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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2008-2014 Mathieu Desnoyers
4 */
5#include <linux/module.h>
6#include <linux/mutex.h>
7#include <linux/types.h>
8#include <linux/jhash.h>
9#include <linux/list.h>
10#include <linux/rcupdate.h>
11#include <linux/tracepoint.h>
12#include <linux/err.h>
13#include <linux/slab.h>
14#include <linux/sched/signal.h>
15#include <linux/sched/task.h>
16#include <linux/static_key.h>
17
18extern tracepoint_ptr_t __start___tracepoints_ptrs[];
19extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
20
21DEFINE_SRCU(tracepoint_srcu);
22EXPORT_SYMBOL_GPL(tracepoint_srcu);
23
24/* Set to 1 to enable tracepoint debug output */
25static const int tracepoint_debug;
26
27#ifdef CONFIG_MODULES
28/*
29 * Tracepoint module list mutex protects the local module list.
30 */
31static DEFINE_MUTEX(tracepoint_module_list_mutex);
32
33/* Local list of struct tp_module */
34static LIST_HEAD(tracepoint_module_list);
35#endif /* CONFIG_MODULES */
36
37/*
38 * tracepoints_mutex protects the builtin and module tracepoints.
39 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
40 */
41static DEFINE_MUTEX(tracepoints_mutex);
42
43static struct rcu_head *early_probes;
44static bool ok_to_free_tracepoints;
45
46/*
47 * Note about RCU :
48 * It is used to delay the free of multiple probes array until a quiescent
49 * state is reached.
50 */
51struct tp_probes {
52 struct rcu_head rcu;
53 struct tracepoint_func probes[0];
54};
55
56static inline void *allocate_probes(int count)
57{
58 struct tp_probes *p = kmalloc(struct_size(p, probes, count),
59 GFP_KERNEL);
60 return p == NULL ? NULL : p->probes;
61}
62
63static void srcu_free_old_probes(struct rcu_head *head)
64{
65 kfree(container_of(head, struct tp_probes, rcu));
66}
67
68static void rcu_free_old_probes(struct rcu_head *head)
69{
70 call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
71}
72
73static __init int release_early_probes(void)
74{
75 struct rcu_head *tmp;
76
77 ok_to_free_tracepoints = true;
78
79 while (early_probes) {
80 tmp = early_probes;
81 early_probes = tmp->next;
82 call_rcu(tmp, rcu_free_old_probes);
83 }
84
85 return 0;
86}
87
88/* SRCU is initialized at core_initcall */
89postcore_initcall(release_early_probes);
90
91static inline void release_probes(struct tracepoint_func *old)
92{
93 if (old) {
94 struct tp_probes *tp_probes = container_of(old,
95 struct tp_probes, probes[0]);
96
97 /*
98 * We can't free probes if SRCU is not initialized yet.
99 * Postpone the freeing till after SRCU is initialized.
100 */
101 if (unlikely(!ok_to_free_tracepoints)) {
102 tp_probes->rcu.next = early_probes;
103 early_probes = &tp_probes->rcu;
104 return;
105 }
106
107 /*
108 * Tracepoint probes are protected by both sched RCU and SRCU,
109 * by calling the SRCU callback in the sched RCU callback we
110 * cover both cases. So let us chain the SRCU and sched RCU
111 * callbacks to wait for both grace periods.
112 */
113 call_rcu(&tp_probes->rcu, rcu_free_old_probes);
114 }
115}
116
117static void debug_print_probes(struct tracepoint_func *funcs)
118{
119 int i;
120
121 if (!tracepoint_debug || !funcs)
122 return;
123
124 for (i = 0; funcs[i].func; i++)
125 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
126}
127
128static struct tracepoint_func *
129func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
130 int prio)
131{
132 struct tracepoint_func *old, *new;
133 int nr_probes = 0;
134 int pos = -1;
135
136 if (WARN_ON(!tp_func->func))
137 return ERR_PTR(-EINVAL);
138
139 debug_print_probes(*funcs);
140 old = *funcs;
141 if (old) {
142 /* (N -> N+1), (N != 0, 1) probes */
143 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
144 /* Insert before probes of lower priority */
145 if (pos < 0 && old[nr_probes].prio < prio)
146 pos = nr_probes;
147 if (old[nr_probes].func == tp_func->func &&
148 old[nr_probes].data == tp_func->data)
149 return ERR_PTR(-EEXIST);
150 }
151 }
152 /* + 2 : one for new probe, one for NULL func */
153 new = allocate_probes(nr_probes + 2);
154 if (new == NULL)
155 return ERR_PTR(-ENOMEM);
156 if (old) {
157 if (pos < 0) {
158 pos = nr_probes;
159 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
160 } else {
161 /* Copy higher priority probes ahead of the new probe */
162 memcpy(new, old, pos * sizeof(struct tracepoint_func));
163 /* Copy the rest after it. */
164 memcpy(new + pos + 1, old + pos,
165 (nr_probes - pos) * sizeof(struct tracepoint_func));
166 }
167 } else
168 pos = 0;
169 new[pos] = *tp_func;
170 new[nr_probes + 1].func = NULL;
171 *funcs = new;
172 debug_print_probes(*funcs);
173 return old;
174}
175
176static void *func_remove(struct tracepoint_func **funcs,
177 struct tracepoint_func *tp_func)
178{
179 int nr_probes = 0, nr_del = 0, i;
180 struct tracepoint_func *old, *new;
181
182 old = *funcs;
183
184 if (!old)
185 return ERR_PTR(-ENOENT);
186
187 debug_print_probes(*funcs);
188 /* (N -> M), (N > 1, M >= 0) probes */
189 if (tp_func->func) {
190 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
191 if (old[nr_probes].func == tp_func->func &&
192 old[nr_probes].data == tp_func->data)
193 nr_del++;
194 }
195 }
196
197 /*
198 * If probe is NULL, then nr_probes = nr_del = 0, and then the
199 * entire entry will be removed.
200 */
201 if (nr_probes - nr_del == 0) {
202 /* N -> 0, (N > 1) */
203 *funcs = NULL;
204 debug_print_probes(*funcs);
205 return old;
206 } else {
207 int j = 0;
208 /* N -> M, (N > 1, M > 0) */
209 /* + 1 for NULL */
210 new = allocate_probes(nr_probes - nr_del + 1);
211 if (new == NULL)
212 return ERR_PTR(-ENOMEM);
213 for (i = 0; old[i].func; i++)
214 if (old[i].func != tp_func->func
215 || old[i].data != tp_func->data)
216 new[j++] = old[i];
217 new[nr_probes - nr_del].func = NULL;
218 *funcs = new;
219 }
220 debug_print_probes(*funcs);
221 return old;
222}
223
224/*
225 * Add the probe function to a tracepoint.
226 */
227static int tracepoint_add_func(struct tracepoint *tp,
228 struct tracepoint_func *func, int prio)
229{
230 struct tracepoint_func *old, *tp_funcs;
231 int ret;
232
233 if (tp->regfunc && !static_key_enabled(&tp->key)) {
234 ret = tp->regfunc();
235 if (ret < 0)
236 return ret;
237 }
238
239 tp_funcs = rcu_dereference_protected(tp->funcs,
240 lockdep_is_held(&tracepoints_mutex));
241 old = func_add(&tp_funcs, func, prio);
242 if (IS_ERR(old)) {
243 WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
244 return PTR_ERR(old);
245 }
246
247 /*
248 * rcu_assign_pointer has as smp_store_release() which makes sure
249 * that the new probe callbacks array is consistent before setting
250 * a pointer to it. This array is referenced by __DO_TRACE from
251 * include/linux/tracepoint.h using rcu_dereference_sched().
252 */
253 rcu_assign_pointer(tp->funcs, tp_funcs);
254 if (!static_key_enabled(&tp->key))
255 static_key_slow_inc(&tp->key);
256 release_probes(old);
257 return 0;
258}
259
260/*
261 * Remove a probe function from a tracepoint.
262 * Note: only waiting an RCU period after setting elem->call to the empty
263 * function insures that the original callback is not used anymore. This insured
264 * by preempt_disable around the call site.
265 */
266static int tracepoint_remove_func(struct tracepoint *tp,
267 struct tracepoint_func *func)
268{
269 struct tracepoint_func *old, *tp_funcs;
270
271 tp_funcs = rcu_dereference_protected(tp->funcs,
272 lockdep_is_held(&tracepoints_mutex));
273 old = func_remove(&tp_funcs, func);
274 if (IS_ERR(old)) {
275 WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
276 return PTR_ERR(old);
277 }
278
279 if (!tp_funcs) {
280 /* Removed last function */
281 if (tp->unregfunc && static_key_enabled(&tp->key))
282 tp->unregfunc();
283
284 if (static_key_enabled(&tp->key))
285 static_key_slow_dec(&tp->key);
286 }
287 rcu_assign_pointer(tp->funcs, tp_funcs);
288 release_probes(old);
289 return 0;
290}
291
292/**
293 * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
294 * @tp: tracepoint
295 * @probe: probe handler
296 * @data: tracepoint data
297 * @prio: priority of this function over other registered functions
298 *
299 * Returns 0 if ok, error value on error.
300 * Note: if @tp is within a module, the caller is responsible for
301 * unregistering the probe before the module is gone. This can be
302 * performed either with a tracepoint module going notifier, or from
303 * within module exit functions.
304 */
305int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
306 void *data, int prio)
307{
308 struct tracepoint_func tp_func;
309 int ret;
310
311 mutex_lock(&tracepoints_mutex);
312 tp_func.func = probe;
313 tp_func.data = data;
314 tp_func.prio = prio;
315 ret = tracepoint_add_func(tp, &tp_func, prio);
316 mutex_unlock(&tracepoints_mutex);
317 return ret;
318}
319EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
320
321/**
322 * tracepoint_probe_register - Connect a probe to a tracepoint
323 * @tp: tracepoint
324 * @probe: probe handler
325 * @data: tracepoint data
326 *
327 * Returns 0 if ok, error value on error.
328 * Note: if @tp is within a module, the caller is responsible for
329 * unregistering the probe before the module is gone. This can be
330 * performed either with a tracepoint module going notifier, or from
331 * within module exit functions.
332 */
333int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
334{
335 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
336}
337EXPORT_SYMBOL_GPL(tracepoint_probe_register);
338
339/**
340 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
341 * @tp: tracepoint
342 * @probe: probe function pointer
343 * @data: tracepoint data
344 *
345 * Returns 0 if ok, error value on error.
346 */
347int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
348{
349 struct tracepoint_func tp_func;
350 int ret;
351
352 mutex_lock(&tracepoints_mutex);
353 tp_func.func = probe;
354 tp_func.data = data;
355 ret = tracepoint_remove_func(tp, &tp_func);
356 mutex_unlock(&tracepoints_mutex);
357 return ret;
358}
359EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
360
361static void for_each_tracepoint_range(
362 tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
363 void (*fct)(struct tracepoint *tp, void *priv),
364 void *priv)
365{
366 tracepoint_ptr_t *iter;
367
368 if (!begin)
369 return;
370 for (iter = begin; iter < end; iter++)
371 fct(tracepoint_ptr_deref(iter), priv);
372}
373
374#ifdef CONFIG_MODULES
375bool trace_module_has_bad_taint(struct module *mod)
376{
377 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
378 (1 << TAINT_UNSIGNED_MODULE));
379}
380
381static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
382
383/**
384 * register_tracepoint_notifier - register tracepoint coming/going notifier
385 * @nb: notifier block
386 *
387 * Notifiers registered with this function are called on module
388 * coming/going with the tracepoint_module_list_mutex held.
389 * The notifier block callback should expect a "struct tp_module" data
390 * pointer.
391 */
392int register_tracepoint_module_notifier(struct notifier_block *nb)
393{
394 struct tp_module *tp_mod;
395 int ret;
396
397 mutex_lock(&tracepoint_module_list_mutex);
398 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
399 if (ret)
400 goto end;
401 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
402 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
403end:
404 mutex_unlock(&tracepoint_module_list_mutex);
405 return ret;
406}
407EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
408
409/**
410 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
411 * @nb: notifier block
412 *
413 * The notifier block callback should expect a "struct tp_module" data
414 * pointer.
415 */
416int unregister_tracepoint_module_notifier(struct notifier_block *nb)
417{
418 struct tp_module *tp_mod;
419 int ret;
420
421 mutex_lock(&tracepoint_module_list_mutex);
422 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
423 if (ret)
424 goto end;
425 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
426 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
427end:
428 mutex_unlock(&tracepoint_module_list_mutex);
429 return ret;
430
431}
432EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
433
434/*
435 * Ensure the tracer unregistered the module's probes before the module
436 * teardown is performed. Prevents leaks of probe and data pointers.
437 */
438static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
439{
440 WARN_ON_ONCE(tp->funcs);
441}
442
443static int tracepoint_module_coming(struct module *mod)
444{
445 struct tp_module *tp_mod;
446 int ret = 0;
447
448 if (!mod->num_tracepoints)
449 return 0;
450
451 /*
452 * We skip modules that taint the kernel, especially those with different
453 * module headers (for forced load), to make sure we don't cause a crash.
454 * Staging, out-of-tree, and unsigned GPL modules are fine.
455 */
456 if (trace_module_has_bad_taint(mod))
457 return 0;
458 mutex_lock(&tracepoint_module_list_mutex);
459 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
460 if (!tp_mod) {
461 ret = -ENOMEM;
462 goto end;
463 }
464 tp_mod->mod = mod;
465 list_add_tail(&tp_mod->list, &tracepoint_module_list);
466 blocking_notifier_call_chain(&tracepoint_notify_list,
467 MODULE_STATE_COMING, tp_mod);
468end:
469 mutex_unlock(&tracepoint_module_list_mutex);
470 return ret;
471}
472
473static void tracepoint_module_going(struct module *mod)
474{
475 struct tp_module *tp_mod;
476
477 if (!mod->num_tracepoints)
478 return;
479
480 mutex_lock(&tracepoint_module_list_mutex);
481 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
482 if (tp_mod->mod == mod) {
483 blocking_notifier_call_chain(&tracepoint_notify_list,
484 MODULE_STATE_GOING, tp_mod);
485 list_del(&tp_mod->list);
486 kfree(tp_mod);
487 /*
488 * Called the going notifier before checking for
489 * quiescence.
490 */
491 for_each_tracepoint_range(mod->tracepoints_ptrs,
492 mod->tracepoints_ptrs + mod->num_tracepoints,
493 tp_module_going_check_quiescent, NULL);
494 break;
495 }
496 }
497 /*
498 * In the case of modules that were tainted at "coming", we'll simply
499 * walk through the list without finding it. We cannot use the "tainted"
500 * flag on "going", in case a module taints the kernel only after being
501 * loaded.
502 */
503 mutex_unlock(&tracepoint_module_list_mutex);
504}
505
506static int tracepoint_module_notify(struct notifier_block *self,
507 unsigned long val, void *data)
508{
509 struct module *mod = data;
510 int ret = 0;
511
512 switch (val) {
513 case MODULE_STATE_COMING:
514 ret = tracepoint_module_coming(mod);
515 break;
516 case MODULE_STATE_LIVE:
517 break;
518 case MODULE_STATE_GOING:
519 tracepoint_module_going(mod);
520 break;
521 case MODULE_STATE_UNFORMED:
522 break;
523 }
524 return ret;
525}
526
527static struct notifier_block tracepoint_module_nb = {
528 .notifier_call = tracepoint_module_notify,
529 .priority = 0,
530};
531
532static __init int init_tracepoints(void)
533{
534 int ret;
535
536 ret = register_module_notifier(&tracepoint_module_nb);
537 if (ret)
538 pr_warn("Failed to register tracepoint module enter notifier\n");
539
540 return ret;
541}
542__initcall(init_tracepoints);
543#endif /* CONFIG_MODULES */
544
545/**
546 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
547 * @fct: callback
548 * @priv: private data
549 */
550void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
551 void *priv)
552{
553 for_each_tracepoint_range(__start___tracepoints_ptrs,
554 __stop___tracepoints_ptrs, fct, priv);
555}
556EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
557
558#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
559
560/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
561static int sys_tracepoint_refcount;
562
563int syscall_regfunc(void)
564{
565 struct task_struct *p, *t;
566
567 if (!sys_tracepoint_refcount) {
568 read_lock(&tasklist_lock);
569 for_each_process_thread(p, t) {
570 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
571 }
572 read_unlock(&tasklist_lock);
573 }
574 sys_tracepoint_refcount++;
575
576 return 0;
577}
578
579void syscall_unregfunc(void)
580{
581 struct task_struct *p, *t;
582
583 sys_tracepoint_refcount--;
584 if (!sys_tracepoint_refcount) {
585 read_lock(&tasklist_lock);
586 for_each_process_thread(p, t) {
587 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
588 }
589 read_unlock(&tasklist_lock);
590 }
591}
592#endif
1/*
2 * Copyright (C) 2008-2014 Mathieu Desnoyers
3 *
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.
8 *
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.
13 *
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.
17 */
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>
29
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
36#ifdef CONFIG_MODULES
37/*
38 * Tracepoint module list mutex protects the local module list.
39 */
40static DEFINE_MUTEX(tracepoint_module_list_mutex);
41
42/* Local list of struct tp_module */
43static LIST_HEAD(tracepoint_module_list);
44#endif /* CONFIG_MODULES */
45
46/*
47 * tracepoints_mutex protects the builtin and module tracepoints.
48 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
49 */
50static DEFINE_MUTEX(tracepoints_mutex);
51
52/*
53 * Note about RCU :
54 * It is used to delay the free of multiple probes array until a quiescent
55 * state is reached.
56 */
57struct tp_probes {
58 struct rcu_head rcu;
59 struct tracepoint_func probes[0];
60};
61
62static inline void *allocate_probes(int count)
63{
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;
67}
68
69static void rcu_free_old_probes(struct rcu_head *head)
70{
71 kfree(container_of(head, struct tp_probes, rcu));
72}
73
74static inline void release_probes(struct tracepoint_func *old)
75{
76 if (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);
80 }
81}
82
83static void debug_print_probes(struct tracepoint_func *funcs)
84{
85 int i;
86
87 if (!tracepoint_debug || !funcs)
88 return;
89
90 for (i = 0; funcs[i].func; i++)
91 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
92}
93
94static struct tracepoint_func *func_add(struct tracepoint_func **funcs,
95 struct tracepoint_func *tp_func)
96{
97 int nr_probes = 0;
98 struct tracepoint_func *old, *new;
99
100 if (WARN_ON(!tp_func->func))
101 return ERR_PTR(-EINVAL);
102
103 debug_print_probes(*funcs);
104 old = *funcs;
105 if (old) {
106 /* (N -> N+1), (N != 0, 1) probes */
107 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
108 if (old[nr_probes].func == tp_func->func &&
109 old[nr_probes].data == tp_func->data)
110 return ERR_PTR(-EEXIST);
111 }
112 /* + 2 : one for new probe, one for NULL func */
113 new = allocate_probes(nr_probes + 2);
114 if (new == NULL)
115 return ERR_PTR(-ENOMEM);
116 if (old)
117 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
118 new[nr_probes] = *tp_func;
119 new[nr_probes + 1].func = NULL;
120 *funcs = new;
121 debug_print_probes(*funcs);
122 return old;
123}
124
125static void *func_remove(struct tracepoint_func **funcs,
126 struct tracepoint_func *tp_func)
127{
128 int nr_probes = 0, nr_del = 0, i;
129 struct tracepoint_func *old, *new;
130
131 old = *funcs;
132
133 if (!old)
134 return ERR_PTR(-ENOENT);
135
136 debug_print_probes(*funcs);
137 /* (N -> M), (N > 1, M >= 0) probes */
138 if (tp_func->func) {
139 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
140 if (old[nr_probes].func == tp_func->func &&
141 old[nr_probes].data == tp_func->data)
142 nr_del++;
143 }
144 }
145
146 /*
147 * If probe is NULL, then nr_probes = nr_del = 0, and then the
148 * entire entry will be removed.
149 */
150 if (nr_probes - nr_del == 0) {
151 /* N -> 0, (N > 1) */
152 *funcs = NULL;
153 debug_print_probes(*funcs);
154 return old;
155 } else {
156 int j = 0;
157 /* N -> M, (N > 1, M > 0) */
158 /* + 1 for NULL */
159 new = allocate_probes(nr_probes - nr_del + 1);
160 if (new == NULL)
161 return ERR_PTR(-ENOMEM);
162 for (i = 0; old[i].func; i++)
163 if (old[i].func != tp_func->func
164 || old[i].data != tp_func->data)
165 new[j++] = old[i];
166 new[nr_probes - nr_del].func = NULL;
167 *funcs = new;
168 }
169 debug_print_probes(*funcs);
170 return old;
171}
172
173/*
174 * Add the probe function to a tracepoint.
175 */
176static int tracepoint_add_func(struct tracepoint *tp,
177 struct tracepoint_func *func)
178{
179 struct tracepoint_func *old, *tp_funcs;
180
181 if (tp->regfunc && !static_key_enabled(&tp->key))
182 tp->regfunc();
183
184 tp_funcs = rcu_dereference_protected(tp->funcs,
185 lockdep_is_held(&tracepoints_mutex));
186 old = func_add(&tp_funcs, func);
187 if (IS_ERR(old)) {
188 WARN_ON_ONCE(1);
189 return PTR_ERR(old);
190 }
191
192 /*
193 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
194 * probe callbacks array is consistent before setting a pointer to it.
195 * This array is referenced by __DO_TRACE from
196 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
197 * is used.
198 */
199 rcu_assign_pointer(tp->funcs, tp_funcs);
200 if (!static_key_enabled(&tp->key))
201 static_key_slow_inc(&tp->key);
202 release_probes(old);
203 return 0;
204}
205
206/*
207 * Remove a probe function from a tracepoint.
208 * Note: only waiting an RCU period after setting elem->call to the empty
209 * function insures that the original callback is not used anymore. This insured
210 * by preempt_disable around the call site.
211 */
212static int tracepoint_remove_func(struct tracepoint *tp,
213 struct tracepoint_func *func)
214{
215 struct tracepoint_func *old, *tp_funcs;
216
217 tp_funcs = rcu_dereference_protected(tp->funcs,
218 lockdep_is_held(&tracepoints_mutex));
219 old = func_remove(&tp_funcs, func);
220 if (IS_ERR(old)) {
221 WARN_ON_ONCE(1);
222 return PTR_ERR(old);
223 }
224
225 if (!tp_funcs) {
226 /* Removed last function */
227 if (tp->unregfunc && static_key_enabled(&tp->key))
228 tp->unregfunc();
229
230 if (static_key_enabled(&tp->key))
231 static_key_slow_dec(&tp->key);
232 }
233 rcu_assign_pointer(tp->funcs, tp_funcs);
234 release_probes(old);
235 return 0;
236}
237
238/**
239 * tracepoint_probe_register - Connect a probe to a tracepoint
240 * @tp: tracepoint
241 * @probe: probe handler
242 *
243 * Returns 0 if ok, error value on error.
244 * Note: if @tp is within a module, the caller is responsible for
245 * unregistering the probe before the module is gone. This can be
246 * performed either with a tracepoint module going notifier, or from
247 * within module exit functions.
248 */
249int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
250{
251 struct tracepoint_func tp_func;
252 int ret;
253
254 mutex_lock(&tracepoints_mutex);
255 tp_func.func = probe;
256 tp_func.data = data;
257 ret = tracepoint_add_func(tp, &tp_func);
258 mutex_unlock(&tracepoints_mutex);
259 return ret;
260}
261EXPORT_SYMBOL_GPL(tracepoint_probe_register);
262
263/**
264 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
265 * @tp: tracepoint
266 * @probe: probe function pointer
267 *
268 * Returns 0 if ok, error value on error.
269 */
270int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
271{
272 struct tracepoint_func tp_func;
273 int ret;
274
275 mutex_lock(&tracepoints_mutex);
276 tp_func.func = probe;
277 tp_func.data = data;
278 ret = tracepoint_remove_func(tp, &tp_func);
279 mutex_unlock(&tracepoints_mutex);
280 return ret;
281}
282EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
283
284#ifdef CONFIG_MODULES
285bool trace_module_has_bad_taint(struct module *mod)
286{
287 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
288 (1 << TAINT_UNSIGNED_MODULE));
289}
290
291static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
292
293/**
294 * register_tracepoint_notifier - register tracepoint coming/going notifier
295 * @nb: notifier block
296 *
297 * Notifiers registered with this function are called on module
298 * coming/going with the tracepoint_module_list_mutex held.
299 * The notifier block callback should expect a "struct tp_module" data
300 * pointer.
301 */
302int register_tracepoint_module_notifier(struct notifier_block *nb)
303{
304 struct tp_module *tp_mod;
305 int ret;
306
307 mutex_lock(&tracepoint_module_list_mutex);
308 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
309 if (ret)
310 goto end;
311 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
312 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
313end:
314 mutex_unlock(&tracepoint_module_list_mutex);
315 return ret;
316}
317EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
318
319/**
320 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
321 * @nb: notifier block
322 *
323 * The notifier block callback should expect a "struct tp_module" data
324 * pointer.
325 */
326int unregister_tracepoint_module_notifier(struct notifier_block *nb)
327{
328 struct tp_module *tp_mod;
329 int ret;
330
331 mutex_lock(&tracepoint_module_list_mutex);
332 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
333 if (ret)
334 goto end;
335 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
336 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
337end:
338 mutex_unlock(&tracepoint_module_list_mutex);
339 return ret;
340
341}
342EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
343
344/*
345 * Ensure the tracer unregistered the module's probes before the module
346 * teardown is performed. Prevents leaks of probe and data pointers.
347 */
348static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
349 struct tracepoint * const *end)
350{
351 struct tracepoint * const *iter;
352
353 if (!begin)
354 return;
355 for (iter = begin; iter < end; iter++)
356 WARN_ON_ONCE((*iter)->funcs);
357}
358
359static int tracepoint_module_coming(struct module *mod)
360{
361 struct tp_module *tp_mod;
362 int ret = 0;
363
364 if (!mod->num_tracepoints)
365 return 0;
366
367 /*
368 * We skip modules that taint the kernel, especially those with different
369 * module headers (for forced load), to make sure we don't cause a crash.
370 * Staging, out-of-tree, and unsigned GPL modules are fine.
371 */
372 if (trace_module_has_bad_taint(mod))
373 return 0;
374 mutex_lock(&tracepoint_module_list_mutex);
375 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
376 if (!tp_mod) {
377 ret = -ENOMEM;
378 goto end;
379 }
380 tp_mod->mod = mod;
381 list_add_tail(&tp_mod->list, &tracepoint_module_list);
382 blocking_notifier_call_chain(&tracepoint_notify_list,
383 MODULE_STATE_COMING, tp_mod);
384end:
385 mutex_unlock(&tracepoint_module_list_mutex);
386 return ret;
387}
388
389static void tracepoint_module_going(struct module *mod)
390{
391 struct tp_module *tp_mod;
392
393 if (!mod->num_tracepoints)
394 return;
395
396 mutex_lock(&tracepoint_module_list_mutex);
397 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
398 if (tp_mod->mod == mod) {
399 blocking_notifier_call_chain(&tracepoint_notify_list,
400 MODULE_STATE_GOING, tp_mod);
401 list_del(&tp_mod->list);
402 kfree(tp_mod);
403 /*
404 * Called the going notifier before checking for
405 * quiescence.
406 */
407 tp_module_going_check_quiescent(mod->tracepoints_ptrs,
408 mod->tracepoints_ptrs + mod->num_tracepoints);
409 break;
410 }
411 }
412 /*
413 * In the case of modules that were tainted at "coming", we'll simply
414 * walk through the list without finding it. We cannot use the "tainted"
415 * flag on "going", in case a module taints the kernel only after being
416 * loaded.
417 */
418 mutex_unlock(&tracepoint_module_list_mutex);
419}
420
421static int tracepoint_module_notify(struct notifier_block *self,
422 unsigned long val, void *data)
423{
424 struct module *mod = data;
425 int ret = 0;
426
427 switch (val) {
428 case MODULE_STATE_COMING:
429 ret = tracepoint_module_coming(mod);
430 break;
431 case MODULE_STATE_LIVE:
432 break;
433 case MODULE_STATE_GOING:
434 tracepoint_module_going(mod);
435 break;
436 case MODULE_STATE_UNFORMED:
437 break;
438 }
439 return ret;
440}
441
442static struct notifier_block tracepoint_module_nb = {
443 .notifier_call = tracepoint_module_notify,
444 .priority = 0,
445};
446
447static __init int init_tracepoints(void)
448{
449 int ret;
450
451 ret = register_module_notifier(&tracepoint_module_nb);
452 if (ret)
453 pr_warning("Failed to register tracepoint module enter notifier\n");
454
455 return ret;
456}
457__initcall(init_tracepoints);
458#endif /* CONFIG_MODULES */
459
460static void for_each_tracepoint_range(struct tracepoint * const *begin,
461 struct tracepoint * const *end,
462 void (*fct)(struct tracepoint *tp, void *priv),
463 void *priv)
464{
465 struct tracepoint * const *iter;
466
467 if (!begin)
468 return;
469 for (iter = begin; iter < end; iter++)
470 fct(*iter, priv);
471}
472
473/**
474 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
475 * @fct: callback
476 * @priv: private data
477 */
478void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
479 void *priv)
480{
481 for_each_tracepoint_range(__start___tracepoints_ptrs,
482 __stop___tracepoints_ptrs, fct, priv);
483}
484EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
485
486#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
487
488/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
489static int sys_tracepoint_refcount;
490
491void syscall_regfunc(void)
492{
493 unsigned long flags;
494 struct task_struct *g, *t;
495
496 if (!sys_tracepoint_refcount) {
497 read_lock_irqsave(&tasklist_lock, flags);
498 do_each_thread(g, t) {
499 /* Skip kernel threads. */
500 if (t->mm)
501 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
502 } while_each_thread(g, t);
503 read_unlock_irqrestore(&tasklist_lock, flags);
504 }
505 sys_tracepoint_refcount++;
506}
507
508void syscall_unregfunc(void)
509{
510 unsigned long flags;
511 struct task_struct *g, *t;
512
513 sys_tracepoint_refcount--;
514 if (!sys_tracepoint_refcount) {
515 read_lock_irqsave(&tasklist_lock, flags);
516 do_each_thread(g, t) {
517 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
518 } while_each_thread(g, t);
519 read_unlock_irqrestore(&tasklist_lock, flags);
520 }
521}
522#endif