Commit | Line | Data |
---|---|---|
01e1abb2 AC |
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/fdtable.h> | |
14 | #include <linux/console.h> | |
15 | #include <linux/timer.h> | |
16 | #include <linux/ctype.h> | |
17 | #include <linux/kd.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/string.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/poll.h> | |
22 | #include <linux/proc_fs.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/smp_lock.h> | |
26 | #include <linux/device.h> | |
27 | #include <linux/wait.h> | |
28 | #include <linux/bitops.h> | |
29 | #include <linux/delay.h> | |
30 | #include <linux/seq_file.h> | |
31 | ||
32 | #include <linux/uaccess.h> | |
33 | #include <asm/system.h> | |
34 | ||
35 | #include <linux/kbd_kern.h> | |
36 | #include <linux/vt_kern.h> | |
37 | #include <linux/selection.h> | |
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 | /** | |
54 | * tty_register_ldisc - install a line discipline | |
55 | * @disc: ldisc number | |
56 | * @new_ldisc: pointer to the ldisc object | |
57 | * | |
58 | * Installs a new line discipline into the kernel. The discipline | |
59 | * is set up as unreferenced and then made available to the kernel | |
60 | * from this point onwards. | |
61 | * | |
62 | * Locking: | |
63 | * takes tty_ldisc_lock to guard against ldisc races | |
64 | */ | |
65 | ||
66 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
67 | { | |
68 | unsigned long flags; | |
69 | int ret = 0; | |
70 | ||
71 | if (disc < N_TTY || disc >= NR_LDISCS) | |
72 | return -EINVAL; | |
73 | ||
74 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
75 | tty_ldiscs[disc] = new_ldisc; | |
76 | new_ldisc->num = disc; | |
77 | new_ldisc->refcount = 0; | |
78 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
79 | ||
80 | return ret; | |
81 | } | |
82 | EXPORT_SYMBOL(tty_register_ldisc); | |
83 | ||
84 | /** | |
85 | * tty_unregister_ldisc - unload a line discipline | |
86 | * @disc: ldisc number | |
87 | * @new_ldisc: pointer to the ldisc object | |
88 | * | |
89 | * Remove a line discipline from the kernel providing it is not | |
90 | * currently in use. | |
91 | * | |
92 | * Locking: | |
93 | * takes tty_ldisc_lock to guard against ldisc races | |
94 | */ | |
95 | ||
96 | int tty_unregister_ldisc(int disc) | |
97 | { | |
98 | unsigned long flags; | |
99 | int ret = 0; | |
100 | ||
101 | if (disc < N_TTY || disc >= NR_LDISCS) | |
102 | return -EINVAL; | |
103 | ||
104 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
105 | if (tty_ldiscs[disc]->refcount) | |
106 | ret = -EBUSY; | |
107 | else | |
108 | tty_ldiscs[disc] = NULL; | |
109 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
110 | ||
111 | return ret; | |
112 | } | |
113 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
114 | ||
115 | ||
116 | /** | |
117 | * tty_ldisc_try_get - try and reference an ldisc | |
118 | * @disc: ldisc number | |
119 | * @ld: tty ldisc structure to complete | |
120 | * | |
121 | * Attempt to open and lock a line discipline into place. Return | |
122 | * the line discipline refcounted and assigned in ld. On an error | |
123 | * report the error code back | |
124 | */ | |
125 | ||
126 | static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld) | |
127 | { | |
128 | unsigned long flags; | |
129 | struct tty_ldisc_ops *ldops; | |
130 | int err = -EINVAL; | |
131 | ||
132 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
133 | ld->ops = NULL; | |
134 | ldops = tty_ldiscs[disc]; | |
135 | /* Check the entry is defined */ | |
136 | if (ldops) { | |
137 | /* If the module is being unloaded we can't use it */ | |
138 | if (!try_module_get(ldops->owner)) | |
139 | err = -EAGAIN; | |
140 | else { | |
141 | /* lock it */ | |
142 | ldops->refcount++; | |
143 | ld->ops = ldops; | |
144 | err = 0; | |
145 | } | |
146 | } | |
147 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
148 | return err; | |
149 | } | |
150 | ||
151 | /** | |
152 | * tty_ldisc_get - take a reference to an ldisc | |
153 | * @disc: ldisc number | |
154 | * @ld: tty line discipline structure to use | |
155 | * | |
156 | * Takes a reference to a line discipline. Deals with refcounts and | |
157 | * module locking counts. Returns NULL if the discipline is not available. | |
158 | * Returns a pointer to the discipline and bumps the ref count if it is | |
159 | * available | |
160 | * | |
161 | * Locking: | |
162 | * takes tty_ldisc_lock to guard against ldisc races | |
163 | */ | |
164 | ||
165 | static int tty_ldisc_get(int disc, struct tty_ldisc *ld) | |
166 | { | |
167 | int err; | |
168 | ||
169 | if (disc < N_TTY || disc >= NR_LDISCS) | |
170 | return -EINVAL; | |
171 | err = tty_ldisc_try_get(disc, ld); | |
3ab36ab6 | 172 | if (err < 0) { |
01e1abb2 AC |
173 | request_module("tty-ldisc-%d", disc); |
174 | err = tty_ldisc_try_get(disc, ld); | |
175 | } | |
176 | return err; | |
177 | } | |
178 | ||
179 | /** | |
180 | * tty_ldisc_put - drop ldisc reference | |
181 | * @disc: ldisc number | |
182 | * | |
183 | * Drop a reference to a line discipline. Manage refcounts and | |
184 | * module usage counts | |
185 | * | |
186 | * Locking: | |
187 | * takes tty_ldisc_lock to guard against ldisc races | |
188 | */ | |
189 | ||
190 | static void tty_ldisc_put(struct tty_ldisc_ops *ld) | |
191 | { | |
192 | unsigned long flags; | |
193 | int disc = ld->num; | |
194 | ||
195 | BUG_ON(disc < N_TTY || disc >= NR_LDISCS); | |
196 | ||
197 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
198 | ld = tty_ldiscs[disc]; | |
199 | BUG_ON(ld->refcount == 0); | |
200 | ld->refcount--; | |
201 | module_put(ld->owner); | |
202 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
203 | } | |
204 | ||
205 | static void * tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) | |
206 | { | |
207 | return (*pos < NR_LDISCS) ? pos : NULL; | |
208 | } | |
209 | ||
210 | static void * tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) | |
211 | { | |
212 | (*pos)++; | |
213 | return (*pos < NR_LDISCS) ? pos : NULL; | |
214 | } | |
215 | ||
216 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
217 | { | |
218 | } | |
219 | ||
220 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
221 | { | |
222 | int i = *(loff_t *)v; | |
223 | struct tty_ldisc ld; | |
224 | ||
225 | if (tty_ldisc_get(i, &ld) < 0) | |
226 | return 0; | |
227 | seq_printf(m, "%-10s %2d\n", ld.ops->name ? ld.ops->name : "???", i); | |
228 | tty_ldisc_put(ld.ops); | |
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_assign - set ldisc on a tty | |
254 | * @tty: tty to assign | |
255 | * @ld: line discipline | |
256 | * | |
257 | * Install an instance of a line discipline into a tty structure. The | |
258 | * ldisc must have a reference count above zero to ensure it remains/ | |
259 | * The tty instance refcount starts at zero. | |
260 | * | |
261 | * Locking: | |
262 | * Caller must hold references | |
263 | */ | |
264 | ||
265 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
266 | { | |
267 | ld->refcount = 0; | |
268 | tty->ldisc = *ld; | |
269 | } | |
270 | ||
271 | /** | |
272 | * tty_ldisc_try - internal helper | |
273 | * @tty: the tty | |
274 | * | |
275 | * Make a single attempt to grab and bump the refcount on | |
276 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
277 | * used to implement both the waiting and non waiting versions | |
278 | * of tty_ldisc_ref | |
279 | * | |
280 | * Locking: takes tty_ldisc_lock | |
281 | */ | |
282 | ||
283 | static int tty_ldisc_try(struct tty_struct *tty) | |
284 | { | |
285 | unsigned long flags; | |
286 | struct tty_ldisc *ld; | |
287 | int ret = 0; | |
288 | ||
289 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
290 | ld = &tty->ldisc; | |
291 | if (test_bit(TTY_LDISC, &tty->flags)) { | |
292 | ld->refcount++; | |
293 | ret = 1; | |
294 | } | |
295 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
296 | return ret; | |
297 | } | |
298 | ||
299 | /** | |
300 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
301 | * @tty: tty device | |
302 | * | |
303 | * Dereference the line discipline for the terminal and take a | |
304 | * reference to it. If the line discipline is in flux then | |
305 | * wait patiently until it changes. | |
306 | * | |
307 | * Note: Must not be called from an IRQ/timer context. The caller | |
308 | * must also be careful not to hold other locks that will deadlock | |
309 | * against a discipline change, such as an existing ldisc reference | |
310 | * (which we check for) | |
311 | * | |
312 | * Locking: call functions take tty_ldisc_lock | |
313 | */ | |
314 | ||
315 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
316 | { | |
317 | /* wait_event is a macro */ | |
318 | wait_event(tty_ldisc_wait, tty_ldisc_try(tty)); | |
c9b3976e | 319 | WARN_ON(tty->ldisc.refcount == 0); |
01e1abb2 AC |
320 | return &tty->ldisc; |
321 | } | |
322 | ||
323 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); | |
324 | ||
325 | /** | |
326 | * tty_ldisc_ref - get the tty ldisc | |
327 | * @tty: tty device | |
328 | * | |
329 | * Dereference the line discipline for the terminal and take a | |
330 | * reference to it. If the line discipline is in flux then | |
331 | * return NULL. Can be called from IRQ and timer functions. | |
332 | * | |
333 | * Locking: called functions take tty_ldisc_lock | |
334 | */ | |
335 | ||
336 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
337 | { | |
338 | if (tty_ldisc_try(tty)) | |
339 | return &tty->ldisc; | |
340 | return NULL; | |
341 | } | |
342 | ||
343 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); | |
344 | ||
345 | /** | |
346 | * tty_ldisc_deref - free a tty ldisc reference | |
347 | * @ld: reference to free up | |
348 | * | |
349 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
350 | * be called in IRQ context. | |
351 | * | |
352 | * Locking: takes tty_ldisc_lock | |
353 | */ | |
354 | ||
355 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
356 | { | |
357 | unsigned long flags; | |
358 | ||
359 | BUG_ON(ld == NULL); | |
360 | ||
361 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
362 | if (ld->refcount == 0) | |
363 | printk(KERN_ERR "tty_ldisc_deref: no references.\n"); | |
364 | else | |
365 | ld->refcount--; | |
366 | if (ld->refcount == 0) | |
367 | wake_up(&tty_ldisc_wait); | |
368 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
369 | } | |
370 | ||
371 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); | |
372 | ||
373 | /** | |
374 | * tty_ldisc_enable - allow ldisc use | |
375 | * @tty: terminal to activate ldisc on | |
376 | * | |
377 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
378 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
379 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 380 | * |
c9b3976e AC |
381 | * Note: nobody should set the TTY_LDISC bit except via this function. |
382 | * Clearing directly is allowed. | |
01e1abb2 AC |
383 | */ |
384 | ||
385 | void tty_ldisc_enable(struct tty_struct *tty) | |
386 | { | |
387 | set_bit(TTY_LDISC, &tty->flags); | |
c9b3976e | 388 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
389 | wake_up(&tty_ldisc_wait); |
390 | } | |
391 | ||
392 | /** | |
393 | * tty_set_termios_ldisc - set ldisc field | |
394 | * @tty: tty structure | |
395 | * @num: line discipline number | |
396 | * | |
397 | * This is probably overkill for real world processors but | |
398 | * they are not on hot paths so a little discipline won't do | |
399 | * any harm. | |
400 | * | |
401 | * Locking: takes termios_mutex | |
402 | */ | |
403 | ||
404 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
405 | { | |
406 | mutex_lock(&tty->termios_mutex); | |
407 | tty->termios->c_line = num; | |
408 | mutex_unlock(&tty->termios_mutex); | |
409 | } | |
410 | ||
411 | ||
412 | /** | |
413 | * tty_ldisc_restore - helper for tty ldisc change | |
414 | * @tty: tty to recover | |
415 | * @old: previous ldisc | |
416 | * | |
417 | * Restore the previous line discipline or N_TTY when a line discipline | |
418 | * change fails due to an open error | |
419 | */ | |
420 | ||
421 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
422 | { | |
423 | char buf[64]; | |
424 | struct tty_ldisc new_ldisc; | |
425 | ||
426 | /* There is an outstanding reference here so this is safe */ | |
427 | tty_ldisc_get(old->ops->num, old); | |
428 | tty_ldisc_assign(tty, old); | |
429 | tty_set_termios_ldisc(tty, old->ops->num); | |
430 | if (old->ops->open && (old->ops->open(tty) < 0)) { | |
431 | tty_ldisc_put(old->ops); | |
432 | /* This driver is always present */ | |
433 | if (tty_ldisc_get(N_TTY, &new_ldisc) < 0) | |
434 | panic("n_tty: get"); | |
435 | tty_ldisc_assign(tty, &new_ldisc); | |
436 | tty_set_termios_ldisc(tty, N_TTY); | |
437 | if (new_ldisc.ops->open) { | |
438 | int r = new_ldisc.ops->open(tty); | |
439 | if (r < 0) | |
440 | panic("Couldn't open N_TTY ldisc for " | |
441 | "%s --- error %d.", | |
442 | tty_name(tty, buf), r); | |
443 | } | |
444 | } | |
445 | } | |
446 | ||
447 | /** | |
448 | * tty_set_ldisc - set line discipline | |
449 | * @tty: the terminal to set | |
450 | * @ldisc: the line discipline | |
451 | * | |
452 | * Set the discipline of a tty line. Must be called from a process | |
453 | * context. | |
454 | * | |
455 | * Locking: takes tty_ldisc_lock. | |
456 | * called functions take termios_mutex | |
457 | */ | |
458 | ||
459 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
460 | { | |
461 | int retval; | |
462 | struct tty_ldisc o_ldisc, new_ldisc; | |
463 | int work; | |
464 | unsigned long flags; | |
465 | struct tty_struct *o_tty; | |
466 | ||
467 | restart: | |
468 | /* This is a bit ugly for now but means we can break the 'ldisc | |
469 | is part of the tty struct' assumption later */ | |
470 | retval = tty_ldisc_get(ldisc, &new_ldisc); | |
471 | if (retval) | |
472 | return retval; | |
473 | ||
474 | /* | |
475 | * Problem: What do we do if this blocks ? | |
476 | */ | |
477 | ||
478 | tty_wait_until_sent(tty, 0); | |
479 | ||
480 | if (tty->ldisc.ops->num == ldisc) { | |
481 | tty_ldisc_put(new_ldisc.ops); | |
482 | return 0; | |
483 | } | |
484 | ||
485 | /* | |
486 | * No more input please, we are switching. The new ldisc | |
487 | * will update this value in the ldisc open function | |
488 | */ | |
489 | ||
490 | tty->receive_room = 0; | |
491 | ||
492 | o_ldisc = tty->ldisc; | |
493 | o_tty = tty->link; | |
494 | ||
495 | /* | |
496 | * Make sure we don't change while someone holds a | |
497 | * reference to the line discipline. The TTY_LDISC bit | |
498 | * prevents anyone taking a reference once it is clear. | |
499 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
500 | * |
501 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
502 | * with a userspace app continually trying to use the tty in | |
503 | * parallel to the change and re-referencing the tty. | |
01e1abb2 | 504 | */ |
c9b3976e AC |
505 | clear_bit(TTY_LDISC, &tty->flags); |
506 | if (o_tty) | |
507 | clear_bit(TTY_LDISC, &o_tty->flags); | |
01e1abb2 AC |
508 | |
509 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
510 | if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) { | |
511 | if (tty->ldisc.refcount) { | |
512 | /* Free the new ldisc we grabbed. Must drop the lock | |
513 | first. */ | |
514 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
515 | tty_ldisc_put(o_ldisc.ops); | |
516 | /* | |
517 | * There are several reasons we may be busy, including | |
518 | * random momentary I/O traffic. We must therefore | |
519 | * retry. We could distinguish between blocking ops | |
520 | * and retries if we made tty_ldisc_wait() smarter. | |
521 | * That is up for discussion. | |
522 | */ | |
523 | if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0) | |
524 | return -ERESTARTSYS; | |
525 | goto restart; | |
526 | } | |
527 | if (o_tty && o_tty->ldisc.refcount) { | |
528 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
529 | tty_ldisc_put(o_tty->ldisc.ops); | |
530 | if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0) | |
531 | return -ERESTARTSYS; | |
532 | goto restart; | |
533 | } | |
534 | } | |
535 | /* | |
536 | * If the TTY_LDISC bit is set, then we are racing against | |
537 | * another ldisc change | |
538 | */ | |
c9b3976e | 539 | if (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { |
01e1abb2 AC |
540 | struct tty_ldisc *ld; |
541 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
542 | tty_ldisc_put(new_ldisc.ops); | |
543 | ld = tty_ldisc_ref_wait(tty); | |
544 | tty_ldisc_deref(ld); | |
545 | goto restart; | |
546 | } | |
c9b3976e AC |
547 | /* |
548 | * This flag is used to avoid two parallel ldisc changes. Once | |
549 | * open and close are fine grained locked this may work better | |
550 | * as a mutex shared with the open/close/hup paths | |
551 | */ | |
552 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
01e1abb2 | 553 | if (o_tty) |
c9b3976e | 554 | set_bit(TTY_LDISC_CHANGING, &o_tty->flags); |
01e1abb2 AC |
555 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
556 | ||
557 | /* | |
558 | * From this point on we know nobody has an ldisc | |
559 | * usage reference, nor can they obtain one until | |
560 | * we say so later on. | |
561 | */ | |
562 | ||
563 | work = cancel_delayed_work(&tty->buf.work); | |
564 | /* | |
565 | * Wait for ->hangup_work and ->buf.work handlers to terminate | |
566 | * MUST NOT hold locks here. | |
567 | */ | |
568 | flush_scheduled_work(); | |
569 | /* Shutdown the current discipline. */ | |
570 | if (o_ldisc.ops->close) | |
571 | (o_ldisc.ops->close)(tty); | |
572 | ||
573 | /* Now set up the new line discipline. */ | |
574 | tty_ldisc_assign(tty, &new_ldisc); | |
575 | tty_set_termios_ldisc(tty, ldisc); | |
576 | if (new_ldisc.ops->open) | |
577 | retval = (new_ldisc.ops->open)(tty); | |
578 | if (retval < 0) { | |
579 | tty_ldisc_put(new_ldisc.ops); | |
580 | tty_ldisc_restore(tty, &o_ldisc); | |
581 | } | |
582 | /* At this point we hold a reference to the new ldisc and a | |
583 | a reference to the old ldisc. If we ended up flipping back | |
584 | to the existing ldisc we have two references to it */ | |
585 | ||
586 | if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc) | |
587 | tty->ops->set_ldisc(tty); | |
588 | ||
589 | tty_ldisc_put(o_ldisc.ops); | |
590 | ||
591 | /* | |
592 | * Allow ldisc referencing to occur as soon as the driver | |
593 | * ldisc callback completes. | |
594 | */ | |
595 | ||
596 | tty_ldisc_enable(tty); | |
597 | if (o_tty) | |
598 | tty_ldisc_enable(o_tty); | |
599 | ||
600 | /* Restart it in case no characters kick it off. Safe if | |
601 | already running */ | |
602 | if (work) | |
603 | schedule_delayed_work(&tty->buf.work, 1); | |
604 | return retval; | |
605 | } | |
606 | ||
607 | ||
608 | /** | |
609 | * tty_ldisc_setup - open line discipline | |
610 | * @tty: tty being shut down | |
611 | * @o_tty: pair tty for pty/tty pairs | |
612 | * | |
613 | * Called during the initial open of a tty/pty pair in order to set up the | |
614 | * line discplines and bind them to the tty. | |
615 | */ | |
616 | ||
617 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
618 | { | |
619 | struct tty_ldisc *ld = &tty->ldisc; | |
620 | int retval; | |
621 | ||
622 | if (ld->ops->open) { | |
623 | retval = (ld->ops->open)(tty); | |
624 | if (retval) | |
625 | return retval; | |
626 | } | |
627 | if (o_tty && o_tty->ldisc.ops->open) { | |
628 | retval = (o_tty->ldisc.ops->open)(o_tty); | |
629 | if (retval) { | |
630 | if (ld->ops->close) | |
631 | (ld->ops->close)(tty); | |
632 | return retval; | |
633 | } | |
634 | tty_ldisc_enable(o_tty); | |
635 | } | |
636 | tty_ldisc_enable(tty); | |
637 | return 0; | |
638 | } | |
639 | ||
640 | /** | |
641 | * tty_ldisc_release - release line discipline | |
642 | * @tty: tty being shut down | |
643 | * @o_tty: pair tty for pty/tty pairs | |
644 | * | |
645 | * Called during the final close of a tty/pty pair in order to shut down the | |
646 | * line discpline layer. | |
647 | */ | |
648 | ||
649 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
650 | { | |
651 | unsigned long flags; | |
652 | struct tty_ldisc ld; | |
653 | /* | |
654 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then | |
655 | * kill any delayed work. As this is the final close it does not | |
656 | * race with the set_ldisc code path. | |
657 | */ | |
658 | clear_bit(TTY_LDISC, &tty->flags); | |
659 | cancel_delayed_work(&tty->buf.work); | |
660 | ||
661 | /* | |
662 | * Wait for ->hangup_work and ->buf.work handlers to terminate | |
663 | */ | |
664 | ||
665 | flush_scheduled_work(); | |
666 | ||
667 | /* | |
668 | * Wait for any short term users (we know they are just driver | |
669 | * side waiters as the file is closing so user count on the file | |
670 | * side is zero. | |
671 | */ | |
672 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
673 | while (tty->ldisc.refcount) { | |
674 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
675 | wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0); | |
676 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
677 | } | |
678 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
679 | /* | |
680 | * Shutdown the current line discipline, and reset it to N_TTY. | |
681 | * | |
682 | * FIXME: this MUST get fixed for the new reflocking | |
683 | */ | |
684 | if (tty->ldisc.ops->close) | |
685 | (tty->ldisc.ops->close)(tty); | |
686 | tty_ldisc_put(tty->ldisc.ops); | |
687 | ||
688 | /* | |
689 | * Switch the line discipline back | |
690 | */ | |
691 | WARN_ON(tty_ldisc_get(N_TTY, &ld)); | |
692 | tty_ldisc_assign(tty, &ld); | |
693 | tty_set_termios_ldisc(tty, N_TTY); | |
694 | if (o_tty) { | |
695 | /* FIXME: could o_tty be in setldisc here ? */ | |
696 | clear_bit(TTY_LDISC, &o_tty->flags); | |
697 | if (o_tty->ldisc.ops->close) | |
698 | (o_tty->ldisc.ops->close)(o_tty); | |
699 | tty_ldisc_put(o_tty->ldisc.ops); | |
700 | WARN_ON(tty_ldisc_get(N_TTY, &ld)); | |
701 | tty_ldisc_assign(o_tty, &ld); | |
702 | tty_set_termios_ldisc(o_tty, N_TTY); | |
703 | } | |
704 | } | |
705 | ||
706 | /** | |
707 | * tty_ldisc_init - ldisc setup for new tty | |
708 | * @tty: tty being allocated | |
709 | * | |
710 | * Set up the line discipline objects for a newly allocated tty. Note that | |
711 | * the tty structure is not completely set up when this call is made. | |
712 | */ | |
713 | ||
714 | void tty_ldisc_init(struct tty_struct *tty) | |
715 | { | |
716 | struct tty_ldisc ld; | |
717 | if (tty_ldisc_get(N_TTY, &ld) < 0) | |
718 | panic("n_tty: init_tty"); | |
719 | tty_ldisc_assign(tty, &ld); | |
720 | } | |
721 | ||
722 | void tty_ldisc_begin(void) | |
723 | { | |
724 | /* Setup the default TTY line discipline. */ | |
725 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
726 | } |