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=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 3908DC433B4 for ; Wed, 14 Apr 2021 20:02:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B27C61154 for ; Wed, 14 Apr 2021 20:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353671AbhDNUCq convert rfc822-to-8bit (ORCPT ); Wed, 14 Apr 2021 16:02:46 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:17260 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353636AbhDNUCh (ORCPT ); Wed, 14 Apr 2021 16:02:37 -0400 Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 13EJsj5Q007359 for ; Wed, 14 Apr 2021 13:02:15 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 37wv5jbnr6-5 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 14 Apr 2021 13:02:14 -0700 Received: from intmgw001.38.frc1.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:11d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 14 Apr 2021 13:02:12 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 052D72ECEBDF; Wed, 14 Apr 2021 13:02:03 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , Subject: [PATCH bpf-next 04/17] libbpf: mark BPF subprogs with hidden visibility as static for BPF verifier Date: Wed, 14 Apr 2021 13:01:33 -0700 Message-ID: <20210414200146.2663044-5-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210414200146.2663044-1-andrii@kernel.org> References: <20210414200146.2663044-1-andrii@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-ORIG-GUID: hpdXXEt2Pq8h1TgoOEndNUUjzYzGsZOv X-Proofpoint-GUID: hpdXXEt2Pq8h1TgoOEndNUUjzYzGsZOv X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-04-14_12:2021-04-14,2021-04-14 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=999 bulkscore=0 spamscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 mlxscore=0 clxscore=1015 phishscore=0 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104140127 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Define __hidden helper macro in bpf_helpers.h, which is a short-hand for __attribute__((visibility("hidden"))). Add libbpf support to mark BPF subprograms marked with __hidden as static in BTF information to enforce BPF verifier's static function validation algorithm, which takes more information (caller's context) into account during a subprogram validation. Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/bpf_helpers.h | 8 ++++++ tools/lib/bpf/btf.c | 5 ---- tools/lib/bpf/libbpf.c | 45 ++++++++++++++++++++++++++++++++- tools/lib/bpf/libbpf_internal.h | 6 +++++ 4 files changed, 58 insertions(+), 6 deletions(-) diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 75c7581b304c..9720dc0b4605 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -47,6 +47,14 @@ #define __weak __attribute__((weak)) #endif +/* + * Use __hidden attribute to mark a non-static BPF subprogram effectively + * static for BPF verifier's verification algorithm purposes, allowing more + * extensive and permissive BPF verification process, taking into account + * subprogram's caller context. + */ +#define __hidden __attribute__((visibility("hidden"))) + /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include * any system-level headers (such as stddef.h, linux/version.h, etc), and * commonly-used macros like NULL and KERNEL_VERSION aren't available through diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index d30e67e7e1e5..d57e13a13798 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1605,11 +1605,6 @@ static void *btf_add_type_mem(struct btf *btf, size_t add_sz) btf->hdr->type_len, UINT_MAX, add_sz); } -static __u32 btf_type_info(int kind, int vlen, int kflag) -{ - return (kflag << 31) | (kind << 24) | vlen; -} - static void btf_type_inc_vlen(struct btf_type *t) { t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t)); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ed5586cce227..b6a7f62521a6 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -71,6 +71,7 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj); static const struct btf_type * skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id); +static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog); static int __base_pr(enum libbpf_print_level level, const char *format, va_list args) @@ -275,6 +276,7 @@ struct bpf_program { bpf_program_clear_priv_t clear_priv; bool load; + bool mark_btf_static; enum bpf_prog_type type; enum bpf_attach_type expected_attach_type; int prog_ifindex; @@ -699,6 +701,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, if (err) return err; + /* if function is a global/weak symbol, but has hidden + * visibility (or any non-default one), mark its BTF FUNC as + * static to enable more permissive BPF verification mode with + * more outside context available to BPF verifier + */ + if (GELF_ST_BIND(sym.st_info) != STB_LOCAL + && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT) + prog->mark_btf_static = true; + nr_progs++; obj->nr_programs = nr_progs; @@ -2619,7 +2630,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj) { struct btf *kern_btf = obj->btf; bool btf_mandatory, sanitize; - int err = 0; + int i, err = 0; if (!obj->btf) return 0; @@ -2633,6 +2644,38 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj) return 0; } + /* Even though some subprogs are global/weak, user might prefer more + * permissive BPF verification process that BPF verifier performs for + * static functions, taking into account more context from the caller + * functions. In such case, they need to mark such subprogs with + * __attribute__((visibility("hidden"))) and libbpf will adjust + * corresponding FUNC BTF type to be marked as static and trigger more + * involved BPF verification process. + */ + for (i = 0; i < obj->nr_programs; i++) { + struct bpf_program *prog = &obj->programs[i]; + struct btf_type *t; + const char *name; + int j, n; + + if (!prog->mark_btf_static || !prog_is_subprog(obj, prog)) + continue; + + n = btf__get_nr_types(obj->btf); + for (j = 1; j <= n; j++) { + t = btf_type_by_id(obj->btf, j); + if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL) + continue; + + name = btf__str_by_offset(obj->btf, t->name_off); + if (strcmp(name, prog->name) != 0) + continue; + + t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0); + break; + } + } + sanitize = btf_needs_sanitization(obj); if (sanitize) { const void *raw_data; diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 6017902c687e..92b7eae10c6d 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -19,6 +19,7 @@ #pragma GCC poison reallocarray #include "libbpf.h" +#include "btf.h" #ifndef EM_BPF #define EM_BPF 247 @@ -132,6 +133,11 @@ struct btf_type; struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id); +static inline __u32 btf_type_info(int kind, int vlen, int kflag) +{ + return (kflag << 31) | (kind << 24) | vlen; +} + void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t cur_cnt, size_t max_cnt, size_t add_cnt); int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt); -- 2.30.2