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. */
65 int enabled
; /* Tracepoint enabled */
71 struct tracepoint_func probes
[0];
74 static inline void *allocate_probes(int count
)
76 struct tp_probes
*p
= kmalloc(count
* sizeof(struct tracepoint_func
)
77 + sizeof(struct tp_probes
), GFP_KERNEL
);
78 return p
== NULL
? NULL
: p
->probes
;
81 static void rcu_free_old_probes(struct rcu_head
*head
)
83 kfree(container_of(head
, struct tp_probes
, rcu
));
86 static inline void release_probes(struct tracepoint_func
*old
)
89 struct tp_probes
*tp_probes
= container_of(old
,
90 struct tp_probes
, probes
[0]);
91 call_rcu_sched(&tp_probes
->rcu
, rcu_free_old_probes
);
95 static void debug_print_probes(struct tracepoint_entry
*entry
)
99 if (!tracepoint_debug
|| !entry
->funcs
)
102 for (i
= 0; entry
->funcs
[i
].func
; i
++)
103 printk(KERN_DEBUG
"Probe %d : %p\n", i
, entry
->funcs
[i
].func
);
106 static struct tracepoint_func
*
107 tracepoint_entry_add_probe(struct tracepoint_entry
*entry
,
108 void *probe
, void *data
)
111 struct tracepoint_func
*old
, *new;
114 return ERR_PTR(-EINVAL
);
116 debug_print_probes(entry
);
119 /* (N -> N+1), (N != 0, 1) probes */
120 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
121 if (old
[nr_probes
].func
== probe
&&
122 old
[nr_probes
].data
== data
)
123 return ERR_PTR(-EEXIST
);
125 /* + 2 : one for new probe, one for NULL func */
126 new = allocate_probes(nr_probes
+ 2);
128 return ERR_PTR(-ENOMEM
);
130 memcpy(new, old
, nr_probes
* sizeof(struct tracepoint_func
));
131 new[nr_probes
].func
= probe
;
132 new[nr_probes
].data
= data
;
133 new[nr_probes
+ 1].func
= NULL
;
134 entry
->refcount
= nr_probes
+ 1;
136 debug_print_probes(entry
);
141 tracepoint_entry_remove_probe(struct tracepoint_entry
*entry
,
142 void *probe
, void *data
)
144 int nr_probes
= 0, nr_del
= 0, i
;
145 struct tracepoint_func
*old
, *new;
150 return ERR_PTR(-ENOENT
);
152 debug_print_probes(entry
);
153 /* (N -> M), (N > 1, M >= 0) probes */
155 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
156 if (old
[nr_probes
].func
== probe
&&
157 old
[nr_probes
].data
== data
)
163 * If probe is NULL, then nr_probes = nr_del = 0, and then the
164 * entire entry will be removed.
166 if (nr_probes
- nr_del
== 0) {
167 /* N -> 0, (N > 1) */
170 debug_print_probes(entry
);
174 /* N -> M, (N > 1, M > 0) */
176 new = allocate_probes(nr_probes
- nr_del
+ 1);
178 return ERR_PTR(-ENOMEM
);
179 for (i
= 0; old
[i
].func
; i
++)
180 if (old
[i
].func
!= probe
|| old
[i
].data
!= data
)
182 new[nr_probes
- nr_del
].func
= NULL
;
183 entry
->refcount
= nr_probes
- nr_del
;
186 debug_print_probes(entry
);
191 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
192 * Must be called with tracepoints_mutex held.
193 * Returns NULL if not present.
195 static struct tracepoint_entry
*get_tracepoint(const char *name
)
197 struct hlist_head
*head
;
198 struct tracepoint_entry
*e
;
199 u32 hash
= jhash(name
, strlen(name
), 0);
201 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
202 hlist_for_each_entry(e
, head
, hlist
) {
203 if (!strcmp(name
, e
->name
))
210 * Add the tracepoint to the tracepoint hash table. Must be called with
211 * tracepoints_mutex held.
213 static struct tracepoint_entry
*add_tracepoint(const char *name
)
215 struct hlist_head
*head
;
216 struct tracepoint_entry
*e
;
217 size_t name_len
= strlen(name
) + 1;
218 u32 hash
= jhash(name
, name_len
-1, 0);
220 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
221 hlist_for_each_entry(e
, head
, hlist
) {
222 if (!strcmp(name
, e
->name
)) {
224 "tracepoint %s busy\n", name
);
225 return ERR_PTR(-EEXIST
); /* Already there */
229 * Using kmalloc here to allocate a variable length element. Could
230 * cause some memory fragmentation if overused.
232 e
= kmalloc(sizeof(struct tracepoint_entry
) + name_len
, GFP_KERNEL
);
234 return ERR_PTR(-ENOMEM
);
235 memcpy(&e
->name
[0], name
, name_len
);
239 hlist_add_head(&e
->hlist
, head
);
244 * Remove the tracepoint from the tracepoint hash table. Must be called with
247 static inline void remove_tracepoint(struct tracepoint_entry
*e
)
249 hlist_del(&e
->hlist
);
254 * Sets the probe callback corresponding to one tracepoint.
256 static void set_tracepoint(struct tracepoint_entry
**entry
,
257 struct tracepoint
*elem
, int active
)
259 WARN_ON(strcmp((*entry
)->name
, elem
->name
) != 0);
261 if (elem
->regfunc
&& !static_key_enabled(&elem
->key
) && active
)
263 else if (elem
->unregfunc
&& static_key_enabled(&elem
->key
) && !active
)
267 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
268 * probe callbacks array is consistent before setting a pointer to it.
269 * This array is referenced by __DO_TRACE from
270 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
273 rcu_assign_pointer(elem
->funcs
, (*entry
)->funcs
);
274 if (active
&& !static_key_enabled(&elem
->key
))
275 static_key_slow_inc(&elem
->key
);
276 else if (!active
&& static_key_enabled(&elem
->key
))
277 static_key_slow_dec(&elem
->key
);
281 * Disable a tracepoint and its probe callback.
282 * Note: only waiting an RCU period after setting elem->call to the empty
283 * function insures that the original callback is not used anymore. This insured
284 * by preempt_disable around the call site.
286 static void disable_tracepoint(struct tracepoint
*elem
)
288 if (elem
->unregfunc
&& static_key_enabled(&elem
->key
))
291 if (static_key_enabled(&elem
->key
))
292 static_key_slow_dec(&elem
->key
);
293 rcu_assign_pointer(elem
->funcs
, NULL
);
297 * tracepoint_update_probe_range - Update a probe range
298 * @begin: beginning of the range
299 * @end: end of the range
301 * Updates the probe callback corresponding to a range of tracepoints.
302 * Called with tracepoints_mutex held.
304 static void tracepoint_update_probe_range(struct tracepoint
* const *begin
,
305 struct tracepoint
* const *end
)
307 struct tracepoint
* const *iter
;
308 struct tracepoint_entry
*mark_entry
;
313 for (iter
= begin
; iter
< end
; iter
++) {
314 mark_entry
= get_tracepoint((*iter
)->name
);
316 set_tracepoint(&mark_entry
, *iter
,
317 !!mark_entry
->refcount
);
318 mark_entry
->enabled
= !!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
376 * @data: probe private data
379 * - 0 if the probe was successfully registered, and tracepoint
380 * callsites are currently loaded for that probe,
381 * - -ENODEV if the probe was successfully registered, but no tracepoint
382 * callsite is currently loaded for that probe,
383 * - other negative error value on error.
385 * When tracepoint_probe_register() returns either 0 or -ENODEV,
386 * parameters @name, @probe, and @data may be used by the tracepoint
387 * infrastructure until the probe is unregistered.
389 * The probe address must at least be aligned on the architecture pointer size.
391 int tracepoint_probe_register(const char *name
, void *probe
, void *data
)
393 struct tracepoint_func
*old
;
394 struct tracepoint_entry
*entry
;
397 mutex_lock(&tracepoints_mutex
);
398 old
= tracepoint_add_probe(name
, probe
, data
);
400 mutex_unlock(&tracepoints_mutex
);
403 tracepoint_update_probes(); /* may update entry */
404 entry
= get_tracepoint(name
);
405 /* Make sure the entry was enabled */
406 if (!entry
|| !entry
->enabled
)
408 mutex_unlock(&tracepoints_mutex
);
412 EXPORT_SYMBOL_GPL(tracepoint_probe_register
);
414 static struct tracepoint_func
*
415 tracepoint_remove_probe(const char *name
, void *probe
, void *data
)
417 struct tracepoint_entry
*entry
;
418 struct tracepoint_func
*old
;
420 entry
= get_tracepoint(name
);
422 return ERR_PTR(-ENOENT
);
423 old
= tracepoint_entry_remove_probe(entry
, probe
, data
);
426 if (!entry
->refcount
)
427 remove_tracepoint(entry
);
432 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
433 * @name: tracepoint name
434 * @probe: probe function pointer
435 * @data: probe private data
437 * We do not need to call a synchronize_sched to make sure the probes have
438 * finished running before doing a module unload, because the module unload
439 * itself uses stop_machine(), which insures that every preempt disabled section
442 int tracepoint_probe_unregister(const char *name
, void *probe
, void *data
)
444 struct tracepoint_func
*old
;
446 mutex_lock(&tracepoints_mutex
);
447 old
= tracepoint_remove_probe(name
, probe
, data
);
449 mutex_unlock(&tracepoints_mutex
);
452 tracepoint_update_probes(); /* may update entry */
453 mutex_unlock(&tracepoints_mutex
);
457 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister
);
460 #ifdef CONFIG_MODULES
461 bool trace_module_has_bad_taint(struct module
*mod
)
463 return mod
->taints
& ~((1 << TAINT_OOT_MODULE
) | (1 << TAINT_CRAP
) |
464 (1 << TAINT_UNSIGNED_MODULE
));
467 static int tracepoint_module_coming(struct module
*mod
)
469 struct tp_module
*tp_mod
;
472 if (!mod
->num_tracepoints
)
476 * We skip modules that taint the kernel, especially those with different
477 * module headers (for forced load), to make sure we don't cause a crash.
478 * Staging, out-of-tree, and unsigned GPL modules are fine.
480 if (trace_module_has_bad_taint(mod
))
482 mutex_lock(&tracepoints_mutex
);
483 tp_mod
= kmalloc(sizeof(struct tp_module
), GFP_KERNEL
);
488 tp_mod
->num_tracepoints
= mod
->num_tracepoints
;
489 tp_mod
->tracepoints_ptrs
= mod
->tracepoints_ptrs
;
490 list_add_tail(&tp_mod
->list
, &tracepoint_module_list
);
491 tracepoint_update_probe_range(mod
->tracepoints_ptrs
,
492 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
);
494 mutex_unlock(&tracepoints_mutex
);
498 static int tracepoint_module_going(struct module
*mod
)
500 struct tp_module
*pos
;
502 if (!mod
->num_tracepoints
)
505 mutex_lock(&tracepoints_mutex
);
506 tracepoint_update_probe_range(mod
->tracepoints_ptrs
,
507 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
);
508 list_for_each_entry(pos
, &tracepoint_module_list
, list
) {
509 if (pos
->tracepoints_ptrs
== mod
->tracepoints_ptrs
) {
510 list_del(&pos
->list
);
516 * In the case of modules that were tainted at "coming", we'll simply
517 * walk through the list without finding it. We cannot use the "tainted"
518 * flag on "going", in case a module taints the kernel only after being
521 mutex_unlock(&tracepoints_mutex
);
525 int tracepoint_module_notify(struct notifier_block
*self
,
526 unsigned long val
, void *data
)
528 struct module
*mod
= data
;
532 case MODULE_STATE_COMING
:
533 ret
= tracepoint_module_coming(mod
);
535 case MODULE_STATE_LIVE
:
537 case MODULE_STATE_GOING
:
538 ret
= tracepoint_module_going(mod
);
544 struct notifier_block tracepoint_module_nb
= {
545 .notifier_call
= tracepoint_module_notify
,
549 static int init_tracepoints(void)
551 return register_module_notifier(&tracepoint_module_nb
);
553 __initcall(init_tracepoints
);
554 #endif /* CONFIG_MODULES */
556 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
558 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
559 static int sys_tracepoint_refcount
;
561 void syscall_regfunc(void)
564 struct task_struct
*g
, *t
;
566 if (!sys_tracepoint_refcount
) {
567 read_lock_irqsave(&tasklist_lock
, flags
);
568 do_each_thread(g
, t
) {
569 /* Skip kernel threads. */
571 set_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
572 } while_each_thread(g
, t
);
573 read_unlock_irqrestore(&tasklist_lock
, flags
);
575 sys_tracepoint_refcount
++;
578 void syscall_unregfunc(void)
581 struct task_struct
*g
, *t
;
583 sys_tracepoint_refcount
--;
584 if (!sys_tracepoint_refcount
) {
585 read_lock_irqsave(&tasklist_lock
, flags
);
586 do_each_thread(g
, t
) {
587 clear_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
588 } while_each_thread(g
, t
);
589 read_unlock_irqrestore(&tasklist_lock
, flags
);