Mitigating side-channel attacks using executable only memory (XOM)

Embodiments include side channel defender circuitry to protect shared code pages in executable only memory (XOM) from side-channel exploits. The side channel defender circuitry receives system calls and determines whether code pages include executable code, whether the code pages include writeable code, and whether the code pages include instructions capable of altering or modifying one or more protection keys associated with code pages stored in XOM. If the code pages contain executable code that is writeable or executable code that includes instructions capable of altering or modifying one or more protection keys associated with code pages stored in XOM the side channel defender circuitry, the side channel defender circuitry aborts the system call.