kernel/jump_label.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * jump label support
   4  *
   5  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
   6  * Copyright (C) 2011 Peter Zijlstra
   7  *
   8  */
   9 #include <linux/memory.h>
  10 #include <linux/uaccess.h>
  11 #include <linux/module.h>
  12 #include <linux/list.h>
  13 #include <linux/slab.h>
  14 #include <linux/sort.h>
  15 #include <linux/err.h>
  16 #include <linux/static_key.h>
  17 #include <linux/jump_label_ratelimit.h>
  18 #include <linux/bug.h>
  19 #include <linux/cpu.h>
  20 #include <asm/sections.h>
  21
  22 /* mutex to protect coming/going of the the jump_label table */
  23 static DEFINE_MUTEX(jump_label_mutex);
  24
  25 void jump_label_lock(void)
  26 {
  27         mutex_lock(&jump_label_mutex);
  28 }
  29
  30 void jump_label_unlock(void)
  31 {
  32         mutex_unlock(&jump_label_mutex);
  33 }
  34
  35 static int jump_label_cmp(const void *a, const void *b)
  36 {
  37         const struct jump_entry *jea = a;
  38         const struct jump_entry *jeb = b;
  39
  40         if (jump_entry_key(jea) < jump_entry_key(jeb))
  41                 return -1;
  42
  43         if (jump_entry_key(jea) > jump_entry_key(jeb))
  44                 return 1;
  45
  46         return 0;
  47 }
  48
  49 static void jump_label_swap(void *a, void *b, int size)
  50 {
  51         long delta = (unsigned long)a - (unsigned long)b;
  52         struct jump_entry *jea = a;
  53         struct jump_entry *jeb = b;
  54         struct jump_entry tmp = *jea;
  55
  56         jea->code       = jeb->code - delta;
  57         jea->target     = jeb->target - delta;
  58         jea->key        = jeb->key - delta;
  59
  60         jeb->code       = tmp.code + delta;
  61         jeb->target     = tmp.target + delta;
  62         jeb->key        = tmp.key + delta;
  63 }
  64
  65 static void
  66 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  67 {
  68         unsigned long size;
  69         void *swapfn = NULL;
  70
  71         if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
  72                 swapfn = jump_label_swap;
  73
  74         size = (((unsigned long)stop - (unsigned long)start)
  75                                         / sizeof(struct jump_entry));
  76         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
  77 }
  78
  79 static void jump_label_update(struct static_key *key);
  80
  81 /*
  82  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
  83  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  84  * kernel headers such as kernel.h and others. Since static_key_count() is not
  85  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
  86  * to have it be a function here. Similarly, for 'static_key_enable()' and
  87  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
  88  * to be included from most/all places for CONFIG_JUMP_LABEL.
  89  */
  90 int static_key_count(struct static_key *key)
  91 {
  92         /*
  93          * -1 means the first static_key_slow_inc() is in progress.
  94          *  static_key_enabled() must return true, so return 1 here.
  95          */
  96         int n = atomic_read(&key->enabled);
  97
  98         return n >= 0 ? n : 1;
  99 }
 100 EXPORT_SYMBOL_GPL(static_key_count);
 101
 102 void static_key_slow_inc_cpuslocked(struct static_key *key)
 103 {
 104         int v, v1;
 105
 106         STATIC_KEY_CHECK_USE(key);
 107         lockdep_assert_cpus_held();
 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                 /*
 132                  * Ensure that if the above cmpxchg loop observes our positive
 133                  * value, it must also observe all the text changes.
 134                  */
 135                 atomic_set_release(&key->enabled, 1);
 136         } else {
 137                 atomic_inc(&key->enabled);
 138         }
 139         jump_label_unlock();
 140 }
 141
 142 void static_key_slow_inc(struct static_key *key)
 143 {
 144         cpus_read_lock();
 145         static_key_slow_inc_cpuslocked(key);
 146         cpus_read_unlock();
 147 }
 148 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 149
 150 void static_key_enable_cpuslocked(struct static_key *key)
 151 {
 152         STATIC_KEY_CHECK_USE(key);
 153         lockdep_assert_cpus_held();
 154
 155         if (atomic_read(&key->enabled) > 0) {
 156                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 157                 return;
 158         }
 159
 160         jump_label_lock();
 161         if (atomic_read(&key->enabled) == 0) {
 162                 atomic_set(&key->enabled, -1);
 163                 jump_label_update(key);
 164                 /*
 165                  * See static_key_slow_inc().
 166                  */
 167                 atomic_set_release(&key->enabled, 1);
 168         }
 169         jump_label_unlock();
 170 }
 171 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 172
 173 void static_key_enable(struct static_key *key)
 174 {
 175         cpus_read_lock();
 176         static_key_enable_cpuslocked(key);
 177         cpus_read_unlock();
 178 }
 179 EXPORT_SYMBOL_GPL(static_key_enable);
 180
 181 void static_key_disable_cpuslocked(struct static_key *key)
 182 {
 183         STATIC_KEY_CHECK_USE(key);
 184         lockdep_assert_cpus_held();
 185
 186         if (atomic_read(&key->enabled) != 1) {
 187                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 188                 return;
 189         }
 190
 191         jump_label_lock();
 192         if (atomic_cmpxchg(&key->enabled, 1, 0))
 193                 jump_label_update(key);
 194         jump_label_unlock();
 195 }
 196 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 197
 198 void static_key_disable(struct static_key *key)
 199 {
 200         cpus_read_lock();
 201         static_key_disable_cpuslocked(key);
 202         cpus_read_unlock();
 203 }
 204 EXPORT_SYMBOL_GPL(static_key_disable);
 205
 206 static bool static_key_slow_try_dec(struct static_key *key)
 207 {
 208         int val;
 209
 210         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 211         if (val == 1)
 212                 return false;
 213
 214         /*
 215          * The negative count check is valid even when a negative
 216          * key->enabled is in use by static_key_slow_inc(); a
 217          * __static_key_slow_dec() before the first static_key_slow_inc()
 218          * returns is unbalanced, because all other static_key_slow_inc()
 219          * instances block while the update is in progress.
 220          */
 221         WARN(val < 0, "jump label: negative count!\n");
 222         return true;
 223 }
 224
 225 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 226 {
 227         lockdep_assert_cpus_held();
 228
 229         if (static_key_slow_try_dec(key))
 230                 return;
 231
 232         jump_label_lock();
 233         if (atomic_dec_and_test(&key->enabled))
 234                 jump_label_update(key);
 235         jump_label_unlock();
 236 }
 237
 238 static void __static_key_slow_dec(struct static_key *key)
 239 {
 240         cpus_read_lock();
 241         __static_key_slow_dec_cpuslocked(key);
 242         cpus_read_unlock();
 243 }
 244
 245 void jump_label_update_timeout(struct work_struct *work)
 246 {
 247         struct static_key_deferred *key =
 248                 container_of(work, struct static_key_deferred, work.work);
 249         __static_key_slow_dec(&key->key);
 250 }
 251 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 252
 253 void static_key_slow_dec(struct static_key *key)
 254 {
 255         STATIC_KEY_CHECK_USE(key);
 256         __static_key_slow_dec(key);
 257 }
 258 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 259
 260 void static_key_slow_dec_cpuslocked(struct static_key *key)
 261 {
 262         STATIC_KEY_CHECK_USE(key);
 263         __static_key_slow_dec_cpuslocked(key);
 264 }
 265
 266 void __static_key_slow_dec_deferred(struct static_key *key,
 267                                     struct delayed_work *work,
 268                                     unsigned long timeout)
 269 {
 270         STATIC_KEY_CHECK_USE(key);
 271
 272         if (static_key_slow_try_dec(key))
 273                 return;
 274
 275         schedule_delayed_work(work, timeout);
 276 }
 277 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 278
 279 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 280 {
 281         STATIC_KEY_CHECK_USE(key);
 282         flush_delayed_work(work);
 283 }
 284 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 285
 286 void jump_label_rate_limit(struct static_key_deferred *key,
 287                 unsigned long rl)
 288 {
 289         STATIC_KEY_CHECK_USE(key);
 290         key->timeout = rl;
 291         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 292 }
 293 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 294
 295 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 296 {
 297         if (jump_entry_code(entry) <= (unsigned long)end &&
 298             jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 299                 return 1;
 300
 301         return 0;
 302 }
 303
 304 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 305                 struct jump_entry *iter_stop, void *start, void *end)
 306 {
 307         struct jump_entry *iter;
 308
 309         iter = iter_start;
 310         while (iter < iter_stop) {
 311                 if (addr_conflict(iter, start, end))
 312                         return 1;
 313                 iter++;
 314         }
 315
 316         return 0;
 317 }
 318
 319 /*
 320  * Update code which is definitely not currently executing.
 321  * Architectures which need heavyweight synchronization to modify
 322  * running code can override this to make the non-live update case
 323  * cheaper.
 324  */
 325 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 326                                             enum jump_label_type type)
 327 {
 328         arch_jump_label_transform(entry, type);
 329 }
 330
 331 static inline struct jump_entry *static_key_entries(struct static_key *key)
 332 {
 333         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 334         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 335 }
 336
 337 static inline bool static_key_type(struct static_key *key)
 338 {
 339         return key->type & JUMP_TYPE_TRUE;
 340 }
 341
 342 static inline bool static_key_linked(struct static_key *key)
 343 {
 344         return key->type & JUMP_TYPE_LINKED;
 345 }
 346
 347 static inline void static_key_clear_linked(struct static_key *key)
 348 {
 349         key->type &= ~JUMP_TYPE_LINKED;
 350 }
 351
 352 static inline void static_key_set_linked(struct static_key *key)
 353 {
 354         key->type |= JUMP_TYPE_LINKED;
 355 }
 356
 357 /***
 358  * A 'struct static_key' uses a union such that it either points directly
 359  * to a table of 'struct jump_entry' or to a linked list of modules which in
 360  * turn point to 'struct jump_entry' tables.
 361  *
 362  * The two lower bits of the pointer are used to keep track of which pointer
 363  * type is in use and to store the initial branch direction, we use an access
 364  * function which preserves these bits.
 365  */
 366 static void static_key_set_entries(struct static_key *key,
 367                                    struct jump_entry *entries)
 368 {
 369         unsigned long type;
 370
 371         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 372         type = key->type & JUMP_TYPE_MASK;
 373         key->entries = entries;
 374         key->type |= type;
 375 }
 376
 377 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 378 {
 379         struct static_key *key = jump_entry_key(entry);
 380         bool enabled = static_key_enabled(key);
 381         bool branch = jump_entry_is_branch(entry);
 382
 383         /* See the comment in linux/jump_label.h */
 384         return enabled ^ branch;
 385 }
 386
 387 static void __jump_label_update(struct static_key *key,
 388                                 struct jump_entry *entry,
 389                                 struct jump_entry *stop,
 390                                 bool init)
 391 {
 392         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 393                 /*
 394                  * An entry->code of 0 indicates an entry which has been
 395                  * disabled because it was in an init text area.
 396                  */
 397                 if (init || !jump_entry_is_init(entry)) {
 398                         if (kernel_text_address(jump_entry_code(entry)))
 399                                 arch_jump_label_transform(entry, jump_label_type(entry));
 400                         else
 401                                 WARN_ONCE(1, "can't patch jump_label at %pS",
 402                                           (void *)jump_entry_code(entry));
 403                 }
 404         }
 405 }
 406
 407 void __init jump_label_init(void)
 408 {
 409         struct jump_entry *iter_start = __start___jump_table;
 410         struct jump_entry *iter_stop = __stop___jump_table;
 411         struct static_key *key = NULL;
 412         struct jump_entry *iter;
 413
 414         /*
 415          * Since we are initializing the static_key.enabled field with
 416          * with the 'raw' int values (to avoid pulling in atomic.h) in
 417          * jump_label.h, let's make sure that is safe. There are only two
 418          * cases to check since we initialize to 0 or 1.
 419          */
 420         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 421         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 422
 423         if (static_key_initialized)
 424                 return;
 425
 426         cpus_read_lock();
 427         jump_label_lock();
 428         jump_label_sort_entries(iter_start, iter_stop);
 429
 430         for (iter = iter_start; iter < iter_stop; iter++) {
 431                 struct static_key *iterk;
 432
 433                 /* rewrite NOPs */
 434                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 435                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 436
 437                 if (init_section_contains((void *)jump_entry_code(iter), 1))
 438                         jump_entry_set_init(iter);
 439
 440                 iterk = jump_entry_key(iter);
 441                 if (iterk == key)
 442                         continue;
 443
 444                 key = iterk;
 445                 static_key_set_entries(key, iter);
 446         }
 447         static_key_initialized = true;
 448         jump_label_unlock();
 449         cpus_read_unlock();
 450 }
 451
 452 #ifdef CONFIG_MODULES
 453
 454 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 455 {
 456         struct static_key *key = jump_entry_key(entry);
 457         bool type = static_key_type(key);
 458         bool branch = jump_entry_is_branch(entry);
 459
 460         /* See the comment in linux/jump_label.h */
 461         return type ^ branch;
 462 }
 463
 464 struct static_key_mod {
 465         struct static_key_mod *next;
 466         struct jump_entry *entries;
 467         struct module *mod;
 468 };
 469
 470 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 471 {
 472         WARN_ON_ONCE(!static_key_linked(key));
 473         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 474 }
 475
 476 /***
 477  * key->type and key->next are the same via union.
 478  * This sets key->next and preserves the type bits.
 479  *
 480  * See additional comments above static_key_set_entries().
 481  */
 482 static void static_key_set_mod(struct static_key *key,
 483                                struct static_key_mod *mod)
 484 {
 485         unsigned long type;
 486
 487         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 488         type = key->type & JUMP_TYPE_MASK;
 489         key->next = mod;
 490         key->type |= type;
 491 }
 492
 493 static int __jump_label_mod_text_reserved(void *start, void *end)
 494 {
 495         struct module *mod;
 496
 497         preempt_disable();
 498         mod = __module_text_address((unsigned long)start);
 499         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 500         preempt_enable();
 501
 502         if (!mod)
 503                 return 0;
 504
 505
 506         return __jump_label_text_reserved(mod->jump_entries,
 507                                 mod->jump_entries + mod->num_jump_entries,
 508                                 start, end);
 509 }
 510
 511 static void __jump_label_mod_update(struct static_key *key)
 512 {
 513         struct static_key_mod *mod;
 514
 515         for (mod = static_key_mod(key); mod; mod = mod->next) {
 516                 struct jump_entry *stop;
 517                 struct module *m;
 518
 519                 /*
 520                  * NULL if the static_key is defined in a module
 521                  * that does not use it
 522                  */
 523                 if (!mod->entries)
 524                         continue;
 525
 526                 m = mod->mod;
 527                 if (!m)
 528                         stop = __stop___jump_table;
 529                 else
 530                         stop = m->jump_entries + m->num_jump_entries;
 531                 __jump_label_update(key, mod->entries, stop,
 532                                     m && m->state == MODULE_STATE_COMING);
 533         }
 534 }
 535
 536 /***
 537  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 538  * @mod: module to patch
 539  *
 540  * Allow for run-time selection of the optimal nops. Before the module
 541  * loads patch these with arch_get_jump_label_nop(), which is specified by
 542  * the arch specific jump label code.
 543  */
 544 void jump_label_apply_nops(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
 550         /* if the module doesn't have jump label entries, just return */
 551         if (iter_start == iter_stop)
 552                 return;
 553
 554         for (iter = iter_start; iter < iter_stop; iter++) {
 555                 /* Only write NOPs for arch_branch_static(). */
 556                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 557                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 558         }
 559 }
 560
 561 static int jump_label_add_module(struct module *mod)
 562 {
 563         struct jump_entry *iter_start = mod->jump_entries;
 564         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 565         struct jump_entry *iter;
 566         struct static_key *key = NULL;
 567         struct static_key_mod *jlm, *jlm2;
 568
 569         /* if the module doesn't have jump label entries, just return */
 570         if (iter_start == iter_stop)
 571                 return 0;
 572
 573         jump_label_sort_entries(iter_start, iter_stop);
 574
 575         for (iter = iter_start; iter < iter_stop; iter++) {
 576                 struct static_key *iterk;
 577
 578                 if (within_module_init(jump_entry_code(iter), mod))
 579                         jump_entry_set_init(iter);
 580
 581                 iterk = jump_entry_key(iter);
 582                 if (iterk == key)
 583                         continue;
 584
 585                 key = iterk;
 586                 if (within_module((unsigned long)key, mod)) {
 587                         static_key_set_entries(key, iter);
 588                         continue;
 589                 }
 590                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 591                 if (!jlm)
 592                         return -ENOMEM;
 593                 if (!static_key_linked(key)) {
 594                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 595                                        GFP_KERNEL);
 596                         if (!jlm2) {
 597                                 kfree(jlm);
 598                                 return -ENOMEM;
 599                         }
 600                         preempt_disable();
 601                         jlm2->mod = __module_address((unsigned long)key);
 602                         preempt_enable();
 603                         jlm2->entries = static_key_entries(key);
 604                         jlm2->next = NULL;
 605                         static_key_set_mod(key, jlm2);
 606                         static_key_set_linked(key);
 607                 }
 608                 jlm->mod = mod;
 609                 jlm->entries = iter;
 610                 jlm->next = static_key_mod(key);
 611                 static_key_set_mod(key, jlm);
 612                 static_key_set_linked(key);
 613
 614                 /* Only update if we've changed from our initial state */
 615                 if (jump_label_type(iter) != jump_label_init_type(iter))
 616                         __jump_label_update(key, iter, iter_stop, true);
 617         }
 618
 619         return 0;
 620 }
 621
 622 static void jump_label_del_module(struct module *mod)
 623 {
 624         struct jump_entry *iter_start = mod->jump_entries;
 625         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 626         struct jump_entry *iter;
 627         struct static_key *key = NULL;
 628         struct static_key_mod *jlm, **prev;
 629
 630         for (iter = iter_start; iter < iter_stop; iter++) {
 631                 if (jump_entry_key(iter) == key)
 632                         continue;
 633
 634                 key = jump_entry_key(iter);
 635
 636                 if (within_module((unsigned long)key, mod))
 637                         continue;
 638
 639                 /* No memory during module load */
 640                 if (WARN_ON(!static_key_linked(key)))
 641                         continue;
 642
 643                 prev = &key->next;
 644                 jlm = static_key_mod(key);
 645
 646                 while (jlm && jlm->mod != mod) {
 647                         prev = &jlm->next;
 648                         jlm = jlm->next;
 649                 }
 650
 651                 /* No memory during module load */
 652                 if (WARN_ON(!jlm))
 653                         continue;
 654
 655                 if (prev == &key->next)
 656                         static_key_set_mod(key, jlm->next);
 657                 else
 658                         *prev = jlm->next;
 659
 660                 kfree(jlm);
 661
 662                 jlm = static_key_mod(key);
 663                 /* if only one etry is left, fold it back into the static_key */
 664                 if (jlm->next == NULL) {
 665                         static_key_set_entries(key, jlm->entries);
 666                         static_key_clear_linked(key);
 667                         kfree(jlm);
 668                 }
 669         }
 670 }
 671
 672 static int
 673 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 674                          void *data)
 675 {
 676         struct module *mod = data;
 677         int ret = 0;
 678
 679         cpus_read_lock();
 680         jump_label_lock();
 681
 682         switch (val) {
 683         case MODULE_STATE_COMING:
 684                 ret = jump_label_add_module(mod);
 685                 if (ret) {
 686                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 687                         jump_label_del_module(mod);
 688                 }
 689                 break;
 690         case MODULE_STATE_GOING:
 691                 jump_label_del_module(mod);
 692                 break;
 693         }
 694
 695         jump_label_unlock();
 696         cpus_read_unlock();
 697
 698         return notifier_from_errno(ret);
 699 }
 700
 701 static struct notifier_block jump_label_module_nb = {
 702         .notifier_call = jump_label_module_notify,
 703         .priority = 1, /* higher than tracepoints */
 704 };
 705
 706 static __init int jump_label_init_module(void)
 707 {
 708         return register_module_notifier(&jump_label_module_nb);
 709 }
 710 early_initcall(jump_label_init_module);
 711
 712 #endif /* CONFIG_MODULES */
 713
 714 /***
 715  * jump_label_text_reserved - check if addr range is reserved
 716  * @start: start text addr
 717  * @end: end text addr
 718  *
 719  * checks if the text addr located between @start and @end
 720  * overlaps with any of the jump label patch addresses. Code
 721  * that wants to modify kernel text should first verify that
 722  * it does not overlap with any of the jump label addresses.
 723  * Caller must hold jump_label_mutex.
 724  *
 725  * returns 1 if there is an overlap, 0 otherwise
 726  */
 727 int jump_label_text_reserved(void *start, void *end)
 728 {
 729         int ret = __jump_label_text_reserved(__start___jump_table,
 730                         __stop___jump_table, start, end);
 731
 732         if (ret)
 733                 return ret;
 734
 735 #ifdef CONFIG_MODULES
 736         ret = __jump_label_mod_text_reserved(start, end);
 737 #endif
 738         return ret;
 739 }
 740
 741 static void jump_label_update(struct static_key *key)
 742 {
 743         struct jump_entry *stop = __stop___jump_table;
 744         struct jump_entry *entry;
 745 #ifdef CONFIG_MODULES
 746         struct module *mod;
 747
 748         if (static_key_linked(key)) {
 749                 __jump_label_mod_update(key);
 750                 return;
 751         }
 752
 753         preempt_disable();
 754         mod = __module_address((unsigned long)key);
 755         if (mod)
 756                 stop = mod->jump_entries + mod->num_jump_entries;
 757         preempt_enable();
 758 #endif
 759         entry = static_key_entries(key);
 760         /* if there are no users, entry can be NULL */
 761         if (entry)
 762                 __jump_label_update(key, entry, stop,
 763                                     system_state < SYSTEM_RUNNING);
 764 }
 765
 766 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 767 static DEFINE_STATIC_KEY_TRUE(sk_true);
 768 static DEFINE_STATIC_KEY_FALSE(sk_false);
 769
 770 static __init int jump_label_test(void)
 771 {
 772         int i;
 773
 774         for (i = 0; i < 2; i++) {
 775                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 776                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 777
 778                 WARN_ON(!static_branch_likely(&sk_true));
 779                 WARN_ON(!static_branch_unlikely(&sk_true));
 780                 WARN_ON(static_branch_likely(&sk_false));
 781                 WARN_ON(static_branch_unlikely(&sk_false));
 782
 783                 static_branch_disable(&sk_true);
 784                 static_branch_enable(&sk_false);
 785
 786                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 787                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 788
 789                 WARN_ON(static_branch_likely(&sk_true));
 790                 WARN_ON(static_branch_unlikely(&sk_true));
 791                 WARN_ON(!static_branch_likely(&sk_false));
 792                 WARN_ON(!static_branch_unlikely(&sk_false));
 793
 794                 static_branch_enable(&sk_true);
 795                 static_branch_disable(&sk_false);
 796         }
 797
 798         return 0;
 799 }
 800 early_initcall(jump_label_test);
 801 #endif /* STATIC_KEYS_SELFTEST */