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);