kernel/jump_label.c

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This source file includes following definitions.
jump_label_lock
jump_label_unlock
jump_label_cmp
jump_label_swap
jump_label_sort_entries
static_key_count
static_key_slow_inc_cpuslocked
static_key_slow_inc
static_key_enable_cpuslocked
static_key_enable
static_key_disable_cpuslocked
static_key_disable
static_key_slow_try_dec
__static_key_slow_dec_cpuslocked
__static_key_slow_dec
jump_label_update_timeout
static_key_slow_dec
static_key_slow_dec_cpuslocked
__static_key_slow_dec_deferred
__static_key_deferred_flush
jump_label_rate_limit
addr_conflict
__jump_label_text_reserved
arch_jump_label_transform_static
static_key_entries
static_key_type
static_key_linked
static_key_clear_linked
static_key_set_linked
static_key_set_entries
jump_label_can_update
__jump_label_update
__jump_label_update
jump_label_init
jump_label_init_type
static_key_set_mod
__jump_label_mod_text_reserved
__jump_label_mod_update
jump_label_apply_nops
jump_label_add_module
jump_label_del_module
jump_label_module_notify
jump_label_init_module
jump_label_text_reserved
jump_label_update
jump_label_test
   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 the jump_label table */
  23 static DEFINE_MUTEX(jump_label_mutex);
  24 
  25 void jump_label_lock(void)
  26 {
  27         mutex_lock(&jump_label_mutex);
  28 }
  29 
  30 void jump_label_unlock(void)
  31 {
  32         mutex_unlock(&jump_label_mutex);
  33 }
  34 
  35 static int jump_label_cmp(const void *a, const void *b)
  36 {
  37         const struct jump_entry *jea = a;
  38         const struct jump_entry *jeb = b;
  39 
  40         /*
  41          * Entrires are sorted by key.
  42          */
  43         if (jump_entry_key(jea) < jump_entry_key(jeb))
  44                 return -1;
  45 
  46         if (jump_entry_key(jea) > jump_entry_key(jeb))
  47                 return 1;
  48 
  49         /*
  50          * In the batching mode, entries should also be sorted by the code
  51          * inside the already sorted list of entries, enabling a bsearch in
  52          * the vector.
  53          */
  54         if (jump_entry_code(jea) < jump_entry_code(jeb))
  55                 return -1;
  56 
  57         if (jump_entry_code(jea) > jump_entry_code(jeb))
  58                 return 1;
  59 
  60         return 0;
  61 }
  62 
  63 static void jump_label_swap(void *a, void *b, int size)
  64 {
  65         long delta = (unsigned long)a - (unsigned long)b;
  66         struct jump_entry *jea = a;
  67         struct jump_entry *jeb = b;
  68         struct jump_entry tmp = *jea;
  69 
  70         jea->code       = jeb->code - delta;
  71         jea->target     = jeb->target - delta;
  72         jea->key        = jeb->key - delta;
  73 
  74         jeb->code       = tmp.code + delta;
  75         jeb->target     = tmp.target + delta;
  76         jeb->key        = tmp.key + delta;
  77 }
  78 
  79 static void
  80 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
  81 {
  82         unsigned long size;
  83         void *swapfn = NULL;
  84 
  85         if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
  86                 swapfn = jump_label_swap;
  87 
  88         size = (((unsigned long)stop - (unsigned long)start)
  89                                         / sizeof(struct jump_entry));
  90         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
  91 }
  92 
  93 static void jump_label_update(struct static_key *key);
  94 
  95 /*
  96  * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h.
  97  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  98  * kernel headers such as kernel.h and others. Since static_key_count() is not
  99  * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok
 100  * to have it be a function here. Similarly, for 'static_key_enable()' and
 101  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
 102  * to be included from most/all places for CONFIG_JUMP_LABEL.
 103  */
 104 int static_key_count(struct static_key *key)
 105 {
 106         /*
 107          * -1 means the first static_key_slow_inc() is in progress.
 108          *  static_key_enabled() must return true, so return 1 here.
 109          */
 110         int n = atomic_read(&key->enabled);
 111 
 112         return n >= 0 ? n : 1;
 113 }
 114 EXPORT_SYMBOL_GPL(static_key_count);
 115 
 116 void static_key_slow_inc_cpuslocked(struct static_key *key)
 117 {
 118         int v, v1;
 119 
 120         STATIC_KEY_CHECK_USE(key);
 121         lockdep_assert_cpus_held();
 122 
 123         /*
 124          * Careful if we get concurrent static_key_slow_inc() calls;
 125          * later calls must wait for the first one to _finish_ the
 126          * jump_label_update() process.  At the same time, however,
 127          * the jump_label_update() call below wants to see
 128          * static_key_enabled(&key) for jumps to be updated properly.
 129          *
 130          * So give a special meaning to negative key->enabled: it sends
 131          * static_key_slow_inc() down the slow path, and it is non-zero
 132          * so it counts as "enabled" in jump_label_update().  Note that
 133          * atomic_inc_unless_negative() checks >= 0, so roll our own.
 134          */
 135         for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 136                 v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 137                 if (likely(v1 == v))
 138                         return;
 139         }
 140 
 141         jump_label_lock();
 142         if (atomic_read(&key->enabled) == 0) {
 143                 atomic_set(&key->enabled, -1);
 144                 jump_label_update(key);
 145                 /*
 146                  * Ensure that if the above cmpxchg loop observes our positive
 147                  * value, it must also observe all the text changes.
 148                  */
 149                 atomic_set_release(&key->enabled, 1);
 150         } else {
 151                 atomic_inc(&key->enabled);
 152         }
 153         jump_label_unlock();
 154 }
 155 
 156 void static_key_slow_inc(struct static_key *key)
 157 {
 158         cpus_read_lock();
 159         static_key_slow_inc_cpuslocked(key);
 160         cpus_read_unlock();
 161 }
 162 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 163 
 164 void static_key_enable_cpuslocked(struct static_key *key)
 165 {
 166         STATIC_KEY_CHECK_USE(key);
 167         lockdep_assert_cpus_held();
 168 
 169         if (atomic_read(&key->enabled) > 0) {
 170                 WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
 171                 return;
 172         }
 173 
 174         jump_label_lock();
 175         if (atomic_read(&key->enabled) == 0) {
 176                 atomic_set(&key->enabled, -1);
 177                 jump_label_update(key);
 178                 /*
 179                  * See static_key_slow_inc().
 180                  */
 181                 atomic_set_release(&key->enabled, 1);
 182         }
 183         jump_label_unlock();
 184 }
 185 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
 186 
 187 void static_key_enable(struct static_key *key)
 188 {
 189         cpus_read_lock();
 190         static_key_enable_cpuslocked(key);
 191         cpus_read_unlock();
 192 }
 193 EXPORT_SYMBOL_GPL(static_key_enable);
 194 
 195 void static_key_disable_cpuslocked(struct static_key *key)
 196 {
 197         STATIC_KEY_CHECK_USE(key);
 198         lockdep_assert_cpus_held();
 199 
 200         if (atomic_read(&key->enabled) != 1) {
 201                 WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
 202                 return;
 203         }
 204 
 205         jump_label_lock();
 206         if (atomic_cmpxchg(&key->enabled, 1, 0))
 207                 jump_label_update(key);
 208         jump_label_unlock();
 209 }
 210 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
 211 
 212 void static_key_disable(struct static_key *key)
 213 {
 214         cpus_read_lock();
 215         static_key_disable_cpuslocked(key);
 216         cpus_read_unlock();
 217 }
 218 EXPORT_SYMBOL_GPL(static_key_disable);
 219 
 220 static bool static_key_slow_try_dec(struct static_key *key)
 221 {
 222         int val;
 223 
 224         val = atomic_fetch_add_unless(&key->enabled, -1, 1);
 225         if (val == 1)
 226                 return false;
 227 
 228         /*
 229          * The negative count check is valid even when a negative
 230          * key->enabled is in use by static_key_slow_inc(); a
 231          * __static_key_slow_dec() before the first static_key_slow_inc()
 232          * returns is unbalanced, because all other static_key_slow_inc()
 233          * instances block while the update is in progress.
 234          */
 235         WARN(val < 0, "jump label: negative count!\n");
 236         return true;
 237 }
 238 
 239 static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 240 {
 241         lockdep_assert_cpus_held();
 242 
 243         if (static_key_slow_try_dec(key))
 244                 return;
 245 
 246         jump_label_lock();
 247         if (atomic_dec_and_test(&key->enabled))
 248                 jump_label_update(key);
 249         jump_label_unlock();
 250 }
 251 
 252 static void __static_key_slow_dec(struct static_key *key)
 253 {
 254         cpus_read_lock();
 255         __static_key_slow_dec_cpuslocked(key);
 256         cpus_read_unlock();
 257 }
 258 
 259 void jump_label_update_timeout(struct work_struct *work)
 260 {
 261         struct static_key_deferred *key =
 262                 container_of(work, struct static_key_deferred, work.work);
 263         __static_key_slow_dec(&key->key);
 264 }
 265 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 266 
 267 void static_key_slow_dec(struct static_key *key)
 268 {
 269         STATIC_KEY_CHECK_USE(key);
 270         __static_key_slow_dec(key);
 271 }
 272 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 273 
 274 void static_key_slow_dec_cpuslocked(struct static_key *key)
 275 {
 276         STATIC_KEY_CHECK_USE(key);
 277         __static_key_slow_dec_cpuslocked(key);
 278 }
 279 
 280 void __static_key_slow_dec_deferred(struct static_key *key,
 281                                     struct delayed_work *work,
 282                                     unsigned long timeout)
 283 {
 284         STATIC_KEY_CHECK_USE(key);
 285 
 286         if (static_key_slow_try_dec(key))
 287                 return;
 288 
 289         schedule_delayed_work(work, timeout);
 290 }
 291 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);
 292 
 293 void __static_key_deferred_flush(void *key, struct delayed_work *work)
 294 {
 295         STATIC_KEY_CHECK_USE(key);
 296         flush_delayed_work(work);
 297 }
 298 EXPORT_SYMBOL_GPL(__static_key_deferred_flush);
 299 
 300 void jump_label_rate_limit(struct static_key_deferred *key,
 301                 unsigned long rl)
 302 {
 303         STATIC_KEY_CHECK_USE(key);
 304         key->timeout = rl;
 305         INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 306 }
 307 EXPORT_SYMBOL_GPL(jump_label_rate_limit);
 308 
 309 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 310 {
 311         if (jump_entry_code(entry) <= (unsigned long)end &&
 312             jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 313                 return 1;
 314 
 315         return 0;
 316 }
 317 
 318 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 319                 struct jump_entry *iter_stop, void *start, void *end)
 320 {
 321         struct jump_entry *iter;
 322 
 323         iter = iter_start;
 324         while (iter < iter_stop) {
 325                 if (addr_conflict(iter, start, end))
 326                         return 1;
 327                 iter++;
 328         }
 329 
 330         return 0;
 331 }
 332 
 333 /*
 334  * Update code which is definitely not currently executing.
 335  * Architectures which need heavyweight synchronization to modify
 336  * running code can override this to make the non-live update case
 337  * cheaper.
 338  */
 339 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 340                                             enum jump_label_type type)
 341 {
 342         arch_jump_label_transform(entry, type);
 343 }
 344 
 345 static inline struct jump_entry *static_key_entries(struct static_key *key)
 346 {
 347         WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
 348         return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
 349 }
 350 
 351 static inline bool static_key_type(struct static_key *key)
 352 {
 353         return key->type & JUMP_TYPE_TRUE;
 354 }
 355 
 356 static inline bool static_key_linked(struct static_key *key)
 357 {
 358         return key->type & JUMP_TYPE_LINKED;
 359 }
 360 
 361 static inline void static_key_clear_linked(struct static_key *key)
 362 {
 363         key->type &= ~JUMP_TYPE_LINKED;
 364 }
 365 
 366 static inline void static_key_set_linked(struct static_key *key)
 367 {
 368         key->type |= JUMP_TYPE_LINKED;
 369 }
 370 
 371 /***
 372  * A 'struct static_key' uses a union such that it either points directly
 373  * to a table of 'struct jump_entry' or to a linked list of modules which in
 374  * turn point to 'struct jump_entry' tables.
 375  *
 376  * The two lower bits of the pointer are used to keep track of which pointer
 377  * type is in use and to store the initial branch direction, we use an access
 378  * function which preserves these bits.
 379  */
 380 static void static_key_set_entries(struct static_key *key,
 381                                    struct jump_entry *entries)
 382 {
 383         unsigned long type;
 384 
 385         WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
 386         type = key->type & JUMP_TYPE_MASK;
 387         key->entries = entries;
 388         key->type |= type;
 389 }
 390 
 391 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 392 {
 393         struct static_key *key = jump_entry_key(entry);
 394         bool enabled = static_key_enabled(key);
 395         bool branch = jump_entry_is_branch(entry);
 396 
 397         /* See the comment in linux/jump_label.h */
 398         return enabled ^ branch;
 399 }
 400 
 401 static bool jump_label_can_update(struct jump_entry *entry, bool init)
 402 {
 403         /*
 404          * Cannot update code that was in an init text area.
 405          */
 406         if (!init && jump_entry_is_init(entry))
 407                 return false;
 408 
 409         if (!kernel_text_address(jump_entry_code(entry))) {
 410                 WARN_ONCE(!jump_entry_is_init(entry),
 411                           "can't patch jump_label at %pS",
 412                           (void *)jump_entry_code(entry));
 413                 return false;
 414         }
 415 
 416         return true;
 417 }
 418 
 419 #ifndef HAVE_JUMP_LABEL_BATCH
 420 static void __jump_label_update(struct static_key *key,
 421                                 struct jump_entry *entry,
 422                                 struct jump_entry *stop,
 423                                 bool init)
 424 {
 425         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 426                 if (jump_label_can_update(entry, init))
 427                         arch_jump_label_transform(entry, jump_label_type(entry));
 428         }
 429 }
 430 #else
 431 static void __jump_label_update(struct static_key *key,
 432                                 struct jump_entry *entry,
 433                                 struct jump_entry *stop,
 434                                 bool init)
 435 {
 436         for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 437 
 438                 if (!jump_label_can_update(entry, init))
 439                         continue;
 440 
 441                 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) {
 442                         /*
 443                          * Queue is full: Apply the current queue and try again.
 444                          */
 445                         arch_jump_label_transform_apply();
 446                         BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry)));
 447                 }
 448         }
 449         arch_jump_label_transform_apply();
 450 }
 451 #endif
 452 
 453 void __init jump_label_init(void)
 454 {
 455         struct jump_entry *iter_start = __start___jump_table;
 456         struct jump_entry *iter_stop = __stop___jump_table;
 457         struct static_key *key = NULL;
 458         struct jump_entry *iter;
 459 
 460         /*
 461          * Since we are initializing the static_key.enabled field with
 462          * with the 'raw' int values (to avoid pulling in atomic.h) in
 463          * jump_label.h, let's make sure that is safe. There are only two
 464          * cases to check since we initialize to 0 or 1.
 465          */
 466         BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 467         BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
 468 
 469         if (static_key_initialized)
 470                 return;
 471 
 472         cpus_read_lock();
 473         jump_label_lock();
 474         jump_label_sort_entries(iter_start, iter_stop);
 475 
 476         for (iter = iter_start; iter < iter_stop; iter++) {
 477                 struct static_key *iterk;
 478 
 479                 /* rewrite NOPs */
 480                 if (jump_label_type(iter) == JUMP_LABEL_NOP)
 481                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 482 
 483                 if (init_section_contains((void *)jump_entry_code(iter), 1))
 484                         jump_entry_set_init(iter);
 485 
 486                 iterk = jump_entry_key(iter);
 487                 if (iterk == key)
 488                         continue;
 489 
 490                 key = iterk;
 491                 static_key_set_entries(key, iter);
 492         }
 493         static_key_initialized = true;
 494         jump_label_unlock();
 495         cpus_read_unlock();
 496 }
 497 
 498 #ifdef CONFIG_MODULES
 499 
 500 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 501 {
 502         struct static_key *key = jump_entry_key(entry);
 503         bool type = static_key_type(key);
 504         bool branch = jump_entry_is_branch(entry);
 505 
 506         /* See the comment in linux/jump_label.h */
 507         return type ^ branch;
 508 }
 509 
 510 struct static_key_mod {
 511         struct static_key_mod *next;
 512         struct jump_entry *entries;
 513         struct module *mod;
 514 };
 515 
 516 static inline struct static_key_mod *static_key_mod(struct static_key *key)
 517 {
 518         WARN_ON_ONCE(!static_key_linked(key));
 519         return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
 520 }
 521 
 522 /***
 523  * key->type and key->next are the same via union.
 524  * This sets key->next and preserves the type bits.
 525  *
 526  * See additional comments above static_key_set_entries().
 527  */
 528 static void static_key_set_mod(struct static_key *key,
 529                                struct static_key_mod *mod)
 530 {
 531         unsigned long type;
 532 
 533         WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
 534         type = key->type & JUMP_TYPE_MASK;
 535         key->next = mod;
 536         key->type |= type;
 537 }
 538 
 539 static int __jump_label_mod_text_reserved(void *start, void *end)
 540 {
 541         struct module *mod;
 542 
 543         preempt_disable();
 544         mod = __module_text_address((unsigned long)start);
 545         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 546         preempt_enable();
 547 
 548         if (!mod)
 549                 return 0;
 550 
 551 
 552         return __jump_label_text_reserved(mod->jump_entries,
 553                                 mod->jump_entries + mod->num_jump_entries,
 554                                 start, end);
 555 }
 556 
 557 static void __jump_label_mod_update(struct static_key *key)
 558 {
 559         struct static_key_mod *mod;
 560 
 561         for (mod = static_key_mod(key); mod; mod = mod->next) {
 562                 struct jump_entry *stop;
 563                 struct module *m;
 564 
 565                 /*
 566                  * NULL if the static_key is defined in a module
 567                  * that does not use it
 568                  */
 569                 if (!mod->entries)
 570                         continue;
 571 
 572                 m = mod->mod;
 573                 if (!m)
 574                         stop = __stop___jump_table;
 575                 else
 576                         stop = m->jump_entries + m->num_jump_entries;
 577                 __jump_label_update(key, mod->entries, stop,
 578                                     m && m->state == MODULE_STATE_COMING);
 579         }
 580 }
 581 
 582 /***
 583  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
 584  * @mod: module to patch
 585  *
 586  * Allow for run-time selection of the optimal nops. Before the module
 587  * loads patch these with arch_get_jump_label_nop(), which is specified by
 588  * the arch specific jump label code.
 589  */
 590 void jump_label_apply_nops(struct module *mod)
 591 {
 592         struct jump_entry *iter_start = mod->jump_entries;
 593         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 594         struct jump_entry *iter;
 595 
 596         /* if the module doesn't have jump label entries, just return */
 597         if (iter_start == iter_stop)
 598                 return;
 599 
 600         for (iter = iter_start; iter < iter_stop; iter++) {
 601                 /* Only write NOPs for arch_branch_static(). */
 602                 if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 603                         arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 604         }
 605 }
 606 
 607 static int jump_label_add_module(struct module *mod)
 608 {
 609         struct jump_entry *iter_start = mod->jump_entries;
 610         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 611         struct jump_entry *iter;
 612         struct static_key *key = NULL;
 613         struct static_key_mod *jlm, *jlm2;
 614 
 615         /* if the module doesn't have jump label entries, just return */
 616         if (iter_start == iter_stop)
 617                 return 0;
 618 
 619         jump_label_sort_entries(iter_start, iter_stop);
 620 
 621         for (iter = iter_start; iter < iter_stop; iter++) {
 622                 struct static_key *iterk;
 623 
 624                 if (within_module_init(jump_entry_code(iter), mod))
 625                         jump_entry_set_init(iter);
 626 
 627                 iterk = jump_entry_key(iter);
 628                 if (iterk == key)
 629                         continue;
 630 
 631                 key = iterk;
 632                 if (within_module((unsigned long)key, mod)) {
 633                         static_key_set_entries(key, iter);
 634                         continue;
 635                 }
 636                 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 637                 if (!jlm)
 638                         return -ENOMEM;
 639                 if (!static_key_linked(key)) {
 640                         jlm2 = kzalloc(sizeof(struct static_key_mod),
 641                                        GFP_KERNEL);
 642                         if (!jlm2) {
 643                                 kfree(jlm);
 644                                 return -ENOMEM;
 645                         }
 646                         preempt_disable();
 647                         jlm2->mod = __module_address((unsigned long)key);
 648                         preempt_enable();
 649                         jlm2->entries = static_key_entries(key);
 650                         jlm2->next = NULL;
 651                         static_key_set_mod(key, jlm2);
 652                         static_key_set_linked(key);
 653                 }
 654                 jlm->mod = mod;
 655                 jlm->entries = iter;
 656                 jlm->next = static_key_mod(key);
 657                 static_key_set_mod(key, jlm);
 658                 static_key_set_linked(key);
 659 
 660                 /* Only update if we've changed from our initial state */
 661                 if (jump_label_type(iter) != jump_label_init_type(iter))
 662                         __jump_label_update(key, iter, iter_stop, true);
 663         }
 664 
 665         return 0;
 666 }
 667 
 668 static void jump_label_del_module(struct module *mod)
 669 {
 670         struct jump_entry *iter_start = mod->jump_entries;
 671         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 672         struct jump_entry *iter;
 673         struct static_key *key = NULL;
 674         struct static_key_mod *jlm, **prev;
 675 
 676         for (iter = iter_start; iter < iter_stop; iter++) {
 677                 if (jump_entry_key(iter) == key)
 678                         continue;
 679 
 680                 key = jump_entry_key(iter);
 681 
 682                 if (within_module((unsigned long)key, mod))
 683                         continue;
 684 
 685                 /* No memory during module load */
 686                 if (WARN_ON(!static_key_linked(key)))
 687                         continue;
 688 
 689                 prev = &key->next;
 690                 jlm = static_key_mod(key);
 691 
 692                 while (jlm && jlm->mod != mod) {
 693                         prev = &jlm->next;
 694                         jlm = jlm->next;
 695                 }
 696 
 697                 /* No memory during module load */
 698                 if (WARN_ON(!jlm))
 699                         continue;
 700 
 701                 if (prev == &key->next)
 702                         static_key_set_mod(key, jlm->next);
 703                 else
 704                         *prev = jlm->next;
 705 
 706                 kfree(jlm);
 707 
 708                 jlm = static_key_mod(key);
 709                 /* if only one etry is left, fold it back into the static_key */
 710                 if (jlm->next == NULL) {
 711                         static_key_set_entries(key, jlm->entries);
 712                         static_key_clear_linked(key);
 713                         kfree(jlm);
 714                 }
 715         }
 716 }
 717 
 718 static int
 719 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 720                          void *data)
 721 {
 722         struct module *mod = data;
 723         int ret = 0;
 724 
 725         cpus_read_lock();
 726         jump_label_lock();
 727 
 728         switch (val) {
 729         case MODULE_STATE_COMING:
 730                 ret = jump_label_add_module(mod);
 731                 if (ret) {
 732                         WARN(1, "Failed to allocate memory: jump_label may not work properly.\n");
 733                         jump_label_del_module(mod);
 734                 }
 735                 break;
 736         case MODULE_STATE_GOING:
 737                 jump_label_del_module(mod);
 738                 break;
 739         }
 740 
 741         jump_label_unlock();
 742         cpus_read_unlock();
 743 
 744         return notifier_from_errno(ret);
 745 }
 746 
 747 static struct notifier_block jump_label_module_nb = {
 748         .notifier_call = jump_label_module_notify,
 749         .priority = 1, /* higher than tracepoints */
 750 };
 751 
 752 static __init int jump_label_init_module(void)
 753 {
 754         return register_module_notifier(&jump_label_module_nb);
 755 }
 756 early_initcall(jump_label_init_module);
 757 
 758 #endif /* CONFIG_MODULES */
 759 
 760 /***
 761  * jump_label_text_reserved - check if addr range is reserved
 762  * @start: start text addr
 763  * @end: end text addr
 764  *
 765  * checks if the text addr located between @start and @end
 766  * overlaps with any of the jump label patch addresses. Code
 767  * that wants to modify kernel text should first verify that
 768  * it does not overlap with any of the jump label addresses.
 769  * Caller must hold jump_label_mutex.
 770  *
 771  * returns 1 if there is an overlap, 0 otherwise
 772  */
 773 int jump_label_text_reserved(void *start, void *end)
 774 {
 775         int ret = __jump_label_text_reserved(__start___jump_table,
 776                         __stop___jump_table, start, end);
 777 
 778         if (ret)
 779                 return ret;
 780 
 781 #ifdef CONFIG_MODULES
 782         ret = __jump_label_mod_text_reserved(start, end);
 783 #endif
 784         return ret;
 785 }
 786 
 787 static void jump_label_update(struct static_key *key)
 788 {
 789         struct jump_entry *stop = __stop___jump_table;
 790         struct jump_entry *entry;
 791 #ifdef CONFIG_MODULES
 792         struct module *mod;
 793 
 794         if (static_key_linked(key)) {
 795                 __jump_label_mod_update(key);
 796                 return;
 797         }
 798 
 799         preempt_disable();
 800         mod = __module_address((unsigned long)key);
 801         if (mod)
 802                 stop = mod->jump_entries + mod->num_jump_entries;
 803         preempt_enable();
 804 #endif
 805         entry = static_key_entries(key);
 806         /* if there are no users, entry can be NULL */
 807         if (entry)
 808                 __jump_label_update(key, entry, stop,
 809                                     system_state < SYSTEM_RUNNING);
 810 }
 811 
 812 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 813 static DEFINE_STATIC_KEY_TRUE(sk_true);
 814 static DEFINE_STATIC_KEY_FALSE(sk_false);
 815 
 816 static __init int jump_label_test(void)
 817 {
 818         int i;
 819 
 820         for (i = 0; i < 2; i++) {
 821                 WARN_ON(static_key_enabled(&sk_true.key) != true);
 822                 WARN_ON(static_key_enabled(&sk_false.key) != false);
 823 
 824                 WARN_ON(!static_branch_likely(&sk_true));
 825                 WARN_ON(!static_branch_unlikely(&sk_true));
 826                 WARN_ON(static_branch_likely(&sk_false));
 827                 WARN_ON(static_branch_unlikely(&sk_false));
 828 
 829                 static_branch_disable(&sk_true);
 830                 static_branch_enable(&sk_false);
 831 
 832                 WARN_ON(static_key_enabled(&sk_true.key) == true);
 833                 WARN_ON(static_key_enabled(&sk_false.key) == false);
 834 
 835                 WARN_ON(static_branch_likely(&sk_true));
 836                 WARN_ON(static_branch_unlikely(&sk_true));
 837                 WARN_ON(!static_branch_likely(&sk_false));
 838                 WARN_ON(!static_branch_unlikely(&sk_false));
 839 
 840                 static_branch_enable(&sk_true);
 841                 static_branch_disable(&sk_false);
 842         }
 843 
 844         return 0;
 845 }
 846 early_initcall(jump_label_test);
 847 #endif /* STATIC_KEYS_SELFTEST */
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root/kernel/jump_label.c

DEFINITIONS
