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 | 22 | |
fc575ee6 PH |
23 | #undef LDISC_DEBUG_HANGUP |
24 | ||
25 | #ifdef LDISC_DEBUG_HANGUP | |
26 | #define tty_ldisc_debug(tty, f, args...) ({ \ | |
27 | char __b[64]; \ | |
28 | printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \ | |
29 | }) | |
30 | #else | |
31 | #define tty_ldisc_debug(tty, f, args...) | |
32 | #endif | |
33 | ||
6fa3eb70 S |
34 | /* lockdep nested classes for tty->ldisc_sem */ |
35 | enum { | |
36 | LDISC_SEM_NORMAL, | |
37 | LDISC_SEM_OTHER, | |
38 | }; | |
39 | ||
40 | ||
01e1abb2 AC |
41 | /* |
42 | * This guards the refcounted line discipline lists. The lock | |
43 | * must be taken with irqs off because there are hangup path | |
44 | * callers who will do ldisc lookups and cannot sleep. | |
45 | */ | |
46 | ||
6fa3eb70 | 47 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
48 | /* Line disc dispatch table */ |
49 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
50 | ||
51 | /** | |
52 | * tty_register_ldisc - install a line discipline | |
53 | * @disc: ldisc number | |
54 | * @new_ldisc: pointer to the ldisc object | |
55 | * | |
56 | * Installs a new line discipline into the kernel. The discipline | |
57 | * is set up as unreferenced and then made available to the kernel | |
58 | * from this point onwards. | |
59 | * | |
60 | * Locking: | |
6fa3eb70 | 61 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
62 | */ |
63 | ||
64 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
65 | { | |
66 | unsigned long flags; | |
67 | int ret = 0; | |
68 | ||
69 | if (disc < N_TTY || disc >= NR_LDISCS) | |
70 | return -EINVAL; | |
71 | ||
6fa3eb70 | 72 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
73 | tty_ldiscs[disc] = new_ldisc; |
74 | new_ldisc->num = disc; | |
75 | new_ldisc->refcount = 0; | |
6fa3eb70 | 76 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
77 | |
78 | return ret; | |
79 | } | |
80 | EXPORT_SYMBOL(tty_register_ldisc); | |
81 | ||
82 | /** | |
83 | * tty_unregister_ldisc - unload a line discipline | |
84 | * @disc: ldisc number | |
85 | * @new_ldisc: pointer to the ldisc object | |
86 | * | |
87 | * Remove a line discipline from the kernel providing it is not | |
88 | * currently in use. | |
89 | * | |
90 | * Locking: | |
6fa3eb70 | 91 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
92 | */ |
93 | ||
94 | int tty_unregister_ldisc(int disc) | |
95 | { | |
96 | unsigned long flags; | |
97 | int ret = 0; | |
98 | ||
99 | if (disc < N_TTY || disc >= NR_LDISCS) | |
100 | return -EINVAL; | |
101 | ||
6fa3eb70 | 102 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
103 | if (tty_ldiscs[disc]->refcount) |
104 | ret = -EBUSY; | |
105 | else | |
106 | tty_ldiscs[disc] = NULL; | |
6fa3eb70 | 107 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
108 | |
109 | return ret; | |
110 | } | |
111 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
112 | ||
f0de0e8d LT |
113 | static struct tty_ldisc_ops *get_ldops(int disc) |
114 | { | |
115 | unsigned long flags; | |
116 | struct tty_ldisc_ops *ldops, *ret; | |
117 | ||
6fa3eb70 | 118 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
119 | ret = ERR_PTR(-EINVAL); |
120 | ldops = tty_ldiscs[disc]; | |
121 | if (ldops) { | |
122 | ret = ERR_PTR(-EAGAIN); | |
123 | if (try_module_get(ldops->owner)) { | |
124 | ldops->refcount++; | |
125 | ret = ldops; | |
126 | } | |
127 | } | |
6fa3eb70 | 128 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
129 | return ret; |
130 | } | |
131 | ||
132 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
133 | { | |
134 | unsigned long flags; | |
135 | ||
6fa3eb70 | 136 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
137 | ldops->refcount--; |
138 | module_put(ldops->owner); | |
6fa3eb70 | 139 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 140 | } |
01e1abb2 | 141 | |
01e1abb2 AC |
142 | /** |
143 | * tty_ldisc_get - take a reference to an ldisc | |
144 | * @disc: ldisc number | |
01e1abb2 AC |
145 | * |
146 | * Takes a reference to a line discipline. Deals with refcounts and | |
147 | * module locking counts. Returns NULL if the discipline is not available. | |
148 | * Returns a pointer to the discipline and bumps the ref count if it is | |
149 | * available | |
150 | * | |
151 | * Locking: | |
6fa3eb70 | 152 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
153 | */ |
154 | ||
6fa3eb70 | 155 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 156 | { |
c65c9bc3 | 157 | struct tty_ldisc *ld; |
182274f8 | 158 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
159 | |
160 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 161 | return ERR_PTR(-EINVAL); |
182274f8 LT |
162 | |
163 | /* | |
164 | * Get the ldisc ops - we may need to request them to be loaded | |
165 | * dynamically and try again. | |
166 | */ | |
167 | ldops = get_ldops(disc); | |
168 | if (IS_ERR(ldops)) { | |
01e1abb2 | 169 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
170 | ldops = get_ldops(disc); |
171 | if (IS_ERR(ldops)) | |
172 | return ERR_CAST(ldops); | |
173 | } | |
174 | ||
175 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
176 | if (ld == NULL) { | |
177 | put_ldops(ldops); | |
178 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 179 | } |
182274f8 LT |
180 | |
181 | ld->ops = ldops; | |
6fa3eb70 | 182 | ld->tty = tty; |
1541f845 | 183 | |
c65c9bc3 | 184 | return ld; |
01e1abb2 AC |
185 | } |
186 | ||
734de249 PH |
187 | /** |
188 | * tty_ldisc_put - release the ldisc | |
189 | * | |
190 | * Complement of tty_ldisc_get(). | |
191 | */ | |
192 | static inline void tty_ldisc_put(struct tty_ldisc *ld) | |
193 | { | |
734de249 PH |
194 | if (WARN_ON_ONCE(!ld)) |
195 | return; | |
196 | ||
6fa3eb70 | 197 | put_ldops(ld->ops); |
734de249 | 198 | kfree(ld); |
734de249 PH |
199 | } |
200 | ||
852e99d2 | 201 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
202 | { |
203 | return (*pos < NR_LDISCS) ? pos : NULL; | |
204 | } | |
205 | ||
852e99d2 | 206 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
207 | { |
208 | (*pos)++; | |
209 | return (*pos < NR_LDISCS) ? pos : NULL; | |
210 | } | |
211 | ||
212 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
213 | { | |
214 | } | |
215 | ||
216 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
217 | { | |
218 | int i = *(loff_t *)v; | |
f0de0e8d | 219 | struct tty_ldisc_ops *ldops; |
852e99d2 | 220 | |
f0de0e8d LT |
221 | ldops = get_ldops(i); |
222 | if (IS_ERR(ldops)) | |
01e1abb2 | 223 | return 0; |
f0de0e8d LT |
224 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
225 | put_ldops(ldops); | |
01e1abb2 AC |
226 | return 0; |
227 | } | |
228 | ||
229 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
230 | .start = tty_ldiscs_seq_start, | |
231 | .next = tty_ldiscs_seq_next, | |
232 | .stop = tty_ldiscs_seq_stop, | |
233 | .show = tty_ldiscs_seq_show, | |
234 | }; | |
235 | ||
236 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
237 | { | |
238 | return seq_open(file, &tty_ldiscs_seq_ops); | |
239 | } | |
240 | ||
241 | const struct file_operations tty_ldiscs_proc_fops = { | |
242 | .owner = THIS_MODULE, | |
243 | .open = proc_tty_ldiscs_open, | |
244 | .read = seq_read, | |
245 | .llseek = seq_lseek, | |
246 | .release = seq_release, | |
247 | }; | |
248 | ||
01e1abb2 AC |
249 | /** |
250 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
251 | * @tty: tty device | |
252 | * | |
253 | * Dereference the line discipline for the terminal and take a | |
254 | * reference to it. If the line discipline is in flux then | |
255 | * wait patiently until it changes. | |
256 | * | |
257 | * Note: Must not be called from an IRQ/timer context. The caller | |
258 | * must also be careful not to hold other locks that will deadlock | |
259 | * against a discipline change, such as an existing ldisc reference | |
260 | * (which we check for) | |
261 | * | |
6fa3eb70 S |
262 | * Note: only callable from a file_operations routine (which |
263 | * guarantees tty->ldisc != NULL when the lock is acquired). | |
01e1abb2 AC |
264 | */ |
265 | ||
266 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
267 | { | |
6fa3eb70 S |
268 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
269 | WARN_ON(!tty->ldisc); | |
270 | return tty->ldisc; | |
01e1abb2 | 271 | } |
01e1abb2 AC |
272 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
273 | ||
274 | /** | |
275 | * tty_ldisc_ref - get the tty ldisc | |
276 | * @tty: tty device | |
277 | * | |
278 | * Dereference the line discipline for the terminal and take a | |
279 | * reference to it. If the line discipline is in flux then | |
280 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
281 | */ |
282 | ||
283 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
284 | { | |
6fa3eb70 S |
285 | struct tty_ldisc *ld = NULL; |
286 | ||
287 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
288 | ld = tty->ldisc; | |
289 | if (!ld) | |
290 | ldsem_up_read(&tty->ldisc_sem); | |
291 | } | |
292 | return ld; | |
01e1abb2 | 293 | } |
01e1abb2 AC |
294 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
295 | ||
296 | /** | |
297 | * tty_ldisc_deref - free a tty ldisc reference | |
298 | * @ld: reference to free up | |
299 | * | |
300 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
301 | * be called in IRQ context. | |
01e1abb2 AC |
302 | */ |
303 | ||
304 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
305 | { | |
6fa3eb70 S |
306 | ldsem_up_read(&ld->tty->ldisc_sem); |
307 | } | |
308 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); | |
ebc9baed | 309 | |
ebc9baed | 310 | |
6fa3eb70 S |
311 | static inline int __lockfunc |
312 | tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) | |
313 | { | |
314 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
315 | } | |
ebc9baed | 316 | |
6fa3eb70 S |
317 | static inline int __lockfunc |
318 | tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) | |
319 | { | |
320 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
321 | LDISC_SEM_OTHER, timeout); | |
01e1abb2 | 322 | } |
01e1abb2 | 323 | |
6fa3eb70 S |
324 | static inline void tty_ldisc_unlock(struct tty_struct *tty) |
325 | { | |
326 | return ldsem_up_write(&tty->ldisc_sem); | |
327 | } | |
328 | ||
329 | static int __lockfunc | |
330 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, | |
331 | unsigned long timeout) | |
332 | { | |
333 | int ret; | |
334 | ||
335 | if (tty < tty2) { | |
336 | ret = tty_ldisc_lock(tty, timeout); | |
337 | if (ret) { | |
338 | ret = tty_ldisc_lock_nested(tty2, timeout); | |
339 | if (!ret) | |
340 | tty_ldisc_unlock(tty); | |
341 | } | |
342 | } else { | |
343 | /* if this is possible, it has lots of implications */ | |
344 | WARN_ON_ONCE(tty == tty2); | |
345 | if (tty2 && tty != tty2) { | |
346 | ret = tty_ldisc_lock(tty2, timeout); | |
347 | if (ret) { | |
348 | ret = tty_ldisc_lock_nested(tty, timeout); | |
349 | if (!ret) | |
350 | tty_ldisc_unlock(tty2); | |
351 | } | |
352 | } else | |
353 | ret = tty_ldisc_lock(tty, timeout); | |
354 | } | |
355 | ||
356 | if (!ret) | |
357 | return -EBUSY; | |
358 | ||
359 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
360 | if (tty2) | |
361 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
362 | return 0; | |
363 | } | |
364 | ||
365 | static void __lockfunc | |
366 | tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) | |
367 | { | |
368 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
369 | } | |
01e1abb2 | 370 | |
6fa3eb70 S |
371 | static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, |
372 | struct tty_struct *tty2) | |
373 | { | |
374 | tty_ldisc_unlock(tty); | |
375 | if (tty2) | |
376 | tty_ldisc_unlock(tty2); | |
377 | } | |
378 | ||
379 | static void __lockfunc tty_ldisc_enable_pair(struct tty_struct *tty, | |
380 | struct tty_struct *tty2) | |
01e1abb2 | 381 | { |
21622939 | 382 | clear_bit(TTY_LDISC_HALTED, &tty->flags); |
6fa3eb70 S |
383 | if (tty2) |
384 | clear_bit(TTY_LDISC_HALTED, &tty2->flags); | |
385 | ||
386 | tty_ldisc_unlock_pair(tty, tty2); | |
01e1abb2 AC |
387 | } |
388 | ||
f2c4c65c AC |
389 | /** |
390 | * tty_ldisc_flush - flush line discipline queue | |
391 | * @tty: tty | |
392 | * | |
393 | * Flush the line discipline queue (if any) for this tty. If there | |
394 | * is no line discipline active this is a no-op. | |
395 | */ | |
396 | ||
397 | void tty_ldisc_flush(struct tty_struct *tty) | |
398 | { | |
399 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
400 | if (ld) { | |
401 | if (ld->ops->flush_buffer) | |
402 | ld->ops->flush_buffer(tty); | |
403 | tty_ldisc_deref(ld); | |
404 | } | |
405 | tty_buffer_flush(tty); | |
406 | } | |
f2c4c65c AC |
407 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
408 | ||
01e1abb2 AC |
409 | /** |
410 | * tty_set_termios_ldisc - set ldisc field | |
411 | * @tty: tty structure | |
412 | * @num: line discipline number | |
413 | * | |
414 | * This is probably overkill for real world processors but | |
415 | * they are not on hot paths so a little discipline won't do | |
416 | * any harm. | |
417 | * | |
4b9e9796 S |
418 | * The line discipline-related tty_struct fields are reset to |
419 | * prevent the ldisc driver from re-using stale information for | |
420 | * the new ldisc instance. | |
421 | * | |
01e1abb2 AC |
422 | * Locking: takes termios_mutex |
423 | */ | |
424 | ||
425 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
426 | { | |
427 | mutex_lock(&tty->termios_mutex); | |
adc8d746 | 428 | tty->termios.c_line = num; |
01e1abb2 | 429 | mutex_unlock(&tty->termios_mutex); |
4b9e9796 S |
430 | |
431 | tty->disc_data = NULL; | |
432 | tty->receive_room = 0; | |
01e1abb2 AC |
433 | } |
434 | ||
c65c9bc3 AC |
435 | /** |
436 | * tty_ldisc_open - open a line discipline | |
437 | * @tty: tty we are opening the ldisc on | |
438 | * @ld: discipline to open | |
439 | * | |
440 | * A helper opening method. Also a convenient debugging and check | |
441 | * point. | |
ec79d605 AB |
442 | * |
443 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
444 | */ |
445 | ||
446 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
447 | { | |
448 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
449 | if (ld->ops->open) { |
450 | int ret; | |
ec79d605 | 451 | /* BTM here locks versus a hangup event */ |
f18f9498 | 452 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
453 | if (ret) |
454 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
f18f9498 AC |
455 | return ret; |
456 | } | |
c65c9bc3 AC |
457 | return 0; |
458 | } | |
459 | ||
460 | /** | |
461 | * tty_ldisc_close - close a line discipline | |
462 | * @tty: tty we are opening the ldisc on | |
463 | * @ld: discipline to close | |
464 | * | |
465 | * A helper close method. Also a convenient debugging and check | |
466 | * point. | |
467 | */ | |
468 | ||
469 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
470 | { | |
471 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
472 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
473 | if (ld->ops->close) | |
474 | ld->ops->close(tty); | |
475 | } | |
01e1abb2 AC |
476 | |
477 | /** | |
478 | * tty_ldisc_restore - helper for tty ldisc change | |
479 | * @tty: tty to recover | |
480 | * @old: previous ldisc | |
481 | * | |
482 | * Restore the previous line discipline or N_TTY when a line discipline | |
483 | * change fails due to an open error | |
484 | */ | |
485 | ||
486 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
487 | { | |
488 | char buf[64]; | |
c65c9bc3 AC |
489 | struct tty_ldisc *new_ldisc; |
490 | int r; | |
01e1abb2 AC |
491 | |
492 | /* There is an outstanding reference here so this is safe */ | |
6fa3eb70 | 493 | old = tty_ldisc_get(tty, old->ops->num); |
c65c9bc3 | 494 | WARN_ON(IS_ERR(old)); |
f4807045 | 495 | tty->ldisc = old; |
01e1abb2 | 496 | tty_set_termios_ldisc(tty, old->ops->num); |
c65c9bc3 AC |
497 | if (tty_ldisc_open(tty, old) < 0) { |
498 | tty_ldisc_put(old); | |
01e1abb2 | 499 | /* This driver is always present */ |
6fa3eb70 | 500 | new_ldisc = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 501 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 502 | panic("n_tty: get"); |
f4807045 | 503 | tty->ldisc = new_ldisc; |
01e1abb2 | 504 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
505 | r = tty_ldisc_open(tty, new_ldisc); |
506 | if (r < 0) | |
507 | panic("Couldn't open N_TTY ldisc for " | |
508 | "%s --- error %d.", | |
509 | tty_name(tty, buf), r); | |
01e1abb2 AC |
510 | } |
511 | } | |
512 | ||
513 | /** | |
514 | * tty_set_ldisc - set line discipline | |
515 | * @tty: the terminal to set | |
516 | * @ldisc: the line discipline | |
517 | * | |
518 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
519 | * context. The ldisc change logic has to protect itself against any |
520 | * overlapping ldisc change (including on the other end of pty pairs), | |
521 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
522 | */ |
523 | ||
524 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
525 | { | |
526 | int retval; | |
c65c9bc3 | 527 | struct tty_ldisc *o_ldisc, *new_ldisc; |
6fa3eb70 | 528 | struct tty_struct *o_tty = tty->link; |
01e1abb2 | 529 | |
6fa3eb70 | 530 | new_ldisc = tty_ldisc_get(tty, ldisc); |
c65c9bc3 AC |
531 | if (IS_ERR(new_ldisc)) |
532 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 533 | |
6fa3eb70 S |
534 | retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ); |
535 | if (retval) { | |
536 | tty_ldisc_put(new_ldisc); | |
537 | return retval; | |
538 | } | |
01e1abb2 | 539 | |
c65c9bc3 AC |
540 | /* |
541 | * Check the no-op case | |
542 | */ | |
543 | ||
544 | if (tty->ldisc->ops->num == ldisc) { | |
6fa3eb70 | 545 | tty_ldisc_enable_pair(tty, o_tty); |
c65c9bc3 | 546 | tty_ldisc_put(new_ldisc); |
01e1abb2 AC |
547 | return 0; |
548 | } | |
549 | ||
6fa3eb70 | 550 | /* FIXME: why 'shutoff' input if the ldisc is locked? */ |
01e1abb2 AC |
551 | tty->receive_room = 0; |
552 | ||
553 | o_ldisc = tty->ldisc; | |
89c8d91e | 554 | tty_lock(tty); |
100eeae2 | 555 | |
6fa3eb70 S |
556 | /* FIXME: for testing only */ |
557 | WARN_ON(test_bit(TTY_HUPPED, &tty->flags)); | |
100eeae2 | 558 | |
40c9f61e | 559 | if (test_bit(TTY_HUPPING, &tty->flags)) { |
c65c9bc3 AC |
560 | /* We were raced by the hangup method. It will have stomped |
561 | the ldisc data and closed the ldisc down */ | |
6fa3eb70 | 562 | tty_ldisc_enable_pair(tty, o_tty); |
c65c9bc3 | 563 | tty_ldisc_put(new_ldisc); |
89c8d91e | 564 | tty_unlock(tty); |
c65c9bc3 AC |
565 | return -EIO; |
566 | } | |
567 | ||
01e1abb2 | 568 | /* Shutdown the current discipline. */ |
c65c9bc3 | 569 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
570 | |
571 | /* Now set up the new line discipline. */ | |
f4807045 | 572 | tty->ldisc = new_ldisc; |
01e1abb2 | 573 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
574 | |
575 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 576 | if (retval < 0) { |
c65c9bc3 AC |
577 | /* Back to the old one or N_TTY if we can't */ |
578 | tty_ldisc_put(new_ldisc); | |
579 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 580 | } |
c65c9bc3 | 581 | |
01e1abb2 AC |
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 | ||
c65c9bc3 | 586 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
587 | tty->ops->set_ldisc(tty); |
588 | ||
c65c9bc3 | 589 | tty_ldisc_put(o_ldisc); |
01e1abb2 AC |
590 | |
591 | /* | |
c65c9bc3 | 592 | * Allow ldisc referencing to occur again |
01e1abb2 | 593 | */ |
6fa3eb70 | 594 | tty_ldisc_enable_pair(tty, o_tty); |
01e1abb2 | 595 | |
c65c9bc3 | 596 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 597 | already running */ |
4f98d467 PH |
598 | schedule_work(&tty->port->buf.work); |
599 | if (o_tty) | |
ecbbfd44 | 600 | schedule_work(&o_tty->port->buf.work); |
4f98d467 | 601 | |
89c8d91e | 602 | tty_unlock(tty); |
01e1abb2 AC |
603 | return retval; |
604 | } | |
605 | ||
c65c9bc3 AC |
606 | /** |
607 | * tty_reset_termios - reset terminal state | |
608 | * @tty: tty to reset | |
609 | * | |
610 | * Restore a terminal to the driver default state. | |
611 | */ | |
612 | ||
613 | static void tty_reset_termios(struct tty_struct *tty) | |
614 | { | |
615 | mutex_lock(&tty->termios_mutex); | |
adc8d746 AC |
616 | tty->termios = tty->driver->init_termios; |
617 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
618 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
c65c9bc3 AC |
619 | mutex_unlock(&tty->termios_mutex); |
620 | } | |
621 | ||
622 | ||
623 | /** | |
624 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
625 | * @tty: tty to reinit | |
638b9648 | 626 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 627 | * |
638b9648 AC |
628 | * Switch the tty to a line discipline and leave the ldisc |
629 | * state closed | |
c65c9bc3 AC |
630 | */ |
631 | ||
1c95ba1e | 632 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 633 | { |
6fa3eb70 | 634 | struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); |
1c95ba1e PR |
635 | |
636 | if (IS_ERR(ld)) | |
637 | return -1; | |
c65c9bc3 AC |
638 | |
639 | tty_ldisc_close(tty, tty->ldisc); | |
640 | tty_ldisc_put(tty->ldisc); | |
c65c9bc3 AC |
641 | /* |
642 | * Switch the line discipline back | |
643 | */ | |
f4807045 | 644 | tty->ldisc = ld; |
638b9648 | 645 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
646 | |
647 | return 0; | |
c65c9bc3 AC |
648 | } |
649 | ||
650 | /** | |
651 | * tty_ldisc_hangup - hangup ldisc reset | |
652 | * @tty: tty being hung up | |
653 | * | |
654 | * Some tty devices reset their termios when they receive a hangup | |
655 | * event. In that situation we must also switch back to N_TTY properly | |
656 | * before we reset the termios data. | |
657 | * | |
658 | * Locking: We can take the ldisc mutex as the rest of the code is | |
659 | * careful to allow for this. | |
660 | * | |
661 | * In the pty pair case this occurs in the close() path of the | |
662 | * tty itself so we must be careful about locking rules. | |
663 | */ | |
664 | ||
665 | void tty_ldisc_hangup(struct tty_struct *tty) | |
666 | { | |
667 | struct tty_ldisc *ld; | |
638b9648 AC |
668 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
669 | int err = 0; | |
c65c9bc3 | 670 | |
fc575ee6 PH |
671 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
672 | ||
c65c9bc3 AC |
673 | ld = tty_ldisc_ref(tty); |
674 | if (ld != NULL) { | |
c65c9bc3 AC |
675 | if (ld->ops->flush_buffer) |
676 | ld->ops->flush_buffer(tty); | |
677 | tty_driver_flush_buffer(tty); | |
678 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
679 | ld->ops->write_wakeup) | |
680 | ld->ops->write_wakeup(tty); | |
681 | if (ld->ops->hangup) | |
682 | ld->ops->hangup(tty); | |
683 | tty_ldisc_deref(ld); | |
684 | } | |
6fa3eb70 | 685 | |
c65c9bc3 AC |
686 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
687 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
6fa3eb70 S |
688 | |
689 | tty_unlock(tty); | |
690 | ||
c65c9bc3 AC |
691 | /* |
692 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
693 | * N_TTY if need be. |
694 | * | |
695 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 696 | */ |
6fa3eb70 S |
697 | tty_ldisc_lock_pair(tty, tty->link); |
698 | tty_lock(tty); | |
60af22d2 | 699 | |
6fa3eb70 | 700 | if (tty->ldisc) { |
c8785241 PH |
701 | |
702 | /* At this point we have a halted ldisc; we want to close it and | |
703 | reopen a new ldisc. We could defer the reopen to the next | |
704 | open but it means auditing a lot of other paths so this is | |
705 | a FIXME */ | |
638b9648 | 706 | if (reset == 0) { |
1c95ba1e | 707 | |
adc8d746 | 708 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
709 | err = tty_ldisc_open(tty, tty->ldisc); |
710 | else | |
711 | err = 1; | |
638b9648 AC |
712 | } |
713 | /* If the re-open fails or we reset then go to N_TTY. The | |
714 | N_TTY open cannot fail */ | |
715 | if (reset || err) { | |
1c95ba1e | 716 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 717 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 718 | } |
c65c9bc3 | 719 | } |
6fa3eb70 | 720 | tty_ldisc_enable_pair(tty, tty->link); |
638b9648 AC |
721 | if (reset) |
722 | tty_reset_termios(tty); | |
fc575ee6 PH |
723 | |
724 | tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); | |
c65c9bc3 | 725 | } |
01e1abb2 AC |
726 | |
727 | /** | |
728 | * tty_ldisc_setup - open line discipline | |
729 | * @tty: tty being shut down | |
730 | * @o_tty: pair tty for pty/tty pairs | |
731 | * | |
732 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
733 | * line disciplines and bind them to the tty. This has no locking issues |
734 | * as the device isn't yet active. | |
01e1abb2 AC |
735 | */ |
736 | ||
737 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
738 | { | |
c65c9bc3 | 739 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
740 | int retval; |
741 | ||
c65c9bc3 AC |
742 | retval = tty_ldisc_open(tty, ld); |
743 | if (retval) | |
744 | return retval; | |
745 | ||
746 | if (o_tty) { | |
747 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 748 | if (retval) { |
c65c9bc3 | 749 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
750 | return retval; |
751 | } | |
01e1abb2 | 752 | } |
01e1abb2 AC |
753 | return 0; |
754 | } | |
89c8d91e AC |
755 | |
756 | static void tty_ldisc_kill(struct tty_struct *tty) | |
757 | { | |
89c8d91e AC |
758 | /* |
759 | * Now kill off the ldisc | |
760 | */ | |
761 | tty_ldisc_close(tty, tty->ldisc); | |
762 | tty_ldisc_put(tty->ldisc); | |
763 | /* Force an oops if we mess this up */ | |
764 | tty->ldisc = NULL; | |
765 | ||
766 | /* Ensure the next open requests the N_TTY ldisc */ | |
767 | tty_set_termios_ldisc(tty, N_TTY); | |
89c8d91e AC |
768 | } |
769 | ||
01e1abb2 AC |
770 | /** |
771 | * tty_ldisc_release - release line discipline | |
772 | * @tty: tty being shut down | |
773 | * @o_tty: pair tty for pty/tty pairs | |
774 | * | |
852e99d2 AC |
775 | * Called during the final close of a tty/pty pair in order to shut down |
776 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 777 | * ldisc has not been opened. |
01e1abb2 AC |
778 | */ |
779 | ||
780 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
781 | { | |
01e1abb2 | 782 | /* |
a2965b7b PH |
783 | * Shutdown this line discipline. As this is the final close, |
784 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 785 | */ |
01e1abb2 | 786 | |
fc575ee6 PH |
787 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
788 | ||
6fa3eb70 | 789 | tty_ldisc_lock_pair(tty, o_tty); |
852e4a81 | 790 | tty_lock_pair(tty, o_tty); |
6fa3eb70 | 791 | |
89c8d91e | 792 | tty_ldisc_kill(tty); |
c65c9bc3 | 793 | if (o_tty) |
89c8d91e | 794 | tty_ldisc_kill(o_tty); |
aef29bc2 | 795 | |
89c8d91e | 796 | tty_unlock_pair(tty, o_tty); |
6fa3eb70 S |
797 | tty_ldisc_unlock_pair(tty, o_tty); |
798 | ||
aef29bc2 AC |
799 | /* And the memory resources remaining (buffers, termios) will be |
800 | disposed of when the kref hits zero */ | |
fc575ee6 PH |
801 | |
802 | tty_ldisc_debug(tty, "ldisc closed\n"); | |
01e1abb2 AC |
803 | } |
804 | ||
805 | /** | |
806 | * tty_ldisc_init - ldisc setup for new tty | |
807 | * @tty: tty being allocated | |
808 | * | |
809 | * Set up the line discipline objects for a newly allocated tty. Note that | |
810 | * the tty structure is not completely set up when this call is made. | |
811 | */ | |
812 | ||
813 | void tty_ldisc_init(struct tty_struct *tty) | |
814 | { | |
6fa3eb70 | 815 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 816 | if (IS_ERR(ld)) |
01e1abb2 | 817 | panic("n_tty: init_tty"); |
f4807045 | 818 | tty->ldisc = ld; |
01e1abb2 AC |
819 | } |
820 | ||
6716671d JS |
821 | /** |
822 | * tty_ldisc_init - ldisc cleanup for new tty | |
823 | * @tty: tty that was allocated recently | |
824 | * | |
825 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
826 | * this call is made. | |
827 | */ | |
828 | void tty_ldisc_deinit(struct tty_struct *tty) | |
829 | { | |
ebc9baed | 830 | tty_ldisc_put(tty->ldisc); |
f4807045 | 831 | tty->ldisc = NULL; |
6716671d JS |
832 | } |
833 | ||
01e1abb2 AC |
834 | void tty_ldisc_begin(void) |
835 | { | |
836 | /* Setup the default TTY line discipline. */ | |
837 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
838 | } |