Commit | Line | Data |
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e3b3d0f5 | 1 | // SPDX-License-Identifier: GPL-2.0 |
01e1abb2 | 2 | #include <linux/types.h> |
01e1abb2 | 3 | #include <linux/errno.h> |
8b3ffa17 | 4 | #include <linux/kmod.h> |
01e1abb2 AC |
5 | #include <linux/sched.h> |
6 | #include <linux/interrupt.h> | |
7 | #include <linux/tty.h> | |
8 | #include <linux/tty_driver.h> | |
01e1abb2 | 9 | #include <linux/file.h> |
01e1abb2 AC |
10 | #include <linux/mm.h> |
11 | #include <linux/string.h> | |
12 | #include <linux/slab.h> | |
13 | #include <linux/poll.h> | |
14 | #include <linux/proc_fs.h> | |
01e1abb2 | 15 | #include <linux/module.h> |
01e1abb2 AC |
16 | #include <linux/device.h> |
17 | #include <linux/wait.h> | |
18 | #include <linux/bitops.h> | |
01e1abb2 | 19 | #include <linux/seq_file.h> |
01e1abb2 | 20 | #include <linux/uaccess.h> |
0c73c08e | 21 | #include <linux/ratelimit.h> |
98602c01 | 22 | #include "tty.h" |
01e1abb2 | 23 | |
fc575ee6 PH |
24 | #undef LDISC_DEBUG_HANGUP |
25 | ||
26 | #ifdef LDISC_DEBUG_HANGUP | |
0a6adc13 | 27 | #define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) |
fc575ee6 PH |
28 | #else |
29 | #define tty_ldisc_debug(tty, f, args...) | |
30 | #endif | |
31 | ||
d2c43890 PH |
32 | /* lockdep nested classes for tty->ldisc_sem */ |
33 | enum { | |
34 | LDISC_SEM_NORMAL, | |
35 | LDISC_SEM_OTHER, | |
36 | }; | |
37 | ||
38 | ||
01e1abb2 AC |
39 | /* |
40 | * This guards the refcounted line discipline lists. The lock | |
41 | * must be taken with irqs off because there are hangup path | |
42 | * callers who will do ldisc lookups and cannot sleep. | |
43 | */ | |
44 | ||
137084bb | 45 | static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
01e1abb2 AC |
46 | /* Line disc dispatch table */ |
47 | static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; | |
48 | ||
49 | /** | |
cbb68f91 JS |
50 | * tty_register_ldisc - install a line discipline |
51 | * @new_ldisc: pointer to the ldisc object | |
01e1abb2 | 52 | * |
cbb68f91 JS |
53 | * Installs a new line discipline into the kernel. The discipline is set up as |
54 | * unreferenced and then made available to the kernel from this point onwards. | |
01e1abb2 | 55 | * |
cbb68f91 | 56 | * Locking: takes %tty_ldiscs_lock to guard against ldisc races |
01e1abb2 | 57 | */ |
fbadf70a | 58 | int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc) |
01e1abb2 AC |
59 | { |
60 | unsigned long flags; | |
01e1abb2 | 61 | |
fbadf70a | 62 | if (new_ldisc->num < N_TTY || new_ldisc->num >= NR_LDISCS) |
01e1abb2 AC |
63 | return -EINVAL; |
64 | ||
137084bb | 65 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
fbadf70a | 66 | tty_ldiscs[new_ldisc->num] = new_ldisc; |
137084bb | 67 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 | 68 | |
728648c7 | 69 | return 0; |
01e1abb2 AC |
70 | } |
71 | EXPORT_SYMBOL(tty_register_ldisc); | |
72 | ||
73 | /** | |
cbb68f91 JS |
74 | * tty_unregister_ldisc - unload a line discipline |
75 | * @ldisc: ldisc number | |
01e1abb2 | 76 | * |
cbb68f91 JS |
77 | * Remove a line discipline from the kernel providing it is not currently in |
78 | * use. | |
01e1abb2 | 79 | * |
cbb68f91 | 80 | * Locking: takes %tty_ldiscs_lock to guard against ldisc races |
01e1abb2 AC |
81 | */ |
82 | ||
f6f19595 | 83 | void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc) |
01e1abb2 AC |
84 | { |
85 | unsigned long flags; | |
01e1abb2 | 86 | |
137084bb | 87 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
19475209 | 88 | tty_ldiscs[ldisc->num] = NULL; |
137084bb | 89 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
01e1abb2 AC |
90 | } |
91 | EXPORT_SYMBOL(tty_unregister_ldisc); | |
92 | ||
f0de0e8d LT |
93 | static struct tty_ldisc_ops *get_ldops(int disc) |
94 | { | |
95 | unsigned long flags; | |
96 | struct tty_ldisc_ops *ldops, *ret; | |
97 | ||
137084bb | 98 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
99 | ret = ERR_PTR(-EINVAL); |
100 | ldops = tty_ldiscs[disc]; | |
101 | if (ldops) { | |
102 | ret = ERR_PTR(-EAGAIN); | |
19475209 | 103 | if (try_module_get(ldops->owner)) |
f0de0e8d | 104 | ret = ldops; |
f0de0e8d | 105 | } |
137084bb | 106 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d LT |
107 | return ret; |
108 | } | |
109 | ||
110 | static void put_ldops(struct tty_ldisc_ops *ldops) | |
111 | { | |
112 | unsigned long flags; | |
113 | ||
137084bb | 114 | raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
f0de0e8d | 115 | module_put(ldops->owner); |
137084bb | 116 | raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
f0de0e8d | 117 | } |
01e1abb2 | 118 | |
5fd8c2d3 | 119 | int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); |
cbb68f91 | 120 | |
01e1abb2 | 121 | /** |
cbb68f91 JS |
122 | * tty_ldisc_get - take a reference to an ldisc |
123 | * @tty: tty device | |
124 | * @disc: ldisc number | |
125 | * | |
126 | * Takes a reference to a line discipline. Deals with refcounts and module | |
127 | * locking counts. If the discipline is not available, its module loaded, if | |
128 | * possible. | |
129 | * | |
130 | * Returns: | |
131 | * * -%EINVAL if the discipline index is not [%N_TTY .. %NR_LDISCS] or if the | |
132 | * discipline is not registered | |
133 | * * -%EAGAIN if request_module() failed to load or register the discipline | |
134 | * * -%ENOMEM if allocation failure | |
135 | * * Otherwise, returns a pointer to the discipline and bumps the ref count | |
136 | * | |
137 | * Locking: takes %tty_ldiscs_lock to guard against ldisc races | |
01e1abb2 | 138 | */ |
36697529 | 139 | static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
01e1abb2 | 140 | { |
c65c9bc3 | 141 | struct tty_ldisc *ld; |
182274f8 | 142 | struct tty_ldisc_ops *ldops; |
01e1abb2 AC |
143 | |
144 | if (disc < N_TTY || disc >= NR_LDISCS) | |
c65c9bc3 | 145 | return ERR_PTR(-EINVAL); |
182274f8 LT |
146 | |
147 | /* | |
148 | * Get the ldisc ops - we may need to request them to be loaded | |
149 | * dynamically and try again. | |
150 | */ | |
151 | ldops = get_ldops(disc); | |
152 | if (IS_ERR(ldops)) { | |
7c0cca7c GKH |
153 | if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) |
154 | return ERR_PTR(-EPERM); | |
01e1abb2 | 155 | request_module("tty-ldisc-%d", disc); |
182274f8 LT |
156 | ldops = get_ldops(disc); |
157 | if (IS_ERR(ldops)) | |
158 | return ERR_CAST(ldops); | |
159 | } | |
160 | ||
bcdd0ca8 TH |
161 | /* |
162 | * There is no way to handle allocation failure of only 16 bytes. | |
163 | * Let's simplify error handling and save more memory. | |
164 | */ | |
165 | ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); | |
182274f8 | 166 | ld->ops = ldops; |
36697529 | 167 | ld->tty = tty; |
1541f845 | 168 | |
c65c9bc3 | 169 | return ld; |
01e1abb2 AC |
170 | } |
171 | ||
cbb68f91 JS |
172 | /** |
173 | * tty_ldisc_put - release the ldisc | |
174 | * @ld: lisdsc to release | |
734de249 | 175 | * |
cbb68f91 | 176 | * Complement of tty_ldisc_get(). |
734de249 | 177 | */ |
cb128f69 | 178 | static void tty_ldisc_put(struct tty_ldisc *ld) |
734de249 | 179 | { |
734de249 PH |
180 | if (WARN_ON_ONCE(!ld)) |
181 | return; | |
182 | ||
36697529 | 183 | put_ldops(ld->ops); |
734de249 | 184 | kfree(ld); |
734de249 PH |
185 | } |
186 | ||
852e99d2 | 187 | static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
01e1abb2 AC |
188 | { |
189 | return (*pos < NR_LDISCS) ? pos : NULL; | |
190 | } | |
191 | ||
852e99d2 | 192 | static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
01e1abb2 AC |
193 | { |
194 | (*pos)++; | |
195 | return (*pos < NR_LDISCS) ? pos : NULL; | |
196 | } | |
197 | ||
198 | static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) | |
199 | { | |
200 | } | |
201 | ||
202 | static int tty_ldiscs_seq_show(struct seq_file *m, void *v) | |
203 | { | |
204 | int i = *(loff_t *)v; | |
f0de0e8d | 205 | struct tty_ldisc_ops *ldops; |
852e99d2 | 206 | |
f0de0e8d LT |
207 | ldops = get_ldops(i); |
208 | if (IS_ERR(ldops)) | |
01e1abb2 | 209 | return 0; |
f0de0e8d LT |
210 | seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
211 | put_ldops(ldops); | |
01e1abb2 AC |
212 | return 0; |
213 | } | |
214 | ||
fddda2b7 | 215 | const struct seq_operations tty_ldiscs_seq_ops = { |
01e1abb2 AC |
216 | .start = tty_ldiscs_seq_start, |
217 | .next = tty_ldiscs_seq_next, | |
218 | .stop = tty_ldiscs_seq_stop, | |
219 | .show = tty_ldiscs_seq_show, | |
220 | }; | |
221 | ||
01e1abb2 | 222 | /** |
cbb68f91 JS |
223 | * tty_ldisc_ref_wait - wait for the tty ldisc |
224 | * @tty: tty device | |
01e1abb2 | 225 | * |
cbb68f91 JS |
226 | * Dereference the line discipline for the terminal and take a reference to it. |
227 | * If the line discipline is in flux then wait patiently until it changes. | |
01e1abb2 | 228 | * |
cbb68f91 JS |
229 | * Returns: %NULL if the tty has been hungup and not re-opened with a new file |
230 | * descriptor, otherwise valid ldisc reference | |
892d1fa7 | 231 | * |
cbb68f91 JS |
232 | * Note 1: Must not be called from an IRQ/timer context. The caller must also |
233 | * be careful not to hold other locks that will deadlock against a discipline | |
234 | * change, such as an existing ldisc reference (which we check for). | |
01e1abb2 | 235 | * |
cbb68f91 JS |
236 | * Note 2: a file_operations routine (read/poll/write) should use this function |
237 | * to wait for any ldisc lifetime events to finish. | |
01e1abb2 | 238 | */ |
01e1abb2 AC |
239 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |
240 | { | |
a4a3e061 DV |
241 | struct tty_ldisc *ld; |
242 | ||
36697529 | 243 | ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
a4a3e061 DV |
244 | ld = tty->ldisc; |
245 | if (!ld) | |
a570a49a | 246 | ldsem_up_read(&tty->ldisc_sem); |
a4a3e061 | 247 | return ld; |
01e1abb2 | 248 | } |
01e1abb2 AC |
249 | EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
250 | ||
251 | /** | |
cbb68f91 JS |
252 | * tty_ldisc_ref - get the tty ldisc |
253 | * @tty: tty device | |
01e1abb2 | 254 | * |
cbb68f91 JS |
255 | * Dereference the line discipline for the terminal and take a reference to it. |
256 | * If the line discipline is in flux then return %NULL. Can be called from IRQ | |
257 | * and timer functions. | |
01e1abb2 | 258 | */ |
01e1abb2 AC |
259 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) |
260 | { | |
36697529 PH |
261 | struct tty_ldisc *ld = NULL; |
262 | ||
263 | if (ldsem_down_read_trylock(&tty->ldisc_sem)) { | |
264 | ld = tty->ldisc; | |
265 | if (!ld) | |
266 | ldsem_up_read(&tty->ldisc_sem); | |
267 | } | |
268 | return ld; | |
01e1abb2 | 269 | } |
01e1abb2 AC |
270 | EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
271 | ||
272 | /** | |
cbb68f91 JS |
273 | * tty_ldisc_deref - free a tty ldisc reference |
274 | * @ld: reference to free up | |
01e1abb2 | 275 | * |
cbb68f91 JS |
276 | * Undoes the effect of tty_ldisc_ref() or tty_ldisc_ref_wait(). May be called |
277 | * in IRQ context. | |
01e1abb2 | 278 | */ |
01e1abb2 AC |
279 | void tty_ldisc_deref(struct tty_ldisc *ld) |
280 | { | |
36697529 | 281 | ldsem_up_read(&ld->tty->ldisc_sem); |
01e1abb2 | 282 | } |
01e1abb2 AC |
283 | EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
284 | ||
d2c43890 | 285 | |
c2bb524b | 286 | static inline int |
e80a10ee | 287 | __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
288 | { |
289 | return ldsem_down_write(&tty->ldisc_sem, timeout); | |
290 | } | |
291 | ||
c2bb524b | 292 | static inline int |
e80a10ee | 293 | __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
d2c43890 PH |
294 | { |
295 | return ldsem_down_write_nested(&tty->ldisc_sem, | |
296 | LDISC_SEM_OTHER, timeout); | |
297 | } | |
298 | ||
e80a10ee | 299 | static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
d2c43890 | 300 | { |
52772ea6 | 301 | ldsem_up_write(&tty->ldisc_sem); |
d2c43890 PH |
302 | } |
303 | ||
b027e229 | 304 | int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
fae76e9a PH |
305 | { |
306 | int ret; | |
307 | ||
c96cf923 DS |
308 | /* Kindly asking blocked readers to release the read side */ |
309 | set_bit(TTY_LDISC_CHANGING, &tty->flags); | |
310 | wake_up_interruptible_all(&tty->read_wait); | |
311 | wake_up_interruptible_all(&tty->write_wait); | |
312 | ||
fae76e9a PH |
313 | ret = __tty_ldisc_lock(tty, timeout); |
314 | if (!ret) | |
315 | return -EBUSY; | |
316 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
317 | return 0; | |
318 | } | |
319 | ||
b027e229 | 320 | void tty_ldisc_unlock(struct tty_struct *tty) |
fae76e9a PH |
321 | { |
322 | clear_bit(TTY_LDISC_HALTED, &tty->flags); | |
c96cf923 DS |
323 | /* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
324 | clear_bit(TTY_LDISC_CHANGING, &tty->flags); | |
fae76e9a PH |
325 | __tty_ldisc_unlock(tty); |
326 | } | |
327 | ||
c2bb524b | 328 | static int |
d2c43890 PH |
329 | tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
330 | unsigned long timeout) | |
331 | { | |
332 | int ret; | |
333 | ||
334 | if (tty < tty2) { | |
e80a10ee | 335 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 | 336 | if (ret) { |
e80a10ee | 337 | ret = __tty_ldisc_lock_nested(tty2, timeout); |
d2c43890 | 338 | if (!ret) |
e80a10ee | 339 | __tty_ldisc_unlock(tty); |
d2c43890 PH |
340 | } |
341 | } else { | |
342 | /* if this is possible, it has lots of implications */ | |
343 | WARN_ON_ONCE(tty == tty2); | |
344 | if (tty2 && tty != tty2) { | |
e80a10ee | 345 | ret = __tty_ldisc_lock(tty2, timeout); |
d2c43890 | 346 | if (ret) { |
e80a10ee | 347 | ret = __tty_ldisc_lock_nested(tty, timeout); |
d2c43890 | 348 | if (!ret) |
e80a10ee | 349 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
350 | } |
351 | } else | |
e80a10ee | 352 | ret = __tty_ldisc_lock(tty, timeout); |
d2c43890 PH |
353 | } |
354 | ||
355 | if (!ret) | |
356 | return -EBUSY; | |
357 | ||
358 | set_bit(TTY_LDISC_HALTED, &tty->flags); | |
359 | if (tty2) | |
360 | set_bit(TTY_LDISC_HALTED, &tty2->flags); | |
361 | return 0; | |
362 | } | |
363 | ||
c2bb524b | 364 | static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
d2c43890 PH |
365 | { |
366 | tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); | |
367 | } | |
368 | ||
c2bb524b PH |
369 | static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
370 | struct tty_struct *tty2) | |
d2c43890 | 371 | { |
e80a10ee | 372 | __tty_ldisc_unlock(tty); |
d2c43890 | 373 | if (tty2) |
e80a10ee | 374 | __tty_ldisc_unlock(tty2); |
d2c43890 PH |
375 | } |
376 | ||
f2c4c65c | 377 | /** |
cbb68f91 JS |
378 | * tty_ldisc_flush - flush line discipline queue |
379 | * @tty: tty to flush ldisc for | |
f2c4c65c | 380 | * |
cbb68f91 JS |
381 | * Flush the line discipline queue (if any) and the tty flip buffers for this |
382 | * @tty. | |
f2c4c65c | 383 | */ |
f2c4c65c AC |
384 | void tty_ldisc_flush(struct tty_struct *tty) |
385 | { | |
386 | struct tty_ldisc *ld = tty_ldisc_ref(tty); | |
86c80a8e PH |
387 | |
388 | tty_buffer_flush(tty, ld); | |
389 | if (ld) | |
f2c4c65c | 390 | tty_ldisc_deref(ld); |
f2c4c65c | 391 | } |
f2c4c65c AC |
392 | EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
393 | ||
01e1abb2 | 394 | /** |
cbb68f91 JS |
395 | * tty_set_termios_ldisc - set ldisc field |
396 | * @tty: tty structure | |
397 | * @disc: line discipline number | |
01e1abb2 | 398 | * |
cbb68f91 JS |
399 | * This is probably overkill for real world processors but they are not on hot |
400 | * paths so a little discipline won't do any harm. | |
01e1abb2 | 401 | * |
cbb68f91 JS |
402 | * The line discipline-related tty_struct fields are reset to prevent the ldisc |
403 | * driver from re-using stale information for the new ldisc instance. | |
dd42bf11 | 404 | * |
cbb68f91 | 405 | * Locking: takes termios_rwsem |
01e1abb2 | 406 | */ |
c12da96f | 407 | static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 408 | { |
6a1c0680 | 409 | down_write(&tty->termios_rwsem); |
c12da96f | 410 | tty->termios.c_line = disc; |
6a1c0680 | 411 | up_write(&tty->termios_rwsem); |
dd42bf11 PH |
412 | |
413 | tty->disc_data = NULL; | |
414 | tty->receive_room = 0; | |
01e1abb2 AC |
415 | } |
416 | ||
c65c9bc3 | 417 | /** |
cbb68f91 JS |
418 | * tty_ldisc_open - open a line discipline |
419 | * @tty: tty we are opening the ldisc on | |
420 | * @ld: discipline to open | |
c65c9bc3 | 421 | * |
cbb68f91 | 422 | * A helper opening method. Also a convenient debugging and check point. |
ec79d605 | 423 | * |
cbb68f91 | 424 | * Locking: always called with BTM already held. |
c65c9bc3 | 425 | */ |
c65c9bc3 AC |
426 | static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) |
427 | { | |
428 | WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); | |
f18f9498 AC |
429 | if (ld->ops->open) { |
430 | int ret; | |
5d3945e8 | 431 | /* BTM here locks versus a hangup event */ |
f18f9498 | 432 | ret = ld->ops->open(tty); |
7f90cfc5 JS |
433 | if (ret) |
434 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
fb6edc91 | 435 | |
a570a49a | 436 | tty_ldisc_debug(tty, "%p: opened\n", ld); |
f18f9498 AC |
437 | return ret; |
438 | } | |
c65c9bc3 AC |
439 | return 0; |
440 | } | |
441 | ||
442 | /** | |
cbb68f91 JS |
443 | * tty_ldisc_close - close a line discipline |
444 | * @tty: tty we are opening the ldisc on | |
445 | * @ld: discipline to close | |
c65c9bc3 | 446 | * |
cbb68f91 | 447 | * A helper close method. Also a convenient debugging and check point. |
c65c9bc3 | 448 | */ |
c65c9bc3 AC |
449 | static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) |
450 | { | |
9ffbe8ac | 451 | lockdep_assert_held_write(&tty->ldisc_sem); |
c65c9bc3 AC |
452 | WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
453 | clear_bit(TTY_LDISC_OPEN, &tty->flags); | |
454 | if (ld->ops->close) | |
455 | ld->ops->close(tty); | |
a570a49a | 456 | tty_ldisc_debug(tty, "%p: closed\n", ld); |
c65c9bc3 | 457 | } |
01e1abb2 | 458 | |
8a8dabf2 | 459 | /** |
cbb68f91 JS |
460 | * tty_ldisc_failto - helper for ldisc failback |
461 | * @tty: tty to open the ldisc on | |
462 | * @ld: ldisc we are trying to fail back to | |
8a8dabf2 | 463 | * |
cbb68f91 JS |
464 | * Helper to try and recover a tty when switching back to the old ldisc fails |
465 | * and we need something attached. | |
8a8dabf2 | 466 | */ |
8a8dabf2 AC |
467 | static int tty_ldisc_failto(struct tty_struct *tty, int ld) |
468 | { | |
469 | struct tty_ldisc *disc = tty_ldisc_get(tty, ld); | |
470 | int r; | |
471 | ||
9ffbe8ac | 472 | lockdep_assert_held_write(&tty->ldisc_sem); |
8a8dabf2 AC |
473 | if (IS_ERR(disc)) |
474 | return PTR_ERR(disc); | |
475 | tty->ldisc = disc; | |
476 | tty_set_termios_ldisc(tty, ld); | |
408795b0 XT |
477 | r = tty_ldisc_open(tty, disc); |
478 | if (r < 0) | |
8a8dabf2 AC |
479 | tty_ldisc_put(disc); |
480 | return r; | |
481 | } | |
482 | ||
a8983d01 | 483 | /** |
cbb68f91 JS |
484 | * tty_ldisc_restore - helper for tty ldisc change |
485 | * @tty: tty to recover | |
486 | * @old: previous ldisc | |
a8983d01 | 487 | * |
cbb68f91 JS |
488 | * Restore the previous line discipline or %N_TTY when a line discipline change |
489 | * fails due to an open error | |
a8983d01 | 490 | */ |
a8983d01 GKH |
491 | static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) |
492 | { | |
a8983d01 | 493 | /* There is an outstanding reference here so this is safe */ |
598c2d41 TH |
494 | if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
495 | const char *name = tty_name(tty); | |
496 | ||
497 | pr_warn("Falling back ldisc for %s.\n", name); | |
72a8dcd7 XT |
498 | /* |
499 | * The traditional behaviour is to fall back to N_TTY, we | |
500 | * want to avoid falling back to N_NULL unless we have no | |
501 | * choice to avoid the risk of breaking anything | |
502 | */ | |
8a8dabf2 AC |
503 | if (tty_ldisc_failto(tty, N_TTY) < 0 && |
504 | tty_ldisc_failto(tty, N_NULL) < 0) | |
598c2d41 | 505 | panic("Couldn't open N_NULL ldisc for %s.", name); |
a8983d01 GKH |
506 | } |
507 | } | |
508 | ||
01e1abb2 | 509 | /** |
cbb68f91 JS |
510 | * tty_set_ldisc - set line discipline |
511 | * @tty: the terminal to set | |
512 | * @disc: the line discipline number | |
513 | * | |
514 | * Set the discipline of a tty line. Must be called from a process context. The | |
515 | * ldisc change logic has to protect itself against any overlapping ldisc | |
516 | * change (including on the other end of pty pairs), the close of one side of a | |
517 | * tty/pty pair, and eventually hangup. | |
01e1abb2 | 518 | */ |
c12da96f | 519 | int tty_set_ldisc(struct tty_struct *tty, int disc) |
01e1abb2 | 520 | { |
a8983d01 GKH |
521 | int retval; |
522 | struct tty_ldisc *old_ldisc, *new_ldisc; | |
523 | ||
524 | new_ldisc = tty_ldisc_get(tty, disc); | |
525 | if (IS_ERR(new_ldisc)) | |
526 | return PTR_ERR(new_ldisc); | |
01e1abb2 | 527 | |
c8483bc9 | 528 | tty_lock(tty); |
276a661a | 529 | retval = tty_ldisc_lock(tty, 5 * HZ); |
63d8cb3f PH |
530 | if (retval) |
531 | goto err; | |
01e1abb2 | 532 | |
a570a49a PH |
533 | if (!tty->ldisc) { |
534 | retval = -EIO; | |
535 | goto out; | |
536 | } | |
537 | ||
63d8cb3f | 538 | /* Check the no-op case */ |
a8983d01 | 539 | if (tty->ldisc->ops->num == disc) |
63d8cb3f | 540 | goto out; |
c65c9bc3 | 541 | |
63d8cb3f PH |
542 | if (test_bit(TTY_HUPPED, &tty->flags)) { |
543 | /* We were raced by hangup */ | |
544 | retval = -EIO; | |
545 | goto out; | |
01e1abb2 AC |
546 | } |
547 | ||
a8983d01 GKH |
548 | old_ldisc = tty->ldisc; |
549 | ||
550 | /* Shutdown the old discipline. */ | |
551 | tty_ldisc_close(tty, old_ldisc); | |
552 | ||
553 | /* Now set up the new line discipline. */ | |
554 | tty->ldisc = new_ldisc; | |
555 | tty_set_termios_ldisc(tty, disc); | |
556 | ||
557 | retval = tty_ldisc_open(tty, new_ldisc); | |
01e1abb2 | 558 | if (retval < 0) { |
c65c9bc3 | 559 | /* Back to the old one or N_TTY if we can't */ |
a8983d01 GKH |
560 | tty_ldisc_put(new_ldisc); |
561 | tty_ldisc_restore(tty, old_ldisc); | |
01e1abb2 | 562 | } |
c65c9bc3 | 563 | |
a8983d01 | 564 | if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
9191aaaa | 565 | down_read(&tty->termios_rwsem); |
01e1abb2 | 566 | tty->ops->set_ldisc(tty); |
9191aaaa PH |
567 | up_read(&tty->termios_rwsem); |
568 | } | |
01e1abb2 | 569 | |
72a8dcd7 XT |
570 | /* |
571 | * At this point we hold a reference to the new ldisc and a | |
572 | * reference to the old ldisc, or we hold two references to | |
573 | * the old ldisc (if it was restored as part of error cleanup | |
574 | * above). In either case, releasing a single reference from | |
575 | * the old ldisc is correct. | |
576 | */ | |
a8983d01 | 577 | new_ldisc = old_ldisc; |
63d8cb3f | 578 | out: |
276a661a | 579 | tty_ldisc_unlock(tty); |
01e1abb2 | 580 | |
72a8dcd7 XT |
581 | /* |
582 | * Restart the work queue in case no characters kick it off. Safe if | |
583 | * already running | |
584 | */ | |
17a69219 | 585 | tty_buffer_restart_work(tty->port); |
63d8cb3f | 586 | err: |
a8983d01 | 587 | tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
89c8d91e | 588 | tty_unlock(tty); |
01e1abb2 AC |
589 | return retval; |
590 | } | |
1ab92da3 | 591 | EXPORT_SYMBOL_GPL(tty_set_ldisc); |
01e1abb2 | 592 | |
6ffeb4b2 | 593 | /** |
cbb68f91 JS |
594 | * tty_ldisc_kill - teardown ldisc |
595 | * @tty: tty being released | |
6ffeb4b2 | 596 | * |
cbb68f91 | 597 | * Perform final close of the ldisc and reset @tty->ldisc |
6ffeb4b2 PH |
598 | */ |
599 | static void tty_ldisc_kill(struct tty_struct *tty) | |
600 | { | |
9ffbe8ac | 601 | lockdep_assert_held_write(&tty->ldisc_sem); |
6ffeb4b2 PH |
602 | if (!tty->ldisc) |
603 | return; | |
604 | /* | |
605 | * Now kill off the ldisc | |
606 | */ | |
607 | tty_ldisc_close(tty, tty->ldisc); | |
608 | tty_ldisc_put(tty->ldisc); | |
609 | /* Force an oops if we mess this up */ | |
610 | tty->ldisc = NULL; | |
611 | } | |
612 | ||
c65c9bc3 | 613 | /** |
cbb68f91 JS |
614 | * tty_reset_termios - reset terminal state |
615 | * @tty: tty to reset | |
c65c9bc3 | 616 | * |
cbb68f91 | 617 | * Restore a terminal to the driver default state. |
c65c9bc3 | 618 | */ |
c65c9bc3 AC |
619 | static void tty_reset_termios(struct tty_struct *tty) |
620 | { | |
6a1c0680 | 621 | down_write(&tty->termios_rwsem); |
adc8d746 AC |
622 | tty->termios = tty->driver->init_termios; |
623 | tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); | |
624 | tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); | |
6a1c0680 | 625 | up_write(&tty->termios_rwsem); |
c65c9bc3 AC |
626 | } |
627 | ||
628 | ||
629 | /** | |
cbb68f91 JS |
630 | * tty_ldisc_reinit - reinitialise the tty ldisc |
631 | * @tty: tty to reinit | |
632 | * @disc: line discipline to reinitialize | |
c65c9bc3 | 633 | * |
cbb68f91 JS |
634 | * Completely reinitialize the line discipline state, by closing the current |
635 | * instance, if there is one, and opening a new instance. If an error occurs | |
636 | * opening the new non-%N_TTY instance, the instance is dropped and @tty->ldisc | |
637 | * reset to %NULL. The caller can then retry with %N_TTY instead. | |
7896f30d | 638 | * |
cbb68f91 | 639 | * Returns: 0 if successful, otherwise error code < 0 |
c65c9bc3 | 640 | */ |
892d1fa7 | 641 | int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
c65c9bc3 | 642 | { |
7896f30d PH |
643 | struct tty_ldisc *ld; |
644 | int retval; | |
1c95ba1e | 645 | |
9ffbe8ac | 646 | lockdep_assert_held_write(&tty->ldisc_sem); |
7896f30d | 647 | ld = tty_ldisc_get(tty, disc); |
a8983d01 GKH |
648 | if (IS_ERR(ld)) { |
649 | BUG_ON(disc == N_TTY); | |
7896f30d | 650 | return PTR_ERR(ld); |
a8983d01 | 651 | } |
c65c9bc3 | 652 | |
7896f30d PH |
653 | if (tty->ldisc) { |
654 | tty_ldisc_close(tty, tty->ldisc); | |
655 | tty_ldisc_put(tty->ldisc); | |
656 | } | |
657 | ||
658 | /* switch the line discipline */ | |
f4807045 | 659 | tty->ldisc = ld; |
c12da96f | 660 | tty_set_termios_ldisc(tty, disc); |
7896f30d PH |
661 | retval = tty_ldisc_open(tty, tty->ldisc); |
662 | if (retval) { | |
e65c62b1 JW |
663 | tty_ldisc_put(tty->ldisc); |
664 | tty->ldisc = NULL; | |
7896f30d PH |
665 | } |
666 | return retval; | |
c65c9bc3 AC |
667 | } |
668 | ||
669 | /** | |
cbb68f91 JS |
670 | * tty_ldisc_hangup - hangup ldisc reset |
671 | * @tty: tty being hung up | |
672 | * @reinit: whether to re-initialise the tty | |
c65c9bc3 | 673 | * |
cbb68f91 JS |
674 | * Some tty devices reset their termios when they receive a hangup event. In |
675 | * that situation we must also switch back to %N_TTY properly before we reset | |
676 | * the termios data. | |
c65c9bc3 | 677 | * |
cbb68f91 JS |
678 | * Locking: We can take the ldisc mutex as the rest of the code is careful to |
679 | * allow for this. | |
c65c9bc3 | 680 | * |
cbb68f91 JS |
681 | * In the pty pair case this occurs in the close() path of the tty itself so we |
682 | * must be careful about locking rules. | |
c65c9bc3 | 683 | */ |
892d1fa7 | 684 | void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) |
c65c9bc3 AC |
685 | { |
686 | struct tty_ldisc *ld; | |
687 | ||
a570a49a | 688 | tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); |
fc575ee6 | 689 | |
c65c9bc3 AC |
690 | ld = tty_ldisc_ref(tty); |
691 | if (ld != NULL) { | |
c65c9bc3 AC |
692 | if (ld->ops->flush_buffer) |
693 | ld->ops->flush_buffer(tty); | |
694 | tty_driver_flush_buffer(tty); | |
695 | if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && | |
696 | ld->ops->write_wakeup) | |
697 | ld->ops->write_wakeup(tty); | |
698 | if (ld->ops->hangup) | |
699 | ld->ops->hangup(tty); | |
700 | tty_ldisc_deref(ld); | |
701 | } | |
36697529 | 702 | |
a9a08845 LT |
703 | wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); |
704 | wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); | |
36697529 | 705 | |
c65c9bc3 AC |
706 | /* |
707 | * Shutdown the current line discipline, and reset it to | |
638b9648 AC |
708 | * N_TTY if need be. |
709 | * | |
710 | * Avoid racing set_ldisc or tty_ldisc_release | |
c65c9bc3 | 711 | */ |
fae76e9a | 712 | tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); |
60af22d2 | 713 | |
892d1fa7 PH |
714 | if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
715 | tty_reset_termios(tty); | |
c8785241 | 716 | |
892d1fa7 PH |
717 | if (tty->ldisc) { |
718 | if (reinit) { | |
e65c62b1 JW |
719 | if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
720 | tty_ldisc_reinit(tty, N_TTY) < 0) | |
721 | WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); | |
892d1fa7 PH |
722 | } else |
723 | tty_ldisc_kill(tty); | |
c65c9bc3 | 724 | } |
fae76e9a | 725 | tty_ldisc_unlock(tty); |
c65c9bc3 | 726 | } |
01e1abb2 AC |
727 | |
728 | /** | |
cbb68f91 JS |
729 | * tty_ldisc_setup - open line discipline |
730 | * @tty: tty being shut down | |
731 | * @o_tty: pair tty for pty/tty pairs | |
01e1abb2 | 732 | * |
cbb68f91 JS |
733 | * Called during the initial open of a tty/pty pair in order to set up the line |
734 | * disciplines and bind them to the @tty. This has no locking issues as the | |
735 | * device isn't yet active. | |
01e1abb2 | 736 | */ |
01e1abb2 AC |
737 | int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) |
738 | { | |
9de2a7ce | 739 | int retval = tty_ldisc_open(tty, tty->ldisc); |
d7238359 | 740 | |
c65c9bc3 AC |
741 | if (retval) |
742 | return retval; | |
743 | ||
744 | if (o_tty) { | |
110b8928 DS |
745 | /* |
746 | * Called without o_tty->ldisc_sem held, as o_tty has been | |
747 | * just allocated and no one has a reference to it. | |
748 | */ | |
c65c9bc3 | 749 | retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
01e1abb2 | 750 | if (retval) { |
9de2a7ce | 751 | tty_ldisc_close(tty, tty->ldisc); |
01e1abb2 AC |
752 | return retval; |
753 | } | |
01e1abb2 | 754 | } |
01e1abb2 AC |
755 | return 0; |
756 | } | |
89c8d91e | 757 | |
01e1abb2 | 758 | /** |
cbb68f91 JS |
759 | * tty_ldisc_release - release line discipline |
760 | * @tty: tty being shut down (or one end of pty pair) | |
3ee175d9 | 761 | * |
cbb68f91 JS |
762 | * Called during the final close of a tty or a pty pair in order to shut down |
763 | * the line discpline layer. On exit, each tty's ldisc is %NULL. | |
01e1abb2 | 764 | */ |
62462aef | 765 | void tty_ldisc_release(struct tty_struct *tty) |
01e1abb2 | 766 | { |
62462aef PH |
767 | struct tty_struct *o_tty = tty->link; |
768 | ||
01e1abb2 | 769 | /* |
a2965b7b PH |
770 | * Shutdown this line discipline. As this is the final close, |
771 | * it does not race with the set_ldisc code path. | |
01e1abb2 | 772 | */ |
01e1abb2 | 773 | |
36697529 | 774 | tty_ldisc_lock_pair(tty, o_tty); |
89c8d91e | 775 | tty_ldisc_kill(tty); |
c65c9bc3 | 776 | if (o_tty) |
89c8d91e | 777 | tty_ldisc_kill(o_tty); |
36697529 PH |
778 | tty_ldisc_unlock_pair(tty, o_tty); |
779 | ||
72a8dcd7 XT |
780 | /* |
781 | * And the memory resources remaining (buffers, termios) will be | |
782 | * disposed of when the kref hits zero | |
783 | */ | |
fc575ee6 | 784 | |
fb6edc91 | 785 | tty_ldisc_debug(tty, "released\n"); |
01e1abb2 AC |
786 | } |
787 | ||
788 | /** | |
cbb68f91 JS |
789 | * tty_ldisc_init - ldisc setup for new tty |
790 | * @tty: tty being allocated | |
01e1abb2 | 791 | * |
cbb68f91 JS |
792 | * Set up the line discipline objects for a newly allocated tty. Note that the |
793 | * tty structure is not completely set up when this call is made. | |
01e1abb2 | 794 | */ |
903f9db1 | 795 | int tty_ldisc_init(struct tty_struct *tty) |
01e1abb2 | 796 | { |
36697529 | 797 | struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
d7238359 | 798 | |
c65c9bc3 | 799 | if (IS_ERR(ld)) |
903f9db1 | 800 | return PTR_ERR(ld); |
f4807045 | 801 | tty->ldisc = ld; |
903f9db1 | 802 | return 0; |
01e1abb2 AC |
803 | } |
804 | ||
6716671d | 805 | /** |
cbb68f91 JS |
806 | * tty_ldisc_deinit - ldisc cleanup for new tty |
807 | * @tty: tty that was allocated recently | |
6716671d | 808 | * |
cbb68f91 JS |
809 | * The tty structure must not be completely set up (tty_ldisc_setup()) when |
810 | * this call is made. | |
6716671d JS |
811 | */ |
812 | void tty_ldisc_deinit(struct tty_struct *tty) | |
813 | { | |
110b8928 | 814 | /* no ldisc_sem, tty is being destroyed */ |
c8b710b3 PH |
815 | if (tty->ldisc) |
816 | tty_ldisc_put(tty->ldisc); | |
f4807045 | 817 | tty->ldisc = NULL; |
6716671d | 818 | } |