xref: /linux-6.15/include/linux/tracepoint.h (revision e8e7be7d)
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 <[email protected]>
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_rcu()
112  * - tracepoint_is_faultable() == true:  call_rcu_tasks_trace()
113  */
114 #ifdef CONFIG_TRACEPOINTS
115 static inline void tracepoint_synchronize_unregister(void)
116 {
117 	synchronize_rcu_tasks_trace();
118 	synchronize_rcu();
119 }
120 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
121 {
122 	return tp->ext && tp->ext->faultable;
123 }
124 #else
125 static inline void tracepoint_synchronize_unregister(void)
126 { }
127 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
128 {
129 	return false;
130 }
131 #endif
132 
133 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
134 extern int syscall_regfunc(void);
135 extern void syscall_unregfunc(void);
136 #endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
137 
138 #ifndef PARAMS
139 #define PARAMS(args...) args
140 #endif
141 
142 #define TRACE_DEFINE_ENUM(x)
143 #define TRACE_DEFINE_SIZEOF(x)
144 
145 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
146 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
147 {
148 	return offset_to_ptr(p);
149 }
150 
151 #define __TRACEPOINT_ENTRY(name)					\
152 	asm("	.section \"__tracepoints_ptrs\", \"a\"		\n"	\
153 	    "	.balign 4					\n"	\
154 	    "	.long 	__tracepoint_" #name " - .		\n"	\
155 	    "	.previous					\n")
156 #else
157 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
158 {
159 	return *p;
160 }
161 
162 #define __TRACEPOINT_ENTRY(name)					 \
163 	static tracepoint_ptr_t __tracepoint_ptr_##name __used		 \
164 	__section("__tracepoints_ptrs") = &__tracepoint_##name
165 #endif
166 
167 #endif /* _LINUX_TRACEPOINT_H */
168 
169 /*
170  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
171  *  file ifdef protection.
172  *  This is due to the way trace events work. If a file includes two
173  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
174  *  will override the TRACE_EVENT and break the second include.
175  */
176 
177 #ifndef DECLARE_TRACE
178 
179 #define TP_PROTO(args...)	args
180 #define TP_ARGS(args...)	args
181 #define TP_CONDITION(args...)	args
182 
183 /*
184  * Individual subsystem my have a separate configuration to
185  * enable their tracepoints. By default, this file will create
186  * the tracepoints if CONFIG_TRACEPOINTS is defined. If a subsystem
187  * wants to be able to disable its tracepoints from being created
188  * it can define NOTRACE before including the tracepoint headers.
189  */
190 #if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
191 #define TRACEPOINTS_ENABLED
192 #endif
193 
194 #ifdef TRACEPOINTS_ENABLED
195 
196 #ifdef CONFIG_HAVE_STATIC_CALL
197 #define __DO_TRACE_CALL(name, args)					\
198 	do {								\
199 		struct tracepoint_func *it_func_ptr;			\
200 		void *__data;						\
201 		it_func_ptr =						\
202 			rcu_dereference_raw((&__tracepoint_##name)->funcs); \
203 		if (it_func_ptr) {					\
204 			__data = (it_func_ptr)->data;			\
205 			static_call(tp_func_##name)(__data, args);	\
206 		}							\
207 	} while (0)
208 #else
209 #define __DO_TRACE_CALL(name, args)	__traceiter_##name(NULL, args)
210 #endif /* CONFIG_HAVE_STATIC_CALL */
211 
212 /*
213  * it_func[0] is never NULL because there is at least one element in the array
214  * when the array itself is non NULL.
215  *
216  * With @syscall=0, the tracepoint callback array dereference is
217  * protected by disabling preemption.
218  * With @syscall=1, the tracepoint callback array dereference is
219  * protected by Tasks Trace RCU, which allows probes to handle page
220  * faults.
221  */
222 #define __DO_TRACE(name, args, cond, syscall)				\
223 	do {								\
224 		int __maybe_unused __idx = 0;				\
225 									\
226 		if (!(cond))						\
227 			return;						\
228 									\
229 		if (syscall)						\
230 			rcu_read_lock_trace();				\
231 		else							\
232 			preempt_disable_notrace();			\
233 									\
234 		__DO_TRACE_CALL(name, TP_ARGS(args));			\
235 									\
236 		if (syscall)						\
237 			rcu_read_unlock_trace();			\
238 		else							\
239 			preempt_enable_notrace();			\
240 	} while (0)
241 
242 /*
243  * Declare an exported function that Rust code can call to trigger this
244  * tracepoint. This function does not include the static branch; that is done
245  * in Rust to avoid a function call when the tracepoint is disabled.
246  */
247 #define DEFINE_RUST_DO_TRACE(name, proto, args)
248 #define __DEFINE_RUST_DO_TRACE(name, proto, args)			\
249 	notrace void rust_do_trace_##name(proto)			\
250 	{								\
251 		__rust_do_trace_##name(args);				\
252 	}
253 
254 /*
255  * Make sure the alignment of the structure in the __tracepoints section will
256  * not add unwanted padding between the beginning of the section and the
257  * structure. Force alignment to the same alignment as the section start.
258  *
259  * When lockdep is enabled, we make sure to always test if RCU is
260  * "watching" regardless if the tracepoint is enabled or not. Tracepoints
261  * require RCU to be active, and it should always warn at the tracepoint
262  * site if it is not watching, as it will need to be active when the
263  * tracepoint is enabled.
264  */
265 #define __DECLARE_TRACE_COMMON(name, proto, args, cond, data_proto)	\
266 	extern int __traceiter_##name(data_proto);			\
267 	DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);	\
268 	extern struct tracepoint __tracepoint_##name;			\
269 	extern void rust_do_trace_##name(proto);			\
270 	static inline int						\
271 	register_trace_##name(void (*probe)(data_proto), void *data)	\
272 	{								\
273 		return tracepoint_probe_register(&__tracepoint_##name,	\
274 						(void *)probe, data);	\
275 	}								\
276 	static inline int						\
277 	register_trace_prio_##name(void (*probe)(data_proto), void *data,\
278 				   int prio)				\
279 	{								\
280 		return tracepoint_probe_register_prio(&__tracepoint_##name, \
281 					      (void *)probe, data, prio); \
282 	}								\
283 	static inline int						\
284 	unregister_trace_##name(void (*probe)(data_proto), void *data)	\
285 	{								\
286 		return tracepoint_probe_unregister(&__tracepoint_##name,\
287 						(void *)probe, data);	\
288 	}								\
289 	static inline void						\
290 	check_trace_callback_type_##name(void (*cb)(data_proto))	\
291 	{								\
292 	}								\
293 	static inline bool						\
294 	trace_##name##_enabled(void)					\
295 	{								\
296 		return static_branch_unlikely(&__tracepoint_##name.key);\
297 	}
298 
299 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)		\
300 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
301 	static inline void __rust_do_trace_##name(proto)		\
302 	{								\
303 		__DO_TRACE(name,					\
304 			TP_ARGS(args),					\
305 			TP_CONDITION(cond), 0);				\
306 	}								\
307 	static inline void trace_##name(proto)				\
308 	{								\
309 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
310 			__DO_TRACE(name,				\
311 				TP_ARGS(args),				\
312 				TP_CONDITION(cond), 0);			\
313 		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {		\
314 			WARN_ONCE(!rcu_is_watching(),			\
315 				  "RCU not watching for tracepoint");	\
316 		}							\
317 	}
318 
319 #define __DECLARE_TRACE_SYSCALL(name, proto, args, cond, data_proto)	\
320 	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
321 	static inline void __rust_do_trace_##name(proto)		\
322 	{								\
323 		__DO_TRACE(name,					\
324 			TP_ARGS(args),					\
325 			TP_CONDITION(cond), 1);				\
326 	}								\
327 	static inline void trace_##name(proto)				\
328 	{								\
329 		might_fault();						\
330 		if (static_branch_unlikely(&__tracepoint_##name.key))	\
331 			__DO_TRACE(name,				\
332 				TP_ARGS(args),				\
333 				TP_CONDITION(cond), 1);			\
334 		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {		\
335 			WARN_ONCE(!rcu_is_watching(),			\
336 				  "RCU not watching for tracepoint");	\
337 		}							\
338 	}
339 
340 /*
341  * We have no guarantee that gcc and the linker won't up-align the tracepoint
342  * structures, so we create an array of pointers that will be used for iteration
343  * on the tracepoints.
344  */
345 #define __DEFINE_TRACE_EXT(_name, _ext, proto, args)			\
346 	static const char __tpstrtab_##_name[]				\
347 	__section("__tracepoints_strings") = #_name;			\
348 	extern struct static_call_key STATIC_CALL_KEY(tp_func_##_name);	\
349 	int __traceiter_##_name(void *__data, proto);			\
350 	void __probestub_##_name(void *__data, proto);			\
351 	struct tracepoint __tracepoint_##_name	__used			\
352 	__section("__tracepoints") = {					\
353 		.name = __tpstrtab_##_name,				\
354 		.key = STATIC_KEY_FALSE_INIT,				\
355 		.static_call_key = &STATIC_CALL_KEY(tp_func_##_name),	\
356 		.static_call_tramp = STATIC_CALL_TRAMP_ADDR(tp_func_##_name), \
357 		.iterator = &__traceiter_##_name,			\
358 		.probestub = &__probestub_##_name,			\
359 		.funcs = NULL,						\
360 		.ext = _ext,						\
361 	};								\
362 	__TRACEPOINT_ENTRY(_name);					\
363 	int __traceiter_##_name(void *__data, proto)			\
364 	{								\
365 		struct tracepoint_func *it_func_ptr;			\
366 		void *it_func;						\
367 									\
368 		it_func_ptr =						\
369 			rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
370 		if (it_func_ptr) {					\
371 			do {						\
372 				it_func = READ_ONCE((it_func_ptr)->func); \
373 				__data = (it_func_ptr)->data;		\
374 				((void(*)(void *, proto))(it_func))(__data, args); \
375 			} while ((++it_func_ptr)->func);		\
376 		}							\
377 		return 0;						\
378 	}								\
379 	void __probestub_##_name(void *__data, proto)			\
380 	{								\
381 	}								\
382 	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);	\
383 	DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))
384 
385 #define DEFINE_TRACE_FN(_name, _reg, _unreg, _proto, _args)		\
386 	static struct tracepoint_ext __tracepoint_ext_##_name = {	\
387 		.regfunc = _reg,					\
388 		.unregfunc = _unreg,					\
389 		.faultable = false,					\
390 	};								\
391 	__DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
392 
393 #define DEFINE_TRACE_SYSCALL(_name, _reg, _unreg, _proto, _args)	\
394 	static struct tracepoint_ext __tracepoint_ext_##_name = {	\
395 		.regfunc = _reg,					\
396 		.unregfunc = _unreg,					\
397 		.faultable = true,					\
398 	};								\
399 	__DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
400 
401 #define DEFINE_TRACE(_name, _proto, _args)				\
402 	__DEFINE_TRACE_EXT(_name, NULL, PARAMS(_proto), PARAMS(_args));
403 
404 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)				\
405 	EXPORT_SYMBOL_GPL(__tracepoint_##name);				\
406 	EXPORT_SYMBOL_GPL(__traceiter_##name);				\
407 	EXPORT_STATIC_CALL_GPL(tp_func_##name)
408 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
409 	EXPORT_SYMBOL(__tracepoint_##name);				\
410 	EXPORT_SYMBOL(__traceiter_##name);				\
411 	EXPORT_STATIC_CALL(tp_func_##name)
412 
413 
414 #else /* !TRACEPOINTS_ENABLED */
415 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)		\
416 	static inline void trace_##name(proto)				\
417 	{ }								\
418 	static inline int						\
419 	register_trace_##name(void (*probe)(data_proto),		\
420 			      void *data)				\
421 	{								\
422 		return -ENOSYS;						\
423 	}								\
424 	static inline int						\
425 	unregister_trace_##name(void (*probe)(data_proto),		\
426 				void *data)				\
427 	{								\
428 		return -ENOSYS;						\
429 	}								\
430 	static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
431 	{								\
432 	}								\
433 	static inline bool						\
434 	trace_##name##_enabled(void)					\
435 	{								\
436 		return false;						\
437 	}
438 
439 #define __DECLARE_TRACE_SYSCALL	__DECLARE_TRACE
440 
441 #define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
442 #define DEFINE_TRACE_SYSCALL(name, reg, unreg, proto, args)
443 #define DEFINE_TRACE(name, proto, args)
444 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
445 #define EXPORT_TRACEPOINT_SYMBOL(name)
446 
447 #endif /* TRACEPOINTS_ENABLED */
448 
449 #ifdef CONFIG_TRACING
450 /**
451  * tracepoint_string - register constant persistent string to trace system
452  * @str - a constant persistent string that will be referenced in tracepoints
453  *
454  * If constant strings are being used in tracepoints, it is faster and
455  * more efficient to just save the pointer to the string and reference
456  * that with a printf "%s" instead of saving the string in the ring buffer
457  * and wasting space and time.
458  *
459  * The problem with the above approach is that userspace tools that read
460  * the binary output of the trace buffers do not have access to the string.
461  * Instead they just show the address of the string which is not very
462  * useful to users.
463  *
464  * With tracepoint_string(), the string will be registered to the tracing
465  * system and exported to userspace via the debugfs/tracing/printk_formats
466  * file that maps the string address to the string text. This way userspace
467  * tools that read the binary buffers have a way to map the pointers to
468  * the ASCII strings they represent.
469  *
470  * The @str used must be a constant string and persistent as it would not
471  * make sense to show a string that no longer exists. But it is still fine
472  * to be used with modules, because when modules are unloaded, if they
473  * had tracepoints, the ring buffers are cleared too. As long as the string
474  * does not change during the life of the module, it is fine to use
475  * tracepoint_string() within a module.
476  */
477 #define tracepoint_string(str)						\
478 	({								\
479 		static const char *___tp_str __tracepoint_string = str; \
480 		___tp_str;						\
481 	})
482 #define __tracepoint_string	__used __section("__tracepoint_str")
483 #else
484 /*
485  * tracepoint_string() is used to save the string address for userspace
486  * tracing tools. When tracing isn't configured, there's no need to save
487  * anything.
488  */
489 # define tracepoint_string(str) str
490 # define __tracepoint_string
491 #endif
492 
493 #define DECLARE_TRACE(name, proto, args)				\
494 	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
495 			cpu_online(raw_smp_processor_id()),		\
496 			PARAMS(void *__data, proto))
497 
498 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)		\
499 	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
500 			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
501 			PARAMS(void *__data, proto))
502 
503 #define DECLARE_TRACE_SYSCALL(name, proto, args)			\
504 	__DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args),	\
505 				cpu_online(raw_smp_processor_id()),	\
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(name, PARAMS(proto), PARAMS(args))
623 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
624 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
625 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
626 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
627 #define DEFINE_EVENT_CONDITION(template, name, proto,		\
628 			       args, cond)			\
629 	DECLARE_TRACE_CONDITION(name, PARAMS(proto),		\
630 				PARAMS(args), PARAMS(cond))
631 
632 #define TRACE_EVENT(name, proto, args, struct, assign, print)	\
633 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
634 #define TRACE_EVENT_FN(name, proto, args, struct,		\
635 		assign, print, reg, unreg)			\
636 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
637 #define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,		\
638 		assign, print, reg, unreg)			\
639 	DECLARE_TRACE_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_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_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