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[173.230.99.219]) by smtp.gmail.com with ESMTPSA id r3sm1145597iov.22.2020.08.20.02.42.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Aug 2020 02:42:17 -0700 (PDT) From: YiFei Zhu To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Stanislav Fomichev , Mahesh Bandewar , YiFei Zhu Subject: [PATCH bpf-next 3/5] libbpf: Add BPF_PROG_BIND_MAP syscall and use it on .metadata section Date: Thu, 20 Aug 2020 04:42:09 -0500 Message-Id: X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org From: YiFei Zhu The patch adds a simple wrapper bpf_prog_bind_map around the syscall. And when using libbpf to load a program, it will probe the kernel for the support of this syscall, and scan for the .metadata ELF section and load it as an internal map like a .data section. In the case that kernel supports the BPF_PROG_BIND_MAP syscall and a .metadata section exists, the map will be explicitly bound to the program via the syscall immediately after program is loaded. -EEXIST is ignored for this syscall. Signed-off-by: YiFei Zhu --- tools/lib/bpf/bpf.c | 11 +++++ tools/lib/bpf/bpf.h | 1 + tools/lib/bpf/libbpf.c | 100 ++++++++++++++++++++++++++++++++++++++- tools/lib/bpf/libbpf.map | 1 + 4 files changed, 112 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 82b983ff6569..383b29ecb1fd 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -872,3 +872,14 @@ int bpf_enable_stats(enum bpf_stats_type type) return sys_bpf(BPF_ENABLE_STATS, &attr, sizeof(attr)); } + +int bpf_prog_bind_map(int prog_fd, int map_fd, int flags) +{ + union bpf_attr attr = {}; + + attr.prog_bind_map.prog_fd = prog_fd; + attr.prog_bind_map.map_fd = map_fd; + attr.prog_bind_map.flags = flags; + + return sys_bpf(BPF_PROG_BIND_MAP, &attr, sizeof(attr)); +} diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 015d13f25fcc..32994a4e0bf6 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -243,6 +243,7 @@ LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf, enum bpf_stats_type; /* defined in up-to-date linux/bpf.h */ LIBBPF_API int bpf_enable_stats(enum bpf_stats_type type); +LIBBPF_API int bpf_prog_bind_map(int prog_fd, int map_fd, int flags); #ifdef __cplusplus } /* extern "C" */ #endif diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 77d420c02094..4725859099c5 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -174,6 +174,8 @@ enum kern_feature_id { FEAT_EXP_ATTACH_TYPE, /* bpf_probe_read_{kernel,user}[_str] helpers */ FEAT_PROBE_READ_KERN, + /* bpf_prog_bind_map helper */ + FEAT_PROG_BIND_MAP, __FEAT_CNT, }; @@ -283,6 +285,7 @@ struct bpf_struct_ops { #define KCONFIG_SEC ".kconfig" #define KSYMS_SEC ".ksyms" #define STRUCT_OPS_SEC ".struct_ops" +#define METADATA_SEC ".metadata" enum libbpf_map_type { LIBBPF_MAP_UNSPEC, @@ -290,6 +293,7 @@ enum libbpf_map_type { LIBBPF_MAP_BSS, LIBBPF_MAP_RODATA, LIBBPF_MAP_KCONFIG, + LIBBPF_MAP_METADATA, }; static const char * const libbpf_type_to_btf_name[] = { @@ -297,6 +301,7 @@ static const char * const libbpf_type_to_btf_name[] = { [LIBBPF_MAP_BSS] = BSS_SEC, [LIBBPF_MAP_RODATA] = RODATA_SEC, [LIBBPF_MAP_KCONFIG] = KCONFIG_SEC, + [LIBBPF_MAP_METADATA] = METADATA_SEC, }; struct bpf_map { @@ -375,6 +380,8 @@ struct bpf_object { size_t nr_maps; size_t maps_cap; + struct bpf_map *metadata_map; + char *kconfig; struct extern_desc *externs; int nr_extern; @@ -398,6 +405,7 @@ struct bpf_object { Elf_Data *rodata; Elf_Data *bss; Elf_Data *st_ops_data; + Elf_Data *metadata; size_t strtabidx; struct { GElf_Shdr shdr; @@ -413,6 +421,7 @@ struct bpf_object { int rodata_shndx; int bss_shndx; int st_ops_shndx; + int metadata_shndx; } efile; /* * All loaded bpf_object is linked in a list, which is @@ -1022,6 +1031,7 @@ static struct bpf_object *bpf_object__new(const char *path, obj->efile.obj_buf_sz = obj_buf_sz; obj->efile.maps_shndx = -1; obj->efile.btf_maps_shndx = -1; + obj->efile.metadata_shndx = -1; obj->efile.data_shndx = -1; obj->efile.rodata_shndx = -1; obj->efile.bss_shndx = -1; @@ -1387,6 +1397,9 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, if (data) memcpy(map->mmaped, data, data_sz); + if (type == LIBBPF_MAP_METADATA) + obj->metadata_map = map; + pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name); return 0; } @@ -1422,6 +1435,14 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj) if (err) return err; } + if (obj->efile.metadata_shndx >= 0) { + err = bpf_object__init_internal_map(obj, LIBBPF_MAP_METADATA, + obj->efile.metadata_shndx, + obj->efile.metadata->d_buf, + obj->efile.metadata->d_size); + if (err) + return err; + } return 0; } @@ -2698,6 +2719,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj) } else if (strcmp(name, STRUCT_OPS_SEC) == 0) { obj->efile.st_ops_data = data; obj->efile.st_ops_shndx = idx; + } else if (strcmp(name, METADATA_SEC) == 0) { + obj->efile.metadata = data; + obj->efile.metadata_shndx = idx; } else { pr_debug("skip section(%d) %s\n", idx, name); } @@ -3111,7 +3135,8 @@ static bool bpf_object__shndx_is_data(const struct bpf_object *obj, { return shndx == obj->efile.data_shndx || shndx == obj->efile.bss_shndx || - shndx == obj->efile.rodata_shndx; + shndx == obj->efile.rodata_shndx || + shndx == obj->efile.metadata_shndx; } static bool bpf_object__shndx_is_maps(const struct bpf_object *obj, @@ -3132,6 +3157,8 @@ bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx) return LIBBPF_MAP_RODATA; else if (shndx == obj->efile.symbols_shndx) return LIBBPF_MAP_KCONFIG; + else if (shndx == obj->efile.metadata_shndx) + return LIBBPF_MAP_METADATA; else return LIBBPF_MAP_UNSPEC; } @@ -3655,6 +3682,60 @@ static int probe_kern_probe_read_kernel(void) return probe_fd(bpf_load_program_xattr(&attr, NULL, 0)); } +static int probe_prog_bind_map(void) +{ + struct bpf_load_program_attr prog_attr; + struct bpf_create_map_attr map_attr; + char *cp, errmsg[STRERR_BUFSIZE]; + struct bpf_insn insns[] = { + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }; + int ret = 0, prog, map; + + if (!kernel_supports(FEAT_GLOBAL_DATA)) + return 0; + + memset(&map_attr, 0, sizeof(map_attr)); + map_attr.map_type = BPF_MAP_TYPE_ARRAY; + map_attr.key_size = sizeof(int); + map_attr.value_size = 32; + map_attr.max_entries = 1; + + map = bpf_create_map_xattr(&map_attr); + if (map < 0) { + ret = -errno; + cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg)); + pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n", + __func__, cp, -ret); + return ret; + } + + memset(&prog_attr, 0, sizeof(prog_attr)); + prog_attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER; + prog_attr.insns = insns; + prog_attr.insns_cnt = ARRAY_SIZE(insns); + prog_attr.license = "GPL"; + + prog = bpf_load_program_xattr(&prog_attr, NULL, 0); + if (prog < 0) { + ret = -errno; + cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg)); + pr_warn("Error in %s():%s(%d). Couldn't create simple program.\n", + __func__, cp, -ret); + + close(map); + return ret; + } + + if (!bpf_prog_bind_map(prog, map, 0)) + ret = 1; + + close(map); + close(prog); + return ret; +} + enum kern_feature_result { FEAT_UNKNOWN = 0, FEAT_SUPPORTED = 1, @@ -3695,6 +3776,9 @@ static struct kern_feature_desc { }, [FEAT_PROBE_READ_KERN] = { "bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel, + }, + [FEAT_PROG_BIND_MAP] = { + "bpf_prog_bind_map() helper", probe_prog_bind_map, } }; @@ -5954,6 +6038,20 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, if (ret >= 0) { if (log_buf && load_attr.log_level) pr_debug("verifier log:\n%s", log_buf); + + if (prog->obj->metadata_map && kernel_supports(FEAT_PROG_BIND_MAP)) { + if (bpf_prog_bind_map(ret, bpf_map__fd(prog->obj->metadata_map), 0) && + errno != EEXIST) { + int fd = ret; + + ret = -errno; + cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg)); + pr_warn("add metadata map failed: %s\n", cp); + close(fd); + goto out; + } + } + *pfd = ret; ret = 0; goto out; diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index e35bd6cdbdbf..4baf18a6df69 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -288,6 +288,7 @@ LIBBPF_0.1.0 { bpf_map__set_value_size; bpf_map__type; bpf_map__value_size; + bpf_prog_bind_map; bpf_program__attach_xdp; bpf_program__autoload; bpf_program__is_sk_lookup; -- 2.28.0