如何从内核模块写入TTY？

首先发布到SO,所以我会尝试将问题做对.

我正在制作一个简单的Linux内核模块,目的是将数据回送到加载内核模块的TTY shell.我遇到的问题是内核"Ooops" - 带有以下消息(用"watch'dmesg | tail -50'"抓住).内核模块的名称是Seraphim:

[  184.222748] SELinux: initialized (dev proc, type proc), uses genfs_contexts
[ 1877.456607] seraphim: module verification failed: signature and/or required key  missing - tainting kernel
[ 1877.457321] ------------------
[ 1877.457324] Seraphim started.
[ 1877.457348] BUG: unable to handle kernel NULL pointer dereference at 0000000000000218
[ 1877.457411] IP: [] seraphim_entry+0x30/0x1000 [seraphim]
[ 1877.457462] PGD 115a2e067 PUD 10aca8067 PMD 0
[ 1877.457498] Oops: 0000 [#1] SMP
[ 1877.457524] Modules linked in: seraphim(OF+) rfcomm bnep nf_conntrack_netbios_ns   nf_conn track_broadcast ipt_MASQUERADE ip6t_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llce btable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_ma etc.

用于将数据写入TTY终端的代码如下:

#include 
#include 
#include 
#include 

static void printString(char *string) {

    struct tty_struct *tty;

    tty = current->signal->tty;

    if(tty != NULL) { 

        (tty->driver->ops->write) (tty, string, strlen(string));
    }

    else
        printk("tty equals to zero");
}

我究竟做错了什么？

我正在关注http://www.tldp.org/LDP/lkmpg/2.6/lkmpg.pdf上的教程,但它已经过时了(我在Fedora 19上使用的内核是3.11.10-200),所以我不得不翻找3.11.10-200源文件,找到足够的结构.