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