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=-19.2 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 B8C16C10F29 for ; Tue, 17 Mar 2020 05:44:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73F4F20663 for ; Tue, 17 Mar 2020 05:44:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="oR20OtKx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725906AbgCQFoF (ORCPT ); Tue, 17 Mar 2020 01:44:05 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:39581 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725876AbgCQFoE (ORCPT ); Tue, 17 Mar 2020 01:44:04 -0400 Received: by mail-pg1-f194.google.com with SMTP id b22so5101333pgb.6 for ; Mon, 16 Mar 2020 22:44:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=5XZNKNf1Nmnnst9nU+EusoDsLPNxMr6FTIAlfC6wQT0=; b=oR20OtKx+2C3GAiAJfcf7IovKUcFdHw34eS+PCcFelkkFgPvOChZi5VdJzlNd7PTh+ EBG+D6wl9XdelkEcJd9fy2qY4tWfE/ISU6E8jgNcf1nMdyNzPhJsUPgb3klpPOY87Wjq +0qWKPAoNJp+yNN2JXkGfI7s1dftPG00ArhTfhUqq4anpUOsNoyXqBQJyO6vOc/iILXQ VuODM7oj0+AHXEP8MheqquYendjz3GP62tbLDiOlardD53GlmqjJocZIW5tssyyJL2Ea EEi1ifz2EQUQ/9wG1ibkj5Jn060CKSAs3ex8lQV+7a+oPms1AbCVqil4n5PngSbHoAAt 9iUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5XZNKNf1Nmnnst9nU+EusoDsLPNxMr6FTIAlfC6wQT0=; b=ha6PSVQmL8HsjJ8o5OzjMRYzyE+hjV8TDth9YA/TUJptKbhqrzCMP6CGgR9vgq/fuR sN4i2CMgyRsVXAUImsExfqd8l+bwmzIsr6BUflpI0Q1B2X+110N8RLLtqfzFpyOWXlMT FFJOnJ++6bkYlVcmneP1i4ZAwClVxykBorBqlkVsZAfRi+QnrQdLqoiTrFCrRbggPB/N ffcXfSlnOlq2F4lW2QtPE0GC0CUC78DEUCs6vxJhz/TZzPik9m2Rj4zWtIKrW2wNuOF9 PrkpAK32MCM6yK++Lh3KUuKJewu7OBFcdJLix3erw/gXQtz08Wqsp4+vi9/J4tPfx7lr By5Q== X-Gm-Message-State: ANhLgQ1Ko9VN/jiRuZLuFakNAOFeStvBb5MG5yzN3i4fk2rlhxepm5mq mZSf8kQ3q/PPcCP9eT9UMTRFkw== X-Google-Smtp-Source: ADFU+vvf2xu89ZSTNjSjPcbteeLzMnTgHmqbGt1ozSM0sRKIo+wX2Hwfc/buXGzXwJdIPDKkYbqV4w== X-Received: by 2002:a63:7e56:: with SMTP id o22mr3269433pgn.136.1584423843100; Mon, 16 Mar 2020 22:44:03 -0700 (PDT) Received: from google.com ([2620:15c:2ce:0:9efe:9f1:9267:2b27]) by smtp.gmail.com with ESMTPSA id e24sm1563191pfi.200.2020.03.16.22.44.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 22:44:02 -0700 (PDT) Date: Mon, 16 Mar 2020 22:43:59 -0700 From: Fangrui Song To: Andrii Nakryiko Cc: bpf , Networking , Daniel Borkmann , Nick Desaulniers , Nathan Chancellor , clang-built-linux@googlegroups.com, Stanislav Fomichev , "David S. Miller" , Alexei Starovoitov Subject: [PATCH bpf v3] bpf: Support llvm-objcopy and llvm-objdump for vmlinux BTF Message-ID: <20200317054359.snyyojyf6gjxufij@google.com> References: <20200317011654.zkx5r7so53skowlc@google.com> <20200317033701.w7jwos7mvfnde2t2@google.com> <20200317052120.diawg3a75kxl5hkn@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2020-03-16, Andrii Nakryiko wrote: >On Mon, Mar 16, 2020 at 10:21 PM Fangrui Song wrote: >> >> >> On 2020-03-16, Andrii Nakryiko wrote: >> >On Mon, Mar 16, 2020 at 8:37 PM Fangrui Song wrote: >> >> >> >> On 2020-03-16, Andrii Nakryiko wrote: >> >> >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... >> >> >> >> Sorry, dropped the whole line:/ >> >> I don't know how to test .BTF . I can only check readelf -S... >> >> >> >> Attached the new patch. >> >> >> >> >> >> From 02afb9417d4f0f8d2175c94fc3797a94a95cc248 Mon Sep 17 00:00:00 2001 >> >> From: Fangrui Song >> >> Date: Mon, 16 Mar 2020 18:02:31 -0700 >> >> Subject: [PATCH bpf v2] bpf: Support llvm-objcopy and llvm-objdump for >> >> vmlinux BTF >> >> >> >> Simplify gen_btf logic to make it work with llvm-objcopy and llvm-objdump. >> >> 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 can be accepted by lld. >> >> >> >> Fixes: df786c9b9476 ("bpf: Force .BTF section start to zero when dumping from vmlinux") >> >> Cc: Stanislav Fomichev >> >> Cc: Nick Desaulniers >> >> Reported-by: Nathan Chancellor >> >> Link: https://github.com/ClangBuiltLinux/linux/issues/871 >> >> Signed-off-by: Fangrui Song >> >> --- >> >> scripts/link-vmlinux.sh | 14 +++----------- >> >> 1 file changed, 3 insertions(+), 11 deletions(-) >> >> >> >> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh >> >> index dd484e92752e..b23313944c89 100755 >> >> --- a/scripts/link-vmlinux.sh >> >> +++ b/scripts/link-vmlinux.sh >> >> @@ -120,18 +120,10 @@ gen_btf() >> >> >> >> info "BTF" ${2} >> >> vmlinux_link ${1} >> >> - LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} >> >> + ${PAHOLE} -J ${1} >> > >> >I'm not sure why you are touching this line at all. LLVM_OBJCOPY part >> >is necessary, pahole assumes llvm-objcopy by default, but that can >> >(and should for objcopy) be overridden with LLVM_OBJCOPY. >> >> Why is LLVM_OBJCOPY assumed? What if llvm-objcopy is not available? > >It's pahole assumption that we have to live with. pahole assumes >llvm-objcopy internally, unless it is overriden with LLVM_OBJCOPY env >var. So please revert this line otherwise you are breaking it for GCC >objcopy case. Acknowledged. Uploaded v3. I added back 2>/dev/null which was removed by a previous change, to suppress GNU objcopy warnings. The warnings could be annoying in V=1 output. >> This is confusing that one tool assumes llvm-objcopy while the block >> below immediately uses GNU objcopy (without this patch). >> >> e83b9f55448afce3fe1abcd1d10db9584f8042a6 "kbuild: add ability to >> generate BTF type info for vmlinux" does not say why LLVM_OBJCOPY is >> set. >> >> >> >> >> - # dump .BTF section into raw binary file to link with final vmlinux >> >> - bin_arch=$(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 >> >> From ca3597477542453e9f63185c27c162da081a4baf Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Mon, 16 Mar 2020 22:38:23 -0700 Subject: [PATCH bpf v3] bpf: Support llvm-objcopy and llvm-objdump for vmlinux BTF Simplify gen_btf logic to make it work with llvm-objcopy and llvm-objdump. Add 2>/dev/null to suppress GNU objcopy (but not llvm-objcopy) warnings "empty loadable segment detected at vaddr=0xffffffff81000000, is this intentional?" Our use of --only-section drops many SHF_ALLOC sections which will essentially nullify program headers. When used as linker input, program headers are simply ignored. We use a dd command to change the e_type field in the ELF header from ET_EXEC to ET_REL so that .btf.vmlinux.bin.o can be accepted by lld. Accepting ET_EXEC as an input file is an extremely rare GNU ld feature that lld does not intend to support, because this is very error-prone. Fixes: df786c9b9476 ("bpf: Force .BTF section start to zero when dumping from vmlinux") Cc: Stanislav Fomichev Cc: Nick Desaulniers Reported-by: Nathan Chancellor Link: https://github.com/ClangBuiltLinux/linux/issues/871 Signed-off-by: Fangrui Song --- scripts/link-vmlinux.sh | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index dd484e92752e..c3e808a89d4a 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -122,16 +122,8 @@ gen_btf() vmlinux_link ${1} LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} - # dump .BTF section into raw binary file to link with final vmlinux - bin_arch=$(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} ${2} 2> /dev/null && printf '\1' | dd of=${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