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