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