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1/*
2 * Public API and common code for kernel->userspace relay file support.
3 *
4 * See Documentation/filesystems/relay.txt 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 * close() vm_op implementation for relay file mapping.
32 */
33static void relay_file_mmap_close(struct vm_area_struct *vma)
34{
35 struct rchan_buf *buf = vma->vm_private_data;
36 buf->chan->cb->buf_unmapped(buf, vma->vm_file);
37}
38
39/*
40 * fault() vm_op implementation for relay file mapping.
41 */
42static int relay_buf_fault(struct vm_fault *vmf)
43{
44 struct page *page;
45 struct rchan_buf *buf = vmf->vma->vm_private_data;
46 pgoff_t pgoff = vmf->pgoff;
47
48 if (!buf)
49 return VM_FAULT_OOM;
50
51 page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
52 if (!page)
53 return VM_FAULT_SIGBUS;
54 get_page(page);
55 vmf->page = page;
56
57 return 0;
58}
59
60/*
61 * vm_ops for relay file mappings.
62 */
63static const struct vm_operations_struct relay_file_mmap_ops = {
64 .fault = relay_buf_fault,
65 .close = relay_file_mmap_close,
66};
67
68/*
69 * allocate an array of pointers of struct page
70 */
71static struct page **relay_alloc_page_array(unsigned int n_pages)
72{
73 const size_t pa_size = n_pages * sizeof(struct page *);
74 if (pa_size > PAGE_SIZE)
75 return vzalloc(pa_size);
76 return kzalloc(pa_size, GFP_KERNEL);
77}
78
79/*
80 * free an array of pointers of struct page
81 */
82static void relay_free_page_array(struct page **array)
83{
84 kvfree(array);
85}
86
87/**
88 * relay_mmap_buf: - mmap channel buffer to process address space
89 * @buf: relay channel buffer
90 * @vma: vm_area_struct describing memory to be mapped
91 *
92 * Returns 0 if ok, negative on error
93 *
94 * Caller should already have grabbed mmap_sem.
95 */
96static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
97{
98 unsigned long length = vma->vm_end - vma->vm_start;
99 struct file *filp = vma->vm_file;
100
101 if (!buf)
102 return -EBADF;
103
104 if (length != (unsigned long)buf->chan->alloc_size)
105 return -EINVAL;
106
107 vma->vm_ops = &relay_file_mmap_ops;
108 vma->vm_flags |= VM_DONTEXPAND;
109 vma->vm_private_data = buf;
110 buf->chan->cb->buf_mapped(buf, filp);
111
112 return 0;
113}
114
115/**
116 * relay_alloc_buf - allocate a channel buffer
117 * @buf: the buffer struct
118 * @size: total size of the buffer
119 *
120 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
121 * passed in size will get page aligned, if it isn't already.
122 */
123static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
124{
125 void *mem;
126 unsigned int i, j, n_pages;
127
128 *size = PAGE_ALIGN(*size);
129 n_pages = *size >> PAGE_SHIFT;
130
131 buf->page_array = relay_alloc_page_array(n_pages);
132 if (!buf->page_array)
133 return NULL;
134
135 for (i = 0; i < n_pages; i++) {
136 buf->page_array[i] = alloc_page(GFP_KERNEL);
137 if (unlikely(!buf->page_array[i]))
138 goto depopulate;
139 set_page_private(buf->page_array[i], (unsigned long)buf);
140 }
141 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
142 if (!mem)
143 goto depopulate;
144
145 memset(mem, 0, *size);
146 buf->page_count = n_pages;
147 return mem;
148
149depopulate:
150 for (j = 0; j < i; j++)
151 __free_page(buf->page_array[j]);
152 relay_free_page_array(buf->page_array);
153 return NULL;
154}
155
156/**
157 * relay_create_buf - allocate and initialize a channel buffer
158 * @chan: the relay channel
159 *
160 * Returns channel buffer if successful, %NULL otherwise.
161 */
162static struct rchan_buf *relay_create_buf(struct rchan *chan)
163{
164 struct rchan_buf *buf;
165
166 if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t *))
167 return NULL;
168
169 buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
170 if (!buf)
171 return NULL;
172 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
173 if (!buf->padding)
174 goto free_buf;
175
176 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
177 if (!buf->start)
178 goto free_buf;
179
180 buf->chan = chan;
181 kref_get(&buf->chan->kref);
182 return buf;
183
184free_buf:
185 kfree(buf->padding);
186 kfree(buf);
187 return NULL;
188}
189
190/**
191 * relay_destroy_channel - free the channel struct
192 * @kref: target kernel reference that contains the relay channel
193 *
194 * Should only be called from kref_put().
195 */
196static void relay_destroy_channel(struct kref *kref)
197{
198 struct rchan *chan = container_of(kref, struct rchan, kref);
199 kfree(chan);
200}
201
202/**
203 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
204 * @buf: the buffer struct
205 */
206static void relay_destroy_buf(struct rchan_buf *buf)
207{
208 struct rchan *chan = buf->chan;
209 unsigned int i;
210
211 if (likely(buf->start)) {
212 vunmap(buf->start);
213 for (i = 0; i < buf->page_count; i++)
214 __free_page(buf->page_array[i]);
215 relay_free_page_array(buf->page_array);
216 }
217 *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
218 kfree(buf->padding);
219 kfree(buf);
220 kref_put(&chan->kref, relay_destroy_channel);
221}
222
223/**
224 * relay_remove_buf - remove a channel buffer
225 * @kref: target kernel reference that contains the relay buffer
226 *
227 * Removes the file from the filesystem, which also frees the
228 * rchan_buf_struct and the channel buffer. Should only be called from
229 * kref_put().
230 */
231static void relay_remove_buf(struct kref *kref)
232{
233 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
234 relay_destroy_buf(buf);
235}
236
237/**
238 * relay_buf_empty - boolean, is the channel buffer empty?
239 * @buf: channel buffer
240 *
241 * Returns 1 if the buffer is empty, 0 otherwise.
242 */
243static int relay_buf_empty(struct rchan_buf *buf)
244{
245 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
246}
247
248/**
249 * relay_buf_full - boolean, is the channel buffer full?
250 * @buf: channel buffer
251 *
252 * Returns 1 if the buffer is full, 0 otherwise.
253 */
254int relay_buf_full(struct rchan_buf *buf)
255{
256 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
257 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
258}
259EXPORT_SYMBOL_GPL(relay_buf_full);
260
261/*
262 * High-level relay kernel API and associated functions.
263 */
264
265/*
266 * rchan_callback implementations defining default channel behavior. Used
267 * in place of corresponding NULL values in client callback struct.
268 */
269
270/*
271 * subbuf_start() default callback. Does nothing.
272 */
273static int subbuf_start_default_callback (struct rchan_buf *buf,
274 void *subbuf,
275 void *prev_subbuf,
276 size_t prev_padding)
277{
278 if (relay_buf_full(buf))
279 return 0;
280
281 return 1;
282}
283
284/*
285 * buf_mapped() default callback. Does nothing.
286 */
287static void buf_mapped_default_callback(struct rchan_buf *buf,
288 struct file *filp)
289{
290}
291
292/*
293 * buf_unmapped() default callback. Does nothing.
294 */
295static void buf_unmapped_default_callback(struct rchan_buf *buf,
296 struct file *filp)
297{
298}
299
300/*
301 * create_buf_file_create() default callback. Does nothing.
302 */
303static struct dentry *create_buf_file_default_callback(const char *filename,
304 struct dentry *parent,
305 umode_t mode,
306 struct rchan_buf *buf,
307 int *is_global)
308{
309 return NULL;
310}
311
312/*
313 * remove_buf_file() default callback. Does nothing.
314 */
315static int remove_buf_file_default_callback(struct dentry *dentry)
316{
317 return -EINVAL;
318}
319
320/* relay channel default callbacks */
321static struct rchan_callbacks default_channel_callbacks = {
322 .subbuf_start = subbuf_start_default_callback,
323 .buf_mapped = buf_mapped_default_callback,
324 .buf_unmapped = buf_unmapped_default_callback,
325 .create_buf_file = create_buf_file_default_callback,
326 .remove_buf_file = remove_buf_file_default_callback,
327};
328
329/**
330 * wakeup_readers - wake up readers waiting on a channel
331 * @work: contains the channel buffer
332 *
333 * This is the function used to defer reader waking
334 */
335static void wakeup_readers(struct irq_work *work)
336{
337 struct rchan_buf *buf;
338
339 buf = container_of(work, struct rchan_buf, wakeup_work);
340 wake_up_interruptible(&buf->read_wait);
341}
342
343/**
344 * __relay_reset - reset a channel buffer
345 * @buf: the channel buffer
346 * @init: 1 if this is a first-time initialization
347 *
348 * See relay_reset() for description of effect.
349 */
350static void __relay_reset(struct rchan_buf *buf, unsigned int init)
351{
352 size_t i;
353
354 if (init) {
355 init_waitqueue_head(&buf->read_wait);
356 kref_init(&buf->kref);
357 init_irq_work(&buf->wakeup_work, wakeup_readers);
358 } else {
359 irq_work_sync(&buf->wakeup_work);
360 }
361
362 buf->subbufs_produced = 0;
363 buf->subbufs_consumed = 0;
364 buf->bytes_consumed = 0;
365 buf->finalized = 0;
366 buf->data = buf->start;
367 buf->offset = 0;
368
369 for (i = 0; i < buf->chan->n_subbufs; i++)
370 buf->padding[i] = 0;
371
372 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
373}
374
375/**
376 * relay_reset - reset the channel
377 * @chan: the channel
378 *
379 * This has the effect of erasing all data from all channel buffers
380 * and restarting the channel in its initial state. The buffers
381 * are not freed, so any mappings are still in effect.
382 *
383 * NOTE. Care should be taken that the channel isn't actually
384 * being used by anything when this call is made.
385 */
386void relay_reset(struct rchan *chan)
387{
388 struct rchan_buf *buf;
389 unsigned int i;
390
391 if (!chan)
392 return;
393
394 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
395 __relay_reset(buf, 0);
396 return;
397 }
398
399 mutex_lock(&relay_channels_mutex);
400 for_each_possible_cpu(i)
401 if ((buf = *per_cpu_ptr(chan->buf, i)))
402 __relay_reset(buf, 0);
403 mutex_unlock(&relay_channels_mutex);
404}
405EXPORT_SYMBOL_GPL(relay_reset);
406
407static inline void relay_set_buf_dentry(struct rchan_buf *buf,
408 struct dentry *dentry)
409{
410 buf->dentry = dentry;
411 d_inode(buf->dentry)->i_size = buf->early_bytes;
412}
413
414static struct dentry *relay_create_buf_file(struct rchan *chan,
415 struct rchan_buf *buf,
416 unsigned int cpu)
417{
418 struct dentry *dentry;
419 char *tmpname;
420
421 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
422 if (!tmpname)
423 return NULL;
424 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
425
426 /* Create file in fs */
427 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
428 S_IRUSR, buf,
429 &chan->is_global);
430
431 kfree(tmpname);
432
433 return dentry;
434}
435
436/*
437 * relay_open_buf - create a new relay channel buffer
438 *
439 * used by relay_open() and CPU hotplug.
440 */
441static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
442{
443 struct rchan_buf *buf = NULL;
444 struct dentry *dentry;
445
446 if (chan->is_global)
447 return *per_cpu_ptr(chan->buf, 0);
448
449 buf = relay_create_buf(chan);
450 if (!buf)
451 return NULL;
452
453 if (chan->has_base_filename) {
454 dentry = relay_create_buf_file(chan, buf, cpu);
455 if (!dentry)
456 goto free_buf;
457 relay_set_buf_dentry(buf, dentry);
458 } else {
459 /* Only retrieve global info, nothing more, nothing less */
460 dentry = chan->cb->create_buf_file(NULL, NULL,
461 S_IRUSR, buf,
462 &chan->is_global);
463 if (WARN_ON(dentry))
464 goto free_buf;
465 }
466
467 buf->cpu = cpu;
468 __relay_reset(buf, 1);
469
470 if(chan->is_global) {
471 *per_cpu_ptr(chan->buf, 0) = buf;
472 buf->cpu = 0;
473 }
474
475 return buf;
476
477free_buf:
478 relay_destroy_buf(buf);
479 return NULL;
480}
481
482/**
483 * relay_close_buf - close a channel buffer
484 * @buf: channel buffer
485 *
486 * Marks the buffer finalized and restores the default callbacks.
487 * The channel buffer and channel buffer data structure are then freed
488 * automatically when the last reference is given up.
489 */
490static void relay_close_buf(struct rchan_buf *buf)
491{
492 buf->finalized = 1;
493 irq_work_sync(&buf->wakeup_work);
494 buf->chan->cb->remove_buf_file(buf->dentry);
495 kref_put(&buf->kref, relay_remove_buf);
496}
497
498static void setup_callbacks(struct rchan *chan,
499 struct rchan_callbacks *cb)
500{
501 if (!cb) {
502 chan->cb = &default_channel_callbacks;
503 return;
504 }
505
506 if (!cb->subbuf_start)
507 cb->subbuf_start = subbuf_start_default_callback;
508 if (!cb->buf_mapped)
509 cb->buf_mapped = buf_mapped_default_callback;
510 if (!cb->buf_unmapped)
511 cb->buf_unmapped = buf_unmapped_default_callback;
512 if (!cb->create_buf_file)
513 cb->create_buf_file = create_buf_file_default_callback;
514 if (!cb->remove_buf_file)
515 cb->remove_buf_file = remove_buf_file_default_callback;
516 chan->cb = cb;
517}
518
519int relay_prepare_cpu(unsigned int cpu)
520{
521 struct rchan *chan;
522 struct rchan_buf *buf;
523
524 mutex_lock(&relay_channels_mutex);
525 list_for_each_entry(chan, &relay_channels, list) {
526 if ((buf = *per_cpu_ptr(chan->buf, cpu)))
527 continue;
528 buf = relay_open_buf(chan, cpu);
529 if (!buf) {
530 pr_err("relay: cpu %d buffer creation failed\n", cpu);
531 mutex_unlock(&relay_channels_mutex);
532 return -ENOMEM;
533 }
534 *per_cpu_ptr(chan->buf, cpu) = buf;
535 }
536 mutex_unlock(&relay_channels_mutex);
537 return 0;
538}
539
540/**
541 * relay_open - create a new relay channel
542 * @base_filename: base name of files to create, %NULL for buffering only
543 * @parent: dentry of parent directory, %NULL for root directory or buffer
544 * @subbuf_size: size of sub-buffers
545 * @n_subbufs: number of sub-buffers
546 * @cb: client callback functions
547 * @private_data: user-defined data
548 *
549 * Returns channel pointer if successful, %NULL otherwise.
550 *
551 * Creates a channel buffer for each cpu using the sizes and
552 * attributes specified. The created channel buffer files
553 * will be named base_filename0...base_filenameN-1. File
554 * permissions will be %S_IRUSR.
555 *
556 * If opening a buffer (@parent = NULL) that you later wish to register
557 * in a filesystem, call relay_late_setup_files() once the @parent dentry
558 * is available.
559 */
560struct rchan *relay_open(const char *base_filename,
561 struct dentry *parent,
562 size_t subbuf_size,
563 size_t n_subbufs,
564 struct rchan_callbacks *cb,
565 void *private_data)
566{
567 unsigned int i;
568 struct rchan *chan;
569 struct rchan_buf *buf;
570
571 if (!(subbuf_size && n_subbufs))
572 return NULL;
573 if (subbuf_size > UINT_MAX / n_subbufs)
574 return NULL;
575
576 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
577 if (!chan)
578 return NULL;
579
580 chan->buf = alloc_percpu(struct rchan_buf *);
581 chan->version = RELAYFS_CHANNEL_VERSION;
582 chan->n_subbufs = n_subbufs;
583 chan->subbuf_size = subbuf_size;
584 chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
585 chan->parent = parent;
586 chan->private_data = private_data;
587 if (base_filename) {
588 chan->has_base_filename = 1;
589 strlcpy(chan->base_filename, base_filename, NAME_MAX);
590 }
591 setup_callbacks(chan, cb);
592 kref_init(&chan->kref);
593
594 mutex_lock(&relay_channels_mutex);
595 for_each_online_cpu(i) {
596 buf = relay_open_buf(chan, i);
597 if (!buf)
598 goto free_bufs;
599 *per_cpu_ptr(chan->buf, i) = buf;
600 }
601 list_add(&chan->list, &relay_channels);
602 mutex_unlock(&relay_channels_mutex);
603
604 return chan;
605
606free_bufs:
607 for_each_possible_cpu(i) {
608 if ((buf = *per_cpu_ptr(chan->buf, i)))
609 relay_close_buf(buf);
610 }
611
612 kref_put(&chan->kref, relay_destroy_channel);
613 mutex_unlock(&relay_channels_mutex);
614 return NULL;
615}
616EXPORT_SYMBOL_GPL(relay_open);
617
618struct rchan_percpu_buf_dispatcher {
619 struct rchan_buf *buf;
620 struct dentry *dentry;
621};
622
623/* Called in atomic context. */
624static void __relay_set_buf_dentry(void *info)
625{
626 struct rchan_percpu_buf_dispatcher *p = info;
627
628 relay_set_buf_dentry(p->buf, p->dentry);
629}
630
631/**
632 * relay_late_setup_files - triggers file creation
633 * @chan: channel to operate on
634 * @base_filename: base name of files to create
635 * @parent: dentry of parent directory, %NULL for root directory
636 *
637 * Returns 0 if successful, non-zero otherwise.
638 *
639 * Use to setup files for a previously buffer-only channel created
640 * by relay_open() with a NULL parent dentry.
641 *
642 * For example, this is useful for perfomring early tracing in kernel,
643 * before VFS is up and then exposing the early results once the dentry
644 * is available.
645 */
646int relay_late_setup_files(struct rchan *chan,
647 const char *base_filename,
648 struct dentry *parent)
649{
650 int err = 0;
651 unsigned int i, curr_cpu;
652 unsigned long flags;
653 struct dentry *dentry;
654 struct rchan_buf *buf;
655 struct rchan_percpu_buf_dispatcher disp;
656
657 if (!chan || !base_filename)
658 return -EINVAL;
659
660 strlcpy(chan->base_filename, base_filename, NAME_MAX);
661
662 mutex_lock(&relay_channels_mutex);
663 /* Is chan already set up? */
664 if (unlikely(chan->has_base_filename)) {
665 mutex_unlock(&relay_channels_mutex);
666 return -EEXIST;
667 }
668 chan->has_base_filename = 1;
669 chan->parent = parent;
670
671 if (chan->is_global) {
672 err = -EINVAL;
673 buf = *per_cpu_ptr(chan->buf, 0);
674 if (!WARN_ON_ONCE(!buf)) {
675 dentry = relay_create_buf_file(chan, buf, 0);
676 if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
677 relay_set_buf_dentry(buf, dentry);
678 err = 0;
679 }
680 }
681 mutex_unlock(&relay_channels_mutex);
682 return err;
683 }
684
685 curr_cpu = get_cpu();
686 /*
687 * The CPU hotplug notifier ran before us and created buffers with
688 * no files associated. So it's safe to call relay_setup_buf_file()
689 * on all currently online CPUs.
690 */
691 for_each_online_cpu(i) {
692 buf = *per_cpu_ptr(chan->buf, i);
693 if (unlikely(!buf)) {
694 WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
695 err = -EINVAL;
696 break;
697 }
698
699 dentry = relay_create_buf_file(chan, buf, i);
700 if (unlikely(!dentry)) {
701 err = -EINVAL;
702 break;
703 }
704
705 if (curr_cpu == i) {
706 local_irq_save(flags);
707 relay_set_buf_dentry(buf, dentry);
708 local_irq_restore(flags);
709 } else {
710 disp.buf = buf;
711 disp.dentry = dentry;
712 smp_mb();
713 /* relay_channels_mutex must be held, so wait. */
714 err = smp_call_function_single(i,
715 __relay_set_buf_dentry,
716 &disp, 1);
717 }
718 if (unlikely(err))
719 break;
720 }
721 put_cpu();
722 mutex_unlock(&relay_channels_mutex);
723
724 return err;
725}
726EXPORT_SYMBOL_GPL(relay_late_setup_files);
727
728/**
729 * relay_switch_subbuf - switch to a new sub-buffer
730 * @buf: channel buffer
731 * @length: size of current event
732 *
733 * Returns either the length passed in or 0 if full.
734 *
735 * Performs sub-buffer-switch tasks such as invoking callbacks,
736 * updating padding counts, waking up readers, etc.
737 */
738size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
739{
740 void *old, *new;
741 size_t old_subbuf, new_subbuf;
742
743 if (unlikely(length > buf->chan->subbuf_size))
744 goto toobig;
745
746 if (buf->offset != buf->chan->subbuf_size + 1) {
747 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
748 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
749 buf->padding[old_subbuf] = buf->prev_padding;
750 buf->subbufs_produced++;
751 if (buf->dentry)
752 d_inode(buf->dentry)->i_size +=
753 buf->chan->subbuf_size -
754 buf->padding[old_subbuf];
755 else
756 buf->early_bytes += buf->chan->subbuf_size -
757 buf->padding[old_subbuf];
758 smp_mb();
759 if (waitqueue_active(&buf->read_wait)) {
760 /*
761 * Calling wake_up_interruptible() from here
762 * will deadlock if we happen to be logging
763 * from the scheduler (trying to re-grab
764 * rq->lock), so defer it.
765 */
766 irq_work_queue(&buf->wakeup_work);
767 }
768 }
769
770 old = buf->data;
771 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
772 new = buf->start + new_subbuf * buf->chan->subbuf_size;
773 buf->offset = 0;
774 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
775 buf->offset = buf->chan->subbuf_size + 1;
776 return 0;
777 }
778 buf->data = new;
779 buf->padding[new_subbuf] = 0;
780
781 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
782 goto toobig;
783
784 return length;
785
786toobig:
787 buf->chan->last_toobig = length;
788 return 0;
789}
790EXPORT_SYMBOL_GPL(relay_switch_subbuf);
791
792/**
793 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
794 * @chan: the channel
795 * @cpu: the cpu associated with the channel buffer to update
796 * @subbufs_consumed: number of sub-buffers to add to current buf's count
797 *
798 * Adds to the channel buffer's consumed sub-buffer count.
799 * subbufs_consumed should be the number of sub-buffers newly consumed,
800 * not the total consumed.
801 *
802 * NOTE. Kernel clients don't need to call this function if the channel
803 * mode is 'overwrite'.
804 */
805void relay_subbufs_consumed(struct rchan *chan,
806 unsigned int cpu,
807 size_t subbufs_consumed)
808{
809 struct rchan_buf *buf;
810
811 if (!chan || cpu >= NR_CPUS)
812 return;
813
814 buf = *per_cpu_ptr(chan->buf, cpu);
815 if (!buf || subbufs_consumed > chan->n_subbufs)
816 return;
817
818 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
819 buf->subbufs_consumed = buf->subbufs_produced;
820 else
821 buf->subbufs_consumed += subbufs_consumed;
822}
823EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
824
825/**
826 * relay_close - close the channel
827 * @chan: the channel
828 *
829 * Closes all channel buffers and frees the channel.
830 */
831void relay_close(struct rchan *chan)
832{
833 struct rchan_buf *buf;
834 unsigned int i;
835
836 if (!chan)
837 return;
838
839 mutex_lock(&relay_channels_mutex);
840 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
841 relay_close_buf(buf);
842 else
843 for_each_possible_cpu(i)
844 if ((buf = *per_cpu_ptr(chan->buf, i)))
845 relay_close_buf(buf);
846
847 if (chan->last_toobig)
848 printk(KERN_WARNING "relay: one or more items not logged "
849 "[item size (%zd) > sub-buffer size (%zd)]\n",
850 chan->last_toobig, chan->subbuf_size);
851
852 list_del(&chan->list);
853 kref_put(&chan->kref, relay_destroy_channel);
854 mutex_unlock(&relay_channels_mutex);
855}
856EXPORT_SYMBOL_GPL(relay_close);
857
858/**
859 * relay_flush - close the channel
860 * @chan: the channel
861 *
862 * Flushes all channel buffers, i.e. forces buffer switch.
863 */
864void relay_flush(struct rchan *chan)
865{
866 struct rchan_buf *buf;
867 unsigned int i;
868
869 if (!chan)
870 return;
871
872 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
873 relay_switch_subbuf(buf, 0);
874 return;
875 }
876
877 mutex_lock(&relay_channels_mutex);
878 for_each_possible_cpu(i)
879 if ((buf = *per_cpu_ptr(chan->buf, i)))
880 relay_switch_subbuf(buf, 0);
881 mutex_unlock(&relay_channels_mutex);
882}
883EXPORT_SYMBOL_GPL(relay_flush);
884
885/**
886 * relay_file_open - open file op for relay files
887 * @inode: the inode
888 * @filp: the file
889 *
890 * Increments the channel buffer refcount.
891 */
892static int relay_file_open(struct inode *inode, struct file *filp)
893{
894 struct rchan_buf *buf = inode->i_private;
895 kref_get(&buf->kref);
896 filp->private_data = buf;
897
898 return nonseekable_open(inode, filp);
899}
900
901/**
902 * relay_file_mmap - mmap file op for relay files
903 * @filp: the file
904 * @vma: the vma describing what to map
905 *
906 * Calls upon relay_mmap_buf() to map the file into user space.
907 */
908static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
909{
910 struct rchan_buf *buf = filp->private_data;
911 return relay_mmap_buf(buf, vma);
912}
913
914/**
915 * relay_file_poll - poll file op for relay files
916 * @filp: the file
917 * @wait: poll table
918 *
919 * Poll implemention.
920 */
921static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
922{
923 __poll_t mask = 0;
924 struct rchan_buf *buf = filp->private_data;
925
926 if (buf->finalized)
927 return EPOLLERR;
928
929 if (filp->f_mode & FMODE_READ) {
930 poll_wait(filp, &buf->read_wait, wait);
931 if (!relay_buf_empty(buf))
932 mask |= EPOLLIN | EPOLLRDNORM;
933 }
934
935 return mask;
936}
937
938/**
939 * relay_file_release - release file op for relay files
940 * @inode: the inode
941 * @filp: the file
942 *
943 * Decrements the channel refcount, as the filesystem is
944 * no longer using it.
945 */
946static int relay_file_release(struct inode *inode, struct file *filp)
947{
948 struct rchan_buf *buf = filp->private_data;
949 kref_put(&buf->kref, relay_remove_buf);
950
951 return 0;
952}
953
954/*
955 * relay_file_read_consume - update the consumed count for the buffer
956 */
957static void relay_file_read_consume(struct rchan_buf *buf,
958 size_t read_pos,
959 size_t bytes_consumed)
960{
961 size_t subbuf_size = buf->chan->subbuf_size;
962 size_t n_subbufs = buf->chan->n_subbufs;
963 size_t read_subbuf;
964
965 if (buf->subbufs_produced == buf->subbufs_consumed &&
966 buf->offset == buf->bytes_consumed)
967 return;
968
969 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
970 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
971 buf->bytes_consumed = 0;
972 }
973
974 buf->bytes_consumed += bytes_consumed;
975 if (!read_pos)
976 read_subbuf = buf->subbufs_consumed % n_subbufs;
977 else
978 read_subbuf = read_pos / buf->chan->subbuf_size;
979 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
980 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
981 (buf->offset == subbuf_size))
982 return;
983 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
984 buf->bytes_consumed = 0;
985 }
986}
987
988/*
989 * relay_file_read_avail - boolean, are there unconsumed bytes available?
990 */
991static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
992{
993 size_t subbuf_size = buf->chan->subbuf_size;
994 size_t n_subbufs = buf->chan->n_subbufs;
995 size_t produced = buf->subbufs_produced;
996 size_t consumed = buf->subbufs_consumed;
997
998 relay_file_read_consume(buf, read_pos, 0);
999
1000 consumed = buf->subbufs_consumed;
1001
1002 if (unlikely(buf->offset > subbuf_size)) {
1003 if (produced == consumed)
1004 return 0;
1005 return 1;
1006 }
1007
1008 if (unlikely(produced - consumed >= n_subbufs)) {
1009 consumed = produced - n_subbufs + 1;
1010 buf->subbufs_consumed = consumed;
1011 buf->bytes_consumed = 0;
1012 }
1013
1014 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
1015 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
1016
1017 if (consumed > produced)
1018 produced += n_subbufs * subbuf_size;
1019
1020 if (consumed == produced) {
1021 if (buf->offset == subbuf_size &&
1022 buf->subbufs_produced > buf->subbufs_consumed)
1023 return 1;
1024 return 0;
1025 }
1026
1027 return 1;
1028}
1029
1030/**
1031 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1032 * @read_pos: file read position
1033 * @buf: relay channel buffer
1034 */
1035static size_t relay_file_read_subbuf_avail(size_t read_pos,
1036 struct rchan_buf *buf)
1037{
1038 size_t padding, avail = 0;
1039 size_t read_subbuf, read_offset, write_subbuf, write_offset;
1040 size_t subbuf_size = buf->chan->subbuf_size;
1041
1042 write_subbuf = (buf->data - buf->start) / subbuf_size;
1043 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1044 read_subbuf = read_pos / subbuf_size;
1045 read_offset = read_pos % subbuf_size;
1046 padding = buf->padding[read_subbuf];
1047
1048 if (read_subbuf == write_subbuf) {
1049 if (read_offset + padding < write_offset)
1050 avail = write_offset - (read_offset + padding);
1051 } else
1052 avail = (subbuf_size - padding) - read_offset;
1053
1054 return avail;
1055}
1056
1057/**
1058 * relay_file_read_start_pos - find the first available byte to read
1059 * @read_pos: file read position
1060 * @buf: relay channel buffer
1061 *
1062 * If the @read_pos is in the middle of padding, return the
1063 * position of the first actually available byte, otherwise
1064 * return the original value.
1065 */
1066static size_t relay_file_read_start_pos(size_t read_pos,
1067 struct rchan_buf *buf)
1068{
1069 size_t read_subbuf, padding, padding_start, padding_end;
1070 size_t subbuf_size = buf->chan->subbuf_size;
1071 size_t n_subbufs = buf->chan->n_subbufs;
1072 size_t consumed = buf->subbufs_consumed % n_subbufs;
1073
1074 if (!read_pos)
1075 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1076 read_subbuf = read_pos / subbuf_size;
1077 padding = buf->padding[read_subbuf];
1078 padding_start = (read_subbuf + 1) * subbuf_size - padding;
1079 padding_end = (read_subbuf + 1) * subbuf_size;
1080 if (read_pos >= padding_start && read_pos < padding_end) {
1081 read_subbuf = (read_subbuf + 1) % n_subbufs;
1082 read_pos = read_subbuf * subbuf_size;
1083 }
1084
1085 return read_pos;
1086}
1087
1088/**
1089 * relay_file_read_end_pos - return the new read position
1090 * @read_pos: file read position
1091 * @buf: relay channel buffer
1092 * @count: number of bytes to be read
1093 */
1094static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1095 size_t read_pos,
1096 size_t count)
1097{
1098 size_t read_subbuf, padding, end_pos;
1099 size_t subbuf_size = buf->chan->subbuf_size;
1100 size_t n_subbufs = buf->chan->n_subbufs;
1101
1102 read_subbuf = read_pos / subbuf_size;
1103 padding = buf->padding[read_subbuf];
1104 if (read_pos % subbuf_size + count + padding == subbuf_size)
1105 end_pos = (read_subbuf + 1) * subbuf_size;
1106 else
1107 end_pos = read_pos + count;
1108 if (end_pos >= subbuf_size * n_subbufs)
1109 end_pos = 0;
1110
1111 return end_pos;
1112}
1113
1114static ssize_t relay_file_read(struct file *filp,
1115 char __user *buffer,
1116 size_t count,
1117 loff_t *ppos)
1118{
1119 struct rchan_buf *buf = filp->private_data;
1120 size_t read_start, avail;
1121 size_t written = 0;
1122 int ret;
1123
1124 if (!count)
1125 return 0;
1126
1127 inode_lock(file_inode(filp));
1128 do {
1129 void *from;
1130
1131 if (!relay_file_read_avail(buf, *ppos))
1132 break;
1133
1134 read_start = relay_file_read_start_pos(*ppos, buf);
1135 avail = relay_file_read_subbuf_avail(read_start, buf);
1136 if (!avail)
1137 break;
1138
1139 avail = min(count, avail);
1140 from = buf->start + read_start;
1141 ret = avail;
1142 if (copy_to_user(buffer, from, avail))
1143 break;
1144
1145 buffer += ret;
1146 written += ret;
1147 count -= ret;
1148
1149 relay_file_read_consume(buf, read_start, ret);
1150 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1151 } while (count);
1152 inode_unlock(file_inode(filp));
1153
1154 return written;
1155}
1156
1157static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1158{
1159 rbuf->bytes_consumed += bytes_consumed;
1160
1161 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1162 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1163 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1164 }
1165}
1166
1167static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1168 struct pipe_buffer *buf)
1169{
1170 struct rchan_buf *rbuf;
1171
1172 rbuf = (struct rchan_buf *)page_private(buf->page);
1173 relay_consume_bytes(rbuf, buf->private);
1174}
1175
1176static const struct pipe_buf_operations relay_pipe_buf_ops = {
1177 .can_merge = 0,
1178 .confirm = generic_pipe_buf_confirm,
1179 .release = relay_pipe_buf_release,
1180 .steal = generic_pipe_buf_steal,
1181 .get = generic_pipe_buf_get,
1182};
1183
1184static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1185{
1186}
1187
1188/*
1189 * subbuf_splice_actor - splice up to one subbuf's worth of data
1190 */
1191static ssize_t subbuf_splice_actor(struct file *in,
1192 loff_t *ppos,
1193 struct pipe_inode_info *pipe,
1194 size_t len,
1195 unsigned int flags,
1196 int *nonpad_ret)
1197{
1198 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1199 struct rchan_buf *rbuf = in->private_data;
1200 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1201 uint64_t pos = (uint64_t) *ppos;
1202 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1203 size_t read_start = (size_t) do_div(pos, alloc_size);
1204 size_t read_subbuf = read_start / subbuf_size;
1205 size_t padding = rbuf->padding[read_subbuf];
1206 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1207 struct page *pages[PIPE_DEF_BUFFERS];
1208 struct partial_page partial[PIPE_DEF_BUFFERS];
1209 struct splice_pipe_desc spd = {
1210 .pages = pages,
1211 .nr_pages = 0,
1212 .nr_pages_max = PIPE_DEF_BUFFERS,
1213 .partial = partial,
1214 .ops = &relay_pipe_buf_ops,
1215 .spd_release = relay_page_release,
1216 };
1217 ssize_t ret;
1218
1219 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1220 return 0;
1221 if (splice_grow_spd(pipe, &spd))
1222 return -ENOMEM;
1223
1224 /*
1225 * Adjust read len, if longer than what is available
1226 */
1227 if (len > (subbuf_size - read_start % subbuf_size))
1228 len = subbuf_size - read_start % subbuf_size;
1229
1230 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1231 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1232 poff = read_start & ~PAGE_MASK;
1233 nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1234
1235 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1236 unsigned int this_len, this_end, private;
1237 unsigned int cur_pos = read_start + total_len;
1238
1239 if (!len)
1240 break;
1241
1242 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1243 private = this_len;
1244
1245 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1246 spd.partial[spd.nr_pages].offset = poff;
1247
1248 this_end = cur_pos + this_len;
1249 if (this_end >= nonpad_end) {
1250 this_len = nonpad_end - cur_pos;
1251 private = this_len + padding;
1252 }
1253 spd.partial[spd.nr_pages].len = this_len;
1254 spd.partial[spd.nr_pages].private = private;
1255
1256 len -= this_len;
1257 total_len += this_len;
1258 poff = 0;
1259 pidx = (pidx + 1) % subbuf_pages;
1260
1261 if (this_end >= nonpad_end) {
1262 spd.nr_pages++;
1263 break;
1264 }
1265 }
1266
1267 ret = 0;
1268 if (!spd.nr_pages)
1269 goto out;
1270
1271 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1272 if (ret < 0 || ret < total_len)
1273 goto out;
1274
1275 if (read_start + ret == nonpad_end)
1276 ret += padding;
1277
1278out:
1279 splice_shrink_spd(&spd);
1280 return ret;
1281}
1282
1283static ssize_t relay_file_splice_read(struct file *in,
1284 loff_t *ppos,
1285 struct pipe_inode_info *pipe,
1286 size_t len,
1287 unsigned int flags)
1288{
1289 ssize_t spliced;
1290 int ret;
1291 int nonpad_ret = 0;
1292
1293 ret = 0;
1294 spliced = 0;
1295
1296 while (len && !spliced) {
1297 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1298 if (ret < 0)
1299 break;
1300 else if (!ret) {
1301 if (flags & SPLICE_F_NONBLOCK)
1302 ret = -EAGAIN;
1303 break;
1304 }
1305
1306 *ppos += ret;
1307 if (ret > len)
1308 len = 0;
1309 else
1310 len -= ret;
1311 spliced += nonpad_ret;
1312 nonpad_ret = 0;
1313 }
1314
1315 if (spliced)
1316 return spliced;
1317
1318 return ret;
1319}
1320
1321const struct file_operations relay_file_operations = {
1322 .open = relay_file_open,
1323 .poll = relay_file_poll,
1324 .mmap = relay_file_mmap,
1325 .read = relay_file_read,
1326 .llseek = no_llseek,
1327 .release = relay_file_release,
1328 .splice_read = relay_file_splice_read,
1329};
1330EXPORT_SYMBOL_GPL(relay_file_operations);
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(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(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(buf->page_array[i], (unsigned long)buf);
125 }
126 mem = vmap(buf->page_array, 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(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, &chan->alloc_size);
163 if (!buf->start)
164 goto free_buf;
165
166 buf->chan = chan;
167 kref_get(&buf->chan->kref);
168 return buf;
169
170free_buf:
171 kfree(buf->padding);
172 kfree(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(chan->buf);
186 kfree(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(buf->start);
200 for (i = 0; i < buf->page_count; i++)
201 __free_page(buf->page_array[i]);
202 relay_free_page_array(buf->page_array);
203 }
204 *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
205 kfree(buf->padding);
206 kfree(buf);
207 kref_put(&chan->kref, 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(&buf->kref);
290 init_irq_work(&buf->wakeup_work, wakeup_readers);
291 } else {
292 irq_work_sync(&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, buf->data, NULL, 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, 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, 0);
336 mutex_unlock(&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(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 = kzalloc(NAME_MAX + 1, GFP_KERNEL);
355 if (!tmpname)
356 return NULL;
357 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
358
359 /* Create file in fs */
360 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
361 S_IRUSR, buf,
362 &chan->is_global);
363 if (IS_ERR(dentry))
364 dentry = NULL;
365
366 kfree(tmpname);
367
368 return dentry;
369}
370
371/*
372 * relay_open_buf - create a new relay channel buffer
373 *
374 * used by relay_open() and CPU hotplug.
375 */
376static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
377{
378 struct rchan_buf *buf;
379 struct dentry *dentry;
380
381 if (chan->is_global)
382 return *per_cpu_ptr(chan->buf, 0);
383
384 buf = relay_create_buf(chan);
385 if (!buf)
386 return NULL;
387
388 if (chan->has_base_filename) {
389 dentry = relay_create_buf_file(chan, buf, cpu);
390 if (!dentry)
391 goto free_buf;
392 relay_set_buf_dentry(buf, dentry);
393 } else {
394 /* Only retrieve global info, nothing more, nothing less */
395 dentry = chan->cb->create_buf_file(NULL, NULL,
396 S_IRUSR, buf,
397 &chan->is_global);
398 if (IS_ERR_OR_NULL(dentry))
399 goto free_buf;
400 }
401
402 buf->cpu = cpu;
403 __relay_reset(buf, 1);
404
405 if(chan->is_global) {
406 *per_cpu_ptr(chan->buf, 0) = buf;
407 buf->cpu = 0;
408 }
409
410 return buf;
411
412free_buf:
413 relay_destroy_buf(buf);
414 return NULL;
415}
416
417/**
418 * relay_close_buf - close a channel buffer
419 * @buf: channel buffer
420 *
421 * Marks the buffer finalized and restores the default callbacks.
422 * The channel buffer and channel buffer data structure are then freed
423 * automatically when the last reference is given up.
424 */
425static void relay_close_buf(struct rchan_buf *buf)
426{
427 buf->finalized = 1;
428 irq_work_sync(&buf->wakeup_work);
429 buf->chan->cb->remove_buf_file(buf->dentry);
430 kref_put(&buf->kref, relay_remove_buf);
431}
432
433int relay_prepare_cpu(unsigned int cpu)
434{
435 struct rchan *chan;
436 struct rchan_buf *buf;
437
438 mutex_lock(&relay_channels_mutex);
439 list_for_each_entry(chan, &relay_channels, list) {
440 if (*per_cpu_ptr(chan->buf, cpu))
441 continue;
442 buf = relay_open_buf(chan, cpu);
443 if (!buf) {
444 pr_err("relay: cpu %d buffer creation failed\n", cpu);
445 mutex_unlock(&relay_channels_mutex);
446 return -ENOMEM;
447 }
448 *per_cpu_ptr(chan->buf, cpu) = buf;
449 }
450 mutex_unlock(&relay_channels_mutex);
451 return 0;
452}
453
454/**
455 * relay_open - create a new relay channel
456 * @base_filename: base name of files to create, %NULL for buffering only
457 * @parent: dentry of parent directory, %NULL for root directory or buffer
458 * @subbuf_size: size of sub-buffers
459 * @n_subbufs: number of sub-buffers
460 * @cb: client callback functions
461 * @private_data: user-defined data
462 *
463 * Returns channel pointer if successful, %NULL otherwise.
464 *
465 * Creates a channel buffer for each cpu using the sizes and
466 * attributes specified. The created channel buffer files
467 * will be named base_filename0...base_filenameN-1. File
468 * permissions will be %S_IRUSR.
469 *
470 * If opening a buffer (@parent = NULL) that you later wish to register
471 * in a filesystem, call relay_late_setup_files() once the @parent dentry
472 * is available.
473 */
474struct rchan *relay_open(const char *base_filename,
475 struct dentry *parent,
476 size_t subbuf_size,
477 size_t n_subbufs,
478 const struct rchan_callbacks *cb,
479 void *private_data)
480{
481 unsigned int i;
482 struct rchan *chan;
483 struct rchan_buf *buf;
484
485 if (!(subbuf_size && n_subbufs))
486 return NULL;
487 if (subbuf_size > UINT_MAX / n_subbufs)
488 return NULL;
489 if (!cb || !cb->create_buf_file || !cb->remove_buf_file)
490 return NULL;
491
492 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
493 if (!chan)
494 return NULL;
495
496 chan->buf = alloc_percpu(struct rchan_buf *);
497 if (!chan->buf) {
498 kfree(chan);
499 return NULL;
500 }
501
502 chan->version = RELAYFS_CHANNEL_VERSION;
503 chan->n_subbufs = n_subbufs;
504 chan->subbuf_size = subbuf_size;
505 chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
506 chan->parent = parent;
507 chan->private_data = private_data;
508 if (base_filename) {
509 chan->has_base_filename = 1;
510 strscpy(chan->base_filename, base_filename, NAME_MAX);
511 }
512 chan->cb = cb;
513 kref_init(&chan->kref);
514
515 mutex_lock(&relay_channels_mutex);
516 for_each_online_cpu(i) {
517 buf = relay_open_buf(chan, i);
518 if (!buf)
519 goto free_bufs;
520 *per_cpu_ptr(chan->buf, i) = buf;
521 }
522 list_add(&chan->list, &relay_channels);
523 mutex_unlock(&relay_channels_mutex);
524
525 return chan;
526
527free_bufs:
528 for_each_possible_cpu(i) {
529 if ((buf = *per_cpu_ptr(chan->buf, i)))
530 relay_close_buf(buf);
531 }
532
533 kref_put(&chan->kref, relay_destroy_channel);
534 mutex_unlock(&relay_channels_mutex);
535 return NULL;
536}
537EXPORT_SYMBOL_GPL(relay_open);
538
539struct rchan_percpu_buf_dispatcher {
540 struct rchan_buf *buf;
541 struct dentry *dentry;
542};
543
544/* Called in atomic context. */
545static void __relay_set_buf_dentry(void *info)
546{
547 struct rchan_percpu_buf_dispatcher *p = info;
548
549 relay_set_buf_dentry(p->buf, p->dentry);
550}
551
552/**
553 * relay_late_setup_files - triggers file creation
554 * @chan: channel to operate on
555 * @base_filename: base name of files to create
556 * @parent: dentry of parent directory, %NULL for root directory
557 *
558 * Returns 0 if successful, non-zero otherwise.
559 *
560 * Use to setup files for a previously buffer-only channel created
561 * by relay_open() with a NULL parent dentry.
562 *
563 * For example, this is useful for perfomring early tracing in kernel,
564 * before VFS is up and then exposing the early results once the dentry
565 * is available.
566 */
567int relay_late_setup_files(struct rchan *chan,
568 const char *base_filename,
569 struct dentry *parent)
570{
571 int err = 0;
572 unsigned int i, curr_cpu;
573 unsigned long flags;
574 struct dentry *dentry;
575 struct rchan_buf *buf;
576 struct rchan_percpu_buf_dispatcher disp;
577
578 if (!chan || !base_filename)
579 return -EINVAL;
580
581 strscpy(chan->base_filename, base_filename, NAME_MAX);
582
583 mutex_lock(&relay_channels_mutex);
584 /* Is chan already set up? */
585 if (unlikely(chan->has_base_filename)) {
586 mutex_unlock(&relay_channels_mutex);
587 return -EEXIST;
588 }
589 chan->has_base_filename = 1;
590 chan->parent = parent;
591
592 if (chan->is_global) {
593 err = -EINVAL;
594 buf = *per_cpu_ptr(chan->buf, 0);
595 if (!WARN_ON_ONCE(!buf)) {
596 dentry = relay_create_buf_file(chan, buf, 0);
597 if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
598 relay_set_buf_dentry(buf, dentry);
599 err = 0;
600 }
601 }
602 mutex_unlock(&relay_channels_mutex);
603 return err;
604 }
605
606 curr_cpu = get_cpu();
607 /*
608 * The CPU hotplug notifier ran before us and created buffers with
609 * no files associated. So it's safe to call relay_setup_buf_file()
610 * on all currently online CPUs.
611 */
612 for_each_online_cpu(i) {
613 buf = *per_cpu_ptr(chan->buf, i);
614 if (unlikely(!buf)) {
615 WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
616 err = -EINVAL;
617 break;
618 }
619
620 dentry = relay_create_buf_file(chan, buf, i);
621 if (unlikely(!dentry)) {
622 err = -EINVAL;
623 break;
624 }
625
626 if (curr_cpu == i) {
627 local_irq_save(flags);
628 relay_set_buf_dentry(buf, dentry);
629 local_irq_restore(flags);
630 } else {
631 disp.buf = buf;
632 disp.dentry = dentry;
633 smp_mb();
634 /* relay_channels_mutex must be held, so wait. */
635 err = smp_call_function_single(i,
636 __relay_set_buf_dentry,
637 &disp, 1);
638 }
639 if (unlikely(err))
640 break;
641 }
642 put_cpu();
643 mutex_unlock(&relay_channels_mutex);
644
645 return err;
646}
647EXPORT_SYMBOL_GPL(relay_late_setup_files);
648
649/**
650 * relay_switch_subbuf - switch to a new sub-buffer
651 * @buf: channel buffer
652 * @length: size of current event
653 *
654 * Returns either the length passed in or 0 if full.
655 *
656 * Performs sub-buffer-switch tasks such as invoking callbacks,
657 * updating padding counts, waking up readers, etc.
658 */
659size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
660{
661 void *old, *new;
662 size_t old_subbuf, new_subbuf;
663
664 if (unlikely(length > buf->chan->subbuf_size))
665 goto toobig;
666
667 if (buf->offset != buf->chan->subbuf_size + 1) {
668 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
669 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
670 buf->padding[old_subbuf] = buf->prev_padding;
671 buf->subbufs_produced++;
672 if (buf->dentry)
673 d_inode(buf->dentry)->i_size +=
674 buf->chan->subbuf_size -
675 buf->padding[old_subbuf];
676 else
677 buf->early_bytes += buf->chan->subbuf_size -
678 buf->padding[old_subbuf];
679 smp_mb();
680 if (waitqueue_active(&buf->read_wait)) {
681 /*
682 * Calling wake_up_interruptible() from here
683 * will deadlock if we happen to be logging
684 * from the scheduler (trying to re-grab
685 * rq->lock), so defer it.
686 */
687 irq_work_queue(&buf->wakeup_work);
688 }
689 }
690
691 old = buf->data;
692 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
693 new = buf->start + new_subbuf * buf->chan->subbuf_size;
694 buf->offset = 0;
695 if (!relay_subbuf_start(buf, new, old, buf->prev_padding)) {
696 buf->offset = buf->chan->subbuf_size + 1;
697 return 0;
698 }
699 buf->data = new;
700 buf->padding[new_subbuf] = 0;
701
702 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
703 goto toobig;
704
705 return length;
706
707toobig:
708 buf->chan->last_toobig = length;
709 return 0;
710}
711EXPORT_SYMBOL_GPL(relay_switch_subbuf);
712
713/**
714 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
715 * @chan: the channel
716 * @cpu: the cpu associated with the channel buffer to update
717 * @subbufs_consumed: number of sub-buffers to add to current buf's count
718 *
719 * Adds to the channel buffer's consumed sub-buffer count.
720 * subbufs_consumed should be the number of sub-buffers newly consumed,
721 * not the total consumed.
722 *
723 * NOTE. Kernel clients don't need to call this function if the channel
724 * mode is 'overwrite'.
725 */
726void relay_subbufs_consumed(struct rchan *chan,
727 unsigned int cpu,
728 size_t subbufs_consumed)
729{
730 struct rchan_buf *buf;
731
732 if (!chan || cpu >= NR_CPUS)
733 return;
734
735 buf = *per_cpu_ptr(chan->buf, cpu);
736 if (!buf || subbufs_consumed > chan->n_subbufs)
737 return;
738
739 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
740 buf->subbufs_consumed = buf->subbufs_produced;
741 else
742 buf->subbufs_consumed += subbufs_consumed;
743}
744EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
745
746/**
747 * relay_close - close the channel
748 * @chan: the channel
749 *
750 * Closes all channel buffers and frees the channel.
751 */
752void relay_close(struct rchan *chan)
753{
754 struct rchan_buf *buf;
755 unsigned int i;
756
757 if (!chan)
758 return;
759
760 mutex_lock(&relay_channels_mutex);
761 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
762 relay_close_buf(buf);
763 else
764 for_each_possible_cpu(i)
765 if ((buf = *per_cpu_ptr(chan->buf, i)))
766 relay_close_buf(buf);
767
768 if (chan->last_toobig)
769 printk(KERN_WARNING "relay: one or more items not logged "
770 "[item size (%zd) > sub-buffer size (%zd)]\n",
771 chan->last_toobig, chan->subbuf_size);
772
773 list_del(&chan->list);
774 kref_put(&chan->kref, relay_destroy_channel);
775 mutex_unlock(&relay_channels_mutex);
776}
777EXPORT_SYMBOL_GPL(relay_close);
778
779/**
780 * relay_flush - close the channel
781 * @chan: the channel
782 *
783 * Flushes all channel buffers, i.e. forces buffer switch.
784 */
785void relay_flush(struct rchan *chan)
786{
787 struct rchan_buf *buf;
788 unsigned int i;
789
790 if (!chan)
791 return;
792
793 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
794 relay_switch_subbuf(buf, 0);
795 return;
796 }
797
798 mutex_lock(&relay_channels_mutex);
799 for_each_possible_cpu(i)
800 if ((buf = *per_cpu_ptr(chan->buf, i)))
801 relay_switch_subbuf(buf, 0);
802 mutex_unlock(&relay_channels_mutex);
803}
804EXPORT_SYMBOL_GPL(relay_flush);
805
806/**
807 * relay_file_open - open file op for relay files
808 * @inode: the inode
809 * @filp: the file
810 *
811 * Increments the channel buffer refcount.
812 */
813static int relay_file_open(struct inode *inode, struct file *filp)
814{
815 struct rchan_buf *buf = inode->i_private;
816 kref_get(&buf->kref);
817 filp->private_data = buf;
818
819 return nonseekable_open(inode, filp);
820}
821
822/**
823 * relay_file_mmap - mmap file op for relay files
824 * @filp: the file
825 * @vma: the vma describing what to map
826 *
827 * Calls upon relay_mmap_buf() to map the file into user space.
828 */
829static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
830{
831 struct rchan_buf *buf = filp->private_data;
832 return relay_mmap_buf(buf, vma);
833}
834
835/**
836 * relay_file_poll - poll file op for relay files
837 * @filp: the file
838 * @wait: poll table
839 *
840 * Poll implemention.
841 */
842static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
843{
844 __poll_t mask = 0;
845 struct rchan_buf *buf = filp->private_data;
846
847 if (buf->finalized)
848 return EPOLLERR;
849
850 if (filp->f_mode & FMODE_READ) {
851 poll_wait(filp, &buf->read_wait, wait);
852 if (!relay_buf_empty(buf))
853 mask |= EPOLLIN | EPOLLRDNORM;
854 }
855
856 return mask;
857}
858
859/**
860 * relay_file_release - release file op for relay files
861 * @inode: the inode
862 * @filp: the file
863 *
864 * Decrements the channel refcount, as the filesystem is
865 * no longer using it.
866 */
867static int relay_file_release(struct inode *inode, struct file *filp)
868{
869 struct rchan_buf *buf = filp->private_data;
870 kref_put(&buf->kref, relay_remove_buf);
871
872 return 0;
873}
874
875/*
876 * relay_file_read_consume - update the consumed count for the buffer
877 */
878static void relay_file_read_consume(struct rchan_buf *buf,
879 size_t read_pos,
880 size_t bytes_consumed)
881{
882 size_t subbuf_size = buf->chan->subbuf_size;
883 size_t n_subbufs = buf->chan->n_subbufs;
884 size_t read_subbuf;
885
886 if (buf->subbufs_produced == buf->subbufs_consumed &&
887 buf->offset == buf->bytes_consumed)
888 return;
889
890 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
891 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
892 buf->bytes_consumed = 0;
893 }
894
895 buf->bytes_consumed += bytes_consumed;
896 if (!read_pos)
897 read_subbuf = buf->subbufs_consumed % n_subbufs;
898 else
899 read_subbuf = read_pos / buf->chan->subbuf_size;
900 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
901 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
902 (buf->offset == subbuf_size))
903 return;
904 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
905 buf->bytes_consumed = 0;
906 }
907}
908
909/*
910 * relay_file_read_avail - boolean, are there unconsumed bytes available?
911 */
912static int relay_file_read_avail(struct rchan_buf *buf)
913{
914 size_t subbuf_size = buf->chan->subbuf_size;
915 size_t n_subbufs = buf->chan->n_subbufs;
916 size_t produced = buf->subbufs_produced;
917 size_t consumed;
918
919 relay_file_read_consume(buf, 0, 0);
920
921 consumed = buf->subbufs_consumed;
922
923 if (unlikely(buf->offset > subbuf_size)) {
924 if (produced == consumed)
925 return 0;
926 return 1;
927 }
928
929 if (unlikely(produced - consumed >= n_subbufs)) {
930 consumed = produced - n_subbufs + 1;
931 buf->subbufs_consumed = consumed;
932 buf->bytes_consumed = 0;
933 }
934
935 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
936 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
937
938 if (consumed > produced)
939 produced += n_subbufs * subbuf_size;
940
941 if (consumed == produced) {
942 if (buf->offset == subbuf_size &&
943 buf->subbufs_produced > buf->subbufs_consumed)
944 return 1;
945 return 0;
946 }
947
948 return 1;
949}
950
951/**
952 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
953 * @read_pos: file read position
954 * @buf: relay channel buffer
955 */
956static size_t relay_file_read_subbuf_avail(size_t read_pos,
957 struct rchan_buf *buf)
958{
959 size_t padding, avail = 0;
960 size_t read_subbuf, read_offset, write_subbuf, write_offset;
961 size_t subbuf_size = buf->chan->subbuf_size;
962
963 write_subbuf = (buf->data - buf->start) / subbuf_size;
964 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
965 read_subbuf = read_pos / subbuf_size;
966 read_offset = read_pos % subbuf_size;
967 padding = buf->padding[read_subbuf];
968
969 if (read_subbuf == write_subbuf) {
970 if (read_offset + padding < write_offset)
971 avail = write_offset - (read_offset + padding);
972 } else
973 avail = (subbuf_size - padding) - read_offset;
974
975 return avail;
976}
977
978/**
979 * relay_file_read_start_pos - find the first available byte to read
980 * @buf: relay channel buffer
981 *
982 * If the read_pos is in the middle of padding, return the
983 * position of the first actually available byte, otherwise
984 * return the original value.
985 */
986static size_t relay_file_read_start_pos(struct rchan_buf *buf)
987{
988 size_t read_subbuf, padding, padding_start, padding_end;
989 size_t subbuf_size = buf->chan->subbuf_size;
990 size_t n_subbufs = buf->chan->n_subbufs;
991 size_t consumed = buf->subbufs_consumed % n_subbufs;
992 size_t read_pos = (consumed * subbuf_size + buf->bytes_consumed)
993 % (n_subbufs * subbuf_size);
994
995 read_subbuf = read_pos / subbuf_size;
996 padding = buf->padding[read_subbuf];
997 padding_start = (read_subbuf + 1) * subbuf_size - padding;
998 padding_end = (read_subbuf + 1) * subbuf_size;
999 if (read_pos >= padding_start && read_pos < padding_end) {
1000 read_subbuf = (read_subbuf + 1) % n_subbufs;
1001 read_pos = read_subbuf * subbuf_size;
1002 }
1003
1004 return read_pos;
1005}
1006
1007/**
1008 * relay_file_read_end_pos - return the new read position
1009 * @read_pos: file read position
1010 * @buf: relay channel buffer
1011 * @count: number of bytes to be read
1012 */
1013static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1014 size_t read_pos,
1015 size_t count)
1016{
1017 size_t read_subbuf, padding, end_pos;
1018 size_t subbuf_size = buf->chan->subbuf_size;
1019 size_t n_subbufs = buf->chan->n_subbufs;
1020
1021 read_subbuf = read_pos / subbuf_size;
1022 padding = buf->padding[read_subbuf];
1023 if (read_pos % subbuf_size + count + padding == subbuf_size)
1024 end_pos = (read_subbuf + 1) * subbuf_size;
1025 else
1026 end_pos = read_pos + count;
1027 if (end_pos >= subbuf_size * n_subbufs)
1028 end_pos = 0;
1029
1030 return end_pos;
1031}
1032
1033static ssize_t relay_file_read(struct file *filp,
1034 char __user *buffer,
1035 size_t count,
1036 loff_t *ppos)
1037{
1038 struct rchan_buf *buf = filp->private_data;
1039 size_t read_start, avail;
1040 size_t written = 0;
1041 int ret;
1042
1043 if (!count)
1044 return 0;
1045
1046 inode_lock(file_inode(filp));
1047 do {
1048 void *from;
1049
1050 if (!relay_file_read_avail(buf))
1051 break;
1052
1053 read_start = relay_file_read_start_pos(buf);
1054 avail = relay_file_read_subbuf_avail(read_start, buf);
1055 if (!avail)
1056 break;
1057
1058 avail = min(count, avail);
1059 from = buf->start + read_start;
1060 ret = avail;
1061 if (copy_to_user(buffer, from, avail))
1062 break;
1063
1064 buffer += ret;
1065 written += ret;
1066 count -= ret;
1067
1068 relay_file_read_consume(buf, read_start, ret);
1069 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1070 } while (count);
1071 inode_unlock(file_inode(filp));
1072
1073 return written;
1074}
1075
1076
1077const struct file_operations relay_file_operations = {
1078 .open = relay_file_open,
1079 .poll = relay_file_poll,
1080 .mmap = relay_file_mmap,
1081 .read = relay_file_read,
1082 .release = relay_file_release,
1083};
1084EXPORT_SYMBOL_GPL(relay_file_operations);