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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/x86/kernel/cpu/rdrand.c
Initial import
Diffstat (limited to 'arch/x86/kernel/cpu/rdrand.c')
-rw-r--r--arch/x86/kernel/cpu/rdrand.c60
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/rdrand.c b/arch/x86/kernel/cpu/rdrand.c
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index 000000000..136ac74de
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+++ b/arch/x86/kernel/cpu/rdrand.c
@@ -0,0 +1,60 @@
+/*
+ * This file is part of the Linux kernel.
+ *
+ * Copyright (c) 2011, Intel Corporation
+ * Authors: Fenghua Yu <fenghua.yu@intel.com>,
+ * H. Peter Anvin <hpa@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <asm/processor.h>
+#include <asm/archrandom.h>
+#include <asm/sections.h>
+
+static int __init x86_rdrand_setup(char *s)
+{
+ setup_clear_cpu_cap(X86_FEATURE_RDRAND);
+ setup_clear_cpu_cap(X86_FEATURE_RDSEED);
+ return 1;
+}
+__setup("nordrand", x86_rdrand_setup);
+
+/*
+ * Force a reseed cycle; we are architecturally guaranteed a reseed
+ * after no more than 512 128-bit chunks of random data. This also
+ * acts as a test of the CPU capability.
+ */
+#define RESEED_LOOP ((512*128)/sizeof(unsigned long))
+
+void x86_init_rdrand(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_ARCH_RANDOM
+ unsigned long tmp;
+ int i, count, ok;
+
+ if (!cpu_has(c, X86_FEATURE_RDRAND))
+ return; /* Nothing to do */
+
+ for (count = i = 0; i < RESEED_LOOP; i++) {
+ ok = rdrand_long(&tmp);
+ if (ok)
+ count++;
+ }
+
+ if (count != RESEED_LOOP)
+ clear_cpu_cap(c, X86_FEATURE_RDRAND);
+#endif
+}