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