1 files changed, 21 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/src/hermit.rs b/third_party/rust/getrandom/src/hermit.rs
new file mode 100644
index 0000000000..570b03d9a5
--- /dev/null
+++ b/third_party/rust/getrandom/src/hermit.rs
@@ -0,0 +1,21 @@
+use crate::Error;
+use core::{cmp::min, mem::MaybeUninit, num::NonZeroU32};
+
+extern "C" {
+    fn sys_read_entropy(buffer: *mut u8, length: usize, flags: u32) -> isize;
+}
+
+pub fn getrandom_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    while !dest.is_empty() {
+        let res = unsafe { sys_read_entropy(dest.as_mut_ptr() as *mut u8, dest.len(), 0) };
+        if res < 0 {
+            // SAFETY: all Hermit error codes use i32 under the hood:
+            // https://github.com/hermitcore/libhermit-rs/blob/master/src/errno.rs
+            let code = unsafe { NonZeroU32::new_unchecked((-res) as u32) };
+            return Err(code.into());
+        }
+        let len = min(res as usize, dest.len());
+        dest = &mut dest[len..];
+    }
+    Ok(())
+}