include/ust/tracepoint.h

   1 #ifndef _UST_TRACEPOINT_H
   2 #define _UST_TRACEPOINT_H
   3
   4 /*
   5  * Copyright (C) 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
   6  * Copyright (C) 2009 Pierre-Marc Fournier
   7  * Copyright (C) 2009 Steven Rostedt <rostedt@goodmis.org>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation;
  12  * version 2.1 of the License.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  22  *
  23  * Heavily inspired from the Linux Kernel Markers.
  24  *
  25  * Ported to userspace by Pierre-Marc Fournier.
  26  */
  27
  28 #include <urcu-bp.h>
  29 #include <urcu/list.h>
  30
  31 struct tracepoint_probe {
  32         void *func;
  33         void *data;
  34 };
  35
  36 struct tracepoint {
  37         const char *name;               /* Tracepoint name */
  38         char state;                     /* State. */
  39         struct tracepoint_probe *probes;
  40 };
  41
  42 /*
  43  * Tracepoints should be added to the instrumented code using the
  44  * "tracepoint()" macro.
  45  */
  46 #define tracepoint(name, args...)       __trace_##name(args)
  47
  48 /*
  49  * Library should be made known to libust by declaring TRACEPOINT_LIB in
  50  * the source file. (Usually at the end of the file, in the outermost
  51  * scope).
  52  */
  53 #define TRACEPOINT_LIB                                                  \
  54         extern struct tracepoint * const __start___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
  55         extern struct tracepoint * const __stop___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
  56         static struct tracepoint * __tracepoint_ptr_dummy               \
  57         __attribute__((used, section("__tracepoints_ptrs")));           \
  58         static void __attribute__((constructor)) __tracepoints__init(void) \
  59         {                                                               \
  60                 tracepoint_register_lib(__start___tracepoints_ptrs,     \
  61                                         __stop___tracepoints_ptrs -     \
  62                                         __start___tracepoints_ptrs);    \
  63         }                                                               \
  64                                                                         \
  65         static void __attribute__((destructor)) __tracepoints__destroy(void) \
  66         {                                                               \
  67                 tracepoint_unregister_lib(__start___tracepoints_ptrs);  \
  68         }
  69
  70 /*
  71  * it_func[0] is never NULL because there is at least one element in the array
  72  * when the array itself is non NULL.
  73  */
  74 #define __DO_TRACE(tp, proto, args)                                     \
  75         do {                                                            \
  76                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  77                 void *__tp_it_func;                                     \
  78                 void *__tp_cb_data;                                     \
  79                                                                         \
  80                 rcu_read_lock();                                        \
  81                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  82                 if (__tp_it_probe_ptr) {                                \
  83                         do {                                            \
  84                                 __tp_it_func = __tp_it_probe_ptr->func; \
  85                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  86                                 ((void(*)(proto))__tp_it_func)(args);   \
  87                         } while ((++__tp_it_probe_ptr)->func);          \
  88                 }                                                       \
  89                 rcu_read_unlock();                                      \
  90         } while (0)
  91
  92 #define TP_PARAMS(args...)      args
  93 #define TP_PROTO(args...)       args
  94 #define TP_ARGS(args...)        args
  95
  96 #define __CHECK_TRACE(name, proto, args)                                \
  97         do {                                                            \
  98                 if (unlikely(__tracepoint_##name.state))                \
  99                         __DO_TRACE(&__tracepoint_##name,                \
 100                                 TP_PROTO(proto), TP_ARGS(args));        \
 101         } while (0)
 102
 103 /*
 104  * Make sure the alignment of the structure in the __tracepoints section will
 105  * not add unwanted padding between the beginning of the section and the
 106  * structure. Force alignment to the same alignment as the section start.
 107  */
 108 #define __DECLARE_TRACEPOINT(name, proto, args, data_proto, data_args)  \
 109         extern struct tracepoint __tracepoint_##name;                   \
 110         static inline void __trace_##name(proto)                        \
 111         {                                                               \
 112                 __CHECK_TRACE(name, TP_PROTO(data_proto),               \
 113                               TP_ARGS(data_args));                      \
 114         }                                                               \
 115         static inline int                                               \
 116         __register_trace_##name(void (*probe)(data_proto), void *data)  \
 117         {                                                               \
 118                 return __tracepoint_probe_register(#name, (void *)probe,\
 119                                                  data);                 \
 120                                                                         \
 121         }                                                               \
 122         static inline int                                               \
 123         __unregister_trace_##name(void (*probe)(data_proto), void *data)\
 124         {                                                               \
 125                 return __tracepoint_probe_unregister(#name, (void *)probe, \
 126                                                    data);               \
 127         }
 128
 129 /*
 130  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 131  * (void). "void" is a special value in a function prototype and can
 132  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 133  * macro adds a data element at the beginning of the prototype,
 134  * we need a way to differentiate "(void *data, proto)" from
 135  * "(void *data, void)". The second prototype is invalid.
 136  *
 137  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 138  * and "void *__tp_cb_data" as the callback prototype.
 139  *
 140  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 141  * "void *__tp_cb_data, proto" as the callback prototype.
 142  */
 143 #define _DECLARE_TRACEPOINT_NOARGS(name)                                \
 144         __DECLARE_TRACEPOINT(name, void, , void *__tp_cb_data, __tp_cb_data)
 145
 146 #define _DECLARE_TRACEPOINT(name, proto, args)                          \
 147         __DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args),   \
 148                         TP_PARAMS(void *__tp_cb_data, proto),           \
 149                         TP_PARAMS(__tp_cb_data, args))
 150
 151 /*
 152  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 153  * the pointer, allowing PIC code.
 154  */
 155 #define _DEFINE_TRACEPOINT(name)                                        \
 156         static const char __tpstrtab_##name[]                           \
 157         __attribute__((section("__tracepoints_strings"))) = #name;      \
 158         struct tracepoint __tracepoint_##name                           \
 159         __attribute__((section("__tracepoints"))) =                     \
 160                 { __tpstrtab_##name, 0, NULL };                         \
 161         static struct tracepoint * __tracepoint_ptr_##name              \
 162         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 163                 &__tracepoint_##name;
 164
 165
 166 #define __register_tracepoint(name, probe, data)                        \
 167                 __register_trace_##name(probe, data)
 168 #define __unregister_tracepoint(name, probe, data)                      \
 169                 __unregister_trace_##name(probe, data)
 170
 171 /*
 172  * Connect a probe to a tracepoint.
 173  * Internal API.
 174  */
 175 extern
 176 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 177
 178 /*
 179  * Disconnect a probe from a tracepoint.
 180  * Internal API.
 181  */
 182 extern
 183 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 184
 185 struct tracepoint_lib {
 186         struct tracepoint * const *tracepoints_start;
 187         int tracepoints_count;
 188         struct cds_list_head list;
 189 };
 190
 191 extern
 192 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 193                             int tracepoints_count);
 194 extern
 195 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 196
 197
 198 #ifndef TRACEPOINT_EVENT
 199 /*
 200  * For use with the TRACEPOINT_EVENT macro:
 201  *
 202  * We define a tracepoint, its arguments, its printf format
 203  * and its 'fast binary record' layout.
 204  *
 205  * Firstly, name your tracepoint via TRACEPOINT_EVENT(name : the
 206  * 'subsystem_event' notation is fine.
 207  *
 208  * Think about this whole construct as the
 209  * 'trace_sched_switch() function' from now on.
 210  *
 211  *
 212  *  TRACEPOINT_EVENT(sched_switch,
 213  *
 214  *      *
 215  *      * A function has a regular function arguments
 216  *      * prototype, declare it via TP_PROTO():
 217  *      *
 218  *
 219  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 220  *               struct task_struct *next),
 221  *
 222  *      *
 223  *      * Define the call signature of the 'function'.
 224  *      * (Design sidenote: we use this instead of a
 225  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 226  *      *
 227  *
 228  *      TP_ARGS(rq, prev, next),
 229  *
 230  *      *
 231  *      * Fast binary tracing: define the trace record via
 232  *      * TP_FIELDS(). You can think about it like a
 233  *      * regular C structure local variable definition.
 234  *      *
 235  *      * This is how the trace record is structured and will
 236  *      * be saved into the ring buffer. These are the fields
 237  *      * that will be exposed to readers.
 238  *      *
 239  *      * tp_field(pid_t, prev_pid, prev->pid) is equivalent
 240  *      * to a standard declaraton:
 241  *      *
 242  *      *       pid_t prev_pid;
 243  *      *
 244  *      * followed by an assignment:
 245  *      *
 246  *      *       prev_pid = prev->pid;
 247  *      *
 248  *      * tp_array(char, prev_comm, TASK_COMM_LEN, prev->comm) is
 249  *      * equivalent to:
 250  *      *
 251  *      *       char prev_comm[TASK_COMM_LEN];
 252  *      *
 253  *      * followed by an assignment:
 254  *      *
 255  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 256  *      *
 257  *
 258  *      TP_FIELDS(
 259  *              tp_array(char,  prev_comm, TASK_COMM_LEN, prev->comm)
 260  *              tp_field(pid_t, prev_pid,  prev->pid)
 261  *              tp_field(int,   prev_prio, prev->prio)
 262  *              tp_array(char,  next_comm, TASK_COMM_LEN, next->comm)
 263  *              tp_field(pid_t, next_pid,  next->pid)
 264  *              tp_field(int,   next_prio, next->prio)
 265  *      )
 266  * );
 267  */
 268
 269 #define TRACEPOINT_EVENT(name, proto, args, fields)                     \
 270         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 271
 272 #define TRACEPOINT_EVENT_CLASS(name, proto, args, fields)
 273 #define TRACEPOINT_EVENT_INSTANCE(template, name, proto, args)          \
 274         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 275
 276 /*
 277  * Declaration of tracepoints that take 0 argument.
 278  */
 279 #define TRACEPOINT_EVENT_NOARGS(name, fields)                           \
 280         _DECLARE_TRACEPOINT_NOARGS(name)
 281
 282 #define TRACEPOINT_EVENT_CLASS_NOARGS(name, fields)
 283 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(template, name)                \
 284         _DECLARE_TRACEPOINT_NOARGS(name)
 285
 286
 287
 288 #define TRACEPOINT_EVENT_LIB                                            \
 289         extern struct trace_event * const __start___trace_events_ptrs[] \
 290         __attribute__((weak, visibility("hidden")));                    \
 291         extern struct trace_event * const __stop___trace_events_ptrs[]  \
 292         __attribute__((weak, visibility("hidden")));                    \
 293         static struct trace_event * __event_ptrs_dummy                  \
 294         __attribute__((used, section("__trace_events_ptrs")));          \
 295         static void __attribute__((constructor))                        \
 296         __trace_events__init(void)                                      \
 297         {                                                               \
 298                 trace_event_register_lib(__start___trace_events_ptrs,   \
 299                                          __stop___trace_events_ptrs -   \
 300                                          __start___trace_events_ptrs);  \
 301         }                                                               \
 302                                                                         \
 303         static void __attribute__((destructor))                         \
 304         __trace_event__destroy(void)                                    \
 305         {                                                               \
 306                 trace_event_unregister_lib(__start___trace_events_ptrs);\
 307         }
 308
 309 struct trace_event {
 310         const char *name;
 311 };
 312
 313 struct trace_event_lib {
 314         struct trace_event * const *trace_events_start;
 315         int trace_events_count;
 316         struct cds_list_head list;
 317 };
 318
 319 extern
 320 int trace_event_register_lib(struct trace_event * const *start_trace_events,
 321                              int trace_event_count);
 322 extern
 323 int trace_event_unregister_lib(struct trace_event * const *start_trace_events);
 324
 325 #endif /* #ifndef TRACEPOINT_EVENT */
 326
 327 #endif /* _UST_TRACEPOINT_H */