1 // SPDX-License-Identifier: MIT
3 * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 #include <side/trace.h>
12 /* Top 8 bits reserved for kernel tracer use. */
13 #define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000
14 #define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000
16 /* Allow 2^24 tracer callbacks to be registered on an event. */
17 #define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFF
19 static struct side_rcu_gp_state rcu_gp
;
22 * Lazy initialization for early use within library constructors.
24 static bool initialized
;
26 static pthread_mutex_t side_lock
= PTHREAD_MUTEX_INITIALIZER
;
30 __attribute__((constructor
));
33 * The empty callback has a NULL function callback pointer, which stops
34 * iteration on the array of callbacks immediately.
36 const struct side_callback side_empty_callback
;
38 void side_call(const struct side_event_description
*desc
, const struct side_arg_vec_description
*sav_desc
)
40 const struct side_callback
*side_cb
;
41 unsigned int rcu_period
;
43 if (side_unlikely(!initialized
))
45 if (side_unlikely(desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
)) {
46 printf("ERROR: unexpected variadic event description\n");
49 if (side_unlikely(*desc
->enabled
& SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK
)) {
50 // TODO: call kernel write.
52 if (side_unlikely(!(*desc
->enabled
& SIDE_EVENT_ENABLED_USER_MASK
)))
55 //TODO: replace tracer_call by rcu iteration on list of registered callbacks
56 tracer_call(desc
, sav_desc
, NULL
);
58 rcu_period
= side_rcu_read_begin(&rcu_gp
);
59 for (side_cb
= side_rcu_dereference(desc
->callbacks
); side_cb
->u
.call
!= NULL
; side_cb
++)
60 side_cb
->u
.call(desc
, sav_desc
, side_cb
->priv
);
61 side_rcu_read_end(&rcu_gp
, rcu_period
);
64 void side_call_variadic(const struct side_event_description
*desc
,
65 const struct side_arg_vec_description
*sav_desc
,
66 const struct side_arg_dynamic_event_struct
*var_struct
)
68 const struct side_callback
*side_cb
;
69 unsigned int rcu_period
;
71 if (side_unlikely(!initialized
))
73 if (side_unlikely(*desc
->enabled
& SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK
)) {
74 // TODO: call kernel write.
76 if (side_unlikely(!(*desc
->enabled
& SIDE_EVENT_ENABLED_USER_MASK
)))
79 //TODO: replace tracer_call by rcu iteration on list of registered callbacks
80 tracer_call_variadic(desc
, sav_desc
, var_struct
, NULL
);
82 rcu_period
= side_rcu_read_begin(&rcu_gp
);
83 for (side_cb
= side_rcu_dereference(desc
->callbacks
); side_cb
->u
.call_variadic
!= NULL
; side_cb
++)
84 side_cb
->u
.call_variadic(desc
, sav_desc
, var_struct
, side_cb
->priv
);
85 side_rcu_read_end(&rcu_gp
, rcu_period
);
89 const struct side_callback
*side_tracer_callback_lookup(
90 const struct side_event_description
*desc
,
91 void (*call
)(), void *priv
)
93 const struct side_callback
*cb
;
95 for (cb
= desc
->callbacks
; cb
->u
.call
!= NULL
; cb
++) {
96 if (cb
->u
.call
== call
&& cb
->priv
== priv
)
103 int _side_tracer_callback_register(struct side_event_description
*desc
,
104 void (*call
)(), void *priv
)
106 struct side_callback
*old_cb
, *new_cb
;
107 int ret
= SIDE_ERROR_OK
;
111 return SIDE_ERROR_INVAL
;
112 pthread_mutex_lock(&side_lock
);
113 old_nr_cb
= *desc
->enabled
& SIDE_EVENT_ENABLED_USER_MASK
;
114 if (old_nr_cb
== SIDE_EVENT_ENABLED_USER_MASK
) {
115 ret
= SIDE_ERROR_INVAL
;
118 /* Reject duplicate (call, priv) tuples. */
119 if (side_tracer_callback_lookup(desc
, call
, priv
)) {
120 ret
= SIDE_ERROR_EXIST
;
123 old_cb
= (struct side_callback
*) desc
->callbacks
;
124 /* old_nr_cb + 1 (new cb) + 1 (NULL) */
125 new_cb
= (struct side_callback
*) calloc(old_nr_cb
+ 2, sizeof(struct side_callback
));
127 ret
= SIDE_ERROR_NOMEM
;
130 memcpy(new_cb
, old_cb
, old_nr_cb
);
131 if (desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
)
132 new_cb
[old_nr_cb
].u
.call_variadic
= call
;
134 new_cb
[old_nr_cb
].u
.call
= call
;
135 new_cb
[old_nr_cb
].priv
= priv
;
136 side_rcu_assign_pointer(desc
->callbacks
, new_cb
);
137 side_rcu_wait_grace_period(&rcu_gp
);
140 /* Increment concurrently with kernel setting the top bits. */
141 (void) __atomic_add_fetch(desc
->enabled
, 1, __ATOMIC_RELAXED
);
143 pthread_mutex_unlock(&side_lock
);
147 int side_tracer_callback_register(struct side_event_description
*desc
,
148 void (*call
)(const struct side_event_description
*desc
,
149 const struct side_arg_vec_description
*sav_desc
,
153 if (desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
)
154 return SIDE_ERROR_INVAL
;
155 return _side_tracer_callback_register(desc
, call
, priv
);
158 int side_tracer_callback_variadic_register(struct side_event_description
*desc
,
159 void (*call_variadic
)(const struct side_event_description
*desc
,
160 const struct side_arg_vec_description
*sav_desc
,
161 const struct side_arg_dynamic_event_struct
*var_struct
,
165 if (!(desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
))
166 return SIDE_ERROR_INVAL
;
167 return _side_tracer_callback_register(desc
, call_variadic
, priv
);
170 int _side_tracer_callback_unregister(struct side_event_description
*desc
,
171 void (*call
)(), void *priv
)
173 struct side_callback
*old_cb
, *new_cb
;
174 const struct side_callback
*cb_pos
;
176 int ret
= SIDE_ERROR_OK
;
180 return SIDE_ERROR_INVAL
;
181 pthread_mutex_lock(&side_lock
);
182 cb_pos
= side_tracer_callback_lookup(desc
, call
, priv
);
184 ret
= SIDE_ERROR_NOENT
;
187 old_nr_cb
= *desc
->enabled
& SIDE_EVENT_ENABLED_USER_MASK
;
188 old_cb
= (struct side_callback
*) desc
->callbacks
;
189 if (old_nr_cb
== 1) {
190 new_cb
= (struct side_callback
*) &side_empty_callback
;
192 pos_idx
= cb_pos
- desc
->callbacks
;
193 /* Remove entry at pos_idx. */
194 /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
195 new_cb
= (struct side_callback
*) calloc(old_nr_cb
, sizeof(struct side_callback
));
197 ret
= SIDE_ERROR_NOMEM
;
200 memcpy(new_cb
, old_cb
, pos_idx
);
201 memcpy(&new_cb
[pos_idx
], &old_cb
[pos_idx
+ 1], old_nr_cb
- pos_idx
- 1);
203 side_rcu_assign_pointer(desc
->callbacks
, new_cb
);
204 side_rcu_wait_grace_period(&rcu_gp
);
206 /* Decrement concurrently with kernel setting the top bits. */
207 (void) __atomic_add_fetch(desc
->enabled
, -1, __ATOMIC_RELAXED
);
209 pthread_mutex_unlock(&side_lock
);
213 int side_tracer_callback_unregister(struct side_event_description
*desc
,
214 void (*call
)(const struct side_event_description
*desc
,
215 const struct side_arg_vec_description
*sav_desc
,
219 if (desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
)
220 return SIDE_ERROR_INVAL
;
221 return _side_tracer_callback_unregister(desc
, call
, priv
);
224 int side_tracer_callback_variadic_unregister(struct side_event_description
*desc
,
225 void (*call_variadic
)(const struct side_event_description
*desc
,
226 const struct side_arg_vec_description
*sav_desc
,
227 const struct side_arg_dynamic_event_struct
*var_struct
,
231 if (!(desc
->flags
& SIDE_EVENT_FLAG_VARIADIC
))
232 return SIDE_ERROR_INVAL
;
233 return _side_tracer_callback_unregister(desc
, call_variadic
, priv
);
241 side_rcu_gp_init(&rcu_gp
);