kernel/jump_label.c

   1 /*
   2  * jump label support
   3  *
   4  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
   5  * Copyright (C) 2011 Peter Zijlstra
   6  *
   7  */
   8 #include <linux/memory.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/module.h>
  11 #include <linux/list.h>
  12 #include <linux/slab.h>
  13 #include <linux/sort.h>
  14 #include <linux/err.h>
  15 #include <linux/static_key.h>
  16 #include <linux/jump_label_ratelimit.h>
  17 #include <linux/bug.h>
  18 #include <linux/cpu.h>
  19 #include <asm/sections.h>
  20
  21 /* mutex to protect coming/going of the the jump_label table */
  22 static DEFINE_MUTEX(jump_label_mutex);
  23
  24 void jump_label_lock(void)
  25 {
  26         mutex_lock(&jump_label_mutex);
  27 }
  28
  29 void jump_label_unlock(void)
  30 {
  31         mutex_unlock(&jump_label_mutex);
  32 }
  33
  34 static int jump_label_cmp(const void *a, const void *b)
  35 {
  36         const struct jump_entry *jea = a;
  37         const struct jump_entry *jeb = b;
  38
  39         if (jump_entry_key(jea) < jump_entry_key(jeb))
  40                 return -1;
  41
  42         if (jump_entry_key(jea) > jump_entry_key(jeb))
  43                 return 1;
  44
  45         return 0;
  46 }
  47
  48 static void jump_label_swap(void *a, void *b, int size)
  49 {
  50         long delta = (unsigned long)a - (unsigned long)b;
  51         struct jump_entry *jea = a;
  52         struct jump_entry *jeb = b;
  53         struct jump_entry tmp = *jea;
  54
  55         jea->code       = jeb->code - delta;
  56         jea->target     = jeb->target - delta;
  57         jea->key        = jeb->key - delta;
  58
  59         jeb->code       = tmp.code + delta;
  60         jeb->target     = tmp.target + delta;
  61         jeb->key        = tmp.key + delta;
  62 }
  63
  64 static void
  65 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  66 {
  67         unsigned long size;
  68         void *swapfn = NULL;
  69
  70         if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
  71                 swapfn = jump_label_swap;
  72
  73         size = (((unsigned long)stop - (unsigned long)start)
  74                                         / sizeof(struct jump_entry));
  75         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
  76 }
  77
  78 static void jump_label_update(struct static_key *key);
  79
  80 /*
  81  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
  82  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  83  * kernel headers such as kernel.h and others. Since static_key_count() is not
  84  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
  85  * to have it be a function here. Similarly, for 'static_key_enable()' and
  86  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
  87  * to be included from most/all places for CONFIG_JUMP_LABEL.
  88  */
  89 int static_key_count(struct static_key *key)
  90 {
  91         /*
  92          * -1 means the first static_key_slow_inc() is in progress.
  93          *  static_key_enabled() must return true, so return 1 here.
  94          */
  95         int n = atomic_read(&key->enabled);
  96
  97         return n >= 0 ? n : 1;
  98 }
  99 EXPORT_SYMBOL_GPL(static_key_count);
 100
 101 void static_key_slow_inc_cpuslocked(struct static_key *key)
 102 {
 103         int v, v1;
 104
 105         STATIC_KEY_CHECK_USE(key);
 106         lockdep_assert_cpus_held();
 107
 108         /*
 109          * Careful if we get concurrent static_key_slow_inc() calls;
 110          * later calls must wait for the first one to _finish_ the
 111          * jump_label_update() process.  At the same time, however,
 112          * the jump_label_update() call below wants to see
 113          * static_key_enabled(&key) for jumps to be updated properly.
 114          *
 115          * So give a special meaning to negative key->enabled: it sends
 116          * static_key_slow_inc() down the slow path, and it is non-zero
 117          * so it counts as "enabled" in jump_label_update().  Note that
 118          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 119          */
 120         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 121                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 122                 if (likely(v1 == v))
 123                         return;
 124         }
 125
 126         jump_label_lock();
 127         if (atomic_read(&key->enabled) == 0) {
 128                 atomic_set(&key->enabled, -1);
 129                 jump_label_update(key);
 130                 /*
 131                  * Ensure that if the above cmpxchg loop observes our positive
 132                  * value, it must also observe all the text changes.
 133                  */
 134                 atomic_set_release(&key->enabled, 1);
 135         } else {
 136                 atomic_inc(&key->enabled);
 137         }
 138         jump_label_unlock();
 139 }
 140
 141 void static_key_slow_inc(struct static_key *key)
 142 {
 143         cpus_read_lock();
 144         static_key_slow_inc_cpuslocked(key);
 145         cpus_read_unlock();
 146 }
 147 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 148
 149 void static_key_enable_cpuslocked(struct static_key *key)
 150 {
 151         STATIC_KEY_CHECK_USE(key);
 152         lockdep_assert_cpus_held();
 153
 154         if (atomic_read(&key->enabled) > 0) {
 155                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 156                 return;
 157         }
 158
 159         jump_label_lock();
 160         if (atomic_read(&key->enabled) == 0) {
 161                 atomic_set(&key->enabled, -1);
 162                 jump_label_update(key);
 163                 /*
 164                  * See static_key_slow_inc().
 165                  */
 166                 atomic_set_release(&key->enabled, 1);
 167         }
 168         jump_label_unlock();
 169 }
 170 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 171
 172 void static_key_enable(struct static_key *key)
 173 {
 174         cpus_read_lock();
 175         static_key_enable_cpuslocked(key);
 176         cpus_read_unlock();
 177 }
 178 EXPORT_SYMBOL_GPL(static_key_enable);
 179
 180 void static_key_disable_cpuslocked(struct static_key *key)
 181 {
 182         STATIC_KEY_CHECK_USE(key);
 183         lockdep_assert_cpus_held();
 184
 185         if (atomic_read(&key->enabled) != 1) {
 186                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 187                 return;
 188         }
 189
 190         jump_label_lock();
 191         if (atomic_cmpxchg(&key->enabled, 1, 0))
 192                 jump_label_update(key);
 193         jump_label_unlock();
 194 }
 195 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 196
 197 void static_key_disable(struct static_key *key)
 198 {
 199         cpus_read_lock();
 200         static_key_disable_cpuslocked(key);
 201         cpus_read_unlock();
 202 }
 203 EXPORT_SYMBOL_GPL(static_key_disable);
 204
 205 static bool static_key_slow_try_dec(struct static_key *key)
 206 {
 207         int val;
 208
 209         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 210         if (val == 1)
 211                 return false;
 212
 213         /*
 214          * The negative count check is valid even when a negative
 215          * key->enabled is in use by static_key_slow_inc(); a
 216          * __static_key_slow_dec() before the first static_key_slow_inc()
 217          * returns is unbalanced, because all other static_key_slow_inc()
 218          * instances block while the update is in progress.
 219          */
 220         WARN(val < 0, "jump label: negative count!\n");
 221         return true;
 222 }
 223
 224 static void __static_key_slow_dec_cpuslocked(struct static_key *key,
 225                                            unsigned long rate_limit,
 226                                            struct delayed_work *work)
 227 {
 228         lockdep_assert_cpus_held();
 229
 230         if (static_key_slow_try_dec(key))
 231                 return;
 232
 233         jump_label_lock();
 234         if (atomic_dec_and_test(&key->enabled)) {
 235                 if (rate_limit) {
 236                         atomic_inc(&key->enabled);
 237                         schedule_delayed_work(work, rate_limit);
 238                 } else {
 239                         jump_label_update(key);
 240                 }
 241         }
 242         jump_label_unlock();
 243 }
 244
 245 static void __static_key_slow_dec(struct static_key *key,
 246                                   unsigned long rate_limit,
 247                                   struct delayed_work *work)
 248 {
 249         cpus_read_lock();
 250         __static_key_slow_dec_cpuslocked(key, rate_limit, work);
 251         cpus_read_unlock();
 252 }
 253
 254 void jump_label_update_timeout(struct work_struct *work)
 255 {
 256         struct static_key_deferred *key =
 257                 container_of(work, struct static_key_deferred, work.work);
 258         __static_key_slow_dec(&key->key, 0, NULL);
 259 }
 260 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 261
 262 void static_key_slow_dec(struct static_key *key)
 263 {
 264         STATIC_KEY_CHECK_USE(key);
 265         __static_key_slow_dec(key, 0, NULL);
 266 }
 267 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 268
 269 void static_key_slow_dec_cpuslocked(struct static_key *key)
 270 {
 271         STATIC_KEY_CHECK_USE(key);
 272         __static_key_slow_dec_cpuslocked(key, 0, NULL);
 273 }
 274
 275 void __static_key_slow_dec_deferred(struct static_key *key,
 276                                     struct delayed_work *work,
 277                                     unsigned long timeout)
 278 {
 279         STATIC_KEY_CHECK_USE(key);
 280         __static_key_slow_dec(key, timeout, work);
 281 }
 282 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 283
 284 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 285 {
 286         STATIC_KEY_CHECK_USE(key);
 287         flush_delayed_work(work);
 288 }
 289 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 290
 291 void jump_label_rate_limit(struct static_key_deferred *key,
 292                 unsigned long rl)
 293 {
 294         STATIC_KEY_CHECK_USE(key);
 295         key->timeout = rl;
 296         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 297 }
 298 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 299
 300 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 301 {
 302         if (jump_entry_code(entry) <= (unsigned long)end &&
 303             jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 304                 return 1;
 305
 306         return 0;
 307 }
 308
 309 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 310                 struct jump_entry *iter_stop, void *start, void *end)
 311 {
 312         struct jump_entry *iter;
 313
 314         iter = iter_start;
 315         while (iter < iter_stop) {
 316                 if (addr_conflict(iter, start, end))
 317                         return 1;
 318                 iter++;
 319         }
 320
 321         return 0;
 322 }
 323
 324 /*
 325  * Update code which is definitely not currently executing.
 326  * Architectures which need heavyweight synchronization to modify
 327  * running code can override this to make the non-live update case
 328  * cheaper.
 329  */
 330 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 331                                             enum jump_label_type type)
 332 {
 333         arch_jump_label_transform(entry, type);
 334 }
 335
 336 static inline struct jump_entry *static_key_entries(struct static_key *key)
 337 {
 338         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 339         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 340 }
 341
 342 static inline bool static_key_type(struct static_key *key)
 343 {
 344         return key->type & JUMP_TYPE_TRUE;
 345 }
 346
 347 static inline bool static_key_linked(struct static_key *key)
 348 {
 349         return key->type & JUMP_TYPE_LINKED;
 350 }
 351
 352 static inline void static_key_clear_linked(struct static_key *key)
 353 {
 354         key->type &= ~JUMP_TYPE_LINKED;
 355 }
 356
 357 static inline void static_key_set_linked(struct static_key *key)
 358 {
 359         key->type |= JUMP_TYPE_LINKED;
 360 }
 361
 362 /***
 363  * A 'struct static_key' uses a union such that it either points directly
 364  * to a table of 'struct jump_entry' or to a linked list of modules which in
 365  * turn point to 'struct jump_entry' tables.
 366  *
 367  * The two lower bits of the pointer are used to keep track of which pointer
 368  * type is in use and to store the initial branch direction, we use an access
 369  * function which preserves these bits.
 370  */
 371 static void static_key_set_entries(struct static_key *key,
 372                                    struct jump_entry *entries)
 373 {
 374         unsigned long type;
 375
 376         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 377         type = key->type & JUMP_TYPE_MASK;
 378         key->entries = entries;
 379         key->type |= type;
 380 }
 381
 382 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 383 {
 384         struct static_key *key = jump_entry_key(entry);
 385         bool enabled = static_key_enabled(key);
 386         bool branch = jump_entry_is_branch(entry);
 387
 388         /* See the comment in linux/jump_label.h */
 389         return enabled ^ branch;
 390 }
 391
 392 static void __jump_label_update(struct static_key *key,
 393                                 struct jump_entry *entry,
 394                                 struct jump_entry *stop,
 395                                 bool init)
 396 {
 397         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 398                 /*
 399                  * An entry->code of 0 indicates an entry which has been
 400                  * disabled because it was in an init text area.
 401                  */
 402                 if (init || !jump_entry_is_init(entry)) {
 403                         if (kernel_text_address(jump_entry_code(entry)))
 404                                 arch_jump_label_transform(entry, jump_label_type(entry));
 405                         else
 406                                 WARN_ONCE(1, "can't patch jump_label at %pS",
 407                                           (void *)jump_entry_code(entry));
 408                 }
 409         }
 410 }
 411
 412 void __init jump_label_init(void)
 413 {
 414         struct jump_entry *iter_start = __start___jump_table;
 415         struct jump_entry *iter_stop = __stop___jump_table;
 416         struct static_key *key = NULL;
 417         struct jump_entry *iter;
 418
 419         /*
 420          * Since we are initializing the static_key.enabled field with
 421          * with the 'raw' int values (to avoid pulling in atomic.h) in
 422          * jump_label.h, let's make sure that is safe. There are only two
 423          * cases to check since we initialize to 0 or 1.
 424          */
 425         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 426         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 427
 428         if (static_key_initialized)
 429                 return;
 430
 431         cpus_read_lock();
 432         jump_label_lock();
 433         jump_label_sort_entries(iter_start, iter_stop);
 434
 435         for (iter = iter_start; iter < iter_stop; iter++) {
 436                 struct static_key *iterk;
 437
 438                 /* rewrite NOPs */
 439                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 440                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 441
 442                 if (init_section_contains((void *)jump_entry_code(iter), 1))
 443                         jump_entry_set_init(iter);
 444
 445                 iterk = jump_entry_key(iter);
 446                 if (iterk == key)
 447                         continue;
 448
 449                 key = iterk;
 450                 static_key_set_entries(key, iter);
 451         }
 452         static_key_initialized = true;
 453         jump_label_unlock();
 454         cpus_read_unlock();
 455 }
 456
 457 #ifdef CONFIG_MODULES
 458
 459 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 460 {
 461         struct static_key *key = jump_entry_key(entry);
 462         bool type = static_key_type(key);
 463         bool branch = jump_entry_is_branch(entry);
 464
 465         /* See the comment in linux/jump_label.h */
 466         return type ^ branch;
 467 }
 468
 469 struct static_key_mod {
 470         struct static_key_mod *next;
 471         struct jump_entry *entries;
 472         struct module *mod;
 473 };
 474
 475 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 476 {
 477         WARN_ON_ONCE(!static_key_linked(key));
 478         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 479 }
 480
 481 /***
 482  * key->type and key->next are the same via union.
 483  * This sets key->next and preserves the type bits.
 484  *
 485  * See additional comments above static_key_set_entries().
 486  */
 487 static void static_key_set_mod(struct static_key *key,
 488                                struct static_key_mod *mod)
 489 {
 490         unsigned long type;
 491
 492         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 493         type = key->type & JUMP_TYPE_MASK;
 494         key->next = mod;
 495         key->type |= type;
 496 }
 497
 498 static int __jump_label_mod_text_reserved(void *start, void *end)
 499 {
 500         struct module *mod;
 501
 502         preempt_disable();
 503         mod = __module_text_address((unsigned long)start);
 504         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 505         preempt_enable();
 506
 507         if (!mod)
 508                 return 0;
 509
 510
 511         return __jump_label_text_reserved(mod->jump_entries,
 512                                 mod->jump_entries + mod->num_jump_entries,
 513                                 start, end);
 514 }
 515
 516 static void __jump_label_mod_update(struct static_key *key)
 517 {
 518         struct static_key_mod *mod;
 519
 520         for (mod = static_key_mod(key); mod; mod = mod->next) {
 521                 struct jump_entry *stop;
 522                 struct module *m;
 523
 524                 /*
 525                  * NULL if the static_key is defined in a module
 526                  * that does not use it
 527                  */
 528                 if (!mod->entries)
 529                         continue;
 530
 531                 m = mod->mod;
 532                 if (!m)
 533                         stop = __stop___jump_table;
 534                 else
 535                         stop = m->jump_entries + m->num_jump_entries;
 536                 __jump_label_update(key, mod->entries, stop,
 537                                     m && m->state == MODULE_STATE_COMING);
 538         }
 539 }
 540
 541 /***
 542  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 543  * @mod: module to patch
 544  *
 545  * Allow for run-time selection of the optimal nops. Before the module
 546  * loads patch these with arch_get_jump_label_nop(), which is specified by
 547  * the arch specific jump label code.
 548  */
 549 void jump_label_apply_nops(struct module *mod)
 550 {
 551         struct jump_entry *iter_start = mod->jump_entries;
 552         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 553         struct jump_entry *iter;
 554
 555         /* if the module doesn't have jump label entries, just return */
 556         if (iter_start == iter_stop)
 557                 return;
 558
 559         for (iter = iter_start; iter < iter_stop; iter++) {
 560                 /* Only write NOPs for arch_branch_static(). */
 561                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 562                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 563         }
 564 }
 565
 566 static int jump_label_add_module(struct module *mod)
 567 {
 568         struct jump_entry *iter_start = mod->jump_entries;
 569         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 570         struct jump_entry *iter;
 571         struct static_key *key = NULL;
 572         struct static_key_mod *jlm, *jlm2;
 573
 574         /* if the module doesn't have jump label entries, just return */
 575         if (iter_start == iter_stop)
 576                 return 0;
 577
 578         jump_label_sort_entries(iter_start, iter_stop);
 579
 580         for (iter = iter_start; iter < iter_stop; iter++) {
 581                 struct static_key *iterk;
 582
 583                 if (within_module_init(jump_entry_code(iter), mod))
 584                         jump_entry_set_init(iter);
 585
 586                 iterk = jump_entry_key(iter);
 587                 if (iterk == key)
 588                         continue;
 589
 590                 key = iterk;
 591                 if (within_module((unsigned long)key, mod)) {
 592                         static_key_set_entries(key, iter);
 593                         continue;
 594                 }
 595                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 596                 if (!jlm)
 597                         return -ENOMEM;
 598                 if (!static_key_linked(key)) {
 599                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 600                                        GFP_KERNEL);
 601                         if (!jlm2) {
 602                                 kfree(jlm);
 603                                 return -ENOMEM;
 604                         }
 605                         preempt_disable();
 606                         jlm2->mod = __module_address((unsigned long)key);
 607                         preempt_enable();
 608                         jlm2->entries = static_key_entries(key);
 609                         jlm2->next = NULL;
 610                         static_key_set_mod(key, jlm2);
 611                         static_key_set_linked(key);
 612                 }
 613                 jlm->mod = mod;
 614                 jlm->entries = iter;
 615                 jlm->next = static_key_mod(key);
 616                 static_key_set_mod(key, jlm);
 617                 static_key_set_linked(key);
 618
 619                 /* Only update if we've changed from our initial state */
 620                 if (jump_label_type(iter) != jump_label_init_type(iter))
 621                         __jump_label_update(key, iter, iter_stop, true);
 622         }
 623
 624         return 0;
 625 }
 626
 627 static void jump_label_del_module(struct module *mod)
 628 {
 629         struct jump_entry *iter_start = mod->jump_entries;
 630         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 631         struct jump_entry *iter;
 632         struct static_key *key = NULL;
 633         struct static_key_mod *jlm, **prev;
 634
 635         for (iter = iter_start; iter < iter_stop; iter++) {
 636                 if (jump_entry_key(iter) == key)
 637                         continue;
 638
 639                 key = jump_entry_key(iter);
 640
 641                 if (within_module((unsigned long)key, mod))
 642                         continue;
 643
 644                 /* No memory during module load */
 645                 if (WARN_ON(!static_key_linked(key)))
 646                         continue;
 647
 648                 prev = &key->next;
 649                 jlm = static_key_mod(key);
 650
 651                 while (jlm && jlm->mod != mod) {
 652                         prev = &jlm->next;
 653                         jlm = jlm->next;
 654                 }
 655
 656                 /* No memory during module load */
 657                 if (WARN_ON(!jlm))
 658                         continue;
 659
 660                 if (prev == &key->next)
 661                         static_key_set_mod(key, jlm->next);
 662                 else
 663                         *prev = jlm->next;
 664
 665                 kfree(jlm);
 666
 667                 jlm = static_key_mod(key);
 668                 /* if only one etry is left, fold it back into the static_key */
 669                 if (jlm->next == NULL) {
 670                         static_key_set_entries(key, jlm->entries);
 671                         static_key_clear_linked(key);
 672                         kfree(jlm);
 673                 }
 674         }
 675 }
 676
 677 static int
 678 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 679                          void *data)
 680 {
 681         struct module *mod = data;
 682         int ret = 0;
 683
 684         cpus_read_lock();
 685         jump_label_lock();
 686
 687         switch (val) {
 688         case MODULE_STATE_COMING:
 689                 ret = jump_label_add_module(mod);
 690                 if (ret) {
 691                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 692                         jump_label_del_module(mod);
 693                 }
 694                 break;
 695         case MODULE_STATE_GOING:
 696                 jump_label_del_module(mod);
 697                 break;
 698         }
 699
 700         jump_label_unlock();
 701         cpus_read_unlock();
 702
 703         return notifier_from_errno(ret);
 704 }
 705
 706 static struct notifier_block jump_label_module_nb = {
 707         .notifier_call = jump_label_module_notify,
 708         .priority = 1, /* higher than tracepoints */
 709 };
 710
 711 static __init int jump_label_init_module(void)
 712 {
 713         return register_module_notifier(&jump_label_module_nb);
 714 }
 715 early_initcall(jump_label_init_module);
 716
 717 #endif /* CONFIG_MODULES */
 718
 719 /***
 720  * jump_label_text_reserved - check if addr range is reserved
 721  * @start: start text addr
 722  * @end: end text addr
 723  *
 724  * checks if the text addr located between @start and @end
 725  * overlaps with any of the jump label patch addresses. Code
 726  * that wants to modify kernel text should first verify that
 727  * it does not overlap with any of the jump label addresses.
 728  * Caller must hold jump_label_mutex.
 729  *
 730  * returns 1 if there is an overlap, 0 otherwise
 731  */
 732 int jump_label_text_reserved(void *start, void *end)
 733 {
 734         int ret = __jump_label_text_reserved(__start___jump_table,
 735                         __stop___jump_table, start, end);
 736
 737         if (ret)
 738                 return ret;
 739
 740 #ifdef CONFIG_MODULES
 741         ret = __jump_label_mod_text_reserved(start, end);
 742 #endif
 743         return ret;
 744 }
 745
 746 static void jump_label_update(struct static_key *key)
 747 {
 748         struct jump_entry *stop = __stop___jump_table;
 749         struct jump_entry *entry;
 750 #ifdef CONFIG_MODULES
 751         struct module *mod;
 752
 753         if (static_key_linked(key)) {
 754                 __jump_label_mod_update(key);
 755                 return;
 756         }
 757
 758         preempt_disable();
 759         mod = __module_address((unsigned long)key);
 760         if (mod)
 761                 stop = mod->jump_entries + mod->num_jump_entries;
 762         preempt_enable();
 763 #endif
 764         entry = static_key_entries(key);
 765         /* if there are no users, entry can be NULL */
 766         if (entry)
 767                 __jump_label_update(key, entry, stop,
 768                                     system_state < SYSTEM_RUNNING);
 769 }
 770
 771 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 772 static DEFINE_STATIC_KEY_TRUE(sk_true);
 773 static DEFINE_STATIC_KEY_FALSE(sk_false);
 774
 775 static __init int jump_label_test(void)
 776 {
 777         int i;
 778
 779         for (i = 0; i < 2; i++) {
 780                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 781                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 782
 783                 WARN_ON(!static_branch_likely(&sk_true));
 784                 WARN_ON(!static_branch_unlikely(&sk_true));
 785                 WARN_ON(static_branch_likely(&sk_false));
 786                 WARN_ON(static_branch_unlikely(&sk_false));
 787
 788                 static_branch_disable(&sk_true);
 789                 static_branch_enable(&sk_false);
 790
 791                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 792                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 793
 794                 WARN_ON(static_branch_likely(&sk_true));
 795                 WARN_ON(static_branch_unlikely(&sk_true));
 796                 WARN_ON(!static_branch_likely(&sk_false));
 797                 WARN_ON(!static_branch_unlikely(&sk_false));
 798
 799                 static_branch_enable(&sk_true);
 800                 static_branch_disable(&sk_false);
 801         }
 802
 803         return 0;
 804 }
 805 early_initcall(jump_label_test);
 806 #endif /* STATIC_KEYS_SELFTEST */