From patchwork Thu Dec 30 19:17:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: andrey.konovalov@linux.dev X-Patchwork-Id: 12701634 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA7D3C433EF for ; Thu, 30 Dec 2021 19:17:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CE1AE6B00C0; Thu, 30 Dec 2021 14:17:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C92EF6B00C3; Thu, 30 Dec 2021 14:17:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B31726B00C4; Thu, 30 Dec 2021 14:17:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0020.hostedemail.com [216.40.44.20]) by kanga.kvack.org (Postfix) with ESMTP id A25916B00C0 for ; Thu, 30 Dec 2021 14:17:19 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6C3B4181AC9CC for ; Thu, 30 Dec 2021 19:17:19 +0000 (UTC) X-FDA: 78975418998.16.EE522C4 Received: from out2.migadu.com (out2.migadu.com [188.165.223.204]) by imf17.hostedemail.com (Postfix) with ESMTP id A7C9C40004 for ; Thu, 30 Dec 2021 19:17:01 +0000 (UTC) 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=1640891838; 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=e/+XOYIRGvIBanpFyjOlgCosMJXg4zB2i7n/+ySGUAUeK9MKOTt9jR1RrGruBNEXa2i9dE CIKHNmHVFnTDkT7cxlEvy+h0hcMpVyWEphmxNbxRxKCfBaXBxVLdyrGUqI0Y0D/7W8G6r2 3wX/o8BqoQVPXbFZ4OtH5y7q+k8fECk= From: andrey.konovalov@linux.dev To: Andrew Morton Cc: Andrey Konovalov , Marco Elver , Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, linux-mm@kvack.org, Vincenzo Frascino , Catalin Marinas , Will Deacon , Mark Rutland , linux-arm-kernel@lists.infradead.org, Peter Collingbourne , Evgenii Stepanov , linux-kernel@vger.kernel.org, Andrey Konovalov Subject: [PATCH mm v5 38/39] kasan: documentation updates Date: Thu, 30 Dec 2021 20:17:13 +0100 Message-Id: In-Reply-To: References: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev X-Rspamd-Queue-Id: A7C9C40004 X-Stat-Signature: 7nan5jnpqhwamid3n9t5r7xmhzwwnd51 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="e/+XOYIR"; spf=pass (imf17.hostedemail.com: domain of andrey.konovalov@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=andrey.konovalov@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspamd-Server: rspam10 X-HE-Tag: 1640891821-361527 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 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.