[musl] Powerpc Linux 'scv' system call ABI proposal take 2

[Szabolcs Nagy]

* Nicholas Piggin <npiggin at gmail.com> [2020-04-20 12:08:36 +1000]:
> Excerpts from Rich Felker's message of April 20, 2020 11:29 am:
> > Also, allowing patching of executable pages is generally frowned upon
> > these days because W^X is a desirable hardening property.
> 
> Right, it would want be write-protected after being patched.

"frowned upon" means that users may have to update
their security policy setting in pax, selinux, apparmor,
seccomp bpf filters and who knows what else that may
monitor and flag W&X mprotect.

libc update can break systems if the new libc does W&X.