kernel/jump_label.c

   1 /*
   2  * jump label support
   3  *
   4  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
   5  * Copyright (C) 2011 Peter Zijlstra
   6  *
   7  */
   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
  19 #ifdef HAVE_JUMP_LABEL
  20
  21 /* mutex to protect coming/going of the the jump_label table */
  22 static DEFINE_MUTEX(jump_label_mutex);
  23
  24 void jump_label_lock(void)
  25 {
  26         mutex_lock(&jump_label_mutex);
  27 }
  28
  29 void jump_label_unlock(void)
  30 {
  31         mutex_unlock(&jump_label_mutex);
  32 }
  33
  34 static int jump_label_cmp(const void *a, const void *b)
  35 {
  36         const struct jump_entry *jea = a;
  37         const struct jump_entry *jeb = b;
  38
  39         if (jea->key < jeb->key)
  40                 return -1;
  41
  42         if (jea->key > jeb->key)
  43                 return 1;
  44
  45         return 0;
  46 }
  47
  48 static void
  49 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  50 {
  51         unsigned long size;
  52
  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);
  56 }
  57
  58 static void jump_label_update(struct static_key *key);
  59
  60 /*
  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.
  68  */
  69 int static_key_count(struct static_key *key)
  70 {
  71         /*
  72          * -1 means the first static_key_slow_inc() is in progress.
  73          *  static_key_enabled() must return true, so return 1 here.
  74          */
  75         int n = atomic_read(&key->enabled);
  76
  77         return n >= 0 ? n : 1;
  78 }
  79 EXPORT_SYMBOL_GPL(static_key_count);
  80
  81 void static_key_enable(struct static_key *key)
  82 {
  83         int count = static_key_count(key);
  84
  85         WARN_ON_ONCE(count < 0 || count > 1);
  86
  87         if (!count)
  88                 static_key_slow_inc(key);
  89 }
  90 EXPORT_SYMBOL_GPL(static_key_enable);
  91
  92 void static_key_disable(struct static_key *key)
  93 {
  94         int count = static_key_count(key);
  95
  96         WARN_ON_ONCE(count < 0 || count > 1);
  97
  98         if (count)
  99                 static_key_slow_dec(key);
 100 }
 101 EXPORT_SYMBOL_GPL(static_key_disable);
 102
 103 void static_key_slow_inc(struct static_key *key)
 104 {
 105         int v, v1;
 106
 107         STATIC_KEY_CHECK_USE();
 108
 109         /*
 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.
 115          *
 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.
 120          */
 121         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 122                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 123                 if (likely(v1 == v))
 124                         return;
 125         }
 126
 127         jump_label_lock();
 128         if (atomic_read(&key->enabled) == 0) {
 129                 atomic_set(&key->enabled, -1);
 130                 jump_label_update(key);
 131                 atomic_set(&key->enabled, 1);
 132         } else {
 133                 atomic_inc(&key->enabled);
 134         }
 135         jump_label_unlock();
 136 }
 137 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 138
 139 static void __static_key_slow_dec(struct static_key *key,
 140                 unsigned long rate_limit, struct delayed_work *work)
 141 {
 142         /*
 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.
 148          */
 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");
 152                 return;
 153         }
 154
 155         if (rate_limit) {
 156                 atomic_inc(&key->enabled);
 157                 schedule_delayed_work(work, rate_limit);
 158         } else {
 159                 jump_label_update(key);
 160         }
 161         jump_label_unlock();
 162 }
 163
 164 static void jump_label_update_timeout(struct work_struct *work)
 165 {
 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);
 169 }
 170
 171 void static_key_slow_dec(struct static_key *key)
 172 {
 173         STATIC_KEY_CHECK_USE();
 174         __static_key_slow_dec(key, 0, NULL);
 175 }
 176 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 177
 178 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 179 {
 180         STATIC_KEY_CHECK_USE();
 181         __static_key_slow_dec(&key->key, key->timeout, &key->work);
 182 }
 183 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
 184
 185 void static_key_deferred_flush(struct static_key_deferred *key)
 186 {
 187         STATIC_KEY_CHECK_USE();
 188         flush_delayed_work(&key->work);
 189 }
 190 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
 191
 192 void jump_label_rate_limit(struct static_key_deferred *key,
 193                 unsigned long rl)
 194 {
 195         STATIC_KEY_CHECK_USE();
 196         key->timeout = rl;
 197         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 198 }
 199 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 200
 201 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 202 {
 203         if (entry->code <= (unsigned long)end &&
 204                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 205                 return 1;
 206
 207         return 0;
 208 }
 209
 210 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 211                 struct jump_entry *iter_stop, void *start, void *end)
 212 {
 213         struct jump_entry *iter;
 214
 215         iter = iter_start;
 216         while (iter < iter_stop) {
 217                 if (addr_conflict(iter, start, end))
 218                         return 1;
 219                 iter++;
 220         }
 221
 222         return 0;
 223 }
 224
 225 /*
 226  * Update code which is definitely not currently executing.
 227  * Architectures which need heavyweight synchronization to modify
 228  * running code can override this to make the non-live update case
 229  * cheaper.
 230  */
 231 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 232                                             enum jump_label_type type)
 233 {
 234         arch_jump_label_transform(entry, type);
 235 }
 236
 237 static inline struct jump_entry *static_key_entries(struct static_key *key)
 238 {
 239         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 240         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 241 }
 242
 243 static inline bool static_key_type(struct static_key *key)
 244 {
 245         return key->type & JUMP_TYPE_TRUE;
 246 }
 247
 248 static inline bool static_key_linked(struct static_key *key)
 249 {
 250         return key->type & JUMP_TYPE_LINKED;
 251 }
 252
 253 static inline void static_key_clear_linked(struct static_key *key)
 254 {
 255         key->type &= ~JUMP_TYPE_LINKED;
 256 }
 257
 258 static inline void static_key_set_linked(struct static_key *key)
 259 {
 260         key->type |= JUMP_TYPE_LINKED;
 261 }
 262
 263 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
 264 {
 265         return (struct static_key *)((unsigned long)entry->key & ~1UL);
 266 }
 267
 268 static bool jump_entry_branch(struct jump_entry *entry)
 269 {
 270         return (unsigned long)entry->key & 1UL;
 271 }
 272
 273 /***
 274  * A 'struct static_key' uses a union such that it either points directly
 275  * to a table of 'struct jump_entry' or to a linked list of modules which in
 276  * turn point to 'struct jump_entry' tables.
 277  *
 278  * The two lower bits of the pointer are used to keep track of which pointer
 279  * type is in use and to store the initial branch direction, we use an access
 280  * function which preserves these bits.
 281  */
 282 static void static_key_set_entries(struct static_key *key,
 283                                    struct jump_entry *entries)
 284 {
 285         unsigned long type;
 286
 287         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 288         type = key->type & JUMP_TYPE_MASK;
 289         key->entries = entries;
 290         key->type |= type;
 291 }
 292
 293 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 294 {
 295         struct static_key *key = jump_entry_key(entry);
 296         bool enabled = static_key_enabled(key);
 297         bool branch = jump_entry_branch(entry);
 298
 299         /* See the comment in linux/jump_label.h */
 300         return enabled ^ branch;
 301 }
 302
 303 static void __jump_label_update(struct static_key *key,
 304                                 struct jump_entry *entry,
 305                                 struct jump_entry *stop)
 306 {
 307         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 308                 /*
 309                  * entry->code set to 0 invalidates module init text sections
 310                  * kernel_text_address() verifies we are not in core kernel
 311                  * init code, see jump_label_invalidate_module_init().
 312                  */
 313                 if (entry->code && kernel_text_address(entry->code))
 314                         arch_jump_label_transform(entry, jump_label_type(entry));
 315         }
 316 }
 317
 318 void __init jump_label_init(void)
 319 {
 320         struct jump_entry *iter_start = __start___jump_table;
 321         struct jump_entry *iter_stop = __stop___jump_table;
 322         struct static_key *key = NULL;
 323         struct jump_entry *iter;
 324
 325         /*
 326          * Since we are initializing the static_key.enabled field with
 327          * with the 'raw' int values (to avoid pulling in atomic.h) in
 328          * jump_label.h, let's make sure that is safe. There are only two
 329          * cases to check since we initialize to 0 or 1.
 330          */
 331         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 332         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 333
 334         if (static_key_initialized)
 335                 return;
 336
 337         jump_label_lock();
 338         jump_label_sort_entries(iter_start, iter_stop);
 339
 340         for (iter = iter_start; iter < iter_stop; iter++) {
 341                 struct static_key *iterk;
 342
 343                 /* rewrite NOPs */
 344                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 345                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 346
 347                 iterk = jump_entry_key(iter);
 348                 if (iterk == key)
 349                         continue;
 350
 351                 key = iterk;
 352                 static_key_set_entries(key, iter);
 353         }
 354         static_key_initialized = true;
 355         jump_label_unlock();
 356 }
 357
 358 #ifdef CONFIG_MODULES
 359
 360 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 361 {
 362         struct static_key *key = jump_entry_key(entry);
 363         bool type = static_key_type(key);
 364         bool branch = jump_entry_branch(entry);
 365
 366         /* See the comment in linux/jump_label.h */
 367         return type ^ branch;
 368 }
 369
 370 struct static_key_mod {
 371         struct static_key_mod *next;
 372         struct jump_entry *entries;
 373         struct module *mod;
 374 };
 375
 376 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 377 {
 378         WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
 379         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 380 }
 381
 382 /***
 383  * key->type and key->next are the same via union.
 384  * This sets key->next and preserves the type bits.
 385  *
 386  * See additional comments above static_key_set_entries().
 387  */
 388 static void static_key_set_mod(struct static_key *key,
 389                                struct static_key_mod *mod)
 390 {
 391         unsigned long type;
 392
 393         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 394         type = key->type & JUMP_TYPE_MASK;
 395         key->next = mod;
 396         key->type |= type;
 397 }
 398
 399 static int __jump_label_mod_text_reserved(void *start, void *end)
 400 {
 401         struct module *mod;
 402
 403         preempt_disable();
 404         mod = __module_text_address((unsigned long)start);
 405         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 406         preempt_enable();
 407
 408         if (!mod)
 409                 return 0;
 410
 411
 412         return __jump_label_text_reserved(mod->jump_entries,
 413                                 mod->jump_entries + mod->num_jump_entries,
 414                                 start, end);
 415 }
 416
 417 static void __jump_label_mod_update(struct static_key *key)
 418 {
 419         struct static_key_mod *mod;
 420
 421         for (mod = static_key_mod(key); mod; mod = mod->next) {
 422                 struct jump_entry *stop;
 423                 struct module *m;
 424
 425                 /*
 426                  * NULL if the static_key is defined in a module
 427                  * that does not use it
 428                  */
 429                 if (!mod->entries)
 430                         continue;
 431
 432                 m = mod->mod;
 433                 if (!m)
 434                         stop = __stop___jump_table;
 435                 else
 436                         stop = m->jump_entries + m->num_jump_entries;
 437                 __jump_label_update(key, mod->entries, stop);
 438         }
 439 }
 440
 441 /***
 442  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 443  * @mod: module to patch
 444  *
 445  * Allow for run-time selection of the optimal nops. Before the module
 446  * loads patch these with arch_get_jump_label_nop(), which is specified by
 447  * the arch specific jump label code.
 448  */
 449 void jump_label_apply_nops(struct module *mod)
 450 {
 451         struct jump_entry *iter_start = mod->jump_entries;
 452         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 453         struct jump_entry *iter;
 454
 455         /* if the module doesn't have jump label entries, just return */
 456         if (iter_start == iter_stop)
 457                 return;
 458
 459         for (iter = iter_start; iter < iter_stop; iter++) {
 460                 /* Only write NOPs for arch_branch_static(). */
 461                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 462                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 463         }
 464 }
 465
 466 static int jump_label_add_module(struct module *mod)
 467 {
 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;
 471         struct static_key *key = NULL;
 472         struct static_key_mod *jlm, *jlm2;
 473
 474         /* if the module doesn't have jump label entries, just return */
 475         if (iter_start == iter_stop)
 476                 return 0;
 477
 478         jump_label_sort_entries(iter_start, iter_stop);
 479
 480         for (iter = iter_start; iter < iter_stop; iter++) {
 481                 struct static_key *iterk;
 482
 483                 iterk = jump_entry_key(iter);
 484                 if (iterk == key)
 485                         continue;
 486
 487                 key = iterk;
 488                 if (within_module(iter->key, mod)) {
 489                         static_key_set_entries(key, iter);
 490                         continue;
 491                 }
 492                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 493                 if (!jlm)
 494                         return -ENOMEM;
 495                 if (!static_key_linked(key)) {
 496                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 497                                        GFP_KERNEL);
 498                         if (!jlm2) {
 499                                 kfree(jlm);
 500                                 return -ENOMEM;
 501                         }
 502                         preempt_disable();
 503                         jlm2->mod = __module_address((unsigned long)key);
 504                         preempt_enable();
 505                         jlm2->entries = static_key_entries(key);
 506                         jlm2->next = NULL;
 507                         static_key_set_mod(key, jlm2);
 508                         static_key_set_linked(key);
 509                 }
 510                 jlm->mod = mod;
 511                 jlm->entries = iter;
 512                 jlm->next = static_key_mod(key);
 513                 static_key_set_mod(key, jlm);
 514                 static_key_set_linked(key);
 515
 516                 /* Only update if we've changed from our initial state */
 517                 if (jump_label_type(iter) != jump_label_init_type(iter))
 518                         __jump_label_update(key, iter, iter_stop);
 519         }
 520
 521         return 0;
 522 }
 523
 524 static void jump_label_del_module(struct module *mod)
 525 {
 526         struct jump_entry *iter_start = mod->jump_entries;
 527         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 528         struct jump_entry *iter;
 529         struct static_key *key = NULL;
 530         struct static_key_mod *jlm, **prev;
 531
 532         for (iter = iter_start; iter < iter_stop; iter++) {
 533                 if (jump_entry_key(iter) == key)
 534                         continue;
 535
 536                 key = jump_entry_key(iter);
 537
 538                 if (within_module(iter->key, mod))
 539                         continue;
 540
 541                 /* No memory during module load */
 542                 if (WARN_ON(!static_key_linked(key)))
 543                         continue;
 544
 545                 prev = &key->next;
 546                 jlm = static_key_mod(key);
 547
 548                 while (jlm && jlm->mod != mod) {
 549                         prev = &jlm->next;
 550                         jlm = jlm->next;
 551                 }
 552
 553                 /* No memory during module load */
 554                 if (WARN_ON(!jlm))
 555                         continue;
 556
 557                 if (prev == &key->next)
 558                         static_key_set_mod(key, jlm->next);
 559                 else
 560                         *prev = jlm->next;
 561
 562                 kfree(jlm);
 563
 564                 jlm = static_key_mod(key);
 565                 /* if only one etry is left, fold it back into the static_key */
 566                 if (jlm->next == NULL) {
 567                         static_key_set_entries(key, jlm->entries);
 568                         static_key_clear_linked(key);
 569                         kfree(jlm);
 570                 }
 571         }
 572 }
 573
 574 static void jump_label_invalidate_module_init(struct module *mod)
 575 {
 576         struct jump_entry *iter_start = mod->jump_entries;
 577         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 578         struct jump_entry *iter;
 579
 580         for (iter = iter_start; iter < iter_stop; iter++) {
 581                 if (within_module_init(iter->code, mod))
 582                         iter->code = 0;
 583         }
 584 }
 585
 586 static int
 587 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 588                          void *data)
 589 {
 590         struct module *mod = data;
 591         int ret = 0;
 592
 593         switch (val) {
 594         case MODULE_STATE_COMING:
 595                 jump_label_lock();
 596                 ret = jump_label_add_module(mod);
 597                 if (ret) {
 598                         WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
 599                         jump_label_del_module(mod);
 600                 }
 601                 jump_label_unlock();
 602                 break;
 603         case MODULE_STATE_GOING:
 604                 jump_label_lock();
 605                 jump_label_del_module(mod);
 606                 jump_label_unlock();
 607                 break;
 608         case MODULE_STATE_LIVE:
 609                 jump_label_lock();
 610                 jump_label_invalidate_module_init(mod);
 611                 jump_label_unlock();
 612                 break;
 613         }
 614
 615         return notifier_from_errno(ret);
 616 }
 617
 618 static struct notifier_block jump_label_module_nb = {
 619         .notifier_call = jump_label_module_notify,
 620         .priority = 1, /* higher than tracepoints */
 621 };
 622
 623 static __init int jump_label_init_module(void)
 624 {
 625         return register_module_notifier(&jump_label_module_nb);
 626 }
 627 early_initcall(jump_label_init_module);
 628
 629 #endif /* CONFIG_MODULES */
 630
 631 /***
 632  * jump_label_text_reserved - check if addr range is reserved
 633  * @start: start text addr
 634  * @end: end text addr
 635  *
 636  * checks if the text addr located between @start and @end
 637  * overlaps with any of the jump label patch addresses. Code
 638  * that wants to modify kernel text should first verify that
 639  * it does not overlap with any of the jump label addresses.
 640  * Caller must hold jump_label_mutex.
 641  *
 642  * returns 1 if there is an overlap, 0 otherwise
 643  */
 644 int jump_label_text_reserved(void *start, void *end)
 645 {
 646         int ret = __jump_label_text_reserved(__start___jump_table,
 647                         __stop___jump_table, start, end);
 648
 649         if (ret)
 650                 return ret;
 651
 652 #ifdef CONFIG_MODULES
 653         ret = __jump_label_mod_text_reserved(start, end);
 654 #endif
 655         return ret;
 656 }
 657
 658 static void jump_label_update(struct static_key *key)
 659 {
 660         struct jump_entry *stop = __stop___jump_table;
 661         struct jump_entry *entry;
 662 #ifdef CONFIG_MODULES
 663         struct module *mod;
 664
 665         if (static_key_linked(key)) {
 666                 __jump_label_mod_update(key);
 667                 return;
 668         }
 669
 670         preempt_disable();
 671         mod = __module_address((unsigned long)key);
 672         if (mod)
 673                 stop = mod->jump_entries + mod->num_jump_entries;
 674         preempt_enable();
 675 #endif
 676         entry = static_key_entries(key);
 677         /* if there are no users, entry can be NULL */
 678         if (entry)
 679                 __jump_label_update(key, entry, stop);
 680 }
 681
 682 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 683 static DEFINE_STATIC_KEY_TRUE(sk_true);
 684 static DEFINE_STATIC_KEY_FALSE(sk_false);
 685
 686 static __init int jump_label_test(void)
 687 {
 688         int i;
 689
 690         for (i = 0; i < 2; i++) {
 691                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 692                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 693
 694                 WARN_ON(!static_branch_likely(&sk_true));
 695                 WARN_ON(!static_branch_unlikely(&sk_true));
 696                 WARN_ON(static_branch_likely(&sk_false));
 697                 WARN_ON(static_branch_unlikely(&sk_false));
 698
 699                 static_branch_disable(&sk_true);
 700                 static_branch_enable(&sk_false);
 701
 702                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 703                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 704
 705                 WARN_ON(static_branch_likely(&sk_true));
 706                 WARN_ON(static_branch_unlikely(&sk_true));
 707                 WARN_ON(!static_branch_likely(&sk_false));
 708                 WARN_ON(!static_branch_unlikely(&sk_false));
 709
 710                 static_branch_enable(&sk_true);
 711                 static_branch_disable(&sk_false);
 712         }
 713
 714         return 0;
 715 }
 716 late_initcall(jump_label_test);
 717 #endif /* STATIC_KEYS_SELFTEST */
 718
 719 #endif /* HAVE_JUMP_LABEL */