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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 4C74EC433DB for ; Thu, 14 Jan 2021 09:39:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 072C323A22 for ; Thu, 14 Jan 2021 09:39:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728339AbhANJit (ORCPT ); Thu, 14 Jan 2021 04:38:49 -0500 Received: from foss.arm.com ([217.140.110.172]:46576 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727382AbhANJiR (ORCPT ); Thu, 14 Jan 2021 04:38:17 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1CB3E1FB; Thu, 14 Jan 2021 01:37:19 -0800 (PST) Received: from [10.0.0.31] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 66C6C3F70D; Thu, 14 Jan 2021 01:37:16 -0800 (PST) Subject: Re: [PATCH v2 1/4] kasan, arm64: Add KASAN light mode To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov , Andrey Konovalov References: <20210107172908.42686-1-vincenzo.frascino@arm.com> <20210107172908.42686-2-vincenzo.frascino@arm.com> <20210113171602.GD27045@gaia> From: Vincenzo Frascino Message-ID: <7125af39-2572-1b08-d223-51f4ea6e686b@arm.com> Date: Thu, 14 Jan 2021 09:40:57 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210113171602.GD27045@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/13/21 5:16 PM, Catalin Marinas wrote: > On Thu, Jan 07, 2021 at 05:29:05PM +0000, Vincenzo Frascino wrote: >> Architectures supported by KASAN HW can provide a light mode of >> execution. On an MTE enabled arm64 hw for example this can be identified >> with the asynch mode of execution. If an async exception occurs, the >> arm64 core updates a register which is asynchronously detected the next >> time in which the kernel is accessed. > > What do you mean by "the kernel is accessed"? Also, there is no > "exception" as such, only a bit in a register updated asynchronously. So > the last sentence could be something like: > > In this mode, if a tag check fault occurs, the TFSR_EL1 register is > updated asynchronously. The kernel checks the corresponding bits > periodically. > > (or you can be more precise on when the kernel checks for such faults) > Yes, I agree, I will change it accordingly. What I wrote has a similar meaning but your exposition is more clear. >> KASAN requires a specific mode of execution to make use of this hw feature. >> >> Add KASAN HW light execution mode. > > Shall we call it "fast"? ;) > >> --- /dev/null >> +++ b/include/linux/kasan_def.h >> @@ -0,0 +1,25 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _LINUX_KASAN_DEF_H >> +#define _LINUX_KASAN_DEF_H >> + >> +enum kasan_arg_mode { >> + KASAN_ARG_MODE_DEFAULT, >> + KASAN_ARG_MODE_OFF, >> + KASAN_ARG_MODE_LIGHT, >> + KASAN_ARG_MODE_PROD, >> + KASAN_ARG_MODE_FULL, >> +}; >> + >> +enum kasan_arg_stacktrace { >> + KASAN_ARG_STACKTRACE_DEFAULT, >> + KASAN_ARG_STACKTRACE_OFF, >> + KASAN_ARG_STACKTRACE_ON, >> +}; >> + >> +enum kasan_arg_fault { >> + KASAN_ARG_FAULT_DEFAULT, >> + KASAN_ARG_FAULT_REPORT, >> + KASAN_ARG_FAULT_PANIC, >> +}; >> + >> +#endif /* _LINUX_KASAN_DEF_H */ > > I thought we agreed not to expose the KASAN internal but come up with > another abstraction. Maybe this was after you posted these patches. > Yes, indeed we agreed and I am going to change it in v3. The agreement temporally came after I posted v2 hence it is not reflected here. -- Regards, Vincenzo