CHROMIUM: add test_module module

Create a module for simple module loading tests.

BUG=chromium-os:37353
TEST=daisy build, security_ModuleLocking passes when using "test_module"

Change-Id: I7ac604b614d69c2f18266a2241a660629b418701
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39918
Reviewed-by: Grant Grundler <grundler@chromium.org>
Tested-by: Grant Grundler <grundler@chromium.org>

kernel/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_MODULE_SIG) += module_signing.o
+obj-$(CONFIG_TEST_MODULE) += test_module.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o

kernel/test_module.c

@@ -0,0 +1,26 @@
+/*
+ * "hello world" kernel module
+ */
+
+#define pr_fmt(fmt) "test_module: " fmt
+
+#include <linux/module.h>
+
+static int __init test_module_init(void)
+{
+	pr_info("Hello, world\n");
+
+	return 0;
+}
+
+module_init(test_module_init);
+
+static void __exit test_module_exit(void)
+{
+	pr_info("Goodbye\n");
+}
+
+module_exit(test_module_exit);
+
+MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
+MODULE_LICENSE("GPL");

lib/Kconfig.debug

@@ -1611,6 +1611,14 @@ config TEST_USER_COPY
 
 	  If unsure, say N.
 
+config TEST_MODULE
+	tristate "Test module loading with 'hello world' module"
+	depends on m
+	help
+	  This builds the "test_module" module that emits "Hello, world"
+	  on printk when loaded. It is designed to be used for basic
+	  evaluation of the module loading subsystem.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"