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.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;
38 * Tracepoint module list mutex protects the local module list.
40 static DEFINE_MUTEX(tracepoint_module_list_mutex);
42 /* Local list of struct tp_module */
43 static LIST_HEAD(tracepoint_module_list);
44 #endif /* CONFIG_MODULES */
47 * tracepoints_mutex protects the builtin and module tracepoints.
48 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
50 static DEFINE_MUTEX(tracepoints_mutex);
54 * It is used to delay the free of multiple probes array until a quiescent
59 struct tracepoint_func probes[0];
62 static inline void *allocate_probes(int count)
64 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
65 + sizeof(struct tp_probes), GFP_KERNEL);
66 return p == NULL ? NULL : p->probes;
69 static void rcu_free_old_probes(struct rcu_head *head)
71 kfree(container_of(head, struct tp_probes, rcu));
74 static inline void release_probes(struct tracepoint_func *old)
77 struct tp_probes *tp_probes = container_of(old,
78 struct tp_probes, probes[0]);
79 call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
83 static void debug_print_probes(struct tracepoint_func *funcs)
87 if (!tracepoint_debug || !funcs)
90 for (i = 0; funcs[i].func; i++)
91 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
94 static struct tracepoint_func *
95 func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
98 struct tracepoint_func *old, *new;
102 if (WARN_ON(!tp_func->func))
103 return ERR_PTR(-EINVAL);
105 debug_print_probes(*funcs);
108 /* (N -> N+1), (N != 0, 1) probes */
109 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
110 /* Insert before probes of lower priority */
111 if (pos < 0 && old[nr_probes].prio < prio)
113 if (old[nr_probes].func == tp_func->func &&
114 old[nr_probes].data == tp_func->data)
115 return ERR_PTR(-EEXIST);
118 /* + 2 : one for new probe, one for NULL func */
119 new = allocate_probes(nr_probes + 2);
121 return ERR_PTR(-ENOMEM);
125 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
127 /* Copy higher priority probes ahead of the new probe */
128 memcpy(new, old, pos * sizeof(struct tracepoint_func));
129 /* Copy the rest after it. */
130 memcpy(new + pos + 1, old + pos,
131 (nr_probes - pos) * sizeof(struct tracepoint_func));
136 new[nr_probes + 1].func = NULL;
138 debug_print_probes(*funcs);
142 static void *func_remove(struct tracepoint_func **funcs,
143 struct tracepoint_func *tp_func)
145 int nr_probes = 0, nr_del = 0, i;
146 struct tracepoint_func *old, *new;
151 return ERR_PTR(-ENOENT);
153 debug_print_probes(*funcs);
154 /* (N -> M), (N > 1, M >= 0) probes */
156 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
157 if (old[nr_probes].func == tp_func->func &&
158 old[nr_probes].data == tp_func->data)
164 * If probe is NULL, then nr_probes = nr_del = 0, and then the
165 * entire entry will be removed.
167 if (nr_probes - nr_del == 0) {
168 /* N -> 0, (N > 1) */
170 debug_print_probes(*funcs);
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 != tp_func->func
181 || old[i].data != tp_func->data)
183 new[nr_probes - nr_del].func = NULL;
186 debug_print_probes(*funcs);
191 * Add the probe function to a tracepoint.
193 static int tracepoint_add_func(struct tracepoint *tp,
194 struct tracepoint_func *func, int prio)
196 struct tracepoint_func *old, *tp_funcs;
198 if (tp->regfunc && !static_key_enabled(&tp->key))
201 tp_funcs = rcu_dereference_protected(tp->funcs,
202 lockdep_is_held(&tracepoints_mutex));
203 old = func_add(&tp_funcs, func, prio);
210 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
211 * probe callbacks array is consistent before setting a pointer to it.
212 * This array is referenced by __DO_TRACE from
213 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
216 rcu_assign_pointer(tp->funcs, tp_funcs);
217 if (!static_key_enabled(&tp->key))
218 static_key_slow_inc(&tp->key);
224 * Remove a probe function from a tracepoint.
225 * Note: only waiting an RCU period after setting elem->call to the empty
226 * function insures that the original callback is not used anymore. This insured
227 * by preempt_disable around the call site.
229 static int tracepoint_remove_func(struct tracepoint *tp,
230 struct tracepoint_func *func)
232 struct tracepoint_func *old, *tp_funcs;
234 tp_funcs = rcu_dereference_protected(tp->funcs,
235 lockdep_is_held(&tracepoints_mutex));
236 old = func_remove(&tp_funcs, func);
243 /* Removed last function */
244 if (tp->unregfunc && static_key_enabled(&tp->key))
247 if (static_key_enabled(&tp->key))
248 static_key_slow_dec(&tp->key);
250 rcu_assign_pointer(tp->funcs, tp_funcs);
256 * tracepoint_probe_register - Connect a probe to a tracepoint
258 * @probe: probe handler
259 * @data: tracepoint data
260 * @prio: priority of this function over other registered functions
262 * Returns 0 if ok, error value on error.
263 * Note: if @tp is within a module, the caller is responsible for
264 * unregistering the probe before the module is gone. This can be
265 * performed either with a tracepoint module going notifier, or from
266 * within module exit functions.
268 int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
269 void *data, int prio)
271 struct tracepoint_func tp_func;
274 mutex_lock(&tracepoints_mutex);
275 tp_func.func = probe;
278 ret = tracepoint_add_func(tp, &tp_func, prio);
279 mutex_unlock(&tracepoints_mutex);
282 EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
285 * tracepoint_probe_register - Connect a probe to a tracepoint
287 * @probe: probe handler
288 * @data: tracepoint data
289 * @prio: priority of this function over other registered functions
291 * Returns 0 if ok, error value on error.
292 * Note: if @tp is within a module, the caller is responsible for
293 * unregistering the probe before the module is gone. This can be
294 * performed either with a tracepoint module going notifier, or from
295 * within module exit functions.
297 int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
299 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
301 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
304 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
306 * @probe: probe function pointer
307 * @data: tracepoint data
309 * Returns 0 if ok, error value on error.
311 int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
313 struct tracepoint_func tp_func;
316 mutex_lock(&tracepoints_mutex);
317 tp_func.func = probe;
319 ret = tracepoint_remove_func(tp, &tp_func);
320 mutex_unlock(&tracepoints_mutex);
323 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
325 #ifdef CONFIG_MODULES
326 bool trace_module_has_bad_taint(struct module *mod)
328 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
329 (1 << TAINT_UNSIGNED_MODULE));
332 static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
335 * register_tracepoint_notifier - register tracepoint coming/going notifier
336 * @nb: notifier block
338 * Notifiers registered with this function are called on module
339 * coming/going with the tracepoint_module_list_mutex held.
340 * The notifier block callback should expect a "struct tp_module" data
343 int register_tracepoint_module_notifier(struct notifier_block *nb)
345 struct tp_module *tp_mod;
348 mutex_lock(&tracepoint_module_list_mutex);
349 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
352 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
353 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
355 mutex_unlock(&tracepoint_module_list_mutex);
358 EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
361 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
362 * @nb: notifier block
364 * The notifier block callback should expect a "struct tp_module" data
367 int unregister_tracepoint_module_notifier(struct notifier_block *nb)
369 struct tp_module *tp_mod;
372 mutex_lock(&tracepoint_module_list_mutex);
373 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
376 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
377 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
379 mutex_unlock(&tracepoint_module_list_mutex);
383 EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
386 * Ensure the tracer unregistered the module's probes before the module
387 * teardown is performed. Prevents leaks of probe and data pointers.
389 static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
390 struct tracepoint * const *end)
392 struct tracepoint * const *iter;
396 for (iter = begin; iter < end; iter++)
397 WARN_ON_ONCE((*iter)->funcs);
400 static int tracepoint_module_coming(struct module *mod)
402 struct tp_module *tp_mod;
405 if (!mod->num_tracepoints)
409 * We skip modules that taint the kernel, especially those with different
410 * module headers (for forced load), to make sure we don't cause a crash.
411 * Staging, out-of-tree, and unsigned GPL modules are fine.
413 if (trace_module_has_bad_taint(mod))
415 mutex_lock(&tracepoint_module_list_mutex);
416 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
422 list_add_tail(&tp_mod->list, &tracepoint_module_list);
423 blocking_notifier_call_chain(&tracepoint_notify_list,
424 MODULE_STATE_COMING, tp_mod);
426 mutex_unlock(&tracepoint_module_list_mutex);
430 static void tracepoint_module_going(struct module *mod)
432 struct tp_module *tp_mod;
434 if (!mod->num_tracepoints)
437 mutex_lock(&tracepoint_module_list_mutex);
438 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
439 if (tp_mod->mod == mod) {
440 blocking_notifier_call_chain(&tracepoint_notify_list,
441 MODULE_STATE_GOING, tp_mod);
442 list_del(&tp_mod->list);
445 * Called the going notifier before checking for
448 tp_module_going_check_quiescent(mod->tracepoints_ptrs,
449 mod->tracepoints_ptrs + mod->num_tracepoints);
454 * In the case of modules that were tainted at "coming", we'll simply
455 * walk through the list without finding it. We cannot use the "tainted"
456 * flag on "going", in case a module taints the kernel only after being
459 mutex_unlock(&tracepoint_module_list_mutex);
462 static int tracepoint_module_notify(struct notifier_block *self,
463 unsigned long val, void *data)
465 struct module *mod = data;
469 case MODULE_STATE_COMING:
470 ret = tracepoint_module_coming(mod);
472 case MODULE_STATE_LIVE:
474 case MODULE_STATE_GOING:
475 tracepoint_module_going(mod);
477 case MODULE_STATE_UNFORMED:
483 static struct notifier_block tracepoint_module_nb = {
484 .notifier_call = tracepoint_module_notify,
488 static __init int init_tracepoints(void)
492 ret = register_module_notifier(&tracepoint_module_nb);
494 pr_warning("Failed to register tracepoint module enter notifier\n");
498 __initcall(init_tracepoints);
499 #endif /* CONFIG_MODULES */
501 static void for_each_tracepoint_range(struct tracepoint * const *begin,
502 struct tracepoint * const *end,
503 void (*fct)(struct tracepoint *tp, void *priv),
506 struct tracepoint * const *iter;
510 for (iter = begin; iter < end; iter++)
515 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
517 * @priv: private data
519 void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
522 for_each_tracepoint_range(__start___tracepoints_ptrs,
523 __stop___tracepoints_ptrs, fct, priv);
525 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
527 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
529 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
530 static int sys_tracepoint_refcount;
532 void syscall_regfunc(void)
534 struct task_struct *p, *t;
536 if (!sys_tracepoint_refcount) {
537 read_lock(&tasklist_lock);
538 for_each_process_thread(p, t) {
539 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
541 read_unlock(&tasklist_lock);
543 sys_tracepoint_refcount++;
546 void syscall_unregfunc(void)
548 struct task_struct *p, *t;
550 sys_tracepoint_refcount--;
551 if (!sys_tracepoint_refcount) {
552 read_lock(&tasklist_lock);
553 for_each_process_thread(p, t) {
554 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
556 read_unlock(&tasklist_lock);