Linux内核和用户空间通信的方式— proc文件和mmap共享内存

/*This program is used to allocate memory in kernel

and pass the physical address to userspace through proc file.*/

#include
<linux/version.h>

#include
<linux/module.h>

#include
<linux/proc_fs.h>

#include
<linux/mm.h>

#define PROC_MEMSHARE_DIR"memshare"

#define PROC_MEMSHARE_PHYADDR"phymem_addr"

#define PROC_MEMSHARE_SIZE"phymem_size"

/*alloc one page. 4096 bytes*/

#define PAGE_ORDER 0

/*this value can get from PAGE_ORDER*/

#define PAGES_NUMBER 1

struct proc_dir_entry
*proc_memshare_dir ;

unsigned long kernel_memaddr= 0;

unsigned long kernel_memsize= 0;

static int proc_read_phymem_addr(char*page,
char **start, off_t off,int
count)

{

return sprintf(page,"%08lx\n", __pa(kernel_memaddr));

}

static int proc_read_phymem_size(char*page,
char **start, off_t off,int
count)

{

return sprintf(page,"%lu\n", kernel_memsize);

}

static int __init init(void)

{

/*build proc dir "memshare"and two proc files: phymem_addr, phymem_size in the dir*/

proc_memshare_dir = proc_mkdir(PROC_MEMSHARE_DIR,NULL);

create_proc_info_entry(PROC_MEMSHARE_PHYADDR, 0, proc_memshare_dir, proc_read_phymem_addr);

create_proc_info_entry(PROC_MEMSHARE_SIZE, 0, proc_memshare_dir, proc_read_phymem_size);

/*alloc one page*/

kernel_memaddr =__get_free_pages(GFP_KERNEL, PAGE_ORDER);

if(!kernel_memaddr)

{

printk("Allocate memory failure!\n");

}

else

{

SetPageReserved(virt_to_page(kernel_memaddr));

内核中申请到页面之后，要调用一下SetPageReserved，相当于告诉系统，这个页面我已经占了。对于每一个申请到的页面，应该都要这样做

kernel_memsize = PAGES_NUMBER
* PAGE_SIZE;

printk("Allocate memory success!. The phy mem addr=%08lx, size=%lu\n", __pa(kernel_memaddr),
kernel_memsize);

}

return 0;

}

static void __exit fini(void)

{

printk("The content written by user is: %s\n",(unsigned
char *) kernel_memaddr);

ClearPageReserved(virt_to_page(kernel_memaddr));

free_pages(kernel_memaddr, PAGE_ORDER);

remove_proc_entry(PROC_MEMSHARE_PHYADDR, proc_memshare_dir);

remove_proc_entry(PROC_MEMSHARE_SIZE, proc_memshare_dir);

remove_proc_entry(PROC_MEMSHARE_DIR,NULL);

return;

}

module_init(init);

module_exit(fini);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Godbach ([email]nylzhaowei@163.com[/email])");

MODULE_DESCRIPTION("Kernel memory share module.");

#include<stdio.h>

#include
<stdlib.h>

#include
<unistd.h>

#include
<string.h>

#include
<fcntl.h>

#include
<sys/stat.h>

#include
<sys/types.h>

#include
<sys/mman.h>

int main(int argc,char* argv[])

{

if(argc!= 2)

{

printf("Usage: %s string\n", argv[0]);

return 0;

}

unsigned long phymem_addr, phymem_size;

char *map_addr;

char s[256];

int fd;

/*get the physical address of allocated memory in kernel*/

fd = open("/proc/memshare/phymem_addr", O_RDONLY);

if(fd
< 0)

{

printf("cannot open file /proc/memshare/phymem_addr\n");

return 0;

}

read(fd, s,sizeof(s));

sscanf(s,"%lx",
&phymem_addr);

close(fd);

/*get the size of allocated memory in kernel*/

fd = open("/proc/memshare/phymem_size", O_RDONLY);

if(fd
< 0)

{

printf("cannot open file /proc/memshare/phymem_size\n");

return 0;

}

read(fd, s,sizeof(s));

sscanf(s,"%lu",
&phymem_size);

close(fd);

printf("phymem_addr=%lx, phymem_size=%lu\n", phymem_addr, phymem_size);

/*memory map*/

int map_fd =open("/dev/mem", O_RDWR);

if(map_fd< 0)

{

printf("cannot open file /dev/mem\n");

return 0;

}

map_addr = mmap(0, phymem_size, PROT_READ|PROT_WRITE,
MAP_SHARED, map_fd, phymem_addr);

strcpy(map_addr, argv[1]);

munmap(map_addr, phymem_size);

close(map_fd);

return 0;

}