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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tty buffer allocation management
4 */
5
6#include <linux/types.h>
7#include <linux/errno.h>
8#include <linux/minmax.h>
9#include <linux/tty.h>
10#include <linux/tty_buffer.h>
11#include <linux/tty_driver.h>
12#include <linux/tty_flip.h>
13#include <linux/timer.h>
14#include <linux/string.h>
15#include <linux/slab.h>
16#include <linux/sched.h>
17#include <linux/wait.h>
18#include <linux/bitops.h>
19#include <linux/delay.h>
20#include <linux/module.h>
21#include <linux/ratelimit.h>
22#include "tty.h"
23
24#define MIN_TTYB_SIZE 256
25#define TTYB_ALIGN_MASK 0xff
26
27/*
28 * Byte threshold to limit memory consumption for flip buffers.
29 * The actual memory limit is > 2x this amount.
30 */
31#define TTYB_DEFAULT_MEM_LIMIT (640 * 1024UL)
32
33/*
34 * We default to dicing tty buffer allocations to this many characters
35 * in order to avoid multiple page allocations. We know the size of
36 * tty_buffer itself but it must also be taken into account that the
37 * buffer is 256 byte aligned. See tty_buffer_find for the allocation
38 * logic this must match.
39 */
40
41#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~TTYB_ALIGN_MASK)
42
43/**
44 * tty_buffer_lock_exclusive - gain exclusive access to buffer
45 * @port: tty port owning the flip buffer
46 *
47 * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
48 * the buffer work and any pending flush from using the flip buffer. Data can
49 * continue to be added concurrently to the flip buffer from the driver side.
50 *
51 * See also tty_buffer_unlock_exclusive().
52 */
53void tty_buffer_lock_exclusive(struct tty_port *port)
54{
55 struct tty_bufhead *buf = &port->buf;
56
57 atomic_inc(&buf->priority);
58 mutex_lock(&buf->lock);
59}
60EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
61
62/**
63 * tty_buffer_unlock_exclusive - release exclusive access
64 * @port: tty port owning the flip buffer
65 *
66 * The buffer work is restarted if there is data in the flip buffer.
67 *
68 * See also tty_buffer_lock_exclusive().
69 */
70void tty_buffer_unlock_exclusive(struct tty_port *port)
71{
72 struct tty_bufhead *buf = &port->buf;
73 bool restart = buf->head->commit != buf->head->read;
74
75 atomic_dec(&buf->priority);
76 mutex_unlock(&buf->lock);
77
78 if (restart)
79 queue_work(system_unbound_wq, &buf->work);
80}
81EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
82
83/**
84 * tty_buffer_space_avail - return unused buffer space
85 * @port: tty port owning the flip buffer
86 *
87 * Returns: the # of bytes which can be written by the driver without reaching
88 * the buffer limit.
89 *
90 * Note: this does not guarantee that memory is available to write the returned
91 * # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
92 * guarantee is required).
93 */
94unsigned int tty_buffer_space_avail(struct tty_port *port)
95{
96 int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
97
98 return max(space, 0);
99}
100EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
101
102static void tty_buffer_reset(struct tty_buffer *p, size_t size)
103{
104 p->used = 0;
105 p->size = size;
106 p->next = NULL;
107 p->commit = 0;
108 p->lookahead = 0;
109 p->read = 0;
110 p->flags = true;
111}
112
113/**
114 * tty_buffer_free_all - free buffers used by a tty
115 * @port: tty port to free from
116 *
117 * Remove all the buffers pending on a tty whether queued with data or in the
118 * free ring. Must be called when the tty is no longer in use.
119 */
120void tty_buffer_free_all(struct tty_port *port)
121{
122 struct tty_bufhead *buf = &port->buf;
123 struct tty_buffer *p, *next;
124 struct llist_node *llist;
125 unsigned int freed = 0;
126 int still_used;
127
128 while ((p = buf->head) != NULL) {
129 buf->head = p->next;
130 freed += p->size;
131 if (p->size > 0)
132 kfree(p);
133 }
134 llist = llist_del_all(&buf->free);
135 llist_for_each_entry_safe(p, next, llist, free)
136 kfree(p);
137
138 tty_buffer_reset(&buf->sentinel, 0);
139 buf->head = &buf->sentinel;
140 buf->tail = &buf->sentinel;
141
142 still_used = atomic_xchg(&buf->mem_used, 0);
143 WARN(still_used != freed, "we still have not freed %d bytes!",
144 still_used - freed);
145}
146
147/**
148 * tty_buffer_alloc - allocate a tty buffer
149 * @port: tty port
150 * @size: desired size (characters)
151 *
152 * Allocate a new tty buffer to hold the desired number of characters. We
153 * round our buffers off in 256 character chunks to get better allocation
154 * behaviour.
155 *
156 * Returns: %NULL if out of memory or the allocation would exceed the per
157 * device queue.
158 */
159static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
160{
161 struct llist_node *free;
162 struct tty_buffer *p;
163
164 /* Round the buffer size out */
165 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
166
167 if (size <= MIN_TTYB_SIZE) {
168 free = llist_del_first(&port->buf.free);
169 if (free) {
170 p = llist_entry(free, struct tty_buffer, free);
171 goto found;
172 }
173 }
174
175 /* Should possibly check if this fails for the largest buffer we
176 * have queued and recycle that ?
177 */
178 if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
179 return NULL;
180 p = kmalloc(struct_size(p, data, 2 * size), GFP_ATOMIC | __GFP_NOWARN);
181 if (p == NULL)
182 return NULL;
183
184found:
185 tty_buffer_reset(p, size);
186 atomic_add(size, &port->buf.mem_used);
187 return p;
188}
189
190/**
191 * tty_buffer_free - free a tty buffer
192 * @port: tty port owning the buffer
193 * @b: the buffer to free
194 *
195 * Free a tty buffer, or add it to the free list according to our internal
196 * strategy.
197 */
198static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
199{
200 struct tty_bufhead *buf = &port->buf;
201
202 /* Dumb strategy for now - should keep some stats */
203 WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
204
205 if (b->size > MIN_TTYB_SIZE)
206 kfree(b);
207 else if (b->size > 0)
208 llist_add(&b->free, &buf->free);
209}
210
211/**
212 * tty_buffer_flush - flush full tty buffers
213 * @tty: tty to flush
214 * @ld: optional ldisc ptr (must be referenced)
215 *
216 * Flush all the buffers containing receive data. If @ld != %NULL, flush the
217 * ldisc input buffer.
218 *
219 * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
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 buf->head->lookahead = buf->head->read;
239
240 if (ld && ld->ops->flush_buffer)
241 ld->ops->flush_buffer(tty);
242
243 atomic_dec(&buf->priority);
244 mutex_unlock(&buf->lock);
245}
246
247/**
248 * __tty_buffer_request_room - grow tty buffer if needed
249 * @port: tty port
250 * @size: size desired
251 * @flags: buffer has to store flags along character data
252 *
253 * Make at least @size bytes of linear space available for the tty buffer.
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 a flags
257 * buffer.
258 *
259 * Returns: the size we managed to find.
260 */
261static int __tty_buffer_request_room(struct tty_port *port, size_t size,
262 bool flags)
263{
264 struct tty_bufhead *buf = &port->buf;
265 struct tty_buffer *n, *b = buf->tail;
266 size_t left = (b->flags ? 1 : 2) * b->size - b->used;
267 bool change = !b->flags && flags;
268
269 if (!change && left >= size)
270 return size;
271
272 /* This is the slow path - looking for new buffers to use */
273 n = tty_buffer_alloc(port, size);
274 if (n == NULL)
275 return change ? 0 : left;
276
277 n->flags = flags;
278 buf->tail = n;
279 /*
280 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
281 * ensures they see all buffer data.
282 */
283 smp_store_release(&b->commit, b->used);
284 /*
285 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
286 * ensures the latest commit value can be read before the head
287 * is advanced to the next buffer.
288 */
289 smp_store_release(&b->next, n);
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, true);
297}
298EXPORT_SYMBOL_GPL(tty_buffer_request_room);
299
300size_t __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
301 const u8 *flags, bool mutable_flags,
302 size_t size)
303{
304 bool need_flags = mutable_flags || flags[0] != TTY_NORMAL;
305 size_t copied = 0;
306
307 do {
308 size_t goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
309 size_t space = __tty_buffer_request_room(port, goal, need_flags);
310 struct tty_buffer *tb = port->buf.tail;
311
312 if (unlikely(space == 0))
313 break;
314
315 memcpy(char_buf_ptr(tb, tb->used), chars, space);
316
317 if (mutable_flags) {
318 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
319 flags += space;
320 } else if (tb->flags) {
321 memset(flag_buf_ptr(tb, tb->used), flags[0], space);
322 } else {
323 /* tb->flags should be available once requested */
324 WARN_ON_ONCE(need_flags);
325 }
326
327 tb->used += space;
328 copied += space;
329 chars += space;
330
331 /* There is a small chance that we need to split the data over
332 * several buffers. If this is the case we must loop.
333 */
334 } while (unlikely(size > copied));
335
336 return copied;
337}
338EXPORT_SYMBOL(__tty_insert_flip_string_flags);
339
340/**
341 * tty_prepare_flip_string - make room for characters
342 * @port: tty port
343 * @chars: return pointer for character write area
344 * @size: desired size
345 *
346 * Prepare a block of space in the buffer for data.
347 *
348 * This is used for drivers that need their own block copy routines into the
349 * buffer. There is no guarantee the buffer is a DMA target!
350 *
351 * Returns: the length available and buffer pointer (@chars) to the space which
352 * is now allocated and accounted for as ready for normal characters.
353 */
354size_t tty_prepare_flip_string(struct tty_port *port, u8 **chars, size_t size)
355{
356 size_t space = __tty_buffer_request_room(port, size, false);
357
358 if (likely(space)) {
359 struct tty_buffer *tb = port->buf.tail;
360
361 *chars = char_buf_ptr(tb, tb->used);
362 if (tb->flags)
363 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
364 tb->used += space;
365 }
366
367 return space;
368}
369EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
370
371/**
372 * tty_ldisc_receive_buf - forward data to line discipline
373 * @ld: line discipline to process input
374 * @p: char buffer
375 * @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
376 * @count: number of bytes to process
377 *
378 * Callers other than flush_to_ldisc() need to exclude the kworker from
379 * concurrent use of the line discipline, see paste_selection().
380 *
381 * Returns: the number of bytes processed.
382 */
383size_t tty_ldisc_receive_buf(struct tty_ldisc *ld, const u8 *p, const u8 *f,
384 size_t count)
385{
386 if (ld->ops->receive_buf2)
387 count = ld->ops->receive_buf2(ld->tty, p, f, count);
388 else {
389 count = min_t(size_t, count, ld->tty->receive_room);
390 if (count && ld->ops->receive_buf)
391 ld->ops->receive_buf(ld->tty, p, f, count);
392 }
393 return count;
394}
395EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
396
397static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
398{
399 head->lookahead = max(head->lookahead, head->read);
400
401 while (head) {
402 struct tty_buffer *next;
403 unsigned int count;
404
405 /*
406 * Paired w/ release in __tty_buffer_request_room();
407 * ensures commit value read is not stale if the head
408 * is advancing to the next buffer.
409 */
410 next = smp_load_acquire(&head->next);
411 /*
412 * Paired w/ release in __tty_buffer_request_room() or in
413 * tty_buffer_flush(); ensures we see the committed buffer data.
414 */
415 count = smp_load_acquire(&head->commit) - head->lookahead;
416 if (!count) {
417 head = next;
418 continue;
419 }
420
421 if (port->client_ops->lookahead_buf) {
422 u8 *p, *f = NULL;
423
424 p = char_buf_ptr(head, head->lookahead);
425 if (head->flags)
426 f = flag_buf_ptr(head, head->lookahead);
427
428 port->client_ops->lookahead_buf(port, p, f, count);
429 }
430
431 head->lookahead += count;
432 }
433}
434
435static size_t
436receive_buf(struct tty_port *port, struct tty_buffer *head, size_t count)
437{
438 u8 *p = char_buf_ptr(head, head->read);
439 const u8 *f = NULL;
440 size_t n;
441
442 if (head->flags)
443 f = flag_buf_ptr(head, head->read);
444
445 n = port->client_ops->receive_buf(port, p, f, count);
446 if (n > 0)
447 memset(p, 0, n);
448 return n;
449}
450
451/**
452 * flush_to_ldisc - flush data from buffer to ldisc
453 * @work: tty structure passed from work queue.
454 *
455 * This routine is called out of the software interrupt to flush data from the
456 * 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 'consumer'.
461 */
462static void flush_to_ldisc(struct work_struct *work)
463{
464 struct tty_port *port = container_of(work, struct tty_port, buf.work);
465 struct tty_bufhead *buf = &port->buf;
466
467 mutex_lock(&buf->lock);
468
469 while (1) {
470 struct tty_buffer *head = buf->head;
471 struct tty_buffer *next;
472 size_t count, rcvd;
473
474 /* Ldisc or user is trying to gain exclusive access */
475 if (atomic_read(&buf->priority))
476 break;
477
478 /* paired w/ release in __tty_buffer_request_room();
479 * ensures commit value read is not stale if the head
480 * is advancing to the next buffer
481 */
482 next = smp_load_acquire(&head->next);
483 /* paired w/ release in __tty_buffer_request_room() or in
484 * tty_buffer_flush(); ensures we see the committed buffer data
485 */
486 count = smp_load_acquire(&head->commit) - head->read;
487 if (!count) {
488 if (next == NULL)
489 break;
490 buf->head = next;
491 tty_buffer_free(port, head);
492 continue;
493 }
494
495 rcvd = receive_buf(port, head, count);
496 head->read += rcvd;
497 if (rcvd < count)
498 lookahead_bufs(port, head);
499 if (!rcvd)
500 break;
501
502 if (need_resched())
503 cond_resched();
504 }
505
506 mutex_unlock(&buf->lock);
507
508}
509
510static inline void tty_flip_buffer_commit(struct tty_buffer *tail)
511{
512 /*
513 * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
514 * buffer data.
515 */
516 smp_store_release(&tail->commit, tail->used);
517}
518
519/**
520 * tty_flip_buffer_push - push terminal buffers
521 * @port: tty port to push
522 *
523 * Queue a push of the terminal flip buffers to the line discipline. Can be
524 * called from IRQ/atomic context.
525 *
526 * In the event of the queue being busy for flipping the work will be held off
527 * and retried later.
528 */
529void tty_flip_buffer_push(struct tty_port *port)
530{
531 struct tty_bufhead *buf = &port->buf;
532
533 tty_flip_buffer_commit(buf->tail);
534 queue_work(system_unbound_wq, &buf->work);
535}
536EXPORT_SYMBOL(tty_flip_buffer_push);
537
538/**
539 * tty_insert_flip_string_and_push_buffer - add characters to the tty buffer and
540 * push
541 * @port: tty port
542 * @chars: characters
543 * @size: size
544 *
545 * The function combines tty_insert_flip_string() and tty_flip_buffer_push()
546 * with the exception of properly holding the @port->lock.
547 *
548 * To be used only internally (by pty currently).
549 *
550 * Returns: the number added.
551 */
552int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
553 const u8 *chars, size_t size)
554{
555 struct tty_bufhead *buf = &port->buf;
556 unsigned long flags;
557
558 spin_lock_irqsave(&port->lock, flags);
559 size = tty_insert_flip_string(port, chars, size);
560 if (size)
561 tty_flip_buffer_commit(buf->tail);
562 spin_unlock_irqrestore(&port->lock, flags);
563
564 queue_work(system_unbound_wq, &buf->work);
565
566 return size;
567}
568
569/**
570 * tty_buffer_init - prepare a tty buffer structure
571 * @port: tty port to initialise
572 *
573 * Set up the initial state of the buffer management for a tty device. Must be
574 * called before the other tty buffer functions are used.
575 */
576void tty_buffer_init(struct tty_port *port)
577{
578 struct tty_bufhead *buf = &port->buf;
579
580 mutex_init(&buf->lock);
581 tty_buffer_reset(&buf->sentinel, 0);
582 buf->head = &buf->sentinel;
583 buf->tail = &buf->sentinel;
584 init_llist_head(&buf->free);
585 atomic_set(&buf->mem_used, 0);
586 atomic_set(&buf->priority, 0);
587 INIT_WORK(&buf->work, flush_to_ldisc);
588 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
589}
590
591/**
592 * tty_buffer_set_limit - change the tty buffer memory limit
593 * @port: tty port to change
594 * @limit: memory limit to set
595 *
596 * Change the tty buffer memory limit.
597 *
598 * Must be called before the other tty buffer functions are used.
599 */
600int tty_buffer_set_limit(struct tty_port *port, int limit)
601{
602 if (limit < MIN_TTYB_SIZE)
603 return -EINVAL;
604 port->buf.mem_limit = limit;
605 return 0;
606}
607EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
608
609/* slave ptys can claim nested buffer lock when handling BRK and INTR */
610void tty_buffer_set_lock_subclass(struct tty_port *port)
611{
612 lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
613}
614
615bool tty_buffer_restart_work(struct tty_port *port)
616{
617 return queue_work(system_unbound_wq, &port->buf.work);
618}
619
620bool tty_buffer_cancel_work(struct tty_port *port)
621{
622 return cancel_work_sync(&port->buf.work);
623}
624
625void tty_buffer_flush_work(struct tty_port *port)
626{
627 flush_work(&port->buf.work);
628}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tty buffer allocation management
4 */
5
6#include <linux/types.h>
7#include <linux/errno.h>
8#include <linux/tty.h>
9#include <linux/tty_driver.h>
10#include <linux/tty_flip.h>
11#include <linux/timer.h>
12#include <linux/string.h>
13#include <linux/slab.h>
14#include <linux/sched.h>
15#include <linux/wait.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/module.h>
19#include <linux/ratelimit.h>
20
21
22#define MIN_TTYB_SIZE 256
23#define TTYB_ALIGN_MASK 255
24
25/*
26 * Byte threshold to limit memory consumption for flip buffers.
27 * The actual memory limit is > 2x this amount.
28 */
29#define TTYB_DEFAULT_MEM_LIMIT 65536
30
31/*
32 * We default to dicing tty buffer allocations to this many characters
33 * in order to avoid multiple page allocations. We know the size of
34 * tty_buffer itself but it must also be taken into account that the
35 * the buffer is 256 byte aligned. See tty_buffer_find for the allocation
36 * logic this must match
37 */
38
39#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
40
41/**
42 * tty_buffer_lock_exclusive - gain exclusive access to buffer
43 * tty_buffer_unlock_exclusive - release exclusive access
44 *
45 * @port - tty_port owning the flip buffer
46 *
47 * Guarantees safe use of the line discipline's receive_buf() method by
48 * excluding the buffer work and any pending flush from using the flip
49 * buffer. Data can continue to be added concurrently to the flip buffer
50 * from the driver side.
51 *
52 * On release, the buffer work is restarted if there is data in the
53 * flip buffer
54 */
55
56void tty_buffer_lock_exclusive(struct tty_port *port)
57{
58 struct tty_bufhead *buf = &port->buf;
59
60 atomic_inc(&buf->priority);
61 mutex_lock(&buf->lock);
62}
63EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
64
65void tty_buffer_unlock_exclusive(struct tty_port *port)
66{
67 struct tty_bufhead *buf = &port->buf;
68 int restart;
69
70 restart = buf->head->commit != buf->head->read;
71
72 atomic_dec(&buf->priority);
73 mutex_unlock(&buf->lock);
74 if (restart)
75 queue_work(system_unbound_wq, &buf->work);
76}
77EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
78
79/**
80 * tty_buffer_space_avail - return unused buffer space
81 * @port - tty_port owning the flip buffer
82 *
83 * Returns the # of bytes which can be written by the driver without
84 * reaching the buffer limit.
85 *
86 * Note: this does not guarantee that memory is available to write
87 * the returned # of bytes (use tty_prepare_flip_string_xxx() to
88 * pre-allocate if memory guarantee is required).
89 */
90
91int tty_buffer_space_avail(struct tty_port *port)
92{
93 int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
94 return max(space, 0);
95}
96EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
97
98static void tty_buffer_reset(struct tty_buffer *p, size_t size)
99{
100 p->used = 0;
101 p->size = size;
102 p->next = NULL;
103 p->commit = 0;
104 p->read = 0;
105 p->flags = 0;
106}
107
108/**
109 * tty_buffer_free_all - free buffers used by a tty
110 * @tty: tty to free from
111 *
112 * Remove all the buffers pending on a tty whether queued with data
113 * or in the free ring. Must be called when the tty is no longer in use
114 */
115
116void tty_buffer_free_all(struct tty_port *port)
117{
118 struct tty_bufhead *buf = &port->buf;
119 struct tty_buffer *p, *next;
120 struct llist_node *llist;
121
122 while ((p = buf->head) != NULL) {
123 buf->head = p->next;
124 if (p->size > 0)
125 kfree(p);
126 }
127 llist = llist_del_all(&buf->free);
128 llist_for_each_entry_safe(p, next, llist, free)
129 kfree(p);
130
131 tty_buffer_reset(&buf->sentinel, 0);
132 buf->head = &buf->sentinel;
133 buf->tail = &buf->sentinel;
134
135 atomic_set(&buf->mem_used, 0);
136}
137
138/**
139 * tty_buffer_alloc - allocate a tty buffer
140 * @tty: tty device
141 * @size: desired size (characters)
142 *
143 * Allocate a new tty buffer to hold the desired number of characters.
144 * We round our buffers off in 256 character chunks to get better
145 * allocation behaviour.
146 * Return NULL if out of memory or the allocation would exceed the
147 * per device queue
148 */
149
150static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
151{
152 struct llist_node *free;
153 struct tty_buffer *p;
154
155 /* Round the buffer size out */
156 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
157
158 if (size <= MIN_TTYB_SIZE) {
159 free = llist_del_first(&port->buf.free);
160 if (free) {
161 p = llist_entry(free, struct tty_buffer, free);
162 goto found;
163 }
164 }
165
166 /* Should possibly check if this fails for the largest buffer we
167 have queued and recycle that ? */
168 if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
169 return NULL;
170 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
171 if (p == NULL)
172 return NULL;
173
174found:
175 tty_buffer_reset(p, size);
176 atomic_add(size, &port->buf.mem_used);
177 return p;
178}
179
180/**
181 * tty_buffer_free - free a tty buffer
182 * @tty: tty owning the buffer
183 * @b: the buffer to free
184 *
185 * Free a tty buffer, or add it to the free list according to our
186 * internal strategy
187 */
188
189static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
190{
191 struct tty_bufhead *buf = &port->buf;
192
193 /* Dumb strategy for now - should keep some stats */
194 WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
195
196 if (b->size > MIN_TTYB_SIZE)
197 kfree(b);
198 else if (b->size > 0)
199 llist_add(&b->free, &buf->free);
200}
201
202/**
203 * tty_buffer_flush - flush full tty buffers
204 * @tty: tty to flush
205 * @ld: optional ldisc ptr (must be referenced)
206 *
207 * flush all the buffers containing receive data. If ld != NULL,
208 * flush the ldisc input buffer.
209 *
210 * Locking: takes buffer lock to ensure single-threaded flip buffer
211 * 'consumer'
212 */
213
214void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
215{
216 struct tty_port *port = tty->port;
217 struct tty_bufhead *buf = &port->buf;
218 struct tty_buffer *next;
219
220 atomic_inc(&buf->priority);
221
222 mutex_lock(&buf->lock);
223 /* paired w/ release in __tty_buffer_request_room; ensures there are
224 * no pending memory accesses to the freed buffer
225 */
226 while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
227 tty_buffer_free(port, buf->head);
228 buf->head = next;
229 }
230 buf->head->read = buf->head->commit;
231
232 if (ld && ld->ops->flush_buffer)
233 ld->ops->flush_buffer(tty);
234
235 atomic_dec(&buf->priority);
236 mutex_unlock(&buf->lock);
237}
238
239/**
240 * tty_buffer_request_room - grow tty buffer if needed
241 * @tty: tty structure
242 * @size: size desired
243 * @flags: buffer flags if new buffer allocated (default = 0)
244 *
245 * Make at least size bytes of linear space available for the tty
246 * buffer. If we fail return the size we managed to find.
247 *
248 * Will change over to a new buffer if the current buffer is encoded as
249 * TTY_NORMAL (so has no flags buffer) and the new buffer requires
250 * a flags buffer.
251 */
252static int __tty_buffer_request_room(struct tty_port *port, size_t size,
253 int flags)
254{
255 struct tty_bufhead *buf = &port->buf;
256 struct tty_buffer *b, *n;
257 int left, change;
258
259 b = buf->tail;
260 if (b->flags & TTYB_NORMAL)
261 left = 2 * b->size - b->used;
262 else
263 left = b->size - b->used;
264
265 change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
266 if (change || left < size) {
267 /* This is the slow path - looking for new buffers to use */
268 n = tty_buffer_alloc(port, size);
269 if (n != NULL) {
270 n->flags = flags;
271 buf->tail = n;
272 /* paired w/ acquire in flush_to_ldisc(); ensures
273 * flush_to_ldisc() sees buffer data.
274 */
275 smp_store_release(&b->commit, b->used);
276 /* paired w/ acquire in flush_to_ldisc(); ensures the
277 * latest commit value can be read before the head is
278 * advanced to the next buffer
279 */
280 smp_store_release(&b->next, n);
281 } else if (change)
282 size = 0;
283 else
284 size = left;
285 }
286 return size;
287}
288
289int tty_buffer_request_room(struct tty_port *port, size_t size)
290{
291 return __tty_buffer_request_room(port, size, 0);
292}
293EXPORT_SYMBOL_GPL(tty_buffer_request_room);
294
295/**
296 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
297 * @port: tty port
298 * @chars: characters
299 * @flag: flag value for each character
300 * @size: size
301 *
302 * Queue a series of bytes to the tty buffering. All the characters
303 * passed are marked with the supplied flag. Returns the number added.
304 */
305
306int tty_insert_flip_string_fixed_flag(struct tty_port *port,
307 const unsigned char *chars, char flag, size_t size)
308{
309 int copied = 0;
310 do {
311 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
312 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
313 int space = __tty_buffer_request_room(port, goal, flags);
314 struct tty_buffer *tb = port->buf.tail;
315 if (unlikely(space == 0))
316 break;
317 memcpy(char_buf_ptr(tb, tb->used), chars, space);
318 if (~tb->flags & TTYB_NORMAL)
319 memset(flag_buf_ptr(tb, tb->used), flag, space);
320 tb->used += space;
321 copied += space;
322 chars += space;
323 /* There is a small chance that we need to split the data over
324 several buffers. If this is the case we must loop */
325 } while (unlikely(size > copied));
326 return copied;
327}
328EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
329
330/**
331 * tty_insert_flip_string_flags - Add characters to the tty buffer
332 * @port: tty port
333 * @chars: characters
334 * @flags: flag bytes
335 * @size: size
336 *
337 * Queue a series of bytes to the tty buffering. For each character
338 * the flags array indicates the status of the character. Returns the
339 * number added.
340 */
341
342int tty_insert_flip_string_flags(struct tty_port *port,
343 const unsigned char *chars, const char *flags, size_t size)
344{
345 int copied = 0;
346 do {
347 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
348 int space = tty_buffer_request_room(port, goal);
349 struct tty_buffer *tb = port->buf.tail;
350 if (unlikely(space == 0))
351 break;
352 memcpy(char_buf_ptr(tb, tb->used), chars, space);
353 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
354 tb->used += space;
355 copied += space;
356 chars += space;
357 flags += space;
358 /* There is a small chance that we need to split the data over
359 several buffers. If this is the case we must loop */
360 } while (unlikely(size > copied));
361 return copied;
362}
363EXPORT_SYMBOL(tty_insert_flip_string_flags);
364
365/**
366 * __tty_insert_flip_char - Add one character to the tty buffer
367 * @port: tty port
368 * @ch: character
369 * @flag: flag byte
370 *
371 * Queue a single byte to the tty buffering, with an optional flag.
372 * This is the slow path of tty_insert_flip_char.
373 */
374int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
375{
376 struct tty_buffer *tb;
377 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
378
379 if (!__tty_buffer_request_room(port, 1, flags))
380 return 0;
381
382 tb = port->buf.tail;
383 if (~tb->flags & TTYB_NORMAL)
384 *flag_buf_ptr(tb, tb->used) = flag;
385 *char_buf_ptr(tb, tb->used++) = ch;
386
387 return 1;
388}
389EXPORT_SYMBOL(__tty_insert_flip_char);
390
391/**
392 * tty_schedule_flip - push characters to ldisc
393 * @port: tty port to push from
394 *
395 * Takes any pending buffers and transfers their ownership to the
396 * ldisc side of the queue. It then schedules those characters for
397 * processing by the line discipline.
398 */
399
400void tty_schedule_flip(struct tty_port *port)
401{
402 struct tty_bufhead *buf = &port->buf;
403
404 /* paired w/ acquire in flush_to_ldisc(); ensures
405 * flush_to_ldisc() sees buffer data.
406 */
407 smp_store_release(&buf->tail->commit, buf->tail->used);
408 queue_work(system_unbound_wq, &buf->work);
409}
410EXPORT_SYMBOL(tty_schedule_flip);
411
412/**
413 * tty_prepare_flip_string - make room for characters
414 * @port: tty port
415 * @chars: return pointer for character write area
416 * @size: desired size
417 *
418 * Prepare a block of space in the buffer for data. Returns the length
419 * available and buffer pointer to the space which is now allocated and
420 * accounted for as ready for normal characters. This is used for drivers
421 * that need their own block copy routines into the buffer. There is no
422 * guarantee the buffer is a DMA target!
423 */
424
425int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
426 size_t size)
427{
428 int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
429 if (likely(space)) {
430 struct tty_buffer *tb = port->buf.tail;
431 *chars = char_buf_ptr(tb, tb->used);
432 if (~tb->flags & TTYB_NORMAL)
433 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
434 tb->used += space;
435 }
436 return space;
437}
438EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
439
440/**
441 * tty_ldisc_receive_buf - forward data to line discipline
442 * @ld: line discipline to process input
443 * @p: char buffer
444 * @f: TTY_* flags buffer
445 * @count: number of bytes to process
446 *
447 * Callers other than flush_to_ldisc() need to exclude the kworker
448 * from concurrent use of the line discipline, see paste_selection().
449 *
450 * Returns the number of bytes processed
451 */
452int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
453 char *f, int count)
454{
455 if (ld->ops->receive_buf2)
456 count = ld->ops->receive_buf2(ld->tty, p, f, count);
457 else {
458 count = min_t(int, count, ld->tty->receive_room);
459 if (count && ld->ops->receive_buf)
460 ld->ops->receive_buf(ld->tty, p, f, count);
461 }
462 return count;
463}
464EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
465
466static int
467receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
468{
469 unsigned char *p = char_buf_ptr(head, head->read);
470 char *f = NULL;
471
472 if (~head->flags & TTYB_NORMAL)
473 f = flag_buf_ptr(head, head->read);
474
475 return port->client_ops->receive_buf(port, p, f, count);
476}
477
478/**
479 * flush_to_ldisc
480 * @work: tty structure passed from work queue.
481 *
482 * This routine is called out of the software interrupt to flush data
483 * from the buffer chain to the line discipline.
484 *
485 * The receive_buf method is single threaded for each tty instance.
486 *
487 * Locking: takes buffer lock to ensure single-threaded flip buffer
488 * 'consumer'
489 */
490
491static void flush_to_ldisc(struct work_struct *work)
492{
493 struct tty_port *port = container_of(work, struct tty_port, buf.work);
494 struct tty_bufhead *buf = &port->buf;
495
496 mutex_lock(&buf->lock);
497
498 while (1) {
499 struct tty_buffer *head = buf->head;
500 struct tty_buffer *next;
501 int count;
502
503 /* Ldisc or user is trying to gain exclusive access */
504 if (atomic_read(&buf->priority))
505 break;
506
507 /* paired w/ release in __tty_buffer_request_room();
508 * ensures commit value read is not stale if the head
509 * is advancing to the next buffer
510 */
511 next = smp_load_acquire(&head->next);
512 /* paired w/ release in __tty_buffer_request_room() or in
513 * tty_buffer_flush(); ensures we see the committed buffer data
514 */
515 count = smp_load_acquire(&head->commit) - head->read;
516 if (!count) {
517 if (next == NULL)
518 break;
519 buf->head = next;
520 tty_buffer_free(port, head);
521 continue;
522 }
523
524 count = receive_buf(port, head, count);
525 if (!count)
526 break;
527 head->read += count;
528 }
529
530 mutex_unlock(&buf->lock);
531
532}
533
534/**
535 * tty_flip_buffer_push - terminal
536 * @port: tty port to push
537 *
538 * Queue a push of the terminal flip buffers to the line discipline.
539 * Can be called from IRQ/atomic context.
540 *
541 * In the event of the queue being busy for flipping the work will be
542 * held off and retried later.
543 */
544
545void tty_flip_buffer_push(struct tty_port *port)
546{
547 tty_schedule_flip(port);
548}
549EXPORT_SYMBOL(tty_flip_buffer_push);
550
551/**
552 * tty_buffer_init - prepare a tty buffer structure
553 * @tty: tty to initialise
554 *
555 * Set up the initial state of the buffer management for a tty device.
556 * Must be called before the other tty buffer functions are used.
557 */
558
559void tty_buffer_init(struct tty_port *port)
560{
561 struct tty_bufhead *buf = &port->buf;
562
563 mutex_init(&buf->lock);
564 tty_buffer_reset(&buf->sentinel, 0);
565 buf->head = &buf->sentinel;
566 buf->tail = &buf->sentinel;
567 init_llist_head(&buf->free);
568 atomic_set(&buf->mem_used, 0);
569 atomic_set(&buf->priority, 0);
570 INIT_WORK(&buf->work, flush_to_ldisc);
571 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
572}
573
574/**
575 * tty_buffer_set_limit - change the tty buffer memory limit
576 * @port: tty port to change
577 *
578 * Change the tty buffer memory limit.
579 * Must be called before the other tty buffer functions are used.
580 */
581
582int tty_buffer_set_limit(struct tty_port *port, int limit)
583{
584 if (limit < MIN_TTYB_SIZE)
585 return -EINVAL;
586 port->buf.mem_limit = limit;
587 return 0;
588}
589EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
590
591/* slave ptys can claim nested buffer lock when handling BRK and INTR */
592void tty_buffer_set_lock_subclass(struct tty_port *port)
593{
594 lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
595}
596
597bool tty_buffer_restart_work(struct tty_port *port)
598{
599 return queue_work(system_unbound_wq, &port->buf.work);
600}
601
602bool tty_buffer_cancel_work(struct tty_port *port)
603{
604 return cancel_work_sync(&port->buf.work);
605}
606
607void tty_buffer_flush_work(struct tty_port *port)
608{
609 flush_work(&port->buf.work);
610}