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  * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  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
  25 struct tracepoint_func {
  26         void *func;
  27         void *data;
  28 };
  29
  30 struct tracepoint {
  31         const char *name;               /* Tracepoint name */
  32         struct static_key key;
  33         void (*regfunc)(void);
  34         void (*unregfunc)(void);
  35         struct tracepoint_func __rcu *funcs;
  36 };
  37
  38 /*
  39  * Connect a probe to a tracepoint.
  40  * Internal API, should not be used directly.
  41  */
  42 extern int tracepoint_probe_register(const char *name, void *probe, void *data);
  43
  44 /*
  45  * Disconnect a probe from a tracepoint.
  46  * Internal API, should not be used directly.
  47  */
  48 extern int
  49 tracepoint_probe_unregister(const char *name, void *probe, void *data);
  50
  51 #ifdef CONFIG_MODULES
  52 struct tp_module {
  53         struct list_head list;
  54         unsigned int num_tracepoints;
  55         struct tracepoint * const *tracepoints_ptrs;
  56 };
  57 bool trace_module_has_bad_taint(struct module *mod);
  58 #else
  59 static inline bool trace_module_has_bad_taint(struct module *mod)
  60 {
  61         return false;
  62 }
  63 #endif /* CONFIG_MODULES */
  64
  65 /*
  66  * tracepoint_synchronize_unregister must be called between the last tracepoint
  67  * probe unregistration and the end of module exit to make sure there is no
  68  * caller executing a probe when it is freed.
  69  */
  70 static inline void tracepoint_synchronize_unregister(void)
  71 {
  72         synchronize_sched();
  73 }
  74
  75 #define PARAMS(args...) args
  76
  77 #endif /* _LINUX_TRACEPOINT_H */
  78
  79 /*
  80  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  81  *  file ifdef protection.
  82  *  This is due to the way trace events work. If a file includes two
  83  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
  84  *  will override the TRACE_EVENT and break the second include.
  85  */
  86
  87 #ifndef DECLARE_TRACE
  88
  89 #define TP_PROTO(args...)       args
  90 #define TP_ARGS(args...)        args
  91 #define TP_CONDITION(args...)   args
  92
  93 #ifdef CONFIG_TRACEPOINTS
  94
  95 /*
  96  * it_func[0] is never NULL because there is at least one element in the array
  97  * when the array itself is non NULL.
  98  *
  99  * Note, the proto and args passed in includes "__data" as the first parameter.
 100  * The reason for this is to handle the "void" prototype. If a tracepoint
 101  * has a "void" prototype, then it is invalid to declare a function
 102  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 103  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 104  */
 105 #define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
 106         do {                                                            \
 107                 struct tracepoint_func *it_func_ptr;                    \
 108                 void *it_func;                                          \
 109                 void *__data;                                           \
 110                                                                         \
 111                 if (!(cond))                                            \
 112                         return;                                         \
 113                 prercu;                                                 \
 114                 rcu_read_lock_sched_notrace();                          \
 115                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
 116                 if (it_func_ptr) {                                      \
 117                         do {                                            \
 118                                 it_func = (it_func_ptr)->func;          \
 119                                 __data = (it_func_ptr)->data;           \
 120                                 ((void(*)(proto))(it_func))(args);      \
 121                         } while ((++it_func_ptr)->func);                \
 122                 }                                                       \
 123                 rcu_read_unlock_sched_notrace();                        \
 124                 postrcu;                                                \
 125         } while (0)
 126
 127 #ifndef MODULE
 128 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)     \
 129         static inline void trace_##name##_rcuidle(proto)                \
 130         {                                                               \
 131                 if (static_key_false(&__tracepoint_##name.key))         \
 132                         __DO_TRACE(&__tracepoint_##name,                \
 133                                 TP_PROTO(data_proto),                   \
 134                                 TP_ARGS(data_args),                     \
 135                                 TP_CONDITION(cond),                     \
 136                                 rcu_irq_enter(),                        \
 137                                 rcu_irq_exit());                        \
 138         }
 139 #else
 140 #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
 141 #endif
 142
 143 /*
 144  * Make sure the alignment of the structure in the __tracepoints section will
 145  * not add unwanted padding between the beginning of the section and the
 146  * structure. Force alignment to the same alignment as the section start.
 147  */
 148 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 149         extern struct tracepoint __tracepoint_##name;                   \
 150         static inline void trace_##name(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         }                                                               \
 158         __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),          \
 159                 PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
 160         static inline int                                               \
 161         register_trace_##name(void (*probe)(data_proto), void *data)    \
 162         {                                                               \
 163                 return tracepoint_probe_register(#name, (void *)probe,  \
 164                                                  data);                 \
 165         }                                                               \
 166         static inline int                                               \
 167         unregister_trace_##name(void (*probe)(data_proto), void *data)  \
 168         {                                                               \
 169                 return tracepoint_probe_unregister(#name, (void *)probe, \
 170                                                    data);               \
 171         }                                                               \
 172         static inline void                                              \
 173         check_trace_callback_type_##name(void (*cb)(data_proto))        \
 174         {                                                               \
 175         }
 176
 177 /*
 178  * We have no guarantee that gcc and the linker won't up-align the tracepoint
 179  * structures, so we create an array of pointers that will be used for iteration
 180  * on the tracepoints.
 181  */
 182 #define DEFINE_TRACE_FN(name, reg, unreg)                                \
 183         static const char __tpstrtab_##name[]                            \
 184         __attribute__((section("__tracepoints_strings"))) = #name;       \
 185         struct tracepoint __tracepoint_##name                            \
 186         __attribute__((section("__tracepoints"))) =                      \
 187                 { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
 188         static struct tracepoint * const __tracepoint_ptr_##name __used  \
 189         __attribute__((section("__tracepoints_ptrs"))) =                 \
 190                 &__tracepoint_##name;
 191
 192 #define DEFINE_TRACE(name)                                              \
 193         DEFINE_TRACE_FN(name, NULL, NULL);
 194
 195 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 196         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 197 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 198         EXPORT_SYMBOL(__tracepoint_##name)
 199
 200 #else /* !CONFIG_TRACEPOINTS */
 201 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 202         static inline void trace_##name(proto)                          \
 203         { }                                                             \
 204         static inline void trace_##name##_rcuidle(proto)                \
 205         { }                                                             \
 206         static inline int                                               \
 207         register_trace_##name(void (*probe)(data_proto),                \
 208                               void *data)                               \
 209         {                                                               \
 210                 return -ENOSYS;                                         \
 211         }                                                               \
 212         static inline int                                               \
 213         unregister_trace_##name(void (*probe)(data_proto),              \
 214                                 void *data)                             \
 215         {                                                               \
 216                 return -ENOSYS;                                         \
 217         }                                                               \
 218         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
 219         {                                                               \
 220         }
 221
 222 #define DEFINE_TRACE_FN(name, reg, unreg)
 223 #define DEFINE_TRACE(name)
 224 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 225 #define EXPORT_TRACEPOINT_SYMBOL(name)
 226
 227 #endif /* CONFIG_TRACEPOINTS */
 228
 229 /*
 230  * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 231  * (void). "void" is a special value in a function prototype and can
 232  * not be combined with other arguments. Since the DECLARE_TRACE()
 233  * macro adds a data element at the beginning of the prototype,
 234  * we need a way to differentiate "(void *data, proto)" from
 235  * "(void *data, void)". The second prototype is invalid.
 236  *
 237  * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 238  * and "void *__data" as the callback prototype.
 239  *
 240  * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 241  * "void *__data, proto" as the callback prototype.
 242  */
 243 #define DECLARE_TRACE_NOARGS(name)                                      \
 244                 __DECLARE_TRACE(name, void, , 1, void *__data, __data)
 245
 246 #define DECLARE_TRACE(name, proto, args)                                \
 247                 __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
 248                                 PARAMS(void *__data, proto),            \
 249                                 PARAMS(__data, args))
 250
 251 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)                \
 252         __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
 253                         PARAMS(void *__data, proto),                    \
 254                         PARAMS(__data, args))
 255
 256 #define TRACE_EVENT_FLAGS(event, flag)
 257
 258 #define TRACE_EVENT_PERF_PERM(event, expr...)
 259
 260 #endif /* DECLARE_TRACE */
 261
 262 #ifndef TRACE_EVENT
 263 /*
 264  * For use with the TRACE_EVENT macro:
 265  *
 266  * We define a tracepoint, its arguments, its printk format
 267  * and its 'fast binary record' layout.
 268  *
 269  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 270  * 'subsystem_event' notation is fine.
 271  *
 272  * Think about this whole construct as the
 273  * 'trace_sched_switch() function' from now on.
 274  *
 275  *
 276  *  TRACE_EVENT(sched_switch,
 277  *
 278  *      *
 279  *      * A function has a regular function arguments
 280  *      * prototype, declare it via TP_PROTO():
 281  *      *
 282  *
 283  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 284  *               struct task_struct *next),
 285  *
 286  *      *
 287  *      * Define the call signature of the 'function'.
 288  *      * (Design sidenote: we use this instead of a
 289  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 290  *      *
 291  *
 292  *      TP_ARGS(rq, prev, next),
 293  *
 294  *      *
 295  *      * Fast binary tracing: define the trace record via
 296  *      * TP_STRUCT__entry(). You can think about it like a
 297  *      * regular C structure local variable definition.
 298  *      *
 299  *      * This is how the trace record is structured and will
 300  *      * be saved into the ring buffer. These are the fields
 301  *      * that will be exposed to user-space in
 302  *      * /sys/kernel/debug/tracing/events/<*>/format.
 303  *      *
 304  *      * The declared 'local variable' is called '__entry'
 305  *      *
 306  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 307  *      *
 308  *      *       pid_t   prev_pid;
 309  *      *
 310  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 311  *      *
 312  *      *       char    prev_comm[TASK_COMM_LEN];
 313  *      *
 314  *
 315  *      TP_STRUCT__entry(
 316  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 317  *              __field(        pid_t,  prev_pid                        )
 318  *              __field(        int,    prev_prio                       )
 319  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 320  *              __field(        pid_t,  next_pid                        )
 321  *              __field(        int,    next_prio                       )
 322  *      ),
 323  *
 324  *      *
 325  *      * Assign the entry into the trace record, by embedding
 326  *      * a full C statement block into TP_fast_assign(). You
 327  *      * can refer to the trace record as '__entry' -
 328  *      * otherwise you can put arbitrary C code in here.
 329  *      *
 330  *      * Note: this C code will execute every time a trace event
 331  *      * happens, on an active tracepoint.
 332  *      *
 333  *
 334  *      TP_fast_assign(
 335  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 336  *              __entry->prev_pid       = prev->pid;
 337  *              __entry->prev_prio      = prev->prio;
 338  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 339  *              __entry->next_pid       = next->pid;
 340  *              __entry->next_prio      = next->prio;
 341  *      ),
 342  *
 343  *      *
 344  *      * Formatted output of a trace record via TP_printk().
 345  *      * This is how the tracepoint will appear under ftrace
 346  *      * plugins that make use of this tracepoint.
 347  *      *
 348  *      * (raw-binary tracing wont actually perform this step.)
 349  *      *
 350  *
 351  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 352  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 353  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 354  *
 355  * );
 356  *
 357  * This macro construct is thus used for the regular printk format
 358  * tracing setup, it is used to construct a function pointer based
 359  * tracepoint callback (this is used by programmatic plugins and
 360  * can also by used by generic instrumentation like SystemTap), and
 361  * it is also used to expose a structured trace record in
 362  * /sys/kernel/debug/tracing/events/.
 363  *
 364  * A set of (un)registration functions can be passed to the variant
 365  * TRACE_EVENT_FN to perform any (un)registration work.
 366  */
 367
 368 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 369 #define DEFINE_EVENT(template, name, proto, args)               \
 370         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 371 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
 372         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 373 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 374         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 375 #define DEFINE_EVENT_CONDITION(template, name, proto,           \
 376                                args, cond)                      \
 377         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 378                                 PARAMS(args), PARAMS(cond))
 379
 380 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 381         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 382 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 383                 assign, print, reg, unreg)                      \
 384         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 385 #define TRACE_EVENT_CONDITION(name, proto, args, cond,          \
 386                               struct, assign, print)            \
 387         DECLARE_TRACE_CONDITION(name, PARAMS(proto),            \
 388                                 PARAMS(args), PARAMS(cond))
 389
 390 #define TRACE_EVENT_FLAGS(event, flag)
 391
 392 #define TRACE_EVENT_PERF_PERM(event, expr...)
 393
 394 #endif /* ifdef TRACE_EVENT (see note above) */