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=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 874D0C433F5 for ; Mon, 20 Sep 2021 23:45:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D70061222 for ; Mon, 20 Sep 2021 23:45:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232773AbhITXrK convert rfc822-to-8bit (ORCPT ); Mon, 20 Sep 2021 19:47:10 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:34954 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S237677AbhITXpI (ORCPT ); Mon, 20 Sep 2021 19:45:08 -0400 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.1.2/8.16.1.2) with SMTP id 18KHwaP1016751 for ; Mon, 20 Sep 2021 16:43:39 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by m0001303.ppops.net with ESMTP id 3b6jr0e2b0-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 20 Sep 2021 16:43:38 -0700 Received: from intmgw001.27.prn2.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Mon, 20 Sep 2021 16:43:36 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 17A414882029; Mon, 20 Sep 2021 16:43:33 -0700 (PDT) From: Andrii Nakryiko To: , , CC: , Subject: [PATCH v2 bpf-next 5/9] libbpf: reduce reliance of attach_fns on sec_def internals Date: Mon, 20 Sep 2021 16:43:16 -0700 Message-ID: <20210920234320.3312820-6-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210920234320.3312820-1-andrii@kernel.org> References: <20210920234320.3312820-1-andrii@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-FB-Source: Intern X-Proofpoint-ORIG-GUID: TezFlbRUwVDHhuVrIvHDndnU8IpuU7UP X-Proofpoint-GUID: TezFlbRUwVDHhuVrIvHDndnU8IpuU7UP X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-09-20_07,2021-09-20_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 spamscore=0 clxscore=1015 impostorscore=0 suspectscore=0 mlxlogscore=999 lowpriorityscore=0 bulkscore=0 phishscore=0 mlxscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109200137 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Move closer to not relying on bpf_sec_def internals that won't be part of public API, when pluggable SEC() handlers will be allowed. Drop pre-calculated prefix length, and in various helpers don't rely on this prefix length availability. Also minimize reliance on knowing bpf_sec_def's prefix for few places where section prefix shortcuts are supported (e.g., tp vs tracepoint, raw_tp vs raw_tracepoint). Given checking some string for having a given string-constant prefix is such a common operation and so annoying to be done with pure C code, add a small macro helper, str_has_pfx(), and reuse it throughout libbpf.c where prefix comparison is performed. With __builtin_constant_p() it's possible to have a convenient helper that checks some string for having a given prefix, where prefix is either string literal (or compile-time known string due to compiler optimization) or just a runtime string pointer, which is quite convenient and saves a lot of typing and string literal duplication. Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 41 ++++++++++++++++++--------------- tools/lib/bpf/libbpf_internal.h | 7 ++++++ 2 files changed, 30 insertions(+), 18 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 8ab2edbf7a3b..52c398fae0af 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -226,7 +226,6 @@ typedef struct bpf_link *(*attach_fn_t)(const struct bpf_program *prog, long coo struct bpf_sec_def { const char *sec; - size_t len; enum bpf_prog_type prog_type; enum bpf_attach_type expected_attach_type; bool is_exp_attach_type_optional; @@ -1671,7 +1670,7 @@ static int bpf_object__process_kconfig_line(struct bpf_object *obj, void *ext_val; __u64 num; - if (strncmp(buf, "CONFIG_", 7)) + if (!str_has_pfx(buf, "CONFIG_")) return 0; sep = strchr(buf, '='); @@ -2919,7 +2918,7 @@ static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn) static bool is_sec_name_dwarf(const char *name) { /* approximation, but the actual list is too long */ - return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0; + return str_has_pfx(name, ".debug_"); } static bool ignore_elf_section(GElf_Shdr *hdr, const char *name) @@ -2941,7 +2940,7 @@ static bool ignore_elf_section(GElf_Shdr *hdr, const char *name) if (is_sec_name_dwarf(name)) return true; - if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) { + if (str_has_pfx(name, ".rel")) { name += sizeof(".rel") - 1; /* DWARF section relocations */ if (is_sec_name_dwarf(name)) @@ -6890,8 +6889,7 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, if (err) return err; pr_debug("extern (kcfg) %s=0x%x\n", ext->name, kver); - } else if (ext->type == EXT_KCFG && - strncmp(ext->name, "CONFIG_", 7) == 0) { + } else if (ext->type == EXT_KCFG && str_has_pfx(ext->name, "CONFIG_")) { need_config = true; } else if (ext->type == EXT_KSYM) { if (ext->ksym.type_id) @@ -7955,7 +7953,6 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog, attachable, attach_btf) \ { \ .sec = string, \ - .len = sizeof(string) - 1, \ .prog_type = ptype, \ .expected_attach_type = eatype, \ .is_exp_attach_type_optional = eatype_optional, \ @@ -7986,7 +7983,6 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog, #define SEC_DEF(sec_pfx, ptype, ...) { \ .sec = sec_pfx, \ - .len = sizeof(sec_pfx) - 1, \ .prog_type = BPF_PROG_TYPE_##ptype, \ .preload_fn = libbpf_preload_prog, \ __VA_ARGS__ \ @@ -8160,10 +8156,8 @@ static const struct bpf_sec_def *find_sec_def(const char *sec_name) int i, n = ARRAY_SIZE(section_defs); for (i = 0; i < n; i++) { - if (strncmp(sec_name, - section_defs[i].sec, section_defs[i].len)) - continue; - return §ion_defs[i]; + if (str_has_pfx(sec_name, section_defs[i].sec)) + return §ion_defs[i]; } return NULL; } @@ -8517,7 +8511,7 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog, int *btf_obj_fd, prog->sec_name); return -ESRCH; } - attach_name = prog->sec_name + prog->sec_def->len; + attach_name = prog->sec_name + strlen(prog->sec_def->sec); /* BPF program's BTF ID */ if (attach_prog_fd) { @@ -9454,8 +9448,11 @@ static struct bpf_link *attach_kprobe(const struct bpf_program *prog, long cooki char *func; int n, err; - func_name = prog->sec_name + prog->sec_def->len; - opts.retprobe = strcmp(prog->sec_def->sec, "kretprobe/") == 0; + opts.retprobe = str_has_pfx(prog->sec_name, "kretprobe/"); + if (opts.retprobe) + func_name = prog->sec_name + sizeof("kretprobe/") - 1; + else + func_name = prog->sec_name + sizeof("kprobe/") - 1; n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset); if (n < 1) { @@ -9627,8 +9624,11 @@ static struct bpf_link *attach_tp(const struct bpf_program *prog, long cookie) if (!sec_name) return libbpf_err_ptr(-ENOMEM); - /* extract "tp//" */ - tp_cat = sec_name + prog->sec_def->len; + /* extract "tp//" or "tracepoint//" */ + if (str_has_pfx(prog->sec_name, "tp/")) + tp_cat = sec_name + sizeof("tp/") - 1; + else + tp_cat = sec_name + sizeof("tracepoint/") - 1; tp_name = strchr(tp_cat, '/'); if (!tp_name) { free(sec_name); @@ -9674,7 +9674,12 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(const struct bpf_program *pr static struct bpf_link *attach_raw_tp(const struct bpf_program *prog, long cookie) { - const char *tp_name = prog->sec_name + prog->sec_def->len; + const char *tp_name; + + if (str_has_pfx(prog->sec_name, "raw_tp/")) + tp_name = prog->sec_name + sizeof("raw_tp/") - 1; + else + tp_name = prog->sec_name + sizeof("raw_tracepoint/") - 1; return bpf_program__attach_raw_tracepoint(prog, tp_name); } diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index ceb0c98979bc..ec79400517d4 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -89,6 +89,13 @@ (offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD)) #endif +/* Check whether a string `str` has prefix `pfx`, regardless if `pfx` is + * a string literal known at compilation time or char * pointer known only at + * runtime. + */ +#define str_has_pfx(str, pfx) \ + (strncmp(str, pfx, __builtin_constant_p(pfx) ? sizeof(pfx) - 1 : strlen(pfx)) == 0) + /* Symbol versioning is different between static and shared library. * Properly versioned symbols are needed for shared library, but * only the symbol of the new version is needed for static library. -- 2.30.2