As an additional thing, even redundant security checks will be plenty fast as long data checked is mostly unchanging and colocated with code. (E.g. struct task

As an additional thing, even redundant security checks will be plenty fast as long data checked is mostly unchanging and colocated with code. (E.g. struct task in Linux) Write syscall being JIT is not even close to what can be achieved when you have to copy data on average 5 times until it reaches a driver. Mailbox style IPC everywhere would help with that immensely, but devices tend to skip DMA and require sleeps or slow port writes to do anything due to hardware issues.