locking/static_keys: Add selftest

Add a little selftest that validates all combinations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 44 insertions, 1 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 8a8ea7110de8..a71cdbe2a04d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -71,6 +71,12 @@ config JUMP_LABEL
          ( On 32-bit x86, the necessary options added to the compiler
            flags may increase the size of the kernel slightly. )
 
+config STATIC_KEYS_SELFTEST
+        bool "Static key selftest"
+        depends on JUMP_LABEL
+        help
+          Boot time self-test of the branch patching code.
+
 config OPTPROBES
         def_bool y
         depends on KPROBES && HAVE_OPTPROBES
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 8fd00d892286..f7dd15d537f9 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -482,4 +482,41 @@ static void jump_label_update(struct static_key *key)
                 __jump_label_update(key, entry, stop);
 }
 
-#endif
+#ifdef CONFIG_STATIC_KEYS_SELFTEST
+static DEFINE_STATIC_KEY_TRUE(sk_true);
+static DEFINE_STATIC_KEY_FALSE(sk_false);
+
+static __init int jump_label_test(void)
+{
+        int i;
+
+        for (i = 0; i < 2; i++) {
+                WARN_ON(static_key_enabled(&sk_true.key) != true);
+                WARN_ON(static_key_enabled(&sk_false.key) != false);
+
+                WARN_ON(!static_branch_likely(&sk_true));
+                WARN_ON(!static_branch_unlikely(&sk_true));
+                WARN_ON(static_branch_likely(&sk_false));
+                WARN_ON(static_branch_unlikely(&sk_false));
+
+                static_branch_disable(&sk_true);
+                static_branch_enable(&sk_false);
+
+                WARN_ON(static_key_enabled(&sk_true.key) == true);
+                WARN_ON(static_key_enabled(&sk_false.key) == false);
+
+                WARN_ON(static_branch_likely(&sk_true));
+                WARN_ON(static_branch_unlikely(&sk_true));
+                WARN_ON(!static_branch_likely(&sk_false));
+                WARN_ON(!static_branch_unlikely(&sk_false));
+
+                static_branch_enable(&sk_true);
+                static_branch_disable(&sk_false);
+        }
+
+        return 0;
+}
+late_initcall(jump_label_test);
+#endif /* STATIC_KEYS_SELFTEST */
+
+#endif /* HAVE_JUMP_LABEL */