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| #include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h> // for basic filesystem
#include <linux/proc_fs.h> // for the proc filesystem
#include <linux/seq_file.h> // for sequence files
#include <linux/jiffies.h> // for jiffies
#include <linux/slab.h> // for kzalloc, kfree
#include <linux/uaccess.h> // for copy_from_user
// global var
static char *str = NULL;
// seq_operations -> show
static int jif_show(struct seq_file *m, void *v)
{
seq_printf(m, "current kernel time is %llu\n", (unsigned long long) get_jiffies_64());
seq_printf(m, "str is %s\n", str);
return 0; //!! must be 0, or will show nothing T.T
}
// file_operations -> write
static ssize_t jif_write(struct file *file, const char __user *buffer, size_t count, loff_t *f_pos)
{
//分配临时缓冲区
char *tmp = kzalloc((count+1), GFP_KERNEL);
if (!tmp)
return -ENOMEM;
//将用户态write的字符串拷贝到内核空间
//copy_to|from_user(to,from,cnt)
if (copy_from_user(tmp, buffer, count)) {
kfree(tmp);
return -EFAULT;
}
//将str的旧空间释放，然后将tmp赋值给str
kfree(str);
str = tmp;
return count;
}
// seq_operations -> open
static int jif_open(struct inode *inode, struct file *file)
{
return single_open(file, jif_show, NULL);
}
static const struct file_operations jif_fops =
{
.owner = THIS_MODULE,
.open = jif_open,
.read = seq_read,
.write = jif_write,
.llseek = seq_lseek,
.release = single_release,
};
// module init
static int __init jif_init(void)
{
struct proc_dir_entry* jif_file;
jif_file = proc_create("jif", 0, NULL, &jif_fops);
if (NULL == jif_file)
{
return -ENOMEM;
}
return 0;
}
// module exit
static void __exit jif_exit(void)
{
remove_proc_entry("jif", NULL);
kfree(str);
}
module_init(jif_init);
module_exit(jif_exit);
MODULE_AUTHOR("aran");
MODULE_LICENSE("GPL");
|
