1 files changed, 54 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c b/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c
new file mode 100644
index 000000000000..2ff1b596e87e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+#define ERRMSG_LEN 64
+
+struct xdp_errmsg {
+	char msg[ERRMSG_LEN];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__type(key, int);
+	__type(value, int);
+} xdp_errmsg_pb SEC(".maps");
+
+struct xdp_attach_error_ctx {
+	unsigned long unused;
+
+	/*
+	 * bpf does not support tracepoint __data_loc directly.
+	 *
+	 * Actually, this field is a 32 bit integer whose value encodes
+	 * information on where to find the actual data. The first 2 bytes is
+	 * the size of the data. The last 2 bytes is the offset from the start
+	 * of the tracepoint struct where the data begins.
+	 * -- https://github.com/iovisor/bpftrace/pull/1542
+	 */
+	__u32 msg; // __data_loc char[] msg;
+};
+
+/*
+ * Catch the error message at the tracepoint.
+ */
+
+SEC("tp/xdp/bpf_xdp_link_attach_failed")
+int tp__xdp__bpf_xdp_link_attach_failed(struct xdp_attach_error_ctx *ctx)
+{
+	char *msg = (void *)(__u64) ((void *) ctx + (__u16) ctx->msg);
+	struct xdp_errmsg errmsg = {};
+
+	bpf_probe_read_kernel_str(&errmsg.msg, ERRMSG_LEN, msg);
+	bpf_perf_event_output(ctx, &xdp_errmsg_pb, BPF_F_CURRENT_CPU, &errmsg,
+			      ERRMSG_LEN);
+	return 0;
+}
+
+/*
+ * Reuse the XDP program in xdp_dummy.c.
+ */
+
+char LICENSE[] SEC("license") = "GPL";