Message ID | 20220408182145.142506-7-Jason@zx2c4.com |
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State | New |
Headers | show
Return-Path: <SRS0=wl4N=US=vger.kernel.org=sparclinux-owner@ozlabs.org> X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=zx2c4.com header.i=@zx2c4.com header.a=rsa-sha256 header.s=20210105 header.b=CLPULdzg; dkim-atps=neutral Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KZmpD3gx6z9sG3 for <incoming@patchwork.ozlabs.org>; Sat, 9 Apr 2022 04:23:16 +1000 (AEST) Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4KZmpD3CC1z4xdc for <incoming@patchwork.ozlabs.org>; Sat, 9 Apr 2022 04:23:16 +1000 (AEST) Received: by gandalf.ozlabs.org (Postfix) id 4KZmpD36vcz4xdf; Sat, 9 Apr 2022 04:23:16 +1000 (AEST) Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: gandalf.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=2620:137:e000::1:20; helo=out1.vger.email; envelope-from=sparclinux-owner@vger.kernel.org; receiver=<UNKNOWN>) Authentication-Results: gandalf.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=zx2c4.com header.i=@zx2c4.com header.a=rsa-sha256 header.s=20210105 header.b=CLPULdzg; dkim-atps=neutral Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4KZmpD2yPbz4xdc for <patchwork-incoming@ozlabs.org>; Sat, 9 Apr 2022 04:23:16 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238624AbiDHSZS (ORCPT <rfc822;patchwork-incoming@ozlabs.org>); Fri, 8 Apr 2022 14:25:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238615AbiDHSZK (ORCPT <rfc822;sparclinux@vger.kernel.org>); Fri, 8 Apr 2022 14:25:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49D8938237B; Fri, 8 Apr 2022 11:23:04 -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 dfw.source.kernel.org (Postfix) with ESMTPS id D981C621E6; Fri, 8 Apr 2022 18:23:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99E13C385A3; Fri, 8 Apr 2022 18:22:59 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="CLPULdzg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1649442178; 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=QhQ1HwDDQ0VBViTeG0LB+139Jo2Xk5438IuvpR3RiNg=; b=CLPULdzgGXJrwK4uCCHM7+j7CQPO/TnUdFHV8jGVPXt2oRPuFGfQuIGVwrwhQmuAXIEyIK +pMFaA2OsSQLAz2u75tmYrg486K8df6y/V/MHRdhzu90z8Dl9A4EKbCnoFVpvWCWqoNp4p IgJX3Y50X9yQA9wOGJqYKrd+/9+6GG8= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 2adbe4d1 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Fri, 8 Apr 2022 18:22:58 +0000 (UTC) From: "Jason A. Donenfeld" <Jason@zx2c4.com> To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, arnd@arndb.de Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>, Theodore Ts'o <tytso@mit.edu>, Dominik Brodowski <linux@dominikbrodowski.net>, Russell King <linux@armlinux.org.uk>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Geert Uytterhoeven <geert@linux-m68k.org>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, "David S . Miller" <davem@davemloft.net>, Richard Weinberger <richard@nod.at>, Anton Ivanov <anton.ivanov@cambridgegreys.com>, Johannes Berg <johannes@sipsolutions.net>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "H . Peter Anvin" <hpa@zytor.com>, Chris Zankel <chris@zankel.net>, Max Filippov <jcmvbkbc@gmail.com>, John Stultz <john.stultz@linaro.org>, Stephen Boyd <sboyd@kernel.org>, 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 RFC v1 06/10] x86: use sched_clock() for random_get_entropy() instead of zero Date: Fri, 8 Apr 2022 20:21:41 +0200 Message-Id: <20220408182145.142506-7-Jason@zx2c4.com> In-Reply-To: <20220408182145.142506-1-Jason@zx2c4.com> References: <20220408182145.142506-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <sparclinux.vger.kernel.org> X-Mailing-List: sparclinux@vger.kernel.org |
Series |
archs/random: fallback to using sched_clock() if no cycle counter
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expand
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diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 01a300a9700b..b0c0b2b9e0f7 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -5,6 +5,7 @@ #ifndef _ASM_X86_TSC_H #define _ASM_X86_TSC_H +#include <linux/sched/clock.h> #include <asm/processor.h> #include <asm/cpufeature.h> @@ -28,6 +29,16 @@ static inline cycles_t get_cycles(void) return rdtsc(); } +static inline unsigned long random_get_entropy(void) +{ +#ifndef CONFIG_X86_TSC + if (!boot_cpu_has(X86_FEATURE_TSC)) + return sched_clock(); +#endif + return rdtsc(); +} +#define random_get_entropy random_get_entropy + extern struct system_counterval_t convert_art_to_tsc(u64 art); extern struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns);
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 sched_clock() would be preferable, because that always needs to return _something_, even falling back to jiffies eventually. It's not as though sched_clock() 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. If CONFIG_X86_TSC=n, then it's possible that we're running on a 486 with no RDTSC, so we only need the fallback code for that case. Cc: Arnd Bergmann <arnd@arndb.de> Cc: x86@kernel.org Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- arch/x86/include/asm/tsc.h | 11 +++++++++++ 1 file changed, 11 insertions(+)