Macro define_syscall 

macro_rules! define_syscall {
    ($(#[$attr:meta])* fn $name:ident($($arg:ident: $typ:ty),*) -> $ret:ty) => { ... };
    ($(#[$attr:meta])* fn $name:ident($($arg:ident: $typ:ty),*)) => { ... };
}

Available on neither target feature static-syscalls, nor target_arch=bpf and crate feature unstable-static-syscalls.