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-rw-r--r--kernel/kcsan/core.c850
1 files changed, 850 insertions, 0 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
new file mode 100644
index 000000000000..15f67949d11e
--- /dev/null
+++ b/kernel/kcsan/core.c
@@ -0,0 +1,850 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#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/random.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+
+#include "atomic.h"
+#include "encoding.h"
+#include "kcsan.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);
+
+bool kcsan_enabled;
+
+/* Per-CPU kcsan_ctx for interrupts */
+static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
+ .disable_count = 0,
+ .atomic_next = 0,
+ .atomic_nest_count = 0,
+ .in_flat_atomic = false,
+ .access_mask = 0,
+ .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);
+
+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);
+}
+
+/* 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 list_head *prev_save = ctx->scoped_accesses.prev;
+ struct kcsan_scoped_access *scoped_access;
+
+ ctx->scoped_accesses.prev = NULL; /* Avoid recursion. */
+ list_for_each_entry(scoped_access, &ctx->scoped_accesses, list)
+ __kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type);
+ ctx->scoped_accesses.prev = prev_save;
+}
+
+/* Rules for generic atomic accesses. Called from fast-path. */
+static __always_inline bool
+is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
+{
+ 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) &&
+ 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(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
+{
+ /*
+ * 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(ptr, size, type, ctx))
+ 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;
+}
+
+static inline void reset_kcsan_skip(void)
+{
+ long skip_count = kcsan_skip_watch -
+ (IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
+ prandom_u32_max(kcsan_skip_watch) :
+ 0);
+ this_cpu_write(kcsan_skip, skip_count);
+}
+
+static __always_inline bool kcsan_is_enabled(void)
+{
+ return READ_ONCE(kcsan_enabled) && get_ctx()->disable_count == 0;
+}
+
+static inline unsigned int get_delay(void)
+{
+ unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
+ return delay - (IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
+ prandom_u32_max(delay) :
+ 0);
+}
+
+/*
+ * 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,
+ atomic_long_t *watchpoint,
+ long encoded_watchpoint)
+{
+ unsigned long flags;
+ bool consumed;
+
+ if (!kcsan_is_enabled())
+ 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.
+ */
+ if (get_ctx()->access_mask != 0)
+ return;
+
+ /*
+ * Consume the watchpoint as soon as possible, to minimize the chances
+ * of !consumed. Consuming the watchpoint must always be guarded by
+ * kcsan_is_enabled() check, as otherwise we might erroneously
+ * triggering reports when disabled.
+ */
+ consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
+
+ /* keep this after try_consume_watchpoint */
+ flags = user_access_save();
+
+ if (consumed) {
+ kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_MAYBE,
+ KCSAN_REPORT_CONSUMED_WATCHPOINT,
+ watchpoint - watchpoints);
+ } 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.
+ */
+ kcsan_counter_inc(KCSAN_COUNTER_REPORT_RACES);
+ }
+
+ if ((type & KCSAN_ACCESS_ASSERT) != 0)
+ kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES);
+ else
+ kcsan_counter_inc(KCSAN_COUNTER_DATA_RACES);
+
+ user_access_restore(flags);
+}
+
+static noinline void
+kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
+{
+ const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
+ const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
+ atomic_long_t *watchpoint;
+ union {
+ u8 _1;
+ u16 _2;
+ u32 _4;
+ u64 _8;
+ } expect_value;
+ unsigned long access_mask;
+ enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
+ unsigned long ua_flags = user_access_save();
+ unsigned long irq_flags = 0;
+
+ /*
+ * Always reset kcsan_skip counter in slow-path to avoid underflow; see
+ * should_watch().
+ */
+ reset_kcsan_skip();
+
+ if (!kcsan_is_enabled())
+ goto out;
+
+ /*
+ * Special atomic rules: unlikely to be true, so we check them here in
+ * the slow-path, and not in the fast-path in is_atomic(). Call after
+ * kcsan_is_enabled(), as we may access memory that is not yet
+ * initialized during early boot.
+ */
+ if (!is_assert && kcsan_is_atomic_special(ptr))
+ goto out;
+
+ if (!check_encodable((unsigned long)ptr, size)) {
+ kcsan_counter_inc(KCSAN_COUNTER_UNENCODABLE_ACCESSES);
+ goto out;
+ }
+
+ if (!kcsan_interrupt_watcher)
+ /* Use raw to avoid lockdep recursion via IRQ flags tracing. */
+ raw_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.
+ */
+ kcsan_counter_inc(KCSAN_COUNTER_NO_CAPACITY);
+ goto out_unlock;
+ }
+
+ kcsan_counter_inc(KCSAN_COUNTER_SETUP_WATCHPOINTS);
+ kcsan_counter_inc(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.
+ */
+ expect_value._8 = 0;
+ switch (size) {
+ case 1:
+ expect_value._1 = READ_ONCE(*(const u8 *)ptr);
+ break;
+ case 2:
+ expect_value._2 = READ_ONCE(*(const u16 *)ptr);
+ break;
+ case 4:
+ expect_value._4 = READ_ONCE(*(const u32 *)ptr);
+ break;
+ case 8:
+ expect_value._8 = READ_ONCE(*(const u64 *)ptr);
+ break;
+ default:
+ break; /* ignore; we do not diff the values */
+ }
+
+ if (IS_ENABLED(CONFIG_KCSAN_DEBUG)) {
+ kcsan_disable_current();
+ pr_err("KCSAN: watching %s, size: %zu, addr: %px [slot: %d, encoded: %lx]\n",
+ is_write ? "write" : "read", size, ptr,
+ watchpoint_slot((unsigned long)ptr),
+ encode_watchpoint((unsigned long)ptr, size, is_write));
+ kcsan_enable_current();
+ }
+
+ /*
+ * Delay this thread, to increase probability of observing a racy
+ * conflicting access.
+ */
+ udelay(get_delay());
+
+ /*
+ * Re-read value, and check if it is as expected; if not, we infer a
+ * racy access.
+ */
+ access_mask = get_ctx()->access_mask;
+ switch (size) {
+ case 1:
+ expect_value._1 ^= READ_ONCE(*(const u8 *)ptr);
+ if (access_mask)
+ expect_value._1 &= (u8)access_mask;
+ break;
+ case 2:
+ expect_value._2 ^= READ_ONCE(*(const u16 *)ptr);
+ if (access_mask)
+ expect_value._2 &= (u16)access_mask;
+ break;
+ case 4:
+ expect_value._4 ^= READ_ONCE(*(const u32 *)ptr);
+ if (access_mask)
+ expect_value._4 &= (u32)access_mask;
+ break;
+ case 8:
+ expect_value._8 ^= READ_ONCE(*(const u64 *)ptr);
+ if (access_mask)
+ expect_value._8 &= (u64)access_mask;
+ break;
+ default:
+ break; /* ignore; we do not diff the values */
+ }
+
+ /* Were we able to observe a value-change? */
+ if (expect_value._8 != 0)
+ 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)
+ kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES);
+
+ kcsan_report(ptr, size, type, value_change, KCSAN_REPORT_RACE_SIGNAL,
+ watchpoint - watchpoints);
+ } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
+ /* Inferring a race, since the value should not have changed. */
+
+ kcsan_counter_inc(KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN);
+ if (is_assert)
+ kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES);
+
+ if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert)
+ kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_TRUE,
+ KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
+ watchpoint - watchpoints);
+ }
+
+ /*
+ * Remove watchpoint; must be after reporting, since the slot may be
+ * reused after this point.
+ */
+ remove_watchpoint(watchpoint);
+ kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
+out_unlock:
+ if (!kcsan_interrupt_watcher)
+ raw_local_irq_restore(irq_flags);
+out:
+ user_access_restore(ua_flags);
+}
+
+static __always_inline void check_access(const volatile void *ptr, size_t size,
+ int type)
+{
+ const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
+ 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;
+
+ /*
+ * 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, !is_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, watchpoint,
+ encoded_watchpoint);
+ else {
+ struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
+
+ if (unlikely(should_watch(ptr, size, type, ctx)))
+ kcsan_setup_watchpoint(ptr, size, type);
+ else if (unlikely(ctx->scoped_accesses.prev))
+ kcsan_check_scoped_accesses();
+ }
+}
+
+/* === Public interface ===================================================== */
+
+void __init kcsan_init(void)
+{
+ BUG_ON(!in_task());
+
+ kcsan_debugfs_init();
+
+ /*
+ * We are in the init task, and no other tasks should be running;
+ * WRITE_ONCE without memory barrier is sufficient.
+ */
+ if (kcsan_early_enable)
+ WRITE_ONCE(kcsan_enabled, true);
+}
+
+/* === 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();
+
+ __kcsan_check_access(ptr, size, type);
+
+ 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;
+
+ 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--;
+
+ __kcsan_check_access(sa->ptr, sa->size, sa->type);
+}
+EXPORT_SYMBOL(kcsan_end_scoped_access);
+
+void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
+{
+ check_access(ptr, size, type);
+}
+EXPORT_SYMBOL(__kcsan_check_access);
+
+/*
+ * 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) \
+ { \
+ check_access(ptr, size, 0); \
+ } \
+ 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) \
+ { \
+ check_access(ptr, size, KCSAN_ACCESS_WRITE); \
+ } \
+ EXPORT_SYMBOL(__tsan_write##size); \
+ void __tsan_unaligned_write##size(void *ptr) \
+ __alias(__tsan_write##size); \
+ EXPORT_SYMBOL(__tsan_unaligned_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)
+{
+ check_access(ptr, size, 0);
+}
+EXPORT_SYMBOL(__tsan_read_range);
+
+void __tsan_write_range(void *ptr, size_t size)
+{
+ check_access(ptr, size, KCSAN_ACCESS_WRITE);
+}
+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) \
+ { \
+ 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); \
+ } \
+ 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) \
+ { \
+ 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)); \
+ } \
+ 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);
+
+/*
+ * The below are not required by KCSAN, but can still be emitted by the
+ * compiler.
+ */
+void __tsan_func_entry(void *call_pc)
+{
+}
+EXPORT_SYMBOL(__tsan_func_entry);
+void __tsan_func_exit(void)
+{
+}
+EXPORT_SYMBOL(__tsan_func_exit);
+void __tsan_init(void)
+{
+}
+EXPORT_SYMBOL(__tsan_init);

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