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authorH. Peter Anvin <hpa@zytor.com>2011-07-31 13:59:29 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-21 09:17:12 -0700
commit5faf9fc361bac926a2f9efe6018fdc16c0e7dad8 (patch)
parentb88ac13a3f1ea5666872c343e54ffb3a9667d3f2 (diff)
x86, random: Architectural inlines to get random integers with RDRAND
commit 628c6246d47b85f5357298601df2444d7f4dd3fd upstream. Architectural inlines to get random ints and longs using the RDRAND instruction. Intel has introduced a new RDRAND instruction, a Digital Random Number Generator (DRNG), which is functionally an high bandwidth entropy source, cryptographic whitener, and integrity monitor all built into hardware. This enables RDRAND to be used directly, bypassing the kernel random number pool. For technical documentation, see: http://software.intel.com/en-us/articles/download-the-latest-bull-mountain-software-implementation-guide/ In this patch, this is *only* used for the nonblocking random number pool. RDRAND is a nonblocking source, similar to our /dev/urandom, and is therefore not a direct replacement for /dev/random. The architectural hooks presented in the previous patch only feed the kernel internal users, which only use the nonblocking pool, and so this is not a problem. Since this instruction is available in userspace, there is no reason to have a /dev/hw_rng device driver for the purpose of feeding rngd. This is especially so since RDRAND is a nonblocking source, and needs additional whitening and reduction (see the above technical documentation for details) in order to be of "pure entropy source" quality. The CONFIG_EXPERT compile-time option can be used to disable this use of RDRAND. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Originally-by: Fenghua Yu <fenghua.yu@intel.com> Cc: Matt Mackall <mpm@selenic.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2 files changed, 82 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 37357a599dca..a0e9bda72fda 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1451,6 +1451,15 @@ config ARCH_USES_PG_UNCACHED
def_bool y
depends on X86_PAT
+ def_bool y
+ prompt "x86 architectural random number generator" if EXPERT
+ ---help---
+ Enable the x86 architectural RDRAND instruction
+ (Intel Bull Mountain technology) to generate random numbers.
+ If supported, this is a high bandwidth, cryptographically
+ secure hardware random number generator.
config EFI
bool "EFI runtime service support"
depends on ACPI
diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
new file mode 100644
index 000000000000..b7b5bc02e361
--- /dev/null
+++ b/arch/x86/include/asm/archrandom.h
@@ -0,0 +1,73 @@
+ * 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/cpufeature.h>
+#include <asm/alternative.h>
+#include <asm/nops.h>
+#define RDRAND_INT ".byte 0x0f,0xc7,0xf0"
+#ifdef CONFIG_X86_64
+# define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0"
+#define GET_RANDOM(name, type, rdrand, nop) \
+static inline int name(type *v) \
+{ \
+ int ok; \
+ alternative_io("movl $0, %0\n\t" \
+ nop, \
+ "\n1: " rdrand "\n\t" \
+ "jc 2f\n\t" \
+ "decl %0\n\t" \
+ "jnz 1b\n\t" \
+ "2:", \
+ ASM_OUTPUT2("=r" (ok), "=a" (*v)), \
+ return ok; \
+#ifdef CONFIG_X86_64
+GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
+GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
+GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
+GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
+#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_ARCH_RANDOM */
+#endif /* ASM_X86_ARCHRANDOM_H */