1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * jump label support 4 * 5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> 6 * Copyright (C) 2011 Peter Zijlstra 7 * 8 */ 9 #include <linux/memory.h> 10 #include <linux/uaccess.h> 11 #include <linux/module.h> 12 #include <linux/list.h> 13 #include <linux/slab.h> 14 #include <linux/sort.h> 15 #include <linux/err.h> 16 #include <linux/static_key.h> 17 #include <linux/jump_label_ratelimit.h> 18 #include <linux/bug.h> 19 #include <linux/cpu.h> 20 #include <asm/sections.h> 21 22 /* mutex to protect coming/going of the jump_label table */ 23 static DEFINE_MUTEX(jump_label_mutex); 24 25 void jump_label_lock(void) 26 { 27 mutex_lock(&jump_label_mutex); 28 } 29 30 void jump_label_unlock(void) 31 { 32 mutex_unlock(&jump_label_mutex); 33 } 34 35 static int jump_label_cmp(const void *a, const void *b) 36 { 37 const struct jump_entry *jea = a; 38 const struct jump_entry *jeb = b; 39 40 /* 41 * Entrires are sorted by key. 42 */ 43 if (jump_entry_key(jea) < jump_entry_key(jeb)) 44 return -1; 45 46 if (jump_entry_key(jea) > jump_entry_key(jeb)) 47 return 1; 48 49 /* 50 * In the batching mode, entries should also be sorted by the code 51 * inside the already sorted list of entries, enabling a bsearch in 52 * the vector. 53 */ 54 if (jump_entry_code(jea) < jump_entry_code(jeb)) 55 return -1; 56 57 if (jump_entry_code(jea) > jump_entry_code(jeb)) 58 return 1; 59 60 return 0; 61 } 62 63 static void jump_label_swap(void *a, void *b, int size) 64 { 65 long delta = (unsigned long)a - (unsigned long)b; 66 struct jump_entry *jea = a; 67 struct jump_entry *jeb = b; 68 struct jump_entry tmp = *jea; 69 70 jea->code = jeb->code - delta; 71 jea->target = jeb->target - delta; 72 jea->key = jeb->key - delta; 73 74 jeb->code = tmp.code + delta; 75 jeb->target = tmp.target + delta; 76 jeb->key = tmp.key + delta; 77 } 78 79 static void 80 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) 81 { 82 unsigned long size; 83 void *swapfn = NULL; 84 85 if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE)) 86 swapfn = jump_label_swap; 87 88 size = (((unsigned long)stop - (unsigned long)start) 89 / sizeof(struct jump_entry)); 90 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn); 91 } 92 93 static void jump_label_update(struct static_key *key); 94 95 /* 96 * There are similar definitions for the !CONFIG_JUMP_LABEL case in jump_label.h. 97 * The use of 'atomic_read()' requires atomic.h and its problematic for some 98 * kernel headers such as kernel.h and others. Since static_key_count() is not 99 * used in the branch statements as it is for the !CONFIG_JUMP_LABEL case its ok 100 * to have it be a function here. Similarly, for 'static_key_enable()' and 101 * 'static_key_disable()', which require bug.h. This should allow jump_label.h 102 * to be included from most/all places for CONFIG_JUMP_LABEL. 103 */ 104 int static_key_count(struct static_key *key) 105 { 106 /* 107 * -1 means the first static_key_slow_inc() is in progress. 108 * static_key_enabled() must return true, so return 1 here. 109 */ 110 int n = atomic_read(&key->enabled); 111 112 return n >= 0 ? n : 1; 113 } 114 EXPORT_SYMBOL_GPL(static_key_count); 115 116 void static_key_slow_inc_cpuslocked(struct static_key *key) 117 { 118 int v, v1; 119 120 STATIC_KEY_CHECK_USE(key); 121 lockdep_assert_cpus_held(); 122 123 /* 124 * Careful if we get concurrent static_key_slow_inc() calls; 125 * later calls must wait for the first one to _finish_ the 126 * jump_label_update() process. At the same time, however, 127 * the jump_label_update() call below wants to see 128 * static_key_enabled(&key) for jumps to be updated properly. 129 * 130 * So give a special meaning to negative key->enabled: it sends 131 * static_key_slow_inc() down the slow path, and it is non-zero 132 * so it counts as "enabled" in jump_label_update(). Note that 133 * atomic_inc_unless_negative() checks >= 0, so roll our own. 134 */ 135 for (v = atomic_read(&key->enabled); v > 0; v = v1) { 136 v1 = atomic_cmpxchg(&key->enabled, v, v + 1); 137 if (likely(v1 == v)) 138 return; 139 } 140 141 jump_label_lock(); 142 if (atomic_read(&key->enabled) == 0) { 143 atomic_set(&key->enabled, -1); 144 jump_label_update(key); 145 /* 146 * Ensure that if the above cmpxchg loop observes our positive 147 * value, it must also observe all the text changes. 148 */ 149 atomic_set_release(&key->enabled, 1); 150 } else { 151 atomic_inc(&key->enabled); 152 } 153 jump_label_unlock(); 154 } 155 156 void static_key_slow_inc(struct static_key *key) 157 { 158 cpus_read_lock(); 159 static_key_slow_inc_cpuslocked(key); 160 cpus_read_unlock(); 161 } 162 EXPORT_SYMBOL_GPL(static_key_slow_inc); 163 164 void static_key_enable_cpuslocked(struct static_key *key) 165 { 166 STATIC_KEY_CHECK_USE(key); 167 lockdep_assert_cpus_held(); 168 169 if (atomic_read(&key->enabled) > 0) { 170 WARN_ON_ONCE(atomic_read(&key->enabled) != 1); 171 return; 172 } 173 174 jump_label_lock(); 175 if (atomic_read(&key->enabled) == 0) { 176 atomic_set(&key->enabled, -1); 177 jump_label_update(key); 178 /* 179 * See static_key_slow_inc(). 180 */ 181 atomic_set_release(&key->enabled, 1); 182 } 183 jump_label_unlock(); 184 } 185 EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked); 186 187 void static_key_enable(struct static_key *key) 188 { 189 cpus_read_lock(); 190 static_key_enable_cpuslocked(key); 191 cpus_read_unlock(); 192 } 193 EXPORT_SYMBOL_GPL(static_key_enable); 194 195 void static_key_disable_cpuslocked(struct static_key *key) 196 { 197 STATIC_KEY_CHECK_USE(key); 198 lockdep_assert_cpus_held(); 199 200 if (atomic_read(&key->enabled) != 1) { 201 WARN_ON_ONCE(atomic_read(&key->enabled) != 0); 202 return; 203 } 204 205 jump_label_lock(); 206 if (atomic_cmpxchg(&key->enabled, 1, 0)) 207 jump_label_update(key); 208 jump_label_unlock(); 209 } 210 EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked); 211 212 void static_key_disable(struct static_key *key) 213 { 214 cpus_read_lock(); 215 static_key_disable_cpuslocked(key); 216 cpus_read_unlock(); 217 } 218 EXPORT_SYMBOL_GPL(static_key_disable); 219 220 static bool static_key_slow_try_dec(struct static_key *key) 221 { 222 int val; 223 224 val = atomic_fetch_add_unless(&key->enabled, -1, 1); 225 if (val == 1) 226 return false; 227 228 /* 229 * The negative count check is valid even when a negative 230 * key->enabled is in use by static_key_slow_inc(); a 231 * __static_key_slow_dec() before the first static_key_slow_inc() 232 * returns is unbalanced, because all other static_key_slow_inc() 233 * instances block while the update is in progress. 234 */ 235 WARN(val < 0, "jump label: negative count!\n"); 236 return true; 237 } 238 239 static void __static_key_slow_dec_cpuslocked(struct static_key *key) 240 { 241 lockdep_assert_cpus_held(); 242 243 if (static_key_slow_try_dec(key)) 244 return; 245 246 jump_label_lock(); 247 if (atomic_dec_and_test(&key->enabled)) 248 jump_label_update(key); 249 jump_label_unlock(); 250 } 251 252 static void __static_key_slow_dec(struct static_key *key) 253 { 254 cpus_read_lock(); 255 __static_key_slow_dec_cpuslocked(key); 256 cpus_read_unlock(); 257 } 258 259 void jump_label_update_timeout(struct work_struct *work) 260 { 261 struct static_key_deferred *key = 262 container_of(work, struct static_key_deferred, work.work); 263 __static_key_slow_dec(&key->key); 264 } 265 EXPORT_SYMBOL_GPL(jump_label_update_timeout); 266 267 void static_key_slow_dec(struct static_key *key) 268 { 269 STATIC_KEY_CHECK_USE(key); 270 __static_key_slow_dec(key); 271 } 272 EXPORT_SYMBOL_GPL(static_key_slow_dec); 273 274 void static_key_slow_dec_cpuslocked(struct static_key *key) 275 { 276 STATIC_KEY_CHECK_USE(key); 277 __static_key_slow_dec_cpuslocked(key); 278 } 279 280 void __static_key_slow_dec_deferred(struct static_key *key, 281 struct delayed_work *work, 282 unsigned long timeout) 283 { 284 STATIC_KEY_CHECK_USE(key); 285 286 if (static_key_slow_try_dec(key)) 287 return; 288 289 schedule_delayed_work(work, timeout); 290 } 291 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred); 292 293 void __static_key_deferred_flush(void *key, struct delayed_work *work) 294 { 295 STATIC_KEY_CHECK_USE(key); 296 flush_delayed_work(work); 297 } 298 EXPORT_SYMBOL_GPL(__static_key_deferred_flush); 299 300 void jump_label_rate_limit(struct static_key_deferred *key, 301 unsigned long rl) 302 { 303 STATIC_KEY_CHECK_USE(key); 304 key->timeout = rl; 305 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); 306 } 307 EXPORT_SYMBOL_GPL(jump_label_rate_limit); 308 309 static int addr_conflict(struct jump_entry *entry, void *start, void *end) 310 { 311 if (jump_entry_code(entry) <= (unsigned long)end && 312 jump_entry_code(entry) + jump_entry_size(entry) > (unsigned long)start) 313 return 1; 314 315 return 0; 316 } 317 318 static int __jump_label_text_reserved(struct jump_entry *iter_start, 319 struct jump_entry *iter_stop, void *start, void *end) 320 { 321 struct jump_entry *iter; 322 323 iter = iter_start; 324 while (iter < iter_stop) { 325 if (addr_conflict(iter, start, end)) 326 return 1; 327 iter++; 328 } 329 330 return 0; 331 } 332 333 /* 334 * Update code which is definitely not currently executing. 335 * Architectures which need heavyweight synchronization to modify 336 * running code can override this to make the non-live update case 337 * cheaper. 338 */ 339 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, 340 enum jump_label_type type) 341 { 342 arch_jump_label_transform(entry, type); 343 } 344 345 static inline struct jump_entry *static_key_entries(struct static_key *key) 346 { 347 WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED); 348 return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK); 349 } 350 351 static inline bool static_key_type(struct static_key *key) 352 { 353 return key->type & JUMP_TYPE_TRUE; 354 } 355 356 static inline bool static_key_linked(struct static_key *key) 357 { 358 return key->type & JUMP_TYPE_LINKED; 359 } 360 361 static inline void static_key_clear_linked(struct static_key *key) 362 { 363 key->type &= ~JUMP_TYPE_LINKED; 364 } 365 366 static inline void static_key_set_linked(struct static_key *key) 367 { 368 key->type |= JUMP_TYPE_LINKED; 369 } 370 371 /*** 372 * A 'struct static_key' uses a union such that it either points directly 373 * to a table of 'struct jump_entry' or to a linked list of modules which in 374 * turn point to 'struct jump_entry' tables. 375 * 376 * The two lower bits of the pointer are used to keep track of which pointer 377 * type is in use and to store the initial branch direction, we use an access 378 * function which preserves these bits. 379 */ 380 static void static_key_set_entries(struct static_key *key, 381 struct jump_entry *entries) 382 { 383 unsigned long type; 384 385 WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK); 386 type = key->type & JUMP_TYPE_MASK; 387 key->entries = entries; 388 key->type |= type; 389 } 390 391 static enum jump_label_type jump_label_type(struct jump_entry *entry) 392 { 393 struct static_key *key = jump_entry_key(entry); 394 bool enabled = static_key_enabled(key); 395 bool branch = jump_entry_is_branch(entry); 396 397 /* See the comment in linux/jump_label.h */ 398 return enabled ^ branch; 399 } 400 401 static bool jump_label_can_update(struct jump_entry *entry, bool init) 402 { 403 /* 404 * Cannot update code that was in an init text area. 405 */ 406 if (!init && jump_entry_is_init(entry)) 407 return false; 408 409 if (!kernel_text_address(jump_entry_code(entry))) { 410 /* 411 * This skips patching built-in __exit, which 412 * is part of init_section_contains() but is 413 * not part of kernel_text_address(). 414 * 415 * Skipping built-in __exit is fine since it 416 * will never be executed. 417 */ 418 WARN_ONCE(!jump_entry_is_init(entry), 419 "can't patch jump_label at %pS", 420 (void *)jump_entry_code(entry)); 421 return false; 422 } 423 424 return true; 425 } 426 427 #ifndef HAVE_JUMP_LABEL_BATCH 428 static void __jump_label_update(struct static_key *key, 429 struct jump_entry *entry, 430 struct jump_entry *stop, 431 bool init) 432 { 433 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) { 434 if (jump_label_can_update(entry, init)) 435 arch_jump_label_transform(entry, jump_label_type(entry)); 436 } 437 } 438 #else 439 static void __jump_label_update(struct static_key *key, 440 struct jump_entry *entry, 441 struct jump_entry *stop, 442 bool init) 443 { 444 for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) { 445 446 if (!jump_label_can_update(entry, init)) 447 continue; 448 449 if (!arch_jump_label_transform_queue(entry, jump_label_type(entry))) { 450 /* 451 * Queue is full: Apply the current queue and try again. 452 */ 453 arch_jump_label_transform_apply(); 454 BUG_ON(!arch_jump_label_transform_queue(entry, jump_label_type(entry))); 455 } 456 } 457 arch_jump_label_transform_apply(); 458 } 459 #endif 460 461 void __init jump_label_init(void) 462 { 463 struct jump_entry *iter_start = __start___jump_table; 464 struct jump_entry *iter_stop = __stop___jump_table; 465 struct static_key *key = NULL; 466 struct jump_entry *iter; 467 468 /* 469 * Since we are initializing the static_key.enabled field with 470 * with the 'raw' int values (to avoid pulling in atomic.h) in 471 * jump_label.h, let's make sure that is safe. There are only two 472 * cases to check since we initialize to 0 or 1. 473 */ 474 BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0); 475 BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1); 476 477 if (static_key_initialized) 478 return; 479 480 cpus_read_lock(); 481 jump_label_lock(); 482 jump_label_sort_entries(iter_start, iter_stop); 483 484 for (iter = iter_start; iter < iter_stop; iter++) { 485 struct static_key *iterk; 486 bool in_init; 487 488 /* rewrite NOPs */ 489 if (jump_label_type(iter) == JUMP_LABEL_NOP) 490 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); 491 492 in_init = init_section_contains((void *)jump_entry_code(iter), 1); 493 jump_entry_set_init(iter, in_init); 494 495 iterk = jump_entry_key(iter); 496 if (iterk == key) 497 continue; 498 499 key = iterk; 500 static_key_set_entries(key, iter); 501 } 502 static_key_initialized = true; 503 jump_label_unlock(); 504 cpus_read_unlock(); 505 } 506 507 #ifdef CONFIG_MODULES 508 509 static enum jump_label_type jump_label_init_type(struct jump_entry *entry) 510 { 511 struct static_key *key = jump_entry_key(entry); 512 bool type = static_key_type(key); 513 bool branch = jump_entry_is_branch(entry); 514 515 /* See the comment in linux/jump_label.h */ 516 return type ^ branch; 517 } 518 519 struct static_key_mod { 520 struct static_key_mod *next; 521 struct jump_entry *entries; 522 struct module *mod; 523 }; 524 525 static inline struct static_key_mod *static_key_mod(struct static_key *key) 526 { 527 WARN_ON_ONCE(!static_key_linked(key)); 528 return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK); 529 } 530 531 /*** 532 * key->type and key->next are the same via union. 533 * This sets key->next and preserves the type bits. 534 * 535 * See additional comments above static_key_set_entries(). 536 */ 537 static void static_key_set_mod(struct static_key *key, 538 struct static_key_mod *mod) 539 { 540 unsigned long type; 541 542 WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK); 543 type = key->type & JUMP_TYPE_MASK; 544 key->next = mod; 545 key->type |= type; 546 } 547 548 static int __jump_label_mod_text_reserved(void *start, void *end) 549 { 550 struct module *mod; 551 int ret; 552 553 preempt_disable(); 554 mod = __module_text_address((unsigned long)start); 555 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); 556 if (!try_module_get(mod)) 557 mod = NULL; 558 preempt_enable(); 559 560 if (!mod) 561 return 0; 562 563 ret = __jump_label_text_reserved(mod->jump_entries, 564 mod->jump_entries + mod->num_jump_entries, 565 start, end); 566 567 module_put(mod); 568 569 return ret; 570 } 571 572 static void __jump_label_mod_update(struct static_key *key) 573 { 574 struct static_key_mod *mod; 575 576 for (mod = static_key_mod(key); mod; mod = mod->next) { 577 struct jump_entry *stop; 578 struct module *m; 579 580 /* 581 * NULL if the static_key is defined in a module 582 * that does not use it 583 */ 584 if (!mod->entries) 585 continue; 586 587 m = mod->mod; 588 if (!m) 589 stop = __stop___jump_table; 590 else 591 stop = m->jump_entries + m->num_jump_entries; 592 __jump_label_update(key, mod->entries, stop, 593 m && m->state == MODULE_STATE_COMING); 594 } 595 } 596 597 /*** 598 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() 599 * @mod: module to patch 600 * 601 * Allow for run-time selection of the optimal nops. Before the module 602 * loads patch these with arch_get_jump_label_nop(), which is specified by 603 * the arch specific jump label code. 604 */ 605 void jump_label_apply_nops(struct module *mod) 606 { 607 struct jump_entry *iter_start = mod->jump_entries; 608 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 609 struct jump_entry *iter; 610 611 /* if the module doesn't have jump label entries, just return */ 612 if (iter_start == iter_stop) 613 return; 614 615 for (iter = iter_start; iter < iter_stop; iter++) { 616 /* Only write NOPs for arch_branch_static(). */ 617 if (jump_label_init_type(iter) == JUMP_LABEL_NOP) 618 arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); 619 } 620 } 621 622 static int jump_label_add_module(struct module *mod) 623 { 624 struct jump_entry *iter_start = mod->jump_entries; 625 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 626 struct jump_entry *iter; 627 struct static_key *key = NULL; 628 struct static_key_mod *jlm, *jlm2; 629 630 /* if the module doesn't have jump label entries, just return */ 631 if (iter_start == iter_stop) 632 return 0; 633 634 jump_label_sort_entries(iter_start, iter_stop); 635 636 for (iter = iter_start; iter < iter_stop; iter++) { 637 struct static_key *iterk; 638 bool in_init; 639 640 in_init = within_module_init(jump_entry_code(iter), mod); 641 jump_entry_set_init(iter, in_init); 642 643 iterk = jump_entry_key(iter); 644 if (iterk == key) 645 continue; 646 647 key = iterk; 648 if (within_module((unsigned long)key, mod)) { 649 static_key_set_entries(key, iter); 650 continue; 651 } 652 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); 653 if (!jlm) 654 return -ENOMEM; 655 if (!static_key_linked(key)) { 656 jlm2 = kzalloc(sizeof(struct static_key_mod), 657 GFP_KERNEL); 658 if (!jlm2) { 659 kfree(jlm); 660 return -ENOMEM; 661 } 662 preempt_disable(); 663 jlm2->mod = __module_address((unsigned long)key); 664 preempt_enable(); 665 jlm2->entries = static_key_entries(key); 666 jlm2->next = NULL; 667 static_key_set_mod(key, jlm2); 668 static_key_set_linked(key); 669 } 670 jlm->mod = mod; 671 jlm->entries = iter; 672 jlm->next = static_key_mod(key); 673 static_key_set_mod(key, jlm); 674 static_key_set_linked(key); 675 676 /* Only update if we've changed from our initial state */ 677 if (jump_label_type(iter) != jump_label_init_type(iter)) 678 __jump_label_update(key, iter, iter_stop, true); 679 } 680 681 return 0; 682 } 683 684 static void jump_label_del_module(struct module *mod) 685 { 686 struct jump_entry *iter_start = mod->jump_entries; 687 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 688 struct jump_entry *iter; 689 struct static_key *key = NULL; 690 struct static_key_mod *jlm, **prev; 691 692 for (iter = iter_start; iter < iter_stop; iter++) { 693 if (jump_entry_key(iter) == key) 694 continue; 695 696 key = jump_entry_key(iter); 697 698 if (within_module((unsigned long)key, mod)) 699 continue; 700 701 /* No memory during module load */ 702 if (WARN_ON(!static_key_linked(key))) 703 continue; 704 705 prev = &key->next; 706 jlm = static_key_mod(key); 707 708 while (jlm && jlm->mod != mod) { 709 prev = &jlm->next; 710 jlm = jlm->next; 711 } 712 713 /* No memory during module load */ 714 if (WARN_ON(!jlm)) 715 continue; 716 717 if (prev == &key->next) 718 static_key_set_mod(key, jlm->next); 719 else 720 *prev = jlm->next; 721 722 kfree(jlm); 723 724 jlm = static_key_mod(key); 725 /* if only one etry is left, fold it back into the static_key */ 726 if (jlm->next == NULL) { 727 static_key_set_entries(key, jlm->entries); 728 static_key_clear_linked(key); 729 kfree(jlm); 730 } 731 } 732 } 733 734 static int 735 jump_label_module_notify(struct notifier_block *self, unsigned long val, 736 void *data) 737 { 738 struct module *mod = data; 739 int ret = 0; 740 741 cpus_read_lock(); 742 jump_label_lock(); 743 744 switch (val) { 745 case MODULE_STATE_COMING: 746 ret = jump_label_add_module(mod); 747 if (ret) { 748 WARN(1, "Failed to allocate memory: jump_label may not work properly.\n"); 749 jump_label_del_module(mod); 750 } 751 break; 752 case MODULE_STATE_GOING: 753 jump_label_del_module(mod); 754 break; 755 } 756 757 jump_label_unlock(); 758 cpus_read_unlock(); 759 760 return notifier_from_errno(ret); 761 } 762 763 static struct notifier_block jump_label_module_nb = { 764 .notifier_call = jump_label_module_notify, 765 .priority = 1, /* higher than tracepoints */ 766 }; 767 768 static __init int jump_label_init_module(void) 769 { 770 return register_module_notifier(&jump_label_module_nb); 771 } 772 early_initcall(jump_label_init_module); 773 774 #endif /* CONFIG_MODULES */ 775 776 /*** 777 * jump_label_text_reserved - check if addr range is reserved 778 * @start: start text addr 779 * @end: end text addr 780 * 781 * checks if the text addr located between @start and @end 782 * overlaps with any of the jump label patch addresses. Code 783 * that wants to modify kernel text should first verify that 784 * it does not overlap with any of the jump label addresses. 785 * Caller must hold jump_label_mutex. 786 * 787 * returns 1 if there is an overlap, 0 otherwise 788 */ 789 int jump_label_text_reserved(void *start, void *end) 790 { 791 int ret = __jump_label_text_reserved(__start___jump_table, 792 __stop___jump_table, start, end); 793 794 if (ret) 795 return ret; 796 797 #ifdef CONFIG_MODULES 798 ret = __jump_label_mod_text_reserved(start, end); 799 #endif 800 return ret; 801 } 802 803 static void jump_label_update(struct static_key *key) 804 { 805 struct jump_entry *stop = __stop___jump_table; 806 bool init = system_state < SYSTEM_RUNNING; 807 struct jump_entry *entry; 808 #ifdef CONFIG_MODULES 809 struct module *mod; 810 811 if (static_key_linked(key)) { 812 __jump_label_mod_update(key); 813 return; 814 } 815 816 preempt_disable(); 817 mod = __module_address((unsigned long)key); 818 if (mod) { 819 stop = mod->jump_entries + mod->num_jump_entries; 820 init = mod->state == MODULE_STATE_COMING; 821 } 822 preempt_enable(); 823 #endif 824 entry = static_key_entries(key); 825 /* if there are no users, entry can be NULL */ 826 if (entry) 827 __jump_label_update(key, entry, stop, init); 828 } 829 830 #ifdef CONFIG_STATIC_KEYS_SELFTEST 831 static DEFINE_STATIC_KEY_TRUE(sk_true); 832 static DEFINE_STATIC_KEY_FALSE(sk_false); 833 834 static __init int jump_label_test(void) 835 { 836 int i; 837 838 for (i = 0; i < 2; i++) { 839 WARN_ON(static_key_enabled(&sk_true.key) != true); 840 WARN_ON(static_key_enabled(&sk_false.key) != false); 841 842 WARN_ON(!static_branch_likely(&sk_true)); 843 WARN_ON(!static_branch_unlikely(&sk_true)); 844 WARN_ON(static_branch_likely(&sk_false)); 845 WARN_ON(static_branch_unlikely(&sk_false)); 846 847 static_branch_disable(&sk_true); 848 static_branch_enable(&sk_false); 849 850 WARN_ON(static_key_enabled(&sk_true.key) == true); 851 WARN_ON(static_key_enabled(&sk_false.key) == false); 852 853 WARN_ON(static_branch_likely(&sk_true)); 854 WARN_ON(static_branch_unlikely(&sk_true)); 855 WARN_ON(!static_branch_likely(&sk_false)); 856 WARN_ON(!static_branch_unlikely(&sk_false)); 857 858 static_branch_enable(&sk_true); 859 static_branch_disable(&sk_false); 860 } 861 862 return 0; 863 } 864 early_initcall(jump_label_test); 865 #endif /* STATIC_KEYS_SELFTEST */ 866