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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 | ||
f0de0e8d LT |
148 | static struct tty_ldisc_ops *get_ldops(int disc) |
149 | { | |
150 | unsigned long flags; | |
151 | struct tty_ldisc_ops *ldops, *ret; | |
152 | ||
153 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
154 | ret = ERR_PTR(-EINVAL); | |
155 | ldops = tty_ldiscs[disc]; | |
156 | if (ldops) { | |
157 | ret = ERR_PTR(-EAGAIN); | |
158 | if (try_module_get(ldops->owner)) { | |
159 | ldops->refcount++; | |
160 | ret = ldops; | |
161 | } | |
162 | } | |
163 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
164 | return ret; | |
165 | } | |
166 | ||
167 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
168 | { | |
169 | unsigned long flags; | |
170 | ||
171 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
172 | ldops->refcount--; | |
173 | module_put(ldops->owner); | |
174 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
175 | } | |
01e1abb2 AC |
176 | |
177 | /** | |
178 | * tty_ldisc_try_get - try and reference an ldisc | |
179 | * @disc: ldisc number | |
01e1abb2 AC |
180 | * |
181 | * Attempt to open and lock a line discipline into place. Return | |
c65c9bc3 | 182 | * the line discipline refcounted or an error. |
01e1abb2 AC |
183 | */ |
184 | ||
c65c9bc3 | 185 | static struct tty_ldisc *tty_ldisc_try_get(int disc) |
01e1abb2 | 186 | { |
c65c9bc3 | 187 | struct tty_ldisc *ld; |
01e1abb2 | 188 | struct tty_ldisc_ops *ldops; |
852e99d2 | 189 | |
c65c9bc3 AC |
190 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); |
191 | if (ld == NULL) | |
192 | return ERR_PTR(-ENOMEM); | |
193 | ||
f0de0e8d LT |
194 | ldops = get_ldops(disc); |
195 | if (IS_ERR(ldops)) { | |
8d2ead74 | 196 | kfree(ld); |
f0de0e8d | 197 | return ERR_CAST(ldops); |
8d2ead74 | 198 | } |
f0de0e8d LT |
199 | |
200 | ld->ops = ldops; | |
201 | atomic_set(&ld->users, 1); | |
c65c9bc3 | 202 | return ld; |
01e1abb2 AC |
203 | } |
204 | ||
205 | /** | |
206 | * tty_ldisc_get - take a reference to an ldisc | |
207 | * @disc: ldisc number | |
01e1abb2 AC |
208 | * |
209 | * Takes a reference to a line discipline. Deals with refcounts and | |
210 | * module locking counts. Returns NULL if the discipline is not available. | |
211 | * Returns a pointer to the discipline and bumps the ref count if it is | |
212 | * available | |
213 | * | |
214 | * Locking: | |
215 | * takes tty_ldisc_lock to guard against ldisc races | |
216 | */ | |
217 | ||
c65c9bc3 | 218 | static struct tty_ldisc *tty_ldisc_get(int disc) |
01e1abb2 | 219 | { |
c65c9bc3 | 220 | struct tty_ldisc *ld; |
01e1abb2 AC |
221 | |
222 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 AC |
223 | return ERR_PTR(-EINVAL); |
224 | ld = tty_ldisc_try_get(disc); | |
225 | if (IS_ERR(ld)) { | |
01e1abb2 | 226 | request_module("tty-ldisc-%d", disc); |
c65c9bc3 | 227 | ld = tty_ldisc_try_get(disc); |
01e1abb2 | 228 | } |
c65c9bc3 | 229 | return ld; |
01e1abb2 AC |
230 | } |
231 | ||
852e99d2 | 232 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
233 | { |
234 | return (*pos < NR_LDISCS) ? pos : NULL; | |
235 | } | |
236 | ||
852e99d2 | 237 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
238 | { |
239 | (*pos)++; | |
240 | return (*pos < NR_LDISCS) ? pos : NULL; | |
241 | } | |
242 | ||
243 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
244 | { | |
245 | } | |
246 | ||
247 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
248 | { | |
249 | int i = *(loff_t *)v; | |
f0de0e8d | 250 | struct tty_ldisc_ops *ldops; |
852e99d2 | 251 | |
f0de0e8d LT |
252 | ldops = get_ldops(i); |
253 | if (IS_ERR(ldops)) | |
01e1abb2 | 254 | return 0; |
f0de0e8d LT |
255 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
256 | put_ldops(ldops); | |
01e1abb2 AC |
257 | return 0; |
258 | } | |
259 | ||
260 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
261 | .start = tty_ldiscs_seq_start, | |
262 | .next = tty_ldiscs_seq_next, | |
263 | .stop = tty_ldiscs_seq_stop, | |
264 | .show = tty_ldiscs_seq_show, | |
265 | }; | |
266 | ||
267 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
268 | { | |
269 | return seq_open(file, &tty_ldiscs_seq_ops); | |
270 | } | |
271 | ||
272 | const struct file_operations tty_ldiscs_proc_fops = { | |
273 | .owner = THIS_MODULE, | |
274 | .open = proc_tty_ldiscs_open, | |
275 | .read = seq_read, | |
276 | .llseek = seq_lseek, | |
277 | .release = seq_release, | |
278 | }; | |
279 | ||
280 | /** | |
281 | * tty_ldisc_assign - set ldisc on a tty | |
282 | * @tty: tty to assign | |
283 | * @ld: line discipline | |
284 | * | |
285 | * Install an instance of a line discipline into a tty structure. The | |
8d2ead74 | 286 | * ldisc must have a reference count above zero to ensure it remains. |
01e1abb2 AC |
287 | * The tty instance refcount starts at zero. |
288 | * | |
289 | * Locking: | |
290 | * Caller must hold references | |
291 | */ | |
292 | ||
293 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
294 | { | |
c65c9bc3 | 295 | tty->ldisc = ld; |
01e1abb2 AC |
296 | } |
297 | ||
298 | /** | |
299 | * tty_ldisc_try - internal helper | |
300 | * @tty: the tty | |
301 | * | |
302 | * Make a single attempt to grab and bump the refcount on | |
303 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
304 | * used to implement both the waiting and non waiting versions | |
305 | * of tty_ldisc_ref | |
306 | * | |
307 | * Locking: takes tty_ldisc_lock | |
308 | */ | |
309 | ||
65b77046 | 310 | static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) |
01e1abb2 AC |
311 | { |
312 | unsigned long flags; | |
313 | struct tty_ldisc *ld; | |
01e1abb2 AC |
314 | |
315 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
65b77046 LT |
316 | ld = NULL; |
317 | if (test_bit(TTY_LDISC, &tty->flags)) | |
318 | ld = get_ldisc(tty->ldisc); | |
01e1abb2 | 319 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
65b77046 | 320 | return ld; |
01e1abb2 AC |
321 | } |
322 | ||
323 | /** | |
324 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
325 | * @tty: tty device | |
326 | * | |
327 | * Dereference the line discipline for the terminal and take a | |
328 | * reference to it. If the line discipline is in flux then | |
329 | * wait patiently until it changes. | |
330 | * | |
331 | * Note: Must not be called from an IRQ/timer context. The caller | |
332 | * must also be careful not to hold other locks that will deadlock | |
333 | * against a discipline change, such as an existing ldisc reference | |
334 | * (which we check for) | |
335 | * | |
336 | * Locking: call functions take tty_ldisc_lock | |
337 | */ | |
338 | ||
339 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
340 | { | |
65b77046 LT |
341 | struct tty_ldisc *ld; |
342 | ||
01e1abb2 | 343 | /* wait_event is a macro */ |
65b77046 LT |
344 | wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); |
345 | return ld; | |
01e1abb2 | 346 | } |
01e1abb2 AC |
347 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
348 | ||
349 | /** | |
350 | * tty_ldisc_ref - get the tty ldisc | |
351 | * @tty: tty device | |
352 | * | |
353 | * Dereference the line discipline for the terminal and take a | |
354 | * reference to it. If the line discipline is in flux then | |
355 | * return NULL. Can be called from IRQ and timer functions. | |
356 | * | |
357 | * Locking: called functions take tty_ldisc_lock | |
358 | */ | |
359 | ||
360 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
361 | { | |
65b77046 | 362 | return tty_ldisc_try(tty); |
01e1abb2 | 363 | } |
01e1abb2 AC |
364 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
365 | ||
366 | /** | |
367 | * tty_ldisc_deref - free a tty ldisc reference | |
368 | * @ld: reference to free up | |
369 | * | |
370 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
371 | * be called in IRQ context. | |
372 | * | |
373 | * Locking: takes tty_ldisc_lock | |
374 | */ | |
375 | ||
376 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
377 | { | |
65b77046 | 378 | put_ldisc(ld); |
01e1abb2 | 379 | } |
01e1abb2 AC |
380 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
381 | ||
65b77046 LT |
382 | static inline void tty_ldisc_put(struct tty_ldisc *ld) |
383 | { | |
384 | put_ldisc(ld); | |
385 | } | |
386 | ||
01e1abb2 AC |
387 | /** |
388 | * tty_ldisc_enable - allow ldisc use | |
389 | * @tty: terminal to activate ldisc on | |
390 | * | |
391 | * Set the TTY_LDISC flag when the line discipline can be called | |
c9b3976e AC |
392 | * again. Do necessary wakeups for existing sleepers. Clear the LDISC |
393 | * changing flag to indicate any ldisc change is now over. | |
01e1abb2 | 394 | * |
c9b3976e AC |
395 | * Note: nobody should set the TTY_LDISC bit except via this function. |
396 | * Clearing directly is allowed. | |
01e1abb2 AC |
397 | */ |
398 | ||
399 | void tty_ldisc_enable(struct tty_struct *tty) | |
400 | { | |
401 | set_bit(TTY_LDISC, &tty->flags); | |
c9b3976e | 402 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
01e1abb2 AC |
403 | wake_up(&tty_ldisc_wait); |
404 | } | |
405 | ||
f2c4c65c AC |
406 | /** |
407 | * tty_ldisc_flush - flush line discipline queue | |
408 | * @tty: tty | |
409 | * | |
410 | * Flush the line discipline queue (if any) for this tty. If there | |
411 | * is no line discipline active this is a no-op. | |
412 | */ | |
413 | ||
414 | void tty_ldisc_flush(struct tty_struct *tty) | |
415 | { | |
416 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
417 | if (ld) { | |
418 | if (ld->ops->flush_buffer) | |
419 | ld->ops->flush_buffer(tty); | |
420 | tty_ldisc_deref(ld); | |
421 | } | |
422 | tty_buffer_flush(tty); | |
423 | } | |
f2c4c65c AC |
424 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
425 | ||
01e1abb2 AC |
426 | /** |
427 | * tty_set_termios_ldisc - set ldisc field | |
428 | * @tty: tty structure | |
429 | * @num: line discipline number | |
430 | * | |
431 | * This is probably overkill for real world processors but | |
432 | * they are not on hot paths so a little discipline won't do | |
433 | * any harm. | |
434 | * | |
435 | * Locking: takes termios_mutex | |
436 | */ | |
437 | ||
438 | static void tty_set_termios_ldisc(struct tty_struct *tty, int num) | |
439 | { | |
440 | mutex_lock(&tty->termios_mutex); | |
441 | tty->termios->c_line = num; | |
442 | mutex_unlock(&tty->termios_mutex); | |
443 | } | |
444 | ||
c65c9bc3 AC |
445 | /** |
446 | * tty_ldisc_open - open a line discipline | |
447 | * @tty: tty we are opening the ldisc on | |
448 | * @ld: discipline to open | |
449 | * | |
450 | * A helper opening method. Also a convenient debugging and check | |
451 | * point. | |
452 | */ | |
453 | ||
454 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
455 | { | |
456 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
457 | if (ld->ops->open) | |
458 | return ld->ops->open(tty); | |
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); | |
c65c9bc3 | 532 | return cancel_delayed_work(&tty->buf.work); |
e8b70e7d AC |
533 | } |
534 | ||
01e1abb2 AC |
535 | /** |
536 | * tty_set_ldisc - set line discipline | |
537 | * @tty: the terminal to set | |
538 | * @ldisc: the line discipline | |
539 | * | |
540 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
541 | * context. The ldisc change logic has to protect itself against any |
542 | * overlapping ldisc change (including on the other end of pty pairs), | |
543 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 544 | * |
c65c9bc3 | 545 | * Locking: takes tty_ldisc_lock, termios_mutex |
01e1abb2 AC |
546 | */ |
547 | ||
548 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
549 | { | |
550 | int retval; | |
c65c9bc3 AC |
551 | struct tty_ldisc *o_ldisc, *new_ldisc; |
552 | int work, o_work = 0; | |
01e1abb2 AC |
553 | struct tty_struct *o_tty; |
554 | ||
c65c9bc3 AC |
555 | new_ldisc = tty_ldisc_get(ldisc); |
556 | if (IS_ERR(new_ldisc)) | |
557 | return PTR_ERR(new_ldisc); | |
01e1abb2 AC |
558 | |
559 | /* | |
c65c9bc3 AC |
560 | * We need to look at the tty locking here for pty/tty pairs |
561 | * when both sides try to change in parallel. | |
01e1abb2 AC |
562 | */ |
563 | ||
c65c9bc3 AC |
564 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
565 | ||
01e1abb2 | 566 | |
c65c9bc3 AC |
567 | /* |
568 | * Check the no-op case | |
569 | */ | |
570 | ||
571 | if (tty->ldisc->ops->num == ldisc) { | |
572 | tty_ldisc_put(new_ldisc); | |
01e1abb2 AC |
573 | return 0; |
574 | } | |
575 | ||
c65c9bc3 AC |
576 | /* |
577 | * Problem: What do we do if this blocks ? | |
578 | * We could deadlock here | |
579 | */ | |
580 | ||
581 | tty_wait_until_sent(tty, 0); | |
582 | ||
583 | mutex_lock(&tty->ldisc_mutex); | |
584 | ||
585 | /* | |
586 | * We could be midstream of another ldisc change which has | |
587 | * dropped the lock during processing. If so we need to wait. | |
588 | */ | |
589 | ||
590 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
591 | mutex_unlock(&tty->ldisc_mutex); | |
592 | wait_event(tty_ldisc_wait, | |
593 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
594 | mutex_lock(&tty->ldisc_mutex); | |
595 | } | |
596 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
852e99d2 | 597 | |
01e1abb2 AC |
598 | /* |
599 | * No more input please, we are switching. The new ldisc | |
600 | * will update this value in the ldisc open function | |
601 | */ | |
602 | ||
603 | tty->receive_room = 0; | |
604 | ||
605 | o_ldisc = tty->ldisc; | |
01e1abb2 AC |
606 | /* |
607 | * Make sure we don't change while someone holds a | |
608 | * reference to the line discipline. The TTY_LDISC bit | |
609 | * prevents anyone taking a reference once it is clear. | |
610 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
611 | * |
612 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
613 | * with a userspace app continually trying to use the tty in | |
614 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
615 | */ |
616 | ||
c65c9bc3 | 617 | work = tty_ldisc_halt(tty); |
01e1abb2 | 618 | if (o_tty) |
c65c9bc3 | 619 | o_work = tty_ldisc_halt(o_tty); |
01e1abb2 | 620 | |
01e1abb2 | 621 | /* |
c65c9bc3 AC |
622 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
623 | * We must drop the mutex here in case a hangup is also in process. | |
01e1abb2 | 624 | */ |
c65c9bc3 AC |
625 | |
626 | mutex_unlock(&tty->ldisc_mutex); | |
627 | ||
01e1abb2 | 628 | flush_scheduled_work(); |
c65c9bc3 | 629 | |
c65c9bc3 AC |
630 | mutex_lock(&tty->ldisc_mutex); |
631 | if (test_bit(TTY_HUPPED, &tty->flags)) { | |
632 | /* We were raced by the hangup method. It will have stomped | |
633 | the ldisc data and closed the ldisc down */ | |
634 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
635 | mutex_unlock(&tty->ldisc_mutex); | |
636 | tty_ldisc_put(new_ldisc); | |
637 | return -EIO; | |
638 | } | |
639 | ||
01e1abb2 | 640 | /* Shutdown the current discipline. */ |
c65c9bc3 | 641 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
642 | |
643 | /* Now set up the new line discipline. */ | |
c65c9bc3 | 644 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 645 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
646 | |
647 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 648 | if (retval < 0) { |
c65c9bc3 AC |
649 | /* Back to the old one or N_TTY if we can't */ |
650 | tty_ldisc_put(new_ldisc); | |
651 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 652 | } |
c65c9bc3 | 653 | |
01e1abb2 AC |
654 | /* At this point we hold a reference to the new ldisc and a |
655 | a reference to the old ldisc. If we ended up flipping back | |
656 | to the existing ldisc we have two references to it */ | |
657 | ||
c65c9bc3 | 658 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
659 | tty->ops->set_ldisc(tty); |
660 | ||
c65c9bc3 | 661 | tty_ldisc_put(o_ldisc); |
01e1abb2 AC |
662 | |
663 | /* | |
c65c9bc3 | 664 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
665 | */ |
666 | ||
667 | tty_ldisc_enable(tty); | |
668 | if (o_tty) | |
669 | tty_ldisc_enable(o_tty); | |
670 | ||
c65c9bc3 | 671 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 AC |
672 | already running */ |
673 | if (work) | |
674 | schedule_delayed_work(&tty->buf.work, 1); | |
c65c9bc3 AC |
675 | if (o_work) |
676 | schedule_delayed_work(&o_tty->buf.work, 1); | |
677 | mutex_unlock(&tty->ldisc_mutex); | |
01e1abb2 AC |
678 | return retval; |
679 | } | |
680 | ||
c65c9bc3 AC |
681 | /** |
682 | * tty_reset_termios - reset terminal state | |
683 | * @tty: tty to reset | |
684 | * | |
685 | * Restore a terminal to the driver default state. | |
686 | */ | |
687 | ||
688 | static void tty_reset_termios(struct tty_struct *tty) | |
689 | { | |
690 | mutex_lock(&tty->termios_mutex); | |
691 | *tty->termios = tty->driver->init_termios; | |
692 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); | |
693 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); | |
694 | mutex_unlock(&tty->termios_mutex); | |
695 | } | |
696 | ||
697 | ||
698 | /** | |
699 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
700 | * @tty: tty to reinit | |
701 | * | |
702 | * Switch the tty back to N_TTY line discipline and leave the | |
703 | * ldisc state closed | |
704 | */ | |
705 | ||
706 | static void tty_ldisc_reinit(struct tty_struct *tty) | |
707 | { | |
708 | struct tty_ldisc *ld; | |
709 | ||
710 | tty_ldisc_close(tty, tty->ldisc); | |
711 | tty_ldisc_put(tty->ldisc); | |
712 | tty->ldisc = NULL; | |
713 | /* | |
714 | * Switch the line discipline back | |
715 | */ | |
716 | ld = tty_ldisc_get(N_TTY); | |
717 | BUG_ON(IS_ERR(ld)); | |
718 | tty_ldisc_assign(tty, ld); | |
719 | tty_set_termios_ldisc(tty, N_TTY); | |
720 | } | |
721 | ||
722 | /** | |
723 | * tty_ldisc_hangup - hangup ldisc reset | |
724 | * @tty: tty being hung up | |
725 | * | |
726 | * Some tty devices reset their termios when they receive a hangup | |
727 | * event. In that situation we must also switch back to N_TTY properly | |
728 | * before we reset the termios data. | |
729 | * | |
730 | * Locking: We can take the ldisc mutex as the rest of the code is | |
731 | * careful to allow for this. | |
732 | * | |
733 | * In the pty pair case this occurs in the close() path of the | |
734 | * tty itself so we must be careful about locking rules. | |
735 | */ | |
736 | ||
737 | void tty_ldisc_hangup(struct tty_struct *tty) | |
738 | { | |
739 | struct tty_ldisc *ld; | |
740 | ||
741 | /* | |
742 | * FIXME! What are the locking issues here? This may me overdoing | |
743 | * things... This question is especially important now that we've | |
744 | * removed the irqlock. | |
745 | */ | |
746 | ld = tty_ldisc_ref(tty); | |
747 | if (ld != NULL) { | |
748 | /* We may have no line discipline at this point */ | |
749 | if (ld->ops->flush_buffer) | |
750 | ld->ops->flush_buffer(tty); | |
751 | tty_driver_flush_buffer(tty); | |
752 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
753 | ld->ops->write_wakeup) | |
754 | ld->ops->write_wakeup(tty); | |
755 | if (ld->ops->hangup) | |
756 | ld->ops->hangup(tty); | |
757 | tty_ldisc_deref(ld); | |
758 | } | |
759 | /* | |
760 | * FIXME: Once we trust the LDISC code better we can wait here for | |
761 | * ldisc completion and fix the driver call race | |
762 | */ | |
763 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
764 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
765 | /* | |
766 | * Shutdown the current line discipline, and reset it to | |
767 | * N_TTY. | |
768 | */ | |
769 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) { | |
5c58ceff LT |
770 | /* Make sure the old ldisc is quiescent */ |
771 | tty_ldisc_halt(tty); | |
772 | flush_scheduled_work(); | |
773 | ||
c8d50041 | 774 | /* Avoid racing set_ldisc or tty_ldisc_release */ |
c65c9bc3 | 775 | mutex_lock(&tty->ldisc_mutex); |
c8d50041 AC |
776 | if (tty->ldisc) { /* Not yet closed */ |
777 | /* Switch back to N_TTY */ | |
c8d50041 AC |
778 | tty_ldisc_reinit(tty); |
779 | /* At this point we have a closed ldisc and we want to | |
780 | reopen it. We could defer this to the next open but | |
781 | it means auditing a lot of other paths so this is | |
782 | a FIXME */ | |
783 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); | |
784 | tty_ldisc_enable(tty); | |
785 | } | |
c65c9bc3 AC |
786 | mutex_unlock(&tty->ldisc_mutex); |
787 | tty_reset_termios(tty); | |
788 | } | |
789 | } | |
01e1abb2 AC |
790 | |
791 | /** | |
792 | * tty_ldisc_setup - open line discipline | |
793 | * @tty: tty being shut down | |
794 | * @o_tty: pair tty for pty/tty pairs | |
795 | * | |
796 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
797 | * line disciplines and bind them to the tty. This has no locking issues |
798 | * as the device isn't yet active. | |
01e1abb2 AC |
799 | */ |
800 | ||
801 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
802 | { | |
c65c9bc3 | 803 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
804 | int retval; |
805 | ||
c65c9bc3 AC |
806 | retval = tty_ldisc_open(tty, ld); |
807 | if (retval) | |
808 | return retval; | |
809 | ||
810 | if (o_tty) { | |
811 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 812 | if (retval) { |
c65c9bc3 | 813 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
814 | return retval; |
815 | } | |
816 | tty_ldisc_enable(o_tty); | |
817 | } | |
818 | tty_ldisc_enable(tty); | |
819 | return 0; | |
820 | } | |
01e1abb2 AC |
821 | /** |
822 | * tty_ldisc_release - release line discipline | |
823 | * @tty: tty being shut down | |
824 | * @o_tty: pair tty for pty/tty pairs | |
825 | * | |
852e99d2 AC |
826 | * Called during the final close of a tty/pty pair in order to shut down |
827 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 828 | * ldisc has not been opened. |
01e1abb2 AC |
829 | */ |
830 | ||
831 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
832 | { | |
01e1abb2 AC |
833 | /* |
834 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then | |
835 | * kill any delayed work. As this is the final close it does not | |
836 | * race with the set_ldisc code path. | |
837 | */ | |
01e1abb2 | 838 | |
e8b70e7d | 839 | tty_ldisc_halt(tty); |
c65c9bc3 | 840 | flush_scheduled_work(); |
01e1abb2 | 841 | |
c8d50041 | 842 | mutex_lock(&tty->ldisc_mutex); |
01e1abb2 | 843 | /* |
aef29bc2 | 844 | * Now kill off the ldisc |
01e1abb2 | 845 | */ |
aef29bc2 AC |
846 | tty_ldisc_close(tty, tty->ldisc); |
847 | tty_ldisc_put(tty->ldisc); | |
848 | /* Force an oops if we mess this up */ | |
849 | tty->ldisc = NULL; | |
850 | ||
851 | /* Ensure the next open requests the N_TTY ldisc */ | |
852 | tty_set_termios_ldisc(tty, N_TTY); | |
c8d50041 | 853 | mutex_unlock(&tty->ldisc_mutex); |
01e1abb2 | 854 | |
c65c9bc3 AC |
855 | /* This will need doing differently if we need to lock */ |
856 | if (o_tty) | |
857 | tty_ldisc_release(o_tty, NULL); | |
aef29bc2 AC |
858 | |
859 | /* And the memory resources remaining (buffers, termios) will be | |
860 | disposed of when the kref hits zero */ | |
01e1abb2 AC |
861 | } |
862 | ||
863 | /** | |
864 | * tty_ldisc_init - ldisc setup for new tty | |
865 | * @tty: tty being allocated | |
866 | * | |
867 | * Set up the line discipline objects for a newly allocated tty. Note that | |
868 | * the tty structure is not completely set up when this call is made. | |
869 | */ | |
870 | ||
871 | void tty_ldisc_init(struct tty_struct *tty) | |
872 | { | |
c65c9bc3 AC |
873 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
874 | if (IS_ERR(ld)) | |
01e1abb2 | 875 | panic("n_tty: init_tty"); |
c65c9bc3 | 876 | tty_ldisc_assign(tty, ld); |
01e1abb2 AC |
877 | } |
878 | ||
879 | void tty_ldisc_begin(void) | |
880 | { | |
881 | /* Setup the default TTY line discipline. */ | |
882 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
883 | } |