2 * Copyright (C) 2008 Mathieu Desnoyers
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 #include <linux/types.h>
21 #include <linux/jhash.h>
22 #include <linux/list.h>
23 #include <linux/rcupdate.h>
24 #include <linux/tracepoint.h>
25 #include <linux/err.h>
26 #include <linux/slab.h>
27 #include <linux/sched.h>
28 #include <linux/static_key.h>
30 extern struct tracepoint
* const __start___tracepoints_ptrs
[];
31 extern struct tracepoint
* const __stop___tracepoints_ptrs
[];
33 /* Set to 1 to enable tracepoint debug output */
34 static const int tracepoint_debug
;
37 * Tracepoints mutex protects the builtin and module tracepoints and the hash
38 * table, as well as the local module list.
40 static DEFINE_MUTEX(tracepoints_mutex
);
43 /* Local list of struct module */
44 static LIST_HEAD(tracepoint_module_list
);
45 #endif /* CONFIG_MODULES */
48 * Tracepoint hash table, containing the active tracepoints.
49 * Protected by tracepoints_mutex.
51 #define TRACEPOINT_HASH_BITS 6
52 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
53 static struct hlist_head tracepoint_table
[TRACEPOINT_TABLE_SIZE
];
57 * It is used to delay the free of multiple probes array until a quiescent
59 * Tracepoint entries modifications are protected by the tracepoints_mutex.
61 struct tracepoint_entry
{
62 struct hlist_node hlist
;
63 struct tracepoint_func
*funcs
;
64 int refcount
; /* Number of times armed. 0 if disarmed. */
71 struct list_head list
;
73 struct tracepoint_func probes
[0];
76 static inline void *allocate_probes(int count
)
78 struct tp_probes
*p
= kmalloc(count
* sizeof(struct tracepoint_func
)
79 + sizeof(struct tp_probes
), GFP_KERNEL
);
80 return p
== NULL
? NULL
: p
->probes
;
83 static void rcu_free_old_probes(struct rcu_head
*head
)
85 kfree(container_of(head
, struct tp_probes
, u
.rcu
));
88 static inline void release_probes(struct tracepoint_func
*old
)
91 struct tp_probes
*tp_probes
= container_of(old
,
92 struct tp_probes
, probes
[0]);
93 call_rcu_sched(&tp_probes
->u
.rcu
, rcu_free_old_probes
);
97 static void debug_print_probes(struct tracepoint_entry
*entry
)
101 if (!tracepoint_debug
|| !entry
->funcs
)
104 for (i
= 0; entry
->funcs
[i
].func
; i
++)
105 printk(KERN_DEBUG
"Probe %d : %p\n", i
, entry
->funcs
[i
].func
);
108 static struct tracepoint_func
*
109 tracepoint_entry_add_probe(struct tracepoint_entry
*entry
,
110 void *probe
, void *data
)
113 struct tracepoint_func
*old
, *new;
116 return ERR_PTR(-EINVAL
);
118 debug_print_probes(entry
);
121 /* (N -> N+1), (N != 0, 1) probes */
122 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
123 if (old
[nr_probes
].func
== probe
&&
124 old
[nr_probes
].data
== data
)
125 return ERR_PTR(-EEXIST
);
127 /* + 2 : one for new probe, one for NULL func */
128 new = allocate_probes(nr_probes
+ 2);
130 return ERR_PTR(-ENOMEM
);
132 memcpy(new, old
, nr_probes
* sizeof(struct tracepoint_func
));
133 new[nr_probes
].func
= probe
;
134 new[nr_probes
].data
= data
;
135 new[nr_probes
+ 1].func
= NULL
;
136 entry
->refcount
= nr_probes
+ 1;
138 debug_print_probes(entry
);
143 tracepoint_entry_remove_probe(struct tracepoint_entry
*entry
,
144 void *probe
, void *data
)
146 int nr_probes
= 0, nr_del
= 0, i
;
147 struct tracepoint_func
*old
, *new;
152 return ERR_PTR(-ENOENT
);
154 debug_print_probes(entry
);
155 /* (N -> M), (N > 1, M >= 0) probes */
157 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
158 if (old
[nr_probes
].func
== probe
&&
159 old
[nr_probes
].data
== data
)
165 * If probe is NULL, then nr_probes = nr_del = 0, and then the
166 * entire entry will be removed.
168 if (nr_probes
- nr_del
== 0) {
169 /* N -> 0, (N > 1) */
172 debug_print_probes(entry
);
176 /* N -> M, (N > 1, M > 0) */
178 new = allocate_probes(nr_probes
- nr_del
+ 1);
180 return ERR_PTR(-ENOMEM
);
181 for (i
= 0; old
[i
].func
; i
++)
182 if (old
[i
].func
!= probe
|| old
[i
].data
!= data
)
184 new[nr_probes
- nr_del
].func
= NULL
;
185 entry
->refcount
= nr_probes
- nr_del
;
188 debug_print_probes(entry
);
193 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
194 * Must be called with tracepoints_mutex held.
195 * Returns NULL if not present.
197 static struct tracepoint_entry
*get_tracepoint(const char *name
)
199 struct hlist_head
*head
;
200 struct tracepoint_entry
*e
;
201 u32 hash
= jhash(name
, strlen(name
), 0);
203 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
204 hlist_for_each_entry(e
, head
, hlist
) {
205 if (!strcmp(name
, e
->name
))
212 * Add the tracepoint to the tracepoint hash table. Must be called with
213 * tracepoints_mutex held.
215 static struct tracepoint_entry
*add_tracepoint(const char *name
)
217 struct hlist_head
*head
;
218 struct tracepoint_entry
*e
;
219 size_t name_len
= strlen(name
) + 1;
220 u32 hash
= jhash(name
, name_len
-1, 0);
222 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
223 hlist_for_each_entry(e
, head
, hlist
) {
224 if (!strcmp(name
, e
->name
)) {
226 "tracepoint %s busy\n", name
);
227 return ERR_PTR(-EEXIST
); /* Already there */
231 * Using kmalloc here to allocate a variable length element. Could
232 * cause some memory fragmentation if overused.
234 e
= kmalloc(sizeof(struct tracepoint_entry
) + name_len
, GFP_KERNEL
);
236 return ERR_PTR(-ENOMEM
);
237 memcpy(&e
->name
[0], name
, name_len
);
240 hlist_add_head(&e
->hlist
, head
);
245 * Remove the tracepoint from the tracepoint hash table. Must be called with
248 static inline void remove_tracepoint(struct tracepoint_entry
*e
)
250 hlist_del(&e
->hlist
);
255 * Sets the probe callback corresponding to one tracepoint.
257 static void set_tracepoint(struct tracepoint_entry
**entry
,
258 struct tracepoint
*elem
, int active
)
260 WARN_ON(strcmp((*entry
)->name
, elem
->name
) != 0);
262 if (elem
->regfunc
&& !static_key_enabled(&elem
->key
) && active
)
264 else if (elem
->unregfunc
&& static_key_enabled(&elem
->key
) && !active
)
268 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
269 * probe callbacks array is consistent before setting a pointer to it.
270 * This array is referenced by __DO_TRACE from
271 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
274 rcu_assign_pointer(elem
->funcs
, (*entry
)->funcs
);
275 if (active
&& !static_key_enabled(&elem
->key
))
276 static_key_slow_inc(&elem
->key
);
277 else if (!active
&& static_key_enabled(&elem
->key
))
278 static_key_slow_dec(&elem
->key
);
282 * Disable a tracepoint and its probe callback.
283 * Note: only waiting an RCU period after setting elem->call to the empty
284 * function insures that the original callback is not used anymore. This insured
285 * by preempt_disable around the call site.
287 static void disable_tracepoint(struct tracepoint
*elem
)
289 if (elem
->unregfunc
&& static_key_enabled(&elem
->key
))
292 if (static_key_enabled(&elem
->key
))
293 static_key_slow_dec(&elem
->key
);
294 rcu_assign_pointer(elem
->funcs
, NULL
);
298 * tracepoint_update_probe_range - Update a probe range
299 * @begin: beginning of the range
300 * @end: end of the range
302 * Updates the probe callback corresponding to a range of tracepoints.
303 * Called with tracepoints_mutex held.
305 static void tracepoint_update_probe_range(struct tracepoint
* const *begin
,
306 struct tracepoint
* const *end
)
308 struct tracepoint
* const *iter
;
309 struct tracepoint_entry
*mark_entry
;
314 for (iter
= begin
; iter
< end
; iter
++) {
315 mark_entry
= get_tracepoint((*iter
)->name
);
317 set_tracepoint(&mark_entry
, *iter
,
318 !!mark_entry
->refcount
);
320 disable_tracepoint(*iter
);
325 #ifdef CONFIG_MODULES
326 void module_update_tracepoints(void)
328 struct tp_module
*tp_mod
;
330 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
)
331 tracepoint_update_probe_range(tp_mod
->tracepoints_ptrs
,
332 tp_mod
->tracepoints_ptrs
+ tp_mod
->num_tracepoints
);
334 #else /* CONFIG_MODULES */
335 void module_update_tracepoints(void)
338 #endif /* CONFIG_MODULES */
342 * Update probes, removing the faulty probes.
343 * Called with tracepoints_mutex held.
345 static void tracepoint_update_probes(void)
347 /* Core kernel tracepoints */
348 tracepoint_update_probe_range(__start___tracepoints_ptrs
,
349 __stop___tracepoints_ptrs
);
350 /* tracepoints in modules. */
351 module_update_tracepoints();
354 static struct tracepoint_func
*
355 tracepoint_add_probe(const char *name
, void *probe
, void *data
)
357 struct tracepoint_entry
*entry
;
358 struct tracepoint_func
*old
;
360 entry
= get_tracepoint(name
);
362 entry
= add_tracepoint(name
);
364 return (struct tracepoint_func
*)entry
;
366 old
= tracepoint_entry_add_probe(entry
, probe
, data
);
367 if (IS_ERR(old
) && !entry
->refcount
)
368 remove_tracepoint(entry
);
373 * tracepoint_probe_register - Connect a probe to a tracepoint
374 * @name: tracepoint name
375 * @probe: probe handler
377 * Returns 0 if ok, error value on error.
378 * The probe address must at least be aligned on the architecture pointer size.
380 int tracepoint_probe_register(const char *name
, void *probe
, void *data
)
382 struct tracepoint_func
*old
;
384 mutex_lock(&tracepoints_mutex
);
385 old
= tracepoint_add_probe(name
, probe
, data
);
387 mutex_unlock(&tracepoints_mutex
);
390 tracepoint_update_probes(); /* may update entry */
391 mutex_unlock(&tracepoints_mutex
);
395 EXPORT_SYMBOL_GPL(tracepoint_probe_register
);
397 static struct tracepoint_func
*
398 tracepoint_remove_probe(const char *name
, void *probe
, void *data
)
400 struct tracepoint_entry
*entry
;
401 struct tracepoint_func
*old
;
403 entry
= get_tracepoint(name
);
405 return ERR_PTR(-ENOENT
);
406 old
= tracepoint_entry_remove_probe(entry
, probe
, data
);
409 if (!entry
->refcount
)
410 remove_tracepoint(entry
);
415 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
416 * @name: tracepoint name
417 * @probe: probe function pointer
419 * We do not need to call a synchronize_sched to make sure the probes have
420 * finished running before doing a module unload, because the module unload
421 * itself uses stop_machine(), which insures that every preempt disabled section
424 int tracepoint_probe_unregister(const char *name
, void *probe
, void *data
)
426 struct tracepoint_func
*old
;
428 mutex_lock(&tracepoints_mutex
);
429 old
= tracepoint_remove_probe(name
, probe
, data
);
431 mutex_unlock(&tracepoints_mutex
);
434 tracepoint_update_probes(); /* may update entry */
435 mutex_unlock(&tracepoints_mutex
);
439 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister
);
441 static LIST_HEAD(old_probes
);
442 static int need_update
;
444 static void tracepoint_add_old_probes(void *old
)
448 struct tp_probes
*tp_probes
= container_of(old
,
449 struct tp_probes
, probes
[0]);
450 list_add(&tp_probes
->u
.list
, &old_probes
);
455 * tracepoint_probe_register_noupdate - register a probe but not connect
456 * @name: tracepoint name
457 * @probe: probe handler
459 * caller must call tracepoint_probe_update_all()
461 int tracepoint_probe_register_noupdate(const char *name
, void *probe
,
464 struct tracepoint_func
*old
;
466 mutex_lock(&tracepoints_mutex
);
467 old
= tracepoint_add_probe(name
, probe
, data
);
469 mutex_unlock(&tracepoints_mutex
);
472 tracepoint_add_old_probes(old
);
473 mutex_unlock(&tracepoints_mutex
);
476 EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate
);
479 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
480 * @name: tracepoint name
481 * @probe: probe function pointer
483 * caller must call tracepoint_probe_update_all()
485 int tracepoint_probe_unregister_noupdate(const char *name
, void *probe
,
488 struct tracepoint_func
*old
;
490 mutex_lock(&tracepoints_mutex
);
491 old
= tracepoint_remove_probe(name
, probe
, data
);
493 mutex_unlock(&tracepoints_mutex
);
496 tracepoint_add_old_probes(old
);
497 mutex_unlock(&tracepoints_mutex
);
500 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate
);
503 * tracepoint_probe_update_all - update tracepoints
505 void tracepoint_probe_update_all(void)
507 LIST_HEAD(release_probes
);
508 struct tp_probes
*pos
, *next
;
510 mutex_lock(&tracepoints_mutex
);
512 mutex_unlock(&tracepoints_mutex
);
515 if (!list_empty(&old_probes
))
516 list_replace_init(&old_probes
, &release_probes
);
518 tracepoint_update_probes();
519 mutex_unlock(&tracepoints_mutex
);
520 list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
521 list_del(&pos
->u
.list
);
522 call_rcu_sched(&pos
->u
.rcu
, rcu_free_old_probes
);
525 EXPORT_SYMBOL_GPL(tracepoint_probe_update_all
);
528 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
529 * @tracepoint: current tracepoints (in), next tracepoint (out)
530 * @begin: beginning of the range
531 * @end: end of the range
533 * Returns whether a next tracepoint has been found (1) or not (0).
534 * Will return the first tracepoint in the range if the input tracepoint is
537 static int tracepoint_get_iter_range(struct tracepoint
* const **tracepoint
,
538 struct tracepoint
* const *begin
, struct tracepoint
* const *end
)
540 if (!*tracepoint
&& begin
!= end
) {
544 if (*tracepoint
>= begin
&& *tracepoint
< end
)
549 #ifdef CONFIG_MODULES
550 static void tracepoint_get_iter(struct tracepoint_iter
*iter
)
553 struct tp_module
*iter_mod
;
555 /* Core kernel tracepoints */
557 found
= tracepoint_get_iter_range(&iter
->tracepoint
,
558 __start___tracepoints_ptrs
,
559 __stop___tracepoints_ptrs
);
563 /* Tracepoints in modules */
564 mutex_lock(&tracepoints_mutex
);
565 list_for_each_entry(iter_mod
, &tracepoint_module_list
, list
) {
569 if (iter_mod
< iter
->module
)
571 else if (iter_mod
> iter
->module
)
572 iter
->tracepoint
= NULL
;
573 found
= tracepoint_get_iter_range(&iter
->tracepoint
,
574 iter_mod
->tracepoints_ptrs
,
575 iter_mod
->tracepoints_ptrs
576 + iter_mod
->num_tracepoints
);
578 iter
->module
= iter_mod
;
582 mutex_unlock(&tracepoints_mutex
);
585 tracepoint_iter_reset(iter
);
587 #else /* CONFIG_MODULES */
588 static void tracepoint_get_iter(struct tracepoint_iter
*iter
)
592 /* Core kernel tracepoints */
593 found
= tracepoint_get_iter_range(&iter
->tracepoint
,
594 __start___tracepoints_ptrs
,
595 __stop___tracepoints_ptrs
);
597 tracepoint_iter_reset(iter
);
599 #endif /* CONFIG_MODULES */
601 void tracepoint_iter_start(struct tracepoint_iter
*iter
)
603 tracepoint_get_iter(iter
);
605 EXPORT_SYMBOL_GPL(tracepoint_iter_start
);
607 void tracepoint_iter_next(struct tracepoint_iter
*iter
)
611 * iter->tracepoint may be invalid because we blindly incremented it.
612 * Make sure it is valid by marshalling on the tracepoints, getting the
613 * tracepoints from following modules if necessary.
615 tracepoint_get_iter(iter
);
617 EXPORT_SYMBOL_GPL(tracepoint_iter_next
);
619 void tracepoint_iter_stop(struct tracepoint_iter
*iter
)
622 EXPORT_SYMBOL_GPL(tracepoint_iter_stop
);
624 void tracepoint_iter_reset(struct tracepoint_iter
*iter
)
626 #ifdef CONFIG_MODULES
628 #endif /* CONFIG_MODULES */
629 iter
->tracepoint
= NULL
;
631 EXPORT_SYMBOL_GPL(tracepoint_iter_reset
);
633 #ifdef CONFIG_MODULES
634 static int tracepoint_module_coming(struct module
*mod
)
636 struct tp_module
*tp_mod
, *iter
;
640 * We skip modules that taint the kernel, especially those with different
641 * module headers (for forced load), to make sure we don't cause a crash.
642 * Staging and out-of-tree GPL modules are fine.
644 if (mod
->taints
& ~((1 << TAINT_OOT_MODULE
) | (1 << TAINT_CRAP
)))
646 mutex_lock(&tracepoints_mutex
);
647 tp_mod
= kmalloc(sizeof(struct tp_module
), GFP_KERNEL
);
652 tp_mod
->num_tracepoints
= mod
->num_tracepoints
;
653 tp_mod
->tracepoints_ptrs
= mod
->tracepoints_ptrs
;
656 * tracepoint_module_list is kept sorted by struct module pointer
657 * address for iteration on tracepoints from a seq_file that can release
658 * the mutex between calls.
660 list_for_each_entry_reverse(iter
, &tracepoint_module_list
, list
) {
661 BUG_ON(iter
== tp_mod
); /* Should never be in the list twice */
663 /* We belong to the location right after iter. */
664 list_add(&tp_mod
->list
, &iter
->list
);
668 /* We belong to the beginning of the list */
669 list_add(&tp_mod
->list
, &tracepoint_module_list
);
671 tracepoint_update_probe_range(mod
->tracepoints_ptrs
,
672 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
);
674 mutex_unlock(&tracepoints_mutex
);
678 static int tracepoint_module_going(struct module
*mod
)
680 struct tp_module
*pos
;
682 mutex_lock(&tracepoints_mutex
);
683 tracepoint_update_probe_range(mod
->tracepoints_ptrs
,
684 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
);
685 list_for_each_entry(pos
, &tracepoint_module_list
, list
) {
686 if (pos
->tracepoints_ptrs
== mod
->tracepoints_ptrs
) {
687 list_del(&pos
->list
);
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
698 mutex_unlock(&tracepoints_mutex
);
702 int tracepoint_module_notify(struct notifier_block
*self
,
703 unsigned long val
, void *data
)
705 struct module
*mod
= data
;
709 case MODULE_STATE_COMING
:
710 ret
= tracepoint_module_coming(mod
);
712 case MODULE_STATE_LIVE
:
714 case MODULE_STATE_GOING
:
715 ret
= tracepoint_module_going(mod
);
721 struct notifier_block tracepoint_module_nb
= {
722 .notifier_call
= tracepoint_module_notify
,
726 static int init_tracepoints(void)
728 return register_module_notifier(&tracepoint_module_nb
);
730 __initcall(init_tracepoints
);
731 #endif /* CONFIG_MODULES */
733 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
735 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
736 static int sys_tracepoint_refcount
;
738 void syscall_regfunc(void)
741 struct task_struct
*g
, *t
;
743 if (!sys_tracepoint_refcount
) {
744 read_lock_irqsave(&tasklist_lock
, flags
);
745 do_each_thread(g
, t
) {
746 /* Skip kernel threads. */
748 set_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
749 } while_each_thread(g
, t
);
750 read_unlock_irqrestore(&tasklist_lock
, flags
);
752 sys_tracepoint_refcount
++;
755 void syscall_unregfunc(void)
758 struct task_struct
*g
, *t
;
760 sys_tracepoint_refcount
--;
761 if (!sys_tracepoint_refcount
) {
762 read_lock_irqsave(&tasklist_lock
, flags
);
763 do_each_thread(g
, t
) {
764 clear_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
765 } while_each_thread(g
, t
);
766 read_unlock_irqrestore(&tasklist_lock
, flags
);