4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 * Copyright (C) 2011 Peter Zijlstra
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>
21 /* mutex to protect coming/going of the the jump_label table */
22 static DEFINE_MUTEX(jump_label_mutex
);
24 void jump_label_lock(void)
26 mutex_lock(&jump_label_mutex
);
29 void jump_label_unlock(void)
31 mutex_unlock(&jump_label_mutex
);
34 static int jump_label_cmp(const void *a
, const void *b
)
36 const struct jump_entry
*jea
= a
;
37 const struct jump_entry
*jeb
= b
;
39 if (jump_entry_key(jea
) < jump_entry_key(jeb
))
42 if (jump_entry_key(jea
) > jump_entry_key(jeb
))
48 static void jump_label_swap(void *a
, void *b
, int size
)
50 long delta
= (unsigned long)a
- (unsigned long)b
;
51 struct jump_entry
*jea
= a
;
52 struct jump_entry
*jeb
= b
;
53 struct jump_entry tmp
= *jea
;
55 jea
->code
= jeb
->code
- delta
;
56 jea
->target
= jeb
->target
- delta
;
57 jea
->key
= jeb
->key
- delta
;
59 jeb
->code
= tmp
.code
+ delta
;
60 jeb
->target
= tmp
.target
+ delta
;
61 jeb
->key
= tmp
.key
+ delta
;
65 jump_label_sort_entries(struct jump_entry
*start
, struct jump_entry
*stop
)
70 if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE
))
71 swapfn
= jump_label_swap
;
73 size
= (((unsigned long)stop
- (unsigned long)start
)
74 / sizeof(struct jump_entry
));
75 sort(start
, size
, sizeof(struct jump_entry
), jump_label_cmp
, swapfn
);
78 static void jump_label_update(struct static_key
*key
);
81 * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
82 * The use of 'atomic_read()' requires atomic.h and its problematic for some
83 * kernel headers such as kernel.h and others. Since static_key_count() is not
84 * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
85 * to have it be a function here. Similarly, for 'static_key_enable()' and
86 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
87 * to be included from most/all places for CONFIG_JUMP_LABEL.
89 int static_key_count(struct static_key
*key
)
92 * -1 means the first static_key_slow_inc() is in progress.
93 * static_key_enabled() must return true, so return 1 here.
95 int n
= atomic_read(&key
->enabled
);
97 return n
>= 0 ? n
: 1;
99 EXPORT_SYMBOL_GPL(static_key_count
);
101 void static_key_slow_inc_cpuslocked(struct static_key
*key
)
105 STATIC_KEY_CHECK_USE(key
);
106 lockdep_assert_cpus_held();
109 * Careful if we get concurrent static_key_slow_inc() calls;
110 * later calls must wait for the first one to _finish_ the
111 * jump_label_update() process. At the same time, however,
112 * the jump_label_update() call below wants to see
113 * static_key_enabled(&key) for jumps to be updated properly.
115 * So give a special meaning to negative key->enabled: it sends
116 * static_key_slow_inc() down the slow path, and it is non-zero
117 * so it counts as "enabled" in jump_label_update(). Note that
118 * atomic_inc_unless_negative() checks >= 0, so roll our own.
120 for (v
= atomic_read(&key
->enabled
); v
> 0; v
= v1
) {
121 v1
= atomic_cmpxchg(&key
->enabled
, v
, v
+ 1);
127 if (atomic_read(&key
->enabled
) == 0) {
128 atomic_set(&key
->enabled
, -1);
129 jump_label_update(key
);
131 * Ensure that if the above cmpxchg loop observes our positive
132 * value, it must also observe all the text changes.
134 atomic_set_release(&key
->enabled
, 1);
136 atomic_inc(&key
->enabled
);
141 void static_key_slow_inc(struct static_key
*key
)
144 static_key_slow_inc_cpuslocked(key
);
147 EXPORT_SYMBOL_GPL(static_key_slow_inc
);
149 void static_key_enable_cpuslocked(struct static_key
*key
)
151 STATIC_KEY_CHECK_USE(key
);
152 lockdep_assert_cpus_held();
154 if (atomic_read(&key
->enabled
) > 0) {
155 WARN_ON_ONCE(atomic_read(&key
->enabled
) != 1);
160 if (atomic_read(&key
->enabled
) == 0) {
161 atomic_set(&key
->enabled
, -1);
162 jump_label_update(key
);
164 * See static_key_slow_inc().
166 atomic_set_release(&key
->enabled
, 1);
170 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked
);
172 void static_key_enable(struct static_key
*key
)
175 static_key_enable_cpuslocked(key
);
178 EXPORT_SYMBOL_GPL(static_key_enable
);
180 void static_key_disable_cpuslocked(struct static_key
*key
)
182 STATIC_KEY_CHECK_USE(key
);
183 lockdep_assert_cpus_held();
185 if (atomic_read(&key
->enabled
) != 1) {
186 WARN_ON_ONCE(atomic_read(&key
->enabled
) != 0);
191 if (atomic_cmpxchg(&key
->enabled
, 1, 0))
192 jump_label_update(key
);
195 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked
);
197 void static_key_disable(struct static_key
*key
)
200 static_key_disable_cpuslocked(key
);
203 EXPORT_SYMBOL_GPL(static_key_disable
);
205 static void __static_key_slow_dec_cpuslocked(struct static_key
*key
,
206 unsigned long rate_limit
,
207 struct delayed_work
*work
)
211 lockdep_assert_cpus_held();
214 * The negative count check is valid even when a negative
215 * key->enabled is in use by static_key_slow_inc(); a
216 * __static_key_slow_dec() before the first static_key_slow_inc()
217 * returns is unbalanced, because all other static_key_slow_inc()
218 * instances block while the update is in progress.
220 val
= atomic_fetch_add_unless(&key
->enabled
, -1, 1);
222 WARN(val
< 0, "jump label: negative count!\n");
227 if (atomic_dec_and_test(&key
->enabled
)) {
229 atomic_inc(&key
->enabled
);
230 schedule_delayed_work(work
, rate_limit
);
232 jump_label_update(key
);
238 static void __static_key_slow_dec(struct static_key
*key
,
239 unsigned long rate_limit
,
240 struct delayed_work
*work
)
243 __static_key_slow_dec_cpuslocked(key
, rate_limit
, work
);
247 static void jump_label_update_timeout(struct work_struct
*work
)
249 struct static_key_deferred
*key
=
250 container_of(work
, struct static_key_deferred
, work
.work
);
251 __static_key_slow_dec(&key
->key
, 0, NULL
);
254 void static_key_slow_dec(struct static_key
*key
)
256 STATIC_KEY_CHECK_USE(key
);
257 __static_key_slow_dec(key
, 0, NULL
);
259 EXPORT_SYMBOL_GPL(static_key_slow_dec
);
261 void static_key_slow_dec_cpuslocked(struct static_key
*key
)
263 STATIC_KEY_CHECK_USE(key
);
264 __static_key_slow_dec_cpuslocked(key
, 0, NULL
);
267 void static_key_slow_dec_deferred(struct static_key_deferred
*key
)
269 STATIC_KEY_CHECK_USE(key
);
270 __static_key_slow_dec(&key
->key
, key
->timeout
, &key
->work
);
272 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred
);
274 void static_key_deferred_flush(struct static_key_deferred
*key
)
276 STATIC_KEY_CHECK_USE(key
);
277 flush_delayed_work(&key
->work
);
279 EXPORT_SYMBOL_GPL(static_key_deferred_flush
);
281 void jump_label_rate_limit(struct static_key_deferred
*key
,
284 STATIC_KEY_CHECK_USE(key
);
286 INIT_DELAYED_WORK(&key
->work
, jump_label_update_timeout
);
288 EXPORT_SYMBOL_GPL(jump_label_rate_limit
);
290 static int addr_conflict(struct jump_entry
*entry
, void *start
, void *end
)
292 if (jump_entry_code(entry
) <= (unsigned long)end
&&
293 jump_entry_code(entry
) + JUMP_LABEL_NOP_SIZE
> (unsigned long)start
)
299 static int __jump_label_text_reserved(struct jump_entry
*iter_start
,
300 struct jump_entry
*iter_stop
, void *start
, void *end
)
302 struct jump_entry
*iter
;
305 while (iter
< iter_stop
) {
306 if (addr_conflict(iter
, start
, end
))
315 * Update code which is definitely not currently executing.
316 * Architectures which need heavyweight synchronization to modify
317 * running code can override this to make the non-live update case
320 void __weak __init_or_module
arch_jump_label_transform_static(struct jump_entry
*entry
,
321 enum jump_label_type type
)
323 arch_jump_label_transform(entry
, type
);
326 static inline struct jump_entry
*static_key_entries(struct static_key
*key
)
328 WARN_ON_ONCE(key
->type
& JUMP_TYPE_LINKED
);
329 return (struct jump_entry
*)(key
->type
& ~JUMP_TYPE_MASK
);
332 static inline bool static_key_type(struct static_key
*key
)
334 return key
->type
& JUMP_TYPE_TRUE
;
337 static inline bool static_key_linked(struct static_key
*key
)
339 return key
->type
& JUMP_TYPE_LINKED
;
342 static inline void static_key_clear_linked(struct static_key
*key
)
344 key
->type
&= ~JUMP_TYPE_LINKED
;
347 static inline void static_key_set_linked(struct static_key
*key
)
349 key
->type
|= JUMP_TYPE_LINKED
;
353 * A 'struct static_key' uses a union such that it either points directly
354 * to a table of 'struct jump_entry' or to a linked list of modules which in
355 * turn point to 'struct jump_entry' tables.
357 * The two lower bits of the pointer are used to keep track of which pointer
358 * type is in use and to store the initial branch direction, we use an access
359 * function which preserves these bits.
361 static void static_key_set_entries(struct static_key
*key
,
362 struct jump_entry
*entries
)
366 WARN_ON_ONCE((unsigned long)entries
& JUMP_TYPE_MASK
);
367 type
= key
->type
& JUMP_TYPE_MASK
;
368 key
->entries
= entries
;
372 static enum jump_label_type
jump_label_type(struct jump_entry
*entry
)
374 struct static_key
*key
= jump_entry_key(entry
);
375 bool enabled
= static_key_enabled(key
);
376 bool branch
= jump_entry_is_branch(entry
);
378 /* See the comment in linux/jump_label.h */
379 return enabled
^ branch
;
382 static void __jump_label_update(struct static_key
*key
,
383 struct jump_entry
*entry
,
384 struct jump_entry
*stop
,
387 for (; (entry
< stop
) && (jump_entry_key(entry
) == key
); entry
++) {
389 * An entry->code of 0 indicates an entry which has been
390 * disabled because it was in an init text area.
392 if (init
|| !jump_entry_is_init(entry
)) {
393 if (kernel_text_address(jump_entry_code(entry
)))
394 arch_jump_label_transform(entry
, jump_label_type(entry
));
396 WARN_ONCE(1, "can't patch jump_label at %pS",
397 (void *)jump_entry_code(entry
));
402 void __init
jump_label_init(void)
404 struct jump_entry
*iter_start
= __start___jump_table
;
405 struct jump_entry
*iter_stop
= __stop___jump_table
;
406 struct static_key
*key
= NULL
;
407 struct jump_entry
*iter
;
410 * Since we are initializing the static_key.enabled field with
411 * with the 'raw' int values (to avoid pulling in atomic.h) in
412 * jump_label.h, let's make sure that is safe. There are only two
413 * cases to check since we initialize to 0 or 1.
415 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
416 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
418 if (static_key_initialized
)
423 jump_label_sort_entries(iter_start
, iter_stop
);
425 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
426 struct static_key
*iterk
;
429 if (jump_label_type(iter
) == JUMP_LABEL_NOP
)
430 arch_jump_label_transform_static(iter
, JUMP_LABEL_NOP
);
432 if (init_section_contains((void *)jump_entry_code(iter
), 1))
433 jump_entry_set_init(iter
);
435 iterk
= jump_entry_key(iter
);
440 static_key_set_entries(key
, iter
);
442 static_key_initialized
= true;
447 #ifdef CONFIG_MODULES
449 static enum jump_label_type
jump_label_init_type(struct jump_entry
*entry
)
451 struct static_key
*key
= jump_entry_key(entry
);
452 bool type
= static_key_type(key
);
453 bool branch
= jump_entry_is_branch(entry
);
455 /* See the comment in linux/jump_label.h */
456 return type
^ branch
;
459 struct static_key_mod
{
460 struct static_key_mod
*next
;
461 struct jump_entry
*entries
;
465 static inline struct static_key_mod
*static_key_mod(struct static_key
*key
)
467 WARN_ON_ONCE(!static_key_linked(key
));
468 return (struct static_key_mod
*)(key
->type
& ~JUMP_TYPE_MASK
);
472 * key->type and key->next are the same via union.
473 * This sets key->next and preserves the type bits.
475 * See additional comments above static_key_set_entries().
477 static void static_key_set_mod(struct static_key
*key
,
478 struct static_key_mod
*mod
)
482 WARN_ON_ONCE((unsigned long)mod
& JUMP_TYPE_MASK
);
483 type
= key
->type
& JUMP_TYPE_MASK
;
488 static int __jump_label_mod_text_reserved(void *start
, void *end
)
493 mod
= __module_text_address((unsigned long)start
);
494 WARN_ON_ONCE(__module_text_address((unsigned long)end
) != mod
);
501 return __jump_label_text_reserved(mod
->jump_entries
,
502 mod
->jump_entries
+ mod
->num_jump_entries
,
506 static void __jump_label_mod_update(struct static_key
*key
)
508 struct static_key_mod
*mod
;
510 for (mod
= static_key_mod(key
); mod
; mod
= mod
->next
) {
511 struct jump_entry
*stop
;
515 * NULL if the static_key is defined in a module
516 * that does not use it
523 stop
= __stop___jump_table
;
525 stop
= m
->jump_entries
+ m
->num_jump_entries
;
526 __jump_label_update(key
, mod
->entries
, stop
,
527 m
&& m
->state
== MODULE_STATE_COMING
);
532 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
533 * @mod: module to patch
535 * Allow for run-time selection of the optimal nops. Before the module
536 * loads patch these with arch_get_jump_label_nop(), which is specified by
537 * the arch specific jump label code.
539 void jump_label_apply_nops(struct module
*mod
)
541 struct jump_entry
*iter_start
= mod
->jump_entries
;
542 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
543 struct jump_entry
*iter
;
545 /* if the module doesn't have jump label entries, just return */
546 if (iter_start
== iter_stop
)
549 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
550 /* Only write NOPs for arch_branch_static(). */
551 if (jump_label_init_type(iter
) == JUMP_LABEL_NOP
)
552 arch_jump_label_transform_static(iter
, JUMP_LABEL_NOP
);
556 static int jump_label_add_module(struct module
*mod
)
558 struct jump_entry
*iter_start
= mod
->jump_entries
;
559 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
560 struct jump_entry
*iter
;
561 struct static_key
*key
= NULL
;
562 struct static_key_mod
*jlm
, *jlm2
;
564 /* if the module doesn't have jump label entries, just return */
565 if (iter_start
== iter_stop
)
568 jump_label_sort_entries(iter_start
, iter_stop
);
570 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
571 struct static_key
*iterk
;
573 if (within_module_init(jump_entry_code(iter
), mod
))
574 jump_entry_set_init(iter
);
576 iterk
= jump_entry_key(iter
);
581 if (within_module((unsigned long)key
, mod
)) {
582 static_key_set_entries(key
, iter
);
585 jlm
= kzalloc(sizeof(struct static_key_mod
), GFP_KERNEL
);
588 if (!static_key_linked(key
)) {
589 jlm2
= kzalloc(sizeof(struct static_key_mod
),
596 jlm2
->mod
= __module_address((unsigned long)key
);
598 jlm2
->entries
= static_key_entries(key
);
600 static_key_set_mod(key
, jlm2
);
601 static_key_set_linked(key
);
605 jlm
->next
= static_key_mod(key
);
606 static_key_set_mod(key
, jlm
);
607 static_key_set_linked(key
);
609 /* Only update if we've changed from our initial state */
610 if (jump_label_type(iter
) != jump_label_init_type(iter
))
611 __jump_label_update(key
, iter
, iter_stop
, true);
617 static void jump_label_del_module(struct module
*mod
)
619 struct jump_entry
*iter_start
= mod
->jump_entries
;
620 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
621 struct jump_entry
*iter
;
622 struct static_key
*key
= NULL
;
623 struct static_key_mod
*jlm
, **prev
;
625 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
626 if (jump_entry_key(iter
) == key
)
629 key
= jump_entry_key(iter
);
631 if (within_module((unsigned long)key
, mod
))
634 /* No memory during module load */
635 if (WARN_ON(!static_key_linked(key
)))
639 jlm
= static_key_mod(key
);
641 while (jlm
&& jlm
->mod
!= mod
) {
646 /* No memory during module load */
650 if (prev
== &key
->next
)
651 static_key_set_mod(key
, jlm
->next
);
657 jlm
= static_key_mod(key
);
658 /* if only one etry is left, fold it back into the static_key */
659 if (jlm
->next
== NULL
) {
660 static_key_set_entries(key
, jlm
->entries
);
661 static_key_clear_linked(key
);
668 jump_label_module_notify(struct notifier_block
*self
, unsigned long val
,
671 struct module
*mod
= data
;
678 case MODULE_STATE_COMING
:
679 ret
= jump_label_add_module(mod
);
681 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
682 jump_label_del_module(mod
);
685 case MODULE_STATE_GOING
:
686 jump_label_del_module(mod
);
693 return notifier_from_errno(ret
);
696 static struct notifier_block jump_label_module_nb
= {
697 .notifier_call
= jump_label_module_notify
,
698 .priority
= 1, /* higher than tracepoints */
701 static __init
int jump_label_init_module(void)
703 return register_module_notifier(&jump_label_module_nb
);
705 early_initcall(jump_label_init_module
);
707 #endif /* CONFIG_MODULES */
710 * jump_label_text_reserved - check if addr range is reserved
711 * @start: start text addr
712 * @end: end text addr
714 * checks if the text addr located between @start and @end
715 * overlaps with any of the jump label patch addresses. Code
716 * that wants to modify kernel text should first verify that
717 * it does not overlap with any of the jump label addresses.
718 * Caller must hold jump_label_mutex.
720 * returns 1 if there is an overlap, 0 otherwise
722 int jump_label_text_reserved(void *start
, void *end
)
724 int ret
= __jump_label_text_reserved(__start___jump_table
,
725 __stop___jump_table
, start
, end
);
730 #ifdef CONFIG_MODULES
731 ret
= __jump_label_mod_text_reserved(start
, end
);
736 static void jump_label_update(struct static_key
*key
)
738 struct jump_entry
*stop
= __stop___jump_table
;
739 struct jump_entry
*entry
;
740 #ifdef CONFIG_MODULES
743 if (static_key_linked(key
)) {
744 __jump_label_mod_update(key
);
749 mod
= __module_address((unsigned long)key
);
751 stop
= mod
->jump_entries
+ mod
->num_jump_entries
;
754 entry
= static_key_entries(key
);
755 /* if there are no users, entry can be NULL */
757 __jump_label_update(key
, entry
, stop
,
758 system_state
< SYSTEM_RUNNING
);
761 #ifdef CONFIG_STATIC_KEYS_SELFTEST
762 static DEFINE_STATIC_KEY_TRUE(sk_true
);
763 static DEFINE_STATIC_KEY_FALSE(sk_false
);
765 static __init
int jump_label_test(void)
769 for (i
= 0; i
< 2; i
++) {
770 WARN_ON(static_key_enabled(&sk_true
.key
) != true);
771 WARN_ON(static_key_enabled(&sk_false
.key
) != false);
773 WARN_ON(!static_branch_likely(&sk_true
));
774 WARN_ON(!static_branch_unlikely(&sk_true
));
775 WARN_ON(static_branch_likely(&sk_false
));
776 WARN_ON(static_branch_unlikely(&sk_false
));
778 static_branch_disable(&sk_true
);
779 static_branch_enable(&sk_false
);
781 WARN_ON(static_key_enabled(&sk_true
.key
) == true);
782 WARN_ON(static_key_enabled(&sk_false
.key
) == false);
784 WARN_ON(static_branch_likely(&sk_true
));
785 WARN_ON(static_branch_unlikely(&sk_true
));
786 WARN_ON(!static_branch_likely(&sk_false
));
787 WARN_ON(!static_branch_unlikely(&sk_false
));
789 static_branch_enable(&sk_true
);
790 static_branch_disable(&sk_false
);
795 early_initcall(jump_label_test
);
796 #endif /* STATIC_KEYS_SELFTEST */