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  * it_func[0] is never NULL because there is at least one element in the array
  50  * when the array itself is non NULL.
  51  */
  52 #define __DO_TRACE(tp, proto, args)                                     \
  53         do {                                                            \
  54                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  55                 void *__tp_it_func;                                     \
  56                 void *__tp_cb_data;                                     \
  57                                                                         \
  58                 rcu_read_lock();                                        \
  59                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  60                 if (__tp_it_probe_ptr) {                                \
  61                         do {                                            \
  62                                 __tp_it_func = __tp_it_probe_ptr->func; \
  63                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  64                                 ((void(*)(proto))__tp_it_func)(args);   \
  65                         } while ((++__tp_it_probe_ptr)->func);          \
  66                 }                                                       \
  67                 rcu_read_unlock();                                      \
  68         } while (0)
  69
  70 #define TP_PARAMS(args...)      args
  71 #define TP_PROTO(args...)       args
  72 #define TP_ARGS(args...)        args
  73
  74 #define __CHECK_TRACE(name, proto, args)                                \
  75         do {                                                            \
  76                 if (unlikely(__tracepoint_##name.state))                \
  77                         __DO_TRACE(&__tracepoint_##name,                \
  78                                 TP_PROTO(proto), TP_ARGS(args));        \
  79         } while (0)
  80
  81 /*
  82  * Make sure the alignment of the structure in the __tracepoints section will
  83  * not add unwanted padding between the beginning of the section and the
  84  * structure. Force alignment to the same alignment as the section start.
  85  */
  86 #define __DECLARE_TRACEPOINT(name, proto, args, data_proto, data_args)  \
  87         extern struct tracepoint __tracepoint_##name;                   \
  88         static inline void __trace_##name(proto)                        \
  89         {                                                               \
  90                 __CHECK_TRACE(name, TP_PROTO(data_proto),               \
  91                               TP_ARGS(data_args));                      \
  92         }                                                               \
  93         static inline int                                               \
  94         __register_trace_##name(void (*probe)(data_proto), void *data)  \
  95         {                                                               \
  96                 return __tracepoint_probe_register(#name, (void *)probe,\
  97                                                  data);                 \
  98                                                                         \
  99         }                                                               \
 100         static inline int                                               \
 101         __unregister_trace_##name(void (*probe)(data_proto), void *data)\
 102         {                                                               \
 103                 return __tracepoint_probe_unregister(#name, (void *)probe, \
 104                                                    data);               \
 105         }
 106
 107 /*
 108  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 109  * (void). "void" is a special value in a function prototype and can
 110  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 111  * macro adds a data element at the beginning of the prototype,
 112  * we need a way to differentiate "(void *data, proto)" from
 113  * "(void *data, void)". The second prototype is invalid.
 114  *
 115  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 116  * and "void *__tp_cb_data" as the callback prototype.
 117  *
 118  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 119  * "void *__tp_cb_data, proto" as the callback prototype.
 120  */
 121 #define _DECLARE_TRACEPOINT_NOARGS(name)                                \
 122         __DECLARE_TRACEPOINT(name, void, , void *__tp_cb_data, __tp_cb_data)
 123
 124 #define _DECLARE_TRACEPOINT(name, proto, args)                          \
 125         __DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args),   \
 126                         TP_PARAMS(void *__tp_cb_data, proto),           \
 127                         TP_PARAMS(__tp_cb_data, args))
 128
 129 /*
 130  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 131  * the pointer, allowing PIC code.
 132  */
 133 #define _DEFINE_TRACEPOINT(name)                                        \
 134         static const char __tpstrtab_##name[]                           \
 135         __attribute__((section("__tracepoints_strings"))) = #name;      \
 136         struct tracepoint __tracepoint_##name                           \
 137         __attribute__((section("__tracepoints"))) =                     \
 138                 { __tpstrtab_##name, 0, NULL };                         \
 139         static struct tracepoint * __tracepoint_ptr_##name              \
 140         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 141                 &__tracepoint_##name;
 142
 143
 144 #define __register_tracepoint(name, probe, data)                        \
 145                 __register_trace_##name(probe, data)
 146 #define __unregister_tracepoint(name, probe, data)                      \
 147                 __unregister_trace_##name(probe, data)
 148
 149 /*
 150  * Connect a probe to a tracepoint.
 151  * Internal API.
 152  */
 153 extern
 154 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 155
 156 /*
 157  * Disconnect a probe from a tracepoint.
 158  * Internal API.
 159  */
 160 extern
 161 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 162
 163 extern
 164 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 165                             int tracepoints_count);
 166 extern
 167 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 168
 169 /*
 170  * These weak symbols, the constructor, and destructor take care of
 171  * registering only _one_ instance of the tracepoints per shared-ojbect
 172  * (or for the whole main program).
 173  * The dummy tracepoint entry ensures that the start/stop pointers get
 174  * initialized by the linker when no tracepoints are present in a
 175  * shared-object (or 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" MUST follow these rules to ensure no namespace clash
 239  * occurs:
 240  *
 241  * For projects (applications and libraries) for which an entity
 242  * specific to the project controls the source code and thus its
 243  * tracepoints (typically with a scope larger than a single company):
 244  *
 245  * either:
 246  *   project_component_event
 247  * or:
 248  *   project_event
 249  *
 250  * Where "project" is the name of the project,
 251  *       "component" is the name of the project component (which may
 252  *       include several levels of sub-components, e.g.
 253  *       ...component_subcomponent_...) where the tracepoint is located
 254  *       (optional),
 255  *       "event" is the name of the tracepoint event.
 256  *
 257  * For projects issued from a single company wishing to advertise that
 258  * the company controls the source code and thus the tracepoints, the
 259  * "com_" prefix should be used:
 260  *
 261  * either:
 262  *   com_company_project_component_event
 263  * or:
 264  *   com_company_project_event
 265  *
 266  * Where "company" is the name of the company,
 267  *       "project" is the name of the project,
 268  *       "component" is the name of the project component (which may
 269  *       include several levels of sub-components, e.g.
 270  *       ...component_subcomponent_...) where the tracepoint is located
 271  *       (optional),
 272  *       "event" is the name of the tracepoint event.
 273  *
 274  *
 275  * As an example, let's consider a user-space application "someproject"
 276  * that would have an internal thread scheduler:
 277  *
 278  *  TRACEPOINT_EVENT(someproject_sched_switch,
 279  *
 280  *      *
 281  *      * A function has a regular function arguments
 282  *      * prototype, declare it via TP_PROTO():
 283  *      *
 284  *
 285  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 286  *               struct task_struct *next),
 287  *
 288  *      *
 289  *      * Define the call signature of the 'function'.
 290  *      * (Design sidenote: we use this instead of a
 291  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 292  *      *
 293  *
 294  *      TP_ARGS(rq, prev, next),
 295  *
 296  *      *
 297  *      * Fast binary tracing: define the trace record via
 298  *      * TP_FIELDS(). You can think about it like a
 299  *      * regular C structure local variable definition.
 300  *      *
 301  *      * This is how the trace record is structured and will
 302  *      * be saved into the ring buffer. These are the fields
 303  *      * that will be exposed to readers.
 304  *      *
 305  *      * ctf_integer(pid_t, prev_pid, prev->pid) is equivalent
 306  *      * to a standard declaraton:
 307  *      *
 308  *      *       pid_t prev_pid;
 309  *      *
 310  *      * followed by an assignment:
 311  *      *
 312  *      *       prev_pid = prev->pid;
 313  *      *
 314  *      * ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN) is
 315  *      * equivalent to:
 316  *      *
 317  *      *       char prev_comm[TASK_COMM_LEN];
 318  *      *
 319  *      * followed by an assignment:
 320  *      *
 321  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 322  *      *
 323  *
 324  *      TP_FIELDS(
 325  *              ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN)
 326  *              ctf_integer(pid_t, prev_pid,  prev->pid)
 327  *              ctf_integer(int, prev_prio, prev->prio)
 328  *              ctf_array(char, next_comm, next->comm, TASK_COMM_LEN)
 329  *              ctf_integer(pid_t, next_pid,  next->pid)
 330  *              ctf_integer(int, next_prio, next->prio)
 331  *      )
 332  * )
 333  */
 334
 335 #define TRACEPOINT_EVENT(name, proto, args, fields)                     \
 336         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 337
 338 #define TRACEPOINT_EVENT_CLASS(name, proto, args, fields)
 339 #define TRACEPOINT_EVENT_INSTANCE(template, name, proto, args)          \
 340         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 341
 342 /*
 343  * Declaration of tracepoints that take 0 argument.
 344  */
 345 #define TRACEPOINT_EVENT_NOARGS(name, fields)                           \
 346         _DECLARE_TRACEPOINT_NOARGS(name)
 347
 348 #define TRACEPOINT_EVENT_CLASS_NOARGS(name, fields)
 349 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(template, name)                \
 350         _DECLARE_TRACEPOINT_NOARGS(name)
 351
 352 #endif /* #ifndef TRACEPOINT_EVENT */
 353
 354 #endif /* _UST_TRACEPOINT_H */