bpf: libbpf: retry loading program on EAGAIN

Commit c3494801cd17 ("bpf: check pending signals while
verifying programs") makes it possible for the BPF_PROG_LOAD
to fail with EAGAIN. Retry unconditionally in this case.

Fixes: c3494801cd17 ("bpf: check pending signals while verifying programs")
Signed-off-by: Lorenz Bauer <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

tools/lib/bpf/bpf.c

···
 	return syscall(__NR_bpf, cmd, attr, size);
 }
 
+static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size)
+{
+	int fd;
+
+	do {
+		fd = sys_bpf(BPF_PROG_LOAD, attr, size);
+	} while (fd < 0 && errno == EAGAIN);
+
+	return fd;
+}
+
 int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 {
 	__u32 name_len = create_attr->name ? strlen(create_attr->name) : 0;
···
 	memcpy(attr.prog_name, load_attr->name,
 	       min(name_len, BPF_OBJ_NAME_LEN - 1));
 
-	fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+	fd = sys_bpf_prog_load(&attr, sizeof(attr));
 	if (fd >= 0)
 		return fd;
 
···
 			break;
 		}
 
-		fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+		fd = sys_bpf_prog_load(&attr, sizeof(attr));
 
 		if (fd >= 0)
 			goto done;
···
 	attr.log_size = log_buf_sz;
 	attr.log_level = 1;
 	log_buf[0] = 0;
-	fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+	fd = sys_bpf_prog_load(&attr, sizeof(attr));
 done:
 	free(finfo);
 	free(linfo);
···
 	attr.kern_version = kern_version;
 	attr.prog_flags = prog_flags;
 
-	return sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+	return sys_bpf_prog_load(&attr, sizeof(attr));
 }
 
 int bpf_map_update_elem(int fd, const void *key, const void *value,