trace_alloc_entry
entry = trace_alloc_entry(call, &entry_size);
e = trace_alloc_entry(tb, sizeof(value));
e = trace_alloc_entry(tb, len + 1);
e = trace_alloc_entry(tb, 0);
e = trace_alloc_entry(tb, 0);
e = trace_alloc_entry(tb, sizeof(reg) + sizeof(value));