From 11826ca46ce135473d84e2abeff83916526301e2 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 12 Apr 2019 11:35:24 +0200
Subject: [efi] Put rdrand workaround in sep. function

---
 src/interface/efi/efi_entropy.c | 57 +++++++++++++++++++++++++----------------
 1 file changed, 35 insertions(+), 22 deletions(-)

(limited to 'src/interface')

diff --git a/src/interface/efi/efi_entropy.c b/src/interface/efi/efi_entropy.c
index 2dd231b22..a1dfaaa79 100644
--- a/src/interface/efi/efi_entropy.c
+++ b/src/interface/efi/efi_entropy.c
@@ -125,28 +125,6 @@ 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 ) {
@@ -168,6 +146,40 @@ static int efi_entropy_tick ( void ) {
 	return low;
 }
 
+/**
+ * Get noise sample from rdrand
+ *
+ * @ret noise		Noise sample
+ * @ret rc		Return status code
+ */
+static int efi_get_noise_rdrand ( noise_sample_t *noise ) {
+#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 ) {
+				*noise = ret;
+				return 0;
+			}
+		}
+		return -EBUSY;
+	}
+#endif
+	return -ENOTSUP;
+}
+
 /**
  * Get noise sample from timer ticks
  *
@@ -244,6 +256,7 @@ static int efi_get_noise ( noise_sample_t *noise ) {
 
 	/* Try RNG first, falling back to timer ticks */
 	if ( ( ( rc = efi_get_noise_rng ( noise ) ) != 0 ) &&
+	     ( ( rc = efi_get_noise_rdrand ( noise ) ) != 0 ) &&
 	     ( ( rc = efi_get_noise_ticks ( noise ) ) != 0 ) )
 		return rc;
 
-- 
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