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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 2FE73C433E0 for ; Wed, 20 Jan 2021 19:19:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0508233EB for ; Wed, 20 Jan 2021 19:19:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392218AbhATTSz (ORCPT ); Wed, 20 Jan 2021 14:18:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392100AbhATTSv (ORCPT ); Wed, 20 Jan 2021 14:18:51 -0500 Received: from mail-lj1-x229.google.com (mail-lj1-x229.google.com [IPv6:2a00:1450:4864:20::229]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD2B1C061575 for ; Wed, 20 Jan 2021 11:18:10 -0800 (PST) Received: by mail-lj1-x229.google.com with SMTP id b10so27374579ljp.6 for ; Wed, 20 Jan 2021 11:18:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dYHtDjpZWN+ukOQQb2DCnkE1qoC/dUOlvltFcfPFpmI=; b=fmWlrjreuQkzitOVzU8EOIExZEbrSOyIjrOgqBvfp7Bjv4WlIYRumi1Bd75+lY95Sd 6nlpNaJGyzezbdMEBkwXNtIM+JHoW075k7RcqmnIKb0zV4dQ46QJ2i4q15lgod9dxAoW LlfeHsvj71rlbiCNldrzUMhVK4yp+KvETzqILtZynsSpags4C+QUOJDJpSAo5Aj8/i1p h1PZCwSE95P2jTQEs5dSECfuQuzbSeyPiQhvZB/JX+ehGVzhKVcoBj2NA3L7hJ49vYT5 0G8cGYGUTisC8rS/Dx1oXau4d8R2VL3BXUInLz5yfmzU9xu2HJJdawxXJZP5sTxCLQge l8Xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dYHtDjpZWN+ukOQQb2DCnkE1qoC/dUOlvltFcfPFpmI=; b=jBJWE37EzAATISDU1aken4e0OBsSmyByPK0GAZLsCfiX2pRmQSXeHiFshog6O1gs5N 2Bgsyab3LT4+oSTNTqmwrJZaasP6xCw17M2veAa1F/6F097QwIMqpOicWkrlJ7jLQz0x Cj3wxGqO63UgIOlxDyzrWzmFFg6eZwlCOogXWKqDOR11dslgfEHDfOjJje51DinCD2KR Tb2M27YNC5eCC2tHYgx4kXNYSI/StF5i01yFVjOkj75mERy23jaMzO9FWC/u6b4dpTrU pqYhXz0FDr7RYrSBrwoQ0/44pAwjUsDuvbVJ2G/Nv+pZv/l5u/VKyRL7tsuSfPRpzDUp Y4SQ== X-Gm-Message-State: AOAM531m4lD01xLmjFgh59AnBXoGtCG0tutYNK89M+fXH1Osu8WVqkAH 6iKQa3dX5qpcxdzmCj6xdaDvUiuIuU8hBDUqpZs= X-Google-Smtp-Source: ABdhPJwoF7aUvCRHiP+4npFhKKIPaQcQ3G+FMBsPe8hc0Cs9OuN5zP3Azygk/ihwVI4vG0CIe/5J+55T1hNq+G8faUc= X-Received: by 2002:a2e:3c01:: with SMTP id j1mr5135586lja.258.1611170289176; Wed, 20 Jan 2021 11:18:09 -0800 (PST) MIME-Version: 1.0 References: <20210119153519.3901963-1-yhs@fb.com> In-Reply-To: <20210119153519.3901963-1-yhs@fb.com> From: Alexei Starovoitov Date: Wed, 20 Jan 2021 11:17:57 -0800 Message-ID: Subject: Re: [PATCH bpf-next] bpf: permit size-0 datasec To: Yonghong Song Cc: bpf , Alexei Starovoitov , Daniel Borkmann , Kernel Team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Jan 19, 2021 at 7:35 AM Yonghong Song wrote: > When loading the ./test.o to the kernel with bpftool, > we see the following error: > libbpf: Error loading BTF: Invalid argument(22) > libbpf: magic: 0xeb9f > ... > [6] ARRAY (anon) type_id=5 index_type_id=7 nr_elems=4 > [7] INT __ARRAY_SIZE_TYPE__ size=4 bits_offset=0 nr_bits=32 encoding=(none) > [8] VAR _license type_id=6 linkage=1 > [9] DATASEC .rodata size=24 vlen=0 vlen == 0 > libbpf: Error loading .BTF into kernel: -22. BTF is optional, ignoring. > > Basically, libbpf changed .rodata datasec size to 24 since elf .rodata > section size is 24. The kernel then rejected the BTF since vlen = 0. > Note that the above kernel verifier failure can be worked around with > changing local variable "fmt" to a static or global, optionally const, variable. > > This patch permits a datasec with vlen = 0 in kernel. > > Signed-off-by: Yonghong Song Applied. Thanks