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/types.h>
  18 #include <linux/rcupdate.h>
  19
  20 struct module;
  21 struct tracepoint;
  22
  23 struct tracepoint {
  24         const char *name;               /* Tracepoint name */
  25         int state;                      /* State. */
  26         void (*regfunc)(void);
  27         void (*unregfunc)(void);
  28         void **funcs;
  29 } __attribute__((aligned(32)));         /*
  30                                          * Aligned on 32 bytes because it is
  31                                          * globally visible and gcc happily
  32                                          * align these on the structure size.
  33                                          * Keep in sync with vmlinux.lds.h.
  34                                          */
  35
  36 #ifndef DECLARE_TRACE
  37
  38 #define TP_PROTO(args...)       args
  39 #define TP_ARGS(args...)        args
  40
  41 #ifdef CONFIG_TRACEPOINTS
  42
  43 /*
  44  * it_func[0] is never NULL because there is at least one element in the array
  45  * when the array itself is non NULL.
  46  */
  47 #define __DO_TRACE(tp, proto, args)                                     \
  48         do {                                                            \
  49                 void **it_func;                                         \
  50                                                                         \
  51                 rcu_read_lock_sched_notrace();                          \
  52                 it_func = rcu_dereference((tp)->funcs);                 \
  53                 if (it_func) {                                          \
  54                         do {                                            \
  55                                 ((void(*)(proto))(*it_func))(args);     \
  56                         } while (*(++it_func));                         \
  57                 }                                                       \
  58                 rcu_read_unlock_sched_notrace();                        \
  59         } while (0)
  60
  61 /*
  62  * Make sure the alignment of the structure in the __tracepoints section will
  63  * not add unwanted padding between the beginning of the section and the
  64  * structure. Force alignment to the same alignment as the section start.
  65  */
  66 #define DECLARE_TRACE(name, proto, args)                                \
  67         extern struct tracepoint __tracepoint_##name;                   \
  68         static inline void trace_##name(proto)                          \
  69         {                                                               \
  70                 if (unlikely(__tracepoint_##name.state))                \
  71                         __DO_TRACE(&__tracepoint_##name,                \
  72                                 TP_PROTO(proto), TP_ARGS(args));        \
  73         }                                                               \
  74         static inline int register_trace_##name(void (*probe)(proto))   \
  75         {                                                               \
  76                 return tracepoint_probe_register(#name, (void *)probe); \
  77         }                                                               \
  78         static inline int unregister_trace_##name(void (*probe)(proto)) \
  79         {                                                               \
  80                 return tracepoint_probe_unregister(#name, (void *)probe);\
  81         }
  82
  83
  84 #define DEFINE_TRACE_FN(name, reg, unreg)                               \
  85         static const char __tpstrtab_##name[]                           \
  86         __attribute__((section("__tracepoints_strings"))) = #name;      \
  87         struct tracepoint __tracepoint_##name                           \
  88         __attribute__((section("__tracepoints"), aligned(32))) =        \
  89                 { __tpstrtab_##name, 0, reg, unreg, NULL }
  90
  91 #define DEFINE_TRACE(name)                                              \
  92         DEFINE_TRACE_FN(name, NULL, NULL);
  93
  94 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
  95         EXPORT_SYMBOL_GPL(__tracepoint_##name)
  96 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
  97         EXPORT_SYMBOL(__tracepoint_##name)
  98
  99 extern void tracepoint_update_probe_range(struct tracepoint *begin,
 100         struct tracepoint *end);
 101
 102 #else /* !CONFIG_TRACEPOINTS */
 103 #define DECLARE_TRACE(name, proto, args)                                \
 104         static inline void _do_trace_##name(struct tracepoint *tp, proto) \
 105         { }                                                             \
 106         static inline void trace_##name(proto)                          \
 107         { }                                                             \
 108         static inline int register_trace_##name(void (*probe)(proto))   \
 109         {                                                               \
 110                 return -ENOSYS;                                         \
 111         }                                                               \
 112         static inline int unregister_trace_##name(void (*probe)(proto)) \
 113         {                                                               \
 114                 return -ENOSYS;                                         \
 115         }
 116
 117 #define DEFINE_TRACE_FN(name, reg, unreg)
 118 #define DEFINE_TRACE(name)
 119 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 120 #define EXPORT_TRACEPOINT_SYMBOL(name)
 121
 122 static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 123         struct tracepoint *end)
 124 { }
 125 #endif /* CONFIG_TRACEPOINTS */
 126 #endif /* DECLARE_TRACE */
 127
 128 /*
 129  * Connect a probe to a tracepoint.
 130  * Internal API, should not be used directly.
 131  */
 132 extern int tracepoint_probe_register(const char *name, void *probe);
 133
 134 /*
 135  * Disconnect a probe from a tracepoint.
 136  * Internal API, should not be used directly.
 137  */
 138 extern int tracepoint_probe_unregister(const char *name, void *probe);
 139
 140 extern int tracepoint_probe_register_noupdate(const char *name, void *probe);
 141 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);
 142 extern void tracepoint_probe_update_all(void);
 143
 144 struct tracepoint_iter {
 145         struct module *module;
 146         struct tracepoint *tracepoint;
 147 };
 148
 149 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
 150 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
 151 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
 152 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
 153 extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
 154         struct tracepoint *begin, struct tracepoint *end);
 155
 156 /*
 157  * tracepoint_synchronize_unregister must be called between the last tracepoint
 158  * probe unregistration and the end of module exit to make sure there is no
 159  * caller executing a probe when it is freed.
 160  */
 161 static inline void tracepoint_synchronize_unregister(void)
 162 {
 163         synchronize_sched();
 164 }
 165
 166 #define PARAMS(args...) args
 167
 168 #endif /* _LINUX_TRACEPOINT_H */
 169
 170 /*
 171  * Note: we keep the TRACE_EVENT outside the include file ifdef protection.
 172  *  This is due to the way trace events work. If a file includes two
 173  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 174  *  will override the TRACE_EVENT and break the second include.
 175  */
 176
 177 #ifndef TRACE_EVENT
 178 /*
 179  * For use with the TRACE_EVENT macro:
 180  *
 181  * We define a tracepoint, its arguments, its printk format
 182  * and its 'fast binay record' layout.
 183  *
 184  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 185  * 'subsystem_event' notation is fine.
 186  *
 187  * Think about this whole construct as the
 188  * 'trace_sched_switch() function' from now on.
 189  *
 190  *
 191  *  TRACE_EVENT(sched_switch,
 192  *
 193  *      *
 194  *      * A function has a regular function arguments
 195  *      * prototype, declare it via TP_PROTO():
 196  *      *
 197  *
 198  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 199  *               struct task_struct *next),
 200  *
 201  *      *
 202  *      * Define the call signature of the 'function'.
 203  *      * (Design sidenote: we use this instead of a
 204  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 205  *      *
 206  *
 207  *      TP_ARGS(rq, prev, next),
 208  *
 209  *      *
 210  *      * Fast binary tracing: define the trace record via
 211  *      * TP_STRUCT__entry(). You can think about it like a
 212  *      * regular C structure local variable definition.
 213  *      *
 214  *      * This is how the trace record is structured and will
 215  *      * be saved into the ring buffer. These are the fields
 216  *      * that will be exposed to user-space in
 217  *      * /sys/kernel/debug/tracing/events/<*>/format.
 218  *      *
 219  *      * The declared 'local variable' is called '__entry'
 220  *      *
 221  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 222  *      *
 223  *      *       pid_t   prev_pid;
 224  *      *
 225  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 226  *      *
 227  *      *       char    prev_comm[TASK_COMM_LEN];
 228  *      *
 229  *
 230  *      TP_STRUCT__entry(
 231  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 232  *              __field(        pid_t,  prev_pid                        )
 233  *              __field(        int,    prev_prio                       )
 234  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 235  *              __field(        pid_t,  next_pid                        )
 236  *              __field(        int,    next_prio                       )
 237  *      ),
 238  *
 239  *      *
 240  *      * Assign the entry into the trace record, by embedding
 241  *      * a full C statement block into TP_fast_assign(). You
 242  *      * can refer to the trace record as '__entry' -
 243  *      * otherwise you can put arbitrary C code in here.
 244  *      *
 245  *      * Note: this C code will execute every time a trace event
 246  *      * happens, on an active tracepoint.
 247  *      *
 248  *
 249  *      TP_fast_assign(
 250  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 251  *              __entry->prev_pid       = prev->pid;
 252  *              __entry->prev_prio      = prev->prio;
 253  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 254  *              __entry->next_pid       = next->pid;
 255  *              __entry->next_prio      = next->prio;
 256  *      )
 257  *
 258  *      *
 259  *      * Formatted output of a trace record via TP_printk().
 260  *      * This is how the tracepoint will appear under ftrace
 261  *      * plugins that make use of this tracepoint.
 262  *      *
 263  *      * (raw-binary tracing wont actually perform this step.)
 264  *      *
 265  *
 266  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 267  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 268  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 269  *
 270  * );
 271  *
 272  * This macro construct is thus used for the regular printk format
 273  * tracing setup, it is used to construct a function pointer based
 274  * tracepoint callback (this is used by programmatic plugins and
 275  * can also by used by generic instrumentation like SystemTap), and
 276  * it is also used to expose a structured trace record in
 277  * /sys/kernel/debug/tracing/events/.
 278  *
 279  * A set of (un)registration functions can be passed to the variant
 280  * TRACE_EVENT_FN to perform any (un)registration work.
 281  */
 282
 283 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 284         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 285 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 286                 assign, print, reg, unreg)                      \
 287         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 288
 289 #endif /* ifdef TRACE_EVENT (see note above) */