Commit | Line | Data |
---|---|---|
01e1abb2 | 1 | #include <linux/types.h> |
01e1abb2 | 2 | #include <linux/errno.h> |
8b3ffa17 | 3 | #include <linux/kmod.h> |
01e1abb2 AC |
4 | #include <linux/sched.h> |
5 | #include <linux/interrupt.h> | |
6 | #include <linux/tty.h> | |
7 | #include <linux/tty_driver.h> | |
01e1abb2 | 8 | #include <linux/file.h> |
01e1abb2 AC |
9 | #include <linux/mm.h> |
10 | #include <linux/string.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/poll.h> | |
13 | #include <linux/proc_fs.h> | |
01e1abb2 | 14 | #include <linux/module.h> |
01e1abb2 AC |
15 | #include <linux/device.h> |
16 | #include <linux/wait.h> | |
17 | #include <linux/bitops.h> | |
01e1abb2 | 18 | #include <linux/seq_file.h> |
01e1abb2 | 19 | #include <linux/uaccess.h> |
0c73c08e | 20 | #include <linux/ratelimit.h> |
01e1abb2 | 21 | |
fc575ee6 PH |
22 | #undef LDISC_DEBUG_HANGUP |
23 | ||
24 | #ifdef LDISC_DEBUG_HANGUP | |
0a6adc13 | 25 | #define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) |
fc575ee6 PH |
26 | #else |
27 | #define tty_ldisc_debug(tty, f, args...) | |
28 | #endif | |
29 | ||
d2c43890 PH |
30 | /* lockdep nested classes for tty->ldisc_sem */ |
31 | enum { | |
32 | LDISC_SEM_NORMAL, | |
33 | LDISC_SEM_OTHER, | |
34 | }; | |
35 | ||
36 | ||
01e1abb2 AC |
37 | /* |
38 | * This guards the refcounted line discipline lists. The lock | |
39 | * must be taken with irqs off because there are hangup path | |
40 | * callers who will do ldisc lookups and cannot sleep. | |
41 | */ | |
42 | ||
137084bb | 43 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
44 | /* Line disc dispatch table */ |
45 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
46 | ||
47 | /** | |
48 | * tty_register_ldisc - install a line discipline | |
49 | * @disc: ldisc number | |
50 | * @new_ldisc: pointer to the ldisc object | |
51 | * | |
52 | * Installs a new line discipline into the kernel. The discipline | |
53 | * is set up as unreferenced and then made available to the kernel | |
54 | * from this point onwards. | |
55 | * | |
56 | * Locking: | |
137084bb | 57 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
58 | */ |
59 | ||
60 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
61 | { | |
62 | unsigned long flags; | |
63 | int ret = 0; | |
64 | ||
65 | if (disc < N_TTY || disc >= NR_LDISCS) | |
66 | return -EINVAL; | |
67 | ||
137084bb | 68 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
69 | tty_ldiscs[disc] = new_ldisc; |
70 | new_ldisc->num = disc; | |
71 | new_ldisc->refcount = 0; | |
137084bb | 72 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
73 | |
74 | return ret; | |
75 | } | |
76 | EXPORT_SYMBOL(tty_register_ldisc); | |
77 | ||
78 | /** | |
79 | * tty_unregister_ldisc - unload a line discipline | |
80 | * @disc: ldisc number | |
81 | * @new_ldisc: pointer to the ldisc object | |
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 | |
01e1abb2 AC |
138 | /** |
139 | * tty_ldisc_get - take a reference to an ldisc | |
140 | * @disc: ldisc number | |
01e1abb2 AC |
141 | * |
142 | * Takes a reference to a line discipline. Deals with refcounts and | |
c0cc1c5d PH |
143 | * module locking counts. |
144 | * | |
145 | * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or | |
146 | * if the discipline is not registered | |
147 | * -EAGAIN if request_module() failed to load or register the | |
148 | * the discipline | |
149 | * -ENOMEM if allocation failure | |
150 | * | |
151 | * Otherwise, returns a pointer to the discipline and bumps the | |
152 | * ref count | |
01e1abb2 AC |
153 | * |
154 | * Locking: | |
137084bb | 155 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
156 | */ |
157 | ||
36697529 | 158 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 159 | { |
c65c9bc3 | 160 | struct tty_ldisc *ld; |
182274f8 | 161 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
162 | |
163 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 164 | return ERR_PTR(-EINVAL); |
182274f8 LT |
165 | |
166 | /* | |
167 | * Get the ldisc ops - we may need to request them to be loaded | |
168 | * dynamically and try again. | |
169 | */ | |
170 | ldops = get_ldops(disc); | |
171 | if (IS_ERR(ldops)) { | |
01e1abb2 | 172 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
173 | ldops = get_ldops(disc); |
174 | if (IS_ERR(ldops)) | |
175 | return ERR_CAST(ldops); | |
176 | } | |
177 | ||
178 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
179 | if (ld == NULL) { | |
180 | put_ldops(ldops); | |
181 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 182 | } |
182274f8 LT |
183 | |
184 | ld->ops = ldops; | |
36697529 | 185 | ld->tty = tty; |
1541f845 | 186 | |
c65c9bc3 | 187 | return ld; |
01e1abb2 AC |
188 | } |
189 | ||
734de249 PH |
190 | /** |
191 | * tty_ldisc_put - release the ldisc | |
192 | * | |
193 | * Complement of tty_ldisc_get(). | |
194 | */ | |
cb128f69 | 195 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 196 | { |
734de249 PH |
197 | if (WARN_ON_ONCE(!ld)) |
198 | return; | |
199 | ||
36697529 | 200 | put_ldops(ld->ops); |
734de249 | 201 | kfree(ld); |
734de249 PH |
202 | } |
203 | ||
852e99d2 | 204 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
205 | { |
206 | return (*pos < NR_LDISCS) ? pos : NULL; | |
207 | } | |
208 | ||
852e99d2 | 209 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
210 | { |
211 | (*pos)++; | |
212 | return (*pos < NR_LDISCS) ? pos : NULL; | |
213 | } | |
214 | ||
215 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
216 | { | |
217 | } | |
218 | ||
219 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
220 | { | |
221 | int i = *(loff_t *)v; | |
f0de0e8d | 222 | struct tty_ldisc_ops *ldops; |
852e99d2 | 223 | |
f0de0e8d LT |
224 | ldops = get_ldops(i); |
225 | if (IS_ERR(ldops)) | |
01e1abb2 | 226 | return 0; |
f0de0e8d LT |
227 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
228 | put_ldops(ldops); | |
01e1abb2 AC |
229 | return 0; |
230 | } | |
231 | ||
232 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
233 | .start = tty_ldiscs_seq_start, | |
234 | .next = tty_ldiscs_seq_next, | |
235 | .stop = tty_ldiscs_seq_stop, | |
236 | .show = tty_ldiscs_seq_show, | |
237 | }; | |
238 | ||
239 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
240 | { | |
241 | return seq_open(file, &tty_ldiscs_seq_ops); | |
242 | } | |
243 | ||
244 | const struct file_operations tty_ldiscs_proc_fops = { | |
245 | .owner = THIS_MODULE, | |
246 | .open = proc_tty_ldiscs_open, | |
247 | .read = seq_read, | |
248 | .llseek = seq_lseek, | |
249 | .release = seq_release, | |
250 | }; | |
251 | ||
01e1abb2 AC |
252 | /** |
253 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
254 | * @tty: tty device | |
255 | * | |
256 | * Dereference the line discipline for the terminal and take a | |
257 | * reference to it. If the line discipline is in flux then | |
258 | * wait patiently until it changes. | |
259 | * | |
260 | * Note: Must not be called from an IRQ/timer context. The caller | |
261 | * must also be careful not to hold other locks that will deadlock | |
262 | * against a discipline change, such as an existing ldisc reference | |
263 | * (which we check for) | |
264 | * | |
e55afd11 PH |
265 | * Note: a file_operations routine (read/poll/write) should use this |
266 | * function to wait for any ldisc lifetime events to finish. | |
01e1abb2 AC |
267 | */ |
268 | ||
269 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
270 | { | |
36697529 | 271 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a570a49a PH |
272 | if (!tty->ldisc) |
273 | ldsem_up_read(&tty->ldisc_sem); | |
36697529 | 274 | return tty->ldisc; |
01e1abb2 | 275 | } |
01e1abb2 AC |
276 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
277 | ||
278 | /** | |
279 | * tty_ldisc_ref - get the tty ldisc | |
280 | * @tty: tty device | |
281 | * | |
282 | * Dereference the line discipline for the terminal and take a | |
283 | * reference to it. If the line discipline is in flux then | |
284 | * return NULL. Can be called from IRQ and timer functions. | |
01e1abb2 AC |
285 | */ |
286 | ||
287 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
288 | { | |
36697529 PH |
289 | struct tty_ldisc *ld = NULL; |
290 | ||
291 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
292 | ld = tty->ldisc; | |
293 | if (!ld) | |
294 | ldsem_up_read(&tty->ldisc_sem); | |
295 | } | |
296 | return ld; | |
01e1abb2 | 297 | } |
01e1abb2 AC |
298 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
299 | ||
300 | /** | |
301 | * tty_ldisc_deref - free a tty ldisc reference | |
302 | * @ld: reference to free up | |
303 | * | |
304 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
305 | * be called in IRQ context. | |
01e1abb2 AC |
306 | */ |
307 | ||
308 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
309 | { | |
36697529 | 310 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 311 | } |
01e1abb2 AC |
312 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
313 | ||
d2c43890 | 314 | |
c2bb524b | 315 | static inline int |
e80a10ee | 316 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
317 | { |
318 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
319 | } | |
320 | ||
c2bb524b | 321 | static inline int |
e80a10ee | 322 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
323 | { |
324 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
325 | LDISC_SEM_OTHER, timeout); | |
326 | } | |
327 | ||
e80a10ee | 328 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 329 | { |
52772ea6 | 330 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
331 | } |
332 | ||
c2bb524b | 333 | static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
334 | { |
335 | int ret; | |
336 | ||
337 | ret = __tty_ldisc_lock(tty, timeout); | |
338 | if (!ret) | |
339 | return -EBUSY; | |
340 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
341 | return 0; | |
342 | } | |
343 | ||
344 | static void tty_ldisc_unlock(struct tty_struct *tty) | |
345 | { | |
346 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
347 | __tty_ldisc_unlock(tty); | |
348 | } | |
349 | ||
c2bb524b | 350 | static int |
d2c43890 PH |
351 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
352 | unsigned long timeout) | |
353 | { | |
354 | int ret; | |
355 | ||
356 | if (tty < tty2) { | |
e80a10ee | 357 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 358 | if (ret) { |
e80a10ee | 359 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 360 | if (!ret) |
e80a10ee | 361 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
362 | } |
363 | } else { | |
364 | /* if this is possible, it has lots of implications */ | |
365 | WARN_ON_ONCE(tty == tty2); | |
366 | if (tty2 && tty != tty2) { | |
e80a10ee | 367 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 368 | if (ret) { |
e80a10ee | 369 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 370 | if (!ret) |
e80a10ee | 371 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
372 | } |
373 | } else | |
e80a10ee | 374 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
375 | } |
376 | ||
377 | if (!ret) | |
378 | return -EBUSY; | |
379 | ||
380 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
381 | if (tty2) | |
382 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
383 | return 0; | |
384 | } | |
385 | ||
c2bb524b | 386 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
387 | { |
388 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
389 | } | |
390 | ||
c2bb524b PH |
391 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
392 | struct tty_struct *tty2) | |
d2c43890 | 393 | { |
e80a10ee | 394 | __tty_ldisc_unlock(tty); |
d2c43890 | 395 | if (tty2) |
e80a10ee | 396 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
397 | } |
398 | ||
f2c4c65c AC |
399 | /** |
400 | * tty_ldisc_flush - flush line discipline queue | |
401 | * @tty: tty | |
402 | * | |
86c80a8e PH |
403 | * Flush the line discipline queue (if any) and the tty flip buffers |
404 | * for this tty. | |
f2c4c65c AC |
405 | */ |
406 | ||
407 | void tty_ldisc_flush(struct tty_struct *tty) | |
408 | { | |
409 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
410 | |
411 | tty_buffer_flush(tty, ld); | |
412 | if (ld) | |
f2c4c65c | 413 | tty_ldisc_deref(ld); |
f2c4c65c | 414 | } |
f2c4c65c AC |
415 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
416 | ||
01e1abb2 AC |
417 | /** |
418 | * tty_set_termios_ldisc - set ldisc field | |
419 | * @tty: tty structure | |
420 | * @num: line discipline number | |
421 | * | |
422 | * This is probably overkill for real world processors but | |
423 | * they are not on hot paths so a little discipline won't do | |
424 | * any harm. | |
425 | * | |
dd42bf11 PH |
426 | * The line discipline-related tty_struct fields are reset to |
427 | * prevent the ldisc driver from re-using stale information for | |
428 | * the new ldisc instance. | |
429 | * | |
6a1c0680 | 430 | * Locking: takes termios_rwsem |
01e1abb2 AC |
431 | */ |
432 | ||
433 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
434 | { | |
6a1c0680 | 435 | down_write(&tty->termios_rwsem); |
adc8d746 | 436 | tty->termios.c_line = num; |
6a1c0680 | 437 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
438 | |
439 | tty->disc_data = NULL; | |
440 | tty->receive_room = 0; | |
01e1abb2 AC |
441 | } |
442 | ||
c65c9bc3 AC |
443 | /** |
444 | * tty_ldisc_open - open a line discipline | |
445 | * @tty: tty we are opening the ldisc on | |
446 | * @ld: discipline to open | |
447 | * | |
448 | * A helper opening method. Also a convenient debugging and check | |
449 | * point. | |
ec79d605 AB |
450 | * |
451 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
452 | */ |
453 | ||
454 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
455 | { | |
456 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
457 | if (ld->ops->open) { |
458 | int ret; | |
ec79d605 | 459 | /* BTM here locks versus a hangup event */ |
f18f9498 | 460 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
461 | if (ret) |
462 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 463 | |
a570a49a | 464 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
465 | return ret; |
466 | } | |
c65c9bc3 AC |
467 | return 0; |
468 | } | |
469 | ||
470 | /** | |
471 | * tty_ldisc_close - close a line discipline | |
472 | * @tty: tty we are opening the ldisc on | |
473 | * @ld: discipline to close | |
474 | * | |
475 | * A helper close method. Also a convenient debugging and check | |
476 | * point. | |
477 | */ | |
478 | ||
479 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
480 | { | |
481 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
482 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
483 | if (ld->ops->close) | |
484 | ld->ops->close(tty); | |
a570a49a | 485 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 486 | } |
01e1abb2 AC |
487 | |
488 | /** | |
489 | * tty_ldisc_restore - helper for tty ldisc change | |
490 | * @tty: tty to recover | |
491 | * @old: previous ldisc | |
492 | * | |
493 | * Restore the previous line discipline or N_TTY when a line discipline | |
494 | * change fails due to an open error | |
495 | */ | |
496 | ||
497 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
498 | { | |
c65c9bc3 AC |
499 | struct tty_ldisc *new_ldisc; |
500 | int r; | |
01e1abb2 AC |
501 | |
502 | /* There is an outstanding reference here so this is safe */ | |
36697529 | 503 | old = tty_ldisc_get(tty, old->ops->num); |
c65c9bc3 | 504 | WARN_ON(IS_ERR(old)); |
f4807045 | 505 | tty->ldisc = old; |
01e1abb2 | 506 | tty_set_termios_ldisc(tty, old->ops->num); |
c65c9bc3 AC |
507 | if (tty_ldisc_open(tty, old) < 0) { |
508 | tty_ldisc_put(old); | |
01e1abb2 | 509 | /* This driver is always present */ |
36697529 | 510 | new_ldisc = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 511 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 512 | panic("n_tty: get"); |
f4807045 | 513 | tty->ldisc = new_ldisc; |
01e1abb2 | 514 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
515 | r = tty_ldisc_open(tty, new_ldisc); |
516 | if (r < 0) | |
517 | panic("Couldn't open N_TTY ldisc for " | |
518 | "%s --- error %d.", | |
429b4749 | 519 | tty_name(tty), r); |
01e1abb2 AC |
520 | } |
521 | } | |
522 | ||
523 | /** | |
524 | * tty_set_ldisc - set line discipline | |
525 | * @tty: the terminal to set | |
526 | * @ldisc: the line discipline | |
527 | * | |
528 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
529 | * context. The ldisc change logic has to protect itself against any |
530 | * overlapping ldisc change (including on the other end of pty pairs), | |
531 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
532 | */ |
533 | ||
534 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
535 | { | |
536 | int retval; | |
9fbfa34c | 537 | struct tty_ldisc *old_ldisc, *new_ldisc; |
01e1abb2 | 538 | |
36697529 | 539 | new_ldisc = tty_ldisc_get(tty, ldisc); |
c65c9bc3 AC |
540 | if (IS_ERR(new_ldisc)) |
541 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 542 | |
c8483bc9 | 543 | tty_lock(tty); |
276a661a | 544 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
545 | if (retval) |
546 | goto err; | |
01e1abb2 | 547 | |
a570a49a PH |
548 | if (!tty->ldisc) { |
549 | retval = -EIO; | |
550 | goto out; | |
551 | } | |
552 | ||
63d8cb3f PH |
553 | /* Check the no-op case */ |
554 | if (tty->ldisc->ops->num == ldisc) | |
555 | goto out; | |
c65c9bc3 | 556 | |
63d8cb3f PH |
557 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
558 | /* We were raced by hangup */ | |
559 | retval = -EIO; | |
560 | goto out; | |
01e1abb2 AC |
561 | } |
562 | ||
9fbfa34c | 563 | old_ldisc = tty->ldisc; |
100eeae2 | 564 | |
9fbfa34c PH |
565 | /* Shutdown the old discipline. */ |
566 | tty_ldisc_close(tty, old_ldisc); | |
01e1abb2 AC |
567 | |
568 | /* Now set up the new line discipline. */ | |
f4807045 | 569 | tty->ldisc = new_ldisc; |
01e1abb2 | 570 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
571 | |
572 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 573 | if (retval < 0) { |
c65c9bc3 AC |
574 | /* Back to the old one or N_TTY if we can't */ |
575 | tty_ldisc_put(new_ldisc); | |
9fbfa34c | 576 | tty_ldisc_restore(tty, old_ldisc); |
01e1abb2 | 577 | } |
c65c9bc3 | 578 | |
9191aaaa PH |
579 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
580 | down_read(&tty->termios_rwsem); | |
01e1abb2 | 581 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
582 | up_read(&tty->termios_rwsem); |
583 | } | |
01e1abb2 | 584 | |
b0e95858 PH |
585 | /* At this point we hold a reference to the new ldisc and a |
586 | reference to the old ldisc, or we hold two references to | |
587 | the old ldisc (if it was restored as part of error cleanup | |
588 | above). In either case, releasing a single reference from | |
589 | the old ldisc is correct. */ | |
63d8cb3f PH |
590 | new_ldisc = old_ldisc; |
591 | out: | |
276a661a | 592 | tty_ldisc_unlock(tty); |
01e1abb2 | 593 | |
c65c9bc3 | 594 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 595 | already running */ |
17a69219 | 596 | tty_buffer_restart_work(tty->port); |
63d8cb3f PH |
597 | err: |
598 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ | |
89c8d91e | 599 | tty_unlock(tty); |
01e1abb2 AC |
600 | return retval; |
601 | } | |
602 | ||
6ffeb4b2 PH |
603 | /** |
604 | * tty_ldisc_kill - teardown ldisc | |
605 | * @tty: tty being released | |
606 | * | |
607 | * Perform final close of the ldisc and reset tty->ldisc | |
608 | */ | |
609 | static void tty_ldisc_kill(struct tty_struct *tty) | |
610 | { | |
611 | if (!tty->ldisc) | |
612 | return; | |
613 | /* | |
614 | * Now kill off the ldisc | |
615 | */ | |
616 | tty_ldisc_close(tty, tty->ldisc); | |
617 | tty_ldisc_put(tty->ldisc); | |
618 | /* Force an oops if we mess this up */ | |
619 | tty->ldisc = NULL; | |
620 | } | |
621 | ||
c65c9bc3 AC |
622 | /** |
623 | * tty_reset_termios - reset terminal state | |
624 | * @tty: tty to reset | |
625 | * | |
626 | * Restore a terminal to the driver default state. | |
627 | */ | |
628 | ||
629 | static void tty_reset_termios(struct tty_struct *tty) | |
630 | { | |
6a1c0680 | 631 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
632 | tty->termios = tty->driver->init_termios; |
633 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
634 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 635 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
636 | } |
637 | ||
638 | ||
639 | /** | |
640 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
641 | * @tty: tty to reinit | |
638b9648 | 642 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 643 | * |
638b9648 AC |
644 | * Switch the tty to a line discipline and leave the ldisc |
645 | * state closed | |
c65c9bc3 AC |
646 | */ |
647 | ||
1c95ba1e | 648 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 649 | { |
36697529 | 650 | struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); |
1c95ba1e PR |
651 | |
652 | if (IS_ERR(ld)) | |
653 | return -1; | |
c65c9bc3 AC |
654 | |
655 | tty_ldisc_close(tty, tty->ldisc); | |
656 | tty_ldisc_put(tty->ldisc); | |
c65c9bc3 AC |
657 | /* |
658 | * Switch the line discipline back | |
659 | */ | |
f4807045 | 660 | tty->ldisc = ld; |
638b9648 | 661 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
662 | |
663 | return 0; | |
c65c9bc3 AC |
664 | } |
665 | ||
666 | /** | |
667 | * tty_ldisc_hangup - hangup ldisc reset | |
668 | * @tty: tty being hung up | |
669 | * | |
670 | * Some tty devices reset their termios when they receive a hangup | |
671 | * event. In that situation we must also switch back to N_TTY properly | |
672 | * before we reset the termios data. | |
673 | * | |
674 | * Locking: We can take the ldisc mutex as the rest of the code is | |
675 | * careful to allow for this. | |
676 | * | |
677 | * In the pty pair case this occurs in the close() path of the | |
678 | * tty itself so we must be careful about locking rules. | |
679 | */ | |
680 | ||
681 | void tty_ldisc_hangup(struct tty_struct *tty) | |
682 | { | |
683 | struct tty_ldisc *ld; | |
638b9648 AC |
684 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
685 | int err = 0; | |
c65c9bc3 | 686 | |
a570a49a | 687 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 688 | |
c65c9bc3 AC |
689 | ld = tty_ldisc_ref(tty); |
690 | if (ld != NULL) { | |
c65c9bc3 AC |
691 | if (ld->ops->flush_buffer) |
692 | ld->ops->flush_buffer(tty); | |
693 | tty_driver_flush_buffer(tty); | |
694 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
695 | ld->ops->write_wakeup) | |
696 | ld->ops->write_wakeup(tty); | |
697 | if (ld->ops->hangup) | |
698 | ld->ops->hangup(tty); | |
699 | tty_ldisc_deref(ld); | |
700 | } | |
36697529 | 701 | |
c65c9bc3 AC |
702 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
703 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
36697529 | 704 | |
c65c9bc3 AC |
705 | /* |
706 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
707 | * N_TTY if need be. |
708 | * | |
709 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 710 | */ |
fae76e9a | 711 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 712 | |
36697529 | 713 | if (tty->ldisc) { |
c8785241 PH |
714 | |
715 | /* At this point we have a halted ldisc; we want to close it and | |
716 | reopen a new ldisc. We could defer the reopen to the next | |
717 | open but it means auditing a lot of other paths so this is | |
718 | a FIXME */ | |
638b9648 | 719 | if (reset == 0) { |
1c95ba1e | 720 | |
adc8d746 | 721 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
722 | err = tty_ldisc_open(tty, tty->ldisc); |
723 | else | |
724 | err = 1; | |
638b9648 AC |
725 | } |
726 | /* If the re-open fails or we reset then go to N_TTY. The | |
727 | N_TTY open cannot fail */ | |
728 | if (reset || err) { | |
1c95ba1e | 729 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 730 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 731 | } |
c65c9bc3 | 732 | } |
fae76e9a | 733 | tty_ldisc_unlock(tty); |
638b9648 AC |
734 | if (reset) |
735 | tty_reset_termios(tty); | |
fc575ee6 | 736 | |
fb6edc91 | 737 | tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc); |
c65c9bc3 | 738 | } |
01e1abb2 AC |
739 | |
740 | /** | |
741 | * tty_ldisc_setup - open line discipline | |
742 | * @tty: tty being shut down | |
743 | * @o_tty: pair tty for pty/tty pairs | |
744 | * | |
745 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
746 | * line disciplines and bind them to the tty. This has no locking issues |
747 | * as the device isn't yet active. | |
01e1abb2 AC |
748 | */ |
749 | ||
750 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
751 | { | |
c65c9bc3 | 752 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
753 | int retval; |
754 | ||
c65c9bc3 AC |
755 | retval = tty_ldisc_open(tty, ld); |
756 | if (retval) | |
757 | return retval; | |
758 | ||
759 | if (o_tty) { | |
760 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 761 | if (retval) { |
c65c9bc3 | 762 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
763 | return retval; |
764 | } | |
01e1abb2 | 765 | } |
01e1abb2 AC |
766 | return 0; |
767 | } | |
89c8d91e | 768 | |
01e1abb2 AC |
769 | /** |
770 | * tty_ldisc_release - release line discipline | |
62462aef | 771 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 772 | * |
62462aef | 773 | * Called during the final close of a tty or a pty pair in order to shut |
5b6e6832 | 774 | * down the line discpline layer. On exit, each tty's ldisc is NULL. |
01e1abb2 AC |
775 | */ |
776 | ||
62462aef | 777 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 778 | { |
62462aef PH |
779 | struct tty_struct *o_tty = tty->link; |
780 | ||
01e1abb2 | 781 | /* |
a2965b7b PH |
782 | * Shutdown this line discipline. As this is the final close, |
783 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 784 | */ |
01e1abb2 | 785 | |
36697529 | 786 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 787 | tty_ldisc_kill(tty); |
c65c9bc3 | 788 | if (o_tty) |
89c8d91e | 789 | tty_ldisc_kill(o_tty); |
36697529 PH |
790 | tty_ldisc_unlock_pair(tty, o_tty); |
791 | ||
aef29bc2 AC |
792 | /* And the memory resources remaining (buffers, termios) will be |
793 | disposed of when the kref hits zero */ | |
fc575ee6 | 794 | |
fb6edc91 | 795 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 AC |
796 | } |
797 | ||
798 | /** | |
799 | * tty_ldisc_init - ldisc setup for new tty | |
800 | * @tty: tty being allocated | |
801 | * | |
802 | * Set up the line discipline objects for a newly allocated tty. Note that | |
803 | * the tty structure is not completely set up when this call is made. | |
804 | */ | |
805 | ||
806 | void tty_ldisc_init(struct tty_struct *tty) | |
807 | { | |
36697529 | 808 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 809 | if (IS_ERR(ld)) |
01e1abb2 | 810 | panic("n_tty: init_tty"); |
f4807045 | 811 | tty->ldisc = ld; |
01e1abb2 AC |
812 | } |
813 | ||
6716671d | 814 | /** |
c8b710b3 | 815 | * tty_ldisc_deinit - ldisc cleanup for new tty |
6716671d JS |
816 | * @tty: tty that was allocated recently |
817 | * | |
818 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
819 | * this call is made. | |
820 | */ | |
821 | void tty_ldisc_deinit(struct tty_struct *tty) | |
822 | { | |
c8b710b3 PH |
823 | if (tty->ldisc) |
824 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 825 | tty->ldisc = NULL; |
6716671d JS |
826 | } |
827 | ||
01e1abb2 AC |
828 | void tty_ldisc_begin(void) |
829 | { | |
830 | /* Setup the default TTY line discipline. */ | |
831 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
832 | } |