Commit | Line | Data |
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e3b3d0f5 | 1 | // SPDX-License-Identifier: GPL-2.0 |
01e1abb2 | 2 | #include <linux/types.h> |
01e1abb2 | 3 | #include <linux/errno.h> |
8b3ffa17 | 4 | #include <linux/kmod.h> |
01e1abb2 AC |
5 | #include <linux/sched.h> |
6 | #include <linux/interrupt.h> | |
7 | #include <linux/tty.h> | |
8 | #include <linux/tty_driver.h> | |
01e1abb2 | 9 | #include <linux/file.h> |
01e1abb2 AC |
10 | #include <linux/mm.h> |
11 | #include <linux/string.h> | |
12 | #include <linux/slab.h> | |
13 | #include <linux/poll.h> | |
14 | #include <linux/proc_fs.h> | |
01e1abb2 | 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 | |
0a6adc13 | 26 | #define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) |
fc575ee6 PH |
27 | #else |
28 | #define tty_ldisc_debug(tty, f, args...) | |
29 | #endif | |
30 | ||
d2c43890 PH |
31 | /* lockdep nested classes for tty->ldisc_sem */ |
32 | enum { | |
33 | LDISC_SEM_NORMAL, | |
34 | LDISC_SEM_OTHER, | |
35 | }; | |
36 | ||
37 | ||
01e1abb2 AC |
38 | /* |
39 | * This guards the refcounted line discipline lists. The lock | |
40 | * must be taken with irqs off because there are hangup path | |
41 | * callers who will do ldisc lookups and cannot sleep. | |
42 | */ | |
43 | ||
137084bb | 44 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
45 | /* Line disc dispatch table */ |
46 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
47 | ||
48 | /** | |
49 | * tty_register_ldisc - install a line discipline | |
50 | * @disc: ldisc number | |
51 | * @new_ldisc: pointer to the ldisc object | |
52 | * | |
53 | * Installs a new line discipline into the kernel. The discipline | |
54 | * is set up as unreferenced and then made available to the kernel | |
55 | * from this point onwards. | |
56 | * | |
57 | * Locking: | |
137084bb | 58 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
59 | */ |
60 | ||
61 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
62 | { | |
63 | unsigned long flags; | |
64 | int ret = 0; | |
65 | ||
66 | if (disc < N_TTY || disc >= NR_LDISCS) | |
67 | return -EINVAL; | |
68 | ||
137084bb | 69 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
70 | tty_ldiscs[disc] = new_ldisc; |
71 | new_ldisc->num = disc; | |
72 | new_ldisc->refcount = 0; | |
137084bb | 73 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
74 | |
75 | return ret; | |
76 | } | |
77 | EXPORT_SYMBOL(tty_register_ldisc); | |
78 | ||
79 | /** | |
80 | * tty_unregister_ldisc - unload a line discipline | |
81 | * @disc: ldisc number | |
82 | * @new_ldisc: pointer to the ldisc object | |
83 | * | |
84 | * Remove a line discipline from the kernel providing it is not | |
85 | * currently in use. | |
86 | * | |
87 | * Locking: | |
137084bb | 88 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
89 | */ |
90 | ||
91 | int tty_unregister_ldisc(int disc) | |
92 | { | |
93 | unsigned long flags; | |
94 | int ret = 0; | |
95 | ||
96 | if (disc < N_TTY || disc >= NR_LDISCS) | |
97 | return -EINVAL; | |
98 | ||
137084bb | 99 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
100 | if (tty_ldiscs[disc]->refcount) |
101 | ret = -EBUSY; | |
102 | else | |
103 | tty_ldiscs[disc] = NULL; | |
137084bb | 104 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
105 | |
106 | return ret; | |
107 | } | |
108 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
109 | ||
f0de0e8d LT |
110 | static struct tty_ldisc_ops *get_ldops(int disc) |
111 | { | |
112 | unsigned long flags; | |
113 | struct tty_ldisc_ops *ldops, *ret; | |
114 | ||
137084bb | 115 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
116 | ret = ERR_PTR(-EINVAL); |
117 | ldops = tty_ldiscs[disc]; | |
118 | if (ldops) { | |
119 | ret = ERR_PTR(-EAGAIN); | |
120 | if (try_module_get(ldops->owner)) { | |
121 | ldops->refcount++; | |
122 | ret = ldops; | |
123 | } | |
124 | } | |
137084bb | 125 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
126 | return ret; |
127 | } | |
128 | ||
129 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
130 | { | |
131 | unsigned long flags; | |
132 | ||
137084bb | 133 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
134 | ldops->refcount--; |
135 | module_put(ldops->owner); | |
137084bb | 136 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 137 | } |
01e1abb2 | 138 | |
01e1abb2 AC |
139 | /** |
140 | * tty_ldisc_get - take a reference to an ldisc | |
141 | * @disc: ldisc number | |
01e1abb2 AC |
142 | * |
143 | * Takes a reference to a line discipline. Deals with refcounts and | |
c0cc1c5d PH |
144 | * module locking counts. |
145 | * | |
146 | * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or | |
147 | * if the discipline is not registered | |
148 | * -EAGAIN if request_module() failed to load or register the | |
149 | * the discipline | |
150 | * -ENOMEM if allocation failure | |
151 | * | |
152 | * Otherwise, returns a pointer to the discipline and bumps the | |
153 | * ref count | |
01e1abb2 AC |
154 | * |
155 | * Locking: | |
137084bb | 156 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
157 | */ |
158 | ||
36697529 | 159 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 160 | { |
c65c9bc3 | 161 | struct tty_ldisc *ld; |
182274f8 | 162 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
163 | |
164 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 165 | return ERR_PTR(-EINVAL); |
182274f8 LT |
166 | |
167 | /* | |
168 | * Get the ldisc ops - we may need to request them to be loaded | |
169 | * dynamically and try again. | |
170 | */ | |
171 | ldops = get_ldops(disc); | |
172 | if (IS_ERR(ldops)) { | |
01e1abb2 | 173 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
174 | ldops = get_ldops(disc); |
175 | if (IS_ERR(ldops)) | |
176 | return ERR_CAST(ldops); | |
177 | } | |
178 | ||
bcdd0ca8 TH |
179 | /* |
180 | * There is no way to handle allocation failure of only 16 bytes. | |
181 | * Let's simplify error handling and save more memory. | |
182 | */ | |
183 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); | |
182274f8 | 184 | ld->ops = ldops; |
36697529 | 185 | ld->tty = tty; |
1541f845 | 186 | |
c65c9bc3 | 187 | return ld; |
01e1abb2 AC |
188 | } |
189 | ||
734de249 PH |
190 | /** |
191 | * tty_ldisc_put - release the ldisc | |
192 | * | |
193 | * Complement of tty_ldisc_get(). | |
194 | */ | |
cb128f69 | 195 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 196 | { |
734de249 PH |
197 | if (WARN_ON_ONCE(!ld)) |
198 | return; | |
199 | ||
36697529 | 200 | put_ldops(ld->ops); |
734de249 | 201 | kfree(ld); |
734de249 PH |
202 | } |
203 | ||
852e99d2 | 204 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
205 | { |
206 | return (*pos < NR_LDISCS) ? pos : NULL; | |
207 | } | |
208 | ||
852e99d2 | 209 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
210 | { |
211 | (*pos)++; | |
212 | return (*pos < NR_LDISCS) ? pos : NULL; | |
213 | } | |
214 | ||
215 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
216 | { | |
217 | } | |
218 | ||
219 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
220 | { | |
221 | int i = *(loff_t *)v; | |
f0de0e8d | 222 | struct tty_ldisc_ops *ldops; |
852e99d2 | 223 | |
f0de0e8d LT |
224 | ldops = get_ldops(i); |
225 | if (IS_ERR(ldops)) | |
01e1abb2 | 226 | return 0; |
f0de0e8d LT |
227 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
228 | put_ldops(ldops); | |
01e1abb2 AC |
229 | return 0; |
230 | } | |
231 | ||
fddda2b7 | 232 | const struct seq_operations tty_ldiscs_seq_ops = { |
01e1abb2 AC |
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 | ||
01e1abb2 AC |
239 | /** |
240 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
241 | * @tty: tty device | |
242 | * | |
243 | * Dereference the line discipline for the terminal and take a | |
244 | * reference to it. If the line discipline is in flux then | |
245 | * wait patiently until it changes. | |
246 | * | |
892d1fa7 PH |
247 | * Returns: NULL if the tty has been hungup and not re-opened with |
248 | * a new file descriptor, otherwise valid ldisc reference | |
249 | * | |
01e1abb2 AC |
250 | * Note: Must not be called from an IRQ/timer context. The caller |
251 | * must also be careful not to hold other locks that will deadlock | |
252 | * against a discipline change, such as an existing ldisc reference | |
253 | * (which we check for) | |
254 | * | |
e55afd11 PH |
255 | * Note: a file_operations routine (read/poll/write) should use this |
256 | * function to wait for any ldisc lifetime events to finish. | |
01e1abb2 AC |
257 | */ |
258 | ||
259 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
260 | { | |
a4a3e061 DV |
261 | struct tty_ldisc *ld; |
262 | ||
36697529 | 263 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
264 | ld = tty->ldisc; |
265 | if (!ld) | |
a570a49a | 266 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 267 | return ld; |
01e1abb2 | 268 | } |
01e1abb2 AC |
269 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
270 | ||
271 | /** | |
272 | * tty_ldisc_ref - get the tty ldisc | |
273 | * @tty: tty device | |
274 | * | |
275 | * Dereference the line discipline for the terminal and take a | |
276 | * reference to it. If the line discipline is in flux then | |
277 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
278 | */ |
279 | ||
280 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
281 | { | |
36697529 PH |
282 | struct tty_ldisc *ld = NULL; |
283 | ||
284 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
285 | ld = tty->ldisc; | |
286 | if (!ld) | |
287 | ldsem_up_read(&tty->ldisc_sem); | |
288 | } | |
289 | return ld; | |
01e1abb2 | 290 | } |
01e1abb2 AC |
291 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
292 | ||
293 | /** | |
294 | * tty_ldisc_deref - free a tty ldisc reference | |
295 | * @ld: reference to free up | |
296 | * | |
297 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
298 | * be called in IRQ context. | |
01e1abb2 AC |
299 | */ |
300 | ||
301 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
302 | { | |
36697529 | 303 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 304 | } |
01e1abb2 AC |
305 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
306 | ||
d2c43890 | 307 | |
c2bb524b | 308 | static inline int |
e80a10ee | 309 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
310 | { |
311 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
312 | } | |
313 | ||
c2bb524b | 314 | static inline int |
e80a10ee | 315 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
316 | { |
317 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
318 | LDISC_SEM_OTHER, timeout); | |
319 | } | |
320 | ||
e80a10ee | 321 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 322 | { |
52772ea6 | 323 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
324 | } |
325 | ||
b027e229 | 326 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
327 | { |
328 | int ret; | |
329 | ||
c96cf923 DS |
330 | /* Kindly asking blocked readers to release the read side */ |
331 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
332 | wake_up_interruptible_all(&tty->read_wait); | |
333 | wake_up_interruptible_all(&tty->write_wait); | |
334 | ||
fae76e9a PH |
335 | ret = __tty_ldisc_lock(tty, timeout); |
336 | if (!ret) | |
337 | return -EBUSY; | |
338 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
339 | return 0; | |
340 | } | |
341 | ||
b027e229 | 342 | void tty_ldisc_unlock(struct tty_struct *tty) |
fae76e9a PH |
343 | { |
344 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
c96cf923 DS |
345 | /* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
346 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
fae76e9a PH |
347 | __tty_ldisc_unlock(tty); |
348 | } | |
349 | ||
c2bb524b | 350 | static int |
d2c43890 PH |
351 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
352 | unsigned long timeout) | |
353 | { | |
354 | int ret; | |
355 | ||
356 | if (tty < tty2) { | |
e80a10ee | 357 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 358 | if (ret) { |
e80a10ee | 359 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 360 | if (!ret) |
e80a10ee | 361 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
362 | } |
363 | } else { | |
364 | /* if this is possible, it has lots of implications */ | |
365 | WARN_ON_ONCE(tty == tty2); | |
366 | if (tty2 && tty != tty2) { | |
e80a10ee | 367 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 368 | if (ret) { |
e80a10ee | 369 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 370 | if (!ret) |
e80a10ee | 371 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
372 | } |
373 | } else | |
e80a10ee | 374 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
375 | } |
376 | ||
377 | if (!ret) | |
378 | return -EBUSY; | |
379 | ||
380 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
381 | if (tty2) | |
382 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
383 | return 0; | |
384 | } | |
385 | ||
c2bb524b | 386 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
387 | { |
388 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
389 | } | |
390 | ||
c2bb524b PH |
391 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
392 | struct tty_struct *tty2) | |
d2c43890 | 393 | { |
e80a10ee | 394 | __tty_ldisc_unlock(tty); |
d2c43890 | 395 | if (tty2) |
e80a10ee | 396 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
397 | } |
398 | ||
f2c4c65c AC |
399 | /** |
400 | * tty_ldisc_flush - flush line discipline queue | |
401 | * @tty: tty | |
402 | * | |
86c80a8e PH |
403 | * Flush the line discipline queue (if any) and the tty flip buffers |
404 | * for this tty. | |
f2c4c65c AC |
405 | */ |
406 | ||
407 | void tty_ldisc_flush(struct tty_struct *tty) | |
408 | { | |
409 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
410 | |
411 | tty_buffer_flush(tty, ld); | |
412 | if (ld) | |
f2c4c65c | 413 | tty_ldisc_deref(ld); |
f2c4c65c | 414 | } |
f2c4c65c AC |
415 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
416 | ||
01e1abb2 AC |
417 | /** |
418 | * tty_set_termios_ldisc - set ldisc field | |
419 | * @tty: tty structure | |
c12da96f | 420 | * @disc: line discipline number |
01e1abb2 AC |
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 | * | |
dd42bf11 PH |
426 | * The line discipline-related tty_struct fields are reset to |
427 | * prevent the ldisc driver from re-using stale information for | |
428 | * the new ldisc instance. | |
429 | * | |
6a1c0680 | 430 | * Locking: takes termios_rwsem |
01e1abb2 AC |
431 | */ |
432 | ||
c12da96f | 433 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 434 | { |
6a1c0680 | 435 | down_write(&tty->termios_rwsem); |
c12da96f | 436 | tty->termios.c_line = disc; |
6a1c0680 | 437 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
438 | |
439 | tty->disc_data = NULL; | |
440 | tty->receive_room = 0; | |
01e1abb2 AC |
441 | } |
442 | ||
c65c9bc3 AC |
443 | /** |
444 | * tty_ldisc_open - open a line discipline | |
445 | * @tty: tty we are opening the ldisc on | |
446 | * @ld: discipline to open | |
447 | * | |
448 | * A helper opening method. Also a convenient debugging and check | |
449 | * point. | |
ec79d605 AB |
450 | * |
451 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
452 | */ |
453 | ||
454 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
455 | { | |
456 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
457 | if (ld->ops->open) { |
458 | int ret; | |
ec79d605 | 459 | /* BTM here locks versus a hangup event */ |
f18f9498 | 460 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
461 | if (ret) |
462 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 463 | |
a570a49a | 464 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
465 | return ret; |
466 | } | |
c65c9bc3 AC |
467 | return 0; |
468 | } | |
469 | ||
470 | /** | |
471 | * tty_ldisc_close - close a line discipline | |
472 | * @tty: tty we are opening the ldisc on | |
473 | * @ld: discipline to close | |
474 | * | |
475 | * A helper close method. Also a convenient debugging and check | |
476 | * point. | |
477 | */ | |
478 | ||
479 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
480 | { | |
481 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
482 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
483 | if (ld->ops->close) | |
484 | ld->ops->close(tty); | |
a570a49a | 485 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 486 | } |
01e1abb2 | 487 | |
8a8dabf2 AC |
488 | /** |
489 | * tty_ldisc_failto - helper for ldisc failback | |
490 | * @tty: tty to open the ldisc on | |
491 | * @ld: ldisc we are trying to fail back to | |
492 | * | |
493 | * Helper to try and recover a tty when switching back to the old | |
494 | * ldisc fails and we need something attached. | |
495 | */ | |
496 | ||
497 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) | |
498 | { | |
499 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
500 | int r; | |
501 | ||
502 | if (IS_ERR(disc)) | |
503 | return PTR_ERR(disc); | |
504 | tty->ldisc = disc; | |
505 | tty_set_termios_ldisc(tty, ld); | |
506 | if ((r = tty_ldisc_open(tty, disc)) < 0) | |
507 | tty_ldisc_put(disc); | |
508 | return r; | |
509 | } | |
510 | ||
a8983d01 GKH |
511 | /** |
512 | * tty_ldisc_restore - helper for tty ldisc change | |
513 | * @tty: tty to recover | |
514 | * @old: previous ldisc | |
515 | * | |
516 | * Restore the previous line discipline or N_TTY when a line discipline | |
517 | * change fails due to an open error | |
518 | */ | |
519 | ||
520 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
521 | { | |
a8983d01 | 522 | /* There is an outstanding reference here so this is safe */ |
598c2d41 TH |
523 | if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
524 | const char *name = tty_name(tty); | |
525 | ||
526 | pr_warn("Falling back ldisc for %s.\n", name); | |
8a8dabf2 AC |
527 | /* The traditional behaviour is to fall back to N_TTY, we |
528 | want to avoid falling back to N_NULL unless we have no | |
529 | choice to avoid the risk of breaking anything */ | |
530 | if (tty_ldisc_failto(tty, N_TTY) < 0 && | |
531 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 532 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
533 | } |
534 | } | |
535 | ||
01e1abb2 AC |
536 | /** |
537 | * tty_set_ldisc - set line discipline | |
538 | * @tty: the terminal to set | |
539 | * @ldisc: the line discipline | |
540 | * | |
541 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
542 | * context. The ldisc change logic has to protect itself against any |
543 | * overlapping ldisc change (including on the other end of pty pairs), | |
544 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
545 | */ |
546 | ||
c12da96f | 547 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 548 | { |
a8983d01 GKH |
549 | int retval; |
550 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
551 | ||
552 | new_ldisc = tty_ldisc_get(tty, disc); | |
553 | if (IS_ERR(new_ldisc)) | |
554 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 555 | |
c8483bc9 | 556 | tty_lock(tty); |
276a661a | 557 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
558 | if (retval) |
559 | goto err; | |
01e1abb2 | 560 | |
a570a49a PH |
561 | if (!tty->ldisc) { |
562 | retval = -EIO; | |
563 | goto out; | |
564 | } | |
565 | ||
63d8cb3f | 566 | /* Check the no-op case */ |
a8983d01 | 567 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 568 | goto out; |
c65c9bc3 | 569 | |
63d8cb3f PH |
570 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
571 | /* We were raced by hangup */ | |
572 | retval = -EIO; | |
573 | goto out; | |
01e1abb2 AC |
574 | } |
575 | ||
a8983d01 GKH |
576 | old_ldisc = tty->ldisc; |
577 | ||
578 | /* Shutdown the old discipline. */ | |
579 | tty_ldisc_close(tty, old_ldisc); | |
580 | ||
581 | /* Now set up the new line discipline. */ | |
582 | tty->ldisc = new_ldisc; | |
583 | tty_set_termios_ldisc(tty, disc); | |
584 | ||
585 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 586 | if (retval < 0) { |
c65c9bc3 | 587 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
588 | tty_ldisc_put(new_ldisc); |
589 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 590 | } |
c65c9bc3 | 591 | |
a8983d01 | 592 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 593 | down_read(&tty->termios_rwsem); |
01e1abb2 | 594 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
595 | up_read(&tty->termios_rwsem); |
596 | } | |
01e1abb2 | 597 | |
a8983d01 GKH |
598 | /* At this point we hold a reference to the new ldisc and a |
599 | reference to the old ldisc, or we hold two references to | |
600 | the old ldisc (if it was restored as part of error cleanup | |
601 | above). In either case, releasing a single reference from | |
602 | the old ldisc is correct. */ | |
603 | new_ldisc = old_ldisc; | |
63d8cb3f | 604 | out: |
276a661a | 605 | tty_ldisc_unlock(tty); |
01e1abb2 | 606 | |
c65c9bc3 | 607 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 608 | already running */ |
17a69219 | 609 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 610 | err: |
a8983d01 | 611 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 612 | tty_unlock(tty); |
01e1abb2 AC |
613 | return retval; |
614 | } | |
1ab92da3 | 615 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 616 | |
6ffeb4b2 PH |
617 | /** |
618 | * tty_ldisc_kill - teardown ldisc | |
619 | * @tty: tty being released | |
620 | * | |
621 | * Perform final close of the ldisc and reset tty->ldisc | |
622 | */ | |
623 | static void tty_ldisc_kill(struct tty_struct *tty) | |
624 | { | |
625 | if (!tty->ldisc) | |
626 | return; | |
627 | /* | |
628 | * Now kill off the ldisc | |
629 | */ | |
630 | tty_ldisc_close(tty, tty->ldisc); | |
631 | tty_ldisc_put(tty->ldisc); | |
632 | /* Force an oops if we mess this up */ | |
633 | tty->ldisc = NULL; | |
634 | } | |
635 | ||
c65c9bc3 AC |
636 | /** |
637 | * tty_reset_termios - reset terminal state | |
638 | * @tty: tty to reset | |
639 | * | |
640 | * Restore a terminal to the driver default state. | |
641 | */ | |
642 | ||
643 | static void tty_reset_termios(struct tty_struct *tty) | |
644 | { | |
6a1c0680 | 645 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
646 | tty->termios = tty->driver->init_termios; |
647 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
648 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 649 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
650 | } |
651 | ||
652 | ||
653 | /** | |
654 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
655 | * @tty: tty to reinit | |
c12da96f | 656 | * @disc: line discipline to reinitialize |
c65c9bc3 | 657 | * |
7896f30d | 658 | * Completely reinitialize the line discipline state, by closing the |
892d1fa7 PH |
659 | * current instance, if there is one, and opening a new instance. If |
660 | * an error occurs opening the new non-N_TTY instance, the instance | |
661 | * is dropped and tty->ldisc reset to NULL. The caller can then retry | |
662 | * with N_TTY instead. | |
7896f30d PH |
663 | * |
664 | * Returns 0 if successful, otherwise error code < 0 | |
c65c9bc3 AC |
665 | */ |
666 | ||
892d1fa7 | 667 | int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
c65c9bc3 | 668 | { |
7896f30d PH |
669 | struct tty_ldisc *ld; |
670 | int retval; | |
1c95ba1e | 671 | |
7896f30d | 672 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
673 | if (IS_ERR(ld)) { |
674 | BUG_ON(disc == N_TTY); | |
7896f30d | 675 | return PTR_ERR(ld); |
a8983d01 | 676 | } |
c65c9bc3 | 677 | |
7896f30d PH |
678 | if (tty->ldisc) { |
679 | tty_ldisc_close(tty, tty->ldisc); | |
680 | tty_ldisc_put(tty->ldisc); | |
681 | } | |
682 | ||
683 | /* switch the line discipline */ | |
f4807045 | 684 | tty->ldisc = ld; |
c12da96f | 685 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
686 | retval = tty_ldisc_open(tty, tty->ldisc); |
687 | if (retval) { | |
e65c62b1 JW |
688 | tty_ldisc_put(tty->ldisc); |
689 | tty->ldisc = NULL; | |
7896f30d PH |
690 | } |
691 | return retval; | |
c65c9bc3 AC |
692 | } |
693 | ||
694 | /** | |
695 | * tty_ldisc_hangup - hangup ldisc reset | |
696 | * @tty: tty being hung up | |
697 | * | |
698 | * Some tty devices reset their termios when they receive a hangup | |
699 | * event. In that situation we must also switch back to N_TTY properly | |
700 | * before we reset the termios data. | |
701 | * | |
702 | * Locking: We can take the ldisc mutex as the rest of the code is | |
703 | * careful to allow for this. | |
704 | * | |
705 | * In the pty pair case this occurs in the close() path of the | |
706 | * tty itself so we must be careful about locking rules. | |
707 | */ | |
708 | ||
892d1fa7 | 709 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
710 | { |
711 | struct tty_ldisc *ld; | |
712 | ||
a570a49a | 713 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 714 | |
c65c9bc3 AC |
715 | ld = tty_ldisc_ref(tty); |
716 | if (ld != NULL) { | |
c65c9bc3 AC |
717 | if (ld->ops->flush_buffer) |
718 | ld->ops->flush_buffer(tty); | |
719 | tty_driver_flush_buffer(tty); | |
720 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
721 | ld->ops->write_wakeup) | |
722 | ld->ops->write_wakeup(tty); | |
723 | if (ld->ops->hangup) | |
724 | ld->ops->hangup(tty); | |
725 | tty_ldisc_deref(ld); | |
726 | } | |
36697529 | 727 | |
a9a08845 LT |
728 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
729 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 730 | |
c65c9bc3 AC |
731 | /* |
732 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
733 | * N_TTY if need be. |
734 | * | |
735 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 736 | */ |
fae76e9a | 737 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 738 | |
892d1fa7 PH |
739 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
740 | tty_reset_termios(tty); | |
c8785241 | 741 | |
892d1fa7 PH |
742 | if (tty->ldisc) { |
743 | if (reinit) { | |
e65c62b1 JW |
744 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
745 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
746 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
747 | } else |
748 | tty_ldisc_kill(tty); | |
c65c9bc3 | 749 | } |
fae76e9a | 750 | tty_ldisc_unlock(tty); |
c65c9bc3 | 751 | } |
01e1abb2 AC |
752 | |
753 | /** | |
754 | * tty_ldisc_setup - open line discipline | |
755 | * @tty: tty being shut down | |
756 | * @o_tty: pair tty for pty/tty pairs | |
757 | * | |
758 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
759 | * line disciplines and bind them to the tty. This has no locking issues |
760 | * as the device isn't yet active. | |
01e1abb2 AC |
761 | */ |
762 | ||
763 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
764 | { | |
9de2a7ce | 765 | int retval = tty_ldisc_open(tty, tty->ldisc); |
c65c9bc3 AC |
766 | if (retval) |
767 | return retval; | |
768 | ||
769 | if (o_tty) { | |
770 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 771 | if (retval) { |
9de2a7ce | 772 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
773 | return retval; |
774 | } | |
01e1abb2 | 775 | } |
01e1abb2 AC |
776 | return 0; |
777 | } | |
89c8d91e | 778 | |
01e1abb2 AC |
779 | /** |
780 | * tty_ldisc_release - release line discipline | |
62462aef | 781 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 782 | * |
62462aef | 783 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 784 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
785 | */ |
786 | ||
62462aef | 787 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 788 | { |
62462aef PH |
789 | struct tty_struct *o_tty = tty->link; |
790 | ||
01e1abb2 | 791 | /* |
a2965b7b PH |
792 | * Shutdown this line discipline. As this is the final close, |
793 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 794 | */ |
01e1abb2 | 795 | |
36697529 | 796 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 797 | tty_ldisc_kill(tty); |
c65c9bc3 | 798 | if (o_tty) |
89c8d91e | 799 | tty_ldisc_kill(o_tty); |
36697529 PH |
800 | tty_ldisc_unlock_pair(tty, o_tty); |
801 | ||
aef29bc2 AC |
802 | /* And the memory resources remaining (buffers, termios) will be |
803 | disposed of when the kref hits zero */ | |
fc575ee6 | 804 | |
fb6edc91 | 805 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 | 806 | } |
1ab92da3 | 807 | EXPORT_SYMBOL_GPL(tty_ldisc_release); |
01e1abb2 AC |
808 | |
809 | /** | |
810 | * tty_ldisc_init - ldisc setup for new tty | |
811 | * @tty: tty being allocated | |
812 | * | |
813 | * Set up the line discipline objects for a newly allocated tty. Note that | |
814 | * the tty structure is not completely set up when this call is made. | |
815 | */ | |
816 | ||
903f9db1 | 817 | int tty_ldisc_init(struct tty_struct *tty) |
01e1abb2 | 818 | { |
36697529 | 819 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 820 | if (IS_ERR(ld)) |
903f9db1 | 821 | return PTR_ERR(ld); |
f4807045 | 822 | tty->ldisc = ld; |
903f9db1 | 823 | return 0; |
01e1abb2 AC |
824 | } |
825 | ||
6716671d | 826 | /** |
c8b710b3 | 827 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
828 | * @tty: tty that was allocated recently |
829 | * | |
830 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
831 | * this call is made. | |
832 | */ | |
833 | void tty_ldisc_deinit(struct tty_struct *tty) | |
834 | { | |
c8b710b3 PH |
835 | if (tty->ldisc) |
836 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 837 | tty->ldisc = NULL; |
6716671d | 838 | } |