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 #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)                               \
 118         do {                                                            \
 119                 struct tracepoint_func *it_func_ptr;                    \
 120                 void *it_func;                                          \
 121                 void *__data;                                           \
 122                                                                         \
 123                 if (!(cond))                                            \
 124                         return;                                         \
 125                 rcu_read_lock_sched_notrace();                          \
 126                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 127                 if (it_func_ptr) {                                      \
 128                         do {                                            \
 129                                 it_func = (it_func_ptr)->func;          \
 130                                 __data = (it_func_ptr)->data;           \
 131                                 ((void(*)(proto))(it_func))(args);      \
 132                         } while ((++it_func_ptr)->func);                \
 133                 }                                                       \
 134                 rcu_read_unlock_sched_notrace();                        \
 135         } while (0)
 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_branch(&__tracepoint_##name.key))            \
 147                         __DO_TRACE(&__tracepoint_##name,                \
 148                                 TP_PROTO(data_proto),                   \
 149                                 TP_ARGS(data_args),                     \
 150                                 TP_CONDITION(cond));                    \
 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 /*
 170  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 171  * structures, so we create an array of pointers that will be used for iteration
 172  * on the tracepoints.
 173  */
 174 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 175         static const char __tpstrtab_##name[]                            \
 176         __attribute__((section("__tracepoints_strings"))) = #name;       \
 177         struct tracepoint __tracepoint_##name                            \
 178         __attribute__((section("__tracepoints"))) =                      \
 179                 { __tpstrtab_##name, JUMP_LABEL_INIT, reg, unreg, NULL };\
 180         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 181         __attribute__((section("__tracepoints_ptrs"))) =                 \
 182                 &__tracepoint_##name;
 183
 184 #define DEFINE_TRACE(name)                                              \
 185         DEFINE_TRACE_FN(name, NULL, NULL);
 186
 187 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 188         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 189 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 190         EXPORT_SYMBOL(__tracepoint_##name)
 191
 192 #else /* !CONFIG_TRACEPOINTS */
 193 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 194         static inline void trace_##name(proto)                          \
 195         { }                                                             \
 196         static inline int                                               \
 197         register_trace_##name(void (*probe)(data_proto),                \
 198                               void *data)                               \
 199         {                                                               \
 200                 return -ENOSYS;                                         \
 201         }                                                               \
 202         static inline int                                               \
 203         unregister_trace_##name(void (*probe)(data_proto),              \
 204                                 void *data)                             \
 205         {                                                               \
 206                 return -ENOSYS;                                         \
 207         }                                                               \
 208         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 209         {                                                               \
 210         }
 211
 212 #define DEFINE_TRACE_FN(name, reg, unreg)
 213 #define DEFINE_TRACE(name)
 214 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 215 #define EXPORT_TRACEPOINT_SYMBOL(name)
 216
 217 #endif /* CONFIG_TRACEPOINTS */
 218
 219 /*
 220  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 221  * (void). "void" is a special value in a function prototype and can
 222  * not be combined with other arguments. Since the DECLARE_TRACE()
 223  * macro adds a data element at the beginning of the prototype,
 224  * we need a way to differentiate "(void *data, proto)" from
 225  * "(void *data, void)". The second prototype is invalid.
 226  *
 227  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 228  * and "void *__data" as the callback prototype.
 229  *
 230  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 231  * "void *__data, proto" as the callback prototype.
 232  */
 233 #define DECLARE_TRACE_NOARGS(name)                                      \
 234                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 235
 236 #define DECLARE_TRACE(name, proto, args)                                \
 237                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 238                                 PARAMS(void *__data, proto),            \
 239                                 PARAMS(__data, args))
 240
 241 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 242         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 243                         PARAMS(void *__data, proto),                    \
 244                         PARAMS(__data, args))
 245
 246 #define TRACE_EVENT_FLAGS(event, flag)
 247
 248 #endif /* DECLARE_TRACE */
 249
 250 #ifndef TRACE_EVENT
 251 /*
 252  * For use with the TRACE_EVENT macro:
 253  *
 254  * We define a tracepoint, its arguments, its printk format
 255  * and its 'fast binay record' layout.
 256  *
 257  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 258  * 'subsystem_event' notation is fine.
 259  *
 260  * Think about this whole construct as the
 261  * 'trace_sched_switch() function' from now on.
 262  *
 263  *
 264  *  TRACE_EVENT(sched_switch,
 265  *
 266  *      *
 267  *      * A function has a regular function arguments
 268  *      * prototype, declare it via TP_PROTO():
 269  *      *
 270  *
 271  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 272  *               struct task_struct *next),
 273  *
 274  *      *
 275  *      * Define the call signature of the 'function'.
 276  *      * (Design sidenote: we use this instead of a
 277  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 278  *      *
 279  *
 280  *      TP_ARGS(rq, prev, next),
 281  *
 282  *      *
 283  *      * Fast binary tracing: define the trace record via
 284  *      * TP_STRUCT__entry(). You can think about it like a
 285  *      * regular C structure local variable definition.
 286  *      *
 287  *      * This is how the trace record is structured and will
 288  *      * be saved into the ring buffer. These are the fields
 289  *      * that will be exposed to user-space in
 290  *      * /sys/kernel/debug/tracing/events/<*>/format.
 291  *      *
 292  *      * The declared 'local variable' is called '__entry'
 293  *      *
 294  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 295  *      *
 296  *      *       pid_t   prev_pid;
 297  *      *
 298  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 299  *      *
 300  *      *       char    prev_comm[TASK_COMM_LEN];
 301  *      *
 302  *
 303  *      TP_STRUCT__entry(
 304  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 305  *              __field(        pid_t,  prev_pid                        )
 306  *              __field(        int,    prev_prio                       )
 307  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 308  *              __field(        pid_t,  next_pid                        )
 309  *              __field(        int,    next_prio                       )
 310  *      ),
 311  *
 312  *      *
 313  *      * Assign the entry into the trace record, by embedding
 314  *      * a full C statement block into TP_fast_assign(). You
 315  *      * can refer to the trace record as '__entry' -
 316  *      * otherwise you can put arbitrary C code in here.
 317  *      *
 318  *      * Note: this C code will execute every time a trace event
 319  *      * happens, on an active tracepoint.
 320  *      *
 321  *
 322  *      TP_fast_assign(
 323  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 324  *              __entry->prev_pid       = prev->pid;
 325  *              __entry->prev_prio      = prev->prio;
 326  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 327  *              __entry->next_pid       = next->pid;
 328  *              __entry->next_prio      = next->prio;
 329  *      ),
 330  *
 331  *      *
 332  *      * Formatted output of a trace record via TP_printk().
 333  *      * This is how the tracepoint will appear under ftrace
 334  *      * plugins that make use of this tracepoint.
 335  *      *
 336  *      * (raw-binary tracing wont actually perform this step.)
 337  *      *
 338  *
 339  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 340  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 341  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 342  *
 343  * );
 344  *
 345  * This macro construct is thus used for the regular printk format
 346  * tracing setup, it is used to construct a function pointer based
 347  * tracepoint callback (this is used by programmatic plugins and
 348  * can also by used by generic instrumentation like SystemTap), and
 349  * it is also used to expose a structured trace record in
 350  * /sys/kernel/debug/tracing/events/.
 351  *
 352  * A set of (un)registration functions can be passed to the variant
 353  * TRACE_EVENT_FN to perform any (un)registration work.
 354  */
 355
 356 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 357 #define DEFINE_EVENT(template, name, proto, args)               \
 358         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 359 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 360         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 361 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 362                                args, cond)                      \
 363         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 364                                 PARAMS(args), PARAMS(cond))
 365
 366 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 367         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 368 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 369                 assign, print, reg, unreg)                      \
 370         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 371 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 372                               struct, assign, print)            \
 373         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 374                                 PARAMS(args), PARAMS(cond))
 375
 376 #define TRACE_EVENT_FLAGS(event, flag)
 377
 378 #endif /* ifdef TRACE_EVENT (see note above) */