include/lttng/tracepoint.h

   1 #ifndef _LTTNG_TRACEPOINT_H
   2 #define _LTTNG_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
  26 #include <urcu-bp.h>
  27 #include <urcu/list.h>
  28 #include <lttng/tracepoint-types.h>
  29
  30 #ifdef __cplusplus
  31 extern "C" {
  32 #endif
  33
  34 /*
  35  * Tracepoints should be added to the instrumented code using the
  36  * "tracepoint()" macro.
  37  */
  38 #define tracepoint(provider, name, args...)     \
  39                 __trace_##provider##___##name(args)
  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                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  48                 void *__tp_it_func;                                     \
  49                 void *__tp_cb_data;                                     \
  50                                                                         \
  51                 rcu_read_lock();                                        \
  52                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  53                 if (__tp_it_probe_ptr) {                                \
  54                         do {                                            \
  55                                 __tp_it_func = __tp_it_probe_ptr->func; \
  56                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  57                                 URCU_FORCE_CAST(void(*)(proto), __tp_it_func)(args); \
  58                         } while ((++__tp_it_probe_ptr)->func);          \
  59                 }                                                       \
  60                 rcu_read_unlock();                                      \
  61         } while (0)
  62
  63 #define TP_PARAMS(args...)      args
  64 #define TP_PROTO(args...)       args
  65 #define TP_VARS(args...)        args
  66
  67 #define __CHECK_TRACE(provider, name, proto, args)                      \
  68         do {                                                            \
  69                 if (caa_unlikely(__tracepoint_##provider##___##name.state))     \
  70                         __DO_TRACE(&__tracepoint_##provider##___##name, \
  71                                 TP_PROTO(proto), TP_VARS(args));        \
  72         } while (0)
  73
  74 /*
  75  * Make sure the alignment of the structure in the __tracepoints section will
  76  * not add unwanted padding between the beginning of the section and the
  77  * structure. Force alignment to the same alignment as the section start.
  78  */
  79 #define __DECLARE_TRACEPOINT(provider, name, proto, args, data_proto, data_args)        \
  80         extern struct tracepoint __tracepoint_##provider##___##name;    \
  81         static inline void __trace_##provider##___##name(proto)         \
  82         {                                                               \
  83                 __CHECK_TRACE(provider, name, TP_PROTO(data_proto),     \
  84                               TP_VARS(data_args));                      \
  85         }                                                               \
  86         static inline int                                               \
  87         __register_trace_##provider##___##name(void (*probe)(data_proto), void *data)   \
  88         {                                                               \
  89                 return __tracepoint_probe_register(#provider ":" #name, (void *) probe, \
  90                                                  data);                 \
  91         }                                                               \
  92         static inline int                                               \
  93         __unregister_trace_##provider##___##name(void (*probe)(data_proto), void *data) \
  94         {                                                               \
  95                 return __tracepoint_probe_unregister(#provider ":" #name, (void *) probe, \
  96                                                    data);               \
  97         }
  98
  99 /*
 100  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 101  * (void). "void" is a special value in a function prototype and can
 102  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 103  * macro adds a data element at the beginning of the prototype,
 104  * we need a way to differentiate "(void *data, proto)" from
 105  * "(void *data, void)". The second prototype is invalid.
 106  *
 107  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 108  * and "void *__tp_cb_data" as the callback prototype.
 109  *
 110  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 111  * "void *__tp_cb_data, proto" as the callback prototype.
 112  */
 113 #define _DECLARE_TRACEPOINT_NOARGS(provider, name)                      \
 114         __DECLARE_TRACEPOINT(provider, name, void, , void *__tp_cb_data, __tp_cb_data)
 115
 116 #define _DECLARE_TRACEPOINT(provider, name, proto, args)                \
 117         __DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args), \
 118                         TP_PARAMS(void *__tp_cb_data, proto),           \
 119                         TP_PARAMS(__tp_cb_data, args))
 120
 121 /*
 122  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 123  * the pointer, allowing PIC code.
 124  */
 125 #define _DEFINE_TRACEPOINT(provider, name)                              \
 126         static const char __tpstrtab_##provider##___##name[]            \
 127         __attribute__((section("__tracepoints_strings"))) =             \
 128                 #provider ":" #name;                                    \
 129         struct tracepoint __tracepoint_##provider##___##name            \
 130         __attribute__((section("__tracepoints"))) =                     \
 131                 { __tpstrtab_##provider##___##name, 0, NULL };          \
 132         static struct tracepoint * __tracepoint_ptr_##provider##___##name       \
 133         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 134                 &__tracepoint_##provider##___##name;
 135
 136
 137 #define __register_tracepoint(provider, name, probe, data)              \
 138                 __register_trace_##provider##___##name(probe, data)
 139 #define __unregister_tracepoint(provider, name, probe, data)            \
 140                 __unregister_trace_##provider##___##name(probe, data)
 141
 142 /*
 143  * Connect a probe to a tracepoint.
 144  * Internal API.
 145  */
 146 extern
 147 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 148
 149 /*
 150  * Disconnect a probe from a tracepoint.
 151  * Internal API.
 152  */
 153 extern
 154 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 155
 156 extern
 157 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 158                             int tracepoints_count);
 159 extern
 160 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 161
 162 /*
 163  * These weak symbols, the constructor, and destructor take care of
 164  * registering only _one_ instance of the tracepoints per shared-ojbect
 165  * (or for the whole main program).
 166  */
 167 extern struct tracepoint * const __start___tracepoints_ptrs[]
 168         __attribute__((weak, visibility("hidden")));
 169 extern struct tracepoint * const __stop___tracepoints_ptrs[]
 170         __attribute__((weak, visibility("hidden")));
 171 int __tracepoint_registered
 172         __attribute__((weak, visibility("hidden")));
 173
 174 static void __attribute__((constructor)) __tracepoints__init(void)
 175 {
 176         if (__tracepoint_registered++)
 177                 return;
 178         tracepoint_register_lib(__start___tracepoints_ptrs,
 179                                 __stop___tracepoints_ptrs -
 180                                 __start___tracepoints_ptrs);
 181 }
 182
 183 static void __attribute__((destructor)) __tracepoints__destroy(void)
 184 {
 185         if (--__tracepoint_registered)
 186                 return;
 187         tracepoint_unregister_lib(__start___tracepoints_ptrs);
 188 }
 189
 190 #ifndef TRACEPOINT_EVENT
 191 /*
 192  * Usage of the TRACEPOINT_EVENT macro:
 193  *
 194  * In short, an example:
 195  *
 196  * TRACEPOINT_EVENT(< [com_company_]project[_component] >, < event >,
 197  *     TP_PROTO(int arg0, void *arg1, char *string, size_t strlen,
 198  *              long *arg4, size_t arg4_len),
 199  *     TP_VARS(arg0, arg1, string, strlen, arg4, arg4_len),
 200  *     TP_FIELDS(
 201  *
 202  *         * Integer, printed in base 10 *
 203  *         ctf_integer(int, field_a, arg0)
 204  *
 205  *         * Integer, printed with 0x base 16 *
 206  *         ctf_integer_hex(unsigned long, field_d, arg1)
 207  *
 208  *         * Array Sequence, printed as UTF8-encoded array of bytes *
 209  *         ctf_array_text(char, field_b, string, FIXED_LEN)
 210  *         ctf_sequence_text(char, field_c, string, size_t, strlen)
 211  *
 212  *         * String, printed as UTF8-encoded string *
 213  *         ctf_string(field_e, string)
 214  *
 215  *         * Array sequence of signed integer values *
 216  *         ctf_array(long, field_f, arg4, FIXED_LEN4)
 217  *         ctf_sequence(long, field_g, arg4, size_t, arg4_len)
 218  *     )
 219  * )
 220  *
 221  * In more detail:
 222  *
 223  * We define a tracepoint, its arguments, and its 'fast binary record'
 224  * layout.
 225  *
 226  * Firstly, name your tracepoint via TRACEPOINT_EVENT(provider, name,
 227  *
 228  * The provider and name should be a proper C99 identifier.
 229  * The "provider" and "name" MUST follow these rules to ensure no
 230  * namespace clash occurs:
 231  *
 232  * For projects (applications and libraries) for which an entity
 233  * specific to the project controls the source code and thus its
 234  * tracepoints (typically with a scope larger than a single company):
 235  *
 236  * either:
 237  *   project_component, event
 238  * or:
 239  *   project, event
 240  *
 241  * Where "project" is the name of the project,
 242  *       "component" is the name of the project component (which may
 243  *       include several levels of sub-components, e.g.
 244  *       ...component_subcomponent_...) where the tracepoint is located
 245  *       (optional),
 246  *       "event" is the name of the tracepoint event.
 247  *
 248  * For projects issued from a single company wishing to advertise that
 249  * the company controls the source code and thus the tracepoints, the
 250  * "com_" prefix should be used:
 251  *
 252  * either:
 253  *   com_company_project_component, event
 254  * or:
 255  *   com_company_project, event
 256  *
 257  * Where "company" is the name of the company,
 258  *       "project" is the name of the project,
 259  *       "component" is the name of the project component (which may
 260  *       include several levels of sub-components, e.g.
 261  *       ...component_subcomponent_...) where the tracepoint is located
 262  *       (optional),
 263  *       "event" is the name of the tracepoint event.
 264  *
 265  * the provider:event identifier is limited to 127 characters.
 266  *
 267  * As an example, let's consider a user-space application "someproject"
 268  * that would have an internal thread scheduler:
 269  *
 270  *  TRACEPOINT_EVENT(someproject_sched, switch,
 271  *
 272  *      *
 273  *      * A function has a regular function arguments
 274  *      * prototype, declare it via TP_PROTO():
 275  *      *
 276  *
 277  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 278  *               struct task_struct *next),
 279  *
 280  *      *
 281  *      * Define the call signature of the 'function'.
 282  *      * (Design sidenote: we use this instead of a
 283  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 284  *      *
 285  *
 286  *      TP_VARS(rq, prev, next),
 287  *
 288  *      *
 289  *      * Fast binary tracing: define the trace record via
 290  *      * TP_FIELDS(). You can think about it like a
 291  *      * regular C structure local variable definition.
 292  *      *
 293  *      * This is how the trace record is structured and will
 294  *      * be saved into the ring buffer. These are the fields
 295  *      * that will be exposed to readers.
 296  *      *
 297  *      * ctf_integer(pid_t, prev_pid, prev->pid) is equivalent
 298  *      * to a standard declaraton:
 299  *      *
 300  *      *       pid_t prev_pid;
 301  *      *
 302  *      * followed by an assignment:
 303  *      *
 304  *      *       prev_pid = prev->pid;
 305  *      *
 306  *      * ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN) is
 307  *      * equivalent to:
 308  *      *
 309  *      *       char prev_comm[TASK_COMM_LEN];
 310  *      *
 311  *      * followed by an assignment:
 312  *      *
 313  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 314  *      *
 315  *
 316  *      TP_FIELDS(
 317  *              ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN)
 318  *              ctf_integer(pid_t, prev_pid,  prev->pid)
 319  *              ctf_integer(int, prev_prio, prev->prio)
 320  *              ctf_array(char, next_comm, next->comm, TASK_COMM_LEN)
 321  *              ctf_integer(pid_t, next_pid,  next->pid)
 322  *              ctf_integer(int, next_prio, next->prio)
 323  *      )
 324  * )
 325  *
 326  * Do _NOT_ add comma (,) nor semicolon (;) after the TRACEPOINT_EVENT
 327  * declaration.
 328  *
 329  * The TRACEPOINT_SYSTEM must be defined when declaring a
 330  * TRACEPOINT_EVENT. See ust/tracepoint-event.h for information about
 331  * usage of other macros controlling TRACEPOINT_EVENT.
 332  */
 333
 334 #define TRACEPOINT_EVENT(provider, name, proto, args, fields)           \
 335         _DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args))
 336
 337 #define TRACEPOINT_EVENT_CLASS(provider, name, proto, args, fields)
 338 #define TRACEPOINT_EVENT_INSTANCE(provider, template, name, proto, args)\
 339         _DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args))
 340
 341 /*
 342  * Declaration of tracepoints that take 0 argument.
 343  */
 344 #define TRACEPOINT_EVENT_NOARGS(provider, name, fields)                 \
 345         _DECLARE_TRACEPOINT_NOARGS(provider, name)
 346
 347 #define TRACEPOINT_EVENT_CLASS_NOARGS(provider, name, fields)
 348 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(provider, template, name)      \
 349         _DECLARE_TRACEPOINT_NOARGS(provider, name)
 350
 351 #endif /* #ifndef TRACEPOINT_EVENT */
 352
 353 #ifndef TRACEPOINT_LOGLEVEL
 354
 355 /*
 356  * Tracepoint Loglevel Declaration Facility
 357  *
 358  * This is a place-holder the tracepoint loglevel declaration,
 359  * overridden by the tracer implementation.
 360  *
 361  * Typical use of these loglevels:
 362  *
 363  * 1) Declare the mapping between loglevel names and an integer values
 364  *    within TRACEPOINT_LOGLEVEL_ENUM, using TP_LOGLEVEL for each tuple.
 365  *    Do _NOT_ add comma (,) nor semicolon (;) between the
 366  *    TRACEPOINT_LOGLEVEL_ENUM entries. Do _NOT_ add comma (,) nor
 367  *    semicolon (;) after the TRACEPOINT_LOGLEVEL_ENUM declaration.  The
 368  *    name should be a proper C99 identifier.
 369  *
 370  *      TRACEPOINT_LOGLEVEL_ENUM(
 371  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 372  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 373  *              ...
 374  *      )
 375  *
 376  *    e.g.:
 377  *
 378  *      TRACEPOINT_LOGLEVEL_ENUM(
 379  *              TP_LOGLEVEL(LOG_EMERG,   0)
 380  *              TP_LOGLEVEL(LOG_ALERT,   1)
 381  *              TP_LOGLEVEL(LOG_CRIT,    2)
 382  *              TP_LOGLEVEL(LOG_ERR,     3)
 383  *              TP_LOGLEVEL(LOG_WARNING, 4)
 384  *              TP_LOGLEVEL(LOG_NOTICE,  5)
 385  *              TP_LOGLEVEL(LOG_INFO,    6)
 386  *              TP_LOGLEVEL(LOG_DEBUG,   7)
 387  *      )
 388  *
 389  * 2) Then, declare tracepoint loglevels for tracepoints. A
 390  *    TRACEPOINT_EVENT should be declared prior to the the
 391  *    TRACEPOINT_LOGLEVEL for a given tracepoint name. The first field
 392  *    is the name of the tracepoint, the second field is the loglevel
 393  *    name.
 394  *
 395  *      TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, < event >,
 396  *              < loglevel_name >)
 397  *
 398  * The TRACEPOINT_SYSTEM must be defined when declaring a
 399  * TRACEPOINT_LOGLEVEL_ENUM and TRACEPOINT_LOGLEVEL. The tracepoint
 400  * loglevel enumeration apply to the entire TRACEPOINT_SYSTEM. Only one
 401  * tracepoint loglevel enumeration should be declared per tracepoint
 402  * system.
 403  */
 404
 405 #define TRACEPOINT_LOGLEVEL_ENUM()
 406 #define TRACEPOINT_LOGLEVEL(name, loglevel)
 407
 408 #endif /* #ifndef TRACEPOINT_LOGLEVEL */
 409
 410 #ifdef __cplusplus
 411 }
 412 #endif
 413
 414 #endif /* _LTTNG_TRACEPOINT_H */