include/linux/tracepoint.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 #ifndef _LINUX_TRACEPOINT_H
   3 #define _LINUX_TRACEPOINT_H
   4
   5 /*
   6  * Kernel Tracepoint API.
   7  *
   8  * See Documentation/trace/tracepoints.rst.
   9  *
  10  * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  11  *
  12  * Heavily inspired from the Linux Kernel Markers.
  13  */
  14
  15 #include <linux/smp.h>
  16 #include <linux/srcu.h>
  17 #include <linux/errno.h>
  18 #include <linux/types.h>
  19 #include <linux/rcupdate.h>
  20 #include <linux/rcupdate_trace.h>
  21 #include <linux/tracepoint-defs.h>
  22 #include <linux/static_call.h>
  23
  24 struct module;
  25 struct tracepoint;
  26 struct notifier_block;
  27
  28 struct trace_eval_map {
  29         const char              *system;
  30         const char              *eval_string;
  31         unsigned long           eval_value;
  32 };
  33
  34 #define TRACEPOINT_DEFAULT_PRIO 10
  35
  36 extern int
  37 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
  38 extern int
  39 tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
  40                                int prio);
  41 extern int
  42 tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe, void *data,
  43                                          int prio);
  44 extern int
  45 tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
  46 static inline int
  47 tracepoint_probe_register_may_exist(struct tracepoint *tp, void *probe,
  48                                     void *data)
  49 {
  50         return tracepoint_probe_register_prio_may_exist(tp, probe, data,
  51                                                         TRACEPOINT_DEFAULT_PRIO);
  52 }
  53 extern void
  54 for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
  55                 void *priv);
  56
  57 #ifdef CONFIG_MODULES
  58 struct tp_module {
  59         struct list_head list;
  60         struct module *mod;
  61 };
  62
  63 bool trace_module_has_bad_taint(struct module *mod);
  64 extern int register_tracepoint_module_notifier(struct notifier_block *nb);
  65 extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
  66 void for_each_module_tracepoint(void (*fct)(struct tracepoint *,
  67                                         struct module *, void *),
  68                                 void *priv);
  69 void for_each_tracepoint_in_module(struct module *,
  70                                    void (*fct)(struct tracepoint *,
  71                                         struct module *, void *),
  72                                    void *priv);
  73 #else
  74 static inline bool trace_module_has_bad_taint(struct module *mod)
  75 {
  76         return false;
  77 }
  78 static inline
  79 int register_tracepoint_module_notifier(struct notifier_block *nb)
  80 {
  81         return 0;
  82 }
  83 static inline
  84 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  85 {
  86         return 0;
  87 }
  88 static inline
  89 void for_each_module_tracepoint(void (*fct)(struct tracepoint *,
  90                                         struct module *, void *),
  91                                 void *priv)
  92 {
  93 }
  94 static inline
  95 void for_each_tracepoint_in_module(struct module *mod,
  96                                    void (*fct)(struct tracepoint *,
  97                                         struct module *, void *),
  98                                    void *priv)
  99 {
 100 }
 101 #endif /* CONFIG_MODULES */
 102
 103 /*
 104  * tracepoint_synchronize_unregister must be called between the last tracepoint
 105  * probe unregistration and the end of module exit to make sure there is no
 106  * caller executing a probe when it is freed.
 107  *
 108  * An alternative is to use the following for batch reclaim associated
 109  * with a given tracepoint:
 110  *
 111  * - tracepoint_is_faultable() == false: call_rcu()
 112  * - tracepoint_is_faultable() == true:  call_rcu_tasks_trace()
 113  */
 114 #ifdef CONFIG_TRACEPOINTS
 115 static inline void tracepoint_synchronize_unregister(void)
 116 {
 117         synchronize_rcu_tasks_trace();
 118         synchronize_rcu();
 119 }
 120 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
 121 {
 122         return tp->ext && tp->ext->faultable;
 123 }
 124 #else
 125 static inline void tracepoint_synchronize_unregister(void)
 126 { }
 127 static inline bool tracepoint_is_faultable(struct tracepoint *tp)
 128 {
 129         return false;
 130 }
 131 #endif
 132
 133 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 134 extern int syscall_regfunc(void);
 135 extern void syscall_unregfunc(void);
 136 #endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
 137
 138 #ifndef PARAMS
 139 #define PARAMS(args...) args
 140 #endif
 141
 142 #define TRACE_DEFINE_ENUM(x)
 143 #define TRACE_DEFINE_SIZEOF(x)
 144
 145 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 146 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 147 {
 148         return offset_to_ptr(p);
 149 }
 150
 151 #define __TRACEPOINT_ENTRY(name)                                        \
 152         asm("   .section \"__tracepoints_ptrs\", \"a\"          \n"     \
 153             "   .balign 4                                       \n"     \
 154             "   .long   __tracepoint_" #name " - .              \n"     \
 155             "   .previous                                       \n")
 156 #else
 157 static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 158 {
 159         return *p;
 160 }
 161
 162 #define __TRACEPOINT_ENTRY(name)                                         \
 163         static tracepoint_ptr_t __tracepoint_ptr_##name __used           \
 164         __section("__tracepoints_ptrs") = &__tracepoint_##name
 165 #endif
 166
 167 #endif /* _LINUX_TRACEPOINT_H */
 168
 169 /*
 170  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
 171  *  file ifdef protection.
 172  *  This is due to the way trace events work. If a file includes two
 173  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 174  *  will override the TRACE_EVENT and break the second include.
 175  */
 176
 177 #ifndef DECLARE_TRACE
 178
 179 #define TP_PROTO(args...)       args
 180 #define TP_ARGS(args...)        args
 181 #define TP_CONDITION(args...)   args
 182
 183 /*
 184  * Individual subsystem my have a separate configuration to
 185  * enable their tracepoints. By default, this file will create
 186  * the tracepoints if CONFIG_TRACEPOINTS is defined. If a subsystem
 187  * wants to be able to disable its tracepoints from being created
 188  * it can define NOTRACE before including the tracepoint headers.
 189  */
 190 #if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
 191 #define TRACEPOINTS_ENABLED
 192 #endif
 193
 194 #ifdef TRACEPOINTS_ENABLED
 195
 196 #ifdef CONFIG_HAVE_STATIC_CALL
 197 #define __DO_TRACE_CALL(name, args)                                     \
 198         do {                                                            \
 199                 struct tracepoint_func *it_func_ptr;                    \
 200                 void *__data;                                           \
 201                 it_func_ptr =                                           \
 202                         rcu_dereference_raw((&__tracepoint_##name)->funcs); \
 203                 if (it_func_ptr) {                                      \
 204                         __data = (it_func_ptr)->data;                   \
 205                         static_call(tp_func_##name)(__data, args);      \
 206                 }                                                       \
 207         } while (0)
 208 #else
 209 #define __DO_TRACE_CALL(name, args)     __traceiter_##name(NULL, args)
 210 #endif /* CONFIG_HAVE_STATIC_CALL */
 211
 212 /*
 213  * Declare an exported function that Rust code can call to trigger this
 214  * tracepoint. This function does not include the static branch; that is done
 215  * in Rust to avoid a function call when the tracepoint is disabled.
 216  */
 217 #define DEFINE_RUST_DO_TRACE(name, proto, args)
 218 #define __DEFINE_RUST_DO_TRACE(name, proto, args)                       \
 219         notrace void rust_do_trace_##name(proto)                        \
 220         {                                                               \
 221                 __do_trace_##name(args);                                \
 222         }
 223
 224 /*
 225  * Make sure the alignment of the structure in the __tracepoints section will
 226  * not add unwanted padding between the beginning of the section and the
 227  * structure. Force alignment to the same alignment as the section start.
 228  *
 229  * When lockdep is enabled, we make sure to always test if RCU is
 230  * "watching" regardless if the tracepoint is enabled or not. Tracepoints
 231  * require RCU to be active, and it should always warn at the tracepoint
 232  * site if it is not watching, as it will need to be active when the
 233  * tracepoint is enabled.
 234  */
 235 #define __DECLARE_TRACE_COMMON(name, proto, args, data_proto)           \
 236         extern int __traceiter_##name(data_proto);                      \
 237         DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);        \
 238         extern struct tracepoint __tracepoint_##name;                   \
 239         extern void rust_do_trace_##name(proto);                        \
 240         static inline int                                               \
 241         register_trace_##name(void (*probe)(data_proto), void *data)    \
 242         {                                                               \
 243                 return tracepoint_probe_register(&__tracepoint_##name,  \
 244                                                 (void *)probe, data);   \
 245         }                                                               \
 246         static inline int                                               \
 247         register_trace_prio_##name(void (*probe)(data_proto), void *data,\
 248                                    int prio)                            \
 249         {                                                               \
 250                 return tracepoint_probe_register_prio(&__tracepoint_##name, \
 251                                               (void *)probe, data, prio); \
 252         }                                                               \
 253         static inline int                                               \
 254         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 255         {                                                               \
 256                 return tracepoint_probe_unregister(&__tracepoint_##name,\
 257                                                 (void *)probe, data);   \
 258         }                                                               \
 259         static inline void                                              \
 260         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 261         {                                                               \
 262         }                                                               \
 263         static inline bool                                              \
 264         trace_##name##_enabled(void)                                    \
 265         {                                                               \
 266                 return static_branch_unlikely(&__tracepoint_##name.key);\
 267         }
 268
 269 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)            \
 270         __DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
 271         static inline void __do_trace_##name(proto)                     \
 272         {                                                               \
 273                 if (cond) {                                             \
 274                         guard(preempt_notrace)();                       \
 275                         __DO_TRACE_CALL(name, TP_ARGS(args));           \
 276                 }                                                       \
 277         }                                                               \
 278         static inline void trace_##name(proto)                          \
 279         {                                                               \
 280                 if (static_branch_unlikely(&__tracepoint_##name.key))   \
 281                         __do_trace_##name(args);                        \
 282                 if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {             \
 283                         WARN_ONCE(!rcu_is_watching(),                   \
 284                                   "RCU not watching for tracepoint");   \
 285                 }                                                       \
 286         }
 287
 288 #define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto)          \
 289         __DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
 290         static inline void __do_trace_##name(proto)                     \
 291         {                                                               \
 292                 guard(rcu_tasks_trace)();                               \
 293                 __DO_TRACE_CALL(name, TP_ARGS(args));                   \
 294         }                                                               \
 295         static inline void trace_##name(proto)                          \
 296         {                                                               \
 297                 might_fault();                                          \
 298                 if (static_branch_unlikely(&__tracepoint_##name.key))   \
 299                         __do_trace_##name(args);                        \
 300                 if (IS_ENABLED(CONFIG_LOCKDEP)) {                       \
 301                         WARN_ONCE(!rcu_is_watching(),                   \
 302                                   "RCU not watching for tracepoint");   \
 303                 }                                                       \
 304         }
 305
 306 /*
 307  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 308  * structures, so we create an array of pointers that will be used for iteration
 309  * on the tracepoints.
 310  *
 311  * it_func[0] is never NULL because there is at least one element in the array
 312  * when the array itself is non NULL.
 313  */
 314 #define __DEFINE_TRACE_EXT(_name, _ext, proto, args)                    \
 315         static const char __tpstrtab_##_name[]                          \
 316         __section("__tracepoints_strings") = #_name;                    \
 317         extern struct static_call_key STATIC_CALL_KEY(tp_func_##_name); \
 318         int __traceiter_##_name(void *__data, proto);                   \
 319         void __probestub_##_name(void *__data, proto);                  \
 320         struct tracepoint __tracepoint_##_name  __used                  \
 321         __section("__tracepoints") = {                                  \
 322                 .name = __tpstrtab_##_name,                             \
 323                 .key = STATIC_KEY_FALSE_INIT,                           \
 324                 .static_call_key = &STATIC_CALL_KEY(tp_func_##_name),   \
 325                 .static_call_tramp = STATIC_CALL_TRAMP_ADDR(tp_func_##_name), \
 326                 .iterator = &__traceiter_##_name,                       \
 327                 .probestub = &__probestub_##_name,                      \
 328                 .funcs = NULL,                                          \
 329                 .ext = _ext,                                            \
 330         };                                                              \
 331         __TRACEPOINT_ENTRY(_name);                                      \
 332         int __traceiter_##_name(void *__data, proto)                    \
 333         {                                                               \
 334                 struct tracepoint_func *it_func_ptr;                    \
 335                 void *it_func;                                          \
 336                                                                         \
 337                 it_func_ptr =                                           \
 338                         rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
 339                 if (it_func_ptr) {                                      \
 340                         do {                                            \
 341                                 it_func = READ_ONCE((it_func_ptr)->func); \
 342                                 __data = (it_func_ptr)->data;           \
 343                                 ((void(*)(void *, proto))(it_func))(__data, args); \
 344                         } while ((++it_func_ptr)->func);                \
 345                 }                                                       \
 346                 return 0;                                               \
 347         }                                                               \
 348         void __probestub_##_name(void *__data, proto)                   \
 349         {                                                               \
 350         }                                                               \
 351         DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);       \
 352         DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))
 353
 354 #define DEFINE_TRACE_FN(_name, _reg, _unreg, _proto, _args)             \
 355         static struct tracepoint_ext __tracepoint_ext_##_name = {       \
 356                 .regfunc = _reg,                                        \
 357                 .unregfunc = _unreg,                                    \
 358                 .faultable = false,                                     \
 359         };                                                              \
 360         __DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
 361
 362 #define DEFINE_TRACE_SYSCALL(_name, _reg, _unreg, _proto, _args)        \
 363         static struct tracepoint_ext __tracepoint_ext_##_name = {       \
 364                 .regfunc = _reg,                                        \
 365                 .unregfunc = _unreg,                                    \
 366                 .faultable = true,                                      \
 367         };                                                              \
 368         __DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
 369
 370 #define DEFINE_TRACE(_name, _proto, _args)                              \
 371         __DEFINE_TRACE_EXT(_name, NULL, PARAMS(_proto), PARAMS(_args));
 372
 373 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 374         EXPORT_SYMBOL_GPL(__tracepoint_##name);                         \
 375         EXPORT_SYMBOL_GPL(__traceiter_##name);                          \
 376         EXPORT_STATIC_CALL_GPL(tp_func_##name)
 377 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 378         EXPORT_SYMBOL(__tracepoint_##name);                             \
 379         EXPORT_SYMBOL(__traceiter_##name);                              \
 380         EXPORT_STATIC_CALL(tp_func_##name)
 381
 382
 383 #else /* !TRACEPOINTS_ENABLED */
 384 #define __DECLARE_TRACE_COMMON(name, proto, args, data_proto)           \
 385         static inline void trace_##name(proto)                          \
 386         { }                                                             \
 387         static inline int                                               \
 388         register_trace_##name(void (*probe)(data_proto),                \
 389                               void *data)                               \
 390         {                                                               \
 391                 return -ENOSYS;                                         \
 392         }                                                               \
 393         static inline int                                               \
 394         unregister_trace_##name(void (*probe)(data_proto),              \
 395                                 void *data)                             \
 396         {                                                               \
 397                 return -ENOSYS;                                         \
 398         }                                                               \
 399         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 400         {                                                               \
 401         }                                                               \
 402         static inline bool                                              \
 403         trace_##name##_enabled(void)                                    \
 404         {                                                               \
 405                 return false;                                           \
 406         }
 407
 408 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)            \
 409         __DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
 410
 411 #define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto)          \
 412         __DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
 413
 414 #define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
 415 #define DEFINE_TRACE_SYSCALL(name, reg, unreg, proto, args)
 416 #define DEFINE_TRACE(name, proto, args)
 417 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 418 #define EXPORT_TRACEPOINT_SYMBOL(name)
 419
 420 #endif /* TRACEPOINTS_ENABLED */
 421
 422 #ifdef CONFIG_TRACING
 423 /**
 424  * tracepoint_string - register constant persistent string to trace system
 425  * @str - a constant persistent string that will be referenced in tracepoints
 426  *
 427  * If constant strings are being used in tracepoints, it is faster and
 428  * more efficient to just save the pointer to the string and reference
 429  * that with a printf "%s" instead of saving the string in the ring buffer
 430  * and wasting space and time.
 431  *
 432  * The problem with the above approach is that userspace tools that read
 433  * the binary output of the trace buffers do not have access to the string.
 434  * Instead they just show the address of the string which is not very
 435  * useful to users.
 436  *
 437  * With tracepoint_string(), the string will be registered to the tracing
 438  * system and exported to userspace via the debugfs/tracing/printk_formats
 439  * file that maps the string address to the string text. This way userspace
 440  * tools that read the binary buffers have a way to map the pointers to
 441  * the ASCII strings they represent.
 442  *
 443  * The @str used must be a constant string and persistent as it would not
 444  * make sense to show a string that no longer exists. But it is still fine
 445  * to be used with modules, because when modules are unloaded, if they
 446  * had tracepoints, the ring buffers are cleared too. As long as the string
 447  * does not change during the life of the module, it is fine to use
 448  * tracepoint_string() within a module.
 449  */
 450 #define tracepoint_string(str)                                          \
 451         ({                                                              \
 452                 static const char *___tp_str __tracepoint_string = str; \
 453                 ___tp_str;                                              \
 454         })
 455 #define __tracepoint_string     __used __section("__tracepoint_str")
 456 #else
 457 /*
 458  * tracepoint_string() is used to save the string address for userspace
 459  * tracing tools. When tracing isn't configured, there's no need to save
 460  * anything.
 461  */
 462 # define tracepoint_string(str) str
 463 # define __tracepoint_string
 464 #endif
 465
 466 #define DECLARE_TRACE(name, proto, args)                                \
 467         __DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),         \
 468                         cpu_online(raw_smp_processor_id()),             \
 469                         PARAMS(void *__data, proto))
 470
 471 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 472         __DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),         \
 473                         cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
 474                         PARAMS(void *__data, proto))
 475
 476 #define DECLARE_TRACE_SYSCALL(name, proto, args)                        \
 477         __DECLARE_TRACE_SYSCALL(name##_tp, PARAMS(proto), PARAMS(args), \
 478                                 PARAMS(void *__data, proto))
 479
 480 #define DECLARE_TRACE_EVENT(name, proto, args)                          \
 481         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
 482                         cpu_online(raw_smp_processor_id()),             \
 483                         PARAMS(void *__data, proto))
 484
 485 #define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)          \
 486         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
 487                         cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
 488                         PARAMS(void *__data, proto))
 489
 490 #define DECLARE_TRACE_EVENT_SYSCALL(name, proto, args)                  \
 491         __DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args),      \
 492                                 PARAMS(void *__data, proto))
 493
 494 #define TRACE_EVENT_FLAGS(event, flag)
 495
 496 #define TRACE_EVENT_PERF_PERM(event, expr...)
 497
 498 #endif /* DECLARE_TRACE */
 499
 500 #ifndef TRACE_EVENT
 501 /*
 502  * For use with the TRACE_EVENT macro:
 503  *
 504  * We define a tracepoint, its arguments, its printk format
 505  * and its 'fast binary record' layout.
 506  *
 507  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 508  * 'subsystem_event' notation is fine.
 509  *
 510  * Think about this whole construct as the
 511  * 'trace_sched_switch() function' from now on.
 512  *
 513  *
 514  *  TRACE_EVENT(sched_switch,
 515  *
 516  *      *
 517  *      * A function has a regular function arguments
 518  *      * prototype, declare it via TP_PROTO():
 519  *      *
 520  *
 521  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 522  *               struct task_struct *next),
 523  *
 524  *      *
 525  *      * Define the call signature of the 'function'.
 526  *      * (Design sidenote: we use this instead of a
 527  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 528  *      *
 529  *
 530  *      TP_ARGS(rq, prev, next),
 531  *
 532  *      *
 533  *      * Fast binary tracing: define the trace record via
 534  *      * TP_STRUCT__entry(). You can think about it like a
 535  *      * regular C structure local variable definition.
 536  *      *
 537  *      * This is how the trace record is structured and will
 538  *      * be saved into the ring buffer. These are the fields
 539  *      * that will be exposed to user-space in
 540  *      * /sys/kernel/tracing/events/<*>/format.
 541  *      *
 542  *      * The declared 'local variable' is called '__entry'
 543  *      *
 544  *      * __field(pid_t, prev_pid) is equivalent to a standard declaration:
 545  *      *
 546  *      *       pid_t   prev_pid;
 547  *      *
 548  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 549  *      *
 550  *      *       char    prev_comm[TASK_COMM_LEN];
 551  *      *
 552  *
 553  *      TP_STRUCT__entry(
 554  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 555  *              __field(        pid_t,  prev_pid                        )
 556  *              __field(        int,    prev_prio                       )
 557  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 558  *              __field(        pid_t,  next_pid                        )
 559  *              __field(        int,    next_prio                       )
 560  *      ),
 561  *
 562  *      *
 563  *      * Assign the entry into the trace record, by embedding
 564  *      * a full C statement block into TP_fast_assign(). You
 565  *      * can refer to the trace record as '__entry' -
 566  *      * otherwise you can put arbitrary C code in here.
 567  *      *
 568  *      * Note: this C code will execute every time a trace event
 569  *      * happens, on an active tracepoint.
 570  *      *
 571  *
 572  *      TP_fast_assign(
 573  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 574  *              __entry->prev_pid       = prev->pid;
 575  *              __entry->prev_prio      = prev->prio;
 576  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 577  *              __entry->next_pid       = next->pid;
 578  *              __entry->next_prio      = next->prio;
 579  *      ),
 580  *
 581  *      *
 582  *      * Formatted output of a trace record via TP_printk().
 583  *      * This is how the tracepoint will appear under ftrace
 584  *      * plugins that make use of this tracepoint.
 585  *      *
 586  *      * (raw-binary tracing wont actually perform this step.)
 587  *      *
 588  *
 589  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 590  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 591  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 592  *
 593  * );
 594  *
 595  * This macro construct is thus used for the regular printk format
 596  * tracing setup, it is used to construct a function pointer based
 597  * tracepoint callback (this is used by programmatic plugins and
 598  * can also by used by generic instrumentation like SystemTap), and
 599  * it is also used to expose a structured trace record in
 600  * /sys/kernel/tracing/events/.
 601  *
 602  * A set of (un)registration functions can be passed to the variant
 603  * TRACE_EVENT_FN to perform any (un)registration work.
 604  */
 605
 606 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 607 #define DEFINE_EVENT(template, name, proto, args)               \
 608         DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 609 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
 610         DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 611 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 612         DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 613 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 614                                args, cond)                      \
 615         DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),      \
 616                                 PARAMS(args), PARAMS(cond))
 617
 618 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 619         DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 620 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 621                 assign, print, reg, unreg)                      \
 622         DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 623 #define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,    \
 624                 assign, print, reg, unreg)                      \
 625         DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),      \
 626                         PARAMS(args), PARAMS(cond))
 627 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 628                               struct, assign, print)            \
 629         DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),      \
 630                                 PARAMS(args), PARAMS(cond))
 631 #define TRACE_EVENT_SYSCALL(name, proto, args, struct, assign,  \
 632                             print, reg, unreg)                  \
 633         DECLARE_TRACE_EVENT_SYSCALL(name, PARAMS(proto), PARAMS(args))
 634
 635 #define TRACE_EVENT_FLAGS(event, flag)
 636
 637 #define TRACE_EVENT_PERF_PERM(event, expr...)
 638
 639 #define DECLARE_EVENT_NOP(name, proto, args)                            \
 640         static inline void trace_##name(proto)                          \
 641         { }                                                             \
 642         static inline bool trace_##name##_enabled(void)                 \
 643         {                                                               \
 644                 return false;                                           \
 645         }
 646
 647 #define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)       \
 648         DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
 649
 650 #define DECLARE_EVENT_CLASS_NOP(name, proto, args, tstruct, assign, print)
 651 #define DEFINE_EVENT_NOP(template, name, proto, args)                   \
 652         DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
 653
 654 #endif /* ifdef TRACE_EVENT (see note above) */