x86, random: Verify RDRAND functionality and allow it to be disabled (49d859d7) · Commits · 戴 / test

Documentation/kernel-parameters.txt

+5 −0

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		@@ -1764,6 +1764,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.

		noresidual [PPC] Don't use residual data on PReP machines.

		nordrand [X86] Disable the direct use of the RDRAND
		instruction even if it is supported by the
		processor. RDRAND is still available to user
		space applications.

		noresume [SWSUSP] Disables resume and restores original swap
		space.

arch/x86/include/asm/archrandom.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -70,4 +70,6 @@ GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);

		#endif /* CONFIG_ARCH_RANDOM */

		extern void x86_init_rdrand(struct cpuinfo_x86 *c);

		#endif /* ASM_X86_ARCHRANDOM_H */

arch/x86/kernel/cpu/Makefile

+1 −0

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		@@ -15,6 +15,7 @@ CFLAGS_common.o := $(nostackp)
		obj-y := intel_cacheinfo.o scattered.o topology.o
		obj-y += proc.o capflags.o powerflags.o common.o
		obj-y += vmware.o hypervisor.o sched.o mshyperv.o
		obj-y += rdrand.o

		obj-$(CONFIG_X86_32) += bugs.o
		obj-$(CONFIG_X86_64) += bugs_64.o

arch/x86/kernel/cpu/common.c

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Original line number	Diff line number	Diff line
		@@ -15,6 +15,7 @@
		#include <asm/stackprotector.h>
		#include <asm/perf_event.h>
		#include <asm/mmu_context.h>
		#include <asm/archrandom.h>
		#include <asm/hypervisor.h>
		#include <asm/processor.h>
		#include <asm/sections.h>
		@@ -857,6 +858,7 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
		#endif

		init_hypervisor(c);
		x86_init_rdrand(c);

		/*
		* Clear/Set all flags overriden by options, need do it

arch/x86/kernel/cpu/rdrand.c

0 → 100644

+73 −0

Original line number	Diff line number	Diff line
		/*
		* 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);
		return 1;
		}
		__setup("nordrand", x86_rdrand_setup);

		/* We can't use arch_get_random_long() here since alternatives haven't run */
		static inline int rdrand_long(unsigned long *v)
		{
		int ok;
		asm volatile("1: " RDRAND_LONG "\n\t"
		"jc 2f\n\t"
		"decl %0\n\t"
		"jnz 1b\n\t"
		"2:"
		: "=r" (ok), "=a" (*v)
		: "0" (RDRAND_RETRY_LOOPS));
		return ok;
		}

		/*
		* 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 __cpuinit 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
		}

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