skbmem systemtap example

gistfile1.txt

function string_ops:string (val) %{
  strlcpy (STAP_RETVALUE, (char*)STAP_ARG_val, MAXSTRINGLEN);
%}

probe kernel.function("__dev_queue_xmit") {
    if (execname() =~ "keepalived")  {
        printf("__dev_queue_xmit %d %s(%d/%d) %s\n", gettimeofday_us(), execname(), pid(), cpu(), $$vars);
        i = 0;
        printf("dump begin, skb->gso %d\n", @cast($skb->head+$skb->end, "skb_shared_info", "")->gso_size);
        for (; i< 14; i++) {
            printf("%02x:", $skb->data[i]);
        }
        // give a backtrace to see which path the function called...
        print(sprint_backtrace());
        print("dump end\n");
    }
}