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(provider, name, args...)     \
  51                 __trace_##provider##___##name(args)
  52
  53 /*
  54  * it_func[0] is never NULL because there is at least one element in the array
  55  * when the array itself is non NULL.
  56  */
  57 #define __DO_TRACE(tp, proto, args)                                     \
  58         do {                                                            \
  59                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  60                 void *__tp_it_func;                                     \
  61                 void *__tp_cb_data;                                     \
  62                                                                         \
  63                 rcu_read_lock();                                        \
  64                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  65                 if (__tp_it_probe_ptr) {                                \
  66                         do {                                            \
  67                                 __tp_it_func = __tp_it_probe_ptr->func; \
  68                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  69                                 URCU_FORCE_CAST(void(*)(proto), __tp_it_func)(args); \
  70                         } while ((++__tp_it_probe_ptr)->func);          \
  71                 }                                                       \
  72                 rcu_read_unlock();                                      \
  73         } while (0)
  74
  75 #define TP_PARAMS(args...)      args
  76 #define TP_PROTO(args...)       args
  77 #define TP_ARGS(args...)        args
  78
  79 #define __CHECK_TRACE(provider, name, proto, args)                      \
  80         do {                                                            \
  81                 if (caa_unlikely(__tracepoint_##provider##___##name.state))     \
  82                         __DO_TRACE(&__tracepoint_##provider##___##name, \
  83                                 TP_PROTO(proto), TP_ARGS(args));        \
  84         } while (0)
  85
  86 /*
  87  * Make sure the alignment of the structure in the __tracepoints section will
  88  * not add unwanted padding between the beginning of the section and the
  89  * structure. Force alignment to the same alignment as the section start.
  90  */
  91 #define __DECLARE_TRACEPOINT(provider, name, proto, args, data_proto, data_args)        \
  92         extern struct tracepoint __tracepoint_##provider##___##name;    \
  93         static inline void __trace_##provider##___##name(proto)         \
  94         {                                                               \
  95                 __CHECK_TRACE(provider, name, TP_PROTO(data_proto),     \
  96                               TP_ARGS(data_args));                      \
  97         }                                                               \
  98         static inline int                                               \
  99         __register_trace_##provider##___##name(void (*probe)(data_proto), void *data)   \
 100         {                                                               \
 101                 return __tracepoint_probe_register(#provider ":" #name, (void *) probe, \
 102                                                  data);                 \
 103         }                                                               \
 104         static inline int                                               \
 105         __unregister_trace_##provider##___##name(void (*probe)(data_proto), void *data) \
 106         {                                                               \
 107                 return __tracepoint_probe_unregister(#provider ":" #name, (void *) probe, \
 108                                                    data);               \
 109         }
 110
 111 /*
 112  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 113  * (void). "void" is a special value in a function prototype and can
 114  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 115  * macro adds a data element at the beginning of the prototype,
 116  * we need a way to differentiate "(void *data, proto)" from
 117  * "(void *data, void)". The second prototype is invalid.
 118  *
 119  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 120  * and "void *__tp_cb_data" as the callback prototype.
 121  *
 122  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 123  * "void *__tp_cb_data, proto" as the callback prototype.
 124  */
 125 #define _DECLARE_TRACEPOINT_NOARGS(provider, name)                      \
 126         __DECLARE_TRACEPOINT(provider, name, void, , void *__tp_cb_data, __tp_cb_data)
 127
 128 #define _DECLARE_TRACEPOINT(provider, name, proto, args)                \
 129         __DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args), \
 130                         TP_PARAMS(void *__tp_cb_data, proto),           \
 131                         TP_PARAMS(__tp_cb_data, args))
 132
 133 /*
 134  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 135  * the pointer, allowing PIC code.
 136  */
 137 #define _DEFINE_TRACEPOINT(provider, name)                              \
 138         static const char __tpstrtab_##provider##___##name[]            \
 139         __attribute__((section("__tracepoints_strings"))) =             \
 140                 #provider ":" #name;                                    \
 141         struct tracepoint __tracepoint_##provider##___##name            \
 142         __attribute__((section("__tracepoints"))) =                     \
 143                 { __tpstrtab_##provider##___##name, 0, NULL };          \
 144         static struct tracepoint * __tracepoint_ptr_##provider##___##name       \
 145         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 146                 &__tracepoint_##provider##___##name;
 147
 148
 149 #define __register_tracepoint(provider, name, probe, data)              \
 150                 __register_trace_##provider##___##name(probe, data)
 151 #define __unregister_tracepoint(provider, name, probe, data)            \
 152                 __unregister_trace_##provider##___##name(probe, data)
 153
 154 /*
 155  * Connect a probe to a tracepoint.
 156  * Internal API.
 157  */
 158 extern
 159 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 160
 161 /*
 162  * Disconnect a probe from a tracepoint.
 163  * Internal API.
 164  */
 165 extern
 166 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 167
 168 extern
 169 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 170                             int tracepoints_count);
 171 extern
 172 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 173
 174 /*
 175  * These weak symbols, the constructor, and destructor take care of
 176  * registering only _one_ instance of the tracepoints per shared-ojbect
 177  * (or for the whole main program).
 178  */
 179 extern struct tracepoint * const __start___tracepoints_ptrs[]
 180         __attribute__((weak, visibility("hidden")));
 181 extern struct tracepoint * const __stop___tracepoints_ptrs[]
 182         __attribute__((weak, visibility("hidden")));
 183 int __tracepoint_registered
 184         __attribute__((weak, visibility("hidden")));
 185
 186 static void __attribute__((constructor)) __tracepoints__init(void)
 187 {
 188         if (__tracepoint_registered++)
 189                 return;
 190         tracepoint_register_lib(__start___tracepoints_ptrs,
 191                                 __stop___tracepoints_ptrs -
 192                                 __start___tracepoints_ptrs);
 193 }
 194
 195 static void __attribute__((destructor)) __tracepoints__destroy(void)
 196 {
 197         if (--__tracepoint_registered)
 198                 return;
 199         tracepoint_unregister_lib(__start___tracepoints_ptrs);
 200 }
 201
 202 #ifndef TRACEPOINT_EVENT
 203 /*
 204  * Usage of the TRACEPOINT_EVENT macro:
 205  *
 206  * In short, an example:
 207  *
 208  * TRACEPOINT_EVENT(< [com_company_]project[_component] >, < event >,
 209  *     TP_PROTO(int arg0, void *arg1, char *string, size_t strlen,
 210  *              long *arg4, size_t arg4_len),
 211  *     TP_ARGS(arg0, arg1, string, strlen, arg4, arg4_len),
 212  *     TP_FIELDS(
 213  *
 214  *         * Integer, printed in base 10 *
 215  *         ctf_integer(int, field_a, arg0)
 216  *
 217  *         * Integer, printed with 0x base 16 *
 218  *         ctf_integer_hex(unsigned long, field_d, arg1)
 219  *
 220  *         * Array Sequence, printed as UTF8-encoded array of bytes *
 221  *         ctf_array_text(char, field_b, string, FIXED_LEN)
 222  *         ctf_sequence_text(char, field_c, string, size_t, strlen)
 223  *
 224  *         * String, printed as UTF8-encoded string *
 225  *         ctf_string(field_e, string)
 226  *
 227  *         * Array sequence of signed integer values *
 228  *         ctf_array(long, field_f, arg4, FIXED_LEN4)
 229  *         ctf_sequence(long, field_g, arg4, size_t, arg4_len)
 230  *     )
 231  * )
 232  *
 233  * In more detail:
 234  *
 235  * We define a tracepoint, its arguments, and its 'fast binary record'
 236  * layout.
 237  *
 238  * Firstly, name your tracepoint via TRACEPOINT_EVENT(provider, name,
 239  *
 240  * The provider and name should be a proper C99 identifier.
 241  * The "provider" and "name" MUST follow these rules to ensure no
 242  * namespace clash occurs:
 243  *
 244  * For projects (applications and libraries) for which an entity
 245  * specific to the project controls the source code and thus its
 246  * tracepoints (typically with a scope larger than a single company):
 247  *
 248  * either:
 249  *   project_component, event
 250  * or:
 251  *   project, event
 252  *
 253  * Where "project" is the name of the project,
 254  *       "component" is the name of the project component (which may
 255  *       include several levels of sub-components, e.g.
 256  *       ...component_subcomponent_...) where the tracepoint is located
 257  *       (optional),
 258  *       "event" is the name of the tracepoint event.
 259  *
 260  * For projects issued from a single company wishing to advertise that
 261  * the company controls the source code and thus the tracepoints, the
 262  * "com_" prefix should be used:
 263  *
 264  * either:
 265  *   com_company_project_component, event
 266  * or:
 267  *   com_company_project, event
 268  *
 269  * Where "company" is the name of the company,
 270  *       "project" is the name of the project,
 271  *       "component" is the name of the project component (which may
 272  *       include several levels of sub-components, e.g.
 273  *       ...component_subcomponent_...) where the tracepoint is located
 274  *       (optional),
 275  *       "event" is the name of the tracepoint event.
 276  *
 277  * the provider:event identifier is limited to 127 characters.
 278  *
 279  * As an example, let's consider a user-space application "someproject"
 280  * that would have an internal thread scheduler:
 281  *
 282  *  TRACEPOINT_EVENT(someproject_sched, switch,
 283  *
 284  *      *
 285  *      * A function has a regular function arguments
 286  *      * prototype, declare it via TP_PROTO():
 287  *      *
 288  *
 289  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 290  *               struct task_struct *next),
 291  *
 292  *      *
 293  *      * Define the call signature of the 'function'.
 294  *      * (Design sidenote: we use this instead of a
 295  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 296  *      *
 297  *
 298  *      TP_ARGS(rq, prev, next),
 299  *
 300  *      *
 301  *      * Fast binary tracing: define the trace record via
 302  *      * TP_FIELDS(). You can think about it like a
 303  *      * regular C structure local variable definition.
 304  *      *
 305  *      * This is how the trace record is structured and will
 306  *      * be saved into the ring buffer. These are the fields
 307  *      * that will be exposed to readers.
 308  *      *
 309  *      * ctf_integer(pid_t, prev_pid, prev->pid) is equivalent
 310  *      * to a standard declaraton:
 311  *      *
 312  *      *       pid_t prev_pid;
 313  *      *
 314  *      * followed by an assignment:
 315  *      *
 316  *      *       prev_pid = prev->pid;
 317  *      *
 318  *      * ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN) is
 319  *      * equivalent to:
 320  *      *
 321  *      *       char prev_comm[TASK_COMM_LEN];
 322  *      *
 323  *      * followed by an assignment:
 324  *      *
 325  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 326  *      *
 327  *
 328  *      TP_FIELDS(
 329  *              ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN)
 330  *              ctf_integer(pid_t, prev_pid,  prev->pid)
 331  *              ctf_integer(int, prev_prio, prev->prio)
 332  *              ctf_array(char, next_comm, next->comm, TASK_COMM_LEN)
 333  *              ctf_integer(pid_t, next_pid,  next->pid)
 334  *              ctf_integer(int, next_prio, next->prio)
 335  *      )
 336  * )
 337  *
 338  * Do _NOT_ add comma (,) nor semicolon (;) after the TRACEPOINT_EVENT
 339  * declaration.
 340  *
 341  * The TRACEPOINT_SYSTEM must be defined when declaring a
 342  * TRACEPOINT_EVENT. See ust/tracepoint-event.h for information about
 343  * usage of other macros controlling TRACEPOINT_EVENT.
 344  */
 345
 346 #define TRACEPOINT_EVENT(provider, name, proto, args, fields)           \
 347         _DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args))
 348
 349 #define TRACEPOINT_EVENT_CLASS(provider, name, proto, args, fields)
 350 #define TRACEPOINT_EVENT_INSTANCE(provider, template, name, proto, args)\
 351         _DECLARE_TRACEPOINT(provider, name, TP_PARAMS(proto), TP_PARAMS(args))
 352
 353 /*
 354  * Declaration of tracepoints that take 0 argument.
 355  */
 356 #define TRACEPOINT_EVENT_NOARGS(provider, name, fields)                 \
 357         _DECLARE_TRACEPOINT_NOARGS(provider, name)
 358
 359 #define TRACEPOINT_EVENT_CLASS_NOARGS(provider, name, fields)
 360 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(provider, template, name)      \
 361         _DECLARE_TRACEPOINT_NOARGS(provider, name)
 362
 363 #endif /* #ifndef TRACEPOINT_EVENT */
 364
 365 #ifndef TRACEPOINT_LOGLEVEL
 366
 367 /*
 368  * Tracepoint Loglevel Declaration Facility
 369  *
 370  * This is a place-holder the tracepoint loglevel declaration,
 371  * overridden by the tracer implementation.
 372  *
 373  * Typical use of these loglevels:
 374  *
 375  * 1) Declare the mapping between loglevel names and an integer values
 376  *    within TRACEPOINT_LOGLEVEL_ENUM, using TP_LOGLEVEL for each tuple.
 377  *    Do _NOT_ add comma (,) nor semicolon (;) between the
 378  *    TRACEPOINT_LOGLEVEL_ENUM entries. Do _NOT_ add comma (,) nor
 379  *    semicolon (;) after the TRACEPOINT_LOGLEVEL_ENUM declaration.  The
 380  *    name should be a proper C99 identifier.
 381  *
 382  *      TRACEPOINT_LOGLEVEL_ENUM(
 383  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 384  *              TP_LOGLEVEL( < loglevel_name >, < value > )
 385  *              ...
 386  *      )
 387  *
 388  *    e.g.:
 389  *
 390  *      TRACEPOINT_LOGLEVEL_ENUM(
 391  *              TP_LOGLEVEL(LOG_EMERG,   0)
 392  *              TP_LOGLEVEL(LOG_ALERT,   1)
 393  *              TP_LOGLEVEL(LOG_CRIT,    2)
 394  *              TP_LOGLEVEL(LOG_ERR,     3)
 395  *              TP_LOGLEVEL(LOG_WARNING, 4)
 396  *              TP_LOGLEVEL(LOG_NOTICE,  5)
 397  *              TP_LOGLEVEL(LOG_INFO,    6)
 398  *              TP_LOGLEVEL(LOG_DEBUG,   7)
 399  *      )
 400  *
 401  * 2) Then, declare tracepoint loglevels for tracepoints. A
 402  *    TRACEPOINT_EVENT should be declared prior to the the
 403  *    TRACEPOINT_LOGLEVEL for a given tracepoint name. The first field
 404  *    is the name of the tracepoint, the second field is the loglevel
 405  *    name.
 406  *
 407  *      TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, < event >,
 408  *              < loglevel_name >)
 409  *
 410  * The TRACEPOINT_SYSTEM must be defined when declaring a
 411  * TRACEPOINT_LOGLEVEL_ENUM and TRACEPOINT_LOGLEVEL. The tracepoint
 412  * loglevel enumeration apply to the entire TRACEPOINT_SYSTEM. Only one
 413  * tracepoint loglevel enumeration should be declared per tracepoint
 414  * system.
 415  */
 416
 417 #define TRACEPOINT_LOGLEVEL_ENUM()
 418 #define TRACEPOINT_LOGLEVEL(name, loglevel)
 419
 420 #endif /* #ifndef TRACEPOINT_LOGLEVEL */
 421
 422 #ifdef __cplusplus
 423 }
 424 #endif
 425
 426 #endif /* _UST_TRACEPOINT_H */