blob: aafdbaebc16a8697df6f16efbaadbce255e05d86 [file] [log] [blame]
Alan Cox01e1abb2008-07-22 11:16:55 +01001#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>
8#include <linux/tty.h>
9#include <linux/tty_driver.h>
10#include <linux/tty_flip.h>
11#include <linux/devpts_fs.h>
12#include <linux/file.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010013#include <linux/console.h>
14#include <linux/timer.h>
15#include <linux/ctype.h>
16#include <linux/kd.h>
17#include <linux/mm.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>
Alan Cox01e1abb2008-07-22 11:16:55 +010024#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>
29
30#include <linux/uaccess.h>
31#include <asm/system.h>
32
33#include <linux/kbd_kern.h>
34#include <linux/vt_kern.h>
35#include <linux/selection.h>
36
37#include <linux/kmod.h>
38#include <linux/nsproxy.h>
39
40/*
41 * This guards the refcounted line discipline lists. The lock
42 * must be taken with irqs off because there are hangup path
43 * callers who will do ldisc lookups and cannot sleep.
44 */
45
46static DEFINE_SPINLOCK(tty_ldisc_lock);
47static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
48/* Line disc dispatch table */
49static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
50
Linus Torvalds65b77042009-08-03 11:11:19 -070051static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
52{
53 if (ld)
54 atomic_inc(&ld->users);
55 return ld;
56}
57
Linus Torvaldscbe93522009-08-03 14:54:56 -070058static void put_ldisc(struct tty_ldisc *ld)
Linus Torvalds65b77042009-08-03 11:11:19 -070059{
Linus Torvaldscbe93522009-08-03 14:54:56 -070060 unsigned long flags;
61
Linus Torvalds65b77042009-08-03 11:11:19 -070062 if (WARN_ON_ONCE(!ld))
63 return;
64
65 /*
66 * If this is the last user, free the ldisc, and
67 * release the ldisc ops.
Linus Torvaldscbe93522009-08-03 14:54:56 -070068 *
69 * We really want an "atomic_dec_and_lock_irqsave()",
70 * but we don't have it, so this does it by hand.
Linus Torvalds65b77042009-08-03 11:11:19 -070071 */
Linus Torvaldscbe93522009-08-03 14:54:56 -070072 local_irq_save(flags);
73 if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
Linus Torvalds65b77042009-08-03 11:11:19 -070074 struct tty_ldisc_ops *ldo = ld->ops;
75
Linus Torvalds65b77042009-08-03 11:11:19 -070076 ldo->refcount--;
77 module_put(ldo->owner);
78 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldscbe93522009-08-03 14:54:56 -070079
80 kfree(ld);
81 return;
Linus Torvalds65b77042009-08-03 11:11:19 -070082 }
Linus Torvaldscbe93522009-08-03 14:54:56 -070083 local_irq_restore(flags);
Linus Torvalds65b77042009-08-03 11:11:19 -070084}
85
Alan Cox01e1abb2008-07-22 11:16:55 +010086/**
87 * tty_register_ldisc - install a line discipline
88 * @disc: ldisc number
89 * @new_ldisc: pointer to the ldisc object
90 *
91 * Installs a new line discipline into the kernel. The discipline
92 * is set up as unreferenced and then made available to the kernel
93 * from this point onwards.
94 *
95 * Locking:
96 * takes tty_ldisc_lock to guard against ldisc races
97 */
98
99int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
100{
101 unsigned long flags;
102 int ret = 0;
103
104 if (disc < N_TTY || disc >= NR_LDISCS)
105 return -EINVAL;
106
107 spin_lock_irqsave(&tty_ldisc_lock, flags);
108 tty_ldiscs[disc] = new_ldisc;
109 new_ldisc->num = disc;
110 new_ldisc->refcount = 0;
111 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
112
113 return ret;
114}
115EXPORT_SYMBOL(tty_register_ldisc);
116
117/**
118 * tty_unregister_ldisc - unload a line discipline
119 * @disc: ldisc number
120 * @new_ldisc: pointer to the ldisc object
121 *
122 * Remove a line discipline from the kernel providing it is not
123 * currently in use.
124 *
125 * Locking:
126 * takes tty_ldisc_lock to guard against ldisc races
127 */
128
129int tty_unregister_ldisc(int disc)
130{
131 unsigned long flags;
132 int ret = 0;
133
134 if (disc < N_TTY || disc >= NR_LDISCS)
135 return -EINVAL;
136
137 spin_lock_irqsave(&tty_ldisc_lock, flags);
138 if (tty_ldiscs[disc]->refcount)
139 ret = -EBUSY;
140 else
141 tty_ldiscs[disc] = NULL;
142 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
143
144 return ret;
145}
146EXPORT_SYMBOL(tty_unregister_ldisc);
147
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700148static struct tty_ldisc_ops *get_ldops(int disc)
149{
150 unsigned long flags;
151 struct tty_ldisc_ops *ldops, *ret;
152
153 spin_lock_irqsave(&tty_ldisc_lock, flags);
154 ret = ERR_PTR(-EINVAL);
155 ldops = tty_ldiscs[disc];
156 if (ldops) {
157 ret = ERR_PTR(-EAGAIN);
158 if (try_module_get(ldops->owner)) {
159 ldops->refcount++;
160 ret = ldops;
161 }
162 }
163 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
164 return ret;
165}
166
167static void put_ldops(struct tty_ldisc_ops *ldops)
168{
169 unsigned long flags;
170
171 spin_lock_irqsave(&tty_ldisc_lock, flags);
172 ldops->refcount--;
173 module_put(ldops->owner);
174 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
175}
Alan Cox01e1abb2008-07-22 11:16:55 +0100176
177/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100178 * tty_ldisc_get - take a reference to an ldisc
179 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100180 *
181 * Takes a reference to a line discipline. Deals with refcounts and
182 * module locking counts. Returns NULL if the discipline is not available.
183 * Returns a pointer to the discipline and bumps the ref count if it is
184 * available
185 *
186 * Locking:
187 * takes tty_ldisc_lock to guard against ldisc races
188 */
189
Alan Coxc65c9bc2009-06-11 12:50:12 +0100190static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100191{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100192 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700193 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100194
195 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100196 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700197
198 /*
199 * Get the ldisc ops - we may need to request them to be loaded
200 * dynamically and try again.
201 */
202 ldops = get_ldops(disc);
203 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100204 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700205 ldops = get_ldops(disc);
206 if (IS_ERR(ldops))
207 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100208 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700209
210 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
211 if (ld == NULL) {
212 put_ldops(ldops);
213 return ERR_PTR(-ENOMEM);
214 }
215
216 ld->ops = ldops;
217 atomic_set(&ld->users, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100218 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100219}
220
Alan Cox852e99d2009-06-11 12:51:41 +0100221static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100222{
223 return (*pos < NR_LDISCS) ? pos : NULL;
224}
225
Alan Cox852e99d2009-06-11 12:51:41 +0100226static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100227{
228 (*pos)++;
229 return (*pos < NR_LDISCS) ? pos : NULL;
230}
231
232static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
233{
234}
235
236static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
237{
238 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700239 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100240
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700241 ldops = get_ldops(i);
242 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100243 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700244 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
245 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100246 return 0;
247}
248
249static const struct seq_operations tty_ldiscs_seq_ops = {
250 .start = tty_ldiscs_seq_start,
251 .next = tty_ldiscs_seq_next,
252 .stop = tty_ldiscs_seq_stop,
253 .show = tty_ldiscs_seq_show,
254};
255
256static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
257{
258 return seq_open(file, &tty_ldiscs_seq_ops);
259}
260
261const struct file_operations tty_ldiscs_proc_fops = {
262 .owner = THIS_MODULE,
263 .open = proc_tty_ldiscs_open,
264 .read = seq_read,
265 .llseek = seq_lseek,
266 .release = seq_release,
267};
268
269/**
270 * tty_ldisc_assign - set ldisc on a tty
271 * @tty: tty to assign
272 * @ld: line discipline
273 *
274 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100275 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100276 * The tty instance refcount starts at zero.
277 *
278 * Locking:
279 * Caller must hold references
280 */
281
282static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
283{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100284 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100285}
286
287/**
288 * tty_ldisc_try - internal helper
289 * @tty: the tty
290 *
291 * Make a single attempt to grab and bump the refcount on
292 * the tty ldisc. Return 0 on failure or 1 on success. This is
293 * used to implement both the waiting and non waiting versions
294 * of tty_ldisc_ref
295 *
296 * Locking: takes tty_ldisc_lock
297 */
298
Linus Torvalds65b77042009-08-03 11:11:19 -0700299static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100300{
301 unsigned long flags;
302 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100303
304 spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700305 ld = NULL;
306 if (test_bit(TTY_LDISC, &tty->flags))
307 ld = get_ldisc(tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100308 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700309 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100310}
311
312/**
313 * tty_ldisc_ref_wait - wait for the tty ldisc
314 * @tty: tty device
315 *
316 * Dereference the line discipline for the terminal and take a
317 * reference to it. If the line discipline is in flux then
318 * wait patiently until it changes.
319 *
320 * Note: Must not be called from an IRQ/timer context. The caller
321 * must also be careful not to hold other locks that will deadlock
322 * against a discipline change, such as an existing ldisc reference
323 * (which we check for)
324 *
325 * Locking: call functions take tty_ldisc_lock
326 */
327
328struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
329{
Linus Torvalds65b77042009-08-03 11:11:19 -0700330 struct tty_ldisc *ld;
331
Alan Cox01e1abb2008-07-22 11:16:55 +0100332 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700333 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
334 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100335}
Alan Cox01e1abb2008-07-22 11:16:55 +0100336EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
337
338/**
339 * tty_ldisc_ref - get the tty ldisc
340 * @tty: tty device
341 *
342 * Dereference the line discipline for the terminal and take a
343 * reference to it. If the line discipline is in flux then
344 * return NULL. Can be called from IRQ and timer functions.
345 *
346 * Locking: called functions take tty_ldisc_lock
347 */
348
349struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
350{
Linus Torvalds65b77042009-08-03 11:11:19 -0700351 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100352}
Alan Cox01e1abb2008-07-22 11:16:55 +0100353EXPORT_SYMBOL_GPL(tty_ldisc_ref);
354
355/**
356 * tty_ldisc_deref - free a tty ldisc reference
357 * @ld: reference to free up
358 *
359 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
360 * be called in IRQ context.
361 *
362 * Locking: takes tty_ldisc_lock
363 */
364
365void tty_ldisc_deref(struct tty_ldisc *ld)
366{
Linus Torvalds65b77042009-08-03 11:11:19 -0700367 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100368}
Alan Cox01e1abb2008-07-22 11:16:55 +0100369EXPORT_SYMBOL_GPL(tty_ldisc_deref);
370
Linus Torvalds65b77042009-08-03 11:11:19 -0700371static inline void tty_ldisc_put(struct tty_ldisc *ld)
372{
373 put_ldisc(ld);
374}
375
Alan Cox01e1abb2008-07-22 11:16:55 +0100376/**
377 * tty_ldisc_enable - allow ldisc use
378 * @tty: terminal to activate ldisc on
379 *
380 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000381 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
382 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100383 *
Alan Coxc9b39762009-01-02 13:44:56 +0000384 * Note: nobody should set the TTY_LDISC bit except via this function.
385 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100386 */
387
388void tty_ldisc_enable(struct tty_struct *tty)
389{
390 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000391 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100392 wake_up(&tty_ldisc_wait);
393}
394
395/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100396 * tty_ldisc_flush - flush line discipline queue
397 * @tty: tty
398 *
399 * Flush the line discipline queue (if any) for this tty. If there
400 * is no line discipline active this is a no-op.
401 */
402
403void tty_ldisc_flush(struct tty_struct *tty)
404{
405 struct tty_ldisc *ld = tty_ldisc_ref(tty);
406 if (ld) {
407 if (ld->ops->flush_buffer)
408 ld->ops->flush_buffer(tty);
409 tty_ldisc_deref(ld);
410 }
411 tty_buffer_flush(tty);
412}
Alan Coxf2c4c652009-06-11 12:50:58 +0100413EXPORT_SYMBOL_GPL(tty_ldisc_flush);
414
415/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100416 * tty_set_termios_ldisc - set ldisc field
417 * @tty: tty structure
418 * @num: line discipline number
419 *
420 * This is probably overkill for real world processors but
421 * they are not on hot paths so a little discipline won't do
422 * any harm.
423 *
424 * Locking: takes termios_mutex
425 */
426
427static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
428{
429 mutex_lock(&tty->termios_mutex);
430 tty->termios->c_line = num;
431 mutex_unlock(&tty->termios_mutex);
432}
433
Alan Coxc65c9bc2009-06-11 12:50:12 +0100434/**
435 * tty_ldisc_open - open a line discipline
436 * @tty: tty we are opening the ldisc on
437 * @ld: discipline to open
438 *
439 * A helper opening method. Also a convenient debugging and check
440 * point.
441 */
442
443static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
444{
445 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
446 if (ld->ops->open)
447 return ld->ops->open(tty);
448 return 0;
449}
450
451/**
452 * tty_ldisc_close - close a line discipline
453 * @tty: tty we are opening the ldisc on
454 * @ld: discipline to close
455 *
456 * A helper close method. Also a convenient debugging and check
457 * point.
458 */
459
460static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
461{
462 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
463 clear_bit(TTY_LDISC_OPEN, &tty->flags);
464 if (ld->ops->close)
465 ld->ops->close(tty);
466}
Alan Cox01e1abb2008-07-22 11:16:55 +0100467
468/**
469 * tty_ldisc_restore - helper for tty ldisc change
470 * @tty: tty to recover
471 * @old: previous ldisc
472 *
473 * Restore the previous line discipline or N_TTY when a line discipline
474 * change fails due to an open error
475 */
476
477static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
478{
479 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100480 struct tty_ldisc *new_ldisc;
481 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100482
483 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100484 old = tty_ldisc_get(old->ops->num);
485 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100486 tty_ldisc_assign(tty, old);
487 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100488 if (tty_ldisc_open(tty, old) < 0) {
489 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100490 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100491 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100492 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100493 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100494 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100495 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100496 r = tty_ldisc_open(tty, new_ldisc);
497 if (r < 0)
498 panic("Couldn't open N_TTY ldisc for "
499 "%s --- error %d.",
500 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100501 }
502}
503
504/**
Alan Coxc65c9bc2009-06-11 12:50:12 +0100505 * tty_ldisc_halt - shut down the line discipline
Alan Coxe8b70e72009-06-11 12:48:02 +0100506 * @tty: tty device
507 *
508 * Shut down the line discipline and work queue for this tty device.
509 * The TTY_LDISC flag being cleared ensures no further references can
510 * be obtained while the delayed work queue halt ensures that no more
511 * data is fed to the ldisc.
512 *
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700513 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
514 * in order to make sure any currently executing ldisc work is also
515 * flushed.
Alan Coxe8b70e72009-06-11 12:48:02 +0100516 */
517
Alan Coxc65c9bc2009-06-11 12:50:12 +0100518static int tty_ldisc_halt(struct tty_struct *tty)
Alan Coxe8b70e72009-06-11 12:48:02 +0100519{
520 clear_bit(TTY_LDISC, &tty->flags);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100521 return cancel_delayed_work(&tty->buf.work);
Alan Coxe8b70e72009-06-11 12:48:02 +0100522}
523
524/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100525 * tty_set_ldisc - set line discipline
526 * @tty: the terminal to set
527 * @ldisc: the line discipline
528 *
529 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100530 * context. The ldisc change logic has to protect itself against any
531 * overlapping ldisc change (including on the other end of pty pairs),
532 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100533 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100534 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100535 */
536
537int tty_set_ldisc(struct tty_struct *tty, int ldisc)
538{
539 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100540 struct tty_ldisc *o_ldisc, *new_ldisc;
541 int work, o_work = 0;
Alan Cox01e1abb2008-07-22 11:16:55 +0100542 struct tty_struct *o_tty;
543
Alan Coxc65c9bc2009-06-11 12:50:12 +0100544 new_ldisc = tty_ldisc_get(ldisc);
545 if (IS_ERR(new_ldisc))
546 return PTR_ERR(new_ldisc);
547
548 /*
549 * We need to look at the tty locking here for pty/tty pairs
550 * when both sides try to change in parallel.
551 */
552
553 o_tty = tty->link; /* o_tty is the pty side or NULL */
554
555
556 /*
557 * Check the no-op case
558 */
559
560 if (tty->ldisc->ops->num == ldisc) {
561 tty_ldisc_put(new_ldisc);
562 return 0;
563 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100564
565 /*
566 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100567 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100568 */
569
570 tty_wait_until_sent(tty, 0);
571
Alan Coxc65c9bc2009-06-11 12:50:12 +0100572 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100573
574 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100575 * We could be midstream of another ldisc change which has
576 * dropped the lock during processing. If so we need to wait.
577 */
578
579 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
580 mutex_unlock(&tty->ldisc_mutex);
581 wait_event(tty_ldisc_wait,
582 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
583 mutex_lock(&tty->ldisc_mutex);
584 }
585 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100586
Alan Coxc65c9bc2009-06-11 12:50:12 +0100587 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100588 * No more input please, we are switching. The new ldisc
589 * will update this value in the ldisc open function
590 */
591
592 tty->receive_room = 0;
593
594 o_ldisc = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100595 /*
596 * Make sure we don't change while someone holds a
597 * reference to the line discipline. The TTY_LDISC bit
598 * prevents anyone taking a reference once it is clear.
599 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000600 *
601 * We must clear the TTY_LDISC bit here to avoid a livelock
602 * with a userspace app continually trying to use the tty in
603 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100604 */
605
Alan Coxc65c9bc2009-06-11 12:50:12 +0100606 work = tty_ldisc_halt(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100607 if (o_tty)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100608 o_work = tty_ldisc_halt(o_tty);
609
Alan Cox01e1abb2008-07-22 11:16:55 +0100610 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100611 * Wait for ->hangup_work and ->buf.work handlers to terminate.
612 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100613 */
614
Alan Coxc65c9bc2009-06-11 12:50:12 +0100615 mutex_unlock(&tty->ldisc_mutex);
616
Alan Cox01e1abb2008-07-22 11:16:55 +0100617 flush_scheduled_work();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100618
Alan Coxc65c9bc2009-06-11 12:50:12 +0100619 mutex_lock(&tty->ldisc_mutex);
620 if (test_bit(TTY_HUPPED, &tty->flags)) {
621 /* We were raced by the hangup method. It will have stomped
622 the ldisc data and closed the ldisc down */
623 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
624 mutex_unlock(&tty->ldisc_mutex);
625 tty_ldisc_put(new_ldisc);
626 return -EIO;
627 }
628
Alan Cox01e1abb2008-07-22 11:16:55 +0100629 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100630 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100631
632 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100633 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100634 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100635
636 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100637 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100638 /* Back to the old one or N_TTY if we can't */
639 tty_ldisc_put(new_ldisc);
640 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100641 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100642
Alan Cox01e1abb2008-07-22 11:16:55 +0100643 /* At this point we hold a reference to the new ldisc and a
644 a reference to the old ldisc. If we ended up flipping back
645 to the existing ldisc we have two references to it */
646
Alan Coxc65c9bc2009-06-11 12:50:12 +0100647 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100648 tty->ops->set_ldisc(tty);
649
Alan Coxc65c9bc2009-06-11 12:50:12 +0100650 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100651
652 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100653 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100654 */
655
656 tty_ldisc_enable(tty);
657 if (o_tty)
658 tty_ldisc_enable(o_tty);
659
Alan Coxc65c9bc2009-06-11 12:50:12 +0100660 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100661 already running */
662 if (work)
663 schedule_delayed_work(&tty->buf.work, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100664 if (o_work)
665 schedule_delayed_work(&o_tty->buf.work, 1);
666 mutex_unlock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100667 return retval;
668}
669
Alan Coxc65c9bc2009-06-11 12:50:12 +0100670/**
671 * tty_reset_termios - reset terminal state
672 * @tty: tty to reset
673 *
674 * Restore a terminal to the driver default state.
675 */
676
677static void tty_reset_termios(struct tty_struct *tty)
678{
679 mutex_lock(&tty->termios_mutex);
680 *tty->termios = tty->driver->init_termios;
681 tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
682 tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
683 mutex_unlock(&tty->termios_mutex);
684}
685
686
687/**
688 * tty_ldisc_reinit - reinitialise the tty ldisc
689 * @tty: tty to reinit
690 *
691 * Switch the tty back to N_TTY line discipline and leave the
692 * ldisc state closed
693 */
694
695static void tty_ldisc_reinit(struct tty_struct *tty)
696{
697 struct tty_ldisc *ld;
698
699 tty_ldisc_close(tty, tty->ldisc);
700 tty_ldisc_put(tty->ldisc);
701 tty->ldisc = NULL;
702 /*
703 * Switch the line discipline back
704 */
705 ld = tty_ldisc_get(N_TTY);
706 BUG_ON(IS_ERR(ld));
707 tty_ldisc_assign(tty, ld);
708 tty_set_termios_ldisc(tty, N_TTY);
709}
710
711/**
712 * tty_ldisc_hangup - hangup ldisc reset
713 * @tty: tty being hung up
714 *
715 * Some tty devices reset their termios when they receive a hangup
716 * event. In that situation we must also switch back to N_TTY properly
717 * before we reset the termios data.
718 *
719 * Locking: We can take the ldisc mutex as the rest of the code is
720 * careful to allow for this.
721 *
722 * In the pty pair case this occurs in the close() path of the
723 * tty itself so we must be careful about locking rules.
724 */
725
726void tty_ldisc_hangup(struct tty_struct *tty)
727{
728 struct tty_ldisc *ld;
729
730 /*
731 * FIXME! What are the locking issues here? This may me overdoing
732 * things... This question is especially important now that we've
733 * removed the irqlock.
734 */
735 ld = tty_ldisc_ref(tty);
736 if (ld != NULL) {
737 /* We may have no line discipline at this point */
738 if (ld->ops->flush_buffer)
739 ld->ops->flush_buffer(tty);
740 tty_driver_flush_buffer(tty);
741 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
742 ld->ops->write_wakeup)
743 ld->ops->write_wakeup(tty);
744 if (ld->ops->hangup)
745 ld->ops->hangup(tty);
746 tty_ldisc_deref(ld);
747 }
748 /*
749 * FIXME: Once we trust the LDISC code better we can wait here for
750 * ldisc completion and fix the driver call race
751 */
752 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
753 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
754 /*
755 * Shutdown the current line discipline, and reset it to
756 * N_TTY.
757 */
758 if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700759 /* Make sure the old ldisc is quiescent */
760 tty_ldisc_halt(tty);
761 flush_scheduled_work();
762
Alan Coxc8d50042009-07-16 16:05:08 +0100763 /* Avoid racing set_ldisc or tty_ldisc_release */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100764 mutex_lock(&tty->ldisc_mutex);
Alan Coxc8d50042009-07-16 16:05:08 +0100765 if (tty->ldisc) { /* Not yet closed */
766 /* Switch back to N_TTY */
Alan Coxc8d50042009-07-16 16:05:08 +0100767 tty_ldisc_reinit(tty);
768 /* At this point we have a closed ldisc and we want to
769 reopen it. We could defer this to the next open but
770 it means auditing a lot of other paths so this is
771 a FIXME */
772 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
773 tty_ldisc_enable(tty);
774 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100775 mutex_unlock(&tty->ldisc_mutex);
776 tty_reset_termios(tty);
777 }
778}
Alan Cox01e1abb2008-07-22 11:16:55 +0100779
780/**
781 * tty_ldisc_setup - open line discipline
782 * @tty: tty being shut down
783 * @o_tty: pair tty for pty/tty pairs
784 *
785 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100786 * line disciplines and bind them to the tty. This has no locking issues
787 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100788 */
789
790int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
791{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100792 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100793 int retval;
794
Alan Coxc65c9bc2009-06-11 12:50:12 +0100795 retval = tty_ldisc_open(tty, ld);
796 if (retval)
797 return retval;
798
799 if (o_tty) {
800 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100801 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100802 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100803 return retval;
804 }
805 tty_ldisc_enable(o_tty);
806 }
807 tty_ldisc_enable(tty);
808 return 0;
809}
Alan Cox01e1abb2008-07-22 11:16:55 +0100810/**
811 * tty_ldisc_release - release line discipline
812 * @tty: tty being shut down
813 * @o_tty: pair tty for pty/tty pairs
814 *
Alan Cox852e99d2009-06-11 12:51:41 +0100815 * Called during the final close of a tty/pty pair in order to shut down
816 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100817 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100818 */
819
820void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
821{
Alan Cox01e1abb2008-07-22 11:16:55 +0100822 /*
823 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
824 * kill any delayed work. As this is the final close it does not
825 * race with the set_ldisc code path.
826 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100827
Alan Coxe8b70e72009-06-11 12:48:02 +0100828 tty_ldisc_halt(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100829 flush_scheduled_work();
Alan Cox01e1abb2008-07-22 11:16:55 +0100830
Alan Coxc8d50042009-07-16 16:05:08 +0100831 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100832 /*
Alan Coxaef29bc2009-06-29 15:21:47 +0100833 * Now kill off the ldisc
Alan Cox01e1abb2008-07-22 11:16:55 +0100834 */
Alan Coxaef29bc2009-06-29 15:21:47 +0100835 tty_ldisc_close(tty, tty->ldisc);
836 tty_ldisc_put(tty->ldisc);
837 /* Force an oops if we mess this up */
838 tty->ldisc = NULL;
Alan Cox01e1abb2008-07-22 11:16:55 +0100839
Alan Coxaef29bc2009-06-29 15:21:47 +0100840 /* Ensure the next open requests the N_TTY ldisc */
841 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc8d50042009-07-16 16:05:08 +0100842 mutex_unlock(&tty->ldisc_mutex);
Alan Coxaef29bc2009-06-29 15:21:47 +0100843
Alan Coxc65c9bc2009-06-11 12:50:12 +0100844 /* This will need doing differently if we need to lock */
845 if (o_tty)
846 tty_ldisc_release(o_tty, NULL);
Alan Coxaef29bc2009-06-29 15:21:47 +0100847
848 /* And the memory resources remaining (buffers, termios) will be
849 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100850}
851
852/**
853 * tty_ldisc_init - ldisc setup for new tty
854 * @tty: tty being allocated
855 *
856 * Set up the line discipline objects for a newly allocated tty. Note that
857 * the tty structure is not completely set up when this call is made.
858 */
859
860void tty_ldisc_init(struct tty_struct *tty)
861{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100862 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
863 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100864 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100865 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100866}
867
868void tty_ldisc_begin(void)
869{
870 /* Setup the default TTY line discipline. */
871 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
872}