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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64B17C433F5 for ; Mon, 23 May 2022 13:57:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236812AbiEWN5E (ORCPT ); Mon, 23 May 2022 09:57:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236786AbiEWN5C (ORCPT ); Mon, 23 May 2022 09:57:02 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4D70562D4; Mon, 23 May 2022 06:57:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 661FFB810BF; Mon, 23 May 2022 13:57:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67746C385AA; Mon, 23 May 2022 13:56:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1653314219; bh=bLx74LGCuJSrln4gwnEZH4RTmeZooGdfAbU6lFv4YMg=; h=Date:Subject:To:References:From:In-Reply-To:From; b=VsVmeth4WWMB62LFq9A8lhVFWoTQsy49D0ojuW4tEM4Esw4fs7J1VKmYNWBdVpKo5 qkcyTa4bRf9QnIXtmAsCoYH48nRk0YNOqxPfi3opDtVIZvPuBmyj1a0AvT0yjLMeDu dCe/RlqoSHQcR5QKac3fLBUth/G7O7FE6nk8QInKmFROLLZFBpnVe/WGiQe41M0plk SIG8tVj6dViIzbs0TtLycqWIiuQyG66iguCNyVTiapQZxBuJZKRpyjQJcwzXetvgZH jtvRUxd9jPr7b1haA7sr/8YFhdpuwhA9BAid8ZgAVP8VaO6JC0EIY1FTAg8xsCWZ4c HXFeEMCp7ozLg== Message-ID: <1a6535c7-df9c-1e08-8818-b8cd2c6d8fc2@kernel.org> Date: Mon, 23 May 2022 08:56:56 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v6 12/17] nios2: use fallback for random_get_entropy() instead of zero Content-Language: en-US To: "Jason A. Donenfeld" , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, tglx@linutronix.de, arnd@arndb.de References: <20220423212623.1957011-1-Jason@zx2c4.com> <20220423212623.1957011-13-Jason@zx2c4.com> From: Dinh Nguyen In-Reply-To: <20220423212623.1957011-13-Jason@zx2c4.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On 4/23/22 16:26, Jason A. Donenfeld wrote: > In the event that random_get_entropy() can't access a cycle counter or > similar, falling back to returning 0 is really not the best we can do. > Instead, at least calling random_get_entropy_fallback() would be > preferable, because that always needs to return _something_, even > falling back to jiffies eventually. It's not as though > random_get_entropy_fallback() is super high precision or guaranteed to > be entropic, but basically anything that's not zero all the time is > better than returning zero all the time. > > Cc: Thomas Gleixner > Cc: Arnd Bergmann > Cc: Dinh Nguyen > Signed-off-by: Jason A. Donenfeld > --- > arch/nios2/include/asm/timex.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/nios2/include/asm/timex.h b/arch/nios2/include/asm/timex.h > index a769f871b28d..40a1adc9bd03 100644 > --- a/arch/nios2/include/asm/timex.h > +++ b/arch/nios2/include/asm/timex.h > @@ -8,5 +8,8 @@ > typedef unsigned long cycles_t; > > extern cycles_t get_cycles(void); > +#define get_cycles get_cycles > + > +#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback()) > > #endif Acked-by: Dinh Nguyen