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 /*
 117  * static_key_fast_inc_not_disabled - adds a user for a static key
 118  * @key: static key that must be already enabled
 119  *
 120  * The caller must make sure that the static key can't get disabled while
 121  * in this function. It doesn't patch jump labels, only adds a user to
 122  * an already enabled static key.
 123  *
 124  * Returns true if the increment was done. Unlike refcount_t the ref counter
 125  * is not saturated, but will fail to increment on overflow.
 126  */
 127 bool static_key_fast_inc_not_disabled(struct static_key *key)
 128 {
 129         int v;
 130
 131         STATIC_KEY_CHECK_USE(key);
 132         /*
 133          * Negative key->enabled has a special meaning: it sends
 134          * static_key_slow_inc() down the slow path, and it is non-zero
 135          * so it counts as "enabled" in jump_label_update().  Note that
 136          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 137          */
 138         v = atomic_read(&key->enabled);
 139         do {
 140                 if (v <= 0 || (v + 1) < 0)
 141                         return false;
 142         } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
 143
 144         return true;
 145 }
 146 EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
 147
 148 bool static_key_slow_inc_cpuslocked(struct static_key *key)
 149 {
 150         lockdep_assert_cpus_held();
 151
 152         /*
 153          * Careful if we get concurrent static_key_slow_inc() calls;
 154          * later calls must wait for the first one to _finish_ the
 155          * jump_label_update() process.  At the same time, however,
 156          * the jump_label_update() call below wants to see
 157          * static_key_enabled(&key) for jumps to be updated properly.
 158          */
 159         if (static_key_fast_inc_not_disabled(key))
 160                 return true;
 161
 162         jump_label_lock();
 163         if (atomic_read(&key->enabled) == 0) {
 164                 atomic_set(&key->enabled, -1);
 165                 jump_label_update(key);
 166                 /*
 167                  * Ensure that if the above cmpxchg loop observes our positive
 168                  * value, it must also observe all the text changes.
 169                  */
 170                 atomic_set_release(&key->enabled, 1);
 171         } else {
 172                 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key))) {
 173                         jump_label_unlock();
 174                         return false;
 175                 }
 176         }
 177         jump_label_unlock();
 178         return true;
 179 }
 180
 181 bool static_key_slow_inc(struct static_key *key)
 182 {
 183         bool ret;
 184
 185         cpus_read_lock();
 186         ret = static_key_slow_inc_cpuslocked(key);
 187         cpus_read_unlock();
 188         return ret;
 189 }
 190 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 191
 192 void static_key_enable_cpuslocked(struct static_key *key)
 193 {
 194         STATIC_KEY_CHECK_USE(key);
 195         lockdep_assert_cpus_held();
 196
 197         if (atomic_read(&key->enabled) > 0) {
 198                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 199                 return;
 200         }
 201
 202         jump_label_lock();
 203         if (atomic_read(&key->enabled) == 0) {
 204                 atomic_set(&key->enabled, -1);
 205                 jump_label_update(key);
 206                 /*
 207                  * See static_key_slow_inc().
 208                  */
 209                 atomic_set_release(&key->enabled, 1);
 210         }
 211         jump_label_unlock();
 212 }
 213 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 214
 215 void static_key_enable(struct static_key *key)
 216 {
 217         cpus_read_lock();
 218         static_key_enable_cpuslocked(key);
 219         cpus_read_unlock();
 220 }
 221 EXPORT_SYMBOL_GPL(static_key_enable);
 222
 223 void static_key_disable_cpuslocked(struct static_key *key)
 224 {
 225         STATIC_KEY_CHECK_USE(key);
 226         lockdep_assert_cpus_held();
 227
 228         if (atomic_read(&key->enabled) != 1) {
 229                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 230                 return;
 231         }
 232
 233         jump_label_lock();
 234         if (atomic_cmpxchg(&key->enabled, 1, 0))
 235                 jump_label_update(key);
 236         jump_label_unlock();
 237 }
 238 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 239
 240 void static_key_disable(struct static_key *key)
 241 {
 242         cpus_read_lock();
 243         static_key_disable_cpuslocked(key);
 244         cpus_read_unlock();
 245 }
 246 EXPORT_SYMBOL_GPL(static_key_disable);
 247
 248 static bool static_key_slow_try_dec(struct static_key *key)
 249 {
 250         int val;
 251
 252         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 253         if (val == 1)
 254                 return false;
 255
 256         /*
 257          * The negative count check is valid even when a negative
 258          * key->enabled is in use by static_key_slow_inc(); a
 259          * __static_key_slow_dec() before the first static_key_slow_inc()
 260          * returns is unbalanced, because all other static_key_slow_inc()
 261          * instances block while the update is in progress.
 262          */
 263         WARN(val < 0, "jump label: negative count!\n");
 264         return true;
 265 }
 266
 267 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 268 {
 269         lockdep_assert_cpus_held();
 270
 271         if (static_key_slow_try_dec(key))
 272                 return;
 273
 274         jump_label_lock();
 275         if (atomic_dec_and_test(&key->enabled))
 276                 jump_label_update(key);
 277         jump_label_unlock();
 278 }
 279
 280 static void __static_key_slow_dec(struct static_key *key)
 281 {
 282         cpus_read_lock();
 283         __static_key_slow_dec_cpuslocked(key);
 284         cpus_read_unlock();
 285 }
 286
 287 void jump_label_update_timeout(struct work_struct *work)
 288 {
 289         struct static_key_deferred *key =
 290                 container_of(work, struct static_key_deferred, work.work);
 291         __static_key_slow_dec(&key->key);
 292 }
 293 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 294
 295 void static_key_slow_dec(struct static_key *key)
 296 {
 297         STATIC_KEY_CHECK_USE(key);
 298         __static_key_slow_dec(key);
 299 }
 300 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 301
 302 void static_key_slow_dec_cpuslocked(struct static_key *key)
 303 {
 304         STATIC_KEY_CHECK_USE(key);
 305         __static_key_slow_dec_cpuslocked(key);
 306 }
 307
 308 void __static_key_slow_dec_deferred(struct static_key *key,
 309                                     struct delayed_work *work,
 310                                     unsigned long timeout)
 311 {
 312         STATIC_KEY_CHECK_USE(key);
 313
 314         if (static_key_slow_try_dec(key))
 315                 return;
 316
 317         schedule_delayed_work(work, timeout);
 318 }
 319 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 320
 321 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 322 {
 323         STATIC_KEY_CHECK_USE(key);
 324         flush_delayed_work(work);
 325 }
 326 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 327
 328 void jump_label_rate_limit(struct static_key_deferred *key,
 329                 unsigned long rl)
 330 {
 331         STATIC_KEY_CHECK_USE(key);
 332         key->timeout = rl;
 333         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 334 }
 335 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 336
 337 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 338 {
 339         if (jump_entry_code(entry) <= (unsigned long)end &&
 340             jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
 341                 return 1;
 342
 343         return 0;
 344 }
 345
 346 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 347                 struct jump_entry *iter_stop, void *start, void *end, bool init)
 348 {
 349         struct jump_entry *iter;
 350
 351         iter = iter_start;
 352         while (iter < iter_stop) {
 353                 if (init || !jump_entry_is_init(iter)) {
 354                         if (addr_conflict(iter, start, end))
 355                                 return 1;
 356                 }
 357                 iter++;
 358         }
 359
 360         return 0;
 361 }
 362
 363 #ifndef arch_jump_label_transform_static
 364 static void arch_jump_label_transform_static(struct jump_entry *entry,
 365                                              enum jump_label_type type)
 366 {
 367         /* nothing to do on most architectures */
 368 }
 369 #endif
 370
 371 static inline struct jump_entry *static_key_entries(struct static_key *key)
 372 {
 373         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 374         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 375 }
 376
 377 static inline bool static_key_type(struct static_key *key)
 378 {
 379         return key->type & JUMP_TYPE_TRUE;
 380 }
 381
 382 static inline bool static_key_linked(struct static_key *key)
 383 {
 384         return key->type & JUMP_TYPE_LINKED;
 385 }
 386
 387 static inline void static_key_clear_linked(struct static_key *key)
 388 {
 389         key->type &= ~JUMP_TYPE_LINKED;
 390 }
 391
 392 static inline void static_key_set_linked(struct static_key *key)
 393 {
 394         key->type |= JUMP_TYPE_LINKED;
 395 }
 396
 397 /***
 398  * A 'struct static_key' uses a union such that it either points directly
 399  * to a table of 'struct jump_entry' or to a linked list of modules which in
 400  * turn point to 'struct jump_entry' tables.
 401  *
 402  * The two lower bits of the pointer are used to keep track of which pointer
 403  * type is in use and to store the initial branch direction, we use an access
 404  * function which preserves these bits.
 405  */
 406 static void static_key_set_entries(struct static_key *key,
 407                                    struct jump_entry *entries)
 408 {
 409         unsigned long type;
 410
 411         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 412         type = key->type & JUMP_TYPE_MASK;
 413         key->entries = entries;
 414         key->type |= type;
 415 }
 416
 417 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 418 {
 419         struct static_key *key = jump_entry_key(entry);
 420         bool enabled = static_key_enabled(key);
 421         bool branch = jump_entry_is_branch(entry);
 422
 423         /* See the comment in linux/jump_label.h */
 424         return enabled ^ branch;
 425 }
 426
 427 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 428 {
 429         /*
 430          * Cannot update code that was in an init text area.
 431          */
 432         if (!init && jump_entry_is_init(entry))
 433                 return false;
 434
 435         if (!kernel_text_address(jump_entry_code(entry))) {
 436                 /*
 437                  * This skips patching built-in __exit, which
 438                  * is part of init_section_contains() but is
 439                  * not part of kernel_text_address().
 440                  *
 441                  * Skipping built-in __exit is fine since it
 442                  * will never be executed.
 443                  */
 444                 WARN_ONCE(!jump_entry_is_init(entry),
 445                           "can't patch jump_label at %pS",
 446                           (void *)jump_entry_code(entry));
 447                 return false;
 448         }
 449
 450         return true;
 451 }
 452
 453 #ifndef HAVE_JUMP_LABEL_BATCH
 454 static void __jump_label_update(struct static_key *key,
 455                                 struct jump_entry *entry,
 456                                 struct jump_entry *stop,
 457                                 bool init)
 458 {
 459         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 460                 if (jump_label_can_update(entry, init))
 461                         arch_jump_label_transform(entry, jump_label_type(entry));
 462         }
 463 }
 464 #else
 465 static void __jump_label_update(struct static_key *key,
 466                                 struct jump_entry *entry,
 467                                 struct jump_entry *stop,
 468                                 bool init)
 469 {
 470         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 471
 472                 if (!jump_label_can_update(entry, init))
 473                         continue;
 474
 475                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 476                         /*
 477                          * Queue is full: Apply the current queue and try again.
 478                          */
 479                         arch_jump_label_transform_apply();
 480                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 481                 }
 482         }
 483         arch_jump_label_transform_apply();
 484 }
 485 #endif
 486
 487 void __init jump_label_init(void)
 488 {
 489         struct jump_entry *iter_start = __start___jump_table;
 490         struct jump_entry *iter_stop = __stop___jump_table;
 491         struct static_key *key = NULL;
 492         struct jump_entry *iter;
 493
 494         /*
 495          * Since we are initializing the static_key.enabled field with
 496          * with the 'raw' int values (to avoid pulling in atomic.h) in
 497          * jump_label.h, let's make sure that is safe. There are only two
 498          * cases to check since we initialize to 0 or 1.
 499          */
 500         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 501         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 502
 503         if (static_key_initialized)
 504                 return;
 505
 506         cpus_read_lock();
 507         jump_label_lock();
 508         jump_label_sort_entries(iter_start, iter_stop);
 509
 510         for (iter = iter_start; iter < iter_stop; iter++) {
 511                 struct static_key *iterk;
 512                 bool in_init;
 513
 514                 /* rewrite NOPs */
 515                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 516                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 517
 518                 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
 519                 jump_entry_set_init(iter, in_init);
 520
 521                 iterk = jump_entry_key(iter);
 522                 if (iterk == key)
 523                         continue;
 524
 525                 key = iterk;
 526                 static_key_set_entries(key, iter);
 527         }
 528         static_key_initialized = true;
 529         jump_label_unlock();
 530         cpus_read_unlock();
 531 }
 532
 533 #ifdef CONFIG_MODULES
 534
 535 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 536 {
 537         struct static_key *key = jump_entry_key(entry);
 538         bool type = static_key_type(key);
 539         bool branch = jump_entry_is_branch(entry);
 540
 541         /* See the comment in linux/jump_label.h */
 542         return type ^ branch;
 543 }
 544
 545 struct static_key_mod {
 546         struct static_key_mod *next;
 547         struct jump_entry *entries;
 548         struct module *mod;
 549 };
 550
 551 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 552 {
 553         WARN_ON_ONCE(!static_key_linked(key));
 554         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 555 }
 556
 557 /***
 558  * key->type and key->next are the same via union.
 559  * This sets key->next and preserves the type bits.
 560  *
 561  * See additional comments above static_key_set_entries().
 562  */
 563 static void static_key_set_mod(struct static_key *key,
 564                                struct static_key_mod *mod)
 565 {
 566         unsigned long type;
 567
 568         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 569         type = key->type & JUMP_TYPE_MASK;
 570         key->next = mod;
 571         key->type |= type;
 572 }
 573
 574 static int __jump_label_mod_text_reserved(void *start, void *end)
 575 {
 576         struct module *mod;
 577         int ret;
 578
 579         preempt_disable();
 580         mod = __module_text_address((unsigned long)start);
 581         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 582         if (!try_module_get(mod))
 583                 mod = NULL;
 584         preempt_enable();
 585
 586         if (!mod)
 587                 return 0;
 588
 589         ret = __jump_label_text_reserved(mod->jump_entries,
 590                                 mod->jump_entries + mod->num_jump_entries,
 591                                 start, end, mod->state == MODULE_STATE_COMING);
 592
 593         module_put(mod);
 594
 595         return ret;
 596 }
 597
 598 static void __jump_label_mod_update(struct static_key *key)
 599 {
 600         struct static_key_mod *mod;
 601
 602         for (mod = static_key_mod(key); mod; mod = mod->next) {
 603                 struct jump_entry *stop;
 604                 struct module *m;
 605
 606                 /*
 607                  * NULL if the static_key is defined in a module
 608                  * that does not use it
 609                  */
 610                 if (!mod->entries)
 611                         continue;
 612
 613                 m = mod->mod;
 614                 if (!m)
 615                         stop = __stop___jump_table;
 616                 else
 617                         stop = m->jump_entries + m->num_jump_entries;
 618                 __jump_label_update(key, mod->entries, stop,
 619                                     m && m->state == MODULE_STATE_COMING);
 620         }
 621 }
 622
 623 static int jump_label_add_module(struct module *mod)
 624 {
 625         struct jump_entry *iter_start = mod->jump_entries;
 626         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 627         struct jump_entry *iter;
 628         struct static_key *key = NULL;
 629         struct static_key_mod *jlm, *jlm2;
 630
 631         /* if the module doesn't have jump label entries, just return */
 632         if (iter_start == iter_stop)
 633                 return 0;
 634
 635         jump_label_sort_entries(iter_start, iter_stop);
 636
 637         for (iter = iter_start; iter < iter_stop; iter++) {
 638                 struct static_key *iterk;
 639                 bool in_init;
 640
 641                 in_init = within_module_init(jump_entry_code(iter), mod);
 642                 jump_entry_set_init(iter, in_init);
 643
 644                 iterk = jump_entry_key(iter);
 645                 if (iterk == key)
 646                         continue;
 647
 648                 key = iterk;
 649                 if (within_module((unsigned long)key, mod)) {
 650                         static_key_set_entries(key, iter);
 651                         continue;
 652                 }
 653                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 654                 if (!jlm)
 655                         return -ENOMEM;
 656                 if (!static_key_linked(key)) {
 657                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 658                                        GFP_KERNEL);
 659                         if (!jlm2) {
 660                                 kfree(jlm);
 661                                 return -ENOMEM;
 662                         }
 663                         preempt_disable();
 664                         jlm2->mod = __module_address((unsigned long)key);
 665                         preempt_enable();
 666                         jlm2->entries = static_key_entries(key);
 667                         jlm2->next = NULL;
 668                         static_key_set_mod(key, jlm2);
 669                         static_key_set_linked(key);
 670                 }
 671                 jlm->mod = mod;
 672                 jlm->entries = iter;
 673                 jlm->next = static_key_mod(key);
 674                 static_key_set_mod(key, jlm);
 675                 static_key_set_linked(key);
 676
 677                 /* Only update if we've changed from our initial state */
 678                 if (jump_label_type(iter) != jump_label_init_type(iter))
 679                         __jump_label_update(key, iter, iter_stop, true);
 680         }
 681
 682         return 0;
 683 }
 684
 685 static void jump_label_del_module(struct module *mod)
 686 {
 687         struct jump_entry *iter_start = mod->jump_entries;
 688         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 689         struct jump_entry *iter;
 690         struct static_key *key = NULL;
 691         struct static_key_mod *jlm, **prev;
 692
 693         for (iter = iter_start; iter < iter_stop; iter++) {
 694                 if (jump_entry_key(iter) == key)
 695                         continue;
 696
 697                 key = jump_entry_key(iter);
 698
 699                 if (within_module((unsigned long)key, mod))
 700                         continue;
 701
 702                 /* No memory during module load */
 703                 if (WARN_ON(!static_key_linked(key)))
 704                         continue;
 705
 706                 prev = &key->next;
 707                 jlm = static_key_mod(key);
 708
 709                 while (jlm && jlm->mod != mod) {
 710                         prev = &jlm->next;
 711                         jlm = jlm->next;
 712                 }
 713
 714                 /* No memory during module load */
 715                 if (WARN_ON(!jlm))
 716                         continue;
 717
 718                 if (prev == &key->next)
 719                         static_key_set_mod(key, jlm->next);
 720                 else
 721                         *prev = jlm->next;
 722
 723                 kfree(jlm);
 724
 725                 jlm = static_key_mod(key);
 726                 /* if only one etry is left, fold it back into the static_key */
 727                 if (jlm->next == NULL) {
 728                         static_key_set_entries(key, jlm->entries);
 729                         static_key_clear_linked(key);
 730                         kfree(jlm);
 731                 }
 732         }
 733 }
 734
 735 static int
 736 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 737                          void *data)
 738 {
 739         struct module *mod = data;
 740         int ret = 0;
 741
 742         cpus_read_lock();
 743         jump_label_lock();
 744
 745         switch (val) {
 746         case MODULE_STATE_COMING:
 747                 ret = jump_label_add_module(mod);
 748                 if (ret) {
 749                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 750                         jump_label_del_module(mod);
 751                 }
 752                 break;
 753         case MODULE_STATE_GOING:
 754                 jump_label_del_module(mod);
 755                 break;
 756         }
 757
 758         jump_label_unlock();
 759         cpus_read_unlock();
 760
 761         return notifier_from_errno(ret);
 762 }
 763
 764 static struct notifier_block jump_label_module_nb = {
 765         .notifier_call = jump_label_module_notify,
 766         .priority = 1, /* higher than tracepoints */
 767 };
 768
 769 static __init int jump_label_init_module(void)
 770 {
 771         return register_module_notifier(&jump_label_module_nb);
 772 }
 773 early_initcall(jump_label_init_module);
 774
 775 #endif /* CONFIG_MODULES */
 776
 777 /***
 778  * jump_label_text_reserved - check if addr range is reserved
 779  * @start: start text addr
 780  * @end: end text addr
 781  *
 782  * checks if the text addr located between @start and @end
 783  * overlaps with any of the jump label patch addresses. Code
 784  * that wants to modify kernel text should first verify that
 785  * it does not overlap with any of the jump label addresses.
 786  * Caller must hold jump_label_mutex.
 787  *
 788  * returns 1 if there is an overlap, 0 otherwise
 789  */
 790 int jump_label_text_reserved(void *start, void *end)
 791 {
 792         bool init = system_state < SYSTEM_RUNNING;
 793         int ret = __jump_label_text_reserved(__start___jump_table,
 794                         __stop___jump_table, start, end, init);
 795
 796         if (ret)
 797                 return ret;
 798
 799 #ifdef CONFIG_MODULES
 800         ret = __jump_label_mod_text_reserved(start, end);
 801 #endif
 802         return ret;
 803 }
 804
 805 static void jump_label_update(struct static_key *key)
 806 {
 807         struct jump_entry *stop = __stop___jump_table;
 808         bool init = system_state < SYSTEM_RUNNING;
 809         struct jump_entry *entry;
 810 #ifdef CONFIG_MODULES
 811         struct module *mod;
 812
 813         if (static_key_linked(key)) {
 814                 __jump_label_mod_update(key);
 815                 return;
 816         }
 817
 818         preempt_disable();
 819         mod = __module_address((unsigned long)key);
 820         if (mod) {
 821                 stop = mod->jump_entries + mod->num_jump_entries;
 822                 init = mod->state == MODULE_STATE_COMING;
 823         }
 824         preempt_enable();
 825 #endif
 826         entry = static_key_entries(key);
 827         /* if there are no users, entry can be NULL */
 828         if (entry)
 829                 __jump_label_update(key, entry, stop, init);
 830 }
 831
 832 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 833 static DEFINE_STATIC_KEY_TRUE(sk_true);
 834 static DEFINE_STATIC_KEY_FALSE(sk_false);
 835
 836 static __init int jump_label_test(void)
 837 {
 838         int i;
 839
 840         for (i = 0; i < 2; i++) {
 841                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 842                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 843
 844                 WARN_ON(!static_branch_likely(&sk_true));
 845                 WARN_ON(!static_branch_unlikely(&sk_true));
 846                 WARN_ON(static_branch_likely(&sk_false));
 847                 WARN_ON(static_branch_unlikely(&sk_false));
 848
 849                 static_branch_disable(&sk_true);
 850                 static_branch_enable(&sk_false);
 851
 852                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 853                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 854
 855                 WARN_ON(static_branch_likely(&sk_true));
 856                 WARN_ON(static_branch_unlikely(&sk_true));
 857                 WARN_ON(!static_branch_likely(&sk_false));
 858                 WARN_ON(!static_branch_unlikely(&sk_false));
 859
 860                 static_branch_enable(&sk_true);
 861                 static_branch_disable(&sk_false);
 862         }
 863
 864         return 0;
 865 }
 866 early_initcall(jump_label_test);
 867 #endif /* STATIC_KEYS_SELFTEST */