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);
116 void static_key_slow_inc_cpuslocked(struct static_key *key)
118 STATIC_KEY_CHECK_USE(key);
119 lockdep_assert_cpus_held();
122 * Careful if we get concurrent static_key_slow_inc() calls;
123 * later calls must wait for the first one to _finish_ the
124 * jump_label_update() process. At the same time, however,
125 * the jump_label_update() call below wants to see
126 * static_key_enabled(&key) for jumps to be updated properly.
128 * So give a special meaning to negative key->enabled: it sends
129 * static_key_slow_inc() down the slow path, and it is non-zero
130 * so it counts as "enabled" in jump_label_update(). Note that
131 * atomic_inc_unless_negative() checks >= 0, so roll our own.
133 for (int v = atomic_read(&key->enabled); v > 0; )
134 if (likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)))
138 if (atomic_read(&key->enabled) == 0) {
139 atomic_set(&key->enabled, -1);
140 jump_label_update(key);
142 * Ensure that if the above cmpxchg loop observes our positive
143 * value, it must also observe all the text changes.
145 atomic_set_release(&key->enabled, 1);
147 atomic_inc(&key->enabled);
152 void static_key_slow_inc(struct static_key *key)
155 static_key_slow_inc_cpuslocked(key);
158 EXPORT_SYMBOL_GPL(static_key_slow_inc);
160 void static_key_enable_cpuslocked(struct static_key *key)
162 STATIC_KEY_CHECK_USE(key);
163 lockdep_assert_cpus_held();
165 if (atomic_read(&key->enabled) > 0) {
166 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
171 if (atomic_read(&key->enabled) == 0) {
172 atomic_set(&key->enabled, -1);
173 jump_label_update(key);
175 * See static_key_slow_inc().
177 atomic_set_release(&key->enabled, 1);
181 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
183 void static_key_enable(struct static_key *key)
186 static_key_enable_cpuslocked(key);
189 EXPORT_SYMBOL_GPL(static_key_enable);
191 void static_key_disable_cpuslocked(struct static_key *key)
193 STATIC_KEY_CHECK_USE(key);
194 lockdep_assert_cpus_held();
196 if (atomic_read(&key->enabled) != 1) {
197 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
202 if (atomic_cmpxchg(&key->enabled, 1, 0))
203 jump_label_update(key);
206 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
208 void static_key_disable(struct static_key *key)
211 static_key_disable_cpuslocked(key);
214 EXPORT_SYMBOL_GPL(static_key_disable);
216 static bool static_key_slow_try_dec(struct static_key *key)
220 val = atomic_fetch_add_unless(&key->enabled, -1, 1);
225 * The negative count check is valid even when a negative
226 * key->enabled is in use by static_key_slow_inc(); a
227 * __static_key_slow_dec() before the first static_key_slow_inc()
228 * returns is unbalanced, because all other static_key_slow_inc()
229 * instances block while the update is in progress.
231 WARN(val < 0, "jump label: negative count!\n");
235 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
237 lockdep_assert_cpus_held();
239 if (static_key_slow_try_dec(key))
243 if (atomic_dec_and_test(&key->enabled))
244 jump_label_update(key);
248 static void __static_key_slow_dec(struct static_key *key)
251 __static_key_slow_dec_cpuslocked(key);
255 void jump_label_update_timeout(struct work_struct *work)
257 struct static_key_deferred *key =
258 container_of(work, struct static_key_deferred, work.work);
259 __static_key_slow_dec(&key->key);
261 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
263 void static_key_slow_dec(struct static_key *key)
265 STATIC_KEY_CHECK_USE(key);
266 __static_key_slow_dec(key);
268 EXPORT_SYMBOL_GPL(static_key_slow_dec);
270 void static_key_slow_dec_cpuslocked(struct static_key *key)
272 STATIC_KEY_CHECK_USE(key);
273 __static_key_slow_dec_cpuslocked(key);
276 void __static_key_slow_dec_deferred(struct static_key *key,
277 struct delayed_work *work,
278 unsigned long timeout)
280 STATIC_KEY_CHECK_USE(key);
282 if (static_key_slow_try_dec(key))
285 schedule_delayed_work(work, timeout);
287 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
289 void __static_key_deferred_flush(void *key, struct delayed_work *work)
291 STATIC_KEY_CHECK_USE(key);
292 flush_delayed_work(work);
294 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
296 void jump_label_rate_limit(struct static_key_deferred *key,
299 STATIC_KEY_CHECK_USE(key);
301 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
303 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
305 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
307 if (jump_entry_code(entry) <= (unsigned long)end &&
308 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
314 static int __jump_label_text_reserved(struct jump_entry *iter_start,
315 struct jump_entry *iter_stop, void *start, void *end, bool init)
317 struct jump_entry *iter;
320 while (iter < iter_stop) {
321 if (init || !jump_entry_is_init(iter)) {
322 if (addr_conflict(iter, start, end))
331 #ifndef arch_jump_label_transform_static
332 static void arch_jump_label_transform_static(struct jump_entry *entry,
333 enum jump_label_type type)
335 /* nothing to do on most architectures */
339 static inline struct jump_entry *static_key_entries(struct static_key *key)
341 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
342 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
345 static inline bool static_key_type(struct static_key *key)
347 return key->type & JUMP_TYPE_TRUE;
350 static inline bool static_key_linked(struct static_key *key)
352 return key->type & JUMP_TYPE_LINKED;
355 static inline void static_key_clear_linked(struct static_key *key)
357 key->type &= ~JUMP_TYPE_LINKED;
360 static inline void static_key_set_linked(struct static_key *key)
362 key->type |= JUMP_TYPE_LINKED;
366 * A 'struct static_key' uses a union such that it either points directly
367 * to a table of 'struct jump_entry' or to a linked list of modules which in
368 * turn point to 'struct jump_entry' tables.
370 * The two lower bits of the pointer are used to keep track of which pointer
371 * type is in use and to store the initial branch direction, we use an access
372 * function which preserves these bits.
374 static void static_key_set_entries(struct static_key *key,
375 struct jump_entry *entries)
379 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
380 type = key->type & JUMP_TYPE_MASK;
381 key->entries = entries;
385 static enum jump_label_type jump_label_type(struct jump_entry *entry)
387 struct static_key *key = jump_entry_key(entry);
388 bool enabled = static_key_enabled(key);
389 bool branch = jump_entry_is_branch(entry);
391 /* See the comment in linux/jump_label.h */
392 return enabled ^ branch;
395 static bool jump_label_can_update(struct jump_entry *entry, bool init)
398 * Cannot update code that was in an init text area.
400 if (!init && jump_entry_is_init(entry))
403 if (!kernel_text_address(jump_entry_code(entry))) {
405 * This skips patching built-in __exit, which
406 * is part of init_section_contains() but is
407 * not part of kernel_text_address().
409 * Skipping built-in __exit is fine since it
410 * will never be executed.
412 WARN_ONCE(!jump_entry_is_init(entry),
413 "can't patch jump_label at %pS",
414 (void *)jump_entry_code(entry));
421 #ifndef HAVE_JUMP_LABEL_BATCH
422 static void __jump_label_update(struct static_key *key,
423 struct jump_entry *entry,
424 struct jump_entry *stop,
427 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
428 if (jump_label_can_update(entry, init))
429 arch_jump_label_transform(entry, jump_label_type(entry));
433 static void __jump_label_update(struct static_key *key,
434 struct jump_entry *entry,
435 struct jump_entry *stop,
438 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
440 if (!jump_label_can_update(entry, init))
443 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
445 * Queue is full: Apply the current queue and try again.
447 arch_jump_label_transform_apply();
448 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
451 arch_jump_label_transform_apply();
455 void __init jump_label_init(void)
457 struct jump_entry *iter_start = __start___jump_table;
458 struct jump_entry *iter_stop = __stop___jump_table;
459 struct static_key *key = NULL;
460 struct jump_entry *iter;
463 * Since we are initializing the static_key.enabled field with
464 * with the 'raw' int values (to avoid pulling in atomic.h) in
465 * jump_label.h, let's make sure that is safe. There are only two
466 * cases to check since we initialize to 0 or 1.
468 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
469 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
471 if (static_key_initialized)
476 jump_label_sort_entries(iter_start, iter_stop);
478 for (iter = iter_start; iter < iter_stop; iter++) {
479 struct static_key *iterk;
483 if (jump_label_type(iter) == JUMP_LABEL_NOP)
484 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
486 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
487 jump_entry_set_init(iter, in_init);
489 iterk = jump_entry_key(iter);
494 static_key_set_entries(key, iter);
496 static_key_initialized = true;
501 #ifdef CONFIG_MODULES
503 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
505 struct static_key *key = jump_entry_key(entry);
506 bool type = static_key_type(key);
507 bool branch = jump_entry_is_branch(entry);
509 /* See the comment in linux/jump_label.h */
510 return type ^ branch;
513 struct static_key_mod {
514 struct static_key_mod *next;
515 struct jump_entry *entries;
519 static inline struct static_key_mod *static_key_mod(struct static_key *key)
521 WARN_ON_ONCE(!static_key_linked(key));
522 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
526 * key->type and key->next are the same via union.
527 * This sets key->next and preserves the type bits.
529 * See additional comments above static_key_set_entries().
531 static void static_key_set_mod(struct static_key *key,
532 struct static_key_mod *mod)
536 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
537 type = key->type & JUMP_TYPE_MASK;
542 static int __jump_label_mod_text_reserved(void *start, void *end)
548 mod = __module_text_address((unsigned long)start);
549 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
550 if (!try_module_get(mod))
557 ret = __jump_label_text_reserved(mod->jump_entries,
558 mod->jump_entries + mod->num_jump_entries,
559 start, end, mod->state == MODULE_STATE_COMING);
566 static void __jump_label_mod_update(struct static_key *key)
568 struct static_key_mod *mod;
570 for (mod = static_key_mod(key); mod; mod = mod->next) {
571 struct jump_entry *stop;
575 * NULL if the static_key is defined in a module
576 * that does not use it
583 stop = __stop___jump_table;
585 stop = m->jump_entries + m->num_jump_entries;
586 __jump_label_update(key, mod->entries, stop,
587 m && m->state == MODULE_STATE_COMING);
591 static int jump_label_add_module(struct module *mod)
593 struct jump_entry *iter_start = mod->jump_entries;
594 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
595 struct jump_entry *iter;
596 struct static_key *key = NULL;
597 struct static_key_mod *jlm, *jlm2;
599 /* if the module doesn't have jump label entries, just return */
600 if (iter_start == iter_stop)
603 jump_label_sort_entries(iter_start, iter_stop);
605 for (iter = iter_start; iter < iter_stop; iter++) {
606 struct static_key *iterk;
609 in_init = within_module_init(jump_entry_code(iter), mod);
610 jump_entry_set_init(iter, in_init);
612 iterk = jump_entry_key(iter);
617 if (within_module((unsigned long)key, mod)) {
618 static_key_set_entries(key, iter);
621 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
624 if (!static_key_linked(key)) {
625 jlm2 = kzalloc(sizeof(struct static_key_mod),
632 jlm2->mod = __module_address((unsigned long)key);
634 jlm2->entries = static_key_entries(key);
636 static_key_set_mod(key, jlm2);
637 static_key_set_linked(key);
641 jlm->next = static_key_mod(key);
642 static_key_set_mod(key, jlm);
643 static_key_set_linked(key);
645 /* Only update if we've changed from our initial state */
646 if (jump_label_type(iter) != jump_label_init_type(iter))
647 __jump_label_update(key, iter, iter_stop, true);
653 static void jump_label_del_module(struct module *mod)
655 struct jump_entry *iter_start = mod->jump_entries;
656 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
657 struct jump_entry *iter;
658 struct static_key *key = NULL;
659 struct static_key_mod *jlm, **prev;
661 for (iter = iter_start; iter < iter_stop; iter++) {
662 if (jump_entry_key(iter) == key)
665 key = jump_entry_key(iter);
667 if (within_module((unsigned long)key, mod))
670 /* No memory during module load */
671 if (WARN_ON(!static_key_linked(key)))
675 jlm = static_key_mod(key);
677 while (jlm && jlm->mod != mod) {
682 /* No memory during module load */
686 if (prev == &key->next)
687 static_key_set_mod(key, jlm->next);
693 jlm = static_key_mod(key);
694 /* if only one etry is left, fold it back into the static_key */
695 if (jlm->next == NULL) {
696 static_key_set_entries(key, jlm->entries);
697 static_key_clear_linked(key);
704 jump_label_module_notify(struct notifier_block *self, unsigned long val,
707 struct module *mod = data;
714 case MODULE_STATE_COMING:
715 ret = jump_label_add_module(mod);
717 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
718 jump_label_del_module(mod);
721 case MODULE_STATE_GOING:
722 jump_label_del_module(mod);
729 return notifier_from_errno(ret);
732 static struct notifier_block jump_label_module_nb = {
733 .notifier_call = jump_label_module_notify,
734 .priority = 1, /* higher than tracepoints */
737 static __init int jump_label_init_module(void)
739 return register_module_notifier(&jump_label_module_nb);
741 early_initcall(jump_label_init_module);
743 #endif /* CONFIG_MODULES */
746 * jump_label_text_reserved - check if addr range is reserved
747 * @start: start text addr
748 * @end: end text addr
750 * checks if the text addr located between @start and @end
751 * overlaps with any of the jump label patch addresses. Code
752 * that wants to modify kernel text should first verify that
753 * it does not overlap with any of the jump label addresses.
754 * Caller must hold jump_label_mutex.
756 * returns 1 if there is an overlap, 0 otherwise
758 int jump_label_text_reserved(void *start, void *end)
760 bool init = system_state < SYSTEM_RUNNING;
761 int ret = __jump_label_text_reserved(__start___jump_table,
762 __stop___jump_table, start, end, init);
767 #ifdef CONFIG_MODULES
768 ret = __jump_label_mod_text_reserved(start, end);
773 static void jump_label_update(struct static_key *key)
775 struct jump_entry *stop = __stop___jump_table;
776 bool init = system_state < SYSTEM_RUNNING;
777 struct jump_entry *entry;
778 #ifdef CONFIG_MODULES
781 if (static_key_linked(key)) {
782 __jump_label_mod_update(key);
787 mod = __module_address((unsigned long)key);
789 stop = mod->jump_entries + mod->num_jump_entries;
790 init = mod->state == MODULE_STATE_COMING;
794 entry = static_key_entries(key);
795 /* if there are no users, entry can be NULL */
797 __jump_label_update(key, entry, stop, init);
800 #ifdef CONFIG_STATIC_KEYS_SELFTEST
801 static DEFINE_STATIC_KEY_TRUE(sk_true);
802 static DEFINE_STATIC_KEY_FALSE(sk_false);
804 static __init int jump_label_test(void)
808 for (i = 0; i < 2; i++) {
809 WARN_ON(static_key_enabled(&sk_true.key) != true);
810 WARN_ON(static_key_enabled(&sk_false.key) != false);
812 WARN_ON(!static_branch_likely(&sk_true));
813 WARN_ON(!static_branch_unlikely(&sk_true));
814 WARN_ON(static_branch_likely(&sk_false));
815 WARN_ON(static_branch_unlikely(&sk_false));
817 static_branch_disable(&sk_true);
818 static_branch_enable(&sk_false);
820 WARN_ON(static_key_enabled(&sk_true.key) == true);
821 WARN_ON(static_key_enabled(&sk_false.key) == false);
823 WARN_ON(static_branch_likely(&sk_true));
824 WARN_ON(static_branch_unlikely(&sk_true));
825 WARN_ON(!static_branch_likely(&sk_false));
826 WARN_ON(!static_branch_unlikely(&sk_false));
828 static_branch_enable(&sk_true);
829 static_branch_disable(&sk_false);
834 early_initcall(jump_label_test);
835 #endif /* STATIC_KEYS_SELFTEST */