code: func syscallMode(p PermissionBits) (o uint32) {
  	o |= uint32(p)
  
  	if p.Setuid() {
  		o |= syscall.S_ISUID
  	}
  	if p.Setgid() {
  		o |= syscall.S_ISGID
  	}
  	if p.Sticky() {
  		o |= syscall.S_ISVTX
  	}
  	return
  }
docs: // syscallMode returns the syscall-specific mode bits from PermissionBits bit positions