Root/
1 | #include <linux/types.h> |
2 | #include <linux/major.h> |
3 | #include <linux/errno.h> |
4 | #include <linux/signal.h> |
5 | #include <linux/fcntl.h> |
6 | #include <linux/sched.h> |
7 | #include <linux/interrupt.h> |
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> |
13 | #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> |
24 | #include <linux/device.h> |
25 | #include <linux/wait.h> |
26 | #include <linux/bitops.h> |
27 | #include <linux/delay.h> |
28 | #include <linux/seq_file.h> |
29 | |
30 | #include <linux/uaccess.h> |
31 | #include <asm/system.h> |
32 | |
33 | #include <linux/kbd_kern.h> |
34 | #include <linux/vt_kern.h> |
35 | #include <linux/selection.h> |
36 | |
37 | #include <linux/smp_lock.h> /* For the moment */ |
38 | |
39 | #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 | |
48 | static DEFINE_SPINLOCK(tty_ldisc_lock); |
49 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); |
50 | /* Line disc dispatch table */ |
51 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; |
52 | |
53 | static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) |
54 | { |
55 | if (ld) |
56 | atomic_inc(&ld->users); |
57 | return ld; |
58 | } |
59 | |
60 | static void put_ldisc(struct tty_ldisc *ld) |
61 | { |
62 | unsigned long flags; |
63 | |
64 | 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. |
70 | * |
71 | * We really want an "atomic_dec_and_lock_irqsave()", |
72 | * but we don't have it, so this does it by hand. |
73 | */ |
74 | local_irq_save(flags); |
75 | if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { |
76 | struct tty_ldisc_ops *ldo = ld->ops; |
77 | |
78 | ldo->refcount--; |
79 | module_put(ldo->owner); |
80 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
81 | |
82 | kfree(ld); |
83 | return; |
84 | } |
85 | local_irq_restore(flags); |
86 | } |
87 | |
88 | /** |
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 | |
101 | int 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 | } |
117 | EXPORT_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 | |
131 | int 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 | } |
148 | EXPORT_SYMBOL(tty_unregister_ldisc); |
149 | |
150 | static 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 | |
169 | static 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 | } |
178 | |
179 | /** |
180 | * tty_ldisc_get - take a reference to an ldisc |
181 | * @disc: ldisc number |
182 | * |
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 | |
192 | static struct tty_ldisc *tty_ldisc_get(int disc) |
193 | { |
194 | struct tty_ldisc *ld; |
195 | struct tty_ldisc_ops *ldops; |
196 | |
197 | if (disc < N_TTY || disc >= NR_LDISCS) |
198 | return ERR_PTR(-EINVAL); |
199 | |
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)) { |
206 | request_module("tty-ldisc-%d", disc); |
207 | ldops = get_ldops(disc); |
208 | if (IS_ERR(ldops)) |
209 | return ERR_CAST(ldops); |
210 | } |
211 | |
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); |
220 | return ld; |
221 | } |
222 | |
223 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
224 | { |
225 | return (*pos < NR_LDISCS) ? pos : NULL; |
226 | } |
227 | |
228 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
229 | { |
230 | (*pos)++; |
231 | return (*pos < NR_LDISCS) ? pos : NULL; |
232 | } |
233 | |
234 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) |
235 | { |
236 | } |
237 | |
238 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) |
239 | { |
240 | int i = *(loff_t *)v; |
241 | struct tty_ldisc_ops *ldops; |
242 | |
243 | ldops = get_ldops(i); |
244 | if (IS_ERR(ldops)) |
245 | return 0; |
246 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
247 | put_ldops(ldops); |
248 | return 0; |
249 | } |
250 | |
251 | static const struct seq_operations tty_ldiscs_seq_ops = { |
252 | .start = tty_ldiscs_seq_start, |
253 | .next = tty_ldiscs_seq_next, |
254 | .stop = tty_ldiscs_seq_stop, |
255 | .show = tty_ldiscs_seq_show, |
256 | }; |
257 | |
258 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) |
259 | { |
260 | return seq_open(file, &tty_ldiscs_seq_ops); |
261 | } |
262 | |
263 | const 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 |
277 | * ldisc must have a reference count above zero to ensure it remains. |
278 | * The tty instance refcount starts at zero. |
279 | * |
280 | * Locking: |
281 | * Caller must hold references |
282 | */ |
283 | |
284 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) |
285 | { |
286 | tty->ldisc = ld; |
287 | } |
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 | |
301 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
302 | { |
303 | unsigned long flags; |
304 | struct tty_ldisc *ld; |
305 | |
306 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
307 | ld = NULL; |
308 | if (test_bit(TTY_LDISC, &tty->flags)) |
309 | ld = get_ldisc(tty->ldisc); |
310 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
311 | return ld; |
312 | } |
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 | |
330 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |
331 | { |
332 | struct tty_ldisc *ld; |
333 | |
334 | /* wait_event is a macro */ |
335 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
336 | return ld; |
337 | } |
338 | EXPORT_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 | |
351 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) |
352 | { |
353 | return tty_ldisc_try(tty); |
354 | } |
355 | EXPORT_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 | |
367 | void tty_ldisc_deref(struct tty_ldisc *ld) |
368 | { |
369 | put_ldisc(ld); |
370 | } |
371 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
372 | |
373 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
374 | { |
375 | put_ldisc(ld); |
376 | } |
377 | |
378 | /** |
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 |
383 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
384 | * changing flag to indicate any ldisc change is now over. |
385 | * |
386 | * Note: nobody should set the TTY_LDISC bit except via this function. |
387 | * Clearing directly is allowed. |
388 | */ |
389 | |
390 | void tty_ldisc_enable(struct tty_struct *tty) |
391 | { |
392 | set_bit(TTY_LDISC, &tty->flags); |
393 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
394 | wake_up(&tty_ldisc_wait); |
395 | } |
396 | |
397 | /** |
398 | * 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 | |
405 | void 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 | } |
415 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
416 | |
417 | /** |
418 | * 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 | |
429 | static 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 | |
436 | /** |
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. |
443 | */ |
444 | |
445 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) |
446 | { |
447 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); |
448 | if (ld->ops->open) { |
449 | int ret; |
450 | /* BKL here locks verus a hangup event */ |
451 | lock_kernel(); |
452 | ret = ld->ops->open(tty); |
453 | unlock_kernel(); |
454 | return ret; |
455 | } |
456 | return 0; |
457 | } |
458 | |
459 | /** |
460 | * tty_ldisc_close - close a line discipline |
461 | * @tty: tty we are opening the ldisc on |
462 | * @ld: discipline to close |
463 | * |
464 | * A helper close method. Also a convenient debugging and check |
465 | * point. |
466 | */ |
467 | |
468 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) |
469 | { |
470 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
471 | clear_bit(TTY_LDISC_OPEN, &tty->flags); |
472 | if (ld->ops->close) |
473 | ld->ops->close(tty); |
474 | } |
475 | |
476 | /** |
477 | * tty_ldisc_restore - helper for tty ldisc change |
478 | * @tty: tty to recover |
479 | * @old: previous ldisc |
480 | * |
481 | * Restore the previous line discipline or N_TTY when a line discipline |
482 | * change fails due to an open error |
483 | */ |
484 | |
485 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) |
486 | { |
487 | char buf[64]; |
488 | struct tty_ldisc *new_ldisc; |
489 | int r; |
490 | |
491 | /* There is an outstanding reference here so this is safe */ |
492 | old = tty_ldisc_get(old->ops->num); |
493 | WARN_ON(IS_ERR(old)); |
494 | tty_ldisc_assign(tty, old); |
495 | tty_set_termios_ldisc(tty, old->ops->num); |
496 | if (tty_ldisc_open(tty, old) < 0) { |
497 | tty_ldisc_put(old); |
498 | /* This driver is always present */ |
499 | new_ldisc = tty_ldisc_get(N_TTY); |
500 | if (IS_ERR(new_ldisc)) |
501 | panic("n_tty: get"); |
502 | tty_ldisc_assign(tty, new_ldisc); |
503 | tty_set_termios_ldisc(tty, N_TTY); |
504 | r = tty_ldisc_open(tty, new_ldisc); |
505 | if (r < 0) |
506 | panic("Couldn't open N_TTY ldisc for " |
507 | "%s --- error %d.", |
508 | tty_name(tty, buf), r); |
509 | } |
510 | } |
511 | |
512 | /** |
513 | * tty_ldisc_halt - shut down the line discipline |
514 | * @tty: tty device |
515 | * |
516 | * Shut down the line discipline and work queue for this tty device. |
517 | * The TTY_LDISC flag being cleared ensures no further references can |
518 | * be obtained while the delayed work queue halt ensures that no more |
519 | * data is fed to the ldisc. |
520 | * |
521 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
522 | * in order to make sure any currently executing ldisc work is also |
523 | * flushed. |
524 | */ |
525 | |
526 | static int tty_ldisc_halt(struct tty_struct *tty) |
527 | { |
528 | clear_bit(TTY_LDISC, &tty->flags); |
529 | return cancel_delayed_work_sync(&tty->buf.work); |
530 | } |
531 | |
532 | /** |
533 | * tty_set_ldisc - set line discipline |
534 | * @tty: the terminal to set |
535 | * @ldisc: the line discipline |
536 | * |
537 | * Set the discipline of a tty line. Must be called from a process |
538 | * context. The ldisc change logic has to protect itself against any |
539 | * overlapping ldisc change (including on the other end of pty pairs), |
540 | * the close of one side of a tty/pty pair, and eventually hangup. |
541 | * |
542 | * Locking: takes tty_ldisc_lock, termios_mutex |
543 | */ |
544 | |
545 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) |
546 | { |
547 | int retval; |
548 | struct tty_ldisc *o_ldisc, *new_ldisc; |
549 | int work, o_work = 0; |
550 | struct tty_struct *o_tty; |
551 | |
552 | new_ldisc = tty_ldisc_get(ldisc); |
553 | if (IS_ERR(new_ldisc)) |
554 | return PTR_ERR(new_ldisc); |
555 | |
556 | lock_kernel(); |
557 | /* |
558 | * We need to look at the tty locking here for pty/tty pairs |
559 | * when both sides try to change in parallel. |
560 | */ |
561 | |
562 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
563 | |
564 | |
565 | /* |
566 | * Check the no-op case |
567 | */ |
568 | |
569 | if (tty->ldisc->ops->num == ldisc) { |
570 | unlock_kernel(); |
571 | tty_ldisc_put(new_ldisc); |
572 | return 0; |
573 | } |
574 | |
575 | unlock_kernel(); |
576 | /* |
577 | * Problem: What do we do if this blocks ? |
578 | * We could deadlock here |
579 | */ |
580 | |
581 | tty_wait_until_sent(tty, 0); |
582 | |
583 | mutex_lock(&tty->ldisc_mutex); |
584 | |
585 | /* |
586 | * We could be midstream of another ldisc change which has |
587 | * dropped the lock during processing. If so we need to wait. |
588 | */ |
589 | |
590 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { |
591 | mutex_unlock(&tty->ldisc_mutex); |
592 | wait_event(tty_ldisc_wait, |
593 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); |
594 | mutex_lock(&tty->ldisc_mutex); |
595 | } |
596 | |
597 | lock_kernel(); |
598 | |
599 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
600 | |
601 | /* |
602 | * No more input please, we are switching. The new ldisc |
603 | * will update this value in the ldisc open function |
604 | */ |
605 | |
606 | tty->receive_room = 0; |
607 | |
608 | o_ldisc = tty->ldisc; |
609 | |
610 | unlock_kernel(); |
611 | /* |
612 | * Make sure we don't change while someone holds a |
613 | * reference to the line discipline. The TTY_LDISC bit |
614 | * prevents anyone taking a reference once it is clear. |
615 | * We need the lock to avoid racing reference takers. |
616 | * |
617 | * We must clear the TTY_LDISC bit here to avoid a livelock |
618 | * with a userspace app continually trying to use the tty in |
619 | * parallel to the change and re-referencing the tty. |
620 | */ |
621 | |
622 | work = tty_ldisc_halt(tty); |
623 | if (o_tty) |
624 | o_work = tty_ldisc_halt(o_tty); |
625 | |
626 | /* |
627 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
628 | * We must drop the mutex here in case a hangup is also in process. |
629 | */ |
630 | |
631 | mutex_unlock(&tty->ldisc_mutex); |
632 | |
633 | flush_scheduled_work(); |
634 | |
635 | mutex_lock(&tty->ldisc_mutex); |
636 | lock_kernel(); |
637 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
638 | /* We were raced by the hangup method. It will have stomped |
639 | the ldisc data and closed the ldisc down */ |
640 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
641 | mutex_unlock(&tty->ldisc_mutex); |
642 | tty_ldisc_put(new_ldisc); |
643 | unlock_kernel(); |
644 | return -EIO; |
645 | } |
646 | |
647 | /* Shutdown the current discipline. */ |
648 | tty_ldisc_close(tty, o_ldisc); |
649 | |
650 | /* Now set up the new line discipline. */ |
651 | tty_ldisc_assign(tty, new_ldisc); |
652 | tty_set_termios_ldisc(tty, ldisc); |
653 | |
654 | retval = tty_ldisc_open(tty, new_ldisc); |
655 | if (retval < 0) { |
656 | /* Back to the old one or N_TTY if we can't */ |
657 | tty_ldisc_put(new_ldisc); |
658 | tty_ldisc_restore(tty, o_ldisc); |
659 | } |
660 | |
661 | /* At this point we hold a reference to the new ldisc and a |
662 | a reference to the old ldisc. If we ended up flipping back |
663 | to the existing ldisc we have two references to it */ |
664 | |
665 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
666 | tty->ops->set_ldisc(tty); |
667 | |
668 | tty_ldisc_put(o_ldisc); |
669 | |
670 | /* |
671 | * Allow ldisc referencing to occur again |
672 | */ |
673 | |
674 | tty_ldisc_enable(tty); |
675 | if (o_tty) |
676 | tty_ldisc_enable(o_tty); |
677 | |
678 | /* Restart the work queue in case no characters kick it off. Safe if |
679 | already running */ |
680 | if (work) |
681 | schedule_delayed_work(&tty->buf.work, 1); |
682 | if (o_work) |
683 | schedule_delayed_work(&o_tty->buf.work, 1); |
684 | mutex_unlock(&tty->ldisc_mutex); |
685 | unlock_kernel(); |
686 | return retval; |
687 | } |
688 | |
689 | /** |
690 | * tty_reset_termios - reset terminal state |
691 | * @tty: tty to reset |
692 | * |
693 | * Restore a terminal to the driver default state. |
694 | */ |
695 | |
696 | static void tty_reset_termios(struct tty_struct *tty) |
697 | { |
698 | mutex_lock(&tty->termios_mutex); |
699 | *tty->termios = tty->driver->init_termios; |
700 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); |
701 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); |
702 | mutex_unlock(&tty->termios_mutex); |
703 | } |
704 | |
705 | |
706 | /** |
707 | * tty_ldisc_reinit - reinitialise the tty ldisc |
708 | * @tty: tty to reinit |
709 | * @ldisc: line discipline to reinitialize |
710 | * |
711 | * Switch the tty to a line discipline and leave the ldisc |
712 | * state closed |
713 | */ |
714 | |
715 | static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
716 | { |
717 | struct tty_ldisc *ld; |
718 | |
719 | tty_ldisc_close(tty, tty->ldisc); |
720 | tty_ldisc_put(tty->ldisc); |
721 | tty->ldisc = NULL; |
722 | /* |
723 | * Switch the line discipline back |
724 | */ |
725 | ld = tty_ldisc_get(ldisc); |
726 | BUG_ON(IS_ERR(ld)); |
727 | tty_ldisc_assign(tty, ld); |
728 | tty_set_termios_ldisc(tty, ldisc); |
729 | } |
730 | |
731 | /** |
732 | * tty_ldisc_hangup - hangup ldisc reset |
733 | * @tty: tty being hung up |
734 | * |
735 | * Some tty devices reset their termios when they receive a hangup |
736 | * event. In that situation we must also switch back to N_TTY properly |
737 | * before we reset the termios data. |
738 | * |
739 | * Locking: We can take the ldisc mutex as the rest of the code is |
740 | * careful to allow for this. |
741 | * |
742 | * In the pty pair case this occurs in the close() path of the |
743 | * tty itself so we must be careful about locking rules. |
744 | */ |
745 | |
746 | void tty_ldisc_hangup(struct tty_struct *tty) |
747 | { |
748 | struct tty_ldisc *ld; |
749 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
750 | int err = 0; |
751 | |
752 | /* |
753 | * FIXME! What are the locking issues here? This may me overdoing |
754 | * things... This question is especially important now that we've |
755 | * removed the irqlock. |
756 | */ |
757 | ld = tty_ldisc_ref(tty); |
758 | if (ld != NULL) { |
759 | /* We may have no line discipline at this point */ |
760 | if (ld->ops->flush_buffer) |
761 | ld->ops->flush_buffer(tty); |
762 | tty_driver_flush_buffer(tty); |
763 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && |
764 | ld->ops->write_wakeup) |
765 | ld->ops->write_wakeup(tty); |
766 | if (ld->ops->hangup) |
767 | ld->ops->hangup(tty); |
768 | tty_ldisc_deref(ld); |
769 | } |
770 | /* |
771 | * FIXME: Once we trust the LDISC code better we can wait here for |
772 | * ldisc completion and fix the driver call race |
773 | */ |
774 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
775 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); |
776 | /* |
777 | * Shutdown the current line discipline, and reset it to |
778 | * N_TTY if need be. |
779 | * |
780 | * Avoid racing set_ldisc or tty_ldisc_release |
781 | */ |
782 | mutex_lock(&tty->ldisc_mutex); |
783 | tty_ldisc_halt(tty); |
784 | /* At this point we have a closed ldisc and we want to |
785 | reopen it. We could defer this to the next open but |
786 | it means auditing a lot of other paths so this is |
787 | a FIXME */ |
788 | if (tty->ldisc) { /* Not yet closed */ |
789 | if (reset == 0) { |
790 | tty_ldisc_reinit(tty, tty->termios->c_line); |
791 | err = tty_ldisc_open(tty, tty->ldisc); |
792 | } |
793 | /* If the re-open fails or we reset then go to N_TTY. The |
794 | N_TTY open cannot fail */ |
795 | if (reset || err) { |
796 | tty_ldisc_reinit(tty, N_TTY); |
797 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
798 | } |
799 | tty_ldisc_enable(tty); |
800 | } |
801 | mutex_unlock(&tty->ldisc_mutex); |
802 | if (reset) |
803 | tty_reset_termios(tty); |
804 | } |
805 | |
806 | /** |
807 | * tty_ldisc_setup - open line discipline |
808 | * @tty: tty being shut down |
809 | * @o_tty: pair tty for pty/tty pairs |
810 | * |
811 | * Called during the initial open of a tty/pty pair in order to set up the |
812 | * line disciplines and bind them to the tty. This has no locking issues |
813 | * as the device isn't yet active. |
814 | */ |
815 | |
816 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) |
817 | { |
818 | struct tty_ldisc *ld = tty->ldisc; |
819 | int retval; |
820 | |
821 | retval = tty_ldisc_open(tty, ld); |
822 | if (retval) |
823 | return retval; |
824 | |
825 | if (o_tty) { |
826 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
827 | if (retval) { |
828 | tty_ldisc_close(tty, ld); |
829 | return retval; |
830 | } |
831 | tty_ldisc_enable(o_tty); |
832 | } |
833 | tty_ldisc_enable(tty); |
834 | return 0; |
835 | } |
836 | /** |
837 | * tty_ldisc_release - release line discipline |
838 | * @tty: tty being shut down |
839 | * @o_tty: pair tty for pty/tty pairs |
840 | * |
841 | * Called during the final close of a tty/pty pair in order to shut down |
842 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the |
843 | * ldisc has not been opened. |
844 | */ |
845 | |
846 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) |
847 | { |
848 | /* |
849 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then |
850 | * kill any delayed work. As this is the final close it does not |
851 | * race with the set_ldisc code path. |
852 | */ |
853 | |
854 | tty_ldisc_halt(tty); |
855 | flush_scheduled_work(); |
856 | |
857 | mutex_lock(&tty->ldisc_mutex); |
858 | /* |
859 | * Now kill off the ldisc |
860 | */ |
861 | tty_ldisc_close(tty, tty->ldisc); |
862 | tty_ldisc_put(tty->ldisc); |
863 | /* Force an oops if we mess this up */ |
864 | tty->ldisc = NULL; |
865 | |
866 | /* Ensure the next open requests the N_TTY ldisc */ |
867 | tty_set_termios_ldisc(tty, N_TTY); |
868 | mutex_unlock(&tty->ldisc_mutex); |
869 | |
870 | /* This will need doing differently if we need to lock */ |
871 | if (o_tty) |
872 | tty_ldisc_release(o_tty, NULL); |
873 | |
874 | /* And the memory resources remaining (buffers, termios) will be |
875 | disposed of when the kref hits zero */ |
876 | } |
877 | |
878 | /** |
879 | * tty_ldisc_init - ldisc setup for new tty |
880 | * @tty: tty being allocated |
881 | * |
882 | * Set up the line discipline objects for a newly allocated tty. Note that |
883 | * the tty structure is not completely set up when this call is made. |
884 | */ |
885 | |
886 | void tty_ldisc_init(struct tty_struct *tty) |
887 | { |
888 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
889 | if (IS_ERR(ld)) |
890 | panic("n_tty: init_tty"); |
891 | tty_ldisc_assign(tty, ld); |
892 | } |
893 | |
894 | void tty_ldisc_begin(void) |
895 | { |
896 | /* Setup the default TTY line discipline. */ |
897 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); |
898 | } |
899 |
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