2 * Copyright (C) 2008-2014 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/signal.h>
28 #include <linux/sched/task.h>
29 #include <linux/static_key.h>
31 extern struct tracepoint
* const __start___tracepoints_ptrs
[];
32 extern struct tracepoint
* const __stop___tracepoints_ptrs
[];
34 /* Set to 1 to enable tracepoint debug output */
35 static const int tracepoint_debug
;
39 * Tracepoint module list mutex protects the local module list.
41 static DEFINE_MUTEX(tracepoint_module_list_mutex
);
43 /* Local list of struct tp_module */
44 static LIST_HEAD(tracepoint_module_list
);
45 #endif /* CONFIG_MODULES */
48 * tracepoints_mutex protects the builtin and module tracepoints.
49 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
51 static DEFINE_MUTEX(tracepoints_mutex
);
55 * It is used to delay the free of multiple probes array until a quiescent
60 struct tracepoint_func probes
[0];
63 static inline void *allocate_probes(int count
)
65 struct tp_probes
*p
= kmalloc(count
* sizeof(struct tracepoint_func
)
66 + sizeof(struct tp_probes
), GFP_KERNEL
);
67 return p
== NULL
? NULL
: p
->probes
;
70 static void rcu_free_old_probes(struct rcu_head
*head
)
72 kfree(container_of(head
, struct tp_probes
, rcu
));
75 static inline void release_probes(struct tracepoint_func
*old
)
78 struct tp_probes
*tp_probes
= container_of(old
,
79 struct tp_probes
, probes
[0]);
80 call_rcu_sched(&tp_probes
->rcu
, rcu_free_old_probes
);
84 static void debug_print_probes(struct tracepoint_func
*funcs
)
88 if (!tracepoint_debug
|| !funcs
)
91 for (i
= 0; funcs
[i
].func
; i
++)
92 printk(KERN_DEBUG
"Probe %d : %p\n", i
, funcs
[i
].func
);
95 static struct tracepoint_func
*
96 func_add(struct tracepoint_func
**funcs
, struct tracepoint_func
*tp_func
,
99 struct tracepoint_func
*old
, *new;
103 if (WARN_ON(!tp_func
->func
))
104 return ERR_PTR(-EINVAL
);
106 debug_print_probes(*funcs
);
109 /* (N -> N+1), (N != 0, 1) probes */
110 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
111 /* Insert before probes of lower priority */
112 if (pos
< 0 && old
[nr_probes
].prio
< prio
)
114 if (old
[nr_probes
].func
== tp_func
->func
&&
115 old
[nr_probes
].data
== tp_func
->data
)
116 return ERR_PTR(-EEXIST
);
119 /* + 2 : one for new probe, one for NULL func */
120 new = allocate_probes(nr_probes
+ 2);
122 return ERR_PTR(-ENOMEM
);
126 memcpy(new, old
, nr_probes
* sizeof(struct tracepoint_func
));
128 /* Copy higher priority probes ahead of the new probe */
129 memcpy(new, old
, pos
* sizeof(struct tracepoint_func
));
130 /* Copy the rest after it. */
131 memcpy(new + pos
+ 1, old
+ pos
,
132 (nr_probes
- pos
) * sizeof(struct tracepoint_func
));
137 new[nr_probes
+ 1].func
= NULL
;
139 debug_print_probes(*funcs
);
143 static void *func_remove(struct tracepoint_func
**funcs
,
144 struct tracepoint_func
*tp_func
)
146 int nr_probes
= 0, nr_del
= 0, i
;
147 struct tracepoint_func
*old
, *new;
152 return ERR_PTR(-ENOENT
);
154 debug_print_probes(*funcs
);
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
== tp_func
->func
&&
159 old
[nr_probes
].data
== tp_func
->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) */
171 debug_print_probes(*funcs
);
175 /* N -> M, (N > 1, M > 0) */
177 new = allocate_probes(nr_probes
- nr_del
+ 1);
179 return ERR_PTR(-ENOMEM
);
180 for (i
= 0; old
[i
].func
; i
++)
181 if (old
[i
].func
!= tp_func
->func
182 || old
[i
].data
!= tp_func
->data
)
184 new[nr_probes
- nr_del
].func
= NULL
;
187 debug_print_probes(*funcs
);
192 * Add the probe function to a tracepoint.
194 static int tracepoint_add_func(struct tracepoint
*tp
,
195 struct tracepoint_func
*func
, int prio
)
197 struct tracepoint_func
*old
, *tp_funcs
;
200 if (tp
->regfunc
&& !static_key_enabled(&tp
->key
)) {
206 tp_funcs
= rcu_dereference_protected(tp
->funcs
,
207 lockdep_is_held(&tracepoints_mutex
));
208 old
= func_add(&tp_funcs
, func
, prio
);
210 WARN_ON_ONCE(PTR_ERR(old
) != -ENOMEM
);
215 * rcu_assign_pointer has as smp_store_release() which makes sure
216 * that the new probe callbacks array is consistent before setting
217 * a pointer to it. This array is referenced by __DO_TRACE from
218 * include/linux/tracepoint.h using rcu_dereference_sched().
220 rcu_assign_pointer(tp
->funcs
, tp_funcs
);
221 if (!static_key_enabled(&tp
->key
))
222 static_key_slow_inc(&tp
->key
);
228 * Remove a probe function from a tracepoint.
229 * Note: only waiting an RCU period after setting elem->call to the empty
230 * function insures that the original callback is not used anymore. This insured
231 * by preempt_disable around the call site.
233 static int tracepoint_remove_func(struct tracepoint
*tp
,
234 struct tracepoint_func
*func
)
236 struct tracepoint_func
*old
, *tp_funcs
;
238 tp_funcs
= rcu_dereference_protected(tp
->funcs
,
239 lockdep_is_held(&tracepoints_mutex
));
240 old
= func_remove(&tp_funcs
, func
);
242 WARN_ON_ONCE(PTR_ERR(old
) != -ENOMEM
);
247 /* Removed last function */
248 if (tp
->unregfunc
&& static_key_enabled(&tp
->key
))
251 if (static_key_enabled(&tp
->key
))
252 static_key_slow_dec(&tp
->key
);
254 rcu_assign_pointer(tp
->funcs
, tp_funcs
);
260 * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
262 * @probe: probe handler
263 * @data: tracepoint data
264 * @prio: priority of this function over other registered functions
266 * Returns 0 if ok, error value on error.
267 * Note: if @tp is within a module, the caller is responsible for
268 * unregistering the probe before the module is gone. This can be
269 * performed either with a tracepoint module going notifier, or from
270 * within module exit functions.
272 int tracepoint_probe_register_prio(struct tracepoint
*tp
, void *probe
,
273 void *data
, int prio
)
275 struct tracepoint_func tp_func
;
278 mutex_lock(&tracepoints_mutex
);
279 tp_func
.func
= probe
;
282 ret
= tracepoint_add_func(tp
, &tp_func
, prio
);
283 mutex_unlock(&tracepoints_mutex
);
286 EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio
);
289 * tracepoint_probe_register - Connect a probe to a tracepoint
291 * @probe: probe handler
292 * @data: tracepoint data
294 * Returns 0 if ok, error value on error.
295 * Note: if @tp is within a module, the caller is responsible for
296 * unregistering the probe before the module is gone. This can be
297 * performed either with a tracepoint module going notifier, or from
298 * within module exit functions.
300 int tracepoint_probe_register(struct tracepoint
*tp
, void *probe
, void *data
)
302 return tracepoint_probe_register_prio(tp
, probe
, data
, TRACEPOINT_DEFAULT_PRIO
);
304 EXPORT_SYMBOL_GPL(tracepoint_probe_register
);
307 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
309 * @probe: probe function pointer
310 * @data: tracepoint data
312 * Returns 0 if ok, error value on error.
314 int tracepoint_probe_unregister(struct tracepoint
*tp
, void *probe
, void *data
)
316 struct tracepoint_func tp_func
;
319 mutex_lock(&tracepoints_mutex
);
320 tp_func
.func
= probe
;
322 ret
= tracepoint_remove_func(tp
, &tp_func
);
323 mutex_unlock(&tracepoints_mutex
);
326 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister
);
328 #ifdef CONFIG_MODULES
329 bool trace_module_has_bad_taint(struct module
*mod
)
331 return mod
->taints
& ~((1 << TAINT_OOT_MODULE
) | (1 << TAINT_CRAP
) |
332 (1 << TAINT_UNSIGNED_MODULE
));
335 static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list
);
338 * register_tracepoint_notifier - register tracepoint coming/going notifier
339 * @nb: notifier block
341 * Notifiers registered with this function are called on module
342 * coming/going with the tracepoint_module_list_mutex held.
343 * The notifier block callback should expect a "struct tp_module" data
346 int register_tracepoint_module_notifier(struct notifier_block
*nb
)
348 struct tp_module
*tp_mod
;
351 mutex_lock(&tracepoint_module_list_mutex
);
352 ret
= blocking_notifier_chain_register(&tracepoint_notify_list
, nb
);
355 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
)
356 (void) nb
->notifier_call(nb
, MODULE_STATE_COMING
, tp_mod
);
358 mutex_unlock(&tracepoint_module_list_mutex
);
361 EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier
);
364 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
365 * @nb: notifier block
367 * The notifier block callback should expect a "struct tp_module" data
370 int unregister_tracepoint_module_notifier(struct notifier_block
*nb
)
372 struct tp_module
*tp_mod
;
375 mutex_lock(&tracepoint_module_list_mutex
);
376 ret
= blocking_notifier_chain_unregister(&tracepoint_notify_list
, nb
);
379 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
)
380 (void) nb
->notifier_call(nb
, MODULE_STATE_GOING
, tp_mod
);
382 mutex_unlock(&tracepoint_module_list_mutex
);
386 EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier
);
389 * Ensure the tracer unregistered the module's probes before the module
390 * teardown is performed. Prevents leaks of probe and data pointers.
392 static void tp_module_going_check_quiescent(struct tracepoint
* const *begin
,
393 struct tracepoint
* const *end
)
395 struct tracepoint
* const *iter
;
399 for (iter
= begin
; iter
< end
; iter
++)
400 WARN_ON_ONCE((*iter
)->funcs
);
403 static int tracepoint_module_coming(struct module
*mod
)
405 struct tp_module
*tp_mod
;
408 if (!mod
->num_tracepoints
)
412 * We skip modules that taint the kernel, especially those with different
413 * module headers (for forced load), to make sure we don't cause a crash.
414 * Staging, out-of-tree, and unsigned GPL modules are fine.
416 if (trace_module_has_bad_taint(mod
))
418 mutex_lock(&tracepoint_module_list_mutex
);
419 tp_mod
= kmalloc(sizeof(struct tp_module
), GFP_KERNEL
);
425 list_add_tail(&tp_mod
->list
, &tracepoint_module_list
);
426 blocking_notifier_call_chain(&tracepoint_notify_list
,
427 MODULE_STATE_COMING
, tp_mod
);
429 mutex_unlock(&tracepoint_module_list_mutex
);
433 static void tracepoint_module_going(struct module
*mod
)
435 struct tp_module
*tp_mod
;
437 if (!mod
->num_tracepoints
)
440 mutex_lock(&tracepoint_module_list_mutex
);
441 list_for_each_entry(tp_mod
, &tracepoint_module_list
, list
) {
442 if (tp_mod
->mod
== mod
) {
443 blocking_notifier_call_chain(&tracepoint_notify_list
,
444 MODULE_STATE_GOING
, tp_mod
);
445 list_del(&tp_mod
->list
);
448 * Called the going notifier before checking for
451 tp_module_going_check_quiescent(mod
->tracepoints_ptrs
,
452 mod
->tracepoints_ptrs
+ mod
->num_tracepoints
);
457 * In the case of modules that were tainted at "coming", we'll simply
458 * walk through the list without finding it. We cannot use the "tainted"
459 * flag on "going", in case a module taints the kernel only after being
462 mutex_unlock(&tracepoint_module_list_mutex
);
465 static int tracepoint_module_notify(struct notifier_block
*self
,
466 unsigned long val
, void *data
)
468 struct module
*mod
= data
;
472 case MODULE_STATE_COMING
:
473 ret
= tracepoint_module_coming(mod
);
475 case MODULE_STATE_LIVE
:
477 case MODULE_STATE_GOING
:
478 tracepoint_module_going(mod
);
480 case MODULE_STATE_UNFORMED
:
486 static struct notifier_block tracepoint_module_nb
= {
487 .notifier_call
= tracepoint_module_notify
,
491 static __init
int init_tracepoints(void)
495 ret
= register_module_notifier(&tracepoint_module_nb
);
497 pr_warn("Failed to register tracepoint module enter notifier\n");
501 __initcall(init_tracepoints
);
502 #endif /* CONFIG_MODULES */
504 static void for_each_tracepoint_range(struct tracepoint
* const *begin
,
505 struct tracepoint
* const *end
,
506 void (*fct
)(struct tracepoint
*tp
, void *priv
),
509 struct tracepoint
* const *iter
;
513 for (iter
= begin
; iter
< end
; iter
++)
518 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
520 * @priv: private data
522 void for_each_kernel_tracepoint(void (*fct
)(struct tracepoint
*tp
, void *priv
),
525 for_each_tracepoint_range(__start___tracepoints_ptrs
,
526 __stop___tracepoints_ptrs
, fct
, priv
);
528 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint
);
530 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
532 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
533 static int sys_tracepoint_refcount
;
535 int syscall_regfunc(void)
537 struct task_struct
*p
, *t
;
539 if (!sys_tracepoint_refcount
) {
540 read_lock(&tasklist_lock
);
541 for_each_process_thread(p
, t
) {
542 set_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
544 read_unlock(&tasklist_lock
);
546 sys_tracepoint_refcount
++;
551 void syscall_unregfunc(void)
553 struct task_struct
*p
, *t
;
555 sys_tracepoint_refcount
--;
556 if (!sys_tracepoint_refcount
) {
557 read_lock(&tasklist_lock
);
558 for_each_process_thread(p
, t
) {
559 clear_tsk_thread_flag(t
, TIF_SYSCALL_TRACEPOINT
);
561 read_unlock(&tasklist_lock
);