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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 BD80FC4363A for ; Tue, 20 Oct 2020 17:05:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C2762222D for ; Tue, 20 Oct 2020 17:05:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="V/PAKYc4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2395096AbgJTRFE (ORCPT ); Tue, 20 Oct 2020 13:05:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389638AbgJTRFE (ORCPT ); Tue, 20 Oct 2020 13:05:04 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 927D6C0613D1 for ; Tue, 20 Oct 2020 10:05:03 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id e22so3838634ejr.4 for ; Tue, 20 Oct 2020 10:05:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=C3MYOAyER7eRaYplTmQSfHj/vWn2iuqLFvr+uBlCcqo=; b=V/PAKYc4GxLuXpfbfMJ0VbWKyR+7WMwU1gnH/2YMxkbSDus2F5e2kUtOPOxVoC8ZT8 9opgnVcA6VPuNqboTwrxIqtb5hjkW48s8OtJ/zJ8t+NRCaa5LQM9yC5ONYmtVU3Q6GUU mUvklSgRgWxehghpVoRtCUSbLLAk/9e3gxvbiH5DVnaHE4OxUZyeQd2/i+x2d6gwMNM+ mh3ZvufUXbZyG9uA8NR096OFziC3Fpj3ssV+svvNfvLNiybSLx7RV7wcnOnwtbbnUtiI 4addjtvIv6hf+ooUbEpB6GD/qhE1nyN6d4TqRjxQp/zE4WZPCwAMncWphqcYGYhZDtuO Nvyg== 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:content-transfer-encoding; bh=C3MYOAyER7eRaYplTmQSfHj/vWn2iuqLFvr+uBlCcqo=; b=rsdWylrzbSIeekz5MVx/BrBZipe/gnXz34M/Sac7FTld6w7VHmmrCdDU/pPZWUyUl6 kefKVdxqJ4yPcpeGGlKoH3axRgFJdVWYaZl4W0CDA97nX0cuAUvISS1iNkKtfOArQLq+ NoUtq+eC/3F9KeNm95PcEAJJiuJv87OzByZUqQZef+FkrOELx6VpoBzI8/Qk359l3rE4 HWq5tmlXXqhDLuSaBUyjO1lkN5REHY3ihNHW/50e1wmOwctRrxH+wjmumfj0KlwLLx4L naq3HXq89xvGgn3v68yNURvXlnpolp7CT9PFsE6STWjHl8pGjDWEkyRTtarJ9ifttPEM gPjA== X-Gm-Message-State: AOAM533Mfy4G1X9hkzvKYlmn85IyKRbNtQ+z228ohu71SUsatCoCXhmu vHoZKp7YZ5WZPG60Qa+ATzdkHWnWKGHTYtT5bulE3w== X-Google-Smtp-Source: ABdhPJyt73d14bElB4Yml6R/uQKVIY6si4kfCKZNS+rE/uUq0/7JvG6q54/gPiIEvdHlSx8R8jv2pJht0NAHu9RBG+s= X-Received: by 2002:a17:906:4e19:: with SMTP id z25mr4369995eju.44.1603213501911; Tue, 20 Oct 2020 10:05:01 -0700 (PDT) MIME-Version: 1.0 References: <82b757bb-1f49-ab02-2f4b-89577d56fec9@kernel.org> <20201020122015.GH2294271@kernel.org> In-Reply-To: <20201020122015.GH2294271@kernel.org> From: Hao Luo Date: Tue, 20 Oct 2020 10:04:50 -0700 Message-ID: Subject: Re: Segfault in pahole 1.18 when building kernel 5.9.1 for arm64 To: Arnaldo Carvalho de Melo Cc: Jiri Slaby , =?UTF-8?B?w4lyaWNvIFJvbGlt?= , dwarves@vger.kernel.org, open list , Arnaldo Carvalho de Melo , Andrii Nakryiko , Alexei Starovoitov , bpf , Andrii Nakryiko Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org Thanks for reporting this and cc'ing me. I forgot to update the error messages when renaming the flags. I will send a patch to fix the error message. The commit commit f3d9054ba8ff1df0fc44e507e3a01c0964cabd42 Author: Hao Luo AuthorDate: Wed Jul 8 13:44:10 2020 -0700 btf_encoder: Teach pahole to store percpu variables in vmlinux BTF. encodes kernel global variables into BTF so that bpf programs can directly access them. If there is no need to access kernel global variables, it's perfectly fine to use '--btf_encode_force' to skip encoding bad symbols into BTF, or '--skip_encoding_btf_vars' to skip encoding all global vars all together. I will add these info into the updated error message. Also cc bpf folks for attention of this bug. Hao On Tue, Oct 20, 2020 at 5:20 AM Arnaldo Carvalho de Melo wrote: > > Em Tue, Oct 20, 2020 at 11:01:39AM +0200, Jiri Slaby escreveu: > > Hi, > > > > On 19. 10. 20, 1:18, =C3=89rico Rolim wrote: > > > I'm trying to build kernel 5.9.1 for arm64, and my dotconfig has > > > `CONFIG_DEBUG_INFO_BTF=3Dy`, which requires pahole for building. Howe= ver, pahole > > > version 1.18 segfaults during the build, as can be seen below: > > > > > > PAHOLE: Error: Found symbol of zero size when encoding btf (sym: > > > '__kvm_nvhe_arm64_ssbd_callback_required', cu: > > > 'arch/arm64/kernel/cpu_errata.c'). > > > > The symbol is an alias coming from arch/arm64/kernel/vmlinux.lds: > > __kvm_nvhe_arm64_ssbd_callback_required =3D arm64_ssbd_callback_require= d;; > > > > > PAHOLE: Error: Use '-j' or '--force' to ignore such symbols and force > > > emit the btf. > > > scripts/link-vmlinux.sh: line 141: 43837 Segmentation fault > > > LLVM_OBJCOPY=3D${OBJCOPY} ${PAHOLE} -J ${1} > > > LD .tmp_vmlinux.kallsyms1 > > > KSYM .tmp_vmlinux.kallsyms1.o > > > LD .tmp_vmlinux.kallsyms2 > > > KSYM .tmp_vmlinux.kallsyms2.o > > > LD vmlinux > > > BTFIDS vmlinux > > > FAILED: load BTF from vmlinux: Unknown error -2make: *** > > > [Makefile:1162: vmlinux] Error 255 > > > > > > It is possible to force the build to continue if > > > > > > LLVM_OBJCOPY=3D${OBJCOPY} ${PAHOLE} -J ${1} > > > > > > in scripts/link-vmlinux.sh is changed to > > > > > > LLVM_OBJCOPY=3D${OBJCOPY} ${PAHOLE} -J --btf_encode_force ${1} > > > > > > The suggested `-j` or `--force` flags don't exist, since they were re= moved in > > > [1]. I believe `--btf_encode_force` should be suggested instead. > > > > Agreed, '--btf_encode_force' makes pahole to proceed without crashes. > > > > > It should be noted that the same build, but with pahole version 1.17,= works > > > without issue, so I think this is either a regression in pahole or th= e script > > > will need to be changed for newer versions of pahole. > > > > Yeah, I observe the very same. I reported it at: > > https://bugzilla.suse.com/show_bug.cgi?id=3D1177921 > > Would it be possible to try with > https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?h=3Dtmp.li= bbtf_encoder > ? > > This switches to using libbpf for the BTF encoder and may have fixed > this problem. > > - Arnaldo > > > The backtrace: > > > (gdb) where > > > #0 __memmove_sse2_unaligned_erms () at > > ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:300 > > > #1 0x00007ffff7f78346 in memcpy (__len=3D, __src=3D > out>, __dest=3D, __dest=3D, __src=3D, > > __len=3D) at /usr/include/bits/string_fortified.h:34 > > > #2 gobuffer__add (gb=3D0x555555569aa0, s=3D0x7fffffffb50c, len=3D12)= at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/gobuffer.c:87 > > > #3 0x00007ffff7f8671f in btf_elf__add_datasec_type > > (btfe=3Dbtfe@entry=3D0x555555569a40, > > section_name=3Dsection_name@entry=3D0x7ffff7fa43ad ".data..percpu", > > var_secinfo_buf=3Dvar_secinfo_buf@entry=3D0x555555569ac0) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/libbtf.c:721 > > > #4 0x00007ffff7f8d766 in btf_elf__encode (flags=3D0 '\000', > > btfe=3D0x555555569a40) at /usr/src/debug/dwarves-1.18-1.1.x86_64/libbtf= .c:857 > > > #5 btf_elf__encode (btfe=3D0x555555569a40, flags=3D) = at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/libbtf.h:71 > > > #6 0x00007ffff7f7fc70 in btf_encoder__encode () at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/btf_encoder.c:213 > > > #7 0x00007ffff7f80d17 in cu__encode_btf (cu=3D0x55555638d9b0, verbos= e=3D0, > > force=3Dfalse, skip_encoding_vars=3Dfalse) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/btf_encoder.c:255 > > > #8 0x000055555555ac4d in pahole_stealer (cu=3D0x55555638d9b0, > > conf_load=3D) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/pahole.c:2366 > > > #9 0x00007ffff7f89dab in finalize_cu (cus=3D0x5555555622d0, > > dcu=3D0x7fffffffd080, conf=3D0x5555555610e0 , cu=3D0x5555563= 8d9b0) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2473 > > > #10 finalize_cu_immediately (conf=3D0x5555555610e0 , > > dcu=3D0x7fffffffd080, cu=3D0x55555638d9b0, cus=3D0x5555555622d0) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2317 > > > #11 cus__load_module (cus=3Dcus@entry=3D0x5555555622d0, conf=3D0x5555= 555610e0 > > , mod=3Dmod@entry=3D0x555555564760, dw=3D0x555555565960, > > elf=3Delf@entry=3D0x555555562360, filename=3D0x7fffffffe846 "ss") at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2473 > > > #12 0x00007ffff7f8a0f1 in cus__process_dwflmod (dwflmod=3D0x555555564= 760, > > userdata=3D, name=3D, base=3D, > > arg=3D0x7fffffffe1b0) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2518 > > > #13 0x00007ffff7d4f571 in dwfl_getmodules () from /usr/lib64/libdw.so= .1 > > > #14 0x00007ffff7f823ed in cus__process_file (filename=3D0x7fffffffe84= 6 "ss", > > fd=3D3, conf=3D, cus=3D0x5555555622d0) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2571 > > > #15 dwarf__load_file (cus=3D0x5555555622d0, conf=3D, > > filename=3D0x7fffffffe846 "ss") at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarf_loader.c:2588 > > > #16 0x00007ffff7f76771 in cus__load_file (cus=3Dcus@entry=3D0x5555555= 622d0, > > conf=3Dconf@entry=3D0x5555555610e0 , filename=3D0x7fffffffe8= 46 "ss") at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarves.c:1958 > > > #17 0x00007ffff7f798a8 in cus__load_files (cus=3D0x5555555622d0, > > conf=3D0x5555555610e0 , filenames=3D0x7fffffffe518) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/dwarves.c:2316 > > > #18 0x00005555555576fc in main (argc=3D3, argv=3D0x7fffffffe508) at > > /usr/src/debug/dwarves-1.18-1.1.x86_64/pahole.c:2687 > > > > > > I suspect: > > commit f3d9054ba8ff1df0fc44e507e3a01c0964cabd42 > > Author: Hao Luo > > AuthorDate: Wed Jul 8 13:44:10 2020 -0700 > > > > btf_encoder: Teach pahole to store percpu variables in vmlinux BTF. > > > > > > Which added this machinery (btf_elf__add_datasec_type in particular). > > > > > - [1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/p= ahole.c?h=3Dv1.18&id=3D1abc001417b579b86a9b27ff88c9095d8f498a46 > > > > > > Thanks, > > > =C3=89rico > > > > > > > > > -- > > js > > suse labs > > -- > > - Arnaldo