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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 91A7DC43441 for ; Tue, 27 Nov 2018 18:24:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 495AC20851 for ; Tue, 27 Nov 2018 18:24:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 495AC20851 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=iogearbox.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731763AbeK1FX3 (ORCPT ); Wed, 28 Nov 2018 00:23:29 -0500 Received: from www62.your-server.de ([213.133.104.62]:60340 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725758AbeK1FX3 (ORCPT ); Wed, 28 Nov 2018 00:23:29 -0500 Received: from [78.46.172.3] (helo=sslproxy06.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1gRi2M-0003j8-1c; Tue, 27 Nov 2018 19:24:42 +0100 Received: from [178.197.249.21] (helo=linux.home) by sslproxy06.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1gRi2L-000RJe-Qs; Tue, 27 Nov 2018 19:24:41 +0100 Subject: Re: [PATCH] arm64/bpf: use movn/movk/movk sequence to generate kernel addresses To: Will Deacon , Ard Biesheuvel Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, ast@fb.com References: <20181123172902.21480-1-ard.biesheuvel@linaro.org> <20181127182203.GA19721@arm.com> From: Daniel Borkmann Message-ID: Date: Tue, 27 Nov 2018 19:24:40 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20181127182203.GA19721@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.2/25158/Tue Nov 27 15:16:14 2018) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/27/2018 07:22 PM, Will Deacon wrote: > Hi Ard, > > On Fri, Nov 23, 2018 at 06:29:02PM +0100, Ard Biesheuvel wrote: >> On arm64, all executable code is guaranteed to reside in the vmalloc >> space (or the module space), and so jump targets will only use 48 >> bits at most, and the remaining bits are guaranteed to be 0x1. >> >> This means we can generate an immediate jump address using a sequence >> of one MOVN (move wide negated) and two MOVK instructions, where the >> first one sets the lower 16 bits but also sets all top bits to 0x1. >> >> Signed-off-by: Ard Biesheuvel >> --- > > Acked-by: Will Deacon > > Denial, Alexei, shall I take this via arm64, or would you rather take > it via davem? Yeah we can take it via bpf trees, thanks. Cheers, Daniel