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
)
341 mod
= __module_text_address((unsigned long)start
);
342 WARN_ON_ONCE(__module_text_address((unsigned long)end
) != mod
);
349 return __jump_label_text_reserved(mod
->jump_entries
,
350 mod
->jump_entries
+ mod
->num_jump_entries
,
354 static void __jump_label_mod_update(struct static_key
*key
)
356 struct static_key_mod
*mod
;
358 for (mod
= key
->next
; mod
; mod
= mod
->next
) {
359 struct module
*m
= mod
->mod
;
361 __jump_label_update(key
, mod
->entries
,
362 m
->jump_entries
+ m
->num_jump_entries
);
367 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
368 * @mod: module to patch
370 * Allow for run-time selection of the optimal nops. Before the module
371 * loads patch these with arch_get_jump_label_nop(), which is specified by
372 * the arch specific jump label code.
374 void jump_label_apply_nops(struct module
*mod
)
376 struct jump_entry
*iter_start
= mod
->jump_entries
;
377 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
378 struct jump_entry
*iter
;
380 /* if the module doesn't have jump label entries, just return */
381 if (iter_start
== iter_stop
)
384 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
385 /* Only write NOPs for arch_branch_static(). */
386 if (jump_label_init_type(iter
) == JUMP_LABEL_NOP
)
387 arch_jump_label_transform_static(iter
, JUMP_LABEL_NOP
);
391 static int jump_label_add_module(struct module
*mod
)
393 struct jump_entry
*iter_start
= mod
->jump_entries
;
394 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
395 struct jump_entry
*iter
;
396 struct static_key
*key
= NULL
;
397 struct static_key_mod
*jlm
;
399 /* if the module doesn't have jump label entries, just return */
400 if (iter_start
== iter_stop
)
403 jump_label_sort_entries(iter_start
, iter_stop
);
405 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
406 struct static_key
*iterk
;
408 iterk
= jump_entry_key(iter
);
413 if (within_module(iter
->key
, mod
)) {
415 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
417 *((unsigned long *)&key
->entries
) += (unsigned long)iter
;
421 jlm
= kzalloc(sizeof(struct static_key_mod
), GFP_KERNEL
);
426 jlm
->next
= key
->next
;
429 /* Only update if we've changed from our initial state */
430 if (jump_label_type(iter
) != jump_label_init_type(iter
))
431 __jump_label_update(key
, iter
, iter_stop
);
437 static void jump_label_del_module(struct module
*mod
)
439 struct jump_entry
*iter_start
= mod
->jump_entries
;
440 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
441 struct jump_entry
*iter
;
442 struct static_key
*key
= NULL
;
443 struct static_key_mod
*jlm
, **prev
;
445 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
446 if (jump_entry_key(iter
) == key
)
449 key
= jump_entry_key(iter
);
451 if (within_module(iter
->key
, mod
))
457 while (jlm
&& jlm
->mod
!= mod
) {
469 static void jump_label_invalidate_module_init(struct module
*mod
)
471 struct jump_entry
*iter_start
= mod
->jump_entries
;
472 struct jump_entry
*iter_stop
= iter_start
+ mod
->num_jump_entries
;
473 struct jump_entry
*iter
;
475 for (iter
= iter_start
; iter
< iter_stop
; iter
++) {
476 if (within_module_init(iter
->code
, mod
))
482 jump_label_module_notify(struct notifier_block
*self
, unsigned long val
,
485 struct module
*mod
= data
;
489 case MODULE_STATE_COMING
:
491 ret
= jump_label_add_module(mod
);
493 jump_label_del_module(mod
);
496 case MODULE_STATE_GOING
:
498 jump_label_del_module(mod
);
501 case MODULE_STATE_LIVE
:
503 jump_label_invalidate_module_init(mod
);
508 return notifier_from_errno(ret
);
511 static struct notifier_block jump_label_module_nb
= {
512 .notifier_call
= jump_label_module_notify
,
513 .priority
= 1, /* higher than tracepoints */
516 static __init
int jump_label_init_module(void)
518 return register_module_notifier(&jump_label_module_nb
);
520 early_initcall(jump_label_init_module
);
522 #endif /* CONFIG_MODULES */
525 * jump_label_text_reserved - check if addr range is reserved
526 * @start: start text addr
527 * @end: end text addr
529 * checks if the text addr located between @start and @end
530 * overlaps with any of the jump label patch addresses. Code
531 * that wants to modify kernel text should first verify that
532 * it does not overlap with any of the jump label addresses.
533 * Caller must hold jump_label_mutex.
535 * returns 1 if there is an overlap, 0 otherwise
537 int jump_label_text_reserved(void *start
, void *end
)
539 int ret
= __jump_label_text_reserved(__start___jump_table
,
540 __stop___jump_table
, start
, end
);
545 #ifdef CONFIG_MODULES
546 ret
= __jump_label_mod_text_reserved(start
, end
);
551 static void jump_label_update(struct static_key
*key
)
553 struct jump_entry
*stop
= __stop___jump_table
;
554 struct jump_entry
*entry
= static_key_entries(key
);
555 #ifdef CONFIG_MODULES
558 __jump_label_mod_update(key
);
561 mod
= __module_address((unsigned long)key
);
563 stop
= mod
->jump_entries
+ mod
->num_jump_entries
;
566 /* if there are no users, entry can be NULL */
568 __jump_label_update(key
, entry
, stop
);
571 #ifdef CONFIG_STATIC_KEYS_SELFTEST
572 static DEFINE_STATIC_KEY_TRUE(sk_true
);
573 static DEFINE_STATIC_KEY_FALSE(sk_false
);
575 static __init
int jump_label_test(void)
579 for (i
= 0; i
< 2; i
++) {
580 WARN_ON(static_key_enabled(&sk_true
.key
) != true);
581 WARN_ON(static_key_enabled(&sk_false
.key
) != false);
583 WARN_ON(!static_branch_likely(&sk_true
));
584 WARN_ON(!static_branch_unlikely(&sk_true
));
585 WARN_ON(static_branch_likely(&sk_false
));
586 WARN_ON(static_branch_unlikely(&sk_false
));
588 static_branch_disable(&sk_true
);
589 static_branch_enable(&sk_false
);
591 WARN_ON(static_key_enabled(&sk_true
.key
) == true);
592 WARN_ON(static_key_enabled(&sk_false
.key
) == false);
594 WARN_ON(static_branch_likely(&sk_true
));
595 WARN_ON(static_branch_unlikely(&sk_true
));
596 WARN_ON(!static_branch_likely(&sk_false
));
597 WARN_ON(!static_branch_unlikely(&sk_false
));
599 static_branch_enable(&sk_true
);
600 static_branch_disable(&sk_false
);
605 late_initcall(jump_label_test
);
606 #endif /* STATIC_KEYS_SELFTEST */
608 #endif /* HAVE_JUMP_LABEL */