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 | ||
530c4ba3 | 159 | static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); |
7c0cca7c | 160 | |
36697529 | 161 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 162 | { |
c65c9bc3 | 163 | struct tty_ldisc *ld; |
182274f8 | 164 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
165 | |
166 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 167 | return ERR_PTR(-EINVAL); |
182274f8 LT |
168 | |
169 | /* | |
170 | * Get the ldisc ops - we may need to request them to be loaded | |
171 | * dynamically and try again. | |
172 | */ | |
173 | ldops = get_ldops(disc); | |
174 | if (IS_ERR(ldops)) { | |
7c0cca7c GKH |
175 | if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) |
176 | return ERR_PTR(-EPERM); | |
01e1abb2 | 177 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
178 | ldops = get_ldops(disc); |
179 | if (IS_ERR(ldops)) | |
180 | return ERR_CAST(ldops); | |
181 | } | |
182 | ||
bcdd0ca8 TH |
183 | /* |
184 | * There is no way to handle allocation failure of only 16 bytes. | |
185 | * Let's simplify error handling and save more memory. | |
186 | */ | |
187 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); | |
182274f8 | 188 | ld->ops = ldops; |
36697529 | 189 | ld->tty = tty; |
1541f845 | 190 | |
c65c9bc3 | 191 | return ld; |
01e1abb2 AC |
192 | } |
193 | ||
734de249 PH |
194 | /** |
195 | * tty_ldisc_put - release the ldisc | |
196 | * | |
197 | * Complement of tty_ldisc_get(). | |
198 | */ | |
cb128f69 | 199 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 200 | { |
734de249 PH |
201 | if (WARN_ON_ONCE(!ld)) |
202 | return; | |
203 | ||
36697529 | 204 | put_ldops(ld->ops); |
734de249 | 205 | kfree(ld); |
734de249 PH |
206 | } |
207 | ||
852e99d2 | 208 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
209 | { |
210 | return (*pos < NR_LDISCS) ? pos : NULL; | |
211 | } | |
212 | ||
852e99d2 | 213 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
214 | { |
215 | (*pos)++; | |
216 | return (*pos < NR_LDISCS) ? pos : NULL; | |
217 | } | |
218 | ||
219 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
220 | { | |
221 | } | |
222 | ||
223 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
224 | { | |
225 | int i = *(loff_t *)v; | |
f0de0e8d | 226 | struct tty_ldisc_ops *ldops; |
852e99d2 | 227 | |
f0de0e8d LT |
228 | ldops = get_ldops(i); |
229 | if (IS_ERR(ldops)) | |
01e1abb2 | 230 | return 0; |
f0de0e8d LT |
231 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
232 | put_ldops(ldops); | |
01e1abb2 AC |
233 | return 0; |
234 | } | |
235 | ||
fddda2b7 | 236 | const struct seq_operations tty_ldiscs_seq_ops = { |
01e1abb2 AC |
237 | .start = tty_ldiscs_seq_start, |
238 | .next = tty_ldiscs_seq_next, | |
239 | .stop = tty_ldiscs_seq_stop, | |
240 | .show = tty_ldiscs_seq_show, | |
241 | }; | |
242 | ||
01e1abb2 AC |
243 | /** |
244 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
245 | * @tty: tty device | |
246 | * | |
247 | * Dereference the line discipline for the terminal and take a | |
248 | * reference to it. If the line discipline is in flux then | |
249 | * wait patiently until it changes. | |
250 | * | |
892d1fa7 PH |
251 | * Returns: NULL if the tty has been hungup and not re-opened with |
252 | * a new file descriptor, otherwise valid ldisc reference | |
253 | * | |
01e1abb2 AC |
254 | * Note: Must not be called from an IRQ/timer context. The caller |
255 | * must also be careful not to hold other locks that will deadlock | |
256 | * against a discipline change, such as an existing ldisc reference | |
257 | * (which we check for) | |
258 | * | |
e55afd11 PH |
259 | * Note: a file_operations routine (read/poll/write) should use this |
260 | * function to wait for any ldisc lifetime events to finish. | |
01e1abb2 AC |
261 | */ |
262 | ||
263 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
264 | { | |
a4a3e061 DV |
265 | struct tty_ldisc *ld; |
266 | ||
36697529 | 267 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
268 | ld = tty->ldisc; |
269 | if (!ld) | |
a570a49a | 270 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 271 | return ld; |
01e1abb2 | 272 | } |
01e1abb2 AC |
273 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
274 | ||
275 | /** | |
276 | * tty_ldisc_ref - get the tty ldisc | |
277 | * @tty: tty device | |
278 | * | |
279 | * Dereference the line discipline for the terminal and take a | |
280 | * reference to it. If the line discipline is in flux then | |
281 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
282 | */ |
283 | ||
284 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
285 | { | |
36697529 PH |
286 | struct tty_ldisc *ld = NULL; |
287 | ||
288 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
289 | ld = tty->ldisc; | |
290 | if (!ld) | |
291 | ldsem_up_read(&tty->ldisc_sem); | |
292 | } | |
293 | return ld; | |
01e1abb2 | 294 | } |
01e1abb2 AC |
295 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
296 | ||
297 | /** | |
298 | * tty_ldisc_deref - free a tty ldisc reference | |
299 | * @ld: reference to free up | |
300 | * | |
301 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
302 | * be called in IRQ context. | |
01e1abb2 AC |
303 | */ |
304 | ||
305 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
306 | { | |
36697529 | 307 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 308 | } |
01e1abb2 AC |
309 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
310 | ||
d2c43890 | 311 | |
c2bb524b | 312 | static inline int |
e80a10ee | 313 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
314 | { |
315 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
316 | } | |
317 | ||
c2bb524b | 318 | static inline int |
e80a10ee | 319 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
320 | { |
321 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
322 | LDISC_SEM_OTHER, timeout); | |
323 | } | |
324 | ||
e80a10ee | 325 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 326 | { |
52772ea6 | 327 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
328 | } |
329 | ||
b027e229 | 330 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
331 | { |
332 | int ret; | |
333 | ||
c96cf923 DS |
334 | /* Kindly asking blocked readers to release the read side */ |
335 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
336 | wake_up_interruptible_all(&tty->read_wait); | |
337 | wake_up_interruptible_all(&tty->write_wait); | |
338 | ||
fae76e9a PH |
339 | ret = __tty_ldisc_lock(tty, timeout); |
340 | if (!ret) | |
341 | return -EBUSY; | |
342 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
343 | return 0; | |
344 | } | |
345 | ||
b027e229 | 346 | void tty_ldisc_unlock(struct tty_struct *tty) |
fae76e9a PH |
347 | { |
348 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
c96cf923 DS |
349 | /* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
350 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
fae76e9a PH |
351 | __tty_ldisc_unlock(tty); |
352 | } | |
353 | ||
c2bb524b | 354 | static int |
d2c43890 PH |
355 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
356 | unsigned long timeout) | |
357 | { | |
358 | int ret; | |
359 | ||
360 | if (tty < tty2) { | |
e80a10ee | 361 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 362 | if (ret) { |
e80a10ee | 363 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 364 | if (!ret) |
e80a10ee | 365 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
366 | } |
367 | } else { | |
368 | /* if this is possible, it has lots of implications */ | |
369 | WARN_ON_ONCE(tty == tty2); | |
370 | if (tty2 && tty != tty2) { | |
e80a10ee | 371 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 372 | if (ret) { |
e80a10ee | 373 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 374 | if (!ret) |
e80a10ee | 375 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
376 | } |
377 | } else | |
e80a10ee | 378 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
379 | } |
380 | ||
381 | if (!ret) | |
382 | return -EBUSY; | |
383 | ||
384 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
385 | if (tty2) | |
386 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
387 | return 0; | |
388 | } | |
389 | ||
c2bb524b | 390 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
391 | { |
392 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
393 | } | |
394 | ||
c2bb524b PH |
395 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
396 | struct tty_struct *tty2) | |
d2c43890 | 397 | { |
e80a10ee | 398 | __tty_ldisc_unlock(tty); |
d2c43890 | 399 | if (tty2) |
e80a10ee | 400 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
401 | } |
402 | ||
f2c4c65c AC |
403 | /** |
404 | * tty_ldisc_flush - flush line discipline queue | |
405 | * @tty: tty | |
406 | * | |
86c80a8e PH |
407 | * Flush the line discipline queue (if any) and the tty flip buffers |
408 | * for this tty. | |
f2c4c65c AC |
409 | */ |
410 | ||
411 | void tty_ldisc_flush(struct tty_struct *tty) | |
412 | { | |
413 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
414 | |
415 | tty_buffer_flush(tty, ld); | |
416 | if (ld) | |
f2c4c65c | 417 | tty_ldisc_deref(ld); |
f2c4c65c | 418 | } |
f2c4c65c AC |
419 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
420 | ||
01e1abb2 AC |
421 | /** |
422 | * tty_set_termios_ldisc - set ldisc field | |
423 | * @tty: tty structure | |
c12da96f | 424 | * @disc: line discipline number |
01e1abb2 AC |
425 | * |
426 | * This is probably overkill for real world processors but | |
427 | * they are not on hot paths so a little discipline won't do | |
428 | * any harm. | |
429 | * | |
dd42bf11 PH |
430 | * The line discipline-related tty_struct fields are reset to |
431 | * prevent the ldisc driver from re-using stale information for | |
432 | * the new ldisc instance. | |
433 | * | |
6a1c0680 | 434 | * Locking: takes termios_rwsem |
01e1abb2 AC |
435 | */ |
436 | ||
c12da96f | 437 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 438 | { |
6a1c0680 | 439 | down_write(&tty->termios_rwsem); |
c12da96f | 440 | tty->termios.c_line = disc; |
6a1c0680 | 441 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
442 | |
443 | tty->disc_data = NULL; | |
444 | tty->receive_room = 0; | |
01e1abb2 AC |
445 | } |
446 | ||
c65c9bc3 AC |
447 | /** |
448 | * tty_ldisc_open - open a line discipline | |
449 | * @tty: tty we are opening the ldisc on | |
450 | * @ld: discipline to open | |
451 | * | |
452 | * A helper opening method. Also a convenient debugging and check | |
453 | * point. | |
ec79d605 AB |
454 | * |
455 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
456 | */ |
457 | ||
458 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
459 | { | |
460 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
461 | if (ld->ops->open) { |
462 | int ret; | |
ec79d605 | 463 | /* BTM here locks versus a hangup event */ |
f18f9498 | 464 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
465 | if (ret) |
466 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 467 | |
a570a49a | 468 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
469 | return ret; |
470 | } | |
c65c9bc3 AC |
471 | return 0; |
472 | } | |
473 | ||
474 | /** | |
475 | * tty_ldisc_close - close a line discipline | |
476 | * @tty: tty we are opening the ldisc on | |
477 | * @ld: discipline to close | |
478 | * | |
479 | * A helper close method. Also a convenient debugging and check | |
480 | * point. | |
481 | */ | |
482 | ||
483 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
484 | { | |
9ffbe8ac | 485 | lockdep_assert_held_write(&tty->ldisc_sem); |
c65c9bc3 AC |
486 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
487 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
488 | if (ld->ops->close) | |
489 | ld->ops->close(tty); | |
a570a49a | 490 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 491 | } |
01e1abb2 | 492 | |
8a8dabf2 AC |
493 | /** |
494 | * tty_ldisc_failto - helper for ldisc failback | |
495 | * @tty: tty to open the ldisc on | |
496 | * @ld: ldisc we are trying to fail back to | |
497 | * | |
498 | * Helper to try and recover a tty when switching back to the old | |
499 | * ldisc fails and we need something attached. | |
500 | */ | |
501 | ||
502 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) | |
503 | { | |
504 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
505 | int r; | |
506 | ||
9ffbe8ac | 507 | lockdep_assert_held_write(&tty->ldisc_sem); |
8a8dabf2 AC |
508 | if (IS_ERR(disc)) |
509 | return PTR_ERR(disc); | |
510 | tty->ldisc = disc; | |
511 | tty_set_termios_ldisc(tty, ld); | |
512 | if ((r = tty_ldisc_open(tty, disc)) < 0) | |
513 | tty_ldisc_put(disc); | |
514 | return r; | |
515 | } | |
516 | ||
a8983d01 GKH |
517 | /** |
518 | * tty_ldisc_restore - helper for tty ldisc change | |
519 | * @tty: tty to recover | |
520 | * @old: previous ldisc | |
521 | * | |
522 | * Restore the previous line discipline or N_TTY when a line discipline | |
523 | * change fails due to an open error | |
524 | */ | |
525 | ||
526 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
527 | { | |
a8983d01 | 528 | /* There is an outstanding reference here so this is safe */ |
598c2d41 TH |
529 | if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
530 | const char *name = tty_name(tty); | |
531 | ||
532 | pr_warn("Falling back ldisc for %s.\n", name); | |
8a8dabf2 AC |
533 | /* The traditional behaviour is to fall back to N_TTY, we |
534 | want to avoid falling back to N_NULL unless we have no | |
535 | choice to avoid the risk of breaking anything */ | |
536 | if (tty_ldisc_failto(tty, N_TTY) < 0 && | |
537 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 538 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
539 | } |
540 | } | |
541 | ||
01e1abb2 AC |
542 | /** |
543 | * tty_set_ldisc - set line discipline | |
544 | * @tty: the terminal to set | |
545 | * @ldisc: the line discipline | |
546 | * | |
547 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
548 | * context. The ldisc change logic has to protect itself against any |
549 | * overlapping ldisc change (including on the other end of pty pairs), | |
550 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
551 | */ |
552 | ||
c12da96f | 553 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 554 | { |
a8983d01 GKH |
555 | int retval; |
556 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
557 | ||
558 | new_ldisc = tty_ldisc_get(tty, disc); | |
559 | if (IS_ERR(new_ldisc)) | |
560 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 561 | |
c8483bc9 | 562 | tty_lock(tty); |
276a661a | 563 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
564 | if (retval) |
565 | goto err; | |
01e1abb2 | 566 | |
a570a49a PH |
567 | if (!tty->ldisc) { |
568 | retval = -EIO; | |
569 | goto out; | |
570 | } | |
571 | ||
63d8cb3f | 572 | /* Check the no-op case */ |
a8983d01 | 573 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 574 | goto out; |
c65c9bc3 | 575 | |
63d8cb3f PH |
576 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
577 | /* We were raced by hangup */ | |
578 | retval = -EIO; | |
579 | goto out; | |
01e1abb2 AC |
580 | } |
581 | ||
a8983d01 GKH |
582 | old_ldisc = tty->ldisc; |
583 | ||
584 | /* Shutdown the old discipline. */ | |
585 | tty_ldisc_close(tty, old_ldisc); | |
586 | ||
587 | /* Now set up the new line discipline. */ | |
588 | tty->ldisc = new_ldisc; | |
589 | tty_set_termios_ldisc(tty, disc); | |
590 | ||
591 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 592 | if (retval < 0) { |
c65c9bc3 | 593 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
594 | tty_ldisc_put(new_ldisc); |
595 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 596 | } |
c65c9bc3 | 597 | |
a8983d01 | 598 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 599 | down_read(&tty->termios_rwsem); |
01e1abb2 | 600 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
601 | up_read(&tty->termios_rwsem); |
602 | } | |
01e1abb2 | 603 | |
a8983d01 GKH |
604 | /* At this point we hold a reference to the new ldisc and a |
605 | reference to the old ldisc, or we hold two references to | |
606 | the old ldisc (if it was restored as part of error cleanup | |
607 | above). In either case, releasing a single reference from | |
608 | the old ldisc is correct. */ | |
609 | new_ldisc = old_ldisc; | |
63d8cb3f | 610 | out: |
276a661a | 611 | tty_ldisc_unlock(tty); |
01e1abb2 | 612 | |
c65c9bc3 | 613 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 614 | already running */ |
17a69219 | 615 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 616 | err: |
a8983d01 | 617 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 618 | tty_unlock(tty); |
01e1abb2 AC |
619 | return retval; |
620 | } | |
1ab92da3 | 621 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 622 | |
6ffeb4b2 PH |
623 | /** |
624 | * tty_ldisc_kill - teardown ldisc | |
625 | * @tty: tty being released | |
626 | * | |
627 | * Perform final close of the ldisc and reset tty->ldisc | |
628 | */ | |
629 | static void tty_ldisc_kill(struct tty_struct *tty) | |
630 | { | |
9ffbe8ac | 631 | lockdep_assert_held_write(&tty->ldisc_sem); |
6ffeb4b2 PH |
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 | |
9ffbe8ac | 679 | lockdep_assert_held_write(&tty->ldisc_sem); |
7896f30d | 680 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
681 | if (IS_ERR(ld)) { |
682 | BUG_ON(disc == N_TTY); | |
7896f30d | 683 | return PTR_ERR(ld); |
a8983d01 | 684 | } |
c65c9bc3 | 685 | |
7896f30d PH |
686 | if (tty->ldisc) { |
687 | tty_ldisc_close(tty, tty->ldisc); | |
688 | tty_ldisc_put(tty->ldisc); | |
689 | } | |
690 | ||
691 | /* switch the line discipline */ | |
f4807045 | 692 | tty->ldisc = ld; |
c12da96f | 693 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
694 | retval = tty_ldisc_open(tty, tty->ldisc); |
695 | if (retval) { | |
e65c62b1 JW |
696 | tty_ldisc_put(tty->ldisc); |
697 | tty->ldisc = NULL; | |
7896f30d PH |
698 | } |
699 | return retval; | |
c65c9bc3 AC |
700 | } |
701 | ||
702 | /** | |
703 | * tty_ldisc_hangup - hangup ldisc reset | |
704 | * @tty: tty being hung up | |
705 | * | |
706 | * Some tty devices reset their termios when they receive a hangup | |
707 | * event. In that situation we must also switch back to N_TTY properly | |
708 | * before we reset the termios data. | |
709 | * | |
710 | * Locking: We can take the ldisc mutex as the rest of the code is | |
711 | * careful to allow for this. | |
712 | * | |
713 | * In the pty pair case this occurs in the close() path of the | |
714 | * tty itself so we must be careful about locking rules. | |
715 | */ | |
716 | ||
892d1fa7 | 717 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
718 | { |
719 | struct tty_ldisc *ld; | |
720 | ||
a570a49a | 721 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 722 | |
c65c9bc3 AC |
723 | ld = tty_ldisc_ref(tty); |
724 | if (ld != NULL) { | |
c65c9bc3 AC |
725 | if (ld->ops->flush_buffer) |
726 | ld->ops->flush_buffer(tty); | |
727 | tty_driver_flush_buffer(tty); | |
728 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
729 | ld->ops->write_wakeup) | |
730 | ld->ops->write_wakeup(tty); | |
731 | if (ld->ops->hangup) | |
732 | ld->ops->hangup(tty); | |
733 | tty_ldisc_deref(ld); | |
734 | } | |
36697529 | 735 | |
a9a08845 LT |
736 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
737 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 738 | |
c65c9bc3 AC |
739 | /* |
740 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
741 | * N_TTY if need be. |
742 | * | |
743 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 744 | */ |
fae76e9a | 745 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 746 | |
892d1fa7 PH |
747 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
748 | tty_reset_termios(tty); | |
c8785241 | 749 | |
892d1fa7 PH |
750 | if (tty->ldisc) { |
751 | if (reinit) { | |
e65c62b1 JW |
752 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
753 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
754 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
755 | } else |
756 | tty_ldisc_kill(tty); | |
c65c9bc3 | 757 | } |
fae76e9a | 758 | tty_ldisc_unlock(tty); |
c65c9bc3 | 759 | } |
01e1abb2 AC |
760 | |
761 | /** | |
762 | * tty_ldisc_setup - open line discipline | |
763 | * @tty: tty being shut down | |
764 | * @o_tty: pair tty for pty/tty pairs | |
765 | * | |
766 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
767 | * line disciplines and bind them to the tty. This has no locking issues |
768 | * as the device isn't yet active. | |
01e1abb2 AC |
769 | */ |
770 | ||
771 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
772 | { | |
9de2a7ce | 773 | int retval = tty_ldisc_open(tty, tty->ldisc); |
c65c9bc3 AC |
774 | if (retval) |
775 | return retval; | |
776 | ||
777 | if (o_tty) { | |
110b8928 DS |
778 | /* |
779 | * Called without o_tty->ldisc_sem held, as o_tty has been | |
780 | * just allocated and no one has a reference to it. | |
781 | */ | |
c65c9bc3 | 782 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
01e1abb2 | 783 | if (retval) { |
9de2a7ce | 784 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
785 | return retval; |
786 | } | |
01e1abb2 | 787 | } |
01e1abb2 AC |
788 | return 0; |
789 | } | |
89c8d91e | 790 | |
01e1abb2 AC |
791 | /** |
792 | * tty_ldisc_release - release line discipline | |
62462aef | 793 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 794 | * |
62462aef | 795 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 796 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
797 | */ |
798 | ||
62462aef | 799 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 800 | { |
62462aef PH |
801 | struct tty_struct *o_tty = tty->link; |
802 | ||
01e1abb2 | 803 | /* |
a2965b7b PH |
804 | * Shutdown this line discipline. As this is the final close, |
805 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 806 | */ |
01e1abb2 | 807 | |
36697529 | 808 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 809 | tty_ldisc_kill(tty); |
c65c9bc3 | 810 | if (o_tty) |
89c8d91e | 811 | tty_ldisc_kill(o_tty); |
36697529 PH |
812 | tty_ldisc_unlock_pair(tty, o_tty); |
813 | ||
aef29bc2 AC |
814 | /* And the memory resources remaining (buffers, termios) will be |
815 | disposed of when the kref hits zero */ | |
fc575ee6 | 816 | |
fb6edc91 | 817 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 | 818 | } |
1ab92da3 | 819 | EXPORT_SYMBOL_GPL(tty_ldisc_release); |
01e1abb2 AC |
820 | |
821 | /** | |
822 | * tty_ldisc_init - ldisc setup for new tty | |
823 | * @tty: tty being allocated | |
824 | * | |
825 | * Set up the line discipline objects for a newly allocated tty. Note that | |
826 | * the tty structure is not completely set up when this call is made. | |
827 | */ | |
828 | ||
903f9db1 | 829 | int tty_ldisc_init(struct tty_struct *tty) |
01e1abb2 | 830 | { |
36697529 | 831 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 832 | if (IS_ERR(ld)) |
903f9db1 | 833 | return PTR_ERR(ld); |
f4807045 | 834 | tty->ldisc = ld; |
903f9db1 | 835 | return 0; |
01e1abb2 AC |
836 | } |
837 | ||
6716671d | 838 | /** |
c8b710b3 | 839 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
840 | * @tty: tty that was allocated recently |
841 | * | |
842 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
843 | * this call is made. | |
844 | */ | |
845 | void tty_ldisc_deinit(struct tty_struct *tty) | |
846 | { | |
110b8928 | 847 | /* no ldisc_sem, tty is being destroyed */ |
c8b710b3 PH |
848 | if (tty->ldisc) |
849 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 850 | tty->ldisc = NULL; |
6716671d | 851 | } |
7c0cca7c | 852 | |
7c0cca7c GKH |
853 | static struct ctl_table tty_table[] = { |
854 | { | |
855 | .procname = "ldisc_autoload", | |
856 | .data = &tty_ldisc_autoload, | |
857 | .maxlen = sizeof(tty_ldisc_autoload), | |
858 | .mode = 0644, | |
859 | .proc_handler = proc_dointvec, | |
eec4844f MC |
860 | .extra1 = SYSCTL_ZERO, |
861 | .extra2 = SYSCTL_ONE, | |
7c0cca7c GKH |
862 | }, |
863 | { } | |
864 | }; | |
865 | ||
866 | static struct ctl_table tty_dir_table[] = { | |
867 | { | |
868 | .procname = "tty", | |
869 | .mode = 0555, | |
870 | .child = tty_table, | |
871 | }, | |
872 | { } | |
873 | }; | |
874 | ||
875 | static struct ctl_table tty_root_table[] = { | |
876 | { | |
877 | .procname = "dev", | |
878 | .mode = 0555, | |
879 | .child = tty_dir_table, | |
880 | }, | |
881 | { } | |
882 | }; | |
883 | ||
884 | void tty_sysctl_init(void) | |
885 | { | |
886 | register_sysctl_table(tty_root_table); | |
887 | } |