Forbid write access to the SDWB block.

api/glue/readwrite.c

@@ -130,6 +130,12 @@ void eb_socket_write(eb_socket_t socketp, eb_width_t widths, eb_address_t addr,
   eb_address_t start, end;
   int fail;
   
+  /* SDWB address? It's read only ... */
+  if (addr < 0x4000) {
+    *error = (*error << 1) | 1;
+    return;
+  }
+  
   socket = EB_SOCKET(socketp);
   for (addressp = socket->first_handler; addressp != EB_NULL; addressp = address->next) {
     address = EB_HANDLER_ADDRESS(addressp);
@@ -190,8 +196,9 @@ eb_data_t eb_socket_read(eb_socket_t socketp, eb_width_t widths, eb_address_t ad
   eb_address_t start, end;
   int fail;
   
+  /* SDWB address? */
   if (addr < 0x4000) {
-    *error <<= 1;
+    *error = (*error << 1);
     return eb_sdwb(socketp, widths, addr);
   }