linux-kernel - [PATCH kcsan 2/8] kcsan: Remove CONFIG_KCSAN

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Date:   Wed, 21 Jul 2021 14:08:06 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        kernel-team@...com, mingo@...nel.org
Cc:     elver@...gle.com, andreyknvl@...gle.com, glider@...gle.com,
        dvyukov@...gle.com, cai@....pw, boqun.feng@...il.com,
        Mark Rutland <mark.rutland@....com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH kcsan 2/8] kcsan: Remove CONFIG_KCSAN_DEBUG

From: Marco Elver <elver@...gle.com>

By this point CONFIG_KCSAN_DEBUG is pretty useless, as the system just
isn't usable with it due to spamming console (I imagine a randconfig
test robot will run into this sooner or later). Remove it.

Back in 2019 I used it occasionally to record traces of watchpoints and
verify the encoding is correct, but these days we have proper tests. If
something similar is needed in future, just add it back ad-hoc.

Signed-off-by: Marco Elver <elver@...gle.com>
Acked-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/kcsan/core.c | 9 ---------
 lib/Kconfig.kcsan   | 3 ---
 2 files changed, 12 deletions(-)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 26709ea65c715..d92977ede7e17 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -479,15 +479,6 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 		break; /* ignore; we do not diff the values */
 	}
 
-	if (IS_ENABLED(CONFIG_KCSAN_DEBUG)) {
-		kcsan_disable_current();
-		pr_err("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.
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 6152fbd5cbb43..5304f211f81f1 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -62,9 +62,6 @@ config KCSAN_VERBOSE
 	  generated from any one of them, system stability may suffer due to
 	  deadlocks or recursion.  If in doubt, say N.
 
-config KCSAN_DEBUG
-	bool "Debugging of KCSAN internals"
-
 config KCSAN_SELFTEST
 	bool "Perform short selftests on boot"
 	default y
-- 
2.31.1.189.g2e36527f23