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