move around examples

tests/c-form/struct_field_tests.bpf.c

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+SEC("tp/syscalls/sys_enter_execve")
+int handle_setuid_entry(struct trace_event_raw_sys_enter *ctx) {
+  bpf_printk("args: %u", (unsigned int)ctx->args[0]);
+  return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";

tests/c-form/xdp_modify.bpf.c

@@ -0,0 +1,21 @@
+// xdp_rewrite.c
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/if_ether.h>
+
+SEC("xdp")
+int xdp_rewrite_mac(struct xdp_md *ctx)
+{
+    void *data_end = (void *)(long)ctx->data_end;
+    void *data     = (void *)(long)ctx->data;
+
+    struct ethhdr *eth = data;
+    if ((void*)(eth + 1) > data_end)
+        return XDP_PASS;
+    __u8 new_src[ETH_ALEN] = {0x02,0x00,0x00,0x00,0x00,0x02};
+    for (int i = 0; i < ETH_ALEN; i++) eth->h_source[i] = new_src[i];
+
+    return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";