tracepoint.h 12 KB

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  1. #ifndef _LINUX_TRACEPOINT_H
  2. #define _LINUX_TRACEPOINT_H
  3. /*
  4. * Kernel Tracepoint API.
  5. *
  6. * See Documentation/trace/tracepoints.txt.
  7. *
  8. * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  9. *
  10. * Heavily inspired from the Linux Kernel Markers.
  11. *
  12. * This file is released under the GPLv2.
  13. * See the file COPYING for more details.
  14. */
  15. #include <linux/errno.h>
  16. #include <linux/types.h>
  17. #include <linux/rcupdate.h>
  18. #include <linux/jump_label.h>
  19. struct module;
  20. struct tracepoint;
  21. struct tracepoint_func {
  22. void *func;
  23. void *data;
  24. };
  25. struct tracepoint {
  26. const char *name; /* Tracepoint name */
  27. struct jump_label_key key;
  28. void (*regfunc)(void);
  29. void (*unregfunc)(void);
  30. struct tracepoint_func __rcu *funcs;
  31. };
  32. /*
  33. * Connect a probe to a tracepoint.
  34. * Internal API, should not be used directly.
  35. */
  36. extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  37. /*
  38. * Disconnect a probe from a tracepoint.
  39. * Internal API, should not be used directly.
  40. */
  41. extern int
  42. tracepoint_probe_unregister(const char *name, void *probe, void *data);
  43. extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  44. void *data);
  45. extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  46. void *data);
  47. extern void tracepoint_probe_update_all(void);
  48. struct tracepoint_iter {
  49. struct module *module;
  50. struct tracepoint * const *tracepoint;
  51. };
  52. extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  53. extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  54. extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  55. extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  56. extern int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
  57. struct tracepoint * const *begin, struct tracepoint * const *end);
  58. /*
  59. * tracepoint_synchronize_unregister must be called between the last tracepoint
  60. * probe unregistration and the end of module exit to make sure there is no
  61. * caller executing a probe when it is freed.
  62. */
  63. static inline void tracepoint_synchronize_unregister(void)
  64. {
  65. synchronize_sched();
  66. }
  67. #define PARAMS(args...) args
  68. #ifdef CONFIG_TRACEPOINTS
  69. extern
  70. void tracepoint_update_probe_range(struct tracepoint * const *begin,
  71. struct tracepoint * const *end);
  72. #else
  73. static inline
  74. void tracepoint_update_probe_range(struct tracepoint * const *begin,
  75. struct tracepoint * const *end)
  76. { }
  77. #endif /* CONFIG_TRACEPOINTS */
  78. #endif /* _LINUX_TRACEPOINT_H */
  79. /*
  80. * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  81. * file ifdef protection.
  82. * This is due to the way trace events work. If a file includes two
  83. * trace event headers under one "CREATE_TRACE_POINTS" the first include
  84. * will override the TRACE_EVENT and break the second include.
  85. */
  86. #ifndef DECLARE_TRACE
  87. #define TP_PROTO(args...) args
  88. #define TP_ARGS(args...) args
  89. #define TP_CONDITION(args...) args
  90. #ifdef CONFIG_TRACEPOINTS
  91. /*
  92. * it_func[0] is never NULL because there is at least one element in the array
  93. * when the array itself is non NULL.
  94. *
  95. * Note, the proto and args passed in includes "__data" as the first parameter.
  96. * The reason for this is to handle the "void" prototype. If a tracepoint
  97. * has a "void" prototype, then it is invalid to declare a function
  98. * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
  99. * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
  100. */
  101. #define __DO_TRACE(tp, proto, args, cond) \
  102. do { \
  103. struct tracepoint_func *it_func_ptr; \
  104. void *it_func; \
  105. void *__data; \
  106. \
  107. if (!(cond)) \
  108. return; \
  109. rcu_read_lock_sched_notrace(); \
  110. it_func_ptr = rcu_dereference_sched((tp)->funcs); \
  111. if (it_func_ptr) { \
  112. do { \
  113. it_func = (it_func_ptr)->func; \
  114. __data = (it_func_ptr)->data; \
  115. ((void(*)(proto))(it_func))(args); \
  116. } while ((++it_func_ptr)->func); \
  117. } \
  118. rcu_read_unlock_sched_notrace(); \
  119. } while (0)
  120. /*
  121. * Make sure the alignment of the structure in the __tracepoints section will
  122. * not add unwanted padding between the beginning of the section and the
  123. * structure. Force alignment to the same alignment as the section start.
  124. */
  125. #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
  126. extern struct tracepoint __tracepoint_##name; \
  127. static inline void trace_##name(proto) \
  128. { \
  129. if (static_branch(&__tracepoint_##name.key)) \
  130. __DO_TRACE(&__tracepoint_##name, \
  131. TP_PROTO(data_proto), \
  132. TP_ARGS(data_args), \
  133. TP_CONDITION(cond)); \
  134. } \
  135. static inline int \
  136. register_trace_##name(void (*probe)(data_proto), void *data) \
  137. { \
  138. return tracepoint_probe_register(#name, (void *)probe, \
  139. data); \
  140. } \
  141. static inline int \
  142. unregister_trace_##name(void (*probe)(data_proto), void *data) \
  143. { \
  144. return tracepoint_probe_unregister(#name, (void *)probe, \
  145. data); \
  146. } \
  147. static inline void \
  148. check_trace_callback_type_##name(void (*cb)(data_proto)) \
  149. { \
  150. }
  151. /*
  152. * We have no guarantee that gcc and the linker won't up-align the tracepoint
  153. * structures, so we create an array of pointers that will be used for iteration
  154. * on the tracepoints.
  155. */
  156. #define DEFINE_TRACE_FN(name, reg, unreg) \
  157. static const char __tpstrtab_##name[] \
  158. __attribute__((section("__tracepoints_strings"))) = #name; \
  159. struct tracepoint __tracepoint_##name \
  160. __attribute__((section("__tracepoints"))) = \
  161. { __tpstrtab_##name, JUMP_LABEL_INIT, reg, unreg, NULL };\
  162. static struct tracepoint * const __tracepoint_ptr_##name __used \
  163. __attribute__((section("__tracepoints_ptrs"))) = \
  164. &__tracepoint_##name;
  165. #define DEFINE_TRACE(name) \
  166. DEFINE_TRACE_FN(name, NULL, NULL);
  167. #define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
  168. EXPORT_SYMBOL_GPL(__tracepoint_##name)
  169. #define EXPORT_TRACEPOINT_SYMBOL(name) \
  170. EXPORT_SYMBOL(__tracepoint_##name)
  171. #else /* !CONFIG_TRACEPOINTS */
  172. #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
  173. static inline void trace_##name(proto) \
  174. { } \
  175. static inline int \
  176. register_trace_##name(void (*probe)(data_proto), \
  177. void *data) \
  178. { \
  179. return -ENOSYS; \
  180. } \
  181. static inline int \
  182. unregister_trace_##name(void (*probe)(data_proto), \
  183. void *data) \
  184. { \
  185. return -ENOSYS; \
  186. } \
  187. static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
  188. { \
  189. }
  190. #define DEFINE_TRACE_FN(name, reg, unreg)
  191. #define DEFINE_TRACE(name)
  192. #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
  193. #define EXPORT_TRACEPOINT_SYMBOL(name)
  194. #endif /* CONFIG_TRACEPOINTS */
  195. /*
  196. * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
  197. * (void). "void" is a special value in a function prototype and can
  198. * not be combined with other arguments. Since the DECLARE_TRACE()
  199. * macro adds a data element at the beginning of the prototype,
  200. * we need a way to differentiate "(void *data, proto)" from
  201. * "(void *data, void)". The second prototype is invalid.
  202. *
  203. * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
  204. * and "void *__data" as the callback prototype.
  205. *
  206. * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
  207. * "void *__data, proto" as the callback prototype.
  208. */
  209. #define DECLARE_TRACE_NOARGS(name) \
  210. __DECLARE_TRACE(name, void, , 1, void *__data, __data)
  211. #define DECLARE_TRACE(name, proto, args) \
  212. __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1, \
  213. PARAMS(void *__data, proto), \
  214. PARAMS(__data, args))
  215. #define DECLARE_TRACE_CONDITION(name, proto, args, cond) \
  216. __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
  217. PARAMS(void *__data, proto), \
  218. PARAMS(__data, args))
  219. #define TRACE_EVENT_FLAGS(event, flag)
  220. #endif /* DECLARE_TRACE */
  221. #ifndef TRACE_EVENT
  222. /*
  223. * For use with the TRACE_EVENT macro:
  224. *
  225. * We define a tracepoint, its arguments, its printk format
  226. * and its 'fast binay record' layout.
  227. *
  228. * Firstly, name your tracepoint via TRACE_EVENT(name : the
  229. * 'subsystem_event' notation is fine.
  230. *
  231. * Think about this whole construct as the
  232. * 'trace_sched_switch() function' from now on.
  233. *
  234. *
  235. * TRACE_EVENT(sched_switch,
  236. *
  237. * *
  238. * * A function has a regular function arguments
  239. * * prototype, declare it via TP_PROTO():
  240. * *
  241. *
  242. * TP_PROTO(struct rq *rq, struct task_struct *prev,
  243. * struct task_struct *next),
  244. *
  245. * *
  246. * * Define the call signature of the 'function'.
  247. * * (Design sidenote: we use this instead of a
  248. * * TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
  249. * *
  250. *
  251. * TP_ARGS(rq, prev, next),
  252. *
  253. * *
  254. * * Fast binary tracing: define the trace record via
  255. * * TP_STRUCT__entry(). You can think about it like a
  256. * * regular C structure local variable definition.
  257. * *
  258. * * This is how the trace record is structured and will
  259. * * be saved into the ring buffer. These are the fields
  260. * * that will be exposed to user-space in
  261. * * /sys/kernel/debug/tracing/events/<*>/format.
  262. * *
  263. * * The declared 'local variable' is called '__entry'
  264. * *
  265. * * __field(pid_t, prev_prid) is equivalent to a standard declariton:
  266. * *
  267. * * pid_t prev_pid;
  268. * *
  269. * * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
  270. * *
  271. * * char prev_comm[TASK_COMM_LEN];
  272. * *
  273. *
  274. * TP_STRUCT__entry(
  275. * __array( char, prev_comm, TASK_COMM_LEN )
  276. * __field( pid_t, prev_pid )
  277. * __field( int, prev_prio )
  278. * __array( char, next_comm, TASK_COMM_LEN )
  279. * __field( pid_t, next_pid )
  280. * __field( int, next_prio )
  281. * ),
  282. *
  283. * *
  284. * * Assign the entry into the trace record, by embedding
  285. * * a full C statement block into TP_fast_assign(). You
  286. * * can refer to the trace record as '__entry' -
  287. * * otherwise you can put arbitrary C code in here.
  288. * *
  289. * * Note: this C code will execute every time a trace event
  290. * * happens, on an active tracepoint.
  291. * *
  292. *
  293. * TP_fast_assign(
  294. * memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
  295. * __entry->prev_pid = prev->pid;
  296. * __entry->prev_prio = prev->prio;
  297. * memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
  298. * __entry->next_pid = next->pid;
  299. * __entry->next_prio = next->prio;
  300. * ),
  301. *
  302. * *
  303. * * Formatted output of a trace record via TP_printk().
  304. * * This is how the tracepoint will appear under ftrace
  305. * * plugins that make use of this tracepoint.
  306. * *
  307. * * (raw-binary tracing wont actually perform this step.)
  308. * *
  309. *
  310. * TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
  311. * __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
  312. * __entry->next_comm, __entry->next_pid, __entry->next_prio),
  313. *
  314. * );
  315. *
  316. * This macro construct is thus used for the regular printk format
  317. * tracing setup, it is used to construct a function pointer based
  318. * tracepoint callback (this is used by programmatic plugins and
  319. * can also by used by generic instrumentation like SystemTap), and
  320. * it is also used to expose a structured trace record in
  321. * /sys/kernel/debug/tracing/events/.
  322. *
  323. * A set of (un)registration functions can be passed to the variant
  324. * TRACE_EVENT_FN to perform any (un)registration work.
  325. */
  326. #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
  327. #define DEFINE_EVENT(template, name, proto, args) \
  328. DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  329. #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
  330. DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  331. #define DEFINE_EVENT_CONDITION(template, name, proto, \
  332. args, cond) \
  333. DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
  334. PARAMS(args), PARAMS(cond))
  335. #define TRACE_EVENT(name, proto, args, struct, assign, print) \
  336. DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  337. #define TRACE_EVENT_FN(name, proto, args, struct, \
  338. assign, print, reg, unreg) \
  339. DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
  340. #define TRACE_EVENT_CONDITION(name, proto, args, cond, \
  341. struct, assign, print) \
  342. DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
  343. PARAMS(args), PARAMS(cond))
  344. #define TRACE_EVENT_FLAGS(event, flag)
  345. #endif /* ifdef TRACE_EVENT (see note above) */