1 files changed, 32 insertions, 0 deletions
diff --git a/src/crypto/rand/rand_batched.go b/src/crypto/rand/rand_batched.go
new file mode 100644
index 0000000..c267f6a
--- /dev/null
+++ b/src/crypto/rand/rand_batched.go
@@ -0,0 +1,32 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux || freebsd || dragonfly || solaris
+
+package rand
+
+import (
+	"errors"
+	"internal/syscall/unix"
+)
+
+// maxGetRandomRead is platform dependent.
+func init() {
+	altGetRandom = batched(getRandomBatch, maxGetRandomRead)
+}
+
+// If the kernel is too old to support the getrandom syscall(),
+// unix.GetRandom will immediately return ENOSYS and we will then fall back to
+// reading from /dev/urandom in rand_unix.go. unix.GetRandom caches the ENOSYS
+// result so we only suffer the syscall overhead once in this case.
+// If the kernel supports the getrandom() syscall, unix.GetRandom will block
+// until the kernel has sufficient randomness (as we don't use GRND_NONBLOCK).
+// In this case, unix.GetRandom will not return an error.
+func getRandomBatch(p []byte) (err error) {
+	n, err := unix.GetRandom(p, 0)
+	if n != len(p) {
+		return errors.New("short read")
+	}
+	return err
+}