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