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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tty buffer allocation management
4 */
5
6#include <linux/types.h>
7#include <linux/errno.h>
8#include <linux/minmax.h>
9#include <linux/tty.h>
10#include <linux/tty_driver.h>
11#include <linux/tty_flip.h>
12#include <linux/timer.h>
13#include <linux/string.h>
14#include <linux/slab.h>
15#include <linux/sched.h>
16#include <linux/wait.h>
17#include <linux/bitops.h>
18#include <linux/delay.h>
19#include <linux/module.h>
20#include <linux/ratelimit.h>
21#include "tty.h"
22
23#define MIN_TTYB_SIZE 256
24#define TTYB_ALIGN_MASK 0xff
25
26/*
27 * Byte threshold to limit memory consumption for flip buffers.
28 * The actual memory limit is > 2x this amount.
29 */
30#define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL)
31
32/*
33 * We default to dicing tty buffer allocations to this many characters
34 * in order to avoid multiple page allocations. We know the size of
35 * tty_buffer itself but it must also be taken into account that the
36 * buffer is 256 byte aligned. See tty_buffer_find for the allocation
37 * logic this must match.
38 */
39
40#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~TTYB_ALIGN_MASK)
41
42/**
43 * tty_buffer_lock_exclusive - gain exclusive access to buffer
44 * @port: tty port owning the flip buffer
45 *
46 * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
47 * the buffer work and any pending flush from using the flip buffer. Data can
48 * continue to be added concurrently to the flip buffer from the driver side.
49 *
50 * See also tty_buffer_unlock_exclusive().
51 */
52void tty_buffer_lock_exclusive(struct tty_port *port)
53{
54 struct tty_bufhead *buf = &port->buf;
55
56 atomic_inc(&buf->priority);
57 mutex_lock(&buf->lock);
58}
59EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
60
61/**
62 * tty_buffer_unlock_exclusive - release exclusive access
63 * @port: tty port owning the flip buffer
64 *
65 * The buffer work is restarted if there is data in the flip buffer.
66 *
67 * See also tty_buffer_lock_exclusive().
68 */
69void tty_buffer_unlock_exclusive(struct tty_port *port)
70{
71 struct tty_bufhead *buf = &port->buf;
72 int restart;
73
74 restart = buf->head->commit != buf->head->read;
75
76 atomic_dec(&buf->priority);
77 mutex_unlock(&buf->lock);
78 if (restart)
79 queue_work(system_unbound_wq, &buf->work);
80}
81EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
82
83/**
84 * tty_buffer_space_avail - return unused buffer space
85 * @port: tty port owning the flip buffer
86 *
87 * Returns: the # of bytes which can be written by the driver without reaching
88 * the buffer limit.
89 *
90 * Note: this does not guarantee that memory is available to write the returned
91 * # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
92 * guarantee is required).
93 */
94unsigned int tty_buffer_space_avail(struct tty_port *port)
95{
96 int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
97
98 return max(space, 0);
99}
100EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
101
102static void tty_buffer_reset(struct tty_buffer *p, size_t size)
103{
104 p->used = 0;
105 p->size = size;
106 p->next = NULL;
107 p->commit = 0;
108 p->lookahead = 0;
109 p->read = 0;
110 p->flags = true;
111}
112
113/**
114 * tty_buffer_free_all - free buffers used by a tty
115 * @port: tty port to free from
116 *
117 * Remove all the buffers pending on a tty whether queued with data or in the
118 * free ring. Must be called when the tty is no longer in use.
119 */
120void tty_buffer_free_all(struct tty_port *port)
121{
122 struct tty_bufhead *buf = &port->buf;
123 struct tty_buffer *p, *next;
124 struct llist_node *llist;
125 unsigned int freed = 0;
126 int still_used;
127
128 while ((p = buf->head) != NULL) {
129 buf->head = p->next;
130 freed += p->size;
131 if (p->size > 0)
132 kfree(p);
133 }
134 llist = llist_del_all(&buf->free);
135 llist_for_each_entry_safe(p, next, llist, free)
136 kfree(p);
137
138 tty_buffer_reset(&buf->sentinel, 0);
139 buf->head = &buf->sentinel;
140 buf->tail = &buf->sentinel;
141
142 still_used = atomic_xchg(&buf->mem_used, 0);
143 WARN(still_used != freed, "we still have not freed %d bytes!",
144 still_used - freed);
145}
146
147/**
148 * tty_buffer_alloc - allocate a tty buffer
149 * @port: tty port
150 * @size: desired size (characters)
151 *
152 * Allocate a new tty buffer to hold the desired number of characters. We
153 * round our buffers off in 256 character chunks to get better allocation
154 * behaviour.
155 *
156 * Returns: %NULL if out of memory or the allocation would exceed the per
157 * device queue.
158 */
159static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
160{
161 struct llist_node *free;
162 struct tty_buffer *p;
163
164 /* Round the buffer size out */
165 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
166
167 if (size <= MIN_TTYB_SIZE) {
168 free = llist_del_first(&port->buf.free);
169 if (free) {
170 p = llist_entry(free, struct tty_buffer, free);
171 goto found;
172 }
173 }
174
175 /* Should possibly check if this fails for the largest buffer we
176 * have queued and recycle that ?
177 */
178 if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
179 return NULL;
180 p = kmalloc(sizeof(struct tty_buffer) + 2 * size,
181 GFP_ATOMIC | __GFP_NOWARN);
182 if (p == NULL)
183 return NULL;
184
185found:
186 tty_buffer_reset(p, size);
187 atomic_add(size, &port->buf.mem_used);
188 return p;
189}
190
191/**
192 * tty_buffer_free - free a tty buffer
193 * @port: tty port owning the buffer
194 * @b: the buffer to free
195 *
196 * Free a tty buffer, or add it to the free list according to our internal
197 * strategy.
198 */
199static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
200{
201 struct tty_bufhead *buf = &port->buf;
202
203 /* Dumb strategy for now - should keep some stats */
204 WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
205
206 if (b->size > MIN_TTYB_SIZE)
207 kfree(b);
208 else if (b->size > 0)
209 llist_add(&b->free, &buf->free);
210}
211
212/**
213 * tty_buffer_flush - flush full tty buffers
214 * @tty: tty to flush
215 * @ld: optional ldisc ptr (must be referenced)
216 *
217 * Flush all the buffers containing receive data. If @ld != %NULL, flush the
218 * ldisc input buffer.
219 *
220 * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
221 */
222void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
223{
224 struct tty_port *port = tty->port;
225 struct tty_bufhead *buf = &port->buf;
226 struct tty_buffer *next;
227
228 atomic_inc(&buf->priority);
229
230 mutex_lock(&buf->lock);
231 /* paired w/ release in __tty_buffer_request_room; ensures there are
232 * no pending memory accesses to the freed buffer
233 */
234 while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
235 tty_buffer_free(port, buf->head);
236 buf->head = next;
237 }
238 buf->head->read = buf->head->commit;
239 buf->head->lookahead = buf->head->read;
240
241 if (ld && ld->ops->flush_buffer)
242 ld->ops->flush_buffer(tty);
243
244 atomic_dec(&buf->priority);
245 mutex_unlock(&buf->lock);
246}
247
248/**
249 * __tty_buffer_request_room - grow tty buffer if needed
250 * @port: tty port
251 * @size: size desired
252 * @flags: buffer has to store flags along character data
253 *
254 * Make at least @size bytes of linear space available for the tty buffer.
255 *
256 * Will change over to a new buffer if the current buffer is encoded as
257 * %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
258 * buffer.
259 *
260 * Returns: the size we managed to find.
261 */
262static int __tty_buffer_request_room(struct tty_port *port, size_t size,
263 bool flags)
264{
265 struct tty_bufhead *buf = &port->buf;
266 struct tty_buffer *b, *n;
267 int left, change;
268
269 b = buf->tail;
270 if (!b->flags)
271 left = 2 * b->size - b->used;
272 else
273 left = b->size - b->used;
274
275 change = !b->flags && flags;
276 if (change || left < size) {
277 /* This is the slow path - looking for new buffers to use */
278 n = tty_buffer_alloc(port, size);
279 if (n != NULL) {
280 n->flags = flags;
281 buf->tail = n;
282 /*
283 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
284 * ensures they see all buffer data.
285 */
286 smp_store_release(&b->commit, b->used);
287 /*
288 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
289 * ensures the latest commit value can be read before the head
290 * is advanced to the next buffer.
291 */
292 smp_store_release(&b->next, n);
293 } else if (change)
294 size = 0;
295 else
296 size = left;
297 }
298 return size;
299}
300
301int tty_buffer_request_room(struct tty_port *port, size_t size)
302{
303 return __tty_buffer_request_room(port, size, true);
304}
305EXPORT_SYMBOL_GPL(tty_buffer_request_room);
306
307/**
308 * tty_insert_flip_string_fixed_flag - add characters to the tty buffer
309 * @port: tty port
310 * @chars: characters
311 * @flag: flag value for each character
312 * @size: size
313 *
314 * Queue a series of bytes to the tty buffering. All the characters passed are
315 * marked with the supplied flag.
316 *
317 * Returns: the number added.
318 */
319int tty_insert_flip_string_fixed_flag(struct tty_port *port,
320 const unsigned char *chars, char flag, size_t size)
321{
322 int copied = 0;
323 bool flags = flag != TTY_NORMAL;
324
325 do {
326 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
327 int space = __tty_buffer_request_room(port, goal, flags);
328 struct tty_buffer *tb = port->buf.tail;
329
330 if (unlikely(space == 0))
331 break;
332 memcpy(char_buf_ptr(tb, tb->used), chars, space);
333 if (tb->flags)
334 memset(flag_buf_ptr(tb, tb->used), flag, space);
335 tb->used += space;
336 copied += space;
337 chars += space;
338 /* There is a small chance that we need to split the data over
339 * several buffers. If this is the case we must loop.
340 */
341 } while (unlikely(size > copied));
342 return copied;
343}
344EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
345
346/**
347 * tty_insert_flip_string_flags - add characters to the tty buffer
348 * @port: tty port
349 * @chars: characters
350 * @flags: flag bytes
351 * @size: size
352 *
353 * Queue a series of bytes to the tty buffering. For each character the flags
354 * array indicates the status of the character.
355 *
356 * Returns: the number added.
357 */
358int tty_insert_flip_string_flags(struct tty_port *port,
359 const unsigned char *chars, const char *flags, size_t size)
360{
361 int copied = 0;
362
363 do {
364 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
365 int space = tty_buffer_request_room(port, goal);
366 struct tty_buffer *tb = port->buf.tail;
367
368 if (unlikely(space == 0))
369 break;
370 memcpy(char_buf_ptr(tb, tb->used), chars, space);
371 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
372 tb->used += space;
373 copied += space;
374 chars += space;
375 flags += space;
376 /* There is a small chance that we need to split the data over
377 * several buffers. If this is the case we must loop.
378 */
379 } while (unlikely(size > copied));
380 return copied;
381}
382EXPORT_SYMBOL(tty_insert_flip_string_flags);
383
384/**
385 * __tty_insert_flip_char - add one character to the tty buffer
386 * @port: tty port
387 * @ch: character
388 * @flag: flag byte
389 *
390 * Queue a single byte @ch to the tty buffering, with an optional flag. This is
391 * the slow path of tty_insert_flip_char().
392 */
393int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
394{
395 struct tty_buffer *tb;
396 bool flags = flag != TTY_NORMAL;
397
398 if (!__tty_buffer_request_room(port, 1, flags))
399 return 0;
400
401 tb = port->buf.tail;
402 if (tb->flags)
403 *flag_buf_ptr(tb, tb->used) = flag;
404 *char_buf_ptr(tb, tb->used++) = ch;
405
406 return 1;
407}
408EXPORT_SYMBOL(__tty_insert_flip_char);
409
410/**
411 * tty_prepare_flip_string - make room for characters
412 * @port: tty port
413 * @chars: return pointer for character write area
414 * @size: desired size
415 *
416 * Prepare a block of space in the buffer for data.
417 *
418 * This is used for drivers that need their own block copy routines into the
419 * buffer. There is no guarantee the buffer is a DMA target!
420 *
421 * Returns: the length available and buffer pointer (@chars) to the space which
422 * is now allocated and accounted for as ready for normal characters.
423 */
424int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
425 size_t size)
426{
427 int space = __tty_buffer_request_room(port, size, false);
428
429 if (likely(space)) {
430 struct tty_buffer *tb = port->buf.tail;
431
432 *chars = char_buf_ptr(tb, tb->used);
433 if (tb->flags)
434 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
435 tb->used += space;
436 }
437 return space;
438}
439EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
440
441/**
442 * tty_ldisc_receive_buf - forward data to line discipline
443 * @ld: line discipline to process input
444 * @p: char buffer
445 * @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
446 * @count: number of bytes to process
447 *
448 * Callers other than flush_to_ldisc() need to exclude the kworker from
449 * concurrent use of the line discipline, see paste_selection().
450 *
451 * Returns: the number of bytes processed.
452 */
453int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
454 const char *f, int count)
455{
456 if (ld->ops->receive_buf2)
457 count = ld->ops->receive_buf2(ld->tty, p, f, count);
458 else {
459 count = min_t(int, count, ld->tty->receive_room);
460 if (count && ld->ops->receive_buf)
461 ld->ops->receive_buf(ld->tty, p, f, count);
462 }
463 return count;
464}
465EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
466
467static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
468{
469 head->lookahead = max(head->lookahead, head->read);
470
471 while (head) {
472 struct tty_buffer *next;
473 unsigned int count;
474
475 /*
476 * Paired w/ release in __tty_buffer_request_room();
477 * ensures commit value read is not stale if the head
478 * is advancing to the next buffer.
479 */
480 next = smp_load_acquire(&head->next);
481 /*
482 * Paired w/ release in __tty_buffer_request_room() or in
483 * tty_buffer_flush(); ensures we see the committed buffer data.
484 */
485 count = smp_load_acquire(&head->commit) - head->lookahead;
486 if (!count) {
487 head = next;
488 continue;
489 }
490
491 if (port->client_ops->lookahead_buf) {
492 unsigned char *p, *f = NULL;
493
494 p = char_buf_ptr(head, head->lookahead);
495 if (head->flags)
496 f = flag_buf_ptr(head, head->lookahead);
497
498 port->client_ops->lookahead_buf(port, p, f, count);
499 }
500
501 head->lookahead += count;
502 }
503}
504
505static int
506receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
507{
508 unsigned char *p = char_buf_ptr(head, head->read);
509 const char *f = NULL;
510 int n;
511
512 if (head->flags)
513 f = flag_buf_ptr(head, head->read);
514
515 n = port->client_ops->receive_buf(port, p, f, count);
516 if (n > 0)
517 memset(p, 0, n);
518 return n;
519}
520
521/**
522 * flush_to_ldisc - flush data from buffer to ldisc
523 * @work: tty structure passed from work queue.
524 *
525 * This routine is called out of the software interrupt to flush data from the
526 * buffer chain to the line discipline.
527 *
528 * The receive_buf() method is single threaded for each tty instance.
529 *
530 * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
531 */
532static void flush_to_ldisc(struct work_struct *work)
533{
534 struct tty_port *port = container_of(work, struct tty_port, buf.work);
535 struct tty_bufhead *buf = &port->buf;
536
537 mutex_lock(&buf->lock);
538
539 while (1) {
540 struct tty_buffer *head = buf->head;
541 struct tty_buffer *next;
542 int count, rcvd;
543
544 /* Ldisc or user is trying to gain exclusive access */
545 if (atomic_read(&buf->priority))
546 break;
547
548 /* paired w/ release in __tty_buffer_request_room();
549 * ensures commit value read is not stale if the head
550 * is advancing to the next buffer
551 */
552 next = smp_load_acquire(&head->next);
553 /* paired w/ release in __tty_buffer_request_room() or in
554 * tty_buffer_flush(); ensures we see the committed buffer data
555 */
556 count = smp_load_acquire(&head->commit) - head->read;
557 if (!count) {
558 if (next == NULL)
559 break;
560 buf->head = next;
561 tty_buffer_free(port, head);
562 continue;
563 }
564
565 rcvd = receive_buf(port, head, count);
566 head->read += rcvd;
567 if (rcvd < count)
568 lookahead_bufs(port, head);
569 if (!rcvd)
570 break;
571
572 if (need_resched())
573 cond_resched();
574 }
575
576 mutex_unlock(&buf->lock);
577
578}
579
580static inline void tty_flip_buffer_commit(struct tty_buffer *tail)
581{
582 /*
583 * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
584 * buffer data.
585 */
586 smp_store_release(&tail->commit, tail->used);
587}
588
589/**
590 * tty_flip_buffer_push - push terminal buffers
591 * @port: tty port to push
592 *
593 * Queue a push of the terminal flip buffers to the line discipline. Can be
594 * called from IRQ/atomic context.
595 *
596 * In the event of the queue being busy for flipping the work will be held off
597 * and retried later.
598 */
599void tty_flip_buffer_push(struct tty_port *port)
600{
601 struct tty_bufhead *buf = &port->buf;
602
603 tty_flip_buffer_commit(buf->tail);
604 queue_work(system_unbound_wq, &buf->work);
605}
606EXPORT_SYMBOL(tty_flip_buffer_push);
607
608/**
609 * tty_insert_flip_string_and_push_buffer - add characters to the tty buffer and
610 * push
611 * @port: tty port
612 * @chars: characters
613 * @size: size
614 *
615 * The function combines tty_insert_flip_string() and tty_flip_buffer_push()
616 * with the exception of properly holding the @port->lock.
617 *
618 * To be used only internally (by pty currently).
619 *
620 * Returns: the number added.
621 */
622int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
623 const unsigned char *chars, size_t size)
624{
625 struct tty_bufhead *buf = &port->buf;
626 unsigned long flags;
627
628 spin_lock_irqsave(&port->lock, flags);
629 size = tty_insert_flip_string(port, chars, size);
630 if (size)
631 tty_flip_buffer_commit(buf->tail);
632 spin_unlock_irqrestore(&port->lock, flags);
633
634 queue_work(system_unbound_wq, &buf->work);
635
636 return size;
637}
638
639/**
640 * tty_buffer_init - prepare a tty buffer structure
641 * @port: tty port to initialise
642 *
643 * Set up the initial state of the buffer management for a tty device. Must be
644 * called before the other tty buffer functions are used.
645 */
646void tty_buffer_init(struct tty_port *port)
647{
648 struct tty_bufhead *buf = &port->buf;
649
650 mutex_init(&buf->lock);
651 tty_buffer_reset(&buf->sentinel, 0);
652 buf->head = &buf->sentinel;
653 buf->tail = &buf->sentinel;
654 init_llist_head(&buf->free);
655 atomic_set(&buf->mem_used, 0);
656 atomic_set(&buf->priority, 0);
657 INIT_WORK(&buf->work, flush_to_ldisc);
658 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
659}
660
661/**
662 * tty_buffer_set_limit - change the tty buffer memory limit
663 * @port: tty port to change
664 * @limit: memory limit to set
665 *
666 * Change the tty buffer memory limit.
667 *
668 * Must be called before the other tty buffer functions are used.
669 */
670int tty_buffer_set_limit(struct tty_port *port, int limit)
671{
672 if (limit < MIN_TTYB_SIZE)
673 return -EINVAL;
674 port->buf.mem_limit = limit;
675 return 0;
676}
677EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
678
679/* slave ptys can claim nested buffer lock when handling BRK and INTR */
680void tty_buffer_set_lock_subclass(struct tty_port *port)
681{
682 lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
683}
684
685bool tty_buffer_restart_work(struct tty_port *port)
686{
687 return queue_work(system_unbound_wq, &port->buf.work);
688}
689
690bool tty_buffer_cancel_work(struct tty_port *port)
691{
692 return cancel_work_sync(&port->buf.work);
693}
694
695void tty_buffer_flush_work(struct tty_port *port)
696{
697 flush_work(&port->buf.work);
698}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tty buffer allocation management
4 */
5
6#include <linux/types.h>
7#include <linux/errno.h>
8#include <linux/tty.h>
9#include <linux/tty_driver.h>
10#include <linux/tty_flip.h>
11#include <linux/timer.h>
12#include <linux/string.h>
13#include <linux/slab.h>
14#include <linux/sched.h>
15#include <linux/wait.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/module.h>
19#include <linux/ratelimit.h>
20
21
22#define MIN_TTYB_SIZE 256
23#define TTYB_ALIGN_MASK 255
24
25/*
26 * Byte threshold to limit memory consumption for flip buffers.
27 * The actual memory limit is > 2x this amount.
28 */
29#define TTYB_DEFAULT_MEM_LIMIT 65536
30
31/*
32 * We default to dicing tty buffer allocations to this many characters
33 * in order to avoid multiple page allocations. We know the size of
34 * tty_buffer itself but it must also be taken into account that the
35 * the buffer is 256 byte aligned. See tty_buffer_find for the allocation
36 * logic this must match
37 */
38
39#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
40
41/**
42 * tty_buffer_lock_exclusive - gain exclusive access to buffer
43 * tty_buffer_unlock_exclusive - release exclusive access
44 *
45 * @port - tty_port owning the flip buffer
46 *
47 * Guarantees safe use of the line discipline's receive_buf() method by
48 * excluding the buffer work and any pending flush from using the flip
49 * buffer. Data can continue to be added concurrently to the flip buffer
50 * from the driver side.
51 *
52 * On release, the buffer work is restarted if there is data in the
53 * flip buffer
54 */
55
56void tty_buffer_lock_exclusive(struct tty_port *port)
57{
58 struct tty_bufhead *buf = &port->buf;
59
60 atomic_inc(&buf->priority);
61 mutex_lock(&buf->lock);
62}
63EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
64
65void tty_buffer_unlock_exclusive(struct tty_port *port)
66{
67 struct tty_bufhead *buf = &port->buf;
68 int restart;
69
70 restart = buf->head->commit != buf->head->read;
71
72 atomic_dec(&buf->priority);
73 mutex_unlock(&buf->lock);
74 if (restart)
75 queue_work(system_unbound_wq, &buf->work);
76}
77EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
78
79/**
80 * tty_buffer_space_avail - return unused buffer space
81 * @port - tty_port owning the flip buffer
82 *
83 * Returns the # of bytes which can be written by the driver without
84 * reaching the buffer limit.
85 *
86 * Note: this does not guarantee that memory is available to write
87 * the returned # of bytes (use tty_prepare_flip_string_xxx() to
88 * pre-allocate if memory guarantee is required).
89 */
90
91int tty_buffer_space_avail(struct tty_port *port)
92{
93 int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
94 return max(space, 0);
95}
96EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
97
98static void tty_buffer_reset(struct tty_buffer *p, size_t size)
99{
100 p->used = 0;
101 p->size = size;
102 p->next = NULL;
103 p->commit = 0;
104 p->read = 0;
105 p->flags = 0;
106}
107
108/**
109 * tty_buffer_free_all - free buffers used by a tty
110 * @tty: tty to free from
111 *
112 * Remove all the buffers pending on a tty whether queued with data
113 * or in the free ring. Must be called when the tty is no longer in use
114 */
115
116void tty_buffer_free_all(struct tty_port *port)
117{
118 struct tty_bufhead *buf = &port->buf;
119 struct tty_buffer *p, *next;
120 struct llist_node *llist;
121
122 while ((p = buf->head) != NULL) {
123 buf->head = p->next;
124 if (p->size > 0)
125 kfree(p);
126 }
127 llist = llist_del_all(&buf->free);
128 llist_for_each_entry_safe(p, next, llist, free)
129 kfree(p);
130
131 tty_buffer_reset(&buf->sentinel, 0);
132 buf->head = &buf->sentinel;
133 buf->tail = &buf->sentinel;
134
135 atomic_set(&buf->mem_used, 0);
136}
137
138/**
139 * tty_buffer_alloc - allocate a tty buffer
140 * @tty: tty device
141 * @size: desired size (characters)
142 *
143 * Allocate a new tty buffer to hold the desired number of characters.
144 * We round our buffers off in 256 character chunks to get better
145 * allocation behaviour.
146 * Return NULL if out of memory or the allocation would exceed the
147 * per device queue
148 */
149
150static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
151{
152 struct llist_node *free;
153 struct tty_buffer *p;
154
155 /* Round the buffer size out */
156 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
157
158 if (size <= MIN_TTYB_SIZE) {
159 free = llist_del_first(&port->buf.free);
160 if (free) {
161 p = llist_entry(free, struct tty_buffer, free);
162 goto found;
163 }
164 }
165
166 /* Should possibly check if this fails for the largest buffer we
167 have queued and recycle that ? */
168 if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
169 return NULL;
170 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
171 if (p == NULL)
172 return NULL;
173
174found:
175 tty_buffer_reset(p, size);
176 atomic_add(size, &port->buf.mem_used);
177 return p;
178}
179
180/**
181 * tty_buffer_free - free a tty buffer
182 * @tty: tty owning the buffer
183 * @b: the buffer to free
184 *
185 * Free a tty buffer, or add it to the free list according to our
186 * internal strategy
187 */
188
189static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
190{
191 struct tty_bufhead *buf = &port->buf;
192
193 /* Dumb strategy for now - should keep some stats */
194 WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
195
196 if (b->size > MIN_TTYB_SIZE)
197 kfree(b);
198 else if (b->size > 0)
199 llist_add(&b->free, &buf->free);
200}
201
202/**
203 * tty_buffer_flush - flush full tty buffers
204 * @tty: tty to flush
205 * @ld: optional ldisc ptr (must be referenced)
206 *
207 * flush all the buffers containing receive data. If ld != NULL,
208 * flush the ldisc input buffer.
209 *
210 * Locking: takes buffer lock to ensure single-threaded flip buffer
211 * 'consumer'
212 */
213
214void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
215{
216 struct tty_port *port = tty->port;
217 struct tty_bufhead *buf = &port->buf;
218 struct tty_buffer *next;
219
220 atomic_inc(&buf->priority);
221
222 mutex_lock(&buf->lock);
223 /* paired w/ release in __tty_buffer_request_room; ensures there are
224 * no pending memory accesses to the freed buffer
225 */
226 while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
227 tty_buffer_free(port, buf->head);
228 buf->head = next;
229 }
230 buf->head->read = buf->head->commit;
231
232 if (ld && ld->ops->flush_buffer)
233 ld->ops->flush_buffer(tty);
234
235 atomic_dec(&buf->priority);
236 mutex_unlock(&buf->lock);
237}
238
239/**
240 * tty_buffer_request_room - grow tty buffer if needed
241 * @tty: tty structure
242 * @size: size desired
243 * @flags: buffer flags if new buffer allocated (default = 0)
244 *
245 * Make at least size bytes of linear space available for the tty
246 * buffer. If we fail return the size we managed to find.
247 *
248 * Will change over to a new buffer if the current buffer is encoded as
249 * TTY_NORMAL (so has no flags buffer) and the new buffer requires
250 * a flags buffer.
251 */
252static int __tty_buffer_request_room(struct tty_port *port, size_t size,
253 int flags)
254{
255 struct tty_bufhead *buf = &port->buf;
256 struct tty_buffer *b, *n;
257 int left, change;
258
259 b = buf->tail;
260 if (b->flags & TTYB_NORMAL)
261 left = 2 * b->size - b->used;
262 else
263 left = b->size - b->used;
264
265 change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
266 if (change || left < size) {
267 /* This is the slow path - looking for new buffers to use */
268 n = tty_buffer_alloc(port, size);
269 if (n != NULL) {
270 n->flags = flags;
271 buf->tail = n;
272 /* paired w/ acquire in flush_to_ldisc(); ensures
273 * flush_to_ldisc() sees buffer data.
274 */
275 smp_store_release(&b->commit, b->used);
276 /* paired w/ acquire in flush_to_ldisc(); ensures the
277 * latest commit value can be read before the head is
278 * advanced to the next buffer
279 */
280 smp_store_release(&b->next, n);
281 } else if (change)
282 size = 0;
283 else
284 size = left;
285 }
286 return size;
287}
288
289int tty_buffer_request_room(struct tty_port *port, size_t size)
290{
291 return __tty_buffer_request_room(port, size, 0);
292}
293EXPORT_SYMBOL_GPL(tty_buffer_request_room);
294
295/**
296 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
297 * @port: tty port
298 * @chars: characters
299 * @flag: flag value for each character
300 * @size: size
301 *
302 * Queue a series of bytes to the tty buffering. All the characters
303 * passed are marked with the supplied flag. Returns the number added.
304 */
305
306int tty_insert_flip_string_fixed_flag(struct tty_port *port,
307 const unsigned char *chars, char flag, size_t size)
308{
309 int copied = 0;
310 do {
311 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
312 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
313 int space = __tty_buffer_request_room(port, goal, flags);
314 struct tty_buffer *tb = port->buf.tail;
315 if (unlikely(space == 0))
316 break;
317 memcpy(char_buf_ptr(tb, tb->used), chars, space);
318 if (~tb->flags & TTYB_NORMAL)
319 memset(flag_buf_ptr(tb, tb->used), flag, space);
320 tb->used += space;
321 copied += space;
322 chars += space;
323 /* There is a small chance that we need to split the data over
324 several buffers. If this is the case we must loop */
325 } while (unlikely(size > copied));
326 return copied;
327}
328EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
329
330/**
331 * tty_insert_flip_string_flags - Add characters to the tty buffer
332 * @port: tty port
333 * @chars: characters
334 * @flags: flag bytes
335 * @size: size
336 *
337 * Queue a series of bytes to the tty buffering. For each character
338 * the flags array indicates the status of the character. Returns the
339 * number added.
340 */
341
342int tty_insert_flip_string_flags(struct tty_port *port,
343 const unsigned char *chars, const char *flags, size_t size)
344{
345 int copied = 0;
346 do {
347 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
348 int space = tty_buffer_request_room(port, goal);
349 struct tty_buffer *tb = port->buf.tail;
350 if (unlikely(space == 0))
351 break;
352 memcpy(char_buf_ptr(tb, tb->used), chars, space);
353 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
354 tb->used += space;
355 copied += space;
356 chars += space;
357 flags += space;
358 /* There is a small chance that we need to split the data over
359 several buffers. If this is the case we must loop */
360 } while (unlikely(size > copied));
361 return copied;
362}
363EXPORT_SYMBOL(tty_insert_flip_string_flags);
364
365/**
366 * __tty_insert_flip_char - Add one character to the tty buffer
367 * @port: tty port
368 * @ch: character
369 * @flag: flag byte
370 *
371 * Queue a single byte to the tty buffering, with an optional flag.
372 * This is the slow path of tty_insert_flip_char.
373 */
374int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
375{
376 struct tty_buffer *tb;
377 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
378
379 if (!__tty_buffer_request_room(port, 1, flags))
380 return 0;
381
382 tb = port->buf.tail;
383 if (~tb->flags & TTYB_NORMAL)
384 *flag_buf_ptr(tb, tb->used) = flag;
385 *char_buf_ptr(tb, tb->used++) = ch;
386
387 return 1;
388}
389EXPORT_SYMBOL(__tty_insert_flip_char);
390
391/**
392 * tty_schedule_flip - push characters to ldisc
393 * @port: tty port to push from
394 *
395 * Takes any pending buffers and transfers their ownership to the
396 * ldisc side of the queue. It then schedules those characters for
397 * processing by the line discipline.
398 */
399
400void tty_schedule_flip(struct tty_port *port)
401{
402 struct tty_bufhead *buf = &port->buf;
403
404 /* paired w/ acquire in flush_to_ldisc(); ensures
405 * flush_to_ldisc() sees buffer data.
406 */
407 smp_store_release(&buf->tail->commit, buf->tail->used);
408 queue_work(system_unbound_wq, &buf->work);
409}
410EXPORT_SYMBOL(tty_schedule_flip);
411
412/**
413 * tty_prepare_flip_string - make room for characters
414 * @port: tty port
415 * @chars: return pointer for character write area
416 * @size: desired size
417 *
418 * Prepare a block of space in the buffer for data. Returns the length
419 * available and buffer pointer to the space which is now allocated and
420 * accounted for as ready for normal characters. This is used for drivers
421 * that need their own block copy routines into the buffer. There is no
422 * guarantee the buffer is a DMA target!
423 */
424
425int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
426 size_t size)
427{
428 int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
429 if (likely(space)) {
430 struct tty_buffer *tb = port->buf.tail;
431 *chars = char_buf_ptr(tb, tb->used);
432 if (~tb->flags & TTYB_NORMAL)
433 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
434 tb->used += space;
435 }
436 return space;
437}
438EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
439
440/**
441 * tty_ldisc_receive_buf - forward data to line discipline
442 * @ld: line discipline to process input
443 * @p: char buffer
444 * @f: TTY_* flags buffer
445 * @count: number of bytes to process
446 *
447 * Callers other than flush_to_ldisc() need to exclude the kworker
448 * from concurrent use of the line discipline, see paste_selection().
449 *
450 * Returns the number of bytes processed
451 */
452int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
453 char *f, int count)
454{
455 if (ld->ops->receive_buf2)
456 count = ld->ops->receive_buf2(ld->tty, p, f, count);
457 else {
458 count = min_t(int, count, ld->tty->receive_room);
459 if (count && ld->ops->receive_buf)
460 ld->ops->receive_buf(ld->tty, p, f, count);
461 }
462 return count;
463}
464EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
465
466static int
467receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
468{
469 unsigned char *p = char_buf_ptr(head, head->read);
470 char *f = NULL;
471
472 if (~head->flags & TTYB_NORMAL)
473 f = flag_buf_ptr(head, head->read);
474
475 return port->client_ops->receive_buf(port, p, f, count);
476}
477
478/**
479 * flush_to_ldisc
480 * @work: tty structure passed from work queue.
481 *
482 * This routine is called out of the software interrupt to flush data
483 * from the buffer chain to the line discipline.
484 *
485 * The receive_buf method is single threaded for each tty instance.
486 *
487 * Locking: takes buffer lock to ensure single-threaded flip buffer
488 * 'consumer'
489 */
490
491static void flush_to_ldisc(struct work_struct *work)
492{
493 struct tty_port *port = container_of(work, struct tty_port, buf.work);
494 struct tty_bufhead *buf = &port->buf;
495
496 mutex_lock(&buf->lock);
497
498 while (1) {
499 struct tty_buffer *head = buf->head;
500 struct tty_buffer *next;
501 int count;
502
503 /* Ldisc or user is trying to gain exclusive access */
504 if (atomic_read(&buf->priority))
505 break;
506
507 /* paired w/ release in __tty_buffer_request_room();
508 * ensures commit value read is not stale if the head
509 * is advancing to the next buffer
510 */
511 next = smp_load_acquire(&head->next);
512 /* paired w/ release in __tty_buffer_request_room() or in
513 * tty_buffer_flush(); ensures we see the committed buffer data
514 */
515 count = smp_load_acquire(&head->commit) - head->read;
516 if (!count) {
517 if (next == NULL)
518 break;
519 buf->head = next;
520 tty_buffer_free(port, head);
521 continue;
522 }
523
524 count = receive_buf(port, head, count);
525 if (!count)
526 break;
527 head->read += count;
528 }
529
530 mutex_unlock(&buf->lock);
531
532}
533
534/**
535 * tty_flip_buffer_push - terminal
536 * @port: tty port to push
537 *
538 * Queue a push of the terminal flip buffers to the line discipline.
539 * Can be called from IRQ/atomic context.
540 *
541 * In the event of the queue being busy for flipping the work will be
542 * held off and retried later.
543 */
544
545void tty_flip_buffer_push(struct tty_port *port)
546{
547 tty_schedule_flip(port);
548}
549EXPORT_SYMBOL(tty_flip_buffer_push);
550
551/**
552 * tty_buffer_init - prepare a tty buffer structure
553 * @tty: tty to initialise
554 *
555 * Set up the initial state of the buffer management for a tty device.
556 * Must be called before the other tty buffer functions are used.
557 */
558
559void tty_buffer_init(struct tty_port *port)
560{
561 struct tty_bufhead *buf = &port->buf;
562
563 mutex_init(&buf->lock);
564 tty_buffer_reset(&buf->sentinel, 0);
565 buf->head = &buf->sentinel;
566 buf->tail = &buf->sentinel;
567 init_llist_head(&buf->free);
568 atomic_set(&buf->mem_used, 0);
569 atomic_set(&buf->priority, 0);
570 INIT_WORK(&buf->work, flush_to_ldisc);
571 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
572}
573
574/**
575 * tty_buffer_set_limit - change the tty buffer memory limit
576 * @port: tty port to change
577 *
578 * Change the tty buffer memory limit.
579 * Must be called before the other tty buffer functions are used.
580 */
581
582int tty_buffer_set_limit(struct tty_port *port, int limit)
583{
584 if (limit < MIN_TTYB_SIZE)
585 return -EINVAL;
586 port->buf.mem_limit = limit;
587 return 0;
588}
589EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
590
591/* slave ptys can claim nested buffer lock when handling BRK and INTR */
592void tty_buffer_set_lock_subclass(struct tty_port *port)
593{
594 lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
595}
596
597bool tty_buffer_restart_work(struct tty_port *port)
598{
599 return queue_work(system_unbound_wq, &port->buf.work);
600}
601
602bool tty_buffer_cancel_work(struct tty_port *port)
603{
604 return cancel_work_sync(&port->buf.work);
605}
606
607void tty_buffer_flush_work(struct tty_port *port)
608{
609 flush_work(&port->buf.work);
610}