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