Commit 96408c43 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

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: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b8dcf8d1

tools/lib/bpf/btf.c

+73 −0
Original line number Diff line number Diff line 
// 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;

tools/lib/bpf/btf.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

tools/lib/bpf/libbpf.c

+9 −63
Original line number Diff line number Diff line
@@ -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;

}

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -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;

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