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 #include <linux/cpu.h>
  19 #include <asm/sections.h>
  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 !CONFIG_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 !CONFIG_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 CONFIG_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_slow_inc_cpuslocked(struct static_key *key)
  82 {
  83         int v, v1;
  84
  85         STATIC_KEY_CHECK_USE(key);
  86
  87         /*
  88          * Careful if we get concurrent static_key_slow_inc() calls;
  89          * later calls must wait for the first one to _finish_ the
  90          * jump_label_update() process.  At the same time, however,
  91          * the jump_label_update() call below wants to see
  92          * static_key_enabled(&key) for jumps to be updated properly.
  93          *
  94          * So give a special meaning to negative key->enabled: it sends
  95          * static_key_slow_inc() down the slow path, and it is non-zero
  96          * so it counts as "enabled" in jump_label_update().  Note that
  97          * atomic_inc_unless_negative() checks >= 0, so roll our own.
  98          */
  99         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 100                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 101                 if (likely(v1 == v))
 102                         return;
 103         }
 104
 105         jump_label_lock();
 106         if (atomic_read(&key->enabled) == 0) {
 107                 atomic_set(&key->enabled, -1);
 108                 jump_label_update(key);
 109                 /*
 110                  * Ensure that if the above cmpxchg loop observes our positive
 111                  * value, it must also observe all the text changes.
 112                  */
 113                 atomic_set_release(&key->enabled, 1);
 114         } else {
 115                 atomic_inc(&key->enabled);
 116         }
 117         jump_label_unlock();
 118 }
 119
 120 void static_key_slow_inc(struct static_key *key)
 121 {
 122         cpus_read_lock();
 123         static_key_slow_inc_cpuslocked(key);
 124         cpus_read_unlock();
 125 }
 126 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 127
 128 void static_key_enable_cpuslocked(struct static_key *key)
 129 {
 130         STATIC_KEY_CHECK_USE(key);
 131
 132         if (atomic_read(&key->enabled) > 0) {
 133                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 134                 return;
 135         }
 136
 137         jump_label_lock();
 138         if (atomic_read(&key->enabled) == 0) {
 139                 atomic_set(&key->enabled, -1);
 140                 jump_label_update(key);
 141                 /*
 142                  * See static_key_slow_inc().
 143                  */
 144                 atomic_set_release(&key->enabled, 1);
 145         }
 146         jump_label_unlock();
 147 }
 148 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 149
 150 void static_key_enable(struct static_key *key)
 151 {
 152         cpus_read_lock();
 153         static_key_enable_cpuslocked(key);
 154         cpus_read_unlock();
 155 }
 156 EXPORT_SYMBOL_GPL(static_key_enable);
 157
 158 void static_key_disable_cpuslocked(struct static_key *key)
 159 {
 160         STATIC_KEY_CHECK_USE(key);
 161
 162         if (atomic_read(&key->enabled) != 1) {
 163                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 164                 return;
 165         }
 166
 167         jump_label_lock();
 168         if (atomic_cmpxchg(&key->enabled, 1, 0))
 169                 jump_label_update(key);
 170         jump_label_unlock();
 171 }
 172 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 173
 174 void static_key_disable(struct static_key *key)
 175 {
 176         cpus_read_lock();
 177         static_key_disable_cpuslocked(key);
 178         cpus_read_unlock();
 179 }
 180 EXPORT_SYMBOL_GPL(static_key_disable);
 181
 182 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
 183                                            unsigned long rate_limit,
 184                                            struct delayed_work *work)
 185 {
 186         /*
 187          * The negative count check is valid even when a negative
 188          * key->enabled is in use by static_key_slow_inc(); a
 189          * __static_key_slow_dec() before the first static_key_slow_inc()
 190          * returns is unbalanced, because all other static_key_slow_inc()
 191          * instances block while the update is in progress.
 192          */
 193         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
 194                 WARN(atomic_read(&key->enabled) < 0,
 195                      "jump label: negative count!\n");
 196                 return;
 197         }
 198
 199         if (rate_limit) {
 200                 atomic_inc(&key->enabled);
 201                 schedule_delayed_work(work, rate_limit);
 202         } else {
 203                 jump_label_update(key);
 204         }
 205         jump_label_unlock();
 206 }
 207
 208 static void __static_key_slow_dec(struct static_key *key,
 209                                   unsigned long rate_limit,
 210                                   struct delayed_work *work)
 211 {
 212         cpus_read_lock();
 213         __static_key_slow_dec_cpuslocked(key, rate_limit, work);
 214         cpus_read_unlock();
 215 }
 216
 217 static void jump_label_update_timeout(struct work_struct *work)
 218 {
 219         struct static_key_deferred *key =
 220                 container_of(work, struct static_key_deferred, work.work);
 221         __static_key_slow_dec(&key->key, 0, NULL);
 222 }
 223
 224 void static_key_slow_dec(struct static_key *key)
 225 {
 226         STATIC_KEY_CHECK_USE(key);
 227         __static_key_slow_dec(key, 0, NULL);
 228 }
 229 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 230
 231 void static_key_slow_dec_cpuslocked(struct static_key *key)
 232 {
 233         STATIC_KEY_CHECK_USE(key);
 234         __static_key_slow_dec_cpuslocked(key, 0, NULL);
 235 }
 236
 237 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 238 {
 239         STATIC_KEY_CHECK_USE(key);
 240         __static_key_slow_dec(&key->key, key->timeout, &key->work);
 241 }
 242 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
 243
 244 void static_key_deferred_flush(struct static_key_deferred *key)
 245 {
 246         STATIC_KEY_CHECK_USE(key);
 247         flush_delayed_work(&key->work);
 248 }
 249 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
 250
 251 void jump_label_rate_limit(struct static_key_deferred *key,
 252                 unsigned long rl)
 253 {
 254         STATIC_KEY_CHECK_USE(key);
 255         key->timeout = rl;
 256         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 257 }
 258 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 259
 260 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 261 {
 262         if (entry->code <= (unsigned long)end &&
 263                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 264                 return 1;
 265
 266         return 0;
 267 }
 268
 269 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 270                 struct jump_entry *iter_stop, void *start, void *end)
 271 {
 272         struct jump_entry *iter;
 273
 274         iter = iter_start;
 275         while (iter < iter_stop) {
 276                 if (addr_conflict(iter, start, end))
 277                         return 1;
 278                 iter++;
 279         }
 280
 281         return 0;
 282 }
 283
 284 /*
 285  * Update code which is definitely not currently executing.
 286  * Architectures which need heavyweight synchronization to modify
 287  * running code can override this to make the non-live update case
 288  * cheaper.
 289  */
 290 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 291                                             enum jump_label_type type)
 292 {
 293         arch_jump_label_transform(entry, type);
 294 }
 295
 296 static inline struct jump_entry *static_key_entries(struct static_key *key)
 297 {
 298         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 299         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 300 }
 301
 302 static inline bool static_key_type(struct static_key *key)
 303 {
 304         return key->type & JUMP_TYPE_TRUE;
 305 }
 306
 307 static inline bool static_key_linked(struct static_key *key)
 308 {
 309         return key->type & JUMP_TYPE_LINKED;
 310 }
 311
 312 static inline void static_key_clear_linked(struct static_key *key)
 313 {
 314         key->type &= ~JUMP_TYPE_LINKED;
 315 }
 316
 317 static inline void static_key_set_linked(struct static_key *key)
 318 {
 319         key->type |= JUMP_TYPE_LINKED;
 320 }
 321
 322 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
 323 {
 324         return (struct static_key *)((unsigned long)entry->key & ~1UL);
 325 }
 326
 327 static bool jump_entry_branch(struct jump_entry *entry)
 328 {
 329         return (unsigned long)entry->key & 1UL;
 330 }
 331
 332 /***
 333  * A 'struct static_key' uses a union such that it either points directly
 334  * to a table of 'struct jump_entry' or to a linked list of modules which in
 335  * turn point to 'struct jump_entry' tables.
 336  *
 337  * The two lower bits of the pointer are used to keep track of which pointer
 338  * type is in use and to store the initial branch direction, we use an access
 339  * function which preserves these bits.
 340  */
 341 static void static_key_set_entries(struct static_key *key,
 342                                    struct jump_entry *entries)
 343 {
 344         unsigned long type;
 345
 346         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 347         type = key->type & JUMP_TYPE_MASK;
 348         key->entries = entries;
 349         key->type |= type;
 350 }
 351
 352 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 353 {
 354         struct static_key *key = jump_entry_key(entry);
 355         bool enabled = static_key_enabled(key);
 356         bool branch = jump_entry_branch(entry);
 357
 358         /* See the comment in linux/jump_label.h */
 359         return enabled ^ branch;
 360 }
 361
 362 static void __jump_label_update(struct static_key *key,
 363                                 struct jump_entry *entry,
 364                                 struct jump_entry *stop)
 365 {
 366         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 367                 /*
 368                  * An entry->code of 0 indicates an entry which has been
 369                  * disabled because it was in an init text area.
 370                  */
 371                 if (entry->code) {
 372                         if (kernel_text_address(entry->code))
 373                                 arch_jump_label_transform(entry, jump_label_type(entry));
 374                         else
 375                                 WARN_ONCE(1, "can't patch jump_label at %pS",
 376                                           (void *)(unsigned long)entry->code);
 377                 }
 378         }
 379 }
 380
 381 void __init jump_label_init(void)
 382 {
 383         struct jump_entry *iter_start = __start___jump_table;
 384         struct jump_entry *iter_stop = __stop___jump_table;
 385         struct static_key *key = NULL;
 386         struct jump_entry *iter;
 387
 388         /*
 389          * Since we are initializing the static_key.enabled field with
 390          * with the 'raw' int values (to avoid pulling in atomic.h) in
 391          * jump_label.h, let's make sure that is safe. There are only two
 392          * cases to check since we initialize to 0 or 1.
 393          */
 394         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 395         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 396
 397         if (static_key_initialized)
 398                 return;
 399
 400         cpus_read_lock();
 401         jump_label_lock();
 402         jump_label_sort_entries(iter_start, iter_stop);
 403
 404         for (iter = iter_start; iter < iter_stop; iter++) {
 405                 struct static_key *iterk;
 406
 407                 /* rewrite NOPs */
 408                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 409                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 410
 411                 iterk = jump_entry_key(iter);
 412                 if (iterk == key)
 413                         continue;
 414
 415                 key = iterk;
 416                 static_key_set_entries(key, iter);
 417         }
 418         static_key_initialized = true;
 419         jump_label_unlock();
 420         cpus_read_unlock();
 421 }
 422
 423 /* Disable any jump label entries in __init/__exit code */
 424 void __init jump_label_invalidate_initmem(void)
 425 {
 426         struct jump_entry *iter_start = __start___jump_table;
 427         struct jump_entry *iter_stop = __stop___jump_table;
 428         struct jump_entry *iter;
 429
 430         for (iter = iter_start; iter < iter_stop; iter++) {
 431                 if (init_section_contains((void *)(unsigned long)iter->code, 1))
 432                         iter->code = 0;
 433         }
 434 }
 435
 436 #ifdef CONFIG_MODULES
 437
 438 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 439 {
 440         struct static_key *key = jump_entry_key(entry);
 441         bool type = static_key_type(key);
 442         bool branch = jump_entry_branch(entry);
 443
 444         /* See the comment in linux/jump_label.h */
 445         return type ^ branch;
 446 }
 447
 448 struct static_key_mod {
 449         struct static_key_mod *next;
 450         struct jump_entry *entries;
 451         struct module *mod;
 452 };
 453
 454 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 455 {
 456         WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
 457         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 458 }
 459
 460 /***
 461  * key->type and key->next are the same via union.
 462  * This sets key->next and preserves the type bits.
 463  *
 464  * See additional comments above static_key_set_entries().
 465  */
 466 static void static_key_set_mod(struct static_key *key,
 467                                struct static_key_mod *mod)
 468 {
 469         unsigned long type;
 470
 471         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 472         type = key->type & JUMP_TYPE_MASK;
 473         key->next = mod;
 474         key->type |= type;
 475 }
 476
 477 static int __jump_label_mod_text_reserved(void *start, void *end)
 478 {
 479         struct module *mod;
 480
 481         preempt_disable();
 482         mod = __module_text_address((unsigned long)start);
 483         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 484         preempt_enable();
 485
 486         if (!mod)
 487                 return 0;
 488
 489
 490         return __jump_label_text_reserved(mod->jump_entries,
 491                                 mod->jump_entries + mod->num_jump_entries,
 492                                 start, end);
 493 }
 494
 495 static void __jump_label_mod_update(struct static_key *key)
 496 {
 497         struct static_key_mod *mod;
 498
 499         for (mod = static_key_mod(key); mod; mod = mod->next) {
 500                 struct jump_entry *stop;
 501                 struct module *m;
 502
 503                 /*
 504                  * NULL if the static_key is defined in a module
 505                  * that does not use it
 506                  */
 507                 if (!mod->entries)
 508                         continue;
 509
 510                 m = mod->mod;
 511                 if (!m)
 512                         stop = __stop___jump_table;
 513                 else
 514                         stop = m->jump_entries + m->num_jump_entries;
 515                 __jump_label_update(key, mod->entries, stop);
 516         }
 517 }
 518
 519 /***
 520  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 521  * @mod: module to patch
 522  *
 523  * Allow for run-time selection of the optimal nops. Before the module
 524  * loads patch these with arch_get_jump_label_nop(), which is specified by
 525  * the arch specific jump label code.
 526  */
 527 void jump_label_apply_nops(struct module *mod)
 528 {
 529         struct jump_entry *iter_start = mod->jump_entries;
 530         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 531         struct jump_entry *iter;
 532
 533         /* if the module doesn't have jump label entries, just return */
 534         if (iter_start == iter_stop)
 535                 return;
 536
 537         for (iter = iter_start; iter < iter_stop; iter++) {
 538                 /* Only write NOPs for arch_branch_static(). */
 539                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 540                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 541         }
 542 }
 543
 544 static int jump_label_add_module(struct module *mod)
 545 {
 546         struct jump_entry *iter_start = mod->jump_entries;
 547         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 548         struct jump_entry *iter;
 549         struct static_key *key = NULL;
 550         struct static_key_mod *jlm, *jlm2;
 551
 552         /* if the module doesn't have jump label entries, just return */
 553         if (iter_start == iter_stop)
 554                 return 0;
 555
 556         jump_label_sort_entries(iter_start, iter_stop);
 557
 558         for (iter = iter_start; iter < iter_stop; iter++) {
 559                 struct static_key *iterk;
 560
 561                 iterk = jump_entry_key(iter);
 562                 if (iterk == key)
 563                         continue;
 564
 565                 key = iterk;
 566                 if (within_module(iter->key, mod)) {
 567                         static_key_set_entries(key, iter);
 568                         continue;
 569                 }
 570                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 571                 if (!jlm)
 572                         return -ENOMEM;
 573                 if (!static_key_linked(key)) {
 574                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 575                                        GFP_KERNEL);
 576                         if (!jlm2) {
 577                                 kfree(jlm);
 578                                 return -ENOMEM;
 579                         }
 580                         preempt_disable();
 581                         jlm2->mod = __module_address((unsigned long)key);
 582                         preempt_enable();
 583                         jlm2->entries = static_key_entries(key);
 584                         jlm2->next = NULL;
 585                         static_key_set_mod(key, jlm2);
 586                         static_key_set_linked(key);
 587                 }
 588                 jlm->mod = mod;
 589                 jlm->entries = iter;
 590                 jlm->next = static_key_mod(key);
 591                 static_key_set_mod(key, jlm);
 592                 static_key_set_linked(key);
 593
 594                 /* Only update if we've changed from our initial state */
 595                 if (jump_label_type(iter) != jump_label_init_type(iter))
 596                         __jump_label_update(key, iter, iter_stop);
 597         }
 598
 599         return 0;
 600 }
 601
 602 static void jump_label_del_module(struct module *mod)
 603 {
 604         struct jump_entry *iter_start = mod->jump_entries;
 605         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 606         struct jump_entry *iter;
 607         struct static_key *key = NULL;
 608         struct static_key_mod *jlm, **prev;
 609
 610         for (iter = iter_start; iter < iter_stop; iter++) {
 611                 if (jump_entry_key(iter) == key)
 612                         continue;
 613
 614                 key = jump_entry_key(iter);
 615
 616                 if (within_module(iter->key, mod))
 617                         continue;
 618
 619                 /* No memory during module load */
 620                 if (WARN_ON(!static_key_linked(key)))
 621                         continue;
 622
 623                 prev = &key->next;
 624                 jlm = static_key_mod(key);
 625
 626                 while (jlm && jlm->mod != mod) {
 627                         prev = &jlm->next;
 628                         jlm = jlm->next;
 629                 }
 630
 631                 /* No memory during module load */
 632                 if (WARN_ON(!jlm))
 633                         continue;
 634
 635                 if (prev == &key->next)
 636                         static_key_set_mod(key, jlm->next);
 637                 else
 638                         *prev = jlm->next;
 639
 640                 kfree(jlm);
 641
 642                 jlm = static_key_mod(key);
 643                 /* if only one etry is left, fold it back into the static_key */
 644                 if (jlm->next == NULL) {
 645                         static_key_set_entries(key, jlm->entries);
 646                         static_key_clear_linked(key);
 647                         kfree(jlm);
 648                 }
 649         }
 650 }
 651
 652 /* Disable any jump label entries in module init code */
 653 static void jump_label_invalidate_module_init(struct module *mod)
 654 {
 655         struct jump_entry *iter_start = mod->jump_entries;
 656         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 657         struct jump_entry *iter;
 658
 659         for (iter = iter_start; iter < iter_stop; iter++) {
 660                 if (within_module_init(iter->code, mod))
 661                         iter->code = 0;
 662         }
 663 }
 664
 665 static int
 666 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 667                          void *data)
 668 {
 669         struct module *mod = data;
 670         int ret = 0;
 671
 672         cpus_read_lock();
 673         jump_label_lock();
 674
 675         switch (val) {
 676         case MODULE_STATE_COMING:
 677                 ret = jump_label_add_module(mod);
 678                 if (ret) {
 679                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 680                         jump_label_del_module(mod);
 681                 }
 682                 break;
 683         case MODULE_STATE_GOING:
 684                 jump_label_del_module(mod);
 685                 break;
 686         case MODULE_STATE_LIVE:
 687                 jump_label_invalidate_module_init(mod);
 688                 break;
 689         }
 690
 691         jump_label_unlock();
 692         cpus_read_unlock();
 693
 694         return notifier_from_errno(ret);
 695 }
 696
 697 static struct notifier_block jump_label_module_nb = {
 698         .notifier_call = jump_label_module_notify,
 699         .priority = 1, /* higher than tracepoints */
 700 };
 701
 702 static __init int jump_label_init_module(void)
 703 {
 704         return register_module_notifier(&jump_label_module_nb);
 705 }
 706 early_initcall(jump_label_init_module);
 707
 708 #endif /* CONFIG_MODULES */
 709
 710 /***
 711  * jump_label_text_reserved - check if addr range is reserved
 712  * @start: start text addr
 713  * @end: end text addr
 714  *
 715  * checks if the text addr located between @start and @end
 716  * overlaps with any of the jump label patch addresses. Code
 717  * that wants to modify kernel text should first verify that
 718  * it does not overlap with any of the jump label addresses.
 719  * Caller must hold jump_label_mutex.
 720  *
 721  * returns 1 if there is an overlap, 0 otherwise
 722  */
 723 int jump_label_text_reserved(void *start, void *end)
 724 {
 725         int ret = __jump_label_text_reserved(__start___jump_table,
 726                         __stop___jump_table, start, end);
 727
 728         if (ret)
 729                 return ret;
 730
 731 #ifdef CONFIG_MODULES
 732         ret = __jump_label_mod_text_reserved(start, end);
 733 #endif
 734         return ret;
 735 }
 736
 737 static void jump_label_update(struct static_key *key)
 738 {
 739         struct jump_entry *stop = __stop___jump_table;
 740         struct jump_entry *entry;
 741 #ifdef CONFIG_MODULES
 742         struct module *mod;
 743
 744         if (static_key_linked(key)) {
 745                 __jump_label_mod_update(key);
 746                 return;
 747         }
 748
 749         preempt_disable();
 750         mod = __module_address((unsigned long)key);
 751         if (mod)
 752                 stop = mod->jump_entries + mod->num_jump_entries;
 753         preempt_enable();
 754 #endif
 755         entry = static_key_entries(key);
 756         /* if there are no users, entry can be NULL */
 757         if (entry)
 758                 __jump_label_update(key, entry, stop);
 759 }
 760
 761 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 762 static DEFINE_STATIC_KEY_TRUE(sk_true);
 763 static DEFINE_STATIC_KEY_FALSE(sk_false);
 764
 765 static __init int jump_label_test(void)
 766 {
 767         int i;
 768
 769         for (i = 0; i < 2; i++) {
 770                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 771                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 772
 773                 WARN_ON(!static_branch_likely(&sk_true));
 774                 WARN_ON(!static_branch_unlikely(&sk_true));
 775                 WARN_ON(static_branch_likely(&sk_false));
 776                 WARN_ON(static_branch_unlikely(&sk_false));
 777
 778                 static_branch_disable(&sk_true);
 779                 static_branch_enable(&sk_false);
 780
 781                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 782                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 783
 784                 WARN_ON(static_branch_likely(&sk_true));
 785                 WARN_ON(static_branch_unlikely(&sk_true));
 786                 WARN_ON(!static_branch_likely(&sk_false));
 787                 WARN_ON(!static_branch_unlikely(&sk_false));
 788
 789                 static_branch_enable(&sk_true);
 790                 static_branch_disable(&sk_false);
 791         }
 792
 793         return 0;
 794 }
 795 early_initcall(jump_label_test);
 796 #endif /* STATIC_KEYS_SELFTEST */