内核读写文件

Posted 2023-03-09 Li-Yongjun

简介

用户空间        内核空间
open()            filp_open()
close()            filp_close()
read()             kernel_read()
write()             kernel_write()

环境

架构：ARM
内核版本：4.15

源码

file.c

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#define FILENAME "/tmp/kernel_file"

static char buf[] = "5555\\n";
static char buf1[10] = 0;

int hello_init(void)

	struct file *filp;
	loff_t pos;

	printk("hello enter\\n");

	filp = filp_open(FILENAME, O_RDWR | O_CREAT, 0644);
	if (IS_ERR(filp)) 
		printk("create file error\\n");
		return -1;
	

	pos = 0;
	kernel_write(filp, buf, sizeof(buf), &pos);

	pos = 0;
	kernel_read(filp, buf1, sizeof(buf1) - 1, &pos);
	printk("read: %s", buf1);

	filp_close(filp, NULL);

	return 0;

void hello_exit(void)

	printk("hello exit\\n");


module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("GPL");

Makefile

obj-m:=file.o  
  
KDIR=/home/liyongjun/project/board/buildroot/Vexpress_4.15/build/linux-4.15.1/
CROSS_COMPILE=/home/liyongjun/project/board/buildroot/Vexpress_4.15/host/bin/arm-linux-

all:
	make -C $(KDIR) M=$(PWD) ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) modules

clean:
	make -C $(KDIR) M=$(PWD) ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) clean

测试

# insmod file.ko 
hello enter
read: 5555
# 
# cat /tmp/kernel_file 
5555