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