1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2008-2014 Mathieu Desnoyers
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>
18 extern tracepoint_ptr_t __start___tracepoints_ptrs[];
19 extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
21 DEFINE_SRCU(tracepoint_srcu);
22 EXPORT_SYMBOL_GPL(tracepoint_srcu);
24 /* Set to 1 to enable tracepoint debug output */
25 static const int tracepoint_debug;
29 * Tracepoint module list mutex protects the local module list.
31 static DEFINE_MUTEX(tracepoint_module_list_mutex);
33 /* Local list of struct tp_module */
34 static LIST_HEAD(tracepoint_module_list);
35 #endif /* CONFIG_MODULES */
38 * tracepoints_mutex protects the builtin and module tracepoints.
39 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
41 static DEFINE_MUTEX(tracepoints_mutex);
43 static struct rcu_head *early_probes;
44 static bool ok_to_free_tracepoints;
48 * It is used to delay the free of multiple probes array until a quiescent
53 struct tracepoint_func probes[];
56 /* Called in removal of a func but failed to allocate a new tp_funcs */
57 static void tp_stub_func(void)
62 static inline void *allocate_probes(int count)
64 struct tp_probes *p = kmalloc(struct_size(p, probes, count),
66 return p == NULL ? NULL : p->probes;
69 static void srcu_free_old_probes(struct rcu_head *head)
71 kfree(container_of(head, struct tp_probes, rcu));
74 static void rcu_free_old_probes(struct rcu_head *head)
76 call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
79 static __init int release_early_probes(void)
83 ok_to_free_tracepoints = true;
85 while (early_probes) {
87 early_probes = tmp->next;
88 call_rcu(tmp, rcu_free_old_probes);
94 /* SRCU is initialized at core_initcall */
95 postcore_initcall(release_early_probes);
97 static inline void release_probes(struct tracepoint_func *old)
100 struct tp_probes *tp_probes = container_of(old,
101 struct tp_probes, probes[0]);
104 * We can't free probes if SRCU is not initialized yet.
105 * Postpone the freeing till after SRCU is initialized.
107 if (unlikely(!ok_to_free_tracepoints)) {
108 tp_probes->rcu.next = early_probes;
109 early_probes = &tp_probes->rcu;
114 * Tracepoint probes are protected by both sched RCU and SRCU,
115 * by calling the SRCU callback in the sched RCU callback we
116 * cover both cases. So let us chain the SRCU and sched RCU
117 * callbacks to wait for both grace periods.
119 call_rcu(&tp_probes->rcu, rcu_free_old_probes);
123 static void debug_print_probes(struct tracepoint_func *funcs)
127 if (!tracepoint_debug || !funcs)
130 for (i = 0; funcs[i].func; i++)
131 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
134 static struct tracepoint_func *
135 func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
138 struct tracepoint_func *old, *new;
139 int iter_probes; /* Iterate over old probe array. */
140 int nr_probes = 0; /* Counter for probes */
141 int pos = -1; /* Insertion position into new array */
143 if (WARN_ON(!tp_func->func))
144 return ERR_PTR(-EINVAL);
146 debug_print_probes(*funcs);
149 /* (N -> N+1), (N != 0, 1) probes */
150 for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
151 if (old[iter_probes].func == tp_stub_func)
152 continue; /* Skip stub functions. */
153 if (old[iter_probes].func == tp_func->func &&
154 old[iter_probes].data == tp_func->data)
155 return ERR_PTR(-EEXIST);
159 /* + 2 : one for new probe, one for NULL func */
160 new = allocate_probes(nr_probes + 2);
162 return ERR_PTR(-ENOMEM);
165 for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
166 if (old[iter_probes].func == tp_stub_func)
168 /* Insert before probes of lower priority */
169 if (pos < 0 && old[iter_probes].prio < prio)
171 new[nr_probes++] = old[iter_probes];
175 /* nr_probes now points to the end of the new array */
178 nr_probes = 1; /* must point at end of array */
181 new[nr_probes].func = NULL;
183 debug_print_probes(*funcs);
187 static void *func_remove(struct tracepoint_func **funcs,
188 struct tracepoint_func *tp_func)
190 int nr_probes = 0, nr_del = 0, i;
191 struct tracepoint_func *old, *new;
196 return ERR_PTR(-ENOENT);
198 debug_print_probes(*funcs);
199 /* (N -> M), (N > 1, M >= 0) probes */
201 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
202 if ((old[nr_probes].func == tp_func->func &&
203 old[nr_probes].data == tp_func->data) ||
204 old[nr_probes].func == tp_stub_func)
210 * If probe is NULL, then nr_probes = nr_del = 0, and then the
211 * entire entry will be removed.
213 if (nr_probes - nr_del == 0) {
214 /* N -> 0, (N > 1) */
216 debug_print_probes(*funcs);
220 /* N -> M, (N > 1, M > 0) */
222 new = allocate_probes(nr_probes - nr_del + 1);
224 for (i = 0; old[i].func; i++) {
225 if ((old[i].func != tp_func->func ||
226 old[i].data != tp_func->data) &&
227 old[i].func != tp_stub_func)
230 new[nr_probes - nr_del].func = NULL;
234 * Failed to allocate, replace the old function
235 * with calls to tp_stub_func.
237 for (i = 0; old[i].func; i++) {
238 if (old[i].func == tp_func->func &&
239 old[i].data == tp_func->data)
240 WRITE_ONCE(old[i].func, tp_stub_func);
245 debug_print_probes(*funcs);
249 static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs, bool sync)
251 void *func = tp->iterator;
253 /* Synthetic events do not have static call sites */
254 if (!tp->static_call_key)
257 if (!tp_funcs[1].func) {
258 func = tp_funcs[0].func;
260 * If going from the iterator back to a single caller,
261 * we need to synchronize with __DO_TRACE to make sure
262 * that the data passed to the callback is the one that
263 * belongs to that callback.
266 tracepoint_synchronize_unregister();
269 __static_call_update(tp->static_call_key, tp->static_call_tramp, func);
273 * Add the probe function to a tracepoint.
275 static int tracepoint_add_func(struct tracepoint *tp,
276 struct tracepoint_func *func, int prio,
279 struct tracepoint_func *old, *tp_funcs;
282 if (tp->regfunc && !static_key_enabled(&tp->key)) {
288 tp_funcs = rcu_dereference_protected(tp->funcs,
289 lockdep_is_held(&tracepoints_mutex));
290 old = func_add(&tp_funcs, func, prio);
292 WARN_ON_ONCE(warn && PTR_ERR(old) != -ENOMEM);
297 * rcu_assign_pointer has as smp_store_release() which makes sure
298 * that the new probe callbacks array is consistent before setting
299 * a pointer to it. This array is referenced by __DO_TRACE from
300 * include/linux/tracepoint.h using rcu_dereference_sched().
302 rcu_assign_pointer(tp->funcs, tp_funcs);
303 tracepoint_update_call(tp, tp_funcs, false);
304 static_key_enable(&tp->key);
311 * Remove a probe function from a tracepoint.
312 * Note: only waiting an RCU period after setting elem->call to the empty
313 * function insures that the original callback is not used anymore. This insured
314 * by preempt_disable around the call site.
316 static int tracepoint_remove_func(struct tracepoint *tp,
317 struct tracepoint_func *func)
319 struct tracepoint_func *old, *tp_funcs;
321 tp_funcs = rcu_dereference_protected(tp->funcs,
322 lockdep_is_held(&tracepoints_mutex));
323 old = func_remove(&tp_funcs, func);
324 if (WARN_ON_ONCE(IS_ERR(old)))
328 /* Failed allocating new tp_funcs, replaced func with stub */
332 /* Removed last function */
333 if (tp->unregfunc && static_key_enabled(&tp->key))
336 static_key_disable(&tp->key);
337 rcu_assign_pointer(tp->funcs, tp_funcs);
339 rcu_assign_pointer(tp->funcs, tp_funcs);
340 tracepoint_update_call(tp, tp_funcs,
341 tp_funcs[0].func != old[0].func);
348 * tracepoint_probe_register_prio_may_exist - Connect a probe to a tracepoint with priority
350 * @probe: probe handler
351 * @data: tracepoint data
352 * @prio: priority of this function over other registered functions
354 * Same as tracepoint_probe_register_prio() except that it will not warn
355 * if the tracepoint is already registered.
357 int tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe,
358 void *data, int prio)
360 struct tracepoint_func tp_func;
363 mutex_lock(&tracepoints_mutex);
364 tp_func.func = probe;
367 ret = tracepoint_add_func(tp, &tp_func, prio, false);
368 mutex_unlock(&tracepoints_mutex);
371 EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio_may_exist);
374 * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
376 * @probe: probe handler
377 * @data: tracepoint data
378 * @prio: priority of this function over other registered functions
380 * Returns 0 if ok, error value on error.
381 * Note: if @tp is within a module, the caller is responsible for
382 * unregistering the probe before the module is gone. This can be
383 * performed either with a tracepoint module going notifier, or from
384 * within module exit functions.
386 int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
387 void *data, int prio)
389 struct tracepoint_func tp_func;
392 mutex_lock(&tracepoints_mutex);
393 tp_func.func = probe;
396 ret = tracepoint_add_func(tp, &tp_func, prio, true);
397 mutex_unlock(&tracepoints_mutex);
400 EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
403 * tracepoint_probe_register - Connect a probe to a tracepoint
405 * @probe: probe handler
406 * @data: tracepoint data
408 * Returns 0 if ok, error value on error.
409 * Note: if @tp is within a module, the caller is responsible for
410 * unregistering the probe before the module is gone. This can be
411 * performed either with a tracepoint module going notifier, or from
412 * within module exit functions.
414 int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
416 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
418 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
421 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
423 * @probe: probe function pointer
424 * @data: tracepoint data
426 * Returns 0 if ok, error value on error.
428 int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
430 struct tracepoint_func tp_func;
433 mutex_lock(&tracepoints_mutex);
434 tp_func.func = probe;
436 ret = tracepoint_remove_func(tp, &tp_func);
437 mutex_unlock(&tracepoints_mutex);
440 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
442 static void for_each_tracepoint_range(
443 tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
444 void (*fct)(struct tracepoint *tp, void *priv),
447 tracepoint_ptr_t *iter;
451 for (iter = begin; iter < end; iter++)
452 fct(tracepoint_ptr_deref(iter), priv);
455 #ifdef CONFIG_MODULES
456 bool trace_module_has_bad_taint(struct module *mod)
458 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
459 (1 << TAINT_UNSIGNED_MODULE));
462 static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
465 * register_tracepoint_notifier - register tracepoint coming/going notifier
466 * @nb: notifier block
468 * Notifiers registered with this function are called on module
469 * coming/going with the tracepoint_module_list_mutex held.
470 * The notifier block callback should expect a "struct tp_module" data
473 int register_tracepoint_module_notifier(struct notifier_block *nb)
475 struct tp_module *tp_mod;
478 mutex_lock(&tracepoint_module_list_mutex);
479 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
482 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
483 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
485 mutex_unlock(&tracepoint_module_list_mutex);
488 EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
491 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
492 * @nb: notifier block
494 * The notifier block callback should expect a "struct tp_module" data
497 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
499 struct tp_module *tp_mod;
502 mutex_lock(&tracepoint_module_list_mutex);
503 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
506 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
507 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
509 mutex_unlock(&tracepoint_module_list_mutex);
513 EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
516 * Ensure the tracer unregistered the module's probes before the module
517 * teardown is performed. Prevents leaks of probe and data pointers.
519 static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
521 WARN_ON_ONCE(tp->funcs);
524 static int tracepoint_module_coming(struct module *mod)
526 struct tp_module *tp_mod;
529 if (!mod->num_tracepoints)
533 * We skip modules that taint the kernel, especially those with different
534 * module headers (for forced load), to make sure we don't cause a crash.
535 * Staging, out-of-tree, and unsigned GPL modules are fine.
537 if (trace_module_has_bad_taint(mod))
539 mutex_lock(&tracepoint_module_list_mutex);
540 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
546 list_add_tail(&tp_mod->list, &tracepoint_module_list);
547 blocking_notifier_call_chain(&tracepoint_notify_list,
548 MODULE_STATE_COMING, tp_mod);
550 mutex_unlock(&tracepoint_module_list_mutex);
554 static void tracepoint_module_going(struct module *mod)
556 struct tp_module *tp_mod;
558 if (!mod->num_tracepoints)
561 mutex_lock(&tracepoint_module_list_mutex);
562 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
563 if (tp_mod->mod == mod) {
564 blocking_notifier_call_chain(&tracepoint_notify_list,
565 MODULE_STATE_GOING, tp_mod);
566 list_del(&tp_mod->list);
569 * Called the going notifier before checking for
572 for_each_tracepoint_range(mod->tracepoints_ptrs,
573 mod->tracepoints_ptrs + mod->num_tracepoints,
574 tp_module_going_check_quiescent, NULL);
579 * In the case of modules that were tainted at "coming", we'll simply
580 * walk through the list without finding it. We cannot use the "tainted"
581 * flag on "going", in case a module taints the kernel only after being
584 mutex_unlock(&tracepoint_module_list_mutex);
587 static int tracepoint_module_notify(struct notifier_block *self,
588 unsigned long val, void *data)
590 struct module *mod = data;
594 case MODULE_STATE_COMING:
595 ret = tracepoint_module_coming(mod);
597 case MODULE_STATE_LIVE:
599 case MODULE_STATE_GOING:
600 tracepoint_module_going(mod);
602 case MODULE_STATE_UNFORMED:
605 return notifier_from_errno(ret);
608 static struct notifier_block tracepoint_module_nb = {
609 .notifier_call = tracepoint_module_notify,
613 static __init int init_tracepoints(void)
617 ret = register_module_notifier(&tracepoint_module_nb);
619 pr_warn("Failed to register tracepoint module enter notifier\n");
623 __initcall(init_tracepoints);
624 #endif /* CONFIG_MODULES */
627 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
629 * @priv: private data
631 void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
634 for_each_tracepoint_range(__start___tracepoints_ptrs,
635 __stop___tracepoints_ptrs, fct, priv);
637 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
639 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
641 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
642 static int sys_tracepoint_refcount;
644 int syscall_regfunc(void)
646 struct task_struct *p, *t;
648 if (!sys_tracepoint_refcount) {
649 read_lock(&tasklist_lock);
650 for_each_process_thread(p, t) {
651 set_task_syscall_work(t, SYSCALL_TRACEPOINT);
653 read_unlock(&tasklist_lock);
655 sys_tracepoint_refcount++;
660 void syscall_unregfunc(void)
662 struct task_struct *p, *t;
664 sys_tracepoint_refcount--;
665 if (!sys_tracepoint_refcount) {
666 read_lock(&tasklist_lock);
667 for_each_process_thread(p, t) {
668 clear_task_syscall_work(t, SYSCALL_TRACEPOINT);
670 read_unlock(&tasklist_lock);