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 bool static_key_slow_try_dec(struct static_key *key)
209 val = atomic_fetch_add_unless(&key->enabled, -1, 1);
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 WARN(val < 0, "jump label: negative count!\n");
224 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
226 lockdep_assert_cpus_held();
228 if (static_key_slow_try_dec(key))
232 if (atomic_dec_and_test(&key->enabled))
233 jump_label_update(key);
237 static void __static_key_slow_dec(struct static_key *key)
240 __static_key_slow_dec_cpuslocked(key);
244 void jump_label_update_timeout(struct work_struct *work)
246 struct static_key_deferred *key =
247 container_of(work, struct static_key_deferred, work.work);
248 __static_key_slow_dec(&key->key);
250 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
252 void static_key_slow_dec(struct static_key *key)
254 STATIC_KEY_CHECK_USE(key);
255 __static_key_slow_dec(key);
257 EXPORT_SYMBOL_GPL(static_key_slow_dec);
259 void static_key_slow_dec_cpuslocked(struct static_key *key)
261 STATIC_KEY_CHECK_USE(key);
262 __static_key_slow_dec_cpuslocked(key);
265 void __static_key_slow_dec_deferred(struct static_key *key,
266 struct delayed_work *work,
267 unsigned long timeout)
269 STATIC_KEY_CHECK_USE(key);
271 if (static_key_slow_try_dec(key))
274 schedule_delayed_work(work, timeout);
276 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
278 void __static_key_deferred_flush(void *key, struct delayed_work *work)
280 STATIC_KEY_CHECK_USE(key);
281 flush_delayed_work(work);
283 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
285 void jump_label_rate_limit(struct static_key_deferred *key,
288 STATIC_KEY_CHECK_USE(key);
290 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
292 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
294 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
296 if (jump_entry_code(entry) <= (unsigned long)end &&
297 jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
303 static int __jump_label_text_reserved(struct jump_entry *iter_start,
304 struct jump_entry *iter_stop, void *start, void *end)
306 struct jump_entry *iter;
309 while (iter < iter_stop) {
310 if (addr_conflict(iter, start, end))
319 * Update code which is definitely not currently executing.
320 * Architectures which need heavyweight synchronization to modify
321 * running code can override this to make the non-live update case
324 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
325 enum jump_label_type type)
327 arch_jump_label_transform(entry, type);
330 static inline struct jump_entry *static_key_entries(struct static_key *key)
332 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
333 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
336 static inline bool static_key_type(struct static_key *key)
338 return key->type & JUMP_TYPE_TRUE;
341 static inline bool static_key_linked(struct static_key *key)
343 return key->type & JUMP_TYPE_LINKED;
346 static inline void static_key_clear_linked(struct static_key *key)
348 key->type &= ~JUMP_TYPE_LINKED;
351 static inline void static_key_set_linked(struct static_key *key)
353 key->type |= JUMP_TYPE_LINKED;
357 * A 'struct static_key' uses a union such that it either points directly
358 * to a table of 'struct jump_entry' or to a linked list of modules which in
359 * turn point to 'struct jump_entry' tables.
361 * The two lower bits of the pointer are used to keep track of which pointer
362 * type is in use and to store the initial branch direction, we use an access
363 * function which preserves these bits.
365 static void static_key_set_entries(struct static_key *key,
366 struct jump_entry *entries)
370 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
371 type = key->type & JUMP_TYPE_MASK;
372 key->entries = entries;
376 static enum jump_label_type jump_label_type(struct jump_entry *entry)
378 struct static_key *key = jump_entry_key(entry);
379 bool enabled = static_key_enabled(key);
380 bool branch = jump_entry_is_branch(entry);
382 /* See the comment in linux/jump_label.h */
383 return enabled ^ branch;
386 static void __jump_label_update(struct static_key *key,
387 struct jump_entry *entry,
388 struct jump_entry *stop,
391 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
393 * An entry->code of 0 indicates an entry which has been
394 * disabled because it was in an init text area.
396 if (init || !jump_entry_is_init(entry)) {
397 if (kernel_text_address(jump_entry_code(entry)))
398 arch_jump_label_transform(entry, jump_label_type(entry));
400 WARN_ONCE(1, "can't patch jump_label at %pS",
401 (void *)jump_entry_code(entry));
406 void __init jump_label_init(void)
408 struct jump_entry *iter_start = __start___jump_table;
409 struct jump_entry *iter_stop = __stop___jump_table;
410 struct static_key *key = NULL;
411 struct jump_entry *iter;
414 * Since we are initializing the static_key.enabled field with
415 * with the 'raw' int values (to avoid pulling in atomic.h) in
416 * jump_label.h, let's make sure that is safe. There are only two
417 * cases to check since we initialize to 0 or 1.
419 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
420 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
422 if (static_key_initialized)
427 jump_label_sort_entries(iter_start, iter_stop);
429 for (iter = iter_start; iter < iter_stop; iter++) {
430 struct static_key *iterk;
433 if (jump_label_type(iter) == JUMP_LABEL_NOP)
434 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
436 if (init_section_contains((void *)jump_entry_code(iter), 1))
437 jump_entry_set_init(iter);
439 iterk = jump_entry_key(iter);
444 static_key_set_entries(key, iter);
446 static_key_initialized = true;
451 #ifdef CONFIG_MODULES
453 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
455 struct static_key *key = jump_entry_key(entry);
456 bool type = static_key_type(key);
457 bool branch = jump_entry_is_branch(entry);
459 /* See the comment in linux/jump_label.h */
460 return type ^ branch;
463 struct static_key_mod {
464 struct static_key_mod *next;
465 struct jump_entry *entries;
469 static inline struct static_key_mod *static_key_mod(struct static_key *key)
471 WARN_ON_ONCE(!static_key_linked(key));
472 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
476 * key->type and key->next are the same via union.
477 * This sets key->next and preserves the type bits.
479 * See additional comments above static_key_set_entries().
481 static void static_key_set_mod(struct static_key *key,
482 struct static_key_mod *mod)
486 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
487 type = key->type & JUMP_TYPE_MASK;
492 static int __jump_label_mod_text_reserved(void *start, void *end)
497 mod = __module_text_address((unsigned long)start);
498 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
505 return __jump_label_text_reserved(mod->jump_entries,
506 mod->jump_entries + mod->num_jump_entries,
510 static void __jump_label_mod_update(struct static_key *key)
512 struct static_key_mod *mod;
514 for (mod = static_key_mod(key); mod; mod = mod->next) {
515 struct jump_entry *stop;
519 * NULL if the static_key is defined in a module
520 * that does not use it
527 stop = __stop___jump_table;
529 stop = m->jump_entries + m->num_jump_entries;
530 __jump_label_update(key, mod->entries, stop,
531 m && m->state == MODULE_STATE_COMING);
536 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
537 * @mod: module to patch
539 * Allow for run-time selection of the optimal nops. Before the module
540 * loads patch these with arch_get_jump_label_nop(), which is specified by
541 * the arch specific jump label code.
543 void jump_label_apply_nops(struct module *mod)
545 struct jump_entry *iter_start = mod->jump_entries;
546 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
547 struct jump_entry *iter;
549 /* if the module doesn't have jump label entries, just return */
550 if (iter_start == iter_stop)
553 for (iter = iter_start; iter < iter_stop; iter++) {
554 /* Only write NOPs for arch_branch_static(). */
555 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
556 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
560 static int jump_label_add_module(struct module *mod)
562 struct jump_entry *iter_start = mod->jump_entries;
563 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
564 struct jump_entry *iter;
565 struct static_key *key = NULL;
566 struct static_key_mod *jlm, *jlm2;
568 /* if the module doesn't have jump label entries, just return */
569 if (iter_start == iter_stop)
572 jump_label_sort_entries(iter_start, iter_stop);
574 for (iter = iter_start; iter < iter_stop; iter++) {
575 struct static_key *iterk;
577 if (within_module_init(jump_entry_code(iter), mod))
578 jump_entry_set_init(iter);
580 iterk = jump_entry_key(iter);
585 if (within_module((unsigned long)key, mod)) {
586 static_key_set_entries(key, iter);
589 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
592 if (!static_key_linked(key)) {
593 jlm2 = kzalloc(sizeof(struct static_key_mod),
600 jlm2->mod = __module_address((unsigned long)key);
602 jlm2->entries = static_key_entries(key);
604 static_key_set_mod(key, jlm2);
605 static_key_set_linked(key);
609 jlm->next = static_key_mod(key);
610 static_key_set_mod(key, jlm);
611 static_key_set_linked(key);
613 /* Only update if we've changed from our initial state */
614 if (jump_label_type(iter) != jump_label_init_type(iter))
615 __jump_label_update(key, iter, iter_stop, true);
621 static void jump_label_del_module(struct module *mod)
623 struct jump_entry *iter_start = mod->jump_entries;
624 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
625 struct jump_entry *iter;
626 struct static_key *key = NULL;
627 struct static_key_mod *jlm, **prev;
629 for (iter = iter_start; iter < iter_stop; iter++) {
630 if (jump_entry_key(iter) == key)
633 key = jump_entry_key(iter);
635 if (within_module((unsigned long)key, mod))
638 /* No memory during module load */
639 if (WARN_ON(!static_key_linked(key)))
643 jlm = static_key_mod(key);
645 while (jlm && jlm->mod != mod) {
650 /* No memory during module load */
654 if (prev == &key->next)
655 static_key_set_mod(key, jlm->next);
661 jlm = static_key_mod(key);
662 /* if only one etry is left, fold it back into the static_key */
663 if (jlm->next == NULL) {
664 static_key_set_entries(key, jlm->entries);
665 static_key_clear_linked(key);
672 jump_label_module_notify(struct notifier_block *self, unsigned long val,
675 struct module *mod = data;
682 case MODULE_STATE_COMING:
683 ret = jump_label_add_module(mod);
685 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
686 jump_label_del_module(mod);
689 case MODULE_STATE_GOING:
690 jump_label_del_module(mod);
697 return notifier_from_errno(ret);
700 static struct notifier_block jump_label_module_nb = {
701 .notifier_call = jump_label_module_notify,
702 .priority = 1, /* higher than tracepoints */
705 static __init int jump_label_init_module(void)
707 return register_module_notifier(&jump_label_module_nb);
709 early_initcall(jump_label_init_module);
711 #endif /* CONFIG_MODULES */
714 * jump_label_text_reserved - check if addr range is reserved
715 * @start: start text addr
716 * @end: end text addr
718 * checks if the text addr located between @start and @end
719 * overlaps with any of the jump label patch addresses. Code
720 * that wants to modify kernel text should first verify that
721 * it does not overlap with any of the jump label addresses.
722 * Caller must hold jump_label_mutex.
724 * returns 1 if there is an overlap, 0 otherwise
726 int jump_label_text_reserved(void *start, void *end)
728 int ret = __jump_label_text_reserved(__start___jump_table,
729 __stop___jump_table, start, end);
734 #ifdef CONFIG_MODULES
735 ret = __jump_label_mod_text_reserved(start, end);
740 static void jump_label_update(struct static_key *key)
742 struct jump_entry *stop = __stop___jump_table;
743 struct jump_entry *entry;
744 #ifdef CONFIG_MODULES
747 if (static_key_linked(key)) {
748 __jump_label_mod_update(key);
753 mod = __module_address((unsigned long)key);
755 stop = mod->jump_entries + mod->num_jump_entries;
758 entry = static_key_entries(key);
759 /* if there are no users, entry can be NULL */
761 __jump_label_update(key, entry, stop,
762 system_state < SYSTEM_RUNNING);
765 #ifdef CONFIG_STATIC_KEYS_SELFTEST
766 static DEFINE_STATIC_KEY_TRUE(sk_true);
767 static DEFINE_STATIC_KEY_FALSE(sk_false);
769 static __init int jump_label_test(void)
773 for (i = 0; i < 2; i++) {
774 WARN_ON(static_key_enabled(&sk_true.key) != true);
775 WARN_ON(static_key_enabled(&sk_false.key) != false);
777 WARN_ON(!static_branch_likely(&sk_true));
778 WARN_ON(!static_branch_unlikely(&sk_true));
779 WARN_ON(static_branch_likely(&sk_false));
780 WARN_ON(static_branch_unlikely(&sk_false));
782 static_branch_disable(&sk_true);
783 static_branch_enable(&sk_false);
785 WARN_ON(static_key_enabled(&sk_true.key) == true);
786 WARN_ON(static_key_enabled(&sk_false.key) == false);
788 WARN_ON(static_branch_likely(&sk_true));
789 WARN_ON(static_branch_unlikely(&sk_true));
790 WARN_ON(!static_branch_likely(&sk_false));
791 WARN_ON(!static_branch_unlikely(&sk_false));
793 static_branch_enable(&sk_true);
794 static_branch_disable(&sk_false);
799 early_initcall(jump_label_test);
800 #endif /* STATIC_KEYS_SELFTEST */