int consoleread (struct inode *ip, char *dst, int n)
{
    uint target;
    int c;

    iunlock(ip);

    target = n;
    acquire(&input.lock);

    while (n > 0) {
        while (input.r == input.w) {
            if (proc->killed) {
                release(&input.lock);
                ilock(ip);
                return -1;
            }

            sleep(&input.r, &input.lock);
        }

        c = input.buf[input.r++ % INPUT_BUF];

        if (c == C('D')) {  // EOF
            if (n < target) {
                // Save ^D for next time, to make sure
                // caller gets a 0-byte result.
                input.r--;
            }

            break;
        }

        *dst++ = c;
        --n;

        if (c == '\n') {
            break;
        }
    }

    release(&input.lock);
    ilock(ip);

    return target - n;
}