Next steps toward mimmutable, from deraadt@

In a recent message to the tech mailing list, Theo de Raadt (deraadt@) summarized the state of the new memory protections work. The thread also includes a followup from Otto Moerbeek (otto@) on consequent changes to the memory allocation mechanisms.

Theo writes,

From: "Theo de Raadt" <deraadt () openbsd ! org>
Date: Fri, 18 Nov 2022 03:10:05 +0000
To: openbsd-tech
Subject: More on mimmutable

[LONG]

I am getting close to having the big final step of mimmutable in the tree.
Here's a refresher on the how it works, what's already done, and the next
bit to land.

DESCRIPTION
     The mimmutable() system call changes currently mapped pages in the region
     to be marked immutable, which means their protection or mapping may not
     be changed in the future.  mmap(2), mprotect(2), and munmap(2) to pages
     marked immutable will return with error EPERM.

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