C Instrumentation Framework

There are some marco definitions intended for some specific list or queue traverses. For instance,

#define skb_queue_walk_safe(queue, skb, tmp)                                    \
                for (skb = (queue)->next, tmp = skb->next;                      \
                     skb != (struct sk_buff *)(queue);                          \
                     skb = tmp, tmp = skb->next)

It's desirable sometimes to have some instructions executed at each iteration of such loops. Here, for example, this macro enables us to detect assignments to skb varaible which is useful in checking for double skb deallocations.

skb_queue_walk_safe(tx_skb_queue, skb, tmp) {
        if (...) {
                ...
                kfree_skb(skb);
        }
}