用户态和内核共享内存：最简单的例子

#include

#include

#include

#include

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Wheelz");

MODULE_DESCRIPTION("mmap demo");

static unsigned long p = 0;

static int __init init(void)

{

//分配共享内存（一个页面）

p = __get_free_pages(GFP_KERNEL, 0);

SetPageReserved(virt_to_page(p));

printk("<1> p = 0x%08x\n", p);

//在共享内存中写上一个字符串

strcpy(p, "Hello world!\n");

return 0;

}

static void __exit fini(void)

{

ClearPageReserved(virt_to_page(p));

free_pages(p, 0);

}

module_init(init);

module_exit(fini);

用户态程序---------------------------------

#include

#include

#include

#include

#include

#define PAGE_SIZE (4*1024)

#define PAGE_OFFSET 0xc0000000

#define KERNEL_VIRT_ADDR 0xc5e3c000

int main()

{

char *buf;

int fd;

unsigned long phy_addr;

fd=open("/dev/mem",O_RDWR);

if(fd == -1)

perror("open");

phy_addr=KERNEL_VIRT_ADDR - PAGE_OFFSET;

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

if(buf == MAP_FAILED)

perror("mmap");

puts(buf);//打印共享内存的内容

munmap(buf,PAGE_SIZE);

close(fd);

return 0;

}