Compiling executable code into a less-trusted address space

Unsafe application programs that implement managed code can be executed in a secure fashion. In particular, an operating system can be configured to execute an application program in user mode, but handle managed code compilation through a type-safe JIT compiler operating in kernel mode. The operating system can also designate a single memory location to be accessed through multiple address spaces with different permission sets. An application program operating in user mode can be executed in the read/execute address space, while the JIT compiler operates in a read/write address space. When encountering one or more pointers to intermediate language code, the application runtime can send one or more compilation requests to a kernel mode security component, which validates the requests. If validated, the JIT compiler will compile the requested intermediate language code, and the application program can access the compiled code from a shared memory heap.