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