xref: /openbmc/linux/kernel/jump_label.c (revision 19b438592238b3b40c3f945bb5f9c4ca971c0c45)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * jump label support
4  *
5  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6  * Copyright (C) 2011 Peter Zijlstra
7  *
8  */
9 #include <linux/memory.h>
10 #include <linux/uaccess.h>
11 #include <linux/module.h>
12 #include <linux/list.h>
13 #include <linux/slab.h>
14 #include <linux/sort.h>
15 #include <linux/err.h>
16 #include <linux/static_key.h>
17 #include <linux/jump_label_ratelimit.h>
18 #include <linux/bug.h>
19 #include <linux/cpu.h>
20 #include <asm/sections.h>
21 
22 /* mutex to protect coming/going of the jump_label table */
23 static DEFINE_MUTEX(jump_label_mutex);
24 
25 void jump_label_lock(void)
26 {
27 	mutex_lock(&jump_label_mutex);
28 }
29 
30 void jump_label_unlock(void)
31 {
32 	mutex_unlock(&jump_label_mutex);
33 }
34 
35 static int jump_label_cmp(const void *a, const void *b)
36 {
37 	const struct jump_entry *jea = a;
38 	const struct jump_entry *jeb = b;
39 
40 	/*
41 	 * Entrires are sorted by key.
42 	 */
43 	if (jump_entry_key(jea) < jump_entry_key(jeb))
44 		return -1;
45 
46 	if (jump_entry_key(jea) > jump_entry_key(jeb))
47 		return 1;
48 
49 	/*
50 	 * In the batching mode, entries should also be sorted by the code
51 	 * inside the already sorted list of entries, enabling a bsearch in
52 	 * the vector.
53 	 */
54 	if (jump_entry_code(jea) < jump_entry_code(jeb))
55 		return -1;
56 
57 	if (jump_entry_code(jea) > jump_entry_code(jeb))
58 		return 1;
59 
60 	return 0;
61 }
62 
63 static void jump_label_swap(void *a, void *b, int size)
64 {
65 	long delta = (unsigned long)a - (unsigned long)b;
66 	struct jump_entry *jea = a;
67 	struct jump_entry *jeb = b;
68 	struct jump_entry tmp = *jea;
69 
70 	jea->code	= jeb->code - delta;
71 	jea->target	= jeb->target - delta;
72 	jea->key	= jeb->key - delta;
73 
74 	jeb->code	= tmp.code + delta;
75 	jeb->target	= tmp.target + delta;
76 	jeb->key	= tmp.key + delta;
77 }
78 
79 static void
80 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
81 {
82 	unsigned long size;
83 	void *swapfn = NULL;
84 
85 	if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
86 		swapfn = jump_label_swap;
87 
88 	size = (((unsigned long)stop - (unsigned long)start)
89 					/ sizeof(struct jump_entry));
90 	sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
91 }
92 
93 static void jump_label_update(struct static_key *key);
94 
95 /*
96  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
97  * The use of 'atomic_read()' requires atomic.h and its problematic for some
98  * kernel headers such as kernel.h and others. Since static_key_count() is not
99  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
100  * to have it be a function here. Similarly, for 'static_key_enable()' and
101  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
102  * to be included from most/all places for CONFIG_JUMP_LABEL.
103  */
104 int static_key_count(struct static_key *key)
105 {
106 	/*
107 	 * -1 means the first static_key_slow_inc() is in progress.
108 	 *  static_key_enabled() must return true, so return 1 here.
109 	 */
110 	int n = atomic_read(&key->enabled);
111 
112 	return n >= 0 ? n : 1;
113 }
114 EXPORT_SYMBOL_GPL(static_key_count);
115 
116 void static_key_slow_inc_cpuslocked(struct static_key *key)
117 {
118 	int v, v1;
119 
120 	STATIC_KEY_CHECK_USE(key);
121 	lockdep_assert_cpus_held();
122 
123 	/*
124 	 * Careful if we get concurrent static_key_slow_inc() calls;
125 	 * later calls must wait for the first one to _finish_ the
126 	 * jump_label_update() process.  At the same time, however,
127 	 * the jump_label_update() call below wants to see
128 	 * static_key_enabled(&key) for jumps to be updated properly.
129 	 *
130 	 * So give a special meaning to negative key->enabled: it sends
131 	 * static_key_slow_inc() down the slow path, and it is non-zero
132 	 * so it counts as "enabled" in jump_label_update().  Note that
133 	 * atomic_inc_unless_negative() checks >= 0, so roll our own.
134 	 */
135 	for (v = atomic_read(&key->enabled); v > 0; v = v1) {
136 		v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
137 		if (likely(v1 == v))
138 			return;
139 	}
140 
141 	jump_label_lock();
142 	if (atomic_read(&key->enabled) == 0) {
143 		atomic_set(&key->enabled, -1);
144 		jump_label_update(key);
145 		/*
146 		 * Ensure that if the above cmpxchg loop observes our positive
147 		 * value, it must also observe all the text changes.
148 		 */
149 		atomic_set_release(&key->enabled, 1);
150 	} else {
151 		atomic_inc(&key->enabled);
152 	}
153 	jump_label_unlock();
154 }
155 
156 void static_key_slow_inc(struct static_key *key)
157 {
158 	cpus_read_lock();
159 	static_key_slow_inc_cpuslocked(key);
160 	cpus_read_unlock();
161 }
162 EXPORT_SYMBOL_GPL(static_key_slow_inc);
163 
164 void static_key_enable_cpuslocked(struct static_key *key)
165 {
166 	STATIC_KEY_CHECK_USE(key);
167 	lockdep_assert_cpus_held();
168 
169 	if (atomic_read(&key->enabled) > 0) {
170 		WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
171 		return;
172 	}
173 
174 	jump_label_lock();
175 	if (atomic_read(&key->enabled) == 0) {
176 		atomic_set(&key->enabled, -1);
177 		jump_label_update(key);
178 		/*
179 		 * See static_key_slow_inc().
180 		 */
181 		atomic_set_release(&key->enabled, 1);
182 	}
183 	jump_label_unlock();
184 }
185 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
186 
187 void static_key_enable(struct static_key *key)
188 {
189 	cpus_read_lock();
190 	static_key_enable_cpuslocked(key);
191 	cpus_read_unlock();
192 }
193 EXPORT_SYMBOL_GPL(static_key_enable);
194 
195 void static_key_disable_cpuslocked(struct static_key *key)
196 {
197 	STATIC_KEY_CHECK_USE(key);
198 	lockdep_assert_cpus_held();
199 
200 	if (atomic_read(&key->enabled) != 1) {
201 		WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
202 		return;
203 	}
204 
205 	jump_label_lock();
206 	if (atomic_cmpxchg(&key->enabled, 1, 0))
207 		jump_label_update(key);
208 	jump_label_unlock();
209 }
210 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
211 
212 void static_key_disable(struct static_key *key)
213 {
214 	cpus_read_lock();
215 	static_key_disable_cpuslocked(key);
216 	cpus_read_unlock();
217 }
218 EXPORT_SYMBOL_GPL(static_key_disable);
219 
220 static bool static_key_slow_try_dec(struct static_key *key)
221 {
222 	int val;
223 
224 	val = atomic_fetch_add_unless(&key->enabled, -1, 1);
225 	if (val == 1)
226 		return false;
227 
228 	/*
229 	 * The negative count check is valid even when a negative
230 	 * key->enabled is in use by static_key_slow_inc(); a
231 	 * __static_key_slow_dec() before the first static_key_slow_inc()
232 	 * returns is unbalanced, because all other static_key_slow_inc()
233 	 * instances block while the update is in progress.
234 	 */
235 	WARN(val < 0, "jump label: negative count!\n");
236 	return true;
237 }
238 
239 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
240 {
241 	lockdep_assert_cpus_held();
242 
243 	if (static_key_slow_try_dec(key))
244 		return;
245 
246 	jump_label_lock();
247 	if (atomic_dec_and_test(&key->enabled))
248 		jump_label_update(key);
249 	jump_label_unlock();
250 }
251 
252 static void __static_key_slow_dec(struct static_key *key)
253 {
254 	cpus_read_lock();
255 	__static_key_slow_dec_cpuslocked(key);
256 	cpus_read_unlock();
257 }
258 
259 void jump_label_update_timeout(struct work_struct *work)
260 {
261 	struct static_key_deferred *key =
262 		container_of(work, struct static_key_deferred, work.work);
263 	__static_key_slow_dec(&key->key);
264 }
265 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
266 
267 void static_key_slow_dec(struct static_key *key)
268 {
269 	STATIC_KEY_CHECK_USE(key);
270 	__static_key_slow_dec(key);
271 }
272 EXPORT_SYMBOL_GPL(static_key_slow_dec);
273 
274 void static_key_slow_dec_cpuslocked(struct static_key *key)
275 {
276 	STATIC_KEY_CHECK_USE(key);
277 	__static_key_slow_dec_cpuslocked(key);
278 }
279 
280 void __static_key_slow_dec_deferred(struct static_key *key,
281 				    struct delayed_work *work,
282 				    unsigned long timeout)
283 {
284 	STATIC_KEY_CHECK_USE(key);
285 
286 	if (static_key_slow_try_dec(key))
287 		return;
288 
289 	schedule_delayed_work(work, timeout);
290 }
291 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
292 
293 void __static_key_deferred_flush(void *key, struct delayed_work *work)
294 {
295 	STATIC_KEY_CHECK_USE(key);
296 	flush_delayed_work(work);
297 }
298 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
299 
300 void jump_label_rate_limit(struct static_key_deferred *key,
301 		unsigned long rl)
302 {
303 	STATIC_KEY_CHECK_USE(key);
304 	key->timeout = rl;
305 	INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
306 }
307 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
308 
309 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
310 {
311 	if (jump_entry_code(entry) <= (unsigned long)end &&
312 	    jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
313 		return 1;
314 
315 	return 0;
316 }
317 
318 static int __jump_label_text_reserved(struct jump_entry *iter_start,
319 		struct jump_entry *iter_stop, void *start, void *end)
320 {
321 	struct jump_entry *iter;
322 
323 	iter = iter_start;
324 	while (iter < iter_stop) {
325 		if (addr_conflict(iter, start, end))
326 			return 1;
327 		iter++;
328 	}
329 
330 	return 0;
331 }
332 
333 /*
334  * Update code which is definitely not currently executing.
335  * Architectures which need heavyweight synchronization to modify
336  * running code can override this to make the non-live update case
337  * cheaper.
338  */
339 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
340 					    enum jump_label_type type)
341 {
342 	arch_jump_label_transform(entry, type);
343 }
344 
345 static inline struct jump_entry *static_key_entries(struct static_key *key)
346 {
347 	WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
348 	return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
349 }
350 
351 static inline bool static_key_type(struct static_key *key)
352 {
353 	return key->type & JUMP_TYPE_TRUE;
354 }
355 
356 static inline bool static_key_linked(struct static_key *key)
357 {
358 	return key->type & JUMP_TYPE_LINKED;
359 }
360 
361 static inline void static_key_clear_linked(struct static_key *key)
362 {
363 	key->type &= ~JUMP_TYPE_LINKED;
364 }
365 
366 static inline void static_key_set_linked(struct static_key *key)
367 {
368 	key->type |= JUMP_TYPE_LINKED;
369 }
370 
371 /***
372  * A 'struct static_key' uses a union such that it either points directly
373  * to a table of 'struct jump_entry' or to a linked list of modules which in
374  * turn point to 'struct jump_entry' tables.
375  *
376  * The two lower bits of the pointer are used to keep track of which pointer
377  * type is in use and to store the initial branch direction, we use an access
378  * function which preserves these bits.
379  */
380 static void static_key_set_entries(struct static_key *key,
381 				   struct jump_entry *entries)
382 {
383 	unsigned long type;
384 
385 	WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
386 	type = key->type & JUMP_TYPE_MASK;
387 	key->entries = entries;
388 	key->type |= type;
389 }
390 
391 static enum jump_label_type jump_label_type(struct jump_entry *entry)
392 {
393 	struct static_key *key = jump_entry_key(entry);
394 	bool enabled = static_key_enabled(key);
395 	bool branch = jump_entry_is_branch(entry);
396 
397 	/* See the comment in linux/jump_label.h */
398 	return enabled ^ branch;
399 }
400 
401 static bool jump_label_can_update(struct jump_entry *entry, bool init)
402 {
403 	/*
404 	 * Cannot update code that was in an init text area.
405 	 */
406 	if (!init && jump_entry_is_init(entry))
407 		return false;
408 
409 	if (!kernel_text_address(jump_entry_code(entry))) {
410 		/*
411 		 * This skips patching built-in __exit, which
412 		 * is part of init_section_contains() but is
413 		 * not part of kernel_text_address().
414 		 *
415 		 * Skipping built-in __exit is fine since it
416 		 * will never be executed.
417 		 */
418 		WARN_ONCE(!jump_entry_is_init(entry),
419 			  "can't patch jump_label at %pS",
420 			  (void *)jump_entry_code(entry));
421 		return false;
422 	}
423 
424 	return true;
425 }
426 
427 #ifndef HAVE_JUMP_LABEL_BATCH
428 static void __jump_label_update(struct static_key *key,
429 				struct jump_entry *entry,
430 				struct jump_entry *stop,
431 				bool init)
432 {
433 	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
434 		if (jump_label_can_update(entry, init))
435 			arch_jump_label_transform(entry, jump_label_type(entry));
436 	}
437 }
438 #else
439 static void __jump_label_update(struct static_key *key,
440 				struct jump_entry *entry,
441 				struct jump_entry *stop,
442 				bool init)
443 {
444 	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
445 
446 		if (!jump_label_can_update(entry, init))
447 			continue;
448 
449 		if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
450 			/*
451 			 * Queue is full: Apply the current queue and try again.
452 			 */
453 			arch_jump_label_transform_apply();
454 			BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
455 		}
456 	}
457 	arch_jump_label_transform_apply();
458 }
459 #endif
460 
461 void __init jump_label_init(void)
462 {
463 	struct jump_entry *iter_start = __start___jump_table;
464 	struct jump_entry *iter_stop = __stop___jump_table;
465 	struct static_key *key = NULL;
466 	struct jump_entry *iter;
467 
468 	/*
469 	 * Since we are initializing the static_key.enabled field with
470 	 * with the 'raw' int values (to avoid pulling in atomic.h) in
471 	 * jump_label.h, let's make sure that is safe. There are only two
472 	 * cases to check since we initialize to 0 or 1.
473 	 */
474 	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
475 	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
476 
477 	if (static_key_initialized)
478 		return;
479 
480 	cpus_read_lock();
481 	jump_label_lock();
482 	jump_label_sort_entries(iter_start, iter_stop);
483 
484 	for (iter = iter_start; iter < iter_stop; iter++) {
485 		struct static_key *iterk;
486 		bool in_init;
487 
488 		/* rewrite NOPs */
489 		if (jump_label_type(iter) == JUMP_LABEL_NOP)
490 			arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
491 
492 		in_init = init_section_contains((void *)jump_entry_code(iter), 1);
493 		jump_entry_set_init(iter, in_init);
494 
495 		iterk = jump_entry_key(iter);
496 		if (iterk == key)
497 			continue;
498 
499 		key = iterk;
500 		static_key_set_entries(key, iter);
501 	}
502 	static_key_initialized = true;
503 	jump_label_unlock();
504 	cpus_read_unlock();
505 }
506 
507 #ifdef CONFIG_MODULES
508 
509 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
510 {
511 	struct static_key *key = jump_entry_key(entry);
512 	bool type = static_key_type(key);
513 	bool branch = jump_entry_is_branch(entry);
514 
515 	/* See the comment in linux/jump_label.h */
516 	return type ^ branch;
517 }
518 
519 struct static_key_mod {
520 	struct static_key_mod *next;
521 	struct jump_entry *entries;
522 	struct module *mod;
523 };
524 
525 static inline struct static_key_mod *static_key_mod(struct static_key *key)
526 {
527 	WARN_ON_ONCE(!static_key_linked(key));
528 	return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
529 }
530 
531 /***
532  * key->type and key->next are the same via union.
533  * This sets key->next and preserves the type bits.
534  *
535  * See additional comments above static_key_set_entries().
536  */
537 static void static_key_set_mod(struct static_key *key,
538 			       struct static_key_mod *mod)
539 {
540 	unsigned long type;
541 
542 	WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
543 	type = key->type & JUMP_TYPE_MASK;
544 	key->next = mod;
545 	key->type |= type;
546 }
547 
548 static int __jump_label_mod_text_reserved(void *start, void *end)
549 {
550 	struct module *mod;
551 	int ret;
552 
553 	preempt_disable();
554 	mod = __module_text_address((unsigned long)start);
555 	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
556 	if (!try_module_get(mod))
557 		mod = NULL;
558 	preempt_enable();
559 
560 	if (!mod)
561 		return 0;
562 
563 	ret = __jump_label_text_reserved(mod->jump_entries,
564 				mod->jump_entries + mod->num_jump_entries,
565 				start, end);
566 
567 	module_put(mod);
568 
569 	return ret;
570 }
571 
572 static void __jump_label_mod_update(struct static_key *key)
573 {
574 	struct static_key_mod *mod;
575 
576 	for (mod = static_key_mod(key); mod; mod = mod->next) {
577 		struct jump_entry *stop;
578 		struct module *m;
579 
580 		/*
581 		 * NULL if the static_key is defined in a module
582 		 * that does not use it
583 		 */
584 		if (!mod->entries)
585 			continue;
586 
587 		m = mod->mod;
588 		if (!m)
589 			stop = __stop___jump_table;
590 		else
591 			stop = m->jump_entries + m->num_jump_entries;
592 		__jump_label_update(key, mod->entries, stop,
593 				    m && m->state == MODULE_STATE_COMING);
594 	}
595 }
596 
597 /***
598  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
599  * @mod: module to patch
600  *
601  * Allow for run-time selection of the optimal nops. Before the module
602  * loads patch these with arch_get_jump_label_nop(), which is specified by
603  * the arch specific jump label code.
604  */
605 void jump_label_apply_nops(struct module *mod)
606 {
607 	struct jump_entry *iter_start = mod->jump_entries;
608 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
609 	struct jump_entry *iter;
610 
611 	/* if the module doesn't have jump label entries, just return */
612 	if (iter_start == iter_stop)
613 		return;
614 
615 	for (iter = iter_start; iter < iter_stop; iter++) {
616 		/* Only write NOPs for arch_branch_static(). */
617 		if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
618 			arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
619 	}
620 }
621 
622 static int jump_label_add_module(struct module *mod)
623 {
624 	struct jump_entry *iter_start = mod->jump_entries;
625 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
626 	struct jump_entry *iter;
627 	struct static_key *key = NULL;
628 	struct static_key_mod *jlm, *jlm2;
629 
630 	/* if the module doesn't have jump label entries, just return */
631 	if (iter_start == iter_stop)
632 		return 0;
633 
634 	jump_label_sort_entries(iter_start, iter_stop);
635 
636 	for (iter = iter_start; iter < iter_stop; iter++) {
637 		struct static_key *iterk;
638 		bool in_init;
639 
640 		in_init = within_module_init(jump_entry_code(iter), mod);
641 		jump_entry_set_init(iter, in_init);
642 
643 		iterk = jump_entry_key(iter);
644 		if (iterk == key)
645 			continue;
646 
647 		key = iterk;
648 		if (within_module((unsigned long)key, mod)) {
649 			static_key_set_entries(key, iter);
650 			continue;
651 		}
652 		jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
653 		if (!jlm)
654 			return -ENOMEM;
655 		if (!static_key_linked(key)) {
656 			jlm2 = kzalloc(sizeof(struct static_key_mod),
657 				       GFP_KERNEL);
658 			if (!jlm2) {
659 				kfree(jlm);
660 				return -ENOMEM;
661 			}
662 			preempt_disable();
663 			jlm2->mod = __module_address((unsigned long)key);
664 			preempt_enable();
665 			jlm2->entries = static_key_entries(key);
666 			jlm2->next = NULL;
667 			static_key_set_mod(key, jlm2);
668 			static_key_set_linked(key);
669 		}
670 		jlm->mod = mod;
671 		jlm->entries = iter;
672 		jlm->next = static_key_mod(key);
673 		static_key_set_mod(key, jlm);
674 		static_key_set_linked(key);
675 
676 		/* Only update if we've changed from our initial state */
677 		if (jump_label_type(iter) != jump_label_init_type(iter))
678 			__jump_label_update(key, iter, iter_stop, true);
679 	}
680 
681 	return 0;
682 }
683 
684 static void jump_label_del_module(struct module *mod)
685 {
686 	struct jump_entry *iter_start = mod->jump_entries;
687 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
688 	struct jump_entry *iter;
689 	struct static_key *key = NULL;
690 	struct static_key_mod *jlm, **prev;
691 
692 	for (iter = iter_start; iter < iter_stop; iter++) {
693 		if (jump_entry_key(iter) == key)
694 			continue;
695 
696 		key = jump_entry_key(iter);
697 
698 		if (within_module((unsigned long)key, mod))
699 			continue;
700 
701 		/* No memory during module load */
702 		if (WARN_ON(!static_key_linked(key)))
703 			continue;
704 
705 		prev = &key->next;
706 		jlm = static_key_mod(key);
707 
708 		while (jlm && jlm->mod != mod) {
709 			prev = &jlm->next;
710 			jlm = jlm->next;
711 		}
712 
713 		/* No memory during module load */
714 		if (WARN_ON(!jlm))
715 			continue;
716 
717 		if (prev == &key->next)
718 			static_key_set_mod(key, jlm->next);
719 		else
720 			*prev = jlm->next;
721 
722 		kfree(jlm);
723 
724 		jlm = static_key_mod(key);
725 		/* if only one etry is left, fold it back into the static_key */
726 		if (jlm->next == NULL) {
727 			static_key_set_entries(key, jlm->entries);
728 			static_key_clear_linked(key);
729 			kfree(jlm);
730 		}
731 	}
732 }
733 
734 static int
735 jump_label_module_notify(struct notifier_block *self, unsigned long val,
736 			 void *data)
737 {
738 	struct module *mod = data;
739 	int ret = 0;
740 
741 	cpus_read_lock();
742 	jump_label_lock();
743 
744 	switch (val) {
745 	case MODULE_STATE_COMING:
746 		ret = jump_label_add_module(mod);
747 		if (ret) {
748 			WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
749 			jump_label_del_module(mod);
750 		}
751 		break;
752 	case MODULE_STATE_GOING:
753 		jump_label_del_module(mod);
754 		break;
755 	}
756 
757 	jump_label_unlock();
758 	cpus_read_unlock();
759 
760 	return notifier_from_errno(ret);
761 }
762 
763 static struct notifier_block jump_label_module_nb = {
764 	.notifier_call = jump_label_module_notify,
765 	.priority = 1, /* higher than tracepoints */
766 };
767 
768 static __init int jump_label_init_module(void)
769 {
770 	return register_module_notifier(&jump_label_module_nb);
771 }
772 early_initcall(jump_label_init_module);
773 
774 #endif /* CONFIG_MODULES */
775 
776 /***
777  * jump_label_text_reserved - check if addr range is reserved
778  * @start: start text addr
779  * @end: end text addr
780  *
781  * checks if the text addr located between @start and @end
782  * overlaps with any of the jump label patch addresses. Code
783  * that wants to modify kernel text should first verify that
784  * it does not overlap with any of the jump label addresses.
785  * Caller must hold jump_label_mutex.
786  *
787  * returns 1 if there is an overlap, 0 otherwise
788  */
789 int jump_label_text_reserved(void *start, void *end)
790 {
791 	int ret = __jump_label_text_reserved(__start___jump_table,
792 			__stop___jump_table, start, end);
793 
794 	if (ret)
795 		return ret;
796 
797 #ifdef CONFIG_MODULES
798 	ret = __jump_label_mod_text_reserved(start, end);
799 #endif
800 	return ret;
801 }
802 
803 static void jump_label_update(struct static_key *key)
804 {
805 	struct jump_entry *stop = __stop___jump_table;
806 	bool init = system_state < SYSTEM_RUNNING;
807 	struct jump_entry *entry;
808 #ifdef CONFIG_MODULES
809 	struct module *mod;
810 
811 	if (static_key_linked(key)) {
812 		__jump_label_mod_update(key);
813 		return;
814 	}
815 
816 	preempt_disable();
817 	mod = __module_address((unsigned long)key);
818 	if (mod) {
819 		stop = mod->jump_entries + mod->num_jump_entries;
820 		init = mod->state == MODULE_STATE_COMING;
821 	}
822 	preempt_enable();
823 #endif
824 	entry = static_key_entries(key);
825 	/* if there are no users, entry can be NULL */
826 	if (entry)
827 		__jump_label_update(key, entry, stop, init);
828 }
829 
830 #ifdef CONFIG_STATIC_KEYS_SELFTEST
831 static DEFINE_STATIC_KEY_TRUE(sk_true);
832 static DEFINE_STATIC_KEY_FALSE(sk_false);
833 
834 static __init int jump_label_test(void)
835 {
836 	int i;
837 
838 	for (i = 0; i < 2; i++) {
839 		WARN_ON(static_key_enabled(&sk_true.key) != true);
840 		WARN_ON(static_key_enabled(&sk_false.key) != false);
841 
842 		WARN_ON(!static_branch_likely(&sk_true));
843 		WARN_ON(!static_branch_unlikely(&sk_true));
844 		WARN_ON(static_branch_likely(&sk_false));
845 		WARN_ON(static_branch_unlikely(&sk_false));
846 
847 		static_branch_disable(&sk_true);
848 		static_branch_enable(&sk_false);
849 
850 		WARN_ON(static_key_enabled(&sk_true.key) == true);
851 		WARN_ON(static_key_enabled(&sk_false.key) == false);
852 
853 		WARN_ON(static_branch_likely(&sk_true));
854 		WARN_ON(static_branch_unlikely(&sk_true));
855 		WARN_ON(!static_branch_likely(&sk_false));
856 		WARN_ON(!static_branch_unlikely(&sk_false));
857 
858 		static_branch_enable(&sk_true);
859 		static_branch_disable(&sk_false);
860 	}
861 
862 	return 0;
863 }
864 early_initcall(jump_label_test);
865 #endif /* STATIC_KEYS_SELFTEST */
866