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/dec() down the slow path, and it is non-zero
 135          * so it counts as "enabled" in jump_label_update().
 136          *
 137          * The INT_MAX overflow condition is either used by the networking
 138          * code to reset or detected in the slow path of
 139          * static_key_slow_inc_cpuslocked().
 140          */
 141         v = atomic_read(&key->enabled);
 142         do {
 143                 if (v <= 0 || v == INT_MAX)
 144                         return false;
 145         } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v + 1)));
 146
 147         return true;
 148 }
 149 EXPORT_SYMBOL_GPL(static_key_fast_inc_not_disabled);
 150
 151 bool static_key_slow_inc_cpuslocked(struct static_key *key)
 152 {
 153         lockdep_assert_cpus_held();
 154
 155         /*
 156          * Careful if we get concurrent static_key_slow_inc/dec() calls;
 157          * later calls must wait for the first one to _finish_ the
 158          * jump_label_update() process.  At the same time, however,
 159          * the jump_label_update() call below wants to see
 160          * static_key_enabled(&key) for jumps to be updated properly.
 161          */
 162         if (static_key_fast_inc_not_disabled(key))
 163                 return true;
 164
 165         guard(mutex)(&jump_label_mutex);
 166         /* Try to mark it as 'enabling in progress. */
 167         if (!atomic_cmpxchg(&key->enabled, 0, -1)) {
 168                 jump_label_update(key);
 169                 /*
 170                  * Ensure that when static_key_fast_inc_not_disabled() or
 171                  * static_key_slow_try_dec() observe the positive value,
 172                  * they must also observe all the text changes.
 173                  */
 174                 atomic_set_release(&key->enabled, 1);
 175         } else {
 176                 /*
 177                  * While holding the mutex this should never observe
 178                  * anything else than a value >= 1 and succeed
 179                  */
 180                 if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key)))
 181                         return false;
 182         }
 183         return true;
 184 }
 185
 186 bool static_key_slow_inc(struct static_key *key)
 187 {
 188         bool ret;
 189
 190         cpus_read_lock();
 191         ret = static_key_slow_inc_cpuslocked(key);
 192         cpus_read_unlock();
 193         return ret;
 194 }
 195 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 196
 197 void static_key_enable_cpuslocked(struct static_key *key)
 198 {
 199         STATIC_KEY_CHECK_USE(key);
 200         lockdep_assert_cpus_held();
 201
 202         if (atomic_read(&key->enabled) > 0) {
 203                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 204                 return;
 205         }
 206
 207         jump_label_lock();
 208         if (atomic_read(&key->enabled) == 0) {
 209                 atomic_set(&key->enabled, -1);
 210                 jump_label_update(key);
 211                 /*
 212                  * See static_key_slow_inc().
 213                  */
 214                 atomic_set_release(&key->enabled, 1);
 215         }
 216         jump_label_unlock();
 217 }
 218 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 219
 220 void static_key_enable(struct static_key *key)
 221 {
 222         cpus_read_lock();
 223         static_key_enable_cpuslocked(key);
 224         cpus_read_unlock();
 225 }
 226 EXPORT_SYMBOL_GPL(static_key_enable);
 227
 228 void static_key_disable_cpuslocked(struct static_key *key)
 229 {
 230         STATIC_KEY_CHECK_USE(key);
 231         lockdep_assert_cpus_held();
 232
 233         if (atomic_read(&key->enabled) != 1) {
 234                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 235                 return;
 236         }
 237
 238         jump_label_lock();
 239         if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
 240                 jump_label_update(key);
 241         jump_label_unlock();
 242 }
 243 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 244
 245 void static_key_disable(struct static_key *key)
 246 {
 247         cpus_read_lock();
 248         static_key_disable_cpuslocked(key);
 249         cpus_read_unlock();
 250 }
 251 EXPORT_SYMBOL_GPL(static_key_disable);
 252
 253 static bool static_key_slow_try_dec(struct static_key *key)
 254 {
 255         int v;
 256
 257         /*
 258          * Go into the slow path if key::enabled is less than or equal than
 259          * one. One is valid to shut down the key, anything less than one
 260          * is an imbalance, which is handled at the call site.
 261          *
 262          * That includes the special case of '-1' which is set in
 263          * static_key_slow_inc_cpuslocked(), but that's harmless as it is
 264          * fully serialized in the slow path below. By the time this task
 265          * acquires the jump label lock the value is back to one and the
 266          * retry under the lock must succeed.
 267          */
 268         v = atomic_read(&key->enabled);
 269         do {
 270                 /*
 271                  * Warn about the '-1' case though; since that means a
 272                  * decrement is concurrent with a first (0->1) increment. IOW
 273                  * people are trying to disable something that wasn't yet fully
 274                  * enabled. This suggests an ordering problem on the user side.
 275                  */
 276                 WARN_ON_ONCE(v < 0);
 277                 if (v <= 1)
 278                         return false;
 279         } while (!likely(atomic_try_cmpxchg(&key->enabled, &v, v - 1)));
 280
 281         return true;
 282 }
 283
 284 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 285 {
 286         lockdep_assert_cpus_held();
 287
 288         if (static_key_slow_try_dec(key))
 289                 return;
 290
 291         guard(mutex)(&jump_label_mutex);
 292         if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
 293                 jump_label_update(key);
 294         else
 295                 WARN_ON_ONCE(!static_key_slow_try_dec(key));
 296 }
 297
 298 static void __static_key_slow_dec(struct static_key *key)
 299 {
 300         cpus_read_lock();
 301         __static_key_slow_dec_cpuslocked(key);
 302         cpus_read_unlock();
 303 }
 304
 305 void jump_label_update_timeout(struct work_struct *work)
 306 {
 307         struct static_key_deferred *key =
 308                 container_of(work, struct static_key_deferred, work.work);
 309         __static_key_slow_dec(&key->key);
 310 }
 311 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 312
 313 void static_key_slow_dec(struct static_key *key)
 314 {
 315         STATIC_KEY_CHECK_USE(key);
 316         __static_key_slow_dec(key);
 317 }
 318 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 319
 320 void static_key_slow_dec_cpuslocked(struct static_key *key)
 321 {
 322         STATIC_KEY_CHECK_USE(key);
 323         __static_key_slow_dec_cpuslocked(key);
 324 }
 325
 326 void __static_key_slow_dec_deferred(struct static_key *key,
 327                                     struct delayed_work *work,
 328                                     unsigned long timeout)
 329 {
 330         STATIC_KEY_CHECK_USE(key);
 331
 332         if (static_key_slow_try_dec(key))
 333                 return;
 334
 335         schedule_delayed_work(work, timeout);
 336 }
 337 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 338
 339 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 340 {
 341         STATIC_KEY_CHECK_USE(key);
 342         flush_delayed_work(work);
 343 }
 344 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 345
 346 void jump_label_rate_limit(struct static_key_deferred *key,
 347                 unsigned long rl)
 348 {
 349         STATIC_KEY_CHECK_USE(key);
 350         key->timeout = rl;
 351         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 352 }
 353 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 354
 355 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 356 {
 357         if (jump_entry_code(entry) <= (unsigned long)end &&
 358             jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start)
 359                 return 1;
 360
 361         return 0;
 362 }
 363
 364 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 365                 struct jump_entry *iter_stop, void *start, void *end, bool init)
 366 {
 367         struct jump_entry *iter;
 368
 369         iter = iter_start;
 370         while (iter < iter_stop) {
 371                 if (init || !jump_entry_is_init(iter)) {
 372                         if (addr_conflict(iter, start, end))
 373                                 return 1;
 374                 }
 375                 iter++;
 376         }
 377
 378         return 0;
 379 }
 380
 381 #ifndef arch_jump_label_transform_static
 382 static void arch_jump_label_transform_static(struct jump_entry *entry,
 383                                              enum jump_label_type type)
 384 {
 385         /* nothing to do on most architectures */
 386 }
 387 #endif
 388
 389 static inline struct jump_entry *static_key_entries(struct static_key *key)
 390 {
 391         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 392         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 393 }
 394
 395 static inline bool static_key_type(struct static_key *key)
 396 {
 397         return key->type & JUMP_TYPE_TRUE;
 398 }
 399
 400 static inline bool static_key_linked(struct static_key *key)
 401 {
 402         return key->type & JUMP_TYPE_LINKED;
 403 }
 404
 405 static inline void static_key_clear_linked(struct static_key *key)
 406 {
 407         key->type &= ~JUMP_TYPE_LINKED;
 408 }
 409
 410 static inline void static_key_set_linked(struct static_key *key)
 411 {
 412         key->type |= JUMP_TYPE_LINKED;
 413 }
 414
 415 /***
 416  * A 'struct static_key' uses a union such that it either points directly
 417  * to a table of 'struct jump_entry' or to a linked list of modules which in
 418  * turn point to 'struct jump_entry' tables.
 419  *
 420  * The two lower bits of the pointer are used to keep track of which pointer
 421  * type is in use and to store the initial branch direction, we use an access
 422  * function which preserves these bits.
 423  */
 424 static void static_key_set_entries(struct static_key *key,
 425                                    struct jump_entry *entries)
 426 {
 427         unsigned long type;
 428
 429         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 430         type = key->type & JUMP_TYPE_MASK;
 431         key->entries = entries;
 432         key->type |= type;
 433 }
 434
 435 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 436 {
 437         struct static_key *key = jump_entry_key(entry);
 438         bool enabled = static_key_enabled(key);
 439         bool branch = jump_entry_is_branch(entry);
 440
 441         /* See the comment in linux/jump_label.h */
 442         return enabled ^ branch;
 443 }
 444
 445 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 446 {
 447         /*
 448          * Cannot update code that was in an init text area.
 449          */
 450         if (!init && jump_entry_is_init(entry))
 451                 return false;
 452
 453         if (!kernel_text_address(jump_entry_code(entry))) {
 454                 /*
 455                  * This skips patching built-in __exit, which
 456                  * is part of init_section_contains() but is
 457                  * not part of kernel_text_address().
 458                  *
 459                  * Skipping built-in __exit is fine since it
 460                  * will never be executed.
 461                  */
 462                 WARN_ONCE(!jump_entry_is_init(entry),
 463                           "can't patch jump_label at %pS",
 464                           (void *)jump_entry_code(entry));
 465                 return false;
 466         }
 467
 468         return true;
 469 }
 470
 471 #ifndef HAVE_JUMP_LABEL_BATCH
 472 static void __jump_label_update(struct static_key *key,
 473                                 struct jump_entry *entry,
 474                                 struct jump_entry *stop,
 475                                 bool init)
 476 {
 477         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 478                 if (jump_label_can_update(entry, init))
 479                         arch_jump_label_transform(entry, jump_label_type(entry));
 480         }
 481 }
 482 #else
 483 static void __jump_label_update(struct static_key *key,
 484                                 struct jump_entry *entry,
 485                                 struct jump_entry *stop,
 486                                 bool init)
 487 {
 488         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 489
 490                 if (!jump_label_can_update(entry, init))
 491                         continue;
 492
 493                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 494                         /*
 495                          * Queue is full: Apply the current queue and try again.
 496                          */
 497                         arch_jump_label_transform_apply();
 498                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 499                 }
 500         }
 501         arch_jump_label_transform_apply();
 502 }
 503 #endif
 504
 505 void __init jump_label_init(void)
 506 {
 507         struct jump_entry *iter_start = __start___jump_table;
 508         struct jump_entry *iter_stop = __stop___jump_table;
 509         struct static_key *key = NULL;
 510         struct jump_entry *iter;
 511
 512         /*
 513          * Since we are initializing the static_key.enabled field with
 514          * with the 'raw' int values (to avoid pulling in atomic.h) in
 515          * jump_label.h, let's make sure that is safe. There are only two
 516          * cases to check since we initialize to 0 or 1.
 517          */
 518         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 519         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 520
 521         if (static_key_initialized)
 522                 return;
 523
 524         cpus_read_lock();
 525         jump_label_lock();
 526         jump_label_sort_entries(iter_start, iter_stop);
 527
 528         for (iter = iter_start; iter < iter_stop; iter++) {
 529                 struct static_key *iterk;
 530                 bool in_init;
 531
 532                 /* rewrite NOPs */
 533                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 534                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 535
 536                 in_init = init_section_contains((void *)jump_entry_code(iter), 1);
 537                 jump_entry_set_init(iter, in_init);
 538
 539                 iterk = jump_entry_key(iter);
 540                 if (iterk == key)
 541                         continue;
 542
 543                 key = iterk;
 544                 static_key_set_entries(key, iter);
 545         }
 546         static_key_initialized = true;
 547         jump_label_unlock();
 548         cpus_read_unlock();
 549 }
 550
 551 static inline bool static_key_sealed(struct static_key *key)
 552 {
 553         return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK);
 554 }
 555
 556 static inline void static_key_seal(struct static_key *key)
 557 {
 558         unsigned long type = key->type & JUMP_TYPE_TRUE;
 559         key->type = JUMP_TYPE_LINKED | type;
 560 }
 561
 562 void jump_label_init_ro(void)
 563 {
 564         struct jump_entry *iter_start = __start___jump_table;
 565         struct jump_entry *iter_stop = __stop___jump_table;
 566         struct jump_entry *iter;
 567
 568         if (WARN_ON_ONCE(!static_key_initialized))
 569                 return;
 570
 571         cpus_read_lock();
 572         jump_label_lock();
 573
 574         for (iter = iter_start; iter < iter_stop; iter++) {
 575                 struct static_key *iterk = jump_entry_key(iter);
 576
 577                 if (!is_kernel_ro_after_init((unsigned long)iterk))
 578                         continue;
 579
 580                 if (static_key_sealed(iterk))
 581                         continue;
 582
 583                 static_key_seal(iterk);
 584         }
 585
 586         jump_label_unlock();
 587         cpus_read_unlock();
 588 }
 589
 590 #ifdef CONFIG_MODULES
 591
 592 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 593 {
 594         struct static_key *key = jump_entry_key(entry);
 595         bool type = static_key_type(key);
 596         bool branch = jump_entry_is_branch(entry);
 597
 598         /* See the comment in linux/jump_label.h */
 599         return type ^ branch;
 600 }
 601
 602 struct static_key_mod {
 603         struct static_key_mod *next;
 604         struct jump_entry *entries;
 605         struct module *mod;
 606 };
 607
 608 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 609 {
 610         WARN_ON_ONCE(!static_key_linked(key));
 611         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 612 }
 613
 614 /***
 615  * key->type and key->next are the same via union.
 616  * This sets key->next and preserves the type bits.
 617  *
 618  * See additional comments above static_key_set_entries().
 619  */
 620 static void static_key_set_mod(struct static_key *key,
 621                                struct static_key_mod *mod)
 622 {
 623         unsigned long type;
 624
 625         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 626         type = key->type & JUMP_TYPE_MASK;
 627         key->next = mod;
 628         key->type |= type;
 629 }
 630
 631 static int __jump_label_mod_text_reserved(void *start, void *end)
 632 {
 633         struct module *mod;
 634         int ret;
 635
 636         preempt_disable();
 637         mod = __module_text_address((unsigned long)start);
 638         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 639         if (!try_module_get(mod))
 640                 mod = NULL;
 641         preempt_enable();
 642
 643         if (!mod)
 644                 return 0;
 645
 646         ret = __jump_label_text_reserved(mod->jump_entries,
 647                                 mod->jump_entries + mod->num_jump_entries,
 648                                 start, end, mod->state == MODULE_STATE_COMING);
 649
 650         module_put(mod);
 651
 652         return ret;
 653 }
 654
 655 static void __jump_label_mod_update(struct static_key *key)
 656 {
 657         struct static_key_mod *mod;
 658
 659         for (mod = static_key_mod(key); mod; mod = mod->next) {
 660                 struct jump_entry *stop;
 661                 struct module *m;
 662
 663                 /*
 664                  * NULL if the static_key is defined in a module
 665                  * that does not use it
 666                  */
 667                 if (!mod->entries)
 668                         continue;
 669
 670                 m = mod->mod;
 671                 if (!m)
 672                         stop = __stop___jump_table;
 673                 else
 674                         stop = m->jump_entries + m->num_jump_entries;
 675                 __jump_label_update(key, mod->entries, stop,
 676                                     m && m->state == MODULE_STATE_COMING);
 677         }
 678 }
 679
 680 static int jump_label_add_module(struct module *mod)
 681 {
 682         struct jump_entry *iter_start = mod->jump_entries;
 683         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 684         struct jump_entry *iter;
 685         struct static_key *key = NULL;
 686         struct static_key_mod *jlm, *jlm2;
 687
 688         /* if the module doesn't have jump label entries, just return */
 689         if (iter_start == iter_stop)
 690                 return 0;
 691
 692         jump_label_sort_entries(iter_start, iter_stop);
 693
 694         for (iter = iter_start; iter < iter_stop; iter++) {
 695                 struct static_key *iterk;
 696                 bool in_init;
 697
 698                 in_init = within_module_init(jump_entry_code(iter), mod);
 699                 jump_entry_set_init(iter, in_init);
 700
 701                 iterk = jump_entry_key(iter);
 702                 if (iterk == key)
 703                         continue;
 704
 705                 key = iterk;
 706                 if (within_module((unsigned long)key, mod)) {
 707                         static_key_set_entries(key, iter);
 708                         continue;
 709                 }
 710
 711                 /*
 712                  * If the key was sealed at init, then there's no need to keep a
 713                  * reference to its module entries - just patch them now and be
 714                  * done with it.
 715                  */
 716                 if (static_key_sealed(key))
 717                         goto do_poke;
 718
 719                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 720                 if (!jlm)
 721                         return -ENOMEM;
 722                 if (!static_key_linked(key)) {
 723                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 724                                        GFP_KERNEL);
 725                         if (!jlm2) {
 726                                 kfree(jlm);
 727                                 return -ENOMEM;
 728                         }
 729                         preempt_disable();
 730                         jlm2->mod = __module_address((unsigned long)key);
 731                         preempt_enable();
 732                         jlm2->entries = static_key_entries(key);
 733                         jlm2->next = NULL;
 734                         static_key_set_mod(key, jlm2);
 735                         static_key_set_linked(key);
 736                 }
 737                 jlm->mod = mod;
 738                 jlm->entries = iter;
 739                 jlm->next = static_key_mod(key);
 740                 static_key_set_mod(key, jlm);
 741                 static_key_set_linked(key);
 742
 743                 /* Only update if we've changed from our initial state */
 744 do_poke:
 745                 if (jump_label_type(iter) != jump_label_init_type(iter))
 746                         __jump_label_update(key, iter, iter_stop, true);
 747         }
 748
 749         return 0;
 750 }
 751
 752 static void jump_label_del_module(struct module *mod)
 753 {
 754         struct jump_entry *iter_start = mod->jump_entries;
 755         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 756         struct jump_entry *iter;
 757         struct static_key *key = NULL;
 758         struct static_key_mod *jlm, **prev;
 759
 760         for (iter = iter_start; iter < iter_stop; iter++) {
 761                 if (jump_entry_key(iter) == key)
 762                         continue;
 763
 764                 key = jump_entry_key(iter);
 765
 766                 if (within_module((unsigned long)key, mod))
 767                         continue;
 768
 769                 /* No @jlm allocated because key was sealed at init. */
 770                 if (static_key_sealed(key))
 771                         continue;
 772
 773                 /* No memory during module load */
 774                 if (WARN_ON(!static_key_linked(key)))
 775                         continue;
 776
 777                 prev = &key->next;
 778                 jlm = static_key_mod(key);
 779
 780                 while (jlm && jlm->mod != mod) {
 781                         prev = &jlm->next;
 782                         jlm = jlm->next;
 783                 }
 784
 785                 /* No memory during module load */
 786                 if (WARN_ON(!jlm))
 787                         continue;
 788
 789                 if (prev == &key->next)
 790                         static_key_set_mod(key, jlm->next);
 791                 else
 792                         *prev = jlm->next;
 793
 794                 kfree(jlm);
 795
 796                 jlm = static_key_mod(key);
 797                 /* if only one etry is left, fold it back into the static_key */
 798                 if (jlm->next == NULL) {
 799                         static_key_set_entries(key, jlm->entries);
 800                         static_key_clear_linked(key);
 801                         kfree(jlm);
 802                 }
 803         }
 804 }
 805
 806 static int
 807 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 808                          void *data)
 809 {
 810         struct module *mod = data;
 811         int ret = 0;
 812
 813         cpus_read_lock();
 814         jump_label_lock();
 815
 816         switch (val) {
 817         case MODULE_STATE_COMING:
 818                 ret = jump_label_add_module(mod);
 819                 if (ret) {
 820                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 821                         jump_label_del_module(mod);
 822                 }
 823                 break;
 824         case MODULE_STATE_GOING:
 825                 jump_label_del_module(mod);
 826                 break;
 827         }
 828
 829         jump_label_unlock();
 830         cpus_read_unlock();
 831
 832         return notifier_from_errno(ret);
 833 }
 834
 835 static struct notifier_block jump_label_module_nb = {
 836         .notifier_call = jump_label_module_notify,
 837         .priority = 1, /* higher than tracepoints */
 838 };
 839
 840 static __init int jump_label_init_module(void)
 841 {
 842         return register_module_notifier(&jump_label_module_nb);
 843 }
 844 early_initcall(jump_label_init_module);
 845
 846 #endif /* CONFIG_MODULES */
 847
 848 /***
 849  * jump_label_text_reserved - check if addr range is reserved
 850  * @start: start text addr
 851  * @end: end text addr
 852  *
 853  * checks if the text addr located between @start and @end
 854  * overlaps with any of the jump label patch addresses. Code
 855  * that wants to modify kernel text should first verify that
 856  * it does not overlap with any of the jump label addresses.
 857  * Caller must hold jump_label_mutex.
 858  *
 859  * returns 1 if there is an overlap, 0 otherwise
 860  */
 861 int jump_label_text_reserved(void *start, void *end)
 862 {
 863         bool init = system_state < SYSTEM_RUNNING;
 864         int ret = __jump_label_text_reserved(__start___jump_table,
 865                         __stop___jump_table, start, end, init);
 866
 867         if (ret)
 868                 return ret;
 869
 870 #ifdef CONFIG_MODULES
 871         ret = __jump_label_mod_text_reserved(start, end);
 872 #endif
 873         return ret;
 874 }
 875
 876 static void jump_label_update(struct static_key *key)
 877 {
 878         struct jump_entry *stop = __stop___jump_table;
 879         bool init = system_state < SYSTEM_RUNNING;
 880         struct jump_entry *entry;
 881 #ifdef CONFIG_MODULES
 882         struct module *mod;
 883
 884         if (static_key_linked(key)) {
 885                 __jump_label_mod_update(key);
 886                 return;
 887         }
 888
 889         preempt_disable();
 890         mod = __module_address((unsigned long)key);
 891         if (mod) {
 892                 stop = mod->jump_entries + mod->num_jump_entries;
 893                 init = mod->state == MODULE_STATE_COMING;
 894         }
 895         preempt_enable();
 896 #endif
 897         entry = static_key_entries(key);
 898         /* if there are no users, entry can be NULL */
 899         if (entry)
 900                 __jump_label_update(key, entry, stop, init);
 901 }
 902
 903 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 904 static DEFINE_STATIC_KEY_TRUE(sk_true);
 905 static DEFINE_STATIC_KEY_FALSE(sk_false);
 906
 907 static __init int jump_label_test(void)
 908 {
 909         int i;
 910
 911         for (i = 0; i < 2; i++) {
 912                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 913                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 914
 915                 WARN_ON(!static_branch_likely(&sk_true));
 916                 WARN_ON(!static_branch_unlikely(&sk_true));
 917                 WARN_ON(static_branch_likely(&sk_false));
 918                 WARN_ON(static_branch_unlikely(&sk_false));
 919
 920                 static_branch_disable(&sk_true);
 921                 static_branch_enable(&sk_false);
 922
 923                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 924                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 925
 926                 WARN_ON(static_branch_likely(&sk_true));
 927                 WARN_ON(static_branch_unlikely(&sk_true));
 928                 WARN_ON(!static_branch_likely(&sk_false));
 929                 WARN_ON(!static_branch_unlikely(&sk_false));
 930
 931                 static_branch_enable(&sk_true);
 932                 static_branch_disable(&sk_false);
 933         }
 934
 935         return 0;
 936 }
 937 early_initcall(jump_label_test);
 938 #endif /* STATIC_KEYS_SELFTEST */