2 * Copyright (C) 2008-2011 Mathieu Desnoyers
3 * Copyright (C) 2009 Pierre-Marc Fournier
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation;
8 * version 2.1 of the License.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 * Ported to userspace by Pierre-Marc Fournier.
28 #include <urcu/arch.h>
30 #include <urcu/hlist.h>
31 #include <urcu/uatomic.h>
32 #include <urcu/compiler.h>
34 #include <lttng/tracepoint.h>
35 #include <lttng/ust-abi.h> /* for LTTNG_UST_SYM_NAME_LEN */
37 #include <usterr-signal-safe.h>
40 #include "tracepoint-internal.h"
41 #include "lttng-tracer-core.h"
45 /* Set to 1 to enable tracepoint debug output */
46 static const int tracepoint_debug
;
47 static int initialized
;
48 static void (*new_tracepoint_cb
)(struct tracepoint
*);
51 * tracepoint_mutex nests inside UST mutex.
53 * Note about interaction with fork/clone: UST does not hold the
54 * tracepoint mutex across fork/clone because it is either:
55 * - nested within UST mutex, in which case holding the UST mutex across
57 * - taken by a library constructor, which should never race with a
58 * fork/clone if the application is expected to continue running with
59 * the same memory layout (no following exec()).
61 static pthread_mutex_t tracepoint_mutex
= PTHREAD_MUTEX_INITIALIZER
;
64 * libraries that contain tracepoints (struct tracepoint_lib).
65 * Protected by tracepoint mutex.
67 static CDS_LIST_HEAD(libs
);
70 * The tracepoint mutex protects the library tracepoints, the hash table, and
72 * All calls to the tracepoint API must be protected by the tracepoint mutex,
73 * excepts calls to tracepoint_register_lib and
74 * tracepoint_unregister_lib, which take the tracepoint mutex themselves.
78 * Tracepoint hash table, containing the active tracepoints.
79 * Protected by tracepoint mutex.
81 #define TRACEPOINT_HASH_BITS 12
82 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
83 static struct cds_hlist_head tracepoint_table
[TRACEPOINT_TABLE_SIZE
];
85 static CDS_LIST_HEAD(old_probes
);
86 static int need_update
;
90 * It is used to to delay the free of multiple probes array until a quiescent
92 * Tracepoint entries modifications are protected by the tracepoint mutex.
94 struct tracepoint_entry
{
95 struct cds_hlist_node hlist
;
96 struct tracepoint_probe
*probes
;
97 int refcount
; /* Number of times armed. 0 if disarmed. */
98 const char *signature
;
104 struct cds_list_head list
;
105 /* Field below only used for call_rcu scheme */
106 /* struct rcu_head head; */
108 struct tracepoint_probe probes
[0];
111 static void *allocate_probes(int count
)
113 struct tp_probes
*p
= zmalloc(count
* sizeof(struct tracepoint_probe
)
114 + sizeof(struct tp_probes
));
115 return p
== NULL
? NULL
: p
->probes
;
118 static void release_probes(void *old
)
121 struct tp_probes
*tp_probes
= caa_container_of(old
,
122 struct tp_probes
, probes
[0]);
128 static void debug_print_probes(struct tracepoint_entry
*entry
)
132 if (!tracepoint_debug
|| !entry
->probes
)
135 for (i
= 0; entry
->probes
[i
].func
; i
++)
136 DBG("Probe %d : %p", i
, entry
->probes
[i
].func
);
140 tracepoint_entry_add_probe(struct tracepoint_entry
*entry
,
141 void (*probe
)(void), void *data
)
144 struct tracepoint_probe
*old
, *new;
148 return ERR_PTR(-EINVAL
);
150 debug_print_probes(entry
);
153 /* (N -> N+1), (N != 0, 1) probes */
154 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
155 if (old
[nr_probes
].func
== probe
&&
156 old
[nr_probes
].data
== data
)
157 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
);
164 memcpy(new, old
, nr_probes
* sizeof(struct tracepoint_probe
));
165 new[nr_probes
].func
= probe
;
166 new[nr_probes
].data
= data
;
167 new[nr_probes
+ 1].func
= NULL
;
168 entry
->refcount
= nr_probes
+ 1;
170 debug_print_probes(entry
);
175 tracepoint_entry_remove_probe(struct tracepoint_entry
*entry
,
176 void (*probe
)(void), void *data
)
178 int nr_probes
= 0, nr_del
= 0, i
;
179 struct tracepoint_probe
*old
, *new;
184 return ERR_PTR(-ENOENT
);
186 debug_print_probes(entry
);
187 /* (N -> M), (N > 1, M >= 0) probes */
188 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
190 (old
[nr_probes
].func
== probe
&&
191 old
[nr_probes
].data
== data
))
195 if (nr_probes
- nr_del
== 0) {
196 /* N -> 0, (N > 1) */
197 entry
->probes
= NULL
;
199 debug_print_probes(entry
);
203 /* N -> M, (N > 1, M > 0) */
205 new = allocate_probes(nr_probes
- nr_del
+ 1);
207 return ERR_PTR(-ENOMEM
);
208 for (i
= 0; old
[i
].func
; i
++)
210 (old
[i
].func
!= probe
|| old
[i
].data
!= data
))
212 new[nr_probes
- nr_del
].func
= NULL
;
213 entry
->refcount
= nr_probes
- nr_del
;
216 debug_print_probes(entry
);
221 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
222 * Must be called with tracepoint mutex held.
223 * Returns NULL if not present.
225 static struct tracepoint_entry
*get_tracepoint(const char *name
)
227 struct cds_hlist_head
*head
;
228 struct cds_hlist_node
*node
;
229 struct tracepoint_entry
*e
;
230 size_t name_len
= strlen(name
);
233 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
234 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
235 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
237 hash
= jhash(name
, name_len
, 0);
238 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
239 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
240 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1))
247 * Add the tracepoint to the tracepoint hash table. Must be called with
248 * tracepoint mutex held.
250 static struct tracepoint_entry
*add_tracepoint(const char *name
,
251 const char *signature
)
253 struct cds_hlist_head
*head
;
254 struct cds_hlist_node
*node
;
255 struct tracepoint_entry
*e
;
256 size_t name_len
= strlen(name
);
259 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
260 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
261 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
263 hash
= jhash(name
, name_len
, 0);
264 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
265 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
266 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1)) {
267 DBG("tracepoint %s busy", name
);
268 return ERR_PTR(-EEXIST
); /* Already there */
272 * Using zmalloc here to allocate a variable length element. Could
273 * cause some memory fragmentation if overused.
275 e
= zmalloc(sizeof(struct tracepoint_entry
) + name_len
+ 1);
277 return ERR_PTR(-ENOMEM
);
278 memcpy(&e
->name
[0], name
, name_len
+ 1);
279 e
->name
[name_len
] = '\0';
282 e
->signature
= signature
;
283 cds_hlist_add_head(&e
->hlist
, head
);
288 * Remove the tracepoint from the tracepoint hash table. Must be called with
289 * tracepoint mutex held.
291 static void remove_tracepoint(struct tracepoint_entry
*e
)
293 cds_hlist_del(&e
->hlist
);
298 * Sets the probe callback corresponding to one tracepoint.
300 static void set_tracepoint(struct tracepoint_entry
**entry
,
301 struct tracepoint
*elem
, int active
)
303 WARN_ON(strncmp((*entry
)->name
, elem
->name
, LTTNG_UST_SYM_NAME_LEN
- 1) != 0);
305 * Check that signatures match before connecting a probe to a
306 * tracepoint. Warn the user if they don't.
308 if (strcmp(elem
->signature
, (*entry
)->signature
) != 0) {
309 static int warned
= 0;
311 /* Only print once, don't flood console. */
313 WARN("Tracepoint signature mismatch, not enabling one or more tracepoints. Ensure that the tracepoint probes prototypes match the application.");
314 WARN("Tracepoint \"%s\" signatures: call: \"%s\" vs probe: \"%s\".",
315 elem
->name
, elem
->signature
, (*entry
)->signature
);
318 /* Don't accept connecting non-matching signatures. */
323 * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new
324 * probe callbacks array is consistent before setting a pointer to it.
325 * This array is referenced by __DO_TRACE from
326 * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends()
329 rcu_assign_pointer(elem
->probes
, (*entry
)->probes
);
330 elem
->state
= active
;
334 * Disable a tracepoint and its probe callback.
335 * Note: only waiting an RCU period after setting elem->call to the empty
336 * function insures that the original callback is not used anymore. This insured
337 * by preempt_disable around the call site.
339 static void disable_tracepoint(struct tracepoint
*elem
)
342 rcu_assign_pointer(elem
->probes
, NULL
);
346 * tracepoint_update_probe_range - Update a probe range
347 * @begin: beginning of the range
348 * @end: end of the range
350 * Updates the probe callback corresponding to a range of tracepoints.
353 void tracepoint_update_probe_range(struct tracepoint
* const *begin
,
354 struct tracepoint
* const *end
)
356 struct tracepoint
* const *iter
;
357 struct tracepoint_entry
*mark_entry
;
359 for (iter
= begin
; iter
< end
; iter
++) {
361 continue; /* skip dummy */
362 if (!(*iter
)->name
) {
363 disable_tracepoint(*iter
);
366 mark_entry
= get_tracepoint((*iter
)->name
);
368 set_tracepoint(&mark_entry
, *iter
,
369 !!mark_entry
->refcount
);
371 disable_tracepoint(*iter
);
376 static void lib_update_tracepoints(void)
378 struct tracepoint_lib
*lib
;
380 cds_list_for_each_entry(lib
, &libs
, list
) {
381 tracepoint_update_probe_range(lib
->tracepoints_start
,
382 lib
->tracepoints_start
+ lib
->tracepoints_count
);
387 * Update probes, removing the faulty probes.
389 static void tracepoint_update_probes(void)
391 /* tracepoints registered from libraries and executable. */
392 lib_update_tracepoints();
395 static struct tracepoint_probe
*
396 tracepoint_add_probe(const char *name
, void (*probe
)(void), void *data
,
397 const char *signature
)
399 struct tracepoint_entry
*entry
;
400 struct tracepoint_probe
*old
;
402 entry
= get_tracepoint(name
);
404 entry
= add_tracepoint(name
, signature
);
406 return (struct tracepoint_probe
*)entry
;
408 old
= tracepoint_entry_add_probe(entry
, probe
, data
);
409 if (IS_ERR(old
) && !entry
->refcount
)
410 remove_tracepoint(entry
);
415 * __tracepoint_probe_register - Connect a probe to a tracepoint
416 * @name: tracepoint name
417 * @probe: probe handler
419 * Returns 0 if ok, error value on error.
420 * The probe address must at least be aligned on the architecture pointer size.
421 * Called with the tracepoint mutex held.
423 int __tracepoint_probe_register(const char *name
, void (*probe
)(void),
424 void *data
, const char *signature
)
429 DBG("Registering probe to tracepoint %s", name
);
431 pthread_mutex_lock(&tracepoint_mutex
);
432 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
438 tracepoint_update_probes(); /* may update entry */
441 pthread_mutex_unlock(&tracepoint_mutex
);
445 static void *tracepoint_remove_probe(const char *name
, void (*probe
)(void),
448 struct tracepoint_entry
*entry
;
451 entry
= get_tracepoint(name
);
453 return ERR_PTR(-ENOENT
);
454 old
= tracepoint_entry_remove_probe(entry
, probe
, data
);
457 if (!entry
->refcount
)
458 remove_tracepoint(entry
);
463 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
464 * @name: tracepoint name
465 * @probe: probe function pointer
466 * @probe: probe data pointer
468 int __tracepoint_probe_unregister(const char *name
, void (*probe
)(void),
474 DBG("Un-registering probe from tracepoint %s", name
);
476 pthread_mutex_lock(&tracepoint_mutex
);
477 old
= tracepoint_remove_probe(name
, probe
, data
);
482 tracepoint_update_probes(); /* may update entry */
485 pthread_mutex_unlock(&tracepoint_mutex
);
489 static void tracepoint_add_old_probes(void *old
)
493 struct tp_probes
*tp_probes
= caa_container_of(old
,
494 struct tp_probes
, probes
[0]);
495 cds_list_add(&tp_probes
->u
.list
, &old_probes
);
500 * tracepoint_probe_register_noupdate - register a probe but not connect
501 * @name: tracepoint name
502 * @probe: probe handler
504 * caller must call tracepoint_probe_update_all()
506 int tracepoint_probe_register_noupdate(const char *name
, void (*probe
)(void),
507 void *data
, const char *signature
)
512 pthread_mutex_lock(&tracepoint_mutex
);
513 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
518 tracepoint_add_old_probes(old
);
520 pthread_mutex_unlock(&tracepoint_mutex
);
525 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
526 * @name: tracepoint name
527 * @probe: probe function pointer
529 * caller must call tracepoint_probe_update_all()
530 * Called with the tracepoint mutex held.
532 int tracepoint_probe_unregister_noupdate(const char *name
, void (*probe
)(void),
538 DBG("Un-registering probe from tracepoint %s", name
);
540 pthread_mutex_lock(&tracepoint_mutex
);
541 old
= tracepoint_remove_probe(name
, probe
, data
);
546 tracepoint_add_old_probes(old
);
548 pthread_mutex_unlock(&tracepoint_mutex
);
553 * tracepoint_probe_update_all - update tracepoints
555 void tracepoint_probe_update_all(void)
557 CDS_LIST_HEAD(release_probes
);
558 struct tp_probes
*pos
, *next
;
560 pthread_mutex_lock(&tracepoint_mutex
);
564 if (!cds_list_empty(&old_probes
))
565 cds_list_replace_init(&old_probes
, &release_probes
);
568 tracepoint_update_probes();
569 cds_list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
570 cds_list_del(&pos
->u
.list
);
575 pthread_mutex_unlock(&tracepoint_mutex
);
578 void tracepoint_set_new_tracepoint_cb(void (*cb
)(struct tracepoint
*))
580 new_tracepoint_cb
= cb
;
583 static void new_tracepoints(struct tracepoint
* const *start
, struct tracepoint
* const *end
)
585 if (new_tracepoint_cb
) {
586 struct tracepoint
* const *t
;
588 for (t
= start
; t
< end
; t
++) {
590 new_tracepoint_cb(*t
);
596 void lib_disable_tracepoints(struct tracepoint
* const *begin
,
597 struct tracepoint
* const *end
)
599 struct tracepoint
* const *iter
;
601 for (iter
= begin
; iter
< end
; iter
++) {
603 continue; /* skip dummy */
604 disable_tracepoint(*iter
);
609 int tracepoint_register_lib(struct tracepoint
* const *tracepoints_start
,
610 int tracepoints_count
)
612 struct tracepoint_lib
*pl
, *iter
;
616 pl
= (struct tracepoint_lib
*) zmalloc(sizeof(struct tracepoint_lib
));
618 pl
->tracepoints_start
= tracepoints_start
;
619 pl
->tracepoints_count
= tracepoints_count
;
621 pthread_mutex_lock(&tracepoint_mutex
);
623 * We sort the libs by struct lib pointer address.
625 cds_list_for_each_entry_reverse(iter
, &libs
, list
) {
626 BUG_ON(iter
== pl
); /* Should never be in the list twice */
628 /* We belong to the location right after iter. */
629 cds_list_add(&pl
->list
, &iter
->list
);
633 /* We should be added at the head of the list */
634 cds_list_add(&pl
->list
, &libs
);
636 new_tracepoints(tracepoints_start
, tracepoints_start
+ tracepoints_count
);
638 /* TODO: update just the loaded lib */
639 lib_update_tracepoints();
640 pthread_mutex_unlock(&tracepoint_mutex
);
642 DBG("just registered a tracepoints section from %p and having %d tracepoints",
643 tracepoints_start
, tracepoints_count
);
647 for (i
= 0; i
< tracepoints_count
; i
++) {
648 DBG("registered tracepoint: %s", tracepoints_start
[i
]->name
);
655 int tracepoint_unregister_lib(struct tracepoint
* const *tracepoints_start
)
657 struct tracepoint_lib
*lib
;
658 int tracepoints_count
;
660 pthread_mutex_lock(&tracepoint_mutex
);
661 cds_list_for_each_entry(lib
, &libs
, list
) {
662 if (lib
->tracepoints_start
== tracepoints_start
) {
663 struct tracepoint_lib
*lib2free
= lib
;
665 cds_list_del(&lib
->list
);
666 tracepoints_count
= lib
->tracepoints_count
;
674 * Force tracepoint disarm for all tracepoints of this lib.
675 * This takes care of destructor of library that would leave a
676 * LD_PRELOAD wrapper override function enabled for tracing, but
677 * the session teardown would not be able to reach the
678 * tracepoint anymore to disable it.
680 lib_disable_tracepoints(tracepoints_start
,
681 tracepoints_start
+ tracepoints_count
);
682 DBG("just unregistered a tracepoints section from %p",
685 pthread_mutex_unlock(&tracepoint_mutex
);
689 void init_tracepoint(void)
691 if (uatomic_xchg(&initialized
, 1) == 1)
696 void exit_tracepoint(void)
702 * Create the wrapper symbols.
704 #undef tp_rcu_read_lock_bp
705 #undef tp_rcu_read_unlock_bp
706 #undef tp_rcu_dereference_bp
708 void tp_rcu_read_lock_bp(void)
713 void tp_rcu_read_unlock_bp(void)
715 rcu_read_unlock_bp();
718 void *tp_rcu_dereference_sym_bp(void *p
)
720 return rcu_dereference_bp(p
);