[PATCH -v2 7/8] jump_label: Add selftest

[Peter Zijlstra]

Add a little selftest that validates all combinations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/Kconfig        |    6 ++++++
 kernel/jump_label.c |   39 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletion(-)

--- 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 JUMP_LABEL_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
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -482,4 +482,41 @@ static void jump_label_update(struct sta
 		__jump_label_update(key, entry, stop);
 }
 
-#endif
+#ifdef CONFIG_JUMP_LABEL_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 /* JUMP_LABEL_SELFTEST */
+
+#endif /* HAVE_JUMP_LABEL */


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