linux_dev_学习笔记_内存映射中mmap()的参数传递

2012年3月25日  Sunday

 

1、内核版本号2.6.33.20

 

2、内存映射中mmap()的参数传递

 

3、驱动模块源文件proc_dev.c

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/fcntl.h>

#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#include <asm/page.h>
#include <linux/mm.h>

#define MMAPCALL_DEV_NAME "mmapcall"
#define MMAPCALL_DEV_MAJOR 240

int mmapcall_open(struct inode *inode,struct file *filp)
{
    return 0;
}

int mmapcall_release(struct inode *inode,struct file *filp)
{
    return 0;
}

int mmapcall_mmap(struct file *filp,struct vm_area_struct *vma)
{
    printk("vm_pgoff [%08X]\n",vma->vm_pgoff<<PAGE_SHIFT);
    printk("vm_start [%08X]\n",vma->vm_start);
    printk("vm_end [%08X]\n",vma->vm_end);
    printk("vm_flags [%08X]\n",vma->vm_flags);

    return -EAGAIN;
}

struct file_operations mmapcall_fops={
    .owner=THIS_MODULE,
    .open=mmapcall_open,
    .release=mmapcall_release,
    .mmap=mmapcall_mmap,
};

int mmapcall_init(void)
{
    int result;

    result=register_chrdev(MMAPCALL_DEV_MAJOR,MMAPCALL_DEV_NAME,&mmapcall_fops);

    if(result<0){
        return result;
    }
    return 0;
}

void mmapcall_exit(void)
{
    unregister_chrdev(MMAPCALL_DEV_MAJOR,MMAPCALL_DEV_NAME);
}

module_init(mmapcall_init);
module_exit(mmapcall_exit);

MODULE_LICENSE("Dual BSD/GPL");

4、Makefile

obj-m += mmapcall_dev.o

CURRENT_PATH := $(shell pwd)

LINUX_KERNEL := $(shell uname -r)

LINUX_KERNEL_PATH := /usr/src/linux-$(LINUX_KERNEL)

all:
    make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules
clean:
    #make -C $(LINUX_KERNEL_PAHT) M=$(CURRENT_PATH) clean
    rm *.mod.*
    rm *.order
    rm *.o
    rm *.symvers

5、应用程序源文件call_dev.c

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

#define DEVICE_FILENAME "/dev/mmapcall"

#define MMAP_SIZE 0x1000

int main()
{
    int dev;
    int loop;
    char *ptrdata;

    dev=open(DEVICE_FILENAME,O_RDWR|O_NDELAY);

    if(dev>=0){
        ptrdata=(char*)mmap(0x12345000,
                MMAP_SIZE,
                PROT_READ|PROT_WRITE,
                MAP_SHARED,
                dev,
                0x87654000);
        munmap(ptrdata,MMAP_SIZE);

        close(dev);
    }
    return 0;

}

6、实施方法及运行结果

~/mmap_params# mknod /dev/mmapcall c 240 0
~/mmap_params# ls -la /dev/mmapcall | grep mmapcall
crw-r--r-- 1 root root 240, 0 2012-03-25 12:38 /dev/mmapcall
~/mmap_params# make
~/mmap_params# gcc mmapcall_app.c -o mmapcall_app
~/mmap_params# insmod mmapcall_dev.ko
~/mmap_params# ./mmapcall_app
~/mmap_params# dmesg
[ 8354.352485] vm_pgoff [87654000]
[ 8354.352497] vm_start [12345000]
[ 8354.352500] vm_end [12346000]
[ 8354.352502] vm_flags [000000FB]

7、移除模块及设备文件

~/mmap_params# rm /dev/mmapcall
~/mmap_params# rmmod mmapcall_dev