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 (jea->key < jeb->key)
42 if (jea->key > jeb->key)
49 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
53 size = (((unsigned long)stop - (unsigned long)start)
54 / sizeof(struct jump_entry));
55 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
58 static void jump_label_update(struct static_key *key);
61 * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
62 * The use of 'atomic_read()' requires atomic.h and its problematic for some
63 * kernel headers such as kernel.h and others. Since static_key_count() is not
64 * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
65 * to have it be a function here. Similarly, for 'static_key_enable()' and
66 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
67 * to be included from most/all places for CONFIG_JUMP_LABEL.
69 int static_key_count(struct static_key *key)
72 * -1 means the first static_key_slow_inc() is in progress.
73 * static_key_enabled() must return true, so return 1 here.
75 int n = atomic_read(&key->enabled);
77 return n >= 0 ? n : 1;
79 EXPORT_SYMBOL_GPL(static_key_count);
81 void static_key_slow_inc_cpuslocked(struct static_key *key)
85 STATIC_KEY_CHECK_USE(key);
86 lockdep_assert_cpus_held();
89 * Careful if we get concurrent static_key_slow_inc() calls;
90 * later calls must wait for the first one to _finish_ the
91 * jump_label_update() process. At the same time, however,
92 * the jump_label_update() call below wants to see
93 * static_key_enabled(&key) for jumps to be updated properly.
95 * So give a special meaning to negative key->enabled: it sends
96 * static_key_slow_inc() down the slow path, and it is non-zero
97 * so it counts as "enabled" in jump_label_update(). Note that
98 * atomic_inc_unless_negative() checks >= 0, so roll our own.
100 for (v = atomic_read(&key->enabled); v > 0; v = v1) {
101 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
107 if (atomic_read(&key->enabled) == 0) {
108 atomic_set(&key->enabled, -1);
109 jump_label_update(key);
111 * Ensure that if the above cmpxchg loop observes our positive
112 * value, it must also observe all the text changes.
114 atomic_set_release(&key->enabled, 1);
116 atomic_inc(&key->enabled);
121 void static_key_slow_inc(struct static_key *key)
124 static_key_slow_inc_cpuslocked(key);
127 EXPORT_SYMBOL_GPL(static_key_slow_inc);
129 void static_key_enable_cpuslocked(struct static_key *key)
131 STATIC_KEY_CHECK_USE(key);
132 lockdep_assert_cpus_held();
134 if (atomic_read(&key->enabled) > 0) {
135 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
140 if (atomic_read(&key->enabled) == 0) {
141 atomic_set(&key->enabled, -1);
142 jump_label_update(key);
144 * See static_key_slow_inc().
146 atomic_set_release(&key->enabled, 1);
150 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
152 void static_key_enable(struct static_key *key)
155 static_key_enable_cpuslocked(key);
158 EXPORT_SYMBOL_GPL(static_key_enable);
160 void static_key_disable_cpuslocked(struct static_key *key)
162 STATIC_KEY_CHECK_USE(key);
163 lockdep_assert_cpus_held();
165 if (atomic_read(&key->enabled) != 1) {
166 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
171 if (atomic_cmpxchg(&key->enabled, 1, 0))
172 jump_label_update(key);
175 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
177 void static_key_disable(struct static_key *key)
180 static_key_disable_cpuslocked(key);
183 EXPORT_SYMBOL_GPL(static_key_disable);
185 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
186 unsigned long rate_limit,
187 struct delayed_work *work)
191 lockdep_assert_cpus_held();
194 * The negative count check is valid even when a negative
195 * key->enabled is in use by static_key_slow_inc(); a
196 * __static_key_slow_dec() before the first static_key_slow_inc()
197 * returns is unbalanced, because all other static_key_slow_inc()
198 * instances block while the update is in progress.
200 val = atomic_fetch_add_unless(&key->enabled, -1, 1);
202 WARN(val < 0, "jump label: negative count!\n");
207 if (atomic_dec_and_test(&key->enabled)) {
209 atomic_inc(&key->enabled);
210 schedule_delayed_work(work, rate_limit);
212 jump_label_update(key);
218 static void __static_key_slow_dec(struct static_key *key,
219 unsigned long rate_limit,
220 struct delayed_work *work)
223 __static_key_slow_dec_cpuslocked(key, rate_limit, work);
227 static void jump_label_update_timeout(struct work_struct *work)
229 struct static_key_deferred *key =
230 container_of(work, struct static_key_deferred, work.work);
231 __static_key_slow_dec(&key->key, 0, NULL);
234 void static_key_slow_dec(struct static_key *key)
236 STATIC_KEY_CHECK_USE(key);
237 __static_key_slow_dec(key, 0, NULL);
239 EXPORT_SYMBOL_GPL(static_key_slow_dec);
241 void static_key_slow_dec_cpuslocked(struct static_key *key)
243 STATIC_KEY_CHECK_USE(key);
244 __static_key_slow_dec_cpuslocked(key, 0, NULL);
247 void static_key_slow_dec_deferred(struct static_key_deferred *key)
249 STATIC_KEY_CHECK_USE(key);
250 __static_key_slow_dec(&key->key, key->timeout, &key->work);
252 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
254 void static_key_deferred_flush(struct static_key_deferred *key)
256 STATIC_KEY_CHECK_USE(key);
257 flush_delayed_work(&key->work);
259 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
261 void jump_label_rate_limit(struct static_key_deferred *key,
264 STATIC_KEY_CHECK_USE(key);
266 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
268 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
270 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
272 if (entry->code <= (unsigned long)end &&
273 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
279 static int __jump_label_text_reserved(struct jump_entry *iter_start,
280 struct jump_entry *iter_stop, void *start, void *end)
282 struct jump_entry *iter;
285 while (iter < iter_stop) {
286 if (addr_conflict(iter, start, end))
295 * Update code which is definitely not currently executing.
296 * Architectures which need heavyweight synchronization to modify
297 * running code can override this to make the non-live update case
300 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
301 enum jump_label_type type)
303 arch_jump_label_transform(entry, type);
306 static inline struct jump_entry *static_key_entries(struct static_key *key)
308 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
309 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
312 static inline bool static_key_type(struct static_key *key)
314 return key->type & JUMP_TYPE_TRUE;
317 static inline bool static_key_linked(struct static_key *key)
319 return key->type & JUMP_TYPE_LINKED;
322 static inline void static_key_clear_linked(struct static_key *key)
324 key->type &= ~JUMP_TYPE_LINKED;
327 static inline void static_key_set_linked(struct static_key *key)
329 key->type |= JUMP_TYPE_LINKED;
332 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
334 return (struct static_key *)((unsigned long)entry->key & ~1UL);
337 static bool jump_entry_branch(struct jump_entry *entry)
339 return (unsigned long)entry->key & 1UL;
343 * A 'struct static_key' uses a union such that it either points directly
344 * to a table of 'struct jump_entry' or to a linked list of modules which in
345 * turn point to 'struct jump_entry' tables.
347 * The two lower bits of the pointer are used to keep track of which pointer
348 * type is in use and to store the initial branch direction, we use an access
349 * function which preserves these bits.
351 static void static_key_set_entries(struct static_key *key,
352 struct jump_entry *entries)
356 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
357 type = key->type & JUMP_TYPE_MASK;
358 key->entries = entries;
362 static enum jump_label_type jump_label_type(struct jump_entry *entry)
364 struct static_key *key = jump_entry_key(entry);
365 bool enabled = static_key_enabled(key);
366 bool branch = jump_entry_branch(entry);
368 /* See the comment in linux/jump_label.h */
369 return enabled ^ branch;
372 static void __jump_label_update(struct static_key *key,
373 struct jump_entry *entry,
374 struct jump_entry *stop)
376 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
378 * An entry->code of 0 indicates an entry which has been
379 * disabled because it was in an init text area.
382 if (kernel_text_address(entry->code))
383 arch_jump_label_transform(entry, jump_label_type(entry));
385 WARN_ONCE(1, "can't patch jump_label at %pS",
386 (void *)(unsigned long)entry->code);
391 void __init jump_label_init(void)
393 struct jump_entry *iter_start = __start___jump_table;
394 struct jump_entry *iter_stop = __stop___jump_table;
395 struct static_key *key = NULL;
396 struct jump_entry *iter;
399 * Since we are initializing the static_key.enabled field with
400 * with the 'raw' int values (to avoid pulling in atomic.h) in
401 * jump_label.h, let's make sure that is safe. There are only two
402 * cases to check since we initialize to 0 or 1.
404 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
405 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
407 if (static_key_initialized)
412 jump_label_sort_entries(iter_start, iter_stop);
414 for (iter = iter_start; iter < iter_stop; iter++) {
415 struct static_key *iterk;
418 if (jump_label_type(iter) == JUMP_LABEL_NOP)
419 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
421 iterk = jump_entry_key(iter);
426 static_key_set_entries(key, iter);
428 static_key_initialized = true;
433 /* Disable any jump label entries in __init/__exit code */
434 void __init jump_label_invalidate_initmem(void)
436 struct jump_entry *iter_start = __start___jump_table;
437 struct jump_entry *iter_stop = __stop___jump_table;
438 struct jump_entry *iter;
440 for (iter = iter_start; iter < iter_stop; iter++) {
441 if (init_section_contains((void *)(unsigned long)iter->code, 1))
446 #ifdef CONFIG_MODULES
448 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
450 struct static_key *key = jump_entry_key(entry);
451 bool type = static_key_type(key);
452 bool branch = jump_entry_branch(entry);
454 /* See the comment in linux/jump_label.h */
455 return type ^ branch;
458 struct static_key_mod {
459 struct static_key_mod *next;
460 struct jump_entry *entries;
464 static inline struct static_key_mod *static_key_mod(struct static_key *key)
466 WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
467 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
471 * key->type and key->next are the same via union.
472 * This sets key->next and preserves the type bits.
474 * See additional comments above static_key_set_entries().
476 static void static_key_set_mod(struct static_key *key,
477 struct static_key_mod *mod)
481 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
482 type = key->type & JUMP_TYPE_MASK;
487 static int __jump_label_mod_text_reserved(void *start, void *end)
492 mod = __module_text_address((unsigned long)start);
493 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
500 return __jump_label_text_reserved(mod->jump_entries,
501 mod->jump_entries + mod->num_jump_entries,
505 static void __jump_label_mod_update(struct static_key *key)
507 struct static_key_mod *mod;
509 for (mod = static_key_mod(key); mod; mod = mod->next) {
510 struct jump_entry *stop;
514 * NULL if the static_key is defined in a module
515 * that does not use it
522 stop = __stop___jump_table;
524 stop = m->jump_entries + m->num_jump_entries;
525 __jump_label_update(key, mod->entries, stop);
530 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
531 * @mod: module to patch
533 * Allow for run-time selection of the optimal nops. Before the module
534 * loads patch these with arch_get_jump_label_nop(), which is specified by
535 * the arch specific jump label code.
537 void jump_label_apply_nops(struct module *mod)
539 struct jump_entry *iter_start = mod->jump_entries;
540 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
541 struct jump_entry *iter;
543 /* if the module doesn't have jump label entries, just return */
544 if (iter_start == iter_stop)
547 for (iter = iter_start; iter < iter_stop; iter++) {
548 /* Only write NOPs for arch_branch_static(). */
549 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
550 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
554 static int jump_label_add_module(struct module *mod)
556 struct jump_entry *iter_start = mod->jump_entries;
557 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
558 struct jump_entry *iter;
559 struct static_key *key = NULL;
560 struct static_key_mod *jlm, *jlm2;
562 /* if the module doesn't have jump label entries, just return */
563 if (iter_start == iter_stop)
566 jump_label_sort_entries(iter_start, iter_stop);
568 for (iter = iter_start; iter < iter_stop; iter++) {
569 struct static_key *iterk;
571 iterk = jump_entry_key(iter);
576 if (within_module(iter->key, mod)) {
577 static_key_set_entries(key, iter);
580 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
583 if (!static_key_linked(key)) {
584 jlm2 = kzalloc(sizeof(struct static_key_mod),
591 jlm2->mod = __module_address((unsigned long)key);
593 jlm2->entries = static_key_entries(key);
595 static_key_set_mod(key, jlm2);
596 static_key_set_linked(key);
600 jlm->next = static_key_mod(key);
601 static_key_set_mod(key, jlm);
602 static_key_set_linked(key);
604 /* Only update if we've changed from our initial state */
605 if (jump_label_type(iter) != jump_label_init_type(iter))
606 __jump_label_update(key, iter, iter_stop);
612 static void jump_label_del_module(struct module *mod)
614 struct jump_entry *iter_start = mod->jump_entries;
615 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
616 struct jump_entry *iter;
617 struct static_key *key = NULL;
618 struct static_key_mod *jlm, **prev;
620 for (iter = iter_start; iter < iter_stop; iter++) {
621 if (jump_entry_key(iter) == key)
624 key = jump_entry_key(iter);
626 if (within_module(iter->key, mod))
629 /* No memory during module load */
630 if (WARN_ON(!static_key_linked(key)))
634 jlm = static_key_mod(key);
636 while (jlm && jlm->mod != mod) {
641 /* No memory during module load */
645 if (prev == &key->next)
646 static_key_set_mod(key, jlm->next);
652 jlm = static_key_mod(key);
653 /* if only one etry is left, fold it back into the static_key */
654 if (jlm->next == NULL) {
655 static_key_set_entries(key, jlm->entries);
656 static_key_clear_linked(key);
662 /* Disable any jump label entries in module init code */
663 static void jump_label_invalidate_module_init(struct module *mod)
665 struct jump_entry *iter_start = mod->jump_entries;
666 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
667 struct jump_entry *iter;
669 for (iter = iter_start; iter < iter_stop; iter++) {
670 if (within_module_init(iter->code, mod))
676 jump_label_module_notify(struct notifier_block *self, unsigned long val,
679 struct module *mod = data;
686 case MODULE_STATE_COMING:
687 ret = jump_label_add_module(mod);
689 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
690 jump_label_del_module(mod);
693 case MODULE_STATE_GOING:
694 jump_label_del_module(mod);
696 case MODULE_STATE_LIVE:
697 jump_label_invalidate_module_init(mod);
704 return notifier_from_errno(ret);
707 static struct notifier_block jump_label_module_nb = {
708 .notifier_call = jump_label_module_notify,
709 .priority = 1, /* higher than tracepoints */
712 static __init int jump_label_init_module(void)
714 return register_module_notifier(&jump_label_module_nb);
716 early_initcall(jump_label_init_module);
718 #endif /* CONFIG_MODULES */
721 * jump_label_text_reserved - check if addr range is reserved
722 * @start: start text addr
723 * @end: end text addr
725 * checks if the text addr located between @start and @end
726 * overlaps with any of the jump label patch addresses. Code
727 * that wants to modify kernel text should first verify that
728 * it does not overlap with any of the jump label addresses.
729 * Caller must hold jump_label_mutex.
731 * returns 1 if there is an overlap, 0 otherwise
733 int jump_label_text_reserved(void *start, void *end)
735 int ret = __jump_label_text_reserved(__start___jump_table,
736 __stop___jump_table, start, end);
741 #ifdef CONFIG_MODULES
742 ret = __jump_label_mod_text_reserved(start, end);
747 static void jump_label_update(struct static_key *key)
749 struct jump_entry *stop = __stop___jump_table;
750 struct jump_entry *entry;
751 #ifdef CONFIG_MODULES
754 if (static_key_linked(key)) {
755 __jump_label_mod_update(key);
760 mod = __module_address((unsigned long)key);
762 stop = mod->jump_entries + mod->num_jump_entries;
765 entry = static_key_entries(key);
766 /* if there are no users, entry can be NULL */
768 __jump_label_update(key, entry, stop);
771 #ifdef CONFIG_STATIC_KEYS_SELFTEST
772 static DEFINE_STATIC_KEY_TRUE(sk_true);
773 static DEFINE_STATIC_KEY_FALSE(sk_false);
775 static __init int jump_label_test(void)
779 for (i = 0; i < 2; i++) {
780 WARN_ON(static_key_enabled(&sk_true.key) != true);
781 WARN_ON(static_key_enabled(&sk_false.key) != false);
783 WARN_ON(!static_branch_likely(&sk_true));
784 WARN_ON(!static_branch_unlikely(&sk_true));
785 WARN_ON(static_branch_likely(&sk_false));
786 WARN_ON(static_branch_unlikely(&sk_false));
788 static_branch_disable(&sk_true);
789 static_branch_enable(&sk_false);
791 WARN_ON(static_key_enabled(&sk_true.key) == true);
792 WARN_ON(static_key_enabled(&sk_false.key) == false);
794 WARN_ON(static_branch_likely(&sk_true));
795 WARN_ON(static_branch_unlikely(&sk_true));
796 WARN_ON(!static_branch_likely(&sk_false));
797 WARN_ON(!static_branch_unlikely(&sk_false));
799 static_branch_enable(&sk_true);
800 static_branch_disable(&sk_false);
805 early_initcall(jump_label_test);
806 #endif /* STATIC_KEYS_SELFTEST */