trace.c source code [linux/kernel/trace/trace.c]

1	// SPDX-License-Identifier: GPL-2.0
2	/*
3	* ring buffer based function tracer
4	*
5	* Copyright (C) 2007-2012 Steven Rostedt <srostedt@redhat.com>
6	* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
7	*
8	* Originally taken from the RT patch by:
9	* Arnaldo Carvalho de Melo <acme@redhat.com>
10	*
11	* Based on code from the latency_tracer, that is:
12	* Copyright (C) 2004-2006 Ingo Molnar
13	* Copyright (C) 2004 Nadia Yvette Chambers
14	*/
15	#include <linux/ring_buffer.h>
16	#include <generated/utsrelease.h>
17	#include <linux/stacktrace.h>
18	#include <linux/writeback.h>
19	#include <linux/kallsyms.h>
20	#include <linux/seq_file.h>
21	#include <linux/notifier.h>
22	#include <linux/irqflags.h>
23	#include <linux/debugfs.h>
24	#include <linux/tracefs.h>
25	#include <linux/pagemap.h>
26	#include <linux/hardirq.h>
27	#include <linux/linkage.h>
28	#include <linux/uaccess.h>
29	#include <linux/vmalloc.h>
30	#include <linux/ftrace.h>
31	#include <linux/module.h>
32	#include <linux/percpu.h>
33	#include <linux/splice.h>
34	#include <linux/kdebug.h>
35	#include <linux/string.h>
36	#include <linux/mount.h>
37	#include <linux/rwsem.h>
38	#include <linux/slab.h>
39	#include <linux/ctype.h>
40	#include <linux/init.h>
41	#include <linux/poll.h>
42	#include <linux/nmi.h>
43	#include <linux/fs.h>
44	#include <linux/trace.h>
45	#include <linux/sched/clock.h>
46	#include <linux/sched/rt.h>
47
48	#include "trace.h"
49	#include "trace_output.h"
50
51	/*
52	* On boot up, the ring buffer is set to the minimum size, so that
53	* we do not waste memory on systems that are not using tracing.
54	*/
55	bool ring_buffer_expanded;
56
57	/*
58	* We need to change this state when a selftest is running.
59	* A selftest will lurk into the ring-buffer to count the
60	* entries inserted during the selftest although some concurrent
61	* insertions into the ring-buffer such as trace_printk could occurred
62	* at the same time, giving false positive or negative results.
63	*/
64	static bool __read_mostly tracing_selftest_running;
65
66	/*
67	* If a tracer is running, we do not want to run SELFTEST.
68	*/
69	bool __read_mostly tracing_selftest_disabled;
70
71	/ Pipe tracepoints to printk /
72	struct trace_iterator *tracepoint_print_iter;
73	int tracepoint_printk;
74	static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key);
75
76	/ For tracers that don't implement custom flags /
77	static struct tracer_opt dummy_tracer_opt[] = {
78	{ }
79	};
80
81	static int
82	dummy_set_flag(struct trace_array tr, u32 old_flags, u32 bit, int* set)
83	{
84	return `0`;
85	}
86
87	/*
88	* To prevent the comm cache from being overwritten when no
89	* tracing is active, only save the comm when a trace event
90	* occurred.
91	*/
92	static DEFINE_PER_CPU(bool, trace_taskinfo_save);
93
94	/*
95	* Kill all tracing for good (never come back).
96	* It is initialized to 1 but will turn to zero if the initialization
97	* of the tracer is successful. But that is the only place that sets
98	* this back to zero.
99	*/
100	static int tracing_disabled = `1`;
101
102	cpumask_var_t __read_mostly tracing_buffer_mask;
103
104	/*
105	* ftrace_dump_on_oops - variable to dump ftrace buffer on oops
106	*
107	* If there is an oops (or kernel panic) and the ftrace_dump_on_oops
108	* is set, then ftrace_dump is called. This will output the contents
109	* of the ftrace buffers to the console. This is very useful for
110	* capturing traces that lead to crashes and outputing it to a
111	* serial console.
112	*
113	* It is default off, but you can enable it with either specifying
114	* "ftrace_dump_on_oops" in the kernel command line, or setting
115	* /proc/sys/kernel/ftrace_dump_on_oops
116	* Set 1 if you want to dump buffers of all CPUs
117	* Set 2 if you want to dump the buffer of the CPU that triggered oops
118	*/
119
120	enum ftrace_dump_mode ftrace_dump_on_oops;
121
122	/ When set, tracing will stop when a WARN() is hit /*
123	int __disable_trace_on_warning;
124
125	#ifdef CONFIG_TRACE_EVAL_MAP_FILE
126	/ Map of enums to their values, for "eval_map" file /
127	struct trace_eval_map_head {
128	struct module *mod;
129	unsigned long length;
130	};
131
132	union trace_eval_map_item;
133
134	struct trace_eval_map_tail {
135	/*
136	* "end" is first and points to NULL as it must be different
137	* than "mod" or "eval_string"
138	*/
139	union trace_eval_map_item *next;
140	const char end; /* points to NULL /
141	};
142
143	static DEFINE_MUTEX(trace_eval_mutex);
144
145	/*
146	* The trace_eval_maps are saved in an array with two extra elements,
147	* one at the beginning, and one at the end. The beginning item contains
148	* the count of the saved maps (head.length), and the module they
149	* belong to if not built in (head.mod). The ending item contains a
150	* pointer to the next array of saved eval_map items.
151	*/
152	union trace_eval_map_item {
153	struct trace_eval_map map;
154	struct trace_eval_map_head head;
155	struct trace_eval_map_tail tail;
156	};
157
158	static union trace_eval_map_item *trace_eval_maps;
159	#endif /* CONFIG_TRACE_EVAL_MAP_FILE */
160
161	static int tracing_set_tracer(struct trace_array tr, const* char *buf);
162
163	#define MAX_TRACER_SIZE 100
164	static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
165	static char *default_bootup_tracer;
166
167	static bool allocate_snapshot;
168
169	static int __init set_cmdline_ftrace(char *str)
170	{
171	strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
172	default_bootup_tracer = bootup_tracer_buf;
173	/ We are using ftrace early, expand it /
174	ring_buffer_expanded = true;
175	return `1`;
176	}
177	__setup("ftrace=", set_cmdline_ftrace);
178
179	static int __init set_ftrace_dump_on_oops(char *str)
180	{
181	if (str++ != `'='` \|\| !str) {
182	ftrace_dump_on_oops = DUMP_ALL;
183	return `1`;
184	}
185
186	if (!strcmp("orig_cpu", str)) {
187	ftrace_dump_on_oops = DUMP_ORIG;
188	return `1`;
189	}
190
191	return `0`;
192	}
193	__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
194
195	static int __init stop_trace_on_warning(char *str)
196	{
197	if ((strcmp(str, "=0") != `0` && strcmp(str, "=off") != `0`))
198	__disable_trace_on_warning = `1`;
199	return `1`;
200	}
201	__setup("traceoff_on_warning", stop_trace_on_warning);
202
203	static int __init boot_alloc_snapshot(char *str)
204	{
205	allocate_snapshot = true;
206	/ We also need the main ring buffer expanded /
207	ring_buffer_expanded = true;
208	return `1`;
209	}
210	__setup("alloc_snapshot", boot_alloc_snapshot);
211
212
213	static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
214
215	static int __init set_trace_boot_options(char *str)
216	{
217	strlcpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
218	return `0`;
219	}
220	__setup("trace_options=", set_trace_boot_options);
221
222	static char trace_boot_clock_buf[MAX_TRACER_SIZE] __initdata;
223	static char *trace_boot_clock __initdata;
224
225	static int __init set_trace_boot_clock(char *str)
226	{
227	strlcpy(trace_boot_clock_buf, str, MAX_TRACER_SIZE);
228	trace_boot_clock = trace_boot_clock_buf;
229	return `0`;
230	}
231	__setup("trace_clock=", set_trace_boot_clock);
232
233	static int __init set_tracepoint_printk(char *str)
234	{
235	if ((strcmp(str, "=0") != `0` && strcmp(str, "=off") != `0`))
236	tracepoint_printk = `1`;
237	return `1`;
238	}
239	__setup("tp_printk", set_tracepoint_printk);
240
241	unsigned long long ns2usecs(u64 nsec)
242	{
243	nsec += `500`;
244	do_div(nsec, `1000`);
245	return nsec;
246	}
247
248	/ trace_flags holds trace_options default values /
249	#define TRACE_DEFAULT_FLAGS \
250	(FUNCTION_DEFAULT_FLAGS \| \
251	TRACE_ITER_PRINT_PARENT \| TRACE_ITER_PRINTK \| \
252	TRACE_ITER_ANNOTATE \| TRACE_ITER_CONTEXT_INFO \| \
253	TRACE_ITER_RECORD_CMD \| TRACE_ITER_OVERWRITE \| \
254	TRACE_ITER_IRQ_INFO \| TRACE_ITER_MARKERS)
255
256	/ trace_options that are only supported by global_trace /
257	#define TOP_LEVEL_TRACE_FLAGS (TRACE_ITER_PRINTK \| \
258	TRACE_ITER_PRINTK_MSGONLY \| TRACE_ITER_RECORD_CMD)
259
260	/ trace_flags that are default zero for instances /
261	#define ZEROED_TRACE_FLAGS \
262	(TRACE_ITER_EVENT_FORK \| TRACE_ITER_FUNC_FORK)
263
264	/*
265	* The global_trace is the descriptor that holds the top-level tracing
266	* buffers for the live tracing.
267	*/
268	static struct trace_array global_trace = {
269	.trace_flags = TRACE_DEFAULT_FLAGS,
270	};
271
272	LIST_HEAD(ftrace_trace_arrays);
273
274	int trace_array_get(struct trace_array *this_tr)
275	{
276	struct trace_array *tr;
277	int ret = -ENODEV;
278
279	mutex_lock(&trace_types_lock);
280	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
281	if (tr == this_tr) {
282	tr->ref++;
283	ret = `0`;
284	break;
285	}
286	}
287	mutex_unlock(&trace_types_lock);
288
289	return ret;
290	}
291
292	static void __trace_array_put(struct trace_array *this_tr)
293	{
294	WARN_ON(!this_tr->ref);
295	this_tr->ref--;
296	}
297
298	void trace_array_put(struct trace_array *this_tr)
299	{
300	mutex_lock(&trace_types_lock);
301	__trace_array_put(this_tr);
302	mutex_unlock(&trace_types_lock);
303	}
304
305	int call_filter_check_discard(struct trace_event_call call, void* *rec,
306	struct ring_buffer *buffer,
307	struct ring_buffer_event *event)
308	{
309	if (unlikely(call->flags & TRACE_EVENT_FL_FILTERED) &&
310	!filter_match_preds(call->filter, rec)) {
311	__trace_event_discard_commit(buffer, event);
312	return `1`;
313	}
314
315	return `0`;
316	}
317
318	void trace_free_pid_list(struct trace_pid_list *pid_list)
319	{
320	vfree(pid_list->pids);
321	kfree(pid_list);
322	}
323
324	/**
325	* trace_find_filtered_pid - check if a pid exists in a filtered_pid list
326	* @filtered_pids: The list of pids to check
327	* @search_pid: The PID to find in @filtered_pids
328	*
329	* Returns true if @search_pid is fonud in @filtered_pids, and false otherwis.
330	*/
331	bool
332	trace_find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_pid)
333	{
334	/*
335	* If pid_max changed after filtered_pids was created, we
336	* by default ignore all pids greater than the previous pid_max.
337	*/
338	if (search_pid >= filtered_pids->pid_max)
339	return false;
340
341	return test_bit(search_pid, filtered_pids->pids);
342	}
343
344	/**
345	* trace_ignore_this_task - should a task be ignored for tracing
346	* @filtered_pids: The list of pids to check
347	* @task: The task that should be ignored if not filtered
348	*
349	* Checks if @task should be traced or not from @filtered_pids.
350	* Returns true if @task should NOT be traced.
351	* Returns false if @task should be traced.
352	*/
353	bool
354	trace_ignore_this_task(struct trace_pid_list filtered_pids, struct* task_struct *task)
355	{
356	/*
357	* Return false, because if filtered_pids does not exist,
358	* all pids are good to trace.
359	*/
360	if (!filtered_pids)
361	return false;
362
363	return !trace_find_filtered_pid(filtered_pids, task->pid);
364	}
365
366	/**
367	* trace_pid_filter_add_remove_task - Add or remove a task from a pid_list
368	* @pid_list: The list to modify
369	* @self: The current task for fork or NULL for exit
370	* @task: The task to add or remove
371	*
372	* If adding a task, if @self is defined, the task is only added if @self
373	* is also included in @pid_list. This happens on fork and tasks should
374	* only be added when the parent is listed. If @self is NULL, then the
375	* @task pid will be removed from the list, which would happen on exit
376	* of a task.
377	*/
378	void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
379	struct task_struct *self,
380	struct task_struct *task)
381	{
382	if (!pid_list)
383	return;
384
385	/ For forks, we only add if the forking task is listed /
386	if (self) {
387	if (!trace_find_filtered_pid(pid_list, self->pid))
388	return;
389	}
390
391	/ Sorry, but we don't support pid_max changing after setting /
392	if (task->pid >= pid_list->pid_max)
393	return;
394
395	/ "self" is set for forks, and NULL for exits /
396	if (self)
397	set_bit(task->pid, pid_list->pids);
398	else
399	clear_bit(task->pid, pid_list->pids);
400	}
401
402	/**
403	* trace_pid_next - Used for seq_file to get to the next pid of a pid_list
404	* @pid_list: The pid list to show
405	* @v: The last pid that was shown (+1 the actual pid to let zero be displayed)
406	* @pos: The position of the file
407	*
408	* This is used by the seq_file "next" operation to iterate the pids
409	* listed in a trace_pid_list structure.
410	*
411	* Returns the pid+1 as we want to display pid of zero, but NULL would
412	* stop the iteration.
413	*/
414	void trace_pid_next(struct* trace_pid_list pid_list, void* v, loff_t pos)
415	{
416	unsigned long pid = (unsigned long)v;
417
418	(*pos)++;
419
420	/ pid already is +1 of the actual prevous bit /
421	pid = find_next_bit(pid_list->pids, pid_list->pid_max, pid);
422
423	/ Return pid + 1 to allow zero to be represented /
424	if (pid < pid_list->pid_max)
425	return (void *)(pid + `1`);
426
427	return NULL;
428	}
429
430	/**
431	* trace_pid_start - Used for seq_file to start reading pid lists
432	* @pid_list: The pid list to show
433	* @pos: The position of the file
434	*
435	* This is used by seq_file "start" operation to start the iteration
436	* of listing pids.
437	*
438	* Returns the pid+1 as we want to display pid of zero, but NULL would
439	* stop the iteration.
440	*/
441	void trace_pid_start(struct* trace_pid_list pid_list, loff_t pos)
442	{
443	unsigned long pid;
444	loff_t l = `0`;
445
446	pid = find_first_bit(pid_list->pids, pid_list->pid_max);
447	if (pid >= pid_list->pid_max)
448	return NULL;
449
450	/ Return pid + 1 so that zero can be the exit value /
451	for (pid++; pid && l < *pos;
452	pid = (unsigned long)trace_pid_next(pid_list, (void *)pid, &l))
453	;
454	return (void *)pid;
455	}
456
457	/**
458	* trace_pid_show - show the current pid in seq_file processing
459	* @m: The seq_file structure to write into
460	* @v: A void pointer of the pid (+1) value to display
461	*
462	* Can be directly used by seq_file operations to display the current
463	* pid value.
464	*/
465	int trace_pid_show(struct seq_file m, void* *v)
466	{
467	unsigned long pid = (unsigned long)v - `1`;
468
469	seq_printf(m, "%lu\n", pid);
470	return `0`;
471	}
472
473	/ 128 should be much more than enough /
474	#define PID_BUF_SIZE 127
475
476	int trace_pid_write(struct trace_pid_list *filtered_pids,
477	struct trace_pid_list **new_pid_list,
478	const char __user *ubuf, size_t cnt)
479	{
480	struct trace_pid_list *pid_list;
481	struct trace_parser parser;
482	unsigned long val;
483	int nr_pids = `0`;
484	ssize_t read = `0`;
485	ssize_t ret = `0`;
486	loff_t pos;
487	pid_t pid;
488
489	if (trace_parser_get_init(&parser, PID_BUF_SIZE + `1`))
490	return -ENOMEM;
491
492	/*
493	* Always recreate a new array. The write is an all or nothing
494	* operation. Always create a new array when adding new pids by
495	* the user. If the operation fails, then the current list is
496	* not modified.
497	*/
498	pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
499	if (!pid_list)
500	return -ENOMEM;
501
502	pid_list->pid_max = READ_ONCE(pid_max);
503
504	/ Only truncating will shrink pid_max /
505	if (filtered_pids && filtered_pids->pid_max > pid_list->pid_max)
506	pid_list->pid_max = filtered_pids->pid_max;
507
508	pid_list->pids = vzalloc((pid_list->pid_max + `7`) >> `3`);
509	if (!pid_list->pids) {
510	kfree(pid_list);
511	return -ENOMEM;
512	}
513
514	if (filtered_pids) {
515	/ copy the current bits to the new max /
516	for_each_set_bit(pid, filtered_pids->pids,
517	filtered_pids->pid_max) {
518	set_bit(pid, pid_list->pids);
519	nr_pids++;
520	}
521	}
522
523	while (cnt > `0`) {
524
525	pos = `0`;
526
527	ret = trace_get_user(&parser, ubuf, cnt, &pos);
528	if (ret < `0` \|\| !trace_parser_loaded(&parser))
529	break;
530
531	read += ret;
532	ubuf += ret;
533	cnt -= ret;
534
535	ret = -EINVAL;
536	if (kstrtoul(parser.buffer, `0`, &val))
537	break;
538	if (val >= pid_list->pid_max)
539	break;
540
541	pid = (pid_t)val;
542
543	set_bit(pid, pid_list->pids);
544	nr_pids++;
545
546	trace_parser_clear(&parser);
547	ret = `0`;
548	}
549	trace_parser_put(&parser);
550
551	if (ret < `0`) {
552	trace_free_pid_list(pid_list);
553	return ret;
554	}
555
556	if (!nr_pids) {
557	/ Cleared the list of pids /
558	trace_free_pid_list(pid_list);
559	read = ret;
560	pid_list = NULL;
561	}
562
563	*new_pid_list = pid_list;
564
565	return read;
566	}
567
568	static u64 buffer_ftrace_now(struct trace_buffer buf, int* cpu)
569	{
570	u64 ts;
571
572	/ Early boot up does not have a buffer yet /
573	if (!buf->buffer)
574	return trace_clock_local();
575
576	ts = ring_buffer_time_stamp(buf->buffer, cpu);
577	ring_buffer_normalize_time_stamp(buf->buffer, cpu, &ts);
578
579	return ts;
580	}
581
582	u64 ftrace_now(int cpu)
583	{
584	return buffer_ftrace_now(&global_trace.trace_buffer, cpu);
585	}
586
587	/**
588	* tracing_is_enabled - Show if global_trace has been disabled
589	*
590	* Shows if the global trace has been enabled or not. It uses the
591	* mirror flag "buffer_disabled" to be used in fast paths such as for
592	* the irqsoff tracer. But it may be inaccurate due to races. If you
593	* need to know the accurate state, use tracing_is_on() which is a little
594	* slower, but accurate.
595	*/
596	int tracing_is_enabled(void)
597	{
598	/*
599	* For quick access (irqsoff uses this in fast path), just
600	* return the mirror variable of the state of the ring buffer.
601	* It's a little racy, but we don't really care.
602	*/
603	smp_rmb();
604	return !global_trace.buffer_disabled;
605	}
606
607	/*
608	* trace_buf_size is the size in bytes that is allocated
609	* for a buffer. Note, the number of bytes is always rounded
610	* to page size.
611	*
612	* This number is purposely set to a low number of 16384.
613	* If the dump on oops happens, it will be much appreciated
614	* to not have to wait for all that output. Anyway this can be
615	* boot time and run time configurable.
616	*/
617	#define TRACE_BUF_SIZE_DEFAULT 1441792UL /* 16384 * 88 (sizeof(entry)) */
618
619	static unsigned long trace_buf_size = TRACE_BUF_SIZE_DEFAULT;
620
621	/ trace_types holds a link list of available tracers. /
622	static struct tracer *trace_types __read_mostly;
623
624	/*
625	* trace_types_lock is used to protect the trace_types list.
626	*/
627	DEFINE_MUTEX(trace_types_lock);
628
629	/*
630	* serialize the access of the ring buffer
631	*
632	* ring buffer serializes readers, but it is low level protection.
633	* The validity of the events (which returns by ring_buffer_peek() ..etc)
634	* are not protected by ring buffer.
635	*
636	* The content of events may become garbage if we allow other process consumes
637	* these events concurrently:
638	* A) the page of the consumed events may become a normal page
639	* (not reader page) in ring buffer, and this page will be rewrited
640	* by events producer.
641	* B) The page of the consumed events may become a page for splice_read,
642	* and this page will be returned to system.
643	*
644	* These primitives allow multi process access to different cpu ring buffer
645	* concurrently.
646	*
647	* These primitives don't distinguish read-only and read-consume access.
648	* Multi read-only access are also serialized.
649	*/
650
651	#ifdef CONFIG_SMP
652	static DECLARE_RWSEM(all_cpu_access_lock);
653	static DEFINE_PER_CPU(struct mutex, cpu_access_lock);
654
655	static inline void trace_access_lock(int cpu)
656	{
657	if (cpu == RING_BUFFER_ALL_CPUS) {
658	/ gain it for accessing the whole ring buffer. /
659	down_write(&all_cpu_access_lock);
660	} else {
661	/ gain it for accessing a cpu ring buffer. /
662
663	/ Firstly block other trace_access_lock(RING_BUFFER_ALL_CPUS). /
664	down_read(&all_cpu_access_lock);
665
666	/ Secondly block other access to this @cpu ring buffer. /
667	mutex_lock(&per_cpu(cpu_access_lock, cpu));
668	}
669	}
670
671	static inline void trace_access_unlock(int cpu)
672	{
673	if (cpu == RING_BUFFER_ALL_CPUS) {
674	up_write(&all_cpu_access_lock);
675	} else {
676	mutex_unlock(&per_cpu(cpu_access_lock, cpu));
677	up_read(&all_cpu_access_lock);
678	}
679	}
680
681	static inline void trace_access_lock_init(void)
682	{
683	int cpu;
684
685	for_each_possible_cpu(cpu)
686	mutex_init(&per_cpu(cpu_access_lock, cpu));
687	}
688
689	#else
690
691	static DEFINE_MUTEX(access_lock);
692
693	static inline void trace_access_lock(int cpu)
694	{
695	(void)cpu;
696	mutex_lock(&access_lock);
697	}
698
699	static inline void trace_access_unlock(int cpu)
700	{
701	(void)cpu;
702	mutex_unlock(&access_lock);
703	}
704
705	static inline void trace_access_lock_init(void)
706	{
707	}
708
709	#endif
710
711	#ifdef CONFIG_STACKTRACE
712	static void __ftrace_trace_stack(struct ring_buffer *buffer,
713	unsigned long flags,
714	int skip, int pc, struct pt_regs *regs);
715	static inline void ftrace_trace_stack(struct trace_array *tr,
716	struct ring_buffer *buffer,
717	unsigned long flags,
718	int skip, int pc, struct pt_regs *regs);
719
720	#else
721	static inline void __ftrace_trace_stack(struct ring_buffer *buffer,
722	unsigned long flags,
723	int skip, int pc, struct pt_regs *regs)
724	{
725	}
726	static inline void ftrace_trace_stack(struct trace_array *tr,
727	struct ring_buffer *buffer,
728	unsigned long flags,
729	int skip, int pc, struct pt_regs *regs)
730	{
731	}
732
733	#endif
734
735	static __always_inline void
736	trace_event_setup(struct ring_buffer_event *event,
737	int type, unsigned long flags, int pc)
738	{
739	struct trace_entry *ent = ring_buffer_event_data(event);
740
741	tracing_generic_entry_update(ent, flags, pc);
742	ent->type = type;
743	}
744
745	static __always_inline struct ring_buffer_event *
746	__trace_buffer_lock_reserve(struct ring_buffer *buffer,
747	int type,
748	unsigned long len,
749	unsigned long flags, int pc)
750	{
751	struct ring_buffer_event *event;
752
753	event = ring_buffer_lock_reserve(buffer, len);
754	if (event != NULL)
755	trace_event_setup(event, type, flags, pc);
756
757	return event;
758	}
759
760	void tracer_tracing_on(struct trace_array *tr)
761	{
762	if (tr->trace_buffer.buffer)
763	ring_buffer_record_on(tr->trace_buffer.buffer);
764	/*
765	* This flag is looked at when buffers haven't been allocated
766	* yet, or by some tracers (like irqsoff), that just want to
767	* know if the ring buffer has been disabled, but it can handle
768	* races of where it gets disabled but we still do a record.
769	* As the check is in the fast path of the tracers, it is more
770	* important to be fast than accurate.
771	*/
772	tr->buffer_disabled = `0`;
773	/ Make the flag seen by readers /
774	smp_wmb();
775	}
776
777	/**
778	* tracing_on - enable tracing buffers
779	*
780	* This function enables tracing buffers that may have been
781	* disabled with tracing_off.
782	*/
783	void tracing_on(void)
784	{
785	tracer_tracing_on(&global_trace);
786	}
787	EXPORT_SYMBOL_GPL(tracing_on);
788
789
790	static __always_inline void
791	__buffer_unlock_commit(struct ring_buffer buffer, struct* ring_buffer_event *event)
792	{
793	__this_cpu_write(trace_taskinfo_save, true);
794
795	/ If this is the temp buffer, we need to commit fully /
796	if (this_cpu_read(trace_buffered_event) == event) {
797	/ Length is in event->array[0] /
798	ring_buffer_write(buffer, event->array[`0`], &event->array[`1`]);
799	/ Release the temp buffer /
800	this_cpu_dec(trace_buffered_event_cnt);
801	} else
802	ring_buffer_unlock_commit(buffer, event);
803	}
804
805	/**
806	* __trace_puts - write a constant string into the trace buffer.
807	* @ip: The address of the caller
808	* @str: The constant string to write
809	* @size: The size of the string.
810	*/
811	int __trace_puts(unsigned long ip, const char str, int* size)
812	{
813	struct ring_buffer_event *event;
814	struct ring_buffer *buffer;
815	struct print_entry *entry;
816	unsigned long irq_flags;
817	int alloc;
818	int pc;
819
820	if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
821	return `0`;
822
823	pc = preempt_count();
824
825	if (unlikely(tracing_selftest_running \|\| tracing_disabled))
826	return `0`;
827
828	alloc = sizeof(entry) + size + `2`; /* possible \n added /
829
830	local_save_flags(irq_flags);
831	buffer = global_trace.trace_buffer.buffer;
832	event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, alloc,
833	irq_flags, pc);
834	if (!event)
835	return `0`;
836
837	entry = ring_buffer_event_data(event);
838	entry->ip = ip;
839
840	memcpy(&entry->buf, str, size);
841
842	/ Add a newline if necessary /
843	if (entry->buf[size - `1`] != `'\n'`) {
844	entry->buf[size] = `'\n'`;
845	entry->buf[size + `1`] = `'\0'`;
846	} else
847	entry->buf[size] = `'\0'`;
848
849	__buffer_unlock_commit(buffer, event);
850	ftrace_trace_stack(&global_trace, buffer, irq_flags, `4`, pc, NULL);
851
852	return size;
853	}
854	EXPORT_SYMBOL_GPL(__trace_puts);
855
856	/**
857	* __trace_bputs - write the pointer to a constant string into trace buffer
858	* @ip: The address of the caller
859	* @str: The constant string to write to the buffer to
860	*/
861	int __trace_bputs(unsigned long ip, const char *str)
862	{
863	struct ring_buffer_event *event;
864	struct ring_buffer *buffer;
865	struct bputs_entry *entry;
866	unsigned long irq_flags;
867	int size = sizeof(struct bputs_entry);
868	int pc;
869
870	if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
871	return `0`;
872
873	pc = preempt_count();
874
875	if (unlikely(tracing_selftest_running \|\| tracing_disabled))
876	return `0`;
877
878	local_save_flags(irq_flags);
879	buffer = global_trace.trace_buffer.buffer;
880	event = __trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,
881	irq_flags, pc);
882	if (!event)
883	return `0`;
884
885	entry = ring_buffer_event_data(event);
886	entry->ip = ip;
887	entry->str = str;
888
889	__buffer_unlock_commit(buffer, event);
890	ftrace_trace_stack(&global_trace, buffer, irq_flags, `4`, pc, NULL);
891
892	return `1`;
893	}
894	EXPORT_SYMBOL_GPL(__trace_bputs);
895
896	#ifdef CONFIG_TRACER_SNAPSHOT
897	void tracing_snapshot_instance_cond(struct trace_array tr, void* *cond_data)
898	{
899	struct tracer *tracer = tr->current_trace;
900	unsigned long flags;
901
902	if (in_nmi()) {
903	internal_trace_puts("* SNAPSHOT CALLED FROM NMI CONTEXT *\n");
904	internal_trace_puts("* snapshot is being ignored *\n");
905	return;
906	}
907
908	if (!tr->allocated_snapshot) {
909	internal_trace_puts("* SNAPSHOT NOT ALLOCATED *\n");
910	internal_trace_puts("* stopping trace here! *\n");
911	tracing_off();
912	return;
913	}
914
915	/ Note, snapshot can not be used when the tracer uses it /
916	if (tracer->use_max_tr) {
917	internal_trace_puts("* LATENCY TRACER ACTIVE *\n");
918	internal_trace_puts("* Can not use snapshot (sorry) *\n");
919	return;
920	}
921
922	local_irq_save(flags);
923	update_max_tr(tr, current, smp_processor_id(), cond_data);
924	local_irq_restore(flags);
925	}
926
927	void tracing_snapshot_instance(struct trace_array *tr)
928	{
929	tracing_snapshot_instance_cond(tr, NULL);
930	}
931
932	/**
933	* tracing_snapshot - take a snapshot of the current buffer.
934	*
935	* This causes a swap between the snapshot buffer and the current live
936	* tracing buffer. You can use this to take snapshots of the live
937	* trace when some condition is triggered, but continue to trace.
938	*
939	* Note, make sure to allocate the snapshot with either
940	* a tracing_snapshot_alloc(), or by doing it manually
941	* with: echo 1 > /sys/kernel/debug/tracing/snapshot
942	*
943	* If the snapshot buffer is not allocated, it will stop tracing.
944	* Basically making a permanent snapshot.
945	*/
946	void tracing_snapshot(void)
947	{
948	struct trace_array *tr = &global_trace;
949
950	tracing_snapshot_instance(tr);
951	}
952	EXPORT_SYMBOL_GPL(tracing_snapshot);
953
954	/**
955	* tracing_snapshot_cond - conditionally take a snapshot of the current buffer.
956	* @tr: The tracing instance to snapshot
957	* @cond_data: The data to be tested conditionally, and possibly saved
958	*
959	* This is the same as tracing_snapshot() except that the snapshot is
960	* conditional - the snapshot will only happen if the
961	* cond_snapshot.update() implementation receiving the cond_data
962	* returns true, which means that the trace array's cond_snapshot
963	* update() operation used the cond_data to determine whether the
964	* snapshot should be taken, and if it was, presumably saved it along
965	* with the snapshot.
966	*/
967	void tracing_snapshot_cond(struct trace_array tr, void* *cond_data)
968	{
969	tracing_snapshot_instance_cond(tr, cond_data);
970	}
971	EXPORT_SYMBOL_GPL(tracing_snapshot_cond);
972
973	/**
974	* tracing_snapshot_cond_data - get the user data associated with a snapshot
975	* @tr: The tracing instance
976	*
977	* When the user enables a conditional snapshot using
978	* tracing_snapshot_cond_enable(), the user-defined cond_data is saved
979	* with the snapshot. This accessor is used to retrieve it.
980	*
981	* Should not be called from cond_snapshot.update(), since it takes
982	* the tr->max_lock lock, which the code calling
983	* cond_snapshot.update() has already done.
984	*
985	* Returns the cond_data associated with the trace array's snapshot.
986	*/
987	void tracing_cond_snapshot_data(struct* trace_array *tr)
988	{
989	void *cond_data = NULL;
990
991	arch_spin_lock(&tr->max_lock);
992
993	if (tr->cond_snapshot)
994	cond_data = tr->cond_snapshot->cond_data;
995
996	arch_spin_unlock(&tr->max_lock);
997
998	return cond_data;
999	}
1000	EXPORT_SYMBOL_GPL(tracing_cond_snapshot_data);
1001
1002	static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
1003	struct trace_buffer size_buf, int* cpu_id);
1004	static void set_buffer_entries(struct trace_buffer buf, unsigned* long val);
1005
1006	int tracing_alloc_snapshot_instance(struct trace_array *tr)
1007	{
1008	int ret;
1009
1010	if (!tr->allocated_snapshot) {
1011
1012	/ allocate spare buffer /
1013	ret = resize_buffer_duplicate_size(&tr->max_buffer,
1014	&tr->trace_buffer, RING_BUFFER_ALL_CPUS);
1015	if (ret < `0`)
1016	return ret;
1017
1018	tr->allocated_snapshot = true;
1019	}
1020
1021	return `0`;
1022	}
1023
1024	static void free_snapshot(struct trace_array *tr)
1025	{
1026	/*
1027	* We don't free the ring buffer. instead, resize it because
1028	* The max_tr ring buffer has some state (e.g. ring->clock) and
1029	* we want preserve it.
1030	*/
1031	ring_buffer_resize(tr->max_buffer.buffer, `1`, RING_BUFFER_ALL_CPUS);
1032	set_buffer_entries(&tr->max_buffer, `1`);
1033	tracing_reset_online_cpus(&tr->max_buffer);
1034	tr->allocated_snapshot = false;
1035	}
1036
1037	/**
1038	* tracing_alloc_snapshot - allocate snapshot buffer.
1039	*
1040	* This only allocates the snapshot buffer if it isn't already
1041	* allocated - it doesn't also take a snapshot.
1042	*
1043	* This is meant to be used in cases where the snapshot buffer needs
1044	* to be set up for events that can't sleep but need to be able to
1045	* trigger a snapshot.
1046	*/
1047	int tracing_alloc_snapshot(void)
1048	{
1049	struct trace_array *tr = &global_trace;
1050	int ret;
1051
1052	ret = tracing_alloc_snapshot_instance(tr);
1053	WARN_ON(ret < `0`);
1054
1055	return ret;
1056	}
1057	EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);
1058
1059	/**
1060	* tracing_snapshot_alloc - allocate and take a snapshot of the current buffer.
1061	*
1062	* This is similar to tracing_snapshot(), but it will allocate the
1063	* snapshot buffer if it isn't already allocated. Use this only
1064	* where it is safe to sleep, as the allocation may sleep.
1065	*
1066	* This causes a swap between the snapshot buffer and the current live
1067	* tracing buffer. You can use this to take snapshots of the live
1068	* trace when some condition is triggered, but continue to trace.
1069	*/
1070	void tracing_snapshot_alloc(void)
1071	{
1072	int ret;
1073
1074	ret = tracing_alloc_snapshot();
1075	if (ret < `0`)
1076	return;
1077
1078	tracing_snapshot();
1079	}
1080	EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
1081
1082	/**
1083	* tracing_snapshot_cond_enable - enable conditional snapshot for an instance
1084	* @tr: The tracing instance
1085	* @cond_data: User data to associate with the snapshot
1086	* @update: Implementation of the cond_snapshot update function
1087	*
1088	* Check whether the conditional snapshot for the given instance has
1089	* already been enabled, or if the current tracer is already using a
1090	* snapshot; if so, return -EBUSY, else create a cond_snapshot and
1091	* save the cond_data and update function inside.
1092	*
1093	* Returns 0 if successful, error otherwise.
1094	*/
1095	int tracing_snapshot_cond_enable(struct trace_array tr, void* *cond_data,
1096	cond_update_fn_t update)
1097	{
1098	struct cond_snapshot *cond_snapshot;
1099	int ret = `0`;
1100
1101	cond_snapshot = kzalloc(sizeof(*cond_snapshot), GFP_KERNEL);
1102	if (!cond_snapshot)
1103	return -ENOMEM;
1104
1105	cond_snapshot->cond_data = cond_data;
1106	cond_snapshot->update = update;
1107
1108	mutex_lock(&trace_types_lock);
1109
1110	ret = tracing_alloc_snapshot_instance(tr);
1111	if (ret)
1112	goto fail_unlock;
1113
1114	if (tr->current_trace->use_max_tr) {
1115	ret = -EBUSY;
1116	goto fail_unlock;
1117	}
1118
1119	/*
1120	* The cond_snapshot can only change to NULL without the
1121	* trace_types_lock. We don't care if we race with it going
1122	* to NULL, but we want to make sure that it's not set to
1123	* something other than NULL when we get here, which we can
1124	* do safely with only holding the trace_types_lock and not
1125	* having to take the max_lock.
1126	*/
1127	if (tr->cond_snapshot) {
1128	ret = -EBUSY;
1129	goto fail_unlock;
1130	}
1131
1132	arch_spin_lock(&tr->max_lock);
1133	tr->cond_snapshot = cond_snapshot;
1134	arch_spin_unlock(&tr->max_lock);
1135
1136	mutex_unlock(&trace_types_lock);
1137
1138	return ret;
1139
1140	fail_unlock:
1141	mutex_unlock(&trace_types_lock);
1142	kfree(cond_snapshot);
1143	return ret;
1144	}
1145	EXPORT_SYMBOL_GPL(tracing_snapshot_cond_enable);
1146
1147	/**
1148	* tracing_snapshot_cond_disable - disable conditional snapshot for an instance
1149	* @tr: The tracing instance
1150	*
1151	* Check whether the conditional snapshot for the given instance is
1152	* enabled; if so, free the cond_snapshot associated with it,
1153	* otherwise return -EINVAL.
1154	*
1155	* Returns 0 if successful, error otherwise.
1156	*/
1157	int tracing_snapshot_cond_disable(struct trace_array *tr)
1158	{
1159	int ret = `0`;
1160
1161	arch_spin_lock(&tr->max_lock);
1162
1163	if (!tr->cond_snapshot)
1164	ret = -EINVAL;
1165	else {
1166	kfree(tr->cond_snapshot);
1167	tr->cond_snapshot = NULL;
1168	}
1169
1170	arch_spin_unlock(&tr->max_lock);
1171
1172	return ret;
1173	}
1174	EXPORT_SYMBOL_GPL(tracing_snapshot_cond_disable);
1175	#else
1176	void tracing_snapshot(void)
1177	{
1178	WARN_ONCE(`1`, "Snapshot feature not enabled, but internal snapshot used");
1179	}
1180	EXPORT_SYMBOL_GPL(tracing_snapshot);
1181	void tracing_snapshot_cond(struct trace_array tr, void* *cond_data)
1182	{
1183	WARN_ONCE(`1`, "Snapshot feature not enabled, but internal conditional snapshot used");
1184	}
1185	EXPORT_SYMBOL_GPL(tracing_snapshot_cond);
1186	int tracing_alloc_snapshot(void)
1187	{
1188	WARN_ONCE(`1`, "Snapshot feature not enabled, but snapshot allocation used");
1189	return -ENODEV;
1190	}
1191	EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);
1192	void tracing_snapshot_alloc(void)
1193	{
1194	/ Give warning /
1195	tracing_snapshot();
1196	}
1197	EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
1198	void tracing_cond_snapshot_data(struct* trace_array *tr)
1199	{
1200	return NULL;
1201	}
1202	EXPORT_SYMBOL_GPL(tracing_cond_snapshot_data);
1203	int tracing_snapshot_cond_enable(struct trace_array tr, void* *cond_data, cond_update_fn_t update)
1204	{
1205	return -ENODEV;
1206	}
1207	EXPORT_SYMBOL_GPL(tracing_snapshot_cond_enable);
1208	int tracing_snapshot_cond_disable(struct trace_array *tr)
1209	{
1210	return false;
1211	}
1212	EXPORT_SYMBOL_GPL(tracing_snapshot_cond_disable);
1213	#endif /* CONFIG_TRACER_SNAPSHOT */
1214
1215	void tracer_tracing_off(struct trace_array *tr)
1216	{
1217	if (tr->trace_buffer.buffer)
1218	ring_buffer_record_off(tr->trace_buffer.buffer);
1219	/*
1220	* This flag is looked at when buffers haven't been allocated
1221	* yet, or by some tracers (like irqsoff), that just want to
1222	* know if the ring buffer has been disabled, but it can handle
1223	* races of where it gets disabled but we still do a record.
1224	* As the check is in the fast path of the tracers, it is more
1225	* important to be fast than accurate.
1226	*/
1227	tr->buffer_disabled = `1`;
1228	/ Make the flag seen by readers /
1229	smp_wmb();
1230	}
1231
1232	/**
1233	* tracing_off - turn off tracing buffers
1234	*
1235	* This function stops the tracing buffers from recording data.
1236	* It does not disable any overhead the tracers themselves may
1237	* be causing. This function simply causes all recording to
1238	* the ring buffers to fail.
1239	*/
1240	void tracing_off(void)
1241	{
1242	tracer_tracing_off(&global_trace);
1243	}
1244	EXPORT_SYMBOL_GPL(tracing_off);
1245
1246	void disable_trace_on_warning(void)
1247	{
1248	if (__disable_trace_on_warning)
1249	tracing_off();
1250	}
1251
1252	/**
1253	* tracer_tracing_is_on - show real state of ring buffer enabled
1254	* @tr : the trace array to know if ring buffer is enabled
1255	*
1256	* Shows real state of the ring buffer if it is enabled or not.
1257	*/
1258	bool tracer_tracing_is_on(struct trace_array *tr)
1259	{
1260	if (tr->trace_buffer.buffer)
1261	return ring_buffer_record_is_on(tr->trace_buffer.buffer);
1262	return !tr->buffer_disabled;
1263	}
1264
1265	/**
1266	* tracing_is_on - show state of ring buffers enabled
1267	*/
1268	int tracing_is_on(void)
1269	{
1270	return tracer_tracing_is_on(&global_trace);
1271	}
1272	EXPORT_SYMBOL_GPL(tracing_is_on);
1273
1274	static int __init set_buf_size(char *str)
1275	{
1276	unsigned long buf_size;
1277
1278	if (!str)
1279	return `0`;
1280	buf_size = memparse(str, &str);
1281	/ nr_entries can not be zero /
1282	if (buf_size == `0`)
1283	return `0`;
1284	trace_buf_size = buf_size;
1285	return `1`;
1286	}
1287	__setup("trace_buf_size=", set_buf_size);
1288
1289	static int __init set_tracing_thresh(char *str)
1290	{
1291	unsigned long threshold;
1292	int ret;
1293
1294	if (!str)
1295	return `0`;
1296	ret = kstrtoul(str, `0`, &threshold);
1297	if (ret < `0`)
1298	return `0`;
1299	tracing_thresh = threshold * `1000`;
1300	return `1`;
1301	}
1302	__setup("tracing_thresh=", set_tracing_thresh);
1303
1304	unsigned long nsecs_to_usecs(unsigned long nsecs)
1305	{
1306	return nsecs / `1000`;
1307	}
1308
1309	/*
1310	* TRACE_FLAGS is defined as a tuple matching bit masks with strings.
1311	* It uses C(a, b) where 'a' is the eval (enum) name and 'b' is the string that
1312	* matches it. By defining "C(a, b) b", TRACE_FLAGS becomes a list
1313	* of strings in the order that the evals (enum) were defined.
1314	*/
1315	#undef C
1316	#define C(a, b) b
1317
1318	/ These must match the bit postions in trace_iterator_flags /
1319	static const char *trace_options[] = {
1320	TRACE_FLAGS
1321	NULL
1322	};
1323
1324	static struct {
1325	u64 (func)(void*);
1326	const char *name;
1327	int in_ns; / is this clock in nanoseconds? /
1328	} trace_clocks[] = {
1329	{ trace_clock_local, "local", `1` },
1330	{ trace_clock_global, "global", `1` },
1331	{ trace_clock_counter, "counter", `0` },
1332	{ trace_clock_jiffies, "uptime", `0` },
1333	{ trace_clock, "perf", `1` },
1334	{ ktime_get_mono_fast_ns, "mono", `1` },
1335	{ ktime_get_raw_fast_ns, "mono_raw", `1` },
1336	{ ktime_get_boot_fast_ns, "boot", `1` },
1337	ARCH_TRACE_CLOCKS
1338	};
1339
1340	bool trace_clock_in_ns(struct trace_array *tr)
1341	{
1342	if (trace_clocks[tr->clock_id].in_ns)
1343	return true;
1344
1345	return false;
1346	}
1347
1348	/*
1349	* trace_parser_get_init - gets the buffer for trace parser
1350	*/
1351	int trace_parser_get_init(struct trace_parser parser, int* size)
1352	{
1353	memset(parser, `0`, sizeof(*parser));
1354
1355	parser->buffer = kmalloc(size, GFP_KERNEL);
1356	if (!parser->buffer)
1357	return `1`;
1358
1359	parser->size = size;
1360	return `0`;
1361	}
1362
1363	/*
1364	* trace_parser_put - frees the buffer for trace parser
1365	*/
1366	void trace_parser_put(struct trace_parser *parser)
1367	{
1368	kfree(parser->buffer);
1369	parser->buffer = NULL;
1370	}
1371
1372	/*
1373	* trace_get_user - reads the user input string separated by space
1374	* (matched by isspace(ch))
1375	*
1376	* For each string found the 'struct trace_parser' is updated,
1377	* and the function returns.
1378	*
1379	* Returns number of bytes read.
1380	*
1381	* See kernel/trace/trace.h for 'struct trace_parser' details.
1382	*/
1383	int trace_get_user(struct trace_parser parser, const* char __user *ubuf,
1384	size_t cnt, loff_t *ppos)
1385	{
1386	char ch;
1387	size_t read = `0`;
1388	ssize_t ret;
1389
1390	if (!*ppos)
1391	trace_parser_clear(parser);
1392
1393	ret = get_user(ch, ubuf++);
1394	if (ret)
1395	goto out;
1396
1397	read++;
1398	cnt--;
1399
1400	/*
1401	* The parser is not finished with the last write,
1402	* continue reading the user input without skipping spaces.
1403	*/
1404	if (!parser->cont) {
1405	/ skip white space /
1406	while (cnt && isspace(ch)) {
1407	ret = get_user(ch, ubuf++);
1408	if (ret)
1409	goto out;
1410	read++;
1411	cnt--;
1412	}
1413
1414	parser->idx = `0`;
1415
1416	/ only spaces were written /
1417	if (isspace(ch) \|\| !ch) {
1418	*ppos += read;
1419	ret = read;
1420	goto out;
1421	}
1422	}
1423
1424	/ read the non-space input /
1425	while (cnt && !isspace(ch) && ch) {
1426	if (parser->idx < parser->size - `1`)
1427	parser->buffer[parser->idx++] = ch;
1428	else {
1429	ret = -EINVAL;
1430	goto out;
1431	}
1432	ret = get_user(ch, ubuf++);
1433	if (ret)
1434	goto out;
1435	read++;
1436	cnt--;
1437	}
1438
1439	/ We either got finished input or we have to wait for another call. /
1440	if (isspace(ch) \|\| !ch) {
1441	parser->buffer[parser->idx] = `0`;
1442	parser->cont = false;
1443	} else if (parser->idx < parser->size - `1`) {
1444	parser->cont = true;
1445	parser->buffer[parser->idx++] = ch;
1446	/ Make sure the parsed string always terminates with '\0'. /
1447	parser->buffer[parser->idx] = `0`;
1448	} else {
1449	ret = -EINVAL;
1450	goto out;
1451	}
1452
1453	*ppos += read;
1454	ret = read;
1455
1456	out:
1457	return ret;
1458	}
1459
1460	/ TODO add a seq_buf_to_buffer() /
1461	static ssize_t trace_seq_to_buffer(struct trace_seq s, void* *buf, size_t cnt)
1462	{
1463	int len;
1464
1465	if (trace_seq_used(s) <= s->seq.readpos)
1466	return -EBUSY;
1467
1468	len = trace_seq_used(s) - s->seq.readpos;
1469	if (cnt > len)
1470	cnt = len;
1471	memcpy(buf, s->buffer + s->seq.readpos, cnt);
1472
1473	s->seq.readpos += cnt;
1474	return cnt;
1475	}
1476
1477	unsigned long __read_mostly tracing_thresh;
1478
1479	#ifdef CONFIG_TRACER_MAX_TRACE
1480	/*
1481	* Copy the new maximum trace into the separate maximum-trace
1482	* structure. (this way the maximum trace is permanently saved,
1483	* for later retrieval via /sys/kernel/tracing/tracing_max_latency)
1484	*/
1485	static void
1486	__update_max_tr(struct trace_array tr, struct* task_struct tsk, int* cpu)
1487	{
1488	struct trace_buffer *trace_buf = &tr->trace_buffer;
1489	struct trace_buffer *max_buf = &tr->max_buffer;
1490	struct trace_array_cpu *data = per_cpu_ptr(trace_buf->data, cpu);
1491	struct trace_array_cpu *max_data = per_cpu_ptr(max_buf->data, cpu);
1492
1493	max_buf->cpu = cpu;
1494	max_buf->time_start = data->preempt_timestamp;
1495
1496	max_data->saved_latency = tr->max_latency;
1497	max_data->critical_start = data->critical_start;
1498	max_data->critical_end = data->critical_end;
1499
1500	strncpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
1501	max_data->pid = tsk->pid;
1502	/*
1503	* If tsk == current, then use current_uid(), as that does not use
1504	* RCU. The irq tracer can be called out of RCU scope.
1505	*/
1506	if (tsk == current)
1507	max_data->uid = current_uid();
1508	else
1509	max_data->uid = task_uid(tsk);
1510
1511	max_data->nice = tsk->static_prio - `20` - MAX_RT_PRIO;
1512	max_data->policy = tsk->policy;
1513	max_data->rt_priority = tsk->rt_priority;
1514
1515	/ record this tasks comm /
1516	tracing_record_cmdline(tsk);
1517	}
1518
1519	/**
1520	* update_max_tr - snapshot all trace buffers from global_trace to max_tr
1521	* @tr: tracer
1522	* @tsk: the task with the latency
1523	* @cpu: The cpu that initiated the trace.
1524	* @cond_data: User data associated with a conditional snapshot
1525	*
1526	* Flip the buffers between the @tr and the max_tr and record information
1527	* about which task was the cause of this latency.
1528	*/
1529	void
1530	update_max_tr(struct trace_array tr, struct* task_struct tsk, int* cpu,
1531	void *cond_data)
1532	{
1533	if (tr->stop_count)
1534	return;
1535
1536	WARN_ON_ONCE(!irqs_disabled());
1537
1538	if (!tr->allocated_snapshot) {
1539	/ Only the nop tracer should hit this when disabling /
1540	WARN_ON_ONCE(tr->current_trace != &nop_trace);
1541	return;
1542	}
1543
1544	arch_spin_lock(&tr->max_lock);
1545
1546	/ Inherit the recordable setting from trace_buffer /
1547	if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer))
1548	ring_buffer_record_on(tr->max_buffer.buffer);
1549	else
1550	ring_buffer_record_off(tr->max_buffer.buffer);
1551
1552	#ifdef CONFIG_TRACER_SNAPSHOT
1553	if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data))
1554	goto out_unlock;
1555	#endif
1556	swap(tr->trace_buffer.buffer, tr->max_buffer.buffer);
1557
1558	__update_max_tr(tr, tsk, cpu);
1559
1560	out_unlock:
1561	arch_spin_unlock(&tr->max_lock);
1562	}
1563
1564	/**
1565	* update_max_tr_single - only copy one trace over, and reset the rest
1566	* @tr - tracer
1567	* @tsk - task with the latency
1568	* @cpu - the cpu of the buffer to copy.
1569	*
1570	* Flip the trace of a single CPU buffer between the @tr and the max_tr.
1571	*/
1572	void
1573	update_max_tr_single(struct trace_array tr, struct* task_struct tsk, int* cpu)
1574	{
1575	int ret;
1576
1577	if (tr->stop_count)
1578	return;
1579
1580	WARN_ON_ONCE(!irqs_disabled());
1581	if (!tr->allocated_snapshot) {
1582	/ Only the nop tracer should hit this when disabling /
1583	WARN_ON_ONCE(tr->current_trace != &nop_trace);
1584	return;
1585	}
1586
1587	arch_spin_lock(&tr->max_lock);
1588
1589	ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->trace_buffer.buffer, cpu);
1590
1591	if (ret == -EBUSY) {
1592	/*
1593	* We failed to swap the buffer due to a commit taking
1594	* place on this CPU. We fail to record, but we reset
1595	* the max trace buffer (no one writes directly to it)
1596	* and flag that it failed.
1597	*/
1598	trace_array_printk_buf(tr->max_buffer.buffer, _THIS_IP_,
1599	"Failed to swap buffers due to commit in progress\n");
1600	}
1601
1602	WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);
1603
1604	__update_max_tr(tr, tsk, cpu);
1605	arch_spin_unlock(&tr->max_lock);
1606	}
1607	#endif /* CONFIG_TRACER_MAX_TRACE */
1608
1609	static int wait_on_pipe(struct trace_iterator iter, int* full)
1610	{
1611	/ Iterators are static, they should be filled or empty /
1612	if (trace_buffer_iter(iter, iter->cpu_file))
1613	return `0`;
1614
1615	return ring_buffer_wait(iter->trace_buffer->buffer, iter->cpu_file,
1616	full);
1617	}
1618
1619	#ifdef CONFIG_FTRACE_STARTUP_TEST
1620	static bool selftests_can_run;
1621
1622	struct trace_selftests {
1623	struct list_head list;
1624	struct tracer *type;
1625	};
1626
1627	static LIST_HEAD(postponed_selftests);
1628
1629	static int save_selftest(struct tracer *type)
1630	{
1631	struct trace_selftests *selftest;
1632
1633	selftest = kmalloc(sizeof(*selftest), GFP_KERNEL);
1634	if (!selftest)
1635	return -ENOMEM;
1636
1637	selftest->type = type;
1638	list_add(&selftest->list, &postponed_selftests);
1639	return `0`;
1640	}
1641
1642	static int run_tracer_selftest(struct tracer *type)
1643	{
1644	struct trace_array *tr = &global_trace;
1645	struct tracer *saved_tracer = tr->current_trace;
1646	int ret;
1647
1648	if (!type->selftest \|\| tracing_selftest_disabled)
1649	return `0`;
1650
1651	/*
1652	* If a tracer registers early in boot up (before scheduling is
1653	* initialized and such), then do not run its selftests yet.
1654	* Instead, run it a little later in the boot process.
1655	*/
1656	if (!selftests_can_run)
1657	return save_selftest(type);
1658
1659	/*
1660	* Run a selftest on this tracer.
1661	* Here we reset the trace buffer, and set the current
1662	* tracer to be this tracer. The tracer can then run some
1663	* internal tracing to verify that everything is in order.
1664	* If we fail, we do not register this tracer.
1665	*/
1666	tracing_reset_online_cpus(&tr->trace_buffer);
1667
1668	tr->current_trace = type;
1669
1670	#ifdef CONFIG_TRACER_MAX_TRACE
1671	if (type->use_max_tr) {
1672	/ If we expanded the buffers, make sure the max is expanded too /
1673	if (ring_buffer_expanded)
1674	ring_buffer_resize(tr->max_buffer.buffer, trace_buf_size,
1675	RING_BUFFER_ALL_CPUS);
1676	tr->allocated_snapshot = true;
1677	}
1678	#endif
1679
1680	/ the test is responsible for initializing and enabling /
1681	pr_info("Testing tracer %s: ", type->name);
1682	ret = type->selftest(type, tr);
1683	/ the test is responsible for resetting too /
1684	tr->current_trace = saved_tracer;
1685	if (ret) {
1686	printk(KERN_CONT "FAILED!\n");
1687	/ Add the warning after printing 'FAILED' /
1688	WARN_ON(`1`);
1689	return -`1`;
1690	}
1691	/ Only reset on passing, to avoid touching corrupted buffers /
1692	tracing_reset_online_cpus(&tr->trace_buffer);
1693
1694	#ifdef CONFIG_TRACER_MAX_TRACE
1695	if (type->use_max_tr) {
1696	tr->allocated_snapshot = false;
1697
1698	/ Shrink the max buffer again /
1699	if (ring_buffer_expanded)
1700	ring_buffer_resize(tr->max_buffer.buffer, `1`,
1701	RING_BUFFER_ALL_CPUS);
1702	}
1703	#endif
1704
1705	printk(KERN_CONT "PASSED\n");
1706	return `0`;
1707	}
1708
1709	static __init int init_trace_selftests(void)
1710	{
1711	struct trace_selftests p, n;
1712	struct tracer t, *last;
1713	int ret;
1714
1715	selftests_can_run = true;
1716
1717	mutex_lock(&trace_types_lock);
1718
1719	if (list_empty(&postponed_selftests))
1720	goto out;
1721
1722	pr_info("Running postponed tracer tests:\n");
1723
1724	list_for_each_entry_safe(p, n, &postponed_selftests, list) {
1725	ret = run_tracer_selftest(p->type);
1726	/ If the test fails, then warn and remove from available_tracers /
1727	if (ret < `0`) {
1728	WARN(`1`, "tracer: %s failed selftest, disabling\n",
1729	p->type->name);
1730	last = &trace_types;
1731	for (t = trace_types; t; t = t->next) {
1732	if (t == p->type) {
1733	*last = t->next;
1734	break;
1735	}
1736	last = &t->next;
1737	}
1738	}
1739	list_del(&p->list);
1740	kfree(p);
1741	}
1742
1743	out:
1744	mutex_unlock(&trace_types_lock);
1745
1746	return `0`;
1747	}
1748	core_initcall(init_trace_selftests);
1749	#else
1750	static inline int run_tracer_selftest(struct tracer *type)
1751	{
1752	return `0`;
1753	}
1754	#endif /* CONFIG_FTRACE_STARTUP_TEST */
1755
1756	static void add_tracer_options(struct trace_array tr, struct* tracer *t);
1757
1758	static void __init apply_trace_boot_options(void);
1759
1760	/**
1761	* register_tracer - register a tracer with the ftrace system.
1762	* @type - the plugin for the tracer
1763	*
1764	* Register a new plugin tracer.
1765	*/
1766	int __init register_tracer(struct tracer *type)
1767	{
1768	struct tracer *t;
1769	int ret = `0`;
1770
1771	if (!type->name) {
1772	pr_info("Tracer must have a name\n");
1773	return -`1`;
1774	}
1775
1776	if (strlen(type->name) >= MAX_TRACER_SIZE) {
1777	pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
1778	return -`1`;
1779	}
1780
1781	mutex_lock(&trace_types_lock);
1782
1783	tracing_selftest_running = true;
1784
1785	for (t = trace_types; t; t = t->next) {
1786	if (strcmp(type->name, t->name) == `0`) {
1787	/ already found /
1788	pr_info("Tracer %s already registered\n",
1789	type->name);
1790	ret = -`1`;
1791	goto out;
1792	}
1793	}
1794
1795	if (!type->set_flag)
1796	type->set_flag = &dummy_set_flag;
1797	if (!type->flags) {
1798	/allocate a dummy tracer_flags/
1799	type->flags = kmalloc(sizeof(*type->flags), GFP_KERNEL);
1800	if (!type->flags) {
1801	ret = -ENOMEM;
1802	goto out;
1803	}
1804	type->flags->val = `0`;
1805	type->flags->opts = dummy_tracer_opt;
1806	} else
1807	if (!type->flags->opts)
1808	type->flags->opts = dummy_tracer_opt;
1809
1810	/ store the tracer for __set_tracer_option /
1811	type->flags->trace = type;
1812
1813	ret = run_tracer_selftest(type);
1814	if (ret < `0`)
1815	goto out;
1816
1817	type->next = trace_types;
1818	trace_types = type;
1819	add_tracer_options(&global_trace, type);
1820
1821	out:
1822	tracing_selftest_running = false;
1823	mutex_unlock(&trace_types_lock);
1824
1825	if (ret \|\| !default_bootup_tracer)
1826	goto out_unlock;
1827
1828	if (strncmp(default_bootup_tracer, type->name, MAX_TRACER_SIZE))
1829	goto out_unlock;
1830
1831	printk(KERN_INFO "Starting tracer '%s'\n", type->name);
1832	/ Do we want this tracer to start on bootup? /
1833	tracing_set_tracer(&global_trace, type->name);
1834	default_bootup_tracer = NULL;
1835
1836	apply_trace_boot_options();
1837
1838	/ disable other selftests, since this will break it. /
1839	tracing_selftest_disabled = true;
1840	#ifdef CONFIG_FTRACE_STARTUP_TEST
1841	printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
1842	type->name);
1843	#endif
1844
1845	out_unlock:
1846	return ret;
1847	}
1848
1849	void tracing_reset(struct trace_buffer buf, int* cpu)
1850	{
1851	struct ring_buffer *buffer = buf->buffer;
1852
1853	if (!buffer)
1854	return;
1855
1856	ring_buffer_record_disable(buffer);
1857
1858	/ Make sure all commits have finished /
1859	synchronize_rcu();
1860	ring_buffer_reset_cpu(buffer, cpu);
1861
1862	ring_buffer_record_enable(buffer);
1863	}
1864
1865	void tracing_reset_online_cpus(struct trace_buffer *buf)
1866	{
1867	struct ring_buffer *buffer = buf->buffer;
1868	int cpu;
1869
1870	if (!buffer)
1871	return;
1872
1873	ring_buffer_record_disable(buffer);
1874
1875	/ Make sure all commits have finished /
1876	synchronize_rcu();
1877
1878	buf->time_start = buffer_ftrace_now(buf, buf->cpu);
1879
1880	for_each_online_cpu(cpu)
1881	ring_buffer_reset_cpu(buffer, cpu);
1882
1883	ring_buffer_record_enable(buffer);
1884	}
1885
1886	/ Must have trace_types_lock held /
1887	void tracing_reset_all_online_cpus(void)
1888	{
1889	struct trace_array *tr;
1890
1891	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
1892	if (!tr->clear_trace)
1893	continue;
1894	tr->clear_trace = false;
1895	tracing_reset_online_cpus(&tr->trace_buffer);
1896	#ifdef CONFIG_TRACER_MAX_TRACE
1897	tracing_reset_online_cpus(&tr->max_buffer);
1898	#endif
1899	}
1900	}
1901
1902	static int *tgid_map;
1903
1904	#define SAVED_CMDLINES_DEFAULT 128
1905	#define NO_CMDLINE_MAP UINT_MAX
1906	static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
1907	struct saved_cmdlines_buffer {
1908	unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+`1`];
1909	unsigned *map_cmdline_to_pid;
1910	unsigned cmdline_num;
1911	int cmdline_idx;
1912	char *saved_cmdlines;
1913	};
1914	static struct saved_cmdlines_buffer *savedcmd;
1915
1916	/ temporary disable recording /
1917	static atomic_t trace_record_taskinfo_disabled __read_mostly;
1918
1919	static inline char get_saved_cmdlines(int* idx)
1920	{
1921	return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
1922	}
1923
1924	static inline void set_cmdline(int idx, const char *cmdline)
1925	{
1926	strncpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
1927	}
1928
1929	static int allocate_cmdlines_buffer(unsigned int val,
1930	struct saved_cmdlines_buffer *s)
1931	{
1932	s->map_cmdline_to_pid = kmalloc_array(val,
1933	sizeof(*s->map_cmdline_to_pid),
1934	GFP_KERNEL);
1935	if (!s->map_cmdline_to_pid)
1936	return -ENOMEM;
1937
1938	s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL);
1939	if (!s->saved_cmdlines) {
1940	kfree(s->map_cmdline_to_pid);
1941	return -ENOMEM;
1942	}
1943
1944	s->cmdline_idx = `0`;
1945	s->cmdline_num = val;
1946	memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
1947	sizeof(s->map_pid_to_cmdline));
1948	memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
1949	val * sizeof(*s->map_cmdline_to_pid));
1950
1951	return `0`;
1952	}
1953
1954	static int trace_create_savedcmd(void)
1955	{
1956	int ret;
1957
1958	savedcmd = kmalloc(sizeof(*savedcmd), GFP_KERNEL);
1959	if (!savedcmd)
1960	return -ENOMEM;
1961
1962	ret = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT, savedcmd);
1963	if (ret < `0`) {
1964	kfree(savedcmd);
1965	savedcmd = NULL;
1966	return -ENOMEM;
1967	}
1968
1969	return `0`;
1970	}
1971
1972	int is_tracing_stopped(void)
1973	{
1974	return global_trace.stop_count;
1975	}
1976
1977	/**
1978	* tracing_start - quick start of the tracer
1979	*
1980	* If tracing is enabled but was stopped by tracing_stop,
1981	* this will start the tracer back up.
1982	*/
1983	void tracing_start(void)
1984	{
1985	struct ring_buffer *buffer;
1986	unsigned long flags;
1987
1988	if (tracing_disabled)
1989	return;
1990
1991	raw_spin_lock_irqsave(&global_trace.start_lock, flags);
1992	if (--global_trace.stop_count) {
1993	if (global_trace.stop_count < `0`) {
1994	/ Someone screwed up their debugging /
1995	WARN_ON_ONCE(`1`);
1996	global_trace.stop_count = `0`;
1997	}
1998	goto out;
1999	}
2000
2001	/ Prevent the buffers from switching /
2002	arch_spin_lock(&global_trace.max_lock);
2003
2004	buffer = global_trace.trace_buffer.buffer;
2005	if (buffer)
2006	ring_buffer_record_enable(buffer);
2007
2008	#ifdef CONFIG_TRACER_MAX_TRACE
2009	buffer = global_trace.max_buffer.buffer;
2010	if (buffer)
2011	ring_buffer_record_enable(buffer);
2012	#endif
2013
2014	arch_spin_unlock(&global_trace.max_lock);
2015
2016	out:
2017	raw_spin_unlock_irqrestore(&global_trace.start_lock, flags);
2018	}
2019
2020	static void tracing_start_tr(struct trace_array *tr)
2021	{
2022	struct ring_buffer *buffer;
2023	unsigned long flags;
2024
2025	if (tracing_disabled)
2026	return;
2027
2028	/ If global, we need to also start the max tracer /
2029	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
2030	return tracing_start();
2031
2032	raw_spin_lock_irqsave(&tr->start_lock, flags);
2033
2034	if (--tr->stop_count) {
2035	if (tr->stop_count < `0`) {
2036	/ Someone screwed up their debugging /
2037	WARN_ON_ONCE(`1`);
2038	tr->stop_count = `0`;
2039	}
2040	goto out;
2041	}
2042
2043	buffer = tr->trace_buffer.buffer;
2044	if (buffer)
2045	ring_buffer_record_enable(buffer);
2046
2047	out:
2048	raw_spin_unlock_irqrestore(&tr->start_lock, flags);
2049	}
2050
2051	/**
2052	* tracing_stop - quick stop of the tracer
2053	*
2054	* Light weight way to stop tracing. Use in conjunction with
2055	* tracing_start.
2056	*/
2057	void tracing_stop(void)
2058	{
2059	struct ring_buffer *buffer;
2060	unsigned long flags;
2061
2062	raw_spin_lock_irqsave(&global_trace.start_lock, flags);
2063	if (global_trace.stop_count++)
2064	goto out;
2065
2066	/ Prevent the buffers from switching /
2067	arch_spin_lock(&global_trace.max_lock);
2068
2069	buffer = global_trace.trace_buffer.buffer;
2070	if (buffer)
2071	ring_buffer_record_disable(buffer);
2072
2073	#ifdef CONFIG_TRACER_MAX_TRACE
2074	buffer = global_trace.max_buffer.buffer;
2075	if (buffer)
2076	ring_buffer_record_disable(buffer);
2077	#endif
2078
2079	arch_spin_unlock(&global_trace.max_lock);
2080
2081	out:
2082	raw_spin_unlock_irqrestore(&global_trace.start_lock, flags);
2083	}
2084
2085	static void tracing_stop_tr(struct trace_array *tr)
2086	{
2087	struct ring_buffer *buffer;
2088	unsigned long flags;
2089
2090	/ If global, we need to also stop the max tracer /
2091	if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
2092	return tracing_stop();
2093
2094	raw_spin_lock_irqsave(&tr->start_lock, flags);
2095	if (tr->stop_count++)
2096	goto out;
2097
2098	buffer = tr->trace_buffer.buffer;
2099	if (buffer)
2100	ring_buffer_record_disable(buffer);
2101
2102	out:
2103	raw_spin_unlock_irqrestore(&tr->start_lock, flags);
2104	}
2105
2106	static int trace_save_cmdline(struct task_struct *tsk)
2107	{
2108	unsigned pid, idx;
2109
2110	/ treat recording of idle task as a success /
2111	if (!tsk->pid)
2112	return `1`;
2113
2114	if (unlikely(tsk->pid > PID_MAX_DEFAULT))
2115	return `0`;
2116
2117	/*
2118	* It's not the end of the world if we don't get
2119	* the lock, but we also don't want to spin
2120	* nor do we want to disable interrupts,
2121	* so if we miss here, then better luck next time.
2122	*/
2123	if (!arch_spin_trylock(&trace_cmdline_lock))
2124	return `0`;
2125
2126	idx = savedcmd->map_pid_to_cmdline[tsk->pid];
2127	if (idx == NO_CMDLINE_MAP) {
2128	idx = (savedcmd->cmdline_idx + `1`) % savedcmd->cmdline_num;
2129
2130	/*
2131	* Check whether the cmdline buffer at idx has a pid
2132	* mapped. We are going to overwrite that entry so we
2133	* need to clear the map_pid_to_cmdline. Otherwise we
2134	* would read the new comm for the old pid.
2135	*/
2136	pid = savedcmd->map_cmdline_to_pid[idx];
2137	if (pid != NO_CMDLINE_MAP)
2138	savedcmd->map_pid_to_cmdline[pid] = NO_CMDLINE_MAP;
2139
2140	savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
2141	savedcmd->map_pid_to_cmdline[tsk->pid] = idx;
2142
2143	savedcmd->cmdline_idx = idx;
2144	}
2145
2146	set_cmdline(idx, tsk->comm);
2147
2148	arch_spin_unlock(&trace_cmdline_lock);
2149
2150	return `1`;
2151	}
2152
2153	static void __trace_find_cmdline(int pid, char comm[])
2154	{
2155	unsigned map;
2156
2157	if (!pid) {
2158	strcpy(comm, "<idle>");
2159	return;
2160	}
2161
2162	if (WARN_ON_ONCE(pid < `0`)) {
2163	strcpy(comm, "<XXX>");
2164	return;
2165	}
2166
2167	if (pid > PID_MAX_DEFAULT) {
2168	strcpy(comm, "<...>");
2169	return;
2170	}
2171
2172	map = savedcmd->map_pid_to_cmdline[pid];
2173	if (map != NO_CMDLINE_MAP)
2174	strlcpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
2175	else
2176	strcpy(comm, "<...>");
2177	}
2178
2179	void trace_find_cmdline(int pid, char comm[])
2180	{
2181	preempt_disable();
2182	arch_spin_lock(&trace_cmdline_lock);
2183
2184	__trace_find_cmdline(pid, comm);
2185
2186	arch_spin_unlock(&trace_cmdline_lock);
2187	preempt_enable();
2188	}
2189
2190	int trace_find_tgid(int pid)
2191	{
2192	if (unlikely(!tgid_map \|\| !pid \|\| pid > PID_MAX_DEFAULT))
2193	return `0`;
2194
2195	return tgid_map[pid];
2196	}
2197
2198	static int trace_save_tgid(struct task_struct *tsk)
2199	{
2200	/ treat recording of idle task as a success /
2201	if (!tsk->pid)
2202	return `1`;
2203
2204	if (unlikely(!tgid_map \|\| tsk->pid > PID_MAX_DEFAULT))
2205	return `0`;
2206
2207	tgid_map[tsk->pid] = tsk->tgid;
2208	return `1`;
2209	}
2210
2211	static bool tracing_record_taskinfo_skip(int flags)
2212	{
2213	if (unlikely(!(flags & (TRACE_RECORD_CMDLINE \| TRACE_RECORD_TGID))))
2214	return true;
2215	if (atomic_read(&trace_record_taskinfo_disabled) \|\| !tracing_is_on())
2216	return true;
2217	if (!__this_cpu_read(trace_taskinfo_save))
2218	return true;
2219	return false;
2220	}
2221
2222	/**
2223	* tracing_record_taskinfo - record the task info of a task
2224	*
2225	* @task - task to record
2226	* @flags - TRACE_RECORD_CMDLINE for recording comm
2227	* - TRACE_RECORD_TGID for recording tgid
2228	*/
2229	void tracing_record_taskinfo(struct task_struct task, int* flags)
2230	{
2231	bool done;
2232
2233	if (tracing_record_taskinfo_skip(flags))
2234	return;
2235
2236	/*
2237	* Record as much task information as possible. If some fail, continue
2238	* to try to record the others.
2239	*/
2240	done = !(flags & TRACE_RECORD_CMDLINE) \|\| trace_save_cmdline(task);
2241	done &= !(flags & TRACE_RECORD_TGID) \|\| trace_save_tgid(task);
2242
2243	/ If recording any information failed, retry again soon. /
2244	if (!done)
2245	return;
2246
2247	__this_cpu_write(trace_taskinfo_save, false);
2248	}
2249
2250	/**
2251	* tracing_record_taskinfo_sched_switch - record task info for sched_switch
2252	*
2253	* @prev - previous task during sched_switch
2254	* @next - next task during sched_switch
2255	* @flags - TRACE_RECORD_CMDLINE for recording comm
2256	* TRACE_RECORD_TGID for recording tgid
2257	*/
2258	void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
2259	struct task_struct next, int* flags)
2260	{
2261	bool done;
2262
2263	if (tracing_record_taskinfo_skip(flags))
2264	return;
2265
2266	/*
2267	* Record as much task information as possible. If some fail, continue
2268	* to try to record the others.
2269	*/
2270	done = !(flags & TRACE_RECORD_CMDLINE) \|\| trace_save_cmdline(prev);
2271	done &= !(flags & TRACE_RECORD_CMDLINE) \|\| trace_save_cmdline(next);
2272	done &= !(flags & TRACE_RECORD_TGID) \|\| trace_save_tgid(prev);
2273	done &= !(flags & TRACE_RECORD_TGID) \|\| trace_save_tgid(next);
2274
2275	/ If recording any information failed, retry again soon. /
2276	if (!done)
2277	return;
2278
2279	__this_cpu_write(trace_taskinfo_save, false);
2280	}
2281
2282	/ Helpers to record a specific task information /
2283	void tracing_record_cmdline(struct task_struct *task)
2284	{
2285	tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
2286	}
2287
2288	void tracing_record_tgid(struct task_struct *task)
2289	{
2290	tracing_record_taskinfo(task, TRACE_RECORD_TGID);
2291	}
2292
2293	/*
2294	* Several functions return TRACE_TYPE_PARTIAL_LINE if the trace_seq
2295	* overflowed, and TRACE_TYPE_HANDLED otherwise. This helper function
2296	* simplifies those functions and keeps them in sync.
2297	*/
2298	enum print_line_t trace_handle_return(struct trace_seq *s)
2299	{
2300	return trace_seq_has_overflowed(s) ?
2301	TRACE_TYPE_PARTIAL_LINE : TRACE_TYPE_HANDLED;
2302	}
2303	EXPORT_SYMBOL_GPL(trace_handle_return);
2304
2305	void
2306	tracing_generic_entry_update(struct trace_entry entry, unsigned* long flags,
2307	int pc)
2308	{
2309	struct task_struct *tsk = current;
2310
2311	entry->preempt_count = pc & `0xff`;
2312	entry->pid = (tsk) ? tsk->pid : `0`;
2313	entry->flags =
2314	#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
2315	(irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : `0`) \|
2316	#else
2317	TRACE_FLAG_IRQS_NOSUPPORT \|
2318	#endif
2319	((pc & NMI_MASK ) ? TRACE_FLAG_NMI : `0`) \|
2320	((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : `0`) \|
2321	((pc & SOFTIRQ_OFFSET) ? TRACE_FLAG_SOFTIRQ : `0`) \|
2322	(tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : `0`) \|
2323	(test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : `0`);
2324	}
2325	EXPORT_SYMBOL_GPL(tracing_generic_entry_update);
2326
2327	struct ring_buffer_event *
2328	trace_buffer_lock_reserve(struct ring_buffer *buffer,
2329	int type,
2330	unsigned long len,
2331	unsigned long flags, int pc)
2332	{
2333	return __trace_buffer_lock_reserve(buffer, type, len, flags, pc);
2334	}
2335
2336	DEFINE_PER_CPU(struct ring_buffer_event *, trace_buffered_event);
2337	DEFINE_PER_CPU(int, trace_buffered_event_cnt);
2338	static int trace_buffered_event_ref;
2339
2340	/**
2341	* trace_buffered_event_enable - enable buffering events
2342	*
2343	* When events are being filtered, it is quicker to use a temporary
2344	* buffer to write the event data into if there's a likely chance
2345	* that it will not be committed. The discard of the ring buffer
2346	* is not as fast as committing, and is much slower than copying
2347	* a commit.
2348	*
2349	* When an event is to be filtered, allocate per cpu buffers to
2350	* write the event data into, and if the event is filtered and discarded
2351	* it is simply dropped, otherwise, the entire data is to be committed
2352	* in one shot.
2353	*/
2354	void trace_buffered_event_enable(void)
2355	{
2356	struct ring_buffer_event *event;
2357	struct page *page;
2358	int cpu;
2359
2360	WARN_ON_ONCE(!mutex_is_locked(&event_mutex));
2361
2362	if (trace_buffered_event_ref++)
2363	return;
2364
2365	for_each_tracing_cpu(cpu) {
2366	page = alloc_pages_node(cpu_to_node(cpu),
2367	GFP_KERNEL \| __GFP_NORETRY, `0`);
2368	if (!page)
2369	goto failed;
2370
2371	event = page_address(page);
2372	memset(event, `0`, sizeof(*event));
2373
2374	per_cpu(trace_buffered_event, cpu) = event;
2375
2376	preempt_disable();
2377	if (cpu == smp_processor_id() &&
2378	this_cpu_read(trace_buffered_event) !=
2379	per_cpu(trace_buffered_event, cpu))
2380	WARN_ON_ONCE(`1`);
2381	preempt_enable();
2382	}
2383
2384	return;
2385	failed:
2386	trace_buffered_event_disable();
2387	}
2388
2389	static void enable_trace_buffered_event(void *data)
2390	{
2391	/ Probably not needed, but do it anyway /
2392	smp_rmb();
2393	this_cpu_dec(trace_buffered_event_cnt);
2394	}
2395
2396	static void disable_trace_buffered_event(void *data)
2397	{
2398	this_cpu_inc(trace_buffered_event_cnt);
2399	}
2400
2401	/**
2402	* trace_buffered_event_disable - disable buffering events
2403	*
2404	* When a filter is removed, it is faster to not use the buffered
2405	* events, and to commit directly into the ring buffer. Free up
2406	* the temp buffers when there are no more users. This requires
2407	* special synchronization with current events.
2408	*/
2409	void trace_buffered_event_disable(void)
2410	{
2411	int cpu;
2412
2413	WARN_ON_ONCE(!mutex_is_locked(&event_mutex));
2414
2415	if (WARN_ON_ONCE(!trace_buffered_event_ref))
2416	return;
2417
2418	if (--trace_buffered_event_ref)
2419	return;
2420
2421	preempt_disable();
2422	/ For each CPU, set the buffer as used. /
2423	smp_call_function_many(tracing_buffer_mask,
2424	disable_trace_buffered_event, NULL, `1`);
2425	preempt_enable();
2426
2427	/ Wait for all current users to finish /
2428	synchronize_rcu();
2429
2430	for_each_tracing_cpu(cpu) {
2431	free_page((unsigned long)per_cpu(trace_buffered_event, cpu));
2432	per_cpu(trace_buffered_event, cpu) = NULL;
2433	}
2434	/*
2435	* Make sure trace_buffered_event is NULL before clearing
2436	* trace_buffered_event_cnt.
2437	*/
2438	smp_wmb();
2439
2440	preempt_disable();
2441	/ Do the work on each cpu /
2442	smp_call_function_many(tracing_buffer_mask,
2443	enable_trace_buffered_event, NULL, `1`);
2444	preempt_enable();
2445	}
2446
2447	static struct ring_buffer *temp_buffer;
2448
2449	struct ring_buffer_event *
2450	trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
2451	struct trace_event_file *trace_file,
2452	int type, unsigned long len,
2453	unsigned long flags, int pc)
2454	{
2455	struct ring_buffer_event *entry;
2456	int val;
2457
2458	*current_rb = trace_file->tr->trace_buffer.buffer;
2459
2460	if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
2461	(EVENT_FILE_FL_SOFT_DISABLED \| EVENT_FILE_FL_FILTERED)) &&
2462	(entry = this_cpu_read(trace_buffered_event))) {
2463	/ Try to use the per cpu buffer first /
2464	val = this_cpu_inc_return(trace_buffered_event_cnt);
2465	if (val == `1`) {
2466	trace_event_setup(entry, type, flags, pc);
2467	entry->array[`0`] = len;
2468	return entry;
2469	}
2470	this_cpu_dec(trace_buffered_event_cnt);
2471	}
2472
2473	entry = __trace_buffer_lock_reserve(*current_rb,
2474	type, len, flags, pc);
2475	/*
2476	* If tracing is off, but we have triggers enabled
2477	* we still need to look at the event data. Use the temp_buffer
2478	* to store the trace event for the tigger to use. It's recusive
2479	* safe and will not be recorded anywhere.
2480	*/
2481	if (!entry && trace_file->flags & EVENT_FILE_FL_TRIGGER_COND) {
2482	*current_rb = temp_buffer;
2483	entry = __trace_buffer_lock_reserve(*current_rb,
2484	type, len, flags, pc);
2485	}
2486	return entry;
2487	}
2488	EXPORT_SYMBOL_GPL(trace_event_buffer_lock_reserve);
2489
2490	static DEFINE_SPINLOCK(tracepoint_iter_lock);
2491	static DEFINE_MUTEX(tracepoint_printk_mutex);
2492
2493	static void output_printk(struct trace_event_buffer *fbuffer)
2494	{
2495	struct trace_event_call *event_call;
2496	struct trace_event *event;
2497	unsigned long flags;
2498	struct trace_iterator *iter = tracepoint_print_iter;
2499
2500	/ We should never get here if iter is NULL /
2501	if (WARN_ON_ONCE(!iter))
2502	return;
2503
2504	event_call = fbuffer->trace_file->event_call;
2505	if (!event_call \|\| !event_call->event.funcs \|\|
2506	!event_call->event.funcs->trace)
2507	return;
2508
2509	event = &fbuffer->trace_file->event_call->event;
2510
2511	spin_lock_irqsave(&tracepoint_iter_lock, flags);
2512	trace_seq_init(&iter->seq);
2513	iter->ent = fbuffer->entry;
2514	event_call->event.funcs->trace(iter, `0`, event);
2515	trace_seq_putc(&iter->seq, `0`);
2516	printk("%s", iter->seq.buffer);
2517
2518	spin_unlock_irqrestore(&tracepoint_iter_lock, flags);
2519	}
2520
2521	int tracepoint_printk_sysctl(struct ctl_table table, int* write,
2522	void __user buffer, size_t lenp,
2523	loff_t *ppos)
2524	{
2525	int save_tracepoint_printk;
2526	int ret;
2527
2528	mutex_lock(&tracepoint_printk_mutex);
2529	save_tracepoint_printk = tracepoint_printk;
2530
2531	ret = proc_dointvec(table, write, buffer, lenp, ppos);
2532
2533	/*
2534	* This will force exiting early, as tracepoint_printk
2535	* is always zero when tracepoint_printk_iter is not allocated
2536	*/
2537	if (!tracepoint_print_iter)
2538	tracepoint_printk = `0`;
2539
2540	if (save_tracepoint_printk == tracepoint_printk)
2541	goto out;
2542
2543	if (tracepoint_printk)
2544	static_key_enable(&tracepoint_printk_key.key);
2545	else
2546	static_key_disable(&tracepoint_printk_key.key);
2547
2548	out:
2549	mutex_unlock(&tracepoint_printk_mutex);
2550
2551	return ret;
2552	}
2553
2554	void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
2555	{
2556	if (static_key_false(&tracepoint_printk_key.key))
2557	output_printk(fbuffer);
2558
2559	event_trigger_unlock_commit(fbuffer->trace_file, fbuffer->buffer,
2560	fbuffer->event, fbuffer->entry,
2561	fbuffer->flags, fbuffer->pc);
2562	}
2563	EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
2564
2565	/*
2566	* Skip 3:
2567	*
2568	* trace_buffer_unlock_commit_regs()
2569	* trace_event_buffer_commit()
2570	* trace_event_raw_event_xxx()
2571	*/
2572	# define STACK_SKIP 3
2573
2574	void trace_buffer_unlock_commit_regs(struct trace_array *tr,
2575	struct ring_buffer *buffer,
2576	struct ring_buffer_event *event,
2577	unsigned long flags, int pc,
2578	struct pt_regs *regs)
2579	{
2580	__buffer_unlock_commit(buffer, event);
2581
2582	/*
2583	* If regs is not set, then skip the necessary functions.
2584	* Note, we can still get here via blktrace, wakeup tracer
2585	* and mmiotrace, but that's ok if they lose a function or
2586	* two. They are not that meaningful.
2587	*/
2588	ftrace_trace_stack(tr, buffer, flags, regs ? `0` : STACK_SKIP, pc, regs);
2589	ftrace_trace_userstack(buffer, flags, pc);
2590	}
2591
2592	/*
2593	* Similar to trace_buffer_unlock_commit_regs() but do not dump stack.
2594	*/
2595	void
2596	trace_buffer_unlock_commit_nostack(struct ring_buffer *buffer,
2597	struct ring_buffer_event *event)
2598	{
2599	__buffer_unlock_commit(buffer, event);
2600	}
2601
2602	static void
2603	trace_process_export(struct trace_export *export,
2604	struct ring_buffer_event *event)
2605	{
2606	struct trace_entry *entry;
2607	unsigned int size = `0`;
2608
2609	entry = ring_buffer_event_data(event);
2610	size = ring_buffer_event_length(event);
2611	export->write(export, entry, size);
2612	}
2613
2614	static DEFINE_MUTEX(ftrace_export_lock);
2615
2616	static struct trace_export __rcu *ftrace_exports_list __read_mostly;
2617
2618	static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
2619
2620	static inline void ftrace_exports_enable(void)
2621	{
2622	static_branch_enable(&ftrace_exports_enabled);
2623	}
2624
2625	static inline void ftrace_exports_disable(void)
2626	{
2627	static_branch_disable(&ftrace_exports_enabled);
2628	}
2629
2630	static void ftrace_exports(struct ring_buffer_event *event)
2631	{
2632	struct trace_export *export;
2633
2634	preempt_disable_notrace();
2635
2636	export = rcu_dereference_raw_notrace(ftrace_exports_list);
2637	while (export) {
2638	trace_process_export(export, event);
2639	export = rcu_dereference_raw_notrace(export->next);
2640	}
2641
2642	preempt_enable_notrace();
2643	}
2644
2645	static inline void
2646	add_trace_export(struct trace_export list, struct** trace_export *export)
2647	{
2648	rcu_assign_pointer(export->next, *list);
2649	/*
2650	* We are entering export into the list but another
2651	* CPU might be walking that list. We need to make sure
2652	* the export->next pointer is valid before another CPU sees
2653	* the export pointer included into the list.
2654	*/
2655	rcu_assign_pointer(*list, export);
2656	}
2657
2658	static inline int
2659	rm_trace_export(struct trace_export list, struct** trace_export *export)
2660	{
2661	struct trace_export **p;
2662
2663	for (p = list; p != NULL; p = &(p)->next)
2664	if (*p == export)
2665	break;
2666
2667	if (*p != export)
2668	return -`1`;
2669
2670	rcu_assign_pointer(p, (p)->next);
2671
2672	return `0`;
2673	}
2674
2675	static inline void
2676	add_ftrace_export(struct trace_export list, struct** trace_export *export)
2677	{
2678	if (*list == NULL)
2679	ftrace_exports_enable();
2680
2681	add_trace_export(list, export);
2682	}
2683
2684	static inline int
2685	rm_ftrace_export(struct trace_export list, struct** trace_export *export)
2686	{
2687	int ret;
2688
2689	ret = rm_trace_export(list, export);
2690	if (*list == NULL)
2691	ftrace_exports_disable();
2692
2693	return ret;
2694	}
2695
2696	int register_ftrace_export(struct trace_export *export)
2697	{
2698	if (WARN_ON_ONCE(!export->write))
2699	return -`1`;
2700
2701	mutex_lock(&ftrace_export_lock);
2702
2703	add_ftrace_export(&ftrace_exports_list, export);
2704
2705	mutex_unlock(&ftrace_export_lock);
2706
2707	return `0`;
2708	}
2709	EXPORT_SYMBOL_GPL(register_ftrace_export);
2710
2711	int unregister_ftrace_export(struct trace_export *export)
2712	{
2713	int ret;
2714
2715	mutex_lock(&ftrace_export_lock);
2716
2717	ret = rm_ftrace_export(&ftrace_exports_list, export);
2718
2719	mutex_unlock(&ftrace_export_lock);
2720
2721	return ret;
2722	}
2723	EXPORT_SYMBOL_GPL(unregister_ftrace_export);
2724
2725	void
2726	trace_function(struct trace_array *tr,
2727	unsigned long ip, unsigned long parent_ip, unsigned long flags,
2728	int pc)
2729	{
2730	struct trace_event_call *call = &event_function;
2731	struct ring_buffer *buffer = tr->trace_buffer.buffer;
2732	struct ring_buffer_event *event;
2733	struct ftrace_entry *entry;
2734
2735	event = __trace_buffer_lock_reserve(buffer, TRACE_FN, sizeof(*entry),
2736	flags, pc);
2737	if (!event)
2738	return;
2739	entry = ring_buffer_event_data(event);
2740	entry->ip = ip;
2741	entry->parent_ip = parent_ip;
2742
2743	if (!call_filter_check_discard(call, entry, buffer, event)) {
2744	if (static_branch_unlikely(&ftrace_exports_enabled))
2745	ftrace_exports(event);
2746	__buffer_unlock_commit(buffer, event);
2747	}
2748	}
2749
2750	#ifdef CONFIG_STACKTRACE
2751
2752	#define FTRACE_STACK_MAX_ENTRIES (PAGE_SIZE / sizeof(unsigned long))
2753	struct ftrace_stack {
2754	unsigned long calls[FTRACE_STACK_MAX_ENTRIES];
2755	};
2756
2757	static DEFINE_PER_CPU(struct ftrace_stack, ftrace_stack);
2758	static DEFINE_PER_CPU(int, ftrace_stack_reserve);
2759
2760	static void __ftrace_trace_stack(struct ring_buffer *buffer,
2761	unsigned long flags,
2762	int skip, int pc, struct pt_regs *regs)
2763	{
2764	struct trace_event_call *call = &event_kernel_stack;
2765	struct ring_buffer_event *event;
2766	struct stack_entry *entry;
2767	struct stack_trace trace;
2768	int use_stack;
2769	int size = FTRACE_STACK_ENTRIES;
2770
2771	trace.nr_entries = `0`;
2772	trace.skip = skip;
2773
2774	/*
2775	* Add one, for this function and the call to save_stack_trace()
2776	* If regs is set, then these functions will not be in the way.
2777	*/
2778	#ifndef CONFIG_UNWINDER_ORC
2779	if (!regs)
2780	trace.skip++;
2781	#endif
2782
2783	/*
2784	* Since events can happen in NMIs there's no safe way to
2785	* use the per cpu ftrace_stacks. We reserve it and if an interrupt
2786	* or NMI comes in, it will just have to use the default
2787	* FTRACE_STACK_SIZE.
2788	*/
2789	preempt_disable_notrace();
2790
2791	use_stack = __this_cpu_inc_return(ftrace_stack_reserve);
2792	/*
2793	* We don't need any atomic variables, just a barrier.
2794	* If an interrupt comes in, we don't care, because it would
2795	* have exited and put the counter back to what we want.
2796	* We just need a barrier to keep gcc from moving things
2797	* around.
2798	*/
2799	barrier();
2800	if (use_stack == `1`) {
2801	trace.entries = this_cpu_ptr(ftrace_stack.calls);
2802	trace.max_entries = FTRACE_STACK_MAX_ENTRIES;
2803
2804	if (regs)
2805	save_stack_trace_regs(regs, &trace);
2806	else
2807	save_stack_trace(&trace);
2808
2809	if (trace.nr_entries > size)
2810	size = trace.nr_entries;
2811	} else
2812	/ From now on, use_stack is a boolean /
2813	use_stack = `0`;
2814
2815	size = sizeof(unsigned* long);
2816
2817	event = __trace_buffer_lock_reserve(buffer, TRACE_STACK,
2818	sizeof(*entry) + size, flags, pc);
2819	if (!event)
2820	goto out;
2821	entry = ring_buffer_event_data(event);
2822
2823	memset(&entry->caller, `0`, size);
2824
2825	if (use_stack)
2826	memcpy(&entry->caller, trace.entries,
2827	trace.nr_entries * sizeof(unsigned long));
2828	else {
2829	trace.max_entries = FTRACE_STACK_ENTRIES;
2830	trace.entries = entry->caller;
2831	if (regs)
2832	save_stack_trace_regs(regs, &trace);
2833	else
2834	save_stack_trace(&trace);
2835	}
2836
2837	entry->size = trace.nr_entries;
2838
2839	if (!call_filter_check_discard(call, entry, buffer, event))
2840	__buffer_unlock_commit(buffer, event);
2841
2842	out:
2843	/ Again, don't let gcc optimize things here /
2844	barrier();
2845	__this_cpu_dec(ftrace_stack_reserve);
2846	preempt_enable_notrace();
2847
2848	}
2849
2850	static inline void ftrace_trace_stack(struct trace_array *tr,
2851	struct ring_buffer *buffer,
2852	unsigned long flags,
2853	int skip, int pc, struct pt_regs *regs)
2854	{
2855	if (!(tr->trace_flags & TRACE_ITER_STACKTRACE))
2856	return;
2857
2858	__ftrace_trace_stack(buffer, flags, skip, pc, regs);
2859	}
2860
2861	void __trace_stack(struct trace_array tr, unsigned* long flags, int skip,
2862	int pc)
2863	{
2864	struct ring_buffer *buffer = tr->trace_buffer.buffer;
2865
2866	if (rcu_is_watching()) {
2867	__ftrace_trace_stack(buffer, flags, skip, pc, NULL);
2868	return;
2869	}
2870
2871	/*
2872	* When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
2873	* but if the above rcu_is_watching() failed, then the NMI
2874	* triggered someplace critical, and rcu_irq_enter() should
2875	* not be called from NMI.
2876	*/
2877	if (unlikely(in_nmi()))
2878	return;
2879
2880	rcu_irq_enter_irqson();
2881	__ftrace_trace_stack(buffer, flags, skip, pc, NULL);
2882	rcu_irq_exit_irqson();
2883	}
2884
2885	/**
2886	* trace_dump_stack - record a stack back trace in the trace buffer
2887	* @skip: Number of functions to skip (helper handlers)
2888	*/
2889	void trace_dump_stack(int skip)
2890	{
2891	unsigned long flags;
2892
2893	if (tracing_disabled \|\| tracing_selftest_running)
2894	return;
2895
2896	local_save_flags(flags);
2897
2898	#ifndef CONFIG_UNWINDER_ORC
2899	/ Skip 1 to skip this function. /
2900	skip++;
2901	#endif
2902	__ftrace_trace_stack(global_trace.trace_buffer.buffer,
2903	flags, skip, preempt_count(), NULL);
2904	}
2905	EXPORT_SYMBOL_GPL(trace_dump_stack);
2906
2907	static DEFINE_PER_CPU(int, user_stack_count);
2908
2909	void
2910	ftrace_trace_userstack(struct ring_buffer buffer, unsigned* long flags, int pc)
2911	{
2912	struct trace_event_call *call = &event_user_stack;
2913	struct ring_buffer_event *event;
2914	struct userstack_entry *entry;
2915	struct stack_trace trace;
2916
2917	if (!(global_trace.trace_flags & TRACE_ITER_USERSTACKTRACE))
2918	return;
2919
2920	/*
2921	* NMIs can not handle page faults, even with fix ups.
2922	* The save user stack can (and often does) fault.
2923	*/
2924	if (unlikely(in_nmi()))
2925	return;
2926
2927	/*
2928	* prevent recursion, since the user stack tracing may
2929	* trigger other kernel events.
2930	*/
2931	preempt_disable();
2932	if (__this_cpu_read(user_stack_count))
2933	goto out;
2934
2935	__this_cpu_inc(user_stack_count);
2936
2937	event = __trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
2938	sizeof(*entry), flags, pc);
2939	if (!event)
2940	goto out_drop_count;
2941	entry = ring_buffer_event_data(event);
2942
2943	entry->tgid = current->tgid;
2944	memset(&entry->caller, `0`, sizeof(entry->caller));
2945
2946	trace.nr_entries = `0`;
2947	trace.max_entries = FTRACE_STACK_ENTRIES;
2948	trace.skip = `0`;
2949	trace.entries = entry->caller;
2950
2951	save_stack_trace_user(&trace);
2952	if (!call_filter_check_discard(call, entry, buffer, event))
2953	__buffer_unlock_commit(buffer, event);
2954
2955	out_drop_count:
2956	__this_cpu_dec(user_stack_count);
2957	out:
2958	preempt_enable();
2959	}
2960
2961	#ifdef UNUSED
2962	static void __trace_userstack(struct trace_array tr, unsigned* long flags)
2963	{
2964	ftrace_trace_userstack(tr, flags, preempt_count());
2965	}
2966	#endif /* UNUSED */
2967
2968	#endif /* CONFIG_STACKTRACE */
2969
2970	/ created for use with alloc_percpu /
2971	struct trace_buffer_struct {
2972	int nesting;
2973	char buffer[`4`][TRACE_BUF_SIZE];
2974	};
2975
2976	static struct trace_buffer_struct *trace_percpu_buffer;
2977
2978	/*
2979	* Thise allows for lockless recording. If we're nested too deeply, then
2980	* this returns NULL.
2981	*/
2982	static char get_trace_buf(void*)
2983	{
2984	struct trace_buffer_struct *buffer = this_cpu_ptr(trace_percpu_buffer);
2985
2986	if (!buffer \|\| buffer->nesting >= `4`)
2987	return NULL;
2988
2989	buffer->nesting++;
2990
2991	/ Interrupts must see nesting incremented before we use the buffer /
2992	barrier();
2993	return &buffer->buffer[buffer->nesting][`0`];
2994	}
2995
2996	static void put_trace_buf(void)
2997	{
2998	/ Don't let the decrement of nesting leak before this /
2999	barrier();
3000	this_cpu_dec(trace_percpu_buffer->nesting);
3001	}
3002
3003	static int alloc_percpu_trace_buffer(void)
3004	{
3005	struct trace_buffer_struct *buffers;
3006
3007	buffers = alloc_percpu(struct trace_buffer_struct);
3008	if (WARN(!buffers, "Could not allocate percpu trace_printk buffer"))
3009	return -ENOMEM;
3010
3011	trace_percpu_buffer = buffers;
3012	return `0`;
3013	}
3014
3015	static int buffers_allocated;
3016
3017	void trace_printk_init_buffers(void)
3018	{
3019	if (buffers_allocated)
3020	return;
3021
3022	if (alloc_percpu_trace_buffer())
3023	return;
3024
3025	/ trace_printk() is for debug use only. Don't use it in production. /
3026
3027	pr_warn("\n");
3028	pr_warn("**********************************************************\n");
3029	pr_warn(" NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE \n");
3030	pr_warn(" \n");
3031	pr_warn(" trace_printk() being used. Allocating extra memory. \n");
3032	pr_warn(" \n");
3033	pr_warn(" This means that this is a DEBUG kernel and it is \n");
3034	pr_warn(" unsafe for production use. \n");
3035	pr_warn(" \n");
3036	pr_warn(" If you see this message and you are not debugging \n");
3037	pr_warn(" the kernel, report this immediately to your vendor! \n");
3038	pr_warn(" \n");
3039	pr_warn(" NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE \n");
3040	pr_warn("**********************************************************\n");
3041
3042	/ Expand the buffers to set size /
3043	tracing_update_buffers();
3044
3045	buffers_allocated = `1`;
3046
3047	/*
3048	* trace_printk_init_buffers() can be called by modules.
3049	* If that happens, then we need to start cmdline recording
3050	* directly here. If the global_trace.buffer is already
3051	* allocated here, then this was called by module code.
3052	*/
3053	if (global_trace.trace_buffer.buffer)
3054	tracing_start_cmdline_record();
3055	}
3056
3057	void trace_printk_start_comm(void)
3058	{
3059	/ Start tracing comms if trace printk is set /
3060	if (!buffers_allocated)
3061	return;
3062	tracing_start_cmdline_record();
3063	}
3064
3065	static void trace_printk_start_stop_comm(int enabled)
3066	{
3067	if (!buffers_allocated)
3068	return;
3069
3070	if (enabled)
3071	tracing_start_cmdline_record();
3072	else
3073	tracing_stop_cmdline_record();
3074	}
3075
3076	/**
3077	* trace_vbprintk - write binary msg to tracing buffer
3078	*
3079	*/
3080	int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
3081	{
3082	struct trace_event_call *call = &event_bprint;
3083	struct ring_buffer_event *event;
3084	struct ring_buffer *buffer;
3085	struct trace_array *tr = &global_trace;
3086	struct bprint_entry *entry;
3087	unsigned long flags;
3088	char *tbuffer;
3089	int len = `0`, size, pc;
3090
3091	if (unlikely(tracing_selftest_running \|\| tracing_disabled))
3092	return `0`;
3093
3094	/ Don't pollute graph traces with trace_vprintk internals /
3095	pause_graph_tracing();
3096
3097	pc = preempt_count();
3098	preempt_disable_notrace();
3099
3100	tbuffer = get_trace_buf();
3101	if (!tbuffer) {
3102	len = `0`;
3103	goto out_nobuffer;
3104	}
3105
3106	len = vbin_printf((u32 )tbuffer, TRACE_BUF_SIZE/sizeof(int*), fmt, args);
3107
3108	if (len > TRACE_BUF_SIZE/sizeof(int) \|\| len < `0`)
3109	goto out;
3110
3111	local_save_flags(flags);
3112	size = sizeof(entry) + sizeof(u32) len;
3113	buffer = tr->trace_buffer.buffer;
3114	event = __trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
3115	flags, pc);
3116	if (!event)
3117	goto out;
3118	entry = ring_buffer_event_data(event);
3119	entry->ip = ip;
3120	entry->fmt = fmt;
3121
3122	memcpy(entry->buf, tbuffer, sizeof(u32) * len);
3123	if (!call_filter_check_discard(call, entry, buffer, event)) {
3124	__buffer_unlock_commit(buffer, event);
3125	ftrace_trace_stack(tr, buffer, flags, `6`, pc, NULL);
3126	}
3127
3128	out:
3129	put_trace_buf();
3130
3131	out_nobuffer:
3132	preempt_enable_notrace();
3133	unpause_graph_tracing();
3134
3135	return len;
3136	}
3137	EXPORT_SYMBOL_GPL(trace_vbprintk);
3138
3139	__printf(`3`, `0`)
3140	static int
3141	__trace_array_vprintk(struct ring_buffer *buffer,
3142	unsigned long ip, const char *fmt, va_list args)
3143	{
3144	struct trace_event_call *call = &event_print;
3145	struct ring_buffer_event *event;
3146	int len = `0`, size, pc;
3147	struct print_entry *entry;
3148	unsigned long flags;
3149	char *tbuffer;
3150
3151	if (tracing_disabled \|\| tracing_selftest_running)
3152	return `0`;
3153
3154	/ Don't pollute graph traces with trace_vprintk internals /
3155	pause_graph_tracing();
3156
3157	pc = preempt_count();
3158	preempt_disable_notrace();
3159
3160
3161	tbuffer = get_trace_buf();
3162	if (!tbuffer) {
3163	len = `0`;
3164	goto out_nobuffer;
3165	}
3166
3167	len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
3168
3169	local_save_flags(flags);
3170	size = sizeof(*entry) + len + `1`;
3171	event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
3172	flags, pc);
3173	if (!event)
3174	goto out;
3175	entry = ring_buffer_event_data(event);
3176	entry->ip = ip;
3177
3178	memcpy(&entry->buf, tbuffer, len + `1`);
3179	if (!call_filter_check_discard(call, entry, buffer, event)) {
3180	__buffer_unlock_commit(buffer, event);
3181	ftrace_trace_stack(&global_trace, buffer, flags, `6`, pc, NULL);
3182	}
3183
3184	out:
3185	put_trace_buf();
3186
3187	out_nobuffer:
3188	preempt_enable_notrace();
3189	unpause_graph_tracing();
3190
3191	return len;
3192	}
3193
3194	__printf(`3`, `0`)
3195	int trace_array_vprintk(struct trace_array *tr,
3196	unsigned long ip, const char *fmt, va_list args)
3197	{
3198	return __trace_array_vprintk(tr->trace_buffer.buffer, ip, fmt, args);
3199	}
3200
3201	__printf(`3`, `0`)
3202	int trace_array_printk(struct trace_array *tr,
3203	unsigned long ip, const char *fmt, ...)
3204	{
3205	int ret;
3206	va_list ap;
3207
3208	if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
3209	return `0`;
3210
3211	va_start(ap, fmt);
3212	ret = trace_array_vprintk(tr, ip, fmt, ap);
3213	va_end(ap);
3214	return ret;
3215	}
3216
3217	__printf(`3`, `4`)
3218	int trace_array_printk_buf(struct ring_buffer *buffer,
3219	unsigned long ip, const char *fmt, ...)
3220	{
3221	int ret;
3222	va_list ap;
3223
3224	if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
3225	return `0`;
3226
3227	va_start(ap, fmt);
3228	ret = __trace_array_vprintk(buffer, ip, fmt, ap);
3229	va_end(ap);
3230	return ret;
3231	}
3232
3233	__printf(`2`, `0`)
3234	int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
3235	{
3236	return trace_array_vprintk(&global_trace, ip, fmt, args);
3237	}
3238	EXPORT_SYMBOL_GPL(trace_vprintk);
3239
3240	static void trace_iterator_increment(struct trace_iterator *iter)
3241	{
3242	struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, iter->cpu);
3243
3244	iter->idx++;
3245	if (buf_iter)
3246	ring_buffer_read(buf_iter, NULL);
3247	}
3248
3249	static struct trace_entry *
3250	peek_next_entry(struct trace_iterator iter, int* cpu, u64 *ts,
3251	unsigned long *lost_events)
3252	{
3253	struct ring_buffer_event *event;
3254	struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, cpu);
3255
3256	if (buf_iter)
3257	event = ring_buffer_iter_peek(buf_iter, ts);
3258	else
3259	event = ring_buffer_peek(iter->trace_buffer->buffer, cpu, ts,
3260	lost_events);
3261
3262	if (event) {
3263	iter->ent_size = ring_buffer_event_length(event);
3264	return ring_buffer_event_data(event);
3265	}
3266	iter->ent_size = `0`;
3267	return NULL;
3268	}
3269
3270	static struct trace_entry *
3271	__find_next_entry(struct trace_iterator iter, int* *ent_cpu,
3272	unsigned long missing_events, u64 ent_ts)
3273	{
3274	struct ring_buffer *buffer = iter->trace_buffer->buffer;
3275	struct trace_entry ent, next = NULL;
3276	unsigned long lost_events = `0`, next_lost = `0`;
3277	int cpu_file = iter->cpu_file;
3278	u64 next_ts = `0`, ts;
3279	int next_cpu = -`1`;
3280	int next_size = `0`;
3281	int cpu;
3282
3283	/*
3284	* If we are in a per_cpu trace file, don't bother by iterating over
3285	* all cpu and peek directly.
3286	*/
3287	if (cpu_file > RING_BUFFER_ALL_CPUS) {
3288	if (ring_buffer_empty_cpu(buffer, cpu_file))
3289	return NULL;
3290	ent = peek_next_entry(iter, cpu_file, ent_ts, missing_events);
3291	if (ent_cpu)
3292	*ent_cpu = cpu_file;
3293
3294	return ent;
3295	}
3296
3297	for_each_tracing_cpu(cpu) {
3298
3299	if (ring_buffer_empty_cpu(buffer, cpu))
3300	continue;
3301
3302	ent = peek_next_entry(iter, cpu, &ts, &lost_events);
3303
3304	/*
3305	* Pick the entry with the smallest timestamp:
3306	*/
3307	if (ent && (!next \|\| ts < next_ts)) {
3308	next = ent;
3309	next_cpu = cpu;
3310	next_ts = ts;
3311	next_lost = lost_events;
3312	next_size = iter->ent_size;
3313	}
3314	}
3315
3316	iter->ent_size = next_size;
3317
3318	if (ent_cpu)
3319	*ent_cpu = next_cpu;
3320
3321	if (ent_ts)
3322	*ent_ts = next_ts;
3323
3324	if (missing_events)
3325	*missing_events = next_lost;
3326
3327	return next;
3328	}
3329
3330	/ Find the next real entry, without updating the iterator itself /
3331	struct trace_entry trace_find_next_entry(struct* trace_iterator *iter,
3332	int ent_cpu, u64 ent_ts)
3333	{
3334	return __find_next_entry(iter, ent_cpu, NULL, ent_ts);
3335	}
3336
3337	/ Find the next real entry, and increment the iterator to the next entry /
3338	void trace_find_next_entry_inc(struct* trace_iterator *iter)
3339	{
3340	iter->ent = __find_next_entry(iter, &iter->cpu,
3341	&iter->lost_events, &iter->ts);
3342
3343	if (iter->ent)
3344	trace_iterator_increment(iter);
3345
3346	return iter->ent ? iter : NULL;
3347	}
3348
3349	static void trace_consume(struct trace_iterator *iter)
3350	{
3351	ring_buffer_consume(iter->trace_buffer->buffer, iter->cpu, &iter->ts,
3352	&iter->lost_events);
3353	}
3354
3355	static void s_next(struct* seq_file m, void* v, loff_t pos)
3356	{
3357	struct trace_iterator *iter = m->private;
3358	int i = (int)*pos;
3359	void *ent;
3360
3361	WARN_ON_ONCE(iter->leftover);
3362
3363	(*pos)++;
3364
3365	/ can't go backwards /
3366	if (iter->idx > i)
3367	return NULL;
3368
3369	if (iter->idx < `0`)
3370	ent = trace_find_next_entry_inc(iter);
3371	else
3372	ent = iter;
3373
3374	while (ent && iter->idx < i)
3375	ent = trace_find_next_entry_inc(iter);
3376
3377	iter->pos = *pos;
3378
3379	return ent;
3380	}
3381
3382	void tracing_iter_reset(struct trace_iterator iter, int* cpu)
3383	{
3384	struct ring_buffer_event *event;
3385	struct ring_buffer_iter *buf_iter;
3386	unsigned long entries = `0`;
3387	u64 ts;
3388
3389	per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = `0`;
3390
3391	buf_iter = trace_buffer_iter(iter, cpu);
3392	if (!buf_iter)
3393	return;
3394
3395	ring_buffer_iter_reset(buf_iter);
3396
3397	/*
3398	* We could have the case with the max latency tracers
3399	* that a reset never took place on a cpu. This is evident
3400	* by the timestamp being before the start of the buffer.
3401	*/
3402	while ((event = ring_buffer_iter_peek(buf_iter, &ts))) {
3403	if (ts >= iter->trace_buffer->time_start)
3404	break;
3405	entries++;
3406	ring_buffer_read(buf_iter, NULL);
3407	}
3408
3409	per_cpu_ptr(iter->trace_buffer->data, cpu)->skipped_entries = entries;
3410	}
3411
3412	/*
3413	* The current tracer is copied to avoid a global locking
3414	* all around.
3415	*/
3416	static void s_start(struct* seq_file m, loff_t pos)
3417	{
3418	struct trace_iterator *iter = m->private;
3419	struct trace_array *tr = iter->tr;
3420	int cpu_file = iter->cpu_file;
3421	void *p = NULL;
3422	loff_t l = `0`;
3423	int cpu;
3424
3425	/*
3426	* copy the tracer to avoid using a global lock all around.
3427	* iter->trace is a copy of current_trace, the pointer to the
3428	* name may be used instead of a strcmp(), as iter->trace->name
3429	* will point to the same string as current_trace->name.
3430	*/
3431	mutex_lock(&trace_types_lock);
3432	if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name))
3433	iter->trace = tr->current_trace;
3434	mutex_unlock(&trace_types_lock);
3435
3436	#ifdef CONFIG_TRACER_MAX_TRACE
3437	if (iter->snapshot && iter->trace->use_max_tr)
3438	return ERR_PTR(-EBUSY);
3439	#endif
3440
3441	if (!iter->snapshot)
3442	atomic_inc(&trace_record_taskinfo_disabled);
3443
3444	if (*pos != iter->pos) {
3445	iter->ent = NULL;
3446	iter->cpu = `0`;
3447	iter->idx = -`1`;
3448
3449	if (cpu_file == RING_BUFFER_ALL_CPUS) {
3450	for_each_tracing_cpu(cpu)
3451	tracing_iter_reset(iter, cpu);
3452	} else
3453	tracing_iter_reset(iter, cpu_file);
3454
3455	iter->leftover = `0`;
3456	for (p = iter; p && l < *pos; p = s_next(m, p, &l))
3457	;
3458
3459	} else {
3460	/*
3461	* If we overflowed the seq_file before, then we want
3462	* to just reuse the trace_seq buffer again.
3463	*/
3464	if (iter->leftover)
3465	p = iter;
3466	else {
3467	l = *pos - `1`;
3468	p = s_next(m, p, &l);
3469	}
3470	}
3471
3472	trace_event_read_lock();
3473	trace_access_lock(cpu_file);
3474	return p;
3475	}
3476
3477	static void s_stop(struct seq_file m, void* *p)
3478	{
3479	struct trace_iterator *iter = m->private;
3480
3481	#ifdef CONFIG_TRACER_MAX_TRACE
3482	if (iter->snapshot && iter->trace->use_max_tr)
3483	return;
3484	#endif
3485
3486	if (!iter->snapshot)
3487	atomic_dec(&trace_record_taskinfo_disabled);
3488
3489	trace_access_unlock(iter->cpu_file);
3490	trace_event_read_unlock();
3491	}
3492
3493	static void
3494	get_total_entries(struct trace_buffer *buf,
3495	unsigned long total, unsigned* long *entries)
3496	{
3497	unsigned long count;
3498	int cpu;
3499
3500	*total = `0`;
3501	*entries = `0`;
3502
3503	for_each_tracing_cpu(cpu) {
3504	count = ring_buffer_entries_cpu(buf->buffer, cpu);
3505	/*
3506	* If this buffer has skipped entries, then we hold all
3507	* entries for the trace and we need to ignore the
3508	* ones before the time stamp.
3509	*/
3510	if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
3511	count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
3512	/ total is the same as the entries /
3513	*total += count;
3514	} else
3515	*total += count +
3516	ring_buffer_overrun_cpu(buf->buffer, cpu);
3517	*entries += count;
3518	}
3519	}
3520
3521	static void print_lat_help_header(struct seq_file *m)
3522	{
3523	seq_puts(m, "# _------=> CPU# \n"
3524	"# / _-----=> irqs-off \n"
3525	"# \| / _----=> need-resched \n"
3526	"# \|\| / _---=> hardirq/softirq \n"
3527	"# \|\|\| / _--=> preempt-depth \n"
3528	"# \|\|\|\| / delay \n"
3529	"# cmd pid \|\|\|\|\| time \| caller \n"
3530	"# \\ / \|\|\|\|\| \\ \| / \n");
3531	}
3532
3533	static void print_event_info(struct

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