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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/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}
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/**
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 *
206 * flush all the buffers containing receive data.
207 *
208 * Locking: takes buffer lock to ensure single-threaded flip buffer
209 * 'consumer'
210 */
211
212void tty_buffer_flush(struct tty_struct *tty)
213{
214 struct tty_port *port = tty->port;
215 struct tty_bufhead *buf = &port->buf;
216 struct tty_buffer *next;
217
218 atomic_inc(&buf->priority);
219
220 mutex_lock(&buf->lock);
221 while ((next = buf->head->next) != NULL) {
222 tty_buffer_free(port, buf->head);
223 buf->head = next;
224 }
225 buf->head->read = buf->head->commit;
226 atomic_dec(&buf->priority);
227 mutex_unlock(&buf->lock);
228}
229
230/**
231 * tty_buffer_request_room - grow tty buffer if needed
232 * @tty: tty structure
233 * @size: size desired
234 * @flags: buffer flags if new buffer allocated (default = 0)
235 *
236 * Make at least size bytes of linear space available for the tty
237 * buffer. If we fail return the size we managed to find.
238 *
239 * Will change over to a new buffer if the current buffer is encoded as
240 * TTY_NORMAL (so has no flags buffer) and the new buffer requires
241 * a flags buffer.
242 */
243static int __tty_buffer_request_room(struct tty_port *port, size_t size,
244 int flags)
245{
246 struct tty_bufhead *buf = &port->buf;
247 struct tty_buffer *b, *n;
248 int left, change;
249
250 b = buf->tail;
251 if (b->flags & TTYB_NORMAL)
252 left = 2 * b->size - b->used;
253 else
254 left = b->size - b->used;
255
256 change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
257 if (change || left < size) {
258 /* This is the slow path - looking for new buffers to use */
259 if ((n = tty_buffer_alloc(port, size)) != NULL) {
260 n->flags = flags;
261 buf->tail = n;
262 b->commit = b->used;
263 /* paired w/ barrier in flush_to_ldisc(); ensures the
264 * latest commit value can be read before the head is
265 * advanced to the next buffer
266 */
267 smp_wmb();
268 b->next = n;
269 } else if (change)
270 size = 0;
271 else
272 size = left;
273 }
274 return size;
275}
276
277int tty_buffer_request_room(struct tty_port *port, size_t size)
278{
279 return __tty_buffer_request_room(port, size, 0);
280}
281EXPORT_SYMBOL_GPL(tty_buffer_request_room);
282
283/**
284 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
285 * @port: tty port
286 * @chars: characters
287 * @flag: flag value for each character
288 * @size: size
289 *
290 * Queue a series of bytes to the tty buffering. All the characters
291 * passed are marked with the supplied flag. Returns the number added.
292 */
293
294int tty_insert_flip_string_fixed_flag(struct tty_port *port,
295 const unsigned char *chars, char flag, size_t size)
296{
297 int copied = 0;
298 do {
299 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
300 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
301 int space = __tty_buffer_request_room(port, goal, flags);
302 struct tty_buffer *tb = port->buf.tail;
303 if (unlikely(space == 0))
304 break;
305 memcpy(char_buf_ptr(tb, tb->used), chars, space);
306 if (~tb->flags & TTYB_NORMAL)
307 memset(flag_buf_ptr(tb, tb->used), flag, space);
308 tb->used += space;
309 copied += space;
310 chars += space;
311 /* There is a small chance that we need to split the data over
312 several buffers. If this is the case we must loop */
313 } while (unlikely(size > copied));
314 return copied;
315}
316EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
317
318/**
319 * tty_insert_flip_string_flags - Add characters to the tty buffer
320 * @port: tty port
321 * @chars: characters
322 * @flags: flag bytes
323 * @size: size
324 *
325 * Queue a series of bytes to the tty buffering. For each character
326 * the flags array indicates the status of the character. Returns the
327 * number added.
328 */
329
330int tty_insert_flip_string_flags(struct tty_port *port,
331 const unsigned char *chars, const char *flags, size_t size)
332{
333 int copied = 0;
334 do {
335 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
336 int space = tty_buffer_request_room(port, goal);
337 struct tty_buffer *tb = port->buf.tail;
338 if (unlikely(space == 0))
339 break;
340 memcpy(char_buf_ptr(tb, tb->used), chars, space);
341 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
342 tb->used += space;
343 copied += space;
344 chars += space;
345 flags += space;
346 /* There is a small chance that we need to split the data over
347 several buffers. If this is the case we must loop */
348 } while (unlikely(size > copied));
349 return copied;
350}
351EXPORT_SYMBOL(tty_insert_flip_string_flags);
352
353/**
354 * tty_schedule_flip - push characters to ldisc
355 * @port: tty port to push from
356 *
357 * Takes any pending buffers and transfers their ownership to the
358 * ldisc side of the queue. It then schedules those characters for
359 * processing by the line discipline.
360 */
361
362void tty_schedule_flip(struct tty_port *port)
363{
364 struct tty_bufhead *buf = &port->buf;
365
366 buf->tail->commit = buf->tail->used;
367 schedule_work(&buf->work);
368}
369EXPORT_SYMBOL(tty_schedule_flip);
370
371/**
372 * tty_prepare_flip_string - make room for characters
373 * @port: tty port
374 * @chars: return pointer for character write area
375 * @size: desired size
376 *
377 * Prepare a block of space in the buffer for data. Returns the length
378 * available and buffer pointer to the space which is now allocated and
379 * accounted for as ready for normal characters. This is used for drivers
380 * that need their own block copy routines into the buffer. There is no
381 * guarantee the buffer is a DMA target!
382 */
383
384int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
385 size_t size)
386{
387 int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
388 if (likely(space)) {
389 struct tty_buffer *tb = port->buf.tail;
390 *chars = char_buf_ptr(tb, tb->used);
391 if (~tb->flags & TTYB_NORMAL)
392 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
393 tb->used += space;
394 }
395 return space;
396}
397EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
398
399
400static int
401receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
402{
403 struct tty_ldisc *disc = tty->ldisc;
404 unsigned char *p = char_buf_ptr(head, head->read);
405 char *f = NULL;
406
407 if (~head->flags & TTYB_NORMAL)
408 f = flag_buf_ptr(head, head->read);
409
410 if (disc->ops->receive_buf2)
411 count = disc->ops->receive_buf2(tty, p, f, count);
412 else {
413 count = min_t(int, count, tty->receive_room);
414 if (count)
415 disc->ops->receive_buf(tty, p, f, count);
416 }
417 head->read += count;
418 return count;
419}
420
421/**
422 * flush_to_ldisc
423 * @work: tty structure passed from work queue.
424 *
425 * This routine is called out of the software interrupt to flush data
426 * from the buffer chain to the line discipline.
427 *
428 * The receive_buf method is single threaded for each tty instance.
429 *
430 * Locking: takes buffer lock to ensure single-threaded flip buffer
431 * 'consumer'
432 */
433
434static void flush_to_ldisc(struct work_struct *work)
435{
436 struct tty_port *port = container_of(work, struct tty_port, buf.work);
437 struct tty_bufhead *buf = &port->buf;
438 struct tty_struct *tty;
439 struct tty_ldisc *disc;
440
441 tty = port->itty;
442 if (tty == NULL)
443 return;
444
445 disc = tty_ldisc_ref(tty);
446 if (disc == NULL)
447 return;
448
449 mutex_lock(&buf->lock);
450
451 while (1) {
452 struct tty_buffer *head = buf->head;
453 struct tty_buffer *next;
454 int count;
455
456 /* Ldisc or user is trying to gain exclusive access */
457 if (atomic_read(&buf->priority))
458 break;
459
460 next = head->next;
461 /* paired w/ barrier in __tty_buffer_request_room();
462 * ensures commit value read is not stale if the head
463 * is advancing to the next buffer
464 */
465 smp_rmb();
466 count = head->commit - head->read;
467 if (!count) {
468 if (next == NULL)
469 break;
470 buf->head = next;
471 tty_buffer_free(port, head);
472 continue;
473 }
474
475 count = receive_buf(tty, head, count);
476 if (!count)
477 break;
478 }
479
480 mutex_unlock(&buf->lock);
481
482 tty_ldisc_deref(disc);
483}
484
485/**
486 * tty_flush_to_ldisc
487 * @tty: tty to push
488 *
489 * Push the terminal flip buffers to the line discipline.
490 *
491 * Must not be called from IRQ context.
492 */
493void tty_flush_to_ldisc(struct tty_struct *tty)
494{
495 flush_work(&tty->port->buf.work);
496}
497
498/**
499 * tty_flip_buffer_push - terminal
500 * @port: tty port to push
501 *
502 * Queue a push of the terminal flip buffers to the line discipline.
503 * Can be called from IRQ/atomic context.
504 *
505 * In the event of the queue being busy for flipping the work will be
506 * held off and retried later.
507 */
508
509void tty_flip_buffer_push(struct tty_port *port)
510{
511 tty_schedule_flip(port);
512}
513EXPORT_SYMBOL(tty_flip_buffer_push);
514
515/**
516 * tty_buffer_init - prepare a tty buffer structure
517 * @tty: tty to initialise
518 *
519 * Set up the initial state of the buffer management for a tty device.
520 * Must be called before the other tty buffer functions are used.
521 */
522
523void tty_buffer_init(struct tty_port *port)
524{
525 struct tty_bufhead *buf = &port->buf;
526
527 mutex_init(&buf->lock);
528 tty_buffer_reset(&buf->sentinel, 0);
529 buf->head = &buf->sentinel;
530 buf->tail = &buf->sentinel;
531 init_llist_head(&buf->free);
532 atomic_set(&buf->mem_used, 0);
533 atomic_set(&buf->priority, 0);
534 INIT_WORK(&buf->work, flush_to_ldisc);
535 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
536}
537
538/**
539 * tty_buffer_set_limit - change the tty buffer memory limit
540 * @port: tty port to change
541 *
542 * Change the tty buffer memory limit.
543 * Must be called before the other tty buffer functions are used.
544 */
545
546int tty_buffer_set_limit(struct tty_port *port, int limit)
547{
548 if (limit < MIN_TTYB_SIZE)
549 return -EINVAL;
550 port->buf.mem_limit = limit;
551 return 0;
552}
553EXPORT_SYMBOL_GPL(tty_buffer_set_limit);