linux/include/linux/tracepoint.h
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   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
  22struct module;
  23struct tracepoint;
  24
  25struct tracepoint_func {
  26        void *func;
  27        void *data;
  28};
  29
  30struct 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 */
  42extern 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 */
  48extern int
  49tracepoint_probe_unregister(const char *name, void *probe, void *data);
  50
  51extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
  52                                              void *data);
  53extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
  54                                                void *data);
  55extern void tracepoint_probe_update_all(void);
  56
  57#ifdef CONFIG_MODULES
  58struct tp_module {
  59        struct list_head list;
  60        unsigned int num_tracepoints;
  61        struct tracepoint * const *tracepoints_ptrs;
  62};
  63#endif /* CONFIG_MODULES */
  64
  65struct tracepoint_iter {
  66#ifdef CONFIG_MODULES
  67        struct tp_module *module;
  68#endif /* CONFIG_MODULES */
  69        struct tracepoint * const *tracepoint;
  70};
  71
  72extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  73extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  74extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  75extern 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 */
  82static 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/*
 140 * Make sure the alignment of the structure in the __tracepoints section will
 141 * not add unwanted padding between the beginning of the section and the
 142 * structure. Force alignment to the same alignment as the section start.
 143 */
 144#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 145        extern struct tracepoint __tracepoint_##name;                   \
 146        static inline void trace_##name(proto)                          \
 147        {                                                               \
 148                if (static_key_false(&__tracepoint_##name.key))         \
 149                        __DO_TRACE(&__tracepoint_##name,                \
 150                                TP_PROTO(data_proto),                   \
 151                                TP_ARGS(data_args),                     \
 152                                TP_CONDITION(cond),,);                  \
 153        }                                                               \
 154        static inline void trace_##name##_rcuidle(proto)                \
 155        {                                                               \
 156                if (static_key_false(&__tracepoint_##name.key))         \
 157                        __DO_TRACE(&__tracepoint_##name,                \
 158                                TP_PROTO(data_proto),                   \
 159                                TP_ARGS(data_args),                     \
 160                                TP_CONDITION(cond),                     \
 161                                rcu_idle_exit(),                        \
 162                                rcu_idle_enter());                      \
 163        }                                                               \
 164        static inline int                                               \
 165        register_trace_##name(void (*probe)(data_proto), void *data)    \
 166        {                                                               \
 167                return tracepoint_probe_register(#name, (void *)probe,  \
 168                                                 data);                 \
 169        }                                                               \
 170        static inline int                                               \
 171        unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 172        {                                                               \
 173                return tracepoint_probe_unregister(#name, (void *)probe, \
 174                                                   data);               \
 175        }                                                               \
 176        static inline void                                              \
 177        check_trace_callback_type_##name(void (*cb)(data_proto))        \
 178        {                                                               \
 179        }
 180
 181/*
 182 * We have no guarantee that gcc and the linker won't up-align the tracepoint
 183 * structures, so we create an array of pointers that will be used for iteration
 184 * on the tracepoints.
 185 */
 186#define DEFINE_TRACE_FN(name, reg, unreg)                                \
 187        static const char __tpstrtab_##name[]                            \
 188        __attribute__((section("__tracepoints_strings"))) = #name;       \
 189        struct tracepoint __tracepoint_##name                            \
 190        __attribute__((section("__tracepoints"))) =                      \
 191                { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 192        static struct tracepoint * const __tracepoint_ptr_##name __used  \
 193        __attribute__((section("__tracepoints_ptrs"))) =                 \
 194                &__tracepoint_##name;
 195
 196#define DEFINE_TRACE(name)                                              \
 197        DEFINE_TRACE_FN(name, NULL, NULL);
 198
 199#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 200        EXPORT_SYMBOL_GPL(__tracepoint_##name)
 201#define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 202        EXPORT_SYMBOL(__tracepoint_##name)
 203
 204#else /* !CONFIG_TRACEPOINTS */
 205#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 206        static inline void trace_##name(proto)                          \
 207        { }                                                             \
 208        static inline void trace_##name##_rcuidle(proto)                \
 209        { }                                                             \
 210        static inline int                                               \
 211        register_trace_##name(void (*probe)(data_proto),                \
 212                              void *data)                               \
 213        {                                                               \
 214                return -ENOSYS;                                         \
 215        }                                                               \
 216        static inline int                                               \
 217        unregister_trace_##name(void (*probe)(data_proto),              \
 218                                void *data)                             \
 219        {                                                               \
 220                return -ENOSYS;                                         \
 221        }                                                               \
 222        static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 223        {                                                               \
 224        }
 225
 226#define DEFINE_TRACE_FN(name, reg, unreg)
 227#define DEFINE_TRACE(name)
 228#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 229#define EXPORT_TRACEPOINT_SYMBOL(name)
 230
 231#endif /* CONFIG_TRACEPOINTS */
 232
 233/*
 234 * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 235 * (void). "void" is a special value in a function prototype and can
 236 * not be combined with other arguments. Since the DECLARE_TRACE()
 237 * macro adds a data element at the beginning of the prototype,
 238 * we need a way to differentiate "(void *data, proto)" from
 239 * "(void *data, void)". The second prototype is invalid.
 240 *
 241 * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 242 * and "void *__data" as the callback prototype.
 243 *
 244 * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 245 * "void *__data, proto" as the callback prototype.
 246 */
 247#define DECLARE_TRACE_NOARGS(name)                                      \
 248                __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 249
 250#define DECLARE_TRACE(name, proto, args)                                \
 251                __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 252                                PARAMS(void *__data, proto),            \
 253                                PARAMS(__data, args))
 254
 255#define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 256        __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 257                        PARAMS(void *__data, proto),                    \
 258                        PARAMS(__data, args))
 259
 260#define TRACE_EVENT_FLAGS(event, flag)
 261
 262#endif /* DECLARE_TRACE */
 263
 264#ifndef TRACE_EVENT
 265/*
 266 * For use with the TRACE_EVENT macro:
 267 *
 268 * We define a tracepoint, its arguments, its printk format
 269 * and its 'fast binay record' layout.
 270 *
 271 * Firstly, name your tracepoint via TRACE_EVENT(name : the
 272 * 'subsystem_event' notation is fine.
 273 *
 274 * Think about this whole construct as the
 275 * 'trace_sched_switch() function' from now on.
 276 *
 277 *
 278 *  TRACE_EVENT(sched_switch,
 279 *
 280 *      *
 281 *      * A function has a regular function arguments
 282 *      * prototype, declare it via TP_PROTO():
 283 *      *
 284 *
 285 *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 286 *               struct task_struct *next),
 287 *
 288 *      *
 289 *      * Define the call signature of the 'function'.
 290 *      * (Design sidenote: we use this instead of a
 291 *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 292 *      *
 293 *
 294 *      TP_ARGS(rq, prev, next),
 295 *
 296 *      *
 297 *      * Fast binary tracing: define the trace record via
 298 *      * TP_STRUCT__entry(). You can think about it like a
 299 *      * regular C structure local variable definition.
 300 *      *
 301 *      * This is how the trace record is structured and will
 302 *      * be saved into the ring buffer. These are the fields
 303 *      * that will be exposed to user-space in
 304 *      * /sys/kernel/debug/tracing/events/<*>/format.
 305 *      *
 306 *      * The declared 'local variable' is called '__entry'
 307 *      *
 308 *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 309 *      *
 310 *      *       pid_t   prev_pid;
 311 *      *
 312 *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 313 *      *
 314 *      *       char    prev_comm[TASK_COMM_LEN];
 315 *      *
 316 *
 317 *      TP_STRUCT__entry(
 318 *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 319 *              __field(        pid_t,  prev_pid                        )
 320 *              __field(        int,    prev_prio                       )
 321 *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 322 *              __field(        pid_t,  next_pid                        )
 323 *              __field(        int,    next_prio                       )
 324 *      ),
 325 *
 326 *      *
 327 *      * Assign the entry into the trace record, by embedding
 328 *      * a full C statement block into TP_fast_assign(). You
 329 *      * can refer to the trace record as '__entry' -
 330 *      * otherwise you can put arbitrary C code in here.
 331 *      *
 332 *      * Note: this C code will execute every time a trace event
 333 *      * happens, on an active tracepoint.
 334 *      *
 335 *
 336 *      TP_fast_assign(
 337 *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 338 *              __entry->prev_pid       = prev->pid;
 339 *              __entry->prev_prio      = prev->prio;
 340 *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 341 *              __entry->next_pid       = next->pid;
 342 *              __entry->next_prio      = next->prio;
 343 *      ),
 344 *
 345 *      *
 346 *      * Formatted output of a trace record via TP_printk().
 347 *      * This is how the tracepoint will appear under ftrace
 348 *      * plugins that make use of this tracepoint.
 349 *      *
 350 *      * (raw-binary tracing wont actually perform this step.)
 351 *      *
 352 *
 353 *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 354 *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 355 *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 356 *
 357 * );
 358 *
 359 * This macro construct is thus used for the regular printk format
 360 * tracing setup, it is used to construct a function pointer based
 361 * tracepoint callback (this is used by programmatic plugins and
 362 * can also by used by generic instrumentation like SystemTap), and
 363 * it is also used to expose a structured trace record in
 364 * /sys/kernel/debug/tracing/events/.
 365 *
 366 * A set of (un)registration functions can be passed to the variant
 367 * TRACE_EVENT_FN to perform any (un)registration work.
 368 */
 369
 370#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 371#define DEFINE_EVENT(template, name, proto, args)               \
 372        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 373#define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 374        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 375#define DEFINE_EVENT_CONDITION(template, name, proto,           \
 376                               args, cond)                      \
 377        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 378                                PARAMS(args), PARAMS(cond))
 379
 380#define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 381        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 382#define TRACE_EVENT_FN(name, proto, args, struct,               \
 383                assign, print, reg, unreg)                      \
 384        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 385#define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 386                              struct, assign, print)            \
 387        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 388                                PARAMS(args), PARAMS(cond))
 389
 390#define TRACE_EVENT_FLAGS(event, flag)
 391
 392#endif /* ifdef TRACE_EVENT (see note above) */
 393
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