From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E624C38A2A for ; Fri, 8 May 2020 11:49:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E092C2145D for ; Fri, 8 May 2020 11:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726636AbgEHLtm (ORCPT ); Fri, 8 May 2020 07:49:42 -0400 Received: from mail.thorsis.com ([92.198.35.195]:59647 "EHLO mail.thorsis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726618AbgEHLtm (ORCPT ); Fri, 8 May 2020 07:49:42 -0400 X-Greylist: delayed 563 seconds by postgrey-1.27 at vger.kernel.org; Fri, 08 May 2020 07:49:41 EDT Received: from localhost (localhost [127.0.0.1]) by mail.thorsis.com (Postfix) with ESMTP id CA36D2A4F for ; Fri, 8 May 2020 13:40:16 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.thorsis.com Received: from mail.thorsis.com ([127.0.0.1]) by localhost (mail.thorsis.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id wqVJSZUIiQHo for ; Fri, 8 May 2020 13:40:12 +0200 (CEST) Received: by mail.thorsis.com (Postfix, from userid 109) id A1BDD29B3; Fri, 8 May 2020 13:40:12 +0200 (CEST) From: Alexander Dahl To: linux-crypto@vger.kernel.org Cc: Stephan =?ISO-8859-1?Q?M=FCller?= Subject: jitterentropy_rng on armv5 embedded target Date: Fri, 08 May 2020 13:40:08 +0200 Message-ID: <2567555.LKkejuagh6@ada> Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Hello, after upgrading OpenSSL to 1.1.1g on an armv5 based embedded target I had a= =20 deeper look into entropy generation for that device and stumbled over the i= n=20 kernel 'jitterentropy_rng' module. As far as I understood it's supposed to do the same as the well known=20 'haveged' or the userspace daemon 'jitterentropy-rngd' by Stephan M=FCller = [1],=20 right? (Although those daemons would solve my problem, I currently try to=20 avoid them, because memory on my platform is very restricted and every=20 additional running userspace process costs at least around 1 MB.) If so, then how is it supposed to be set up? I built it for 4.9.x LTS, but= =20 after loading it with 'modprobe' I see nothing in the kernel log and there'= s=20 no significant change in /proc/sys/kernel/random/entropy_avail (stays well= =20 below 100 most of the time). Isn't that module supposed to gather entropy f= rom=20 cpu timing jitter? Puzzled Alex [1] https://www.chronox.de/jent.html