From: Harald Freudenberger Subject: [PATCH 1/2] crypto: hwrng use rng source with best quality Date: Tue, 11 Jul 2017 09:36:22 +0200 Message-ID: <1499758583-14626-2-git-send-email-freude@linux.vnet.ibm.com> References: <1499758583-14626-1-git-send-email-freude@linux.vnet.ibm.com> Cc: herbert@gondor.apana.org.au, arnd@arndb.de, gregkh@linuxfoundation.org, prasannatsmkumar@gmail.com, schwidefsky@de.ibm.com, Harald Freudenberger To: linux-crypto@vger.kernel.org Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34373 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755410AbdGKHhK (ORCPT ); Tue, 11 Jul 2017 03:37:10 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6B7YMqA060392 for ; Tue, 11 Jul 2017 03:37:09 -0400 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0b-001b2d01.pphosted.com with ESMTP id 2bmc7nbdhk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 11 Jul 2017 03:37:09 -0400 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Jul 2017 08:37:07 +0100 In-Reply-To: <1499758583-14626-1-git-send-email-freude@linux.vnet.ibm.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: This patch rewoks the hwrng to always use the rng source with best entropy quality. On registation and unregistration the hwrng now tries to choose the best (= highest quality value) rng source. The handling of the internal list of registered rng sources is now always sorted by quality and the top most rng chosen. Signed-off-by: Harald Freudenberger Reviewed-by: PrasannaKumar Muralidharan --- drivers/char/hw_random/core.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 503a41d..e9dda16 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -29,6 +29,7 @@ static struct hwrng *current_rng; static struct task_struct *hwrng_fill; +/* list of registered rngs, sorted decending by quality */ static LIST_HEAD(rng_list); /* Protects rng_list and current_rng */ static DEFINE_MUTEX(rng_mutex); @@ -417,6 +418,7 @@ int hwrng_register(struct hwrng *rng) { int err = -EINVAL; struct hwrng *old_rng, *tmp; + struct list_head *rng_list_ptr; if (!rng->name || (!rng->data_read && !rng->read)) goto out; @@ -432,14 +434,25 @@ int hwrng_register(struct hwrng *rng) init_completion(&rng->cleanup_done); complete(&rng->cleanup_done); + /* rng_list is sorted by decreasing quality */ + list_for_each(rng_list_ptr, &rng_list) { + tmp = list_entry(rng_list_ptr, struct hwrng, list); + if (tmp->quality < rng->quality) + break; + } + list_add_tail(&rng->list, rng_list_ptr); + old_rng = current_rng; err = 0; - if (!old_rng) { + if (!old_rng || (rng->quality > old_rng->quality)) { + /* + * Set new rng as current as the new rng source + * provides better entropy quality. + */ err = set_current_rng(rng); if (err) goto out_unlock; } - list_add_tail(&rng->list, &rng_list); if (old_rng && !rng->init) { /* @@ -466,12 +479,12 @@ void hwrng_unregister(struct hwrng *rng) list_del(&rng->list); if (current_rng == rng) { drop_current_rng(); + /* rng_list is sorted by quality, use the best (=first) one */ if (!list_empty(&rng_list)) { - struct hwrng *tail; - - tail = list_entry(rng_list.prev, struct hwrng, list); + struct hwrng *new_rng; - set_current_rng(tail); + new_rng = list_entry(rng_list.next, struct hwrng, list); + set_current_rng(new_rng); } } -- 2.7.4