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