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 * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  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;
  24struct notifier_block;
  25
  26struct tracepoint_func {
  27        void *func;
  28        void *data;
  29};
  30
  31struct tracepoint {
  32        const char *name;               /* Tracepoint name */
  33        struct static_key key;
  34        void (*regfunc)(void);
  35        void (*unregfunc)(void);
  36        struct tracepoint_func __rcu *funcs;
  37};
  38
  39struct trace_enum_map {
  40        const char              *system;
  41        const char              *enum_string;
  42        unsigned long           enum_value;
  43};
  44
  45extern int
  46tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
  47extern int
  48tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
  49extern void
  50for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
  51                void *priv);
  52
  53#ifdef CONFIG_MODULES
  54struct tp_module {
  55        struct list_head list;
  56        struct module *mod;
  57};
  58
  59bool trace_module_has_bad_taint(struct module *mod);
  60extern int register_tracepoint_module_notifier(struct notifier_block *nb);
  61extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
  62#else
  63static inline bool trace_module_has_bad_taint(struct module *mod)
  64{
  65        return false;
  66}
  67static inline
  68int register_tracepoint_module_notifier(struct notifier_block *nb)
  69{
  70        return 0;
  71}
  72static inline
  73int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  74{
  75        return 0;
  76}
  77#endif /* CONFIG_MODULES */
  78
  79/*
  80 * tracepoint_synchronize_unregister must be called between the last tracepoint
  81 * probe unregistration and the end of module exit to make sure there is no
  82 * caller executing a probe when it is freed.
  83 */
  84static inline void tracepoint_synchronize_unregister(void)
  85{
  86        synchronize_sched();
  87}
  88
  89#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
  90extern void syscall_regfunc(void);
  91extern void syscall_unregfunc(void);
  92#endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
  93
  94#define PARAMS(args...) args
  95
  96#define TRACE_DEFINE_ENUM(x)
  97
  98#endif /* _LINUX_TRACEPOINT_H */
  99
 100/*
 101 * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
 102 *  file ifdef protection.
 103 *  This is due to the way trace events work. If a file includes two
 104 *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 105 *  will override the TRACE_EVENT and break the second include.
 106 */
 107
 108#ifndef DECLARE_TRACE
 109
 110#define TP_PROTO(args...)       args
 111#define TP_ARGS(args...)        args
 112#define TP_CONDITION(args...)   args
 113
 114#ifdef CONFIG_TRACEPOINTS
 115
 116/*
 117 * it_func[0] is never NULL because there is at least one element in the array
 118 * when the array itself is non NULL.
 119 *
 120 * Note, the proto and args passed in includes "__data" as the first parameter.
 121 * The reason for this is to handle the "void" prototype. If a tracepoint
 122 * has a "void" prototype, then it is invalid to declare a function
 123 * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 124 * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 125 */
 126#define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
 127        do {                                                            \
 128                struct tracepoint_func *it_func_ptr;                    \
 129                void *it_func;                                          \
 130                void *__data;                                           \
 131                                                                        \
 132                if (!(cond))                                            \
 133                        return;                                         \
 134                prercu;                                                 \
 135                rcu_read_lock_sched_notrace();                          \
 136                it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 137                if (it_func_ptr) {                                      \
 138                        do {                                            \
 139                                it_func = (it_func_ptr)->func;          \
 140                                __data = (it_func_ptr)->data;           \
 141                                ((void(*)(proto))(it_func))(args);      \
 142                        } while ((++it_func_ptr)->func);                \
 143                }                                                       \
 144                rcu_read_unlock_sched_notrace();                        \
 145                postrcu;                                                \
 146        } while (0)
 147
 148#ifndef MODULE
 149#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
 150        static inline void trace_##name##_rcuidle(proto)                \
 151        {                                                               \
 152                if (static_key_false(&__tracepoint_##name.key))         \
 153                        __DO_TRACE(&__tracepoint_##name,                \
 154                                TP_PROTO(data_proto),                   \
 155                                TP_ARGS(data_args),                     \
 156                                TP_CONDITION(cond),                     \
 157                                rcu_irq_enter(),                        \
 158                                rcu_irq_exit());                        \
 159        }
 160#else
 161#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 162#endif
 163
 164/*
 165 * Make sure the alignment of the structure in the __tracepoints section will
 166 * not add unwanted padding between the beginning of the section and the
 167 * structure. Force alignment to the same alignment as the section start.
 168 *
 169 * When lockdep is enabled, we make sure to always do the RCU portions of
 170 * the tracepoint code, regardless of whether tracing is on or we match the
 171 * condition.  This lets us find RCU issues triggered with tracepoints even
 172 * when this tracepoint is off.  This code has no purpose other than poking
 173 * RCU a bit.
 174 */
 175#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 176        extern struct tracepoint __tracepoint_##name;                   \
 177        static inline void trace_##name(proto)                          \
 178        {                                                               \
 179                if (static_key_false(&__tracepoint_##name.key))         \
 180                        __DO_TRACE(&__tracepoint_##name,                \
 181                                TP_PROTO(data_proto),                   \
 182                                TP_ARGS(data_args),                     \
 183                                TP_CONDITION(cond),,);                  \
 184                if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {             \
 185                        rcu_read_lock_sched_notrace();                  \
 186                        rcu_dereference_sched(__tracepoint_##name.funcs);\
 187                        rcu_read_unlock_sched_notrace();                \
 188                }                                                       \
 189        }                                                               \
 190        __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 191                PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 192        static inline int                                               \
 193        register_trace_##name(void (*probe)(data_proto), void *data)    \
 194        {                                                               \
 195                return tracepoint_probe_register(&__tracepoint_##name,  \
 196                                                (void *)probe, data);   \
 197        }                                                               \
 198        static inline int                                               \
 199        unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 200        {                                                               \
 201                return tracepoint_probe_unregister(&__tracepoint_##name,\
 202                                                (void *)probe, data);   \
 203        }                                                               \
 204        static inline void                                              \
 205        check_trace_callback_type_##name(void (*cb)(data_proto))        \
 206        {                                                               \
 207        }                                                               \
 208        static inline bool                                              \
 209        trace_##name##_enabled(void)                                    \
 210        {                                                               \
 211                return static_key_false(&__tracepoint_##name.key);      \
 212        }
 213
 214/*
 215 * We have no guarantee that gcc and the linker won't up-align the tracepoint
 216 * structures, so we create an array of pointers that will be used for iteration
 217 * on the tracepoints.
 218 */
 219#define DEFINE_TRACE_FN(name, reg, unreg)                                \
 220        static const char __tpstrtab_##name[]                            \
 221        __attribute__((section("__tracepoints_strings"))) = #name;       \
 222        struct tracepoint __tracepoint_##name                            \
 223        __attribute__((section("__tracepoints"))) =                      \
 224                { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 225        static struct tracepoint * const __tracepoint_ptr_##name __used  \
 226        __attribute__((section("__tracepoints_ptrs"))) =                 \
 227                &__tracepoint_##name;
 228
 229#define DEFINE_TRACE(name)                                              \
 230        DEFINE_TRACE_FN(name, NULL, NULL);
 231
 232#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 233        EXPORT_SYMBOL_GPL(__tracepoint_##name)
 234#define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 235        EXPORT_SYMBOL(__tracepoint_##name)
 236
 237#else /* !CONFIG_TRACEPOINTS */
 238#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 239        static inline void trace_##name(proto)                          \
 240        { }                                                             \
 241        static inline void trace_##name##_rcuidle(proto)                \
 242        { }                                                             \
 243        static inline int                                               \
 244        register_trace_##name(void (*probe)(data_proto),                \
 245                              void *data)                               \
 246        {                                                               \
 247                return -ENOSYS;                                         \
 248        }                                                               \
 249        static inline int                                               \
 250        unregister_trace_##name(void (*probe)(data_proto),              \
 251                                void *data)                             \
 252        {                                                               \
 253                return -ENOSYS;                                         \
 254        }                                                               \
 255        static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 256        {                                                               \
 257        }                                                               \
 258        static inline bool                                              \
 259        trace_##name##_enabled(void)                                    \
 260        {                                                               \
 261                return false;                                           \
 262        }
 263
 264#define DEFINE_TRACE_FN(name, reg, unreg)
 265#define DEFINE_TRACE(name)
 266#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 267#define EXPORT_TRACEPOINT_SYMBOL(name)
 268
 269#endif /* CONFIG_TRACEPOINTS */
 270
 271#ifdef CONFIG_TRACING
 272/**
 273 * tracepoint_string - register constant persistent string to trace system
 274 * @str - a constant persistent string that will be referenced in tracepoints
 275 *
 276 * If constant strings are being used in tracepoints, it is faster and
 277 * more efficient to just save the pointer to the string and reference
 278 * that with a printf "%s" instead of saving the string in the ring buffer
 279 * and wasting space and time.
 280 *
 281 * The problem with the above approach is that userspace tools that read
 282 * the binary output of the trace buffers do not have access to the string.
 283 * Instead they just show the address of the string which is not very
 284 * useful to users.
 285 *
 286 * With tracepoint_string(), the string will be registered to the tracing
 287 * system and exported to userspace via the debugfs/tracing/printk_formats
 288 * file that maps the string address to the string text. This way userspace
 289 * tools that read the binary buffers have a way to map the pointers to
 290 * the ASCII strings they represent.
 291 *
 292 * The @str used must be a constant string and persistent as it would not
 293 * make sense to show a string that no longer exists. But it is still fine
 294 * to be used with modules, because when modules are unloaded, if they
 295 * had tracepoints, the ring buffers are cleared too. As long as the string
 296 * does not change during the life of the module, it is fine to use
 297 * tracepoint_string() within a module.
 298 */
 299#define tracepoint_string(str)                                          \
 300        ({                                                              \
 301                static const char *___tp_str __tracepoint_string = str; \
 302                ___tp_str;                                              \
 303        })
 304#define __tracepoint_string     __attribute__((section("__tracepoint_str")))
 305#else
 306/*
 307 * tracepoint_string() is used to save the string address for userspace
 308 * tracing tools. When tracing isn't configured, there's no need to save
 309 * anything.
 310 */
 311# define tracepoint_string(str) str
 312# define __tracepoint_string
 313#endif
 314
 315/*
 316 * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 317 * (void). "void" is a special value in a function prototype and can
 318 * not be combined with other arguments. Since the DECLARE_TRACE()
 319 * macro adds a data element at the beginning of the prototype,
 320 * we need a way to differentiate "(void *data, proto)" from
 321 * "(void *data, void)". The second prototype is invalid.
 322 *
 323 * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 324 * and "void *__data" as the callback prototype.
 325 *
 326 * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 327 * "void *__data, proto" as the callback prototype.
 328 */
 329#define DECLARE_TRACE_NOARGS(name)                                      \
 330                __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 331
 332#define DECLARE_TRACE(name, proto, args)                                \
 333                __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 334                                PARAMS(void *__data, proto),            \
 335                                PARAMS(__data, args))
 336
 337#define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 338        __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 339                        PARAMS(void *__data, proto),                    \
 340                        PARAMS(__data, args))
 341
 342#define TRACE_EVENT_FLAGS(event, flag)
 343
 344#define TRACE_EVENT_PERF_PERM(event, expr...)
 345
 346#endif /* DECLARE_TRACE */
 347
 348#ifndef TRACE_EVENT
 349/*
 350 * For use with the TRACE_EVENT macro:
 351 *
 352 * We define a tracepoint, its arguments, its printk format
 353 * and its 'fast binary record' layout.
 354 *
 355 * Firstly, name your tracepoint via TRACE_EVENT(name : the
 356 * 'subsystem_event' notation is fine.
 357 *
 358 * Think about this whole construct as the
 359 * 'trace_sched_switch() function' from now on.
 360 *
 361 *
 362 *  TRACE_EVENT(sched_switch,
 363 *
 364 *      *
 365 *      * A function has a regular function arguments
 366 *      * prototype, declare it via TP_PROTO():
 367 *      *
 368 *
 369 *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 370 *               struct task_struct *next),
 371 *
 372 *      *
 373 *      * Define the call signature of the 'function'.
 374 *      * (Design sidenote: we use this instead of a
 375 *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 376 *      *
 377 *
 378 *      TP_ARGS(rq, prev, next),
 379 *
 380 *      *
 381 *      * Fast binary tracing: define the trace record via
 382 *      * TP_STRUCT__entry(). You can think about it like a
 383 *      * regular C structure local variable definition.
 384 *      *
 385 *      * This is how the trace record is structured and will
 386 *      * be saved into the ring buffer. These are the fields
 387 *      * that will be exposed to user-space in
 388 *      * /sys/kernel/debug/tracing/events/<*>/format.
 389 *      *
 390 *      * The declared 'local variable' is called '__entry'
 391 *      *
 392 *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 393 *      *
 394 *      *       pid_t   prev_pid;
 395 *      *
 396 *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 397 *      *
 398 *      *       char    prev_comm[TASK_COMM_LEN];
 399 *      *
 400 *
 401 *      TP_STRUCT__entry(
 402 *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 403 *              __field(        pid_t,  prev_pid                        )
 404 *              __field(        int,    prev_prio                       )
 405 *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 406 *              __field(        pid_t,  next_pid                        )
 407 *              __field(        int,    next_prio                       )
 408 *      ),
 409 *
 410 *      *
 411 *      * Assign the entry into the trace record, by embedding
 412 *      * a full C statement block into TP_fast_assign(). You
 413 *      * can refer to the trace record as '__entry' -
 414 *      * otherwise you can put arbitrary C code in here.
 415 *      *
 416 *      * Note: this C code will execute every time a trace event
 417 *      * happens, on an active tracepoint.
 418 *      *
 419 *
 420 *      TP_fast_assign(
 421 *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 422 *              __entry->prev_pid       = prev->pid;
 423 *              __entry->prev_prio      = prev->prio;
 424 *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 425 *              __entry->next_pid       = next->pid;
 426 *              __entry->next_prio      = next->prio;
 427 *      ),
 428 *
 429 *      *
 430 *      * Formatted output of a trace record via TP_printk().
 431 *      * This is how the tracepoint will appear under ftrace
 432 *      * plugins that make use of this tracepoint.
 433 *      *
 434 *      * (raw-binary tracing wont actually perform this step.)
 435 *      *
 436 *
 437 *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 438 *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 439 *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 440 *
 441 * );
 442 *
 443 * This macro construct is thus used for the regular printk format
 444 * tracing setup, it is used to construct a function pointer based
 445 * tracepoint callback (this is used by programmatic plugins and
 446 * can also by used by generic instrumentation like SystemTap), and
 447 * it is also used to expose a structured trace record in
 448 * /sys/kernel/debug/tracing/events/.
 449 *
 450 * A set of (un)registration functions can be passed to the variant
 451 * TRACE_EVENT_FN to perform any (un)registration work.
 452 */
 453
 454#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 455#define DEFINE_EVENT(template, name, proto, args)               \
 456        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 457#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
 458        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 459#define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 460        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 461#define DEFINE_EVENT_CONDITION(template, name, proto,           \
 462                               args, cond)                      \
 463        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 464                                PARAMS(args), PARAMS(cond))
 465
 466#define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 467        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 468#define TRACE_EVENT_FN(name, proto, args, struct,               \
 469                assign, print, reg, unreg)                      \
 470        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 471#define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 472                              struct, assign, print)            \
 473        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 474                                PARAMS(args), PARAMS(cond))
 475
 476#define TRACE_EVENT_FLAGS(event, flag)
 477
 478#define TRACE_EVENT_PERF_PERM(event, expr...)
 479
 480#endif /* ifdef TRACE_EVENT (see note above) */
 481