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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 238AAC2D0E4 for ; Fri, 18 Dec 2020 22:03:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E02D923B87 for ; Fri, 18 Dec 2020 22:03:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725898AbgLRWDt (ORCPT ); Fri, 18 Dec 2020 17:03:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:36832 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726347AbgLRWDt (ORCPT ); Fri, 18 Dec 2020 17:03:49 -0500 Date: Fri, 18 Dec 2020 14:03:33 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608329013; bh=qpMIML1/gII246ISYK6mXLCd8OVwFtW20z8VkUZtJjY=; h=From:To:Subject:In-Reply-To:From; b=nzIH8Bzw6W1TZE6QLZ7KALeB1jqEZw/SDei2dyRlbz3YbwpFL5DAN1GCQ7sogHr1H eXbFMN1j2JwdmraxdgXkJ32mPi32PYwdMDH/L5Z+qMNarBMYAn5wMc5scDrJzLzjQB Z4GVGelKM/uHqT2rDDe9ljMTOEAyKXQ4wCaH40/o= From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, aryabinin@virtuozzo.com, Branislav.Rankov@arm.com, catalin.marinas@arm.com, dvyukov@google.com, elver@google.com, eugenis@google.com, glider@google.com, gor@linux.ibm.com, kevin.brodsky@arm.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vincenzo.frascino@arm.com, will.deacon@arm.com Subject: [patch 39/78] arm64: mte: add in-kernel tag fault handler Message-ID: <20201218220333.9v99rO2V0%akpm@linux-foundation.org> In-Reply-To: <20201218140046.497484741326828e5b5d46ec@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Vincenzo Frascino Subject: arm64: mte: add in-kernel tag fault handler Add the implementation of the in-kernel fault handler. When a tag fault happens on a kernel address: * MTE is disabled on the current CPU, * the execution continues. When a tag fault happens on a user address: * the kernel executes do_bad_area() and panics. The tag fault handler for kernel addresses is currently empty and will be filled in by a future commit. Link: https://lkml.kernel.org/r/ad31529b073e22840b7a2246172c2b67747ed7c4.1606161801.git.andreyknvl@google.com Signed-off-by: Vincenzo Frascino Co-developed-by: Andrey Konovalov Signed-off-by: Andrey Konovalov Signed-off-by: Catalin Marinas Reviewed-by: Catalin Marinas Tested-by: Vincenzo Frascino Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Branislav Rankov Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Kevin Brodsky Cc: Marco Elver Cc: Vasily Gorbik Cc: Will Deacon [catalin.marinas@arm.com: ensure CONFIG_ARM64_PAN is enabled with MTE] Link: https://lkml.kernel.org/r/20201203102628.GB2224@gaia Signed-off-by: Andrew Morton --- arch/arm64/Kconfig | 2 + arch/arm64/include/asm/uaccess.h | 23 ++++++++++++++ arch/arm64/mm/fault.c | 45 +++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+) --- a/arch/arm64/include/asm/uaccess.h~arm64-mte-add-in-kernel-tag-fault-handler +++ a/arch/arm64/include/asm/uaccess.h @@ -159,8 +159,28 @@ static inline void __uaccess_enable_hw_p CONFIG_ARM64_PAN)); } +/* + * The Tag Check Flag (TCF) mode for MTE is per EL, hence TCF0 + * affects EL0 and TCF affects EL1 irrespective of which TTBR is + * used. + * The kernel accesses TTBR0 usually with LDTR/STTR instructions + * when UAO is available, so these would act as EL0 accesses using + * TCF0. + * However futex.h code uses exclusives which would be executed as + * EL1, this can potentially cause a tag check fault even if the + * user disables TCF0. + * + * To address the problem we set the PSTATE.TCO bit in uaccess_enable() + * and reset it in uaccess_disable(). + * + * The Tag check override (TCO) bit disables temporarily the tag checking + * preventing the issue. + */ static inline void uaccess_disable_privileged(void) { + asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0), + ARM64_MTE, CONFIG_KASAN_HW_TAGS)); + if (uaccess_ttbr0_disable()) return; @@ -169,6 +189,9 @@ static inline void uaccess_disable_privi static inline void uaccess_enable_privileged(void) { + asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1), + ARM64_MTE, CONFIG_KASAN_HW_TAGS)); + if (uaccess_ttbr0_enable()) return; --- a/arch/arm64/Kconfig~arm64-mte-add-in-kernel-tag-fault-handler +++ a/arch/arm64/Kconfig @@ -1649,6 +1649,8 @@ config ARM64_MTE default y depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI depends on AS_HAS_ARMV8_5 + # Required for tag checking in the uaccess routines + depends on ARM64_PAN select ARCH_USES_HIGH_VMA_FLAGS help Memory Tagging (part of the ARMv8.5 Extensions) provides --- a/arch/arm64/mm/fault.c~arm64-mte-add-in-kernel-tag-fault-handler +++ a/arch/arm64/mm/fault.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include #include @@ -296,6 +297,44 @@ static void die_kernel_fault(const char do_exit(SIGKILL); } +static void report_tag_fault(unsigned long addr, unsigned int esr, + struct pt_regs *regs) +{ +} + +static void do_tag_recovery(unsigned long addr, unsigned int esr, + struct pt_regs *regs) +{ + static bool reported; + + if (!READ_ONCE(reported)) { + report_tag_fault(addr, esr, regs); + WRITE_ONCE(reported, true); + } + + /* + * Disable MTE Tag Checking on the local CPU for the current EL. + * It will be done lazily on the other CPUs when they will hit a + * tag fault. + */ + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_NONE); + isb(); +} + +static bool is_el1_mte_sync_tag_check_fault(unsigned int esr) +{ + unsigned int ec = ESR_ELx_EC(esr); + unsigned int fsc = esr & ESR_ELx_FSC; + + if (ec != ESR_ELx_EC_DABT_CUR) + return false; + + if (fsc == ESR_ELx_FSC_MTE) + return true; + + return false; +} + static void __do_kernel_fault(unsigned long addr, unsigned int esr, struct pt_regs *regs) { @@ -312,6 +351,12 @@ static void __do_kernel_fault(unsigned l "Ignoring spurious kernel translation fault at virtual address %016lx\n", addr)) return; + if (is_el1_mte_sync_tag_check_fault(esr)) { + do_tag_recovery(addr, esr, regs); + + return; + } + if (is_el1_permission_fault(addr, esr, regs)) { if (esr & ESR_ELx_WNR) msg = "write to read-only memory"; _