trace.c 123 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
/*
 * ring buffer based function tracer
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * Originally taken from the RT patch by:
 *    Arnaldo Carvalho de Melo <acme@redhat.com>
 *
 * Based on code from the latency_tracer, that is:
 *  Copyright (C) 2004-2006 Ingo Molnar
12
 *  Copyright (C) 2004 Nadia Yvette Chambers
13
 */
14
#include <linux/ring_buffer.h>
15
#include <generated/utsrelease.h>
16
17
#include <linux/stacktrace.h>
#include <linux/writeback.h>
18
19
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
20
#include <linux/notifier.h>
21
#include <linux/irqflags.h>
22
#include <linux/irq_work.h>
23
#include <linux/debugfs.h>
24
#include <linux/pagemap.h>
25
26
27
#include <linux/hardirq.h>
#include <linux/linkage.h>
#include <linux/uaccess.h>
28
#include <linux/kprobes.h>
29
30
31
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/percpu.h>
32
#include <linux/splice.h>
33
#include <linux/kdebug.h>
34
#include <linux/string.h>
35
#include <linux/rwsem.h>
36
#include <linux/slab.h>
37
38
#include <linux/ctype.h>
#include <linux/init.h>
39
#include <linux/poll.h>
40
#include <linux/nmi.h>
41
#include <linux/fs.h>
42
#include <linux/sched/rt.h>
Ingo Molnar's avatar
Ingo Molnar committed
43

44
#include "trace.h"
45
#include "trace_output.h"
46

47
48
49
50
/*
 * On boot up, the ring buffer is set to the minimum size, so that
 * we do not waste memory on systems that are not using tracing.
 */
51
int ring_buffer_expanded;
52

53
54
/*
 * We need to change this state when a selftest is running.
55
56
 * A selftest will lurk into the ring-buffer to count the
 * entries inserted during the selftest although some concurrent
57
 * insertions into the ring-buffer such as trace_printk could occurred
58
59
 * at the same time, giving false positive or negative results.
 */
60
static bool __read_mostly tracing_selftest_running;
61

62
63
64
/*
 * If a tracer is running, we do not want to run SELFTEST.
 */
65
bool __read_mostly tracing_selftest_disabled;
66

67
68
69
70
71
72
73
74
75
76
77
78
79
80
/* For tracers that don't implement custom flags */
static struct tracer_opt dummy_tracer_opt[] = {
	{ }
};

static struct tracer_flags dummy_tracer_flags = {
	.val = 0,
	.opts = dummy_tracer_opt
};

static int dummy_set_flag(u32 old_flags, u32 bit, int set)
{
	return 0;
}
81

82
83
84
85
86
87
88
/*
 * To prevent the comm cache from being overwritten when no
 * tracing is active, only save the comm when a trace event
 * occurred.
 */
static DEFINE_PER_CPU(bool, trace_cmdline_save);

89
90
91
92
93
94
95
96
/*
 * When a reader is waiting for data, then this variable is
 * set to true.
 */
static bool trace_wakeup_needed;

static struct irq_work trace_work_wakeup;

97
98
99
100
101
102
/*
 * Kill all tracing for good (never come back).
 * It is initialized to 1 but will turn to zero if the initialization
 * of the tracer is successful. But that is the only place that sets
 * this back to zero.
 */
103
static int tracing_disabled = 1;
104

105
DEFINE_PER_CPU(int, ftrace_cpu_disabled);
106

107
cpumask_var_t __read_mostly	tracing_buffer_mask;
108

109
110
111
112
113
114
115
116
117
118
119
/*
 * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
 *
 * If there is an oops (or kernel panic) and the ftrace_dump_on_oops
 * is set, then ftrace_dump is called. This will output the contents
 * of the ftrace buffers to the console.  This is very useful for
 * capturing traces that lead to crashes and outputing it to a
 * serial console.
 *
 * It is default off, but you can enable it with either specifying
 * "ftrace_dump_on_oops" in the kernel command line, or setting
120
121
122
 * /proc/sys/kernel/ftrace_dump_on_oops
 * Set 1 if you want to dump buffers of all CPUs
 * Set 2 if you want to dump the buffer of the CPU that triggered oops
123
 */
124
125

enum ftrace_dump_mode ftrace_dump_on_oops;
126

127
128
static int tracing_set_tracer(const char *buf);

Li Zefan's avatar
Li Zefan committed
129
130
#define MAX_TRACER_SIZE		100
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
131
static char *default_bootup_tracer;
132

133
static int __init set_cmdline_ftrace(char *str)
134
{
Li Zefan's avatar
Li Zefan committed
135
	strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
136
	default_bootup_tracer = bootup_tracer_buf;
137
138
	/* We are using ftrace early, expand it */
	ring_buffer_expanded = 1;
139
140
	return 1;
}
141
__setup("ftrace=", set_cmdline_ftrace);
142

143
144
static int __init set_ftrace_dump_on_oops(char *str)
{
145
146
147
148
149
150
151
152
153
154
155
	if (*str++ != '=' || !*str) {
		ftrace_dump_on_oops = DUMP_ALL;
		return 1;
	}

	if (!strcmp("orig_cpu", str)) {
		ftrace_dump_on_oops = DUMP_ORIG;
                return 1;
        }

        return 0;
156
157
}
__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
Steven Rostedt's avatar
Steven Rostedt committed
158

159
160
161
162
163
164
165
166
167
168
169
170

static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
static char *trace_boot_options __initdata;

static int __init set_trace_boot_options(char *str)
{
	strncpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
	trace_boot_options = trace_boot_options_buf;
	return 0;
}
__setup("trace_options=", set_trace_boot_options);

171
unsigned long long ns2usecs(cycle_t nsec)
172
173
174
175
176
177
{
	nsec += 500;
	do_div(nsec, 1000);
	return nsec;
}

Steven Rostedt's avatar
Steven Rostedt committed
178
179
180
181
182
183
184
185
186
187
188
189
/*
 * The global_trace is the descriptor that holds the tracing
 * buffers for the live tracing. For each CPU, it contains
 * a link list of pages that will store trace entries. The
 * page descriptor of the pages in the memory is used to hold
 * the link list by linking the lru item in the page descriptor
 * to each of the pages in the buffer per CPU.
 *
 * For each active CPU there is a data field that holds the
 * pages for the buffer for that CPU. Each CPU has the same number
 * of pages allocated for its buffer.
 */
190
191
192
193
static struct trace_array	global_trace;

static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);

194
195
int filter_current_check_discard(struct ring_buffer *buffer,
				 struct ftrace_event_call *call, void *rec,
196
197
				 struct ring_buffer_event *event)
{
198
	return filter_check_discard(call, rec, buffer, event);
199
}
200
EXPORT_SYMBOL_GPL(filter_current_check_discard);
201

202
203
204
205
206
207
208
209
210
211
212
213
214
cycle_t ftrace_now(int cpu)
{
	u64 ts;

	/* Early boot up does not have a buffer yet */
	if (!global_trace.buffer)
		return trace_clock_local();

	ts = ring_buffer_time_stamp(global_trace.buffer, cpu);
	ring_buffer_normalize_time_stamp(global_trace.buffer, cpu, &ts);

	return ts;
}
215

Steven Rostedt's avatar
Steven Rostedt committed
216
217
218
219
220
221
222
223
224
225
/*
 * The max_tr is used to snapshot the global_trace when a maximum
 * latency is reached. Some tracers will use this to store a maximum
 * trace while it continues examining live traces.
 *
 * The buffers for the max_tr are set up the same as the global_trace.
 * When a snapshot is taken, the link list of the max_tr is swapped
 * with the link list of the global_trace and the buffers are reset for
 * the global_trace so the tracing can continue.
 */
226
227
static struct trace_array	max_tr;

228
static DEFINE_PER_CPU(struct trace_array_cpu, max_tr_data);
229

230
231
int tracing_is_enabled(void)
{
232
	return tracing_is_on();
233
234
}

Steven Rostedt's avatar
Steven Rostedt committed
235
/*
236
237
238
 * trace_buf_size is the size in bytes that is allocated
 * for a buffer. Note, the number of bytes is always rounded
 * to page size.
239
240
241
242
243
 *
 * This number is purposely set to a low number of 16384.
 * If the dump on oops happens, it will be much appreciated
 * to not have to wait for all that output. Anyway this can be
 * boot time and run time configurable.
Steven Rostedt's avatar
Steven Rostedt committed
244
 */
245
#define TRACE_BUF_SIZE_DEFAULT	1441792UL /* 16384 * 88 (sizeof(entry)) */
246

247
static unsigned long		trace_buf_size = TRACE_BUF_SIZE_DEFAULT;
248

Steven Rostedt's avatar
Steven Rostedt committed
249
/* trace_types holds a link list of available tracers. */
250
static struct tracer		*trace_types __read_mostly;
Steven Rostedt's avatar
Steven Rostedt committed
251
252

/* current_trace points to the tracer that is currently active */
253
static struct tracer		*current_trace __read_mostly = &nop_trace;
Steven Rostedt's avatar
Steven Rostedt committed
254
255
256
257

/*
 * trace_types_lock is used to protect the trace_types list.
 */
258
static DEFINE_MUTEX(trace_types_lock);
Steven Rostedt's avatar
Steven Rostedt committed
259

260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
/*
 * serialize the access of the ring buffer
 *
 * ring buffer serializes readers, but it is low level protection.
 * The validity of the events (which returns by ring_buffer_peek() ..etc)
 * are not protected by ring buffer.
 *
 * The content of events may become garbage if we allow other process consumes
 * these events concurrently:
 *   A) the page of the consumed events may become a normal page
 *      (not reader page) in ring buffer, and this page will be rewrited
 *      by events producer.
 *   B) The page of the consumed events may become a page for splice_read,
 *      and this page will be returned to system.
 *
 * These primitives allow multi process access to different cpu ring buffer
 * concurrently.
 *
 * These primitives don't distinguish read-only and read-consume access.
 * Multi read-only access are also serialized.
 */

#ifdef CONFIG_SMP
static DECLARE_RWSEM(all_cpu_access_lock);
static DEFINE_PER_CPU(struct mutex, cpu_access_lock);

static inline void trace_access_lock(int cpu)
{
	if (cpu == TRACE_PIPE_ALL_CPU) {
		/* gain it for accessing the whole ring buffer. */
		down_write(&all_cpu_access_lock);
	} else {
		/* gain it for accessing a cpu ring buffer. */

		/* Firstly block other trace_access_lock(TRACE_PIPE_ALL_CPU). */
		down_read(&all_cpu_access_lock);

		/* Secondly block other access to this @cpu ring buffer. */
		mutex_lock(&per_cpu(cpu_access_lock, cpu));
	}
}

static inline void trace_access_unlock(int cpu)
{
	if (cpu == TRACE_PIPE_ALL_CPU) {
		up_write(&all_cpu_access_lock);
	} else {
		mutex_unlock(&per_cpu(cpu_access_lock, cpu));
		up_read(&all_cpu_access_lock);
	}
}

static inline void trace_access_lock_init(void)
{
	int cpu;

	for_each_possible_cpu(cpu)
		mutex_init(&per_cpu(cpu_access_lock, cpu));
}

#else

static DEFINE_MUTEX(access_lock);

static inline void trace_access_lock(int cpu)
{
	(void)cpu;
	mutex_lock(&access_lock);
}

static inline void trace_access_unlock(int cpu)
{
	(void)cpu;
	mutex_unlock(&access_lock);
}

static inline void trace_access_lock_init(void)
{
}

#endif

Steven Rostedt's avatar
Steven Rostedt committed
342
/* trace_wait is a waitqueue for tasks blocked on trace_poll */
343
344
static DECLARE_WAIT_QUEUE_HEAD(trace_wait);

345
/* trace_flags holds trace_options default values */
346
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
347
	TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
348
	TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |
349
	TRACE_ITER_IRQ_INFO | TRACE_ITER_MARKERS;
350

351
static int trace_stop_count;
352
static DEFINE_RAW_SPINLOCK(tracing_start_lock);
353

354
355
356
357
358
359
360
361
/**
 * trace_wake_up - wake up tasks waiting for trace input
 *
 * Schedules a delayed work to wake up any task that is blocked on the
 * trace_wait queue. These is used with trace_poll for tasks polling the
 * trace.
 */
static void trace_wake_up(struct irq_work *work)
362
{
363
	wake_up_all(&trace_wait);
364

365
}
366

367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
/**
 * tracing_on - enable tracing buffers
 *
 * This function enables tracing buffers that may have been
 * disabled with tracing_off.
 */
void tracing_on(void)
{
	if (global_trace.buffer)
		ring_buffer_record_on(global_trace.buffer);
	/*
	 * This flag is only looked at when buffers haven't been
	 * allocated yet. We don't really care about the race
	 * between setting this flag and actually turning
	 * on the buffer.
	 */
	global_trace.buffer_disabled = 0;
}
EXPORT_SYMBOL_GPL(tracing_on);

/**
 * tracing_off - turn off tracing buffers
 *
 * This function stops the tracing buffers from recording data.
 * It does not disable any overhead the tracers themselves may
 * be causing. This function simply causes all recording to
 * the ring buffers to fail.
 */
void tracing_off(void)
{
	if (global_trace.buffer)
398
		ring_buffer_record_off(global_trace.buffer);
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
	/*
	 * This flag is only looked at when buffers haven't been
	 * allocated yet. We don't really care about the race
	 * between setting this flag and actually turning
	 * on the buffer.
	 */
	global_trace.buffer_disabled = 1;
}
EXPORT_SYMBOL_GPL(tracing_off);

/**
 * tracing_is_on - show state of ring buffers enabled
 */
int tracing_is_on(void)
{
	if (global_trace.buffer)
		return ring_buffer_record_is_on(global_trace.buffer);
	return !global_trace.buffer_disabled;
}
EXPORT_SYMBOL_GPL(tracing_is_on);

420
static int __init set_buf_size(char *str)
421
{
422
	unsigned long buf_size;
423

424
425
	if (!str)
		return 0;
426
	buf_size = memparse(str, &str);
427
	/* nr_entries can not be zero */
428
	if (buf_size == 0)
429
		return 0;
430
	trace_buf_size = buf_size;
431
432
	return 1;
}
433
__setup("trace_buf_size=", set_buf_size);
434

435
436
static int __init set_tracing_thresh(char *str)
{
437
	unsigned long threshold;
438
439
440
441
	int ret;

	if (!str)
		return 0;
442
	ret = kstrtoul(str, 0, &threshold);
443
444
	if (ret < 0)
		return 0;
445
	tracing_thresh = threshold * 1000;
446
447
448
449
	return 1;
}
__setup("tracing_thresh=", set_tracing_thresh);

Steven Rostedt's avatar
Steven Rostedt committed
450
451
452
453
454
unsigned long nsecs_to_usecs(unsigned long nsecs)
{
	return nsecs / 1000;
}

Steven Rostedt's avatar
Steven Rostedt committed
455
/* These must match the bit postions in trace_iterator_flags */
456
457
458
459
460
static const char *trace_options[] = {
	"print-parent",
	"sym-offset",
	"sym-addr",
	"verbose",
Ingo Molnar's avatar
Ingo Molnar committed
461
	"raw",
462
	"hex",
Ingo Molnar's avatar
Ingo Molnar committed
463
	"bin",
464
	"block",
Ingo Molnar's avatar
Ingo Molnar committed
465
	"stacktrace",
466
	"trace_printk",
467
	"ftrace_preempt",
468
	"branch",
469
	"annotate",
470
	"userstacktrace",
471
	"sym-userobj",
472
	"printk-msg-only",
473
	"context-info",
474
	"latency-format",
475
	"sleep-time",
476
	"graph-time",
477
	"record-cmd",
478
	"overwrite",
479
	"disable_on_free",
480
	"irq-info",
481
	"markers",
482
483
484
	NULL
};

485
486
487
static struct {
	u64 (*func)(void);
	const char *name;
488
	int in_ns;		/* is this clock in nanoseconds? */
489
} trace_clocks[] = {
490
491
492
	{ trace_clock_local,	"local",	1 },
	{ trace_clock_global,	"global",	1 },
	{ trace_clock_counter,	"counter",	0 },
493
	ARCH_TRACE_CLOCKS
494
495
496
497
};

int trace_clock_id;

498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
/*
 * trace_parser_get_init - gets the buffer for trace parser
 */
int trace_parser_get_init(struct trace_parser *parser, int size)
{
	memset(parser, 0, sizeof(*parser));

	parser->buffer = kmalloc(size, GFP_KERNEL);
	if (!parser->buffer)
		return 1;

	parser->size = size;
	return 0;
}

/*
 * trace_parser_put - frees the buffer for trace parser
 */
void trace_parser_put(struct trace_parser *parser)
{
	kfree(parser->buffer);
}

/*
 * trace_get_user - reads the user input string separated by  space
 * (matched by isspace(ch))
 *
 * For each string found the 'struct trace_parser' is updated,
 * and the function returns.
 *
 * Returns number of bytes read.
 *
 * See kernel/trace/trace.h for 'struct trace_parser' details.
 */
int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
	size_t cnt, loff_t *ppos)
{
	char ch;
	size_t read = 0;
	ssize_t ret;

	if (!*ppos)
		trace_parser_clear(parser);

	ret = get_user(ch, ubuf++);
	if (ret)
		goto out;

	read++;
	cnt--;

	/*
	 * The parser is not finished with the last write,
	 * continue reading the user input without skipping spaces.
	 */
	if (!parser->cont) {
		/* skip white space */
		while (cnt && isspace(ch)) {
			ret = get_user(ch, ubuf++);
			if (ret)
				goto out;
			read++;
			cnt--;
		}

		/* only spaces were written */
		if (isspace(ch)) {
			*ppos += read;
			ret = read;
			goto out;
		}

		parser->idx = 0;
	}

	/* read the non-space input */
	while (cnt && !isspace(ch)) {
575
		if (parser->idx < parser->size - 1)
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
			parser->buffer[parser->idx++] = ch;
		else {
			ret = -EINVAL;
			goto out;
		}
		ret = get_user(ch, ubuf++);
		if (ret)
			goto out;
		read++;
		cnt--;
	}

	/* We either got finished input or we have to wait for another call. */
	if (isspace(ch)) {
		parser->buffer[parser->idx] = 0;
		parser->cont = false;
	} else {
		parser->cont = true;
		parser->buffer[parser->idx++] = ch;
	}

	*ppos += read;
	ret = read;

out:
	return ret;
}

604
605
606
607
608
ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
{
	int len;
	int ret;

609
610
611
	if (!cnt)
		return 0;

612
613
614
615
616
617
618
	if (s->len <= s->readpos)
		return -EBUSY;

	len = s->len - s->readpos;
	if (cnt > len)
		cnt = len;
	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
619
	if (ret == cnt)
620
621
		return -EFAULT;

622
623
	cnt -= ret;

624
	s->readpos += cnt;
625
	return cnt;
626
627
}

628
static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
629
630
631
632
633
634
635
636
637
{
	int len;

	if (s->len <= s->readpos)
		return -EBUSY;

	len = s->len - s->readpos;
	if (cnt > len)
		cnt = len;
638
	memcpy(buf, s->buffer + s->readpos, cnt);
639

640
	s->readpos += cnt;
641
642
643
	return cnt;
}

644
645
646
647
648
649
/*
 * ftrace_max_lock is used to protect the swapping of buffers
 * when taking a max snapshot. The buffers themselves are
 * protected by per_cpu spinlocks. But the action of the swap
 * needs its own lock.
 *
650
 * This is defined as a arch_spinlock_t in order to help
651
652
653
654
655
656
 * with performance when lockdep debugging is enabled.
 *
 * It is also used in other places outside the update_max_tr
 * so it needs to be defined outside of the
 * CONFIG_TRACER_MAX_TRACE.
 */
657
static arch_spinlock_t ftrace_max_lock =
658
	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
659

660
661
unsigned long __read_mostly	tracing_thresh;

662
663
664
665
666
667
668
669
670
671
672
673
#ifdef CONFIG_TRACER_MAX_TRACE
unsigned long __read_mostly	tracing_max_latency;

/*
 * Copy the new maximum trace into the separate maximum-trace
 * structure. (this way the maximum trace is permanently saved,
 * for later retrieval via /sys/kernel/debug/tracing/latency_trace)
 */
static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
	struct trace_array_cpu *data = tr->data[cpu];
674
	struct trace_array_cpu *max_data;
675
676
677
678

	max_tr.cpu = cpu;
	max_tr.time_start = data->preempt_timestamp;

679
680
681
682
	max_data = max_tr.data[cpu];
	max_data->saved_latency = tracing_max_latency;
	max_data->critical_start = data->critical_start;
	max_data->critical_end = data->critical_end;
683

684
	memcpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
685
686
687
688
689
	max_data->pid = tsk->pid;
	max_data->uid = task_uid(tsk);
	max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
	max_data->policy = tsk->policy;
	max_data->rt_priority = tsk->rt_priority;
690
691
692
693
694

	/* record this tasks comm */
	tracing_record_cmdline(tsk);
}

Steven Rostedt's avatar
Steven Rostedt committed
695
696
697
698
699
700
701
702
703
/**
 * update_max_tr - snapshot all trace buffers from global_trace to max_tr
 * @tr: tracer
 * @tsk: the task with the latency
 * @cpu: The cpu that initiated the trace.
 *
 * Flip the buffers between the @tr and the max_tr and record information
 * about which task was the cause of this latency.
 */
Ingo Molnar's avatar
Ingo Molnar committed
704
void
705
706
update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
707
	struct ring_buffer *buf = tr->buffer;
708

709
710
711
	if (trace_stop_count)
		return;

712
	WARN_ON_ONCE(!irqs_disabled());
713

714
715
716
	if (!current_trace->allocated_snapshot) {
		/* Only the nop tracer should hit this when disabling */
		WARN_ON_ONCE(current_trace != &nop_trace);
717
		return;
718
	}
719

720
	arch_spin_lock(&ftrace_max_lock);
721
722
723
724

	tr->buffer = max_tr.buffer;
	max_tr.buffer = buf;

725
	__update_max_tr(tr, tsk, cpu);
726
	arch_spin_unlock(&ftrace_max_lock);
727
728
729
730
731
732
733
}

/**
 * update_max_tr_single - only copy one trace over, and reset the rest
 * @tr - tracer
 * @tsk - task with the latency
 * @cpu - the cpu of the buffer to copy.
Steven Rostedt's avatar
Steven Rostedt committed
734
735
 *
 * Flip the trace of a single CPU buffer between the @tr and the max_tr.
736
 */
Ingo Molnar's avatar
Ingo Molnar committed
737
void
738
739
update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
740
	int ret;
741

742
743
744
	if (trace_stop_count)
		return;

745
	WARN_ON_ONCE(!irqs_disabled());
746
	if (WARN_ON_ONCE(!current_trace->allocated_snapshot))
747
748
		return;

749
	arch_spin_lock(&ftrace_max_lock);
750

751
752
	ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu);

753
754
755
756
757
758
759
760
761
762
763
764
	if (ret == -EBUSY) {
		/*
		 * We failed to swap the buffer due to a commit taking
		 * place on this CPU. We fail to record, but we reset
		 * the max trace buffer (no one writes directly to it)
		 * and flag that it failed.
		 */
		trace_array_printk(&max_tr, _THIS_IP_,
			"Failed to swap buffers due to commit in progress\n");
	}

	WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);
765
766

	__update_max_tr(tr, tsk, cpu);
767
	arch_spin_unlock(&ftrace_max_lock);
768
}
769
#endif /* CONFIG_TRACER_MAX_TRACE */
770

771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
static void default_wait_pipe(struct trace_iterator *iter)
{
	DEFINE_WAIT(wait);

	prepare_to_wait(&trace_wait, &wait, TASK_INTERRUPTIBLE);

	/*
	 * The events can happen in critical sections where
	 * checking a work queue can cause deadlocks.
	 * After adding a task to the queue, this flag is set
	 * only to notify events to try to wake up the queue
	 * using irq_work.
	 *
	 * We don't clear it even if the buffer is no longer
	 * empty. The flag only causes the next event to run
	 * irq_work to do the work queue wake up. The worse
	 * that can happen if we race with !trace_empty() is that
	 * an event will cause an irq_work to try to wake up
	 * an empty queue.
	 *
	 * There's no reason to protect this flag either, as
	 * the work queue and irq_work logic will do the necessary
	 * synchronization for the wake ups. The only thing
	 * that is necessary is that the wake up happens after
	 * a task has been queued. It's OK for spurious wake ups.
	 */
	trace_wakeup_needed = true;

	if (trace_empty(iter))
		schedule();

	finish_wait(&trace_wait, &wait);
}

Steven Rostedt's avatar
Steven Rostedt committed
805
806
807
808
809
810
/**
 * register_tracer - register a tracer with the ftrace system.
 * @type - the plugin for the tracer
 *
 * Register a new plugin tracer.
 */
811
812
813
814
815
816
817
818
819
820
int register_tracer(struct tracer *type)
{
	struct tracer *t;
	int ret = 0;

	if (!type->name) {
		pr_info("Tracer must have a name\n");
		return -1;
	}

821
	if (strlen(type->name) >= MAX_TRACER_SIZE) {
Li Zefan's avatar
Li Zefan committed
822
823
824
825
		pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
		return -1;
	}

826
	mutex_lock(&trace_types_lock);
Ingo Molnar's avatar
Ingo Molnar committed
827

828
829
	tracing_selftest_running = true;

830
831
832
	for (t = trace_types; t; t = t->next) {
		if (strcmp(type->name, t->name) == 0) {
			/* already found */
Li Zefan's avatar
Li Zefan committed
833
			pr_info("Tracer %s already registered\n",
834
835
836
837
838
839
				type->name);
			ret = -1;
			goto out;
		}
	}

840
841
842
843
844
845
846
	if (!type->set_flag)
		type->set_flag = &dummy_set_flag;
	if (!type->flags)
		type->flags = &dummy_tracer_flags;
	else
		if (!type->flags->opts)
			type->flags->opts = dummy_tracer_opt;
847
848
849
	if (!type->wait_pipe)
		type->wait_pipe = default_wait_pipe;

850

Steven Rostedt's avatar
Steven Rostedt committed
851
#ifdef CONFIG_FTRACE_STARTUP_TEST
852
	if (type->selftest && !tracing_selftest_disabled) {
Steven Rostedt's avatar
Steven Rostedt committed
853
854
		struct tracer *saved_tracer = current_trace;
		struct trace_array *tr = &global_trace;
855

Steven Rostedt's avatar
Steven Rostedt committed
856
857
858
859
860
861
862
		/*
		 * Run a selftest on this tracer.
		 * Here we reset the trace buffer, and set the current
		 * tracer to be this tracer. The tracer can then run some
		 * internal tracing to verify that everything is in order.
		 * If we fail, we do not register this tracer.
		 */
863
		tracing_reset_online_cpus(tr);
Ingo Molnar's avatar
Ingo Molnar committed
864

Steven Rostedt's avatar
Steven Rostedt committed
865
		current_trace = type;
866

867
868
869
870
871
872
873
		if (type->use_max_tr) {
			/* If we expanded the buffers, make sure the max is expanded too */
			if (ring_buffer_expanded)
				ring_buffer_resize(max_tr.buffer, trace_buf_size,
						   RING_BUFFER_ALL_CPUS);
			type->allocated_snapshot = true;
		}
874

Steven Rostedt's avatar
Steven Rostedt committed
875
876
877
878
879
880
881
		/* the test is responsible for initializing and enabling */
		pr_info("Testing tracer %s: ", type->name);
		ret = type->selftest(type, tr);
		/* the test is responsible for resetting too */
		current_trace = saved_tracer;
		if (ret) {
			printk(KERN_CONT "FAILED!\n");
882
883
			/* Add the warning after printing 'FAILED' */
			WARN_ON(1);
Steven Rostedt's avatar
Steven Rostedt committed
884
885
			goto out;
		}
Steven Rostedt's avatar
Steven Rostedt committed
886
		/* Only reset on passing, to avoid touching corrupted buffers */
887
		tracing_reset_online_cpus(tr);
Ingo Molnar's avatar
Ingo Molnar committed
888

889
890
891
892
893
894
895
896
		if (type->use_max_tr) {
			type->allocated_snapshot = false;

			/* Shrink the max buffer again */
			if (ring_buffer_expanded)
				ring_buffer_resize(max_tr.buffer, 1,
						   RING_BUFFER_ALL_CPUS);
		}
897

Steven Rostedt's avatar
Steven Rostedt committed
898
899
900
901
		printk(KERN_CONT "PASSED\n");
	}
#endif

902
903
	type->next = trace_types;
	trace_types = type;
Steven Rostedt's avatar
Steven Rostedt committed
904

905
 out:
906
	tracing_selftest_running = false;
907
908
	mutex_unlock(&trace_types_lock);

Steven Rostedt's avatar
Steven Rostedt committed
909
910
911
	if (ret || !default_bootup_tracer)
		goto out_unlock;

Li Zefan's avatar
Li Zefan committed
912
	if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
Steven Rostedt's avatar
Steven Rostedt committed
913
914
915
916
917
918
919
920
		goto out_unlock;

	printk(KERN_INFO "Starting tracer '%s'\n", type->name);
	/* Do we want this tracer to start on bootup? */
	tracing_set_tracer(type->name);
	default_bootup_tracer = NULL;
	/* disable other selftests, since this will break it. */
	tracing_selftest_disabled = 1;
921
#ifdef CONFIG_FTRACE_STARTUP_TEST
Steven Rostedt's avatar
Steven Rostedt committed
922
923
	printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
	       type->name);
924
925
#endif

Steven Rostedt's avatar
Steven Rostedt committed
926
 out_unlock:
927
928
929
	return ret;
}

930
931
932
933
void tracing_reset(struct trace_array *tr, int cpu)
{
	struct ring_buffer *buffer = tr->buffer;

934
935
936
	if (!buffer)
		return;

937
938
939
940
	ring_buffer_record_disable(buffer);

	/* Make sure all commits have finished */
	synchronize_sched();
941
	ring_buffer_reset_cpu(buffer, cpu);
942
943
944
945

	ring_buffer_record_enable(buffer);
}

946
947
void tracing_reset_online_cpus(struct trace_array *tr)
{
948
	struct ring_buffer *buffer = tr->buffer;
949
950
	int cpu;

951
952
953
	if (!buffer)
		return;

954
955
956
957
958
	ring_buffer_record_disable(buffer);

	/* Make sure all commits have finished */
	synchronize_sched();

959
960
961
	tr->time_start = ftrace_now(tr->cpu);

	for_each_online_cpu(cpu)
962
		ring_buffer_reset_cpu(buffer, cpu);
963
964

	ring_buffer_record_enable(buffer);
965
966
}

967
968
969
970
971
972
973
974
975
976
void tracing_reset_current(int cpu)
{
	tracing_reset(&global_trace, cpu);
}

void tracing_reset_current_online_cpus(void)
{
	tracing_reset_online_cpus(&global_trace);
}

977
#define SAVED_CMDLINES 128
978
#define NO_CMDLINE_MAP UINT_MAX
979
980
981
982
static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
static int cmdline_idx;
983
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
984
985

/* temporary disable recording */
986
static atomic_t trace_record_cmdline_disabled __read_mostly;
987
988
989

static void trace_init_cmdlines(void)
{
990
991
	memset(&map_pid_to_cmdline, NO_CMDLINE_MAP, sizeof(map_pid_to_cmdline));
	memset(&map_cmdline_to_pid, NO_CMDLINE_MAP, sizeof(map_cmdline_to_pid));
992
993
994
	cmdline_idx = 0;
}

995
996
997
998
999
int is_tracing_stopped(void)
{
	return trace_stop_count;
}

1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
/**
 * ftrace_off_permanent - disable all ftrace code permanently
 *
 * This should only be called when a serious anomally has
 * been detected.  This will turn off the function tracing,
 * ring buffers, and other tracing utilites. It takes no
 * locks and can be called from any context.
 */
void ftrace_off_permanent(void)
{
	tracing_disabled = 1;
	ftrace_stop();
	tracing_off_permanent();
}

1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
/**
 * tracing_start - quick start of the tracer
 *
 * If tracing is enabled but was stopped by tracing_stop,
 * this will start the tracer back up.
 */
void tracing_start(void)
{
	struct ring_buffer *buffer;
	unsigned long flags;

	if (tracing_disabled)
		return;

1029
	raw_spin_lock_irqsave(&tracing_start_lock, flags);
1030
1031
1032
1033
1034
1035
	if (--trace_stop_count) {
		if (trace_stop_count < 0) {
			/* Someone screwed up their debugging */
			WARN_ON_ONCE(1);
			trace_stop_count = 0;
		}
1036
1037
1038
		goto out;
	}

1039
1040
	/* Prevent the buffers from switching */
	arch_spin_lock(&ftrace_max_lock);
1041
1042
1043
1044
1045
1046
1047
1048
1049

	buffer = global_trace.buffer;
	if (buffer)
		ring_buffer_record_enable(buffer);

	buffer = max_tr.buffer;
	if (buffer)
		ring_buffer_record_enable(buffer);

1050
1051
	arch_spin_unlock(&ftrace_max_lock);

1052
1053
	ftrace_start();
 out:
1054
	raw_spin_unlock_irqrestore(&tracing_start_lock, flags);
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
}

/**
 * tracing_stop - quick stop of the tracer
 *
 * Light weight way to stop tracing. Use in conjunction with
 * tracing_start.
 */
void tracing_stop(void)
{
	struct ring_buffer *buffer;
	unsigned long flags;

	ftrace_stop();
1069
	raw_spin_lock_irqsave(&tracing_start_lock, flags);
1070
1071
1072
	if (trace_stop_count++)
		goto out;

1073
1074
1075
	/* Prevent the buffers from switching */
	arch_spin_lock(&ftrace_max_lock);

1076
1077
1078
1079
1080
1081
1082
1083
	buffer = global_trace.buffer;
	if (buffer)
		ring_buffer_record_disable(buffer);

	buffer = max_tr.buffer;
	if (buffer)
		ring_buffer_record_disable(buffer);

1084
1085
	arch_spin_unlock(&ftrace_max_lock);

1086
 out:
1087
	raw_spin_unlock_irqrestore(&tracing_start_lock, flags);
1088
1089
}

Ingo Molnar's avatar
Ingo Molnar committed
1090
void trace_stop_cmdline_recording(void);
1091

Ingo Molnar's avatar
Ingo Molnar committed
1092
static void trace_save_cmdline(struct task_struct *tsk)
1093
{
1094
	unsigned pid, idx;
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104

	if (!tsk->pid || unlikely(tsk->pid > PID_MAX_DEFAULT))
		return;

	/*
	 * It's not the end of the world if we don't get
	 * the lock, but we also don't want to spin
	 * nor do we want to disable interrupts,
	 * so if we miss here, then better luck next time.
	 */
1105
	if (!arch_spin_trylock(&trace_cmdline_lock))
1106
1107
1108
		return;

	idx = map_pid_to_cmdline[tsk->pid];
1109
	if (idx == NO_CMDLINE_MAP) {
1110
1111
		idx = (cmdline_idx + 1) % SAVED_CMDLINES;

1112
1113
1114
1115
1116
1117
1118
1119
1120
		/*
		 * Check whether the cmdline buffer at idx has a pid
		 * mapped. We are going to overwrite that entry so we
		 * need to clear the map_pid_to_cmdline. Otherwise we
		 * would read the new comm for the old pid.
		 */
		pid = map_cmdline_to_pid[idx];
		if (pid != NO_CMDLINE_MAP)
			map_pid_to_cmdline[pid] = NO_CMDLINE_MAP;
1121

1122
		map_cmdline_to_pid[idx] = tsk->pid;
1123
1124
1125
1126
1127
1128
1129
		map_pid_to_cmdline[tsk->pid] = idx;

		cmdline_idx = idx;
	}

	memcpy(&saved_cmdlines[idx], tsk->comm, TASK_COMM_LEN);

1130
	arch_spin_unlock(&trace_cmdline_lock);
1131
1132
}

1133
void trace_find_cmdline(int pid, char comm[])
1134
1135
1136
{
	unsigned map;

1137
1138
1139
1140
	if (!pid) {
		strcpy(comm, "<idle>");
		return;
	}
1141

1142
1143
1144
1145
1146
	if (WARN_ON_ONCE(pid < 0)) {
		strcpy(comm, "<XXX>");
		return;
	}

1147
1148
1149
1150
	if (pid > PID_MAX_DEFAULT) {
		strcpy(comm, "<...>");
		return;
	}
1151

1152
	preempt_disable();
1153
	arch_spin_lock(&trace_cmdline_lock);
1154
	map = map_pid_to_cmdline[pid];
1155
1156
1157
1158
	if (map != NO_CMDLINE_MAP)
		strcpy(comm, saved_cmdlines[map]);
	else
		strcpy(comm, "<...>");
1159

1160
	arch_spin_unlock(&trace_cmdline_lock);
1161
	preempt_enable();
1162
1163
}

Ingo Molnar's avatar
Ingo Molnar committed
1164
void tracing_record_cmdline(struct task_struct *tsk)
1165
{
1166
	if (atomic_read(&trace_record_cmdline_disabled) || !tracing_is_on())
1167
1168
		return;

1169
1170
1171
1172
1173
	if (!__this_cpu_read(trace_cmdline_save))
		return;

	__this_cpu_write(trace_cmdline_save, false);

1174
1175
1176
	trace_save_cmdline(tsk);
}

1177
void
1178
1179
tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
			     int pc)
1180
1181
1182
{
	struct task_struct *tsk = current;

1183
1184
1185
	entry->preempt_count		= pc & 0xff;
	entry->pid			= (tsk) ? tsk->pid : 0;
	entry->flags =
1186
#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
1187
		(irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
1188
1189
1190
#else
		TRACE_FLAG_IRQS_NOSUPPORT |
#endif
1191
1192
1193
1194
		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
		(need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
}
1195
EXPORT_SYMBOL_GPL(tracing_generic_entry_update);
1196

1197
1198
1199
1200
1201
struct ring_buffer_event *
trace_buffer_lock_reserve(struct ring_buffer *buffer,
			  int type,
			  unsigned long len,
			  unsigned long flags, int pc)
1202
1203
1204
{
	struct ring_buffer_event *event;

1205
	event = ring_buffer_lock_reserve(buffer, len);
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
	if (event != NULL) {
		struct trace_entry *ent = ring_buffer_event_data(event);

		tracing_generic_entry_update(ent, flags, pc);
		ent->type = type;
	}

	return event;
}

1216
1217
1218
1219
void
__buffer_unlock_commit(struct ring_buffer *buffer, struct ring_buffer_event *event)
{
	__this_cpu_write(trace_cmdline_save, true);
1220
1221
1222
1223
1224
	if (trace_wakeup_needed) {
		trace_wakeup_needed = false;
		/* irq_work_queue() supplies it's own memory barriers */
		irq_work_queue(&trace_work_wakeup);
	}
1225
1226
1227
	ring_buffer_unlock_commit(buffer, event);
}

1228
1229
1230
static inline void
__trace_buffer_unlock_commit(struct ring_buffer *buffer,
			     struct ring_buffer_event *event,
1231
			     unsigned long flags, int pc)
1232
{
1233
	__buffer_unlock_commit(buffer, event);
1234

1235
1236
	ftrace_trace_stack(buffer, flags, 6, pc);
	ftrace_trace_userstack(buffer, flags, pc);
1237
1238
}

1239
1240
1241
void trace_buffer_unlock_commit(struct ring_buffer *buffer,
				struct ring_buffer_event *event,
				unsigned long flags, int pc)
1242
{
1243
	__trace_buffer_unlock_commit(buffer, event, flags, pc);
1244
}
1245
EXPORT_SYMBOL_GPL(trace_buffer_unlock_commit);
1246

1247
struct ring_buffer_event *
1248
1249
trace_current_buffer_lock_reserve(struct ring_buffer **current_rb,
				  int type, unsigned long len,
1250
1251
				  unsigned long flags, int pc)
{
1252
1253
	*current_rb = global_trace.buffer;
	return trace_buffer_lock_reserve(*current_rb,
1254
1255
					 type, len, flags, pc);
}
1256
EXPORT_SYMBOL_GPL(trace_current_buffer_lock_reserve);
1257

1258
1259
void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
					struct ring_buffer_event *event,
1260
1261
					unsigned long flags, int pc)
{
1262
	__trace_buffer_unlock_commit(buffer, event, flags, pc);
1263
}
1264
EXPORT_SYMBOL_GPL(trace_current_buffer_unlock_commit);
1265

1266
1267
1268
1269
void trace_buffer_unlock_commit_regs(struct ring_buffer *buffer,
				     struct ring_buffer_event *event,
				     unsigned long flags, int pc,
				     struct pt_regs *regs)
1270
{
Steven Rostedt's avatar