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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 B35ADC433E2 for ; Thu, 17 Sep 2020 16:15:56 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2629E20639 for ; Thu, 17 Sep 2020 16:15:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gkR6f+Rk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2629E20639 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=LtzbgvB1OBEkamLGu4vkfktbx3nrs3KElxfiM6st8Mk=; b=gkR6f+RksPrtWq4XsLpQwOSR8 rxFTtpqLxYkzH1sMSsHYpy6BicgSVGiebAHy6guOcWFYwDteAdYil8DN+DUN1/18w3u/qz624okLM jgtPb17eZdLGT5NKcw6dshf0e9bcxeN3fDwwg6wkuiX58z4jaiDzBe5r1IjCl1Yx2A2GRMcaEHUCV OfLMGEdrbA83E2q/kPNt9N0EbktBPj4GRnko+l4zaTzQThNRszbYZ5G1sRuXdh5/G4IkTnHknP/jA mkao+bxRaLZIegrV/eO9MWUP2FXUfO/eyfKRFCpVRlLt2A3IMr0Njg3P2mxodZq/gquGZeq2loEVp jddg0sffg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kIwYV-0001J1-Gh; Thu, 17 Sep 2020 16:14:43 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kIwYS-0001Ha-8u for linux-arm-kernel@lists.infradead.org; Thu, 17 Sep 2020 16:14:41 +0000 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 DD34D11D4; Thu, 17 Sep 2020 09:14:36 -0700 (PDT) Received: from [10.37.8.97] (unknown [10.37.8.97]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BC3BF3F68F; Thu, 17 Sep 2020 09:14:33 -0700 (PDT) Subject: Re: [PATCH v2 22/37] arm64: mte: Add in-kernel MTE helpers To: Catalin Marinas , Andrey Konovalov References: <4ac1ed624dd1b0851d8cf2861b4f4aac4d2dbc83.1600204505.git.andreyknvl@google.com> <20200917134653.GB10662@gaia> From: Vincenzo Frascino Message-ID: <9ef0a773-71f0-c1d6-b67e-ccf7d8bcbbe6@arm.com> Date: Thu, 17 Sep 2020 17:17:00 +0100 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: <20200917134653.GB10662@gaia> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200917_121440_582582_2A047B72 X-CRM114-Status: GOOD ( 17.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org, Marco Elver , Elena Petrova , Kevin Brodsky , Will Deacon , Branislav Rankov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , Andrew Morton , Evgenii Stepanov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/17/20 2:46 PM, Catalin Marinas wrote: >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c >> index 52a0638ed967..e238ffde2679 100644 >> --- a/arch/arm64/kernel/mte.c >> +++ b/arch/arm64/kernel/mte.c >> @@ -72,6 +74,52 @@ int memcmp_pages(struct page *page1, struct page *page2) >> return ret; >> } >> >> +u8 mte_get_mem_tag(void *addr) >> +{ >> + if (system_supports_mte()) >> + asm volatile(ALTERNATIVE("ldr %0, [%0]", >> + __MTE_PREAMBLE "ldg %0, [%0]", >> + ARM64_MTE) >> + : "+r" (addr)); > This doesn't do what you think it does. LDG indeed reads the tag from > memory but LDR loads the actual data at that address. Instead of the > first LDR, you may want something like "mov %0, #0xf << 56" (and use > some macros to avoid the hard-coded 56). > Seems I can't encode a shift of 56 neither in mov nor in orr. I propose to replace both with an and of the address with itself. This should not change anything. Thoughts? >> + >> + return 0xF0 | mte_get_ptr_tag(addr); >> +} >> + >> +u8 mte_get_random_tag(void) >> +{ >> + u8 tag = 0xF; >> + u64 addr = 0; >> + >> + if (system_supports_mte()) { >> + asm volatile(ALTERNATIVE("add %0, %0, %0", >> + __MTE_PREAMBLE "irg %0, %0", >> + ARM64_MTE) >> + : "+r" (addr)); > What was the intention here? The first ADD doubles the pointer value and > gets a tag out of it (possibly doubled as well, depends on the carry > from bit 55). Better use something like "orr %0, %0, #0xf << 56". > -- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel