nhmk/examples/procfs2.c

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2021-07-22 06:35:24 +08:00
/**
* procfs2.c - create a "file" in /proc
*
*/
#include <linux/module.h> /* Specifically, a module */
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/proc_fs.h> /* Necessary because we use the proc fs */
#include <linux/uaccess.h> /* for copy_from_user */
#define PROCFS_MAX_SIZE 1024
#define PROCFS_NAME "buffer1k"
/**
* This structure hold information about the /proc file
*
*/
static struct proc_dir_entry *Our_Proc_File;
/**
* The buffer used to store character for this module
*
*/
static char procfs_buffer[PROCFS_MAX_SIZE];
/**
* The size of the buffer
*
*/
static unsigned long procfs_buffer_size = 0;
/**
* This function is called then the /proc file is read
*
*/
ssize_t procfile_read(struct file *filePointer,char *buffer,
size_t buffer_length, loff_t * offset)
{
int ret=0;
if(strlen(buffer) ==0) {
pr_info("procfile read %s\n",filePointer->f_path.dentry->d_name.name);
ret=copy_to_user(buffer,"HelloWorld!\n",sizeof("HelloWorld!\n"));
ret=sizeof("HelloWorld!\n");
}
return ret;
}
/**
* This function is called with the /proc file is written
*
*/
static ssize_t procfile_write(struct file *file, const char *buff,
size_t len, loff_t *off)
{
procfs_buffer_size = len;
if (procfs_buffer_size > PROCFS_MAX_SIZE)
procfs_buffer_size = PROCFS_MAX_SIZE;
if (copy_from_user(procfs_buffer, buff, procfs_buffer_size))
return -EFAULT;
procfs_buffer[procfs_buffer_size] = '\0';
return procfs_buffer_size;
}
static const struct proc_ops proc_file_fops = {
.proc_read = procfile_read,
.proc_write = procfile_write,
};
/**
*This function is called when the module is loaded
*
*/
int init_module()
{
Our_Proc_File = proc_create(PROCFS_NAME,0644,NULL,&proc_file_fops);
if(NULL==Our_Proc_File) {
proc_remove(Our_Proc_File);
pr_alert("Error:Could not initialize /proc/%s\n",PROCFS_NAME);
return -ENOMEM;
}
pr_info("/proc/%s created\n", PROCFS_NAME);
return 0;
}
/**
*This function is called when the module is unloaded
*
*/
void cleanup_module()
{
proc_remove(Our_Proc_File);
pr_info("/proc/%s removed\n", PROCFS_NAME);
}
MODULE_LICENSE("GPL");