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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 2F321C433E0 for ; Tue, 9 Feb 2021 06:10:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1DE264E8A for ; Tue, 9 Feb 2021 06:10:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229916AbhBIGKe (ORCPT ); Tue, 9 Feb 2021 01:10:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbhBIGK2 (ORCPT ); Tue, 9 Feb 2021 01:10:28 -0500 Received: from mail-yb1-xb36.google.com (mail-yb1-xb36.google.com [IPv6:2607:f8b0:4864:20::b36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39E0DC06178B; Mon, 8 Feb 2021 22:09:48 -0800 (PST) Received: by mail-yb1-xb36.google.com with SMTP id p193so3342917yba.4; Mon, 08 Feb 2021 22:09:48 -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=MTPoQ0Q6XAkl3H6eGQ5w2fvWx5OkrV+GZHc8bRprjjs=; b=EQWHBrZlWxeHnFuMUEORZJ5Gdz6jSsegK0zxZW68I7O9eDp6TITtdi+U9X/LUNB/mF XSv0fWTq93PpgclmdwbW9wpK+41sR39Hh5EzcE8YHPWEswVIWEbNqh0X/Xjd6Nc7yLfa b+yK59LcLSwksCs6QRzxr5qe+9pdCBZ00Mvnbf2rE5QuHXPmzKH8SOLfhUKrBue61R7R 8Lvw3bFqTXkvItDgovvAqVlv5l1W2Co6Chrm6t5GfmBMoozhuO5378bWaFOVlxSHozIy 0q9JHZFfJr/ZAnvT5/FkNfAsmuhryXWnTZCT+/CSW0Xx8iPctLZNrdlZjD37jEbG4fAw LkIw== 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=MTPoQ0Q6XAkl3H6eGQ5w2fvWx5OkrV+GZHc8bRprjjs=; b=KxJrwMnJnztXUql8nPwvpL9IWWStep1oqnS0aUBwM7hMwniz62gQKjxYrecLycD8hX Vm/R9MrLnRtohw7+YBu7dNICBSHKj2wTfIhT37QN2lqMNSlVOVuWMLwjr86kmCDp/cn7 1HwV3bOxiA7CvTddaqezHTv5pxEaRA9GtoxaH+JQ+WieeO1U3cdN1KUev//Ux4N4sem7 Jn7DM00ZcfXBEr6UJtwEeL5iMrshao6ctgjqYpHvYdysR6A6lqO0FIsGjCZn5MBB/BVT qcWpzLqFJYi1c++GYgfHdk0/wW3ObYKW5WaNJ59qJ/9V8NkpXcfHMvQnXVyiGzSpwW/r 8kqw== X-Gm-Message-State: AOAM531EmH9URiDUbSyqItYdCFaKFzke900GccCHz5FQU98L1HboETg2 EWQWV7MkO/3bERWmaehk+ta26wBXtIqy5An6m10= X-Google-Smtp-Source: ABdhPJyrJL+l0TZ2vtqs6c8jUQ1PE0mrqvQzIw/gGKqZqKc48X9B4x2Vs7rwka4MeUd5DEcSyk1sMjvPPl3MpdUCvR8= X-Received: by 2002:a25:f40e:: with SMTP id q14mr30484178ybd.230.1612850987521; Mon, 08 Feb 2021 22:09:47 -0800 (PST) MIME-Version: 1.0 References: <20210209034416.GA1669105@ubuntu-m3-large-x86> <20210209052311.GA125918@ubuntu-m3-large-x86> In-Reply-To: <20210209052311.GA125918@ubuntu-m3-large-x86> From: Andrii Nakryiko Date: Mon, 8 Feb 2021 22:09:36 -0800 Message-ID: Subject: Re: FAILED unresolved symbol vfs_truncate on arm64 with LLVM To: Nathan Chancellor Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Nick Desaulniers , Networking , bpf , clang-built-linux , Veronika Kabatova , Jiri Olsa Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Feb 8, 2021 at 9:23 PM Nathan Chancellor wrote: > > On Mon, Feb 08, 2021 at 08:45:43PM -0800, Andrii Nakryiko wrote: > > On Mon, Feb 8, 2021 at 7:44 PM Nathan Chancellor wrote: > > > > > > Hi all, > > > > > > Recently, an issue with CONFIG_DEBUG_INFO_BTF was reported for arm64: > > > https://groups.google.com/g/clang-built-linux/c/de_mNh23FOc/m/E7cu5BwbBAAJ > > > > > > $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \ > > > LLVM=1 O=build/aarch64 defconfig > > > > > > $ scripts/config \ > > > --file build/aarch64/.config \ > > > -e BPF_SYSCALL \ > > > -e DEBUG_INFO_BTF \ > > > -e FTRACE \ > > > -e FUNCTION_TRACER > > > > > > $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \ > > > LLVM=1 O=build/aarch64 olddefconfig all > > > ... > > > FAILED unresolved symbol vfs_truncate > > > ... > > > > > > My bisect landed on commit 6e22ab9da793 ("bpf: Add d_path helper") > > > although that seems obvious given that is what introduced > > > BTF_ID(func, vfs_truncate). > > > > > > I am using the latest pahole v1.20 and LLVM is at > > > https://github.com/llvm/llvm-project/commit/14da287e18846ea86e45b421dc47f78ecc5aa7cb > > > although I can reproduce back to LLVM 10.0.1, which is the earliest > > > version that the kernel supports. I am very unfamiliar with BPF so I > > > have no idea what is going wrong here. Is this a known issue? > > > > > > > I'll skip the reproduction games this time and will just request the > > vmlinux image. Please upload somewhere so that we can look at DWARF > > and see what's going on. Thanks. > > > > Sure thing, let me know if this works. I uploaded in two places to make > it easier to grab: > > zstd compressed: > https://github.com/nathanchance/bug-files/blob/3b2873751e29311e084ae2c71604a1963f5e1a48/btf-aarch64/vmlinux.zst > Thanks. I clearly see at least one instance of seemingly well-formed vfs_truncate DWARF declaration. Also there is a proper ELF symbol for it. Which means it should have been generated in BTF, but it doesn't appear to be, so it does seem like a pahole bug. I (or someone else before me) will continue tomorrow. $ llvm-dwarfdump vmlinux ... 0x00052e6f: DW_TAG_subprogram DW_AT_name ("vfs_truncate") DW_AT_decl_file ("/home/nathan/cbl/src/linux/include/linux/fs.h") DW_AT_decl_line (2520) DW_AT_prototyped (true) DW_AT_type (0x000452cb "long int") DW_AT_declaration (true) DW_AT_external (true) 0x00052e7b: DW_TAG_formal_parameter DW_AT_type (0x00045fc6 "const path*") 0x00052e80: DW_TAG_formal_parameter DW_AT_type (0x00045213 "long long int") ... $ llvm-readelf -s vmlinux | rg vfs_truncate 15013: ffff800011c22418 4 OBJECT LOCAL DEFAULT 24 __BTF_ID__func__vfs_truncate__609 22531: ffff80001189fe0d 0 NOTYPE LOCAL DEFAULT 17 __kstrtab_vfs_truncate 22532: ffff8000118a985b 0 NOTYPE LOCAL DEFAULT 17 __kstrtabns_vfs_truncate 22534: ffff800011873b7c 0 NOTYPE LOCAL DEFAULT 8 __ksymtab_vfs_truncate 176099: ffff80001031f430 360 FUNC GLOBAL DEFAULT 2 vfs_truncate $ bpftool btf dump file vmlinux | rg vfs_truncate > uncompressed: > https://1drv.ms/u/s!AsQNYeB-IEbqjQiUOspbEdXx49o7?e=ipA9Hv > > Cheers, > Nathan