libbpf: Document bpf_{btf,link,map,prog}_get_info_by_fd()

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */

/*

 * common eBPF ELF operations.

 * Common BPF ELF operations.

 *

 * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>

 * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>

LIBBPF_API int bpf_link_get_fd_by_id_opts(__u32 id,

				const struct bpf_get_fd_by_id_opts *opts);

LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);

/* Type-safe variants of bpf_obj_get_info_by_fd(). The callers still needs to

 * pass info_len, which should normally be

 * sizeof(struct bpf_{prog,map,btf,link}_info), in order to be compatible with

 * different libbpf and kernel versions.

/**

 * @brief **bpf_prog_get_info_by_fd()** obtains information about the BPF

 * program corresponding to *prog_fd*.

 *

 * Populates up to *info_len* bytes of *info* and updates *info_len* with the

 * actual number of bytes written to *info*.

 *

 * @param prog_fd BPF program file descriptor

 * @param info pointer to **struct bpf_prog_info** that will be populated with

 * BPF program information

 * @param info_len pointer to the size of *info*; on success updated with the

 * number of bytes written to *info*

 * @return 0, on success; negative error code, otherwise (errno is also set to

 * the error code)

 */

LIBBPF_API int bpf_prog_get_info_by_fd(int prog_fd, struct bpf_prog_info *info, __u32 *info_len);

/**

 * @brief **bpf_map_get_info_by_fd()** obtains information about the BPF

 * map corresponding to *map_fd*.

 *

 * Populates up to *info_len* bytes of *info* and updates *info_len* with the

 * actual number of bytes written to *info*.

 *

 * @param map_fd BPF map file descriptor

 * @param info pointer to **struct bpf_map_info** that will be populated with

 * BPF map information

 * @param info_len pointer to the size of *info*; on success updated with the

 * number of bytes written to *info*

 * @return 0, on success; negative error code, otherwise (errno is also set to

 * the error code)

 */

LIBBPF_API int bpf_map_get_info_by_fd(int map_fd, struct bpf_map_info *info, __u32 *info_len);

/**

 * @brief **bpf_btf_get_info_by_fd()** obtains information about the 

 * BTF object corresponding to *btf_fd*.

 *

 * Populates up to *info_len* bytes of *info* and updates *info_len* with the

 * actual number of bytes written to *info*.

 *

 * @param btf_fd BTF object file descriptor

 * @param info pointer to **struct bpf_btf_info** that will be populated with

 * BTF object information

 * @param info_len pointer to the size of *info*; on success updated with the

 * number of bytes written to *info*

 * @return 0, on success; negative error code, otherwise (errno is also set to

 * the error code)

 */

LIBBPF_API int bpf_btf_get_info_by_fd(int btf_fd, struct bpf_btf_info *info, __u32 *info_len);

/**

 * @brief **bpf_btf_get_info_by_fd()** obtains information about the BPF

 * link corresponding to *link_fd*.

 *

 * Populates up to *info_len* bytes of *info* and updates *info_len* with the

 * actual number of bytes written to *info*.

 *

 * @param link_fd BPF link file descriptor

 * @param info pointer to **struct bpf_link_info** that will be populated with

 * BPF link information

 * @param info_len pointer to the size of *info*; on success updated with the

 * number of bytes written to *info*

 * @return 0, on success; negative error code, otherwise (errno is also set to

 * the error code)

 */

LIBBPF_API int bpf_link_get_info_by_fd(int link_fd, struct bpf_link_info *info, __u32 *info_len);

struct bpf_prog_query_opts {