I think the most immediate problem would be ELF segments that aren't 16kb aligned. Code will abut data, you can't add a gap without breaking offsets inside the

I think the most immediate problem would be ELF segments that aren't 16kb aligned. Code will abut data, you can't add a gap without breaking offsets inside the ELF, and you'll induce the segfault during every write to a global at the start of the writable code, or executing code at the end of the code segment. A less safe option would be for permissions to be a union in that region, as code rarely depends on a permission being absent. That would be quite the security hole though.