From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932885Ab3J1PHq (ORCPT ); Mon, 28 Oct 2013 11:07:46 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:51043 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756944Ab3J1Osr (ORCPT ); Mon, 28 Oct 2013 10:48:47 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Theodore Ts'o" , Luis Henriques Subject: [PATCH 3.5 11/64] random: allow architectures to optionally define random_get_entropy() Date: Mon, 28 Oct 2013 14:47:30 +0000 Message-Id: <1382971703-17393-12-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1382971703-17393-1-git-send-email-luis.henriques@canonical.com> References: <1382971703-17393-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.24 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit 61875f30daf60305712e25b209ef41ced2635bad upstream. Allow architectures which have a disabled get_cycles() function to provide a random_get_entropy() function which provides a fine-grained, rapidly changing counter that can be used by the /dev/random driver. For example, an architecture might have a rapidly changing register used to control random TLB cache eviction, or DRAM refresh that doesn't meet the requirements of get_cycles(), but which is good enough for the needs of the random driver. Signed-off-by: "Theodore Ts'o" Signed-off-by: Luis Henriques --- drivers/char/random.c | 8 ++++---- include/linux/timex.h | 14 ++++++++++++++ 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index e0b3680..08b4e70 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -646,7 +646,7 @@ struct timer_rand_state { */ void add_device_randomness(const void *buf, unsigned int size) { - unsigned long time = get_cycles() ^ jiffies; + unsigned long time = random_get_entropy() ^ jiffies; mix_pool_bytes(&input_pool, buf, size, NULL); mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); @@ -683,7 +683,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) goto out; sample.jiffies = jiffies; - sample.cycles = get_cycles(); + sample.cycles = random_get_entropy(); sample.num = num; mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); @@ -750,7 +750,7 @@ void add_interrupt_randomness(int irq, int irq_flags) struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness); struct pt_regs *regs = get_irq_regs(); unsigned long now = jiffies; - __u32 input[4], cycles = get_cycles(); + __u32 input[4], cycles = random_get_entropy(); input[0] = cycles ^ jiffies; input[1] = irq; @@ -1470,7 +1470,7 @@ unsigned int get_random_int(void) hash = get_cpu_var(get_random_int_hash); - hash[0] += current->pid + jiffies + get_cycles(); + hash[0] += current->pid + jiffies + random_get_entropy(); md5_transform(hash, random_int_secret); ret = hash[0]; put_cpu_var(get_random_int_hash); diff --git a/include/linux/timex.h b/include/linux/timex.h index 99bc88b..a647f36 100644 --- a/include/linux/timex.h +++ b/include/linux/timex.h @@ -173,6 +173,20 @@ struct timex { #include +#ifndef random_get_entropy +/* + * The random_get_entropy() function is used by the /dev/random driver + * in order to extract entropy via the relative unpredictability of + * when an interrupt takes places versus a high speed, fine-grained + * timing source or cycle counter. Since it will be occurred on every + * single interrupt, it must have a very low cost/overhead. + * + * By default we use get_cycles() for this purpose, but individual + * architectures may override this in their asm/timex.h header file. + */ +#define random_get_entropy() get_cycles() +#endif + /* * SHIFT_PLL is used as a dampening factor to define how much we * adjust the frequency correction for a given offset in PLL mode. -- 1.8.3.2