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 #ifdef HAVE_JUMP_LABEL
23 /* mutex to protect coming/going of the the jump_label table */
24 static DEFINE_MUTEX(jump_label_mutex);
26 void jump_label_lock(void)
28 mutex_lock(&jump_label_mutex);
31 void jump_label_unlock(void)
33 mutex_unlock(&jump_label_mutex);
36 static int jump_label_cmp(const void *a, const void *b)
38 const struct jump_entry *jea = a;
39 const struct jump_entry *jeb = b;
41 if (jea->key < jeb->key)
44 if (jea->key > jeb->key)
51 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
55 size = (((unsigned long)stop - (unsigned long)start)
56 / sizeof(struct jump_entry));
57 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
60 static void jump_label_update(struct static_key *key);
63 * There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h.
64 * The use of 'atomic_read()' requires atomic.h and its problematic for some
65 * kernel headers such as kernel.h and others. Since static_key_count() is not
66 * used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok
67 * to have it be a function here. Similarly, for 'static_key_enable()' and
68 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
69 * to be included from most/all places for HAVE_JUMP_LABEL.
71 int static_key_count(struct static_key *key)
74 * -1 means the first static_key_slow_inc() is in progress.
75 * static_key_enabled() must return true, so return 1 here.
77 int n = atomic_read(&key->enabled);
79 return n >= 0 ? n : 1;
81 EXPORT_SYMBOL_GPL(static_key_count);
83 void static_key_slow_inc_cpuslocked(struct static_key *key)
87 STATIC_KEY_CHECK_USE(key);
90 * Careful if we get concurrent static_key_slow_inc() calls;
91 * later calls must wait for the first one to _finish_ the
92 * jump_label_update() process. At the same time, however,
93 * the jump_label_update() call below wants to see
94 * static_key_enabled(&key) for jumps to be updated properly.
96 * So give a special meaning to negative key->enabled: it sends
97 * static_key_slow_inc() down the slow path, and it is non-zero
98 * so it counts as "enabled" in jump_label_update(). Note that
99 * atomic_inc_unless_negative() checks >= 0, so roll our own.
101 for (v = atomic_read(&key->enabled); v > 0; v = v1) {
102 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
108 if (atomic_read(&key->enabled) == 0) {
109 atomic_set(&key->enabled, -1);
110 jump_label_update(key);
112 * Ensure that if the above cmpxchg loop observes our positive
113 * value, it must also observe all the text changes.
115 atomic_set_release(&key->enabled, 1);
117 atomic_inc(&key->enabled);
122 void static_key_slow_inc(struct static_key *key)
125 static_key_slow_inc_cpuslocked(key);
128 EXPORT_SYMBOL_GPL(static_key_slow_inc);
130 void static_key_enable_cpuslocked(struct static_key *key)
132 STATIC_KEY_CHECK_USE(key);
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);
164 if (atomic_read(&key->enabled) != 1) {
165 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
170 if (atomic_cmpxchg(&key->enabled, 1, 0))
171 jump_label_update(key);
174 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
176 void static_key_disable(struct static_key *key)
179 static_key_disable_cpuslocked(key);
182 EXPORT_SYMBOL_GPL(static_key_disable);
184 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
185 unsigned long rate_limit,
186 struct delayed_work *work)
189 * The negative count check is valid even when a negative
190 * key->enabled is in use by static_key_slow_inc(); a
191 * __static_key_slow_dec() before the first static_key_slow_inc()
192 * returns is unbalanced, because all other static_key_slow_inc()
193 * instances block while the update is in progress.
195 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
196 WARN(atomic_read(&key->enabled) < 0,
197 "jump label: negative count!\n");
202 atomic_inc(&key->enabled);
203 schedule_delayed_work(work, rate_limit);
205 jump_label_update(key);
210 static void __static_key_slow_dec(struct static_key *key,
211 unsigned long rate_limit,
212 struct delayed_work *work)
215 __static_key_slow_dec_cpuslocked(key, rate_limit, work);
219 static void jump_label_update_timeout(struct work_struct *work)
221 struct static_key_deferred *key =
222 container_of(work, struct static_key_deferred, work.work);
223 __static_key_slow_dec(&key->key, 0, NULL);
226 void static_key_slow_dec(struct static_key *key)
228 STATIC_KEY_CHECK_USE(key);
229 __static_key_slow_dec(key, 0, NULL);
231 EXPORT_SYMBOL_GPL(static_key_slow_dec);
233 void static_key_slow_dec_cpuslocked(struct static_key *key)
235 STATIC_KEY_CHECK_USE(key);
236 __static_key_slow_dec_cpuslocked(key, 0, NULL);
239 void static_key_slow_dec_deferred(struct static_key_deferred *key)
241 STATIC_KEY_CHECK_USE(key);
242 __static_key_slow_dec(&key->key, key->timeout, &key->work);
244 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
246 void static_key_deferred_flush(struct static_key_deferred *key)
248 STATIC_KEY_CHECK_USE(key);
249 flush_delayed_work(&key->work);
251 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
253 void jump_label_rate_limit(struct static_key_deferred *key,
256 STATIC_KEY_CHECK_USE(key);
258 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
260 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
262 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
264 if (entry->code <= (unsigned long)end &&
265 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
271 static int __jump_label_text_reserved(struct jump_entry *iter_start,
272 struct jump_entry *iter_stop, void *start, void *end)
274 struct jump_entry *iter;
277 while (iter < iter_stop) {
278 if (addr_conflict(iter, start, end))
287 * Update code which is definitely not currently executing.
288 * Architectures which need heavyweight synchronization to modify
289 * running code can override this to make the non-live update case
292 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
293 enum jump_label_type type)
295 arch_jump_label_transform(entry, type);
298 static inline struct jump_entry *static_key_entries(struct static_key *key)
300 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
301 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
304 static inline bool static_key_type(struct static_key *key)
306 return key->type & JUMP_TYPE_TRUE;
309 static inline bool static_key_linked(struct static_key *key)
311 return key->type & JUMP_TYPE_LINKED;
314 static inline void static_key_clear_linked(struct static_key *key)
316 key->type &= ~JUMP_TYPE_LINKED;
319 static inline void static_key_set_linked(struct static_key *key)
321 key->type |= JUMP_TYPE_LINKED;
324 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
326 return (struct static_key *)((unsigned long)entry->key & ~1UL);
329 static bool jump_entry_branch(struct jump_entry *entry)
331 return (unsigned long)entry->key & 1UL;
335 * A 'struct static_key' uses a union such that it either points directly
336 * to a table of 'struct jump_entry' or to a linked list of modules which in
337 * turn point to 'struct jump_entry' tables.
339 * The two lower bits of the pointer are used to keep track of which pointer
340 * type is in use and to store the initial branch direction, we use an access
341 * function which preserves these bits.
343 static void static_key_set_entries(struct static_key *key,
344 struct jump_entry *entries)
348 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
349 type = key->type & JUMP_TYPE_MASK;
350 key->entries = entries;
354 static enum jump_label_type jump_label_type(struct jump_entry *entry)
356 struct static_key *key = jump_entry_key(entry);
357 bool enabled = static_key_enabled(key);
358 bool branch = jump_entry_branch(entry);
360 /* See the comment in linux/jump_label.h */
361 return enabled ^ branch;
364 static void __jump_label_update(struct static_key *key,
365 struct jump_entry *entry,
366 struct jump_entry *stop)
368 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
370 * entry->code set to 0 invalidates module init text sections
371 * kernel_text_address() verifies we are not in core kernel
372 * init code, see jump_label_invalidate_module_init().
374 if (entry->code && kernel_text_address(entry->code))
375 arch_jump_label_transform(entry, jump_label_type(entry));
379 void __init jump_label_init(void)
381 struct jump_entry *iter_start = __start___jump_table;
382 struct jump_entry *iter_stop = __stop___jump_table;
383 struct static_key *key = NULL;
384 struct jump_entry *iter;
387 * Since we are initializing the static_key.enabled field with
388 * with the 'raw' int values (to avoid pulling in atomic.h) in
389 * jump_label.h, let's make sure that is safe. There are only two
390 * cases to check since we initialize to 0 or 1.
392 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
393 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
395 if (static_key_initialized)
400 jump_label_sort_entries(iter_start, iter_stop);
402 for (iter = iter_start; iter < iter_stop; iter++) {
403 struct static_key *iterk;
406 if (jump_label_type(iter) == JUMP_LABEL_NOP)
407 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
409 iterk = jump_entry_key(iter);
414 static_key_set_entries(key, iter);
416 static_key_initialized = true;
421 /* Disable any jump label entries in __init code */
422 void __init jump_label_invalidate_init(void)
424 struct jump_entry *iter_start = __start___jump_table;
425 struct jump_entry *iter_stop = __stop___jump_table;
426 struct jump_entry *iter;
428 for (iter = iter_start; iter < iter_stop; iter++) {
429 if (iter->code >= (unsigned long)_sinittext &&
430 iter->code < (unsigned long)_einittext)
435 #ifdef CONFIG_MODULES
437 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
439 struct static_key *key = jump_entry_key(entry);
440 bool type = static_key_type(key);
441 bool branch = jump_entry_branch(entry);
443 /* See the comment in linux/jump_label.h */
444 return type ^ branch;
447 struct static_key_mod {
448 struct static_key_mod *next;
449 struct jump_entry *entries;
453 static inline struct static_key_mod *static_key_mod(struct static_key *key)
455 WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
456 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
460 * key->type and key->next are the same via union.
461 * This sets key->next and preserves the type bits.
463 * See additional comments above static_key_set_entries().
465 static void static_key_set_mod(struct static_key *key,
466 struct static_key_mod *mod)
470 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
471 type = key->type & JUMP_TYPE_MASK;
476 static int __jump_label_mod_text_reserved(void *start, void *end)
481 mod = __module_text_address((unsigned long)start);
482 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
489 return __jump_label_text_reserved(mod->jump_entries,
490 mod->jump_entries + mod->num_jump_entries,
494 static void __jump_label_mod_update(struct static_key *key)
496 struct static_key_mod *mod;
498 for (mod = static_key_mod(key); mod; mod = mod->next) {
499 struct jump_entry *stop;
503 * NULL if the static_key is defined in a module
504 * that does not use it
511 stop = __stop___jump_table;
513 stop = m->jump_entries + m->num_jump_entries;
514 __jump_label_update(key, mod->entries, stop);
519 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
520 * @mod: module to patch
522 * Allow for run-time selection of the optimal nops. Before the module
523 * loads patch these with arch_get_jump_label_nop(), which is specified by
524 * the arch specific jump label code.
526 void jump_label_apply_nops(struct module *mod)
528 struct jump_entry *iter_start = mod->jump_entries;
529 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
530 struct jump_entry *iter;
532 /* if the module doesn't have jump label entries, just return */
533 if (iter_start == iter_stop)
536 for (iter = iter_start; iter < iter_stop; iter++) {
537 /* Only write NOPs for arch_branch_static(). */
538 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
539 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
543 static int jump_label_add_module(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;
548 struct static_key *key = NULL;
549 struct static_key_mod *jlm, *jlm2;
551 /* if the module doesn't have jump label entries, just return */
552 if (iter_start == iter_stop)
555 jump_label_sort_entries(iter_start, iter_stop);
557 for (iter = iter_start; iter < iter_stop; iter++) {
558 struct static_key *iterk;
560 iterk = jump_entry_key(iter);
565 if (within_module(iter->key, mod)) {
566 static_key_set_entries(key, iter);
569 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
572 if (!static_key_linked(key)) {
573 jlm2 = kzalloc(sizeof(struct static_key_mod),
580 jlm2->mod = __module_address((unsigned long)key);
582 jlm2->entries = static_key_entries(key);
584 static_key_set_mod(key, jlm2);
585 static_key_set_linked(key);
589 jlm->next = static_key_mod(key);
590 static_key_set_mod(key, jlm);
591 static_key_set_linked(key);
593 /* Only update if we've changed from our initial state */
594 if (jump_label_type(iter) != jump_label_init_type(iter))
595 __jump_label_update(key, iter, iter_stop);
601 static void jump_label_del_module(struct module *mod)
603 struct jump_entry *iter_start = mod->jump_entries;
604 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
605 struct jump_entry *iter;
606 struct static_key *key = NULL;
607 struct static_key_mod *jlm, **prev;
609 for (iter = iter_start; iter < iter_stop; iter++) {
610 if (jump_entry_key(iter) == key)
613 key = jump_entry_key(iter);
615 if (within_module(iter->key, mod))
618 /* No memory during module load */
619 if (WARN_ON(!static_key_linked(key)))
623 jlm = static_key_mod(key);
625 while (jlm && jlm->mod != mod) {
630 /* No memory during module load */
634 if (prev == &key->next)
635 static_key_set_mod(key, jlm->next);
641 jlm = static_key_mod(key);
642 /* if only one etry is left, fold it back into the static_key */
643 if (jlm->next == NULL) {
644 static_key_set_entries(key, jlm->entries);
645 static_key_clear_linked(key);
651 /* Disable any jump label entries in module init code */
652 static void jump_label_invalidate_module_init(struct module *mod)
654 struct jump_entry *iter_start = mod->jump_entries;
655 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
656 struct jump_entry *iter;
658 for (iter = iter_start; iter < iter_stop; iter++) {
659 if (within_module_init(iter->code, mod))
665 jump_label_module_notify(struct notifier_block *self, unsigned long val,
668 struct module *mod = data;
675 case MODULE_STATE_COMING:
676 ret = jump_label_add_module(mod);
678 WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
679 jump_label_del_module(mod);
682 case MODULE_STATE_GOING:
683 jump_label_del_module(mod);
685 case MODULE_STATE_LIVE:
686 jump_label_invalidate_module_init(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);
760 #ifdef CONFIG_STATIC_KEYS_SELFTEST
761 static DEFINE_STATIC_KEY_TRUE(sk_true);
762 static DEFINE_STATIC_KEY_FALSE(sk_false);
764 static __init int jump_label_test(void)
768 for (i = 0; i < 2; i++) {
769 WARN_ON(static_key_enabled(&sk_true.key) != true);
770 WARN_ON(static_key_enabled(&sk_false.key) != false);
772 WARN_ON(!static_branch_likely(&sk_true));
773 WARN_ON(!static_branch_unlikely(&sk_true));
774 WARN_ON(static_branch_likely(&sk_false));
775 WARN_ON(static_branch_unlikely(&sk_false));
777 static_branch_disable(&sk_true);
778 static_branch_enable(&sk_false);
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_enable(&sk_true);
789 static_branch_disable(&sk_false);
794 early_initcall(jump_label_test);
795 #endif /* STATIC_KEYS_SELFTEST */
797 #endif /* HAVE_JUMP_LABEL */