user.c

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

#define PAGE_SIZE (4 * 1024)

#define KERNEL_PHY_ADDR 0x77128000
int main()
{
	char *buf;
	int fd;

	fd = open(“/dev/mem”,O_RDWR);
	if (fd == -1)
		perror(“open”);

	buf = mmap(0, PAGE_SIZE,
		   PROT_READ|PROT_WRITE, MAP_SHARED,
		   fd, KERNEL_PHY_ADDR);

	if (buf == MAP_FAILED)
		perror(“mmap”);

	puts(buf);

	munmap(buf,PAGE_SIZE);

	close(fd);
	return 0;
}