From 8a138aed4a807ceb143882fb23a423d524dcdb35 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 18 Apr 2018 15:56:05 -0700 Subject: 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 "_key" and "_value". If they cannot be found, it will continue without using the BTF. Signed-off-by: Martin KaFai Lau Acked-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 148 ++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 135 insertions(+), 13 deletions(-) (limited to 'tools/lib/bpf/libbpf.c') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3d35bacf656f..6513e0b08795 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -45,6 +45,7 @@ #include "libbpf.h" #include "bpf.h" +#include "btf.h" #ifndef EM_BPF #define EM_BPF 247 @@ -212,6 +213,8 @@ struct bpf_map { char *name; size_t offset; struct bpf_map_def def; + uint32_t btf_key_id; + uint32_t btf_value_id; void *priv; bpf_map_clear_priv_t clear_priv; }; @@ -256,6 +259,8 @@ struct bpf_object { */ struct list_head list; + struct btf *btf; + void *priv; bpf_object_clear_priv_t clear_priv; @@ -819,7 +824,15 @@ static int bpf_object__elf_collect(struct bpf_object *obj) data->d_size); else if (strcmp(name, "maps") == 0) obj->efile.maps_shndx = idx; - else if (sh.sh_type == SHT_SYMTAB) { + else if (strcmp(name, BTF_ELF_SEC) == 0) { + obj->btf = btf__new(data->d_buf, data->d_size, + __pr_debug); + if (IS_ERR(obj->btf)) { + pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n", + BTF_ELF_SEC, PTR_ERR(obj->btf)); + obj->btf = NULL; + } + } else if (sh.sh_type == SHT_SYMTAB) { if (obj->efile.symbols) { pr_warning("bpf: multiple SYMTAB in %s\n", obj->path); @@ -996,33 +1009,126 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr, return 0; } +static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf) +{ + struct bpf_map_def *def = &map->def; + const size_t max_name = 256; + int64_t key_size, value_size; + int32_t key_id, value_id; + char name[max_name]; + + /* Find key type by name from BTF */ + if (snprintf(name, max_name, "%s_key", map->name) == max_name) { + pr_warning("map:%s length of BTF key_type:%s_key is too long\n", + map->name, map->name); + return -EINVAL; + } + + key_id = btf__find_by_name(btf, name); + if (key_id < 0) { + pr_debug("map:%s key_type:%s cannot be found in BTF\n", + map->name, name); + return key_id; + } + + key_size = btf__resolve_size(btf, key_id); + if (key_size < 0) { + pr_warning("map:%s key_type:%s cannot get the BTF type_size\n", + map->name, name); + return key_size; + } + + if (def->key_size != key_size) { + pr_warning("map:%s key_type:%s has BTF type_size:%ld != key_size:%u\n", + map->name, name, key_size, def->key_size); + return -EINVAL; + } + + /* Find value type from BTF */ + if (snprintf(name, max_name, "%s_value", map->name) == max_name) { + pr_warning("map:%s length of BTF value_type:%s_value is too long\n", + map->name, map->name); + return -EINVAL; + } + + value_id = btf__find_by_name(btf, name); + if (value_id < 0) { + pr_debug("map:%s value_type:%s cannot be found in BTF\n", + map->name, name); + return value_id; + } + + value_size = btf__resolve_size(btf, value_id); + if (value_size < 0) { + pr_warning("map:%s value_type:%s cannot get the BTF type_size\n", + map->name, name); + return value_size; + } + + if (def->value_size != value_size) { + pr_warning("map:%s value_type:%s has BTF type_size:%ld != value_size:%u\n", + map->name, name, value_size, def->value_size); + return -EINVAL; + } + + map->btf_key_id = key_id; + map->btf_value_id = value_id; + + return 0; +} + static int bpf_object__create_maps(struct bpf_object *obj) { + struct bpf_create_map_attr create_attr = {}; unsigned int i; + int err; for (i = 0; i < obj->nr_maps; i++) { - struct bpf_map_def *def = &obj->maps[i].def; - int *pfd = &obj->maps[i].fd; - - *pfd = bpf_create_map_name(def->type, - obj->maps[i].name, - def->key_size, - def->value_size, - def->max_entries, - def->map_flags); + struct bpf_map *map = &obj->maps[i]; + struct bpf_map_def *def = &map->def; + int *pfd = &map->fd; + + create_attr.name = map->name; + create_attr.map_type = def->type; + create_attr.map_flags = def->map_flags; + create_attr.key_size = def->key_size; + create_attr.value_size = def->value_size; + create_attr.max_entries = def->max_entries; + create_attr.btf_fd = 0; + create_attr.btf_key_id = 0; + create_attr.btf_value_id = 0; + + if (obj->btf && !bpf_map_find_btf_info(map, obj->btf)) { + create_attr.btf_fd = btf__fd(obj->btf); + create_attr.btf_key_id = map->btf_key_id; + create_attr.btf_value_id = map->btf_value_id; + } + + *pfd = bpf_create_map_xattr(&create_attr); + if (*pfd < 0 && create_attr.btf_key_id) { + pr_warning("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n", + map->name, strerror(errno), errno); + create_attr.btf_fd = 0; + create_attr.btf_key_id = 0; + create_attr.btf_value_id = 0; + map->btf_key_id = 0; + map->btf_value_id = 0; + *pfd = bpf_create_map_xattr(&create_attr); + } + if (*pfd < 0) { size_t j; - int err = *pfd; + err = *pfd; pr_warning("failed to create map (name: '%s'): %s\n", - obj->maps[i].name, + map->name, strerror(errno)); for (j = 0; j < i; j++) zclose(obj->maps[j].fd); return err; } - pr_debug("create map %s: fd=%d\n", obj->maps[i].name, *pfd); + pr_debug("create map %s: fd=%d\n", map->name, *pfd); } return 0; @@ -1641,6 +1747,7 @@ void bpf_object__close(struct bpf_object *obj) bpf_object__elf_finish(obj); bpf_object__unload(obj); + btf__free(obj->btf); for (i = 0; i < obj->nr_maps; i++) { zfree(&obj->maps[i].name); @@ -1692,6 +1799,11 @@ unsigned int bpf_object__kversion(struct bpf_object *obj) return obj ? obj->kern_version : 0; } +int bpf_object__btf_fd(const struct bpf_object *obj) +{ + return obj->btf ? btf__fd(obj->btf) : -1; +} + int bpf_object__set_priv(struct bpf_object *obj, void *priv, bpf_object_clear_priv_t clear_priv) { @@ -1937,6 +2049,16 @@ const char *bpf_map__name(struct bpf_map *map) return map ? map->name : NULL; } +uint32_t bpf_map__btf_key_id(const struct bpf_map *map) +{ + return map ? map->btf_key_id : 0; +} + +uint32_t bpf_map__btf_value_id(const struct bpf_map *map) +{ + return map ? map->btf_value_id : 0; +} + int bpf_map__set_priv(struct bpf_map *map, void *priv, bpf_map_clear_priv_t clear_priv) { -- cgit v1.2.3-55-g7522