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>
19 #ifdef HAVE_JUMP_LABEL
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 !HAVE_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 !HAVE_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 HAVE_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_enable(struct static_key *key)
83 int count = static_key_count(key);
85 WARN_ON_ONCE(count < 0 || count > 1);
88 static_key_slow_inc(key);
90 EXPORT_SYMBOL_GPL(static_key_enable);
92 void static_key_disable(struct static_key *key)
94 int count = static_key_count(key);
96 WARN_ON_ONCE(count < 0 || count > 1);
99 static_key_slow_dec(key);
101 EXPORT_SYMBOL_GPL(static_key_disable);
103 void static_key_slow_inc(struct static_key *key)
107 STATIC_KEY_CHECK_USE();
110 * Careful if we get concurrent static_key_slow_inc() calls;
111 * later calls must wait for the first one to _finish_ the
112 * jump_label_update() process. At the same time, however,
113 * the jump_label_update() call below wants to see
114 * static_key_enabled(&key) for jumps to be updated properly.
116 * So give a special meaning to negative key->enabled: it sends
117 * static_key_slow_inc() down the slow path, and it is non-zero
118 * so it counts as "enabled" in jump_label_update(). Note that
119 * atomic_inc_unless_negative() checks >= 0, so roll our own.
121 for (v = atomic_read(&key->enabled); v > 0; v = v1) {
122 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
128 if (atomic_read(&key->enabled) == 0) {
129 atomic_set(&key->enabled, -1);
130 jump_label_update(key);
131 atomic_set(&key->enabled, 1);
133 atomic_inc(&key->enabled);
137 EXPORT_SYMBOL_GPL(static_key_slow_inc);
139 static void __static_key_slow_dec(struct static_key *key,
140 unsigned long rate_limit, struct delayed_work *work)
143 * The negative count check is valid even when a negative
144 * key->enabled is in use by static_key_slow_inc(); a
145 * __static_key_slow_dec() before the first static_key_slow_inc()
146 * returns is unbalanced, because all other static_key_slow_inc()
147 * instances block while the update is in progress.
149 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
150 WARN(atomic_read(&key->enabled) < 0,
151 "jump label: negative count!\n");
156 atomic_inc(&key->enabled);
157 schedule_delayed_work(work, rate_limit);
159 jump_label_update(key);
164 static void jump_label_update_timeout(struct work_struct *work)
166 struct static_key_deferred *key =
167 container_of(work, struct static_key_deferred, work.work);
168 __static_key_slow_dec(&key->key, 0, NULL);
171 void static_key_slow_dec(struct static_key *key)
173 STATIC_KEY_CHECK_USE();
174 __static_key_slow_dec(key, 0, NULL);
176 EXPORT_SYMBOL_GPL(static_key_slow_dec);
178 void static_key_slow_dec_deferred(struct static_key_deferred *key)
180 STATIC_KEY_CHECK_USE();
181 __static_key_slow_dec(&key->key, key->timeout, &key->work);
183 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
185 void jump_label_rate_limit(struct static_key_deferred *key,
188 STATIC_KEY_CHECK_USE();
190 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
192 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
194 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
196 if (entry->code <= (unsigned long)end &&
197 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
203 static int __jump_label_text_reserved(struct jump_entry *iter_start,
204 struct jump_entry *iter_stop, void *start, void *end)
206 struct jump_entry *iter;
209 while (iter < iter_stop) {
210 if (addr_conflict(iter, start, end))
219 * Update code which is definitely not currently executing.
220 * Architectures which need heavyweight synchronization to modify
221 * running code can override this to make the non-live update case
224 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
225 enum jump_label_type type)
227 arch_jump_label_transform(entry, type);
230 static inline struct jump_entry *static_key_entries(struct static_key *key)
232 return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
235 static inline bool static_key_type(struct static_key *key)
237 return (unsigned long)key->entries & JUMP_TYPE_MASK;
240 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
242 return (struct static_key *)((unsigned long)entry->key & ~1UL);
245 static bool jump_entry_branch(struct jump_entry *entry)
247 return (unsigned long)entry->key & 1UL;
250 static enum jump_label_type jump_label_type(struct jump_entry *entry)
252 struct static_key *key = jump_entry_key(entry);
253 bool enabled = static_key_enabled(key);
254 bool branch = jump_entry_branch(entry);
256 /* See the comment in linux/jump_label.h */
257 return enabled ^ branch;
260 static void __jump_label_update(struct static_key *key,
261 struct jump_entry *entry,
262 struct jump_entry *stop)
264 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
266 * entry->code set to 0 invalidates module init text sections
267 * kernel_text_address() verifies we are not in core kernel
268 * init code, see jump_label_invalidate_module_init().
270 if (entry->code && kernel_text_address(entry->code))
271 arch_jump_label_transform(entry, jump_label_type(entry));
275 void __init jump_label_init(void)
277 struct jump_entry *iter_start = __start___jump_table;
278 struct jump_entry *iter_stop = __stop___jump_table;
279 struct static_key *key = NULL;
280 struct jump_entry *iter;
283 * Since we are initializing the static_key.enabled field with
284 * with the 'raw' int values (to avoid pulling in atomic.h) in
285 * jump_label.h, let's make sure that is safe. There are only two
286 * cases to check since we initialize to 0 or 1.
288 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
289 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
292 jump_label_sort_entries(iter_start, iter_stop);
294 for (iter = iter_start; iter < iter_stop; iter++) {
295 struct static_key *iterk;
298 if (jump_label_type(iter) == JUMP_LABEL_NOP)
299 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
301 iterk = jump_entry_key(iter);
307 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
309 *((unsigned long *)&key->entries) += (unsigned long)iter;
310 #ifdef CONFIG_MODULES
314 static_key_initialized = true;
318 #ifdef CONFIG_MODULES
320 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
322 struct static_key *key = jump_entry_key(entry);
323 bool type = static_key_type(key);
324 bool branch = jump_entry_branch(entry);
326 /* See the comment in linux/jump_label.h */
327 return type ^ branch;
330 struct static_key_mod {
331 struct static_key_mod *next;
332 struct jump_entry *entries;
336 static int __jump_label_mod_text_reserved(void *start, void *end)
340 mod = __module_text_address((unsigned long)start);
344 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
346 return __jump_label_text_reserved(mod->jump_entries,
347 mod->jump_entries + mod->num_jump_entries,
351 static void __jump_label_mod_update(struct static_key *key)
353 struct static_key_mod *mod;
355 for (mod = key->next; mod; mod = mod->next) {
356 struct module *m = mod->mod;
358 __jump_label_update(key, mod->entries,
359 m->jump_entries + m->num_jump_entries);
364 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
365 * @mod: module to patch
367 * Allow for run-time selection of the optimal nops. Before the module
368 * loads patch these with arch_get_jump_label_nop(), which is specified by
369 * the arch specific jump label code.
371 void jump_label_apply_nops(struct module *mod)
373 struct jump_entry *iter_start = mod->jump_entries;
374 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
375 struct jump_entry *iter;
377 /* if the module doesn't have jump label entries, just return */
378 if (iter_start == iter_stop)
381 for (iter = iter_start; iter < iter_stop; iter++) {
382 /* Only write NOPs for arch_branch_static(). */
383 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
384 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
388 static int jump_label_add_module(struct module *mod)
390 struct jump_entry *iter_start = mod->jump_entries;
391 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
392 struct jump_entry *iter;
393 struct static_key *key = NULL;
394 struct static_key_mod *jlm;
396 /* if the module doesn't have jump label entries, just return */
397 if (iter_start == iter_stop)
400 jump_label_sort_entries(iter_start, iter_stop);
402 for (iter = iter_start; iter < iter_stop; iter++) {
403 struct static_key *iterk;
405 iterk = jump_entry_key(iter);
410 if (within_module(iter->key, mod)) {
412 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
414 *((unsigned long *)&key->entries) += (unsigned long)iter;
418 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
423 jlm->next = key->next;
426 /* Only update if we've changed from our initial state */
427 if (jump_label_type(iter) != jump_label_init_type(iter))
428 __jump_label_update(key, iter, iter_stop);
434 static void jump_label_del_module(struct module *mod)
436 struct jump_entry *iter_start = mod->jump_entries;
437 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
438 struct jump_entry *iter;
439 struct static_key *key = NULL;
440 struct static_key_mod *jlm, **prev;
442 for (iter = iter_start; iter < iter_stop; iter++) {
443 if (jump_entry_key(iter) == key)
446 key = jump_entry_key(iter);
448 if (within_module(iter->key, mod))
454 while (jlm && jlm->mod != mod) {
466 static void jump_label_invalidate_module_init(struct module *mod)
468 struct jump_entry *iter_start = mod->jump_entries;
469 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
470 struct jump_entry *iter;
472 for (iter = iter_start; iter < iter_stop; iter++) {
473 if (within_module_init(iter->code, mod))
479 jump_label_module_notify(struct notifier_block *self, unsigned long val,
482 struct module *mod = data;
486 case MODULE_STATE_COMING:
488 ret = jump_label_add_module(mod);
490 jump_label_del_module(mod);
493 case MODULE_STATE_GOING:
495 jump_label_del_module(mod);
498 case MODULE_STATE_LIVE:
500 jump_label_invalidate_module_init(mod);
505 return notifier_from_errno(ret);
508 static struct notifier_block jump_label_module_nb = {
509 .notifier_call = jump_label_module_notify,
510 .priority = 1, /* higher than tracepoints */
513 static __init int jump_label_init_module(void)
515 return register_module_notifier(&jump_label_module_nb);
517 early_initcall(jump_label_init_module);
519 #endif /* CONFIG_MODULES */
522 * jump_label_text_reserved - check if addr range is reserved
523 * @start: start text addr
524 * @end: end text addr
526 * checks if the text addr located between @start and @end
527 * overlaps with any of the jump label patch addresses. Code
528 * that wants to modify kernel text should first verify that
529 * it does not overlap with any of the jump label addresses.
530 * Caller must hold jump_label_mutex.
532 * returns 1 if there is an overlap, 0 otherwise
534 int jump_label_text_reserved(void *start, void *end)
536 int ret = __jump_label_text_reserved(__start___jump_table,
537 __stop___jump_table, start, end);
542 #ifdef CONFIG_MODULES
543 ret = __jump_label_mod_text_reserved(start, end);
548 static void jump_label_update(struct static_key *key)
550 struct jump_entry *stop = __stop___jump_table;
551 struct jump_entry *entry = static_key_entries(key);
552 #ifdef CONFIG_MODULES
555 __jump_label_mod_update(key);
558 mod = __module_address((unsigned long)key);
560 stop = mod->jump_entries + mod->num_jump_entries;
563 /* if there are no users, entry can be NULL */
565 __jump_label_update(key, entry, stop);
568 #ifdef CONFIG_STATIC_KEYS_SELFTEST
569 static DEFINE_STATIC_KEY_TRUE(sk_true);
570 static DEFINE_STATIC_KEY_FALSE(sk_false);
572 static __init int jump_label_test(void)
576 for (i = 0; i < 2; i++) {
577 WARN_ON(static_key_enabled(&sk_true.key) != true);
578 WARN_ON(static_key_enabled(&sk_false.key) != false);
580 WARN_ON(!static_branch_likely(&sk_true));
581 WARN_ON(!static_branch_unlikely(&sk_true));
582 WARN_ON(static_branch_likely(&sk_false));
583 WARN_ON(static_branch_unlikely(&sk_false));
585 static_branch_disable(&sk_true);
586 static_branch_enable(&sk_false);
588 WARN_ON(static_key_enabled(&sk_true.key) == true);
589 WARN_ON(static_key_enabled(&sk_false.key) == false);
591 WARN_ON(static_branch_likely(&sk_true));
592 WARN_ON(static_branch_unlikely(&sk_true));
593 WARN_ON(!static_branch_likely(&sk_false));
594 WARN_ON(!static_branch_unlikely(&sk_false));
596 static_branch_enable(&sk_true);
597 static_branch_disable(&sk_false);
602 late_initcall(jump_label_test);
603 #endif /* STATIC_KEYS_SELFTEST */
605 #endif /* HAVE_JUMP_LABEL */