1/*
2 * Public API and common code for kernel->userspace relay file support.
3 *
4 * See Documentation/filesystems/relay.rst for an overview.
5 *
6 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
7 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
8 *
9 * Moved to kernel/relay.c by Paul Mundt, 2006.
10 * November 2006 - CPU hotplug support by Mathieu Desnoyers
11 * (mathieu.desnoyers@polymtl.ca)
12 *
13 * This file is released under the GPL.
14 */
15#include <linux/errno.h>
16#include <linux/stddef.h>
17#include <linux/slab.h>
18#include <linux/export.h>
19#include <linux/string.h>
20#include <linux/relay.h>
21#include <linux/vmalloc.h>
22#include <linux/mm.h>
23#include <linux/cpu.h>
24#include <linux/splice.h>
25
26/* list of open channels, for cpu hotplug */
27static DEFINE_MUTEX(relay_channels_mutex);
28static LIST_HEAD(relay_channels);
29
30/*
31 * fault() vm_op implementation for relay file mapping.
32 */
33static vm_fault_t relay_buf_fault(struct vm_fault *vmf)
34{
35 struct page *page;
36 struct rchan_buf *buf = vmf->vma->vm_private_data;
37 pgoff_t pgoff = vmf->pgoff;
38
39 if (!buf)
40 return VM_FAULT_OOM;
41
42 page = vmalloc_to_page(addr: buf->start + (pgoff << PAGE_SHIFT));
43 if (!page)
44 return VM_FAULT_SIGBUS;
45 get_page(page);
46 vmf->page = page;
47
48 return 0;
49}
50
51/*
52 * vm_ops for relay file mappings.
53 */
54static const struct vm_operations_struct relay_file_mmap_ops = {
55 .fault = relay_buf_fault,
56};
57
58/*
59 * allocate an array of pointers of struct page
60 */
61static struct page **relay_alloc_page_array(unsigned int n_pages)
62{
63 return kvcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
64}
65
66/*
67 * free an array of pointers of struct page
68 */
69static void relay_free_page_array(struct page **array)
70{
71 kvfree(addr: array);
72}
73
74/**
75 * relay_mmap_buf: - mmap channel buffer to process address space
76 * @buf: relay channel buffer
77 * @vma: vm_area_struct describing memory to be mapped
78 *
79 * Returns 0 if ok, negative on error
80 *
81 * Caller should already have grabbed mmap_lock.
82 */
83static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
84{
85 unsigned long length = vma->vm_end - vma->vm_start;
86
87 if (!buf)
88 return -EBADF;
89
90 if (length != (unsigned long)buf->chan->alloc_size)
91 return -EINVAL;
92
93 vma->vm_ops = &relay_file_mmap_ops;
94 vm_flags_set(vma, VM_DONTEXPAND);
95 vma->vm_private_data = buf;
96
97 return 0;
98}
99
100/**
101 * relay_alloc_buf - allocate a channel buffer
102 * @buf: the buffer struct
103 * @size: total size of the buffer
104 *
105 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
106 * passed in size will get page aligned, if it isn't already.
107 */
108static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
109{
110 void *mem;
111 unsigned int i, j, n_pages;
112
113 *size = PAGE_ALIGN(*size);
114 n_pages = *size >> PAGE_SHIFT;
115
116 buf->page_array = relay_alloc_page_array(n_pages);
117 if (!buf->page_array)
118 return NULL;
119
120 for (i = 0; i < n_pages; i++) {
121 buf->page_array[i] = alloc_page(GFP_KERNEL);
122 if (unlikely(!buf->page_array[i]))
123 goto depopulate;
124 set_page_private(page: buf->page_array[i], private: (unsigned long)buf);
125 }
126 mem = vmap(pages: buf->page_array, count: n_pages, VM_MAP, PAGE_KERNEL);
127 if (!mem)
128 goto depopulate;
129
130 memset(mem, 0, *size);
131 buf->page_count = n_pages;
132 return mem;
133
134depopulate:
135 for (j = 0; j < i; j++)
136 __free_page(buf->page_array[j]);
137 relay_free_page_array(array: buf->page_array);
138 return NULL;
139}
140
141/**
142 * relay_create_buf - allocate and initialize a channel buffer
143 * @chan: the relay channel
144 *
145 * Returns channel buffer if successful, %NULL otherwise.
146 */
147static struct rchan_buf *relay_create_buf(struct rchan *chan)
148{
149 struct rchan_buf *buf;
150
151 if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t))
152 return NULL;
153
154 buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
155 if (!buf)
156 return NULL;
157 buf->padding = kmalloc_array(chan->n_subbufs, sizeof(size_t),
158 GFP_KERNEL);
159 if (!buf->padding)
160 goto free_buf;
161
162 buf->start = relay_alloc_buf(buf, size: &chan->alloc_size);
163 if (!buf->start)
164 goto free_buf;
165
166 buf->chan = chan;
167 kref_get(kref: &buf->chan->kref);
168 return buf;
169
170free_buf:
171 kfree(objp: buf->padding);
172 kfree(objp: buf);
173 return NULL;
174}
175
176/**
177 * relay_destroy_channel - free the channel struct
178 * @kref: target kernel reference that contains the relay channel
179 *
180 * Should only be called from kref_put().
181 */
182static void relay_destroy_channel(struct kref *kref)
183{
184 struct rchan *chan = container_of(kref, struct rchan, kref);
185 free_percpu(pdata: chan->buf);
186 kfree(objp: chan);
187}
188
189/**
190 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
191 * @buf: the buffer struct
192 */
193static void relay_destroy_buf(struct rchan_buf *buf)
194{
195 struct rchan *chan = buf->chan;
196 unsigned int i;
197
198 if (likely(buf->start)) {
199 vunmap(addr: buf->start);
200 for (i = 0; i < buf->page_count; i++)
201 __free_page(buf->page_array[i]);
202 relay_free_page_array(array: buf->page_array);
203 }
204 *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
205 kfree(objp: buf->padding);
206 kfree(objp: buf);
207 kref_put(kref: &chan->kref, release: relay_destroy_channel);
208}
209
210/**
211 * relay_remove_buf - remove a channel buffer
212 * @kref: target kernel reference that contains the relay buffer
213 *
214 * Removes the file from the filesystem, which also frees the
215 * rchan_buf_struct and the channel buffer. Should only be called from
216 * kref_put().
217 */
218static void relay_remove_buf(struct kref *kref)
219{
220 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
221 relay_destroy_buf(buf);
222}
223
224/**
225 * relay_buf_empty - boolean, is the channel buffer empty?
226 * @buf: channel buffer
227 *
228 * Returns 1 if the buffer is empty, 0 otherwise.
229 */
230static int relay_buf_empty(struct rchan_buf *buf)
231{
232 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
233}
234
235/**
236 * relay_buf_full - boolean, is the channel buffer full?
237 * @buf: channel buffer
238 *
239 * Returns 1 if the buffer is full, 0 otherwise.
240 */
241int relay_buf_full(struct rchan_buf *buf)
242{
243 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
244 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
245}
246EXPORT_SYMBOL_GPL(relay_buf_full);
247
248/*
249 * High-level relay kernel API and associated functions.
250 */
251
252static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf,
253 void *prev_subbuf, size_t prev_padding)
254{
255 if (!buf->chan->cb->subbuf_start)
256 return !relay_buf_full(buf);
257
258 return buf->chan->cb->subbuf_start(buf, subbuf,
259 prev_subbuf, prev_padding);
260}
261
262/**
263 * wakeup_readers - wake up readers waiting on a channel
264 * @work: contains the channel buffer
265 *
266 * This is the function used to defer reader waking
267 */
268static void wakeup_readers(struct irq_work *work)
269{
270 struct rchan_buf *buf;
271
272 buf = container_of(work, struct rchan_buf, wakeup_work);
273 wake_up_interruptible(&buf->read_wait);
274}
275
276/**
277 * __relay_reset - reset a channel buffer
278 * @buf: the channel buffer
279 * @init: 1 if this is a first-time initialization
280 *
281 * See relay_reset() for description of effect.
282 */
283static void __relay_reset(struct rchan_buf *buf, unsigned int init)
284{
285 size_t i;
286
287 if (init) {
288 init_waitqueue_head(&buf->read_wait);
289 kref_init(kref: &buf->kref);
290 init_irq_work(work: &buf->wakeup_work, func: wakeup_readers);
291 } else {
292 irq_work_sync(work: &buf->wakeup_work);
293 }
294
295 buf->subbufs_produced = 0;
296 buf->subbufs_consumed = 0;
297 buf->bytes_consumed = 0;
298 buf->finalized = 0;
299 buf->data = buf->start;
300 buf->offset = 0;
301
302 for (i = 0; i < buf->chan->n_subbufs; i++)
303 buf->padding[i] = 0;
304
305 relay_subbuf_start(buf, subbuf: buf->data, NULL, prev_padding: 0);
306}
307
308/**
309 * relay_reset - reset the channel
310 * @chan: the channel
311 *
312 * This has the effect of erasing all data from all channel buffers
313 * and restarting the channel in its initial state. The buffers
314 * are not freed, so any mappings are still in effect.
315 *
316 * NOTE. Care should be taken that the channel isn't actually
317 * being used by anything when this call is made.
318 */
319void relay_reset(struct rchan *chan)
320{
321 struct rchan_buf *buf;
322 unsigned int i;
323
324 if (!chan)
325 return;
326
327 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
328 __relay_reset(buf, init: 0);
329 return;
330 }
331
332 mutex_lock(&relay_channels_mutex);
333 for_each_possible_cpu(i)
334 if ((buf = *per_cpu_ptr(chan->buf, i)))
335 __relay_reset(buf, init: 0);
336 mutex_unlock(lock: &relay_channels_mutex);
337}
338EXPORT_SYMBOL_GPL(relay_reset);
339
340static inline void relay_set_buf_dentry(struct rchan_buf *buf,
341 struct dentry *dentry)
342{
343 buf->dentry = dentry;
344 d_inode(dentry: buf->dentry)->i_size = buf->early_bytes;
345}
346
347static struct dentry *relay_create_buf_file(struct rchan *chan,
348 struct rchan_buf *buf,
349 unsigned int cpu)
350{
351 struct dentry *dentry;
352 char *tmpname;
353
354 tmpname = kasprintf(GFP_KERNEL, fmt: "%s%d", chan->base_filename, cpu);
355 if (!tmpname)
356 return NULL;
357
358 /* Create file in fs */
359 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
360 S_IRUSR, buf,
361 &chan->is_global);
362 if (IS_ERR(ptr: dentry))
363 dentry = NULL;
364
365 kfree(objp: tmpname);
366
367 return dentry;
368}
369
370/*
371 * relay_open_buf - create a new relay channel buffer
372 *
373 * used by relay_open() and CPU hotplug.
374 */
375static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
376{
377 struct rchan_buf *buf;
378 struct dentry *dentry;
379
380 if (chan->is_global)
381 return *per_cpu_ptr(chan->buf, 0);
382
383 buf = relay_create_buf(chan);
384 if (!buf)
385 return NULL;
386
387 if (chan->has_base_filename) {
388 dentry = relay_create_buf_file(chan, buf, cpu);
389 if (!dentry)
390 goto free_buf;
391 relay_set_buf_dentry(buf, dentry);
392 } else {
393 /* Only retrieve global info, nothing more, nothing less */
394 dentry = chan->cb->create_buf_file(NULL, NULL,
395 S_IRUSR, buf,
396 &chan->is_global);
397 if (IS_ERR_OR_NULL(ptr: dentry))
398 goto free_buf;
399 }
400
401 buf->cpu = cpu;
402 __relay_reset(buf, init: 1);
403
404 if(chan->is_global) {
405 *per_cpu_ptr(chan->buf, 0) = buf;
406 buf->cpu = 0;
407 }
408
409 return buf;
410
411free_buf:
412 relay_destroy_buf(buf);
413 return NULL;
414}
415
416/**
417 * relay_close_buf - close a channel buffer
418 * @buf: channel buffer
419 *
420 * Marks the buffer finalized and restores the default callbacks.
421 * The channel buffer and channel buffer data structure are then freed
422 * automatically when the last reference is given up.
423 */
424static void relay_close_buf(struct rchan_buf *buf)
425{
426 buf->finalized = 1;
427 irq_work_sync(work: &buf->wakeup_work);
428 buf->chan->cb->remove_buf_file(buf->dentry);
429 kref_put(kref: &buf->kref, release: relay_remove_buf);
430}
431
432int relay_prepare_cpu(unsigned int cpu)
433{
434 struct rchan *chan;
435 struct rchan_buf *buf;
436
437 mutex_lock(&relay_channels_mutex);
438 list_for_each_entry(chan, &relay_channels, list) {
439 if (*per_cpu_ptr(chan->buf, cpu))
440 continue;
441 buf = relay_open_buf(chan, cpu);
442 if (!buf) {
443 pr_err("relay: cpu %d buffer creation failed\n", cpu);
444 mutex_unlock(lock: &relay_channels_mutex);
445 return -ENOMEM;
446 }
447 *per_cpu_ptr(chan->buf, cpu) = buf;
448 }
449 mutex_unlock(lock: &relay_channels_mutex);
450 return 0;
451}
452
453/**
454 * relay_open - create a new relay channel
455 * @base_filename: base name of files to create
456 * @parent: dentry of parent directory, %NULL for root directory or buffer
457 * @subbuf_size: size of sub-buffers
458 * @n_subbufs: number of sub-buffers
459 * @cb: client callback functions
460 * @private_data: user-defined data
461 *
462 * Returns channel pointer if successful, %NULL otherwise.
463 *
464 * Creates a channel buffer for each cpu using the sizes and
465 * attributes specified. The created channel buffer files
466 * will be named base_filename0...base_filenameN-1. File
467 * permissions will be %S_IRUSR.
468 */
469struct rchan *relay_open(const char *base_filename,
470 struct dentry *parent,
471 size_t subbuf_size,
472 size_t n_subbufs,
473 const struct rchan_callbacks *cb,
474 void *private_data)
475{
476 unsigned int i;
477 struct rchan *chan;
478 struct rchan_buf *buf;
479
480 if (!(subbuf_size && n_subbufs))
481 return NULL;
482 if (subbuf_size > UINT_MAX / n_subbufs)
483 return NULL;
484 if (!cb || !cb->create_buf_file || !cb->remove_buf_file)
485 return NULL;
486
487 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
488 if (!chan)
489 return NULL;
490
491 chan->buf = alloc_percpu(struct rchan_buf *);
492 if (!chan->buf) {
493 kfree(objp: chan);
494 return NULL;
495 }
496
497 chan->version = RELAYFS_CHANNEL_VERSION;
498 chan->n_subbufs = n_subbufs;
499 chan->subbuf_size = subbuf_size;
500 chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
501 chan->parent = parent;
502 chan->private_data = private_data;
503 if (base_filename) {
504 chan->has_base_filename = 1;
505 strscpy(chan->base_filename, base_filename, NAME_MAX);
506 }
507 chan->cb = cb;
508 kref_init(kref: &chan->kref);
509
510 mutex_lock(&relay_channels_mutex);
511 for_each_online_cpu(i) {
512 buf = relay_open_buf(chan, cpu: i);
513 if (!buf)
514 goto free_bufs;
515 *per_cpu_ptr(chan->buf, i) = buf;
516 }
517 list_add(new: &chan->list, head: &relay_channels);
518 mutex_unlock(lock: &relay_channels_mutex);
519
520 return chan;
521
522free_bufs:
523 for_each_possible_cpu(i) {
524 if ((buf = *per_cpu_ptr(chan->buf, i)))
525 relay_close_buf(buf);
526 }
527
528 kref_put(kref: &chan->kref, release: relay_destroy_channel);
529 mutex_unlock(lock: &relay_channels_mutex);
530 return NULL;
531}
532EXPORT_SYMBOL_GPL(relay_open);
533
534struct rchan_percpu_buf_dispatcher {
535 struct rchan_buf *buf;
536 struct dentry *dentry;
537};
538
539/**
540 * relay_switch_subbuf - switch to a new sub-buffer
541 * @buf: channel buffer
542 * @length: size of current event
543 *
544 * Returns either the length passed in or 0 if full.
545 *
546 * Performs sub-buffer-switch tasks such as invoking callbacks,
547 * updating padding counts, waking up readers, etc.
548 */
549size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
550{
551 void *old, *new;
552 size_t old_subbuf, new_subbuf;
553
554 if (unlikely(length > buf->chan->subbuf_size))
555 goto toobig;
556
557 if (buf->offset != buf->chan->subbuf_size + 1) {
558 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
559 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
560 buf->padding[old_subbuf] = buf->prev_padding;
561 buf->subbufs_produced++;
562 if (buf->dentry)
563 d_inode(dentry: buf->dentry)->i_size +=
564 buf->chan->subbuf_size -
565 buf->padding[old_subbuf];
566 else
567 buf->early_bytes += buf->chan->subbuf_size -
568 buf->padding[old_subbuf];
569 smp_mb();
570 if (waitqueue_active(wq_head: &buf->read_wait)) {
571 /*
572 * Calling wake_up_interruptible() from here
573 * will deadlock if we happen to be logging
574 * from the scheduler (trying to re-grab
575 * rq->lock), so defer it.
576 */
577 irq_work_queue(work: &buf->wakeup_work);
578 }
579 }
580
581 old = buf->data;
582 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
583 new = buf->start + new_subbuf * buf->chan->subbuf_size;
584 buf->offset = 0;
585 if (!relay_subbuf_start(buf, subbuf: new, prev_subbuf: old, prev_padding: buf->prev_padding)) {
586 buf->offset = buf->chan->subbuf_size + 1;
587 return 0;
588 }
589 buf->data = new;
590 buf->padding[new_subbuf] = 0;
591
592 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
593 goto toobig;
594
595 return length;
596
597toobig:
598 buf->chan->last_toobig = length;
599 return 0;
600}
601EXPORT_SYMBOL_GPL(relay_switch_subbuf);
602
603/**
604 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
605 * @chan: the channel
606 * @cpu: the cpu associated with the channel buffer to update
607 * @subbufs_consumed: number of sub-buffers to add to current buf's count
608 *
609 * Adds to the channel buffer's consumed sub-buffer count.
610 * subbufs_consumed should be the number of sub-buffers newly consumed,
611 * not the total consumed.
612 *
613 * NOTE. Kernel clients don't need to call this function if the channel
614 * mode is 'overwrite'.
615 */
616void relay_subbufs_consumed(struct rchan *chan,
617 unsigned int cpu,
618 size_t subbufs_consumed)
619{
620 struct rchan_buf *buf;
621
622 if (!chan || cpu >= NR_CPUS)
623 return;
624
625 buf = *per_cpu_ptr(chan->buf, cpu);
626 if (!buf || subbufs_consumed > chan->n_subbufs)
627 return;
628
629 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
630 buf->subbufs_consumed = buf->subbufs_produced;
631 else
632 buf->subbufs_consumed += subbufs_consumed;
633}
634EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
635
636/**
637 * relay_close - close the channel
638 * @chan: the channel
639 *
640 * Closes all channel buffers and frees the channel.
641 */
642void relay_close(struct rchan *chan)
643{
644 struct rchan_buf *buf;
645 unsigned int i;
646
647 if (!chan)
648 return;
649
650 mutex_lock(&relay_channels_mutex);
651 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
652 relay_close_buf(buf);
653 else
654 for_each_possible_cpu(i)
655 if ((buf = *per_cpu_ptr(chan->buf, i)))
656 relay_close_buf(buf);
657
658 if (chan->last_toobig)
659 printk(KERN_WARNING "relay: one or more items not logged "
660 "[item size (%zd) > sub-buffer size (%zd)]\n",
661 chan->last_toobig, chan->subbuf_size);
662
663 list_del(entry: &chan->list);
664 kref_put(kref: &chan->kref, release: relay_destroy_channel);
665 mutex_unlock(lock: &relay_channels_mutex);
666}
667EXPORT_SYMBOL_GPL(relay_close);
668
669/**
670 * relay_flush - close the channel
671 * @chan: the channel
672 *
673 * Flushes all channel buffers, i.e. forces buffer switch.
674 */
675void relay_flush(struct rchan *chan)
676{
677 struct rchan_buf *buf;
678 unsigned int i;
679
680 if (!chan)
681 return;
682
683 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
684 relay_switch_subbuf(buf, 0);
685 return;
686 }
687
688 mutex_lock(&relay_channels_mutex);
689 for_each_possible_cpu(i)
690 if ((buf = *per_cpu_ptr(chan->buf, i)))
691 relay_switch_subbuf(buf, 0);
692 mutex_unlock(lock: &relay_channels_mutex);
693}
694EXPORT_SYMBOL_GPL(relay_flush);
695
696/**
697 * relay_file_open - open file op for relay files
698 * @inode: the inode
699 * @filp: the file
700 *
701 * Increments the channel buffer refcount.
702 */
703static int relay_file_open(struct inode *inode, struct file *filp)
704{
705 struct rchan_buf *buf = inode->i_private;
706 kref_get(kref: &buf->kref);
707 filp->private_data = buf;
708
709 return nonseekable_open(inode, filp);
710}
711
712/**
713 * relay_file_mmap - mmap file op for relay files
714 * @filp: the file
715 * @vma: the vma describing what to map
716 *
717 * Calls upon relay_mmap_buf() to map the file into user space.
718 */
719static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
720{
721 struct rchan_buf *buf = filp->private_data;
722 return relay_mmap_buf(buf, vma);
723}
724
725/**
726 * relay_file_poll - poll file op for relay files
727 * @filp: the file
728 * @wait: poll table
729 *
730 * Poll implemention.
731 */
732static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
733{
734 __poll_t mask = 0;
735 struct rchan_buf *buf = filp->private_data;
736
737 if (buf->finalized)
738 return EPOLLERR;
739
740 if (filp->f_mode & FMODE_READ) {
741 poll_wait(filp, wait_address: &buf->read_wait, p: wait);
742 if (!relay_buf_empty(buf))
743 mask |= EPOLLIN | EPOLLRDNORM;
744 }
745
746 return mask;
747}
748
749/**
750 * relay_file_release - release file op for relay files
751 * @inode: the inode
752 * @filp: the file
753 *
754 * Decrements the channel refcount, as the filesystem is
755 * no longer using it.
756 */
757static int relay_file_release(struct inode *inode, struct file *filp)
758{
759 struct rchan_buf *buf = filp->private_data;
760 kref_put(kref: &buf->kref, release: relay_remove_buf);
761
762 return 0;
763}
764
765/*
766 * relay_file_read_consume - update the consumed count for the buffer
767 */
768static void relay_file_read_consume(struct rchan_buf *buf,
769 size_t read_pos,
770 size_t bytes_consumed)
771{
772 size_t subbuf_size = buf->chan->subbuf_size;
773 size_t n_subbufs = buf->chan->n_subbufs;
774 size_t read_subbuf;
775
776 if (buf->subbufs_produced == buf->subbufs_consumed &&
777 buf->offset == buf->bytes_consumed)
778 return;
779
780 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
781 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
782 buf->bytes_consumed = 0;
783 }
784
785 buf->bytes_consumed += bytes_consumed;
786 if (!read_pos)
787 read_subbuf = buf->subbufs_consumed % n_subbufs;
788 else
789 read_subbuf = read_pos / buf->chan->subbuf_size;
790 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
791 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
792 (buf->offset == subbuf_size))
793 return;
794 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
795 buf->bytes_consumed = 0;
796 }
797}
798
799/*
800 * relay_file_read_avail - boolean, are there unconsumed bytes available?
801 */
802static int relay_file_read_avail(struct rchan_buf *buf)
803{
804 size_t subbuf_size = buf->chan->subbuf_size;
805 size_t n_subbufs = buf->chan->n_subbufs;
806 size_t produced = buf->subbufs_produced;
807 size_t consumed;
808
809 relay_file_read_consume(buf, read_pos: 0, bytes_consumed: 0);
810
811 consumed = buf->subbufs_consumed;
812
813 if (unlikely(buf->offset > subbuf_size)) {
814 if (produced == consumed)
815 return 0;
816 return 1;
817 }
818
819 if (unlikely(produced - consumed >= n_subbufs)) {
820 consumed = produced - n_subbufs + 1;
821 buf->subbufs_consumed = consumed;
822 buf->bytes_consumed = 0;
823 }
824
825 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
826 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
827
828 if (consumed > produced)
829 produced += n_subbufs * subbuf_size;
830
831 if (consumed == produced) {
832 if (buf->offset == subbuf_size &&
833 buf->subbufs_produced > buf->subbufs_consumed)
834 return 1;
835 return 0;
836 }
837
838 return 1;
839}
840
841/**
842 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
843 * @read_pos: file read position
844 * @buf: relay channel buffer
845 */
846static size_t relay_file_read_subbuf_avail(size_t read_pos,
847 struct rchan_buf *buf)
848{
849 size_t padding, avail = 0;
850 size_t read_subbuf, read_offset, write_subbuf, write_offset;
851 size_t subbuf_size = buf->chan->subbuf_size;
852
853 write_subbuf = (buf->data - buf->start) / subbuf_size;
854 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
855 read_subbuf = read_pos / subbuf_size;
856 read_offset = read_pos % subbuf_size;
857 padding = buf->padding[read_subbuf];
858
859 if (read_subbuf == write_subbuf) {
860 if (read_offset + padding < write_offset)
861 avail = write_offset - (read_offset + padding);
862 } else
863 avail = (subbuf_size - padding) - read_offset;
864
865 return avail;
866}
867
868/**
869 * relay_file_read_start_pos - find the first available byte to read
870 * @buf: relay channel buffer
871 *
872 * If the read_pos is in the middle of padding, return the
873 * position of the first actually available byte, otherwise
874 * return the original value.
875 */
876static size_t relay_file_read_start_pos(struct rchan_buf *buf)
877{
878 size_t read_subbuf, padding, padding_start, padding_end;
879 size_t subbuf_size = buf->chan->subbuf_size;
880 size_t n_subbufs = buf->chan->n_subbufs;
881 size_t consumed = buf->subbufs_consumed % n_subbufs;
882 size_t read_pos = (consumed * subbuf_size + buf->bytes_consumed)
883 % (n_subbufs * subbuf_size);
884
885 read_subbuf = read_pos / subbuf_size;
886 padding = buf->padding[read_subbuf];
887 padding_start = (read_subbuf + 1) * subbuf_size - padding;
888 padding_end = (read_subbuf + 1) * subbuf_size;
889 if (read_pos >= padding_start && read_pos < padding_end) {
890 read_subbuf = (read_subbuf + 1) % n_subbufs;
891 read_pos = read_subbuf * subbuf_size;
892 }
893
894 return read_pos;
895}
896
897/**
898 * relay_file_read_end_pos - return the new read position
899 * @read_pos: file read position
900 * @buf: relay channel buffer
901 * @count: number of bytes to be read
902 */
903static size_t relay_file_read_end_pos(struct rchan_buf *buf,
904 size_t read_pos,
905 size_t count)
906{
907 size_t read_subbuf, padding, end_pos;
908 size_t subbuf_size = buf->chan->subbuf_size;
909 size_t n_subbufs = buf->chan->n_subbufs;
910
911 read_subbuf = read_pos / subbuf_size;
912 padding = buf->padding[read_subbuf];
913 if (read_pos % subbuf_size + count + padding == subbuf_size)
914 end_pos = (read_subbuf + 1) * subbuf_size;
915 else
916 end_pos = read_pos + count;
917 if (end_pos >= subbuf_size * n_subbufs)
918 end_pos = 0;
919
920 return end_pos;
921}
922
923static ssize_t relay_file_read(struct file *filp,
924 char __user *buffer,
925 size_t count,
926 loff_t *ppos)
927{
928 struct rchan_buf *buf = filp->private_data;
929 size_t read_start, avail;
930 size_t written = 0;
931 int ret;
932
933 if (!count)
934 return 0;
935
936 inode_lock(inode: file_inode(f: filp));
937 do {
938 void *from;
939
940 if (!relay_file_read_avail(buf))
941 break;
942
943 read_start = relay_file_read_start_pos(buf);
944 avail = relay_file_read_subbuf_avail(read_pos: read_start, buf);
945 if (!avail)
946 break;
947
948 avail = min(count, avail);
949 from = buf->start + read_start;
950 ret = avail;
951 if (copy_to_user(to: buffer, from, n: avail))
952 break;
953
954 buffer += ret;
955 written += ret;
956 count -= ret;
957
958 relay_file_read_consume(buf, read_pos: read_start, bytes_consumed: ret);
959 *ppos = relay_file_read_end_pos(buf, read_pos: read_start, count: ret);
960 } while (count);
961 inode_unlock(inode: file_inode(f: filp));
962
963 return written;
964}
965
966
967const struct file_operations relay_file_operations = {
968 .open = relay_file_open,
969 .poll = relay_file_poll,
970 .mmap = relay_file_mmap,
971 .read = relay_file_read,
972 .release = relay_file_release,
973};
974EXPORT_SYMBOL_GPL(relay_file_operations);
975

source code of linux/kernel/relay.c

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