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 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         /*
  41          * Entrires are sorted by key.
  42          */
  43         if (jump_entry_key(jea) < jump_entry_key(jeb))
  44                 return -1;
  45
  46         if (jump_entry_key(jea) > jump_entry_key(jeb))
  47                 return 1;
  48
  49         /*
  50          * In the batching mode, entries should also be sorted by the code
  51          * inside the already sorted list of entries, enabling a bsearch in
  52          * the vector.
  53          */
  54         if (jump_entry_code(jea) < jump_entry_code(jeb))
  55                 return -1;
  56
  57         if (jump_entry_code(jea) > jump_entry_code(jeb))
  58                 return 1;
  59
  60         return 0;
  61 }
  62
  63 static void jump_label_swap(void *a, void *b, int size)
  64 {
  65         long delta = (unsigned long)a - (unsigned long)b;
  66         struct jump_entry *jea = a;
  67         struct jump_entry *jeb = b;
  68         struct jump_entry tmp = *jea;
  69
  70         jea->code       = jeb->code - delta;
  71         jea->target     = jeb->target - delta;
  72         jea->key        = jeb->key - delta;
  73
  74         jeb->code       = tmp.code + delta;
  75         jeb->target     = tmp.target + delta;
  76         jeb->key        = tmp.key + delta;
  77 }
  78
  79 static void
  80 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  81 {
  82         unsigned long size;
  83         void *swapfn = NULL;
  84
  85         if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
  86                 swapfn = jump_label_swap;
  87
  88         size = (((unsigned long)stop - (unsigned long)start)
  89                                         / sizeof(struct jump_entry));
  90         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
  91 }
  92
  93 static void jump_label_update(struct static_key *key);
  94
  95 /*
  96  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
  97  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  98  * kernel headers such as kernel.h and others. Since static_key_count() is not
  99  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
 100  * to have it be a function here. Similarly, for 'static_key_enable()' and
 101  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
 102  * to be included from most/all places for CONFIG_JUMP_LABEL.
 103  */
 104 int static_key_count(struct static_key *key)
 105 {
 106         /*
 107          * -1 means the first static_key_slow_inc() is in progress.
 108          *  static_key_enabled() must return true, so return 1 here.
 109          */
 110         int n = atomic_read(&key->enabled);
 111
 112         return n >= 0 ? n : 1;
 113 }
 114 EXPORT_SYMBOL_GPL(static_key_count);
 115
 116 void static_key_slow_inc_cpuslocked(struct static_key *key)
 117 {
 118         STATIC_KEY_CHECK_USE(key);
 119         lockdep_assert_cpus_held();
 120
 121         /*
 122          * Careful if we get concurrent static_key_slow_inc() calls;
 123          * later calls must wait for the first one to _finish_ the
 124          * jump_label_update() process.  At the same time, however,
 125          * the jump_label_update() call below wants to see
 126          * static_key_enabled(&key) for jumps to be updated properly.
 127          *
 128          * So give a special meaning to negative key->enabled: it sends
 129          * static_key_slow_inc() down the slow path, and it is non-zero
 130          * so it counts as "enabled" in jump_label_update().  Note that
 131          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 132          */
 133         for (int v = atomic_read(&key->enabled); v > 0; )
 134                 if (likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)))
 135                         return;
 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                  * Ensure that if the above cmpxchg loop observes our positive
 143                  * value, it must also observe all the text changes.
 144                  */
 145                 atomic_set_release(&key->enabled, 1);
 146         } else {
 147                 atomic_inc(&key->enabled);
 148         }
 149         jump_label_unlock();
 150 }
 151
 152 void static_key_slow_inc(struct static_key *key)
 153 {
 154         cpus_read_lock();
 155         static_key_slow_inc_cpuslocked(key);
 156         cpus_read_unlock();
 157 }
 158 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 159
 160 void static_key_enable_cpuslocked(struct static_key *key)
 161 {
 162         STATIC_KEY_CHECK_USE(key);
 163         lockdep_assert_cpus_held();
 164
 165         if (atomic_read(&key->enabled) > 0) {
 166                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 167                 return;
 168         }
 169
 170         jump_label_lock();
 171         if (atomic_read(&key->enabled) == 0) {
 172                 atomic_set(&key->enabled, -1);
 173                 jump_label_update(key);
 174                 /*
 175                  * See static_key_slow_inc().
 176                  */
 177                 atomic_set_release(&key->enabled, 1);
 178         }
 179         jump_label_unlock();
 180 }
 181 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 182
 183 void static_key_enable(struct static_key *key)
 184 {
 185         cpus_read_lock();
 186         static_key_enable_cpuslocked(key);
 187         cpus_read_unlock();
 188 }
 189 EXPORT_SYMBOL_GPL(static_key_enable);
 190
 191 void static_key_disable_cpuslocked(struct static_key *key)
 192 {
 193         STATIC_KEY_CHECK_USE(key);
 194         lockdep_assert_cpus_held();
 195
 196         if (atomic_read(&key->enabled) != 1) {
 197                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 198                 return;
 199         }
 200
 201         jump_label_lock();
 202         if (atomic_cmpxchg(&key->enabled, 1, 0))
 203                 jump_label_update(key);
 204         jump_label_unlock();
 205 }
 206 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 207
 208 void static_key_disable(struct static_key *key)
 209 {
 210         cpus_read_lock();
 211         static_key_disable_cpuslocked(key);
 212         cpus_read_unlock();
 213 }
 214 EXPORT_SYMBOL_GPL(static_key_disable);
 215
 216 static bool static_key_slow_try_dec(struct static_key *key)
 217 {
 218         int val;
 219
 220         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 221         if (val == 1)
 222                 return false;
 223
 224         /*
 225          * The negative count check is valid even when a negative
 226          * key->enabled is in use by static_key_slow_inc(); a
 227          * __static_key_slow_dec() before the first static_key_slow_inc()
 228          * returns is unbalanced, because all other static_key_slow_inc()
 229          * instances block while the update is in progress.
 230          */
 231         WARN(val < 0, "jump label: negative count!\n");
 232         return true;
 233 }
 234
 235 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 236 {
 237         lockdep_assert_cpus_held();
 238
 239         if (static_key_slow_try_dec(key))
 240                 return;
 241
 242         jump_label_lock();
 243         if (atomic_dec_and_test(&key->enabled))
 244                 jump_label_update(key);
 245         jump_label_unlock();
 246 }
 247
 248 static void __static_key_slow_dec(struct static_key *key)
 249 {
 250         cpus_read_lock();
 251         __static_key_slow_dec_cpuslocked(key);
 252         cpus_read_unlock();
 253 }
 254
 255 void jump_label_update_timeout(struct work_struct *work)
 256 {
 257         struct static_key_deferred *key =
 258                 container_of(work, struct static_key_deferred, work.work);
 259         __static_key_slow_dec(&key->key);
 260 }
 261 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 262
 263 void static_key_slow_dec(struct static_key *key)
 264 {
 265         STATIC_KEY_CHECK_USE(key);
 266         __static_key_slow_dec(key);
 267 }
 268 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 269
 270 void static_key_slow_dec_cpuslocked(struct static_key *key)
 271 {
 272         STATIC_KEY_CHECK_USE(key);
 273         __static_key_slow_dec_cpuslocked(key);
 274 }
 275
 276 void __static_key_slow_dec_deferred(struct static_key *key,
 277                                     struct delayed_work *work,
 278                                     unsigned long timeout)
 279 {
 280         STATIC_KEY_CHECK_USE(key);
 281
 282         if (static_key_slow_try_dec(key))
 283                 return;
 284
 285         schedule_delayed_work(work, timeout);
 286 }
 287 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 288
 289 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 290 {
 291         STATIC_KEY_CHECK_USE(key);
 292         flush_delayed_work(work);
 293 }
 294 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 295
 296 void jump_label_rate_limit(struct static_key_deferred *key,
 297                 unsigned long rl)
 298 {
 299         STATIC_KEY_CHECK_USE(key);
 300         key->timeout = rl;
 301         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 302 }
 303 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 304
 305 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 306 {
 307         if (jump_entry_code(entry) <= (unsigned long)end &&
 308             jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
 309                 return 1;
 310
 311         return 0;
 312 }
 313
 314 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 315                 struct jump_entry *iter_stop, void *start, void *end, bool init)
 316 {
 317         struct jump_entry *iter;
 318
 319         iter = iter_start;
 320         while (iter < iter_stop) {
 321                 if (init || !jump_entry_is_init(iter)) {
 322                         if (addr_conflict(iter, start, end))
 323                                 return 1;
 324                 }
 325                 iter++;
 326         }
 327
 328         return 0;
 329 }
 330
 331 #ifndef arch_jump_label_transform_static
 332 static void arch_jump_label_transform_static(struct jump_entry *entry,
 333                                              enum jump_label_type type)
 334 {
 335         /* nothing to do on most architectures */
 336 }
 337 #endif
 338
 339 static inline struct jump_entry *static_key_entries(struct static_key *key)
 340 {
 341         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 342         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 343 }
 344
 345 static inline bool static_key_type(struct static_key *key)
 346 {
 347         return key->type & JUMP_TYPE_TRUE;
 348 }
 349
 350 static inline bool static_key_linked(struct static_key *key)
 351 {
 352         return key->type & JUMP_TYPE_LINKED;
 353 }
 354
 355 static inline void static_key_clear_linked(struct static_key *key)
 356 {
 357         key->type &= ~JUMP_TYPE_LINKED;
 358 }
 359
 360 static inline void static_key_set_linked(struct static_key *key)
 361 {
 362         key->type |= JUMP_TYPE_LINKED;
 363 }
 364
 365 /***
 366  * A 'struct static_key' uses a union such that it either points directly
 367  * to a table of 'struct jump_entry' or to a linked list of modules which in
 368  * turn point to 'struct jump_entry' tables.
 369  *
 370  * The two lower bits of the pointer are used to keep track of which pointer
 371  * type is in use and to store the initial branch direction, we use an access
 372  * function which preserves these bits.
 373  */
 374 static void static_key_set_entries(struct static_key *key,
 375                                    struct jump_entry *entries)
 376 {
 377         unsigned long type;
 378
 379         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 380         type = key->type & JUMP_TYPE_MASK;
 381         key->entries = entries;
 382         key->type |= type;
 383 }
 384
 385 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 386 {
 387         struct static_key *key = jump_entry_key(entry);
 388         bool enabled = static_key_enabled(key);
 389         bool branch = jump_entry_is_branch(entry);
 390
 391         /* See the comment in linux/jump_label.h */
 392         return enabled ^ branch;
 393 }
 394
 395 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 396 {
 397         /*
 398          * Cannot update code that was in an init text area.
 399          */
 400         if (!init && jump_entry_is_init(entry))
 401                 return false;
 402
 403         if (!kernel_text_address(jump_entry_code(entry))) {
 404                 /*
 405                  * This skips patching built-in __exit, which
 406                  * is part of init_section_contains() but is
 407                  * not part of kernel_text_address().
 408                  *
 409                  * Skipping built-in __exit is fine since it
 410                  * will never be executed.
 411                  */
 412                 WARN_ONCE(!jump_entry_is_init(entry),
 413                           "can't patch jump_label at %pS",
 414                           (void *)jump_entry_code(entry));
 415                 return false;
 416         }
 417
 418         return true;
 419 }
 420
 421 #ifndef HAVE_JUMP_LABEL_BATCH
 422 static void __jump_label_update(struct static_key *key,
 423                                 struct jump_entry *entry,
 424                                 struct jump_entry *stop,
 425                                 bool init)
 426 {
 427         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 428                 if (jump_label_can_update(entry, init))
 429                         arch_jump_label_transform(entry, jump_label_type(entry));
 430         }
 431 }
 432 #else
 433 static void __jump_label_update(struct static_key *key,
 434                                 struct jump_entry *entry,
 435                                 struct jump_entry *stop,
 436                                 bool init)
 437 {
 438         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 439
 440                 if (!jump_label_can_update(entry, init))
 441                         continue;
 442
 443                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 444                         /*
 445                          * Queue is full: Apply the current queue and try again.
 446                          */
 447                         arch_jump_label_transform_apply();
 448                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 449                 }
 450         }
 451         arch_jump_label_transform_apply();
 452 }
 453 #endif
 454
 455 void __init jump_label_init(void)
 456 {
 457         struct jump_entry *iter_start = __start___jump_table;
 458         struct jump_entry *iter_stop = __stop___jump_table;
 459         struct static_key *key = NULL;
 460         struct jump_entry *iter;
 461
 462         /*
 463          * Since we are initializing the static_key.enabled field with
 464          * with the 'raw' int values (to avoid pulling in atomic.h) in
 465          * jump_label.h, let's make sure that is safe. There are only two
 466          * cases to check since we initialize to 0 or 1.
 467          */
 468         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 469         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 470
 471         if (static_key_initialized)
 472                 return;
 473
 474         cpus_read_lock();
 475         jump_label_lock();
 476         jump_label_sort_entries(iter_start, iter_stop);
 477
 478         for (iter = iter_start; iter < iter_stop; iter++) {
 479                 struct static_key *iterk;
 480                 bool in_init;
 481
 482                 /* rewrite NOPs */
 483                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 484                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 485
 486                 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
 487                 jump_entry_set_init(iter, in_init);
 488
 489                 iterk = jump_entry_key(iter);
 490                 if (iterk == key)
 491                         continue;
 492
 493                 key = iterk;
 494                 static_key_set_entries(key, iter);
 495         }
 496         static_key_initialized = true;
 497         jump_label_unlock();
 498         cpus_read_unlock();
 499 }
 500
 501 #ifdef CONFIG_MODULES
 502
 503 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 504 {
 505         struct static_key *key = jump_entry_key(entry);
 506         bool type = static_key_type(key);
 507         bool branch = jump_entry_is_branch(entry);
 508
 509         /* See the comment in linux/jump_label.h */
 510         return type ^ branch;
 511 }
 512
 513 struct static_key_mod {
 514         struct static_key_mod *next;
 515         struct jump_entry *entries;
 516         struct module *mod;
 517 };
 518
 519 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 520 {
 521         WARN_ON_ONCE(!static_key_linked(key));
 522         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 523 }
 524
 525 /***
 526  * key->type and key->next are the same via union.
 527  * This sets key->next and preserves the type bits.
 528  *
 529  * See additional comments above static_key_set_entries().
 530  */
 531 static void static_key_set_mod(struct static_key *key,
 532                                struct static_key_mod *mod)
 533 {
 534         unsigned long type;
 535
 536         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 537         type = key->type & JUMP_TYPE_MASK;
 538         key->next = mod;
 539         key->type |= type;
 540 }
 541
 542 static int __jump_label_mod_text_reserved(void *start, void *end)
 543 {
 544         struct module *mod;
 545         int ret;
 546
 547         preempt_disable();
 548         mod = __module_text_address((unsigned long)start);
 549         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 550         if (!try_module_get(mod))
 551                 mod = NULL;
 552         preempt_enable();
 553
 554         if (!mod)
 555                 return 0;
 556
 557         ret = __jump_label_text_reserved(mod->jump_entries,
 558                                 mod->jump_entries + mod->num_jump_entries,
 559                                 start, end, mod->state == MODULE_STATE_COMING);
 560
 561         module_put(mod);
 562
 563         return ret;
 564 }
 565
 566 static void __jump_label_mod_update(struct static_key *key)
 567 {
 568         struct static_key_mod *mod;
 569
 570         for (mod = static_key_mod(key); mod; mod = mod->next) {
 571                 struct jump_entry *stop;
 572                 struct module *m;
 573
 574                 /*
 575                  * NULL if the static_key is defined in a module
 576                  * that does not use it
 577                  */
 578                 if (!mod->entries)
 579                         continue;
 580
 581                 m = mod->mod;
 582                 if (!m)
 583                         stop = __stop___jump_table;
 584                 else
 585                         stop = m->jump_entries + m->num_jump_entries;
 586                 __jump_label_update(key, mod->entries, stop,
 587                                     m && m->state == MODULE_STATE_COMING);
 588         }
 589 }
 590
 591 static int jump_label_add_module(struct module *mod)
 592 {
 593         struct jump_entry *iter_start = mod->jump_entries;
 594         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 595         struct jump_entry *iter;
 596         struct static_key *key = NULL;
 597         struct static_key_mod *jlm, *jlm2;
 598
 599         /* if the module doesn't have jump label entries, just return */
 600         if (iter_start == iter_stop)
 601                 return 0;
 602
 603         jump_label_sort_entries(iter_start, iter_stop);
 604
 605         for (iter = iter_start; iter < iter_stop; iter++) {
 606                 struct static_key *iterk;
 607                 bool in_init;
 608
 609                 in_init = within_module_init(jump_entry_code(iter), mod);
 610                 jump_entry_set_init(iter, in_init);
 611
 612                 iterk = jump_entry_key(iter);
 613                 if (iterk == key)
 614                         continue;
 615
 616                 key = iterk;
 617                 if (within_module((unsigned long)key, mod)) {
 618                         static_key_set_entries(key, iter);
 619                         continue;
 620                 }
 621                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 622                 if (!jlm)
 623                         return -ENOMEM;
 624                 if (!static_key_linked(key)) {
 625                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 626                                        GFP_KERNEL);
 627                         if (!jlm2) {
 628                                 kfree(jlm);
 629                                 return -ENOMEM;
 630                         }
 631                         preempt_disable();
 632                         jlm2->mod = __module_address((unsigned long)key);
 633                         preempt_enable();
 634                         jlm2->entries = static_key_entries(key);
 635                         jlm2->next = NULL;
 636                         static_key_set_mod(key, jlm2);
 637                         static_key_set_linked(key);
 638                 }
 639                 jlm->mod = mod;
 640                 jlm->entries = iter;
 641                 jlm->next = static_key_mod(key);
 642                 static_key_set_mod(key, jlm);
 643                 static_key_set_linked(key);
 644
 645                 /* Only update if we've changed from our initial state */
 646                 if (jump_label_type(iter) != jump_label_init_type(iter))
 647                         __jump_label_update(key, iter, iter_stop, true);
 648         }
 649
 650         return 0;
 651 }
 652
 653 static void jump_label_del_module(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         struct static_key *key = NULL;
 659         struct static_key_mod *jlm, **prev;
 660
 661         for (iter = iter_start; iter < iter_stop; iter++) {
 662                 if (jump_entry_key(iter) == key)
 663                         continue;
 664
 665                 key = jump_entry_key(iter);
 666
 667                 if (within_module((unsigned long)key, mod))
 668                         continue;
 669
 670                 /* No memory during module load */
 671                 if (WARN_ON(!static_key_linked(key)))
 672                         continue;
 673
 674                 prev = &key->next;
 675                 jlm = static_key_mod(key);
 676
 677                 while (jlm && jlm->mod != mod) {
 678                         prev = &jlm->next;
 679                         jlm = jlm->next;
 680                 }
 681
 682                 /* No memory during module load */
 683                 if (WARN_ON(!jlm))
 684                         continue;
 685
 686                 if (prev == &key->next)
 687                         static_key_set_mod(key, jlm->next);
 688                 else
 689                         *prev = jlm->next;
 690
 691                 kfree(jlm);
 692
 693                 jlm = static_key_mod(key);
 694                 /* if only one etry is left, fold it back into the static_key */
 695                 if (jlm->next == NULL) {
 696                         static_key_set_entries(key, jlm->entries);
 697                         static_key_clear_linked(key);
 698                         kfree(jlm);
 699                 }
 700         }
 701 }
 702
 703 static int
 704 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 705                          void *data)
 706 {
 707         struct module *mod = data;
 708         int ret = 0;
 709
 710         cpus_read_lock();
 711         jump_label_lock();
 712
 713         switch (val) {
 714         case MODULE_STATE_COMING:
 715                 ret = jump_label_add_module(mod);
 716                 if (ret) {
 717                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 718                         jump_label_del_module(mod);
 719                 }
 720                 break;
 721         case MODULE_STATE_GOING:
 722                 jump_label_del_module(mod);
 723                 break;
 724         }
 725
 726         jump_label_unlock();
 727         cpus_read_unlock();
 728
 729         return notifier_from_errno(ret);
 730 }
 731
 732 static struct notifier_block jump_label_module_nb = {
 733         .notifier_call = jump_label_module_notify,
 734         .priority = 1, /* higher than tracepoints */
 735 };
 736
 737 static __init int jump_label_init_module(void)
 738 {
 739         return register_module_notifier(&jump_label_module_nb);
 740 }
 741 early_initcall(jump_label_init_module);
 742
 743 #endif /* CONFIG_MODULES */
 744
 745 /***
 746  * jump_label_text_reserved - check if addr range is reserved
 747  * @start: start text addr
 748  * @end: end text addr
 749  *
 750  * checks if the text addr located between @start and @end
 751  * overlaps with any of the jump label patch addresses. Code
 752  * that wants to modify kernel text should first verify that
 753  * it does not overlap with any of the jump label addresses.
 754  * Caller must hold jump_label_mutex.
 755  *
 756  * returns 1 if there is an overlap, 0 otherwise
 757  */
 758 int jump_label_text_reserved(void *start, void *end)
 759 {
 760         bool init = system_state < SYSTEM_RUNNING;
 761         int ret = __jump_label_text_reserved(__start___jump_table,
 762                         __stop___jump_table, start, end, init);
 763
 764         if (ret)
 765                 return ret;
 766
 767 #ifdef CONFIG_MODULES
 768         ret = __jump_label_mod_text_reserved(start, end);
 769 #endif
 770         return ret;
 771 }
 772
 773 static void jump_label_update(struct static_key *key)
 774 {
 775         struct jump_entry *stop = __stop___jump_table;
 776         bool init = system_state < SYSTEM_RUNNING;
 777         struct jump_entry *entry;
 778 #ifdef CONFIG_MODULES
 779         struct module *mod;
 780
 781         if (static_key_linked(key)) {
 782                 __jump_label_mod_update(key);
 783                 return;
 784         }
 785
 786         preempt_disable();
 787         mod = __module_address((unsigned long)key);
 788         if (mod) {
 789                 stop = mod->jump_entries + mod->num_jump_entries;
 790                 init = mod->state == MODULE_STATE_COMING;
 791         }
 792         preempt_enable();
 793 #endif
 794         entry = static_key_entries(key);
 795         /* if there are no users, entry can be NULL */
 796         if (entry)
 797                 __jump_label_update(key, entry, stop, init);
 798 }
 799
 800 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 801 static DEFINE_STATIC_KEY_TRUE(sk_true);
 802 static DEFINE_STATIC_KEY_FALSE(sk_false);
 803
 804 static __init int jump_label_test(void)
 805 {
 806         int i;
 807
 808         for (i = 0; i < 2; i++) {
 809                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 810                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 811
 812                 WARN_ON(!static_branch_likely(&sk_true));
 813                 WARN_ON(!static_branch_unlikely(&sk_true));
 814                 WARN_ON(static_branch_likely(&sk_false));
 815                 WARN_ON(static_branch_unlikely(&sk_false));
 816
 817                 static_branch_disable(&sk_true);
 818                 static_branch_enable(&sk_false);
 819
 820                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 821                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 822
 823                 WARN_ON(static_branch_likely(&sk_true));
 824                 WARN_ON(static_branch_unlikely(&sk_true));
 825                 WARN_ON(!static_branch_likely(&sk_false));
 826                 WARN_ON(!static_branch_unlikely(&sk_false));
 827
 828                 static_branch_enable(&sk_true);
 829                 static_branch_disable(&sk_false);
 830         }
 831
 832         return 0;
 833 }
 834 early_initcall(jump_label_test);
 835 #endif /* STATIC_KEYS_SELFTEST */