KDB_CMD_HISTORY_COUNT
cmdptr = (cmdptr + KDB_CMD_HISTORY_COUNT - 1) %
KDB_CMD_HISTORY_COUNT;
cmdptr = (cmdptr+1) % KDB_CMD_HISTORY_COUNT;
cmd_head = (cmd_head+1) % KDB_CMD_HISTORY_COUNT;
cmd_tail = (cmd_tail+1) % KDB_CMD_HISTORY_COUNT;
static char cmd_hist[KDB_CMD_HISTORY_COUNT][CMD_BUFLEN];