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