tracing: Move tracepoint callbacks from declaration to definition
[linux-2.6.git] / 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 (*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 #ifndef TRACE_EVENT
169 /*
170  * For use with the TRACE_EVENT macro:
171  *
172  * We define a tracepoint, its arguments, its printk format
173  * and its 'fast binay record' layout.
174  *
175  * Firstly, name your tracepoint via TRACE_EVENT(name : the
176  * 'subsystem_event' notation is fine.
177  *
178  * Think about this whole construct as the
179  * 'trace_sched_switch() function' from now on.
180  *
181  *
182  *  TRACE_EVENT(sched_switch,
183  *
184  *      *
185  *      * A function has a regular function arguments
186  *      * prototype, declare it via TP_PROTO():
187  *      *
188  *
189  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
190  *               struct task_struct *next),
191  *
192  *      *
193  *      * Define the call signature of the 'function'.
194  *      * (Design sidenote: we use this instead of a
195  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
196  *      *
197  *
198  *      TP_ARGS(rq, prev, next),
199  *
200  *      *
201  *      * Fast binary tracing: define the trace record via
202  *      * TP_STRUCT__entry(). You can think about it like a
203  *      * regular C structure local variable definition.
204  *      *
205  *      * This is how the trace record is structured and will
206  *      * be saved into the ring buffer. These are the fields
207  *      * that will be exposed to user-space in
208  *      * /sys/kernel/debug/tracing/events/<*>/format.
209  *      *
210  *      * The declared 'local variable' is called '__entry'
211  *      *
212  *      * __field(pid_t, prev_prid) is equivalent to a standard declariton:
213  *      *
214  *      *       pid_t   prev_pid;
215  *      *
216  *      * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
217  *      *
218  *      *       char    prev_comm[TASK_COMM_LEN];
219  *      *
220  *
221  *      TP_STRUCT__entry(
222  *              __array(        char,   prev_comm,      TASK_COMM_LEN   )
223  *              __field(        pid_t,  prev_pid                        )
224  *              __field(        int,    prev_prio                       )
225  *              __array(        char,   next_comm,      TASK_COMM_LEN   )
226  *              __field(        pid_t,  next_pid                        )
227  *              __field(        int,    next_prio                       )
228  *      ),
229  *
230  *      *
231  *      * Assign the entry into the trace record, by embedding
232  *      * a full C statement block into TP_fast_assign(). You
233  *      * can refer to the trace record as '__entry' -
234  *      * otherwise you can put arbitrary C code in here.
235  *      *
236  *      * Note: this C code will execute every time a trace event
237  *      * happens, on an active tracepoint.
238  *      *
239  *
240  *      TP_fast_assign(
241  *              memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
242  *              __entry->prev_pid       = prev->pid;
243  *              __entry->prev_prio      = prev->prio;
244  *              memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
245  *              __entry->next_pid       = next->pid;
246  *              __entry->next_prio      = next->prio;
247  *      )
248  *
249  *      *
250  *      * Formatted output of a trace record via TP_printk().
251  *      * This is how the tracepoint will appear under ftrace
252  *      * plugins that make use of this tracepoint.
253  *      *
254  *      * (raw-binary tracing wont actually perform this step.)
255  *      *
256  *
257  *      TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
258  *              __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
259  *              __entry->next_comm, __entry->next_pid, __entry->next_prio),
260  *
261  * );
262  *
263  * This macro construct is thus used for the regular printk format
264  * tracing setup, it is used to construct a function pointer based
265  * tracepoint callback (this is used by programmatic plugins and
266  * can also by used by generic instrumentation like SystemTap), and
267  * it is also used to expose a structured trace record in
268  * /sys/kernel/debug/tracing/events/.
269  *
270  * A set of (un)registration functions can be passed to the variant
271  * TRACE_EVENT_FN to perform any (un)registration work.
272  */
273
274 #define TRACE_EVENT(name, proto, args, struct, assign, print)   \
275         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
276 #define TRACE_EVENT_FN(name, proto, args, struct,               \
277                 assign, print, reg, unreg)                      \
278         DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
279 #endif
280
281 #endif