From a58276abdde401bae19525c7c5895c6fbbfc22e2 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 15 Feb 2019 10:38:49 +0100
Subject: [efi] Add very ugly hack to use HW RNG on EFI

This is just added in the completely wrong spot, but makes very slow
initialization on efi go away.
---
 src/interface/efi/efi_entropy.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'src/interface')

diff --git a/src/interface/efi/efi_entropy.c b/src/interface/efi/efi_entropy.c
index 2a2fc9054..2dd231b22 100644
--- a/src/interface/efi/efi_entropy.c
+++ b/src/interface/efi/efi_entropy.c
@@ -30,6 +30,11 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/Protocol/Rng.h>
 
+#if defined(__i386) || defined(__x86_64)
+#include <ipxe/cpuid.h>
+static char have_hwrnd = 0;
+#endif
+
 /** @file
  *
  * EFI entropy source
@@ -120,6 +125,28 @@ static int efi_entropy_tick ( void ) {
 	EFI_STATUS efirc;
 	int rc;
 
+#if defined(__i386) || defined(__x86_64)
+	if ( have_hwrnd == 0 ) {
+		struct x86_features features;
+		x86_features( &features );
+		if ( features.intel.ecx & ( 1 << 30 ) ) {
+			have_hwrnd = 1;
+		} else {
+			have_hwrnd = 2;
+		}
+		DBGC( &tick, "Have RDRAND: %s\n", ( have_hwrnd == 1 ? "YES!" : "NO :-(" ) );
+	}
+	if ( have_hwrnd == 1 ) {
+		int ret, retries = 10;
+		char ok;
+		while ( --retries > 0 ) {
+			__asm__ volatile ( "rdrand %0; setc %1" : "=r" ( ret ), "=qm" ( ok ) );
+			if ( ok )
+				return ret & 0x7fffffff;
+		}
+	}
+#endif
+
 	/* Wait for next timer tick */
 	if ( ( efirc = bs->SetTimer ( tick, TimerRelative,
 				      EFI_ENTROPY_TRIGGER_TIME ) ) != 0 ) {
-- 
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