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