[tip: locking/debug] kcsan: Print if strict or non-strict during init

[tip-bot2 for Marco Elver]

The following commit has been merged into the locking/debug branch of tip:

Commit-ID:     9c827cd1fcdf54bb50f874f91af0d5de2aceb035
Gitweb:        https://git.kernel.org/tip/9c827cd1fcdf54bb50f874f91af0d5de2aceb035
Author:        Marco Elver <elver@xxxxxxxxxx>
AuthorDate:    Mon, 07 Jun 2021 14:56:52 +02:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Tue, 20 Jul 2021 13:49:44 -07:00

kcsan: Print if strict or non-strict during init

Show a brief message if KCSAN is strict or non-strict, and if non-strict
also say that CONFIG_KCSAN_STRICT=y can be used to see all data races.

This is to hint to users of KCSAN who blindly use the default config
that their configuration might miss data races of interest.

Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/kcsan/core.c |  9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 439edb9..76e67d1 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -656,6 +656,15 @@ void __init kcsan_init(void)
 		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 =================================================== */