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=-11.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 08190C10F29 for ; Tue, 17 Mar 2020 03:10:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB35D20663 for ; Tue, 17 Mar 2020 03:10:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="FmkrITYH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726821AbgCQDKq (ORCPT ); Mon, 16 Mar 2020 23:10:46 -0400 Received: from mail-qk1-f194.google.com ([209.85.222.194]:45124 "EHLO mail-qk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726803AbgCQDKq (ORCPT ); Mon, 16 Mar 2020 23:10:46 -0400 Received: by mail-qk1-f194.google.com with SMTP id c145so30152616qke.12; Mon, 16 Mar 2020 20:10:43 -0700 (PDT) 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=xytRqayxQuC5eMurSet0/Fcn3iTENtGu+EYSbqGw130=; b=FmkrITYHFTvNr2BFMCHmyNzEbaygEXkRwYT+8L0le+HLxl7aGPYi36zK0x7FfTwSwB uZb59tI0dw8kYrxot+xGA3E0atoOHLXnDg8yjGywR3tFsrMUZAgS7rsKgUzzrRFsqd3U UuTgqQCIWnkl0sX1kPaECVc/M2Bv3iWdvE0TVecs9OBdTxt/DSu42AMmUgkkxz07mwar vjvvu7NBP9WWChqr5SkBnBvXL2eeHdzSIUK7vUNFt+AyTmP0FKg2g4KqFG1YW54J9ynC 6qnTG5K+o1V/6vBZB+Lfr7jqPol3wCokdknh0ecTlMiEOsBfz74g3L+YuTxysQg5ZkUa AxzQ== 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=xytRqayxQuC5eMurSet0/Fcn3iTENtGu+EYSbqGw130=; b=d/6Q3TVCC6Rhr/PQtoWt3o4dYCMftxwWclvUVzLngXbAeTD7EubMs7L8LlGjl4ZoyG wotdiImTMMmdG/K8gbvEKrAf+zo5oeAjM7NrDIExmJqmKcCITJ6SYck6I4TvLchg37id yv6BTgRwxVRT0AJXS74PC7KO4EqG2vnoutmWDqewZ5TWvWV6/AlQXNJCxttEQgu8LL/v XLgLGUAwcPATc1UywztMAMeiQP1yVzN0ePFKaDH2hCGU6f5OmBqKMuiJmHcBqVCbLPS1 lBLdfvPZToXqVD0hm7F64N/lKR1weAZdTu284lFAF6aC1pwnW5iklX19bhCwiZhyl4Xa 1EpQ== X-Gm-Message-State: ANhLgQ3oedVauUvxM1aSusP49Pw867efEZw7nXZd7wHPv0LKUeU+NEgm CIFEMcqbc3ilqcWMYxoLaGnprFfhjG9+99MasPgEXcVG X-Google-Smtp-Source: ADFU+vsxWiPD6zajQiVO96SdqcjDR+VfTl8TzIOFs4++mO88cdmCIZd5MLG43yOIn7OfsmfddPz3GyqCL0uQlTwBZ7c= X-Received: by 2002:ae9:c011:: with SMTP id u17mr2924638qkk.92.1584414642995; Mon, 16 Mar 2020 20:10:42 -0700 (PDT) MIME-Version: 1.0 References: <20200317011654.zkx5r7so53skowlc@google.com> In-Reply-To: <20200317011654.zkx5r7so53skowlc@google.com> From: Andrii Nakryiko Date: Mon, 16 Mar 2020 20:10:31 -0700 Message-ID: Subject: Re: [PATCH bpf] bpf: Support llvm-objcopy and llvm-objdump for vmlinux BTF To: Fangrui Song Cc: bpf , Networking , Daniel Borkmann , Nick Desaulniers , Nathan Chancellor , clang-built-linux@googlegroups.com, Stanislav Fomichev , "David S. Miller" , Alexei Starovoitov Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Mar 16, 2020 at 6:17 PM Fangrui Song wrote: > > Simplify gen_btf logic to make it work with llvm-objcopy and > llvm-objdump. We just need to retain one section .BTF. To do so, we can > use a simple objcopy --only-section=.BTF instead of jumping all the > hoops via an architecture-less binary file. > > We use a dd comment to change the e_type field in the ELF header from > ET_EXEC to ET_REL so that .btf.vmlinux.bin.o will be accepted by lld. > > Fixes: df786c9b9476 ("bpf: Force .BTF section start to zero when dumping from vmlinux") > Cc: Stanislav Fomichev > Cc: Nick Desaulniers > Tested-by: Nick Desaulniers > Reported-by: Nathan Chancellor > Link: https://github.com/ClangBuiltLinux/linux/issues/871 > Signed-off-by: Fangrui Song > --- > scripts/link-vmlinux.sh | 13 ++----------- > 1 file changed, 2 insertions(+), 11 deletions(-) > > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh > index dd484e92752e..84be8d7c361d 100755 > --- a/scripts/link-vmlinux.sh > +++ b/scripts/link-vmlinux.sh > @@ -120,18 +120,9 @@ gen_btf() > > info "BTF" ${2} > vmlinux_link ${1} > - LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} Is it really tested? Seems like you just dropped .BTF generation step completely... > > - # dump .BTF section into raw binary file to link with final vmlinux > - bin_arch=$(LANG=C ${OBJDUMP} -f ${1} | grep architecture | \ > - cut -d, -f1 | cut -d' ' -f2) > - bin_format=$(LANG=C ${OBJDUMP} -f ${1} | grep 'file format' | \ > - awk '{print $4}') > - ${OBJCOPY} --change-section-address .BTF=0 \ > - --set-section-flags .BTF=alloc -O binary \ > - --only-section=.BTF ${1} .btf.vmlinux.bin > - ${OBJCOPY} -I binary -O ${bin_format} -B ${bin_arch} \ > - --rename-section .data=.BTF .btf.vmlinux.bin ${2} > + # Extract .BTF section, change e_type to ET_REL, to link with final vmlinux > + ${OBJCOPY} --only-section=.BTF ${1} ${2} && printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 > } > > # Create ${2} .o file with all symbols from the ${1} object file > -- > 2.25.1.481.gfbce0eb801-goog