blob: 412f9775d19c5f2deee27b2174532e35ab3e14d1 [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
Alan Coxeeb89d92009-11-30 13:18:29 +000037#include <linux/smp_lock.h> /* For the moment */
38
Alan Cox01e1abb2008-07-22 11:16:55 +010039#include <linux/kmod.h>
40#include <linux/nsproxy.h>
41
42/*
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.
46 */
47
48static DEFINE_SPINLOCK(tty_ldisc_lock);
49static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
50/* Line disc dispatch table */
51static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
52
Linus Torvalds65b77042009-08-03 11:11:19 -070053static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
54{
55 if (ld)
56 atomic_inc(&ld->users);
57 return ld;
58}
59
Linus Torvaldscbe93522009-08-03 14:54:56 -070060static void put_ldisc(struct tty_ldisc *ld)
Linus Torvalds65b77042009-08-03 11:11:19 -070061{
Linus Torvaldscbe93522009-08-03 14:54:56 -070062 unsigned long flags;
63
Linus Torvalds65b77042009-08-03 11:11:19 -070064 if (WARN_ON_ONCE(!ld))
65 return;
66
67 /*
68 * If this is the last user, free the ldisc, and
69 * release the ldisc ops.
Linus Torvaldscbe93522009-08-03 14:54:56 -070070 *
71 * We really want an "atomic_dec_and_lock_irqsave()",
72 * but we don't have it, so this does it by hand.
Linus Torvalds65b77042009-08-03 11:11:19 -070073 */
Linus Torvaldscbe93522009-08-03 14:54:56 -070074 local_irq_save(flags);
75 if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
Linus Torvalds65b77042009-08-03 11:11:19 -070076 struct tty_ldisc_ops *ldo = ld->ops;
77
Linus Torvalds65b77042009-08-03 11:11:19 -070078 ldo->refcount--;
79 module_put(ldo->owner);
80 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldscbe93522009-08-03 14:54:56 -070081
82 kfree(ld);
83 return;
Linus Torvalds65b77042009-08-03 11:11:19 -070084 }
Linus Torvaldscbe93522009-08-03 14:54:56 -070085 local_irq_restore(flags);
Linus Torvalds65b77042009-08-03 11:11:19 -070086}
87
Alan Cox01e1abb2008-07-22 11:16:55 +010088/**
89 * tty_register_ldisc - install a line discipline
90 * @disc: ldisc number
91 * @new_ldisc: pointer to the ldisc object
92 *
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.
96 *
97 * Locking:
98 * takes tty_ldisc_lock to guard against ldisc races
99 */
100
101int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
102{
103 unsigned long flags;
104 int ret = 0;
105
106 if (disc < N_TTY || disc >= NR_LDISCS)
107 return -EINVAL;
108
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);
114
115 return ret;
116}
117EXPORT_SYMBOL(tty_register_ldisc);
118
119/**
120 * tty_unregister_ldisc - unload a line discipline
121 * @disc: ldisc number
122 * @new_ldisc: pointer to the ldisc object
123 *
124 * Remove a line discipline from the kernel providing it is not
125 * currently in use.
126 *
127 * Locking:
128 * takes tty_ldisc_lock to guard against ldisc races
129 */
130
131int tty_unregister_ldisc(int disc)
132{
133 unsigned long flags;
134 int ret = 0;
135
136 if (disc < N_TTY || disc >= NR_LDISCS)
137 return -EINVAL;
138
139 spin_lock_irqsave(&tty_ldisc_lock, flags);
140 if (tty_ldiscs[disc]->refcount)
141 ret = -EBUSY;
142 else
143 tty_ldiscs[disc] = NULL;
144 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
145
146 return ret;
147}
148EXPORT_SYMBOL(tty_unregister_ldisc);
149
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700150static struct tty_ldisc_ops *get_ldops(int disc)
151{
152 unsigned long flags;
153 struct tty_ldisc_ops *ldops, *ret;
154
155 spin_lock_irqsave(&tty_ldisc_lock, flags);
156 ret = ERR_PTR(-EINVAL);
157 ldops = tty_ldiscs[disc];
158 if (ldops) {
159 ret = ERR_PTR(-EAGAIN);
160 if (try_module_get(ldops->owner)) {
161 ldops->refcount++;
162 ret = ldops;
163 }
164 }
165 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
166 return ret;
167}
168
169static void put_ldops(struct tty_ldisc_ops *ldops)
170{
171 unsigned long flags;
172
173 spin_lock_irqsave(&tty_ldisc_lock, flags);
174 ldops->refcount--;
175 module_put(ldops->owner);
176 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
177}
Alan Cox01e1abb2008-07-22 11:16:55 +0100178
179/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100180 * tty_ldisc_get - take a reference to an ldisc
181 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100182 *
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
186 * available
187 *
188 * Locking:
189 * takes tty_ldisc_lock to guard against ldisc races
190 */
191
Alan Coxc65c9bc2009-06-11 12:50:12 +0100192static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100193{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100194 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700195 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100196
197 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100198 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700199
200 /*
201 * Get the ldisc ops - we may need to request them to be loaded
202 * dynamically and try again.
203 */
204 ldops = get_ldops(disc);
205 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100206 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700207 ldops = get_ldops(disc);
208 if (IS_ERR(ldops))
209 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100210 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700211
212 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
213 if (ld == NULL) {
214 put_ldops(ldops);
215 return ERR_PTR(-ENOMEM);
216 }
217
218 ld->ops = ldops;
219 atomic_set(&ld->users, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100220 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100221}
222
Alan Cox852e99d2009-06-11 12:51:41 +0100223static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100224{
225 return (*pos < NR_LDISCS) ? pos : NULL;
226}
227
Alan Cox852e99d2009-06-11 12:51:41 +0100228static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100229{
230 (*pos)++;
231 return (*pos < NR_LDISCS) ? pos : NULL;
232}
233
234static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
235{
236}
237
238static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
239{
240 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700241 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100242
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700243 ldops = get_ldops(i);
244 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100245 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700246 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
247 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100248 return 0;
249}
250
251static 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,
256};
257
258static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
259{
260 return seq_open(file, &tty_ldiscs_seq_ops);
261}
262
263const struct file_operations tty_ldiscs_proc_fops = {
264 .owner = THIS_MODULE,
265 .open = proc_tty_ldiscs_open,
266 .read = seq_read,
267 .llseek = seq_lseek,
268 .release = seq_release,
269};
270
271/**
272 * tty_ldisc_assign - set ldisc on a tty
273 * @tty: tty to assign
274 * @ld: line discipline
275 *
276 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100277 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100278 * The tty instance refcount starts at zero.
279 *
280 * Locking:
281 * Caller must hold references
282 */
283
284static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
285{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100286 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100287}
288
289/**
290 * tty_ldisc_try - internal helper
291 * @tty: the tty
292 *
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
296 * of tty_ldisc_ref
297 *
298 * Locking: takes tty_ldisc_lock
299 */
300
Linus Torvalds65b77042009-08-03 11:11:19 -0700301static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100302{
303 unsigned long flags;
304 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100305
306 spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700307 ld = NULL;
308 if (test_bit(TTY_LDISC, &tty->flags))
309 ld = get_ldisc(tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100310 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700311 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100312}
313
314/**
315 * tty_ldisc_ref_wait - wait for the tty ldisc
316 * @tty: tty device
317 *
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.
321 *
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)
326 *
327 * Locking: call functions take tty_ldisc_lock
328 */
329
330struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
331{
Linus Torvalds65b77042009-08-03 11:11:19 -0700332 struct tty_ldisc *ld;
333
Alan Cox01e1abb2008-07-22 11:16:55 +0100334 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700335 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
336 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100337}
Alan Cox01e1abb2008-07-22 11:16:55 +0100338EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
339
340/**
341 * tty_ldisc_ref - get the tty ldisc
342 * @tty: tty device
343 *
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.
347 *
348 * Locking: called functions take tty_ldisc_lock
349 */
350
351struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
352{
Linus Torvalds65b77042009-08-03 11:11:19 -0700353 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100354}
Alan Cox01e1abb2008-07-22 11:16:55 +0100355EXPORT_SYMBOL_GPL(tty_ldisc_ref);
356
357/**
358 * tty_ldisc_deref - free a tty ldisc reference
359 * @ld: reference to free up
360 *
361 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
362 * be called in IRQ context.
363 *
364 * Locking: takes tty_ldisc_lock
365 */
366
367void tty_ldisc_deref(struct tty_ldisc *ld)
368{
Linus Torvalds65b77042009-08-03 11:11:19 -0700369 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100370}
Alan Cox01e1abb2008-07-22 11:16:55 +0100371EXPORT_SYMBOL_GPL(tty_ldisc_deref);
372
Linus Torvalds65b77042009-08-03 11:11:19 -0700373static inline void tty_ldisc_put(struct tty_ldisc *ld)
374{
375 put_ldisc(ld);
376}
377
Alan Cox01e1abb2008-07-22 11:16:55 +0100378/**
379 * tty_ldisc_enable - allow ldisc use
380 * @tty: terminal to activate ldisc on
381 *
382 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000383 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
384 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100385 *
Alan Coxc9b39762009-01-02 13:44:56 +0000386 * Note: nobody should set the TTY_LDISC bit except via this function.
387 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100388 */
389
390void tty_ldisc_enable(struct tty_struct *tty)
391{
392 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000393 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100394 wake_up(&tty_ldisc_wait);
395}
396
397/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100398 * tty_ldisc_flush - flush line discipline queue
399 * @tty: tty
400 *
401 * Flush the line discipline queue (if any) for this tty. If there
402 * is no line discipline active this is a no-op.
403 */
404
405void tty_ldisc_flush(struct tty_struct *tty)
406{
407 struct tty_ldisc *ld = tty_ldisc_ref(tty);
408 if (ld) {
409 if (ld->ops->flush_buffer)
410 ld->ops->flush_buffer(tty);
411 tty_ldisc_deref(ld);
412 }
413 tty_buffer_flush(tty);
414}
Alan Coxf2c4c652009-06-11 12:50:58 +0100415EXPORT_SYMBOL_GPL(tty_ldisc_flush);
416
417/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100418 * tty_set_termios_ldisc - set ldisc field
419 * @tty: tty structure
420 * @num: line discipline number
421 *
422 * This is probably overkill for real world processors but
423 * they are not on hot paths so a little discipline won't do
424 * any harm.
425 *
426 * Locking: takes termios_mutex
427 */
428
429static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
430{
431 mutex_lock(&tty->termios_mutex);
432 tty->termios->c_line = num;
433 mutex_unlock(&tty->termios_mutex);
434}
435
Alan Coxc65c9bc2009-06-11 12:50:12 +0100436/**
437 * tty_ldisc_open - open a line discipline
438 * @tty: tty we are opening the ldisc on
439 * @ld: discipline to open
440 *
441 * A helper opening method. Also a convenient debugging and check
442 * point.
Arnd Bergmannec79d602010-06-01 22:53:01 +0200443 *
444 * Locking: always called with BTM already held.
Alan Coxc65c9bc2009-06-11 12:50:12 +0100445 */
446
447static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
448{
449 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
Alan Coxf18f9492009-11-30 13:18:35 +0000450 if (ld->ops->open) {
451 int ret;
Arnd Bergmannec79d602010-06-01 22:53:01 +0200452 /* BTM here locks versus a hangup event */
Arnd Bergmannddcd9fb2010-06-01 22:53:08 +0200453 WARN_ON(!tty_locked());
Alan Coxf18f9492009-11-30 13:18:35 +0000454 ret = ld->ops->open(tty);
Alan Coxf18f9492009-11-30 13:18:35 +0000455 return ret;
456 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100457 return 0;
458}
459
460/**
461 * tty_ldisc_close - close a line discipline
462 * @tty: tty we are opening the ldisc on
463 * @ld: discipline to close
464 *
465 * A helper close method. Also a convenient debugging and check
466 * point.
467 */
468
469static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
470{
471 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
472 clear_bit(TTY_LDISC_OPEN, &tty->flags);
473 if (ld->ops->close)
474 ld->ops->close(tty);
475}
Alan Cox01e1abb2008-07-22 11:16:55 +0100476
477/**
478 * tty_ldisc_restore - helper for tty ldisc change
479 * @tty: tty to recover
480 * @old: previous ldisc
481 *
482 * Restore the previous line discipline or N_TTY when a line discipline
483 * change fails due to an open error
484 */
485
486static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
487{
488 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100489 struct tty_ldisc *new_ldisc;
490 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100491
492 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100493 old = tty_ldisc_get(old->ops->num);
494 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100495 tty_ldisc_assign(tty, old);
496 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100497 if (tty_ldisc_open(tty, old) < 0) {
498 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100499 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100500 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100501 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100502 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100503 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100504 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100505 r = tty_ldisc_open(tty, new_ldisc);
506 if (r < 0)
507 panic("Couldn't open N_TTY ldisc for "
508 "%s --- error %d.",
509 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100510 }
511}
512
513/**
Alan Coxc65c9bc2009-06-11 12:50:12 +0100514 * tty_ldisc_halt - shut down the line discipline
Alan Coxe8b70e72009-06-11 12:48:02 +0100515 * @tty: tty device
516 *
517 * Shut down the line discipline and work queue for this tty device.
518 * The TTY_LDISC flag being cleared ensures no further references can
519 * be obtained while the delayed work queue halt ensures that no more
520 * data is fed to the ldisc.
521 *
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700522 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
523 * in order to make sure any currently executing ldisc work is also
524 * flushed.
Alan Coxe8b70e72009-06-11 12:48:02 +0100525 */
526
Alan Coxc65c9bc2009-06-11 12:50:12 +0100527static int tty_ldisc_halt(struct tty_struct *tty)
Alan Coxe8b70e72009-06-11 12:48:02 +0100528{
529 clear_bit(TTY_LDISC, &tty->flags);
Linus Torvalds0b5759c2009-10-03 21:44:21 -0700530 return cancel_delayed_work_sync(&tty->buf.work);
Alan Coxe8b70e72009-06-11 12:48:02 +0100531}
532
533/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100534 * tty_set_ldisc - set line discipline
535 * @tty: the terminal to set
536 * @ldisc: the line discipline
537 *
538 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100539 * context. The ldisc change logic has to protect itself against any
540 * overlapping ldisc change (including on the other end of pty pairs),
541 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100542 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100543 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100544 */
545
546int tty_set_ldisc(struct tty_struct *tty, int ldisc)
547{
548 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100549 struct tty_ldisc *o_ldisc, *new_ldisc;
550 int work, o_work = 0;
Alan Cox01e1abb2008-07-22 11:16:55 +0100551 struct tty_struct *o_tty;
552
Alan Coxc65c9bc2009-06-11 12:50:12 +0100553 new_ldisc = tty_ldisc_get(ldisc);
554 if (IS_ERR(new_ldisc))
555 return PTR_ERR(new_ldisc);
556
Arnd Bergmannec79d602010-06-01 22:53:01 +0200557 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100558 /*
559 * We need to look at the tty locking here for pty/tty pairs
560 * when both sides try to change in parallel.
561 */
562
563 o_tty = tty->link; /* o_tty is the pty side or NULL */
564
565
566 /*
567 * Check the no-op case
568 */
569
570 if (tty->ldisc->ops->num == ldisc) {
Arnd Bergmannec79d602010-06-01 22:53:01 +0200571 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100572 tty_ldisc_put(new_ldisc);
573 return 0;
574 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100575
Arnd Bergmannec79d602010-06-01 22:53:01 +0200576 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100577 /*
578 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100579 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100580 */
581
582 tty_wait_until_sent(tty, 0);
583
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200584 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100585 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100586
587 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100588 * We could be midstream of another ldisc change which has
589 * dropped the lock during processing. If so we need to wait.
590 */
591
592 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
593 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200594 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100595 wait_event(tty_ldisc_wait,
596 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200597 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100598 mutex_lock(&tty->ldisc_mutex);
599 }
Alan Coxeeb89d92009-11-30 13:18:29 +0000600
Alan Coxc65c9bc2009-06-11 12:50:12 +0100601 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100602
Alan Coxc65c9bc2009-06-11 12:50:12 +0100603 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100604 * No more input please, we are switching. The new ldisc
605 * will update this value in the ldisc open function
606 */
607
608 tty->receive_room = 0;
609
610 o_ldisc = tty->ldisc;
Alan Coxeeb89d92009-11-30 13:18:29 +0000611
Arnd Bergmannec79d602010-06-01 22:53:01 +0200612 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100613 /*
614 * Make sure we don't change while someone holds a
615 * reference to the line discipline. The TTY_LDISC bit
616 * prevents anyone taking a reference once it is clear.
617 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000618 *
619 * We must clear the TTY_LDISC bit here to avoid a livelock
620 * with a userspace app continually trying to use the tty in
621 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100622 */
623
Alan Coxc65c9bc2009-06-11 12:50:12 +0100624 work = tty_ldisc_halt(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100625 if (o_tty)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100626 o_work = tty_ldisc_halt(o_tty);
627
Alan Cox01e1abb2008-07-22 11:16:55 +0100628 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100629 * Wait for ->hangup_work and ->buf.work handlers to terminate.
630 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100631 */
632
Alan Coxc65c9bc2009-06-11 12:50:12 +0100633 mutex_unlock(&tty->ldisc_mutex);
634
Alan Cox01e1abb2008-07-22 11:16:55 +0100635 flush_scheduled_work();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100636
Arnd Bergmannec79d602010-06-01 22:53:01 +0200637 tty_lock();
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200638 mutex_lock(&tty->ldisc_mutex);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100639 if (test_bit(TTY_HUPPED, &tty->flags)) {
640 /* We were raced by the hangup method. It will have stomped
641 the ldisc data and closed the ldisc down */
642 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
643 mutex_unlock(&tty->ldisc_mutex);
644 tty_ldisc_put(new_ldisc);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200645 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100646 return -EIO;
647 }
648
Alan Cox01e1abb2008-07-22 11:16:55 +0100649 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100650 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100651
652 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100653 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100654 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100655
656 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100657 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100658 /* Back to the old one or N_TTY if we can't */
659 tty_ldisc_put(new_ldisc);
660 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100661 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100662
Alan Cox01e1abb2008-07-22 11:16:55 +0100663 /* At this point we hold a reference to the new ldisc and a
664 a reference to the old ldisc. If we ended up flipping back
665 to the existing ldisc we have two references to it */
666
Alan Coxc65c9bc2009-06-11 12:50:12 +0100667 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100668 tty->ops->set_ldisc(tty);
669
Alan Coxc65c9bc2009-06-11 12:50:12 +0100670 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100671
672 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100673 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100674 */
675
676 tty_ldisc_enable(tty);
677 if (o_tty)
678 tty_ldisc_enable(o_tty);
679
Alan Coxc65c9bc2009-06-11 12:50:12 +0100680 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100681 already running */
682 if (work)
683 schedule_delayed_work(&tty->buf.work, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100684 if (o_work)
685 schedule_delayed_work(&o_tty->buf.work, 1);
686 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200687 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100688 return retval;
689}
690
Alan Coxc65c9bc2009-06-11 12:50:12 +0100691/**
692 * tty_reset_termios - reset terminal state
693 * @tty: tty to reset
694 *
695 * Restore a terminal to the driver default state.
696 */
697
698static void tty_reset_termios(struct tty_struct *tty)
699{
700 mutex_lock(&tty->termios_mutex);
701 *tty->termios = tty->driver->init_termios;
702 tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
703 tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
704 mutex_unlock(&tty->termios_mutex);
705}
706
707
708/**
709 * tty_ldisc_reinit - reinitialise the tty ldisc
710 * @tty: tty to reinit
Alan Cox638b9642010-02-08 10:09:26 +0000711 * @ldisc: line discipline to reinitialize
Alan Coxc65c9bc2009-06-11 12:50:12 +0100712 *
Alan Cox638b9642010-02-08 10:09:26 +0000713 * Switch the tty to a line discipline and leave the ldisc
714 * state closed
Alan Coxc65c9bc2009-06-11 12:50:12 +0100715 */
716
Alan Cox638b9642010-02-08 10:09:26 +0000717static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100718{
719 struct tty_ldisc *ld;
720
721 tty_ldisc_close(tty, tty->ldisc);
722 tty_ldisc_put(tty->ldisc);
723 tty->ldisc = NULL;
724 /*
725 * Switch the line discipline back
726 */
Alan Cox638b9642010-02-08 10:09:26 +0000727 ld = tty_ldisc_get(ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100728 BUG_ON(IS_ERR(ld));
729 tty_ldisc_assign(tty, ld);
Alan Cox638b9642010-02-08 10:09:26 +0000730 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100731}
732
733/**
734 * tty_ldisc_hangup - hangup ldisc reset
735 * @tty: tty being hung up
736 *
737 * Some tty devices reset their termios when they receive a hangup
738 * event. In that situation we must also switch back to N_TTY properly
739 * before we reset the termios data.
740 *
741 * Locking: We can take the ldisc mutex as the rest of the code is
742 * careful to allow for this.
743 *
744 * In the pty pair case this occurs in the close() path of the
745 * tty itself so we must be careful about locking rules.
746 */
747
748void tty_ldisc_hangup(struct tty_struct *tty)
749{
750 struct tty_ldisc *ld;
Alan Cox638b9642010-02-08 10:09:26 +0000751 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
752 int err = 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100753
754 /*
755 * FIXME! What are the locking issues here? This may me overdoing
756 * things... This question is especially important now that we've
757 * removed the irqlock.
758 */
759 ld = tty_ldisc_ref(tty);
760 if (ld != NULL) {
761 /* We may have no line discipline at this point */
762 if (ld->ops->flush_buffer)
763 ld->ops->flush_buffer(tty);
764 tty_driver_flush_buffer(tty);
765 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
766 ld->ops->write_wakeup)
767 ld->ops->write_wakeup(tty);
768 if (ld->ops->hangup)
769 ld->ops->hangup(tty);
770 tty_ldisc_deref(ld);
771 }
772 /*
773 * FIXME: Once we trust the LDISC code better we can wait here for
774 * ldisc completion and fix the driver call race
775 */
776 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
777 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
778 /*
779 * Shutdown the current line discipline, and reset it to
Alan Cox638b9642010-02-08 10:09:26 +0000780 * N_TTY if need be.
781 *
782 * Avoid racing set_ldisc or tty_ldisc_release
Alan Coxc65c9bc2009-06-11 12:50:12 +0100783 */
Alan Cox638b9642010-02-08 10:09:26 +0000784 mutex_lock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200785
786 /*
787 * this is like tty_ldisc_halt, but we need to give up
788 * the BTM before calling cancel_delayed_work_sync,
789 * which may need to wait for another function taking the BTM
790 */
791 clear_bit(TTY_LDISC, &tty->flags);
792 tty_unlock();
793 cancel_delayed_work_sync(&tty->buf.work);
794 mutex_unlock(&tty->ldisc_mutex);
795
796 tty_lock();
797 mutex_lock(&tty->ldisc_mutex);
798
Alan Cox638b9642010-02-08 10:09:26 +0000799 /* At this point we have a closed ldisc and we want to
800 reopen it. We could defer this to the next open but
801 it means auditing a lot of other paths so this is
802 a FIXME */
803 if (tty->ldisc) { /* Not yet closed */
804 if (reset == 0) {
805 tty_ldisc_reinit(tty, tty->termios->c_line);
806 err = tty_ldisc_open(tty, tty->ldisc);
Alan Coxc8d50042009-07-16 16:05:08 +0100807 }
Alan Cox638b9642010-02-08 10:09:26 +0000808 /* If the re-open fails or we reset then go to N_TTY. The
809 N_TTY open cannot fail */
810 if (reset || err) {
811 tty_ldisc_reinit(tty, N_TTY);
812 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
813 }
814 tty_ldisc_enable(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100815 }
Alan Cox638b9642010-02-08 10:09:26 +0000816 mutex_unlock(&tty->ldisc_mutex);
817 if (reset)
818 tty_reset_termios(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100819}
Alan Cox01e1abb2008-07-22 11:16:55 +0100820
821/**
822 * tty_ldisc_setup - open line discipline
823 * @tty: tty being shut down
824 * @o_tty: pair tty for pty/tty pairs
825 *
826 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100827 * line disciplines and bind them to the tty. This has no locking issues
828 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100829 */
830
831int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
832{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100833 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100834 int retval;
835
Alan Coxc65c9bc2009-06-11 12:50:12 +0100836 retval = tty_ldisc_open(tty, ld);
837 if (retval)
838 return retval;
839
840 if (o_tty) {
841 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100842 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100843 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100844 return retval;
845 }
846 tty_ldisc_enable(o_tty);
847 }
848 tty_ldisc_enable(tty);
849 return 0;
850}
Alan Cox01e1abb2008-07-22 11:16:55 +0100851/**
852 * tty_ldisc_release - release line discipline
853 * @tty: tty being shut down
854 * @o_tty: pair tty for pty/tty pairs
855 *
Alan Cox852e99d2009-06-11 12:51:41 +0100856 * Called during the final close of a tty/pty pair in order to shut down
857 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100858 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100859 */
860
861void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
862{
Alan Cox01e1abb2008-07-22 11:16:55 +0100863 /*
864 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
865 * kill any delayed work. As this is the final close it does not
866 * race with the set_ldisc code path.
867 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100868
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200869 tty_unlock();
Alan Coxe8b70e72009-06-11 12:48:02 +0100870 tty_ldisc_halt(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100871 flush_scheduled_work();
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200872 tty_lock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100873
Alan Coxc8d50042009-07-16 16:05:08 +0100874 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100875 /*
Alan Coxaef29bc2009-06-29 15:21:47 +0100876 * Now kill off the ldisc
Alan Cox01e1abb2008-07-22 11:16:55 +0100877 */
Alan Coxaef29bc2009-06-29 15:21:47 +0100878 tty_ldisc_close(tty, tty->ldisc);
879 tty_ldisc_put(tty->ldisc);
880 /* Force an oops if we mess this up */
881 tty->ldisc = NULL;
Alan Cox01e1abb2008-07-22 11:16:55 +0100882
Alan Coxaef29bc2009-06-29 15:21:47 +0100883 /* Ensure the next open requests the N_TTY ldisc */
884 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc8d50042009-07-16 16:05:08 +0100885 mutex_unlock(&tty->ldisc_mutex);
Alan Coxaef29bc2009-06-29 15:21:47 +0100886
Alan Coxc65c9bc2009-06-11 12:50:12 +0100887 /* This will need doing differently if we need to lock */
888 if (o_tty)
889 tty_ldisc_release(o_tty, NULL);
Alan Coxaef29bc2009-06-29 15:21:47 +0100890
891 /* And the memory resources remaining (buffers, termios) will be
892 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100893}
894
895/**
896 * tty_ldisc_init - ldisc setup for new tty
897 * @tty: tty being allocated
898 *
899 * Set up the line discipline objects for a newly allocated tty. Note that
900 * the tty structure is not completely set up when this call is made.
901 */
902
903void tty_ldisc_init(struct tty_struct *tty)
904{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100905 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
906 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100907 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100908 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100909}
910
911void tty_ldisc_begin(void)
912{
913 /* Setup the default TTY line discipline. */
914 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
915}