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