Commit | Line | Data |
---|---|---|
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 | |
01e1abb2 AC |
82 | * |
83 | * Remove a line discipline from the kernel providing it is not | |
84 | * currently in use. | |
85 | * | |
86 | * Locking: | |
137084bb | 87 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
88 | */ |
89 | ||
90 | int tty_unregister_ldisc(int disc) | |
91 | { | |
92 | unsigned long flags; | |
93 | int ret = 0; | |
94 | ||
95 | if (disc < N_TTY || disc >= NR_LDISCS) | |
96 | return -EINVAL; | |
97 | ||
137084bb | 98 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
99 | if (tty_ldiscs[disc]->refcount) |
100 | ret = -EBUSY; | |
101 | else | |
102 | tty_ldiscs[disc] = NULL; | |
137084bb | 103 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
104 | |
105 | return ret; | |
106 | } | |
107 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
108 | ||
f0de0e8d LT |
109 | static struct tty_ldisc_ops *get_ldops(int disc) |
110 | { | |
111 | unsigned long flags; | |
112 | struct tty_ldisc_ops *ldops, *ret; | |
113 | ||
137084bb | 114 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
115 | ret = ERR_PTR(-EINVAL); |
116 | ldops = tty_ldiscs[disc]; | |
117 | if (ldops) { | |
118 | ret = ERR_PTR(-EAGAIN); | |
119 | if (try_module_get(ldops->owner)) { | |
120 | ldops->refcount++; | |
121 | ret = ldops; | |
122 | } | |
123 | } | |
137084bb | 124 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
125 | return ret; |
126 | } | |
127 | ||
128 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
129 | { | |
130 | unsigned long flags; | |
131 | ||
137084bb | 132 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
133 | ldops->refcount--; |
134 | module_put(ldops->owner); | |
137084bb | 135 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 136 | } |
01e1abb2 | 137 | |
8eddcca2 | 138 | static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); |
01e1abb2 AC |
139 | /** |
140 | * tty_ldisc_get - take a reference to an ldisc | |
8a3bdec1 | 141 | * @tty: tty device |
01e1abb2 | 142 | * @disc: ldisc number |
01e1abb2 AC |
143 | * |
144 | * Takes a reference to a line discipline. Deals with refcounts and | |
c0cc1c5d PH |
145 | * module locking counts. |
146 | * | |
147 | * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or | |
148 | * if the discipline is not registered | |
149 | * -EAGAIN if request_module() failed to load or register the | |
b8958546 | 150 | * discipline |
c0cc1c5d PH |
151 | * -ENOMEM if allocation failure |
152 | * | |
153 | * Otherwise, returns a pointer to the discipline and bumps the | |
154 | * ref count | |
01e1abb2 AC |
155 | * |
156 | * Locking: | |
137084bb | 157 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
158 | */ |
159 | ||
36697529 | 160 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 161 | { |
c65c9bc3 | 162 | struct tty_ldisc *ld; |
182274f8 | 163 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
164 | |
165 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 166 | return ERR_PTR(-EINVAL); |
182274f8 LT |
167 | |
168 | /* | |
169 | * Get the ldisc ops - we may need to request them to be loaded | |
170 | * dynamically and try again. | |
171 | */ | |
172 | ldops = get_ldops(disc); | |
173 | if (IS_ERR(ldops)) { | |
7c0cca7c GKH |
174 | if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) |
175 | return ERR_PTR(-EPERM); | |
01e1abb2 | 176 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
177 | ldops = get_ldops(disc); |
178 | if (IS_ERR(ldops)) | |
179 | return ERR_CAST(ldops); | |
180 | } | |
181 | ||
bcdd0ca8 TH |
182 | /* |
183 | * There is no way to handle allocation failure of only 16 bytes. | |
184 | * Let's simplify error handling and save more memory. | |
185 | */ | |
186 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); | |
182274f8 | 187 | ld->ops = ldops; |
36697529 | 188 | ld->tty = tty; |
1541f845 | 189 | |
c65c9bc3 | 190 | return ld; |
01e1abb2 AC |
191 | } |
192 | ||
8eddcca2 | 193 | /* |
734de249 PH |
194 | * tty_ldisc_put - release the ldisc |
195 | * | |
196 | * Complement of tty_ldisc_get(). | |
197 | */ | |
cb128f69 | 198 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 199 | { |
734de249 PH |
200 | if (WARN_ON_ONCE(!ld)) |
201 | return; | |
202 | ||
36697529 | 203 | put_ldops(ld->ops); |
734de249 | 204 | kfree(ld); |
734de249 PH |
205 | } |
206 | ||
852e99d2 | 207 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
208 | { |
209 | return (*pos < NR_LDISCS) ? pos : NULL; | |
210 | } | |
211 | ||
852e99d2 | 212 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
213 | { |
214 | (*pos)++; | |
215 | return (*pos < NR_LDISCS) ? pos : NULL; | |
216 | } | |
217 | ||
218 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
219 | { | |
220 | } | |
221 | ||
222 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
223 | { | |
224 | int i = *(loff_t *)v; | |
f0de0e8d | 225 | struct tty_ldisc_ops *ldops; |
852e99d2 | 226 | |
f0de0e8d LT |
227 | ldops = get_ldops(i); |
228 | if (IS_ERR(ldops)) | |
01e1abb2 | 229 | return 0; |
f0de0e8d LT |
230 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
231 | put_ldops(ldops); | |
01e1abb2 AC |
232 | return 0; |
233 | } | |
234 | ||
fddda2b7 | 235 | const struct seq_operations tty_ldiscs_seq_ops = { |
01e1abb2 AC |
236 | .start = tty_ldiscs_seq_start, |
237 | .next = tty_ldiscs_seq_next, | |
238 | .stop = tty_ldiscs_seq_stop, | |
239 | .show = tty_ldiscs_seq_show, | |
240 | }; | |
241 | ||
01e1abb2 AC |
242 | /** |
243 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
244 | * @tty: tty device | |
245 | * | |
246 | * Dereference the line discipline for the terminal and take a | |
247 | * reference to it. If the line discipline is in flux then | |
248 | * wait patiently until it changes. | |
249 | * | |
892d1fa7 PH |
250 | * Returns: NULL if the tty has been hungup and not re-opened with |
251 | * a new file descriptor, otherwise valid ldisc reference | |
252 | * | |
8eddcca2 | 253 | * Note 1: Must not be called from an IRQ/timer context. The caller |
01e1abb2 AC |
254 | * must also be careful not to hold other locks that will deadlock |
255 | * against a discipline change, such as an existing ldisc reference | |
256 | * (which we check for) | |
257 | * | |
8eddcca2 | 258 | * Note 2: a file_operations routine (read/poll/write) should use this |
e55afd11 | 259 | * function to wait for any ldisc lifetime events to finish. |
01e1abb2 AC |
260 | */ |
261 | ||
262 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
263 | { | |
a4a3e061 DV |
264 | struct tty_ldisc *ld; |
265 | ||
36697529 | 266 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
267 | ld = tty->ldisc; |
268 | if (!ld) | |
a570a49a | 269 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 270 | return ld; |
01e1abb2 | 271 | } |
01e1abb2 AC |
272 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
273 | ||
274 | /** | |
275 | * tty_ldisc_ref - get the tty ldisc | |
276 | * @tty: tty device | |
277 | * | |
278 | * Dereference the line discipline for the terminal and take a | |
279 | * reference to it. If the line discipline is in flux then | |
280 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
281 | */ |
282 | ||
283 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
284 | { | |
36697529 PH |
285 | struct tty_ldisc *ld = NULL; |
286 | ||
287 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
288 | ld = tty->ldisc; | |
289 | if (!ld) | |
290 | ldsem_up_read(&tty->ldisc_sem); | |
291 | } | |
292 | return ld; | |
01e1abb2 | 293 | } |
01e1abb2 AC |
294 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
295 | ||
296 | /** | |
297 | * tty_ldisc_deref - free a tty ldisc reference | |
298 | * @ld: reference to free up | |
299 | * | |
300 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
301 | * be called in IRQ context. | |
01e1abb2 AC |
302 | */ |
303 | ||
304 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
305 | { | |
36697529 | 306 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 307 | } |
01e1abb2 AC |
308 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
309 | ||
d2c43890 | 310 | |
c2bb524b | 311 | static inline int |
e80a10ee | 312 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
313 | { |
314 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
315 | } | |
316 | ||
c2bb524b | 317 | static inline int |
e80a10ee | 318 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
319 | { |
320 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
321 | LDISC_SEM_OTHER, timeout); | |
322 | } | |
323 | ||
e80a10ee | 324 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 325 | { |
52772ea6 | 326 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
327 | } |
328 | ||
b027e229 | 329 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
330 | { |
331 | int ret; | |
332 | ||
c96cf923 DS |
333 | /* Kindly asking blocked readers to release the read side */ |
334 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
335 | wake_up_interruptible_all(&tty->read_wait); | |
336 | wake_up_interruptible_all(&tty->write_wait); | |
337 | ||
fae76e9a PH |
338 | ret = __tty_ldisc_lock(tty, timeout); |
339 | if (!ret) | |
340 | return -EBUSY; | |
341 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
342 | return 0; | |
343 | } | |
344 | ||
b027e229 | 345 | void tty_ldisc_unlock(struct tty_struct *tty) |
fae76e9a PH |
346 | { |
347 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
c96cf923 DS |
348 | /* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
349 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
fae76e9a PH |
350 | __tty_ldisc_unlock(tty); |
351 | } | |
352 | ||
c2bb524b | 353 | static int |
d2c43890 PH |
354 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
355 | unsigned long timeout) | |
356 | { | |
357 | int ret; | |
358 | ||
359 | if (tty < tty2) { | |
e80a10ee | 360 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 361 | if (ret) { |
e80a10ee | 362 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 363 | if (!ret) |
e80a10ee | 364 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
365 | } |
366 | } else { | |
367 | /* if this is possible, it has lots of implications */ | |
368 | WARN_ON_ONCE(tty == tty2); | |
369 | if (tty2 && tty != tty2) { | |
e80a10ee | 370 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 371 | if (ret) { |
e80a10ee | 372 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 373 | if (!ret) |
e80a10ee | 374 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
375 | } |
376 | } else | |
e80a10ee | 377 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
378 | } |
379 | ||
380 | if (!ret) | |
381 | return -EBUSY; | |
382 | ||
383 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
384 | if (tty2) | |
385 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
386 | return 0; | |
387 | } | |
388 | ||
c2bb524b | 389 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
390 | { |
391 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
392 | } | |
393 | ||
c2bb524b PH |
394 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
395 | struct tty_struct *tty2) | |
d2c43890 | 396 | { |
e80a10ee | 397 | __tty_ldisc_unlock(tty); |
d2c43890 | 398 | if (tty2) |
e80a10ee | 399 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
400 | } |
401 | ||
f2c4c65c AC |
402 | /** |
403 | * tty_ldisc_flush - flush line discipline queue | |
404 | * @tty: tty | |
405 | * | |
86c80a8e PH |
406 | * Flush the line discipline queue (if any) and the tty flip buffers |
407 | * for this tty. | |
f2c4c65c AC |
408 | */ |
409 | ||
410 | void tty_ldisc_flush(struct tty_struct *tty) | |
411 | { | |
412 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
413 | |
414 | tty_buffer_flush(tty, ld); | |
415 | if (ld) | |
f2c4c65c | 416 | tty_ldisc_deref(ld); |
f2c4c65c | 417 | } |
f2c4c65c AC |
418 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
419 | ||
01e1abb2 AC |
420 | /** |
421 | * tty_set_termios_ldisc - set ldisc field | |
422 | * @tty: tty structure | |
c12da96f | 423 | * @disc: line discipline number |
01e1abb2 AC |
424 | * |
425 | * This is probably overkill for real world processors but | |
426 | * they are not on hot paths so a little discipline won't do | |
427 | * any harm. | |
428 | * | |
dd42bf11 PH |
429 | * The line discipline-related tty_struct fields are reset to |
430 | * prevent the ldisc driver from re-using stale information for | |
431 | * the new ldisc instance. | |
432 | * | |
6a1c0680 | 433 | * Locking: takes termios_rwsem |
01e1abb2 AC |
434 | */ |
435 | ||
c12da96f | 436 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 437 | { |
6a1c0680 | 438 | down_write(&tty->termios_rwsem); |
c12da96f | 439 | tty->termios.c_line = disc; |
6a1c0680 | 440 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
441 | |
442 | tty->disc_data = NULL; | |
443 | tty->receive_room = 0; | |
01e1abb2 AC |
444 | } |
445 | ||
c65c9bc3 AC |
446 | /** |
447 | * tty_ldisc_open - open a line discipline | |
448 | * @tty: tty we are opening the ldisc on | |
449 | * @ld: discipline to open | |
450 | * | |
451 | * A helper opening method. Also a convenient debugging and check | |
452 | * point. | |
ec79d605 AB |
453 | * |
454 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
455 | */ |
456 | ||
457 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
458 | { | |
459 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
460 | if (ld->ops->open) { |
461 | int ret; | |
5d3945e8 | 462 | /* BTM here locks versus a hangup event */ |
f18f9498 | 463 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
464 | if (ret) |
465 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 466 | |
a570a49a | 467 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
468 | return ret; |
469 | } | |
c65c9bc3 AC |
470 | return 0; |
471 | } | |
472 | ||
473 | /** | |
474 | * tty_ldisc_close - close a line discipline | |
475 | * @tty: tty we are opening the ldisc on | |
476 | * @ld: discipline to close | |
477 | * | |
478 | * A helper close method. Also a convenient debugging and check | |
479 | * point. | |
480 | */ | |
481 | ||
482 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
483 | { | |
9ffbe8ac | 484 | lockdep_assert_held_write(&tty->ldisc_sem); |
c65c9bc3 AC |
485 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
486 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
487 | if (ld->ops->close) | |
488 | ld->ops->close(tty); | |
a570a49a | 489 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 490 | } |
01e1abb2 | 491 | |
8a8dabf2 AC |
492 | /** |
493 | * tty_ldisc_failto - helper for ldisc failback | |
494 | * @tty: tty to open the ldisc on | |
495 | * @ld: ldisc we are trying to fail back to | |
496 | * | |
497 | * Helper to try and recover a tty when switching back to the old | |
498 | * ldisc fails and we need something attached. | |
499 | */ | |
500 | ||
501 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) | |
502 | { | |
503 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
504 | int r; | |
505 | ||
9ffbe8ac | 506 | lockdep_assert_held_write(&tty->ldisc_sem); |
8a8dabf2 AC |
507 | if (IS_ERR(disc)) |
508 | return PTR_ERR(disc); | |
509 | tty->ldisc = disc; | |
510 | tty_set_termios_ldisc(tty, ld); | |
408795b0 XT |
511 | r = tty_ldisc_open(tty, disc); |
512 | if (r < 0) | |
8a8dabf2 AC |
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); | |
72a8dcd7 XT |
533 | /* |
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 | */ | |
8a8dabf2 AC |
538 | if (tty_ldisc_failto(tty, N_TTY) < 0 && |
539 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 540 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
541 | } |
542 | } | |
543 | ||
01e1abb2 AC |
544 | /** |
545 | * tty_set_ldisc - set line discipline | |
546 | * @tty: the terminal to set | |
fa441954 | 547 | * @disc: the line discipline number |
01e1abb2 AC |
548 | * |
549 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
550 | * context. The ldisc change logic has to protect itself against any |
551 | * overlapping ldisc change (including on the other end of pty pairs), | |
552 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
553 | */ |
554 | ||
c12da96f | 555 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 556 | { |
a8983d01 GKH |
557 | int retval; |
558 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
559 | ||
560 | new_ldisc = tty_ldisc_get(tty, disc); | |
561 | if (IS_ERR(new_ldisc)) | |
562 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 563 | |
c8483bc9 | 564 | tty_lock(tty); |
276a661a | 565 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
566 | if (retval) |
567 | goto err; | |
01e1abb2 | 568 | |
a570a49a PH |
569 | if (!tty->ldisc) { |
570 | retval = -EIO; | |
571 | goto out; | |
572 | } | |
573 | ||
63d8cb3f | 574 | /* Check the no-op case */ |
a8983d01 | 575 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 576 | goto out; |
c65c9bc3 | 577 | |
63d8cb3f PH |
578 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
579 | /* We were raced by hangup */ | |
580 | retval = -EIO; | |
581 | goto out; | |
01e1abb2 AC |
582 | } |
583 | ||
a8983d01 GKH |
584 | old_ldisc = tty->ldisc; |
585 | ||
586 | /* Shutdown the old discipline. */ | |
587 | tty_ldisc_close(tty, old_ldisc); | |
588 | ||
589 | /* Now set up the new line discipline. */ | |
590 | tty->ldisc = new_ldisc; | |
591 | tty_set_termios_ldisc(tty, disc); | |
592 | ||
593 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 594 | if (retval < 0) { |
c65c9bc3 | 595 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
596 | tty_ldisc_put(new_ldisc); |
597 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 598 | } |
c65c9bc3 | 599 | |
a8983d01 | 600 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 601 | down_read(&tty->termios_rwsem); |
01e1abb2 | 602 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
603 | up_read(&tty->termios_rwsem); |
604 | } | |
01e1abb2 | 605 | |
72a8dcd7 XT |
606 | /* |
607 | * At this point we hold a reference to the new ldisc and a | |
608 | * reference to the old ldisc, or we hold two references to | |
609 | * the old ldisc (if it was restored as part of error cleanup | |
610 | * above). In either case, releasing a single reference from | |
611 | * the old ldisc is correct. | |
612 | */ | |
a8983d01 | 613 | new_ldisc = old_ldisc; |
63d8cb3f | 614 | out: |
276a661a | 615 | tty_ldisc_unlock(tty); |
01e1abb2 | 616 | |
72a8dcd7 XT |
617 | /* |
618 | * Restart the work queue in case no characters kick it off. Safe if | |
619 | * already running | |
620 | */ | |
17a69219 | 621 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 622 | err: |
a8983d01 | 623 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 624 | tty_unlock(tty); |
01e1abb2 AC |
625 | return retval; |
626 | } | |
1ab92da3 | 627 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 628 | |
6ffeb4b2 PH |
629 | /** |
630 | * tty_ldisc_kill - teardown ldisc | |
631 | * @tty: tty being released | |
632 | * | |
633 | * Perform final close of the ldisc and reset tty->ldisc | |
634 | */ | |
635 | static void tty_ldisc_kill(struct tty_struct *tty) | |
636 | { | |
9ffbe8ac | 637 | lockdep_assert_held_write(&tty->ldisc_sem); |
6ffeb4b2 PH |
638 | if (!tty->ldisc) |
639 | return; | |
640 | /* | |
641 | * Now kill off the ldisc | |
642 | */ | |
643 | tty_ldisc_close(tty, tty->ldisc); | |
644 | tty_ldisc_put(tty->ldisc); | |
645 | /* Force an oops if we mess this up */ | |
646 | tty->ldisc = NULL; | |
647 | } | |
648 | ||
c65c9bc3 AC |
649 | /** |
650 | * tty_reset_termios - reset terminal state | |
651 | * @tty: tty to reset | |
652 | * | |
653 | * Restore a terminal to the driver default state. | |
654 | */ | |
655 | ||
656 | static void tty_reset_termios(struct tty_struct *tty) | |
657 | { | |
6a1c0680 | 658 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
659 | tty->termios = tty->driver->init_termios; |
660 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
661 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 662 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
663 | } |
664 | ||
665 | ||
666 | /** | |
667 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
668 | * @tty: tty to reinit | |
c12da96f | 669 | * @disc: line discipline to reinitialize |
c65c9bc3 | 670 | * |
7896f30d | 671 | * Completely reinitialize the line discipline state, by closing the |
892d1fa7 PH |
672 | * current instance, if there is one, and opening a new instance. If |
673 | * an error occurs opening the new non-N_TTY instance, the instance | |
674 | * is dropped and tty->ldisc reset to NULL. The caller can then retry | |
675 | * with N_TTY instead. | |
7896f30d PH |
676 | * |
677 | * Returns 0 if successful, otherwise error code < 0 | |
c65c9bc3 AC |
678 | */ |
679 | ||
892d1fa7 | 680 | int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
c65c9bc3 | 681 | { |
7896f30d PH |
682 | struct tty_ldisc *ld; |
683 | int retval; | |
1c95ba1e | 684 | |
9ffbe8ac | 685 | lockdep_assert_held_write(&tty->ldisc_sem); |
7896f30d | 686 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
687 | if (IS_ERR(ld)) { |
688 | BUG_ON(disc == N_TTY); | |
7896f30d | 689 | return PTR_ERR(ld); |
a8983d01 | 690 | } |
c65c9bc3 | 691 | |
7896f30d PH |
692 | if (tty->ldisc) { |
693 | tty_ldisc_close(tty, tty->ldisc); | |
694 | tty_ldisc_put(tty->ldisc); | |
695 | } | |
696 | ||
697 | /* switch the line discipline */ | |
f4807045 | 698 | tty->ldisc = ld; |
c12da96f | 699 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
700 | retval = tty_ldisc_open(tty, tty->ldisc); |
701 | if (retval) { | |
e65c62b1 JW |
702 | tty_ldisc_put(tty->ldisc); |
703 | tty->ldisc = NULL; | |
7896f30d PH |
704 | } |
705 | return retval; | |
c65c9bc3 AC |
706 | } |
707 | ||
708 | /** | |
709 | * tty_ldisc_hangup - hangup ldisc reset | |
710 | * @tty: tty being hung up | |
8eddcca2 | 711 | * @reinit: whether to re-initialise the tty |
c65c9bc3 AC |
712 | * |
713 | * Some tty devices reset their termios when they receive a hangup | |
714 | * event. In that situation we must also switch back to N_TTY properly | |
715 | * before we reset the termios data. | |
716 | * | |
717 | * Locking: We can take the ldisc mutex as the rest of the code is | |
718 | * careful to allow for this. | |
719 | * | |
720 | * In the pty pair case this occurs in the close() path of the | |
721 | * tty itself so we must be careful about locking rules. | |
722 | */ | |
723 | ||
892d1fa7 | 724 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
725 | { |
726 | struct tty_ldisc *ld; | |
727 | ||
a570a49a | 728 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 729 | |
c65c9bc3 AC |
730 | ld = tty_ldisc_ref(tty); |
731 | if (ld != NULL) { | |
c65c9bc3 AC |
732 | if (ld->ops->flush_buffer) |
733 | ld->ops->flush_buffer(tty); | |
734 | tty_driver_flush_buffer(tty); | |
735 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
736 | ld->ops->write_wakeup) | |
737 | ld->ops->write_wakeup(tty); | |
738 | if (ld->ops->hangup) | |
739 | ld->ops->hangup(tty); | |
740 | tty_ldisc_deref(ld); | |
741 | } | |
36697529 | 742 | |
a9a08845 LT |
743 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
744 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 745 | |
c65c9bc3 AC |
746 | /* |
747 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
748 | * N_TTY if need be. |
749 | * | |
750 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 751 | */ |
fae76e9a | 752 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 753 | |
892d1fa7 PH |
754 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
755 | tty_reset_termios(tty); | |
c8785241 | 756 | |
892d1fa7 PH |
757 | if (tty->ldisc) { |
758 | if (reinit) { | |
e65c62b1 JW |
759 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
760 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
761 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
762 | } else |
763 | tty_ldisc_kill(tty); | |
c65c9bc3 | 764 | } |
fae76e9a | 765 | tty_ldisc_unlock(tty); |
c65c9bc3 | 766 | } |
01e1abb2 AC |
767 | |
768 | /** | |
769 | * tty_ldisc_setup - open line discipline | |
770 | * @tty: tty being shut down | |
771 | * @o_tty: pair tty for pty/tty pairs | |
772 | * | |
773 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
774 | * line disciplines and bind them to the tty. This has no locking issues |
775 | * as the device isn't yet active. | |
01e1abb2 AC |
776 | */ |
777 | ||
778 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
779 | { | |
9de2a7ce | 780 | int retval = tty_ldisc_open(tty, tty->ldisc); |
d7238359 | 781 | |
c65c9bc3 AC |
782 | if (retval) |
783 | return retval; | |
784 | ||
785 | if (o_tty) { | |
110b8928 DS |
786 | /* |
787 | * Called without o_tty->ldisc_sem held, as o_tty has been | |
788 | * just allocated and no one has a reference to it. | |
789 | */ | |
c65c9bc3 | 790 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
01e1abb2 | 791 | if (retval) { |
9de2a7ce | 792 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
793 | return retval; |
794 | } | |
01e1abb2 | 795 | } |
01e1abb2 AC |
796 | return 0; |
797 | } | |
89c8d91e | 798 | |
01e1abb2 AC |
799 | /** |
800 | * tty_ldisc_release - release line discipline | |
62462aef | 801 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 802 | * |
62462aef | 803 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 804 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
805 | */ |
806 | ||
62462aef | 807 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 808 | { |
62462aef PH |
809 | struct tty_struct *o_tty = tty->link; |
810 | ||
01e1abb2 | 811 | /* |
a2965b7b PH |
812 | * Shutdown this line discipline. As this is the final close, |
813 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 814 | */ |
01e1abb2 | 815 | |
36697529 | 816 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 817 | tty_ldisc_kill(tty); |
c65c9bc3 | 818 | if (o_tty) |
89c8d91e | 819 | tty_ldisc_kill(o_tty); |
36697529 PH |
820 | tty_ldisc_unlock_pair(tty, o_tty); |
821 | ||
72a8dcd7 XT |
822 | /* |
823 | * And the memory resources remaining (buffers, termios) will be | |
824 | * disposed of when the kref hits zero | |
825 | */ | |
fc575ee6 | 826 | |
fb6edc91 | 827 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 | 828 | } |
1ab92da3 | 829 | EXPORT_SYMBOL_GPL(tty_ldisc_release); |
01e1abb2 AC |
830 | |
831 | /** | |
832 | * tty_ldisc_init - ldisc setup for new tty | |
833 | * @tty: tty being allocated | |
834 | * | |
835 | * Set up the line discipline objects for a newly allocated tty. Note that | |
836 | * the tty structure is not completely set up when this call is made. | |
837 | */ | |
838 | ||
903f9db1 | 839 | int tty_ldisc_init(struct tty_struct *tty) |
01e1abb2 | 840 | { |
36697529 | 841 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
d7238359 | 842 | |
c65c9bc3 | 843 | if (IS_ERR(ld)) |
903f9db1 | 844 | return PTR_ERR(ld); |
f4807045 | 845 | tty->ldisc = ld; |
903f9db1 | 846 | return 0; |
01e1abb2 AC |
847 | } |
848 | ||
6716671d | 849 | /** |
c8b710b3 | 850 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
851 | * @tty: tty that was allocated recently |
852 | * | |
853 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
854 | * this call is made. | |
855 | */ | |
856 | void tty_ldisc_deinit(struct tty_struct *tty) | |
857 | { | |
110b8928 | 858 | /* no ldisc_sem, tty is being destroyed */ |
c8b710b3 PH |
859 | if (tty->ldisc) |
860 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 861 | tty->ldisc = NULL; |
6716671d | 862 | } |
7c0cca7c | 863 | |
7c0cca7c GKH |
864 | static struct ctl_table tty_table[] = { |
865 | { | |
866 | .procname = "ldisc_autoload", | |
867 | .data = &tty_ldisc_autoload, | |
868 | .maxlen = sizeof(tty_ldisc_autoload), | |
869 | .mode = 0644, | |
870 | .proc_handler = proc_dointvec, | |
eec4844f MC |
871 | .extra1 = SYSCTL_ZERO, |
872 | .extra2 = SYSCTL_ONE, | |
7c0cca7c GKH |
873 | }, |
874 | { } | |
875 | }; | |
876 | ||
877 | static struct ctl_table tty_dir_table[] = { | |
878 | { | |
879 | .procname = "tty", | |
880 | .mode = 0555, | |
881 | .child = tty_table, | |
882 | }, | |
883 | { } | |
884 | }; | |
885 | ||
886 | static struct ctl_table tty_root_table[] = { | |
887 | { | |
888 | .procname = "dev", | |
889 | .mode = 0555, | |
890 | .child = tty_dir_table, | |
891 | }, | |
892 | { } | |
893 | }; | |
894 | ||
895 | void tty_sysctl_init(void) | |
896 | { | |
897 | register_sysctl_table(tty_root_table); | |
898 | } |