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         int state;                      /* State. */
  33         void (*regfunc)(void);
  34         void (*unregfunc)(void);
  35         struct tracepoint_func *funcs;
  36 } __attribute__((aligned(32)));         /*
  37                                          * Aligned on 32 bytes because it is
  38                                          * globally visible and gcc happily
  39                                          * align these on the structure size.
  40                                          * Keep in sync with vmlinux.lds.h.
  41                                          */
  42
  43 /*
  44  * Connect a probe to a tracepoint.
  45  * Internal API, should not be used directly.
  46  */
  47 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  48
  49 /*
  50  * Disconnect a probe from a tracepoint.
  51  * Internal API, should not be used directly.
  52  */
  53 extern int
  54 tracepoint_probe_unregister(const char *name, void *probe, void *data);
  55
  56 extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  57                                               void *data);
  58 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  59                                                 void *data);
  60 extern void tracepoint_probe_update_all(void);
  61
  62 struct tracepoint_iter {
  63         struct module *module;
  64         struct tracepoint *tracepoint;
  65 };
  66
  67 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  68 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  69 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  70 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  71 extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
  72         struct tracepoint *begin, struct tracepoint *end);
  73
  74 /*
  75  * tracepoint_synchronize_unregister must be called between the last tracepoint
  76  * probe unregistration and the end of module exit to make sure there is no
  77  * caller executing a probe when it is freed.
  78  */
  79 static inline void tracepoint_synchronize_unregister(void)
  80 {
  81         synchronize_sched();
  82 }
  83
  84 #define PARAMS(args...) args
  85
  86 #ifdef CONFIG_TRACEPOINTS
  87 extern void tracepoint_update_probe_range(struct tracepoint *begin,
  88         struct tracepoint *end);
  89 #else
  90 static inline void tracepoint_update_probe_range(struct tracepoint *begin,
  91         struct tracepoint *end)
  92 { }
  93 #endif /* CONFIG_TRACEPOINTS */
  94
  95 #endif /* _LINUX_TRACEPOINT_H */
  96
  97 /*
  98  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  99  *  file ifdef protection.
 100  *  This is due to the way trace events work. If a file includes two
 101  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 102  *  will override the TRACE_EVENT and break the second include.
 103  */
 104
 105 #ifndef DECLARE_TRACE
 106
 107 #define TP_PROTO(args...)       args
 108 #define TP_ARGS(args...)        args
 109
 110 #ifdef CONFIG_TRACEPOINTS
 111
 112 /*
 113  * it_func[0] is never NULL because there is at least one element in the array
 114  * when the array itself is non NULL.
 115  *
 116  * Note, the proto and args passed in includes "__data" as the first parameter.
 117  * The reason for this is to handle the "void" prototype. If a tracepoint
 118  * has a "void" prototype, then it is invalid to declare a function
 119  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 120  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 121  */
 122 #define __DO_TRACE(tp, proto, args)                                     \
 123         do {                                                            \
 124                 struct tracepoint_func *it_func_ptr;                    \
 125                 void *it_func;                                          \
 126                 void *__data;                                           \
 127                                                                         \
 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, data_proto, data_args)       \
 146         extern struct tracepoint __tracepoint_##name;                   \
 147         static inline void trace_##name(proto)                          \
 148         {                                                               \
 149                 JUMP_LABEL(&__tracepoint_##name.state, do_trace);       \
 150                 return;                                                 \
 151 do_trace:                                                               \
 152                         __DO_TRACE(&__tracepoint_##name,                \
 153                                 TP_PROTO(data_proto),                   \
 154                                 TP_ARGS(data_args));                    \
 155         }                                                               \
 156         static inline int                                               \
 157         register_trace_##name(void (*probe)(data_proto), void *data)    \
 158         {                                                               \
 159                 return tracepoint_probe_register(#name, (void *)probe,  \
 160                                                  data);                 \
 161         }                                                               \
 162         static inline int                                               \
 163         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 164         {                                                               \
 165                 return tracepoint_probe_unregister(#name, (void *)probe, \
 166                                                    data);               \
 167         }                                                               \
 168         static inline void                                              \
 169         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 170         {                                                               \
 171         }
 172
 173 #define DEFINE_TRACE_FN(name, reg, unreg)                               \
 174         static const char __tpstrtab_##name[]                           \
 175         __attribute__((section("__tracepoints_strings"))) = #name;      \
 176         struct tracepoint __tracepoint_##name                           \
 177         __attribute__((section("__tracepoints"), aligned(32))) =        \
 178                 { __tpstrtab_##name, 0, reg, unreg, NULL }
 179
 180 #define DEFINE_TRACE(name)                                              \
 181         DEFINE_TRACE_FN(name, NULL, NULL);
 182
 183 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 184         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 185 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 186         EXPORT_SYMBOL(__tracepoint_##name)
 187
 188 #else /* !CONFIG_TRACEPOINTS */
 189 #define __DECLARE_TRACE(name, proto, args, data_proto, data_args)       \
 190         static inline void trace_##name(proto)                          \
 191         { }                                                             \
 192         static inline int                                               \
 193         register_trace_##name(void (*probe)(data_proto),                \
 194                               void *data)                               \
 195         {                                                               \
 196                 return -ENOSYS;                                         \
 197         }                                                               \
 198         static inline int                                               \
 199         unregister_trace_##name(void (*probe)(data_proto),              \
 200                                 void *data)                             \
 201         {                                                               \
 202                 return -ENOSYS;                                         \
 203         }                                                               \
 204         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 205         {                                                               \
 206         }
 207
 208 #define DEFINE_TRACE_FN(name, reg, unreg)
 209 #define DEFINE_TRACE(name)
 210 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 211 #define EXPORT_TRACEPOINT_SYMBOL(name)
 212
 213 #endif /* CONFIG_TRACEPOINTS */
 214
 215 /*
 216  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 217  * (void). "void" is a special value in a function prototype and can
 218  * not be combined with other arguments. Since the DECLARE_TRACE()
 219  * macro adds a data element at the beginning of the prototype,
 220  * we need a way to differentiate "(void *data, proto)" from
 221  * "(void *data, void)". The second prototype is invalid.
 222  *
 223  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 224  * and "void *__data" as the callback prototype.
 225  *
 226  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 227  * "void *__data, proto" as the callback prototype.
 228  */
 229 #define DECLARE_TRACE_NOARGS(name)                                      \
 230                 __DECLARE_TRACE(name, void, , void *__data, __data)
 231
 232 #define DECLARE_TRACE(name, proto, args)                                \
 233                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),      \
 234                                 PARAMS(void *__data, proto),            \
 235                                 PARAMS(__data, args))
 236
 237 #endif /* DECLARE_TRACE */
 238
 239 #ifndef TRACE_EVENT
 240 /*
 241  * For use with the TRACE_EVENT macro:
 242  *
 243  * We define a tracepoint, its arguments, its printk format
 244  * and its 'fast binay record' layout.
 245  *
 246  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 247  * 'subsystem_event' notation is fine.
 248  *
 249  * Think about this whole construct as the
 250  * 'trace_sched_switch() function' from now on.
 251  *
 252  *
 253  *  TRACE_EVENT(sched_switch,
 254  *
 255  *      *
 256  *      * A function has a regular function arguments
 257  *      * prototype, declare it via TP_PROTO():
 258  *      *
 259  *
 260  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 261  *               struct task_struct *next),
 262  *
 263  *      *
 264  *      * Define the call signature of the 'function'.
 265  *      * (Design sidenote: we use this instead of a
 266  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 267  *      *
 268  *
 269  *      TP_ARGS(rq, prev, next),
 270  *
 271  *      *
 272  *      * Fast binary tracing: define the trace record via
 273  *      * TP_STRUCT__entry(). You can think about it like a
 274  *      * regular C structure local variable definition.
 275  *      *
 276  *      * This is how the trace record is structured and will
 277  *      * be saved into the ring buffer. These are the fields
 278  *      * that will be exposed to user-space in
 279  *      * /sys/kernel/debug/tracing/events/<*>/format.
 280  *      *
 281  *      * The declared 'local variable' is called '__entry'
 282  *      *
 283  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 284  *      *
 285  *      *       pid_t   prev_pid;
 286  *      *
 287  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 288  *      *
 289  *      *       char    prev_comm[TASK_COMM_LEN];
 290  *      *
 291  *
 292  *      TP_STRUCT__entry(
 293  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 294  *              __field(        pid_t,  prev_pid                        )
 295  *              __field(        int,    prev_prio                       )
 296  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 297  *              __field(        pid_t,  next_pid                        )
 298  *              __field(        int,    next_prio                       )
 299  *      ),
 300  *
 301  *      *
 302  *      * Assign the entry into the trace record, by embedding
 303  *      * a full C statement block into TP_fast_assign(). You
 304  *      * can refer to the trace record as '__entry' -
 305  *      * otherwise you can put arbitrary C code in here.
 306  *      *
 307  *      * Note: this C code will execute every time a trace event
 308  *      * happens, on an active tracepoint.
 309  *      *
 310  *
 311  *      TP_fast_assign(
 312  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 313  *              __entry->prev_pid       = prev->pid;
 314  *              __entry->prev_prio      = prev->prio;
 315  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 316  *              __entry->next_pid       = next->pid;
 317  *              __entry->next_prio      = next->prio;
 318  *      )
 319  *
 320  *      *
 321  *      * Formatted output of a trace record via TP_printk().
 322  *      * This is how the tracepoint will appear under ftrace
 323  *      * plugins that make use of this tracepoint.
 324  *      *
 325  *      * (raw-binary tracing wont actually perform this step.)
 326  *      *
 327  *
 328  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 329  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 330  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 331  *
 332  * );
 333  *
 334  * This macro construct is thus used for the regular printk format
 335  * tracing setup, it is used to construct a function pointer based
 336  * tracepoint callback (this is used by programmatic plugins and
 337  * can also by used by generic instrumentation like SystemTap), and
 338  * it is also used to expose a structured trace record in
 339  * /sys/kernel/debug/tracing/events/.
 340  *
 341  * A set of (un)registration functions can be passed to the variant
 342  * TRACE_EVENT_FN to perform any (un)registration work.
 343  */
 344
 345 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 346 #define DEFINE_EVENT(template, name, proto, args)               \
 347         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 348 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 349         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 350
 351 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 352         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 353 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 354                 assign, print, reg, unreg)                      \
 355         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 356
 357 #endif /* ifdef TRACE_EVENT (see note above) */