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