jump_label.c

  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 */
 23static DEFINE_MUTEX(jump_label_mutex);
 24
 25void jump_label_lock(void)
 26{
 27	mutex_lock(&jump_label_mutex);
 28}
 29
 30void jump_label_unlock(void)
 31{
 32	mutex_unlock(&jump_label_mutex);
 33}
 34
 35static 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
 63static 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
 79static void
 80jump_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
 93static 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 */
104int 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}
114EXPORT_SYMBOL_GPL(static_key_count);
115
116/*
117 * static_key_fast_inc_not_disabled - adds a user for a static key
118 * @key: static key that must be already enabled
119 *
120 * The caller must make sure that the static key can't get disabled while
121 * in this function. It doesn't patch jump labels, only adds a user to
122 * an already enabled static key.
123 *
124 * Returns true if the increment was done. Unlike refcount_t the ref counter
125 * is not saturated, but will fail to increment on overflow.
126 */
127bool static_key_fast_inc_not_disabled(struct static_key *key)
128{
129	int v;
130
131	STATIC_KEY_CHECK_USE(key);
132	/*
133	 * Negative key->enabled has a special meaning: it sends
134	 * static_key_slow_inc/dec() down the slow path, and it is non-zero
135	 * so it counts as "enabled" in jump_label_update().
136	 *
137	 * The INT_MAX overflow condition is either used by the networking
138	 * code to reset or detected in the slow path of
139	 * static_key_slow_inc_cpuslocked().
140	 */
141	v = atomic_read(&key->enabled);
142	do {
143		if (v <= 0 || v == INT_MAX)
144			return false;
145	} while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
146
147	return true;
148}
149EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
150
151bool static_key_slow_inc_cpuslocked(struct static_key *key)
152{
153	lockdep_assert_cpus_held();
154
155	/*
156	 * Careful if we get concurrent static_key_slow_inc/dec() calls;
157	 * later calls must wait for the first one to _finish_ the
158	 * jump_label_update() process.  At the same time, however,
159	 * the jump_label_update() call below wants to see
160	 * static_key_enabled(&key) for jumps to be updated properly.
161	 */
162	if (static_key_fast_inc_not_disabled(key))
163		return true;
164
165	guard(mutex)(&jump_label_mutex);
166	/* Try to mark it as 'enabling in progress. */
167	if (!atomic_cmpxchg(&key->enabled, 0, -1)) {
168		jump_label_update(key);
169		/*
170		 * Ensure that when static_key_fast_inc_not_disabled() or
171		 * static_key_dec_not_one() observe the positive value,
172		 * they must also observe all the text changes.
173		 */
174		atomic_set_release(&key->enabled, 1);
175	} else {
176		/*
177		 * While holding the mutex this should never observe
178		 * anything else than a value >= 1 and succeed
179		 */
180		if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key)))
181			return false;
182	}
183	return true;
184}
185
186bool static_key_slow_inc(struct static_key *key)
187{
188	bool ret;
189
190	cpus_read_lock();
191	ret = static_key_slow_inc_cpuslocked(key);
192	cpus_read_unlock();
193	return ret;
194}
195EXPORT_SYMBOL_GPL(static_key_slow_inc);
196
197void static_key_enable_cpuslocked(struct static_key *key)
198{
199	STATIC_KEY_CHECK_USE(key);
200	lockdep_assert_cpus_held();
201
202	if (atomic_read(&key->enabled) > 0) {
203		WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
204		return;
205	}
206
207	jump_label_lock();
208	if (atomic_read(&key->enabled) == 0) {
209		atomic_set(&key->enabled, -1);
210		jump_label_update(key);
211		/*
212		 * See static_key_slow_inc().
213		 */
214		atomic_set_release(&key->enabled, 1);
215	}
216	jump_label_unlock();
217}
218EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
219
220void static_key_enable(struct static_key *key)
221{
222	cpus_read_lock();
223	static_key_enable_cpuslocked(key);
224	cpus_read_unlock();
225}
226EXPORT_SYMBOL_GPL(static_key_enable);
227
228void static_key_disable_cpuslocked(struct static_key *key)
229{
230	STATIC_KEY_CHECK_USE(key);
231	lockdep_assert_cpus_held();
232
233	if (atomic_read(&key->enabled) != 1) {
234		WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
235		return;
236	}
237
238	jump_label_lock();
239	if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
240		jump_label_update(key);
241	jump_label_unlock();
242}
243EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
244
245void static_key_disable(struct static_key *key)
246{
247	cpus_read_lock();
248	static_key_disable_cpuslocked(key);
249	cpus_read_unlock();
250}
251EXPORT_SYMBOL_GPL(static_key_disable);
252
253static bool static_key_dec_not_one(struct static_key *key)
254{
255	int v;
256
257	/*
258	 * Go into the slow path if key::enabled is less than or equal than
259	 * one. One is valid to shut down the key, anything less than one
260	 * is an imbalance, which is handled at the call site.
261	 *
262	 * That includes the special case of '-1' which is set in
263	 * static_key_slow_inc_cpuslocked(), but that's harmless as it is
264	 * fully serialized in the slow path below. By the time this task
265	 * acquires the jump label lock the value is back to one and the
266	 * retry under the lock must succeed.
267	 */
268	v = atomic_read(&key->enabled);
269	do {
270		/*
271		 * Warn about the '-1' case though; since that means a
272		 * decrement is concurrent with a first (0->1) increment. IOW
273		 * people are trying to disable something that wasn't yet fully
274		 * enabled. This suggests an ordering problem on the user side.
275		 */
276		WARN_ON_ONCE(v < 0);
277
278		/*
279		 * Warn about underflow, and lie about success in an attempt to
280		 * not make things worse.
281		 */
282		if (WARN_ON_ONCE(v == 0))
283			return true;
284
285		if (v <= 1)
286			return false;
287	} while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
288
289	return true;
290}
291
292static void __static_key_slow_dec_cpuslocked(struct static_key *key)
293{
294	lockdep_assert_cpus_held();
295	int val;
296
297	if (static_key_dec_not_one(key))
298		return;
299
300	guard(mutex)(&jump_label_mutex);
301	val = atomic_read(&key->enabled);
302	/*
303	 * It should be impossible to observe -1 with jump_label_mutex held,
304	 * see static_key_slow_inc_cpuslocked().
305	 */
306	if (WARN_ON_ONCE(val == -1))
307		return;
308	/*
309	 * Cannot already be 0, something went sideways.
310	 */
311	if (WARN_ON_ONCE(val == 0))
312		return;
313
314	if (atomic_dec_and_test(&key->enabled))
315		jump_label_update(key);
316}
317
318static void __static_key_slow_dec(struct static_key *key)
319{
320	cpus_read_lock();
321	__static_key_slow_dec_cpuslocked(key);
322	cpus_read_unlock();
323}
324
325void jump_label_update_timeout(struct work_struct *work)
326{
327	struct static_key_deferred *key =
328		container_of(work, struct static_key_deferred, work.work);
329	__static_key_slow_dec(&key->key);
330}
331EXPORT_SYMBOL_GPL(jump_label_update_timeout);
332
333void static_key_slow_dec(struct static_key *key)
334{
335	STATIC_KEY_CHECK_USE(key);
336	__static_key_slow_dec(key);
337}
338EXPORT_SYMBOL_GPL(static_key_slow_dec);
339
340void static_key_slow_dec_cpuslocked(struct static_key *key)
341{
342	STATIC_KEY_CHECK_USE(key);
343	__static_key_slow_dec_cpuslocked(key);
344}
345
346void __static_key_slow_dec_deferred(struct static_key *key,
347				    struct delayed_work *work,
348				    unsigned long timeout)
349{
350	STATIC_KEY_CHECK_USE(key);
351
352	if (static_key_dec_not_one(key))
353		return;
354
355	schedule_delayed_work(work, timeout);
356}
357EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
358
359void __static_key_deferred_flush(void *key, struct delayed_work *work)
360{
361	STATIC_KEY_CHECK_USE(key);
362	flush_delayed_work(work);
363}
364EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
365
366void jump_label_rate_limit(struct static_key_deferred *key,
367		unsigned long rl)
368{
369	STATIC_KEY_CHECK_USE(key);
370	key->timeout = rl;
371	INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
372}
373EXPORT_SYMBOL_GPL(jump_label_rate_limit);
374
375static int addr_conflict(struct jump_entry *entry, void *start, void *end)
376{
377	if (jump_entry_code(entry) <= (unsigned long)end &&
378	    jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
379		return 1;
380
381	return 0;
382}
383
384static int __jump_label_text_reserved(struct jump_entry *iter_start,
385		struct jump_entry *iter_stop, void *start, void *end, bool init)
386{
387	struct jump_entry *iter;
388
389	iter = iter_start;
390	while (iter < iter_stop) {
391		if (init || !jump_entry_is_init(iter)) {
392			if (addr_conflict(iter, start, end))
393				return 1;
394		}
395		iter++;
396	}
397
398	return 0;
399}
400
401#ifndef arch_jump_label_transform_static
402static void arch_jump_label_transform_static(struct jump_entry *entry,
403					     enum jump_label_type type)
404{
405	/* nothing to do on most architectures */
406}
407#endif
408
409static inline struct jump_entry *static_key_entries(struct static_key *key)
410{
411	WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
412	return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
413}
414
415static inline bool static_key_type(struct static_key *key)
416{
417	return key->type & JUMP_TYPE_TRUE;
418}
419
420static inline bool static_key_linked(struct static_key *key)
421{
422	return key->type & JUMP_TYPE_LINKED;
423}
424
425static inline void static_key_clear_linked(struct static_key *key)
426{
427	key->type &= ~JUMP_TYPE_LINKED;
428}
429
430static inline void static_key_set_linked(struct static_key *key)
431{
432	key->type |= JUMP_TYPE_LINKED;
433}
434
435/***
436 * A 'struct static_key' uses a union such that it either points directly
437 * to a table of 'struct jump_entry' or to a linked list of modules which in
438 * turn point to 'struct jump_entry' tables.
439 *
440 * The two lower bits of the pointer are used to keep track of which pointer
441 * type is in use and to store the initial branch direction, we use an access
442 * function which preserves these bits.
443 */
444static void static_key_set_entries(struct static_key *key,
445				   struct jump_entry *entries)
446{
447	unsigned long type;
448
449	WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
450	type = key->type & JUMP_TYPE_MASK;
451	key->entries = entries;
452	key->type |= type;
453}
454
455static enum jump_label_type jump_label_type(struct jump_entry *entry)
456{
457	struct static_key *key = jump_entry_key(entry);
458	bool enabled = static_key_enabled(key);
459	bool branch = jump_entry_is_branch(entry);
460
461	/* See the comment in linux/jump_label.h */
462	return enabled ^ branch;
463}
464
465static bool jump_label_can_update(struct jump_entry *entry, bool init)
466{
467	/*
468	 * Cannot update code that was in an init text area.
469	 */
470	if (!init && jump_entry_is_init(entry))
471		return false;
472
473	if (!kernel_text_address(jump_entry_code(entry))) {
474		/*
475		 * This skips patching built-in __exit, which
476		 * is part of init_section_contains() but is
477		 * not part of kernel_text_address().
478		 *
479		 * Skipping built-in __exit is fine since it
480		 * will never be executed.
481		 */
482		WARN_ONCE(!jump_entry_is_init(entry),
483			  "can't patch jump_label at %pS",
484			  (void *)jump_entry_code(entry));
485		return false;
486	}
487
488	return true;
489}
490
491#ifndef HAVE_JUMP_LABEL_BATCH
492static void __jump_label_update(struct static_key *key,
493				struct jump_entry *entry,
494				struct jump_entry *stop,
495				bool init)
496{
497	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
498		if (jump_label_can_update(entry, init))
499			arch_jump_label_transform(entry, jump_label_type(entry));
500	}
501}
502#else
503static void __jump_label_update(struct static_key *key,
504				struct jump_entry *entry,
505				struct jump_entry *stop,
506				bool init)
507{
508	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
509
510		if (!jump_label_can_update(entry, init))
511			continue;
512
513		if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
514			/*
515			 * Queue is full: Apply the current queue and try again.
516			 */
517			arch_jump_label_transform_apply();
518			BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
519		}
520	}
521	arch_jump_label_transform_apply();
522}
523#endif
524
525void __init jump_label_init(void)
526{
527	struct jump_entry *iter_start = __start___jump_table;
528	struct jump_entry *iter_stop = __stop___jump_table;
529	struct static_key *key = NULL;
530	struct jump_entry *iter;
531
532	/*
533	 * Since we are initializing the static_key.enabled field with
534	 * with the 'raw' int values (to avoid pulling in atomic.h) in
535	 * jump_label.h, let's make sure that is safe. There are only two
536	 * cases to check since we initialize to 0 or 1.
537	 */
538	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
539	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
540
541	if (static_key_initialized)
542		return;
543
544	cpus_read_lock();
545	jump_label_lock();
546	jump_label_sort_entries(iter_start, iter_stop);
547
548	for (iter = iter_start; iter < iter_stop; iter++) {
549		struct static_key *iterk;
550		bool in_init;
551
552		/* rewrite NOPs */
553		if (jump_label_type(iter) == JUMP_LABEL_NOP)
554			arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
555
556		in_init = init_section_contains((void *)jump_entry_code(iter), 1);
557		jump_entry_set_init(iter, in_init);
558
559		iterk = jump_entry_key(iter);
560		if (iterk == key)
561			continue;
562
563		key = iterk;
564		static_key_set_entries(key, iter);
565	}
566	static_key_initialized = true;
567	jump_label_unlock();
568	cpus_read_unlock();
569}
570
571static inline bool static_key_sealed(struct static_key *key)
572{
573	return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK);
574}
575
576static inline void static_key_seal(struct static_key *key)
577{
578	unsigned long type = key->type & JUMP_TYPE_TRUE;
579	key->type = JUMP_TYPE_LINKED | type;
580}
581
582void jump_label_init_ro(void)
583{
584	struct jump_entry *iter_start = __start___jump_table;
585	struct jump_entry *iter_stop = __stop___jump_table;
586	struct jump_entry *iter;
587
588	if (WARN_ON_ONCE(!static_key_initialized))
589		return;
590
591	cpus_read_lock();
592	jump_label_lock();
593
594	for (iter = iter_start; iter < iter_stop; iter++) {
595		struct static_key *iterk = jump_entry_key(iter);
596
597		if (!is_kernel_ro_after_init((unsigned long)iterk))
598			continue;
599
600		if (static_key_sealed(iterk))
601			continue;
602
603		static_key_seal(iterk);
604	}
605
606	jump_label_unlock();
607	cpus_read_unlock();
608}
609
610#ifdef CONFIG_MODULES
611
612enum jump_label_type jump_label_init_type(struct jump_entry *entry)
613{
614	struct static_key *key = jump_entry_key(entry);
615	bool type = static_key_type(key);
616	bool branch = jump_entry_is_branch(entry);
617
618	/* See the comment in linux/jump_label.h */
619	return type ^ branch;
620}
621
622struct static_key_mod {
623	struct static_key_mod *next;
624	struct jump_entry *entries;
625	struct module *mod;
626};
627
628static inline struct static_key_mod *static_key_mod(struct static_key *key)
629{
630	WARN_ON_ONCE(!static_key_linked(key));
631	return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
632}
633
634/***
635 * key->type and key->next are the same via union.
636 * This sets key->next and preserves the type bits.
637 *
638 * See additional comments above static_key_set_entries().
639 */
640static void static_key_set_mod(struct static_key *key,
641			       struct static_key_mod *mod)
642{
643	unsigned long type;
644
645	WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
646	type = key->type & JUMP_TYPE_MASK;
647	key->next = mod;
648	key->type |= type;
649}
650
651static int __jump_label_mod_text_reserved(void *start, void *end)
652{
653	struct module *mod;
654	int ret;
655
656	scoped_guard(rcu) {
657		mod = __module_text_address((unsigned long)start);
658		WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
659		if (!try_module_get(mod))
660			mod = NULL;
661	}
662	if (!mod)
663		return 0;
664
665	ret = __jump_label_text_reserved(mod->jump_entries,
666				mod->jump_entries + mod->num_jump_entries,
667				start, end, mod->state == MODULE_STATE_COMING);
668
669	module_put(mod);
670
671	return ret;
672}
673
674static void __jump_label_mod_update(struct static_key *key)
675{
676	struct static_key_mod *mod;
677
678	for (mod = static_key_mod(key); mod; mod = mod->next) {
679		struct jump_entry *stop;
680		struct module *m;
681
682		/*
683		 * NULL if the static_key is defined in a module
684		 * that does not use it
685		 */
686		if (!mod->entries)
687			continue;
688
689		m = mod->mod;
690		if (!m)
691			stop = __stop___jump_table;
692		else
693			stop = m->jump_entries + m->num_jump_entries;
694		__jump_label_update(key, mod->entries, stop,
695				    m && m->state == MODULE_STATE_COMING);
696	}
697}
698
699static int jump_label_add_module(struct module *mod)
700{
701	struct jump_entry *iter_start = mod->jump_entries;
702	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
703	struct jump_entry *iter;
704	struct static_key *key = NULL;
705	struct static_key_mod *jlm, *jlm2;
706
707	/* if the module doesn't have jump label entries, just return */
708	if (iter_start == iter_stop)
709		return 0;
710
711	jump_label_sort_entries(iter_start, iter_stop);
712
713	for (iter = iter_start; iter < iter_stop; iter++) {
714		struct static_key *iterk;
715		bool in_init;
716
717		in_init = within_module_init(jump_entry_code(iter), mod);
718		jump_entry_set_init(iter, in_init);
719
720		iterk = jump_entry_key(iter);
721		if (iterk == key)
722			continue;
723
724		key = iterk;
725		if (within_module((unsigned long)key, mod)) {
726			static_key_set_entries(key, iter);
727			continue;
728		}
729
730		/*
731		 * If the key was sealed at init, then there's no need to keep a
732		 * reference to its module entries - just patch them now and be
733		 * done with it.
734		 */
735		if (static_key_sealed(key))
736			goto do_poke;
737
738		jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
739		if (!jlm)
740			return -ENOMEM;
741		if (!static_key_linked(key)) {
742			jlm2 = kzalloc(sizeof(struct static_key_mod),
743				       GFP_KERNEL);
744			if (!jlm2) {
745				kfree(jlm);
746				return -ENOMEM;
747			}
748			scoped_guard(rcu)
749				jlm2->mod = __module_address((unsigned long)key);
750
751			jlm2->entries = static_key_entries(key);
752			jlm2->next = NULL;
753			static_key_set_mod(key, jlm2);
754			static_key_set_linked(key);
755		}
756		jlm->mod = mod;
757		jlm->entries = iter;
758		jlm->next = static_key_mod(key);
759		static_key_set_mod(key, jlm);
760		static_key_set_linked(key);
761
762		/* Only update if we've changed from our initial state */
763do_poke:
764		if (jump_label_type(iter) != jump_label_init_type(iter))
765			__jump_label_update(key, iter, iter_stop, true);
766	}
767
768	return 0;
769}
770
771static void jump_label_del_module(struct module *mod)
772{
773	struct jump_entry *iter_start = mod->jump_entries;
774	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
775	struct jump_entry *iter;
776	struct static_key *key = NULL;
777	struct static_key_mod *jlm, **prev;
778
779	for (iter = iter_start; iter < iter_stop; iter++) {
780		if (jump_entry_key(iter) == key)
781			continue;
782
783		key = jump_entry_key(iter);
784
785		if (within_module((unsigned long)key, mod))
786			continue;
787
788		/* No @jlm allocated because key was sealed at init. */
789		if (static_key_sealed(key))
790			continue;
791
792		/* No memory during module load */
793		if (WARN_ON(!static_key_linked(key)))
794			continue;
795
796		prev = &key->next;
797		jlm = static_key_mod(key);
798
799		while (jlm && jlm->mod != mod) {
800			prev = &jlm->next;
801			jlm = jlm->next;
802		}
803
804		/* No memory during module load */
805		if (WARN_ON(!jlm))
806			continue;
807
808		if (prev == &key->next)
809			static_key_set_mod(key, jlm->next);
810		else
811			*prev = jlm->next;
812
813		kfree(jlm);
814
815		jlm = static_key_mod(key);
816		/* if only one etry is left, fold it back into the static_key */
817		if (jlm->next == NULL) {
818			static_key_set_entries(key, jlm->entries);
819			static_key_clear_linked(key);
820			kfree(jlm);
821		}
822	}
823}
824
825static int
826jump_label_module_notify(struct notifier_block *self, unsigned long val,
827			 void *data)
828{
829	struct module *mod = data;
830	int ret = 0;
831
832	cpus_read_lock();
833	jump_label_lock();
834
835	switch (val) {
836	case MODULE_STATE_COMING:
837		ret = jump_label_add_module(mod);
838		if (ret) {
839			WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
840			jump_label_del_module(mod);
841		}
842		break;
843	case MODULE_STATE_GOING:
844		jump_label_del_module(mod);
845		break;
846	}
847
848	jump_label_unlock();
849	cpus_read_unlock();
850
851	return notifier_from_errno(ret);
852}
853
854static struct notifier_block jump_label_module_nb = {
855	.notifier_call = jump_label_module_notify,
856	.priority = 1, /* higher than tracepoints */
857};
858
859static __init int jump_label_init_module(void)
860{
861	return register_module_notifier(&jump_label_module_nb);
862}
863early_initcall(jump_label_init_module);
864
865#endif /* CONFIG_MODULES */
866
867/***
868 * jump_label_text_reserved - check if addr range is reserved
869 * @start: start text addr
870 * @end: end text addr
871 *
872 * checks if the text addr located between @start and @end
873 * overlaps with any of the jump label patch addresses. Code
874 * that wants to modify kernel text should first verify that
875 * it does not overlap with any of the jump label addresses.
876 * Caller must hold jump_label_mutex.
877 *
878 * returns 1 if there is an overlap, 0 otherwise
879 */
880int jump_label_text_reserved(void *start, void *end)
881{
882	bool init = system_state < SYSTEM_RUNNING;
883	int ret = __jump_label_text_reserved(__start___jump_table,
884			__stop___jump_table, start, end, init);
885
886	if (ret)
887		return ret;
888
889#ifdef CONFIG_MODULES
890	ret = __jump_label_mod_text_reserved(start, end);
891#endif
892	return ret;
893}
894
895static void jump_label_update(struct static_key *key)
896{
897	struct jump_entry *stop = __stop___jump_table;
898	bool init = system_state < SYSTEM_RUNNING;
899	struct jump_entry *entry;
900#ifdef CONFIG_MODULES
901	struct module *mod;
902
903	if (static_key_linked(key)) {
904		__jump_label_mod_update(key);
905		return;
906	}
907
908	scoped_guard(rcu) {
909		mod = __module_address((unsigned long)key);
910		if (mod) {
911			stop = mod->jump_entries + mod->num_jump_entries;
912			init = mod->state == MODULE_STATE_COMING;
913		}
914	}
915#endif
916	entry = static_key_entries(key);
917	/* if there are no users, entry can be NULL */
918	if (entry)
919		__jump_label_update(key, entry, stop, init);
920}
921
922#ifdef CONFIG_STATIC_KEYS_SELFTEST
923static DEFINE_STATIC_KEY_TRUE(sk_true);
924static DEFINE_STATIC_KEY_FALSE(sk_false);
925
926static __init int jump_label_test(void)
927{
928	int i;
929
930	for (i = 0; i < 2; i++) {
931		WARN_ON(static_key_enabled(&sk_true.key) != true);
932		WARN_ON(static_key_enabled(&sk_false.key) != false);
933
934		WARN_ON(!static_branch_likely(&sk_true));
935		WARN_ON(!static_branch_unlikely(&sk_true));
936		WARN_ON(static_branch_likely(&sk_false));
937		WARN_ON(static_branch_unlikely(&sk_false));
938
939		static_branch_disable(&sk_true);
940		static_branch_enable(&sk_false);
941
942		WARN_ON(static_key_enabled(&sk_true.key) == true);
943		WARN_ON(static_key_enabled(&sk_false.key) == false);
944
945		WARN_ON(static_branch_likely(&sk_true));
946		WARN_ON(static_branch_unlikely(&sk_true));
947		WARN_ON(!static_branch_likely(&sk_false));
948		WARN_ON(!static_branch_unlikely(&sk_false));
949
950		static_branch_enable(&sk_true);
951		static_branch_disable(&sk_false);
952	}
953
954	return 0;
955}
956early_initcall(jump_label_test);
957#endif /* STATIC_KEYS_SELFTEST */