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 | ||
7c0cca7c GKH |
159 | #if defined(CONFIG_LDISC_AUTOLOAD) |
160 | #define INITIAL_AUTOLOAD_STATE 1 | |
161 | #else | |
162 | #define INITIAL_AUTOLOAD_STATE 0 | |
163 | #endif | |
164 | static int tty_ldisc_autoload = INITIAL_AUTOLOAD_STATE; | |
165 | ||
36697529 | 166 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 167 | { |
c65c9bc3 | 168 | struct tty_ldisc *ld; |
182274f8 | 169 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
170 | |
171 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 172 | return ERR_PTR(-EINVAL); |
182274f8 LT |
173 | |
174 | /* | |
175 | * Get the ldisc ops - we may need to request them to be loaded | |
176 | * dynamically and try again. | |
177 | */ | |
178 | ldops = get_ldops(disc); | |
179 | if (IS_ERR(ldops)) { | |
7c0cca7c GKH |
180 | if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) |
181 | return ERR_PTR(-EPERM); | |
01e1abb2 | 182 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
183 | ldops = get_ldops(disc); |
184 | if (IS_ERR(ldops)) | |
185 | return ERR_CAST(ldops); | |
186 | } | |
187 | ||
bcdd0ca8 TH |
188 | /* |
189 | * There is no way to handle allocation failure of only 16 bytes. | |
190 | * Let's simplify error handling and save more memory. | |
191 | */ | |
192 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); | |
182274f8 | 193 | ld->ops = ldops; |
36697529 | 194 | ld->tty = tty; |
1541f845 | 195 | |
c65c9bc3 | 196 | return ld; |
01e1abb2 AC |
197 | } |
198 | ||
734de249 PH |
199 | /** |
200 | * tty_ldisc_put - release the ldisc | |
201 | * | |
202 | * Complement of tty_ldisc_get(). | |
203 | */ | |
cb128f69 | 204 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 205 | { |
734de249 PH |
206 | if (WARN_ON_ONCE(!ld)) |
207 | return; | |
208 | ||
36697529 | 209 | put_ldops(ld->ops); |
734de249 | 210 | kfree(ld); |
734de249 PH |
211 | } |
212 | ||
852e99d2 | 213 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
214 | { |
215 | return (*pos < NR_LDISCS) ? pos : NULL; | |
216 | } | |
217 | ||
852e99d2 | 218 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
219 | { |
220 | (*pos)++; | |
221 | return (*pos < NR_LDISCS) ? pos : NULL; | |
222 | } | |
223 | ||
224 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
225 | { | |
226 | } | |
227 | ||
228 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
229 | { | |
230 | int i = *(loff_t *)v; | |
f0de0e8d | 231 | struct tty_ldisc_ops *ldops; |
852e99d2 | 232 | |
f0de0e8d LT |
233 | ldops = get_ldops(i); |
234 | if (IS_ERR(ldops)) | |
01e1abb2 | 235 | return 0; |
f0de0e8d LT |
236 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
237 | put_ldops(ldops); | |
01e1abb2 AC |
238 | return 0; |
239 | } | |
240 | ||
fddda2b7 | 241 | const struct seq_operations tty_ldiscs_seq_ops = { |
01e1abb2 AC |
242 | .start = tty_ldiscs_seq_start, |
243 | .next = tty_ldiscs_seq_next, | |
244 | .stop = tty_ldiscs_seq_stop, | |
245 | .show = tty_ldiscs_seq_show, | |
246 | }; | |
247 | ||
01e1abb2 AC |
248 | /** |
249 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
250 | * @tty: tty device | |
251 | * | |
252 | * Dereference the line discipline for the terminal and take a | |
253 | * reference to it. If the line discipline is in flux then | |
254 | * wait patiently until it changes. | |
255 | * | |
892d1fa7 PH |
256 | * Returns: NULL if the tty has been hungup and not re-opened with |
257 | * a new file descriptor, otherwise valid ldisc reference | |
258 | * | |
01e1abb2 AC |
259 | * Note: Must not be called from an IRQ/timer context. The caller |
260 | * must also be careful not to hold other locks that will deadlock | |
261 | * against a discipline change, such as an existing ldisc reference | |
262 | * (which we check for) | |
263 | * | |
e55afd11 PH |
264 | * Note: a file_operations routine (read/poll/write) should use this |
265 | * function to wait for any ldisc lifetime events to finish. | |
01e1abb2 AC |
266 | */ |
267 | ||
268 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
269 | { | |
a4a3e061 DV |
270 | struct tty_ldisc *ld; |
271 | ||
36697529 | 272 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
273 | ld = tty->ldisc; |
274 | if (!ld) | |
a570a49a | 275 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 276 | return ld; |
01e1abb2 | 277 | } |
01e1abb2 AC |
278 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
279 | ||
280 | /** | |
281 | * tty_ldisc_ref - get the tty ldisc | |
282 | * @tty: tty device | |
283 | * | |
284 | * Dereference the line discipline for the terminal and take a | |
285 | * reference to it. If the line discipline is in flux then | |
286 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
287 | */ |
288 | ||
289 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
290 | { | |
36697529 PH |
291 | struct tty_ldisc *ld = NULL; |
292 | ||
293 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
294 | ld = tty->ldisc; | |
295 | if (!ld) | |
296 | ldsem_up_read(&tty->ldisc_sem); | |
297 | } | |
298 | return ld; | |
01e1abb2 | 299 | } |
01e1abb2 AC |
300 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
301 | ||
302 | /** | |
303 | * tty_ldisc_deref - free a tty ldisc reference | |
304 | * @ld: reference to free up | |
305 | * | |
306 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
307 | * be called in IRQ context. | |
01e1abb2 AC |
308 | */ |
309 | ||
310 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
311 | { | |
36697529 | 312 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 313 | } |
01e1abb2 AC |
314 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
315 | ||
d2c43890 | 316 | |
c2bb524b | 317 | static inline int |
e80a10ee | 318 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
319 | { |
320 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
321 | } | |
322 | ||
c2bb524b | 323 | static inline int |
e80a10ee | 324 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
325 | { |
326 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
327 | LDISC_SEM_OTHER, timeout); | |
328 | } | |
329 | ||
e80a10ee | 330 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 331 | { |
52772ea6 | 332 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
333 | } |
334 | ||
b027e229 | 335 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
336 | { |
337 | int ret; | |
338 | ||
c96cf923 DS |
339 | /* Kindly asking blocked readers to release the read side */ |
340 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
341 | wake_up_interruptible_all(&tty->read_wait); | |
342 | wake_up_interruptible_all(&tty->write_wait); | |
343 | ||
fae76e9a PH |
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); | |
c96cf923 DS |
354 | /* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
355 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
fae76e9a PH |
356 | __tty_ldisc_unlock(tty); |
357 | } | |
358 | ||
c2bb524b | 359 | static int |
d2c43890 PH |
360 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
361 | unsigned long timeout) | |
362 | { | |
363 | int ret; | |
364 | ||
365 | if (tty < tty2) { | |
e80a10ee | 366 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 367 | if (ret) { |
e80a10ee | 368 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 369 | if (!ret) |
e80a10ee | 370 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
371 | } |
372 | } else { | |
373 | /* if this is possible, it has lots of implications */ | |
374 | WARN_ON_ONCE(tty == tty2); | |
375 | if (tty2 && tty != tty2) { | |
e80a10ee | 376 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 377 | if (ret) { |
e80a10ee | 378 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 379 | if (!ret) |
e80a10ee | 380 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
381 | } |
382 | } else | |
e80a10ee | 383 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
384 | } |
385 | ||
386 | if (!ret) | |
387 | return -EBUSY; | |
388 | ||
389 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
390 | if (tty2) | |
391 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
392 | return 0; | |
393 | } | |
394 | ||
c2bb524b | 395 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
396 | { |
397 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
398 | } | |
399 | ||
c2bb524b PH |
400 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
401 | struct tty_struct *tty2) | |
d2c43890 | 402 | { |
e80a10ee | 403 | __tty_ldisc_unlock(tty); |
d2c43890 | 404 | if (tty2) |
e80a10ee | 405 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
406 | } |
407 | ||
f2c4c65c AC |
408 | /** |
409 | * tty_ldisc_flush - flush line discipline queue | |
410 | * @tty: tty | |
411 | * | |
86c80a8e PH |
412 | * Flush the line discipline queue (if any) and the tty flip buffers |
413 | * for this tty. | |
f2c4c65c AC |
414 | */ |
415 | ||
416 | void tty_ldisc_flush(struct tty_struct *tty) | |
417 | { | |
418 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
419 | |
420 | tty_buffer_flush(tty, ld); | |
421 | if (ld) | |
f2c4c65c | 422 | tty_ldisc_deref(ld); |
f2c4c65c | 423 | } |
f2c4c65c AC |
424 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
425 | ||
01e1abb2 AC |
426 | /** |
427 | * tty_set_termios_ldisc - set ldisc field | |
428 | * @tty: tty structure | |
c12da96f | 429 | * @disc: line discipline number |
01e1abb2 AC |
430 | * |
431 | * This is probably overkill for real world processors but | |
432 | * they are not on hot paths so a little discipline won't do | |
433 | * any harm. | |
434 | * | |
dd42bf11 PH |
435 | * The line discipline-related tty_struct fields are reset to |
436 | * prevent the ldisc driver from re-using stale information for | |
437 | * the new ldisc instance. | |
438 | * | |
6a1c0680 | 439 | * Locking: takes termios_rwsem |
01e1abb2 AC |
440 | */ |
441 | ||
c12da96f | 442 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 443 | { |
6a1c0680 | 444 | down_write(&tty->termios_rwsem); |
c12da96f | 445 | tty->termios.c_line = disc; |
6a1c0680 | 446 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
447 | |
448 | tty->disc_data = NULL; | |
449 | tty->receive_room = 0; | |
01e1abb2 AC |
450 | } |
451 | ||
c65c9bc3 AC |
452 | /** |
453 | * tty_ldisc_open - open a line discipline | |
454 | * @tty: tty we are opening the ldisc on | |
455 | * @ld: discipline to open | |
456 | * | |
457 | * A helper opening method. Also a convenient debugging and check | |
458 | * point. | |
ec79d605 AB |
459 | * |
460 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
461 | */ |
462 | ||
463 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
464 | { | |
465 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
466 | if (ld->ops->open) { |
467 | int ret; | |
ec79d605 | 468 | /* BTM here locks versus a hangup event */ |
f18f9498 | 469 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
470 | if (ret) |
471 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 472 | |
a570a49a | 473 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
474 | return ret; |
475 | } | |
c65c9bc3 AC |
476 | return 0; |
477 | } | |
478 | ||
479 | /** | |
480 | * tty_ldisc_close - close a line discipline | |
481 | * @tty: tty we are opening the ldisc on | |
482 | * @ld: discipline to close | |
483 | * | |
484 | * A helper close method. Also a convenient debugging and check | |
485 | * point. | |
486 | */ | |
487 | ||
488 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
489 | { | |
110b8928 | 490 | lockdep_assert_held_exclusive(&tty->ldisc_sem); |
c65c9bc3 AC |
491 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
492 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
493 | if (ld->ops->close) | |
494 | ld->ops->close(tty); | |
a570a49a | 495 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 496 | } |
01e1abb2 | 497 | |
8a8dabf2 AC |
498 | /** |
499 | * tty_ldisc_failto - helper for ldisc failback | |
500 | * @tty: tty to open the ldisc on | |
501 | * @ld: ldisc we are trying to fail back to | |
502 | * | |
503 | * Helper to try and recover a tty when switching back to the old | |
504 | * ldisc fails and we need something attached. | |
505 | */ | |
506 | ||
507 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) | |
508 | { | |
509 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
510 | int r; | |
511 | ||
110b8928 | 512 | lockdep_assert_held_exclusive(&tty->ldisc_sem); |
8a8dabf2 AC |
513 | if (IS_ERR(disc)) |
514 | return PTR_ERR(disc); | |
515 | tty->ldisc = disc; | |
516 | tty_set_termios_ldisc(tty, ld); | |
517 | if ((r = tty_ldisc_open(tty, disc)) < 0) | |
518 | tty_ldisc_put(disc); | |
519 | return r; | |
520 | } | |
521 | ||
a8983d01 GKH |
522 | /** |
523 | * tty_ldisc_restore - helper for tty ldisc change | |
524 | * @tty: tty to recover | |
525 | * @old: previous ldisc | |
526 | * | |
527 | * Restore the previous line discipline or N_TTY when a line discipline | |
528 | * change fails due to an open error | |
529 | */ | |
530 | ||
531 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
532 | { | |
a8983d01 | 533 | /* There is an outstanding reference here so this is safe */ |
598c2d41 TH |
534 | if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
535 | const char *name = tty_name(tty); | |
536 | ||
537 | pr_warn("Falling back ldisc for %s.\n", name); | |
8a8dabf2 AC |
538 | /* The traditional behaviour is to fall back to N_TTY, we |
539 | want to avoid falling back to N_NULL unless we have no | |
540 | choice to avoid the risk of breaking anything */ | |
541 | if (tty_ldisc_failto(tty, N_TTY) < 0 && | |
542 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 543 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
544 | } |
545 | } | |
546 | ||
01e1abb2 AC |
547 | /** |
548 | * tty_set_ldisc - set line discipline | |
549 | * @tty: the terminal to set | |
550 | * @ldisc: the line discipline | |
551 | * | |
552 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
553 | * context. The ldisc change logic has to protect itself against any |
554 | * overlapping ldisc change (including on the other end of pty pairs), | |
555 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
556 | */ |
557 | ||
c12da96f | 558 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 559 | { |
a8983d01 GKH |
560 | int retval; |
561 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
562 | ||
563 | new_ldisc = tty_ldisc_get(tty, disc); | |
564 | if (IS_ERR(new_ldisc)) | |
565 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 566 | |
c8483bc9 | 567 | tty_lock(tty); |
276a661a | 568 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
569 | if (retval) |
570 | goto err; | |
01e1abb2 | 571 | |
a570a49a PH |
572 | if (!tty->ldisc) { |
573 | retval = -EIO; | |
574 | goto out; | |
575 | } | |
576 | ||
63d8cb3f | 577 | /* Check the no-op case */ |
a8983d01 | 578 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 579 | goto out; |
c65c9bc3 | 580 | |
63d8cb3f PH |
581 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
582 | /* We were raced by hangup */ | |
583 | retval = -EIO; | |
584 | goto out; | |
01e1abb2 AC |
585 | } |
586 | ||
a8983d01 GKH |
587 | old_ldisc = tty->ldisc; |
588 | ||
589 | /* Shutdown the old discipline. */ | |
590 | tty_ldisc_close(tty, old_ldisc); | |
591 | ||
592 | /* Now set up the new line discipline. */ | |
593 | tty->ldisc = new_ldisc; | |
594 | tty_set_termios_ldisc(tty, disc); | |
595 | ||
596 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 597 | if (retval < 0) { |
c65c9bc3 | 598 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
599 | tty_ldisc_put(new_ldisc); |
600 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 601 | } |
c65c9bc3 | 602 | |
a8983d01 | 603 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 604 | down_read(&tty->termios_rwsem); |
01e1abb2 | 605 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
606 | up_read(&tty->termios_rwsem); |
607 | } | |
01e1abb2 | 608 | |
a8983d01 GKH |
609 | /* At this point we hold a reference to the new ldisc and a |
610 | reference to the old ldisc, or we hold two references to | |
611 | the old ldisc (if it was restored as part of error cleanup | |
612 | above). In either case, releasing a single reference from | |
613 | the old ldisc is correct. */ | |
614 | new_ldisc = old_ldisc; | |
63d8cb3f | 615 | out: |
276a661a | 616 | tty_ldisc_unlock(tty); |
01e1abb2 | 617 | |
c65c9bc3 | 618 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 619 | already running */ |
17a69219 | 620 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 621 | err: |
a8983d01 | 622 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 623 | tty_unlock(tty); |
01e1abb2 AC |
624 | return retval; |
625 | } | |
1ab92da3 | 626 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 627 | |
6ffeb4b2 PH |
628 | /** |
629 | * tty_ldisc_kill - teardown ldisc | |
630 | * @tty: tty being released | |
631 | * | |
632 | * Perform final close of the ldisc and reset tty->ldisc | |
633 | */ | |
634 | static void tty_ldisc_kill(struct tty_struct *tty) | |
635 | { | |
110b8928 | 636 | lockdep_assert_held_exclusive(&tty->ldisc_sem); |
6ffeb4b2 PH |
637 | if (!tty->ldisc) |
638 | return; | |
639 | /* | |
640 | * Now kill off the ldisc | |
641 | */ | |
642 | tty_ldisc_close(tty, tty->ldisc); | |
643 | tty_ldisc_put(tty->ldisc); | |
644 | /* Force an oops if we mess this up */ | |
645 | tty->ldisc = NULL; | |
646 | } | |
647 | ||
c65c9bc3 AC |
648 | /** |
649 | * tty_reset_termios - reset terminal state | |
650 | * @tty: tty to reset | |
651 | * | |
652 | * Restore a terminal to the driver default state. | |
653 | */ | |
654 | ||
655 | static void tty_reset_termios(struct tty_struct *tty) | |
656 | { | |
6a1c0680 | 657 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
658 | tty->termios = tty->driver->init_termios; |
659 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
660 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 661 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
662 | } |
663 | ||
664 | ||
665 | /** | |
666 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
667 | * @tty: tty to reinit | |
c12da96f | 668 | * @disc: line discipline to reinitialize |
c65c9bc3 | 669 | * |
7896f30d | 670 | * Completely reinitialize the line discipline state, by closing the |
892d1fa7 PH |
671 | * current instance, if there is one, and opening a new instance. If |
672 | * an error occurs opening the new non-N_TTY instance, the instance | |
673 | * is dropped and tty->ldisc reset to NULL. The caller can then retry | |
674 | * with N_TTY instead. | |
7896f30d PH |
675 | * |
676 | * Returns 0 if successful, otherwise error code < 0 | |
c65c9bc3 AC |
677 | */ |
678 | ||
892d1fa7 | 679 | int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
c65c9bc3 | 680 | { |
7896f30d PH |
681 | struct tty_ldisc *ld; |
682 | int retval; | |
1c95ba1e | 683 | |
110b8928 | 684 | lockdep_assert_held_exclusive(&tty->ldisc_sem); |
7896f30d | 685 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
686 | if (IS_ERR(ld)) { |
687 | BUG_ON(disc == N_TTY); | |
7896f30d | 688 | return PTR_ERR(ld); |
a8983d01 | 689 | } |
c65c9bc3 | 690 | |
7896f30d PH |
691 | if (tty->ldisc) { |
692 | tty_ldisc_close(tty, tty->ldisc); | |
693 | tty_ldisc_put(tty->ldisc); | |
694 | } | |
695 | ||
696 | /* switch the line discipline */ | |
f4807045 | 697 | tty->ldisc = ld; |
c12da96f | 698 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
699 | retval = tty_ldisc_open(tty, tty->ldisc); |
700 | if (retval) { | |
e65c62b1 JW |
701 | tty_ldisc_put(tty->ldisc); |
702 | tty->ldisc = NULL; | |
7896f30d PH |
703 | } |
704 | return retval; | |
c65c9bc3 AC |
705 | } |
706 | ||
707 | /** | |
708 | * tty_ldisc_hangup - hangup ldisc reset | |
709 | * @tty: tty being hung up | |
710 | * | |
711 | * Some tty devices reset their termios when they receive a hangup | |
712 | * event. In that situation we must also switch back to N_TTY properly | |
713 | * before we reset the termios data. | |
714 | * | |
715 | * Locking: We can take the ldisc mutex as the rest of the code is | |
716 | * careful to allow for this. | |
717 | * | |
718 | * In the pty pair case this occurs in the close() path of the | |
719 | * tty itself so we must be careful about locking rules. | |
720 | */ | |
721 | ||
892d1fa7 | 722 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
723 | { |
724 | struct tty_ldisc *ld; | |
725 | ||
a570a49a | 726 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 727 | |
c65c9bc3 AC |
728 | ld = tty_ldisc_ref(tty); |
729 | if (ld != NULL) { | |
c65c9bc3 AC |
730 | if (ld->ops->flush_buffer) |
731 | ld->ops->flush_buffer(tty); | |
732 | tty_driver_flush_buffer(tty); | |
733 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
734 | ld->ops->write_wakeup) | |
735 | ld->ops->write_wakeup(tty); | |
736 | if (ld->ops->hangup) | |
737 | ld->ops->hangup(tty); | |
738 | tty_ldisc_deref(ld); | |
739 | } | |
36697529 | 740 | |
a9a08845 LT |
741 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
742 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 743 | |
c65c9bc3 AC |
744 | /* |
745 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
746 | * N_TTY if need be. |
747 | * | |
748 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 749 | */ |
fae76e9a | 750 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 751 | |
892d1fa7 PH |
752 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
753 | tty_reset_termios(tty); | |
c8785241 | 754 | |
892d1fa7 PH |
755 | if (tty->ldisc) { |
756 | if (reinit) { | |
e65c62b1 JW |
757 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
758 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
759 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
760 | } else |
761 | tty_ldisc_kill(tty); | |
c65c9bc3 | 762 | } |
fae76e9a | 763 | tty_ldisc_unlock(tty); |
c65c9bc3 | 764 | } |
01e1abb2 AC |
765 | |
766 | /** | |
767 | * tty_ldisc_setup - open line discipline | |
768 | * @tty: tty being shut down | |
769 | * @o_tty: pair tty for pty/tty pairs | |
770 | * | |
771 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
772 | * line disciplines and bind them to the tty. This has no locking issues |
773 | * as the device isn't yet active. | |
01e1abb2 AC |
774 | */ |
775 | ||
776 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
777 | { | |
9de2a7ce | 778 | int retval = tty_ldisc_open(tty, tty->ldisc); |
c65c9bc3 AC |
779 | if (retval) |
780 | return retval; | |
781 | ||
782 | if (o_tty) { | |
110b8928 DS |
783 | /* |
784 | * Called without o_tty->ldisc_sem held, as o_tty has been | |
785 | * just allocated and no one has a reference to it. | |
786 | */ | |
c65c9bc3 | 787 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
01e1abb2 | 788 | if (retval) { |
9de2a7ce | 789 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
790 | return retval; |
791 | } | |
01e1abb2 | 792 | } |
01e1abb2 AC |
793 | return 0; |
794 | } | |
89c8d91e | 795 | |
01e1abb2 AC |
796 | /** |
797 | * tty_ldisc_release - release line discipline | |
62462aef | 798 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 799 | * |
62462aef | 800 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 801 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
802 | */ |
803 | ||
62462aef | 804 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 805 | { |
62462aef PH |
806 | struct tty_struct *o_tty = tty->link; |
807 | ||
01e1abb2 | 808 | /* |
a2965b7b PH |
809 | * Shutdown this line discipline. As this is the final close, |
810 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 811 | */ |
01e1abb2 | 812 | |
36697529 | 813 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 814 | tty_ldisc_kill(tty); |
c65c9bc3 | 815 | if (o_tty) |
89c8d91e | 816 | tty_ldisc_kill(o_tty); |
36697529 PH |
817 | tty_ldisc_unlock_pair(tty, o_tty); |
818 | ||
aef29bc2 AC |
819 | /* And the memory resources remaining (buffers, termios) will be |
820 | disposed of when the kref hits zero */ | |
fc575ee6 | 821 | |
fb6edc91 | 822 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 | 823 | } |
1ab92da3 | 824 | EXPORT_SYMBOL_GPL(tty_ldisc_release); |
01e1abb2 AC |
825 | |
826 | /** | |
827 | * tty_ldisc_init - ldisc setup for new tty | |
828 | * @tty: tty being allocated | |
829 | * | |
830 | * Set up the line discipline objects for a newly allocated tty. Note that | |
831 | * the tty structure is not completely set up when this call is made. | |
832 | */ | |
833 | ||
903f9db1 | 834 | int tty_ldisc_init(struct tty_struct *tty) |
01e1abb2 | 835 | { |
36697529 | 836 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 837 | if (IS_ERR(ld)) |
903f9db1 | 838 | return PTR_ERR(ld); |
f4807045 | 839 | tty->ldisc = ld; |
903f9db1 | 840 | return 0; |
01e1abb2 AC |
841 | } |
842 | ||
6716671d | 843 | /** |
c8b710b3 | 844 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
845 | * @tty: tty that was allocated recently |
846 | * | |
847 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
848 | * this call is made. | |
849 | */ | |
850 | void tty_ldisc_deinit(struct tty_struct *tty) | |
851 | { | |
110b8928 | 852 | /* no ldisc_sem, tty is being destroyed */ |
c8b710b3 PH |
853 | if (tty->ldisc) |
854 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 855 | tty->ldisc = NULL; |
6716671d | 856 | } |
7c0cca7c GKH |
857 | |
858 | static int zero; | |
859 | static int one = 1; | |
860 | static struct ctl_table tty_table[] = { | |
861 | { | |
862 | .procname = "ldisc_autoload", | |
863 | .data = &tty_ldisc_autoload, | |
864 | .maxlen = sizeof(tty_ldisc_autoload), | |
865 | .mode = 0644, | |
866 | .proc_handler = proc_dointvec, | |
867 | .extra1 = &zero, | |
868 | .extra2 = &one, | |
869 | }, | |
870 | { } | |
871 | }; | |
872 | ||
873 | static struct ctl_table tty_dir_table[] = { | |
874 | { | |
875 | .procname = "tty", | |
876 | .mode = 0555, | |
877 | .child = tty_table, | |
878 | }, | |
879 | { } | |
880 | }; | |
881 | ||
882 | static struct ctl_table tty_root_table[] = { | |
883 | { | |
884 | .procname = "dev", | |
885 | .mode = 0555, | |
886 | .child = tty_dir_table, | |
887 | }, | |
888 | { } | |
889 | }; | |
890 | ||
891 | void tty_sysctl_init(void) | |
892 | { | |
893 | register_sysctl_table(tty_root_table); | |
894 | } |