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Marchesi" X-Patchwork-Id: 13151799 X-Patchwork-Delegate: bpf@iogearbox.net 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 F36A9C6FA8E for ; Fri, 24 Feb 2023 20:06:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229525AbjBXUGN (ORCPT ); Fri, 24 Feb 2023 15:06:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229509AbjBXUGM (ORCPT ); Fri, 24 Feb 2023 15:06:12 -0500 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C62B6F434 for ; Fri, 24 Feb 2023 12:05:42 -0800 (PST) Received: from pps.filterd (m0246617.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 31OHiB4L025488; Fri, 24 Feb 2023 20:04:16 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : content-type : mime-version; s=corp-2022-7-12; bh=9GpMp+3Egdvc9ZDZT/eNwemTaWbbvuVCQA+4viRmvdc=; b=mwAPw2qHe2fqrzrD6Bm3q4AjLNK8tyg9HGz9567msXkY4aKpACSuzM/DKmxRg2cnnWma DF9yciRspCr2EjapiNpbbhNYFE5exi3W01QAIHX/Z+FtjlBRe1y9dEC9LX5mu0zgnnd2 d0RuHz7iXi1r8/sWINTkV8JX6UFOwxeVs9HQ1QtyDHsOOO9t93kDeiEsk61N19blitud OH7YNbuP3x7rjS01ftQK5VZsNSUmivtrCg0axHOqh5zZRuQI8e3umVcpLMtWVQvA/b9M gAS9JJIJs7+aHGe8q1aU54T/k8KRTz/LPz+OLSq6q/cgYw7OfVkYShWSnaH7ZXfbkRlX Zg== Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.appoci.oracle.com [138.1.114.2]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3ntq7unvfm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Feb 2023 20:04:16 +0000 Received: from pps.filterd (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (8.17.1.5/8.17.1.5) with ESMTP id 31OJegq2025984; Fri, 24 Feb 2023 20:04:16 GMT Received: from nam11-dm6-obe.outbound.protection.outlook.com (mail-dm6nam11lp2176.outbound.protection.outlook.com [104.47.57.176]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 3ntn49xefg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Feb 2023 20:04:15 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=lua53lWl1iu7qihmMD1v1ycq0JwqAzFoLG+ZFTnRHHhWxWt87TPliAwvbqwa2wvnyC5QFFEPYLRKrSKAdCl3YIGelpFRDKEejlS6alVjMtmRa9P+QgvvnjgF4bac11yW1jYaDIq4Ec5n1XaD+zLjs1U1lH/GzbwmhVu0feYAIUt00l5wOGEwL15B5nj/NjKLzuDrWaxvNrNTJR3bSL6noS58kcDtj2qbYbf4vTs6ppE4/WIXGbKws0vQSJK1iqMYOeHVOvQp1xtKybwEfldgEnyivcr+51E7PcwIlESJX5y3sZ3EF++ZtWLtm29ksEpKm+6fZE315+mXQ4GEkXh8rw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=9GpMp+3Egdvc9ZDZT/eNwemTaWbbvuVCQA+4viRmvdc=; b=gmU5wTc2iA56oCz947wtJZe8ODgJUyrgbLvCQQKQc65U/RcHX88lgHFjjq7JOMNNqtNfJxNfd3CZa7IJECrym2MoHIVA6QRvCfXIR2EOGrKex1jz9vUYhALV2pdYeDzXZMbv4NBHnF8nE1/NQIAPIsYuoMUVK6iDckZLf44lgK1g3Je1zzXEgWPcGkTd8nB3dkFTNgy0wezBbcXOOKXxmaBsTuGk8H5dkeAq0L3l0+gP9GvSqw+YKLrwpRL66U0oy7wLUfidH1oGsudGukI1THmXJxXTCqXzXBaUK89WhyWC+j33g5eZXpGqkGyu+Qd/21+68fEJv3BXBEM3DOanzA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=9GpMp+3Egdvc9ZDZT/eNwemTaWbbvuVCQA+4viRmvdc=; b=nAJXa/6bnvTpY7KjKL3UUtyKUXhbyje+nKrxygarvmwIqIL40auQYzFppdnxIQ5Dr1amaDwlFpvSZjE8uOtGA+SjeKMCaOKZUV46z447Sq8tFKL4dct5tt0SWG0qOM77IzQNwZCczjIeX7IrZ04difROV4n4UBYiRVOck1Jv5TA= Received: from BYAPR10MB2888.namprd10.prod.outlook.com (2603:10b6:a03:88::32) by SA3PR10MB7024.namprd10.prod.outlook.com (2603:10b6:806:318::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6156.11; Fri, 24 Feb 2023 20:04:13 +0000 Received: from BYAPR10MB2888.namprd10.prod.outlook.com ([fe80::486a:626e:635a:3ce2]) by BYAPR10MB2888.namprd10.prod.outlook.com ([fe80::486a:626e:635a:3ce2%3]) with mapi id 15.20.6156.010; Fri, 24 Feb 2023 20:04:13 +0000 From: "Jose E. Marchesi" To: bpf Cc: Alexei Starovoitov , bpf@ietf.org Subject: [PATCH] bpf, docs: Document BPF insn encoding in term of stored bytes Date: Fri, 24 Feb 2023 21:04:07 +0100 Message-ID: <87y1om25l4.fsf@oracle.com> User-Agent: Gnus/5.13 (Gnus v5.13) X-ClientProxiedBy: LO2P265CA0295.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:a5::19) To BYAPR10MB2888.namprd10.prod.outlook.com (2603:10b6:a03:88::32) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BYAPR10MB2888:EE_|SA3PR10MB7024:EE_ X-MS-Office365-Filtering-Correlation-Id: f7cca548-0ae5-4a22-e489-08db16a24c9d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR10MB2888.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230025)(366004)(396003)(376002)(136003)(346002)(39860400002)(451199018)(36756003)(2906002)(83380400001)(26005)(186003)(2616005)(6506007)(316002)(38100700002)(66946007)(6916009)(66476007)(66556008)(4326008)(8676002)(5660300002)(8936002)(41300700001)(478600001)(6512007)(6666004)(86362001)(6486002);DIR:OUT;SFP:1101; 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This is hopefully easier to understand by implementors looking to generate and/or consume bytes conforming BPF instructions. The patch also clarifies that the unused bytes in a pseudo-instruction shall be cleared with zeros. Signed-off-by: Jose E. Marchesi --- Documentation/bpf/instruction-set.rst | 43 +++++++++++++-------------- 1 file changed, 21 insertions(+), 22 deletions(-) diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst index 01802ed9b29b..9b28c0e15bb6 100644 --- a/Documentation/bpf/instruction-set.rst +++ b/Documentation/bpf/instruction-set.rst @@ -38,15 +38,13 @@ eBPF has two instruction encodings: * the wide instruction encoding, which appends a second 64-bit immediate (i.e., constant) value after the basic instruction for a total of 128 bits. -The basic instruction encoding looks as follows for a little-endian processor, -where MSB and LSB mean the most significant bits and least significant bits, -respectively: +The fields conforming an encoded basic instruction are stored in the +following order: -============= ======= ======= ======= ============ -32 bits (MSB) 16 bits 4 bits 4 bits 8 bits (LSB) -============= ======= ======= ======= ============ -imm offset src_reg dst_reg opcode -============= ======= ======= ======= ============ + opcode:8 src:4 dst:4 offset:16 imm:32 // In little-endian BPF. + opcode:8 dst:4 src:4 offset:16 imm:32 // In big-endian BPF. + +Where, **imm** signed integer immediate value @@ -64,16 +62,17 @@ imm offset src_reg dst_reg opcode **opcode** operation to perform -and as follows for a big-endian processor: +Note that the contents of multi-byte fields ('imm' and 'offset') are +stored using big-endian byte ordering in big-endian BPF and +little-endian byte ordering in little-endian BPF. -============= ======= ======= ======= ============ -32 bits (MSB) 16 bits 4 bits 4 bits 8 bits (LSB) -============= ======= ======= ======= ============ -imm offset dst_reg src_reg opcode -============= ======= ======= ======= ============ +For example: -Multi-byte fields ('imm' and 'offset') are similarly stored in -the byte order of the processor. + opcode offset imm assembly + src dst + 07 0 1 00 00 44 33 22 11 r1 += 0x11223344 // little + dst src + 07 1 0 00 00 11 22 33 44 r1 += 0x11223344 // big Note that most instructions do not use all of the fields. Unused fields shall be cleared to zero. @@ -84,18 +83,18 @@ The 64 bits following the basic instruction contain a pseudo instruction using the same format but with opcode, dst_reg, src_reg, and offset all set to zero, and imm containing the high 32 bits of the immediate value. -================= ================== -64 bits (MSB) 64 bits (LSB) -================= ================== -basic instruction pseudo instruction -================= ================== +This is depicted in the following figure: + + basic_instruction pseudo_instruction + code:8 regs:16 offset:16 imm:32 | unused:32 imm:32 Thus the 64-bit immediate value is constructed as follows: imm64 = (next_imm << 32) | imm where 'next_imm' refers to the imm value of the pseudo instruction -following the basic instruction. +following the basic instruction. The unused bytes in the pseudo +instruction shall be cleared to zero. Instruction classes -------------------