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=-2.8 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,SPF_HELO_NONE,SPF_PASS 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 06E8BC433DB for ; Fri, 19 Mar 2021 18:39:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C529B61980 for ; Fri, 19 Mar 2021 18:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230336AbhCSSj0 (ORCPT ); Fri, 19 Mar 2021 14:39:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231268AbhCSSjN (ORCPT ); Fri, 19 Mar 2021 14:39:13 -0400 Received: from mail-yb1-xb32.google.com (mail-yb1-xb32.google.com [IPv6:2607:f8b0:4864:20::b32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D244C06174A; Fri, 19 Mar 2021 11:39:13 -0700 (PDT) Received: by mail-yb1-xb32.google.com with SMTP id o83so7305340ybg.1; Fri, 19 Mar 2021 11:39:13 -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=oECfPVWZh88FdDeweITHIouwjzeldtTpzGePira8Ucg=; b=Nva22x3T0stY9HEci3Ps9OHRXjUPdSFSDa6dEZti4/i5OCCmliQ3Ibc6zl3rUIq3KH o76ii4xKP8oiwa9UouR7NORfF0ySWCcvFq8MwUeORULGGWP1356i1G2BUcjU9ZUWYc9A psFP+0ibkNVYp+HgBG2L1N5SM5A2qnZw2RekBRaHNoxBBpfEDYlOal4/eIZK+mjLJJCv HLJofxZasfo23S4Z6aVW3mcx5nYX3MnF5V+G9MMgqkZdvxe70UozNi28S6k9Cbr+pHwp ozweqqG35mFgD+6D+1nF1Ensx3L5FDxEQsY5wVKLYHFGKPCQh+lfYG2IGUOy54RBeCDh Gofw== 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=oECfPVWZh88FdDeweITHIouwjzeldtTpzGePira8Ucg=; b=msapWhSfDzePxl0NGTSEVxXFCjC7xOMJI8l83VdznxRUxyiWnXvCch36mMGyzODUyr 5MkGmVuDEPWomQQcJV4qi8kTv6JDKrgt1F4i6MiuP2b9crGtE6IFVeog4Q29LsOnTI3p UeO1NPD51Fo7hBUVmmfSuQ9TjNhp7bcQLxBVBDeFuYxKqXjcMX9Kx2Yi4V0CzOF/W2+J 9TitsMqGK7ZUdl600/kahXeX4c+pMiHUSVruRhGs91z6wyeVQB2o+JrI9Ray1EUq6Kv1 JU0RM0va0l1qNG6i3JYsrAfEg3KATqXahIH8uQANv1V2K1ufOlGZgG9A0OytwFKeZWre ejJQ== X-Gm-Message-State: AOAM531z6V1R3B1ZGCFPjMlsJFCeJUePKP8z65WDuwqLL8+uk5OtdC9V JFheNrANEzQyrE8RIObMBWdritisIbxHaadWkAs= X-Google-Smtp-Source: ABdhPJwXsTDjC6gYPn7/4fQFUECymKwZL1FjAuvwhRp/zAi+cF592gSHW2+UAbMOFw3ZqG1IF5m80r7swrCZeDQTTXg= X-Received: by 2002:a25:74cb:: with SMTP id p194mr8386232ybc.347.1616179152532; Fri, 19 Mar 2021 11:39:12 -0700 (PDT) MIME-Version: 1.0 References: <20210318194036.3521577-1-andrii@kernel.org> <20210318194036.3521577-8-andrii@kernel.org> In-Reply-To: From: Andrii Nakryiko Date: Fri, 19 Mar 2021 11:39:01 -0700 Message-ID: Subject: Re: [PATCH v4 bpf-next 07/12] libbpf: add BPF static linker BTF and BTF.ext support To: Jiri Olsa Cc: Andrii Nakryiko , bpf , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Mar 19, 2021 at 9:23 AM Jiri Olsa wrote: > > On Thu, Mar 18, 2021 at 12:40:31PM -0700, Andrii Nakryiko wrote: > > SNIP > > > + > > + return NULL; > > +} > > + > > +static int linker_fixup_btf(struct src_obj *obj) > > +{ > > + const char *sec_name; > > + struct src_sec *sec; > > + int i, j, n, m; > > + > > + n = btf__get_nr_types(obj->btf); > > hi, > I'm getting bpftool crash when building tests, > > looks like above obj->btf can be NULL: I lost if (!obj->btf) return 0; somewhere along the rebases. I'll send a fix shortly. But how did you end up with selftests BPF objects built without BTF? > > (gdb) r gen object /home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.linked1.o /home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.o > Starting program: /home/jolsa/linux/tools/testing/selftests/bpf/tools/sbin/bpftool gen object /home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.linked1.o /home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.o > > Program received signal SIGSEGV, Segmentation fault. > btf__get_nr_types (btf=0x0) at btf.c:425 > > 425 return btf->start_id + btf->nr_types - 1; > Missing separate debuginfos, use: dnf debuginfo-install elfutils-libelf-0.182-1.fc33.x86_64 libcap-2.48-2.fc33.x86_64 zlib-1.2.11-23.fc33.x86_64 > (gdb) > (gdb) bt > #0 btf__get_nr_types (btf=0x0) at btf.c:425 > #1 0x000000000043c4ba in linker_fixup_btf (obj=obj@entry=0x7fffffffda50) at linker.c:1316 > #2 0x000000000043caf7 in linker_load_obj_file (linker=linker@entry=0x8612a0, filename=filename@entry=0x7fffffffe0db "/home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.o", > obj=obj@entry=0x7fffffffda50) at linker.c:653 > #3 0x000000000043df43 in bpf_linker__add_file (linker=linker@entry=0x8612a0, filename=filename@entry=0x7fffffffe0db "/home/jolsa/linux/tools/testing/selftests/bpf/btf_data2.o") at linker.c:412 > #4 0x000000000040d710 in do_object (argc=0, argv=0x7fffffffdce0) at gen.c:639 > #5 0x000000000040efd7 in cmd_select (cmds=cmds@entry=0x50a600 , argc=3, argv=0x7fffffffdcc8, help=help@entry=0x40c6f7 ) at main.c:134 > #6 0x000000000040d7c4 in do_gen (argc=, argv=) at gen.c:686 > #7 0x000000000040efd7 in cmd_select (cmds=cmds@entry=0x50b400 , argc=4, argv=0x7fffffffdcc0, help=help@entry=0x40ee93 ) at main.c:134 > #8 0x000000000040f88e in main (argc=, argv=) at main.c:469 > > I'm on current bpf-next/master > > > jirka > > > > + for (i = 1; i <= n; i++) { > > + struct btf_var_secinfo *vi; > > + struct btf_type *t; > > + > > + t = btf_type_by_id(obj->btf, i); > > + if (btf_kind(t) != BTF_KIND_DATASEC) > > + continue; > > + > > + sec_name = btf__str_by_offset(obj->btf, t->name_off); > > + sec = find_src_sec_by_name(obj, sec_name); > > + if (sec) { > > + /* record actual section size, unless ephemeral */ > > + if (sec->shdr) > > + t->size = sec->shdr->sh_size; > > + } else { > > + /* BTF can have some sections that are not represented > > + * in ELF, e.g., .kconfig and .ksyms, which are used > > + * for special extern variables. Here we'll > > + * pre-create "section shells" for them to be able to > > + * keep track of extra per-section metadata later > > + * (e.g., BTF variables). > > + */ > > + sec = add_src_sec(obj, sec_name); > > + if (!sec) > > + return -ENOMEM; > > + > > + sec->ephemeral = true; > > + sec->sec_idx = 0; /* will match UNDEF shndx in ELF */ > > + } > > + > > + /* remember ELF section and its BTF type ID match */ > > + sec->sec_type_id = i; > > + > > + /* fix up variable offsets */ > > + vi = btf_var_secinfos(t); > > + for (j = 0, m = btf_vlen(t); j < m; j++, vi++) { > > + const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type); > > + const char *var_name = btf__str_by_offset(obj->btf, vt->name_off); > > + int var_linkage = btf_var(vt)->linkage; > > + Elf64_Sym *sym; > > + > > + /* no need to patch up static or extern vars */ > > + if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED) > > + continue; > > + > > + sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name); > > + if (!sym) { > > + pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name); > > + return -ENOENT; > > + } > > + > > + vi->offset = sym->st_value; > > + } > > + } > > + > > + return 0; > > +} > > SNIP >