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> | |
14 | #include <linux/init.h> | |
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 | |
26 | #define tty_ldisc_debug(tty, f, args...) ({ \ | |
27 | char __b[64]; \ | |
28 | printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \ | |
29 | }) | |
30 | #else | |
31 | #define tty_ldisc_debug(tty, f, args...) | |
32 | #endif | |
33 | ||
01e1abb2 AC |
34 | /* |
35 | * This guards the refcounted line discipline lists. The lock | |
36 | * must be taken with irqs off because there are hangup path | |
37 | * callers who will do ldisc lookups and cannot sleep. | |
38 | */ | |
39 | ||
137084bb | 40 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
41 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); |
42 | /* Line disc dispatch table */ | |
43 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
44 | ||
45 | /** | |
46 | * tty_register_ldisc - install a line discipline | |
47 | * @disc: ldisc number | |
48 | * @new_ldisc: pointer to the ldisc object | |
49 | * | |
50 | * Installs a new line discipline into the kernel. The discipline | |
51 | * is set up as unreferenced and then made available to the kernel | |
52 | * from this point onwards. | |
53 | * | |
54 | * Locking: | |
137084bb | 55 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
56 | */ |
57 | ||
58 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
59 | { | |
60 | unsigned long flags; | |
61 | int ret = 0; | |
62 | ||
63 | if (disc < N_TTY || disc >= NR_LDISCS) | |
64 | return -EINVAL; | |
65 | ||
137084bb | 66 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
67 | tty_ldiscs[disc] = new_ldisc; |
68 | new_ldisc->num = disc; | |
69 | new_ldisc->refcount = 0; | |
137084bb | 70 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
71 | |
72 | return ret; | |
73 | } | |
74 | EXPORT_SYMBOL(tty_register_ldisc); | |
75 | ||
76 | /** | |
77 | * tty_unregister_ldisc - unload a line discipline | |
78 | * @disc: ldisc number | |
79 | * @new_ldisc: pointer to the ldisc object | |
80 | * | |
81 | * Remove a line discipline from the kernel providing it is not | |
82 | * currently in use. | |
83 | * | |
84 | * Locking: | |
137084bb | 85 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
86 | */ |
87 | ||
88 | int tty_unregister_ldisc(int disc) | |
89 | { | |
90 | unsigned long flags; | |
91 | int ret = 0; | |
92 | ||
93 | if (disc < N_TTY || disc >= NR_LDISCS) | |
94 | return -EINVAL; | |
95 | ||
137084bb | 96 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
97 | if (tty_ldiscs[disc]->refcount) |
98 | ret = -EBUSY; | |
99 | else | |
100 | tty_ldiscs[disc] = NULL; | |
137084bb | 101 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
102 | |
103 | return ret; | |
104 | } | |
105 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
106 | ||
f0de0e8d LT |
107 | static struct tty_ldisc_ops *get_ldops(int disc) |
108 | { | |
109 | unsigned long flags; | |
110 | struct tty_ldisc_ops *ldops, *ret; | |
111 | ||
137084bb | 112 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
113 | ret = ERR_PTR(-EINVAL); |
114 | ldops = tty_ldiscs[disc]; | |
115 | if (ldops) { | |
116 | ret = ERR_PTR(-EAGAIN); | |
117 | if (try_module_get(ldops->owner)) { | |
118 | ldops->refcount++; | |
119 | ret = ldops; | |
120 | } | |
121 | } | |
137084bb | 122 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
123 | return ret; |
124 | } | |
125 | ||
126 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
127 | { | |
128 | unsigned long flags; | |
129 | ||
137084bb | 130 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
131 | ldops->refcount--; |
132 | module_put(ldops->owner); | |
137084bb | 133 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 134 | } |
01e1abb2 | 135 | |
01e1abb2 AC |
136 | /** |
137 | * tty_ldisc_get - take a reference to an ldisc | |
138 | * @disc: ldisc number | |
01e1abb2 AC |
139 | * |
140 | * Takes a reference to a line discipline. Deals with refcounts and | |
141 | * module locking counts. Returns NULL if the discipline is not available. | |
142 | * Returns a pointer to the discipline and bumps the ref count if it is | |
143 | * available | |
144 | * | |
145 | * Locking: | |
137084bb | 146 | * takes tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
147 | */ |
148 | ||
c65c9bc3 | 149 | static struct tty_ldisc *tty_ldisc_get(int disc) |
01e1abb2 | 150 | { |
c65c9bc3 | 151 | struct tty_ldisc *ld; |
182274f8 | 152 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
153 | |
154 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 155 | return ERR_PTR(-EINVAL); |
182274f8 LT |
156 | |
157 | /* | |
158 | * Get the ldisc ops - we may need to request them to be loaded | |
159 | * dynamically and try again. | |
160 | */ | |
161 | ldops = get_ldops(disc); | |
162 | if (IS_ERR(ldops)) { | |
01e1abb2 | 163 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
164 | ldops = get_ldops(disc); |
165 | if (IS_ERR(ldops)) | |
166 | return ERR_CAST(ldops); | |
167 | } | |
168 | ||
169 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
170 | if (ld == NULL) { | |
171 | put_ldops(ldops); | |
172 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 173 | } |
182274f8 LT |
174 | |
175 | ld->ops = ldops; | |
176 | atomic_set(&ld->users, 1); | |
1541f845 IS |
177 | init_waitqueue_head(&ld->wq_idle); |
178 | ||
c65c9bc3 | 179 | return ld; |
01e1abb2 AC |
180 | } |
181 | ||
734de249 PH |
182 | /** |
183 | * tty_ldisc_put - release the ldisc | |
184 | * | |
185 | * Complement of tty_ldisc_get(). | |
186 | */ | |
187 | static inline void tty_ldisc_put(struct tty_ldisc *ld) | |
188 | { | |
189 | unsigned long flags; | |
190 | ||
191 | if (WARN_ON_ONCE(!ld)) | |
192 | return; | |
193 | ||
137084bb | 194 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
734de249 PH |
195 | |
196 | /* unreleased reader reference(s) will cause this WARN */ | |
197 | WARN_ON(!atomic_dec_and_test(&ld->users)); | |
198 | ||
199 | ld->ops->refcount--; | |
200 | module_put(ld->ops->owner); | |
201 | kfree(ld); | |
137084bb | 202 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
734de249 PH |
203 | } |
204 | ||
852e99d2 | 205 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
206 | { |
207 | return (*pos < NR_LDISCS) ? pos : NULL; | |
208 | } | |
209 | ||
852e99d2 | 210 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
211 | { |
212 | (*pos)++; | |
213 | return (*pos < NR_LDISCS) ? pos : NULL; | |
214 | } | |
215 | ||
216 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
217 | { | |
218 | } | |
219 | ||
220 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
221 | { | |
222 | int i = *(loff_t *)v; | |
f0de0e8d | 223 | struct tty_ldisc_ops *ldops; |
852e99d2 | 224 | |
f0de0e8d LT |
225 | ldops = get_ldops(i); |
226 | if (IS_ERR(ldops)) | |
01e1abb2 | 227 | return 0; |
f0de0e8d LT |
228 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
229 | put_ldops(ldops); | |
01e1abb2 AC |
230 | return 0; |
231 | } | |
232 | ||
233 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
234 | .start = tty_ldiscs_seq_start, | |
235 | .next = tty_ldiscs_seq_next, | |
236 | .stop = tty_ldiscs_seq_stop, | |
237 | .show = tty_ldiscs_seq_show, | |
238 | }; | |
239 | ||
240 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
241 | { | |
242 | return seq_open(file, &tty_ldiscs_seq_ops); | |
243 | } | |
244 | ||
245 | const struct file_operations tty_ldiscs_proc_fops = { | |
246 | .owner = THIS_MODULE, | |
247 | .open = proc_tty_ldiscs_open, | |
248 | .read = seq_read, | |
249 | .llseek = seq_lseek, | |
250 | .release = seq_release, | |
251 | }; | |
252 | ||
01e1abb2 AC |
253 | /** |
254 | * tty_ldisc_try - internal helper | |
255 | * @tty: the tty | |
256 | * | |
257 | * Make a single attempt to grab and bump the refcount on | |
258 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
259 | * used to implement both the waiting and non waiting versions | |
260 | * of tty_ldisc_ref | |
261 | * | |
137084bb | 262 | * Locking: takes tty_ldiscs_lock |
01e1abb2 AC |
263 | */ |
264 | ||
65b77046 | 265 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
01e1abb2 AC |
266 | { |
267 | unsigned long flags; | |
268 | struct tty_ldisc *ld; | |
01e1abb2 | 269 | |
16759f6c | 270 | /* FIXME: this allows reference acquire after TTY_LDISC is cleared */ |
137084bb | 271 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
65b77046 | 272 | ld = NULL; |
16759f6c PH |
273 | if (test_bit(TTY_LDISC, &tty->flags) && tty->ldisc) { |
274 | ld = tty->ldisc; | |
275 | atomic_inc(&ld->users); | |
276 | } | |
137084bb | 277 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
65b77046 | 278 | return ld; |
01e1abb2 AC |
279 | } |
280 | ||
281 | /** | |
282 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
283 | * @tty: tty device | |
284 | * | |
285 | * Dereference the line discipline for the terminal and take a | |
286 | * reference to it. If the line discipline is in flux then | |
287 | * wait patiently until it changes. | |
288 | * | |
289 | * Note: Must not be called from an IRQ/timer context. The caller | |
290 | * must also be careful not to hold other locks that will deadlock | |
291 | * against a discipline change, such as an existing ldisc reference | |
292 | * (which we check for) | |
293 | * | |
137084bb | 294 | * Locking: call functions take tty_ldiscs_lock |
01e1abb2 AC |
295 | */ |
296 | ||
297 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
298 | { | |
65b77046 LT |
299 | struct tty_ldisc *ld; |
300 | ||
01e1abb2 | 301 | /* wait_event is a macro */ |
65b77046 LT |
302 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
303 | return ld; | |
01e1abb2 | 304 | } |
01e1abb2 AC |
305 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
306 | ||
307 | /** | |
308 | * tty_ldisc_ref - get the tty ldisc | |
309 | * @tty: tty device | |
310 | * | |
311 | * Dereference the line discipline for the terminal and take a | |
312 | * reference to it. If the line discipline is in flux then | |
313 | * return NULL. Can be called from IRQ and timer functions. | |
314 | * | |
137084bb | 315 | * Locking: called functions take tty_ldiscs_lock |
01e1abb2 AC |
316 | */ |
317 | ||
318 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
319 | { | |
65b77046 | 320 | return tty_ldisc_try(tty); |
01e1abb2 | 321 | } |
01e1abb2 AC |
322 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
323 | ||
324 | /** | |
325 | * tty_ldisc_deref - free a tty ldisc reference | |
326 | * @ld: reference to free up | |
327 | * | |
328 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
329 | * be called in IRQ context. | |
330 | * | |
137084bb | 331 | * Locking: takes tty_ldiscs_lock |
01e1abb2 AC |
332 | */ |
333 | ||
334 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
335 | { | |
ebc9baed PH |
336 | unsigned long flags; |
337 | ||
338 | if (WARN_ON_ONCE(!ld)) | |
339 | return; | |
340 | ||
137084bb | 341 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
ebc9baed PH |
342 | /* |
343 | * WARNs if one-too-many reader references were released | |
344 | * - the last reference must be released with tty_ldisc_put | |
345 | */ | |
346 | WARN_ON(atomic_dec_and_test(&ld->users)); | |
137084bb | 347 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
ebc9baed PH |
348 | |
349 | if (waitqueue_active(&ld->wq_idle)) | |
350 | wake_up(&ld->wq_idle); | |
01e1abb2 | 351 | } |
01e1abb2 AC |
352 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
353 | ||
354 | /** | |
355 | * tty_ldisc_enable - allow ldisc use | |
356 | * @tty: terminal to activate ldisc on | |
357 | * | |
358 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
359 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
360 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 361 | * |
c9b3976e AC |
362 | * Note: nobody should set the TTY_LDISC bit except via this function. |
363 | * Clearing directly is allowed. | |
01e1abb2 AC |
364 | */ |
365 | ||
d9121566 | 366 | static void tty_ldisc_enable(struct tty_struct *tty) |
01e1abb2 | 367 | { |
21622939 | 368 | clear_bit(TTY_LDISC_HALTED, &tty->flags); |
01e1abb2 | 369 | set_bit(TTY_LDISC, &tty->flags); |
c9b3976e | 370 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
371 | wake_up(&tty_ldisc_wait); |
372 | } | |
373 | ||
f2c4c65c AC |
374 | /** |
375 | * tty_ldisc_flush - flush line discipline queue | |
376 | * @tty: tty | |
377 | * | |
378 | * Flush the line discipline queue (if any) for this tty. If there | |
379 | * is no line discipline active this is a no-op. | |
380 | */ | |
381 | ||
382 | void tty_ldisc_flush(struct tty_struct *tty) | |
383 | { | |
384 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
385 | if (ld) { | |
386 | if (ld->ops->flush_buffer) | |
387 | ld->ops->flush_buffer(tty); | |
388 | tty_ldisc_deref(ld); | |
389 | } | |
390 | tty_buffer_flush(tty); | |
391 | } | |
f2c4c65c AC |
392 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
393 | ||
01e1abb2 AC |
394 | /** |
395 | * tty_set_termios_ldisc - set ldisc field | |
396 | * @tty: tty structure | |
397 | * @num: line discipline number | |
398 | * | |
399 | * This is probably overkill for real world processors but | |
400 | * they are not on hot paths so a little discipline won't do | |
401 | * any harm. | |
402 | * | |
403 | * Locking: takes termios_mutex | |
404 | */ | |
405 | ||
406 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
407 | { | |
408 | mutex_lock(&tty->termios_mutex); | |
adc8d746 | 409 | tty->termios.c_line = num; |
01e1abb2 AC |
410 | mutex_unlock(&tty->termios_mutex); |
411 | } | |
412 | ||
c65c9bc3 AC |
413 | /** |
414 | * tty_ldisc_open - open a line discipline | |
415 | * @tty: tty we are opening the ldisc on | |
416 | * @ld: discipline to open | |
417 | * | |
418 | * A helper opening method. Also a convenient debugging and check | |
419 | * point. | |
ec79d605 AB |
420 | * |
421 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
422 | */ |
423 | ||
424 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
425 | { | |
426 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
427 | if (ld->ops->open) { |
428 | int ret; | |
ec79d605 | 429 | /* BTM here locks versus a hangup event */ |
f18f9498 | 430 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
431 | if (ret) |
432 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
f18f9498 AC |
433 | return ret; |
434 | } | |
c65c9bc3 AC |
435 | return 0; |
436 | } | |
437 | ||
438 | /** | |
439 | * tty_ldisc_close - close a line discipline | |
440 | * @tty: tty we are opening the ldisc on | |
441 | * @ld: discipline to close | |
442 | * | |
443 | * A helper close method. Also a convenient debugging and check | |
444 | * point. | |
445 | */ | |
446 | ||
447 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
448 | { | |
449 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
450 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
451 | if (ld->ops->close) | |
452 | ld->ops->close(tty); | |
453 | } | |
01e1abb2 AC |
454 | |
455 | /** | |
456 | * tty_ldisc_restore - helper for tty ldisc change | |
457 | * @tty: tty to recover | |
458 | * @old: previous ldisc | |
459 | * | |
460 | * Restore the previous line discipline or N_TTY when a line discipline | |
461 | * change fails due to an open error | |
462 | */ | |
463 | ||
464 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
465 | { | |
466 | char buf[64]; | |
c65c9bc3 AC |
467 | struct tty_ldisc *new_ldisc; |
468 | int r; | |
01e1abb2 AC |
469 | |
470 | /* There is an outstanding reference here so this is safe */ | |
c65c9bc3 AC |
471 | old = tty_ldisc_get(old->ops->num); |
472 | WARN_ON(IS_ERR(old)); | |
f4807045 | 473 | tty->ldisc = old; |
01e1abb2 | 474 | tty_set_termios_ldisc(tty, old->ops->num); |
c65c9bc3 AC |
475 | if (tty_ldisc_open(tty, old) < 0) { |
476 | tty_ldisc_put(old); | |
01e1abb2 | 477 | /* This driver is always present */ |
852e99d2 | 478 | new_ldisc = tty_ldisc_get(N_TTY); |
c65c9bc3 | 479 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 480 | panic("n_tty: get"); |
f4807045 | 481 | tty->ldisc = new_ldisc; |
01e1abb2 | 482 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
483 | r = tty_ldisc_open(tty, new_ldisc); |
484 | if (r < 0) | |
485 | panic("Couldn't open N_TTY ldisc for " | |
486 | "%s --- error %d.", | |
487 | tty_name(tty, buf), r); | |
01e1abb2 AC |
488 | } |
489 | } | |
490 | ||
100eeae2 JS |
491 | /** |
492 | * tty_ldisc_wait_idle - wait for the ldisc to become idle | |
493 | * @tty: tty to wait for | |
df92d056 | 494 | * @timeout: for how long to wait at most |
100eeae2 JS |
495 | * |
496 | * Wait for the line discipline to become idle. The discipline must | |
497 | * have been halted for this to guarantee it remains idle. | |
498 | */ | |
df92d056 | 499 | static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) |
100eeae2 | 500 | { |
df92d056 | 501 | long ret; |
1541f845 | 502 | ret = wait_event_timeout(tty->ldisc->wq_idle, |
df92d056 | 503 | atomic_read(&tty->ldisc->users) == 1, timeout); |
100eeae2 JS |
504 | return ret > 0 ? 0 : -EBUSY; |
505 | } | |
506 | ||
11cf48ea PH |
507 | /** |
508 | * tty_ldisc_halt - shut down the line discipline | |
509 | * @tty: tty device | |
f4cf7a38 | 510 | * @o_tty: paired pty device (can be NULL) |
cf528476 | 511 | * @timeout: # of jiffies to wait for ldisc refs to be released |
11cf48ea | 512 | * |
f4cf7a38 PH |
513 | * Shut down the line discipline and work queue for this tty device and |
514 | * its paired pty (if exists). Clearing the TTY_LDISC flag ensures | |
4f98d467 PH |
515 | * no further references can be obtained, while waiting for existing |
516 | * references to be released ensures no more data is fed to the ldisc. | |
cf528476 | 517 | * |
11cf48ea PH |
518 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
519 | * in order to make sure any currently executing ldisc work is also | |
520 | * flushed. | |
521 | */ | |
522 | ||
f4cf7a38 | 523 | static int tty_ldisc_halt(struct tty_struct *tty, struct tty_struct *o_tty, |
4f98d467 | 524 | long timeout) |
11cf48ea | 525 | { |
4f98d467 | 526 | int retval; |
cf528476 | 527 | |
11cf48ea | 528 | clear_bit(TTY_LDISC, &tty->flags); |
f4cf7a38 PH |
529 | if (o_tty) |
530 | clear_bit(TTY_LDISC, &o_tty->flags); | |
531 | ||
cf528476 | 532 | retval = tty_ldisc_wait_idle(tty, timeout); |
f4cf7a38 PH |
533 | if (!retval && o_tty) |
534 | retval = tty_ldisc_wait_idle(o_tty, timeout); | |
cf528476 PH |
535 | if (retval) |
536 | return retval; | |
537 | ||
11cf48ea | 538 | set_bit(TTY_LDISC_HALTED, &tty->flags); |
4f98d467 | 539 | if (o_tty) |
f4cf7a38 | 540 | set_bit(TTY_LDISC_HALTED, &o_tty->flags); |
f4cf7a38 | 541 | |
cf528476 | 542 | return 0; |
11cf48ea PH |
543 | } |
544 | ||
168942c9 | 545 | /** |
76bc35e7 PH |
546 | * tty_ldisc_hangup_halt - halt the line discipline for hangup |
547 | * @tty: tty being hung up | |
168942c9 | 548 | * |
76bc35e7 PH |
549 | * Shut down the line discipline and work queue for the tty device |
550 | * being hungup. Clear the TTY_LDISC flag to ensure no further | |
4f98d467 PH |
551 | * references can be obtained and wait for remaining references to be |
552 | * released to ensure no more data is fed to this ldisc. | |
168942c9 | 553 | * Caller must hold legacy and ->ldisc_mutex. |
2276ad97 PH |
554 | * |
555 | * NB: tty_set_ldisc() is prevented from changing the ldisc concurrently | |
556 | * with this function by checking the TTY_HUPPING flag. | |
168942c9 | 557 | */ |
76bc35e7 | 558 | static bool tty_ldisc_hangup_halt(struct tty_struct *tty) |
168942c9 | 559 | { |
2276ad97 PH |
560 | char cur_n[TASK_COMM_LEN], tty_n[64]; |
561 | long timeout = 3 * HZ; | |
562 | ||
76bc35e7 PH |
563 | clear_bit(TTY_LDISC, &tty->flags); |
564 | ||
2276ad97 PH |
565 | if (tty->ldisc) { /* Not yet closed */ |
566 | tty_unlock(tty); | |
567 | ||
568 | while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) { | |
569 | timeout = MAX_SCHEDULE_TIMEOUT; | |
570 | printk_ratelimited(KERN_WARNING | |
571 | "%s: waiting (%s) for %s took too long, but we keep waiting...\n", | |
572 | __func__, get_task_comm(cur_n, current), | |
573 | tty_name(tty, tty_n)); | |
168942c9 | 574 | } |
76bc35e7 | 575 | |
76bc35e7 PH |
576 | set_bit(TTY_LDISC_HALTED, &tty->flags); |
577 | ||
2276ad97 PH |
578 | /* must reacquire both locks and preserve lock order */ |
579 | mutex_unlock(&tty->ldisc_mutex); | |
580 | tty_lock(tty); | |
581 | mutex_lock(&tty->ldisc_mutex); | |
168942c9 PH |
582 | } |
583 | return !!tty->ldisc; | |
584 | } | |
585 | ||
01e1abb2 AC |
586 | /** |
587 | * tty_set_ldisc - set line discipline | |
588 | * @tty: the terminal to set | |
589 | * @ldisc: the line discipline | |
590 | * | |
591 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
592 | * context. The ldisc change logic has to protect itself against any |
593 | * overlapping ldisc change (including on the other end of pty pairs), | |
594 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 595 | * |
137084bb | 596 | * Locking: takes tty_ldiscs_lock, termios_mutex |
01e1abb2 AC |
597 | */ |
598 | ||
599 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
600 | { | |
601 | int retval; | |
c65c9bc3 | 602 | struct tty_ldisc *o_ldisc, *new_ldisc; |
01e1abb2 AC |
603 | struct tty_struct *o_tty; |
604 | ||
c65c9bc3 AC |
605 | new_ldisc = tty_ldisc_get(ldisc); |
606 | if (IS_ERR(new_ldisc)) | |
607 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 608 | |
89c8d91e | 609 | tty_lock(tty); |
01e1abb2 | 610 | /* |
c65c9bc3 AC |
611 | * We need to look at the tty locking here for pty/tty pairs |
612 | * when both sides try to change in parallel. | |
01e1abb2 AC |
613 | */ |
614 | ||
c65c9bc3 AC |
615 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
616 | ||
01e1abb2 | 617 | |
c65c9bc3 AC |
618 | /* |
619 | * Check the no-op case | |
620 | */ | |
621 | ||
622 | if (tty->ldisc->ops->num == ldisc) { | |
89c8d91e | 623 | tty_unlock(tty); |
c65c9bc3 | 624 | tty_ldisc_put(new_ldisc); |
01e1abb2 AC |
625 | return 0; |
626 | } | |
627 | ||
c65c9bc3 AC |
628 | mutex_lock(&tty->ldisc_mutex); |
629 | ||
630 | /* | |
631 | * We could be midstream of another ldisc change which has | |
632 | * dropped the lock during processing. If so we need to wait. | |
633 | */ | |
634 | ||
635 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
636 | mutex_unlock(&tty->ldisc_mutex); | |
89c8d91e | 637 | tty_unlock(tty); |
c65c9bc3 AC |
638 | wait_event(tty_ldisc_wait, |
639 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
89c8d91e | 640 | tty_lock(tty); |
c65c9bc3 AC |
641 | mutex_lock(&tty->ldisc_mutex); |
642 | } | |
eeb89d91 | 643 | |
c65c9bc3 | 644 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
852e99d2 | 645 | |
01e1abb2 AC |
646 | /* |
647 | * No more input please, we are switching. The new ldisc | |
648 | * will update this value in the ldisc open function | |
649 | */ | |
650 | ||
651 | tty->receive_room = 0; | |
652 | ||
653 | o_ldisc = tty->ldisc; | |
eeb89d91 | 654 | |
89c8d91e | 655 | tty_unlock(tty); |
01e1abb2 AC |
656 | /* |
657 | * Make sure we don't change while someone holds a | |
658 | * reference to the line discipline. The TTY_LDISC bit | |
659 | * prevents anyone taking a reference once it is clear. | |
660 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
661 | * |
662 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
663 | * with a userspace app continually trying to use the tty in | |
664 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
665 | */ |
666 | ||
4f98d467 | 667 | retval = tty_ldisc_halt(tty, o_tty, 5 * HZ); |
01e1abb2 | 668 | |
01e1abb2 | 669 | /* |
a2965b7b | 670 | * Wait for hangup to complete, if pending. |
c65c9bc3 | 671 | * We must drop the mutex here in case a hangup is also in process. |
01e1abb2 | 672 | */ |
c65c9bc3 AC |
673 | |
674 | mutex_unlock(&tty->ldisc_mutex); | |
675 | ||
a2965b7b | 676 | flush_work(&tty->hangup_work); |
c65c9bc3 | 677 | |
89c8d91e | 678 | tty_lock(tty); |
60af22d2 | 679 | mutex_lock(&tty->ldisc_mutex); |
100eeae2 JS |
680 | |
681 | /* handle wait idle failure locked */ | |
682 | if (retval) { | |
683 | tty_ldisc_put(new_ldisc); | |
684 | goto enable; | |
685 | } | |
686 | ||
40c9f61e | 687 | if (test_bit(TTY_HUPPING, &tty->flags)) { |
c65c9bc3 AC |
688 | /* We were raced by the hangup method. It will have stomped |
689 | the ldisc data and closed the ldisc down */ | |
690 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
691 | mutex_unlock(&tty->ldisc_mutex); | |
692 | tty_ldisc_put(new_ldisc); | |
89c8d91e | 693 | tty_unlock(tty); |
c65c9bc3 AC |
694 | return -EIO; |
695 | } | |
696 | ||
01e1abb2 | 697 | /* Shutdown the current discipline. */ |
c65c9bc3 | 698 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
699 | |
700 | /* Now set up the new line discipline. */ | |
f4807045 | 701 | tty->ldisc = new_ldisc; |
01e1abb2 | 702 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
703 | |
704 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 705 | if (retval < 0) { |
c65c9bc3 AC |
706 | /* Back to the old one or N_TTY if we can't */ |
707 | tty_ldisc_put(new_ldisc); | |
708 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 709 | } |
c65c9bc3 | 710 | |
01e1abb2 AC |
711 | /* At this point we hold a reference to the new ldisc and a |
712 | a reference to the old ldisc. If we ended up flipping back | |
713 | to the existing ldisc we have two references to it */ | |
714 | ||
c65c9bc3 | 715 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
716 | tty->ops->set_ldisc(tty); |
717 | ||
c65c9bc3 | 718 | tty_ldisc_put(o_ldisc); |
01e1abb2 | 719 | |
100eeae2 | 720 | enable: |
01e1abb2 | 721 | /* |
c65c9bc3 | 722 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
723 | */ |
724 | ||
725 | tty_ldisc_enable(tty); | |
726 | if (o_tty) | |
727 | tty_ldisc_enable(o_tty); | |
728 | ||
c65c9bc3 | 729 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 730 | already running */ |
4f98d467 PH |
731 | schedule_work(&tty->port->buf.work); |
732 | if (o_tty) | |
ecbbfd44 | 733 | schedule_work(&o_tty->port->buf.work); |
4f98d467 | 734 | |
c65c9bc3 | 735 | mutex_unlock(&tty->ldisc_mutex); |
89c8d91e | 736 | tty_unlock(tty); |
01e1abb2 AC |
737 | return retval; |
738 | } | |
739 | ||
c65c9bc3 AC |
740 | /** |
741 | * tty_reset_termios - reset terminal state | |
742 | * @tty: tty to reset | |
743 | * | |
744 | * Restore a terminal to the driver default state. | |
745 | */ | |
746 | ||
747 | static void tty_reset_termios(struct tty_struct *tty) | |
748 | { | |
749 | mutex_lock(&tty->termios_mutex); | |
adc8d746 AC |
750 | tty->termios = tty->driver->init_termios; |
751 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
752 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
c65c9bc3 AC |
753 | mutex_unlock(&tty->termios_mutex); |
754 | } | |
755 | ||
756 | ||
757 | /** | |
758 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
759 | * @tty: tty to reinit | |
638b9648 | 760 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 761 | * |
638b9648 AC |
762 | * Switch the tty to a line discipline and leave the ldisc |
763 | * state closed | |
c65c9bc3 AC |
764 | */ |
765 | ||
1c95ba1e | 766 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 767 | { |
1c95ba1e PR |
768 | struct tty_ldisc *ld = tty_ldisc_get(ldisc); |
769 | ||
770 | if (IS_ERR(ld)) | |
771 | return -1; | |
c65c9bc3 AC |
772 | |
773 | tty_ldisc_close(tty, tty->ldisc); | |
774 | tty_ldisc_put(tty->ldisc); | |
c65c9bc3 AC |
775 | /* |
776 | * Switch the line discipline back | |
777 | */ | |
f4807045 | 778 | tty->ldisc = ld; |
638b9648 | 779 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
780 | |
781 | return 0; | |
c65c9bc3 AC |
782 | } |
783 | ||
784 | /** | |
785 | * tty_ldisc_hangup - hangup ldisc reset | |
786 | * @tty: tty being hung up | |
787 | * | |
788 | * Some tty devices reset their termios when they receive a hangup | |
789 | * event. In that situation we must also switch back to N_TTY properly | |
790 | * before we reset the termios data. | |
791 | * | |
792 | * Locking: We can take the ldisc mutex as the rest of the code is | |
793 | * careful to allow for this. | |
794 | * | |
795 | * In the pty pair case this occurs in the close() path of the | |
796 | * tty itself so we must be careful about locking rules. | |
797 | */ | |
798 | ||
799 | void tty_ldisc_hangup(struct tty_struct *tty) | |
800 | { | |
801 | struct tty_ldisc *ld; | |
638b9648 AC |
802 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
803 | int err = 0; | |
c65c9bc3 | 804 | |
fc575ee6 PH |
805 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
806 | ||
c65c9bc3 AC |
807 | /* |
808 | * FIXME! What are the locking issues here? This may me overdoing | |
809 | * things... This question is especially important now that we've | |
810 | * removed the irqlock. | |
811 | */ | |
812 | ld = tty_ldisc_ref(tty); | |
813 | if (ld != NULL) { | |
814 | /* We may have no line discipline at this point */ | |
815 | if (ld->ops->flush_buffer) | |
816 | ld->ops->flush_buffer(tty); | |
817 | tty_driver_flush_buffer(tty); | |
818 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
819 | ld->ops->write_wakeup) | |
820 | ld->ops->write_wakeup(tty); | |
821 | if (ld->ops->hangup) | |
822 | ld->ops->hangup(tty); | |
823 | tty_ldisc_deref(ld); | |
824 | } | |
825 | /* | |
826 | * FIXME: Once we trust the LDISC code better we can wait here for | |
827 | * ldisc completion and fix the driver call race | |
828 | */ | |
829 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
830 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
831 | /* | |
832 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
833 | * N_TTY if need be. |
834 | * | |
835 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 836 | */ |
638b9648 | 837 | mutex_lock(&tty->ldisc_mutex); |
60af22d2 | 838 | |
76bc35e7 | 839 | if (tty_ldisc_hangup_halt(tty)) { |
c8785241 PH |
840 | |
841 | /* At this point we have a halted ldisc; we want to close it and | |
842 | reopen a new ldisc. We could defer the reopen to the next | |
843 | open but it means auditing a lot of other paths so this is | |
844 | a FIXME */ | |
638b9648 | 845 | if (reset == 0) { |
1c95ba1e | 846 | |
adc8d746 | 847 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
848 | err = tty_ldisc_open(tty, tty->ldisc); |
849 | else | |
850 | err = 1; | |
638b9648 AC |
851 | } |
852 | /* If the re-open fails or we reset then go to N_TTY. The | |
853 | N_TTY open cannot fail */ | |
854 | if (reset || err) { | |
1c95ba1e | 855 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 856 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 857 | } |
638b9648 | 858 | tty_ldisc_enable(tty); |
c65c9bc3 | 859 | } |
638b9648 AC |
860 | mutex_unlock(&tty->ldisc_mutex); |
861 | if (reset) | |
862 | tty_reset_termios(tty); | |
fc575ee6 PH |
863 | |
864 | tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); | |
c65c9bc3 | 865 | } |
01e1abb2 AC |
866 | |
867 | /** | |
868 | * tty_ldisc_setup - open line discipline | |
869 | * @tty: tty being shut down | |
870 | * @o_tty: pair tty for pty/tty pairs | |
871 | * | |
872 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
873 | * line disciplines and bind them to the tty. This has no locking issues |
874 | * as the device isn't yet active. | |
01e1abb2 AC |
875 | */ |
876 | ||
877 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
878 | { | |
c65c9bc3 | 879 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
880 | int retval; |
881 | ||
c65c9bc3 AC |
882 | retval = tty_ldisc_open(tty, ld); |
883 | if (retval) | |
884 | return retval; | |
885 | ||
886 | if (o_tty) { | |
887 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 888 | if (retval) { |
c65c9bc3 | 889 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
890 | return retval; |
891 | } | |
892 | tty_ldisc_enable(o_tty); | |
893 | } | |
894 | tty_ldisc_enable(tty); | |
895 | return 0; | |
896 | } | |
89c8d91e AC |
897 | |
898 | static void tty_ldisc_kill(struct tty_struct *tty) | |
899 | { | |
900 | mutex_lock(&tty->ldisc_mutex); | |
901 | /* | |
902 | * Now kill off the ldisc | |
903 | */ | |
904 | tty_ldisc_close(tty, tty->ldisc); | |
905 | tty_ldisc_put(tty->ldisc); | |
906 | /* Force an oops if we mess this up */ | |
907 | tty->ldisc = NULL; | |
908 | ||
909 | /* Ensure the next open requests the N_TTY ldisc */ | |
910 | tty_set_termios_ldisc(tty, N_TTY); | |
911 | mutex_unlock(&tty->ldisc_mutex); | |
912 | } | |
913 | ||
01e1abb2 AC |
914 | /** |
915 | * tty_ldisc_release - release line discipline | |
916 | * @tty: tty being shut down | |
917 | * @o_tty: pair tty for pty/tty pairs | |
918 | * | |
852e99d2 AC |
919 | * Called during the final close of a tty/pty pair in order to shut down |
920 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 921 | * ldisc has not been opened. |
01e1abb2 AC |
922 | */ |
923 | ||
924 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
925 | { | |
01e1abb2 | 926 | /* |
a2965b7b PH |
927 | * Shutdown this line discipline. As this is the final close, |
928 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 929 | */ |
01e1abb2 | 930 | |
fc575ee6 PH |
931 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
932 | ||
4f98d467 | 933 | tty_ldisc_halt(tty, o_tty, MAX_SCHEDULE_TIMEOUT); |
d155255a | 934 | |
852e4a81 | 935 | tty_lock_pair(tty, o_tty); |
6d31a88c | 936 | /* This will need doing differently if we need to lock */ |
89c8d91e | 937 | tty_ldisc_kill(tty); |
c65c9bc3 | 938 | if (o_tty) |
89c8d91e | 939 | tty_ldisc_kill(o_tty); |
aef29bc2 | 940 | |
89c8d91e | 941 | tty_unlock_pair(tty, o_tty); |
aef29bc2 AC |
942 | /* And the memory resources remaining (buffers, termios) will be |
943 | disposed of when the kref hits zero */ | |
fc575ee6 PH |
944 | |
945 | tty_ldisc_debug(tty, "ldisc closed\n"); | |
01e1abb2 AC |
946 | } |
947 | ||
948 | /** | |
949 | * tty_ldisc_init - ldisc setup for new tty | |
950 | * @tty: tty being allocated | |
951 | * | |
952 | * Set up the line discipline objects for a newly allocated tty. Note that | |
953 | * the tty structure is not completely set up when this call is made. | |
954 | */ | |
955 | ||
956 | void tty_ldisc_init(struct tty_struct *tty) | |
957 | { | |
c65c9bc3 AC |
958 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
959 | if (IS_ERR(ld)) | |
01e1abb2 | 960 | panic("n_tty: init_tty"); |
f4807045 | 961 | tty->ldisc = ld; |
01e1abb2 AC |
962 | } |
963 | ||
6716671d JS |
964 | /** |
965 | * tty_ldisc_init - ldisc cleanup for new tty | |
966 | * @tty: tty that was allocated recently | |
967 | * | |
968 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
969 | * this call is made. | |
970 | */ | |
971 | void tty_ldisc_deinit(struct tty_struct *tty) | |
972 | { | |
ebc9baed | 973 | tty_ldisc_put(tty->ldisc); |
f4807045 | 974 | tty->ldisc = NULL; |
6716671d JS |
975 | } |
976 | ||
01e1abb2 AC |
977 | void tty_ldisc_begin(void) |
978 | { | |
979 | /* Setup the default TTY line discipline. */ | |
980 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
981 | } |