From patchwork Fri Dec 18 22:02:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11983051 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=-20.8 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,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 CBE53C4361B for ; Fri, 18 Dec 2020 22:02:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5F6B323BAC for ; Fri, 18 Dec 2020 22:02:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F6B323BAC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F23E66B007D; Fri, 18 Dec 2020 17:02:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ED49D6B007E; Fri, 18 Dec 2020 17:02:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DED236B0080; Fri, 18 Dec 2020 17:02:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id C6D7D6B007D for ; Fri, 18 Dec 2020 17:02:12 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 97F442497 for ; Fri, 18 Dec 2020 22:02:12 +0000 (UTC) X-FDA: 77607776904.04.wish30_3705c8827440 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id 786AA801A3B6 for ; Fri, 18 Dec 2020 22:02:12 +0000 (UTC) X-HE-Tag: wish30_3705c8827440 X-Filterd-Recvd-Size: 11362 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Fri, 18 Dec 2020 22:02:11 +0000 (UTC) Date: Fri, 18 Dec 2020 14:02:10 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608328931; bh=AexJ2vMYIopIJOlUAiEGDR3hvR4BxmRpff6tzMYmp+c=; h=From:To:Subject:In-Reply-To:From; b=JUA+tpJ66NOP3BB9s/C96gQ8V99yRNuZu532uDQe4rQOf6AGeQ/lYAPprNqJtRUwL Y0wlURho2rrtugThzI032gJJIj9C13St+6t9iaB+NcOREmF3zHUyn2j/t4OjPjjcRG ZhyMBRG36bEDk4lQm9ZX5YwdIlchy3WSIkz8XA1M= From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, aryabinin@virtuozzo.com, Branislav.Rankov@arm.com, catalin.marinas@arm.com, dvyukov@google.com, elver@google.com, eugenis@google.com, glider@google.com, gor@linux.ibm.com, kevin.brodsky@arm.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vincenzo.frascino@arm.com, will.deacon@arm.com Subject: [patch 14/78] kasan: drop unnecessary GPL text from comment headers Message-ID: <20201218220210.Dw1XK0QbY%akpm@linux-foundation.org> In-Reply-To: <20201218140046.497484741326828e5b5d46ec@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Andrey Konovalov Subject: kasan: drop unnecessary GPL text from comment headers Patch series "kasan: add hardware tag-based mode for arm64", v11. This patchset adds a new hardware tag-based mode to KASAN [1]. The new mode is similar to the existing software tag-based KASAN, but relies on arm64 Memory Tagging Extension (MTE) [2] to perform memory and pointer tagging (instead of shadow memory and compiler instrumentation). This patchset is co-developed and tested by Vincenzo Frascino . This patchset is available here: https://github.com/xairy/linux/tree/up-kasan-mte-v11 For testing in QEMU hardware tag-based KASAN requires: 1. QEMU built from master [4] (use "-machine virt,mte=on -cpu max" arguments to run). 2. GCC version 10. [1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html [2] https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/enhancing-memory-safety [3] git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux for-next/mte [4] https://github.com/qemu/qemu ====== Overview The underlying ideas of the approach used by hardware tag-based KASAN are: 1. By relying on the Top Byte Ignore (TBI) arm64 CPU feature, pointer tags are stored in the top byte of each kernel pointer. 2. With the Memory Tagging Extension (MTE) arm64 CPU feature, memory tags for kernel memory allocations are stored in a dedicated memory not accessible via normal instuctions. 3. On each memory allocation, a random tag is generated, embedded it into the returned pointer, and the corresponding memory is tagged with the same tag value. 4. With MTE the CPU performs a check on each memory access to make sure that the pointer tag matches the memory tag. 5. On a tag mismatch the CPU generates a tag fault, and a KASAN report is printed. Same as other KASAN modes, hardware tag-based KASAN is intended as a debugging feature at this point. ====== Rationale There are two main reasons for this new hardware tag-based mode: 1. Previously implemented software tag-based KASAN is being successfully used on dogfood testing devices due to its low memory overhead (as initially planned). The new hardware mode keeps the same low memory overhead, and is expected to have significantly lower performance impact, due to the tag checks being performed by the hardware. Therefore the new mode can be used as a better alternative in dogfood testing for hardware that supports MTE. 2. The new mode lays the groundwork for the planned in-kernel MTE-based memory corruption mitigation to be used in production. ====== Technical details Considering the implementation perspective, hardware tag-based KASAN is almost identical to the software mode. The key difference is using MTE for assigning and checking tags. Compared to the software mode, the hardware mode uses 4 bits per tag, as dictated by MTE. Pointer tags are stored in bits [56:60), the top 4 bits have the normal value 0xF. Having less distict tags increases the probablity of false negatives (from ~1/256 to ~1/16) in certain cases. Only synchronous exceptions are set up and used by hardware tag-based KASAN. ====== Benchmarks Note: all measurements have been performed with software emulation of Memory Tagging Extension, performance numbers for hardware tag-based KASAN on the actual hardware are expected to be better. Boot time [1]: * 2.8 sec for clean kernel * 5.7 sec for hardware tag-based KASAN * 11.8 sec for software tag-based KASAN * 11.6 sec for generic KASAN Slab memory usage after boot [2]: * 7.0 kb for clean kernel * 9.7 kb for hardware tag-based KASAN * 9.7 kb for software tag-based KASAN * 41.3 kb for generic KASAN Measurements have been performed with: * defconfig-based configs * Manually built QEMU master * QEMU arguments: -machine virt,mte=on -cpu max * CONFIG_KASAN_STACK_ENABLE disabled * CONFIG_KASAN_INLINE enabled * clang-10 as the compiler and gcc-10 as the assembler [1] Time before the ext4 driver is initialized. [2] Measured as `cat /proc/meminfo | grep Slab`. ====== Notes The cover letter for software tag-based KASAN patchset can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0116523cfffa62aeb5aa3b85ce7419f3dae0c1b8 ===== Tags Tested-by: Vincenzo Frascino This patch (of 41): Don't mention "GNU General Public License version 2" text explicitly, as it's already covered by the SPDX-License-Identifier. Link: https://lkml.kernel.org/r/cover.1606161801.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/6ea9f5f4aa9dbbffa0d0c0a780b37699a4531034.1606161801.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Signed-off-by: Vincenzo Frascino Reviewed-by: Marco Elver Reviewed-by: Alexander Potapenko Tested-by: Vincenzo Frascino Cc: Catalin Marinas Cc: Will Deacon Cc: Dmitry Vyukov Cc: Andrey Ryabinin Cc: Evgenii Stepanov Cc: Branislav Rankov Cc: Kevin Brodsky Cc: Vasily Gorbik Signed-off-by: Andrew Morton --- mm/kasan/common.c | 5 ----- mm/kasan/generic.c | 5 ----- mm/kasan/generic_report.c | 5 ----- mm/kasan/init.c | 5 ----- mm/kasan/quarantine.c | 10 ---------- mm/kasan/report.c | 5 ----- mm/kasan/tags.c | 5 ----- mm/kasan/tags_report.c | 5 ----- 8 files changed, 45 deletions(-) --- a/mm/kasan/common.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/common.c @@ -7,11 +7,6 @@ * * Some code borrowed from https://github.com/xairy/kasan-prototype by * Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #include --- a/mm/kasan/generic.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/generic.c @@ -7,11 +7,6 @@ * * Some code borrowed from https://github.com/xairy/kasan-prototype by * Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt --- a/mm/kasan/generic_report.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/generic_report.c @@ -7,11 +7,6 @@ * * Some code borrowed from https://github.com/xairy/kasan-prototype by * Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #include --- a/mm/kasan/init.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/init.c @@ -4,11 +4,6 @@ * * Copyright (c) 2015 Samsung Electronics Co., Ltd. * Author: Andrey Ryabinin - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #include --- a/mm/kasan/quarantine.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/quarantine.c @@ -6,16 +6,6 @@ * Copyright (C) 2016 Google, Inc. * * Based on code by Dmitry Chernenkov. - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * version 2 as published by the Free Software Foundation. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * General Public License for more details. - * */ #include --- a/mm/kasan/report.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/report.c @@ -7,11 +7,6 @@ * * Some code borrowed from https://github.com/xairy/kasan-prototype by * Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #include --- a/mm/kasan/tags.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/tags.c @@ -4,11 +4,6 @@ * * Copyright (c) 2018 Google, Inc. * Author: Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt --- a/mm/kasan/tags_report.c~kasan-drop-unnecessary-gpl-text-from-comment-headers +++ a/mm/kasan/tags_report.c @@ -7,11 +7,6 @@ * * Some code borrowed from https://github.com/xairy/kasan-prototype by * Andrey Konovalov - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #include