1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * Copyright (C) 2008-2014 Mathieu Desnoyers |
4 | */ |
5 | #include <linux/module.h> |
6 | #include <linux/mutex.h> |
7 | #include <linux/types.h> |
8 | #include <linux/jhash.h> |
9 | #include <linux/list.h> |
10 | #include <linux/rcupdate.h> |
11 | #include <linux/tracepoint.h> |
12 | #include <linux/err.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/sched/signal.h> |
15 | #include <linux/sched/task.h> |
16 | #include <linux/static_key.h> |
17 | |
18 | enum tp_func_state { |
19 | TP_FUNC_0, |
20 | TP_FUNC_1, |
21 | TP_FUNC_2, |
22 | TP_FUNC_N, |
23 | }; |
24 | |
25 | extern tracepoint_ptr_t __start___tracepoints_ptrs[]; |
26 | extern tracepoint_ptr_t __stop___tracepoints_ptrs[]; |
27 | |
28 | DEFINE_SRCU(tracepoint_srcu); |
29 | EXPORT_SYMBOL_GPL(tracepoint_srcu); |
30 | |
31 | enum tp_transition_sync { |
32 | TP_TRANSITION_SYNC_1_0_1, |
33 | TP_TRANSITION_SYNC_N_2_1, |
34 | |
35 | _NR_TP_TRANSITION_SYNC, |
36 | }; |
37 | |
38 | struct tp_transition_snapshot { |
39 | unsigned long rcu; |
40 | unsigned long srcu; |
41 | bool ongoing; |
42 | }; |
43 | |
44 | /* Protected by tracepoints_mutex */ |
45 | static struct tp_transition_snapshot tp_transition_snapshot[_NR_TP_TRANSITION_SYNC]; |
46 | |
47 | static void tp_rcu_get_state(enum tp_transition_sync sync) |
48 | { |
49 | struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync]; |
50 | |
51 | /* Keep the latest get_state snapshot. */ |
52 | snapshot->rcu = get_state_synchronize_rcu(); |
53 | snapshot->srcu = start_poll_synchronize_srcu(ssp: &tracepoint_srcu); |
54 | snapshot->ongoing = true; |
55 | } |
56 | |
57 | static void tp_rcu_cond_sync(enum tp_transition_sync sync) |
58 | { |
59 | struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync]; |
60 | |
61 | if (!snapshot->ongoing) |
62 | return; |
63 | cond_synchronize_rcu(oldstate: snapshot->rcu); |
64 | if (!poll_state_synchronize_srcu(ssp: &tracepoint_srcu, cookie: snapshot->srcu)) |
65 | synchronize_srcu(ssp: &tracepoint_srcu); |
66 | snapshot->ongoing = false; |
67 | } |
68 | |
69 | /* Set to 1 to enable tracepoint debug output */ |
70 | static const int tracepoint_debug; |
71 | |
72 | #ifdef CONFIG_MODULES |
73 | /* |
74 | * Tracepoint module list mutex protects the local module list. |
75 | */ |
76 | static DEFINE_MUTEX(tracepoint_module_list_mutex); |
77 | |
78 | /* Local list of struct tp_module */ |
79 | static LIST_HEAD(tracepoint_module_list); |
80 | #endif /* CONFIG_MODULES */ |
81 | |
82 | /* |
83 | * tracepoints_mutex protects the builtin and module tracepoints. |
84 | * tracepoints_mutex nests inside tracepoint_module_list_mutex. |
85 | */ |
86 | static DEFINE_MUTEX(tracepoints_mutex); |
87 | |
88 | static struct rcu_head *early_probes; |
89 | static bool ok_to_free_tracepoints; |
90 | |
91 | /* |
92 | * Note about RCU : |
93 | * It is used to delay the free of multiple probes array until a quiescent |
94 | * state is reached. |
95 | */ |
96 | struct tp_probes { |
97 | struct rcu_head rcu; |
98 | struct tracepoint_func probes[]; |
99 | }; |
100 | |
101 | /* Called in removal of a func but failed to allocate a new tp_funcs */ |
102 | static void tp_stub_func(void) |
103 | { |
104 | return; |
105 | } |
106 | |
107 | static inline void *allocate_probes(int count) |
108 | { |
109 | struct tp_probes *p = kmalloc(struct_size(p, probes, count), |
110 | GFP_KERNEL); |
111 | return p == NULL ? NULL : p->probes; |
112 | } |
113 | |
114 | static void srcu_free_old_probes(struct rcu_head *head) |
115 | { |
116 | kfree(container_of(head, struct tp_probes, rcu)); |
117 | } |
118 | |
119 | static void rcu_free_old_probes(struct rcu_head *head) |
120 | { |
121 | call_srcu(ssp: &tracepoint_srcu, head, func: srcu_free_old_probes); |
122 | } |
123 | |
124 | static __init int release_early_probes(void) |
125 | { |
126 | struct rcu_head *tmp; |
127 | |
128 | ok_to_free_tracepoints = true; |
129 | |
130 | while (early_probes) { |
131 | tmp = early_probes; |
132 | early_probes = tmp->next; |
133 | call_rcu(head: tmp, func: rcu_free_old_probes); |
134 | } |
135 | |
136 | return 0; |
137 | } |
138 | |
139 | /* SRCU is initialized at core_initcall */ |
140 | postcore_initcall(release_early_probes); |
141 | |
142 | static inline void release_probes(struct tracepoint_func *old) |
143 | { |
144 | if (old) { |
145 | struct tp_probes *tp_probes = container_of(old, |
146 | struct tp_probes, probes[0]); |
147 | |
148 | /* |
149 | * We can't free probes if SRCU is not initialized yet. |
150 | * Postpone the freeing till after SRCU is initialized. |
151 | */ |
152 | if (unlikely(!ok_to_free_tracepoints)) { |
153 | tp_probes->rcu.next = early_probes; |
154 | early_probes = &tp_probes->rcu; |
155 | return; |
156 | } |
157 | |
158 | /* |
159 | * Tracepoint probes are protected by both sched RCU and SRCU, |
160 | * by calling the SRCU callback in the sched RCU callback we |
161 | * cover both cases. So let us chain the SRCU and sched RCU |
162 | * callbacks to wait for both grace periods. |
163 | */ |
164 | call_rcu(head: &tp_probes->rcu, func: rcu_free_old_probes); |
165 | } |
166 | } |
167 | |
168 | static void debug_print_probes(struct tracepoint_func *funcs) |
169 | { |
170 | int i; |
171 | |
172 | if (!tracepoint_debug || !funcs) |
173 | return; |
174 | |
175 | for (i = 0; funcs[i].func; i++) |
176 | printk(KERN_DEBUG "Probe %d : %p\n" , i, funcs[i].func); |
177 | } |
178 | |
179 | static struct tracepoint_func * |
180 | func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func, |
181 | int prio) |
182 | { |
183 | struct tracepoint_func *old, *new; |
184 | int iter_probes; /* Iterate over old probe array. */ |
185 | int nr_probes = 0; /* Counter for probes */ |
186 | int pos = -1; /* Insertion position into new array */ |
187 | |
188 | if (WARN_ON(!tp_func->func)) |
189 | return ERR_PTR(error: -EINVAL); |
190 | |
191 | debug_print_probes(funcs: *funcs); |
192 | old = *funcs; |
193 | if (old) { |
194 | /* (N -> N+1), (N != 0, 1) probes */ |
195 | for (iter_probes = 0; old[iter_probes].func; iter_probes++) { |
196 | if (old[iter_probes].func == tp_stub_func) |
197 | continue; /* Skip stub functions. */ |
198 | if (old[iter_probes].func == tp_func->func && |
199 | old[iter_probes].data == tp_func->data) |
200 | return ERR_PTR(error: -EEXIST); |
201 | nr_probes++; |
202 | } |
203 | } |
204 | /* + 2 : one for new probe, one for NULL func */ |
205 | new = allocate_probes(count: nr_probes + 2); |
206 | if (new == NULL) |
207 | return ERR_PTR(error: -ENOMEM); |
208 | if (old) { |
209 | nr_probes = 0; |
210 | for (iter_probes = 0; old[iter_probes].func; iter_probes++) { |
211 | if (old[iter_probes].func == tp_stub_func) |
212 | continue; |
213 | /* Insert before probes of lower priority */ |
214 | if (pos < 0 && old[iter_probes].prio < prio) |
215 | pos = nr_probes++; |
216 | new[nr_probes++] = old[iter_probes]; |
217 | } |
218 | if (pos < 0) |
219 | pos = nr_probes++; |
220 | /* nr_probes now points to the end of the new array */ |
221 | } else { |
222 | pos = 0; |
223 | nr_probes = 1; /* must point at end of array */ |
224 | } |
225 | new[pos] = *tp_func; |
226 | new[nr_probes].func = NULL; |
227 | *funcs = new; |
228 | debug_print_probes(funcs: *funcs); |
229 | return old; |
230 | } |
231 | |
232 | static void *func_remove(struct tracepoint_func **funcs, |
233 | struct tracepoint_func *tp_func) |
234 | { |
235 | int nr_probes = 0, nr_del = 0, i; |
236 | struct tracepoint_func *old, *new; |
237 | |
238 | old = *funcs; |
239 | |
240 | if (!old) |
241 | return ERR_PTR(error: -ENOENT); |
242 | |
243 | debug_print_probes(funcs: *funcs); |
244 | /* (N -> M), (N > 1, M >= 0) probes */ |
245 | if (tp_func->func) { |
246 | for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
247 | if ((old[nr_probes].func == tp_func->func && |
248 | old[nr_probes].data == tp_func->data) || |
249 | old[nr_probes].func == tp_stub_func) |
250 | nr_del++; |
251 | } |
252 | } |
253 | |
254 | /* |
255 | * If probe is NULL, then nr_probes = nr_del = 0, and then the |
256 | * entire entry will be removed. |
257 | */ |
258 | if (nr_probes - nr_del == 0) { |
259 | /* N -> 0, (N > 1) */ |
260 | *funcs = NULL; |
261 | debug_print_probes(funcs: *funcs); |
262 | return old; |
263 | } else { |
264 | int j = 0; |
265 | /* N -> M, (N > 1, M > 0) */ |
266 | /* + 1 for NULL */ |
267 | new = allocate_probes(count: nr_probes - nr_del + 1); |
268 | if (new) { |
269 | for (i = 0; old[i].func; i++) { |
270 | if ((old[i].func != tp_func->func || |
271 | old[i].data != tp_func->data) && |
272 | old[i].func != tp_stub_func) |
273 | new[j++] = old[i]; |
274 | } |
275 | new[nr_probes - nr_del].func = NULL; |
276 | *funcs = new; |
277 | } else { |
278 | /* |
279 | * Failed to allocate, replace the old function |
280 | * with calls to tp_stub_func. |
281 | */ |
282 | for (i = 0; old[i].func; i++) { |
283 | if (old[i].func == tp_func->func && |
284 | old[i].data == tp_func->data) |
285 | WRITE_ONCE(old[i].func, tp_stub_func); |
286 | } |
287 | *funcs = old; |
288 | } |
289 | } |
290 | debug_print_probes(funcs: *funcs); |
291 | return old; |
292 | } |
293 | |
294 | /* |
295 | * Count the number of functions (enum tp_func_state) in a tp_funcs array. |
296 | */ |
297 | static enum tp_func_state nr_func_state(const struct tracepoint_func *tp_funcs) |
298 | { |
299 | if (!tp_funcs) |
300 | return TP_FUNC_0; |
301 | if (!tp_funcs[1].func) |
302 | return TP_FUNC_1; |
303 | if (!tp_funcs[2].func) |
304 | return TP_FUNC_2; |
305 | return TP_FUNC_N; /* 3 or more */ |
306 | } |
307 | |
308 | static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs) |
309 | { |
310 | void *func = tp->iterator; |
311 | |
312 | /* Synthetic events do not have static call sites */ |
313 | if (!tp->static_call_key) |
314 | return; |
315 | if (nr_func_state(tp_funcs) == TP_FUNC_1) |
316 | func = tp_funcs[0].func; |
317 | __static_call_update(key: tp->static_call_key, tramp: tp->static_call_tramp, func); |
318 | } |
319 | |
320 | /* |
321 | * Add the probe function to a tracepoint. |
322 | */ |
323 | static int tracepoint_add_func(struct tracepoint *tp, |
324 | struct tracepoint_func *func, int prio, |
325 | bool warn) |
326 | { |
327 | struct tracepoint_func *old, *tp_funcs; |
328 | int ret; |
329 | |
330 | if (tp->regfunc && !static_key_enabled(&tp->key)) { |
331 | ret = tp->regfunc(); |
332 | if (ret < 0) |
333 | return ret; |
334 | } |
335 | |
336 | tp_funcs = rcu_dereference_protected(tp->funcs, |
337 | lockdep_is_held(&tracepoints_mutex)); |
338 | old = func_add(funcs: &tp_funcs, tp_func: func, prio); |
339 | if (IS_ERR(ptr: old)) { |
340 | WARN_ON_ONCE(warn && PTR_ERR(old) != -ENOMEM); |
341 | return PTR_ERR(ptr: old); |
342 | } |
343 | |
344 | /* |
345 | * rcu_assign_pointer has as smp_store_release() which makes sure |
346 | * that the new probe callbacks array is consistent before setting |
347 | * a pointer to it. This array is referenced by __DO_TRACE from |
348 | * include/linux/tracepoint.h using rcu_dereference_sched(). |
349 | */ |
350 | switch (nr_func_state(tp_funcs)) { |
351 | case TP_FUNC_1: /* 0->1 */ |
352 | /* |
353 | * Make sure new static func never uses old data after a |
354 | * 1->0->1 transition sequence. |
355 | */ |
356 | tp_rcu_cond_sync(sync: TP_TRANSITION_SYNC_1_0_1); |
357 | /* Set static call to first function */ |
358 | tracepoint_update_call(tp, tp_funcs); |
359 | /* Both iterator and static call handle NULL tp->funcs */ |
360 | rcu_assign_pointer(tp->funcs, tp_funcs); |
361 | static_key_enable(key: &tp->key); |
362 | break; |
363 | case TP_FUNC_2: /* 1->2 */ |
364 | /* Set iterator static call */ |
365 | tracepoint_update_call(tp, tp_funcs); |
366 | /* |
367 | * Iterator callback installed before updating tp->funcs. |
368 | * Requires ordering between RCU assign/dereference and |
369 | * static call update/call. |
370 | */ |
371 | fallthrough; |
372 | case TP_FUNC_N: /* N->N+1 (N>1) */ |
373 | rcu_assign_pointer(tp->funcs, tp_funcs); |
374 | /* |
375 | * Make sure static func never uses incorrect data after a |
376 | * N->...->2->1 (N>1) transition sequence. |
377 | */ |
378 | if (tp_funcs[0].data != old[0].data) |
379 | tp_rcu_get_state(sync: TP_TRANSITION_SYNC_N_2_1); |
380 | break; |
381 | default: |
382 | WARN_ON_ONCE(1); |
383 | break; |
384 | } |
385 | |
386 | release_probes(old); |
387 | return 0; |
388 | } |
389 | |
390 | /* |
391 | * Remove a probe function from a tracepoint. |
392 | * Note: only waiting an RCU period after setting elem->call to the empty |
393 | * function insures that the original callback is not used anymore. This insured |
394 | * by preempt_disable around the call site. |
395 | */ |
396 | static int tracepoint_remove_func(struct tracepoint *tp, |
397 | struct tracepoint_func *func) |
398 | { |
399 | struct tracepoint_func *old, *tp_funcs; |
400 | |
401 | tp_funcs = rcu_dereference_protected(tp->funcs, |
402 | lockdep_is_held(&tracepoints_mutex)); |
403 | old = func_remove(funcs: &tp_funcs, tp_func: func); |
404 | if (WARN_ON_ONCE(IS_ERR(old))) |
405 | return PTR_ERR(ptr: old); |
406 | |
407 | if (tp_funcs == old) |
408 | /* Failed allocating new tp_funcs, replaced func with stub */ |
409 | return 0; |
410 | |
411 | switch (nr_func_state(tp_funcs)) { |
412 | case TP_FUNC_0: /* 1->0 */ |
413 | /* Removed last function */ |
414 | if (tp->unregfunc && static_key_enabled(&tp->key)) |
415 | tp->unregfunc(); |
416 | |
417 | static_key_disable(key: &tp->key); |
418 | /* Set iterator static call */ |
419 | tracepoint_update_call(tp, tp_funcs); |
420 | /* Both iterator and static call handle NULL tp->funcs */ |
421 | rcu_assign_pointer(tp->funcs, NULL); |
422 | /* |
423 | * Make sure new static func never uses old data after a |
424 | * 1->0->1 transition sequence. |
425 | */ |
426 | tp_rcu_get_state(sync: TP_TRANSITION_SYNC_1_0_1); |
427 | break; |
428 | case TP_FUNC_1: /* 2->1 */ |
429 | rcu_assign_pointer(tp->funcs, tp_funcs); |
430 | /* |
431 | * Make sure static func never uses incorrect data after a |
432 | * N->...->2->1 (N>2) transition sequence. If the first |
433 | * element's data has changed, then force the synchronization |
434 | * to prevent current readers that have loaded the old data |
435 | * from calling the new function. |
436 | */ |
437 | if (tp_funcs[0].data != old[0].data) |
438 | tp_rcu_get_state(sync: TP_TRANSITION_SYNC_N_2_1); |
439 | tp_rcu_cond_sync(sync: TP_TRANSITION_SYNC_N_2_1); |
440 | /* Set static call to first function */ |
441 | tracepoint_update_call(tp, tp_funcs); |
442 | break; |
443 | case TP_FUNC_2: /* N->N-1 (N>2) */ |
444 | fallthrough; |
445 | case TP_FUNC_N: |
446 | rcu_assign_pointer(tp->funcs, tp_funcs); |
447 | /* |
448 | * Make sure static func never uses incorrect data after a |
449 | * N->...->2->1 (N>2) transition sequence. |
450 | */ |
451 | if (tp_funcs[0].data != old[0].data) |
452 | tp_rcu_get_state(sync: TP_TRANSITION_SYNC_N_2_1); |
453 | break; |
454 | default: |
455 | WARN_ON_ONCE(1); |
456 | break; |
457 | } |
458 | release_probes(old); |
459 | return 0; |
460 | } |
461 | |
462 | /** |
463 | * tracepoint_probe_register_prio_may_exist - Connect a probe to a tracepoint with priority |
464 | * @tp: tracepoint |
465 | * @probe: probe handler |
466 | * @data: tracepoint data |
467 | * @prio: priority of this function over other registered functions |
468 | * |
469 | * Same as tracepoint_probe_register_prio() except that it will not warn |
470 | * if the tracepoint is already registered. |
471 | */ |
472 | int tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe, |
473 | void *data, int prio) |
474 | { |
475 | struct tracepoint_func tp_func; |
476 | int ret; |
477 | |
478 | mutex_lock(&tracepoints_mutex); |
479 | tp_func.func = probe; |
480 | tp_func.data = data; |
481 | tp_func.prio = prio; |
482 | ret = tracepoint_add_func(tp, func: &tp_func, prio, warn: false); |
483 | mutex_unlock(lock: &tracepoints_mutex); |
484 | return ret; |
485 | } |
486 | EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio_may_exist); |
487 | |
488 | /** |
489 | * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority |
490 | * @tp: tracepoint |
491 | * @probe: probe handler |
492 | * @data: tracepoint data |
493 | * @prio: priority of this function over other registered functions |
494 | * |
495 | * Returns 0 if ok, error value on error. |
496 | * Note: if @tp is within a module, the caller is responsible for |
497 | * unregistering the probe before the module is gone. This can be |
498 | * performed either with a tracepoint module going notifier, or from |
499 | * within module exit functions. |
500 | */ |
501 | int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, |
502 | void *data, int prio) |
503 | { |
504 | struct tracepoint_func tp_func; |
505 | int ret; |
506 | |
507 | mutex_lock(&tracepoints_mutex); |
508 | tp_func.func = probe; |
509 | tp_func.data = data; |
510 | tp_func.prio = prio; |
511 | ret = tracepoint_add_func(tp, func: &tp_func, prio, warn: true); |
512 | mutex_unlock(lock: &tracepoints_mutex); |
513 | return ret; |
514 | } |
515 | EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio); |
516 | |
517 | /** |
518 | * tracepoint_probe_register - Connect a probe to a tracepoint |
519 | * @tp: tracepoint |
520 | * @probe: probe handler |
521 | * @data: tracepoint data |
522 | * |
523 | * Returns 0 if ok, error value on error. |
524 | * Note: if @tp is within a module, the caller is responsible for |
525 | * unregistering the probe before the module is gone. This can be |
526 | * performed either with a tracepoint module going notifier, or from |
527 | * within module exit functions. |
528 | */ |
529 | int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data) |
530 | { |
531 | return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO); |
532 | } |
533 | EXPORT_SYMBOL_GPL(tracepoint_probe_register); |
534 | |
535 | /** |
536 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
537 | * @tp: tracepoint |
538 | * @probe: probe function pointer |
539 | * @data: tracepoint data |
540 | * |
541 | * Returns 0 if ok, error value on error. |
542 | */ |
543 | int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data) |
544 | { |
545 | struct tracepoint_func tp_func; |
546 | int ret; |
547 | |
548 | mutex_lock(&tracepoints_mutex); |
549 | tp_func.func = probe; |
550 | tp_func.data = data; |
551 | ret = tracepoint_remove_func(tp, func: &tp_func); |
552 | mutex_unlock(lock: &tracepoints_mutex); |
553 | return ret; |
554 | } |
555 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); |
556 | |
557 | static void for_each_tracepoint_range( |
558 | tracepoint_ptr_t *begin, tracepoint_ptr_t *end, |
559 | void (*fct)(struct tracepoint *tp, void *priv), |
560 | void *priv) |
561 | { |
562 | tracepoint_ptr_t *iter; |
563 | |
564 | if (!begin) |
565 | return; |
566 | for (iter = begin; iter < end; iter++) |
567 | fct(tracepoint_ptr_deref(p: iter), priv); |
568 | } |
569 | |
570 | #ifdef CONFIG_MODULES |
571 | bool trace_module_has_bad_taint(struct module *mod) |
572 | { |
573 | return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) | |
574 | (1 << TAINT_UNSIGNED_MODULE) | (1 << TAINT_TEST) | |
575 | (1 << TAINT_LIVEPATCH)); |
576 | } |
577 | |
578 | static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list); |
579 | |
580 | /** |
581 | * register_tracepoint_module_notifier - register tracepoint coming/going notifier |
582 | * @nb: notifier block |
583 | * |
584 | * Notifiers registered with this function are called on module |
585 | * coming/going with the tracepoint_module_list_mutex held. |
586 | * The notifier block callback should expect a "struct tp_module" data |
587 | * pointer. |
588 | */ |
589 | int register_tracepoint_module_notifier(struct notifier_block *nb) |
590 | { |
591 | struct tp_module *tp_mod; |
592 | int ret; |
593 | |
594 | mutex_lock(&tracepoint_module_list_mutex); |
595 | ret = blocking_notifier_chain_register(nh: &tracepoint_notify_list, nb); |
596 | if (ret) |
597 | goto end; |
598 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) |
599 | (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod); |
600 | end: |
601 | mutex_unlock(lock: &tracepoint_module_list_mutex); |
602 | return ret; |
603 | } |
604 | EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier); |
605 | |
606 | /** |
607 | * unregister_tracepoint_module_notifier - unregister tracepoint coming/going notifier |
608 | * @nb: notifier block |
609 | * |
610 | * The notifier block callback should expect a "struct tp_module" data |
611 | * pointer. |
612 | */ |
613 | int unregister_tracepoint_module_notifier(struct notifier_block *nb) |
614 | { |
615 | struct tp_module *tp_mod; |
616 | int ret; |
617 | |
618 | mutex_lock(&tracepoint_module_list_mutex); |
619 | ret = blocking_notifier_chain_unregister(nh: &tracepoint_notify_list, nb); |
620 | if (ret) |
621 | goto end; |
622 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) |
623 | (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod); |
624 | end: |
625 | mutex_unlock(lock: &tracepoint_module_list_mutex); |
626 | return ret; |
627 | |
628 | } |
629 | EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier); |
630 | |
631 | /* |
632 | * Ensure the tracer unregistered the module's probes before the module |
633 | * teardown is performed. Prevents leaks of probe and data pointers. |
634 | */ |
635 | static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv) |
636 | { |
637 | WARN_ON_ONCE(tp->funcs); |
638 | } |
639 | |
640 | static int tracepoint_module_coming(struct module *mod) |
641 | { |
642 | struct tp_module *tp_mod; |
643 | |
644 | if (!mod->num_tracepoints) |
645 | return 0; |
646 | |
647 | /* |
648 | * We skip modules that taint the kernel, especially those with different |
649 | * module headers (for forced load), to make sure we don't cause a crash. |
650 | * Staging, out-of-tree, unsigned GPL, and test modules are fine. |
651 | */ |
652 | if (trace_module_has_bad_taint(mod)) |
653 | return 0; |
654 | |
655 | tp_mod = kmalloc(size: sizeof(struct tp_module), GFP_KERNEL); |
656 | if (!tp_mod) |
657 | return -ENOMEM; |
658 | tp_mod->mod = mod; |
659 | |
660 | mutex_lock(&tracepoint_module_list_mutex); |
661 | list_add_tail(new: &tp_mod->list, head: &tracepoint_module_list); |
662 | blocking_notifier_call_chain(nh: &tracepoint_notify_list, |
663 | val: MODULE_STATE_COMING, v: tp_mod); |
664 | mutex_unlock(lock: &tracepoint_module_list_mutex); |
665 | return 0; |
666 | } |
667 | |
668 | static void tracepoint_module_going(struct module *mod) |
669 | { |
670 | struct tp_module *tp_mod; |
671 | |
672 | if (!mod->num_tracepoints) |
673 | return; |
674 | |
675 | mutex_lock(&tracepoint_module_list_mutex); |
676 | list_for_each_entry(tp_mod, &tracepoint_module_list, list) { |
677 | if (tp_mod->mod == mod) { |
678 | blocking_notifier_call_chain(nh: &tracepoint_notify_list, |
679 | val: MODULE_STATE_GOING, v: tp_mod); |
680 | list_del(entry: &tp_mod->list); |
681 | kfree(objp: tp_mod); |
682 | /* |
683 | * Called the going notifier before checking for |
684 | * quiescence. |
685 | */ |
686 | for_each_tracepoint_range(begin: mod->tracepoints_ptrs, |
687 | end: mod->tracepoints_ptrs + mod->num_tracepoints, |
688 | fct: tp_module_going_check_quiescent, NULL); |
689 | break; |
690 | } |
691 | } |
692 | /* |
693 | * In the case of modules that were tainted at "coming", we'll simply |
694 | * walk through the list without finding it. We cannot use the "tainted" |
695 | * flag on "going", in case a module taints the kernel only after being |
696 | * loaded. |
697 | */ |
698 | mutex_unlock(lock: &tracepoint_module_list_mutex); |
699 | } |
700 | |
701 | static int tracepoint_module_notify(struct notifier_block *self, |
702 | unsigned long val, void *data) |
703 | { |
704 | struct module *mod = data; |
705 | int ret = 0; |
706 | |
707 | switch (val) { |
708 | case MODULE_STATE_COMING: |
709 | ret = tracepoint_module_coming(mod); |
710 | break; |
711 | case MODULE_STATE_LIVE: |
712 | break; |
713 | case MODULE_STATE_GOING: |
714 | tracepoint_module_going(mod); |
715 | break; |
716 | case MODULE_STATE_UNFORMED: |
717 | break; |
718 | } |
719 | return notifier_from_errno(err: ret); |
720 | } |
721 | |
722 | static struct notifier_block tracepoint_module_nb = { |
723 | .notifier_call = tracepoint_module_notify, |
724 | .priority = 0, |
725 | }; |
726 | |
727 | static __init int init_tracepoints(void) |
728 | { |
729 | int ret; |
730 | |
731 | ret = register_module_notifier(nb: &tracepoint_module_nb); |
732 | if (ret) |
733 | pr_warn("Failed to register tracepoint module enter notifier\n" ); |
734 | |
735 | return ret; |
736 | } |
737 | __initcall(init_tracepoints); |
738 | #endif /* CONFIG_MODULES */ |
739 | |
740 | /** |
741 | * for_each_kernel_tracepoint - iteration on all kernel tracepoints |
742 | * @fct: callback |
743 | * @priv: private data |
744 | */ |
745 | void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv), |
746 | void *priv) |
747 | { |
748 | for_each_tracepoint_range(begin: __start___tracepoints_ptrs, |
749 | end: __stop___tracepoints_ptrs, fct, priv); |
750 | } |
751 | EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint); |
752 | |
753 | #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS |
754 | |
755 | /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ |
756 | static int sys_tracepoint_refcount; |
757 | |
758 | int syscall_regfunc(void) |
759 | { |
760 | struct task_struct *p, *t; |
761 | |
762 | if (!sys_tracepoint_refcount) { |
763 | read_lock(&tasklist_lock); |
764 | for_each_process_thread(p, t) { |
765 | set_task_syscall_work(t, SYSCALL_TRACEPOINT); |
766 | } |
767 | read_unlock(&tasklist_lock); |
768 | } |
769 | sys_tracepoint_refcount++; |
770 | |
771 | return 0; |
772 | } |
773 | |
774 | void syscall_unregfunc(void) |
775 | { |
776 | struct task_struct *p, *t; |
777 | |
778 | sys_tracepoint_refcount--; |
779 | if (!sys_tracepoint_refcount) { |
780 | read_lock(&tasklist_lock); |
781 | for_each_process_thread(p, t) { |
782 | clear_task_syscall_work(t, SYSCALL_TRACEPOINT); |
783 | } |
784 | read_unlock(&tasklist_lock); |
785 | } |
786 | } |
787 | #endif |
788 | |