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