From patchwork Sat Apr 23 21:26:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 565804 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 C22ADC433F5 for ; Sat, 23 Apr 2022 21:28:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237212AbiDWVbm (ORCPT ); Sat, 23 Apr 2022 17:31:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237247AbiDWVbD (ORCPT ); Sat, 23 Apr 2022 17:31:03 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A22135DE1; Sat, 23 Apr 2022 14:27:37 -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 169BAB80D67; Sat, 23 Apr 2022 21:27:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08187C385A0; Sat, 23 Apr 2022 21:27:33 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="MSYQwMzg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1650749253; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YrlrsyxX3sZtzfHNKb7mYg+twm6XjlLCpZCvOEwIgSU=; b=MSYQwMzgIpC6YbxDKPWXfTD4jWLjHswJbBAN+ATkmr1lT1ocWvery8XGXzhBpoyw1qCYD3 Eg3XvfWI5qXOEjI4gnSgqfSAhcHyykC7szHgryMCTX1vHcE+FfC8cmWQ2pkeLKTX6mQlDE 9FAfLbA4u3ZheDVeQ+XZGEKfP3VhOz8= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id d31ac3b4 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Sat, 23 Apr 2022 21:27:33 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, tglx@linutronix.de, arnd@arndb.de Cc: "Jason A. Donenfeld" , Jonas Bonn , Stefan Kristiansson , Stafford Horne Subject: [PATCH v6 11/17] openrisc: use fallback for random_get_entropy() instead of zero Date: Sat, 23 Apr 2022 23:26:17 +0200 Message-Id: <20220423212623.1957011-12-Jason@zx2c4.com> In-Reply-To: <20220423212623.1957011-1-Jason@zx2c4.com> References: <20220423212623.1957011-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org 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: Jonas Bonn Cc: Stefan Kristiansson Cc: Stafford Horne Signed-off-by: Jason A. Donenfeld --- arch/openrisc/include/asm/timex.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/openrisc/include/asm/timex.h b/arch/openrisc/include/asm/timex.h index d52b4e536e3f..115e89b336cd 100644 --- a/arch/openrisc/include/asm/timex.h +++ b/arch/openrisc/include/asm/timex.h @@ -23,6 +23,9 @@ static inline cycles_t get_cycles(void) { return mfspr(SPR_TTCR); } +#define get_cycles get_cycles + +#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback()) /* This isn't really used any more */ #define CLOCK_TICK_RATE 1000