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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 2B537C4321A for ; Fri, 28 Jun 2019 09:35:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 046EC20665 for ; Fri, 28 Jun 2019 09:35:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726567AbfF1Jff (ORCPT ); Fri, 28 Jun 2019 05:35:35 -0400 Received: from foss.arm.com ([217.140.110.172]:43706 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726420AbfF1Jff (ORCPT ); Fri, 28 Jun 2019 05:35:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 97EB928; Fri, 28 Jun 2019 02:35:34 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 27E9F3F718; Fri, 28 Jun 2019 02:35:32 -0700 (PDT) Date: Fri, 28 Jun 2019 10:35:30 +0100 From: Mark Rutland To: Hsin-Yi Wang Cc: linux-arm-kernel@lists.infradead.org, Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Frank Rowand , Catalin Marinas , Will Deacon , Andrew Morton , Mike Rapoport , Ard Biesheuvel , Miles Chen , James Morse , Andrew Murray , Jun Yao , Yu Zhao , Robin Murphy , Laura Abbott , Stephen Boyd , Kees Cook Subject: Re: [PATCH v6 2/3] fdt: add support for rng-seed Message-ID: <20190628093529.GB36437@lakrids.cambridge.arm.com> References: <20190612043258.166048-1-hsinyi@chromium.org> <20190612043258.166048-3-hsinyi@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190612043258.166048-3-hsinyi@chromium.org> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 12, 2019 at 12:33:00PM +0800, Hsin-Yi Wang wrote: > Introducing a chosen node, rng-seed, which is an entropy that can be > passed to kernel called very early to increase initial device > randomness. Bootloader should provide this entropy and the value is > read from /chosen/rng-seed in DT. Could you please elaborate on this? * What is this initial entropy used by, and why is this important? I assume that devices which can populate this will have a HW RNG that the kernel will eventually make use of. * How much entropy is necessary or sufficient? * Why is the DT the right mechanism for this? Thanks, Mark. > > Signed-off-by: Hsin-Yi Wang > Reviewed-by: Stephen Boyd > --- > change log v5->v6: > * remove Documentation change > --- > drivers/of/fdt.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > index 3d36b5afd9bd..369130dbd42c 100644 > --- a/drivers/of/fdt.c > +++ b/drivers/of/fdt.c > @@ -24,6 +24,7 @@ > #include > #include > #include > +#include > > #include /* for COMMAND_LINE_SIZE */ > #include > @@ -1052,6 +1053,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname, > { > int l; > const char *p; > + const void *rng_seed; > > pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname); > > @@ -1086,6 +1088,14 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname, > > pr_debug("Command line is: %s\n", (char*)data); > > + rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l); > + if (rng_seed && l > 0) { > + add_device_randomness(rng_seed, l); > + > + /* try to clear seed so it won't be found. */ > + fdt_nop_property(initial_boot_params, node, "rng-seed"); > + } > + > /* break now */ > return 1; > } > -- > 2.20.1 >