Function mremap 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn mremap(
    old_address: *mut c_void,
    old_size: size_t,
    new_size: size_t,
    flags: c_int,
    ...
) -> *mut c_void

Non-POSIX, see https://www.man7.org/linux/man-pages/man2/mremap.2.html.