]>
Commit | Line | Data |
---|---|---|
01e1abb2 AC |
1 | #include <linux/types.h> |
2 | #include <linux/major.h> | |
3 | #include <linux/errno.h> | |
4 | #include <linux/signal.h> | |
5 | #include <linux/fcntl.h> | |
6 | #include <linux/sched.h> | |
7 | #include <linux/interrupt.h> | |
8 | #include <linux/tty.h> | |
9 | #include <linux/tty_driver.h> | |
10 | #include <linux/tty_flip.h> | |
11 | #include <linux/devpts_fs.h> | |
12 | #include <linux/file.h> | |
01e1abb2 AC |
13 | #include <linux/console.h> |
14 | #include <linux/timer.h> | |
15 | #include <linux/ctype.h> | |
16 | #include <linux/kd.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/string.h> | |
19 | #include <linux/slab.h> | |
20 | #include <linux/poll.h> | |
21 | #include <linux/proc_fs.h> | |
22 | #include <linux/init.h> | |
23 | #include <linux/module.h> | |
01e1abb2 AC |
24 | #include <linux/device.h> |
25 | #include <linux/wait.h> | |
26 | #include <linux/bitops.h> | |
27 | #include <linux/delay.h> | |
28 | #include <linux/seq_file.h> | |
29 | ||
30 | #include <linux/uaccess.h> | |
31 | #include <asm/system.h> | |
32 | ||
33 | #include <linux/kbd_kern.h> | |
34 | #include <linux/vt_kern.h> | |
35 | #include <linux/selection.h> | |
36 | ||
eeb89d91 AC |
37 | #include <linux/smp_lock.h> /* For the moment */ |
38 | ||
01e1abb2 AC |
39 | #include <linux/kmod.h> |
40 | #include <linux/nsproxy.h> | |
41 | ||
42 | /* | |
43 | * This guards the refcounted line discipline lists. The lock | |
44 | * must be taken with irqs off because there are hangup path | |
45 | * callers who will do ldisc lookups and cannot sleep. | |
46 | */ | |
47 | ||
48 | static DEFINE_SPINLOCK(tty_ldisc_lock); | |
49 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); | |
100eeae2 | 50 | static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle); |
01e1abb2 AC |
51 | /* Line disc dispatch table */ |
52 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
53 | ||
65b77046 LT |
54 | static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) |
55 | { | |
56 | if (ld) | |
57 | atomic_inc(&ld->users); | |
58 | return ld; | |
59 | } | |
60 | ||
cbe9352f | 61 | static void put_ldisc(struct tty_ldisc *ld) |
65b77046 | 62 | { |
cbe9352f LT |
63 | unsigned long flags; |
64 | ||
65b77046 LT |
65 | if (WARN_ON_ONCE(!ld)) |
66 | return; | |
67 | ||
68 | /* | |
69 | * If this is the last user, free the ldisc, and | |
70 | * release the ldisc ops. | |
cbe9352f LT |
71 | * |
72 | * We really want an "atomic_dec_and_lock_irqsave()", | |
73 | * but we don't have it, so this does it by hand. | |
65b77046 | 74 | */ |
cbe9352f LT |
75 | local_irq_save(flags); |
76 | if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { | |
65b77046 LT |
77 | struct tty_ldisc_ops *ldo = ld->ops; |
78 | ||
65b77046 LT |
79 | ldo->refcount--; |
80 | module_put(ldo->owner); | |
81 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
cbe9352f LT |
82 | |
83 | kfree(ld); | |
84 | return; | |
65b77046 | 85 | } |
cbe9352f | 86 | local_irq_restore(flags); |
100eeae2 | 87 | wake_up(&tty_ldisc_idle); |
65b77046 LT |
88 | } |
89 | ||
01e1abb2 AC |
90 | /** |
91 | * tty_register_ldisc - install a line discipline | |
92 | * @disc: ldisc number | |
93 | * @new_ldisc: pointer to the ldisc object | |
94 | * | |
95 | * Installs a new line discipline into the kernel. The discipline | |
96 | * is set up as unreferenced and then made available to the kernel | |
97 | * from this point onwards. | |
98 | * | |
99 | * Locking: | |
100 | * takes tty_ldisc_lock to guard against ldisc races | |
101 | */ | |
102 | ||
103 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
104 | { | |
105 | unsigned long flags; | |
106 | int ret = 0; | |
107 | ||
108 | if (disc < N_TTY || disc >= NR_LDISCS) | |
109 | return -EINVAL; | |
110 | ||
111 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
112 | tty_ldiscs[disc] = new_ldisc; | |
113 | new_ldisc->num = disc; | |
114 | new_ldisc->refcount = 0; | |
115 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
116 | ||
117 | return ret; | |
118 | } | |
119 | EXPORT_SYMBOL(tty_register_ldisc); | |
120 | ||
121 | /** | |
122 | * tty_unregister_ldisc - unload a line discipline | |
123 | * @disc: ldisc number | |
124 | * @new_ldisc: pointer to the ldisc object | |
125 | * | |
126 | * Remove a line discipline from the kernel providing it is not | |
127 | * currently in use. | |
128 | * | |
129 | * Locking: | |
130 | * takes tty_ldisc_lock to guard against ldisc races | |
131 | */ | |
132 | ||
133 | int tty_unregister_ldisc(int disc) | |
134 | { | |
135 | unsigned long flags; | |
136 | int ret = 0; | |
137 | ||
138 | if (disc < N_TTY || disc >= NR_LDISCS) | |
139 | return -EINVAL; | |
140 | ||
141 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
142 | if (tty_ldiscs[disc]->refcount) | |
143 | ret = -EBUSY; | |
144 | else | |
145 | tty_ldiscs[disc] = NULL; | |
146 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
147 | ||
148 | return ret; | |
149 | } | |
150 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
151 | ||
f0de0e8d LT |
152 | static struct tty_ldisc_ops *get_ldops(int disc) |
153 | { | |
154 | unsigned long flags; | |
155 | struct tty_ldisc_ops *ldops, *ret; | |
156 | ||
157 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
158 | ret = ERR_PTR(-EINVAL); | |
159 | ldops = tty_ldiscs[disc]; | |
160 | if (ldops) { | |
161 | ret = ERR_PTR(-EAGAIN); | |
162 | if (try_module_get(ldops->owner)) { | |
163 | ldops->refcount++; | |
164 | ret = ldops; | |
165 | } | |
166 | } | |
167 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
168 | return ret; | |
169 | } | |
170 | ||
171 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
172 | { | |
173 | unsigned long flags; | |
174 | ||
175 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
176 | ldops->refcount--; | |
177 | module_put(ldops->owner); | |
178 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
179 | } | |
01e1abb2 | 180 | |
01e1abb2 AC |
181 | /** |
182 | * tty_ldisc_get - take a reference to an ldisc | |
183 | * @disc: ldisc number | |
01e1abb2 AC |
184 | * |
185 | * Takes a reference to a line discipline. Deals with refcounts and | |
186 | * module locking counts. Returns NULL if the discipline is not available. | |
187 | * Returns a pointer to the discipline and bumps the ref count if it is | |
188 | * available | |
189 | * | |
190 | * Locking: | |
191 | * takes tty_ldisc_lock to guard against ldisc races | |
192 | */ | |
193 | ||
c65c9bc3 | 194 | static struct tty_ldisc *tty_ldisc_get(int disc) |
01e1abb2 | 195 | { |
c65c9bc3 | 196 | struct tty_ldisc *ld; |
182274f8 | 197 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
198 | |
199 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 200 | return ERR_PTR(-EINVAL); |
182274f8 LT |
201 | |
202 | /* | |
203 | * Get the ldisc ops - we may need to request them to be loaded | |
204 | * dynamically and try again. | |
205 | */ | |
206 | ldops = get_ldops(disc); | |
207 | if (IS_ERR(ldops)) { | |
01e1abb2 | 208 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
209 | ldops = get_ldops(disc); |
210 | if (IS_ERR(ldops)) | |
211 | return ERR_CAST(ldops); | |
212 | } | |
213 | ||
214 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); | |
215 | if (ld == NULL) { | |
216 | put_ldops(ldops); | |
217 | return ERR_PTR(-ENOMEM); | |
01e1abb2 | 218 | } |
182274f8 LT |
219 | |
220 | ld->ops = ldops; | |
221 | atomic_set(&ld->users, 1); | |
c65c9bc3 | 222 | return ld; |
01e1abb2 AC |
223 | } |
224 | ||
852e99d2 | 225 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
226 | { |
227 | return (*pos < NR_LDISCS) ? pos : NULL; | |
228 | } | |
229 | ||
852e99d2 | 230 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
231 | { |
232 | (*pos)++; | |
233 | return (*pos < NR_LDISCS) ? pos : NULL; | |
234 | } | |
235 | ||
236 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
237 | { | |
238 | } | |
239 | ||
240 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
241 | { | |
242 | int i = *(loff_t *)v; | |
f0de0e8d | 243 | struct tty_ldisc_ops *ldops; |
852e99d2 | 244 | |
f0de0e8d LT |
245 | ldops = get_ldops(i); |
246 | if (IS_ERR(ldops)) | |
01e1abb2 | 247 | return 0; |
f0de0e8d LT |
248 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
249 | put_ldops(ldops); | |
01e1abb2 AC |
250 | return 0; |
251 | } | |
252 | ||
253 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
254 | .start = tty_ldiscs_seq_start, | |
255 | .next = tty_ldiscs_seq_next, | |
256 | .stop = tty_ldiscs_seq_stop, | |
257 | .show = tty_ldiscs_seq_show, | |
258 | }; | |
259 | ||
260 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
261 | { | |
262 | return seq_open(file, &tty_ldiscs_seq_ops); | |
263 | } | |
264 | ||
265 | const struct file_operations tty_ldiscs_proc_fops = { | |
266 | .owner = THIS_MODULE, | |
267 | .open = proc_tty_ldiscs_open, | |
268 | .read = seq_read, | |
269 | .llseek = seq_lseek, | |
270 | .release = seq_release, | |
271 | }; | |
272 | ||
273 | /** | |
274 | * tty_ldisc_assign - set ldisc on a tty | |
275 | * @tty: tty to assign | |
276 | * @ld: line discipline | |
277 | * | |
278 | * Install an instance of a line discipline into a tty structure. The | |
8d2ead74 | 279 | * ldisc must have a reference count above zero to ensure it remains. |
01e1abb2 AC |
280 | * The tty instance refcount starts at zero. |
281 | * | |
282 | * Locking: | |
283 | * Caller must hold references | |
284 | */ | |
285 | ||
286 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
287 | { | |
c65c9bc3 | 288 | tty->ldisc = ld; |
01e1abb2 AC |
289 | } |
290 | ||
291 | /** | |
292 | * tty_ldisc_try - internal helper | |
293 | * @tty: the tty | |
294 | * | |
295 | * Make a single attempt to grab and bump the refcount on | |
296 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
297 | * used to implement both the waiting and non waiting versions | |
298 | * of tty_ldisc_ref | |
299 | * | |
300 | * Locking: takes tty_ldisc_lock | |
301 | */ | |
302 | ||
65b77046 | 303 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
01e1abb2 AC |
304 | { |
305 | unsigned long flags; | |
306 | struct tty_ldisc *ld; | |
01e1abb2 AC |
307 | |
308 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
65b77046 LT |
309 | ld = NULL; |
310 | if (test_bit(TTY_LDISC, &tty->flags)) | |
311 | ld = get_ldisc(tty->ldisc); | |
01e1abb2 | 312 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
65b77046 | 313 | return ld; |
01e1abb2 AC |
314 | } |
315 | ||
316 | /** | |
317 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
318 | * @tty: tty device | |
319 | * | |
320 | * Dereference the line discipline for the terminal and take a | |
321 | * reference to it. If the line discipline is in flux then | |
322 | * wait patiently until it changes. | |
323 | * | |
324 | * Note: Must not be called from an IRQ/timer context. The caller | |
325 | * must also be careful not to hold other locks that will deadlock | |
326 | * against a discipline change, such as an existing ldisc reference | |
327 | * (which we check for) | |
328 | * | |
329 | * Locking: call functions take tty_ldisc_lock | |
330 | */ | |
331 | ||
332 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
333 | { | |
65b77046 LT |
334 | struct tty_ldisc *ld; |
335 | ||
01e1abb2 | 336 | /* wait_event is a macro */ |
65b77046 LT |
337 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
338 | return ld; | |
01e1abb2 | 339 | } |
01e1abb2 AC |
340 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
341 | ||
342 | /** | |
343 | * tty_ldisc_ref - get the tty ldisc | |
344 | * @tty: tty device | |
345 | * | |
346 | * Dereference the line discipline for the terminal and take a | |
347 | * reference to it. If the line discipline is in flux then | |
348 | * return NULL. Can be called from IRQ and timer functions. | |
349 | * | |
350 | * Locking: called functions take tty_ldisc_lock | |
351 | */ | |
352 | ||
353 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
354 | { | |
65b77046 | 355 | return tty_ldisc_try(tty); |
01e1abb2 | 356 | } |
01e1abb2 AC |
357 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
358 | ||
359 | /** | |
360 | * tty_ldisc_deref - free a tty ldisc reference | |
361 | * @ld: reference to free up | |
362 | * | |
363 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
364 | * be called in IRQ context. | |
365 | * | |
366 | * Locking: takes tty_ldisc_lock | |
367 | */ | |
368 | ||
369 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
370 | { | |
65b77046 | 371 | put_ldisc(ld); |
01e1abb2 | 372 | } |
01e1abb2 AC |
373 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
374 | ||
65b77046 LT |
375 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
376 | { | |
377 | put_ldisc(ld); | |
378 | } | |
379 | ||
01e1abb2 AC |
380 | /** |
381 | * tty_ldisc_enable - allow ldisc use | |
382 | * @tty: terminal to activate ldisc on | |
383 | * | |
384 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
385 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
386 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 387 | * |
c9b3976e AC |
388 | * Note: nobody should set the TTY_LDISC bit except via this function. |
389 | * Clearing directly is allowed. | |
01e1abb2 AC |
390 | */ |
391 | ||
392 | void tty_ldisc_enable(struct tty_struct *tty) | |
393 | { | |
394 | set_bit(TTY_LDISC, &tty->flags); | |
c9b3976e | 395 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
396 | wake_up(&tty_ldisc_wait); |
397 | } | |
398 | ||
f2c4c65c AC |
399 | /** |
400 | * tty_ldisc_flush - flush line discipline queue | |
401 | * @tty: tty | |
402 | * | |
403 | * Flush the line discipline queue (if any) for this tty. If there | |
404 | * is no line discipline active this is a no-op. | |
405 | */ | |
406 | ||
407 | void tty_ldisc_flush(struct tty_struct *tty) | |
408 | { | |
409 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
410 | if (ld) { | |
411 | if (ld->ops->flush_buffer) | |
412 | ld->ops->flush_buffer(tty); | |
413 | tty_ldisc_deref(ld); | |
414 | } | |
415 | tty_buffer_flush(tty); | |
416 | } | |
f2c4c65c AC |
417 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
418 | ||
01e1abb2 AC |
419 | /** |
420 | * tty_set_termios_ldisc - set ldisc field | |
421 | * @tty: tty structure | |
422 | * @num: line discipline number | |
423 | * | |
424 | * This is probably overkill for real world processors but | |
425 | * they are not on hot paths so a little discipline won't do | |
426 | * any harm. | |
427 | * | |
428 | * Locking: takes termios_mutex | |
429 | */ | |
430 | ||
431 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
432 | { | |
433 | mutex_lock(&tty->termios_mutex); | |
434 | tty->termios->c_line = num; | |
435 | mutex_unlock(&tty->termios_mutex); | |
436 | } | |
437 | ||
c65c9bc3 AC |
438 | /** |
439 | * tty_ldisc_open - open a line discipline | |
440 | * @tty: tty we are opening the ldisc on | |
441 | * @ld: discipline to open | |
442 | * | |
443 | * A helper opening method. Also a convenient debugging and check | |
444 | * point. | |
ec79d605 AB |
445 | * |
446 | * Locking: always called with BTM already held. | |
c65c9bc3 AC |
447 | */ |
448 | ||
449 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
450 | { | |
451 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
452 | if (ld->ops->open) { |
453 | int ret; | |
ec79d605 | 454 | /* BTM here locks versus a hangup event */ |
ddcd9fb6 | 455 | WARN_ON(!tty_locked()); |
f18f9498 | 456 | ret = ld->ops->open(tty); |
f18f9498 AC |
457 | return ret; |
458 | } | |
c65c9bc3 AC |
459 | return 0; |
460 | } | |
461 | ||
462 | /** | |
463 | * tty_ldisc_close - close a line discipline | |
464 | * @tty: tty we are opening the ldisc on | |
465 | * @ld: discipline to close | |
466 | * | |
467 | * A helper close method. Also a convenient debugging and check | |
468 | * point. | |
469 | */ | |
470 | ||
471 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
472 | { | |
473 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
474 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
475 | if (ld->ops->close) | |
476 | ld->ops->close(tty); | |
477 | } | |
01e1abb2 AC |
478 | |
479 | /** | |
480 | * tty_ldisc_restore - helper for tty ldisc change | |
481 | * @tty: tty to recover | |
482 | * @old: previous ldisc | |
483 | * | |
484 | * Restore the previous line discipline or N_TTY when a line discipline | |
485 | * change fails due to an open error | |
486 | */ | |
487 | ||
488 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
489 | { | |
490 | char buf[64]; | |
c65c9bc3 AC |
491 | struct tty_ldisc *new_ldisc; |
492 | int r; | |
01e1abb2 AC |
493 | |
494 | /* There is an outstanding reference here so this is safe */ | |
c65c9bc3 AC |
495 | old = tty_ldisc_get(old->ops->num); |
496 | WARN_ON(IS_ERR(old)); | |
01e1abb2 AC |
497 | tty_ldisc_assign(tty, old); |
498 | tty_set_termios_ldisc(tty, old->ops->num); | |
c65c9bc3 AC |
499 | if (tty_ldisc_open(tty, old) < 0) { |
500 | tty_ldisc_put(old); | |
01e1abb2 | 501 | /* This driver is always present */ |
852e99d2 | 502 | new_ldisc = tty_ldisc_get(N_TTY); |
c65c9bc3 | 503 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 504 | panic("n_tty: get"); |
c65c9bc3 | 505 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 506 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
507 | r = tty_ldisc_open(tty, new_ldisc); |
508 | if (r < 0) | |
509 | panic("Couldn't open N_TTY ldisc for " | |
510 | "%s --- error %d.", | |
511 | tty_name(tty, buf), r); | |
01e1abb2 AC |
512 | } |
513 | } | |
514 | ||
e8b70e7d | 515 | /** |
c65c9bc3 | 516 | * tty_ldisc_halt - shut down the line discipline |
e8b70e7d AC |
517 | * @tty: tty device |
518 | * | |
519 | * Shut down the line discipline and work queue for this tty device. | |
520 | * The TTY_LDISC flag being cleared ensures no further references can | |
521 | * be obtained while the delayed work queue halt ensures that no more | |
522 | * data is fed to the ldisc. | |
523 | * | |
5c58ceff LT |
524 | * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) |
525 | * in order to make sure any currently executing ldisc work is also | |
526 | * flushed. | |
e8b70e7d AC |
527 | */ |
528 | ||
c65c9bc3 | 529 | static int tty_ldisc_halt(struct tty_struct *tty) |
e8b70e7d AC |
530 | { |
531 | clear_bit(TTY_LDISC, &tty->flags); | |
0b5759c6 | 532 | return cancel_delayed_work_sync(&tty->buf.work); |
e8b70e7d AC |
533 | } |
534 | ||
100eeae2 JS |
535 | /** |
536 | * tty_ldisc_wait_idle - wait for the ldisc to become idle | |
537 | * @tty: tty to wait for | |
538 | * | |
539 | * Wait for the line discipline to become idle. The discipline must | |
540 | * have been halted for this to guarantee it remains idle. | |
541 | */ | |
542 | static int tty_ldisc_wait_idle(struct tty_struct *tty) | |
543 | { | |
544 | int ret; | |
545 | ret = wait_event_interruptible_timeout(tty_ldisc_idle, | |
546 | atomic_read(&tty->ldisc->users) == 1, 5 * HZ); | |
547 | if (ret < 0) | |
548 | return ret; | |
549 | return ret > 0 ? 0 : -EBUSY; | |
550 | } | |
551 | ||
01e1abb2 AC |
552 | /** |
553 | * tty_set_ldisc - set line discipline | |
554 | * @tty: the terminal to set | |
555 | * @ldisc: the line discipline | |
556 | * | |
557 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
558 | * context. The ldisc change logic has to protect itself against any |
559 | * overlapping ldisc change (including on the other end of pty pairs), | |
560 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 561 | * |
c65c9bc3 | 562 | * Locking: takes tty_ldisc_lock, termios_mutex |
01e1abb2 AC |
563 | */ |
564 | ||
565 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
566 | { | |
567 | int retval; | |
c65c9bc3 AC |
568 | struct tty_ldisc *o_ldisc, *new_ldisc; |
569 | int work, o_work = 0; | |
01e1abb2 AC |
570 | struct tty_struct *o_tty; |
571 | ||
c65c9bc3 AC |
572 | new_ldisc = tty_ldisc_get(ldisc); |
573 | if (IS_ERR(new_ldisc)) | |
574 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 575 | |
ec79d605 | 576 | tty_lock(); |
01e1abb2 | 577 | /* |
c65c9bc3 AC |
578 | * We need to look at the tty locking here for pty/tty pairs |
579 | * when both sides try to change in parallel. | |
01e1abb2 AC |
580 | */ |
581 | ||
c65c9bc3 AC |
582 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
583 | ||
01e1abb2 | 584 | |
c65c9bc3 AC |
585 | /* |
586 | * Check the no-op case | |
587 | */ | |
588 | ||
589 | if (tty->ldisc->ops->num == ldisc) { | |
ec79d605 | 590 | tty_unlock(); |
c65c9bc3 | 591 | tty_ldisc_put(new_ldisc); |
01e1abb2 AC |
592 | return 0; |
593 | } | |
594 | ||
ec79d605 | 595 | tty_unlock(); |
c65c9bc3 AC |
596 | /* |
597 | * Problem: What do we do if this blocks ? | |
598 | * We could deadlock here | |
599 | */ | |
600 | ||
601 | tty_wait_until_sent(tty, 0); | |
602 | ||
60af22d2 | 603 | tty_lock(); |
c65c9bc3 AC |
604 | mutex_lock(&tty->ldisc_mutex); |
605 | ||
606 | /* | |
607 | * We could be midstream of another ldisc change which has | |
608 | * dropped the lock during processing. If so we need to wait. | |
609 | */ | |
610 | ||
611 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
612 | mutex_unlock(&tty->ldisc_mutex); | |
60af22d2 | 613 | tty_unlock(); |
c65c9bc3 AC |
614 | wait_event(tty_ldisc_wait, |
615 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
60af22d2 | 616 | tty_lock(); |
c65c9bc3 AC |
617 | mutex_lock(&tty->ldisc_mutex); |
618 | } | |
eeb89d91 | 619 | |
c65c9bc3 | 620 | set_bit(TTY_LDISC_CHANGING, &tty->flags); |
852e99d2 | 621 | |
01e1abb2 AC |
622 | /* |
623 | * No more input please, we are switching. The new ldisc | |
624 | * will update this value in the ldisc open function | |
625 | */ | |
626 | ||
627 | tty->receive_room = 0; | |
628 | ||
629 | o_ldisc = tty->ldisc; | |
eeb89d91 | 630 | |
ec79d605 | 631 | tty_unlock(); |
01e1abb2 AC |
632 | /* |
633 | * Make sure we don't change while someone holds a | |
634 | * reference to the line discipline. The TTY_LDISC bit | |
635 | * prevents anyone taking a reference once it is clear. | |
636 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
637 | * |
638 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
639 | * with a userspace app continually trying to use the tty in | |
640 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
641 | */ |
642 | ||
c65c9bc3 | 643 | work = tty_ldisc_halt(tty); |
01e1abb2 | 644 | if (o_tty) |
c65c9bc3 | 645 | o_work = tty_ldisc_halt(o_tty); |
01e1abb2 | 646 | |
01e1abb2 | 647 | /* |
c65c9bc3 AC |
648 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
649 | * We must drop the mutex here in case a hangup is also in process. | |
01e1abb2 | 650 | */ |
c65c9bc3 AC |
651 | |
652 | mutex_unlock(&tty->ldisc_mutex); | |
653 | ||
01e1abb2 | 654 | flush_scheduled_work(); |
c65c9bc3 | 655 | |
100eeae2 JS |
656 | retval = tty_ldisc_wait_idle(tty); |
657 | ||
ec79d605 | 658 | tty_lock(); |
60af22d2 | 659 | mutex_lock(&tty->ldisc_mutex); |
100eeae2 JS |
660 | |
661 | /* handle wait idle failure locked */ | |
662 | if (retval) { | |
663 | tty_ldisc_put(new_ldisc); | |
664 | goto enable; | |
665 | } | |
666 | ||
c65c9bc3 AC |
667 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
668 | /* We were raced by the hangup method. It will have stomped | |
669 | the ldisc data and closed the ldisc down */ | |
670 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
671 | mutex_unlock(&tty->ldisc_mutex); | |
672 | tty_ldisc_put(new_ldisc); | |
ec79d605 | 673 | tty_unlock(); |
c65c9bc3 AC |
674 | return -EIO; |
675 | } | |
676 | ||
01e1abb2 | 677 | /* Shutdown the current discipline. */ |
c65c9bc3 | 678 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
679 | |
680 | /* Now set up the new line discipline. */ | |
c65c9bc3 | 681 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 682 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
683 | |
684 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 685 | if (retval < 0) { |
c65c9bc3 AC |
686 | /* Back to the old one or N_TTY if we can't */ |
687 | tty_ldisc_put(new_ldisc); | |
688 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 689 | } |
c65c9bc3 | 690 | |
01e1abb2 AC |
691 | /* At this point we hold a reference to the new ldisc and a |
692 | a reference to the old ldisc. If we ended up flipping back | |
693 | to the existing ldisc we have two references to it */ | |
694 | ||
c65c9bc3 | 695 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
696 | tty->ops->set_ldisc(tty); |
697 | ||
c65c9bc3 | 698 | tty_ldisc_put(o_ldisc); |
01e1abb2 | 699 | |
100eeae2 | 700 | enable: |
01e1abb2 | 701 | /* |
c65c9bc3 | 702 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
703 | */ |
704 | ||
705 | tty_ldisc_enable(tty); | |
706 | if (o_tty) | |
707 | tty_ldisc_enable(o_tty); | |
708 | ||
c65c9bc3 | 709 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 AC |
710 | already running */ |
711 | if (work) | |
712 | schedule_delayed_work(&tty->buf.work, 1); | |
c65c9bc3 AC |
713 | if (o_work) |
714 | schedule_delayed_work(&o_tty->buf.work, 1); | |
715 | mutex_unlock(&tty->ldisc_mutex); | |
ec79d605 | 716 | tty_unlock(); |
01e1abb2 AC |
717 | return retval; |
718 | } | |
719 | ||
c65c9bc3 AC |
720 | /** |
721 | * tty_reset_termios - reset terminal state | |
722 | * @tty: tty to reset | |
723 | * | |
724 | * Restore a terminal to the driver default state. | |
725 | */ | |
726 | ||
727 | static void tty_reset_termios(struct tty_struct *tty) | |
728 | { | |
729 | mutex_lock(&tty->termios_mutex); | |
730 | *tty->termios = tty->driver->init_termios; | |
731 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); | |
732 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); | |
733 | mutex_unlock(&tty->termios_mutex); | |
734 | } | |
735 | ||
736 | ||
737 | /** | |
738 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
739 | * @tty: tty to reinit | |
638b9648 | 740 | * @ldisc: line discipline to reinitialize |
c65c9bc3 | 741 | * |
638b9648 AC |
742 | * Switch the tty to a line discipline and leave the ldisc |
743 | * state closed | |
c65c9bc3 AC |
744 | */ |
745 | ||
1c95ba1e | 746 | static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
c65c9bc3 | 747 | { |
1c95ba1e PR |
748 | struct tty_ldisc *ld = tty_ldisc_get(ldisc); |
749 | ||
750 | if (IS_ERR(ld)) | |
751 | return -1; | |
c65c9bc3 AC |
752 | |
753 | tty_ldisc_close(tty, tty->ldisc); | |
754 | tty_ldisc_put(tty->ldisc); | |
755 | tty->ldisc = NULL; | |
756 | /* | |
757 | * Switch the line discipline back | |
758 | */ | |
c65c9bc3 | 759 | tty_ldisc_assign(tty, ld); |
638b9648 | 760 | tty_set_termios_ldisc(tty, ldisc); |
1c95ba1e PR |
761 | |
762 | return 0; | |
c65c9bc3 AC |
763 | } |
764 | ||
765 | /** | |
766 | * tty_ldisc_hangup - hangup ldisc reset | |
767 | * @tty: tty being hung up | |
768 | * | |
769 | * Some tty devices reset their termios when they receive a hangup | |
770 | * event. In that situation we must also switch back to N_TTY properly | |
771 | * before we reset the termios data. | |
772 | * | |
773 | * Locking: We can take the ldisc mutex as the rest of the code is | |
774 | * careful to allow for this. | |
775 | * | |
776 | * In the pty pair case this occurs in the close() path of the | |
777 | * tty itself so we must be careful about locking rules. | |
778 | */ | |
779 | ||
780 | void tty_ldisc_hangup(struct tty_struct *tty) | |
781 | { | |
782 | struct tty_ldisc *ld; | |
638b9648 AC |
783 | int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
784 | int err = 0; | |
c65c9bc3 AC |
785 | |
786 | /* | |
787 | * FIXME! What are the locking issues here? This may me overdoing | |
788 | * things... This question is especially important now that we've | |
789 | * removed the irqlock. | |
790 | */ | |
791 | ld = tty_ldisc_ref(tty); | |
792 | if (ld != NULL) { | |
793 | /* We may have no line discipline at this point */ | |
794 | if (ld->ops->flush_buffer) | |
795 | ld->ops->flush_buffer(tty); | |
796 | tty_driver_flush_buffer(tty); | |
797 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
798 | ld->ops->write_wakeup) | |
799 | ld->ops->write_wakeup(tty); | |
800 | if (ld->ops->hangup) | |
801 | ld->ops->hangup(tty); | |
802 | tty_ldisc_deref(ld); | |
803 | } | |
804 | /* | |
805 | * FIXME: Once we trust the LDISC code better we can wait here for | |
806 | * ldisc completion and fix the driver call race | |
807 | */ | |
808 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
809 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
810 | /* | |
811 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
812 | * N_TTY if need be. |
813 | * | |
814 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 815 | */ |
638b9648 | 816 | mutex_lock(&tty->ldisc_mutex); |
60af22d2 AB |
817 | |
818 | /* | |
819 | * this is like tty_ldisc_halt, but we need to give up | |
820 | * the BTM before calling cancel_delayed_work_sync, | |
821 | * which may need to wait for another function taking the BTM | |
822 | */ | |
823 | clear_bit(TTY_LDISC, &tty->flags); | |
824 | tty_unlock(); | |
825 | cancel_delayed_work_sync(&tty->buf.work); | |
826 | mutex_unlock(&tty->ldisc_mutex); | |
827 | ||
828 | tty_lock(); | |
829 | mutex_lock(&tty->ldisc_mutex); | |
830 | ||
638b9648 AC |
831 | /* At this point we have a closed ldisc and we want to |
832 | reopen it. We could defer this to the next open but | |
833 | it means auditing a lot of other paths so this is | |
834 | a FIXME */ | |
835 | if (tty->ldisc) { /* Not yet closed */ | |
836 | if (reset == 0) { | |
1c95ba1e PR |
837 | |
838 | if (!tty_ldisc_reinit(tty, tty->termios->c_line)) | |
839 | err = tty_ldisc_open(tty, tty->ldisc); | |
840 | else | |
841 | err = 1; | |
638b9648 AC |
842 | } |
843 | /* If the re-open fails or we reset then go to N_TTY. The | |
844 | N_TTY open cannot fail */ | |
845 | if (reset || err) { | |
1c95ba1e | 846 | BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
c8d50041 | 847 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
c8d50041 | 848 | } |
638b9648 | 849 | tty_ldisc_enable(tty); |
c65c9bc3 | 850 | } |
638b9648 AC |
851 | mutex_unlock(&tty->ldisc_mutex); |
852 | if (reset) | |
853 | tty_reset_termios(tty); | |
c65c9bc3 | 854 | } |
01e1abb2 AC |
855 | |
856 | /** | |
857 | * tty_ldisc_setup - open line discipline | |
858 | * @tty: tty being shut down | |
859 | * @o_tty: pair tty for pty/tty pairs | |
860 | * | |
861 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
862 | * line disciplines and bind them to the tty. This has no locking issues |
863 | * as the device isn't yet active. | |
01e1abb2 AC |
864 | */ |
865 | ||
866 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
867 | { | |
c65c9bc3 | 868 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
869 | int retval; |
870 | ||
c65c9bc3 AC |
871 | retval = tty_ldisc_open(tty, ld); |
872 | if (retval) | |
873 | return retval; | |
874 | ||
875 | if (o_tty) { | |
876 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 877 | if (retval) { |
c65c9bc3 | 878 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
879 | return retval; |
880 | } | |
881 | tty_ldisc_enable(o_tty); | |
882 | } | |
883 | tty_ldisc_enable(tty); | |
884 | return 0; | |
885 | } | |
01e1abb2 AC |
886 | /** |
887 | * tty_ldisc_release - release line discipline | |
888 | * @tty: tty being shut down | |
889 | * @o_tty: pair tty for pty/tty pairs | |
890 | * | |
852e99d2 AC |
891 | * Called during the final close of a tty/pty pair in order to shut down |
892 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 893 | * ldisc has not been opened. |
01e1abb2 AC |
894 | */ |
895 | ||
896 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
897 | { | |
01e1abb2 AC |
898 | /* |
899 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then | |
900 | * kill any delayed work. As this is the final close it does not | |
901 | * race with the set_ldisc code path. | |
902 | */ | |
01e1abb2 | 903 | |
60af22d2 | 904 | tty_unlock(); |
e8b70e7d | 905 | tty_ldisc_halt(tty); |
c65c9bc3 | 906 | flush_scheduled_work(); |
60af22d2 | 907 | tty_lock(); |
01e1abb2 | 908 | |
c8d50041 | 909 | mutex_lock(&tty->ldisc_mutex); |
01e1abb2 | 910 | /* |
aef29bc2 | 911 | * Now kill off the ldisc |
01e1abb2 | 912 | */ |
aef29bc2 AC |
913 | tty_ldisc_close(tty, tty->ldisc); |
914 | tty_ldisc_put(tty->ldisc); | |
915 | /* Force an oops if we mess this up */ | |
916 | tty->ldisc = NULL; | |
917 | ||
918 | /* Ensure the next open requests the N_TTY ldisc */ | |
919 | tty_set_termios_ldisc(tty, N_TTY); | |
c8d50041 | 920 | mutex_unlock(&tty->ldisc_mutex); |
01e1abb2 | 921 | |
c65c9bc3 AC |
922 | /* This will need doing differently if we need to lock */ |
923 | if (o_tty) | |
924 | tty_ldisc_release(o_tty, NULL); | |
aef29bc2 AC |
925 | |
926 | /* And the memory resources remaining (buffers, termios) will be | |
927 | disposed of when the kref hits zero */ | |
01e1abb2 AC |
928 | } |
929 | ||
930 | /** | |
931 | * tty_ldisc_init - ldisc setup for new tty | |
932 | * @tty: tty being allocated | |
933 | * | |
934 | * Set up the line discipline objects for a newly allocated tty. Note that | |
935 | * the tty structure is not completely set up when this call is made. | |
936 | */ | |
937 | ||
938 | void tty_ldisc_init(struct tty_struct *tty) | |
939 | { | |
c65c9bc3 AC |
940 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
941 | if (IS_ERR(ld)) | |
01e1abb2 | 942 | panic("n_tty: init_tty"); |
c65c9bc3 | 943 | tty_ldisc_assign(tty, ld); |
01e1abb2 AC |
944 | } |
945 | ||
946 | void tty_ldisc_begin(void) | |
947 | { | |
948 | /* Setup the default TTY line discipline. */ | |
949 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
950 | } |