include/side/trace.h

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  */
   5
   6 #ifndef _SIDE_TRACE_H
   7 #define _SIDE_TRACE_H
   8
   9 #include <stdint.h>
  10 #include <inttypes.h>
  11 #include <stdlib.h>
  12 #include <stdio.h>
  13 #include <math.h>
  14 #include <stdbool.h>
  15 #include <stddef.h>
  16 #include <side/macros.h>
  17 #include <side/endian.h>
  18
  19 /*
  20  * SIDE stands for "Software Instrumentation Dynamically Enabled"
  21  *
  22  * This is an instrumentation ABI for Linux user-space, which exposes an
  23  * instrumentation type system and facilities allowing a kernel or
  24  * user-space tracer to consume user-space instrumentation.
  25  *
  26  * The extensibility scheme for the SIDE ABI for event state is as
  27  * follows:
  28  *
  29  * * If the semantic of the "struct side_event_state_N" fields change,
  30  *   the SIDE_EVENT_STATE_ABI_VERSION should be increased. The
  31  *   "struct side_event_state_N" is not extensible and must have its
  32  *   ABI version increased whenever it is changed. Note that increasing
  33  *   the version of SIDE_EVENT_DESCRIPTION_ABI_VERSION is not necessary
  34  *   when changing the layout of "struct side_event_state_N".
  35  */
  36
  37 #define SIDE_EVENT_STATE_ABI_VERSION            0
  38
  39 #include <side/abi/event-description.h>
  40 #include <side/abi/type-argument.h>
  41 #include <side/instrumentation-c-api.h>
  42
  43 enum side_error {
  44         SIDE_ERROR_OK = 0,
  45         SIDE_ERROR_INVAL = 1,
  46         SIDE_ERROR_EXIST = 2,
  47         SIDE_ERROR_NOMEM = 3,
  48         SIDE_ERROR_NOENT = 4,
  49         SIDE_ERROR_EXITING = 5,
  50 };
  51
  52 /*
  53  * This structure is _not_ packed to allow atomic operations on its
  54  * fields. Changes to this structure must bump the "Event state ABI
  55  * version" and tracers _must_ learn how to deal with this ABI,
  56  * otherwise they should reject the event.
  57  */
  58
  59 struct side_event_state {
  60         uint32_t version;       /* Event state ABI version. */
  61 };
  62
  63 struct side_event_state_0 {
  64         struct side_event_state parent;         /* Required first field. */
  65         uint32_t nr_callbacks;
  66         uintptr_t enabled;
  67         const struct side_callback *callbacks;
  68         struct side_event_description *desc;
  69 };
  70
  71 #ifdef __cplusplus
  72 extern "C" {
  73 #endif
  74
  75 struct side_callback;
  76
  77 extern const char side_empty_callback[];
  78
  79 void side_call(const struct side_event_state *state,
  80         const struct side_arg_vec *side_arg_vec);
  81 void side_call_variadic(const struct side_event_state *state,
  82         const struct side_arg_vec *side_arg_vec,
  83         const struct side_arg_dynamic_struct *var_struct);
  84
  85 struct side_events_register_handle *side_events_register(struct side_event_description **events,
  86                 uint32_t nr_events);
  87 void side_events_unregister(struct side_events_register_handle *handle);
  88
  89 /*
  90  * Userspace tracer registration API. This allows userspace tracers to
  91  * register event notification callbacks to be notified of the currently
  92  * registered instrumentation, and to register their callbacks to
  93  * specific events.
  94  */
  95 typedef void (*side_tracer_callback_func)(const struct side_event_description *desc,
  96                         const struct side_arg_vec *side_arg_vec,
  97                         void *priv);
  98 typedef void (*side_tracer_callback_variadic_func)(const struct side_event_description *desc,
  99                         const struct side_arg_vec *side_arg_vec,
 100                         const struct side_arg_dynamic_struct *var_struct,
 101                         void *priv);
 102
 103 int side_tracer_callback_register(struct side_event_description *desc,
 104                 side_tracer_callback_func call,
 105                 void *priv);
 106 int side_tracer_callback_variadic_register(struct side_event_description *desc,
 107                 side_tracer_callback_variadic_func call_variadic,
 108                 void *priv);
 109 int side_tracer_callback_unregister(struct side_event_description *desc,
 110                 side_tracer_callback_func call,
 111                 void *priv);
 112 int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
 113                 side_tracer_callback_variadic_func call_variadic,
 114                 void *priv);
 115
 116 enum side_tracer_notification {
 117         SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
 118         SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
 119 };
 120
 121 /* Callback is invoked with side library internal lock held. */
 122 struct side_tracer_handle *side_tracer_event_notification_register(
 123                 void (*cb)(enum side_tracer_notification notif,
 124                         struct side_event_description **events, uint32_t nr_events, void *priv),
 125                 void *priv);
 126 void side_tracer_event_notification_unregister(struct side_tracer_handle *handle);
 127
 128 /*
 129  * Explicit hooks to initialize/finalize the side instrumentation
 130  * library. Those are also library constructor/destructor.
 131  */
 132 void side_init(void) __attribute__((constructor));
 133 void side_exit(void) __attribute__((destructor));
 134
 135 /*
 136  * The following constructors/destructors perform automatic registration
 137  * of the declared side events. Those may have to be called explicitly
 138  * in a statically linked library.
 139  */
 140
 141 /*
 142  * These weak symbols, the constructor, and destructor take care of
 143  * registering only _one_ instance of the side instrumentation per
 144  * shared-ojbect (or for the whole main program).
 145  */
 146 extern struct side_event_description * __start_side_event_description_ptr[]
 147         __attribute__((weak, visibility("hidden")));
 148 extern struct side_event_description * __stop_side_event_description_ptr[]
 149         __attribute__((weak, visibility("hidden")));
 150 int side_event_description_ptr_registered
 151         __attribute__((weak, visibility("hidden")));
 152 struct side_events_register_handle *side_events_handle
 153         __attribute__((weak, visibility("hidden")));
 154
 155 static void
 156 side_event_description_ptr_init(void)
 157         __attribute__((no_instrument_function))
 158         __attribute__((constructor));
 159 static void
 160 side_event_description_ptr_init(void)
 161 {
 162         if (side_event_description_ptr_registered++)
 163                 return;
 164         side_events_handle = side_events_register(__start_side_event_description_ptr,
 165                 __stop_side_event_description_ptr - __start_side_event_description_ptr);
 166 }
 167
 168 static void
 169 side_event_description_ptr_exit(void)
 170         __attribute__((no_instrument_function))
 171         __attribute__((destructor));
 172 static void
 173 side_event_description_ptr_exit(void)
 174 {
 175         if (--side_event_description_ptr_registered)
 176                 return;
 177         side_events_unregister(side_events_handle);
 178         side_events_handle = NULL;
 179 }
 180
 181 #ifdef __cplusplus
 182 }
 183 #endif
 184
 185 #endif /* _SIDE_TRACE_H */