include/linux/tracepoint.h

   1 #ifndef _LINUX_TRACEPOINT_H
   2 #define _LINUX_TRACEPOINT_H
   3
   4 /*
   5  * Kernel Tracepoint API.
   6  *
   7  * See Documentation/tracepoint.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 **funcs;
  27 } __attribute__((aligned(32)));         /*
  28                                          * Aligned on 32 bytes because it is
  29                                          * globally visible and gcc happily
  30                                          * align these on the structure size.
  31                                          * Keep in sync with vmlinux.lds.h.
  32                                          */
  33
  34 #ifndef DECLARE_TRACE
  35
  36 #define TP_PROTO(args...)       args
  37 #define TP_ARGS(args...)                args
  38
  39 #ifdef CONFIG_TRACEPOINTS
  40
  41 /*
  42  * it_func[0] is never NULL because there is at least one element in the array
  43  * when the array itself is non NULL.
  44  */
  45 #define __DO_TRACE(tp, proto, args)                                     \
  46         do {                                                            \
  47                 void **it_func;                                         \
  48                                                                         \
  49                 rcu_read_lock_sched_notrace();                          \
  50                 it_func = rcu_dereference((tp)->funcs);                 \
  51                 if (it_func) {                                          \
  52                         do {                                            \
  53                                 ((void(*)(proto))(*it_func))(args);     \
  54                         } while (*(++it_func));                         \
  55                 }                                                       \
  56                 rcu_read_unlock_sched_notrace();                        \
  57         } while (0)
  58
  59 /*
  60  * Make sure the alignment of the structure in the __tracepoints section will
  61  * not add unwanted padding between the beginning of the section and the
  62  * structure. Force alignment to the same alignment as the section start.
  63  */
  64 #define DECLARE_TRACE(name, proto, args)                                \
  65         extern struct tracepoint __tracepoint_##name;                   \
  66         static inline void trace_##name(proto)                          \
  67         {                                                               \
  68                 if (unlikely(__tracepoint_##name.state))                \
  69                         __DO_TRACE(&__tracepoint_##name,                \
  70                                 TP_PROTO(proto), TP_ARGS(args));        \
  71         }                                                               \
  72         static inline int register_trace_##name(void (*probe)(proto))   \
  73         {                                                               \
  74                 return tracepoint_probe_register(#name, (void *)probe); \
  75         }                                                               \
  76         static inline int unregister_trace_##name(void (*probe)(proto)) \
  77         {                                                               \
  78                 return tracepoint_probe_unregister(#name, (void *)probe);\
  79         }
  80
  81 #define DEFINE_TRACE(name)                                              \
  82         static const char __tpstrtab_##name[]                           \
  83         __attribute__((section("__tracepoints_strings"))) = #name;      \
  84         struct tracepoint __tracepoint_##name                           \
  85         __attribute__((section("__tracepoints"), aligned(32))) =        \
  86                 { __tpstrtab_##name, 0, NULL }
  87
  88 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
  89         EXPORT_SYMBOL_GPL(__tracepoint_##name)
  90 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
  91         EXPORT_SYMBOL(__tracepoint_##name)
  92
  93 extern void tracepoint_update_probe_range(struct tracepoint *begin,
  94         struct tracepoint *end);
  95
  96 #else /* !CONFIG_TRACEPOINTS */
  97 #define DECLARE_TRACE(name, proto, args)                                \
  98         static inline void _do_trace_##name(struct tracepoint *tp, proto) \
  99         { }                                                             \
 100         static inline void trace_##name(proto)                          \
 101         { }                                                             \
 102         static inline int register_trace_##name(void (*probe)(proto))   \
 103         {                                                               \
 104                 return -ENOSYS;                                         \
 105         }                                                               \
 106         static inline int unregister_trace_##name(void (*probe)(proto)) \
 107         {                                                               \
 108                 return -ENOSYS;                                         \
 109         }
 110
 111 #define DEFINE_TRACE(name)
 112 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 113 #define EXPORT_TRACEPOINT_SYMBOL(name)
 114
 115 static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 116         struct tracepoint *end)
 117 { }
 118 #endif /* CONFIG_TRACEPOINTS */
 119 #endif /* DECLARE_TRACE */
 120
 121 /*
 122  * Connect a probe to a tracepoint.
 123  * Internal API, should not be used directly.
 124  */
 125 extern int tracepoint_probe_register(const char *name, void *probe);
 126
 127 /*
 128  * Disconnect a probe from a tracepoint.
 129  * Internal API, should not be used directly.
 130  */
 131 extern int tracepoint_probe_unregister(const char *name, void *probe);
 132
 133 extern int tracepoint_probe_register_noupdate(const char *name, void *probe);
 134 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);
 135 extern void tracepoint_probe_update_all(void);
 136
 137 struct tracepoint_iter {
 138         struct module *module;
 139         struct tracepoint *tracepoint;
 140 };
 141
 142 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
 143 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
 144 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
 145 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
 146 extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
 147         struct tracepoint *begin, struct tracepoint *end);
 148
 149 /*
 150  * tracepoint_synchronize_unregister must be called between the last tracepoint
 151  * probe unregistration and the end of module exit to make sure there is no
 152  * caller executing a probe when it is freed.
 153  */
 154 static inline void tracepoint_synchronize_unregister(void)
 155 {
 156         synchronize_sched();
 157 }
 158
 159 #define PARAMS(args...) args
 160
 161 #ifndef TRACE_EVENT
 162 /*
 163  * For use with the TRACE_EVENT macro:
 164  *
 165  * We define a tracepoint, its arguments, its printk format
 166  * and its 'fast binay record' layout.
 167  *
 168  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 169  * 'subsystem_event' notation is fine.
 170  *
 171  * Think about this whole construct as the
 172  * 'trace_sched_switch() function' from now on.
 173  *
 174  *
 175  *  TRACE_EVENT(sched_switch,
 176  *
 177  *      *
 178  *      * A function has a regular function arguments
 179  *      * prototype, declare it via TP_PROTO():
 180  *      *
 181  *
 182  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 183  *               struct task_struct *next),
 184  *
 185  *      *
 186  *      * Define the call signature of the 'function'.
 187  *      * (Design sidenote: we use this instead of a
 188  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 189  *      *
 190  *
 191  *      TP_ARGS(rq, prev, next),
 192  *
 193  *      *
 194  *      * Fast binary tracing: define the trace record via
 195  *      * TP_STRUCT__entry(). You can think about it like a
 196  *      * regular C structure local variable definition.
 197  *      *
 198  *      * This is how the trace record is structured and will
 199  *      * be saved into the ring buffer. These are the fields
 200  *      * that will be exposed to user-space in
 201  *      * /debug/tracing/events/<*>/format.
 202  *      *
 203  *      * The declared 'local variable' is called '__entry'
 204  *      *
 205  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 206  *      *
 207  *      *       pid_t   prev_pid;
 208  *      *
 209  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 210  *      *
 211  *      *       char    prev_comm[TASK_COMM_LEN];
 212  *      *
 213  *
 214  *      TP_STRUCT__entry(
 215  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 216  *              __field(        pid_t,  prev_pid                        )
 217  *              __field(        int,    prev_prio                       )
 218  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 219  *              __field(        pid_t,  next_pid                        )
 220  *              __field(        int,    next_prio                       )
 221  *      ),
 222  *
 223  *      *
 224  *      * Assign the entry into the trace record, by embedding
 225  *      * a full C statement block into TP_fast_assign(). You
 226  *      * can refer to the trace record as '__entry' -
 227  *      * otherwise you can put arbitrary C code in here.
 228  *      *
 229  *      * Note: this C code will execute every time a trace event
 230  *      * happens, on an active tracepoint.
 231  *      *
 232  *
 233  *      TP_fast_assign(
 234  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 235  *              __entry->prev_pid       = prev->pid;
 236  *              __entry->prev_prio      = prev->prio;
 237  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 238  *              __entry->next_pid       = next->pid;
 239  *              __entry->next_prio      = next->prio;
 240  *      )
 241  *
 242  *      *
 243  *      * Formatted output of a trace record via TP_printk().
 244  *      * This is how the tracepoint will appear under ftrace
 245  *      * plugins that make use of this tracepoint.
 246  *      *
 247  *      * (raw-binary tracing wont actually perform this step.)
 248  *      *
 249  *
 250  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 251  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 252  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 253  *
 254  * );
 255  *
 256  * This macro construct is thus used for the regular printk format
 257  * tracing setup, it is used to construct a function pointer based
 258  * tracepoint callback (this is used by programmatic plugins and
 259  * can also by used by generic instrumentation like SystemTap), and
 260  * it is also used to expose a structured trace record in
 261  * /debug/tracing/events/.
 262  */
 263
 264 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 265         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 266 #endif
 267
 268 #endif