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bpf: btf: Add BTF support to libbpf
If the ".BTF" elf section exists, libbpf will try to create a btf_fd (through BPF_BTF_LOAD). If that fails, it will still continue loading the bpf prog/map without the BTF. If the bpf_object has a BTF loaded, it will create a map with the btf_fd. libbpf will try to figure out the btf_key_id and btf_value_id of a map by finding the BTF type with name "<map_name>_key" and "<map_name>_value". If they cannot be found, it will continue without using the BTF. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau
Daniel Borkmann
parent
3bd86a8409
commit
8a138aed4a
7 changed files with 627 additions and 32 deletions
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@ -45,6 +45,7 @@
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#include "libbpf.h"
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#include "bpf.h"
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#include "btf.h"
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#ifndef EM_BPF
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#define EM_BPF 247
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@ -212,6 +213,8 @@ struct bpf_map {
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char *name;
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size_t offset;
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struct bpf_map_def def;
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uint32_t btf_key_id;
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uint32_t btf_value_id;
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void *priv;
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bpf_map_clear_priv_t clear_priv;
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};
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@ -256,6 +259,8 @@ struct bpf_object {
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*/
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struct list_head list;
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struct btf *btf;
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void *priv;
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bpf_object_clear_priv_t clear_priv;
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@ -819,7 +824,15 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
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data->d_size);
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else if (strcmp(name, "maps") == 0)
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obj->efile.maps_shndx = idx;
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else if (sh.sh_type == SHT_SYMTAB) {
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else if (strcmp(name, BTF_ELF_SEC) == 0) {
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obj->btf = btf__new(data->d_buf, data->d_size,
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__pr_debug);
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if (IS_ERR(obj->btf)) {
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pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
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BTF_ELF_SEC, PTR_ERR(obj->btf));
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obj->btf = NULL;
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}
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} else if (sh.sh_type == SHT_SYMTAB) {
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if (obj->efile.symbols) {
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pr_warning("bpf: multiple SYMTAB in %s\n",
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obj->path);
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@ -996,33 +1009,126 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
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return 0;
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}
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static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf)
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{
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struct bpf_map_def *def = &map->def;
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const size_t max_name = 256;
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int64_t key_size, value_size;
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int32_t key_id, value_id;
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char name[max_name];
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/* Find key type by name from BTF */
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if (snprintf(name, max_name, "%s_key", map->name) == max_name) {
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pr_warning("map:%s length of BTF key_type:%s_key is too long\n",
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map->name, map->name);
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return -EINVAL;
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}
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key_id = btf__find_by_name(btf, name);
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if (key_id < 0) {
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pr_debug("map:%s key_type:%s cannot be found in BTF\n",
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map->name, name);
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return key_id;
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}
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key_size = btf__resolve_size(btf, key_id);
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if (key_size < 0) {
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pr_warning("map:%s key_type:%s cannot get the BTF type_size\n",
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map->name, name);
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return key_size;
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}
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if (def->key_size != key_size) {
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pr_warning("map:%s key_type:%s has BTF type_size:%ld != key_size:%u\n",
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map->name, name, key_size, def->key_size);
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return -EINVAL;
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}
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/* Find value type from BTF */
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if (snprintf(name, max_name, "%s_value", map->name) == max_name) {
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pr_warning("map:%s length of BTF value_type:%s_value is too long\n",
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map->name, map->name);
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return -EINVAL;
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}
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value_id = btf__find_by_name(btf, name);
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if (value_id < 0) {
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pr_debug("map:%s value_type:%s cannot be found in BTF\n",
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map->name, name);
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return value_id;
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}
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value_size = btf__resolve_size(btf, value_id);
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if (value_size < 0) {
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pr_warning("map:%s value_type:%s cannot get the BTF type_size\n",
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map->name, name);
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return value_size;
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}
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if (def->value_size != value_size) {
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pr_warning("map:%s value_type:%s has BTF type_size:%ld != value_size:%u\n",
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map->name, name, value_size, def->value_size);
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return -EINVAL;
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}
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map->btf_key_id = key_id;
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map->btf_value_id = value_id;
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return 0;
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}
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static int
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bpf_object__create_maps(struct bpf_object *obj)
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{
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struct bpf_create_map_attr create_attr = {};
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unsigned int i;
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int err;
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for (i = 0; i < obj->nr_maps; i++) {
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struct bpf_map_def *def = &obj->maps[i].def;
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int *pfd = &obj->maps[i].fd;
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struct bpf_map *map = &obj->maps[i];
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struct bpf_map_def *def = &map->def;
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int *pfd = &map->fd;
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create_attr.name = map->name;
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create_attr.map_type = def->type;
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create_attr.map_flags = def->map_flags;
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create_attr.key_size = def->key_size;
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create_attr.value_size = def->value_size;
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create_attr.max_entries = def->max_entries;
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create_attr.btf_fd = 0;
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create_attr.btf_key_id = 0;
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create_attr.btf_value_id = 0;
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if (obj->btf && !bpf_map_find_btf_info(map, obj->btf)) {
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create_attr.btf_fd = btf__fd(obj->btf);
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create_attr.btf_key_id = map->btf_key_id;
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create_attr.btf_value_id = map->btf_value_id;
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}
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*pfd = bpf_create_map_xattr(&create_attr);
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if (*pfd < 0 && create_attr.btf_key_id) {
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pr_warning("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
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map->name, strerror(errno), errno);
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create_attr.btf_fd = 0;
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create_attr.btf_key_id = 0;
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create_attr.btf_value_id = 0;
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map->btf_key_id = 0;
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map->btf_value_id = 0;
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*pfd = bpf_create_map_xattr(&create_attr);
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}
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*pfd = bpf_create_map_name(def->type,
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obj->maps[i].name,
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def->key_size,
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def->value_size,
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def->max_entries,
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def->map_flags);
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if (*pfd < 0) {
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size_t j;
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int err = *pfd;
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err = *pfd;
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pr_warning("failed to create map (name: '%s'): %s\n",
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obj->maps[i].name,
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map->name,
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strerror(errno));
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for (j = 0; j < i; j++)
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zclose(obj->maps[j].fd);
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return err;
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}
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pr_debug("create map %s: fd=%d\n", obj->maps[i].name, *pfd);
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pr_debug("create map %s: fd=%d\n", map->name, *pfd);
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}
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return 0;
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@ -1641,6 +1747,7 @@ void bpf_object__close(struct bpf_object *obj)
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bpf_object__elf_finish(obj);
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bpf_object__unload(obj);
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btf__free(obj->btf);
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for (i = 0; i < obj->nr_maps; i++) {
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zfree(&obj->maps[i].name);
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@ -1692,6 +1799,11 @@ unsigned int bpf_object__kversion(struct bpf_object *obj)
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return obj ? obj->kern_version : 0;
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}
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int bpf_object__btf_fd(const struct bpf_object *obj)
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{
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return obj->btf ? btf__fd(obj->btf) : -1;
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}
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int bpf_object__set_priv(struct bpf_object *obj, void *priv,
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bpf_object_clear_priv_t clear_priv)
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{
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@ -1937,6 +2049,16 @@ const char *bpf_map__name(struct bpf_map *map)
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return map ? map->name : NULL;
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}
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uint32_t bpf_map__btf_key_id(const struct bpf_map *map)
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{
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return map ? map->btf_key_id : 0;
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}
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uint32_t bpf_map__btf_value_id(const struct bpf_map *map)
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{
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return map ? map->btf_value_id : 0;
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}
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int bpf_map__set_priv(struct bpf_map *map, void *priv,
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bpf_map_clear_priv_t clear_priv)
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{
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