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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 | ||
c9739941 | 40 | static DEFINE_RAW_SPINLOCK(tty_ldisc_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: | |
55 | * takes tty_ldisc_lock to guard against ldisc races | |
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 | ||
c9739941 | 66 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); |
01e1abb2 AC |
67 | tty_ldiscs[disc] = new_ldisc; |
68 | new_ldisc->num = disc; | |
69 | new_ldisc->refcount = 0; | |
c9739941 | 70 | raw_spin_unlock_irqrestore(&tty_ldisc_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: | |
85 | * takes tty_ldisc_lock to guard against ldisc races | |
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 | ||
c9739941 | 96 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); |
01e1abb2 AC |
97 | if (tty_ldiscs[disc]->refcount) |
98 | ret = -EBUSY; | |
99 | else | |
100 | tty_ldiscs[disc] = NULL; | |
c9739941 | 101 | raw_spin_unlock_irqrestore(&tty_ldisc_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 | ||
c9739941 | 112 | raw_spin_lock_irqsave(&tty_ldisc_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 | } | |
c9739941 | 122 | raw_spin_unlock_irqrestore(&tty_ldisc_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 | ||
c9739941 | 130 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); |
f0de0e8d LT |
131 | ldops->refcount--; |
132 | module_put(ldops->owner); | |
c9739941 | 133 | raw_spin_unlock_irqrestore(&tty_ldisc_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: | |
146 | * takes tty_ldisc_lock to guard against ldisc races | |
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 | ||
852e99d2 | 182 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
183 | { |
184 | return (*pos < NR_LDISCS) ? pos : NULL; | |
185 | } | |
186 | ||
852e99d2 | 187 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
188 | { |
189 | (*pos)++; | |
190 | return (*pos < NR_LDISCS) ? pos : NULL; | |
191 | } | |
192 | ||
193 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
194 | { | |
195 | } | |
196 | ||
197 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
198 | { | |
199 | int i = *(loff_t *)v; | |
f0de0e8d | 200 | struct tty_ldisc_ops *ldops; |
852e99d2 | 201 | |
f0de0e8d LT |
202 | ldops = get_ldops(i); |
203 | if (IS_ERR(ldops)) | |
01e1abb2 | 204 | return 0; |
f0de0e8d LT |
205 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
206 | put_ldops(ldops); | |
01e1abb2 AC |
207 | return 0; |
208 | } | |
209 | ||
210 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
211 | .start = tty_ldiscs_seq_start, | |
212 | .next = tty_ldiscs_seq_next, | |
213 | .stop = tty_ldiscs_seq_stop, | |
214 | .show = tty_ldiscs_seq_show, | |
215 | }; | |
216 | ||
217 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
218 | { | |
219 | return seq_open(file, &tty_ldiscs_seq_ops); | |
220 | } | |
221 | ||
222 | const struct file_operations tty_ldiscs_proc_fops = { | |
223 | .owner = THIS_MODULE, | |
224 | .open = proc_tty_ldiscs_open, | |
225 | .read = seq_read, | |
226 | .llseek = seq_lseek, | |
227 | .release = seq_release, | |
228 | }; | |
229 | ||
230 | /** | |
231 | * tty_ldisc_assign - set ldisc on a tty | |
232 | * @tty: tty to assign | |
233 | * @ld: line discipline | |
234 | * | |
235 | * Install an instance of a line discipline into a tty structure. The | |
8d2ead74 | 236 | * ldisc must have a reference count above zero to ensure it remains. |
01e1abb2 AC |
237 | * The tty instance refcount starts at zero. |
238 | * | |
239 | * Locking: | |
240 | * Caller must hold references | |
241 | */ | |
242 | ||
243 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
244 | { | |
c65c9bc3 | 245 | tty->ldisc = ld; |
01e1abb2 AC |
246 | } |
247 | ||
248 | /** | |
249 | * tty_ldisc_try - internal helper | |
250 | * @tty: the tty | |
251 | * | |
252 | * Make a single attempt to grab and bump the refcount on | |
253 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
254 | * used to implement both the waiting and non waiting versions | |
255 | * of tty_ldisc_ref | |
256 | * | |
257 | * Locking: takes tty_ldisc_lock | |
258 | */ | |
259 | ||
65b77046 | 260 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
01e1abb2 AC |
261 | { |
262 | unsigned long flags; | |
263 | struct tty_ldisc *ld; | |
01e1abb2 | 264 | |
16759f6c | 265 | /* FIXME: this allows reference acquire after TTY_LDISC is cleared */ |
c9739941 | 266 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); |
65b77046 | 267 | ld = NULL; |
16759f6c PH |
268 | if (test_bit(TTY_LDISC, &tty->flags) && tty->ldisc) { |
269 | ld = tty->ldisc; | |
270 | atomic_inc(&ld->users); | |
271 | } | |
c9739941 | 272 | raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
65b77046 | 273 | return ld; |
01e1abb2 AC |
274 | } |
275 | ||
276 | /** | |
277 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
278 | * @tty: tty device | |
279 | * | |
280 | * Dereference the line discipline for the terminal and take a | |
281 | * reference to it. If the line discipline is in flux then | |
282 | * wait patiently until it changes. | |
283 | * | |
284 | * Note: Must not be called from an IRQ/timer context. The caller | |
285 | * must also be careful not to hold other locks that will deadlock | |
286 | * against a discipline change, such as an existing ldisc reference | |
287 | * (which we check for) | |
288 | * | |
289 | * Locking: call functions take tty_ldisc_lock | |
290 | */ | |
291 | ||
292 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
293 | { | |
65b77046 LT |
294 | struct tty_ldisc *ld; |
295 | ||
01e1abb2 | 296 | /* wait_event is a macro */ |
65b77046 LT |
297 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
298 | return ld; | |
01e1abb2 | 299 | } |
01e1abb2 AC |
300 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
301 | ||
302 | /** | |
303 | * tty_ldisc_ref - get the tty ldisc | |
304 | * @tty: tty device | |
305 | * | |
306 | * Dereference the line discipline for the terminal and take a | |
307 | * reference to it. If the line discipline is in flux then | |
308 | * return NULL. Can be called from IRQ and timer functions. | |
309 | * | |
310 | * Locking: called functions take tty_ldisc_lock | |
311 | */ | |
312 | ||
313 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
314 | { | |
65b77046 | 315 | return tty_ldisc_try(tty); |
01e1abb2 | 316 | } |
01e1abb2 AC |
317 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
318 | ||
319 | /** | |
320 | * tty_ldisc_deref - free a tty ldisc reference | |
321 | * @ld: reference to free up | |
322 | * | |
323 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
324 | * be called in IRQ context. | |
325 | * | |
326 | * Locking: takes tty_ldisc_lock | |
327 | */ | |
328 | ||
329 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
330 | { | |
ebc9baed PH |
331 | unsigned long flags; |
332 | ||
333 | if (WARN_ON_ONCE(!ld)) | |
334 | return; | |
335 | ||
336 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); | |
337 | /* | |
338 | * WARNs if one-too-many reader references were released | |
339 | * - the last reference must be released with tty_ldisc_put | |
340 | */ | |
341 | WARN_ON(atomic_dec_and_test(&ld->users)); | |
342 | raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
343 | ||
344 | if (waitqueue_active(&ld->wq_idle)) | |
345 | wake_up(&ld->wq_idle); | |
01e1abb2 | 346 | } |
01e1abb2 AC |
347 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
348 | ||
ebc9baed PH |
349 | /** |
350 | * tty_ldisc_put - release the ldisc | |
351 | * | |
352 | * Complement of tty_ldisc_get(). | |
353 | */ | |
65b77046 LT |
354 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
355 | { | |
ebc9baed PH |
356 | unsigned long flags; |
357 | ||
358 | if (WARN_ON_ONCE(!ld)) | |
359 | return; | |
360 | ||
361 | raw_spin_lock_irqsave(&tty_ldisc_lock, flags); | |
362 | ||
363 | /* unreleased reader reference(s) will cause this WARN */ | |
364 | WARN_ON(!atomic_dec_and_test(&ld->users)); | |
365 | ||
366 | ld->ops->refcount--; | |
367 | module_put(ld->ops->owner); | |
368 | kfree(ld); | |
369 | raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
65b77046 LT |
370 | } |
371 | ||
01e1abb2 AC |
372 | /** |
373 | * tty_ldisc_enable - allow ldisc use | |
374 | * @tty: terminal to activate ldisc on | |
375 | * | |
376 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
377 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
378 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 379 | * |
c9b3976e AC |
380 | * Note: nobody should set the TTY_LDISC bit except via this function. |
381 | * Clearing directly is allowed. | |
01e1abb2 AC |
382 | */ |
383 | ||
d9121566 | 384 | static void tty_ldisc_enable(struct tty_struct *tty) |
01e1abb2 | 385 | { |
21622939 | 386 | clear_bit(TTY_LDISC_HALTED, &tty->flags); |
01e1abb2 | 387 | set_bit(TTY_LDISC, &tty->flags); |
c9b3976e | 388 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
389 | wake_up(&tty_ldisc_wait); |
390 | } | |
391 | ||
f2c4c65c AC |
392 | /** |
393 | * tty_ldisc_flush - flush line discipline queue | |
394 | * @tty: tty | |
395 | * | |
396 | * Flush the line discipline queue (if any) for this tty. If there | |
397 | * is no line discipline active this is a no-op. | |
398 | */ | |
399 | ||
400 | void tty_ldisc_flush(struct tty_struct *tty) | |
401 | { | |
402 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
403 | if (ld) { | |
404 | if (ld->ops->flush_buffer) | |
405 | ld->ops->flush_buffer(tty); | |
406 | tty_ldisc_deref(ld); | |
407 | } | |
408 | tty_buffer_flush(tty); | |
409 | } | |
f2c4c65c AC |
410 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
411 | ||
01e1abb2 AC |
412 | /** |
413 | * tty_set_termios_ldisc - set ldisc field | |
414 | * @tty: tty structure | |
415 | * @num: line discipline number | |
416 | * | |
417 | * This is probably overkill for real world processors but | |
418 | * they are not on hot paths so a little discipline won't do | |
419 | * any harm. | |
420 | * | |
421 | * Locking: takes termios_mutex | |
422 | */ | |
423 | ||
424 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
425 | { | |
426 | mutex_lock(&tty->termios_mutex); | |
adc8d746 | 427 | tty->termios.c_line = num; |
01e1abb2 AC |
428 | mutex_unlock(&tty->termios_mutex); |
429 | } | |
430 | ||
c65c9bc3 AC |
431 | /** |
432 | * tty_ldisc_open - open a line discipline | |
433 | * @tty: tty we are opening the ldisc on | |
434 | * @ld: discipline to open | |
435 | * | |
436 | * A helper opening method. Also a convenient debugging and check | |
437 | * point. | |
ec79d605 AB |
438 | * |
439 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
440 | */ |
441 | ||
442 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
443 | { | |
444 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
445 | if (ld->ops->open) { |
446 | int ret; | |
ec79d605 | 447 | /* BTM here locks versus a hangup event */ |
f18f9498 | 448 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
449 | if (ret) |
450 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
f18f9498 AC |
451 | return ret; |
452 | } | |
c65c9bc3 AC |
453 | return 0; |
454 | } | |
455 | ||
456 | /** | |
457 | * tty_ldisc_close - close a line discipline | |
458 | * @tty: tty we are opening the ldisc on | |
459 | * @ld: discipline to close | |
460 | * | |
461 | * A helper close method. Also a convenient debugging and check | |
462 | * point. | |
463 | */ | |
464 | ||
465 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
466 | { | |
467 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
468 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
469 | if (ld->ops->close) | |
470 | ld->ops->close(tty); | |
471 | } | |
01e1abb2 AC |
472 | |
473 | /** | |
474 | * tty_ldisc_restore - helper for tty ldisc change | |
475 | * @tty: tty to recover | |
476 | * @old: previous ldisc | |
477 | * | |
478 | * Restore the previous line discipline or N_TTY when a line discipline | |
479 | * change fails due to an open error | |
480 | */ | |
481 | ||
482 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
483 | { | |
484 | char buf[64]; | |
c65c9bc3 AC |
485 | struct tty_ldisc *new_ldisc; |
486 | int r; | |
01e1abb2 AC |
487 | |
488 | /* There is an outstanding reference here so this is safe */ | |
c65c9bc3 AC |
489 | old = tty_ldisc_get(old->ops->num); |
490 | WARN_ON(IS_ERR(old)); | |
01e1abb2 AC |
491 | tty_ldisc_assign(tty, old); |
492 | tty_set_termios_ldisc(tty, old->ops->num); | |
c65c9bc3 AC |
493 | if (tty_ldisc_open(tty, old) < 0) { |
494 | tty_ldisc_put(old); | |
01e1abb2 | 495 | /* This driver is always present */ |
852e99d2 | 496 | new_ldisc = tty_ldisc_get(N_TTY); |
c65c9bc3 | 497 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 498 | panic("n_tty: get"); |
c65c9bc3 | 499 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 500 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
501 | r = tty_ldisc_open(tty, new_ldisc); |
502 | if (r < 0) | |
503 | panic("Couldn't open N_TTY ldisc for " | |
504 | "%s --- error %d.", | |
505 | tty_name(tty, buf), r); | |
01e1abb2 AC |
506 | } |
507 | } | |
508 | ||
100eeae2 JS |
509 | /** |
510 | * tty_ldisc_wait_idle - wait for the ldisc to become idle | |
511 | * @tty: tty to wait for | |
df92d056 | 512 | * @timeout: for how long to wait at most |
100eeae2 JS |
513 | * |
514 | * Wait for the line discipline to become idle. The discipline must | |
515 | * have been halted for this to guarantee it remains idle. | |
516 | */ | |
df92d056 | 517 | static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) |
100eeae2 | 518 | { |
df92d056 | 519 | long ret; |
1541f845 | 520 | ret = wait_event_timeout(tty->ldisc->wq_idle, |
df92d056 | 521 | atomic_read(&tty->ldisc->users) == 1, timeout); |
100eeae2 JS |
522 | return ret > 0 ? 0 : -EBUSY; |
523 | } | |
524 | ||
11cf48ea PH |
525 | /** |
526 | * tty_ldisc_halt - shut down the line discipline | |
527 | * @tty: tty device | |
f4cf7a38 | 528 | * @o_tty: paired pty device (can be NULL) |
cf528476 | 529 | * @timeout: # of jiffies to wait for ldisc refs to be released |
11cf48ea | 530 | * |
f4cf7a38 PH |
531 | * Shut down the line discipline and work queue for this tty device and |
532 | * its paired pty (if exists). Clearing the TTY_LDISC flag ensures | |
4f98d467 PH |
533 | * no further references can be obtained, while waiting for existing |
534 | * references to be released ensures no more data is fed to the ldisc. | |
cf528476 | 535 | * |
11cf48ea PH |
536 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
537 | * in order to make sure any currently executing ldisc work is also | |
538 | * flushed. | |
539 | */ | |
540 | ||
f4cf7a38 | 541 | static int tty_ldisc_halt(struct tty_struct *tty, struct tty_struct *o_tty, |
4f98d467 | 542 | long timeout) |
11cf48ea | 543 | { |
4f98d467 | 544 | int retval; |
cf528476 | 545 | |
11cf48ea | 546 | clear_bit(TTY_LDISC, &tty->flags); |
f4cf7a38 PH |
547 | if (o_tty) |
548 | clear_bit(TTY_LDISC, &o_tty->flags); | |
549 | ||
cf528476 | 550 | retval = tty_ldisc_wait_idle(tty, timeout); |
f4cf7a38 PH |
551 | if (!retval && o_tty) |
552 | retval = tty_ldisc_wait_idle(o_tty, timeout); | |
cf528476 PH |
553 | if (retval) |
554 | return retval; | |
555 | ||
11cf48ea | 556 | set_bit(TTY_LDISC_HALTED, &tty->flags); |
4f98d467 | 557 | if (o_tty) |
f4cf7a38 | 558 | set_bit(TTY_LDISC_HALTED, &o_tty->flags); |
f4cf7a38 | 559 | |
cf528476 | 560 | return 0; |
11cf48ea PH |
561 | } |
562 | ||
168942c9 | 563 | /** |
76bc35e7 PH |
564 | * tty_ldisc_hangup_halt - halt the line discipline for hangup |
565 | * @tty: tty being hung up | |
168942c9 | 566 | * |
76bc35e7 PH |
567 | * Shut down the line discipline and work queue for the tty device |
568 | * being hungup. Clear the TTY_LDISC flag to ensure no further | |
4f98d467 PH |
569 | * references can be obtained and wait for remaining references to be |
570 | * released to ensure no more data is fed to this ldisc. | |
168942c9 | 571 | * Caller must hold legacy and ->ldisc_mutex. |
2276ad97 PH |
572 | * |
573 | * NB: tty_set_ldisc() is prevented from changing the ldisc concurrently | |
574 | * with this function by checking the TTY_HUPPING flag. | |
168942c9 | 575 | */ |
76bc35e7 | 576 | static bool tty_ldisc_hangup_halt(struct tty_struct *tty) |
168942c9 | 577 | { |
2276ad97 PH |
578 | char cur_n[TASK_COMM_LEN], tty_n[64]; |
579 | long timeout = 3 * HZ; | |
580 | ||
76bc35e7 PH |
581 | clear_bit(TTY_LDISC, &tty->flags); |
582 | ||
2276ad97 PH |
583 | if (tty->ldisc) { /* Not yet closed */ |
584 | tty_unlock(tty); | |
585 | ||
586 | while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) { | |
587 | timeout = MAX_SCHEDULE_TIMEOUT; | |
588 | printk_ratelimited(KERN_WARNING | |
589 | "%s: waiting (%s) for %s took too long, but we keep waiting...\n", | |
590 | __func__, get_task_comm(cur_n, current), | |
591 | tty_name(tty, tty_n)); | |
168942c9 | 592 | } |
76bc35e7 | 593 | |
76bc35e7 PH |
594 | set_bit(TTY_LDISC_HALTED, &tty->flags); |
595 | ||
2276ad97 PH |
596 | /* must reacquire both locks and preserve lock order */ |
597 | mutex_unlock(&tty->ldisc_mutex); | |
598 | tty_lock(tty); | |
599 | mutex_lock(&tty->ldisc_mutex); | |
168942c9 PH |
600 | } |
601 | return !!tty->ldisc; | |
602 | } | |
603 | ||
01e1abb2 AC |
604 | /** |
605 | * tty_set_ldisc - set line discipline | |
606 | * @tty: the terminal to set | |
607 | * @ldisc: the line discipline | |
608 | * | |
609 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
610 | * context. The ldisc change logic has to protect itself against any |
611 | * overlapping ldisc change (including on the other end of pty pairs), | |
612 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 613 | * |
c65c9bc3 | 614 | * Locking: takes tty_ldisc_lock, termios_mutex |
01e1abb2 AC |
615 | */ |
616 | ||
617 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
618 | { | |
619 | int retval; | |
c65c9bc3 | 620 | struct tty_ldisc *o_ldisc, *new_ldisc; |
01e1abb2 AC |
621 | struct tty_struct *o_tty; |
622 | ||
c65c9bc3 AC |
623 | new_ldisc = tty_ldisc_get(ldisc); |
624 | if (IS_ERR(new_ldisc)) | |
625 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 626 | |
89c8d91e | 627 | tty_lock(tty); |
01e1abb2 | 628 | /* |
c65c9bc3 AC |
629 | * We need to look at the tty locking here for pty/tty pairs |
630 | * when both sides try to change in parallel. | |
01e1abb2 AC |
631 | */ |
632 | ||
c65c9bc3 AC |
633 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
634 | ||
01e1abb2 | 635 | |
c65c9bc3 AC |
636 | /* |
637 | * Check the no-op case | |
638 | */ | |
639 | ||
640 | if (tty->ldisc->ops->num == ldisc) { | |
89c8d91e | 641 | tty_unlock(tty); |
c65c9bc3 | 642 | tty_ldisc_put(new_ldisc); |
01e1abb2 AC |
643 | return 0; |
644 | } | |
645 | ||
89c8d91e | 646 | tty_unlock(tty); |
c65c9bc3 AC |
647 | /* |
648 | * Problem: What do we do if this blocks ? | |
649 | * We could deadlock here | |
650 | */ | |
651 | ||
652 | tty_wait_until_sent(tty, 0); | |
653 | ||
89c8d91e | 654 | tty_lock(tty); |
c65c9bc3 AC |
655 | mutex_lock(&tty->ldisc_mutex); |
656 | ||
657 | /* | |
658 | * We could be midstream of another ldisc change which has | |
659 | * dropped the lock during processing. If so we need to wait. | |
660 | */ | |
661 | ||
662 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
663 | mutex_unlock(&tty->ldisc_mutex); | |
89c8d91e | 664 | tty_unlock(tty); |
c65c9bc3 AC |
665 | wait_event(tty_ldisc_wait, |
666 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
89c8d91e | 667 | tty_lock(tty); |
c65c9bc3 AC |
668 | mutex_lock(&tty->ldisc_mutex); |
669 | } | |
eeb89d91 | 670 | |
c65c9bc3 | 671 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
852e99d2 | 672 | |
01e1abb2 AC |
673 | /* |
674 | * No more input please, we are switching. The new ldisc | |
675 | * will update this value in the ldisc open function | |
676 | */ | |
677 | ||
678 | tty->receive_room = 0; | |
679 | ||
680 | o_ldisc = tty->ldisc; | |
eeb89d91 | 681 | |
89c8d91e | 682 | tty_unlock(tty); |
01e1abb2 AC |
683 | /* |
684 | * Make sure we don't change while someone holds a | |
685 | * reference to the line discipline. The TTY_LDISC bit | |
686 | * prevents anyone taking a reference once it is clear. | |
687 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
688 | * |
689 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
690 | * with a userspace app continually trying to use the tty in | |
691 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
692 | */ |
693 | ||
4f98d467 | 694 | retval = tty_ldisc_halt(tty, o_tty, 5 * HZ); |
01e1abb2 | 695 | |
01e1abb2 | 696 | /* |
a2965b7b | 697 | * Wait for hangup to complete, if pending. |
c65c9bc3 | 698 | * We must drop the mutex here in case a hangup is also in process. |
01e1abb2 | 699 | */ |
c65c9bc3 AC |
700 | |
701 | mutex_unlock(&tty->ldisc_mutex); | |
702 | ||
a2965b7b | 703 | flush_work(&tty->hangup_work); |
c65c9bc3 | 704 | |
89c8d91e | 705 | tty_lock(tty); |
60af22d2 | 706 | mutex_lock(&tty->ldisc_mutex); |
100eeae2 JS |
707 | |
708 | /* handle wait idle failure locked */ | |
709 | if (retval) { | |
710 | tty_ldisc_put(new_ldisc); | |
711 | goto enable; | |
712 | } | |
713 | ||
40c9f61e | 714 | if (test_bit(TTY_HUPPING, &tty->flags)) { |
c65c9bc3 AC |
715 | /* We were raced by the hangup method. It will have stomped |
716 | the ldisc data and closed the ldisc down */ | |
717 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
718 | mutex_unlock(&tty->ldisc_mutex); | |
719 | tty_ldisc_put(new_ldisc); | |
89c8d91e | 720 | tty_unlock(tty); |
c65c9bc3 AC |
721 | return -EIO; |
722 | } | |
723 | ||
01e1abb2 | 724 | /* Shutdown the current discipline. */ |
c65c9bc3 | 725 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
726 | |
727 | /* Now set up the new line discipline. */ | |
c65c9bc3 | 728 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 729 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
730 | |
731 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 732 | if (retval < 0) { |
c65c9bc3 AC |
733 | /* Back to the old one or N_TTY if we can't */ |
734 | tty_ldisc_put(new_ldisc); | |
735 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 736 | } |
c65c9bc3 | 737 | |
01e1abb2 AC |
738 | /* At this point we hold a reference to the new ldisc and a |
739 | a reference to the old ldisc. If we ended up flipping back | |
740 | to the existing ldisc we have two references to it */ | |
741 | ||
c65c9bc3 | 742 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
743 | tty->ops->set_ldisc(tty); |
744 | ||
c65c9bc3 | 745 | tty_ldisc_put(o_ldisc); |
01e1abb2 | 746 | |
100eeae2 | 747 | enable: |
01e1abb2 | 748 | /* |
c65c9bc3 | 749 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
750 | */ |
751 | ||
752 | tty_ldisc_enable(tty); | |
753 | if (o_tty) | |
754 | tty_ldisc_enable(o_tty); | |
755 | ||
c65c9bc3 | 756 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 | 757 | already running */ |
4f98d467 PH |
758 | schedule_work(&tty->port->buf.work); |
759 | if (o_tty) | |
ecbbfd44 | 760 | schedule_work(&o_tty->port->buf.work); |
4f98d467 | 761 | |
c65c9bc3 | 762 | mutex_unlock(&tty->ldisc_mutex); |
89c8d91e | 763 | tty_unlock(tty); |
01e1abb2 AC |
764 | return retval; |
765 | } | |
766 | ||
c65c9bc3 AC |
767 | /** |
768 | * tty_reset_termios - reset terminal state | |
769 | * @tty: tty to reset | |
770 | * | |
771 | * Restore a terminal to the driver default state. | |
772 | */ | |
773 | ||
774 | static void tty_reset_termios(struct tty_struct *tty) | |
775 | { | |
776 | mutex_lock(&tty->termios_mutex); | |
adc8d746 AC |
777 | tty->termios = tty->driver->init_termios; |
778 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
779 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
c65c9bc3 AC |
780 | mutex_unlock(&tty->termios_mutex); |
781 | } | |
782 | ||
783 | ||
784 | /** | |
785 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
786 | * @tty: tty to reinit | |
638b9648 | 787 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 788 | * |
638b9648 AC |
789 | * Switch the tty to a line discipline and leave the ldisc |
790 | * state closed | |
c65c9bc3 AC |
791 | */ |
792 | ||
1c95ba1e | 793 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 794 | { |
1c95ba1e PR |
795 | struct tty_ldisc *ld = tty_ldisc_get(ldisc); |
796 | ||
797 | if (IS_ERR(ld)) | |
798 | return -1; | |
c65c9bc3 AC |
799 | |
800 | tty_ldisc_close(tty, tty->ldisc); | |
801 | tty_ldisc_put(tty->ldisc); | |
802 | tty->ldisc = NULL; | |
803 | /* | |
804 | * Switch the line discipline back | |
805 | */ | |
c65c9bc3 | 806 | tty_ldisc_assign(tty, ld); |
638b9648 | 807 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
808 | |
809 | return 0; | |
c65c9bc3 AC |
810 | } |
811 | ||
812 | /** | |
813 | * tty_ldisc_hangup - hangup ldisc reset | |
814 | * @tty: tty being hung up | |
815 | * | |
816 | * Some tty devices reset their termios when they receive a hangup | |
817 | * event. In that situation we must also switch back to N_TTY properly | |
818 | * before we reset the termios data. | |
819 | * | |
820 | * Locking: We can take the ldisc mutex as the rest of the code is | |
821 | * careful to allow for this. | |
822 | * | |
823 | * In the pty pair case this occurs in the close() path of the | |
824 | * tty itself so we must be careful about locking rules. | |
825 | */ | |
826 | ||
827 | void tty_ldisc_hangup(struct tty_struct *tty) | |
828 | { | |
829 | struct tty_ldisc *ld; | |
638b9648 AC |
830 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
831 | int err = 0; | |
c65c9bc3 | 832 | |
fc575ee6 PH |
833 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
834 | ||
c65c9bc3 AC |
835 | /* |
836 | * FIXME! What are the locking issues here? This may me overdoing | |
837 | * things... This question is especially important now that we've | |
838 | * removed the irqlock. | |
839 | */ | |
840 | ld = tty_ldisc_ref(tty); | |
841 | if (ld != NULL) { | |
842 | /* We may have no line discipline at this point */ | |
843 | if (ld->ops->flush_buffer) | |
844 | ld->ops->flush_buffer(tty); | |
845 | tty_driver_flush_buffer(tty); | |
846 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
847 | ld->ops->write_wakeup) | |
848 | ld->ops->write_wakeup(tty); | |
849 | if (ld->ops->hangup) | |
850 | ld->ops->hangup(tty); | |
851 | tty_ldisc_deref(ld); | |
852 | } | |
853 | /* | |
854 | * FIXME: Once we trust the LDISC code better we can wait here for | |
855 | * ldisc completion and fix the driver call race | |
856 | */ | |
857 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
858 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
859 | /* | |
860 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
861 | * N_TTY if need be. |
862 | * | |
863 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 864 | */ |
638b9648 | 865 | mutex_lock(&tty->ldisc_mutex); |
60af22d2 | 866 | |
76bc35e7 | 867 | if (tty_ldisc_hangup_halt(tty)) { |
c8785241 PH |
868 | |
869 | /* At this point we have a halted ldisc; we want to close it and | |
870 | reopen a new ldisc. We could defer the reopen to the next | |
871 | open but it means auditing a lot of other paths so this is | |
872 | a FIXME */ | |
638b9648 | 873 | if (reset == 0) { |
1c95ba1e | 874 | |
adc8d746 | 875 | if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
1c95ba1e PR |
876 | err = tty_ldisc_open(tty, tty->ldisc); |
877 | else | |
878 | err = 1; | |
638b9648 AC |
879 | } |
880 | /* If the re-open fails or we reset then go to N_TTY. The | |
881 | N_TTY open cannot fail */ | |
882 | if (reset || err) { | |
1c95ba1e | 883 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 884 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 885 | } |
638b9648 | 886 | tty_ldisc_enable(tty); |
c65c9bc3 | 887 | } |
638b9648 AC |
888 | mutex_unlock(&tty->ldisc_mutex); |
889 | if (reset) | |
890 | tty_reset_termios(tty); | |
fc575ee6 PH |
891 | |
892 | tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); | |
c65c9bc3 | 893 | } |
01e1abb2 AC |
894 | |
895 | /** | |
896 | * tty_ldisc_setup - open line discipline | |
897 | * @tty: tty being shut down | |
898 | * @o_tty: pair tty for pty/tty pairs | |
899 | * | |
900 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
901 | * line disciplines and bind them to the tty. This has no locking issues |
902 | * as the device isn't yet active. | |
01e1abb2 AC |
903 | */ |
904 | ||
905 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
906 | { | |
c65c9bc3 | 907 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
908 | int retval; |
909 | ||
c65c9bc3 AC |
910 | retval = tty_ldisc_open(tty, ld); |
911 | if (retval) | |
912 | return retval; | |
913 | ||
914 | if (o_tty) { | |
915 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 916 | if (retval) { |
c65c9bc3 | 917 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
918 | return retval; |
919 | } | |
920 | tty_ldisc_enable(o_tty); | |
921 | } | |
922 | tty_ldisc_enable(tty); | |
923 | return 0; | |
924 | } | |
89c8d91e AC |
925 | |
926 | static void tty_ldisc_kill(struct tty_struct *tty) | |
927 | { | |
928 | mutex_lock(&tty->ldisc_mutex); | |
929 | /* | |
930 | * Now kill off the ldisc | |
931 | */ | |
932 | tty_ldisc_close(tty, tty->ldisc); | |
933 | tty_ldisc_put(tty->ldisc); | |
934 | /* Force an oops if we mess this up */ | |
935 | tty->ldisc = NULL; | |
936 | ||
937 | /* Ensure the next open requests the N_TTY ldisc */ | |
938 | tty_set_termios_ldisc(tty, N_TTY); | |
939 | mutex_unlock(&tty->ldisc_mutex); | |
940 | } | |
941 | ||
01e1abb2 AC |
942 | /** |
943 | * tty_ldisc_release - release line discipline | |
944 | * @tty: tty being shut down | |
945 | * @o_tty: pair tty for pty/tty pairs | |
946 | * | |
852e99d2 AC |
947 | * Called during the final close of a tty/pty pair in order to shut down |
948 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 949 | * ldisc has not been opened. |
01e1abb2 AC |
950 | */ |
951 | ||
952 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
953 | { | |
01e1abb2 | 954 | /* |
a2965b7b PH |
955 | * Shutdown this line discipline. As this is the final close, |
956 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 957 | */ |
01e1abb2 | 958 | |
fc575ee6 PH |
959 | tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
960 | ||
4f98d467 | 961 | tty_ldisc_halt(tty, o_tty, MAX_SCHEDULE_TIMEOUT); |
d155255a | 962 | |
852e4a81 | 963 | tty_lock_pair(tty, o_tty); |
6d31a88c | 964 | /* This will need doing differently if we need to lock */ |
89c8d91e | 965 | tty_ldisc_kill(tty); |
c65c9bc3 | 966 | if (o_tty) |
89c8d91e | 967 | tty_ldisc_kill(o_tty); |
aef29bc2 | 968 | |
89c8d91e | 969 | tty_unlock_pair(tty, o_tty); |
aef29bc2 AC |
970 | /* And the memory resources remaining (buffers, termios) will be |
971 | disposed of when the kref hits zero */ | |
fc575ee6 PH |
972 | |
973 | tty_ldisc_debug(tty, "ldisc closed\n"); | |
01e1abb2 AC |
974 | } |
975 | ||
976 | /** | |
977 | * tty_ldisc_init - ldisc setup for new tty | |
978 | * @tty: tty being allocated | |
979 | * | |
980 | * Set up the line discipline objects for a newly allocated tty. Note that | |
981 | * the tty structure is not completely set up when this call is made. | |
982 | */ | |
983 | ||
984 | void tty_ldisc_init(struct tty_struct *tty) | |
985 | { | |
c65c9bc3 AC |
986 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
987 | if (IS_ERR(ld)) | |
01e1abb2 | 988 | panic("n_tty: init_tty"); |
c65c9bc3 | 989 | tty_ldisc_assign(tty, ld); |
01e1abb2 AC |
990 | } |
991 | ||
6716671d JS |
992 | /** |
993 | * tty_ldisc_init - ldisc cleanup for new tty | |
994 | * @tty: tty that was allocated recently | |
995 | * | |
996 | * The tty structure must not becompletely set up (tty_ldisc_setup) when | |
997 | * this call is made. | |
998 | */ | |
999 | void tty_ldisc_deinit(struct tty_struct *tty) | |
1000 | { | |
ebc9baed | 1001 | tty_ldisc_put(tty->ldisc); |
6716671d JS |
1002 | tty_ldisc_assign(tty, NULL); |
1003 | } | |
1004 | ||
01e1abb2 AC |
1005 | void tty_ldisc_begin(void) |
1006 | { | |
1007 | /* Setup the default TTY line discipline. */ | |
1008 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
1009 | } |