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这是我的第一个内核，在下面的示例程序中，我创建了一个简单的 proc/文件系统。每当我对内核进行分类时，我都会看到 READ 被调用 3 次。想知道它为什么这样做。

出来，代码如下。

cat /proc/myKernel
dmesg | grep -i myKernel
myKernel: Read (/proc/myKernel) called
myKernel: Read (/proc/myKernel) called
myKernel: Read (/proc/myKernel) called

int myKernel_read( char *buffer, char **bufferLocation, off_t offset, int bufferLength, int *eof, void *data )
{
    int ret = 0;
    u64 msrvalue;

    printk(KERN_INFO "myKernel: Read (/proc/%s) called\n", procFile_name);
    ret = sprintf(buffer, "Hello World\n");

    return ret;
}

static int __init myKernel_init(void)
{
    entry = create_proc_entry(procFile_name, 0644, NULL);
    if(!entry)
        printk(KERN_INFO "myKernel: error registering proc control file\n");
    else 
    {
        entry->read_proc = myKernel_read;
    }

    return 0;
}
4

1 回答 1

2

问题在于 ret 值。我仍然不知道为什么这被称为三次，但是当偏移量小于零时我必须进行实际读取。

int myKernel_read( char *buffer, char **bufferLocation, off_t offset, int bufferLength, int *eof, void *data )
{
    int ret;
    u64 msrvalue;

    if (offset > 0) 
    {
        /* we have finished to read, return 0 */
        ret  = 0;
    } else 
    {
        /* fill the buffer, return the buffer size */
                // DO THE READ HERE. NOT OUTSIDE
                //
                printk(KERN_INFO "myKernel: Read (/proc/%s) called\n", procFile_name);
        ret = sprintf(buffer, "MyKernel = %x\n", 0);
    }

    return ret;
}
于 2012-10-26T20:41:51.777 回答