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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 C4FF2C433E0 for ; Fri, 22 Jan 2021 11:28:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E2CD2376F for ; Fri, 22 Jan 2021 11:28:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728088AbhAVL1r (ORCPT ); Fri, 22 Jan 2021 06:27:47 -0500 Received: from foss.arm.com ([217.140.110.172]:42332 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728176AbhAVLWu (ORCPT ); Fri, 22 Jan 2021 06:22:50 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 15C6B139F; Fri, 22 Jan 2021 03:22:00 -0800 (PST) Received: from [10.37.8.28] (unknown [10.37.8.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2479F3F719; Fri, 22 Jan 2021 03:21:58 -0800 (PST) Subject: Re: [PATCH v5 2/6] kasan: Add KASAN mode kernel parameter To: Andrey Konovalov Cc: Linux ARM , LKML , kasan-dev , Catalin Marinas , Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov References: <20210121163943.9889-1-vincenzo.frascino@arm.com> <20210121163943.9889-3-vincenzo.frascino@arm.com> From: Vincenzo Frascino Message-ID: <770c1426-3e62-e320-9928-37f6ac580c79@arm.com> Date: Fri, 22 Jan 2021 11:25:49 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/21/21 5:34 PM, Andrey Konovalov wrote: >> +- ``kasan.mode=sync`` or ``=async`` controls whether KASAN is configured in >> + synchronous or asynchronous mode of execution (default: ``sync``). >> + ``synchronous mode``: an exception is triggered if a tag check fault occurs. > Synchronous mode: a bad access is detected immediately when a tag > check fault occurs. > > (No need for `` here, "synchronous mode" is not an inline snippet.) > Ok will do in v5. >> + ``asynchronous mode``: if a tag check fault occurs, the information is stored >> + asynchronously in hardware (e.g. in the TFSR_EL1 register for arm64). The kernel >> + checks the hardware location and reports an error if the fault is detected. > Asynchronous mode: a bad access detection is delayed. When a tag check > fault occurs, the information is stored in hardware (in the TFSR_EL1 > register for arm64). The kernel periodically checks the hardware and > only reports tag faults during these checks. > Will do in v5. >> + >> - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack >> traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``, otherwise >> ``off``). >> diff --git a/lib/test_kasan.c b/lib/test_kasan.c >> index d16ec9e66806..7285dcf9fcc1 100644 >> --- a/lib/test_kasan.c >> +++ b/lib/test_kasan.c >> @@ -97,7 +97,7 @@ static void kasan_test_exit(struct kunit *test) >> READ_ONCE(fail_data.report_found)); \ >> if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) { \ >> if (READ_ONCE(fail_data.report_found)) \ >> - hw_enable_tagging(); \ >> + hw_enable_tagging_sync(); \ >> migrate_enable(); \ >> } \ >> } while (0) >> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c >> index e529428e7a11..224a2187839c 100644 >> --- a/mm/kasan/hw_tags.c >> +++ b/mm/kasan/hw_tags.c >> @@ -25,6 +25,11 @@ enum kasan_arg { >> KASAN_ARG_ON, >> }; >> >> +enum kasan_arg_mode { >> + KASAN_ARG_MODE_SYNC, >> + KASAN_ARG_MODE_ASYNC, > For other modes I explicitly added a _DEFAULT option first. It makes > sense to do this here as well for consistency. > Will do in v5. >> +}; >> + >> enum kasan_arg_stacktrace { >> KASAN_ARG_STACKTRACE_DEFAULT, >> KASAN_ARG_STACKTRACE_OFF, >> @@ -38,6 +43,7 @@ enum kasan_arg_fault { >> }; >> >> static enum kasan_arg kasan_arg __ro_after_init; >> +static enum kasan_arg_mode kasan_arg_mode __ro_after_init; >> static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init; >> static enum kasan_arg_fault kasan_arg_fault __ro_after_init; >> >> @@ -68,6 +74,21 @@ static int __init early_kasan_flag(char *arg) >> } >> early_param("kasan", early_kasan_flag); >> >> +/* kasan.mode=sync/async */ >> +static int __init early_kasan_mode(char *arg) >> +{ >> + /* If arg is not set the default mode is sync */ >> + if ((!arg) || !strcmp(arg, "sync")) >> + kasan_arg_mode = KASAN_ARG_MODE_SYNC; >> + else if (!strcmp(arg, "async")) >> + kasan_arg_mode = KASAN_ARG_MODE_ASYNC; >> + else >> + return -EINVAL; >> + >> + return 0; >> +} >> +early_param("kasan.mode", early_kasan_mode); >> + >> /* kasan.stacktrace=off/on */ >> static int __init early_kasan_flag_stacktrace(char *arg) >> { >> @@ -115,7 +136,11 @@ void kasan_init_hw_tags_cpu(void) >> return; >> >> hw_init_tags(KASAN_TAG_MAX); >> - hw_enable_tagging(); >> + > Let's add a comment: > > /* Enable async mode only when explicitly requested through the command line. */ > Will do in v5. -- Regards, Vincenzo