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 jump_label_rate_limit(struct static_key_deferred *key,
 186                 unsigned long rl)
 187 {
 188         STATIC_KEY_CHECK_USE();
 189         key->timeout = rl;
 190         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 191 }
 192 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 193
 194 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 195 {
 196         if (entry->code <= (unsigned long)end &&
 197                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 198                 return 1;
 199
 200         return 0;
 201 }
 202
 203 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 204                 struct jump_entry *iter_stop, void *start, void *end)
 205 {
 206         struct jump_entry *iter;
 207
 208         iter = iter_start;
 209         while (iter < iter_stop) {
 210                 if (addr_conflict(iter, start, end))
 211                         return 1;
 212                 iter++;
 213         }
 214
 215         return 0;
 216 }
 217
 218 /*
 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
 222  * cheaper.
 223  */
 224 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 225                                             enum jump_label_type type)
 226 {
 227         arch_jump_label_transform(entry, type);
 228 }
 229
 230 static inline struct jump_entry *static_key_entries(struct static_key *key)
 231 {
 232         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 233         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 234 }
 235
 236 static inline bool static_key_type(struct static_key *key)
 237 {
 238         return key->type & JUMP_TYPE_TRUE;
 239 }
 240
 241 static inline bool static_key_linked(struct static_key *key)
 242 {
 243         return key->type & JUMP_TYPE_LINKED;
 244 }
 245
 246 static inline void static_key_clear_linked(struct static_key *key)
 247 {
 248         key->type &= ~JUMP_TYPE_LINKED;
 249 }
 250
 251 static inline void static_key_set_linked(struct static_key *key)
 252 {
 253         key->type |= JUMP_TYPE_LINKED;
 254 }
 255
 256 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
 257 {
 258         return (struct static_key *)((unsigned long)entry->key & ~1UL);
 259 }
 260
 261 static bool jump_entry_branch(struct jump_entry *entry)
 262 {
 263         return (unsigned long)entry->key & 1UL;
 264 }
 265
 266 /***
 267  * A 'struct static_key' uses a union such that it either points directly
 268  * to a table of 'struct jump_entry' or to a linked list of modules which in
 269  * turn point to 'struct jump_entry' tables.
 270  *
 271  * The two lower bits of the pointer are used to keep track of which pointer
 272  * type is in use and to store the initial branch direction, we use an access
 273  * function which preserves these bits.
 274  */
 275 static void static_key_set_entries(struct static_key *key,
 276                                    struct jump_entry *entries)
 277 {
 278         unsigned long type;
 279
 280         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 281         type = key->type & JUMP_TYPE_MASK;
 282         key->entries = entries;
 283         key->type |= type;
 284 }
 285
 286 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 287 {
 288         struct static_key *key = jump_entry_key(entry);
 289         bool enabled = static_key_enabled(key);
 290         bool branch = jump_entry_branch(entry);
 291
 292         /* See the comment in linux/jump_label.h */
 293         return enabled ^ branch;
 294 }
 295
 296 static void __jump_label_update(struct static_key *key,
 297                                 struct jump_entry *entry,
 298                                 struct jump_entry *stop)
 299 {
 300         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 301                 /*
 302                  * entry->code set to 0 invalidates module init text sections
 303                  * kernel_text_address() verifies we are not in core kernel
 304                  * init code, see jump_label_invalidate_module_init().
 305                  */
 306                 if (entry->code && kernel_text_address(entry->code))
 307                         arch_jump_label_transform(entry, jump_label_type(entry));
 308         }
 309 }
 310
 311 void __init jump_label_init(void)
 312 {
 313         struct jump_entry *iter_start = __start___jump_table;
 314         struct jump_entry *iter_stop = __stop___jump_table;
 315         struct static_key *key = NULL;
 316         struct jump_entry *iter;
 317
 318         /*
 319          * Since we are initializing the static_key.enabled field with
 320          * with the 'raw' int values (to avoid pulling in atomic.h) in
 321          * jump_label.h, let's make sure that is safe. There are only two
 322          * cases to check since we initialize to 0 or 1.
 323          */
 324         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 325         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 326
 327         if (static_key_initialized)
 328                 return;
 329
 330         jump_label_lock();
 331         jump_label_sort_entries(iter_start, iter_stop);
 332
 333         for (iter = iter_start; iter < iter_stop; iter++) {
 334                 struct static_key *iterk;
 335
 336                 /* rewrite NOPs */
 337                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 338                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 339
 340                 iterk = jump_entry_key(iter);
 341                 if (iterk == key)
 342                         continue;
 343
 344                 key = iterk;
 345                 static_key_set_entries(key, iter);
 346         }
 347         static_key_initialized = true;
 348         jump_label_unlock();
 349 }
 350
 351 #ifdef CONFIG_MODULES
 352
 353 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 354 {
 355         struct static_key *key = jump_entry_key(entry);
 356         bool type = static_key_type(key);
 357         bool branch = jump_entry_branch(entry);
 358
 359         /* See the comment in linux/jump_label.h */
 360         return type ^ branch;
 361 }
 362
 363 struct static_key_mod {
 364         struct static_key_mod *next;
 365         struct jump_entry *entries;
 366         struct module *mod;
 367 };
 368
 369 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 370 {
 371         WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
 372         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 373 }
 374
 375 /***
 376  * key->type and key->next are the same via union.
 377  * This sets key->next and preserves the type bits.
 378  *
 379  * See additional comments above static_key_set_entries().
 380  */
 381 static void static_key_set_mod(struct static_key *key,
 382                                struct static_key_mod *mod)
 383 {
 384         unsigned long type;
 385
 386         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 387         type = key->type & JUMP_TYPE_MASK;
 388         key->next = mod;
 389         key->type |= type;
 390 }
 391
 392 static int __jump_label_mod_text_reserved(void *start, void *end)
 393 {
 394         struct module *mod;
 395
 396         preempt_disable();
 397         mod = __module_text_address((unsigned long)start);
 398         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 399         preempt_enable();
 400
 401         if (!mod)
 402                 return 0;
 403
 404
 405         return __jump_label_text_reserved(mod->jump_entries,
 406                                 mod->jump_entries + mod->num_jump_entries,
 407                                 start, end);
 408 }
 409
 410 static void __jump_label_mod_update(struct static_key *key)
 411 {
 412         struct static_key_mod *mod;
 413
 414         for (mod = static_key_mod(key); mod; mod = mod->next) {
 415                 struct jump_entry *stop;
 416                 struct module *m;
 417
 418                 /*
 419                  * NULL if the static_key is defined in a module
 420                  * that does not use it
 421                  */
 422                 if (!mod->entries)
 423                         continue;
 424
 425                 m = mod->mod;
 426                 if (!m)
 427                         stop = __stop___jump_table;
 428                 else
 429                         stop = m->jump_entries + m->num_jump_entries;
 430                 __jump_label_update(key, mod->entries, stop);
 431         }
 432 }
 433
 434 /***
 435  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 436  * @mod: module to patch
 437  *
 438  * Allow for run-time selection of the optimal nops. Before the module
 439  * loads patch these with arch_get_jump_label_nop(), which is specified by
 440  * the arch specific jump label code.
 441  */
 442 void jump_label_apply_nops(struct module *mod)
 443 {
 444         struct jump_entry *iter_start = mod->jump_entries;
 445         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 446         struct jump_entry *iter;
 447
 448         /* if the module doesn't have jump label entries, just return */
 449         if (iter_start == iter_stop)
 450                 return;
 451
 452         for (iter = iter_start; iter < iter_stop; iter++) {
 453                 /* Only write NOPs for arch_branch_static(). */
 454                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 455                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 456         }
 457 }
 458
 459 static int jump_label_add_module(struct module *mod)
 460 {
 461         struct jump_entry *iter_start = mod->jump_entries;
 462         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 463         struct jump_entry *iter;
 464         struct static_key *key = NULL;
 465         struct static_key_mod *jlm, *jlm2;
 466
 467         /* if the module doesn't have jump label entries, just return */
 468         if (iter_start == iter_stop)
 469                 return 0;
 470
 471         jump_label_sort_entries(iter_start, iter_stop);
 472
 473         for (iter = iter_start; iter < iter_stop; iter++) {
 474                 struct static_key *iterk;
 475
 476                 iterk = jump_entry_key(iter);
 477                 if (iterk == key)
 478                         continue;
 479
 480                 key = iterk;
 481                 if (within_module(iter->key, mod)) {
 482                         static_key_set_entries(key, iter);
 483                         continue;
 484                 }
 485                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 486                 if (!jlm)
 487                         return -ENOMEM;
 488                 if (!static_key_linked(key)) {
 489                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 490                                        GFP_KERNEL);
 491                         if (!jlm2) {
 492                                 kfree(jlm);
 493                                 return -ENOMEM;
 494                         }
 495                         preempt_disable();
 496                         jlm2->mod = __module_address((unsigned long)key);
 497                         preempt_enable();
 498                         jlm2->entries = static_key_entries(key);
 499                         jlm2->next = NULL;
 500                         static_key_set_mod(key, jlm2);
 501                         static_key_set_linked(key);
 502                 }
 503                 jlm->mod = mod;
 504                 jlm->entries = iter;
 505                 jlm->next = static_key_mod(key);
 506                 static_key_set_mod(key, jlm);
 507                 static_key_set_linked(key);
 508
 509                 /* Only update if we've changed from our initial state */
 510                 if (jump_label_type(iter) != jump_label_init_type(iter))
 511                         __jump_label_update(key, iter, iter_stop);
 512         }
 513
 514         return 0;
 515 }
 516
 517 static void jump_label_del_module(struct module *mod)
 518 {
 519         struct jump_entry *iter_start = mod->jump_entries;
 520         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 521         struct jump_entry *iter;
 522         struct static_key *key = NULL;
 523         struct static_key_mod *jlm, **prev;
 524
 525         for (iter = iter_start; iter < iter_stop; iter++) {
 526                 if (jump_entry_key(iter) == key)
 527                         continue;
 528
 529                 key = jump_entry_key(iter);
 530
 531                 if (within_module(iter->key, mod))
 532                         continue;
 533
 534                 /* No memory during module load */
 535                 if (WARN_ON(!static_key_linked(key)))
 536                         continue;
 537
 538                 prev = &key->next;
 539                 jlm = static_key_mod(key);
 540
 541                 while (jlm && jlm->mod != mod) {
 542                         prev = &jlm->next;
 543                         jlm = jlm->next;
 544                 }
 545
 546                 /* No memory during module load */
 547                 if (WARN_ON(!jlm))
 548                         continue;
 549
 550                 if (prev == &key->next)
 551                         static_key_set_mod(key, jlm->next);
 552                 else
 553                         *prev = jlm->next;
 554
 555                 kfree(jlm);
 556
 557                 jlm = static_key_mod(key);
 558                 /* if only one etry is left, fold it back into the static_key */
 559                 if (jlm->next == NULL) {
 560                         static_key_set_entries(key, jlm->entries);
 561                         static_key_clear_linked(key);
 562                         kfree(jlm);
 563                 }
 564         }
 565 }
 566
 567 static void jump_label_invalidate_module_init(struct module *mod)
 568 {
 569         struct jump_entry *iter_start = mod->jump_entries;
 570         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 571         struct jump_entry *iter;
 572
 573         for (iter = iter_start; iter < iter_stop; iter++) {
 574                 if (within_module_init(iter->code, mod))
 575                         iter->code = 0;
 576         }
 577 }
 578
 579 static int
 580 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 581                          void *data)
 582 {
 583         struct module *mod = data;
 584         int ret = 0;
 585
 586         switch (val) {
 587         case MODULE_STATE_COMING:
 588                 jump_label_lock();
 589                 ret = jump_label_add_module(mod);
 590                 if (ret) {
 591                         WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
 592                         jump_label_del_module(mod);
 593                 }
 594                 jump_label_unlock();
 595                 break;
 596         case MODULE_STATE_GOING:
 597                 jump_label_lock();
 598                 jump_label_del_module(mod);
 599                 jump_label_unlock();
 600                 break;
 601         case MODULE_STATE_LIVE:
 602                 jump_label_lock();
 603                 jump_label_invalidate_module_init(mod);
 604                 jump_label_unlock();
 605                 break;
 606         }
 607
 608         return notifier_from_errno(ret);
 609 }
 610
 611 static struct notifier_block jump_label_module_nb = {
 612         .notifier_call = jump_label_module_notify,
 613         .priority = 1, /* higher than tracepoints */
 614 };
 615
 616 static __init int jump_label_init_module(void)
 617 {
 618         return register_module_notifier(&jump_label_module_nb);
 619 }
 620 early_initcall(jump_label_init_module);
 621
 622 #endif /* CONFIG_MODULES */
 623
 624 /***
 625  * jump_label_text_reserved - check if addr range is reserved
 626  * @start: start text addr
 627  * @end: end text addr
 628  *
 629  * checks if the text addr located between @start and @end
 630  * overlaps with any of the jump label patch addresses. Code
 631  * that wants to modify kernel text should first verify that
 632  * it does not overlap with any of the jump label addresses.
 633  * Caller must hold jump_label_mutex.
 634  *
 635  * returns 1 if there is an overlap, 0 otherwise
 636  */
 637 int jump_label_text_reserved(void *start, void *end)
 638 {
 639         int ret = __jump_label_text_reserved(__start___jump_table,
 640                         __stop___jump_table, start, end);
 641
 642         if (ret)
 643                 return ret;
 644
 645 #ifdef CONFIG_MODULES
 646         ret = __jump_label_mod_text_reserved(start, end);
 647 #endif
 648         return ret;
 649 }
 650
 651 static void jump_label_update(struct static_key *key)
 652 {
 653         struct jump_entry *stop = __stop___jump_table;
 654         struct jump_entry *entry;
 655 #ifdef CONFIG_MODULES
 656         struct module *mod;
 657
 658         if (static_key_linked(key)) {
 659                 __jump_label_mod_update(key);
 660                 return;
 661         }
 662
 663         preempt_disable();
 664         mod = __module_address((unsigned long)key);
 665         if (mod)
 666                 stop = mod->jump_entries + mod->num_jump_entries;
 667         preempt_enable();
 668 #endif
 669         entry = static_key_entries(key);
 670         /* if there are no users, entry can be NULL */
 671         if (entry)
 672                 __jump_label_update(key, entry, stop);
 673 }
 674
 675 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 676 static DEFINE_STATIC_KEY_TRUE(sk_true);
 677 static DEFINE_STATIC_KEY_FALSE(sk_false);
 678
 679 static __init int jump_label_test(void)
 680 {
 681         int i;
 682
 683         for (i = 0; i < 2; i++) {
 684                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 685                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 686
 687                 WARN_ON(!static_branch_likely(&sk_true));
 688                 WARN_ON(!static_branch_unlikely(&sk_true));
 689                 WARN_ON(static_branch_likely(&sk_false));
 690                 WARN_ON(static_branch_unlikely(&sk_false));
 691
 692                 static_branch_disable(&sk_true);
 693                 static_branch_enable(&sk_false);
 694
 695                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 696                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 697
 698                 WARN_ON(static_branch_likely(&sk_true));
 699                 WARN_ON(static_branch_unlikely(&sk_true));
 700                 WARN_ON(!static_branch_likely(&sk_false));
 701                 WARN_ON(!static_branch_unlikely(&sk_false));
 702
 703                 static_branch_enable(&sk_true);
 704                 static_branch_disable(&sk_false);
 705         }
 706
 707         return 0;
 708 }
 709 late_initcall(jump_label_test);
 710 #endif /* STATIC_KEYS_SELFTEST */
 711
 712 #endif /* HAVE_JUMP_LABEL */