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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 | ||
51 | /** | |
52 | * tty_register_ldisc - install a line discipline | |
53 | * @disc: ldisc number | |
54 | * @new_ldisc: pointer to the ldisc object | |
55 | * | |
56 | * Installs a new line discipline into the kernel. The discipline | |
57 | * is set up as unreferenced and then made available to the kernel | |
58 | * from this point onwards. | |
59 | * | |
60 | * Locking: | |
61 | * takes tty_ldisc_lock to guard against ldisc races | |
62 | */ | |
63 | ||
64 | int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) | |
65 | { | |
66 | unsigned long flags; | |
67 | int ret = 0; | |
68 | ||
69 | if (disc < N_TTY || disc >= NR_LDISCS) | |
70 | return -EINVAL; | |
71 | ||
72 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
73 | tty_ldiscs[disc] = new_ldisc; | |
74 | new_ldisc->num = disc; | |
75 | new_ldisc->refcount = 0; | |
76 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
77 | ||
78 | return ret; | |
79 | } | |
80 | EXPORT_SYMBOL(tty_register_ldisc); | |
81 | ||
82 | /** | |
83 | * tty_unregister_ldisc - unload a line discipline | |
84 | * @disc: ldisc number | |
85 | * @new_ldisc: pointer to the ldisc object | |
86 | * | |
87 | * Remove a line discipline from the kernel providing it is not | |
88 | * currently in use. | |
89 | * | |
90 | * Locking: | |
91 | * takes tty_ldisc_lock to guard against ldisc races | |
92 | */ | |
93 | ||
94 | int tty_unregister_ldisc(int disc) | |
95 | { | |
96 | unsigned long flags; | |
97 | int ret = 0; | |
98 | ||
99 | if (disc < N_TTY || disc >= NR_LDISCS) | |
100 | return -EINVAL; | |
101 | ||
102 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
103 | if (tty_ldiscs[disc]->refcount) | |
104 | ret = -EBUSY; | |
105 | else | |
106 | tty_ldiscs[disc] = NULL; | |
107 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
108 | ||
109 | return ret; | |
110 | } | |
111 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
112 | ||
113 | ||
114 | /** | |
115 | * tty_ldisc_try_get - try and reference an ldisc | |
116 | * @disc: ldisc number | |
01e1abb2 AC |
117 | * |
118 | * Attempt to open and lock a line discipline into place. Return | |
c65c9bc3 | 119 | * the line discipline refcounted or an error. |
01e1abb2 AC |
120 | */ |
121 | ||
c65c9bc3 | 122 | static struct tty_ldisc *tty_ldisc_try_get(int disc) |
01e1abb2 AC |
123 | { |
124 | unsigned long flags; | |
c65c9bc3 | 125 | struct tty_ldisc *ld; |
01e1abb2 AC |
126 | struct tty_ldisc_ops *ldops; |
127 | int err = -EINVAL; | |
852e99d2 | 128 | |
c65c9bc3 AC |
129 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); |
130 | if (ld == NULL) | |
131 | return ERR_PTR(-ENOMEM); | |
132 | ||
01e1abb2 AC |
133 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
134 | ld->ops = NULL; | |
135 | ldops = tty_ldiscs[disc]; | |
136 | /* Check the entry is defined */ | |
137 | if (ldops) { | |
138 | /* If the module is being unloaded we can't use it */ | |
139 | if (!try_module_get(ldops->owner)) | |
140 | err = -EAGAIN; | |
141 | else { | |
142 | /* lock it */ | |
143 | ldops->refcount++; | |
144 | ld->ops = ldops; | |
c65c9bc3 | 145 | ld->refcount = 0; |
01e1abb2 AC |
146 | err = 0; |
147 | } | |
148 | } | |
149 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
8d2ead74 AC |
150 | if (err) { |
151 | kfree(ld); | |
c65c9bc3 | 152 | return ERR_PTR(err); |
8d2ead74 | 153 | } |
c65c9bc3 | 154 | return ld; |
01e1abb2 AC |
155 | } |
156 | ||
157 | /** | |
158 | * tty_ldisc_get - take a reference to an ldisc | |
159 | * @disc: ldisc number | |
01e1abb2 AC |
160 | * |
161 | * Takes a reference to a line discipline. Deals with refcounts and | |
162 | * module locking counts. Returns NULL if the discipline is not available. | |
163 | * Returns a pointer to the discipline and bumps the ref count if it is | |
164 | * available | |
165 | * | |
166 | * Locking: | |
167 | * takes tty_ldisc_lock to guard against ldisc races | |
168 | */ | |
169 | ||
c65c9bc3 | 170 | static struct tty_ldisc *tty_ldisc_get(int disc) |
01e1abb2 | 171 | { |
c65c9bc3 | 172 | struct tty_ldisc *ld; |
01e1abb2 AC |
173 | |
174 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 AC |
175 | return ERR_PTR(-EINVAL); |
176 | ld = tty_ldisc_try_get(disc); | |
177 | if (IS_ERR(ld)) { | |
01e1abb2 | 178 | request_module("tty-ldisc-%d", disc); |
c65c9bc3 | 179 | ld = tty_ldisc_try_get(disc); |
01e1abb2 | 180 | } |
c65c9bc3 | 181 | return ld; |
01e1abb2 AC |
182 | } |
183 | ||
184 | /** | |
185 | * tty_ldisc_put - drop ldisc reference | |
c65c9bc3 | 186 | * @ld: ldisc |
01e1abb2 AC |
187 | * |
188 | * Drop a reference to a line discipline. Manage refcounts and | |
c65c9bc3 | 189 | * module usage counts. Free the ldisc once the recount hits zero. |
01e1abb2 AC |
190 | * |
191 | * Locking: | |
192 | * takes tty_ldisc_lock to guard against ldisc races | |
193 | */ | |
194 | ||
c65c9bc3 | 195 | static void tty_ldisc_put(struct tty_ldisc *ld) |
01e1abb2 AC |
196 | { |
197 | unsigned long flags; | |
c65c9bc3 AC |
198 | int disc = ld->ops->num; |
199 | struct tty_ldisc_ops *ldo; | |
01e1abb2 AC |
200 | |
201 | BUG_ON(disc < N_TTY || disc >= NR_LDISCS); | |
202 | ||
203 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
c65c9bc3 AC |
204 | ldo = tty_ldiscs[disc]; |
205 | BUG_ON(ldo->refcount == 0); | |
206 | ldo->refcount--; | |
207 | module_put(ldo->owner); | |
01e1abb2 | 208 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
677ca306 | 209 | WARN_ON(ld->refcount); |
c65c9bc3 | 210 | kfree(ld); |
01e1abb2 AC |
211 | } |
212 | ||
852e99d2 | 213 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
214 | { |
215 | return (*pos < NR_LDISCS) ? pos : NULL; | |
216 | } | |
217 | ||
852e99d2 | 218 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
219 | { |
220 | (*pos)++; | |
221 | return (*pos < NR_LDISCS) ? pos : NULL; | |
222 | } | |
223 | ||
224 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
225 | { | |
226 | } | |
227 | ||
228 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
229 | { | |
230 | int i = *(loff_t *)v; | |
c65c9bc3 | 231 | struct tty_ldisc *ld; |
852e99d2 | 232 | |
c65c9bc3 AC |
233 | ld = tty_ldisc_try_get(i); |
234 | if (IS_ERR(ld)) | |
01e1abb2 | 235 | return 0; |
c65c9bc3 AC |
236 | seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i); |
237 | tty_ldisc_put(ld); | |
01e1abb2 AC |
238 | return 0; |
239 | } | |
240 | ||
241 | static const struct seq_operations tty_ldiscs_seq_ops = { | |
242 | .start = tty_ldiscs_seq_start, | |
243 | .next = tty_ldiscs_seq_next, | |
244 | .stop = tty_ldiscs_seq_stop, | |
245 | .show = tty_ldiscs_seq_show, | |
246 | }; | |
247 | ||
248 | static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) | |
249 | { | |
250 | return seq_open(file, &tty_ldiscs_seq_ops); | |
251 | } | |
252 | ||
253 | const struct file_operations tty_ldiscs_proc_fops = { | |
254 | .owner = THIS_MODULE, | |
255 | .open = proc_tty_ldiscs_open, | |
256 | .read = seq_read, | |
257 | .llseek = seq_lseek, | |
258 | .release = seq_release, | |
259 | }; | |
260 | ||
261 | /** | |
262 | * tty_ldisc_assign - set ldisc on a tty | |
263 | * @tty: tty to assign | |
264 | * @ld: line discipline | |
265 | * | |
266 | * Install an instance of a line discipline into a tty structure. The | |
8d2ead74 | 267 | * ldisc must have a reference count above zero to ensure it remains. |
01e1abb2 AC |
268 | * The tty instance refcount starts at zero. |
269 | * | |
270 | * Locking: | |
271 | * Caller must hold references | |
272 | */ | |
273 | ||
274 | static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) | |
275 | { | |
c65c9bc3 | 276 | tty->ldisc = ld; |
01e1abb2 AC |
277 | } |
278 | ||
279 | /** | |
280 | * tty_ldisc_try - internal helper | |
281 | * @tty: the tty | |
282 | * | |
283 | * Make a single attempt to grab and bump the refcount on | |
284 | * the tty ldisc. Return 0 on failure or 1 on success. This is | |
285 | * used to implement both the waiting and non waiting versions | |
286 | * of tty_ldisc_ref | |
287 | * | |
288 | * Locking: takes tty_ldisc_lock | |
289 | */ | |
290 | ||
291 | static int tty_ldisc_try(struct tty_struct *tty) | |
292 | { | |
293 | unsigned long flags; | |
294 | struct tty_ldisc *ld; | |
295 | int ret = 0; | |
296 | ||
297 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
c65c9bc3 | 298 | ld = tty->ldisc; |
01e1abb2 AC |
299 | if (test_bit(TTY_LDISC, &tty->flags)) { |
300 | ld->refcount++; | |
301 | ret = 1; | |
302 | } | |
303 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
304 | return ret; | |
305 | } | |
306 | ||
307 | /** | |
308 | * tty_ldisc_ref_wait - wait for the tty ldisc | |
309 | * @tty: tty device | |
310 | * | |
311 | * Dereference the line discipline for the terminal and take a | |
312 | * reference to it. If the line discipline is in flux then | |
313 | * wait patiently until it changes. | |
314 | * | |
315 | * Note: Must not be called from an IRQ/timer context. The caller | |
316 | * must also be careful not to hold other locks that will deadlock | |
317 | * against a discipline change, such as an existing ldisc reference | |
318 | * (which we check for) | |
319 | * | |
320 | * Locking: call functions take tty_ldisc_lock | |
321 | */ | |
322 | ||
323 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) | |
324 | { | |
325 | /* wait_event is a macro */ | |
326 | wait_event(tty_ldisc_wait, tty_ldisc_try(tty)); | |
c65c9bc3 AC |
327 | WARN_ON(tty->ldisc->refcount == 0); |
328 | return tty->ldisc; | |
01e1abb2 | 329 | } |
01e1abb2 AC |
330 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
331 | ||
332 | /** | |
333 | * tty_ldisc_ref - get the tty ldisc | |
334 | * @tty: tty device | |
335 | * | |
336 | * Dereference the line discipline for the terminal and take a | |
337 | * reference to it. If the line discipline is in flux then | |
338 | * return NULL. Can be called from IRQ and timer functions. | |
339 | * | |
340 | * Locking: called functions take tty_ldisc_lock | |
341 | */ | |
342 | ||
343 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) | |
344 | { | |
345 | if (tty_ldisc_try(tty)) | |
c65c9bc3 | 346 | return tty->ldisc; |
01e1abb2 AC |
347 | return NULL; |
348 | } | |
01e1abb2 AC |
349 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
350 | ||
351 | /** | |
352 | * tty_ldisc_deref - free a tty ldisc reference | |
353 | * @ld: reference to free up | |
354 | * | |
355 | * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May | |
356 | * be called in IRQ context. | |
357 | * | |
358 | * Locking: takes tty_ldisc_lock | |
359 | */ | |
360 | ||
361 | void tty_ldisc_deref(struct tty_ldisc *ld) | |
362 | { | |
363 | unsigned long flags; | |
364 | ||
365 | BUG_ON(ld == NULL); | |
366 | ||
367 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
368 | if (ld->refcount == 0) | |
369 | printk(KERN_ERR "tty_ldisc_deref: no references.\n"); | |
370 | else | |
371 | ld->refcount--; | |
372 | if (ld->refcount == 0) | |
373 | wake_up(&tty_ldisc_wait); | |
374 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
375 | } | |
01e1abb2 AC |
376 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
377 | ||
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. | |
443 | */ | |
444 | ||
445 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) | |
446 | { | |
447 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
448 | if (ld->ops->open) | |
449 | return ld->ops->open(tty); | |
450 | return 0; | |
451 | } | |
452 | ||
453 | /** | |
454 | * tty_ldisc_close - close a line discipline | |
455 | * @tty: tty we are opening the ldisc on | |
456 | * @ld: discipline to close | |
457 | * | |
458 | * A helper close method. Also a convenient debugging and check | |
459 | * point. | |
460 | */ | |
461 | ||
462 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) | |
463 | { | |
464 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); | |
465 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
466 | if (ld->ops->close) | |
467 | ld->ops->close(tty); | |
468 | } | |
01e1abb2 AC |
469 | |
470 | /** | |
471 | * tty_ldisc_restore - helper for tty ldisc change | |
472 | * @tty: tty to recover | |
473 | * @old: previous ldisc | |
474 | * | |
475 | * Restore the previous line discipline or N_TTY when a line discipline | |
476 | * change fails due to an open error | |
477 | */ | |
478 | ||
479 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) | |
480 | { | |
481 | char buf[64]; | |
c65c9bc3 AC |
482 | struct tty_ldisc *new_ldisc; |
483 | int r; | |
01e1abb2 AC |
484 | |
485 | /* There is an outstanding reference here so this is safe */ | |
c65c9bc3 AC |
486 | old = tty_ldisc_get(old->ops->num); |
487 | WARN_ON(IS_ERR(old)); | |
01e1abb2 AC |
488 | tty_ldisc_assign(tty, old); |
489 | tty_set_termios_ldisc(tty, old->ops->num); | |
c65c9bc3 AC |
490 | if (tty_ldisc_open(tty, old) < 0) { |
491 | tty_ldisc_put(old); | |
01e1abb2 | 492 | /* This driver is always present */ |
852e99d2 | 493 | new_ldisc = tty_ldisc_get(N_TTY); |
c65c9bc3 | 494 | if (IS_ERR(new_ldisc)) |
01e1abb2 | 495 | panic("n_tty: get"); |
c65c9bc3 | 496 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 497 | tty_set_termios_ldisc(tty, N_TTY); |
c65c9bc3 AC |
498 | r = tty_ldisc_open(tty, new_ldisc); |
499 | if (r < 0) | |
500 | panic("Couldn't open N_TTY ldisc for " | |
501 | "%s --- error %d.", | |
502 | tty_name(tty, buf), r); | |
01e1abb2 AC |
503 | } |
504 | } | |
505 | ||
e8b70e7d | 506 | /** |
c65c9bc3 | 507 | * tty_ldisc_halt - shut down the line discipline |
e8b70e7d AC |
508 | * @tty: tty device |
509 | * | |
510 | * Shut down the line discipline and work queue for this tty device. | |
511 | * The TTY_LDISC flag being cleared ensures no further references can | |
512 | * be obtained while the delayed work queue halt ensures that no more | |
513 | * data is fed to the ldisc. | |
514 | * | |
852e99d2 | 515 | * In order to wait for any existing references to complete see |
e8b70e7d AC |
516 | * tty_ldisc_wait_idle. |
517 | */ | |
518 | ||
c65c9bc3 | 519 | static int tty_ldisc_halt(struct tty_struct *tty) |
e8b70e7d AC |
520 | { |
521 | clear_bit(TTY_LDISC, &tty->flags); | |
c65c9bc3 | 522 | return cancel_delayed_work(&tty->buf.work); |
e8b70e7d AC |
523 | } |
524 | ||
525 | /** | |
526 | * tty_ldisc_wait_idle - wait for the ldisc to become idle | |
527 | * @tty: tty to wait for | |
528 | * | |
529 | * Wait for the line discipline to become idle. The discipline must | |
530 | * have been halted for this to guarantee it remains idle. | |
531 | * | |
c65c9bc3 | 532 | * tty_ldisc_lock protects the ref counts currently. |
e8b70e7d AC |
533 | */ |
534 | ||
c65c9bc3 | 535 | static int tty_ldisc_wait_idle(struct tty_struct *tty) |
e8b70e7d AC |
536 | { |
537 | unsigned long flags; | |
538 | spin_lock_irqsave(&tty_ldisc_lock, flags); | |
c65c9bc3 | 539 | while (tty->ldisc->refcount) { |
e8b70e7d | 540 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); |
c65c9bc3 AC |
541 | if (wait_event_timeout(tty_ldisc_wait, |
542 | tty->ldisc->refcount == 0, 5 * HZ) == 0) | |
543 | return -EBUSY; | |
e8b70e7d AC |
544 | spin_lock_irqsave(&tty_ldisc_lock, flags); |
545 | } | |
546 | spin_unlock_irqrestore(&tty_ldisc_lock, flags); | |
c65c9bc3 | 547 | return 0; |
e8b70e7d AC |
548 | } |
549 | ||
01e1abb2 AC |
550 | /** |
551 | * tty_set_ldisc - set line discipline | |
552 | * @tty: the terminal to set | |
553 | * @ldisc: the line discipline | |
554 | * | |
555 | * Set the discipline of a tty line. Must be called from a process | |
c65c9bc3 AC |
556 | * context. The ldisc change logic has to protect itself against any |
557 | * overlapping ldisc change (including on the other end of pty pairs), | |
558 | * the close of one side of a tty/pty pair, and eventually hangup. | |
01e1abb2 | 559 | * |
c65c9bc3 | 560 | * Locking: takes tty_ldisc_lock, termios_mutex |
01e1abb2 AC |
561 | */ |
562 | ||
563 | int tty_set_ldisc(struct tty_struct *tty, int ldisc) | |
564 | { | |
565 | int retval; | |
c65c9bc3 AC |
566 | struct tty_ldisc *o_ldisc, *new_ldisc; |
567 | int work, o_work = 0; | |
01e1abb2 AC |
568 | struct tty_struct *o_tty; |
569 | ||
c65c9bc3 AC |
570 | new_ldisc = tty_ldisc_get(ldisc); |
571 | if (IS_ERR(new_ldisc)) | |
572 | return PTR_ERR(new_ldisc); | |
01e1abb2 AC |
573 | |
574 | /* | |
c65c9bc3 AC |
575 | * We need to look at the tty locking here for pty/tty pairs |
576 | * when both sides try to change in parallel. | |
01e1abb2 AC |
577 | */ |
578 | ||
c65c9bc3 AC |
579 | o_tty = tty->link; /* o_tty is the pty side or NULL */ |
580 | ||
01e1abb2 | 581 | |
c65c9bc3 AC |
582 | /* |
583 | * Check the no-op case | |
584 | */ | |
585 | ||
586 | if (tty->ldisc->ops->num == ldisc) { | |
587 | tty_ldisc_put(new_ldisc); | |
01e1abb2 AC |
588 | return 0; |
589 | } | |
590 | ||
c65c9bc3 AC |
591 | /* |
592 | * Problem: What do we do if this blocks ? | |
593 | * We could deadlock here | |
594 | */ | |
595 | ||
596 | tty_wait_until_sent(tty, 0); | |
597 | ||
598 | mutex_lock(&tty->ldisc_mutex); | |
599 | ||
600 | /* | |
601 | * We could be midstream of another ldisc change which has | |
602 | * dropped the lock during processing. If so we need to wait. | |
603 | */ | |
604 | ||
605 | while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { | |
606 | mutex_unlock(&tty->ldisc_mutex); | |
607 | wait_event(tty_ldisc_wait, | |
608 | test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); | |
609 | mutex_lock(&tty->ldisc_mutex); | |
610 | } | |
611 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
852e99d2 | 612 | |
01e1abb2 AC |
613 | /* |
614 | * No more input please, we are switching. The new ldisc | |
615 | * will update this value in the ldisc open function | |
616 | */ | |
617 | ||
618 | tty->receive_room = 0; | |
619 | ||
620 | o_ldisc = tty->ldisc; | |
01e1abb2 AC |
621 | /* |
622 | * Make sure we don't change while someone holds a | |
623 | * reference to the line discipline. The TTY_LDISC bit | |
624 | * prevents anyone taking a reference once it is clear. | |
625 | * We need the lock to avoid racing reference takers. | |
c9b3976e AC |
626 | * |
627 | * We must clear the TTY_LDISC bit here to avoid a livelock | |
628 | * with a userspace app continually trying to use the tty in | |
629 | * parallel to the change and re-referencing the tty. | |
01e1abb2 AC |
630 | */ |
631 | ||
c65c9bc3 | 632 | work = tty_ldisc_halt(tty); |
01e1abb2 | 633 | if (o_tty) |
c65c9bc3 | 634 | o_work = tty_ldisc_halt(o_tty); |
01e1abb2 | 635 | |
01e1abb2 | 636 | /* |
c65c9bc3 AC |
637 | * Wait for ->hangup_work and ->buf.work handlers to terminate. |
638 | * We must drop the mutex here in case a hangup is also in process. | |
01e1abb2 | 639 | */ |
c65c9bc3 AC |
640 | |
641 | mutex_unlock(&tty->ldisc_mutex); | |
642 | ||
01e1abb2 | 643 | flush_scheduled_work(); |
c65c9bc3 AC |
644 | |
645 | /* Let any existing reference holders finish */ | |
646 | retval = tty_ldisc_wait_idle(tty); | |
647 | if (retval < 0) { | |
648 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
649 | tty_ldisc_put(new_ldisc); | |
650 | return retval; | |
651 | } | |
652 | ||
653 | mutex_lock(&tty->ldisc_mutex); | |
654 | if (test_bit(TTY_HUPPED, &tty->flags)) { | |
655 | /* We were raced by the hangup method. It will have stomped | |
656 | the ldisc data and closed the ldisc down */ | |
657 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
658 | mutex_unlock(&tty->ldisc_mutex); | |
659 | tty_ldisc_put(new_ldisc); | |
660 | return -EIO; | |
661 | } | |
662 | ||
01e1abb2 | 663 | /* Shutdown the current discipline. */ |
c65c9bc3 | 664 | tty_ldisc_close(tty, o_ldisc); |
01e1abb2 AC |
665 | |
666 | /* Now set up the new line discipline. */ | |
c65c9bc3 | 667 | tty_ldisc_assign(tty, new_ldisc); |
01e1abb2 | 668 | tty_set_termios_ldisc(tty, ldisc); |
c65c9bc3 AC |
669 | |
670 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 671 | if (retval < 0) { |
c65c9bc3 AC |
672 | /* Back to the old one or N_TTY if we can't */ |
673 | tty_ldisc_put(new_ldisc); | |
674 | tty_ldisc_restore(tty, o_ldisc); | |
01e1abb2 | 675 | } |
c65c9bc3 | 676 | |
01e1abb2 AC |
677 | /* At this point we hold a reference to the new ldisc and a |
678 | a reference to the old ldisc. If we ended up flipping back | |
679 | to the existing ldisc we have two references to it */ | |
680 | ||
c65c9bc3 | 681 | if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
01e1abb2 AC |
682 | tty->ops->set_ldisc(tty); |
683 | ||
c65c9bc3 | 684 | tty_ldisc_put(o_ldisc); |
01e1abb2 AC |
685 | |
686 | /* | |
c65c9bc3 | 687 | * Allow ldisc referencing to occur again |
01e1abb2 AC |
688 | */ |
689 | ||
690 | tty_ldisc_enable(tty); | |
691 | if (o_tty) | |
692 | tty_ldisc_enable(o_tty); | |
693 | ||
c65c9bc3 | 694 | /* Restart the work queue in case no characters kick it off. Safe if |
01e1abb2 AC |
695 | already running */ |
696 | if (work) | |
697 | schedule_delayed_work(&tty->buf.work, 1); | |
c65c9bc3 AC |
698 | if (o_work) |
699 | schedule_delayed_work(&o_tty->buf.work, 1); | |
700 | mutex_unlock(&tty->ldisc_mutex); | |
01e1abb2 AC |
701 | return retval; |
702 | } | |
703 | ||
c65c9bc3 AC |
704 | /** |
705 | * tty_reset_termios - reset terminal state | |
706 | * @tty: tty to reset | |
707 | * | |
708 | * Restore a terminal to the driver default state. | |
709 | */ | |
710 | ||
711 | static void tty_reset_termios(struct tty_struct *tty) | |
712 | { | |
713 | mutex_lock(&tty->termios_mutex); | |
714 | *tty->termios = tty->driver->init_termios; | |
715 | tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); | |
716 | tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); | |
717 | mutex_unlock(&tty->termios_mutex); | |
718 | } | |
719 | ||
720 | ||
721 | /** | |
722 | * tty_ldisc_reinit - reinitialise the tty ldisc | |
723 | * @tty: tty to reinit | |
724 | * | |
725 | * Switch the tty back to N_TTY line discipline and leave the | |
726 | * ldisc state closed | |
727 | */ | |
728 | ||
729 | static void tty_ldisc_reinit(struct tty_struct *tty) | |
730 | { | |
731 | struct tty_ldisc *ld; | |
732 | ||
733 | tty_ldisc_close(tty, tty->ldisc); | |
734 | tty_ldisc_put(tty->ldisc); | |
735 | tty->ldisc = NULL; | |
736 | /* | |
737 | * Switch the line discipline back | |
738 | */ | |
739 | ld = tty_ldisc_get(N_TTY); | |
740 | BUG_ON(IS_ERR(ld)); | |
741 | tty_ldisc_assign(tty, ld); | |
742 | tty_set_termios_ldisc(tty, N_TTY); | |
743 | } | |
744 | ||
745 | /** | |
746 | * tty_ldisc_hangup - hangup ldisc reset | |
747 | * @tty: tty being hung up | |
748 | * | |
749 | * Some tty devices reset their termios when they receive a hangup | |
750 | * event. In that situation we must also switch back to N_TTY properly | |
751 | * before we reset the termios data. | |
752 | * | |
753 | * Locking: We can take the ldisc mutex as the rest of the code is | |
754 | * careful to allow for this. | |
755 | * | |
756 | * In the pty pair case this occurs in the close() path of the | |
757 | * tty itself so we must be careful about locking rules. | |
758 | */ | |
759 | ||
760 | void tty_ldisc_hangup(struct tty_struct *tty) | |
761 | { | |
762 | struct tty_ldisc *ld; | |
763 | ||
764 | /* | |
765 | * FIXME! What are the locking issues here? This may me overdoing | |
766 | * things... This question is especially important now that we've | |
767 | * removed the irqlock. | |
768 | */ | |
769 | ld = tty_ldisc_ref(tty); | |
770 | if (ld != NULL) { | |
771 | /* We may have no line discipline at this point */ | |
772 | if (ld->ops->flush_buffer) | |
773 | ld->ops->flush_buffer(tty); | |
774 | tty_driver_flush_buffer(tty); | |
775 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
776 | ld->ops->write_wakeup) | |
777 | ld->ops->write_wakeup(tty); | |
778 | if (ld->ops->hangup) | |
779 | ld->ops->hangup(tty); | |
780 | tty_ldisc_deref(ld); | |
781 | } | |
782 | /* | |
783 | * FIXME: Once we trust the LDISC code better we can wait here for | |
784 | * ldisc completion and fix the driver call race | |
785 | */ | |
786 | wake_up_interruptible_poll(&tty->write_wait, POLLOUT); | |
787 | wake_up_interruptible_poll(&tty->read_wait, POLLIN); | |
788 | /* | |
789 | * Shutdown the current line discipline, and reset it to | |
790 | * N_TTY. | |
791 | */ | |
792 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) { | |
793 | /* Avoid racing set_ldisc */ | |
794 | mutex_lock(&tty->ldisc_mutex); | |
795 | /* Switch back to N_TTY */ | |
52856ed7 AC |
796 | tty_ldisc_halt(tty); |
797 | tty_ldisc_wait_idle(tty); | |
c65c9bc3 AC |
798 | tty_ldisc_reinit(tty); |
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 a FIXME */ | |
802 | WARN_ON(tty_ldisc_open(tty, tty->ldisc)); | |
803 | tty_ldisc_enable(tty); | |
804 | mutex_unlock(&tty->ldisc_mutex); | |
805 | tty_reset_termios(tty); | |
806 | } | |
807 | } | |
01e1abb2 AC |
808 | |
809 | /** | |
810 | * tty_ldisc_setup - open line discipline | |
811 | * @tty: tty being shut down | |
812 | * @o_tty: pair tty for pty/tty pairs | |
813 | * | |
814 | * Called during the initial open of a tty/pty pair in order to set up the | |
c65c9bc3 AC |
815 | * line disciplines and bind them to the tty. This has no locking issues |
816 | * as the device isn't yet active. | |
01e1abb2 AC |
817 | */ |
818 | ||
819 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) | |
820 | { | |
c65c9bc3 | 821 | struct tty_ldisc *ld = tty->ldisc; |
01e1abb2 AC |
822 | int retval; |
823 | ||
c65c9bc3 AC |
824 | retval = tty_ldisc_open(tty, ld); |
825 | if (retval) | |
826 | return retval; | |
827 | ||
828 | if (o_tty) { | |
829 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); | |
01e1abb2 | 830 | if (retval) { |
c65c9bc3 | 831 | tty_ldisc_close(tty, ld); |
01e1abb2 AC |
832 | return retval; |
833 | } | |
834 | tty_ldisc_enable(o_tty); | |
835 | } | |
836 | tty_ldisc_enable(tty); | |
837 | return 0; | |
838 | } | |
01e1abb2 AC |
839 | /** |
840 | * tty_ldisc_release - release line discipline | |
841 | * @tty: tty being shut down | |
842 | * @o_tty: pair tty for pty/tty pairs | |
843 | * | |
852e99d2 AC |
844 | * Called during the final close of a tty/pty pair in order to shut down |
845 | * the line discpline layer. On exit the ldisc assigned is N_TTY and the | |
c65c9bc3 | 846 | * ldisc has not been opened. |
01e1abb2 AC |
847 | */ |
848 | ||
849 | void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) | |
850 | { | |
01e1abb2 AC |
851 | /* |
852 | * Prevent flush_to_ldisc() from rescheduling the work for later. Then | |
853 | * kill any delayed work. As this is the final close it does not | |
854 | * race with the set_ldisc code path. | |
855 | */ | |
01e1abb2 | 856 | |
e8b70e7d | 857 | tty_ldisc_halt(tty); |
c65c9bc3 | 858 | flush_scheduled_work(); |
01e1abb2 AC |
859 | |
860 | /* | |
861 | * Wait for any short term users (we know they are just driver | |
862 | * side waiters as the file is closing so user count on the file | |
863 | * side is zero. | |
864 | */ | |
e8b70e7d AC |
865 | |
866 | tty_ldisc_wait_idle(tty); | |
867 | ||
01e1abb2 | 868 | /* |
aef29bc2 | 869 | * Now kill off the ldisc |
01e1abb2 | 870 | */ |
aef29bc2 AC |
871 | tty_ldisc_close(tty, tty->ldisc); |
872 | tty_ldisc_put(tty->ldisc); | |
873 | /* Force an oops if we mess this up */ | |
874 | tty->ldisc = NULL; | |
875 | ||
876 | /* Ensure the next open requests the N_TTY ldisc */ | |
877 | tty_set_termios_ldisc(tty, N_TTY); | |
01e1abb2 | 878 | |
c65c9bc3 AC |
879 | /* This will need doing differently if we need to lock */ |
880 | if (o_tty) | |
881 | tty_ldisc_release(o_tty, NULL); | |
aef29bc2 AC |
882 | |
883 | /* And the memory resources remaining (buffers, termios) will be | |
884 | disposed of when the kref hits zero */ | |
01e1abb2 AC |
885 | } |
886 | ||
887 | /** | |
888 | * tty_ldisc_init - ldisc setup for new tty | |
889 | * @tty: tty being allocated | |
890 | * | |
891 | * Set up the line discipline objects for a newly allocated tty. Note that | |
892 | * the tty structure is not completely set up when this call is made. | |
893 | */ | |
894 | ||
895 | void tty_ldisc_init(struct tty_struct *tty) | |
896 | { | |
c65c9bc3 AC |
897 | struct tty_ldisc *ld = tty_ldisc_get(N_TTY); |
898 | if (IS_ERR(ld)) | |
01e1abb2 | 899 | panic("n_tty: init_tty"); |
c65c9bc3 | 900 | tty_ldisc_assign(tty, ld); |
01e1abb2 AC |
901 | } |
902 | ||
903 | void tty_ldisc_begin(void) | |
904 | { | |
905 | /* Setup the default TTY line discipline. */ | |
906 | (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); | |
907 | } |