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 AEF54C433F5 for ; Thu, 26 May 2022 20:57:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344729AbiEZU5D (ORCPT ); Thu, 26 May 2022 16:57:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239530AbiEZU44 (ORCPT ); Thu, 26 May 2022 16:56:56 -0400 Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CC2C5C346 for ; Thu, 26 May 2022 13:56:53 -0700 (PDT) Received: from ip5b412258.dynamic.kabel-deutschland.de ([91.65.34.88] helo=phil.lan) by gloria.sntech.de with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nuKXL-0006ZH-FQ; Thu, 26 May 2022 22:56:51 +0200 From: Heiko Stuebner To: palmer@dabbelt.com, paul.walmsley@sifive.com Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, wefu@redhat.com, guoren@kernel.org, mick@ics.forth.gr, samuel@sholland.org, cmuellner@linux.com, philipp.tomsich@vrull.eu, hch@lst.de, Heiko Stuebner Subject: [PATCH v2 5/5] riscv: remove usage of function-pointers from cpufeatures and t-head errata Date: Thu, 26 May 2022 22:56:46 +0200 Message-Id: <20220526205646.258337-6-heiko@sntech.de> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220526205646.258337-1-heiko@sntech.de> References: <20220526205646.258337-1-heiko@sntech.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Having a list of alternatives to check with a per-entry function pointer to a check function is nice style-wise. But in case of early-alternatives it can clash with the non-relocated kernel and the function pointer in the list pointing to a completely wrong location. This isn't an issue with one or two list entries, as in that case the compiler seems to unroll the loop and even usage of the list structure and then only does relative jumps into the check functions based on this. When adding a third entry to either list though, the issue that was hiding there from the beginning is triggered resulting a jump to a memory address that isn't part of the kernel at all. The list of features/erratas only contained an unused name and the pointer to the check function, so an easy solution for the problem is to just unroll the loop in code, dismantle the whole list structure and just call the relevant check functions one by one ourself. For the T-Head errata this includes moving the stage-check inside the check functions. The issue is only relevant for things that might be called for early- alternatives (T-Head and possible future main extensions), so the SiFive erratas were not affected from the beginning, as they got an early return for early-alternatives in the original patchset. Signed-off-by: Heiko Stuebner --- arch/riscv/errata/thead/errata.c | 38 ++++++++++---------------------- arch/riscv/kernel/cpufeature.c | 32 +++++++++------------------ 2 files changed, 22 insertions(+), 48 deletions(-) diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c index e5d75270b99c..cc155228247d 100644 --- a/arch/riscv/errata/thead/errata.c +++ b/arch/riscv/errata/thead/errata.c @@ -14,40 +14,26 @@ #include #include -struct errata_info { - char name[ERRATA_STRING_LENGTH_MAX]; - bool (*check_func)(unsigned long arch_id, unsigned long impid); - unsigned int stage; -}; - -static bool errata_mt_check_func(unsigned long arch_id, unsigned long impid) +static bool errata_probe_pbmt(unsigned int stage, + unsigned long arch_id, unsigned long impid) { if (arch_id != 0 || impid != 0) return false; - return true; -} -static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = { - { - .name = "memory-types", - .stage = RISCV_ALTERNATIVES_EARLY_BOOT, - .check_func = errata_mt_check_func - }, -}; + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT || + stage == RISCV_ALTERNATIVES_MODULE) + return true; + + return false; +} -static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid) +static u32 thead_errata_probe(unsigned int stage, + unsigned long archid, unsigned long impid) { - const struct errata_info *info; u32 cpu_req_errata = 0; - int idx; - - for (idx = 0; idx < ERRATA_THEAD_NUMBER; idx++) { - info = &errata_list[idx]; - if ((stage == RISCV_ALTERNATIVES_MODULE || - info->stage == stage) && info->check_func(archid, impid)) - cpu_req_errata |= (1U << idx); - } + if (errata_probe_pbmt(stage, archid, impid)) + cpu_req_errata |= (1U << ERRATA_THEAD_PBMT); return cpu_req_errata; } diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index b33564df81e1..b63c25c55bf1 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -246,12 +246,7 @@ void __init riscv_fill_hwcap(void) } #ifdef CONFIG_RISCV_ALTERNATIVE -struct cpufeature_info { - char name[ERRATA_STRING_LENGTH_MAX]; - bool (*check_func)(unsigned int stage); -}; - -static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage) +static bool __init_or_module cpufeature_probe_svpbmt(unsigned int stage) { #ifdef CONFIG_RISCV_ISA_SVPBMT switch (stage) { @@ -265,26 +260,19 @@ static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage) return false; } -static const struct cpufeature_info __initdata_or_module -cpufeature_list[CPUFEATURE_NUMBER] = { - { - .name = "svpbmt", - .check_func = cpufeature_svpbmt_check_func - }, -}; - +/* + * Probe presence of individual extensions. + * + * This code may also be executed before kernel relocation, so we cannot use + * addresses generated by the address-of operator as they won't be valid in + * this context. + */ static u32 __init_or_module cpufeature_probe(unsigned int stage) { - const struct cpufeature_info *info; u32 cpu_req_feature = 0; - int idx; - - for (idx = 0; idx < CPUFEATURE_NUMBER; idx++) { - info = &cpufeature_list[idx]; - if (info->check_func(stage)) - cpu_req_feature |= (1U << idx); - } + if (cpufeature_probe_svpbmt(stage)) + cpu_req_feature |= (1U << CPUFEATURE_SVPBMT); return cpu_req_feature; } -- 2.35.1