);
701 * tty_ldisc_reinit - reinitialise the tty ldisc
702 * @tty: tty to reinit
704 * Switch the tty back to N_TTY line discipline and leave the
708 static void tty_ldisc_reinit(struct tty_struct *tty)
710 struct tty_ldisc *ld;
712 tty_ldisc_close(tty, tty->ldisc);
713 tty_ldisc_put(tty->ldisc);
716 * Switch the line discipline back
718 ld = tty_ldisc_get(N_TTY);
720 tty_ldisc_assign(tty, ld);
721 tty_set_termios_ldisc(tty, N_TTY);
725 * tty_ldisc_hangup - hangup ldisc reset
726 * @tty: tty being hung up
728 * Some tty devices reset their termios when they receive a hangup
729 * event. In that situation we must also switch back to N_TTY properly
730 * before we reset the termios data.
732 * Locking: We can take the ldisc mutex as the rest of the code is
733 * careful to allow for this.
735 * In the pty pair case this occurs in the close() path of the
736 * tty itself so we must be careful about locking rules.
739 void tty_ldisc_hangup(struct tty_struct *tty)
741 struct tty_ldisc *ld;
744 * FIXME! What are the locking issues here? This may me overdoing
745 * things... This question is especially important now that we've
746 * removed the irqlock.
748 ld = tty_ldisc_ref(tty);
750 /* We may have no line discipline at this point */
751 if (ld->ops->flush_buffer)
752 ld->ops->flush_buffer(tty);
753 tty_driver_flush_buffer(tty);
754 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
755 ld->ops->write_wakeup)
756 ld->ops->write_wakeup(tty);
758 ld->ops->hangup(tty);
762 * FIXME: Once we trust the LDISC code better we can wait here for
763 * ldisc completion and fix the driver call race
765 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
766 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
768 * Shutdown the current line discipline, and reset it to
771 if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
772 /* Avoid racing set_ldisc or tty_ldisc_release */
773 mutex_lock(&tty->ldisc_mutex);
775 if (tty->ldisc) { /* Not yet closed */
776 /* Switch back to N_TTY */
777 tty_ldisc_reinit(tty);
778 /* At this point we have a closed ldisc and we want to
779 reopen it. We could defer this to the next open but
780 it means auditing a lot of other paths so this is
782 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
783 tty_ldisc_enable(tty);
785 mutex_unlock(&tty->ldisc_mutex);
786 tty_reset_termios(tty);
791 * tty_ldisc_setup - open line discipline
792 * @tty: tty being shut down
793 * @o_tty: pair tty for pty/tty pairs
795 * Called during the initial open of a tty/pty pair in order to set up the
796 * line disciplines and bind them to the tty. This has no locking issues
797 * as the device isn't yet active.
800 int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
802 struct tty_ldisc *ld = tty->ldisc;
805 retval = tty_ldisc_open(tty, ld);
810 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
812 tty_ldisc_close(tty, ld);
815 tty_ldisc_enable(o_tty);
817 tty_ldisc_enable(tty);
821 * tty_ldisc_release - release line discipline
822 * @tty: tty being shut down
823 * @o_tty: pair tty for pty/tty pairs
825 * Called during the final close of a tty/pty pair in order to shut down
826 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
827 * ldisc has not been opened.
830 void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
833 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
834 * kill any delayed work. As this is the final close it does not
835 * race with the set_ldisc code path.
839 flush_scheduled_work();
841 mutex_lock(&tty->ldisc_mutex);
843 * Now kill off the ldisc
845 tty_ldisc_close(tty, tty->ldisc);
846 tty_ldisc_put(tty->ldisc);
847 /* Force an oops if we mess this up */
850 /* Ensure the next open requests the N_TTY ldisc */
851 tty_set_termios_ldisc(tty, N_TTY);
852 mutex_unlock(&tty->ldisc_mutex);
854 /* This will need doing differently if we need to lock */
856 tty_ldisc_release(o_tty, NULL);
858 /* And the memory resources remaining (buffers, termios) will be
859 disposed of when the kref hits zero */
863 * tty_ldisc_init - ldisc setup for new tty
864 * @tty: tty being allocated
866 * Set up the line discipline objects for a newly allocated tty. Note that
867 * the tty structure is not completely set up when this call is made.
870 void tty_ldisc_init(struct tty_struct *tty)
872 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
874 panic("n_tty: init_tty");
875 tty_ldisc_assign(tty, ld);
878 void tty_ldisc_begin(void)
880 /* Setup the default TTY line discipline. */
881 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);