tools/bpf: implement libbpf btf__get_map_kv_tids() API function

Currently, to get map key/value type id's, the macro
  BPF_ANNOTATE_KV_PAIR(<map_name>, <key_type>, <value_type>)
needs to be defined in the bpf program for the
corresponding map.

During program/map loading time,
the local static function bpf_map_find_btf_info()
in libbpf.c is implemented to retrieve the key/value
type ids given the map name.

The patch refactored function bpf_map_find_btf_info()
to create an API btf__get_map_kv_tids() which includes
the bulk of implementation for the original function.
The API btf__get_map_kv_tids() can be used by bcc,
a JIT based bpf compilation system, which uses the
same BPF_ANNOTATE_KV_PAIR to record map key/value types.

Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 51a0db0..7ec0463 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 /* Copyright (c) 2018 Facebook */
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -504,6 +505,78 @@ exit_free:
        return err;
 }
 
+int btf__get_map_kv_tids(const struct btf *btf, char *map_name,
+                        __u32 expected_key_size, __u32 expected_value_size,
+                        __u32 *key_type_id, __u32 *value_type_id)
+{
+       const struct btf_type *container_type;
+       const struct btf_member *key, *value;
+       const size_t max_name = 256;
+       char container_name[max_name];
+       __s64 key_size, value_size;
+       __s32 container_id;
+
+       if (snprintf(container_name, max_name, "____btf_map_%s", map_name) ==
+           max_name) {
+               pr_warning("map:%s length of '____btf_map_%s' is too long\n",
+                          map_name, map_name);
+               return -EINVAL;
+       }
+
+       container_id = btf__find_by_name(btf, container_name);
+       if (container_id < 0) {
+               pr_warning("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
+                          map_name, container_name);
+               return container_id;
+       }
+
+       container_type = btf__type_by_id(btf, container_id);
+       if (!container_type) {
+               pr_warning("map:%s cannot find BTF type for container_id:%u\n",
+                          map_name, container_id);
+               return -EINVAL;
+       }
+
+       if (BTF_INFO_KIND(container_type->info) != BTF_KIND_STRUCT ||
+           BTF_INFO_VLEN(container_type->info) < 2) {
+               pr_warning("map:%s container_name:%s is an invalid container struct\n",
+                          map_name, container_name);
+               return -EINVAL;
+       }
+
+       key = (struct btf_member *)(container_type + 1);
+       value = key + 1;
+
+       key_size = btf__resolve_size(btf, key->type);
+       if (key_size < 0) {
+               pr_warning("map:%s invalid BTF key_type_size\n", map_name);
+               return key_size;
+       }
+
+       if (expected_key_size != key_size) {
+               pr_warning("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
+                          map_name, (__u32)key_size, expected_key_size);
+               return -EINVAL;
+       }
+
+       value_size = btf__resolve_size(btf, value->type);
+       if (value_size < 0) {
+               pr_warning("map:%s invalid BTF value_type_size\n", map_name);
+               return value_size;
+       }
+
+       if (expected_value_size != value_size) {
+               pr_warning("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
+                          map_name, (__u32)value_size, expected_value_size);
+               return -EINVAL;
+       }
+
+       *key_type_id = key->type;
+       *value_type_id = value->type;
+
+       return 0;
+}
+
 struct btf_ext_sec_copy_param {
        __u32 off;
        __u32 len;

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 418389e..258c87e 100644 (file)
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -66,6 +66,10 @@ LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id);
 LIBBPF_API int btf__fd(const struct btf *btf);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
+LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, char *map_name,
+                                   __u32 expected_key_size,
+                                   __u32 expected_value_size,
+                                   __u32 *key_type_id, __u32 *value_type_id);
 
 LIBBPF_API struct btf_ext *btf_ext__new(__u8 *data, __u32 size);
 LIBBPF_API void btf_ext__free(struct btf_ext *btf_ext);

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ce209ab..84ca6c2 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1056,72 +1056,18 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
 
 static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf)
 {
-       const struct btf_type *container_type;
-       const struct btf_member *key, *value;
        struct bpf_map_def *def = &map->def;
-       const size_t max_name = 256;
-       char container_name[max_name];
-       __s64 key_size, value_size;
-       __s32 container_id;
-
-       if (snprintf(container_name, max_name, "____btf_map_%s", map->name) ==
-           max_name) {
-               pr_warning("map:%s length of '____btf_map_%s' is too long\n",
-                          map->name, map->name);
-               return -EINVAL;
-       }
-
-       container_id = btf__find_by_name(btf, container_name);
-       if (container_id < 0) {
-               pr_debug("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
-                        map->name, container_name);
-               return container_id;
-       }
-
-       container_type = btf__type_by_id(btf, container_id);
-       if (!container_type) {
-               pr_warning("map:%s cannot find BTF type for container_id:%u\n",
-                          map->name, container_id);
-               return -EINVAL;
-       }
-
-       if (BTF_INFO_KIND(container_type->info) != BTF_KIND_STRUCT ||
-           BTF_INFO_VLEN(container_type->info) < 2) {
-               pr_warning("map:%s container_name:%s is an invalid container struct\n",
-                          map->name, container_name);
-               return -EINVAL;
-       }
-
-       key = (struct btf_member *)(container_type + 1);
-       value = key + 1;
-
-       key_size = btf__resolve_size(btf, key->type);
-       if (key_size < 0) {
-               pr_warning("map:%s invalid BTF key_type_size\n",
-                          map->name);
-               return key_size;
-       }
-
-       if (def->key_size != key_size) {
-               pr_warning("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
-                          map->name, (__u32)key_size, def->key_size);
-               return -EINVAL;
-       }
-
-       value_size = btf__resolve_size(btf, value->type);
-       if (value_size < 0) {
-               pr_warning("map:%s invalid BTF value_type_size\n", map->name);
-               return value_size;
-       }
+       __u32 key_type_id, value_type_id;
+       int ret;
 
-       if (def->value_size != value_size) {
-               pr_warning("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
-                          map->name, (__u32)value_size, def->value_size);
-               return -EINVAL;
-       }
+       ret = btf__get_map_kv_tids(btf, map->name, def->key_size,
+                                  def->value_size, &key_type_id,
+                                  &value_type_id);
+       if (ret)
+               return ret;
 
-       map->btf_key_type_id = key->type;
-       map->btf_value_type_id = value->type;
+       map->btf_key_type_id = key_type_id;
+       map->btf_value_type_id = value_type_id;
 
        return 0;
 }

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 46441c5..7990e85 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -133,6 +133,7 @@ LIBBPF_0.0.2 {
                bpf_map_lookup_elem_flags;
                bpf_object__find_map_fd_by_name;
                bpf_get_link_xdp_id;
+               btf__get_map_kv_tids;
                btf_ext__free;
                btf_ext__func_info_rec_size;
                btf_ext__line_info_rec_size;