[rng] Add RDRAND as an entropy source

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/arch/x86/include/ipxe/rdrand.h b/src/arch/x86/include/ipxe/rdrand.h
new file mode 100644
index 000000000..c9c170fb0
--- /dev/null
+++ b/src/arch/x86/include/ipxe/rdrand.h
@@ -0,0 +1,37 @@
+#ifndef _IPXE_RDRAND_H
+#define _IPXE_RDRAND_H
+
+/** @file
+ *
+ * Hardware random number generator
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/drbg.h>
+
+#ifdef ENTROPY_RDRAND
+#define ENTROPY_PREFIX_rdrand
+#else
+#define ENTROPY_PREFIX_rdrand __rdrand_
+#endif
+
+/**
+ * min-entropy per sample
+ *
+ * @ret min_entropy	min-entropy of each sample
+ */
+static inline __always_inline min_entropy_t
+ENTROPY_INLINE ( rdrand, min_entropy_per_sample ) ( void ) {
+
+	/* Data returned by RDRAND is theoretically full entropy, up
+	 * to a security strength of 128 bits.
+	 */
+	if ( DRBG_SECURITY_STRENGTH > 128 )
+		return 0;
+	return MIN_ENTROPY ( 8 * sizeof ( noise_sample_t ) );
+}
+
+#endif /* _IPXE_RDRAND_H */