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linux-next/arch/x86/include/asm/archrandom.h

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x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
/*
* This file is part of the Linux kernel.
*
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
* Copyright (c) 2011-2014, Intel Corporation
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
* 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.
*
*/
#ifndef ASM_X86_ARCHRANDOM_H
#define ASM_X86_ARCHRANDOM_H
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/alternative.h>
#include <asm/nops.h>
#define RDRAND_RETRY_LOOPS 10
#define RDRAND_INT ".byte 0x0f,0xc7,0xf0"
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
#define RDSEED_INT ".byte 0x0f,0xc7,0xf8"
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#ifdef CONFIG_X86_64
# define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0"
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
# define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8"
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#else
# define RDRAND_LONG RDRAND_INT
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
# define RDSEED_LONG RDSEED_INT
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#endif
#ifdef CONFIG_ARCH_RANDOM
x86, kaslr: Provide randomness functions Adds potential sources of randomness: RDRAND, RDTSC, or the i8254. This moves the pre-alternatives inline rdrand function into the header so both pieces of code can use it. Availability of RDRAND is then controlled by CONFIG_ARCH_RANDOM, if someone wants to disable it even for kASLR. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/1381450698-28710-4-git-send-email-keescook@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2013-10-11 08:18:15 +08:00
/* Instead of arch_get_random_long() when 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;
}
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
/* A single attempt at RDSEED */
static inline bool rdseed_long(unsigned long *v)
{
unsigned char ok;
asm volatile(RDSEED_LONG "\n\t"
"setc %0"
: "=qm" (ok), "=a" (*v));
return ok;
}
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#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:", \
X86_FEATURE_RDRAND, \
ASM_OUTPUT2("=r" (ok), "=a" (*v)), \
"0" (RDRAND_RETRY_LOOPS)); \
return ok; \
}
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
#define GET_SEED(name, type, rdseed, nop) \
static inline int name(type *v) \
{ \
unsigned char ok; \
alternative_io("movb $0, %0\n\t" \
nop, \
rdseed "\n\t" \
"setc %0", \
X86_FEATURE_RDSEED, \
ASM_OUTPUT2("=q" (ok), "=a" (*v))); \
return ok; \
}
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#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);
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP5);
GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#else
GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
GET_SEED(arch_get_random_seed_long, unsigned long, RDSEED_LONG, ASM_NOP4);
GET_SEED(arch_get_random_seed_int, unsigned int, RDSEED_INT, ASM_NOP4);
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#endif /* CONFIG_X86_64 */
x86, kaslr: Provide randomness functions Adds potential sources of randomness: RDRAND, RDTSC, or the i8254. This moves the pre-alternatives inline rdrand function into the header so both pieces of code can use it. Availability of RDRAND is then controlled by CONFIG_ARCH_RANDOM, if someone wants to disable it even for kASLR. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/1381450698-28710-4-git-send-email-keescook@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2013-10-11 08:18:15 +08:00
#else
static inline int rdrand_long(unsigned long *v)
{
return 0;
}
x86, random: Enable the RDSEED instruction Upcoming Intel silicon adds a new RDSEED instruction, which is similar to RDRAND but provides a stronger guarantee: unlike RDRAND, RDSEED will always reseed the PRNG from the true random number source between each read. Thus, the output of RDSEED is guaranteed to be 100% entropic, unlike RDRAND which is only architecturally guaranteed to be 1/512 entropic (although in practice is much more.) The RDSEED instruction takes the same time to execute as RDRAND, but RDSEED unlike RDRAND can legitimately return failure (CF=0) due to entropy exhaustion if too many threads on too many cores are hammering the RDSEED instruction at the same time. Therefore, we have to be more conservative and only use it in places where we can tolerate failures. This patch introduces the primitives arch_get_random_seed_{int,long}() but does not use it yet. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2014-03-18 07:36:27 +08:00
static inline bool rdseed_long(unsigned long *v)
{
return 0;
}
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#endif /* CONFIG_ARCH_RANDOM */
x86, random: Verify RDRAND functionality and allow it to be disabled If the CPU declares that RDRAND is available, go through a guranteed reseed sequence, and make sure that it is actually working (producing data.) If it does not, disable the CPU feature flag. Allow RDRAND to be disabled on the command line (as opposed to at compile time) for a user who has special requirements with regards to random numbers. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Matt Mackall <mpm@selenic.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "Theodore Ts'o" <tytso@mit.edu>
2011-08-01 05:02:19 +08:00
extern void x86_init_rdrand(struct cpuinfo_x86 *c);
x86, random: Architectural inlines to get random integers with RDRAND 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>
2011-08-01 04:59:29 +08:00
#endif /* ASM_X86_ARCHRANDOM_H */
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