libbpf: Introduce bpf_btf_get_fd_by_id_opts()

Introduce bpf_btf_get_fd_by_id_opts(), for symmetry with
bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced
data structure bpf_get_fd_by_id_opts. Keep the existing
bpf_btf_get_fd_by_id(), and call bpf_btf_get_fd_by_id_opts() with NULL as
opts argument, to prevent setting open_flags.

Currently, the kernel does not support non-zero open_flags for
bpf_btf_get_fd_by_id_opts(), and a call with them will result in an error
returned by the bpf() system call. The caller should always pass zero
open_flags.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221006110736.84253-5-roberto.sassu@huaweicloud.com

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 03be8c9..b95fed0 100644 (file)
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -981,19 +981,29 @@ int bpf_map_get_fd_by_id(__u32 id)
        return bpf_map_get_fd_by_id_opts(id, NULL);
 }
 
-int bpf_btf_get_fd_by_id(__u32 id)
+int bpf_btf_get_fd_by_id_opts(__u32 id,
+                             const struct bpf_get_fd_by_id_opts *opts)
 {
        const size_t attr_sz = offsetofend(union bpf_attr, open_flags);
        union bpf_attr attr;
        int fd;
 
+       if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts))
+               return libbpf_err(-EINVAL);
+
        memset(&attr, 0, attr_sz);
        attr.btf_id = id;
+       attr.open_flags = OPTS_GET(opts, open_flags, 0);
 
        fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz);
        return libbpf_err_errno(fd);
 }
 
+int bpf_btf_get_fd_by_id(__u32 id)
+{
+       return bpf_btf_get_fd_by_id_opts(id, NULL);
+}
+
 int bpf_link_get_fd_by_id(__u32 id)
 {
        const size_t attr_sz = offsetofend(union bpf_attr, open_flags);

diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 4558baf..4b48730 100644 (file)
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -380,6 +380,8 @@ LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id,
                                const struct bpf_get_fd_by_id_opts *opts);
 LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id,
+                               const struct bpf_get_fd_by_id_opts *opts);
 LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);
 

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index c3604ea..7011d5e 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -371,6 +371,7 @@ LIBBPF_1.0.0 {
 
 LIBBPF_1.1.0 {
        global:
+               bpf_btf_get_fd_by_id_opts;
                bpf_map_get_fd_by_id_opts;
                bpf_prog_get_fd_by_id_opts;
                user_ring_buffer__discard;