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