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