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 (jump_entry_key(jea) < jump_entry_key(jeb))
  40                 return -1;
  41
  42         if (jump_entry_key(jea) > jump_entry_key(jeb))
  43                 return 1;
  44
  45         return 0;
  46 }
  47
  48 static void jump_label_swap(void *a, void *b, int size)
  49 {
  50         long delta = (unsigned long)a - (unsigned long)b;
  51         struct jump_entry *jea = a;
  52         struct jump_entry *jeb = b;
  53         struct jump_entry tmp = *jea;
  54
  55         jea->code       = jeb->code - delta;
  56         jea->target     = jeb->target - delta;
  57         jea->key        = jeb->key - delta;
  58
  59         jeb->code       = tmp.code + delta;
  60         jeb->target     = tmp.target + delta;
  61         jeb->key        = tmp.key + delta;
  62 }
  63
  64 static void
  65 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  66 {
  67         unsigned long size;
  68         void *swapfn = NULL;
  69
  70         if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
  71                 swapfn = jump_label_swap;
  72
  73         size = (((unsigned long)stop - (unsigned long)start)
  74                                         / sizeof(struct jump_entry));
  75         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
  76 }
  77
  78 static void jump_label_update(struct static_key *key);
  79
  80 /*
  81  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
  82  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  83  * kernel headers such as kernel.h and others. Since static_key_count() is not
  84  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
  85  * to have it be a function here. Similarly, for 'static_key_enable()' and
  86  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
  87  * to be included from most/all places for CONFIG_JUMP_LABEL.
  88  */
  89 int static_key_count(struct static_key *key)
  90 {
  91         /*
  92          * -1 means the first static_key_slow_inc() is in progress.
  93          *  static_key_enabled() must return true, so return 1 here.
  94          */
  95         int n = atomic_read(&key->enabled);
  96
  97         return n >= 0 ? n : 1;
  98 }
  99 EXPORT_SYMBOL_GPL(static_key_count);
 100
 101 void static_key_slow_inc_cpuslocked(struct static_key *key)
 102 {
 103         int v, v1;
 104
 105         STATIC_KEY_CHECK_USE(key);
 106         lockdep_assert_cpus_held();
 107
 108         /*
 109          * Careful if we get concurrent static_key_slow_inc() calls;
 110          * later calls must wait for the first one to _finish_ the
 111          * jump_label_update() process.  At the same time, however,
 112          * the jump_label_update() call below wants to see
 113          * static_key_enabled(&key) for jumps to be updated properly.
 114          *
 115          * So give a special meaning to negative key->enabled: it sends
 116          * static_key_slow_inc() down the slow path, and it is non-zero
 117          * so it counts as "enabled" in jump_label_update().  Note that
 118          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 119          */
 120         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 121                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 122                 if (likely(v1 == v))
 123                         return;
 124         }
 125
 126         jump_label_lock();
 127         if (atomic_read(&key->enabled) == 0) {
 128                 atomic_set(&key->enabled, -1);
 129                 jump_label_update(key);
 130                 /*
 131                  * Ensure that if the above cmpxchg loop observes our positive
 132                  * value, it must also observe all the text changes.
 133                  */
 134                 atomic_set_release(&key->enabled, 1);
 135         } else {
 136                 atomic_inc(&key->enabled);
 137         }
 138         jump_label_unlock();
 139 }
 140
 141 void static_key_slow_inc(struct static_key *key)
 142 {
 143         cpus_read_lock();
 144         static_key_slow_inc_cpuslocked(key);
 145         cpus_read_unlock();
 146 }
 147 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 148
 149 void static_key_enable_cpuslocked(struct static_key *key)
 150 {
 151         STATIC_KEY_CHECK_USE(key);
 152         lockdep_assert_cpus_held();
 153
 154         if (atomic_read(&key->enabled) > 0) {
 155                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 156                 return;
 157         }
 158
 159         jump_label_lock();
 160         if (atomic_read(&key->enabled) == 0) {
 161                 atomic_set(&key->enabled, -1);
 162                 jump_label_update(key);
 163                 /*
 164                  * See static_key_slow_inc().
 165                  */
 166                 atomic_set_release(&key->enabled, 1);
 167         }
 168         jump_label_unlock();
 169 }
 170 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 171
 172 void static_key_enable(struct static_key *key)
 173 {
 174         cpus_read_lock();
 175         static_key_enable_cpuslocked(key);
 176         cpus_read_unlock();
 177 }
 178 EXPORT_SYMBOL_GPL(static_key_enable);
 179
 180 void static_key_disable_cpuslocked(struct static_key *key)
 181 {
 182         STATIC_KEY_CHECK_USE(key);
 183         lockdep_assert_cpus_held();
 184
 185         if (atomic_read(&key->enabled) != 1) {
 186                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 187                 return;
 188         }
 189
 190         jump_label_lock();
 191         if (atomic_cmpxchg(&key->enabled, 1, 0))
 192                 jump_label_update(key);
 193         jump_label_unlock();
 194 }
 195 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 196
 197 void static_key_disable(struct static_key *key)
 198 {
 199         cpus_read_lock();
 200         static_key_disable_cpuslocked(key);
 201         cpus_read_unlock();
 202 }
 203 EXPORT_SYMBOL_GPL(static_key_disable);
 204
 205 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
 206                                            unsigned long rate_limit,
 207                                            struct delayed_work *work)
 208 {
 209         int val;
 210
 211         lockdep_assert_cpus_held();
 212
 213         /*
 214          * The negative count check is valid even when a negative
 215          * key->enabled is in use by static_key_slow_inc(); a
 216          * __static_key_slow_dec() before the first static_key_slow_inc()
 217          * returns is unbalanced, because all other static_key_slow_inc()
 218          * instances block while the update is in progress.
 219          */
 220         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 221         if (val != 1) {
 222                 WARN(val < 0, "jump label: negative count!\n");
 223                 return;
 224         }
 225
 226         jump_label_lock();
 227         if (atomic_dec_and_test(&key->enabled)) {
 228                 if (rate_limit) {
 229                         atomic_inc(&key->enabled);
 230                         schedule_delayed_work(work, rate_limit);
 231                 } else {
 232                         jump_label_update(key);
 233                 }
 234         }
 235         jump_label_unlock();
 236 }
 237
 238 static void __static_key_slow_dec(struct static_key *key,
 239                                   unsigned long rate_limit,
 240                                   struct delayed_work *work)
 241 {
 242         cpus_read_lock();
 243         __static_key_slow_dec_cpuslocked(key, rate_limit, work);
 244         cpus_read_unlock();
 245 }
 246
 247 static void jump_label_update_timeout(struct work_struct *work)
 248 {
 249         struct static_key_deferred *key =
 250                 container_of(work, struct static_key_deferred, work.work);
 251         __static_key_slow_dec(&key->key, 0, NULL);
 252 }
 253
 254 void static_key_slow_dec(struct static_key *key)
 255 {
 256         STATIC_KEY_CHECK_USE(key);
 257         __static_key_slow_dec(key, 0, NULL);
 258 }
 259 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 260
 261 void static_key_slow_dec_cpuslocked(struct static_key *key)
 262 {
 263         STATIC_KEY_CHECK_USE(key);
 264         __static_key_slow_dec_cpuslocked(key, 0, NULL);
 265 }
 266
 267 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 268 {
 269         STATIC_KEY_CHECK_USE(key);
 270         __static_key_slow_dec(&key->key, key->timeout, &key->work);
 271 }
 272 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
 273
 274 void static_key_deferred_flush(struct static_key_deferred *key)
 275 {
 276         STATIC_KEY_CHECK_USE(key);
 277         flush_delayed_work(&key->work);
 278 }
 279 EXPORT_SYMBOL_GPL(static_key_deferred_flush);
 280
 281 void jump_label_rate_limit(struct static_key_deferred *key,
 282                 unsigned long rl)
 283 {
 284         STATIC_KEY_CHECK_USE(key);
 285         key->timeout = rl;
 286         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 287 }
 288 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 289
 290 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 291 {
 292         if (jump_entry_code(entry) <= (unsigned long)end &&
 293             jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 294                 return 1;
 295
 296         return 0;
 297 }
 298
 299 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 300                 struct jump_entry *iter_stop, void *start, void *end)
 301 {
 302         struct jump_entry *iter;
 303
 304         iter = iter_start;
 305         while (iter < iter_stop) {
 306                 if (addr_conflict(iter, start, end))
 307                         return 1;
 308                 iter++;
 309         }
 310
 311         return 0;
 312 }
 313
 314 /*
 315  * Update code which is definitely not currently executing.
 316  * Architectures which need heavyweight synchronization to modify
 317  * running code can override this to make the non-live update case
 318  * cheaper.
 319  */
 320 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 321                                             enum jump_label_type type)
 322 {
 323         arch_jump_label_transform(entry, type);
 324 }
 325
 326 static inline struct jump_entry *static_key_entries(struct static_key *key)
 327 {
 328         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 329         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 330 }
 331
 332 static inline bool static_key_type(struct static_key *key)
 333 {
 334         return key->type & JUMP_TYPE_TRUE;
 335 }
 336
 337 static inline bool static_key_linked(struct static_key *key)
 338 {
 339         return key->type & JUMP_TYPE_LINKED;
 340 }
 341
 342 static inline void static_key_clear_linked(struct static_key *key)
 343 {
 344         key->type &= ~JUMP_TYPE_LINKED;
 345 }
 346
 347 static inline void static_key_set_linked(struct static_key *key)
 348 {
 349         key->type |= JUMP_TYPE_LINKED;
 350 }
 351
 352 /***
 353  * A 'struct static_key' uses a union such that it either points directly
 354  * to a table of 'struct jump_entry' or to a linked list of modules which in
 355  * turn point to 'struct jump_entry' tables.
 356  *
 357  * The two lower bits of the pointer are used to keep track of which pointer
 358  * type is in use and to store the initial branch direction, we use an access
 359  * function which preserves these bits.
 360  */
 361 static void static_key_set_entries(struct static_key *key,
 362                                    struct jump_entry *entries)
 363 {
 364         unsigned long type;
 365
 366         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 367         type = key->type & JUMP_TYPE_MASK;
 368         key->entries = entries;
 369         key->type |= type;
 370 }
 371
 372 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 373 {
 374         struct static_key *key = jump_entry_key(entry);
 375         bool enabled = static_key_enabled(key);
 376         bool branch = jump_entry_is_branch(entry);
 377
 378         /* See the comment in linux/jump_label.h */
 379         return enabled ^ branch;
 380 }
 381
 382 static void __jump_label_update(struct static_key *key,
 383                                 struct jump_entry *entry,
 384                                 struct jump_entry *stop,
 385                                 bool init)
 386 {
 387         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 388                 /*
 389                  * An entry->code of 0 indicates an entry which has been
 390                  * disabled because it was in an init text area.
 391                  */
 392                 if (init || !jump_entry_is_init(entry)) {
 393                         if (kernel_text_address(jump_entry_code(entry)))
 394                                 arch_jump_label_transform(entry, jump_label_type(entry));
 395                         else
 396                                 WARN_ONCE(1, "can't patch jump_label at %pS",
 397                                           (void *)jump_entry_code(entry));
 398                 }
 399         }
 400 }
 401
 402 void __init jump_label_init(void)
 403 {
 404         struct jump_entry *iter_start = __start___jump_table;
 405         struct jump_entry *iter_stop = __stop___jump_table;
 406         struct static_key *key = NULL;
 407         struct jump_entry *iter;
 408
 409         /*
 410          * Since we are initializing the static_key.enabled field with
 411          * with the 'raw' int values (to avoid pulling in atomic.h) in
 412          * jump_label.h, let's make sure that is safe. There are only two
 413          * cases to check since we initialize to 0 or 1.
 414          */
 415         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 416         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 417
 418         if (static_key_initialized)
 419                 return;
 420
 421         cpus_read_lock();
 422         jump_label_lock();
 423         jump_label_sort_entries(iter_start, iter_stop);
 424
 425         for (iter = iter_start; iter < iter_stop; iter++) {
 426                 struct static_key *iterk;
 427
 428                 /* rewrite NOPs */
 429                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 430                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 431
 432                 if (init_section_contains((void *)jump_entry_code(iter), 1))
 433                         jump_entry_set_init(iter);
 434
 435                 iterk = jump_entry_key(iter);
 436                 if (iterk == key)
 437                         continue;
 438
 439                 key = iterk;
 440                 static_key_set_entries(key, iter);
 441         }
 442         static_key_initialized = true;
 443         jump_label_unlock();
 444         cpus_read_unlock();
 445 }
 446
 447 #ifdef CONFIG_MODULES
 448
 449 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 450 {
 451         struct static_key *key = jump_entry_key(entry);
 452         bool type = static_key_type(key);
 453         bool branch = jump_entry_is_branch(entry);
 454
 455         /* See the comment in linux/jump_label.h */
 456         return type ^ branch;
 457 }
 458
 459 struct static_key_mod {
 460         struct static_key_mod *next;
 461         struct jump_entry *entries;
 462         struct module *mod;
 463 };
 464
 465 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 466 {
 467         WARN_ON_ONCE(!static_key_linked(key));
 468         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 469 }
 470
 471 /***
 472  * key->type and key->next are the same via union.
 473  * This sets key->next and preserves the type bits.
 474  *
 475  * See additional comments above static_key_set_entries().
 476  */
 477 static void static_key_set_mod(struct static_key *key,
 478                                struct static_key_mod *mod)
 479 {
 480         unsigned long type;
 481
 482         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 483         type = key->type & JUMP_TYPE_MASK;
 484         key->next = mod;
 485         key->type |= type;
 486 }
 487
 488 static int __jump_label_mod_text_reserved(void *start, void *end)
 489 {
 490         struct module *mod;
 491
 492         preempt_disable();
 493         mod = __module_text_address((unsigned long)start);
 494         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 495         preempt_enable();
 496
 497         if (!mod)
 498                 return 0;
 499
 500
 501         return __jump_label_text_reserved(mod->jump_entries,
 502                                 mod->jump_entries + mod->num_jump_entries,
 503                                 start, end);
 504 }
 505
 506 static void __jump_label_mod_update(struct static_key *key)
 507 {
 508         struct static_key_mod *mod;
 509
 510         for (mod = static_key_mod(key); mod; mod = mod->next) {
 511                 struct jump_entry *stop;
 512                 struct module *m;
 513
 514                 /*
 515                  * NULL if the static_key is defined in a module
 516                  * that does not use it
 517                  */
 518                 if (!mod->entries)
 519                         continue;
 520
 521                 m = mod->mod;
 522                 if (!m)
 523                         stop = __stop___jump_table;
 524                 else
 525                         stop = m->jump_entries + m->num_jump_entries;
 526                 __jump_label_update(key, mod->entries, stop,
 527                                     m && m->state == MODULE_STATE_COMING);
 528         }
 529 }
 530
 531 /***
 532  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 533  * @mod: module to patch
 534  *
 535  * Allow for run-time selection of the optimal nops. Before the module
 536  * loads patch these with arch_get_jump_label_nop(), which is specified by
 537  * the arch specific jump label code.
 538  */
 539 void jump_label_apply_nops(struct module *mod)
 540 {
 541         struct jump_entry *iter_start = mod->jump_entries;
 542         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 543         struct jump_entry *iter;
 544
 545         /* if the module doesn't have jump label entries, just return */
 546         if (iter_start == iter_stop)
 547                 return;
 548
 549         for (iter = iter_start; iter < iter_stop; iter++) {
 550                 /* Only write NOPs for arch_branch_static(). */
 551                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 552                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 553         }
 554 }
 555
 556 static int jump_label_add_module(struct module *mod)
 557 {
 558         struct jump_entry *iter_start = mod->jump_entries;
 559         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 560         struct jump_entry *iter;
 561         struct static_key *key = NULL;
 562         struct static_key_mod *jlm, *jlm2;
 563
 564         /* if the module doesn't have jump label entries, just return */
 565         if (iter_start == iter_stop)
 566                 return 0;
 567
 568         jump_label_sort_entries(iter_start, iter_stop);
 569
 570         for (iter = iter_start; iter < iter_stop; iter++) {
 571                 struct static_key *iterk;
 572
 573                 if (within_module_init(jump_entry_code(iter), mod))
 574                         jump_entry_set_init(iter);
 575
 576                 iterk = jump_entry_key(iter);
 577                 if (iterk == key)
 578                         continue;
 579
 580                 key = iterk;
 581                 if (within_module((unsigned long)key, mod)) {
 582                         static_key_set_entries(key, iter);
 583                         continue;
 584                 }
 585                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 586                 if (!jlm)
 587                         return -ENOMEM;
 588                 if (!static_key_linked(key)) {
 589                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 590                                        GFP_KERNEL);
 591                         if (!jlm2) {
 592                                 kfree(jlm);
 593                                 return -ENOMEM;
 594                         }
 595                         preempt_disable();
 596                         jlm2->mod = __module_address((unsigned long)key);
 597                         preempt_enable();
 598                         jlm2->entries = static_key_entries(key);
 599                         jlm2->next = NULL;
 600                         static_key_set_mod(key, jlm2);
 601                         static_key_set_linked(key);
 602                 }
 603                 jlm->mod = mod;
 604                 jlm->entries = iter;
 605                 jlm->next = static_key_mod(key);
 606                 static_key_set_mod(key, jlm);
 607                 static_key_set_linked(key);
 608
 609                 /* Only update if we've changed from our initial state */
 610                 if (jump_label_type(iter) != jump_label_init_type(iter))
 611                         __jump_label_update(key, iter, iter_stop, true);
 612         }
 613
 614         return 0;
 615 }
 616
 617 static void jump_label_del_module(struct module *mod)
 618 {
 619         struct jump_entry *iter_start = mod->jump_entries;
 620         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 621         struct jump_entry *iter;
 622         struct static_key *key = NULL;
 623         struct static_key_mod *jlm, **prev;
 624
 625         for (iter = iter_start; iter < iter_stop; iter++) {
 626                 if (jump_entry_key(iter) == key)
 627                         continue;
 628
 629                 key = jump_entry_key(iter);
 630
 631                 if (within_module((unsigned long)key, mod))
 632                         continue;
 633
 634                 /* No memory during module load */
 635                 if (WARN_ON(!static_key_linked(key)))
 636                         continue;
 637
 638                 prev = &key->next;
 639                 jlm = static_key_mod(key);
 640
 641                 while (jlm && jlm->mod != mod) {
 642                         prev = &jlm->next;
 643                         jlm = jlm->next;
 644                 }
 645
 646                 /* No memory during module load */
 647                 if (WARN_ON(!jlm))
 648                         continue;
 649
 650                 if (prev == &key->next)
 651                         static_key_set_mod(key, jlm->next);
 652                 else
 653                         *prev = jlm->next;
 654
 655                 kfree(jlm);
 656
 657                 jlm = static_key_mod(key);
 658                 /* if only one etry is left, fold it back into the static_key */
 659                 if (jlm->next == NULL) {
 660                         static_key_set_entries(key, jlm->entries);
 661                         static_key_clear_linked(key);
 662                         kfree(jlm);
 663                 }
 664         }
 665 }
 666
 667 static int
 668 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 669                          void *data)
 670 {
 671         struct module *mod = data;
 672         int ret = 0;
 673
 674         cpus_read_lock();
 675         jump_label_lock();
 676
 677         switch (val) {
 678         case MODULE_STATE_COMING:
 679                 ret = jump_label_add_module(mod);
 680                 if (ret) {
 681                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 682                         jump_label_del_module(mod);
 683                 }
 684                 break;
 685         case MODULE_STATE_GOING:
 686                 jump_label_del_module(mod);
 687                 break;
 688         }
 689
 690         jump_label_unlock();
 691         cpus_read_unlock();
 692
 693         return notifier_from_errno(ret);
 694 }
 695
 696 static struct notifier_block jump_label_module_nb = {
 697         .notifier_call = jump_label_module_notify,
 698         .priority = 1, /* higher than tracepoints */
 699 };
 700
 701 static __init int jump_label_init_module(void)
 702 {
 703         return register_module_notifier(&jump_label_module_nb);
 704 }
 705 early_initcall(jump_label_init_module);
 706
 707 #endif /* CONFIG_MODULES */
 708
 709 /***
 710  * jump_label_text_reserved - check if addr range is reserved
 711  * @start: start text addr
 712  * @end: end text addr
 713  *
 714  * checks if the text addr located between @start and @end
 715  * overlaps with any of the jump label patch addresses. Code
 716  * that wants to modify kernel text should first verify that
 717  * it does not overlap with any of the jump label addresses.
 718  * Caller must hold jump_label_mutex.
 719  *
 720  * returns 1 if there is an overlap, 0 otherwise
 721  */
 722 int jump_label_text_reserved(void *start, void *end)
 723 {
 724         int ret = __jump_label_text_reserved(__start___jump_table,
 725                         __stop___jump_table, start, end);
 726
 727         if (ret)
 728                 return ret;
 729
 730 #ifdef CONFIG_MODULES
 731         ret = __jump_label_mod_text_reserved(start, end);
 732 #endif
 733         return ret;
 734 }
 735
 736 static void jump_label_update(struct static_key *key)
 737 {
 738         struct jump_entry *stop = __stop___jump_table;
 739         struct jump_entry *entry;
 740 #ifdef CONFIG_MODULES
 741         struct module *mod;
 742
 743         if (static_key_linked(key)) {
 744                 __jump_label_mod_update(key);
 745                 return;
 746         }
 747
 748         preempt_disable();
 749         mod = __module_address((unsigned long)key);
 750         if (mod)
 751                 stop = mod->jump_entries + mod->num_jump_entries;
 752         preempt_enable();
 753 #endif
 754         entry = static_key_entries(key);
 755         /* if there are no users, entry can be NULL */
 756         if (entry)
 757                 __jump_label_update(key, entry, stop,
 758                                     system_state < SYSTEM_RUNNING);
 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 */