Methods and systems for securely executing untrusted software are described. In one embodiment, two virtual memory mappings are used (one readable/writeable-RW and the other readable/executable-RX). In one embodiment, compiled software is used at run time through pointers to the RX virtual memory space and a compiler causes the storage of the compiled software in the RW virtual memory space through the use of an executable function (e.g. a memory copy like function) stored in an executable only memory region.