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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 75165C433E9 for ; Fri, 12 Mar 2021 14:25:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EFB56500D for ; Fri, 12 Mar 2021 14:25:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232176AbhCLOY5 (ORCPT ); Fri, 12 Mar 2021 09:24:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbhCLOYm (ORCPT ); Fri, 12 Mar 2021 09:24:42 -0500 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9528C061574 for ; Fri, 12 Mar 2021 06:24:41 -0800 (PST) Received: by mail-ed1-x549.google.com with SMTP id i19so11650439edy.18 for ; Fri, 12 Mar 2021 06:24:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=YmrfZsjCUnsbI/dxLimuvoNopBZleUT55sQpN4+LAO4=; b=j/FaqdN61zL6WvpcKOGOU2tM9vngAJHnvFQAG9snOCBc7cjO4jQA4laHGxNPE3iol7 bTvUQd9R4paQnOS0/atIt5fTkAnxkGcZasXLem38BWaBtqHdLhpa1rd+rSx+RaSpW7tN M72oqJz0uX8j54HywoEZ70+yXJavAEboopaFmB8Z2A92JySJCH5xEqOay87JMUkyK37q erxXZWqAntLuDrpnqt4kiGbh71iP4qJjfpkORzXPvCeODseooVn6Qe6rBeUicTzcZyID 2TvJc/8mEXO9WXK1Fcg15bqM8m3gGLQ4LW1ASek4Pcc8JAwE6/h92cXjTVzPLsq/lmst vFxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=YmrfZsjCUnsbI/dxLimuvoNopBZleUT55sQpN4+LAO4=; b=qQ2qav310tdE6z9/fQ3z3j8AiNp1chuoJxNZHTLPCl61aLKaW2MFs2XfDPNDeAxE65 R4mV1mlbxfG5tyDRattsH4AZkyXEVRgrzKskNSSAgGuQ4QKdW7SEYn2fCsOQrrnbG0Fh nv+1rrXWYJEtUrE2bEv+dh9ZD1Nwp0U7+8KJ5JQE8lgNG2dhizpiiHt70vInZMEmROWN LPhFr4Heqp2ITSx63sDuRA7VXVY/gZQs7LhiaPUTtlNShiZZf42CgVvVg3Jrx71TFxcK Uh5mg7DCWz/RazbAkWmKPW+2tYgDTfm/IO53WFeP7mTmYTrTIldBI85CLfBK5pJWsBYy M8PQ== X-Gm-Message-State: AOAM532p1brCXAwcpeKcNsGGQ5lpKFXMibFTriKgrOXBUEY57mkEyZrv a6D0n2CAJJ/AKlBVSa2XTOoccbJvM709eeOw X-Google-Smtp-Source: ABdhPJxp7kOe5CQTLKqSu61Pmt1p/02N6FRencBxyisW0zbM9w4CjKAGwVOwb28H7CndKCl0Pj/9qXZbp1GrMyxc X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:95a:d8a8:4925:42be]) (user=andreyknvl job=sendgmr) by 2002:a17:906:a049:: with SMTP id bg9mr8819448ejb.186.1615559080372; Fri, 12 Mar 2021 06:24:40 -0800 (PST) Date: Fri, 12 Mar 2021 15:24:25 +0100 In-Reply-To: Message-Id: <1486fba8514de3d7db2f47df2192db59228b0a7b.1615559068.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.31.0.rc2.261.g7f71774620-goog Subject: [PATCH v2 02/11] kasan: docs: update overview section From: Andrey Konovalov To: Andrew Morton , Alexander Potapenko , Marco Elver Cc: Andrey Ryabinin , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Andrey Konovalov --- Changes v1->v2: - Mention GCC support for HW_TAGS. --- Documentation/dev-tools/kasan.rst | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index b3b2c517db55..2f2697b290d5 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -11,17 +11,31 @@ designed to find out-of-bound and use-after-free bugs. KASAN has three modes: 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. -Currently generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390 +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+. + +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 choose between CONFIG_KASAN_OUTLINE and 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, -- 2.31.0.rc2.261.g7f71774620-goog