mirror of
https://github.com/torvalds/linux.git
synced 2024-12-27 05:11:48 +00:00
d20f78d252
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>
134 lines
3.6 KiB
C
134 lines
3.6 KiB
C
/*
|
|
* This file is part of the Linux kernel.
|
|
*
|
|
* Copyright (c) 2011-2014, 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.
|
|
*
|
|
*/
|
|
|
|
#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"
|
|
#define RDSEED_INT ".byte 0x0f,0xc7,0xf8"
|
|
#ifdef CONFIG_X86_64
|
|
# define RDRAND_LONG ".byte 0x48,0x0f,0xc7,0xf0"
|
|
# define RDSEED_LONG ".byte 0x48,0x0f,0xc7,0xf8"
|
|
#else
|
|
# define RDRAND_LONG RDRAND_INT
|
|
# define RDSEED_LONG RDSEED_INT
|
|
#endif
|
|
|
|
#ifdef CONFIG_ARCH_RANDOM
|
|
|
|
/* 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;
|
|
}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
#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; \
|
|
}
|
|
|
|
#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; \
|
|
}
|
|
|
|
#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_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);
|
|
|
|
#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);
|
|
|
|
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);
|
|
|
|
#endif /* CONFIG_X86_64 */
|
|
|
|
#else
|
|
|
|
static inline int rdrand_long(unsigned long *v)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline bool rdseed_long(unsigned long *v)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
#endif /* CONFIG_ARCH_RANDOM */
|
|
|
|
extern void x86_init_rdrand(struct cpuinfo_x86 *c);
|
|
|
|
#endif /* ASM_X86_ARCHRANDOM_H */
|