aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/kcsan/core.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/kcsan/core.c')
-rw-r--r--kernel/kcsan/core.c1310
1 files changed, 1310 insertions, 0 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
new file mode 100644
index 000000000000..fe12dfe254ec
--- /dev/null
+++ b/kernel/kcsan/core.c
@@ -0,0 +1,1310 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KCSAN core runtime.
+ *
+ * Copyright (C) 2019, Google LLC.
+ */
+
+#define pr_fmt(fmt) "kcsan: " fmt
+
+#include <linux/atomic.h>
+#include <linux/bug.h>
+#include <linux/delay.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+
+#include "encoding.h"
+#include "kcsan.h"
+#include "permissive.h"
+
+static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);
+unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;
+unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;
+static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;
+static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER);
+
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "kcsan."
+module_param_named(early_enable, kcsan_early_enable, bool, 0);
+module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);
+module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
+module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
+module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
+
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+static bool kcsan_weak_memory = true;
+module_param_named(weak_memory, kcsan_weak_memory, bool, 0644);
+#else
+#define kcsan_weak_memory false
+#endif
+
+bool kcsan_enabled;
+
+/* Per-CPU kcsan_ctx for interrupts */
+static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
+ .scoped_accesses = {LIST_POISON1, NULL},
+};
+
+/*
+ * Helper macros to index into adjacent slots, starting from address slot
+ * itself, followed by the right and left slots.
+ *
+ * The purpose is 2-fold:
+ *
+ * 1. if during insertion the address slot is already occupied, check if
+ * any adjacent slots are free;
+ * 2. accesses that straddle a slot boundary due to size that exceeds a
+ * slot's range may check adjacent slots if any watchpoint matches.
+ *
+ * Note that accesses with very large size may still miss a watchpoint; however,
+ * given this should be rare, this is a reasonable trade-off to make, since this
+ * will avoid:
+ *
+ * 1. excessive contention between watchpoint checks and setup;
+ * 2. larger number of simultaneous watchpoints without sacrificing
+ * performance.
+ *
+ * Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
+ *
+ * slot=0: [ 1, 2, 0]
+ * slot=9: [10, 11, 9]
+ * slot=63: [64, 65, 63]
+ */
+#define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
+
+/*
+ * SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
+ * slot (middle) is fine if we assume that races occur rarely. The set of
+ * indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
+ * {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
+ */
+#define SLOT_IDX_FAST(slot, i) (slot + i)
+
+/*
+ * Watchpoints, with each entry encoded as defined in encoding.h: in order to be
+ * able to safely update and access a watchpoint without introducing locking
+ * overhead, we encode each watchpoint as a single atomic long. The initial
+ * zero-initialized state matches INVALID_WATCHPOINT.
+ *
+ * Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
+ * use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
+ */
+static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
+
+/*
+ * Instructions to skip watching counter, used in should_watch(). We use a
+ * per-CPU counter to avoid excessive contention.
+ */
+static DEFINE_PER_CPU(long, kcsan_skip);
+
+/* For kcsan_prandom_u32_max(). */
+static DEFINE_PER_CPU(u32, kcsan_rand_state);
+
+static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
+ size_t size,
+ bool expect_write,
+ long *encoded_watchpoint)
+{
+ const int slot = watchpoint_slot(addr);
+ const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
+ atomic_long_t *watchpoint;
+ unsigned long wp_addr_masked;
+ size_t wp_size;
+ bool is_write;
+ int i;
+
+ BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
+
+ for (i = 0; i < NUM_SLOTS; ++i) {
+ watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
+ *encoded_watchpoint = atomic_long_read(watchpoint);
+ if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
+ &wp_size, &is_write))
+ continue;
+
+ if (expect_write && !is_write)
+ continue;
+
+ /* Check if the watchpoint matches the access. */
+ if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
+ return watchpoint;
+ }
+
+ return NULL;
+}
+
+static inline atomic_long_t *
+insert_watchpoint(unsigned long addr, size_t size, bool is_write)
+{
+ const int slot = watchpoint_slot(addr);
+ const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
+ atomic_long_t *watchpoint;
+ int i;
+
+ /* Check slot index logic, ensuring we stay within array bounds. */
+ BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
+ BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
+ BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
+ BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
+
+ for (i = 0; i < NUM_SLOTS; ++i) {
+ long expect_val = INVALID_WATCHPOINT;
+
+ /* Try to acquire this slot. */
+ watchpoint = &watchpoints[SLOT_IDX(slot, i)];
+ if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
+ return watchpoint;
+ }
+
+ return NULL;
+}
+
+/*
+ * Return true if watchpoint was successfully consumed, false otherwise.
+ *
+ * This may return false if:
+ *
+ * 1. another thread already consumed the watchpoint;
+ * 2. the thread that set up the watchpoint already removed it;
+ * 3. the watchpoint was removed and then re-used.
+ */
+static __always_inline bool
+try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
+{
+ return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
+}
+
+/* Return true if watchpoint was not touched, false if already consumed. */
+static inline bool consume_watchpoint(atomic_long_t *watchpoint)
+{
+ return atomic_long_xchg_relaxed(watchpoint, CONSUMED_WATCHPOINT) != CONSUMED_WATCHPOINT;
+}
+
+/* Remove the watchpoint -- its slot may be reused after. */
+static inline void remove_watchpoint(atomic_long_t *watchpoint)
+{
+ atomic_long_set(watchpoint, INVALID_WATCHPOINT);
+}
+
+static __always_inline struct kcsan_ctx *get_ctx(void)
+{
+ /*
+ * In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
+ * also result in calls that generate warnings in uaccess regions.
+ */
+ return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
+}
+
+static __always_inline void
+check_access(const volatile void *ptr, size_t size, int type, unsigned long ip);
+
+/* Check scoped accesses; never inline because this is a slow-path! */
+static noinline void kcsan_check_scoped_accesses(void)
+{
+ struct kcsan_ctx *ctx = get_ctx();
+ struct kcsan_scoped_access *scoped_access;
+
+ if (ctx->disable_scoped)
+ return;
+
+ ctx->disable_scoped++;
+ list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) {
+ check_access(scoped_access->ptr, scoped_access->size,
+ scoped_access->type, scoped_access->ip);
+ }
+ ctx->disable_scoped--;
+}
+
+/* Rules for generic atomic accesses. Called from fast-path. */
+static __always_inline bool
+is_atomic(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
+{
+ if (type & KCSAN_ACCESS_ATOMIC)
+ return true;
+
+ /*
+ * Unless explicitly declared atomic, never consider an assertion access
+ * as atomic. This allows using them also in atomic regions, such as
+ * seqlocks, without implicitly changing their semantics.
+ */
+ if (type & KCSAN_ACCESS_ASSERT)
+ return false;
+
+ if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
+ (type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) &&
+ !(type & KCSAN_ACCESS_COMPOUND) && IS_ALIGNED((unsigned long)ptr, size))
+ return true; /* Assume aligned writes up to word size are atomic. */
+
+ if (ctx->atomic_next > 0) {
+ /*
+ * Because we do not have separate contexts for nested
+ * interrupts, in case atomic_next is set, we simply assume that
+ * the outer interrupt set atomic_next. In the worst case, we
+ * will conservatively consider operations as atomic. This is a
+ * reasonable trade-off to make, since this case should be
+ * extremely rare; however, even if extremely rare, it could
+ * lead to false positives otherwise.
+ */
+ if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
+ --ctx->atomic_next; /* in task, or outer interrupt */
+ return true;
+ }
+
+ return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic;
+}
+
+static __always_inline bool
+should_watch(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
+{
+ /*
+ * Never set up watchpoints when memory operations are atomic.
+ *
+ * Need to check this first, before kcsan_skip check below: (1) atomics
+ * should not count towards skipped instructions, and (2) to actually
+ * decrement kcsan_atomic_next for consecutive instruction stream.
+ */
+ if (is_atomic(ctx, ptr, size, type))
+ return false;
+
+ if (this_cpu_dec_return(kcsan_skip) >= 0)
+ return false;
+
+ /*
+ * NOTE: If we get here, kcsan_skip must always be reset in slow path
+ * via reset_kcsan_skip() to avoid underflow.
+ */
+
+ /* this operation should be watched */
+ return true;
+}
+
+/*
+ * Returns a pseudo-random number in interval [0, ep_ro). Simple linear
+ * congruential generator, using constants from "Numerical Recipes".
+ */
+static u32 kcsan_prandom_u32_max(u32 ep_ro)
+{
+ u32 state = this_cpu_read(kcsan_rand_state);
+
+ state = 1664525 * state + 1013904223;
+ this_cpu_write(kcsan_rand_state, state);
+
+ return state % ep_ro;
+}
+
+static inline void reset_kcsan_skip(void)
+{
+ long skip_count = kcsan_skip_watch -
+ (IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
+ kcsan_prandom_u32_max(kcsan_skip_watch) :
+ 0);
+ this_cpu_write(kcsan_skip, skip_count);
+}
+
+static __always_inline bool kcsan_is_enabled(struct kcsan_ctx *ctx)
+{
+ return READ_ONCE(kcsan_enabled) && !ctx->disable_count;
+}
+
+/* Introduce delay depending on context and configuration. */
+static void delay_access(int type)
+{
+ unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
+ /* For certain access types, skew the random delay to be longer. */
+ unsigned int skew_delay_order =
+ (type & (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_ASSERT)) ? 1 : 0;
+
+ delay -= IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
+ kcsan_prandom_u32_max(delay >> skew_delay_order) :
+ 0;
+ udelay(delay);
+}
+
+/*
+ * Reads the instrumented memory for value change detection; value change
+ * detection is currently done for accesses up to a size of 8 bytes.
+ */
+static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
+{
+ switch (size) {
+ case 1: return READ_ONCE(*(const u8 *)ptr);
+ case 2: return READ_ONCE(*(const u16 *)ptr);
+ case 4: return READ_ONCE(*(const u32 *)ptr);
+ case 8: return READ_ONCE(*(const u64 *)ptr);
+ default: return 0; /* Ignore; we do not diff the values. */
+ }
+}
+
+void kcsan_save_irqtrace(struct task_struct *task)
+{
+#ifdef CONFIG_TRACE_IRQFLAGS
+ task->kcsan_save_irqtrace = task->irqtrace;
+#endif
+}
+
+void kcsan_restore_irqtrace(struct task_struct *task)
+{
+#ifdef CONFIG_TRACE_IRQFLAGS
+ task->irqtrace = task->kcsan_save_irqtrace;
+#endif
+}
+
+static __always_inline int get_kcsan_stack_depth(void)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ return current->kcsan_stack_depth;
+#else
+ BUILD_BUG();
+ return 0;
+#endif
+}
+
+static __always_inline void add_kcsan_stack_depth(int val)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ current->kcsan_stack_depth += val;
+#else
+ BUILD_BUG();
+#endif
+}
+
+static __always_inline struct kcsan_scoped_access *get_reorder_access(struct kcsan_ctx *ctx)
+{
+#ifdef CONFIG_KCSAN_WEAK_MEMORY
+ return ctx->disable_scoped ? NULL : &ctx->reorder_access;
+#else
+ return NULL;
+#endif
+}
+
+static __always_inline bool
+find_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
+ int type, unsigned long ip)
+{
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (!reorder_access)
+ return false;
+
+ /*
+ * Note: If accesses are repeated while reorder_access is identical,
+ * never matches the new access, because !(type & KCSAN_ACCESS_SCOPED).
+ */
+ return reorder_access->ptr == ptr && reorder_access->size == size &&
+ reorder_access->type == type && reorder_access->ip == ip;
+}
+
+static inline void
+set_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
+ int type, unsigned long ip)
+{
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (!reorder_access || !kcsan_weak_memory)
+ return;
+
+ /*
+ * To avoid nested interrupts or scheduler (which share kcsan_ctx)
+ * reading an inconsistent reorder_access, ensure that the below has
+ * exclusive access to reorder_access by disallowing concurrent use.
+ */
+ ctx->disable_scoped++;
+ barrier();
+ reorder_access->ptr = ptr;
+ reorder_access->size = size;
+ reorder_access->type = type | KCSAN_ACCESS_SCOPED;
+ reorder_access->ip = ip;
+ reorder_access->stack_depth = get_kcsan_stack_depth();
+ barrier();
+ ctx->disable_scoped--;
+}
+
+/*
+ * Pull everything together: check_access() below contains the performance
+ * critical operations; the fast-path (including check_access) functions should
+ * all be inlinable by the instrumentation functions.
+ *
+ * The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
+ * non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
+ * be filtered from the stacktrace, as well as give them unique names for the
+ * UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
+ * since they do not access any user memory, but instrumentation is still
+ * emitted in UACCESS regions.
+ */
+
+static noinline void kcsan_found_watchpoint(const volatile void *ptr,
+ size_t size,
+ int type,
+ unsigned long ip,
+ atomic_long_t *watchpoint,
+ long encoded_watchpoint)
+{
+ const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
+ struct kcsan_ctx *ctx = get_ctx();
+ unsigned long flags;
+ bool consumed;
+
+ /*
+ * We know a watchpoint exists. Let's try to keep the race-window
+ * between here and finally consuming the watchpoint below as small as
+ * possible -- avoid unneccessarily complex code until consumed.
+ */
+
+ if (!kcsan_is_enabled(ctx))
+ return;
+
+ /*
+ * The access_mask check relies on value-change comparison. To avoid
+ * reporting a race where e.g. the writer set up the watchpoint, but the
+ * reader has access_mask!=0, we have to ignore the found watchpoint.
+ *
+ * reorder_access is never created from an access with access_mask set.
+ */
+ if (ctx->access_mask && !find_reorder_access(ctx, ptr, size, type, ip))
+ return;
+
+ /*
+ * If the other thread does not want to ignore the access, and there was
+ * a value change as a result of this thread's operation, we will still
+ * generate a report of unknown origin.
+ *
+ * Use CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n to filter.
+ */
+ if (!is_assert && kcsan_ignore_address(ptr))
+ return;
+
+ /*
+ * Consuming the watchpoint must be guarded by kcsan_is_enabled() to
+ * avoid erroneously triggering reports if the context is disabled.
+ */
+ consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
+
+ /* keep this after try_consume_watchpoint */
+ flags = user_access_save();
+
+ if (consumed) {
+ kcsan_save_irqtrace(current);
+ kcsan_report_set_info(ptr, size, type, ip, watchpoint - watchpoints);
+ kcsan_restore_irqtrace(current);
+ } else {
+ /*
+ * The other thread may not print any diagnostics, as it has
+ * already removed the watchpoint, or another thread consumed
+ * the watchpoint before this thread.
+ */
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]);
+ }
+
+ if (is_assert)
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
+ else
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]);
+
+ user_access_restore(flags);
+}
+
+static noinline void
+kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned long ip)
+{
+ const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
+ const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
+ atomic_long_t *watchpoint;
+ u64 old, new, diff;
+ enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
+ bool interrupt_watcher = kcsan_interrupt_watcher;
+ unsigned long ua_flags = user_access_save();
+ struct kcsan_ctx *ctx = get_ctx();
+ unsigned long access_mask = ctx->access_mask;
+ unsigned long irq_flags = 0;
+ bool is_reorder_access;
+
+ /*
+ * Always reset kcsan_skip counter in slow-path to avoid underflow; see
+ * should_watch().
+ */
+ reset_kcsan_skip();
+
+ if (!kcsan_is_enabled(ctx))
+ goto out;
+
+ /*
+ * Check to-ignore addresses after kcsan_is_enabled(), as we may access
+ * memory that is not yet initialized during early boot.
+ */
+ if (!is_assert && kcsan_ignore_address(ptr))
+ goto out;
+
+ if (!check_encodable((unsigned long)ptr, size)) {
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]);
+ goto out;
+ }
+
+ /*
+ * The local CPU cannot observe reordering of its own accesses, and
+ * therefore we need to take care of 2 cases to avoid false positives:
+ *
+ * 1. Races of the reordered access with interrupts. To avoid, if
+ * the current access is reorder_access, disable interrupts.
+ * 2. Avoid races of scoped accesses from nested interrupts (below).
+ */
+ is_reorder_access = find_reorder_access(ctx, ptr, size, type, ip);
+ if (is_reorder_access)
+ interrupt_watcher = false;
+ /*
+ * Avoid races of scoped accesses from nested interrupts (or scheduler).
+ * Assume setting up a watchpoint for a non-scoped (normal) access that
+ * also conflicts with a current scoped access. In a nested interrupt,
+ * which shares the context, it would check a conflicting scoped access.
+ * To avoid, disable scoped access checking.
+ */
+ ctx->disable_scoped++;
+
+ /*
+ * Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
+ * runtime is entered for every memory access, and potentially useful
+ * information is lost if dirtied by KCSAN.
+ */
+ kcsan_save_irqtrace(current);
+ if (!interrupt_watcher)
+ local_irq_save(irq_flags);
+
+ watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
+ if (watchpoint == NULL) {
+ /*
+ * Out of capacity: the size of 'watchpoints', and the frequency
+ * with which should_watch() returns true should be tweaked so
+ * that this case happens very rarely.
+ */
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]);
+ goto out_unlock;
+ }
+
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]);
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
+
+ /*
+ * Read the current value, to later check and infer a race if the data
+ * was modified via a non-instrumented access, e.g. from a device.
+ */
+ old = is_reorder_access ? 0 : read_instrumented_memory(ptr, size);
+
+ /*
+ * Delay this thread, to increase probability of observing a racy
+ * conflicting access.
+ */
+ delay_access(type);
+
+ /*
+ * Re-read value, and check if it is as expected; if not, we infer a
+ * racy access.
+ */
+ if (!is_reorder_access) {
+ new = read_instrumented_memory(ptr, size);
+ } else {
+ /*
+ * Reordered accesses cannot be used for value change detection,
+ * because the memory location may no longer be accessible and
+ * could result in a fault.
+ */
+ new = 0;
+ access_mask = 0;
+ }
+
+ diff = old ^ new;
+ if (access_mask)
+ diff &= access_mask;
+
+ /*
+ * Check if we observed a value change.
+ *
+ * Also check if the data race should be ignored (the rules depend on
+ * non-zero diff); if it is to be ignored, the below rules for
+ * KCSAN_VALUE_CHANGE_MAYBE apply.
+ */
+ if (diff && !kcsan_ignore_data_race(size, type, old, new, diff))
+ value_change = KCSAN_VALUE_CHANGE_TRUE;
+
+ /* Check if this access raced with another. */
+ if (!consume_watchpoint(watchpoint)) {
+ /*
+ * Depending on the access type, map a value_change of MAYBE to
+ * TRUE (always report) or FALSE (never report).
+ */
+ if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
+ if (access_mask != 0) {
+ /*
+ * For access with access_mask, we require a
+ * value-change, as it is likely that races on
+ * ~access_mask bits are expected.
+ */
+ value_change = KCSAN_VALUE_CHANGE_FALSE;
+ } else if (size > 8 || is_assert) {
+ /* Always assume a value-change. */
+ value_change = KCSAN_VALUE_CHANGE_TRUE;
+ }
+ }
+
+ /*
+ * No need to increment 'data_races' counter, as the racing
+ * thread already did.
+ *
+ * Count 'assert_failures' for each failed ASSERT access,
+ * therefore both this thread and the racing thread may
+ * increment this counter.
+ */
+ if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
+
+ kcsan_report_known_origin(ptr, size, type, ip,
+ value_change, watchpoint - watchpoints,
+ old, new, access_mask);
+ } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
+ /* Inferring a race, since the value should not have changed. */
+
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]);
+ if (is_assert)
+ atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
+
+ if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) {
+ kcsan_report_unknown_origin(ptr, size, type, ip,
+ old, new, access_mask);
+ }
+ }
+
+ /*
+ * Remove watchpoint; must be after reporting, since the slot may be
+ * reused after this point.
+ */
+ remove_watchpoint(watchpoint);
+ atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
+
+out_unlock:
+ if (!interrupt_watcher)
+ local_irq_restore(irq_flags);
+ kcsan_restore_irqtrace(current);
+ ctx->disable_scoped--;
+
+ /*
+ * Reordered accesses cannot be used for value change detection,
+ * therefore never consider for reordering if access_mask is set.
+ * ASSERT_EXCLUSIVE are not real accesses, ignore them as well.
+ */
+ if (!access_mask && !is_assert)
+ set_reorder_access(ctx, ptr, size, type, ip);
+out:
+ user_access_restore(ua_flags);
+}
+
+static __always_inline void
+check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
+{
+ atomic_long_t *watchpoint;
+ long encoded_watchpoint;
+
+ /*
+ * Do nothing for 0 sized check; this comparison will be optimized out
+ * for constant sized instrumentation (__tsan_{read,write}N).
+ */
+ if (unlikely(size == 0))
+ return;
+
+again:
+ /*
+ * Avoid user_access_save in fast-path: find_watchpoint is safe without
+ * user_access_save, as the address that ptr points to is only used to
+ * check if a watchpoint exists; ptr is never dereferenced.
+ */
+ watchpoint = find_watchpoint((unsigned long)ptr, size,
+ !(type & KCSAN_ACCESS_WRITE),
+ &encoded_watchpoint);
+ /*
+ * It is safe to check kcsan_is_enabled() after find_watchpoint in the
+ * slow-path, as long as no state changes that cause a race to be
+ * detected and reported have occurred until kcsan_is_enabled() is
+ * checked.
+ */
+
+ if (unlikely(watchpoint != NULL))
+ kcsan_found_watchpoint(ptr, size, type, ip, watchpoint, encoded_watchpoint);
+ else {
+ struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
+
+ if (unlikely(should_watch(ctx, ptr, size, type))) {
+ kcsan_setup_watchpoint(ptr, size, type, ip);
+ return;
+ }
+
+ if (!(type & KCSAN_ACCESS_SCOPED)) {
+ struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
+
+ if (reorder_access) {
+ /*
+ * reorder_access check: simulates reordering of
+ * the access after subsequent operations.
+ */
+ ptr = reorder_access->ptr;
+ type = reorder_access->type;
+ ip = reorder_access->ip;
+ /*
+ * Upon a nested interrupt, this context's
+ * reorder_access can be modified (shared ctx).
+ * We know that upon return, reorder_access is
+ * always invalidated by setting size to 0 via
+ * __tsan_func_exit(). Therefore we must read
+ * and check size after the other fields.
+ */
+ barrier();
+ size = READ_ONCE(reorder_access->size);
+ if (size)
+ goto again;
+ }
+ }
+
+ /*
+ * Always checked last, right before returning from runtime;
+ * if reorder_access is valid, checked after it was checked.
+ */
+ if (unlikely(ctx->scoped_accesses.prev))
+ kcsan_check_scoped_accesses();
+ }
+}
+
+/* === Public interface ===================================================== */
+
+void __init kcsan_init(void)
+{
+ int cpu;
+
+ BUG_ON(!in_task());
+
+ for_each_possible_cpu(cpu)
+ per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
+
+ /*
+ * We are in the init task, and no other tasks should be running;
+ * WRITE_ONCE without memory barrier is sufficient.
+ */
+ if (kcsan_early_enable) {
+ pr_info("enabled early\n");
+ WRITE_ONCE(kcsan_enabled, true);
+ }
+
+ if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) ||
+ IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) ||
+ IS_ENABLED(CONFIG_KCSAN_PERMISSIVE) ||
+ IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
+ pr_warn("non-strict mode configured - use CONFIG_KCSAN_STRICT=y to see all data races\n");
+ } else {
+ pr_info("strict mode configured\n");
+ }
+}
+
+/* === Exported interface =================================================== */
+
+void kcsan_disable_current(void)
+{
+ ++get_ctx()->disable_count;
+}
+EXPORT_SYMBOL(kcsan_disable_current);
+
+void kcsan_enable_current(void)
+{
+ if (get_ctx()->disable_count-- == 0) {
+ /*
+ * Warn if kcsan_enable_current() calls are unbalanced with
+ * kcsan_disable_current() calls, which causes disable_count to
+ * become negative and should not happen.
+ */
+ kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
+ kcsan_disable_current(); /* disable to generate warning */
+ WARN(1, "Unbalanced %s()", __func__);
+ kcsan_enable_current();
+ }
+}
+EXPORT_SYMBOL(kcsan_enable_current);
+
+void kcsan_enable_current_nowarn(void)
+{
+ if (get_ctx()->disable_count-- == 0)
+ kcsan_disable_current();
+}
+EXPORT_SYMBOL(kcsan_enable_current_nowarn);
+
+void kcsan_nestable_atomic_begin(void)
+{
+ /*
+ * Do *not* check and warn if we are in a flat atomic region: nestable
+ * and flat atomic regions are independent from each other.
+ * See include/linux/kcsan.h: struct kcsan_ctx comments for more
+ * comments.
+ */
+
+ ++get_ctx()->atomic_nest_count;
+}
+EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
+
+void kcsan_nestable_atomic_end(void)
+{
+ if (get_ctx()->atomic_nest_count-- == 0) {
+ /*
+ * Warn if kcsan_nestable_atomic_end() calls are unbalanced with
+ * kcsan_nestable_atomic_begin() calls, which causes
+ * atomic_nest_count to become negative and should not happen.
+ */
+ kcsan_nestable_atomic_begin(); /* restore to 0 */
+ kcsan_disable_current(); /* disable to generate warning */
+ WARN(1, "Unbalanced %s()", __func__);
+ kcsan_enable_current();
+ }
+}
+EXPORT_SYMBOL(kcsan_nestable_atomic_end);
+
+void kcsan_flat_atomic_begin(void)
+{
+ get_ctx()->in_flat_atomic = true;
+}
+EXPORT_SYMBOL(kcsan_flat_atomic_begin);
+
+void kcsan_flat_atomic_end(void)
+{
+ get_ctx()->in_flat_atomic = false;
+}
+EXPORT_SYMBOL(kcsan_flat_atomic_end);
+
+void kcsan_atomic_next(int n)
+{
+ get_ctx()->atomic_next = n;
+}
+EXPORT_SYMBOL(kcsan_atomic_next);
+
+void kcsan_set_access_mask(unsigned long mask)
+{
+ get_ctx()->access_mask = mask;
+}
+EXPORT_SYMBOL(kcsan_set_access_mask);
+
+struct kcsan_scoped_access *
+kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
+ struct kcsan_scoped_access *sa)
+{
+ struct kcsan_ctx *ctx = get_ctx();
+
+ check_access(ptr, size, type, _RET_IP_);
+
+ ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
+
+ INIT_LIST_HEAD(&sa->list);
+ sa->ptr = ptr;
+ sa->size = size;
+ sa->type = type;
+ sa->ip = _RET_IP_;
+
+ if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
+ INIT_LIST_HEAD(&ctx->scoped_accesses);
+ list_add(&sa->list, &ctx->scoped_accesses);
+
+ ctx->disable_count--;
+ return sa;
+}
+EXPORT_SYMBOL(kcsan_begin_scoped_access);
+
+void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
+{
+ struct kcsan_ctx *ctx = get_ctx();
+
+ if (WARN(!ctx->scoped_accesses.prev, "Unbalanced %s()?", __func__))
+ return;
+
+ ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
+
+ list_del(&sa->list);
+ if (list_empty(&ctx->scoped_accesses))
+ /*
+ * Ensure we do not enter kcsan_check_scoped_accesses()
+ * slow-path if unnecessary, and avoids requiring list_empty()
+ * in the fast-path (to avoid a READ_ONCE() and potential
+ * uaccess warning).
+ */
+ ctx->scoped_accesses.prev = NULL;
+
+ ctx->disable_count--;
+
+ check_access(sa->ptr, sa->size, sa->type, sa->ip);
+}
+EXPORT_SYMBOL(kcsan_end_scoped_access);
+
+void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
+{
+ check_access(ptr, size, type, _RET_IP_);
+}
+EXPORT_SYMBOL(__kcsan_check_access);
+
+#define DEFINE_MEMORY_BARRIER(name, order_before_cond) \
+ void __kcsan_##name(void) \
+ { \
+ struct kcsan_scoped_access *sa = get_reorder_access(get_ctx()); \
+ if (!sa) \
+ return; \
+ if (order_before_cond) \
+ sa->size = 0; \
+ } \
+ EXPORT_SYMBOL(__kcsan_##name)
+
+DEFINE_MEMORY_BARRIER(mb, true);
+DEFINE_MEMORY_BARRIER(wmb, sa->type & (KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND));
+DEFINE_MEMORY_BARRIER(rmb, !(sa->type & KCSAN_ACCESS_WRITE) || (sa->type & KCSAN_ACCESS_COMPOUND));
+DEFINE_MEMORY_BARRIER(release, true);
+
+/*
+ * KCSAN uses the same instrumentation that is emitted by supported compilers
+ * for ThreadSanitizer (TSAN).
+ *
+ * When enabled, the compiler emits instrumentation calls (the functions
+ * prefixed with "__tsan" below) for all loads and stores that it generated;
+ * inline asm is not instrumented.
+ *
+ * Note that, not all supported compiler versions distinguish aligned/unaligned
+ * accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
+ * version to the generic version, which can handle both.
+ */
+
+#define DEFINE_TSAN_READ_WRITE(size) \
+ void __tsan_read##size(void *ptr); \
+ void __tsan_read##size(void *ptr) \
+ { \
+ check_access(ptr, size, 0, _RET_IP_); \
+ } \
+ EXPORT_SYMBOL(__tsan_read##size); \
+ void __tsan_unaligned_read##size(void *ptr) \
+ __alias(__tsan_read##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_read##size); \
+ void __tsan_write##size(void *ptr); \
+ void __tsan_write##size(void *ptr) \
+ { \
+ check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_); \
+ } \
+ EXPORT_SYMBOL(__tsan_write##size); \
+ void __tsan_unaligned_write##size(void *ptr) \
+ __alias(__tsan_write##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_write##size); \
+ void __tsan_read_write##size(void *ptr); \
+ void __tsan_read_write##size(void *ptr) \
+ { \
+ check_access(ptr, size, \
+ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, \
+ _RET_IP_); \
+ } \
+ EXPORT_SYMBOL(__tsan_read_write##size); \
+ void __tsan_unaligned_read_write##size(void *ptr) \
+ __alias(__tsan_read_write##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
+
+DEFINE_TSAN_READ_WRITE(1);
+DEFINE_TSAN_READ_WRITE(2);
+DEFINE_TSAN_READ_WRITE(4);
+DEFINE_TSAN_READ_WRITE(8);
+DEFINE_TSAN_READ_WRITE(16);
+
+void __tsan_read_range(void *ptr, size_t size);
+void __tsan_read_range(void *ptr, size_t size)
+{
+ check_access(ptr, size, 0, _RET_IP_);
+}
+EXPORT_SYMBOL(__tsan_read_range);
+
+void __tsan_write_range(void *ptr, size_t size);
+void __tsan_write_range(void *ptr, size_t size)
+{
+ check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_);
+}
+EXPORT_SYMBOL(__tsan_write_range);
+
+/*
+ * Use of explicit volatile is generally disallowed [1], however, volatile is
+ * still used in various concurrent context, whether in low-level
+ * synchronization primitives or for legacy reasons.
+ * [1] https://lwn.net/Articles/233479/
+ *
+ * We only consider volatile accesses atomic if they are aligned and would pass
+ * the size-check of compiletime_assert_rwonce_type().
+ */
+#define DEFINE_TSAN_VOLATILE_READ_WRITE(size) \
+ void __tsan_volatile_read##size(void *ptr); \
+ void __tsan_volatile_read##size(void *ptr) \
+ { \
+ const bool is_atomic = size <= sizeof(long long) && \
+ IS_ALIGNED((unsigned long)ptr, size); \
+ if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
+ return; \
+ check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0, \
+ _RET_IP_); \
+ } \
+ EXPORT_SYMBOL(__tsan_volatile_read##size); \
+ void __tsan_unaligned_volatile_read##size(void *ptr) \
+ __alias(__tsan_volatile_read##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size); \
+ void __tsan_volatile_write##size(void *ptr); \
+ void __tsan_volatile_write##size(void *ptr) \
+ { \
+ const bool is_atomic = size <= sizeof(long long) && \
+ IS_ALIGNED((unsigned long)ptr, size); \
+ if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
+ return; \
+ check_access(ptr, size, \
+ KCSAN_ACCESS_WRITE | \
+ (is_atomic ? KCSAN_ACCESS_ATOMIC : 0), \
+ _RET_IP_); \
+ } \
+ EXPORT_SYMBOL(__tsan_volatile_write##size); \
+ void __tsan_unaligned_volatile_write##size(void *ptr) \
+ __alias(__tsan_volatile_write##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
+
+DEFINE_TSAN_VOLATILE_READ_WRITE(1);
+DEFINE_TSAN_VOLATILE_READ_WRITE(2);
+DEFINE_TSAN_VOLATILE_READ_WRITE(4);
+DEFINE_TSAN_VOLATILE_READ_WRITE(8);
+DEFINE_TSAN_VOLATILE_READ_WRITE(16);
+
+/*
+ * Function entry and exit are used to determine the validty of reorder_access.
+ * Reordering of the access ends at the end of the function scope where the
+ * access happened. This is done for two reasons:
+ *
+ * 1. Artificially limits the scope where missing barriers are detected.
+ * This minimizes false positives due to uninstrumented functions that
+ * contain the required barriers but were missed.
+ *
+ * 2. Simplifies generating the stack trace of the access.
+ */
+void __tsan_func_entry(void *call_pc);
+noinline void __tsan_func_entry(void *call_pc)
+{
+ if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ return;
+
+ add_kcsan_stack_depth(1);
+}
+EXPORT_SYMBOL(__tsan_func_entry);
+
+void __tsan_func_exit(void);
+noinline void __tsan_func_exit(void)
+{
+ struct kcsan_scoped_access *reorder_access;
+
+ if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
+ return;
+
+ reorder_access = get_reorder_access(get_ctx());
+ if (!reorder_access)
+ goto out;
+
+ if (get_kcsan_stack_depth() <= reorder_access->stack_depth) {
+ /*
+ * Access check to catch cases where write without a barrier
+ * (supposed release) was last access in function: because
+ * instrumentation is inserted before the real access, a data
+ * race due to the write giving up a c-s would only be caught if
+ * we do the conflicting access after.
+ */
+ check_access(reorder_access->ptr, reorder_access->size,
+ reorder_access->type, reorder_access->ip);
+ reorder_access->size = 0;
+ reorder_access->stack_depth = INT_MIN;
+ }
+out:
+ add_kcsan_stack_depth(-1);
+}
+EXPORT_SYMBOL(__tsan_func_exit);
+
+void __tsan_init(void);
+void __tsan_init(void)
+{
+}
+EXPORT_SYMBOL(__tsan_init);
+
+/*
+ * Instrumentation for atomic builtins (__atomic_*, __sync_*).
+ *
+ * Normal kernel code _should not_ be using them directly, but some
+ * architectures may implement some or all atomics using the compilers'
+ * builtins.
+ *
+ * Note: If an architecture decides to fully implement atomics using the
+ * builtins, because they are implicitly instrumented by KCSAN (and KASAN,
+ * etc.), implementing the ARCH_ATOMIC interface (to get instrumentation via
+ * atomic-instrumented) is no longer necessary.
+ *
+ * TSAN instrumentation replaces atomic accesses with calls to any of the below
+ * functions, whose job is to also execute the operation itself.
+ */
+
+static __always_inline void kcsan_atomic_builtin_memorder(int memorder)
+{
+ if (memorder == __ATOMIC_RELEASE ||
+ memorder == __ATOMIC_SEQ_CST ||
+ memorder == __ATOMIC_ACQ_REL)
+ __kcsan_release();
+}
+
+#define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits) \
+ u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder); \
+ u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder) \
+ { \
+ kcsan_atomic_builtin_memorder(memorder); \
+ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
+ check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC, _RET_IP_); \
+ } \
+ return __atomic_load_n(ptr, memorder); \
+ } \
+ EXPORT_SYMBOL(__tsan_atomic##bits##_load); \
+ void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder); \
+ void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder) \
+ { \
+ kcsan_atomic_builtin_memorder(memorder); \
+ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
+ check_access(ptr, bits / BITS_PER_BYTE, \
+ KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC, _RET_IP_); \
+ } \
+ __atomic_store_n(ptr, v, memorder); \
+ } \
+ EXPORT_SYMBOL(__tsan_atomic##bits##_store)
+
+#define DEFINE_TSAN_ATOMIC_RMW(op, bits, suffix) \
+ u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder); \
+ u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder) \
+ { \
+ kcsan_atomic_builtin_memorder(memorder); \
+ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
+ check_access(ptr, bits / BITS_PER_BYTE, \
+ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
+ KCSAN_ACCESS_ATOMIC, _RET_IP_); \
+ } \
+ return __atomic_##op##suffix(ptr, v, memorder); \
+ } \
+ EXPORT_SYMBOL(__tsan_atomic##bits##_##op)
+
+/*
+ * Note: CAS operations are always classified as write, even in case they
+ * fail. We cannot perform check_access() after a write, as it might lead to
+ * false positives, in cases such as:
+ *
+ * T0: __atomic_compare_exchange_n(&p->flag, &old, 1, ...)
+ *
+ * T1: if (__atomic_load_n(&p->flag, ...)) {
+ * modify *p;
+ * p->flag = 0;
+ * }
+ *
+ * The only downside is that, if there are 3 threads, with one CAS that
+ * succeeds, another CAS that fails, and an unmarked racing operation, we may
+ * point at the wrong CAS as the source of the race. However, if we assume that
+ * all CAS can succeed in some other execution, the data race is still valid.
+ */
+#define DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strength, weak) \
+ int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
+ u##bits val, int mo, int fail_mo); \
+ int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
+ u##bits val, int mo, int fail_mo) \
+ { \
+ kcsan_atomic_builtin_memorder(mo); \
+ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
+ check_access(ptr, bits / BITS_PER_BYTE, \
+ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
+ KCSAN_ACCESS_ATOMIC, _RET_IP_); \
+ } \
+ return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo); \
+ } \
+ EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_##strength)
+
+#define DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits) \
+ u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
+ int mo, int fail_mo); \
+ u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
+ int mo, int fail_mo) \
+ { \
+ kcsan_atomic_builtin_memorder(mo); \
+ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
+ check_access(ptr, bits / BITS_PER_BYTE, \
+ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
+ KCSAN_ACCESS_ATOMIC, _RET_IP_); \
+ } \
+ __atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo); \
+ return exp; \
+ } \
+ EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_val)
+
+#define DEFINE_TSAN_ATOMIC_OPS(bits) \
+ DEFINE_TSAN_ATOMIC_LOAD_STORE(bits); \
+ DEFINE_TSAN_ATOMIC_RMW(exchange, bits, _n); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_add, bits, ); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_sub, bits, ); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_and, bits, ); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_or, bits, ); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_xor, bits, ); \
+ DEFINE_TSAN_ATOMIC_RMW(fetch_nand, bits, ); \
+ DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strong, 0); \
+ DEFINE_TSAN_ATOMIC_CMPXCHG(bits, weak, 1); \
+ DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)
+
+DEFINE_TSAN_ATOMIC_OPS(8);
+DEFINE_TSAN_ATOMIC_OPS(16);
+DEFINE_TSAN_ATOMIC_OPS(32);
+DEFINE_TSAN_ATOMIC_OPS(64);
+
+void __tsan_atomic_thread_fence(int memorder);
+void __tsan_atomic_thread_fence(int memorder)
+{
+ kcsan_atomic_builtin_memorder(memorder);
+ __atomic_thread_fence(memorder);
+}
+EXPORT_SYMBOL(__tsan_atomic_thread_fence);
+
+/*
+ * In instrumented files, we emit instrumentation for barriers by mapping the
+ * kernel barriers to an __atomic_signal_fence(), which is interpreted specially
+ * and otherwise has no relation to a real __atomic_signal_fence(). No known
+ * kernel code uses __atomic_signal_fence().
+ *
+ * Since fsanitize=thread instrumentation handles __atomic_signal_fence(), which
+ * are turned into calls to __tsan_atomic_signal_fence(), such instrumentation
+ * can be disabled via the __no_kcsan function attribute (vs. an explicit call
+ * which could not). When __no_kcsan is requested, __atomic_signal_fence()
+ * generates no code.
+ *
+ * Note: The result of using __atomic_signal_fence() with KCSAN enabled is
+ * potentially limiting the compiler's ability to reorder operations; however,
+ * if barriers were instrumented with explicit calls (without LTO), the compiler
+ * couldn't optimize much anyway. The result of a hypothetical architecture
+ * using __atomic_signal_fence() in normal code would be KCSAN false negatives.
+ */
+void __tsan_atomic_signal_fence(int memorder);
+noinline void __tsan_atomic_signal_fence(int memorder)
+{
+ switch (memorder) {
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_mb:
+ __kcsan_mb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_wmb:
+ __kcsan_wmb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_rmb:
+ __kcsan_rmb();
+ break;
+ case __KCSAN_BARRIER_TO_SIGNAL_FENCE_release:
+ __kcsan_release();
+ break;
+ default:
+ break;
+ }
+}
+EXPORT_SYMBOL(__tsan_atomic_signal_fence);