1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6 * Copyright (C) 2011 Peter Zijlstra
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>
22 /* mutex to protect coming/going of the jump_label table */
23 static DEFINE_MUTEX(jump_label_mutex
);
25 void jump_label_lock(void)
27 mutex_lock(&jump_label_mutex
);
30 void jump_label_unlock(void)
32 mutex_unlock(&jump_label_mutex
);
35 static int jump_label_cmp(const void *a
, const void *b
)
37 const struct jump_entry
*jea
= a
;
38 const struct jump_entry
*jeb
= b
;
41 * Entrires are sorted by key.
43 if (jump_entry_key(jea
) < jump_entry_key(jeb
))
46 if (jump_entry_key(jea
) > jump_entry_key(jeb
))
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
54 if (jump_entry_code(jea
) < jump_entry_code(jeb
))
57 if (jump_entry_code(jea
) > jump_entry_code(jeb
))
63 static void jump_label_swap(void *a
, void *b
, int size
)
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
;
70 jea
->code
= jeb
->code
- delta
;
71 jea
->target
= jeb
->target
- delta
;
72 jea
->key
= jeb
->key
- delta
;
74 jeb
->code
= tmp
.code
+ delta
;
75 jeb
->target
= tmp
.target
+ delta
;
76 jeb
->key
= tmp
.key
+ delta
;
80 jump_label_sort_entries(struct jump_entry
*start
, struct jump_entry
*stop
)
85 if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE
))
86 swapfn
= jump_label_swap
;
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
);
93 static void jump_label_update(struct static_key
*key
);
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.
104 int static_key_count(struct static_key
*key
)
107 * -1 means the first static_key_slow_inc() is in progress.
108 * static_key_enabled() must return true, so return 1 here.
110 int n
= atomic_read(&key
->enabled
);
112 return n
>= 0 ? n
: 1;
114 EXPORT_SYMBOL_GPL(static_key_count
);
117 * static_key_fast_inc_not_disabled - adds a user for a static key
118 * @key: static key that must be already enabled
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.
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.
127 bool static_key_fast_inc_not_disabled(struct static_key
*key
)
131 STATIC_KEY_CHECK_USE(key
);
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.
138 v
= atomic_read(&key
->enabled
);
140 if (v
<= 0 || (v
+ 1) < 0)
142 } while (!likely(atomic_try_cmpxchg(&key
->enabled
, &v
, v
+ 1)));
146 EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled
);
148 bool static_key_slow_inc_cpuslocked(struct static_key
*key
)
150 lockdep_assert_cpus_held();
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.
159 if (static_key_fast_inc_not_disabled(key
))
163 if (atomic_read(&key
->enabled
) == 0) {
164 atomic_set(&key
->enabled
, -1);
165 jump_label_update(key
);
167 * Ensure that if the above cmpxchg loop observes our positive
168 * value, it must also observe all the text changes.
170 atomic_set_release(&key
->enabled
, 1);
172 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key
))) {
181 bool static_key_slow_inc(struct static_key
*key
)
186 ret
= static_key_slow_inc_cpuslocked(key
);
190 EXPORT_SYMBOL_GPL(static_key_slow_inc
);
192 void static_key_enable_cpuslocked(struct static_key
*key
)
194 STATIC_KEY_CHECK_USE(key
);
195 lockdep_assert_cpus_held();
197 if (atomic_read(&key
->enabled
) > 0) {
198 WARN_ON_ONCE(atomic_read(&key
->enabled
) != 1);
203 if (atomic_read(&key
->enabled
) == 0) {
204 atomic_set(&key
->enabled
, -1);
205 jump_label_update(key
);
207 * See static_key_slow_inc().
209 atomic_set_release(&key
->enabled
, 1);
213 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked
);
215 void static_key_enable(struct static_key
*key
)
218 static_key_enable_cpuslocked(key
);
221 EXPORT_SYMBOL_GPL(static_key_enable
);
223 void static_key_disable_cpuslocked(struct static_key
*key
)
225 STATIC_KEY_CHECK_USE(key
);
226 lockdep_assert_cpus_held();
228 if (atomic_read(&key
->enabled
) != 1) {
229 WARN_ON_ONCE(atomic_read(&key
->enabled
) != 0);
234 if (atomic_cmpxchg(&key
->enabled
, 1, 0))
235 jump_label_update(key
);
238 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked
);
240 void static_key_disable(struct static_key
*key
)
243 static_key_disable_cpuslocked(key
);
246 EXPORT_SYMBOL_GPL(static_key_disable
);
248 static bool static_key_slow_try_dec(struct static_key
*key
)
252 val
= atomic_fetch_add_unless(&key
->enabled
, -1, 1);
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.
263 WARN(val
< 0, "jump label: negative count!\n");
267 static void __static_key_slow_dec_cpuslocked(struct static_key
*key
)
269 lockdep_assert_cpus_held();
271 if (static_key_slow_try_dec(key
))
275 if (atomic_dec_and_test(&key
->enabled
))
276 jump_label_update(key
);
280 static void __static_key_slow_dec(struct static_key
*key
)
283 __static_key_slow_dec_cpuslocked(key
);
287 void jump_label_update_timeout(struct work_struct
*work
)
289 struct static_key_deferred
*key
=
290 container_of(work
, struct static_key_deferred
, work
.work
);
291 __static_key_slow_dec(&key
->key
);
293 EXPORT_SYMBOL_GPL(jump_label_update_timeout
);
295 void static_key_slow_dec(struct static_key
*key
)
297 STATIC_KEY_CHECK_USE(key
);
298 __static_key_slow_dec(key
);
300 EXPORT_SYMBOL_GPL(static_key_slow_dec
);
302 void static_key_slow_dec_cpuslocked(struct static_key
*key
)
304 STATIC_KEY_CHECK_USE(key
);
305 __static_key_slow_dec_cpuslocked(key
);
308 void __static_key_slow_dec_deferred(struct static_key
*key
,
309 struct delayed_work
*work
,
310 unsigned long timeout
)
312 STATIC_KEY_CHECK_USE(key
);
314 if (static_key_slow_try_dec(key
))
317 schedule_delayed_work(work
, timeout
);
319 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred
);
321 void __static_key_deferred_flush(void *key
, struct delayed_work
*work
)
323 STATIC_KEY_CHECK_USE(key
);
324 flush_delayed_work(work
);
326 EXPORT_SYMBOL_GPL(__static_key_deferred_flush
);
328 void jump_label_rate_limit(struct static_key_deferred
*key
,
331 STATIC_KEY_CHECK_USE(key
);
333 INIT_DELAYED_WORK(&key
->work
, jump_label_update_timeout
);
335 EXPORT_SYMBOL_GPL(jump_label_rate_limit
);
337 static int addr_conflict(struct jump_entry
*entry
, void *start
, void *end
)
339 if (jump_entry_code(entry
) <= (unsigned long)end
&&
340 jump_entry_code(entry
) + jump_entry_size(entry
) > (unsigned long)start
)
346 static int __jump_label_text_reserved(struct jump_entry
*iter_start
,
347 struct jump_entry
*iter_stop
, void *start
, void *end
, bool init
)
349 struct jump_entry
*iter
;
352 while (iter
< iter_stop
) {
353 if (init
|| !jump_entry_is_init(iter
)) {
354 if (addr_conflict(iter
, start
, end
))
363 #ifndef arch_jump_label_transform_static
364 static void arch_jump_label_transform_static(struct jump_entry
*entry
,
365 enum jump_label_type type
)
367 /* nothing to do on most architectures */
371 static inline struct jump_entry
*static_key_entries(struct static_key
*key
)
373 WARN_ON_ONCE(key
->type
& JUMP_TYPE_LINKED
);
374 return (struct jump_entry
*)(key
->type
& ~JUMP_TYPE_MASK
);
377 static inline bool static_key_type(struct static_key
*key
)
379 return key
->type
& JUMP_TYPE_TRUE
;
382 static inline bool static_key_linked(struct static_key
*key
)
384 return key
->type
& JUMP_TYPE_LINKED
;
387 static inline void static_key_clear_linked(struct static_key
*key
)
389 key
->type
&= ~JUMP_TYPE_LINKED
;
392 static inline void static_key_set_linked(struct static_key
*key
)
394 key
->type
|= JUMP_TYPE_LINKED
;
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.
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.
406 static void static_key_set_entries(struct static_key
*key
,
407 struct jump_entry
*entries
)
411 WARN_ON_ONCE((unsigned long)entries
& JUMP_TYPE_MASK
);
412 type
= key
->type
& JUMP_TYPE_MASK
;
413 key
->entries
= entries
;
417 static enum jump_label_type
jump_label_type(struct jump_entry
*entry
)
419 struct static_key
*key
= jump_entry_key(entry
);
420 bool enabled
= static_key_enabled(key
);
421 bool branch
= jump_entry_is_branch(entry
);
423 /* See the comment in linux/jump_label.h */
424 return enabled
^ branch
;
427 static bool jump_label_can_update(struct jump_entry
*entry
, bool init
)
430 * Cannot update code that was in an init text area.
432 if (!init
&& jump_entry_is_init(entry
))
435 if (!kernel_text_address(jump_entry_code(entry
))) {
437 * This skips patching built-in __exit, which
438 * is part of init_section_contains() but is
439 * not part of kernel_text_address().
441 * Skipping built-in __exit is fine since it
442 * will never be executed.
444 WARN_ONCE(!jump_entry_is_init(entry
),
445 "can't patch jump_label at %pS",
446 (void *)jump_entry_code(entry
));
453 #ifndef HAVE_JUMP_LABEL_BATCH
454 static void __jump_label_update(struct static_key
*key
,
455 struct jump_entry
*entry
,
456 struct jump_entry
*stop
,
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
));
465 static void __jump_label_update(struct static_key
*key
,
466 struct jump_entry
*entry
,
467 struct jump_entry
*stop
,
470 for (; (entry
< stop
) && (jump_entry_key(entry
) == key
); entry
++) {
472 if (!jump_label_can_update(entry
, init
))
475 if (!arch_jump_label_transform_queue(entry
, jump_label_type(entry
))) {
477 * Queue is full: Apply the current queue and try again.
479 arch_jump_label_transform_apply();
480 BUG_ON(!arch_jump_label_transform_queue(entry
, jump_label_type(entry
)));
483 arch_jump_label_transform_apply();
487 void __init
jump_label_init(void)
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
;
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.
500 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
501 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
503 if (static_key_initialized
)
508 jump_label_sort_entries(iter_start
, iter_stop
);
510 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
511 struct static_key
*iterk
;
515 if (jump_label_type(iter
) == JUMP_LABEL_NOP
)
516 arch_jump_label_transform_static(iter
, JUMP_LABEL_NOP
);
518 in_init
= init_section_contains((void *)jump_entry_code(iter
), 1);
519 jump_entry_set_init(iter
, in_init
);
521 iterk
= jump_entry_key(iter
);
526 static_key_set_entries(key
, iter
);
528 static_key_initialized
= true;
533 #ifdef CONFIG_MODULES
535 enum jump_label_type
jump_label_init_type(struct jump_entry
*entry
)
537 struct static_key
*key
= jump_entry_key(entry
);
538 bool type
= static_key_type(key
);
539 bool branch
= jump_entry_is_branch(entry
);
541 /* See the comment in linux/jump_label.h */
542 return type
^ branch
;
545 struct static_key_mod
{
546 struct static_key_mod
*next
;
547 struct jump_entry
*entries
;
551 static inline struct static_key_mod
*static_key_mod(struct static_key
*key
)
553 WARN_ON_ONCE(!static_key_linked(key
));
554 return (struct static_key_mod
*)(key
->type
& ~JUMP_TYPE_MASK
);
558 * key->type and key->next are the same via union.
559 * This sets key->next and preserves the type bits.
561 * See additional comments above static_key_set_entries().
563 static void static_key_set_mod(struct static_key
*key
,
564 struct static_key_mod
*mod
)
568 WARN_ON_ONCE((unsigned long)mod
& JUMP_TYPE_MASK
);
569 type
= key
->type
& JUMP_TYPE_MASK
;
574 static int __jump_label_mod_text_reserved(void *start
, void *end
)
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
))
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
);
598 static void __jump_label_mod_update(struct static_key
*key
)
600 struct static_key_mod
*mod
;
602 for (mod
= static_key_mod(key
); mod
; mod
= mod
->next
) {
603 struct jump_entry
*stop
;
607 * NULL if the static_key is defined in a module
608 * that does not use it
615 stop
= __stop___jump_table
;
617 stop
= m
->jump_entries
+ m
->num_jump_entries
;
618 __jump_label_update(key
, mod
->entries
, stop
,
619 m
&& m
->state
== MODULE_STATE_COMING
);
623 static int jump_label_add_module(struct module
*mod
)
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
;
631 /* if the module doesn't have jump label entries, just return */
632 if (iter_start
== iter_stop
)
635 jump_label_sort_entries(iter_start
, iter_stop
);
637 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
638 struct static_key
*iterk
;
641 in_init
= within_module_init(jump_entry_code(iter
), mod
);
642 jump_entry_set_init(iter
, in_init
);
644 iterk
= jump_entry_key(iter
);
649 if (within_module((unsigned long)key
, mod
)) {
650 static_key_set_entries(key
, iter
);
653 jlm
= kzalloc(sizeof(struct static_key_mod
), GFP_KERNEL
);
656 if (!static_key_linked(key
)) {
657 jlm2
= kzalloc(sizeof(struct static_key_mod
),
664 jlm2
->mod
= __module_address((unsigned long)key
);
666 jlm2
->entries
= static_key_entries(key
);
668 static_key_set_mod(key
, jlm2
);
669 static_key_set_linked(key
);
673 jlm
->next
= static_key_mod(key
);
674 static_key_set_mod(key
, jlm
);
675 static_key_set_linked(key
);
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);
685 static void jump_label_del_module(struct module
*mod
)
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
;
693 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
694 if (jump_entry_key(iter
) == key
)
697 key
= jump_entry_key(iter
);
699 if (within_module((unsigned long)key
, mod
))
702 /* No memory during module load */
703 if (WARN_ON(!static_key_linked(key
)))
707 jlm
= static_key_mod(key
);
709 while (jlm
&& jlm
->mod
!= mod
) {
714 /* No memory during module load */
718 if (prev
== &key
->next
)
719 static_key_set_mod(key
, jlm
->next
);
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
);
736 jump_label_module_notify(struct notifier_block
*self
, unsigned long val
,
739 struct module
*mod
= data
;
746 case MODULE_STATE_COMING
:
747 ret
= jump_label_add_module(mod
);
749 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
750 jump_label_del_module(mod
);
753 case MODULE_STATE_GOING
:
754 jump_label_del_module(mod
);
761 return notifier_from_errno(ret
);
764 static struct notifier_block jump_label_module_nb
= {
765 .notifier_call
= jump_label_module_notify
,
766 .priority
= 1, /* higher than tracepoints */
769 static __init
int jump_label_init_module(void)
771 return register_module_notifier(&jump_label_module_nb
);
773 early_initcall(jump_label_init_module
);
775 #endif /* CONFIG_MODULES */
778 * jump_label_text_reserved - check if addr range is reserved
779 * @start: start text addr
780 * @end: end text addr
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.
788 * returns 1 if there is an overlap, 0 otherwise
790 int jump_label_text_reserved(void *start
, void *end
)
792 bool init
= system_state
< SYSTEM_RUNNING
;
793 int ret
= __jump_label_text_reserved(__start___jump_table
,
794 __stop___jump_table
, start
, end
, init
);
799 #ifdef CONFIG_MODULES
800 ret
= __jump_label_mod_text_reserved(start
, end
);
805 static void jump_label_update(struct static_key
*key
)
807 struct jump_entry
*stop
= __stop___jump_table
;
808 bool init
= system_state
< SYSTEM_RUNNING
;
809 struct jump_entry
*entry
;
810 #ifdef CONFIG_MODULES
813 if (static_key_linked(key
)) {
814 __jump_label_mod_update(key
);
819 mod
= __module_address((unsigned long)key
);
821 stop
= mod
->jump_entries
+ mod
->num_jump_entries
;
822 init
= mod
->state
== MODULE_STATE_COMING
;
826 entry
= static_key_entries(key
);
827 /* if there are no users, entry can be NULL */
829 __jump_label_update(key
, entry
, stop
, init
);
832 #ifdef CONFIG_STATIC_KEYS_SELFTEST
833 static DEFINE_STATIC_KEY_TRUE(sk_true
);
834 static DEFINE_STATIC_KEY_FALSE(sk_false
);
836 static __init
int jump_label_test(void)
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);
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
));
849 static_branch_disable(&sk_true
);
850 static_branch_enable(&sk_false
);
852 WARN_ON(static_key_enabled(&sk_true
.key
) == true);
853 WARN_ON(static_key_enabled(&sk_false
.key
) == false);
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
));
860 static_branch_enable(&sk_true
);
861 static_branch_disable(&sk_false
);
866 early_initcall(jump_label_test
);
867 #endif /* STATIC_KEYS_SELFTEST */