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         int v, v1;
 119
 120         STATIC_KEY_CHECK_USE(key);
 121         lockdep_assert_cpus_held();
 122
 123         /*
 124          * Careful if we get concurrent static_key_slow_inc() calls;
 125          * later calls must wait for the first one to _finish_ the
 126          * jump_label_update() process.  At the same time, however,
 127          * the jump_label_update() call below wants to see
 128          * static_key_enabled(&key) for jumps to be updated properly.
 129          *
 130          * So give a special meaning to negative key->enabled: it sends
 131          * static_key_slow_inc() down the slow path, and it is non-zero
 132          * so it counts as "enabled" in jump_label_update().  Note that
 133          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 134          */
 135         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 136                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 137                 if (likely(v1 == v))
 138                         return;
 139         }
 140
 141         jump_label_lock();
 142         if (atomic_read(&key->enabled) == 0) {
 143                 atomic_set(&key->enabled, -1);
 144                 jump_label_update(key);
 145                 /*
 146                  * Ensure that if the above cmpxchg loop observes our positive
 147                  * value, it must also observe all the text changes.
 148                  */
 149                 atomic_set_release(&key->enabled, 1);
 150         } else {
 151                 atomic_inc(&key->enabled);
 152         }
 153         jump_label_unlock();
 154 }
 155
 156 void static_key_slow_inc(struct static_key *key)
 157 {
 158         cpus_read_lock();
 159         static_key_slow_inc_cpuslocked(key);
 160         cpus_read_unlock();
 161 }
 162 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 163
 164 void static_key_enable_cpuslocked(struct static_key *key)
 165 {
 166         STATIC_KEY_CHECK_USE(key);
 167         lockdep_assert_cpus_held();
 168
 169         if (atomic_read(&key->enabled) > 0) {
 170                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 171                 return;
 172         }
 173
 174         jump_label_lock();
 175         if (atomic_read(&key->enabled) == 0) {
 176                 atomic_set(&key->enabled, -1);
 177                 jump_label_update(key);
 178                 /*
 179                  * See static_key_slow_inc().
 180                  */
 181                 atomic_set_release(&key->enabled, 1);
 182         }
 183         jump_label_unlock();
 184 }
 185 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 186
 187 void static_key_enable(struct static_key *key)
 188 {
 189         cpus_read_lock();
 190         static_key_enable_cpuslocked(key);
 191         cpus_read_unlock();
 192 }
 193 EXPORT_SYMBOL_GPL(static_key_enable);
 194
 195 void static_key_disable_cpuslocked(struct static_key *key)
 196 {
 197         STATIC_KEY_CHECK_USE(key);
 198         lockdep_assert_cpus_held();
 199
 200         if (atomic_read(&key->enabled) != 1) {
 201                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 202                 return;
 203         }
 204
 205         jump_label_lock();
 206         if (atomic_cmpxchg(&key->enabled, 1, 0))
 207                 jump_label_update(key);
 208         jump_label_unlock();
 209 }
 210 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 211
 212 void static_key_disable(struct static_key *key)
 213 {
 214         cpus_read_lock();
 215         static_key_disable_cpuslocked(key);
 216         cpus_read_unlock();
 217 }
 218 EXPORT_SYMBOL_GPL(static_key_disable);
 219
 220 static bool static_key_slow_try_dec(struct static_key *key)
 221 {
 222         int val;
 223
 224         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 225         if (val == 1)
 226                 return false;
 227
 228         /*
 229          * The negative count check is valid even when a negative
 230          * key->enabled is in use by static_key_slow_inc(); a
 231          * __static_key_slow_dec() before the first static_key_slow_inc()
 232          * returns is unbalanced, because all other static_key_slow_inc()
 233          * instances block while the update is in progress.
 234          */
 235         WARN(val < 0, "jump label: negative count!\n");
 236         return true;
 237 }
 238
 239 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 240 {
 241         lockdep_assert_cpus_held();
 242
 243         if (static_key_slow_try_dec(key))
 244                 return;
 245
 246         jump_label_lock();
 247         if (atomic_dec_and_test(&key->enabled))
 248                 jump_label_update(key);
 249         jump_label_unlock();
 250 }
 251
 252 static void __static_key_slow_dec(struct static_key *key)
 253 {
 254         cpus_read_lock();
 255         __static_key_slow_dec_cpuslocked(key);
 256         cpus_read_unlock();
 257 }
 258
 259 void jump_label_update_timeout(struct work_struct *work)
 260 {
 261         struct static_key_deferred *key =
 262                 container_of(work, struct static_key_deferred, work.work);
 263         __static_key_slow_dec(&key->key);
 264 }
 265 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 266
 267 void static_key_slow_dec(struct static_key *key)
 268 {
 269         STATIC_KEY_CHECK_USE(key);
 270         __static_key_slow_dec(key);
 271 }
 272 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 273
 274 void static_key_slow_dec_cpuslocked(struct static_key *key)
 275 {
 276         STATIC_KEY_CHECK_USE(key);
 277         __static_key_slow_dec_cpuslocked(key);
 278 }
 279
 280 void __static_key_slow_dec_deferred(struct static_key *key,
 281                                     struct delayed_work *work,
 282                                     unsigned long timeout)
 283 {
 284         STATIC_KEY_CHECK_USE(key);
 285
 286         if (static_key_slow_try_dec(key))
 287                 return;
 288
 289         schedule_delayed_work(work, timeout);
 290 }
 291 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 292
 293 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 294 {
 295         STATIC_KEY_CHECK_USE(key);
 296         flush_delayed_work(work);
 297 }
 298 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 299
 300 void jump_label_rate_limit(struct static_key_deferred *key,
 301                 unsigned long rl)
 302 {
 303         STATIC_KEY_CHECK_USE(key);
 304         key->timeout = rl;
 305         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 306 }
 307 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 308
 309 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 310 {
 311         if (jump_entry_code(entry) <= (unsigned long)end &&
 312             jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
 313                 return 1;
 314
 315         return 0;
 316 }
 317
 318 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 319                 struct jump_entry *iter_stop, void *start, void *end, bool init)
 320 {
 321         struct jump_entry *iter;
 322
 323         iter = iter_start;
 324         while (iter < iter_stop) {
 325                 if (init || !jump_entry_is_init(iter)) {
 326                         if (addr_conflict(iter, start, end))
 327                                 return 1;
 328                 }
 329                 iter++;
 330         }
 331
 332         return 0;
 333 }
 334
 335 #ifndef arch_jump_label_transform_static
 336 static void arch_jump_label_transform_static(struct jump_entry *entry,
 337                                              enum jump_label_type type)
 338 {
 339         /* nothing to do on most architectures */
 340 }
 341 #endif
 342
 343 static inline struct jump_entry *static_key_entries(struct static_key *key)
 344 {
 345         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 346         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 347 }
 348
 349 static inline bool static_key_type(struct static_key *key)
 350 {
 351         return key->type & JUMP_TYPE_TRUE;
 352 }
 353
 354 static inline bool static_key_linked(struct static_key *key)
 355 {
 356         return key->type & JUMP_TYPE_LINKED;
 357 }
 358
 359 static inline void static_key_clear_linked(struct static_key *key)
 360 {
 361         key->type &= ~JUMP_TYPE_LINKED;
 362 }
 363
 364 static inline void static_key_set_linked(struct static_key *key)
 365 {
 366         key->type |= JUMP_TYPE_LINKED;
 367 }
 368
 369 /***
 370  * A 'struct static_key' uses a union such that it either points directly
 371  * to a table of 'struct jump_entry' or to a linked list of modules which in
 372  * turn point to 'struct jump_entry' tables.
 373  *
 374  * The two lower bits of the pointer are used to keep track of which pointer
 375  * type is in use and to store the initial branch direction, we use an access
 376  * function which preserves these bits.
 377  */
 378 static void static_key_set_entries(struct static_key *key,
 379                                    struct jump_entry *entries)
 380 {
 381         unsigned long type;
 382
 383         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 384         type = key->type & JUMP_TYPE_MASK;
 385         key->entries = entries;
 386         key->type |= type;
 387 }
 388
 389 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 390 {
 391         struct static_key *key = jump_entry_key(entry);
 392         bool enabled = static_key_enabled(key);
 393         bool branch = jump_entry_is_branch(entry);
 394
 395         /* See the comment in linux/jump_label.h */
 396         return enabled ^ branch;
 397 }
 398
 399 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 400 {
 401         /*
 402          * Cannot update code that was in an init text area.
 403          */
 404         if (!init && jump_entry_is_init(entry))
 405                 return false;
 406
 407         if (!kernel_text_address(jump_entry_code(entry))) {
 408                 /*
 409                  * This skips patching built-in __exit, which
 410                  * is part of init_section_contains() but is
 411                  * not part of kernel_text_address().
 412                  *
 413                  * Skipping built-in __exit is fine since it
 414                  * will never be executed.
 415                  */
 416                 WARN_ONCE(!jump_entry_is_init(entry),
 417                           "can't patch jump_label at %pS",
 418                           (void *)jump_entry_code(entry));
 419                 return false;
 420         }
 421
 422         return true;
 423 }
 424
 425 #ifndef HAVE_JUMP_LABEL_BATCH
 426 static void __jump_label_update(struct static_key *key,
 427                                 struct jump_entry *entry,
 428                                 struct jump_entry *stop,
 429                                 bool init)
 430 {
 431         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 432                 if (jump_label_can_update(entry, init))
 433                         arch_jump_label_transform(entry, jump_label_type(entry));
 434         }
 435 }
 436 #else
 437 static void __jump_label_update(struct static_key *key,
 438                                 struct jump_entry *entry,
 439                                 struct jump_entry *stop,
 440                                 bool init)
 441 {
 442         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 443
 444                 if (!jump_label_can_update(entry, init))
 445                         continue;
 446
 447                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 448                         /*
 449                          * Queue is full: Apply the current queue and try again.
 450                          */
 451                         arch_jump_label_transform_apply();
 452                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 453                 }
 454         }
 455         arch_jump_label_transform_apply();
 456 }
 457 #endif
 458
 459 void __init jump_label_init(void)
 460 {
 461         struct jump_entry *iter_start = __start___jump_table;
 462         struct jump_entry *iter_stop = __stop___jump_table;
 463         struct static_key *key = NULL;
 464         struct jump_entry *iter;
 465
 466         /*
 467          * Since we are initializing the static_key.enabled field with
 468          * with the 'raw' int values (to avoid pulling in atomic.h) in
 469          * jump_label.h, let's make sure that is safe. There are only two
 470          * cases to check since we initialize to 0 or 1.
 471          */
 472         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 473         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 474
 475         if (static_key_initialized)
 476                 return;
 477
 478         cpus_read_lock();
 479         jump_label_lock();
 480         jump_label_sort_entries(iter_start, iter_stop);
 481
 482         for (iter = iter_start; iter < iter_stop; iter++) {
 483                 struct static_key *iterk;
 484                 bool in_init;
 485
 486                 /* rewrite NOPs */
 487                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 488                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 489
 490                 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
 491                 jump_entry_set_init(iter, in_init);
 492
 493                 iterk = jump_entry_key(iter);
 494                 if (iterk == key)
 495                         continue;
 496
 497                 key = iterk;
 498                 static_key_set_entries(key, iter);
 499         }
 500         static_key_initialized = true;
 501         jump_label_unlock();
 502         cpus_read_unlock();
 503 }
 504
 505 #ifdef CONFIG_MODULES
 506
 507 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 508 {
 509         struct static_key *key = jump_entry_key(entry);
 510         bool type = static_key_type(key);
 511         bool branch = jump_entry_is_branch(entry);
 512
 513         /* See the comment in linux/jump_label.h */
 514         return type ^ branch;
 515 }
 516
 517 struct static_key_mod {
 518         struct static_key_mod *next;
 519         struct jump_entry *entries;
 520         struct module *mod;
 521 };
 522
 523 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 524 {
 525         WARN_ON_ONCE(!static_key_linked(key));
 526         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 527 }
 528
 529 /***
 530  * key->type and key->next are the same via union.
 531  * This sets key->next and preserves the type bits.
 532  *
 533  * See additional comments above static_key_set_entries().
 534  */
 535 static void static_key_set_mod(struct static_key *key,
 536                                struct static_key_mod *mod)
 537 {
 538         unsigned long type;
 539
 540         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 541         type = key->type & JUMP_TYPE_MASK;
 542         key->next = mod;
 543         key->type |= type;
 544 }
 545
 546 static int __jump_label_mod_text_reserved(void *start, void *end)
 547 {
 548         struct module *mod;
 549         int ret;
 550
 551         preempt_disable();
 552         mod = __module_text_address((unsigned long)start);
 553         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 554         if (!try_module_get(mod))
 555                 mod = NULL;
 556         preempt_enable();
 557
 558         if (!mod)
 559                 return 0;
 560
 561         ret = __jump_label_text_reserved(mod->jump_entries,
 562                                 mod->jump_entries + mod->num_jump_entries,
 563                                 start, end, mod->state == MODULE_STATE_COMING);
 564
 565         module_put(mod);
 566
 567         return ret;
 568 }
 569
 570 static void __jump_label_mod_update(struct static_key *key)
 571 {
 572         struct static_key_mod *mod;
 573
 574         for (mod = static_key_mod(key); mod; mod = mod->next) {
 575                 struct jump_entry *stop;
 576                 struct module *m;
 577
 578                 /*
 579                  * NULL if the static_key is defined in a module
 580                  * that does not use it
 581                  */
 582                 if (!mod->entries)
 583                         continue;
 584
 585                 m = mod->mod;
 586                 if (!m)
 587                         stop = __stop___jump_table;
 588                 else
 589                         stop = m->jump_entries + m->num_jump_entries;
 590                 __jump_label_update(key, mod->entries, stop,
 591                                     m && m->state == MODULE_STATE_COMING);
 592         }
 593 }
 594
 595 static int jump_label_add_module(struct module *mod)
 596 {
 597         struct jump_entry *iter_start = mod->jump_entries;
 598         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 599         struct jump_entry *iter;
 600         struct static_key *key = NULL;
 601         struct static_key_mod *jlm, *jlm2;
 602
 603         /* if the module doesn't have jump label entries, just return */
 604         if (iter_start == iter_stop)
 605                 return 0;
 606
 607         jump_label_sort_entries(iter_start, iter_stop);
 608
 609         for (iter = iter_start; iter < iter_stop; iter++) {
 610                 struct static_key *iterk;
 611                 bool in_init;
 612
 613                 in_init = within_module_init(jump_entry_code(iter), mod);
 614                 jump_entry_set_init(iter, in_init);
 615
 616                 iterk = jump_entry_key(iter);
 617                 if (iterk == key)
 618                         continue;
 619
 620                 key = iterk;
 621                 if (within_module((unsigned long)key, mod)) {
 622                         static_key_set_entries(key, iter);
 623                         continue;
 624                 }
 625                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 626                 if (!jlm)
 627                         return -ENOMEM;
 628                 if (!static_key_linked(key)) {
 629                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 630                                        GFP_KERNEL);
 631                         if (!jlm2) {
 632                                 kfree(jlm);
 633                                 return -ENOMEM;
 634                         }
 635                         preempt_disable();
 636                         jlm2->mod = __module_address((unsigned long)key);
 637                         preempt_enable();
 638                         jlm2->entries = static_key_entries(key);
 639                         jlm2->next = NULL;
 640                         static_key_set_mod(key, jlm2);
 641                         static_key_set_linked(key);
 642                 }
 643                 jlm->mod = mod;
 644                 jlm->entries = iter;
 645                 jlm->next = static_key_mod(key);
 646                 static_key_set_mod(key, jlm);
 647                 static_key_set_linked(key);
 648
 649                 /* Only update if we've changed from our initial state */
 650                 if (jump_label_type(iter) != jump_label_init_type(iter))
 651                         __jump_label_update(key, iter, iter_stop, true);
 652         }
 653
 654         return 0;
 655 }
 656
 657 static void jump_label_del_module(struct module *mod)
 658 {
 659         struct jump_entry *iter_start = mod->jump_entries;
 660         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 661         struct jump_entry *iter;
 662         struct static_key *key = NULL;
 663         struct static_key_mod *jlm, **prev;
 664
 665         for (iter = iter_start; iter < iter_stop; iter++) {
 666                 if (jump_entry_key(iter) == key)
 667                         continue;
 668
 669                 key = jump_entry_key(iter);
 670
 671                 if (within_module((unsigned long)key, mod))
 672                         continue;
 673
 674                 /* No memory during module load */
 675                 if (WARN_ON(!static_key_linked(key)))
 676                         continue;
 677
 678                 prev = &key->next;
 679                 jlm = static_key_mod(key);
 680
 681                 while (jlm && jlm->mod != mod) {
 682                         prev = &jlm->next;
 683                         jlm = jlm->next;
 684                 }
 685
 686                 /* No memory during module load */
 687                 if (WARN_ON(!jlm))
 688                         continue;
 689
 690                 if (prev == &key->next)
 691                         static_key_set_mod(key, jlm->next);
 692                 else
 693                         *prev = jlm->next;
 694
 695                 kfree(jlm);
 696
 697                 jlm = static_key_mod(key);
 698                 /* if only one etry is left, fold it back into the static_key */
 699                 if (jlm->next == NULL) {
 700                         static_key_set_entries(key, jlm->entries);
 701                         static_key_clear_linked(key);
 702                         kfree(jlm);
 703                 }
 704         }
 705 }
 706
 707 static int
 708 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 709                          void *data)
 710 {
 711         struct module *mod = data;
 712         int ret = 0;
 713
 714         cpus_read_lock();
 715         jump_label_lock();
 716
 717         switch (val) {
 718         case MODULE_STATE_COMING:
 719                 ret = jump_label_add_module(mod);
 720                 if (ret) {
 721                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 722                         jump_label_del_module(mod);
 723                 }
 724                 break;
 725         case MODULE_STATE_GOING:
 726                 jump_label_del_module(mod);
 727                 break;
 728         }
 729
 730         jump_label_unlock();
 731         cpus_read_unlock();
 732
 733         return notifier_from_errno(ret);
 734 }
 735
 736 static struct notifier_block jump_label_module_nb = {
 737         .notifier_call = jump_label_module_notify,
 738         .priority = 1, /* higher than tracepoints */
 739 };
 740
 741 static __init int jump_label_init_module(void)
 742 {
 743         return register_module_notifier(&jump_label_module_nb);
 744 }
 745 early_initcall(jump_label_init_module);
 746
 747 #endif /* CONFIG_MODULES */
 748
 749 /***
 750  * jump_label_text_reserved - check if addr range is reserved
 751  * @start: start text addr
 752  * @end: end text addr
 753  *
 754  * checks if the text addr located between @start and @end
 755  * overlaps with any of the jump label patch addresses. Code
 756  * that wants to modify kernel text should first verify that
 757  * it does not overlap with any of the jump label addresses.
 758  * Caller must hold jump_label_mutex.
 759  *
 760  * returns 1 if there is an overlap, 0 otherwise
 761  */
 762 int jump_label_text_reserved(void *start, void *end)
 763 {
 764         bool init = system_state < SYSTEM_RUNNING;
 765         int ret = __jump_label_text_reserved(__start___jump_table,
 766                         __stop___jump_table, start, end, init);
 767
 768         if (ret)
 769                 return ret;
 770
 771 #ifdef CONFIG_MODULES
 772         ret = __jump_label_mod_text_reserved(start, end);
 773 #endif
 774         return ret;
 775 }
 776
 777 static void jump_label_update(struct static_key *key)
 778 {
 779         struct jump_entry *stop = __stop___jump_table;
 780         bool init = system_state < SYSTEM_RUNNING;
 781         struct jump_entry *entry;
 782 #ifdef CONFIG_MODULES
 783         struct module *mod;
 784
 785         if (static_key_linked(key)) {
 786                 __jump_label_mod_update(key);
 787                 return;
 788         }
 789
 790         preempt_disable();
 791         mod = __module_address((unsigned long)key);
 792         if (mod) {
 793                 stop = mod->jump_entries + mod->num_jump_entries;
 794                 init = mod->state == MODULE_STATE_COMING;
 795         }
 796         preempt_enable();
 797 #endif
 798         entry = static_key_entries(key);
 799         /* if there are no users, entry can be NULL */
 800         if (entry)
 801                 __jump_label_update(key, entry, stop, init);
 802 }
 803
 804 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 805 static DEFINE_STATIC_KEY_TRUE(sk_true);
 806 static DEFINE_STATIC_KEY_FALSE(sk_false);
 807
 808 static __init int jump_label_test(void)
 809 {
 810         int i;
 811
 812         for (i = 0; i < 2; i++) {
 813                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 814                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 815
 816                 WARN_ON(!static_branch_likely(&sk_true));
 817                 WARN_ON(!static_branch_unlikely(&sk_true));
 818                 WARN_ON(static_branch_likely(&sk_false));
 819                 WARN_ON(static_branch_unlikely(&sk_false));
 820
 821                 static_branch_disable(&sk_true);
 822                 static_branch_enable(&sk_false);
 823
 824                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 825                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 826
 827                 WARN_ON(static_branch_likely(&sk_true));
 828                 WARN_ON(static_branch_unlikely(&sk_true));
 829                 WARN_ON(!static_branch_likely(&sk_false));
 830                 WARN_ON(!static_branch_unlikely(&sk_false));
 831
 832                 static_branch_enable(&sk_true);
 833                 static_branch_disable(&sk_false);
 834         }
 835
 836         return 0;
 837 }
 838 early_initcall(jump_label_test);
 839 #endif /* STATIC_KEYS_SELFTEST */