In a data processing apparatus that switches between a secure mode and a normal mode during execution, the secure mode allowing access to secure resources to be protected, the normal mode not allowing access to the secure resources, when the secure resources increase in the secure mode, the load on a protection mechanism for protecting the resources becomes large. Thus, there is a demand for data processing apparatuses that are able to reduce secure resources. The present invention relates to a data processing apparatus that stores therein a secure program including one or more processing procedures which use secure resources and a call instruction for calling a normal program to be executed in a normal mode. While executing the secure program, the data processing apparatus calls the normal program with the call instruction and operates according to the called normal program.