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