xref: /linux/include/linux/tracepoint.h (revision c17ee635fd3a482b2ad2bf5e269755c2eae5f25e)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 #ifndef _LINUX_TRACEPOINT_H
3 #define _LINUX_TRACEPOINT_H
4 
5 /*
6  * Kernel Tracepoint API.
7  *
8  * See Documentation/trace/tracepoints.rst.
9  *
10  * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
11  *
12  * Heavily inspired from the Linux Kernel Markers.
13  */
14 
15 #include <linux/smp.h>
16 #include <linux/srcu.h>
17 #include <linux/errno.h>
18 #include <linux/types.h>
19 #include <linux/rcupdate.h>
20 #include <linux/rcupdate_trace.h>
21 #include <linux/tracepoint-defs.h>
22 #include <linux/static_call.h>
23 
24 struct module;
25 struct tracepoint;
26 struct notifier_block;
27 
28 struct trace_eval_map {
29 	const char		*system;
30 	const char		*eval_string;
31 	unsigned long		eval_value;
32 };
33 
34 #define TRACEPOINT_DEFAULT_PRIO	10
35 
36 extern int
37 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
38 extern int
39 tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
40 			       int prio);
41 extern int
42 tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe, void *data,
43 					 int prio);
44 extern int
45 tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
46 static inline int
47 tracepoint_probe_register_may_exist(struct tracepoint *tp, void *probe,
48 				    void *data)
49 {
50 	return tracepoint_probe_register_prio_may_exist(tp, probe, data,
51 							TRACEPOINT_DEFAULT_PRIO);
52 }
53 extern void
54 for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
55 		void *priv);
56 
57 #ifdef CONFIG_MODULES
58 struct tp_module {
59 	struct list_head list;
60 	struct module *mod;
61 };
62 
63 bool trace_module_has_bad_taint(struct module *mod);
64 extern int register_tracepoint_module_notifier(struct notifier_block *nb);
65 extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
66 void for_each_module_tracepoint(void (*fct)(struct tracepoint *,
67 					struct module *, void *),
68 				void *priv);
69 void for_each_tracepoint_in_module(struct module *,
70 				   void (*fct)(struct tracepoint *,
71 					struct module *, void *),
72 				   void *priv);
73 #else
74 static inline bool trace_module_has_bad_taint(struct module *mod)
75 {
76 	return false;
77 }
78 static inline
79 int register_tracepoint_module_notifier(struct notifier_block *nb)
80 {
81 	return 0;
82 }
83 static inline
84 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
85 {
86 	return 0;
87 }
88 static inline
89 void for_each_module_tracepoint(void (*fct)(struct tracepoint *,
90 					struct module *, void *),
91 				void *priv)
92 {
93 }
94 static inline
95 void for_each_tracepoint_in_module(struct module *mod,
96 				   void (*fct)(struct tracepoint *,
97 					struct module *, void *),
98 				   void *priv)
99 {
100 }
101 #endif /* CONFIG_MODULES */
102 
103 /*
104  * tracepoint_synchronize_unregister must be called between the last tracepoint
105  * probe unregistration and the end of module exit to make sure there is no
106  * caller executing a probe when it is freed.
107  *
108  * An alternative is to use the following for batch reclaim associated
109  * with a given tracepoint:
110  *
111  * - tracepoint_is_faultable() == false: call_srcu()
112  * - tracepoint_is_faultable() == true:  call_rcu_tasks_trace()
113  */
114 #ifdef CONFIG_TRACEPOINTS
115 extern struct srcu_struct tracepoint_srcu;
116 static inline void tracepoint_synchronize_unregister(void)
117 {
118 	synchronize_rcu_tasks_trace();
119 	synchronize_srcu(&tracepoint_srcu);
120 }
121 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
122 {
123 	return tp->ext && tp->ext->faultable;
124 }
125 #else
126 static inline void tracepoint_synchronize_unregister(void)
127 { }
128 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
129 {
130 	return false;
131 }
132 #endif
133 
134 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
135 extern int syscall_regfunc(void);
136 extern void syscall_unregfunc(void);
137 #endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
138 
139 #ifndef PARAMS
140 #define PARAMS(args...) args
141 #endif
142 
143 #define TRACE_DEFINE_ENUM(x)
144 #define TRACE_DEFINE_SIZEOF(x)
145 
146 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
147 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
148 {
149 	return offset_to_ptr(p);
150 }
151 
152 #define __TRACEPOINT_ENTRY(name)					\
153 	asm("	.section \"__tracepoints_ptrs\", \"a\"		\n"	\
154 	    "	.balign 4					\n"	\
155 	    "	.long 	__tracepoint_" #name " - .		\n"	\
156 	    "	.previous					\n")
157 #else
158 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
159 {
160 	return *p;
161 }
162 
163 #define __TRACEPOINT_ENTRY(name)					 \
164 	static tracepoint_ptr_t __tracepoint_ptr_##name __used		 \
165 	__section("__tracepoints_ptrs") = &__tracepoint_##name
166 #endif
167 
168 #endif /* _LINUX_TRACEPOINT_H */
169 
170 /*
171  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
172  *  file ifdef protection.
173  *  This is due to the way trace events work. If a file includes two
174  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
175  *  will override the TRACE_EVENT and break the second include.
176  */
177 
178 #ifndef DECLARE_TRACE
179 
180 #define TP_PROTO(args...)	args
181 #define TP_ARGS(args...)	args
182 #define TP_CONDITION(args...)	args
183 
184 /*
185  * Individual subsystem my have a separate configuration to
186  * enable their tracepoints. By default, this file will create
187  * the tracepoints if CONFIG_TRACEPOINTS is defined. If a subsystem
188  * wants to be able to disable its tracepoints from being created
189  * it can define NOTRACE before including the tracepoint headers.
190  */
191 #if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
192 #define TRACEPOINTS_ENABLED
193 #endif
194 
195 #ifdef TRACEPOINTS_ENABLED
196 
197 #ifdef CONFIG_HAVE_STATIC_CALL
198 #define __DO_TRACE_CALL(name, args)					\
199 	do {								\
200 		struct tracepoint_func *it_func_ptr;			\
201 		void *__data;						\
202 		it_func_ptr =						\
203 			rcu_dereference_raw((&__tracepoint_##name)->funcs); \
204 		if (it_func_ptr) {					\
205 			__data = (it_func_ptr)->data;			\
206 			static_call(tp_func_##name)(__data, args);	\
207 		}							\
208 	} while (0)
209 #else
210 #define __DO_TRACE_CALL(name, args)	__traceiter_##name(NULL, args)
211 #endif /* CONFIG_HAVE_STATIC_CALL */
212 
213 /*
214  * Declare an exported function that Rust code can call to trigger this
215  * tracepoint. This function does not include the static branch; that is done
216  * in Rust to avoid a function call when the tracepoint is disabled.
217  */
218 #define DEFINE_RUST_DO_TRACE(name, proto, args)
219 #define __DEFINE_RUST_DO_TRACE(name, proto, args)			\
220 	notrace void rust_do_trace_##name(proto)			\
221 	{								\
222 		__do_trace_##name(args);				\
223 	}
224 
225 /*
226  * When a tracepoint is used, it's name is added to the __tracepoint_check
227  * section. This section is only used at build time to make sure all
228  * defined tracepoints are used. It is discarded after the build.
229  */
230 # define TRACEPOINT_CHECK(name)						\
231 	static const char __used __section("__tracepoint_check")	\
232 	__trace_check_##name[] = #name;
233 
234 /*
235  * Make sure the alignment of the structure in the __tracepoints section will
236  * not add unwanted padding between the beginning of the section and the
237  * structure. Force alignment to the same alignment as the section start.
238  *
239  * When lockdep is enabled, we make sure to always test if RCU is
240  * "watching" regardless if the tracepoint is enabled or not. Tracepoints
241  * require RCU to be active, and it should always warn at the tracepoint
242  * site if it is not watching, as it will need to be active when the
243  * tracepoint is enabled.
244  */
245 #define __DECLARE_TRACE_COMMON(name, proto, args, data_proto)		\
246 	extern int __traceiter_##name(data_proto);			\
247 	DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);	\
248 	extern struct tracepoint __tracepoint_##name;			\
249 	extern void rust_do_trace_##name(proto);			\
250 	static inline int						\
251 	register_trace_##name(void (*probe)(data_proto), void *data)	\
252 	{								\
253 		return tracepoint_probe_register(&__tracepoint_##name,	\
254 						(void *)probe, data);	\
255 	}								\
256 	static inline int						\
257 	register_trace_prio_##name(void (*probe)(data_proto), void *data,\
258 				   int prio)				\
259 	{								\
260 		return tracepoint_probe_register_prio(&__tracepoint_##name, \
261 					      (void *)probe, data, prio); \
262 	}								\
263 	static inline int						\
264 	unregister_trace_##name(void (*probe)(data_proto), void *data)	\
265 	{								\
266 		return tracepoint_probe_unregister(&__tracepoint_##name,\
267 						(void *)probe, data);	\
268 	}								\
269 	static inline void						\
270 	check_trace_callback_type_##name(void (*cb)(data_proto))	\
271 	{								\
272 	}								\
273 	static inline bool						\
274 	trace_##name##_enabled(void)					\
275 	{								\
276 		return static_branch_unlikely(&__tracepoint_##name.key);\
277 	}
278 
279 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)			\
280 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
281 	static inline void __do_trace_##name(proto)			\
282 	{								\
283 		TRACEPOINT_CHECK(name)					\
284 		if (cond) {						\
285 			guard(srcu_fast_notrace)(&tracepoint_srcu);	\
286 			__DO_TRACE_CALL(name, TP_ARGS(args));		\
287 		}							\
288 	}								\
289 	static inline void trace_##name(proto)				\
290 	{								\
291 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
292 			__do_trace_##name(args);			\
293 		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {		\
294 			WARN_ONCE(!rcu_is_watching(),			\
295 				  "RCU not watching for tracepoint");	\
296 		}							\
297 	}
298 
299 #define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto)		\
300 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
301 	static inline void __do_trace_##name(proto)			\
302 	{								\
303 		TRACEPOINT_CHECK(name)					\
304 		guard(rcu_tasks_trace)();				\
305 		__DO_TRACE_CALL(name, TP_ARGS(args));			\
306 	}								\
307 	static inline void trace_##name(proto)				\
308 	{								\
309 		might_fault();						\
310 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
311 			__do_trace_##name(args);			\
312 		if (IS_ENABLED(CONFIG_LOCKDEP)) {			\
313 			WARN_ONCE(!rcu_is_watching(),			\
314 				  "RCU not watching for tracepoint");	\
315 		}							\
316 	}
317 
318 /*
319  * We have no guarantee that gcc and the linker won't up-align the tracepoint
320  * structures, so we create an array of pointers that will be used for iteration
321  * on the tracepoints.
322  *
323  * it_func[0] is never NULL because there is at least one element in the array
324  * when the array itself is non NULL.
325  */
326 #define __DEFINE_TRACE_EXT(_name, _ext, proto, args)			\
327 	static const char __tpstrtab_##_name[]				\
328 	__section("__tracepoints_strings") = #_name;			\
329 	extern struct static_call_key STATIC_CALL_KEY(tp_func_##_name);	\
330 	int __traceiter_##_name(void *__data, proto);			\
331 	void __probestub_##_name(void *__data, proto);			\
332 	struct tracepoint __tracepoint_##_name	__used			\
333 	__section("__tracepoints") = {					\
334 		.name = __tpstrtab_##_name,				\
335 		.key = STATIC_KEY_FALSE_INIT,				\
336 		.static_call_key = &STATIC_CALL_KEY(tp_func_##_name),	\
337 		.static_call_tramp = STATIC_CALL_TRAMP_ADDR(tp_func_##_name), \
338 		.iterator = &__traceiter_##_name,			\
339 		.probestub = &__probestub_##_name,			\
340 		.funcs = NULL,						\
341 		.ext = _ext,						\
342 	};								\
343 	__TRACEPOINT_ENTRY(_name);					\
344 	int __traceiter_##_name(void *__data, proto)			\
345 	{								\
346 		struct tracepoint_func *it_func_ptr;			\
347 		void *it_func;						\
348 									\
349 		it_func_ptr =						\
350 			rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
351 		if (it_func_ptr) {					\
352 			do {						\
353 				it_func = READ_ONCE((it_func_ptr)->func); \
354 				__data = (it_func_ptr)->data;		\
355 				((void(*)(void *, proto))(it_func))(__data, args); \
356 			} while ((++it_func_ptr)->func);		\
357 		}							\
358 		return 0;						\
359 	}								\
360 	void __probestub_##_name(void *__data, proto)			\
361 	{								\
362 	}								\
363 	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);	\
364 	DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))
365 
366 #define DEFINE_TRACE_FN(_name, _reg, _unreg, _proto, _args)		\
367 	static struct tracepoint_ext __tracepoint_ext_##_name = {	\
368 		.regfunc = _reg,					\
369 		.unregfunc = _unreg,					\
370 		.faultable = false,					\
371 	};								\
372 	__DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
373 
374 #define DEFINE_TRACE_SYSCALL(_name, _reg, _unreg, _proto, _args)	\
375 	static struct tracepoint_ext __tracepoint_ext_##_name = {	\
376 		.regfunc = _reg,					\
377 		.unregfunc = _unreg,					\
378 		.faultable = true,					\
379 	};								\
380 	__DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
381 
382 #define DEFINE_TRACE(_name, _proto, _args)				\
383 	__DEFINE_TRACE_EXT(_name, NULL, PARAMS(_proto), PARAMS(_args));
384 
385 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)				\
386 	TRACEPOINT_CHECK(name)						\
387 	EXPORT_SYMBOL_GPL(__tracepoint_##name);				\
388 	EXPORT_SYMBOL_GPL(__traceiter_##name);				\
389 	EXPORT_STATIC_CALL_GPL(tp_func_##name)
390 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
391 	TRACEPOINT_CHECK(name)						\
392 	EXPORT_SYMBOL(__tracepoint_##name);				\
393 	EXPORT_SYMBOL(__traceiter_##name);				\
394 	EXPORT_STATIC_CALL(tp_func_##name)
395 
396 
397 #else /* !TRACEPOINTS_ENABLED */
398 #define __DECLARE_TRACE_COMMON(name, proto, args, data_proto)		\
399 	static inline void trace_##name(proto)				\
400 	{ }								\
401 	static inline int						\
402 	register_trace_##name(void (*probe)(data_proto),		\
403 			      void *data)				\
404 	{								\
405 		return -ENOSYS;						\
406 	}								\
407 	static inline int						\
408 	unregister_trace_##name(void (*probe)(data_proto),		\
409 				void *data)				\
410 	{								\
411 		return -ENOSYS;						\
412 	}								\
413 	static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
414 	{								\
415 	}								\
416 	static inline bool						\
417 	trace_##name##_enabled(void)					\
418 	{								\
419 		return false;						\
420 	}
421 
422 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)		\
423 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
424 
425 #define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto)		\
426 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
427 
428 #define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
429 #define DEFINE_TRACE_SYSCALL(name, reg, unreg, proto, args)
430 #define DEFINE_TRACE(name, proto, args)
431 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
432 #define EXPORT_TRACEPOINT_SYMBOL(name)
433 
434 #endif /* TRACEPOINTS_ENABLED */
435 
436 #ifdef CONFIG_TRACING
437 /**
438  * tracepoint_string - register constant persistent string to trace system
439  * @str - a constant persistent string that will be referenced in tracepoints
440  *
441  * If constant strings are being used in tracepoints, it is faster and
442  * more efficient to just save the pointer to the string and reference
443  * that with a printf "%s" instead of saving the string in the ring buffer
444  * and wasting space and time.
445  *
446  * The problem with the above approach is that userspace tools that read
447  * the binary output of the trace buffers do not have access to the string.
448  * Instead they just show the address of the string which is not very
449  * useful to users.
450  *
451  * With tracepoint_string(), the string will be registered to the tracing
452  * system and exported to userspace via the debugfs/tracing/printk_formats
453  * file that maps the string address to the string text. This way userspace
454  * tools that read the binary buffers have a way to map the pointers to
455  * the ASCII strings they represent.
456  *
457  * The @str used must be a constant string and persistent as it would not
458  * make sense to show a string that no longer exists. But it is still fine
459  * to be used with modules, because when modules are unloaded, if they
460  * had tracepoints, the ring buffers are cleared too. As long as the string
461  * does not change during the life of the module, it is fine to use
462  * tracepoint_string() within a module.
463  */
464 #define tracepoint_string(str)						\
465 	({								\
466 		static const char *___tp_str __tracepoint_string = str; \
467 		___tp_str;						\
468 	})
469 #define __tracepoint_string	__used __section("__tracepoint_str")
470 #else
471 /*
472  * tracepoint_string() is used to save the string address for userspace
473  * tracing tools. When tracing isn't configured, there's no need to save
474  * anything.
475  */
476 # define tracepoint_string(str) str
477 # define __tracepoint_string
478 #endif
479 
480 #define DECLARE_TRACE(name, proto, args)				\
481 	__DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),		\
482 			cpu_online(raw_smp_processor_id()),		\
483 			PARAMS(void *__data, proto))
484 
485 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)		\
486 	__DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),		\
487 			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
488 			PARAMS(void *__data, proto))
489 
490 #define DECLARE_TRACE_SYSCALL(name, proto, args)			\
491 	__DECLARE_TRACE_SYSCALL(name##_tp, PARAMS(proto), PARAMS(args),	\
492 				PARAMS(void *__data, proto))
493 
494 #define DECLARE_TRACE_EVENT(name, proto, args)				\
495 	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
496 			cpu_online(raw_smp_processor_id()),		\
497 			PARAMS(void *__data, proto))
498 
499 #define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)		\
500 	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
501 			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
502 			PARAMS(void *__data, proto))
503 
504 #define DECLARE_TRACE_EVENT_SYSCALL(name, proto, args)			\
505 	__DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args),	\
506 				PARAMS(void *__data, proto))
507 
508 #define TRACE_EVENT_FLAGS(event, flag)
509 
510 #define TRACE_EVENT_PERF_PERM(event, expr...)
511 
512 #endif /* DECLARE_TRACE */
513 
514 #ifndef TRACE_EVENT
515 /*
516  * For use with the TRACE_EVENT macro:
517  *
518  * We define a tracepoint, its arguments, its printk format
519  * and its 'fast binary record' layout.
520  *
521  * Firstly, name your tracepoint via TRACE_EVENT(name : the
522  * 'subsystem_event' notation is fine.
523  *
524  * Think about this whole construct as the
525  * 'trace_sched_switch() function' from now on.
526  *
527  *
528  *  TRACE_EVENT(sched_switch,
529  *
530  *	*
531  *	* A function has a regular function arguments
532  *	* prototype, declare it via TP_PROTO():
533  *	*
534  *
535  *	TP_PROTO(struct rq *rq, struct task_struct *prev,
536  *		 struct task_struct *next),
537  *
538  *	*
539  *	* Define the call signature of the 'function'.
540  *	* (Design sidenote: we use this instead of a
541  *	*  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
542  *	*
543  *
544  *	TP_ARGS(rq, prev, next),
545  *
546  *	*
547  *	* Fast binary tracing: define the trace record via
548  *	* TP_STRUCT__entry(). You can think about it like a
549  *	* regular C structure local variable definition.
550  *	*
551  *	* This is how the trace record is structured and will
552  *	* be saved into the ring buffer. These are the fields
553  *	* that will be exposed to user-space in
554  *	* /sys/kernel/tracing/events/<*>/format.
555  *	*
556  *	* The declared 'local variable' is called '__entry'
557  *	*
558  *	* __field(pid_t, prev_pid) is equivalent to a standard declaration:
559  *	*
560  *	*	pid_t	prev_pid;
561  *	*
562  *	* __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
563  *	*
564  *	*	char	prev_comm[TASK_COMM_LEN];
565  *	*
566  *
567  *	TP_STRUCT__entry(
568  *		__array(	char,	prev_comm,	TASK_COMM_LEN	)
569  *		__field(	pid_t,	prev_pid			)
570  *		__field(	int,	prev_prio			)
571  *		__array(	char,	next_comm,	TASK_COMM_LEN	)
572  *		__field(	pid_t,	next_pid			)
573  *		__field(	int,	next_prio			)
574  *	),
575  *
576  *	*
577  *	* Assign the entry into the trace record, by embedding
578  *	* a full C statement block into TP_fast_assign(). You
579  *	* can refer to the trace record as '__entry' -
580  *	* otherwise you can put arbitrary C code in here.
581  *	*
582  *	* Note: this C code will execute every time a trace event
583  *	* happens, on an active tracepoint.
584  *	*
585  *
586  *	TP_fast_assign(
587  *		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
588  *		__entry->prev_pid	= prev->pid;
589  *		__entry->prev_prio	= prev->prio;
590  *		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
591  *		__entry->next_pid	= next->pid;
592  *		__entry->next_prio	= next->prio;
593  *	),
594  *
595  *	*
596  *	* Formatted output of a trace record via TP_printk().
597  *	* This is how the tracepoint will appear under ftrace
598  *	* plugins that make use of this tracepoint.
599  *	*
600  *	* (raw-binary tracing wont actually perform this step.)
601  *	*
602  *
603  *	TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
604  *		__entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
605  *		__entry->next_comm, __entry->next_pid, __entry->next_prio),
606  *
607  * );
608  *
609  * This macro construct is thus used for the regular printk format
610  * tracing setup, it is used to construct a function pointer based
611  * tracepoint callback (this is used by programmatic plugins and
612  * can also by used by generic instrumentation like SystemTap), and
613  * it is also used to expose a structured trace record in
614  * /sys/kernel/tracing/events/.
615  *
616  * A set of (un)registration functions can be passed to the variant
617  * TRACE_EVENT_FN to perform any (un)registration work.
618  */
619 
620 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
621 #define DEFINE_EVENT(template, name, proto, args)		\
622 	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
623 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
624 	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
625 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
626 	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
627 #define DEFINE_EVENT_CONDITION(template, name, proto,		\
628 			       args, cond)			\
629 	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
630 				PARAMS(args), PARAMS(cond))
631 
632 #define TRACE_EVENT(name, proto, args, struct, assign, print)	\
633 	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
634 #define TRACE_EVENT_FN(name, proto, args, struct,		\
635 		assign, print, reg, unreg)			\
636 	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
637 #define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,	\
638 		assign, print, reg, unreg)			\
639 	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
640 			PARAMS(args), PARAMS(cond))
641 #define TRACE_EVENT_CONDITION(name, proto, args, cond,		\
642 			      struct, assign, print)		\
643 	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
644 				PARAMS(args), PARAMS(cond))
645 #define TRACE_EVENT_SYSCALL(name, proto, args, struct, assign,	\
646 			    print, reg, unreg)			\
647 	DECLARE_TRACE_EVENT_SYSCALL(name, PARAMS(proto), PARAMS(args))
648 
649 #define TRACE_EVENT_FLAGS(event, flag)
650 
651 #define TRACE_EVENT_PERF_PERM(event, expr...)
652 
653 #define DECLARE_EVENT_NOP(name, proto, args)				\
654 	static inline void trace_##name(proto)				\
655 	{ }								\
656 	static inline bool trace_##name##_enabled(void)			\
657 	{								\
658 		return false;						\
659 	}
660 
661 #define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)	\
662 	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
663 
664 #define DECLARE_EVENT_CLASS_NOP(name, proto, args, tstruct, assign, print)
665 #define DEFINE_EVENT_NOP(template, name, proto, args)			\
666 	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
667 
668 #endif /* ifdef TRACE_EVENT (see note above) */
669