BUFSZ
buf = kmalloc(BUFSZ, GFP_KERNEL);
stack_depot_snprint(node->stack, buf, BUFSZ, 0);
unsigned char tmp[BUFSZ];
unsigned char buf1[BUFSZ] = {0};
unsigned char buf2[BUFSZ] = {0};
if (len > BUFSZ)
len = BUFSZ;