[tip: core/static_call] static_call: Add simple self-test for static calls

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the core/static_call branch of tip:

Commit-ID:     f03c412915f5f69f2d17bcd20ecdd69320bcbf7b
Gitweb:        https://git.kernel.org/tip/f03c412915f5f69f2d17bcd20ecdd69320bcbf7b
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 18 Aug 2020 15:57:46 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 01 Sep 2020 09:58:05 +02:00

static_call: Add simple self-test for static calls

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200818135804.922581202@xxxxxxxxxxxxx
---
 arch/Kconfig         |  6 ++++++-
 kernel/static_call.c | 43 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 2c4936a..76ec339 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -106,6 +106,12 @@ config STATIC_KEYS_SELFTEST
 	help
 	  Boot time self-test of the branch patching code.
 
+config STATIC_CALL_SELFTEST
+	bool "Static call selftest"
+	depends on HAVE_STATIC_CALL
+	help
+	  Boot time self-test of the call patching code.
+
 config OPTPROBES
 	def_bool y
 	depends on KPROBES && HAVE_OPTPROBES
diff --git a/kernel/static_call.c b/kernel/static_call.c
index 753b2f1..97142cb 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -369,3 +369,46 @@ static void __init static_call_init(void)
 #endif
 }
 early_initcall(static_call_init);
+
+#ifdef CONFIG_STATIC_CALL_SELFTEST
+
+static int func_a(int x)
+{
+	return x+1;
+}
+
+static int func_b(int x)
+{
+	return x+2;
+}
+
+DEFINE_STATIC_CALL(sc_selftest, func_a);
+
+static struct static_call_data {
+      int (*func)(int);
+      int val;
+      int expect;
+} static_call_data [] __initdata = {
+      { NULL,   2, 3 },
+      { func_b, 2, 4 },
+      { func_a, 2, 3 }
+};
+
+static int __init test_static_call_init(void)
+{
+      int i;
+
+      for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
+	      struct static_call_data *scd = &static_call_data[i];
+
+              if (scd->func)
+                      static_call_update(sc_selftest, scd->func);
+
+              WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
+      }
+
+      return 0;
+}
+early_initcall(test_static_call_init);
+
+#endif /* CONFIG_STATIC_CALL_SELFTEST */