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	vma->vm_flags |= 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 = NULL;
 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
 994	read_subbuf = read_pos / subbuf_size;
 995	padding = buf->padding[read_subbuf];
 996	padding_start = (read_subbuf + 1) * subbuf_size - padding;
 997	padding_end = (read_subbuf + 1) * subbuf_size;
 998	if (read_pos >= padding_start && read_pos < padding_end) {
 999		read_subbuf = (read_subbuf + 1) % n_subbufs;
1000		read_pos = read_subbuf * subbuf_size;
1001	}
1002
1003	return read_pos;
1004}
1005
1006/**
1007 *	relay_file_read_end_pos - return the new read position
1008 *	@read_pos: file read position
1009 *	@buf: relay channel buffer
1010 *	@count: number of bytes to be read
1011 */
1012static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1013				      size_t read_pos,
1014				      size_t count)
1015{
1016	size_t read_subbuf, padding, end_pos;
1017	size_t subbuf_size = buf->chan->subbuf_size;
1018	size_t n_subbufs = buf->chan->n_subbufs;
1019
1020	read_subbuf = read_pos / subbuf_size;
1021	padding = buf->padding[read_subbuf];
1022	if (read_pos % subbuf_size + count + padding == subbuf_size)
1023		end_pos = (read_subbuf + 1) * subbuf_size;
1024	else
1025		end_pos = read_pos + count;
1026	if (end_pos >= subbuf_size * n_subbufs)
1027		end_pos = 0;
1028
1029	return end_pos;
1030}
1031
1032static ssize_t relay_file_read(struct file *filp,
1033			       char __user *buffer,
1034			       size_t count,
1035			       loff_t *ppos)
1036{
1037	struct rchan_buf *buf = filp->private_data;
1038	size_t read_start, avail;
1039	size_t written = 0;
1040	int ret;
1041
1042	if (!count)
1043		return 0;
1044
1045	inode_lock(file_inode(filp));
1046	do {
1047		void *from;
1048
1049		if (!relay_file_read_avail(buf))
1050			break;
1051
1052		read_start = relay_file_read_start_pos(buf);
1053		avail = relay_file_read_subbuf_avail(read_start, buf);
1054		if (!avail)
1055			break;
1056
1057		avail = min(count, avail);
1058		from = buf->start + read_start;
1059		ret = avail;
1060		if (copy_to_user(buffer, from, avail))
1061			break;
1062
1063		buffer += ret;
1064		written += ret;
1065		count -= ret;
1066
1067		relay_file_read_consume(buf, read_start, ret);
1068		*ppos = relay_file_read_end_pos(buf, read_start, ret);
1069	} while (count);
1070	inode_unlock(file_inode(filp));
1071
1072	return written;
1073}
1074
1075static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1076{
1077	rbuf->bytes_consumed += bytes_consumed;
1078
1079	if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1080		relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1081		rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1082	}
1083}
1084
1085static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1086				   struct pipe_buffer *buf)
1087{
1088	struct rchan_buf *rbuf;
1089
1090	rbuf = (struct rchan_buf *)page_private(buf->page);
1091	relay_consume_bytes(rbuf, buf->private);
1092}
1093
1094static const struct pipe_buf_operations relay_pipe_buf_ops = {
1095	.release	= relay_pipe_buf_release,
1096	.try_steal	= generic_pipe_buf_try_steal,
1097	.get		= generic_pipe_buf_get,
1098};
1099
1100static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1101{
1102}
1103
1104/*
1105 *	subbuf_splice_actor - splice up to one subbuf's worth of data
1106 */
1107static ssize_t subbuf_splice_actor(struct file *in,
1108			       loff_t *ppos,
1109			       struct pipe_inode_info *pipe,
1110			       size_t len,
1111			       unsigned int flags,
1112			       int *nonpad_ret)
1113{
1114	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1115	struct rchan_buf *rbuf = in->private_data;
1116	unsigned int subbuf_size = rbuf->chan->subbuf_size;
1117	uint64_t pos = (uint64_t) *ppos;
1118	uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1119	size_t read_start = (size_t) do_div(pos, alloc_size);
1120	size_t read_subbuf = read_start / subbuf_size;
1121	size_t padding = rbuf->padding[read_subbuf];
1122	size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1123	struct page *pages[PIPE_DEF_BUFFERS];
1124	struct partial_page partial[PIPE_DEF_BUFFERS];
1125	struct splice_pipe_desc spd = {
1126		.pages = pages,
1127		.nr_pages = 0,
1128		.nr_pages_max = PIPE_DEF_BUFFERS,
1129		.partial = partial,
1130		.ops = &relay_pipe_buf_ops,
1131		.spd_release = relay_page_release,
1132	};
1133	ssize_t ret;
1134
1135	if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1136		return 0;
1137	if (splice_grow_spd(pipe, &spd))
1138		return -ENOMEM;
1139
1140	/*
1141	 * Adjust read len, if longer than what is available
1142	 */
1143	if (len > (subbuf_size - read_start % subbuf_size))
1144		len = subbuf_size - read_start % subbuf_size;
1145
1146	subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1147	pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1148	poff = read_start & ~PAGE_MASK;
1149	nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1150
1151	for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1152		unsigned int this_len, this_end, private;
1153		unsigned int cur_pos = read_start + total_len;
1154
1155		if (!len)
1156			break;
1157
1158		this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1159		private = this_len;
1160
1161		spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1162		spd.partial[spd.nr_pages].offset = poff;
1163
1164		this_end = cur_pos + this_len;
1165		if (this_end >= nonpad_end) {
1166			this_len = nonpad_end - cur_pos;
1167			private = this_len + padding;
1168		}
1169		spd.partial[spd.nr_pages].len = this_len;
1170		spd.partial[spd.nr_pages].private = private;
1171
1172		len -= this_len;
1173		total_len += this_len;
1174		poff = 0;
1175		pidx = (pidx + 1) % subbuf_pages;
1176
1177		if (this_end >= nonpad_end) {
1178			spd.nr_pages++;
1179			break;
1180		}
1181	}
1182
1183	ret = 0;
1184	if (!spd.nr_pages)
1185		goto out;
1186
1187	ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1188	if (ret < 0 || ret < total_len)
1189		goto out;
1190
1191        if (read_start + ret == nonpad_end)
1192                ret += padding;
1193
1194out:
1195	splice_shrink_spd(&spd);
1196	return ret;
1197}
1198
1199static ssize_t relay_file_splice_read(struct file *in,
1200				      loff_t *ppos,
1201				      struct pipe_inode_info *pipe,
1202				      size_t len,
1203				      unsigned int flags)
1204{
1205	ssize_t spliced;
1206	int ret;
1207	int nonpad_ret = 0;
1208
1209	ret = 0;
1210	spliced = 0;
1211
1212	while (len && !spliced) {
1213		ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1214		if (ret < 0)
1215			break;
1216		else if (!ret) {
1217			if (flags & SPLICE_F_NONBLOCK)
1218				ret = -EAGAIN;
1219			break;
1220		}
1221
1222		*ppos += ret;
1223		if (ret > len)
1224			len = 0;
1225		else
1226			len -= ret;
1227		spliced += nonpad_ret;
1228		nonpad_ret = 0;
1229	}
1230
1231	if (spliced)
1232		return spliced;
1233
1234	return ret;
1235}
1236
1237const struct file_operations relay_file_operations = {
1238	.open		= relay_file_open,
1239	.poll		= relay_file_poll,
1240	.mmap		= relay_file_mmap,
1241	.read		= relay_file_read,
1242	.llseek		= no_llseek,
1243	.release	= relay_file_release,
1244	.splice_read	= relay_file_splice_read,
1245};
1246EXPORT_SYMBOL_GPL(relay_file_operations);