LXR linux/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/cpumask.h>
  20#include <linux/rcupdate.h>
  21#include <linux/tracepoint-defs.h>
  22
  23struct module;
  24struct tracepoint;
  25struct notifier_block;
  26
  27struct trace_eval_map {
  28        const char              *system;
  29        const char              *eval_string;
  30        unsigned long           eval_value;
  31};
  32
  33#define TRACEPOINT_DEFAULT_PRIO 10
  34
  35extern struct srcu_struct tracepoint_srcu;
  36
  37extern int
  38tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
  39extern int
  40tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
  41                               int prio);
  42extern int
  43tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
  44extern void
  45for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
  46                void *priv);
  47
  48#ifdef CONFIG_MODULES
  49struct tp_module {
  50        struct list_head list;
  51        struct module *mod;
  52};
  53
  54bool trace_module_has_bad_taint(struct module *mod);
  55extern int register_tracepoint_module_notifier(struct notifier_block *nb);
  56extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
  57#else
  58static inline bool trace_module_has_bad_taint(struct module *mod)
  59{
  60        return false;
  61}
  62static inline
  63int register_tracepoint_module_notifier(struct notifier_block *nb)
  64{
  65        return 0;
  66}
  67static inline
  68int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  69{
  70        return 0;
  71}
  72#endif /* CONFIG_MODULES */
  73
  74/*
  75 * tracepoint_synchronize_unregister must be called between the last tracepoint
  76 * probe unregistration and the end of module exit to make sure there is no
  77 * caller executing a probe when it is freed.
  78 */
  79#ifdef CONFIG_TRACEPOINTS
  80static inline void tracepoint_synchronize_unregister(void)
  81{
  82        synchronize_srcu(&tracepoint_srcu);
  83        synchronize_rcu();
  84}
  85#else
  86static inline void tracepoint_synchronize_unregister(void)
  87{ }
  88#endif
  89
  90#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
  91extern int syscall_regfunc(void);
  92extern void syscall_unregfunc(void);
  93#endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
  94
  95#define PARAMS(args...) args
  96
  97#define TRACE_DEFINE_ENUM(x)
  98#define TRACE_DEFINE_SIZEOF(x)
  99
 100#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 101static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 102{
 103        return offset_to_ptr(p);
 104}
 105
 106#define __TRACEPOINT_ENTRY(name)                                        \
 107        asm("   .section \"__tracepoints_ptrs\", \"a\"          \n"     \
 108            "   .balign 4                                       \n"     \
 109            "   .long   __tracepoint_" #name " - .              \n"     \
 110            "   .previous                                       \n")
 111#else
 112static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 113{
 114        return *p;
 115}
 116
 117#define __TRACEPOINT_ENTRY(name)                                         \
 118        static tracepoint_ptr_t __tracepoint_ptr_##name __used           \
 119        __attribute__((section("__tracepoints_ptrs"))) =                 \
 120                &__tracepoint_##name
 121#endif
 122
 123#endif /* _LINUX_TRACEPOINT_H */
 124
 125/*
 126 * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
 127 *  file ifdef protection.
 128 *  This is due to the way trace events work. If a file includes two
 129 *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 130 *  will override the TRACE_EVENT and break the second include.
 131 */
 132
 133#ifndef DECLARE_TRACE
 134
 135#define TP_PROTO(args...)       args
 136#define TP_ARGS(args...)        args
 137#define TP_CONDITION(args...)   args
 138
 139/*
 140 * Individual subsystem my have a separate configuration to
 141 * enable their tracepoints. By default, this file will create
 142 * the tracepoints if CONFIG_TRACEPOINT is defined. If a subsystem
 143 * wants to be able to disable its tracepoints from being created
 144 * it can define NOTRACE before including the tracepoint headers.
 145 */
 146#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
 147#define TRACEPOINTS_ENABLED
 148#endif
 149
 150#ifdef TRACEPOINTS_ENABLED
 151
 152/*
 153 * it_func[0] is never NULL because there is at least one element in the array
 154 * when the array itself is non NULL.
 155 *
 156 * Note, the proto and args passed in includes "__data" as the first parameter.
 157 * The reason for this is to handle the "void" prototype. If a tracepoint
 158 * has a "void" prototype, then it is invalid to declare a function
 159 * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 160 * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 161 */
 162#define __DO_TRACE(tp, proto, args, cond, rcuidle)                      \
 163        do {                                                            \
 164                struct tracepoint_func *it_func_ptr;                    \
 165                void *it_func;                                          \
 166                void *__data;                                           \
 167                int __maybe_unused __idx = 0;                           \
 168                                                                        \
 169                if (!(cond))                                            \
 170                        return;                                         \
 171                                                                        \
 172                /* srcu can't be used from NMI */                       \
 173                WARN_ON_ONCE(rcuidle && in_nmi());                      \
 174                                                                        \
 175                /* keep srcu and sched-rcu usage consistent */          \
 176                preempt_disable_notrace();                              \
 177                                                                        \
 178                /*                                                      \
 179                 * For rcuidle callers, use srcu since sched-rcu        \
 180                 * doesn't work from the idle path.                     \
 181                 */                                                     \
 182                if (rcuidle) {                                          \
 183                        __idx = srcu_read_lock_notrace(&tracepoint_srcu);\
 184                        rcu_irq_enter_irqson();                         \
 185                }                                                       \
 186                                                                        \
 187                it_func_ptr = rcu_dereference_raw((tp)->funcs);         \
 188                                                                        \
 189                if (it_func_ptr) {                                      \
 190                        do {                                            \
 191                                it_func = (it_func_ptr)->func;          \
 192                                __data = (it_func_ptr)->data;           \
 193                                ((void(*)(proto))(it_func))(args);      \
 194                        } while ((++it_func_ptr)->func);                \
 195                }                                                       \
 196                                                                        \
 197                if (rcuidle) {                                          \
 198                        rcu_irq_exit_irqson();                          \
 199                        srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
 200                }                                                       \
 201                                                                        \
 202                preempt_enable_notrace();                               \
 203        } while (0)
 204
 205#ifndef MODULE
 206#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
 207        static inline void trace_##name##_rcuidle(proto)                \
 208        {                                                               \
 209                if (static_key_false(&__tracepoint_##name.key))         \
 210                        __DO_TRACE(&__tracepoint_##name,                \
 211                                TP_PROTO(data_proto),                   \
 212                                TP_ARGS(data_args),                     \
 213                                TP_CONDITION(cond), 1);                 \
 214        }
 215#else
 216#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 217#endif
 218
 219/*
 220 * Make sure the alignment of the structure in the __tracepoints section will
 221 * not add unwanted padding between the beginning of the section and the
 222 * structure. Force alignment to the same alignment as the section start.
 223 *
 224 * When lockdep is enabled, we make sure to always do the RCU portions of
 225 * the tracepoint code, regardless of whether tracing is on. However,
 226 * don't check if the condition is false, due to interaction with idle
 227 * instrumentation. This lets us find RCU issues triggered with tracepoints
 228 * even when this tracepoint is off. This code has no purpose other than
 229 * poking RCU a bit.
 230 */
 231#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 232        extern struct tracepoint __tracepoint_##name;                   \
 233        static inline void trace_##name(proto)                          \
 234        {                                                               \
 235                if (static_key_false(&__tracepoint_##name.key))         \
 236                        __DO_TRACE(&__tracepoint_##name,                \
 237                                TP_PROTO(data_proto),                   \
 238                                TP_ARGS(data_args),                     \
 239                                TP_CONDITION(cond), 0);                 \
 240                if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {             \
 241                        rcu_read_lock_sched_notrace();                  \
 242                        rcu_dereference_sched(__tracepoint_##name.funcs);\
 243                        rcu_read_unlock_sched_notrace();                \
 244                }                                                       \
 245        }                                                               \
 246        __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 247                PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 248        static inline int                                               \
 249        register_trace_##name(void (*probe)(data_proto), void *data)    \
 250        {                                                               \
 251                return tracepoint_probe_register(&__tracepoint_##name,  \
 252                                                (void *)probe, data);   \
 253        }                                                               \
 254        static inline int                                               \
 255        register_trace_prio_##name(void (*probe)(data_proto), void *data,\
 256                                   int prio)                            \
 257        {                                                               \
 258                return tracepoint_probe_register_prio(&__tracepoint_##name, \
 259                                              (void *)probe, data, prio); \
 260        }                                                               \
 261        static inline int                                               \
 262        unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 263        {                                                               \
 264                return tracepoint_probe_unregister(&__tracepoint_##name,\
 265                                                (void *)probe, data);   \
 266        }                                                               \
 267        static inline void                                              \
 268        check_trace_callback_type_##name(void (*cb)(data_proto))        \
 269        {                                                               \
 270        }                                                               \
 271        static inline bool                                              \
 272        trace_##name##_enabled(void)                                    \
 273        {                                                               \
 274                return static_key_false(&__tracepoint_##name.key);      \
 275        }
 276
 277/*
 278 * We have no guarantee that gcc and the linker won't up-align the tracepoint
 279 * structures, so we create an array of pointers that will be used for iteration
 280 * on the tracepoints.
 281 */
 282#define DEFINE_TRACE_FN(name, reg, unreg)                                \
 283        static const char __tpstrtab_##name[]                            \
 284        __attribute__((section("__tracepoints_strings"))) = #name;       \
 285        struct tracepoint __tracepoint_##name                            \
 286        __attribute__((section("__tracepoints"), used)) =                \
 287                { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 288        __TRACEPOINT_ENTRY(name);
 289
 290#define DEFINE_TRACE(name)                                              \
 291        DEFINE_TRACE_FN(name, NULL, NULL);
 292
 293#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 294        EXPORT_SYMBOL_GPL(__tracepoint_##name)
 295#define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 296        EXPORT_SYMBOL(__tracepoint_##name)
 297
 298#else /* !TRACEPOINTS_ENABLED */
 299#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 300        static inline void trace_##name(proto)                          \
 301        { }                                                             \
 302        static inline void trace_##name##_rcuidle(proto)                \
 303        { }                                                             \
 304        static inline int                                               \
 305        register_trace_##name(void (*probe)(data_proto),                \
 306                              void *data)                               \
 307        {                                                               \
 308                return -ENOSYS;                                         \
 309        }                                                               \
 310        static inline int                                               \
 311        unregister_trace_##name(void (*probe)(data_proto),              \
 312                                void *data)                             \
 313        {                                                               \
 314                return -ENOSYS;                                         \
 315        }                                                               \
 316        static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 317        {                                                               \
 318        }                                                               \
 319        static inline bool                                              \
 320        trace_##name##_enabled(void)                                    \
 321        {                                                               \
 322                return false;                                           \
 323        }
 324
 325#define DEFINE_TRACE_FN(name, reg, unreg)
 326#define DEFINE_TRACE(name)
 327#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 328#define EXPORT_TRACEPOINT_SYMBOL(name)
 329
 330#endif /* TRACEPOINTS_ENABLED */
 331
 332#ifdef CONFIG_TRACING
 333/**
 334 * tracepoint_string - register constant persistent string to trace system
 335 * @str - a constant persistent string that will be referenced in tracepoints
 336 *
 337 * If constant strings are being used in tracepoints, it is faster and
 338 * more efficient to just save the pointer to the string and reference
 339 * that with a printf "%s" instead of saving the string in the ring buffer
 340 * and wasting space and time.
 341 *
 342 * The problem with the above approach is that userspace tools that read
 343 * the binary output of the trace buffers do not have access to the string.
 344 * Instead they just show the address of the string which is not very
 345 * useful to users.
 346 *
 347 * With tracepoint_string(), the string will be registered to the tracing
 348 * system and exported to userspace via the debugfs/tracing/printk_formats
 349 * file that maps the string address to the string text. This way userspace
 350 * tools that read the binary buffers have a way to map the pointers to
 351 * the ASCII strings they represent.
 352 *
 353 * The @str used must be a constant string and persistent as it would not
 354 * make sense to show a string that no longer exists. But it is still fine
 355 * to be used with modules, because when modules are unloaded, if they
 356 * had tracepoints, the ring buffers are cleared too. As long as the string
 357 * does not change during the life of the module, it is fine to use
 358 * tracepoint_string() within a module.
 359 */
 360#define tracepoint_string(str)                                          \
 361        ({                                                              \
 362                static const char *___tp_str __tracepoint_string = str; \
 363                ___tp_str;                                              \
 364        })
 365#define __tracepoint_string     __attribute__((section("__tracepoint_str")))
 366#else
 367/*
 368 * tracepoint_string() is used to save the string address for userspace
 369 * tracing tools. When tracing isn't configured, there's no need to save
 370 * anything.
 371 */
 372# define tracepoint_string(str) str
 373# define __tracepoint_string
 374#endif
 375
 376/*
 377 * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 378 * (void). "void" is a special value in a function prototype and can
 379 * not be combined with other arguments. Since the DECLARE_TRACE()
 380 * macro adds a data element at the beginning of the prototype,
 381 * we need a way to differentiate "(void *data, proto)" from
 382 * "(void *data, void)". The second prototype is invalid.
 383 *
 384 * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 385 * and "void *__data" as the callback prototype.
 386 *
 387 * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 388 * "void *__data, proto" as the callback prototype.
 389 */
 390#define DECLARE_TRACE_NOARGS(name)                                      \
 391        __DECLARE_TRACE(name, void, ,                                   \
 392                        cpu_online(raw_smp_processor_id()),             \
 393                        void *__data, __data)
 394
 395#define DECLARE_TRACE(name, proto, args)                                \
 396        __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
 397                        cpu_online(raw_smp_processor_id()),             \
 398                        PARAMS(void *__data, proto),                    \
 399                        PARAMS(__data, args))
 400
 401#define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 402        __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),              \
 403                        cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
 404                        PARAMS(void *__data, proto),                    \
 405                        PARAMS(__data, args))
 406
 407#define TRACE_EVENT_FLAGS(event, flag)
 408
 409#define TRACE_EVENT_PERF_PERM(event, expr...)
 410
 411#endif /* DECLARE_TRACE */
 412
 413#ifndef TRACE_EVENT
 414/*
 415 * For use with the TRACE_EVENT macro:
 416 *
 417 * We define a tracepoint, its arguments, its printk format
 418 * and its 'fast binary record' layout.
 419 *
 420 * Firstly, name your tracepoint via TRACE_EVENT(name : the
 421 * 'subsystem_event' notation is fine.
 422 *
 423 * Think about this whole construct as the
 424 * 'trace_sched_switch() function' from now on.
 425 *
 426 *
 427 *  TRACE_EVENT(sched_switch,
 428 *
 429 *      *
 430 *      * A function has a regular function arguments
 431 *      * prototype, declare it via TP_PROTO():
 432 *      *
 433 *
 434 *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 435 *               struct task_struct *next),
 436 *
 437 *      *
 438 *      * Define the call signature of the 'function'.
 439 *      * (Design sidenote: we use this instead of a
 440 *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 441 *      *
 442 *
 443 *      TP_ARGS(rq, prev, next),
 444 *
 445 *      *
 446 *      * Fast binary tracing: define the trace record via
 447 *      * TP_STRUCT__entry(). You can think about it like a
 448 *      * regular C structure local variable definition.
 449 *      *
 450 *      * This is how the trace record is structured and will
 451 *      * be saved into the ring buffer. These are the fields
 452 *      * that will be exposed to user-space in
 453 *      * /sys/kernel/debug/tracing/events/<*>/format.
 454 *      *
 455 *      * The declared 'local variable' is called '__entry'
 456 *      *
 457 *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 458 *      *
 459 *      *       pid_t   prev_pid;
 460 *      *
 461 *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 462 *      *
 463 *      *       char    prev_comm[TASK_COMM_LEN];
 464 *      *
 465 *
 466 *      TP_STRUCT__entry(
 467 *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 468 *              __field(        pid_t,  prev_pid                        )
 469 *              __field(        int,    prev_prio                       )
 470 *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 471 *              __field(        pid_t,  next_pid                        )
 472 *              __field(        int,    next_prio                       )
 473 *      ),
 474 *
 475 *      *
 476 *      * Assign the entry into the trace record, by embedding
 477 *      * a full C statement block into TP_fast_assign(). You
 478 *      * can refer to the trace record as '__entry' -
 479 *      * otherwise you can put arbitrary C code in here.
 480 *      *
 481 *      * Note: this C code will execute every time a trace event
 482 *      * happens, on an active tracepoint.
 483 *      *
 484 *
 485 *      TP_fast_assign(
 486 *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 487 *              __entry->prev_pid       = prev->pid;
 488 *              __entry->prev_prio      = prev->prio;
 489 *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 490 *              __entry->next_pid       = next->pid;
 491 *              __entry->next_prio      = next->prio;
 492 *      ),
 493 *
 494 *      *
 495 *      * Formatted output of a trace record via TP_printk().
 496 *      * This is how the tracepoint will appear under ftrace
 497 *      * plugins that make use of this tracepoint.
 498 *      *
 499 *      * (raw-binary tracing wont actually perform this step.)
 500 *      *
 501 *
 502 *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 503 *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 504 *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 505 *
 506 * );
 507 *
 508 * This macro construct is thus used for the regular printk format
 509 * tracing setup, it is used to construct a function pointer based
 510 * tracepoint callback (this is used by programmatic plugins and
 511 * can also by used by generic instrumentation like SystemTap), and
 512 * it is also used to expose a structured trace record in
 513 * /sys/kernel/debug/tracing/events/.
 514 *
 515 * A set of (un)registration functions can be passed to the variant
 516 * TRACE_EVENT_FN to perform any (un)registration work.
 517 */
 518
 519#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 520#define DEFINE_EVENT(template, name, proto, args)               \
 521        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 522#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
 523        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 524#define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 525        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 526#define DEFINE_EVENT_CONDITION(template, name, proto,           \
 527                               args, cond)                      \
 528        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 529                                PARAMS(args), PARAMS(cond))
 530
 531#define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 532        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 533#define TRACE_EVENT_FN(name, proto, args, struct,               \
 534                assign, print, reg, unreg)                      \
 535        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 536#define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,            \
 537                assign, print, reg, unreg)                      \
 538        DECLARE_TRACE_CONDITION(name, PARAMS(proto),    \
 539                        PARAMS(args), PARAMS(cond))
 540#define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 541                              struct, assign, print)            \
 542        DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 543                                PARAMS(args), PARAMS(cond))
 544
 545#define TRACE_EVENT_FLAGS(event, flag)
 546
 547#define TRACE_EVENT_PERF_PERM(event, expr...)
 548
 549#define DECLARE_EVENT_NOP(name, proto, args)                            \
 550        static inline void trace_##name(proto)                          \
 551        { }                                                             \
 552        static inline bool trace_##name##_enabled(void)                 \
 553        {                                                               \
 554                return false;                                           \
 555        }
 556
 557#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)       \
 558        DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
 559
 560#define DECLARE_EVENT_CLASS_NOP(name, proto, args, tstruct, assign, print)
 561#define DEFINE_EVENT_NOP(template, name, proto, args)                   \
 562        DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
 563
 564#endif /* ifdef TRACE_EVENT (see note above) */
 565