Function syscall_never_reaches_tracer 

pub fn syscall_never_reaches_tracer(sysno: Sysno) -> bool

True for a syscall that never reaches Hermit’s tracer on the ptrace backend, whatever Detcore subscribes to: Reverie lets rt_sigreturn run untraced from its private page so a signal frame is restored safely. A syscall anchor on one could never fire, so the run refuses it.