include/ust/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 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  * These weak symbols, the constructor, and destructor take care of
  50  * registering only _one_ instance of the tracepoints per shared-ojbect
  51  * (or for the whole main program).
  52  * The dummy tracepoint entry ensures that the start/stop pointers get
  53  * initialized by the linker when no tracepoints are present in a
  54  * shared-object (or main program).
  55  */
  56 extern struct tracepoint * const __start___tracepoints_ptrs[]
  57         __attribute__((weak, visibility("hidden")));
  58 extern struct tracepoint * const __stop___tracepoints_ptrs[]
  59         __attribute__((weak, visibility("hidden")));
  60 int __tracepoint_registered
  61         __attribute__((weak, visibility("hidden")));
  62
  63 static void __attribute__((constructor)) __tracepoints__init(void)
  64 {
  65         if (__tracepoint_registered++)
  66                 return;
  67         tracepoint_register_lib(__start___tracepoints_ptrs,
  68                                 __stop___tracepoints_ptrs -
  69                                 __start___tracepoints_ptrs);
  70 }
  71
  72 static void __attribute__((destructor)) __tracepoints__destroy(void)
  73 {
  74         if (--__tracepoint_registered)
  75                 return;
  76         tracepoint_unregister_lib(__start___tracepoints_ptrs);
  77 }
  78
  79 /*
  80  * it_func[0] is never NULL because there is at least one element in the array
  81  * when the array itself is non NULL.
  82  */
  83 #define __DO_TRACE(tp, proto, args)                                     \
  84         do {                                                            \
  85                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  86                 void *__tp_it_func;                                     \
  87                 void *__tp_cb_data;                                     \
  88                                                                         \
  89                 rcu_read_lock();                                        \
  90                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  91                 if (__tp_it_probe_ptr) {                                \
  92                         do {                                            \
  93                                 __tp_it_func = __tp_it_probe_ptr->func; \
  94                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  95                                 ((void(*)(proto))__tp_it_func)(args);   \
  96                         } while ((++__tp_it_probe_ptr)->func);          \
  97                 }                                                       \
  98                 rcu_read_unlock();                                      \
  99         } while (0)
 100
 101 #define TP_PARAMS(args...)      args
 102 #define TP_PROTO(args...)       args
 103 #define TP_ARGS(args...)        args
 104
 105 #define __CHECK_TRACE(name, proto, args)                                \
 106         do {                                                            \
 107                 if (unlikely(__tracepoint_##name.state))                \
 108                         __DO_TRACE(&__tracepoint_##name,                \
 109                                 TP_PROTO(proto), TP_ARGS(args));        \
 110         } while (0)
 111
 112 /*
 113  * Make sure the alignment of the structure in the __tracepoints section will
 114  * not add unwanted padding between the beginning of the section and the
 115  * structure. Force alignment to the same alignment as the section start.
 116  */
 117 #define __DECLARE_TRACEPOINT(name, proto, args, data_proto, data_args)  \
 118         extern struct tracepoint __tracepoint_##name;                   \
 119         static inline void __trace_##name(proto)                        \
 120         {                                                               \
 121                 __CHECK_TRACE(name, TP_PROTO(data_proto),               \
 122                               TP_ARGS(data_args));                      \
 123         }                                                               \
 124         static inline int                                               \
 125         __register_trace_##name(void (*probe)(data_proto), void *data)  \
 126         {                                                               \
 127                 return __tracepoint_probe_register(#name, (void *)probe,\
 128                                                  data);                 \
 129                                                                         \
 130         }                                                               \
 131         static inline int                                               \
 132         __unregister_trace_##name(void (*probe)(data_proto), void *data)\
 133         {                                                               \
 134                 return __tracepoint_probe_unregister(#name, (void *)probe, \
 135                                                    data);               \
 136         }
 137
 138 /*
 139  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 140  * (void). "void" is a special value in a function prototype and can
 141  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 142  * macro adds a data element at the beginning of the prototype,
 143  * we need a way to differentiate "(void *data, proto)" from
 144  * "(void *data, void)". The second prototype is invalid.
 145  *
 146  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 147  * and "void *__tp_cb_data" as the callback prototype.
 148  *
 149  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 150  * "void *__tp_cb_data, proto" as the callback prototype.
 151  */
 152 #define _DECLARE_TRACEPOINT_NOARGS(name)                                \
 153         __DECLARE_TRACEPOINT(name, void, , void *__tp_cb_data, __tp_cb_data)
 154
 155 #define _DECLARE_TRACEPOINT(name, proto, args)                          \
 156         __DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args),   \
 157                         TP_PARAMS(void *__tp_cb_data, proto),           \
 158                         TP_PARAMS(__tp_cb_data, args))
 159
 160 /*
 161  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 162  * the pointer, allowing PIC code.
 163  */
 164 #define _DEFINE_TRACEPOINT(name)                                        \
 165         static const char __tpstrtab_##name[]                           \
 166         __attribute__((section("__tracepoints_strings"))) = #name;      \
 167         struct tracepoint __tracepoint_##name                           \
 168         __attribute__((section("__tracepoints"))) =                     \
 169                 { __tpstrtab_##name, 0, NULL };                         \
 170         static struct tracepoint * __tracepoint_ptr_##name              \
 171         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 172                 &__tracepoint_##name;
 173
 174
 175 #define __register_tracepoint(name, probe, data)                        \
 176                 __register_trace_##name(probe, data)
 177 #define __unregister_tracepoint(name, probe, data)                      \
 178                 __unregister_trace_##name(probe, data)
 179
 180 /*
 181  * Connect a probe to a tracepoint.
 182  * Internal API.
 183  */
 184 extern
 185 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 186
 187 /*
 188  * Disconnect a probe from a tracepoint.
 189  * Internal API.
 190  */
 191 extern
 192 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 193
 194 extern
 195 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 196                             int tracepoints_count);
 197 extern
 198 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 199
 200
 201 #ifndef TRACEPOINT_EVENT
 202 /*
 203  * Usage of the TRACEPOINT_EVENT macro:
 204  *
 205  * In short, an example:
 206  *
 207  * TRACEPOINT_EVENT(< [com_company_]project_[component_]event >,
 208  *     TP_PROTO(int arg0, void *arg1, char *string, size_t strlen,
 209  *              long *arg4, size_t arg4_len),
 210  *     TP_ARGS(arg0, arg1, string, strlen, arg4, arg4_len),
 211  *     TP_FIELDS(
 212  *
 213  *         * Integer, printed in base 10 *
 214  *         ctf_integer(int, field_a, arg0)
 215  *
 216  *         * Integer, printed with 0x base 16 *
 217  *         ctf_integer_hex(unsigned long, field_d, arg1)
 218  *
 219  *         * Array Sequence, printed as UTF8-encoded array of bytes *
 220  *         ctf_array_text(char, field_b, string, FIXED_LEN)
 221  *         ctf_sequence_text(char, field_c, string, size_t, strlen)
 222  *
 223  *         * String, printed as UTF8-encoded string *
 224  *         ctf_string(field_e, string)
 225  *
 226  *         * Array sequence of signed integer values *
 227  *         ctf_array(long, field_f, arg4, FIXED_LEN4)
 228  *         ctf_sequence(long, field_g, arg4, size_t, arg4_len)
 229  *     )
 230  * )
 231  *
 232  * In more detail:
 233  *
 234  * We define a tracepoint, its arguments, and its 'fast binary record'
 235  * layout.
 236  *
 237  * Firstly, name your tracepoint via TRACEPOINT_EVENT(name,
 238  *
 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
 336 #define TRACEPOINT_EVENT(name, proto, args, fields)                     \
 337         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 338
 339 #define TRACEPOINT_EVENT_CLASS(name, proto, args, fields)
 340 #define TRACEPOINT_EVENT_INSTANCE(template, name, proto, args)          \
 341         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 342
 343 /*
 344  * Declaration of tracepoints that take 0 argument.
 345  */
 346 #define TRACEPOINT_EVENT_NOARGS(name, fields)                           \
 347         _DECLARE_TRACEPOINT_NOARGS(name)
 348
 349 #define TRACEPOINT_EVENT_CLASS_NOARGS(name, fields)
 350 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(template, name)                \
 351         _DECLARE_TRACEPOINT_NOARGS(name)
 352
 353 #endif /* #ifndef TRACEPOINT_EVENT */
 354
 355 #endif /* _UST_TRACEPOINT_H */