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         lockdep_assert_cpus_held();
  87
  88         /*
  89          * Careful if we get concurrent static_key_slow_inc() calls;
  90          * later calls must wait for the first one to _finish_ the
  91          * jump_label_update() process.  At the same time, however,
  92          * the jump_label_update() call below wants to see
  93          * static_key_enabled(&key) for jumps to be updated properly.
  94          *
  95          * So give a special meaning to negative key->enabled: it sends
  96          * static_key_slow_inc() down the slow path, and it is non-zero
  97          * so it counts as "enabled" in jump_label_update().  Note that
  98          * atomic_inc_unless_negative() checks >= 0, so roll our own.
  99          */
 100         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 101                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 102                 if (likely(v1 == v))
 103                         return;
 104         }
 105
 106         jump_label_lock();
 107         if (atomic_read(&key->enabled) == 0) {
 108                 atomic_set(&key->enabled, -1);
 109                 jump_label_update(key);
 110                 /*
 111                  * Ensure that if the above cmpxchg loop observes our positive
 112                  * value, it must also observe all the text changes.
 113                  */
 114                 atomic_set_release(&key->enabled, 1);
 115         } else {
 116                 atomic_inc(&key->enabled);
 117         }
 118         jump_label_unlock();
 119 }
 120
 121 void static_key_slow_inc(struct static_key *key)
 122 {
 123         cpus_read_lock();
 124         static_key_slow_inc_cpuslocked(key);
 125         cpus_read_unlock();
 126 }
 127 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 128
 129 void static_key_enable_cpuslocked(struct static_key *key)
 130 {
 131         STATIC_KEY_CHECK_USE(key);
 132         lockdep_assert_cpus_held();
 133
 134         if (atomic_read(&key->enabled) > 0) {
 135                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 136                 return;
 137         }
 138
 139         jump_label_lock();
 140         if (atomic_read(&key->enabled) == 0) {
 141                 atomic_set(&key->enabled, -1);
 142                 jump_label_update(key);
 143                 /*
 144                  * See static_key_slow_inc().
 145                  */
 146                 atomic_set_release(&key->enabled, 1);
 147         }
 148         jump_label_unlock();
 149 }
 150 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 151
 152 void static_key_enable(struct static_key *key)
 153 {
 154         cpus_read_lock();
 155         static_key_enable_cpuslocked(key);
 156         cpus_read_unlock();
 157 }
 158 EXPORT_SYMBOL_GPL(static_key_enable);
 159
 160 void static_key_disable_cpuslocked(struct static_key *key)
 161 {
 162         STATIC_KEY_CHECK_USE(key);
 163         lockdep_assert_cpus_held();
 164
 165         if (atomic_read(&key->enabled) != 1) {
 166                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 167                 return;
 168         }
 169
 170         jump_label_lock();
 171         if (atomic_cmpxchg(&key->enabled, 1, 0))
 172                 jump_label_update(key);
 173         jump_label_unlock();
 174 }
 175 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 176
 177 void static_key_disable(struct static_key *key)
 178 {
 179         cpus_read_lock();
 180         static_key_disable_cpuslocked(key);
 181         cpus_read_unlock();
 182 }
 183 EXPORT_SYMBOL_GPL(static_key_disable);
 184
 185 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
 186                                            unsigned long rate_limit,
 187                                            struct delayed_work *work)
 188 {
 189         int val;
 190
 191         lockdep_assert_cpus_held();
 192
 193         /*
 194          * The negative count check is valid even when a negative
 195          * key->enabled is in use by static_key_slow_inc(); a
 196          * __static_key_slow_dec() before the first static_key_slow_inc()
 197          * returns is unbalanced, because all other static_key_slow_inc()
 198          * instances block while the update is in progress.
 199          */
 200         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 201         if (val != 1) {
 202                 WARN(val < 0, "jump label: negative count!\n");
 203                 return;
 204         }
 205
 206         jump_label_lock();
 207         if (atomic_dec_and_test(&key->enabled)) {
 208                 if (rate_limit) {
 209                         atomic_inc(&key->enabled);
 210                         schedule_delayed_work(work, rate_limit);
 211                 } else {
 212                         jump_label_update(key);
 213                 }
 214         }
 215         jump_label_unlock();
 216 }
 217
 218 static void __static_key_slow_dec(struct static_key *key,
 219                                   unsigned long rate_limit,
 220                                   struct delayed_work *work)
 221 {
 222         cpus_read_lock();
 223         __static_key_slow_dec_cpuslocked(key, rate_limit, work);
 224         cpus_read_unlock();
 225 }
 226
 227 static void jump_label_update_timeout(struct work_struct *work)
 228 {
 229         struct static_key_deferred *key =
 230                 container_of(work, struct static_key_deferred, work.work);
 231         __static_key_slow_dec(&key->key, 0, NULL);
 232 }
 233
 234 void static_key_slow_dec(struct static_key *key)
 235 {
 236         STATIC_KEY_CHECK_USE(key);
 237         __static_key_slow_dec(key, 0, NULL);
 238 }
 239 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 240
 241 void static_key_slow_dec_cpuslocked(struct static_key *key)
 242 {
 243         STATIC_KEY_CHECK_USE(key);
 244         __static_key_slow_dec_cpuslocked(key, 0, NULL);
 245 }
 246
 247 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 248 {
 249         STATIC_KEY_CHECK_USE(key);
 250         __static_key_slow_dec(&key->key, key->timeout, &key->work);
 251 }
 252 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
 253
 254 void static_key_deferred_flush(struct static_key_deferred *key)
 255 {
 256         STATIC_KEY_CHECK_USE(key);
 257         flush_delayed_work(&key->work);
 258 }
 259 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
 260
 261 void jump_label_rate_limit(struct static_key_deferred *key,
 262                 unsigned long rl)
 263 {
 264         STATIC_KEY_CHECK_USE(key);
 265         key->timeout = rl;
 266         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 267 }
 268 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 269
 270 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 271 {
 272         if (entry->code <= (unsigned long)end &&
 273                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 274                 return 1;
 275
 276         return 0;
 277 }
 278
 279 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 280                 struct jump_entry *iter_stop, void *start, void *end)
 281 {
 282         struct jump_entry *iter;
 283
 284         iter = iter_start;
 285         while (iter < iter_stop) {
 286                 if (addr_conflict(iter, start, end))
 287                         return 1;
 288                 iter++;
 289         }
 290
 291         return 0;
 292 }
 293
 294 /*
 295  * Update code which is definitely not currently executing.
 296  * Architectures which need heavyweight synchronization to modify
 297  * running code can override this to make the non-live update case
 298  * cheaper.
 299  */
 300 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 301                                             enum jump_label_type type)
 302 {
 303         arch_jump_label_transform(entry, type);
 304 }
 305
 306 static inline struct jump_entry *static_key_entries(struct static_key *key)
 307 {
 308         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 309         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 310 }
 311
 312 static inline bool static_key_type(struct static_key *key)
 313 {
 314         return key->type & JUMP_TYPE_TRUE;
 315 }
 316
 317 static inline bool static_key_linked(struct static_key *key)
 318 {
 319         return key->type & JUMP_TYPE_LINKED;
 320 }
 321
 322 static inline void static_key_clear_linked(struct static_key *key)
 323 {
 324         key->type &= ~JUMP_TYPE_LINKED;
 325 }
 326
 327 static inline void static_key_set_linked(struct static_key *key)
 328 {
 329         key->type |= JUMP_TYPE_LINKED;
 330 }
 331
 332 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
 333 {
 334         return (struct static_key *)((unsigned long)entry->key & ~1UL);
 335 }
 336
 337 static bool jump_entry_branch(struct jump_entry *entry)
 338 {
 339         return (unsigned long)entry->key & 1UL;
 340 }
 341
 342 /***
 343  * A 'struct static_key' uses a union such that it either points directly
 344  * to a table of 'struct jump_entry' or to a linked list of modules which in
 345  * turn point to 'struct jump_entry' tables.
 346  *
 347  * The two lower bits of the pointer are used to keep track of which pointer
 348  * type is in use and to store the initial branch direction, we use an access
 349  * function which preserves these bits.
 350  */
 351 static void static_key_set_entries(struct static_key *key,
 352                                    struct jump_entry *entries)
 353 {
 354         unsigned long type;
 355
 356         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 357         type = key->type & JUMP_TYPE_MASK;
 358         key->entries = entries;
 359         key->type |= type;
 360 }
 361
 362 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 363 {
 364         struct static_key *key = jump_entry_key(entry);
 365         bool enabled = static_key_enabled(key);
 366         bool branch = jump_entry_branch(entry);
 367
 368         /* See the comment in linux/jump_label.h */
 369         return enabled ^ branch;
 370 }
 371
 372 static void __jump_label_update(struct static_key *key,
 373                                 struct jump_entry *entry,
 374                                 struct jump_entry *stop)
 375 {
 376         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 377                 /*
 378                  * An entry->code of 0 indicates an entry which has been
 379                  * disabled because it was in an init text area.
 380                  */
 381                 if (entry->code) {
 382                         if (kernel_text_address(entry->code))
 383                                 arch_jump_label_transform(entry, jump_label_type(entry));
 384                         else
 385                                 WARN_ONCE(1, "can't patch jump_label at %pS",
 386                                           (void *)(unsigned long)entry->code);
 387                 }
 388         }
 389 }
 390
 391 void __init jump_label_init(void)
 392 {
 393         struct jump_entry *iter_start = __start___jump_table;
 394         struct jump_entry *iter_stop = __stop___jump_table;
 395         struct static_key *key = NULL;
 396         struct jump_entry *iter;
 397
 398         /*
 399          * Since we are initializing the static_key.enabled field with
 400          * with the 'raw' int values (to avoid pulling in atomic.h) in
 401          * jump_label.h, let's make sure that is safe. There are only two
 402          * cases to check since we initialize to 0 or 1.
 403          */
 404         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 405         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 406
 407         if (static_key_initialized)
 408                 return;
 409
 410         cpus_read_lock();
 411         jump_label_lock();
 412         jump_label_sort_entries(iter_start, iter_stop);
 413
 414         for (iter = iter_start; iter < iter_stop; iter++) {
 415                 struct static_key *iterk;
 416
 417                 /* rewrite NOPs */
 418                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 419                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 420
 421                 iterk = jump_entry_key(iter);
 422                 if (iterk == key)
 423                         continue;
 424
 425                 key = iterk;
 426                 static_key_set_entries(key, iter);
 427         }
 428         static_key_initialized = true;
 429         jump_label_unlock();
 430         cpus_read_unlock();
 431 }
 432
 433 /* Disable any jump label entries in __init/__exit code */
 434 void __init jump_label_invalidate_initmem(void)
 435 {
 436         struct jump_entry *iter_start = __start___jump_table;
 437         struct jump_entry *iter_stop = __stop___jump_table;
 438         struct jump_entry *iter;
 439
 440         for (iter = iter_start; iter < iter_stop; iter++) {
 441                 if (init_section_contains((void *)(unsigned long)iter->code, 1))
 442                         iter->code = 0;
 443         }
 444 }
 445
 446 #ifdef CONFIG_MODULES
 447
 448 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 449 {
 450         struct static_key *key = jump_entry_key(entry);
 451         bool type = static_key_type(key);
 452         bool branch = jump_entry_branch(entry);
 453
 454         /* See the comment in linux/jump_label.h */
 455         return type ^ branch;
 456 }
 457
 458 struct static_key_mod {
 459         struct static_key_mod *next;
 460         struct jump_entry *entries;
 461         struct module *mod;
 462 };
 463
 464 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 465 {
 466         WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
 467         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 468 }
 469
 470 /***
 471  * key->type and key->next are the same via union.
 472  * This sets key->next and preserves the type bits.
 473  *
 474  * See additional comments above static_key_set_entries().
 475  */
 476 static void static_key_set_mod(struct static_key *key,
 477                                struct static_key_mod *mod)
 478 {
 479         unsigned long type;
 480
 481         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 482         type = key->type & JUMP_TYPE_MASK;
 483         key->next = mod;
 484         key->type |= type;
 485 }
 486
 487 static int __jump_label_mod_text_reserved(void *start, void *end)
 488 {
 489         struct module *mod;
 490
 491         preempt_disable();
 492         mod = __module_text_address((unsigned long)start);
 493         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 494         preempt_enable();
 495
 496         if (!mod)
 497                 return 0;
 498
 499
 500         return __jump_label_text_reserved(mod->jump_entries,
 501                                 mod->jump_entries + mod->num_jump_entries,
 502                                 start, end);
 503 }
 504
 505 static void __jump_label_mod_update(struct static_key *key)
 506 {
 507         struct static_key_mod *mod;
 508
 509         for (mod = static_key_mod(key); mod; mod = mod->next) {
 510                 struct jump_entry *stop;
 511                 struct module *m;
 512
 513                 /*
 514                  * NULL if the static_key is defined in a module
 515                  * that does not use it
 516                  */
 517                 if (!mod->entries)
 518                         continue;
 519
 520                 m = mod->mod;
 521                 if (!m)
 522                         stop = __stop___jump_table;
 523                 else
 524                         stop = m->jump_entries + m->num_jump_entries;
 525                 __jump_label_update(key, mod->entries, stop);
 526         }
 527 }
 528
 529 /***
 530  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 531  * @mod: module to patch
 532  *
 533  * Allow for run-time selection of the optimal nops. Before the module
 534  * loads patch these with arch_get_jump_label_nop(), which is specified by
 535  * the arch specific jump label code.
 536  */
 537 void jump_label_apply_nops(struct module *mod)
 538 {
 539         struct jump_entry *iter_start = mod->jump_entries;
 540         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 541         struct jump_entry *iter;
 542
 543         /* if the module doesn't have jump label entries, just return */
 544         if (iter_start == iter_stop)
 545                 return;
 546
 547         for (iter = iter_start; iter < iter_stop; iter++) {
 548                 /* Only write NOPs for arch_branch_static(). */
 549                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 550                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 551         }
 552 }
 553
 554 static int jump_label_add_module(struct module *mod)
 555 {
 556         struct jump_entry *iter_start = mod->jump_entries;
 557         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 558         struct jump_entry *iter;
 559         struct static_key *key = NULL;
 560         struct static_key_mod *jlm, *jlm2;
 561
 562         /* if the module doesn't have jump label entries, just return */
 563         if (iter_start == iter_stop)
 564                 return 0;
 565
 566         jump_label_sort_entries(iter_start, iter_stop);
 567
 568         for (iter = iter_start; iter < iter_stop; iter++) {
 569                 struct static_key *iterk;
 570
 571                 iterk = jump_entry_key(iter);
 572                 if (iterk == key)
 573                         continue;
 574
 575                 key = iterk;
 576                 if (within_module(iter->key, mod)) {
 577                         static_key_set_entries(key, iter);
 578                         continue;
 579                 }
 580                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 581                 if (!jlm)
 582                         return -ENOMEM;
 583                 if (!static_key_linked(key)) {
 584                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 585                                        GFP_KERNEL);
 586                         if (!jlm2) {
 587                                 kfree(jlm);
 588                                 return -ENOMEM;
 589                         }
 590                         preempt_disable();
 591                         jlm2->mod = __module_address((unsigned long)key);
 592                         preempt_enable();
 593                         jlm2->entries = static_key_entries(key);
 594                         jlm2->next = NULL;
 595                         static_key_set_mod(key, jlm2);
 596                         static_key_set_linked(key);
 597                 }
 598                 jlm->mod = mod;
 599                 jlm->entries = iter;
 600                 jlm->next = static_key_mod(key);
 601                 static_key_set_mod(key, jlm);
 602                 static_key_set_linked(key);
 603
 604                 /* Only update if we've changed from our initial state */
 605                 if (jump_label_type(iter) != jump_label_init_type(iter))
 606                         __jump_label_update(key, iter, iter_stop);
 607         }
 608
 609         return 0;
 610 }
 611
 612 static void jump_label_del_module(struct module *mod)
 613 {
 614         struct jump_entry *iter_start = mod->jump_entries;
 615         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 616         struct jump_entry *iter;
 617         struct static_key *key = NULL;
 618         struct static_key_mod *jlm, **prev;
 619
 620         for (iter = iter_start; iter < iter_stop; iter++) {
 621                 if (jump_entry_key(iter) == key)
 622                         continue;
 623
 624                 key = jump_entry_key(iter);
 625
 626                 if (within_module(iter->key, mod))
 627                         continue;
 628
 629                 /* No memory during module load */
 630                 if (WARN_ON(!static_key_linked(key)))
 631                         continue;
 632
 633                 prev = &key->next;
 634                 jlm = static_key_mod(key);
 635
 636                 while (jlm && jlm->mod != mod) {
 637                         prev = &jlm->next;
 638                         jlm = jlm->next;
 639                 }
 640
 641                 /* No memory during module load */
 642                 if (WARN_ON(!jlm))
 643                         continue;
 644
 645                 if (prev == &key->next)
 646                         static_key_set_mod(key, jlm->next);
 647                 else
 648                         *prev = jlm->next;
 649
 650                 kfree(jlm);
 651
 652                 jlm = static_key_mod(key);
 653                 /* if only one etry is left, fold it back into the static_key */
 654                 if (jlm->next == NULL) {
 655                         static_key_set_entries(key, jlm->entries);
 656                         static_key_clear_linked(key);
 657                         kfree(jlm);
 658                 }
 659         }
 660 }
 661
 662 /* Disable any jump label entries in module init code */
 663 static void jump_label_invalidate_module_init(struct module *mod)
 664 {
 665         struct jump_entry *iter_start = mod->jump_entries;
 666         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 667         struct jump_entry *iter;
 668
 669         for (iter = iter_start; iter < iter_stop; iter++) {
 670                 if (within_module_init(iter->code, mod))
 671                         iter->code = 0;
 672         }
 673 }
 674
 675 static int
 676 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 677                          void *data)
 678 {
 679         struct module *mod = data;
 680         int ret = 0;
 681
 682         cpus_read_lock();
 683         jump_label_lock();
 684
 685         switch (val) {
 686         case MODULE_STATE_COMING:
 687                 ret = jump_label_add_module(mod);
 688                 if (ret) {
 689                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 690                         jump_label_del_module(mod);
 691                 }
 692                 break;
 693         case MODULE_STATE_GOING:
 694                 jump_label_del_module(mod);
 695                 break;
 696         case MODULE_STATE_LIVE:
 697                 jump_label_invalidate_module_init(mod);
 698                 break;
 699         }
 700
 701         jump_label_unlock();
 702         cpus_read_unlock();
 703
 704         return notifier_from_errno(ret);
 705 }
 706
 707 static struct notifier_block jump_label_module_nb = {
 708         .notifier_call = jump_label_module_notify,
 709         .priority = 1, /* higher than tracepoints */
 710 };
 711
 712 static __init int jump_label_init_module(void)
 713 {
 714         return register_module_notifier(&jump_label_module_nb);
 715 }
 716 early_initcall(jump_label_init_module);
 717
 718 #endif /* CONFIG_MODULES */
 719
 720 /***
 721  * jump_label_text_reserved - check if addr range is reserved
 722  * @start: start text addr
 723  * @end: end text addr
 724  *
 725  * checks if the text addr located between @start and @end
 726  * overlaps with any of the jump label patch addresses. Code
 727  * that wants to modify kernel text should first verify that
 728  * it does not overlap with any of the jump label addresses.
 729  * Caller must hold jump_label_mutex.
 730  *
 731  * returns 1 if there is an overlap, 0 otherwise
 732  */
 733 int jump_label_text_reserved(void *start, void *end)
 734 {
 735         int ret = __jump_label_text_reserved(__start___jump_table,
 736                         __stop___jump_table, start, end);
 737
 738         if (ret)
 739                 return ret;
 740
 741 #ifdef CONFIG_MODULES
 742         ret = __jump_label_mod_text_reserved(start, end);
 743 #endif
 744         return ret;
 745 }
 746
 747 static void jump_label_update(struct static_key *key)
 748 {
 749         struct jump_entry *stop = __stop___jump_table;
 750         struct jump_entry *entry;
 751 #ifdef CONFIG_MODULES
 752         struct module *mod;
 753
 754         if (static_key_linked(key)) {
 755                 __jump_label_mod_update(key);
 756                 return;
 757         }
 758
 759         preempt_disable();
 760         mod = __module_address((unsigned long)key);
 761         if (mod)
 762                 stop = mod->jump_entries + mod->num_jump_entries;
 763         preempt_enable();
 764 #endif
 765         entry = static_key_entries(key);
 766         /* if there are no users, entry can be NULL */
 767         if (entry)
 768                 __jump_label_update(key, entry, stop);
 769 }
 770
 771 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 772 static DEFINE_STATIC_KEY_TRUE(sk_true);
 773 static DEFINE_STATIC_KEY_FALSE(sk_false);
 774
 775 static __init int jump_label_test(void)
 776 {
 777         int i;
 778
 779         for (i = 0; i < 2; i++) {
 780                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 781                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 782
 783                 WARN_ON(!static_branch_likely(&sk_true));
 784                 WARN_ON(!static_branch_unlikely(&sk_true));
 785                 WARN_ON(static_branch_likely(&sk_false));
 786                 WARN_ON(static_branch_unlikely(&sk_false));
 787
 788                 static_branch_disable(&sk_true);
 789                 static_branch_enable(&sk_false);
 790
 791                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 792                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 793
 794                 WARN_ON(static_branch_likely(&sk_true));
 795                 WARN_ON(static_branch_unlikely(&sk_true));
 796                 WARN_ON(!static_branch_likely(&sk_false));
 797                 WARN_ON(!static_branch_unlikely(&sk_false));
 798
 799                 static_branch_enable(&sk_true);
 800                 static_branch_disable(&sk_false);
 801         }
 802
 803         return 0;
 804 }
 805 early_initcall(jump_label_test);
 806 #endif /* STATIC_KEYS_SELFTEST */