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().
136 *
137 * The INT_MAX overflow condition is either used by the networking
138 * code to reset or detected in the slow path of
139 * static_key_slow_inc_cpuslocked().
140 */
141 v = atomic_read(&key->enabled);
142 do {
143 if (v <= 0 || v == INT_MAX)
144 return false;
145 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
146
147 return true;
148 }
149 EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
150
static_key_slow_inc_cpuslocked(struct static_key * key)151 bool static_key_slow_inc_cpuslocked(struct static_key *key)
152 {
153 lockdep_assert_cpus_held();
154
155 /*
156 * Careful if we get concurrent static_key_slow_inc/dec() calls;
157 * later calls must wait for the first one to _finish_ the
158 * jump_label_update() process. At the same time, however,
159 * the jump_label_update() call below wants to see
160 * static_key_enabled(&key) for jumps to be updated properly.
161 */
162 if (static_key_fast_inc_not_disabled(key))
163 return true;
164
165 guard(mutex)(&jump_label_mutex);
166 /* Try to mark it as 'enabling in progress. */
167 if (!atomic_cmpxchg(&key->enabled, 0, -1)) {
168 jump_label_update(key);
169 /*
170 * Ensure that when static_key_fast_inc_not_disabled() or
171 * static_key_slow_try_dec() observe the positive value,
172 * they must also observe all the text changes.
173 */
174 atomic_set_release(&key->enabled, 1);
175 } else {
176 /*
177 * While holding the mutex this should never observe
178 * anything else than a value >= 1 and succeed
179 */
180 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key)))
181 return false;
182 }
183 return true;
184 }
185
static_key_slow_inc(struct static_key * key)186 bool static_key_slow_inc(struct static_key *key)
187 {
188 bool ret;
189
190 cpus_read_lock();
191 ret = static_key_slow_inc_cpuslocked(key);
192 cpus_read_unlock();
193 return ret;
194 }
195 EXPORT_SYMBOL_GPL(static_key_slow_inc);
196
static_key_enable_cpuslocked(struct static_key * key)197 void static_key_enable_cpuslocked(struct static_key *key)
198 {
199 STATIC_KEY_CHECK_USE(key);
200 lockdep_assert_cpus_held();
201
202 if (atomic_read(&key->enabled) > 0) {
203 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
204 return;
205 }
206
207 jump_label_lock();
208 if (atomic_read(&key->enabled) == 0) {
209 atomic_set(&key->enabled, -1);
210 jump_label_update(key);
211 /*
212 * See static_key_slow_inc().
213 */
214 atomic_set_release(&key->enabled, 1);
215 }
216 jump_label_unlock();
217 }
218 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
219
static_key_enable(struct static_key * key)220 void static_key_enable(struct static_key *key)
221 {
222 cpus_read_lock();
223 static_key_enable_cpuslocked(key);
224 cpus_read_unlock();
225 }
226 EXPORT_SYMBOL_GPL(static_key_enable);
227
static_key_disable_cpuslocked(struct static_key * key)228 void static_key_disable_cpuslocked(struct static_key *key)
229 {
230 STATIC_KEY_CHECK_USE(key);
231 lockdep_assert_cpus_held();
232
233 if (atomic_read(&key->enabled) != 1) {
234 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
235 return;
236 }
237
238 jump_label_lock();
239 if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
240 jump_label_update(key);
241 jump_label_unlock();
242 }
243 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
244
static_key_disable(struct static_key * key)245 void static_key_disable(struct static_key *key)
246 {
247 cpus_read_lock();
248 static_key_disable_cpuslocked(key);
249 cpus_read_unlock();
250 }
251 EXPORT_SYMBOL_GPL(static_key_disable);
252
static_key_slow_try_dec(struct static_key * key)253 static bool static_key_slow_try_dec(struct static_key *key)
254 {
255 int v;
256
257 /*
258 * Go into the slow path if key::enabled is less than or equal than
259 * one. One is valid to shut down the key, anything less than one
260 * is an imbalance, which is handled at the call site.
261 *
262 * That includes the special case of '-1' which is set in
263 * static_key_slow_inc_cpuslocked(), but that's harmless as it is
264 * fully serialized in the slow path below. By the time this task
265 * acquires the jump label lock the value is back to one and the
266 * retry under the lock must succeed.
267 */
268 v = atomic_read(&key->enabled);
269 do {
270 /*
271 * Warn about the '-1' case though; since that means a
272 * decrement is concurrent with a first (0->1) increment. IOW
273 * people are trying to disable something that wasn't yet fully
274 * enabled. This suggests an ordering problem on the user side.
275 */
276 WARN_ON_ONCE(v < 0);
277 if (v <= 1)
278 return false;
279 } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
280
281 return true;
282 }
283
__static_key_slow_dec_cpuslocked(struct static_key * key)284 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
285 {
286 lockdep_assert_cpus_held();
287
288 if (static_key_slow_try_dec(key))
289 return;
290
291 guard(mutex)(&jump_label_mutex);
292 if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
293 jump_label_update(key);
294 else
295 WARN_ON_ONCE(!static_key_slow_try_dec(key));
296 }
297
__static_key_slow_dec(struct static_key * key)298 static void __static_key_slow_dec(struct static_key *key)
299 {
300 cpus_read_lock();
301 __static_key_slow_dec_cpuslocked(key);
302 cpus_read_unlock();
303 }
304
jump_label_update_timeout(struct work_struct * work)305 void jump_label_update_timeout(struct work_struct *work)
306 {
307 struct static_key_deferred *key =
308 container_of(work, struct static_key_deferred, work.work);
309 __static_key_slow_dec(&key->key);
310 }
311 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
312
static_key_slow_dec(struct static_key * key)313 void static_key_slow_dec(struct static_key *key)
314 {
315 STATIC_KEY_CHECK_USE(key);
316 __static_key_slow_dec(key);
317 }
318 EXPORT_SYMBOL_GPL(static_key_slow_dec);
319
static_key_slow_dec_cpuslocked(struct static_key * key)320 void static_key_slow_dec_cpuslocked(struct static_key *key)
321 {
322 STATIC_KEY_CHECK_USE(key);
323 __static_key_slow_dec_cpuslocked(key);
324 }
325
__static_key_slow_dec_deferred(struct static_key * key,struct delayed_work * work,unsigned long timeout)326 void __static_key_slow_dec_deferred(struct static_key *key,
327 struct delayed_work *work,
328 unsigned long timeout)
329 {
330 STATIC_KEY_CHECK_USE(key);
331
332 if (static_key_slow_try_dec(key))
333 return;
334
335 schedule_delayed_work(work, timeout);
336 }
337 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
338
__static_key_deferred_flush(void * key,struct delayed_work * work)339 void __static_key_deferred_flush(void *key, struct delayed_work *work)
340 {
341 STATIC_KEY_CHECK_USE(key);
342 flush_delayed_work(work);
343 }
344 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
345
jump_label_rate_limit(struct static_key_deferred * key,unsigned long rl)346 void jump_label_rate_limit(struct static_key_deferred *key,
347 unsigned long rl)
348 {
349 STATIC_KEY_CHECK_USE(key);
350 key->timeout = rl;
351 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
352 }
353 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
354
addr_conflict(struct jump_entry * entry,void * start,void * end)355 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
356 {
357 if (jump_entry_code(entry) <= (unsigned long)end &&
358 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
359 return 1;
360
361 return 0;
362 }
363
__jump_label_text_reserved(struct jump_entry * iter_start,struct jump_entry * iter_stop,void * start,void * end,bool init)364 static int __jump_label_text_reserved(struct jump_entry *iter_start,
365 struct jump_entry *iter_stop, void *start, void *end, bool init)
366 {
367 struct jump_entry *iter;
368
369 iter = iter_start;
370 while (iter < iter_stop) {
371 if (init || !jump_entry_is_init(iter)) {
372 if (addr_conflict(iter, start, end))
373 return 1;
374 }
375 iter++;
376 }
377
378 return 0;
379 }
380
381 #ifndef arch_jump_label_transform_static
arch_jump_label_transform_static(struct jump_entry * entry,enum jump_label_type type)382 static void arch_jump_label_transform_static(struct jump_entry *entry,
383 enum jump_label_type type)
384 {
385 /* nothing to do on most architectures */
386 }
387 #endif
388
static_key_entries(struct static_key * key)389 static inline struct jump_entry *static_key_entries(struct static_key *key)
390 {
391 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
392 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
393 }
394
static_key_type(struct static_key * key)395 static inline bool static_key_type(struct static_key *key)
396 {
397 return key->type & JUMP_TYPE_TRUE;
398 }
399
static_key_linked(struct static_key * key)400 static inline bool static_key_linked(struct static_key *key)
401 {
402 return key->type & JUMP_TYPE_LINKED;
403 }
404
static_key_clear_linked(struct static_key * key)405 static inline void static_key_clear_linked(struct static_key *key)
406 {
407 key->type &= ~JUMP_TYPE_LINKED;
408 }
409
static_key_set_linked(struct static_key * key)410 static inline void static_key_set_linked(struct static_key *key)
411 {
412 key->type |= JUMP_TYPE_LINKED;
413 }
414
415 /***
416 * A 'struct static_key' uses a union such that it either points directly
417 * to a table of 'struct jump_entry' or to a linked list of modules which in
418 * turn point to 'struct jump_entry' tables.
419 *
420 * The two lower bits of the pointer are used to keep track of which pointer
421 * type is in use and to store the initial branch direction, we use an access
422 * function which preserves these bits.
423 */
static_key_set_entries(struct static_key * key,struct jump_entry * entries)424 static void static_key_set_entries(struct static_key *key,
425 struct jump_entry *entries)
426 {
427 unsigned long type;
428
429 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
430 type = key->type & JUMP_TYPE_MASK;
431 key->entries = entries;
432 key->type |= type;
433 }
434
jump_label_type(struct jump_entry * entry)435 static enum jump_label_type jump_label_type(struct jump_entry *entry)
436 {
437 struct static_key *key = jump_entry_key(entry);
438 bool enabled = static_key_enabled(key);
439 bool branch = jump_entry_is_branch(entry);
440
441 /* See the comment in linux/jump_label.h */
442 return enabled ^ branch;
443 }
444
jump_label_can_update(struct jump_entry * entry,bool init)445 static bool jump_label_can_update(struct jump_entry *entry, bool init)
446 {
447 /*
448 * Cannot update code that was in an init text area.
449 */
450 if (!init && jump_entry_is_init(entry))
451 return false;
452
453 if (!kernel_text_address(jump_entry_code(entry))) {
454 /*
455 * This skips patching built-in __exit, which
456 * is part of init_section_contains() but is
457 * not part of kernel_text_address().
458 *
459 * Skipping built-in __exit is fine since it
460 * will never be executed.
461 */
462 WARN_ONCE(!jump_entry_is_init(entry),
463 "can't patch jump_label at %pS",
464 (void *)jump_entry_code(entry));
465 return false;
466 }
467
468 return true;
469 }
470
471 #ifndef HAVE_JUMP_LABEL_BATCH
__jump_label_update(struct static_key * key,struct jump_entry * entry,struct jump_entry * stop,bool init)472 static void __jump_label_update(struct static_key *key,
473 struct jump_entry *entry,
474 struct jump_entry *stop,
475 bool init)
476 {
477 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
478 if (jump_label_can_update(entry, init))
479 arch_jump_label_transform(entry, jump_label_type(entry));
480 }
481 }
482 #else
__jump_label_update(struct static_key * key,struct jump_entry * entry,struct jump_entry * stop,bool init)483 static void __jump_label_update(struct static_key *key,
484 struct jump_entry *entry,
485 struct jump_entry *stop,
486 bool init)
487 {
488 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
489
490 if (!jump_label_can_update(entry, init))
491 continue;
492
493 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
494 /*
495 * Queue is full: Apply the current queue and try again.
496 */
497 arch_jump_label_transform_apply();
498 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
499 }
500 }
501 arch_jump_label_transform_apply();
502 }
503 #endif
504
jump_label_init(void)505 void __init jump_label_init(void)
506 {
507 struct jump_entry *iter_start = __start___jump_table;
508 struct jump_entry *iter_stop = __stop___jump_table;
509 struct static_key *key = NULL;
510 struct jump_entry *iter;
511
512 /*
513 * Since we are initializing the static_key.enabled field with
514 * with the 'raw' int values (to avoid pulling in atomic.h) in
515 * jump_label.h, let's make sure that is safe. There are only two
516 * cases to check since we initialize to 0 or 1.
517 */
518 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
519 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
520
521 if (static_key_initialized)
522 return;
523
524 cpus_read_lock();
525 jump_label_lock();
526 jump_label_sort_entries(iter_start, iter_stop);
527
528 for (iter = iter_start; iter < iter_stop; iter++) {
529 struct static_key *iterk;
530 bool in_init;
531
532 /* rewrite NOPs */
533 if (jump_label_type(iter) == JUMP_LABEL_NOP)
534 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
535
536 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
537 jump_entry_set_init(iter, in_init);
538
539 iterk = jump_entry_key(iter);
540 if (iterk == key)
541 continue;
542
543 key = iterk;
544 static_key_set_entries(key, iter);
545 }
546 static_key_initialized = true;
547 jump_label_unlock();
548 cpus_read_unlock();
549 }
550
static_key_sealed(struct static_key * key)551 static inline bool static_key_sealed(struct static_key *key)
552 {
553 return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK);
554 }
555
static_key_seal(struct static_key * key)556 static inline void static_key_seal(struct static_key *key)
557 {
558 unsigned long type = key->type & JUMP_TYPE_TRUE;
559 key->type = JUMP_TYPE_LINKED | type;
560 }
561
jump_label_init_ro(void)562 void jump_label_init_ro(void)
563 {
564 struct jump_entry *iter_start = __start___jump_table;
565 struct jump_entry *iter_stop = __stop___jump_table;
566 struct jump_entry *iter;
567
568 if (WARN_ON_ONCE(!static_key_initialized))
569 return;
570
571 cpus_read_lock();
572 jump_label_lock();
573
574 for (iter = iter_start; iter < iter_stop; iter++) {
575 struct static_key *iterk = jump_entry_key(iter);
576
577 if (!is_kernel_ro_after_init((unsigned long)iterk))
578 continue;
579
580 if (static_key_sealed(iterk))
581 continue;
582
583 static_key_seal(iterk);
584 }
585
586 jump_label_unlock();
587 cpus_read_unlock();
588 }
589
590 #ifdef CONFIG_MODULES
591
jump_label_init_type(struct jump_entry * entry)592 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
593 {
594 struct static_key *key = jump_entry_key(entry);
595 bool type = static_key_type(key);
596 bool branch = jump_entry_is_branch(entry);
597
598 /* See the comment in linux/jump_label.h */
599 return type ^ branch;
600 }
601
602 struct static_key_mod {
603 struct static_key_mod *next;
604 struct jump_entry *entries;
605 struct module *mod;
606 };
607
static_key_mod(struct static_key * key)608 static inline struct static_key_mod *static_key_mod(struct static_key *key)
609 {
610 WARN_ON_ONCE(!static_key_linked(key));
611 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
612 }
613
614 /***
615 * key->type and key->next are the same via union.
616 * This sets key->next and preserves the type bits.
617 *
618 * See additional comments above static_key_set_entries().
619 */
static_key_set_mod(struct static_key * key,struct static_key_mod * mod)620 static void static_key_set_mod(struct static_key *key,
621 struct static_key_mod *mod)
622 {
623 unsigned long type;
624
625 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
626 type = key->type & JUMP_TYPE_MASK;
627 key->next = mod;
628 key->type |= type;
629 }
630
__jump_label_mod_text_reserved(void * start,void * end)631 static int __jump_label_mod_text_reserved(void *start, void *end)
632 {
633 struct module *mod;
634 int ret;
635
636 preempt_disable();
637 mod = __module_text_address((unsigned long)start);
638 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
639 if (!try_module_get(mod))
640 mod = NULL;
641 preempt_enable();
642
643 if (!mod)
644 return 0;
645
646 ret = __jump_label_text_reserved(mod->jump_entries,
647 mod->jump_entries + mod->num_jump_entries,
648 start, end, mod->state == MODULE_STATE_COMING);
649
650 module_put(mod);
651
652 return ret;
653 }
654
__jump_label_mod_update(struct static_key * key)655 static void __jump_label_mod_update(struct static_key *key)
656 {
657 struct static_key_mod *mod;
658
659 for (mod = static_key_mod(key); mod; mod = mod->next) {
660 struct jump_entry *stop;
661 struct module *m;
662
663 /*
664 * NULL if the static_key is defined in a module
665 * that does not use it
666 */
667 if (!mod->entries)
668 continue;
669
670 m = mod->mod;
671 if (!m)
672 stop = __stop___jump_table;
673 else
674 stop = m->jump_entries + m->num_jump_entries;
675 __jump_label_update(key, mod->entries, stop,
676 m && m->state == MODULE_STATE_COMING);
677 }
678 }
679
jump_label_add_module(struct module * mod)680 static int jump_label_add_module(struct module *mod)
681 {
682 struct jump_entry *iter_start = mod->jump_entries;
683 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
684 struct jump_entry *iter;
685 struct static_key *key = NULL;
686 struct static_key_mod *jlm, *jlm2;
687
688 /* if the module doesn't have jump label entries, just return */
689 if (iter_start == iter_stop)
690 return 0;
691
692 jump_label_sort_entries(iter_start, iter_stop);
693
694 for (iter = iter_start; iter < iter_stop; iter++) {
695 struct static_key *iterk;
696 bool in_init;
697
698 in_init = within_module_init(jump_entry_code(iter), mod);
699 jump_entry_set_init(iter, in_init);
700
701 iterk = jump_entry_key(iter);
702 if (iterk == key)
703 continue;
704
705 key = iterk;
706 if (within_module((unsigned long)key, mod)) {
707 static_key_set_entries(key, iter);
708 continue;
709 }
710
711 /*
712 * If the key was sealed at init, then there's no need to keep a
713 * reference to its module entries - just patch them now and be
714 * done with it.
715 */
716 if (static_key_sealed(key))
717 goto do_poke;
718
719 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
720 if (!jlm)
721 return -ENOMEM;
722 if (!static_key_linked(key)) {
723 jlm2 = kzalloc(sizeof(struct static_key_mod),
724 GFP_KERNEL);
725 if (!jlm2) {
726 kfree(jlm);
727 return -ENOMEM;
728 }
729 preempt_disable();
730 jlm2->mod = __module_address((unsigned long)key);
731 preempt_enable();
732 jlm2->entries = static_key_entries(key);
733 jlm2->next = NULL;
734 static_key_set_mod(key, jlm2);
735 static_key_set_linked(key);
736 }
737 jlm->mod = mod;
738 jlm->entries = iter;
739 jlm->next = static_key_mod(key);
740 static_key_set_mod(key, jlm);
741 static_key_set_linked(key);
742
743 /* Only update if we've changed from our initial state */
744 do_poke:
745 if (jump_label_type(iter) != jump_label_init_type(iter))
746 __jump_label_update(key, iter, iter_stop, true);
747 }
748
749 return 0;
750 }
751
jump_label_del_module(struct module * mod)752 static void jump_label_del_module(struct module *mod)
753 {
754 struct jump_entry *iter_start = mod->jump_entries;
755 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
756 struct jump_entry *iter;
757 struct static_key *key = NULL;
758 struct static_key_mod *jlm, **prev;
759
760 for (iter = iter_start; iter < iter_stop; iter++) {
761 if (jump_entry_key(iter) == key)
762 continue;
763
764 key = jump_entry_key(iter);
765
766 if (within_module((unsigned long)key, mod))
767 continue;
768
769 /* No @jlm allocated because key was sealed at init. */
770 if (static_key_sealed(key))
771 continue;
772
773 /* No memory during module load */
774 if (WARN_ON(!static_key_linked(key)))
775 continue;
776
777 prev = &key->next;
778 jlm = static_key_mod(key);
779
780 while (jlm && jlm->mod != mod) {
781 prev = &jlm->next;
782 jlm = jlm->next;
783 }
784
785 /* No memory during module load */
786 if (WARN_ON(!jlm))
787 continue;
788
789 if (prev == &key->next)
790 static_key_set_mod(key, jlm->next);
791 else
792 *prev = jlm->next;
793
794 kfree(jlm);
795
796 jlm = static_key_mod(key);
797 /* if only one etry is left, fold it back into the static_key */
798 if (jlm->next == NULL) {
799 static_key_set_entries(key, jlm->entries);
800 static_key_clear_linked(key);
801 kfree(jlm);
802 }
803 }
804 }
805
806 static int
jump_label_module_notify(struct notifier_block * self,unsigned long val,void * data)807 jump_label_module_notify(struct notifier_block *self, unsigned long val,
808 void *data)
809 {
810 struct module *mod = data;
811 int ret = 0;
812
813 cpus_read_lock();
814 jump_label_lock();
815
816 switch (val) {
817 case MODULE_STATE_COMING:
818 ret = jump_label_add_module(mod);
819 if (ret) {
820 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
821 jump_label_del_module(mod);
822 }
823 break;
824 case MODULE_STATE_GOING:
825 jump_label_del_module(mod);
826 break;
827 }
828
829 jump_label_unlock();
830 cpus_read_unlock();
831
832 return notifier_from_errno(ret);
833 }
834
835 static struct notifier_block jump_label_module_nb = {
836 .notifier_call = jump_label_module_notify,
837 .priority = 1, /* higher than tracepoints */
838 };
839
jump_label_init_module(void)840 static __init int jump_label_init_module(void)
841 {
842 return register_module_notifier(&jump_label_module_nb);
843 }
844 early_initcall(jump_label_init_module);
845
846 #endif /* CONFIG_MODULES */
847
848 /***
849 * jump_label_text_reserved - check if addr range is reserved
850 * @start: start text addr
851 * @end: end text addr
852 *
853 * checks if the text addr located between @start and @end
854 * overlaps with any of the jump label patch addresses. Code
855 * that wants to modify kernel text should first verify that
856 * it does not overlap with any of the jump label addresses.
857 * Caller must hold jump_label_mutex.
858 *
859 * returns 1 if there is an overlap, 0 otherwise
860 */
jump_label_text_reserved(void * start,void * end)861 int jump_label_text_reserved(void *start, void *end)
862 {
863 bool init = system_state < SYSTEM_RUNNING;
864 int ret = __jump_label_text_reserved(__start___jump_table,
865 __stop___jump_table, start, end, init);
866
867 if (ret)
868 return ret;
869
870 #ifdef CONFIG_MODULES
871 ret = __jump_label_mod_text_reserved(start, end);
872 #endif
873 return ret;
874 }
875
jump_label_update(struct static_key * key)876 static void jump_label_update(struct static_key *key)
877 {
878 struct jump_entry *stop = __stop___jump_table;
879 bool init = system_state < SYSTEM_RUNNING;
880 struct jump_entry *entry;
881 #ifdef CONFIG_MODULES
882 struct module *mod;
883
884 if (static_key_linked(key)) {
885 __jump_label_mod_update(key);
886 return;
887 }
888
889 preempt_disable();
890 mod = __module_address((unsigned long)key);
891 if (mod) {
892 stop = mod->jump_entries + mod->num_jump_entries;
893 init = mod->state == MODULE_STATE_COMING;
894 }
895 preempt_enable();
896 #endif
897 entry = static_key_entries(key);
898 /* if there are no users, entry can be NULL */
899 if (entry)
900 __jump_label_update(key, entry, stop, init);
901 }
902
903 #ifdef CONFIG_STATIC_KEYS_SELFTEST
904 static DEFINE_STATIC_KEY_TRUE(sk_true);
905 static DEFINE_STATIC_KEY_FALSE(sk_false);
906
jump_label_test(void)907 static __init int jump_label_test(void)
908 {
909 int i;
910
911 for (i = 0; i < 2; i++) {
912 WARN_ON(static_key_enabled(&sk_true.key) != true);
913 WARN_ON(static_key_enabled(&sk_false.key) != false);
914
915 WARN_ON(!static_branch_likely(&sk_true));
916 WARN_ON(!static_branch_unlikely(&sk_true));
917 WARN_ON(static_branch_likely(&sk_false));
918 WARN_ON(static_branch_unlikely(&sk_false));
919
920 static_branch_disable(&sk_true);
921 static_branch_enable(&sk_false);
922
923 WARN_ON(static_key_enabled(&sk_true.key) == true);
924 WARN_ON(static_key_enabled(&sk_false.key) == false);
925
926 WARN_ON(static_branch_likely(&sk_true));
927 WARN_ON(static_branch_unlikely(&sk_true));
928 WARN_ON(!static_branch_likely(&sk_false));
929 WARN_ON(!static_branch_unlikely(&sk_false));
930
931 static_branch_enable(&sk_true);
932 static_branch_disable(&sk_false);
933 }
934
935 return 0;
936 }
937 early_initcall(jump_label_test);
938 #endif /* STATIC_KEYS_SELFTEST */
939