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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 | ||
179 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
180 | if (ld == NULL) { | |
181 | put_ldops(ldops); | |
182 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 183 | } |
182274f8 LT |
184 | |
185 | ld->ops = ldops; | |
36697529 | 186 | ld->tty = tty; |
1541f845 | 187 | |
c65c9bc3 | 188 | return ld; |
01e1abb2 AC |
189 | } |
190 | ||
734de249 PH |
191 | /** |
192 | * tty_ldisc_put - release the ldisc | |
193 | * | |
194 | * Complement of tty_ldisc_get(). | |
195 | */ | |
cb128f69 | 196 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 197 | { |
734de249 PH |
198 | if (WARN_ON_ONCE(!ld)) |
199 | return; | |
200 | ||
36697529 | 201 | put_ldops(ld->ops); |
734de249 | 202 | kfree(ld); |
734de249 PH |
203 | } |
204 | ||
852e99d2 | 205 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
206 | { |
207 | return (*pos < NR_LDISCS) ? pos : NULL; | |
208 | } | |
209 | ||
852e99d2 | 210 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
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; | |
f0de0e8d | 223 | struct tty_ldisc_ops *ldops; |
852e99d2 | 224 | |
f0de0e8d LT |
225 | ldops = get_ldops(i); |
226 | if (IS_ERR(ldops)) | |
01e1abb2 | 227 | return 0; |
f0de0e8d LT |
228 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
229 | put_ldops(ldops); | |
01e1abb2 AC |
230 | return 0; |
231 | } | |
232 | ||
233 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
234 | .start = tty_ldiscs_seq_start, | |
235 | .next = tty_ldiscs_seq_next, | |
236 | .stop = tty_ldiscs_seq_stop, | |
237 | .show = tty_ldiscs_seq_show, | |
238 | }; | |
239 | ||
240 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
241 | { | |
242 | return seq_open(file, &tty_ldiscs_seq_ops); | |
243 | } | |
244 | ||
245 | const struct file_operations tty_ldiscs_proc_fops = { | |
246 | .owner = THIS_MODULE, | |
247 | .open = proc_tty_ldiscs_open, | |
248 | .read = seq_read, | |
249 | .llseek = seq_lseek, | |
250 | .release = seq_release, | |
251 | }; | |
252 | ||
01e1abb2 AC |
253 | /** |
254 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
255 | * @tty: tty device | |
256 | * | |
257 | * Dereference the line discipline for the terminal and take a | |
258 | * reference to it. If the line discipline is in flux then | |
259 | * wait patiently until it changes. | |
260 | * | |
892d1fa7 PH |
261 | * Returns: NULL if the tty has been hungup and not re-opened with |
262 | * a new file descriptor, otherwise valid ldisc reference | |
263 | * | |
01e1abb2 AC |
264 | * Note: Must not be called from an IRQ/timer context. The caller |
265 | * must also be careful not to hold other locks that will deadlock | |
266 | * against a discipline change, such as an existing ldisc reference | |
267 | * (which we check for) | |
268 | * | |
e55afd11 PH |
269 | * Note: a file_operations routine (read/poll/write) should use this |
270 | * function to wait for any ldisc lifetime events to finish. | |
01e1abb2 AC |
271 | */ |
272 | ||
273 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
274 | { | |
a4a3e061 DV |
275 | struct tty_ldisc *ld; |
276 | ||
36697529 | 277 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
278 | ld = tty->ldisc; |
279 | if (!ld) | |
a570a49a | 280 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 281 | return ld; |
01e1abb2 | 282 | } |
01e1abb2 AC |
283 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
284 | ||
285 | /** | |
286 | * tty_ldisc_ref - get the tty ldisc | |
287 | * @tty: tty device | |
288 | * | |
289 | * Dereference the line discipline for the terminal and take a | |
290 | * reference to it. If the line discipline is in flux then | |
291 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
292 | */ |
293 | ||
294 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
295 | { | |
36697529 PH |
296 | struct tty_ldisc *ld = NULL; |
297 | ||
298 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
299 | ld = tty->ldisc; | |
300 | if (!ld) | |
301 | ldsem_up_read(&tty->ldisc_sem); | |
302 | } | |
303 | return ld; | |
01e1abb2 | 304 | } |
01e1abb2 AC |
305 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
306 | ||
307 | /** | |
308 | * tty_ldisc_deref - free a tty ldisc reference | |
309 | * @ld: reference to free up | |
310 | * | |
311 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
312 | * be called in IRQ context. | |
01e1abb2 AC |
313 | */ |
314 | ||
315 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
316 | { | |
36697529 | 317 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 318 | } |
01e1abb2 AC |
319 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
320 | ||
d2c43890 | 321 | |
c2bb524b | 322 | static inline int |
e80a10ee | 323 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
324 | { |
325 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
326 | } | |
327 | ||
c2bb524b | 328 | static inline int |
e80a10ee | 329 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
330 | { |
331 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
332 | LDISC_SEM_OTHER, timeout); | |
333 | } | |
334 | ||
e80a10ee | 335 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 336 | { |
52772ea6 | 337 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
338 | } |
339 | ||
b027e229 | 340 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
341 | { |
342 | int ret; | |
343 | ||
344 | ret = __tty_ldisc_lock(tty, timeout); | |
345 | if (!ret) | |
346 | return -EBUSY; | |
347 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
348 | return 0; | |
349 | } | |
350 | ||
b027e229 | 351 | void tty_ldisc_unlock(struct tty_struct *tty) |
fae76e9a PH |
352 | { |
353 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
354 | __tty_ldisc_unlock(tty); | |
355 | } | |
356 | ||
c2bb524b | 357 | static int |
d2c43890 PH |
358 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
359 | unsigned long timeout) | |
360 | { | |
361 | int ret; | |
362 | ||
363 | if (tty < tty2) { | |
e80a10ee | 364 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 365 | if (ret) { |
e80a10ee | 366 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 367 | if (!ret) |
e80a10ee | 368 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
369 | } |
370 | } else { | |
371 | /* if this is possible, it has lots of implications */ | |
372 | WARN_ON_ONCE(tty == tty2); | |
373 | if (tty2 && tty != tty2) { | |
e80a10ee | 374 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 375 | if (ret) { |
e80a10ee | 376 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 377 | if (!ret) |
e80a10ee | 378 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
379 | } |
380 | } else | |
e80a10ee | 381 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
382 | } |
383 | ||
384 | if (!ret) | |
385 | return -EBUSY; | |
386 | ||
387 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
388 | if (tty2) | |
389 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
390 | return 0; | |
391 | } | |
392 | ||
c2bb524b | 393 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
394 | { |
395 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
396 | } | |
397 | ||
c2bb524b PH |
398 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
399 | struct tty_struct *tty2) | |
d2c43890 | 400 | { |
e80a10ee | 401 | __tty_ldisc_unlock(tty); |
d2c43890 | 402 | if (tty2) |
e80a10ee | 403 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
404 | } |
405 | ||
f2c4c65c AC |
406 | /** |
407 | * tty_ldisc_flush - flush line discipline queue | |
408 | * @tty: tty | |
409 | * | |
86c80a8e PH |
410 | * Flush the line discipline queue (if any) and the tty flip buffers |
411 | * for this tty. | |
f2c4c65c AC |
412 | */ |
413 | ||
414 | void tty_ldisc_flush(struct tty_struct *tty) | |
415 | { | |
416 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
417 | |
418 | tty_buffer_flush(tty, ld); | |
419 | if (ld) | |
f2c4c65c | 420 | tty_ldisc_deref(ld); |
f2c4c65c | 421 | } |
f2c4c65c AC |
422 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
423 | ||
01e1abb2 AC |
424 | /** |
425 | * tty_set_termios_ldisc - set ldisc field | |
426 | * @tty: tty structure | |
c12da96f | 427 | * @disc: line discipline number |
01e1abb2 AC |
428 | * |
429 | * This is probably overkill for real world processors but | |
430 | * they are not on hot paths so a little discipline won't do | |
431 | * any harm. | |
432 | * | |
dd42bf11 PH |
433 | * The line discipline-related tty_struct fields are reset to |
434 | * prevent the ldisc driver from re-using stale information for | |
435 | * the new ldisc instance. | |
436 | * | |
6a1c0680 | 437 | * Locking: takes termios_rwsem |
01e1abb2 AC |
438 | */ |
439 | ||
c12da96f | 440 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 441 | { |
6a1c0680 | 442 | down_write(&tty->termios_rwsem); |
c12da96f | 443 | tty->termios.c_line = disc; |
6a1c0680 | 444 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
445 | |
446 | tty->disc_data = NULL; | |
447 | tty->receive_room = 0; | |
01e1abb2 AC |
448 | } |
449 | ||
c65c9bc3 AC |
450 | /** |
451 | * tty_ldisc_open - open a line discipline | |
452 | * @tty: tty we are opening the ldisc on | |
453 | * @ld: discipline to open | |
454 | * | |
455 | * A helper opening method. Also a convenient debugging and check | |
456 | * point. | |
ec79d605 AB |
457 | * |
458 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
459 | */ |
460 | ||
461 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
462 | { | |
463 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
464 | if (ld->ops->open) { |
465 | int ret; | |
ec79d605 | 466 | /* BTM here locks versus a hangup event */ |
f18f9498 | 467 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
468 | if (ret) |
469 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 470 | |
a570a49a | 471 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
472 | return ret; |
473 | } | |
c65c9bc3 AC |
474 | return 0; |
475 | } | |
476 | ||
477 | /** | |
478 | * tty_ldisc_close - close a line discipline | |
479 | * @tty: tty we are opening the ldisc on | |
480 | * @ld: discipline to close | |
481 | * | |
482 | * A helper close method. Also a convenient debugging and check | |
483 | * point. | |
484 | */ | |
485 | ||
486 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
487 | { | |
488 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
489 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
490 | if (ld->ops->close) | |
491 | ld->ops->close(tty); | |
a570a49a | 492 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 493 | } |
01e1abb2 | 494 | |
8a8dabf2 AC |
495 | /** |
496 | * tty_ldisc_failto - helper for ldisc failback | |
497 | * @tty: tty to open the ldisc on | |
498 | * @ld: ldisc we are trying to fail back to | |
499 | * | |
500 | * Helper to try and recover a tty when switching back to the old | |
501 | * ldisc fails and we need something attached. | |
502 | */ | |
503 | ||
504 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) | |
505 | { | |
506 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
507 | int r; | |
508 | ||
509 | if (IS_ERR(disc)) | |
510 | return PTR_ERR(disc); | |
511 | tty->ldisc = disc; | |
512 | tty_set_termios_ldisc(tty, ld); | |
513 | if ((r = tty_ldisc_open(tty, disc)) < 0) | |
514 | tty_ldisc_put(disc); | |
515 | return r; | |
516 | } | |
517 | ||
a8983d01 GKH |
518 | /** |
519 | * tty_ldisc_restore - helper for tty ldisc change | |
520 | * @tty: tty to recover | |
521 | * @old: previous ldisc | |
522 | * | |
523 | * Restore the previous line discipline or N_TTY when a line discipline | |
524 | * change fails due to an open error | |
525 | */ | |
526 | ||
527 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
528 | { | |
a8983d01 | 529 | /* There is an outstanding reference here so this is safe */ |
598c2d41 TH |
530 | if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
531 | const char *name = tty_name(tty); | |
532 | ||
533 | pr_warn("Falling back ldisc for %s.\n", name); | |
8a8dabf2 AC |
534 | /* The traditional behaviour is to fall back to N_TTY, we |
535 | want to avoid falling back to N_NULL unless we have no | |
536 | choice to avoid the risk of breaking anything */ | |
537 | if (tty_ldisc_failto(tty, N_TTY) < 0 && | |
538 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 539 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
540 | } |
541 | } | |
542 | ||
01e1abb2 AC |
543 | /** |
544 | * tty_set_ldisc - set line discipline | |
545 | * @tty: the terminal to set | |
546 | * @ldisc: the line discipline | |
547 | * | |
548 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
549 | * context. The ldisc change logic has to protect itself against any |
550 | * overlapping ldisc change (including on the other end of pty pairs), | |
551 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
552 | */ |
553 | ||
c12da96f | 554 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 555 | { |
a8983d01 GKH |
556 | int retval; |
557 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
558 | ||
559 | new_ldisc = tty_ldisc_get(tty, disc); | |
560 | if (IS_ERR(new_ldisc)) | |
561 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 562 | |
c8483bc9 | 563 | tty_lock(tty); |
276a661a | 564 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
565 | if (retval) |
566 | goto err; | |
01e1abb2 | 567 | |
a570a49a PH |
568 | if (!tty->ldisc) { |
569 | retval = -EIO; | |
570 | goto out; | |
571 | } | |
572 | ||
63d8cb3f | 573 | /* Check the no-op case */ |
a8983d01 | 574 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 575 | goto out; |
c65c9bc3 | 576 | |
63d8cb3f PH |
577 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
578 | /* We were raced by hangup */ | |
579 | retval = -EIO; | |
580 | goto out; | |
01e1abb2 AC |
581 | } |
582 | ||
a8983d01 GKH |
583 | old_ldisc = tty->ldisc; |
584 | ||
585 | /* Shutdown the old discipline. */ | |
586 | tty_ldisc_close(tty, old_ldisc); | |
587 | ||
588 | /* Now set up the new line discipline. */ | |
589 | tty->ldisc = new_ldisc; | |
590 | tty_set_termios_ldisc(tty, disc); | |
591 | ||
592 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 593 | if (retval < 0) { |
c65c9bc3 | 594 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
595 | tty_ldisc_put(new_ldisc); |
596 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 597 | } |
c65c9bc3 | 598 | |
a8983d01 | 599 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 600 | down_read(&tty->termios_rwsem); |
01e1abb2 | 601 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
602 | up_read(&tty->termios_rwsem); |
603 | } | |
01e1abb2 | 604 | |
a8983d01 GKH |
605 | /* At this point we hold a reference to the new ldisc and a |
606 | reference to the old ldisc, or we hold two references to | |
607 | the old ldisc (if it was restored as part of error cleanup | |
608 | above). In either case, releasing a single reference from | |
609 | the old ldisc is correct. */ | |
610 | new_ldisc = old_ldisc; | |
63d8cb3f | 611 | out: |
276a661a | 612 | tty_ldisc_unlock(tty); |
01e1abb2 | 613 | |
c65c9bc3 | 614 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 615 | already running */ |
17a69219 | 616 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 617 | err: |
a8983d01 | 618 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 619 | tty_unlock(tty); |
01e1abb2 AC |
620 | return retval; |
621 | } | |
1ab92da3 | 622 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 623 | |
6ffeb4b2 PH |
624 | /** |
625 | * tty_ldisc_kill - teardown ldisc | |
626 | * @tty: tty being released | |
627 | * | |
628 | * Perform final close of the ldisc and reset tty->ldisc | |
629 | */ | |
630 | static void tty_ldisc_kill(struct tty_struct *tty) | |
631 | { | |
632 | if (!tty->ldisc) | |
633 | return; | |
634 | /* | |
635 | * Now kill off the ldisc | |
636 | */ | |
637 | tty_ldisc_close(tty, tty->ldisc); | |
638 | tty_ldisc_put(tty->ldisc); | |
639 | /* Force an oops if we mess this up */ | |
640 | tty->ldisc = NULL; | |
641 | } | |
642 | ||
c65c9bc3 AC |
643 | /** |
644 | * tty_reset_termios - reset terminal state | |
645 | * @tty: tty to reset | |
646 | * | |
647 | * Restore a terminal to the driver default state. | |
648 | */ | |
649 | ||
650 | static void tty_reset_termios(struct tty_struct *tty) | |
651 | { | |
6a1c0680 | 652 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
653 | tty->termios = tty->driver->init_termios; |
654 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
655 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 656 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
657 | } |
658 | ||
659 | ||
660 | /** | |
661 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
662 | * @tty: tty to reinit | |
c12da96f | 663 | * @disc: line discipline to reinitialize |
c65c9bc3 | 664 | * |
7896f30d | 665 | * Completely reinitialize the line discipline state, by closing the |
892d1fa7 PH |
666 | * current instance, if there is one, and opening a new instance. If |
667 | * an error occurs opening the new non-N_TTY instance, the instance | |
668 | * is dropped and tty->ldisc reset to NULL. The caller can then retry | |
669 | * with N_TTY instead. | |
7896f30d PH |
670 | * |
671 | * Returns 0 if successful, otherwise error code < 0 | |
c65c9bc3 AC |
672 | */ |
673 | ||
892d1fa7 | 674 | int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
c65c9bc3 | 675 | { |
7896f30d PH |
676 | struct tty_ldisc *ld; |
677 | int retval; | |
1c95ba1e | 678 | |
7896f30d | 679 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
680 | if (IS_ERR(ld)) { |
681 | BUG_ON(disc == N_TTY); | |
7896f30d | 682 | return PTR_ERR(ld); |
a8983d01 | 683 | } |
c65c9bc3 | 684 | |
7896f30d PH |
685 | if (tty->ldisc) { |
686 | tty_ldisc_close(tty, tty->ldisc); | |
687 | tty_ldisc_put(tty->ldisc); | |
688 | } | |
689 | ||
690 | /* switch the line discipline */ | |
f4807045 | 691 | tty->ldisc = ld; |
c12da96f | 692 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
693 | retval = tty_ldisc_open(tty, tty->ldisc); |
694 | if (retval) { | |
e65c62b1 JW |
695 | tty_ldisc_put(tty->ldisc); |
696 | tty->ldisc = NULL; | |
7896f30d PH |
697 | } |
698 | return retval; | |
c65c9bc3 AC |
699 | } |
700 | ||
701 | /** | |
702 | * tty_ldisc_hangup - hangup ldisc reset | |
703 | * @tty: tty being hung up | |
704 | * | |
705 | * Some tty devices reset their termios when they receive a hangup | |
706 | * event. In that situation we must also switch back to N_TTY properly | |
707 | * before we reset the termios data. | |
708 | * | |
709 | * Locking: We can take the ldisc mutex as the rest of the code is | |
710 | * careful to allow for this. | |
711 | * | |
712 | * In the pty pair case this occurs in the close() path of the | |
713 | * tty itself so we must be careful about locking rules. | |
714 | */ | |
715 | ||
892d1fa7 | 716 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
717 | { |
718 | struct tty_ldisc *ld; | |
719 | ||
a570a49a | 720 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 721 | |
c65c9bc3 AC |
722 | ld = tty_ldisc_ref(tty); |
723 | if (ld != NULL) { | |
c65c9bc3 AC |
724 | if (ld->ops->flush_buffer) |
725 | ld->ops->flush_buffer(tty); | |
726 | tty_driver_flush_buffer(tty); | |
727 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
728 | ld->ops->write_wakeup) | |
729 | ld->ops->write_wakeup(tty); | |
730 | if (ld->ops->hangup) | |
731 | ld->ops->hangup(tty); | |
732 | tty_ldisc_deref(ld); | |
733 | } | |
36697529 | 734 | |
a9a08845 LT |
735 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
736 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 737 | |
c65c9bc3 AC |
738 | /* |
739 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
740 | * N_TTY if need be. |
741 | * | |
742 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 743 | */ |
fae76e9a | 744 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 745 | |
892d1fa7 PH |
746 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
747 | tty_reset_termios(tty); | |
c8785241 | 748 | |
892d1fa7 PH |
749 | if (tty->ldisc) { |
750 | if (reinit) { | |
e65c62b1 JW |
751 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
752 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
753 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
754 | } else |
755 | tty_ldisc_kill(tty); | |
c65c9bc3 | 756 | } |
fae76e9a | 757 | tty_ldisc_unlock(tty); |
c65c9bc3 | 758 | } |
01e1abb2 AC |
759 | |
760 | /** | |
761 | * tty_ldisc_setup - open line discipline | |
762 | * @tty: tty being shut down | |
763 | * @o_tty: pair tty for pty/tty pairs | |
764 | * | |
765 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
766 | * line disciplines and bind them to the tty. This has no locking issues |
767 | * as the device isn't yet active. | |
01e1abb2 AC |
768 | */ |
769 | ||
770 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
771 | { | |
9de2a7ce | 772 | int retval = tty_ldisc_open(tty, tty->ldisc); |
c65c9bc3 AC |
773 | if (retval) |
774 | return retval; | |
775 | ||
776 | if (o_tty) { | |
777 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 778 | if (retval) { |
9de2a7ce | 779 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
780 | return retval; |
781 | } | |
01e1abb2 | 782 | } |
01e1abb2 AC |
783 | return 0; |
784 | } | |
89c8d91e | 785 | |
01e1abb2 AC |
786 | /** |
787 | * tty_ldisc_release - release line discipline | |
62462aef | 788 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 789 | * |
62462aef | 790 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 791 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
792 | */ |
793 | ||
62462aef | 794 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 795 | { |
62462aef PH |
796 | struct tty_struct *o_tty = tty->link; |
797 | ||
01e1abb2 | 798 | /* |
a2965b7b PH |
799 | * Shutdown this line discipline. As this is the final close, |
800 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 801 | */ |
01e1abb2 | 802 | |
36697529 | 803 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 804 | tty_ldisc_kill(tty); |
c65c9bc3 | 805 | if (o_tty) |
89c8d91e | 806 | tty_ldisc_kill(o_tty); |
36697529 PH |
807 | tty_ldisc_unlock_pair(tty, o_tty); |
808 | ||
aef29bc2 AC |
809 | /* And the memory resources remaining (buffers, termios) will be |
810 | disposed of when the kref hits zero */ | |
fc575ee6 | 811 | |
fb6edc91 | 812 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 | 813 | } |
1ab92da3 | 814 | EXPORT_SYMBOL_GPL(tty_ldisc_release); |
01e1abb2 AC |
815 | |
816 | /** | |
817 | * tty_ldisc_init - ldisc setup for new tty | |
818 | * @tty: tty being allocated | |
819 | * | |
820 | * Set up the line discipline objects for a newly allocated tty. Note that | |
821 | * the tty structure is not completely set up when this call is made. | |
822 | */ | |
823 | ||
824 | void tty_ldisc_init(struct tty_struct *tty) | |
825 | { | |
36697529 | 826 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 827 | if (IS_ERR(ld)) |
01e1abb2 | 828 | panic("n_tty: init_tty"); |
f4807045 | 829 | tty->ldisc = ld; |
01e1abb2 AC |
830 | } |
831 | ||
6716671d | 832 | /** |
c8b710b3 | 833 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
834 | * @tty: tty that was allocated recently |
835 | * | |
836 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
837 | * this call is made. | |
838 | */ | |
839 | void tty_ldisc_deinit(struct tty_struct *tty) | |
840 | { | |
c8b710b3 PH |
841 | if (tty->ldisc) |
842 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 843 | tty->ldisc = NULL; |
6716671d | 844 | } |