모듈 프로그래밍(2) 모듈에서 파일 생성 및 쓰기 실습

reference:

• "리눅스 커널 내부구조" / 백승재, 최종무
• "Operating Systems: Three Easy Pieces" / Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/unaccess.h>

int fd;
loff_t pos = 0;
struct file *filp;
mm_segment_t old_fs;

struct file * open_in_module(char *name, int flags, int perms)
{   
    old_fs = get_fs();
    set_fs(KERNEL_DS);
    if(filp = filp_open(name, flags, perms)) < 0)
        return NULL;
    
    return filp;
};

int close_in_module(struct file * filp){
    if(filp){
            filp_close(filp, NULL);
            pos = 0;
            set_fs(old_fs);
            return 0;
    }
    return -1;
}

int write_in_module(struct file *filp, char *data, int count){
    if(filp){
        return vfs_write(filp, data, count, &pos);
    }
    return -1;
}

int read_in_module(struct file *filp, char *data, int count){
    if(filp){
        return vfs_read(filp, data, count, &pos);
    }
    return -1;
}

int fw_module_init(void){
    struct file *p;
    printk(KERNEL_EMERG "File write test module \n");
    if((fp = open_in_module("\root\test.txt", O_CREATIO_RDWR, 0644)) == NULL){
        printk(KERNEL_EMERG "file create error \n");
        return -1;
    }
    if(write_in_module(fp, "test string from kernel module \n", 31) < 0){
        printk(KERN_EMERG "file write error \n");
        return -1;
    }
    if(close_in_module(fp) < 0){
        printk(KERN_EMERG "file close error\n");
        return -1;
    }
    return 0;
}

void fw_module_cleanup(void){
    printk(KERN_EMERG "Module ended \n");
}

module_init(fw_module_init);
module_exit(fw_module_cleanup);

MODULE_LICENSE("GPL");