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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29E9FCA1008 for ; Tue, 5 Sep 2023 21:32:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243679AbjIEVcy (ORCPT ); Tue, 5 Sep 2023 17:32:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232877AbjIEVcx (ORCPT ); Tue, 5 Sep 2023 17:32:53 -0400 Received: from pandora.armlinux.org.uk (unknown [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5EE19C; Tue, 5 Sep 2023 14:32:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=LKja5aws2FuNbyMoiBbVd5qqc3cfPi6iSJhvodwsuqM=; b=bhse1LJf0wCvKVxWcxMHkE2xQX 1w5p5Ls0CgbTqToctz5FOJayXxu22r1vtmpavi6mHDvw/EhXjGib6Fscu//F6EUB5d74kx6/oi/UG BgZ8htWEgiRNfZ3c1eUF+s8rRjhn6mh1Z99+md+APBnvyVuU0q5xkxF4nnkRVv1BkfKrtxL0RkpIM EQKrBeLwSPQLCfK0fxY3yWnHDq7XmgDtYXMZgtBhjxcinQFjK0y2w/ekb9o/PJKMEan8mJRGCkTkg x/6sGZHymUxuu/mWm4bR7iT7vE/1Jl8sVsAA/H5Kd5rxK6zZQRULsAaCu6uMz7CnK/qsweZIWS+ni 9AsRTH0g==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:36498) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1qddez-0008Kz-3A; Tue, 05 Sep 2023 22:32:34 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1qddez-000424-EO; Tue, 05 Sep 2023 22:32:33 +0100 Date: Tue, 5 Sep 2023 22:32:33 +0100 From: "Russell King (Oracle)" To: Puranjay Mohan Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shubham Bansal , Mykola Lysenko , Shuah Khan , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 4/8] arm32, bpf: add support for unconditional bswap instruction Message-ID: References: <20230905210621.1711859-1-puranjay12@gmail.com> <20230905210621.1711859-5-puranjay12@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230905210621.1711859-5-puranjay12@gmail.com> Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Sep 05, 2023 at 09:06:17PM +0000, Puranjay Mohan wrote: > The cpuv4 added a new unconditional bswap instruction with following > behaviour: > > BPF_ALU64 | BPF_TO_LE | BPF_END with imm = 16/32/64 means: > dst = bswap16(dst) > dst = bswap32(dst) > dst = bswap64(dst) > > As we already support converting to big-endian from little-endian we can > use the same for unconditional bswap. > Since ARM32 is always little-endian, just treat the unconditional scenario This is not true. Arm32 BPF is disabled for BE32 but not for BE8. It's entirely possible to build a kernel using BE8 for ARMv7 and have the BPF JIT enabled: select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32 So it's not true to say "Since ARM32 is always little-endian". -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!