Add support for the Nintendo 3DS (armv6k-nintendo-3ds) (#248)

Author: AzureMarker

.github/workflows/tests.yml

@@ -316,6 +316,8 @@ jobs:
         run: cargo build -Z build-std=core --target=x86_64-wrs-vxworks
       - name: SOLID
         run: cargo build -Z build-std=core --target=aarch64-kmc-solid_asp3
+      - name: Nintendo 3DS
+        run: cargo build -Z build-std=core --target=armv6k-nintendo-3ds
 
   clippy-fmt:
     name: Clippy + rustfmt

Cargo.toml

@@ -18,7 +18,7 @@ compiler_builtins = { version = "0.1", optional = true }
 core = { version = "1.0", optional = true, package = "rustc-std-workspace-core" }
 
 [target.'cfg(unix)'.dependencies]
-libc = { version = "0.2.64", default-features = false }
+libc = { version = "0.2.120", default-features = false }
 
 [target.'cfg(target_os = "wasi")'.dependencies]
 wasi = "0.10"

src/3ds.rs

@@ -0,0 +1,17 @@
+// Copyright 2021 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 Nintendo 3DS
+use crate::util_libc::sys_fill_exact;
+use crate::Error;
+
+pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+    sys_fill_exact(dest, |buf| unsafe {
+        libc::getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
+    })
+}

src/lib.rs

@@ -33,6 +33,7 @@
 //! | Web Browser       | `wasm32‑*‑unknown` | [`Crypto.getRandomValues`], see [WebAssembly support]
 //! | Node.js           | `wasm32‑*‑unknown` | [`crypto.randomBytes`], see [WebAssembly support]
 //! | SOLID             | `*-kmc-solid_*`    | `SOLID_RNG_SampleRandomBytes`
+//! | Nintendo 3DS      | `armv6k-nintendo-3ds` | [`getrandom`][1]
 //!
 //! There is no blanket implementation on `unix` targets that reads from
 //! `/dev/urandom`. This ensures all supported targets are using the recommended
@@ -223,6 +224,11 @@ cfg_if! {
     } else if #[cfg(all(feature = "js",
                         target_arch = "wasm32", target_os = "unknown"))] {
         #[path = "js.rs"] mod imp;
+    } else if #[cfg(all(target_os = "horizon", target_arch = "arm"))] {
+        // We check for target_arch = "arm" because the Nintendo Switch also
+        // uses Horizon OS (it is aarch64).
+        mod util_libc;
+        #[path = "3ds.rs"] mod imp;
     } else if #[cfg(feature = "custom")] {
         use custom as imp;
     } else if #[cfg(all(target_arch = "wasm32", target_os = "unknown"))] {

src/util_libc.rs

@@ -20,6 +20,12 @@ cfg_if! {
         use libc::__error as errno_location;
     } else if #[cfg(target_os = "haiku")] {
         use libc::_errnop as errno_location;
+    } else if #[cfg(all(target_os = "horizon", target_arch = "arm"))] {
+        extern "C" {
+            // Not provided by libc: https://github.com/rust-lang/libc/issues/1995
+            fn __errno() -> *mut libc::c_int;
+        }
+        use __errno as errno_location;
     }
 }