title: Read eBPF tracepoint argument
body: <p>Assume that I have a tracepoint eBPF probe that hooks into the chown function.</p>
  <pre><code>SEC(&quot;tracepoint/syscalls/sys_enter_chown&quot;)
  int bpf_prog(void *ctx) {
    // someone changed ownership of a file
    char msg[] = &quot;Ownership change of file!&quot;;
    bpf_trace_printk(msg, sizeof(msg));
  }
  </code></pre>
  <p>How can I access the context of the call? For example, what if I want to print out the file that changed ownership or the new owner?</p>