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