gistfile1.c

asmlinkage long receive(pid_t* sender, void* mesg, int* len, bool block)
{
    mailbox* my_mail;
    message* msg;

    my_mail = map_get(current->pid);

    if (!my_mail)
    {
        my_mail = make_mailbox(current -> pid);
        map_put(my_mail);
    }
    
    do
    {
        wait_event(my_mail -> access, atomic_read(my_mail -> r_w) == 0);
        atomic_inc(my_mail -> r_w);

        msg = my_mail -> contents;
        
        if (msg)
        {
            if (copy_to_user(sender, &(msg->sender), sizeof(pid_t)))
            {
                printk(KERN_INFO "EFUALT @recieve_mail_1 EF_id: %i, proc: %i", EFAULT, current->pid);
                atomic_dec(my_mail -> r_w);
                wake_up(my_mail -> access);
                return MAILBOX_ERROR;
            }

            if (copy_to_user(mesg, msg->data, msg->real_len))
            {
                printk(KERN_INFO "EFUALT @recieve_mail_2 EF_id: %i, proc: %i", EFAULT, current->pid);
                atomic_dec(my_mail -> r_w);
                wake_up(my_mail -> access);
                return MAILBOX_ERROR;
            }

            if (copy_to_user(len, &(msg->real_len), sizeof(int)))
            {
                printk(KERN_INFO "EFUALT @recieve_mail_3 EF_id: %i, proc: %i", EFAULT, current->pid);
                atomic_dec(my_mail -> r_w);
                wake_up(my_mail -> access);
                return MAILBOX_ERROR;
            }

            my_mail -> contents = my_mail -> contents -> next;
            mem_cache_free(messages, msg);
            atomic_dec(my_mail -> r_w);
            wake_up(my_mail -> access);
            return 0;
        }
    }
    while(block);
    

    return MAILBOX_EMPTY;
}