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