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>

1 files changed, 30 insertions, 0 deletions

diff --git a/kernel/params.c b/kernel/params.c
index b7635c025e9b..324624ed620f 100644
--- a/kernel/params.c
+++ b/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)
 {