Linux 内存映射函数 mmap（）函数详解

驱动程序：

#include <linux/miscdevice.h>  
 #include <linux/delay.h>  
 #include <linux/kernel.h>  
 #include <linux/module.h>  
 #include <linux/init.h>  
 #include <linux/mm.h>  
 #include <linux/fs.h>  
 #include <linux/types.h>  
 #include <linux/delay.h>  
 #include <linux/moduleparam.h>  
 #include <linux/slab.h>  
 #include <linux/errno.h>  
 #include <linux/ioctl.h>  
 #include <linux/cdev.h>  
 #include <linux/string.h>  
 #include <linux/list.h>  
 #include <linux/pci.h>  
 #include <linux/gpio.h>  
       
       
 #define DEVICE_NAME "mymap"  
       
       
 static unsigned char array[10]={0,1,2,3,4,5,6,7,8,9};  
 static unsigned char *buffer;  
       
       
 static int my_open(struct inode *inode, struct file *file)  
 {  
     return 0;  
 }  
       
       
 static int my_map(struct file *filp, struct vm_area_struct *vma)  
 {      
     unsigned long page;  
     unsigned char i;  
     unsigned long start = (unsigned long)vma->vm_start;  
     //unsigned long end =  (unsigned long)vma->vm_end;  
     unsigned long size = (unsigned long)(vma->vm_end - vma->vm_start);  
       
     //得到物理地址  
     page = virt_to_phys(buffer);      
     //将用户空间的一个vma虚拟内存区映射到以page开始的一段连续物理页面上  
     if(remap_pfn_range(vma,start,page>>PAGE_SHIFT,size,PAGE_SHARED))//第三个参数是页帧号，由物理地址右移PAGE_SHIFT得到  
         return -1;  
       
     //往该内存写10字节数据  
     for(i=0;i<10;i++)  
         buffer[i] = array[i];  
           
     return 0;  
 }  
       
       
 static struct file_operations dev_fops = {  
     .owner    = THIS_MODULE,  
     .open    = my_open,  
     .mmap   = my_map,  
 };  
       
 static struct miscdevice misc = {  
     .minor = MISC_DYNAMIC_MINOR,  
     .name = DEVICE_NAME,  
     .fops = &dev_fops,  
 };  
       
       
 static int __init dev_init(void)  
 {  
     int ret;      
       
     //注册混杂设备  
     ret = misc_register(&misc);  
     //内存分配  
     buffer = (unsigned char *)kmalloc(PAGE_SIZE,GFP_KERNEL);  
     //将该段内存设置为保留  
     SetPageReserved(virt_to_page(buffer));  
       
     return ret;  
 }  
       
       
 static void __exit dev_exit(void)  
 {  
     //注销设备  
     misc_deregister(&misc);  
     //清除保留  
     ClearPageReserved(virt_to_page(buffer));  
     //释放内存  
     kfree(buffer);  
 }  
       
       
 module_init(dev_init);  
 module_exit(dev_exit);  
 MODULE_LICENSE("GPL");  
 MODULE_AUTHOR("LKN@SCUT");

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