test host randomness access

Author: RalfJung

tests/run-pass/communication.rs renamed to tests/run-pass/env-without-isolation.rs

@@ -0,0 +1,18 @@
+// Unfortunately, compiletest_rs does not support 'only-linux',
+// so we need to ignore Windows and macOS instead.
+// ignore-macos: Uses Linux-only APIs
+// ignore-windows: Uses Linux-only APIs
+// compile-flags: -Zmiri-disable-isolation
+#![feature(rustc_private)]
+extern crate libc;
+
+fn main() {
+    let mut buf = [0u8; 5];
+    unsafe {
+        assert_eq!(libc::syscall(libc::SYS_getrandom, 0 as *mut libc::c_void, 0 as libc::size_t, 0 as libc::c_uint), 0);
+        assert_eq!(libc::syscall(libc::SYS_getrandom, buf.as_mut_ptr() as *mut libc::c_void, 5 as libc::size_t, 0 as libc::c_uint), 5);
+
+        assert_eq!(libc::getrandom(0 as *mut libc::c_void, 0 as libc::size_t, 0 as libc::c_uint), 0);
+        assert_eq!(libc::getrandom(buf.as_mut_ptr() as *mut libc::c_void, 5 as libc::size_t, 0 as libc::c_uint), 5);
+    }
+}