libbpf: Add auto-pinning of maps when loading BPF objects
This adds support to libbpf for setting map pinning information as part of the BTF map declaration, to get automatic map pinning (and reuse) on load. The pinning type currently only supports a single PIN_BY_NAME mode, where each map will be pinned by its name in a path that can be overridden, but defaults to /sys/fs/bpf. Since auto-pinning only does something if any maps actually have a 'pinning' BTF attribute set, we default the new option to enabled, on the assumption that seamless pinning is what most callers want. When a map has a pin_path set at load time, libbpf will compare the map pinned at that location (if any), and if the attributes match, will re-use that map instead of creating a new one. If no existing map is found, the newly created map will instead be pinned at the location. Programs wanting to customise the pinning can override the pinning paths using bpf_map__set_pin_path() before calling bpf_object__load() (including setting it to NULL to disable pinning of a particular map). Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/157269298092.394725.3966306029218559681.stgit@toke.dk
This commit is contained in:
Toke Høiland-Jørgensen
Alexei Starovoitov
Родитель
196f8487f5
Коммит
57a00f4164
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@ -38,4 +38,10 @@ struct bpf_map_def {
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unsigned int map_flags;
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};
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enum libbpf_pin_type {
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LIBBPF_PIN_NONE,
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/* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
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LIBBPF_PIN_BY_NAME,
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};
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#endif
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@ -1093,10 +1093,32 @@ static bool get_map_field_int(const char *map_name, const struct btf *btf,
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return true;
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}
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static int build_map_pin_path(struct bpf_map *map, const char *path)
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{
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char buf[PATH_MAX];
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int err, len;
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if (!path)
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path = "/sys/fs/bpf";
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len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
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if (len < 0)
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return -EINVAL;
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else if (len >= PATH_MAX)
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return -ENAMETOOLONG;
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err = bpf_map__set_pin_path(map, buf);
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if (err)
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return err;
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return 0;
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}
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static int bpf_object__init_user_btf_map(struct bpf_object *obj,
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const struct btf_type *sec,
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int var_idx, int sec_idx,
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const Elf_Data *data, bool strict)
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const Elf_Data *data, bool strict,
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const char *pin_root_path)
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{
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const struct btf_type *var, *def, *t;
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const struct btf_var_secinfo *vi;
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@ -1271,6 +1293,30 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
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}
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map->def.value_size = sz;
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map->btf_value_type_id = t->type;
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} else if (strcmp(name, "pinning") == 0) {
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__u32 val;
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int err;
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if (!get_map_field_int(map_name, obj->btf, def, m,
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&val))
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return -EINVAL;
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pr_debug("map '%s': found pinning = %u.\n",
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map_name, val);
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if (val != LIBBPF_PIN_NONE &&
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val != LIBBPF_PIN_BY_NAME) {
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pr_warn("map '%s': invalid pinning value %u.\n",
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map_name, val);
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return -EINVAL;
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}
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if (val == LIBBPF_PIN_BY_NAME) {
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err = build_map_pin_path(map, pin_root_path);
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if (err) {
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pr_warn("map '%s': couldn't build pin path.\n",
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map_name);
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return err;
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}
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}
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} else {
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if (strict) {
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pr_warn("map '%s': unknown field '%s'.\n",
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@ -1290,7 +1336,8 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
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return 0;
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}
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static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict)
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static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
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const char *pin_root_path)
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{
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const struct btf_type *sec = NULL;
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int nr_types, i, vlen, err;
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@ -1332,7 +1379,7 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict)
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for (i = 0; i < vlen; i++) {
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err = bpf_object__init_user_btf_map(obj, sec, i,
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obj->efile.btf_maps_shndx,
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data, strict);
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data, strict, pin_root_path);
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if (err)
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return err;
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}
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@ -1340,7 +1387,8 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict)
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return 0;
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}
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static int bpf_object__init_maps(struct bpf_object *obj, bool relaxed_maps)
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static int bpf_object__init_maps(struct bpf_object *obj, bool relaxed_maps,
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const char *pin_root_path)
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{
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bool strict = !relaxed_maps;
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int err;
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@ -1349,7 +1397,7 @@ static int bpf_object__init_maps(struct bpf_object *obj, bool relaxed_maps)
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if (err)
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return err;
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err = bpf_object__init_user_btf_maps(obj, strict);
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err = bpf_object__init_user_btf_maps(obj, strict, pin_root_path);
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if (err)
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return err;
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@ -1538,7 +1586,8 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
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return 0;
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}
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static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps)
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static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps,
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const char *pin_root_path)
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{
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Elf *elf = obj->efile.elf;
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GElf_Ehdr *ep = &obj->efile.ehdr;
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@ -1673,7 +1722,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps)
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}
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err = bpf_object__init_btf(obj, btf_data, btf_ext_data);
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if (!err)
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err = bpf_object__init_maps(obj, relaxed_maps);
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err = bpf_object__init_maps(obj, relaxed_maps, pin_root_path);
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if (!err)
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err = bpf_object__sanitize_and_load_btf(obj);
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if (!err)
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@ -2129,6 +2178,66 @@ bpf_object__probe_caps(struct bpf_object *obj)
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return 0;
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}
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static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
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{
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struct bpf_map_info map_info = {};
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char msg[STRERR_BUFSIZE];
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__u32 map_info_len;
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map_info_len = sizeof(map_info);
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if (bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len)) {
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pr_warn("failed to get map info for map FD %d: %s\n",
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map_fd, libbpf_strerror_r(errno, msg, sizeof(msg)));
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return false;
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}
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return (map_info.type == map->def.type &&
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map_info.key_size == map->def.key_size &&
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map_info.value_size == map->def.value_size &&
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map_info.max_entries == map->def.max_entries &&
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map_info.map_flags == map->def.map_flags);
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}
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static int
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bpf_object__reuse_map(struct bpf_map *map)
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{
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char *cp, errmsg[STRERR_BUFSIZE];
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int err, pin_fd;
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pin_fd = bpf_obj_get(map->pin_path);
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if (pin_fd < 0) {
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err = -errno;
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if (err == -ENOENT) {
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pr_debug("found no pinned map to reuse at '%s'\n",
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map->pin_path);
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return 0;
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}
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cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
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pr_warn("couldn't retrieve pinned map '%s': %s\n",
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map->pin_path, cp);
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return err;
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}
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if (!map_is_reuse_compat(map, pin_fd)) {
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pr_warn("couldn't reuse pinned map at '%s': parameter mismatch\n",
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map->pin_path);
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close(pin_fd);
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return -EINVAL;
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}
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err = bpf_map__reuse_fd(map, pin_fd);
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if (err) {
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close(pin_fd);
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return err;
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}
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map->pinned = true;
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pr_debug("reused pinned map at '%s'\n", map->pin_path);
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return 0;
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}
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static int
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bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
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{
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@ -2171,6 +2280,15 @@ bpf_object__create_maps(struct bpf_object *obj)
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char *cp, errmsg[STRERR_BUFSIZE];
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int *pfd = &map->fd;
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if (map->pin_path) {
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err = bpf_object__reuse_map(map);
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if (err) {
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pr_warn("error reusing pinned map %s\n",
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map->name);
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return err;
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}
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}
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if (map->fd >= 0) {
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pr_debug("skip map create (preset) %s: fd=%d\n",
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map->name, map->fd);
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@ -2249,6 +2367,15 @@ err_out:
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}
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}
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if (map->pin_path && !map->pinned) {
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err = bpf_map__pin(map, NULL);
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if (err) {
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pr_warn("failed to auto-pin map name '%s' at '%s'\n",
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map->name, map->pin_path);
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return err;
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}
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}
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pr_debug("created map %s: fd=%d\n", map->name, *pfd);
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}
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@ -3623,6 +3750,7 @@ static struct bpf_object *
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__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
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struct bpf_object_open_opts *opts)
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{
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const char *pin_root_path;
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struct bpf_program *prog;
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struct bpf_object *obj;
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const char *obj_name;
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@ -3657,11 +3785,13 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
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obj->relaxed_core_relocs = OPTS_GET(opts, relaxed_core_relocs, false);
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relaxed_maps = OPTS_GET(opts, relaxed_maps, false);
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pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
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CHECK_ERR(bpf_object__elf_init(obj), err, out);
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CHECK_ERR(bpf_object__check_endianness(obj), err, out);
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CHECK_ERR(bpf_object__probe_caps(obj), err, out);
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CHECK_ERR(bpf_object__elf_collect(obj, relaxed_maps), err, out);
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CHECK_ERR(bpf_object__elf_collect(obj, relaxed_maps, pin_root_path),
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err, out);
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CHECK_ERR(bpf_object__collect_reloc(obj), err, out);
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bpf_object__elf_finish(obj);
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@ -103,8 +103,13 @@ struct bpf_object_open_opts {
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bool relaxed_maps;
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/* process CO-RE relocations non-strictly, allowing them to fail */
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bool relaxed_core_relocs;
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/* maps that set the 'pinning' attribute in their definition will have
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* their pin_path attribute set to a file in this directory, and be
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* auto-pinned to that path on load; defaults to "/sys/fs/bpf".
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*/
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const char *pin_root_path;
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};
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#define bpf_object_open_opts__last_field relaxed_core_relocs
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#define bpf_object_open_opts__last_field pin_root_path
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LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
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LIBBPF_API struct bpf_object *
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@ -125,6 +130,12 @@ int bpf_object__section_size(const struct bpf_object *obj, const char *name,
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int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,
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__u32 *off);
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enum libbpf_pin_type {
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LIBBPF_PIN_NONE,
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/* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
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LIBBPF_PIN_BY_NAME,
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};
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/* pin_maps and unpin_maps can both be called with a NULL path, in which case
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* they will use the pin_path attribute of each map (and ignore all maps that
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* don't have a pin_path set).
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