kernel/kcsan/core.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #define pr_fmt(fmt) "kcsan: " fmt
   4
   5 #include <linux/atomic.h>
   6 #include <linux/bug.h>
   7 #include <linux/delay.h>
   8 #include <linux/export.h>
   9 #include <linux/init.h>
  10 #include <linux/kernel.h>
  11 #include <linux/list.h>
  12 #include <linux/minmax.h>
  13 #include <linux/moduleparam.h>
  14 #include <linux/percpu.h>
  15 #include <linux/preempt.h>
  16 #include <linux/sched.h>
  17 #include <linux/string.h>
  18 #include <linux/uaccess.h>
  19
  20 #include "atomic.h"
  21 #include "encoding.h"
  22 #include "kcsan.h"
  23
  24 static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);
  25 unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;
  26 unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;
  27 static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;
  28 static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER);
  29
  30 #ifdef MODULE_PARAM_PREFIX
  31 #undef MODULE_PARAM_PREFIX
  32 #endif
  33 #define MODULE_PARAM_PREFIX "kcsan."
  34 module_param_named(early_enable, kcsan_early_enable, bool, 0);
  35 module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);
  36 module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
  37 module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
  38 module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
  39
  40 bool kcsan_enabled;
  41
  42 /* Per-CPU kcsan_ctx for interrupts */
  43 static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
  44         .disable_count          = 0,
  45         .atomic_next            = 0,
  46         .atomic_nest_count      = 0,
  47         .in_flat_atomic         = false,
  48         .access_mask            = 0,
  49         .scoped_accesses        = {LIST_POISON1, NULL},
  50 };
  51
  52 /*
  53  * Helper macros to index into adjacent slots, starting from address slot
  54  * itself, followed by the right and left slots.
  55  *
  56  * The purpose is 2-fold:
  57  *
  58  *      1. if during insertion the address slot is already occupied, check if
  59  *         any adjacent slots are free;
  60  *      2. accesses that straddle a slot boundary due to size that exceeds a
  61  *         slot's range may check adjacent slots if any watchpoint matches.
  62  *
  63  * Note that accesses with very large size may still miss a watchpoint; however,
  64  * given this should be rare, this is a reasonable trade-off to make, since this
  65  * will avoid:
  66  *
  67  *      1. excessive contention between watchpoint checks and setup;
  68  *      2. larger number of simultaneous watchpoints without sacrificing
  69  *         performance.
  70  *
  71  * Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
  72  *
  73  *   slot=0:  [ 1,  2,  0]
  74  *   slot=9:  [10, 11,  9]
  75  *   slot=63: [64, 65, 63]
  76  */
  77 #define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
  78
  79 /*
  80  * SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
  81  * slot (middle) is fine if we assume that races occur rarely. The set of
  82  * indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
  83  * {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
  84  */
  85 #define SLOT_IDX_FAST(slot, i) (slot + i)
  86
  87 /*
  88  * Watchpoints, with each entry encoded as defined in encoding.h: in order to be
  89  * able to safely update and access a watchpoint without introducing locking
  90  * overhead, we encode each watchpoint as a single atomic long. The initial
  91  * zero-initialized state matches INVALID_WATCHPOINT.
  92  *
  93  * Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
  94  * use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
  95  */
  96 static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
  97
  98 /*
  99  * Instructions to skip watching counter, used in should_watch(). We use a
 100  * per-CPU counter to avoid excessive contention.
 101  */
 102 static DEFINE_PER_CPU(long, kcsan_skip);
 103
 104 /* For kcsan_prandom_u32_max(). */
 105 static DEFINE_PER_CPU(u32, kcsan_rand_state);
 106
 107 static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
 108                                                       size_t size,
 109                                                       bool expect_write,
 110                                                       long *encoded_watchpoint)
 111 {
 112         const int slot = watchpoint_slot(addr);
 113         const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
 114         atomic_long_t *watchpoint;
 115         unsigned long wp_addr_masked;
 116         size_t wp_size;
 117         bool is_write;
 118         int i;
 119
 120         BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
 121
 122         for (i = 0; i < NUM_SLOTS; ++i) {
 123                 watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
 124                 *encoded_watchpoint = atomic_long_read(watchpoint);
 125                 if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
 126                                        &wp_size, &is_write))
 127                         continue;
 128
 129                 if (expect_write && !is_write)
 130                         continue;
 131
 132                 /* Check if the watchpoint matches the access. */
 133                 if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
 134                         return watchpoint;
 135         }
 136
 137         return NULL;
 138 }
 139
 140 static inline atomic_long_t *
 141 insert_watchpoint(unsigned long addr, size_t size, bool is_write)
 142 {
 143         const int slot = watchpoint_slot(addr);
 144         const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
 145         atomic_long_t *watchpoint;
 146         int i;
 147
 148         /* Check slot index logic, ensuring we stay within array bounds. */
 149         BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
 150         BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
 151         BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
 152         BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
 153
 154         for (i = 0; i < NUM_SLOTS; ++i) {
 155                 long expect_val = INVALID_WATCHPOINT;
 156
 157                 /* Try to acquire this slot. */
 158                 watchpoint = &watchpoints[SLOT_IDX(slot, i)];
 159                 if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
 160                         return watchpoint;
 161         }
 162
 163         return NULL;
 164 }
 165
 166 /*
 167  * Return true if watchpoint was successfully consumed, false otherwise.
 168  *
 169  * This may return false if:
 170  *
 171  *      1. another thread already consumed the watchpoint;
 172  *      2. the thread that set up the watchpoint already removed it;
 173  *      3. the watchpoint was removed and then re-used.
 174  */
 175 static __always_inline bool
 176 try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
 177 {
 178         return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
 179 }
 180
 181 /* Return true if watchpoint was not touched, false if already consumed. */
 182 static inline bool consume_watchpoint(atomic_long_t *watchpoint)
 183 {
 184         return atomic_long_xchg_relaxed(watchpoint, CONSUMED_WATCHPOINT) != CONSUMED_WATCHPOINT;
 185 }
 186
 187 /* Remove the watchpoint -- its slot may be reused after. */
 188 static inline void remove_watchpoint(atomic_long_t *watchpoint)
 189 {
 190         atomic_long_set(watchpoint, INVALID_WATCHPOINT);
 191 }
 192
 193 static __always_inline struct kcsan_ctx *get_ctx(void)
 194 {
 195         /*
 196          * In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
 197          * also result in calls that generate warnings in uaccess regions.
 198          */
 199         return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
 200 }
 201
 202 /* Check scoped accesses; never inline because this is a slow-path! */
 203 static noinline void kcsan_check_scoped_accesses(void)
 204 {
 205         struct kcsan_ctx *ctx = get_ctx();
 206         struct list_head *prev_save = ctx->scoped_accesses.prev;
 207         struct kcsan_scoped_access *scoped_access;
 208
 209         ctx->scoped_accesses.prev = NULL;  /* Avoid recursion. */
 210         list_for_each_entry(scoped_access, &ctx->scoped_accesses, list)
 211                 __kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type);
 212         ctx->scoped_accesses.prev = prev_save;
 213 }
 214
 215 /* Rules for generic atomic accesses. Called from fast-path. */
 216 static __always_inline bool
 217 is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
 218 {
 219         if (type & KCSAN_ACCESS_ATOMIC)
 220                 return true;
 221
 222         /*
 223          * Unless explicitly declared atomic, never consider an assertion access
 224          * as atomic. This allows using them also in atomic regions, such as
 225          * seqlocks, without implicitly changing their semantics.
 226          */
 227         if (type & KCSAN_ACCESS_ASSERT)
 228                 return false;
 229
 230         if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
 231             (type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) &&
 232             !(type & KCSAN_ACCESS_COMPOUND) && IS_ALIGNED((unsigned long)ptr, size))
 233                 return true; /* Assume aligned writes up to word size are atomic. */
 234
 235         if (ctx->atomic_next > 0) {
 236                 /*
 237                  * Because we do not have separate contexts for nested
 238                  * interrupts, in case atomic_next is set, we simply assume that
 239                  * the outer interrupt set atomic_next. In the worst case, we
 240                  * will conservatively consider operations as atomic. This is a
 241                  * reasonable trade-off to make, since this case should be
 242                  * extremely rare; however, even if extremely rare, it could
 243                  * lead to false positives otherwise.
 244                  */
 245                 if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
 246                         --ctx->atomic_next; /* in task, or outer interrupt */
 247                 return true;
 248         }
 249
 250         return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic;
 251 }
 252
 253 static __always_inline bool
 254 should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
 255 {
 256         /*
 257          * Never set up watchpoints when memory operations are atomic.
 258          *
 259          * Need to check this first, before kcsan_skip check below: (1) atomics
 260          * should not count towards skipped instructions, and (2) to actually
 261          * decrement kcsan_atomic_next for consecutive instruction stream.
 262          */
 263         if (is_atomic(ptr, size, type, ctx))
 264                 return false;
 265
 266         if (this_cpu_dec_return(kcsan_skip) >= 0)
 267                 return false;
 268
 269         /*
 270          * NOTE: If we get here, kcsan_skip must always be reset in slow path
 271          * via reset_kcsan_skip() to avoid underflow.
 272          */
 273
 274         /* this operation should be watched */
 275         return true;
 276 }
 277
 278 /*
 279  * Returns a pseudo-random number in interval [0, ep_ro). Simple linear
 280  * congruential generator, using constants from "Numerical Recipes".
 281  */
 282 static u32 kcsan_prandom_u32_max(u32 ep_ro)
 283 {
 284         u32 state = this_cpu_read(kcsan_rand_state);
 285
 286         state = 1664525 * state + 1013904223;
 287         this_cpu_write(kcsan_rand_state, state);
 288
 289         return state % ep_ro;
 290 }
 291
 292 static inline void reset_kcsan_skip(void)
 293 {
 294         long skip_count = kcsan_skip_watch -
 295                           (IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
 296                                    kcsan_prandom_u32_max(kcsan_skip_watch) :
 297                                    0);
 298         this_cpu_write(kcsan_skip, skip_count);
 299 }
 300
 301 static __always_inline bool kcsan_is_enabled(void)
 302 {
 303         return READ_ONCE(kcsan_enabled) && get_ctx()->disable_count == 0;
 304 }
 305
 306 /* Introduce delay depending on context and configuration. */
 307 static void delay_access(int type)
 308 {
 309         unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
 310         /* For certain access types, skew the random delay to be longer. */
 311         unsigned int skew_delay_order =
 312                 (type & (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_ASSERT)) ? 1 : 0;
 313
 314         delay -= IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
 315                                kcsan_prandom_u32_max(delay >> skew_delay_order) :
 316                                0;
 317         udelay(delay);
 318 }
 319
 320 void kcsan_save_irqtrace(struct task_struct *task)
 321 {
 322 #ifdef CONFIG_TRACE_IRQFLAGS
 323         task->kcsan_save_irqtrace = task->irqtrace;
 324 #endif
 325 }
 326
 327 void kcsan_restore_irqtrace(struct task_struct *task)
 328 {
 329 #ifdef CONFIG_TRACE_IRQFLAGS
 330         task->irqtrace = task->kcsan_save_irqtrace;
 331 #endif
 332 }
 333
 334 /*
 335  * Pull everything together: check_access() below contains the performance
 336  * critical operations; the fast-path (including check_access) functions should
 337  * all be inlinable by the instrumentation functions.
 338  *
 339  * The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
 340  * non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
 341  * be filtered from the stacktrace, as well as give them unique names for the
 342  * UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
 343  * since they do not access any user memory, but instrumentation is still
 344  * emitted in UACCESS regions.
 345  */
 346
 347 static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 348                                             size_t size,
 349                                             int type,
 350                                             atomic_long_t *watchpoint,
 351                                             long encoded_watchpoint)
 352 {
 353         unsigned long flags;
 354         bool consumed;
 355
 356         if (!kcsan_is_enabled())
 357                 return;
 358
 359         /*
 360          * The access_mask check relies on value-change comparison. To avoid
 361          * reporting a race where e.g. the writer set up the watchpoint, but the
 362          * reader has access_mask!=0, we have to ignore the found watchpoint.
 363          */
 364         if (get_ctx()->access_mask != 0)
 365                 return;
 366
 367         /*
 368          * Consume the watchpoint as soon as possible, to minimize the chances
 369          * of !consumed. Consuming the watchpoint must always be guarded by
 370          * kcsan_is_enabled() check, as otherwise we might erroneously
 371          * triggering reports when disabled.
 372          */
 373         consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
 374
 375         /* keep this after try_consume_watchpoint */
 376         flags = user_access_save();
 377
 378         if (consumed) {
 379                 kcsan_save_irqtrace(current);
 380                 kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_MAYBE,
 381                              KCSAN_REPORT_CONSUMED_WATCHPOINT,
 382                              watchpoint - watchpoints);
 383                 kcsan_restore_irqtrace(current);
 384         } else {
 385                 /*
 386                  * The other thread may not print any diagnostics, as it has
 387                  * already removed the watchpoint, or another thread consumed
 388                  * the watchpoint before this thread.
 389                  */
 390                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]);
 391         }
 392
 393         if ((type & KCSAN_ACCESS_ASSERT) != 0)
 394                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 395         else
 396                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]);
 397
 398         user_access_restore(flags);
 399 }
 400
 401 static noinline void
 402 kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 403 {
 404         const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 405         const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
 406         atomic_long_t *watchpoint;
 407         union {
 408                 u8 _1;
 409                 u16 _2;
 410                 u32 _4;
 411                 u64 _8;
 412         } expect_value;
 413         unsigned long access_mask;
 414         enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
 415         unsigned long ua_flags = user_access_save();
 416         unsigned long irq_flags = 0;
 417
 418         /*
 419          * Always reset kcsan_skip counter in slow-path to avoid underflow; see
 420          * should_watch().
 421          */
 422         reset_kcsan_skip();
 423
 424         if (!kcsan_is_enabled())
 425                 goto out;
 426
 427         /*
 428          * Special atomic rules: unlikely to be true, so we check them here in
 429          * the slow-path, and not in the fast-path in is_atomic(). Call after
 430          * kcsan_is_enabled(), as we may access memory that is not yet
 431          * initialized during early boot.
 432          */
 433         if (!is_assert && kcsan_is_atomic_special(ptr))
 434                 goto out;
 435
 436         if (!check_encodable((unsigned long)ptr, size)) {
 437                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]);
 438                 goto out;
 439         }
 440
 441         /*
 442          * Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
 443          * runtime is entered for every memory access, and potentially useful
 444          * information is lost if dirtied by KCSAN.
 445          */
 446         kcsan_save_irqtrace(current);
 447         if (!kcsan_interrupt_watcher)
 448                 local_irq_save(irq_flags);
 449
 450         watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
 451         if (watchpoint == NULL) {
 452                 /*
 453                  * Out of capacity: the size of 'watchpoints', and the frequency
 454                  * with which should_watch() returns true should be tweaked so
 455                  * that this case happens very rarely.
 456                  */
 457                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]);
 458                 goto out_unlock;
 459         }
 460
 461         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]);
 462         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
 463
 464         /*
 465          * Read the current value, to later check and infer a race if the data
 466          * was modified via a non-instrumented access, e.g. from a device.
 467          */
 468         expect_value._8 = 0;
 469         switch (size) {
 470         case 1:
 471                 expect_value._1 = READ_ONCE(*(const u8 *)ptr);
 472                 break;
 473         case 2:
 474                 expect_value._2 = READ_ONCE(*(const u16 *)ptr);
 475                 break;
 476         case 4:
 477                 expect_value._4 = READ_ONCE(*(const u32 *)ptr);
 478                 break;
 479         case 8:
 480                 expect_value._8 = READ_ONCE(*(const u64 *)ptr);
 481                 break;
 482         default:
 483                 break; /* ignore; we do not diff the values */
 484         }
 485
 486         if (IS_ENABLED(CONFIG_KCSAN_DEBUG)) {
 487                 kcsan_disable_current();
 488                 pr_err("watching %s, size: %zu, addr: %px [slot: %d, encoded: %lx]\n",
 489                        is_write ? "write" : "read", size, ptr,
 490                        watchpoint_slot((unsigned long)ptr),
 491                        encode_watchpoint((unsigned long)ptr, size, is_write));
 492                 kcsan_enable_current();
 493         }
 494
 495         /*
 496          * Delay this thread, to increase probability of observing a racy
 497          * conflicting access.
 498          */
 499         delay_access(type);
 500
 501         /*
 502          * Re-read value, and check if it is as expected; if not, we infer a
 503          * racy access.
 504          */
 505         access_mask = get_ctx()->access_mask;
 506         switch (size) {
 507         case 1:
 508                 expect_value._1 ^= READ_ONCE(*(const u8 *)ptr);
 509                 if (access_mask)
 510                         expect_value._1 &= (u8)access_mask;
 511                 break;
 512         case 2:
 513                 expect_value._2 ^= READ_ONCE(*(const u16 *)ptr);
 514                 if (access_mask)
 515                         expect_value._2 &= (u16)access_mask;
 516                 break;
 517         case 4:
 518                 expect_value._4 ^= READ_ONCE(*(const u32 *)ptr);
 519                 if (access_mask)
 520                         expect_value._4 &= (u32)access_mask;
 521                 break;
 522         case 8:
 523                 expect_value._8 ^= READ_ONCE(*(const u64 *)ptr);
 524                 if (access_mask)
 525                         expect_value._8 &= (u64)access_mask;
 526                 break;
 527         default:
 528                 break; /* ignore; we do not diff the values */
 529         }
 530
 531         /* Were we able to observe a value-change? */
 532         if (expect_value._8 != 0)
 533                 value_change = KCSAN_VALUE_CHANGE_TRUE;
 534
 535         /* Check if this access raced with another. */
 536         if (!consume_watchpoint(watchpoint)) {
 537                 /*
 538                  * Depending on the access type, map a value_change of MAYBE to
 539                  * TRUE (always report) or FALSE (never report).
 540                  */
 541                 if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
 542                         if (access_mask != 0) {
 543                                 /*
 544                                  * For access with access_mask, we require a
 545                                  * value-change, as it is likely that races on
 546                                  * ~access_mask bits are expected.
 547                                  */
 548                                 value_change = KCSAN_VALUE_CHANGE_FALSE;
 549                         } else if (size > 8 || is_assert) {
 550                                 /* Always assume a value-change. */
 551                                 value_change = KCSAN_VALUE_CHANGE_TRUE;
 552                         }
 553                 }
 554
 555                 /*
 556                  * No need to increment 'data_races' counter, as the racing
 557                  * thread already did.
 558                  *
 559                  * Count 'assert_failures' for each failed ASSERT access,
 560                  * therefore both this thread and the racing thread may
 561                  * increment this counter.
 562                  */
 563                 if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
 564                         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 565
 566                 kcsan_report(ptr, size, type, value_change, KCSAN_REPORT_RACE_SIGNAL,
 567                              watchpoint - watchpoints);
 568         } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
 569                 /* Inferring a race, since the value should not have changed. */
 570
 571                 atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]);
 572                 if (is_assert)
 573                         atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 574
 575                 if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert)
 576                         kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_TRUE,
 577                                      KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
 578                                      watchpoint - watchpoints);
 579         }
 580
 581         /*
 582          * Remove watchpoint; must be after reporting, since the slot may be
 583          * reused after this point.
 584          */
 585         remove_watchpoint(watchpoint);
 586         atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
 587 out_unlock:
 588         if (!kcsan_interrupt_watcher)
 589                 local_irq_restore(irq_flags);
 590         kcsan_restore_irqtrace(current);
 591 out:
 592         user_access_restore(ua_flags);
 593 }
 594
 595 static __always_inline void check_access(const volatile void *ptr, size_t size,
 596                                          int type)
 597 {
 598         const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 599         atomic_long_t *watchpoint;
 600         long encoded_watchpoint;
 601
 602         /*
 603          * Do nothing for 0 sized check; this comparison will be optimized out
 604          * for constant sized instrumentation (__tsan_{read,write}N).
 605          */
 606         if (unlikely(size == 0))
 607                 return;
 608
 609         /*
 610          * Avoid user_access_save in fast-path: find_watchpoint is safe without
 611          * user_access_save, as the address that ptr points to is only used to
 612          * check if a watchpoint exists; ptr is never dereferenced.
 613          */
 614         watchpoint = find_watchpoint((unsigned long)ptr, size, !is_write,
 615                                      &encoded_watchpoint);
 616         /*
 617          * It is safe to check kcsan_is_enabled() after find_watchpoint in the
 618          * slow-path, as long as no state changes that cause a race to be
 619          * detected and reported have occurred until kcsan_is_enabled() is
 620          * checked.
 621          */
 622
 623         if (unlikely(watchpoint != NULL))
 624                 kcsan_found_watchpoint(ptr, size, type, watchpoint,
 625                                        encoded_watchpoint);
 626         else {
 627                 struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
 628
 629                 if (unlikely(should_watch(ptr, size, type, ctx)))
 630                         kcsan_setup_watchpoint(ptr, size, type);
 631                 else if (unlikely(ctx->scoped_accesses.prev))
 632                         kcsan_check_scoped_accesses();
 633         }
 634 }
 635
 636 /* === Public interface ===================================================== */
 637
 638 void __init kcsan_init(void)
 639 {
 640         int cpu;
 641
 642         BUG_ON(!in_task());
 643
 644         for_each_possible_cpu(cpu)
 645                 per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
 646
 647         /*
 648          * We are in the init task, and no other tasks should be running;
 649          * WRITE_ONCE without memory barrier is sufficient.
 650          */
 651         if (kcsan_early_enable) {
 652                 pr_info("enabled early\n");
 653                 WRITE_ONCE(kcsan_enabled, true);
 654         }
 655 }
 656
 657 /* === Exported interface =================================================== */
 658
 659 void kcsan_disable_current(void)
 660 {
 661         ++get_ctx()->disable_count;
 662 }
 663 EXPORT_SYMBOL(kcsan_disable_current);
 664
 665 void kcsan_enable_current(void)
 666 {
 667         if (get_ctx()->disable_count-- == 0) {
 668                 /*
 669                  * Warn if kcsan_enable_current() calls are unbalanced with
 670                  * kcsan_disable_current() calls, which causes disable_count to
 671                  * become negative and should not happen.
 672                  */
 673                 kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
 674                 kcsan_disable_current(); /* disable to generate warning */
 675                 WARN(1, "Unbalanced %s()", __func__);
 676                 kcsan_enable_current();
 677         }
 678 }
 679 EXPORT_SYMBOL(kcsan_enable_current);
 680
 681 void kcsan_enable_current_nowarn(void)
 682 {
 683         if (get_ctx()->disable_count-- == 0)
 684                 kcsan_disable_current();
 685 }
 686 EXPORT_SYMBOL(kcsan_enable_current_nowarn);
 687
 688 void kcsan_nestable_atomic_begin(void)
 689 {
 690         /*
 691          * Do *not* check and warn if we are in a flat atomic region: nestable
 692          * and flat atomic regions are independent from each other.
 693          * See include/linux/kcsan.h: struct kcsan_ctx comments for more
 694          * comments.
 695          */
 696
 697         ++get_ctx()->atomic_nest_count;
 698 }
 699 EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
 700
 701 void kcsan_nestable_atomic_end(void)
 702 {
 703         if (get_ctx()->atomic_nest_count-- == 0) {
 704                 /*
 705                  * Warn if kcsan_nestable_atomic_end() calls are unbalanced with
 706                  * kcsan_nestable_atomic_begin() calls, which causes
 707                  * atomic_nest_count to become negative and should not happen.
 708                  */
 709                 kcsan_nestable_atomic_begin(); /* restore to 0 */
 710                 kcsan_disable_current(); /* disable to generate warning */
 711                 WARN(1, "Unbalanced %s()", __func__);
 712                 kcsan_enable_current();
 713         }
 714 }
 715 EXPORT_SYMBOL(kcsan_nestable_atomic_end);
 716
 717 void kcsan_flat_atomic_begin(void)
 718 {
 719         get_ctx()->in_flat_atomic = true;
 720 }
 721 EXPORT_SYMBOL(kcsan_flat_atomic_begin);
 722
 723 void kcsan_flat_atomic_end(void)
 724 {
 725         get_ctx()->in_flat_atomic = false;
 726 }
 727 EXPORT_SYMBOL(kcsan_flat_atomic_end);
 728
 729 void kcsan_atomic_next(int n)
 730 {
 731         get_ctx()->atomic_next = n;
 732 }
 733 EXPORT_SYMBOL(kcsan_atomic_next);
 734
 735 void kcsan_set_access_mask(unsigned long mask)
 736 {
 737         get_ctx()->access_mask = mask;
 738 }
 739 EXPORT_SYMBOL(kcsan_set_access_mask);
 740
 741 struct kcsan_scoped_access *
 742 kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
 743                           struct kcsan_scoped_access *sa)
 744 {
 745         struct kcsan_ctx *ctx = get_ctx();
 746
 747         __kcsan_check_access(ptr, size, type);
 748
 749         ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
 750
 751         INIT_LIST_HEAD(&sa->list);
 752         sa->ptr = ptr;
 753         sa->size = size;
 754         sa->type = type;
 755
 756         if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
 757                 INIT_LIST_HEAD(&ctx->scoped_accesses);
 758         list_add(&sa->list, &ctx->scoped_accesses);
 759
 760         ctx->disable_count--;
 761         return sa;
 762 }
 763 EXPORT_SYMBOL(kcsan_begin_scoped_access);
 764
 765 void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
 766 {
 767         struct kcsan_ctx *ctx = get_ctx();
 768
 769         if (WARN(!ctx->scoped_accesses.prev, "Unbalanced %s()?", __func__))
 770                 return;
 771
 772         ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
 773
 774         list_del(&sa->list);
 775         if (list_empty(&ctx->scoped_accesses))
 776                 /*
 777                  * Ensure we do not enter kcsan_check_scoped_accesses()
 778                  * slow-path if unnecessary, and avoids requiring list_empty()
 779                  * in the fast-path (to avoid a READ_ONCE() and potential
 780                  * uaccess warning).
 781                  */
 782                 ctx->scoped_accesses.prev = NULL;
 783
 784         ctx->disable_count--;
 785
 786         __kcsan_check_access(sa->ptr, sa->size, sa->type);
 787 }
 788 EXPORT_SYMBOL(kcsan_end_scoped_access);
 789
 790 void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
 791 {
 792         check_access(ptr, size, type);
 793 }
 794 EXPORT_SYMBOL(__kcsan_check_access);
 795
 796 /*
 797  * KCSAN uses the same instrumentation that is emitted by supported compilers
 798  * for ThreadSanitizer (TSAN).
 799  *
 800  * When enabled, the compiler emits instrumentation calls (the functions
 801  * prefixed with "__tsan" below) for all loads and stores that it generated;
 802  * inline asm is not instrumented.
 803  *
 804  * Note that, not all supported compiler versions distinguish aligned/unaligned
 805  * accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
 806  * version to the generic version, which can handle both.
 807  */
 808
 809 #define DEFINE_TSAN_READ_WRITE(size)                                           \
 810         void __tsan_read##size(void *ptr);                                     \
 811         void __tsan_read##size(void *ptr)                                      \
 812         {                                                                      \
 813                 check_access(ptr, size, 0);                                    \
 814         }                                                                      \
 815         EXPORT_SYMBOL(__tsan_read##size);                                      \
 816         void __tsan_unaligned_read##size(void *ptr)                            \
 817                 __alias(__tsan_read##size);                                    \
 818         EXPORT_SYMBOL(__tsan_unaligned_read##size);                            \
 819         void __tsan_write##size(void *ptr);                                    \
 820         void __tsan_write##size(void *ptr)                                     \
 821         {                                                                      \
 822                 check_access(ptr, size, KCSAN_ACCESS_WRITE);                   \
 823         }                                                                      \
 824         EXPORT_SYMBOL(__tsan_write##size);                                     \
 825         void __tsan_unaligned_write##size(void *ptr)                           \
 826                 __alias(__tsan_write##size);                                   \
 827         EXPORT_SYMBOL(__tsan_unaligned_write##size);                           \
 828         void __tsan_read_write##size(void *ptr);                               \
 829         void __tsan_read_write##size(void *ptr)                                \
 830         {                                                                      \
 831                 check_access(ptr, size,                                        \
 832                              KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE);      \
 833         }                                                                      \
 834         EXPORT_SYMBOL(__tsan_read_write##size);                                \
 835         void __tsan_unaligned_read_write##size(void *ptr)                      \
 836                 __alias(__tsan_read_write##size);                              \
 837         EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
 838
 839 DEFINE_TSAN_READ_WRITE(1);
 840 DEFINE_TSAN_READ_WRITE(2);
 841 DEFINE_TSAN_READ_WRITE(4);
 842 DEFINE_TSAN_READ_WRITE(8);
 843 DEFINE_TSAN_READ_WRITE(16);
 844
 845 void __tsan_read_range(void *ptr, size_t size);
 846 void __tsan_read_range(void *ptr, size_t size)
 847 {
 848         check_access(ptr, size, 0);
 849 }
 850 EXPORT_SYMBOL(__tsan_read_range);
 851
 852 void __tsan_write_range(void *ptr, size_t size);
 853 void __tsan_write_range(void *ptr, size_t size)
 854 {
 855         check_access(ptr, size, KCSAN_ACCESS_WRITE);
 856 }
 857 EXPORT_SYMBOL(__tsan_write_range);
 858
 859 /*
 860  * Use of explicit volatile is generally disallowed [1], however, volatile is
 861  * still used in various concurrent context, whether in low-level
 862  * synchronization primitives or for legacy reasons.
 863  * [1] https://lwn.net/Articles/233479/
 864  *
 865  * We only consider volatile accesses atomic if they are aligned and would pass
 866  * the size-check of compiletime_assert_rwonce_type().
 867  */
 868 #define DEFINE_TSAN_VOLATILE_READ_WRITE(size)                                  \
 869         void __tsan_volatile_read##size(void *ptr);                            \
 870         void __tsan_volatile_read##size(void *ptr)                             \
 871         {                                                                      \
 872                 const bool is_atomic = size <= sizeof(long long) &&            \
 873                                        IS_ALIGNED((unsigned long)ptr, size);   \
 874                 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic)      \
 875                         return;                                                \
 876                 check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0);  \
 877         }                                                                      \
 878         EXPORT_SYMBOL(__tsan_volatile_read##size);                             \
 879         void __tsan_unaligned_volatile_read##size(void *ptr)                   \
 880                 __alias(__tsan_volatile_read##size);                           \
 881         EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size);                   \
 882         void __tsan_volatile_write##size(void *ptr);                           \
 883         void __tsan_volatile_write##size(void *ptr)                            \
 884         {                                                                      \
 885                 const bool is_atomic = size <= sizeof(long long) &&            \
 886                                        IS_ALIGNED((unsigned long)ptr, size);   \
 887                 if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic)      \
 888                         return;                                                \
 889                 check_access(ptr, size,                                        \
 890                              KCSAN_ACCESS_WRITE |                              \
 891                                      (is_atomic ? KCSAN_ACCESS_ATOMIC : 0));   \
 892         }                                                                      \
 893         EXPORT_SYMBOL(__tsan_volatile_write##size);                            \
 894         void __tsan_unaligned_volatile_write##size(void *ptr)                  \
 895                 __alias(__tsan_volatile_write##size);                          \
 896         EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
 897
 898 DEFINE_TSAN_VOLATILE_READ_WRITE(1);
 899 DEFINE_TSAN_VOLATILE_READ_WRITE(2);
 900 DEFINE_TSAN_VOLATILE_READ_WRITE(4);
 901 DEFINE_TSAN_VOLATILE_READ_WRITE(8);
 902 DEFINE_TSAN_VOLATILE_READ_WRITE(16);
 903
 904 /*
 905  * The below are not required by KCSAN, but can still be emitted by the
 906  * compiler.
 907  */
 908 void __tsan_func_entry(void *call_pc);
 909 void __tsan_func_entry(void *call_pc)
 910 {
 911 }
 912 EXPORT_SYMBOL(__tsan_func_entry);
 913 void __tsan_func_exit(void);
 914 void __tsan_func_exit(void)
 915 {
 916 }
 917 EXPORT_SYMBOL(__tsan_func_exit);
 918 void __tsan_init(void);
 919 void __tsan_init(void)
 920 {
 921 }
 922 EXPORT_SYMBOL(__tsan_init);
 923
 924 /*
 925  * Instrumentation for atomic builtins (__atomic_*, __sync_*).
 926  *
 927  * Normal kernel code _should not_ be using them directly, but some
 928  * architectures may implement some or all atomics using the compilers'
 929  * builtins.
 930  *
 931  * Note: If an architecture decides to fully implement atomics using the
 932  * builtins, because they are implicitly instrumented by KCSAN (and KASAN,
 933  * etc.), implementing the ARCH_ATOMIC interface (to get instrumentation via
 934  * atomic-instrumented) is no longer necessary.
 935  *
 936  * TSAN instrumentation replaces atomic accesses with calls to any of the below
 937  * functions, whose job is to also execute the operation itself.
 938  */
 939
 940 #define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits)                                                        \
 941         u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder);                      \
 942         u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder)                       \
 943         {                                                                                          \
 944                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 945                         check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC);              \
 946                 }                                                                                  \
 947                 return __atomic_load_n(ptr, memorder);                                             \
 948         }                                                                                          \
 949         EXPORT_SYMBOL(__tsan_atomic##bits##_load);                                                 \
 950         void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder);                   \
 951         void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder)                    \
 952         {                                                                                          \
 953                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 954                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
 955                                      KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC);                    \
 956                 }                                                                                  \
 957                 __atomic_store_n(ptr, v, memorder);                                                \
 958         }                                                                                          \
 959         EXPORT_SYMBOL(__tsan_atomic##bits##_store)
 960
 961 #define DEFINE_TSAN_ATOMIC_RMW(op, bits, suffix)                                                   \
 962         u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder);                 \
 963         u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder)                  \
 964         {                                                                                          \
 965                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 966                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
 967                                      KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
 968                                              KCSAN_ACCESS_ATOMIC);                                 \
 969                 }                                                                                  \
 970                 return __atomic_##op##suffix(ptr, v, memorder);                                    \
 971         }                                                                                          \
 972         EXPORT_SYMBOL(__tsan_atomic##bits##_##op)
 973
 974 /*
 975  * Note: CAS operations are always classified as write, even in case they
 976  * fail. We cannot perform check_access() after a write, as it might lead to
 977  * false positives, in cases such as:
 978  *
 979  *      T0: __atomic_compare_exchange_n(&p->flag, &old, 1, ...)
 980  *
 981  *      T1: if (__atomic_load_n(&p->flag, ...)) {
 982  *              modify *p;
 983  *              p->flag = 0;
 984  *          }
 985  *
 986  * The only downside is that, if there are 3 threads, with one CAS that
 987  * succeeds, another CAS that fails, and an unmarked racing operation, we may
 988  * point at the wrong CAS as the source of the race. However, if we assume that
 989  * all CAS can succeed in some other execution, the data race is still valid.
 990  */
 991 #define DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strength, weak)                                           \
 992         int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp,          \
 993                                                               u##bits val, int mo, int fail_mo);   \
 994         int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp,          \
 995                                                               u##bits val, int mo, int fail_mo)    \
 996         {                                                                                          \
 997                 if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 998                         check_access(ptr, bits / BITS_PER_BYTE,                                    \
 999                                      KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
1000                                              KCSAN_ACCESS_ATOMIC);                                 \
1001                 }                                                                                  \
1002                 return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo);              \
1003         }                                                                                          \
1004         EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_##strength)
1005
1006 #define DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)                                                       \
1007         u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
1008                                                            int mo, int fail_mo);                   \
1009         u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
1010                                                            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                 __atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo);                       \
1018                 return exp;                                                                        \
1019         }                                                                                          \
1020         EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_val)
1021
1022 #define DEFINE_TSAN_ATOMIC_OPS(bits)                                                               \
1023         DEFINE_TSAN_ATOMIC_LOAD_STORE(bits);                                                       \
1024         DEFINE_TSAN_ATOMIC_RMW(exchange, bits, _n);                                                \
1025         DEFINE_TSAN_ATOMIC_RMW(fetch_add, bits, );                                                 \
1026         DEFINE_TSAN_ATOMIC_RMW(fetch_sub, bits, );                                                 \
1027         DEFINE_TSAN_ATOMIC_RMW(fetch_and, bits, );                                                 \
1028         DEFINE_TSAN_ATOMIC_RMW(fetch_or, bits, );                                                  \
1029         DEFINE_TSAN_ATOMIC_RMW(fetch_xor, bits, );                                                 \
1030         DEFINE_TSAN_ATOMIC_RMW(fetch_nand, bits, );                                                \
1031         DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strong, 0);                                               \
1032         DEFINE_TSAN_ATOMIC_CMPXCHG(bits, weak, 1);                                                 \
1033         DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)
1034
1035 DEFINE_TSAN_ATOMIC_OPS(8);
1036 DEFINE_TSAN_ATOMIC_OPS(16);
1037 DEFINE_TSAN_ATOMIC_OPS(32);
1038 #ifdef CONFIG_64BIT
1039 DEFINE_TSAN_ATOMIC_OPS(64);
1040 #endif
1041
1042 void __tsan_atomic_thread_fence(int memorder);
1043 void __tsan_atomic_thread_fence(int memorder)
1044 {
1045         __atomic_thread_fence(memorder);
1046 }
1047 EXPORT_SYMBOL(__tsan_atomic_thread_fence);
1048
1049 void __tsan_atomic_signal_fence(int memorder);
1050 void __tsan_atomic_signal_fence(int memorder) { }
1051 EXPORT_SYMBOL(__tsan_atomic_signal_fence);
1052
1053 #ifdef __HAVE_ARCH_MEMSET
1054 void *__tsan_memset(void *s, int c, size_t count);
1055 noinline void *__tsan_memset(void *s, int c, size_t count)
1056 {
1057         /*
1058          * Instead of not setting up watchpoints where accessed size is greater
1059          * than MAX_ENCODABLE_SIZE, truncate checked size to MAX_ENCODABLE_SIZE.
1060          */
1061         size_t check_len = min_t(size_t, count, MAX_ENCODABLE_SIZE);
1062
1063         check_access(s, check_len, KCSAN_ACCESS_WRITE);
1064         return memset(s, c, count);
1065 }
1066 #else
1067 void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
1068 #endif
1069 EXPORT_SYMBOL(__tsan_memset);
1070
1071 #ifdef __HAVE_ARCH_MEMMOVE
1072 void *__tsan_memmove(void *dst, const void *src, size_t len);
1073 noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
1074 {
1075         size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
1076
1077         check_access(dst, check_len, KCSAN_ACCESS_WRITE);
1078         check_access(src, check_len, 0);
1079         return memmove(dst, src, len);
1080 }
1081 #else
1082 void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
1083 #endif
1084 EXPORT_SYMBOL(__tsan_memmove);
1085
1086 #ifdef __HAVE_ARCH_MEMCPY
1087 void *__tsan_memcpy(void *dst, const void *src, size_t len);
1088 noinline void *__tsan_memcpy(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 memcpy(dst, src, len);
1095 }
1096 #else
1097 void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
1098 #endif
1099 EXPORT_SYMBOL(__tsan_memcpy);