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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 76D77C433DF for ; Thu, 27 Aug 2020 11:10:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3A8DF22CAF for ; Thu, 27 Aug 2020 11:10:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A8DF22CAF 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 D5C996B0008; Thu, 27 Aug 2020 07:10:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D0CC6900002; Thu, 27 Aug 2020 07:10:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C22386B000C; Thu, 27 Aug 2020 07:10:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id AC8C76B0008 for ; Thu, 27 Aug 2020 07:10:35 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 630FB180AD80F for ; Thu, 27 Aug 2020 11:10:35 +0000 (UTC) X-FDA: 77196080430.11.key79_15069312706c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin11.hostedemail.com (Postfix) with ESMTP id DED8C180F8B86 for ; Thu, 27 Aug 2020 11:10:34 +0000 (UTC) X-HE-Tag: key79_15069312706c X-Filterd-Recvd-Size: 3871 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Thu, 27 Aug 2020 11:10:34 +0000 (UTC) Received: from gaia (unknown [46.69.195.127]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 39DEE22BF3; Thu, 27 Aug 2020 11:10:31 +0000 (UTC) Date: Thu, 27 Aug 2020 12:10:28 +0100 From: Catalin Marinas To: Vincenzo Frascino Cc: Andrey Konovalov , Dmitry Vyukov , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 20/35] arm64: mte: Add in-kernel MTE helpers Message-ID: <20200827111027.GJ29264@gaia> References: <2cf260bdc20793419e32240d2a3e692b0adf1f80.1597425745.git.andreyknvl@google.com> <20200827093808.GB29264@gaia> <588f3812-c9d0-8dbe-fce2-1ea89f558bd2@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <588f3812-c9d0-8dbe-fce2-1ea89f558bd2@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: DED8C180F8B86 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On Thu, Aug 27, 2020 at 11:31:56AM +0100, Vincenzo Frascino wrote: > On 8/27/20 10:38 AM, Catalin Marinas wrote: > > On Fri, Aug 14, 2020 at 07:27:02PM +0200, Andrey Konovalov wrote: > >> +void * __must_check mte_set_mem_tag_range(void *addr, size_t size, u8 tag) > >> +{ > >> + void *ptr = addr; > >> + > >> + if ((!system_supports_mte()) || (size == 0)) > >> + return addr; > >> + > >> + tag = 0xF0 | (tag & 0xF); > >> + ptr = (void *)__tag_set(ptr, tag); > >> + size = ALIGN(size, MTE_GRANULE_SIZE); > > > > I think aligning the size is dangerous. Can we instead turn it into a > > WARN_ON if not already aligned? At a quick look, the callers of > > kasan_{un,}poison_memory() already align the size. > > The size here is used only for tagging purposes and if we want to tag a > subgranule amount of memory we end up tagging the granule anyway. Why do you > think it can be dangerous? In principle, I don't like expanding the size unless you are an allocator. Since this code doesn't control the placement of the object it was given, a warn seems more appropriate. > >> +/* > >> + * Assign allocation tags for a region of memory based on the pointer tag > >> + * x0 - source pointer > >> + * x1 - size > >> + * > >> + * Note: size is expected to be MTE_GRANULE_SIZE aligned > >> + */ > >> +SYM_FUNC_START(mte_assign_mem_tag_range) > >> + /* if (src == NULL) return; */ > >> + cbz x0, 2f > >> + /* if (size == 0) return; */ > > > > You could skip the cbz here and just document that the size should be > > non-zero and aligned. The caller already takes care of this check. > > I would prefer to keep the check here, unless there is a valid reason, since > allocate(0) is a viable option hence tag(x, 0) should be as well. The caller > takes care of it in one place, today, but I do not know where the API will be > used in future. That's why I said just document it in the comment above the function. The check is also insufficient if the size is not aligned to an MTE granule, so it's not really consistent. This function should end with a subs followed by b.gt as cbnz will get stuck in a loop for unaligned size. -- Catalin