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