cfg_if::cfg_if! {
    if #[cfg(not(target_os = "none"))] {
        mod hosted;
        pub use self::hosted::*;
    } else if #[cfg(target_arch = "riscv64")] {
        mod riscv64;
        pub use self::riscv64::*;
    } else {
        compile_error!("unsupported platform");
    }
}

/// The size of a regular-sized page of memory.
pub const PAGE_SIZE: usize = 1 << PAGE_SIZE_BITS;