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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 7F8FFC433E0 for ; Fri, 7 Aug 2020 21:06:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4838D22CA1 for ; Fri, 7 Aug 2020 21:06:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="J1OgXTEs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726582AbgHGVGm (ORCPT ); Fri, 7 Aug 2020 17:06:42 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:61706 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726067AbgHGVGl (ORCPT ); Fri, 7 Aug 2020 17:06:41 -0400 Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 077KsA1L013865 for ; Fri, 7 Aug 2020 14:06:40 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=JFenIw8IBV9oYWzueV2mqeUEk3vDBpYF1PNutqwBb0Y=; b=J1OgXTEsfkeji8CEAri+jifyfNSsFhII5jOdP/ZKh8Yxc97ixLeuQjVRHWvnwSy7Iewv VQlHvWXUgOyaR2/UNFa7wqVUoLZrd+QP6rZtQwC/mhfAgKicXHhm5008//kNaQ4Nori4 qtX/vauOmFLH8bSqAqfN3gjy9u0iwLsfduk= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 32qy47mmy5-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 07 Aug 2020 14:06:40 -0700 Received: from intmgw002.08.frc2.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:21d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Fri, 7 Aug 2020 14:06:39 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id D00D82EC5494; Fri, 7 Aug 2020 14:06:36 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , CC: , , Andrii Nakryiko Smtp-Origin-Cluster: ftw2c04 Subject: [RFC PATCH bpf-next 2/7] libbpf: make kernel feature probing lazy Date: Fri, 7 Aug 2020 14:06:24 -0700 Message-ID: <20200807210629.394335-3-andriin@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200807210629.394335-1-andriin@fb.com> References: <20200807210629.394335-1-andriin@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-07_20:2020-08-06,2020-08-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 phishscore=0 spamscore=0 suspectscore=9 mlxlogscore=999 malwarescore=0 clxscore=1015 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008070147 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Turn libbpf's kernel feature probing into lazily-performed checks. This a= llows to skip performing unnecessary feature checks, if a given BPF application doesn't rely on a particular kernel feature. As we grow number of feature probes, libbpf might perform less unnecessary syscalls and scale better w= ith number of feature probes long-term. By decoupling feature checks from bpf_object, it's also possible to perfo= rm feature probing from libbpf static helpers and low-level APIs, if necessa= ry. Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 150 +++++++++++++++++++++++------------------ 1 file changed, 86 insertions(+), 64 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 7be04e45d29c..8e329c57be51 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -165,23 +165,26 @@ static inline __u64 ptr_to_u64(const void *ptr) return (__u64) (unsigned long) ptr; } =20 -struct bpf_capabilities { +enum kern_feature_id { /* v4.14: kernel support for program & map names. */ - __u32 name:1; + FEAT_PROG_NAME, /* v5.2: kernel support for global data sections. */ - __u32 global_data:1; + FEAT_GLOBAL_DATA, /* BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO support */ - __u32 btf_func:1; + FEAT_BTF_FUNC, /* BTF_KIND_VAR and BTF_KIND_DATASEC support */ - __u32 btf_datasec:1; - /* BPF_F_MMAPABLE is supported for arrays */ - __u32 array_mmap:1; + FEAT_BTF_DATASEC, /* BTF_FUNC_GLOBAL is supported */ - __u32 btf_func_global:1; + FEAT_BTF_GLOBAL_FUNC, + /* BPF_F_MMAPABLE is supported for arrays */ + FEAT_ARRAY_MMAP, /* kernel support for expected_attach_type in BPF_PROG_LOAD */ - __u32 exp_attach_type:1; + FEAT_EXP_ATTACH_TYPE, + __FEAT_CNT, }; =20 +static bool kernel_supports(enum kern_feature_id feat_id); + enum reloc_type { RELO_LD64, RELO_CALL, @@ -253,8 +256,6 @@ struct bpf_program { __u32 func_info_rec_size; __u32 func_info_cnt; =20 - struct bpf_capabilities *caps; - void *line_info; __u32 line_info_rec_size; __u32 line_info_cnt; @@ -436,8 +437,6 @@ struct bpf_object { void *priv; bpf_object_clear_priv_t clear_priv; =20 - struct bpf_capabilities caps; - char path[]; }; #define obj_elf_valid(o) ((o)->efile.elf) @@ -561,7 +560,6 @@ bpf_object__add_program(struct bpf_object *obj, void = *data, size_t size, if (err) return err; =20 - prog.caps =3D &obj->caps; progs =3D obj->programs; nr_progs =3D obj->nr_programs; =20 @@ -2340,18 +2338,18 @@ static bool section_have_execinstr(struct bpf_obj= ect *obj, int idx) =20 static bool btf_needs_sanitization(struct bpf_object *obj) { - bool has_func_global =3D obj->caps.btf_func_global; - bool has_datasec =3D obj->caps.btf_datasec; - bool has_func =3D obj->caps.btf_func; + bool has_func_global =3D kernel_supports(FEAT_BTF_GLOBAL_FUNC); + bool has_datasec =3D kernel_supports(FEAT_BTF_DATASEC); + bool has_func =3D kernel_supports(FEAT_BTF_FUNC); =20 return !has_func || !has_datasec || !has_func_global; } =20 static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf = *btf) { - bool has_func_global =3D obj->caps.btf_func_global; - bool has_datasec =3D obj->caps.btf_datasec; - bool has_func =3D obj->caps.btf_func; + bool has_func_global =3D kernel_supports(FEAT_BTF_GLOBAL_FUNC); + bool has_datasec =3D kernel_supports(FEAT_BTF_DATASEC); + bool has_func =3D kernel_supports(FEAT_BTF_FUNC); struct btf_type *t; int i, j, vlen; =20 @@ -3429,8 +3427,7 @@ bpf_object__probe_loading(struct bpf_object *obj) return 0; } =20 -static int -bpf_object__probe_name(struct bpf_object *obj) +static int probe_kern_prog_name(void) { struct bpf_load_program_attr attr; struct bpf_insn insns[] =3D { @@ -3449,15 +3446,14 @@ bpf_object__probe_name(struct bpf_object *obj) attr.name =3D "test"; ret =3D bpf_load_program_xattr(&attr, NULL, 0); if (ret >=3D 0) { - obj->caps.name =3D 1; close(ret); + return 1; } =20 return 0; } =20 -static int -bpf_object__probe_global_data(struct bpf_object *obj) +static int probe_kern_global_data(void) { struct bpf_load_program_attr prg_attr; struct bpf_create_map_attr map_attr; @@ -3493,16 +3489,16 @@ bpf_object__probe_global_data(struct bpf_object *= obj) prg_attr.license =3D "GPL"; =20 ret =3D bpf_load_program_xattr(&prg_attr, NULL, 0); + close(map); if (ret >=3D 0) { - obj->caps.global_data =3D 1; close(ret); + return 1; } =20 - close(map); return 0; } =20 -static int bpf_object__probe_btf_func(struct bpf_object *obj) +static int probe_kern_btf_func(void) { static const char strs[] =3D "\0int\0x\0a"; /* void x(int a) {} */ @@ -3520,7 +3516,6 @@ static int bpf_object__probe_btf_func(struct bpf_ob= ject *obj) btf_fd =3D libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs)); if (btf_fd >=3D 0) { - obj->caps.btf_func =3D 1; close(btf_fd); return 1; } @@ -3528,7 +3523,7 @@ static int bpf_object__probe_btf_func(struct bpf_ob= ject *obj) return 0; } =20 -static int bpf_object__probe_btf_func_global(struct bpf_object *obj) +static int probe_kern_btf_func_global(void) { static const char strs[] =3D "\0int\0x\0a"; /* static void x(int a) {} */ @@ -3546,7 +3541,6 @@ static int bpf_object__probe_btf_func_global(struct= bpf_object *obj) btf_fd =3D libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs)); if (btf_fd >=3D 0) { - obj->caps.btf_func_global =3D 1; close(btf_fd); return 1; } @@ -3554,7 +3548,7 @@ static int bpf_object__probe_btf_func_global(struct= bpf_object *obj) return 0; } =20 -static int bpf_object__probe_btf_datasec(struct bpf_object *obj) +static int probe_kern_btf_datasec(void) { static const char strs[] =3D "\0x\0.data"; /* static int a; */ @@ -3573,7 +3567,6 @@ static int bpf_object__probe_btf_datasec(struct bpf= _object *obj) btf_fd =3D libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs)); if (btf_fd >=3D 0) { - obj->caps.btf_datasec =3D 1; close(btf_fd); return 1; } @@ -3581,7 +3574,7 @@ static int bpf_object__probe_btf_datasec(struct bpf= _object *obj) return 0; } =20 -static int bpf_object__probe_array_mmap(struct bpf_object *obj) +static int probe_kern_array_mmap(void) { struct bpf_create_map_attr attr =3D { .map_type =3D BPF_MAP_TYPE_ARRAY, @@ -3594,16 +3587,13 @@ static int bpf_object__probe_array_mmap(struct bp= f_object *obj) =20 fd =3D bpf_create_map_xattr(&attr); if (fd >=3D 0) { - obj->caps.array_mmap =3D 1; close(fd); return 1; } - return 0; } =20 -static int -bpf_object__probe_exp_attach_type(struct bpf_object *obj) +static int probe_kern_exp_attach_type(void) { struct bpf_load_program_attr attr; struct bpf_insn insns[] =3D { @@ -3626,34 +3616,67 @@ bpf_object__probe_exp_attach_type(struct bpf_obje= ct *obj) =20 fd =3D bpf_load_program_xattr(&attr, NULL, 0); if (fd >=3D 0) { - obj->caps.exp_attach_type =3D 1; close(fd); return 1; } return 0; } =20 -static int -bpf_object__probe_caps(struct bpf_object *obj) -{ - int (*probe_fn[])(struct bpf_object *obj) =3D { - bpf_object__probe_name, - bpf_object__probe_global_data, - bpf_object__probe_btf_func, - bpf_object__probe_btf_func_global, - bpf_object__probe_btf_datasec, - bpf_object__probe_array_mmap, - bpf_object__probe_exp_attach_type, - }; - int i, ret; +enum kern_feature_result { + FEAT_UNKNOWN =3D 0, + FEAT_SUPPORTED =3D 1, + FEAT_MISSING =3D 2, +}; =20 - for (i =3D 0; i < ARRAY_SIZE(probe_fn); i++) { - ret =3D probe_fn[i](obj); - if (ret < 0) - pr_debug("Probe #%d failed with %d.\n", i, ret); +typedef int (*feature_probe_fn)(void); + +static struct kern_feature_desc { + const char *desc; + feature_probe_fn probe; + enum kern_feature_result res; +} feature_probes[__FEAT_CNT] =3D { + [FEAT_PROG_NAME] =3D { + "BPF program name", probe_kern_prog_name, + }, + [FEAT_GLOBAL_DATA] =3D { + "global variables", probe_kern_global_data, + }, + [FEAT_BTF_FUNC] =3D { + "BTF functions", probe_kern_btf_func, + }, + [FEAT_BTF_GLOBAL_FUNC] =3D { + "BTF global function", probe_kern_btf_func_global, + }, + [FEAT_BTF_DATASEC] =3D { + "BTF data section and variable", probe_kern_btf_datasec, + }, + [FEAT_ARRAY_MMAP] =3D { + "ARRAY map mmap()", probe_kern_array_mmap, + }, + [FEAT_EXP_ATTACH_TYPE] =3D { + "BPF_PROG_LOAD expected_attach_type attribute", + probe_kern_exp_attach_type, + }, +}; + +static bool kernel_supports(enum kern_feature_id feat_id) +{ + struct kern_feature_desc *feat =3D &feature_probes[feat_id]; + int ret; + + if (READ_ONCE(feat->res) =3D=3D FEAT_UNKNOWN) { + ret =3D feat->probe(); + if (ret > 0) { + WRITE_ONCE(feat->res, FEAT_SUPPORTED); + } else if (ret =3D=3D 0) { + WRITE_ONCE(feat->res, FEAT_MISSING); + } else { + pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, re= t); + WRITE_ONCE(feat->res, FEAT_MISSING); + } } =20 - return 0; + return READ_ONCE(feat->res) =3D=3D FEAT_SUPPORTED; } =20 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd) @@ -3755,7 +3778,7 @@ static int bpf_object__create_map(struct bpf_object= *obj, struct bpf_map *map) =20 memset(&create_attr, 0, sizeof(create_attr)); =20 - if (obj->caps.name) + if (kernel_supports(FEAT_PROG_NAME)) create_attr.name =3D map->name; create_attr.map_ifindex =3D map->map_ifindex; create_attr.map_type =3D def->type; @@ -5355,12 +5378,12 @@ load_program(struct bpf_program *prog, struct bpf= _insn *insns, int insns_cnt, memset(&load_attr, 0, sizeof(struct bpf_load_program_attr)); load_attr.prog_type =3D prog->type; /* old kernels might not support specifying expected_attach_type */ - if (!prog->caps->exp_attach_type && prog->sec_def && + if (!kernel_supports(FEAT_EXP_ATTACH_TYPE) && prog->sec_def && prog->sec_def->is_exp_attach_type_optional) load_attr.expected_attach_type =3D 0; else load_attr.expected_attach_type =3D prog->expected_attach_type; - if (prog->caps->name) + if (kernel_supports(FEAT_PROG_NAME)) load_attr.name =3D prog->name; load_attr.insns =3D insns; load_attr.insns_cnt =3D insns_cnt; @@ -5378,7 +5401,7 @@ load_program(struct bpf_program *prog, struct bpf_i= nsn *insns, int insns_cnt, } /* specify func_info/line_info only if kernel supports them */ btf_fd =3D bpf_object__btf_fd(prog->obj); - if (btf_fd >=3D 0 && prog->obj->caps.btf_func) { + if (btf_fd >=3D 0 && kernel_supports(FEAT_BTF_FUNC)) { load_attr.prog_btf_fd =3D btf_fd; load_attr.func_info =3D prog->func_info; load_attr.func_info_rec_size =3D prog->func_info_rec_size; @@ -5741,11 +5764,11 @@ static int bpf_object__sanitize_maps(struct bpf_o= bject *obj) bpf_object__for_each_map(m, obj) { if (!bpf_map__is_internal(m)) continue; - if (!obj->caps.global_data) { + if (!kernel_supports(FEAT_GLOBAL_DATA)) { pr_warn("kernel doesn't support global data\n"); return -ENOTSUP; } - if (!obj->caps.array_mmap) + if (!kernel_supports(FEAT_ARRAY_MMAP)) m->def.map_flags ^=3D BPF_F_MMAPABLE; } =20 @@ -5895,7 +5918,6 @@ int bpf_object__load_xattr(struct bpf_object_load_a= ttr *attr) } =20 err =3D bpf_object__probe_loading(obj); - err =3D err ? : bpf_object__probe_caps(obj); err =3D err ? : bpf_object__resolve_externs(obj, obj->kconfig); err =3D err ? : bpf_object__sanitize_and_load_btf(obj); err =3D err ? : bpf_object__sanitize_maps(obj); --=20 2.24.1