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_LABEL_NOP_SIZE > (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)
 320 {
 321         struct jump_entry *iter;
 322
 323         iter = iter_start;
 324         while (iter < iter_stop) {
 325                 if (addr_conflict(iter, start, end))
 326                         return 1;
 327                 iter++;
 328         }
 329
 330         return 0;
 331 }
 332
 333 /*
 334  * Update code which is definitely not currently executing.
 335  * Architectures which need heavyweight synchronization to modify
 336  * running code can override this to make the non-live update case
 337  * cheaper.
 338  */
 339 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 340                                             enum jump_label_type type)
 341 {
 342         arch_jump_label_transform(entry, type);
 343 }
 344
 345 static inline struct jump_entry *static_key_entries(struct static_key *key)
 346 {
 347         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 348         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 349 }
 350
 351 static inline bool static_key_type(struct static_key *key)
 352 {
 353         return key->type & JUMP_TYPE_TRUE;
 354 }
 355
 356 static inline bool static_key_linked(struct static_key *key)
 357 {
 358         return key->type & JUMP_TYPE_LINKED;
 359 }
 360
 361 static inline void static_key_clear_linked(struct static_key *key)
 362 {
 363         key->type &= ~JUMP_TYPE_LINKED;
 364 }
 365
 366 static inline void static_key_set_linked(struct static_key *key)
 367 {
 368         key->type |= JUMP_TYPE_LINKED;
 369 }
 370
 371 /***
 372  * A 'struct static_key' uses a union such that it either points directly
 373  * to a table of 'struct jump_entry' or to a linked list of modules which in
 374  * turn point to 'struct jump_entry' tables.
 375  *
 376  * The two lower bits of the pointer are used to keep track of which pointer
 377  * type is in use and to store the initial branch direction, we use an access
 378  * function which preserves these bits.
 379  */
 380 static void static_key_set_entries(struct static_key *key,
 381                                    struct jump_entry *entries)
 382 {
 383         unsigned long type;
 384
 385         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 386         type = key->type & JUMP_TYPE_MASK;
 387         key->entries = entries;
 388         key->type |= type;
 389 }
 390
 391 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 392 {
 393         struct static_key *key = jump_entry_key(entry);
 394         bool enabled = static_key_enabled(key);
 395         bool branch = jump_entry_is_branch(entry);
 396
 397         /* See the comment in linux/jump_label.h */
 398         return enabled ^ branch;
 399 }
 400
 401 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 402 {
 403         /*
 404          * Cannot update code that was in an init text area.
 405          */
 406         if (!init && jump_entry_is_init(entry))
 407                 return false;
 408
 409         if (!kernel_text_address(jump_entry_code(entry))) {
 410                 /*
 411                  * This skips patching built-in __exit, which
 412                  * is part of init_section_contains() but is
 413                  * not part of kernel_text_address().
 414                  *
 415                  * Skipping built-in __exit is fine since it
 416                  * will never be executed.
 417                  */
 418                 WARN_ONCE(!jump_entry_is_init(entry),
 419                           "can't patch jump_label at %pS",
 420                           (void *)jump_entry_code(entry));
 421                 return false;
 422         }
 423
 424         return true;
 425 }
 426
 427 #ifndef HAVE_JUMP_LABEL_BATCH
 428 static void __jump_label_update(struct static_key *key,
 429                                 struct jump_entry *entry,
 430                                 struct jump_entry *stop,
 431                                 bool init)
 432 {
 433         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 434                 if (jump_label_can_update(entry, init))
 435                         arch_jump_label_transform(entry, jump_label_type(entry));
 436         }
 437 }
 438 #else
 439 static void __jump_label_update(struct static_key *key,
 440                                 struct jump_entry *entry,
 441                                 struct jump_entry *stop,
 442                                 bool init)
 443 {
 444         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 445
 446                 if (!jump_label_can_update(entry, init))
 447                         continue;
 448
 449                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 450                         /*
 451                          * Queue is full: Apply the current queue and try again.
 452                          */
 453                         arch_jump_label_transform_apply();
 454                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 455                 }
 456         }
 457         arch_jump_label_transform_apply();
 458 }
 459 #endif
 460
 461 void __init jump_label_init(void)
 462 {
 463         struct jump_entry *iter_start = __start___jump_table;
 464         struct jump_entry *iter_stop = __stop___jump_table;
 465         struct static_key *key = NULL;
 466         struct jump_entry *iter;
 467
 468         /*
 469          * Since we are initializing the static_key.enabled field with
 470          * with the 'raw' int values (to avoid pulling in atomic.h) in
 471          * jump_label.h, let's make sure that is safe. There are only two
 472          * cases to check since we initialize to 0 or 1.
 473          */
 474         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 475         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 476
 477         if (static_key_initialized)
 478                 return;
 479
 480         cpus_read_lock();
 481         jump_label_lock();
 482         jump_label_sort_entries(iter_start, iter_stop);
 483
 484         for (iter = iter_start; iter < iter_stop; iter++) {
 485                 struct static_key *iterk;
 486
 487                 /* rewrite NOPs */
 488                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 489                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 490
 491                 if (init_section_contains((void *)jump_entry_code(iter), 1))
 492                         jump_entry_set_init(iter);
 493
 494                 iterk = jump_entry_key(iter);
 495                 if (iterk == key)
 496                         continue;
 497
 498                 key = iterk;
 499                 static_key_set_entries(key, iter);
 500         }
 501         static_key_initialized = true;
 502         jump_label_unlock();
 503         cpus_read_unlock();
 504 }
 505
 506 #ifdef CONFIG_MODULES
 507
 508 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 509 {
 510         struct static_key *key = jump_entry_key(entry);
 511         bool type = static_key_type(key);
 512         bool branch = jump_entry_is_branch(entry);
 513
 514         /* See the comment in linux/jump_label.h */
 515         return type ^ branch;
 516 }
 517
 518 struct static_key_mod {
 519         struct static_key_mod *next;
 520         struct jump_entry *entries;
 521         struct module *mod;
 522 };
 523
 524 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 525 {
 526         WARN_ON_ONCE(!static_key_linked(key));
 527         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 528 }
 529
 530 /***
 531  * key->type and key->next are the same via union.
 532  * This sets key->next and preserves the type bits.
 533  *
 534  * See additional comments above static_key_set_entries().
 535  */
 536 static void static_key_set_mod(struct static_key *key,
 537                                struct static_key_mod *mod)
 538 {
 539         unsigned long type;
 540
 541         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 542         type = key->type & JUMP_TYPE_MASK;
 543         key->next = mod;
 544         key->type |= type;
 545 }
 546
 547 static int __jump_label_mod_text_reserved(void *start, void *end)
 548 {
 549         struct module *mod;
 550         int ret;
 551
 552         preempt_disable();
 553         mod = __module_text_address((unsigned long)start);
 554         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 555         if (!try_module_get(mod))
 556                 mod = NULL;
 557         preempt_enable();
 558
 559         if (!mod)
 560                 return 0;
 561
 562         ret = __jump_label_text_reserved(mod->jump_entries,
 563                                 mod->jump_entries + mod->num_jump_entries,
 564                                 start, end);
 565
 566         module_put(mod);
 567
 568         return ret;
 569 }
 570
 571 static void __jump_label_mod_update(struct static_key *key)
 572 {
 573         struct static_key_mod *mod;
 574
 575         for (mod = static_key_mod(key); mod; mod = mod->next) {
 576                 struct jump_entry *stop;
 577                 struct module *m;
 578
 579                 /*
 580                  * NULL if the static_key is defined in a module
 581                  * that does not use it
 582                  */
 583                 if (!mod->entries)
 584                         continue;
 585
 586                 m = mod->mod;
 587                 if (!m)
 588                         stop = __stop___jump_table;
 589                 else
 590                         stop = m->jump_entries + m->num_jump_entries;
 591                 __jump_label_update(key, mod->entries, stop,
 592                                     m && m->state == MODULE_STATE_COMING);
 593         }
 594 }
 595
 596 /***
 597  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 598  * @mod: module to patch
 599  *
 600  * Allow for run-time selection of the optimal nops. Before the module
 601  * loads patch these with arch_get_jump_label_nop(), which is specified by
 602  * the arch specific jump label code.
 603  */
 604 void jump_label_apply_nops(struct module *mod)
 605 {
 606         struct jump_entry *iter_start = mod->jump_entries;
 607         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 608         struct jump_entry *iter;
 609
 610         /* if the module doesn't have jump label entries, just return */
 611         if (iter_start == iter_stop)
 612                 return;
 613
 614         for (iter = iter_start; iter < iter_stop; iter++) {
 615                 /* Only write NOPs for arch_branch_static(). */
 616                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 617                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 618         }
 619 }
 620
 621 static int jump_label_add_module(struct module *mod)
 622 {
 623         struct jump_entry *iter_start = mod->jump_entries;
 624         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 625         struct jump_entry *iter;
 626         struct static_key *key = NULL;
 627         struct static_key_mod *jlm, *jlm2;
 628
 629         /* if the module doesn't have jump label entries, just return */
 630         if (iter_start == iter_stop)
 631                 return 0;
 632
 633         jump_label_sort_entries(iter_start, iter_stop);
 634
 635         for (iter = iter_start; iter < iter_stop; iter++) {
 636                 struct static_key *iterk;
 637
 638                 if (within_module_init(jump_entry_code(iter), mod))
 639                         jump_entry_set_init(iter);
 640
 641                 iterk = jump_entry_key(iter);
 642                 if (iterk == key)
 643                         continue;
 644
 645                 key = iterk;
 646                 if (within_module((unsigned long)key, mod)) {
 647                         static_key_set_entries(key, iter);
 648                         continue;
 649                 }
 650                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 651                 if (!jlm)
 652                         return -ENOMEM;
 653                 if (!static_key_linked(key)) {
 654                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 655                                        GFP_KERNEL);
 656                         if (!jlm2) {
 657                                 kfree(jlm);
 658                                 return -ENOMEM;
 659                         }
 660                         preempt_disable();
 661                         jlm2->mod = __module_address((unsigned long)key);
 662                         preempt_enable();
 663                         jlm2->entries = static_key_entries(key);
 664                         jlm2->next = NULL;
 665                         static_key_set_mod(key, jlm2);
 666                         static_key_set_linked(key);
 667                 }
 668                 jlm->mod = mod;
 669                 jlm->entries = iter;
 670                 jlm->next = static_key_mod(key);
 671                 static_key_set_mod(key, jlm);
 672                 static_key_set_linked(key);
 673
 674                 /* Only update if we've changed from our initial state */
 675                 if (jump_label_type(iter) != jump_label_init_type(iter))
 676                         __jump_label_update(key, iter, iter_stop, true);
 677         }
 678
 679         return 0;
 680 }
 681
 682 static void jump_label_del_module(struct module *mod)
 683 {
 684         struct jump_entry *iter_start = mod->jump_entries;
 685         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 686         struct jump_entry *iter;
 687         struct static_key *key = NULL;
 688         struct static_key_mod *jlm, **prev;
 689
 690         for (iter = iter_start; iter < iter_stop; iter++) {
 691                 if (jump_entry_key(iter) == key)
 692                         continue;
 693
 694                 key = jump_entry_key(iter);
 695
 696                 if (within_module((unsigned long)key, mod))
 697                         continue;
 698
 699                 /* No memory during module load */
 700                 if (WARN_ON(!static_key_linked(key)))
 701                         continue;
 702
 703                 prev = &key->next;
 704                 jlm = static_key_mod(key);
 705
 706                 while (jlm && jlm->mod != mod) {
 707                         prev = &jlm->next;
 708                         jlm = jlm->next;
 709                 }
 710
 711                 /* No memory during module load */
 712                 if (WARN_ON(!jlm))
 713                         continue;
 714
 715                 if (prev == &key->next)
 716                         static_key_set_mod(key, jlm->next);
 717                 else
 718                         *prev = jlm->next;
 719
 720                 kfree(jlm);
 721
 722                 jlm = static_key_mod(key);
 723                 /* if only one etry is left, fold it back into the static_key */
 724                 if (jlm->next == NULL) {
 725                         static_key_set_entries(key, jlm->entries);
 726                         static_key_clear_linked(key);
 727                         kfree(jlm);
 728                 }
 729         }
 730 }
 731
 732 static int
 733 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 734                          void *data)
 735 {
 736         struct module *mod = data;
 737         int ret = 0;
 738
 739         cpus_read_lock();
 740         jump_label_lock();
 741
 742         switch (val) {
 743         case MODULE_STATE_COMING:
 744                 ret = jump_label_add_module(mod);
 745                 if (ret) {
 746                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 747                         jump_label_del_module(mod);
 748                 }
 749                 break;
 750         case MODULE_STATE_GOING:
 751                 jump_label_del_module(mod);
 752                 break;
 753         }
 754
 755         jump_label_unlock();
 756         cpus_read_unlock();
 757
 758         return notifier_from_errno(ret);
 759 }
 760
 761 static struct notifier_block jump_label_module_nb = {
 762         .notifier_call = jump_label_module_notify,
 763         .priority = 1, /* higher than tracepoints */
 764 };
 765
 766 static __init int jump_label_init_module(void)
 767 {
 768         return register_module_notifier(&jump_label_module_nb);
 769 }
 770 early_initcall(jump_label_init_module);
 771
 772 #endif /* CONFIG_MODULES */
 773
 774 /***
 775  * jump_label_text_reserved - check if addr range is reserved
 776  * @start: start text addr
 777  * @end: end text addr
 778  *
 779  * checks if the text addr located between @start and @end
 780  * overlaps with any of the jump label patch addresses. Code
 781  * that wants to modify kernel text should first verify that
 782  * it does not overlap with any of the jump label addresses.
 783  * Caller must hold jump_label_mutex.
 784  *
 785  * returns 1 if there is an overlap, 0 otherwise
 786  */
 787 int jump_label_text_reserved(void *start, void *end)
 788 {
 789         int ret = __jump_label_text_reserved(__start___jump_table,
 790                         __stop___jump_table, start, end);
 791
 792         if (ret)
 793                 return ret;
 794
 795 #ifdef CONFIG_MODULES
 796         ret = __jump_label_mod_text_reserved(start, end);
 797 #endif
 798         return ret;
 799 }
 800
 801 static void jump_label_update(struct static_key *key)
 802 {
 803         struct jump_entry *stop = __stop___jump_table;
 804         bool init = system_state < SYSTEM_RUNNING;
 805         struct jump_entry *entry;
 806 #ifdef CONFIG_MODULES
 807         struct module *mod;
 808
 809         if (static_key_linked(key)) {
 810                 __jump_label_mod_update(key);
 811                 return;
 812         }
 813
 814         preempt_disable();
 815         mod = __module_address((unsigned long)key);
 816         if (mod) {
 817                 stop = mod->jump_entries + mod->num_jump_entries;
 818                 init = mod->state == MODULE_STATE_COMING;
 819         }
 820         preempt_enable();
 821 #endif
 822         entry = static_key_entries(key);
 823         /* if there are no users, entry can be NULL */
 824         if (entry)
 825                 __jump_label_update(key, entry, stop, init);
 826 }
 827
 828 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 829 static DEFINE_STATIC_KEY_TRUE(sk_true);
 830 static DEFINE_STATIC_KEY_FALSE(sk_false);
 831
 832 static __init int jump_label_test(void)
 833 {
 834         int i;
 835
 836         for (i = 0; i < 2; i++) {
 837                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 838                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 839
 840                 WARN_ON(!static_branch_likely(&sk_true));
 841                 WARN_ON(!static_branch_unlikely(&sk_true));
 842                 WARN_ON(static_branch_likely(&sk_false));
 843                 WARN_ON(static_branch_unlikely(&sk_false));
 844
 845                 static_branch_disable(&sk_true);
 846                 static_branch_enable(&sk_false);
 847
 848                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 849                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 850
 851                 WARN_ON(static_branch_likely(&sk_true));
 852                 WARN_ON(static_branch_unlikely(&sk_true));
 853                 WARN_ON(!static_branch_likely(&sk_false));
 854                 WARN_ON(!static_branch_unlikely(&sk_false));
 855
 856                 static_branch_enable(&sk_true);
 857                 static_branch_disable(&sk_false);
 858         }
 859
 860         return 0;
 861 }
 862 early_initcall(jump_label_test);
 863 #endif /* STATIC_KEYS_SELFTEST */