Add Hermit support

Cargo.toml

@@ -27,6 +27,9 @@ libc = { version = "0.2.64", default-features = false }
 [target.'cfg(target_os = "wasi")'.dependencies]
 wasi = "0.10"
 
+[target.'cfg(target_os = "hermit")'.dependencies]
+hermit-abi = "0.1"
+
 [target.'cfg(all(target_arch = "wasm32", target_os = "unknown", cargo_web))'.dependencies]
 stdweb = { version = "0.4.18", default-features = false, optional = true }
 [target.'cfg(all(target_arch = "wasm32", target_os = "unknown", not(cargo_web)))'.dependencies]

src/error.rs

@@ -53,6 +53,8 @@ impl Error {
     pub const NODE_CRYPTO: Error = internal_error(12);
     /// NodeJS does not have support for `crypto.randomFillSync`.
     pub const NODE_RANDOM_FILL_SYNC: Error = internal_error(13);
+    /// RNG hardware is not available for Hermit.
+    pub const HERMIT_NO_HARDWARE: Error = internal_error(14);
 
     /// Codes below this point represent OS Errors (i.e. positive i32 values).
     /// Codes at or above this point, but below [`Error::CUSTOM_START`] are

src/hermit.rs

@@ -0,0 +1,31 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Implementation for Hermit
+use crate::Error;
+use hermit_abi::secure_rand64;
+
+pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+    unsafe {
+        let mut chunks = dest.chunks_exact_mut(8);
+        for chunk in &mut chunks {
+            let bytes = secure_rand64()
+                .ok_or(Error::HERMIT_NO_HARDWARE)?
+                .to_ne_bytes();
+            chunk.copy_from_slice(&bytes);
+        }
+        let rem = chunks.into_remainder();
+        if !rem.is_empty() {
+            let bytes = secure_rand64()
+                .ok_or(Error::HERMIT_NO_HARDWARE)?
+                .to_ne_bytes();
+            rem.copy_from_slice(&bytes[..rem.len()]);
+        }
+    }
+    Ok(())
+}

src/lib.rs

@@ -26,6 +26,7 @@
 //! | Redox             | `*‑redox`          | [`rand:`][12]
 //! | CloudABI          | `*‑cloudabi`       | [`cloudabi_sys_random_get`][13]
 //! | Haiku             | `*‑haiku`          | `/dev/random` (identical to `/dev/urandom`)
+//! | Hermit            | `*-hermit`         | [`secure_rand64`][24]
 //! | SGX               | `x86_64‑*‑sgx`     | [RDRAND][18]
 //! | VxWorks           | `*‑wrs‑vxworks‑*`  | `randABytes` after checking entropy pool initialization with `randSecure`
 //! | Emscripten        | `*‑emscripten`     | `/dev/random` (identical to `/dev/urandom`)
@@ -144,6 +145,7 @@
 //! [21]: https://www.freebsd.org/cgi/man.cgi?query=getrandom&manpath=FreeBSD+12.0-stable
 //! [22]: https://docs.microsoft.com/en-us/windows/uwp/
 //! [23]: https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom
+//! [24]: https://hermitcore.github.io/rusty-hermit/hermit_abi/fn.secure_rand64.html
 
 #![doc(
     html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
@@ -190,6 +192,8 @@ cfg_if! {
         #[path = "cloudabi.rs"] mod imp;
     } else if #[cfg(target_os = "fuchsia")] {
         #[path = "fuchsia.rs"] mod imp;
+    } else if #[cfg(target_os = "hermit")] {
+        #[path = "hermit.rs"] mod imp;
     } else if #[cfg(target_os = "ios")] {
         #[path = "ios.rs"] mod imp;
     } else if #[cfg(target_os = "macos")] {