is it possible to mount /proc as read-only on embedded system

[Lev Olshvang]

Hello all,

I am trying to harden the embedded system.
Is it possible and safe to mount /proc file system in a read-only mode and how to do this?
I have embedded system with systemd where /proc is mounted rw.
I suspect that systemd mounts it when it bebins to bootsrtap user space. 

On my  very simple QEMU busybox system with no systemd  I was able to remount /proc read-only.
But when I changed fstab to mount it as a read-only it  is still mounted 
rw,relatime after reboot

So at what s boot stage and how I can mount /proc read-only ?
Perhaps it is hardcoded in busybox init or in  systemd ?



Regards,
Lev