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Commit d7f5b5e0 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

tools/bpf: refactor to implement btf_get_from_id() in lib/bpf 



The function get_btf() is implemented in tools/bpf/bpftool/map.c
to get a btf structure given a map_info. This patch
refactored this function to be function btf_get_from_id()
in tools/lib/bpf so that it can be used later.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9ce6ae22

tools/bpf/bpftool/map.c

+2 −66
Original line number Diff line number Diff line
@@ -215,70 +215,6 @@ static int do_dump_btf(const struct btf_dumper *d, 
	return ret;

}



static int get_btf(struct bpf_map_info *map_info, struct btf **btf)

{

	struct bpf_btf_info btf_info = { 0 };

	__u32 len = sizeof(btf_info);

	__u32 last_size;

	int btf_fd;

	void *ptr;

	int err;



	err = 0;

	*btf = NULL;

	btf_fd = bpf_btf_get_fd_by_id(map_info->btf_id);

	if (btf_fd < 0)

		return 0;



	/* we won't know btf_size until we call bpf_obj_get_info_by_fd(). so

	 * let's start with a sane default - 4KiB here - and resize it only if

	 * bpf_obj_get_info_by_fd() needs a bigger buffer.

	 */

	btf_info.btf_size = 4096;

	last_size = btf_info.btf_size;

	ptr = malloc(last_size);

	if (!ptr) {

		err = -ENOMEM;

		goto exit_free;

	}



	bzero(ptr, last_size);

	btf_info.btf = ptr_to_u64(ptr);

	err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);



	if (!err && btf_info.btf_size > last_size) {

		void *temp_ptr;



		last_size = btf_info.btf_size;

		temp_ptr = realloc(ptr, last_size);

		if (!temp_ptr) {

			err = -ENOMEM;

			goto exit_free;

		}

		ptr = temp_ptr;

		bzero(ptr, last_size);

		btf_info.btf = ptr_to_u64(ptr);

		err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);

	}



	if (err || btf_info.btf_size > last_size) {

		err = errno;

		goto exit_free;

	}



	*btf = btf__new((__u8 *)btf_info.btf, btf_info.btf_size, NULL);

	if (IS_ERR(*btf)) {

		err = PTR_ERR(*btf);

		*btf = NULL;

	}



exit_free:

	close(btf_fd);

	free(ptr);



	return err;

}



static json_writer_t *get_btf_writer(void)

{

	json_writer_t *jw = jsonw_new(stdout);
@@ -775,7 +711,7 @@ static int do_dump(int argc, char **argv) 


	prev_key = NULL;



	err = get_btf(&info, &btf);

	err = btf_get_from_id(info.btf_id, &btf);

	if (err) {

		p_err("failed to get btf");

		goto exit_free;
@@ -919,7 +855,7 @@ static int do_lookup(int argc, char **argv) 
	}



	/* here means bpf_map_lookup_elem() succeeded */

	err = get_btf(&info, &btf);

	err = btf_get_from_id(info.btf_id, &btf);

	if (err) {

		p_err("failed to get btf");

		goto exit_free;

tools/lib/bpf/btf.c

+69 −0
Original line number Diff line number Diff line
@@ -49,6 +49,11 @@ struct bpf_func_info_min { 
	__u32   type_id;

};



static inline __u64 ptr_to_u64(const void *ptr)

{

	return (__u64) (unsigned long) ptr;

}



static int btf_add_type(struct btf *btf, struct btf_type *t)

{

	if (btf->types_size - btf->nr_types < 2) {
@@ -410,6 +415,70 @@ const char *btf__name_by_offset(const struct btf *btf, __u32 offset) 
		return NULL;

}



int btf_get_from_id(__u32 id, struct btf **btf)

{

	struct bpf_btf_info btf_info = { 0 };

	__u32 len = sizeof(btf_info);

	__u32 last_size;

	int btf_fd;

	void *ptr;

	int err;



	err = 0;

	*btf = NULL;

	btf_fd = bpf_btf_get_fd_by_id(id);

	if (btf_fd < 0)

		return 0;



	/* we won't know btf_size until we call bpf_obj_get_info_by_fd(). so

	 * let's start with a sane default - 4KiB here - and resize it only if

	 * bpf_obj_get_info_by_fd() needs a bigger buffer.

	 */

	btf_info.btf_size = 4096;

	last_size = btf_info.btf_size;

	ptr = malloc(last_size);

	if (!ptr) {

		err = -ENOMEM;

		goto exit_free;

	}



	bzero(ptr, last_size);

	btf_info.btf = ptr_to_u64(ptr);

	err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);



	if (!err && btf_info.btf_size > last_size) {

		void *temp_ptr;



		last_size = btf_info.btf_size;

		temp_ptr = realloc(ptr, last_size);

		if (!temp_ptr) {

			err = -ENOMEM;

			goto exit_free;

		}

		ptr = temp_ptr;

		bzero(ptr, last_size);

		btf_info.btf = ptr_to_u64(ptr);

		err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);

	}



	if (err || btf_info.btf_size > last_size) {

		err = errno;

		goto exit_free;

	}



	*btf = btf__new((__u8 *)btf_info.btf, btf_info.btf_size, NULL);

	if (IS_ERR(*btf)) {

		err = PTR_ERR(*btf);

		*btf = NULL;

	}



exit_free:

	close(btf_fd);

	free(ptr);



	return err;

}



static int btf_ext_validate_func_info(const void *finfo, __u32 size,

				      btf_print_fn_t err_log)

{

tools/lib/bpf/btf.h

+1 −0
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id); 
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);



struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log);

void btf_ext__free(struct btf_ext *btf_ext);