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 #ifndef MODULE
 140 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
 141         static inline void trace_##name##_rcuidle(proto)                \
 142         {                                                               \
 143                 if (static_key_false(&__tracepoint_##name.key))         \
 144                         __DO_TRACE(&__tracepoint_##name,                \
 145                                 TP_PROTO(data_proto),                   \
 146                                 TP_ARGS(data_args),                     \
 147                                 TP_CONDITION(cond),                     \
 148                                 rcu_irq_enter(),                        \
 149                                 rcu_irq_exit());                        \
 150         }
 151 #else
 152 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 153 #endif
 154
 155 /*
 156  * Make sure the alignment of the structure in the __tracepoints section will
 157  * not add unwanted padding between the beginning of the section and the
 158  * structure. Force alignment to the same alignment as the section start.
 159  */
 160 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 161         extern struct tracepoint __tracepoint_##name;                   \
 162         static inline void trace_##name(proto)                          \
 163         {                                                               \
 164                 if (static_key_false(&__tracepoint_##name.key))         \
 165                         __DO_TRACE(&__tracepoint_##name,                \
 166                                 TP_PROTO(data_proto),                   \
 167                                 TP_ARGS(data_args),                     \
 168                                 TP_CONDITION(cond),,);                  \
 169         }                                                               \
 170         __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 171                 PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 172         static inline int                                               \
 173         register_trace_##name(void (*probe)(data_proto), void *data)    \
 174         {                                                               \
 175                 return tracepoint_probe_register(#name, (void *)probe,  \
 176                                                  data);                 \
 177         }                                                               \
 178         static inline int                                               \
 179         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 180         {                                                               \
 181                 return tracepoint_probe_unregister(#name, (void *)probe, \
 182                                                    data);               \
 183         }                                                               \
 184         static inline void                                              \
 185         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 186         {                                                               \
 187         }
 188
 189 /*
 190  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 191  * structures, so we create an array of pointers that will be used for iteration
 192  * on the tracepoints.
 193  */
 194 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 195         static const char __tpstrtab_##name[]                            \
 196         __attribute__((section("__tracepoints_strings"))) = #name;       \
 197         struct tracepoint __tracepoint_##name                            \
 198         __attribute__((section("__tracepoints"))) =                      \
 199                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 200         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 201         __attribute__((section("__tracepoints_ptrs"))) =                 \
 202                 &__tracepoint_##name;
 203
 204 #define DEFINE_TRACE(name)                                              \
 205         DEFINE_TRACE_FN(name, NULL, NULL);
 206
 207 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 208         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 209 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 210         EXPORT_SYMBOL(__tracepoint_##name)
 211
 212 #else /* !CONFIG_TRACEPOINTS */
 213 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 214         static inline void trace_##name(proto)                          \
 215         { }                                                             \
 216         static inline void trace_##name##_rcuidle(proto)                \
 217         { }                                                             \
 218         static inline int                                               \
 219         register_trace_##name(void (*probe)(data_proto),                \
 220                               void *data)                               \
 221         {                                                               \
 222                 return -ENOSYS;                                         \
 223         }                                                               \
 224         static inline int                                               \
 225         unregister_trace_##name(void (*probe)(data_proto),              \
 226                                 void *data)                             \
 227         {                                                               \
 228                 return -ENOSYS;                                         \
 229         }                                                               \
 230         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 231         {                                                               \
 232         }
 233
 234 #define DEFINE_TRACE_FN(name, reg, unreg)
 235 #define DEFINE_TRACE(name)
 236 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 237 #define EXPORT_TRACEPOINT_SYMBOL(name)
 238
 239 #endif /* CONFIG_TRACEPOINTS */
 240
 241 /*
 242  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 243  * (void). "void" is a special value in a function prototype and can
 244  * not be combined with other arguments. Since the DECLARE_TRACE()
 245  * macro adds a data element at the beginning of the prototype,
 246  * we need a way to differentiate "(void *data, proto)" from
 247  * "(void *data, void)". The second prototype is invalid.
 248  *
 249  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 250  * and "void *__data" as the callback prototype.
 251  *
 252  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 253  * "void *__data, proto" as the callback prototype.
 254  */
 255 #define DECLARE_TRACE_NOARGS(name)                                      \
 256                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 257
 258 #define DECLARE_TRACE(name, proto, args)                                \
 259                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 260                                 PARAMS(void *__data, proto),            \
 261                                 PARAMS(__data, args))
 262
 263 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 264         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 265                         PARAMS(void *__data, proto),                    \
 266                         PARAMS(__data, args))
 267
 268 #define TRACE_EVENT_FLAGS(event, flag)
 269
 270 #endif /* DECLARE_TRACE */
 271
 272 #ifndef TRACE_EVENT
 273 /*
 274  * For use with the TRACE_EVENT macro:
 275  *
 276  * We define a tracepoint, its arguments, its printk format
 277  * and its 'fast binay record' layout.
 278  *
 279  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 280  * 'subsystem_event' notation is fine.
 281  *
 282  * Think about this whole construct as the
 283  * 'trace_sched_switch() function' from now on.
 284  *
 285  *
 286  *  TRACE_EVENT(sched_switch,
 287  *
 288  *      *
 289  *      * A function has a regular function arguments
 290  *      * prototype, declare it via TP_PROTO():
 291  *      *
 292  *
 293  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 294  *               struct task_struct *next),
 295  *
 296  *      *
 297  *      * Define the call signature of the 'function'.
 298  *      * (Design sidenote: we use this instead of a
 299  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 300  *      *
 301  *
 302  *      TP_ARGS(rq, prev, next),
 303  *
 304  *      *
 305  *      * Fast binary tracing: define the trace record via
 306  *      * TP_STRUCT__entry(). You can think about it like a
 307  *      * regular C structure local variable definition.
 308  *      *
 309  *      * This is how the trace record is structured and will
 310  *      * be saved into the ring buffer. These are the fields
 311  *      * that will be exposed to user-space in
 312  *      * /sys/kernel/debug/tracing/events/<*>/format.
 313  *      *
 314  *      * The declared 'local variable' is called '__entry'
 315  *      *
 316  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 317  *      *
 318  *      *       pid_t   prev_pid;
 319  *      *
 320  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 321  *      *
 322  *      *       char    prev_comm[TASK_COMM_LEN];
 323  *      *
 324  *
 325  *      TP_STRUCT__entry(
 326  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 327  *              __field(        pid_t,  prev_pid                        )
 328  *              __field(        int,    prev_prio                       )
 329  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 330  *              __field(        pid_t,  next_pid                        )
 331  *              __field(        int,    next_prio                       )
 332  *      ),
 333  *
 334  *      *
 335  *      * Assign the entry into the trace record, by embedding
 336  *      * a full C statement block into TP_fast_assign(). You
 337  *      * can refer to the trace record as '__entry' -
 338  *      * otherwise you can put arbitrary C code in here.
 339  *      *
 340  *      * Note: this C code will execute every time a trace event
 341  *      * happens, on an active tracepoint.
 342  *      *
 343  *
 344  *      TP_fast_assign(
 345  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 346  *              __entry->prev_pid       = prev->pid;
 347  *              __entry->prev_prio      = prev->prio;
 348  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 349  *              __entry->next_pid       = next->pid;
 350  *              __entry->next_prio      = next->prio;
 351  *      ),
 352  *
 353  *      *
 354  *      * Formatted output of a trace record via TP_printk().
 355  *      * This is how the tracepoint will appear under ftrace
 356  *      * plugins that make use of this tracepoint.
 357  *      *
 358  *      * (raw-binary tracing wont actually perform this step.)
 359  *      *
 360  *
 361  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 362  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 363  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 364  *
 365  * );
 366  *
 367  * This macro construct is thus used for the regular printk format
 368  * tracing setup, it is used to construct a function pointer based
 369  * tracepoint callback (this is used by programmatic plugins and
 370  * can also by used by generic instrumentation like SystemTap), and
 371  * it is also used to expose a structured trace record in
 372  * /sys/kernel/debug/tracing/events/.
 373  *
 374  * A set of (un)registration functions can be passed to the variant
 375  * TRACE_EVENT_FN to perform any (un)registration work.
 376  */
 377
 378 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 379 #define DEFINE_EVENT(template, name, proto, args)               \
 380         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 381 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 382         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 383 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 384                                args, cond)                      \
 385         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 386                                 PARAMS(args), PARAMS(cond))
 387
 388 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 389         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 390 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 391                 assign, print, reg, unreg)                      \
 392         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 393 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 394                               struct, assign, print)            \
 395         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 396                                 PARAMS(args), PARAMS(cond))
 397
 398 #define TRACE_EVENT_FLAGS(event, flag)
 399
 400 #endif /* ifdef TRACE_EVENT (see note above) */