summaryrefslogtreecommitdiff
path: root/kernel/kcsan
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/kcsan')
-rw-r--r--kernel/kcsan/core.c44
-rw-r--r--kernel/kcsan/debugfs.c1
-rw-r--r--kernel/kcsan/kcsan.h7
-rw-r--r--kernel/kcsan/report.c43
4 files changed, 77 insertions, 18 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 82c2bef827d4..87ef01e40199 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -56,7 +56,7 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
/*
* SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
- * slot (middle) is fine if we assume that data races occur rarely. The set of
+ * 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)}.
*/
@@ -178,6 +178,14 @@ is_atomic(const volatile void *ptr, size_t size, int type)
if ((type & KCSAN_ACCESS_ATOMIC) != 0)
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) != 0)
+ return false;
+
if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
(type & KCSAN_ACCESS_WRITE) != 0 && size <= sizeof(long) &&
IS_ALIGNED((unsigned long)ptr, size))
@@ -298,7 +306,11 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
*/
kcsan_counter_inc(KCSAN_COUNTER_REPORT_RACES);
}
- kcsan_counter_inc(KCSAN_COUNTER_DATA_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);
}
@@ -307,6 +319,7 @@ 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;
@@ -429,13 +442,32 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
/*
* 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.
*/
- kcsan_report(ptr, size, type, size > 8 || value_change,
- smp_processor_id(), KCSAN_REPORT_RACE_SIGNAL);
+ if (is_assert)
+ kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES);
+
+ /*
+ * - If we were not able to observe a value change due to size
+ * constraints, always assume a value change.
+ * - If the access type is an assertion, we also always assume a
+ * value change to always report the race.
+ */
+ value_change = value_change || size > 8 || is_assert;
+
+ kcsan_report(ptr, size, type, value_change, smp_processor_id(),
+ KCSAN_REPORT_RACE_SIGNAL);
} else if (value_change) {
/* Inferring a race, since the value should not have changed. */
+
kcsan_counter_inc(KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN);
- if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_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, true,
smp_processor_id(),
KCSAN_REPORT_RACE_UNKNOWN_ORIGIN);
@@ -471,7 +503,7 @@ static __always_inline void check_access(const volatile void *ptr, size_t size,
&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 data race to be
+ * 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.
*/
diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
index bec42dab32ee..a9dad44130e6 100644
--- a/kernel/kcsan/debugfs.c
+++ b/kernel/kcsan/debugfs.c
@@ -44,6 +44,7 @@ static const char *counter_to_name(enum kcsan_counter_id id)
case KCSAN_COUNTER_USED_WATCHPOINTS: return "used_watchpoints";
case KCSAN_COUNTER_SETUP_WATCHPOINTS: return "setup_watchpoints";
case KCSAN_COUNTER_DATA_RACES: return "data_races";
+ case KCSAN_COUNTER_ASSERT_FAILURES: return "assert_failures";
case KCSAN_COUNTER_NO_CAPACITY: return "no_capacity";
case KCSAN_COUNTER_REPORT_RACES: return "report_races";
case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN: return "races_unknown_origin";
diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h
index 8492da45494b..50078e7d43c3 100644
--- a/kernel/kcsan/kcsan.h
+++ b/kernel/kcsan/kcsan.h
@@ -40,6 +40,13 @@ enum kcsan_counter_id {
KCSAN_COUNTER_DATA_RACES,
/*
+ * Total number of ASSERT failures due to races. If the observed race is
+ * due to two conflicting ASSERT type accesses, then both will be
+ * counted.
+ */
+ KCSAN_COUNTER_ASSERT_FAILURES,
+
+ /*
* Number of times no watchpoints were available.
*/
KCSAN_COUNTER_NO_CAPACITY,
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index 7cd34285df74..3bc590e6be7e 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -34,11 +34,11 @@ static struct {
} other_info = { .ptr = NULL };
/*
- * Information about reported data races; used to rate limit reporting.
+ * Information about reported races; used to rate limit reporting.
*/
struct report_time {
/*
- * The last time the data race was reported.
+ * The last time the race was reported.
*/
unsigned long time;
@@ -57,7 +57,7 @@ struct report_time {
*
* Therefore, we use a fixed-size array, which at most will occupy a page. This
* still adequately rate limits reports, assuming that a) number of unique data
- * races is not excessive, and b) occurrence of unique data races within the
+ * races is not excessive, and b) occurrence of unique races within the
* same time window is limited.
*/
#define REPORT_TIMES_MAX (PAGE_SIZE / sizeof(struct report_time))
@@ -74,7 +74,7 @@ static struct report_time report_times[REPORT_TIMES_SIZE];
static DEFINE_SPINLOCK(report_lock);
/*
- * Checks if the data race identified by thread frames frame1 and frame2 has
+ * Checks if the race identified by thread frames frame1 and frame2 has
* been reported since (now - KCSAN_REPORT_ONCE_IN_MS).
*/
static bool rate_limit_report(unsigned long frame1, unsigned long frame2)
@@ -90,7 +90,7 @@ static bool rate_limit_report(unsigned long frame1, unsigned long frame2)
invalid_before = jiffies - msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS);
- /* Check if a matching data race report exists. */
+ /* Check if a matching race report exists. */
for (i = 0; i < REPORT_TIMES_SIZE; ++i) {
struct report_time *rt = &report_times[i];
@@ -114,7 +114,7 @@ static bool rate_limit_report(unsigned long frame1, unsigned long frame2)
if (time_before(rt->time, invalid_before))
continue; /* before KCSAN_REPORT_ONCE_IN_MS ago */
- /* Reported recently, check if data race matches. */
+ /* Reported recently, check if race matches. */
if ((rt->frame1 == frame1 && rt->frame2 == frame2) ||
(rt->frame1 == frame2 && rt->frame2 == frame1))
return true;
@@ -142,11 +142,12 @@ skip_report(bool value_change, unsigned long top_frame)
* 3. write watchpoint, conflicting write (value_change==true): report;
* 4. write watchpoint, conflicting write (value_change==false): skip;
* 5. write watchpoint, conflicting read (value_change==false): skip;
- * 6. write watchpoint, conflicting read (value_change==true): impossible;
+ * 6. write watchpoint, conflicting read (value_change==true): report;
*
* Cases 1-4 are intuitive and expected; case 5 ensures we do not report
- * data races where the write may have rewritten the same value; and
- * case 6 is simply impossible.
+ * data races where the write may have rewritten the same value; case 6
+ * is possible either if the size is larger than what we check value
+ * changes for or the access type is KCSAN_ACCESS_ASSERT.
*/
if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && !value_change) {
/*
@@ -178,11 +179,27 @@ static const char *get_access_type(int type)
return "write";
case KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
return "write (marked)";
+
+ /*
+ * ASSERT variants:
+ */
+ case KCSAN_ACCESS_ASSERT:
+ case KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_ATOMIC:
+ return "assert no writes";
+ case KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE:
+ case KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
+ return "assert no accesses";
+
default:
BUG();
}
}
+static const char *get_bug_type(int type)
+{
+ return (type & KCSAN_ACCESS_ASSERT) != 0 ? "assert: race" : "data-race";
+}
+
/* Return thread description: in task or interrupt. */
static const char *get_thread_desc(int task_id)
{
@@ -268,13 +285,15 @@ static bool print_report(const volatile void *ptr, size_t size, int access_type,
* Do not print offset of functions to keep title short.
*/
cmp = sym_strcmp((void *)other_frame, (void *)this_frame);
- pr_err("BUG: KCSAN: data-race in %ps / %ps\n",
+ pr_err("BUG: KCSAN: %s in %ps / %ps\n",
+ get_bug_type(access_type | other_info.access_type),
(void *)(cmp < 0 ? other_frame : this_frame),
(void *)(cmp < 0 ? this_frame : other_frame));
} break;
case KCSAN_REPORT_RACE_UNKNOWN_ORIGIN:
- pr_err("BUG: KCSAN: data-race in %pS\n", (void *)this_frame);
+ pr_err("BUG: KCSAN: %s in %pS\n", get_bug_type(access_type),
+ (void *)this_frame);
break;
default:
@@ -427,7 +446,7 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type,
/*
* With TRACE_IRQFLAGS, lockdep's IRQ trace state becomes corrupted if
* we do not turn off lockdep here; this could happen due to recursion
- * into lockdep via KCSAN if we detect a data race in utilities used by
+ * into lockdep via KCSAN if we detect a race in utilities used by
* lockdep.
*/
lockdep_off();
generated by cgit v1.2.3-70-g09d2 (git 2.47.1) at 2024-12-24 20:17:47 +0000