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Linux/include/linux/tracepoint.h

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  1 #ifndef _LINUX_TRACEPOINT_H
  2 #define _LINUX_TRACEPOINT_H
  3 
  4 /*
  5  * Kernel Tracepoint API.
  6  *
  7  * See Documentation/trace/tracepoints.rst.
  8  *
  9  * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 10  *
 11  * Heavily inspired from the Linux Kernel Markers.
 12  *
 13  * This file is released under the GPLv2.
 14  * See the file COPYING for more details.
 15  */
 16 
 17 #include <linux/smp.h>
 18 #include <linux/errno.h>
 19 #include <linux/types.h>
 20 #include <linux/cpumask.h>
 21 #include <linux/rcupdate.h>
 22 #include <linux/tracepoint-defs.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_unregister(struct tracepoint *tp, void *probe, void *data);
 43 extern void
 44 for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
 45                 void *priv);
 46 
 47 #ifdef CONFIG_MODULES
 48 struct tp_module {
 49         struct list_head list;
 50         struct module *mod;
 51 };
 52 
 53 bool trace_module_has_bad_taint(struct module *mod);
 54 extern int register_tracepoint_module_notifier(struct notifier_block *nb);
 55 extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
 56 #else
 57 static inline bool trace_module_has_bad_taint(struct module *mod)
 58 {
 59         return false;
 60 }
 61 static inline
 62 int register_tracepoint_module_notifier(struct notifier_block *nb)
 63 {
 64         return 0;
 65 }
 66 static inline
 67 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
 68 {
 69         return 0;
 70 }
 71 #endif /* CONFIG_MODULES */
 72 
 73 /*
 74  * tracepoint_synchronize_unregister must be called between the last tracepoint
 75  * probe unregistration and the end of module exit to make sure there is no
 76  * caller executing a probe when it is freed.
 77  */
 78 static inline void tracepoint_synchronize_unregister(void)
 79 {
 80         synchronize_sched();
 81 }
 82 
 83 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 84 extern int syscall_regfunc(void);
 85 extern void syscall_unregfunc(void);
 86 #endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
 87 
 88 #define PARAMS(args...) args
 89 
 90 #define TRACE_DEFINE_ENUM(x)
 91 #define TRACE_DEFINE_SIZEOF(x)
 92 
 93 #endif /* _LINUX_TRACEPOINT_H */
 94 
 95 /*
 96  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
 97  *  file ifdef protection.
 98  *  This is due to the way trace events work. If a file includes two
 99  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
100  *  will override the TRACE_EVENT and break the second include.
101  */
102 
103 #ifndef DECLARE_TRACE
104 
105 #define TP_PROTO(args...)       args
106 #define TP_ARGS(args...)        args
107 #define TP_CONDITION(args...)   args
108 
109 /*
110  * Individual subsystem my have a separate configuration to
111  * enable their tracepoints. By default, this file will create
112  * the tracepoints if CONFIG_TRACEPOINT is defined. If a subsystem
113  * wants to be able to disable its tracepoints from being created
114  * it can define NOTRACE before including the tracepoint headers.
115  */
116 #if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
117 #define TRACEPOINTS_ENABLED
118 #endif
119 
120 #ifdef TRACEPOINTS_ENABLED
121 
122 /*
123  * it_func[0] is never NULL because there is at least one element in the array
124  * when the array itself is non NULL.
125  *
126  * Note, the proto and args passed in includes "__data" as the first parameter.
127  * The reason for this is to handle the "void" prototype. If a tracepoint
128  * has a "void" prototype, then it is invalid to declare a function
129  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
130  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
131  */
132 #define __DO_TRACE(tp, proto, args, cond, rcucheck)                     \
133         do {                                                            \
134                 struct tracepoint_func *it_func_ptr;                    \
135                 void *it_func;                                          \
136                 void *__data;                                           \
137                                                                         \
138                 if (!(cond))                                            \
139                         return;                                         \
140                 if (rcucheck)                                           \
141                         rcu_irq_enter_irqson();                         \
142                 rcu_read_lock_sched_notrace();                          \
143                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
144                 if (it_func_ptr) {                                      \
145                         do {                                            \
146                                 it_func = (it_func_ptr)->func;          \
147                                 __data = (it_func_ptr)->data;           \
148                                 ((void(*)(proto))(it_func))(args);      \
149                         } while ((++it_func_ptr)->func);                \
150                 }                                                       \
151                 rcu_read_unlock_sched_notrace();                        \
152                 if (rcucheck)                                           \
153                         rcu_irq_exit_irqson();                          \
154         } while (0)
155 
156 #ifndef MODULE
157 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
158         static inline void trace_##name##_rcuidle(proto)                \
159         {                                                               \
160                 if (static_key_false(&__tracepoint_##name.key))         \
161                         __DO_TRACE(&__tracepoint_##name,                \
162                                 TP_PROTO(data_proto),                   \
163                                 TP_ARGS(data_args),                     \
164                                 TP_CONDITION(cond), 1);                 \
165         }
166 #else
167 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
168 #endif
169 
170 /*
171  * Make sure the alignment of the structure in the __tracepoints section will
172  * not add unwanted padding between the beginning of the section and the
173  * structure. Force alignment to the same alignment as the section start.
174  *
175  * When lockdep is enabled, we make sure to always do the RCU portions of
176  * the tracepoint code, regardless of whether tracing is on. However,
177  * don't check if the condition is false, due to interaction with idle
178  * instrumentation. This lets us find RCU issues triggered with tracepoints
179  * even when this tracepoint is off. This code has no purpose other than
180  * poking RCU a bit.
181  */
182 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
183         extern struct tracepoint __tracepoint_##name;                   \
184         static inline void trace_##name(proto)                          \
185         {                                                               \
186                 if (static_key_false(&__tracepoint_##name.key))         \
187                         __DO_TRACE(&__tracepoint_##name,                \
188                                 TP_PROTO(data_proto),                   \
189                                 TP_ARGS(data_args),                     \
190                                 TP_CONDITION(cond), 0);                 \
191                 if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {             \
192                         rcu_read_lock_sched_notrace();                  \
193                         rcu_dereference_sched(__tracepoint_##name.funcs);\
194                         rcu_read_unlock_sched_notrace();                \
195                 }                                                       \
196         }                                                               \
197         __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
198                 PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
199         static inline int                                               \
200         register_trace_##name(void (*probe)(data_proto), void *data)    \
201         {                                                               \
202                 return tracepoint_probe_register(&__tracepoint_##name,  \
203                                                 (void *)probe, data);   \
204         }                                                               \
205         static inline int                                               \
206         register_trace_prio_##name(void (*probe)(data_proto), void *data,\
207                                    int prio)                            \
208         {                                                               \
209                 return tracepoint_probe_register_prio(&__tracepoint_##name, \
210                                               (void *)probe, data, prio); \
211         }                                                               \
212         static inline int                                               \
213         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
214         {                                                               \
215                 return tracepoint_probe_unregister(&__tracepoint_##name,\
216                                                 (void *)probe, data);   \
217         }                                                               \
218         static inline void                                              \
219         check_trace_callback_type_##name(void (*cb)(data_proto))        \
220         {                                                               \
221         }                                                               \
222         static inline bool                                              \
223         trace_##name##_enabled(void)                                    \
224         {                                                               \
225                 return static_key_false(&__tracepoint_##name.key);      \
226         }
227 
228 /*
229  * We have no guarantee that gcc and the linker won't up-align the tracepoint
230  * structures, so we create an array of pointers that will be used for iteration
231  * on the tracepoints.
232  */
233 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
234         static const char __tpstrtab_##name[]                            \
235         __attribute__((section("__tracepoints_strings"))) = #name;       \
236         struct tracepoint __tracepoint_##name                            \
237         __attribute__((section("__tracepoints"))) =                      \
238                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
239         static struct tracepoint * const __tracepoint_ptr_##name __used  \
240         __attribute__((section("__tracepoints_ptrs"))) =                 \
241                 &__tracepoint_##name;
242 
243 #define DEFINE_TRACE(name)                                              \
244         DEFINE_TRACE_FN(name, NULL, NULL);
245 
246 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
247         EXPORT_SYMBOL_GPL(__tracepoint_##name)
248 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
249         EXPORT_SYMBOL(__tracepoint_##name)
250 
251 #else /* !TRACEPOINTS_ENABLED */
252 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
253         static inline void trace_##name(proto)                          \
254         { }                                                             \
255         static inline void trace_##name##_rcuidle(proto)                \
256         { }                                                             \
257         static inline int                                               \
258         register_trace_##name(void (*probe)(data_proto),                \
259                               void *data)                               \
260         {                                                               \
261                 return -ENOSYS;                                         \
262         }                                                               \
263         static inline int                                               \
264         unregister_trace_##name(void (*probe)(data_proto),              \
265                                 void *data)                             \
266         {                                                               \
267                 return -ENOSYS;                                         \
268         }                                                               \
269         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
270         {                                                               \
271         }                                                               \
272         static inline bool                                              \
273         trace_##name##_enabled(void)                                    \
274         {                                                               \
275                 return false;                                           \
276         }
277 
278 #define DEFINE_TRACE_FN(name, reg, unreg)
279 #define DEFINE_TRACE(name)
280 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
281 #define EXPORT_TRACEPOINT_SYMBOL(name)
282 
283 #endif /* TRACEPOINTS_ENABLED */
284 
285 #ifdef CONFIG_TRACING
286 /**
287  * tracepoint_string - register constant persistent string to trace system
288  * @str - a constant persistent string that will be referenced in tracepoints
289  *
290  * If constant strings are being used in tracepoints, it is faster and
291  * more efficient to just save the pointer to the string and reference
292  * that with a printf "%s" instead of saving the string in the ring buffer
293  * and wasting space and time.
294  *
295  * The problem with the above approach is that userspace tools that read
296  * the binary output of the trace buffers do not have access to the string.
297  * Instead they just show the address of the string which is not very
298  * useful to users.
299  *
300  * With tracepoint_string(), the string will be registered to the tracing
301  * system and exported to userspace via the debugfs/tracing/printk_formats
302  * file that maps the string address to the string text. This way userspace
303  * tools that read the binary buffers have a way to map the pointers to
304  * the ASCII strings they represent.
305  *
306  * The @str used must be a constant string and persistent as it would not
307  * make sense to show a string that no longer exists. But it is still fine
308  * to be used with modules, because when modules are unloaded, if they
309  * had tracepoints, the ring buffers are cleared too. As long as the string
310  * does not change during the life of the module, it is fine to use
311  * tracepoint_string() within a module.
312  */
313 #define tracepoint_string(str)                                          \
314         ({                                                              \
315                 static const char *___tp_str __tracepoint_string = str; \
316                 ___tp_str;                                              \
317         })
318 #define __tracepoint_string     __attribute__((section("__tracepoint_str")))
319 #else
320 /*
321  * tracepoint_string() is used to save the string address for userspace
322  * tracing tools. When tracing isn't configured, there's no need to save
323  * anything.
324  */
325 # define tracepoint_string(str) str
326 # define __tracepoint_string
327 #endif
328 
329 /*
330  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
331  * (void). "void" is a special value in a function prototype and can
332  * not be combined with other arguments. Since the DECLARE_TRACE()
333  * macro adds a data element at the beginning of the prototype,
334  * we need a way to differentiate "(void *data, proto)" from
335  * "(void *data, void)". The second prototype is invalid.
336  *
337  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
338  * and "void *__data" as the callback prototype.
339  *
340  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
341  * "void *__data, proto" as the callback prototype.
342  */
343 #define DECLARE_TRACE_NOARGS(name)                                      \
344         __DECLARE_TRACE(name, void, ,                                   \
345                         cpu_online(raw_smp_processor_id()),             \
346                         void *__data, __data)
347 
348 #define DECLARE_TRACE(name, proto, args)                                \
349         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
350                         cpu_online(raw_smp_processor_id()),             \
351                         PARAMS(void *__data, proto),                    \
352                         PARAMS(__data, args))
353 
354 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
355         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
356                         cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
357                         PARAMS(void *__data, proto),                    \
358                         PARAMS(__data, args))
359 
360 #define TRACE_EVENT_FLAGS(event, flag)
361 
362 #define TRACE_EVENT_PERF_PERM(event, expr...)
363 
364 #endif /* DECLARE_TRACE */
365 
366 #ifndef TRACE_EVENT
367 /*
368  * For use with the TRACE_EVENT macro:
369  *
370  * We define a tracepoint, its arguments, its printk format
371  * and its 'fast binary record' layout.
372  *
373  * Firstly, name your tracepoint via TRACE_EVENT(name : the
374  * 'subsystem_event' notation is fine.
375  *
376  * Think about this whole construct as the
377  * 'trace_sched_switch() function' from now on.
378  *
379  *
380  *  TRACE_EVENT(sched_switch,
381  *
382  *      *
383  *      * A function has a regular function arguments
384  *      * prototype, declare it via TP_PROTO():
385  *      *
386  *
387  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
388  *               struct task_struct *next),
389  *
390  *      *
391  *      * Define the call signature of the 'function'.
392  *      * (Design sidenote: we use this instead of a
393  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
394  *      *
395  *
396  *      TP_ARGS(rq, prev, next),
397  *
398  *      *
399  *      * Fast binary tracing: define the trace record via
400  *      * TP_STRUCT__entry(). You can think about it like a
401  *      * regular C structure local variable definition.
402  *      *
403  *      * This is how the trace record is structured and will
404  *      * be saved into the ring buffer. These are the fields
405  *      * that will be exposed to user-space in
406  *      * /sys/kernel/debug/tracing/events/<*>/format.
407  *      *
408  *      * The declared 'local variable' is called '__entry'
409  *      *
410  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
411  *      *
412  *      *       pid_t   prev_pid;
413  *      *
414  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
415  *      *
416  *      *       char    prev_comm[TASK_COMM_LEN];
417  *      *
418  *
419  *      TP_STRUCT__entry(
420  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
421  *              __field(        pid_t,  prev_pid                        )
422  *              __field(        int,    prev_prio                       )
423  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
424  *              __field(        pid_t,  next_pid                        )
425  *              __field(        int,    next_prio                       )
426  *      ),
427  *
428  *      *
429  *      * Assign the entry into the trace record, by embedding
430  *      * a full C statement block into TP_fast_assign(). You
431  *      * can refer to the trace record as '__entry' -
432  *      * otherwise you can put arbitrary C code in here.
433  *      *
434  *      * Note: this C code will execute every time a trace event
435  *      * happens, on an active tracepoint.
436  *      *
437  *
438  *      TP_fast_assign(
439  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
440  *              __entry->prev_pid       = prev->pid;
441  *              __entry->prev_prio      = prev->prio;
442  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
443  *              __entry->next_pid       = next->pid;
444  *              __entry->next_prio      = next->prio;
445  *      ),
446  *
447  *      *
448  *      * Formatted output of a trace record via TP_printk().
449  *      * This is how the tracepoint will appear under ftrace
450  *      * plugins that make use of this tracepoint.
451  *      *
452  *      * (raw-binary tracing wont actually perform this step.)
453  *      *
454  *
455  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
456  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
457  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
458  *
459  * );
460  *
461  * This macro construct is thus used for the regular printk format
462  * tracing setup, it is used to construct a function pointer based
463  * tracepoint callback (this is used by programmatic plugins and
464  * can also by used by generic instrumentation like SystemTap), and
465  * it is also used to expose a structured trace record in
466  * /sys/kernel/debug/tracing/events/.
467  *
468  * A set of (un)registration functions can be passed to the variant
469  * TRACE_EVENT_FN to perform any (un)registration work.
470  */
471 
472 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
473 #define DEFINE_EVENT(template, name, proto, args)               \
474         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
475 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
476         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
477 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
478         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
479 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
480                                args, cond)                      \
481         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
482                                 PARAMS(args), PARAMS(cond))
483 
484 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
485         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
486 #define TRACE_EVENT_FN(name, proto, args, struct,               \
487                 assign, print, reg, unreg)                      \
488         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
489 #define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,            \
490                 assign, print, reg, unreg)                      \
491         DECLARE_TRACE_CONDITION(name, PARAMS(proto),    \
492                         PARAMS(args), PARAMS(cond))
493 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
494                               struct, assign, print)            \
495         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
496                                 PARAMS(args), PARAMS(cond))
497 
498 #define TRACE_EVENT_FLAGS(event, flag)
499 
500 #define TRACE_EVENT_PERF_PERM(event, expr...)
501 
502 #endif /* ifdef TRACE_EVENT (see note above) */
503 

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