From d20f78d252778e0fae8f8256e602bd682eb2185c Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 17 Mar 2014 16:36:27 -0700 Subject: 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 Reviewed-by: Ingo Molnar Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Signed-off-by: Theodore Ts'o --- arch/powerpc/include/asm/archrandom.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/powerpc') diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h index d853d163ba47..801beba4e64b 100644 --- a/arch/powerpc/include/asm/archrandom.h +++ b/arch/powerpc/include/asm/archrandom.h @@ -27,6 +27,15 @@ static inline int arch_get_random_int(unsigned int *v) int powernv_get_random_long(unsigned long *v); +static inline int arch_get_random_seed_long(unsigned long *v) +{ + return 0; +} +static inline int arch_get_random_seed_int(unsigned int *v) +{ + return 0; +} + #endif /* CONFIG_ARCH_RANDOM */ #endif /* _ASM_POWERPC_ARCHRANDOM_H */ -- cgit v1.2.1 From 7b878d4b48c4e04b936918bb83836a107ba453b3 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 17 Mar 2014 16:36:30 -0700 Subject: random: Add arch_has_random[_seed]() Add predicate functions for having arch_get_random[_seed]*(). The only current use is to avoid the loop in arch_random_refill() when arch_get_random_seed_long() is unavailable. Signed-off-by: H. Peter Anvin Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Signed-off-by: Theodore Ts'o --- arch/powerpc/include/asm/archrandom.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/powerpc') diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h index 801beba4e64b..bde531103638 100644 --- a/arch/powerpc/include/asm/archrandom.h +++ b/arch/powerpc/include/asm/archrandom.h @@ -25,6 +25,11 @@ static inline int arch_get_random_int(unsigned int *v) return rc; } +static inline int arch_has_random(void) +{ + return !!ppc_md.get_random_long; +} + int powernv_get_random_long(unsigned long *v); static inline int arch_get_random_seed_long(unsigned long *v) @@ -35,6 +40,10 @@ static inline int arch_get_random_seed_int(unsigned int *v) { return 0; } +static inline int arch_has_random_seed(void) +{ + return 0; +} #endif /* CONFIG_ARCH_RANDOM */ -- cgit v1.2.1