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  * Library should be made known to libust by declaring TRACEPOINT_LIB in
  50  * the source file. (Usually at the end of the file, in the outermost
  51  * scope).
  52  */
  53 #define TRACEPOINT_LIB                                                  \
  54         extern struct tracepoint * const __start___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
  55         extern struct tracepoint * const __stop___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
  56         static struct tracepoint * __tracepoint_ptr_dummy               \
  57         __attribute__((used, section("__tracepoints_ptrs")));           \
  58         static void __attribute__((constructor)) __tracepoints__init(void) \
  59         {                                                               \
  60                 tracepoint_register_lib(__start___tracepoints_ptrs,     \
  61                                         __stop___tracepoints_ptrs -     \
  62                                         __start___tracepoints_ptrs);    \
  63         }                                                               \
  64                                                                         \
  65         static void __attribute__((destructor)) __tracepoints__destroy(void) \
  66         {                                                               \
  67                 tracepoint_unregister_lib(__start___tracepoints_ptrs);  \
  68         }
  69
  70 /*
  71  * it_func[0] is never NULL because there is at least one element in the array
  72  * when the array itself is non NULL.
  73  */
  74 #define __DO_TRACE(tp, proto, args)                                     \
  75         do {                                                            \
  76                 struct tracepoint_probe *__tp_it_probe_ptr;             \
  77                 void *__tp_it_func;                                     \
  78                 void *__tp_cb_data;                                     \
  79                                                                         \
  80                 rcu_read_lock();                                        \
  81                 __tp_it_probe_ptr = rcu_dereference((tp)->probes);      \
  82                 if (__tp_it_probe_ptr) {                                \
  83                         do {                                            \
  84                                 __tp_it_func = __tp_it_probe_ptr->func; \
  85                                 __tp_cb_data = __tp_it_probe_ptr->data; \
  86                                 ((void(*)(proto))__tp_it_func)(args);   \
  87                         } while ((++__tp_it_probe_ptr)->func);          \
  88                 }                                                       \
  89                 rcu_read_unlock();                                      \
  90         } while (0)
  91
  92 #define TP_PARAMS(args...)      args
  93 #define TP_PROTO(args...)       args
  94 #define TP_ARGS(args...)        args
  95
  96 #define __CHECK_TRACE(name, proto, args)                                \
  97         do {                                                            \
  98                 if (unlikely(__tracepoint_##name.state))                \
  99                         __DO_TRACE(&__tracepoint_##name,                \
 100                                 TP_PROTO(proto), TP_ARGS(args));        \
 101         } while (0)
 102
 103 /*
 104  * Make sure the alignment of the structure in the __tracepoints section will
 105  * not add unwanted padding between the beginning of the section and the
 106  * structure. Force alignment to the same alignment as the section start.
 107  */
 108 #define __DECLARE_TRACEPOINT(name, proto, args, data_proto, data_args)  \
 109         extern struct tracepoint __tracepoint_##name;                   \
 110         static inline void __trace_##name(proto)                        \
 111         {                                                               \
 112                 __CHECK_TRACE(name, TP_PROTO(data_proto),               \
 113                               TP_ARGS(data_args));                      \
 114         }                                                               \
 115         static inline int                                               \
 116         __register_trace_##name(void (*probe)(data_proto), void *data)  \
 117         {                                                               \
 118                 return __tracepoint_probe_register(#name, (void *)probe,\
 119                                                  data);                 \
 120                                                                         \
 121         }                                                               \
 122         static inline int                                               \
 123         __unregister_trace_##name(void (*probe)(data_proto), void *data)\
 124         {                                                               \
 125                 return __tracepoint_probe_unregister(#name, (void *)probe, \
 126                                                    data);               \
 127         }
 128
 129 /*
 130  * The need for the _DECLARE_TRACEPOINT_NOARGS() is to handle the prototype
 131  * (void). "void" is a special value in a function prototype and can
 132  * not be combined with other arguments. Since the DECLARE_TRACEPOINT()
 133  * macro adds a data element at the beginning of the prototype,
 134  * we need a way to differentiate "(void *data, proto)" from
 135  * "(void *data, void)". The second prototype is invalid.
 136  *
 137  * DECLARE_TRACEPOINT_NOARGS() passes "void" as the tracepoint prototype
 138  * and "void *__tp_cb_data" as the callback prototype.
 139  *
 140  * DECLARE_TRACEPOINT() passes "proto" as the tracepoint protoype and
 141  * "void *__tp_cb_data, proto" as the callback prototype.
 142  */
 143 #define _DECLARE_TRACEPOINT_NOARGS(name)                                \
 144         __DECLARE_TRACEPOINT(name, void, , void *__tp_cb_data, __tp_cb_data)
 145
 146 #define _DECLARE_TRACEPOINT(name, proto, args)                          \
 147         __DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args),   \
 148                         TP_PARAMS(void *__tp_cb_data, proto),           \
 149                         TP_PARAMS(__tp_cb_data, args))
 150
 151 /*
 152  * __tracepoints_ptrs section is not const (read-only) to let the linker update
 153  * the pointer, allowing PIC code.
 154  */
 155 #define _DEFINE_TRACEPOINT(name)                                        \
 156         static const char __tpstrtab_##name[]                           \
 157         __attribute__((section("__tracepoints_strings"))) = #name;      \
 158         struct tracepoint __tracepoint_##name                           \
 159         __attribute__((section("__tracepoints"))) =                     \
 160                 { __tpstrtab_##name, 0, NULL };                         \
 161         static struct tracepoint * __tracepoint_ptr_##name              \
 162         __attribute__((used, section("__tracepoints_ptrs"))) =          \
 163                 &__tracepoint_##name;
 164
 165
 166 #define __register_tracepoint(name, probe, data)                        \
 167                 __register_trace_##name(probe, data)
 168 #define __unregister_tracepoint(name, probe, data)                      \
 169                 __unregister_trace_##name(probe, data)
 170
 171 /*
 172  * Connect a probe to a tracepoint.
 173  * Internal API.
 174  */
 175 extern
 176 int __tracepoint_probe_register(const char *name, void *probe, void *data);
 177
 178 /*
 179  * Disconnect a probe from a tracepoint.
 180  * Internal API.
 181  */
 182 extern
 183 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 184
 185 struct tracepoint_lib {
 186         struct tracepoint * const *tracepoints_start;
 187         int tracepoints_count;
 188         struct cds_list_head list;
 189 };
 190
 191 extern
 192 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
 193                             int tracepoints_count);
 194 extern
 195 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 196
 197
 198 #ifndef TRACEPOINT_EVENT
 199 /*
 200  * Usage of the TRACEPOINT_EVENT macro:
 201  *
 202  * In short, an example:
 203  *
 204  * TRACEPOINT_EVENT(< [com_company_]project_[component_]event >,
 205  *     TP_PROTO(int arg0, void *arg1, char *string, size_t strlen,
 206  *              long *arg4, size_t arg4_len),
 207  *     TP_ARGS(arg0, arg1, string, strlen, arg4, arg4_len),
 208  *     TP_FIELDS(
 209  *
 210  *         * Integer, printed in base 10 *
 211  *         ctf_integer(int, field_a, arg0)
 212  *
 213  *         * Integer, printed with 0x base 16 *
 214  *         ctf_integer_hex(unsigned long, field_d, arg1)
 215  *
 216  *         * Array Sequence, printed as UTF8-encoded array of bytes *
 217  *         ctf_array_text(char, field_b, string, FIXED_LEN)
 218  *         ctf_sequence_text(char, field_c, string, size_t, strlen)
 219  *
 220  *         * String, printed as UTF8-encoded string *
 221  *         ctf_string(field_e, string)
 222  *
 223  *         * Array sequence of signed integer values *
 224  *         ctf_array(long, field_f, arg4, FIXED_LEN4)
 225  *         ctf_sequence(long, field_g, arg4, size_t, arg4_len)
 226  *     )
 227  * )
 228  *
 229  * In more detail:
 230  *
 231  * We define a tracepoint, its arguments, and its 'fast binary record'
 232  * layout.
 233  *
 234  * Firstly, name your tracepoint via TRACEPOINT_EVENT(name,
 235  *
 236  * The "name" MUST follow these rules to ensure no namespace clash
 237  * occurs:
 238  *
 239  * For projects (applications and libraries) for which an entity
 240  * specific to the project controls the source code and thus its
 241  * tracepoints (typically with a scope larger than a single company):
 242  *
 243  * either:
 244  *   project_component_event
 245  * or:
 246  *   project_event
 247  *
 248  * Where "project" is the name of the project,
 249  *       "component" is the name of the project component (which may
 250  *       include several levels of sub-components, e.g.
 251  *       ...component_subcomponent_...) where the tracepoint is located
 252  *       (optional),
 253  *       "event" is the name of the tracepoint event.
 254  *
 255  * For projects issued from a single company wishing to advertise that
 256  * the company controls the source code and thus the tracepoints, the
 257  * "com_" prefix should be used:
 258  *
 259  * either:
 260  *   com_company_project_component_event
 261  * or:
 262  *   com_company_project_event
 263  *
 264  * Where "company" is the name of the company,
 265  *       "project" is the name of the project,
 266  *       "component" is the name of the project component (which may
 267  *       include several levels of sub-components, e.g.
 268  *       ...component_subcomponent_...) where the tracepoint is located
 269  *       (optional),
 270  *       "event" is the name of the tracepoint event.
 271  *
 272  *
 273  * As an example, let's consider a user-space application "someproject"
 274  * that would have an internal thread scheduler:
 275  *
 276  *  TRACEPOINT_EVENT(someproject_sched_switch,
 277  *
 278  *      *
 279  *      * A function has a regular function arguments
 280  *      * prototype, declare it via TP_PROTO():
 281  *      *
 282  *
 283  *      TP_PROTO(struct rq *rq, struct task_struct *prev,
 284  *               struct task_struct *next),
 285  *
 286  *      *
 287  *      * Define the call signature of the 'function'.
 288  *      * (Design sidenote: we use this instead of a
 289  *      *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 290  *      *
 291  *
 292  *      TP_ARGS(rq, prev, next),
 293  *
 294  *      *
 295  *      * Fast binary tracing: define the trace record via
 296  *      * TP_FIELDS(). You can think about it like a
 297  *      * regular C structure local variable definition.
 298  *      *
 299  *      * This is how the trace record is structured and will
 300  *      * be saved into the ring buffer. These are the fields
 301  *      * that will be exposed to readers.
 302  *      *
 303  *      * ctf_integer(pid_t, prev_pid, prev->pid) is equivalent
 304  *      * to a standard declaraton:
 305  *      *
 306  *      *       pid_t prev_pid;
 307  *      *
 308  *      * followed by an assignment:
 309  *      *
 310  *      *       prev_pid = prev->pid;
 311  *      *
 312  *      * ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN) is
 313  *      * equivalent to:
 314  *      *
 315  *      *       char prev_comm[TASK_COMM_LEN];
 316  *      *
 317  *      * followed by an assignment:
 318  *      *
 319  *      *       memcpy(prev_comm, prev->comm, TASK_COMM_LEN);
 320  *      *
 321  *
 322  *      TP_FIELDS(
 323  *              ctf_array(char, prev_comm, prev->comm, TASK_COMM_LEN)
 324  *              ctf_integer(pid_t, prev_pid,  prev->pid)
 325  *              ctf_integer(int, prev_prio, prev->prio)
 326  *              ctf_array(char, next_comm, next->comm, TASK_COMM_LEN)
 327  *              ctf_integer(pid_t, next_pid,  next->pid)
 328  *              ctf_integer(int, next_prio, next->prio)
 329  *      )
 330  * )
 331  */
 332
 333 #define TRACEPOINT_EVENT(name, proto, args, fields)                     \
 334         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 335
 336 #define TRACEPOINT_EVENT_CLASS(name, proto, args, fields)
 337 #define TRACEPOINT_EVENT_INSTANCE(template, name, proto, args)          \
 338         _DECLARE_TRACEPOINT(name, TP_PARAMS(proto), TP_PARAMS(args))
 339
 340 /*
 341  * Declaration of tracepoints that take 0 argument.
 342  */
 343 #define TRACEPOINT_EVENT_NOARGS(name, fields)                           \
 344         _DECLARE_TRACEPOINT_NOARGS(name)
 345
 346 #define TRACEPOINT_EVENT_CLASS_NOARGS(name, fields)
 347 #define TRACEPOINT_EVENT_INSTANCE_NOARGS(template, name)                \
 348         _DECLARE_TRACEPOINT_NOARGS(name)
 349
 350 #endif /* #ifndef TRACEPOINT_EVENT */
 351
 352 #endif /* _UST_TRACEPOINT_H */