kernel/params.c: generalize bool_enable_only

This takes out the bool_enable_only implementation from
the module loading code and generalizes it so that others
can make use of it.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: cocci@systeme.lip6.fr
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/moduleparam.h

@@ -427,6 +427,12 @@ extern int param_set_bool(const char *val, const struct kernel_param *kp);
 extern int param_get_bool(char *buffer, const struct kernel_param *kp);
 #define param_check_bool(name, p) __param_check(name, p, bool)
 
+extern const struct kernel_param_ops param_ops_bool_enable_only;
+extern int param_set_bool_enable_only(const char *val,
+				      const struct kernel_param *kp);
+/* getter is the same as for the regular bool */
+#define param_check_bool_enable_only param_check_bool
+
 extern const struct kernel_param_ops param_ops_invbool;
 extern int param_set_invbool(const char *val, const struct kernel_param *kp);
 extern int param_get_invbool(char *buffer, const struct kernel_param *kp);

kernel/module.c

@@ -298,37 +298,6 @@ static bool sig_enforce = true;
 #else
 static bool sig_enforce = false;
 
-static int param_set_bool_enable_only(const char *val,
-				      const struct kernel_param *kp)
-{
-	int err = 0;
-	bool new_value;
-	bool orig_value = *(bool *)kp->arg;
-	struct kernel_param dummy_kp = *kp;
-
-	dummy_kp.arg = &new_value;
-
-	err = param_set_bool(val, &dummy_kp);
-	if (err)
-		return err;
-
-	/* Don't let them unset it once it's set! */
-	if (!new_value && orig_value)
-		return -EROFS;
-
-	if (new_value)
-		err = param_set_bool(val, kp);
-
-	return err;
-}
-
-static const struct kernel_param_ops param_ops_bool_enable_only = {
-	.flags = KERNEL_PARAM_OPS_FL_NOARG,
-	.set = param_set_bool_enable_only,
-	.get = param_get_bool,
-};
-#define param_check_bool_enable_only param_check_bool
-
 module_param(sig_enforce, bool_enable_only, 0644);
 #endif /* !CONFIG_MODULE_SIG_FORCE */
 #endif /* CONFIG_MODULE_SIG */

kernel/params.c

@@ -335,6 +335,36 @@ const struct kernel_param_ops param_ops_bool = {
 };
 EXPORT_SYMBOL(param_ops_bool);
 
+int param_set_bool_enable_only(const char *val, const struct kernel_param *kp)
+{
+	int err = 0;
+	bool new_value;
+	bool orig_value = *(bool *)kp->arg;
+	struct kernel_param dummy_kp = *kp;
+
+	dummy_kp.arg = &new_value;
+
+	err = param_set_bool(val, &dummy_kp);
+	if (err)
+		return err;
+
+	/* Don't let them unset it once it's set! */
+	if (!new_value && orig_value)
+		return -EROFS;
+
+	if (new_value)
+		err = param_set_bool(val, kp);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(param_set_bool_enable_only);
+
+const struct kernel_param_ops param_ops_bool_enable_only = {
+	.flags = KERNEL_PARAM_OPS_FL_NOARG,
+	.set = param_set_bool_enable_only,
+	.get = param_get_bool,
+};
+
 /* This one must be bool. */
 int param_set_invbool(const char *val, const struct kernel_param *kp)
 {