From patchwork Wed Apr 13 11:54:04 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: 12811952 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 83255C433EF for ; Wed, 13 Apr 2022 11:58:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=uKt6HLQXeM9ZK5whXmcx8FE/1zlmuelAd2HLdUo2yBM=; b=vStZkgVKURbUIQ skdhoavg1J+Oa9RPWEDOQSEgXzNaYSt/pmz8kKIk3Tvjhqs5QLNlEMWIRWPL8ud+ami/Ksg+SqIcF HcBZ2u6+oY4w7Y4SVR4xUtUy9/Heqb8TiXki7d4PGiwkVJ0vbKar72XlTOwEpICK6t8qgMsIULYj7 K+lasiovhBqKclBAjHnq0odQYccgUHv58EahKZKZR4n8kK+Ex/RiWWhThKvXhskAQxdxZLERXA7kc jfoVOqW94dUnwFBROX1hsgKJK/rOCdx48XJ4Nl2iGhacrZPgUxODeR5toPFSwpf0UcYAfxDOjF5SH l251qPJAdhe0tt2zcxbw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nebc6-000pxf-Um; Wed, 13 Apr 2022 11:56:47 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nebaZ-000p36-3U; Wed, 13 Apr 2022 11:55:12 +0000 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 dfw.source.kernel.org (Postfix) with ESMTPS id 9767561E02; Wed, 13 Apr 2022 11:55:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27237C385A4; Wed, 13 Apr 2022 11:55:06 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="C2i/j6CO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1649850905; 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=IHzRJmPvA7OgZjJx+ZTbqcYHIM/uCZIijqXsNo6FZ2U=; b=C2i/j6COYrH2Ir/9YfejGPtCEir9fLD3flKTNzWxM3qtFKGfSSvDfd7Id1ygvKepoM/pol Ki+JEztNXLkml4iO4CuGyueab/W/2Sh2YlsHRyldHvXhCd9zlKZyZklBEK6Qj8S9W7+Lc6 9hBIabkwBgsudPJcl+vU3Bd5hRFaD68= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 5b8e3e5e (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 13 Apr 2022 11:55:04 +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" , Theodore Ts'o , Dominik Brodowski , Russell King , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Thomas Bogendoerfer , Paul Walmsley , Palmer Dabbelt , Albert Ou , "David S . Miller" , Richard Weinberger , Anton Ivanov , Johannes Berg , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Chris Zankel , Max Filippov , John Stultz , Stephen Boyd , Dinh Nguyen , linux-arm-kernel@lists.infradead.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, x86@kernel.org, linux-xtensa@linux-xtensa.org Subject: [PATCH v4 04/11] mips: use fallback for random_get_entropy() instead of zero Date: Wed, 13 Apr 2022 13:54:04 +0200 Message-Id: <20220413115411.21489-5-Jason@zx2c4.com> In-Reply-To: <20220413115411.21489-1-Jason@zx2c4.com> References: <20220413115411.21489-1-Jason@zx2c4.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220413_045511_292645_7CE64976 X-CRM114-Status: GOOD ( 16.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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: Thomas Bogendoerfer Signed-off-by: Jason A. Donenfeld Acked-by: Thomas Bogendoerfer --- arch/mips/include/asm/timex.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/include/asm/timex.h b/arch/mips/include/asm/timex.h index b05bb70a2e46..abc60a6395e3 100644 --- a/arch/mips/include/asm/timex.h +++ b/arch/mips/include/asm/timex.h @@ -94,7 +94,7 @@ static inline unsigned long random_get_entropy(void) else if (likely(imp != PRID_IMP_R6000 && imp != PRID_IMP_R6000A)) return read_c0_random(); else - return 0; /* no usable register */ + return random_get_entropy_fallback(); /* no usable register */ } #define random_get_entropy random_get_entropy