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