projects/linux·blob v5.10 · refs

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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 ([email protected]), IBM Corp
7 * Copyright (C) 1999-2005 - Karim Yaghmour ([email protected])
8 *
9 * Moved to kernel/relay.c by Paul Mundt, 2006.
10 * November 2006 - CPU hotplug support by Mathieu Desnoyers
11 * ([email protected])
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 vm_fault_t 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_lock.
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_array(chan->n_subbufs, sizeof(size_t *),
173 GFP_KERNEL);
174 if (!buf->padding)
175 goto free_buf;
176
177 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
178 if (!buf->start)
179 goto free_buf;
180
181 buf->chan = chan;
182 kref_get(&buf->chan->kref);
183 return buf;
184
185free_buf:
186 kfree(buf->padding);
187 kfree(buf);
188 return NULL;
189}
190
191/**
192 * relay_destroy_channel - free the channel struct
193 * @kref: target kernel reference that contains the relay channel
194 *
195 * Should only be called from kref_put().
196 */
197static void relay_destroy_channel(struct kref *kref)
198{
199 struct rchan *chan = container_of(kref, struct rchan, kref);
200 free_percpu(chan->buf);
201 kfree(chan);
202}
203
204/**
205 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
206 * @buf: the buffer struct
207 */
208static void relay_destroy_buf(struct rchan_buf *buf)
209{
210 struct rchan *chan = buf->chan;
211 unsigned int i;
212
213 if (likely(buf->start)) {
214 vunmap(buf->start);
215 for (i = 0; i < buf->page_count; i++)
216 __free_page(buf->page_array[i]);
217 relay_free_page_array(buf->page_array);
218 }
219 *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
220 kfree(buf->padding);
221 kfree(buf);
222 kref_put(&chan->kref, relay_destroy_channel);
223}
224
225/**
226 * relay_remove_buf - remove a channel buffer
227 * @kref: target kernel reference that contains the relay buffer
228 *
229 * Removes the file from the filesystem, which also frees the
230 * rchan_buf_struct and the channel buffer. Should only be called from
231 * kref_put().
232 */
233static void relay_remove_buf(struct kref *kref)
234{
235 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
236 relay_destroy_buf(buf);
237}
238
239/**
240 * relay_buf_empty - boolean, is the channel buffer empty?
241 * @buf: channel buffer
242 *
243 * Returns 1 if the buffer is empty, 0 otherwise.
244 */
245static int relay_buf_empty(struct rchan_buf *buf)
246{
247 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
248}
249
250/**
251 * relay_buf_full - boolean, is the channel buffer full?
252 * @buf: channel buffer
253 *
254 * Returns 1 if the buffer is full, 0 otherwise.
255 */
256int relay_buf_full(struct rchan_buf *buf)
257{
258 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
259 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
260}
261EXPORT_SYMBOL_GPL(relay_buf_full);
262
263/*
264 * High-level relay kernel API and associated functions.
265 */
266
267/*
268 * rchan_callback implementations defining default channel behavior. Used
269 * in place of corresponding NULL values in client callback struct.
270 */
271
272/*
273 * subbuf_start() default callback. Does nothing.
274 */
275static int subbuf_start_default_callback (struct rchan_buf *buf,
276 void *subbuf,
277 void *prev_subbuf,
278 size_t prev_padding)
279{
280 if (relay_buf_full(buf))
281 return 0;
282
283 return 1;
284}
285
286/*
287 * buf_mapped() default callback. Does nothing.
288 */
289static void buf_mapped_default_callback(struct rchan_buf *buf,
290 struct file *filp)
291{
292}
293
294/*
295 * buf_unmapped() default callback. Does nothing.
296 */
297static void buf_unmapped_default_callback(struct rchan_buf *buf,
298 struct file *filp)
299{
300}
301
302/*
303 * create_buf_file_create() default callback. Does nothing.
304 */
305static struct dentry *create_buf_file_default_callback(const char *filename,
306 struct dentry *parent,
307 umode_t mode,
308 struct rchan_buf *buf,
309 int *is_global)
310{
311 return NULL;
312}
313
314/*
315 * remove_buf_file() default callback. Does nothing.
316 */
317static int remove_buf_file_default_callback(struct dentry *dentry)
318{
319 return -EINVAL;
320}
321
322/* relay channel default callbacks */
323static struct rchan_callbacks default_channel_callbacks = {
324 .subbuf_start = subbuf_start_default_callback,
325 .buf_mapped = buf_mapped_default_callback,
326 .buf_unmapped = buf_unmapped_default_callback,
327 .create_buf_file = create_buf_file_default_callback,
328 .remove_buf_file = remove_buf_file_default_callback,
329};
330
331/**
332 * wakeup_readers - wake up readers waiting on a channel
333 * @work: contains the channel buffer
334 *
335 * This is the function used to defer reader waking
336 */
337static void wakeup_readers(struct irq_work *work)
338{
339 struct rchan_buf *buf;
340
341 buf = container_of(work, struct rchan_buf, wakeup_work);
342 wake_up_interruptible(&buf->read_wait);
343}
344
345/**
346 * __relay_reset - reset a channel buffer
347 * @buf: the channel buffer
348 * @init: 1 if this is a first-time initialization
349 *
350 * See relay_reset() for description of effect.
351 */
352static void __relay_reset(struct rchan_buf *buf, unsigned int init)
353{
354 size_t i;
355
356 if (init) {
357 init_waitqueue_head(&buf->read_wait);
358 kref_init(&buf->kref);
359 init_irq_work(&buf->wakeup_work, wakeup_readers);
360 } else {
361 irq_work_sync(&buf->wakeup_work);
362 }
363
364 buf->subbufs_produced = 0;
365 buf->subbufs_consumed = 0;
366 buf->bytes_consumed = 0;
367 buf->finalized = 0;
368 buf->data = buf->start;
369 buf->offset = 0;
370
371 for (i = 0; i < buf->chan->n_subbufs; i++)
372 buf->padding[i] = 0;
373
374 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
375}
376
377/**
378 * relay_reset - reset the channel
379 * @chan: the channel
380 *
381 * This has the effect of erasing all data from all channel buffers
382 * and restarting the channel in its initial state. The buffers
383 * are not freed, so any mappings are still in effect.
384 *
385 * NOTE. Care should be taken that the channel isn't actually
386 * being used by anything when this call is made.
387 */
388void relay_reset(struct rchan *chan)
389{
390 struct rchan_buf *buf;
391 unsigned int i;
392
393 if (!chan)
394 return;
395
396 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
397 __relay_reset(buf, 0);
398 return;
399 }
400
401 mutex_lock(&relay_channels_mutex);
402 for_each_possible_cpu(i)
403 if ((buf = *per_cpu_ptr(chan->buf, i)))
404 __relay_reset(buf, 0);
405 mutex_unlock(&relay_channels_mutex);
406}
407EXPORT_SYMBOL_GPL(relay_reset);
408
409static inline void relay_set_buf_dentry(struct rchan_buf *buf,
410 struct dentry *dentry)
411{
412 buf->dentry = dentry;
413 d_inode(buf->dentry)->i_size = buf->early_bytes;
414}
415
416static struct dentry *relay_create_buf_file(struct rchan *chan,
417 struct rchan_buf *buf,
418 unsigned int cpu)
419{
420 struct dentry *dentry;
421 char *tmpname;
422
423 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
424 if (!tmpname)
425 return NULL;
426 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
427
428 /* Create file in fs */
429 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
430 S_IRUSR, buf,
431 &chan->is_global);
432 if (IS_ERR(dentry))
433 dentry = NULL;
434
435 kfree(tmpname);
436
437 return dentry;
438}
439
440/*
441 * relay_open_buf - create a new relay channel buffer
442 *
443 * used by relay_open() and CPU hotplug.
444 */
445static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
446{
447 struct rchan_buf *buf = NULL;
448 struct dentry *dentry;
449
450 if (chan->is_global)
451 return *per_cpu_ptr(chan->buf, 0);
452
453 buf = relay_create_buf(chan);
454 if (!buf)
455 return NULL;
456
457 if (chan->has_base_filename) {
458 dentry = relay_create_buf_file(chan, buf, cpu);
459 if (!dentry)
460 goto free_buf;
461 relay_set_buf_dentry(buf, dentry);
462 } else {
463 /* Only retrieve global info, nothing more, nothing less */
464 dentry = chan->cb->create_buf_file(NULL, NULL,
465 S_IRUSR, buf,
466 &chan->is_global);
467 if (IS_ERR_OR_NULL(dentry))
468 goto free_buf;
469 }
470
471 buf->cpu = cpu;
472 __relay_reset(buf, 1);
473
474 if(chan->is_global) {
475 *per_cpu_ptr(chan->buf, 0) = buf;
476 buf->cpu = 0;
477 }
478
479 return buf;
480
481free_buf:
482 relay_destroy_buf(buf);
483 return NULL;
484}
485
486/**
487 * relay_close_buf - close a channel buffer
488 * @buf: channel buffer
489 *
490 * Marks the buffer finalized and restores the default callbacks.
491 * The channel buffer and channel buffer data structure are then freed
492 * automatically when the last reference is given up.
493 */
494static void relay_close_buf(struct rchan_buf *buf)
495{
496 buf->finalized = 1;
497 irq_work_sync(&buf->wakeup_work);
498 buf->chan->cb->remove_buf_file(buf->dentry);
499 kref_put(&buf->kref, relay_remove_buf);
500}
501
502static void setup_callbacks(struct rchan *chan,
503 struct rchan_callbacks *cb)
504{
505 if (!cb) {
506 chan->cb = &default_channel_callbacks;
507 return;
508 }
509
510 if (!cb->subbuf_start)
511 cb->subbuf_start = subbuf_start_default_callback;
512 if (!cb->buf_mapped)
513 cb->buf_mapped = buf_mapped_default_callback;
514 if (!cb->buf_unmapped)
515 cb->buf_unmapped = buf_unmapped_default_callback;
516 if (!cb->create_buf_file)
517 cb->create_buf_file = create_buf_file_default_callback;
518 if (!cb->remove_buf_file)
519 cb->remove_buf_file = remove_buf_file_default_callback;
520 chan->cb = cb;
521}
522
523int relay_prepare_cpu(unsigned int cpu)
524{
525 struct rchan *chan;
526 struct rchan_buf *buf;
527
528 mutex_lock(&relay_channels_mutex);
529 list_for_each_entry(chan, &relay_channels, list) {
530 if ((buf = *per_cpu_ptr(chan->buf, cpu)))
531 continue;
532 buf = relay_open_buf(chan, cpu);
533 if (!buf) {
534 pr_err("relay: cpu %d buffer creation failed\n", cpu);
535 mutex_unlock(&relay_channels_mutex);
536 return -ENOMEM;
537 }
538 *per_cpu_ptr(chan->buf, cpu) = buf;
539 }
540 mutex_unlock(&relay_channels_mutex);
541 return 0;
542}
543
544/**
545 * relay_open - create a new relay channel
546 * @base_filename: base name of files to create, %NULL for buffering only
547 * @parent: dentry of parent directory, %NULL for root directory or buffer
548 * @subbuf_size: size of sub-buffers
549 * @n_subbufs: number of sub-buffers
550 * @cb: client callback functions
551 * @private_data: user-defined data
552 *
553 * Returns channel pointer if successful, %NULL otherwise.
554 *
555 * Creates a channel buffer for each cpu using the sizes and
556 * attributes specified. The created channel buffer files
557 * will be named base_filename0...base_filenameN-1. File
558 * permissions will be %S_IRUSR.
559 *
560 * If opening a buffer (@parent = NULL) that you later wish to register
561 * in a filesystem, call relay_late_setup_files() once the @parent dentry
562 * is available.
563 */
564struct rchan *relay_open(const char *base_filename,
565 struct dentry *parent,
566 size_t subbuf_size,
567 size_t n_subbufs,
568 struct rchan_callbacks *cb,
569 void *private_data)
570{
571 unsigned int i;
572 struct rchan *chan;
573 struct rchan_buf *buf;
574
575 if (!(subbuf_size && n_subbufs))
576 return NULL;
577 if (subbuf_size > UINT_MAX / n_subbufs)
578 return NULL;
579
580 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
581 if (!chan)
582 return NULL;
583
584 chan->buf = alloc_percpu(struct rchan_buf *);
585 if (!chan->buf) {
586 kfree(chan);
587 return NULL;
588 }
589
590 chan->version = RELAYFS_CHANNEL_VERSION;
591 chan->n_subbufs = n_subbufs;
592 chan->subbuf_size = subbuf_size;
593 chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
594 chan->parent = parent;
595 chan->private_data = private_data;
596 if (base_filename) {
597 chan->has_base_filename = 1;
598 strlcpy(chan->base_filename, base_filename, NAME_MAX);
599 }
600 setup_callbacks(chan, cb);
601 kref_init(&chan->kref);
602
603 mutex_lock(&relay_channels_mutex);
604 for_each_online_cpu(i) {
605 buf = relay_open_buf(chan, i);
606 if (!buf)
607 goto free_bufs;
608 *per_cpu_ptr(chan->buf, i) = buf;
609 }
610 list_add(&chan->list, &relay_channels);
611 mutex_unlock(&relay_channels_mutex);
612
613 return chan;
614
615free_bufs:
616 for_each_possible_cpu(i) {
617 if ((buf = *per_cpu_ptr(chan->buf, i)))
618 relay_close_buf(buf);
619 }
620
621 kref_put(&chan->kref, relay_destroy_channel);
622 mutex_unlock(&relay_channels_mutex);
623 return NULL;
624}
625EXPORT_SYMBOL_GPL(relay_open);
626
627struct rchan_percpu_buf_dispatcher {
628 struct rchan_buf *buf;
629 struct dentry *dentry;
630};
631
632/* Called in atomic context. */
633static void __relay_set_buf_dentry(void *info)
634{
635 struct rchan_percpu_buf_dispatcher *p = info;
636
637 relay_set_buf_dentry(p->buf, p->dentry);
638}
639
640/**
641 * relay_late_setup_files - triggers file creation
642 * @chan: channel to operate on
643 * @base_filename: base name of files to create
644 * @parent: dentry of parent directory, %NULL for root directory
645 *
646 * Returns 0 if successful, non-zero otherwise.
647 *
648 * Use to setup files for a previously buffer-only channel created
649 * by relay_open() with a NULL parent dentry.
650 *
651 * For example, this is useful for perfomring early tracing in kernel,
652 * before VFS is up and then exposing the early results once the dentry
653 * is available.
654 */
655int relay_late_setup_files(struct rchan *chan,
656 const char *base_filename,
657 struct dentry *parent)
658{
659 int err = 0;
660 unsigned int i, curr_cpu;
661 unsigned long flags;
662 struct dentry *dentry;
663 struct rchan_buf *buf;
664 struct rchan_percpu_buf_dispatcher disp;
665
666 if (!chan || !base_filename)
667 return -EINVAL;
668
669 strlcpy(chan->base_filename, base_filename, NAME_MAX);
670
671 mutex_lock(&relay_channels_mutex);
672 /* Is chan already set up? */
673 if (unlikely(chan->has_base_filename)) {
674 mutex_unlock(&relay_channels_mutex);
675 return -EEXIST;
676 }
677 chan->has_base_filename = 1;
678 chan->parent = parent;
679
680 if (chan->is_global) {
681 err = -EINVAL;
682 buf = *per_cpu_ptr(chan->buf, 0);
683 if (!WARN_ON_ONCE(!buf)) {
684 dentry = relay_create_buf_file(chan, buf, 0);
685 if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
686 relay_set_buf_dentry(buf, dentry);
687 err = 0;
688 }
689 }
690 mutex_unlock(&relay_channels_mutex);
691 return err;
692 }
693
694 curr_cpu = get_cpu();
695 /*
696 * The CPU hotplug notifier ran before us and created buffers with
697 * no files associated. So it's safe to call relay_setup_buf_file()
698 * on all currently online CPUs.
699 */
700 for_each_online_cpu(i) {
701 buf = *per_cpu_ptr(chan->buf, i);
702 if (unlikely(!buf)) {
703 WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
704 err = -EINVAL;
705 break;
706 }
707
708 dentry = relay_create_buf_file(chan, buf, i);
709 if (unlikely(!dentry)) {
710 err = -EINVAL;
711 break;
712 }
713
714 if (curr_cpu == i) {
715 local_irq_save(flags);
716 relay_set_buf_dentry(buf, dentry);
717 local_irq_restore(flags);
718 } else {
719 disp.buf = buf;
720 disp.dentry = dentry;
721 smp_mb();
722 /* relay_channels_mutex must be held, so wait. */
723 err = smp_call_function_single(i,
724 __relay_set_buf_dentry,
725 &disp, 1);
726 }
727 if (unlikely(err))
728 break;
729 }
730 put_cpu();
731 mutex_unlock(&relay_channels_mutex);
732
733 return err;
734}
735EXPORT_SYMBOL_GPL(relay_late_setup_files);
736
737/**
738 * relay_switch_subbuf - switch to a new sub-buffer
739 * @buf: channel buffer
740 * @length: size of current event
741 *
742 * Returns either the length passed in or 0 if full.
743 *
744 * Performs sub-buffer-switch tasks such as invoking callbacks,
745 * updating padding counts, waking up readers, etc.
746 */
747size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
748{
749 void *old, *new;
750 size_t old_subbuf, new_subbuf;
751
752 if (unlikely(length > buf->chan->subbuf_size))
753 goto toobig;
754
755 if (buf->offset != buf->chan->subbuf_size + 1) {
756 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
757 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
758 buf->padding[old_subbuf] = buf->prev_padding;
759 buf->subbufs_produced++;
760 if (buf->dentry)
761 d_inode(buf->dentry)->i_size +=
762 buf->chan->subbuf_size -
763 buf->padding[old_subbuf];
764 else
765 buf->early_bytes += buf->chan->subbuf_size -
766 buf->padding[old_subbuf];
767 smp_mb();
768 if (waitqueue_active(&buf->read_wait)) {
769 /*
770 * Calling wake_up_interruptible() from here
771 * will deadlock if we happen to be logging
772 * from the scheduler (trying to re-grab
773 * rq->lock), so defer it.
774 */
775 irq_work_queue(&buf->wakeup_work);
776 }
777 }
778
779 old = buf->data;
780 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
781 new = buf->start + new_subbuf * buf->chan->subbuf_size;
782 buf->offset = 0;
783 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
784 buf->offset = buf->chan->subbuf_size + 1;
785 return 0;
786 }
787 buf->data = new;
788 buf->padding[new_subbuf] = 0;
789
790 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
791 goto toobig;
792
793 return length;
794
795toobig:
796 buf->chan->last_toobig = length;
797 return 0;
798}
799EXPORT_SYMBOL_GPL(relay_switch_subbuf);
800
801/**
802 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
803 * @chan: the channel
804 * @cpu: the cpu associated with the channel buffer to update
805 * @subbufs_consumed: number of sub-buffers to add to current buf's count
806 *
807 * Adds to the channel buffer's consumed sub-buffer count.
808 * subbufs_consumed should be the number of sub-buffers newly consumed,
809 * not the total consumed.
810 *
811 * NOTE. Kernel clients don't need to call this function if the channel
812 * mode is 'overwrite'.
813 */
814void relay_subbufs_consumed(struct rchan *chan,
815 unsigned int cpu,
816 size_t subbufs_consumed)
817{
818 struct rchan_buf *buf;
819
820 if (!chan || cpu >= NR_CPUS)
821 return;
822
823 buf = *per_cpu_ptr(chan->buf, cpu);
824 if (!buf || subbufs_consumed > chan->n_subbufs)
825 return;
826
827 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
828 buf->subbufs_consumed = buf->subbufs_produced;
829 else
830 buf->subbufs_consumed += subbufs_consumed;
831}
832EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
833
834/**
835 * relay_close - close the channel
836 * @chan: the channel
837 *
838 * Closes all channel buffers and frees the channel.
839 */
840void relay_close(struct rchan *chan)
841{
842 struct rchan_buf *buf;
843 unsigned int i;
844
845 if (!chan)
846 return;
847
848 mutex_lock(&relay_channels_mutex);
849 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
850 relay_close_buf(buf);
851 else
852 for_each_possible_cpu(i)
853 if ((buf = *per_cpu_ptr(chan->buf, i)))
854 relay_close_buf(buf);
855
856 if (chan->last_toobig)
857 printk(KERN_WARNING "relay: one or more items not logged "
858 "[item size (%zd) > sub-buffer size (%zd)]\n",
859 chan->last_toobig, chan->subbuf_size);
860
861 list_del(&chan->list);
862 kref_put(&chan->kref, relay_destroy_channel);
863 mutex_unlock(&relay_channels_mutex);
864}
865EXPORT_SYMBOL_GPL(relay_close);
866
867/**
868 * relay_flush - close the channel
869 * @chan: the channel
870 *
871 * Flushes all channel buffers, i.e. forces buffer switch.
872 */
873void relay_flush(struct rchan *chan)
874{
875 struct rchan_buf *buf;
876 unsigned int i;
877
878 if (!chan)
879 return;
880
881 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
882 relay_switch_subbuf(buf, 0);
883 return;
884 }
885
886 mutex_lock(&relay_channels_mutex);
887 for_each_possible_cpu(i)
888 if ((buf = *per_cpu_ptr(chan->buf, i)))
889 relay_switch_subbuf(buf, 0);
890 mutex_unlock(&relay_channels_mutex);
891}
892EXPORT_SYMBOL_GPL(relay_flush);
893
894/**
895 * relay_file_open - open file op for relay files
896 * @inode: the inode
897 * @filp: the file
898 *
899 * Increments the channel buffer refcount.
900 */
901static int relay_file_open(struct inode *inode, struct file *filp)
902{
903 struct rchan_buf *buf = inode->i_private;
904 kref_get(&buf->kref);
905 filp->private_data = buf;
906
907 return nonseekable_open(inode, filp);
908}
909
910/**
911 * relay_file_mmap - mmap file op for relay files
912 * @filp: the file
913 * @vma: the vma describing what to map
914 *
915 * Calls upon relay_mmap_buf() to map the file into user space.
916 */
917static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
918{
919 struct rchan_buf *buf = filp->private_data;
920 return relay_mmap_buf(buf, vma);
921}
922
923/**
924 * relay_file_poll - poll file op for relay files
925 * @filp: the file
926 * @wait: poll table
927 *
928 * Poll implemention.
929 */
930static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
931{
932 __poll_t mask = 0;
933 struct rchan_buf *buf = filp->private_data;
934
935 if (buf->finalized)
936 return EPOLLERR;
937
938 if (filp->f_mode & FMODE_READ) {
939 poll_wait(filp, &buf->read_wait, wait);
940 if (!relay_buf_empty(buf))
941 mask |= EPOLLIN | EPOLLRDNORM;
942 }
943
944 return mask;
945}
946
947/**
948 * relay_file_release - release file op for relay files
949 * @inode: the inode
950 * @filp: the file
951 *
952 * Decrements the channel refcount, as the filesystem is
953 * no longer using it.
954 */
955static int relay_file_release(struct inode *inode, struct file *filp)
956{
957 struct rchan_buf *buf = filp->private_data;
958 kref_put(&buf->kref, relay_remove_buf);
959
960 return 0;
961}
962
963/*
964 * relay_file_read_consume - update the consumed count for the buffer
965 */
966static void relay_file_read_consume(struct rchan_buf *buf,
967 size_t read_pos,
968 size_t bytes_consumed)
969{
970 size_t subbuf_size = buf->chan->subbuf_size;
971 size_t n_subbufs = buf->chan->n_subbufs;
972 size_t read_subbuf;
973
974 if (buf->subbufs_produced == buf->subbufs_consumed &&
975 buf->offset == buf->bytes_consumed)
976 return;
977
978 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
979 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
980 buf->bytes_consumed = 0;
981 }
982
983 buf->bytes_consumed += bytes_consumed;
984 if (!read_pos)
985 read_subbuf = buf->subbufs_consumed % n_subbufs;
986 else
987 read_subbuf = read_pos / buf->chan->subbuf_size;
988 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
989 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
990 (buf->offset == subbuf_size))
991 return;
992 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
993 buf->bytes_consumed = 0;
994 }
995}
996
997/*
998 * relay_file_read_avail - boolean, are there unconsumed bytes available?
999 */
1000static int relay_file_read_avail(struct rchan_buf *buf)
1001{
1002 size_t subbuf_size = buf->chan->subbuf_size;
1003 size_t n_subbufs = buf->chan->n_subbufs;
1004 size_t produced = buf->subbufs_produced;
1005 size_t consumed;
1006
1007 relay_file_read_consume(buf, 0, 0);
1008
1009 consumed = buf->subbufs_consumed;
1010
1011 if (unlikely(buf->offset > subbuf_size)) {
1012 if (produced == consumed)
1013 return 0;
1014 return 1;
1015 }
1016
1017 if (unlikely(produced - consumed >= n_subbufs)) {
1018 consumed = produced - n_subbufs + 1;
1019 buf->subbufs_consumed = consumed;
1020 buf->bytes_consumed = 0;
1021 }
1022
1023 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
1024 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
1025
1026 if (consumed > produced)
1027 produced += n_subbufs * subbuf_size;
1028
1029 if (consumed == produced) {
1030 if (buf->offset == subbuf_size &&
1031 buf->subbufs_produced > buf->subbufs_consumed)
1032 return 1;
1033 return 0;
1034 }
1035
1036 return 1;
1037}
1038
1039/**
1040 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1041 * @read_pos: file read position
1042 * @buf: relay channel buffer
1043 */
1044static size_t relay_file_read_subbuf_avail(size_t read_pos,
1045 struct rchan_buf *buf)
1046{
1047 size_t padding, avail = 0;
1048 size_t read_subbuf, read_offset, write_subbuf, write_offset;
1049 size_t subbuf_size = buf->chan->subbuf_size;
1050
1051 write_subbuf = (buf->data - buf->start) / subbuf_size;
1052 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1053 read_subbuf = read_pos / subbuf_size;
1054 read_offset = read_pos % subbuf_size;
1055 padding = buf->padding[read_subbuf];
1056
1057 if (read_subbuf == write_subbuf) {
1058 if (read_offset + padding < write_offset)
1059 avail = write_offset - (read_offset + padding);
1060 } else
1061 avail = (subbuf_size - padding) - read_offset;
1062
1063 return avail;
1064}
1065
1066/**
1067 * relay_file_read_start_pos - find the first available byte to read
1068 * @buf: relay channel buffer
1069 *
1070 * If the read_pos is in the middle of padding, return the
1071 * position of the first actually available byte, otherwise
1072 * return the original value.
1073 */
1074static size_t relay_file_read_start_pos(struct rchan_buf *buf)
1075{
1076 size_t read_subbuf, padding, padding_start, padding_end;
1077 size_t subbuf_size = buf->chan->subbuf_size;
1078 size_t n_subbufs = buf->chan->n_subbufs;
1079 size_t consumed = buf->subbufs_consumed % n_subbufs;
1080 size_t read_pos = consumed * subbuf_size + buf->bytes_consumed;
1081
1082 read_subbuf = read_pos / subbuf_size;
1083 padding = buf->padding[read_subbuf];
1084 padding_start = (read_subbuf + 1) * subbuf_size - padding;
1085 padding_end = (read_subbuf + 1) * subbuf_size;
1086 if (read_pos >= padding_start && read_pos < padding_end) {
1087 read_subbuf = (read_subbuf + 1) % n_subbufs;
1088 read_pos = read_subbuf * subbuf_size;
1089 }
1090
1091 return read_pos;
1092}
1093
1094/**
1095 * relay_file_read_end_pos - return the new read position
1096 * @read_pos: file read position
1097 * @buf: relay channel buffer
1098 * @count: number of bytes to be read
1099 */
1100static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1101 size_t read_pos,
1102 size_t count)
1103{
1104 size_t read_subbuf, padding, end_pos;
1105 size_t subbuf_size = buf->chan->subbuf_size;
1106 size_t n_subbufs = buf->chan->n_subbufs;
1107
1108 read_subbuf = read_pos / subbuf_size;
1109 padding = buf->padding[read_subbuf];
1110 if (read_pos % subbuf_size + count + padding == subbuf_size)
1111 end_pos = (read_subbuf + 1) * subbuf_size;
1112 else
1113 end_pos = read_pos + count;
1114 if (end_pos >= subbuf_size * n_subbufs)
1115 end_pos = 0;
1116
1117 return end_pos;
1118}
1119
1120static ssize_t relay_file_read(struct file *filp,
1121 char __user *buffer,
1122 size_t count,
1123 loff_t *ppos)
1124{
1125 struct rchan_buf *buf = filp->private_data;
1126 size_t read_start, avail;
1127 size_t written = 0;
1128 int ret;
1129
1130 if (!count)
1131 return 0;
1132
1133 inode_lock(file_inode(filp));
1134 do {
1135 void *from;
1136
1137 if (!relay_file_read_avail(buf))
1138 break;
1139
1140 read_start = relay_file_read_start_pos(buf);
1141 avail = relay_file_read_subbuf_avail(read_start, buf);
1142 if (!avail)
1143 break;
1144
1145 avail = min(count, avail);
1146 from = buf->start + read_start;
1147 ret = avail;
1148 if (copy_to_user(buffer, from, avail))
1149 break;
1150
1151 buffer += ret;
1152 written += ret;
1153 count -= ret;
1154
1155 relay_file_read_consume(buf, read_start, ret);
1156 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1157 } while (count);
1158 inode_unlock(file_inode(filp));
1159
1160 return written;
1161}
1162
1163static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1164{
1165 rbuf->bytes_consumed += bytes_consumed;
1166
1167 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1168 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1169 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1170 }
1171}
1172
1173static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1174 struct pipe_buffer *buf)
1175{
1176 struct rchan_buf *rbuf;
1177
1178 rbuf = (struct rchan_buf *)page_private(buf->page);
1179 relay_consume_bytes(rbuf, buf->private);
1180}
1181
1182static const struct pipe_buf_operations relay_pipe_buf_ops = {
1183 .release = relay_pipe_buf_release,
1184 .try_steal = generic_pipe_buf_try_steal,
1185 .get = generic_pipe_buf_get,
1186};
1187
1188static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1189{
1190}
1191
1192/*
1193 * subbuf_splice_actor - splice up to one subbuf's worth of data
1194 */
1195static ssize_t subbuf_splice_actor(struct file *in,
1196 loff_t *ppos,
1197 struct pipe_inode_info *pipe,
1198 size_t len,
1199 unsigned int flags,
1200 int *nonpad_ret)
1201{
1202 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1203 struct rchan_buf *rbuf = in->private_data;
1204 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1205 uint64_t pos = (uint64_t) *ppos;
1206 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1207 size_t read_start = (size_t) do_div(pos, alloc_size);
1208 size_t read_subbuf = read_start / subbuf_size;
1209 size_t padding = rbuf->padding[read_subbuf];
1210 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1211 struct page *pages[PIPE_DEF_BUFFERS];
1212 struct partial_page partial[PIPE_DEF_BUFFERS];
1213 struct splice_pipe_desc spd = {
1214 .pages = pages,
1215 .nr_pages = 0,
1216 .nr_pages_max = PIPE_DEF_BUFFERS,
1217 .partial = partial,
1218 .ops = &relay_pipe_buf_ops,
1219 .spd_release = relay_page_release,
1220 };
1221 ssize_t ret;
1222
1223 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1224 return 0;
1225 if (splice_grow_spd(pipe, &spd))
1226 return -ENOMEM;
1227
1228 /*
1229 * Adjust read len, if longer than what is available
1230 */
1231 if (len > (subbuf_size - read_start % subbuf_size))
1232 len = subbuf_size - read_start % subbuf_size;
1233
1234 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1235 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1236 poff = read_start & ~PAGE_MASK;
1237 nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1238
1239 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1240 unsigned int this_len, this_end, private;
1241 unsigned int cur_pos = read_start + total_len;
1242
1243 if (!len)
1244 break;
1245
1246 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1247 private = this_len;
1248
1249 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1250 spd.partial[spd.nr_pages].offset = poff;
1251
1252 this_end = cur_pos + this_len;
1253 if (this_end >= nonpad_end) {
1254 this_len = nonpad_end - cur_pos;
1255 private = this_len + padding;
1256 }
1257 spd.partial[spd.nr_pages].len = this_len;
1258 spd.partial[spd.nr_pages].private = private;
1259
1260 len -= this_len;
1261 total_len += this_len;
1262 poff = 0;
1263 pidx = (pidx + 1) % subbuf_pages;
1264
1265 if (this_end >= nonpad_end) {
1266 spd.nr_pages++;
1267 break;
1268 }
1269 }
1270
1271 ret = 0;
1272 if (!spd.nr_pages)
1273 goto out;
1274
1275 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1276 if (ret < 0 || ret < total_len)
1277 goto out;
1278
1279 if (read_start + ret == nonpad_end)
1280 ret += padding;
1281
1282out:
1283 splice_shrink_spd(&spd);
1284 return ret;
1285}
1286
1287static ssize_t relay_file_splice_read(struct file *in,
1288 loff_t *ppos,
1289 struct pipe_inode_info *pipe,
1290 size_t len,
1291 unsigned int flags)
1292{
1293 ssize_t spliced;
1294 int ret;
1295 int nonpad_ret = 0;
1296
1297 ret = 0;
1298 spliced = 0;
1299
1300 while (len && !spliced) {
1301 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1302 if (ret < 0)
1303 break;
1304 else if (!ret) {
1305 if (flags & SPLICE_F_NONBLOCK)
1306 ret = -EAGAIN;
1307 break;
1308 }
1309
1310 *ppos += ret;
1311 if (ret > len)
1312 len = 0;
1313 else
1314 len -= ret;
1315 spliced += nonpad_ret;
1316 nonpad_ret = 0;
1317 }
1318
1319 if (spliced)
1320 return spliced;
1321
1322 return ret;
1323}
1324
1325const struct file_operations relay_file_operations = {
1326 .open = relay_file_open,
1327 .poll = relay_file_poll,
1328 .mmap = relay_file_mmap,
1329 .read = relay_file_read,
1330 .llseek = no_llseek,
1331 .release = relay_file_release,
1332 .splice_read = relay_file_splice_read,
1333};
1334EXPORT_SYMBOL_GPL(relay_file_operations);