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>
20 #ifdef HAVE_JUMP_LABEL
22 /* mutex to protect coming/going of the 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;
40 if (jea->key < jeb->key)
43 if (jea->key > jeb->key)
50 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
54 size = (((unsigned long)stop - (unsigned long)start)
55 / sizeof(struct jump_entry));
56 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
59 static void jump_label_update(struct static_key *key);
62 * There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h.
63 * The use of 'atomic_read()' requires atomic.h and its problematic for some
64 * kernel headers such as kernel.h and others. Since static_key_count() is not
65 * used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok
66 * to have it be a function here. Similarly, for 'static_key_enable()' and
67 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
68 * to be included from most/all places for HAVE_JUMP_LABEL.
70 int static_key_count(struct static_key *key)
73 * -1 means the first static_key_slow_inc() is in progress.
74 * static_key_enabled() must return true, so return 1 here.
76 int n = atomic_read(&key->enabled);
78 return n >= 0 ? n : 1;
80 EXPORT_SYMBOL_GPL(static_key_count);
82 void static_key_slow_inc_cpuslocked(struct static_key *key)
86 STATIC_KEY_CHECK_USE(key);
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);
133 if (atomic_read(&key->enabled) > 0) {
134 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
139 if (atomic_read(&key->enabled) == 0) {
140 atomic_set(&key->enabled, -1);
141 jump_label_update(key);
143 * See static_key_slow_inc().
145 atomic_set_release(&key->enabled, 1);
149 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
151 void static_key_enable(struct static_key *key)
154 static_key_enable_cpuslocked(key);
157 EXPORT_SYMBOL_GPL(static_key_enable);
159 void static_key_disable_cpuslocked(struct static_key *key)
161 STATIC_KEY_CHECK_USE(key);
163 if (atomic_read(&key->enabled) != 1) {
164 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
169 if (atomic_cmpxchg(&key->enabled, 1, 0))
170 jump_label_update(key);
173 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
175 void static_key_disable(struct static_key *key)
178 static_key_disable_cpuslocked(key);
181 EXPORT_SYMBOL_GPL(static_key_disable);
183 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
184 unsigned long rate_limit,
185 struct delayed_work *work)
188 * The negative count check is valid even when a negative
189 * key->enabled is in use by static_key_slow_inc(); a
190 * __static_key_slow_dec() before the first static_key_slow_inc()
191 * returns is unbalanced, because all other static_key_slow_inc()
192 * instances block while the update is in progress.
194 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
195 WARN(atomic_read(&key->enabled) < 0,
196 "jump label: negative count!\n");
201 atomic_inc(&key->enabled);
202 schedule_delayed_work(work, rate_limit);
204 jump_label_update(key);
209 static void __static_key_slow_dec(struct static_key *key,
210 unsigned long rate_limit,
211 struct delayed_work *work)
214 __static_key_slow_dec_cpuslocked(key, rate_limit, work);
218 static void jump_label_update_timeout(struct work_struct *work)
220 struct static_key_deferred *key =
221 container_of(work, struct static_key_deferred, work.work);
222 __static_key_slow_dec(&key->key, 0, NULL);
225 void static_key_slow_dec(struct static_key *key)
227 STATIC_KEY_CHECK_USE(key);
228 __static_key_slow_dec(key, 0, NULL);
230 EXPORT_SYMBOL_GPL(static_key_slow_dec);
232 void static_key_slow_dec_cpuslocked(struct static_key *key)
234 STATIC_KEY_CHECK_USE(key);
235 __static_key_slow_dec_cpuslocked(key, 0, NULL);
238 void static_key_slow_dec_deferred(struct static_key_deferred *key)
240 STATIC_KEY_CHECK_USE(key);
241 __static_key_slow_dec(&key->key, key->timeout, &key->work);
243 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
245 void static_key_deferred_flush(struct static_key_deferred *key)
247 STATIC_KEY_CHECK_USE(key);
248 flush_delayed_work(&key->work);
250 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
252 void jump_label_rate_limit(struct static_key_deferred *key,
255 STATIC_KEY_CHECK_USE(key);
257 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
259 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
261 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
263 if (entry->code <= (unsigned long)end &&
264 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
270 static int __jump_label_text_reserved(struct jump_entry *iter_start,
271 struct jump_entry *iter_stop, void *start, void *end)
273 struct jump_entry *iter;
276 while (iter < iter_stop) {
277 if (addr_conflict(iter, start, end))
286 * Update code which is definitely not currently executing.
287 * Architectures which need heavyweight synchronization to modify
288 * running code can override this to make the non-live update case
291 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
292 enum jump_label_type type)
294 arch_jump_label_transform(entry, type);
297 static inline struct jump_entry *static_key_entries(struct static_key *key)
299 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
300 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
303 static inline bool static_key_type(struct static_key *key)
305 return key->type & JUMP_TYPE_TRUE;
308 static inline bool static_key_linked(struct static_key *key)
310 return key->type & JUMP_TYPE_LINKED;
313 static inline void static_key_clear_linked(struct static_key *key)
315 key->type &= ~JUMP_TYPE_LINKED;
318 static inline void static_key_set_linked(struct static_key *key)
320 key->type |= JUMP_TYPE_LINKED;
323 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
325 return (struct static_key *)((unsigned long)entry->key & ~1UL);
328 static bool jump_entry_branch(struct jump_entry *entry)
330 return (unsigned long)entry->key & 1UL;
334 * A 'struct static_key' uses a union such that it either points directly
335 * to a table of 'struct jump_entry' or to a linked list of modules which in
336 * turn point to 'struct jump_entry' tables.
338 * The two lower bits of the pointer are used to keep track of which pointer
339 * type is in use and to store the initial branch direction, we use an access
340 * function which preserves these bits.
342 static void static_key_set_entries(struct static_key *key,
343 struct jump_entry *entries)
347 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
348 type = key->type & JUMP_TYPE_MASK;
349 key->entries = entries;
353 static enum jump_label_type jump_label_type(struct jump_entry *entry)
355 struct static_key *key = jump_entry_key(entry);
356 bool enabled = static_key_enabled(key);
357 bool branch = jump_entry_branch(entry);
359 /* See the comment in linux/jump_label.h */
360 return enabled ^ branch;
363 static void __jump_label_update(struct static_key *key,
364 struct jump_entry *entry,
365 struct jump_entry *stop)
367 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
369 * An entry->code of 0 indicates an entry which has been
370 * disabled because it was in an init text area.
373 if (kernel_text_address(entry->code))
374 arch_jump_label_transform(entry, jump_label_type(entry));
376 WARN_ONCE(1, "can't patch jump_label at %pS",
377 (void *)(unsigned long)entry->code);
382 void __init jump_label_init(void)
384 struct jump_entry *iter_start = __start___jump_table;
385 struct jump_entry *iter_stop = __stop___jump_table;
386 struct static_key *key = NULL;
387 struct jump_entry *iter;
390 * Since we are initializing the static_key.enabled field with
391 * with the 'raw' int values (to avoid pulling in atomic.h) in
392 * jump_label.h, let's make sure that is safe. There are only two
393 * cases to check since we initialize to 0 or 1.
395 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
396 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
398 if (static_key_initialized)
403 jump_label_sort_entries(iter_start, iter_stop);
405 for (iter = iter_start; iter < iter_stop; iter++) {
406 struct static_key *iterk;
409 if (jump_label_type(iter) == JUMP_LABEL_NOP)
410 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
412 iterk = jump_entry_key(iter);
417 static_key_set_entries(key, iter);
419 static_key_initialized = true;
424 /* Disable any jump label entries in __init code */
425 void __init jump_label_invalidate_init(void)
427 struct jump_entry *iter_start = __start___jump_table;
428 struct jump_entry *iter_stop = __stop___jump_table;
429 struct jump_entry *iter;
431 for (iter = iter_start; iter < iter_stop; iter++) {
432 if (init_kernel_text(iter->code))
437 #ifdef CONFIG_MODULES
439 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
441 struct static_key *key = jump_entry_key(entry);
442 bool type = static_key_type(key);
443 bool branch = jump_entry_branch(entry);
445 /* See the comment in linux/jump_label.h */
446 return type ^ branch;
449 struct static_key_mod {
450 struct static_key_mod *next;
451 struct jump_entry *entries;
455 static inline struct static_key_mod *static_key_mod(struct static_key *key)
457 WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
458 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
462 * key->type and key->next are the same via union.
463 * This sets key->next and preserves the type bits.
465 * See additional comments above static_key_set_entries().
467 static void static_key_set_mod(struct static_key *key,
468 struct static_key_mod *mod)
472 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
473 type = key->type & JUMP_TYPE_MASK;
478 static int __jump_label_mod_text_reserved(void *start, void *end)
483 mod = __module_text_address((unsigned long)start);
484 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
491 return __jump_label_text_reserved(mod->jump_entries,
492 mod->jump_entries + mod->num_jump_entries,
496 static void __jump_label_mod_update(struct static_key *key)
498 struct static_key_mod *mod;
500 for (mod = static_key_mod(key); mod; mod = mod->next) {
501 struct jump_entry *stop;
505 * NULL if the static_key is defined in a module
506 * that does not use it
513 stop = __stop___jump_table;
515 stop = m->jump_entries + m->num_jump_entries;
516 __jump_label_update(key, mod->entries, stop);
521 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
522 * @mod: module to patch
524 * Allow for run-time selection of the optimal nops. Before the module
525 * loads patch these with arch_get_jump_label_nop(), which is specified by
526 * the arch specific jump label code.
528 void jump_label_apply_nops(struct module *mod)
530 struct jump_entry *iter_start = mod->jump_entries;
531 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
532 struct jump_entry *iter;
534 /* if the module doesn't have jump label entries, just return */
535 if (iter_start == iter_stop)
538 for (iter = iter_start; iter < iter_stop; iter++) {
539 /* Only write NOPs for arch_branch_static(). */
540 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
541 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
545 static int jump_label_add_module(struct module *mod)
547 struct jump_entry *iter_start = mod->jump_entries;
548 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
549 struct jump_entry *iter;
550 struct static_key *key = NULL;
551 struct static_key_mod *jlm, *jlm2;
553 /* if the module doesn't have jump label entries, just return */
554 if (iter_start == iter_stop)
557 jump_label_sort_entries(iter_start, iter_stop);
559 for (iter = iter_start; iter < iter_stop; iter++) {
560 struct static_key *iterk;
562 iterk = jump_entry_key(iter);
567 if (within_module(iter->key, mod)) {
568 static_key_set_entries(key, iter);
571 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
574 if (!static_key_linked(key)) {
575 jlm2 = kzalloc(sizeof(struct static_key_mod),
582 jlm2->mod = __module_address((unsigned long)key);
584 jlm2->entries = static_key_entries(key);
586 static_key_set_mod(key, jlm2);
587 static_key_set_linked(key);
591 jlm->next = static_key_mod(key);
592 static_key_set_mod(key, jlm);
593 static_key_set_linked(key);
595 /* Only update if we've changed from our initial state */
596 if (jump_label_type(iter) != jump_label_init_type(iter))
597 __jump_label_update(key, iter, iter_stop);
603 static void jump_label_del_module(struct module *mod)
605 struct jump_entry *iter_start = mod->jump_entries;
606 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
607 struct jump_entry *iter;
608 struct static_key *key = NULL;
609 struct static_key_mod *jlm, **prev;
611 for (iter = iter_start; iter < iter_stop; iter++) {
612 if (jump_entry_key(iter) == key)
615 key = jump_entry_key(iter);
617 if (within_module(iter->key, mod))
620 /* No memory during module load */
621 if (WARN_ON(!static_key_linked(key)))
625 jlm = static_key_mod(key);
627 while (jlm && jlm->mod != mod) {
632 /* No memory during module load */
636 if (prev == &key->next)
637 static_key_set_mod(key, jlm->next);
643 jlm = static_key_mod(key);
644 /* if only one etry is left, fold it back into the static_key */
645 if (jlm->next == NULL) {
646 static_key_set_entries(key, jlm->entries);
647 static_key_clear_linked(key);
653 /* Disable any jump label entries in module init code */
654 static void jump_label_invalidate_module_init(struct module *mod)
656 struct jump_entry *iter_start = mod->jump_entries;
657 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
658 struct jump_entry *iter;
660 for (iter = iter_start; iter < iter_stop; iter++) {
661 if (within_module_init(iter->code, mod))
667 jump_label_module_notify(struct notifier_block *self, unsigned long val,
670 struct module *mod = data;
677 case MODULE_STATE_COMING:
678 ret = jump_label_add_module(mod);
680 WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
681 jump_label_del_module(mod);
684 case MODULE_STATE_GOING:
685 jump_label_del_module(mod);
687 case MODULE_STATE_LIVE:
688 jump_label_invalidate_module_init(mod);
695 return notifier_from_errno(ret);
698 static struct notifier_block jump_label_module_nb = {
699 .notifier_call = jump_label_module_notify,
700 .priority = 1, /* higher than tracepoints */
703 static __init int jump_label_init_module(void)
705 return register_module_notifier(&jump_label_module_nb);
707 early_initcall(jump_label_init_module);
709 #endif /* CONFIG_MODULES */
712 * jump_label_text_reserved - check if addr range is reserved
713 * @start: start text addr
714 * @end: end text addr
716 * checks if the text addr located between @start and @end
717 * overlaps with any of the jump label patch addresses. Code
718 * that wants to modify kernel text should first verify that
719 * it does not overlap with any of the jump label addresses.
720 * Caller must hold jump_label_mutex.
722 * returns 1 if there is an overlap, 0 otherwise
724 int jump_label_text_reserved(void *start, void *end)
726 int ret = __jump_label_text_reserved(__start___jump_table,
727 __stop___jump_table, start, end);
732 #ifdef CONFIG_MODULES
733 ret = __jump_label_mod_text_reserved(start, end);
738 static void jump_label_update(struct static_key *key)
740 struct jump_entry *stop = __stop___jump_table;
741 struct jump_entry *entry;
742 #ifdef CONFIG_MODULES
745 if (static_key_linked(key)) {
746 __jump_label_mod_update(key);
751 mod = __module_address((unsigned long)key);
753 stop = mod->jump_entries + mod->num_jump_entries;
756 entry = static_key_entries(key);
757 /* if there are no users, entry can be NULL */
759 __jump_label_update(key, entry, stop);
762 #ifdef CONFIG_STATIC_KEYS_SELFTEST
763 static DEFINE_STATIC_KEY_TRUE(sk_true);
764 static DEFINE_STATIC_KEY_FALSE(sk_false);
766 static __init int jump_label_test(void)
770 for (i = 0; i < 2; i++) {
771 WARN_ON(static_key_enabled(&sk_true.key) != true);
772 WARN_ON(static_key_enabled(&sk_false.key) != false);
774 WARN_ON(!static_branch_likely(&sk_true));
775 WARN_ON(!static_branch_unlikely(&sk_true));
776 WARN_ON(static_branch_likely(&sk_false));
777 WARN_ON(static_branch_unlikely(&sk_false));
779 static_branch_disable(&sk_true);
780 static_branch_enable(&sk_false);
782 WARN_ON(static_key_enabled(&sk_true.key) == true);
783 WARN_ON(static_key_enabled(&sk_false.key) == false);
785 WARN_ON(static_branch_likely(&sk_true));
786 WARN_ON(static_branch_unlikely(&sk_true));
787 WARN_ON(!static_branch_likely(&sk_false));
788 WARN_ON(!static_branch_unlikely(&sk_false));
790 static_branch_enable(&sk_true);
791 static_branch_disable(&sk_false);
796 early_initcall(jump_label_test);
797 #endif /* STATIC_KEYS_SELFTEST */
799 #endif /* HAVE_JUMP_LABEL */