From patchwork Wed Aug 19 22:40:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 1348028 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20161025 header.b=KEVm/sGP; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4BX2nD56bDz9sRK for ; Thu, 20 Aug 2020 08:41:04 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727927AbgHSWk7 (ORCPT ); Wed, 19 Aug 2020 18:40:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727888AbgHSWkt (ORCPT ); Wed, 19 Aug 2020 18:40:49 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06789C061348 for ; Wed, 19 Aug 2020 15:40:43 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id y12so40157qva.8 for ; Wed, 19 Aug 2020 15:40:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=o5hcafLIur4TPskQP5E6KPZVFbh+qjZrYmSthTwVB04=; b=KEVm/sGPyfyG51HlhTXV0YroOEI5zQYZmoLUdxXgIMqVb18ASyPW/KbBdlS7ux/IYv py7s5CBpnuj5Z2kI0U5feqHgVdccNJ+ILv5x/tYIgODbbvld+P0r4wahQGtF0n0SOEe+ YeshFbT8qj9ZXs9EgwKnXGF7Mwlc35Fi/xc3ryWZp9MNsYPfcpSuUnoyD/sjHjkd8fMe HyQ6yQr7/g1qaABSsKISXqpygyG+prMVRoGAr81nHP3iHvFjQg4CnPfYp/0Ob3zKEpGQ gPHLQRFCRb51ZDeq8u5vgR6X66B0t92iLLHDiNdQi0I8CUu8qonHMcXHm4Iaw5HGqpVI IcdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=o5hcafLIur4TPskQP5E6KPZVFbh+qjZrYmSthTwVB04=; b=pqLi/l6cuLpORNyNA3auz/FJZ88PVekpDyI2xs7+4kbBjdUWLxCk3Di4VnFWOjm9Wf vgP+joXSHmYSptGKmVrdB/Ltg0LI4yx02Zn5XlXTTpXAQnwvF91H9aQBMnJYxMc/IPLR HOoUhO7FZVyOFcyDFK0ZTwS9V6jpdCUWxLoS+pD0eoKe/6ZOO3ym9G+bbTIDq1juQHmc JvA17UOV9/Nk/6InH+uuu5V2KUp4Py9+bF0K9XuuulK6WFCqYckH6h/7IIanHBHx/Yuy L2Cndr3+TRAcBT1pPET2HTuNS4PImIiagHNT9bgh2Ml9Frxm2oSzBobDvE3zT8LMiPck CIMA== X-Gm-Message-State: AOAM53289Ba3qm8ZEEcsIkTAlKn6ztY0KCo/jdD2FDT5QJ6A6J9+8n79 +uWdFcr2qDRDq3oZjf9WkPT9v9lSXnc= X-Google-Smtp-Source: ABdhPJxyHUudWy1NYp/N8b6eKKKkk9EiTNiuow7ZaLf2G2NTFN8IF+TFATrnL0TqyK5NApAWp9Is+3Q5V9c= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:f693:9fff:fef4:e444]) (user=haoluo job=sendgmr) by 2002:a0c:ee41:: with SMTP id m1mr476956qvs.214.1597876842123; Wed, 19 Aug 2020 15:40:42 -0700 (PDT) Date: Wed, 19 Aug 2020 15:40:26 -0700 In-Reply-To: <20200819224030.1615203-1-haoluo@google.com> Message-Id: <20200819224030.1615203-5-haoluo@google.com> Mime-Version: 1.0 References: <20200819224030.1615203-1-haoluo@google.com> X-Mailer: git-send-email 2.28.0.220.ged08abb693-goog Subject: [PATCH bpf-next v1 4/8] bpf/libbpf: BTF support for typed ksyms From: Hao Luo To: netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Shuah Khan , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Quentin Monnet , Hao Luo , Steven Rostedt , Ingo Molnar , Andrey Ignatov , Jakub Sitnicki Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org If a ksym is defined with a type, libbpf will try to find the ksym's btf information from kernel btf. If a valid btf entry for the ksym is found, libbpf can pass in the found btf id to the verifier, which validates the ksym's type and value. Typeless ksyms (i.e. those defined as 'void') will not have such btf_id, but it has the symbol's address (read from kallsyms) and its value is treated as a raw pointer. Signed-off-by: Hao Luo --- tools/lib/bpf/libbpf.c | 130 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 114 insertions(+), 16 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 4a81c6b2d21b..94eff612c7c2 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -357,7 +357,16 @@ struct extern_desc { bool is_signed; } kcfg; struct { - unsigned long long addr; + /* + * 1. If ksym is typeless, the field 'addr' is valid. + * 2. If ksym is typed, the field 'vmlinux_btf_id' is + * valid. + */ + bool is_typeless; + union { + unsigned long long addr; + int vmlinux_btf_id; + }; } ksym; }; }; @@ -382,6 +391,7 @@ struct bpf_object { bool loaded; bool has_pseudo_calls; + bool has_typed_ksyms; /* * Information when doing elf related work. Only valid if fd @@ -2521,6 +2531,10 @@ static int bpf_object__load_vmlinux_btf(struct bpf_object *obj) if (obj->btf_ext && obj->btf_ext->core_relo_info.len) need_vmlinux_btf = true; + /* Support for typed ksyms needs kernel BTF */ + if (obj->has_typed_ksyms) + need_vmlinux_btf = true; + bpf_object__for_each_program(prog, obj) { if (!prog->load) continue; @@ -2975,10 +2989,10 @@ static int bpf_object__collect_externs(struct bpf_object *obj) ext->type = EXT_KSYM; vt = skip_mods_and_typedefs(obj->btf, t->type, NULL); - if (!btf_is_void(vt)) { - pr_warn("extern (ksym) '%s' is not typeless (void)\n", ext_name); - return -ENOTSUP; - } + ext->ksym.is_typeless = btf_is_void(vt); + + if (!obj->has_typed_ksyms && !ext->ksym.is_typeless) + obj->has_typed_ksyms = true; } else { pr_warn("unrecognized extern section '%s'\n", sec_name); return -ENOTSUP; @@ -2992,9 +3006,9 @@ static int bpf_object__collect_externs(struct bpf_object *obj) /* sort externs by type, for kcfg ones also by (align, size, name) */ qsort(obj->externs, obj->nr_extern, sizeof(*ext), cmp_externs); - /* for .ksyms section, we need to turn all externs into allocated - * variables in BTF to pass kernel verification; we do this by - * pretending that each extern is a 8-byte variable + /* for .ksyms section, we need to turn all typeless externs into + * allocated variables in BTF to pass kernel verification; we do + * this by pretending that each typeless extern is a 8-byte variable */ if (ksym_sec) { /* find existing 4-byte integer type in BTF to use for fake @@ -3012,7 +3026,7 @@ static int bpf_object__collect_externs(struct bpf_object *obj) sec = ksym_sec; n = btf_vlen(sec); - for (i = 0, off = 0; i < n; i++, off += sizeof(int)) { + for (i = 0, off = 0; i < n; i++) { struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i; struct btf_type *vt; @@ -3025,9 +3039,14 @@ static int bpf_object__collect_externs(struct bpf_object *obj) return -ESRCH; } btf_var(vt)->linkage = BTF_VAR_GLOBAL_ALLOCATED; - vt->type = int_btf_id; + if (ext->ksym.is_typeless) { + vt->type = int_btf_id; + vs->size = sizeof(int); + } vs->offset = off; - vs->size = sizeof(int); + off += vs->size; + pr_debug("ksym var_secinfo: var '%s', type #%d, size %d, offset %d\n", + ext->name, vt->type, vs->size, vs->offset); } sec->size = off; } @@ -5300,8 +5319,13 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) insn[0].imm = obj->maps[obj->kconfig_map_idx].fd; insn[1].imm = ext->kcfg.data_off; } else /* EXT_KSYM */ { - insn[0].imm = (__u32)ext->ksym.addr; - insn[1].imm = ext->ksym.addr >> 32; + if (ext->ksym.is_typeless) { /* typelss ksyms */ + insn[0].imm = (__u32)ext->ksym.addr; + insn[1].imm = ext->ksym.addr >> 32; + } else { /* typed ksyms */ + insn[0].src_reg = BPF_PSEUDO_BTF_ID; + insn[0].imm = ext->ksym.vmlinux_btf_id; + } } break; case RELO_CALL: @@ -6019,6 +6043,10 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj) if (!ext || ext->type != EXT_KSYM) continue; + /* Typed ksyms have the verifier to fill their addresses. */ + if (!ext->ksym.is_typeless) + continue; + if (ext->is_set && ext->ksym.addr != sym_addr) { pr_warn("extern (ksym) '%s' resolution is ambiguous: 0x%llx or 0x%llx\n", sym_name, ext->ksym.addr, sym_addr); @@ -6037,10 +6065,72 @@ static int bpf_object__read_kallsyms_file(struct bpf_object *obj) return err; } +static int bpf_object__resolve_ksyms_btf_id(struct bpf_object *obj) +{ + struct extern_desc *ext; + int i, id; + + if (!obj->btf_vmlinux) { + pr_warn("support of typed ksyms needs kernel btf.\n"); + return -ENOENT; + } + + for (i = 0; i < obj->nr_extern; i++) { + const struct btf_type *v, *vx; /* VARs in object and vmlinux btf */ + const struct btf_type *t, *tx; /* TYPEs in btf */ + __u32 vt, vtx; /* btf_ids of TYPEs */ + + ext = &obj->externs[i]; + if (ext->type != EXT_KSYM) + continue; + + if (ext->ksym.is_typeless) + continue; + + if (ext->is_set) { + pr_warn("typed ksym '%s' resolved as typeless ksyms.\n", + ext->name); + return -EFAULT; + } + + id = btf__find_by_name_kind(obj->btf_vmlinux, ext->name, + BTF_KIND_VAR); + if (id <= 0) { + pr_warn("no btf entry for ksym '%s' in vmlinux.\n", + ext->name); + return -ESRCH; + } + + vx = btf__type_by_id(obj->btf_vmlinux, id); + tx = skip_mods_and_typedefs(obj->btf_vmlinux, vx->type, &vtx); + + v = btf__type_by_id(obj->btf, ext->btf_id); + t = skip_mods_and_typedefs(obj->btf, v->type, &vt); + + if (!btf_ksym_type_match(obj->btf_vmlinux, vtx, obj->btf, vt)) { + const char *tname, *txname; /* names of TYPEs */ + + txname = btf__name_by_offset(obj->btf_vmlinux, tx->name_off); + tname = btf__name_by_offset(obj->btf, t->name_off); + + pr_warn("ksym '%s' expects type '%s' (vmlinux_btf_id: #%d), " + "but got '%s' (btf_id: #%d)\n", ext->name, + txname, vtx, tname, vt); + return -EINVAL; + } + + ext->is_set = true; + ext->ksym.vmlinux_btf_id = id; + pr_debug("extern (ksym) %s=vmlinux_btf_id(#%d)\n", ext->name, id); + } + return 0; +} + static int bpf_object__resolve_externs(struct bpf_object *obj, const char *extra_kconfig) { - bool need_config = false, need_kallsyms = false; + bool need_config = false; + bool need_kallsyms = false, need_vmlinux_btf = false; struct extern_desc *ext; void *kcfg_data = NULL; int err, i; @@ -6071,7 +6161,10 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, strncmp(ext->name, "CONFIG_", 7) == 0) { need_config = true; } else if (ext->type == EXT_KSYM) { - need_kallsyms = true; + if (ext->ksym.is_typeless) + need_kallsyms = true; + else + need_vmlinux_btf = true; } else { pr_warn("unrecognized extern '%s'\n", ext->name); return -EINVAL; @@ -6100,6 +6193,11 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, if (err) return -EINVAL; } + if (need_vmlinux_btf) { + err = bpf_object__resolve_ksyms_btf_id(obj); + if (err) + return -EINVAL; + } for (i = 0; i < obj->nr_extern; i++) { ext = &obj->externs[i]; @@ -6132,10 +6230,10 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) } err = bpf_object__probe_loading(obj); + err = err ? : bpf_object__load_vmlinux_btf(obj); err = err ? : bpf_object__resolve_externs(obj, obj->kconfig); err = err ? : bpf_object__sanitize_and_load_btf(obj); err = err ? : bpf_object__sanitize_maps(obj); - err = err ? : bpf_object__load_vmlinux_btf(obj); err = err ? : bpf_object__init_kern_struct_ops_maps(obj); err = err ? : bpf_object__create_maps(obj); err = err ? : bpf_object__relocate(obj, attr->target_btf_path);