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