libbpf: Add opts-based bpf_obj_pin() API and add support for path_fd

Add path_fd support for bpf_obj_pin() and bpf_obj_get() operations
(through their opts-based variants). This allows to take advantage of
new kernel-side support for O_PATH-based pin/get location specification.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230523170013.728457-4-andrii@kernel.org
Signed-off-by: Daniel Müller <deso@posteo.net>

src/bpf.c

@@ -572,20 +572,30 @@ int bpf_map_update_batch(int fd, const void *keys, const void *values, __u32 *co
 				    (void *)keys, (void *)values, count, opts);
 }
 
-int bpf_obj_pin(int fd, const char *pathname)
+int bpf_obj_pin_opts(int fd, const char *pathname, const struct bpf_obj_pin_opts *opts)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, file_flags);
+	const size_t attr_sz = offsetofend(union bpf_attr, path_fd);
 	union bpf_attr attr;
 	int ret;
 
+	if (!OPTS_VALID(opts, bpf_obj_pin_opts))
+		return libbpf_err(-EINVAL);
+
 	memset(&attr, 0, attr_sz);
+	attr.path_fd = OPTS_GET(opts, path_fd, 0);
 	attr.pathname = ptr_to_u64((void *)pathname);
+	attr.file_flags = OPTS_GET(opts, file_flags, 0);
 	attr.bpf_fd = fd;
 
 	ret = sys_bpf(BPF_OBJ_PIN, &attr, attr_sz);
 	return libbpf_err_errno(ret);
 }
 
+int bpf_obj_pin(int fd, const char *pathname)
+{
+	return bpf_obj_pin_opts(fd, pathname, NULL);
+}
+
 int bpf_obj_get(const char *pathname)
 {
 	return bpf_obj_get_opts(pathname, NULL);
@@ -593,7 +603,7 @@ int bpf_obj_get(const char *pathname)
 
 int bpf_obj_get_opts(const char *pathname, const struct bpf_obj_get_opts *opts)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, file_flags);
+	const size_t attr_sz = offsetofend(union bpf_attr, path_fd);
 	union bpf_attr attr;
 	int fd;
 
@@ -601,6 +611,7 @@ int bpf_obj_get_opts(const char *pathname, const struct bpf_obj_get_opts *opts)
 		return libbpf_err(-EINVAL);
 
 	memset(&attr, 0, attr_sz);
+	attr.path_fd = OPTS_GET(opts, path_fd, 0);
 	attr.pathname = ptr_to_u64((void *)pathname);
 	attr.file_flags = OPTS_GET(opts, file_flags, 0);
 

src/bpf.h

@@ -284,16 +284,30 @@ LIBBPF_API int bpf_map_update_batch(int fd, const void *keys, const void *values
 				    __u32 *count,
 				    const struct bpf_map_batch_opts *opts);
 
+struct bpf_obj_pin_opts {
+	size_t sz; /* size of this struct for forward/backward compatibility */
+
+	__u32 file_flags;
+	int path_fd;
+
+	size_t :0;
+};
+#define bpf_obj_pin_opts__last_field path_fd
+
+LIBBPF_API int bpf_obj_pin(int fd, const char *pathname);
+LIBBPF_API int bpf_obj_pin_opts(int fd, const char *pathname,
+				const struct bpf_obj_pin_opts *opts);
+
 struct bpf_obj_get_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
 
 	__u32 file_flags;
+	int path_fd;
 
 	size_t :0;
 };
-#define bpf_obj_get_opts__last_field file_flags
+#define bpf_obj_get_opts__last_field path_fd
 
-LIBBPF_API int bpf_obj_pin(int fd, const char *pathname);
 LIBBPF_API int bpf_obj_get(const char *pathname);
 LIBBPF_API int bpf_obj_get_opts(const char *pathname,
 				const struct bpf_obj_get_opts *opts);

src/libbpf.map

@@ -393,4 +393,6 @@ LIBBPF_1.2.0 {
 } LIBBPF_1.1.0;
 
 LIBBPF_1.3.0 {
+	global:
+		bpf_obj_pin_opts;
 } LIBBPF_1.2.0;