從使用者介面傳入參數

如果我們想要從command line傳入參數到kernel裡面，模組裡面必須將變數設為全域變數，然後利用一個 module_param()的函式將想要接收使用者介面傳入參數的變數帶入，這個函式被定義在linux/moduleparam.h。另外module_param()提供的是整數的傳入，如果想要傳入陣列或是字串可以使用 module_param_array()和 module_param_string()。

int myint = 3;
module_param(myint, int, 0);

int myintarray[2];
module_param_array(myintarray, int, NULL, 0);

int myshortarray[4];
int count;
module_parm_array(myshortarray, short, , 0);

以下提供較完整範例:

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/stat.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peter Jay Salzman");
static short int myshort = 1;
static int myint = 420;
static long int mylong = 9999;
static char *mystring = "blah";
static int myintArray[2] = { −1, −1 };
static int arr_argc = 0;
/* 
 * module_param(foo, int, 0000)
 * The first param is the parameters name
 * The second param is it's data type
 * The final argument is the permissions bits, 
 * for exposing parameters in sysfs (if non−zero) at a later stage.
 */
module_param(myshort, short, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
MODULE_PARM_DESC(myshort, "A short integer");
module_param(myint, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
MODULE_PARM_DESC(myint, "An integer");
module_param(mylong, long, S_IRUSR);
MODULE_PARM_DESC(mylong, "A long integer");
module_param(mystring, charp, 0000);
MODULE_PARM_DESC(mystring, "A character string");
/*
 * module_param_array(name, type, num, perm);
 * The first param is the parameter's (in this case the array's) name
 * The second param is the data type of the elements of the array
 * The third argument is a pointer to the variable that will store the number 
 * of elements of the array initialized by the user at module loading time
 * The fourth argument is the permission bits
*/
module_param_array(myintArray, int, &arr_argc, 0000);
MODULE_PARM_DESC(myintArray, "An array of integers");
static int __init hello_5_init(void)
{
        int i;
        printk(KERN_INFO "Hello, world 5\n=============\n");
        printk(KERN_INFO "myshort is a short integer: %hd\n", myshort);
        printk(KERN_INFO "myint is an integer: %d\n", myint);
        printk(KERN_INFO "mylong is a long integer: %ld\n", mylong);
        printk(KERN_INFO "mystring is a string: %s\n", mystring);
        for (i = 0; i < (sizeof myintArray / sizeof (int)); i++)
        {
                printk(KERN_INFO "myintArray[%d] = %d\n", i, myintArray[i]);
        }
        printk(KERN_INFO "got %d arguments for myintArray.\n", arr_argc);
        return 0;
}
static void __exit hello_5_exit(void)
{
        printk(KERN_INFO "Goodbye, world 5\n");
}
module_init(hello_5_init);
module_exit(hello_5_exit);

之後我們輸入一些參數看看結果如何:

satan# insmod hello−5.ko mystring="bebop" mybyte=255 myintArray=−1
mybyte is an 8 bit integer: 255
myshort is a short integer: 1
myint is an integer: 20
mylong is a long integer: 9999
mystring is a string: bebop
myintArray is −1 and 420
satan# rmmod hello−5
Goodbye, world 5
satan# insmod hello−5.ko mystring="supercalifragilisticexpialidocious" \
> mybyte=256 myintArray=−1,−1
mybyte is an 8 bit integer: 0
myshort is a short integer: 1
myint is an integer: 20
mylong is a long integer: 9999
mystring is a string: supercalifragilisticexpialidocious
myintArray is −1 and −1
satan# rmmod hello−5
Goodbye, world 5
satan# insmod hello−5.ko mylong=hello
hello−5.o: invalid argument syntax for mylong: 'h'