BPF_PROG_CHUNK_SHIFT
ptr = (void *)(pack->ptr) + (pos << BPF_PROG_CHUNK_SHIFT);
pos = ((unsigned long)ptr - (unsigned long)pack->ptr) >> BPF_PROG_CHUNK_SHIFT;
#define BPF_PROG_CHUNK_SIZE (1 << BPF_PROG_CHUNK_SHIFT)