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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 63363CA90AF for ; Wed, 13 May 2020 10:49:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2C80720675 for ; Wed, 13 May 2020 10:49:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C80720675 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AEE8B900123; Wed, 13 May 2020 06:48:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A9DA69000F3; Wed, 13 May 2020 06:48:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9B2C9900123; Wed, 13 May 2020 06:48:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0223.hostedemail.com [216.40.44.223]) by kanga.kvack.org (Postfix) with ESMTP id 81A0A9000F3 for ; Wed, 13 May 2020 06:48:59 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 3F7FA181AEF07 for ; Wed, 13 May 2020 10:48:59 +0000 (UTC) X-FDA: 76811373198.01.cord22_88a24d049751c X-HE-Tag: cord22_88a24d049751c X-Filterd-Recvd-Size: 4356 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 May 2020 10:48:58 +0000 (UTC) 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 084221FB; Wed, 13 May 2020 03:48:58 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 454D23F71E; Wed, 13 May 2020 03:48:56 -0700 (PDT) Date: Wed, 13 May 2020 11:48:50 +0100 From: Catalin Marinas To: Luis Machado Cc: linux-arm-kernel@lists.infradead.org, Will Deacon , Vincenzo Frascino , Szabolcs Nagy , Richard Earnshaw , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , linux-mm@kvack.org, linux-arch@vger.kernel.org, Alan Hayward , Omair Javaid Subject: Re: [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support Message-ID: <20200513104849.GC2719@gaia> References: <20200421142603.3894-1-catalin.marinas@arm.com> <20200421142603.3894-20-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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: Hi Luis, On Tue, May 12, 2020 at 04:05:15PM -0300, Luis Machado wrote: > On 4/21/20 11:25 AM, Catalin Marinas wrote: > > Add support for bulk setting/getting of the MTE tags in a tracee's > > address space at 'addr' in the ptrace() syscall prototype. 'data' points > > to a struct iovec in the tracer's address space with iov_base > > representing the address of a tracer's buffer of length iov_len. The > > tags to be copied to/from the tracer's buffer are stored as one tag per > > byte. > > > > On successfully copying at least one tag, ptrace() returns 0 and updates > > the tracer's iov_len with the number of tags copied. In case of error, > > either -EIO or -EFAULT is returned, trying to follow the ptrace() man > > page. > > > > Note that the tag copying functions are not performance critical, > > therefore they lack optimisations found in typical memory copy routines. > > > > Signed-off-by: Catalin Marinas > > Cc: Will Deacon > > Cc: Alan Hayward > > Cc: Luis Machado > > Cc: Omair Javaid > > --- > > > > Notes: > > New in v3. > > > > arch/arm64/include/asm/mte.h | 17 ++++ > > arch/arm64/include/uapi/asm/ptrace.h | 3 + > > arch/arm64/kernel/mte.c | 127 +++++++++++++++++++++++++++ > > arch/arm64/kernel/ptrace.c | 15 +++- > > arch/arm64/lib/mte.S | 50 +++++++++++ > > 5 files changed, 211 insertions(+), 1 deletion(-) > > > I started working on MTE support for GDB and I'm wondering if we've already > defined a way to check for runtime MTE support (as opposed to a HWCAP2-based > check) in a traced process. > > Originally we were going to do it via empty-parameter ptrace calls, but you > had mentioned something about a proc-based method, if I'm not mistaken. We could expose more information via proc_pid_arch_status() but that would be the tagged address ABI and tag check fault mode and intended for human consumption mostly. We don't have any ptrace interface that exposes HWCAPs. Since the gdbserver runs on the same machine as the debugged process, it can check the HWCAPs itself, they are the same for all processes. BTW, in my pre-v4 patches (hopefully I'll post v4 this week), I changed the ptrace tag access slightly to return an error (and no tags copied) if the page has not been mapped with PROT_MTE. The other option would have been read-as-zero/write-ignored as per the hardware behaviour. Either option is fine by me but I thought the write-ignored part would be more confusing for the debugger. If you have any preference here, please let me know. -- Catalin