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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 0FFB2C433DF for ; Fri, 7 Aug 2020 06:24:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7FE322CAF for ; Fri, 7 Aug 2020 06:24:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781473; bh=O7UkGCmIaQsRzlwYMDLRds2JWhI++2Unus3K9L/h+Ms=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=R9Z1fy6sh/cGQukcNu9mBgQ8pZ8vrt567Ynrmv1rK1Ap2lQwr8SCKESpfZdZZ/yo/ gVM+Q3mg+LYTmT68zvrYO8PKzQpmPm6P0atO2QK8c72VKmtwuj90j4Ug5lQdjbRlBR SnRyz2OvsTIbFZ8U4HuedifcKpbR8T+g/TQJHRkY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725805AbgHGGYd (ORCPT ); Fri, 7 Aug 2020 02:24:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:33370 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725379AbgHGGYd (ORCPT ); Fri, 7 Aug 2020 02:24:33 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1C25E22CAE; Fri, 7 Aug 2020 06:24:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596781472; bh=O7UkGCmIaQsRzlwYMDLRds2JWhI++2Unus3K9L/h+Ms=; h=Date:From:To:Subject:In-Reply-To:From; b=F4H/PHk08xSdqm1uleXkPYVAd++k470U+sAD7H6IQ/qBKxujbULjuRUggNo88JYZS VqLDKyrN+JotcDSNKKsK9Plim+ZzzZxiMEa7GKiYciuCT4pDrjAVt+i/Rkd3G5FNML coirlf8tMiAANxTZ2IsxUlqDTDAARtvj1IPwVxko= Date: Thu, 06 Aug 2020 23:24:31 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, arnd@arndb.de, aryabinin@virtuozzo.com, dja@axtens.net, dvyukov@google.com, elver@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, ndesaulniers@google.com, torvalds@linux-foundation.org, walter-zh.wu@mediatek.com Subject: [patch 129/163] kasan: update required compiler versions in documentation Message-ID: <20200807062431.ohz9Pz_Qw%akpm@linux-foundation.org> In-Reply-To: <20200806231643.a2711a608dd0f18bff2caf2b@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Marco Elver Subject: kasan: update required compiler versions in documentation Updates the recently changed compiler requirements for KASAN. In particular, we require GCC >= 8.3.0, and add a note that Clang 11 supports OOB detection of globals. Link: http://lkml.kernel.org/r/20200629104157.3242503-2-elver@google.com Fixes: 7b861a53e46b ("kasan: Bump required compiler version") Fixes: acf7b0bf7dcf ("kasan: Fix required compiler version") Signed-off-by: Marco Elver Reviewed-by: Andrey Konovalov Cc: Dmitry Vyukov Cc: Andrey Ryabinin Cc: Nick Desaulniers Cc: Walter Wu Cc: Arnd Bergmann Cc: Daniel Axtens Signed-off-by: Andrew Morton --- Documentation/dev-tools/kasan.rst | 7 ++----- lib/Kconfig.kasan | 24 +++++++++++++++--------- 2 files changed, 17 insertions(+), 14 deletions(-) --- a/Documentation/dev-tools/kasan.rst~kasan-update-required-compiler-versions-in-documentation +++ a/Documentation/dev-tools/kasan.rst @@ -13,11 +13,8 @@ KASAN uses compile-time instrumentation memory access, and therefore requires a compiler version that supports that. Generic KASAN is supported in both GCC and Clang. With GCC it requires version -4.9.2 or later for basic support and version 5.0 or later for detection of -out-of-bounds accesses for stack and global variables and for inline -instrumentation mode (see the Usage section). With Clang it requires version -7.0.0 or later and it doesn't support detection of out-of-bounds accesses for -global variables yet. +8.3.0 or later. With Clang it requires version 7.0.0 or later, but detection of +out-of-bounds accesses for global variables is only supported since Clang 11. Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later. --- a/lib/Kconfig.kasan~kasan-update-required-compiler-versions-in-documentation +++ a/lib/Kconfig.kasan @@ -40,6 +40,7 @@ choice software tag-based KASAN (a version based on software memory tagging, arm64 only, similar to userspace HWASan, enabled with CONFIG_KASAN_SW_TAGS). + Both generic and tag-based KASAN are strictly debugging features. config KASAN_GENERIC @@ -51,16 +52,18 @@ config KASAN_GENERIC select STACKDEPOT help Enables generic KASAN mode. - Supported in both GCC and Clang. With GCC it requires version 4.9.2 - or later for basic support and version 5.0 or later for detection of - out-of-bounds accesses for stack and global variables and for inline - instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires - version 3.7.0 or later and it doesn't support detection of - out-of-bounds accesses for global variables yet. + + This mode is supported in both GCC and Clang. With GCC it requires + version 8.3.0 or later. With Clang it requires version 7.0.0 or + later, but detection of out-of-bounds accesses for global variables + is supported only since Clang 11. + This mode consumes about 1/8th of available memory at kernel start and introduces an overhead of ~x1.5 for the rest of the allocations. The performance slowdown is ~x3. + For better error detection enable CONFIG_STACKTRACE. + Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB (the resulting kernel does not boot). @@ -73,15 +76,19 @@ config KASAN_SW_TAGS select STACKDEPOT help Enables software tag-based KASAN mode. + This mode requires Top Byte Ignore support by the CPU and therefore - is only supported for arm64. - This mode requires Clang version 7.0.0 or later. + is only supported for arm64. This mode requires Clang version 7.0.0 + or later. + This mode consumes about 1/16th of available memory at kernel start and introduces an overhead of ~20% for the rest of the allocations. This mode may potentially introduce problems relating to pointer casting and comparison, as it embeds tags into the top byte of each pointer. + For better error detection enable CONFIG_STACKTRACE. + Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB (the resulting kernel does not boot). @@ -107,7 +114,6 @@ config KASAN_INLINE memory accesses. This is faster than outline (in some workloads it gives about x2 boost over outline instrumentation), but make kernel's .text size much bigger. - For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later. endchoice _