# mimmutable() for OpenBSD

OpenBSD founder Theo de Raadt first proposed a new system call, called mimmutable(), at the beginning of September. After numerous revisions, the system call looks to be merged as:

int mimmutable(void *addr, size_t len);

A call to mimmutable() will render the mapping of the len bytes of memory starting at addr immutable, meaning that the kernel will not allow any changes to either the memory protections or the mapping in that range. As a result, system calls like mmap() or mprotect() that would affect that range will, instead, fail.