selinux: Remove SECURITY_SELINUX_BOOTPARAM_VALUE

In preparation for removing CONFIG_DEFAULT_SECURITY, this removes the
soon-to-be redundant SECURITY_SELINUX_BOOTPARAM_VALUE. Since explicit
ordering via CONFIG_LSM or "lsm=" will define whether an LSM is enabled or
not, this CONFIG will become effectively ignored, so remove it. However,
in order to stay backward-compatible with "security=selinux", the enable
variable defaults to true.
Signed-off-by: Kees Cook <keescook@chromium.org>

security/selinux/Kconfig

@@ -22,21 +22,6 @@ config SECURITY_SELINUX_BOOTPARAM
 
 	  If you are unsure how to answer this question, answer N.
 
-config SECURITY_SELINUX_BOOTPARAM_VALUE
-	int "NSA SELinux boot parameter default value"
-	depends on SECURITY_SELINUX_BOOTPARAM
-	range 0 1
-	default 1
-	help
-	  This option sets the default value for the kernel parameter
-	  'selinux', which allows SELinux to be disabled at boot.  If this
-	  option is set to 0 (zero), the SELinux kernel parameter will
-	  default to 0, disabling SELinux at bootup.  If this option is
-	  set to 1 (one), the SELinux kernel parameter will default to 1,
-	  enabling SELinux at bootup.
-
-	  If you are unsure how to answer this question, answer 1.
-
 config SECURITY_SELINUX_DISABLE
 	bool "NSA SELinux runtime disable"
 	depends on SECURITY_SELINUX

security/selinux/hooks.c

@@ -121,9 +121,8 @@ __setup("enforcing=", enforcing_setup);
 #define selinux_enforcing_boot 1
 #endif
 
+int selinux_enabled __lsm_ro_after_init = 1;
 #ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM
-int selinux_enabled = CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE;
-
 static int __init selinux_enabled_setup(char *str)
 {
 	unsigned long enabled;
@@ -132,8 +131,6 @@ static int __init selinux_enabled_setup(char *str)
 	return 1;
 }
 __setup("selinux=", selinux_enabled_setup);
-#else
-int selinux_enabled = 1;
 #endif
 
 static unsigned int selinux_checkreqprot_boot =