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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
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}
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/init.h>
15#include <linux/wait.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/module.h>
19
20/**
21 * tty_buffer_free_all - free buffers used by a tty
22 * @tty: tty to free from
23 *
24 * Remove all the buffers pending on a tty whether queued with data
25 * or in the free ring. Must be called when the tty is no longer in use
26 *
27 * Locking: none
28 */
29
30void tty_buffer_free_all(struct tty_struct *tty)
31{
32 struct tty_buffer *thead;
33 while ((thead = tty->buf.head) != NULL) {
34 tty->buf.head = thead->next;
35 kfree(thead);
36 }
37 while ((thead = tty->buf.free) != NULL) {
38 tty->buf.free = thead->next;
39 kfree(thead);
40 }
41 tty->buf.tail = NULL;
42 tty->buf.memory_used = 0;
43}
44
45/**
46 * tty_buffer_alloc - allocate a tty buffer
47 * @tty: tty device
48 * @size: desired size (characters)
49 *
50 * Allocate a new tty buffer to hold the desired number of characters.
51 * Return NULL if out of memory or the allocation would exceed the
52 * per device queue
53 *
54 * Locking: Caller must hold tty->buf.lock
55 */
56
57static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
58{
59 struct tty_buffer *p;
60
61 if (tty->buf.memory_used + size > 65536)
62 return NULL;
63 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
64 if (p == NULL)
65 return NULL;
66 p->used = 0;
67 p->size = size;
68 p->next = NULL;
69 p->commit = 0;
70 p->read = 0;
71 p->char_buf_ptr = (char *)(p->data);
72 p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
73 tty->buf.memory_used += size;
74 return p;
75}
76
77/**
78 * tty_buffer_free - free a tty buffer
79 * @tty: tty owning the buffer
80 * @b: the buffer to free
81 *
82 * Free a tty buffer, or add it to the free list according to our
83 * internal strategy
84 *
85 * Locking: Caller must hold tty->buf.lock
86 */
87
88static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
89{
90 /* Dumb strategy for now - should keep some stats */
91 tty->buf.memory_used -= b->size;
92 WARN_ON(tty->buf.memory_used < 0);
93
94 if (b->size >= 512)
95 kfree(b);
96 else {
97 b->next = tty->buf.free;
98 tty->buf.free = b;
99 }
100}
101
102/**
103 * __tty_buffer_flush - flush full tty buffers
104 * @tty: tty to flush
105 *
106 * flush all the buffers containing receive data. Caller must
107 * hold the buffer lock and must have ensured no parallel flush to
108 * ldisc is running.
109 *
110 * Locking: Caller must hold tty->buf.lock
111 */
112
113static void __tty_buffer_flush(struct tty_struct *tty)
114{
115 struct tty_buffer *thead;
116
117 while ((thead = tty->buf.head) != NULL) {
118 tty->buf.head = thead->next;
119 tty_buffer_free(tty, thead);
120 }
121 tty->buf.tail = NULL;
122}
123
124/**
125 * tty_buffer_flush - flush full tty buffers
126 * @tty: tty to flush
127 *
128 * flush all the buffers containing receive data. If the buffer is
129 * being processed by flush_to_ldisc then we defer the processing
130 * to that function
131 *
132 * Locking: none
133 */
134
135void tty_buffer_flush(struct tty_struct *tty)
136{
137 unsigned long flags;
138 spin_lock_irqsave(&tty->buf.lock, flags);
139
140 /* If the data is being pushed to the tty layer then we can't
141 process it here. Instead set a flag and the flush_to_ldisc
142 path will process the flush request before it exits */
143 if (test_bit(TTY_FLUSHING, &tty->flags)) {
144 set_bit(TTY_FLUSHPENDING, &tty->flags);
145 spin_unlock_irqrestore(&tty->buf.lock, flags);
146 wait_event(tty->read_wait,
147 test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
148 return;
149 } else
150 __tty_buffer_flush(tty);
151 spin_unlock_irqrestore(&tty->buf.lock, flags);
152}
153
154/**
155 * tty_buffer_find - find a free tty buffer
156 * @tty: tty owning the buffer
157 * @size: characters wanted
158 *
159 * Locate an existing suitable tty buffer or if we are lacking one then
160 * allocate a new one. We round our buffers off in 256 character chunks
161 * to get better allocation behaviour.
162 *
163 * Locking: Caller must hold tty->buf.lock
164 */
165
166static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
167{
168 struct tty_buffer **tbh = &tty->buf.free;
169 while ((*tbh) != NULL) {
170 struct tty_buffer *t = *tbh;
171 if (t->size >= size) {
172 *tbh = t->next;
173 t->next = NULL;
174 t->used = 0;
175 t->commit = 0;
176 t->read = 0;
177 tty->buf.memory_used += t->size;
178 return t;
179 }
180 tbh = &((*tbh)->next);
181 }
182 /* Round the buffer size out */
183 size = (size + 0xFF) & ~0xFF;
184 return tty_buffer_alloc(tty, size);
185 /* Should possibly check if this fails for the largest buffer we
186 have queued and recycle that ? */
187}
188
189/**
190 * tty_buffer_request_room - grow tty buffer if needed
191 * @tty: tty structure
192 * @size: size desired
193 *
194 * Make at least size bytes of linear space available for the tty
195 * buffer. If we fail return the size we managed to find.
196 *
197 * Locking: Takes tty->buf.lock
198 */
199int tty_buffer_request_room(struct tty_struct *tty, size_t size)
200{
201 struct tty_buffer *b, *n;
202 int left;
203 unsigned long flags;
204
205 spin_lock_irqsave(&tty->buf.lock, flags);
206
207 /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
208 remove this conditional if its worth it. This would be invisible
209 to the callers */
210 if ((b = tty->buf.tail) != NULL)
211 left = b->size - b->used;
212 else
213 left = 0;
214
215 if (left < size) {
216 /* This is the slow path - looking for new buffers to use */
217 if ((n = tty_buffer_find(tty, size)) != NULL) {
218 if (b != NULL) {
219 b->next = n;
220 b->commit = b->used;
221 } else
222 tty->buf.head = n;
223 tty->buf.tail = n;
224 } else
225 size = left;
226 }
227
228 spin_unlock_irqrestore(&tty->buf.lock, flags);
229 return size;
230}
231EXPORT_SYMBOL_GPL(tty_buffer_request_room);
232
233/**
234 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
235 * @tty: tty structure
236 * @chars: characters
237 * @flag: flag value for each character
238 * @size: size
239 *
240 * Queue a series of bytes to the tty buffering. All the characters
241 * passed are marked with the supplied flag. Returns the number added.
242 *
243 * Locking: Called functions may take tty->buf.lock
244 */
245
246int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
247 const unsigned char *chars, char flag, size_t size)
248{
249 int copied = 0;
250 do {
251 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
252 int space = tty_buffer_request_room(tty, goal);
253 struct tty_buffer *tb = tty->buf.tail;
254 /* If there is no space then tb may be NULL */
255 if (unlikely(space == 0))
256 break;
257 memcpy(tb->char_buf_ptr + tb->used, chars, space);
258 memset(tb->flag_buf_ptr + tb->used, flag, space);
259 tb->used += space;
260 copied += space;
261 chars += space;
262 /* There is a small chance that we need to split the data over
263 several buffers. If this is the case we must loop */
264 } while (unlikely(size > copied));
265 return copied;
266}
267EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
268
269/**
270 * tty_insert_flip_string_flags - Add characters to the tty buffer
271 * @tty: tty structure
272 * @chars: characters
273 * @flags: flag bytes
274 * @size: size
275 *
276 * Queue a series of bytes to the tty buffering. For each character
277 * the flags array indicates the status of the character. Returns the
278 * number added.
279 *
280 * Locking: Called functions may take tty->buf.lock
281 */
282
283int tty_insert_flip_string_flags(struct tty_struct *tty,
284 const unsigned char *chars, const char *flags, size_t size)
285{
286 int copied = 0;
287 do {
288 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
289 int space = tty_buffer_request_room(tty, goal);
290 struct tty_buffer *tb = tty->buf.tail;
291 /* If there is no space then tb may be NULL */
292 if (unlikely(space == 0))
293 break;
294 memcpy(tb->char_buf_ptr + tb->used, chars, space);
295 memcpy(tb->flag_buf_ptr + tb->used, flags, space);
296 tb->used += space;
297 copied += space;
298 chars += space;
299 flags += space;
300 /* There is a small chance that we need to split the data over
301 several buffers. If this is the case we must loop */
302 } while (unlikely(size > copied));
303 return copied;
304}
305EXPORT_SYMBOL(tty_insert_flip_string_flags);
306
307/**
308 * tty_schedule_flip - push characters to ldisc
309 * @tty: tty to push from
310 *
311 * Takes any pending buffers and transfers their ownership to the
312 * ldisc side of the queue. It then schedules those characters for
313 * processing by the line discipline.
314 *
315 * Locking: Takes tty->buf.lock
316 */
317
318void tty_schedule_flip(struct tty_struct *tty)
319{
320 unsigned long flags;
321 spin_lock_irqsave(&tty->buf.lock, flags);
322 if (tty->buf.tail != NULL)
323 tty->buf.tail->commit = tty->buf.tail->used;
324 spin_unlock_irqrestore(&tty->buf.lock, flags);
325 schedule_work(&tty->buf.work);
326}
327EXPORT_SYMBOL(tty_schedule_flip);
328
329/**
330 * tty_prepare_flip_string - make room for characters
331 * @tty: tty
332 * @chars: return pointer for character write area
333 * @size: desired size
334 *
335 * Prepare a block of space in the buffer for data. Returns the length
336 * available and buffer pointer to the space which is now allocated and
337 * accounted for as ready for normal characters. This is used for drivers
338 * that need their own block copy routines into the buffer. There is no
339 * guarantee the buffer is a DMA target!
340 *
341 * Locking: May call functions taking tty->buf.lock
342 */
343
344int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
345 size_t size)
346{
347 int space = tty_buffer_request_room(tty, size);
348 if (likely(space)) {
349 struct tty_buffer *tb = tty->buf.tail;
350 *chars = tb->char_buf_ptr + tb->used;
351 memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
352 tb->used += space;
353 }
354 return space;
355}
356EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
357
358/**
359 * tty_prepare_flip_string_flags - make room for characters
360 * @tty: tty
361 * @chars: return pointer for character write area
362 * @flags: return pointer for status flag write area
363 * @size: desired size
364 *
365 * Prepare a block of space in the buffer for data. Returns the length
366 * available and buffer pointer to the space which is now allocated and
367 * accounted for as ready for characters. This is used for drivers
368 * that need their own block copy routines into the buffer. There is no
369 * guarantee the buffer is a DMA target!
370 *
371 * Locking: May call functions taking tty->buf.lock
372 */
373
374int tty_prepare_flip_string_flags(struct tty_struct *tty,
375 unsigned char **chars, char **flags, size_t size)
376{
377 int space = tty_buffer_request_room(tty, size);
378 if (likely(space)) {
379 struct tty_buffer *tb = tty->buf.tail;
380 *chars = tb->char_buf_ptr + tb->used;
381 *flags = tb->flag_buf_ptr + tb->used;
382 tb->used += space;
383 }
384 return space;
385}
386EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
387
388
389
390/**
391 * flush_to_ldisc
392 * @work: tty structure passed from work queue.
393 *
394 * This routine is called out of the software interrupt to flush data
395 * from the buffer chain to the line discipline.
396 *
397 * Locking: holds tty->buf.lock to guard buffer list. Drops the lock
398 * while invoking the line discipline receive_buf method. The
399 * receive_buf method is single threaded for each tty instance.
400 */
401
402static void flush_to_ldisc(struct work_struct *work)
403{
404 struct tty_struct *tty =
405 container_of(work, struct tty_struct, buf.work);
406 unsigned long flags;
407 struct tty_ldisc *disc;
408
409 disc = tty_ldisc_ref(tty);
410 if (disc == NULL) /* !TTY_LDISC */
411 return;
412
413 spin_lock_irqsave(&tty->buf.lock, flags);
414
415 if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
416 struct tty_buffer *head;
417 while ((head = tty->buf.head) != NULL) {
418 int count;
419 char *char_buf;
420 unsigned char *flag_buf;
421
422 count = head->commit - head->read;
423 if (!count) {
424 if (head->next == NULL)
425 break;
426 tty->buf.head = head->next;
427 tty_buffer_free(tty, head);
428 continue;
429 }
430 /* Ldisc or user is trying to flush the buffers
431 we are feeding to the ldisc, stop feeding the
432 line discipline as we want to empty the queue */
433 if (test_bit(TTY_FLUSHPENDING, &tty->flags))
434 break;
435 if (!tty->receive_room)
436 break;
437 if (count > tty->receive_room)
438 count = tty->receive_room;
439 char_buf = head->char_buf_ptr + head->read;
440 flag_buf = head->flag_buf_ptr + head->read;
441 head->read += count;
442 spin_unlock_irqrestore(&tty->buf.lock, flags);
443 disc->ops->receive_buf(tty, char_buf,
444 flag_buf, count);
445 spin_lock_irqsave(&tty->buf.lock, flags);
446 }
447 clear_bit(TTY_FLUSHING, &tty->flags);
448 }
449
450 /* We may have a deferred request to flush the input buffer,
451 if so pull the chain under the lock and empty the queue */
452 if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
453 __tty_buffer_flush(tty);
454 clear_bit(TTY_FLUSHPENDING, &tty->flags);
455 wake_up(&tty->read_wait);
456 }
457 spin_unlock_irqrestore(&tty->buf.lock, flags);
458
459 tty_ldisc_deref(disc);
460}
461
462/**
463 * tty_flush_to_ldisc
464 * @tty: tty to push
465 *
466 * Push the terminal flip buffers to the line discipline.
467 *
468 * Must not be called from IRQ context.
469 */
470void tty_flush_to_ldisc(struct tty_struct *tty)
471{
472 flush_work(&tty->buf.work);
473}
474
475/**
476 * tty_flip_buffer_push - terminal
477 * @tty: tty to push
478 *
479 * Queue a push of the terminal flip buffers to the line discipline. This
480 * function must not be called from IRQ context if tty->low_latency is set.
481 *
482 * In the event of the queue being busy for flipping the work will be
483 * held off and retried later.
484 *
485 * Locking: tty buffer lock. Driver locks in low latency mode.
486 */
487
488void tty_flip_buffer_push(struct tty_struct *tty)
489{
490 unsigned long flags;
491 spin_lock_irqsave(&tty->buf.lock, flags);
492 if (tty->buf.tail != NULL)
493 tty->buf.tail->commit = tty->buf.tail->used;
494 spin_unlock_irqrestore(&tty->buf.lock, flags);
495
496 if (tty->low_latency)
497 flush_to_ldisc(&tty->buf.work);
498 else
499 schedule_work(&tty->buf.work);
500}
501EXPORT_SYMBOL(tty_flip_buffer_push);
502
503/**
504 * tty_buffer_init - prepare a tty buffer structure
505 * @tty: tty to initialise
506 *
507 * Set up the initial state of the buffer management for a tty device.
508 * Must be called before the other tty buffer functions are used.
509 *
510 * Locking: none
511 */
512
513void tty_buffer_init(struct tty_struct *tty)
514{
515 spin_lock_init(&tty->buf.lock);
516 tty->buf.head = NULL;
517 tty->buf.tail = NULL;
518 tty->buf.free = NULL;
519 tty->buf.memory_used = 0;
520 INIT_WORK(&tty->buf.work, flush_to_ldisc);
521}
522