ARM64: Adding write-protect bit for Userfaultfd

[Mohamed Husain Noor Mohamed]

Hi,

I am Mohamed Husain. I am a graduate student, working on a research
project using a userfaultfd for distributed shared memory.
We are trying to use Write-Protect mode in ARM64 but based on the
kernel commits we see the support only exists for the x86 kernel.
https://lwn.net/Articles/777258/

I am trying to add the write-protect support, so I am looking for the
unused bits in the PTE. Do you guys have any suggestions on the bits I
could use, or does it require hardware support?

Thanks,
Mohamed