kernel/kcsan/core.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * KCSAN core runtime.
   4  *
   5  * Copyright (C) 2019, Google LLC.
   6  */
   7
   8 #define pr_fmt(fmt) "kcsan: " fmt
   9
  10 #include <linux/atomic.h>
  11 #include <linux/bug.h>
  12 #include <linux/delay.h>
  13 #include <linux/export.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/list.h>
  17 #include <linux/minmax.h>
  18 #include <linux/moduleparam.h>
  19 #include <linux/percpu.h>
  20 #include <linux/preempt.h>
  21 #include <linux/sched.h>
  22 #include <linux/string.h>
  23 #include <linux/uaccess.h>
  24
  25 #include "encoding.h"
  26 #include "kcsan.h"
  27 #include "permissive.h"
  28
  29 static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);
  30 unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;
  31 unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;
  32 static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;
  33 static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER);
  34
  35 #ifdef MODULE_PARAM_PREFIX
  36 #undef MODULE_PARAM_PREFIX
  37 #endif
  38 #define MODULE_PARAM_PREFIX "kcsan."
  39 module_param_named(early_enable, kcsan_early_enable, bool, 0);
  40 module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);
  41 module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
  42 module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
  43 module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
  44
  45 bool kcsan_enabled;
  46
  47 /* Per-CPU kcsan_ctx for interrupts */
  48 static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
  49         .disable_count          = 0,
  50         .atomic_next            = 0,
  51         .atomic_nest_count      = 0,
  52         .in_flat_atomic         = false,
  53         .access_mask            = 0,
  54         .scoped_accesses        = {LIST_POISON1, NULL},
  55 };
  56
  57 /*
  58  * Helper macros to index into adjacent slots, starting from address slot
  59  * itself, followed by the right and left slots.
  60  *
  61  * The purpose is 2-fold:
  62  *
  63  *      1. if during insertion the address slot is already occupied, check if
  64  *         any adjacent slots are free;
  65  *      2. accesses that straddle a slot boundary due to size that exceeds a
  66  *         slot's range may check adjacent slots if any watchpoint matches.
  67  *
  68  * Note that accesses with very large size may still miss a watchpoint; however,
  69  * given this should be rare, this is a reasonable trade-off to make, since this
  70  * will avoid:
  71  *
  72  *      1. excessive contention between watchpoint checks and setup;
  73  *      2. larger number of simultaneous watchpoints without sacrificing
  74  *         performance.
  75  *
  76  * Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
  77  *
  78  *   slot=0:  [ 1,  2,  0]
  79  *   slot=9:  [10, 11,  9]
  80  *   slot=63: [64, 65, 63]
  81  */
  82 #define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
  83
  84 /*
  85  * SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
  86  * slot (middle) is fine if we assume that races occur rarely. The set of
  87  * indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
  88  * {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
  89  */
  90 #define SLOT_IDX_FAST(slot, i) (slot + i)
  91
  92 /*
  93  * Watchpoints, with each entry encoded as defined in encoding.h: in order to be
  94  * able to safely update and access a watchpoint without introducing locking
  95  * overhead, we encode each watchpoint as a single atomic long. The initial
  96  * zero-initialized state matches INVALID_WATCHPOINT.
  97  *
  98  * Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
  99  * use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
 100  */
 101 static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
 102
 103 /*
 104  * Instructions to skip watching counter, used in should_watch(). We use a
 105  * per-CPU counter to avoid excessive contention.
 106  */
 107 static DEFINE_PER_CPU(long, kcsan_skip);
 108
 109 /* For kcsan_prandom_u32_max(). */
 110 static DEFINE_PER_CPU(u32, kcsan_rand_state);
 111
 112 static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
 113                                                       size_t size,
 114                                                       bool expect_write,
 115                                                       long *encoded_watchpoint)
 116 {
 117         const int slot = watchpoint_slot(addr);
 118         const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
 119         atomic_long_t *watchpoint;
 120         unsigned long wp_addr_masked;
 121         size_t wp_size;
 122         bool is_write;
 123         int i;
 124
 125         BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
 126
 127         for (i = 0; i < NUM_SLOTS; ++i) {
 128                 watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
 129                 *encoded_watchpoint = atomic_long_read(watchpoint);
 130                 if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
 131                                        &wp_size, &is_write))
 132                         continue;
 133
 134                 if (expect_write && !is_write)
 135                         continue;
 136
 137                 /* Check if the watchpoint matches the access. */
 138                 if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
 139                         return watchpoint;
 140         }
 141
 142         return NULL;
 143 }
 144
 145 static inline atomic_long_t *
 146 insert_watchpoint(unsigned long addr, size_t size, bool is_write)
 147 {
 148         const int slot = watchpoint_slot(addr);
 149         const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
 150         atomic_long_t *watchpoint;
 151         int i;
 152
 153         /* Check slot index logic, ensuring we stay within array bounds. */
 154         BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
 155         BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
 156         BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
 157         BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
 158
 159         for (i = 0; i < NUM_SLOTS; ++i) {
 160                 long expect_val = INVALID_WATCHPOINT;
 161
 162                 /* Try to acquire this slot. */
 163                 watchpoint = &watchpoints[SLOT_IDX(slot, i)];
 164                 if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
 165                         return watchpoint;
 166         }
 167
 168         return NULL;
 169 }
 170
 171 /*
 172  * Return true if watchpoint was successfully consumed, false otherwise.
 173  *
 174  * This may return false if:
 175  *
 176  *      1. another thread already consumed the watchpoint;
 177  *      2. the thread that set up the watchpoint already removed it;
 178  *      3. the watchpoint was removed and then re-used.
 179  */
 180 static __always_inline bool
 181 try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
 182 {
 183         return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
 184 }
 185
 186 /* Return true if watchpoint was not touched, false if already consumed. */
 187 static inline bool consume_watchpoint(atomic_long_t *watchpoint)
 188 {
 189         return atomic_long_xchg_relaxed(watchpoint, CONSUMED_WATCHPOINT) != CONSUMED_WATCHPOINT;
 190 }
 191
 192 /* Remove the watchpoint -- its slot may be reused after. */
 193 static inline void remove_watchpoint(atomic_long_t *watchpoint)
 194 {
 195         atomic_long_set(watchpoint, INVALID_WATCHPOINT);
 196 }
 197
 198 static __always_inline struct kcsan_ctx *get_ctx(void)
 199 {
 200         /*
 201          * In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
 202          * also result in calls that generate warnings in uaccess regions.
 203          */
 204         return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
 205 }
 206
 207 /* Check scoped accesses; never inline because this is a slow-path! */
 208 static noinline void kcsan_check_scoped_accesses(void)
 209 {
 210         struct kcsan_ctx *ctx = get_ctx();
 211         struct list_head *prev_save = ctx->scoped_accesses.prev;
 212         struct kcsan_scoped_access *scoped_access;
 213
 214         ctx->scoped_accesses.prev = NULL;  /* Avoid recursion. */
 215         list_for_each_entry(scoped_access, &ctx->scoped_accesses, list)
 216                 __kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type);
 217         ctx->scoped_accesses.prev = prev_save;
 218 }
 219
 220 /* Rules for generic atomic accesses. Called from fast-path. */
 221 static __always_inline bool
 222 is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
 223 {
 224         if (type & KCSAN_ACCESS_ATOMIC)
 225                 return true;
 226
 227         /*
 228          * Unless explicitly declared atomic, never consider an assertion access
 229          * as atomic. This allows using them also in atomic regions, such as
 230          * seqlocks, without implicitly changing their semantics.
 231          */
 232         if (type & KCSAN_ACCESS_ASSERT)
 233                 return false;
 234
 235         if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
 236             (type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) &&
 237             !(type & KCSAN_ACCESS_COMPOUND) && IS_ALIGNED((unsigned long)ptr, size))
 238                 return true; /* Assume aligned writes up to word size are atomic. */
 239
 240         if (ctx->atomic_next > 0) {
 241                 /*
 242                  * Because we do not have separate contexts for nested
 243                  * interrupts, in case atomic_next is set, we simply assume that
 244                  * the outer interrupt set atomic_next. In the worst case, we
 245                  * will conservatively consider operations as atomic. This is a
 246                  * reasonable trade-off to make, since this case should be
 247                  * extremely rare; however, even if extremely rare, it could
 248                  * lead to false positives otherwise.
 249                  */
 250                 if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
 251                         --ctx->atomic_next; /* in task, or outer interrupt */
 252                 return true;
 253         }
 254
 255         return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic;
 256 }
 257
 258 static __always_inline bool
 259 should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
 260 {
 261         /*
 262          * Never set up watchpoints when memory operations are atomic.
 263          *
 264          * Need to check this first, before kcsan_skip check below: (1) atomics
 265          * should not count towards skipped instructions, and (2) to actually
 266          * decrement kcsan_atomic_next for consecutive instruction stream.
 267          */
 268         if (is_atomic(ptr, size, type, ctx))
 269                 return false;
 270
 271         if (this_cpu_dec_return(kcsan_skip) >= 0)
 272                 return false;
 273
 274         /*
 275          * NOTE: If we get here, kcsan_skip must always be reset in slow path
 276          * via reset_kcsan_skip() to avoid underflow.
 277          */
 278
 279         /* this operation should be watched */
 280         return true;
 281 }
 282
 283 /*
 284  * Returns a pseudo-random number in interval [0, ep_ro). Simple linear
 285  * congruential generator, using constants from "Numerical Recipes".
 286  */
 287 static u32 kcsan_prandom_u32_max(u32 ep_ro)
 288 {
 289         u32 state = this_cpu_read(kcsan_rand_state);
 290
 291         state = 1664525 * state + 1013904223;
 292         this_cpu_write(kcsan_rand_state, state);
 293
 294         return state % ep_ro;
 295 }
 296
 297 static inline void reset_kcsan_skip(void)
 298 {
 299         long skip_count = kcsan_skip_watch -
 300                           (IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
 301                                    kcsan_prandom_u32_max(kcsan_skip_watch) :
 302                                    0);
 303         this_cpu_write(kcsan_skip, skip_count);
 304 }
 305
 306 static __always_inline bool kcsan_is_enabled(struct kcsan_ctx *ctx)
 307 {
 308         return READ_ONCE(kcsan_enabled) && !ctx->disable_count;
 309 }
 310
 311 /* Introduce delay depending on context and configuration. */
 312 static void delay_access(int type)
 313 {
 314         unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
 315         /* For certain access types, skew the random delay to be longer. */
 316         unsigned int skew_delay_order =
 317                 (type & (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_ASSERT)) ? 1 : 0;
 318
 319         delay -= IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
 320                                kcsan_prandom_u32_max(delay >> skew_delay_order) :
 321                                0;
 322         udelay(delay);
 323 }
 324
 325 void kcsan_save_irqtrace(struct task_struct *task)
 326 {
 327 #ifdef CONFIG_TRACE_IRQFLAGS
 328         task->kcsan_save_irqtrace = task->irqtrace;
 329 #endif
 330 }
 331
 332 void kcsan_restore_irqtrace(struct task_struct *task)
 333 {
 334 #ifdef CONFIG_TRACE_IRQFLAGS
 335         task->irqtrace = task->kcsan_save_irqtrace;
 336 #endif
 337 }
 338
 339 /*
 340  * Pull everything together: check_access() below contains the performance
 341  * critical operations; the fast-path (including check_access) functions should
 342  * all be inlinable by the instrumentation functions.
 343  *
 344  * The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
 345  * non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
 346  * be filtered from the stacktrace, as well as give them unique names for the
 347  * UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
 348  * since they do not access any user memory, but instrumentation is still
 349  * emitted in UACCESS regions.
 350  */
 351
 352 static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 353                                             size_t size,
 354                                             int type,
 355                                             atomic_long_t *watchpoint,
 356                                             long encoded_watchpoint)
 357 {
 358         const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
 359         struct kcsan_ctx *ctx = get_ctx();
 360         unsigned long flags;
 361         bool consumed;
 362
 363         /*
 364          * We know a watchpoint exists. Let's try to keep the race-window
 365          * between here and finally consuming the watchpoint below as small as
 366          * possible -- avoid unneccessarily complex code until consumed.
 367          */
 368
 369         if (!kcsan_is_enabled(ctx))
 370                 return;
 371
 372         /*
 373          * The access_mask check relies on value-change comparison. To avoid
 374          * reporting a race where e.g. the writer set up the watchpoint, but the
 375          * reader has access_mask!=0, we have to ignore the found watchpoint.
 376          */
 377         if (ctx->access_mask)
 378                 return;
 379
 380         /*
 381          * If the other thread does not want to ignore the access, and there was
 382          * a value change as a result of this thread's operation, we will still
 383          * generate a report of unknown origin.
 384          *
 385          * Use CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n to filter.
 386          */
 387         if (!is_assert && kcsan_ignore_address(ptr))
 388                 return;
 389
 390         /*
 391          * Consuming the watchpoint must be guarded by kcsan_is_enabled() to
 392          * avoid erroneously triggering reports if the context is disabled.
 393          */
 394         consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
 395
 396         /* keep this after try_consume_watchpoint */
 397         flags = user_access_save();
 398
 399         if (consumed) {
 400                 kcsan_save_irqtrace(current);
 401                 kcsan_report_set_info(ptr, size, type, watchpoint - watchpoints);
 402                 kcsan_restore_irqtrace(current);
 403         } else {
 404                 /*
 405                  * The other thread may not print any diagnostics, as it has
 406                  * already removed the watchpoint, or another thread consumed
 407                  * the watchpoint before this thread.
 408                  */
 409                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]);
 410         }
 411
 412         if (is_assert)
 413                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 414         else
 415                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]);
 416
 417         user_access_restore(flags);
 418 }
 419
 420 static noinline void
 421 kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 422 {
 423         const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 424         const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
 425         atomic_long_t *watchpoint;
 426         u64 old, new, diff;
 427         unsigned long access_mask;
 428         enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
 429         unsigned long ua_flags = user_access_save();
 430         struct kcsan_ctx *ctx = get_ctx();
 431         unsigned long irq_flags = 0;
 432
 433         /*
 434          * Always reset kcsan_skip counter in slow-path to avoid underflow; see
 435          * should_watch().
 436          */
 437         reset_kcsan_skip();
 438
 439         if (!kcsan_is_enabled(ctx))
 440                 goto out;
 441
 442         /*
 443          * Check to-ignore addresses after kcsan_is_enabled(), as we may access
 444          * memory that is not yet initialized during early boot.
 445          */
 446         if (!is_assert && kcsan_ignore_address(ptr))
 447                 goto out;
 448
 449         if (!check_encodable((unsigned long)ptr, size)) {
 450                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]);
 451                 goto out;
 452         }
 453
 454         /*
 455          * Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
 456          * runtime is entered for every memory access, and potentially useful
 457          * information is lost if dirtied by KCSAN.
 458          */
 459         kcsan_save_irqtrace(current);
 460         if (!kcsan_interrupt_watcher)
 461                 local_irq_save(irq_flags);
 462
 463         watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
 464         if (watchpoint == NULL) {
 465                 /*
 466                  * Out of capacity: the size of 'watchpoints', and the frequency
 467                  * with which should_watch() returns true should be tweaked so
 468                  * that this case happens very rarely.
 469                  */
 470                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]);
 471                 goto out_unlock;
 472         }
 473
 474         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]);
 475         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
 476
 477         /*
 478          * Read the current value, to later check and infer a race if the data
 479          * was modified via a non-instrumented access, e.g. from a device.
 480          */
 481         old = 0;
 482         switch (size) {
 483         case 1:
 484                 old = READ_ONCE(*(const u8 *)ptr);
 485                 break;
 486         case 2:
 487                 old = READ_ONCE(*(const u16 *)ptr);
 488                 break;
 489         case 4:
 490                 old = READ_ONCE(*(const u32 *)ptr);
 491                 break;
 492         case 8:
 493                 old = READ_ONCE(*(const u64 *)ptr);
 494                 break;
 495         default:
 496                 break; /* ignore; we do not diff the values */
 497         }
 498
 499         /*
 500          * Delay this thread, to increase probability of observing a racy
 501          * conflicting access.
 502          */
 503         delay_access(type);
 504
 505         /*
 506          * Re-read value, and check if it is as expected; if not, we infer a
 507          * racy access.
 508          */
 509         access_mask = ctx->access_mask;
 510         new = 0;
 511         switch (size) {
 512         case 1:
 513                 new = READ_ONCE(*(const u8 *)ptr);
 514                 break;
 515         case 2:
 516                 new = READ_ONCE(*(const u16 *)ptr);
 517                 break;
 518         case 4:
 519                 new = READ_ONCE(*(const u32 *)ptr);
 520                 break;
 521         case 8:
 522                 new = READ_ONCE(*(const u64 *)ptr);
 523                 break;
 524         default:
 525                 break; /* ignore; we do not diff the values */
 526         }
 527
 528         diff = old ^ new;
 529         if (access_mask)
 530                 diff &= access_mask;
 531
 532         /*
 533          * Check if we observed a value change.
 534          *
 535          * Also check if the data race should be ignored (the rules depend on
 536          * non-zero diff); if it is to be ignored, the below rules for
 537          * KCSAN_VALUE_CHANGE_MAYBE apply.
 538          */
 539         if (diff && !kcsan_ignore_data_race(size, type, old, new, diff))
 540                 value_change = KCSAN_VALUE_CHANGE_TRUE;
 541
 542         /* Check if this access raced with another. */
 543         if (!consume_watchpoint(watchpoint)) {
 544                 /*
 545                  * Depending on the access type, map a value_change of MAYBE to
 546                  * TRUE (always report) or FALSE (never report).
 547                  */
 548                 if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
 549                         if (access_mask != 0) {
 550                                 /*
 551                                  * For access with access_mask, we require a
 552                                  * value-change, as it is likely that races on
 553                                  * ~access_mask bits are expected.
 554                                  */
 555                                 value_change = KCSAN_VALUE_CHANGE_FALSE;
 556                         } else if (size > 8 || is_assert) {
 557                                 /* Always assume a value-change. */
 558                                 value_change = KCSAN_VALUE_CHANGE_TRUE;
 559                         }
 560                 }
 561
 562                 /*
 563                  * No need to increment 'data_races' counter, as the racing
 564                  * thread already did.
 565                  *
 566                  * Count 'assert_failures' for each failed ASSERT access,
 567                  * therefore both this thread and the racing thread may
 568                  * increment this counter.
 569                  */
 570                 if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
 571                         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 572
 573                 kcsan_report_known_origin(ptr, size, type, value_change,
 574                                           watchpoint - watchpoints,
 575                                           old, new, access_mask);
 576         } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
 577                 /* Inferring a race, since the value should not have changed. */
 578
 579                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]);
 580                 if (is_assert)
 581                         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 582
 583                 if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert)
 584                         kcsan_report_unknown_origin(ptr, size, type, old, new, access_mask);
 585         }
 586
 587         /*
 588          * Remove watchpoint; must be after reporting, since the slot may be
 589          * reused after this point.
 590          */
 591         remove_watchpoint(watchpoint);
 592         atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
 593 out_unlock:
 594         if (!kcsan_interrupt_watcher)
 595                 local_irq_restore(irq_flags);
 596         kcsan_restore_irqtrace(current);
 597 out:
 598         user_access_restore(ua_flags);
 599 }
 600
 601 static __always_inline void check_access(const volatile void *ptr, size_t size,
 602                                          int type)
 603 {
 604         const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 605         atomic_long_t *watchpoint;
 606         long encoded_watchpoint;
 607
 608         /*
 609          * Do nothing for 0 sized check; this comparison will be optimized out
 610          * for constant sized instrumentation (__tsan_{read,write}N).
 611          */
 612         if (unlikely(size == 0))
 613                 return;
 614
 615         /*
 616          * Avoid user_access_save in fast-path: find_watchpoint is safe without
 617          * user_access_save, as the address that ptr points to is only used to
 618          * check if a watchpoint exists; ptr is never dereferenced.
 619          */
 620         watchpoint = find_watchpoint((unsigned long)ptr, size, !is_write,
 621                                      &encoded_watchpoint);
 622         /*
 623          * It is safe to check kcsan_is_enabled() after find_watchpoint in the
 624          * slow-path, as long as no state changes that cause a race to be
 625          * detected and reported have occurred until kcsan_is_enabled() is
 626          * checked.
 627          */
 628
 629         if (unlikely(watchpoint != NULL))
 630                 kcsan_found_watchpoint(ptr, size, type, watchpoint,
 631                                        encoded_watchpoint);
 632         else {
 633                 struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
 634
 635                 if (unlikely(should_watch(ptr, size, type, ctx)))
 636                         kcsan_setup_watchpoint(ptr, size, type);
 637                 else if (unlikely(ctx->scoped_accesses.prev))
 638                         kcsan_check_scoped_accesses();
 639         }
 640 }
 641
 642 /* === Public interface ===================================================== */
 643
 644 void __init kcsan_init(void)
 645 {
 646         int cpu;
 647
 648         BUG_ON(!in_task());
 649
 650         for_each_possible_cpu(cpu)
 651                 per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
 652
 653         /*
 654          * We are in the init task, and no other tasks should be running;
 655          * WRITE_ONCE without memory barrier is sufficient.
 656          */
 657         if (kcsan_early_enable) {
 658                 pr_info("enabled early\n");
 659                 WRITE_ONCE(kcsan_enabled, true);
 660         }
 661
 662         if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) ||
 663             IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) ||
 664             IS_ENABLED(CONFIG_KCSAN_PERMISSIVE) ||
 665             IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
 666                 pr_warn("non-strict mode configured - use CONFIG_KCSAN_STRICT=y to see all data races\n");
 667         } else {
 668                 pr_info("strict mode configured\n");
 669         }
 670 }
 671
 672 /* === Exported interface =================================================== */
 673
 674 void kcsan_disable_current(void)
 675 {
 676         ++get_ctx()->disable_count;
 677 }
 678 EXPORT_SYMBOL(kcsan_disable_current);
 679
 680 void kcsan_enable_current(void)
 681 {
 682         if (get_ctx()->disable_count-- == 0) {
 683                 /*
 684                  * Warn if kcsan_enable_current() calls are unbalanced with
 685                  * kcsan_disable_current() calls, which causes disable_count to
 686                  * become negative and should not happen.
 687                  */
 688                 kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
 689                 kcsan_disable_current(); /* disable to generate warning */
 690                 WARN(1, "Unbalanced %s()", __func__);
 691                 kcsan_enable_current();
 692         }
 693 }
 694 EXPORT_SYMBOL(kcsan_enable_current);
 695
 696 void kcsan_enable_current_nowarn(void)
 697 {
 698         if (get_ctx()->disable_count-- == 0)
 699                 kcsan_disable_current();
 700 }
 701 EXPORT_SYMBOL(kcsan_enable_current_nowarn);
 702
 703 void kcsan_nestable_atomic_begin(void)
 704 {
 705         /*
 706          * Do *not* check and warn if we are in a flat atomic region: nestable
 707          * and flat atomic regions are independent from each other.
 708          * See include/linux/kcsan.h: struct kcsan_ctx comments for more
 709          * comments.
 710          */
 711
 712         ++get_ctx()->atomic_nest_count;
 713 }
 714 EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
 715
 716 void kcsan_nestable_atomic_end(void)
 717 {
 718         if (get_ctx()->atomic_nest_count-- == 0) {
 719                 /*
 720                  * Warn if kcsan_nestable_atomic_end() calls are unbalanced with
 721                  * kcsan_nestable_atomic_begin() calls, which causes
 722                  * atomic_nest_count to become negative and should not happen.
 723                  */
 724                 kcsan_nestable_atomic_begin(); /* restore to 0 */
 725                 kcsan_disable_current(); /* disable to generate warning */
 726                 WARN(1, "Unbalanced %s()", __func__);
 727                 kcsan_enable_current();
 728         }
 729 }
 730 EXPORT_SYMBOL(kcsan_nestable_atomic_end);
 731
 732 void kcsan_flat_atomic_begin(void)
 733 {
 734         get_ctx()->in_flat_atomic = true;
 735 }
 736 EXPORT_SYMBOL(kcsan_flat_atomic_begin);
 737
 738 void kcsan_flat_atomic_end(void)
 739 {
 740         get_ctx()->in_flat_atomic = false;
 741 }
 742 EXPORT_SYMBOL(kcsan_flat_atomic_end);
 743
 744 void kcsan_atomic_next(int n)
 745 {
 746         get_ctx()->atomic_next = n;
 747 }
 748 EXPORT_SYMBOL(kcsan_atomic_next);
 749
 750 void kcsan_set_access_mask(unsigned long mask)
 751 {
 752         get_ctx()->access_mask = mask;
 753 }
 754 EXPORT_SYMBOL(kcsan_set_access_mask);
 755
 756 struct kcsan_scoped_access *
 757 kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
 758                           struct kcsan_scoped_access *sa)
 759 {
 760         struct kcsan_ctx *ctx = get_ctx();
 761
 762         __kcsan_check_access(ptr, size, type);
 763
 764         ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
 765
 766         INIT_LIST_HEAD(&sa->list);
 767         sa->ptr = ptr;
 768         sa->size = size;
 769         sa->type = type;
 770
 771         if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
 772                 INIT_LIST_HEAD(&ctx->scoped_accesses);
 773         list_add(&sa->list, &ctx->scoped_accesses);
 774
 775         ctx->disable_count--;
 776         return sa;
 777 }
 778 EXPORT_SYMBOL(kcsan_begin_scoped_access);
 779
 780 void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
 781 {
 782         struct kcsan_ctx *ctx = get_ctx();
 783
 784         if (WARN(!ctx->scoped_accesses.prev, "Unbalanced %s()?", __func__))
 785                 return;
 786
 787         ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
 788
 789         list_del(&sa->list);
 790         if (list_empty(&ctx->scoped_accesses))
 791                 /*
 792                  * Ensure we do not enter kcsan_check_scoped_accesses()
 793                  * slow-path if unnecessary, and avoids requiring list_empty()
 794                  * in the fast-path (to avoid a READ_ONCE() and potential
 795                  * uaccess warning).
 796                  */
 797                 ctx->scoped_accesses.prev = NULL;
 798
 799         ctx->disable_count--;
 800
 801         __kcsan_check_access(sa->ptr, sa->size, sa->type);
 802 }
 803 EXPORT_SYMBOL(kcsan_end_scoped_access);
 804
 805 void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
 806 {
 807         check_access(ptr, size, type);
 808 }
 809 EXPORT_SYMBOL(__kcsan_check_access);
 810
 811 /*
 812  * KCSAN uses the same instrumentation that is emitted by supported compilers
 813  * for ThreadSanitizer (TSAN).
 814  *
 815  * When enabled, the compiler emits instrumentation calls (the functions
 816  * prefixed with "__tsan" below) for all loads and stores that it generated;
 817  * inline asm is not instrumented.
 818  *
 819  * Note that, not all supported compiler versions distinguish aligned/unaligned
 820  * accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
 821  * version to the generic version, which can handle both.
 822  */
 823
 824 #define DEFINE_TSAN_READ_WRITE(size)                                           \
 825         void __tsan_read##size(void *ptr);                                     \
 826         void __tsan_read##size(void *ptr)                                      \
 827         {                                                                      \
 828                 check_access(ptr, size, 0);                                    \
 829         }                                                                      \
 830         EXPORT_SYMBOL(__tsan_read##size);                                      \
 831         void __tsan_unaligned_read##size(void *ptr)                            \
 832                 __alias(__tsan_read##size);                                    \
 833         EXPORT_SYMBOL(__tsan_unaligned_read##size);                            \
 834         void __tsan_write##size(void *ptr);                                    \
 835         void __tsan_write##size(void *ptr)                                     \
 836         {                                                                      \
 837                 check_access(ptr, size, KCSAN_ACCESS_WRITE);                   \
 838         }                                                                      \
 839         EXPORT_SYMBOL(__tsan_write##size);                                     \
 840         void __tsan_unaligned_write##size(void *ptr)                           \
 841                 __alias(__tsan_write##size);                                   \
 842         EXPORT_SYMBOL(__tsan_unaligned_write##size);                           \
 843         void __tsan_read_write##size(void *ptr);                               \
 844         void __tsan_read_write##size(void *ptr)                                \
 845         {                                                                      \
 846                 check_access(ptr, size,                                        \
 847                              KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE);      \
 848         }                                                                      \
 849         EXPORT_SYMBOL(__tsan_read_write##size);                                \
 850         void __tsan_unaligned_read_write##size(void *ptr)                      \
 851                 __alias(__tsan_read_write##size);                              \
 852         EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
 853
 854 DEFINE_TSAN_READ_WRITE(1);
 855 DEFINE_TSAN_READ_WRITE(2);
 856 DEFINE_TSAN_READ_WRITE(4);
 857 DEFINE_TSAN_READ_WRITE(8);
 858 DEFINE_TSAN_READ_WRITE(16);
 859
 860 void __tsan_read_range(void *ptr, size_t size);
 861 void __tsan_read_range(void *ptr, size_t size)
 862 {
 863         check_access(ptr, size, 0);
 864 }
 865 EXPORT_SYMBOL(__tsan_read_range);
 866
 867 void __tsan_write_range(void *ptr, size_t size);
 868 void __tsan_write_range(void *ptr, size_t size)
 869 {
 870         check_access(ptr, size, KCSAN_ACCESS_WRITE);
 871 }
 872 EXPORT_SYMBOL(__tsan_write_range);
 873
 874 /*
 875  * Use of explicit volatile is generally disallowed [1], however, volatile is
 876  * still used in various concurrent context, whether in low-level
 877  * synchronization primitives or for legacy reasons.
 878  * [1] https://lwn.net/Articles/233479/
 879  *
 880  * We only consider volatile accesses atomic if they are aligned and would pass
 881  * the size-check of compiletime_assert_rwonce_type().
 882  */
 883 #define DEFINE_TSAN_VOLATILE_READ_WRITE(size)                                  \
 884         void __tsan_volatile_read##size(void *ptr);                            \
 885         void __tsan_volatile_read##size(void *ptr)                             \
 886         {                                                                      \
 887                 const bool is_atomic = size <= sizeof(long long) &&            \
 888                                        IS_ALIGNED((unsigned long)ptr, size);   \
 889                 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic)      \
 890                         return;                                                \
 891                 check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0);  \
 892         }                                                                      \
 893         EXPORT_SYMBOL(__tsan_volatile_read##size);                             \
 894         void __tsan_unaligned_volatile_read##size(void *ptr)                   \
 895                 __alias(__tsan_volatile_read##size);                           \
 896         EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size);                   \
 897         void __tsan_volatile_write##size(void *ptr);                           \
 898         void __tsan_volatile_write##size(void *ptr)                            \
 899         {                                                                      \
 900                 const bool is_atomic = size <= sizeof(long long) &&            \
 901                                        IS_ALIGNED((unsigned long)ptr, size);   \
 902                 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic)      \
 903                         return;                                                \
 904                 check_access(ptr, size,                                        \
 905                              KCSAN_ACCESS_WRITE |                              \
 906                                      (is_atomic ? KCSAN_ACCESS_ATOMIC : 0));   \
 907         }                                                                      \
 908         EXPORT_SYMBOL(__tsan_volatile_write##size);                            \
 909         void __tsan_unaligned_volatile_write##size(void *ptr)                  \
 910                 __alias(__tsan_volatile_write##size);                          \
 911         EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
 912
 913 DEFINE_TSAN_VOLATILE_READ_WRITE(1);
 914 DEFINE_TSAN_VOLATILE_READ_WRITE(2);
 915 DEFINE_TSAN_VOLATILE_READ_WRITE(4);
 916 DEFINE_TSAN_VOLATILE_READ_WRITE(8);
 917 DEFINE_TSAN_VOLATILE_READ_WRITE(16);
 918
 919 /*
 920  * The below are not required by KCSAN, but can still be emitted by the
 921  * compiler.
 922  */
 923 void __tsan_func_entry(void *call_pc);
 924 void __tsan_func_entry(void *call_pc)
 925 {
 926 }
 927 EXPORT_SYMBOL(__tsan_func_entry);
 928 void __tsan_func_exit(void);
 929 void __tsan_func_exit(void)
 930 {
 931 }
 932 EXPORT_SYMBOL(__tsan_func_exit);
 933 void __tsan_init(void);
 934 void __tsan_init(void)
 935 {
 936 }
 937 EXPORT_SYMBOL(__tsan_init);
 938
 939 /*
 940  * Instrumentation for atomic builtins (__atomic_*, __sync_*).
 941  *
 942  * Normal kernel code _should not_ be using them directly, but some
 943  * architectures may implement some or all atomics using the compilers'
 944  * builtins.
 945  *
 946  * Note: If an architecture decides to fully implement atomics using the
 947  * builtins, because they are implicitly instrumented by KCSAN (and KASAN,
 948  * etc.), implementing the ARCH_ATOMIC interface (to get instrumentation via
 949  * atomic-instrumented) is no longer necessary.
 950  *
 951  * TSAN instrumentation replaces atomic accesses with calls to any of the below
 952  * functions, whose job is to also execute the operation itself.
 953  */
 954
 955 #define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits)                                                        \
 956         u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder);                      \
 957         u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder)                       \
 958         {                                                                                          \
 959                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 960                         check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC);              \
 961                 }                                                                                  \
 962                 return __atomic_load_n(ptr, memorder);                                             \
 963         }                                                                                          \
 964         EXPORT_SYMBOL(__tsan_atomic##bits##_load);                                                 \
 965         void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder);                   \
 966         void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder)                    \
 967         {                                                                                          \
 968                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 969                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
 970                                      KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC);                    \
 971                 }                                                                                  \
 972                 __atomic_store_n(ptr, v, memorder);                                                \
 973         }                                                                                          \
 974         EXPORT_SYMBOL(__tsan_atomic##bits##_store)
 975
 976 #define DEFINE_TSAN_ATOMIC_RMW(op, bits, suffix)                                                   \
 977         u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder);                 \
 978         u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder)                  \
 979         {                                                                                          \
 980                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 981                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
 982                                      KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
 983                                              KCSAN_ACCESS_ATOMIC);                                 \
 984                 }                                                                                  \
 985                 return __atomic_##op##suffix(ptr, v, memorder);                                    \
 986         }                                                                                          \
 987         EXPORT_SYMBOL(__tsan_atomic##bits##_##op)
 988
 989 /*
 990  * Note: CAS operations are always classified as write, even in case they
 991  * fail. We cannot perform check_access() after a write, as it might lead to
 992  * false positives, in cases such as:
 993  *
 994  *      T0: __atomic_compare_exchange_n(&p->flag, &old, 1, ...)
 995  *
 996  *      T1: if (__atomic_load_n(&p->flag, ...)) {
 997  *              modify *p;
 998  *              p->flag = 0;
 999  *          }
1000  *
1001  * The only downside is that, if there are 3 threads, with one CAS that
1002  * succeeds, another CAS that fails, and an unmarked racing operation, we may
1003  * point at the wrong CAS as the source of the race. However, if we assume that
1004  * all CAS can succeed in some other execution, the data race is still valid.
1005  */
1006 #define DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strength, weak)                                           \
1007         int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp,          \
1008                                                               u##bits val, int mo, int fail_mo);   \
1009         int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp,          \
1010                                                               u##bits val, int mo, int fail_mo)    \
1011         {                                                                                          \
1012                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
1013                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
1014                                      KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
1015                                              KCSAN_ACCESS_ATOMIC);                                 \
1016                 }                                                                                  \
1017                 return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo);              \
1018         }                                                                                          \
1019         EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_##strength)
1020
1021 #define DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)                                                       \
1022         u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
1023                                                            int mo, int fail_mo);                   \
1024         u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
1025                                                            int mo, int fail_mo)                    \
1026         {                                                                                          \
1027                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
1028                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
1029                                      KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
1030                                              KCSAN_ACCESS_ATOMIC);                                 \
1031                 }                                                                                  \
1032                 __atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo);                       \
1033                 return exp;                                                                        \
1034         }                                                                                          \
1035         EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_val)
1036
1037 #define DEFINE_TSAN_ATOMIC_OPS(bits)                                                               \
1038         DEFINE_TSAN_ATOMIC_LOAD_STORE(bits);                                                       \
1039         DEFINE_TSAN_ATOMIC_RMW(exchange, bits, _n);                                                \
1040         DEFINE_TSAN_ATOMIC_RMW(fetch_add, bits, );                                                 \
1041         DEFINE_TSAN_ATOMIC_RMW(fetch_sub, bits, );                                                 \
1042         DEFINE_TSAN_ATOMIC_RMW(fetch_and, bits, );                                                 \
1043         DEFINE_TSAN_ATOMIC_RMW(fetch_or, bits, );                                                  \
1044         DEFINE_TSAN_ATOMIC_RMW(fetch_xor, bits, );                                                 \
1045         DEFINE_TSAN_ATOMIC_RMW(fetch_nand, bits, );                                                \
1046         DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strong, 0);                                               \
1047         DEFINE_TSAN_ATOMIC_CMPXCHG(bits, weak, 1);                                                 \
1048         DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)
1049
1050 DEFINE_TSAN_ATOMIC_OPS(8);
1051 DEFINE_TSAN_ATOMIC_OPS(16);
1052 DEFINE_TSAN_ATOMIC_OPS(32);
1053 #ifdef CONFIG_64BIT
1054 DEFINE_TSAN_ATOMIC_OPS(64);
1055 #endif
1056
1057 void __tsan_atomic_thread_fence(int memorder);
1058 void __tsan_atomic_thread_fence(int memorder)
1059 {
1060         __atomic_thread_fence(memorder);
1061 }
1062 EXPORT_SYMBOL(__tsan_atomic_thread_fence);
1063
1064 void __tsan_atomic_signal_fence(int memorder);
1065 void __tsan_atomic_signal_fence(int memorder) { }
1066 EXPORT_SYMBOL(__tsan_atomic_signal_fence);
1067
1068 #ifdef __HAVE_ARCH_MEMSET
1069 void *__tsan_memset(void *s, int c, size_t count);
1070 noinline void *__tsan_memset(void *s, int c, size_t count)
1071 {
1072         /*
1073          * Instead of not setting up watchpoints where accessed size is greater
1074          * than MAX_ENCODABLE_SIZE, truncate checked size to MAX_ENCODABLE_SIZE.
1075          */
1076         size_t check_len = min_t(size_t, count, MAX_ENCODABLE_SIZE);
1077
1078         check_access(s, check_len, KCSAN_ACCESS_WRITE);
1079         return memset(s, c, count);
1080 }
1081 #else
1082 void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
1083 #endif
1084 EXPORT_SYMBOL(__tsan_memset);
1085
1086 #ifdef __HAVE_ARCH_MEMMOVE
1087 void *__tsan_memmove(void *dst, const void *src, size_t len);
1088 noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
1089 {
1090         size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
1091
1092         check_access(dst, check_len, KCSAN_ACCESS_WRITE);
1093         check_access(src, check_len, 0);
1094         return memmove(dst, src, len);
1095 }
1096 #else
1097 void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
1098 #endif
1099 EXPORT_SYMBOL(__tsan_memmove);
1100
1101 #ifdef __HAVE_ARCH_MEMCPY
1102 void *__tsan_memcpy(void *dst, const void *src, size_t len);
1103 noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
1104 {
1105         size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
1106
1107         check_access(dst, check_len, KCSAN_ACCESS_WRITE);
1108         check_access(src, check_len, 0);
1109         return memcpy(dst, src, len);
1110 }
1111 #else
1112 void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
1113 #endif
1114 EXPORT_SYMBOL(__tsan_memcpy);