(本章基於：linux-4.4.0-37)

在使用者態下程式設計可以通過main()來傳遞命令列引數，而編寫一個核心模組則可通過巨集module_param()來傳遞命令列引數.

先來看看這個巨集的定義（Linux-4.4.0-37）

#define module_param(name, type, perm)				\
	module_param_named(name, name, type, perm)

type：引數型別，byte, short, ushort, int, uint, long, ulong, charp, bool, invbool

perm：許可權S_IRUGO, S_IWUGO

例：hello.c

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

static int num = 0;
static char *name = NULL;

module_param(num, int, S_IRUGO);
module_param(name, charp, S_IRUGO);

static __init int hello_init(void)
{
        printk(KERN_WARNING "helloworld init!\n");
        printk(KERN_ALERT "num=%d\nname=%s\n", num, name);
        return 0;
}

static __exit void hello_exit(void)
{
        printk(KERN_WARNING "helloworld exit!\n");
}

module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stone");
 

可在載入模組時帶入引數初始值：

#insmod helloworld.ko name=aaaa  num=43

檢視核心引數

可在/sys/module/helloworld/parameters/中看到各引數對應的檔案，cat其內容可看到引數具體值。

備註：書上說若引數具有許可權S_IWUGO即可修改引數值，但試驗後發現加上S_IWUGO後無法通過編譯，錯誤如下，望大神指點：

include/linux/bug.h:33:45: error: negative width in bit-field ‘<anonymous>’
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
                                             ^
include/linux/kernel.h:831:3: note: in expansion of macro ‘BUILD_BUG_ON_ZERO’
   BUILD_BUG_ON_ZERO((perms) & 2) +     \
   ^
include/linux/moduleparam.h:225:6: note: in expansion of macro ‘VERIFY_OCTAL_PERMISSIONS’
      VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } }
      ^
include/linux/moduleparam.h:167:2: note: in expansion of macro ‘__module_param_call’
  __module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1, 0)
  ^
include/linux/moduleparam.h:147:2: note: in expansion of macro ‘module_param_cb’
  module_param_cb(name, ¶m_ops_##type, &value, perm);     \
  ^
include/linux/moduleparam.h:126:2: note: in expansion of macro ‘module_param_named’
  module_param_named(name, name, type, perm)
  ^
/root/modules/helloworld/hello.c:10:1: note: in expansion of macro ‘module_param’
 module_param(name, charp, S_IWUGO);
 ^
scripts/Makefile.build:258: recipe for target '/root/modules/helloworld/hello.o' failed