include/linux/tracepoint.h

   1 #ifndef _LINUX_TRACEPOINT_H
   2 #define _LINUX_TRACEPOINT_H
   3
   4 /*
   5  * Kernel Tracepoint API.
   6  *
   7  * See Documentation/trace/tracepoints.txt.
   8  *
   9  * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  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/errno.h>
  18 #include <linux/types.h>
  19 #include <linux/rcupdate.h>
  20 #include <linux/static_key.h>
  21
  22 struct module;
  23 struct tracepoint;
  24
  25 struct tracepoint_func {
  26         void *func;
  27         void *data;
  28 };
  29
  30 struct tracepoint {
  31         const char *name;               /* Tracepoint name */
  32         struct static_key key;
  33         void (*regfunc)(void);
  34         void (*unregfunc)(void);
  35         struct tracepoint_func __rcu *funcs;
  36 };
  37
  38 /*
  39  * Connect a probe to a tracepoint.
  40  * Internal API, should not be used directly.
  41  */
  42 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  43
  44 /*
  45  * Disconnect a probe from a tracepoint.
  46  * Internal API, should not be used directly.
  47  */
  48 extern int
  49 tracepoint_probe_unregister(const char *name, void *probe, void *data);
  50
  51 extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  52                                               void *data);
  53 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  54                                                 void *data);
  55 extern void tracepoint_probe_update_all(void);
  56
  57 #ifdef CONFIG_MODULES
  58 struct tp_module {
  59         struct list_head list;
  60         unsigned int num_tracepoints;
  61         struct tracepoint * const *tracepoints_ptrs;
  62 };
  63 #endif /* CONFIG_MODULES */
  64
  65 struct tracepoint_iter {
  66 #ifdef CONFIG_MODULES
  67         struct tp_module *module;
  68 #endif /* CONFIG_MODULES */
  69         struct tracepoint * const *tracepoint;
  70 };
  71
  72 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  73 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  74 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  75 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  76
  77 /*
  78  * tracepoint_synchronize_unregister must be called between the last tracepoint
  79  * probe unregistration and the end of module exit to make sure there is no
  80  * caller executing a probe when it is freed.
  81  */
  82 static inline void tracepoint_synchronize_unregister(void)
  83 {
  84         synchronize_sched();
  85 }
  86
  87 #define PARAMS(args...) args
  88
  89 #endif /* _LINUX_TRACEPOINT_H */
  90
  91 /*
  92  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  93  *  file ifdef protection.
  94  *  This is due to the way trace events work. If a file includes two
  95  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
  96  *  will override the TRACE_EVENT and break the second include.
  97  */
  98
  99 #ifndef DECLARE_TRACE
 100
 101 #define TP_PROTO(args...)       args
 102 #define TP_ARGS(args...)        args
 103 #define TP_CONDITION(args...)   args
 104
 105 #ifdef CONFIG_TRACEPOINTS
 106
 107 /*
 108  * it_func[0] is never NULL because there is at least one element in the array
 109  * when the array itself is non NULL.
 110  *
 111  * Note, the proto and args passed in includes "__data" as the first parameter.
 112  * The reason for this is to handle the "void" prototype. If a tracepoint
 113  * has a "void" prototype, then it is invalid to declare a function
 114  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 115  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 116  */
 117 #define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
 118         do {                                                            \
 119                 struct tracepoint_func *it_func_ptr;                    \
 120                 void *it_func;                                          \
 121                 void *__data;                                           \
 122                                                                         \
 123                 if (!(cond))                                            \
 124                         return;                                         \
 125                 prercu;                                                 \
 126                 rcu_read_lock_sched_notrace();                          \
 127                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 128                 if (it_func_ptr) {                                      \
 129                         do {                                            \
 130                                 it_func = (it_func_ptr)->func;          \
 131                                 __data = (it_func_ptr)->data;           \
 132                                 ((void(*)(proto))(it_func))(args);      \
 133                         } while ((++it_func_ptr)->func);                \
 134                 }                                                       \
 135                 rcu_read_unlock_sched_notrace();                        \
 136                 postrcu;                                                \
 137         } while (0)
 138
 139 /*
 140  * Make sure the alignment of the structure in the __tracepoints section will
 141  * not add unwanted padding between the beginning of the section and the
 142  * structure. Force alignment to the same alignment as the section start.
 143  */
 144 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 145         extern struct tracepoint __tracepoint_##name;                   \
 146         static inline void trace_##name(proto)                          \
 147         {                                                               \
 148                 if (static_key_false(&__tracepoint_##name.key))         \
 149                         __DO_TRACE(&__tracepoint_##name,                \
 150                                 TP_PROTO(data_proto),                   \
 151                                 TP_ARGS(data_args),                     \
 152                                 TP_CONDITION(cond),,);                  \
 153         }                                                               \
 154         static inline void trace_##name##_rcuidle(proto)                \
 155         {                                                               \
 156                 if (static_branch(&__tracepoint_##name.key))            \
 157                         __DO_TRACE(&__tracepoint_##name,                \
 158                                 TP_PROTO(data_proto),                   \
 159                                 TP_ARGS(data_args),                     \
 160                                 TP_CONDITION(cond),                     \
 161                                 rcu_idle_exit(),                        \
 162                                 rcu_idle_enter());                      \
 163         }                                                               \
 164         static inline int                                               \
 165         register_trace_##name(void (*probe)(data_proto), void *data)    \
 166         {                                                               \
 167                 return tracepoint_probe_register(#name, (void *)probe,  \
 168                                                  data);                 \
 169         }                                                               \
 170         static inline int                                               \
 171         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 172         {                                                               \
 173                 return tracepoint_probe_unregister(#name, (void *)probe, \
 174                                                    data);               \
 175         }                                                               \
 176         static inline void                                              \
 177         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 178         {                                                               \
 179         }
 180
 181 /*
 182  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 183  * structures, so we create an array of pointers that will be used for iteration
 184  * on the tracepoints.
 185  */
 186 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 187         static const char __tpstrtab_##name[]                            \
 188         __attribute__((section("__tracepoints_strings"))) = #name;       \
 189         struct tracepoint __tracepoint_##name                            \
 190         __attribute__((section("__tracepoints"))) =                      \
 191                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 192         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 193         __attribute__((section("__tracepoints_ptrs"))) =                 \
 194                 &__tracepoint_##name;
 195
 196 #define DEFINE_TRACE(name)                                              \
 197         DEFINE_TRACE_FN(name, NULL, NULL);
 198
 199 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 200         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 201 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 202         EXPORT_SYMBOL(__tracepoint_##name)
 203
 204 #else /* !CONFIG_TRACEPOINTS */
 205 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 206         static inline void trace_##name(proto)                          \
 207         { }                                                             \
 208         static inline void trace_##name##_rcuidle(proto)                \
 209         { }                                                             \
 210         static inline int                                               \
 211         register_trace_##name(void (*probe)(data_proto),                \
 212                               void *data)                               \
 213         {                                                               \
 214                 return -ENOSYS;                                         \
 215         }                                                               \
 216         static inline int                                               \
 217         unregister_trace_##name(void (*probe)(data_proto),              \
 218                                 void *data)                             \
 219         {                                                               \
 220                 return -ENOSYS;                                         \
 221         }                                                               \
 222         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 223         {                                                               \
 224         }
 225
 226 #define DEFINE_TRACE_FN(name, reg, unreg)
 227 #define DEFINE_TRACE(name)
 228 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 229 #define EXPORT_TRACEPOINT_SYMBOL(name)
 230
 231 #endif /* CONFIG_TRACEPOINTS */
 232
 233 /*
 234  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 235  * (void). "void" is a special value in a function prototype and can
 236  * not be combined with other arguments. Since the DECLARE_TRACE()
 237  * macro adds a data element at the beginning of the prototype,
 238  * we need a way to differentiate "(void *data, proto)" from
 239  * "(void *data, void)". The second prototype is invalid.
 240  *
 241  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 242  * and "void *__data" as the callback prototype.
 243  *
 244  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 245  * "void *__data, proto" as the callback prototype.
 246  */
 247 #define DECLARE_TRACE_NOARGS(name)                                      \
 248                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 249
 250 #define DECLARE_TRACE(name, proto, args)                                \
 251                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 252                                 PARAMS(void *__data, proto),            \
 253                                 PARAMS(__data, args))
 254
 255 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 256         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 257                         PARAMS(void *__data, proto),                    \
 258                         PARAMS(__data, args))
 259
 260 #define TRACE_EVENT_FLAGS(event, flag)
 261
 262 #endif /* DECLARE_TRACE */
 263
 264 #ifndef TRACE_EVENT
 265 /*
 266  * For use with the TRACE_EVENT macro:
 267  *
 268  * We define a tracepoint, its arguments, its printk format
 269  * and its 'fast binay record' layout.
 270  *
 271  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 272  * 'subsystem_event' notation is fine.
 273  *
 274  * Think about this whole construct as the
 275  * 'trace_sched_switch() function' from now on.
 276  *
 277  *
 278  *  TRACE_EVENT(sched_switch,
 279  *
 280  *      *
 281  *      * A function has a regular function arguments
 282  *      * prototype, declare it via TP_PROTO():
 283  *      *
 284  *
 285  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 286  *               struct task_struct *next),
 287  *
 288  *      *
 289  *      * Define the call signature of the 'function'.
 290  *      * (Design sidenote: we use this instead of a
 291  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 292  *      *
 293  *
 294  *      TP_ARGS(rq, prev, next),
 295  *
 296  *      *
 297  *      * Fast binary tracing: define the trace record via
 298  *      * TP_STRUCT__entry(). You can think about it like a
 299  *      * regular C structure local variable definition.
 300  *      *
 301  *      * This is how the trace record is structured and will
 302  *      * be saved into the ring buffer. These are the fields
 303  *      * that will be exposed to user-space in
 304  *      * /sys/kernel/debug/tracing/events/<*>/format.
 305  *      *
 306  *      * The declared 'local variable' is called '__entry'
 307  *      *
 308  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 309  *      *
 310  *      *       pid_t   prev_pid;
 311  *      *
 312  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 313  *      *
 314  *      *       char    prev_comm[TASK_COMM_LEN];
 315  *      *
 316  *
 317  *      TP_STRUCT__entry(
 318  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 319  *              __field(        pid_t,  prev_pid                        )
 320  *              __field(        int,    prev_prio                       )
 321  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 322  *              __field(        pid_t,  next_pid                        )
 323  *              __field(        int,    next_prio                       )
 324  *      ),
 325  *
 326  *      *
 327  *      * Assign the entry into the trace record, by embedding
 328  *      * a full C statement block into TP_fast_assign(). You
 329  *      * can refer to the trace record as '__entry' -
 330  *      * otherwise you can put arbitrary C code in here.
 331  *      *
 332  *      * Note: this C code will execute every time a trace event
 333  *      * happens, on an active tracepoint.
 334  *      *
 335  *
 336  *      TP_fast_assign(
 337  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 338  *              __entry->prev_pid       = prev->pid;
 339  *              __entry->prev_prio      = prev->prio;
 340  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 341  *              __entry->next_pid       = next->pid;
 342  *              __entry->next_prio      = next->prio;
 343  *      ),
 344  *
 345  *      *
 346  *      * Formatted output of a trace record via TP_printk().
 347  *      * This is how the tracepoint will appear under ftrace
 348  *      * plugins that make use of this tracepoint.
 349  *      *
 350  *      * (raw-binary tracing wont actually perform this step.)
 351  *      *
 352  *
 353  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 354  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 355  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 356  *
 357  * );
 358  *
 359  * This macro construct is thus used for the regular printk format
 360  * tracing setup, it is used to construct a function pointer based
 361  * tracepoint callback (this is used by programmatic plugins and
 362  * can also by used by generic instrumentation like SystemTap), and
 363  * it is also used to expose a structured trace record in
 364  * /sys/kernel/debug/tracing/events/.
 365  *
 366  * A set of (un)registration functions can be passed to the variant
 367  * TRACE_EVENT_FN to perform any (un)registration work.
 368  */
 369
 370 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 371 #define DEFINE_EVENT(template, name, proto, args)               \
 372         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 373 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 374         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 375 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 376                                args, cond)                      \
 377         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 378                                 PARAMS(args), PARAMS(cond))
 379
 380 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 381         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 382 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 383                 assign, print, reg, unreg)                      \
 384         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 385 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 386                               struct, assign, print)            \
 387         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 388                                 PARAMS(args), PARAMS(cond))
 389
 390 #define TRACE_EVENT_FLAGS(event, flag)
 391
 392 #endif /* ifdef TRACE_EVENT (see note above) */