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=-17.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham 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 AF4A9C433DF for ; Mon, 29 Jun 2020 20:45:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88F7D20663 for ; Mon, 29 Jun 2020 20:45:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nAWQ987y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732496AbgF2Upm (ORCPT ); Mon, 29 Jun 2020 16:45:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731571AbgF2TN5 (ORCPT ); Mon, 29 Jun 2020 15:13:57 -0400 Received: from mail-wm1-x34a.google.com (mail-wm1-x34a.google.com [IPv6:2a00:1450:4864:20::34a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75C37C008623 for ; Mon, 29 Jun 2020 03:42:27 -0700 (PDT) Received: by mail-wm1-x34a.google.com with SMTP id f68so8291821wmf.1 for ; Mon, 29 Jun 2020 03:42:27 -0700 (PDT) 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=YyMZU7GxNPbypFBfmDC57uoWU5tN/2mz7Tk7sznQPgo=; b=nAWQ987yfOBPOOEYeLfBpTKXjHDjRk++j9AZflXKZXWLCMXVvd7yIsAChgHiHkG1Sb Ro38pXUoJKYD0KZynPUgyFkyXcggBZGtHKERFokBWq0fCQ+qKUB3HKLP7JCPiKvS2DDU 1utkIHtk9qixo7oMbkagnHxUtzaR/8DJlPuCsGHhKo5gp92ooPOwjZo0VDpbtmLWlIP7 flby1Y3JacGPnRjvosmrKnWbZ8lxhinI0u/YB/CamcoduNbgp/eZQuK398sUFUxKl5hY D5luhsAxu540KejG7TSErFAVenWrZqEs+zkoMYCh436eVyjx/ikSt4cxCc35SUYPGzAa HCIA== 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=YyMZU7GxNPbypFBfmDC57uoWU5tN/2mz7Tk7sznQPgo=; b=nsSkhaElOtKxUeAnr8SbIdH+1gEqmLS1nLYk6H4wKq7jvL+PX6AxGXJv+JK3nqyBet ElKzEj54T7HE/Esi9joh5kd0XshhJQOWONAb0VxxpQKQ5a8BezTbRqaIxR3dFxAreT7M NKhcjdO0Su2Dkxl/Lxxti4a74qQk+Qi3UCyNLtv0x1mfx/yQAZLfb6miBkTr1xHkhPSA X5w1AZ9AbBSmwrpMOW8d30reMupxmqk1VUoKwuBaBEy2tk+L7NtbNOgivGbKQOCl/CYm GZ2xA6HWDgjrkwA3bq5c9RV06PtxaP6EFO+kp6r0SNZJdaELornH2FVo96F5EgZvGHKq Pn+Q== X-Gm-Message-State: AOAM531PLzVjrcy02xf2K5S6g9lcZQxiL+olGVSmtjSh4/uqDi/IWgNK NkwXauvJTx2X70GycX/MPu1YF2Ec7Q== X-Google-Smtp-Source: ABdhPJyMWL2D57ylMog0xr3NH7coG2BEQ8Z7wiwp0oZ1Ynp0EmpoOKeBp65JMLFjr+o/s1Uhc9XWJsZreA== X-Received: by 2002:a1c:1b90:: with SMTP id b138mr15963963wmb.21.1593427346060; Mon, 29 Jun 2020 03:42:26 -0700 (PDT) Date: Mon, 29 Jun 2020 12:41:57 +0200 In-Reply-To: <20200629104157.3242503-1-elver@google.com> Message-Id: <20200629104157.3242503-2-elver@google.com> Mime-Version: 1.0 References: <20200629104157.3242503-1-elver@google.com> X-Mailer: git-send-email 2.27.0.212.ge8ba1cc988-goog Subject: [PATCH 2/2] kasan: Update required compiler versions in documentation From: Marco Elver To: elver@google.com, akpm@linux-foundation.org Cc: dvyukov@google.com, glider@google.com, andreyknvl@google.com, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, aryabinin@virtuozzo.com, ndesaulniers@google.com, walter-zh.wu@mediatek.com, arnd@arndb.de, dja@axtens.net, linux-doc@vger.kernel.org, clang-built-linux@googlegroups.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Fixes: 7b861a53e46b ("kasan: Bump required compiler version") Fixes: acf7b0bf7dcf ("kasan: Fix required compiler version") Signed-off-by: Marco Elver --- Documentation/dev-tools/kasan.rst | 7 ++----- lib/Kconfig.kasan | 24 +++++++++++++++--------- 2 files changed, 17 insertions(+), 14 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index c652d740735d..15a2a53e77b0 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -13,11 +13,8 @@ KASAN uses compile-time instrumentation to insert validity checks before every 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. diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 89053defc0d9..047b53dbfd58 100644 --- a/lib/Kconfig.kasan +++ b/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 -- 2.27.0.212.ge8ba1cc988-goog