0 准备工作。
0.0 系统环境：Ubuntu18.04.1 amd64。
0.1 安装必要软件包
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sudo
apt
install
build-essential bison flex libssl-dev libelf-dev
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1 下载内核源码，构建源码树
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sudo
apt
install
linux-
source
-4.15.0 -y
cd
/usr/src/linux-source-4
.15.0/
sudo
tar
xf linux-
source
-4.15.0.
tar
.bz2
cd
linux-
source
-4.15.0/
sudo
make
oldconfig
sudo
make
prepare
sudo
make
scripts
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2 编译驱动源码
源码需要改动几处：
copy_to_user()改为raw_copy_to_user();
copy_from_user()改为raw_copy_from_user();
init_MUTEX((&scull_device->sem);改为sema_init(&scull_device->sem, 1);
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make
sudo
insmod scull.ko
sudo
rmmod scull.ko
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附1：scull.c
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#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include "scull.h"
int
scull_major = SCULL_MAJOR;
int
scull_minor = 0;
module_param(scull_major,
int
, S_IRUGO);
module_param(scull_minor,
int
, S_IRUGO);
struct
scull_dev *scull_device;
int
scull_trim(
struct
scull_dev *dev)
{
if
(dev)
{
if
(dev->data)
{
kfree(dev->data);
}
dev->data = NULL;
dev->size = 0;
}
return
0;
}
int
scull_open(
struct
inode *inode,
struct
file *filp)
{
struct
scull_dev *dev;
dev = container_of(inode->i_cdev,
struct
scull_dev, cdev);
filp->private_data = dev;
if
((filp->f_flags & O_ACCMODE) == O_WRONLY)
{
if
(down_interruptible(&dev->sem))
{
return
-ERESTARTSYS;
}
scull_trim(dev);
up(&dev->sem);
}
return
0;
}
int
scull_release(
struct
inode *inode,
struct
file *filp)
{
return
0;
}
ssize_t scull_read(
struct
file *filp,
char
__user *buf,
size_t
count, loff_t *f_pos)
{
struct
scull_dev *dev = filp->private_data;
ssize_t retval = 0;
if
(down_interruptible(&dev->sem))
{
return
-ERESTARTSYS;
}
if
(*f_pos >= dev->size)
{
goto
out;
}
if
(*f_pos + count > dev->size)
{
count = dev->size - *f_pos;
}
if
(!dev->data)
{
goto
out;
}
if
(raw_copy_to_user(buf, dev->data + *f_pos, count))
{
retval = -EFAULT;
goto
out;
}
*f_pos += count;
retval = count;
out:
up(&dev->sem);
return
retval;
}
ssize_t scull_write(
struct
file *filp,
const
char
__user *buf,
size_t
count, loff_t *f_pos)
{
struct
scull_dev *dev = filp->private_data;
ssize_t retval = -ENOMEM;
if
(down_interruptible(&dev->sem))
{
return
-ERESTARTSYS;
}
if
(!dev->data)
{
dev->data = kmalloc(SCULL_BUFFER_SIZE, GFP_KERNEL);
if
(!dev->data)
{
goto
out;
}
memset
(dev->data, 0, SCULL_BUFFER_SIZE);
}
if
(count > SCULL_BUFFER_SIZE - dev->size)
{
count = SCULL_BUFFER_SIZE - dev->size;
}
if
(raw_copy_from_user(dev->data + dev->size, buf, count))
{
retval = -EFAULT;
goto
out;
}
dev->size += count;
retval = count;
out:
up(&dev->sem);
return
retval;
}
loff_t scull_llseek(
struct
file *filp, loff_t off,
int
whence)
{
struct
scull_dev *dev = filp->private_data;
loff_t newpos;
switch
(whence)
{
case
0:
newpos = off;
break
;
case
1:
newpos = filp->f_pos + off;
break
;
case
2:
newpos = dev->size + off;
break
;
default
:
return
-EINVAL;
}
if
(newpos < 0)
{
return
-EINVAL;
}
filp->f_pos = newpos;
return
newpos;
}
struct
file_operations scull_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.open = scull_open,
.release = scull_release,
};
void
scull_cleanup_module(
void
)
{
dev_t devno = MKDEV(scull_major, scull_minor);
if
(scull_device)
{
scull_trim(scull_device);
cdev_del(&scull_device->cdev);
kfree(scull_device);
}
unregister_chrdev_region(devno, 1);
}
static
void
scull_setup_cdev(
struct
scull_dev *dev)
{
int
err, devno = MKDEV(scull_major, scull_minor);
cdev_init(&dev->cdev, &scull_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &scull_fops;
err = cdev_add(&dev->cdev, devno, 1);
if
(err)
{
printk(KERN_NOTICE
"Error %d adding scull"
, err);
}
}
static
int
__init scull_init_module(
void
)
{
int
result;
dev_t dev = 0;
if
(scull_major)
{
dev = MKDEV(scull_major, scull_minor);
result = register_chrdev_region(dev, 1,
"scull"
);
}
else
{
result = alloc_chrdev_region(&dev, scull_minor, 1,
"scull"
);
scull_major = MAJOR(dev);
}
if
(result < 0)
{
printk(KERN_WARNING
"scull: can't get major %d\n"
, scull_major);
return
result;
}
scull_device = kmalloc(
sizeof
(
struct
scull_dev), GFP_KERNEL);
if
(!scull_device)
{
result = -ENOMEM;
goto
fail;
}
memset
(scull_device, 0,
sizeof
(
struct
scull_dev));
sema_init(&scull_device->sem, 1);
scull_setup_cdev(scull_device);
return
0;
fail:
scull_cleanup_module();
return
result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module);
MODULE_LICENSE(
"GPL"
);
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附2：scull.h
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#ifndef _SCULL_H
#define _SCULL_H
#define SCULL_MAJOR 0
#define SCULL_BUFFER_SIZE PAGE_SIZE
struct
scull_dev {
char
*data;
unsigned
long
size;
struct
semaphore sem;
struct
cdev cdev;
};
#endif
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附3：Makefile
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#sample driver module
obj-m := scull.o
KDIR =
/root/linux-2
.6.36.4/
PWD:=$(shell
pwd
)
INSTALLDIR=$(PWD)
modules:
$(MAKE) -C
/lib/modules/
`
uname
-r`
/build
M=`
pwd
` modules
clean:
rm
-f *.mod.c *.mod.o *.ko *.o *.tmp_versions
.PHONY:modules clean
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