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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        kernel-team@fb.com, mingo@kernel.org
Cc:     elver@google.com, andreyknvl@google.com, glider@google.com,
        dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com,
        Mark Rutland <mark.rutland@arm.com>,
        "Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH kcsan 6/8] kcsan: Print if strict or non-strict during init
Date:   Wed, 21 Jul 2021 14:08:10 -0700
Message-Id: <20210721210812.844740-6-paulmck@kernel.org>
In-Reply-To: <20210721210726.GA828672@paulmck-ThinkPad-P17-Gen-1>
References: <20210721210726.GA828672@paulmck-ThinkPad-P17-Gen-1>
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From: Marco Elver <elver@google.com>

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@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 439edb9dcbb13..76e67d1e02d48 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 =================================================== */
-- 
2.31.1.189.g2e36527f23