From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id B2F6C1A01E3 for ; Fri, 17 Jul 2015 19:16:09 +1000 (AEST) Date: Fri, 17 Jul 2015 19:15:58 +1000 From: Paul Mackerras To: linuxppc-dev@ozlabs.org Cc: tytso@mit.edu, keescook@chromium.org, hpa@linux.intel.com, mpe@ellerman.id.au, mpm@selenic.com, herbert@gondor.apana.org.au Subject: [PATCH] powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_* Message-ID: <20150717091558.GA5916@iris.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , The hardware RNG on POWER8 and POWER7+ can be relatively slow, since it can only supply one 64-bit value per microsecond. Currently we read it in arch_get_random_long(), but that slows down reading from /dev/urandom since the code in random.c calls arch_get_random_long() for every longword read from /dev/urandom. Since the hardware RNG supplies high-quality entropy on every read, it matches the semantics of arch_get_random_seed_long() better than those of arch_get_random_long(). Therefore this commit makes the code use the POWER8/7+ hardware RNG only for arch_get_random_seed_{long,int} and not for arch_get_random_{long,int}. This won't affect any other PowerPC-based platforms because none of them currently support a hardware RNG. Signed-off-by: Paul Mackerras --- arch/powerpc/include/asm/archrandom.h | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h index 0cc6eed..a4c3f54 100644 --- a/arch/powerpc/include/asm/archrandom.h +++ b/arch/powerpc/include/asm/archrandom.h @@ -7,13 +7,22 @@ static inline int arch_get_random_long(unsigned long *v) { + return 0; +} + +static inline int arch_get_random_int(unsigned int *v) +{ + return 0; +} + +static inline int arch_get_random_seed_long(unsigned long *v) +{ if (ppc_md.get_random_long) return ppc_md.get_random_long(v); return 0; } - -static inline int arch_get_random_int(unsigned int *v) +static inline int arch_get_random_seed_int(unsigned int *v) { unsigned long val; int rc; @@ -27,22 +36,13 @@ static inline int arch_get_random_int(unsigned int *v) static inline int arch_has_random(void) { - return !!ppc_md.get_random_long; -} - -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; } + static inline int arch_has_random_seed(void) { - return 0; + return !!ppc_md.get_random_long; } - #endif /* CONFIG_ARCH_RANDOM */ #ifdef CONFIG_PPC_POWERNV -- 2.1.4