Dear all:
I wrote two programs to test how to communicate with the kernel module.
The first one is a user program (user.c) , it opens file(rw_test) in the
/proc, and
write test data to the rw_test file, then read these data from it.
Another one is a kernel module(module.c), it register a /proc
file(rw_test).And
manipulate read and write opertions.
I execute the following commands:
gcc -o user user.c
gcc -c module.c -D__KERNEL__ -DMODULE -Wall -O
insmod module.o
./user
but the user program print error(can't open the /proc/rw_test file)
why??
I feel so sad.
Ariel Chen in Taiwan
the following is the source code I wrote.
/*========================== user.c =================*/
/*
* User program : to write something to module program
*/
#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
main(void)
{
int fd;
char test1[80],test2[80];
sprintf(test1,"This is a test");
if( (fd=open("/proc/rw_test",O_RDWR))==-1)
printf("error");
if( write(fd,test,14)==-1)
printf("error");
read(fd,test2,14);
printf("test2=%s\n",test2);
}
/*=================== module.c =========================*/
/*
* Module Program : to communicate with user program
*/
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/module.h> /* Specifically, a module */
#include <linux/stat.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h> /* for get_user and put_user */
#define MESSAGE_LENGTH 80
static char Message[MESSAGE_LENGTH];
static ssize_t module_output(
struct file *file, /* The file read */
char *buf, /* The buffer to put data to (in the
* user segment) */
size_t len, /* The length of the buffer */
loff_t *offset) /* Offset in the file - ignore */
{
int i;
char message[MESSAGE_LENGTH+30];
sprintf(message, "Last input:%s", Message);
for(i=0; i<len && message[i]; i++)
put_user(message[i], buf+i);
return i; /* Return the number of bytes "read" */
}
static ssize_t module_input(
struct file *file, /* The file itself */
const char *buf, /* The buffer with input */
size_t length, /* The buffer's length */
loff_t *offset) /* offset to file - ignore */
{
int i;
for(i=0; i<MESSAGE_LENGTH-1 && i<length; i++)
get_user(Message[i], buf+i);
return i;
}
static int module_permission(struct inode *inode, int op)
{
if (op == 4 || (op == 2 && current->euid == 0))
return 0;
return -EACCES;
}
int module_open(struct inode *inode, struct file *file)
{
MOD_INC_USE_COUNT;
return 0;
}
int module_close(struct inode *inode, struct file *file)
{
MOD_DEC_USE_COUNT;
return 0; /* success */
}
static struct file_operations File_Ops_4_Our_Proc_File =
{
NULL, /* lseek */
module_output, /* "read" from the file */
module_input, /* "write" to the file */
NULL, /* readdir */
NULL, /* select */
NULL, /* ioctl */
NULL, /* mmap */
module_open, /* Somebody opened the file */
NULL, /* flush, added here in version 2.2 */
module_close, /* Somebody closed the file */
NULL,
NULL,
NULL,
NULL,
NULL
};
static struct inode_operations Inode_Ops_4_Our_Proc_File =
{
&File_Ops_4_Our_Proc_File,
NULL, /* create */
NULL, /* lookup */
NULL, /* link */
NULL, /* unlink */
NULL, /* symlink */
NULL, /* mkdir */
NULL, /* rmdir */
NULL, /* mknod */
NULL, /* rename */
NULL, /* readlink */
NULL, /* follow_link */
NULL, /* readpage */
NULL, /* writepage */
NULL, /* bmap */
NULL,
module_permission,
NULL,
NULL,
NULL
};
static struct proc_dir_entry Our_Proc_File =
{
0,
7,
"rw_test",
S_IFREG | S_IRUGO | S_IWUSR,
1, /* Number of links (directories where the
* file is referenced) */
0, 0, /* The uid and gid for the file -
* we give it to root */
80, /* The size of the file reported by ls. */
&Inode_Ops_4_Our_Proc_File,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
0,0
};
int init_module()
{
return proc_register(&proc_root, &Our_Proc_File);
}
void cleanup_module()
{
proc_unregister(&proc_root, Our_Proc_File.low_ino);
}
/*====================== End =========================*/
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This archive was generated by hypermail 2b29 : Tue Mar 21 2000 - 11:18:42 EST