From patchwork Mon Jun 8 13:39:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maria Teguiani X-Patchwork-Id: 224733 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=-22.4 required=3.0 tests=DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT,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 5C75DC433E0 for ; Mon, 8 Jun 2020 13:40:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2ED64206C3 for ; Mon, 8 Jun 2020 13:40:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="vfFfuKk/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729553AbgFHNku (ORCPT ); Mon, 8 Jun 2020 09:40:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729169AbgFHNkt (ORCPT ); Mon, 8 Jun 2020 09:40:49 -0400 Received: from mail-qt1-x849.google.com (mail-qt1-x849.google.com [IPv6:2607:f8b0:4864:20::849]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CBF3C08C5C2 for ; Mon, 8 Jun 2020 06:40:49 -0700 (PDT) Received: by mail-qt1-x849.google.com with SMTP id y7so15493206qti.8 for ; Mon, 08 Jun 2020 06:40:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=mdIufafxfrrN5p97gfztvM+9hSR3y2gR4LCb968Y1MQ=; b=vfFfuKk/I1t3OBBfnlUqXqVDJd7Ev54XpJ2HYXKe35Zz0K6k7tkdmNjZcmYRV+4JJJ ZOKiiNC+uB6qm1DxudDToCs74ExaLLm40Hf/oEkRCPs89jexvDvVUBMHNXiXrNg9Jtsc W2rrHaCJuuTsixfvNbJzwy1UD57BCvIlht4yeCtSr+SyI2mTX9eR4UoJ5X8bzsq16gJe iDb9xWNfCdjANKMaVrr9vfoESWoElX9wyl74gunnO1w1rY70SQRJqaUnTxnvwx/FP9FV DBiiOPUI4RaXAG7i4ckgUD2QdKbYz5gfs06m1Gt0d4c/8Ijrj4SZr6Ci4OH8f9FWj20B 9JYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=mdIufafxfrrN5p97gfztvM+9hSR3y2gR4LCb968Y1MQ=; b=qqhx8nuyY3m/O92vObQSe/cBCSAWMgpitTdYtq19gliy6PRYUBl7HlWe+OW9LOxeaD xndjuoohvFJ3r5kjwKadocwaOC4FCXDUVdAcLhuBea3WiNpYGKzT6LR7eAShThpThHTo dKMmiOk4P1LdktXnjCkEUW5Hd4zbKxuMK80zhNVXr5dTKeXm9XZAmwcI83sM7oPuNYzN CmpPGLu4fdcdPvDGgq6bCJIozwlFd8SAKC5LxIW/Hi0dIiDBU/b54ZBP7IQH7QXbzWLm 2QR8jKpjo2kkiTeSSui8B8JhZfey8HE7keCu68bs7yMjD4Fj4gBWQa/7imGC9Vgkc/uA qFTg== X-Gm-Message-State: AOAM530hxtTZBHHOZzeRt+dEDHAsauBYy+ObkCZWpXgXmTHT+w9Jt/m7 eHNQecD0xI8e8ypCOfTYQFxmuxdzHl8tZMwXBqiCs5EjsUVoqspagtntZd+HRHcjc1oaYKR7e+B d6t6MHtBDDh+IQ9eW9o59Lw7FhoWvqZyj0Gd2cEc5MGtyfrZfqFSxBdoJUhjgP0+r0dY= X-Google-Smtp-Source: ABdhPJwLNU3ymgsYXVRJM1llnASREqqoSd8JvQ67LZEDhepUSaN/pYdvxhlZMkvUV6ogILOfvQWUadDwCwE2ZA== X-Received: by 2002:ad4:50c8:: with SMTP id e8mr9014540qvq.98.1591623648283; Mon, 08 Jun 2020 06:40:48 -0700 (PDT) Date: Mon, 8 Jun 2020 13:39:59 +0000 Message-Id: <20200608133959.97810-1-teguiani@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.27.0.278.ge193c7cf3a9-goog Subject: [PATCH] bpf: Support llvm-objcopy for vmlinux BTF From: Maria Teguiani To: stable@vger.kernel.org Cc: kernel-team@android.com, Fangrui Song , Nathan Chancellor , Daniel Borkmann , Stanislav Fomichev , Andrii Nakryiko , Kees Cook , Michael Ellerman , Maria Teguiani Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Fangrui Song Simplify gen_btf logic to make it work with llvm-objcopy. The existing 'file format' and 'architecture' parsing logic is brittle and does not work with llvm-objcopy/llvm-objdump. 'file format' output of llvm-objdump>=11 will match GNU objdump, but 'architecture' (bfdarch) may not. .BTF in .tmp_vmlinux.btf is non-SHF_ALLOC. Add the SHF_ALLOC flag because it is part of vmlinux image used for introspection. C code can reference the section via linker script defined __start_BTF and __stop_BTF. This fixes a small problem that previous .BTF had the SHF_WRITE flag (objcopy -I binary -O elf* synthesized .data). Additionally, `objcopy -I binary` synthesized symbols _binary__btf_vmlinux_bin_start and _binary__btf_vmlinux_bin_stop (not used elsewhere) are replaced with more commonplace __start_BTF and __stop_BTF. Add 2>/dev/null because GNU objcopy (but not llvm-objcopy) warns "empty loadable segment detected at vaddr=0xffffffff81000000, is this intentional?" We use a dd command to change the e_type field in the ELF header from ET_EXEC to ET_REL so that lld will accept .btf.vmlinux.bin.o. Accepting ET_EXEC as an input file is an extremely rare GNU ld feature that lld does not intend to support, because this is error-prone. The output section description .BTF in include/asm-generic/vmlinux.lds.h avoids potential subtle orphan section placement issues and suppresses --orphan-handling=warn warnings. Fixes: df786c9b9476 ("bpf: Force .BTF section start to zero when dumping from vmlinux") Fixes: cb0cc635c7a9 ("powerpc: Include .BTF section") Reported-by: Nathan Chancellor Signed-off-by: Fangrui Song Signed-off-by: Daniel Borkmann Tested-by: Stanislav Fomichev Tested-by: Andrii Nakryiko Reviewed-by: Stanislav Fomichev Reviewed-by: Kees Cook Acked-by: Andrii Nakryiko Acked-by: Michael Ellerman (powerpc) Link: https://github.com/ClangBuiltLinux/linux/issues/871 Link: https://lore.kernel.org/bpf/20200318222746.173648-1-maskray@google.com (cherry picked from commit 90ceddcb495008ac8ba7a3dce297841efcd7d584) Cc: # 5.4.x Signed-off-by: Maria Teguiani --- arch/powerpc/kernel/vmlinux.lds.S | 6 ------ include/asm-generic/vmlinux.lds.h | 22 +++++++++++++++++++--- kernel/bpf/sysfs_btf.c | 11 +++++------ scripts/link-vmlinux.sh | 24 ++++++++++-------------- 4 files changed, 34 insertions(+), 29 deletions(-) diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 4638d2863388..060a1acd7c6d 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -326,12 +326,6 @@ SECTIONS *(.branch_lt) } -#ifdef CONFIG_DEBUG_INFO_BTF - .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { - *(.BTF) - } -#endif - .opd : AT(ADDR(.opd) - LOAD_OFFSET) { __start_opd = .; KEEP(*(.opd)) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index dae64600ccbf..b6d7347ccda7 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -496,10 +496,12 @@ __start___modver = .; \ KEEP(*(__modver)) \ __stop___modver = .; \ - . = ALIGN((align)); \ - __end_rodata = .; \ } \ - . = ALIGN((align)); + \ + BTF \ + \ + . = ALIGN((align)); \ + __end_rodata = .; /* RODATA & RO_DATA provided for backward compatibility. * All archs are supposed to use RO_DATA() */ @@ -588,6 +590,20 @@ __stop___ex_table = .; \ } +/* + * .BTF + */ +#ifdef CONFIG_DEBUG_INFO_BTF +#define BTF \ + .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \ + __start_BTF = .; \ + *(.BTF) \ + __stop_BTF = .; \ + } +#else +#define BTF +#endif + /* * Init task */ diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index 7ae5dddd1fe6..3b495773de5a 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -9,15 +9,15 @@ #include /* See scripts/link-vmlinux.sh, gen_btf() func for details */ -extern char __weak _binary__btf_vmlinux_bin_start[]; -extern char __weak _binary__btf_vmlinux_bin_end[]; +extern char __weak __start_BTF[]; +extern char __weak __stop_BTF[]; static ssize_t btf_vmlinux_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) { - memcpy(buf, _binary__btf_vmlinux_bin_start + off, len); + memcpy(buf, __start_BTF + off, len); return len; } @@ -30,15 +30,14 @@ static struct kobject *btf_kobj; static int __init btf_vmlinux_init(void) { - if (!_binary__btf_vmlinux_bin_start) + if (!__start_BTF) return 0; btf_kobj = kobject_create_and_add("btf", kernel_kobj); if (!btf_kobj) return -ENOMEM; - bin_attr_btf_vmlinux.size = _binary__btf_vmlinux_bin_end - - _binary__btf_vmlinux_bin_start; + bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux); } diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index aa1386079f0c..8b6325c2dfc5 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -113,9 +113,6 @@ vmlinux_link() gen_btf() { local pahole_ver - local bin_arch - local bin_format - local bin_file if ! [ -x "$(command -v ${PAHOLE})" ]; then echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available" @@ -133,17 +130,16 @@ gen_btf() info "BTF" ${2} LLVM_OBJCOPY=${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}') - bin_file=.btf.vmlinux.bin - ${OBJCOPY} --change-section-address .BTF=0 \ - --set-section-flags .BTF=alloc -O binary \ - --only-section=.BTF ${1} $bin_file - ${OBJCOPY} -I binary -O ${bin_format} -B ${bin_arch} \ - --rename-section .data=.BTF $bin_file ${2} + # Create ${2} which contains just .BTF section but no symbols. Add + # SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all + # deletes all symbols including __start_BTF and __stop_BTF, which will + # be redefined in the linker script. Add 2>/dev/null to suppress GNU + # objcopy warnings: "empty loadable segment detected at ..." + ${OBJCOPY} --only-section=.BTF --set-section-flags .BTF=alloc,readonly \ + --strip-all ${1} ${2} 2>/dev/null + # Change e_type to ET_REL so that it can be used to link final vmlinux. + # Unlike GNU ld, lld does not allow an ET_EXEC input. + printf '\1' | dd of=${2} conv=notrunc bs=1 seek=16 status=none } # Create ${2} .o file with all symbols from the ${1} object file