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 /*
  37  * Connect a probe to a tracepoint.
  38  * Internal API, should not be used directly.
  39  */
  40 extern int tracepoint_probe_register(const char *name, void *probe);
  41
  42 /*
  43  * Disconnect a probe from a tracepoint.
  44  * Internal API, should not be used directly.
  45  */
  46 extern int tracepoint_probe_unregister(const char *name, void *probe);
  47
  48 extern int tracepoint_probe_register_noupdate(const char *name, void *probe);
  49 extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);
  50 extern void tracepoint_probe_update_all(void);
  51
  52 struct tracepoint_iter {
  53         struct module *module;
  54         struct tracepoint *tracepoint;
  55 };
  56
  57 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
  58 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
  59 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
  60 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
  61 extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
  62         struct tracepoint *begin, struct tracepoint *end);
  63
  64 /*
  65  * tracepoint_synchronize_unregister must be called between the last tracepoint
  66  * probe unregistration and the end of module exit to make sure there is no
  67  * caller executing a probe when it is freed.
  68  */
  69 static inline void tracepoint_synchronize_unregister(void)
  70 {
  71         synchronize_sched();
  72 }
  73
  74 #define PARAMS(args...) args
  75
  76 #ifdef CONFIG_TRACEPOINTS
  77 extern void tracepoint_update_probe_range(struct tracepoint *begin,
  78         struct tracepoint *end);
  79 #else
  80 static inline void tracepoint_update_probe_range(struct tracepoint *begin,
  81         struct tracepoint *end)
  82 { }
  83 #endif /* CONFIG_TRACEPOINTS */
  84
  85 #endif /* _LINUX_TRACEPOINT_H */
  86
  87 /*
  88  * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
  89  *  file ifdef protection.
  90  *  This is due to the way trace events work. If a file includes two
  91  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
  92  *  will override the TRACE_EVENT and break the second include.
  93  */
  94
  95 #ifndef DECLARE_TRACE
  96
  97 #define TP_PROTO(args...)       args
  98 #define TP_ARGS(args...)        args
  99
 100 #ifdef CONFIG_TRACEPOINTS
 101
 102 /*
 103  * it_func[0] is never NULL because there is at least one element in the array
 104  * when the array itself is non NULL.
 105  */
 106 #define __DO_TRACE(tp, proto, args)                                     \
 107         do {                                                            \
 108                 void **it_func;                                         \
 109                                                                         \
 110                 rcu_read_lock_sched_notrace();                          \
 111                 it_func = rcu_dereference_sched((tp)->funcs);           \
 112                 if (it_func) {                                          \
 113                         do {                                            \
 114                                 ((void(*)(proto))(*it_func))(args);     \
 115                         } while (*(++it_func));                         \
 116                 }                                                       \
 117                 rcu_read_unlock_sched_notrace();                        \
 118         } while (0)
 119
 120 /*
 121  * Make sure the alignment of the structure in the __tracepoints section will
 122  * not add unwanted padding between the beginning of the section and the
 123  * structure. Force alignment to the same alignment as the section start.
 124  */
 125 #define DECLARE_TRACE(name, proto, args)                                \
 126         extern struct tracepoint __tracepoint_##name;                   \
 127         static inline void trace_##name(proto)                          \
 128         {                                                               \
 129                 if (unlikely(__tracepoint_##name.state))                \
 130                         __DO_TRACE(&__tracepoint_##name,                \
 131                                 TP_PROTO(proto), TP_ARGS(args));        \
 132         }                                                               \
 133         static inline int register_trace_##name(void (*probe)(proto))   \
 134         {                                                               \
 135                 return tracepoint_probe_register(#name, (void *)probe); \
 136         }                                                               \
 137         static inline int unregister_trace_##name(void (*probe)(proto)) \
 138         {                                                               \
 139                 return tracepoint_probe_unregister(#name, (void *)probe);\
 140         }
 141
 142
 143 #define DEFINE_TRACE_FN(name, reg, unreg)                               \
 144         static const char __tpstrtab_##name[]                           \
 145         __attribute__((section("__tracepoints_strings"))) = #name;      \
 146         struct tracepoint __tracepoint_##name                           \
 147         __attribute__((section("__tracepoints"), aligned(32))) =        \
 148                 { __tpstrtab_##name, 0, reg, unreg, NULL }
 149
 150 #define DEFINE_TRACE(name)                                              \
 151         DEFINE_TRACE_FN(name, NULL, NULL);
 152
 153 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                              \
 154         EXPORT_SYMBOL_GPL(__tracepoint_##name)
 155 #define EXPORT_TRACEPOINT_SYMBOL(name)                                  \
 156         EXPORT_SYMBOL(__tracepoint_##name)
 157
 158 #else /* !CONFIG_TRACEPOINTS */
 159 #define DECLARE_TRACE(name, proto, args)                                \
 160         static inline void _do_trace_##name(struct tracepoint *tp, proto) \
 161         { }                                                             \
 162         static inline void trace_##name(proto)                          \
 163         { }                                                             \
 164         static inline int register_trace_##name(void (*probe)(proto))   \
 165         {                                                               \
 166                 return -ENOSYS;                                         \
 167         }                                                               \
 168         static inline int unregister_trace_##name(void (*probe)(proto)) \
 169         {                                                               \
 170                 return -ENOSYS;                                         \
 171         }
 172
 173 #define DEFINE_TRACE_FN(name, reg, unreg)
 174 #define DEFINE_TRACE(name)
 175 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 176 #define EXPORT_TRACEPOINT_SYMBOL(name)
 177
 178 #endif /* CONFIG_TRACEPOINTS */
 179 #endif /* DECLARE_TRACE */
 180
 181 #ifndef TRACE_EVENT
 182 /*
 183  * For use with the TRACE_EVENT macro:
 184  *
 185  * We define a tracepoint, its arguments, its printk format
 186  * and its 'fast binay record' layout.
 187  *
 188  * Firstly, name your tracepoint via TRACE_EVENT(name : the
 189  * 'subsystem_event' notation is fine.
 190  *
 191  * Think about this whole construct as the
 192  * 'trace_sched_switch() function' from now on.
 193  *
 194  *
 195  *  TRACE_EVENT(sched_switch,
 196  *
 197  *      *
 198  *      * A function has a regular function arguments
 199  *      * prototype, declare it via TP_PROTO():
 200  *      *
 201  *
 202  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 203  *               struct task_struct *next),
 204  *
 205  *      *
 206  *      * Define the call signature of the 'function'.
 207  *      * (Design sidenote: we use this instead of a
 208  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 209  *      *
 210  *
 211  *      TP_ARGS(rq, prev, next),
 212  *
 213  *      *
 214  *      * Fast binary tracing: define the trace record via
 215  *      * TP_STRUCT__entry(). You can think about it like a
 216  *      * regular C structure local variable definition.
 217  *      *
 218  *      * This is how the trace record is structured and will
 219  *      * be saved into the ring buffer. These are the fields
 220  *      * that will be exposed to user-space in
 221  *      * /sys/kernel/debug/tracing/events/<*>/format.
 222  *      *
 223  *      * The declared 'local variable' is called '__entry'
 224  *      *
 225  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 226  *      *
 227  *      *       pid_t   prev_pid;
 228  *      *
 229  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 230  *      *
 231  *      *       char    prev_comm[TASK_COMM_LEN];
 232  *      *
 233  *
 234  *      TP_STRUCT__entry(
 235  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
 236  *              __field(        pid_t,  prev_pid                        )
 237  *              __field(        int,    prev_prio                       )
 238  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
 239  *              __field(        pid_t,  next_pid                        )
 240  *              __field(        int,    next_prio                       )
 241  *      ),
 242  *
 243  *      *
 244  *      * Assign the entry into the trace record, by embedding
 245  *      * a full C statement block into TP_fast_assign(). You
 246  *      * can refer to the trace record as '__entry' -
 247  *      * otherwise you can put arbitrary C code in here.
 248  *      *
 249  *      * Note: this C code will execute every time a trace event
 250  *      * happens, on an active tracepoint.
 251  *      *
 252  *
 253  *      TP_fast_assign(
 254  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 255  *              __entry->prev_pid       = prev->pid;
 256  *              __entry->prev_prio      = prev->prio;
 257  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 258  *              __entry->next_pid       = next->pid;
 259  *              __entry->next_prio      = next->prio;
 260  *      )
 261  *
 262  *      *
 263  *      * Formatted output of a trace record via TP_printk().
 264  *      * This is how the tracepoint will appear under ftrace
 265  *      * plugins that make use of this tracepoint.
 266  *      *
 267  *      * (raw-binary tracing wont actually perform this step.)
 268  *      *
 269  *
 270  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 271  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 272  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
 273  *
 274  * );
 275  *
 276  * This macro construct is thus used for the regular printk format
 277  * tracing setup, it is used to construct a function pointer based
 278  * tracepoint callback (this is used by programmatic plugins and
 279  * can also by used by generic instrumentation like SystemTap), and
 280  * it is also used to expose a structured trace record in
 281  * /sys/kernel/debug/tracing/events/.
 282  *
 283  * A set of (un)registration functions can be passed to the variant
 284  * TRACE_EVENT_FN to perform any (un)registration work.
 285  */
 286
 287 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 288 #define DEFINE_EVENT(template, name, proto, args)               \
 289         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 290 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
 291         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 292
 293 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
 294         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 295 #define TRACE_EVENT_FN(name, proto, args, struct,               \
 296                 assign, print, reg, unreg)                      \
 297         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 298
 299 #endif /* ifdef TRACE_EVENT (see note above) */