Commit | Line | Data |
---|---|---|
01e1abb2 | 1 | #include <linux/types.h> |
01e1abb2 | 2 | #include <linux/errno.h> |
8b3ffa17 | 3 | #include <linux/kmod.h> |
01e1abb2 AC |
4 | #include <linux/sched.h> |
5 | #include <linux/interrupt.h> | |
6 | #include <linux/tty.h> | |
7 | #include <linux/tty_driver.h> | |
01e1abb2 | 8 | #include <linux/file.h> |
01e1abb2 AC |
9 | #include <linux/mm.h> |
10 | #include <linux/string.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/poll.h> | |
13 | #include <linux/proc_fs.h> | |
14 | #include <linux/init.h> | |
15 | #include <linux/module.h> | |
01e1abb2 AC |
16 | #include <linux/device.h> |
17 | #include <linux/wait.h> | |
18 | #include <linux/bitops.h> | |
01e1abb2 | 19 | #include <linux/seq_file.h> |
01e1abb2 | 20 | #include <linux/uaccess.h> |
0c73c08e | 21 | #include <linux/ratelimit.h> |
01e1abb2 AC |
22 | |
23 | /* | |
24 | * This guards the refcounted line discipline lists. The lock | |
25 | * must be taken with irqs off because there are hangup path | |
26 | * callers who will do ldisc lookups and cannot sleep. | |
27 | */ | |
28 | ||
29 | static DEFINE_SPINLOCK(tty_ldisc_lock); | |
30 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); | |
31 | /* Line disc dispatch table */ | |
32 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
33 | ||
65b77046 LT |
34 | static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) |
35 | { | |
36 | if (ld) | |
37 | atomic_inc(&ld->users); | |
38 | return ld; | |
39 | } | |
40 | ||
cbe9352f | 41 | static void put_ldisc(struct tty_ldisc *ld) |
65b77046 | 42 | { |
cbe9352f LT |
43 | unsigned long flags; |
44 | ||
65b77046 LT |
45 | if (WARN_ON_ONCE(!ld)) |
46 | return; | |
47 | ||
48 | /* | |
49 | * If this is the last user, free the ldisc, and | |
50 | * release the ldisc ops. | |
cbe9352f LT |
51 | * |
52 | * We really want an "atomic_dec_and_lock_irqsave()", | |
53 | * but we don't have it, so this does it by hand. | |
65b77046 | 54 | */ |
cbe9352f LT |
55 | local_irq_save(flags); |
56 | if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { | |
65b77046 LT |
57 | struct tty_ldisc_ops *ldo = ld->ops; |
58 | ||
65b77046 LT |
59 | ldo->refcount--; |
60 | module_put(ldo->owner); | |
61 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
cbe9352f LT |
62 | |
63 | kfree(ld); | |
64 | return; | |
65b77046 | 65 | } |
cbe9352f | 66 | local_irq_restore(flags); |
1541f845 | 67 | wake_up(&ld->wq_idle); |
65b77046 LT |
68 | } |
69 | ||
01e1abb2 AC |
70 | /** |
71 | * tty_register_ldisc - install a line discipline | |
72 | * @disc: ldisc number | |
73 | * @new_ldisc: pointer to the ldisc object | |
74 | * | |
75 | * Installs a new line discipline into the kernel. The discipline | |
76 | * is set up as unreferenced and then made available to the kernel | |
77 | * from this point onwards. | |
78 | * | |
79 | * Locking: | |
80 | * takes tty_ldisc_lock to guard against ldisc races | |
81 | */ | |
82 | ||
83 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
84 | { | |
85 | unsigned long flags; | |
86 | int ret = 0; | |
87 | ||
88 | if (disc < N_TTY || disc >= NR_LDISCS) | |
89 | return -EINVAL; | |
90 | ||
91 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
92 | tty_ldiscs[disc] = new_ldisc; | |
93 | new_ldisc->num = disc; | |
94 | new_ldisc->refcount = 0; | |
95 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
96 | ||
97 | return ret; | |
98 | } | |
99 | EXPORT_SYMBOL(tty_register_ldisc); | |
100 | ||
101 | /** | |
102 | * tty_unregister_ldisc - unload a line discipline | |
103 | * @disc: ldisc number | |
104 | * @new_ldisc: pointer to the ldisc object | |
105 | * | |
106 | * Remove a line discipline from the kernel providing it is not | |
107 | * currently in use. | |
108 | * | |
109 | * Locking: | |
110 | * takes tty_ldisc_lock to guard against ldisc races | |
111 | */ | |
112 | ||
113 | int tty_unregister_ldisc(int disc) | |
114 | { | |
115 | unsigned long flags; | |
116 | int ret = 0; | |
117 | ||
118 | if (disc < N_TTY || disc >= NR_LDISCS) | |
119 | return -EINVAL; | |
120 | ||
121 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
122 | if (tty_ldiscs[disc]->refcount) | |
123 | ret = -EBUSY; | |
124 | else | |
125 | tty_ldiscs[disc] = NULL; | |
126 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
127 | ||
128 | return ret; | |
129 | } | |
130 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
131 | ||
f0de0e8d LT |
132 | static struct tty_ldisc_ops *get_ldops(int disc) |
133 | { | |
134 | unsigned long flags; | |
135 | struct tty_ldisc_ops *ldops, *ret; | |
136 | ||
137 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
138 | ret = ERR_PTR(-EINVAL); | |
139 | ldops = tty_ldiscs[disc]; | |
140 | if (ldops) { | |
141 | ret = ERR_PTR(-EAGAIN); | |
142 | if (try_module_get(ldops->owner)) { | |
143 | ldops->refcount++; | |
144 | ret = ldops; | |
145 | } | |
146 | } | |
147 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
148 | return ret; | |
149 | } | |
150 | ||
151 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
152 | { | |
153 | unsigned long flags; | |
154 | ||
155 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
156 | ldops->refcount--; | |
157 | module_put(ldops->owner); | |
158 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
159 | } | |
01e1abb2 | 160 | |
01e1abb2 AC |
161 | /** |
162 | * tty_ldisc_get - take a reference to an ldisc | |
163 | * @disc: ldisc number | |
01e1abb2 AC |
164 | * |
165 | * Takes a reference to a line discipline. Deals with refcounts and | |
166 | * module locking counts. Returns NULL if the discipline is not available. | |
167 | * Returns a pointer to the discipline and bumps the ref count if it is | |
168 | * available | |
169 | * | |
170 | * Locking: | |
171 | * takes tty_ldisc_lock to guard against ldisc races | |
172 | */ | |
173 | ||
c65c9bc3 | 174 | static struct tty_ldisc *tty_ldisc_get(int disc) |
01e1abb2 | 175 | { |
c65c9bc3 | 176 | struct tty_ldisc *ld; |
182274f8 | 177 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
178 | |
179 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 180 | return ERR_PTR(-EINVAL); |
182274f8 LT |
181 | |
182 | /* | |
183 | * Get the ldisc ops - we may need to request them to be loaded | |
184 | * dynamically and try again. | |
185 | */ | |
186 | ldops = get_ldops(disc); | |
187 | if (IS_ERR(ldops)) { | |
01e1abb2 | 188 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
189 | ldops = get_ldops(disc); |
190 | if (IS_ERR(ldops)) | |
191 | return ERR_CAST(ldops); | |
192 | } | |
193 | ||
194 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
195 | if (ld == NULL) { | |
196 | put_ldops(ldops); | |
197 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 198 | } |
182274f8 LT |
199 | |
200 | ld->ops = ldops; | |
201 | atomic_set(&ld->users, 1); | |
1541f845 IS |
202 | init_waitqueue_head(&ld->wq_idle); |
203 | ||
c65c9bc3 | 204 | return ld; |
01e1abb2 AC |
205 | } |
206 | ||
852e99d2 | 207 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
208 | { |
209 | return (*pos < NR_LDISCS) ? pos : NULL; | |
210 | } | |
211 | ||
852e99d2 | 212 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
213 | { |
214 | (*pos)++; | |
215 | return (*pos < NR_LDISCS) ? pos : NULL; | |
216 | } | |
217 | ||
218 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
219 | { | |
220 | } | |
221 | ||
222 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
223 | { | |
224 | int i = *(loff_t *)v; | |
f0de0e8d | 225 | struct tty_ldisc_ops *ldops; |
852e99d2 | 226 | |
f0de0e8d LT |
227 | ldops = get_ldops(i); |
228 | if (IS_ERR(ldops)) | |
01e1abb2 | 229 | return 0; |
f0de0e8d LT |
230 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
231 | put_ldops(ldops); | |
01e1abb2 AC |
232 | return 0; |
233 | } | |
234 | ||
235 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
236 | .start = tty_ldiscs_seq_start, | |
237 | .next = tty_ldiscs_seq_next, | |
238 | .stop = tty_ldiscs_seq_stop, | |
239 | .show = tty_ldiscs_seq_show, | |
240 | }; | |
241 | ||
242 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
243 | { | |
244 | return seq_open(file, &tty_ldiscs_seq_ops); | |
245 | } | |
246 | ||
247 | const struct file_operations tty_ldiscs_proc_fops = { | |
248 | .owner = THIS_MODULE, | |
249 | .open = proc_tty_ldiscs_open, | |
250 | .read = seq_read, | |
251 | .llseek = seq_lseek, | |
252 | .release = seq_release, | |
253 | }; | |
254 | ||
255 | /** | |
256 | * tty_ldisc_assign - set ldisc on a tty | |
257 | * @tty: tty to assign | |
258 | * @ld: line discipline | |
259 | * | |
260 | * Install an instance of a line discipline into a tty structure. The | |
8d2ead74 | 261 | * ldisc must have a reference count above zero to ensure it remains. |
01e1abb2 AC |
262 | * The tty instance refcount starts at zero. |
263 | * | |
264 | * Locking: | |
265 | * Caller must hold references | |
266 | */ | |
267 | ||
268 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
269 | { | |
c65c9bc3 | 270 | tty->ldisc = ld; |
01e1abb2 AC |
271 | } |
272 | ||
273 | /** | |
274 | * tty_ldisc_try - internal helper | |
275 | * @tty: the tty | |
276 | * | |
277 | * Make a single attempt to grab and bump the refcount on | |
278 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
279 | * used to implement both the waiting and non waiting versions | |
280 | * of tty_ldisc_ref | |
281 | * | |
282 | * Locking: takes tty_ldisc_lock | |
283 | */ | |
284 | ||
65b77046 | 285 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
01e1abb2 AC |
286 | { |
287 | unsigned long flags; | |
288 | struct tty_ldisc *ld; | |
01e1abb2 AC |
289 | |
290 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
65b77046 LT |
291 | ld = NULL; |
292 | if (test_bit(TTY_LDISC, &tty->flags)) | |
293 | ld = get_ldisc(tty->ldisc); | |
01e1abb2 | 294 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
65b77046 | 295 | return ld; |
01e1abb2 AC |
296 | } |
297 | ||
298 | /** | |
299 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
300 | * @tty: tty device | |
301 | * | |
302 | * Dereference the line discipline for the terminal and take a | |
303 | * reference to it. If the line discipline is in flux then | |
304 | * wait patiently until it changes. | |
305 | * | |
306 | * Note: Must not be called from an IRQ/timer context. The caller | |
307 | * must also be careful not to hold other locks that will deadlock | |
308 | * against a discipline change, such as an existing ldisc reference | |
309 | * (which we check for) | |
310 | * | |
311 | * Locking: call functions take tty_ldisc_lock | |
312 | */ | |
313 | ||
314 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
315 | { | |
65b77046 LT |
316 | struct tty_ldisc *ld; |
317 | ||
01e1abb2 | 318 | /* wait_event is a macro */ |
65b77046 LT |
319 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
320 | return ld; | |
01e1abb2 | 321 | } |
01e1abb2 AC |
322 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
323 | ||
324 | /** | |
325 | * tty_ldisc_ref - get the tty ldisc | |
326 | * @tty: tty device | |
327 | * | |
328 | * Dereference the line discipline for the terminal and take a | |
329 | * reference to it. If the line discipline is in flux then | |
330 | * return NULL. Can be called from IRQ and timer functions. | |
331 | * | |
332 | * Locking: called functions take tty_ldisc_lock | |
333 | */ | |
334 | ||
335 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
336 | { | |
65b77046 | 337 | return tty_ldisc_try(tty); |
01e1abb2 | 338 | } |
01e1abb2 AC |
339 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
340 | ||
341 | /** | |
342 | * tty_ldisc_deref - free a tty ldisc reference | |
343 | * @ld: reference to free up | |
344 | * | |
345 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
346 | * be called in IRQ context. | |
347 | * | |
348 | * Locking: takes tty_ldisc_lock | |
349 | */ | |
350 | ||
351 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
352 | { | |
65b77046 | 353 | put_ldisc(ld); |
01e1abb2 | 354 | } |
01e1abb2 AC |
355 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
356 | ||
65b77046 LT |
357 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
358 | { | |
359 | put_ldisc(ld); | |
360 | } | |
361 | ||
01e1abb2 AC |
362 | /** |
363 | * tty_ldisc_enable - allow ldisc use | |
364 | * @tty: terminal to activate ldisc on | |
365 | * | |
366 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
367 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
368 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 369 | * |
c9b3976e AC |
370 | * Note: nobody should set the TTY_LDISC bit except via this function. |
371 | * Clearing directly is allowed. | |
01e1abb2 AC |
372 | */ |
373 | ||
374 | void tty_ldisc_enable(struct tty_struct *tty) | |
375 | { | |
376 | set_bit(TTY_LDISC, &tty->flags); | |
c9b3976e | 377 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
378 | wake_up(&tty_ldisc_wait); |
379 | } | |
380 | ||
f2c4c65c AC |
381 | /** |
382 | * tty_ldisc_flush - flush line discipline queue | |
383 | * @tty: tty | |
384 | * | |
385 | * Flush the line discipline queue (if any) for this tty. If there | |
386 | * is no line discipline active this is a no-op. | |
387 | */ | |
388 | ||
389 | void tty_ldisc_flush(struct tty_struct *tty) | |
390 | { | |
391 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
392 | if (ld) { | |
393 | if (ld->ops->flush_buffer) | |
394 | ld->ops->flush_buffer(tty); | |
395 | tty_ldisc_deref(ld); | |
396 | } | |
397 | tty_buffer_flush(tty); | |
398 | } | |
f2c4c65c AC |
399 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
400 | ||
01e1abb2 AC |
401 | /** |
402 | * tty_set_termios_ldisc - set ldisc field | |
403 | * @tty: tty structure | |
404 | * @num: line discipline number | |
405 | * | |
406 | * This is probably overkill for real world processors but | |
407 | * they are not on hot paths so a little discipline won't do | |
408 | * any harm. | |
409 | * | |
410 | * Locking: takes termios_mutex | |
411 | */ | |
412 | ||
413 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
414 | { | |
415 | mutex_lock(&tty->termios_mutex); | |
416 | tty->termios->c_line = num; | |
417 | mutex_unlock(&tty->termios_mutex); | |
418 | } | |
419 | ||
c65c9bc3 AC |
420 | /** |
421 | * tty_ldisc_open - open a line discipline | |
422 | * @tty: tty we are opening the ldisc on | |
423 | * @ld: discipline to open | |
424 | * | |
425 | * A helper opening method. Also a convenient debugging and check | |
426 | * point. | |
ec79d605 AB |
427 | * |
428 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
429 | */ |
430 | ||
431 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
432 | { | |
433 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
434 | if (ld->ops->open) { |
435 | int ret; | |
ec79d605 | 436 | /* BTM here locks versus a hangup event */ |
f18f9498 | 437 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
438 | if (ret) |
439 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
f18f9498 AC |
440 | return ret; |
441 | } | |
c65c9bc3 AC |
442 | return 0; |
443 | } | |
444 | ||
445 | /** | |
446 | * tty_ldisc_close - close a line discipline | |
447 | * @tty: tty we are opening the ldisc on | |
448 | * @ld: discipline to close | |
449 | * | |
450 | * A helper close method. Also a convenient debugging and check | |
451 | * point. | |
452 | */ | |
453 | ||
454 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
455 | { | |
456 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
457 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
458 | if (ld->ops->close) | |
459 | ld->ops->close(tty); | |
460 | } | |
01e1abb2 AC |
461 | |
462 | /** | |
463 | * tty_ldisc_restore - helper for tty ldisc change | |
464 | * @tty: tty to recover | |
465 | * @old: previous ldisc | |
466 | * | |
467 | * Restore the previous line discipline or N_TTY when a line discipline | |
468 | * change fails due to an open error | |
469 | */ | |
470 | ||
471 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
472 | { | |
473 | char buf[64]; | |
c65c9bc3 AC |
474 | struct tty_ldisc *new_ldisc; |
475 | int r; | |
01e1abb2 AC |
476 | |
477 | /* There is an outstanding reference here so this is safe */ | |
c65c9bc3 AC |
478 | old = tty_ldisc_get(old->ops->num); |
479 | WARN_ON(IS_ERR(old)); | |
01e1abb2 AC |
480 | tty_ldisc_assign(tty, old); |
481 | tty_set_termios_ldisc(tty, old->ops->num); | |
c65c9bc3 AC |
482 | if (tty_ldisc_open(tty, old) < 0) { |
483 | tty_ldisc_put(old); | |
01e1abb2 | 484 | /* This driver is always present */ |
852e99d2 | 485 | new_ldisc = tty_ldisc_get(N_TTY); |
c65c9bc3 | 486 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 487 | panic("n_tty: get"); |
c65c9bc3 | 488 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 489 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
490 | r = tty_ldisc_open(tty, new_ldisc); |
491 | if (r < 0) | |
492 | panic("Couldn't open N_TTY ldisc for " | |
493 | "%s --- error %d.", | |
494 | tty_name(tty, buf), r); | |
01e1abb2 AC |
495 | } |
496 | } | |
497 | ||
e8b70e7d | 498 | /** |
c65c9bc3 | 499 | * tty_ldisc_halt - shut down the line discipline |
e8b70e7d AC |
500 | * @tty: tty device |
501 | * | |
502 | * Shut down the line discipline and work queue for this tty device. | |
503 | * The TTY_LDISC flag being cleared ensures no further references can | |
504 | * be obtained while the delayed work queue halt ensures that no more | |
505 | * data is fed to the ldisc. | |
506 | * | |
5c58ceff LT |
507 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
508 | * in order to make sure any currently executing ldisc work is also | |
509 | * flushed. | |
e8b70e7d AC |
510 | */ |
511 | ||
c65c9bc3 | 512 | static int tty_ldisc_halt(struct tty_struct *tty) |
e8b70e7d AC |
513 | { |
514 | clear_bit(TTY_LDISC, &tty->flags); | |
f23eb2b2 | 515 | return cancel_work_sync(&tty->buf.work); |
e8b70e7d AC |
516 | } |
517 | ||
0a1f1a0b TH |
518 | /** |
519 | * tty_ldisc_flush_works - flush all works of a tty | |
520 | * @tty: tty device to flush works for | |
521 | * | |
522 | * Sync flush all works belonging to @tty. | |
523 | */ | |
524 | static void tty_ldisc_flush_works(struct tty_struct *tty) | |
525 | { | |
526 | flush_work_sync(&tty->hangup_work); | |
527 | flush_work_sync(&tty->SAK_work); | |
f23eb2b2 | 528 | flush_work_sync(&tty->buf.work); |
0a1f1a0b TH |
529 | } |
530 | ||
100eeae2 JS |
531 | /** |
532 | * tty_ldisc_wait_idle - wait for the ldisc to become idle | |
533 | * @tty: tty to wait for | |
df92d056 | 534 | * @timeout: for how long to wait at most |
100eeae2 JS |
535 | * |
536 | * Wait for the line discipline to become idle. The discipline must | |
537 | * have been halted for this to guarantee it remains idle. | |
538 | */ | |
df92d056 | 539 | static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) |
100eeae2 | 540 | { |
df92d056 | 541 | long ret; |
1541f845 | 542 | ret = wait_event_timeout(tty->ldisc->wq_idle, |
df92d056 | 543 | atomic_read(&tty->ldisc->users) == 1, timeout); |
100eeae2 JS |
544 | return ret > 0 ? 0 : -EBUSY; |
545 | } | |
546 | ||
01e1abb2 AC |
547 | /** |
548 | * tty_set_ldisc - set line discipline | |
549 | * @tty: the terminal to set | |
550 | * @ldisc: the line discipline | |
551 | * | |
552 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
553 | * context. The ldisc change logic has to protect itself against any |
554 | * overlapping ldisc change (including on the other end of pty pairs), | |
555 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 556 | * |
c65c9bc3 | 557 | * Locking: takes tty_ldisc_lock, termios_mutex |
01e1abb2 AC |
558 | */ |
559 | ||
560 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
561 | { | |
562 | int retval; | |
c65c9bc3 AC |
563 | struct tty_ldisc *o_ldisc, *new_ldisc; |
564 | int work, o_work = 0; | |
01e1abb2 AC |
565 | struct tty_struct *o_tty; |
566 | ||
c65c9bc3 AC |
567 | new_ldisc = tty_ldisc_get(ldisc); |
568 | if (IS_ERR(new_ldisc)) | |
569 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 570 | |
f309532b | 571 | tty_lock(); |
01e1abb2 | 572 | /* |
c65c9bc3 AC |
573 | * We need to look at the tty locking here for pty/tty pairs |
574 | * when both sides try to change in parallel. | |
01e1abb2 AC |
575 | */ |
576 | ||
c65c9bc3 AC |
577 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
578 | ||
01e1abb2 | 579 | |
c65c9bc3 AC |
580 | /* |
581 | * Check the no-op case | |
582 | */ | |
583 | ||
584 | if (tty->ldisc->ops->num == ldisc) { | |
f309532b | 585 | tty_unlock(); |
c65c9bc3 | 586 | tty_ldisc_put(new_ldisc); |
01e1abb2 AC |
587 | return 0; |
588 | } | |
589 | ||
f309532b | 590 | tty_unlock(); |
c65c9bc3 AC |
591 | /* |
592 | * Problem: What do we do if this blocks ? | |
593 | * We could deadlock here | |
594 | */ | |
595 | ||
596 | tty_wait_until_sent(tty, 0); | |
597 | ||
f309532b | 598 | tty_lock(); |
c65c9bc3 AC |
599 | mutex_lock(&tty->ldisc_mutex); |
600 | ||
601 | /* | |
602 | * We could be midstream of another ldisc change which has | |
603 | * dropped the lock during processing. If so we need to wait. | |
604 | */ | |
605 | ||
606 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
607 | mutex_unlock(&tty->ldisc_mutex); | |
f309532b | 608 | tty_unlock(); |
c65c9bc3 AC |
609 | wait_event(tty_ldisc_wait, |
610 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
f309532b | 611 | tty_lock(); |
c65c9bc3 AC |
612 | mutex_lock(&tty->ldisc_mutex); |
613 | } | |
eeb89d91 | 614 | |
c65c9bc3 | 615 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
852e99d2 | 616 | |
01e1abb2 AC |
617 | /* |
618 | * No more input please, we are switching. The new ldisc | |
619 | * will update this value in the ldisc open function | |
620 | */ | |
621 | ||
622 | tty->receive_room = 0; | |
623 | ||
624 | o_ldisc = tty->ldisc; | |
eeb89d91 | 625 | |
f309532b | 626 | tty_unlock(); |
01e1abb2 AC |
627 | /* |
628 | * Make sure we don't change while someone holds a | |
629 | * reference to the line discipline. The TTY_LDISC bit | |
630 | * prevents anyone taking a reference once it is clear. | |
631 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
632 | * |
633 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
634 | * with a userspace app continually trying to use the tty in | |
635 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
636 | */ |
637 | ||
c65c9bc3 | 638 | work = tty_ldisc_halt(tty); |
01e1abb2 | 639 | if (o_tty) |
c65c9bc3 | 640 | o_work = tty_ldisc_halt(o_tty); |
01e1abb2 | 641 | |
01e1abb2 | 642 | /* |
c65c9bc3 AC |
643 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
644 | * We must drop the mutex here in case a hangup is also in process. | |
01e1abb2 | 645 | */ |
c65c9bc3 AC |
646 | |
647 | mutex_unlock(&tty->ldisc_mutex); | |
648 | ||
0a1f1a0b | 649 | tty_ldisc_flush_works(tty); |
c65c9bc3 | 650 | |
df92d056 | 651 | retval = tty_ldisc_wait_idle(tty, 5 * HZ); |
100eeae2 | 652 | |
f309532b | 653 | tty_lock(); |
60af22d2 | 654 | mutex_lock(&tty->ldisc_mutex); |
100eeae2 JS |
655 | |
656 | /* handle wait idle failure locked */ | |
657 | if (retval) { | |
658 | tty_ldisc_put(new_ldisc); | |
659 | goto enable; | |
660 | } | |
661 | ||
aa3c8af8 | 662 | if (test_bit(TTY_HUPPING, &tty->flags)) { |
c65c9bc3 AC |
663 | /* We were raced by the hangup method. It will have stomped |
664 | the ldisc data and closed the ldisc down */ | |
665 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
666 | mutex_unlock(&tty->ldisc_mutex); | |
667 | tty_ldisc_put(new_ldisc); | |
f309532b | 668 | tty_unlock(); |
c65c9bc3 AC |
669 | return -EIO; |
670 | } | |
671 | ||
01e1abb2 | 672 | /* Shutdown the current discipline. */ |
c65c9bc3 | 673 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
674 | |
675 | /* Now set up the new line discipline. */ | |
c65c9bc3 | 676 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 677 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
678 | |
679 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 680 | if (retval < 0) { |
c65c9bc3 AC |
681 | /* Back to the old one or N_TTY if we can't */ |
682 | tty_ldisc_put(new_ldisc); | |
683 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 684 | } |
c65c9bc3 | 685 | |
01e1abb2 AC |
686 | /* At this point we hold a reference to the new ldisc and a |
687 | a reference to the old ldisc. If we ended up flipping back | |
688 | to the existing ldisc we have two references to it */ | |
689 | ||
c65c9bc3 | 690 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
691 | tty->ops->set_ldisc(tty); |
692 | ||
c65c9bc3 | 693 | tty_ldisc_put(o_ldisc); |
01e1abb2 | 694 | |
100eeae2 | 695 | enable: |
01e1abb2 | 696 | /* |
c65c9bc3 | 697 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
698 | */ |
699 | ||
700 | tty_ldisc_enable(tty); | |
701 | if (o_tty) | |
702 | tty_ldisc_enable(o_tty); | |
703 | ||
c65c9bc3 | 704 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 AC |
705 | already running */ |
706 | if (work) | |
f23eb2b2 | 707 | schedule_work(&tty->buf.work); |
c65c9bc3 | 708 | if (o_work) |
f23eb2b2 | 709 | schedule_work(&o_tty->buf.work); |
c65c9bc3 | 710 | mutex_unlock(&tty->ldisc_mutex); |
f309532b | 711 | tty_unlock(); |
01e1abb2 AC |
712 | return retval; |
713 | } | |
714 | ||
c65c9bc3 AC |
715 | /** |
716 | * tty_reset_termios - reset terminal state | |
717 | * @tty: tty to reset | |
718 | * | |
719 | * Restore a terminal to the driver default state. | |
720 | */ | |
721 | ||
722 | static void tty_reset_termios(struct tty_struct *tty) | |
723 | { | |
724 | mutex_lock(&tty->termios_mutex); | |
725 | *tty->termios = tty->driver->init_termios; | |
726 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); | |
727 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); | |
728 | mutex_unlock(&tty->termios_mutex); | |
729 | } | |
730 | ||
731 | ||
732 | /** | |
733 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
734 | * @tty: tty to reinit | |
638b9648 | 735 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 736 | * |
638b9648 AC |
737 | * Switch the tty to a line discipline and leave the ldisc |
738 | * state closed | |
c65c9bc3 AC |
739 | */ |
740 | ||
1c95ba1e | 741 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 742 | { |
1c95ba1e PR |
743 | struct tty_ldisc *ld = tty_ldisc_get(ldisc); |
744 | ||
745 | if (IS_ERR(ld)) | |
746 | return -1; | |
c65c9bc3 AC |
747 | |
748 | tty_ldisc_close(tty, tty->ldisc); | |
749 | tty_ldisc_put(tty->ldisc); | |
750 | tty->ldisc = NULL; | |
751 | /* | |
752 | * Switch the line discipline back | |
753 | */ | |
c65c9bc3 | 754 | tty_ldisc_assign(tty, ld); |
638b9648 | 755 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
756 | |
757 | return 0; | |
c65c9bc3 AC |
758 | } |
759 | ||
760 | /** | |
761 | * tty_ldisc_hangup - hangup ldisc reset | |
762 | * @tty: tty being hung up | |
763 | * | |
764 | * Some tty devices reset their termios when they receive a hangup | |
765 | * event. In that situation we must also switch back to N_TTY properly | |
766 | * before we reset the termios data. | |
767 | * | |
768 | * Locking: We can take the ldisc mutex as the rest of the code is | |
769 | * careful to allow for this. | |
770 | * | |
771 | * In the pty pair case this occurs in the close() path of the | |
772 | * tty itself so we must be careful about locking rules. | |
773 | */ | |
774 | ||
775 | void tty_ldisc_hangup(struct tty_struct *tty) | |
776 | { | |
777 | struct tty_ldisc *ld; | |
638b9648 AC |
778 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
779 | int err = 0; | |
c65c9bc3 AC |
780 | |
781 | /* | |
782 | * FIXME! What are the locking issues here? This may me overdoing | |
783 | * things... This question is especially important now that we've | |
784 | * removed the irqlock. | |
785 | */ | |
786 | ld = tty_ldisc_ref(tty); | |
787 | if (ld != NULL) { | |
788 | /* We may have no line discipline at this point */ | |
789 | if (ld->ops->flush_buffer) | |
790 | ld->ops->flush_buffer(tty); | |
791 | tty_driver_flush_buffer(tty); | |
792 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
793 | ld->ops->write_wakeup) | |
794 | ld->ops->write_wakeup(tty); | |
795 | if (ld->ops->hangup) | |
796 | ld->ops->hangup(tty); | |
797 | tty_ldisc_deref(ld); | |
798 | } | |
799 | /* | |
800 | * FIXME: Once we trust the LDISC code better we can wait here for | |
801 | * ldisc completion and fix the driver call race | |
802 | */ | |
803 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
804 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
805 | /* | |
806 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
807 | * N_TTY if need be. |
808 | * | |
809 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 810 | */ |
638b9648 | 811 | mutex_lock(&tty->ldisc_mutex); |
60af22d2 AB |
812 | |
813 | /* | |
814 | * this is like tty_ldisc_halt, but we need to give up | |
f23eb2b2 LT |
815 | * the BTM before calling cancel_work_sync, which may |
816 | * need to wait for another function taking the BTM | |
60af22d2 AB |
817 | */ |
818 | clear_bit(TTY_LDISC, &tty->flags); | |
f309532b | 819 | tty_unlock(); |
f23eb2b2 | 820 | cancel_work_sync(&tty->buf.work); |
60af22d2 | 821 | mutex_unlock(&tty->ldisc_mutex); |
0c73c08e | 822 | retry: |
f309532b | 823 | tty_lock(); |
60af22d2 AB |
824 | mutex_lock(&tty->ldisc_mutex); |
825 | ||
638b9648 AC |
826 | /* At this point we have a closed ldisc and we want to |
827 | reopen it. We could defer this to the next open but | |
828 | it means auditing a lot of other paths so this is | |
829 | a FIXME */ | |
830 | if (tty->ldisc) { /* Not yet closed */ | |
0c73c08e JS |
831 | if (atomic_read(&tty->ldisc->users) != 1) { |
832 | char cur_n[TASK_COMM_LEN], tty_n[64]; | |
833 | long timeout = 3 * HZ; | |
f309532b | 834 | tty_unlock(); |
0c73c08e JS |
835 | |
836 | while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) { | |
837 | timeout = MAX_SCHEDULE_TIMEOUT; | |
838 | printk_ratelimited(KERN_WARNING | |
839 | "%s: waiting (%s) for %s took too long, but we keep waiting...\n", | |
840 | __func__, get_task_comm(cur_n, current), | |
841 | tty_name(tty, tty_n)); | |
842 | } | |
843 | mutex_unlock(&tty->ldisc_mutex); | |
844 | goto retry; | |
845 | } | |
30042072 | 846 | |
638b9648 | 847 | if (reset == 0) { |
1c95ba1e PR |
848 | |
849 | if (!tty_ldisc_reinit(tty, tty->termios->c_line)) | |
850 | err = tty_ldisc_open(tty, tty->ldisc); | |
851 | else | |
852 | err = 1; | |
638b9648 AC |
853 | } |
854 | /* If the re-open fails or we reset then go to N_TTY. The | |
855 | N_TTY open cannot fail */ | |
856 | if (reset || err) { | |
1c95ba1e | 857 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 858 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 859 | } |
638b9648 | 860 | tty_ldisc_enable(tty); |
c65c9bc3 | 861 | } |
638b9648 AC |
862 | mutex_unlock(&tty->ldisc_mutex); |
863 | if (reset) | |
864 | tty_reset_termios(tty); | |
c65c9bc3 | 865 | } |
01e1abb2 AC |
866 | |
867 | /** | |
868 | * tty_ldisc_setup - open line discipline | |
869 | * @tty: tty being shut down | |
870 | * @o_tty: pair tty for pty/tty pairs | |
871 | * | |
872 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
873 | * line disciplines and bind them to the tty. This has no locking issues |
874 | * as the device isn't yet active. | |
01e1abb2 AC |
875 | */ |
876 | ||
877 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
878 | { | |
c65c9bc3 | 879 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
880 | int retval; |
881 | ||
c65c9bc3 AC |
882 | retval = tty_ldisc_open(tty, ld); |
883 | if (retval) | |
884 | return retval; | |
885 | ||
886 | if (o_tty) { | |
887 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 888 | if (retval) { |
c65c9bc3 | 889 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
890 | return retval; |
891 | } | |
892 | tty_ldisc_enable(o_tty); | |
893 | } | |
894 | tty_ldisc_enable(tty); | |
895 | return 0; | |
896 | } | |
01e1abb2 AC |
897 | /** |
898 | * tty_ldisc_release - release line discipline | |
899 | * @tty: tty being shut down | |
900 | * @o_tty: pair tty for pty/tty pairs | |
901 | * | |
852e99d2 AC |
902 | * Called during the final close of a tty/pty pair in order to shut down |
903 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 904 | * ldisc has not been opened. |
01e1abb2 AC |
905 | */ |
906 | ||
907 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
908 | { | |
01e1abb2 AC |
909 | /* |
910 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then | |
911 | * kill any delayed work. As this is the final close it does not | |
912 | * race with the set_ldisc code path. | |
913 | */ | |
01e1abb2 | 914 | |
f309532b | 915 | tty_unlock(); |
e8b70e7d | 916 | tty_ldisc_halt(tty); |
0a1f1a0b | 917 | tty_ldisc_flush_works(tty); |
f309532b | 918 | tty_lock(); |
aef29bc2 | 919 | |
f309532b LT |
920 | mutex_lock(&tty->ldisc_mutex); |
921 | /* | |
922 | * Now kill off the ldisc | |
923 | */ | |
924 | tty_ldisc_close(tty, tty->ldisc); | |
925 | tty_ldisc_put(tty->ldisc); | |
926 | /* Force an oops if we mess this up */ | |
927 | tty->ldisc = NULL; | |
928 | ||
929 | /* Ensure the next open requests the N_TTY ldisc */ | |
930 | tty_set_termios_ldisc(tty, N_TTY); | |
931 | mutex_unlock(&tty->ldisc_mutex); | |
01e1abb2 | 932 | |
f309532b | 933 | /* This will need doing differently if we need to lock */ |
c65c9bc3 | 934 | if (o_tty) |
f309532b | 935 | tty_ldisc_release(o_tty, NULL); |
aef29bc2 AC |
936 | |
937 | /* And the memory resources remaining (buffers, termios) will be | |
938 | disposed of when the kref hits zero */ | |
01e1abb2 AC |
939 | } |
940 | ||
941 | /** | |
942 | * tty_ldisc_init - ldisc setup for new tty | |
943 | * @tty: tty being allocated | |
944 | * | |
945 | * Set up the line discipline objects for a newly allocated tty. Note that | |
946 | * the tty structure is not completely set up when this call is made. | |
947 | */ | |
948 | ||
949 | void tty_ldisc_init(struct tty_struct *tty) | |
950 | { | |
c65c9bc3 AC |
951 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
952 | if (IS_ERR(ld)) | |
01e1abb2 | 953 | panic("n_tty: init_tty"); |
c65c9bc3 | 954 | tty_ldisc_assign(tty, ld); |
01e1abb2 AC |
955 | } |
956 | ||
6716671d JS |
957 | /** |
958 | * tty_ldisc_init - ldisc cleanup for new tty | |
959 | * @tty: tty that was allocated recently | |
960 | * | |
961 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
962 | * this call is made. | |
963 | */ | |
964 | void tty_ldisc_deinit(struct tty_struct *tty) | |
965 | { | |
966 | put_ldisc(tty->ldisc); | |
967 | tty_ldisc_assign(tty, NULL); | |
968 | } | |
969 | ||
01e1abb2 AC |
970 | void tty_ldisc_begin(void) |
971 | { | |
972 | /* Setup the default TTY line discipline. */ | |
973 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
974 | } |