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;
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 (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
151 /* Insert before probes of lower priority */
152 if (pos
< 0 && old
[nr_probes
].prio
< prio
)
154 if (old
[nr_probes
].func
== tp_func
->func
&&
155 old
[nr_probes
].data
== tp_func
->data
)
156 return ERR_PTR(-EEXIST
);
157 if (old
[nr_probes
].func
== tp_stub_func
)
161 /* + 2 : one for new probe, one for NULL func - stub functions */
162 new = allocate_probes(nr_probes
+ 2 - stub_funcs
);
164 return ERR_PTR(-ENOMEM
);
167 /* Need to copy one at a time to remove stubs */
171 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
172 if (old
[nr_probes
].func
== tp_stub_func
)
174 if (pos
< 0 && old
[nr_probes
].prio
< prio
)
176 new[probes
++] = old
[nr_probes
];
182 nr_probes
--; /* Account for insertion */
184 } else if (pos
< 0) {
186 memcpy(new, old
, nr_probes
* sizeof(struct tracepoint_func
));
188 /* Copy higher priority probes ahead of the new probe */
189 memcpy(new, old
, pos
* sizeof(struct tracepoint_func
));
190 /* Copy the rest after it. */
191 memcpy(new + pos
+ 1, old
+ pos
,
192 (nr_probes
- pos
) * sizeof(struct tracepoint_func
));
197 new[nr_probes
+ 1].func
= NULL
;
199 debug_print_probes(*funcs
);
203 static void *func_remove(struct tracepoint_func
**funcs
,
204 struct tracepoint_func
*tp_func
)
206 int nr_probes
= 0, nr_del
= 0, i
;
207 struct tracepoint_func
*old
, *new;
212 return ERR_PTR(-ENOENT
);
214 debug_print_probes(*funcs
);
215 /* (N -> M), (N > 1, M >= 0) probes */
217 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
218 if ((old
[nr_probes
].func
== tp_func
->func
&&
219 old
[nr_probes
].data
== tp_func
->data
) ||
220 old
[nr_probes
].func
== tp_stub_func
)
226 * If probe is NULL, then nr_probes = nr_del = 0, and then the
227 * entire entry will be removed.
229 if (nr_probes
- nr_del
== 0) {
230 /* N -> 0, (N > 1) */
232 debug_print_probes(*funcs
);
236 /* N -> M, (N > 1, M > 0) */
238 new = allocate_probes(nr_probes
- nr_del
+ 1);
240 for (i
= 0; old
[i
].func
; i
++)
241 if ((old
[i
].func
!= tp_func
->func
242 || old
[i
].data
!= tp_func
->data
)
243 && old
[i
].func
!= tp_stub_func
)
245 new[nr_probes
- nr_del
].func
= NULL
;
249 * Failed to allocate, replace the old function
250 * with calls to tp_stub_func.
252 for (i
= 0; old
[i
].func
; i
++)
253 if (old
[i
].func
== tp_func
->func
&&
254 old
[i
].data
== tp_func
->data
) {
255 old
[i
].func
= tp_stub_func
;
256 /* Set the prio to the next event. */
266 debug_print_probes(*funcs
);
270 static void tracepoint_update_call(struct tracepoint
*tp
, struct tracepoint_func
*tp_funcs
, bool sync
)
272 void *func
= tp
->iterator
;
274 /* Synthetic events do not have static call sites */
275 if (!tp
->static_call_key
)
278 if (!tp_funcs
[1].func
) {
279 func
= tp_funcs
[0].func
;
281 * If going from the iterator back to a single caller,
282 * we need to synchronize with __DO_TRACE to make sure
283 * that the data passed to the callback is the one that
284 * belongs to that callback.
287 tracepoint_synchronize_unregister();
290 __static_call_update(tp
->static_call_key
, tp
->static_call_tramp
, func
);
294 * Add the probe function to a tracepoint.
296 static int tracepoint_add_func(struct tracepoint
*tp
,
297 struct tracepoint_func
*func
, int prio
)
299 struct tracepoint_func
*old
, *tp_funcs
;
302 if (tp
->regfunc
&& !static_key_enabled(&tp
->key
)) {
308 tp_funcs
= rcu_dereference_protected(tp
->funcs
,
309 lockdep_is_held(&tracepoints_mutex
));
310 old
= func_add(&tp_funcs
, func
, prio
);
312 WARN_ON_ONCE(PTR_ERR(old
) != -ENOMEM
);
317 * rcu_assign_pointer has as smp_store_release() which makes sure
318 * that the new probe callbacks array is consistent before setting
319 * a pointer to it. This array is referenced by __DO_TRACE from
320 * include/linux/tracepoint.h using rcu_dereference_sched().
322 rcu_assign_pointer(tp
->funcs
, tp_funcs
);
323 tracepoint_update_call(tp
, tp_funcs
, false);
324 static_key_enable(&tp
->key
);
331 * Remove a probe function from a tracepoint.
332 * Note: only waiting an RCU period after setting elem->call to the empty
333 * function insures that the original callback is not used anymore. This insured
334 * by preempt_disable around the call site.
336 static int tracepoint_remove_func(struct tracepoint
*tp
,
337 struct tracepoint_func
*func
)
339 struct tracepoint_func
*old
, *tp_funcs
;
341 tp_funcs
= rcu_dereference_protected(tp
->funcs
,
342 lockdep_is_held(&tracepoints_mutex
));
343 old
= func_remove(&tp_funcs
, func
);
344 if (WARN_ON_ONCE(IS_ERR(old
)))
348 /* Failed allocating new tp_funcs, replaced func with stub */
352 /* Removed last function */
353 if (tp
->unregfunc
&& static_key_enabled(&tp
->key
))
356 static_key_disable(&tp
->key
);
357 rcu_assign_pointer(tp
->funcs
, tp_funcs
);
359 rcu_assign_pointer(tp
->funcs
, tp_funcs
);
360 tracepoint_update_call(tp
, tp_funcs
,
361 tp_funcs
[0].func
!= old
[0].func
);
368 * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
370 * @probe: probe handler
371 * @data: tracepoint data
372 * @prio: priority of this function over other registered functions
374 * Returns 0 if ok, error value on error.
375 * Note: if @tp is within a module, the caller is responsible for
376 * unregistering the probe before the module is gone. This can be
377 * performed either with a tracepoint module going notifier, or from
378 * within module exit functions.
380 int tracepoint_probe_register_prio(struct tracepoint
*tp
, void *probe
,
381 void *data
, int prio
)
383 struct tracepoint_func tp_func
;
386 mutex_lock(&tracepoints_mutex
);
387 tp_func
.func
= probe
;
390 ret
= tracepoint_add_func(tp
, &tp_func
, prio
);
391 mutex_unlock(&tracepoints_mutex
);
394 EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio
);
397 * tracepoint_probe_register - Connect a probe to a tracepoint
399 * @probe: probe handler
400 * @data: tracepoint data
402 * Returns 0 if ok, error value on error.
403 * Note: if @tp is within a module, the caller is responsible for
404 * unregistering the probe before the module is gone. This can be
405 * performed either with a tracepoint module going notifier, or from
406 * within module exit functions.
408 int tracepoint_probe_register(struct tracepoint
*tp
, void *probe
, void *data
)
410 return tracepoint_probe_register_prio(tp
, probe
, data
, TRACEPOINT_DEFAULT_PRIO
);
412 EXPORT_SYMBOL_GPL(tracepoint_probe_register
);
415 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
417 * @probe: probe function pointer
418 * @data: tracepoint data
420 * Returns 0 if ok, error value on error.
422 int tracepoint_probe_unregister(struct tracepoint
*tp
, void *probe
, void *data
)
424 struct tracepoint_func tp_func
;
427 mutex_lock(&tracepoints_mutex
);
428 tp_func
.func
= probe
;
430 ret
= tracepoint_remove_func(tp
, &tp_func
);
431 mutex_unlock(&tracepoints_mutex
);
434 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister
);
436 static void for_each_tracepoint_range(
437 tracepoint_ptr_t
*begin
, tracepoint_ptr_t
*end
,
438 void (*fct
)(struct tracepoint
*tp
, void *priv
),
441 tracepoint_ptr_t
*iter
;
445 for (iter
= begin
; iter
< end
; iter
++)
446 fct(tracepoint_ptr_deref(iter
), priv
);
449 #ifdef CONFIG_MODULES
450 bool trace_module_has_bad_taint(struct module
*mod
)
452 return mod
->taints
& ~((1 << TAINT_OOT_MODULE
) | (1 << TAINT_CRAP
) |
453 (1 << TAINT_UNSIGNED_MODULE
));
456 static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list
);
459 * register_tracepoint_notifier - register tracepoint coming/going notifier
460 * @nb: notifier block
462 * Notifiers registered with this function are called on module
463 * coming/going with the tracepoint_module_list_mutex held.
464 * The notifier block callback should expect a "struct tp_module" data
467 int register_tracepoint_module_notifier(struct notifier_block
*nb
)
469 struct tp_module
*tp_mod
;
472 mutex_lock(&tracepoint_module_list_mutex
);
473 ret
= blocking_notifier_chain_register(&tracepoint_notify_list
, nb
);
476 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
)
477 (void) nb
->notifier_call(nb
, MODULE_STATE_COMING
, tp_mod
);
479 mutex_unlock(&tracepoint_module_list_mutex
);
482 EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier
);
485 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
486 * @nb: notifier block
488 * The notifier block callback should expect a "struct tp_module" data
491 int unregister_tracepoint_module_notifier(struct notifier_block
*nb
)
493 struct tp_module
*tp_mod
;
496 mutex_lock(&tracepoint_module_list_mutex
);
497 ret
= blocking_notifier_chain_unregister(&tracepoint_notify_list
, nb
);
500 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
)
501 (void) nb
->notifier_call(nb
, MODULE_STATE_GOING
, tp_mod
);
503 mutex_unlock(&tracepoint_module_list_mutex
);
507 EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier
);
510 * Ensure the tracer unregistered the module's probes before the module
511 * teardown is performed. Prevents leaks of probe and data pointers.
513 static void tp_module_going_check_quiescent(struct tracepoint
*tp
, void *priv
)
515 WARN_ON_ONCE(tp
->funcs
);
518 static int tracepoint_module_coming(struct module
*mod
)
520 struct tp_module
*tp_mod
;
523 if (!mod
->num_tracepoints
)
527 * We skip modules that taint the kernel, especially those with different
528 * module headers (for forced load), to make sure we don't cause a crash.
529 * Staging, out-of-tree, and unsigned GPL modules are fine.
531 if (trace_module_has_bad_taint(mod
))
533 mutex_lock(&tracepoint_module_list_mutex
);
534 tp_mod
= kmalloc(sizeof(struct tp_module
), GFP_KERNEL
);
540 list_add_tail(&tp_mod
->list
, &tracepoint_module_list
);
541 blocking_notifier_call_chain(&tracepoint_notify_list
,
542 MODULE_STATE_COMING
, tp_mod
);
544 mutex_unlock(&tracepoint_module_list_mutex
);
548 static void tracepoint_module_going(struct module
*mod
)
550 struct tp_module
*tp_mod
;
552 if (!mod
->num_tracepoints
)
555 mutex_lock(&tracepoint_module_list_mutex
);
556 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
) {
557 if (tp_mod
->mod
== mod
) {
558 blocking_notifier_call_chain(&tracepoint_notify_list
,
559 MODULE_STATE_GOING
, tp_mod
);
560 list_del(&tp_mod
->list
);
563 * Called the going notifier before checking for
566 for_each_tracepoint_range(mod
->tracepoints_ptrs
,
567 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
,
568 tp_module_going_check_quiescent
, NULL
);
573 * In the case of modules that were tainted at "coming", we'll simply
574 * walk through the list without finding it. We cannot use the "tainted"
575 * flag on "going", in case a module taints the kernel only after being
578 mutex_unlock(&tracepoint_module_list_mutex
);
581 static int tracepoint_module_notify(struct notifier_block
*self
,
582 unsigned long val
, void *data
)
584 struct module
*mod
= data
;
588 case MODULE_STATE_COMING
:
589 ret
= tracepoint_module_coming(mod
);
591 case MODULE_STATE_LIVE
:
593 case MODULE_STATE_GOING
:
594 tracepoint_module_going(mod
);
596 case MODULE_STATE_UNFORMED
:
599 return notifier_from_errno(ret
);
602 static struct notifier_block tracepoint_module_nb
= {
603 .notifier_call
= tracepoint_module_notify
,
607 static __init
int init_tracepoints(void)
611 ret
= register_module_notifier(&tracepoint_module_nb
);
613 pr_warn("Failed to register tracepoint module enter notifier\n");
617 __initcall(init_tracepoints
);
618 #endif /* CONFIG_MODULES */
621 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
623 * @priv: private data
625 void for_each_kernel_tracepoint(void (*fct
)(struct tracepoint
*tp
, void *priv
),
628 for_each_tracepoint_range(__start___tracepoints_ptrs
,
629 __stop___tracepoints_ptrs
, fct
, priv
);
631 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint
);
633 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
635 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
636 static int sys_tracepoint_refcount
;
638 int syscall_regfunc(void)
640 struct task_struct
*p
, *t
;
642 if (!sys_tracepoint_refcount
) {
643 read_lock(&tasklist_lock
);
644 for_each_process_thread(p
, t
) {
645 set_task_syscall_work(t
, SYSCALL_TRACEPOINT
);
647 read_unlock(&tasklist_lock
);
649 sys_tracepoint_refcount
++;
654 void syscall_unregfunc(void)
656 struct task_struct
*p
, *t
;
658 sys_tracepoint_refcount
--;
659 if (!sys_tracepoint_refcount
) {
660 read_lock(&tasklist_lock
);
661 for_each_process_thread(p
, t
) {
662 clear_task_syscall_work(t
, SYSCALL_TRACEPOINT
);
664 read_unlock(&tasklist_lock
);