Memory Access Problem

I have a problem in kernel 2.4.4

I use readw to access memory below 1MB , report "Segmentation fault"
and stall in memory

simple code below (this will get paraller port)
==
int init_module(void){
	unsigned int   *BIOS_Data=(unsigned int *)0x400;
	u32 test;
                test = readw(BIOS_Data);

	 printk(KERN_CRIT  "0x400:%x\n",test);
}
==
but those can work in kernel 2.2.19 , no problem .

can anyone help me ?
--
Richliu