5984ed04c03b9cc4faa0bef247801d3ec2f70e0f
[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 **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