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         unsigned int num_tracepoints;
  51         struct tracepoint * const *tracepoints_ptrs;
  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 static inline void tracepoint_synchronize_unregister(void)
  80 {
  81         synchronize_sched();
  82 }
  83
  84 #define PARAMS(args...) args
  85
  86 #endif /* _LINUX_TRACEPOINT_H */
  87
  88 /*
  89  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  90  *  file ifdef protection.
  91  *  This is due to the way trace events work. If a file includes two
  92  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
  93  *  will override the TRACE_EVENT and break the second include.
  94  */
  95
  96 #ifndef DECLARE_TRACE
  97
  98 #define TP_PROTO(args...)       args
  99 #define TP_ARGS(args...)        args
 100 #define TP_CONDITION(args...)   args
 101
 102 #ifdef CONFIG_TRACEPOINTS
 103
 104 /*
 105  * it_func[0] is never NULL because there is at least one element in the array
 106  * when the array itself is non NULL.
 107  *
 108  * Note, the proto and args passed in includes "__data" as the first parameter.
 109  * The reason for this is to handle the "void" prototype. If a tracepoint
 110  * has a "void" prototype, then it is invalid to declare a function
 111  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 112  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 113  */
 114 #define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
 115         do {                                                            \
 116                 struct tracepoint_func *it_func_ptr;                    \
 117                 void *it_func;                                          \
 118                 void *__data;                                           \
 119                                                                         \
 120                 if (!(cond))                                            \
 121                         return;                                         \
 122                 prercu;                                                 \
 123                 rcu_read_lock_sched_notrace();                          \
 124                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 125                 if (it_func_ptr) {                                      \
 126                         do {                                            \
 127                                 it_func = (it_func_ptr)->func;          \
 128                                 __data = (it_func_ptr)->data;           \
 129                                 ((void(*)(proto))(it_func))(args);      \
 130                         } while ((++it_func_ptr)->func);                \
 131                 }                                                       \
 132                 rcu_read_unlock_sched_notrace();                        \
 133                 postrcu;                                                \
 134         } while (0)
 135
 136 #ifndef MODULE
 137 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
 138         static inline void trace_##name##_rcuidle(proto)                \
 139         {                                                               \
 140                 if (static_key_false(&__tracepoint_##name.key))         \
 141                         __DO_TRACE(&__tracepoint_##name,                \
 142                                 TP_PROTO(data_proto),                   \
 143                                 TP_ARGS(data_args),                     \
 144                                 TP_CONDITION(cond),                     \
 145                                 rcu_irq_enter(),                        \
 146                                 rcu_irq_exit());                        \
 147         }
 148 #else
 149 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 150 #endif
 151
 152 /*
 153  * Make sure the alignment of the structure in the __tracepoints section will
 154  * not add unwanted padding between the beginning of the section and the
 155  * structure. Force alignment to the same alignment as the section start.
 156  */
 157 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 158         extern struct tracepoint __tracepoint_##name;                   \
 159         static inline void trace_##name(proto)                          \
 160         {                                                               \
 161                 if (static_key_false(&__tracepoint_##name.key))         \
 162                         __DO_TRACE(&__tracepoint_##name,                \
 163                                 TP_PROTO(data_proto),                   \
 164                                 TP_ARGS(data_args),                     \
 165                                 TP_CONDITION(cond),,);                  \
 166         }                                                               \
 167         __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 168                 PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 169         static inline int                                               \
 170         register_trace_##name(void (*probe)(data_proto), void *data)    \
 171         {                                                               \
 172                 return tracepoint_probe_register(&__tracepoint_##name,  \
 173                                                 (void *)probe, data);   \
 174         }                                                               \
 175         static inline int                                               \
 176         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 177         {                                                               \
 178                 return tracepoint_probe_unregister(&__tracepoint_##name,\
 179                                                 (void *)probe, data);   \
 180         }                                                               \
 181         static inline void                                              \
 182         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 183         {                                                               \
 184         }
 185
 186 /*
 187  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 188  * structures, so we create an array of pointers that will be used for iteration
 189  * on the tracepoints.
 190  */
 191 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 192         static const char __tpstrtab_##name[]                            \
 193         __attribute__((section("__tracepoints_strings"))) = #name;       \
 194         struct tracepoint __tracepoint_##name                            \
 195         __attribute__((section("__tracepoints"))) =                      \
 196                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 197         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 198         __attribute__((section("__tracepoints_ptrs"))) =                 \
 199                 &__tracepoint_##name;
 200
 201 #define DEFINE_TRACE(name)                                              \
 202         DEFINE_TRACE_FN(name, NULL, NULL);
 203
 204 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 205         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 206 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 207         EXPORT_SYMBOL(__tracepoint_##name)
 208
 209 #else /* !CONFIG_TRACEPOINTS */
 210 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 211         static inline void trace_##name(proto)                          \
 212         { }                                                             \
 213         static inline void trace_##name##_rcuidle(proto)                \
 214         { }                                                             \
 215         static inline int                                               \
 216         register_trace_##name(void (*probe)(data_proto),                \
 217                               void *data)                               \
 218         {                                                               \
 219                 return -ENOSYS;                                         \
 220         }                                                               \
 221         static inline int                                               \
 222         unregister_trace_##name(void (*probe)(data_proto),              \
 223                                 void *data)                             \
 224         {                                                               \
 225                 return -ENOSYS;                                         \
 226         }                                                               \
 227         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 228         {                                                               \
 229         }
 230
 231 #define DEFINE_TRACE_FN(name, reg, unreg)
 232 #define DEFINE_TRACE(name)
 233 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 234 #define EXPORT_TRACEPOINT_SYMBOL(name)
 235
 236 #endif /* CONFIG_TRACEPOINTS */
 237
 238 /*
 239  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 240  * (void). "void" is a special value in a function prototype and can
 241  * not be combined with other arguments. Since the DECLARE_TRACE()
 242  * macro adds a data element at the beginning of the prototype,
 243  * we need a way to differentiate "(void *data, proto)" from
 244  * "(void *data, void)". The second prototype is invalid.
 245  *
 246  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 247  * and "void *__data" as the callback prototype.
 248  *
 249  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 250  * "void *__data, proto" as the callback prototype.
 251  */
 252 #define DECLARE_TRACE_NOARGS(name)                                      \
 253                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 254
 255 #define DECLARE_TRACE(name, proto, args)                                \
 256                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 257                                 PARAMS(void *__data, proto),            \
 258                                 PARAMS(__data, args))
 259
 260 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 261         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 262                         PARAMS(void *__data, proto),                    \
 263                         PARAMS(__data, args))
 264
 265 #define TRACE_EVENT_FLAGS(event, flag)
 266
 267 #define TRACE_EVENT_PERF_PERM(event, expr...)
 268
 269 #endif /* DECLARE_TRACE */
 270
 271 #ifndef TRACE_EVENT
 272 /*
 273  * For use with the TRACE_EVENT macro:
 274  *
 275  * We define a tracepoint, its arguments, its printk format
 276  * and its 'fast binary record' layout.
 277  *
 278  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 279  * 'subsystem_event' notation is fine.
 280  *
 281  * Think about this whole construct as the
 282  * 'trace_sched_switch() function' from now on.
 283  *
 284  *
 285  *  TRACE_EVENT(sched_switch,
 286  *
 287  *      *
 288  *      * A function has a regular function arguments
 289  *      * prototype, declare it via TP_PROTO():
 290  *      *
 291  *
 292  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 293  *               struct task_struct *next),
 294  *
 295  *      *
 296  *      * Define the call signature of the 'function'.
 297  *      * (Design sidenote: we use this instead of a
 298  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 299  *      *
 300  *
 301  *      TP_ARGS(rq, prev, next),
 302  *
 303  *      *
 304  *      * Fast binary tracing: define the trace record via
 305  *      * TP_STRUCT__entry(). You can think about it like a
 306  *      * regular C structure local variable definition.
 307  *      *
 308  *      * This is how the trace record is structured and will
 309  *      * be saved into the ring buffer. These are the fields
 310  *      * that will be exposed to user-space in
 311  *      * /sys/kernel/debug/tracing/events/<*>/format.
 312  *      *
 313  *      * The declared 'local variable' is called '__entry'
 314  *      *
 315  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 316  *      *
 317  *      *       pid_t   prev_pid;
 318  *      *
 319  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 320  *      *
 321  *      *       char    prev_comm[TASK_COMM_LEN];
 322  *      *
 323  *
 324  *      TP_STRUCT__entry(
 325  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 326  *              __field(        pid_t,  prev_pid                        )
 327  *              __field(        int,    prev_prio                       )
 328  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 329  *              __field(        pid_t,  next_pid                        )
 330  *              __field(        int,    next_prio                       )
 331  *      ),
 332  *
 333  *      *
 334  *      * Assign the entry into the trace record, by embedding
 335  *      * a full C statement block into TP_fast_assign(). You
 336  *      * can refer to the trace record as '__entry' -
 337  *      * otherwise you can put arbitrary C code in here.
 338  *      *
 339  *      * Note: this C code will execute every time a trace event
 340  *      * happens, on an active tracepoint.
 341  *      *
 342  *
 343  *      TP_fast_assign(
 344  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 345  *              __entry->prev_pid       = prev->pid;
 346  *              __entry->prev_prio      = prev->prio;
 347  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 348  *              __entry->next_pid       = next->pid;
 349  *              __entry->next_prio      = next->prio;
 350  *      ),
 351  *
 352  *      *
 353  *      * Formatted output of a trace record via TP_printk().
 354  *      * This is how the tracepoint will appear under ftrace
 355  *      * plugins that make use of this tracepoint.
 356  *      *
 357  *      * (raw-binary tracing wont actually perform this step.)
 358  *      *
 359  *
 360  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 361  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 362  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 363  *
 364  * );
 365  *
 366  * This macro construct is thus used for the regular printk format
 367  * tracing setup, it is used to construct a function pointer based
 368  * tracepoint callback (this is used by programmatic plugins and
 369  * can also by used by generic instrumentation like SystemTap), and
 370  * it is also used to expose a structured trace record in
 371  * /sys/kernel/debug/tracing/events/.
 372  *
 373  * A set of (un)registration functions can be passed to the variant
 374  * TRACE_EVENT_FN to perform any (un)registration work.
 375  */
 376
 377 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 378 #define DEFINE_EVENT(template, name, proto, args)               \
 379         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 380 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
 381         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 382 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 383         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 384 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 385                                args, cond)                      \
 386         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 387                                 PARAMS(args), PARAMS(cond))
 388
 389 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 390         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 391 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 392                 assign, print, reg, unreg)                      \
 393         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 394 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 395                               struct, assign, print)            \
 396         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 397                                 PARAMS(args), PARAMS(cond))
 398
 399 #define TRACE_EVENT_FLAGS(event, flag)
 400
 401 #define TRACE_EVENT_PERF_PERM(event, expr...)
 402
 403 #endif /* ifdef TRACE_EVENT (see note above) */