问下关于put_user问题 - Linux/Unix

来源：百度文库编辑：神马文学网时间：2024/06/06 09:35:56

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/*
* char-read.c
*
* Character driver with read operation
*
* Copyright (C) 2005 Farsight
*
* 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 2 of the License, or
* (at your option) 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, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/

#include
#include
#include
#include
#include
#include

MODULE_LICENSE ("GPL");

int hello_major = 253;
int hello_minor = 0;
int number_of_devices = 1;
char data[50]="foobar not equal to barfoo";

struct cdev cdev;
dev_t dev = 0;

static int hello_open (struct inode *inode, struct file *file)
{
printk (KERN_INFO "Hey! device opened\n");
return 0;
}

static int hello_release (struct inode *inode, struct file *file)
{
printk (KERN_INFO "Hmmm... device closed\n");
return 0;
}
ssize_t hello_read (struct file *filp, char *buff, size_t count, loff_t *offp)
{
ssize_t result = 0;
/*这里的buff仅是演示如把内核空间的变量传递给用户空间*/
if (copy_to_user (buff, data, sizeof(data)-1))
result = -EFAULT;
else
printk (KERN_INFO "wrote %d bytes\n", count);
return result;
}

ssize_t hello_write (struct file *filp, const char *buf, size_t count, loff_t *f_pos)
{
ssize_t ret = 0;
printk (KERN_INFO "Writing %d bytes\n", count);
if (count>127) return -ENOMEM;
if (count<0) return -EINVAL;
if (copy_from_user (data, buf, count)) {
ret = -EFAULT;
}
else {
data[127]='\0';
printk (KERN_INFO"Received: %s\n", data);
ret = count;
}
return ret;
}

struct file_operations hello_fops = {
.owner = THIS_MODULE,
.open = hello_open,
.release = hello_release,
.read = hello_read,
.write = hello_write
};

static void char_reg_setup_cdev (void)
{
int error, devno = MKDEV (hello_major, hello_minor);
cdev_init (&cdev, &hello_fops);
cdev.owner = THIS_MODULE;
cdev.ops = &hello_fops;
error = cdev_add (&cdev, devno , 1);
if (error)
printk (KERN_NOTICE "Error %d adding char_reg_setup_cdev", error);

}

static int __init hello_2_init (void)
{
int result;

dev = MKDEV (hello_major, hello_minor);
result = register_chrdev_region (dev, number_of_devices, "hello");

if (result<0) {
printk (KERN_WARNING "hello: can't get major number %d\n", hello_major);
return result;
}

char_reg_setup_cdev ();
printk (KERN_INFO "char device registered\n");
return 0;
}

static void __exit hello_2_exit (void)
{
dev_t devno = MKDEV (hello_major, hello_minor);

cdev_del (&cdev);

unregister_chrdev_region (devno, number_of_devices);

}

module_init (hello_2_init);
module_exit (hello_2_exit);

测试程序
/*
* test.c
*
* Test application code for char-read.c
*
* Copyright (C) 2005 Farsight
*
* 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 2 of the License, or
* (at your option) 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, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/

#include
#include
#include
#include

int main (void)
{
int fd;
char buff[50];
fd = open ("/dev/hello",O_RDWR);
if (fd < 0) {
printf ("fd open failed\n");
exit(0);
}
printf ("\n/dev/hello opened, fd=%d\n",fd);
memset (buff, '\0', 50);
printf ("Read returns %d\n", read (fd, buff, sizeof(buff)));
buff[50]='0';
printf ("buff = %s\n", buff);
close (fd);
printf ("/dev/hello closed :)\n");
return 0;
}

Makefile：

#KERNELDIR 变量换成你的目标内核源码

KERNELDIR ?= /home/lht/kernel2.6/linux-2.6.14
obj-m += char-read.o

all:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions

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