Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DD5FC433EF for ; Mon, 6 Dec 2021 21:47:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355870AbhLFVut (ORCPT ); Mon, 6 Dec 2021 16:50:49 -0500 Received: from out2.migadu.com ([188.165.223.204]:65152 "EHLO out2.migadu.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354630AbhLFVuq (ORCPT ); Mon, 6 Dec 2021 16:50:46 -0500 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1638827236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AV0M9szKvSlfXhwybxJe1jA9V5abexpCELFOGxjWDjg=; b=AbHNSooVjpyjTe3n28e2qeKWOSnqnQZToUN0NB3Ok/5lzPMsEokA5mj+OvjlVTA12oKMj2 /MHikLO0YXIdSqWmN8jOTpSl3elzNCdpfkuhh7vXYb0fQ0qQK4rfsOSqI7fLnZqic2wDYx A/0fT96PN8xSzDrK7+RCWJFJh2DXKMo= From: andrey.konovalov@linux.dev To: Marco Elver , Alexander Potapenko , Vincenzo Frascino , Catalin Marinas , Peter Collingbourne Cc: Andrey Konovalov , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, Andrew Morton , linux-mm@kvack.org, Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, Evgenii Stepanov , linux-kernel@vger.kernel.org, Andrey Konovalov Subject: [PATCH v2 33/34] kasan: documentation updates Date: Mon, 6 Dec 2021 22:44:10 +0100 Message-Id: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrey Konovalov Update KASAN documentation: - Bump Clang version requirement for HW_TAGS as ARM64_MTE depends on AS_HAS_LSE_ATOMICS as of commit 2decad92f4731 ("arm64: mte: Ensure TIF_MTE_ASYNC_FAULT is set atomically"), which requires Clang 12. - Add description of the new kasan.vmalloc command line flag. - Mention that SW_TAGS and HW_TAGS modes now support vmalloc tagging. - Explicitly say that the "Shadow memory" section is only applicable to software KASAN modes. - Mention that shadow-based KASAN_VMALLOC is supported on arm64. Signed-off-by: Andrey Konovalov --- Documentation/dev-tools/kasan.rst | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index 8089c559d339..7614a1fc30fa 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -30,7 +30,7 @@ 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+. +This mode is supported in GCC 10+ and Clang 12+. Both software KASAN modes work with SLUB and SLAB memory allocators, while the hardware tag-based KASAN currently only supports SLUB. @@ -206,6 +206,9 @@ additional boot parameters that allow disabling KASAN or controlling features: Asymmetric mode: a bad access is detected synchronously on reads and asynchronously on writes. +- ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc + allocations (default: ``on``). + - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack traces collection (default: ``on``). @@ -279,8 +282,8 @@ Software tag-based KASAN uses 0xFF as a match-all pointer tag (accesses through pointers with the 0xFF pointer tag are not checked). The value 0xFE is currently reserved to tag freed memory regions. -Software tag-based KASAN currently only supports tagging of slab and page_alloc -memory. +Software tag-based KASAN currently only supports tagging of slab, page_alloc, +and vmalloc memory. Hardware tag-based KASAN ~~~~~~~~~~~~~~~~~~~~~~~~ @@ -303,8 +306,8 @@ Hardware tag-based KASAN uses 0xFF as a match-all pointer tag (accesses through pointers with the 0xFF pointer tag are not checked). The value 0xFE is currently reserved to tag freed memory regions. -Hardware tag-based KASAN currently only supports tagging of slab and page_alloc -memory. +Hardware tag-based KASAN currently only supports tagging of slab, page_alloc, +and VM_ALLOC-based vmalloc memory. If the hardware does not support MTE (pre ARMv8.5), hardware tag-based KASAN will not be enabled. In this case, all KASAN boot parameters are ignored. @@ -319,6 +322,8 @@ checking gets disabled. Shadow memory ------------- +The contents of this section are only applicable to software KASAN modes. + The kernel maps memory in several different parts of the address space. The range of kernel virtual addresses is large: there is not enough real memory to support a real shadow region for every address that could be @@ -349,7 +354,7 @@ CONFIG_KASAN_VMALLOC With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the cost of greater memory usage. Currently, this is supported on x86, -riscv, s390, and powerpc. +arm64, riscv, s390, and powerpc. This works by hooking into vmalloc and vmap and dynamically allocating real shadow memory to back the mappings. -- 2.25.1