sgi-xp: Use designated initializers

Prepare to mark sensitive kernel structures for randomization by making
sure they're using designated initializers. In this case, no initializers
are needed (they can be NULL initialized and callers adjusted to check
for NULL, which is more efficient than an indirect call).

Cc: Robin Holt <robinmholt@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@infradead.org>

drivers/misc/sgi-xp/xp.h

@@ -309,6 +309,9 @@ static inline enum xp_retval
 xpc_send(short partid, int ch_number, u32 flags, void *payload,
 	 u16 payload_size)
 {
+	if (!xpc_interface.send)
+		return xpNotLoaded;
+
 	return xpc_interface.send(partid, ch_number, flags, payload,
 				  payload_size);
 }
@@ -317,6 +320,9 @@ static inline enum xp_retval
 xpc_send_notify(short partid, int ch_number, u32 flags, void *payload,
 		u16 payload_size, xpc_notify_func func, void *key)
 {
+	if (!xpc_interface.send_notify)
+		return xpNotLoaded;
+
 	return xpc_interface.send_notify(partid, ch_number, flags, payload,
 					 payload_size, func, key);
 }
@@ -324,12 +330,16 @@ xpc_send_notify(short partid, int ch_number, u32 flags, void *payload,
 static inline void
 xpc_received(short partid, int ch_number, void *payload)
 {
-	return xpc_interface.received(partid, ch_number, payload);
+	if (xpc_interface.received)
+		xpc_interface.received(partid, ch_number, payload);
 }
 
 static inline enum xp_retval
 xpc_partid_to_nasids(short partid, void *nasids)
 {
+	if (!xpc_interface.partid_to_nasids)
+		return xpNotLoaded;
+
 	return xpc_interface.partid_to_nasids(partid, nasids);
 }
 

drivers/misc/sgi-xp/xp_main.c

@@ -69,23 +69,9 @@ struct xpc_registration xpc_registrations[XPC_MAX_NCHANNELS];
 EXPORT_SYMBOL_GPL(xpc_registrations);
 
 /*
- * Initialize the XPC interface to indicate that XPC isn't loaded.
+ * Initialize the XPC interface to NULL to indicate that XPC isn't loaded.
  */
-static enum xp_retval
-xpc_notloaded(void)
-{
-	return xpNotLoaded;
-}
-
-struct xpc_interface xpc_interface = {
-	(void (*)(int))xpc_notloaded,
-	(void (*)(int))xpc_notloaded,
-	(enum xp_retval(*)(short, int, u32, void *, u16))xpc_notloaded,
-	(enum xp_retval(*)(short, int, u32, void *, u16, xpc_notify_func,
-			   void *))xpc_notloaded,
-	(void (*)(short, int, void *))xpc_notloaded,
-	(enum xp_retval(*)(short, void *))xpc_notloaded
-};
+struct xpc_interface xpc_interface = { };
 EXPORT_SYMBOL_GPL(xpc_interface);
 
 /*
@@ -115,17 +101,7 @@ EXPORT_SYMBOL_GPL(xpc_set_interface);
 void
 xpc_clear_interface(void)
 {
-	xpc_interface.connect = (void (*)(int))xpc_notloaded;
-	xpc_interface.disconnect = (void (*)(int))xpc_notloaded;
-	xpc_interface.send = (enum xp_retval(*)(short, int, u32, void *, u16))
-	    xpc_notloaded;
-	xpc_interface.send_notify = (enum xp_retval(*)(short, int, u32, void *,
-						       u16, xpc_notify_func,
-						       void *))xpc_notloaded;
-	xpc_interface.received = (void (*)(short, int, void *))
-	    xpc_notloaded;
-	xpc_interface.partid_to_nasids = (enum xp_retval(*)(short, void *))
-	    xpc_notloaded;
+	memset(&xpc_interface, 0, sizeof(xpc_interface));
 }
 EXPORT_SYMBOL_GPL(xpc_clear_interface);
 
@@ -188,7 +164,8 @@ xpc_connect(int ch_number, xpc_channel_func func, void *key, u16 payload_size,
 
 	mutex_unlock(&registration->mutex);
 
-	xpc_interface.connect(ch_number);
+	if (xpc_interface.connect)
+		xpc_interface.connect(ch_number);
 
 	return xpSuccess;
 }
@@ -237,7 +214,8 @@ xpc_disconnect(int ch_number)
 	registration->assigned_limit = 0;
 	registration->idle_limit = 0;
 
-	xpc_interface.disconnect(ch_number);
+	if (xpc_interface.disconnect)
+		xpc_interface.disconnect(ch_number);
 
 	mutex_unlock(&registration->mutex);