1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * jump label support
4 *
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6 * Copyright (C) 2011 Peter Zijlstra
7 *
8 */
9 #include <linux/memory.h>
10 #include <linux/uaccess.h>
11 #include <linux/module.h>
12 #include <linux/list.h>
13 #include <linux/slab.h>
14 #include <linux/sort.h>
15 #include <linux/err.h>
16 #include <linux/static_key.h>
17 #include <linux/jump_label_ratelimit.h>
18 #include <linux/bug.h>
19 #include <linux/cpu.h>
20 #include <asm/sections.h>
21
22 /* mutex to protect coming/going of the jump_label table */
23 static DEFINE_MUTEX(jump_label_mutex);
24
jump_label_lock(void)25 void jump_label_lock(void)
26 {
27 mutex_lock(&jump_label_mutex);
28 }
29
jump_label_unlock(void)30 void jump_label_unlock(void)
31 {
32 mutex_unlock(&jump_label_mutex);
33 }
34
jump_label_cmp(const void * a,const void * b)35 static int jump_label_cmp(const void *a, const void *b)
36 {
37 const struct jump_entry *jea = a;
38 const struct jump_entry *jeb = b;
39
40 /*
41 * Entrires are sorted by key.
42 */
43 if (jump_entry_key(jea) < jump_entry_key(jeb))
44 return -1;
45
46 if (jump_entry_key(jea) > jump_entry_key(jeb))
47 return 1;
48
49 /*
50 * In the batching mode, entries should also be sorted by the code
51 * inside the already sorted list of entries, enabling a bsearch in
52 * the vector.
53 */
54 if (jump_entry_code(jea) < jump_entry_code(jeb))
55 return -1;
56
57 if (jump_entry_code(jea) > jump_entry_code(jeb))
58 return 1;
59
60 return 0;
61 }
62
jump_label_swap(void * a,void * b,int size)63 static void jump_label_swap(void *a, void *b, int size)
64 {
65 long delta = (unsigned long)a - (unsigned long)b;
66 struct jump_entry *jea = a;
67 struct jump_entry *jeb = b;
68 struct jump_entry tmp = *jea;
69
70 jea->code = jeb->code - delta;
71 jea->target = jeb->target - delta;
72 jea->key = jeb->key - delta;
73
74 jeb->code = tmp.code + delta;
75 jeb->target = tmp.target + delta;
76 jeb->key = tmp.key + delta;
77 }
78
79 static void
jump_label_sort_entries(struct jump_entry * start,struct jump_entry * stop)80 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
81 {
82 unsigned long size;
83 void *swapfn = NULL;
84
85 if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
86 swapfn = jump_label_swap;
87
88 size = (((unsigned long)stop - (unsigned long)start)
89 / sizeof(struct jump_entry));
90 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
91 }
92
93 static void jump_label_update(struct static_key *key);
94
95 /*
96 * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
97 * The use of 'atomic_read()' requires atomic.h and its problematic for some
98 * kernel headers such as kernel.h and others. Since static_key_count() is not
99 * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
100 * to have it be a function here. Similarly, for 'static_key_enable()' and
101 * 'static_key_disable()', which require bug.h. This should allow jump_label.h
102 * to be included from most/all places for CONFIG_JUMP_LABEL.
103 */
static_key_count(struct static_key * key)104 int static_key_count(struct static_key *key)
105 {
106 /*
107 * -1 means the first static_key_slow_inc() is in progress.
108 * static_key_enabled() must return true, so return 1 here.
109 */
110 int n = atomic_read(&key->enabled);
111
112 return n >= 0 ? n : 1;
113 }
114 EXPORT_SYMBOL_GPL(static_key_count);
115
116 /*
117 * static_key_fast_inc_not_disabled - adds a user for a static key
118 * @key: static key that must be already enabled
119 *
120 * The caller must make sure that the static key can't get disabled while
121 * in this function. It doesn't patch jump labels, only adds a user to
122 * an already enabled static key.
123 *
124 * Returns true if the increment was done. Unlike refcount_t the ref counter
125 * is not saturated, but will fail to increment on overflow.
126 */
static_key_fast_inc_not_disabled(struct static_key * key)127 bool static_key_fast_inc_not_disabled(struct static_key *key)
128 {
129 int v;
130
131 STATIC_KEY_CHECK_USE(key);
132 /*
133 * Negative key->enabled has a special meaning: it sends
134 * static_key_slow_inc/dec() down the slow path, and it is non-zero
135 * so it counts as "enabled" in jump_label_update(). Note that
136 * atomic_inc_unless_negative() checks >= 0, so roll our own.
137 */
138 v = atomic_read(&key->enabled);
139 do {
140 if (v <= 0 || (v + 1) < 0)
141 return false;
142 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
143
144 return true;
145 }
146 EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
147
static_key_slow_inc_cpuslocked(struct static_key * key)148 bool static_key_slow_inc_cpuslocked(struct static_key *key)
149 {
150 lockdep_assert_cpus_held();
151
152 /*
153 * Careful if we get concurrent static_key_slow_inc/dec() calls;
154 * later calls must wait for the first one to _finish_ the
155 * jump_label_update() process. At the same time, however,
156 * the jump_label_update() call below wants to see
157 * static_key_enabled(&key) for jumps to be updated properly.
158 */
159 if (static_key_fast_inc_not_disabled(key))
160 return true;
161
162 jump_label_lock();
163 if (atomic_read(&key->enabled) == 0) {
164 atomic_set(&key->enabled, -1);
165 jump_label_update(key);
166 /*
167 * Ensure that if the above cmpxchg loop observes our positive
168 * value, it must also observe all the text changes.
169 */
170 atomic_set_release(&key->enabled, 1);
171 } else {
172 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key))) {
173 jump_label_unlock();
174 return false;
175 }
176 }
177 jump_label_unlock();
178 return true;
179 }
180
static_key_slow_inc(struct static_key * key)181 bool static_key_slow_inc(struct static_key *key)
182 {
183 bool ret;
184
185 cpus_read_lock();
186 ret = static_key_slow_inc_cpuslocked(key);
187 cpus_read_unlock();
188 return ret;
189 }
190 EXPORT_SYMBOL_GPL(static_key_slow_inc);
191
static_key_enable_cpuslocked(struct static_key * key)192 void static_key_enable_cpuslocked(struct static_key *key)
193 {
194 STATIC_KEY_CHECK_USE(key);
195 lockdep_assert_cpus_held();
196
197 if (atomic_read(&key->enabled) > 0) {
198 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
199 return;
200 }
201
202 jump_label_lock();
203 if (atomic_read(&key->enabled) == 0) {
204 atomic_set(&key->enabled, -1);
205 jump_label_update(key);
206 /*
207 * See static_key_slow_inc().
208 */
209 atomic_set_release(&key->enabled, 1);
210 }
211 jump_label_unlock();
212 }
213 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
214
static_key_enable(struct static_key * key)215 void static_key_enable(struct static_key *key)
216 {
217 cpus_read_lock();
218 static_key_enable_cpuslocked(key);
219 cpus_read_unlock();
220 }
221 EXPORT_SYMBOL_GPL(static_key_enable);
222
static_key_disable_cpuslocked(struct static_key * key)223 void static_key_disable_cpuslocked(struct static_key *key)
224 {
225 STATIC_KEY_CHECK_USE(key);
226 lockdep_assert_cpus_held();
227
228 if (atomic_read(&key->enabled) != 1) {
229 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
230 return;
231 }
232
233 jump_label_lock();
234 if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
235 jump_label_update(key);
236 jump_label_unlock();
237 }
238 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
239
static_key_disable(struct static_key * key)240 void static_key_disable(struct static_key *key)
241 {
242 cpus_read_lock();
243 static_key_disable_cpuslocked(key);
244 cpus_read_unlock();
245 }
246 EXPORT_SYMBOL_GPL(static_key_disable);
247
static_key_slow_try_dec(struct static_key * key)248 static bool static_key_slow_try_dec(struct static_key *key)
249 {
250 int v;
251
252 /*
253 * Go into the slow path if key::enabled is less than or equal than
254 * one. One is valid to shut down the key, anything less than one
255 * is an imbalance, which is handled at the call site.
256 *
257 * That includes the special case of '-1' which is set in
258 * static_key_slow_inc_cpuslocked(), but that's harmless as it is
259 * fully serialized in the slow path below. By the time this task
260 * acquires the jump label lock the value is back to one and the
261 * retry under the lock must succeed.
262 */
263 v = atomic_read(&key->enabled);
264 do {
265 /*
266 * Warn about the '-1' case though; since that means a
267 * decrement is concurrent with a first (0->1) increment. IOW
268 * people are trying to disable something that wasn't yet fully
269 * enabled. This suggests an ordering problem on the user side.
270 */
271 WARN_ON_ONCE(v < 0);
272 if (v <= 1)
273 return false;
274 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
275
276 return true;
277 }
278
__static_key_slow_dec_cpuslocked(struct static_key * key)279 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
280 {
281 lockdep_assert_cpus_held();
282
283 if (static_key_slow_try_dec(key))
284 return;
285
286 guard(mutex)(&jump_label_mutex);
287 if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
288 jump_label_update(key);
289 else
290 WARN_ON_ONCE(!static_key_slow_try_dec(key));
291 }
292
__static_key_slow_dec(struct static_key * key)293 static void __static_key_slow_dec(struct static_key *key)
294 {
295 cpus_read_lock();
296 __static_key_slow_dec_cpuslocked(key);
297 cpus_read_unlock();
298 }
299
jump_label_update_timeout(struct work_struct * work)300 void jump_label_update_timeout(struct work_struct *work)
301 {
302 struct static_key_deferred *key =
303 container_of(work, struct static_key_deferred, work.work);
304 __static_key_slow_dec(&key->key);
305 }
306 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
307
static_key_slow_dec(struct static_key * key)308 void static_key_slow_dec(struct static_key *key)
309 {
310 STATIC_KEY_CHECK_USE(key);
311 __static_key_slow_dec(key);
312 }
313 EXPORT_SYMBOL_GPL(static_key_slow_dec);
314
static_key_slow_dec_cpuslocked(struct static_key * key)315 void static_key_slow_dec_cpuslocked(struct static_key *key)
316 {
317 STATIC_KEY_CHECK_USE(key);
318 __static_key_slow_dec_cpuslocked(key);
319 }
320
__static_key_slow_dec_deferred(struct static_key * key,struct delayed_work * work,unsigned long timeout)321 void __static_key_slow_dec_deferred(struct static_key *key,
322 struct delayed_work *work,
323 unsigned long timeout)
324 {
325 STATIC_KEY_CHECK_USE(key);
326
327 if (static_key_slow_try_dec(key))
328 return;
329
330 schedule_delayed_work(work, timeout);
331 }
332 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
333
__static_key_deferred_flush(void * key,struct delayed_work * work)334 void __static_key_deferred_flush(void *key, struct delayed_work *work)
335 {
336 STATIC_KEY_CHECK_USE(key);
337 flush_delayed_work(work);
338 }
339 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
340
jump_label_rate_limit(struct static_key_deferred * key,unsigned long rl)341 void jump_label_rate_limit(struct static_key_deferred *key,
342 unsigned long rl)
343 {
344 STATIC_KEY_CHECK_USE(key);
345 key->timeout = rl;
346 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
347 }
348 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
349
addr_conflict(struct jump_entry * entry,void * start,void * end)350 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
351 {
352 if (jump_entry_code(entry) <= (unsigned long)end &&
353 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
354 return 1;
355
356 return 0;
357 }
358
__jump_label_text_reserved(struct jump_entry * iter_start,struct jump_entry * iter_stop,void * start,void * end,bool init)359 static int __jump_label_text_reserved(struct jump_entry *iter_start,
360 struct jump_entry *iter_stop, void *start, void *end, bool init)
361 {
362 struct jump_entry *iter;
363
364 iter = iter_start;
365 while (iter < iter_stop) {
366 if (init || !jump_entry_is_init(iter)) {
367 if (addr_conflict(iter, start, end))
368 return 1;
369 }
370 iter++;
371 }
372
373 return 0;
374 }
375
376 #ifndef arch_jump_label_transform_static
arch_jump_label_transform_static(struct jump_entry * entry,enum jump_label_type type)377 static void arch_jump_label_transform_static(struct jump_entry *entry,
378 enum jump_label_type type)
379 {
380 /* nothing to do on most architectures */
381 }
382 #endif
383
static_key_entries(struct static_key * key)384 static inline struct jump_entry *static_key_entries(struct static_key *key)
385 {
386 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
387 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
388 }
389
static_key_type(struct static_key * key)390 static inline bool static_key_type(struct static_key *key)
391 {
392 return key->type & JUMP_TYPE_TRUE;
393 }
394
static_key_linked(struct static_key * key)395 static inline bool static_key_linked(struct static_key *key)
396 {
397 return key->type & JUMP_TYPE_LINKED;
398 }
399
static_key_clear_linked(struct static_key * key)400 static inline void static_key_clear_linked(struct static_key *key)
401 {
402 key->type &= ~JUMP_TYPE_LINKED;
403 }
404
static_key_set_linked(struct static_key * key)405 static inline void static_key_set_linked(struct static_key *key)
406 {
407 key->type |= JUMP_TYPE_LINKED;
408 }
409
410 /***
411 * A 'struct static_key' uses a union such that it either points directly
412 * to a table of 'struct jump_entry' or to a linked list of modules which in
413 * turn point to 'struct jump_entry' tables.
414 *
415 * The two lower bits of the pointer are used to keep track of which pointer
416 * type is in use and to store the initial branch direction, we use an access
417 * function which preserves these bits.
418 */
static_key_set_entries(struct static_key * key,struct jump_entry * entries)419 static void static_key_set_entries(struct static_key *key,
420 struct jump_entry *entries)
421 {
422 unsigned long type;
423
424 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
425 type = key->type & JUMP_TYPE_MASK;
426 key->entries = entries;
427 key->type |= type;
428 }
429
jump_label_type(struct jump_entry * entry)430 static enum jump_label_type jump_label_type(struct jump_entry *entry)
431 {
432 struct static_key *key = jump_entry_key(entry);
433 bool enabled = static_key_enabled(key);
434 bool branch = jump_entry_is_branch(entry);
435
436 /* See the comment in linux/jump_label.h */
437 return enabled ^ branch;
438 }
439
jump_label_can_update(struct jump_entry * entry,bool init)440 static bool jump_label_can_update(struct jump_entry *entry, bool init)
441 {
442 /*
443 * Cannot update code that was in an init text area.
444 */
445 if (!init && jump_entry_is_init(entry))
446 return false;
447
448 if (!kernel_text_address(jump_entry_code(entry))) {
449 /*
450 * This skips patching built-in __exit, which
451 * is part of init_section_contains() but is
452 * not part of kernel_text_address().
453 *
454 * Skipping built-in __exit is fine since it
455 * will never be executed.
456 */
457 WARN_ONCE(!jump_entry_is_init(entry),
458 "can't patch jump_label at %pS",
459 (void *)jump_entry_code(entry));
460 return false;
461 }
462
463 return true;
464 }
465
466 #ifndef HAVE_JUMP_LABEL_BATCH
__jump_label_update(struct static_key * key,struct jump_entry * entry,struct jump_entry * stop,bool init)467 static void __jump_label_update(struct static_key *key,
468 struct jump_entry *entry,
469 struct jump_entry *stop,
470 bool init)
471 {
472 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
473 if (jump_label_can_update(entry, init))
474 arch_jump_label_transform(entry, jump_label_type(entry));
475 }
476 }
477 #else
__jump_label_update(struct static_key * key,struct jump_entry * entry,struct jump_entry * stop,bool init)478 static void __jump_label_update(struct static_key *key,
479 struct jump_entry *entry,
480 struct jump_entry *stop,
481 bool init)
482 {
483 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
484
485 if (!jump_label_can_update(entry, init))
486 continue;
487
488 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
489 /*
490 * Queue is full: Apply the current queue and try again.
491 */
492 arch_jump_label_transform_apply();
493 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
494 }
495 }
496 arch_jump_label_transform_apply();
497 }
498 #endif
499
jump_label_init(void)500 void __init jump_label_init(void)
501 {
502 struct jump_entry *iter_start = __start___jump_table;
503 struct jump_entry *iter_stop = __stop___jump_table;
504 struct static_key *key = NULL;
505 struct jump_entry *iter;
506
507 /*
508 * Since we are initializing the static_key.enabled field with
509 * with the 'raw' int values (to avoid pulling in atomic.h) in
510 * jump_label.h, let's make sure that is safe. There are only two
511 * cases to check since we initialize to 0 or 1.
512 */
513 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
514 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
515
516 if (static_key_initialized)
517 return;
518
519 cpus_read_lock();
520 jump_label_lock();
521 jump_label_sort_entries(iter_start, iter_stop);
522
523 for (iter = iter_start; iter < iter_stop; iter++) {
524 struct static_key *iterk;
525 bool in_init;
526
527 /* rewrite NOPs */
528 if (jump_label_type(iter) == JUMP_LABEL_NOP)
529 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
530
531 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
532 jump_entry_set_init(iter, in_init);
533
534 iterk = jump_entry_key(iter);
535 if (iterk == key)
536 continue;
537
538 key = iterk;
539 static_key_set_entries(key, iter);
540 }
541 static_key_initialized = true;
542 jump_label_unlock();
543 cpus_read_unlock();
544 }
545
546 #ifdef CONFIG_MODULES
547
jump_label_init_type(struct jump_entry * entry)548 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
549 {
550 struct static_key *key = jump_entry_key(entry);
551 bool type = static_key_type(key);
552 bool branch = jump_entry_is_branch(entry);
553
554 /* See the comment in linux/jump_label.h */
555 return type ^ branch;
556 }
557
558 struct static_key_mod {
559 struct static_key_mod *next;
560 struct jump_entry *entries;
561 struct module *mod;
562 };
563
static_key_mod(struct static_key * key)564 static inline struct static_key_mod *static_key_mod(struct static_key *key)
565 {
566 WARN_ON_ONCE(!static_key_linked(key));
567 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
568 }
569
570 /***
571 * key->type and key->next are the same via union.
572 * This sets key->next and preserves the type bits.
573 *
574 * See additional comments above static_key_set_entries().
575 */
static_key_set_mod(struct static_key * key,struct static_key_mod * mod)576 static void static_key_set_mod(struct static_key *key,
577 struct static_key_mod *mod)
578 {
579 unsigned long type;
580
581 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
582 type = key->type & JUMP_TYPE_MASK;
583 key->next = mod;
584 key->type |= type;
585 }
586
__jump_label_mod_text_reserved(void * start,void * end)587 static int __jump_label_mod_text_reserved(void *start, void *end)
588 {
589 struct module *mod;
590 int ret;
591
592 preempt_disable();
593 mod = __module_text_address((unsigned long)start);
594 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
595 if (!try_module_get(mod))
596 mod = NULL;
597 preempt_enable();
598
599 if (!mod)
600 return 0;
601
602 ret = __jump_label_text_reserved(mod->jump_entries,
603 mod->jump_entries + mod->num_jump_entries,
604 start, end, mod->state == MODULE_STATE_COMING);
605
606 module_put(mod);
607
608 return ret;
609 }
610
__jump_label_mod_update(struct static_key * key)611 static void __jump_label_mod_update(struct static_key *key)
612 {
613 struct static_key_mod *mod;
614
615 for (mod = static_key_mod(key); mod; mod = mod->next) {
616 struct jump_entry *stop;
617 struct module *m;
618
619 /*
620 * NULL if the static_key is defined in a module
621 * that does not use it
622 */
623 if (!mod->entries)
624 continue;
625
626 m = mod->mod;
627 if (!m)
628 stop = __stop___jump_table;
629 else
630 stop = m->jump_entries + m->num_jump_entries;
631 __jump_label_update(key, mod->entries, stop,
632 m && m->state == MODULE_STATE_COMING);
633 }
634 }
635
jump_label_add_module(struct module * mod)636 static int jump_label_add_module(struct module *mod)
637 {
638 struct jump_entry *iter_start = mod->jump_entries;
639 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
640 struct jump_entry *iter;
641 struct static_key *key = NULL;
642 struct static_key_mod *jlm, *jlm2;
643
644 /* if the module doesn't have jump label entries, just return */
645 if (iter_start == iter_stop)
646 return 0;
647
648 jump_label_sort_entries(iter_start, iter_stop);
649
650 for (iter = iter_start; iter < iter_stop; iter++) {
651 struct static_key *iterk;
652 bool in_init;
653
654 in_init = within_module_init(jump_entry_code(iter), mod);
655 jump_entry_set_init(iter, in_init);
656
657 iterk = jump_entry_key(iter);
658 if (iterk == key)
659 continue;
660
661 key = iterk;
662 if (within_module((unsigned long)key, mod)) {
663 static_key_set_entries(key, iter);
664 continue;
665 }
666 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
667 if (!jlm)
668 return -ENOMEM;
669 if (!static_key_linked(key)) {
670 jlm2 = kzalloc(sizeof(struct static_key_mod),
671 GFP_KERNEL);
672 if (!jlm2) {
673 kfree(jlm);
674 return -ENOMEM;
675 }
676 preempt_disable();
677 jlm2->mod = __module_address((unsigned long)key);
678 preempt_enable();
679 jlm2->entries = static_key_entries(key);
680 jlm2->next = NULL;
681 static_key_set_mod(key, jlm2);
682 static_key_set_linked(key);
683 }
684 jlm->mod = mod;
685 jlm->entries = iter;
686 jlm->next = static_key_mod(key);
687 static_key_set_mod(key, jlm);
688 static_key_set_linked(key);
689
690 /* Only update if we've changed from our initial state */
691 if (jump_label_type(iter) != jump_label_init_type(iter))
692 __jump_label_update(key, iter, iter_stop, true);
693 }
694
695 return 0;
696 }
697
jump_label_del_module(struct module * mod)698 static void jump_label_del_module(struct module *mod)
699 {
700 struct jump_entry *iter_start = mod->jump_entries;
701 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
702 struct jump_entry *iter;
703 struct static_key *key = NULL;
704 struct static_key_mod *jlm, **prev;
705
706 for (iter = iter_start; iter < iter_stop; iter++) {
707 if (jump_entry_key(iter) == key)
708 continue;
709
710 key = jump_entry_key(iter);
711
712 if (within_module((unsigned long)key, mod))
713 continue;
714
715 /* No memory during module load */
716 if (WARN_ON(!static_key_linked(key)))
717 continue;
718
719 prev = &key->next;
720 jlm = static_key_mod(key);
721
722 while (jlm && jlm->mod != mod) {
723 prev = &jlm->next;
724 jlm = jlm->next;
725 }
726
727 /* No memory during module load */
728 if (WARN_ON(!jlm))
729 continue;
730
731 if (prev == &key->next)
732 static_key_set_mod(key, jlm->next);
733 else
734 *prev = jlm->next;
735
736 kfree(jlm);
737
738 jlm = static_key_mod(key);
739 /* if only one etry is left, fold it back into the static_key */
740 if (jlm->next == NULL) {
741 static_key_set_entries(key, jlm->entries);
742 static_key_clear_linked(key);
743 kfree(jlm);
744 }
745 }
746 }
747
748 static int
jump_label_module_notify(struct notifier_block * self,unsigned long val,void * data)749 jump_label_module_notify(struct notifier_block *self, unsigned long val,
750 void *data)
751 {
752 struct module *mod = data;
753 int ret = 0;
754
755 cpus_read_lock();
756 jump_label_lock();
757
758 switch (val) {
759 case MODULE_STATE_COMING:
760 ret = jump_label_add_module(mod);
761 if (ret) {
762 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
763 jump_label_del_module(mod);
764 }
765 break;
766 case MODULE_STATE_GOING:
767 jump_label_del_module(mod);
768 break;
769 }
770
771 jump_label_unlock();
772 cpus_read_unlock();
773
774 return notifier_from_errno(ret);
775 }
776
777 static struct notifier_block jump_label_module_nb = {
778 .notifier_call = jump_label_module_notify,
779 .priority = 1, /* higher than tracepoints */
780 };
781
jump_label_init_module(void)782 static __init int jump_label_init_module(void)
783 {
784 return register_module_notifier(&jump_label_module_nb);
785 }
786 early_initcall(jump_label_init_module);
787
788 #endif /* CONFIG_MODULES */
789
790 /***
791 * jump_label_text_reserved - check if addr range is reserved
792 * @start: start text addr
793 * @end: end text addr
794 *
795 * checks if the text addr located between @start and @end
796 * overlaps with any of the jump label patch addresses. Code
797 * that wants to modify kernel text should first verify that
798 * it does not overlap with any of the jump label addresses.
799 * Caller must hold jump_label_mutex.
800 *
801 * returns 1 if there is an overlap, 0 otherwise
802 */
jump_label_text_reserved(void * start,void * end)803 int jump_label_text_reserved(void *start, void *end)
804 {
805 bool init = system_state < SYSTEM_RUNNING;
806 int ret = __jump_label_text_reserved(__start___jump_table,
807 __stop___jump_table, start, end, init);
808
809 if (ret)
810 return ret;
811
812 #ifdef CONFIG_MODULES
813 ret = __jump_label_mod_text_reserved(start, end);
814 #endif
815 return ret;
816 }
817
jump_label_update(struct static_key * key)818 static void jump_label_update(struct static_key *key)
819 {
820 struct jump_entry *stop = __stop___jump_table;
821 bool init = system_state < SYSTEM_RUNNING;
822 struct jump_entry *entry;
823 #ifdef CONFIG_MODULES
824 struct module *mod;
825
826 if (static_key_linked(key)) {
827 __jump_label_mod_update(key);
828 return;
829 }
830
831 preempt_disable();
832 mod = __module_address((unsigned long)key);
833 if (mod) {
834 stop = mod->jump_entries + mod->num_jump_entries;
835 init = mod->state == MODULE_STATE_COMING;
836 }
837 preempt_enable();
838 #endif
839 entry = static_key_entries(key);
840 /* if there are no users, entry can be NULL */
841 if (entry)
842 __jump_label_update(key, entry, stop, init);
843 }
844
845 #ifdef CONFIG_STATIC_KEYS_SELFTEST
846 static DEFINE_STATIC_KEY_TRUE(sk_true);
847 static DEFINE_STATIC_KEY_FALSE(sk_false);
848
jump_label_test(void)849 static __init int jump_label_test(void)
850 {
851 int i;
852
853 for (i = 0; i < 2; i++) {
854 WARN_ON(static_key_enabled(&sk_true.key) != true);
855 WARN_ON(static_key_enabled(&sk_false.key) != false);
856
857 WARN_ON(!static_branch_likely(&sk_true));
858 WARN_ON(!static_branch_unlikely(&sk_true));
859 WARN_ON(static_branch_likely(&sk_false));
860 WARN_ON(static_branch_unlikely(&sk_false));
861
862 static_branch_disable(&sk_true);
863 static_branch_enable(&sk_false);
864
865 WARN_ON(static_key_enabled(&sk_true.key) == true);
866 WARN_ON(static_key_enabled(&sk_false.key) == false);
867
868 WARN_ON(static_branch_likely(&sk_true));
869 WARN_ON(static_branch_unlikely(&sk_true));
870 WARN_ON(!static_branch_likely(&sk_false));
871 WARN_ON(!static_branch_unlikely(&sk_false));
872
873 static_branch_enable(&sk_true);
874 static_branch_disable(&sk_false);
875 }
876
877 return 0;
878 }
879 early_initcall(jump_label_test);
880 #endif /* STATIC_KEYS_SELFTEST */
881