1	// SPDX-License-Identifier: GPL-2.0
2	/*
3	* Generic ring buffer
4	*
5	* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6	*/
7	#include <linux/trace_recursion.h>
8	#include <linux/trace_events.h>
9	#include <linux/ring_buffer.h>
10	#include <linux/trace_clock.h>
11	#include <linux/sched/clock.h>
12	#include <linux/trace_seq.h>
13	#include <linux/spinlock.h>
14	#include <linux/irq_work.h>
15	#include <linux/security.h>
16	#include <linux/uaccess.h>
17	#include <linux/hardirq.h>
18	#include <linux/kthread.h> /* for self test */
19	#include <linux/module.h>
20	#include <linux/percpu.h>
21	#include <linux/mutex.h>
22	#include <linux/delay.h>
23	#include <linux/slab.h>
24	#include <linux/init.h>
25	#include <linux/hash.h>
26	#include <linux/list.h>
27	#include <linux/cpu.h>
28	#include <linux/oom.h>
29
30	#include <asm/local64.h>
31	#include <asm/local.h>
32
33	/*
34	* The "absolute" timestamp in the buffer is only 59 bits.
35	* If a clock has the 5 MSBs set, it needs to be saved and
36	* reinserted.
37	*/
38	#define TS_MSB (0xf8ULL << 56)
39	#define ABS_TS_MASK (~TS_MSB)
40
41	static void update_pages_handler(struct work_struct *work);
42
43	/*
44	* The ring buffer header is special. We must manually up keep it.
45	*/
46	int ring_buffer_print_entry_header(struct trace_seq *s)
47	{
48	trace_seq_puts(s, str: "# compressed entry header\n");
49	trace_seq_puts(s, str: "\ttype_len : 5 bits\n");
50	trace_seq_puts(s, str: "\ttime_delta : 27 bits\n");
51	trace_seq_puts(s, str: "\tarray : 32 bits\n");
52	trace_seq_putc(s, c: '\n');
53	trace_seq_printf(s, fmt: "\tpadding : type == %d\n",
54	RINGBUF_TYPE_PADDING);
55	trace_seq_printf(s, fmt: "\ttime_extend : type == %d\n",
56	RINGBUF_TYPE_TIME_EXTEND);
57	trace_seq_printf(s, fmt: "\ttime_stamp : type == %d\n",
58	RINGBUF_TYPE_TIME_STAMP);
59	trace_seq_printf(s, fmt: "\tdata max type_len == %d\n",
60	RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
61
62	return !trace_seq_has_overflowed(s);
63	}
64
65	/*
66	* The ring buffer is made up of a list of pages. A separate list of pages is
67	* allocated for each CPU. A writer may only write to a buffer that is
68	* associated with the CPU it is currently executing on. A reader may read
69	* from any per cpu buffer.
70	*
71	* The reader is special. For each per cpu buffer, the reader has its own
72	* reader page. When a reader has read the entire reader page, this reader
73	* page is swapped with another page in the ring buffer.
74	*
75	* Now, as long as the writer is off the reader page, the reader can do what
76	* ever it wants with that page. The writer will never write to that page
77	* again (as long as it is out of the ring buffer).
78	*
79	* Here's some silly ASCII art.
80	*
81	* +------+
82	* |reader| RING BUFFER
83	* |page |
84	* +------+ +---+ +---+ +---+
85	* | |-->| |-->| |
86	* +---+ +---+ +---+
87	* ^ |
88	* | |
89	* +---------------+
90	*
91	*
92	* +------+
93	* |reader| RING BUFFER
94	* |page |------------------v
95	* +------+ +---+ +---+ +---+
96	* | |-->| |-->| |
97	* +---+ +---+ +---+
98	* ^ |
99	* | |
100	* +---------------+
101	*
102	*
103	* +------+
104	* |reader| RING BUFFER
105	* |page |------------------v
106	* +------+ +---+ +---+ +---+
107	* ^ | |-->| |-->| |
108	* | +---+ +---+ +---+
109	* | |
110	* | |
111	* +------------------------------+
112	*
113	*
114	* +------+
115	* |buffer| RING BUFFER
116	* |page |------------------v
117	* +------+ +---+ +---+ +---+
118	* ^ | | | |-->| |
119	* | New +---+ +---+ +---+
120	* | Reader------^ |
121	* | page |
122	* +------------------------------+
123	*
124	*
125	* After we make this swap, the reader can hand this page off to the splice
126	* code and be done with it. It can even allocate a new page if it needs to
127	* and swap that into the ring buffer.
128	*
129	* We will be using cmpxchg soon to make all this lockless.
130	*
131	*/
132
133	/* Used for individual buffers (after the counter) */
134	#define RB_BUFFER_OFF (1 << 20)
135
136	#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
137
138	#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
139	#define RB_ALIGNMENT 4U
140	#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
141	#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
142
143	#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
144	# define RB_FORCE_8BYTE_ALIGNMENT 0
145	# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
146	#else
147	# define RB_FORCE_8BYTE_ALIGNMENT 1
148	# define RB_ARCH_ALIGNMENT 8U
149	#endif
150
151	#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
152
153	/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
154	#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
155
156	enum {
157	RB_LEN_TIME_EXTEND = 8,
158	RB_LEN_TIME_STAMP = 8,
159	};
160
161	#define skip_time_extend(event) \
162	((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
163
164	#define extended_time(event) \
165	(event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
166
167	static inline bool rb_null_event(struct ring_buffer_event *event)
168	{
169	return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
170	}
171
172	static void rb_event_set_padding(struct ring_buffer_event *event)
173	{
174	/* padding has a NULL time_delta */
175	event->type_len = RINGBUF_TYPE_PADDING;
176	event->time_delta = 0;
177	}
178
179	static unsigned
180	rb_event_data_length(struct ring_buffer_event *event)
181	{
182	unsigned length;
183
184	if (event->type_len)
185	length = event->type_len * RB_ALIGNMENT;
186	else
187	length = event->array[0];
188	return length + RB_EVNT_HDR_SIZE;
189	}
190
191	/*
192	* Return the length of the given event. Will return
193	* the length of the time extend if the event is a
194	* time extend.
195	*/
196	static inline unsigned
197	rb_event_length(struct ring_buffer_event *event)
198	{
199	switch (event->type_len) {
200	case RINGBUF_TYPE_PADDING:
201	if (rb_null_event(event))
202	/* undefined */
203	return -1;
204	return event->array[0] + RB_EVNT_HDR_SIZE;
205
206	case RINGBUF_TYPE_TIME_EXTEND:
207	return RB_LEN_TIME_EXTEND;
208
209	case RINGBUF_TYPE_TIME_STAMP:
210	return RB_LEN_TIME_STAMP;
211
212	case RINGBUF_TYPE_DATA:
213	return rb_event_data_length(event);
214	default:
215	WARN_ON_ONCE(1);
216	}
217	/* not hit */
218	return 0;
219	}
220
221	/*
222	* Return total length of time extend and data,
223	* or just the event length for all other events.
224	*/
225	static inline unsigned
226	rb_event_ts_length(struct ring_buffer_event *event)
227	{
228	unsigned len = 0;
229
230	if (extended_time(event)) {
231	/* time extends include the data event after it */
232	len = RB_LEN_TIME_EXTEND;
233	event = skip_time_extend(event);
234	}
235	return len + rb_event_length(event);
236	}
237
238	/**
239	* ring_buffer_event_length - return the length of the event
240	* @event: the event to get the length of
241	*
242	* Returns the size of the data load of a data event.
243	* If the event is something other than a data event, it
244	* returns the size of the event itself. With the exception
245	* of a TIME EXTEND, where it still returns the size of the
246	* data load of the data event after it.
247	*/
248	unsigned ring_buffer_event_length(struct ring_buffer_event *event)
249	{
250	unsigned length;
251
252	if (extended_time(event))
253	event = skip_time_extend(event);
254
255	length = rb_event_length(event);
256	if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
257	return length;
258	length -= RB_EVNT_HDR_SIZE;
259	if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
260	length -= sizeof(event->array[0]);
261	return length;
262	}
263	EXPORT_SYMBOL_GPL(ring_buffer_event_length);
264
265	/* inline for ring buffer fast paths */
266	static __always_inline void *
267	rb_event_data(struct ring_buffer_event *event)
268	{
269	if (extended_time(event))
270	event = skip_time_extend(event);
271	WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
272	/* If length is in len field, then array[0] has the data */
273	if (event->type_len)
274	return (void *)&event->array[0];
275	/* Otherwise length is in array[0] and array[1] has the data */
276	return (void *)&event->array[1];
277	}
278
279	/**
280	* ring_buffer_event_data - return the data of the event
281	* @event: the event to get the data from
282	*/
283	void *ring_buffer_event_data(struct ring_buffer_event *event)
284	{
285	return rb_event_data(event);
286	}
287	EXPORT_SYMBOL_GPL(ring_buffer_event_data);
288
289	#define for_each_buffer_cpu(buffer, cpu) \
290	for_each_cpu(cpu, buffer->cpumask)
291
292	#define for_each_online_buffer_cpu(buffer, cpu) \
293	for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
294
295	#define TS_SHIFT 27
296	#define TS_MASK ((1ULL << TS_SHIFT) - 1)
297	#define TS_DELTA_TEST (~TS_MASK)
298
299	static u64 rb_event_time_stamp(struct ring_buffer_event *event)
300	{
301	u64 ts;
302
303	ts = event->array[0];
304	ts <<= TS_SHIFT;
305	ts += event->time_delta;
306
307	return ts;
308	}
309
310	/* Flag when events were overwritten */
311	#define RB_MISSED_EVENTS (1 << 31)
312	/* Missed count stored at end */
313	#define RB_MISSED_STORED (1 << 30)
314
315	struct buffer_data_page {
316	u64 time_stamp; /* page time stamp */
317	local_t commit; /* write committed index */
318	unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
319	};
320
321	struct buffer_data_read_page {
322	unsigned order; /* order of the page */
323	struct buffer_data_page *data; /* actual data, stored in this page */
324	};
325
326	/*
327	* Note, the buffer_page list must be first. The buffer pages
328	* are allocated in cache lines, which means that each buffer
329	* page will be at the beginning of a cache line, and thus
330	* the least significant bits will be zero. We use this to
331	* add flags in the list struct pointers, to make the ring buffer
332	* lockless.
333	*/
334	struct buffer_page {
335	struct list_head list; /* list of buffer pages */
336	local_t write; /* index for next write */
337	unsigned read; /* index for next read */
338	local_t entries; /* entries on this page */
339	unsigned long real_end; /* real end of data */
340	unsigned order; /* order of the page */
341	struct buffer_data_page *page; /* Actual data page */
342	};
343
344	/*
345	* The buffer page counters, write and entries, must be reset
346	* atomically when crossing page boundaries. To synchronize this
347	* update, two counters are inserted into the number. One is
348	* the actual counter for the write position or count on the page.
349	*
350	* The other is a counter of updaters. Before an update happens
351	* the update partition of the counter is incremented. This will
352	* allow the updater to update the counter atomically.
353	*
354	* The counter is 20 bits, and the state data is 12.
355	*/
356	#define RB_WRITE_MASK 0xfffff
357	#define RB_WRITE_INTCNT (1 << 20)
358
359	static void rb_init_page(struct buffer_data_page *bpage)
360	{
361	local_set(&bpage->commit, 0);
362	}
363
364	static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
365	{
366	return local_read(&bpage->page->commit);
367	}
368
369	static void free_buffer_page(struct buffer_page *bpage)
370	{
371	free_pages(addr: (unsigned long)bpage->page, order: bpage->order);
372	kfree(objp: bpage);
373	}
374
375	/*
376	* We need to fit the time_stamp delta into 27 bits.
377	*/
378	static inline bool test_time_stamp(u64 delta)
379	{
380	return !!(delta & TS_DELTA_TEST);
381	}
382
383	struct rb_irq_work {
384	struct irq_work work;
385	wait_queue_head_t waiters;
386	wait_queue_head_t full_waiters;
387	atomic_t seq;
388	bool waiters_pending;
389	bool full_waiters_pending;
390	bool wakeup_full;
391	};
392
393	/*
394	* Structure to hold event state and handle nested events.
395	*/
396	struct rb_event_info {
397	u64 ts;
398	u64 delta;
399	u64 before;
400	u64 after;
401	unsigned long length;
402	struct buffer_page *tail_page;
403	int add_timestamp;
404	};
405
406	/*
407	* Used for the add_timestamp
408	* NONE
409	* EXTEND - wants a time extend
410	* ABSOLUTE - the buffer requests all events to have absolute time stamps
411	* FORCE - force a full time stamp.
412	*/
413	enum {
414	RB_ADD_STAMP_NONE = 0,
415	RB_ADD_STAMP_EXTEND = BIT(1),
416	RB_ADD_STAMP_ABSOLUTE = BIT(2),
417	RB_ADD_STAMP_FORCE = BIT(3)
418	};
419	/*
420	* Used for which event context the event is in.
421	* TRANSITION = 0
422	* NMI = 1
423	* IRQ = 2
424	* SOFTIRQ = 3
425	* NORMAL = 4
426	*
427	* See trace_recursive_lock() comment below for more details.
428	*/
429	enum {
430	RB_CTX_TRANSITION,
431	RB_CTX_NMI,
432	RB_CTX_IRQ,
433	RB_CTX_SOFTIRQ,
434	RB_CTX_NORMAL,
435	RB_CTX_MAX
436	};
437
438	struct rb_time_struct {
439	local64_t time;
440	};
441	typedef struct rb_time_struct rb_time_t;
442
443	#define MAX_NEST 5
444
445	/*
446	* head_page == tail_page && head == tail then buffer is empty.
447	*/
448	struct ring_buffer_per_cpu {
449	int cpu;
450	atomic_t record_disabled;
451	atomic_t resize_disabled;
452	struct trace_buffer *buffer;
453	raw_spinlock_t reader_lock; /* serialize readers */
454	arch_spinlock_t lock;
455	struct lock_class_key lock_key;
456	struct buffer_data_page *free_page;
457	unsigned long nr_pages;
458	unsigned int current_context;
459	struct list_head *pages;
460	struct buffer_page *head_page; /* read from head */
461	struct buffer_page *tail_page; /* write to tail */
462	struct buffer_page *commit_page; /* committed pages */
463	struct buffer_page *reader_page;
464	unsigned long lost_events;
465	unsigned long last_overrun;
466	unsigned long nest;
467	local_t entries_bytes;
468	local_t entries;
469	local_t overrun;
470	local_t commit_overrun;
471	local_t dropped_events;
472	local_t committing;
473	local_t commits;
474	local_t pages_touched;
475	local_t pages_lost;
476	local_t pages_read;
477	long last_pages_touch;
478	size_t shortest_full;
479	unsigned long read;
480	unsigned long read_bytes;
481	rb_time_t write_stamp;
482	rb_time_t before_stamp;
483	u64 event_stamp[MAX_NEST];
484	u64 read_stamp;
485	/* pages removed since last reset */
486	unsigned long pages_removed;
487	/* ring buffer pages to update, > 0 to add, < 0 to remove */
488	long nr_pages_to_update;
489	struct list_head new_pages; /* new pages to add */
490	struct work_struct update_pages_work;
491	struct completion update_done;
492
493	struct rb_irq_work irq_work;
494	};
495
496	struct trace_buffer {
497	unsigned flags;
498	int cpus;
499	atomic_t record_disabled;
500	atomic_t resizing;
501	cpumask_var_t cpumask;
502
503	struct lock_class_key *reader_lock_key;
504
505	struct mutex mutex;
506
507	struct ring_buffer_per_cpu **buffers;
508
509	struct hlist_node node;
510	u64 (*clock)(void);
511
512	struct rb_irq_work irq_work;
513	bool time_stamp_abs;
514
515	unsigned int subbuf_size;
516	unsigned int subbuf_order;
517	unsigned int max_data_size;
518	};
519
520	struct ring_buffer_iter {
521	struct ring_buffer_per_cpu *cpu_buffer;
522	unsigned long head;
523	unsigned long next_event;
524	struct buffer_page *head_page;
525	struct buffer_page *cache_reader_page;
526	unsigned long cache_read;
527	unsigned long cache_pages_removed;
528	u64 read_stamp;
529	u64 page_stamp;
530	struct ring_buffer_event *event;
531	size_t event_size;
532	int missed_events;
533	};
534
535	int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
536	{
537	struct buffer_data_page field;
538
539	trace_seq_printf(s, fmt: "\tfield: u64 timestamp;\t"
540	"offset:0;\tsize:%u;\tsigned:%u;\n",
541	(unsigned int)sizeof(field.time_stamp),
542	(unsigned int)is_signed_type(u64));
543
544	trace_seq_printf(s, fmt: "\tfield: local_t commit;\t"
545	"offset:%u;\tsize:%u;\tsigned:%u;\n",
546	(unsigned int)offsetof(typeof(field), commit),
547	(unsigned int)sizeof(field.commit),
548	(unsigned int)is_signed_type(long));
549
550	trace_seq_printf(s, fmt: "\tfield: int overwrite;\t"
551	"offset:%u;\tsize:%u;\tsigned:%u;\n",
552	(unsigned int)offsetof(typeof(field), commit),
553	1,
554	(unsigned int)is_signed_type(long));
555
556	trace_seq_printf(s, fmt: "\tfield: char data;\t"
557	"offset:%u;\tsize:%u;\tsigned:%u;\n",
558	(unsigned int)offsetof(typeof(field), data),
559	(unsigned int)buffer->subbuf_size,
560	(unsigned int)is_signed_type(char));
561
562	return !trace_seq_has_overflowed(s);
563	}
564
565	static inline void rb_time_read(rb_time_t *t, u64 *ret)
566	{
567	*ret = local64_read(&t->time);
568	}
569	static void rb_time_set(rb_time_t *t, u64 val)
570	{
571	local64_set(&t->time, val);
572	}
573
574	/*
575	* Enable this to make sure that the event passed to
576	* ring_buffer_event_time_stamp() is not committed and also
577	* is on the buffer that it passed in.
578	*/
579	//#define RB_VERIFY_EVENT
580	#ifdef RB_VERIFY_EVENT
581	static struct list_head *rb_list_head(struct list_head *list);
582	static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
583	void *event)
584	{
585	struct buffer_page *page = cpu_buffer->commit_page;
586	struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
587	struct list_head *next;
588	long commit, write;
589	unsigned long addr = (unsigned long)event;
590	bool done = false;
591	int stop = 0;
592
593	/* Make sure the event exists and is not committed yet */
594	do {
595	if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
596	done = true;
597	commit = local_read(&page->page->commit);
598	write = local_read(&page->write);
599	if (addr >= (unsigned long)&page->page->data[commit] &&
600	addr < (unsigned long)&page->page->data[write])
601	return;
602
603	next = rb_list_head(page->list.next);
604	page = list_entry(next, struct buffer_page, list);
605	} while (!done);
606	WARN_ON_ONCE(1);
607	}
608	#else
609	static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
610	void *event)
611	{
612	}
613	#endif
614
615	/*
616	* The absolute time stamp drops the 5 MSBs and some clocks may
617	* require them. The rb_fix_abs_ts() will take a previous full
618	* time stamp, and add the 5 MSB of that time stamp on to the
619	* saved absolute time stamp. Then they are compared in case of
620	* the unlikely event that the latest time stamp incremented
621	* the 5 MSB.
622	*/
623	static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
624	{
625	if (save_ts & TS_MSB) {
626	abs |= save_ts & TS_MSB;
627	/* Check for overflow */
628	if (unlikely(abs < save_ts))
629	abs += 1ULL << 59;
630	}
631	return abs;
632	}
633
634	static inline u64 rb_time_stamp(struct trace_buffer *buffer);
635
636	/**
637	* ring_buffer_event_time_stamp - return the event's current time stamp
638	* @buffer: The buffer that the event is on
639	* @event: the event to get the time stamp of
640	*
641	* Note, this must be called after @event is reserved, and before it is
642	* committed to the ring buffer. And must be called from the same
643	* context where the event was reserved (normal, softirq, irq, etc).
644	*
645	* Returns the time stamp associated with the current event.
646	* If the event has an extended time stamp, then that is used as
647	* the time stamp to return.
648	* In the highly unlikely case that the event was nested more than
649	* the max nesting, then the write_stamp of the buffer is returned,
650	* otherwise current time is returned, but that really neither of
651	* the last two cases should ever happen.
652	*/
653	u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
654	struct ring_buffer_event *event)
655	{
656	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
657	unsigned int nest;
658	u64 ts;
659
660	/* If the event includes an absolute time, then just use that */
661	if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
662	ts = rb_event_time_stamp(event);
663	return rb_fix_abs_ts(abs: ts, save_ts: cpu_buffer->tail_page->page->time_stamp);
664	}
665
666	nest = local_read(&cpu_buffer->committing);
667	verify_event(cpu_buffer, event);
668	if (WARN_ON_ONCE(!nest))
669	goto fail;
670
671	/* Read the current saved nesting level time stamp */
672	if (likely(--nest < MAX_NEST))
673	return cpu_buffer->event_stamp[nest];
674
675	/* Shouldn't happen, warn if it does */
676	WARN_ONCE(1, "nest (%d) greater than max", nest);
677
678	fail:
679	rb_time_read(t: &cpu_buffer->write_stamp, ret: &ts);
680
681	return ts;
682	}
683
684	/**
685	* ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
686	* @buffer: The ring_buffer to get the number of pages from
687	* @cpu: The cpu of the ring_buffer to get the number of pages from
688	*
689	* Returns the number of pages used by a per_cpu buffer of the ring buffer.
690	*/
691	size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
692	{
693	return buffer->buffers[cpu]->nr_pages;
694	}
695
696	/**
697	* ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
698	* @buffer: The ring_buffer to get the number of pages from
699	* @cpu: The cpu of the ring_buffer to get the number of pages from
700	*
701	* Returns the number of pages that have content in the ring buffer.
702	*/
703	size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
704	{
705	size_t read;
706	size_t lost;
707	size_t cnt;
708
709	read = local_read(&buffer->buffers[cpu]->pages_read);
710	lost = local_read(&buffer->buffers[cpu]->pages_lost);
711	cnt = local_read(&buffer->buffers[cpu]->pages_touched);
712
713	if (WARN_ON_ONCE(cnt < lost))
714	return 0;
715
716	cnt -= lost;
717
718	/* The reader can read an empty page, but not more than that */
719	if (cnt < read) {
720	WARN_ON_ONCE(read > cnt + 1);
721	return 0;
722	}
723
724	return cnt - read;
725	}
726
727	static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
728	{
729	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
730	size_t nr_pages;
731	size_t dirty;
732
733	nr_pages = cpu_buffer->nr_pages;
734	if (!nr_pages || !full)
735	return true;
736
737	/*
738	* Add one as dirty will never equal nr_pages, as the sub-buffer
739	* that the writer is on is not counted as dirty.
740	* This is needed if "buffer_percent" is set to 100.
741	*/
742	dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
743
744	return (dirty * 100) >= (full * nr_pages);
745	}
746
747	/*
748	* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
749	*
750	* Schedules a delayed work to wake up any task that is blocked on the
751	* ring buffer waiters queue.
752	*/
753	static void rb_wake_up_waiters(struct irq_work *work)
754	{
755	struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
756
757	/* For waiters waiting for the first wake up */
758	(void)atomic_fetch_inc_release(v: &rbwork->seq);
759
760	wake_up_all(&rbwork->waiters);
761	if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
762	/* Only cpu_buffer sets the above flags */
763	struct ring_buffer_per_cpu *cpu_buffer =
764	container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
765
766	/* Called from interrupt context */
767	raw_spin_lock(&cpu_buffer->reader_lock);
768	rbwork->wakeup_full = false;
769	rbwork->full_waiters_pending = false;
770
771	/* Waking up all waiters, they will reset the shortest full */
772	cpu_buffer->shortest_full = 0;
773	raw_spin_unlock(&cpu_buffer->reader_lock);
774
775	wake_up_all(&rbwork->full_waiters);
776	}
777	}
778
779	/**
780	* ring_buffer_wake_waiters - wake up any waiters on this ring buffer
781	* @buffer: The ring buffer to wake waiters on
782	* @cpu: The CPU buffer to wake waiters on
783	*
784	* In the case of a file that represents a ring buffer is closing,
785	* it is prudent to wake up any waiters that are on this.
786	*/
787	void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
788	{
789	struct ring_buffer_per_cpu *cpu_buffer;
790	struct rb_irq_work *rbwork;
791
792	if (!buffer)
793	return;
794
795	if (cpu == RING_BUFFER_ALL_CPUS) {
796
797	/* Wake up individual ones too. One level recursion */
798	for_each_buffer_cpu(buffer, cpu)
799	ring_buffer_wake_waiters(buffer, cpu);
800
801	rbwork = &buffer->irq_work;
802	} else {
803	if (WARN_ON_ONCE(!buffer->buffers))
804	return;
805	if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
806	return;
807
808	cpu_buffer = buffer->buffers[cpu];
809	/* The CPU buffer may not have been initialized yet */
810	if (!cpu_buffer)
811	return;
812	rbwork = &cpu_buffer->irq_work;
813	}
814
815	/* This can be called in any context */
816	irq_work_queue(work: &rbwork->work);
817	}
818
819	static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
820	{
821	struct ring_buffer_per_cpu *cpu_buffer;
822	bool ret = false;
823
824	/* Reads of all CPUs always waits for any data */
825	if (cpu == RING_BUFFER_ALL_CPUS)
826	return !ring_buffer_empty(buffer);
827
828	cpu_buffer = buffer->buffers[cpu];
829
830	if (!ring_buffer_empty_cpu(buffer, cpu)) {
831	unsigned long flags;
832	bool pagebusy;
833
834	if (!full)
835	return true;
836
837	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
838	pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
839	ret = !pagebusy && full_hit(buffer, cpu, full);
840
841	if (!ret && (!cpu_buffer->shortest_full ||
842	cpu_buffer->shortest_full > full)) {
843	cpu_buffer->shortest_full = full;
844	}
845	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
846	}
847	return ret;
848	}
849
850	static inline bool
851	rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
852	int cpu, int full, ring_buffer_cond_fn cond, void *data)
853	{
854	if (rb_watermark_hit(buffer, cpu, full))
855	return true;
856
857	if (cond(data))
858	return true;
859
860	/*
861	* The events can happen in critical sections where
862	* checking a work queue can cause deadlocks.
863	* After adding a task to the queue, this flag is set
864	* only to notify events to try to wake up the queue
865	* using irq_work.
866	*
867	* We don't clear it even if the buffer is no longer
868	* empty. The flag only causes the next event to run
869	* irq_work to do the work queue wake up. The worse
870	* that can happen if we race with !trace_empty() is that
871	* an event will cause an irq_work to try to wake up
872	* an empty queue.
873	*
874	* There's no reason to protect this flag either, as
875	* the work queue and irq_work logic will do the necessary
876	* synchronization for the wake ups. The only thing
877	* that is necessary is that the wake up happens after
878	* a task has been queued. It's OK for spurious wake ups.
879	*/
880	if (full)
881	rbwork->full_waiters_pending = true;
882	else
883	rbwork->waiters_pending = true;
884
885	return false;
886	}
887
888	struct rb_wait_data {
889	struct rb_irq_work *irq_work;
890	int seq;
891	};
892
893	/*
894	* The default wait condition for ring_buffer_wait() is to just to exit the
895	* wait loop the first time it is woken up.
896	*/
897	static bool rb_wait_once(void *data)
898	{
899	struct rb_wait_data *rdata = data;
900	struct rb_irq_work *rbwork = rdata->irq_work;
901
902	return atomic_read_acquire(v: &rbwork->seq) != rdata->seq;
903	}
904
905	/**
906	* ring_buffer_wait - wait for input to the ring buffer
907	* @buffer: buffer to wait on
908	* @cpu: the cpu buffer to wait on
909	* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
910	* @cond: condition function to break out of wait (NULL to run once)
911	* @data: the data to pass to @cond.
912	*
913	* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
914	* as data is added to any of the @buffer's cpu buffers. Otherwise
915	* it will wait for data to be added to a specific cpu buffer.
916	*/
917	int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
918	ring_buffer_cond_fn cond, void *data)
919	{
920	struct ring_buffer_per_cpu *cpu_buffer;
921	struct wait_queue_head *waitq;
922	struct rb_irq_work *rbwork;
923	struct rb_wait_data rdata;
924	int ret = 0;
925
926	/*
927	* Depending on what the caller is waiting for, either any
928	* data in any cpu buffer, or a specific buffer, put the
929	* caller on the appropriate wait queue.
930	*/
931	if (cpu == RING_BUFFER_ALL_CPUS) {
932	rbwork = &buffer->irq_work;
933	/* Full only makes sense on per cpu reads */
934	full = 0;
935	} else {
936	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
937	return -ENODEV;
938	cpu_buffer = buffer->buffers[cpu];
939	rbwork = &cpu_buffer->irq_work;
940	}
941
942	if (full)
943	waitq = &rbwork->full_waiters;
944	else
945	waitq = &rbwork->waiters;
946
947	/* Set up to exit loop as soon as it is woken */
948	if (!cond) {
949	cond = rb_wait_once;
950	rdata.irq_work = rbwork;
951	rdata.seq = atomic_read_acquire(v: &rbwork->seq);
952	data = &rdata;
953	}
954
955	ret = wait_event_interruptible((*waitq),
956	rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
957
958	return ret;
959	}
960
961	/**
962	* ring_buffer_poll_wait - poll on buffer input
963	* @buffer: buffer to wait on
964	* @cpu: the cpu buffer to wait on
965	* @filp: the file descriptor
966	* @poll_table: The poll descriptor
967	* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
968	*
969	* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
970	* as data is added to any of the @buffer's cpu buffers. Otherwise
971	* it will wait for data to be added to a specific cpu buffer.
972	*
973	* Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
974	* zero otherwise.
975	*/
976	__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
977	struct file *filp, poll_table *poll_table, int full)
978	{
979	struct ring_buffer_per_cpu *cpu_buffer;
980	struct rb_irq_work *rbwork;
981
982	if (cpu == RING_BUFFER_ALL_CPUS) {
983	rbwork = &buffer->irq_work;
984	full = 0;
985	} else {
986	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
987	return EPOLLERR;
988
989	cpu_buffer = buffer->buffers[cpu];
990	rbwork = &cpu_buffer->irq_work;
991	}
992
993	if (full) {
994	poll_wait(filp, wait_address: &rbwork->full_waiters, p: poll_table);
995
996	if (rb_watermark_hit(buffer, cpu, full))
997	return EPOLLIN | EPOLLRDNORM;
998	/*
999	* Only allow full_waiters_pending update to be seen after
1000	* the shortest_full is set (in rb_watermark_hit). If the
1001	* writer sees the full_waiters_pending flag set, it will
1002	* compare the amount in the ring buffer to shortest_full.
1003	* If the amount in the ring buffer is greater than the
1004	* shortest_full percent, it will call the irq_work handler
1005	* to wake up this list. The irq_handler will reset shortest_full
1006	* back to zero. That's done under the reader_lock, but
1007	* the below smp_mb() makes sure that the update to
1008	* full_waiters_pending doesn't leak up into the above.
1009	*/
1010	smp_mb();
1011	rbwork->full_waiters_pending = true;
1012	return 0;
1013	}
1014
1015	poll_wait(filp, wait_address: &rbwork->waiters, p: poll_table);
1016	rbwork->waiters_pending = true;
1017
1018	/*
1019	* There's a tight race between setting the waiters_pending and
1020	* checking if the ring buffer is empty. Once the waiters_pending bit
1021	* is set, the next event will wake the task up, but we can get stuck
1022	* if there's only a single event in.
1023	*
1024	* FIXME: Ideally, we need a memory barrier on the writer side as well,
1025	* but adding a memory barrier to all events will cause too much of a
1026	* performance hit in the fast path. We only need a memory barrier when
1027	* the buffer goes from empty to having content. But as this race is
1028	* extremely small, and it's not a problem if another event comes in, we
1029	* will fix it later.
1030	*/
1031	smp_mb();
1032
1033	if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1034	(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1035	return EPOLLIN | EPOLLRDNORM;
1036	return 0;
1037	}
1038
1039	/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1040	#define RB_WARN_ON(b, cond) \
1041	({ \
1042	int _____ret = unlikely(cond); \
1043	if (_____ret) { \
1044	if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1045	struct ring_buffer_per_cpu *__b = \
1046	(void *)b; \
1047	atomic_inc(&__b->buffer->record_disabled); \
1048	} else \
1049	atomic_inc(&b->record_disabled); \
1050	WARN_ON(1); \
1051	} \
1052	_____ret; \
1053	})
1054
1055	/* Up this if you want to test the TIME_EXTENTS and normalization */
1056	#define DEBUG_SHIFT 0
1057
1058	static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1059	{
1060	u64 ts;
1061
1062	/* Skip retpolines :-( */
1063	if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1064	ts = trace_clock_local();
1065	else
1066	ts = buffer->clock();
1067
1068	/* shift to debug/test normalization and TIME_EXTENTS */
1069	return ts << DEBUG_SHIFT;
1070	}
1071
1072	u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1073	{
1074	u64 time;
1075
1076	preempt_disable_notrace();
1077	time = rb_time_stamp(buffer);
1078	preempt_enable_notrace();
1079
1080	return time;
1081	}
1082	EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1083
1084	void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1085	int cpu, u64 *ts)
1086	{
1087	/* Just stupid testing the normalize function and deltas */
1088	*ts >>= DEBUG_SHIFT;
1089	}
1090	EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1091
1092	/*
1093	* Making the ring buffer lockless makes things tricky.
1094	* Although writes only happen on the CPU that they are on,
1095	* and they only need to worry about interrupts. Reads can
1096	* happen on any CPU.
1097	*
1098	* The reader page is always off the ring buffer, but when the
1099	* reader finishes with a page, it needs to swap its page with
1100	* a new one from the buffer. The reader needs to take from
1101	* the head (writes go to the tail). But if a writer is in overwrite
1102	* mode and wraps, it must push the head page forward.
1103	*
1104	* Here lies the problem.
1105	*
1106	* The reader must be careful to replace only the head page, and
1107	* not another one. As described at the top of the file in the
1108	* ASCII art, the reader sets its old page to point to the next
1109	* page after head. It then sets the page after head to point to
1110	* the old reader page. But if the writer moves the head page
1111	* during this operation, the reader could end up with the tail.
1112	*
1113	* We use cmpxchg to help prevent this race. We also do something
1114	* special with the page before head. We set the LSB to 1.
1115	*
1116	* When the writer must push the page forward, it will clear the
1117	* bit that points to the head page, move the head, and then set
1118	* the bit that points to the new head page.
1119	*
1120	* We also don't want an interrupt coming in and moving the head
1121	* page on another writer. Thus we use the second LSB to catch
1122	* that too. Thus:
1123	*
1124	* head->list->prev->next bit 1 bit 0
1125	* ------- -------
1126	* Normal page 0 0
1127	* Points to head page 0 1
1128	* New head page 1 0
1129	*
1130	* Note we can not trust the prev pointer of the head page, because:
1131	*
1132	* +----+ +-----+ +-----+
1133	* | |------>| T |---X--->| N |
1134	* | |<------| | | |
1135	* +----+ +-----+ +-----+
1136	* ^ ^ |
1137	* | +-----+ | |
1138	* +----------| R |----------+ |
1139	* | |<-----------+
1140	* +-----+
1141	*
1142	* Key: ---X--> HEAD flag set in pointer
1143	* T Tail page
1144	* R Reader page
1145	* N Next page
1146	*
1147	* (see __rb_reserve_next() to see where this happens)
1148	*
1149	* What the above shows is that the reader just swapped out
1150	* the reader page with a page in the buffer, but before it
1151	* could make the new header point back to the new page added
1152	* it was preempted by a writer. The writer moved forward onto
1153	* the new page added by the reader and is about to move forward
1154	* again.
1155	*
1156	* You can see, it is legitimate for the previous pointer of
1157	* the head (or any page) not to point back to itself. But only
1158	* temporarily.
1159	*/
1160
1161	#define RB_PAGE_NORMAL 0UL
1162	#define RB_PAGE_HEAD 1UL
1163	#define RB_PAGE_UPDATE 2UL
1164
1165
1166	#define RB_FLAG_MASK 3UL
1167
1168	/* PAGE_MOVED is not part of the mask */
1169	#define RB_PAGE_MOVED 4UL
1170
1171	/*
1172	* rb_list_head - remove any bit
1173	*/
1174	static struct list_head *rb_list_head(struct list_head *list)
1175	{
1176	unsigned long val = (unsigned long)list;
1177
1178	return (struct list_head *)(val & ~RB_FLAG_MASK);
1179	}
1180
1181	/*
1182	* rb_is_head_page - test if the given page is the head page
1183	*
1184	* Because the reader may move the head_page pointer, we can
1185	* not trust what the head page is (it may be pointing to
1186	* the reader page). But if the next page is a header page,
1187	* its flags will be non zero.
1188	*/
1189	static inline int
1190	rb_is_head_page(struct buffer_page *page, struct list_head *list)
1191	{
1192	unsigned long val;
1193
1194	val = (unsigned long)list->next;
1195
1196	if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1197	return RB_PAGE_MOVED;
1198
1199	return val & RB_FLAG_MASK;
1200	}
1201
1202	/*
1203	* rb_is_reader_page
1204	*
1205	* The unique thing about the reader page, is that, if the
1206	* writer is ever on it, the previous pointer never points
1207	* back to the reader page.
1208	*/
1209	static bool rb_is_reader_page(struct buffer_page *page)
1210	{
1211	struct list_head *list = page->list.prev;
1212
1213	return rb_list_head(list: list->next) != &page->list;
1214	}
1215
1216	/*
1217	* rb_set_list_to_head - set a list_head to be pointing to head.
1218	*/
1219	static void rb_set_list_to_head(struct list_head *list)
1220	{
1221	unsigned long *ptr;
1222
1223	ptr = (unsigned long *)&list->next;
1224	*ptr |= RB_PAGE_HEAD;
1225	*ptr &= ~RB_PAGE_UPDATE;
1226	}
1227
1228	/*
1229	* rb_head_page_activate - sets up head page
1230	*/
1231	static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1232	{
1233	struct buffer_page *head;
1234
1235	head = cpu_buffer->head_page;
1236	if (!head)
1237	return;
1238
1239	/*
1240	* Set the previous list pointer to have the HEAD flag.
1241	*/
1242	rb_set_list_to_head(list: head->list.prev);
1243	}
1244
1245	static void rb_list_head_clear(struct list_head *list)
1246	{
1247	unsigned long *ptr = (unsigned long *)&list->next;
1248
1249	*ptr &= ~RB_FLAG_MASK;
1250	}
1251
1252	/*
1253	* rb_head_page_deactivate - clears head page ptr (for free list)
1254	*/
1255	static void
1256	rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1257	{
1258	struct list_head *hd;
1259
1260	/* Go through the whole list and clear any pointers found. */
1261	rb_list_head_clear(list: cpu_buffer->pages);
1262
1263	list_for_each(hd, cpu_buffer->pages)
1264	rb_list_head_clear(list: hd);
1265	}
1266
1267	static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1268	struct buffer_page *head,
1269	struct buffer_page *prev,
1270	int old_flag, int new_flag)
1271	{
1272	struct list_head *list;
1273	unsigned long val = (unsigned long)&head->list;
1274	unsigned long ret;
1275
1276	list = &prev->list;
1277
1278	val &= ~RB_FLAG_MASK;
1279
1280	ret = cmpxchg((unsigned long *)&list->next,
1281	val | old_flag, val | new_flag);
1282
1283	/* check if the reader took the page */
1284	if ((ret & ~RB_FLAG_MASK) != val)
1285	return RB_PAGE_MOVED;
1286
1287	return ret & RB_FLAG_MASK;
1288	}
1289
1290	static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1291	struct buffer_page *head,
1292	struct buffer_page *prev,
1293	int old_flag)
1294	{
1295	return rb_head_page_set(cpu_buffer, head, prev,
1296	old_flag, RB_PAGE_UPDATE);
1297	}
1298
1299	static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1300	struct buffer_page *head,
1301	struct buffer_page *prev,
1302	int old_flag)
1303	{
1304	return rb_head_page_set(cpu_buffer, head, prev,
1305	old_flag, RB_PAGE_HEAD);
1306	}
1307
1308	static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1309	struct buffer_page *head,
1310	struct buffer_page *prev,
1311	int old_flag)
1312	{
1313	return rb_head_page_set(cpu_buffer, head, prev,
1314	old_flag, RB_PAGE_NORMAL);
1315	}
1316
1317	static inline void rb_inc_page(struct buffer_page **bpage)
1318	{
1319	struct list_head *p = rb_list_head(list: (*bpage)->list.next);
1320
1321	*bpage = list_entry(p, struct buffer_page, list);
1322	}
1323
1324	static struct buffer_page *
1325	rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1326	{
1327	struct buffer_page *head;
1328	struct buffer_page *page;
1329	struct list_head *list;
1330	int i;
1331
1332	if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1333	return NULL;
1334
1335	/* sanity check */
1336	list = cpu_buffer->pages;
1337	if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1338	return NULL;
1339
1340	page = head = cpu_buffer->head_page;
1341	/*
1342	* It is possible that the writer moves the header behind
1343	* where we started, and we miss in one loop.
1344	* A second loop should grab the header, but we'll do
1345	* three loops just because I'm paranoid.
1346	*/
1347	for (i = 0; i < 3; i++) {
1348	do {
1349	if (rb_is_head_page(page, list: page->list.prev)) {
1350	cpu_buffer->head_page = page;
1351	return page;
1352	}
1353	rb_inc_page(bpage: &page);
1354	} while (page != head);
1355	}
1356
1357	RB_WARN_ON(cpu_buffer, 1);
1358
1359	return NULL;
1360	}
1361
1362	static bool rb_head_page_replace(struct buffer_page *old,
1363	struct buffer_page *new)
1364	{
1365	unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1366	unsigned long val;
1367
1368	val = *ptr & ~RB_FLAG_MASK;
1369	val |= RB_PAGE_HEAD;
1370
1371	return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1372	}
1373
1374	/*
1375	* rb_tail_page_update - move the tail page forward
1376	*/
1377	static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1378	struct buffer_page *tail_page,
1379	struct buffer_page *next_page)
1380	{
1381	unsigned long old_entries;
1382	unsigned long old_write;
1383
1384	/*
1385	* The tail page now needs to be moved forward.
1386	*
1387	* We need to reset the tail page, but without messing
1388	* with possible erasing of data brought in by interrupts
1389	* that have moved the tail page and are currently on it.
1390	*
1391	* We add a counter to the write field to denote this.
1392	*/
1393	old_write = local_add_return(RB_WRITE_INTCNT, l: &next_page->write);
1394	old_entries = local_add_return(RB_WRITE_INTCNT, l: &next_page->entries);
1395
1396	/*
1397	* Just make sure we have seen our old_write and synchronize
1398	* with any interrupts that come in.
1399	*/
1400	barrier();
1401
1402	/*
1403	* If the tail page is still the same as what we think
1404	* it is, then it is up to us to update the tail
1405	* pointer.
1406	*/
1407	if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1408	/* Zero the write counter */
1409	unsigned long val = old_write & ~RB_WRITE_MASK;
1410	unsigned long eval = old_entries & ~RB_WRITE_MASK;
1411
1412	/*
1413	* This will only succeed if an interrupt did
1414	* not come in and change it. In which case, we
1415	* do not want to modify it.
1416	*
1417	* We add (void) to let the compiler know that we do not care
1418	* about the return value of these functions. We use the
1419	* cmpxchg to only update if an interrupt did not already
1420	* do it for us. If the cmpxchg fails, we don't care.
1421	*/
1422	(void)local_cmpxchg(l: &next_page->write, old: old_write, new: val);
1423	(void)local_cmpxchg(l: &next_page->entries, old: old_entries, new: eval);
1424
1425	/*
1426	* No need to worry about races with clearing out the commit.
1427	* it only can increment when a commit takes place. But that
1428	* only happens in the outer most nested commit.
1429	*/
1430	local_set(&next_page->page->commit, 0);
1431
1432	/* Either we update tail_page or an interrupt does */
1433	if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1434	local_inc(l: &cpu_buffer->pages_touched);
1435	}
1436	}
1437
1438	static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1439	struct buffer_page *bpage)
1440	{
1441	unsigned long val = (unsigned long)bpage;
1442
1443	RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1444	}
1445
1446	/**
1447	* rb_check_pages - integrity check of buffer pages
1448	* @cpu_buffer: CPU buffer with pages to test
1449	*
1450	* As a safety measure we check to make sure the data pages have not
1451	* been corrupted.
1452	*/
1453	static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1454	{
1455	struct list_head *head = rb_list_head(list: cpu_buffer->pages);
1456	struct list_head *tmp;
1457
1458	if (RB_WARN_ON(cpu_buffer,
1459	rb_list_head(rb_list_head(head->next)->prev) != head))
1460	return;
1461
1462	if (RB_WARN_ON(cpu_buffer,
1463	rb_list_head(rb_list_head(head->prev)->next) != head))
1464	return;
1465
1466	for (tmp = rb_list_head(list: head->next); tmp != head; tmp = rb_list_head(list: tmp->next)) {
1467	if (RB_WARN_ON(cpu_buffer,
1468	rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
1469	return;
1470
1471	if (RB_WARN_ON(cpu_buffer,
1472	rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
1473	return;
1474	}
1475	}
1476
1477	static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1478	long nr_pages, struct list_head *pages)
1479	{
1480	struct buffer_page *bpage, *tmp;
1481	bool user_thread = current->mm != NULL;
1482	gfp_t mflags;
1483	long i;
1484
1485	/*
1486	* Check if the available memory is there first.
1487	* Note, si_mem_available() only gives us a rough estimate of available
1488	* memory. It may not be accurate. But we don't care, we just want
1489	* to prevent doing any allocation when it is obvious that it is
1490	* not going to succeed.
1491	*/
1492	i = si_mem_available();
1493	if (i < nr_pages)
1494	return -ENOMEM;
1495
1496	/*
1497	* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1498	* gracefully without invoking oom-killer and the system is not
1499	* destabilized.
1500	*/
1501	mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1502
1503	/*
1504	* If a user thread allocates too much, and si_mem_available()
1505	* reports there's enough memory, even though there is not.
1506	* Make sure the OOM killer kills this thread. This can happen
1507	* even with RETRY_MAYFAIL because another task may be doing
1508	* an allocation after this task has taken all memory.
1509	* This is the task the OOM killer needs to take out during this
1510	* loop, even if it was triggered by an allocation somewhere else.
1511	*/
1512	if (user_thread)
1513	set_current_oom_origin();
1514	for (i = 0; i < nr_pages; i++) {
1515	struct page *page;
1516
1517	bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1518	flags: mflags, cpu_to_node(cpu: cpu_buffer->cpu));
1519	if (!bpage)
1520	goto free_pages;
1521
1522	rb_check_bpage(cpu_buffer, bpage);
1523
1524	list_add(new: &bpage->list, head: pages);
1525
1526	page = alloc_pages_node(cpu_to_node(cpu: cpu_buffer->cpu),
1527	gfp_mask: mflags | __GFP_ZERO,
1528	order: cpu_buffer->buffer->subbuf_order);
1529	if (!page)
1530	goto free_pages;
1531	bpage->page = page_address(page);
1532	bpage->order = cpu_buffer->buffer->subbuf_order;
1533	rb_init_page(bpage: bpage->page);
1534
1535	if (user_thread && fatal_signal_pending(current))
1536	goto free_pages;
1537	}
1538	if (user_thread)
1539	clear_current_oom_origin();
1540
1541	return 0;
1542
1543	free_pages:
1544	list_for_each_entry_safe(bpage, tmp, pages, list) {
1545	list_del_init(entry: &bpage->list);
1546	free_buffer_page(bpage);
1547	}
1548	if (user_thread)
1549	clear_current_oom_origin();
1550
1551	return -ENOMEM;
1552	}
1553
1554	static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1555	unsigned long nr_pages)
1556	{
1557	LIST_HEAD(pages);
1558
1559	WARN_ON(!nr_pages);
1560
1561	if (__rb_allocate_pages(cpu_buffer, nr_pages, pages: &pages))
1562	return -ENOMEM;
1563
1564	/*
1565	* The ring buffer page list is a circular list that does not
1566	* start and end with a list head. All page list items point to
1567	* other pages.
1568	*/
1569	cpu_buffer->pages = pages.next;
1570	list_del(entry: &pages);
1571
1572	cpu_buffer->nr_pages = nr_pages;
1573
1574	rb_check_pages(cpu_buffer);
1575
1576	return 0;
1577	}
1578
1579	static struct ring_buffer_per_cpu *
1580	rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1581	{
1582	struct ring_buffer_per_cpu *cpu_buffer;
1583	struct buffer_page *bpage;
1584	struct page *page;
1585	int ret;
1586
1587	cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1588	GFP_KERNEL, cpu_to_node(cpu));
1589	if (!cpu_buffer)
1590	return NULL;
1591
1592	cpu_buffer->cpu = cpu;
1593	cpu_buffer->buffer = buffer;
1594	raw_spin_lock_init(&cpu_buffer->reader_lock);
1595	lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1596	cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1597	INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1598	init_completion(x: &cpu_buffer->update_done);
1599	init_irq_work(work: &cpu_buffer->irq_work.work, func: rb_wake_up_waiters);
1600	init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1601	init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1602
1603	bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1604	GFP_KERNEL, cpu_to_node(cpu));
1605	if (!bpage)
1606	goto fail_free_buffer;
1607
1608	rb_check_bpage(cpu_buffer, bpage);
1609
1610	cpu_buffer->reader_page = bpage;
1611
1612	page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_ZERO,
1613	order: cpu_buffer->buffer->subbuf_order);
1614	if (!page)
1615	goto fail_free_reader;
1616	bpage->page = page_address(page);
1617	rb_init_page(bpage: bpage->page);
1618
1619	INIT_LIST_HEAD(list: &cpu_buffer->reader_page->list);
1620	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
1621
1622	ret = rb_allocate_pages(cpu_buffer, nr_pages);
1623	if (ret < 0)
1624	goto fail_free_reader;
1625
1626	cpu_buffer->head_page
1627	= list_entry(cpu_buffer->pages, struct buffer_page, list);
1628	cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1629
1630	rb_head_page_activate(cpu_buffer);
1631
1632	return cpu_buffer;
1633
1634	fail_free_reader:
1635	free_buffer_page(bpage: cpu_buffer->reader_page);
1636
1637	fail_free_buffer:
1638	kfree(objp: cpu_buffer);
1639	return NULL;
1640	}
1641
1642	static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1643	{
1644	struct list_head *head = cpu_buffer->pages;
1645	struct buffer_page *bpage, *tmp;
1646
1647	irq_work_sync(work: &cpu_buffer->irq_work.work);
1648
1649	free_buffer_page(bpage: cpu_buffer->reader_page);
1650
1651	if (head) {
1652	rb_head_page_deactivate(cpu_buffer);
1653
1654	list_for_each_entry_safe(bpage, tmp, head, list) {
1655	list_del_init(entry: &bpage->list);
1656	free_buffer_page(bpage);
1657	}
1658	bpage = list_entry(head, struct buffer_page, list);
1659	free_buffer_page(bpage);
1660	}
1661
1662	free_page((unsigned long)cpu_buffer->free_page);
1663
1664	kfree(objp: cpu_buffer);
1665	}
1666
1667	/**
1668	* __ring_buffer_alloc - allocate a new ring_buffer
1669	* @size: the size in bytes per cpu that is needed.
1670	* @flags: attributes to set for the ring buffer.
1671	* @key: ring buffer reader_lock_key.
1672	*
1673	* Currently the only flag that is available is the RB_FL_OVERWRITE
1674	* flag. This flag means that the buffer will overwrite old data
1675	* when the buffer wraps. If this flag is not set, the buffer will
1676	* drop data when the tail hits the head.
1677	*/
1678	struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1679	struct lock_class_key *key)
1680	{
1681	struct trace_buffer *buffer;
1682	long nr_pages;
1683	int bsize;
1684	int cpu;
1685	int ret;
1686
1687	/* keep it in its own cache line */
1688	buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1689	GFP_KERNEL);
1690	if (!buffer)
1691	return NULL;
1692
1693	if (!zalloc_cpumask_var(mask: &buffer->cpumask, GFP_KERNEL))
1694	goto fail_free_buffer;
1695
1696	/* Default buffer page size - one system page */
1697	buffer->subbuf_order = 0;
1698	buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
1699
1700	/* Max payload is buffer page size - header (8bytes) */
1701	buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
1702
1703	nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
1704	buffer->flags = flags;
1705	buffer->clock = trace_clock_local;
1706	buffer->reader_lock_key = key;
1707
1708	init_irq_work(work: &buffer->irq_work.work, func: rb_wake_up_waiters);
1709	init_waitqueue_head(&buffer->irq_work.waiters);
1710
1711	/* need at least two pages */
1712	if (nr_pages < 2)
1713	nr_pages = 2;
1714
1715	buffer->cpus = nr_cpu_ids;
1716
1717	bsize = sizeof(void *) * nr_cpu_ids;
1718	buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1719	GFP_KERNEL);
1720	if (!buffer->buffers)
1721	goto fail_free_cpumask;
1722
1723	cpu = raw_smp_processor_id();
1724	cpumask_set_cpu(cpu, dstp: buffer->cpumask);
1725	buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1726	if (!buffer->buffers[cpu])
1727	goto fail_free_buffers;
1728
1729	ret = cpuhp_state_add_instance(state: CPUHP_TRACE_RB_PREPARE, node: &buffer->node);
1730	if (ret < 0)
1731	goto fail_free_buffers;
1732
1733	mutex_init(&buffer->mutex);
1734
1735	return buffer;
1736
1737	fail_free_buffers:
1738	for_each_buffer_cpu(buffer, cpu) {
1739	if (buffer->buffers[cpu])
1740	rb_free_cpu_buffer(cpu_buffer: buffer->buffers[cpu]);
1741	}
1742	kfree(objp: buffer->buffers);
1743
1744	fail_free_cpumask:
1745	free_cpumask_var(mask: buffer->cpumask);
1746
1747	fail_free_buffer:
1748	kfree(objp: buffer);
1749	return NULL;
1750	}
1751	EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1752
1753	/**
1754	* ring_buffer_free - free a ring buffer.
1755	* @buffer: the buffer to free.
1756	*/
1757	void
1758	ring_buffer_free(struct trace_buffer *buffer)
1759	{
1760	int cpu;
1761
1762	cpuhp_state_remove_instance(state: CPUHP_TRACE_RB_PREPARE, node: &buffer->node);
1763
1764	irq_work_sync(work: &buffer->irq_work.work);
1765
1766	for_each_buffer_cpu(buffer, cpu)
1767	rb_free_cpu_buffer(cpu_buffer: buffer->buffers[cpu]);
1768
1769	kfree(objp: buffer->buffers);
1770	free_cpumask_var(mask: buffer->cpumask);
1771
1772	kfree(objp: buffer);
1773	}
1774	EXPORT_SYMBOL_GPL(ring_buffer_free);
1775
1776	void ring_buffer_set_clock(struct trace_buffer *buffer,
1777	u64 (*clock)(void))
1778	{
1779	buffer->clock = clock;
1780	}
1781
1782	void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1783	{
1784	buffer->time_stamp_abs = abs;
1785	}
1786
1787	bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1788	{
1789	return buffer->time_stamp_abs;
1790	}
1791
1792	static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1793
1794	static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1795	{
1796	return local_read(&bpage->entries) & RB_WRITE_MASK;
1797	}
1798
1799	static inline unsigned long rb_page_write(struct buffer_page *bpage)
1800	{
1801	return local_read(&bpage->write) & RB_WRITE_MASK;
1802	}
1803
1804	static bool
1805	rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1806	{
1807	struct list_head *tail_page, *to_remove, *next_page;
1808	struct buffer_page *to_remove_page, *tmp_iter_page;
1809	struct buffer_page *last_page, *first_page;
1810	unsigned long nr_removed;
1811	unsigned long head_bit;
1812	int page_entries;
1813
1814	head_bit = 0;
1815
1816	raw_spin_lock_irq(&cpu_buffer->reader_lock);
1817	atomic_inc(v: &cpu_buffer->record_disabled);
1818	/*
1819	* We don't race with the readers since we have acquired the reader
1820	* lock. We also don't race with writers after disabling recording.
1821	* This makes it easy to figure out the first and the last page to be
1822	* removed from the list. We unlink all the pages in between including
1823	* the first and last pages. This is done in a busy loop so that we
1824	* lose the least number of traces.
1825	* The pages are freed after we restart recording and unlock readers.
1826	*/
1827	tail_page = &cpu_buffer->tail_page->list;
1828
1829	/*
1830	* tail page might be on reader page, we remove the next page
1831	* from the ring buffer
1832	*/
1833	if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1834	tail_page = rb_list_head(list: tail_page->next);
1835	to_remove = tail_page;
1836
1837	/* start of pages to remove */
1838	first_page = list_entry(rb_list_head(to_remove->next),
1839	struct buffer_page, list);
1840
1841	for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1842	to_remove = rb_list_head(list: to_remove)->next;
1843	head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1844	}
1845	/* Read iterators need to reset themselves when some pages removed */
1846	cpu_buffer->pages_removed += nr_removed;
1847
1848	next_page = rb_list_head(list: to_remove)->next;
1849
1850	/*
1851	* Now we remove all pages between tail_page and next_page.
1852	* Make sure that we have head_bit value preserved for the
1853	* next page
1854	*/
1855	tail_page->next = (struct list_head *)((unsigned long)next_page |
1856	head_bit);
1857	next_page = rb_list_head(list: next_page);
1858	next_page->prev = tail_page;
1859
1860	/* make sure pages points to a valid page in the ring buffer */
1861	cpu_buffer->pages = next_page;
1862
1863	/* update head page */
1864	if (head_bit)
1865	cpu_buffer->head_page = list_entry(next_page,
1866	struct buffer_page, list);
1867
1868	/* pages are removed, resume tracing and then free the pages */
1869	atomic_dec(v: &cpu_buffer->record_disabled);
1870	raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1871
1872	RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1873
1874	/* last buffer page to remove */
1875	last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1876	list);
1877	tmp_iter_page = first_page;
1878
1879	do {
1880	cond_resched();
1881
1882	to_remove_page = tmp_iter_page;
1883	rb_inc_page(bpage: &tmp_iter_page);
1884
1885	/* update the counters */
1886	page_entries = rb_page_entries(bpage: to_remove_page);
1887	if (page_entries) {
1888	/*
1889	* If something was added to this page, it was full
1890	* since it is not the tail page. So we deduct the
1891	* bytes consumed in ring buffer from here.
1892	* Increment overrun to account for the lost events.
1893	*/
1894	local_add(i: page_entries, l: &cpu_buffer->overrun);
1895	local_sub(i: rb_page_commit(bpage: to_remove_page), l: &cpu_buffer->entries_bytes);
1896	local_inc(l: &cpu_buffer->pages_lost);
1897	}
1898
1899	/*
1900	* We have already removed references to this list item, just
1901	* free up the buffer_page and its page
1902	*/
1903	free_buffer_page(bpage: to_remove_page);
1904	nr_removed--;
1905
1906	} while (to_remove_page != last_page);
1907
1908	RB_WARN_ON(cpu_buffer, nr_removed);
1909
1910	return nr_removed == 0;
1911	}
1912
1913	static bool
1914	rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1915	{
1916	struct list_head *pages = &cpu_buffer->new_pages;
1917	unsigned long flags;
1918	bool success;
1919	int retries;
1920
1921	/* Can be called at early boot up, where interrupts must not been enabled */
1922	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1923	/*
1924	* We are holding the reader lock, so the reader page won't be swapped
1925	* in the ring buffer. Now we are racing with the writer trying to
1926	* move head page and the tail page.
1927	* We are going to adapt the reader page update process where:
1928	* 1. We first splice the start and end of list of new pages between
1929	* the head page and its previous page.
1930	* 2. We cmpxchg the prev_page->next to point from head page to the
1931	* start of new pages list.
1932	* 3. Finally, we update the head->prev to the end of new list.
1933	*
1934	* We will try this process 10 times, to make sure that we don't keep
1935	* spinning.
1936	*/
1937	retries = 10;
1938	success = false;
1939	while (retries--) {
1940	struct list_head *head_page, *prev_page;
1941	struct list_head *last_page, *first_page;
1942	struct list_head *head_page_with_bit;
1943	struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
1944
1945	if (!hpage)
1946	break;
1947	head_page = &hpage->list;
1948	prev_page = head_page->prev;
1949
1950	first_page = pages->next;
1951	last_page = pages->prev;
1952
1953	head_page_with_bit = (struct list_head *)
1954	((unsigned long)head_page | RB_PAGE_HEAD);
1955
1956	last_page->next = head_page_with_bit;
1957	first_page->prev = prev_page;
1958
1959	/* caution: head_page_with_bit gets updated on cmpxchg failure */
1960	if (try_cmpxchg(&prev_page->next,
1961	&head_page_with_bit, first_page)) {
1962	/*
1963	* yay, we replaced the page pointer to our new list,
1964	* now, we just have to update to head page's prev
1965	* pointer to point to end of list
1966	*/
1967	head_page->prev = last_page;
1968	success = true;
1969	break;
1970	}
1971	}
1972
1973	if (success)
1974	INIT_LIST_HEAD(list: pages);
1975	/*
1976	* If we weren't successful in adding in new pages, warn and stop
1977	* tracing
1978	*/
1979	RB_WARN_ON(cpu_buffer, !success);
1980	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1981
1982	/* free pages if they weren't inserted */
1983	if (!success) {
1984	struct buffer_page *bpage, *tmp;
1985	list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1986	list) {
1987	list_del_init(entry: &bpage->list);
1988	free_buffer_page(bpage);
1989	}
1990	}
1991	return success;
1992	}
1993
1994	static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1995	{
1996	bool success;
1997
1998	if (cpu_buffer->nr_pages_to_update > 0)
1999	success = rb_insert_pages(cpu_buffer);
2000	else
2001	success = rb_remove_pages(cpu_buffer,
2002	nr_pages: -cpu_buffer->nr_pages_to_update);
2003
2004	if (success)
2005	cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2006	}
2007
2008	static void update_pages_handler(struct work_struct *work)
2009	{
2010	struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2011	struct ring_buffer_per_cpu, update_pages_work);
2012	rb_update_pages(cpu_buffer);
2013	complete(&cpu_buffer->update_done);
2014	}
2015
2016	/**
2017	* ring_buffer_resize - resize the ring buffer
2018	* @buffer: the buffer to resize.
2019	* @size: the new size.
2020	* @cpu_id: the cpu buffer to resize
2021	*
2022	* Minimum size is 2 * buffer->subbuf_size.
2023	*
2024	* Returns 0 on success and < 0 on failure.
2025	*/
2026	int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2027	int cpu_id)
2028	{
2029	struct ring_buffer_per_cpu *cpu_buffer;
2030	unsigned long nr_pages;
2031	int cpu, err;
2032
2033	/*
2034	* Always succeed at resizing a non-existent buffer:
2035	*/
2036	if (!buffer)
2037	return 0;
2038
2039	/* Make sure the requested buffer exists */
2040	if (cpu_id != RING_BUFFER_ALL_CPUS &&
2041	!cpumask_test_cpu(cpu: cpu_id, cpumask: buffer->cpumask))
2042	return 0;
2043
2044	nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2045
2046	/* we need a minimum of two pages */
2047	if (nr_pages < 2)
2048	nr_pages = 2;
2049
2050	/* prevent another thread from changing buffer sizes */
2051	mutex_lock(&buffer->mutex);
2052	atomic_inc(v: &buffer->resizing);
2053
2054	if (cpu_id == RING_BUFFER_ALL_CPUS) {
2055	/*
2056	* Don't succeed if resizing is disabled, as a reader might be
2057	* manipulating the ring buffer and is expecting a sane state while
2058	* this is true.
2059	*/
2060	for_each_buffer_cpu(buffer, cpu) {
2061	cpu_buffer = buffer->buffers[cpu];
2062	if (atomic_read(v: &cpu_buffer->resize_disabled)) {
2063	err = -EBUSY;
2064	goto out_err_unlock;
2065	}
2066	}
2067
2068	/* calculate the pages to update */
2069	for_each_buffer_cpu(buffer, cpu) {
2070	cpu_buffer = buffer->buffers[cpu];
2071
2072	cpu_buffer->nr_pages_to_update = nr_pages -
2073	cpu_buffer->nr_pages;
2074	/*
2075	* nothing more to do for removing pages or no update
2076	*/
2077	if (cpu_buffer->nr_pages_to_update <= 0)
2078	continue;
2079	/*
2080	* to add pages, make sure all new pages can be
2081	* allocated without receiving ENOMEM
2082	*/
2083	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
2084	if (__rb_allocate_pages(cpu_buffer, nr_pages: cpu_buffer->nr_pages_to_update,
2085	pages: &cpu_buffer->new_pages)) {
2086	/* not enough memory for new pages */
2087	err = -ENOMEM;
2088	goto out_err;
2089	}
2090
2091	cond_resched();
2092	}
2093
2094	cpus_read_lock();
2095	/*
2096	* Fire off all the required work handlers
2097	* We can't schedule on offline CPUs, but it's not necessary
2098	* since we can change their buffer sizes without any race.
2099	*/
2100	for_each_buffer_cpu(buffer, cpu) {
2101	cpu_buffer = buffer->buffers[cpu];
2102	if (!cpu_buffer->nr_pages_to_update)
2103	continue;
2104
2105	/* Can't run something on an offline CPU. */
2106	if (!cpu_online(cpu)) {
2107	rb_update_pages(cpu_buffer);
2108	cpu_buffer->nr_pages_to_update = 0;
2109	} else {
2110	/* Run directly if possible. */
2111	migrate_disable();
2112	if (cpu != smp_processor_id()) {
2113	migrate_enable();
2114	schedule_work_on(cpu,
2115	work: &cpu_buffer->update_pages_work);
2116	} else {
2117	update_pages_handler(work: &cpu_buffer->update_pages_work);
2118	migrate_enable();
2119	}
2120	}
2121	}
2122
2123	/* wait for all the updates to complete */
2124	for_each_buffer_cpu(buffer, cpu) {
2125	cpu_buffer = buffer->buffers[cpu];
2126	if (!cpu_buffer->nr_pages_to_update)
2127	continue;
2128
2129	if (cpu_online(cpu))
2130	wait_for_completion(&cpu_buffer->update_done);
2131	cpu_buffer->nr_pages_to_update = 0;
2132	}
2133
2134	cpus_read_unlock();
2135	} else {
2136	cpu_buffer = buffer->buffers[cpu_id];
2137
2138	if (nr_pages == cpu_buffer->nr_pages)
2139	goto out;
2140
2141	/*
2142	* Don't succeed if resizing is disabled, as a reader might be
2143	* manipulating the ring buffer and is expecting a sane state while
2144	* this is true.
2145	*/
2146	if (atomic_read(v: &cpu_buffer->resize_disabled)) {
2147	err = -EBUSY;
2148	goto out_err_unlock;
2149	}
2150
2151	cpu_buffer->nr_pages_to_update = nr_pages -
2152	cpu_buffer->nr_pages;
2153
2154	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
2155	if (cpu_buffer->nr_pages_to_update > 0 &&
2156	__rb_allocate_pages(cpu_buffer, nr_pages: cpu_buffer->nr_pages_to_update,
2157	pages: &cpu_buffer->new_pages)) {
2158	err = -ENOMEM;
2159	goto out_err;
2160	}
2161
2162	cpus_read_lock();
2163
2164	/* Can't run something on an offline CPU. */
2165	if (!cpu_online(cpu: cpu_id))
2166	rb_update_pages(cpu_buffer);
2167	else {
2168	/* Run directly if possible. */
2169	migrate_disable();
2170	if (cpu_id == smp_processor_id()) {
2171	rb_update_pages(cpu_buffer);
2172	migrate_enable();
2173	} else {
2174	migrate_enable();
2175	schedule_work_on(cpu: cpu_id,
2176	work: &cpu_buffer->update_pages_work);
2177	wait_for_completion(&cpu_buffer->update_done);
2178	}
2179	}
2180
2181	cpu_buffer->nr_pages_to_update = 0;
2182	cpus_read_unlock();
2183	}
2184
2185	out:
2186	/*
2187	* The ring buffer resize can happen with the ring buffer
2188	* enabled, so that the update disturbs the tracing as little
2189	* as possible. But if the buffer is disabled, we do not need
2190	* to worry about that, and we can take the time to verify
2191	* that the buffer is not corrupt.
2192	*/
2193	if (atomic_read(v: &buffer->record_disabled)) {
2194	atomic_inc(v: &buffer->record_disabled);
2195	/*
2196	* Even though the buffer was disabled, we must make sure
2197	* that it is truly disabled before calling rb_check_pages.
2198	* There could have been a race between checking
2199	* record_disable and incrementing it.
2200	*/
2201	synchronize_rcu();
2202	for_each_buffer_cpu(buffer, cpu) {
2203	cpu_buffer = buffer->buffers[cpu];
2204	rb_check_pages(cpu_buffer);
2205	}
2206	atomic_dec(v: &buffer->record_disabled);
2207	}
2208
2209	atomic_dec(v: &buffer->resizing);
2210	mutex_unlock(lock: &buffer->mutex);
2211	return 0;
2212
2213	out_err:
2214	for_each_buffer_cpu(buffer, cpu) {
2215	struct buffer_page *bpage, *tmp;
2216
2217	cpu_buffer = buffer->buffers[cpu];
2218	cpu_buffer->nr_pages_to_update = 0;
2219
2220	if (list_empty(head: &cpu_buffer->new_pages))
2221	continue;
2222
2223	list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2224	list) {
2225	list_del_init(entry: &bpage->list);
2226	free_buffer_page(bpage);
2227	}
2228	}
2229	out_err_unlock:
2230	atomic_dec(v: &buffer->resizing);
2231	mutex_unlock(lock: &buffer->mutex);
2232	return err;
2233	}
2234	EXPORT_SYMBOL_GPL(ring_buffer_resize);
2235
2236	void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2237	{
2238	mutex_lock(&buffer->mutex);
2239	if (val)
2240	buffer->flags |= RB_FL_OVERWRITE;
2241	else
2242	buffer->flags &= ~RB_FL_OVERWRITE;
2243	mutex_unlock(lock: &buffer->mutex);
2244	}
2245	EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2246
2247	static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2248	{
2249	return bpage->page->data + index;
2250	}
2251
2252	static __always_inline struct ring_buffer_event *
2253	rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2254	{
2255	return __rb_page_index(bpage: cpu_buffer->reader_page,
2256	index: cpu_buffer->reader_page->read);
2257	}
2258
2259	static struct ring_buffer_event *
2260	rb_iter_head_event(struct ring_buffer_iter *iter)
2261	{
2262	struct ring_buffer_event *event;
2263	struct buffer_page *iter_head_page = iter->head_page;
2264	unsigned long commit;
2265	unsigned length;
2266
2267	if (iter->head != iter->next_event)
2268	return iter->event;
2269
2270	/*
2271	* When the writer goes across pages, it issues a cmpxchg which
2272	* is a mb(), which will synchronize with the rmb here.
2273	* (see rb_tail_page_update() and __rb_reserve_next())
2274	*/
2275	commit = rb_page_commit(bpage: iter_head_page);
2276	smp_rmb();
2277
2278	/* An event needs to be at least 8 bytes in size */
2279	if (iter->head > commit - 8)
2280	goto reset;
2281
2282	event = __rb_page_index(bpage: iter_head_page, index: iter->head);
2283	length = rb_event_length(event);
2284
2285	/*
2286	* READ_ONCE() doesn't work on functions and we don't want the
2287	* compiler doing any crazy optimizations with length.
2288	*/
2289	barrier();
2290
2291	if ((iter->head + length) > commit || length > iter->event_size)
2292	/* Writer corrupted the read? */
2293	goto reset;
2294
2295	memcpy(iter->event, event, length);
2296	/*
2297	* If the page stamp is still the same after this rmb() then the
2298	* event was safely copied without the writer entering the page.
2299	*/
2300	smp_rmb();
2301
2302	/* Make sure the page didn't change since we read this */
2303	if (iter->page_stamp != iter_head_page->page->time_stamp ||
2304	commit > rb_page_commit(bpage: iter_head_page))
2305	goto reset;
2306
2307	iter->next_event = iter->head + length;
2308	return iter->event;
2309	reset:
2310	/* Reset to the beginning */
2311	iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2312	iter->head = 0;
2313	iter->next_event = 0;
2314	iter->missed_events = 1;
2315	return NULL;
2316	}
2317
2318	/* Size is determined by what has been committed */
2319	static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2320	{
2321	return rb_page_commit(bpage);
2322	}
2323
2324	static __always_inline unsigned
2325	rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2326	{
2327	return rb_page_commit(bpage: cpu_buffer->commit_page);
2328	}
2329
2330	static __always_inline unsigned
2331	rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
2332	{
2333	unsigned long addr = (unsigned long)event;
2334
2335	addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
2336
2337	return addr - BUF_PAGE_HDR_SIZE;
2338	}
2339
2340	static void rb_inc_iter(struct ring_buffer_iter *iter)
2341	{
2342	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2343
2344	/*
2345	* The iterator could be on the reader page (it starts there).
2346	* But the head could have moved, since the reader was
2347	* found. Check for this case and assign the iterator
2348	* to the head page instead of next.
2349	*/
2350	if (iter->head_page == cpu_buffer->reader_page)
2351	iter->head_page = rb_set_head_page(cpu_buffer);
2352	else
2353	rb_inc_page(bpage: &iter->head_page);
2354
2355	iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2356	iter->head = 0;
2357	iter->next_event = 0;
2358	}
2359
2360	/*
2361	* rb_handle_head_page - writer hit the head page
2362	*
2363	* Returns: +1 to retry page
2364	* 0 to continue
2365	* -1 on error
2366	*/
2367	static int
2368	rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2369	struct buffer_page *tail_page,
2370	struct buffer_page *next_page)
2371	{
2372	struct buffer_page *new_head;
2373	int entries;
2374	int type;
2375	int ret;
2376
2377	entries = rb_page_entries(bpage: next_page);
2378
2379	/*
2380	* The hard part is here. We need to move the head
2381	* forward, and protect against both readers on
2382	* other CPUs and writers coming in via interrupts.
2383	*/
2384	type = rb_head_page_set_update(cpu_buffer, head: next_page, prev: tail_page,
2385	RB_PAGE_HEAD);
2386
2387	/*
2388	* type can be one of four:
2389	* NORMAL - an interrupt already moved it for us
2390	* HEAD - we are the first to get here.
2391	* UPDATE - we are the interrupt interrupting
2392	* a current move.
2393	* MOVED - a reader on another CPU moved the next
2394	* pointer to its reader page. Give up
2395	* and try again.
2396	*/
2397
2398	switch (type) {
2399	case RB_PAGE_HEAD:
2400	/*
2401	* We changed the head to UPDATE, thus
2402	* it is our responsibility to update
2403	* the counters.
2404	*/
2405	local_add(i: entries, l: &cpu_buffer->overrun);
2406	local_sub(i: rb_page_commit(bpage: next_page), l: &cpu_buffer->entries_bytes);
2407	local_inc(l: &cpu_buffer->pages_lost);
2408
2409	/*
2410	* The entries will be zeroed out when we move the
2411	* tail page.
2412	*/
2413
2414	/* still more to do */
2415	break;
2416
2417	case RB_PAGE_UPDATE:
2418	/*
2419	* This is an interrupt that interrupt the
2420	* previous update. Still more to do.
2421	*/
2422	break;
2423	case RB_PAGE_NORMAL:
2424	/*
2425	* An interrupt came in before the update
2426	* and processed this for us.
2427	* Nothing left to do.
2428	*/
2429	return 1;
2430	case RB_PAGE_MOVED:
2431	/*
2432	* The reader is on another CPU and just did
2433	* a swap with our next_page.
2434	* Try again.
2435	*/
2436	return 1;
2437	default:
2438	RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2439	return -1;
2440	}
2441
2442	/*
2443	* Now that we are here, the old head pointer is
2444	* set to UPDATE. This will keep the reader from
2445	* swapping the head page with the reader page.
2446	* The reader (on another CPU) will spin till
2447	* we are finished.
2448	*
2449	* We just need to protect against interrupts
2450	* doing the job. We will set the next pointer
2451	* to HEAD. After that, we set the old pointer
2452	* to NORMAL, but only if it was HEAD before.
2453	* otherwise we are an interrupt, and only
2454	* want the outer most commit to reset it.
2455	*/
2456	new_head = next_page;
2457	rb_inc_page(bpage: &new_head);
2458
2459	ret = rb_head_page_set_head(cpu_buffer, head: new_head, prev: next_page,
2460	RB_PAGE_NORMAL);
2461
2462	/*
2463	* Valid returns are:
2464	* HEAD - an interrupt came in and already set it.
2465	* NORMAL - One of two things:
2466	* 1) We really set it.
2467	* 2) A bunch of interrupts came in and moved
2468	* the page forward again.
2469	*/
2470	switch (ret) {
2471	case RB_PAGE_HEAD:
2472	case RB_PAGE_NORMAL:
2473	/* OK */
2474	break;
2475	default:
2476	RB_WARN_ON(cpu_buffer, 1);
2477	return -1;
2478	}
2479
2480	/*
2481	* It is possible that an interrupt came in,
2482	* set the head up, then more interrupts came in
2483	* and moved it again. When we get back here,
2484	* the page would have been set to NORMAL but we
2485	* just set it back to HEAD.
2486	*
2487	* How do you detect this? Well, if that happened
2488	* the tail page would have moved.
2489	*/
2490	if (ret == RB_PAGE_NORMAL) {
2491	struct buffer_page *buffer_tail_page;
2492
2493	buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2494	/*
2495	* If the tail had moved passed next, then we need
2496	* to reset the pointer.
2497	*/
2498	if (buffer_tail_page != tail_page &&
2499	buffer_tail_page != next_page)
2500	rb_head_page_set_normal(cpu_buffer, head: new_head,
2501	prev: next_page,
2502	RB_PAGE_HEAD);
2503	}
2504
2505	/*
2506	* If this was the outer most commit (the one that
2507	* changed the original pointer from HEAD to UPDATE),
2508	* then it is up to us to reset it to NORMAL.
2509	*/
2510	if (type == RB_PAGE_HEAD) {
2511	ret = rb_head_page_set_normal(cpu_buffer, head: next_page,
2512	prev: tail_page,
2513	RB_PAGE_UPDATE);
2514	if (RB_WARN_ON(cpu_buffer,
2515	ret != RB_PAGE_UPDATE))
2516	return -1;
2517	}
2518
2519	return 0;
2520	}
2521
2522	static inline void
2523	rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2524	unsigned long tail, struct rb_event_info *info)
2525	{
2526	unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
2527	struct buffer_page *tail_page = info->tail_page;
2528	struct ring_buffer_event *event;
2529	unsigned long length = info->length;
2530
2531	/*
2532	* Only the event that crossed the page boundary
2533	* must fill the old tail_page with padding.
2534	*/
2535	if (tail >= bsize) {
2536	/*
2537	* If the page was filled, then we still need
2538	* to update the real_end. Reset it to zero
2539	* and the reader will ignore it.
2540	*/
2541	if (tail == bsize)
2542	tail_page->real_end = 0;
2543
2544	local_sub(i: length, l: &tail_page->write);
2545	return;
2546	}
2547
2548	event = __rb_page_index(bpage: tail_page, index: tail);
2549
2550	/*
2551	* Save the original length to the meta data.
2552	* This will be used by the reader to add lost event
2553	* counter.
2554	*/
2555	tail_page->real_end = tail;
2556
2557	/*
2558	* If this event is bigger than the minimum size, then
2559	* we need to be careful that we don't subtract the
2560	* write counter enough to allow another writer to slip
2561	* in on this page.
2562	* We put in a discarded commit instead, to make sure
2563	* that this space is not used again, and this space will
2564	* not be accounted into 'entries_bytes'.
2565	*
2566	* If we are less than the minimum size, we don't need to
2567	* worry about it.
2568	*/
2569	if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
2570	/* No room for any events */
2571
2572	/* Mark the rest of the page with padding */
2573	rb_event_set_padding(event);
2574
2575	/* Make sure the padding is visible before the write update */
2576	smp_wmb();
2577
2578	/* Set the write back to the previous setting */
2579	local_sub(i: length, l: &tail_page->write);
2580	return;
2581	}
2582
2583	/* Put in a discarded event */
2584	event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
2585	event->type_len = RINGBUF_TYPE_PADDING;
2586	/* time delta must be non zero */
2587	event->time_delta = 1;
2588
2589	/* account for padding bytes */
2590	local_add(i: bsize - tail, l: &cpu_buffer->entries_bytes);
2591
2592	/* Make sure the padding is visible before the tail_page->write update */
2593	smp_wmb();
2594
2595	/* Set write to end of buffer */
2596	length = (tail + length) - bsize;
2597	local_sub(i: length, l: &tail_page->write);
2598	}
2599
2600	static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2601
2602	/*
2603	* This is the slow path, force gcc not to inline it.
2604	*/
2605	static noinline struct ring_buffer_event *
2606	rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2607	unsigned long tail, struct rb_event_info *info)
2608	{
2609	struct buffer_page *tail_page = info->tail_page;
2610	struct buffer_page *commit_page = cpu_buffer->commit_page;
2611	struct trace_buffer *buffer = cpu_buffer->buffer;
2612	struct buffer_page *next_page;
2613	int ret;
2614
2615	next_page = tail_page;
2616
2617	rb_inc_page(bpage: &next_page);
2618
2619	/*
2620	* If for some reason, we had an interrupt storm that made
2621	* it all the way around the buffer, bail, and warn
2622	* about it.
2623	*/
2624	if (unlikely(next_page == commit_page)) {
2625	local_inc(l: &cpu_buffer->commit_overrun);
2626	goto out_reset;
2627	}
2628
2629	/*
2630	* This is where the fun begins!
2631	*
2632	* We are fighting against races between a reader that
2633	* could be on another CPU trying to swap its reader
2634	* page with the buffer head.
2635	*
2636	* We are also fighting against interrupts coming in and
2637	* moving the head or tail on us as well.
2638	*
2639	* If the next page is the head page then we have filled
2640	* the buffer, unless the commit page is still on the
2641	* reader page.
2642	*/
2643	if (rb_is_head_page(page: next_page, list: &tail_page->list)) {
2644
2645	/*
2646	* If the commit is not on the reader page, then
2647	* move the header page.
2648	*/
2649	if (!rb_is_reader_page(page: cpu_buffer->commit_page)) {
2650	/*
2651	* If we are not in overwrite mode,
2652	* this is easy, just stop here.
2653	*/
2654	if (!(buffer->flags & RB_FL_OVERWRITE)) {
2655	local_inc(l: &cpu_buffer->dropped_events);
2656	goto out_reset;
2657	}
2658
2659	ret = rb_handle_head_page(cpu_buffer,
2660	tail_page,
2661	next_page);
2662	if (ret < 0)
2663	goto out_reset;
2664	if (ret)
2665	goto out_again;
2666	} else {
2667	/*
2668	* We need to be careful here too. The
2669	* commit page could still be on the reader
2670	* page. We could have a small buffer, and
2671	* have filled up the buffer with events
2672	* from interrupts and such, and wrapped.
2673	*
2674	* Note, if the tail page is also on the
2675	* reader_page, we let it move out.
2676	*/
2677	if (unlikely((cpu_buffer->commit_page !=
2678	cpu_buffer->tail_page) &&
2679	(cpu_buffer->commit_page ==
2680	cpu_buffer->reader_page))) {
2681	local_inc(l: &cpu_buffer->commit_overrun);
2682	goto out_reset;
2683	}
2684	}
2685	}
2686
2687	rb_tail_page_update(cpu_buffer, tail_page, next_page);
2688
2689	out_again:
2690
2691	rb_reset_tail(cpu_buffer, tail, info);
2692
2693	/* Commit what we have for now. */
2694	rb_end_commit(cpu_buffer);
2695	/* rb_end_commit() decs committing */
2696	local_inc(l: &cpu_buffer->committing);
2697
2698	/* fail and let the caller try again */
2699	return ERR_PTR(error: -EAGAIN);
2700
2701	out_reset:
2702	/* reset write */
2703	rb_reset_tail(cpu_buffer, tail, info);
2704
2705	return NULL;
2706	}
2707
2708	/* Slow path */
2709	static struct ring_buffer_event *
2710	rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2711	struct ring_buffer_event *event, u64 delta, bool abs)
2712	{
2713	if (abs)
2714	event->type_len = RINGBUF_TYPE_TIME_STAMP;
2715	else
2716	event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2717
2718	/* Not the first event on the page, or not delta? */
2719	if (abs || rb_event_index(cpu_buffer, event)) {
2720	event->time_delta = delta & TS_MASK;
2721	event->array[0] = delta >> TS_SHIFT;
2722	} else {
2723	/* nope, just zero it */
2724	event->time_delta = 0;
2725	event->array[0] = 0;
2726	}
2727
2728	return skip_time_extend(event);
2729	}
2730
2731	#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2732	static inline bool sched_clock_stable(void)
2733	{
2734	return true;
2735	}
2736	#endif
2737
2738	static void
2739	rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2740	struct rb_event_info *info)
2741	{
2742	u64 write_stamp;
2743
2744	WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2745	(unsigned long long)info->delta,
2746	(unsigned long long)info->ts,
2747	(unsigned long long)info->before,
2748	(unsigned long long)info->after,
2749	(unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
2750	sched_clock_stable() ? "" :
2751	"If you just came from a suspend/resume,\n"
2752	"please switch to the trace global clock:\n"
2753	" echo global > /sys/kernel/tracing/trace_clock\n"
2754	"or add trace_clock=global to the kernel command line\n");
2755	}
2756
2757	static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2758	struct ring_buffer_event **event,
2759	struct rb_event_info *info,
2760	u64 *delta,
2761	unsigned int *length)
2762	{
2763	bool abs = info->add_timestamp &
2764	(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2765
2766	if (unlikely(info->delta > (1ULL << 59))) {
2767	/*
2768	* Some timers can use more than 59 bits, and when a timestamp
2769	* is added to the buffer, it will lose those bits.
2770	*/
2771	if (abs && (info->ts & TS_MSB)) {
2772	info->delta &= ABS_TS_MASK;
2773
2774	/* did the clock go backwards */
2775	} else if (info->before == info->after && info->before > info->ts) {
2776	/* not interrupted */
2777	static int once;
2778
2779	/*
2780	* This is possible with a recalibrating of the TSC.
2781	* Do not produce a call stack, but just report it.
2782	*/
2783	if (!once) {
2784	once++;
2785	pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2786	info->before, info->ts);
2787	}
2788	} else
2789	rb_check_timestamp(cpu_buffer, info);
2790	if (!abs)
2791	info->delta = 0;
2792	}
2793	*event = rb_add_time_stamp(cpu_buffer, event: *event, delta: info->delta, abs);
2794	*length -= RB_LEN_TIME_EXTEND;
2795	*delta = 0;
2796	}
2797
2798	/**
2799	* rb_update_event - update event type and data
2800	* @cpu_buffer: The per cpu buffer of the @event
2801	* @event: the event to update
2802	* @info: The info to update the @event with (contains length and delta)
2803	*
2804	* Update the type and data fields of the @event. The length
2805	* is the actual size that is written to the ring buffer,
2806	* and with this, we can determine what to place into the
2807	* data field.
2808	*/
2809	static void
2810	rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2811	struct ring_buffer_event *event,
2812	struct rb_event_info *info)
2813	{
2814	unsigned length = info->length;
2815	u64 delta = info->delta;
2816	unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2817
2818	if (!WARN_ON_ONCE(nest >= MAX_NEST))
2819	cpu_buffer->event_stamp[nest] = info->ts;
2820
2821	/*
2822	* If we need to add a timestamp, then we
2823	* add it to the start of the reserved space.
2824	*/
2825	if (unlikely(info->add_timestamp))
2826	rb_add_timestamp(cpu_buffer, event: &event, info, delta: &delta, length: &length);
2827
2828	event->time_delta = delta;
2829	length -= RB_EVNT_HDR_SIZE;
2830	if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2831	event->type_len = 0;
2832	event->array[0] = length;
2833	} else
2834	event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2835	}
2836
2837	static unsigned rb_calculate_event_length(unsigned length)
2838	{
2839	struct ring_buffer_event event; /* Used only for sizeof array */
2840
2841	/* zero length can cause confusions */
2842	if (!length)
2843	length++;
2844
2845	if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2846	length += sizeof(event.array[0]);
2847
2848	length += RB_EVNT_HDR_SIZE;
2849	length = ALIGN(length, RB_ARCH_ALIGNMENT);
2850
2851	/*
2852	* In case the time delta is larger than the 27 bits for it
2853	* in the header, we need to add a timestamp. If another
2854	* event comes in when trying to discard this one to increase
2855	* the length, then the timestamp will be added in the allocated
2856	* space of this event. If length is bigger than the size needed
2857	* for the TIME_EXTEND, then padding has to be used. The events
2858	* length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2859	* to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2860	* As length is a multiple of 4, we only need to worry if it
2861	* is 12 (RB_LEN_TIME_EXTEND + 4).
2862	*/
2863	if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2864	length += RB_ALIGNMENT;
2865
2866	return length;
2867	}
2868
2869	static inline bool
2870	rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2871	struct ring_buffer_event *event)
2872	{
2873	unsigned long new_index, old_index;
2874	struct buffer_page *bpage;
2875	unsigned long addr;
2876
2877	new_index = rb_event_index(cpu_buffer, event);
2878	old_index = new_index + rb_event_ts_length(event);
2879	addr = (unsigned long)event;
2880	addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
2881
2882	bpage = READ_ONCE(cpu_buffer->tail_page);
2883
2884	/*
2885	* Make sure the tail_page is still the same and
2886	* the next write location is the end of this event
2887	*/
2888	if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2889	unsigned long write_mask =
2890	local_read(&bpage->write) & ~RB_WRITE_MASK;
2891	unsigned long event_length = rb_event_length(event);
2892
2893	/*
2894	* For the before_stamp to be different than the write_stamp
2895	* to make sure that the next event adds an absolute
2896	* value and does not rely on the saved write stamp, which
2897	* is now going to be bogus.
2898	*
2899	* By setting the before_stamp to zero, the next event
2900	* is not going to use the write_stamp and will instead
2901	* create an absolute timestamp. This means there's no
2902	* reason to update the wirte_stamp!
2903	*/
2904	rb_time_set(t: &cpu_buffer->before_stamp, val: 0);
2905
2906	/*
2907	* If an event were to come in now, it would see that the
2908	* write_stamp and the before_stamp are different, and assume
2909	* that this event just added itself before updating
2910	* the write stamp. The interrupting event will fix the
2911	* write stamp for us, and use an absolute timestamp.
2912	*/
2913
2914	/*
2915	* This is on the tail page. It is possible that
2916	* a write could come in and move the tail page
2917	* and write to the next page. That is fine
2918	* because we just shorten what is on this page.
2919	*/
2920	old_index += write_mask;
2921	new_index += write_mask;
2922
2923	/* caution: old_index gets updated on cmpxchg failure */
2924	if (local_try_cmpxchg(l: &bpage->write, old: &old_index, new: new_index)) {
2925	/* update counters */
2926	local_sub(i: event_length, l: &cpu_buffer->entries_bytes);
2927	return true;
2928	}
2929	}
2930
2931	/* could not discard */
2932	return false;
2933	}
2934
2935	static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2936	{
2937	local_inc(l: &cpu_buffer->committing);
2938	local_inc(l: &cpu_buffer->commits);
2939	}
2940
2941	static __always_inline void
2942	rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2943	{
2944	unsigned long max_count;
2945
2946	/*
2947	* We only race with interrupts and NMIs on this CPU.
2948	* If we own the commit event, then we can commit
2949	* all others that interrupted us, since the interruptions
2950	* are in stack format (they finish before they come
2951	* back to us). This allows us to do a simple loop to
2952	* assign the commit to the tail.
2953	*/
2954	again:
2955	max_count = cpu_buffer->nr_pages * 100;
2956
2957	while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2958	if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2959	return;
2960	if (RB_WARN_ON(cpu_buffer,
2961	rb_is_reader_page(cpu_buffer->tail_page)))
2962	return;
2963	/*
2964	* No need for a memory barrier here, as the update
2965	* of the tail_page did it for this page.
2966	*/
2967	local_set(&cpu_buffer->commit_page->page->commit,
2968	rb_page_write(cpu_buffer->commit_page));
2969	rb_inc_page(bpage: &cpu_buffer->commit_page);
2970	/* add barrier to keep gcc from optimizing too much */
2971	barrier();
2972	}
2973	while (rb_commit_index(cpu_buffer) !=
2974	rb_page_write(bpage: cpu_buffer->commit_page)) {
2975
2976	/* Make sure the readers see the content of what is committed. */
2977	smp_wmb();
2978	local_set(&cpu_buffer->commit_page->page->commit,
2979	rb_page_write(cpu_buffer->commit_page));
2980	RB_WARN_ON(cpu_buffer,
2981	local_read(&cpu_buffer->commit_page->page->commit) &
2982	~RB_WRITE_MASK);
2983	barrier();
2984	}
2985
2986	/* again, keep gcc from optimizing */
2987	barrier();
2988
2989	/*
2990	* If an interrupt came in just after the first while loop
2991	* and pushed the tail page forward, we will be left with
2992	* a dangling commit that will never go forward.
2993	*/
2994	if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2995	goto again;
2996	}
2997
2998	static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2999	{
3000	unsigned long commits;
3001
3002	if (RB_WARN_ON(cpu_buffer,
3003	!local_read(&cpu_buffer->committing)))
3004	return;
3005
3006	again:
3007	commits = local_read(&cpu_buffer->commits);
3008	/* synchronize with interrupts */
3009	barrier();
3010	if (local_read(&cpu_buffer->committing) == 1)
3011	rb_set_commit_to_write(cpu_buffer);
3012
3013	local_dec(l: &cpu_buffer->committing);
3014
3015	/* synchronize with interrupts */
3016	barrier();
3017
3018	/*
3019	* Need to account for interrupts coming in between the
3020	* updating of the commit page and the clearing of the
3021	* committing counter.
3022	*/
3023	if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3024	!local_read(&cpu_buffer->committing)) {
3025	local_inc(l: &cpu_buffer->committing);
3026	goto again;
3027	}
3028	}
3029
3030	static inline void rb_event_discard(struct ring_buffer_event *event)
3031	{
3032	if (extended_time(event))
3033	event = skip_time_extend(event);
3034
3035	/* array[0] holds the actual length for the discarded event */
3036	event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3037	event->type_len = RINGBUF_TYPE_PADDING;
3038	/* time delta must be non zero */
3039	if (!event->time_delta)
3040	event->time_delta = 1;
3041	}
3042
3043	static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3044	{
3045	local_inc(l: &cpu_buffer->entries);
3046	rb_end_commit(cpu_buffer);
3047	}
3048
3049	static __always_inline void
3050	rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3051	{
3052	if (buffer->irq_work.waiters_pending) {
3053	buffer->irq_work.waiters_pending = false;
3054	/* irq_work_queue() supplies it's own memory barriers */
3055	irq_work_queue(work: &buffer->irq_work.work);
3056	}
3057
3058	if (cpu_buffer->irq_work.waiters_pending) {
3059	cpu_buffer->irq_work.waiters_pending = false;
3060	/* irq_work_queue() supplies it's own memory barriers */
3061	irq_work_queue(work: &cpu_buffer->irq_work.work);
3062	}
3063
3064	if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3065	return;
3066
3067	if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3068	return;
3069
3070	if (!cpu_buffer->irq_work.full_waiters_pending)
3071	return;
3072
3073	cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3074
3075	if (!full_hit(buffer, cpu: cpu_buffer->cpu, full: cpu_buffer->shortest_full))
3076	return;
3077
3078	cpu_buffer->irq_work.wakeup_full = true;
3079	cpu_buffer->irq_work.full_waiters_pending = false;
3080	/* irq_work_queue() supplies it's own memory barriers */
3081	irq_work_queue(work: &cpu_buffer->irq_work.work);
3082	}
3083
3084	#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3085	# define do_ring_buffer_record_recursion() \
3086	do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3087	#else
3088	# define do_ring_buffer_record_recursion() do { } while (0)
3089	#endif
3090
3091	/*
3092	* The lock and unlock are done within a preempt disable section.
3093	* The current_context per_cpu variable can only be modified
3094	* by the current task between lock and unlock. But it can
3095	* be modified more than once via an interrupt. To pass this
3096	* information from the lock to the unlock without having to
3097	* access the 'in_interrupt()' functions again (which do show
3098	* a bit of overhead in something as critical as function tracing,
3099	* we use a bitmask trick.
3100	*
3101	* bit 1 = NMI context
3102	* bit 2 = IRQ context
3103	* bit 3 = SoftIRQ context
3104	* bit 4 = normal context.
3105	*
3106	* This works because this is the order of contexts that can
3107	* preempt other contexts. A SoftIRQ never preempts an IRQ
3108	* context.
3109	*
3110	* When the context is determined, the corresponding bit is
3111	* checked and set (if it was set, then a recursion of that context
3112	* happened).
3113	*
3114	* On unlock, we need to clear this bit. To do so, just subtract
3115	* 1 from the current_context and AND it to itself.
3116	*
3117	* (binary)
3118	* 101 - 1 = 100
3119	* 101 & 100 = 100 (clearing bit zero)
3120	*
3121	* 1010 - 1 = 1001
3122	* 1010 & 1001 = 1000 (clearing bit 1)
3123	*
3124	* The least significant bit can be cleared this way, and it
3125	* just so happens that it is the same bit corresponding to
3126	* the current context.
3127	*
3128	* Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3129	* is set when a recursion is detected at the current context, and if
3130	* the TRANSITION bit is already set, it will fail the recursion.
3131	* This is needed because there's a lag between the changing of
3132	* interrupt context and updating the preempt count. In this case,
3133	* a false positive will be found. To handle this, one extra recursion
3134	* is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3135	* bit is already set, then it is considered a recursion and the function
3136	* ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3137	*
3138	* On the trace_recursive_unlock(), the TRANSITION bit will be the first
3139	* to be cleared. Even if it wasn't the context that set it. That is,
3140	* if an interrupt comes in while NORMAL bit is set and the ring buffer
3141	* is called before preempt_count() is updated, since the check will
3142	* be on the NORMAL bit, the TRANSITION bit will then be set. If an
3143	* NMI then comes in, it will set the NMI bit, but when the NMI code
3144	* does the trace_recursive_unlock() it will clear the TRANSITION bit
3145	* and leave the NMI bit set. But this is fine, because the interrupt
3146	* code that set the TRANSITION bit will then clear the NMI bit when it
3147	* calls trace_recursive_unlock(). If another NMI comes in, it will
3148	* set the TRANSITION bit and continue.
3149	*
3150	* Note: The TRANSITION bit only handles a single transition between context.
3151	*/
3152
3153	static __always_inline bool
3154	trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3155	{
3156	unsigned int val = cpu_buffer->current_context;
3157	int bit = interrupt_context_level();
3158
3159	bit = RB_CTX_NORMAL - bit;
3160
3161	if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3162	/*
3163	* It is possible that this was called by transitioning
3164	* between interrupt context, and preempt_count() has not
3165	* been updated yet. In this case, use the TRANSITION bit.
3166	*/
3167	bit = RB_CTX_TRANSITION;
3168	if (val & (1 << (bit + cpu_buffer->nest))) {
3169	do_ring_buffer_record_recursion();
3170	return true;
3171	}
3172	}
3173
3174	val |= (1 << (bit + cpu_buffer->nest));
3175	cpu_buffer->current_context = val;
3176
3177	return false;
3178	}
3179
3180	static __always_inline void
3181	trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3182	{
3183	cpu_buffer->current_context &=
3184	cpu_buffer->current_context - (1 << cpu_buffer->nest);
3185	}
3186
3187	/* The recursive locking above uses 5 bits */
3188	#define NESTED_BITS 5
3189
3190	/**
3191	* ring_buffer_nest_start - Allow to trace while nested
3192	* @buffer: The ring buffer to modify
3193	*
3194	* The ring buffer has a safety mechanism to prevent recursion.
3195	* But there may be a case where a trace needs to be done while
3196	* tracing something else. In this case, calling this function
3197	* will allow this function to nest within a currently active
3198	* ring_buffer_lock_reserve().
3199	*
3200	* Call this function before calling another ring_buffer_lock_reserve() and
3201	* call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3202	*/
3203	void ring_buffer_nest_start(struct trace_buffer *buffer)
3204	{
3205	struct ring_buffer_per_cpu *cpu_buffer;
3206	int cpu;
3207
3208	/* Enabled by ring_buffer_nest_end() */
3209	preempt_disable_notrace();
3210	cpu = raw_smp_processor_id();
3211	cpu_buffer = buffer->buffers[cpu];
3212	/* This is the shift value for the above recursive locking */
3213	cpu_buffer->nest += NESTED_BITS;
3214	}
3215
3216	/**
3217	* ring_buffer_nest_end - Allow to trace while nested
3218	* @buffer: The ring buffer to modify
3219	*
3220	* Must be called after ring_buffer_nest_start() and after the
3221	* ring_buffer_unlock_commit().
3222	*/
3223	void ring_buffer_nest_end(struct trace_buffer *buffer)
3224	{
3225	struct ring_buffer_per_cpu *cpu_buffer;
3226	int cpu;
3227
3228	/* disabled by ring_buffer_nest_start() */
3229	cpu = raw_smp_processor_id();
3230	cpu_buffer = buffer->buffers[cpu];
3231	/* This is the shift value for the above recursive locking */
3232	cpu_buffer->nest -= NESTED_BITS;
3233	preempt_enable_notrace();
3234	}
3235
3236	/**
3237	* ring_buffer_unlock_commit - commit a reserved
3238	* @buffer: The buffer to commit to
3239	*
3240	* This commits the data to the ring buffer, and releases any locks held.
3241	*
3242	* Must be paired with ring_buffer_lock_reserve.
3243	*/
3244	int ring_buffer_unlock_commit(struct trace_buffer *buffer)
3245	{
3246	struct ring_buffer_per_cpu *cpu_buffer;
3247	int cpu = raw_smp_processor_id();
3248
3249	cpu_buffer = buffer->buffers[cpu];
3250
3251	rb_commit(cpu_buffer);
3252
3253	rb_wakeups(buffer, cpu_buffer);
3254
3255	trace_recursive_unlock(cpu_buffer);
3256
3257	preempt_enable_notrace();
3258
3259	return 0;
3260	}
3261	EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3262
3263	/* Special value to validate all deltas on a page. */
3264	#define CHECK_FULL_PAGE 1L
3265
3266	#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3267
3268	static const char *show_irq_str(int bits)
3269	{
3270	const char *type[] = {
3271	".", // 0
3272	"s", // 1
3273	"h", // 2
3274	"Hs", // 3
3275	"n", // 4
3276	"Ns", // 5
3277	"Nh", // 6
3278	"NHs", // 7
3279	};
3280
3281	return type[bits];
3282	}
3283
3284	/* Assume this is an trace event */
3285	static const char *show_flags(struct ring_buffer_event *event)
3286	{
3287	struct trace_entry *entry;
3288	int bits = 0;
3289
3290	if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3291	return "X";
3292
3293	entry = ring_buffer_event_data(event);
3294
3295	if (entry->flags & TRACE_FLAG_SOFTIRQ)
3296	bits |= 1;
3297
3298	if (entry->flags & TRACE_FLAG_HARDIRQ)
3299	bits |= 2;
3300
3301	if (entry->flags & TRACE_FLAG_NMI)
3302	bits |= 4;
3303
3304	return show_irq_str(bits);
3305	}
3306
3307	static const char *show_irq(struct ring_buffer_event *event)
3308	{
3309	struct trace_entry *entry;
3310
3311	if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3312	return "";
3313
3314	entry = ring_buffer_event_data(event);
3315	if (entry->flags & TRACE_FLAG_IRQS_OFF)
3316	return "d";
3317	return "";
3318	}
3319
3320	static const char *show_interrupt_level(void)
3321	{
3322	unsigned long pc = preempt_count();
3323	unsigned char level = 0;
3324
3325	if (pc & SOFTIRQ_OFFSET)
3326	level |= 1;
3327
3328	if (pc & HARDIRQ_MASK)
3329	level |= 2;
3330
3331	if (pc & NMI_MASK)
3332	level |= 4;
3333
3334	return show_irq_str(bits: level);
3335	}
3336
3337	static void dump_buffer_page(struct buffer_data_page *bpage,
3338	struct rb_event_info *info,
3339	unsigned long tail)
3340	{
3341	struct ring_buffer_event *event;
3342	u64 ts, delta;
3343	int e;
3344
3345	ts = bpage->time_stamp;
3346	pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3347
3348	for (e = 0; e < tail; e += rb_event_length(event)) {
3349
3350	event = (struct ring_buffer_event *)(bpage->data + e);
3351
3352	switch (event->type_len) {
3353
3354	case RINGBUF_TYPE_TIME_EXTEND:
3355	delta = rb_event_time_stamp(event);
3356	ts += delta;
3357	pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
3358	e, ts, delta);
3359	break;
3360
3361	case RINGBUF_TYPE_TIME_STAMP:
3362	delta = rb_event_time_stamp(event);
3363	ts = rb_fix_abs_ts(abs: delta, save_ts: ts);
3364	pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
3365	e, ts, delta);
3366	break;
3367
3368	case RINGBUF_TYPE_PADDING:
3369	ts += event->time_delta;
3370	pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
3371	e, ts, event->time_delta);
3372	break;
3373
3374	case RINGBUF_TYPE_DATA:
3375	ts += event->time_delta;
3376	pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
3377	e, ts, event->time_delta,
3378	show_flags(event), show_irq(event));
3379	break;
3380
3381	default:
3382	break;
3383	}
3384	}
3385	pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
3386	}
3387
3388	static DEFINE_PER_CPU(atomic_t, checking);
3389	static atomic_t ts_dump;
3390
3391	#define buffer_warn_return(fmt, ...) \
3392	do { \
3393	/* If another report is happening, ignore this one */ \
3394	if (atomic_inc_return(&ts_dump) != 1) { \
3395	atomic_dec(&ts_dump); \
3396	goto out; \
3397	} \
3398	atomic_inc(&cpu_buffer->record_disabled); \
3399	pr_warn(fmt, ##__VA_ARGS__); \
3400	dump_buffer_page(bpage, info, tail); \
3401	atomic_dec(&ts_dump); \
3402	/* There's some cases in boot up that this can happen */ \
3403	if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
3404	/* Do not re-enable checking */ \
3405	return; \
3406	} while (0)
3407
3408	/*
3409	* Check if the current event time stamp matches the deltas on
3410	* the buffer page.
3411	*/
3412	static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3413	struct rb_event_info *info,
3414	unsigned long tail)
3415	{
3416	struct ring_buffer_event *event;
3417	struct buffer_data_page *bpage;
3418	u64 ts, delta;
3419	bool full = false;
3420	int e;
3421
3422	bpage = info->tail_page->page;
3423
3424	if (tail == CHECK_FULL_PAGE) {
3425	full = true;
3426	tail = local_read(&bpage->commit);
3427	} else if (info->add_timestamp &
3428	(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3429	/* Ignore events with absolute time stamps */
3430	return;
3431	}
3432
3433	/*
3434	* Do not check the first event (skip possible extends too).
3435	* Also do not check if previous events have not been committed.
3436	*/
3437	if (tail <= 8 || tail > local_read(&bpage->commit))
3438	return;
3439
3440	/*
3441	* If this interrupted another event,
3442	*/
3443	if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3444	goto out;
3445
3446	ts = bpage->time_stamp;
3447
3448	for (e = 0; e < tail; e += rb_event_length(event)) {
3449
3450	event = (struct ring_buffer_event *)(bpage->data + e);
3451
3452	switch (event->type_len) {
3453
3454	case RINGBUF_TYPE_TIME_EXTEND:
3455	delta = rb_event_time_stamp(event);
3456	ts += delta;
3457	break;
3458
3459	case RINGBUF_TYPE_TIME_STAMP:
3460	delta = rb_event_time_stamp(event);
3461	delta = rb_fix_abs_ts(abs: delta, save_ts: ts);
3462	if (delta < ts) {
3463	buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
3464	cpu_buffer->cpu, ts, delta);
3465	}
3466	ts = delta;
3467	break;
3468
3469	case RINGBUF_TYPE_PADDING:
3470	if (event->time_delta == 1)
3471	break;
3472	fallthrough;
3473	case RINGBUF_TYPE_DATA:
3474	ts += event->time_delta;
3475	break;
3476
3477	default:
3478	RB_WARN_ON(cpu_buffer, 1);
3479	}
3480	}
3481	if ((full && ts > info->ts) ||
3482	(!full && ts + info->delta != info->ts)) {
3483	buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
3484	cpu_buffer->cpu,
3485	ts + info->delta, info->ts, info->delta,
3486	info->before, info->after,
3487	full ? " (full)" : "", show_interrupt_level());
3488	}
3489	out:
3490	atomic_dec(this_cpu_ptr(&checking));
3491	}
3492	#else
3493	static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3494	struct rb_event_info *info,
3495	unsigned long tail)
3496	{
3497	}
3498	#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3499
3500	static struct ring_buffer_event *
3501	__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3502	struct rb_event_info *info)
3503	{
3504	struct ring_buffer_event *event;
3505	struct buffer_page *tail_page;
3506	unsigned long tail, write, w;
3507
3508	/* Don't let the compiler play games with cpu_buffer->tail_page */
3509	tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3510
3511	/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3512	barrier();
3513	rb_time_read(t: &cpu_buffer->before_stamp, ret: &info->before);
3514	rb_time_read(t: &cpu_buffer->write_stamp, ret: &info->after);
3515	barrier();
3516	info->ts = rb_time_stamp(buffer: cpu_buffer->buffer);
3517
3518	if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3519	info->delta = info->ts;
3520	} else {
3521	/*
3522	* If interrupting an event time update, we may need an
3523	* absolute timestamp.
3524	* Don't bother if this is the start of a new page (w == 0).
3525	*/
3526	if (!w) {
3527	/* Use the sub-buffer timestamp */
3528	info->delta = 0;
3529	} else if (unlikely(info->before != info->after)) {
3530	info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3531	info->length += RB_LEN_TIME_EXTEND;
3532	} else {
3533	info->delta = info->ts - info->after;
3534	if (unlikely(test_time_stamp(info->delta))) {
3535	info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3536	info->length += RB_LEN_TIME_EXTEND;
3537	}
3538	}
3539	}
3540
3541	/*B*/ rb_time_set(t: &cpu_buffer->before_stamp, val: info->ts);
3542
3543	/*C*/ write = local_add_return(i: info->length, l: &tail_page->write);
3544
3545	/* set write to only the index of the write */
3546	write &= RB_WRITE_MASK;
3547
3548	tail = write - info->length;
3549
3550	/* See if we shot pass the end of this buffer page */
3551	if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
3552	check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3553	return rb_move_tail(cpu_buffer, tail, info);
3554	}
3555
3556	if (likely(tail == w)) {
3557	/* Nothing interrupted us between A and C */
3558	/*D*/ rb_time_set(t: &cpu_buffer->write_stamp, val: info->ts);
3559	/*
3560	* If something came in between C and D, the write stamp
3561	* may now not be in sync. But that's fine as the before_stamp
3562	* will be different and then next event will just be forced
3563	* to use an absolute timestamp.
3564	*/
3565	if (likely(!(info->add_timestamp &
3566	(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3567	/* This did not interrupt any time update */
3568	info->delta = info->ts - info->after;
3569	else
3570	/* Just use full timestamp for interrupting event */
3571	info->delta = info->ts;
3572	check_buffer(cpu_buffer, info, tail);
3573	} else {
3574	u64 ts;
3575	/* SLOW PATH - Interrupted between A and C */
3576
3577	/* Save the old before_stamp */
3578	rb_time_read(t: &cpu_buffer->before_stamp, ret: &info->before);
3579
3580	/*
3581	* Read a new timestamp and update the before_stamp to make
3582	* the next event after this one force using an absolute
3583	* timestamp. This is in case an interrupt were to come in
3584	* between E and F.
3585	*/
3586	ts = rb_time_stamp(buffer: cpu_buffer->buffer);
3587	rb_time_set(t: &cpu_buffer->before_stamp, val: ts);
3588
3589	barrier();
3590	/*E*/ rb_time_read(t: &cpu_buffer->write_stamp, ret: &info->after);
3591	barrier();
3592	/*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3593	info->after == info->before && info->after < ts) {
3594	/*
3595	* Nothing came after this event between C and F, it is
3596	* safe to use info->after for the delta as it
3597	* matched info->before and is still valid.
3598	*/
3599	info->delta = ts - info->after;
3600	} else {
3601	/*
3602	* Interrupted between C and F:
3603	* Lost the previous events time stamp. Just set the
3604	* delta to zero, and this will be the same time as
3605	* the event this event interrupted. And the events that
3606	* came after this will still be correct (as they would
3607	* have built their delta on the previous event.
3608	*/
3609	info->delta = 0;
3610	}
3611	info->ts = ts;
3612	info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3613	}
3614
3615	/*
3616	* If this is the first commit on the page, then it has the same
3617	* timestamp as the page itself.
3618	*/
3619	if (unlikely(!tail && !(info->add_timestamp &
3620	(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3621	info->delta = 0;
3622
3623	/* We reserved something on the buffer */
3624
3625	event = __rb_page_index(bpage: tail_page, index: tail);
3626	rb_update_event(cpu_buffer, event, info);
3627
3628	local_inc(l: &tail_page->entries);
3629
3630	/*
3631	* If this is the first commit on the page, then update
3632	* its timestamp.
3633	*/
3634	if (unlikely(!tail))
3635	tail_page->page->time_stamp = info->ts;
3636
3637	/* account for these added bytes */
3638	local_add(i: info->length, l: &cpu_buffer->entries_bytes);
3639
3640	return event;
3641	}
3642
3643	static __always_inline struct ring_buffer_event *
3644	rb_reserve_next_event(struct trace_buffer *buffer,
3645	struct ring_buffer_per_cpu *cpu_buffer,
3646	unsigned long length)
3647	{
3648	struct ring_buffer_event *event;
3649	struct rb_event_info info;
3650	int nr_loops = 0;
3651	int add_ts_default;
3652
3653	/* ring buffer does cmpxchg, make sure it is safe in NMI context */
3654	if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
3655	(unlikely(in_nmi()))) {
3656	return NULL;
3657	}
3658
3659	rb_start_commit(cpu_buffer);
3660	/* The commit page can not change after this */
3661
3662	#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3663	/*
3664	* Due to the ability to swap a cpu buffer from a buffer
3665	* it is possible it was swapped before we committed.
3666	* (committing stops a swap). We check for it here and
3667	* if it happened, we have to fail the write.
3668	*/
3669	barrier();
3670	if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3671	local_dec(l: &cpu_buffer->committing);
3672	local_dec(l: &cpu_buffer->commits);
3673	return NULL;
3674	}
3675	#endif
3676
3677	info.length = rb_calculate_event_length(length);
3678
3679	if (ring_buffer_time_stamp_abs(buffer: cpu_buffer->buffer)) {
3680	add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3681	info.length += RB_LEN_TIME_EXTEND;
3682	if (info.length > cpu_buffer->buffer->max_data_size)
3683	goto out_fail;
3684	} else {
3685	add_ts_default = RB_ADD_STAMP_NONE;
3686	}
3687
3688	again:
3689	info.add_timestamp = add_ts_default;
3690	info.delta = 0;
3691
3692	/*
3693	* We allow for interrupts to reenter here and do a trace.
3694	* If one does, it will cause this original code to loop
3695	* back here. Even with heavy interrupts happening, this
3696	* should only happen a few times in a row. If this happens
3697	* 1000 times in a row, there must be either an interrupt
3698	* storm or we have something buggy.
3699	* Bail!
3700	*/
3701	if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3702	goto out_fail;
3703
3704	event = __rb_reserve_next(cpu_buffer, info: &info);
3705
3706	if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3707	if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3708	info.length -= RB_LEN_TIME_EXTEND;
3709	goto again;
3710	}
3711
3712	if (likely(event))
3713	return event;
3714	out_fail:
3715	rb_end_commit(cpu_buffer);
3716	return NULL;
3717	}
3718
3719	/**
3720	* ring_buffer_lock_reserve - reserve a part of the buffer
3721	* @buffer: the ring buffer to reserve from
3722	* @length: the length of the data to reserve (excluding event header)
3723	*
3724	* Returns a reserved event on the ring buffer to copy directly to.
3725	* The user of this interface will need to get the body to write into
3726	* and can use the ring_buffer_event_data() interface.
3727	*
3728	* The length is the length of the data needed, not the event length
3729	* which also includes the event header.
3730	*
3731	* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3732	* If NULL is returned, then nothing has been allocated or locked.
3733	*/
3734	struct ring_buffer_event *
3735	ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3736	{
3737	struct ring_buffer_per_cpu *cpu_buffer;
3738	struct ring_buffer_event *event;
3739	int cpu;
3740
3741	/* If we are tracing schedule, we don't want to recurse */
3742	preempt_disable_notrace();
3743
3744	if (unlikely(atomic_read(&buffer->record_disabled)))
3745	goto out;
3746
3747	cpu = raw_smp_processor_id();
3748
3749	if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3750	goto out;
3751
3752	cpu_buffer = buffer->buffers[cpu];
3753
3754	if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3755	goto out;
3756
3757	if (unlikely(length > buffer->max_data_size))
3758	goto out;
3759
3760	if (unlikely(trace_recursive_lock(cpu_buffer)))
3761	goto out;
3762
3763	event = rb_reserve_next_event(buffer, cpu_buffer, length);
3764	if (!event)
3765	goto out_unlock;
3766
3767	return event;
3768
3769	out_unlock:
3770	trace_recursive_unlock(cpu_buffer);
3771	out:
3772	preempt_enable_notrace();
3773	return NULL;
3774	}
3775	EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3776
3777	/*
3778	* Decrement the entries to the page that an event is on.
3779	* The event does not even need to exist, only the pointer
3780	* to the page it is on. This may only be called before the commit
3781	* takes place.
3782	*/
3783	static inline void
3784	rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3785	struct ring_buffer_event *event)
3786	{
3787	unsigned long addr = (unsigned long)event;
3788	struct buffer_page *bpage = cpu_buffer->commit_page;
3789	struct buffer_page *start;
3790
3791	addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3792
3793	/* Do the likely case first */
3794	if (likely(bpage->page == (void *)addr)) {
3795	local_dec(l: &bpage->entries);
3796	return;
3797	}
3798
3799	/*
3800	* Because the commit page may be on the reader page we
3801	* start with the next page and check the end loop there.
3802	*/
3803	rb_inc_page(bpage: &bpage);
3804	start = bpage;
3805	do {
3806	if (bpage->page == (void *)addr) {
3807	local_dec(l: &bpage->entries);
3808	return;
3809	}
3810	rb_inc_page(bpage: &bpage);
3811	} while (bpage != start);
3812
3813	/* commit not part of this buffer?? */
3814	RB_WARN_ON(cpu_buffer, 1);
3815	}
3816
3817	/**
3818	* ring_buffer_discard_commit - discard an event that has not been committed
3819	* @buffer: the ring buffer
3820	* @event: non committed event to discard
3821	*
3822	* Sometimes an event that is in the ring buffer needs to be ignored.
3823	* This function lets the user discard an event in the ring buffer
3824	* and then that event will not be read later.
3825	*
3826	* This function only works if it is called before the item has been
3827	* committed. It will try to free the event from the ring buffer
3828	* if another event has not been added behind it.
3829	*
3830	* If another event has been added behind it, it will set the event
3831	* up as discarded, and perform the commit.
3832	*
3833	* If this function is called, do not call ring_buffer_unlock_commit on
3834	* the event.
3835	*/
3836	void ring_buffer_discard_commit(struct trace_buffer *buffer,
3837	struct ring_buffer_event *event)
3838	{
3839	struct ring_buffer_per_cpu *cpu_buffer;
3840	int cpu;
3841
3842	/* The event is discarded regardless */
3843	rb_event_discard(event);
3844
3845	cpu = smp_processor_id();
3846	cpu_buffer = buffer->buffers[cpu];
3847
3848	/*
3849	* This must only be called if the event has not been
3850	* committed yet. Thus we can assume that preemption
3851	* is still disabled.
3852	*/
3853	RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3854
3855	rb_decrement_entry(cpu_buffer, event);
3856	if (rb_try_to_discard(cpu_buffer, event))
3857	goto out;
3858
3859	out:
3860	rb_end_commit(cpu_buffer);
3861
3862	trace_recursive_unlock(cpu_buffer);
3863
3864	preempt_enable_notrace();
3865
3866	}
3867	EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3868
3869	/**
3870	* ring_buffer_write - write data to the buffer without reserving
3871	* @buffer: The ring buffer to write to.
3872	* @length: The length of the data being written (excluding the event header)
3873	* @data: The data to write to the buffer.
3874	*
3875	* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3876	* one function. If you already have the data to write to the buffer, it
3877	* may be easier to simply call this function.
3878	*
3879	* Note, like ring_buffer_lock_reserve, the length is the length of the data
3880	* and not the length of the event which would hold the header.
3881	*/
3882	int ring_buffer_write(struct trace_buffer *buffer,
3883	unsigned long length,
3884	void *data)
3885	{
3886	struct ring_buffer_per_cpu *cpu_buffer;
3887	struct ring_buffer_event *event;
3888	void *body;
3889	int ret = -EBUSY;
3890	int cpu;
3891
3892	preempt_disable_notrace();
3893
3894	if (atomic_read(v: &buffer->record_disabled))
3895	goto out;
3896
3897	cpu = raw_smp_processor_id();
3898
3899	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
3900	goto out;
3901
3902	cpu_buffer = buffer->buffers[cpu];
3903
3904	if (atomic_read(v: &cpu_buffer->record_disabled))
3905	goto out;
3906
3907	if (length > buffer->max_data_size)
3908	goto out;
3909
3910	if (unlikely(trace_recursive_lock(cpu_buffer)))
3911	goto out;
3912
3913	event = rb_reserve_next_event(buffer, cpu_buffer, length);
3914	if (!event)
3915	goto out_unlock;
3916
3917	body = rb_event_data(event);
3918
3919	memcpy(body, data, length);
3920
3921	rb_commit(cpu_buffer);
3922
3923	rb_wakeups(buffer, cpu_buffer);
3924
3925	ret = 0;
3926
3927	out_unlock:
3928	trace_recursive_unlock(cpu_buffer);
3929
3930	out:
3931	preempt_enable_notrace();
3932
3933	return ret;
3934	}
3935	EXPORT_SYMBOL_GPL(ring_buffer_write);
3936
3937	static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3938	{
3939	struct buffer_page *reader = cpu_buffer->reader_page;
3940	struct buffer_page *head = rb_set_head_page(cpu_buffer);
3941	struct buffer_page *commit = cpu_buffer->commit_page;
3942
3943	/* In case of error, head will be NULL */
3944	if (unlikely(!head))
3945	return true;
3946
3947	/* Reader should exhaust content in reader page */
3948	if (reader->read != rb_page_commit(bpage: reader))
3949	return false;
3950
3951	/*
3952	* If writers are committing on the reader page, knowing all
3953	* committed content has been read, the ring buffer is empty.
3954	*/
3955	if (commit == reader)
3956	return true;
3957
3958	/*
3959	* If writers are committing on a page other than reader page
3960	* and head page, there should always be content to read.
3961	*/
3962	if (commit != head)
3963	return false;
3964
3965	/*
3966	* Writers are committing on the head page, we just need
3967	* to care about there're committed data, and the reader will
3968	* swap reader page with head page when it is to read data.
3969	*/
3970	return rb_page_commit(bpage: commit) == 0;
3971	}
3972
3973	/**
3974	* ring_buffer_record_disable - stop all writes into the buffer
3975	* @buffer: The ring buffer to stop writes to.
3976	*
3977	* This prevents all writes to the buffer. Any attempt to write
3978	* to the buffer after this will fail and return NULL.
3979	*
3980	* The caller should call synchronize_rcu() after this.
3981	*/
3982	void ring_buffer_record_disable(struct trace_buffer *buffer)
3983	{
3984	atomic_inc(v: &buffer->record_disabled);
3985	}
3986	EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3987
3988	/**
3989	* ring_buffer_record_enable - enable writes to the buffer
3990	* @buffer: The ring buffer to enable writes
3991	*
3992	* Note, multiple disables will need the same number of enables
3993	* to truly enable the writing (much like preempt_disable).
3994	*/
3995	void ring_buffer_record_enable(struct trace_buffer *buffer)
3996	{
3997	atomic_dec(v: &buffer->record_disabled);
3998	}
3999	EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4000
4001	/**
4002	* ring_buffer_record_off - stop all writes into the buffer
4003	* @buffer: The ring buffer to stop writes to.
4004	*
4005	* This prevents all writes to the buffer. Any attempt to write
4006	* to the buffer after this will fail and return NULL.
4007	*
4008	* This is different than ring_buffer_record_disable() as
4009	* it works like an on/off switch, where as the disable() version
4010	* must be paired with a enable().
4011	*/
4012	void ring_buffer_record_off(struct trace_buffer *buffer)
4013	{
4014	unsigned int rd;
4015	unsigned int new_rd;
4016
4017	rd = atomic_read(v: &buffer->record_disabled);
4018	do {
4019	new_rd = rd | RB_BUFFER_OFF;
4020	} while (!atomic_try_cmpxchg(v: &buffer->record_disabled, old: &rd, new: new_rd));
4021	}
4022	EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4023
4024	/**
4025	* ring_buffer_record_on - restart writes into the buffer
4026	* @buffer: The ring buffer to start writes to.
4027	*
4028	* This enables all writes to the buffer that was disabled by
4029	* ring_buffer_record_off().
4030	*
4031	* This is different than ring_buffer_record_enable() as
4032	* it works like an on/off switch, where as the enable() version
4033	* must be paired with a disable().
4034	*/
4035	void ring_buffer_record_on(struct trace_buffer *buffer)
4036	{
4037	unsigned int rd;
4038	unsigned int new_rd;
4039
4040	rd = atomic_read(v: &buffer->record_disabled);
4041	do {
4042	new_rd = rd & ~RB_BUFFER_OFF;
4043	} while (!atomic_try_cmpxchg(v: &buffer->record_disabled, old: &rd, new: new_rd));
4044	}
4045	EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4046
4047	/**
4048	* ring_buffer_record_is_on - return true if the ring buffer can write
4049	* @buffer: The ring buffer to see if write is enabled
4050	*
4051	* Returns true if the ring buffer is in a state that it accepts writes.
4052	*/
4053	bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4054	{
4055	return !atomic_read(v: &buffer->record_disabled);
4056	}
4057
4058	/**
4059	* ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4060	* @buffer: The ring buffer to see if write is set enabled
4061	*
4062	* Returns true if the ring buffer is set writable by ring_buffer_record_on().
4063	* Note that this does NOT mean it is in a writable state.
4064	*
4065	* It may return true when the ring buffer has been disabled by
4066	* ring_buffer_record_disable(), as that is a temporary disabling of
4067	* the ring buffer.
4068	*/
4069	bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4070	{
4071	return !(atomic_read(v: &buffer->record_disabled) & RB_BUFFER_OFF);
4072	}
4073
4074	/**
4075	* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4076	* @buffer: The ring buffer to stop writes to.
4077	* @cpu: The CPU buffer to stop
4078	*
4079	* This prevents all writes to the buffer. Any attempt to write
4080	* to the buffer after this will fail and return NULL.
4081	*
4082	* The caller should call synchronize_rcu() after this.
4083	*/
4084	void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4085	{
4086	struct ring_buffer_per_cpu *cpu_buffer;
4087
4088	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4089	return;
4090
4091	cpu_buffer = buffer->buffers[cpu];
4092	atomic_inc(v: &cpu_buffer->record_disabled);
4093	}
4094	EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4095
4096	/**
4097	* ring_buffer_record_enable_cpu - enable writes to the buffer
4098	* @buffer: The ring buffer to enable writes
4099	* @cpu: The CPU to enable.
4100	*
4101	* Note, multiple disables will need the same number of enables
4102	* to truly enable the writing (much like preempt_disable).
4103	*/
4104	void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4105	{
4106	struct ring_buffer_per_cpu *cpu_buffer;
4107
4108	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4109	return;
4110
4111	cpu_buffer = buffer->buffers[cpu];
4112	atomic_dec(v: &cpu_buffer->record_disabled);
4113	}
4114	EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4115
4116	/*
4117	* The total entries in the ring buffer is the running counter
4118	* of entries entered into the ring buffer, minus the sum of
4119	* the entries read from the ring buffer and the number of
4120	* entries that were overwritten.
4121	*/
4122	static inline unsigned long
4123	rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4124	{
4125	return local_read(&cpu_buffer->entries) -
4126	(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4127	}
4128
4129	/**
4130	* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4131	* @buffer: The ring buffer
4132	* @cpu: The per CPU buffer to read from.
4133	*/
4134	u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4135	{
4136	unsigned long flags;
4137	struct ring_buffer_per_cpu *cpu_buffer;
4138	struct buffer_page *bpage;
4139	u64 ret = 0;
4140
4141	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4142	return 0;
4143
4144	cpu_buffer = buffer->buffers[cpu];
4145	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4146	/*
4147	* if the tail is on reader_page, oldest time stamp is on the reader
4148	* page
4149	*/
4150	if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4151	bpage = cpu_buffer->reader_page;
4152	else
4153	bpage = rb_set_head_page(cpu_buffer);
4154	if (bpage)
4155	ret = bpage->page->time_stamp;
4156	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4157
4158	return ret;
4159	}
4160	EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4161
4162	/**
4163	* ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4164	* @buffer: The ring buffer
4165	* @cpu: The per CPU buffer to read from.
4166	*/
4167	unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4168	{
4169	struct ring_buffer_per_cpu *cpu_buffer;
4170	unsigned long ret;
4171
4172	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4173	return 0;
4174
4175	cpu_buffer = buffer->buffers[cpu];
4176	ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4177
4178	return ret;
4179	}
4180	EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4181
4182	/**
4183	* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4184	* @buffer: The ring buffer
4185	* @cpu: The per CPU buffer to get the entries from.
4186	*/
4187	unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4188	{
4189	struct ring_buffer_per_cpu *cpu_buffer;
4190
4191	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4192	return 0;
4193
4194	cpu_buffer = buffer->buffers[cpu];
4195
4196	return rb_num_of_entries(cpu_buffer);
4197	}
4198	EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4199
4200	/**
4201	* ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4202	* buffer wrapping around (only if RB_FL_OVERWRITE is on).
4203	* @buffer: The ring buffer
4204	* @cpu: The per CPU buffer to get the number of overruns from
4205	*/
4206	unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4207	{
4208	struct ring_buffer_per_cpu *cpu_buffer;
4209	unsigned long ret;
4210
4211	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4212	return 0;
4213
4214	cpu_buffer = buffer->buffers[cpu];
4215	ret = local_read(&cpu_buffer->overrun);
4216
4217	return ret;
4218	}
4219	EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4220
4221	/**
4222	* ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4223	* commits failing due to the buffer wrapping around while there are uncommitted
4224	* events, such as during an interrupt storm.
4225	* @buffer: The ring buffer
4226	* @cpu: The per CPU buffer to get the number of overruns from
4227	*/
4228	unsigned long
4229	ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4230	{
4231	struct ring_buffer_per_cpu *cpu_buffer;
4232	unsigned long ret;
4233
4234	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4235	return 0;
4236
4237	cpu_buffer = buffer->buffers[cpu];
4238	ret = local_read(&cpu_buffer->commit_overrun);
4239
4240	return ret;
4241	}
4242	EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4243
4244	/**
4245	* ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4246	* the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4247	* @buffer: The ring buffer
4248	* @cpu: The per CPU buffer to get the number of overruns from
4249	*/
4250	unsigned long
4251	ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4252	{
4253	struct ring_buffer_per_cpu *cpu_buffer;
4254	unsigned long ret;
4255
4256	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4257	return 0;
4258
4259	cpu_buffer = buffer->buffers[cpu];
4260	ret = local_read(&cpu_buffer->dropped_events);
4261
4262	return ret;
4263	}
4264	EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4265
4266	/**
4267	* ring_buffer_read_events_cpu - get the number of events successfully read
4268	* @buffer: The ring buffer
4269	* @cpu: The per CPU buffer to get the number of events read
4270	*/
4271	unsigned long
4272	ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4273	{
4274	struct ring_buffer_per_cpu *cpu_buffer;
4275
4276	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4277	return 0;
4278
4279	cpu_buffer = buffer->buffers[cpu];
4280	return cpu_buffer->read;
4281	}
4282	EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4283
4284	/**
4285	* ring_buffer_entries - get the number of entries in a buffer
4286	* @buffer: The ring buffer
4287	*
4288	* Returns the total number of entries in the ring buffer
4289	* (all CPU entries)
4290	*/
4291	unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4292	{
4293	struct ring_buffer_per_cpu *cpu_buffer;
4294	unsigned long entries = 0;
4295	int cpu;
4296
4297	/* if you care about this being correct, lock the buffer */
4298	for_each_buffer_cpu(buffer, cpu) {
4299	cpu_buffer = buffer->buffers[cpu];
4300	entries += rb_num_of_entries(cpu_buffer);
4301	}
4302
4303	return entries;
4304	}
4305	EXPORT_SYMBOL_GPL(ring_buffer_entries);
4306
4307	/**
4308	* ring_buffer_overruns - get the number of overruns in buffer
4309	* @buffer: The ring buffer
4310	*
4311	* Returns the total number of overruns in the ring buffer
4312	* (all CPU entries)
4313	*/
4314	unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4315	{
4316	struct ring_buffer_per_cpu *cpu_buffer;
4317	unsigned long overruns = 0;
4318	int cpu;
4319
4320	/* if you care about this being correct, lock the buffer */
4321	for_each_buffer_cpu(buffer, cpu) {
4322	cpu_buffer = buffer->buffers[cpu];
4323	overruns += local_read(&cpu_buffer->overrun);
4324	}
4325
4326	return overruns;
4327	}
4328	EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4329
4330	static void rb_iter_reset(struct ring_buffer_iter *iter)
4331	{
4332	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4333
4334	/* Iterator usage is expected to have record disabled */
4335	iter->head_page = cpu_buffer->reader_page;
4336	iter->head = cpu_buffer->reader_page->read;
4337	iter->next_event = iter->head;
4338
4339	iter->cache_reader_page = iter->head_page;
4340	iter->cache_read = cpu_buffer->read;
4341	iter->cache_pages_removed = cpu_buffer->pages_removed;
4342
4343	if (iter->head) {
4344	iter->read_stamp = cpu_buffer->read_stamp;
4345	iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4346	} else {
4347	iter->read_stamp = iter->head_page->page->time_stamp;
4348	iter->page_stamp = iter->read_stamp;
4349	}
4350	}
4351
4352	/**
4353	* ring_buffer_iter_reset - reset an iterator
4354	* @iter: The iterator to reset
4355	*
4356	* Resets the iterator, so that it will start from the beginning
4357	* again.
4358	*/
4359	void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4360	{
4361	struct ring_buffer_per_cpu *cpu_buffer;
4362	unsigned long flags;
4363
4364	if (!iter)
4365	return;
4366
4367	cpu_buffer = iter->cpu_buffer;
4368
4369	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4370	rb_iter_reset(iter);
4371	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4372	}
4373	EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4374
4375	/**
4376	* ring_buffer_iter_empty - check if an iterator has no more to read
4377	* @iter: The iterator to check
4378	*/
4379	int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4380	{
4381	struct ring_buffer_per_cpu *cpu_buffer;
4382	struct buffer_page *reader;
4383	struct buffer_page *head_page;
4384	struct buffer_page *commit_page;
4385	struct buffer_page *curr_commit_page;
4386	unsigned commit;
4387	u64 curr_commit_ts;
4388	u64 commit_ts;
4389
4390	cpu_buffer = iter->cpu_buffer;
4391	reader = cpu_buffer->reader_page;
4392	head_page = cpu_buffer->head_page;
4393	commit_page = READ_ONCE(cpu_buffer->commit_page);
4394	commit_ts = commit_page->page->time_stamp;
4395
4396	/*
4397	* When the writer goes across pages, it issues a cmpxchg which
4398	* is a mb(), which will synchronize with the rmb here.
4399	* (see rb_tail_page_update())
4400	*/
4401	smp_rmb();
4402	commit = rb_page_commit(bpage: commit_page);
4403	/* We want to make sure that the commit page doesn't change */
4404	smp_rmb();
4405
4406	/* Make sure commit page didn't change */
4407	curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4408	curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4409
4410	/* If the commit page changed, then there's more data */
4411	if (curr_commit_page != commit_page ||
4412	curr_commit_ts != commit_ts)
4413	return 0;
4414
4415	/* Still racy, as it may return a false positive, but that's OK */
4416	return ((iter->head_page == commit_page && iter->head >= commit) ||
4417	(iter->head_page == reader && commit_page == head_page &&
4418	head_page->read == commit &&
4419	iter->head == rb_page_commit(bpage: cpu_buffer->reader_page)));
4420	}
4421	EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4422
4423	static void
4424	rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4425	struct ring_buffer_event *event)
4426	{
4427	u64 delta;
4428
4429	switch (event->type_len) {
4430	case RINGBUF_TYPE_PADDING:
4431	return;
4432
4433	case RINGBUF_TYPE_TIME_EXTEND:
4434	delta = rb_event_time_stamp(event);
4435	cpu_buffer->read_stamp += delta;
4436	return;
4437
4438	case RINGBUF_TYPE_TIME_STAMP:
4439	delta = rb_event_time_stamp(event);
4440	delta = rb_fix_abs_ts(abs: delta, save_ts: cpu_buffer->read_stamp);
4441	cpu_buffer->read_stamp = delta;
4442	return;
4443
4444	case RINGBUF_TYPE_DATA:
4445	cpu_buffer->read_stamp += event->time_delta;
4446	return;
4447
4448	default:
4449	RB_WARN_ON(cpu_buffer, 1);
4450	}
4451	}
4452
4453	static void
4454	rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4455	struct ring_buffer_event *event)
4456	{
4457	u64 delta;
4458
4459	switch (event->type_len) {
4460	case RINGBUF_TYPE_PADDING:
4461	return;
4462
4463	case RINGBUF_TYPE_TIME_EXTEND:
4464	delta = rb_event_time_stamp(event);
4465	iter->read_stamp += delta;
4466	return;
4467
4468	case RINGBUF_TYPE_TIME_STAMP:
4469	delta = rb_event_time_stamp(event);
4470	delta = rb_fix_abs_ts(abs: delta, save_ts: iter->read_stamp);
4471	iter->read_stamp = delta;
4472	return;
4473
4474	case RINGBUF_TYPE_DATA:
4475	iter->read_stamp += event->time_delta;
4476	return;
4477
4478	default:
4479	RB_WARN_ON(iter->cpu_buffer, 1);
4480	}
4481	}
4482
4483	static struct buffer_page *
4484	rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4485	{
4486	struct buffer_page *reader = NULL;
4487	unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
4488	unsigned long overwrite;
4489	unsigned long flags;
4490	int nr_loops = 0;
4491	bool ret;
4492
4493	local_irq_save(flags);
4494	arch_spin_lock(&cpu_buffer->lock);
4495
4496	again:
4497	/*
4498	* This should normally only loop twice. But because the
4499	* start of the reader inserts an empty page, it causes
4500	* a case where we will loop three times. There should be no
4501	* reason to loop four times (that I know of).
4502	*/
4503	if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4504	reader = NULL;
4505	goto out;
4506	}
4507
4508	reader = cpu_buffer->reader_page;
4509
4510	/* If there's more to read, return this page */
4511	if (cpu_buffer->reader_page->read < rb_page_size(bpage: reader))
4512	goto out;
4513
4514	/* Never should we have an index greater than the size */
4515	if (RB_WARN_ON(cpu_buffer,
4516	cpu_buffer->reader_page->read > rb_page_size(reader)))
4517	goto out;
4518
4519	/* check if we caught up to the tail */
4520	reader = NULL;
4521	if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4522	goto out;
4523
4524	/* Don't bother swapping if the ring buffer is empty */
4525	if (rb_num_of_entries(cpu_buffer) == 0)
4526	goto out;
4527
4528	/*
4529	* Reset the reader page to size zero.
4530	*/
4531	local_set(&cpu_buffer->reader_page->write, 0);
4532	local_set(&cpu_buffer->reader_page->entries, 0);
4533	local_set(&cpu_buffer->reader_page->page->commit, 0);
4534	cpu_buffer->reader_page->real_end = 0;
4535
4536	spin:
4537	/*
4538	* Splice the empty reader page into the list around the head.
4539	*/
4540	reader = rb_set_head_page(cpu_buffer);
4541	if (!reader)
4542	goto out;
4543	cpu_buffer->reader_page->list.next = rb_list_head(list: reader->list.next);
4544	cpu_buffer->reader_page->list.prev = reader->list.prev;
4545
4546	/*
4547	* cpu_buffer->pages just needs to point to the buffer, it
4548	* has no specific buffer page to point to. Lets move it out
4549	* of our way so we don't accidentally swap it.
4550	*/
4551	cpu_buffer->pages = reader->list.prev;
4552
4553	/* The reader page will be pointing to the new head */
4554	rb_set_list_to_head(list: &cpu_buffer->reader_page->list);
4555
4556	/*
4557	* We want to make sure we read the overruns after we set up our
4558	* pointers to the next object. The writer side does a
4559	* cmpxchg to cross pages which acts as the mb on the writer
4560	* side. Note, the reader will constantly fail the swap
4561	* while the writer is updating the pointers, so this
4562	* guarantees that the overwrite recorded here is the one we
4563	* want to compare with the last_overrun.
4564	*/
4565	smp_mb();
4566	overwrite = local_read(&(cpu_buffer->overrun));
4567
4568	/*
4569	* Here's the tricky part.
4570	*
4571	* We need to move the pointer past the header page.
4572	* But we can only do that if a writer is not currently
4573	* moving it. The page before the header page has the
4574	* flag bit '1' set if it is pointing to the page we want.
4575	* but if the writer is in the process of moving it
4576	* than it will be '2' or already moved '0'.
4577	*/
4578
4579	ret = rb_head_page_replace(old: reader, new: cpu_buffer->reader_page);
4580
4581	/*
4582	* If we did not convert it, then we must try again.
4583	*/
4584	if (!ret)
4585	goto spin;
4586
4587	/*
4588	* Yay! We succeeded in replacing the page.
4589	*
4590	* Now make the new head point back to the reader page.
4591	*/
4592	rb_list_head(list: reader->list.next)->prev = &cpu_buffer->reader_page->list;
4593	rb_inc_page(bpage: &cpu_buffer->head_page);
4594
4595	local_inc(l: &cpu_buffer->pages_read);
4596
4597	/* Finally update the reader page to the new head */
4598	cpu_buffer->reader_page = reader;
4599	cpu_buffer->reader_page->read = 0;
4600
4601	if (overwrite != cpu_buffer->last_overrun) {
4602	cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4603	cpu_buffer->last_overrun = overwrite;
4604	}
4605
4606	goto again;
4607
4608	out:
4609	/* Update the read_stamp on the first event */
4610	if (reader && reader->read == 0)
4611	cpu_buffer->read_stamp = reader->page->time_stamp;
4612
4613	arch_spin_unlock(&cpu_buffer->lock);
4614	local_irq_restore(flags);
4615
4616	/*
4617	* The writer has preempt disable, wait for it. But not forever
4618	* Although, 1 second is pretty much "forever"
4619	*/
4620	#define USECS_WAIT 1000000
4621	for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4622	/* If the write is past the end of page, a writer is still updating it */
4623	if (likely(!reader || rb_page_write(reader) <= bsize))
4624	break;
4625
4626	udelay(1);
4627
4628	/* Get the latest version of the reader write value */
4629	smp_rmb();
4630	}
4631
4632	/* The writer is not moving forward? Something is wrong */
4633	if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4634	reader = NULL;
4635
4636	/*
4637	* Make sure we see any padding after the write update
4638	* (see rb_reset_tail()).
4639	*
4640	* In addition, a writer may be writing on the reader page
4641	* if the page has not been fully filled, so the read barrier
4642	* is also needed to make sure we see the content of what is
4643	* committed by the writer (see rb_set_commit_to_write()).
4644	*/
4645	smp_rmb();
4646
4647
4648	return reader;
4649	}
4650
4651	static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4652	{
4653	struct ring_buffer_event *event;
4654	struct buffer_page *reader;
4655	unsigned length;
4656
4657	reader = rb_get_reader_page(cpu_buffer);
4658
4659	/* This function should not be called when buffer is empty */
4660	if (RB_WARN_ON(cpu_buffer, !reader))
4661	return;
4662
4663	event = rb_reader_event(cpu_buffer);
4664
4665	if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4666	cpu_buffer->read++;
4667
4668	rb_update_read_stamp(cpu_buffer, event);
4669
4670	length = rb_event_length(event);
4671	cpu_buffer->reader_page->read += length;
4672	cpu_buffer->read_bytes += length;
4673	}
4674
4675	static void rb_advance_iter(struct ring_buffer_iter *iter)
4676	{
4677	struct ring_buffer_per_cpu *cpu_buffer;
4678
4679	cpu_buffer = iter->cpu_buffer;
4680
4681	/* If head == next_event then we need to jump to the next event */
4682	if (iter->head == iter->next_event) {
4683	/* If the event gets overwritten again, there's nothing to do */
4684	if (rb_iter_head_event(iter) == NULL)
4685	return;
4686	}
4687
4688	iter->head = iter->next_event;
4689
4690	/*
4691	* Check if we are at the end of the buffer.
4692	*/
4693	if (iter->next_event >= rb_page_size(bpage: iter->head_page)) {
4694	/* discarded commits can make the page empty */
4695	if (iter->head_page == cpu_buffer->commit_page)
4696	return;
4697	rb_inc_iter(iter);
4698	return;
4699	}
4700
4701	rb_update_iter_read_stamp(iter, event: iter->event);
4702	}
4703
4704	static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4705	{
4706	return cpu_buffer->lost_events;
4707	}
4708
4709	static struct ring_buffer_event *
4710	rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4711	unsigned long *lost_events)
4712	{
4713	struct ring_buffer_event *event;
4714	struct buffer_page *reader;
4715	int nr_loops = 0;
4716
4717	if (ts)
4718	*ts = 0;
4719	again:
4720	/*
4721	* We repeat when a time extend is encountered.
4722	* Since the time extend is always attached to a data event,
4723	* we should never loop more than once.
4724	* (We never hit the following condition more than twice).
4725	*/
4726	if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4727	return NULL;
4728
4729	reader = rb_get_reader_page(cpu_buffer);
4730	if (!reader)
4731	return NULL;
4732
4733	event = rb_reader_event(cpu_buffer);
4734
4735	switch (event->type_len) {
4736	case RINGBUF_TYPE_PADDING:
4737	if (rb_null_event(event))
4738	RB_WARN_ON(cpu_buffer, 1);
4739	/*
4740	* Because the writer could be discarding every
4741	* event it creates (which would probably be bad)
4742	* if we were to go back to "again" then we may never
4743	* catch up, and will trigger the warn on, or lock
4744	* the box. Return the padding, and we will release
4745	* the current locks, and try again.
4746	*/
4747	return event;
4748
4749	case RINGBUF_TYPE_TIME_EXTEND:
4750	/* Internal data, OK to advance */
4751	rb_advance_reader(cpu_buffer);
4752	goto again;
4753
4754	case RINGBUF_TYPE_TIME_STAMP:
4755	if (ts) {
4756	*ts = rb_event_time_stamp(event);
4757	*ts = rb_fix_abs_ts(abs: *ts, save_ts: reader->page->time_stamp);
4758	ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4759	cpu_buffer->cpu, ts);
4760	}
4761	/* Internal data, OK to advance */
4762	rb_advance_reader(cpu_buffer);
4763	goto again;
4764
4765	case RINGBUF_TYPE_DATA:
4766	if (ts && !(*ts)) {
4767	*ts = cpu_buffer->read_stamp + event->time_delta;
4768	ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4769	cpu_buffer->cpu, ts);
4770	}
4771	if (lost_events)
4772	*lost_events = rb_lost_events(cpu_buffer);
4773	return event;
4774
4775	default:
4776	RB_WARN_ON(cpu_buffer, 1);
4777	}
4778
4779	return NULL;
4780	}
4781	EXPORT_SYMBOL_GPL(ring_buffer_peek);
4782
4783	static struct ring_buffer_event *
4784	rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4785	{
4786	struct trace_buffer *buffer;
4787	struct ring_buffer_per_cpu *cpu_buffer;
4788	struct ring_buffer_event *event;
4789	int nr_loops = 0;
4790
4791	if (ts)
4792	*ts = 0;
4793
4794	cpu_buffer = iter->cpu_buffer;
4795	buffer = cpu_buffer->buffer;
4796
4797	/*
4798	* Check if someone performed a consuming read to the buffer
4799	* or removed some pages from the buffer. In these cases,
4800	* iterator was invalidated and we need to reset it.
4801	*/
4802	if (unlikely(iter->cache_read != cpu_buffer->read ||
4803	iter->cache_reader_page != cpu_buffer->reader_page ||
4804	iter->cache_pages_removed != cpu_buffer->pages_removed))
4805	rb_iter_reset(iter);
4806
4807	again:
4808	if (ring_buffer_iter_empty(iter))
4809	return NULL;
4810
4811	/*
4812	* As the writer can mess with what the iterator is trying
4813	* to read, just give up if we fail to get an event after
4814	* three tries. The iterator is not as reliable when reading
4815	* the ring buffer with an active write as the consumer is.
4816	* Do not warn if the three failures is reached.
4817	*/
4818	if (++nr_loops > 3)
4819	return NULL;
4820
4821	if (rb_per_cpu_empty(cpu_buffer))
4822	return NULL;
4823
4824	if (iter->head >= rb_page_size(bpage: iter->head_page)) {
4825	rb_inc_iter(iter);
4826	goto again;
4827	}
4828
4829	event = rb_iter_head_event(iter);
4830	if (!event)
4831	goto again;
4832
4833	switch (event->type_len) {
4834	case RINGBUF_TYPE_PADDING:
4835	if (rb_null_event(event)) {
4836	rb_inc_iter(iter);
4837	goto again;
4838	}
4839	rb_advance_iter(iter);
4840	return event;
4841
4842	case RINGBUF_TYPE_TIME_EXTEND:
4843	/* Internal data, OK to advance */
4844	rb_advance_iter(iter);
4845	goto again;
4846
4847	case RINGBUF_TYPE_TIME_STAMP:
4848	if (ts) {
4849	*ts = rb_event_time_stamp(event);
4850	*ts = rb_fix_abs_ts(abs: *ts, save_ts: iter->head_page->page->time_stamp);
4851	ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4852	cpu_buffer->cpu, ts);
4853	}
4854	/* Internal data, OK to advance */
4855	rb_advance_iter(iter);
4856	goto again;
4857
4858	case RINGBUF_TYPE_DATA:
4859	if (ts && !(*ts)) {
4860	*ts = iter->read_stamp + event->time_delta;
4861	ring_buffer_normalize_time_stamp(buffer,
4862	cpu_buffer->cpu, ts);
4863	}
4864	return event;
4865
4866	default:
4867	RB_WARN_ON(cpu_buffer, 1);
4868	}
4869
4870	return NULL;
4871	}
4872	EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4873
4874	static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4875	{
4876	if (likely(!in_nmi())) {
4877	raw_spin_lock(&cpu_buffer->reader_lock);
4878	return true;
4879	}
4880
4881	/*
4882	* If an NMI die dumps out the content of the ring buffer
4883	* trylock must be used to prevent a deadlock if the NMI
4884	* preempted a task that holds the ring buffer locks. If
4885	* we get the lock then all is fine, if not, then continue
4886	* to do the read, but this can corrupt the ring buffer,
4887	* so it must be permanently disabled from future writes.
4888	* Reading from NMI is a oneshot deal.
4889	*/
4890	if (raw_spin_trylock(&cpu_buffer->reader_lock))
4891	return true;
4892
4893	/* Continue without locking, but disable the ring buffer */
4894	atomic_inc(v: &cpu_buffer->record_disabled);
4895	return false;
4896	}
4897
4898	static inline void
4899	rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4900	{
4901	if (likely(locked))
4902	raw_spin_unlock(&cpu_buffer->reader_lock);
4903	}
4904
4905	/**
4906	* ring_buffer_peek - peek at the next event to be read
4907	* @buffer: The ring buffer to read
4908	* @cpu: The cpu to peak at
4909	* @ts: The timestamp counter of this event.
4910	* @lost_events: a variable to store if events were lost (may be NULL)
4911	*
4912	* This will return the event that will be read next, but does
4913	* not consume the data.
4914	*/
4915	struct ring_buffer_event *
4916	ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4917	unsigned long *lost_events)
4918	{
4919	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4920	struct ring_buffer_event *event;
4921	unsigned long flags;
4922	bool dolock;
4923
4924	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
4925	return NULL;
4926
4927	again:
4928	local_irq_save(flags);
4929	dolock = rb_reader_lock(cpu_buffer);
4930	event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4931	if (event && event->type_len == RINGBUF_TYPE_PADDING)
4932	rb_advance_reader(cpu_buffer);
4933	rb_reader_unlock(cpu_buffer, locked: dolock);
4934	local_irq_restore(flags);
4935
4936	if (event && event->type_len == RINGBUF_TYPE_PADDING)
4937	goto again;
4938
4939	return event;
4940	}
4941
4942	/** ring_buffer_iter_dropped - report if there are dropped events
4943	* @iter: The ring buffer iterator
4944	*
4945	* Returns true if there was dropped events since the last peek.
4946	*/
4947	bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4948	{
4949	bool ret = iter->missed_events != 0;
4950
4951	iter->missed_events = 0;
4952	return ret;
4953	}
4954	EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4955
4956	/**
4957	* ring_buffer_iter_peek - peek at the next event to be read
4958	* @iter: The ring buffer iterator
4959	* @ts: The timestamp counter of this event.
4960	*
4961	* This will return the event that will be read next, but does
4962	* not increment the iterator.
4963	*/
4964	struct ring_buffer_event *
4965	ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4966	{
4967	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4968	struct ring_buffer_event *event;
4969	unsigned long flags;
4970
4971	again:
4972	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4973	event = rb_iter_peek(iter, ts);
4974	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4975
4976	if (event && event->type_len == RINGBUF_TYPE_PADDING)
4977	goto again;
4978
4979	return event;
4980	}
4981
4982	/**
4983	* ring_buffer_consume - return an event and consume it
4984	* @buffer: The ring buffer to get the next event from
4985	* @cpu: the cpu to read the buffer from
4986	* @ts: a variable to store the timestamp (may be NULL)
4987	* @lost_events: a variable to store if events were lost (may be NULL)
4988	*
4989	* Returns the next event in the ring buffer, and that event is consumed.
4990	* Meaning, that sequential reads will keep returning a different event,
4991	* and eventually empty the ring buffer if the producer is slower.
4992	*/
4993	struct ring_buffer_event *
4994	ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4995	unsigned long *lost_events)
4996	{
4997	struct ring_buffer_per_cpu *cpu_buffer;
4998	struct ring_buffer_event *event = NULL;
4999	unsigned long flags;
5000	bool dolock;
5001
5002	again:
5003	/* might be called in atomic */
5004	preempt_disable();
5005
5006	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5007	goto out;
5008
5009	cpu_buffer = buffer->buffers[cpu];
5010	local_irq_save(flags);
5011	dolock = rb_reader_lock(cpu_buffer);
5012
5013	event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5014	if (event) {
5015	cpu_buffer->lost_events = 0;
5016	rb_advance_reader(cpu_buffer);
5017	}
5018
5019	rb_reader_unlock(cpu_buffer, locked: dolock);
5020	local_irq_restore(flags);
5021
5022	out:
5023	preempt_enable();
5024
5025	if (event && event->type_len == RINGBUF_TYPE_PADDING)
5026	goto again;
5027
5028	return event;
5029	}
5030	EXPORT_SYMBOL_GPL(ring_buffer_consume);
5031
5032	/**
5033	* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5034	* @buffer: The ring buffer to read from
5035	* @cpu: The cpu buffer to iterate over
5036	* @flags: gfp flags to use for memory allocation
5037	*
5038	* This performs the initial preparations necessary to iterate
5039	* through the buffer. Memory is allocated, buffer recording
5040	* is disabled, and the iterator pointer is returned to the caller.
5041	*
5042	* Disabling buffer recording prevents the reading from being
5043	* corrupted. This is not a consuming read, so a producer is not
5044	* expected.
5045	*
5046	* After a sequence of ring_buffer_read_prepare calls, the user is
5047	* expected to make at least one call to ring_buffer_read_prepare_sync.
5048	* Afterwards, ring_buffer_read_start is invoked to get things going
5049	* for real.
5050	*
5051	* This overall must be paired with ring_buffer_read_finish.
5052	*/
5053	struct ring_buffer_iter *
5054	ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5055	{
5056	struct ring_buffer_per_cpu *cpu_buffer;
5057	struct ring_buffer_iter *iter;
5058
5059	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5060	return NULL;
5061
5062	iter = kzalloc(size: sizeof(*iter), flags);
5063	if (!iter)
5064	return NULL;
5065
5066	/* Holds the entire event: data and meta data */
5067	iter->event_size = buffer->subbuf_size;
5068	iter->event = kmalloc(size: iter->event_size, flags);
5069	if (!iter->event) {
5070	kfree(objp: iter);
5071	return NULL;
5072	}
5073
5074	cpu_buffer = buffer->buffers[cpu];
5075
5076	iter->cpu_buffer = cpu_buffer;
5077
5078	atomic_inc(v: &cpu_buffer->resize_disabled);
5079
5080	return iter;
5081	}
5082	EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5083
5084	/**
5085	* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5086	*
5087	* All previously invoked ring_buffer_read_prepare calls to prepare
5088	* iterators will be synchronized. Afterwards, read_buffer_read_start
5089	* calls on those iterators are allowed.
5090	*/
5091	void
5092	ring_buffer_read_prepare_sync(void)
5093	{
5094	synchronize_rcu();
5095	}
5096	EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5097
5098	/**
5099	* ring_buffer_read_start - start a non consuming read of the buffer
5100	* @iter: The iterator returned by ring_buffer_read_prepare
5101	*
5102	* This finalizes the startup of an iteration through the buffer.
5103	* The iterator comes from a call to ring_buffer_read_prepare and
5104	* an intervening ring_buffer_read_prepare_sync must have been
5105	* performed.
5106	*
5107	* Must be paired with ring_buffer_read_finish.
5108	*/
5109	void
5110	ring_buffer_read_start(struct ring_buffer_iter *iter)
5111	{
5112	struct ring_buffer_per_cpu *cpu_buffer;
5113	unsigned long flags;
5114
5115	if (!iter)
5116	return;
5117
5118	cpu_buffer = iter->cpu_buffer;
5119
5120	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5121	arch_spin_lock(&cpu_buffer->lock);
5122	rb_iter_reset(iter);
5123	arch_spin_unlock(&cpu_buffer->lock);
5124	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5125	}
5126	EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5127
5128	/**
5129	* ring_buffer_read_finish - finish reading the iterator of the buffer
5130	* @iter: The iterator retrieved by ring_buffer_start
5131	*
5132	* This re-enables the recording to the buffer, and frees the
5133	* iterator.
5134	*/
5135	void
5136	ring_buffer_read_finish(struct ring_buffer_iter *iter)
5137	{
5138	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5139	unsigned long flags;
5140
5141	/*
5142	* Ring buffer is disabled from recording, here's a good place
5143	* to check the integrity of the ring buffer.
5144	* Must prevent readers from trying to read, as the check
5145	* clears the HEAD page and readers require it.
5146	*/
5147	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5148	rb_check_pages(cpu_buffer);
5149	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5150
5151	atomic_dec(v: &cpu_buffer->resize_disabled);
5152	kfree(objp: iter->event);
5153	kfree(objp: iter);
5154	}
5155	EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5156
5157	/**
5158	* ring_buffer_iter_advance - advance the iterator to the next location
5159	* @iter: The ring buffer iterator
5160	*
5161	* Move the location of the iterator such that the next read will
5162	* be the next location of the iterator.
5163	*/
5164	void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5165	{
5166	struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5167	unsigned long flags;
5168
5169	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5170
5171	rb_advance_iter(iter);
5172
5173	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5174	}
5175	EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5176
5177	/**
5178	* ring_buffer_size - return the size of the ring buffer (in bytes)
5179	* @buffer: The ring buffer.
5180	* @cpu: The CPU to get ring buffer size from.
5181	*/
5182	unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5183	{
5184	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5185	return 0;
5186
5187	return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5188	}
5189	EXPORT_SYMBOL_GPL(ring_buffer_size);
5190
5191	/**
5192	* ring_buffer_max_event_size - return the max data size of an event
5193	* @buffer: The ring buffer.
5194	*
5195	* Returns the maximum size an event can be.
5196	*/
5197	unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5198	{
5199	/* If abs timestamp is requested, events have a timestamp too */
5200	if (ring_buffer_time_stamp_abs(buffer))
5201	return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5202	return buffer->max_data_size;
5203	}
5204	EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5205
5206	static void rb_clear_buffer_page(struct buffer_page *page)
5207	{
5208	local_set(&page->write, 0);
5209	local_set(&page->entries, 0);
5210	rb_init_page(bpage: page->page);
5211	page->read = 0;
5212	}
5213
5214	static void
5215	rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5216	{
5217	struct buffer_page *page;
5218
5219	rb_head_page_deactivate(cpu_buffer);
5220
5221	cpu_buffer->head_page
5222	= list_entry(cpu_buffer->pages, struct buffer_page, list);
5223	rb_clear_buffer_page(page: cpu_buffer->head_page);
5224	list_for_each_entry(page, cpu_buffer->pages, list) {
5225	rb_clear_buffer_page(page);
5226	}
5227
5228	cpu_buffer->tail_page = cpu_buffer->head_page;
5229	cpu_buffer->commit_page = cpu_buffer->head_page;
5230
5231	INIT_LIST_HEAD(list: &cpu_buffer->reader_page->list);
5232	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
5233	rb_clear_buffer_page(page: cpu_buffer->reader_page);
5234
5235	local_set(&cpu_buffer->entries_bytes, 0);
5236	local_set(&cpu_buffer->overrun, 0);
5237	local_set(&cpu_buffer->commit_overrun, 0);
5238	local_set(&cpu_buffer->dropped_events, 0);
5239	local_set(&cpu_buffer->entries, 0);
5240	local_set(&cpu_buffer->committing, 0);
5241	local_set(&cpu_buffer->commits, 0);
5242	local_set(&cpu_buffer->pages_touched, 0);
5243	local_set(&cpu_buffer->pages_lost, 0);
5244	local_set(&cpu_buffer->pages_read, 0);
5245	cpu_buffer->last_pages_touch = 0;
5246	cpu_buffer->shortest_full = 0;
5247	cpu_buffer->read = 0;
5248	cpu_buffer->read_bytes = 0;
5249
5250	rb_time_set(t: &cpu_buffer->write_stamp, val: 0);
5251	rb_time_set(t: &cpu_buffer->before_stamp, val: 0);
5252
5253	memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5254
5255	cpu_buffer->lost_events = 0;
5256	cpu_buffer->last_overrun = 0;
5257
5258	rb_head_page_activate(cpu_buffer);
5259	cpu_buffer->pages_removed = 0;
5260	}
5261
5262	/* Must have disabled the cpu buffer then done a synchronize_rcu */
5263	static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5264	{
5265	unsigned long flags;
5266
5267	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5268
5269	if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5270	goto out;
5271
5272	arch_spin_lock(&cpu_buffer->lock);
5273
5274	rb_reset_cpu(cpu_buffer);
5275
5276	arch_spin_unlock(&cpu_buffer->lock);
5277
5278	out:
5279	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5280	}
5281
5282	/**
5283	* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5284	* @buffer: The ring buffer to reset a per cpu buffer of
5285	* @cpu: The CPU buffer to be reset
5286	*/
5287	void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5288	{
5289	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5290
5291	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5292	return;
5293
5294	/* prevent another thread from changing buffer sizes */
5295	mutex_lock(&buffer->mutex);
5296
5297	atomic_inc(v: &cpu_buffer->resize_disabled);
5298	atomic_inc(v: &cpu_buffer->record_disabled);
5299
5300	/* Make sure all commits have finished */
5301	synchronize_rcu();
5302
5303	reset_disabled_cpu_buffer(cpu_buffer);
5304
5305	atomic_dec(v: &cpu_buffer->record_disabled);
5306	atomic_dec(v: &cpu_buffer->resize_disabled);
5307
5308	mutex_unlock(lock: &buffer->mutex);
5309	}
5310	EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5311
5312	/* Flag to ensure proper resetting of atomic variables */
5313	#define RESET_BIT (1 << 30)
5314
5315	/**
5316	* ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5317	* @buffer: The ring buffer to reset a per cpu buffer of
5318	*/
5319	void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5320	{
5321	struct ring_buffer_per_cpu *cpu_buffer;
5322	int cpu;
5323
5324	/* prevent another thread from changing buffer sizes */
5325	mutex_lock(&buffer->mutex);
5326
5327	for_each_online_buffer_cpu(buffer, cpu) {
5328	cpu_buffer = buffer->buffers[cpu];
5329
5330	atomic_add(RESET_BIT, v: &cpu_buffer->resize_disabled);
5331	atomic_inc(v: &cpu_buffer->record_disabled);
5332	}
5333
5334	/* Make sure all commits have finished */
5335	synchronize_rcu();
5336
5337	for_each_buffer_cpu(buffer, cpu) {
5338	cpu_buffer = buffer->buffers[cpu];
5339
5340	/*
5341	* If a CPU came online during the synchronize_rcu(), then
5342	* ignore it.
5343	*/
5344	if (!(atomic_read(v: &cpu_buffer->resize_disabled) & RESET_BIT))
5345	continue;
5346
5347	reset_disabled_cpu_buffer(cpu_buffer);
5348
5349	atomic_dec(v: &cpu_buffer->record_disabled);
5350	atomic_sub(RESET_BIT, v: &cpu_buffer->resize_disabled);
5351	}
5352
5353	mutex_unlock(lock: &buffer->mutex);
5354	}
5355
5356	/**
5357	* ring_buffer_reset - reset a ring buffer
5358	* @buffer: The ring buffer to reset all cpu buffers
5359	*/
5360	void ring_buffer_reset(struct trace_buffer *buffer)
5361	{
5362	struct ring_buffer_per_cpu *cpu_buffer;
5363	int cpu;
5364
5365	/* prevent another thread from changing buffer sizes */
5366	mutex_lock(&buffer->mutex);
5367
5368	for_each_buffer_cpu(buffer, cpu) {
5369	cpu_buffer = buffer->buffers[cpu];
5370
5371	atomic_inc(v: &cpu_buffer->resize_disabled);
5372	atomic_inc(v: &cpu_buffer->record_disabled);
5373	}
5374
5375	/* Make sure all commits have finished */
5376	synchronize_rcu();
5377
5378	for_each_buffer_cpu(buffer, cpu) {
5379	cpu_buffer = buffer->buffers[cpu];
5380
5381	reset_disabled_cpu_buffer(cpu_buffer);
5382
5383	atomic_dec(v: &cpu_buffer->record_disabled);
5384	atomic_dec(v: &cpu_buffer->resize_disabled);
5385	}
5386
5387	mutex_unlock(lock: &buffer->mutex);
5388	}
5389	EXPORT_SYMBOL_GPL(ring_buffer_reset);
5390
5391	/**
5392	* ring_buffer_empty - is the ring buffer empty?
5393	* @buffer: The ring buffer to test
5394	*/
5395	bool ring_buffer_empty(struct trace_buffer *buffer)
5396	{
5397	struct ring_buffer_per_cpu *cpu_buffer;
5398	unsigned long flags;
5399	bool dolock;
5400	bool ret;
5401	int cpu;
5402
5403	/* yes this is racy, but if you don't like the race, lock the buffer */
5404	for_each_buffer_cpu(buffer, cpu) {
5405	cpu_buffer = buffer->buffers[cpu];
5406	local_irq_save(flags);
5407	dolock = rb_reader_lock(cpu_buffer);
5408	ret = rb_per_cpu_empty(cpu_buffer);
5409	rb_reader_unlock(cpu_buffer, locked: dolock);
5410	local_irq_restore(flags);
5411
5412	if (!ret)
5413	return false;
5414	}
5415
5416	return true;
5417	}
5418	EXPORT_SYMBOL_GPL(ring_buffer_empty);
5419
5420	/**
5421	* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5422	* @buffer: The ring buffer
5423	* @cpu: The CPU buffer to test
5424	*/
5425	bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5426	{
5427	struct ring_buffer_per_cpu *cpu_buffer;
5428	unsigned long flags;
5429	bool dolock;
5430	bool ret;
5431
5432	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5433	return true;
5434
5435	cpu_buffer = buffer->buffers[cpu];
5436	local_irq_save(flags);
5437	dolock = rb_reader_lock(cpu_buffer);
5438	ret = rb_per_cpu_empty(cpu_buffer);
5439	rb_reader_unlock(cpu_buffer, locked: dolock);
5440	local_irq_restore(flags);
5441
5442	return ret;
5443	}
5444	EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5445
5446	#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5447	/**
5448	* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5449	* @buffer_a: One buffer to swap with
5450	* @buffer_b: The other buffer to swap with
5451	* @cpu: the CPU of the buffers to swap
5452	*
5453	* This function is useful for tracers that want to take a "snapshot"
5454	* of a CPU buffer and has another back up buffer lying around.
5455	* it is expected that the tracer handles the cpu buffer not being
5456	* used at the moment.
5457	*/
5458	int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5459	struct trace_buffer *buffer_b, int cpu)
5460	{
5461	struct ring_buffer_per_cpu *cpu_buffer_a;
5462	struct ring_buffer_per_cpu *cpu_buffer_b;
5463	int ret = -EINVAL;
5464
5465	if (!cpumask_test_cpu(cpu, cpumask: buffer_a->cpumask) ||
5466	!cpumask_test_cpu(cpu, cpumask: buffer_b->cpumask))
5467	goto out;
5468
5469	cpu_buffer_a = buffer_a->buffers[cpu];
5470	cpu_buffer_b = buffer_b->buffers[cpu];
5471
5472	/* At least make sure the two buffers are somewhat the same */
5473	if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5474	goto out;
5475
5476	if (buffer_a->subbuf_order != buffer_b->subbuf_order)
5477	goto out;
5478
5479	ret = -EAGAIN;
5480
5481	if (atomic_read(v: &buffer_a->record_disabled))
5482	goto out;
5483
5484	if (atomic_read(v: &buffer_b->record_disabled))
5485	goto out;
5486
5487	if (atomic_read(v: &cpu_buffer_a->record_disabled))
5488	goto out;
5489
5490	if (atomic_read(v: &cpu_buffer_b->record_disabled))
5491	goto out;
5492
5493	/*
5494	* We can't do a synchronize_rcu here because this
5495	* function can be called in atomic context.
5496	* Normally this will be called from the same CPU as cpu.
5497	* If not it's up to the caller to protect this.
5498	*/
5499	atomic_inc(v: &cpu_buffer_a->record_disabled);
5500	atomic_inc(v: &cpu_buffer_b->record_disabled);
5501
5502	ret = -EBUSY;
5503	if (local_read(&cpu_buffer_a->committing))
5504	goto out_dec;
5505	if (local_read(&cpu_buffer_b->committing))
5506	goto out_dec;
5507
5508	/*
5509	* When resize is in progress, we cannot swap it because
5510	* it will mess the state of the cpu buffer.
5511	*/
5512	if (atomic_read(v: &buffer_a->resizing))
5513	goto out_dec;
5514	if (atomic_read(v: &buffer_b->resizing))
5515	goto out_dec;
5516
5517	buffer_a->buffers[cpu] = cpu_buffer_b;
5518	buffer_b->buffers[cpu] = cpu_buffer_a;
5519
5520	cpu_buffer_b->buffer = buffer_a;
5521	cpu_buffer_a->buffer = buffer_b;
5522
5523	ret = 0;
5524
5525	out_dec:
5526	atomic_dec(v: &cpu_buffer_a->record_disabled);
5527	atomic_dec(v: &cpu_buffer_b->record_disabled);
5528	out:
5529	return ret;
5530	}
5531	EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5532	#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5533
5534	/**
5535	* ring_buffer_alloc_read_page - allocate a page to read from buffer
5536	* @buffer: the buffer to allocate for.
5537	* @cpu: the cpu buffer to allocate.
5538	*
5539	* This function is used in conjunction with ring_buffer_read_page.
5540	* When reading a full page from the ring buffer, these functions
5541	* can be used to speed up the process. The calling function should
5542	* allocate a few pages first with this function. Then when it
5543	* needs to get pages from the ring buffer, it passes the result
5544	* of this function into ring_buffer_read_page, which will swap
5545	* the page that was allocated, with the read page of the buffer.
5546	*
5547	* Returns:
5548	* The page allocated, or ERR_PTR
5549	*/
5550	struct buffer_data_read_page *
5551	ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5552	{
5553	struct ring_buffer_per_cpu *cpu_buffer;
5554	struct buffer_data_read_page *bpage = NULL;
5555	unsigned long flags;
5556	struct page *page;
5557
5558	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5559	return ERR_PTR(error: -ENODEV);
5560
5561	bpage = kzalloc(size: sizeof(*bpage), GFP_KERNEL);
5562	if (!bpage)
5563	return ERR_PTR(error: -ENOMEM);
5564
5565	bpage->order = buffer->subbuf_order;
5566	cpu_buffer = buffer->buffers[cpu];
5567	local_irq_save(flags);
5568	arch_spin_lock(&cpu_buffer->lock);
5569
5570	if (cpu_buffer->free_page) {
5571	bpage->data = cpu_buffer->free_page;
5572	cpu_buffer->free_page = NULL;
5573	}
5574
5575	arch_spin_unlock(&cpu_buffer->lock);
5576	local_irq_restore(flags);
5577
5578	if (bpage->data)
5579	goto out;
5580
5581	page = alloc_pages_node(cpu_to_node(cpu),
5582	GFP_KERNEL | __GFP_NORETRY | __GFP_ZERO,
5583	order: cpu_buffer->buffer->subbuf_order);
5584	if (!page) {
5585	kfree(objp: bpage);
5586	return ERR_PTR(error: -ENOMEM);
5587	}
5588
5589	bpage->data = page_address(page);
5590
5591	out:
5592	rb_init_page(bpage: bpage->data);
5593
5594	return bpage;
5595	}
5596	EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5597
5598	/**
5599	* ring_buffer_free_read_page - free an allocated read page
5600	* @buffer: the buffer the page was allocate for
5601	* @cpu: the cpu buffer the page came from
5602	* @data_page: the page to free
5603	*
5604	* Free a page allocated from ring_buffer_alloc_read_page.
5605	*/
5606	void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
5607	struct buffer_data_read_page *data_page)
5608	{
5609	struct ring_buffer_per_cpu *cpu_buffer;
5610	struct buffer_data_page *bpage = data_page->data;
5611	struct page *page = virt_to_page(bpage);
5612	unsigned long flags;
5613
5614	if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
5615	return;
5616
5617	cpu_buffer = buffer->buffers[cpu];
5618
5619	/*
5620	* If the page is still in use someplace else, or order of the page
5621	* is different from the subbuffer order of the buffer -
5622	* we can't reuse it
5623	*/
5624	if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
5625	goto out;
5626
5627	local_irq_save(flags);
5628	arch_spin_lock(&cpu_buffer->lock);
5629
5630	if (!cpu_buffer->free_page) {
5631	cpu_buffer->free_page = bpage;
5632	bpage = NULL;
5633	}
5634
5635	arch_spin_unlock(&cpu_buffer->lock);
5636	local_irq_restore(flags);
5637
5638	out:
5639	free_pages(addr: (unsigned long)bpage, order: data_page->order);
5640	kfree(objp: data_page);
5641	}
5642	EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5643
5644	/**
5645	* ring_buffer_read_page - extract a page from the ring buffer
5646	* @buffer: buffer to extract from
5647	* @data_page: the page to use allocated from ring_buffer_alloc_read_page
5648	* @len: amount to extract
5649	* @cpu: the cpu of the buffer to extract
5650	* @full: should the extraction only happen when the page is full.
5651	*
5652	* This function will pull out a page from the ring buffer and consume it.
5653	* @data_page must be the address of the variable that was returned
5654	* from ring_buffer_alloc_read_page. This is because the page might be used
5655	* to swap with a page in the ring buffer.
5656	*
5657	* for example:
5658	* rpage = ring_buffer_alloc_read_page(buffer, cpu);
5659	* if (IS_ERR(rpage))
5660	* return PTR_ERR(rpage);
5661	* ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
5662	* if (ret >= 0)
5663	* process_page(ring_buffer_read_page_data(rpage), ret);
5664	* ring_buffer_free_read_page(buffer, cpu, rpage);
5665	*
5666	* When @full is set, the function will not return true unless
5667	* the writer is off the reader page.
5668	*
5669	* Note: it is up to the calling functions to handle sleeps and wakeups.
5670	* The ring buffer can be used anywhere in the kernel and can not
5671	* blindly call wake_up. The layer that uses the ring buffer must be
5672	* responsible for that.
5673	*
5674	* Returns:
5675	* >=0 if data has been transferred, returns the offset of consumed data.
5676	* <0 if no data has been transferred.
5677	*/
5678	int ring_buffer_read_page(struct trace_buffer *buffer,
5679	struct buffer_data_read_page *data_page,
5680	size_t len, int cpu, int full)
5681	{
5682	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5683	struct ring_buffer_event *event;
5684	struct buffer_data_page *bpage;
5685	struct buffer_page *reader;
5686	unsigned long missed_events;
5687	unsigned long flags;
5688	unsigned int commit;
5689	unsigned int read;
5690	u64 save_timestamp;
5691	int ret = -1;
5692
5693	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5694	goto out;
5695
5696	/*
5697	* If len is not big enough to hold the page header, then
5698	* we can not copy anything.
5699	*/
5700	if (len <= BUF_PAGE_HDR_SIZE)
5701	goto out;
5702
5703	len -= BUF_PAGE_HDR_SIZE;
5704
5705	if (!data_page || !data_page->data)
5706	goto out;
5707	if (data_page->order != buffer->subbuf_order)
5708	goto out;
5709
5710	bpage = data_page->data;
5711	if (!bpage)
5712	goto out;
5713
5714	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5715
5716	reader = rb_get_reader_page(cpu_buffer);
5717	if (!reader)
5718	goto out_unlock;
5719
5720	event = rb_reader_event(cpu_buffer);
5721
5722	read = reader->read;
5723	commit = rb_page_commit(bpage: reader);
5724
5725	/* Check if any events were dropped */
5726	missed_events = cpu_buffer->lost_events;
5727
5728	/*
5729	* If this page has been partially read or
5730	* if len is not big enough to read the rest of the page or
5731	* a writer is still on the page, then
5732	* we must copy the data from the page to the buffer.
5733	* Otherwise, we can simply swap the page with the one passed in.
5734	*/
5735	if (read || (len < (commit - read)) ||
5736	cpu_buffer->reader_page == cpu_buffer->commit_page) {
5737	struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5738	unsigned int rpos = read;
5739	unsigned int pos = 0;
5740	unsigned int size;
5741
5742	/*
5743	* If a full page is expected, this can still be returned
5744	* if there's been a previous partial read and the
5745	* rest of the page can be read and the commit page is off
5746	* the reader page.
5747	*/
5748	if (full &&
5749	(!read || (len < (commit - read)) ||
5750	cpu_buffer->reader_page == cpu_buffer->commit_page))
5751	goto out_unlock;
5752
5753	if (len > (commit - read))
5754	len = (commit - read);
5755
5756	/* Always keep the time extend and data together */
5757	size = rb_event_ts_length(event);
5758
5759	if (len < size)
5760	goto out_unlock;
5761
5762	/* save the current timestamp, since the user will need it */
5763	save_timestamp = cpu_buffer->read_stamp;
5764
5765	/* Need to copy one event at a time */
5766	do {
5767	/* We need the size of one event, because
5768	* rb_advance_reader only advances by one event,
5769	* whereas rb_event_ts_length may include the size of
5770	* one or two events.
5771	* We have already ensured there's enough space if this
5772	* is a time extend. */
5773	size = rb_event_length(event);
5774	memcpy(bpage->data + pos, rpage->data + rpos, size);
5775
5776	len -= size;
5777
5778	rb_advance_reader(cpu_buffer);
5779	rpos = reader->read;
5780	pos += size;
5781
5782	if (rpos >= commit)
5783	break;
5784
5785	event = rb_reader_event(cpu_buffer);
5786	/* Always keep the time extend and data together */
5787	size = rb_event_ts_length(event);
5788	} while (len >= size);
5789
5790	/* update bpage */
5791	local_set(&bpage->commit, pos);
5792	bpage->time_stamp = save_timestamp;
5793
5794	/* we copied everything to the beginning */
5795	read = 0;
5796	} else {
5797	/* update the entry counter */
5798	cpu_buffer->read += rb_page_entries(bpage: reader);
5799	cpu_buffer->read_bytes += rb_page_commit(bpage: reader);
5800
5801	/* swap the pages */
5802	rb_init_page(bpage);
5803	bpage = reader->page;
5804	reader->page = data_page->data;
5805	local_set(&reader->write, 0);
5806	local_set(&reader->entries, 0);
5807	reader->read = 0;
5808	data_page->data = bpage;
5809
5810	/*
5811	* Use the real_end for the data size,
5812	* This gives us a chance to store the lost events
5813	* on the page.
5814	*/
5815	if (reader->real_end)
5816	local_set(&bpage->commit, reader->real_end);
5817	}
5818	ret = read;
5819
5820	cpu_buffer->lost_events = 0;
5821
5822	commit = local_read(&bpage->commit);
5823	/*
5824	* Set a flag in the commit field if we lost events
5825	*/
5826	if (missed_events) {
5827	/* If there is room at the end of the page to save the
5828	* missed events, then record it there.
5829	*/
5830	if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
5831	memcpy(&bpage->data[commit], &missed_events,
5832	sizeof(missed_events));
5833	local_add(RB_MISSED_STORED, l: &bpage->commit);
5834	commit += sizeof(missed_events);
5835	}
5836	local_add(RB_MISSED_EVENTS, l: &bpage->commit);
5837	}
5838
5839	/*
5840	* This page may be off to user land. Zero it out here.
5841	*/
5842	if (commit < buffer->subbuf_size)
5843	memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
5844
5845	out_unlock:
5846	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5847
5848	out:
5849	return ret;
5850	}
5851	EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5852
5853	/**
5854	* ring_buffer_read_page_data - get pointer to the data in the page.
5855	* @page: the page to get the data from
5856	*
5857	* Returns pointer to the actual data in this page.
5858	*/
5859	void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
5860	{
5861	return page->data;
5862	}
5863	EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
5864
5865	/**
5866	* ring_buffer_subbuf_size_get - get size of the sub buffer.
5867	* @buffer: the buffer to get the sub buffer size from
5868	*
5869	* Returns size of the sub buffer, in bytes.
5870	*/
5871	int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
5872	{
5873	return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
5874	}
5875	EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
5876
5877	/**
5878	* ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
5879	* @buffer: The ring_buffer to get the system sub page order from
5880	*
5881	* By default, one ring buffer sub page equals to one system page. This parameter
5882	* is configurable, per ring buffer. The size of the ring buffer sub page can be
5883	* extended, but must be an order of system page size.
5884	*
5885	* Returns the order of buffer sub page size, in system pages:
5886	* 0 means the sub buffer size is 1 system page and so forth.
5887	* In case of an error < 0 is returned.
5888	*/
5889	int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
5890	{
5891	if (!buffer)
5892	return -EINVAL;
5893
5894	return buffer->subbuf_order;
5895	}
5896	EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
5897
5898	/**
5899	* ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
5900	* @buffer: The ring_buffer to set the new page size.
5901	* @order: Order of the system pages in one sub buffer page
5902	*
5903	* By default, one ring buffer pages equals to one system page. This API can be
5904	* used to set new size of the ring buffer page. The size must be order of
5905	* system page size, that's why the input parameter @order is the order of
5906	* system pages that are allocated for one ring buffer page:
5907	* 0 - 1 system page
5908	* 1 - 2 system pages
5909	* 3 - 4 system pages
5910	* ...
5911	*
5912	* Returns 0 on success or < 0 in case of an error.
5913	*/
5914	int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
5915	{
5916	struct ring_buffer_per_cpu *cpu_buffer;
5917	struct buffer_page *bpage, *tmp;
5918	int old_order, old_size;
5919	int nr_pages;
5920	int psize;
5921	int err;
5922	int cpu;
5923
5924	if (!buffer || order < 0)
5925	return -EINVAL;
5926
5927	if (buffer->subbuf_order == order)
5928	return 0;
5929
5930	psize = (1 << order) * PAGE_SIZE;
5931	if (psize <= BUF_PAGE_HDR_SIZE)
5932	return -EINVAL;
5933
5934	/* Size of a subbuf cannot be greater than the write counter */
5935	if (psize > RB_WRITE_MASK + 1)
5936	return -EINVAL;
5937
5938	old_order = buffer->subbuf_order;
5939	old_size = buffer->subbuf_size;
5940
5941	/* prevent another thread from changing buffer sizes */
5942	mutex_lock(&buffer->mutex);
5943	atomic_inc(v: &buffer->record_disabled);
5944
5945	/* Make sure all commits have finished */
5946	synchronize_rcu();
5947
5948	buffer->subbuf_order = order;
5949	buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
5950
5951	/* Make sure all new buffers are allocated, before deleting the old ones */
5952	for_each_buffer_cpu(buffer, cpu) {
5953
5954	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5955	continue;
5956
5957	cpu_buffer = buffer->buffers[cpu];
5958
5959	/* Update the number of pages to match the new size */
5960	nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
5961	nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
5962
5963	/* we need a minimum of two pages */
5964	if (nr_pages < 2)
5965	nr_pages = 2;
5966
5967	cpu_buffer->nr_pages_to_update = nr_pages;
5968
5969	/* Include the reader page */
5970	nr_pages++;
5971
5972	/* Allocate the new size buffer */
5973	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
5974	if (__rb_allocate_pages(cpu_buffer, nr_pages,
5975	pages: &cpu_buffer->new_pages)) {
5976	/* not enough memory for new pages */
5977	err = -ENOMEM;
5978	goto error;
5979	}
5980	}
5981
5982	for_each_buffer_cpu(buffer, cpu) {
5983
5984	if (!cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
5985	continue;
5986
5987	cpu_buffer = buffer->buffers[cpu];
5988
5989	/* Clear the head bit to make the link list normal to read */
5990	rb_head_page_deactivate(cpu_buffer);
5991
5992	/* Now walk the list and free all the old sub buffers */
5993	list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) {
5994	list_del_init(entry: &bpage->list);
5995	free_buffer_page(bpage);
5996	}
5997	/* The above loop stopped an the last page needing to be freed */
5998	bpage = list_entry(cpu_buffer->pages, struct buffer_page, list);
5999	free_buffer_page(bpage);
6000
6001	/* Free the current reader page */
6002	free_buffer_page(bpage: cpu_buffer->reader_page);
6003
6004	/* One page was allocated for the reader page */
6005	cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6006	struct buffer_page, list);
6007	list_del_init(entry: &cpu_buffer->reader_page->list);
6008
6009	/* The cpu_buffer pages are a link list with no head */
6010	cpu_buffer->pages = cpu_buffer->new_pages.next;
6011	cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev;
6012	cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next;
6013
6014	/* Clear the new_pages list */
6015	INIT_LIST_HEAD(list: &cpu_buffer->new_pages);
6016
6017	cpu_buffer->head_page
6018	= list_entry(cpu_buffer->pages, struct buffer_page, list);
6019	cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6020
6021	cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6022	cpu_buffer->nr_pages_to_update = 0;
6023
6024	free_pages(addr: (unsigned long)cpu_buffer->free_page, order: old_order);
6025	cpu_buffer->free_page = NULL;
6026
6027	rb_head_page_activate(cpu_buffer);
6028
6029	rb_check_pages(cpu_buffer);
6030	}
6031
6032	atomic_dec(v: &buffer->record_disabled);
6033	mutex_unlock(lock: &buffer->mutex);
6034
6035	return 0;
6036
6037	error:
6038	buffer->subbuf_order = old_order;
6039	buffer->subbuf_size = old_size;
6040
6041	atomic_dec(v: &buffer->record_disabled);
6042	mutex_unlock(lock: &buffer->mutex);
6043
6044	for_each_buffer_cpu(buffer, cpu) {
6045	cpu_buffer = buffer->buffers[cpu];
6046
6047	if (!cpu_buffer->nr_pages_to_update)
6048	continue;
6049
6050	list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6051	list_del_init(entry: &bpage->list);
6052	free_buffer_page(bpage);
6053	}
6054	}
6055
6056	return err;
6057	}
6058	EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6059
6060	/*
6061	* We only allocate new buffers, never free them if the CPU goes down.
6062	* If we were to free the buffer, then the user would lose any trace that was in
6063	* the buffer.
6064	*/
6065	int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
6066	{
6067	struct trace_buffer *buffer;
6068	long nr_pages_same;
6069	int cpu_i;
6070	unsigned long nr_pages;
6071
6072	buffer = container_of(node, struct trace_buffer, node);
6073	if (cpumask_test_cpu(cpu, cpumask: buffer->cpumask))
6074	return 0;
6075
6076	nr_pages = 0;
6077	nr_pages_same = 1;
6078	/* check if all cpu sizes are same */
6079	for_each_buffer_cpu(buffer, cpu_i) {
6080	/* fill in the size from first enabled cpu */
6081	if (nr_pages == 0)
6082	nr_pages = buffer->buffers[cpu_i]->nr_pages;
6083	if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
6084	nr_pages_same = 0;
6085	break;
6086	}
6087	}
6088	/* allocate minimum pages, user can later expand it */
6089	if (!nr_pages_same)
6090	nr_pages = 2;
6091	buffer->buffers[cpu] =
6092	rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
6093	if (!buffer->buffers[cpu]) {
6094	WARN(1, "failed to allocate ring buffer on CPU %u\n",
6095	cpu);
6096	return -ENOMEM;
6097	}
6098	smp_wmb();
6099	cpumask_set_cpu(cpu, dstp: buffer->cpumask);
6100	return 0;
6101	}
6102
6103	#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
6104	/*
6105	* This is a basic integrity check of the ring buffer.
6106	* Late in the boot cycle this test will run when configured in.
6107	* It will kick off a thread per CPU that will go into a loop
6108	* writing to the per cpu ring buffer various sizes of data.
6109	* Some of the data will be large items, some small.
6110	*
6111	* Another thread is created that goes into a spin, sending out
6112	* IPIs to the other CPUs to also write into the ring buffer.
6113	* this is to test the nesting ability of the buffer.
6114	*
6115	* Basic stats are recorded and reported. If something in the
6116	* ring buffer should happen that's not expected, a big warning
6117	* is displayed and all ring buffers are disabled.
6118	*/
6119	static struct task_struct *rb_threads[NR_CPUS] __initdata;
6120
6121	struct rb_test_data {
6122	struct trace_buffer *buffer;
6123	unsigned long events;
6124	unsigned long bytes_written;
6125	unsigned long bytes_alloc;
6126	unsigned long bytes_dropped;
6127	unsigned long events_nested;
6128	unsigned long bytes_written_nested;
6129	unsigned long bytes_alloc_nested;
6130	unsigned long bytes_dropped_nested;
6131	int min_size_nested;
6132	int max_size_nested;
6133	int max_size;
6134	int min_size;
6135	int cpu;
6136	int cnt;
6137	};
6138
6139	static struct rb_test_data rb_data[NR_CPUS] __initdata;
6140
6141	/* 1 meg per cpu */
6142	#define RB_TEST_BUFFER_SIZE 1048576
6143
6144	static char rb_string[] __initdata =
6145	"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
6146	"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
6147	"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
6148
6149	static bool rb_test_started __initdata;
6150
6151	struct rb_item {
6152	int size;
6153	char str[];
6154	};
6155
6156	static __init int rb_write_something(struct rb_test_data *data, bool nested)
6157	{
6158	struct ring_buffer_event *event;
6159	struct rb_item *item;
6160	bool started;
6161	int event_len;
6162	int size;
6163	int len;
6164	int cnt;
6165
6166	/* Have nested writes different that what is written */
6167	cnt = data->cnt + (nested ? 27 : 0);
6168
6169	/* Multiply cnt by ~e, to make some unique increment */
6170	size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
6171
6172	len = size + sizeof(struct rb_item);
6173
6174	started = rb_test_started;
6175	/* read rb_test_started before checking buffer enabled */
6176	smp_rmb();
6177
6178	event = ring_buffer_lock_reserve(data->buffer, len);
6179	if (!event) {
6180	/* Ignore dropped events before test starts. */
6181	if (started) {
6182	if (nested)
6183	data->bytes_dropped += len;
6184	else
6185	data->bytes_dropped_nested += len;
6186	}
6187	return len;
6188	}
6189
6190	event_len = ring_buffer_event_length(event);
6191
6192	if (RB_WARN_ON(data->buffer, event_len < len))
6193	goto out;
6194
6195	item = ring_buffer_event_data(event);
6196	item->size = size;
6197	memcpy(item->str, rb_string, size);
6198
6199	if (nested) {
6200	data->bytes_alloc_nested += event_len;
6201	data->bytes_written_nested += len;
6202	data->events_nested++;
6203	if (!data->min_size_nested || len < data->min_size_nested)
6204	data->min_size_nested = len;
6205	if (len > data->max_size_nested)
6206	data->max_size_nested = len;
6207	} else {
6208	data->bytes_alloc += event_len;
6209	data->bytes_written += len;
6210	data->events++;
6211	if (!data->min_size || len < data->min_size)
6212	data->max_size = len;
6213	if (len > data->max_size)
6214	data->max_size = len;
6215	}
6216
6217	out:
6218	ring_buffer_unlock_commit(data->buffer);
6219
6220	return 0;
6221	}
6222
6223	static __init int rb_test(void *arg)
6224	{
6225	struct rb_test_data *data = arg;
6226
6227	while (!kthread_should_stop()) {
6228	rb_write_something(data, nested: false);
6229	data->cnt++;
6230
6231	set_current_state(TASK_INTERRUPTIBLE);
6232	/* Now sleep between a min of 100-300us and a max of 1ms */
6233	usleep_range(min: ((data->cnt % 3) + 1) * 100, max: 1000);
6234	}
6235
6236	return 0;
6237	}
6238
6239	static __init void rb_ipi(void *ignore)
6240	{
6241	struct rb_test_data *data;
6242	int cpu = smp_processor_id();
6243
6244	data = &rb_data[cpu];
6245	rb_write_something(data, nested: true);
6246	}
6247
6248	static __init int rb_hammer_test(void *arg)
6249	{
6250	while (!kthread_should_stop()) {
6251
6252	/* Send an IPI to all cpus to write data! */
6253	smp_call_function(func: rb_ipi, NULL, wait: 1);
6254	/* No sleep, but for non preempt, let others run */
6255	schedule();
6256	}
6257
6258	return 0;
6259	}
6260
6261	static __init int test_ringbuffer(void)
6262	{
6263	struct task_struct *rb_hammer;
6264	struct trace_buffer *buffer;
6265	int cpu;
6266	int ret = 0;
6267
6268	if (security_locked_down(what: LOCKDOWN_TRACEFS)) {
6269	pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6270	return 0;
6271	}
6272
6273	pr_info("Running ring buffer tests...\n");
6274
6275	buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6276	if (WARN_ON(!buffer))
6277	return 0;
6278
6279	/* Disable buffer so that threads can't write to it yet */
6280	ring_buffer_record_off(buffer);
6281
6282	for_each_online_cpu(cpu) {
6283	rb_data[cpu].buffer = buffer;
6284	rb_data[cpu].cpu = cpu;
6285	rb_data[cpu].cnt = cpu;
6286	rb_threads[cpu] = kthread_run_on_cpu(threadfn: rb_test, data: &rb_data[cpu],
6287	cpu, namefmt: "rbtester/%u");
6288	if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6289	pr_cont("FAILED\n");
6290	ret = PTR_ERR(ptr: rb_threads[cpu]);
6291	goto out_free;
6292	}
6293	}
6294
6295	/* Now create the rb hammer! */
6296	rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6297	if (WARN_ON(IS_ERR(rb_hammer))) {
6298	pr_cont("FAILED\n");
6299	ret = PTR_ERR(ptr: rb_hammer);
6300	goto out_free;
6301	}
6302
6303	ring_buffer_record_on(buffer);
6304	/*
6305	* Show buffer is enabled before setting rb_test_started.
6306	* Yes there's a small race window where events could be
6307	* dropped and the thread wont catch it. But when a ring
6308	* buffer gets enabled, there will always be some kind of
6309	* delay before other CPUs see it. Thus, we don't care about
6310	* those dropped events. We care about events dropped after
6311	* the threads see that the buffer is active.
6312	*/
6313	smp_wmb();
6314	rb_test_started = true;
6315
6316	set_current_state(TASK_INTERRUPTIBLE);
6317	/* Just run for 10 seconds */;
6318	schedule_timeout(timeout: 10 * HZ);
6319
6320	kthread_stop(k: rb_hammer);
6321
6322	out_free:
6323	for_each_online_cpu(cpu) {
6324	if (!rb_threads[cpu])
6325	break;
6326	kthread_stop(k: rb_threads[cpu]);
6327	}
6328	if (ret) {
6329	ring_buffer_free(buffer);
6330	return ret;
6331	}
6332
6333	/* Report! */
6334	pr_info("finished\n");
6335	for_each_online_cpu(cpu) {
6336	struct ring_buffer_event *event;
6337	struct rb_test_data *data = &rb_data[cpu];
6338	struct rb_item *item;
6339	unsigned long total_events;
6340	unsigned long total_dropped;
6341	unsigned long total_written;
6342	unsigned long total_alloc;
6343	unsigned long total_read = 0;
6344	unsigned long total_size = 0;
6345	unsigned long total_len = 0;
6346	unsigned long total_lost = 0;
6347	unsigned long lost;
6348	int big_event_size;
6349	int small_event_size;
6350
6351	ret = -1;
6352
6353	total_events = data->events + data->events_nested;
6354	total_written = data->bytes_written + data->bytes_written_nested;
6355	total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6356	total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6357
6358	big_event_size = data->max_size + data->max_size_nested;
6359	small_event_size = data->min_size + data->min_size_nested;
6360
6361	pr_info("CPU %d:\n", cpu);
6362	pr_info(" events: %ld\n", total_events);
6363	pr_info(" dropped bytes: %ld\n", total_dropped);
6364	pr_info(" alloced bytes: %ld\n", total_alloc);
6365	pr_info(" written bytes: %ld\n", total_written);
6366	pr_info(" biggest event: %d\n", big_event_size);
6367	pr_info(" smallest event: %d\n", small_event_size);
6368
6369	if (RB_WARN_ON(buffer, total_dropped))
6370	break;
6371
6372	ret = 0;
6373
6374	while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6375	total_lost += lost;
6376	item = ring_buffer_event_data(event);
6377	total_len += ring_buffer_event_length(event);
6378	total_size += item->size + sizeof(struct rb_item);
6379	if (memcmp(p: &item->str[0], q: rb_string, size: item->size) != 0) {
6380	pr_info("FAILED!\n");
6381	pr_info("buffer had: %.*s\n", item->size, item->str);
6382	pr_info("expected: %.*s\n", item->size, rb_string);
6383	RB_WARN_ON(buffer, 1);
6384	ret = -1;
6385	break;
6386	}
6387	total_read++;
6388	}
6389	if (ret)
6390	break;
6391
6392	ret = -1;
6393
6394	pr_info(" read events: %ld\n", total_read);
6395	pr_info(" lost events: %ld\n", total_lost);
6396	pr_info(" total events: %ld\n", total_lost + total_read);
6397	pr_info(" recorded len bytes: %ld\n", total_len);
6398	pr_info(" recorded size bytes: %ld\n", total_size);
6399	if (total_lost) {
6400	pr_info(" With dropped events, record len and size may not match\n"
6401	" alloced and written from above\n");
6402	} else {
6403	if (RB_WARN_ON(buffer, total_len != total_alloc ||
6404	total_size != total_written))
6405	break;
6406	}
6407	if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6408	break;
6409
6410	ret = 0;
6411	}
6412	if (!ret)
6413	pr_info("Ring buffer PASSED!\n");
6414
6415	ring_buffer_free(buffer);
6416	return 0;
6417	}
6418
6419	late_initcall(test_ringbuffer);
6420	#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
6421