include/lttng/tracepoint.h

   1 #ifndef _UST_TRACEPOINT_H
   2 #define _UST_TRACEPOINT_H
   3
   4 /*
   5  * Copyright (C) 2008-2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   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 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 struct tracepoint_probe {
  36         void *func;
  37         void *data;
  38 };
  39
  40 struct tracepoint {
  41         const char *name;               /* Tracepoint name */
  42         char state;                     /* State. */
  43         struct tracepoint_probe *probes;
  44 };
  45
  46 /*
  47  * Tracepoints should be added to the instrumented code using the
  48  * "tracepoint()" macro.
  49  */
  50 #define tracepoint(name, args...)       __trace_##name(args)
  51
  52 /*
  53  * it_func[0] is never NULL because there is at least one element in the array
  54  * when the array itself is non NULL.
  55  */
  56 #define __DO_TRACE(tp, proto, args)                                     \
  57         do {                                                            \
  58                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  59                 void *__tp_it_func;                                     \
  60                 void *__tp_cb_data;                                     \
  61                                                                         \
  62                 rcu_read_lock();                                        \
  63                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  64                 if (__tp_it_probe_ptr) {                                \
  65                         do {                                            \
  66                                 __tp_it_func = __tp_it_probe_ptr->func; \
  67                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  68                                 URCU_FORCE_CAST(void(*)(proto), __tp_it_func)(args); \
  69                         } while ((++__tp_it_probe_ptr)->func);          \
  70                 }                                                       \
  71                 rcu_read_unlock();                                      \
  72         } while (0)
  73
  74 #define TP_PARAMS(args...)      args
  75 #define TP_PROTO(args...)       args
  76 #define TP_ARGS(args...)        args
  77
  78 #define __CHECK_TRACE(name, proto, args)                                \
  79         do {                                                            \
  80                 if (caa_unlikely(__tracepoint_##name.state))            \
  81                         __DO_TRACE(&__tracepoint_##name,                \
  82                                 TP_PROTO(proto), TP_ARGS(args));        \
  83         } while (0)
  84
  85 /*
  86  * Make sure the alignment of the structure in the __tracepoints section will
  87  * not add unwanted padding between the beginning of the section and the
  88  * structure. Force alignment to the same alignment as the section start.
  89  */
  90 #define __DECLARE_TRACEPOINT(name, proto, args, data_proto, data_args)  \
  91         extern struct tracepoint __tracepoint_##name;                   \
  92         static inline void __trace_##name(proto)                        \
  93         {                                                               \
  94                 __CHECK_TRACE(name, TP_PROTO(data_proto),               \
  95                               TP_ARGS(data_args));                      \
  96         }                                                               \
  97         static inline int                                               \
  98         __register_trace_##name(void (*probe)(data_proto), void *data)  \
  99         {                                                               \
 100                 return __tracepoint_probe_register(#name, (void *)probe,\
 101                                                  data);                 \
 102         }                                                               \
 103         static inline int                                               \
 104         __unregister_trace_##name(void (*probe)(data_proto), void *data)\
 105         {                                                               \
 106                 return __tracepoint_probe_unregister(#name, (void *)probe, \
 107                                                    data);               \
 108         }
 109
 110 /*
 111  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 112  * (void). "void" is a special value in a function prototype and can
 113  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 114  * macro adds a data element at the beginning of the prototype,
 115  * we need a way to differentiate "(void *data, proto)" from
 116  * "(void *data, void)". The second prototype is invalid.
 117  *
 118  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 119  * and "void *__tp_cb_data" as the callback prototype.
 120  *
 121  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 122  * "void *__tp_cb_data, proto" as the callback prototype.
 123  */
 124 #define _DECLARE_TRACEPOINT_NOARGS(name)                                \
 125         __DECLARE_TRACEPOINT(name, void, , void *__tp_cb_data, __tp_cb_data)
 126
 127 #define _DECLARE_TRACEPOINT(name, proto, args)                          \
 128         __DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args),   \
 129                         TP_PARAMS(void *__tp_cb_data, proto),           \
 130                         TP_PARAMS(__tp_cb_data, args))
 131
 132 /*
 133  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 134  * the pointer, allowing PIC code.
 135  */
 136 #define _DEFINE_TRACEPOINT(name)                                        \
 137         static const char __tpstrtab_##name[]                           \
 138         __attribute__((section("__tracepoints_strings"))) = #name;      \
 139         struct tracepoint __tracepoint_##name                           \
 140         __attribute__((section("__tracepoints"))) =                     \
 141                 { __tpstrtab_##name, 0, NULL };                         \
 142         static struct tracepoint * __tracepoint_ptr_##name              \
 143         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 144                 &__tracepoint_##name;
 145
 146
 147 #define __register_tracepoint(name, probe, data)                        \
 148                 __register_trace_##name(probe, data)
 149 #define __unregister_tracepoint(name, probe, data)                      \
 150                 __unregister_trace_##name(probe, data)
 151
 152 /*
 153  * Connect a probe to a tracepoint.
 154  * Internal API.
 155  */
 156 extern
 157 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 158
 159 /*
 160  * Disconnect a probe from a tracepoint.
 161  * Internal API.
 162  */
 163 extern
 164 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 165
 166 extern
 167 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 168                             int tracepoints_count);
 169 extern
 170 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 171
 172 /*
 173  * These weak symbols, the constructor, and destructor take care of
 174  * registering only _one_ instance of the tracepoints per shared-ojbect
 175  * (or for the whole main program).
 176  */
 177 extern struct tracepoint * const __start___tracepoints_ptrs[]
 178         __attribute__((weak, visibility("hidden")));
 179 extern struct tracepoint * const __stop___tracepoints_ptrs[]
 180         __attribute__((weak, visibility("hidden")));
 181 int __tracepoint_registered
 182         __attribute__((weak, visibility("hidden")));
 183
 184 static void __attribute__((constructor)) __tracepoints__init(void)
 185 {
 186         if (__tracepoint_registered++)
 187                 return;
 188         tracepoint_register_lib(__start___tracepoints_ptrs,
 189                                 __stop___tracepoints_ptrs -
 190                                 __start___tracepoints_ptrs);
 191 }
 192
 193 static void __attribute__((destructor)) __tracepoints__destroy(void)
 194 {
 195         if (--__tracepoint_registered)
 196                 return;
 197         tracepoint_unregister_lib(__start___tracepoints_ptrs);
 198 }
 199
 200 #ifndef TRACEPOINT_EVENT
 201 /*
 202  * Usage of the TRACEPOINT_EVENT macro:
 203  *
 204  * In short, an example:
 205  *
 206  * TRACEPOINT_EVENT(< [com_company_]project_[component_]event >,
 207  *     TP_PROTO(int arg0, void *arg1, char *string, size_t strlen,
 208  *              long *arg4, size_t arg4_len),
 209  *     TP_ARGS(arg0, arg1, string, strlen, arg4, arg4_len),
 210  *     TP_FIELDS(
 211  *
 212  *         * Integer, printed in base 10 *
 213  *         ctf_integer(int, field_a, arg0)
 214  *
 215  *         * Integer, printed with 0x base 16 *
 216  *         ctf_integer_hex(unsigned long, field_d, arg1)
 217  *
 218  *         * Array Sequence, printed as UTF8-encoded array of bytes *
 219  *         ctf_array_text(char, field_b, string, FIXED_LEN)
 220  *         ctf_sequence_text(char, field_c, string, size_t, strlen)
 221  *
 222  *         * String, printed as UTF8-encoded string *
 223  *         ctf_string(field_e, string)
 224  *
 225  *         * Array sequence of signed integer values *
 226  *         ctf_array(long, field_f, arg4, FIXED_LEN4)
 227  *         ctf_sequence(long, field_g, arg4, size_t, arg4_len)
 228  *     )
 229  * )
 230  *
 231  * In more detail:
 232  *
 233  * We define a tracepoint, its arguments, and its 'fast binary record'
 234  * layout.
 235  *
 236  * Firstly, name your tracepoint via TRACEPOINT_EVENT(name,
 237  *
 238  * The name should be a proper C99 identifier.
 239  * The "name" MUST follow these rules to ensure no namespace clash
 240  * occurs:
 241  *
 242  * For projects (applications and libraries) for which an entity
 243  * specific to the project controls the source code and thus its
 244  * tracepoints (typically with a scope larger than a single company):
 245  *
 246  * either:
 247  *   project_component_event
 248  * or:
 249  *   project_event
 250  *
 251  * Where "project" is the name of the project,
 252  *       "component" is the name of the project component (which may
 253  *       include several levels of sub-components, e.g.
 254  *       ...component_subcomponent_...) where the tracepoint is located
 255  *       (optional),
 256  *       "event" is the name of the tracepoint event.
 257  *
 258  * For projects issued from a single company wishing to advertise that
 259  * the company controls the source code and thus the tracepoints, the
 260  * "com_" prefix should be used:
 261  *
 262  * either:
 263  *   com_company_project_component_event
 264  * or:
 265  *   com_company_project_event
 266  *
 267  * Where "company" is the name of the company,
 268  *       "project" is the name of the project,
 269  *       "component" is the name of the project component (which may
 270  *       include several levels of sub-components, e.g.
 271  *       ...component_subcomponent_...) where the tracepoint is located
 272  *       (optional),
 273  *       "event" is the name of the tracepoint event.
 274  *
 275  *
 276  * As an example, let's consider a user-space application "someproject"
 277  * that would have an internal thread scheduler:
 278  *
 279  *  TRACEPOINT_EVENT(someproject_sched_switch,
 280  *
 281  *      *
 282  *      * A function has a regular function arguments
 283  *      * prototype, declare it via TP_PROTO():
 284  *      *
 285  *
 286  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 287  *               struct task_struct *next),
 288  *
 289  *      *
 290  *      * Define the call signature of the 'function'.
 291  *      * (Design sidenote: we use this instead of a
 292  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 293  *      *
 294  *
 295  *      TP_ARGS(rq, prev, next),
 296  *
 297  *      *
 298  *      * Fast binary tracing: define the trace record via
 299  *      * TP_FIELDS(). You can think about it like a
 300  *      * regular C structure local variable definition.
 301  *      *
 302  *      * This is how the trace record is structured and will
 303  *      * be saved into the ring buffer. These are the fields
 304  *      * that will be exposed to readers.
 305  *      *
 306  *      * ctf_integer(pid_t, prev_pid, prev->pid) is equivalent
 307  *      * to a standard declaraton:
 308  *      *
 309  *      *       pid_t prev_pid;
 310  *      *
 311  *      * followed by an assignment:
 312  *      *
 313  *      *       prev_pid = prev->pid;
 314  *      *
 315  *      * ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN) is
 316  *      * equivalent to:
 317  *      *
 318  *      *       char prev_comm[TASK_COMM_LEN];
 319  *      *
 320  *      * followed by an assignment:
 321  *      *
 322  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 323  *      *
 324  *
 325  *      TP_FIELDS(
 326  *              ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN)
 327  *              ctf_integer(pid_t, prev_pid,  prev->pid)
 328  *              ctf_integer(int, prev_prio, prev->prio)
 329  *              ctf_array(char, next_comm, next->comm, TASK_COMM_LEN)
 330  *              ctf_integer(pid_t, next_pid,  next->pid)
 331  *              ctf_integer(int, next_prio, next->prio)
 332  *      )
 333  * )
 334  *
 335  * Do _NOT_ add comma (,) nor semicolon (;) after the TRACEPOINT_EVENT
 336  * declaration.
 337  *
 338  * The TRACEPOINT_SYSTEM must be defined when declaring a
 339  * TRACEPOINT_EVENT. See ust/tracepoint-event.h for information about
 340  * usage of other macros controlling TRACEPOINT_EVENT.
 341  */
 342
 343 #define TRACEPOINT_EVENT(name, proto, args, fields)                     \
 344         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 345
 346 #define TRACEPOINT_EVENT_CLASS(name, proto, args, fields)
 347 #define TRACEPOINT_EVENT_INSTANCE(template, name, proto, args)          \
 348         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 349
 350 /*
 351  * Declaration of tracepoints that take 0 argument.
 352  */
 353 #define TRACEPOINT_EVENT_NOARGS(name, fields)                           \
 354         _DECLARE_TRACEPOINT_NOARGS(name)
 355
 356 #define TRACEPOINT_EVENT_CLASS_NOARGS(name, fields)
 357 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(template, name)                \
 358         _DECLARE_TRACEPOINT_NOARGS(name)
 359
 360 #endif /* #ifndef TRACEPOINT_EVENT */
 361
 362 #ifndef TRACEPOINT_LOGLEVEL
 363
 364 /*
 365  * Tracepoint Loglevel Declaration Facility
 366  *
 367  * This is a place-holder the tracepoint loglevel declaration,
 368  * overridden by the tracer implementation.
 369  *
 370  * Typical use of these loglevels:
 371  *
 372  * 1) Declare the mapping between loglevel names and an integer values
 373  *    within TRACEPOINT_LOGLEVEL_ENUM, using TP_LOGLEVEL for each tuple.
 374  *    Do _NOT_ add comma (,) nor semicolon (;) between the
 375  *    TRACEPOINT_LOGLEVEL_ENUM entries. Do _NOT_ add comma (,) nor
 376  *    semicolon (;) after the TRACEPOINT_LOGLEVEL_ENUM declaration.  The
 377  *    name should be a proper C99 identifier.
 378  *
 379  *      TRACEPOINT_LOGLEVEL_ENUM(
 380  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 381  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 382  *              ...
 383  *      )
 384  *
 385  *    e.g.:
 386  *
 387  *      TRACEPOINT_LOGLEVEL_ENUM(
 388  *              TP_LOGLEVEL(LOG_EMERG,   0)
 389  *              TP_LOGLEVEL(LOG_ALERT,   1)
 390  *              TP_LOGLEVEL(LOG_CRIT,    2)
 391  *              TP_LOGLEVEL(LOG_ERR,     3)
 392  *              TP_LOGLEVEL(LOG_WARNING, 4)
 393  *              TP_LOGLEVEL(LOG_NOTICE,  5)
 394  *              TP_LOGLEVEL(LOG_INFO,    6)
 395  *              TP_LOGLEVEL(LOG_DEBUG,   7)
 396  *      )
 397  *
 398  * 2) Then, declare tracepoint loglevels for tracepoints. A
 399  *    TRACEPOINT_EVENT should be declared prior to the the
 400  *    TRACEPOINT_LOGLEVEL for a given tracepoint name. The first field
 401  *    is the name of the tracepoint, the second field is the loglevel
 402  *    name.
 403  *
 404  *      TRACEPOINT_LOGLEVEL(< [com_company_]project_[component_]event >,
 405  *              < loglevel_name >)
 406  *
 407  * The TRACEPOINT_SYSTEM must be defined when declaring a
 408  * TRACEPOINT_LOGLEVEL_ENUM and TRACEPOINT_LOGLEVEL. The tracepoint
 409  * loglevel enumeration apply to the entire TRACEPOINT_SYSTEM. Only one
 410  * tracepoint loglevel enumeration should be declared per tracepoint
 411  * system.
 412  */
 413
 414 #define TRACEPOINT_LOGLEVEL_ENUM()
 415 #define TRACEPOINT_LOGLEVEL(name, loglevel)
 416
 417 #endif /* #ifndef TRACEPOINT_LOGLEVEL */
 418
 419 #ifdef __cplusplus
 420 }
 421 #endif
 422
 423 #endif /* _UST_TRACEPOINT_H */