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> | |
01e1abb2 | 14 | #include <linux/module.h> |
01e1abb2 AC |
15 | #include <linux/device.h> |
16 | #include <linux/wait.h> | |
17 | #include <linux/bitops.h> | |
01e1abb2 | 18 | #include <linux/seq_file.h> |
01e1abb2 | 19 | #include <linux/uaccess.h> |
0c73c08e | 20 | #include <linux/ratelimit.h> |
01e1abb2 | 21 | |
fc575ee6 PH |
22 | #undef LDISC_DEBUG_HANGUP |
23 | ||
24 | #ifdef LDISC_DEBUG_HANGUP | |
25 | #define tty_ldisc_debug(tty, f, args...) ({ \ | |
26 | char __b[64]; \ | |
27 | printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \ | |
28 | }) | |
29 | #else | |
30 | #define tty_ldisc_debug(tty, f, args...) | |
31 | #endif | |
32 | ||
d2c43890 PH |
33 | /* lockdep nested classes for tty->ldisc_sem */ |
34 | enum { | |
35 | LDISC_SEM_NORMAL, | |
36 | LDISC_SEM_OTHER, | |
37 | }; | |
38 | ||
39 | ||
01e1abb2 AC |
40 | /* |
41 | * This guards the refcounted line discipline lists. The lock | |
42 | * must be taken with irqs off because there are hangup path | |
43 | * callers who will do ldisc lookups and cannot sleep. | |
44 | */ | |
45 | ||
137084bb | 46 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
47 | /* Line disc dispatch table */ |
48 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
49 | ||
50 | /** | |
51 | * tty_register_ldisc - install a line discipline | |
52 | * @disc: ldisc number | |
53 | * @new_ldisc: pointer to the ldisc object | |
54 | * | |
55 | * Installs a new line discipline into the kernel. The discipline | |
56 | * is set up as unreferenced and then made available to the kernel | |
57 | * from this point onwards. | |
58 | * | |
59 | * Locking: | |
137084bb | 60 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
61 | */ |
62 | ||
63 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
64 | { | |
65 | unsigned long flags; | |
66 | int ret = 0; | |
67 | ||
68 | if (disc < N_TTY || disc >= NR_LDISCS) | |
69 | return -EINVAL; | |
70 | ||
137084bb | 71 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
72 | tty_ldiscs[disc] = new_ldisc; |
73 | new_ldisc->num = disc; | |
74 | new_ldisc->refcount = 0; | |
137084bb | 75 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
76 | |
77 | return ret; | |
78 | } | |
79 | EXPORT_SYMBOL(tty_register_ldisc); | |
80 | ||
81 | /** | |
82 | * tty_unregister_ldisc - unload a line discipline | |
83 | * @disc: ldisc number | |
84 | * @new_ldisc: pointer to the ldisc object | |
85 | * | |
86 | * Remove a line discipline from the kernel providing it is not | |
87 | * currently in use. | |
88 | * | |
89 | * Locking: | |
137084bb | 90 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
91 | */ |
92 | ||
93 | int tty_unregister_ldisc(int disc) | |
94 | { | |
95 | unsigned long flags; | |
96 | int ret = 0; | |
97 | ||
98 | if (disc < N_TTY || disc >= NR_LDISCS) | |
99 | return -EINVAL; | |
100 | ||
137084bb | 101 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
102 | if (tty_ldiscs[disc]->refcount) |
103 | ret = -EBUSY; | |
104 | else | |
105 | tty_ldiscs[disc] = NULL; | |
137084bb | 106 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
107 | |
108 | return ret; | |
109 | } | |
110 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
111 | ||
f0de0e8d LT |
112 | static struct tty_ldisc_ops *get_ldops(int disc) |
113 | { | |
114 | unsigned long flags; | |
115 | struct tty_ldisc_ops *ldops, *ret; | |
116 | ||
137084bb | 117 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
118 | ret = ERR_PTR(-EINVAL); |
119 | ldops = tty_ldiscs[disc]; | |
120 | if (ldops) { | |
121 | ret = ERR_PTR(-EAGAIN); | |
122 | if (try_module_get(ldops->owner)) { | |
123 | ldops->refcount++; | |
124 | ret = ldops; | |
125 | } | |
126 | } | |
137084bb | 127 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
128 | return ret; |
129 | } | |
130 | ||
131 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
132 | { | |
133 | unsigned long flags; | |
134 | ||
137084bb | 135 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
136 | ldops->refcount--; |
137 | module_put(ldops->owner); | |
137084bb | 138 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 139 | } |
01e1abb2 | 140 | |
01e1abb2 AC |
141 | /** |
142 | * tty_ldisc_get - take a reference to an ldisc | |
143 | * @disc: ldisc number | |
01e1abb2 AC |
144 | * |
145 | * Takes a reference to a line discipline. Deals with refcounts and | |
146 | * module locking counts. Returns NULL if the discipline is not available. | |
147 | * Returns a pointer to the discipline and bumps the ref count if it is | |
148 | * available | |
149 | * | |
150 | * Locking: | |
137084bb | 151 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
152 | */ |
153 | ||
36697529 | 154 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 155 | { |
c65c9bc3 | 156 | struct tty_ldisc *ld; |
182274f8 | 157 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
158 | |
159 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 160 | return ERR_PTR(-EINVAL); |
182274f8 LT |
161 | |
162 | /* | |
163 | * Get the ldisc ops - we may need to request them to be loaded | |
164 | * dynamically and try again. | |
165 | */ | |
166 | ldops = get_ldops(disc); | |
167 | if (IS_ERR(ldops)) { | |
01e1abb2 | 168 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
169 | ldops = get_ldops(disc); |
170 | if (IS_ERR(ldops)) | |
171 | return ERR_CAST(ldops); | |
172 | } | |
173 | ||
174 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
175 | if (ld == NULL) { | |
176 | put_ldops(ldops); | |
177 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 178 | } |
182274f8 LT |
179 | |
180 | ld->ops = ldops; | |
36697529 | 181 | ld->tty = tty; |
1541f845 | 182 | |
c65c9bc3 | 183 | return ld; |
01e1abb2 AC |
184 | } |
185 | ||
734de249 PH |
186 | /** |
187 | * tty_ldisc_put - release the ldisc | |
188 | * | |
189 | * Complement of tty_ldisc_get(). | |
190 | */ | |
191 | static inline void tty_ldisc_put(struct tty_ldisc *ld) | |
192 | { | |
734de249 PH |
193 | if (WARN_ON_ONCE(!ld)) |
194 | return; | |
195 | ||
36697529 | 196 | put_ldops(ld->ops); |
734de249 | 197 | kfree(ld); |
734de249 PH |
198 | } |
199 | ||
852e99d2 | 200 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
201 | { |
202 | return (*pos < NR_LDISCS) ? pos : NULL; | |
203 | } | |
204 | ||
852e99d2 | 205 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
206 | { |
207 | (*pos)++; | |
208 | return (*pos < NR_LDISCS) ? pos : NULL; | |
209 | } | |
210 | ||
211 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
212 | { | |
213 | } | |
214 | ||
215 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
216 | { | |
217 | int i = *(loff_t *)v; | |
f0de0e8d | 218 | struct tty_ldisc_ops *ldops; |
852e99d2 | 219 | |
f0de0e8d LT |
220 | ldops = get_ldops(i); |
221 | if (IS_ERR(ldops)) | |
01e1abb2 | 222 | return 0; |
f0de0e8d LT |
223 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
224 | put_ldops(ldops); | |
01e1abb2 AC |
225 | return 0; |
226 | } | |
227 | ||
228 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
229 | .start = tty_ldiscs_seq_start, | |
230 | .next = tty_ldiscs_seq_next, | |
231 | .stop = tty_ldiscs_seq_stop, | |
232 | .show = tty_ldiscs_seq_show, | |
233 | }; | |
234 | ||
235 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
236 | { | |
237 | return seq_open(file, &tty_ldiscs_seq_ops); | |
238 | } | |
239 | ||
240 | const struct file_operations tty_ldiscs_proc_fops = { | |
241 | .owner = THIS_MODULE, | |
242 | .open = proc_tty_ldiscs_open, | |
243 | .read = seq_read, | |
244 | .llseek = seq_lseek, | |
245 | .release = seq_release, | |
246 | }; | |
247 | ||
01e1abb2 AC |
248 | /** |
249 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
250 | * @tty: tty device | |
251 | * | |
252 | * Dereference the line discipline for the terminal and take a | |
253 | * reference to it. If the line discipline is in flux then | |
254 | * wait patiently until it changes. | |
255 | * | |
256 | * Note: Must not be called from an IRQ/timer context. The caller | |
257 | * must also be careful not to hold other locks that will deadlock | |
258 | * against a discipline change, such as an existing ldisc reference | |
259 | * (which we check for) | |
260 | * | |
36697529 PH |
261 | * Note: only callable from a file_operations routine (which |
262 | * guarantees tty->ldisc != NULL when the lock is acquired). | |
01e1abb2 AC |
263 | */ |
264 | ||
265 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
266 | { | |
36697529 PH |
267 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
268 | WARN_ON(!tty->ldisc); | |
269 | return tty->ldisc; | |
01e1abb2 | 270 | } |
01e1abb2 AC |
271 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
272 | ||
273 | /** | |
274 | * tty_ldisc_ref - get the tty ldisc | |
275 | * @tty: tty device | |
276 | * | |
277 | * Dereference the line discipline for the terminal and take a | |
278 | * reference to it. If the line discipline is in flux then | |
279 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
280 | */ |
281 | ||
282 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
283 | { | |
36697529 PH |
284 | struct tty_ldisc *ld = NULL; |
285 | ||
286 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
287 | ld = tty->ldisc; | |
288 | if (!ld) | |
289 | ldsem_up_read(&tty->ldisc_sem); | |
290 | } | |
291 | return ld; | |
01e1abb2 | 292 | } |
01e1abb2 AC |
293 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
294 | ||
295 | /** | |
296 | * tty_ldisc_deref - free a tty ldisc reference | |
297 | * @ld: reference to free up | |
298 | * | |
299 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
300 | * be called in IRQ context. | |
01e1abb2 AC |
301 | */ |
302 | ||
303 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
304 | { | |
36697529 | 305 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 306 | } |
01e1abb2 AC |
307 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
308 | ||
d2c43890 PH |
309 | |
310 | static inline int __lockfunc | |
e80a10ee | 311 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
312 | { |
313 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
314 | } | |
315 | ||
316 | static inline int __lockfunc | |
e80a10ee | 317 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
318 | { |
319 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
320 | LDISC_SEM_OTHER, timeout); | |
321 | } | |
322 | ||
e80a10ee | 323 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 PH |
324 | { |
325 | return ldsem_up_write(&tty->ldisc_sem); | |
326 | } | |
327 | ||
fae76e9a PH |
328 | static int __lockfunc |
329 | tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) | |
330 | { | |
331 | int ret; | |
332 | ||
333 | ret = __tty_ldisc_lock(tty, timeout); | |
334 | if (!ret) | |
335 | return -EBUSY; | |
336 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
337 | return 0; | |
338 | } | |
339 | ||
340 | static void tty_ldisc_unlock(struct tty_struct *tty) | |
341 | { | |
342 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
343 | __tty_ldisc_unlock(tty); | |
344 | } | |
345 | ||
d2c43890 PH |
346 | static int __lockfunc |
347 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, | |
348 | unsigned long timeout) | |
349 | { | |
350 | int ret; | |
351 | ||
352 | if (tty < tty2) { | |
e80a10ee | 353 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 354 | if (ret) { |
e80a10ee | 355 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 356 | if (!ret) |
e80a10ee | 357 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
358 | } |
359 | } else { | |
360 | /* if this is possible, it has lots of implications */ | |
361 | WARN_ON_ONCE(tty == tty2); | |
362 | if (tty2 && tty != tty2) { | |
e80a10ee | 363 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 364 | if (ret) { |
e80a10ee | 365 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 366 | if (!ret) |
e80a10ee | 367 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
368 | } |
369 | } else | |
e80a10ee | 370 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
371 | } |
372 | ||
373 | if (!ret) | |
374 | return -EBUSY; | |
375 | ||
376 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
377 | if (tty2) | |
378 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
379 | return 0; | |
380 | } | |
381 | ||
382 | static void __lockfunc | |
383 | tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) | |
384 | { | |
385 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
386 | } | |
387 | ||
388 | static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, | |
389 | struct tty_struct *tty2) | |
390 | { | |
e80a10ee | 391 | __tty_ldisc_unlock(tty); |
d2c43890 | 392 | if (tty2) |
e80a10ee | 393 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
394 | } |
395 | ||
f2c4c65c AC |
396 | /** |
397 | * tty_ldisc_flush - flush line discipline queue | |
398 | * @tty: tty | |
399 | * | |
86c80a8e PH |
400 | * Flush the line discipline queue (if any) and the tty flip buffers |
401 | * for this tty. | |
f2c4c65c AC |
402 | */ |
403 | ||
404 | void tty_ldisc_flush(struct tty_struct *tty) | |
405 | { | |
406 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
407 | |
408 | tty_buffer_flush(tty, ld); | |
409 | if (ld) | |
f2c4c65c | 410 | tty_ldisc_deref(ld); |
f2c4c65c | 411 | } |
f2c4c65c AC |
412 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
413 | ||
01e1abb2 AC |
414 | /** |
415 | * tty_set_termios_ldisc - set ldisc field | |
416 | * @tty: tty structure | |
417 | * @num: line discipline number | |
418 | * | |
419 | * This is probably overkill for real world processors but | |
420 | * they are not on hot paths so a little discipline won't do | |
421 | * any harm. | |
422 | * | |
6a1c0680 | 423 | * Locking: takes termios_rwsem |
01e1abb2 AC |
424 | */ |
425 | ||
426 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
427 | { | |
6a1c0680 | 428 | down_write(&tty->termios_rwsem); |
adc8d746 | 429 | tty->termios.c_line = num; |
6a1c0680 | 430 | up_write(&tty->termios_rwsem); |
01e1abb2 AC |
431 | } |
432 | ||
c65c9bc3 AC |
433 | /** |
434 | * tty_ldisc_open - open a line discipline | |
435 | * @tty: tty we are opening the ldisc on | |
436 | * @ld: discipline to open | |
437 | * | |
438 | * A helper opening method. Also a convenient debugging and check | |
439 | * point. | |
ec79d605 AB |
440 | * |
441 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
442 | */ |
443 | ||
444 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
445 | { | |
446 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
447 | if (ld->ops->open) { |
448 | int ret; | |
ec79d605 | 449 | /* BTM here locks versus a hangup event */ |
f18f9498 | 450 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
451 | if (ret) |
452 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
f18f9498 AC |
453 | return ret; |
454 | } | |
c65c9bc3 AC |
455 | return 0; |
456 | } | |
457 | ||
458 | /** | |
459 | * tty_ldisc_close - close a line discipline | |
460 | * @tty: tty we are opening the ldisc on | |
461 | * @ld: discipline to close | |
462 | * | |
463 | * A helper close method. Also a convenient debugging and check | |
464 | * point. | |
465 | */ | |
466 | ||
467 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
468 | { | |
469 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
470 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
471 | if (ld->ops->close) | |
472 | ld->ops->close(tty); | |
473 | } | |
01e1abb2 AC |
474 | |
475 | /** | |
476 | * tty_ldisc_restore - helper for tty ldisc change | |
477 | * @tty: tty to recover | |
478 | * @old: previous ldisc | |
479 | * | |
480 | * Restore the previous line discipline or N_TTY when a line discipline | |
481 | * change fails due to an open error | |
482 | */ | |
483 | ||
484 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
485 | { | |
486 | char buf[64]; | |
c65c9bc3 AC |
487 | struct tty_ldisc *new_ldisc; |
488 | int r; | |
01e1abb2 AC |
489 | |
490 | /* There is an outstanding reference here so this is safe */ | |
36697529 | 491 | old = tty_ldisc_get(tty, old->ops->num); |
c65c9bc3 | 492 | WARN_ON(IS_ERR(old)); |
f4807045 | 493 | tty->ldisc = old; |
01e1abb2 | 494 | tty_set_termios_ldisc(tty, old->ops->num); |
c65c9bc3 AC |
495 | if (tty_ldisc_open(tty, old) < 0) { |
496 | tty_ldisc_put(old); | |
01e1abb2 | 497 | /* This driver is always present */ |
36697529 | 498 | new_ldisc = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 499 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 500 | panic("n_tty: get"); |
f4807045 | 501 | tty->ldisc = new_ldisc; |
01e1abb2 | 502 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
503 | r = tty_ldisc_open(tty, new_ldisc); |
504 | if (r < 0) | |
505 | panic("Couldn't open N_TTY ldisc for " | |
506 | "%s --- error %d.", | |
507 | tty_name(tty, buf), r); | |
01e1abb2 AC |
508 | } |
509 | } | |
510 | ||
511 | /** | |
512 | * tty_set_ldisc - set line discipline | |
513 | * @tty: the terminal to set | |
514 | * @ldisc: the line discipline | |
515 | * | |
516 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
517 | * context. The ldisc change logic has to protect itself against any |
518 | * overlapping ldisc change (including on the other end of pty pairs), | |
519 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
520 | */ |
521 | ||
522 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
523 | { | |
524 | int retval; | |
9fbfa34c | 525 | struct tty_ldisc *old_ldisc, *new_ldisc; |
01e1abb2 | 526 | |
36697529 | 527 | new_ldisc = tty_ldisc_get(tty, ldisc); |
c65c9bc3 AC |
528 | if (IS_ERR(new_ldisc)) |
529 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 530 | |
c8483bc9 | 531 | tty_lock(tty); |
276a661a | 532 | retval = tty_ldisc_lock(tty, 5 * HZ); |
36697529 PH |
533 | if (retval) { |
534 | tty_ldisc_put(new_ldisc); | |
c8483bc9 | 535 | tty_unlock(tty); |
36697529 PH |
536 | return retval; |
537 | } | |
01e1abb2 | 538 | |
c65c9bc3 AC |
539 | /* |
540 | * Check the no-op case | |
541 | */ | |
542 | ||
543 | if (tty->ldisc->ops->num == ldisc) { | |
276a661a | 544 | tty_ldisc_unlock(tty); |
c65c9bc3 | 545 | tty_ldisc_put(new_ldisc); |
c8483bc9 | 546 | tty_unlock(tty); |
01e1abb2 AC |
547 | return 0; |
548 | } | |
549 | ||
9fbfa34c | 550 | old_ldisc = tty->ldisc; |
100eeae2 | 551 | |
3ff51a19 | 552 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
c65c9bc3 AC |
553 | /* We were raced by the hangup method. It will have stomped |
554 | the ldisc data and closed the ldisc down */ | |
276a661a | 555 | tty_ldisc_unlock(tty); |
c65c9bc3 | 556 | tty_ldisc_put(new_ldisc); |
89c8d91e | 557 | tty_unlock(tty); |
c65c9bc3 AC |
558 | return -EIO; |
559 | } | |
560 | ||
9fbfa34c PH |
561 | /* Shutdown the old discipline. */ |
562 | tty_ldisc_close(tty, old_ldisc); | |
01e1abb2 AC |
563 | |
564 | /* Now set up the new line discipline. */ | |
f4807045 | 565 | tty->ldisc = new_ldisc; |
01e1abb2 | 566 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
567 | |
568 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 569 | if (retval < 0) { |
c65c9bc3 AC |
570 | /* Back to the old one or N_TTY if we can't */ |
571 | tty_ldisc_put(new_ldisc); | |
9fbfa34c | 572 | tty_ldisc_restore(tty, old_ldisc); |
01e1abb2 | 573 | } |
c65c9bc3 | 574 | |
9191aaaa PH |
575 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
576 | down_read(&tty->termios_rwsem); | |
01e1abb2 | 577 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
578 | up_read(&tty->termios_rwsem); |
579 | } | |
01e1abb2 | 580 | |
b0e95858 PH |
581 | /* At this point we hold a reference to the new ldisc and a |
582 | reference to the old ldisc, or we hold two references to | |
583 | the old ldisc (if it was restored as part of error cleanup | |
584 | above). In either case, releasing a single reference from | |
585 | the old ldisc is correct. */ | |
586 | ||
9fbfa34c | 587 | tty_ldisc_put(old_ldisc); |
01e1abb2 AC |
588 | |
589 | /* | |
c65c9bc3 | 590 | * Allow ldisc referencing to occur again |
01e1abb2 | 591 | */ |
276a661a | 592 | tty_ldisc_unlock(tty); |
01e1abb2 | 593 | |
c65c9bc3 | 594 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 595 | already running */ |
4f98d467 | 596 | schedule_work(&tty->port->buf.work); |
4f98d467 | 597 | |
89c8d91e | 598 | tty_unlock(tty); |
01e1abb2 AC |
599 | return retval; |
600 | } | |
601 | ||
c65c9bc3 AC |
602 | /** |
603 | * tty_reset_termios - reset terminal state | |
604 | * @tty: tty to reset | |
605 | * | |
606 | * Restore a terminal to the driver default state. | |
607 | */ | |
608 | ||
609 | static void tty_reset_termios(struct tty_struct *tty) | |
610 | { | |
6a1c0680 | 611 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
612 | tty->termios = tty->driver->init_termios; |
613 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
614 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 615 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
616 | } |
617 | ||
618 | ||
619 | /** | |
620 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
621 | * @tty: tty to reinit | |
638b9648 | 622 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 623 | * |
638b9648 AC |
624 | * Switch the tty to a line discipline and leave the ldisc |
625 | * state closed | |
c65c9bc3 AC |
626 | */ |
627 | ||
1c95ba1e | 628 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 629 | { |
36697529 | 630 | struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); |
1c95ba1e PR |
631 | |
632 | if (IS_ERR(ld)) | |
633 | return -1; | |
c65c9bc3 AC |
634 | |
635 | tty_ldisc_close(tty, tty->ldisc); | |
636 | tty_ldisc_put(tty->ldisc); | |
c65c9bc3 AC |
637 | /* |
638 | * Switch the line discipline back | |
639 | */ | |
f4807045 | 640 | tty->ldisc = ld; |
638b9648 | 641 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
642 | |
643 | return 0; | |
c65c9bc3 AC |
644 | } |
645 | ||
646 | /** | |
647 | * tty_ldisc_hangup - hangup ldisc reset | |
648 | * @tty: tty being hung up | |
649 | * | |
650 | * Some tty devices reset their termios when they receive a hangup | |
651 | * event. In that situation we must also switch back to N_TTY properly | |
652 | * before we reset the termios data. | |
653 | * | |
654 | * Locking: We can take the ldisc mutex as the rest of the code is | |
655 | * careful to allow for this. | |
656 | * | |
657 | * In the pty pair case this occurs in the close() path of the | |
658 | * tty itself so we must be careful about locking rules. | |
659 | */ | |
660 | ||
661 | void tty_ldisc_hangup(struct tty_struct *tty) | |
662 | { | |
663 | struct tty_ldisc *ld; | |
638b9648 AC |
664 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
665 | int err = 0; | |
c65c9bc3 | 666 | |
fc575ee6 PH |
667 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
668 | ||
c65c9bc3 AC |
669 | ld = tty_ldisc_ref(tty); |
670 | if (ld != NULL) { | |
c65c9bc3 AC |
671 | if (ld->ops->flush_buffer) |
672 | ld->ops->flush_buffer(tty); | |
673 | tty_driver_flush_buffer(tty); | |
674 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
675 | ld->ops->write_wakeup) | |
676 | ld->ops->write_wakeup(tty); | |
677 | if (ld->ops->hangup) | |
678 | ld->ops->hangup(tty); | |
679 | tty_ldisc_deref(ld); | |
680 | } | |
36697529 | 681 | |
c65c9bc3 AC |
682 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
683 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
36697529 | 684 | |
c65c9bc3 AC |
685 | /* |
686 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
687 | * N_TTY if need be. |
688 | * | |
689 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 690 | */ |
fae76e9a | 691 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 692 | |
36697529 | 693 | if (tty->ldisc) { |
c8785241 PH |
694 | |
695 | /* At this point we have a halted ldisc; we want to close it and | |
696 | reopen a new ldisc. We could defer the reopen to the next | |
697 | open but it means auditing a lot of other paths so this is | |
698 | a FIXME */ | |
638b9648 | 699 | if (reset == 0) { |
1c95ba1e | 700 | |
adc8d746 | 701 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
702 | err = tty_ldisc_open(tty, tty->ldisc); |
703 | else | |
704 | err = 1; | |
638b9648 AC |
705 | } |
706 | /* If the re-open fails or we reset then go to N_TTY. The | |
707 | N_TTY open cannot fail */ | |
708 | if (reset || err) { | |
1c95ba1e | 709 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 710 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 711 | } |
c65c9bc3 | 712 | } |
fae76e9a | 713 | tty_ldisc_unlock(tty); |
638b9648 AC |
714 | if (reset) |
715 | tty_reset_termios(tty); | |
fc575ee6 PH |
716 | |
717 | tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); | |
c65c9bc3 | 718 | } |
01e1abb2 AC |
719 | |
720 | /** | |
721 | * tty_ldisc_setup - open line discipline | |
722 | * @tty: tty being shut down | |
723 | * @o_tty: pair tty for pty/tty pairs | |
724 | * | |
725 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
726 | * line disciplines and bind them to the tty. This has no locking issues |
727 | * as the device isn't yet active. | |
01e1abb2 AC |
728 | */ |
729 | ||
730 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
731 | { | |
c65c9bc3 | 732 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
733 | int retval; |
734 | ||
c65c9bc3 AC |
735 | retval = tty_ldisc_open(tty, ld); |
736 | if (retval) | |
737 | return retval; | |
738 | ||
739 | if (o_tty) { | |
740 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 741 | if (retval) { |
c65c9bc3 | 742 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
743 | return retval; |
744 | } | |
01e1abb2 | 745 | } |
01e1abb2 AC |
746 | return 0; |
747 | } | |
89c8d91e AC |
748 | |
749 | static void tty_ldisc_kill(struct tty_struct *tty) | |
750 | { | |
89c8d91e AC |
751 | /* |
752 | * Now kill off the ldisc | |
753 | */ | |
754 | tty_ldisc_close(tty, tty->ldisc); | |
755 | tty_ldisc_put(tty->ldisc); | |
756 | /* Force an oops if we mess this up */ | |
757 | tty->ldisc = NULL; | |
758 | ||
759 | /* Ensure the next open requests the N_TTY ldisc */ | |
760 | tty_set_termios_ldisc(tty, N_TTY); | |
89c8d91e AC |
761 | } |
762 | ||
01e1abb2 AC |
763 | /** |
764 | * tty_ldisc_release - release line discipline | |
62462aef | 765 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 766 | * |
62462aef PH |
767 | * Called during the final close of a tty or a pty pair in order to shut |
768 | * down the line discpline layer. On exit, each ldisc assigned is N_TTY and | |
769 | * each ldisc has not been opened. | |
01e1abb2 AC |
770 | */ |
771 | ||
62462aef | 772 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 773 | { |
62462aef PH |
774 | struct tty_struct *o_tty = tty->link; |
775 | ||
01e1abb2 | 776 | /* |
a2965b7b PH |
777 | * Shutdown this line discipline. As this is the final close, |
778 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 779 | */ |
01e1abb2 | 780 | |
fc575ee6 PH |
781 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
782 | ||
36697529 | 783 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 784 | tty_ldisc_kill(tty); |
c65c9bc3 | 785 | if (o_tty) |
89c8d91e | 786 | tty_ldisc_kill(o_tty); |
36697529 PH |
787 | tty_ldisc_unlock_pair(tty, o_tty); |
788 | ||
aef29bc2 AC |
789 | /* And the memory resources remaining (buffers, termios) will be |
790 | disposed of when the kref hits zero */ | |
fc575ee6 PH |
791 | |
792 | tty_ldisc_debug(tty, "ldisc closed\n"); | |
01e1abb2 AC |
793 | } |
794 | ||
795 | /** | |
796 | * tty_ldisc_init - ldisc setup for new tty | |
797 | * @tty: tty being allocated | |
798 | * | |
799 | * Set up the line discipline objects for a newly allocated tty. Note that | |
800 | * the tty structure is not completely set up when this call is made. | |
801 | */ | |
802 | ||
803 | void tty_ldisc_init(struct tty_struct *tty) | |
804 | { | |
36697529 | 805 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 806 | if (IS_ERR(ld)) |
01e1abb2 | 807 | panic("n_tty: init_tty"); |
f4807045 | 808 | tty->ldisc = ld; |
01e1abb2 AC |
809 | } |
810 | ||
6716671d JS |
811 | /** |
812 | * tty_ldisc_init - ldisc cleanup for new tty | |
813 | * @tty: tty that was allocated recently | |
814 | * | |
815 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
816 | * this call is made. | |
817 | */ | |
818 | void tty_ldisc_deinit(struct tty_struct *tty) | |
819 | { | |
ebc9baed | 820 | tty_ldisc_put(tty->ldisc); |
f4807045 | 821 | tty->ldisc = NULL; |
6716671d JS |
822 | } |
823 | ||
01e1abb2 AC |
824 | void tty_ldisc_begin(void) |
825 | { | |
826 | /* Setup the default TTY line discipline. */ | |
827 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
828 | } |