Practical character driver
Sameer Rahmani
lxsameer at gmail.com
Sat Feb 26 23:57:47 EST 2011
hi
i write a a character device driver practically, when i load it in kernel,
kernel kill the driver because of a crash. i also put the C file in this
mail so please review my code please,
i want to know problem, mistakes, hints and ....
thank you so much
here is a tracback
=========================
[ 704.202596] Pid: 6912, comm: insmod Not tainted 2.6.37-2 #2
33238RG/33238RG
[ 704.202648] RIP: 0010:[<ffffffffa00db0da>] [<ffffffffa00db0da>]
module_initial+0xda/0x146 [memchar]
[ 704.202722] RSP: 0018:ffff880031c85f08 EFLAGS: 00010246
[ 704.202763] RAX: ffff8801317bf5c0 RBX: 0000000000000000 RCX:
0000000000000000
[ 704.202816] RDX: ffff8801317bf5c0 RSI: ffffffffa00a1320 RDI:
0000000000000008
[ 704.202868] RBP: 0000000000000008 R08: ffff8800bb016350 R09:
ffff8800ab0b49c0
[ 704.202921] R10: 0000000000000000 R11: 00000000000136c0 R12:
0000000000000000
[ 704.202974] R13: 0000000000026085 R14: 0000000000040000 R15:
0000000000000003
[ 704.203027] FS: 00007fe95def9700(0000) GS:ffff8800bb000000(0000)
knlGS:0000000000000000
[ 704.203087] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 704.203130] CR2: 0000000000000000 CR3: 00000000ab169000 CR4:
00000000000006f0
[ 704.203182] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 704.203240] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
0000000000000400
[ 704.203293] Process insmod (pid: 6912, threadinfo ffff880031c84000, task
ffff880131741a00)
[ 704.203353] Stack:
[ 704.203371] 00000000ffffffff 0fc00001810b0439 0000000000000000
0000000000000000
[ 704.203439] ffffffffa00db000 ffffffff8100204a 0000000000026085
ffffffffa00a1400
[ 704.203507] 0000000000026085 0000000000a9c010 0000000000026085
ffffffff810c5b79
[ 704.203574] Call Trace:
[ 704.203600] [<ffffffffa00db000>] ? module_initial+0x0/0x146 [memchar]
[ 704.203653] [<ffffffff8100204a>] ? do_one_initcall+0x3a/0x180
[ 704.203702] [<ffffffff810c5b79>] ? sys_init_module+0xb9/0x200
[ 704.203749] [<ffffffff81040f52>] ? system_call_fastpath+0x16/0x1b
[ 704.203796] Code: 8a 00 00 00 45 31 e4 48 63 0d 2b 63 fc ff 31 c0 48 89
d7 49 8d 6c 24 08 f3 aa 48 c7 c6 20 13 0a a0 48 8b 05 81 65 fc ff 48 89 ef
<49> 89 04 24 8b 1d 7c 65 fc ff c1 e3 14 0b 1d ff 62 fc ff e8 8e
[ 704.204218] RIP [<ffffffffa00db0da>] module_initial+0xda/0x146 [memchar]
[ 704.204275] RSP <ffff880031c85f08>
[ 704.204303] CR2: 0000000000000000
[ 704.213239] ---[ end trace 84796bda6e0d2134 ]---
========================================
/*
memchar - Memory map driver
Copyright (C) 2011 Sameer Rahmani <lxsameer at gnu.org>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/stat.h>
#include <linux/moduleparam.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <asm/uaccess.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sameer Rahmani <lxsameer at gnu.org>");
MODULE_DESCRIPTION("Memory map driver");
struct memmap {
char *device;
struct cdev cdev;
int position;
bool eof;
};
static int major = 0;
static int minor = 1;
static int map_size = 100;
char *device;
module_param(major, int, S_IRUGO);
module_param(minor, int, S_IRUGO);
module_param(map_size, int, S_IRUGO);
static void module_cleanup(void)
{
dev_t dev;
kfree(device);
dev = MKDEV(major, minor);
unregister_chrdev_region(dev, 1);
printk(KERN_ALERT "memchar module un-loaded.\n");
}
/*
* open function.
*/
int mem_open(struct inode *inode, struct file *filp)
{
struct memmap *memory;
memory = container_of(inode->i_cdev, struct memmap, cdev);
memory->device = device;
filp->private_data = memory;
/* write-only */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
memory->position = 0;
memory->eof = false;
}
return 0; /* success */
}
/* close function */
int mem_release(struct inode *inode, struct file *filp)
{
return 0;
}
/* read function */
ssize_t mem_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos)
{
struct memmap *memory = filp->private_data; ;
int counter;
if (memory->eof)
{
return 0;
}
counter = count;
if (count + memory->position > map_size)
{
counter = map_size - memory->position;
}
if(copy_to_user(buf, memory->device, counter))
{
counter = -EFAULT;
return counter;
}
memory->position += counter;
if (memory->position == map_size)
memory->eof = true;
return counter;
}
/* write function */
ssize_t mem_write(struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos)
{
struct memmap *memory = filp->private_data; ;
int counter;
if (memory->eof)
return 0;
counter = count;
if (count + memory->position > map_size)
{
counter = map_size - memory->position;
}
if(copy_from_user(memory->device, buf, counter))
{
counter = -EFAULT;
return counter;
}
memory->position += counter;
if (memory->position == map_size)
memory->eof = true;
return counter;
}
struct file_operations mem_fops = {
.owner = THIS_MODULE,
.read = mem_read,
.write = mem_write,
.open = mem_open,
.release = mem_release,
};
/*
* Set up the char_dev structure for this device.
*/
static void mem_setup_cdev(struct memmap *dev)
{
int err, devno = MKDEV(major, minor);
cdev_init(&dev->cdev, &mem_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &mem_fops;
err = cdev_add (&dev->cdev, devno, 1);
/* Fail gracefully if need be */
if (err)
printk(KERN_NOTICE "Error %d adding memchar", err);
}
static int __init module_initial(void)
{
dev_t dev;
int result;
struct memmap *memory;
if (major)
{
dev = MKDEV(major, minor);
result = register_chrdev_region(dev, 1, "memchar");
}
else
{
result = alloc_chrdev_region(&dev, minor, 1,
"memchar");
major = MAJOR(dev);
}
if (result < 0)
{
printk (KERN_ALERT "Cannot register major number.\n");
return result;
}
device = kmalloc(sizeof(char) * map_size, GFP_KERNEL);
if (! device)
{
printk (KERN_ALERT "Allocating device failed.\n");
result = -ENOMEM;
goto fail;
}
memset(device, 0, sizeof(char) * map_size);
memory->device = device;
mem_setup_cdev(memory);
printk(KERN_ALERT "Major: %d", major);
return 0;
fail:
module_cleanup();
return result;
}
module_init(module_initial);
module_exit(module_cleanup);
=================================
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