From nobody Sun Feb 8 16:31:56 2026 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 B3423EB64DC for ; Wed, 28 Jun 2023 13:15:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231613AbjF1NPQ (ORCPT ); Wed, 28 Jun 2023 09:15:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231182AbjF1NPJ (ORCPT ); Wed, 28 Jun 2023 09:15:09 -0400 Received: from mail-wr1-x42d.google.com (mail-wr1-x42d.google.com [IPv6:2a00:1450:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CAD82119 for ; Wed, 28 Jun 2023 06:15:08 -0700 (PDT) Received: by mail-wr1-x42d.google.com with SMTP id ffacd0b85a97d-313e12db357so6180926f8f.0 for ; Wed, 28 Jun 2023 06:15:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20221208.gappssmtp.com; s=20221208; t=1687958107; x=1690550107; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=UEDUaqobIEXKBJUJL2QuyVEVDAnOAPT+PycLhsHH0e4=; b=PzpxfbdG1hP8JaT6dGu5MFaJuWjRSgEZs4u66K6iR/KAiam4nJBUjYSvQ8TGXoy+4q v3msqKsXNd1yS7SRhQcy7ZL8ICOg8OxVsNenTnJDmuHHE8o0XnzV17PUmR1OaqTFJUHb l80kTHBXJUsESLmsFFexDiSxsOPxOGvvD/4t7V9fnRf0eAA+AtbX/IyAKiXIbpophLiG 0Lu6napv/3ofoE5nfu0y1S7R6XrhGd53UBqqOr+9cYm+QU9rQa7eNEfhv3Vp08SLGuil o/frg8rQgA65BNf+0YiOOOUxHToVQf0mEehTnG/XL4E8vslfJFMrz5UYOTH2oNXNmBS+ ODIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687958107; x=1690550107; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=UEDUaqobIEXKBJUJL2QuyVEVDAnOAPT+PycLhsHH0e4=; b=ejnmrpF/QIVYEFUO0g1qRV61u82mivXJTsMcFAdkSNFv2EHk9kJvMVOmlbgivGvFcg RgXsqnNwpZ7nrmzo5mWuzYk71FWm8kl8xn/HQDsr7ildGd133V1mgJmBoxClv34cTD3a gFfNG3uxGluMz8JN+5VyqxP1rJrunFubv0ehO48rA0sE6V8Azcr61aDjEIRNZ9fYaCtC Ll7qmrgkL1AMgOnMqwxHEmGRfSIq2fJ0myKui4JO03LfbDk0fQdsXrJWCDT6t0GPhOxb WEQq0MErmjHp02kiBNQpwpsv5si97+TpasMSiUyfvNzaZdDn2ra5LZcDgygzTRfh/hWa pwBw== X-Gm-Message-State: ABy/qLabNaqBeJB8HBSLlWteRftMa3hUQjWgb7GeSCJgYOjX6vPW7xdj yzIlaOPxK9tLe7m985Wf3cJAvg== X-Google-Smtp-Source: APBJJlFWGkJY32HwEpO3mKHGbpfiLr3WFCRee+GHsQt33NWy53Chldwzwg/XwfF9jbPeqO/4lWMJ8A== X-Received: by 2002:adf:eb11:0:b0:314:122a:9fe0 with SMTP id s17-20020adfeb11000000b00314122a9fe0mr35636wrn.8.1687958107035; Wed, 28 Jun 2023 06:15:07 -0700 (PDT) Received: from vermeer.tail79c99.ts.net ([2a01:cb1d:81a9:dd00:b570:b34c:ffd4:c805]) by smtp.gmail.com with ESMTPSA id a11-20020a056000050b00b003110dc7f408sm13456946wrf.41.2023.06.28.06.15.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jun 2023 06:15:06 -0700 (PDT) From: Samuel Ortiz To: Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-riscv@lists.infradead.org Cc: Samuel Ortiz , linux@rivosinc.com, Conor Dooley , Andrew Jones , Heiko Stuebner , Anup Patel , linux-kernel@vger.kernel.org, "Hongren (Zenithal) Zheng" , Guo Ren , Atish Patra , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Evan Green Subject: [PATCH v2 3/3] RISC-V: Implement archrandom when Zkr is available Date: Wed, 28 Jun 2023 15:14:35 +0200 Message-ID: <20230628131442.3022772-4-sameo@rivosinc.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230628131442.3022772-1-sameo@rivosinc.com> References: <20230628131442.3022772-1-sameo@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The Zkr extension is ratified and provides 16 bits of entropy seed when reading the SEED CSR. We can implement arch_get_random_seed_longs() by doing multiple csrrw to that CSR and filling an unsigned long with valid entropy bits. Signed-off-by: Samuel Ortiz --- arch/riscv/include/asm/archrandom.h | 70 +++++++++++++++++++++++++++++ arch/riscv/include/asm/csr.h | 9 ++++ 2 files changed, 79 insertions(+) create mode 100644 arch/riscv/include/asm/archrandom.h diff --git a/arch/riscv/include/asm/archrandom.h b/arch/riscv/include/asm/a= rchrandom.h new file mode 100644 index 000000000000..8987cd0b891d --- /dev/null +++ b/arch/riscv/include/asm/archrandom.h @@ -0,0 +1,70 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Kernel interface for the RISCV arch_random_* functions + * + * Copyright (c) 2023 by Rivos Inc. + * + */ + +#ifndef ASM_RISCV_ARCHRANDOM_H +#define ASM_RISCV_ARCHRANDOM_H + +#include + +#define SEED_RETRY_LOOPS 10 + +static inline bool __must_check csr_seed_long(unsigned long *v) +{ + unsigned int retry =3D SEED_RETRY_LOOPS, valid_seeds =3D 0; + const int needed_seeds =3D sizeof(long) / sizeof(u16); + u16 *entropy =3D (u16 *)v; + + do { + /* + * The SEED CSR (0x015) must be accessed with a read-write + * instruction. + */ + unsigned long csr_seed =3D csr_swap(CSR_SEED, 0); + + switch (csr_seed & SEED_OPST_MASK) { + case SEED_OPST_ES16: + entropy[valid_seeds++] =3D csr_seed & SEED_ENTROPY_MASK; + if (valid_seeds =3D=3D needed_seeds) + return true; + break; + + case SEED_OPST_DEAD: + pr_err_once("archrandom: Unrecoverable error\n"); + return false; + + case SEED_OPST_BIST: + case SEED_OPST_WAIT: + default: + continue; + } + } while (--retry); + + return false; +} + +static inline size_t __must_check arch_get_random_longs(unsigned long *v, = size_t max_longs) +{ + return 0; +} + +static inline size_t __must_check arch_get_random_seed_longs(unsigned long= *v, size_t max_longs) +{ + if (!max_longs) + return 0; + + /* + * If Zkr is supported and csr_seed_long succeeds, we return one long + * worth of entropy. + */ + if (riscv_has_extension_likely(RISCV_ISA_EXT_ZKR) && csr_seed_long(v)) + return 1; + + return 0; +} + +#endif /* ASM_RISCV_ARCHRANDOM_H */ diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h index b98b3b6c9da2..7d0ca9082c66 100644 --- a/arch/riscv/include/asm/csr.h +++ b/arch/riscv/include/asm/csr.h @@ -389,6 +389,15 @@ #define CSR_VTYPE 0xc21 #define CSR_VLENB 0xc22 =20 +/* Scalar Crypto Extension - Entropy */ +#define CSR_SEED 0x015 +#define SEED_OPST_MASK _AC(0xC0000000, UL) +#define SEED_OPST_BIST _AC(0x00000000, UL) +#define SEED_OPST_WAIT _AC(0x40000000, UL) +#define SEED_OPST_ES16 _AC(0x80000000, UL) +#define SEED_OPST_DEAD _AC(0xC0000000, UL) +#define SEED_ENTROPY_MASK _AC(0xFFFF, UL) + #ifdef CONFIG_RISCV_M_MODE # define CSR_STATUS CSR_MSTATUS # define CSR_IE CSR_MIE --=20 2.41.0