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=-15.7 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 030F9C43460 for ; Fri, 30 Apr 2021 06:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCA0361492 for ; Fri, 30 Apr 2021 06:00:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230308AbhD3GBO (ORCPT ); Fri, 30 Apr 2021 02:01:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:54348 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230182AbhD3GBF (ORCPT ); Fri, 30 Apr 2021 02:01:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4FB8561463; Fri, 30 Apr 2021 06:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1619762416; bh=Jf/tT5aNzgRJOGdT2PY3mk486F/+iF6QWd4893S7RqM=; h=Date:From:To:Subject:In-Reply-To:From; b=MD1F264vg4d+gQM5s4odry4GsxDzk40/ISz8VU9HVtAfJIBXa4WJvFzos+gOzcU8V U2TElotPmcc1SgGTgx6h8ALzhAMMMBFG4TbXMj+7A0gPD3Vi4LSMfOYC2hg024NQjp bxmEsW+Mn+/Rewp10lDkvOomnN0OMdLBm4nGxkzY= Date: Thu, 29 Apr 2021 23:00:15 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, aryabinin@virtuozzo.com, dvyukov@google.com, elver@google.com, glider@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 137/178] kasan: docs: update overview section Message-ID: <20210430060015.bEfbe3IHI%akpm@linux-foundation.org> In-Reply-To: <20210429225251.02b6386d21b69255b4f6c163@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: Andrey Konovalov Subject: kasan: docs: update overview section Update the "Overview" section in KASAN documentation: - Outline main use cases for each mode. - Mention that HW_TAGS mode need compiler support too. - Move the part about SLUB/SLAB support from "Usage" to "Overview". - Punctuation, readability, and other minor clean-ups. Link: https://lkml.kernel.org/r/1486fba8514de3d7db2f47df2192db59228b0a7b.1615559068.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Dmitry Vyukov Signed-off-by: Andrew Morton --- Documentation/dev-tools/kasan.rst | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) --- a/Documentation/dev-tools/kasan.rst~kasan-docs-update-overview-section +++ a/Documentation/dev-tools/kasan.rst @@ -11,17 +11,31 @@ designed to find out-of-bound and use-af 2. software tag-based KASAN (similar to userspace HWASan), 3. hardware tag-based KASAN (based on hardware memory tagging). -Software KASAN modes (1 and 2) use compile-time instrumentation to insert -validity checks before every memory access, and therefore require a compiler +Generic KASAN is mainly used for debugging due to a large memory overhead. +Software tag-based KASAN can be used for dogfood testing as it has a lower +memory overhead that allows using it with real workloads. Hardware tag-based +KASAN comes with low memory and performance overheads and, therefore, can be +used in production. Either as an in-field memory bug detector or as a security +mitigation. + +Software KASAN modes (#1 and #2) use compile-time instrumentation to insert +validity checks before every memory access and, therefore, require a compiler version that supports that. -Generic KASAN is supported in both GCC and Clang. With GCC it requires version +Generic KASAN is supported in GCC and Clang. With GCC, it requires version 8.3.0 or later. Any supported Clang version is compatible, but detection of out-of-bounds accesses for global variables is only supported since Clang 11. -Tag-based KASAN is only supported in Clang. +Software tag-based KASAN mode is only supported in Clang. + +The hardware KASAN mode (#3) relies on hardware to perform the checks but +still requires a compiler version that supports memory tagging instructions. +This mode is supported in GCC 10+ and Clang 11+. -Currently generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390 +Both software KASAN modes work with SLUB and SLAB memory allocators, +while the hardware tag-based KASAN currently only supports SLUB. + +Currently, generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390, and riscv architectures, and tag-based KASAN modes are supported only for arm64. Usage @@ -39,9 +53,6 @@ For software modes, you also need to cho CONFIG_KASAN_INLINE. Outline and inline are compiler instrumentation types. The former produces smaller binary while the latter is 1.1 - 2 times faster. -Both software KASAN modes work with both SLUB and SLAB memory allocators, -while the hardware tag-based KASAN currently only support SLUB. - For better error reports that include stack traces, enable CONFIG_STACKTRACE. To augment reports with last allocation and freeing stack of the physical page, _