proc 文件的创建和读写
内核版本
Linux version 5.8.0-44-generic
mydev.c
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#define BUFSIZE 100
static int irq = 20;
static int mode = 1;
static struct proc_dir_entry *ent;
static ssize_t mywrite(struct file *file, const char __user *ubuf, size_t count, loff_t *ppos)
{
int num, c, i, m;
char buf[BUFSIZE] = {0};
if (*ppos > 0 || count > BUFSIZE)
return -EFAULT;
if (copy_from_user(buf, ubuf, count))
return -EFAULT;
num = sscanf(buf, "%d %d", &i, &m);
if (num != 2)
return -EFAULT;
irq = i;
mode = m;
c = strlen(buf);
*ppos = c;
return c;
}
static ssize_t myread(struct file *file, char __user *ubuf, size_t count, loff_t *ppos)
{
char buf[BUFSIZE] = {0};
int len = 0;
if (*ppos > 0 || count < BUFSIZE)
return 0;
len += sprintf(buf, "irq = %d\n", irq);
len += sprintf(buf + len, "mode = %d\n", mode);
if (copy_to_user(ubuf, buf, len))
return -EFAULT;
*ppos = len;
return len;
}
static struct file_operations myops = {
.owner = THIS_MODULE,
.read = myread,
.write = mywrite,
};
static int simple_init(void)
{
ent = proc_create("mydev", 0666, NULL, (struct proc_ops *)&myops);
printk(KERN_ALERT "hello...\n");
return 0;
}
static void simple_cleanup(void)
{
proc_remove(ent);
printk(KERN_WARNING "bye ...\n");
}
module_param(irq, int, 0660);
module_param(mode, int, 0660);
module_init(simple_init);
module_exit(simple_cleanup);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Liran B.H");
Makefile
obj-m:=mydev.o
CURRENT_PATH:=$(shell pwd)
VERSION_NUM:=$(shell uname -r)
LINUX_PATH:=/usr/src/linux-headers-$(VERSION_NUM)
all :
make -C $(LINUX_PATH) M=$(CURRENT_PATH) modules
clean:
make -C $(LINUX_PATH) M=$(CURRENT_PATH) clean
make && install
$ make
make -C /usr/src/linux-headers-5.8.0-44-generic M=/home/liyongjun/project/c/study/kernel/proc modules
make[1]: 进入目录“/usr/src/linux-headers-5.8.0-44-generic”
CC [M] /home/liyongjun/project/c/study/kernel/proc/mydev.o
MODPOST /home/liyongjun/project/c/study/kernel/proc/Module.symvers
CC [M] /home/liyongjun/project/c/study/kernel/proc/mydev.mod.o
LD [M] /home/liyongjun/project/c/study/kernel/proc/mydev.ko
make[1]: 离开目录“/usr/src/linux-headers-5.8.0-44-generic”
insmod
$ sudo insmod mydev.ko
read
$ cat /proc/mydev
irq = 20
mode = 1
write
$ echo 55 6 > /proc/mydev
$ cat /proc/mydev
irq = 55
mode = 6
user_app.c
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
void main(void)
{
char buf[100] = {0};
int fd = open("/proc/mydev", O_RDWR);
read(fd, buf, 100);
puts(buf);
lseek(fd, 0, SEEK_SET);
write(fd, "33 4", 5);
lseek(fd, 0, SEEK_SET);
read(fd, buf, 100);
puts(buf);
}
编译
$ gcc user_app.c -o user_app.out
运行
$ ./user_app.out
irq = 55
mode = 6
irq = 33
mode = 4
rmmod
$ sudo rmmod mydev