Kernel_module_param

module_param 内核传参

用户态C语言中，函数传参使用main(int argc, char ** argv)，而内核态传参数使用:

在内核函数中使用 module_param指定模块参数。
加载内核时传递参数给模块。

module_param 函数

$itop_kernel/include/linux/moduleparam.h

/**
 * module_param - typesafe helper for a module/cmdline parameter
 * @value: the variable to alter, and exposed parameter name.
 * @type: the type of the parameter
 * @perm: visibility in sysfs.
 *
 * @value becomes the module parameter, or (prefixed by KBUILD_MODNAME and a
 * ".") the kernel commandline parameter.  Note that - is changed to _, so
 * the user can use "foo-bar=1" even for variable "foo_bar".
 *
 * @perm is 0 if the the variable is not to appear in sysfs, or 0444
 * for world-readable, 0644 for root-writable, etc.  Note that if it
 * is writable, you may need to use kparam_block_sysfs_write() around
 * accesses (esp. charp, which can be kfreed when it changes).
 *
 * The @type is simply pasted to refer to a param_ops_##type and a
 * param_check_##type: for convenience many standard types are provided but
 * you can create your own by defining those variables.
 *
 * Standard types are:
 *	byte, short, ushort, int, uint, long, ulong
 *	charp: a character pointer
 *	bool: a bool, values 0/1, y/n, Y/N.
 *	invbool: the above, only sense-reversed (N = true).
 */
#define module_param(name, type, perm)				\
	module_param_named(name, name, type, perm)
/**
*  name: 内核中参数的名称
*  type: 数据类型,  byte, short, int, long, ulong, bool, charp(字符指针)
*  perm: 内核参数权限。   可以查看 include/linux/stat.h
**/

#define S_ISUID  0004000
#define S_ISGID  0002000
#define S_ISVTX  0001000

#define S_IRWXU 00700
#define S_IRUSR 00400
#define S_IWUSR 00200
#define S_IXUSR 00100

#define S_IRWXG 00070
#define S_IRGRP 00040
#define S_IWGRP 00020
#define S_IXGRP 00010

#define S_IRWXO 00007
#define S_IROTH 00004
#define S_IWOTH 00002
#define S_IXOTH 00001

#endif

#ifdef __KERNEL__
#define S_IRWXUGO	(S_IRWXU|S_IRWXG|S_IRWXO)
#define S_IALLUGO	(S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
#define S_IRUGO		(S_IRUSR|S_IRGRP|S_IROTH)
#define S_IWUGO		(S_IWUSR|S_IWGRP|S_IWOTH)
#define S_IXUGO		(S_IXUSR|S_IXGRP|S_IXOTH)

示例

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

static int age = 25;
static char *name = "Li Gang";

static int __init hello_init(void)
{
	printk("age = %d, name = [ %s ]\n", age, name);
	return 0;
}


static void __exit hello_exit(void)
{
	printk("module: exit hello module\n");
}

module_init(hello_init);
module_exit(hello_exit);

module_param(age, int, 0754);
module_param(name, charp, 0754);


MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("rocky");

运行

$ sudo insmod module_param.ko age=100
Dec 22 00:11:53 ubuntu kernel: [54928.625291] age = 100, name = [ Li Gang ]

$ sudo insmod module_param.ko 
Dec 22 00:12:19 ubuntu kernel: [54954.592554] age = 25, name = [ Li Gang ]

问题

module_param err