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6841ae81 MD |
1 | // SPDX-License-Identifier: MIT |
2 | /* | |
3 | * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
4 | */ | |
5 | ||
6 | #include <side/trace.h> | |
a3f36db7 MD |
7 | #include <string.h> |
8 | ||
6841ae81 | 9 | #include "tracer.h" |
85b765b8 | 10 | #include "rcu.h" |
6841ae81 | 11 | |
054b7b5c MD |
12 | /* Top 8 bits reserved for kernel tracer use. */ |
13 | #define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000 | |
29b3374e MD |
14 | #define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000 |
15 | ||
a3f36db7 | 16 | /* Allow 2^24 tracer callbacks to be registered on an event. */ |
054b7b5c MD |
17 | #define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFF |
18 | ||
a3f36db7 | 19 | static struct side_rcu_gp_state rcu_gp; |
075ceef7 MD |
20 | |
21 | /* | |
22 | * Lazy initialization for early use within library constructors. | |
23 | */ | |
24 | static bool initialized; | |
25 | ||
a3f36db7 MD |
26 | static pthread_mutex_t side_lock = PTHREAD_MUTEX_INITIALIZER; |
27 | ||
075ceef7 MD |
28 | static |
29 | void side_init(void) | |
30 | __attribute__((constructor)); | |
31 | ||
a3f36db7 MD |
32 | /* |
33 | * The empty callback has a NULL function callback pointer, which stops | |
34 | * iteration on the array of callbacks immediately. | |
35 | */ | |
054b7b5c MD |
36 | const struct side_callback side_empty_callback; |
37 | ||
6841ae81 MD |
38 | void side_call(const struct side_event_description *desc, const struct side_arg_vec_description *sav_desc) |
39 | { | |
054b7b5c MD |
40 | const struct side_callback *side_cb; |
41 | unsigned int rcu_period; | |
42 | ||
075ceef7 MD |
43 | if (side_unlikely(!initialized)) |
44 | side_init(); | |
6841ae81 MD |
45 | if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) { |
46 | printf("ERROR: unexpected variadic event description\n"); | |
47 | abort(); | |
48 | } | |
d5cdb129 | 49 | if (side_unlikely(*desc->enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
dda82f46 | 50 | // TODO: call kernel write. |
6841ae81 | 51 | } |
054b7b5c MD |
52 | if (side_unlikely(!(*desc->enabled & SIDE_EVENT_ENABLED_USER_MASK))) |
53 | return; | |
54 | ||
6841ae81 | 55 | //TODO: replace tracer_call by rcu iteration on list of registered callbacks |
4a7d8700 | 56 | tracer_call(desc, sav_desc, NULL); |
054b7b5c MD |
57 | |
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); | |
6841ae81 MD |
62 | } |
63 | ||
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) | |
67 | { | |
054b7b5c MD |
68 | const struct side_callback *side_cb; |
69 | unsigned int rcu_period; | |
70 | ||
075ceef7 MD |
71 | if (side_unlikely(!initialized)) |
72 | side_init(); | |
d5cdb129 | 73 | if (side_unlikely(*desc->enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { |
dda82f46 | 74 | // TODO: call kernel write. |
6841ae81 | 75 | } |
054b7b5c MD |
76 | if (side_unlikely(!(*desc->enabled & SIDE_EVENT_ENABLED_USER_MASK))) |
77 | return; | |
78 | ||
6841ae81 | 79 | //TODO: replace tracer_call by rcu iteration on list of registered callbacks |
4a7d8700 | 80 | tracer_call_variadic(desc, sav_desc, var_struct, NULL); |
054b7b5c MD |
81 | |
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); | |
6841ae81 | 86 | } |
075ceef7 | 87 | |
a3f36db7 MD |
88 | static |
89 | const struct side_callback *side_tracer_callback_lookup( | |
90 | const struct side_event_description *desc, | |
91 | void (*call)(), void *priv) | |
92 | { | |
93 | const struct side_callback *cb; | |
94 | ||
95 | for (cb = desc->callbacks; cb->u.call != NULL; cb++) { | |
96 | if (cb->u.call == call && cb->priv == priv) | |
97 | return cb; | |
98 | } | |
99 | return NULL; | |
100 | } | |
101 | ||
102 | static | |
103 | int _side_tracer_callback_register(struct side_event_description *desc, | |
104 | void (*call)(), void *priv) | |
105 | { | |
106 | struct side_callback *old_cb, *new_cb; | |
107 | int ret = SIDE_ERROR_OK; | |
108 | uint32_t old_nr_cb; | |
109 | ||
110 | if (!call) | |
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; | |
116 | goto unlock; | |
117 | } | |
118 | /* Reject duplicate (call, priv) tuples. */ | |
119 | if (side_tracer_callback_lookup(desc, call, priv)) { | |
120 | ret = SIDE_ERROR_EXIST; | |
121 | goto unlock; | |
122 | } | |
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)); | |
126 | if (!new_cb) { | |
127 | ret = SIDE_ERROR_NOMEM; | |
128 | goto unlock; | |
129 | } | |
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; | |
133 | else | |
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); | |
138 | if (old_nr_cb) | |
139 | free(old_cb); | |
140 | /* Increment concurrently with kernel setting the top bits. */ | |
141 | (void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED); | |
142 | unlock: | |
143 | pthread_mutex_unlock(&side_lock); | |
144 | return ret; | |
145 | } | |
146 | ||
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, | |
150 | void *priv), | |
151 | void *priv) | |
152 | { | |
153 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) | |
154 | return SIDE_ERROR_INVAL; | |
155 | return _side_tracer_callback_register(desc, call, priv); | |
156 | } | |
157 | ||
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, | |
162 | void *priv), | |
163 | void *priv) | |
164 | { | |
165 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) | |
166 | return SIDE_ERROR_INVAL; | |
167 | return _side_tracer_callback_register(desc, call_variadic, priv); | |
168 | } | |
169 | ||
170 | int _side_tracer_callback_unregister(struct side_event_description *desc, | |
171 | void (*call)(), void *priv) | |
172 | { | |
173 | struct side_callback *old_cb, *new_cb; | |
174 | const struct side_callback *cb_pos; | |
175 | uint32_t pos_idx; | |
176 | int ret = SIDE_ERROR_OK; | |
177 | uint32_t old_nr_cb; | |
178 | ||
179 | if (!call) | |
180 | return SIDE_ERROR_INVAL; | |
181 | pthread_mutex_lock(&side_lock); | |
a3f36db7 MD |
182 | cb_pos = side_tracer_callback_lookup(desc, call, priv); |
183 | if (!cb_pos) { | |
184 | ret = SIDE_ERROR_NOENT; | |
185 | goto unlock; | |
186 | } | |
9a83b759 MD |
187 | old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK; |
188 | old_cb = (struct side_callback *) desc->callbacks; | |
a3f36db7 MD |
189 | if (old_nr_cb == 1) { |
190 | new_cb = (struct side_callback *) &side_empty_callback; | |
191 | } else { | |
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)); | |
196 | if (!new_cb) { | |
197 | ret = SIDE_ERROR_NOMEM; | |
198 | goto unlock; | |
199 | } | |
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); | |
202 | } | |
203 | side_rcu_assign_pointer(desc->callbacks, new_cb); | |
204 | side_rcu_wait_grace_period(&rcu_gp); | |
205 | free(old_cb); | |
206 | /* Decrement concurrently with kernel setting the top bits. */ | |
207 | (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED); | |
208 | unlock: | |
209 | pthread_mutex_unlock(&side_lock); | |
210 | return ret; | |
211 | } | |
212 | ||
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, | |
216 | void *priv), | |
217 | void *priv) | |
218 | { | |
219 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) | |
220 | return SIDE_ERROR_INVAL; | |
221 | return _side_tracer_callback_unregister(desc, call, priv); | |
222 | } | |
223 | ||
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, | |
228 | void *priv), | |
229 | void *priv) | |
230 | { | |
231 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) | |
232 | return SIDE_ERROR_INVAL; | |
233 | return _side_tracer_callback_unregister(desc, call_variadic, priv); | |
234 | } | |
235 | ||
236 | static | |
075ceef7 MD |
237 | void side_init(void) |
238 | { | |
239 | if (initialized) | |
240 | return; | |
054b7b5c | 241 | side_rcu_gp_init(&rcu_gp); |
075ceef7 MD |
242 | initialized = true; |
243 | } |