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67337c4a MD |
1 | // SPDX-License-Identifier: MIT |
2 | /* | |
3 | * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
4 | */ | |
5 | ||
6 | #include <side/trace.h> | |
7 | #include <string.h> | |
8 | ||
9 | #include "rcu.h" | |
10 | #include "list.h" | |
11 | ||
12 | /* Top 8 bits reserved for kernel tracer use. */ | |
13 | #if SIDE_BITS_PER_LONG == 64 | |
14 | # define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF00000000000000ULL | |
15 | # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x8000000000000000ULL | |
16 | ||
17 | /* Allow 2^56 tracer references on an event. */ | |
18 | # define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFFFFFFFFFULL | |
19 | #else | |
20 | # define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000UL | |
21 | # define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000UL | |
22 | ||
23 | /* Allow 2^24 tracer references on an event. */ | |
24 | # define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL | |
25 | #endif | |
26 | ||
27 | struct side_events_register_handle { | |
28 | struct side_list_node node; | |
29 | struct side_event_description **events; | |
30 | uint32_t nr_events; | |
31 | }; | |
32 | ||
33 | struct side_tracer_handle { | |
34 | struct side_list_node node; | |
35 | void (*cb)(enum side_tracer_notification notif, | |
36 | struct side_event_description **events, uint32_t nr_events, void *priv); | |
37 | void *priv; | |
38 | }; | |
39 | ||
40 | static struct side_rcu_gp_state rcu_gp; | |
41 | ||
42 | /* | |
43 | * Lazy initialization for early use within library constructors. | |
44 | */ | |
45 | static bool initialized; | |
46 | /* | |
47 | * Do not register/unregister any more events after destructor. | |
48 | */ | |
49 | static bool finalized; | |
50 | ||
51 | /* | |
52 | * Recursive mutex to allow tracer callbacks to use the side API. | |
53 | */ | |
54 | static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; | |
55 | ||
56 | static DEFINE_SIDE_LIST_HEAD(side_events_list); | |
57 | static DEFINE_SIDE_LIST_HEAD(side_tracer_list); | |
58 | ||
59 | /* | |
60 | * The empty callback has a NULL function callback pointer, which stops | |
61 | * iteration on the array of callbacks immediately. | |
62 | */ | |
63 | const struct side_callback side_empty_callback = { }; | |
64 | ||
65 | void side_call(const struct side_event_description *desc, const struct side_arg_vec *side_arg_vec) | |
66 | { | |
67 | struct side_rcu_read_state rcu_read_state; | |
68 | const struct side_callback *side_cb; | |
69 | uintptr_t enabled; | |
70 | ||
71 | if (side_unlikely(finalized)) | |
72 | return; | |
73 | if (side_unlikely(!initialized)) | |
74 | side_init(); | |
75 | if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) { | |
76 | printf("ERROR: unexpected variadic event description\n"); | |
77 | abort(); | |
78 | } | |
79 | enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED); | |
80 | if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { | |
81 | // TODO: call kernel write. | |
82 | } | |
83 | side_rcu_read_begin(&rcu_gp, &rcu_read_state); | |
84 | for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++) | |
85 | side_cb->u.call(desc, side_arg_vec, side_cb->priv); | |
86 | side_rcu_read_end(&rcu_gp, &rcu_read_state); | |
87 | } | |
88 | ||
89 | void side_call_variadic(const struct side_event_description *desc, | |
90 | const struct side_arg_vec *side_arg_vec, | |
91 | const struct side_arg_dynamic_struct *var_struct) | |
92 | { | |
93 | struct side_rcu_read_state rcu_read_state; | |
94 | const struct side_callback *side_cb; | |
95 | uintptr_t enabled; | |
96 | ||
97 | if (side_unlikely(finalized)) | |
98 | return; | |
99 | if (side_unlikely(!initialized)) | |
100 | side_init(); | |
101 | if (side_unlikely(!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))) { | |
102 | printf("ERROR: unexpected non-variadic event description\n"); | |
103 | abort(); | |
104 | } | |
105 | enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED); | |
106 | if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) { | |
107 | // TODO: call kernel write. | |
108 | } | |
109 | side_rcu_read_begin(&rcu_gp, &rcu_read_state); | |
110 | for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++) | |
111 | side_cb->u.call_variadic(desc, side_arg_vec, var_struct, side_cb->priv); | |
112 | side_rcu_read_end(&rcu_gp, &rcu_read_state); | |
113 | } | |
114 | ||
115 | static | |
116 | const struct side_callback *side_tracer_callback_lookup( | |
117 | const struct side_event_description *desc, | |
118 | void *call, void *priv) | |
119 | { | |
120 | const struct side_callback *cb; | |
121 | ||
122 | for (cb = desc->callbacks; cb->u.call != NULL; cb++) { | |
123 | if ((void *) cb->u.call == call && cb->priv == priv) | |
124 | return cb; | |
125 | } | |
126 | return NULL; | |
127 | } | |
128 | ||
129 | static | |
130 | int _side_tracer_callback_register(struct side_event_description *desc, | |
131 | void *call, void *priv) | |
132 | { | |
133 | struct side_callback *old_cb, *new_cb; | |
134 | int ret = SIDE_ERROR_OK; | |
135 | uint32_t old_nr_cb; | |
136 | ||
137 | if (!call) | |
138 | return SIDE_ERROR_INVAL; | |
139 | if (finalized) | |
140 | return SIDE_ERROR_EXITING; | |
141 | if (!initialized) | |
142 | side_init(); | |
143 | pthread_mutex_lock(&side_lock); | |
144 | old_nr_cb = desc->nr_callbacks; | |
145 | if (old_nr_cb == UINT32_MAX) { | |
146 | ret = SIDE_ERROR_INVAL; | |
147 | goto unlock; | |
148 | } | |
149 | /* Reject duplicate (call, priv) tuples. */ | |
150 | if (side_tracer_callback_lookup(desc, call, priv)) { | |
151 | ret = SIDE_ERROR_EXIST; | |
152 | goto unlock; | |
153 | } | |
154 | old_cb = (struct side_callback *) desc->callbacks; | |
155 | /* old_nr_cb + 1 (new cb) + 1 (NULL) */ | |
156 | new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback)); | |
157 | if (!new_cb) { | |
158 | ret = SIDE_ERROR_NOMEM; | |
159 | goto unlock; | |
160 | } | |
161 | memcpy(new_cb, old_cb, old_nr_cb); | |
162 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) | |
163 | new_cb[old_nr_cb].u.call_variadic = | |
164 | (side_tracer_callback_variadic_func) call; | |
165 | else | |
166 | new_cb[old_nr_cb].u.call = | |
167 | (side_tracer_callback_func) call; | |
168 | new_cb[old_nr_cb].priv = priv; | |
169 | side_rcu_assign_pointer(desc->callbacks, new_cb); | |
170 | side_rcu_wait_grace_period(&rcu_gp); | |
171 | if (old_nr_cb) | |
172 | free(old_cb); | |
173 | desc->nr_callbacks++; | |
174 | /* Increment concurrently with kernel setting the top bits. */ | |
175 | if (!old_nr_cb) | |
176 | (void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED); | |
177 | unlock: | |
178 | pthread_mutex_unlock(&side_lock); | |
179 | return ret; | |
180 | } | |
181 | ||
182 | int side_tracer_callback_register(struct side_event_description *desc, | |
183 | side_tracer_callback_func call, | |
184 | void *priv) | |
185 | { | |
186 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) | |
187 | return SIDE_ERROR_INVAL; | |
188 | return _side_tracer_callback_register(desc, (void *) call, priv); | |
189 | } | |
190 | ||
191 | int side_tracer_callback_variadic_register(struct side_event_description *desc, | |
192 | side_tracer_callback_variadic_func call_variadic, | |
193 | void *priv) | |
194 | { | |
195 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) | |
196 | return SIDE_ERROR_INVAL; | |
197 | return _side_tracer_callback_register(desc, (void *) call_variadic, priv); | |
198 | } | |
199 | ||
200 | static int _side_tracer_callback_unregister(struct side_event_description *desc, | |
201 | void *call, void *priv) | |
202 | { | |
203 | struct side_callback *old_cb, *new_cb; | |
204 | const struct side_callback *cb_pos; | |
205 | uint32_t pos_idx; | |
206 | int ret = SIDE_ERROR_OK; | |
207 | uint32_t old_nr_cb; | |
208 | ||
209 | if (!call) | |
210 | return SIDE_ERROR_INVAL; | |
211 | if (finalized) | |
212 | return SIDE_ERROR_EXITING; | |
213 | if (!initialized) | |
214 | side_init(); | |
215 | pthread_mutex_lock(&side_lock); | |
216 | cb_pos = side_tracer_callback_lookup(desc, call, priv); | |
217 | if (!cb_pos) { | |
218 | ret = SIDE_ERROR_NOENT; | |
219 | goto unlock; | |
220 | } | |
221 | old_nr_cb = desc->nr_callbacks; | |
222 | old_cb = (struct side_callback *) desc->callbacks; | |
223 | if (old_nr_cb == 1) { | |
224 | new_cb = (struct side_callback *) &side_empty_callback; | |
225 | } else { | |
226 | pos_idx = cb_pos - desc->callbacks; | |
227 | /* Remove entry at pos_idx. */ | |
228 | /* old_nr_cb - 1 (removed cb) + 1 (NULL) */ | |
229 | new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback)); | |
230 | if (!new_cb) { | |
231 | ret = SIDE_ERROR_NOMEM; | |
232 | goto unlock; | |
233 | } | |
234 | memcpy(new_cb, old_cb, pos_idx); | |
235 | memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1); | |
236 | } | |
237 | side_rcu_assign_pointer(desc->callbacks, new_cb); | |
238 | side_rcu_wait_grace_period(&rcu_gp); | |
239 | free(old_cb); | |
240 | desc->nr_callbacks--; | |
241 | /* Decrement concurrently with kernel setting the top bits. */ | |
242 | if (old_nr_cb == 1) | |
243 | (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED); | |
244 | unlock: | |
245 | pthread_mutex_unlock(&side_lock); | |
246 | return ret; | |
247 | } | |
248 | ||
249 | int side_tracer_callback_unregister(struct side_event_description *desc, | |
250 | side_tracer_callback_func call, | |
251 | void *priv) | |
252 | { | |
253 | if (desc->flags & SIDE_EVENT_FLAG_VARIADIC) | |
254 | return SIDE_ERROR_INVAL; | |
255 | return _side_tracer_callback_unregister(desc, (void *) call, priv); | |
256 | } | |
257 | ||
258 | int side_tracer_callback_variadic_unregister(struct side_event_description *desc, | |
259 | side_tracer_callback_variadic_func call_variadic, | |
260 | void *priv) | |
261 | { | |
262 | if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) | |
263 | return SIDE_ERROR_INVAL; | |
264 | return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv); | |
265 | } | |
266 | ||
267 | struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events) | |
268 | { | |
269 | struct side_events_register_handle *events_handle = NULL; | |
270 | struct side_tracer_handle *tracer_handle; | |
271 | ||
272 | if (finalized) | |
273 | return NULL; | |
274 | if (!initialized) | |
275 | side_init(); | |
276 | events_handle = (struct side_events_register_handle *) | |
277 | calloc(1, sizeof(struct side_events_register_handle)); | |
278 | if (!events_handle) | |
279 | return NULL; | |
280 | events_handle->events = events; | |
281 | events_handle->nr_events = nr_events; | |
282 | ||
283 | pthread_mutex_lock(&side_lock); | |
284 | side_list_insert_node_tail(&side_events_list, &events_handle->node); | |
285 | side_list_for_each_entry(tracer_handle, &side_tracer_list, node) { | |
286 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS, | |
287 | events, nr_events, tracer_handle->priv); | |
288 | } | |
289 | pthread_mutex_unlock(&side_lock); | |
290 | //TODO: call event batch register ioctl | |
291 | return events_handle; | |
292 | } | |
293 | ||
294 | static | |
295 | void side_event_remove_callbacks(struct side_event_description *desc) | |
296 | { | |
297 | uint32_t nr_cb = desc->nr_callbacks; | |
298 | struct side_callback *old_cb; | |
299 | ||
300 | if (!nr_cb) | |
301 | return; | |
302 | old_cb = (struct side_callback *) desc->callbacks; | |
303 | (void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED); | |
304 | /* | |
305 | * Setting the state back to 0 cb and empty callbacks out of | |
306 | * caution. This should not matter because instrumentation is | |
307 | * unreachable. | |
308 | */ | |
309 | desc->nr_callbacks = 0; | |
310 | side_rcu_assign_pointer(desc->callbacks, &side_empty_callback); | |
311 | /* | |
312 | * No need to wait for grace period because instrumentation is | |
313 | * unreachable. | |
314 | */ | |
315 | free(old_cb); | |
316 | } | |
317 | ||
318 | /* | |
319 | * Unregister event handle. At this point, all side events in that | |
320 | * handle should be unreachable. | |
321 | */ | |
322 | void side_events_unregister(struct side_events_register_handle *events_handle) | |
323 | { | |
324 | struct side_tracer_handle *tracer_handle; | |
325 | uint32_t i; | |
326 | ||
327 | if (!events_handle) | |
328 | return; | |
329 | if (finalized) | |
330 | return; | |
331 | if (!initialized) | |
332 | side_init(); | |
333 | pthread_mutex_lock(&side_lock); | |
334 | side_list_remove_node(&events_handle->node); | |
335 | side_list_for_each_entry(tracer_handle, &side_tracer_list, node) { | |
336 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS, | |
337 | events_handle->events, events_handle->nr_events, | |
338 | tracer_handle->priv); | |
339 | } | |
340 | for (i = 0; i < events_handle->nr_events; i++) { | |
341 | struct side_event_description *event = events_handle->events[i]; | |
342 | ||
343 | /* Skip NULL pointers */ | |
344 | if (!event) | |
345 | continue; | |
346 | side_event_remove_callbacks(event); | |
347 | } | |
348 | pthread_mutex_unlock(&side_lock); | |
349 | //TODO: call event batch unregister ioctl | |
350 | free(events_handle); | |
351 | } | |
352 | ||
353 | struct side_tracer_handle *side_tracer_event_notification_register( | |
354 | void (*cb)(enum side_tracer_notification notif, | |
355 | struct side_event_description **events, uint32_t nr_events, void *priv), | |
356 | void *priv) | |
357 | { | |
358 | struct side_tracer_handle *tracer_handle; | |
359 | struct side_events_register_handle *events_handle; | |
360 | ||
361 | if (finalized) | |
362 | return NULL; | |
363 | if (!initialized) | |
364 | side_init(); | |
365 | tracer_handle = (struct side_tracer_handle *) | |
366 | calloc(1, sizeof(struct side_tracer_handle)); | |
367 | if (!tracer_handle) | |
368 | return NULL; | |
369 | pthread_mutex_lock(&side_lock); | |
370 | tracer_handle->cb = cb; | |
371 | tracer_handle->priv = priv; | |
372 | side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node); | |
373 | side_list_for_each_entry(events_handle, &side_events_list, node) { | |
374 | cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS, | |
375 | events_handle->events, events_handle->nr_events, priv); | |
376 | } | |
377 | pthread_mutex_unlock(&side_lock); | |
378 | return tracer_handle; | |
379 | } | |
380 | ||
381 | void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle) | |
382 | { | |
383 | struct side_events_register_handle *events_handle; | |
384 | ||
385 | if (finalized) | |
386 | return; | |
387 | if (!initialized) | |
388 | side_init(); | |
389 | pthread_mutex_lock(&side_lock); | |
390 | side_list_for_each_entry(events_handle, &side_events_list, node) { | |
391 | tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS, | |
392 | events_handle->events, events_handle->nr_events, | |
393 | tracer_handle->priv); | |
394 | } | |
395 | side_list_remove_node(&tracer_handle->node); | |
396 | pthread_mutex_unlock(&side_lock); | |
397 | } | |
398 | ||
399 | void side_init(void) | |
400 | { | |
401 | if (initialized) | |
402 | return; | |
403 | side_rcu_gp_init(&rcu_gp); | |
404 | initialized = true; | |
405 | } | |
406 | ||
407 | /* | |
408 | * side_exit() is executed from a library destructor. It can be called | |
409 | * explicitly at application exit as well. Concurrent side API use is | |
410 | * not expected at that point. | |
411 | */ | |
412 | void side_exit(void) | |
413 | { | |
414 | struct side_events_register_handle *handle, *tmp; | |
415 | ||
416 | if (finalized) | |
417 | return; | |
418 | side_list_for_each_entry_safe(handle, tmp, &side_events_list, node) | |
419 | side_events_unregister(handle); | |
420 | side_rcu_gp_exit(&rcu_gp); | |
421 | finalized = true; | |
422 | } |