[RFC,v3,05/15] libbpf: Introduce bpf_btf_get_fd_by_id_opts()

Commit Message

Roberto Sassu July 22, 2022, 5:18 p.m. UTC

Introduce bpf_btf_get_fd_by_id_opts(), to let the caller specify the needed
permissions for the operation. Keep the existing bpf_btf_get_fd_by_id()
function, to request read-write permissions.

Currently, setting permissions in the data structure has no effect, as the
kernel does not evaluate them. The new variant has been introduced anyway
for symmetry with bpf_map_get_fd_by_id_opts(). Evaluating permissions could
be done in future kernel versions.

Signed-off-by: Roberto Sassu <[e-mail]>
---
 tools/lib/bpf/bpf.c      | 13 ++++++++++++-
 tools/lib/bpf/bpf.h      |  2 ++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 15 insertions(+), 1 deletion(-)

Patch

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 4b574ad046f3..b131bbc8509e 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -979,18 +979,29 @@  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_opts *opts)
 {
 	union bpf_attr attr;
 	int fd;
 
+	if (!OPTS_VALID(opts, bpf_get_fd_opts))
+		return libbpf_err(-EINVAL);
+
 	memset(&attr, 0, sizeof(attr));
 	attr.btf_id = id;
+	if (kernel_supports(NULL, FEAT_GET_FD_BY_ID_OPEN_FLAGS))
+		attr.open_flags = OPTS_GET(opts, flags, 0);
 
 	fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, sizeof(attr));
 	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)
 {
 	union bpf_attr attr;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index d4b84d3f7e16..45d3739d901f 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -369,6 +369,8 @@  LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id,
 					 const struct bpf_get_fd_opts *opts);
 LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id,
+					 const struct bpf_get_fd_opts *opts);
 LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
 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 83dc18b5e5cf..ee6755dbf004 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -366,4 +366,5 @@  LIBBPF_1.0.0 {
 		perf_buffer__buffer;
 		bpf_prog_get_fd_by_id_opts;
 		bpf_map_get_fd_by_id_opts;
+		bpf_btf_get_fd_by_id_opts;
 };