抱着试一试的心态给偶像写了一封求助e-mail，回复了！！！我的小心脏啊~
呵呵~Rubini是谁不解释了...
我的HELP原文主要的关于setconsole.c的问题，这个是LDD3的一个小程序
/*
* setconsole.c -- choose a console to receive kernel messages
*
* Copyright (C) 1998,2000,2001 Alessandro Rubini
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
int main(int argc, char **argv)
{
char bytes[2] = {11,0}; /* 11 is the TIOCLINUX cmd number */
if (argc==2) bytes[1] = atoi(argv[1]); /* the chosen console */
else {
fprintf(stderr, "%s: need a single arg\n",argv[0]); exit(1);
}
if (ioctl(STDIN_FILENO, TIOCLINUX, bytes)<0) { /* use stdin */
fprintf(stderr,"%s: ioctl(stdin, TIOCLINUX): %s\n",
argv[0], strerror(errno));
exit(1);
}
exit(0);
}下面是Rubini 对我的回复：
首先指出了我的误区
1. ioctl(TIOCLINUX) 影响的并不是printf，而是printk！
2.tty 或者 terminal 不是console! 通过ctrl + alt + F* (1~6 )达到的都是控制台，F7是图形环境，不是console！
Allan Cruse 在2007年对setconsole做了一点改进
//----------------------------------------------------------------
// setconsole.cpp
//
// This utility allows a user possessing root privilege
// to redirect 'printk' output to a designated console.
//
// compile using:
// root# gcc -o setconsole setconsole.cpp
// root# chmod a+s setconsole
//
// execute using:
// user$ setconsole 4
//
// Code used here is from an example by Alesandro Rubini,
// "Linux Device Drivers (2nd Edition)," pages 99-100.
//
// programmer: ALLAN CRUSE
// written on: 24 NOV 2002
// revised on: 24 JUN 2007 -- to use "/dev/console" device
//----------------------------------------------------------------
#include <fcntl.h> // for open() <--- added
#include <stdio.h> // for fprintf()
#include <errno.h> // for errno
#include <stdlib.h> // for exit()
#include <unistd.h> // for STDIN_FILENO
#include <string.h> // for strerror()
#include <sys/ioctl.h> // for ioctl()
#include <asm/ioctls.h> // for TIOCLINUX
int main( int argc, char **argv )
{
char bytes[ 2 ] = { 11, 0 }; // 11 is the TIOCLINUX command-number
if ( argc == 2 ) bytes[1] = atoi( argv[1] ); // console id-number
else {
fprintf( stderr, "%s: need a single argument\n", argv[0] );
exit(1);
}
int fd = open( "/dev/console", O_RDWR ); // <--- added
if ( fd < 0 ) { perror( "/dev/console" ); exit(1); } // <--- added
if ( ioctl( fd, TIOCLINUX, bytes ) < 0 ) // <--- changed
{
fprintf( stderr, "%s: ioctl( fd, TIOCLINUX ): %s\n", // <---
argv[0], strerror( errno ) );
exit(1);
}
exit(0);
}是可以在console之间重定向IO的！！
这幅图看到的是tty4，我把控制台的IO重定向到了console 3,也就是/dev/tty3
切换到tty2，我们插入hello.ko 模块，调用printk，打印hello world
我故意执行了tty这个shell程序，提示读者当前我们在tty2,进行insmod操作
明明是有hello world的为什么不打印呢？去哪儿了？console 3!
我们ctrl + alt + F3 切换到console 3看看
终于搞定了！利用ioctl实现了对于不同console之间的IO重定向！
最后谢谢偶像~ Alesssandro Rubini & Allan Cruse
关于<LDD3> "setconsole.c" Alesssandro Rubini 的邮件回复
原文地址：http://blog.csdn.net/cinmyheart/article/details/38960967
