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1 | #include <linux/types.h> | |
2 | #include <linux/errno.h> | |
3 | #include <linux/kmod.h> | |
4 | #include <linux/sched.h> | |
5 | #include <linux/interrupt.h> | |
6 | #include <linux/tty.h> | |
7 | #include <linux/tty_driver.h> | |
8 | #include <linux/file.h> | |
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/module.h> | |
15 | #include <linux/device.h> | |
16 | #include <linux/wait.h> | |
17 | #include <linux/bitops.h> | |
18 | #include <linux/seq_file.h> | |
19 | #include <linux/uaccess.h> | |
20 | #include <linux/ratelimit.h> | |
21 | ||
22 | #undef LDISC_DEBUG_HANGUP | |
23 | ||
24 | #ifdef LDISC_DEBUG_HANGUP | |
25 | #define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) | |
26 | #else | |
27 | #define tty_ldisc_debug(tty, f, args...) | |
28 | #endif | |
29 | ||
30 | /* lockdep nested classes for tty->ldisc_sem */ | |
31 | enum { | |
32 | LDISC_SEM_NORMAL, | |
33 | LDISC_SEM_OTHER, | |
34 | }; | |
35 | ||
36 | ||
37 | /* | |
38 | * This guards the refcounted line discipline lists. The lock | |
39 | * must be taken with irqs off because there are hangup path | |
40 | * callers who will do ldisc lookups and cannot sleep. | |
41 | */ | |
42 | ||
43 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); | |
44 | /* Line disc dispatch table */ | |
45 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
46 | ||
47 | /** | |
48 | * tty_register_ldisc - install a line discipline | |
49 | * @disc: ldisc number | |
50 | * @new_ldisc: pointer to the ldisc object | |
51 | * | |
52 | * Installs a new line discipline into the kernel. The discipline | |
53 | * is set up as unreferenced and then made available to the kernel | |
54 | * from this point onwards. | |
55 | * | |
56 | * Locking: | |
57 | * takes tty_ldiscs_lock to guard against ldisc races | |
58 | */ | |
59 | ||
60 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
61 | { | |
62 | unsigned long flags; | |
63 | int ret = 0; | |
64 | ||
65 | if (disc < N_TTY || disc >= NR_LDISCS) | |
66 | return -EINVAL; | |
67 | ||
68 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); | |
69 | tty_ldiscs[disc] = new_ldisc; | |
70 | new_ldisc->num = disc; | |
71 | new_ldisc->refcount = 0; | |
72 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); | |
73 | ||
74 | return ret; | |
75 | } | |
76 | EXPORT_SYMBOL(tty_register_ldisc); | |
77 | ||
78 | /** | |
79 | * tty_unregister_ldisc - unload a line discipline | |
80 | * @disc: ldisc number | |
81 | * @new_ldisc: pointer to the ldisc object | |
82 | * | |
83 | * Remove a line discipline from the kernel providing it is not | |
84 | * currently in use. | |
85 | * | |
86 | * Locking: | |
87 | * takes tty_ldiscs_lock to guard against ldisc races | |
88 | */ | |
89 | ||
90 | int tty_unregister_ldisc(int disc) | |
91 | { | |
92 | unsigned long flags; | |
93 | int ret = 0; | |
94 | ||
95 | if (disc < N_TTY || disc >= NR_LDISCS) | |
96 | return -EINVAL; | |
97 | ||
98 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); | |
99 | if (tty_ldiscs[disc]->refcount) | |
100 | ret = -EBUSY; | |
101 | else | |
102 | tty_ldiscs[disc] = NULL; | |
103 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); | |
104 | ||
105 | return ret; | |
106 | } | |
107 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
108 | ||
109 | static struct tty_ldisc_ops *get_ldops(int disc) | |
110 | { | |
111 | unsigned long flags; | |
112 | struct tty_ldisc_ops *ldops, *ret; | |
113 | ||
114 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); | |
115 | ret = ERR_PTR(-EINVAL); | |
116 | ldops = tty_ldiscs[disc]; | |
117 | if (ldops) { | |
118 | ret = ERR_PTR(-EAGAIN); | |
119 | if (try_module_get(ldops->owner)) { | |
120 | ldops->refcount++; | |
121 | ret = ldops; | |
122 | } | |
123 | } | |
124 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); | |
125 | return ret; | |
126 | } | |
127 | ||
128 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
129 | { | |
130 | unsigned long flags; | |
131 | ||
132 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); | |
133 | ldops->refcount--; | |
134 | module_put(ldops->owner); | |
135 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); | |
136 | } | |
137 | ||
138 | /** | |
139 | * tty_ldisc_get - take a reference to an ldisc | |
140 | * @disc: ldisc number | |
141 | * | |
142 | * Takes a reference to a line discipline. Deals with refcounts and | |
143 | * module locking counts. | |
144 | * | |
145 | * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or | |
146 | * if the discipline is not registered | |
147 | * -EAGAIN if request_module() failed to load or register the | |
148 | * the discipline | |
149 | * -ENOMEM if allocation failure | |
150 | * | |
151 | * Otherwise, returns a pointer to the discipline and bumps the | |
152 | * ref count | |
153 | * | |
154 | * Locking: | |
155 | * takes tty_ldiscs_lock to guard against ldisc races | |
156 | */ | |
157 | ||
158 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) | |
159 | { | |
160 | struct tty_ldisc *ld; | |
161 | struct tty_ldisc_ops *ldops; | |
162 | ||
163 | if (disc < N_TTY || disc >= NR_LDISCS) | |
164 | return ERR_PTR(-EINVAL); | |
165 | ||
166 | /* | |
167 | * Get the ldisc ops - we may need to request them to be loaded | |
168 | * dynamically and try again. | |
169 | */ | |
170 | ldops = get_ldops(disc); | |
171 | if (IS_ERR(ldops)) { | |
172 | request_module("tty-ldisc-%d", disc); | |
173 | ldops = get_ldops(disc); | |
174 | if (IS_ERR(ldops)) | |
175 | return ERR_CAST(ldops); | |
176 | } | |
177 | ||
178 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
179 | if (ld == NULL) { | |
180 | put_ldops(ldops); | |
181 | return ERR_PTR(-ENOMEM); | |
182 | } | |
183 | ||
184 | ld->ops = ldops; | |
185 | ld->tty = tty; | |
186 | ||
187 | return ld; | |
188 | } | |
189 | ||
190 | /** | |
191 | * tty_ldisc_put - release the ldisc | |
192 | * | |
193 | * Complement of tty_ldisc_get(). | |
194 | */ | |
195 | static void tty_ldisc_put(struct tty_ldisc *ld) | |
196 | { | |
197 | if (WARN_ON_ONCE(!ld)) | |
198 | return; | |
199 | ||
200 | put_ldops(ld->ops); | |
201 | kfree(ld); | |
202 | } | |
203 | ||
204 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) | |
205 | { | |
206 | return (*pos < NR_LDISCS) ? pos : NULL; | |
207 | } | |
208 | ||
209 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) | |
210 | { | |
211 | (*pos)++; | |
212 | return (*pos < NR_LDISCS) ? pos : NULL; | |
213 | } | |
214 | ||
215 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
216 | { | |
217 | } | |
218 | ||
219 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
220 | { | |
221 | int i = *(loff_t *)v; | |
222 | struct tty_ldisc_ops *ldops; | |
223 | ||
224 | ldops = get_ldops(i); | |
225 | if (IS_ERR(ldops)) | |
226 | return 0; | |
227 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); | |
228 | put_ldops(ldops); | |
229 | return 0; | |
230 | } | |
231 | ||
232 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
233 | .start = tty_ldiscs_seq_start, | |
234 | .next = tty_ldiscs_seq_next, | |
235 | .stop = tty_ldiscs_seq_stop, | |
236 | .show = tty_ldiscs_seq_show, | |
237 | }; | |
238 | ||
239 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
240 | { | |
241 | return seq_open(file, &tty_ldiscs_seq_ops); | |
242 | } | |
243 | ||
244 | const struct file_operations tty_ldiscs_proc_fops = { | |
245 | .owner = THIS_MODULE, | |
246 | .open = proc_tty_ldiscs_open, | |
247 | .read = seq_read, | |
248 | .llseek = seq_lseek, | |
249 | .release = seq_release, | |
250 | }; | |
251 | ||
252 | /** | |
253 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
254 | * @tty: tty device | |
255 | * | |
256 | * Dereference the line discipline for the terminal and take a | |
257 | * reference to it. If the line discipline is in flux then | |
258 | * wait patiently until it changes. | |
259 | * | |
260 | * Note: Must not be called from an IRQ/timer context. The caller | |
261 | * must also be careful not to hold other locks that will deadlock | |
262 | * against a discipline change, such as an existing ldisc reference | |
263 | * (which we check for) | |
264 | * | |
265 | * Note: only callable from a file_operations routine (which | |
266 | * guarantees tty->ldisc != NULL when the lock is acquired). | |
267 | */ | |
268 | ||
269 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
270 | { | |
271 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); | |
272 | WARN_ON(!tty->ldisc); | |
273 | return tty->ldisc; | |
274 | } | |
275 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); | |
276 | ||
277 | /** | |
278 | * tty_ldisc_ref - get the tty ldisc | |
279 | * @tty: tty device | |
280 | * | |
281 | * Dereference the line discipline for the terminal and take a | |
282 | * reference to it. If the line discipline is in flux then | |
283 | * return NULL. Can be called from IRQ and timer functions. | |
284 | */ | |
285 | ||
286 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
287 | { | |
288 | struct tty_ldisc *ld = NULL; | |
289 | ||
290 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
291 | ld = tty->ldisc; | |
292 | if (!ld) | |
293 | ldsem_up_read(&tty->ldisc_sem); | |
294 | } | |
295 | return ld; | |
296 | } | |
297 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); | |
298 | ||
299 | /** | |
300 | * tty_ldisc_deref - free a tty ldisc reference | |
301 | * @ld: reference to free up | |
302 | * | |
303 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
304 | * be called in IRQ context. | |
305 | */ | |
306 | ||
307 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
308 | { | |
309 | ldsem_up_read(&ld->tty->ldisc_sem); | |
310 | } | |
311 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); | |
312 | ||
313 | ||
314 | static inline int | |
315 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) | |
316 | { | |
317 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
318 | } | |
319 | ||
320 | static inline int | |
321 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) | |
322 | { | |
323 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
324 | LDISC_SEM_OTHER, timeout); | |
325 | } | |
326 | ||
327 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) | |
328 | { | |
329 | ldsem_up_write(&tty->ldisc_sem); | |
330 | } | |
331 | ||
332 | static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) | |
333 | { | |
334 | int ret; | |
335 | ||
336 | ret = __tty_ldisc_lock(tty, timeout); | |
337 | if (!ret) | |
338 | return -EBUSY; | |
339 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
340 | return 0; | |
341 | } | |
342 | ||
343 | static void tty_ldisc_unlock(struct tty_struct *tty) | |
344 | { | |
345 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
346 | __tty_ldisc_unlock(tty); | |
347 | } | |
348 | ||
349 | static int | |
350 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, | |
351 | unsigned long timeout) | |
352 | { | |
353 | int ret; | |
354 | ||
355 | if (tty < tty2) { | |
356 | ret = __tty_ldisc_lock(tty, timeout); | |
357 | if (ret) { | |
358 | ret = __tty_ldisc_lock_nested(tty2, timeout); | |
359 | if (!ret) | |
360 | __tty_ldisc_unlock(tty); | |
361 | } | |
362 | } else { | |
363 | /* if this is possible, it has lots of implications */ | |
364 | WARN_ON_ONCE(tty == tty2); | |
365 | if (tty2 && tty != tty2) { | |
366 | ret = __tty_ldisc_lock(tty2, timeout); | |
367 | if (ret) { | |
368 | ret = __tty_ldisc_lock_nested(tty, timeout); | |
369 | if (!ret) | |
370 | __tty_ldisc_unlock(tty2); | |
371 | } | |
372 | } else | |
373 | ret = __tty_ldisc_lock(tty, timeout); | |
374 | } | |
375 | ||
376 | if (!ret) | |
377 | return -EBUSY; | |
378 | ||
379 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
380 | if (tty2) | |
381 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
382 | return 0; | |
383 | } | |
384 | ||
385 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) | |
386 | { | |
387 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
388 | } | |
389 | ||
390 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, | |
391 | struct tty_struct *tty2) | |
392 | { | |
393 | __tty_ldisc_unlock(tty); | |
394 | if (tty2) | |
395 | __tty_ldisc_unlock(tty2); | |
396 | } | |
397 | ||
398 | /** | |
399 | * tty_ldisc_flush - flush line discipline queue | |
400 | * @tty: tty | |
401 | * | |
402 | * Flush the line discipline queue (if any) and the tty flip buffers | |
403 | * for this tty. | |
404 | */ | |
405 | ||
406 | void tty_ldisc_flush(struct tty_struct *tty) | |
407 | { | |
408 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
409 | ||
410 | tty_buffer_flush(tty, ld); | |
411 | if (ld) | |
412 | tty_ldisc_deref(ld); | |
413 | } | |
414 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); | |
415 | ||
416 | /** | |
417 | * tty_set_termios_ldisc - set ldisc field | |
418 | * @tty: tty structure | |
419 | * @num: line discipline number | |
420 | * | |
421 | * This is probably overkill for real world processors but | |
422 | * they are not on hot paths so a little discipline won't do | |
423 | * any harm. | |
424 | * | |
425 | * The line discipline-related tty_struct fields are reset to | |
426 | * prevent the ldisc driver from re-using stale information for | |
427 | * the new ldisc instance. | |
428 | * | |
429 | * Locking: takes termios_rwsem | |
430 | */ | |
431 | ||
432 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
433 | { | |
434 | down_write(&tty->termios_rwsem); | |
435 | tty->termios.c_line = num; | |
436 | up_write(&tty->termios_rwsem); | |
437 | ||
438 | tty->disc_data = NULL; | |
439 | tty->receive_room = 0; | |
440 | } | |
441 | ||
442 | /** | |
443 | * tty_ldisc_open - open a line discipline | |
444 | * @tty: tty we are opening the ldisc on | |
445 | * @ld: discipline to open | |
446 | * | |
447 | * A helper opening method. Also a convenient debugging and check | |
448 | * point. | |
449 | * | |
450 | * Locking: always called with BTM already held. | |
451 | */ | |
452 | ||
453 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
454 | { | |
455 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
456 | if (ld->ops->open) { | |
457 | int ret; | |
458 | /* BTM here locks versus a hangup event */ | |
459 | ret = ld->ops->open(tty); | |
460 | if (ret) | |
461 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
462 | ||
463 | tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc); | |
464 | return ret; | |
465 | } | |
466 | return 0; | |
467 | } | |
468 | ||
469 | /** | |
470 | * tty_ldisc_close - close a line discipline | |
471 | * @tty: tty we are opening the ldisc on | |
472 | * @ld: discipline to close | |
473 | * | |
474 | * A helper close method. Also a convenient debugging and check | |
475 | * point. | |
476 | */ | |
477 | ||
478 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
479 | { | |
480 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
481 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
482 | if (ld->ops->close) | |
483 | ld->ops->close(tty); | |
484 | tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc); | |
485 | } | |
486 | ||
487 | /** | |
488 | * tty_ldisc_restore - helper for tty ldisc change | |
489 | * @tty: tty to recover | |
490 | * @old: previous ldisc | |
491 | * | |
492 | * Restore the previous line discipline or N_TTY when a line discipline | |
493 | * change fails due to an open error | |
494 | */ | |
495 | ||
496 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
497 | { | |
498 | struct tty_ldisc *new_ldisc; | |
499 | int r; | |
500 | ||
501 | /* There is an outstanding reference here so this is safe */ | |
502 | old = tty_ldisc_get(tty, old->ops->num); | |
503 | WARN_ON(IS_ERR(old)); | |
504 | tty->ldisc = old; | |
505 | tty_set_termios_ldisc(tty, old->ops->num); | |
506 | if (tty_ldisc_open(tty, old) < 0) { | |
507 | tty_ldisc_put(old); | |
508 | /* This driver is always present */ | |
509 | new_ldisc = tty_ldisc_get(tty, N_TTY); | |
510 | if (IS_ERR(new_ldisc)) | |
511 | panic("n_tty: get"); | |
512 | tty->ldisc = new_ldisc; | |
513 | tty_set_termios_ldisc(tty, N_TTY); | |
514 | r = tty_ldisc_open(tty, new_ldisc); | |
515 | if (r < 0) | |
516 | panic("Couldn't open N_TTY ldisc for " | |
517 | "%s --- error %d.", | |
518 | tty_name(tty), r); | |
519 | } | |
520 | } | |
521 | ||
522 | /** | |
523 | * tty_set_ldisc - set line discipline | |
524 | * @tty: the terminal to set | |
525 | * @ldisc: the line discipline | |
526 | * | |
527 | * Set the discipline of a tty line. Must be called from a process | |
528 | * context. The ldisc change logic has to protect itself against any | |
529 | * overlapping ldisc change (including on the other end of pty pairs), | |
530 | * the close of one side of a tty/pty pair, and eventually hangup. | |
531 | */ | |
532 | ||
533 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
534 | { | |
535 | int retval; | |
536 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
537 | ||
538 | new_ldisc = tty_ldisc_get(tty, ldisc); | |
539 | if (IS_ERR(new_ldisc)) | |
540 | return PTR_ERR(new_ldisc); | |
541 | ||
542 | tty_lock(tty); | |
543 | retval = tty_ldisc_lock(tty, 5 * HZ); | |
544 | if (retval) | |
545 | goto err; | |
546 | ||
547 | /* Check the no-op case */ | |
548 | if (tty->ldisc->ops->num == ldisc) | |
549 | goto out; | |
550 | ||
551 | if (test_bit(TTY_HUPPED, &tty->flags)) { | |
552 | /* We were raced by hangup */ | |
553 | retval = -EIO; | |
554 | goto out; | |
555 | } | |
556 | ||
557 | old_ldisc = tty->ldisc; | |
558 | ||
559 | /* Shutdown the old discipline. */ | |
560 | tty_ldisc_close(tty, old_ldisc); | |
561 | ||
562 | /* Now set up the new line discipline. */ | |
563 | tty->ldisc = new_ldisc; | |
564 | tty_set_termios_ldisc(tty, ldisc); | |
565 | ||
566 | retval = tty_ldisc_open(tty, new_ldisc); | |
567 | if (retval < 0) { | |
568 | /* Back to the old one or N_TTY if we can't */ | |
569 | tty_ldisc_put(new_ldisc); | |
570 | tty_ldisc_restore(tty, old_ldisc); | |
571 | } | |
572 | ||
573 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { | |
574 | down_read(&tty->termios_rwsem); | |
575 | tty->ops->set_ldisc(tty); | |
576 | up_read(&tty->termios_rwsem); | |
577 | } | |
578 | ||
579 | /* At this point we hold a reference to the new ldisc and a | |
580 | reference to the old ldisc, or we hold two references to | |
581 | the old ldisc (if it was restored as part of error cleanup | |
582 | above). In either case, releasing a single reference from | |
583 | the old ldisc is correct. */ | |
584 | new_ldisc = old_ldisc; | |
585 | out: | |
586 | tty_ldisc_unlock(tty); | |
587 | ||
588 | /* Restart the work queue in case no characters kick it off. Safe if | |
589 | already running */ | |
590 | tty_buffer_restart_work(tty->port); | |
591 | err: | |
592 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ | |
593 | tty_unlock(tty); | |
594 | return retval; | |
595 | } | |
596 | ||
597 | /** | |
598 | * tty_reset_termios - reset terminal state | |
599 | * @tty: tty to reset | |
600 | * | |
601 | * Restore a terminal to the driver default state. | |
602 | */ | |
603 | ||
604 | static void tty_reset_termios(struct tty_struct *tty) | |
605 | { | |
606 | down_write(&tty->termios_rwsem); | |
607 | tty->termios = tty->driver->init_termios; | |
608 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
609 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
610 | up_write(&tty->termios_rwsem); | |
611 | } | |
612 | ||
613 | ||
614 | /** | |
615 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
616 | * @tty: tty to reinit | |
617 | * @ldisc: line discipline to reinitialize | |
618 | * | |
619 | * Switch the tty to a line discipline and leave the ldisc | |
620 | * state closed | |
621 | */ | |
622 | ||
623 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) | |
624 | { | |
625 | struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); | |
626 | ||
627 | if (IS_ERR(ld)) | |
628 | return -1; | |
629 | ||
630 | tty_ldisc_close(tty, tty->ldisc); | |
631 | tty_ldisc_put(tty->ldisc); | |
632 | /* | |
633 | * Switch the line discipline back | |
634 | */ | |
635 | tty->ldisc = ld; | |
636 | tty_set_termios_ldisc(tty, ldisc); | |
637 | ||
638 | return 0; | |
639 | } | |
640 | ||
641 | /** | |
642 | * tty_ldisc_hangup - hangup ldisc reset | |
643 | * @tty: tty being hung up | |
644 | * | |
645 | * Some tty devices reset their termios when they receive a hangup | |
646 | * event. In that situation we must also switch back to N_TTY properly | |
647 | * before we reset the termios data. | |
648 | * | |
649 | * Locking: We can take the ldisc mutex as the rest of the code is | |
650 | * careful to allow for this. | |
651 | * | |
652 | * In the pty pair case this occurs in the close() path of the | |
653 | * tty itself so we must be careful about locking rules. | |
654 | */ | |
655 | ||
656 | void tty_ldisc_hangup(struct tty_struct *tty) | |
657 | { | |
658 | struct tty_ldisc *ld; | |
659 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; | |
660 | int err = 0; | |
661 | ||
662 | tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc); | |
663 | ||
664 | ld = tty_ldisc_ref(tty); | |
665 | if (ld != NULL) { | |
666 | if (ld->ops->flush_buffer) | |
667 | ld->ops->flush_buffer(tty); | |
668 | tty_driver_flush_buffer(tty); | |
669 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
670 | ld->ops->write_wakeup) | |
671 | ld->ops->write_wakeup(tty); | |
672 | if (ld->ops->hangup) | |
673 | ld->ops->hangup(tty); | |
674 | tty_ldisc_deref(ld); | |
675 | } | |
676 | ||
677 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
678 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
679 | ||
680 | /* | |
681 | * Shutdown the current line discipline, and reset it to | |
682 | * N_TTY if need be. | |
683 | * | |
684 | * Avoid racing set_ldisc or tty_ldisc_release | |
685 | */ | |
686 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); | |
687 | ||
688 | if (tty->ldisc) { | |
689 | ||
690 | /* At this point we have a halted ldisc; we want to close it and | |
691 | reopen a new ldisc. We could defer the reopen to the next | |
692 | open but it means auditing a lot of other paths so this is | |
693 | a FIXME */ | |
694 | if (reset == 0) { | |
695 | ||
696 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) | |
697 | err = tty_ldisc_open(tty, tty->ldisc); | |
698 | else | |
699 | err = 1; | |
700 | } | |
701 | /* If the re-open fails or we reset then go to N_TTY. The | |
702 | N_TTY open cannot fail */ | |
703 | if (reset || err) { | |
704 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); | |
705 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); | |
706 | } | |
707 | } | |
708 | tty_ldisc_unlock(tty); | |
709 | if (reset) | |
710 | tty_reset_termios(tty); | |
711 | ||
712 | tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc); | |
713 | } | |
714 | ||
715 | /** | |
716 | * tty_ldisc_setup - open line discipline | |
717 | * @tty: tty being shut down | |
718 | * @o_tty: pair tty for pty/tty pairs | |
719 | * | |
720 | * Called during the initial open of a tty/pty pair in order to set up the | |
721 | * line disciplines and bind them to the tty. This has no locking issues | |
722 | * as the device isn't yet active. | |
723 | */ | |
724 | ||
725 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
726 | { | |
727 | struct tty_ldisc *ld = tty->ldisc; | |
728 | int retval; | |
729 | ||
730 | retval = tty_ldisc_open(tty, ld); | |
731 | if (retval) | |
732 | return retval; | |
733 | ||
734 | if (o_tty) { | |
735 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
736 | if (retval) { | |
737 | tty_ldisc_close(tty, ld); | |
738 | return retval; | |
739 | } | |
740 | } | |
741 | return 0; | |
742 | } | |
743 | ||
744 | static void tty_ldisc_kill(struct tty_struct *tty) | |
745 | { | |
746 | /* | |
747 | * Now kill off the ldisc | |
748 | */ | |
749 | tty_ldisc_close(tty, tty->ldisc); | |
750 | tty_ldisc_put(tty->ldisc); | |
751 | /* Force an oops if we mess this up */ | |
752 | tty->ldisc = NULL; | |
753 | } | |
754 | ||
755 | /** | |
756 | * tty_ldisc_release - release line discipline | |
757 | * @tty: tty being shut down (or one end of pty pair) | |
758 | * | |
759 | * Called during the final close of a tty or a pty pair in order to shut | |
760 | * down the line discpline layer. On exit, each tty's ldisc is NULL. | |
761 | */ | |
762 | ||
763 | void tty_ldisc_release(struct tty_struct *tty) | |
764 | { | |
765 | struct tty_struct *o_tty = tty->link; | |
766 | ||
767 | /* | |
768 | * Shutdown this line discipline. As this is the final close, | |
769 | * it does not race with the set_ldisc code path. | |
770 | */ | |
771 | ||
772 | tty_ldisc_lock_pair(tty, o_tty); | |
773 | tty_ldisc_kill(tty); | |
774 | if (o_tty) | |
775 | tty_ldisc_kill(o_tty); | |
776 | tty_ldisc_unlock_pair(tty, o_tty); | |
777 | ||
778 | /* And the memory resources remaining (buffers, termios) will be | |
779 | disposed of when the kref hits zero */ | |
780 | ||
781 | tty_ldisc_debug(tty, "released\n"); | |
782 | } | |
783 | ||
784 | /** | |
785 | * tty_ldisc_init - ldisc setup for new tty | |
786 | * @tty: tty being allocated | |
787 | * | |
788 | * Set up the line discipline objects for a newly allocated tty. Note that | |
789 | * the tty structure is not completely set up when this call is made. | |
790 | */ | |
791 | ||
792 | void tty_ldisc_init(struct tty_struct *tty) | |
793 | { | |
794 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); | |
795 | if (IS_ERR(ld)) | |
796 | panic("n_tty: init_tty"); | |
797 | tty->ldisc = ld; | |
798 | } | |
799 | ||
800 | /** | |
801 | * tty_ldisc_deinit - ldisc cleanup for new tty | |
802 | * @tty: tty that was allocated recently | |
803 | * | |
804 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
805 | * this call is made. | |
806 | */ | |
807 | void tty_ldisc_deinit(struct tty_struct *tty) | |
808 | { | |
809 | if (tty->ldisc) | |
810 | tty_ldisc_put(tty->ldisc); | |
811 | tty->ldisc = NULL; | |
812 | } | |
813 | ||
814 | void tty_ldisc_begin(void) | |
815 | { | |
816 | /* Setup the default TTY line discipline. */ | |
817 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
818 | } |