Comment 60 for bug 1640518

This is the other thing I am trying. I've modified the Canary object to use a 128k stack zone and then use mprotect to mark the aligned 64k page that's in the middle of it read-only. When the destructor is called, it changes it back to read-write. This should cause any write to this region to get a segv, and give us an idea of what is writing on the stack in the resulting coredump.