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>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3d35bac..6513e0b 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;
+ struct bpf_map *map = &obj->maps[i];
+ struct bpf_map_def *def = &map->def;
+ int *pfd = &map->fd;
- *pfd = bpf_create_map_name(def->type,
- obj->maps[i].name,
- def->key_size,
- def->value_size,
- def->max_entries,
- def->map_flags);
+ 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)
{