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 PH |
306 | |
307 | static inline int __lockfunc | |
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 | ||
313 | static inline int __lockfunc | |
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 | ||
fae76e9a PH |
325 | static int __lockfunc |
326 | tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) | |
327 | { | |
328 | int ret; | |
329 | ||
330 | ret = __tty_ldisc_lock(tty, timeout); | |
331 | if (!ret) | |
332 | return -EBUSY; | |
333 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
334 | return 0; | |
335 | } | |
336 | ||
337 | static void tty_ldisc_unlock(struct tty_struct *tty) | |
338 | { | |
339 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
340 | __tty_ldisc_unlock(tty); | |
341 | } | |
342 | ||
d2c43890 PH |
343 | static int __lockfunc |
344 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, | |
345 | unsigned long timeout) | |
346 | { | |
347 | int ret; | |
348 | ||
349 | if (tty < tty2) { | |
e80a10ee | 350 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 351 | if (ret) { |
e80a10ee | 352 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 353 | if (!ret) |
e80a10ee | 354 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
355 | } |
356 | } else { | |
357 | /* if this is possible, it has lots of implications */ | |
358 | WARN_ON_ONCE(tty == tty2); | |
359 | if (tty2 && tty != tty2) { | |
e80a10ee | 360 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 361 | if (ret) { |
e80a10ee | 362 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 363 | if (!ret) |
e80a10ee | 364 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
365 | } |
366 | } else | |
e80a10ee | 367 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
368 | } |
369 | ||
370 | if (!ret) | |
371 | return -EBUSY; | |
372 | ||
373 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
374 | if (tty2) | |
375 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
376 | return 0; | |
377 | } | |
378 | ||
379 | static void __lockfunc | |
380 | tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) | |
381 | { | |
382 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
383 | } | |
384 | ||
385 | static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, | |
386 | struct tty_struct *tty2) | |
387 | { | |
e80a10ee | 388 | __tty_ldisc_unlock(tty); |
d2c43890 | 389 | if (tty2) |
e80a10ee | 390 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
391 | } |
392 | ||
f2c4c65c AC |
393 | /** |
394 | * tty_ldisc_flush - flush line discipline queue | |
395 | * @tty: tty | |
396 | * | |
86c80a8e PH |
397 | * Flush the line discipline queue (if any) and the tty flip buffers |
398 | * for this tty. | |
f2c4c65c AC |
399 | */ |
400 | ||
401 | void tty_ldisc_flush(struct tty_struct *tty) | |
402 | { | |
403 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
404 | |
405 | tty_buffer_flush(tty, ld); | |
406 | if (ld) | |
f2c4c65c | 407 | tty_ldisc_deref(ld); |
f2c4c65c | 408 | } |
f2c4c65c AC |
409 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
410 | ||
01e1abb2 AC |
411 | /** |
412 | * tty_set_termios_ldisc - set ldisc field | |
413 | * @tty: tty structure | |
414 | * @num: line discipline number | |
415 | * | |
416 | * This is probably overkill for real world processors but | |
417 | * they are not on hot paths so a little discipline won't do | |
418 | * any harm. | |
419 | * | |
dd42bf11 PH |
420 | * The line discipline-related tty_struct fields are reset to |
421 | * prevent the ldisc driver from re-using stale information for | |
422 | * the new ldisc instance. | |
423 | * | |
6a1c0680 | 424 | * Locking: takes termios_rwsem |
01e1abb2 AC |
425 | */ |
426 | ||
427 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
428 | { | |
6a1c0680 | 429 | down_write(&tty->termios_rwsem); |
adc8d746 | 430 | tty->termios.c_line = num; |
6a1c0680 | 431 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
432 | |
433 | tty->disc_data = NULL; | |
434 | tty->receive_room = 0; | |
01e1abb2 AC |
435 | } |
436 | ||
c65c9bc3 AC |
437 | /** |
438 | * tty_ldisc_open - open a line discipline | |
439 | * @tty: tty we are opening the ldisc on | |
440 | * @ld: discipline to open | |
441 | * | |
442 | * A helper opening method. Also a convenient debugging and check | |
443 | * point. | |
ec79d605 AB |
444 | * |
445 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
446 | */ |
447 | ||
448 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
449 | { | |
450 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
451 | if (ld->ops->open) { |
452 | int ret; | |
ec79d605 | 453 | /* BTM here locks versus a hangup event */ |
f18f9498 | 454 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
455 | if (ret) |
456 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 PH |
457 | |
458 | tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc); | |
f18f9498 AC |
459 | return ret; |
460 | } | |
c65c9bc3 AC |
461 | return 0; |
462 | } | |
463 | ||
464 | /** | |
465 | * tty_ldisc_close - close a line discipline | |
466 | * @tty: tty we are opening the ldisc on | |
467 | * @ld: discipline to close | |
468 | * | |
469 | * A helper close method. Also a convenient debugging and check | |
470 | * point. | |
471 | */ | |
472 | ||
473 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
474 | { | |
475 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
476 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
477 | if (ld->ops->close) | |
478 | ld->ops->close(tty); | |
fb6edc91 | 479 | tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc); |
c65c9bc3 | 480 | } |
01e1abb2 AC |
481 | |
482 | /** | |
483 | * tty_ldisc_restore - helper for tty ldisc change | |
484 | * @tty: tty to recover | |
485 | * @old: previous ldisc | |
486 | * | |
487 | * Restore the previous line discipline or N_TTY when a line discipline | |
488 | * change fails due to an open error | |
489 | */ | |
490 | ||
491 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
492 | { | |
c65c9bc3 AC |
493 | struct tty_ldisc *new_ldisc; |
494 | int r; | |
01e1abb2 AC |
495 | |
496 | /* There is an outstanding reference here so this is safe */ | |
36697529 | 497 | old = tty_ldisc_get(tty, old->ops->num); |
c65c9bc3 | 498 | WARN_ON(IS_ERR(old)); |
f4807045 | 499 | tty->ldisc = old; |
01e1abb2 | 500 | tty_set_termios_ldisc(tty, old->ops->num); |
c65c9bc3 AC |
501 | if (tty_ldisc_open(tty, old) < 0) { |
502 | tty_ldisc_put(old); | |
01e1abb2 | 503 | /* This driver is always present */ |
36697529 | 504 | new_ldisc = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 505 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 506 | panic("n_tty: get"); |
f4807045 | 507 | tty->ldisc = new_ldisc; |
01e1abb2 | 508 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
509 | r = tty_ldisc_open(tty, new_ldisc); |
510 | if (r < 0) | |
511 | panic("Couldn't open N_TTY ldisc for " | |
512 | "%s --- error %d.", | |
429b4749 | 513 | tty_name(tty), r); |
01e1abb2 AC |
514 | } |
515 | } | |
516 | ||
517 | /** | |
518 | * tty_set_ldisc - set line discipline | |
519 | * @tty: the terminal to set | |
520 | * @ldisc: the line discipline | |
521 | * | |
522 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
523 | * context. The ldisc change logic has to protect itself against any |
524 | * overlapping ldisc change (including on the other end of pty pairs), | |
525 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 AC |
526 | */ |
527 | ||
528 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
529 | { | |
530 | int retval; | |
9fbfa34c | 531 | struct tty_ldisc *old_ldisc, *new_ldisc; |
01e1abb2 | 532 | |
36697529 | 533 | new_ldisc = tty_ldisc_get(tty, ldisc); |
c65c9bc3 AC |
534 | if (IS_ERR(new_ldisc)) |
535 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 536 | |
c8483bc9 | 537 | tty_lock(tty); |
276a661a | 538 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
539 | if (retval) |
540 | goto err; | |
01e1abb2 | 541 | |
63d8cb3f PH |
542 | /* Check the no-op case */ |
543 | if (tty->ldisc->ops->num == ldisc) | |
544 | goto out; | |
c65c9bc3 | 545 | |
63d8cb3f PH |
546 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
547 | /* We were raced by hangup */ | |
548 | retval = -EIO; | |
549 | goto out; | |
01e1abb2 AC |
550 | } |
551 | ||
9fbfa34c | 552 | old_ldisc = tty->ldisc; |
100eeae2 | 553 | |
9fbfa34c PH |
554 | /* Shutdown the old discipline. */ |
555 | tty_ldisc_close(tty, old_ldisc); | |
01e1abb2 AC |
556 | |
557 | /* Now set up the new line discipline. */ | |
f4807045 | 558 | tty->ldisc = new_ldisc; |
01e1abb2 | 559 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
560 | |
561 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 562 | if (retval < 0) { |
c65c9bc3 AC |
563 | /* Back to the old one or N_TTY if we can't */ |
564 | tty_ldisc_put(new_ldisc); | |
9fbfa34c | 565 | tty_ldisc_restore(tty, old_ldisc); |
01e1abb2 | 566 | } |
c65c9bc3 | 567 | |
9191aaaa PH |
568 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
569 | down_read(&tty->termios_rwsem); | |
01e1abb2 | 570 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
571 | up_read(&tty->termios_rwsem); |
572 | } | |
01e1abb2 | 573 | |
b0e95858 PH |
574 | /* At this point we hold a reference to the new ldisc and a |
575 | reference to the old ldisc, or we hold two references to | |
576 | the old ldisc (if it was restored as part of error cleanup | |
577 | above). In either case, releasing a single reference from | |
578 | the old ldisc is correct. */ | |
63d8cb3f PH |
579 | new_ldisc = old_ldisc; |
580 | out: | |
276a661a | 581 | tty_ldisc_unlock(tty); |
01e1abb2 | 582 | |
c65c9bc3 | 583 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 584 | already running */ |
17a69219 | 585 | tty_buffer_restart_work(tty->port); |
63d8cb3f PH |
586 | err: |
587 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ | |
89c8d91e | 588 | tty_unlock(tty); |
01e1abb2 AC |
589 | return retval; |
590 | } | |
591 | ||
c65c9bc3 AC |
592 | /** |
593 | * tty_reset_termios - reset terminal state | |
594 | * @tty: tty to reset | |
595 | * | |
596 | * Restore a terminal to the driver default state. | |
597 | */ | |
598 | ||
599 | static void tty_reset_termios(struct tty_struct *tty) | |
600 | { | |
6a1c0680 | 601 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
602 | tty->termios = tty->driver->init_termios; |
603 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
604 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 605 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
606 | } |
607 | ||
608 | ||
609 | /** | |
610 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
611 | * @tty: tty to reinit | |
638b9648 | 612 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 613 | * |
638b9648 AC |
614 | * Switch the tty to a line discipline and leave the ldisc |
615 | * state closed | |
c65c9bc3 AC |
616 | */ |
617 | ||
1c95ba1e | 618 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 619 | { |
36697529 | 620 | struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); |
1c95ba1e PR |
621 | |
622 | if (IS_ERR(ld)) | |
623 | return -1; | |
c65c9bc3 AC |
624 | |
625 | tty_ldisc_close(tty, tty->ldisc); | |
626 | tty_ldisc_put(tty->ldisc); | |
c65c9bc3 AC |
627 | /* |
628 | * Switch the line discipline back | |
629 | */ | |
f4807045 | 630 | tty->ldisc = ld; |
638b9648 | 631 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
632 | |
633 | return 0; | |
c65c9bc3 AC |
634 | } |
635 | ||
636 | /** | |
637 | * tty_ldisc_hangup - hangup ldisc reset | |
638 | * @tty: tty being hung up | |
639 | * | |
640 | * Some tty devices reset their termios when they receive a hangup | |
641 | * event. In that situation we must also switch back to N_TTY properly | |
642 | * before we reset the termios data. | |
643 | * | |
644 | * Locking: We can take the ldisc mutex as the rest of the code is | |
645 | * careful to allow for this. | |
646 | * | |
647 | * In the pty pair case this occurs in the close() path of the | |
648 | * tty itself so we must be careful about locking rules. | |
649 | */ | |
650 | ||
651 | void tty_ldisc_hangup(struct tty_struct *tty) | |
652 | { | |
653 | struct tty_ldisc *ld; | |
638b9648 AC |
654 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
655 | int err = 0; | |
c65c9bc3 | 656 | |
fb6edc91 | 657 | tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc); |
fc575ee6 | 658 | |
c65c9bc3 AC |
659 | ld = tty_ldisc_ref(tty); |
660 | if (ld != NULL) { | |
c65c9bc3 AC |
661 | if (ld->ops->flush_buffer) |
662 | ld->ops->flush_buffer(tty); | |
663 | tty_driver_flush_buffer(tty); | |
664 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
665 | ld->ops->write_wakeup) | |
666 | ld->ops->write_wakeup(tty); | |
667 | if (ld->ops->hangup) | |
668 | ld->ops->hangup(tty); | |
669 | tty_ldisc_deref(ld); | |
670 | } | |
36697529 | 671 | |
c65c9bc3 AC |
672 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
673 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
36697529 | 674 | |
c65c9bc3 AC |
675 | /* |
676 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
677 | * N_TTY if need be. |
678 | * | |
679 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 680 | */ |
fae76e9a | 681 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 682 | |
36697529 | 683 | if (tty->ldisc) { |
c8785241 PH |
684 | |
685 | /* At this point we have a halted ldisc; we want to close it and | |
686 | reopen a new ldisc. We could defer the reopen to the next | |
687 | open but it means auditing a lot of other paths so this is | |
688 | a FIXME */ | |
638b9648 | 689 | if (reset == 0) { |
1c95ba1e | 690 | |
adc8d746 | 691 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
692 | err = tty_ldisc_open(tty, tty->ldisc); |
693 | else | |
694 | err = 1; | |
638b9648 AC |
695 | } |
696 | /* If the re-open fails or we reset then go to N_TTY. The | |
697 | N_TTY open cannot fail */ | |
698 | if (reset || err) { | |
1c95ba1e | 699 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 700 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 701 | } |
c65c9bc3 | 702 | } |
fae76e9a | 703 | tty_ldisc_unlock(tty); |
638b9648 AC |
704 | if (reset) |
705 | tty_reset_termios(tty); | |
fc575ee6 | 706 | |
fb6edc91 | 707 | tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc); |
c65c9bc3 | 708 | } |
01e1abb2 AC |
709 | |
710 | /** | |
711 | * tty_ldisc_setup - open line discipline | |
712 | * @tty: tty being shut down | |
713 | * @o_tty: pair tty for pty/tty pairs | |
714 | * | |
715 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
716 | * line disciplines and bind them to the tty. This has no locking issues |
717 | * as the device isn't yet active. | |
01e1abb2 AC |
718 | */ |
719 | ||
720 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
721 | { | |
c65c9bc3 | 722 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
723 | int retval; |
724 | ||
c65c9bc3 AC |
725 | retval = tty_ldisc_open(tty, ld); |
726 | if (retval) | |
727 | return retval; | |
728 | ||
729 | if (o_tty) { | |
730 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 731 | if (retval) { |
c65c9bc3 | 732 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
733 | return retval; |
734 | } | |
01e1abb2 | 735 | } |
01e1abb2 AC |
736 | return 0; |
737 | } | |
89c8d91e AC |
738 | |
739 | static void tty_ldisc_kill(struct tty_struct *tty) | |
740 | { | |
89c8d91e AC |
741 | /* |
742 | * Now kill off the ldisc | |
743 | */ | |
744 | tty_ldisc_close(tty, tty->ldisc); | |
745 | tty_ldisc_put(tty->ldisc); | |
746 | /* Force an oops if we mess this up */ | |
747 | tty->ldisc = NULL; | |
748 | ||
749 | /* Ensure the next open requests the N_TTY ldisc */ | |
750 | tty_set_termios_ldisc(tty, N_TTY); | |
89c8d91e AC |
751 | } |
752 | ||
01e1abb2 AC |
753 | /** |
754 | * tty_ldisc_release - release line discipline | |
62462aef | 755 | * @tty: tty being shut down (or one end of pty pair) |
3ee175d9 | 756 | * |
62462aef PH |
757 | * Called during the final close of a tty or a pty pair in order to shut |
758 | * down the line discpline layer. On exit, each ldisc assigned is N_TTY and | |
759 | * each ldisc has not been opened. | |
01e1abb2 AC |
760 | */ |
761 | ||
62462aef | 762 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 763 | { |
62462aef PH |
764 | struct tty_struct *o_tty = tty->link; |
765 | ||
01e1abb2 | 766 | /* |
a2965b7b PH |
767 | * Shutdown this line discipline. As this is the final close, |
768 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 769 | */ |
01e1abb2 | 770 | |
36697529 | 771 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 772 | tty_ldisc_kill(tty); |
c65c9bc3 | 773 | if (o_tty) |
89c8d91e | 774 | tty_ldisc_kill(o_tty); |
36697529 PH |
775 | tty_ldisc_unlock_pair(tty, o_tty); |
776 | ||
aef29bc2 AC |
777 | /* And the memory resources remaining (buffers, termios) will be |
778 | disposed of when the kref hits zero */ | |
fc575ee6 | 779 | |
fb6edc91 | 780 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 AC |
781 | } |
782 | ||
783 | /** | |
784 | * tty_ldisc_init - ldisc setup for new tty | |
785 | * @tty: tty being allocated | |
786 | * | |
787 | * Set up the line discipline objects for a newly allocated tty. Note that | |
788 | * the tty structure is not completely set up when this call is made. | |
789 | */ | |
790 | ||
791 | void tty_ldisc_init(struct tty_struct *tty) | |
792 | { | |
36697529 | 793 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
c65c9bc3 | 794 | if (IS_ERR(ld)) |
01e1abb2 | 795 | panic("n_tty: init_tty"); |
f4807045 | 796 | tty->ldisc = ld; |
01e1abb2 AC |
797 | } |
798 | ||
6716671d JS |
799 | /** |
800 | * tty_ldisc_init - ldisc cleanup for new tty | |
801 | * @tty: tty that was allocated recently | |
802 | * | |
803 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
804 | * this call is made. | |
805 | */ | |
806 | void tty_ldisc_deinit(struct tty_struct *tty) | |
807 | { | |
ebc9baed | 808 | tty_ldisc_put(tty->ldisc); |
f4807045 | 809 | tty->ldisc = NULL; |
6716671d JS |
810 | } |
811 | ||
01e1abb2 AC |
812 | void tty_ldisc_begin(void) |
813 | { | |
814 | /* Setup the default TTY line discipline. */ | |
815 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
816 | } |